WorldWideScience

Sample records for harmonic power doppler

  1. Radiofrequency thermal ablation of hepatocellular carcinoma: using contrast-enhanced harmonic power doppler sonography to assess treatment outcome.

    Science.gov (United States)

    Cioni, D; Lencioni, R; Rossi, S; Garbagnati, F; Donati, F; Crocetti, L; Bartolozzi, C

    2001-10-01

    We evaluated the accuracy of contrast-enhanced harmonic power Doppler sonography in assessing the outcome of radiofrequency thermal ablation of hepatocellular carcinoma. Fifty patients with 65 hepatocellular carcinoma nodules (1-5 cm in diameter; mean diameter, 2.5 cm) were studied using unenhanced and contrast-enhanced harmonic power Doppler sonography before and after IV administration of a microbubble contrast agent. The examinations were repeated after treatment of the tumors with radiofrequency ablation. Findings of the Doppler studies were compared with those of dual-phase helical CT, which were used as points of reference for assessing treatment outcome. Before radiofrequency treatment, intratumoral blood flow was revealed by unenhanced power Doppler sonography in 48 (74%) of 65 hepatocellular carcinoma nodules. After injection of the contrast agent, intratumoral enhancement was observed in 61 (94%) of 65 hepatocellular carcinomas (p enhancement on power Doppler sonograms. In nine of the 10 lesions that showed a residual viable tumor on helical CT scans, persistent intratumoral enhancement-matching the enhancing areas on helical CT images-was revealed by power Doppler sonography. These nine hepatocellular carcinomas were subjected to repeated radiofrequency thermal ablation with the guidance of contrast-enhanced power Doppler sonography. Complete necrosis was seen after the second treatment session in six of the nine lesions. Contrast-enhanced harmonic power Doppler sonography is an accurate technique for assessing the outcome of radiofrequency thermal ablation of hepatocellular carcinoma and may be useful in guiding additional treatment in patients with incomplete response to initial efforts.

  2. Power quality issues current harmonics

    CERN Document Server

    Mikkili, Suresh

    2015-01-01

    Power Quality Issues: Current Harmonics provides solutions for the mitigation of power quality problems related to harmonics. Focusing on active power filters (APFs) due to their excellent harmonic and reactive power compensation in two-wire (single phase), three-wire (three-phase without neutral), and four-wire (three-phase with neutral) AC power networks with nonlinear loads, the text:Introduces the APF technology, describing various APF configurations and offering guidelines for the selection of APFs for specific application considerationsCompares shunt active filter (SHAF) control strategi

  3. Harmonics in transmission power systems

    DEFF Research Database (Denmark)

    Wiechowski, Wojciech Tomasz

    Some time ago, Energinet.dk, the Transmission System Operator of the 150 kV and 400 kV transmission network in Denmark, had experienced operational malfunctions of some of the measuring and protection equipment. Also an overloading of a harmonic filter has been reported, and therefore, a need...... to perform more detailed harmonic studies emerged. Since the transmission network has a complex structure and its impedance varies with frequency in a nonlinear fashion, such harmonic study would require a detailed computer model of the network. Consequently, a PhD project proposal titled "Harmonics......, provided that background harmonic distortion, and the network configuration, are not changing during the measurement. It is shown that switching of a shunt linear power system component can result in variation of the harmonic levels that can be measured and used to verify the harmonic model of the network...

  4. Prony Analysis for Power System Transient Harmonics

    Directory of Open Access Journals (Sweden)

    David Cartes

    2007-01-01

    Full Text Available Proliferation of nonlinear loads in power systems has increased harmonic pollution and deteriorated power quality. Not required to have prior knowledge of existing harmonics, Prony analysis detects frequencies, magnitudes, phases, and especially damping factors of exponential decaying or growing transient harmonics. In this paper, Prony analysis is implemented to supervise power system transient harmonics, or time-varying harmonics. Further, to improve power quality when transient harmonics appear, the dominant harmonics identified from Prony analysis are used as the harmonic reference for harmonic selective active filters. Simulation results of two test systems during transformer energizing and induction motor starting confirm the effectiveness of the Prony analysis in supervising and canceling power system transient harmonics.

  5. Probabilistic Harmonic Modeling of Wind Power Plants

    DEFF Research Database (Denmark)

    Guest, Emerson; Jensen, Kim H.; Rasmussen, Tonny Wederberg

    2017-01-01

    A probabilistic sequence domain (SD) harmonic model of a grid-connected voltage-source converter is used to estimate harmonic emissions in a wind power plant (WPP) comprised of Type-IV wind turbines. The SD representation naturally partitioned converter generated voltage harmonics into those...... with deterministic phase and those with probabilistic phase. A case study performed on a string of ten 3MW, Type-IV wind turbines implemented in PSCAD was used to verify the probabilistic SD harmonic model. The probabilistic SD harmonic model can be employed in the planning phase of WPP projects to assess harmonic...

  6. Optimal Selective Harmonic Control for Power Harmonics Mitigation

    DEFF Research Database (Denmark)

    Zhou, Keliang; Yang, Yongheng; Blaabjerg, Frede

    2015-01-01

    of power harmonics. The proposed optimal SHC is of hybrid structure: all recursive SHC modules with weighted gains are connected in parallel. It bridges the real “nk+-m order RC” and the complex “parallel structure RC”. Compared to other IMP based control solutions, it offers an optimal trade-off among...

  7. Selective harmonic control for power converters

    DEFF Research Database (Denmark)

    Zhou, Keliang; Yang, Yongheng; Blaabjerg, Frede

    2014-01-01

    This paper proposes an Internal Model Principle (IMP) based Selective Harmonic Controller (SHC) for power converters. The proposed SHC offers an optimal control solution for power converters to mitigate power harmonics. It makes a good trade-off among cost, complexity and performance. It has high...... accuracy and fast transient response, and it is cost-effective, easy for real-time implementation, and compatible for design rules-of-thumb. An application on a three-phase PWM converter has confirmed the effectiveness of the proposed control scheme in terms of harmonic mitigation....

  8. Harmonics in a Wind Power Plant: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Preciado, V.; Madrigal, M.; Muljadi, E.; Gevorgian, V.

    2015-04-02

    Wind power generation has been growing at a very fast pace for the past decade, and its influence and impact on the electric power grid is significant. As in a conventional power plant, a wind power plant (WPP) must ensure that the quality of the power being delivered to the grid is excellent. At the same time, the wind turbine should be able to operate immune to small disturbances coming from the grid. Harmonics are one of the more common power quality issues presented by large WPPs because of the high switching frequency of the power converters and the possible nonlinear behavior from electric machines (generator, transformer, reactors) within a power plant. This paper presents a summary of the most important issues related to harmonics in WPPs and discusses practical experiences with actual Type 1 and Type 3 wind turbines in two WPPs.

  9. Harmonic Resonances in Wind Power Plants

    DEFF Research Database (Denmark)

    Fernandez, Francisco Daniel Freijedo; Chaudhary, Sanjay; Teodorescu, Remus

    2015-01-01

    This work reviews the state-of-the-art in the field of harmonic resonance problems in Wind Power Plants (WPPs). Firstly, a generic WPP is modeled according to the equivalent circuits of its passive and active components. Main focus is put on modeling active components, i.e. the ones based on power...... converters. Subsequently, pros and cons of frequency and time domain analysis methods are outlined. The next sections are devoted to mitigation methods implemented in the power electronics converters. From the wind turbine perspective, different techniques to enhance the robustness of the controller...... are analyzed. Subsequently, the suitability for active damping of harmonics using STATCOM devices is assessed, with focus both on control techniques and power converter technologies....

  10. Power and color Doppler ultrasound settings for inflammatory flow

    DEFF Research Database (Denmark)

    Torp-Pedersen, Søren; Christensen, Robin; Szkudlarek, Marcin

    2015-01-01

    OBJECTIVE: To determine how settings for power and color Doppler ultrasound sensitivity vary on different high- and intermediate-range ultrasound machines and to evaluate the impact of these changes on Doppler scoring of inflamed joints. METHODS: Six different types of ultrasound machines were used....... On each machine, the factory setting for superficial musculoskeletal scanning was used unchanged for both color and power Doppler modalities. The settings were then adjusted for increased Doppler sensitivity, and these settings were designated study settings. Eleven patients with rheumatoid arthritis (RA......) with wrist involvement were scanned on the 6 machines, each with 4 settings, generating 264 Doppler images for scoring and color quantification. Doppler sensitivity was measured with a quantitative assessment of Doppler activity: color fraction. Higher color fraction indicated higher sensitivity. RESULTS...

  11. Ultrasonography with color Doppler and power Doppler in the diagnosis of periapical lesions

    Directory of Open Access Journals (Sweden)

    Sumit Goel

    2011-01-01

    Full Text Available Aim: To evaluate the efficacy of ultrasonography (USG with color Doppler and power Doppler applications over conventional radiography in the diagnosis of periapical lesions. Materials and Methods: Thirty patients having inflammatory periapical lesions of the maxillary or mandibular anterior teeth and requiring endodontic surgery were selected for inclusion in this study. All patients consented to participate in the study. We used conventional periapical radiographs as well as USG with color Doppler and power Doppler for the diagnosis of these lesions. Their diagnostic performances were compared against histopathologic examination. All data were compared and statistically analyzed. Results: USG examination with color Doppler and power Doppler identified 29 (19 cysts and 10 granulomas of 30 periapical lesions accurately, with a sensitivity of 100% for cysts and 90.91% for granulomas and a specificity of 90.91% for cysts and 100% for granulomas. In comparison, conventional intraoral radiography identified only 21 lesions (sensitivity of 78.9% for cysts and 45.4% for granulomas and specificity of 45.4% for cysts and 78.9% for granulomas. There was definite correlation between the echotexture of the lesions and the histopathological features except in one case. Conclusions: USG imaging with color Doppler and power Doppler is superior to conventional intraoral radiographic methods for diagnosing the nature of periapical lesions in the anterior jaws. This study reveals the potential of USG examination in the study of other jaw lesions.

  12. Ultrasonography with color Doppler and power Doppler in the diagnosis of periapical lesions

    Science.gov (United States)

    Goel, Sumit; Nagendrareddy, Suma Gundareddy; Raju, Manthena Srinivasa; Krishnojirao, Dayashankara Rao Jingade; Rastogi, Rajul; Mohan, Ravi Prakash Sasankoti; Gupta, Swati

    2011-01-01

    Aim: To evaluate the efficacy of ultrasonography (USG) with color Doppler and power Doppler applications over conventional radiography in the diagnosis of periapical lesions. Materials and Methods: Thirty patients having inflammatory periapical lesions of the maxillary or mandibular anterior teeth and requiring endodontic surgery were selected for inclusion in this study. All patients consented to participate in the study. We used conventional periapical radiographs as well as USG with color Doppler and power Doppler for the diagnosis of these lesions. Their diagnostic performances were compared against histopathologic examination. All data were compared and statistically analyzed. Results: USG examination with color Doppler and power Doppler identified 29 (19 cysts and 10 granulomas) of 30 periapical lesions accurately, with a sensitivity of 100% for cysts and 90.91% for granulomas and a specificity of 90.91% for cysts and 100% for granulomas. In comparison, conventional intraoral radiography identified only 21 lesions (sensitivity of 78.9% for cysts and 45.4% for granulomas and specificity of 45.4% for cysts and 78.9% for granulomas). There was definite correlation between the echotexture of the lesions and the histopathological features except in one case. Conclusions: USG imaging with color Doppler and power Doppler is superior to conventional intraoral radiographic methods for diagnosing the nature of periapical lesions in the anterior jaws. This study reveals the potential of USG examination in the study of other jaw lesions. PMID:22223940

  13. Comparison of power Doppler and color Doppler ultrasonography in the detection of intrasticular blood flow of normal infants

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Sung Ran; Lee, Ho Kyoung; Lee, Won Gyun; Youk, Dong Joon; Rho, Taek Soo; Lee, Min Jin; Lee, Sang Chun [Seoul Red Cross Hospital, Seoul (Korea, Republic of)

    1999-09-15

    To compare color Doppler ultrasonography (US) and power Doppler US in the detection of intratesticular blood flow in normal infants and to asses the symmetry of blood flow. Testicular blood flow was assessed prospectively in 100 testes of 50 infants with both power and color Doppler US. We compared the power Doppler with color Doppler to detect intratesticular blood. When the flow was detected, intratesticular blood flow was graded as follows: grade 1: single intratesticular Doppler signal ; grade 2: multiple intratesticular Doppler signals. The symmetry of intratesticular flow was assessed by using the same method. Intratesticular flow was detected in 72 (72%) and 68 (68%) testes on power and color Doppler US, respectively. In 76 testes (76%), intratesticular flow was detected in either one or both techniques. On power Doppler US, grade 1 was seen in 40 tests and grade 2 in 32 testes. On color Doppler US, grade 1 was noted in 52 testes and grade 2 in 16 testes. Testicular blood flow was symmetric on both power and color Doppler US in each patient. There was no difference between power Doppler and color Doppler ultrasonography in detecting intratesticular blood flow in normal infants.

  14. Harmonics and voltage stability analysis in power systems including ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    steady-state voltage stability analysis. 4. Harmonic power flow algorithm. Network voltages and currents can be expressed by Fourier series for the harmonic power flow analysis, which was developed by Xia & Heydt (1982). Voltages and nonlinear element parameters form the bus variable vector ( ), given in. [X] = [. [ ˙V (1). ] ...

  15. Harmonic Analysis and Active Filtering in Offshore Wind Power Plants

    DEFF Research Database (Denmark)

    Chaudhary, Sanjay Kumar; Freijedo Fernandez, Francisco Daniel; Guerrero, Josep M.

    2015-01-01

    at the point of common coupling (PCC). The resonance conditions should be avoided in all cases. This paper describes the harmonic analysis techniques applied on an OWPP network model. A method is proposed to estimate the harmonic current compensation from a shunt-connected active power filter to mitigate......Due to presence of long high voltage cable networks, and power transformers for the grid connection, the offshore wind power plants (OWPPs) are susceptible to harmonic distortion and resonances. The grid connection of OWPP should not cause the harmonic distortion beyond the permissible limits...... the harmonic voltage distortion at the PCC. Finally the harmonic distortions in the compensated and the uncompensated systems are compared to demonstrate the efficacy of the compensation....

  16. Direct harmonic voltage control strategy for shunt active power filter

    DEFF Research Database (Denmark)

    Munir, Hafiz Mudassir; Zou, JianXiao; Xie, Chuan

    2017-01-01

    Shunt active power filters (S-APF) are highly popular ways for harmonic compensation due to the high performance and simplicity of installation. S-APF is commonly controlled in current control mode with load harmonic current detection, which is not quite suitable for the distributed power...... generation system (DPGS) where the nonlinear loads are highly dispersed. Local harmonic voltage detection based Resistive-APF (R-APF) seems more suitable to be applied in the DPGS, however, R-APF suffers from poor compensation performance and difficulty of parameter tuning. In this paper, a direct harmonic...

  17. An Enhanced Islanding Microgrid Reactive Power, Imbalance Power, and Harmonic Power Sharing Scheme

    DEFF Research Database (Denmark)

    He, Jinwei; Lin, Yun Wei; Blaabjerg, Frede

    2015-01-01

    To address inaccurate power sharing problems in autonomous islanding microgrids, an enhanced droop control method through online virtual impedance adjustment is proposed. First, a term associated with DG reactive power, imbalance power, or harmonic power is added to the conventional real power......-frequency droop control. The transient real power variations caused by this term are captured to realize DG series virtual impedance tuning. With the regulation of DG virtual impedance at fundamental positive sequence, fundamental negative sequence, and harmonic frequencies, an accurate power sharing can...... unit local controllers. The feasibility of the proposed method is verified by simulated and experimental results from a low-power three-phase microgrid prototype....

  18. Monitoring treatment response with color and power Doppler.

    Science.gov (United States)

    Lagalla, R; Caruso, G; Finazzo, M

    1998-05-01

    Color and power Doppler are now widely used to monitor treatment response because of the latest technologic advances and of the increasing use of echo-enhancing agents. The assessment of treatment response is based on the amount of necrosis obtained and changes in local vascularization indicate a successful treatment. To date, clinical experiences have mainly concerned the treatment of hepatocellular carcinomas, hyperfunctioning nodules of the thyroid and parathyroid glands and the neoadjuvant chemotherapy of breast cancer. Aim of this review is to describe the role and potentials of color and power Doppler in this field. Hepatocellular carcinomas are currently treated with surgery or percutaneous ethanol injection and/or chemoembolization. Treatment response can be monitored with color Doppler: after a successful treatment, color signals are no longer detectable on color Doppler images. Conversely, the presence of arterial signals indicates persistent viable tumor. Unfortunately, color Doppler is limited when the hepatocellular carcinoma is hypovascular, small or deep. Echo-enhancing agents may help overcome these limitations, although spiral computed tomography or dynamic magnetic resonance imaging cannot be replaced yet in the definitive assessment of tumor necrosis. Color and power Doppler are well-established tools in the study of functioning thyroid and parathyroid adenomas after percutaneous ethanol injection. Echo-enhancing agents may improve Doppler sensitivity in the detection of residual viable tissue. Other interesting applications of color and power Doppler in this field are secondary hyperparathyroidism and hyperfunctioning thyreopathies (Graves' disease) treated with mercaptoimidazole. The evaluation of systolic flow velocity in the inferior thyroid artery is more reliable than the quantitative analysis of color signals in monitoring treatment response in Graves' disease. In our experience, systolic velocity in the inferior thyroid artery decreased

  19. An accurate autonomous islanding microgrid reactive power, imbalance power and harmonic power sharing scheme

    DEFF Research Database (Denmark)

    He, Jinwei; Li, Yun Wei; Blaabjerg, Frede

    2013-01-01

    To address inaccurate power sharing problems in autonomous islanding microgrids, an enhanced droop control method through adaptive virtual impedance adjustment is proposed. First, a term associated with DG reactive power, imbalance power or harmonic power is added to the conventional real power......-frequency droop control. The transient real power variations caused by this additional term are captured to realize DG series virtual impedance tuning. With the regulation of DG virtual impedance at fundamental positive sequence, fundamental negative sequence, and harmonic frequencies, an accurate power sharing...

  20. Voltage Harmonics Mitigation through Hybrid Active Power Filter

    Directory of Open Access Journals (Sweden)

    Anwer Ali Sahito

    2016-01-01

    Full Text Available Fast dynamic response, high efficiency, low cost and small size of power electronic converters have exponentially increased their use in modern power system which resulted in harmonically distorted voltage and currents. Voltage harmonics mainly caused by current harmonics are more dangerous as performance and expected operating life of other power system equipment are affected by harmonically distorted supply voltage. Electronic filter circuits are used to improve system power quality by mitigating adverse effects of harmonics. Hybrid filters having advantages of both passive and active filters are preferred to resolve the problem of harmonics efficiently and avoiding any chance of resonance. In this paper, a three phase three wire network is considered to supply an adjustable speed drive represented by a resistive load connected across a three phase bridge rectifier. Simulation of the considered system shows THD (Total Harmonic Distortion of 18.91 and 7.61% in supply current and voltage respectively. A HAPF (Hybrid Active Power Filter is proposed to reduce these THD values below 5% as recommended by IEEE Standard-519. P-Q theorem is used to calculate required parameters for proposed filter, which is implemented through hysteresis control. Simulation results confirm the effectiveness of the designed filter as THD for both current and voltage have reduced below allowable limit of 5%.

  1. Digital Filter Design with Harmonics Estimation for Power Supplies

    Science.gov (United States)

    Shah, P. J.; Saxena, R.; Chawla, M. P. S.

    2012-06-01

    The quality of voltage waveforms is nowadays an issue of the utmost importance for power utilities and electronic equipment. Modern frequency power converters generate a wide spectrum of harmonic components, which deteriorate the quality of the delivered energy, increase the energy losses as well as decrease their liability of a power supplies. In large converters systems not only harmonics, but also considerable interharmonics strongly deteriorate the quality of the power supply voltage. The estimation of the components parameters is very important for control and protection tasks. Digital low pass filter overcome the voltage drift, temperature drift and time drift problems and can be used for harmonic detection for better utilization in real-time. Real-time detection of harmonics can be implemented using MATLAB software and developing simulation circuit set up. With the appropriate cutoff frequency f c and nth order of filter, low pass filter and band-pass filter for real-time harmonic detection can be analyzed. In this paper the aim is to design filters using different methods including Prony analysis. The monitoring of power system harmonics an important issue in the frame of modern power system management and control can be achieved easily using digital filters.

  2. Microgrid Reactive and Harmonic Power Sharing Using Enhanced Virtual Impedance

    DEFF Research Database (Denmark)

    He, Jinwei; Wei Li, Yun; Guerrero, Josep M.

    2013-01-01

    only a line current feed-forward term is added to the DG voltage reference, the proposed virtual impedances at fundamental and harmonic frequencies are realized using DG line current and point of common coupling (PCC) voltage feed-forward terms, respectively. With this modification, the mismatched DG......To address the load sharing problem in islanding microgrids, this paper proposes an improved approach which regulates the distributed generation (DG) unit interfacing virtual impedance at fundamental and selected harmonic frequencies. In contrast to the conventional virtual impedance control where...... feeder impedances can be properly compensated, resulting in accurate reactive and harmonic power sharing at the same time. In addition, this paper shows that the microgrid PCC harmonic voltages can be mitigated by reducing the magnitude of DG unit equivalent harmonic impedance. Finally, an improved...

  3. Intramuscular blood flow quantification with power doppler ultrasonography.

    Science.gov (United States)

    Dori, Amir; Abbasi, Hiba; Zaidman, Craig M

    2016-11-01

    Quantification of blood flow to muscle using ultrasound is limited to large vessels. Small vessel intramuscular blood flow cannot be quantified using ultrasound without specialized methods or intravenous contrast. We describe a technique using power Doppler to quantify postcontraction hyperemia in intramuscular vessels that can be used at the bedside. In 11 healthy subjects, postcontraction intramuscular blood flow in the forearm flexors and tibialis anterior muscles increased with stronger and repeated contractions. Intravascular blood flow measured by pulsed Doppler in the brachial artery similarly increased. Three patients with muscular dystrophies showed a negligible increase of postcontraction intramuscular blood flow. Intramuscular blood flow can be quantified using power Doppler ultrasonography; it increases following contraction and may be reduced in patients with muscular dystrophies. This quantitative, noninvasive technique can be applied at the bedside and may facilitate studies of disease impact on intramuscular blood flow. Muscle Nerve 54: 872-878, 2016. © 2016 Wiley Periodicals, Inc.

  4. Hyperemia in plantar fasciitis determined by power Doppler ultrasound.

    Science.gov (United States)

    McMillan, Andrew M; Landorf, Karl B; Gregg, Julie M; De Luca, Jason; Cotchett, Matthew P; Menz, Hylton B

    2013-12-01

    Cross-sectional observational study. To investigate the presence of soft tissue hyperemia in plantar fasciitis with power Doppler ultrasound. Localized hyperemia is an established feature of tendinopathy, suggesting that neurovascular in-growth may contribute to tendon-associated pain in some patients. The presence of abnormal soft tissue vascularity can be assessed with Doppler ultrasound, and a positive finding can assist with targeted treatment plans. However, very little is known regarding the presence of hyperemia in plantar fasciitis and the ability of routine Doppler ultrasound to identify vascular in-growth in the plantar fascia near its proximal insertion. This observational study included 30 participants with plantar fasciitis unrelated to systemic disease and 30 age- and sex-matched controls. Ultrasound examination was performed with a 13- to 5-MHz linear transducer, and power Doppler images were assessed by 2 blinded investigators. Hyperemia of the plantar fascia was present in 8 of 30 participants with plantar fasciitis and in 2 of 30 controls. The between-group difference for hyperemia, using a 4-point scale, was statistically significant, with participants with plantar fasciitis showing increased Doppler ultrasound signal compared to controls (Mann-Whitney U, P = .03). However, the majority of participants with plantar fasciitis with evidence of hyperemia demonstrated very mild color changes, and only 3 were found to have moderate or marked hyperemia. Mild hyperemia can occur with plantar fasciitis, but most individuals will not exhibit greater soft tissue vascularity when assessed with routine Doppler ultrasound. Clinicians treating plantar fasciitis should not consider a positive Doppler signal as essential for diagnosis of the condition but, rather, as a feature that may help to refine the treatment plan for an individual patient.

  5. Harmonic Mitigation Techniques Applied to Power Distribution Networks

    Directory of Open Access Journals (Sweden)

    Hussein A. Kazem

    2013-01-01

    Full Text Available A growing number of harmonic mitigation techniques are now available including active and passive methods, and the selection of the best-suited technique for a particular case can be a complicated decision-making process. The performance of some of these techniques is largely dependent on system conditions, while others require extensive system analysis to prevent resonance problems and capacitor failure. A classification of the various available harmonic mitigation techniques is presented in this paper aimed at presenting a review of harmonic mitigation methods to researchers, designers, and engineers dealing with power distribution systems.

  6. Systematic harmonic power laws inter-relating multiple fundamental constants

    Science.gov (United States)

    Chakeres, Donald; Buckhanan, Wayne; Andrianarijaona, Vola

    2017-01-01

    Power laws and harmonic systems are ubiquitous in physics. We hypothesize that 2, π, the electron, Bohr radius, Rydberg constant, neutron, fine structure constant, Higgs boson, top quark, kaons, pions, muon, Tau, W, and Z when scaled in a common single unit are all inter-related by systematic harmonic powers laws. This implies that if the power law is known it is possible to derive a fundamental constant's scale in the absence of any direct experimental data of that constant. This is true for the case of the hydrogen constants. We created a power law search engine computer program that randomly generated possible positive or negative powers searching when the product of logical groups of constants equals 1, confirming they are physically valid. For 2, π, and the hydrogen constants the search engine found Planck's constant, Coulomb's energy law, and the kinetic energy law. The product of ratios defined by two constants each was the standard general format. The search engine found systematic resonant power laws based on partial harmonic fraction powers of the neutron for all of the constants with products near 1, within their known experimental precision, when utilized with appropriate hydrogen constants. We conclude that multiple fundamental constants are inter-related within a harmonic power law system.

  7. Harmonics and voltage stability analysis in power systems including ...

    Indian Academy of Sciences (India)

    In this study, non-sinusoidal quantities and voltage stability, both known as power quality criteria, are examined together in detail. The widespread use of power electronics elements cause the existence of significant non-sinusoidal quantities in the system. These non-sinusoidal quantities can create serious harmonic ...

  8. Predicting Harmonic Distortion of Multiple Converters in a Power System

    Directory of Open Access Journals (Sweden)

    P. M. Ivry

    2017-01-01

    Full Text Available Various uncertainties arise in the operation and management of power systems containing Renewable Energy Sources (RES that affect the systems power quality. These uncertainties may arise due to system parameter changes or design parameter choice. In this work, the impact of uncertainties on the prediction of harmonics in a power system containing multiple Voltage Source Converters (VSCs is investigated. The study focuses on the prediction of harmonic distortion level in multiple VSCs when some system or design parameters are only known within certain constraints. The Univariate Dimension Reduction (UDR method was utilized in this study as an efficient predictive tool for the level of harmonic distortion of the VSCs measured at the Point of Common Coupling (PCC to the grid. Two case studies were considered and the UDR technique was also experimentally validated. The obtained results were compared with that of the Monte Carlo Simulation (MCS results.

  9. Power Quality and Harmonic Analysis of End User Devices

    Directory of Open Access Journals (Sweden)

    Sonia Leva

    2012-12-01

    Full Text Available Among the non-linear loads used in household, Compact Fluorescent Lamps (CFLs and LED lamps are becoming more widespread, while incandescent lamps are intended to be replaced by these types of lighting devices. LEDs and CFLs are significantly more efficient and economical than incandescent lamps, and are expected to be used in 100% of residential lighting in the future. As nonlinear loads, LEDs and CFLs produce highly distorted currents. A large number of customers using LEDs or CFLs for domestic, commercial and industrial lighting could determine important Power Quality problems. The paper reports experimental measurement results regarding Power Quality in indoor lighting systems. The harmonic absorptions of several types of luminaries are analyzed, highlighting the impact behavior of different lamps function of used luminaries’ technologies. The recorded harmonic absorption allows characterizing the harmonic spectrum variability of the investigated lamps.

  10. Power system harmonics and passive filter designs

    CERN Document Server

    Das, J C

    2015-01-01

    J.C. Das is a consultant of electrical power systems at Power Systems Studies, Inc., USA. He is Life Fellow of IEEE (UK), Fellow of IET (India), and has authored approximately sixty technical papers and published 190 study reports of real-world power systems. He is the author of three books including ARC Flash Hazard Analysis and Mitigation. He is a registered P.E. in the states of Georgia and Oklahoma, C.Eng. in UK, and Eur Ing in Europe. J. C. Das is also a member of CIGRE, Federation of European Engineers, and other technical associations and organizations.

  11. Estimation and reduction of harmonic currents from power converters

    DEFF Research Database (Denmark)

    Asiminoaei, Lucian

    power supplies. Although their design takes into account a certain level of harmonic voltage distortion, there are many real-life cases when the equipments experience abnormal operation, malfunction or failure. One such case appeared at a local company in Denmark, a Heat Power Station where due...... to the existing large power Adjustable Speed Drives (ASD), a fault-trip is reported at one of the control equipments. The fault-trip does not allow the operation of the plant at a loading further than 80 % of the total designed power. This case shaped the research directions of the project, to study methods....... Such a topology, in essence a harmonic trap filter customized for ASD's installation, is investigated and analytically modelled here. Its design and performance are analyzed, which indicate a better stability compared to classical PPF's. Based on simulations it is found, that for the given Heat Power Station case...

  12. Shunt hybrid active power filter for harmonic mitigation: A practical ...

    Indian Academy of Sciences (India)

    Home; Journals; Sadhana; Volume 40; Issue 4. Shunt hybrid active power filter for harmonic mitigation: A practical design approach. Unnikrishnan A K ... This paper presents a control strategy and design criteria for transformer-less shunt HAPF with special attention to the integration of series passive filter. The paper also ...

  13. Pseudospectral Maxwell solvers for an accurate modeling of Doppler harmonic generation on plasma mirrors with particle-in-cell codes

    Science.gov (United States)

    Blaclard, G.; Vincenti, H.; Lehe, R.; Vay, J. L.

    2017-09-01

    With the advent of petawatt class lasers, the very large laser intensities attainable on target should enable the production of intense high-order Doppler harmonics from relativistic laser-plasma mirror interactions. At present, the modeling of these harmonics with particle-in-cell (PIC) codes is extremely challenging as it implies an accurate description of tens to hundreds of harmonic orders on a broad range of angles. In particular, we show here that due to the numerical dispersion of waves they induce in vacuum, standard finite difference time domain (FDTD) Maxwell solvers employed in most PIC codes can induce a spurious angular deviation of harmonic beams potentially degrading simulation results. This effect was extensively studied and a simple toy model based on the Snell-Descartes law was developed that allows us to finely predict the angular deviation of harmonics depending on the spatiotemporal resolution and the Maxwell solver used in the simulations. Our model demonstrates that the mitigation of this numerical artifact with FDTD solvers mandates very high spatiotemporal resolution preventing realistic three-dimensional (3D) simulations even on the largest computers available at the time of writing. We finally show that nondispersive pseudospectral analytical time domain solvers can considerably reduce the spatiotemporal resolution required to mitigate this spurious deviation and should enable in the near future 3D accurate modeling on supercomputers in a realistic time to solution.

  14. Three phase active power filter with selective harmonics elimination

    Directory of Open Access Journals (Sweden)

    Sozański Krzysztof

    2016-03-01

    Full Text Available This paper describes a three phase shunt active power filter with selective harmonics elimination. The control algorithm is based on a digital filter bank. The moving Discrete Fourier Transformation is used as an analysis filter bank. The correctness of the algorithm has been verified by simulation and experimental research. The paper includes exemplary results of current waveforms and their spectra from a three phase active power filter.

  15. Economical implications regarding the operation of power transformers in harmonic polluted power systems

    Directory of Open Access Journals (Sweden)

    G.V. Pop

    2009-12-01

    Full Text Available The segment of loads causing harmonic pollution of power systems is increasing due to the rising volume of electronic and power electronic components. Each nonlinear load generates periodic events (e.g. harmonics that could lead to serious problems within power system networks and its components (e.g. transformers. If transformers operate in networks where the harmonic spectra exceed a certain limit, they will additionally be heated up and losses are increased,compared to operation under normal conditions. This paper discusses different effects of harmonics on power ransformers, such as increasing power losses, reduction of efficiency, decrease of power factor and derating of transformers. An economical analysis is performed in order to determinate the life cycle cost of transformers for different rated powers.

  16. Accuracy of Gray-scale and Three-dimensional Power Doppler ...

    African Journals Online (AJOL)

    uterine serosa–bladder interface were the best 3D power Doppler parameters for the detection of difficult placental separation, considerable intraoperative ... Moodley et al. concluded that color flow Doppler was more specific in the diagnosis ... Two views of 3D power. Doppler were usually analyzed; lateral view to observe.

  17. Can Three-dimensional (3D power Doppler and uterine artery Doppler differentiate between fibroids and adenomyomas?

    Directory of Open Access Journals (Sweden)

    Eman Elkattan

    2016-03-01

    Full Text Available Purpose: To determine if the three-dimensional power Doppler and uterine arteries Doppler were able to differentiate between fibroids and adenomyomas. Methods: 123 patients who were scheduled for hysterectomy were enrolled in the study. They were evaluated by ultrasound before hysterectomy. We included only cases with either fibroids or adenomymas. For each benign myometrial mass, mass volume, 3D power Doppler vascularization index (VI, flow index (FI and vascularization flow index (VFI and uterine artery Doppler indices were measured. The results were compared with the histopathological examination. Results: No significant difference was detected between the volume of the fibroids or the adenomyomas (P = 0.896. There was significant difference in the vascular location of the power Doppler flow between fibroids and adenomyomas being more scattered in adenomyoma and more peripheral in fibroids (P < 0.00. In fibroids, higher 3D power Doppler vascular flow (VI = 2.42 ± 2.0, FI = 39.931 ± 5.8 and VFI = 1.29 ± 1.54 than adenomyomas (VI = 1.19 ± 1.04, FI = 28.33 ± 6.88, VFI = 0.89 ± 0.49. That was statistically significant (P = 0.005, 0.00, 0.004 respectively. The uterine artery Doppler indices (RI, PI showed no significant difference between fibroids and adenomyoma (P = 0.349, 0.067. Conclusion: 3D power Doppler can differentiate between fibroids and adenomyomas. The uterine arteries Doppler Can’t differentiate between fibroids and adenomyomas.

  18. Active power filters for harmonic cancellation in conventional and advanced aircraft electric power systems

    Energy Technology Data Exchange (ETDEWEB)

    Eid, A.; El-Mohandes, T. [South Valley University (Egypt); Abdel-Salam, M. [Electrical Engineering Department, Assiut University, Al-Gamaa street, Assiut 71518 (Egypt); El-Kishky, H. [University of Texas at Tyler (United States)

    2009-01-15

    Conventional and advanced civil aircraft electric power systems are simulated and controlled to be within standards regarding the voltage magnitude and frequency everywhere in the system at different loading scenarios. Harmonics in conventional and advanced aircraft power systems are calculated and reduced using a well-designed active power filter. The control circuit of the filter is based on the perfect harmonic cancellation method. The designed filter results in bringing the harmonics in both aircraft systems down to be within the standard limits of IEEE-519 and MIL-STD-704E. (author)

  19. Consensus-based Distributed Control for Accurate Reactive, Harmonic and Imbalance Power Sharing in Microgrids

    DEFF Research Database (Denmark)

    Zhou, Jianguo; Kim, Sunghyok; Zhang, Huaguang

    2017-01-01

    This paper investigates the issue of accurate reactive, harmonic and imbalance power sharing in a microgrid. Harmonic and imbalance droop controllers are developed to proportionally share the harmonic power and the imbalance power among distributed generation (DG) units and improve the voltage qu...

  20. Three-dimensional power Doppler transanal ultrasonography, to monitor haemorrhoidal blood flow after Doppler-guided ALTA sclerosing therapy.

    Science.gov (United States)

    Miyamoto, H; Asanoma, M; Miyamoto, H; Takasu, C; Shimada, M

    2013-02-01

    The study aimed to use power Doppler imaging (PDI) transanal ultrasonography to produce three-dimensional power Doppler angiography images of haemorrhoidal tissue and to monitor the effects of Doppler-guided aluminium potassium sulfate and tannic acid (DGALTA) sclerotherapy. Ninety-six haemorrhoids in 43 patients were examined using PDI transanal ultrasonography, and DGALTA sclerotherapy was performed from April 2011 to April 2012. DGALTA sclerotherapy was conducted using a four-step injection process with pulse wave Doppler ultrasound under perianal local anaesthesia. A three-dimensional power Doppler angiography image of the blood flow in haemorrhoidal tissue was produced using PDI transanal ultrasonography. The cross-sectional area of blood flow in the haemorrhoidal tissue (PDI area) significantly decreased after DGALTA sclerotherapy. The PDI areas in the preoperative state and 1 and 3 months after treatment were 0.35±0.27, 0.03±0.05 and 0.04±0.05 cm(2) (Ppower Doppler angiography image of the haemorrhoidal tissue was technically possible and showed blood flow in the haemorrhoidal tissue to be significantly decreased after DGALTA sclerotherapy. © 2012 The Authors. Colorectal Disease © 2012 The Association of Coloproctology of Great Britain and Ireland.

  1. Evaluation of harmonic detection methods for active power filter applications

    DEFF Research Database (Denmark)

    Asiminoaei, Lucian; Blaabjerg, Frede; Hansen, Steffan

    2005-01-01

    In the attempt to minimize the harmonic disturbances created by the non-linear loads the choice of the active power filters comes out to improve the filtering efficiency and to solve many issues existing with classical passive filters. One of the key points for a proper implementation of an active...... implementation issues. The conclusions are collected and a comparison is given at the end, which is useful in deciding the future hardware setup implementation. The comparison shows that the choice of numerical filtering is a key factor for obtaining good accuracies and dynamics for an active filter....... theories. Then, the work here proposes a simulation setup that decouples the harmonic reference generator from the active filter model and its controller. In this way the selected methods can be equally analyzed and compared with respect to their performance, which helps anticipating possible...

  2. Cyclic variation of Doppler power as a function of hematocrit and vessel wall compliance

    DEFF Research Database (Denmark)

    Misaridis, Athanasios; Shung, K.K.

    1998-01-01

    In order to better understand the relationship between the power of the Doppler spectrum and blood flow abnormalities, a systematic study of all factors that may affect the Doppler power is required. In the study, three important factors were investigated in vitro using a mock flow loop: a) the p...

  3. Sound Power Estimation by Laser Doppler Vibration Measurement Techniques

    Directory of Open Access Journals (Sweden)

    G.M. Revel

    1998-01-01

    Full Text Available The aim of this paper is to propose simple and quick methods for the determination of the sound power emitted by a vibrating surface, by using non-contact vibration measurement techniques. In order to calculate the acoustic power by vibration data processing, two different approaches are presented. The first is based on the method proposed in the Standard ISO/TR 7849, while the second is based on the superposition theorem. A laser-Doppler scanning vibrometer has been employed for vibration measurements. Laser techniques open up new possibilities in this field because of their high spatial resolution and their non-intrusivity. The technique has been applied here to estimate the acoustic power emitted by a loudspeaker diaphragm. Results have been compared with those from a commercial Boundary Element Method (BEM software and experimentally validated by acoustic intensity measurements. Predicted and experimental results seem to be in agreement (differences lower than 1 dB thus showing that the proposed techniques can be employed as rapid solutions for many practical and industrial applications. Uncertainty sources are addressed and their effect is discussed.

  4. Pseudo-spectral Maxwell solvers for an accurate modeling of Doppler harmonic generation on plasma mirrors with Particle-In-Cell codes

    CERN Document Server

    Blaclard, G; Lehe, R; Vay, J L

    2016-01-01

    With the advent of PW class lasers, the very large laser intensities attainable on-target should enable the production of intense high order Doppler harmonics from relativistic laser-plasma mirrors interactions. At present, the modeling of these harmonics with Particle-In-Cell (PIC) codes is extremely challenging as it implies an accurate description of tens of harmonic orders on a a broad range of angles. In particular, we show here that standard Finite Difference Time Domain (FDTD) Maxwell solvers used in most PIC codes partly fail to model Doppler harmonic generation because they induce numerical dispersion of electromagnetic waves in vacuum which is responsible for a spurious angular deviation of harmonic beams. This effect was extensively studied and a simple toy-model based on Snell-Descartes law was developed that allows us to finely predict the angular deviation of harmonics depending on the spatio-temporal resolution and the Maxwell solver used in the simulations. Our model demonstrates that the miti...

  5. Musculoskeletal colour/power Doppler in sports medicine

    DEFF Research Database (Denmark)

    Boesen, M I; Boesen, M; Langberg, Henning

    2010-01-01

    This review article discusses the aspects of sports medicine where musculoskeletal Doppler ultrasound has valuable contribution in diagnosis and/or treatment of some of the typical musculoskeletal sports injuries. Also, conditions where the Doppler ultrasound has no value are discussed. Some...

  6. FUZZY LOGIC CONTROLLER BASED ACTIVE POWER LINE CONDITIONERS FOR COMPENSATING REACTIVE POWER AND HARMONICS

    Directory of Open Access Journals (Sweden)

    Karuppanan.P

    2010-07-01

    Full Text Available This article explores a novel fuzzy logic controller (FLC based threephase shunt active power line conditioners (APLC for power quality improvements due to the non-linear loads. The fuzzy logic controller is Mamdani-type and linguistic description, so it does not necessitate a mathematical model of the system. The FLC controller is capable of controlling harmonic current and dc-side capacitor voltage of the inverter to improve the performance of the active power filter. Hysteresis current controller (HCC is used to generate the switching signals from the comparison of reference current and actual current for driving the current controlled voltage source inverter (VSI. Extensive simulation executed and tested under different non-linear load conditions. The simulation results reveal that the APLC with fuzzy logic controller is a perfect candidate for current harmonics and reactive power compensation.

  7. Harmonic Pollution Produced by Low Power Nonlinear Loads: Mathematical Model and Practical Cases

    Directory of Open Access Journals (Sweden)

    Mora–Barajas M.A.

    2010-04-01

    Full Text Available Many household electrical appliances like televisions, video recorders and computers are sources of voltage and current harmonics, which increase power losses and contaminate the AC power line. These harmonics can cause serious problems in both, utilities and electrical equipments connected to the same AC line. This paper shows a mathematical analysis of harmonics content on the electrical current for a circuit representing a non linear residential load. A comparative harmonic distortion study produced by the residential loads on the electrical power lines, measured experimentally, is also shown.

  8. Acute Effects of Lateral Thigh Foam Rolling on Arterial Tissue Perfusion Determined by Spectral Doppler and Power Doppler Ultrasound.

    Science.gov (United States)

    Hotfiel, Thilo; Swoboda, Bernd; Krinner, Sebastian; Grim, Casper; Engelhardt, Martin; Uder, Michael; Heiss, Rafael U

    2017-04-01

    Hotfiel, T, Swoboda, B, Krinner, S, Grim, C, Engelhardt, M, Uder, M, and Heiss, R. Acute effects of lateral thigh foam rolling on arterial tissue perfusion determined by spectral Doppler and power Doppler ultrasound. J Strength Cond Res 31(4): 893-900, 2017-Foam rolling has been developed as a popular intervention in training and rehabilitation. However, evidence on its effects on the cellular and physiological level is lacking. The aim of this study was to assess the effect of foam rolling on arterial blood flow of the lateral thigh. Twenty-one healthy participants (age, 25 ± 2 years; height, 177 ± 9 cm; body weight, 74 ± 9 kg) were recruited from the medical and sports faculty. Arterial tissue perfusion was determined by spectral Doppler and power Doppler ultrasound, represented as peak flow (Vmax), time average velocity maximum (TAMx), time average velocity mean (TAMn), and resistive index (RI), and with semiquantitative grading that was assessed by 4 blindfolded investigators. Measurement values were assessed under resting conditions and twice after foam rolling exercises of the lateral thigh (0 and 30 minutes after intervention). The trochanteric region, mid portion, and distal tibial insertion of the lateral thigh were representative for data analysis. Arterial blood flow of the lateral thigh increased significantly after foam rolling exercises compared with baseline (p ≤ 0.05). We detected a relative increase in Vmax of 73.6% (0 minutes) and 52.7% (30 minutes) (p Doppler scores at all portions revealed increased average grading of 1.96 after intervention and 2.04 after 30 minutes compared with 0.75 at baseline. Our results may contribute to the understanding of local physiological reactions to self-myofascial release.

  9. The effect of foot position on Power Doppler Ultrasound grading of Achilles enthesitis.

    Science.gov (United States)

    Zappia, Marcello; Cuomo, Giovanna; Martino, Maria Teresa; Reginelli, Alfonso; Brunese, Luca

    2016-06-01

    The aim of this study was to determine whether foot position could modify power Doppler grading in evaluation of the Achilles enthesis. Eighteen patients with clinical Achilles enthesitis were studied with power Doppler ultrasound (PDUS) in five different positions of the foot: active and passive dorsiflexion, neutral position, active and passive plantar flexion. The Doppler signal was graded in any position and compared with the others. The Doppler signal was higher with the foot in plantar flexion and decreased gradually, sometimes till to disappear, while increasing dorsiflexion. The Doppler signal was always less during the active keeping of the position of the joint, than during the passive. The PDUS examination of the Achilles enthesis should be performed also with the foot in passive plantar flexion, in order not to underestimate the degree of vascularization.

  10. An Enhanced Power Sharing Scheme for Voltage unbalance and harmonics compensation in an islanded AC microgrid

    DEFF Research Database (Denmark)

    Han, Yang; Shen, Pan; Zhao, Xin

    2016-01-01

    controllers, the selective virtual impedance loop, the unbalance and harmonics compensators, the secondary control for voltage amplitude and frequency restoration, and the auxiliary control to achieve a high voltage quality at the point of common coupling (PCC). By using the proposed unbalance and harmonics......In this paper, an enhanced hierarchical control structure with multiple current loop damping schemes for voltage unbalance and harmonics compensation in ac islanded microgrid is proposed to address unequal power sharing problems. The distributed generation (DG) is properly controlled...... to autonomously compensate voltage unbalance and harmonics while sharing the compensation effort for the real power, reactive power, unbalance and harmonic powers. The proposed control system of the microgrid mainly consists of the positive sequence real and reactive power droop controllers, voltage and current...

  11. Voltage Feedback based Harmonic Compensation for an Offshore Wind Power Plant

    DEFF Research Database (Denmark)

    Chaudhary, Sanjay K.; Lascu, Cristian; Teodorescu, Remus

    2016-01-01

    the harmonic distortion at the point of common coupling within the planning level limits using harmonic compensation, which is usually done by passive filters. In this paper a novel active harmonic compensation technique using voltage feedback from a non-local bus has been proposed and analyzed. Its......When an offshore wind power plant is connected to the grid, there is a risk of amplification of certain harmonics and appearance resonances at the point of connection due to the interaction between the grid network and the wind power plant network. Hence, the plant developer is obliged to maintain...

  12. Consensus-based Distributed Control for Accurate Reactive, Harmonic and Imbalance Power Sharing in Microgrids

    DEFF Research Database (Denmark)

    Zhou, Jianguo; Kim, Sunghyok; Zhang, Huaguang

    2017-01-01

    quality at the point of common coupling (PCC). Further, a distributed consensus protocol is developed to adaptively regulate the virtual impedance at fundamental frequency and selected harmonic frequencies. Additionally, a dynamic consensus based method is adopted to restore the voltage to their average......This paper investigates the issue of accurate reactive, harmonic and imbalance power sharing in a microgrid. Harmonic and imbalance droop controllers are developed to proportionally share the harmonic power and the imbalance power among distributed generation (DG) units and improve the voltage...... voltage. With the proposed methods, the microgrid system reliability and flexibility can be enhanced and the knowledge of the line impedance is not required. And the reactive, harmonic and imbalance power can be proportionally shared among the DG units. Moreover, the quality of the voltage at PCC can...

  13. Low-frequency high-definition power Doppler in visualizing and defining fetal pulmonary venous connections.

    Science.gov (United States)

    Liu, Lin; He, Yihua; Li, Zhian; Gu, Xiaoyan; Zhang, Ye; Zhang, Lianzhong

    2014-07-01

    The use of low-frequency high-definition power Doppler in assessing and defining pulmonary venous connections was investigated. Study A included 260 fetuses at gestational ages ranging from 18 to 36 weeks. Pulmonary veins were assessed by performing two-dimensional B-mode imaging, color Doppler flow imaging (CDFI), and low-frequency high-definition power Doppler. A score of 1 was assigned if one pulmonary vein was visualized, 2 if two pulmonary veins were visualized, 3 if three pulmonary veins were visualized, and 4 if four pulmonary veins were visualized. The detection rate between Exam-1 and Exam-2 (intra-observer variability) and between Exam-1 and Exam-3 (inter-observer variability) was compared. In study B, five cases with abnormal pulmonary venous connection were diagnosed and compared to their anatomical examination. In study A, there was a significant difference between CDFI and low-frequency high-definition power Doppler for the four pulmonary veins observed (P definition power Doppler was higher than that when employing two-dimensional B-mode imaging or CDFI. There was no significant difference between the intra- and inter-observer variabilities using low-frequency high-definition power Doppler display of pulmonary veins (P > 0.05). The coefficient correlation between Exam-1 and Exam-2 was 0.844, and the coefficient correlation between Exam-1 and Exam-3 was 0.821. In study B, one case of total anomalous pulmonary venous return and four cases of partial anomalous pulmonary venous return were diagnosed by low-frequency high-definition power Doppler and confirmed by autopsy. The assessment of pulmonary venous connections by low-frequency high-definition power Doppler is advantageous. Pulmonary venous anatomy can and should be monitored during fetal heart examination.

  14. Color and power Doppler combined with Fetal Intelligent Navigation Echocardiography (FINE) to evaluate the fetal heart.

    Science.gov (United States)

    Yeo, L; Romero, R

    2017-10-01

    To evaluate the performance of color and bidirectional power Doppler ultrasound combined with Fetal Intelligent Navigation Echocardiography (FINE) in examining the fetal heart. A prospective cohort study was conducted of fetuses in the second and third trimesters with a normal heart or with congenital heart disease (CHD). One or more spatiotemporal image correlation (STIC) volume datasets, combined with color or bidirectional power Doppler (S-flow) imaging, were acquired in the apical four-chamber view. Each successfully obtained STIC volume was evaluated by STICLoop™ to determine its appropriateness before applying the FINE method. Visualization rates for standard fetal echocardiography views using diagnostic planes and/or Virtual Intelligent Sonographer Assistance (VIS-Assistance®) were calculated for grayscale (removal of Doppler signal), color Doppler and S-flow Doppler. In four cases with CHD (one case each of tetralogy of Fallot, hypoplastic left heart and coarctation of the aorta, interrupted inferior vena cava with azygos vein continuation and asplenia, and coarctation of the aorta with tricuspid regurgitation and hydrops), the diagnostic potential of this new technology was presented. A total of 169 STIC volume datasets of the normal fetal heart (color Doppler, n = 78; S-flow Doppler, n = 91) were obtained from 37 patients. Only a single STIC volume of color Doppler and/or a single volume of S-flow Doppler per patient were analyzed using FINE. Therefore, 60 STIC volumes (color Doppler, n = 27; S-flow Doppler, n = 33) comprised the final study group. Median gestational age at sonographic examination was 23 (interquartile range, 21-27.5) weeks. Color Doppler FINE generated nine fetal echocardiography views (grayscale) using (1) diagnostic planes in 73-100% of cases, (2) VIS-Assistance in 100% of cases, and (3) a combination of diagnostic planes and/or VIS-Assistance in 100% of cases. The rate of generating successfully eight fetal echocardiography views

  15. Active harmonic filtering using current-controlled, grid-connected DG units with closed-loop power control

    DEFF Research Database (Denmark)

    He, Jinwei; Li, Yun Wei; Blaabjerg, Frede

    2014-01-01

    The increasing application of nonlinear loads may cause distribution system power quality issues. In order to utilize distributed generation (DG) unit interfacing converters to actively compensate harmonics, this paper proposes an enhanced current control approach, which seamlessly integrates...... system harmonic mitigation capabilities with the primary DG power generation function. As the proposed current controller has two well-decoupled control branches to independently control fundamental and harmonic DG currents, local nonlinear load harmonic current detection and distribution system harmonic...

  16. The impact of harmonic distortion on power transformers operating near the thermal limit

    OpenAIRE

    2009-01-01

    M.Ing. The study looks into the impact of harmonic distortion on power-plant equipment in general, and then focuses on the impact it has on power transformers operating near the thermal limit. The feasibility of the study is firstly evaluated and then the theory on harmonics and transformer losses is analysed. The study had been narrowed down to power transformers due to the high numbers of failures nationally and internationally attributed to unknown causes. A transformer model is then de...

  17. A Novel Multimode Waveguide Coupler for Accurate Power Measurement of Traveling Wave Tube Harmonic Frequencies

    Science.gov (United States)

    Wintucky, Edwin G.; Simons, Rainee N.

    2014-01-01

    This paper presents the design, fabrication and test results for a novel waveguide multimode directional coupler (MDC). The coupler fabricated from two dissimilar waveguides is capable of isolating the power at the second harmonic frequency from the fundamental power at the output port of a traveling-wave tube (TWT). In addition to accurate power measurements at harmonic frequencies, a potential application of the MDC is in the design of a beacon source for atmospheric propagation studies at millimeter-wave frequencies.

  18. New hybrid active power filter for harmonic current suppression and reactive power compensation

    Science.gov (United States)

    Biricik, Samet; Cemal Ozerdem, Ozgur; Redif, Soydan; Sezai Dincer, Mustafa

    2016-08-01

    In the case of undistorted and balanced grid voltages, low ratio shunt active power filters (APFs) can give unity power factors and achieve current harmonic cancellation. However, this is not possible when source voltages are distorted and unbalanced. In this study, the cost-effective hybrid active power filter (HAPF) topology for satisfying the requirements of harmonic current suppression and non-active power compensation for industry is presented. An effective strategy is developed to observe the effect of the placement of power capacitors and LC filters with the shunt APF. A new method for alleviating the negative effects of a nonideal grid voltage is proposed that uses a self-tuning filter algorithm with instantaneous reactive power theory. The real-time control of the studied system was achieved with a field-programmable gate array (FPGA) architecture, which was developed using the OPAL-RT system. The performance result of the proposed HAPF system is tested and presented under nonideal supply voltage conditions.

  19. Harmonic Active Filtering and Impedance-based Stability Analysis in Offshore Wind Power Plants

    DEFF Research Database (Denmark)

    Dhua, Debasish; Yang, Guangya; Zhang, Zhe

    2017-01-01

    installation and provides effectively similar functionality as passive filters. This work is focused on harmonic propagation studies in wind power plants, power quality evaluation at the point of connection and harmonic mitigation by active filtering. Finally, an impedance-based stability analysis......Nowadays, to eliminate harmonics injected by the wind turbines in offshore wind power plants there is a need to install passive filters. Moreover, the passive filters are not adaptive to harmonic profile changes due to topology changes, grid loading etc. Therefore, active filters in wind turbines...... are proposed as a flexible harmonic mitigation measure. The motivation of this study is to explore the possibility of embedding active filtering in wind turbine grid-side converters without having to change the system electrical infrastructure. The active filtering method can prevent additional equipment...

  20. A harmonic cancellation technique for an ultrasound transducer excited by a switched-mode power converter.

    Science.gov (United States)

    Tang, Sai Chun; Clement, Gregory T

    2008-02-01

    The aim of this study is to evaluate the feasibility of using harmonic cancellation for a therapeutic ultrasound transducer excited by a switched-mode power converter without an additional output filter. A switching waveform without the third harmonic was created by cascading two switched-mode power inverter modules at which their output waveforms were pi/3 phase shifted from each other. A PSPICE simulation model for the power converter output stage was developed. The simulated results were in good agreement with the measurement. The waveform and harmonic contents of the acoustic pressure generated by a 1-MHz, self-focused piezoelectric transducer with and without harmonic cancellation have been evaluated. Measured results indicated that the acoustic third harmonicto- fundamental ratio at the focus was small (-48 dB) with harmonic cancellation, compared to that without harmonic cancellation (-20 dB). The measured acoustic levels of the fifth harmonic for both cases with and without harmonic cancellation also were small (-46 dB) compared to the fundamental. This study shows that it is viable to drive a piezoelectric ultrasound transducer using a switched-mode power converter without the requirement of an additional output filter in many high-intensity focused ultrasound (HIFU) applications.

  1. Reactive Power Sharing and Voltage Harmonic Distortion Compensation of Droop Controlled Single Phase Islanded Microgrids

    DEFF Research Database (Denmark)

    Micallef, Alexander; Apap, Maurice; Spiteri-Staines, Cyril

    2014-01-01

    and reduction of the voltage harmonic distortion at the point of common coupling (PCC). Experimental results were then presented to show the suitability of the proposed algorithms in achieving reactive power sharing and in improving the voltage harmonic distortion at the PCC....

  2. A Portable Low-Power Harmonic Radar System and Conformal Tag for Insect Tracking

    Science.gov (United States)

    Harmonic radar systems provide an effective modality for tracking insect behavior. This paper presents a harmonic radar system proposed to track the migration of the Emerald Ash Borer (EAB). The system offers a unique combination of portability, low power and small tag design. It is comprised of a...

  3. Extended Gersgorin Theorem-Based Parameter Feasible Domain to Prevent Harmonic Resonance in Power Grid

    Directory of Open Access Journals (Sweden)

    Tao Lin

    2017-10-01

    Full Text Available Harmonic resonance may cause abnormal operation and even damage of power facilities, further threatening normal and safe operation of power systems. For renewable energy generations, controlled loads and parallel reactive power compensating equipment, their operating statuses can vary frequently. Therefore, the parameters of equivalent fundamental and harmonic admittance/impedance of these components exist in uncertainty, which will change the elements and eigenvalues of harmonic network admittance matrix. Consequently, harmonic resonance in power grid is becoming increasingly more complex. Hence, intense research about prevention and suppression of harmonic resonance, particularly the parameter feasible domain (PFD which can keep away from harmonic resonance, are needed. For rapid online evaluation of PFD, a novel method without time-consuming pointwise precise eigenvalue computations is proposed. By analyzing the singularity of harmonic network admittance matrix, the explicit sufficient condition that the matrix elements should meet to prevent harmonic resonance is derived by the extended Gersgorin theorem. Further, via the non-uniqueness of similar transformation matrix (STM, a strategy to determine the appropriate STM is proposed to minimize the conservation of the obtained PFD. Eventually, the availability and advantages in computation efficiency and conservation of the method, are demonstrated through four different scale benchmarks.

  4. Harmonic Stability Analysis of Inverter-Fed Power Systems Using Component Connection Method

    DEFF Research Database (Denmark)

    Wang, Yanbo; Wang, Xiongfei; Blaabjerg, Frede

    2016-01-01

    This paper presents a Component Connection Method (CCM)-based harmonic stability analysis for ac power-electronic-fed power systems. In the approach, the system is partitioned as individual components, including the controllers of DG units, LC filters, network impedances, and power loads...... is formulated. And the harmonic stability is assessed based on eigenvalue traces of the composite model. Simulations and experimental results are given to validate the effectiveness of the analysis method, which can be employed to assess the system harmonic stability for any combinations of system parameters...

  5. Detailed Equivalent VSC-HVDC Modelling for Time Domain Harmonic Stability Studies in Wind Power Plants

    DEFF Research Database (Denmark)

    Glasdam, Jakob Bærholm; Bak, Claus Leth; Kocewiak, Lukasz Hubert

    2017-01-01

    system with 201 voltage levels, without loss of accuracy compared to conventional modelling of the converter. Harmonic stability is a core concern for both existing and future offshore wind power plants (OWPPs). A harmonic stability study will be undertaken with focus on the number of wind turbine...... generators in service, as this is known to influence the harmonic stability in OWPPs. The paper demonstrates the necessity of the inclusion of a detailed equivalent model of the HVDC converter for harmonic stability studies in the time domain. By implementation of active filtering in the converters...

  6. The impacts of piezoelectric element's defects on color and power doppler images

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kyung Sung [Dept. of Radiotechnology, Cheju Halla University, Cheju (Korea, Republic of)

    2015-12-15

    An ultrasound probe has a big impact on Doppler images even though it has very high risk of frequent function-breakdowns occurring in medical ultrasound scanners. This study experimentally analyses the impacts of an ultrasonic probe’s defected elements on power and color Doppler images. The results show that, the bigger the size of defected probe elements is, and the closer a group of action elements is to the center, the more the brightness of images and the velocity of Doppler diminish. When elements’ defects increase in color and power Doppler images, false images are formed to be mistaken for blood-vessel plaque in neighboring regions. Accordingly, whenever element defects are suspected, we need check-up process in B-mode. From this respective, it is advisable to have primary interest in a probe and carry out continuous probe QA for ultrasonography.

  7. Power Doppler US patterns of vascularity and spectral Doppler US parameters in predicting malignancy in thyroid nodules

    Energy Technology Data Exchange (ETDEWEB)

    Tamsel, S. [Departments of Radiology, Ege University School of Medicine, Bornova, Izmir (Turkey)]. E-mail: sadiktamsel@yahoo.com; Demirpolat, G. [Departments of Radiology, Ege University School of Medicine, Bornova, Izmir (Turkey); Erdogan, M. [Endocrinology, Ege University School of Medicine, Bornova, Izmir (Turkey); Nart, D. [Pathology, Ege University School of Medicine, Bornova, Izmir (Turkey); Karadeniz, M. [Endocrinology, Ege University School of Medicine, Bornova, Izmir (Turkey); Uluer, H. [Biostatistics, Ege University School of Medicine, Bornova, Izmir (Turkey); Ozgen, A.G. [Endocrinology, Ege University School of Medicine, Bornova, Izmir (Turkey)

    2007-03-15

    Aim: The purpose of this study was to determine whether spectral Doppler ultrasound (US) parameters, including resistive index (RI) and maximal systolic velocity (MSV), or vascular pattern can be used to distinguish malignant from benign thyroid nodules. Materials and methods: We prospectively examined 169 thyroid nodules in 134 patients undergoing sonographically guided fine-needle aspiration biopsy (FNAB). Vascularity as determined by power Doppler US imaging was defined as absent, perinodular alone, or intranodular. For each nodule, the RI and MSV values were recorded as the average of the recordings obtained. Results of the FNAB and surgical pathological examination, if available, were used as a proof of final diagnosis to categorize all nodules as benign or malignant. Results: Seven nodules were excluded from study because of non-diagnostic FNAB results due to hypocellular or insufficient cytological material. Of the remaining nodules, nine were malignant (all confirmed at surgery) and 153 were benign. Of the 145 nodules with intranodular vascularity, nine (6.2%) were malignant and the remaining 136 (93.8%) were benign. The malignant nodules had a mean RI of 0.60 on intranodular and 0.58 on perinodular arteries. These values were not significantly higher than those associated with benign nodules (RI = 0.57 and RI = 0.56, respectively). Malignant nodules had a mean MSV of 20.4 cm/s on intranodular and 35.3 cm/s on perinodular arteries that were also not significantly different from those associated with benign nodules (p > 0.05). Conclusion: The results of this study indicate that Doppler US characteristics including vascular pattern, RI and MSV are not useful parameters for distinguishing malignant from benign thyroid nodules. Therefore, Doppler US characteristics including vascular pattern, RI and MSV values of thyroid nodules can not be used as a diagnostic method to determine which nodules should undergo FNAB.

  8. Power Doppler flow mapping and four-dimensional ultrasound for evaluating tubal patency compared with laparoscopy.

    Science.gov (United States)

    Soliman, Amr A; Shaalan, Waleed; Abdel-Dayem, Tamer; Awad, Elsayed Elbadawy; Elkassar, Yasser; Lüdders, Dörte; Malik, Eduard; Sallam, Hassan N

    2015-12-01

    To study the accuracy of four-dimensional (4D) ultrasound and power Doppler flow mapping in detecting tubal patency in women with sub-/infertility, and compare it with laparoscopy and chromopertubation. A prospective study. The study was performed in the outpatient clinic and infertility unit of a university hospital. The sonographic team and laparoscopic team were blinded to the results of each other. Women aged younger than 43 years seeking medical advice due to primary or secondary infertility and who planned to have a diagnostic laparoscopy performed, were recruited to the study after signing an informed consent. All of the recruited patients had power Doppler flow mapping and 4D hysterosalpingo-sonography by injecting sterile saline into the fallopian tubes 1 day before surgery. Registering Doppler signals, while using power Doppler, both at the tubal ostia and fimbrial end and the ability to demonstrate the course of the tube especially the isthmus and fimbrial end, while using 4D mode, was considered a patent tube. Out of 50 recruited patients, 33 women had bilateral patent tubes and five had unilateral patent tubes as shown by chromopertubation during diagnostic laparoscopy. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy for two-dimensional power Doppler hysterosalpingography were 94.4%, 100%, 100%, 89.2%, and 96.2%, respectively and for 4D ultrasound were 70.4%, 100%, 100%, 70.4%, and 82.6%, respectively. Four-dimensional saline hysterosalpingography has acceptable accuracy in detecting tubal patency, but is surpassed by power Doppler saline hysterosalpingography. Power Doppler saline hysterosalpingography could be incorporated into the routine sub-/infertility workup. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  9. Harmonic Resonance Damping with a Hybrid Compensation System in Power Systems with Dispersed Generation

    DEFF Research Database (Denmark)

    Chen, Zhe; Pedersen, John Kim; Blaabjerg, Frede

    2004-01-01

    A hybrid compensation system consisting of an active filter and a group of distributed passive filters has been studied previously. The passive filters are used for each distorting load or Dispersed Generation (DG) unit to remove major harmonics and provide reactive power compensation. The active...... filter is connected in parallel with the distributed passive filters and loads/DGs to correct the system unbalance and remove the remaining harmonic components. The effectiveness of the presented compensation system has also been demonstrated. This paper studies the performance of the hybrid compensation...... system under system harmonic resonance. The harmonic resonance and the characteristics of harmonic sources are briefly described. The damping effects of the active filter in the hybrid filter system are analyzed with a simplified circuit. An example system including various power electronic interfaces...

  10. Current Harmonics Compensation in Microgrids Exploiting the Power Electronics Interfaces of Renewable Energy Sources

    Directory of Open Access Journals (Sweden)

    Ioannis Bouloumpasis

    2015-03-01

    Full Text Available This work presents a method of current harmonic reduction in a distorted distribution system. In order to evaluate the proposed method a grid with high-order current harmonics is assumed. The reduction of current distortion is feasible due to the pulse modulation of an active filter, which consists of a buck-boost converter connected back-to-back to a polarity swapping inverter. For a practical application, this system would be the power electronic interface of a Renewable Energy Source (RES and therefore it changes a source of harmonics to a damping harmonics system. Using the proposed method, the current Total Harmonic Distortion (THD of the grid is reduced below the acceptable limits and thus the general power quality of the system is improved. Simulations in the MATLAB/SIMULINK platform and experiments have been performed in order to verify the effectiveness of the proposed method.

  11. Site Selection Strategy of Single-Frequency Tuned R-APF for Background Harmonic Voltage Damping in Power Systems

    DEFF Research Database (Denmark)

    Sun, Xiaofeng; Zeng, Jian; Chen, Zhe

    2013-01-01

    Series resonance between capacitance and line inductance may magnify background harmonic voltage and worsen the harmonic voltage distortion in power systems. To solve this problem, in this paper, the transmission line theory is used to set up the distributed parameter model of power system feeders......, and analyze the harmonic voltage propagation caused by the background harmonic voltage in power systems. Then, a new strategy is proposed for the site selection of resistive active power filter to damp the background harmonic voltage in power systems. Experiments have been performed to verify the theoretical...

  12. Higher-order power harmonics of pulsed electrical stimulation modulates corticospinal contribution of peripheral nerve stimulation.

    Science.gov (United States)

    Chen, Chiun-Fan; Bikson, Marom; Chou, Li-Wei; Shan, Chunlei; Khadka, Niranjan; Chen, Wen-Shiang; Fregni, Felipe

    2017-03-03

    It is well established that electrical-stimulation frequency is crucial to determining the scale of induced neuromodulation, particularly when attempting to modulate corticospinal excitability. However, the modulatory effects of stimulation frequency are not only determined by its absolute value but also by other parameters such as power at harmonics. The stimulus pulse shape further influences parameters such as excitation threshold and fiber selectivity. The explicit role of the power in these harmonics in determining the outcome of stimulation has not previously been analyzed. In this study, we adopted an animal model of peripheral electrical stimulation that includes an amplitude-adapted pulse train which induces force enhancements with a corticospinal contribution. We report that the electrical-stimulation-induced force enhancements were correlated with the amplitude of stimulation power harmonics during the amplitude-adapted pulse train. In an exploratory analysis, different levels of correlation were observed between force enhancement and power harmonics of 20-80 Hz (r = 0.4247, p = 0.0243), 100-180 Hz (r = 0.5894, p = 0.0001), 200-280 Hz (r = 0.7002, p power harmonics. This is a pilot, but important first demonstration that power at high order harmonics in the frequency spectrum of electrical stimulation pulses may contribute to neuromodulation, thus warrant explicit attention in therapy design and analysis.

  13. Coherent flow power Doppler (CFPD): flow detection using spatial coherence beamforming.

    Science.gov (United States)

    Li, You Leo; Dahl, Jeremy J

    2015-06-01

    Power Doppler imaging is a widely used method of flow detection for tissue perfusion monitoring, inflammatory hyperemia detection, deep vein thrombosis diagnosis, and other clinical applications. However, thermal noise and clutter limit its sensitivity and ability to detect slow flow. In addition, large ensembles are required to obtain sufficient sensitivity, which limits frame rate and yields flash artifacts during moderate tissue motion. We propose an alternative method of flow detection using the spatial coherence of backscattered ultrasound echoes. The method enhances slow flow detection and frame rate, while maintaining or improving the signal quality of conventional power Doppler techniques. The feasibility of this method is demonstrated with simulations, flow-phantom experiments, and an in vivo human thyroid study. In comparison with conventional power Doppler imaging, the proposed method can produce Doppler images with 15- to 30-dB SNR improvement. Therefore, the method is able to detect flow with velocities approximately 50% lower than conventional power Doppler, or improve the frame rate by a factor of 3 with comparable image quality. The results show promise for clinical applications of the method.

  14. Harmonic Mitigation Methods in Large Offshore Wind Power Plants

    DEFF Research Database (Denmark)

    Kocewiak, Łukasz Hubert; Chaudhary, Sanjay; Hesselbæk, Bo

    2013-01-01

    and remedial harmonic mitigation methods in terms of passive and active filtering are described. It is shown that WPP components such as long HVAC cables and park transformers can introduce significant low-frequency resonances which can affect wind turbine control system operation and overall WPP stability...

  15. [Power Doppler e mezzi di contrasto nello studio della membrana sinoviale reumatoide].

    Science.gov (United States)

    Carotti, M; Filippucci, E; Salaffi, F

    2002-01-01

    Pannus formation is a fundamental event in the pathogenesis of rheumatoid arthritis and its hypervascularisation seems to be crucial to the development of joint damage. High-resolution greyscale ultrasonography is a safe, quick, and inexpensive imaging tool that allows an accurate detection of even minimal morphostructural changes in patients with rheumatoid arthritis, including joint effusion, thickening of synovial membrane and bone erosions. More recently, power Doppler sonography has proved to be a reliable tool for semiquantitative assessment of the vascularity of the synovial tissue. The contrast-enhanced power Doppler sonography seems to be a helpful adjunct in assessing synovitis and the therapeutic response to the different therapies in patients with rheumatoid arthritis. The aim of this radiological vignette was to show a representative example of use of power Doppler sonography with contrast agent in assessing rheumatoid synovitis.

  16. Harmonic Stability and Resonance Analysis in Large PMSG-Based Wind Power Plants

    DEFF Research Database (Denmark)

    Ebrahimzadeh, Esmaeil; Blaabjerg, Frede; Wang, Xiongfei

    2017-01-01

    system and the resonance frequencies are identified based on the element amplitudes of the MIMO matrix. An active damping controller is used to set the poles of the WPP in a desired location in order to mitigate the harmonic instability problems. Multiple case studies are provided to depict that Wind......Compared to the conventional power systems, large Wind Power Plants (WPPs) present a more challenging system where the interactions between the passive elements and the wideband control systems of power converters may result in harmonic instability and new resonance frequencies. Most of researches...... about harmonic stability focus on small-scale systems, and it has not pay much attention yet to identify the mentioned resonance frequencies. This paper models and analyzes the harmonic instability and resonance frequencies in large Permanent Magnet Synchronous Generator (PMSG) based WPPs with full...

  17. An Enhanced Instantaneous Circulating Current Control for Reactive power and Harmonic Load Sharing in Islanded Microgrids

    DEFF Research Database (Denmark)

    Lorzadeh, Iman; Askarian Abyaneh, Hossein; Savaghebi, Mehdi

    2017-01-01

    To address inaccurate load demand sharing problems among parallel inverter-interfaced voltage-controlled distributed generation (DG) units in islanded microgrids with different DG power ratings and mismatched feeder impedances, an enhanced voltage control scheme based on actively compensation...... branches, the reactive power and harmonic currents can be independently shared without having remarkable effects on the amplitude and quality of the DGs voltage, even if nonlinear (harmonic) loads are directly connected at the output terminal of units. In addition, the accurate load sharing can also...... of circulating voltage drops is proposed in this paper. Using proposed strategy, reactive power and harmonic currents sharing are shared accurately and proportionally without knowledge of feeder impedances. As the proposed local controller consists of two well-separated fundamental and harmonic voltage control...

  18. Harmonic incursion at the point of common coupling due to small grid-connected power stations

    Directory of Open Access Journals (Sweden)

    Majid Mumtaz

    2015-12-01

    Full Text Available The orthodox electric power distribution systems used to be generally radial and direction of flow of power was often from grid towards consumer. Sometimes, the transmission of power generated from newly set small power stations by using transmission network is not feasible due to the transmission losses, service cost on transmission lines and other related issues. That is why, in many cases, small power stations are connected directly to the local distribution network. These small power stations inject active and reactive power to the existing network, badly disturbing the flow of power hence injecting harmonics in the system at the point of common coupling (PCC. This harmonic injection at PCC due to a direct grid-connection of small power stations to the existing large electric power systems is identified. Also, the impact of harmonic incursion by these small generation units is analysed using a straightforward and an effortless method. This simulation based method uses power system components simplified to basic inductive and capacitive elements and can be very helpful for a fast assessment of harmonic incursion at PCC if extended to the practical large inter-connected electric power systems.

  19. Design Practices in Harmonic Analysis Studies Applied to Industrial Electrical Power Systems

    Directory of Open Access Journals (Sweden)

    S. F. Mekhamer

    2013-08-01

    Full Text Available Power system harmonics may cause several problems, such as malfunctions of electrical equipment, premature equipment failures and plant shutdowns. Accordingly, mitigation of these harmonics is considered an important target especially for industrial applications where any short downtime period may lead to great economic losses. Harmonic analysis studies are necessary to analyze the current and voltage harmonic levels and check if these levels comply with the contractual or international standard limits. If the studies reveal that the preset limits are exceeded, then a suitable harmonic mitigation technique should be installed. Harmonic analysis studies in the industrial electrical systems are discussed in many references. However, a comprehensive procedure for the steps required to perform a harmonic study is rarely found in the literature even though it is strongly needed for design engineers. This paper provides a comprehensive procedure for the steps required to perform a harmonic study in the form of a flowchart, based on industrial research and experience. Hence, this paper may be considered as a helpful guide for design engineers and consultants of the industrial sector.

  20. Remote Electromagnetic Vibration of Steerable Needles for Imaging in Power Doppler Ultrasound

    Science.gov (United States)

    Cabreros, Sarah S.; Jimenez, Nina M.; Greer, Joseph D.; Adebar, Troy K.; Okamura, Allison M.

    2015-01-01

    Robotic needle steering systems for minimally invasive medical procedures require complementary medical imaging systems to track the needles in real time. Ultrasound is a promising imaging modality because it offers relatively low-cost, real-time imaging of the needle. Previous methods applied vibration to the base of the needle using a voice coil actuator, in order to make the needle visible in power Doppler ultrasound. We propose a new method for needle tip vibration, using electromagnetic actuation of small permanent magnets placed inside the needle to improve needle tip visibility in power Doppler imaging. Robotic needle insertion experiments using artificial tissue and ex vivo porcine liver showed that the electromagnetic tip vibration method can generate a stronger Doppler response compared to the previous base vibration method, resulting in better imaging at greater needle depth in tissue. It also eliminates previous issues with vibration damping along the shaft of the needle. PMID:26413379

  1. Control Algorithms of Shunt Active Power Filter for Harmonics Mitigation: A Review

    Directory of Open Access Journals (Sweden)

    Yap Hoon

    2017-12-01

    Full Text Available Current harmonics is one of the most significant power quality issues which has attracted tremendous research interest. Shunt active power filter (SAPF is the best solution to minimize harmonic contamination, but its effectiveness is strictly dependent on how quickly and accurately its control algorithms can perform. This manuscript reviews various types of existing control algorithms which have been employed for controlling operation of SAPF. Harmonic extraction, DC-link capacitor voltage regulation, current control and synchronizer algorithms are examined and discussed. The most relevant techniques which have been applied for each control algorithm are described and contrasted in an organized manner to identify their respective strengths and weaknesses. It is found that the applied control algorithms differ in two conditions: (1 the condition where harmonic current distortion is treated by the SAPF in the presence of non-ideal source voltage; and (2 the condition where multilevel inverter is employed as the circuit topology of SAPF.

  2. Active power filter for harmonic compensation using a digital dual-mode-structure repetitive control approach

    DEFF Research Database (Denmark)

    Zou, Zhixiang; Wang, Zheng; Cheng, Ming

    2012-01-01

    This paper presents an digital dual-mode-structure repetitive control approach for the single-phase shunt active power filter (APF), which aims to enhance the tracking ability and eliminate arbitrary order harmonic. The proposed repetitive control scheme blends the characteristics of both odd......-harmonic repetitive control and even-harmonic repetitive control. Moreover, the convergence rate is faster than conventional repetitive controller. Additionally, the parameters have been designed and optimized for the dual-mode structure repetitive control to improve the performance of APF system. Experimental...... results on a laboratory setup are given to verify the proposed control scheme....

  3. Frequency Domain Modeling and Simulation of DC Power Electronic Systems Using Harmonic State Space Method

    DEFF Research Database (Denmark)

    Kwon, Jun Bum; Wang, Xiongfei; Blaabjerg, Frede

    2017-01-01

    . Through this method, the required computation time and CPU memory can be reduced, where this faster simulation can be an advantage of a large network simulation. Besides, the achieved results show the same results as the non-linear time-domain simulation. Furthermore, the HSS modeling can describe how...... with different switching frequency or harmonics from ac-dc converters makes that harmonics and frequency coupling are both problems of ac system and challenges of dc system. This paper presents a modeling and simulation method for a large dc power electronic system by using Harmonic State Space (HSS) modeling...

  4. Eigenvalue-based harmonic stability analysis method in inverter-fed power systems

    DEFF Research Database (Denmark)

    Wang, Yanbo; Wang, Xiongfei; Blaabjerg, Frede

    2015-01-01

    This paper presents an eigenvalue-based harmonic stability analysis method for inverter-fed power systems. A full-order small-signal model for a droop-controlled Distributed Generation (DG) inverter is built first, including the time delay of digital control system, inner current and voltage...... resonance and instability in the power system. Eigenvalues associated with time delay of inverter and inner controller parameters is obtained, which shows the time delay has an important effect on harmonic instability of inverter-fed power systems. Simulation results are given for validating the proposed...... control loops, and outer droop-based power control loop. Based on the inverter model, an overall small-signal model of a two-inverter-fed system is then established, and the eigenvalue-based stability analysis is subsequently performed to assess the influence of controller parameters on the harmonic...

  5. Shunt hybrid active power filter for harmonic mitigation: A practical ...

    Indian Academy of Sciences (India)

    Abstract. The increasing importance of Power Quality problems has been respon- sible for several improvements in Active Power Filter (APF) typologies in the last decade. The increased cost and switching losses make a pure shunt APF economi- cally impractical for high power applications. In higher power levels shunt ...

  6. Characteristics of Three-Dimensional Power Doppler in Gestational Trophoblastic Disease

    Directory of Open Access Journals (Sweden)

    Wei Wang

    2015-01-01

    Full Text Available Purpose. In the present study, the three-dimensional power Doppler was used as a quantitative method to evaluate its reliability in detecting and assessing of gestational trophoblastic disease (GTD. Methods. 52 GTD patients who received diagnosis and treatment at the first affiliated hospitals of Xi’an Jiaotong University in China between 2011 and 2013 were evaluated using Voluson E8 (GE Medical System. Demographic information, pathological characteristics, clinical history, sonographic images, and related indices (resistance index, vascularization index, and flow and vascularization index were evaluated. Result. Three-dimension power Doppler indicated that there were significant differences in the resistance index, vascularization index, flow index, and vascularization-flow index between the healthy individuals and each subgroup of patients (P<0.01. Further, in combining invasive hydatidiform mole and choriocarcinoma groups, there was a significant difference between hydatidiform mole and the combined malignant group (P<0.01. And the abnormal sonographic and power Doppler findings in GTD were resolved when chemotherapy was done successfully. Conclusion. Combined with the clinical features, sonography and three-dimension power Doppler imaging were helpful in diagnosing GTD as a noninvasive method, distinguishing the invasive nature of disease, detecting the recurrence of the disease, and assessing the effectiveness of the chemotherapy.

  7. Contrast-enhanced power Doppler ultrasonography of the metacarpophalangeal joints in rheumatoid arthritis

    DEFF Research Database (Denmark)

    Szkudlarek, Marcin; Court-Payen, Michel; Strandberg, Charlotte

    2003-01-01

    The aim of this study was to examine, with dynamic contrast-enhanced MRI as the reference, if contrast-enhanced power Doppler ultrasonography (CE PDUS) of rheumatoid arthritis (RA) metacarpophalangeal (MCP) joints provides additional information for evaluation of synovial inflammation compared...

  8. Accuracy of Gray‑scale and Three‑dimensional Power Doppler ...

    African Journals Online (AJOL)

    Background: Morbidly adherent placenta (MAP) is usually associated with excess blood loss, bladder injuries, and hysterectomies. Aim: This study was designed to evaluate the accuracy of grayscale and three-dimensional (3D) power Doppler ultrasound parameters in the diagnosis of MAP. Subjects and Methods: Fifty ...

  9. Analysis of harmonics in the power supply networks of electric welding equipment of alternating voltage

    Directory of Open Access Journals (Sweden)

    Василь Ількович Гудим

    2015-11-01

    Full Text Available Electric arc welding is widely used in construction and engineering for rigid connections of metal elements. Substantial nonlinearity of dynamic voltage-current characteristics of electric arcs in such equipment is a source of distortion in current and voltage sinusoids at the points of other electric receivers parallel joints. The voltage fluctuations from the nominal value result in changing luminous flux of bulbs, while current higher harmonics result in additional losses in electric motors. However, the problem of electric welding equipment influence on power lines wasn’t paid proper attention to. Therefore, this work is to research electric arc equipment influence on power lines in order to find out the values and the spectrum of higher harmonics, and the prevailing amplitudes dynamics of change. In this paper the results of experimental researches of harmonics spectrum in electrical circuits of electric arc welding machine of alternating voltage that it generates during the technological process and the main energy parameters, that influence negatively on the power supply networks of 0,4/0,23 kV. Analyzing the results of the measurements we come to the conclusion that if the load factor is about 35% the power coefficient of the welding machine is 0,46, that is rather low. Such a result is economically disadvantageous since high reactive power results in a significant increase of active power losses in the elements of power supply. That’s why reactive power compensation as well as higher harmonics filtration are necessitated

  10. Photovoltaic power converter system with a controller configured to actively compensate load harmonics

    Science.gov (United States)

    de Rooij, Michael Andrew; Steigerwald, Robert Louis; Delgado, Eladio Clemente

    2008-12-16

    Photovoltaic power converter system including a controller configured to reduce load harmonics is provided. The system comprises a photovoltaic array and an inverter electrically coupled to the array to generate an output current for energizing a load connected to the inverter and to a mains grid supply voltage. The system further comprises a controller including a first circuit coupled to receive a load current to measure a harmonic current in the load current. The controller includes a second circuit to generate a fundamental reference drawn by the load. The controller further includes a third circuit for combining the measured harmonic current and the fundamental reference to generate a command output signal for generating the output current for energizing the load connected to the inverter. The photovoltaic system may be configured to compensate harmonic currents that may be drawn by the load.

  11. Concept for power scaling second harmonic generation using a cascade of nonlinear crystals

    DEFF Research Database (Denmark)

    Hansen, Anders Kragh; Tawfieq, Mahmoud; Jensen, Ole Bjarlin

    2015-01-01

    Within the field of high-power second harmonic generation (SHG), power scaling is often hindered by adverse crystal effects such as thermal dephasing arising from the second harmonic (SH) light, which imposes limits on the power that can be generated in many crystals. Here we demonstrate a concept...... for efficient power scaling of single-pass SHG beyond such limits using a cascade of nonlinear crystals, in which the first crystal is chosen for high nonlinear efficiency and the subsequent crystal(s) are chosen for power handling ability. Using this highly efficient singlepass concept, we generate 3.7 W...... of continuous-wave diffraction-limited 2 ( 1.25) M = light at 532 nm from 9.5 W of non-diffraction-limited 2 ( 7.7) M = light from a tapered laser diode, while avoiding significant thermal effects. Besides constituting the highest SH power yet achieved using a laser diode, this demonstrates that the concept...

  12. Simulation and transient analysis of conventional and advanced aircraft electric power systems with harmonics mitigation

    Energy Technology Data Exchange (ETDEWEB)

    Eid, A.; El-Mohandes, T. [South Valley University (Egypt); Abdel-Salam, M. [Assiut University, Electrical Engineering Department, Al-Gamaa Street, Assiut 71518 (Egypt); El-Kishky, H. [The University of Texas at Tyler (United States)

    2009-04-15

    This paper presents the simulation and transient analysis of conventional and advanced aircraft electric power systems with harmonics mitigation. Complete modeling of aircraft electric power systems is proposed. The conventional aircraft electrical power system is analyzed considering equivalent passive AC and DC loads under transient and steady-state operating conditions. The electric power source is simulated to ensure constant frequency and voltage which meet the aircraft electrical standards for all loading cases. To mitigate the harmonics generated by the converters, passive input filters are designed to keep THD values within the standard limits. Furthermore, the advanced aircraft electrical system is simulated and analyzed under the same electric power source and loads. The results are compared to those of the conventional aircraft electric power system. (author)

  13. Experimental and Analytical Power Flow in Beams Using a Scanning Laser Doppler Vibrometer

    Directory of Open Access Journals (Sweden)

    Jonathan D. Blotter

    1996-01-01

    Full Text Available An experimental spatial power-flow (ESPF method is presented. This method provides a spatially continuous model of the power-flow vector field derived from experimental measurements. The power-flow vector field clearly indicates locations of energy sources and sinks as well as paths of energy transmission. In the ESPF approach, a scanning laser Doppler vibrometer acquires spatially dense measurements of the vibrating test structure. These measurements are used in solving for a spatially continuous 3-dimensional complex-valued model of the steady-state dynamic response. From this experimentally derived dynamics model, a spatial representation of the power flow is computed.

  14. An Improved Harmonic Current Detection Method Based on Parallel Active Power Filter

    Science.gov (United States)

    Zeng, Zhiwu; Xie, Yunxiang; Wang, Yingpin; Guan, Yuanpeng; Li, Lanfang; Zhang, Xiaoyu

    2017-05-01

    Harmonic detection technology plays an important role in the applications of active power filter. The accuracy and real-time performance of harmonic detection are the precondition to ensure the compensation performance of Active Power Filter (APF). This paper proposed an improved instantaneous reactive power harmonic current detection algorithm. The algorithm uses an improved ip -iq algorithm which is combined with the moving average value filter. The proposed ip -iq algorithm can remove the αβ and dq coordinate transformation, decreasing the cost of calculation, simplifying the extraction process of fundamental components of load currents, and improving the detection speed. The traditional low-pass filter is replaced by the moving average filter, detecting the harmonic currents more precisely and quickly. Compared with the traditional algorithm, the THD (Total Harmonic Distortion) of the grid currents is reduced from 4.41% to 3.89% for the simulations and from 8.50% to 4.37% for the experiments after the improvement. The results show the proposed algorithm is more accurate and efficient.

  15. Active power filter equivalent to an infinite feeder for harmonic suppression in radial distribution systems

    DEFF Research Database (Denmark)

    Shen, Hong; Yang, Lili; Sun, Xiaofeng

    2016-01-01

    This study proposes to install a novel active power filter (IF-APF) mimicking the character of an infinitely long transmission line at the end of a radial feeder. The proposed IF-APF eliminates the reflected wave and realises the background harmonic voltage suppression capability throughout...... the feeder by mimicking the characteristic of an infinite feeder. The proposed IF-APF shows a better harmonic damping performance than the traditional resistive active power filter (R-APF). Moreover, the proposed IF-APF achieves a better harmonic suppression performance than the traditional R-APF, especially...... when the characteristic impedance of the feeder changes or there are non-linear loads. Simulation and experimental results verify the theoretical analysis and demonstrate the effectiveness of the proposed IF-APF....

  16. A novel power harmonic analysis method based on Nuttall-Kaiser combination window double spectrum interpolated FFT algorithm

    Science.gov (United States)

    Jin, Tao; Chen, Yiyang; Flesch, Rodolfo C. C.

    2017-11-01

    Harmonics pose a great threat to safe and economical operation of power grids. Therefore, it is critical to detect harmonic parameters accurately to design harmonic compensation equipment. The fast Fourier transform (FFT) is widely used for electrical popular power harmonics analysis. However, the barrier effect produced by the algorithm itself and spectrum leakage caused by asynchronous sampling often affects the harmonic analysis accuracy. This paper examines a new approach for harmonic analysis based on deducing the modifier formulas of frequency, phase angle, and amplitude, utilizing the Nuttall-Kaiser window double spectrum line interpolation method, which overcomes the shortcomings in traditional FFT harmonic calculations. The proposed approach is verified numerically and experimentally to be accurate and reliable.

  17. Correlation of power Doppler with microvessel density in assessing prostate needle biopsy

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, N.M. E-mail: osamanagwa@hotmail.com; Masoud, A.M.; Barsoum, H.B.; Refaat, M.M.; Moustafa, M.I.; Kamal, T.A

    2004-10-01

    AIM: To correlate hypervascular power Doppler ultrasonography with the histological evaluation of microvasculature in the prostate using trans-rectal ultrasound (TRUS)-guided needle biopsy. MATERIALS AND METHODS: Ninety-six patients with a lower urinary tract symptoms (LUTS) and prostate specific antigen (PSA) value more than 4 ng/ml were evaluated using power Doppler ultrasonography before biopsy. The vascularity of the peripheral zone was graded on a scale of PZ0 to PZ2. Core needle biopsies were immunostained with CD31(DAKO) and counting was performed manually on separate high power fields (HPF;x400) in areas containing the highest number of vessels. RESULTS: There was a significant correlation between the grading system used for power Doppler and the microvessel density (MVD; PZ0 28.61{+-}8.97,PZ1 36.00{+-}12.11 and PZ2 64.008{+-}15.86; p<0.001). There was also a significant difference in MVD between benign, malignant and tissue cores with atypia and prostatic intra-epithelial neoplasia (PIN; p<0.001 and p<0.018, respectively). There was a significant correlation between malignant tissue having a higher Gleason score and increased MVD (p<0.001). Furthermore, cancer biopsies having a high flow PZ2 are nearly twice as likely (63.2%) to have a Gleason score of 7 or more when compared those having a Gleason score of less than 7 (36.8%). CONCLUSION: The grading system of assessing the power Doppler flow signals appears to be of value as an indicator of MVD. It also correlates with a higher Gleason score and this may reflect the clinical outcome in prostate cancer. It deserves further study and evaluation as a prognostic indicator.

  18. Monolithic high peak-power coherent Doppler lidar system

    Science.gov (United States)

    Kotov, Leonid V.; Töws, Albert; Kurtz, Alfred; Bobkov, Konstantin K.; Aleshkina, Svetlana S.; Bubnov, Mikhail M.; Lipatov, Denis S.; Guryanov, Alexey N.; Likhachev, Mikhail

    2016-03-01

    In this work we present a monolithic lidar system, based on a newly-developed double-clad large mode area (LMA) polarization-maintaining Er-doped fiber and specially designed LMA passive components. Optimization of the fiber designs resulted in as high as 100 W of SBS limited peak power. The amplifier and its passive components (circulator and collimator) were integrated in an existing lidar system. The enhanced lidar system provides three times increase of scanning range compared to one based on standard telecom-grade amplifiers.

  19. Flow angle dependent photoacoustic Doppler power spectra under intensity-modulated continuous wave laser excitation

    Directory of Open Access Journals (Sweden)

    Yu Tong

    2016-02-01

    Full Text Available Photoacoustic Doppler (PAD power spectra showing an evident Doppler shift represent the major characteristics of the continuous wave-excited or burst wave-excited versions of PAD flow measurements. In this paper, the flow angle dependences of the PAD power spectra are investigated using an experiment setup that was established based on intensity-modulated continuous wave laser excitation. The setup has an overall configuration that is similar to a previously reported configuration, but is more sophisticated in that it accurately aligns the laser illumination with the ultrasound detection process, and in that it picks up the correct sample position. In the analysis of the power spectra data, we find that the background power spectra can be extracted by combining the output signals from the two channels of the lock-in amplifier, which is very useful for identification of the PAD power spectra. The power spectra are presented and analyzed in opposite flow directions, at different flow speeds, and at different flow angles. The power spectra at a 90° flow angle show the unique properties of symmetrical shapes due to PAD broadening. For the other flow angles, the smoothed power spectra clearly show a flow angle cosine relationship.

  20. Two-dimensional multi-frequency imaging of a tumor inclusion in a homogeneous breast phantom using the harmonic motion Doppler imaging method

    Science.gov (United States)

    Kamali Tafreshi, Azadeh; Barış Top, Can; Güneri Gençer, Nevzat

    2017-06-01

    Harmonic motion microwave Doppler imaging (HMMDI) is a novel imaging modality for imaging the coupled electrical and mechanical properties of body tissues. In this paper, we used two experimental systems with different receiver configurations to obtain HMMDI images from tissue-mimicking phantoms at multiple vibration frequencies between 15 Hz and 35 Hz. In the first system, we used a spectrum analyzer to obtain the Doppler data in the frequency domain, while in the second one, we used a homodyne receiver that was designed to acquire time-domain data. The developed phantoms mimicked the elastic and dielectric properties of breast fat tissue, and included a 14~\\text{mm}× 9 mm cylindrical inclusion representing the tumor. A focused ultrasound probe was mechanically scanned in two lateral dimensions to obtain two-dimensional HMMDI images of the phantoms. The inclusions were resolved inside the fat phantom using both experimental setups. The image resolution increased with increasing vibration frequency. The designed receiver showed higher sensitivity than the spectrum analyzer measurements. The results also showed that time-domain data acquisition should be used to fully exploit the potential of the HMMDI method.

  1. Efficient Approach for Harmonic Resonance Identification of Large Wind Power Plants

    DEFF Research Database (Denmark)

    Ebrahimzadeh, Esmaeil; Blaabjerg, Frede; Wang, Xiongfei

    2016-01-01

    Unlike conventional power systems where the resonance frequencies are mainly determined by the passive components parameters, large Wind Power Plants (WPPs) may introduce additional harmonic resonances because of the interactions of the wideband control systems of power converters with each other...... system by considering the linearized models of the inner control loops of grid-side converters. Therefore, the resonance frequencies of the WPP resulting from passive components and the control loop interactions are identified based on the determinant of the transfer function matrix of the introduced...... and with passive components. This paper presents an efficient approach for identification of harmonic resonances in large WPPs containing power electronic converters, cable, transformer, capacitor banks, shunt reactors, etc. The proposed approach introduces a large WPP as a Multi-Input Multi-Output (MIMO) control...

  2. Harmonic Domain Modelling of Transformer Core Nonlinearities Using the DIgSILENT PowerFactory Software

    DEFF Research Database (Denmark)

    Bak, Claus Leth; Bak-Jensen, Birgitte; Wiechowski, Wojciech

    2008-01-01

    This paper demonstrates the results of implementation and verification of an already existing algorithm that allows for calculating saturation characteristics of singlephase power transformers. The algorithm was described for the first time in 1993. Now this algorithm has been implemented using...... the DIgSILENT Programming Language (DPL) as an external script in the harmonic domain calculations of a power system analysis tool PowerFactory [10]. The algorithm is verified by harmonic measurements on a single-phase power transformer. A theoretical analysis of the core nonlinearities phenomena...... in single and three-phase transformers is also presented. This analysis leads to the conclusion that the method can be applied for modelling nonlinearities of three-phase autotransformers....

  3. Power-line harmonic radiation - Can it significantly affect the earth's radiation belts

    Science.gov (United States)

    Thorne, R. M.; Tsurutani, B. T.

    1979-01-01

    It has been suggested that harmonic radiation from the earth's 50- and 60-hertz power transmission lines might significantly influence the distribution of electrons in the radiation belts. On the basis of observations presented here, it seems advisable to accept such a hypothesis with caution. New evidence suggests that power-line radiation does not play any major role in the nonadiabatic dynamics of radiation belt electrons.

  4. Spherical Harmonic Analyses of Intensity Mapping Power Spectra

    Science.gov (United States)

    Liu, Adrian; Zhang, Yunfan; Parsons, Aaron R.

    2016-12-01

    Intensity mapping is a promising technique for surveying the large-scale structure of our universe from z = 0 to z ˜ 150, using the brightness temperature field of spectral lines to directly observe previously unexplored portions of our cosmic timeline. Examples of targeted lines include the 21 cm hyperfine transition of neutral hydrogen, rotational lines of carbon monoxide, and fine-structure lines of singly ionized carbon. Recent efforts have focused on detections of the power spectrum of spatial fluctuations, but have been hindered by systematics such as foreground contamination. This has motivated the decomposition of data into Fourier modes perpendicular and parallel to the line of sight, which has been shown to be a particularly powerful way to diagnose systematics. However, such a method is well-defined only in the limit of a narrow-field, flat-sky approximation. This limits the sensitivity of intensity mapping experiments, as it means that wide surveys must be separately analyzed as a patchwork of smaller fields. In this paper, we develop a framework for analyzing intensity mapping data in a spherical Fourier-Bessel basis, which incorporates curved sky effects without difficulty. We use our framework to generalize a number of techniques in intensity mapping data analysis from the flat sky to the curved sky. These include visibility-based estimators for the power spectrum, treatments of interloper lines, and the “foreground wedge” signature of spectrally smooth foregrounds.

  5. The effect of blood acceleration on the ultrasound power Doppler spectrum

    Science.gov (United States)

    Matchenko, O. S.; Barannik, E. A.

    2017-09-01

    The purpose of the present work was to study the influence of blood acceleration and time window length on the power Doppler spectrum for Gaussian ultrasound beams. The work has been carried out on the basis of continuum model of the ultrasound scattering from inhomogeneities in fluid flow. Correlation function of fluctuations has been considered for uniformly accelerated scatterers, and the resulting power Doppler spectra have been calculated. It is shown that within the initial phase of systole uniformly accelerated slow blood flow in pulmonary artery and aorta tends to make the correlation function about 4.89 and 7.83 times wider, respectively, than the sensitivity function of typical probing system. Given peak flow velocities, the sensitivity function becomes, vice versa, about 4.34 and 3.84 times wider, respectively, then the correlation function. In these limiting cases, the resulting spectra can be considered as Gaussian. The optimal time window duration decreases with increasing acceleration of blood flow and equals to 11.62 and 7.54 ms for pulmonary artery and aorta, respectively. The width of the resulting power Doppler spectrum is shown to be defined mostly by the wave vector of the incident field, the duration of signal and the acceleration of scatterers in the case of low flow velocities. In the opposite case geometrical properties of probing field and the average velocity itself are more essential. In the sense of signal-noise ratio, the optimal duration of time window can be found. Abovementioned results may contribute to the improved techniques of Doppler ultrasound diagnostics of cardiovascular system.

  6. A zero power harmonic transponder sensor for ubiquitous wireless μL liquid-volume monitoring.

    Science.gov (United States)

    Huang, Haiyu; Chen, Pai-Yen; Hung, Cheng-Hsien; Gharpurey, Ranjit; Akinwande, Deji

    2016-01-06

    Autonomous liquid-volume monitoring is crucial in ubiquitous healthcare. However, conventional approach is based on either human visual observation or expensive detectors, which are costly for future pervasive monitoring. Here we introduce a novel approach based on passive harmonic transponder antenna sensor and frequency hopping spread spectrum (FHSS) pattern analysis, to provide a very low cost wireless μL-resolution liquid-volume monitoring without battery or digital circuits. In our conceptual demonstration, the harmonic transponder comprises of a passive nonlinear frequency multiplier connected to a metamaterial-inspired 3-D antenna designed to be highly sensitive to the liquid-volume within a confined region. The transponder first receives some FHSS signal from an interrogator, then converts such signal to its harmonic band and re-radiates through the antenna sensor. The harmonic signal is picked up by a sniffer receiver and decoded through pattern analysis of the high dimensional FHSS signal strength data. A robust, zero power, absolute accuracy wireless liquid-volume monitoring is realized in the presence of strong direct coupling, background scatters, distance variance as well as near-field human-body interference. The concepts of passive harmonic transponder sensor, metamaterial-inspired antenna sensor, and FHSS pattern analysis based sensor decoding may help establishing cost-effective, energy-efficient and intelligent wireless pervasive healthcare monitoring platforms.

  7. A zero power harmonic transponder sensor for ubiquitous wireless μL liquid-volume monitoring

    Science.gov (United States)

    Huang, Haiyu; Chen, Pai-Yen; Hung, Cheng-Hsien; Gharpurey, Ranjit; Akinwande, Deji

    2016-01-01

    Autonomous liquid-volume monitoring is crucial in ubiquitous healthcare. However, conventional approach is based on either human visual observation or expensive detectors, which are costly for future pervasive monitoring. Here we introduce a novel approach based on passive harmonic transponder antenna sensor and frequency hopping spread spectrum (FHSS) pattern analysis, to provide a very low cost wireless μL-resolution liquid-volume monitoring without battery or digital circuits. In our conceptual demonstration, the harmonic transponder comprises of a passive nonlinear frequency multiplier connected to a metamaterial-inspired 3-D antenna designed to be highly sensitive to the liquid-volume within a confined region. The transponder first receives some FHSS signal from an interrogator, then converts such signal to its harmonic band and re-radiates through the antenna sensor. The harmonic signal is picked up by a sniffer receiver and decoded through pattern analysis of the high dimensional FHSS signal strength data. A robust, zero power, absolute accuracy wireless liquid-volume monitoring is realized in the presence of strong direct coupling, background scatters, distance variance as well as near-field human-body interference. The concepts of passive harmonic transponder sensor, metamaterial-inspired antenna sensor, and FHSS pattern analysis based sensor decoding may help establishing cost-effective, energy-efficient and intelligent wireless pervasive healthcare monitoring platforms. PMID:26732251

  8. CALCULATION METHOD OF ELECTRIC POWER LINES MAGNETIC FIELD STRENGTH BASED ON CYLINDRICAL SPATIAL HARMONICS

    Directory of Open Access Journals (Sweden)

    A.V. Erisov

    2016-05-01

    Full Text Available Purpose. Simplification of accounting ratio to determine the magnetic field strength of electric power lines, and assessment of their environmental safety. Methodology. Description of the transmission lines of the magnetic field by using techniques of spatial harmonic analysis in the cylindrical coordinate system is carried out. Results. For engineering calculations of electric power lines magnetic field with sufficient accuracy describes their first spatial harmonic magnetic field. Originality. Substantial simplification of the definition of the impact of the construction of transmission line poles on the value of its magnetic field and the bands of land alienation sizes. Practical value. The environmentally friendly projection electric power lines on the level of the magnetic field.

  9. Inverse class-f power amplifier using slot resonators as a harmonic filter

    Directory of Open Access Journals (Sweden)

    Rassokhina Yu. V.

    2014-06-01

    Full Text Available The authors proposed and experimentally verified the power amplifier circuit of inverse class F (F–1 based on GaN transistor NPTB00004, operating at 1,7 GHz. The novelty of this scheme is the application of a three-layer structure based on slot rectangular shaped resonators in the ground plane of the microstrip transmission line as a filter of higher harmonics. To control the levels of the second and third harmonics in the output signal spectrum and simultaneously to match the 50 ohm load at the operating frequency of the amplifier, a planar periodic structure is used, consisting of two slot resonators of different lengths. Power added efficiency for experimental model of the amplifier is 60% at an output power of 3.9 W and a gain factor of 13 dB.

  10. Measuring Doppler-like power spectra and dermal perfusion using laser speckle contrast with multiple exposures

    Science.gov (United States)

    Thompson, O. B.; Andrews, M. K.

    2010-02-01

    Laser speckle contrast measurements provide effectively instantaneous maps of dermal perfusion, using easily obtainable hardware, but such maps are qualitative. Clinical applications of these techniques require a good theoretical and experimental foundation of understanding before relating them to a physiologically significant, quantitative perfusion value. We have confirmed that multiple-exposure laser speckle methods produce the same spectral information as laser Doppler measurements when applied to targets such as human tissue with embedded moving scatterers. This confirmation is based on both computer simulation of laser speckle data and experimental measurements on Brownian motion and skin perfusion using a laser Doppler system and a multiple-exposure laser speckle system. The Power Spectral Density (PSD) measurements of the light fluctuations derived using both techniques are equivalent. Dermal perfusion images can therefore be measured in exactly equivalent terms by either laser speckle contrast or more laborious scanning laser Doppler methods. Most analyses relating laser speckle contrast to perfusion depend on assuming a particular temporal autocorrelation function for the light intensity fluctuations in biospeckle. Using multiple-exposure laser speckle allows the autocorrelation function to be measured rather than assumed. Measured autocorrelation functions and their related power spectra for dermal perfusion are presented, including measurements under arterial occlusion to investigate a 'biological zero': the speckle blur relating to the remaining movement of tissue constituents when there is no net blood flow.

  11. Evaluation of nonunion fractures in dogs by use of B-mode ultrasonography, power Doppler ultrasonography, radiography, and histologic examination.

    Science.gov (United States)

    Risselada, Marije; van Bree, Henri; Kramer, Martin; Chiers, Koen; Duchateau, Luc; Verleyen, Piet; Saunders, Jimmy H

    2006-08-01

    To investigate the use of ultrasonography to assess nonunion of fractures in dogs and to compare results of ultrasonography, radiography, and histologic examination. 8 nonunion fractures in 6 dogs (1 each in 5 dogs and 3 in 1 dog); dogs ranged from 7 to 94 months of age and weighed 6 to 30 kg. Diagnostic assessment consisted of complete clinical and orthopedic examinations, radiography, B-mode (brightness mode) ultrasonography, and power Doppler ultrasonography. Biopsy samples were obtained during surgery for histologic examination. They were stained with H&E and immunolabeled by use of anti-CD31 antibodies. Correlations of power Doppler score, power Doppler count, vessel area, and radiographic prediction with the mean number of vessels counted per hpf were derived. Radiographically, 7 of 8 nonunion fractures were diagnosed as atrophic and were therefore estimated to be nonviable. Vascularity of nonunion fractures during power Doppler ultrasonography ranged from nonvascularized to highly vascularized. Absolute vessel count during histologic examination ranged from 0 to 63 vessels/hpf; 5 nonunion sites had a mean count of > 10 vessels/hpf. Vascularity during power Doppler ultrasonography was highly correlated with the number of vessels per hpf, whereas the correlation between the radiographic assessment and histologic evaluation was low. Radiographic prediction of the viability of nonunion fractures underestimated the histologically assessed vascularity of the tissue. Power Doppler ultrasonography provided a more accurate estimation of the viability of the tissue and therefore the necessity for debridement and autografts during revision surgery.

  12. Stator Current Harmonic Reduction in a Novel Half Quasi-Z-Source Wind Power Generation System

    Directory of Open Access Journals (Sweden)

    Shoudao Huang

    2016-09-01

    Full Text Available The generator stator current gets distorted with unacceptable levels of total harmonic distortion (THD because impedance-source wind power generation systems use three-phase diode rectifiers. The stator current harmonics will cause increasing losses and torque ripple, which reduce the efficiency and stability of the system. This paper proposes a novel half quasi-Z-source inverter (H-qZSI for grid-connected wind power generation systems, which can reduce the generator stator current harmonics a great deal. When H-qZSI operates in the shoot-through zero state, the derivative of the generator stator current is only determined by the instantaneous value of the generator stator voltage, so the nonlinear relationship between generator stator current and stator voltage is improved compared with the traditional impedance-source inverter. Theoretically, it is indicated that the stator current harmonics can be reduced effectively by means of the proposed H-qZSI. Finally, simulation and experimental results are given to verify the theoretical analysis.

  13. Reactive power compensation considering high harmonics generation from internal and external nonlinear load

    Science.gov (United States)

    Skamyin, A. N.; Belsky, A. A.

    2017-10-01

    The paper deals with reactive power compensation by means of condenser batteries with harmonic distortions in voltage and current, resulting from internal and external nonlinear load regarding the connection point shared by consumers. The paper presents the dependencies of the capacitor’s overloading factor from the required reactive power for compensating. These relations can help to determine in which capacity area of the capacitor banks its operation is ensured without overload. The paper also presents algorithm for selecting parameters of condenser batteries which leads to minimization of the capacitors overload and maximization of the network power factor.

  14. Modified Perfect Harmonics Cancellation Control of a Grid Interfaced SPV Power Generation

    Science.gov (United States)

    Singh, B.; Shahani, D. T.; Verma, A. K.

    2015-03-01

    This paper deals with a grid interfaced solar photo voltaic (SPV) power generating system with modified perfect harmonic cancellation (MPHC) control for power quality improvement in terms of mitigation of the current harmonics, power factor correction, control of point of common coupling (PCC) voltage with reactive power compensation and load balancing in a three phase distribution system. The proposed grid interfaced SPV system consists of a SPV array, a dc-dc boost converter and a voltage source converter (VSC) used for the compensation of other connected linear and nonlinear loads at PCC. The reference grid currents are estimated using MPHC method and control signals are derived by using pulse width modulation (PWM) current controller of VSC. The SPV power is fed to the common dc bus of VSC and dc-dc boost converter using maximum power point tracking (MPPT). The dc link voltage of VSC is regulated by using dc voltage proportional integral (PI) controller. The analysis of the proposed SPV power generating system is carried out under dc/ac short circuit and severe SPV-SX and SPV-TX intrusion.

  15. Power characteristics of CW second harmonic generation in periodically poled LiNbO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Bong Hoon; Rhee, Bum Ku [Dept. of Physics, Sogang University, Seoul (Korea, Republic of); Cha, Myoung Sik [Research Center for Dielectric and Advanced Matter Physics. Busan National University, Busan (Korea, Republic of)

    2002-07-01

    Power characteristics of CW second harmonic generation (SHG) in 0.5-mm-thick periodically poled LiNbO{sub 3} (PPLN) witha 6.5 μm domain period were investigated as a function of crystal length, and confocal parameter which was varied by using a lens of different focal length. We found there is the optimum condition of confocal parameter for SHG for a given intensity.

  16. Power Doppler assessment of the neovascularization during uncomplicated fracture healing of long bones in dogs and cats.

    Science.gov (United States)

    Risselada, Marije; Kramer, Martin; Saunders, Jimmy H; Verleyen, Piet; Van Bree, Henri

    2006-01-01

    The aims of this prospective study were to test the feasibility of assessing neovascularization with power Doppler ultrasonography and to investigate its usefulness to follow fracture healing of long bones in dogs and cats. A total of 51 patients (44 dogs and seven cats) were followed. Fracture types differed from simple to comminuted. Therapy ranged from external coaptation to plate osteosynthesis. Patients were followed with radiography, B-mode real time and power Doppler ultrasonography every 2-4 weeks until the fracture was healed. All fractures healed uneventfully. A semi-quantitative numerical score based on signal intensity, vessel area, and number of Doppler signals was assigned and the mean value was used to compare patients and examinations. Time postoperatively was divided into periods of 10 days. No Doppler signal was present during the first 10 days. The mean of the scores was highest between 11 and 20 days postoperatively and the median of the scores peaked between 21 and 30 days. A gradual decrease was seen thereafter. The mean of the scores was zero at 71-80 days and the median at 51-0 days postoperatively for the grouped results. In all positive power Doppler examinations, signals were present in and close to the callus. In seven patients (five dogs and two cats) signals were also present in the peripheral soft tissues in one of the follow up examinations. The normal healing process of fractured bones can be visualized using power Doppler ultrasonography and follows a distinctive time-dependent pattern.

  17. 3D power Doppler ultrasound assessment of placental perfusion during uterine contraction in labor.

    Science.gov (United States)

    Sato, Miki; Noguchi, Junko; Mashima, Masato; Tanaka, Hirokazu; Hata, Toshiyuki

    2016-09-01

    To assess placental perfusion during spontaneous or induced uterine contraction in labor at term using placental vascular sonobiopsy (PVS) by 3D power Doppler ultrasound with the VOCAL imaging analysis program. PVS was performed in 50 normal pregnancies (32 in spontaneous labor group [SLG], and 18 in induced labor group with oxytocin or prostaglandin F2α [ILG]) at 37-41 weeks of gestation to assess placental perfusion during uterine contraction in labor. Only pregnancies with an entirely visualized anterior placenta were included in the study. Data acquisition was performed before, during (at the peak of contraction), and after uterine contraction. 3D power Doppler indices such as the vascularization index (VI), flow index (FI), and vascularization flow index (VFI) were calculated in each placenta. There were no abnormal fetal heart rate tracings during contraction in either group. VI and VFI values were significantly reduced during uterine contraction in both groups (SLG, -33.4% [-97.0-15.2%], and ILG, -49.6% [-78.2--4.0%]), respectively (P reduction in placental perfusion. Reduced placental blood flow in induced uterine contraction has a tendency to be marked compared with that in spontaneous uterine contraction. To the best of our knowledge, this is the first study on the non-invasive assessment of placental perfusion during uterine contraction in labor using 3D power Doppler ultrasound. However, the data and their interpretation in the present study should be taken with some degree of caution because of the small number of subjects studied. Further studies involving a larger sample size are needed to assess placental perfusion and vascularity using PVS during normal and abnormal uterine contractions in normal and high-risk pregnancies. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Power spectrum and blood flow velocity images obtained by dual-beam backscatter laser Doppler velocimetry

    Science.gov (United States)

    Ishida, Hiroki; Yasue, Youichi; Hachiga, Tadashi; Andoh, Tsugunobu; Akiguchi, Shunsuke; Kuraishi, Yasushi; Shimizu, Tadamichi

    2014-07-01

    We developed a micro multipoint laser Doppler velocimeter (μ-MLDV) for noninvasive in-vivo measurements of blood flow and we presented the results of demonstrations performed on experimental animals. In this paper, we investigate the validity of power spectrum analysis for determining the flow velocity and the minimum power of the semiconductor laser in the μ-MLDV. Although average velocity is generally estimated from a peak position ( f peak) in the power spectrum, the power spectrum of blood flow included an additional component in the high-frequency region. The conventional method for determining the average velocity of flows of transparent artificial fluids, which involves determining the average velocity from f peak, is unsuitable for in-vivo measurements of blood flow. The laser power was reduced from 140 to 30mW since 30mW was the minimum power at which images of blood flow velocity in microvessels could be obtained. About 30mW (power density of 15mW/mm2) is the maximum power which can be irradiated to humans. Further reduction in the laser power is necessary before this technique can be applied to humans.

  19. Harmonic-resonator-based triboelectric nanogenerator as a sustainable power source and a self-powered active vibration sensor.

    Science.gov (United States)

    Chen, Jun; Zhu, Guang; Yang, Weiqing; Jing, Qingshen; Bai, Peng; Yang, Ya; Hou, Te-Chien; Wang, Zhong Lin

    2013-11-13

    A harmonic-resonator-based triboelectric nanogenerator (TENG) is presented as a sustainable power source and an active vibration sensor. It can effectively respond to vibration frequencies ranging from 2 to 200 Hz with a considerably wide working bandwidth of 13.4 Hz. This work not only presents a new principle in the field of vibration energy harvesting but also greatly expands the applicability of TENGs. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Improved Contrast-Enhanced Power Doppler Using a Coherence-Based Estimator.

    Science.gov (United States)

    Tremblay-Darveau, Charles; Bar-Zion, Avinoam; Williams, Ross; Sheeran, Paul S; Milot, Laurent; Loupas, Thanasis; Adam, Dan; Bruce, Matthew; Burns, Peter N

    2017-09-01

    While plane-wave imaging can improve the performance of power Doppler by enabling much longer ensembles than systems using focused beams, the long-ensemble averaging of the zero-lag autocorrelation R(0) estimates does not directly decrease the mean noise level, but only decreases its variance. Spatial variation of the noise due to the time-gain compensation and the received beamforming aperture ultimately limits sensitivity. In this paper, we demonstrate that the performance of power Doppler imaging can be improved by leveraging the higher lags of the autocorrelation [e.g., R(1), R(2),…] instead of the signal power (R(0)). As noise is completely uncorrelated from pulse-to-pulse while the flow signal remains correlated significantly longer, weak signals just above the noise floor can be made visible through the reduction of the noise floor. Finally, as coherence decreases proportionally with respect to velocity, we demonstrate how signal coherence can be targeted to separate flows of different velocities. For instance, we show how long-time-range coherence of microbubble contrast-enhanced flow specifically isolates slow capillary perfusion (as opposed to conduit flow).

  1. Modeling and Simulation of DC Power Electronics Systems Using Harmonic State Space (HSS) Method

    DEFF Research Database (Denmark)

    Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth

    2015-01-01

    based on the state-space averaging and generalized averaging, these also have limitations to show the same results as with the non-linear time domain simulations. This paper presents a modeling and simulation method for a large dc power electronic system by using Harmonic State Space (HSS) modeling....... Through this method, the required computation time and CPU memory for large dc power electronics systems can be reduced. Besides, the achieved results show the same results as with the non-linear time domain simulation, but with the faster simulation time which is beneficial in a large network....

  2. Effect of Precompression on the Power Doppler Assessment of Breast Lesion Vascularity.

    Science.gov (United States)

    DeVita, Robert; Barr, Richard G

    2017-02-01

    To evaluate the effect of precompression on power Doppler visualization of blood flow in breast masses. This Institutional Review Board-approved and Health Insurance Portability and Accountability Act-compliant study evaluated 30 patients with breast masses (16 benign and 14 malignant) undergoing ultrasound-guided breast biopsy. A computational mathematics program was used to calculate the number of color pixels in a region of interest at various degrees of compression of the breast by the transducer. The amount of precompression was calculated as previously described. The percentage of color pixels compared to minimal compression was plotted against the percentage of precompression. The amount of precompression needed to decrease the number of color pixels by 50% and 100% was calculated. The differences between benign and malignant lesions were compared. The mean percentages of precompression ± SD needed to decrease the number of color voxels by 50% in were 15.9% ± 6.43% (range, 8%-30%) for benign lesions and 14.0% ± 4.17% (range, 8%-20%) for malignant lesions (P = .35). The percentages of precompression needed to decrease the number of color pixels by 100% in were 34.7% ± 12.33% (range, 23%-62%) for benign lesions and for malignant lesions 26.7% ± 3.89% (range, 18%-31%), which were statistically significant (P = .027). The amount of precompression normally used when obtaining B-mode images can substantially decrease the number of color voxels on power Doppler sonography. When performing quantitative work on Doppler evaluation of breast lesions, precompression needs to be controlled. © 2016 by the American Institute of Ultrasound in Medicine.

  3. Relative blood flow changes measured using calibrated frequency-weighted Doppler power at different hematocrit levels.

    Science.gov (United States)

    Wallace, Sean; Logallo, Nicola; Faiz, Kashif W; Lund, Christian; Brucher, Rainer; Russell, David

    2014-04-01

    In theory, the power of a trans-cranial Doppler signal may be used to measure changes in blood flow and vessel diameter in addition to velocity. In this study, a flow index (FI) of relative changes in blood flow was derived from frequency-weighted Doppler power signals. The FI, plotted against velocity, was calibrated to the zero intercept with absent flow to reduce the effects of non-uniform vessel insonation. An area index was also calculated. FIs were compared with actual flow in four silicone tubes of different diameter at increasing flow rates and increasing hematocrit (Hct) in a closed-loop phantom model. FI values were strongly correlated with actual flow, at constant Hct, but varied substantially with changes in Hct. Percentage changes in area indexes, relative to the 4-mm tube, were strongly correlated with tube cross-sectional area. The implications of these results for in vivo use are discussed. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  4. Quantitative analysis of normal fetal brain volume and flow by three-dimensional power Doppler ultrasound.

    Science.gov (United States)

    Hsu, Ju-Chun; Wu, Yi-Cheng; Wang, Peng-Hui; Wang, Hsing-I; Juang, Chi-Mou; Chen, Yi-Jen; Chang, Chia-Ming; Horng, Huann-Cheng; Chen, Chih-Yao; Yang, Ming-Jie; Yen, Ming-Shyen; Chao, Kuan-Chong

    2013-09-01

    Assessment of the fetal brain volume and blood flow is important in the evaluation of fetal growth. We used three-dimensional (3D) ultrasound and power Doppler to assess the fetal brain volume and the blood flow index during normal gestation. The relationships of these parameters were further analyzed. We assessed the total volume and the blood flow index of the fetal brain in normal pregnancies using 3D ultrasound (Voluson 730). The bilateral parietal diameter (BPD) plane was measured by a 3D transabdominal probe to scan the fetal brain under the power Doppler mode. Then, we quantitatively assessed the total volume of the fetal brain, mean grey area (MG), vascularization index (VI), flow index (FI), and vascularization-flow index (VFI) by applying Kretz VOCAL software. The study included 126 fetuses, ranging from 15 to 38 weeks of gestation. The total volume of the fetal brain was highly positively correlated with the gestational age (GA) (correlation coefficient [r] = 0.976, p flow development quantitatively. Our study indicates that the fetal brain vascularization and blood flow correlates significantly with the advancement of GA. This information may serve as a reference point for further studies of the fetal brain volume and blood flow in abnormal conditions. Copyright © 2013. Published by Elsevier B.V.

  5. Prostate vascular flow: The effect of the ejaculation on the power doppler ultrasonographic examination.

    Science.gov (United States)

    Alonge, S; Melandri, M; Fanciullo, L; Lacalandra, G M; Aiudi, G

    2018-02-01

    Power Doppler sonography (PD) can accurately depict tissue perfusion, recognize slow flows, and is relatively angle independent. The monitoring of local blood flow by Doppler ultrasonography is helpful in differentiating prostatic physio-pathological conditions, but the recognizing of physiological variables that could affect it is crucial to apply this technique in clinical practice. This study aimed to evaluate if ejaculation affects blood flow to the prostate and to state how long this effect lasts. Serial PD examinations of prostate were performed in 18 dogs (1-5 years, 6-40 kg) immediately before (T0) and after (T1) the ejaculation, and repeated 6 (T2), 18 (T3) and 24 (T4) hours later. For each examination, two representative PD images were chosen and ranked by two independent observers according to the following scoring system: 0 = mild subcapsular (S) vascularization without clear evidence of parenchymal (P) vascularization; 1 = moderate P and S vascularization; 2 = severe S and moderate P vascularization; 3 = severe P and moderate S vascularization; 4 = severe P and S vascularization. Interobserver agreement was assessed using Kappa of Cohen. Ranked data, grouped according to time, were compared by ANOVA and Tukey HSD test (p flow pattern at different times were observed for all dogs. The statistical analysis evidenced a significant difference for T0 vs T1 and vs T2 and vs T3 (p  .05). Interobserver agreement was very good (Kappa of Cohen = 0.86). This study demonstrated a definite increase in vascular flow to the prostate after ejaculation. The present results suggest a minimum of 24 hr sexual rest before the PD examination of the gland. This result should be taken into account whenever Doppler sonography is used to evaluate potential hyperaemia in dogs suspected of having prostate abnormalities. © 2017 Blackwell Verlag GmbH.

  6. Visualization of Small-Diameter Vessels by Reduction of Incoherent Reverberation With Coherent Flow Power Doppler.

    Science.gov (United States)

    Li, You Leo; Hyun, Dongwoon; Abou-Elkacem, Lotfi; Willmann, Juergen Karl; Dahl, Jeremy J

    2016-11-01

    Power Doppler (PD) imaging is a widely used technique for flow detection. Despite the wide use of Doppler ultrasound, limitations exist in the ability of Doppler ultrasound to assess slow flow in the small-diameter vasculature, such as the maternal spiral arteries and fetal villous arteries of the placenta and focal liver lesions. The sensitivity of PD in small vessel detection is limited by the low signal produced by slow flow and the noise associated with small vessels. The noise sources include electronic noise, stationary or slowly moving tissue clutter, reverberation clutter, and off-axis scattering from tissue, among others. In order to provide more sensitive detection of slow flow in small diameter vessels, a coherent flow imaging technique, termed coherent flow PD (CFPD), is characterized and evaluated with simulation, flow phantom experiment studies, and an in vivo animal small vessel detection study. CFPD imaging was introduced as a technique to detect slow blood flow. It has been demonstrated to detect slow flow below the detection threshold of conventional PD imaging using identical pulse sequences and filter parameters. In this paper, we compare CFPD with PD in the detection of blood flow in small-diameter vessels. The results from the study suggest that CFPD is able to provide a 7.5-12.5-dB increase in the signal-to-noise ratio (SNR) over PD images for the same physiological conditions and is less susceptible to reverberation clutter and thermal noise. Due to the increase in SNR, CFPD is able to detect small vessels in high channel noise cases, for which PD was unable to generate enough contrast to observe the vessel.

  7. Understanding the Influence of Flow Velocity, Wall Motion Filter, Pulse Repetition Frequency, and Aliasing on Power Doppler Image Quantification.

    Science.gov (United States)

    Martins, Maricy R; Martins, Wellington P; Soares, Carlos A M; Miyague, Andre H; Kudla, Marek J; Pavan, Theo Z

    2018-01-01

    Although power Doppler imaging has been used to quantify tissue and organ vascularity, many studies showed that limitations in defining adequate ultrasound machine settings and attenuation make such measurements complex to be achieved. However, most of these studies were conducted by using the output of proprietary software, such as Virtual Organ computer-aided analysis (GE Healthcare, Kretz, Zipf, Austria); therefore, many conclusions may not be generalizable because of unknown settings and parameters used by the software. To overcome this limitation, our goal was to evaluate the impact of the flow velocity, pulse repetition frequency (PRF), and wall motion filter (WMF) on power Doppler image quantification using beam-formed ultrasonic radiofrequency data. The setup consisted of a blood-mimicking fluid flowing through a phantom. Radiofrequency signals were collected using PRFs ranging from 0.6 to 10 kHz for 6 different flow velocities (5-40 cm/s). Wall motion filter cutoff frequencies were varied between 50 and 250 Hz. The power Doppler magnitude was deeply influenced by the WMF cutoff frequency. The effect of using different WMF values varied with the PRF; therefore, the power Doppler signal intensity was dependent on the PRF. Finally, we verified that power Doppler quantification can be affected by the aliasing effect, especially when using a PRF lower than 1.3 kHz. The WMF and PRF greatly influenced power Doppler quantification, mainly when flow velocities lower than 20 cm/s were used. Although the experiments were conducted in a nonclinical environment, the evaluated parameters are equivalent to those used in clinical practice, which makes them valuable for aiding the interpretation of related data in future research. © 2017 by the American Institute of Ultrasound in Medicine.

  8. Evaluation of Harmonic Content from a Tap Transformer Based Grid Connection System for Wind Power

    Directory of Open Access Journals (Sweden)

    S. Apelfröjd

    2013-01-01

    Full Text Available Simulations done in MATLAB/Simulink together with experiments conducted at the Ångströms laboratory are used to evaluate and discuss the total harmonic distortion (THD and total demand distortion (TDD of a tap transformer based grid connection system. The grid connection topology can be used with different turbine and generator topologies and is here applied on a vertical axis wind turbine (VAWT with a permanent magnet synchronous generator (PMSG and its operational scheme. The full variable-speed wind conversion system consists of a diode rectifier, DC link, IGBT inverter, LCL-filter, and tap transformer. The full variable-speed operation is enabled by the use of the different step-up ratios of the tap transformer. In the laboratory study, a full experimental setup of the system was used, a clone of the on-site PMSG driven by a motor was used, and the grid was replaced with a resistive load. With a resistive load, grid harmonics and possible unbalances are removed. The results show a TDD and THD below 5% for the full operating range and harmonic values within the limits set up by IEEE-519. Furthermore, a change in tap, going to a lower step-up ratio, results in a reduction in both THD and TDD for the same output power.

  9. An Active Power Filter Based on a Three-Level Inverter and 3D-SVPWM for Selective Harmonic and Reactive Compensation

    OpenAIRE

    José Luis Monroy-Morales; David Campos-Gaona; Máximo Hernández-Ángeles; Rafael Peña-Alzola; José Leonardo Guardado-Zavala

    2017-01-01

    Active Power Filters (APFs) have been used for reducing waveform distortion and improving power quality. However, this function can be improved by means of a selective harmonic compensation. Since an APF has rating restrictions, it is convenient to have the option of selecting an individual or a set of particular harmonics in order to compensate and apply the total APF capabilities to eliminate these harmonics, in particular those with a greater impact on the Total Harmonic Distortion (THD). ...

  10. Low-Power Analog Processing for Sensing Applications: Low-Frequency Harmonic Signal Classification

    Directory of Open Access Journals (Sweden)

    Sina Balkir

    2013-07-01

    Full Text Available A low-power analog sensor front-end is described that reduces the energy required to extract environmental sensing spectral features without using Fast Fouri´er Transform (FFT or wavelet transforms. An Analog Harmonic Transform (AHT allows selection of only the features needed by the back-end, in contrast to the FFT, where all coefficients must be calculated simultaneously. We also show that the FFT coefficients can be easily calculated from the AHT results by a simple back-substitution. The scheme is tailored for low-power, parallel analog implementation in an integrated circuit (IC. Two different applications are tested with an ideal front-end model and compared to existing studies with the same data sets. Results from the military vehicle classification and identification of machine-bearing fault applications shows that the front-end suits a wide range of harmonic signal sources. Analog-related errors are modeled to evaluate the feasibility of and to set design parameters for an IC implementation to maintain good system-level performance. Design of a preliminary transistor-level integrator circuit in a 0:µm complementary metal-oxide-silicon (CMOS integrated circuit process showed the ability to use online self-calibration to reduce fabrication errors to a sufficiently low level. Estimated power dissipation is about three orders of magnitude less than similar vehicle classification systems that use commercially available FFT spectral extraction.

  11. A comparison of Power Doppler with conventional sonographic imaging for the evaluation of renal artery stenosis

    Directory of Open Access Journals (Sweden)

    Coppolino Frank

    2004-01-01

    Full Text Available Abstract Background Power Doppler (PD has improved diagnostic capabilities of vascular sonography, mainly because it is independent from the angle of insonation. We evaluated this technique in a prospective comparison with conventional imaging, consisting in Duplex and Color Doppler, for the evaluation of Renal Artery (RA stenosis. Methods Sensitivity, specificity and predictive values of PD and conventional imaging were assessed in a blinded fashion on eighteen patients, 9 with angiographic evidence of unilateral RA stenosis (hypertensive patients and 9 with angiographically normal arteries (control group. PD images were interpreted with an angiography-like criteria. Results In the control group both techniques allowed correct visualization of 16 out of the 18 normal arteries (93% specificity. Only in five hypertensive patients RA stenosis was correctly identified with conventional technique (56% sensitivity and 86% negative predictive value; PD was successful in all hypertensive patients (100% sensitivity and negative predictive value, since the operators could obtain in each case of RA stenosis a sharp color signal of the whole vessel with a clear "minus" at the point of narrowing of the lumen. All results were statistically significant (p Conclusions This study demonstrates that PD is superior to conventional imaging, in terms of sensitivity and specificity, for the diagnosis of RA stenosis, because it allows a clear visualization of the whole stenotic vascular lumen. Especially if it is used in concert with the other sonographic techniques, PD can enable a more accurate imaging of renovascular disease with results that seem comparable to selective angiography.

  12. Power spectral density of velocity fluctuations estimated from phase Doppler data

    Directory of Open Access Journals (Sweden)

    Jicha Miroslav

    2012-04-01

    Full Text Available Laser Doppler Anemometry (LDA and its modifications such as PhaseDoppler Particle Anemometry (P/DPA is point-wise method for optical nonintrusive measurement of particle velocity with high data rate. Conversion of the LDA velocity data from temporal to frequency domain – calculation of power spectral density (PSD of velocity fluctuations, is a non trivial task due to nonequidistant data sampling in time. We briefly discuss possibilities for the PSD estimation and specify limitations caused by seeding density and other factors of the flow and LDA setup. Arbitrary results of LDA measurements are compared with corresponding Hot Wire Anemometry (HWA data in the frequency domain. Slot correlation (SC method implemented in software program Kern by Nobach (2006 is used for the PSD estimation. Influence of several input parameters on resulting PSDs is described. Optimum setup of the software for our data of particle-laden air flow in realistic human airway model is documented. Typical character of the flow is described using PSD plots of velocity fluctuations with comments on specific properties of the flow. Some recommendations for improvements of future experiments to acquire better PSD results are given.

  13. Precise Model Analysis for 3-phase High Power Converter using the Harmonic State Space Modeling

    DEFF Research Database (Denmark)

    Kwon, Jun Bum; Wang, Xiongfei; Blaabjerg, Frede

    2015-01-01

    This paper presents about the generalized multi-frequency modeling and analysis methodology, which can be used in control loop design and stability analysis. In terms of the switching frequency of high power converter, there can be harmonics interruption if the voltage source converter has a low....... The modeling procedure shows the precision in the analysis of the stability as well as the controller design. The overall results are validated by using not only the non-linear time domain simulation, but also the analytical model....

  14. Calculation of harmonic losses and ampacity in low-voltage power cables when used for feeding large LED lighting loads

    Directory of Open Access Journals (Sweden)

    N. J. Milardovich

    2014-10-01

    Full Text Available A numerical investigation on the harmonic disturbances in low-voltage cables feeding large LED loads is reported. A frequency domain analysis on several commercially-available LEDs was performed to investigate the signature of the harmonic current injected into the power system. Four-core cables and four single-core cable arrangements (three phases and neutral of small, medium, and large conductor cross sections, with the neutral conductor cross section approximately equal to the half of the phase conductors, were examined. The cables were modelled by using electromagnetic finite-element analysis software. High harmonic power losses (up to 2.5 times the value corresponding to an undistorted current of the same rms value of the first harmonic of the LED current were found. A generalized ampacity model was employed for re-rating the cables. It was found that the cross section of the neutral conductor plays an important role in the derating of the cable ampacity due to the presence of a high-level of triplen harmonics in the distorted current. The ampacity of the cables should be derated by about 40 %, almost independent of the conductor cross sections. The calculation have shown that an incoming widespread use of LED lamps in lighting could create significant additional harmonic losses in the supplying low-voltage lines, and thus more severely harmonic emission limits should be defined for LED lamps.

  15. Outcomes of an international initiative for harmonization of low power and shutdown probabilistic safety assessment

    Directory of Open Access Journals (Sweden)

    Manna Giustino

    2010-01-01

    Full Text Available Many probabilistic safety assessment studies completed to the date have demonstrated that the risk dealing with low power and shutdown operation of nuclear power plants is often comparable with the risk of at-power operation, and the main contributors to the low power and shutdown risk often deal with human factors. Since the beginning of the nuclear power generation, human performance has been a very important factor in all phases of the plant lifecycle: design, commissioning, operation, maintenance, surveillance, modification, decommissioning and dismantling. The importance of this aspect has been confirmed by recent operating experience. This paper provides the insights and conclusions of a workshop organized in 2007 by the IAEA and the Joint Research Centre of the European Commission, on Harmonization of low power and shutdown probabilistic safety assessment for WWER nuclear power plants. The major objective of the workshop was to provide a comparison of the approaches and the results of human reliability analyses and gain insights in the enhanced handling of human factors.

  16. dSPACE Implementation of the Third Harmonic Insertion based Modulation on the Three Phase Power Inverter

    Directory of Open Access Journals (Sweden)

    Marian Gaiceanu

    2014-09-01

    Full Text Available This paper shows the implementation of real-time modulation based on the third order harmonic insertion in three-phase power inverter. Two methods of implementation have been proposed. As a working methodology the mathematical model of the duty cycles of the three- phase power inverter have been designed and implemented in Matlab/Simulink®. By an adequate design the appropriate ControlDesk interface send the adequate signals to power inverter and collect all the necessay data to be viewed. Harmonic analysis has been performed. The advantages of using this type of modulation are highlighted.

  17. Placental three-dimensional power Doppler indices in mid-pregnancy and late pregnancy complicated by gestational diabetes mellitus.

    Science.gov (United States)

    Surányi, A; Kozinszky, Z; Molnár, A; Nyári, T; Bitó, T; Pál, A

    2013-10-01

    The aim of our study was to evaluate placental three-dimensional power Doppler indices in diabetic pregnancies in the second and third trimesters and to compare them with those of the normal controls. Placental vascularization of pregnant women was determined by three-dimensional power Doppler ultrasound technique. The calculated indices included vascularization index (VI), flow index (FI), and vascularization flow index (VFI). Uncomplicated pregnancies (n = 113) were compared with pregnancies complicated by gestational diabetes mellitus (n = 56) and diabetes mellitus (n = 43). The three-dimensional power Doppler indices were not significantly different between the two diabetic subgroups. All the indices in diabetic patients were significantly reduced compared with those in non-diabetic individuals (p pregnancy [regression coefficients: -0.23 (FI), -0.06 (VI), and -0.04 (VFI)] and normal pregnancy [regression coefficients: -0.13 (FI), -0.20 (VI), and -0.11 (VFI)]. The uteroplacental circulation (umbilical and uterine artery) was not correlated significantly to the three-dimensional power Doppler indices. If all placental indices are low during late pregnancy, then the odds of the diabetes are significantly high (adjusted odds ratio: 1.10). A decreased placental vascularization could be an adjunct sonographic marker in the diagnosis of diabetic pregnancy in mid-gestation and late gestation. © 2013 John Wiley & Sons, Ltd.

  18. A method to validate quantitative high-frequency power doppler ultrasound with fluorescence in vivo video microscopy.

    Science.gov (United States)

    Pinter, Stephen Z; Kim, Dae-Ro; Hague, M Nicole; Chambers, Ann F; MacDonald, Ian C; Lacefield, James C

    2014-08-01

    Flow quantification with high-frequency (>20 MHz) power Doppler ultrasound can be performed objectively using the wall-filter selection curve (WFSC) method to select the cutoff velocity that yields a best-estimate color pixel density (CPD). An in vivo video microscopy system (IVVM) is combined with high-frequency power Doppler ultrasound to provide a method for validation of CPD measurements based on WFSCs in mouse testicular vessels. The ultrasound and IVVM systems are instrumented so that the mouse remains on the same imaging platform when switching between the two modalities. In vivo video microscopy provides gold-standard measurements of vascular diameter to validate power Doppler CPD estimates. Measurements in four image planes from three mice exhibit wide variation in the optimal cutoff velocity and indicate that a predetermined cutoff velocity setting can introduce significant errors in studies intended to quantify vascularity. Consistent with previously published flow-phantom data, in vivo WFSCs exhibited three characteristic regions and detectable plateaus. Selection of a cutoff velocity at the right end of the plateau yielded a CPD close to the gold-standard vascular volume fraction estimated using IVVM. An investigator can implement the WFSC method to help adapt cutoff velocity to current blood flow conditions and thereby improve the accuracy of power Doppler for quantitative microvascular imaging. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  19. Evaluation of algorithms for microperfusion assessment by fast simulations of laser Doppler power spectral density.

    Science.gov (United States)

    Wojtkiewicz, S; Liebert, A; Rix, H; Maniewski, R

    2011-12-21

    In classical laser Doppler (LD) perfusion measurements, zeroth- and first-order moments of the power spectral density of the LD signal are utilized for the calculation of a signal corresponding to the concentration, speed and flow of red blood cells (RBCs). We have analysed the nonlinearities of the moments in relation to RBC speed distributions, parameters of filters utilized in LD instruments and the signal-to-noise ratio. We have developed a new method for fast simulation of the spectrum of the LD signal. The method is based on a superposition of analytically calculated Doppler shift probability distributions derived for the assumed light scattering phase function. We have validated the method by a comparison of the analytically calculated spectra with results of Monte Carlo (MC) simulations. For the semi-infinite, homogeneous medium and the single Doppler scattering regime, the analytical calculation describes LD spectra with the same accuracy as the MC simulation. The method allows for simulating the LD signal in time domain and furthermore analysing the index of perfusion for the assumed wavelength of the light, optical properties of the tissue and concentration of RBCs. Fast simulations of the LD signal in time domain and its frequency spectrum can be utilized in applications where knowledge of the LD photocurrent is required, e.g. in the development of detectors for tissue microperfusion monitoring or in measurements of the LD autocorrelation function for perfusion measurements. The presented fast method for LD spectra calculation can be used as a tool for evaluation of signal processing algorithms used in the LD method and/or for the development of new algorithms of the LD flowmetry and imaging. We analysed LD spectra obtained by analytical calculations using a classical algorithm applied in classical LD perfusion measurements. We observed nonlinearity of the first moment M₁ for low and high speeds of particles (v 10 mm s⁻¹). It was also noted that

  20. Power Transformer Differential Protection Based on Neural Network Principal Component Analysis, Harmonic Restraint and Park's Plots

    Directory of Open Access Journals (Sweden)

    Manoj Tripathy

    2012-01-01

    Full Text Available This paper describes a new approach for power transformer differential protection which is based on the wave-shape recognition technique. An algorithm based on neural network principal component analysis (NNPCA with back-propagation learning is proposed for digital differential protection of power transformer. The principal component analysis is used to preprocess the data from power system in order to eliminate redundant information and enhance hidden pattern of differential current to discriminate between internal faults from inrush and overexcitation conditions. This algorithm has been developed by considering optimal number of neurons in hidden layer and optimal number of neurons at output layer. The proposed algorithm makes use of ratio of voltage to frequency and amplitude of differential current for transformer operating condition detection. This paper presents a comparative study of power transformer differential protection algorithms based on harmonic restraint method, NNPCA, feed forward back propagation neural network (FFBPNN, space vector analysis of the differential signal, and their time characteristic shapes in Park’s plane. The algorithms are compared as to their speed of response, computational burden, and the capability to distinguish between a magnetizing inrush and power transformer internal fault. The mathematical basis for each algorithm is briefly described. All the algorithms are evaluated using simulation performed with PSCAD/EMTDC and MATLAB.

  1. A hybrid filter to mitigate harmonics caused by nonlinear load and resonance caused by power factor correction capacitor

    Science.gov (United States)

    Adan, N. F.; Soomro, D. M.

    2017-01-01

    Power factor correction capacitor (PFCC) is commonly installed in industrial applications for power factor correction (PFC). With the expanding use of non-linear equipment such as ASDs, power converters, etc., power factor (PF) improvement has become difficult due to the presence of harmonics. The resulting capacitive impedance of the PFCC may form a resonant circuit with the source inductive reactance at a certain frequency, which is likely to coincide with one of the harmonic frequency of the load. This condition will trigger large oscillatory currents and voltages that may stress the insulation and cause subsequent damage to the PFCC and equipment connected to the power system (PS). Besides, high PF cannot be achieved due to power distortion. This paper presents the design of a three-phase hybrid filter consisting of a single tuned passive filter (STPF) and shunt active power filter (SAPF) to mitigate harmonics and resonance in the PS through simulation using PSCAD/EMTDC software. SAPF was developed using p-q theory. The hybrid filter has resulted in significant improvement on both total harmonic distortion for voltage (THDV) and total demand distortion for current (TDDI) with maximum values of 2.93% and 9.84% respectively which were within the recommended IEEE 519-2014 standard limits. Regarding PF improvement, the combined filters have achieved PF close to desired PF at 0.95 for firing angle, α values up to 40°.

  2. Effect of laparoscopic ovarian drilling on vascular endothelial growth factor and ovarian stromal blood flow using 3-dimensional power Doppler.

    Science.gov (United States)

    El Behery, Manal M; Diab, Abdalla E; Mowafy, Hala; Ebrahiem, Moustafa A; Shehata, Amal E

    2011-02-01

    To determine, by using 3-dimensional power Doppler ultrasonography, the effect of laparoscopic ovarian drilling (LOD) on the serum level of vascular endothelial growth factor (VEGF) and ovarian stromal blood flow changes in polycystic ovary syndrome (PCOS). A prospective controlled clinical study was conducted on 26 clomiphene-resistant women with PCOS who were scheduled for LOD and a control group of 22 fertile regularly menstruating women. VEGF and 3 ovarian Doppler indices-vascularization index, flow index, and vascularization flow index-were measured and compared between the 2 groups, and before and after LOD in the PCOS group. Serum VEGF and the Doppler indices of ovarian stromal blood flow were significantly higher in the PCOS group than in the control group. Serum VEGF and the ovarian stromal blood flow Doppler indices were significantly reduced in the PCOS group after LOD. Increased vascularity in PCOS demonstrated by Doppler blood flow measurements might be explained by the high level of VEGF. LOD reduced ovarian vascularization and serum VEGF. Copyright © 2010 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.

  3. Optimal Power and Efficiency of Quantum Thermoacoustic Micro-cycle Working in 1D Harmonic Trap

    Science.gov (United States)

    E, Qing; Wu, Feng; Yin, Yong; Liu, XiaoWei

    2017-10-01

    Thermoacoustic engines (including heat engines and refrigerators) are energy conversion devices without moving part. They have great potential in aviation, new energy utilization, power technology, refrigerating and cryogenics. The thermoacoustic parcels, which compose the working fluid of a thermoacoustic engine, oscillate within the sound channel with a temperature gradient. The thermodynamic foundation of a thermoacoustic engine is the thermoacoustic micro-cycle (TAMC). In this paper, the theory of quantum mechanics is applied to the study of the actual thermoacoustic micro-cycle for the first time. A quantum mechanics model of the TAMC working in a 1D harmonic trap, which is named as a quantum thermoacoustic micro-cycle (QTAMC), is established. The QTAMC is composed of two constant force processes connected by two straight line processes. Analytic expressions of the power output and the efficiency for QTAMC have been derived. The effects of the trap width and the temperature amplitude on the power output and the thermal efficiency have been discussed. Some optimal characteristic curves of power output versus efficiency are plotted, and then the optimization region of QTAMC is given in this paper. The results obtained here not only enrich the thermoacoustic theory but also expand the application of quantum thermodynamics.

  4. ANALYSIS OF THE HARMONIC LOSSES WITH ARTIFICIAL NEURAL NETWORKS IN UNBALANCED SYSTEM LOSSES USING BALANCED ELECTRIC POWER SYSTEM DATA

    Directory of Open Access Journals (Sweden)

    Aslan İNAN

    2005-01-01

    Full Text Available The losses in the power systems should be low as possible as. Saving energy instead of loses (kWh in power utilities can supply much more energy to the consumers. The lower losses the more energy is saved and thus the power system becomes more economical. In recent years, the increasing number of applications and power ratings of the devices which have nonlinear voltage-current characteristics cause voltage waveform distortion and additional losses. While evaluating losses considering harmonics will provide more contribution to obtain more accurate results. In this study, Artificial Neural Networks (ANN method has been presented to predict the harmonic losses in unbalanced power systems by using the data from balanced power system with nonlinear loads.

  5. dSPACE Implementation of the Third Harmonic Insertion based Modulation on the Three Phase Power Inverter

    OpenAIRE

    Marian Gaiceanu; Cristian Nichita

    2014-01-01

    This paper shows the implementation of real-time modulation based on the third order harmonic insertion in three-phase power inverter. Two methods of implementation have been proposed. As a working methodology the mathematical model of the duty cycles of the three- phase power inverter have been designed and implemented in Matlab/Simulink®. By an adequate design the appropriate ControlDesk interface send the adequate signals to power inverter and collect all the necessay dat...

  6. Extremum seeking x-ray position feedback using power line harmonic leakage as the perturbation

    Energy Technology Data Exchange (ETDEWEB)

    Zohar, S.; Kissick, D. J.; Venugopalan, N.; Ogata, C. M.; Makarov, O.; Stepanov, S.; Fischetti, R. F.

    2016-09-01

    Small x-ray beam sizes necessary for probing nanoscale phenomena require exquisite stability to prevent data corruption by noise. One source of instability at synchrotron radiation x-ray beamlines is the slow detuning of x-ray optics to marginal alignment where the onset of clipping increases the beam's susceptibility to higher frequency position oscillations. In this article, we show that a 1 mu m amplitude horizontal x-ray beam oscillation driven by power line harmonic leakage into the electron storage ring can be used as perturbation for horizontal position extremum seeking feedback. Feedback performance is characterized by convergence to 1.5% away from maximum intensity at optimal alignment.

  7. Extremum seeking x-ray position feedback using power line harmonic leakage as the perturbation

    Energy Technology Data Exchange (ETDEWEB)

    Zohar, S.; Kissick, D. J.; Venugopalan, N.; Ogata, C. M.; Makarov, O.; Stepanov, S.; Fischetti, R. F.

    2016-09-01

    Small X-ray beam sizes necessary for probing nanoscale phenomena require exquisite stability to prevent data corruption by noise. One source of instability at synchrotron radiation X-ray beamlines is the slow detuning of X-ray optics to marginal alignment where the onset of clipping increases the beam’s susceptibility to higher frequency position oscillations. In this article, we show that a 1 µm amplitude horizontal X-ray beam oscillation driven by power line harmonic leakage into the electron storage ring can be used as perturbation for horizontal position extremum seeking feedback. Feedback performance is characterized by convergence to 1.5% away from maximum intensity at optimal alignment.

  8. Extremum seeking x-ray position feedback using power line harmonic leakage as the perturbation

    Directory of Open Access Journals (Sweden)

    S. Zohar

    2016-09-01

    Full Text Available Small x-ray beam sizes necessary for probing nanoscale phenomena require exquisite stability to prevent data corruption by noise. One source of instability at synchrotron radiation x-ray beamlines is the slow detuning of x-ray optics to marginal alignment where the onset of clipping increases the beam’s susceptibility to higher frequency position oscillations. In this article, we show that a 1  μm amplitude horizontal x-ray beam oscillation driven by power line harmonic leakage into the electron storage ring can be used as perturbation for horizontal position extremum seeking feedback. Feedback performance is characterized by convergence to 1.5% away from maximum intensity at optimal alignment.

  9. Musculoskeletal colour/power Doppler in sports medicine: image parameters, artefacts, image interpretation and therapy

    DEFF Research Database (Denmark)

    Boesen, M I; Boesen, Mikael; Kønig, Merete Juhl

    2010-01-01

    This review article discusses the aspects of sports medicine where musculoskeletal Doppler ultrasound has valuable contribution in diagnosis and/or treatment of some of the typical musculoskeletal sports injuries. Also, conditions where the Doppler ultrasound has no value are discussed. Some...

  10. Musculoskeletal colour/power Doppler in sports medicine: image parameters, artefacts, image interpretation and therapy

    DEFF Research Database (Denmark)

    Boesen, M I; Boesen, Mikael; Kønig, Merete Juhl

    2011-01-01

    This review article discusses the aspects of sports medicine where musculoskeletal Doppler ultrasound has valuable contribution in diagnosis and/or treatment of some of the typical musculoskeletal sports injuries. Also, conditions where the Doppler ultrasound has no value are discussed. Some...

  11. Harmonics in Offshore Wind Power Plants Employing Power Electronic Devices in the Transmission System

    DEFF Research Database (Denmark)

    Glasdam, Jakob Bærholm

    of wind power. The onshore as well as offshore wind power plants (OWPPs) therefore have to meet the same stringent requirement as the conventional power plants. This can be accommodated by employment of flexible alternating current transmission system (FACTS) devices, such as the static compensator...... approach. Previously, a detailed equivalent model of the MMCC VSC-HVDC has been devised based on the “Nested Fast and Simultaneous Solution” procedure. However, there are some limitations to the previous model as it is specifically intended for the MMCC employing half-bridge converters in the SMs....... The somewhat more complex structure of the full-bridge converter employed in the MMCC STATCOM makes it complex to apply the existing modelling approach for the STATCOM. A universal modelling technique is proposed, which is able to represent both the half- and full-bridge based SMs. The modelling technique...

  12. Three-dimensional power Doppler study of endometrial and subendometrial microvascularization in women with intrauterine device-induced menorrhagia.

    Science.gov (United States)

    El-Mazny, Akmal; Abou-Salem, Nermeen; Elshenoufy, Hossam

    2013-06-01

    To evaluate endometrial and subendometrial microvascularization, using three-dimensional (3D) power Doppler ultrasound, in women with intrauterine device (IUD)-induced menorrhagia; and whether those potential findings could predict the risk of bleeding before IUD insertion. Prospective clinical trial. University teaching hospital. One hundred twenty women, who requested the insertion of a copper IUD for contraception. Endometrial thickness and volume, uterine artery pulsatility index and resistance index, and endometrial and subendometrial 3D power Doppler vascularization index, flow index, and vascularization flow index were measured twice: immediately before and 3 months after IUD insertion. Doppler indices before and after IUD insertion. Before IUD insertion, no significant difference was detected in the clinical characteristics, endometrial thickness and volume, and Doppler indices between women who had IUD-induced menorrhagia (n = 47) and those without menorrhagia (n = 73). However, after IUD insertion, there was a significant increase in the endometrial and subendometrial vascularization index, flow index, and vascularization flow index in women with menorrhagia, whereas other parameters remained not significantly different between the two groups. Endometrial and subendometrial microvascularization increases in women with IUD-induced menorrhagia; however, this finding has no predictive value before IUD insertion. Copyright © 2013 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

  13. Capacity Calculation of Shunt Active Power Filters for Electric Vehicle Charging Stations Based on Harmonic Parameter Estimation and Analytical Modeling

    Directory of Open Access Journals (Sweden)

    Niancheng Zhou

    2014-08-01

    Full Text Available The influence of electric vehicle charging stations on power grid harmonics is becoming increasingly significant as their presence continues to grow. This paper studies the operational principles of the charging current in the continuous and discontinuous modes for a three-phase uncontrolled rectification charger with a passive power factor correction link, which is affected by the charging power. A parameter estimation method is proposed for the equivalent circuit of the charger by using the measured characteristic AC (Alternating Current voltage and current data combined with the charging circuit constraints in the conduction process, and this method is verified using an experimental platform. The sensitivity of the current harmonics to the changes in the parameters is analyzed. An analytical harmonic model of the charging station is created by separating the chargers into groups by type. Then, the harmonic current amplification caused by the shunt active power filter is researched, and the analytical formula for the overload factor is derived to further correct the capacity of the shunt active power filter. Finally, this method is validated through a field test of a charging station.

  14. Second-Order Harmonic Reduction Technique for Photovoltaic Power Conditioning Systems Using a Proportional-Resonant Controller

    Directory of Open Access Journals (Sweden)

    Hae-Gwang Jeong

    2013-01-01

    Full Text Available This paper proposes a second-order harmonic reduction technique using a proportional-resonant (PR controller for a photovoltaic (PV power conditioning system (PCS. In a grid-connected single-phase system, inverters create a second-order harmonic at twice the fundamental frequency. A ripple component unsettles the operating points of the PV array and deteriorates the operation of the maximum power point tracking (MPPT technique. The second-order harmonic component in PV PCS is analyzed using an equivalent circuit of the DC/DC converter and the DC/AC inverter. A new feed-forward compensation technique using a PR controller for ripple reduction is proposed. The proposed algorithm is advantageous in that additional devices are not required and complex calculations are unnecessary. Therefore, this method is cost-effective and simple to implement. The proposed feed-forward compensation technique is verified by simulation and experimental results.

  15. A Numerical Matrix-Based Method for Stability and Power Quality Studies Based on Harmonic Transfer Functions

    DEFF Research Database (Denmark)

    Dowlatabadi, Mohammadkazem Bakhshizadeh; Blaabjerg, Frede; Hjerrild, Jesper

    2017-01-01

    Some couplings exist between the positive- and negative-sequence impedances of a voltage sourced power converter especially in the low frequency range due to the nonlinearities and low bandwidth control loops like the PLL. In this paper, a new numerical method based on the Harmonic Transfer...... these couplings a matrix based method should be used. No information about the structure of the converter is needed and elements are modelled as black boxes with known terminal characteristics. The proposed method is applicable for both power quality (harmonic and inter-harmonic emissions) and stability studies...... Function for analysis of the Linear Time Periodic systems is presented, which is able to handle these couplings. In a balanced three-phase system, there is only one coupling term, but in an unbalanced (asymmetrical) system, there are more couplings, and therefore, in order to study the interactions between...

  16. Measurement of the Stopping Power of Water for Carbon Ions Using Inverted Doppler Shift Attenuation

    Energy Technology Data Exchange (ETDEWEB)

    Rahm, J.M. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); II. Physikalisches Institut, Universitaet Goettingen (Germany); Baek, W.Y.; Rabus, H. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Hofsaess, H. [II. Physikalisches Institut, Universitaet Goettingen (Germany)

    2015-07-01

    Carbon ion therapy has gained importance in cancer treatment due to its locally well confined dose distribution, but there is a significant lack of experimental data which is needed for dose calculations and estimation of biological damage. Since tissue is mainly comprised of water, the energy-dependent stopping power of water is the critical measure. Importantly, previous data gathered from experiments with light ions has been limited to water vapour and ice and neglected water in its liquid phase. Additionally, theoretical models regarding the stopping power cannot yet describe the complex charge transfer interactions of the projectile at velocities in the range of the mean velocity of the valence electrons of the traversed medium. There are also discrepancies in the amount of phase effects concerning water and water vapour cross sections. Despite its importance there exists no experimental data for the stopping power of water for carbon ions in the energy region between 1 MeV and 5 MeV. This may be due to the short track length of carbon ions which makes traditional transmission experiments unfeasible. Therefore a project was launched to measure the stopping power of liquid water for carbon ions in the vicinity of the Bragg peak which corresponds to the energy regime of the maximum stopping power. For this measurement the inverted Doppler shift attenuation method was used. This uses the gamma quanta emitted from excited carbon nuclei which are produced by means of the {sup 12}C(α,α'){sup 12}C* reaction. The recorded γ-spectra contain the information of the projectiles velocity at the time they decay to their ground state and an internal clock provided by the exponential decay law. The deceleration of the projectile is directly connected to the stopping power which can be determined with this method as a function of the projectiles kinetic energy. Further measurements have been carried out to improve the experimental method. The setup and the preliminary

  17. Development of a single-phase harmonic power flow program to study the 20 kHz AC power system for large spacecraft

    Science.gov (United States)

    Kraft, L. Alan; Kankam, M. David

    1991-01-01

    The development of software is described to aid in design and analysis of AC power systems for large spacecraft. The algorithm is an important version of harmonic power flow program, HARMFLO, used for the study of AC power quality. The new program is applicable to three-phase systems typified by terrestrial power systems, and single-phase systems characteristic of space power systems. The modified HARMFLO accommodates system operating frequencies ranging from terrestrial 60 Hz to and beyond aerospace 20 kHz, and can handle both source and load-end harmonic distortions. Comparison of simulation and test results of a representative spacecraft power system shows a satisfactory correlation. Recommendations are made for the direction of future improvements to the software, to enhance its usefulness to power system designer and analysts.

  18. Edge loss of high-harmonic fast-wave heating power in NSTX: a cylindrical model

    Science.gov (United States)

    Perkins, R. J.; Hosea, J. C.; Bertelli, N.; Taylor, G.; Wilson, J. R.

    2017-11-01

    Efficient high-harmonic fast-wave (HHFW) heating in the National Spherical Torus Experiment Upgrade (NSTX-U) would facilitate experiments in turbulence, transport, fast-ion studies, and more. However, previous HHFW operation in NSTX exhibited a large loss of fast-wave power to the divertor along the scrape-off layer field lines for edge densities above the fast-wave cutoff. It was postulated that the wave amplitude is enhanced in the scrape-off layer due to cavity-like modes, and that these enhanced fields drive sheath losses through RF rectification. As part of ongoing work to confirm this hypothesis, we have developed a cylindrical cold-plasma model to identify and understand scenarios where a substantial fraction of wave power is confined to the plasma periphery. We previously identified a peculiar class of modes, named annulus resonances, that conduct approximately half of their wave power in the periphery and can also account for a significant fraction of the total wave power. Here, we study the influence of annulus resonances on wave field reconstructions and find instances where annulus-resonant modes dominate the spectrum and trap over half of the total wave power at the edge. The work is part of an ongoing effort to determine the mechanism underlying these scrape-off layer losses in NSTX, identify optimal conditions for operation in NSTX-U, and predict whether similar losses occur for the ion-cyclotron minority heating scheme for both current experiments and future devices such as ITER.

  19. Role of Duplex Power Doppler Ultrasound in Differentiation between Malignant and Benign Thyroid Nodules

    Energy Technology Data Exchange (ETDEWEB)

    Algin, Oktay [Ataturk Training and Research Hospital Bilkent, Ankara (Turkmenistan); Algin, Efnan [Gazi University Medical Faculty, Ankara (Turkmenistan); Gokalp, Gokhan; Ocakog, Gokhan; Erdog an, Cuneyt; Saraydaroglu, Ozlem; Ercan Tuncel, Prof [Uludag University Medical Faculty, Bursa (Turkmenistan)

    2010-12-15

    To evaluate the usage of duplex power Doppler ultrasound (PDUS) for the differentiation of benign and malignant thyroid nodules. We prospectively examined 77 thyroid nodules in 60 patients undergoing ultrasound-guided fine needle aspiration biopsy (FNAB). Each nodule was described according to size, inner structure, borders, parenchymal echogenicity, peripheral halo formation, and the presence of calcification (Bmode ultrasound findings). Vascularity as determined by PDUS imaging was defined as non-vascular, peripheral, central, or of mixed type. For each nodule, the pulsatility index (PI) and resistive index (RI) values were obtained. Results of FNAB and surgical pathological examination (if available) were used as a proof of final diagnosis to categorize all nodules as benign or malignant. A receiver operating characteristic (ROC) curve analysis was performed to establish cut-off, sensitivity, and specificity values associated with RI-PI values. A significant relationship was observed between malignancy and irregular margins, microcalcifications, and hypoechogenicity on ultrasound examination (p < 0.05). The pattern of vascularity as determined by PDUS analysis was not a statistically significant criterion to suggest benign or malignant disease in this study (p > 0.05). The central, peripheral, and mean RI-PI values were higher in malignant nodules when compared to the other cytologies (p < 0.05). Vascularity is not a useful parameter for distinguishing malignant from benign thyroid nodules. However, RI and PI values are useful in distinguishing malignant from benign thyroid nodules

  20. Harmonic Composition of the Currents of Power Windings in 500 KV Thyristor Controlled Shunt Reactor with Split Valveside Windings

    Energy Technology Data Exchange (ETDEWEB)

    Matinyan, A. M., E-mail: al-drm@mail.ru; Peshkov, M. V.; Karpov, V. N.; Alekseev, N. A. [JSC “R& D Center at Federal Grid Company of Unified Power System” (Russian Federation)

    2016-09-15

    The design and current spectrum of a thyristor valve controlled shunt reactor (TCSR) with split valveside windings are described. The dependence of the amplitudes of higher-order harmonics of the power winding current on the TCSR operating regime are presented for this TCSR design.

  1. Ground States for the Schrödinger Systems with Harmonic Potential and Combined Power-Type Nonlinearities

    Directory of Open Access Journals (Sweden)

    Baiyu Liu

    2014-01-01

    Full Text Available We consider a class of coupled nonlinear Schrödinger systems with potential terms and combined power-type nonlinearities. We establish the existence of ground states, by using a variational method. As an application, some symmetry results for ground states of Schrödinger systems with harmonic potential terms are obtained.

  2. Harmonic Injection-Based Power Fluctuation Control of Three-Phase PV Systems under Unbalanced Grid Voltage Conditions

    Directory of Open Access Journals (Sweden)

    Nian-Cheng Zhou

    2015-02-01

    Full Text Available Unbalanced voltage will inevitably cause power and DC voltage fluctuations in a three-phase PV system. The deterioration of power quality will do great harm to the PV panels and the loads, so it is necessary to suppress the power fluctuations. This paper further explores the coefficients control strategy of PV converters under unbalanced voltage conditions, aiming to suppress power fluctuations by controlling the injection of some specific orders of current harmonics into the grid. In order to achieve this, the current reference of the PV inverter has been changed by bringing in two control coefficients, and the expression of each order of the current harmonics has been deduced. Based on the standards of PV systems, the regions from which the coefficients can be selected are determined. Then, by tuning these coefficients in the feasible regions, the output parameters (power fluctuation, current THD and odd harmonics can be controlled precisely. The model of this method is built and simulated in PSCAD/EMTDC, and as a result, it is shown that the power fluctuations can be restricted according to different power quality requirements.

  3. The Contribution of Three-Dimensional Power Doppler Imaging in the Preoperative Assessment of Breast Tumors: A Preliminary Report

    Directory of Open Access Journals (Sweden)

    K. Kalmantis

    2009-01-01

    Methods. One hundred and twenty five women with clinically or mammographically suspicious findings were referred for 3D Power Doppler ultrasound prior to surgery. Histological diagnosis was conducted after surgery and compared with ultrasound findings. Sonographic criteria used for breast cancer diagnosis were based on a system that included morphological characteristics and criteria of the vascular pattern of a breast mass by Power Doppler imaging. Results. Seventy-two lesions were histopathologically diagnosed as benign and 53 tumors as malignant. Three-dimensional ultrasound identified 49 out of 53 histologically confirmed breast cancers resulting in a sensitivity of 92.4% and a specificity of 86.1% in diagnosing breast malignancy (PPV: 0.83, NPV:0.94. Conclusions. 3D ultrasonography is a valuable tool in identifying preoperatively the possibility of a tumor to be malignant.

  4. Power grid current harmonics mitigation drawn on low voltage rated switching devices with effortless control

    Energy Technology Data Exchange (ETDEWEB)

    Marques, Hugo S.; Anunciada, Victor; Borges, Beatriz V. [Power Electronics Group, Instituto de Telecomunicacoes, Lisbon (Portugal); Instituto Superior Tecnico - Universidade Tecnica de Lisboa, Lisbon (Portugal)

    2010-01-15

    The great majority of the existing hybrid active power filter solutions is normally focused in 3{phi} systems and, in general, concentrates its domain of application in specific loads with deterministic behavior. Because common use grids do not exhibit these characteristics, it is mandatory to develop solutions for more generic scenarios, encouraging the use of less classical hybrid solutions. In fact, due to the widely use of switch mode converters in a great variety of consumer electronics, the problematic of mains current harmonic mitigation is no longer an exclusive matter of 3{phi} systems. The contribution of this paper is to present a shunt hybrid active power filter topology, initially conceived to work in 1{phi} domestic grids, able to operate the inverter at a voltage rate that can be lower than 10% of the mains voltage magnitude, even under nonspecific working conditions. In addition, the results shown in this paper demonstrate that this topology can, without lack of generality, be suitable to medium voltage (1{phi} or 3{phi}) systems. A new control approach for the proposed topology is discussed in this paper. The control method exhibits an extremely simple architecture requiring single point current sensing only, with no need for any kind of reference. Its practical implementation can be fulfilled by using very few, common use, operational amplifiers. The principle of operation, design criteria, simulation predictions and experimental results are presented and discussed. (author)

  5. Harmonic statistics

    Energy Technology Data Exchange (ETDEWEB)

    Eliazar, Iddo, E-mail: eliazar@post.tau.ac.il

    2017-05-15

    The exponential, the normal, and the Poisson statistical laws are of major importance due to their universality. Harmonic statistics are as universal as the three aforementioned laws, but yet they fall short in their ‘public relations’ for the following reason: the full scope of harmonic statistics cannot be described in terms of a statistical law. In this paper we describe harmonic statistics, in their full scope, via an object termed harmonic Poisson process: a Poisson process, over the positive half-line, with a harmonic intensity. The paper reviews the harmonic Poisson process, investigates its properties, and presents the connections of this object to an assortment of topics: uniform statistics, scale invariance, random multiplicative perturbations, Pareto and inverse-Pareto statistics, exponential growth and exponential decay, power-law renormalization, convergence and domains of attraction, the Langevin equation, diffusions, Benford’s law, and 1/f noise. - Highlights: • Harmonic statistics are described and reviewed in detail. • Connections to various statistical laws are established. • Connections to perturbation, renormalization and dynamics are established.

  6. Characterization of quasi-phase-matching gratings in quadratic media through double-pass second-harmonic power measurements

    DEFF Research Database (Denmark)

    Johansen, Steffen Kjær; Baldi, Pascal

    2004-01-01

    A new scheme for nondestructive characterization of quasi-phase-matching grating structures and temperature gradients through inverse Fourier theory using second-harmonic-generation experiments is proposed. By inserting a mirror to reflect the signals back through the sample, we show how it is po......A new scheme for nondestructive characterization of quasi-phase-matching grating structures and temperature gradients through inverse Fourier theory using second-harmonic-generation experiments is proposed. By inserting a mirror to reflect the signals back through the sample, we show how...... it is possible to retrieve the relevant information by measuring only the generated second-harmonic power, avoiding more complicated phase measurements. The potential of the scheme is emphasized through theoretical and numerical investigations in the case of periodically poled lithium niobate bulk crystals....

  7. Forecasting of harmonics distortions in electric power systems, using impedance matrix of harmonic bus; Previsao de distorcoes harmonicas em sistemas eletricos de potencia, utilizando-se matriz impedancia de barra harmonica

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Clider Adriane de Sousa

    1993-11-01

    The present work is a contribution to the study of harmonics in electric power systems. It presents a focus returned to the planning area, in the sense of evaluating in a qualitative way the possible situations of harmonic distortions of voltage that can occur when of the installation of electric loads with not-linear behaviors in a power system. Using the domain of the frequency, as well as a monophase treatment, it intends to present a computational method of simple and fast processing to be used for evaluation of these harmonic distortions of voltage in power systems. Its main characteristic is the methodology used for the treatment of the harmonic injections on the part of non-linear loads, that it allows to supply a previous diagnosis of the behavior of the system, before the presence of such loads, before even of its effective installation.

  8. Power Doppler ultrasound phenotyping of expanding versus collapsed popliteal lymph nodes in murine inflammatory arthritis.

    Directory of Open Access Journals (Sweden)

    Echoe M Bouta

    Full Text Available Rheumatoid arthritis is a chronic inflammatory disease manifested by episodic flares in affected joints that are challenging to predict and treat. Longitudinal contrast enhanced-MRI (CE-MRI of inflammatory arthritis in tumor necrosis factor-transgenic (TNF-Tg mice has demonstrated that popliteal lymph nodes (PLN increase in volume and contrast enhancement during the pre-arthritic "expanding" phase of the disease, and then suddenly "collapse" during knee flare. Given the potential of this biomarker of arthritic flare, we aimed to develop a more cost-effective means of phenotyping PLN using ultrasound (US imaging. Initially we attempted to recapitulate CE-MRI of PLN with subcutaneous footpad injection of US microbubbles (DEFINITY®. While this approach allowed for phenotyping via quantification of lymphatic sinuses in PLN, which showed a dramatic decrease in collapsed PLN versus expanding or wild-type (WT PLN, electron microscopy demonstrated that DEFINITY® injection also resulted in destruction of the lymphatic vessels afferent to the PLN. In contrast, Power Doppler (PD US is innocuous to and efficiently quantifies blood flow within PLN of WT and TNF-Tg mice. PD-US demonstrated that expanding PLN have a significantly higher normalized PD volume (NPDV versus collapsed PLN (0.553 ± 0.007 vs. 0.008 ± 0.003; p0.030 and lower (<0.016 quartile NPDVs in this cohort of mice, which serve as conservative thresholds to phenotype PLN as expanding and collapsed, respectively. Interestingly, of the 12 PLN phenotyped by the two methods, there was disagreement in 4 cases in which they were determined to be expanding by CE-MRI and collapsed by PD-US. Since the adjacent knee had evidence of synovitis in all 4 cases, we concluded that the PD-US phenotyping was correct, and that this approach is currently the safest and most cost-effective in vivo approach to phenotype murine PLN as a biomarker of arthritic flare.

  9. Radial artery cannulation decreases the distal arterial blood flow measured by power Doppler ultrasound.

    Science.gov (United States)

    Numaguchi, Atsushi; Adachi, Yushi U; Aoki, Yoshitaka; Ishii, Yasuhiro; Suzuki, Katsumi; Obata, Yukako; Sato, Shigehito; Nishiwaki, Kimitoshi; Matsuda, Naoyuki

    2015-10-01

    Radial arterial cannulation is a popular technique for continuous hemodynamic monitoring in an area of anesthesia and intensive care. Although the risk for invasive monitoring is considerable, there is scarce information about the change in blood flow of cannulated vessel after the catheterization. In the current investigation, we evaluated the change in the cannulated arterial blood flow. Six volunteers (study 1) and eight post-surgical patients (study 2) were enrolled into the studies. In the study 1, the both side of diameter of radial artery (RA), ulnar artery (UA) and dorsal branch of radial artery (DBRA) of participants were measured using power Doppler ultrasound (PDU) with or without proximal oppression. In the study 2, the diameter of RA, UA and DBRA of the both intact and cannulated side were compared. Study 1: The diameter of RA was 3.4 (0.52) [mean (SD)] mm and the proximal oppression significantly decreased the diameter to 1.8 (0.59) mm. The diameter of DBRA measured by PDU also decreased 2.0 (0.60)-1.3 (0.59) mm. Study 2: There was no difference between the diameters of right and left RA, however, the UA was larger [3.4 (0.60) vs. 2.8 (0.83) mm] and the DBRA was narrower [1.4 (0.43) vs. 2.0 (0.47) mm] in the cannulated side. The diameters of DBRA were different between the intact and cannulated side in the patients. Although there is no information of relationships between cause of severe complication and decreased flow, significant reduction of blood flow should be concerned.

  10. Power Doppler Ultrasonography and Shear Wave Elastography as Complementary Imaging Methods for Suspected Local Breast Cancer Recurrence.

    Science.gov (United States)

    Jales, Rodrigo Menezes; Dória, Maira Teixeira; Serra, Kátia Piton; Miranda, Mila Meneguelli; Menossi, Carlos Alberto; Schumacher, Klaus; Sarian, Luis Otávio

    2017-12-04

    To prospectively investigate the diagnostic accuracy and clinical consequences of power Doppler morphologic criteria and shear wave elastography (SWE) as complementary imaging methods for evaluation of suspected local breast cancer recurrence in the ipsilateral breast or chest wall. Thirty-two breast masses with a suspicion of local breast cancer recurrence on B-mode ultrasonography underwent complementary power Doppler and SWE evaluations. Power Doppler morphologic criteria were classified as avascular, hypovascular, or hypervascular. Shear wave elastography was classified according to a 5-point scale (SWE score) and SWE maximum elasticity. Diagnostic accuracy was assessed by the sensitivity, specificity, and area under the curve. A decision curve analysis assessed clinical consequences of each method. The reference standard for diagnosis was defined as core needle or excisional biopsy. Histopathologic examinations revealed 9 (28.2%) benign and 23 (71.8%) malignant cases. Power Doppler ultrasonography (US) had sensitivity of 34.8% (95% confidence interval [CI], 6.6%-62.9%) and specificity of 45.4% (95% CI, 19.3%-71.5%). The SWE score (≥3) had sensitivity of 87.0% (95% CI, 66.4%-97.2%) and specificity of 44.4% (95% CI, 13.7%-78.8%). The SWE maximum elasticity (velocity > 6.5cm/s) had sensitivity of 87% (95% CI, 66.4%-97.2%) and specificity of 77.8% (95% CI, 40.0% to 97.2%). The areas under the curves for the SWE score and SWE maximum elasticity were 0.71 (95% CI, 0.53-0.87) and 0.82 (95% CI, 0.64-0.93), respectively (P = .32). Power Doppler US is unsuitable for discrimination between local breast cancer recurrence and fibrosis. Although the SWE score and SWE maximum elasticity can make this discrimination, the use of these methods to determine biopsy may lead to poorer clinical outcomes than the current practice of performing biopsies of all suspicious masses. © 2017 by the American Institute of Ultrasound in Medicine.

  11. Frequency Response Analysis of Current Controllers for Selective Harmonic Compensation in Active Power Filters

    DEFF Research Database (Denmark)

    Lascu, C.; Asiminoaei, L.; Boldea, I.

    2009-01-01

    different. It emerges that the fourth one has superior behavior and robustness and can stably work at higher frequencies than the others. Theoretical findings and analysis are supported by comparative experimental results on a 7-kVA laboratory setup. The highest harmonic frequency that can be stably...... to achieve zero phase shift and unity gain in the closed-loop transfer function for selected harmonics. The complete current controller is the superposition of all individual harmonic controllers and may be implemented in various reference frames. The analysis is focused on the comparison of harmonic...... and total closed-loop transfer functions for each controller. Analytical similarities and differences between schemes in terms of frequency response characteristics are emphasized. It is concluded that three of them have identical harmonic behavior despite the fact that their implementation is significantly...

  12. Power and pulsed Doppler evaluation of prostatic artery blood flow in normal and benign prostatic hyperplasia-affected dogs.

    Science.gov (United States)

    Zelli, R; Orlandi, R; Troisi, A; Cardinali, L; Polisca, A

    2013-10-01

    This study was carried out with the objectives to test the differences in the haemodynamic characteristics of the prostatic artery in normal and benign prostatic hyperplasia (BPH)-affected dogs using Doppler ultrasonography. In sixteen male German shepherd dogs, prostatic volume was detected and prostatic biopsy was performed. The prostatic artery blood flow parameters determined were as follows: peak systolic velocity (PSV), end diastolic velocity (EDV), Resistive Index (RI) and Pulsatility Index. The power Doppler mode was used for colour flow mapping of the prostatic artery. In PW mode at marginal locations, the waveforms recorded showed a continuous pattern typical of the high-resistance vessels, while in subcapsular locations, the waveforms recorded were continuous characteristic of the low-resistance vessel. Peak systolic velocity and EDV in both locations were significantly higher in BPH group (p flow in the prostatic artery in dogs affected with BPH. Moreover, statistically significant differences of blood flow velocities in prostatic artery in normal and BPH-affected dogs were detected. The RI was not able to differentiate normal dogs from dogs affected by BPH and therefore is not a parameter usable for diagnostic purposes, while Power Doppler could represent an additional diagnostic tool. © 2013 Blackwell Verlag GmbH.

  13. Sliding mode controller for four leg shunt active power filter to eliminating zero sequence current, compensating harmonics and reactive power with fixed switching frequency

    Directory of Open Access Journals (Sweden)

    Chebabhi Ali

    2015-01-01

    Full Text Available In this paper, the four leg inverter controlled by the three dimensional space vector modulation (3D SVM is used as the shunt active power filter (SAPF for compensating the three phase four wire electrical network, by using the four leg inverter with 3D SVM advantages to eliminated zero sequence current, fixed switching frequency of inverter switches, and reduced switching losses. This four leg inverter is employed as shunt active power filter to minimizing harmonic currents, reducing magnitude of neutral wire current, eliminating zero sequence current caused by nonlinear single phase loads and compensating reactive power, and a nonlinear sliding mode control technique (SMC is proposed for harmonic currents and DC bus voltage control to improve the performances of the three phase four wire four leg shunt active power filter based on Synchronous Reference Frame (SRF theory in the dq0 axes, and to decoupling the four leg SAPF mathematical model.

  14. Waveguide Multimode Directional Coupler for Harvesting Harmonic Power from the Output of Traveling-Wave Tube Amplifiers

    Science.gov (United States)

    Simons, Rainee N.; Wintucky, Edwin G.

    2017-01-01

    The paper presents the design, fabrication, and test results for a novel waveguide multimode directional coupler (MDC). The coupler fabricated from dissimilar frequency band waveguides, is capable of isolating power at the 2nd harmonic frequency from the fundamental power at the output port of a high power traveling-wave tube amplifier. The major advantage of the MDC is significantly lower insertion loss compared to a diplexer. The presentation slides for the paper that was approved is attached. The tracking number for the paper that was approved is TN 37015.

  15. High-power green light generation by second harmonic generation of single-frequency tapered diode lasers

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin; Andersen, Peter E.; Sumpf, Bernd

    2010-01-01

    laser emits in excess of 9 W single-frequency output power with a good beam quality. The output from the tapered diode laser is frequency doubled using periodically poled MgO:LiNbO3. We investigate the modulation potential of the green light and improve the modulation depth from 1:4 to 1:50.......We demonstrate the generation of high power (>1.5W) and single-frequency green light by single-pass second harmonic generation of a high power tapered diode laser. The tapered diode laser consists of a DBR grating for wavelength selectivity, a ridge section and a tapered section. The DBR tapered...

  16. Evaluation of the effect of machine settings on quantitative three-dimensional power Doppler angiography: an in-vitro flow phantom experiment.

    Science.gov (United States)

    Raine-Fenning, N J; Nordin, N M; Ramnarine, K V; Campbell, B K; Clewes, J S; Perkins, A; Johnson, I R

    2008-09-01

    Three-dimensional (3D) ultrasound is being used increasingly to acquire and subsequently quantify power Doppler data within the clinical setting. One proprietary software package calculates three 3D vascular indices: the vascularization index (VI), the flow index (FI), and the vascularization flow index (VFI). Our aim was to evaluate how different settings affect the Doppler signal in terms of its quantification by these three indices within a 3D dataset. A computer-driven 'flow phantom' was used to continuously pump a nylon particle-based blood mimic (Orgasol(trade mark)) around a closed system through a C-flex(trade mark) tube embedded in an agar-based tissue mimic. The test tanks were insonated with a modified 3D transvaginal 4-8-MHz ultrasound transducer (V530D) and power Doppler data were acquired over a series of different settings. Each experiment involved the manipulation of just one Doppler setting in order to study it in isolation. As expected, all of the power Doppler settings, when altered, were found to effect significant changes (P effect, producing no Doppler signals at the lowest settings and the highest recordable indices at the maximum settings. The pulse repetition frequency (PRF) was the next most influential setting but a Doppler signal was seen and measurable at all of the different settings. The other Doppler settings had a much less profound effect on the vascular indices, with subtle but significantly different measures across the full range of settings. The speed of data acquisition was also found to affect the vascular indices, all of which were reduced when the fast mode was used although the only significant effect was on the VFI. The VI, FI and VFI are all affected significantly by variations in power Doppler settings and by the speed of acquisition. The gain and signal power have the greatest effect on the power Doppler signal, followed closely by the PRF. The other settings and speed of acquisition also influence the signal, but to a

  17. Achilles tendon (TA) size and power Doppler ultrasound (PD) changes compared to MRI: A preliminary observational study

    Energy Technology Data Exchange (ETDEWEB)

    Richards, P.J.; Dheer, A.K.; McCall, I.M

    2001-10-01

    AIM: To assess whether abnormal Achilles tendon (TA) magnetic resonance imaging (MRI) and spectral ultrasound (US) features have associated development of microvascular power Doppler (PD) flow. MATERIALS AND METHODS: In a prospective, controlled and blinded study six patients with TA symptoms were compared to five with other ankle abnormalities. Two radiologists independently measured the mean maximal anteroposterior diameter on MRI and conventional US (categorized as normal <6 mm, mild 6.1-10 mm, moderate 1.1-1.5 cm and severely enlarged > 1.6 cm), assessed morphology and studied the vessels using power Doppler. They formed a consensus over discrepancies. Sonography of the contralateral side within 24 h was used as a control. RESULTS: Twenty-one tendons in six women and five men, aged 45-77 years (mean 57.6 years), were examined, 12 tendons were of normal US morphology and size (<6 mm), and did not exhibit PD's flow (interobserver agreement K > 0.74). Of the 12 tendons studied by MRI five were normal, seven tendons were enlarged, five of which had a proportionate increase in PD flow at the margin on the deep surface and four also had vessels in the centre of the tendon. All five of these tendons had high signal on T2-weighting (T2W). Of the two mildly enlarged tendons of intermediate signal on T1 and T2W, one showed PD flow and the other did not. CONCLUSIONS: In patients with TA disease power Doppler ultrasound shows proliferation of vessels in enlarged, abnormal tendons demonstrated on MRI and standard ultrasound, in the absence of definite tears. Richards, P.J. Dheer, A.K. and McCall, I.M. (2001)

  18. An Active Power Filter Based on a Three-Level Inverter and 3D-SVPWM for Selective Harmonic and Reactive Compensation

    Directory of Open Access Journals (Sweden)

    José Luis Monroy-Morales

    2017-03-01

    Full Text Available Active Power Filters (APFs have been used for reducing waveform distortion and improving power quality. However, this function can be improved by means of a selective harmonic compensation. Since an APF has rating restrictions, it is convenient to have the option of selecting an individual or a set of particular harmonics in order to compensate and apply the total APF capabilities to eliminate these harmonics, in particular those with a greater impact on the Total Harmonic Distortion (THD. This paper presents the development of a new APF prototype based on a three-phase three-level Neutral Point Clamped (NPC inverter with selective harmonic compensation capabilities and reactive power compensation. The selective harmonic compensation approach uses several Synchronous Rotating Frames (SRF, to detect and control individual or a set of harmonics using d and q variables. The APF includes a Three-Dimensional Space Vector Modulator (3D-SVPWM in order to generate the compensation currents. Because of its multilevel topology, the proposed active power filter can be used in diverse power quality applications at sub-transmission and distribution voltage levels. Simulation and experimental results are shown to validate the proposed solution and assess the prototype performance in different scenarios.

  19. Power Quality Improvement in a Cascaded Multilevel Inverter Interfaced Grid Connected System Using a Modified Inductive–Capacitive–Inductive Filter with Reduced Power Loss and Improved Harmonic Attenuation

    Directory of Open Access Journals (Sweden)

    Meenakshi Jayaraman

    2017-11-01

    Full Text Available Recently, multilevel inverters are more researched due to the advantages they offer over conventional voltage source inverters in grid connected applications. Passive filters are connected at the output of these inverters to produce sinusoidal waveforms with reduced harmonics and to satisfy grid interconnection standard requirements. This work proposes a new passive filter topology for a pulse width modulated five-level cascaded inverter interfaced grid connected system. The proposed passive filter inserts an additional resistance-capacitance branch in parallel to the filter capacitor of the traditional inductive–capacitive–inductive filter in addition to a resistance in series with it to reduce damping power loss. It can attenuate the switching frequency harmonic current components much better than the traditional filter while maintaining the same overall inductance, reduced capacitance and resistance values. The basic parameter design procedure and an approach to discover the parameters of the proposed filter is introduced. Further, a novel methodology using Particle Swarm Optimization (PSO is recommended to guarantee minimum damping loss while ensuring reduced peak during resonance. In addition, PSO algorithm is newly employed in this work to maximize harmonic attenuation in and around the switching frequency on the premise of allowable values of filter inductance and capacitance. A comparative discussion considering traditional passive filters and the proposed filter is presented and evaluated through experiments conducted on a 110 V, 1 kW five-level grid connected inverter. The modulation algorithm for the multilevel inverter is implemented using a SPARTAN 6-XC6SLX25 Field Programmable Gate Array (FPGA processor. The analysis shows that the proposed filter not only provides decreased damping power loss but also is capable of providing considerable harmonic ripple reduction in the high frequency band, improved output waveforms and lesser

  20. Analysis of the reactive power consumption and the harmonics in the network by the non-linear electrical loads

    Energy Technology Data Exchange (ETDEWEB)

    Cogo, Joao Roberto [Escola Federal de Engenharia de Itajuba, MG (Brazil)

    1994-12-31

    The non linear electrical loads can give rise to a number of disturbances in electrical power networks. Among them, the high consumption of relative power is to be noted and so is the several harmonic components which may be injected in the industry system and very often in the utility system. So, by using appropriate technical considerations, as well as measurements in typical special electrical loads, such negative effects are analyzed and ways of minimizing them are suggested. (author) 3 refs., 11 figs., 6 tabs.

  1. The utility of ultrasound superb microvascular imaging for evaluation of breast tumour vascularity: comparison with colour and power Doppler imaging regarding diagnostic performance.

    Science.gov (United States)

    Park, A Y; Seo, B K; Woo, O H; Jung, K S; Cho, K R; Park, E K; Cha, S H; Cha, J

    2017-11-06

    To investigate the utility of superb microvascular imaging (SMI) for evaluating the vascularity of breast masses in comparison with colour or power Doppler ultrasound (US) and the effect on diagnostic performance. A total of 191 biopsy-proven masses (99 benign and 92 malignant) in 166 women with greyscale, colour Doppler, power Doppler, and SMI images were enrolled in this retrospective study. Three radiologists analysed the vascular images using a three-factor scoring system to evaluate the number, morphology, and distribution of tumour vessels. They assessed the Breast Imaging-Reporting and Data System categories for greyscale US alone and combinations of greyscale US and each type of vascular US. The Kruskal-Wallis test was performed and the area under the receiver-operating characteristic curve (AUC) measured. On SMI, vascular scores were compared between benign and malignant masses and the optimal cut-off value for the overall score was determined. SMI showed higher vascular scores than colour or power Doppler US and malignant masses had higher scores than benign masses (pDoppler US (AUC, 0.815 versus 0.774, 0.789, 0.791; pDoppler US for characterising the vascularity in breast masses and improving diagnostic performance. Copyright © 2017 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

  2. Assessment by three-dimensional power Doppler ultrasound of cerebral blood flow perfusion in fetuses with congenital heart disease.

    Science.gov (United States)

    Zeng, S; Zhou, J; Peng, Q; Tian, L; Xu, G; Zhao, Y; Wang, T; Zhou, Q

    2015-06-01

    To use three-dimensional (3D) power Doppler ultrasound to investigate cerebral blood flow perfusion in fetuses with congenital heart disease (CHD). The vascularization index (VI), flow index (FI) and vascularization flow index (VFI) in the total intracranial volume and the main arterial territories (middle cerebral artery (MCA), anterior cerebral artery (ACA) and posterior cerebral artery (PCA)) were evaluated prospectively and compared in 112 fetuses with CHD and 112 normal fetuses using 3D power Doppler. Correlations between the 3D power Doppler indices and neurodevelopment scores at 12 months of age were assessed in a subset of the CHD group, and values were compared with those of controls. Compared with the controls, the VI, FI and VFI of the total intracranial volume and the three main arteries were significantly higher in fetuses with hypoplastic left heart syndrome and left-sided obstructive lesions (P power Doppler values in the ACA territory were significantly higher in fetuses with transposition of the great arteries (P flow perfusion indices in the fetuses with CHD relative to controls was observed in the ACA territory (P flow perfusion was increased relative to controls in most fetuses with CHD and was associated with neurodevelopment scores at 12 months. Prenatal 3D power Doppler ultrasound might help to identify cases of brain vasodilatation earlier and inform parental counseling. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

  3. Intervillous and uteroplacental circulation in normal early pregnancy and early pregnancy loss assessed by 3-dimensional power Doppler angiography.

    Science.gov (United States)

    Mercé, Luis T; Barco, María J; Alcázar, Juan L; Sabatel, Rosa; Troyano, Juan

    2009-03-01

    To assess intervillous and uteroplacental circulation in early normal pregnancies and miscarriages. One hundred normal pregnancies and 46 delayed miscarriages were evaluated by 3-dimensional vaginal ultrasound and power Doppler angiography. Volumes of the early placenta and the subplacental area were obtained between 5 and 12.6 weeks' gestation. The placental volume, vascularization index, flow index, and vascularization flow index was calculated. Intraclass correlation coefficients ranged from 0.961 for placental volume to 0.885 for intervillous flow index. Intervillous power Doppler signals were not detected before the sixth week. Placental volume (R(2) = 0.68), intervillous vascularization index (R(2) = 0.30), flow index (R(2) = 0.33) and vascularization flow index (R(2) = 0.35), uteroplacental flow index (R(2) = 0.34), and vascularization flow index (R(2) = 0.17) increase significantly (P < .001) throughout the first trimester of normal pregnancies. Uteroplacental vascularization index was not significantly related to gestational age. Intervillous vasculariztion index, flow index, and vascularization flow index were significantly raised in miscarriages, but there were no significant differences for uteroplacental vascularization index, flow index, or vascularization flow index. Intervillous and uteroplacental blood flow increases throughout the first trimester of normal pregnancies. Intervillous circulation is abnormally increased when a miscarriage is diagnosed.

  4. Periovulatory follicular volume and vascularization determined by 3D and power Doppler sonography as pregnancy predictors in intrauterine insemination cycles.

    Science.gov (United States)

    Engels, Virginia; Sanfrutos, Luis; Perez-Medina, Tirso; Alvarez, Pilar; Zapardiel, Ignacio; Godoy-Tundidor, Sonia; Salazar, Francisco J; Troyano, Juan; Bajo-Arenas, Jose M

    2011-06-01

    To evaluate the relationship between volume and vascularization of the periovulatory follicle and subfollicular area measured by three-dimensional power Doppler ultrasound (US), and ovulation and pregnancy in patients undergoing intrauterine insemination (IUI). We studied 79 consecutive cycles of IUI on hCG administration day. We measured the periovulatory follicle and subfollicular area by means of three-dimensional power Doppler US. The stored volumes were processed with the VOCAL image processing software to calculate the volume of the follicle and the following vascular indices: vascularization index (VI), flow index (FI), and vascularization flow index (VFI). The follicular volume was higher in anovulatory cycles (7.7 ± 3.7 cubic centimeters (CC) versus 4.1 ± 2.0 CC; p < 0.001). There was no difference between the follicular volumes in cycles with or without subsequent pregnancy. The vascular indices of the follicle did not differ significantly between ovulatory and anovulatory cycles, and between cycles that did and did not achieve pregnancy. Periovulatory subfollicular VI and VFI were lower in women who became pregnant (VI: 2.9 ± 2.3% versus 5.6 ± 4.6%; p < 0.05, and VFI: 1.1 ± 0.8 versus 2.2 ± 2.2; p < 0.01). High values of follicular volume were associated with anovulatory cycles. Subfollicular VI and VFI might be used as markers of follicular quality and pregnancy predictors. Copyright © 2011 Wiley Periodicals, Inc.

  5. Very different performance of the power Doppler modalities of several ultrasound machines ascertained by a microvessel flow phantom.

    Science.gov (United States)

    Ten Cate, David F; Luime, Jolanda J; van der Ven, Myrthe; Hazes, Johanna M W; Kooiman, Klazina; de Jong, Nico; Bosch, Johannes G

    2013-10-24

    In many patients with rheumatoid arthritis (RA) subclinical disease activity can be detected with ultrasound (US), especially using power Doppler US (PDUS). However, PDUS may be highly dependent on the type of machine. This could create problems both in clinical trials and in daily clinical practice. To clarify how the PDUS signal differs between machines we created a microvessel flow phantom. The flow phantom contained three microvessels (150, 1000, 2000 microns). A syringe pump was used to generate flows. Five US machines were used. Settings were optimised to assess the lowest detectable flow for each US machine. The minimal detectable flow velocities showed very large differences between the machines. Only two of the machines may be able to detect the very low flows in the capillaries of inflamed joints. There was no clear relation with price. One of the lower-end machines actually performed best in all three vessel sizes. We created a flow phantom to test the sensitivity of US machines to very low flows in small vessels. The sensitivity of the power Doppler modalities of 5 different machines was very different. The differences found between the machines are probably caused by fundamental differences in processing of the PD signal or internal settings inaccessible to users. Machines considered for PDUS assessment of RA patients should be tested using a flow phantom similar to ours. Within studies, only a single machine type should be used.

  6. Quantitative analysis of normal fetal medulla oblongata volume and flow by three-dimensional power Doppler ultrasound.

    Science.gov (United States)

    Shyu, Ing-Luen; Wang, Peng-Hui; Chen, Chih-Yao; Chen, Yi-Jen; Chang, Chia-Ming; Horng, Huann-Cheng; Yang, Ming-Jie; Yen, Ming-Shyen

    2016-06-01

    Assessment of the fetal medulla oblongata volume (MOV) and blood flow might be important in the evaluation of fetal brain growth. We used three-dimensional power Doppler ultrasound (3DPDUS) to assess the fetal MOV and blood flow index in normal gestation. The relationships between these parameters were further analyzed. We assessed the total volume and blood flow index of the fetal MO in normal pregnancies using a 3DPDUS (Voluson 730 Expert). The true sagittal plane over the fetal occipital area was measured by a 3D transabdominal probe to scan the fetal MO under the power Doppler mode. Then, we quantitatively assessed the total volume of the fetal MOV, mean gray area (MG), vascularization index (VI), and flow index (FI). A total of 106 fetuses, ranging from 19 weeks to 39 weeks of gestation, were involved in our study. The volume of the fetal MO was highly positively correlated with gestational age [correlation coefficient (r) = 0.686, p flow development quantitatively. Our study indicated that fetal MOV and blood flow correlated significantly with the advancement of gestational age. This information may serve as reference data for further studies of the fetal brain and blood flow under abnormal conditions. Copyright © 2016. Published by Elsevier B.V.

  7. Using Flow Characteristics in Three-Dimensional Power Doppler Ultrasound Imaging to Predict Complete Responses in Patients Undergoing Neoadjuvant Chemotherapy.

    Science.gov (United States)

    Shia, Wei-Chung; Huang, Yu-Len; Wu, Hwa-Koon; Chen, Dar-Ren

    2017-05-01

    Strategies are needed for the identification of a poor response to treatment and determination of appropriate chemotherapy strategies for patients in the early stages of neoadjuvant chemotherapy for breast cancer. We hypothesize that power Doppler ultrasound imaging can provide useful information on predicting response to neoadjuvant chemotherapy. The solid directional flow of vessels in breast tumors was used as a marker of pathologic complete responses (pCR) in patients undergoing neoadjuvant chemotherapy. Thirty-one breast cancer patients who received neoadjuvant chemotherapy and had tumors of 2 to 5 cm were recruited. Three-dimensional power Doppler ultrasound with high-definition flow imaging technology was used to acquire the indices of tumor blood flow/volume, and the chemotherapy response prediction was established, followed by support vector machine classification. The accuracy of pCR prediction before the first chemotherapy treatment was 83.87% (area under the ROC curve [AUC] = 0.6957). After the second chemotherapy treatment, the accuracy of was 87.9% (AUC = 0.756). Trend analysis showed that good and poor responders exhibited different trends in vascular flow during chemotherapy. This preliminary study demonstrates the feasibility of using the vascular flow in breast tumors to predict chemotherapeutic efficacy. © 2017 by the American Institute of Ultrasound in Medicine.

  8. Harmonization of initial estimates of shale gas life cycle greenhouse gas emissions for electric power generation.

    Science.gov (United States)

    Heath, Garvin A; O'Donoughue, Patrick; Arent, Douglas J; Bazilian, Morgan

    2014-08-05

    Recent technological advances in the recovery of unconventional natural gas, particularly shale gas, have served to dramatically increase domestic production and reserve estimates for the United States and internationally. This trend has led to lowered prices and increased scrutiny on production practices. Questions have been raised as to how greenhouse gas (GHG) emissions from the life cycle of shale gas production and use compares with that of conventionally produced natural gas or other fuel sources such as coal. Recent literature has come to different conclusions on this point, largely due to differing assumptions, comparison baselines, and system boundaries. Through a meta-analytical procedure we call harmonization, we develop robust, analytically consistent, and updated comparisons of estimates of life cycle GHG emissions for electricity produced from shale gas, conventionally produced natural gas, and coal. On a per-unit electrical output basis, harmonization reveals that median estimates of GHG emissions from shale gas-generated electricity are similar to those for conventional natural gas, with both approximately half that of the central tendency of coal. Sensitivity analysis on the harmonized estimates indicates that assumptions regarding liquids unloading and estimated ultimate recovery (EUR) of wells have the greatest influence on life cycle GHG emissions, whereby shale gas life cycle GHG emissions could approach the range of best-performing coal-fired generation under certain scenarios. Despite clarification of published estimates through harmonization, these initial assessments should be confirmed through methane emissions measurements at components and in the atmosphere and through better characterization of EUR and practices.

  9. Harmonic modelling, propagation and mitigation for large wind power plants connected via long HVAC cables

    DEFF Research Database (Denmark)

    Dowlatabadi, Mohammadkazem Bakhshizadeh; Hjerrild, Jesper; Kocewiak, Łukasz

    2016-01-01

    be reduced and operational availability and the reliability can be improved. Challenges hereto include lower resonance frequencies due to the long cables, frequency dependent modelling of long submarine cables, passive filtering, and PLL dynamics in the control loops (from a harmonic stability point of view)....

  10. Voltage Unbalance and Harmonic Compensation in Microgrids by Cooperation of Distributed Generators and Active Power Filters

    DEFF Research Database (Denmark)

    Hashempour, Mohammad M.; Savaghebi, Mehdi; Quintero, Juan Carlos Vasquez

    2016-01-01

    , selective virtual impedance and voltage/current regulators. Based on the secondary control, at first voltage harmonic compensation and voltage unbalance compensation of point of common coupling (PCC), that might includes sensitive loads, is carried out by DGs. Voltage compensation of PCC by DGs may cause...

  11. High Performance Current Controller for Selective Harmonic Compensation in Active Power Filters

    DEFF Research Database (Denmark)

    Lascu, Cristian; Asiminoaei, Lucian; Boldea, I.

    2007-01-01

    computational effort. The proposed controller design is based on the pole-zero cancellation technique, taking into account the load transfer function at each harmonic frequency. Two design methods are provided, which give controller transfer functions with superior frequency response. The complete current...

  12. Modeling of VSC-Based Power Systems in The Extended Harmonic Domain

    DEFF Research Database (Denmark)

    Esparza, Miguel; Segundo-Ramirez, Juan; Kwon, Jun Bum

    2017-01-01

    Averaged modeling is a commonly used approach used to obtain mathematical representations of VSC-based systems. However, essential characteristics mainly related to the modulation process and the harmonic distortion of the signals are not able to be accurately captured and analyzed. The extended ...

  13. In vitro dual perfusion of human placental lobules as a flow phantom to investigate the relationship between fetoplacental flow and quantitative 3D power doppler angiography.

    Science.gov (United States)

    Jones, N W; Hutchinson, E S; Brownbill, P; Crocker, I P; Eccles, D; Bugg, G J; Raine-Fenning, N J

    2009-02-01

    Flow phantoms have been used to investigate and quantify three-dimensional power Doppler data but this is the first study to use the in vitro, dual perfused, placental perfusion model. We used this model to investigate and quantify the effect of variation in fetal-side flow rates and attenuation on 3D power Doppler angiography. Perfusion of a placental lobule was commenced within 30 min of delivery and experimentation was successful in 8 of the 18 placenta obtained. Fetal and maternal perfusate was modified Earle's bicarbonate buffer which, following equilibration, was supplemented on the fetal side with whole heparinised cord blood. Imaging was performed with a Voluson-i ultrasound machine. A 'vascular biopsy' the thickness of the placental lobule was defined and signal quantified within using VOCAL (GE Medical Systems, Zipf, Austria). Three vascular indices are generated: vascularisation index (VI) defined as the percentage of power Doppler data within a volume of interest; flow index (FI), the mean signal intensity of the power Doppler information; and vascularisation flow index (VFI), a combination of both factors derived through their multiplication. Attenuation was investigated in this model with the addition of tissue mimic blocks. Our results showed a predictable relationship between flow rates and the vascular indices VI and VFI. However the FI was a less reliable predictor of flow; thus it should be interpreted with caution. The power Doppler signal was markedly affected by attenuation leading to a complete loss of information at a depth of 6 cm in the model used. In conclusion this model can be adapted to provide a phantom to analyse and quantify 3D power Doppler signals and demonstrates that vascular indices within a tissue remain related to volume flow. This model provides further evidence that depth dependent attenuation of signal needs to be accounted for in any in vivo work where the probe is not in direct contact with the tissue of interest.

  14. Restraint Method of Voltage Total Harmonic Distortion in Distribution Network by Power Conditioner Systems using Measured Data from IT Switches

    Science.gov (United States)

    Kawasaki, Shoji; Shimoda, Kazuki; Tanaka, Motohiro; Taoka, Hisao; Matsuki, Junya; Hayashi, Yasuhiro

    Recently, the amount of distributed generation (DG) such as photovoltaic system and wind power generator system installed in a distribution system has been increasing because of reduction of the effects on the environment. However, the harmonic troubles in the distribution system are apprehended in the background of the increase of connection of DGs through the inverters and the spread of power electronics equipment. In this paper, the authors propose a restraint method of voltage total harmonic distortion (THD) in a whole distribution network by active filter (AF) operation of plural power conditioner systems (PCS). Moreover, the authors propose a determination method of the optimal gain of AF operation so as to minimize the maximum value of voltage THD in the distribution network by the real-time feedback control with measured data from the information technology (IT) switches. In order to verify the validity of the proposed method, the numerical calculations are carried out by using an analytical model of distribution network interconnected DGs with PCS.

  15. High-power terahertz optical pulse generation with a dual-wavelength harmonically mode-locked Yb:YAG laser

    Science.gov (United States)

    Zhuang, W. Z.; Chang, M. T.; Su, K. W.; Huang, K. F.; Chen, Y. F.

    2013-07-01

    We report on high-power terahertz optical pulse generation with a dual-wavelength harmonically mode-locked Yb:YAG laser. A semiconductor saturable absorber mirror is developed to achieve synchronously mode-locked operation at two spectral bands centered at 1031.67 and 1049.42 nm with a pulse duration of 1.54 ps and a pulse repetition rate of 80.3 GHz. With a diamond heat spreader to improve the heat removal efficiency, the average output power can be up to 1.1 W at an absorbed pump power of 5.18 W. The autocorrelation traces reveal that the mode-locked pulse is modulated with a beat frequency of 4.92 THz and displays a modulation depth to be greater than 80%.

  16. Multiband Reconfigurable Harmonically Tuned Gallium Nitride (GaN) Solid-State Power Amplifier (SSPA) for Cognitive Radios

    Science.gov (United States)

    Waldstein, Seth W.; Kortright, Barbosa Miguel A.; Simons, Rainee N.

    2017-01-01

    The paper presents the architecture of a wideband reconfigurable harmonically-tuned Gallium Nitride (GaN) Solid State Power Amplifier (SSPA) for cognitive radios. When interfaced with the physical layer of a cognitive communication system, this amplifier topology offers broadband high efficiency through the use of multiple tuned input/output matching networks. This feature enables the cognitive radio to reconfigure the operating frequency without sacrificing efficiency. This paper additionally presents as a proof-of-concept the design, fabrication, and test results for a GaN inverse Class-F type amplifier operating at X-band (8.4 GHz) that achieves a maximum output power of 5.14-W, Power Added Efficiency (PAE) of 38.6 percent, and Drain Efficiency (DE) of 48.9 percent under continuous wave (CW) operation.

  17. Harmonization of initial estimates of shale gas life cycle greenhouse gas emissions for electric power generation

    Science.gov (United States)

    Heath, Garvin A.; O’Donoughue, Patrick; Arent, Douglas J.; Bazilian, Morgan

    2014-01-01

    Recent technological advances in the recovery of unconventional natural gas, particularly shale gas, have served to dramatically increase domestic production and reserve estimates for the United States and internationally. This trend has led to lowered prices and increased scrutiny on production practices. Questions have been raised as to how greenhouse gas (GHG) emissions from the life cycle of shale gas production and use compares with that of conventionally produced natural gas or other fuel sources such as coal. Recent literature has come to different conclusions on this point, largely due to differing assumptions, comparison baselines, and system boundaries. Through a meta-analytical procedure we call harmonization, we develop robust, analytically consistent, and updated comparisons of estimates of life cycle GHG emissions for electricity produced from shale gas, conventionally produced natural gas, and coal. On a per-unit electrical output basis, harmonization reveals that median estimates of GHG emissions from shale gas-generated electricity are similar to those for conventional natural gas, with both approximately half that of the central tendency of coal. Sensitivity analysis on the harmonized estimates indicates that assumptions regarding liquids unloading and estimated ultimate recovery (EUR) of wells have the greatest influence on life cycle GHG emissions, whereby shale gas life cycle GHG emissions could approach the range of best-performing coal-fired generation under certain scenarios. Despite clarification of published estimates through harmonization, these initial assessments should be confirmed through methane emissions measurements at components and in the atmosphere and through better characterization of EUR and practices. PMID:25049378

  18. The use of power Doppler colour scoring to predict successful expectant management in women with an incomplete miscarriage.

    Science.gov (United States)

    Casikar, Ishwari; Lu, Chuan; Oates, Jennifer; Bignardi, Tommaso; Alhamdan, Dalya; Condous, George

    2012-03-01

    To evaluate whether the use of power Doppler to confirm the presence or absence of blood flow within retained products of conception (RPC) in women with an incomplete miscarriage can predict subsequent successful expectant management. Prospective observational study in the Acute Gynaecology and Early Pregnancy Unit (AGEPU) at Nepean Hospital from November 2006 to February 2009. Incomplete miscarriage was defined by the presence of a measurable focus of hyperechoeic material, in three planes, within the endometrial cavity using two-dimensional greyscale transvaginal ultrasound (TVS). Subjective qualitative power Doppler colour scoring (PDCS) of the RPC was performed. The vascularization of the RPC was scored using the colour scoring system of the International Ovarian Tumour Analysis (IOTA) group. PDCS 1 meant absence of vascularity, PCDS 2 represented minimal vascularity, PDCS 3 rather strong vascularity and PDCS 4 very strong vascularity. The correlation between the PDCS and successful expectant management of miscarriage was analysed. The volume of RPC was calculated using the ellipsoid formula and then compared with both the PDCS and the outcome of expectant management. Successful expectant management was defined as the resolution of symptoms and the absence of RPC on follow-up TVS. A total of 1395 consecutive pregnant women underwent TVS. Of them, 198 women were diagnosed with an incomplete miscarriage; 172 were managed expectantly. Complete data were available on 158 cases. In total 84.8% (134/158) were managed successfully whilst 15.2% (24/158) failed expectant management. Of the total, 89% (121/136) of women with a PDCS 1 had successful expectant management compared with 57.1 (8/14) with PDCS 2 and 62.5% (5/8) with PDCS 3. Comparing absence of flow (PDCS 1) to presence of flow (PDCS 2 or more), the rate of success was significantly higher in the first group (89 versus 60.9%, Fisher's exact test P= 0.00136). In the prediction of success, the absence of flow

  19. Harmonic polynomials, hyperspherical harmonics, and atomic spectra

    Science.gov (United States)

    Avery, John Scales

    2010-01-01

    The properties of monomials, homogeneous polynomials and harmonic polynomials in d-dimensional spaces are discussed. The properties are shown to lead to formulas for the canonical decomposition of homogeneous polynomials and formulas for harmonic projection. Many important properties of spherical harmonics, Gegenbauer polynomials and hyperspherical harmonics follow from these formulas. Harmonic projection also provides alternative ways of treating angular momentum and generalised angular momentum. Several powerful theorems for angular integration and hyperangular integration can be derived in this way. These purely mathematical considerations have important physical applications because hyperspherical harmonics are related to Coulomb Sturmians through the Fock projection, and because both Sturmians and generalised Sturmians have shown themselves to be extremely useful in the quantum theory of atoms and molecules.

  20. Subendometrial blood flow changes by 3-dimensional power Doppler ultrasound after hysteroscopic lysis of severe intrauterine adhesions: preliminary study.

    Science.gov (United States)

    Mohamed Amer, Mohamed Ibrahim; Omar, Omar H; El Sherbiny Hamed, Mohamed; Dahroug, Enas G

    2015-01-01

    To evaluate the changes in subendometrial blood flow and endometrial volume after hysteroscopic lysis of severe intrauterine adhesions (IUAs). A pilot observational study. Forty infertile women with severe IUAs served as their own controls and were included in this study only once, to avoid selection bias. Three-dimensional power Doppler ultrasound was performed in all patients 1 day before hysteroscopic lysis of severe IUA, and repeated 1 month later, to assess subendometrial blood flow [as measured by vascularization index (VI), flow index (FI), and vascularization flow index (VFI)] and endometrial volume. Main outcome measures were subendometrial blood flow (VI, FI, VFI) and endometrial volume. There were statistically significant postoperative increases in endometrial volume, VI, FI, and VFI. Subendometrial blood flow improved in 14 women (35%), and menstrual improvement occurred in 15 women (37.5%). Hysteroscopic lysis of severe IUAs improves subendometrial blood flow, with subsequent increases in endometrial volume. Copyright © 2015 AAGL. Published by Elsevier Inc. All rights reserved.

  1. The Assessment of Unilateral Uterine Artery Ligation in Radical Abdominal Trachelectomy with Three-Dimensional Power Doppler Ultrasonography

    Directory of Open Access Journals (Sweden)

    Wen-Jui Yang

    2008-03-01

    Full Text Available The conservation of uterine arteries during radical trachelectomy has led to considerable debate among gynecologic oncologists. Some authors have reported successful case studies of the ligation of bilateral uterine arteries, but other authors remain unconvinced of the artery ligation procedure. We report a case that employed three-dimensional power Doppler ultrasonography (3D-PDUS to assess the microvascular pattern of uterine blood circulation after the ligation of a unilateral uterine artery during radical abdominal trachelectomy. The assessment of the uterine vascular circulation via the 3D-PDUS revealed no significant differences in the vascular blood supply of bilateral uterine arteries 4 months postoperatively. [International Journal of Gerontology 2008; 2(1: 22–25

  2. Evaluation of the relationship between renal function and renal volume-vascular indices using 3D power Doppler ultrasound

    Energy Technology Data Exchange (ETDEWEB)

    Cansu, Aysegul, E-mail: drcansu@gmail.com; Kupeli, Ali; Kul, Sibel; Eyuboglu, Ilker; Oguz, Sukru; Ozturk, Mehmet Halil; Dinc, Hasan

    2014-07-15

    Purpose: To investigate the relationship between renal function and total renal volume-vascular indices using 3D power Doppler ultrasound (3DPDUS). Materials and methods: One hundred six patients with hypertensive proteinuric nephropathy (HPN) (49 male, 57 female) and 65 healthy controls (32 male, 33 female) were evaluated prospectively using 3DPDUS. Total renal volume (RV), vascularization index (VI), flow index (FI) and vascularization flow index (VFI) were calculated using Virtual Organ Computer-aided Analysis (VOCAL). The estimated glomerular filtration rates (GFRs) of the patients with HPN and the control group were calculated. The patients with HPN were divided into two groups on the basis of GFR, normal (≥90) or reduced (<90). Differences between groups were compared using ANOVA. Correlations between GFR, renal volume and vascular indices were analyzed using Pearson's correlation analysis. Significance was set at p < 0.05. Results: The mean total RV, VI, FI and VFI values in the reduced GFR, normal GFR and control groups were RV (ml): 234.7, 280.7 and 294.6; VI: 17.6, 27.6 and 46.8; FI: 79.1, 88.7 and 93.9 and VFI: 7.1, 12.7 and 23.8. There were statistically significant differences between the groups (p < 0.001). Total RVs and vascular indices exhibited significant correlations with estimated GFR (r = 0.53–0.59, p < 0.001) Conclusion: Three-dimensional power Doppler ultrasound is a reliable predictive technique in renal function analysis.

  3. Automated assessment of joint synovitis activity from medical ultrasound and power doppler examinations using image processing and machine learning methods.

    Science.gov (United States)

    Cupek, Rafal; Ziębiński, Adam

    2016-01-01

    Rheumatoid arthritis is the most common rheumatic disease with arthritis, and causes substantial functional disability in approximately 50% patients after 10 years. Accurate measurement of the disease activity is crucial to provide an adequate treatment and care to the patients. The aim of this study is focused on a computer aided diagnostic system that supports an assessment of synovitis severity. This paper focus on a computer aided diagnostic system that was developed within joint Polish-Norwegian research project related to the automated assessment of the severity of synovitis. Semiquantitative ultrasound with power Doppler is a reliable and widely used method of assessing synovitis. Synovitis is estimated by ultrasound examiner using the scoring system graded from 0 to 3. Activity score is estimated on the basis of the examiner's experience or standardized ultrasound atlases. The method needs trained medical personnel and the result can be affected by a human error. The porotype of a computer-aided diagnostic system and algorithms essential for an analysis of ultrasonic images of finger joints are main scientific output of the MEDUSA project. Medusa Evaluation System prototype uses bone, skin, joint and synovitis area detectors for mutual structural model based evaluation of synovitis. Finally, several algorithms that support the semi-automatic or automatic detection of the bone region were prepared as well as a system that uses the statistical data processing approach in order to automatically localize the regions of interest. Semiquantitative ultrasound with power Doppler is a reliable and widely used method of assessing synovitis. Activity score is estimated on the basis of the examiner's experience and the result can be affected by a human error. In this paper we presented the MEDUSA project which is focused on a computer aided diagnostic system that supports an assessment of synovitis severity.

  4. [3D power Doppler ultrasound: new possibilities in the diagnosis and documentation of tumors of the base of the tongue].

    Science.gov (United States)

    Keberle, M; Jenett, M; Scharfenberger, M; Hahn, D

    2000-04-01

    To evaluate a novel 3-D power Doppler ultrasound technique (3-D PDUS) in the diagnosis and documentation of tumors of the base of the tongue. Twenty patients with tumors of the base of the tongue (2T1, 6T2, 6T3, and 6T4 carcinomas) prospectively underwent two-dimensional gray scale and power Doppler ultrasound and 3-D PDUS (3-Scape). All examinations were performed with a 7.5 MHz transducer and the Sonoline Elegra Advanced. Two independent observers compared the examinations regarding clear tumor margins, maximal diameter of the tumor, midline crossing, infiltration of the mylohyoid muscle, infrahyoidal tumor, contact to the lingual artery, vascularization in the tumor and in surrounding tissue, and evaluated the documentary use of the 3-D reconstruction. All relevant pretreatment parameters were accessible in the 3-D data; results of both observers were almost identical. An acquisition and reconstruction of the 3-D data takes only a couple of minutes. In addition to two-dimensional ultrasound 3-D PDUS allows reconstruction of axial images of the base of the tongue similar to CT images and a 3-D visualization of tumor vascularization. 3-Scape is a novel user-friendly method that allows uninterrupted acquisition of large 3-D volumes, and digital storage and transmission of ultrasound studies without loss of information. US images can be reconstructed in any desired plane or visualized in 3-D. In the future, additional software will permit exact determination of the volume and degree of vascularization of tumors.

  5. Perifollicular vascularity as a potential variable affecting outcome in stimulated intrauterine insemination treatment cycles: a study using transvaginal power Doppler.

    Science.gov (United States)

    Bhal, P S; Pugh, N D; Gregory, L; O'Brien, S; Shaw, R W

    2001-08-01

    The aim of the present study was to assess any potential relationship between perifollicular vascularity and outcome in an in-vivo environment following human chorionic gonadotrophin (HCG) administration. A total of 182 unselected consecutive patients undergoing stimulated intrauterine insemination (IUI) cycles was recruited where the perifollicular vascularity of follicles > or =16 mm was studied using a subjective grading system and transvaginal power Doppler ultrasonography, 36 h after HCG administration. A total of 601 follicles was studied. The incidence of follicles showing high-grade perifollicular vascularity (3 and 4) was higher than those with low-grade vascularity (1 and 2) (80 versus 20%). Treatment cycles were divided according to uniformity of vascularity grades of follicles > or =16 mm on the day of IUI [55% all high (3/4) grade; 33% mixed (1/2 and 3/4) and 12% all low (1/2) grade]. The mean age and duration of subfertility were significantly higher (P or =16 mm pre/post HCG, serum oestradiol and incidence of ultrashort gonadotrophin-releasing hormone (GnRH) agonist use were all significantly lower (P cycles with uniformly low follicular vascularity grades compared with mixed or uniformly high-grade cycles. However, on subjecting the data to multiple logistic regression analysis, the only independent variables that affected pregnancy rates appeared to be serum oestradiol (OR 1.28, 1.01--1.62) and high-grade follicular vascularity (OR 2.41, 1.08--5.40). These data would suggest that perifollicular vascularity has an important role to play in the outcome of IUI cycles, and that power Doppler has the potential to refine the management of assisted reproduction treatment cycles.

  6. Assessment of endometrial and ovarian characteristics using three dimensional power Doppler ultrasound to predict response in frozen embryo transfer cycles.

    Science.gov (United States)

    Zácková, Tamara; Järvelä, Ilkka Y; Tapanainen, Juha S; Feyereisl, Jaroslav

    2009-12-25

    To evaluate whether endometrial or ovarian parameters as measured using 3D power Doppler ultrasound would predict the outcome in frozen embryo transfer (FET) cycles. Thirty women with no known gynecological pathology undergoing FET were recruited. The FET was carried out in the natural menstrual cycle 3-4 days after the first positive LH test result. Blood samples for hormonal analysis were collected, and three-dimensional (3D) ultrasonographic examination was performed on the day of the FET and repeated with analysis of the total hCG one week later. The demographic, clinical, and embryological characteristics were similar between the pregnant (15/30) and nonpregnant groups (15/30). There were no differences between the groups in endometrial/subendometrial thickness, volume, or vascularization index (VI). The endometrial triple-line pattern was more often present in the pregnant group on the day of the FET (93.3% vs. 40.0%, 95% CI 25.5-81.2%). No differences in the ovaries were observed on the day of the FET. At the second visit, the triple-line pattern was still more often present in those patients who had conceived (91.7% vs. 42.9%, 95% CI 18.5-79.1%), and their corpus luteum was more active as judged by the rise in 17-hydroxyprogesterone and estradiol levels. No differences were observed in the dominant ovarian vasculature. According to our results, measurement of power Doppler indices using 3D ultrasound on the day of the FET does not provide any additional information concerning the outcome of the cycle. The existence of the triple-line pattern on the day of the FET seems to be a prognostic sign of a prosperous outcome after FET. The dominant ovary in the pregnant group seems to be already activated one week after the FET.

  7. On the reduction of the third-order harmonic losses in low–voltage power cables used for feeding large LED and CFL lighting loads

    Directory of Open Access Journals (Sweden)

    N. J. Milardovich

    2017-10-01

    Full Text Available An experimental investigation of diversity factors of CFL (compact fluorescent lamps in combination with LED (light emitting diode lamps is presented in this paper. Attention was paid to the reduction of low–order harmonic currents, especially the third one; which is mainly responsible for the strong increase in power losses in the neutral conductor of low–voltage installations. The harmonic currents drawn by several LED and CFL lamps with nominal powers < 25 W were first measured to investigate the electrical characteristics of individual lamps. In addition, a series of experiments was conducted in which LED lamps were powered between lines through small autotransformers thus avoiding the use of the neutral conductor. The results showed in both cases a sensible reduction of the harmonic current of third order and therefore a marked reduction of the power losses associated with them.

  8. Measurement of harmonics in electrical power systems; Medicion de armonicas en sistemas electricos

    Energy Technology Data Exchange (ETDEWEB)

    Calderon Gonzalez, Gustavo Adolfo

    1998-07-01

    In this thesis project a system for the quantification and study of the harmonics content in electrical systems was developed. The study is focused to signals of feeding current to a Long Arc furnace. The system developed for the quantification of the harmonics content is formed by the following parts: (a) Data acquisition system: The application of a data acquisition system makes possible for us to take samples from an analogous voltage signal. The acquired samples that represent an analogous signal, can later be processed in a digital computer. The data acquisition system is constituted by: An IBM-PC microcomputer, a digitalization card of analogous signals, and programs to conduct signals sampling (b) Digital processing of the acquired signals: With the purpose of obtaining the harmonic content, the Fast Fourier Transform method was used. The analysis by means of the Fast Fourier Transform allows us to obtain the signals spectra in the frequency dominion. Through the analysis by means of the Fast Fourier Transform a substantial diminution of the calculation time of the coefficients corresponding to the harmonics is obtained, this compared with the method of Discreet Fourier Series. (c) Analysis of obtained results: Several line current and capacitors measurements of the feeding system signals of an arc furnace were made. For each measurement made the magnitude and the phase for each harmonic was obtained. Of the assembly of coefficient magnitudes and phases, the average value and its standard deviation were calculated. Graphs of the magnitude variation with time and phase of each harmonic are shown. Also, graphs of the waveform of the signal in analysis are obtained, bar charts of the average spectral content and a report of the standard deviation of the magnitude and the phase for each harmonica, is obtained. Results of a simulation of the electrical system in analysis are included and the results are compared. [Spanish] En este proyecto de tesis se desarrollo

  9. Plasma harmonics

    CERN Document Server

    Ganeev, Rashid A

    2014-01-01

    Preface; Why plasma harmonics? A very brief introduction Early stage of plasma harmonic studies - hopes and frustrations New developments in plasma harmonics studies: first successes Improvements of plasma harmonics; Theoretical basics of plasma harmonics; Basics of HHG Harmonic generation in fullerenes using few-cycle pulsesVarious approaches for description of observed peculiarities of resonant enhancement of a single harmonic in laser plasmaTwo-colour pump resonance-induced enhancement of odd and even harmonics from a tin plasmaCalculations of single harmonic generation from Mn plasma;Low-o

  10. CURIE: A low power X-band, low atmospheric boundary layer doppler radar

    Energy Technology Data Exchange (ETDEWEB)

    Al-Sakka, Hassan; Weill, Alain; Le Gac, Christophe; Ney, Richard; Chardenal, Laurent; Vinson, Jean Paul; Barthes, Laurent [Lab. Atmospheres, Milieux, Observations Spatiales, LATMOS/IPSL, Velizy (France); Dupont, Eric [EDF, R and D, CEREA, Chatou (France)

    2009-06-15

    A new X-band Doppler miniradar, the CURIE radar (Canopy Urban Research on Interactions and Exchanges), mainly adapted to low Atmospheric Boundary Layer ABL sounding has been developed at LATMOS (Laboratoire Atmospheres, Milieux, Observations Spatiales) formerly CETP (Centre d'etude des Environnements Terrestre et Planetaires). After a brief description of the measurement conditions in a turbulent atmosphere, the main characteristics of the new sensor are presented. As an example, we compare CURIE vertical velocity fluctuations with UHF observations to show the vertical velocity measurement validity. As a prospective area of application in clear air, we focus on a first observation of vertical velocity variance which is supposed to be related to entrainment across the inversion layer. As our objective is to study low boundary layers during different atmospheric conditions and since the radar works in the presence of precipitation (as all X-band radar do), we also show vertical rain soundings in the lower part of the ABL and illustrate our findings with results demonstrating comparable reflectivity and precipitation rates as estimated with a disdrometer and with a rain gauge. (orig.)

  11. Features of design of the Doppler reflectometry diagnostics at the L-2M stellarator intended for operation under conditions of high ECRH power

    Science.gov (United States)

    Kharchevskii, A. A.; Bogachev, N. N.; Malakhov, D. V.; Nefedov, V. I.; Skvortsova, N. N.

    2017-10-01

    Features of design of the Doppler reflectometry diagnostics at the L-2M stellarator are discussed. This contact-free diagnostics is intended for experiments carried out under conditions of high-power microwave plasma heating at a frequency of electron cyclotron resonance. Resources of the proposed Doppler reflectometry scheme were studied with allowance for the installation of a new system of rejection microwave filters involving the Fabry–Perot resonance filter and pin-shaped waveguide filters. The simulation results of the resonator-filter operation as well as the results of test measurements using the MVNA-8-350 millimeter vector network analyzer are presented.

  12. Editorial Special Section on Harmonics Stability and Mitigation in Power Electronics

    DEFF Research Database (Denmark)

    Blaabjerg, Frede

    2016-01-01

    The global electrical energy consumption is still increasing, which demands that the power capacity and power transmission capabilities must be more than double within 20 years. This is not only resulting from the rising electricity demand but also caused by an ever-increasing amount of electrifi...... electronics usage is changing the characteristic of the power system by introducing more highly nonlinear and time-delayed dynamic systems, therefore increasing the risk of instability and power quality problems in the future power systems....... of electrification in the society. Electric power production has been changing from conventional fossil energy sources to renewable energy sources—in 2014, 60% of all installed production capacity came from renewables. The global shift to renewable-energy-based power generation brings in an unprecedented opportunity...... for the development of highly efficient and sustainable power electronics technology. As an enabling technology for a full control of electric power, power electronics are increasingly used for power generation, transmission/distribution, and various end-user applications. Such a large-scale expansion of power...

  13. Quantitative Assessment of Synovial Vascularity Using Contrast-Enhanced Power Doppler Ultrasonography: Correlation with Histologic Findings and MR Imaging Findings in Arthritic Rabbit Knee Model

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Hoon; Shin, Myung Jin; Kim, Seong Moon; Kim, Namkug; Suh, Sang Hyun [Asan Medical Center, University of Ulsan College of Medicine, Seoul (Korea, Republic of); Suh, Jin Suck [Yonsei University College of Medicine, Seoul (Korea, Republic of)

    2008-02-15

    To validate contrast-enhanced power Doppler ultrasonography (PD US) for the evaluation of synovial vascularity in an arthritic rabbit knee model in correlation with MR and histological findings. Power Doppler ultrasonography was performed for carrageenin-induced arthritic left knee and control right knee of 13 rabbits, first without and then with sonic contrast agent enhancement (Levovist, Schering, Berlin Germany), followed by gadolinium-enhanced MR imaging. Synovial vascularity was quantitatively assessed by calculating the color pixel area in power Doppler sonography using a computer-aided image analysis program and by grading the enhancement on MR images: grade 1, enhancement of knee joint is less than one-third of the area; grade 2, one-third to two-thirds enhancement; and grade 3, more than two-thirds enhancement. Microvessel density (MVD) was measured on slides stained immunohistochemically for CD31 antigen for histological assessment. The mean area of color pixels in PD US changed from 4.37 to 16.42 mm{sup 2} in the arthritic knee after enhancement (p < 0.05), whereas it changed from 0.77 to 2.31 mm{sup 2} in the control knee (p < 0.05). Arthritic knees had greater power Doppler signal than control knees both before and after contrast administration (p < 0.05). The average MVD was 88 in arthritic knees and 46 in control knees. MVDs correlated with color pixel areas of contrast-enhanced power Doppler imaging in arthritic knees. In MR grading of arthritic knees, five were grade 2 and eight were grade 3. MVD and PD US revealed no significant difference between grade 2 and 3 arthritic knees (p > 0.05). Sonic contrast-enhanced PD US improves the visualization of synovial vascularity and allows quantitative measurement in experimentally induced rabbit arthritic knees.

  14. Fetal ECG Extraction from Abdominal Signals: A Review on Suppression of Fundamental Power Line Interference Component and Its Harmonics

    Directory of Open Access Journals (Sweden)

    Dragoş-Daniel Ţarălungă

    2014-01-01

    Full Text Available Interference of power line (PLI (fundamental frequency and its harmonics is usually present in biopotential measurements. Despite all countermeasures, the PLI still corrupts physiological signals, for example, electromyograms (EMG, electroencephalograms (EEG, and electrocardiograms (ECG. When analyzing the fetal ECG (fECG recorded on the maternal abdomen, the PLI represents a particular strong noise component, being sometimes 10 times greater than the fECG signal, and thus impairing the extraction of any useful information regarding the fetal health state. Many signal processing methods for cancelling the PLI from biopotentials are available in the literature. In this review study, six different principles are analyzed and discussed, and their performance is evaluated on simulated data (three different scenarios, based on five quantitative performance indices.

  15. Multiple second order generalized integrators for harmonic synchronization of power converters

    DEFF Research Database (Denmark)

    Rodriguez, Pedro; Luna, Alvaro; Etxeberría, Ion

    2009-01-01

    This paper presents a new frequency-adaptive synchronization method for grid-connected power converters which allows estimating not only the positive- and negativesequence components of the power signal at the fundamental frequency, but also other sequence components at multiple frequencies. The ...

  16. Harmonic balance finite element method applications in nonlinear electromagnetics and power systems

    CERN Document Server

    Lu, Junwei; Yamada, Sotoshi

    2016-01-01

    The first book applying HBFEM to practical electronic nonlinear field and circuit problems * Examines and solves wide aspects of practical electrical and electronic nonlinear field and circuit problems presented by HBFEM * Combines the latest research work with essential background knowledge, providing an all-encompassing reference for researchers, power engineers and students of applied electromagnetics analysis * There are very few books dealing with the solution of nonlinear electric- power-related problems * The contents are based on the authors' many years' research and industry experience; they approach the subject in a well-designed and logical way * It is expected that HBFEM will become a more useful and practical technique over the next 5 years due to the HVDC power system, renewable energy system and Smart Grid, HF magnetic used in DC/DC converter, and Multi-pulse transformer for HVDC power supply * HBFEM can provide effective and economic solutions to R&D product development * Includes Matlab e...

  17. Customized power quality service provided by converter interfaced microgrids — Voltage harmonics as a study case

    DEFF Research Database (Denmark)

    Meng, Lexuan; Chaudhary, Sanjay K.; Guerrero, Josep M.

    2017-01-01

    Customers may have different power quality requirements, thus, the economic operational strategy can try to provide them with distinctive quality levels as customized service. An optimization based method is proposed in this paper to realize this functionality, offering the possibility...

  18. Use of three-dimensional power Doppler sonography in the diagnosis of uterine arteriovenous malformation and follow-up after uterine artery embolization: Case report and brief review of literature.

    Science.gov (United States)

    Tullius, Thomas G; Ross, Jason Robert; Flores, Melanie; Ghaleb, Melhem; Kupesic Plavsic, Sanja

    2015-06-01

    Arteriovenous malformations (AVM) of the uterus can cause life-threatening hemorrhage. Unexplained, heavy vaginal bleeding in a reproductive age woman should raise suspicion for an AVM. Here a 37-year-old woman had increasingly severe vaginal bleeding for 15 days. Serum β-hCG was elevated. Two-dimensional transvaginal ultrasound suggested retained products of conception. Before dilation and curettage (D&C), color Doppler and three-dimensional (3D) power Doppler demonstrated findings indicative of uterine AVM. A bilateral uterine artery embolization was performed without complications. Three months after uterine artery embolization, 3D power Doppler ultrasonography found complete resolution of the AVM. This case illustrates the importance of assessing both gray-scale and 3D power Doppler, and the ability of postprocedure Doppler to assess resolution. © 2014 Wiley Periodicals, Inc.

  19. Evaluation of early vascular complications after liver transplantation: Usefulness of power Doppler US with a microbubble contrast agent -Preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Dong Kil; Lim, Hyo Keun; Kim, Seung Hoon; Cho, Jae Min; Lee, Ji Yeon; Lee, Won Jae; Lim, Jae Hoon; Pyeujn, Yong Seon; Joh, Jae Won; Kim, Sung Joo [Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of)

    2001-03-15

    To evaluate the usefulness of power Doppler ultrasonography (PDUS) with a microbubble contrast agent in assessing the early vascular complications after liver transplantation (LT). In 15 patients with orthotopic LT (n=12) and living -related donor LT (n=3), PDUS examinations, before and after intravenous injection of a microbubble contrast agent (Levovist, Schering AG, Berlin, Germany) were performed one day after the LT. We compared the results of unenhanced PDUS with those of contrast-enhanced PDUS in terms of depicting the complications and conspicuity of the lesions. In three (20%) of 15 patients, flow signal of hepatic artery was not detected on unenhanced PDUS, while contrast PDUS showed flow signals of the hepatic artery in all patients. Both unenhanced and contrast-enhanced PDUS showed portal vein thromboses in two (13%) of 15 patients, but conspicuity of portal vein thromboses was better appreciated on contrast- enhanced PDUS. Compared with unenhanced PDUS, contrast-enhanced PDUS showed better detection of hepatic arterial flow and increased conspicuity od portal vein thromboses on day after LT. Our preliminary data suggest that contrast-enhanced PDUS can be a promising noninvasive technique the early vascular complications after LT.

  20. Prediction of ovarian response and IVF/ICSI outcome by three-dimensional ultrasonography and power Doppler angiography.

    Science.gov (United States)

    Mercé, Luis T; Barco, María J; Bau, Santiago; Troyano, Juan M

    2007-05-01

    The objective was to evaluate whether three-dimensional ultrasonography (3D-US) and power Doppler angiography (PDA) measurements can predict ovarian response and/or are associated with IVF/ICSI outcome. A prospective clinical study in 65 women undergoing IVF cycles. Ovarian volume (OV), number of antral follicles > or =2mm (NAF) and PDA indices: vascularisation index (VI), flow index (FI), and vascularisation flow index (VFI) were evaluated by 3D-US and PDA on the day of pituitary suppression control. These measurements, age and BMI were correlated with the number of follicles>10mm on the hCG day and the number of oocytes retrieved. Ovarian volume, NAF, VI, FI and FVI correlate significantly (P<0.01) with the number of follicles and oocytes recovered. Ovarian volume and the number of antral follicles predicted significantly the number of follicles (R=0.67; adjusted R(2)=0.43) and oocytes retrieved (R=0.63; adjusted R(2)=0.37). The oestradiol peak and the number of follicles, oocytes and Grade 1 embryos transferred were higher in the pregnant group. Three-dimensional ultrasound and PDA make it easier to evaluate all the sonographic parameters implied in ovarian response. Ovarian volume and the number of antral follicles are the only independent predictors of the number of follicles developed and oocytes retrieved.

  1. Assessment of wrist joint inflammation in patients with rheumatoid arthritis by quantitative two- and three-dimensional power Doppler ultrasonography.

    Science.gov (United States)

    Lai, Kuo-Lung; Chen, Der-Yuan; Chen, Yi-Hsing; Huang, Wen-Nan; Hsieh, Tsu-Yi; Hsieh, Chia-Wei; Chen, Yi-Ming; Hung, Wei-Ting; Chen, Hsin-Hua

    2014-01-01

    We aimed to compare the use of computer-aided quantification methods with 3 different power Doppler ultrasonography (PDUS) modes to assess wrist inflammation in patients with rheumatoid arthritis (RA). This study enrolled 49 patients (60 hand joints) with RA. Clinical parameters (rheumatoid factor [RF], erythrocyte sedimentation rate [ESR], and C-reactive protein [CRP]) were measured and pain was evaluated by a visual analogue scale (VAS, range: 0 to 10). Imaging of the affected wrist joints was performed with 2D- and 3D-PDUS imaging. The 2D imaging used a volumetric transducer and a linear transducer and the 3D imaging employed a volumetric transducer. Software was used to calculate the vascularisation index (VI), flow index (FI), and vascularisation flow index (VFI) under different measurement conditions. There were 8 males and 41 females, with an average age of 47.59±15.17 years, and average VAS score of 3.63±2.22. In 2D-PDUS with a linear probe, there were significant correlations of ESR with VI and VFI, and of CRP with area, VI, and VFI (pwrist inflammation. These results suggest that use of a 3D transducer, which is more expensive and time-consuming, is not necessary for assessment of wrist inflammation.

  2. Effect of pregestational diabetes mellitus on first trimester placental characteristics: three-dimensional placental volume and power Doppler indices.

    Science.gov (United States)

    Gonzalez Gonzalez, N L; Gonzalez Davila, E; Castro, A; Padron, E; Plasencia, W

    2014-03-01

    To investigate whether pregestational diabetes mellitus (DM) induces changes in vascular placental development detectable at first trimester. This was a prospective case-control study in 69 women with pregestational DM and 94 controls undergoing first-trimester combined screening for aneuploidies. Maternal characteristics, fetal nuchal translucency thickness, maternal serum pregnancy-associated plasma protein A (PAPP-A) and free β human chorionic gonadotrophin (β-hCG) were evaluated. Three-dimensional ultrasound was used to measure placental volume and three dimensional power Doppler (3D-PD) placental vascular indices including: vascularization index (VI), flow index (FI) and vascularization flow index (VFI). Pregnancy-associated hypertensive complications (PAHC) and perinatal outcomes were analyzed. The total group of diabetic women and the group of diabetic women without PAHC were compared separately with the control group. 3D-PD placental vascular indexes were significantly lower in women with DM than in controls (VI p = 0.007, FI p = 0.003 and VFI p = 0.04). These differences remained on excluding cases with PAHC in the DM group. No differences were found in placental volumes between the DM group and controls. Serum PAPP-A levels were also lower in diabetic women (p effect is independent of the later development of PAHC. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Power Doppler assessment of follicle vascularity at the time of oocyte retrieval in in vitro fertilization cycles.

    Science.gov (United States)

    Robson, Stephen J; Barry, Michael; Norman, Robert J

    2008-12-01

    To assess the practicality of using power Doppler (PD) to assess follicular vascularity at the time of oocyte retrieval. Prospective study. University-affiliated IVF unit. Twenty-six women undergoing IVF treatment. Evaluation of follicular vascularity by using PD during oocyte retrieval. Subjective assessment of the impact of PD estimation of follicle vascularity during oocyte retrieval; reproducibility of grading of follicle vascularity. Assessment of follicle vascularity by using PD during oocyte retrieval was found to be reproducible and to add minimally to the workload of the clinician and embryologist. The grade of follicle vascularity did not correlate with the yield of oocytes, fertilization rate, or concentration of hormones in follicular fluid. Although the study group was small, there was a statistically significant trend toward higher clinical pregnancy rates when the embryo transfer cohort contained at least one embryo from a highly vascular follicle (50% vs. 15.4%). Assessment of follicle vascularity by using PD at the time of oocyte retrieval was found to be a practical alternative to other methods.

  4. Harmonic components of demand and its effects over the electric power distribution networks; Los componentes armonicos de la demanda e sus efectos sobre las redes de distribucion electrica

    Energy Technology Data Exchange (ETDEWEB)

    Brugnoni, Mario [Buenos Aires Univ. (Argentina). Facultad de Ingenieria. Grupo Energia y Ambiente

    1997-12-31

    The steady increase in harmonic pollution creates new problems in electricity distribution networks. In this area, power factor correction and the neutral conductor deserve attention. In this paper we present an approach to dealing with this problems. (author) 14 refs., 8 figs., 2 tabs.; e-mail: gea at aleph.fi.uba.ar

  5. Wavelength diversification of high-power external cavity diamond Raman lasers using intracavity harmonic generation.

    Science.gov (United States)

    Jasbeer, Hadiya; Williams, Robert J; Kitzler, Ondrej; McKay, Aaron; Mildren, Richard P

    2018-01-22

    We report a high power quasi-continuous-wave (QCW) 620 nm laser from an external cavity diamond Raman laser utilizing intracavity frequency doubling in lithium triborate. Output power of 30 W for durations of 0.25 ms at 15% conversion efficiency was achieved with a beam quality factor M2 = 1.1 from a free-running Nd:YAG pump laser of M2 = 1.5. The critical design parameters that affect conversion efficiency and power were analysed with the aid of an analytical model. By adaptation to other pump technologies, the diamond approach provides a novel pathway towards high brightness CW beam generation in the visible and ultraviolet regions.

  6. Hybrid Active Filter with Variable Conductance for Harmonic Resonance Suppression in Industrial Power Systems

    DEFF Research Database (Denmark)

    Lee, Tzung-Lin; Wang, Yen-Ching; Li, Jian-Cheng

    2015-01-01

    -tuned passive filter and an active filter in series connection, both dc voltage and kVA rating of the active filter are dramatically decreased compared with the pure shunt active filter. In real application, this feature is very attractive since the active power filter with fully power electronics is very...... expensive. A reasonable trade-off between filtering performances and cost is to use the hybrid active filter. Design consideration are presented and experimental results are provided to validate effectiveness of the proposed method. Furthermore, this paper discusses filtering performances on line impedance...

  7. Harmonic Domain Modeling of a Distribution System Using the DIgSILENT PowerFactory Software

    DEFF Research Database (Denmark)

    Wasilewski, J.; Wiechowski, Wojciech Tomasz; Bak, Claus Leth

    The first part of this paper presents the comparison between two models of distribution system created in computer simulation software PowerFactory (PF). Model A is an exciting simplified equivalent model of the distribution system used by Transmission System Operator (TSO) Eltra for balenced load...

  8. Harmonic Stability Studies in VSC-HVDC Grid Connected Offshore Wind Power Plants

    DEFF Research Database (Denmark)

    Glasdam, Jakob Bærholm; Gevorgian, Vahan; Bak, Claus Leth

    2017-01-01

    Converter rich grids such as offshore wind power plants (OWPPs) are prone to become unstable due to control interaction with e.g. the extensive sub-marine cabling. There exists a need to investigate the stability in high voltage direct current (HVDC)grid connected OWPPs, as the electrical...

  9. Integration of Renewable Energy for the Harmonic Current and Reactive Power Compensation

    DEFF Research Database (Denmark)

    Pouresmaeil, Edris; Shaker, Hamid Reza; Mehrasa, Majid

    2015-01-01

    This paper deals with a control technique for multilevel converter topologies base on Direct Lyapunov Control Method (DLCM) for integration of Renewable Energy Resources (RER) into the power grid. The compensation of variations in reference current components is considered properly in this control...

  10. Differentiation of a pancreatic metastasis of a renal cell carcinoma from a primary pancreatic carcinoma by echo-enhanced power Doppler sonography.

    Science.gov (United States)

    Flath, B; Rickes, S; Schweigert, M; Lochs, H; Possinger, K; Wermke, W

    2003-01-01

    In a 70-year-old patient who had been treated for a renal cell carcinoma, a pancreatic mass was detected on CT scan. To differentiate a pancreatic metastasis of the renal cell carcinoma from a pancreatic carcinoma, an echo-enhanced power Doppler sonography was performed. The pancreatic mass demonstrated a strong echo enhancement, proving its hypervascularization. This behaviour favoured the diagnosis of a pancreatic metastasis of the renal cell carcinoma which was confirmed by histology. The principles and the role of echo-enhanced power Doppler sonography in the differential diagnosis between a primary pancreatic carcinoma and a metastasis of a renal carcinoma in the pancreas are discussed. We conclude that this technique can provide an important contribution to the diagnosis in this special instance. However, histology is the standard in the differential diagnosis of pancreatic tumours. Copyright 2003 S. Karger AG, Basel and IAP

  11. Endometrial volume and vascularity measurements by transvaginal three-dimensional ultrasonography and power Doppler angiography in stimulated and tumoral endometria: intraobserver reproducibility.

    Science.gov (United States)

    Mercé, Luis T; Alcázar, Juan L; Engels, Virginia; Troyano, Juan; Bau, Santiago; Bajo, José M

    2006-03-01

    To assess intraobserver reproducibility of the endometrial volume (EV) and 3D power Doppler indices (vascularization index, VI; flow index, FI; and vascularization flow index, VFI) of the endometrium and subendometrial area using three-dimensional power Doppler angiography (3D-PDA). Twenty-five women on the hCG day after controlled ovarian stimulation and 15 patients presenting with uterine bleeding and suspicious endometrial thickening (10 endometrial cancers and 5 endometrial hyperplasias) were scanned. Eighty volume data sets were analyzed using the VOCAL imaging program. EV and VI, FI and VFI of the endometrium and subendometrium (5 mm shell) were manually calculated in the longitudinal and coronal planes with 15 degrees and 9 degrees rotation steps. Intraclass correlation coefficient (ICC) and 95% confidence intervals were used to assess reliability. RESULTS.: EV measurements were highly reproducible (ICC > or = 0.97) without significant differences between planes and rotation steps. Endometrial and subendometrial VI, FI, and VFI presented ICCs above 0.90 with the exception of the subendometrial FI (ICC > or = 0.80). There were no significant differences according to measurement plane and rotation step except for subendometrial VFI. Nevertheless, 3D power Doppler indices calculated in the coronal plane and 9 degrees rotation step obtained the highest ICC. ICCs for 3D-PDA indices from the tumoral endometria were significantly higher than those calculated from the stimulated endometria. Endometrial volume and endometrial and subendometrial 3D power Doppler indices have an acceptable reproducibility, significantly higher in tumoral endometria. The reliability of measurements does not seem to be significantly influenced by the rotation plane and degrees of rotation. These results support that 3D-PDA and VOCAL are reliable methods to evaluate the physiological and pathological changes of the endometrium.

  12. Longitudinal microvascularity in achilles tendinopathy (power doppler ultrasound, magnetic resonance imaging time-intensity curves and the Victorian Institute of Sport Assessment-Achilles questionnaire): a pilot study

    Energy Technology Data Exchange (ETDEWEB)

    Richards, Paula J. [University Hospital of North Staffordshire NHS Trust (UHNS), Stoke on Trent, Staffordshire (United Kingdom); Keele University, Keele, Staffordshire (United Kingdom); North Staffs. Royal Infirmary, X-ray Department, Stoke on Trent, Staffordshire (United Kingdom); McCall, Iain W. [Keele University, Keele, Staffordshire (United Kingdom); North Staffordshire NHS Trust, Stoke on Trent, Staffordshire (United Kingdom); Day, Christopher [University Hospital of North Staffordshire NHS Trust (UHNS), Stoke on Trent, Staffordshire (United Kingdom); Belcher, John [Cardiff University, Department of Primary Care and Public Health, North Wales Clinical School, Cardiff (United Kingdom); Maffulli, Nicola [Keele University, Keele, Staffordshire (United Kingdom)

    2010-06-15

    To evaluate the imaging of the natural history of Achilles tendinopathy microvascularisation in comparison with symptoms, using a validated disease-specific questionnaire [the Victorian Institute of Sport Assessment-Achilles (VISA-A)]. A longitudinal prospective pilot study of nine patients with post-contrast magnetic resonance imaging (MRI), time-intensity curve (TIC) enhancement, ultrasound (US) and power Doppler (PD) evaluation of tendinopathy of the mid-Achilles tendon undergoing conservative management (eccentric exercise) over 1 year. There were five men and four women [mean age 47 (range 30-62) years]. Six asymptomatic tendons with normal US and MRI appearance showed less enhancement than the tibial metaphysis did and showed a flat, constant, but very low rate of enhancement in the bone and Achilles tendon (9-73 arbitrary TIC units). These normal Achilles tendons on imaging showed a constant size throughout the year (mean 4.9 mm). At baseline the TIC enhancement in those with tendinopathy ranged from 90 arbitrary units to 509 arbitrary units. Over time, 11 abnormal Achilles tendons, whose symptoms settled, were associated with a reduction in MRI enhancement mirrored by a reduction in the number of vessels on power Doppler (8.0 to 2.7), with an improvement in morphology and a reduction in tendon size (mean 15-10.6 mm). One tendon did not change its abnormal imaging features, despite improving symptoms. Two patients developed contralateral symptoms and tendinopathy, and one had more abnormal vascularity on power Doppler and higher MRI TIC peaks in the asymptomatic side. In patient with conservatively managed tendinopathy of the mid-Achilles tendon over 1 year there was a reduction of MRI enhancement and number of vessels on power Doppler, followed by morphological improvements and a reduction in size. Vessels per se related to the abnormal morphology and size of the tendon rather than symptoms. Symptoms improve before the Achilles size reduces and the

  13. Contribution in the area of harmonics in electric power systems; Contribuicoes na area de harmonicos em sistemas eletricos de potencia

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Aloisio de

    1989-07-01

    A general approach of the state of art of the harmonic generation, its sources, its limits, its measurement methods and its effects on the electric system components is presented. This thesis shows that this is an open field to research, modelling and solutions. It also helps towards the investigation of the effects caused by harmonics on the conventional KWh energy meters and on potential and current transformers. It presents the basis for the development and construction of prototypes to be utilized in the generation and measurement of harmonics. Finally a practical approach has been given to calculate the equivalent harmonic impedance as seen by a giving consumer. (author)

  14. Diagnostic utility of an echo-contrast agent in patients with synovitis using power Doppler ultrasound: a preliminary study with comparison to contrast-enhanced MRI

    Energy Technology Data Exchange (ETDEWEB)

    Magarelli, N.; Tartaro, A.; Bonomo, L. [Istituto di Radiologia, Universita di Chieti (Italy); Guglielmi, G. [Istituto di Radiologia, IRCCS, San Giovanni Rotondo (Italy); Di Matteo, L. [Istituto di Reumatologia, Pescara (Italy); Mattei, P.A. [Facolta di Medicina, Universita Chieti (Italy)

    2001-06-01

    The purpose of this study was to first evaluate Levovist (Schering, Berlin, Germany), an echo-contrast agent, during power Doppler sonography (PDS) in patients with synovitis using asymptomatic joints as controls. Then we evaluated the accuracy of this technique against contrast-enhanced MRI. Forty patients (19 men and 21 women; mean age 40 years) were enrolled on the basis of clinical signs, laboratory tests, and radiographic findings positive for articular inflammatory disease. They were examined with conventional ultrasonography (US) and PDS techniques before and after intravenous contrast medium injection. Fourteen patients then underwent MRI with and without contrast medium 8-14 days after PDS studies. Three expert readers independently evaluated each examination. After contrast medium, synovium in inflammatory arthritis enhanced on PDS compared with normal joints in the same patient. Power Doppler sonography after contrast medium and MRI were concordant in all cases. Power Doppler sonography with contrast medium showed a qualitative increase in signal from synovial vessels, the first sign of synovial changes in inflammatory diseases. (orig.)

  15. [Pancreatic metastases of renal cell carcinomas - evaluation of the contrast behavior at echo-enhanced power-Doppler sonography in comparison to primary pancreatic tumors].

    Science.gov (United States)

    Rickes, S; Flath, B; Unkrodt, K; Ocran, K; Neye, H; Lochs, H; Wermke, W

    2001-08-01

    Renal cell carcinomas are the most common primary tumors leading to pancreatic metastases. The differentiation of metastases from primary pancreatic tumors is important for the prognosis. Echo-enhanced power-Doppler sonography may be used for the differential diagnosis of tumors. In this study, the contrast behavior of metastases of renal cell carcinomas was evaluated in comparison to primary pancreatic tumors. Each 5 patients with pancreatic metastases of a renal cell carcinoma, a ductal carcinoma, a neuroendocrine tumor and a pancreatitis-associated mass were investigated by B-mode sonography, fundamental and echo-enhanced power-Doppler sonography. Similar to neuroendocrine tumors, metastases of renal cell carcinomas were found to be hypervascularized. In contrast, ductal carcinomas are hypovascularized compared to the surrounding tissue. Tumors associated with pancreatitis show different vascularization pattern depending on inflammation and necrosis. Metastases of renal cell carcinomas and ductal carcinomas show different vascularization pattern at echo-enhanced power-Doppler sonography. Renal cell metastases and neuroendocrine tumors have similar contrast behaviors, therefore, clinical symptoms should be referred for their differentiation. However, histology is the standard of reference for the differential diagnosis of pancreatic tumors.

  16. The role of endometrial and subendometrial vascularity measured by three-dimensional power Doppler ultrasound in the prediction of pregnancy during frozen-thawed embryo transfer cycles.

    Science.gov (United States)

    Ng, Ernest Hung Yu; Chan, Carina Chi Wai; Tang, Oi Shan; Yeung, William Shu Biu; Ho, Pak Chung

    2006-06-01

    A good blood supply to the endometrium is usually considered as an essential requirement for implantation. The aim of this study was to evaluate the role of endometrial and subendometrial vascularity in the prediction of pregnancy during frozen-thawed embryo transfer (FET) cycles. Women undergoing FET in natural or clomiphene-induced cycles after the first stimulated IVF treatment were recruited. A three-dimensional (3D) ultrasound examination with power Doppler was performed 1 day after the LH surge to determine endometrial thickness, endometrial pattern, pulsatility index (PI) and resistance index (RI) of uterine vessels, endometrial volume, vascularization index, flow index and vascularization flow index of endometrial and subendometrial regions. Women in the pregnant group were significantly younger and used less gonadotrophins in their stimulated cycle. Endometrial thickness, endometrial volume, endometrial pattern, uterine PI, uterine RI, endometrial and subendometrial 3D power Doppler flow indices were similar between the nonpregnant and the pregnant groups. The age of women was the only predictive factor for pregnancy. Receiver operating characteristic curve analysis revealed that the area under the curve was around 0.5 for all ultrasound parameters for endometrial receptivity. Vascularity of endometrial and subendometrial layers measured by 3D power Doppler ultrasound is not a good predictor of pregnancy in FET cycles if measured at one time point only.

  17. Endometrial and Subendometrial Vascularity by Three-Dimensional (3D) Power Doppler and Its Correlation with Pregnancy Outcome in Frozen Embryo Transfer (FET) Cycles.

    Science.gov (United States)

    Mishra, Vineet V; Agarwal, Ritu; Sharma, Urmila; Aggarwal, Rohina; Choudhary, Sumesh; Bandwal, Pradeep

    2016-10-01

    To study the role of endometrial and subendometrial blood flow measured by 3D power Doppler as predictors of pregnancy in frozen embryo transfer (FET) cycles. A hospital-based prospective study of two hundred and twenty-one (221) women undergoing FET cycles with a triple-line endometrium ≥7 mm on day 14 endometrial and subendometrial blood flow was assessed using 3D power Doppler, and various indices endometrial volume, subendometrial volume and their vascularisation index (VI), flow index (FI) and vascularisation flow index (VFI) were obtained and compared between the pregnant and the non-pregnant group. Primary outcome was clinical pregnancy. Out of 221 women, 97(43.89 %) became pregnant, while 124 (56.10 %) failed to become pregnant. The endometrial volume was comparable between the two groups. Endometrial VI, FI and VFI were significantly higher in the pregnant as compared to the non-pregnant group. There was a significant difference in subendometrial VI and VFI between the two groups, but FI was similar. Endometrial and subendometrial vascularity by 3D power Doppler can be a useful parameter in predicting pregnancy in FET cycles.

  18. Harmonic pollution produced by low power nonlinear loads: mathematical model and practical cases; Contaminacion armonica producida por cargas no lineales de baja potencia: modelo matematico y casos practicos

    Energy Technology Data Exchange (ETDEWEB)

    Mora Barajas, M.A.; Banuelos Sanchez, P. [Universidad de las Americas Puebla (Mexico)]. E-mail: marco.morabs@udlap.mx; pedro.banuelos@udlap.mx

    2010-04-15

    Many household electrical appliances like televisions, video recorders and computers are sources of voltage and current harmonics, which increase power losses and contaminate the AC power line. These harmonics can cause serious problems in both, utilities and electrical equipment connected to the same AC line. This paper shows a mathematical analysis of harmonics content on the electrical current for a circuit representing a non linear residential load. A comparative harmonic distortion study produced by the residential loads on the electrical power lines, measured experimentally, is also shown. [Spanish] Muchos de los aparatos electricos que tenemos en casa como televisores, videograbadoras y computadoras, generan armonicos de voltaje y de corriente que incrementan las perdidas de potencia y contaminan las lineas de suministro electrico, pudiendo ocasionar severos danos tanto a las redes de energia como a los equipos que de ellas se alimentan. En este articulo se muestra un analisis matematico del contenido armonico en la corriente de un circuito que representa a una carga residencial no lineal. Ademas, a partir de mediciones electricas realizadas de manera experimental, se presente un estudio comparativo de la contaminacion armonica que este tipo de cargas introduce a las lineas de suministro electrico.

  19. Three-Dimensional Power Doppler Evaluation of Cerebral Vascular Blood Flow: A Novel Tool in the Assessment of Fetal Growth Restriction.

    Science.gov (United States)

    Goetzinger, Katherine R; Cahill, Alison G; Odibo, Linda; Macones, George A; Odibo, Anthony O

    2018-01-01

    To determine whether fetuses with fetal growth restriction (FGR) are more likely to have abnormal cerebral vascular flow patterns compared to fetuses who are appropriate for gestational age (AGA) when quantified by using 3-dimensional (3D) power Doppler ultrasound. We conducted a prospective cohort study of singleton gestations presenting for growth ultrasound examination between 24 and 36 weeks' gestation. Patients with FGR (estimated fetal weight power Doppler image of the middle cerebral artery territory was obtained from each patient. The vascularization index (VI), flow index (FI), and vascularization-flow index (VFI) were calculated by the Virtual Organ computer-aided analysis technique (GE Healthcare, Milwaukee, WI). These indices were compared between FGR and AGA fetuses and correlated with 2-dimensional Doppler parameters. Neonatal outcomes were also compared with respect to the 3D parameters. Of 306 patients, there were 151 cases of FGR. There was no difference in the VI (6.0 versus 5.7; P = .65) or VFI (2.0 versus 1.8; P = .31) between the groups; however, the FI was significantly higher in FGR fetuses compared to AGA controls (33.9 versus 32.3; P = .009). There was a weak, but significant, negative correlation between the FI and both the middle cerebral artery pulsatility index (r = -0.34; P power Doppler measurement of cerebral blood flow, but not the vascularization pattern, is significantly altered in FGR. This measurement may play a future role in distinguishing pathologic FGR from constitutionally small growth. © 2017 by the American Institute of Ultrasound in Medicine.

  20. A Novel Ku-Band/Ka-Band and Ka-Band/E-Band Multimode Waveguide Couplers for Power Measurement of Traveling-Wave Tube Amplifier Harmonic Frequencies

    Science.gov (United States)

    Wintucky, Edwin G.; Simons, Rainee N.

    2015-01-01

    This paper presents the design, fabrication and test results for a novel waveguide multimode directional coupler (MDC). The coupler, fabricated from two dissimilar frequency band waveguides, is capable of isolating power at the second harmonic frequency from the fundamental power at the output port of a traveling-wave tube (TWT) amplifier. Test results from proof-of-concept demonstrations are presented for a Ku-band/Ka-band MDC and a Ka-band/E-band MDC. In addition to power measurements at harmonic frequencies, a potential application of the MDC is in the design of a satellite borne beacon source for atmospheric propagation studies at millimeter-wave (mm-wave) frequencies (Ka-band and E-band).

  1. Asymptomatic Versus Symptomatic Ankle Joints in Rheumatoid Arthritis: A High-Resolution B-Mode and Power Doppler Ultrasound Study.

    Science.gov (United States)

    Alsuwaidi, Mohammed; Ehrenstein, Boris; Fleck, Martin; Hartung, Wolfgang

    2016-06-01

    Ankle joints are frequently neglected in activity scoring systems, including the Disease Activity Score in 28 joints (DAS28). Only a few studies have assessed pathologies detected by ultrasonography of the ankles in symptomatic rheumatoid arthritis (RA) patients. We evaluated ankle joints in RA patients regardless of symptomatology, using musculoskeletal ultrasound (MSUS) as well as power Doppler ultrasound (PDUS). A total of 160 ankle joints of 80 RA patients were examined using MSUS and PDUS, according to the European League Against Rheumatism MSUS guidelines. Additionally, the talonavicular joints (TNJs) and the medial and the lateral tendon compartments were examined. The visual analog scale (VAS) score was recorded for each patient. A total of 80 RA patients with a median age of 60 years and disease duration of 5 years were enrolled in our study. The median DAS28 score was 5. A total of 97 ankles were painful (VAS 1-10), whereas 63 ankles were asymptomatic (VAS 0). Overall, the predominant pathology was arthritis of the tibiotalar joint (TTJ) and/or TNJ in 124 ankles (77%), followed by tenosynovitis of the medial compartment tendons in 44 ankles (28%). Arthritis of the TTJ was present in 59% and synovitis of the TNJ in 35% of the symptomatic ankles. In asymptomatic ankles, TTJ synovitis was detected in 35%, whereas TNJ arthritis was observed in 18%. PDUS activity was higher in the subgroup of symptomatic ankles. The most frequent pathologies detected by MSUS were arthritis of the TTJ and TNJ, followed by tenosynovitis of the medial compartment tendons. Pathologic findings were more frequent in symptomatic but also common in asymptomatic patients, whereas PDUS activity was generally low and mainly observed in symptomatic patients. © 2016, American College of Rheumatology.

  2. Intrinsic subtypes and tumor grades in breast cancer are associated with distinct 3-D power Doppler sonographic vascular features

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Yeun-Chung [Department of Medical Imaging, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei 10041, Taiwan, ROC (China); Huang, Yao-Sian [Department of Computer Science and Information Engineering, National Taiwan University, Taipei 10617, Taiwan, ROC (China); Huang, Chiun-Sheng [Department of Surgery, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei 10041, Taiwan, ROC (China); Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei 10617, Taiwan, ROC (China); Chen, Jeon-Hor [Center for Functional Onco-Imaging and Department of Radiological Science, University of California Irvine, California, CA 92868 (United States); Department of Radiology, E-Da Hospital and I-Shou University, Kaohsiung 82445, Taiwan, ROC (China); Chang, Ruey-Feng, E-mail: rfchang@csie.ntu.edu.tw [Department of Computer Science and Information Engineering, National Taiwan University, Taipei 10617, Taiwan, ROC (China); Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei 10617, Taiwan, ROC (China)

    2014-08-15

    Purpose: This study aimed to investigate the three-dimensional (3-D) power Doppler ultrasonographic (PDUS) vascular features of breast carcinoma according to intrinsic subtypes, nodal stage, and tumor grade. Materials and methods: Total 115 receiving mastectomy breast carcinomas (mean size, 2.5 cm; range, 0.7–6.5 cm), including 102 invasive ductal carcinomas (IDC), 10 ductal carcinomas in situ (DCIS), and 3 invasive lobular carcinomas (ILC) diagnosed after mastectomy, were used in this retrospective study. Sixty IDC had nodal status and histopathologic tumor grades available for analysis. Vascular features, including number of vascular trees (NV), longest path length (LPL), total vessel length (TVL), number of bifurcations (NB), distance metric (DM), inflection count metric (ICM), vessel diameter (VD), and vessel-to-volume ratio (VVR) were extracted using 3-D thinning method. The Mann–Whitney U test, Student's t-test, one-way ANOVA, and Kruskal–Wallis test were performed as appropriate. Results: There was no significant difference of vascular features among IDC, DCIS and ILC. Except VD, vascular features in luminal type were significantly lower compared to HER2-enriched or triple negative types (p < 0.05). Compared to ER+ (estrogen receptor positive) tumors, all features in ER− (estrogen receptor negative) tumors were significantly higher (p < 0.01). Despite some significantly higher vascular features in high grade IDC compared to low and intermediate grade, there was no significant correlation between vascular features and nodal stages. Conclusion: Differences in 3-D PDUS vascular features among intrinsic types of IDC are attributed to their ER status. Vascular features extracted by 3-D PDUS correlate with tumor grades but not nodal stage in IDC.

  3. Core density fluctuations observed on Tore Supra by Doppler back-scattering: perpendicular velocity modification in high power ICRH experiments

    Energy Technology Data Exchange (ETDEWEB)

    Hennequin, P.; Honore, C.; Truc, T.; Quemeneur, A. [Ecole Polytechnique de Palaiseau, Lab. de Physique et Technologie des Plasmas, CNRS (UMR 7648), 91 - Palaiseau (France); Fenzi-Bonizec, C.; Bourdelle, C.; Garbet, X.; Hoang, G.T. [Association Euratom-CEA, CEA/DSM/DRFC, Centre de Cadarache, 13 Saint Paul lez Durance (France)

    2005-07-01

    Backscattering of a microwave beam close to the cut-off allows for measurement of density fluctuations n(k(perpendicular)) at a specified wave-number, selected by the scattering geometry k(perpendicular) = -2*k{sub i}, where k{sub i} is the beam wave-number at the reflection layer. On the system installed on Tore Supra, both the scattering wave-number k(perpendicular) and the scattering localisation r/a can be changed during the shot for probing 0.5 < r/a < 0.95 and 2 < k < 15 cm{sup -1}, owing to the adjustable probing frequency and the motorized antenna. The perpendicular fluctuation velocity in the laboratory frame is obtained from the Doppler shift of the frequency spectrum {delta}{omega} = k(perpendicular)*v(perpendicular). It is dominated by the plasma E{sub r} x B velocity. In the core, the latter is mainly due to the projection of the toroidal velocity, as this is shown by comparison with measurements by charge exchange recombination spectroscopy. In the set of analysed Tore Supra ohmic and ICRH (ion cyclotron resonance heating) plasmas, the observed rotation is consistent with a poloidal velocity in the electron diamagnetic direction and/or a toroidal velocity in the counter current direction. Strong modification of velocity profiles and turbulence level are observed together with improved confinement in experiments with ICRH heating at high power and high concentration of minority ions. Preliminary results on associated wave number spectra will also be shown. (authors)

  4. The value of power Doppler ultrasound in patients with rheumatoid arthritis in clinical remission: Reclassifying disease activity?

    Science.gov (United States)

    Vergara, Facundo; Ruta, Santiago; Rosa, Javier; Marín, Josefina; García-Mónaco, Ricardo; Soriano, Enrique R

    2017-03-18

    The aim of the present study was to describe the ultrasound (US) findings in patients with rheumatoid arthritis (RA) in clinical remission, and to evaluate the ability of power Doppler (PD) US to reclassify disease activity in these patients. We included consecutive patients with RA according to 2010 American College of Rheumatology/European League Against Rheumatism criteria, who were in clinical remission by the Disease Activity Score (DAS28<2.6). Twenty joints of both hands were assessed by US. PD signal was evaluated on a semi-quantitative scale from 0 to 3. Three different US-modified DAS28 (US-DAS28) were constructed, replacing the clinical swollen joint count by the PD US joint count using PD score ≥1, ≥2 or ≥3, respectively. Eighty-six patients were included. Twenty-three (26.7%) patients had at least one joint with abnormal US-positive PD signal. Thirteen percent of patients were reclassified to low disease activity by applying the US-DAS28 when joints were considered active with a PD signal ≥1; 12%, when a PD signal ≥2 was considered, and 2% of the patients were reclassified when a PD score of 3 was considered. No patients were reclassified to a level of moderate or high activity applying US-DAS28. Although around a quarter of patients with RA in clinical remission showed PD US features indicating residual activity, only a small percentage were reclassified to a state of low activity and none to a level of moderate or high activity, applying the proposed US-DAS28. Copyright © 2017 Elsevier España, S.L.U. and Sociedad Española de Reumatología y Colegio Mexicano de Reumatología. All rights reserved.

  5. Power Doppler sonography, a non-invasive method of assessment of the synovial inflammation in patients with early rheumatoid arthritis.

    Science.gov (United States)

    Vreju, Fl; Ciurea, M; Roşu, Anca; Muşetescu, Anca; Grecu, D; Ciurea, Paulina

    2011-01-01

    To detect synovitis is important in both the diagnosis and outcome assessment of early rheumatoid arthritis. This study was meant to assess the validity and reproducibility of ultrasonography (US) as a mean of detection for the knee synovitis, by comparing US findings with clinical examination and histopathological findings in synovial membrane. The study group included 65 patients with early rheumatoid arthritis - below 12 months from the debut, naive for DMARDs, in whom demographic data - gender, age, disease duration, the number of tender and swollen joints, HAQ score (Health Assessment Questionnaire) and serum samples for CRP, RF, anti-CCP2 antibodies (ELISA, QUANTA LiteTM, CCP IgG, INOVA Diagnostics Inc, USA), VEGF (ELISA, VEGF2, DRG International, IRC, USA) determination were recorded. Disease Activity Score for 28 joints (DAS28) was calculated. PDS signal was scored from 0 to 3 according to the overall expression of PDS findings at the knees. A sample of synovial tissue was obtained in 35 patients during the arthroscopy, and the vascularisation of the synovial tissue was evaluated by immunohistochemistry and was analyzed qualitatively by a pathologist who was unaware of the PDS findings. Written, informed consent was obtained from each patient before entering the study. They all had active synovitis of the knee, ultrasonographically confirmed, with the identification of the target biopsy sites. The study was approved by the Ethics Committee of the University of Medicine and Pharmacy of Craiova. Angiogenesis was evaluated and quantified by immunohistochemical evaluation of synovial VEGF, one of the most specific endothelial growing factors, that proved to correlate significantly with the serum levels of VEGF, DAS28 as well as with the power Doppler sonography (PDS) score. The statistical analysis of the data showed that PDS could be used as non-invasive marker with predictive value regarding synovial inflammation and disease progression in early forms of the

  6. The relationship of patient-reported joints with active synovitis detected by power Doppler ultrasonography in rheumatoid arthritis.

    Science.gov (United States)

    Cheung, Peter P; Gossec, Laure; Ruyssen-Witrand, Adeline; Le Bourlout, Catherine; Mézières, Maryse; Dougados, Maxime

    2013-01-01

    This paper aims to evaluate the relationship of patient-reported tender and swollen joints with active inflammation as detected by power Doppler (PDUS) and whether this relationship is affected by significant joint damage. Fifty rheumatoid arthritis patients self-assessed 28 tender and swollen joints and were followed by PDUS assessment. Relationship of tender and swollen joints with active synovitis (PDUS 'gold standard') was assessed at the joint level by: a) percentage agreement at each PDUS semiquantitative grade (grade 1 to 3), b) positive likelihood ratio (LR) of agreement with PDUS, and c) LR of agreement with PDUS according to radiographic damage (significant erosive disease vs. non-erosive disease). Correlation of tender and swollen joint counts with disease activity markers was analysed by Spearman's. Sensitivity analyses examined the influence of disease activity or global pain on level of agreement at the joint level. Of joints with significant active inflammation (e.g. grade 3 PDUS), patients identified 75% as tender and 63% as swollen. Swollen joints showed strong association at the joint level with active synovitis when there was no significant radiographic damage (LR 2.54, 95%CI 1.93-3.34), but with no significant radiographic damage (LR 1.32, 95%CI 0.75-2.32). Swollen joint counts were statistically correlated with PDUS-DAS28 and CRP, but not PDUS score. Sensitivity analysis showed better agreement of tender and swollen joints with active synovitis when DAS28 was ≤ 3.2 and when patient global pain was joints and active synovitis is stronger in the setting of low disease activity without erosive disease, affected also by degree of reported global pain. Further longitudinal studies of patient-reported joints are needed.

  7. A Numerical Matrix-Based method in Harmonic Studies in Wind Power Plants

    DEFF Research Database (Denmark)

    Dowlatabadi, Mohammadkazem Bakhshizadeh; Hjerrild, Jesper; Kocewiak, Łukasz Hubert

    2016-01-01

    In the low frequency range, there are some couplings between the positive- and negative-sequence small-signal impedances of the power converter due to the nonlinear and low bandwidth control loops such as the synchronization loop. In this paper, a new numerical method which also considers...... these couplings will be presented. The numerical data are advantageous to the parametric differential equations, because analysing the high order and complex transfer functions is very difficult, and finally one uses the numerical evaluation methods. This paper proposes a numerical matrix-based method, which...... is not only able to deal with those mentioned numerical data, but also it is able to consider all couplings between the positive and negative sequences....

  8. Harmonic analysis

    CERN Document Server

    Helson, Henry

    2010-01-01

    This second edition has been enlarged and considerably rewritten. Among the new topics are infinite product spaces with applications to probability, disintegration of measures on product spaces, positive definite functions on the line, and additional information about Weyl's theorems on equidistribution. Topics that have continued from the first edition include Minkowski's theorem, measures with bounded powers, idempotent measures, spectral sets of bounded functions and a theorem of Szego, and the Wiener Tauberian theorem. Readers of the book should have studied the Lebesgue integral, the elementary theory of analytic and harmonic functions, and the basic theory of Banach spaces. The treatment is classical and as simple as possible. This is an instructional book, not a treatise. Mathematics students interested in analysis will find here what they need to know about Fourier analysis. Physicists and others can use the book as a reference for more advanced topics.

  9. Harmonization of standards for parabolic trough collector testing in solar thermal power plants

    Science.gov (United States)

    Sallaberry, Fabienne; Valenzuela, Loreto; Palacin, Luis G.; Leon, Javier; Fischer, Stephan; Bohren, Andreas

    2017-06-01

    The technology of parabolic trough collectors (PTC) is used widely in concentrating Solar Power (CSP) plants worldwide. However this type of large-size collectors cannot be officially tested by an accredited laboratory and certified by an accredited certification body so far, as there is no standard adapted to its particularity, and the current published standard for solar thermal collectors are not completely applicable to them. Recently some standardization committees have been working on this technology. This paper aims to give a summary of the standardized testing methodology of large-size PTC for CSP plants, giving the physical model chosen for modeling the thermal performance of the collector in the new revision of standard ISO 9806 and the points still to be improved in the standard draft IEC 62862-3-2. In this paper, a summary of the testing validation performed on one parabolic trough collector installed in one of the test facilities at the Plataforma Solar de Almería (PSA) with this new model is also presented.

  10. Stimulated angiogenesis for fracture healing augmented by low-magnitude, high-frequency vibration in a rat model-evaluation of pulsed-wave doppler, 3-D power Doppler ultrasonography and micro-CT microangiography.

    Science.gov (United States)

    Cheung, Wing-Hoi; Sun, Ming-Hui; Zheng, Yong-Ping; Chu, Winnie Chiu-Wing; Leung, Andraay Hon-Chi; Qin, Ling; Wei, Fang-Yuan; Leung, Kwok-Sui

    2012-12-01

    This study aimed to investigate the mechanism of low-magnitude high-frequency vibration (LMHFV) treatment on angiogenesis and blood flow for enhancement of fracture healing. Nine-month-old ovariectomized (OVX) and sham-operated (Sham) rats received closed fractures creation at the femora and were randomized into LMHFV treatment (Sham-V, OVX-V) or control (Sham-C, OVX-C) groups. Pulsed-wave Doppler indicated an increase in blood flow velocity of the femoral artery at weeks 2 (OVX pair: p = 0.030) and 4 (OVX pair: p = 0.012; Sham pair: p = 0.020) post-treatment. Significantly enhanced vascular volume (VV) at the fracture site in the vibration groups was demonstrated by 3-D high-frequency power Doppler at week 2 (Sham pair: p = 0.021) and micro-computed tomography (microCT) microangiography at weeks 2 (OVX pair: p = 0.009) and 4 (OVX pair: p = 0.034), which echoed the osteogenesis findings by radiographic and microCT analysis. VV in the OVX groups was inferior to the Sham groups. However, OVX-V showed higher percentages of angiogenic enhancement than Sham-V. Despite impaired neo-angiogenesis in osteoporotic fractures, LMHFV could increase blood flow and angiogenesis in both normal and osteoporotic fractures, thus enhancing fracture healing. Copyright © 2012 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  11. Impact of laparoscopic ovarian drilling on anti-Müllerian hormone levels and ovarian stromal blood flow using three-dimensional power Doppler in women with anovulatory polycystic ovary syndrome.

    Science.gov (United States)

    Elmashad, Ashraf I

    2011-06-01

    To evaluate the effect of laparoscopic ovarian drilling (LOD) on plasma levels of anti-Müllerian hormone (AMH) and ovarian stromal blood flow changes, by using three-dimensional power Doppler ultrasonography, in polycystic ovary syndrome (PCOS). Prospective controlled study. Taiba hospital, Kuwait. Twenty-three anovulatory clomiphene citrate (CC)-resistant women with PCOS and 20 fertile women as a control group. Laparoscopic ovarian drilling. Serum levels of AMH, ovarian three-dimensional power Doppler indices (vascularization index, flow index, and vascularization flow index) and occurrence of ovulation or pregnancy. Plasma AMH and power Doppler indices of ovarian stromal blood flow were significantly higher in the PCOS group than in the control group. Plasma AMH and ovarian stromal blood flow Doppler indices were significantly reduced in the PCOS group after LOD. Women who ovulated after LOD had a significantly lower preoperative AMH compared with the nonresponders. There was a significant positive correlation between AMH and power Doppler flow indices before and after LOD in PCOS group. Measuring AMH and ovarian stromal three-dimensional power Doppler blood flow for women with anovulatory PCOS undergoing LOD may provide a useful tool in evaluating the outcome of LOD. Copyright © 2011 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

  12. Correlations in photoacoustic estimates of tumor oxygenation during novel cancer therapies with power Doppler measurements (Conference Presentation)

    Science.gov (United States)

    Hysi, Eno; Wirtzfeld, Lauren A.; Al-Mahrouki, Azza; Elfarnawany, Mai; Lacefield, James C.; Czarnota, Gregory J.; Kolios, Michael C.

    2017-03-01

    Photoacoustic (PA) imaging of tumor oxygenation can be used to monitor vascular-targeted novel therapies. This study examines how a combination treatment, ultrasound-microbubbles (USMB)/radiation-therapy (XRT) alters oxygen saturation (sO2) estimates, which are then compared to power Doppler (PD) assessments of tumor vascularity. SCID mice were inoculated with subcutaneous, hind-leg PC3 tumors. The treatment consisted of XRT/MB (XRT: 8Gy/single-fraction; USMB: 3%/500 kHz/570kPa; n=3), USMB (n=3) and XRT (n=5) alone and untreated control (n=5). PA/PD imaging was acquired pre-treatment and 2h/24h post-treatment using the VevoLAZR (21 MHz, 750/850 nm). The volumetric tumor sO2 was quantified using histogram distributions and the average mode was computed. The vascularization index (VI), a PD metric of tumor vessel density, was studied along with the sO2 mode by comparing changes at 2h with pre-treatment. Mice whose pre-treatment sO2 levels were over 65%, exhibited a 15% drop in oxygenation at 2h, remaining unchanged by 24h. Examining the sO2 and VI relationships revealed differences between the groups. All groups (except control) exhibited a positive correlation when the ∆VI was plotted as a function of ∆sO2 (r2≥0.85). Mice in the XRT/MB group had the largest slope (11.7) suggesting that a change in sO2 was accompanied by the largest change in vessel density. The slope of the USMB and XRT treatments was 5.6 and 2.9, respectively. The combination treatment induced the largest changes in vessel density and sO2. Early PA estimates of tumor oxygenation appear to correlate with the treatment-induced vascular changes. Such measure could potentially be used for predicting treatment outcome.

  13. Effect of metformin treatment on endometrial vascular indices in anovulatory obese/overweight women with polycystic ovarian syndrome using three-dimensional power doppler ultrasonography.

    Science.gov (United States)

    Mohsen, Iman Abdel; Elkattan, Eman; Nabil, Hala; Khattab, Sherif

    2013-06-01

    Metformin has been shown to be an effective treatment for anovulatory polycystic ovary syndrome (PCOS) patients in terms of menstrual cyclicity, ovulation, and pregnancy, as well as reduction of early miscarriage rate. The aim of the study is to assess the effect of metformin on the endometrial vascular indices in anovulatory obese PCOS women using three-dimensional power Doppler sonography (3DPDUS). A prospective study was set to determine the beneficial effects of metformin on PCOS patients. Fifty anovulatory obese PCOS patients were compared with another 50 healthy volunteers who were age- and body mass index-matched (control group). PCOS patients were treated with metformin (Glucophage; MerckSerono) 850 mg 3 times a day for 6 months. Assessment of the endometrial thickness and volume, uterine Doppler indices, and Doppler vascular indices of the endometrium and subendometrium in the periovulatory and midluteal phases were performed with 3DPDUS. There was a significant increase in the endometrial thickness, endometrial volume, and endometrial and subendometrial vascularity indices (vascularization index, flow index, vascularization flow index) after 6 months of metformin treatment in PCOS women, whereas there was no change in the resistance index and the pulsatility index of the uterine artery in both periovulatory and midluteal phases. Metformin, owing to its metabolic, endocrine, vascular, and anti-inflammatory effects, improves markers of endometrial receptivity. Copyright © 2012 Wiley Periodicals, Inc.

  14. Influence of gain adjustment on 3-dimensional power Doppler indices and on spatiotemporal image correlation volumetric pulsatility indices using a flow phantom.

    Science.gov (United States)

    Miyague, Andre H; Raine-Fenning, Nicholas J; Pavan, Theo Z; Polanski, Lukasz T; Baumgarten, Miriam N; Nastri, Carolina O; Martins, Wellington P

    2013-10-01

    Spatiotemporal image correlation can be used to acquire 3-dimensional power Doppler information across a single cardiac cycle. Assessment and comparison of the systolic and diastolic components of the data sets allow measurement of the recently introduced "volumetric pulsatility index" (vPI) through algorithms comparable with those used in 2-dimensional Doppler waveform analysis. The vPI could potentially overcome the dependency on certain machine settings, such as power, color gain, pulse repetition frequency, and attenuation, since these factors would affect the power Doppler signal equally throughout the cardiac cycle. The objective of this study was to compare the effect of color gain on the vascularization index (VI), vascularization-flow index (VFI), and vPI using an in vitro flow phantom model. We separated gains into 3 bands: -8 to -1 (no noise), -1 to +5 (low noise), and +5 to +8 (obvious noise). The vPI was determined from the 3-dimensional VI or VFI using the formula vPI = (maximum - minimum)/mean. Using no-noise gains, we observed that although the VI and VFI increased linearly with gain, the vPI was substantially less dependent on this adjustment. The VI and VFI continued to increase linearly with gain, whereas the vPI decreased slightly using low-noise gains. When gain was increased above the lower limit of obvious noise (+5), the VI and VFI increased noticeably, and there were marked reductions in both vPI values. We conclude that the vPI is less affected by changes in color gain than the VI and VFI at no-noise gains.

  15. Detection of Harmonic Occurring using Kalman Filtering

    DEFF Research Database (Denmark)

    Hussain, Dil Muhammad Akbar; Shoro, Ghulam Mustafa; Imran, Raja Muhammed

    2014-01-01

    As long as the load to a power system is linear which has been the case before 80's, typically no harmonics are produced. However, the modern power electronic equipment for controlled power consumption produces harmonic disturbances, these devices/equipment possess nonlinear voltage/current chara...... using Kalman filter. This may be very useful for example to quickly switching on certain filters based on the harmonic present. We are using a unique technique to detect the occurrence of harmonics....

  16. Two-dimensional power Doppler-three-dimensional ultrasound imaging of a cesarean section dehiscence with utero-peritoneal fistula: a case report

    Directory of Open Access Journals (Sweden)

    Royo Pedro

    2009-01-01

    Full Text Available Abstract Introduction An imaging diagnosis after an iterative cesarean delivery is reviewed demonstrating a fine ultrasound-pathologic correlation. Case presentation A 33-year-old woman (G3, P3 presented referring intense dysmenorrhea and intermenstrual spotting since her third cesarean delivery, 1 year before. A cesarean section dehiscence with utero-peritoneal fistula was diagnosed by transvaginal ultrasound. Conclusion We can conclude that transvaginal two-dimensional power Doppler and three-dimensional ultrasound are highly accurate in detecting cesarean section dehiscence and uterine fistula.

  17. Inter- and intra-observer agreement of high-resolution ultrasonography and power Doppler in assessment of joint inflammation and bone erosions in patients with rheumatoid arthritis.

    Science.gov (United States)

    Chávez-López, Mario Alfredo; Hernández-Díaz, Cristina; Moya, Carlos; Pineda, Carlos; Ventura-Ríos, Lucio; Möller, Ingrid; Naredo, Esperanza; Espinosa, Rolando; Peña, Angélica; Rosas-Cabral, Alejandro; Filippucci, Emilio

    2013-01-01

    To assess the inter- and intra-observer reproducibility of musculoskeletal ultrasonography among rheumatologist in detecting inflammatory and morphostructural changes in small joints of the hands in patients with rheumatoid arthritis (RA). Five members of the "Escuela de Ecografía del Colegio Mexicano de Reumatología" tested their inter- and intra-observer reliabilities in the assessment of basic sonographic findings of joint inflammation and bone erosion. Their results were compared to those obtained by a group of international experts from European League Against Rheumatism. A clinical rheumatologist evaluated eight RA patients. Five Siemens Acuson Antares ultrasound machines (7-13 MHz linear probes) were used. The OMERACT preliminary definitions of joint effusion, synovial hypertrophy, bone erosions and tenosynovitis were adopted. Inter-observer and intra-observer agreement was calculated by overall agreement and kappa statistics. Mean kappa value for joint effusion was good, 0.654 (85%); synovial hypertrophy, 0.550 (77.2%); power Doppler signal, 0.550 (82.5%); bone erosions, 0.549 (81%); and tenosynovitis, 0.500 (91.5%). Mean and overall intra-observer agreement for semiquantitative score was good for joint effusion, 0.630 (77.2%) and bone erosions, 0.605 (56.25%); and moderate to synovial hypertrophy, 0.476 (65%) and power Doppler signal, 0.471 (80%). Mean kappa value for joint effusion was 0.381 (95%), synovial hypertrophy, 0.447 (72%); power Doppler signal, 0.496 (81%); bone erosions, 0.294 (81%); and tenosynovitis, 0.030 (66%). Mean and overall inter-observer agreement for semiquantitative score was poor for joint effusion, 0.325 (57%) and bone erosions, 0.360 (43%); and moderate to synovial hypertrophy, 0.431 (55%) and power Doppler signal, 0.496 (81%). Intra-observer variability reached the highest levels of agreement. Factors related to the experience of the rheumatologist, the time spent in each examination and knowledge of the software ultrasound

  18. Fabrication of a PMN-PT Single Crystal-Based Transcranial Doppler Transducer and the Power Regulation of Its Detection System

    Directory of Open Access Journals (Sweden)

    Qingwen Yue

    2014-12-01

    Full Text Available Doppler sonographic measurement of flow velocity in the basal cerebral arteries through the intact skull was developed using a pulsed Doppler technique and 2 MHz emitting frequency. Relaxor-based ferroelectric single crystals Pb(Mg1/3Nb2/3O3-PbTiO3 (PMN-PT were chosen to be the piezoelectric transducer material due to their ultrahigh piezoelectric coefficients, high electromechanical coupling coefficients and low dielectric loss. The pulse-echo response of the transducer was measured using the conventional pulse-echo method in a water bath at room temperature. The −6 dB bandwidth of the transducer is 68.4% and the sensitivity is −17.4 dB. In order to get a good match between transducer and detection system, different transmission powers have been regulated by changing the impedance of the transmitting electric circuit. In the middle cerebral artery (MCA measurement photograph results, as the transmission power is increasing, the detection results become clearer and clearer. A comparison at the same transmission power for different transducers shows that the detection photograph obtained by the crystal transducer was clearer than that obtained with a commercial transducer, which should make it easier for doctors to find the cerebral arteries.

  19. Multi-MW 22.8 GHz Harmonic Multiplier - RF Power Source for High-Gradient Accelerator R&D

    Energy Technology Data Exchange (ETDEWEB)

    Jay L. Hirshfield

    2012-07-26

    Electrodynamic and particle simulation studies have been carried out to optimize design of a two-cavity harmonic frequency multiplier, in which a linear electron beam is energized by rotating fields near cyclotron resonance in a TE111 cavity in a uniform magnetic field, and in which the beam then radiates coherently at the nth harmonic into a TEn11 output cavity. Examples are worked out in detail for 7th and 2nd harmonic converters, showing RF-to-RF conversion efficiencies of 45% and 88%, respectively at 19.992 GHz (K-band) and 5.712 GHz (C-band), for a drive frequency of 2.856 GHz. Details are shown of RF infrastructure (S-band klystron, modulator) and harmonic converter components (drive cavity, output cavities, electron beam source and modulator, beam collector) for the two harmonic converters to be tested. Details are also given for the two-frequency (S- and C-band) coherent multi-MW test stand for RF breakdown and RF gun studies.

  20. Relative power of harmonics in human frequency-following responses associated with voice pitch in American and Chinese adults.

    Science.gov (United States)

    Jeng, Fuh-Cherng; Costilow, Cassie E; Stangherlin, Daniela P; Lin, Chia-Der

    2011-08-01

    When the fundamental frequency (f0) is removed from a complex stimulus, the pitch of the f0 is still perceived by the listener. Through the use of the scalp-recorded frequency-following response, this study examined the relative contributions of thef0 and its harmonics in pitch processing by systematically manipulating the speech stimulus to remove component frequencies. 12 American and 12 Chinese adults were recruited. There were statistically significant effects of pitch strength and frequency error for the experimental-condition factor. There were significantly larger responses to the harmonics-only conditions than those obtained in the f0-only and control conditions. No statistically significant difference was observed between the two groups of participants. These findings indicate that neural responses associated with individual harmonics dominate the pitch processing in the human brainstem, irrespective of whether the listener's native language is nontonal or tonal.

  1. Comparisons between PW Doppler system and enhanced FM Doppler system

    DEFF Research Database (Denmark)

    Wilhjelm, Jens E.; Pedersen, P. C.

    1995-01-01

    This paper presents a new implementation of an echo-ranging FM Doppler system with improved performance, relative to the FM Doppler system reported previously. The use of long sweeps provides a significant reduction in peak to average power ratio compared to pulsed wave (PW) emission. A PW Doppler...... system exploits the direct relationship between arrival time of the received signal and range from the transducer. In the FM Doppler systems, a similar relationship exists in the spectral domain of the demodulated received signals, so that range is represented by frequency. Thus, a shift in location...... of moving scatterers between consecutive emissions corresponds to a frequency shift in the spectral signature. The improvement relative to the earlier version of the FM Doppler system is attained by utilizing cross-correlation of real spectra rather than of magnitude spectra for assessing flow velocity...

  2. Monitoring anti-interleukin 6 receptor antibody treatment for rheumatoid arthritis by quantitative magnetic resonance imaging of the hand and power Doppler ultrasonography of the finger

    Energy Technology Data Exchange (ETDEWEB)

    Kamishima, Tamotsu; Terae, Satoshi [Hokkaido University Hospital, Department of Radiology, Sapporo (Japan); Tanimura, Kazuhide; Shimizu, Masato; Matsuhashi, Megumi; Fukae, Jun; Hagiwara, Hiromi; Narita, Akihiro; Aoki, Yuko [Hokkaido Medical Center for Rheumatic Diseases, Sapporo (Japan); Kon, Yujiro [St Thomas' Hospital, London (United Kingdom); Kosaka, Naoki [Tokeidai Memorial Hospital, Sapporo (Japan); Atsumi, Tatsuya [Hokkaido University Graduate School of Medicine, Department of Medicine, Sapporo (Japan); Shirato, Hiroki [Hokkaido University Graduate School of Medicine, Department of Radiology, Sapporo (Japan)

    2011-06-15

    To compare quantitative magnetic resonance imaging (MRI) and power Doppler ultrasonography (PDUS) with conventional measures of disease activity in rheumatoid arthritis (RA) patients treated with the anti-interleukin 6 (anti-IL 6) receptor antibody tocilizumab in terms of responsiveness at a few months to disease activity and ability to predict structural damage at 1 year. A cohort of patients with RA (n = 29) was evaluated clinically including disease activity score 28 (DAS28) and by semiquantitative (SQ-) and quantitative (Q-) PDUS (bilateral metacarpophalangeal joints) and MRI (one hand and wrist) at initiation of treatment with anti-IL 6 receptor antibody agents and after 2 and 5 months. Conventional radiography for both hands and wrists was performed at baseline and at 12 months. Responsiveness was assessed by standardized response means (SRM). Areas under the curve (AUC) for measures at baseline, 2 and 5 months were correlated with structural damage at 1 year. Among the laboratory and clinical parameters, DAS28-ESR was the most responsive with a large effect size of SRM. Structural damage progressions for radiography and MR erosion were correlated with AUC of MR bone erosion and Q-PDUS, respectively. In the evaluation of disease activity in RA patients in the first few months after starting anti-IL 6 receptor antibody tocilizumab treatment, the semiquantitative MR bone erosion score of the hand and quantitative value for power Doppler signal in the finger joint were both responsive and predictive of structural damage progression at 1 year. (orig.)

  3. Correlation of pretreatment polarographically measured oxygen pressures with quantified contrast-enhanced power doppler ultrasonography in spontaneous canine tumors and their impact on outcome after radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Rohrer Bley, Carla; Laluhova, Dagmar [Section of Radiooncology, Vetsuisse Faculty, Univ. of Zurich (Switzerland); Roos, Malgorzata [Inst. for Social and Preventive Medicine, Medical Faculty, Univ. of Zurich (Switzerland); Kaser-Hotz, Barbara [Section of Radiooncology, Vetsuisse Faculty, Univ. of Zurich (Switzerland); Section Imaging Diagnostics, Vetsuisse Faculty, Univ. of Zurich (Switzerland); Ohlerth, Stefanie [Section Imaging Diagnostics, Vetsuisse Faculty, Univ. of Zurich (Switzerland)

    2009-11-15

    Purpose: to evaluate the use of noninvasive quantified contrast-enhanced power Doppler ultrasonography as a surrogate in the estimation of tumor hypoxia measured by invasive pO{sub 2} histography in canine tumors. Material and methods: data of pretreatment tumor oxygenation status, tumor vascularity and blood volume, and tumor response after radiation therapy was collected in 48 spontaneous malignant oral tumors (Table 1). Tumor oxygenation status was correlated to vascularity and blood volume, and influences on outcome after treatment were analyzed. Results: although vascularity and blood volume correlated moderately with median pO{sub 2} (r = 0.51 and 0.61; p = 0.001 and < 0.0001) and percentage of pO{sub 2} readings {<=} 2.5, 5, and 10 mmHg (r = -0.37 to -0.42; p < 0.01-0.03) for all tumors, they did not correlate within the different histology groups (p = 0.06-0.9). For all tumors, pretreatment oxygenation status, vascularity and blood volume were not found to be of prognostic value. Conclusion: these analyses show that quantified contrast-enhanced power Doppler ultrasonography does not represent a non-invasive indirect method to assess tumor hypoxia measured by invasive pO{sub 2} histography. Both technologies were nonprognostic indicators in spontaneous malignant canine oral tumors. (orig.)

  4. Evaluation of endometrial and subendometrial vascularization and endometrial volume by 3-D power Doppler ultrasound and its relationship with age and pregnancy in intrauterine insemination cycles.

    Science.gov (United States)

    Engels, V; Sanfrutos, L; Pérez-Medina, T; Álvarez, P; Zapardiel, I; Bueno, B; Godoy-Tundidor, S; Bajo-Arenas, J M

    2011-01-01

    To measure endometrial volume and endometrial-subendometrial vascularization by 3-D power Doppler ultrasound in patients undergoing cycles of artificial insemination with ovarian stimulation, to evaluate their relationship with patients' age and pregnancy development. We included patients with primary and secondary infertility of one year of evolution. We measured vascular indexes and endometrial volume by 3-D power Doppler ultrasound. Seventy-nine consecutive cycles were studied. Endometrial volume average was 4.7 ± 2.66 ml. We did not find any difference between the endometrial volumes in women who did versus did not become pregnant (9 vs. 70 women, respectively). The endometrial vascular index was significantly higher in patients aged between 31 and 33 years old. In patients between the ages of 31 and 33, both the endometrial flow index (FI; p = 0.017) and the endometrial vascular FI (p = 0.013) were higher. At the subendometrial area, the vascular FI was lower in women older than 33 years old (p = 0.024), while the FI was higher in patients that achieved pregnancy (p = 0.047). Endometrial volumes were independent of pregnancy development. Endometrial and subendometrial vascularization FIs were significantly higher in younger women. The subendometrial FI was significantly higher in patients who achieved pregnancy. Copyright © 2011 S. Karger AG, Basel.

  5. Can TRUS Power Doppler Predict the Preservation of Erectile Function in HIFU Treatment of Localised Prostate Cancer? — A Preliminary Study

    Science.gov (United States)

    Hoh, I. M.; Calleary, J. G.; Moore, C.; Emberton, M.; Allen, C.

    2006-05-01

    Perhaps the single most significant unifying feature in men diagnosed with organ confined prostate cancer is the hope of erectile preservation in the treatment that offers cure. Although it is not 100% certain that the preservation of neurovascular bundle (NVB) can actually lead to intact sexual function, there is evidence that non-sparing nerve radical prostatectomy has a much higher incidence of impotence compared to nerve-sparing ones. The idea to monitor NVB flow can be realized using a simple power Doppler technique that was done before and after HIFU. The NVB flow was found intact in all patients (n=14). Tumescence returned in 93% of patients with a mean time of 6 weeks for this to occur. The erectile function score, IIEF-15 decreased by a third but shows a trend towards recovery. This preliminary study demonstrates the feasibility of transrectal power Doppler as a monitoring tool to provide immediate feedback on the NVB flow which was found intact in all patients. Although early reports of the tumescence proved encouraging, its full impact on erectile function will require longer follow-up.

  6. Pre-hCG 3D and 3D power Doppler assessment of the follicle for improving pregnancy rates in intrauterine insemination cycles

    Directory of Open Access Journals (Sweden)

    Sonal Panchal

    2009-01-01

    Full Text Available Background: The assessment of follicular maturity at the time of human chorionic gonadotropin (hCG is one of the key factors for the success of all assisted reproductive techniques. Aim: To assess follicles by three dimensional (3D and 3D power Doppler (PD before giving hCG to improve pregnancy rates in intrauterine insemination (IUI cycles. Design: Prospective randomized study. Materials and Methods: Ultrasound for pre-hCG follicular assessment was performed over a period of 10 months for all 1000 cycles of IUI. Follicular assessment was performed using a transvaginal multifrequency volume probe. Follicles considered mature by 2D US and color Doppler were assessed by 3D and 3D PD. These values were independently evaluated for the conception and the non-conception groups. Results: Conception rates were 32.3 and 27% respectively and individually when the perifollicular resistance index was 11 cm/s 10-12 h before hCG. Conception rates of 32% were achieved with a follicular volume between 3 and 7 cc. The conception rate was 32.3% in the cumulus group. A perifollicular vascularity index of between six and 20 gave conception rates of 35% and perifollicular flow index of 27-43 gave conception rates of 33%. Conclusions: 3D ultrasound is much more accurate for volume assessment of the follicle. Presence of cumulus increases the surety of the presence of a mature ovum in the follicle. 3D and 3D PD when used with 2D US and color Doppler for pre-hCG follicular assessment would definitely improve pregnancy rates in IUI cycles.

  7. Pre-hCG 3D and 3D power Doppler assessment of the follicle for improving pregnancy rates in intrauterine insemination cycles.

    Science.gov (United States)

    Panchal, Sonal; Nagori, C B

    2009-07-01

    The assessment of follicular maturity at the time of human chorionic gonadotropin (hCG) is one of the key factors for the success of all assisted reproductive techniques. To assess follicles by three dimensional (3D) and 3D power Doppler (PD) before giving hCG to improve pregnancy rates in intrauterine insemination (IUI) cycles. Prospective randomized study. Ultrasound for pre-hCG follicular assessment was performed over a period of 10 months for all 1000 cycles of IUI. Follicular assessment was performed using a transvaginal multifrequency volume probe. Follicles considered mature by 2D US and color Doppler were assessed by 3D and 3D PD. These values were independently evaluated for the conception and the non-conception groups. Conception rates were 32.3 and 27% respectively and individually when the perifollicular resistance index was 11 cm/s 10-12 h before hCG. Conception rates of 32% were achieved with a follicular volume between 3 and 7 cc. The conception rate was 32.3% in the cumulus group. A perifollicular vascularity index of between six and 20 gave conception rates of 35% and perifollicular flow index of 27-43 gave conception rates of 33%. 3D ultrasound is much more accurate for volume assessment of the follicle. Presence of cumulus increases the surety of the presence of a mature ovum in the follicle. 3D and 3D PD when used with 2D US and color Doppler for pre-hCG follicular assessment would definitely improve pregnancy rates in IUI cycles.

  8. Effect of intertrochanteric osteotomy on the proximal femur of rabbits: assessment with power Doppler sonography and scintigraphy Efeito da osteotomia intertrocantérica no femur proximal de coelhos: avaliação com utra-sonografia power Doppler e cintilografia

    Directory of Open Access Journals (Sweden)

    Andrea S. Doria

    2007-01-01

    Full Text Available OBJECTIVE: In bone injury, repair results in local increased vascularity and bone marrow remodeling. Characterizing the vascular and metabolic imaging patterns of the proximal femur following an intertrochanteric osteotomy may help clinicians decide proper management of the patient. Our objective was to measure Doppler sonography and scintigraphy interval changes in the proximal femur following intertrochanteric osteotomy and compare imaging and histomorphometric measurements in the late post-operative stage (6 weeks after surgery in a rabbit model of bone injury. MATERIALS AND METHODS: Both hips of 12 adult rabbits were imaged with power Doppler sonography and scintigraphy prior to and after (7 days and 6 weeks unilateral osteotomy. Accuracy of the imaging methods was evaluated using hip operative status and histomorphometric results (vascular fractional area and number of vessels per area unit as reference standard measures. RESULTS: A significant difference in the mean number of pixels was noted between operated and non-operated femura in late post-operative power Doppler examinations (P=0.049. Although without reaching statistical significance, the AUC of Doppler measurements (AUC=0.99 was numerically greater than the AUC of scintigraphy measurements (AUC=0.857±0.099 (P=0.15 in differentiating proximal femura with regard to their fractional vascular areas in the late post-operative stage. In contrast, scintigraphy tended to perform better (AUC=0.984±0.022 than Doppler ultrasound (AUC=0.746±0.131 to demonstrate the vascularity intensity per area unit (P=0.07 in the late stage. CONCLUSION: Our results warrant further investigation to determine the value of different imaging modalities for assessment of pathologic changes following hip surgery. Power Doppler sonography demonstrated larger AUCs (representing higher accuracy for the discrimination of vascular fractional areas and scintigraphy, for discrimination of the number of vessels per

  9. Coronary sinus flow measured by pulsed Doppler ultrasound is a powerful indicator of coronary blood supply- a pig heart in vitro study.

    Science.gov (United States)

    Zheng, Xiao-Zhi; Wu, Jing; Hua, Jie

    2016-06-01

    To evaluate the correlation between the coronary sinus flow and the infusion volume in the coronaries and assess the performance of coronary sinus flow in predicting coronary artery occlusion in an isolated pig heart. The coronary sinus flow was measured in 16 isolated pig hearts by pulsed Doppler ultrasound. The correlation between the coronary sinus flow and the infusion volume in different coronary artery was analyzed, and the performance of coronary sinus flow in predicting different coronary artery occlusion was deducted. There were no statistically significant differences between the coronary sinus flow and the infusion volume in different coronary artery (p>0.05). The correlations between the coronary sinus flow and the infusion volume in left anterior descending coronary artery (LAD), left circumflex coronary artery (LCX), LAD and LCX, and LAD, LCX and right coronary artery (RCA) were all higher than 0.85 (p85% sensitivity and specificity. Excepting RCA mild occlusion (80% sensitivity and specificity. Conclusions The coronary sinus flow measured by pulsed Doppler ultrasound can effectively and exactly reflect the infusion volume in coronaries, which is a powerful indicator of coronary blood supply.

  10. Static harmonization of dynamically harmonized Fourier transform ion cyclotron resonance cell.

    Science.gov (United States)

    Zhdanova, Ekaterina; Kostyukevich, Yury; Nikolaev, Eugene

    2017-08-01

    Static harmonization in the Fourier transform ion cyclotron resonance cell improves the resolving power of the cell and prevents dephasing of the ion cloud in the case of any trajectory of the charged particle, not necessarily axisymmetric cyclotron (as opposed to dynamic harmonization). We reveal that the Fourier transform ion cyclotron resonance cell with dynamic harmonization (paracell) is proved to be statically harmonized. The volume of the statically harmonized potential distribution increases with an increase in the number of trap segments.

  11. [Color Doppler sonography of focal abdominal lesions].

    Science.gov (United States)

    Licanin, Zoran; Lincender, Lidija; Djurović, V; Salihefendić, Nizama; Smajlović, Fahrudin

    2004-01-01

    Color Doppler sonography (CDS--spectral, color and power), harmonic imaging techniques (THI, PHI), possibility of 3D analysis of picture, usage of contrast agents, have raised the values of ultrasound as a diagnostic method to a very high level. THI--non-linear gray scale modality, is based on the processing of higher reflected frequencies, that has improved a picture resolution, which is presented with less artifacts and limiting effects of obesity and gases. Ultrasound contrast agents improve analysis of micro and macro circulation of the examined area, and with the assessment of velocity of supply in ROI (wash in), distribution and time of signal weakening (wash out), are significantly increasing diagnostic value of ultrasound. Besides the anatomical and topographic presentation of examined region (color, power), Color Doppler sonography gives us haemodynamic-functional information on vascularisation of that region, as well as on pathologic vascularisation if present. Avascular aspect of a focal pathologic lesion corresponds to a cyst or haematoma, while coloration and positive spectral curve discover that anechogenic lesions actually represents aneurysms, pseudoaneurysms or AVF. In local inflammatory lesion, abscess in an acute phase, CDS shows first increased, and then decreased central perfusion, while in a chronic phase, a pericapsular vascularisation is present. Contribution of CDS in differentiation of hepatic tumors (hemangioma, HCC and metastasis) is very significant. Central color dots along the peripheral blood vessels and the blush phenomenon are characteristics of capillary hemangioma, peritumoral vascular ring "basket" of HCC, and "detour" sign of metastasis. The central artery, RI from 0.45 to 0.60 and radial spreading characterize FNH. Hepatic adenoma is characterized by an intratumoral vein, and rarely by a vascular hallo. Further on, blood velocity in tumor defined by Color Doppler, distinguishes malignant from benign lesion, where 40 cm/s is a

  12. Dynamic Model and Vibration Power Flow of a Rigid-Flexible Coupling and Harmonic-Disturbance Exciting System for Flexible Robotic Manipulator with Elastic Joints

    Directory of Open Access Journals (Sweden)

    Yufei Liu

    2015-01-01

    Full Text Available This paper investigates the dynamic of a flexible robotic manipulator (FRM which consists of rigid driving base, flexible links, and flexible joints. With considering the motion fluctuations caused by the coupling effect, such as the motor parameters and mechanism inertias, as harmonic disturbances, the system investigated in this paper remains a parametrically excited system. An elastic restraint model of the FRM with elastic joints (FRMEJ is proposed, which considers the elastic properties of the connecting joints between the flexible arm and the driving base, as well as the harmonic disturbances aroused by the electromechanical coupling effect. As a consequence, the FRMEJ accordingly remains a flexible multibody system which conveys the effects of rigid-flexible couple and electromechanical couple. The Lagrangian function and Hamilton’s principle are used to establish the dynamic model of the FRMEJ. Based on the dynamic model proposed, the vibration power flow is introduced to show the vibration energy distribution. Numerical simulations are conducted to investigate the effect of the joint elasticities and the disturbance excitations, and the influences of the structure parameters and motion parameters on the vibration power flow are studied. The results obtained in this paper contribute to the structure design, motion optimization, and vibration control of FRMs.

  13. Acoustic noise reduction of a 6/4 SRM drive based on third harmonic real power cancellation and mutual coupling flux enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Chuang, T.-S., E-mail: thchuang@mail.mcut.edu.t [Department of Electrical Engineering, Ming Chi University of Technology, 84 Gungjuan Road, Taishan, Taipei 24301, Taiwan (China)

    2010-03-15

    In this paper, an effective technology is presented for noise reduction and torque increase in a three-phase 6/4 switched reluctance motor (SRM) drive without position sensors. Using a three-phase full bridge inverter and Y-typed connection of winding configuration, three-phase sinusoidal currents in each commutation region can be controlled to form long and short-flux paths. Long main flux can be added by short mutual coupling flux to enhance the stator flux; the resulting current-oriented control scheme can obtain a higher electromagnetic torque and cancel the third harmonic real power. To verify the effectiveness of the proposed scheme, it was applied to a 350 W three-phase 6/4 SRM drive system operating below 1500 rpm. Experimental results yield maximal acoustic noise at 74 dB and maximal torque at 21 kg cm. Moreover, the 6th harmonic real power is found to be the dominant source of acoustic noises in the SRM system.

  14. Power Doppler ultrasonography for assessment of synovitis in the metacarpophalangeal joints of patients with rheumatoid arthritis: a comparison with dynamic magnetic resonance imaging

    DEFF Research Database (Denmark)

    Szkudlarek, Marcin; Court-Payen, M; Strandberg, C

    2001-01-01

    postinjection) was calculated and compared with the flow signal on PDUS, which was scored as present or absent. RESULTS: In RA patients, flow signal on PDUS was detected in 17 of 54 MCP joints examined. Postcontrast MR images revealed an RESE of > or = 1.0%/second in 18 of 54 RA MCP joints. PDUS showed no flow...... of the second through the fifth MCP joints was obtained, with intravenous injection of gadolinium diethylenetriaminepentaacetic acid after the fourth image (dynamic MRI). From the MR images, the rate of early synovial enhancement (RESE; defined as the relative enhancement per second during the first 55 seconds......OBJECTIVE: To evaluate the effectiveness of power Doppler ultrasonography (PDUS) for assessing inflammatory activity in the metacarpophalangeal (MCP) joints of patients with rheumatoid arthritis (RA), using dynamic magnetic resonance imaging (MRI) as a reference method. METHODS: PDUS and dynamic...

  15. Are endometrial parameters by three-dimensional ultrasound and power Doppler angiography related to in vitro fertilization/embryo transfer outcome?

    Science.gov (United States)

    Mercé, Luis T; Barco, María J; Bau, Santiago; Troyano, Juan

    2008-01-01

    To evaluate whether endometrial parameters by three-dimensional ultrasonography and power Doppler angiography (3D US-PDA) can predict in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) outcome. Prospective clinical study. Assisted reproduction unit in a referral hospital. Eighty women who underwent IVF cycles. Endometrial 3D US-PDA evaluated by VOCAL software (plane C and 9 degrees of rotational steps). Endometrial pattern, endometrial thickness (ET), endometrial volume (EV), and PDA indexes of vascularization index (VI), flow index (FI), and vascularization flow index (VFI) were measured on the day of human chorionic gonadotropin (hCG) administration. These measurements were related to IVF/ICSI and embryo transfer outcome. In the pregnant group, EV, VI, FI, and FVI but not triple-line pattern and ET were statistically significantly higher. The area under receiver operating characteristic (ROC) curve was statistically significant for EV (0.746), VI (0.724), FI (0.828), and VFI (0.800) when no grade 1 embryos or only one were transferred (43 cycles, 14 pregnancies) but not when two or three grade 1 embryos were transferred. Moreover, these parameters were statistically significant in predicting a normal pregnancy outcome (no early pregnancy loss) but were not related to multiple pregnancies. In IVF/ICSI cycles, 3D US-PDA is useful for evaluating endometrial receptivity. Endometrial volume and 3D power Doppler indexes are statistically significant in predicting the cycle outcome when one grade 1 or no grade 1 embryos are transferred, which could be helpful data in a single-embryo transfer policy.

  16. Roles of ultrasound and power Doppler ultrasound for diagnosis of Hashimoto thyroiditis in anti-thyroid marker-positive euthyroid subjects.

    Science.gov (United States)

    Ceylan, Isin; Yener, Serkan; Bayraktar, Firat; Secil, Mustafa

    2014-08-01

    The present study was performed to investigate the contribution of ultrasonographic (US) findings to diagnosis in anti-thyroid marker-positive patients with normal hormone levels among euthyroid subjects with Hashimoto's thyroiditis (HT). Forty premenopausal euthyroid patients with a median age of 32 years (range, 20-44 years) with normal levels of free triiodothyronine (FT3) and free thyroxine (FT4), and elevated anti-thyroid peroxidase (TPO) antibodies were enrolled in this study. A control group of 46 healthy individuals with a median age of 29 years (range, 18-43 years) was composed of randomly selected volunteers. The examinations included basic morphometric (measurement of thyroid gland dimensions in three axes, the volume of each thyroid lobe, and the total thyroid volume), morphological grayscale imaging (echogenicity, nodularity, septations, undulation of the margins, and reactive lymph nodes), and thyroid gland vascularity. There were no statistically significant differences in morphometric parameters of the thyroid gland between the study and control groups. There were significant differences in the presence of nodularity, undulation of the gland margins, septations inside the glands, infrathyroidal and/or pretracheal reactive lymph nodes, and increased vascularity on power Doppler imaging between the groups. The use of all parameters together yielded a sensitivity of 90%, specificity of 84.8%, positive predictive value (PPV) of 83.7%, negative predictive value (NPV) of 90.7%, and accuracy of 87.2% for diagnosis of HT. US and power Doppler US are helpful for the diagnosis of HT in anti-thyroid marker-positive patients with normal thyroid hormone levels.

  17. Harmonic Analysis

    Indian Academy of Sciences (India)

    Harish-Chandra, Gelfand and several other mathematicians and physicists, group-theoretic harmonic analysis is a flourishing industry today paving the way to new developments in the con- text of noncompact Lie groups as well as quantum groups. Since B(n, z) = zn the expansion (3) suggests a link between Fourier series.

  18. Harmonic Analysis

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 1; Issue 10. Harmonic Analysis Fourier Series and Beyond. K R Parthasarathy. Book Review Volume 1 Issue 10 October 1996 pp 87-91. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/001/10/0087-0091 ...

  19. Methodology for the analysis of electric power systems at harmonic frequencies; Metodologia para el analisis de sistemas electricos a frecuencias armonicas

    Energy Technology Data Exchange (ETDEWEB)

    Silva Farias, Jose Luis

    1989-07-01

    The presence of harmonics is a problem that has existed for many years in the electric power systems. Nevertheless, at the present time the increase of the generating loads the harmonics have increased considerably as an answer to the industry development and the commodities that modern living demands. In order to carry out this research work the electrical network of an industrial plant, which has three electrical furnaces in arc dedicated to the steel production, is considered. The selection of this system is very important since the arc furnaces are one of the main harmonics source due to the power they handle and to the unpredictable magnitude of their harmonic content. This way, continuity to the research line, initiated in other thesis works, is given. As a result of these works one has, basically, the three following advances: the software and the necessary hardware to acquire signals, the required routines for its processing, and the signals of measured voltage and current in the filter. As one first stage of this investigation, the verification of the infrastructure good operation, whereupon is counted on, is included. The second stage deals with the modeling of the electrical arc, as well as its validation. This represents the fundamental objective of this work. The proposed model is a quasi lineal model and it is based on the approximation of the characteristic V versus I of the signals measured in the arc by means of a series of straight lines. The satisfactory conclusion of this work will allow to count on a methodology for the harmonics analysis in electric systems. This constitutes a basic tool for the adequate selection of the remedies in presence of the resonance problem and in the specification of the capacity of the equipment to be installed. On the other hand, it allows the verification of the elimination mechanisms of existing harmonics. The development of this work is divided into eight chapters which are next briefly described. The first

  20. Odd Harmonics in Exoplanet Photometry: Weather or Artifact?

    Science.gov (United States)

    Cowan, Nicolas B.; Chayes, Victoria; Bouffard, Élie; Meynig, Max; Haggard, Hal M.

    2017-05-01

    In addition to the transits of a planet in front of its star and the eclipses of the planet by its star, researchers have reported flux variations at the orbital frequency and its harmonics: planetary reflection and/or emission and Doppler beaming of starlight produce one peak per orbit, while ellipsoidal variations of a tidally distorted star and/or planet produce two maxima per orbit. Researchers have also reported significant photometric variability at three times the orbital frequency, as yet unexplained. Reflected phase variations of homogeneous planets only contain power at the orbital frequency and its even harmonics. We show that odd harmonics can, however, be produced by an edge-on planet with a time-variable map, or an inclined planet with a north-south (N-S) asymmetric map. For tidally locked planets with thick atmospheres, either of these scenarios entail weather: planets with zero obliquity experience N-S symmetric stellar forcing. North-south asymmetry would therefore suggest stochastic localized features, I.e. weather. However, we find that previous claims of large-amplitude odd modes in Kepler photometry are artefacts of removing planetary transits rather than modelling them. The only reliable claims of odd harmonics remain HAT-P-7b and Kepler-13Ab, for which the third mode amplitude is 6-8 per cent of the planetary flux. Although time-variable albedo maps could in principle explain these odd harmonics, upper-limits on the infrared variability of other hot Jupiters make this scenario unlikely. We recommend further studying the tidal effects of close-in planets on their host stars, as this remains the only plausible hypothesis.

  1. Transthoracic Doppler echocardiography compared with positron emission tomography for assessment of coronary microvascular dysfunction: The iPOWER study.

    Science.gov (United States)

    Michelsen, Marie Mide; Mygind, Naja Dam; Pena, Adam; Olsen, Rasmus Huan; Christensen, Thomas Emil; Ghotbi, Adam Ali; Hasbak, Philip; Kjaer, Andreas; Gustafsson, Ida; Hansen, Peter Riis; Hansen, Henrik Steen; Høst, Nis; Kastrup, Jens; Prescott, Eva

    2017-02-01

    Coronary microvascular function can be assessed by transthoracic Doppler echocardiography as a coronary flow velocity reserve (TTDE CFVR) and by positron emission tomography as a myocardial blood flow reserve (PET MBFR). PET MBFR is regarded the noninvasive reference standard for measuring coronary microvascular function but has limited availability. We compared TTDE CFVR with PET MBFR in women with angina pectoris and no obstructive coronary artery disease and assessed repeatability of TTDE CFVR. From a cohort of women with angina and no obstructive coronary artery stenosis at invasive coronary angiography, TTDE CFVR by dipyridamole induced stress and MBFR by rubidium-82 PET with adenosine was successfully measured in 107 subjects. Repeatability of TTDE CFVR was assessed in 10 symptomatic women and in 10 healthy individuals. MBFR was systematically higher than CFVR. Median MBFR (interquartile range, IQR) was 2.68 (2.29-3.10) and CFVR (IQR) was 2.31 (1.89-2.72). Pearson's correlation coefficient was 0.36 (p<0.01). Limits of agreement (2·standard deviation) assessed by the Bland-Altman (confidence interval, CI) method was 1.49 (1.29;1.69) and unaffected by time-interval between examinations. Results were similar when adjusting for rate pressure product or focusing on perfusion of the left anterior descending artery region. Limits of agreement (CI) for repeated CFVR in 10 healthy individuals and in 10 women with angina was 0.44 (0.21;0.68) and 0.48 (0.22; 0.74), respectively. CFVR had a good repeatability, but the agreement between CFVR and MBFR was modest. Divergence could be due to methodology differences; TTDE estimates flow velocities whereas PET estimates myocardial blood flow. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  2. High-power ultraviolet 278 nm laser from fourth-harmonic generation of a Nd:YAG laser in CsB3O5.

    Science.gov (United States)

    Wang, Zhichao; Yang, Feng; Zhang, Guochun; Bo, Yong; Liu, Shanshan; Xie, Shiyong; Xu, Yiting; Zong, Nan; Li, Fangqin; Liu, Biaolong; Xu, Jialin; Peng, Qinjun; Zhang, Jingyuan; Cui, Dafu; Wu, Yicheng; Xu, Zuyan

    2012-06-15

    We demonstrate a high-power UV 278 nm laser by fourth-harmonic generation (FHG) of a 1112 nm Nd:YAG laser in a nonlinear optical (NLO) crystal CsB3O5 (CBO) for the first time, to our best knowledge. A 30 W level diode-pumped Q-switched Nd:YAG laser at 1112 nm with beam quality factor M2=1.2 was used as the fundamental light source at a pulse width of 500 ns. With an LiB3O5 crystal, the 1112 nm laser was first frequency-doubled to 556 nm with an average output power of 13.5 W. It was then frequency doubled again in a CBO crystal to obtain the FHG output at 278 nm. The maximum average output power of the 278 nm laser is up to 1.5 W. The results demonstrated that CBO crystal is a promising NLO material for UV high-power lasers below 300 nm.

  3. Twelve million resolving power on 4.7 T Fourier transform ion cyclotron resonance instrument with dynamically harmonized cell--observation of fine structure in peptide mass spectra.

    Science.gov (United States)

    Popov, Igor A; Nagornov, Konstantin; Vladimirov, Gleb N; Kostyukevich, Yury I; Nikolaev, Eugene N

    2014-05-01

    Resolving power of about 12,000 000 at m/z 675 has been achieved on low field homogeneity 4.7 T magnet using a dynamically harmonized Fourier transform ion cyclotron resonance (FT ICR) cell. Mass spectra of the fine structure of the isotopic distribution of a peptide were obtained and strong discrimination of small intensity peaks was observed in case of resonance excitation of the ions of the whole isotopic cluster to the same cyclotron radius. The absence of some peaks from the mass spectra of the fine structure was explained basing on results of computer simulations showing strong ion cloud interactions, which cause the coalescence of peaks with m/z close to that of the highest magnitude peak. The way to prevent peak discrimination is to excite ion clouds of different m/z to different cyclotron radii, which was demonstrated and investigated both experimentally and by computer simulations.

  4. Harmonic engine

    Science.gov (United States)

    Bennett, Charles L [Livermore, CA

    2009-10-20

    A high efficiency harmonic engine based on a resonantly reciprocating piston expander that extracts work from heat and pressurizes working fluid in a reciprocating piston compressor. The engine preferably includes harmonic oscillator valves capable of oscillating at a resonant frequency for controlling the flow of working fluid into and out of the expander, and also preferably includes a shunt line connecting an expansion chamber of the expander to a buffer chamber of the expander for minimizing pressure variations in the fluidic circuit of the engine. The engine is especially designed to operate with very high temperature input to the expander and very low temperature input to the compressor, to produce very high thermal conversion efficiency.

  5. Experiments on ion cyclotron damping at the deuterium fourth harmonic in DIII-D

    Energy Technology Data Exchange (ETDEWEB)

    Pinsker, R.I.; Petty, C.C. [General Atomics, San Diego, CA (United States); Baity, F.W. [Oak Ridge National Lab., TN (United States); Bernabei, S.; Greenough, N. [Princeton Plasma Physics Lab., NJ (United States); Heidbrink, W.W. [Univ. of California, Irvine, CA (United States); Mau, T.K. [Univ. of California, San Diego, CA (United States); Porkolab, M. [Massachusetts Inst. of Tech., Cambridge, MA (United States)

    1999-05-01

    Absorption of fast Alfven waves by the energetic ions of an injected beam is evaluated in the DIII-D tokamak. Ion cyclotron resonance absorption at the fourth harmonic of the deuteron cyclotron frequency is observed with deuterium neutral beam injection (f = 60 MHz, B{sub T} = 1.9 T). Enhanced D-D neutron rates are evidence of absorption at the Doppler-shifted cyclotron resonance. Characteristics of global energy confinement provide further proof of substantial beam acceleration by the rf. In many cases, the accelerated deuterons cause temporary stabilization of the sawtooth (monster sawteeth), at relatively low rf power levels of {approximately}1 MW.

  6. The doppler ultrasound. La ecografia Doppler

    Energy Technology Data Exchange (ETDEWEB)

    Contreras Cecilia, E.; Lozano Setien, E.; Hernandez Montero, J.; Ganado Diaz, T.; Jorquera Moya, M.; Blasco Pascual, E. (Hospital Universitario San Carlos. Madrid (Spain))

    1994-01-01

    The discovery and development of Doppler ultrasound has had a great influence on Medical practice since it allows the noninvasive study of vascular pathology, both arterial and venous, as well as the flow patterns of the different parenchyma. This article deals with the principles, limitations and interpretation of the Doppler signal, as well as the different Doppler ultrasound systems routinely employed in Medicine.

  7. Doppler tracking

    Science.gov (United States)

    Thomas, Christopher Jacob

    This study addresses the development of a methodology using the Doppler Effect for high-resolution, short-range tracking of small projectiles and vehicles. Minimal impact on the design of the moving object is achieved by incorporating only a transmitter in it and using ground stations for all other components. This is particularly useful for tracking objects such as sports balls that have configurations and materials that are not conducive to housing onboard instrumentation. The methodology developed here uses four or more receivers to monitor a constant frequency signal emitted by the object. Efficient and accurate schemes for filtering the raw signals, determining the instantaneous frequencies, time synching the frequencies from each receiver, smoothing the synced frequencies, determining the relative velocity and radius of the object and solving the nonlinear system of equations for object position in three dimensions as a function of time are developed and described here.

  8. First-trimester 3-dimensional power Doppler placental vascularization indices from the whole placenta versus the placental bed to predict preeclampsia: does pregnancy-associated plasma protein a or uterine artery Doppler sonography help?

    Science.gov (United States)

    Hannaford, Karen E; Tuuli, Methodius; Goetzinger, Katherine R; Odibo, Linda; Cahill, Alison G; Macones, George; Odibo, Anthony O

    2015-06-01

    The purpose of this study was to compare the use of vascular indices derived from the whole placenta to those from the placental bed only for predicting preeclampsia and to determine whether the addition of pregnancy-associated plasma protein A (PAPP-A) and mean uterine artery Doppler values improves prediction. We conducted a secondary analysis of a prospective cohort of women with singletons between 11 and 14 weeks' gestation undergoing sonography for aneuploidy screening. Placental vascularization indices from the whole placenta versus the placental bed were combined with first-trimester maternal serum PAPP-A levels, mean uterine artery Doppler values, or the combination of both to predict the development of preeclampsia or early preeclampsia (delivery PAPP-A, uterine artery Doppler values, or both. The variables in the model were more sensitive for the prediction of early preeclampsia than preeclampsia. Although placental bed vascular indices are modestly predictive of preeclampsia, the addition of PAPP-A and uterine artery Doppler values to vascularization indices in the whole placenta or the placental bed did not significantly improve their predictive ability. © 2015 by the American Institute of Ultrasound in Medicine.

  9. A comparative study of modelling AC electric arc by one-dimensional interpolation for power system harmonics analysis

    Directory of Open Access Journals (Sweden)

    Liu Yu-Jen

    2016-01-01

    Full Text Available Electric arc is a discharge phenomenon caused by particular electrical events and arc produced facilities in power system, for example the occurrence of short-circuit fault in feeders and the use of electric arc furnace for steel-making. All of these electric arcs have a highly nonlinear nature and can be considered as a significant source of power quality problems. To investigate the impacts of the electric arcs on power quality studies the development of the electric arc models for simulation analysis is became necessary. This paper thus presents the use of different one-dimensional interpolation methods for modelling the alternating current electric arc. The performances of different methods are compared by simulation results that are derived from the modelling of an alternating current electric arc furnace load and a low-frequency fluorescent tube.

  10. Limiting overdiagnosis of low-risk prostate cancer through an evaluation of the predictive value of transrectal and power Doppler ultrasonography.

    Science.gov (United States)

    Sauvain, Jean Luc; Sauvain, Elise; Papavero, Roger; Louis, Didier; Rohmer, Paul

    2016-12-01

    Overdiagnosis induced by prostate cancer screening makes necessary a better selection of candidate patients for prostate biopsy. The objective of our study is to assess the probability of having a high- or low-risk lesion that could require active surveillance (AS) after biopsies and a normal or abnormal examination, including transrectal and power Doppler ultrasonography (TRUS-PDS). Four hundred and twenty-nine consecutive patients with a PSA level risk of a biological recurrence and Dall'Era's criteria to assess possible AS. The TRUS-PDS was considered positive if one biopsy was positive in the same sextant as the suspect image. One hundred and seventy-seven out of 429 (41 %) T1c cancers were diagnosed; 131 out of 177 (74 %) could be qualified as low risk, and 119 out of 177 (67 %) could require AS. The TRUS-PDS was normal in 285 of 429 patients (66 %). With a normal TRUS-PDS, the probability of not having cancer with a high or intermediate risk was 96 % (negative predictive value). With an abnormal TRUS-PDS, the probability of having a positive biopsy was 59 %, and the probability of having a significant cancer was 30 %, according to the Dall'Era criteria. When TRUS-PDS was normal, these probabilities significantly decreased to 32 and 5 %, respectively ( p  risk of high- or intermediate-risk cancer.

  11. Correlation between computerised findings and Newman's scaling on vascularity using power Doppler ultrasonography imaging and its predictive value in patients with plantar fasciitis

    Science.gov (United States)

    Chen, H; Ho, H M; Ying, M; Fu, S N

    2012-01-01

    Objectives The purpose of this study was to correlate findings on small vessel vascularity between computerised findings and Newman's scaling using power Doppler ultrasonography (PDU) imaging and its predictive value in patients with plantar fasciitis. Methods PDU was performed on 44 patients (age range 30–66 years; mean age 48 years) with plantar fasciitis and 46 healthy subjects (age range 18–61 years; mean age 36 years). The vascularity was quantified using ultrasound images by a customised software program and graded by Newman's grading scale. Vascular index (VI) was calculated from the software program as the ratio of the number of colour pixels to the total number of pixels within a standardised selected area of proximal plantar fascia. The 46 healthy subjects were examined on 2 occasions 7–10 days apart, and 18 of them were assessed by 2 examiners. Statistical analyses were performed using intraclass correlation coefficient and linear regression analysis. Results Good correlation was found between the averaged VI ratios and Newman's qualitative scale (ρ = 0.70; pplantar fascia, and can predict pain reduction after intervention. This index can be used to characterise the changes in vascularity of patients with plantar fasciitis, and it may also be helpful for evaluating treatment and monitoring the progress after intervention in future studies. PMID:22167513

  12. Brief Report: Power Doppler Ultrasonography for Detection of Increased Vascularity in the Fascia: A Potential Early Diagnostic Tool in Fasciitis of Dermatomyositis.

    Science.gov (United States)

    Yoshida, Ken; Nishioka, Makiko; Matsushima, Satoshi; Joh, Kensuke; Oto, Yosuke; Yoshiga, Masayuki; Otani, Kazuhiro; Ito, Haruyasu; Hirai, Kenichiro; Furuya, Kazuhiro; Ukichi, Taro; Noda, Kentaro; Kingetsu, Isamu; Kurosaka, Daitaro

    2016-12-01

    We previously demonstrated that fasciitis is a common lesion of dermatomyositis (DM) that is detectable early after disease onset by en bloc muscle biopsy combined with magnetic resonance imaging (MRI). Power Doppler ultrasonography (PDUS) is a useful method for detection of inflammation and vascularity in rheumatic diseases. We undertook this study to determine whether fasciitis was detectable by PDUS in patients with DM. We prospectively evaluated 7 patients with DM and 7 patients with polymyositis (PM) for the detection of fasciitis with PDUS. MRI and PDUS were both performed in all patients. Fasciitis was histologically confirmed by en bloc biopsy. Among all patients with DM, 4 showed signs of fasciitis on MRI, while increased blood flow signals were observed along the fascia by PDUS in 6 DM patients, including 4 patients with early disease (fascia. Immunohistochemical staining for CD31 indicated abnormal neovascular proliferation in the fascia in patients with DM. None of the PM patients showed signs of fasciitis or increased vascularity by MRI, PDUS, or en bloc biopsy. In our limited population, PDUS was useful for the detection of fasciitis associated with DM, especially in the early stage of disease. The increased blood flow signal as detected by PDUS is involved in angiogenesis accompanying fasciitis in patients with DM. © 2016, American College of Rheumatology.

  13. Comparison of endometrial and subendometrial blood flow measured by three-dimensional power Doppler ultrasound between stimulated and natural cycles in the same patients.

    Science.gov (United States)

    Ng, Ernest Hung Yu; Chan, Carina Chi Wai; Tang, Oi Shan; Yeung, William Shu Biu; Ho, Pak Chung

    2004-10-01

    Low implantation rates in stimulated IVF cycles may be related to suboptimal endometrial perfusion. Endometrial and subendometrial blood flow was compared between stimulated and natural cycles in the same patients undergoing IVF. Three-dimensional (3D) ultrasound examination with power Doppler was performed in stimulated and natural cycles of 67 consecutive patients to measure endometrial thickness, uterine artery pulsatility index/resistance index, endometrial volume, vascularization index (VI)/flow index (FI)/vascularization flow index (VFI) of endometrial and subendometrial regions. Endometrial and subendometrial blood flow was absent in four (6.0%) patients in the stimulated cycle and two (3.0%) patients in the natural cycle. Endometrial and subendometrial VI/FI/VFI were significantly lower in stimulated cycles than those in natural cycles. The median (95% CI) decreases in endometrial VI/FI/VFI were 35.8% (-2.5, 216.8), 5.0% (0.1, 12.3) and 48.4% (2.5, 315.3) respectively whereas the corresponding decreases in the subendometrial region were 66.6% (-0.2, 220.5), 4.3% (0.8, 16.2) and 76.3% (41.0, 303.4) respectively. Endometrial and subendometrial blood flow was significantly lower in the stimulated cycle than that in the natural cycle.

  14. Autonomous Control of Current and Voltage Controlled DG Interface Inverters for Reactive Power Sharing and Harmonics Compensation in Islanded Microgrids

    DEFF Research Database (Denmark)

    Mousazadeh, Seyyed Yousef; Jalilain, Alireza; Savaghebi, Mehdi

    2018-01-01

    by using capacitive virtual impedance which can fully compensate the effect of output inductance of the LCL filters. Furthermore, an adaptive virtual admittance regulated based on remaining capacity of the CCM units is implemented for the CCM units. For reactive power sharing, modified droop and reverse...... droop control methods are used for VCM and CCM units, respectively. The related droop coefficients are set by taking the limited capacity of the inverters and the distorted power into account. An experimental prototype is developed to evaluate the effectiveness of the proposed control scheme...

  15. Optimal Selective Harmonic Mitigation Technique on Variable DC Link Cascaded H-Bridge Converter to Meet Power Quality Standards

    DEFF Research Database (Denmark)

    Najjar, Mohammad; Moeini, Amirhossein; Dowlatabadi, Mohammadkazem Bakhshizadeh

    2016-01-01

    /4 power quality standard, which has the strictest grid codes at medium voltage level, will also be met in the whole range of the modulation indices. In order to achieve this goal, symmetrical CHB with variable DC Links are employed, while the converter has a low number of switching transitions. In other...

  16. Harmonic engine

    Science.gov (United States)

    Bennett, Charles L.; Sewall, Noel; Boroa, Carl

    2014-08-19

    An engine based on a reciprocating piston engine that extracts work from pressurized working fluid. The engine includes a harmonic oscillator inlet valve capable of oscillating at a resonant frequency for controlling the flow of working fluid into of the engine. In particular, the inlet valve includes an inlet valve head and a spring arranged together as a harmonic oscillator so that the inlet valve head is moveable from an unbiased equilibrium position to a biased closed position occluding an inlet. Upon releasing the inlet valve the inlet valve head undergoes a single oscillation past the equilibrium positio to a maximum open position and returns to a biased return position close to the closed position to choke the flow and produce a pressure drop across the inlet valve causing the inlet valve to close. Protrusions carried either by the inlet valve head or piston head are used to bump open the inlet valve from the closed position and initiate the single oscillation of the inlet valve head, and protrusions carried either by the outlet valve head or piston head are used to close the outlet valve ahead of the bump opening of the inlet valve.

  17. High-order harmonic generation in laser plasma: Recent achievements

    Science.gov (United States)

    Ganeev, R. A.

    2012-07-01

    Recent studies of high-order harmonic generation of laser radiation in laser-produced plasma show new attractive developments in this field. Those include generation of extended harmonics in plasma plumes, new approaches in application of two-color pump, generation of extremely broadened harmonics, further developments in harmonic generation in clusters (fullerenes, carbon nanotubes, in-situ produced nanoparticles), destructive interference of harmonics from different emitters, resonance-induced enhancement of harmonics, applications of high pulse repetition rate lasers for the enhancement of average power of generating harmonics, observation of quantum path signatures, etc. We review some of these recent developments.

  18. Optimization Based Shunt APF Controller to Mitigate Reactive Power, Burden of Neutral Conductor, Current Harmonics and Improve cosɸ

    Directory of Open Access Journals (Sweden)

    P. Anjana

    2017-03-01

    Full Text Available This paper presents a Modified Gravitational Search Algorithm (MGSA to improve the performance of PI controller in varying load condition. The proposed approach is capable of mitigating reactive power, neutral current, source current THD and significant improvement in power factor nearly unity (0.997. The DC link voltage across the capacitor is controlled by PI controller which is deciding the performance of shunt APF. Hence, the robust optimization technique based integral time square error (ITSE with consideration of weight factor (α & β, maximum overshoot ((|(∆_Ve ̅〖(n〗_max | and setling time t_s-t_0, is providing the optimum solution of Kp & Ki. The robustness of proposed objective function and algorithm compared with GSA based three other error criterion techniques. The efficiency of the proposed controller has been tested over nonlinear and unbalance loading condition. The performance of ITSE based MGSA-PI controller is batter then other three error criterion techniques. The values of THD are below the mark of 5% specified in IEEE-519 standard.

  19. Enhanced power coupling efficiency in inductive discharges with RF substrate bias driven at consecutive harmonics with adjustable phase

    Science.gov (United States)

    Berger, Birk; Steinberger, Thomas; Schüngel, Edmund; Koepke, Mark; Mussenbrock, Thomas; Awakowicz, Peter; Schulze, Julian

    2017-11-01

    Inductive discharges with radio-frequency (RF) substrate bias are frequently used for various technological applications. We operate such a hybrid discharge with a phase-locked RF substrate bias at twice the frequency of the inductive coupling with fixed but adjustable phase between both RF sources in neon at low pressures of a few Pa. The ion flux to the substrate is found to be a function of this relative phase in the H-mode at constant RF powers as long as some residual capacitive coupling of the planar coil is present. For distinct choices of the phase, Phase Resolved Optical Emission Spectroscopy measurements show that energetic beam electrons generated by the expanding boundary sheaths (i) are well confined, (ii) are accelerated efficiently, and (iii) propagate vertically through the inductive skin layer at the times of maximum azimuthal induced electric field within the fundamental RF period. This enhances the inductive stochastic electron heating, the power coupling efficiency, and finally the ion flux.

  20. APF for harmonic voltage resonance suppression in distribution system

    DEFF Research Database (Denmark)

    Sun, Xiaofeng; Zeng, Jian; Chen, Zhe

    2010-01-01

    Traditional active power filter (APF) can prevent harmonic current from injecting into power system, but can not damp harmonic propagation in distribution system whereas voltage detection can do. This paper proposes a compound control method of APF based on detection of load current and harmonic...

  1. Harmonic Generation by Microwave-frequency Microplasma

    Science.gov (United States)

    Parsons, Stephen; Hoskinson, Alan; Hopwood, Jeffrey

    2013-09-01

    A microplasma may operate as a nonlinear circuit element and generate power at the harmonics of the drive frequency. As an example, microplasma is sustained using 1 W of power at 1.3 GHz in a small discharge gap formed in a split-ring resonator. A probe extends into the microplasma and extracts the 3rd harmonic power through a tuned resonator at 3.9 GHz. The experimental data show that this non-optimized system produces a +38 dB increase in 3rd harmonic power in the presence of a microplasma. Two origins of nonlinearity are described: the harmonic conduction current due to electron collection by microelectrodes, and the harmonic displacement current due to the voltage-dependent sheath capacitance. PIC-MC simulations suggest that the microplasma nonlinearity may also be exploited at frequencies of 100 GHz. Support was provided by the DARPA Microscale Plasma Devices program under award FA9550-12-1-0006.

  2. Third-order-harmonic generation in coherently spinning molecules

    Science.gov (United States)

    Prost, E.; Zhang, H.; Hertz, E.; Billard, F.; Lavorel, B.; Bejot, P.; Zyss, Joseph; Averbukh, Ilya Sh.; Faucher, O.

    2017-10-01

    The rotational Doppler effect occurs when circularly polarized light interacts with a rotating anisotropic material. It is manifested by the appearance of a spectral shift ensuing from the transfer of angular momentum and energy between radiation and matter. Recently, we reported terahertz-range rotational Doppler shifts produced in third-order nonlinear optical conversion [O. Faucher et al., Phys. Rev. A 94, 051402(R) (2016), 10.1103/PhysRevA.94.051402]. The experiment was performed in an ensemble of coherently spinning molecules prepared by a short laser pulse exhibiting a twisted linear polarization. The present work provides an extensive analysis of the rotational Doppler effect in third-order-harmonic generation from spinning linear molecules. The underlying physics is investigated both experimentally and theoretically. The implication of the rotational Doppler effect in higher-order processes like high-order-harmonic generation is discussed.

  3. Phononic High Harmonic Generation

    OpenAIRE

    Ganesan, Adarsh; Do, Cuong; Seshia, Ashwin A.

    2016-01-01

    This paper reports the first experimental evidence for phononic low-order to high-order harmonic conversion leading to high harmonic generation. Similar to parametric resonance, phononic high harmonic generation is also mediated by a threshold dependent instability of a driven phonon mode. Once the threshold for instability is met, a cascade of harmonic generation processes is triggered. Firstly, the up-conversion of first harmonic phonons into second harmonic phonons is established. Subseque...

  4. Power Doppler signal calibration between ultrasound machines by use of a capillary-flow phantom for pannus vascularity in rheumatoid finger joints: a basic study.

    Science.gov (United States)

    Sakano, Ryosuke; Kamishima, Tamotsu; Nishida, Mutsumi; Horie, Tatsunori

    2015-01-01

    Ultrasound allows the detection and grading of inflammation in rheumatology. Despite these advantages of ultrasound in the management of rheumatoid patients, it is well known that there are significant machine-to-machine disagreements regarding signal quantification. In this study, we tried to calibrate the power Doppler (PD) signal of two models of ultrasound machines by using a capillary-flow phantom. After flow velocity analysis in the perfusion cartridge at various injection rates (0.1-0.5 ml/s), we measured the signal count in the perfusion cartridge at various injection rates and pulse repetition frequencies (PRFs) by using PD, perfusing an ultrasound micro-bubble contrast agent diluted with normal saline simulating human blood. By use of the data from two models of ultrasound machines, Aplio 500 (Toshiba) and Avius (Hitachi Aloka), the quantitative PD (QPD) index [the summation of the colored pixels in a 1 cm × 1 cm rectangular region of interest (ROI)] was calculated via Image J (internet free software). We found a positive correlation between the injection rate and the flow velocity. In Aplio 500 and Avius, we found negative correlations between the PRF and the QPD index when the flow velocity was constant, and a positive correlation between flow velocity and the QPD index at constant PRF. The equation for the relationship of the PRF between Aplio 500 and Avius was: y = 0.023x + 0.36 [y = PRF of Avius (kHz), x = PRF of Aplio 500 (kHz)]. Our results suggested that the signal calibration of various models of ultrasound machines is possible by adjustment of the PRF setting.

  5. Greyscale and power Doppler ultrasonographic evaluation of normal synovial joints: correlation with pro- and anti-inflammatory cytokines and angiogenic factors.

    Science.gov (United States)

    Kitchen, Joanne; Kane, David

    2015-03-01

    US is a promising tool in evaluating RA synovitis, but abnormal US findings have been reported in small subsets of normal joints in healthy subjects. This study aimed to systematically assess greyscale US (GSUS) and power Doppler US (PDUS) findings in 40 peripheral joints-the 28-joint DAS (DAS28) set, ankles and MTP joints-in healthy subjects. A composite score of abnormal US findings in 40 joints was compared with serum levels of pro-inflammatory cytokines. US of 60 standard views in 40 joints was performed in 30 healthy subjects (total 3600 images). GSUS and PDUS were scored semi-quantitatively (0-3). Serum samples were obtained at the time of US and analysed for IL-1α, IL-1β, IL-2, IL-6, IL-8, VEGF, TNF-α and IFN-γ using biochip array technology. GSUS abnormalities were more frequent than PDUS abnormalities [mean total GSUS score = 20.07 (range 6-45; maximum potential score = 180), mean total PDUS score = 4.8 (range 0-13)]. GSUS score increased with increasing age (Spearman's ρ = 0.383, P = 0.037). A PDUS signal >1 was observed only in the wrist (8%) and MTP1 (3%). GSUS scores did not correlate with any pro-inflammatory cytokine level. The total PDUS score correlated significantly with serum VEGF (r = 0.395, P = 0.046). PDUS signals >1 are rarely seen in normal synovial joints. GSUS synovitis, but not PDUS, may reflect age-related joint changes. PDUS correlated with VEGF, providing further evidence of a central role for VEGF in synovial neo-angiogenesis. © The Author 2014. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  6. Value of Power Doppler and Gray-Scale US in the Diagnosis of Carpal Tunnel Syndrome: Contribution of Cross-Sectional Area just before the Tunnel Inlet as Compared with the Cross-Sectional Area at the Tunnel

    Energy Technology Data Exchange (ETDEWEB)

    Akcar, Nevbahar; Ozkan, Serhat; Mehmetoglu, Ozlem; Calisir, Cuneyt; Adapinar, Baki [Osmangazi University Hospital, Eskisehir (Turkmenistan)

    2010-12-15

    To determine the value of gray-scale and power Doppler ultrasonography in the evaluation of carpal tunnel syndrome (CTS). Median nerves at the carpal tunnel were evaluated by using gray-scale and power Doppler ultrasonography and by using accepted and new criteria in 42 patients with CTS (62 wrists) confirmed by electromyogram and 33 control subjects. We evaluated the cross-sectional area of the nerve just proximal to the tunnel inlet (CSAa), and at mid level (CSAb). We then calculated the percentage area increase of CSAb, and area difference (CSAb-CSAa). We measured two dimensions of the nerve at the distal level to calculate the flattening ratio. The power Doppler ultrasonography was used to assess the number of vessels, which proceeded to give a score according to the vessel number, and lastly evaluated the statistical significance by comparing the means of patients with control subjects by the Student t test for independent samples. Sensitivities and specificities were determined for sonographic characteristics mentioned above. We obtained the receiver operating characteristic (ROC) curve to assess the optimal cut-off values for the diagnosis of CTS. A statistically significant difference was found between patients and the control group for mean CSAb, area difference, percentage area increase, and flattening ratio (p < 0.001, p < 0.001, p < 0.001, p < 0.05, respectively). From the ROC curve we obtained optimal cut-off values of 11 mm{sup 2} for CSAb, 3.65 for area difference, 50% for the percentage of area increase, and 2.6 for the flattening ratio. The mean number of vessels obtained by power Doppler ultrasonography from the median nerve was 1.2. We could not detect vessels from healthy volunteers. Mean CSAbs related to vascularity intensity scores were as follows: score 0: 12.3 {+-} 2.8 mm{sup 2}, score 1: 12.3 {+-} 3.1 mm{sup 2}, score 2: 14.95 {+-} 3.5 mm{sup 2}, score 3: 19.3 {+-} 3.8 mm{sup 2}. The mean PI value in vessels of the median nerve was 4

  7. Harmonics Monitoring Survey on LED Lamps

    OpenAIRE

    Abdelrahman Ahmed Akila; Kamelia Youssef; Ibrahim Yassin

    2017-01-01

    Light Emitting Diode (LED) lamps are being increasingly used in many applications. These LED lamps operate using a driver, which is a switching device. Hence, LED lamps will be a source of harmonics in the power system. These harmonics if not well treated, may cause severe performance and operational problems. In this paper, harmonics (amplitude and phase angles) generated by both LED lamps and conventional fluorescent lamps will be studied practically. Then they will be analyzed and evaluate...

  8. Harmonic Interaction Analysis in Grid Connected Converter using Harmonic State Space (HSS) Modeling

    DEFF Research Database (Denmark)

    Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth

    2015-01-01

    An increasing number of power electronics based Distributed Generation (DG) systems and loads generate coupled harmonic as well as non-characteristic harmonic with each other. Several methods like impedance based analysis, which is derived from conventional small signal- and average...... during the modeling process. This paper investigates grid connected converter by means of Harmonic State Space (HSS) small signal model, which is modeled from Linear Time varying Periodically (LTP) system. Further, a grid connected converter harmonic matrix is investigated to analyze the harmonic...

  9. HARMONIC DRIVE SELECTION

    Directory of Open Access Journals (Sweden)

    Piotr FOLĘGA

    2014-03-01

    Full Text Available The variety of types and sizes currently in production harmonic drive is a problem in their rational choice. Properly selected harmonic drive must meet certain requirements during operation, and achieve the anticipated service life. The paper discusses the problems associated with the selection of the harmonic drive. It also presents the algorithm correct choice of harmonic drive. The main objective of this study was to develop a computer program that allows the correct choice of harmonic drive by developed algorithm.

  10. Abatacept reduces disease activity and ultrasound power Doppler in ACPA-negative undifferentiated arthritis: a proof-of-concept clinical and imaging study.

    Science.gov (United States)

    Buch, Maya H; Hensor, Elizabeth M A; Rakieh, Chadi; Freeston, Jane E; Middleton, Edward; Horton, Sarah; Das, Sudipto; Peterfy, Charles; Tan, Ai Lyn; Wakefield, Richard J; Emery, Paul

    2017-01-01

    No proven treatment exists for ACPA-negative undifferentiated arthritis (UA). The aim of this study was to evaluate whether abatacept is effective in treating poor prognosis, ACPA-negative UA, including its effect on power Doppler on US (PDUS). A proof-of-concept, open-label, prospective study of 20 patients with DMARD-naïve, ACPA-negative UA (⩾2 joint synovitis) and PDUS ⩾ 1 with clinical and 20-joint US (grey scale/PDUS) assessments at baseline, 6, 12, 18 and 24 months. All patients received 12 months of abatacept (monotherapy for minimum first 6 months). The primary end point was a composite of the proportion of patients that at 6 months achieved DAS44 remission, a maximum of one swollen joint for at least 3 consecutive months and no radiographic progression (over 0-12 months). Twenty of the 23 patients screened were enrolled [14 female; mean (sd) age 53.4 (11.2) years, symptom duration 7.5 (0.9) months]. Two (10%) achieved the composite primary end point. A reduction in the mean (sd) DAS44 was observed from a baseline value of 2.66 (0.77) to 2.01 (0.81) at 6 months and to 1.78 (0.95) at 12 months. The DAS44 remission rates were 6/20 (30%; 95% CI: 15, 51%) at 6 months and 8/20 (40%; 95% CI: 22, 62%) at 12 months. A striking decrease in the median (interquartile range; IQR) total PDUS score was noted from 10 (4-23) at baseline to 3 (2-12) and 3 (0-5) at 6 and 12 months, respectively. This report is a first in potentially identifying an effective therapy, abatacept monotherapy, for poor-prognosis, ACPA-negative UA, supported by a clear reduction in PDUS. These data justify evaluation in a controlled study. © The Author 2016. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  11. Correlation of subendometrial-endometrial blood flow assessment by two-dimensional power Doppler with pregnancy outcome in frozen-thawed embryo transfer cycles.

    Science.gov (United States)

    Sardana, Divya; Upadhyay, Amit Jitendra; Deepika, K; Pranesh, Gautham T; Rao, Kamini A

    2014-04-01

    Various markers have been proposed to evaluate endometrial receptivity, such as molecular markers and sonographic markers. Commonly used sonographic markers include endometrial thickness and pattern. A good endometrial blood flow is considered necessary for improved pregnancy outcome. The aim of the present study is to evaluate the role of subendometrial endometrial blood flow with two-dimensional-power Doppler (2D-PD) in predicting pregnancy outcome in hormone replacement frozen-thawed embryo transfer (FET) cycles. Prospective, non-randomized observational study. A total of 165 patients undergoing their first FET cycle were evaluated for subendometrial-endometrial blood flow by 2D-PD once the endometrium was ≥7 mm thick. Group A consisted of 127 women showing the presence of subendometrial-endometrial blood flow. Group B comprised of 38 women in whom subendometrial blood flow was absent. Progesterone supplement was added and transfer of 2-3 cleavage stage good quality embryos was done after 3 days. Independent two-tailed t-test and Chi-square test. There was no significant difference in body mass index, endometrial thickness, follicle stimulating hormone, luteinizing hormone levels, number of mature oocytes, semen parameters and the number of good quality embryos in the two groups (P > 0.05). The mean age in Group A was 32.05 years and 33.73 years in Group B, and the difference was statistically significant (P = 0.04). Overall pregnancy rate (PR) was 30.90%. PRs were significantly higher in the presence of subendometrial-endometrial blood flow than in its absence (35.43% vs. 15.78%, P = 0.02). Furthermore, clinical pregnancy rate and implantation rate were significantly higher in Group A when compared to Group B (31.49% and 14.79% vs. 13.15% and 6.52%, P = 0.02 and 0.03, respectively). The presence of endometrial blood flow significantly improves cycle outcome in hormone replacement therapy-FET cycles.

  12. A Harmonic Resonance Suppression Strategy for a High-Speed Railway Traction Power Supply System with a SHE-PWM Four-Quadrant Converter Based on Active-Set Secondary Optimization

    Directory of Open Access Journals (Sweden)

    Runze Zhang

    2017-10-01

    Full Text Available Pulse width modulation (PWM technology is widely used in traction converters for high-speed railways. The harmonic distribution caused by PWM is quite extensive, and increases the possibility of grid–train coupling resonance in the traction power supply system (TPSS. This paper first analyzes the mechanism of resonance, when the characteristic harmonic frequency of a four-quadrant converter (4QC current that injects into the traction grid matches the resonant frequency of the traction grid, which may result in resonance in the system. To suppress resonance, this paper adopts specific harmonic elimination–pulse width modulation (SHE-PWM technology combined with a transient direct current control strategy to eliminate the harmonics in the resonant frequency, which may suppress the grid–train coupling resonance. Due to the fact that the SHE-PWM process with multiple switching angles contains complex transcendental equations, the initial value is difficult to provide, and is difficult to solve using ordinary iterative algorithms. In this paper, an active-set secondary optimization method is used to solve the equation. The algorithm has the benefits of low dependence on initial values, fast convergence and high solution accuracy. Finally, the feasibility of the resonant suppression algorithm is verified by means of Matlab simulation.

  13. The use of 3D rendering, VCI-C, 3D power Doppler and B-flow in the evaluation of interstitial pregnancy with arteriovenous malformation treated by selective uterine artery embolization.

    Science.gov (United States)

    Valsky, D V; Hamani, Y; Verstandig, A; Yagel, S

    2007-03-01

    Cornual pregnancy is a rare form of ectopic pregnancy. We describe a case of cornual pregnancy suspected by two-dimensional ultrasonography (2DUS) and confirmed by three-dimensional volume contrast imaging in the C-plane. Three-dimensional power Doppler showed a particularly rich blood supply and two-dimensional color Doppler mapping demonstrated arteriovenous malformation (AVM). The feeding vessel originating from the right uterine artery and AVM were demonstrated with B-flow spatio-temporal image correlation (STIC) modality. Conservative management was chosen to preserve the uterus. Angiography confirmed the diagnosis of AVM; embolization with polyvinyl alcohol particles and embolization coils was performed through the right uterine artery until occlusion of the AVM and feeding vessels had occurred. Postprocedure color Doppler mapping and B-flow STIC modalities demonstrated absence of flow in the AVM. Serum human chorionic gonadotropin (hCG) levels gradually fell to non-pregnant levels during the ensuing 5 weeks. To the best of our knowledge this is the first report of cornual pregnancy with AVM. We demonstrate here the value of new three-dimensional ultrasound modalities in the diagnosis of cornual pregnancy and the use of embolization as an effective therapeutic option when conservative treatment with uterine preservation is desired.

  14. Harmonics Monitoring Survey on LED Lamps

    Directory of Open Access Journals (Sweden)

    Abdelrahman Ahmed Akila

    2017-03-01

    Full Text Available Light Emitting Diode (LED lamps are being increasingly used in many applications. These LED lamps operate using a driver, which is a switching device. Hence, LED lamps will be a source of harmonics in the power system. These harmonics if not well treated, may cause severe performance and operational problems. In this paper, harmonics (amplitude and phase angles generated by both LED lamps and conventional fluorescent lamps will be studied practically. Then they will be analyzed and evaluated. Compared to each other harmonics generated by both LED and conventional florescent lamps, self mitigation may occur based on the phase angle of these harmonics. All data will be measured using power analyzer and will be done on a sample of actual lamps.

  15. Electric power quality analysis methods. Application to voltage dips and harmonic disturbances; Methodes d'analyse de la qualite de l'energie electrique. Application aux creux de tension et a la pollution harmonique

    Energy Technology Data Exchange (ETDEWEB)

    Vanya, Ignatova

    2006-10-15

    The power quality concerns all the actors in the energy domains, that they are network administrators, suppliers, producers, or consumers of electricity. The research work presented in this PhD thesis is situated in the field of the power quality monitoring. Its objective is to introduce new techniques for analysis of power quality problems. There are different methods designed for the analysis of the power quality disturbances. This method reaches very good performances in the voltage dips analysis, as it allows segmenting, classifying and characterising these power quality disturbances. The periodic systems method allows the theoretical study of the generation and the propagation of harmonic disturbances in the network. Finally, the statistical matrix method has the objective to represent statistically electrical signals without loss of important information. (author)

  16. Harmonics mitigation on industrial loads using series and parallel ...

    African Journals Online (AJOL)

    This work compared the use of series and parallel resonant harmonic filters in suppressing harmonics using Simulink model of the power system of NICHEMTEX, a Textile industry in Nigeria as a case study. Mathematical analysis representing current harmonics distributions on industrials loads with and without capacitor ...

  17. Harmonic Damping in DG-Penetrated Distribution Network

    DEFF Research Database (Denmark)

    Lu, Jinghang; Savaghebi, Mehdi; Guerrero, Josep M.

    2016-01-01

    Grid background harmonics may be amplified, propagate through a long distribution feeder and even lead to power system instability. In this paper, harmonic propagation issue is investigated and mitigation of the harmonics is analyzed by using transmission line theory which has already been applie...

  18. Voltage harmonic elimination with RLC based interface smoothing filter

    Science.gov (United States)

    Chandrasekaran, K.; Ramachandaramurthy, V. K.

    2015-04-01

    A method is proposed for designing a Dynamic Voltage Restorer (DVR) with RLC interface smoothing filter. The RLC filter connected between the IGBT based Voltage Source Inverter (VSI) is attempted to eliminate voltage harmonics in the busbar voltage and switching harmonics from VSI by producing a PWM controlled harmonic voltage. In this method, the DVR or series active filter produces PWM voltage that cancels the existing harmonic voltage due to any harmonic voltage source. The proposed method is valid for any distorted busbar voltage. The operating VSI handles no active power but only harmonic power. The DVR is able to suppress the lower order switching harmonics generated by the IGBT based VSI. Good dynamic and transient results obtained. The Total Harmonic Distortion (THD) is minimized to zero at the sensitive load end. Digital simulations are carried out using PSCAD/EMTDC to validate the performance of RLC filter. Simulated results are presented.

  19. Methodology for the prediction and solution of the harmonic distortion in the distribution power lines; Metodologia para la prediccion y solucion de la distorsion armonica en las redes electricas de distribucion

    Energy Technology Data Exchange (ETDEWEB)

    Velazquez Sanchez, Raul [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1994-03-01

    The harmonic distortion in the distribution electric systems, caused by the increment in the utilization of power electronics, presents a growing problem for the power supply enterprises, as well as for their users. The distortion of the voltage wave shape in the distribution electric systems can produce additional heating in transformers, damage in motors, faults in capacitor banks, frequent fuse capacitors banks operation and inadequate operation of controllers and protecting schemes. This paper presents a general overview on the harmonics problem in distribution systems. The sources of harmonic currents, their effects in the electric system and the methodology implemented in the Instituto de Investigaciones Electricas (IIE) for their detection, measurement and control, are described. [Espanol] La distorsion armonica en los sistemas electricos de distribucion, ocasionada por el incremento en la utilizacion de la electronica de potencia, presenta un problema creciente tanto para las empresas suministradoras de energia electrica como para sus usuarios. La distorsion de la forma de onda del voltaje en los sistemas de distribucion de energia electrica puede producir calentamiento adicional en transformadores, dano en motores, fallas en bancos de capacitores, operacion frecuente de fusibles de bancos de capacitores y operacion inadecuada de controladores y esquemas de proteccion. En este trabajo se presenta un panorama general sobre el problema de armonicas en redes de distribucion. Se describen las fuentes de corrientes armonicas, sus efectos en el sistema electrico y la metodologia implantada en el Instituto de Investigaciones Electricas (IIE) para detectarlas, medirlas y controlarlas.

  20. Generalized Doppler and aberration kernel for frequency-dependent cosmological observables

    Science.gov (United States)

    Yasini, Siavash; Pierpaoli, Elena

    2017-11-01

    We introduce a frequency-dependent Doppler and aberration transformation kernel for the harmonic multipoles of a general cosmological observable with spin weight s , Doppler weight d and arbitrary frequency spectrum. In the context of cosmic microwave background (CMB) studies, the frequency-dependent formalism allows to correct for the motion-induced aberration and Doppler effects on individual frequency maps with different masks. It also permits to deboost background radiations with non-blackbody frequency spectra, like extragalactic foregrounds and CMB spectra with primordial spectral distortions. The formalism can also be used to correct individual E and B polarization modes and account for motion-induced E/B mixing of polarized observables with d ≠1 at different frequencies. We apply the generalized aberration kernel on polarized and unpolarized specific intensity at 100 and 217 GHz and show that the motion-induced effects typically increase with the frequency of observation. In all-sky CMB experiments, the frequency-dependence of the motion-induced effects for a blackbody spectrum are overall negligible. However in a cut-sky analysis, ignoring the frequency dependence can lead to percent level error in the polarized and unpolarized power spectra over all angular scales. In the specific cut-sky used in our analysis (b >4 5 ° ,fsky≃14 % ), and for the dipole-inferred velocity β =0.00123 typically attributed to our peculiar motion, the Doppler and aberration effects can change polarized and unpolarized power spectra of specific intensity in the CMB rest frame by 1 - 2 % , but we find the polarization cross-leakage between E and B modes to be negligible.

  1. Advances in Doppler OCT

    Science.gov (United States)

    Liu, Gangjun; Chen, Zhongping

    2014-01-01

    We review the principle and some recent applications of Doppler optical coherence tomography (OCT). The advances of the phase-resolved Doppler OCT method are described. Functional OCT algorithms which are based on an extension of the phase-resolved scheme are also introduced. Recent applications of Doppler OCT for quantification of flow, imaging of microvasculature and vocal fold vibration, and optical coherence elastography are briefly discussed. PMID:24443649

  2. Doppler flowmetry in preeclampsia.

    Science.gov (United States)

    Zahumensky, J

    2009-01-01

    The purpose of this study was to summarize the new published data on the Doppler flowmetry in preeclampsia. We summarize the new published data on the Doppler flowmetry in uteroplacental, fetoplacental and fetal circulation in preeclampsia. The present review summarized the results of clinical research on the Doppler flowmetry in the screening of risk of preclampsia, in the diagnosis of preclampsia and in the fetal risk in preclampsia (Ref. 19). Full Text (Free, PDF) www.bmj.sk.

  3. Doppler micro sense and avoid radar

    Science.gov (United States)

    Gorwara, Ashok; Molchanov, Pavlo; Asmolova, Olga

    2015-10-01

    There is a need for small Sense and Avoid (SAA) systems for small and micro Unmanned Aerial Systems (UAS) to avoid collisions with obstacles and other aircraft. The proposed SAA systems will give drones the ability to "see" close up and give them the agility to maneuver through tight areas. Doppler radar is proposed for use in this sense and avoid system because in contrast to optical or infrared (IR) systems Doppler can work in more harsh conditions such as at dusk, and in rain and snow. And in contrast to ultrasound based systems, Doppler can better sense small sized obstacles such as wires and it can provide a sensing range from a few inches to several miles. An SAA systems comprised of Doppler radar modules and an array of directional antennas that are distributed around the perimeter of the drone can cover the entire sky. These modules are designed so that they can provide the direction to the obstacle and simultaneously generate an alarm signal if the obstacle enters within the SAA system's adjustable "Protection Border". The alarm signal alerts the drone's autopilot to automatically initiate an avoidance maneuver. A series of Doppler radar modules with different ranges, angles of view and transmitting power have been designed for drones of different sizes and applications. The proposed Doppler radar micro SAA system has simple circuitry, works from a 5 volt source and has low power consumption. It is light weight, inexpensive and it can be used for a variety of small unmanned aircraft.

  4. Harmonic Morphisms Projecting Harmonic Functions to Harmonic Functions

    OpenAIRE

    Mustafa, M. T.

    2012-01-01

    For Riemannian manifolds $M$ and $N$ , admitting a submersion $\\varphi $ with compact fibres, we introduce the projection of a function via its decomposition intohorizontal and vertical components. By comparing the Laplacians on $M$ and $N$ , we determine conditions under which a harmonic function on $U={\\varphi }^{-1}(V)\\subset M$ projects down, via its horizontal component, to a harmonic function on $V\\subset N$ .

  5. Effectiveness of evaluating tumor vascularization using 3D power Doppler ultrasound with high-definition flow technology in the prediction of the response to neoadjuvant chemotherapy for T2 breast cancer: a preliminary report.

    Science.gov (United States)

    Shia, Wei-Chung; Chen, Dar-Ren; Huang, Yu-Len; Wu, Hwa-Koon; Kuo, Shou-Jen

    2015-10-07

    The aim of this study was to evaluate the effectiveness of advanced ultrasound (US) imaging of vascular flow and morphological features in the prediction of a pathologic complete response (pCR) and a partial response (PR) to neoadjuvant chemotherapy for T2 breast cancer.Twenty-nine consecutive patients with T2 breast cancer treated with six courses of anthracycline-based neoadjuvant chemotherapy were enrolled. Three-dimensional (3D) power Doppler US with high-definition flow (HDF) technology was used to investigate the blood flow in and morphological features of the tumors. Six vascularity quantization features, three morphological features, and two vascular direction features were selected and extracted from the US images. A support vector machine was used to evaluate the changes in vascularity after neoadjuvant chemotherapy, and pCR and PR were predicted on the basis of these changes.The most accurate prediction of pCR was achieved after the first chemotherapy cycle, with an accuracy of 93.1% and a specificity of 85.5%, while that of a PR was achieved after the second cycle, with an accuracy of 79.31% and a specificity of 72.22%.Vascularity data can be useful to predict the effects of neoadjuvant chemotherapy. Determination of changes in vascularity after neoadjuvant chemotherapy using 3D power Doppler US with HDF can generate accurate predictions of the patient response, facilitating early decision-making.

  6. Effectiveness of evaluating tumor vascularization using 3D power Doppler ultrasound with high-definition flow technology in the prediction of the response to neoadjuvant chemotherapy for T2 breast cancer: a preliminary report

    Science.gov (United States)

    Shia, Wei-Chung; Chen, Dar-Ren; Huang, Yu-Len; Wu, Hwa-Koon; Kuo, Shou-Jen

    2015-10-01

    The aim of this study was to evaluate the effectiveness of advanced ultrasound (US) imaging of vascular flow and morphological features in the prediction of a pathologic complete response (pCR) and a partial response (PR) to neoadjuvant chemotherapy for T2 breast cancer. Twenty-nine consecutive patients with T2 breast cancer treated with six courses of anthracycline-based neoadjuvant chemotherapy were enrolled. Three-dimensional (3D) power Doppler US with high-definition flow (HDF) technology was used to investigate the blood flow in and morphological features of the tumors. Six vascularity quantization features, three morphological features, and two vascular direction features were selected and extracted from the US images. A support vector machine was used to evaluate the changes in vascularity after neoadjuvant chemotherapy, and pCR and PR were predicted on the basis of these changes. The most accurate prediction of pCR was achieved after the first chemotherapy cycle, with an accuracy of 93.1% and a specificity of 85.5%, while that of a PR was achieved after the second cycle, with an accuracy of 79.31% and a specificity of 72.22%. Vascularity data can be useful to predict the effects of neoadjuvant chemotherapy. Determination of changes in vascularity after neoadjuvant chemotherapy using 3D power Doppler US with HDF can generate accurate predictions of the patient response, facilitating early decision-making.

  7. Adaptive harmonic analysis

    NARCIS (Netherlands)

    Heemink, Arnold; de Jong, B.; Prins, Harrie

    1991-01-01

    In this paper we describe a new approach to the harmonic analysis of the tide. For a number of reasons the harmonic constants are not really constant but vary slowly in time. Therefore, we introduce a narrow-band noise process to model the time-varying behaviour of these harmonic parameters.

  8. Path-length-resolved optical Doppler perfusion monitoring

    OpenAIRE

    Varghese, Babu; Rajan, Vinayakrishnan; van Leeuwen, Ton; Steenbergen, Wiendelt

    2007-01-01

    We report the first path-length-resolved perfusion measurements on human skin measured with a phase-modulated low-coherence Mach-Zehnder interferometer with spatially separated fibers for illumination and detection. Optical path lengths of Doppler shifted and unshifted light and path-length-dependent Doppler broadening of multiply scattered light from skin are measured from the Doppler broadened interference peaks appearing in the power spectrum. Perfusion and its variations during occlusion ...

  9. Tendinopathy and Doppler activity

    DEFF Research Database (Denmark)

    Boesen, M I; Koenig, M J; Torp-Pedersen, S

    2006-01-01

    Intratendinous Doppler activity has been interpreted as an equivalent of neovessels in the Achilles tendon and as a sign of tendinosis (AT).......Intratendinous Doppler activity has been interpreted as an equivalent of neovessels in the Achilles tendon and as a sign of tendinosis (AT)....

  10. The Doppler Effect

    OpenAIRE

    Riedel, Adric

    2014-01-01

    This presentation of 7 animations demonstrates the Doppler effect, which is used by astronomers to learn about the motions of stars, and to find planets.  The principle is simple - in fact, even the animations consist only of expanding circles - but the effect is impressive.   http://starguyspeaks.wordpress.com/2014/10/12/on-the-doppler-effect/

  11. Ultrasonic colour Doppler imaging

    DEFF Research Database (Denmark)

    Evans, David H.; Jensen, Jørgen Arendt; Nielsen, Michael Bachmann

    2011-01-01

    Ultrasonic colour Doppler is an imaging technique that combines anatomical information derived using ultrasonic pulse-echo techniques with velocity information derived using ultrasonic Doppler techniques to generate colour-coded maps of tissue velocity superimposed on grey-scale images of tissue...... anatomy. The most common use of the technique is to image the movement of blood through the heart, arteries and veins, but it may also be used to image the motion of solid tissues such as the heart walls. Colour Doppler imaging is now provided on almost all commercial ultrasound machines, and has been...... vectors. This review briefly introduces the principles behind colour Doppler imaging and describes some clinical applications. It then describes the basic components of conventional colour Doppler systems and the methods used to derive velocity information from the ultrasound signal. Next, a number of new...

  12. Differential doppler heterodyning technique

    DEFF Research Database (Denmark)

    Lading, Lars

    1971-01-01

    Measuring velocity without disturbing the moving object is possible by use of the laser doppler heterodyning technique. Theoretical considerations on the doppler shift show that the antenna property of the photodetector can solve an apparent conflict between two different ways of calculating...... the detected doppler frequency. It is found that the doppler frequency for this particular setup is independent of the direction of detection. Investigations of the signal-to-noise ratio (SNR) show that the maximum SNR-considering the optical setup-is obtained by measuring the frequency difference between two...... doppler-shifted beams rather than by measuring the shift of a single beam by comparing it with a reference beam. Measurements seem to be in agreement with the theoretical consideration...

  13. Measurement of the stopping power of water for carbon ions in the energy range of 1 MeV-6 MeV using the inverted Doppler-shift attenuation method

    Energy Technology Data Exchange (ETDEWEB)

    Rahm, Johannes Martin

    2016-10-31

    Cancer therapy using carbon ions has gained increasing interest in the last decade due to its advantageous dose distributions. For the dosimetry and treatment planning, the accurate knowledge of the stopping power of water for carbon ions is of crucial importance. In the high energy region, the stopping power can be calculated rather accurately by means of the Bethe-Bloch formula. In the case of projectile velocities comparable to those of the valence electrons of the target, these calculations are subject to large uncertainties. There exist no experimental data for the stopping power of water for projectile energies prevailing in the so-called Bragg peak region. The currently available stopping power data for water are derived from measurements in water vapour or D{sub 2}O ice and, hence, neglect the dependence on the state of aggregation. The stopping power of water for charged particles is of high interest not only for practical applications but also to consider how physical and chemical state of the target influence the collisional energy transfer. For the measurement of the stopping power of water, the inverted Doppler-shift attenuation method was used in this work. This method has the advantage that the projectile itself is not needed to be detected and can be slowed down entirely in the target. In this method, the stopping power is determined from the Doppler-shift of the gamma-quanta emitted by projectiles during their slow down. This experiment can be performed at atmospheric pressure and consequently, the stopping power of water can be measured in its real physiological condition. In this work, the stopping power of water for carbon ions was measured for the first time in the energy range between 1 MeV and 6 MeV covering the kinetic energies of carbon ions in the Bragg peak region. The experimental method is presented in detail along with the design of the apparatus and of the data acquisition system. A comprehensive analysis of instrumental effects

  14. Harmonic function theory

    CERN Document Server

    Axler, Sheldon; Ramey, Wade

    2013-01-01

    This is a book about harmonic functions in Euclidean space. Readers with a background in real and complex analysis at the beginning graduate level will feel comfortable with the material presented here. The authors have taken unusual care to motivate concepts and simplify proofs. Topics include: basic properties of harmonic functions, Poisson integrals, the Kelvin transform, spherical harmonics, harmonic Hardy spaces, harmonic Bergman spaces, the decomposition theorem, Laurent expansions, isolated singularities, and the Dirichlet problem. The new edition contains a completely rewritten chapter on spherical harmonics, a new section on extensions of Bocher's Theorem, new exercises and proofs, as well as revisions throughout to improve the text. A unique software package-designed by the authors and available by e-mail - supplements the text for readers who wish to explore harmonic function theory on a computer.

  15. Sequence Domain Harmonic Modeling of Type-IV Wind Turbines

    DEFF Research Database (Denmark)

    Guest, Emerson; Jensen, Kim Høj; Rasmussen, Tonny Wederberg

    2017-01-01

    A sequence domain (SD) harmonic model of a gridconnected voltage-source converter is developed for decoupling converter generated voltage harmonics from voltage harmonics in the external grid. The modeling procedure includes a derivation of the baseband frequency response for regular......-sampled pulsewidth modulation and an analysis of converter generated voltage harmonics due to compensated dead-time. The decoupling capabilities of the proposed the SD harmonic model are verified through a power quality (PQ) assessment of a 3MW Type-IV wind turbine. The assessment shows that the magnitude and phase...... of low-order odd converter generated voltage harmonics are dependent on the converter operating point and the phase of the fundamental component of converter current respectively. The SD harmonic model can be used to make PQ assessments of Type-IV wind turbines or incorporated into harmonic load flows...

  16. Superharmonic microbubble Doppler effect in ultrasound therapy

    Science.gov (United States)

    Pouliopoulos, Antonios N; Choi, James J

    2016-01-01

    Abstract The introduction of microbubbles in focused ultrasound therapies has enabled a diverse range of non-invasive technologies: sonoporation to deliver drugs into cells, sonothrombolysis to dissolve blood clots, and blood-brain barrier opening to deliver drugs into the brain. Current methods for passively monitoring the microbubble dynamics responsible for these therapeutic effects can identify the cavitation position by passive acoustic mapping and cavitation mode by spectral analysis. Here, we introduce a new feature that can be monitored: microbubble effective velocity. Previous studies have shown that echoes from short imaging pulses had a Doppler shift that was produced by the movement of microbubbles. Therapeutic pulses are longer (>1 000 cycles) and thus produce a larger alteration of microbubble distribution due to primary and secondary acoustic radiation force effects which cannot be monitored using pulse-echo techniques. In our experiments, we captured and analyzed the Doppler shift during long therapeutic pulses using a passive cavitation detector. A population of microbubbles (5  ×  104–5  ×  107 microbubbles ml−1) was embedded in a vessel (inner diameter: 4 mm) and sonicated using a 0.5 MHz focused ultrasound transducer (peak-rarefactional pressure: 75–366 kPa, pulse length: 50 000 cycles or 100 ms) within a water tank. Microbubble acoustic emissions were captured with a coaxially aligned 7.5 MHz passive cavitation detector and spectrally analyzed to measure the Doppler shift for multiple harmonics above the 10th harmonic (i.e. superharmonics). A Doppler shift was observed on the order of tens of kHz with respect to the primary superharmonic peak and is due to the axial movement of the microbubbles. The position, amplitude and width of the Doppler peaks depended on the acoustic pressure and the microbubble concentration. Higher pressures increased the effective velocity of the microbubbles up to 3 m s−1, prior to

  17. Superharmonic microbubble Doppler effect in ultrasound therapy.

    Science.gov (United States)

    Pouliopoulos, Antonios N; Choi, James J

    2016-08-21

    The introduction of microbubbles in focused ultrasound therapies has enabled a diverse range of non-invasive technologies: sonoporation to deliver drugs into cells, sonothrombolysis to dissolve blood clots, and blood-brain barrier opening to deliver drugs into the brain. Current methods for passively monitoring the microbubble dynamics responsible for these therapeutic effects can identify the cavitation position by passive acoustic mapping and cavitation mode by spectral analysis. Here, we introduce a new feature that can be monitored: microbubble effective velocity. Previous studies have shown that echoes from short imaging pulses had a Doppler shift that was produced by the movement of microbubbles. Therapeutic pulses are longer (>1 000 cycles) and thus produce a larger alteration of microbubble distribution due to primary and secondary acoustic radiation force effects which cannot be monitored using pulse-echo techniques. In our experiments, we captured and analyzed the Doppler shift during long therapeutic pulses using a passive cavitation detector. A population of microbubbles (5  ×  10(4)-5  ×  10(7) microbubbles ml(-1)) was embedded in a vessel (inner diameter: 4 mm) and sonicated using a 0.5 MHz focused ultrasound transducer (peak-rarefactional pressure: 75-366 kPa, pulse length: 50 000 cycles or 100 ms) within a water tank. Microbubble acoustic emissions were captured with a coaxially aligned 7.5 MHz passive cavitation detector and spectrally analyzed to measure the Doppler shift for multiple harmonics above the 10th harmonic (i.e. superharmonics). A Doppler shift was observed on the order of tens of kHz with respect to the primary superharmonic peak and is due to the axial movement of the microbubbles. The position, amplitude and width of the Doppler peaks depended on the acoustic pressure and the microbubble concentration. Higher pressures increased the effective velocity of the microbubbles up to 3 m s(-1), prior to the onset

  18. Path-length-resolved optical Doppler perfusion monitoring.

    Science.gov (United States)

    Varghese, Babu; Rajan, Vinayakrishnan; Van Leeuwen, Ton G; Steenbergen, Wiendelt

    2007-01-01

    We report the first path-length-resolved perfusion measurements on human skin measured with a phase-modulated low-coherence Mach-Zehnder interferometer with spatially separated fibers for illumination and detection. Optical path lengths of Doppler shifted and unshifted light and path-length-dependent Doppler broadening of multiply scattered light from skin are measured from the Doppler broadened interference peaks appearing in the power spectrum. Perfusion and its variations during occlusion are measured in real time for a given optical path length, and the results are compared with the perfusion signal obtained with a conventional laser Doppler perfusion monitor.

  19. Assessment of changes in vascularity and blood volume in canine sarcomas and squamous cell carcinomas during fractionated radiation therapy using quantified contrast-enhanced power Doppler ultrasonography: a preliminary study.

    Science.gov (United States)

    Ohlerth, Stefanie; Bley, Carla Rohrer; Laluhová, Dagmar; Roos, Malgorzata; Kaser-Hotz, Barbara

    2010-10-01

    Radiation therapy does not only target tumour cells but also affects tumour vascularity. In the present study, changes in tumour vascularity and blood volume were investigated in five grade 1 oral fibrosarcomas, eight other sarcomas (non-oral soft tissue and bone sarcomas) and 12 squamous cell carcinomas in dogs during fractionated radiation therapy (total dose, 45-56 Gy). Contrast-enhanced power Doppler ultrasound was performed before fraction 1, 3, 6, 8, 10, 12, 14 and 15 or 16 (sarcomas) or 17 (squamous cell carcinomas). Prior to treatment, median vascularity and blood volume were significantly higher in squamous cell carcinomas (P=0.0005 and 0.001), whereas measurements did not differ between oral fibrosarcomas and other sarcomas (P=0.88 and 0.999). During the course of radiation therapy, only small, non-significant changes in vascularity and blood volume were observed in all three tumour histology groups (P=0.08 and P=0.213), whereas median tumour volume significantly decreased until the end of treatment (P=0.04 for fibrosarcomas and other sarcomas, P=0.008 for squamous cell carcinomas). It appeared that there was a proportional decrease in tumour volume, vascularity and blood volume. Doppler measurements did not predict progression free interval or survival in any of the three tumour groups (P=0.06-0.86). However, the number of tumours investigated was small and therefore, the results can only be considered preliminary. Copyright © 2009 Elsevier Ltd. All rights reserved.

  20. Harmonic Oscillator SUSY Partners and Evolution Loops

    Directory of Open Access Journals (Sweden)

    David J. Fernández

    2012-07-01

    Full Text Available Supersymmetric quantum mechanics is a powerful tool for generating exactly solvable potentials departing from a given initial one. If applied to the harmonic oscillator, a family of Hamiltonians ruled by polynomial Heisenberg algebras is obtained. In this paper it will be shown that the SUSY partner Hamiltonians of the harmonic oscillator can produce evolution loops. The corresponding geometric phases will be as well studied.

  1. Measuring Spherical Harmonic Coefficients on a Sphere

    Energy Technology Data Exchange (ETDEWEB)

    Pollaine, S; Haan, S W

    2003-05-16

    The eigenfunctions of Rayleigh-Taylor modes on a spherical capsule are the spherical harmonics Y{sub l,m} These can be measured by measuring the surface perturbations along great circles and fitting them to the first few modes by a procedure described in this article. For higher mode numbers, it is more convenient to average the Fourier power spectra along the great circles, and then transform them to spherical harmonic modes by an algorithm derived here.

  2. Compact fluorescent lamps, LED lamps and harmonic distortion

    Science.gov (United States)

    Franco, A. M. R.; Debatin, R. M.; Cotia, F. C. G.; Silva, M. V. M.; Ribeiro, R. S.; Zampilis, R. R. N.

    2015-01-01

    The aim of this paper is to evaluate the harmonic distortion in the current waveform of Compact Fluorescent Lamps (CFL) and Lamps Lighting Emitting Diode (LED). For this, we analysed the power factor, voltage waveform, current waveform, total harmonic distortion (THD) and active power consumed.

  3. Coherent harmonic production using a two-section undulator FEL

    Energy Technology Data Exchange (ETDEWEB)

    Jaroszynski, D.A. [Commissariat a l`Energie, Bruyeres-le-Chatel (France); Prazeres, R.; Glotin, F. [Centre Universitaire Paris-Sud (France)] [and others

    1995-12-31

    We present measurements and a theoretical analysis of a new method of generating harmonic radiation in a free-electron laser oscillator with a two section undulator in a single optical cavity. To produce coherent harmonic radiation the undulator is arranged so that the downstream undulator section resonance frequency matches a harmonic of the upstream undulator. Both the fundamental and the harmonic optical fields evolve in the same optical cavity and are coupled out with different extraction fractions using a hole in one of the cavity mirrors. We present measurements that show that the optical power at the second and third harmonic can be enhanced by more than an order of magnitude in this fundamental/harmonic configuration. We compare the production of harmonic radiation of a two sectioned fundamental/harmonic undulator with that produced from a FEL operating at its highest efficiency with a step-tapered undulator, where the bunching at the end of the first section is very large. We examine, the dependence of the harmonic power on the intracavity power by adjusting the optical cavity desynchronism, {delta}L. We also examine the evolution of the fundamental and harmonic powers as a function of cavity roundtrip number to evaluate the importance of the small signal gain at the harmonic. We compare our measurements with predictions of a multi-electron numerical model that follows the evolution of fundamental and harmonic power to saturation. This fundamental/harmonic mode, of operation of the FEL may have useful applications in the production of coherent X-ray and VUV radiation, a spectral range where high reflectivity optical cavity mirrors are difficult or impossible to manufacture.

  4. Experiments on ion cyclotron damping at the deuterium fourth harmonic in DIII-D

    Energy Technology Data Exchange (ETDEWEB)

    Pinsker, R. I. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Baity, F. W. [Oak Ridge National Laboratory, Oak Ridge, Tennessee (United States); Bernabei, S. [Princeton Plasma Physics Laboratory, Princeton, New Jersey (United States); Greenough, N. [Princeton Plasma Physics Laboratory, Princeton, New Jersey (United States); Heidbrink, W. W. [University of California, Irvine, California (United States); Mau, T. K. [University of California, San Diego, California (United States); Petty, C. C. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Porkolab, M. [Massachusetts Institute of Technology, Cambridge, Massachusetts (United States)

    1999-09-20

    Absorption of fast Alfven waves by the energetic ions of an injected beam is evaluated in the DIII-D tokamak. Ion cyclotron resonance absorption at the fourth harmonic of the deuteron cyclotron frequency is observed with deuterium neutral beam injection (f=60 MHz, B{sub T}=1.9 T). Enhanced D-D neutron rates are evidence of absorption at the Doppler-shifted cyclotron resonance. Characteristics of global energy confinement provide further proof of substantial beam acceleration by the rf. In many cases, the accelerated deuterons cause temporary stabilization of the sawtooth (''monster sawteeth''), at relatively low rf power levels of {approx}1 MW. (c) 1999 American Institute of Physics.

  5. Evaluation of canine hepatic masses by use of triphasic computed tomography and B-mode, color flow, power, and pulsed-wave Doppler ultrasonography and correlation with histopathologic classification.

    Science.gov (United States)

    Griebie, Erin R; David, Frederic H; Ober, Christopher P; Feeney, Daniel A; Anderson, Kari L; Wuenschmann, Arno; Jessen, Carl R

    2017-11-01

    OBJECTIVE To determine clinical relevance for quantitative and qualitative features of canine hepatic masses evaluated by use of triphasic CT and B-mode, color flow, power, and pulsed-wave Doppler ultrasonography and to compare diagnostic accuracy of these modalities for predicting mass type on the basis of histopathologic classification. ANIMALS 44 client-owned dogs. PROCEDURES Dogs with histopathologic confirmation (needle core, punch, or excisional biopsy) of a hepatic mass were enrolled. Triphasic CT and B-mode, color flow, power, and pulsed-wave Doppler ultrasonography of each hepatic mass were performed. Seventy quantitative and qualitative variables of each hepatic mass were recorded by 5 separate observers and statistically evaluated with discriminant and stepwise analyses. Significant variables were entered in equation-based predictions for the histopathologic diagnosis. RESULTS An equation that included the lowest delayed-phase absolute enhancement of the mass and the highest venous-phase mass conspicuity was used to correctly classify 43 of 46 (93.5%) hepatic masses as benign or malignant. An equation that included only the lowest delayed-phase absolute enhancement of the mass could be used to correctly classify 42 of 46 (91.3%) masses (with expectation of malignancy if this value was < 37 Hounsfield units). For ultrasonography, categorization of the masses with cavitations as malignant achieved a diagnostic accuracy of 80.4%. CONCLUSIONS AND CLINICAL RELEVANCE Triphasic CT had a higher accuracy than ultrasonography for use in predicting hepatic lesion classification. The lowest delayed-phase absolute enhancement of the mass was a simple calculation that required 2 measurements and aided in the differentiation of benign versus malignant hepatic masses.

  6. Harmonic ratcheting for fast acceleration

    Directory of Open Access Journals (Sweden)

    N. Cook

    2014-04-01

    Full Text Available A major challenge in the design of rf cavities for the acceleration of medium-energy charged ions is the need to rapidly sweep the radio frequency over a large range. From low-power medical synchrotrons to high-power accelerator driven subcritical reactor systems, and from fixed focus alternating gradient accelerators to rapid cycling synchrotrons, there is a strong need for more efficient, and faster, acceleration of protons and light ions in the semirelativistic range of hundreds of MeV/u. A conventional way to achieve a large, rapid frequency sweep (perhaps over a range of a factor of 6 is to use custom-designed ferrite-loaded cavities. Ferrite rings enable the precise tuning of the resonant frequency of a cavity, through the control of the incremental permeability that is possible by introducing a pseudoconstant azimuthal magnetic field. However, rapid changes over large permeability ranges incur anomalous behavior such as the “Q-loss” and “f-dot” loss phenomena that limit performance while requiring high bias currents. Notwithstanding the incomplete understanding of these phenomena, they can be ameliorated by introducing a “harmonic ratcheting” acceleration scheme in which two or more rf cavities take turns accelerating the beam—one turns on when the other turns off, at different harmonics—so that the radio frequency can be constrained to remain in a smaller range. Harmonic ratcheting also has straightforward performance advantages, depending on the particular parameter set at hand. In some typical cases it is possible to halve the length of the cavities, or to double the effective gap voltage, or to double the repetition rate. This paper discusses and quantifies the advantages of harmonic ratcheting in general. Simulation results for the particular case of a rapid cycling medical synchrotron ratcheting from harmonic number 9 to 2 show that stability and performance criteria are met even when realistic engineering details

  7. Reduction of Harmonics by 18-Pulse Rectifier

    Directory of Open Access Journals (Sweden)

    Stanislav Kocman

    2008-01-01

    Full Text Available Operation of such electrical devices as data processing and electronics devices, adjustable speed drives or uninterruptible power supply can cause problems by generating harmonic currents into the network, from which they are supplied. Effects of these harmonic currents are various, they can get worse the quality of supply voltage in the network or to have negative influences on devices connected to this network. There are various technical solutions for reduction of harmonics. One of them is using of multi-pulse rectifiers, whereas the 18-pulse rectifier in the structure of adjustable speed drive is briefly presented in this paper including some results of its behaviour. The examined experimental measurements confirmed its very good efficiency in the harmonic mitigation.

  8. Harmonic Analysis and Mitigation of Low- Frequency Switching Voltage Source Inverter with Auxiliary VSI

    DEFF Research Database (Denmark)

    Bai, Haofeng; Wang, Xiongfei; Blaabjerg, Frede

    2018-01-01

    The output currents of high-power Voltage Source Inverters (VSIs) are distorted by the switching harmonics and the background harmonics in the grid voltage. This paper presents an active harmonic filtering scheme for high-power, low-frequency switching VSIs with an additional auxiliary VSI...

  9. harmonic load modeling: a case study of 33 kv abuja steel mill feeder

    African Journals Online (AJOL)

    HOD

    An in-depth study of the harmonic orders inherent in a power system network is required before mitigation techniques are adopted. This paper studied the harmonic orders of the 33 kV Abuja Steel Feeder modeled as a harmonic source using measured data. Readings of kW, kVar, kV and Hz were obtained using power ...

  10. Análisis de la compensación de potencia reactiva en sistemas contaminados con armónicos; Analysis of the Reactive Power Compensation in Contaminated Systems with Harmonics

    Directory of Open Access Journals (Sweden)

    Secundino Marrero Ramírez

    2011-02-01

    Full Text Available En este artículo se presentan los resultados obtenidos en la evaluación de una red industrial con presenciade contaminación armónica, donde las cargas no lineales corresponden fundamentalmente a rectificadoresy variadores de velocidad. Se establecieron los armónicos típicos generados por estas cargas y ellopermitió determinar los niveles de distorsión armónica de tensión y corriente para analizar su influencia enla selección del banco de condensadores durante la compensación de la potencia reactiva atendiendo alcomportamiento del sistema ante diferentes estados de carga.  The article is given the evaluation obtained of an industrial network with the presence of harmoniccontamination, where the non lineal loads correspond fundamentally to rectifiers and variators of speed.Where the typical harmonic generated by these loads settled down and it allowed it to determine the levelsof harmonic distortion of tension and current to analyze their influence in the selection of the bank ofcondensers during the compensation of the power it reactivates assisting to the behavior of the systembefore different load states.

  11. Phenomena induced by powerful HF pumping towards magnetic zenith with a frequency near the F-region critical frequency and the third electron gyro harmonic frequency

    Directory of Open Access Journals (Sweden)

    N. F. Blagoveshchenskaya

    2009-01-01

    Full Text Available Multi-instrument observational data from an experiment on 13 October 2006 at the EISCAT/HEATING facility at Tromsø, Norway are analysed. The experiment was carried out in the evening hours when the electron density in the F-region dropped, and the HF pump frequency fH was near and then above the critical frequency of the F2 layer. The distinctive feature of this experiment is that the pump frequency was just below the third electron gyro harmonic frequency, while both the HF pump beam and UHF radar beam were directed towards the magnetic zenith (MZ. The HF pump-induced phenomena were diagnosed with several instruments: the bi-static HF radio scatter on the London-Tromsø-St. Petersburg path, the CUTLASS radar in Hankasalmi (Finland, the European Incoherent Scatter (EISCAT UHF radar at Tromsø and the Tromsø ionosonde (dynasonde. The results show thermal electron excitation of the HF-induced striations seen simultaneously from HF bi-static scatter and CUTLASS radar observations, accompanied by increases of electron temperature when the heater frequency was near and then above the critical frequency of the F2 layer by up to 0.4 MHz. An increase of the electron density up to 25% accompanied by strong HF-induced electron heating was observed, only when the heater frequency was near the critical frequency and just below the third electron gyro harmonic frequency. It is concluded that the combined effect of upper hybrid resonance and gyro resonance at the same altitude gives rise to strong electron heating, the excitation of striations, HF ray trapping and extension of HF waves to altitudes where they can excite Langmuir turbulence and fluxes of electrons accelerated to energies that produce ionization.

  12. Phenomena induced by powerful HF pumping towards magnetic zenith with a frequency near the F-region critical frequency and the third electron gyro harmonic frequency

    Directory of Open Access Journals (Sweden)

    N. F. Blagoveshchenskaya

    2009-01-01

    Full Text Available Multi-instrument observational data from an experiment on 13 October 2006 at the EISCAT/HEATING facility at Tromsø, Norway are analysed. The experiment was carried out in the evening hours when the electron density in the F-region dropped, and the HF pump frequency fH was near and then above the critical frequency of the F2 layer. The distinctive feature of this experiment is that the pump frequency was just below the third electron gyro harmonic frequency, while both the HF pump beam and UHF radar beam were directed towards the magnetic zenith (MZ. The HF pump-induced phenomena were diagnosed with several instruments: the bi-static HF radio scatter on the London-Tromsø-St. Petersburg path, the CUTLASS radar in Hankasalmi (Finland, the European Incoherent Scatter (EISCAT UHF radar at Tromsø and the Tromsø ionosonde (dynasonde. The results show thermal electron excitation of the HF-induced striations seen simultaneously from HF bi-static scatter and CUTLASS radar observations, accompanied by increases of electron temperature when the heater frequency was near and then above the critical frequency of the F2 layer by up to 0.4 MHz. An increase of the electron density up to 25% accompanied by strong HF-induced electron heating was observed, only when the heater frequency was near the critical frequency and just below the third electron gyro harmonic frequency. It is concluded that the combined effect of upper hybrid resonance and gyro resonance at the same altitude gives rise to strong electron heating, the excitation of striations, HF ray trapping and extension of HF waves to altitudes where they can excite Langmuir turbulence and fluxes of electrons accelerated to energies that produce ionization.

  13. LED lamp modelling for harmonic studies in distribution systems

    OpenAIRE

    Molina, Julio; Mesas García, Juan José; Mesbahi, Nadhir; Sainz Sapera, Luis

    2017-01-01

    Energy saving policies have boosted the use of light emitting diode (LED) lamps in distribution networks. These lamps are non-linear loads which inject harmonic currents into the distribution system, which has led to a decrease in the system power quality. Study of the modelling of these lamps would allow the prediction of harmonic emissions into distribution systems. This study presents a frequency-domain LED lamp model for harmonic emission calculation, together with a simple estimation pro...

  14. A current controller of grid-connected converter for harmonic damping in a distribution network

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Blaabjerg, Frede; Chen, Zhe

    2011-01-01

    Harmonic resonance caused by the increased use of shunt-connected capacitors in LCL-filters and power factor correction devices may become a serious power quality challenge in electric distribution systems. A voltage-detection method based on current control is developed to damp harmonic resonances....... However, it is susceptible to the mismatch between harmonic conductance and characteristic impedance of distribution feeder. This paper proposes a current controller which allows discrete adjustment of harmonic conductance for both the characteristic harmonic and the non-characteristic harmonic voltages...

  15. Ultrasonic colour Doppler imaging

    DEFF Research Database (Denmark)

    Evans, David H; Jensen, Jørgen Arendt; Nielsen, Michael Bachmann

    2011-01-01

    anatomy. The most common use of the technique is to image the movement of blood through the heart, arteries and veins, but it may also be used to image the motion of solid tissues such as the heart walls. Colour Doppler imaging is now provided on almost all commercial ultrasound machines, and has been...... vectors. This review briefly introduces the principles behind colour Doppler imaging and describes some clinical applications. It then describes the basic components of conventional colour Doppler systems and the methods used to derive velocity information from the ultrasound signal. Next, a number of new...... techniques that seek to overcome the vector problem mentioned above are described. Finally, some examples of vector velocity images are presented....

  16. Harmonic Interaction Analysis in Grid-connected Converter using Harmonic State Space (HSS) Modeling

    DEFF Research Database (Denmark)

    Kwon, Jun Bum; Wang, Xiongfei; Blaabjerg, Frede

    2017-01-01

    . Furthermore, a harmonic matrix of the grid-connected converter is developed to analyze the harmonic interaction at the steady-state behavior. Besides, the frequency-domain results are compared with time-domain simulation results by using HSS modeling to verify the theoretical analysis. Experimental results...... research about the harmonic interaction. However, it is found that the Linear Time Invariant (LTI) based model analysis makes it difficult to analyze these phenomena because of the time-varying properties of the power electronic based systems. This paper investigates grid-connected converter by using...

  17. Microwave harmonic generation and nonlinearity in microplasmas

    Science.gov (United States)

    Gregório, José; Parsons, Stephen; Hopwood, Jeffrey

    2016-06-01

    Nonlinearities in microplasmas excited by microwaves are described both experimentally and through a 2D fluid model. A split-ring resonator generates a microplasma in a 150 μm discharge gap at 1 GHz. Nonlinearity generates both radiated and conducted harmonics which are measured from 0.2-760 Torr (Ar) for power levels between 0.5 and 3 W. Asymmetric electrode configurations produce the highest 3rd harmonic power (>10 mW) at an optimal pressure of the order of 0.3 Torr. The microplasma is also demonstrated as a mixer. The experimental results are explained with the aid of a fluid model of the microplasma. The model shows that the smaller electrode in an asymmetric device is forced to attain a large microwave potential that strongly modulates the sheath thickness and the local electron energy. The voltage-dependent sheath width gives rises to a nonlinear sheath capacitance as well as short pulses of hot electron flux to the electrode. The modeled 3rd harmonic current is converted to an extractable harmonic power by a microwave circuit model. Using this technique the modeled and measured harmonic production of the microplasma are found to compare favorably.

  18. Penile Doppler ultrasonography revisited

    Directory of Open Access Journals (Sweden)

    Dae Chul Jung

    2018-01-01

    Full Text Available Penile Doppler ultrasonography is a high-performing, noninvasive or minimally-invasive imaging modality that allows the depiction of the normal anatomy and macroscopic pathologic changes in real time. Moreover, functional changes in penile blood flow, as seen in erectile dysfunction (ED, can be analyzed using color Doppler ultrasonography (CDUS. This review article describes the normal sonographic anatomy of the penis, the sonographic technique for evaluating ED, the normal phases of erection, and the various causes of ED. Additionally, we describe the interpretation of different parameters and findings on penile CDUS for the diagnosis and classification of ED, priapism, and Peyronie disease.

  19. Doppler radar physiological sensing

    CERN Document Server

    Lubecke, Victor M; Droitcour, Amy D; Park, Byung-Kwon; Singh, Aditya

    2016-01-01

    Presents a comprehensive description of the theory and practical implementation of Doppler radar-based physiological monitoring. This book includes an overview of current physiological monitoring techniques and explains the fundamental technology used in remote non-contact monitoring methods. Basic radio wave propagation and radar principles are introduced along with the fundamentals of physiological motion and measurement. Specific design and implementation considerations for physiological monitoring radar systems are then discussed in detail. The authors address current research and commercial development of Doppler radar based physiological monitoring for healthcare and other applications.

  20. Pulse Doppler radar

    CERN Document Server

    Alabaster, Clive

    2012-01-01

    This book is a practitioner's guide to all aspects of pulse Doppler radar. It concentrates on airborne military radar systems since they are the most used, most complex, and most interesting of the pulse Doppler radars; however, ground-based and non-military systems are also included. It covers the fundamental science, signal processing, hardware issues, systems design and case studies of typical systems. It will be a useful resource for engineers of all types (hardware, software and systems), academics, post-graduate students, scientists in radar and radar electronic warfare sectors and milit

  1. Harmonizing Tort Law

    NARCIS (Netherlands)

    W.H. van Boom (Willem)

    2009-01-01

    textabstractThis paper presents a review of the literature on comparative tort law and economics. It pays special attention to the economics arguments against and in favour of harmonization of tort law in Europe.

  2. Harmonic vibro-acoustography.

    Science.gov (United States)

    Chen, Shigao; Kinnick, Randall R; Greenleaf, James F; Fatemi, Mostafa

    2007-07-01

    Vibro-acoustography is an imaging method that uses the radiation force of two interfering ultrasound beams of slightly different frequency to probe an object. An image is made using the acoustic emission resulted from the object vibration at the difference frequency. In this paper, the feasibility of imaging objects at twice the difference frequency (harmonic acoustic emission) is studied. Several possible origins of harmonic acoustic emission are explored. As an example, it is shown that microbubbles close to resonance can produce significant harmonic acoustic emission due to its high nonlinearity. Experiments demonstrate that, compared to the fundamental acoustic emission, harmonic acoustic emission greatly improves the contrast between microbubbles and other objects in vibro-acoustography (an improvement of 17-23 dB in these experiments). Applications of this technique include imaging the nonlinearity of the object and selective detection of microbubbles for perfusion imaging. The impact of microbubble destruction during the imaging process also is discussed.

  3. Scanning laser Doppler vibrometry

    DEFF Research Database (Denmark)

    Brøns, Marie; Thomsen, Jon Juel

    With a Scanning Laser Doppler Vibrometer (SLDV) a vibrating surface is automatically scanned over predefined grid points, and data processed for displaying vibration properties like mode shapes, natural frequencies, damping ratios, and operational deflection shapes. Our SLDV – a PSV-500H from...

  4. Adaptive Spectral Doppler Estimation

    DEFF Research Database (Denmark)

    Gran, Fredrik; Jakobsson, Andreas; Jensen, Jørgen Arendt

    2009-01-01

    In this paper, 2 adaptive spectral estimation techniques are analyzed for spectral Doppler ultrasound. The purpose is to minimize the observation window needed to estimate the spectrogram to provide a better temporal resolution and gain more flexibility when designing the data acquisition sequence...

  5. The Doppler Pendulum Experiment

    Science.gov (United States)

    Lee, C. K.; Wong, H. K.

    2011-01-01

    An experiment to verify the Doppler effect of sound waves is described. An ultrasonic source is mounted at the end of a simple pendulum. As the pendulum swings, the rapid change of frequency can be recorded by a stationary receiver using a simple frequency-to-voltage converter. The experimental results are in close agreement with the Doppler…

  6. Deterministic and Stochastic Study of Wind Farm Harmonic Currents

    DEFF Research Database (Denmark)

    Sainz, Luis; Mesas, Juan Jose; Teodorescu, Remus

    2010-01-01

    Wind farm harmonic emissions are a well-known power quality problem, but little data based on actual wind farm measurements are available in literature. In this paper, harmonic emissions of an 18 MW wind farm are investigated using extensive measurements, and the deterministic and stochastic char...

  7. Determination of Total Harmonic Distortion (THD) on a 33kv ...

    African Journals Online (AJOL)

    This paper presents the estimation of Total Harmonic Distortion (THD) of the Distribution lines in the 33kV distribution network of Island Business District, Eko Electricity Distribution Plc, taken as a case study using a set of busbar voltage results, obtained from previous studies on power flow and harmonic analyses of each ...

  8. Harmonic Orientation of Pulse Width Modulation Technique in Multilevel Inverters

    OpenAIRE

    Urmila Bandaru; Subba D Rayudu

    2011-01-01

    The Multilevel Inverter topology gives the advantages of usage in high power and high voltage application with reduced harmonic distortion without a transformer. This paper presents a comparative study of orientation of higher ordered harmonics with increase in switching frequency around the frequency modulation index of nine level diode clamped inverter for different Switching frequency Multicarrier Pulse width Modulation.

  9. harmonics mitigation on industrial loads using series and parallel

    African Journals Online (AJOL)

    user

    system efficiency and provide great energy saving, their vulnerability to harmonics ... wave. Typical examples of harmonics sources include fluorescent lighting, computer switch mode power supplies, static var compensators, variable frequency motor drives, dc-dc converters, inverters, chillers etc. [13]. When considering ...

  10. Harmonic analysis of DC capacitor current in sinusoidal and space ...

    Indian Academy of Sciences (India)

    The voltage ripple and power loss in the DC-capacitor of a voltage source inverter depend on the harmonic currents flowing through the capacitor. This paper presents a double Fourier series based analysis of the harmonic contents of the DC capacitor current in a three-level neutral-point clamped (NPC) inverter, modulated ...

  11. Harmonic currents Compensator Grid-Connected Inverter at the Microgrid

    DEFF Research Database (Denmark)

    Asuhaimi Mohd Zin, A.; Naderipour, A.; Habibuddin, M.H.

    2016-01-01

    The main challenge associated with the grid-connected inverter in distributed generation (DG) systems is to maintain the harmonic contents in output current below the specified values and compensates for unbalanced loads even when the grid is subject to disturbances such as harmonic distortion...... loads are unbalanced and/or nonlinear and also compensate of the harmonic currents and control the active and reactive power. The main advantage and objective of this method is to effectively compensate for the harmonic currents content of the grid current and microgrid without using any compensation...

  12. Harmonic lasing in X-ray FELs

    Energy Technology Data Exchange (ETDEWEB)

    Schneidmiller, E.A.; Yurkov, M.V.

    2012-05-15

    Harmonic lasing in a free electron laser with a planar undulator (under the condition that the fundamental frequency is suppressed) might be a cheap and efficient way of extension of wavelength ranges of existing and planned X-ray FEL facilities. Contrary to nonlinear harmonic generation, harmonic lasing can provide much more intense, stable, and narrow-band FEL beam which is easier to handle due to the suppressed fundamental frequency. In this paper we perform a parametrization of the solution of the eigenvalue equation for lasing at odd harmonics, and present an explicit expression for FEL gain length, taking into account all essential effects. We propose and discuss methods for suppression of the fundamental harmonic. We also suggest a combined use of harmonic lasing and lasing at the retuned fundamental wavelength in order to reduce bandwidth and to increase brilliance of X-ray beam at saturation. Considering 3rd harmonic lasing as a practical example, we come to the conclusion that it is much more robust than usually thought, and can be widely used in the existing or planned X-ray FEL facilities. In particular, LCLS after a minor modification can lase to saturation at the 3rd harmonic up to the photon energy of 25-30 keV providing multi-gigawatt power level and narrow bandwidth. As for the European XFEL, harmonic lasing would allow to extend operating range (ultimately up to 100 keV), to reduce FEL bandwidth and to increase brilliance, to enable two-color operation for pump-probe experiments, and to provide more flexible operation at different electron energies. Similar improvements can be realized in other X-ray FEL facilities with gap-tunable undulators like FLASH II, SACLA, LCLS II, etc. Harmonic lasing can be an attractive option for compact X-ray FELs (driven by electron beams with a relatively low energy), allowing the use of the standard undulator technology instead of small-gap in-vacuum devices. Finally, in this paper we discover that in a part of the

  13. Harmonic analysis of Doubly Fed Induction Generators

    DEFF Research Database (Denmark)

    Lindholm, Morten; Rasmussen, Tonny Wederberg

    2003-01-01

    This paper gives an overview of the frequency spectrum of the stator and rotor currents in a doubly fed induction generator (DFIG) used in wind power applications. The paper also presents a method to eliminate higher harmonics and interharmonics in the DFIG stator current. The method is implemented...

  14. Assessment of the ovarian volume, number and volume of follicles and ovarian vascularity by three-dimensional ultrasonography and power Doppler angiography on the HCG day to predict the outcome in IVF/ICSI cycles.

    Science.gov (United States)

    Mercé, Luis T; Bau, Santiago; Barco, María J; Troyano, Juan; Gay, Rosina; Sotos, Florencia; Villa, Amelia

    2006-05-01

    The aim of this prospective study was to investigate whether ovarian blood flow is related to embryological parameters and whether it could be a predictor of outcomes of IVF/ICSI. Eighty infertile women underwent ovarian stimulation with gonadotrophins after a long protocol with GnRH agonists. The ovarian volume (OV), number of follicles (NF) and follicular volume (FV) of all follicles >10 mm and vascularization index (VI), flow index (FI) and vascularization-flow index (VFI) were obtained by three-dimensional (3D) ultrasonography and power Doppler angiography (PDA) on the day of HCG administration. These parameters were tested for their relation with IVF laboratory parameters. The OV, FV, VI, FI and VFI were significantly greater in the pregnant group. The NF and FV were the only independent predictors of the number of oocytes retrieved, mature and fertilized, and the number of embryos developed and their cumulative embryo score. Nevertheless, the number of grade 1 embryos depends on the NF and the VI. The ovarian FI and the number of transferred grade 1 embryos can predict gestation in 76% of IVF patients. A low FI and non-grade 1 embryo transferred are also associated with an increased pregnancy loss. 3D ultrasonography and PDA allow for an easier ovarian assessment in IVF cycles. The predictive value of IVF outcome suggests a high clinical usefulness of this new technique.

  15. Random Harmonic Detection and Compensation Based on Synchronous Reference Frame

    Directory of Open Access Journals (Sweden)

    Yanbo Che

    2017-01-01

    Full Text Available Algorithms for harmonic detection and compensation are important guarantees for an active power filter (APF to achieve the harmonic control function and directly determine the overall performance. Existing algorithms usually need a large amount of computation, and the compensation effect of specified order harmonic is also limited. DC side capacitor voltage at sudden change of load is affected by the algorithm as well. This paper proposes a new algorithm for harmonic detection and compensation based on synchronous reference frame (SRF, in which a band-pass filter with center frequency of 6kth harmonic is designed in fundamental frequency SRF to extract random harmonic current with two different frequencies of (6k±1th harmonic in stationary reference frame. This new algorithm can rapidly detect any specified harmonic, and it can adjust the power factor to compensate reactive power. Meanwhile, it has few impacts on DC side capacitor voltage under complicated operating conditions such as sudden change of load. The correctness and effectiveness of this new algorithm are verified by simulation and experiment.

  16. ADAPTIVE NOISE CANCELLATION OF DOPPLER SHIFTED SIGNALS: A LINEAR FRAMEWORK

    OpenAIRE

    Stewart, R. W.; Weiss, S.

    1996-01-01

    In this paper we investigate the performance of single channel adaptive noise cancellation techniques for situations where the noise signal received by the two microphones cannot be related by a fixed weight canceller's (linear) digital filter due to Doppler shift on the two signals. A mathematical signal model is produced, which shows that the adaptive filter is in fact required to identify a time-varying system which incorporates Doppler shift, and potential rapid variations in signal power...

  17. Frequency Adaptability of Harmonics Controllers for Grid-Interfaced Converters

    DEFF Research Database (Denmark)

    Yang, Yongheng; Zhou, Keliang; Blaabjerg, Frede

    2017-01-01

    A wider spread adoption of power electronic converters interfaced renewable energy systems has brought more attention to harmonic issues to the electrical grid, and means are taken to improve it in the control. More advanced closed-loop harmonic controllers are thus demanded to enhance...... sensitivity of the most popular harmonic controllers for grid-interfaced converters. The frequency adaptability of these harmonic controllers is evaluated in the presence of a variable grid frequency within a specified reasonable range, e.g., +-1% of the nominal grid frequency (50 Hz). Solutions...... the renewable energy integration in order to be grid-friendly. However, usually being treated as a constant factor in the design of harmonic controllers, the grid frequency varies with the generation-load imbalance, and thus may lead to deterioration of the power quality. This paper explores the frequency...

  18. Doppler ultrasound exam of an arm or leg

    Science.gov (United States)

    ... related deaths are caused by cardiovascular problems, not lung cancer. Alternative Names Peripheral vascular disease - Doppler; PVD - Doppler; PAD - Doppler; Blockage of leg arteries - Doppler; Intermittent claudication - Doppler; Arterial insufficiency of the legs - Doppler; Leg pain and cramping - ...

  19. Laser Doppler anemometry

    Science.gov (United States)

    Johnson, Dennis A.

    1988-01-01

    The material in this NASA TM is to appear as a chapter on Laser Doppler Anemometry (LDA) in the AGARDograph entitled, A Survey of Measurements and Measuring Techniques in Rapidly Distorted Compressible Turbulent Boundary Layers. The application of LDA (specifically, the dual-beam, burst-counter approach) to compressible flows is discussed. Subjects treated include signal processing, particle light scattering and tracking, data reduction and sampling bias, and three-dimensional measurements.

  20. Practical Solutions for Harmonics Problems Produced in the Distribution Networks

    Directory of Open Access Journals (Sweden)

    A. F. Zobaa

    2006-03-01

    Full Text Available Harmonic distortion on the power system is a modern concern due to the technological advances in silicon technology as it presents an increased non-linear loading of the power system. The effects of harmonics are well known: customers could experience major production losses due to the loss of supply as an example, on the other hand, harmonic load currents cause the utility to supply a higher real energy input then the actual real power needed to maintain a plant’s production at a certain level. The utility carries the extra transmission losses due to the harmonic currents. Different solutions will be reviewed as concepts for solving certain types of problems related to power quality. Both theoretical and a case study are presented.

  1. Doppler Optical Coherence Tomography

    Science.gov (United States)

    Leitgeb, Rainer A.; Werkmeister, René M.; Blatter, Cedric; Schmetterer, Leopold

    2014-01-01

    Optical Coherence Tomography (OCT) has revolutionized ophthalmology. Since its introduction in the early 1990s it has continuously improved in terms of speed, resolution and sensitivity. The technique has also seen a variety of extensions aiming to assess functional aspects of the tissue in addition to morphology. One of these approaches is Doppler OCT (DOCT), which aims to visualize and quantify blood flow. Such extensions were already implemented in time domain systems, but have gained importance with the introduction of Fourier domain OCT. Nowadays phase-sensitive detection techniques are most widely used to extract blood velocity and blood flow from tissues. A common problem with the technique is that the Doppler angle is not known and several approaches have been realized to obtain absolute velocity and flow data from the retina. Additional studies are required to elucidate which of these techniques is most promising. In the recent years, however, several groups have shown that data can be obtained with high validity and reproducibility. In addition, several groups have published values for total retinal blood flow. Another promising application relates to non-invasive angiography. As compared to standard techniques such as fluorescein and indocyanine-green angiography the technique offers two major advantages: no dye is required and depth resolution is required is provided. As such Doppler OCT has the potential to improve our abilities to diagnose and monitor ocular vascular diseases. PMID:24704352

  2. Fast Harmonic Chirp Summation

    DEFF Research Database (Denmark)

    Nielsen, Jesper Kjær; Jensen, Tobias Lindstrøm; Jensen, Jesper Rindom

    2017-01-01

    The harmonic chirp signal model has only very recently been in- troduced for modelling approximately periodic signals with a time- varying fundamental frequency. A number of estimators for the pa- rameters of this model have already been proposed, but they are ei- ther inaccurate, non-robust to n......The harmonic chirp signal model has only very recently been in- troduced for modelling approximately periodic signals with a time- varying fundamental frequency. A number of estimators for the pa- rameters of this model have already been proposed, but they are ei- ther inaccurate, non......-robust to noise, or very computationally inten- sive. In this paper, we propose a fast algorithm for the harmonic chirp summation method which has been demonstrated in the liter- ature to be accurate and robust to noise. The proposed algorithm is orders of magnitudes faster than previous algorithms which is also...

  3. Harmonic uniflow engine

    Science.gov (United States)

    Bennett, Charles L.

    2016-03-22

    A reciprocating-piston uniflow engine includes a harmonic oscillator inlet valve capable of oscillating at a resonant frequency for controlling the flow of working fluid into the engine. In particular, the inlet valve includes an inlet valve head and a spring arranged together as a harmonic oscillator so that the inlet valve head is moveable from an unbiased equilibrium position to a biased closed position occluding an inlet. When released, the inlet valve head undergoes a single oscillation past the equilibrium position to a maximum open position and returns to a biased return position close to the closed position to choke the flow and produce a pressure drop across the inlet valve causing the inlet valve to close. In other embodiments, the harmonic oscillator arrangement of the inlet valve enables the uniflow engine to be reversibly operated as a uniflow compressor.

  4. Second harmonic generation imaging

    CERN Document Server

    2013-01-01

    Second-harmonic generation (SHG) microscopy has shown great promise for imaging live cells and tissues, with applications in basic science, medical research, and tissue engineering. Second Harmonic Generation Imaging offers a complete guide to this optical modality, from basic principles, instrumentation, methods, and image analysis to biomedical applications. The book features contributions by experts in second-harmonic imaging, including many pioneering researchers in the field. Written for researchers at all levels, it takes an in-depth look at the current state of the art and possibilities of SHG microscopy. Organized into three sections, the book: Provides an introduction to the physics of the process, step-by-step instructions on how to build an SHG microscope, and comparisons with related imaging techniques Gives an overview of the capabilities of SHG microscopy for imaging tissues and cells—including cell membranes, muscle, collagen in tissues, and microtubules in live cells—by summarizing experi...

  5. The harmonic oscillator and nuclear physics

    Science.gov (United States)

    Rowe, D. J.

    1993-01-01

    The three-dimensional harmonic oscillator plays a central role in nuclear physics. It provides the underlying structure of the independent-particle shell model and gives rise to the dynamical group structures on which models of nuclear collective motion are based. It is shown that the three-dimensional harmonic oscillator features a rich variety of coherent states, including vibrations of the monopole, dipole, and quadrupole types, and rotations of the rigid flow, vortex flow, and irrotational flow types. Nuclear collective states exhibit all of these flows. It is also shown that the coherent state representations, which have their origins in applications to the dynamical groups of the simple harmonic oscillator, can be extended to vector coherent state representations with a much wider range of applicability. As a result, coherent state theory and vector coherent state theory become powerful tools in the application of algebraic methods in physics.

  6. General Criterion for Harmonicity

    Science.gov (United States)

    Proesmans, Karel; Vandebroek, Hans; Van den Broeck, Christian

    2017-10-01

    Inspired by Kubo-Anderson Markov processes, we introduce a new class of transfer matrices whose largest eigenvalue is determined by a simple explicit algebraic equation. Applications include the free energy calculation for various equilibrium systems and a general criterion for perfect harmonicity, i.e., a free energy that is exactly quadratic in the external field. As an illustration, we construct a "perfect spring," namely, a polymer with non-Gaussian, exponentially distributed subunits which, nevertheless, remains harmonic until it is fully stretched. This surprising discovery is confirmed by Monte Carlo and Langevin simulations.

  7. Harmonic arbitrary waveform generator

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Brock Franklin

    2017-11-28

    High frequency arbitrary waveforms have applications in radar, communications, medical imaging, therapy, electronic warfare, and charged particle acceleration and control. State of the art arbitrary waveform generators are limited in the frequency they can operate by the speed of the Digital to Analog converters that directly create their arbitrary waveforms. The architecture of the Harmonic Arbitrary Waveform Generator allows the phase and amplitude of the high frequency content of waveforms to be controlled without taxing the Digital to Analog converters that control them. The Harmonic Arbitrary Waveform Generator converts a high frequency input, into a precision, adjustable, high frequency arbitrary waveform.

  8. Quantum harmonically kicked environments

    Science.gov (United States)

    Custódio, M. S.; Strunz, W. T.; Beims, M. W.

    2017-11-01

    In this work we derive a generalized map which describes the time evolution of a quantum system coupled to a quantum environment composed by a finite number of free particles kicked harmonically at periodic times. Dissipation is introduced via the interaction between system and environment, which is switched on and off simultaneously at regular time intervals. The dynamics of the environmental particles occurs along rotated ellipsis in phase space and can be described by unrotated harmonic oscillators with a new frequency which depends on the kicking time. With the definition of a thermal bath we show that our quantum kicked environment induces an unusual fluctuation-dissipation relation.

  9. Booster Double Harmonic Setup Notes

    Energy Technology Data Exchange (ETDEWEB)

    Gardner, C. J. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.

    2015-02-17

    The motivation behind implementing a booster double harmonic include the reduced transverse space charge force from a reduced peak beam current and reduced momentum spread of the beam, both of which can be achieved from flattening the RF bucket. RF capture and acceleration of polarized protons (PP) is first set up in the single harmonic mode with RF harmonic h=1. Once capture and acceleration have been set up in the single harmonic mode, the second harmonic system is brought on and programmed to operate in concert with the single harmonic system.

  10. Harmonic Intravascular Ultrasound

    NARCIS (Netherlands)

    M.E. Frijlink (Martijn)

    2006-01-01

    textabstractMedical ultrasound is a popular imaging modality in cardiology. Harmonic Imaging is a technique that has been shown to increase the image quality of diagnostic ultrasound at frequencies below 10 MHz. However, Intravascular Ultrasound, which is a technique to acoustically investigate

  11. Young children's harmonic perception.

    Science.gov (United States)

    Costa-Giomi, Eugenia

    2003-11-01

    Harmony and tonality are two of the most difficult elements for young children to perceive and manipulate and are seldom taught in the schools until the end of early childhood. Children's gradual harmonic and tonal development has been attributed to their cumulative exposure to Western tonal music and their increasing experiential knowledge of its rules and principles. Two questions that are relevant to this problem are: (1) Can focused and systematic teaching accelerate the learning of the harmonic/tonal principles that seem to occur in an implicit way throughout childhood? (2) Are there cognitive constraints that make it difficult for young children to perceive and/or manipulate certain harmonic and tonal principles? A series of studies specifically addressed the first question and suggested some possible answers to the second one. Results showed that harmonic instruction has limited effects on children's perception of harmony and indicated that the drastic improvement in the perception of implied harmony noted approximately at age 9 is due to development rather than instruction. I propose that young children's difficulty in perceiving implied harmony stems from their attention behaviors. Older children have less memory constraints and more strategies to direct their attention to the relevant cues of the stimulus. Younger children focus their attention on the melody, if present in the stimulus, and specifically on its concrete elements such as rhythm, pitch, and contour rather than its abstract elements such as harmony and key. The inference of the abstract harmonic organization of a melody required in the perception of implied harmony is thus an elusive task for the young child.

  12. Harmonic Patterns in Forex Trading

    OpenAIRE

    Nemček, Sebastian

    2013-01-01

    This diploma thesis is committed to examination of validity of Harmonic Patterns in Forex trading. Scott Carney described existing and introduced new Harmonic Patterns in 1999 in his book Harmonic Trader. These patterns use the Fibonacci principle to analyze price action and to provide both bullish and bearish trading signals. The goal of this thesis is to find out whether harmonic trading strategy on selected pairs is profitable in FX market, which patterns are the most profitable and what i...

  13. Sideband-Harmonic Instability of Paralleled Inverters with Asynchronous Carriers

    DEFF Research Database (Denmark)

    Yang, Dongsheng; Wang, Xiongfei; Blaabjerg, Frede

    2017-01-01

    Paralleled inverters with asynchronous carriers are increasingly emerging into renewable power plants and other power-electronic-based power systems. The sideband harmonics resulting from the pulse width modulation tend to be different from one inverter to another, which may trigger sideband-harmonic...... resonances among the paralleled inverters. To address the sideband-harmonic instability, the nonlinearity of the digital pulse width modulator is analyzed first in this paper based on the harmonic balance principle. It is revealed that the dynamic sideband components corresponding to a given small......-signal perturbation can be far below the Nyquist frequency, and they may not be effectively attenuated by anti-aliasing filters. A multi-frequency impedance model is then developed for the inverter, which characterizes the dynamic coupling between the perturbed frequency component and the sideband frequency component...

  14. Harmonic Analysis and Mitigation of Low-Frequency Switching Voltage Source Inverter with Series LC Filtered VSI

    DEFF Research Database (Denmark)

    Bai, Haofeng; Wang, Xiongfei; Loh, Poh Chiang

    2017-01-01

    The output currents of high power Voltage Source Inverters (VSIs) are distorted by the switching harmonics and the backgroud harmonics in the grid voltage. In this paper, a hybrid power conversion system composed of a high power VSI with low switching frequency and an auxiliary series LC filtered...... VSI is proposed. The auxiliary VSI compensates both the switching harmonics of the high power VSI and the low order harmonics. The output current of the system remains sinusoidal when grid voltage is distorted. Impedance models of the system are built in different frequency ranges and harmonic...

  15. Neonatal pig brain: lack of heating during Doppler US.

    Science.gov (United States)

    Taylor, G A; Barnewolt, C E; Dunning, P S

    1998-05-01

    To evaluate potential local brain-heating effects of Doppler ultrasound (US) at high power output settings. After craniotomy, a temperature probe was inserted into deep white matter or basal ganglia in 12 anesthetized newborn piglets. The range gate and focal zone were placed directly over the temperature sensor. Brain and core (rectal) temperatures were measured before and during 5 minutes of continuous transdural duplex or color Doppler US, with transmitter power output settings of less than 500 mW in situ spatial peak temporal average or less than 800 mW in situ spatial peak temporal average. Temperature also was measured during administration of a US contrast agent with duplex US at less than 500 mW in situ spatial peak temporal average and after death at the same output setting. Maximal differences between the baseline and the post-US temperatures were, on average, less than 0.3 degree C (P > .5) and were highly correlated with changes in core temperature (r = .9, P heating during pulsed Doppler US (P > .6). There was no association between an increase in estimated power output and brain temperature change (P = .9). In addition, brain ischemia (postmortem exposure) was not associated with focal brain heating during pulsed Doppler US. Transfontanellar Doppler US alone or with administration of a contrast agent does not produce statistically significant focal brain heating at high transmitter power levels.

  16. Recursive Harmonic Numbers and Binomial Coefficients

    OpenAIRE

    Maw, Aung Phone; Kyaw, Aung

    2017-01-01

    We define recursive harmonic numbers as a generalization of harmonic numbers. The table of recursive harmonic numbers, which is like Pascal's triangle, is constructed. A formula for recursive harmonic numbers containing binomial coefficients is also presented.

  17. Asymmetric micro-Doppler frequency comb generation via magnetoelectric coupling

    Science.gov (United States)

    Filonov, Dmitry; Steinberg, Ben Z.; Ginzburg, Pavel

    2017-06-01

    Electromagnetic scattering from moving bodies, being an inherently time-dependent phenomenon, gives rise to a generation of new frequencies, which can be used to characterize the motion. Whereas an ordinary motion along a linear path produces a constant Doppler shift, an accelerated scatterer can generate a micro-Doppler frequency comb. The spectra produced by rotating objects were studied and observed in a bistatic lock-in detection scheme. The internal geometry of a scatterer was shown to determine the spectrum, and the degree of structural asymmetry was suggested to be identified via signatures in the micro-Doppler comb. In particular, hybrid magnetoelectric particles, showing an ultimate degree of asymmetry in forward and backward scattering directions, were investigated. It was shown that the comb in the backward direction has signatures at the fundamental rotation frequency and its odd harmonics, whereas the comb of the forward scattered field has a prevailing peak at the doubled frequency and its multiples. Additional features of the comb were shown to be affected by the dimensions of the particle and by the strength of the magnetoelectric coupling. Experimental verification was performed with a printed circuit board antenna based on a wire and a split ring, while the structure was illuminated at a 2 GHz carrier frequency. Detailed analysis of micro-Doppler combs enables remote detection of asymmetric features of distant objects and could find use in a span of applications, including stellar radiometry and radio identification.

  18. Principles of harmonic analysis

    CERN Document Server

    Deitmar, Anton

    2014-01-01

    This book offers a complete and streamlined treatment of the central principles of abelian harmonic analysis: Pontryagin duality, the Plancherel theorem and the Poisson summation formula, as well as their respective generalizations to non-abelian groups, including the Selberg trace formula. The principles are then applied to spectral analysis of Heisenberg manifolds and Riemann surfaces. This new edition contains a new chapter on p-adic and adelic groups, as well as a complementary section on direct and projective limits. Many of the supporting proofs have been revised and refined. The book is an excellent resource for graduate students who wish to learn and understand harmonic analysis and for researchers seeking to apply it.

  19. Simulation of the Doppler effect in a waveguide

    Science.gov (United States)

    Kolomoitsev, V. F.; Kravchenko, A. V.; Krys', V. Ia.; Privalov, V. N.; Sokolovskii, I. I.

    1988-03-01

    Experimental results are presented on a 3-cm-band Doppler simulator based on a modified double T-bridge and a single varactor diode. Experimental tests have demonstrated the high efficiency of the simulator. At a frequency of 9.5 GHz, a frequency shift of 5-70 kHz was achieved with the following characteristics: (1) a conversion loss of less than 5 dB, (2) a carrier suppression of greater than 50 dB, and (3) a harmonic suppression of not less than 15 dB.

  20. Laser Doppler Imaging of Microflow

    CERN Document Server

    Gross, Michel; Leng, Jacques

    2013-01-01

    We report a pilot study with a wide-field laser Doppler detection scheme used to perform laser Doppler anemometry and imaging of particle seeded microflow. The optical field carrying the local scatterers (particles) dynamic state, as a consequence of momentum transfer at each scattering event, is analyzed in the temporal frequencies domain. The setup is based on heterodyne digital holography, which is used to map the scattered field in the object plane at a tunable frequency with a multipixel detector. We show that wide-field heterodyne laser Doppler imaging can be used for quantitative microflow diagnosis; in the presented study, maps of the first-order moment of the Doppler frequency shift are used as a quantitative and directional estimator of the Doppler signature of particles velocity.

  1. Harmonic and geometric analysis

    CERN Document Server

    Citti, Giovanna; Pérez, Carlos; Sarti, Alessandro; Zhong, Xiao

    2015-01-01

    This book presents an expanded version of four series of lectures delivered by the authors at the CRM. Harmonic analysis, understood in a broad sense, has a very wide interplay with partial differential equations and in particular with the theory of quasiconformal mappings and its applications. Some areas in which real analysis has been extremely influential are PDE's and geometric analysis. Their foundations and subsequent developments made extensive use of the Calderón–Zygmund theory, especially the Lp inequalities for Calderón–Zygmund operators (Beurling transform and Riesz transform, among others) and the theory of Muckenhoupt weights.  The first chapter is an application of harmonic analysis and the Heisenberg group to understanding human vision, while the second and third chapters cover some of the main topics on linear and multilinear harmonic analysis. The last serves as a comprehensive introduction to a deep result from De Giorgi, Moser and Nash on the regularity of elliptic partial differen...

  2. An improved current control scheme for grid-connected DG unit based distribution system harmonic compensation

    DEFF Research Database (Denmark)

    He, Jinwei; Wei Li, Yun; Wang, Xiongfei

    2013-01-01

    In order to utilize DG unit interfacing converters to actively compensate distribution system harmonics, this paper proposes an enhanced current control approach. It seamlessly integrates system harmonic mitigation capabilities with the primary DG power generation function. As the proposed current...... controller has two well decoupled control branches to independently control fundamental and harmonic DG currents, phase-locked loops (PLL) and system harmonic component extractions can be avoided during system harmonic compensation. Moreover, a closed-loop power control scheme is also employed to derive...... the fundamental current reference. The proposed power control scheme effectively eliminates the impacts of steady-state fundamental current tracking errors in the DG units. Thus, an accurate power control is realized even when the harmonic compensation functions are activated. Experimental results from a single...

  3. System-on-chip based Doppler radar occupancy sensor.

    Science.gov (United States)

    Yavari, Ehsan; Song, Chenyan; Lubecke, Victor; Boric-Lubecke, Olga

    2011-01-01

    System-on-Chip (SoC) based Doppler radar occupancy sensor is developed through non contact detection of respiratory signals. The radio was developed using off the shelf low power RF CC2530 SoC chip by Texas Instruments. In order to save power, the transmitter sends signal intermittently at 2.405 GHz. Reflected pulses are demodulated, and the baseband signals are processed to recover periodic motion. The system was tested both with mechanical target and a human subject. In both cases Doppler radar detected periodic motion closely matched the actual motion, and it has been shown that an SoC based system can be used for subject detection.

  4. Three-dimensional simulations of harmonic radiation and harmonic lasing

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, M.J.; McVey, B.D.

    1990-01-01

    Characteristics of the harmonic emission from free-electron lasers (FELs) are examined in the spontaneous, coherent-spontaneous and stimulated emission regimes. The radiation at both odd and even harmonic frequencies is treated for electron beams with finite emittance and energy spread. In the spontaneous emission regime, the transverse radiation patterns including the transverse frequency dependences, are given. How this expression is modified to include energy spread and emittance is described. In the coherent-spontaneous emission and stimulated emission regimes, the interaction of the radiation fields with the electrons must be treated self-consistently. Here, a single-frequency distributed transverse source function for each electron is used in the harmonic version of the 3-D code FELEX to model the harmonic radiation. The code has recently been modified to simultaneously model the fundamental and harmonic interactions for multiple-pass oscillator simulations. These modifications facilitate the examination of FELs under various operating conditions. When the FEL is lasing at the fundamental, the evolution of the harmonic fields can be examined. This evolution is unique in the sense that the electron beam radiates at the harmonic frequencies in the presence of the harmonic radiation circulating in the cavity. As a result, enhancements of the harmonic emission can be observed. Finally, harmonic lasing can occur in cases where there is sufficient gain to overcome cavity losses and lasing at the fundamental can be suppressed. The characteristics and efficiency of these interactions are explored. 11 refs., 9 figs.

  5. First harmonic injection locking of 24-GHz-oscillators

    Directory of Open Access Journals (Sweden)

    M. R. Kühn

    2003-01-01

    Full Text Available An increasing number of applications is proposed for the 24 GHz ISM-band, like automotive radar systems and short-range communication links. These applications demand for oscillators providing moderate output power of a few mW and moderate frequency stability of about 0.5%. The maximum oscillation frequency of low-cost off-theshelf transistors is too low for stable operation of a fundamental 24GHz oscillator. Thus, we designed a 24 GHz first harmonic oscillator, where the power generated at the fundamental frequency (12 GHz is reflected resulting in effective generation of output power at the first harmonic. We measured a radiated power from an integrated planar antenna of more than 1mW. Though this oscillator provides superior frequency stability compared to fundamental oscillators, for some applications additional stabilization is required. As a low-cost measure, injection locking can be used to phase lock oscillators that provide sufficient stability in free running mode. Due to our harmonic oscillator concept injection locking has to be achieved at the first harmonic, since only the antenna is accessible for signal injection. We designed, fabricated and characterized a harmonic oscillator using the antenna as a port for injection locking. The locking range was measured versus various parameters. In addition, phase-noise improvement was investigated. A theoretical approach for the mechanism of first harmonic injection locking is presented.

  6. A Passive Harmonic Tag for Humidity Sensing

    OpenAIRE

    Antonio Lazaro; Ramon Villarino; David Girbau

    2014-01-01

    This paper describes a passive harmonic tag for radio frequency identification (RFID) and wireless sensor applications. The tag uses a dual polarized UHF patch antenna as an input antenna. One of the outputs is connected to a frequency doubler, which consists of a Schottky diode with its output connected to a patch tuned at twice the input frequency. The other output of the input antenna feeds a DC power harvested converter that drives an oscillator which modulates its output signal by contro...

  7. Adaptive Harmonic Compensation in Residential Distribution Grid by Roof-Top PV Systems

    DEFF Research Database (Denmark)

    Zangeneh Bighash, Esmaeil; Sadeghzadeh, Seyed Mohammad; Ebrahimzadeh, Esmaeil

    2018-01-01

    Fourier Transform (SDFT) algorithm and then individually compensate the measured harmonics by the proposed adaptive harmonic compensator. In the proposed approach, a current reference is separately determined for compensating each harmonic component. Then, a specific amount of additional current capacity...... grid- connected roof-top PV inverters in residential distribution grid can be an opportunity to engage these systems in the power quality issues as custom power devices. By implementing a proper control for roof-top PV inverters, these systems may in addition to inject the fundamental current......, additionally act like a virtual harmonic resistance and dedicate their additional current capacity to compensate the harmonics of residential distribution grid. In this paper, each roof-top PV system is a grid harmonic supervisor, where it continually measures the PCC voltage harmonics by Sliding Discrete...

  8. Harmonic current prediction by impedance modeling of grid-tied inverters

    DEFF Research Database (Denmark)

    Pereira, Heverton A.; Freijedo, Francisco D.; Silva, M. M.

    2017-01-01

    and harmonic voltage profiles. Results reinforce that impedance models can represent with relatively accuracy the harmonic current emitted by the PV plants at the point of common coupling (PCC). Lastly, a stress test is performed to show how a variation in the harmonic voltage phase angle impacts the PV plant...... impedance models when used in harmonic integration studies. It is aimed to estimate the harmonic current contribution as a function of the background harmonic voltages components. Time domain simulations based on detailed and average models are compared with the impedance model developed in frequency domain....... In grids with harmonic voltages, impedance models can predict the current distortion for all active power injection scenarios. Furthermore, measurements in a 1.4 MW PV plant connected in a distributed grid are used to validate the simulation based on impedance models during different power injections...

  9. Dynamic color Doppler sonography in the assessment of erectile dysfunctions; Utilizzazione dell'eco color Doppler dinamico del pene nello studio delle disfunzioni erettili

    Energy Technology Data Exchange (ETDEWEB)

    Aversa, A.; Bonifacio, V.; Isidori, A.; Fabbri, A. [Rome Univ. (Italy). Cattedra di Andrologia. Dipt. di Fisiopatologia Medica; Bertucci, B. [Azienda Ospedaliera Pugliese Ciaccio, Catanzaro (Italy). Servizio di Radiologia

    1999-06-01

    The authors investigated the diagnostic accuracy of dynamic color Doppler sonography (D-CDS) in men with erectile dysfunctions (ED). Terminal microcirculation alterations and their correlation with erectile response after drug testing were investigated with power Doppler energy. Penile sonography in the flaccid state can show calcificic plaques and/or fibrosis of the corpora. Redosing of PGE{sub 1} plus phentolamine during D-CDS is a safe procedure and improves diagnostic accuracy in erectile dysfunctions, with significantly fewer non-responders than redosing of PGE{sub 1} alone. Power Doppler energy shows altered morphology of helicine arterioles otherwise missed at color Doppler and is thus recommended to make an accurate diagnosis in some men with erectile dysfunctions. [Italian] Scopo dello studio e' quello di valutare l'accuratezza diagnostica dell'eco color Doppler dinamico del pene nei soggetti affetti da disfunzione erettile. Inoltre si e' voluto verificale la presenza di alterazioni della vascolarizzazione arteriosa terminale con modulo power Doppler e come la presenza di queste alterazioni del microcircolo si correlino con la risposta erettiva della farmacoinfusione intracavernosa. Con l'eco color Doppler penieno basale e' possibile identificare placche calcifiche e/o fibrosi nei corpi cavernosi. Durante la fase dinamica con color Doppler , la re-iniezione con PGE{sub 1} e fentolamina si e' dimostrata sicura e ha migliorato l'accuratezza diagnostica riducendo il numero di soggetti con mancata risposta erettiva rispetto alla sola PGE{sub 1}. Con power Doppler sono state identificate alterazioni morfologiche delle arterioleelicine non visibili con il color Doppler consentendo la diagnosi piu' precisain alcuni casi di disfunzione erettile.

  10. Power

    OpenAIRE

    Bowles, Samuel; Gintis, Herbert

    2007-01-01

    We consider the exercise of power in competitive markets for goods, labour and credit. We offer a definition of power and show that if contracts are incomplete it may be exercised either in Pareto-improving ways or to the disadvantage of those without power. Contrasting conceptions of power including bargaining power, market power, and consumer sovereignty are considered. Because the exercise of power may alter prices and other aspects of exchanges, abstracting from power may miss essential a...

  11. Nonlinear Diffuse fs-Pulse Reflectometry of Harmonic Upconversion Nanoparticles

    Directory of Open Access Journals (Sweden)

    Christian Kijatkin

    2017-02-01

    Full Text Available Nonlinear diffuse femtosecond-pulse reflectometry is introduced as a powerful experimental tool for the unambiguous characterization of polar and non-polar point symmetry groups of harmonic upconversion nanoparticles. Using intense ultrashort 40 femtosecond laser pulses and an appropriate figure of merit (FOM, second and third harmonic emission serve for the structural characterization of polar Yb-doped lithium niobate and non-polar titanium dioxide nanoparticles. The tool is capable of differentiating these two samples by FOM values that differ by up to 13 orders of magnitude. The general applicability to harmonic upconversion nanoparticles over a broad range of intensities and wavelength spectrum, is discussed.

  12. Sound power spectrum and wave drag of a propeller in flight

    Science.gov (United States)

    Hanson, D. B.

    1989-01-01

    Theory is presented for the sound power and sound power spectrum of a single rotation propeller in forward flight. Calculations are based on the linear wave equation with sources distributed over helicoidal surfaces to represent effects of blade thickness and steady loading. Sound power is distributed continuously over frequecy, as would be expected from Doppler effects, rather than in discrete harmonics. The theory is applied to study effects of sweep and Mach number in propfans. An acoustic efficiency is defined as the ratio of radiated sound power to shaft input power. This value is the linear estimate of the effect of wave drag due to the supersonic blade section speeds. It is shown that the acoustic efficiency is somewhat less than 1 percent for a well designed propfan.

  13. The Modeling and Harmonic Coupling Analysis of Multiple-Parallel Connected Inverter Using Harmonic State Space (HSS)

    DEFF Research Database (Denmark)

    Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth

    2015-01-01

    As the number of power electronics based systems are increasing, studies about overall stability and harmonic problems are rising. In order to analyze harmonics and stability, most research is using an analysis method, which is based on the Linear Time Invariant (LTI) approach. However, this can...... change compared to the conventional operation. In this paper, a Harmonic State Space modeling method, which is based on the Linear Time varying theory, is used to analyze different operating points of the parallel connected converters. The analyzed results show that the HSS modeling approach explicitly...

  14. Software Defined Doppler Radar as a Contactless Multipurpose Microwave Sensor for Vibrations Monitoring

    Directory of Open Access Journals (Sweden)

    Antonio Raffo

    2017-01-01

    Full Text Available A vibration sensor based on the use of a Software-Defined Radio (SDR platform is adopted in this work to provide a contactless and multipurpose solution for low-cost real-time vibrations monitoring. In order to test the vibration detection ability of the proposed non-contact method, a 1 GHz Doppler radar sensor is simulated and successfully assessed on targets at various distances, with various oscillation frequencies and amplitudes. Furthermore, an SDR Doppler platform is practically realized, and preliminary experimental validations on a device able to produce a harmonic motion are illustrated to prove the effectiveness of the proposed approach.

  15. Software Defined Doppler Radar as a Contactless Multipurpose Microwave Sensor for Vibrations Monitoring.

    Science.gov (United States)

    Raffo, Antonio; Costanzo, Sandra; Di Massa, Giuseppe

    2017-01-08

    A vibration sensor based on the use of a Software-Defined Radio (SDR) platform is adopted in this work to provide a contactless and multipurpose solution for low-cost real-time vibrations monitoring. In order to test the vibration detection ability of the proposed non-contact method, a 1 GHz Doppler radar sensor is simulated and successfully assessed on targets at various distances, with various oscillation frequencies and amplitudes. Furthermore, an SDR Doppler platform is practically realized, and preliminary experimental validations on a device able to produce a harmonic motion are illustrated to prove the effectiveness of the proposed approach.

  16. Why plasma harmonics?

    Energy Technology Data Exchange (ETDEWEB)

    Ganeev, R A [Ophthalmology and Advanced Laser Medical Center, Saitama Medical University, Saitama 350-0495 (Japan)

    2015-09-30

    We discuss the emergence of interest in the high-order harmonic generation (HHG) of ultrashort pulses propagated through laser-produced plasmas. It is shown that, during the last few years, substantial amendments of plasma HHG allowed in some cases the characteristics of gas HHG to be surpassed. The attractiveness of a new approach in coherent extreme ultraviolet radiation generation is demonstrated, which can also be used as a tool for laser-ablation-induced HHG spectroscopy of a giant class of solids. We present general ideas and prospects for this relatively new field of nonlinear optics. (review)

  17. Harmonic analysis and applications

    CERN Document Server

    Heil, Christopher

    2007-01-01

    This self-contained volume in honor of John J. Benedetto covers a wide range of topics in harmonic analysis and related areas. These include weighted-norm inequalities, frame theory, wavelet theory, time-frequency analysis, and sampling theory. The chapters are clustered by topic to provide authoritative expositions that will be of lasting interest. The original papers collected are written by prominent researchers and professionals in the field. The book pays tribute to John J. Benedetto's achievements and expresses an appreciation for the mathematical and personal inspiration he has given to

  18. Harmonic Adaptability Remote Testing Method for Offshore Wind Turbines

    Directory of Open Access Journals (Sweden)

    Zimin Jiang

    2017-11-01

    Full Text Available Harmonic adaptability (HA capability is required for large-scale onshore and offshore wind turbines (WTs connected to the grid. To ensure that the distortion of the harmonic voltage at the grid access point generated by grid simulator is in accordance with the required value, this paper proposes an on-site HA remote testing method for offshore WTs to eliminate submarine cable effects. The deviation compensation method detects the integer harmonic voltage distortion based on instantaneous reactive power theory, and the deviation from the required value is compensated by series active power filter. In order to further reduce the capacity of the designed device, integer harmonics close to the resonant frequency are suppressed by the selective harmonic damping (SHD method initially. Owing to the attenuation of extreme amplification, the deviation determining the equipment capacity is decreased correspondingly. As a small synthesized impedance working for the selected frequency can suppress the amplification significantly, a low power ratings design for the SHD method can be achieved, and undesired resonance can be avoided. Simulation results indicate that the proposed method can make the harmonic distortion within the error tolerance.

  19. Transmission media effects on precise Doppler tracking

    Science.gov (United States)

    Callahan, P. S.

    1978-01-01

    The effects of the transmission media - the earth's troposphere and ionosphere, and the solar wind - on precise Doppler tracking are discussed. The charged particle effects can be largely removed by dual frequency observations; however there are limitations to these corrections (besides system noise and/or finite integration times) including the effects of magnetic fields, diffraction, and differential refraction, all of which must be carefully evaluated. The earth's troposphere can contribute an error of delta f/f approximately 10 to the minus 14th power.

  20. Harmonic generation at high peak power

    Energy Technology Data Exchange (ETDEWEB)

    Summers, M.A.; Williams, J.D.; Johnson, B.C.; Eimerl, D.

    1985-12-13

    This report reviews progress made in recent years in frequency conversion of laser radiation. By using a material such as potassium dihydrogen phosphate (KDP), intense, coherent light is made available at wavelengths unavailable from the source laser medium. Tests were performed on an array of KDP crystals at the Nova Facility. The tests revealed unexpected losses due to various non-linear effects. (JDH)

  1. Experimental observation of a theoretically predicted nonlinear sleep spindle harmonic in human EEG.

    Science.gov (United States)

    Abeysuriya, R G; Rennie, C J; Robinson, P A; Kim, J W

    2014-10-01

    To investigate the properties of a sleep spindle harmonic oscillation previously predicted by a theoretical neural field model of the brain. Spindle oscillations were extracted from EEG data from nine subjects using an automated algorithm. The power and frequency of the spindle oscillation and the harmonic oscillation were compared across subjects. The bicoherence of the EEG was calculated to identify nonlinear coupling. All subjects displayed a spindle harmonic at almost exactly twice the frequency of the spindle. The power of the harmonic scaled nonlinearly with that of the spindle peak, consistent with model predictions. Bicoherence was observed at the spindle frequency, confirming the nonlinear origin of the harmonic oscillation. The properties of the sleep spindle harmonic were consistent with the theoretical modeling of the sleep spindle harmonic as a nonlinear phenomenon. Most models of sleep spindle generation are unable to produce a spindle harmonic oscillation, so the observation and theoretical explanation of the harmonic is a significant step in understanding the mechanisms of sleep spindle generation. Unlike seizures, sleep spindles produce nonlinear effects that can be observed in healthy controls, and unlike the alpha oscillation, there is no linearly generated harmonic that can obscure nonlinear effects. This makes the spindle harmonic a good candidate for future investigation of nonlinearity in the brain. Copyright © 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  2. Dual-Doppler Feasibility Study

    Science.gov (United States)

    Huddleston, Lisa L.

    2012-01-01

    When two or more Doppler weather radar systems are monitoring the same region, the Doppler velocities can be combined to form a three-dimensional (3-D) wind vector field thus providing for a more intuitive analysis of the wind field. A real-time display of the 3-D winds can assist forecasters in predicting the onset of convection and severe weather. The data can also be used to initialize local numerical weather prediction models. Two operational Doppler Radar systems are in the vicinity of Kennedy Space Center (KSC) and Cape Canaveral Air Force Station (CCAFS); these systems are operated by the 45th Space Wing (45 SW) and the National Weather Service Melbourne, Fla. (NWS MLB). Dual-Doppler applications were considered by the 45 SW in choosing the site for the new radar. Accordingly, the 45th Weather Squadron (45 WS), NWS MLB and the National Aeronautics and Space Administration tasked the Applied Meteorology Unit (AMU) to investigate the feasibility of establishing dual-Doppler capability using the two existing systems. This study investigated technical, hardware, and software requirements necessary to enable the establishment of a dual-Doppler capability. Review of the available literature pertaining to the dual-Doppler technique and consultation with experts revealed that the physical locations and resulting beam crossing angles of the 45 SW and NWS MLB radars make them ideally suited for a dual-Doppler capability. The dual-Doppler equations were derived to facilitate complete understanding of dual-Doppler synthesis; to determine the technical information requirements; and to determine the components of wind velocity from the equation of continuity and radial velocity data collected by the two Doppler radars. Analysis confirmed the suitability of the existing systems to provide the desired capability. In addition, it is possible that both 45 SW radar data and Terminal Doppler Weather Radar data from Orlando International Airport could be used to alleviate any

  3. Doppler characteristics of sea clutter.

    Energy Technology Data Exchange (ETDEWEB)

    Raynal, Ann Marie; Doerry, Armin Walter

    2010-06-01

    Doppler radars can distinguish targets from clutter if the target's velocity along the radar line of sight is beyond that of the clutter. Some targets of interest may have a Doppler shift similar to that of clutter. The nature of sea clutter is different in the clutter and exo-clutter regions. This behavior requires special consideration regarding where a radar can expect to find sea-clutter returns in Doppler space and what detection algorithms are most appropriate to help mitigate false alarms and increase probability of detection of a target. This paper studies the existing state-of-the-art in the understanding of Doppler characteristics of sea clutter and scattering from the ocean to better understand the design and performance choices of a radar in differentiating targets from clutter under prevailing sea conditions.

  4. Equatorial oscillations maintained by gravity waves as described with the Doppler Spread Parameterization: II. Heuristic analysis

    Science.gov (United States)

    Mayr, H. G.; Hartle, R. E.; Chan, K. L.

    1998-01-01

    The Doppler Spread Parameterization (DSP) for gravity waves (GW) developed by Hines is applied to the zonal momentum budget at the equator. For sufficiently large oscillation amplitudes in the background zonal winds, comparable to the GW induced wind variability, the momentum source is intermittent and as such it represents a nonlinearity of third or generally odd order. This kind of nonlinearity generates, besides higher harmonics, the fundamental harmonic itself which is retained in a simplified analytical solution that can describe self-sustained oscillations without invoking external, time dependent forcing. The formulation is discussed to provide some understanding of the numerical results presented in the companion paper.

  5. A Passive Harmonic Tag for Humidity Sensing

    Directory of Open Access Journals (Sweden)

    Antonio Lazaro

    2014-01-01

    Full Text Available This paper describes a passive harmonic tag for radio frequency identification (RFID and wireless sensor applications. The tag uses a dual polarized UHF patch antenna as an input antenna. One of the outputs is connected to a frequency doubler, which consists of a Schottky diode with its output connected to a patch tuned at twice the input frequency. The other output of the input antenna feeds a DC power harvested converter that drives an oscillator which modulates its output signal by controlling the bias point of the Schottky diode. The antenna’s output is also used as a humidity sensor. To achieve this, the antenna is loaded with an interdigital capacitor with humidity-dependent capacitance. The antenna is consequently detuned when humidity varies, and therefore the second harmonic power is received. The tag is manufactured using standard fiberglass substrate. The basic theory of harmonic tag operation is described and compared with the standard backscattering approach. Experimental results with a proof of concept using commercial components are presented.

  6. Statement for Doppler waveforms analysis.

    Science.gov (United States)

    Mahé, Guillaume; Boulon, Carine; Desormais, Ileana; Lacroix, Philippe; Bressollette, Luc; Guilmot, Jean-Louis; Le Hello, Claire; Sevestre, Marie-Antoinette; Pernod, Gilles; Constans, Joel; Boissier, Christian; Bura-Rivière, Alessandra

    2017-08-01

    Peripheral artery disease of the lower limbs (PAD) is a common disease. Evaluation of PAD is primarily based on non-invasive examinations with analysis of the arterial Doppler signal being a key element. However, the description of arterial Doppler waveforms morphologies varies considerably across medical schools and from country to country. In order to overcome this issue, the French College of Teachers for Vascular Medicine (Collège des Enseignants de Médecine Vasculaire; CEMV) has summarised the published data on Doppler waveforms analysis and proposes a new "Saint-Bonnet" classification system to describe Doppler waveforms morphologies. The simplified Saint-Bonnet classification comprises eight types and allows taking into account if the Doppler signal does not revert to baseline. This classification, which is based on previous classifications, could improve the descriptions of both physiological and pathological waveforms, recorded in lower limb arteries. According to the reviewed literature, recommendations about the use of Doppler waveforms are proposed. This statement is a preamble to reach an international consensus on the subject, which would standardize the description of arterial waveforms and improve the management of PAD patients.

  7. Generation of higher harmonic internal waves by oscillating spheroids

    Science.gov (United States)

    Shmakova, Natalia; Ermanyuk, Evgeny; Flór, Jan-Bert

    2017-11-01

    Oscillating bodies in stratified fluids may emit higher harmonics in addition to fundamental waves. In the present experimental study, we consider higher harmonics of an internal wave field generated by a horizontally oscillating spheroid in a linearly stratified fluid for moderate to high oscillation amplitudes, i.e., scaled oscillation amplitude A /a ≥0.5 , with a the minor radius of the spheroid. Three different spheroid shapes are tested. The results are discussed in the context of the different theories on the generation of higher harmonics. Higher harmonics are observed at the intersections of fundamental wave beams, and at the critical points of the topography where the topographic slope equals the wave slope. The velocity amplitudes of the fundamental, second, and third harmonic waves grow respectively linearly, quadratically, and with the third power of the scaled oscillation amplitude A /a . Though these amplitudes are generally higher when the object's slope is larger, the increase in amplitude above and below the axisymmetric oscillating objects is found to be due to the effect of focusing. In order to discern the relative importance of the harmonics to the fundamental wave, the horizontal structure of the wave amplitude is measured. The results suggest that the n th harmonic of the internal wave field is associated with a radiation diagram corresponding to a multipole of order 2n, with 2 n directions of propagation.

  8. Second and third harmonic measurements at the linac coherent light source

    Directory of Open Access Journals (Sweden)

    D. Ratner

    2011-06-01

    Full Text Available The linac coherent light source (LCLS is a self-amplified spontaneous emission (SASE free-electron laser (FEL operating at fundamental photon energies from 0.5 to 10 keV. Characterization of the higher harmonics present in the FEL beam is important to users, for whom harder x rays can either extend the useful operating wavelength range or increase experimental backgrounds. We present measurements of the power in both the second and third harmonics, and compare the results to expectations from simulations. We also present studies of the transport of harmonics to the users, and the harmonic power as a function of electron beam quality.

  9. Multimode Directional Coupler for Utilization of Harmonic Frequencies from TWTAs

    Science.gov (United States)

    Simmons, Rainee N.; Wintucky, Edwin G.

    2013-01-01

    A novel waveguide multimode directional coupler (MDC) intended for the measurement and potential utilization of the second and higher order harmonic frequencies from high-power traveling wave tube amplifiers (TWTAs) has been successfully designed, fabricated, and tested. The design is based on the characteristic multiple propagation modes of the electrical and magnetic field components of electromagnetic waves in a rectangular waveguide. The purpose was to create a rugged, easily constructed, more efficient waveguide- based MDC for extraction and exploitation of the second harmonic signal from the RF output of high-power TWTs used for space communications. The application would be a satellitebased beacon source needed for Qband and V/W-band atmospheric propagation studies. The MDC could function as a CW narrow-band source or as a wideband source for study of atmospheric group delay effects on highdata- rate links. The MDC is fabricated from two sections of waveguide - a primary one for the fundamental frequency and a secondary waveguide for the second harmonic - that are joined together such that the second harmonic higher order modes are selectively coupled via precision- machined slots for propagation in the secondary waveguide. In the TWTA output waveguide port, both the fundamental and the second harmonic signals are present. These signals propagate in the output waveguide as the dominant and higher order modes, respectively. By including an appropriate mode selective waveguide directional coupler, such as the MDC presented here at the output of the TWTA, the power at the second harmonic can be sampled and amplified to the power level needed for atmospheric propagation studies. The important conclusions from the preliminary test results for the multimode directional coupler are: (1) the second harmonic (Ka-band) can be measured and effectively separated from the fundamental (Ku-band) with no coupling of the latter, (2) power losses in the fundamental frequency

  10. Harmonic Impact of Plug-In Hybrid Electric Vehicle on Electric Distribution System

    Directory of Open Access Journals (Sweden)

    A. Aljanad

    2016-01-01

    Full Text Available This paper presents the harmonic effects of plug-in hybrid electric vehicles (PHEV on the IEEE 37-bus distribution system at different PHEV penetration levels considering a practical daily residential load shape. The PHEV is modeled as a current harmonic source by using the Open-Source Distribution System Simulator (OpenDSS and DSSimpc software. Time series harmonic simulation was conducted to investigate the harmonic impact of PHEV on the system by using harmonic data obtained from a real electric vehicle. Harmonic effects on the system voltage profile and circuit power losses are also investigated by using OpenDSS and MATLAB software. Current/voltage total harmonic distortion (THD produced from the large scale of PHEV is investigated. Test results show that the voltage and current THDs are increased up to 9.5% and 50%, respectively, due to high PHEV penetrations and these THD values are significantly larger than the limits prescribed by the IEEE standards.

  11. Mitigation of Voltage and Current Harmonics in Grid-Connected Microgrids

    DEFF Research Database (Denmark)

    Savaghebi, Mehdi; Guerrero, Josep M.; Jalilian, Alireza

    2012-01-01

    coupling (PCC), voltage compensation mode is activated in order to provide a high voltage quality at PCC. Otherwise, grid current harmonics are mitigated (current compensation mode) in order to avoid excessive harmonic supply by the grid. In both modes, harmonic compensation is achieved through proper......In this paper, a control approach is proposed for selective compensation of main voltage and current harmonics in grid-connected microgrids. Two modes of compensation are considered, i.e. voltage and current compensation modes. In the case that sensitive loads are connected to the point of common...... control of distributed generators (DGs) interface converters. The compensation effort of each harmonic is shared considering the corresponding current harmonic supplied by the DGs. The control system of each DG comprises harmonic compensator, power controllers, voltage and current controllers and virtual...

  12. Prototype for harmonic compensation in three phase systems

    Directory of Open Access Journals (Sweden)

    Alfonso Alzate Gómez

    2017-02-01

    Full Text Available Context: The traditional methodology for the control of harmonics consists in the use of passive filters tuned to the harmonic components to be eliminated. Passive filters require a frequency-demanding design to avoid resonance phenomena with other elements and they not respond to changes in the dynamics of the electric power system. Method: A best-performing solution alternative is parallel power active filters. These filters, unlike passive filters, inject compensation currents into the network and have adaptation  to changes in operating conditions. The implementation of an active filter involves hardware development but also software development. Algorithms are required for calculation of compensation currents and dc bus voltage control. Results: In this work a prototype for the harmonic compensation of 5kVA is designed and built in three phase distribution systems of 220V. The hardware fundamental elements are: coupling coil, capacitor, semiconductor devices and controller. The control algorithms that are responsible for the operation of the active filter at each instant of time are PQ theory, Linear Control-PWM and PI Control. Conclusions: The active power filters are a solution to the presence of harmonics in power systems. They compensate the harmonics generated by nonlinear loads and they don‘t have resonance problems and good dynamic response.

  13. Harmonic Series Meets Fibonacci Sequence

    Science.gov (United States)

    Chen, Hongwei; Kennedy, Chris

    2012-01-01

    The terms of a conditionally convergent series may be rearranged to converge to any prescribed real value. What if the harmonic series is grouped into Fibonacci length blocks? Or the harmonic series is arranged in alternating Fibonacci length blocks? Or rearranged and alternated into separate blocks of even and odd terms of Fibonacci length?

  14. Accommodations assessment: Spaceborne Doppler lidar wind measuring system

    Science.gov (United States)

    1981-01-01

    An accommodations analysis performed by the MSFC Preliminary Design Office for a spaceborne Doppler lidar wind measuring system is summarized. A dedicated, free-flying spacecraft design concept is described. Mass and beginning-of-life power requirements are estimated at 2260 kg and 6.0 - 8.5 kW respectively, to support a pulsed, CO2, Doppler lidar having a pulse energy of 10 J, pulse rate of 8 Hz, and efficiency of approximately 5%. Under the assumptions of the analysis, such a system would provide wind measurements on a global scale, with accuracies of a few meters per second.

  15. Improved Active Harmonic Current Elimination Based on Voltage Detection.

    Directory of Open Access Journals (Sweden)

    Tianyuan Tan

    Full Text Available With the increasing penetration of power electronic equipment in modern residential distribution systems, harmonics mitigation through the distributed generation (DG interfacing converters has received significant attention. Among recently proposed methods, the so-called active resonance damper (ARD and harmonic voltage compensator (HVC based on voltage detection can effectively reduce the harmonic distortions in selected areas of distribution systems. However, it is found out that when traditional ARD algorithm is used to eliminate harmonic current injected by non-linear loads, its performance is constrained by stability problems and can at most eliminate half of the load harmonic currents. Thus, inspired by the duality between ARD and HVC, this paper presents a novel improved resistive active power filter (R-APF algorithm based on integral-decoupling control. The design guideline for its parameters is then investigated through carefully analyzing the closed-loop poles' trajectory. Computer studies demonstrate that the proposed algorithm can effectively mitigate the load harmonic currents and its performance is much better than traditional ARD based on proportional control.

  16. Improved Active Harmonic Current Elimination Based on Voltage Detection

    Science.gov (United States)

    Tan, Tianyuan; Dong, Shuan; Huang, Yingwei; Liu, Jian; Le, Jian; Liu, Kaipei

    2016-01-01

    With the increasing penetration of power electronic equipment in modern residential distribution systems, harmonics mitigation through the distributed generation (DG) interfacing converters has received significant attention. Among recently proposed methods, the so-called active resonance damper (ARD) and harmonic voltage compensator (HVC) based on voltage detection can effectively reduce the harmonic distortions in selected areas of distribution systems. However, it is found out that when traditional ARD algorithm is used to eliminate harmonic current injected by non-linear loads, its performance is constrained by stability problems and can at most eliminate half of the load harmonic currents. Thus, inspired by the duality between ARD and HVC, this paper presents a novel improved resistive active power filter (R-APF) algorithm based on integral-decoupling control. The design guideline for its parameters is then investigated through carefully analyzing the closed-loop poles’ trajectory. Computer studies demonstrate that the proposed algorithm can effectively mitigate the load harmonic currents and its performance is much better than traditional ARD based on proportional control. PMID:27295213

  17. High Order Voltage and Current Harmonic Mitigation Using the Modular Multilevel Converter STATCOM

    DEFF Research Database (Denmark)

    Kontos, Epameinondas; Tsolaridis, Georgios; Teodorescu, Remus

    2017-01-01

    Due to the increase of power electronic-based loads, the maintenance of high power quality poses a challenge in modern power systems. To limit the total harmonic distortion in the line voltage and currents at the point of the common coupling (PCC), active power filters are commonly employed....... This paper investigates the use of the multilevel modular converter (MMC) for harmonics mitigation due to its high bandwidth compared with conventional converters. A selective harmonics detection method and a harmonics controller are implemented, while the output current controller of the MMC is tuned...... to selectively inject the necessary harmonic currents. Unlike previous studies, focus is laid on the experimental verification of the active filtering capability of the MMC. For this reason an MMC-based double-star STATCOM is developed and tested for two representative case studies, i.e., for grid currents...

  18. Studies of harmonic generation in free electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Goldammer, K.

    2007-11-12

    Nonlinear harmonic generation is one of the most interesting aspects of Free Electron Lasers under study today. It provides for coherent, high intensity radiation at higher harmonics of the FEL resonant frequency. The sources, numerical simulation and applications of harmonic radiation in cascaded High Gain Harmonic Generation FELs were the subject of this thesis. Harmonic emission in FELs originates from harmonic microbunching of the particles and the particular electron trajectory during FEL interaction. Numerical FEL simulation codes model these analytical equations and predict the performance of Free Electron Lasers with good accuracy. This thesis has relied heavily upon the FEL simulation code Genesis 1.3 which has been upgraded in the framework of this thesis to compute harmonic generation in a self-consistent manner. Tests against analytical predictions suggest that the harmonic power levels as well as harmonic gain lengths are simulated correctly. A benchmark with the FEL simulation code GINGER yields excellent agreement of the harmonic saturation length and saturation power. The new version of the simulation code Genesis was also tested against measurements from the VUV-FEL FLASH at DESY. The spectral power distributions of fundamental and third harmonic radiation were recorded at 25.9 nm and 8.6 nm, respectively. The relative bandwidths (FWHM) were in the range of 2 % for both the fundamental as well as the third harmonic, which was accurately reproduced by time-dependent simulations with Genesis. The new code was also used to propose and evaluate a new design for the BESSY Soft X-Ray FEL, a cascaded High Gain Harmonic Generation FEL proposed by BESSY in Berlin. The original design for the BESSY High Energy FEL line requires four HGHG stages to convert the initial seed laser wavelength of 297.5 nm down to 1.24 nm. A new scheme is proposed that makes use of fifth harmonic radiation from the first stage and reduces the number of HGHG stages to three. It

  19. Microflow imaging: New Doppler technology to detect low-grade inflammation in patients with arthritis.

    Science.gov (United States)

    Lim, A K P; Satchithananda, K; Dick, E A; Abraham, S; Cosgrove, D O

    2018-03-01

    To assess the efficacy of microvascular imaging in detecting low-grade inflammation in arthritis compared with Power Doppler ultrasound (PDUS). Patients presenting for ultrasound with arthralgia were assessed with grey-scale, PDUS and Superb Microvascular Imaging (SMI). Videoclips were stored for analysis at a later date. Three musculoskeletal radiologists scored grey-scale changes, signal on PDUS and/or SMI within these joints. If a signal was detected on both PDUS and SMI, the readers graded the conspicuity of vascular signal from the two Doppler techniques using a visual analogue scale. Eighty-three patients were recruited with 134 small joints assessed. Eighty-nine of these demonstrated vascular flow with both PD and SMI, whilst in five no flow was detected. In 40 joints, vascularity was detected with SMI but not with PDUS (p = 0.007). Out of the 89 joints with vascularity on both SMI and PDUS, 23 were rated as being equal; while SMI scored moderately or markedly better in 45 cases (p Doppler technique that increases conspicuity of Doppler vascularity in symptomatic joints when compared to PDUS. This allows detection of low grade inflammation not visualised with Power Doppler in patients with arthritis. • SMI detects vascularity with improved resolution and sensitivity compared to Power Doppler. • SMI can detect low-grade inflammation not seen with Power Doppler. • Earlier detection of active inflammation could have significant impact on treatment paradigms.

  20. Analysis of Harmonic Coupling and Stability in Back-to-Back Converter Systems for Wind Turbines using Harmonic State Space (HSS)

    DEFF Research Database (Denmark)

    Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth

    2015-01-01

    points and harmonic coupling analysis. Hence, it is critically needed to develop the advanced converter model, which can include almost all the possibilities. This paper develops the advanced Back to Back (BtB) converter model for wind farm application by means of Harmonic State Space (HSS) modeling...... method. The modeling and analysis results are remarkable that this model can include non-linear component and also show different operating points and harmonic coupling point, where this means each wind power converter can show the different impedance characteristics. The developed model can easily......Understanding about harmonic propagation in wind turbine converter is fundamental to research the influence of these on a large network harmonic distortion. Therefore, the analysis of wind turbine converter harmonic spectrum as well as the influence of converter operating point into the network...

  1. Harmonic Instability Analysis of a Single-Phase Grid-Connected Converter Using a Harmonic State-Space Modeling Method

    DEFF Research Database (Denmark)

    Kwon, Jun Bum; Wang, Xiongfei; Blaabjerg, Frede

    2016-01-01

    The increasing number of renewable energy sources in the distribution grid is becoming a major issue for utility companies since grid-connected converters are operating at different operating points due to the probabilistic characteristics of the renewable energy. Usually, the harmonics and imped...... the harmonic coupling characteristic as well as different dynamic characteristics. The theoretical modeling and analysis are verified by simulations as well as experimental results.......The increasing number of renewable energy sources in the distribution grid is becoming a major issue for utility companies since grid-connected converters are operating at different operating points due to the probabilistic characteristics of the renewable energy. Usually, the harmonics...... and impedance from other renewable energy sources are not taken carefully into account in the installation and design of the systems. It can bring an unknown harmonic instability into a multiple power sourced system and makes the analysis difficult due to the complexity of the grid network. This paper proposes...

  2. Diagnostic performance of power doppler and ultrasound contrast agents in early imaging-based diagnosis of organ-confined prostate cancer: Is it possible to spare cores with contrast-guided biopsy?

    Energy Technology Data Exchange (ETDEWEB)

    Delgado Oliva, F., E-mail: frandelgol@hotmail.com; Arlandis Guzman, S.; Bonillo García, M.; Broseta Rico, E.; Boronat Tormo, F.

    2016-10-15

    Objectives: To evaluate the diagnostic performance of gray scale transrectal ultrasound-B-mode US (BMUS), power Doppler (PDUS), and sonographic contrast (CEUS) in early imaging-based diagnosis of localized prostate cancer (PCa) and to compare the diagnostic profitability of randomized biopsy (RB), US-targeted prostate biopsy by means of PDUS and CEUS. Material and methods: A single-center, prospective, transversal, epidemiological study was conducted from January 2010 to January 2014. We consecutively included patients who an imaging study of the prostate with BMUS, PDUS, and CEUS was performed, followed by prostate biopsy due to clinical suspicion of prostate cancer (PSA 4–20 ng/mL and/or rectal exam suggestive of malignancy). The diagnostic performance of BMUS, PDUS, and CEUS was determined by calculating the Sensitivity (S), Specificity (Sp), Predictive values (PV), and diagnostic odds ratio (OR) of the diagnosis tests and, for these variables, in the population general and based on their clinical stage according to rectal exam (cT1 and cT2). PCa detection rates determined by means of a randomized 10-core biopsy scheme were compared with detection rates of CEUS-targeted (SonoVue) 2-core biopsies. Results: Of the initial 984 patients, US contrast SonoVue was administered to 179 (18.2%). The PCa detection rate by organ of BMUS/PDUS in the global population was 38% versus 43% in the subpopulation with CEUS. The mean age of the patients was 64.3 ± 7.01 years (95% CI, 63.75–64.70); mean total PSA was 8.9 ± 3.61 ng/mL (95% CI, 8.67–9.13) and the mean prostate volume was 56.2 ± 29 cc (95% CI, 54.2–58.1). The detection rate by organ of targeted biopsy with BMUS, PDUS, and CEUS were as follows: Global population (10.6, 8.2, 24.5%), stage cT1 (5.6, 4.2, 16.4%), and stage cT2 (32.4, 22.3, 43.5%). Comparing the detection rates of the CEUS-targeted biopsy and randomized biopsy, the following results were obtained: Global population (24.5% vs. 41.8%), stage cT1 (16

  3. The effect of dead elements on the accuracy of Doppler ultrasound measurements.

    Science.gov (United States)

    Vachutka, Jaromir; Dolezal, Ladislav; Kollmann, Christian; Klein, Jakob

    2014-01-01

    The objective of this study is to investigate the effect of multiple dead elements in an ultrasound probe on the accuracy of Doppler ultrasound measurements. For this work, we used a specially designed ultrasound imaging system, the Ultrasonix Sonix RP, that provides the user with the ability to disable selected elements in the probe. Using fully functional convex, linear, and phased array probes, we established a performance baseline by measuring the parameters of a laminar parabolic flow profile. These same parameters were then measured using probes with 1 to 10 disabled elements. The acquired velocity spectra from the functional probes and the probes with disabled elements were then analyzed to determine the overall Doppler power, maximum flow velocity, and average flow velocity. Color Flow Doppler images were also evaluated in a similar manner. The analysis of the Doppler spectra indicates that the overall Doppler power as well as the detected maximum and average velocities decrease with the increasing number of disabled elements. With multiple disabled elements, decreases in the detected maximum and average velocities greater than 20% were recorded. Similar results were also observed with Color Flow Doppler measurements. Our results confirmed that the degradation of the ultrasound probe through the loss of viable elements will negatively affect the quality of the Doppler-derived diagnostic information. We conclude that the results of Doppler measurements cannot be considered accurate or reliable if there are four or more contiguous dead elements in any given probe.

  4. Application of exponential homotopy algorithm in the inverter harmonic elimination

    Science.gov (United States)

    Zhang, Li

    2017-02-01

    Eliminating harmonic pollution and improving power factor are the quite important task in the field of power electronics. From the mathematical point of view, harmonic elimination problems can be translated into nonlinear equations. But it is difficult to directly solve the nonlinear equations because of complexity. For this reason, exponential homotopy method is proposed based on homotopy method in this paper. It has focused on built up homotopy equations by modifying the singularities of Jacobian matrix, and on this basis homotopy equations are transformed into the differential initial value problems. Numerical results show that the new exponential homotopy method has higher precision than other algorithms, and the singularity is improved.

  5. General principles of carotid Doppler ultrasonography

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Whal [Dept. of Radiology, Seoul National University College of Medicine, Seoul (Korea, Republic of)

    2014-03-15

    Carotid Doppler ultrasonography is a popular tool for evaluating atherosclerosis of the carotid artery. Its two-dimensional gray scale can be used for measuring the intima-media thickness, which is very good biomarker for atherosclerosis and can aid in plaque characterization. The plaque morphology is related to the risk of stroke. The ulceration of plaque is also known as one of the strong predictors of future embolic event risk. Color Doppler ultrasonography and pulse Doppler ultrasonography have been used for detecting carotid artery stenosis. Doppler ultrasonography has unique physical properties. The operator should be familiar with the physics and other parameters of Doppler ultrasonography to perform optimal Doppler ultrasonography studies.

  6. Third harmonic generation of CO2 laser radiation in AgGaSe2 crystal

    Indian Academy of Sciences (India)

    ... for second harmonic and third harmonic generations are 6.3% and 2.4% respectively with the input fundamental pump power density of 5.9 MW/cm2 only. The wavelength of the fundamental CO2 laser radiation used for the generation of harmonics is 10.6 m, (20) line. A compact TEA CO2 laser source has been built in ...

  7. Novel adaptation of the demodulation technology for gear damage detection to variable amplitudes of mesh harmonics

    OpenAIRE

    Combet, Francois; Gelman, Leonid

    2011-01-01

    In this paper, a novel adaptive demodulation technique including a new diagnostic feature is proposed for gear diagnosis in conditions of variable amplitudes of the mesh harmonics. This vibration technique employs the time synchronous average (TSA) of vibration signals. The new adaptive diagnostic feature is defined as the ratio of the sum of the sideband components of the envelope spectrum of a mesh harmonic to the measured power of the mesh harmonic. The proposed adaptation of the technique...

  8. Effect of gel-instillation sonography on Doppler ultrasound findings in endometrial polyps.

    Science.gov (United States)

    Van Den Bosch, T; Van Schoubroeck, D; Luts, J; Bignardi, T; Condous, G; Epstein, E; Leone, F P; Testa, A C; Valentin, L; Van Huffel, S; Bourne, T; Timmerman, D

    2011-09-01

    Saline infusion sonohysterography has been reported to suppress the color signal within the endometrium at color or power Doppler evaluation. The aim of this study was to evaluate if gel-instillation sonography (GIS) affects the power Doppler signal in patients with endometrial polyps. Ultrasound volumes of the uterus, obtained by three-dimensional ultrasound imaging of 25 women with histologically confirmed endometrial polyps, were assessed offline by six gynecologists with a special interest in gynecological ultrasound. Each woman contributed four volumes: one gray-scale volume and one power Doppler volume before GIS, and one gray-scale volume and one power Doppler volume at GIS. Power Doppler features before and after gel infusion were compared. At unenhanced ultrasound a pedicle artery was seen in 27-46% of cases, whereas, after gel infusion the examiners reported a pedicle artery in 30-46% of cases (Exact McNemar's test P-values ranged from 0.50 to 1.00). The level of agreement between unenhanced ultrasound and GIS ranged from 59 to 91% (Cohen's kappa values ranged from 0.17 to 0.79). There was no tendency for a pedicle artery to be identified less often at GIS than before gel instillation. Gel infusion does not affect the power Doppler signal in patients with endometrial polyps. Copyright © 2011 ISUOG. Published by John Wiley & Sons, Ltd.

  9. Selective harmonic elimination strategy in eleven level inverter for PV system with unbalanced DC sources

    Science.gov (United States)

    Ghoudelbourk, Sihem.; Dib, D.; Meghni, B.; Zouli, M.

    2017-02-01

    The paper deals with the multilevel converters control strategy for photovoltaic system integrated in distribution grids. The objective of the proposed work is to design multilevel inverters for solar energy applications so as to reduce the Total Harmonic Distortion (THD) and to improve the power quality. The multilevel inverter power structure plays a vital role in every aspect of the power system. It is easier to produce a high-power, high-voltage inverter with the multilevel structure. The topologies of multilevel inverter have several advantages such as high output voltage, lower total harmonic distortion (THD) and reduction of voltage ratings of the power semiconductor switching devices. The proposed control strategy ensures an implementation of selective harmonic elimination (SHE) modulation for eleven levels. SHE is a very important and efficient strategy of eliminating selected harmonics by judicious selection of the firing angles of the inverter. Harmonics elimination technique eliminates the need of the expensive low pass filters in the system. Previous research considered that constant and equal DC sources with invariant behavior; however, this research extends earlier work to include variant DC sources, which are typical of lead-acid batteries when used in system PV. This Study also investigates methods to minimize the total harmonic distortion of the synthesized multilevel waveform and to help balance the battery voltage. The harmonic elimination method was used to eliminate selected lower dominant harmonics resulting from the inverter switching action.

  10. Quantitative analysis of vascular heterogeneity in breast lesions using contrast-enhanced 3-D harmonic and subharmonic ultrasound imaging.

    Science.gov (United States)

    Sridharan, Anush; Eisenbrey, John R; Machado, Priscilla; Ojeda-Fournier, Haydee; Wilkes, Annina; Sevrukov, Alexander; Mattrey, Robert F; Wallace, Kirk; Chalek, Carl L; Thomenius, Kai E; Forsberg, Flemming

    2015-03-01

    Ability to visualize breast lesion vascularity and quantify the vascular heterogeneity using contrast-enhanced 3-D harmonic (HI) and subharmonic (SHI) ultrasound imaging was investigated in a clinical population. Patients (n = 134) identified with breast lesions on mammography were scanned using power Doppler imaging, contrast-enhanced 3-D HI, and 3-D SHI on a modified Logiq 9 scanner (GE Healthcare). A region of interest corresponding to ultrasound contrast agent flow was identified in 4D View (GE Medical Systems) and mapped to raw slice data to generate a map of time-intensity curves for the lesion volume. Time points corresponding to baseline, peak intensity, and washout of ultrasound contrast agent were identified and used to generate and compare vascular heterogeneity plots for malignant and benign lesions. Vascularity was observed with power Doppler imaging in 84 lesions (63 benign and 21 malignant). The 3-D HI showed flow in 8 lesions (5 benign and 3 malignant), whereas 3-D SHI visualized flow in 68 lesions (49 benign and 19 malignant). Analysis of vascular heterogeneity in the 3-D SHI volumes found benign lesions having a significant difference in vascularity between central and peripheral sections (1.71 ± 0.96 vs. 1.13 ± 0.79 dB, p < 0.001, respectively), whereas malignant lesions showed no difference (1.66 ± 1.39 vs. 1.24 ± 1.14 dB, p = 0.24), indicative of more vascular coverage. These preliminary results suggest quantitative evaluation of vascular heterogeneity in breast lesions using contrast-enhanced 3-D SHI is feasible and able to detect variations in vascularity between central and peripheral sections for benign and malignant lesions.

  11. Power

    DEFF Research Database (Denmark)

    Elmholdt, Claus Westergård; Fogsgaard, Morten

    2016-01-01

    In this chapter, we will explore the dynamics of power in processes of creativity, and show its paradoxical nature as both a bridge and a barrier to creativity in organisations. Recent social psychological experimental research (Slighte, de Dreu & Nijstad, 2011) on the relation between power...... and creativity suggests that when managers give people the opportunity to gain power and explicate that there is reason to be more creative, people will show a boost in creative behaviour. Moreover, this process works best in unstable power hierarchies, which implies that power is treated as a negotiable...... and floating source for empowering people in the organisation. We will explore and discuss here the potentials, challenges and pitfalls of power in relation to creativity in the life of organisations today. The aim is to demonstrate that power struggles may be utilised as constructive sources of creativity...

  12. Inverse Doppler Effects in Flute

    CERN Document Server

    Zhao, Xiao P; Liu, Song; Shen, Fang L; Li, Lin L; Luo, Chun R

    2015-01-01

    Here we report the observation of the inverse Doppler effects in a flute. It is experimentally verified that, when there is a relative movement between the source and the observer, the inverse Doppler effect could be detected for all seven pitches of a musical scale produced by a flute. Higher tone is associated with a greater shift in frequency. The effect of the inverse frequency shift may provide new insights into why the flute, with its euphonious tone, has been popular for thousands of years in Asia and Europe.

  13. Observation of redshifting and harmonic radiation in inverse Compton scattering

    Science.gov (United States)

    Sakai, Y.; Pogorelsky, I.; Williams, O.; O'Shea, F.; Barber, S.; Gadjev, I.; Duris, J.; Musumeci, P.; Fedurin, M.; Korostyshevsky, A.; Malone, B.; Swinson, C.; Stenby, G.; Kusche, K.; Babzien, M.; Montemagno, M.; Jacob, P.; Zhong, Z.; Polyanskiy, M.; Yakimenko, V.; Rosenzweig, J.

    2015-06-01

    Inverse Compton scattering of laser photons by ultrarelativistic electron beam provides polarized x- to γ -ray pulses due to the Doppler blueshifting. Nonlinear electrodynamics in the relativistically intense linearly polarized laser field changes the radiation kinetics established during the Compton interaction. These are due to the induced figure-8 motion, which introduces an overall redshift in the radiation spectrum, with the concomitant emission of higher order harmonics. To experimentally analyze the strong field physics associated with the nonlinear electron-laser interaction, clear modifications to the angular and wavelength distributions of x rays are observed. The relativistic photon wave field is provided by the ps CO2 laser of peak normalized vector potential of 0.5 laser [M. Babzien et al., Phys. Rev. Lett. 96, 054802 (2006)]. The angular spectral characteristics are revealed using K -, L -edge, and high energy attenuation filters. The observation indicates existence of the electrons' longitudinal motion through frequency redshifting understood as the mass shift effect. Thus, the 3rd harmonic radiation has been observed containing on-axis x-ray component that is directly associated with the induced figure-8 motion. These are further supported by an initial evidence of off-axis 2nd harmonic radiation produced in a circularly polarized laser wave field. Total x-ray photon number per pulse, scattered by 65 MeV electron beam of 0.3 nC, at the interaction point is measured to be approximately 109 .

  14. Harmonic Instability Source Identification in Large Wind Farms

    DEFF Research Database (Denmark)

    Ebrahimzadeh, Esmaeil; Blaabjerg, Frede; Wang, Xiongfei

    2017-01-01

    A large-scale power electronics based power system like a wind farm introduces the passive and active impedances. The interactions between the active and passive impedances can lead to harmonic-frequency oscillations above the fundamental frequency, which can be called harmonic instability....... This paper presents an approach to identify which wind turbine and which bus has more contribution to the harmonic instability problems. In the approach, a wind farm is modeled as a Multi-Input Multi-Output (MIMO) dynamic system. The poles of the MIMO transfer matrix are used to predict the system...... instability and the eigenvalues sensitivity analysis in respect to the elements of the MIMO matrix locates the most influencing buses of the wind farm. Time-domain simulations in PSCAD software environment for a 400-MW wind farm validate that the presented approach is an effective tool to determine the main...

  15. Duplex/doppler ultrasound test (image)

    Science.gov (United States)

    The duplex/doppler ultrasound test examines the blood flow in the major arteries and veins in the arms and legs. The ... duplex ultrasonagraphy to visualize the blood flow and doppler ultrasonagraphy provides an audio means to hear the ...

  16. Harmonic filter design consideration for a tire-rubber factory

    Energy Technology Data Exchange (ETDEWEB)

    Zebardast, A. [Azad Univ., Tehran (Iran, Islamic Republic of). Abhar Branch]|[Sharif Univ., Tehran (Iran, Islamic Republic of); Mokhtari, H. [Azad Univ., Tehran (Iran, Islamic Republic of)

    2005-07-01

    Nonlinear loads and arc furnace loads are the main sources of harmonic currents in power distribution systems. Harmonic currents can cause reductions in system efficiency, and shorten the lifespan of transformers and capacitor banks. This paper provided details of a filter designed to attenuate harmonic currents at a tire company in Iran. The tire company was supplied by 3 distribution transformers and an emergency transformer. Main supply was through a 132 kV/20 kV transformer, which was connected to 2 A and B stations. The AC/DC drivers generated harmonics. Harmonic measurements were performed to determine the type and size of the required filters. A summary of site harmonic measurements was provided. A passive filter was placed at a medium voltage location. A sensitivity analysis was then performed in order to assess loading effects on filter performance. The analysis was performed on all possible configurations in the plant, including load change, capacitor bank step change, and transformer energization. Resonance conditions were also examined. Results showed that attention must be paid to the filter component rating in addition to potential resonant conditions. It was concluded that resonant conditions alter when system operating conditions change. 5 refs., 7 figs.

  17. Introduction to abstract harmonic analysis

    CERN Document Server

    Loomis, Lynn H

    2011-01-01

    Written by a prominent figure in the field of harmonic analysis, this classic monograph is geared toward advanced undergraduates and graduate students and focuses on methods related to Gelfand's theory of Banach algebra. 1953 edition.

  18. Tissue Harmonic Synthetic Aperture Imaging

    DEFF Research Database (Denmark)

    Rasmussen, Joachim

    The main purpose of this PhD project is to develop an ultrasonic method for tissue harmonic synthetic aperture imaging. The motivation is to advance the field of synthetic aperture imaging in ultrasound, which has shown great potentials in the clinic. Suggestions for synthetic aperture tissue...... system complexity compared to conventional synthetic aperture techniques. In this project, SASB is sought combined with a pulse inversion technique for 2nd harmonic tissue harmonic imaging. The advantages in tissue harmonic imaging (THI) are expected to further improve the image quality of SASB....... The first part of the scientific contribution investigates an implementation of pulse inversion for THI on the experimental ultrasound system SARUS. The technique is initially implemented for linear array transducers and then expanded for convex array transducers. The technique is evaluated based on spatial...

  19. Understanding Doppler Broadening of Gamma Rays

    Energy Technology Data Exchange (ETDEWEB)

    Rawool-Sullivan, Mohini [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sullivan, John P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-07-03

    Doppler-broadened gamma ray peaks are observed routinely in the collection and analysis of gamma-ray spectra. If not recognized and understood, the appearance of Doppler broadening can complicate the interpretation of a spectrum and the correct identification of the gamma ray-emitting material. We have conducted a study using a simulation code to demonstrate how Doppler broadening arises and provide a real-world example in which Doppler broadening is found. This report describes that study and its results.

  20. Harmonic structures and intrinsic torsion

    DEFF Research Database (Denmark)

    Conti, Diego; Madsen, Thomas Bruun

    We discuss the construction of 8-manifolds with harmonic Sp(2)Sp(1)-structures. In particular, we find 10 new examples of nilmanifolds that admit a closed 4-form Omega whose stabiliser is Sp(2)Sp(1). Our constructions entail the notion of SO(4)-structures on 7-manifolds. We present a thorough inv...... investigation of the intrinsic torsion of such structures; in addition to the construction of harmonic structures, this analysis leads to explicit Lie group examples with invariant intrinsic torsion....

  1. Power

    OpenAIRE

    Hafford-Letchfield, Trish

    2015-01-01

    This chapter looks at the concept of power in social work by focusing on what this means as a ‘professional’ and theorizes competing discourses of empowerment in social work and its key concepts, drawing in particular on the explanatory powers of critical theorist Michel Foucault (1991). The chapter problematizes the concept of power by explicitly drawing on both users’ and carers’ accounts from the literature to demonstrate different external and internal influences on the root causes of dis...

  2. Selective Compensation of Voltage Harmonics in a Grid-Connected Microgrid

    DEFF Research Database (Denmark)

    Savaghebi, M.; Guerrero, Josep M.; Jalilian, A.

    2011-01-01

    In this paper, a method for selective voltage harmonic compensation in a grid-connected microgrid is presented. Harmonic compensation is done through proper control of distributed generators (DGs) interface converters. In order to achieve proper sharing of compensation effort among the DGs, a power...

  3. Micro-Doppler Analysis of Small UAVs

    NARCIS (Netherlands)

    Wit, J.J.M. de; Harmanny, R.I.A.; Prémel Cabic, G.

    2012-01-01

    Coherent radar measures micro-Doppler properties of moving objects. The micro-Doppler signature depends on parts of an object moving and rotating in addition to the main body motion (e.g. rotor blades) and is therefore characteristic for the type of object. In this study, the micro-Doppler signature

  4. Speckles in laser doppler perfusion imaging

    NARCIS (Netherlands)

    Rajan, V.V.

    2007-01-01

    Laser Doppler Flowmetry (LDF) is a noninvasive diagnostic method to measure blood flow in tissue [1]. The technique is based on measuring the Doppler shift induced by moving red blood cells to the illuminating coherent light. A laser Doppler instrument often gives output signals related to the flux,

  5. The Doppler Effect--A New Approach

    Science.gov (United States)

    Allen, J.

    1973-01-01

    Discusses the Doppler effect as it applies to different situations, such as a stationary source of sound with the observer moving, a stationary observer, and the sound source and observer both moving. Police radar, satellite surveillance radar, radar astronomy, and the Doppler navigator, are discussed as applications of Doppler shift. (JR)

  6. Harmonic models of a back-to-back converter in large offshore wind farms compared with measurement data

    DEFF Research Database (Denmark)

    Kocewiak, Lukasz Hubert; Hjerrild, Jesper; Bak, Claus Leth

    2009-01-01

    and assess harmonic emission in the point of common coupling. Different modelling methods of power electronic devices installed in wind turbines are presented. Harmonic load flow analysis and impedance frequency characteristics calculation are conducted to present differences between the models. Simulation...... results are compared with measurement data from the Burbo Bank offshore wind farm. The delimitations of both power converter models with referent to harmonic analysis are shown in this paper....

  7. General Lp-harmonic Blaschke bodies

    Indian Academy of Sciences (India)

    Lutwak introduced the harmonic Blaschke combination and the harmonic Blaschke body of a star body. Further, Feng and Wang introduced the concept of the -harmonic Blaschke body of a star body. In this paper, we define the notion of general -harmonic Blaschke bodies and establish some of its properties.

  8. General Lp-harmonic Blaschke bodies

    Indian Academy of Sciences (India)

    Abstract. Lutwak introduced the harmonic Blaschke combination and the harmonic. Blaschke body of a star body. Further, Feng and Wang introduced the concept of the L p- harmonic Blaschke body of a star body. In this paper, we define the notion of general. L p-harmonic Blaschke bodies and establish some of its ...

  9. [Importance of color Doppler in diagnostics of breast diseases].

    Science.gov (United States)

    Kavtaradze, S N; Mosidze, T G

    2010-01-01

    The breast cancer occupies one of the first places among women's malignant neoplasms. Breast cancer case rate annually increases in the majority of the countries of the world. It is very important early diagnostics and active revealing of breast pre-tumor diseases. With the purpose of definition of value of color Doppler, there were inspected 127 patients with various breast pathologies. Breast ultrasonic research, color Doppler and power Doppler allowed obtaining the essential additional data for carrying out of differential diagnostics. According to the results, concentration of vessels in a zone of tumor unit with a primary locating on periphery is characteristic for malignant formations of breast. It is, accordingly, cause of rising vascularisation of tissues of breast, and also high parameters of linear speed of blood-flow - Vmax - 0,34+/-0,05 m/s, Pi (Pulls index )- 1,42+/-0,04, Ri (Resistance index) - 0,71+/-0,02. Parameters of linear rate of a blood-flow are lower for non malignant nodal formations - Vmax from 0,14+/-0,02-0,19+/-0,02 m/s, Pi - 1,42+/-0,12-1,42+/-0,06, Ri - 0,60+/-0,02-0,62+/-0,02. In cases of weak vascularised of nodal formations the method of power Doppler was used. The maximal rate in circumflex vessels of the pathological formations in most cases did not exceed 0,25 m/s, when size of formation was up to 1,5 sm and 0,7 m/s when size of formations was more than 3 sm. At use of ultrasonic intervention combining with color Doppler and power Doppler sensitivity of diagnostics has made 93,8% and specificity - 88,6%. Proceeding from, color Doppler especially in a combination to other methods of research is the effective method, allowing increase of diagnostic accuracy. Dopplerography, allowing to visualization of blood-flow in fine vessels and even perfusion in a tissue of breast, undoubtedly, soon will occupy the one of the conducting places in diagnostics of breast diseases.

  10. Theory of surface second-harmonic generation in silica nanowires

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper

    2010-01-01

    -based nanowires is critically discussed, based on simulations of second-harmonic generation in nanowires with a fluctuating phase-matching wavelength. It is concluded that efficient wavelength conversion will require strong improvements in the nanowire uniformity, peak powers well in excess of 10 KW, increase...

  11. High-Efficiency Harmonically Terminated Diode and Transistor Rectifiers

    Energy Technology Data Exchange (ETDEWEB)

    Roberg, M; Reveyrand, T; Ramos, I; Falkenstein, EA; Popovic, Z

    2012-12-01

    This paper presents a theoretical analysis of harmonically terminated high-efficiency power rectifiers and experimental validation on a class-C single Schottky-diode rectifier and a class-F-1 GaN transistor rectifier. The theory is based on a Fourier analysis of current and voltage waveforms, which arise across the rectifying element when different harmonic terminations are presented at its terminals. An analogy to harmonically terminated power amplifier (PA) theory is discussed. From the analysis, one can obtain an optimal value for the dc load given the RF circuit design. An upper limit on rectifier efficiency is derived for each case as a function of the device on-resistance. Measured results from fundamental frequency source-pull measurement of a Schottky diode rectifier with short-circuit terminations at the second and third harmonics are presented. A maximal device rectification efficiency of 72.8% at 2.45 GHz matches the theoretical prediction. A 2.14-GHz GaN HEMT rectifier is designed based on a class-F-1 PA. The gate of the transistor is terminated in an optimal impedance for self-synchronous rectification. Measurements of conversion efficiency and output dc voltage for varying gate RF impedance, dc load, and gate bias are shown with varying input RF power at the drain. The rectifier demonstrates an efficiency of 85% for a 10-W input RF power at the transistor drain with a dc voltage of 30 V across a 98-Omega resistor.

  12. Second-harmonic ion cyclotron resonance heating scenarios of ...

    Indian Academy of Sciences (India)

    at high field side. Direct electron heating experiment on the Aditya tokamak using fast waves (FW) in the IC frequency range has already been carried out in [3] and ... 1Spec (solid line) shows the power deposition profile of ions due to ... The vertical line indicates the second-harmonic resonance layer for hydrogen ions. 716.

  13. Validation of phantom-based harmonization for patient harmonization.

    Science.gov (United States)

    Panetta, Joseph V; Daube-Witherspoon, Margaret E; Karp, Joel S

    2017-07-01

    To improve the precision of multicenter clinical trials, several efforts are underway to determine scanner-specific parameters for harmonization using standardized phantom measurements. The goal of this study was to test the correspondence between quantification in phantom and patient images and validate the use of phantoms for harmonization of patient images. The National Electrical Manufacturers' Association image quality phantom with hot spheres was scanned on two time-of-flight PET scanners. Whole-body [18 F]-fluorodeoxyglucose (FDG)-PET scans were acquired of subjects on the same systems. List-mode events from spheres (diam.: 10-28 mm) measured in air on each scanner were embedded into the phantom and subject list-mode data from each scanner to create lesions with known uptake with respect to the local background in the phantom and each subject's liver and lung regions, as a proxy to characterize true lesion quantification. Images were analyzed using the contrast recovery coefficient (CRC) typically used in phantom studies and serving as a surrogate for the standardized uptake value used clinically. Postreconstruction filtering (resolution recovery and Gaussian smoothing) was applied to determine if the effect on the phantom images translates equivalently to subject images. Three postfiltering strategies were selected to harmonize the CRCmean or CRCmax values between the two scanners based on the phantom measurements and then applied to the subject images. Both the average CRCmean and CRCmax values for lesions embedded in the lung and liver in four subjects (BMI range 25-38) agreed to within 5% with the CRC values for lesions embedded in the phantom for all lesion sizes. In addition, the relative changes in CRCmean and CRCmax resulting from the application of the postfilters on the subject and phantom images were consistent within measurement uncertainty. Further, the root mean squared percent difference (RMSpd ) between CRC values on the two scanners

  14. Organized Aggregation of Porphyrins in Lipid Bilayers for Third Harmonic Generation Microscopy.

    Science.gov (United States)

    Cui, Liyang; Tokarz, Danielle; Cisek, Richard; Ng, Kenneth K; Wang, Fan; Chen, Juan; Barzda, Virginijus; Zheng, Gang

    2015-11-16

    Nonlinear optical microscopy has become a powerful tool for high-resolution imaging of cellular and subcellular composition, morphology, and interactions because of its high spatial resolution, deep penetration, and low photo-damage to tissue. Developing specific harmonic probes is essential for exploiting nonlinear microscopic imaging for biomedical applications. We report an organized aggregate of porphyrins (OAP) that formed within lipidic nanoparticles showing fingerprint spectroscopic properties, structure-associated second harmonic generation, and superradiant third harmonic generation. The OAP facilitated harmonic microscopic imaging of living cells with significantly enhanced contrast. The structure-dependent switch between harmonic (OAP-intact) and fluorescence (OAP-disrupted) generation enabled real-time multi-modality imaging of the cellular fate of nanoparticles. Robustly produced under various conditions and easily incorporated into pre-formed lipid nanovesicles, OAP provides a biocompatible nanoplatform for harmonic imaging. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Ion gyro-harmonic structuring in the stimulated radiation spectrum and optical emissions during electron gyro-harmonic heating

    Science.gov (United States)

    Mahmoudian, A.; Scales, W. A.; Bernhardt, P. A.; Samimi, A.; Kendall, E.; Ruohoniemi, J. M.; Isham, B.; Vega-Cancel, O.; Bordikar, M.

    2013-03-01

    Stimulated electromagnetic emissions (SEEs) are secondary radiation produced during active space experiments in which the ionosphere is actively heated with high power high frequency (HF) ground-based radio transmitters. Recently, there has been significant interest in ion gyro-harmonic structuring the SEE spectrum due to the potential for new diagnostic information available such as electron acceleration and creation of artificial ionization layers. These relatively recently discovered gyro-harmonic spectral features have almost exclusively been studied when the transmitting frequency is near the second electron gyro-harmonic frequency. The first extensive systematic experimental investigations of the possibility of these spectral features for third electron gyro-harmonic heating are provided here. Discrete spectral features shifted from the transmit frequency ordered by harmonics of the ion gyro-frequency were observed for third electron gyro-harmonic heating for the first time at a recent campaign at the High Frequency Active Auroral Research Program (HAARP) facility. These features were also closely correlated with a broader band feature at a larger frequency shift from the transmit frequency known as the downshifted peak (DP). The power threshold of these spectral features was measured, as well as their behavior with heater beam angle, and proximity of the transmit frequency to the third electron gyro-harmonic frequency. Comparisons were also made with similar spectral features observed during second electron gyro-harmonic heating during the same campaign. A theoretical model is provided that interprets these spectral features as resulting from parametric decay instabilities in which the pump field ultimately decays into high frequency upper hybrid/electron Bernstein and low frequency neutralized ion Bernstein IB and/or obliquely propagating ion acoustic waves at the upper hybrid interaction altitude. Coordinated optical and SEE observations were carried out

  16. High Order Voltage and Current Harmonic Mitigation Using the Modular Multilevel Converter STATCOM

    NARCIS (Netherlands)

    Kontos, E.; Tsolaridis, Georgios; Teodorescu, Remus; Bauer, P.

    2017-01-01

    Due to the increase of power electronic-based loads, the maintenance of high power quality poses a challenge in modern power systems. To limit the total harmonic distortion in the line voltage and currents at the point of the common coupling (PCC), active power filters are commonly employed. This

  17. Doppler tomography in fusion plasmas and astrophysics

    DEFF Research Database (Denmark)

    Salewski, Mirko; Geiger, B.; Heidbrink, W. W.

    2015-01-01

    Doppler tomography is a well-known method in astrophysics to image the accretion flow, often in the shape of thin discs, in compact binary stars. As accretion discs rotate, all emitted line radiation is Doppler-shifted. In fast-ion Dα (FIDA) spectroscopy measurements in magnetically confined plasma......, the Dα-photons are likewise Doppler-shifted ultimately due to gyration of the fast ions. In either case, spectra of Doppler-shifted line emission are sensitive to the velocity distribution of the emitters. Astrophysical Doppler tomography has lead to images of accretion discs of binaries revealing bright...... spots, spiral structures and flow patterns. Fusion plasma Doppler tomography has led to an image of the fast-ion velocity distribution function in the tokamak ASDEX Upgrade. This image matched numerical simulations very well. Here we discuss achievements of the Doppler tomography approach, its promise...

  18. TAX HARMONIZATION VERSUS FISCAL COMPETITION

    Directory of Open Access Journals (Sweden)

    Florin Alexandru MACSIM

    2016-12-01

    Full Text Available Recent years have brought into discussion once again subjects like tax harmonization and fiscal competition. Every time the European Union tends to take a step forward critics enter the scene and give contrary arguments to European integration. Through this article we have offered our readers a compelling view over the “battle” between tax harmonization and fiscal competition. While tax harmonization has key advantages as less costs regarding public revenues, leads to higher degree of integration and allows the usage of fiscal transfers between regions, fiscal competition is no less and presents key advantages as high reductions in tax rates and opens a large path for new investments, especially FDI. Choosing tax harmonization or fiscal competition depends on a multitude of variables, of circumstances, the decision of choosing one path or the other being ultimately influenced by the view of central and local authorities. Our analysis indicates that if we refer to a group of countries that are a part of a monetary union or that form a federation, tax harmonization seems to be the best path to choose. Moving the analysis to a group of regions that aren’t taking any kind of correlated actions or that have not signed any major treaties regarding monetary or fiscal policies, the optimal solution is fiscal competition.

  19. On-line grid impedance estimation based on harmonic injection for grid-connected PV inverter

    DEFF Research Database (Denmark)

    Ciobotaru, Mihai; Teodorescu, Remus; Blaabjerg, Frede

    2007-01-01

    The paper presents an on-line software method for impedance estimation of the energized impedances such as power system grid. The proposed method is based on producing a perturbation on the output of the power converter that is in the form of periodical injection of one or two voltage harmonic...... signals. The single harmonic injection uses a 600 Hz signal and the double harmonic injection uses a 400 Hz and 600 Hz signals, respectively. During the perturbation, the current response(s) at the same frequency as the injected signal(s) is/are measured. The value of the grid impedance is estimated using...... two different signal processing algorithms. The DFT technique is used for the single harmonic injection and the statistic technique is used for the double harmonic injection. The grid impedance estimation is used for compliance with the anti-islanding requirements of the German standard (VDE0126...

  20. Resonant second harmonic generation in a gallium nitride two-dimensional photonic crystal on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Y.; Roland, I.; Checoury, X.; Han, Z.; El Kurdi, M.; Sauvage, S.; Boucaud, P., E-mail: philippe.boucaud@ief.u-psud.fr [Institut d' Electronique Fondamentale, CNRS - Univ. Paris Sud 11, Bâtiment 220, F-91405 Orsay (France); Gayral, B. [Univ. Grenoble Alpes, INAC-SP2M, CEA-CNRS group Nanophysique et Semiconducteurs, F-38000 Grenoble (France); CEA, INAC-SP2M, CEA-CNRS group Nanophysique et Semiconducteurs, F-38000 Grenoble (France); Brimont, C.; Guillet, T. [Université Montpellier 2, Laboratoire Charles Coulomb UMR 5221, F-34905 Montpellier (France); Mexis, M.; Semond, F. [CRHEA-CNRS, Rue Bernard Grégory, F-06560 Valbonne (France)

    2015-02-23

    We demonstrate second harmonic generation in a gallium nitride photonic crystal cavity embedded in a two-dimensional free-standing photonic crystal platform on silicon. The photonic crystal nanocavity is optically pumped with a continuous-wave laser at telecom wavelengths in the transparency window of the nitride material. The harmonic generation is evidenced by the spectral range of the emitted signal, the quadratic power dependence vs. input power, and the spectral dependence of second harmonic signal. The harmonic emission pattern is correlated to the harmonic polarization generated by the second-order nonlinear susceptibilities χ{sub zxx}{sup (2)}, χ{sub zyy}{sup (2)} and the electric fields of the fundamental cavity mode.

  1. Investigation of Surface Preparations to Enhance Photon Doppler Velocimetry Measurements

    Science.gov (United States)

    2015-08-01

    of Angle, Surface Profilometery, and Optical Photography at 10-, 20-, and 40-Times Magnifications 53 Appendix J. Kevlar Reflected Power...those recognized by Christian Doppler in 1842.3 Recently, academics studying within the field of shock physics recognized that the invent of fiber ...1.55-μm light that was generated from an IPG ytterbium fiber laser (model ELR- 2-1550-LP-SF). The light was projected to the surfaces through open

  2. Ankle-brachial pressure index estimated by laser Doppler in patients suffering from peripheral arterial obstructive disease.

    Science.gov (United States)

    Ludyga, Tomasz; Kuczmik, Waclaw B; Kazibudzki, Marek; Nowakowski, Przemyslaw; Orawczyk, Tomasz; Glanowski, Michal; Kucharzewski, Marcin; Ziaja, Damion; Szaniewski, Krzysztof; Ziaja, Krzysztof

    2007-07-01

    Ankle-brachial index (ABI) measurements are widely used for evaluating the functional state of circulation in the lower limbs. However, there is some evidence that the value of ABI does not accurately reflect the degree of walking impairment in symptomatic patients with peripheral arterial obstructive disease (PAOD). We investigated the diagnostic value of ABI estimated by means of laser Doppler flowmetry (IT) for evaluating limb ischemia. We wanted to know whether laser Doppler could be more sensitive than the Doppler method in predicting walking capacity in patients with stable intermittent claudication. We analyzed a group of 30 patients with intermittent claudication (Fontain II, II/III) who were admitted for reconstructive treatment. There were 21 men and 9 women, aged 46-74 (mean 61) years. All patients underwent the treadmill test, and pain-free walking distances were measured. In each patient, we measured ABI using the two different methods: Doppler ultrasound device (ABI-Doppler) and laser Doppler (ABI-laser Doppler). The claudication distances were 25-200 m (mean 73 +/- 50.2 m). ABI-Doppler was 0.2-0.7 (0.582 +/- 0.195). ABI-laser Doppler measurements were 0.581 (+/-0.218). A correlation was found between ABI-Doppler and claudication distance (r = 0.46, P = 0.009). Also, ABI-laser Doppler values significantly correlated with claudication distances (r = 0.536, P = 0.002). The ABI evaluated by laser Doppler correlated well with claudication distances in patients with PAOD. Comparison of Doppler and laser Doppler measurements used for determining ABI showed that both methods have similar predictive power for walking capacity; however, higher correlation was observed between claudication distances and ABI measured by laser Doppler flowmetry. ABI-laser Doppler measurements are easier, are quicker, and seem to be better suited for noncompliant patients. Further investigation should be undertaken to determine whether laser Doppler is superior to the Doppler

  3. Pulsed multigated Doppler ultrasonography in the diagnosis of carotid artery disease

    DEFF Research Database (Denmark)

    Sillesen, H; Bitsch, K R; Schroeder, T

    1988-01-01

    To evaluate the accuracy of a pulsed multigated Doppler system, 128 carotid arteries were examined. The spectral broadening index was calculated from the power spectrum of a small sample volume located in the center of the stream according to the flow profile and was related to the degree of sten...... by a multigated Doppler system may add valuable information concerning blood flow characteristics not obtainable by single-gated systems....

  4. Power flow for Josephson elements.

    Science.gov (United States)

    Thompson, E. D.

    1973-01-01

    General relations are presented for the power flow at the frequencies of interest in a Josephson element. These general power flow relations depend upon whether the autonomous frequency is phase-locked, either harmonically or subharmonically, to a frequency in the system or is unlocked. The results presented generalize those given previously by Russer (1971) for the harmonically locked case.

  5. HARMONIZED EUROPE OR EUROPEAN HARMONY?

    Directory of Open Access Journals (Sweden)

    Cosmin Marinescu

    2007-07-01

    Full Text Available Recent evolutions in Europe raise questions on the viability of the present economic and social model that defines the European construction project. In this paper, the author will try to explain the viability of institutional European model that sticks between free market mechanisms and protectionism. The main challenge for the EU is about the possibility to bring together the institutional convergence and the welfare for all Europeans. This is the result of the view, still dominant, of European politics elite, according to which institutional harmonization is the solution of a more dynamic and prosper Europe. But, economic realities convince us that, more and more, a harmonized, standardized Europe is not necessarily identical with a Europe of harmony and social cooperation. If „development through integration” seems to be harmonization through „institutional transplant”, how could then be the European model one sufficiently wide open to market, which creates the prosperity so long waited for by new member countries?

  6. A look-up-table digital predistortion technique for high-voltage power amplifiers in ultrasonic applications.

    Science.gov (United States)

    Gao, Zheng; Gui, Ping

    2012-07-01

    In this paper, we present a digital predistortion technique to improve the linearity and power efficiency of a high-voltage class-AB power amplifier (PA) for ultrasound transmitters. The system is composed of a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), and a field-programmable gate array (FPGA) in which the digital predistortion (DPD) algorithm is implemented. The DPD algorithm updates the error, which is the difference between the ideal signal and the attenuated distorted output signal, in the look-up table (LUT) memory during each cycle of a sinusoidal signal using the least-mean-square (LMS) algorithm. On the next signal cycle, the error data are used to equalize the signal with negative harmonic components to cancel the amplifier's nonlinear response. The algorithm also includes a linear interpolation method applied to the windowed sinusoidal signals for the B-mode and Doppler modes. The measurement test bench uses an arbitrary function generator as the DAC to generate the input signal, an oscilloscope as the ADC to capture the output waveform, and software to implement the DPD algorithm. The measurement results show that the proposed system is able to reduce the second-order harmonic distortion (HD2) by 20 dB and the third-order harmonic distortion (HD3) by 14.5 dB, while at the same time improving the power efficiency by 18%.

  7. SELENE mission: mathematical model for SST Doppler measurements

    Science.gov (United States)

    Ping, J.; Kono, Y.; Kawano, N.; Hanada, H.; Matsumoto, K.

    2001-09-01

    Japanese lunar exploration mission, SELENE, has been planned to be launched into space by using H II-a rocket in the Summer of 2004. This mission is composed of 3 subsatellites, a main lunar orbiter, a relay satellite and a free flying VLBI radio source. One of its main scientific objectives is the estimation of high order and degree spherical harmonic coefficients for the lunar gravity field. Different tracking methods will be employed in SELENE. The key tracking method is 4 way Satellite-to-Satellite Tracking (SST) technique. By this way, the tracking data can be obtained through the relay when the low altitude main orbiter is flying at the far-side of the Moon and can not be "seen" from the Earth. To success the historical tracking data, a complete coverage of Doppler tracking from an orbiter at sufficiently low altitude with high tracking accuracy can be obtained. The 4 way SST has various configurations. For SELENE, the SST tracking mode is introduced here, the mathematical relation between range rate and 4 way Doppler count number is established, and a data processing stream frame by using GEODYN II is suggested.

  8. Elements of abstract harmonic analysis

    CERN Document Server

    Bachman, George

    2013-01-01

    Elements of Abstract Harmonic Analysis provides an introduction to the fundamental concepts and basic theorems of abstract harmonic analysis. In order to give a reasonably complete and self-contained introduction to the subject, most of the proofs have been presented in great detail thereby making the development understandable to a very wide audience. Exercises have been supplied at the end of each chapter. Some of these are meant to extend the theory slightly while others should serve to test the reader's understanding of the material presented. The first chapter and part of the second give

  9. Harmonic functions with varying coefficients

    Directory of Open Access Journals (Sweden)

    Jacek Dziok

    2016-05-01

    Full Text Available Abstract Complex-valued harmonic functions that are univalent and sense preserving in the open unit disk can be written in the form f = h + g ‾ $f=h+\\overline{g}$ , where h and g are analytic. In this paper we investigate some classes of univalent harmonic functions with varying coefficients related to Janowski functions. By using the extreme points theory we obtain necessary and sufficient convolution conditions, coefficients estimates, distortion theorems, and integral mean inequalities for these classes of functions. The radii of starlikeness and convexity for these classes are also determined.

  10. Measurement research on magnetic properties of electrical sheet steel under different temperature, harmonic and dc bias

    Directory of Open Access Journals (Sweden)

    Dezhi Chen

    2017-05-01

    Full Text Available The iron core of large power transformer is mainly composed of electrical sheet steel, which is easily affected by temperature, harmonic, and DC bias. Therefore, it is necessary to measure the magnetic properties of electrical sheet steel under different temperature, harmonic and DC Bias. This paper presents the experiment measurement system for the 30ZH120 electrical steel sheet. The B-H magnetization curve, permeability, and loss curve under different temperature, different harmonic, and different DC bias are given, respectively. The simulation of transformer is carried out by using measuring result under DC bias. The presented research provides a reference for optimizing the design of power transformer.

  11. Harmonic Instability Analysis of Single-Phase Grid Connected Converter using Harmonic State Space (HSS) modeling method

    DEFF Research Database (Denmark)

    Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth

    2015-01-01

    The increasing number of renewable energy sources at the distribution grid is becoming a major issue for utility companies, since the grid connected converters are operating at different operating points due to the probabilistic characteristics of renewable energy. Besides, typically, the harmoni...... impedance matrixes, where that represents the harmonic coupling characteristic as well as the different instability characteristics. The theoretical modeling and analysis are verified by simulations and also experimental results.......The increasing number of renewable energy sources at the distribution grid is becoming a major issue for utility companies, since the grid connected converters are operating at different operating points due to the probabilistic characteristics of renewable energy. Besides, typically, the harmonics...... and impedance from other renewable energy sources are not taken carefully into account in the installation and design. However, this may bring an unknown harmonic instability into the multiple power sourced system and also make the analysis difficult due to the complexity of the grid network. This paper...

  12. Highlighting the harmonic regime generated by electric locomotives equipped with DC motors

    Science.gov (United States)

    Baciu, I.; Cunţan, C. D.

    2018-01-01

    The paper presents the results of measurements made using the C.A. 8334 power quality analyzer on an electric locomotive equipped with DC motors. We carried out determinations of the current-voltage regime using a locomotive motor. The harmonic regime of the other motors being identical to the analysed one, we could easily deduce the effects caused by the entire locomotive. The data measured with the analyzer were firstly transferred into a computer system using the Qualistar software, followed by data processing in Excel, enabling therefore a graphical representation of the characteristic parameters of power quality. Based on the acquired data, we determined the power factor, as well as the active, reactive and apparent power. The measurements revealed high values of the current harmonics, fact that required some measures to be taken for reducing the values of these harmonics. For this, we ran a simulation using the PSCAD/EMTDC software, by introducing LC filters in tune with the harmonic frequencies. The result was a significant reduction in the harmonic regime, either in the harmonics values or the power factor and reactive power.

  13. Modeling and Identification of Harmonic Instability Problems In Wind Farms

    DEFF Research Database (Denmark)

    Ebrahimzadeh, Esmaeil; Blaabjerg, Frede; Wang, Xiongfei

    2016-01-01

    to identify harmonic instability problems in wind farms, where many wind turbines, cables, transformers, capacitor banks, shunt reactors, etc, typically are located. This methodology introduces the wind farm as a Multi-Input Multi-Outpur (MIMO) control system, where the linearized models of fast inner control...... loops of the grid-side converters are considered. Therefore, instability problems of the whole wind farm are predicted based on the poles of the introduced MIMO system. In order to confirm the effectiveness of the proposed analytical approach, time-domain simulations are performed in the PSCAD......In power electronics based power systems like wind farms, the interactions between the inner control systems of the power converters and the passive components may lead to high frequency oscillations, which can be called harmonic instability. In this paper, a simple methodology is presented...

  14. Advances in transcranial Doppler clinical applications.

    Science.gov (United States)

    Topcuoglu, Mehmet Akif; Unal, Ali; Arsava, Ethem Murat

    2010-07-01

    Diagnostic neurosonology techniques including transcranial Doppler (TCD), transcranial color Doppler imaging (TCDI) and power motion-mode (PMD) TCD provide information about various aspects of cerebrovascular status such as microemboli detection, dynamic autoregulation and long-duration real-time monitoring of flow characteristics. Although most of the information provided cannot be obtained by any other imaging methodology, and is critical in clinical decision-making in the care of various neurovascular diseases, these modalities are widely underutilized. Increasing the familiarity to neurosonological techniques is of crucial importance. After briefly reviewing TCD, TCDI and PMD techniques, classical features are summarized and recent developments in the clinical neurosonology applications with specific interest in the neurovascular disorders. Practical perspectives of ultrasound evaluation of intracranial arterial status in various neurovascular diseases including sickle cell vasculopathy and vasospasm are reviewed in detail. Pearls on the neurosonological monitoring of acute ischemic stroke and increased intracranial pressure increase is provided. Standards of cerebral microembolism detection, right to left shunts diagnosis and cerebral autoregulation assessment are discussed methodologically. Future perspectives of therapeutic neurosonology including sonothrombolysis, microbubble-ultrasound-mediated gene and drug delivery into the brain, and alteration of the brain-blood barrier permeability are summarized. Suitable with future medicine, neurosonology brings imaging to the bedside, which enables the treating physician to monitor a given intervention in real time. A non-invasive neurosonology-guided treatment of various diseases could be possible in the near future. The first and foremost step in gaining mastery in this very fruitful field is beginning to use it.

  15. Sums of Generalized Harmonic Series

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 20; Issue 9. Sums of Generalized Harmonic Series: For Kids from Five to Fifteen. Zurab Silagadze. General Article Volume 20 Issue 9 September 2015 pp 822-843 ... Keywords. Riemann zeta function; integral representation; Basel problem.

  16. General principles of carotid Doppler ultrasonography

    Directory of Open Access Journals (Sweden)

    Whal Lee

    2014-01-01

    Full Text Available

    Carotid Doppler ultrasonography is a popular tool for evaluating atherosclerosis of the carotid artery. Its two-dimensional gray scale can be used for measuring the intima-media thickness, which is very good biomarker for atherosclerosis and can aid in plaque characterization. The plaque morphology is related to the risk of stroke. The ulceration of plaque is also known as one of the strong predictors of future embolic event risk. Color Doppler ultrasonography and pulse Doppler ultrasonography have been used for detecting carotid artery stenosis. Doppler ultrasonography has unique physical properties. The operator should be familiar with the physics and other parameters of Doppler ultrasonography to perform optimal Doppler ultrasonography studies.

  17. Classification of human activity on water through micro-Dopplers using deep convolutional neural networks

    Science.gov (United States)

    Kim, Youngwook; Moon, Taesup

    2016-05-01

    Detecting humans and classifying their activities on the water has significant applications for surveillance, border patrols, and rescue operations. When humans are illuminated by radar signal, they produce micro-Doppler signatures due to moving limbs. There has been a number of research into recognizing humans on land by their unique micro-Doppler signatures, but there is scant research into detecting humans on water. In this study, we investigate the micro-Doppler signatures of humans on water, including a swimming person, a swimming person pulling a floating object, and a rowing person in a small boat. The measured swimming styles were free stroke, backstroke, and breaststroke. Each activity was observed to have a unique micro-Doppler signature. Human activities were classified based on their micro-Doppler signatures. For the classification, we propose to apply deep convolutional neural networks (DCNN), a powerful deep learning technique. Rather than using conventional supervised learning that relies on handcrafted features, we present an alternative deep learning approach. We apply the DCNN, one of the most successful deep learning algorithms for image recognition, directly to a raw micro-Doppler spectrogram of humans on the water. Without extracting any explicit features from the micro-Dopplers, the DCNN can learn the necessary features and build classification boundaries using the training data. We show that the DCNN can achieve accuracy of more than 87.8% for activity classification using 5- fold cross validation.

  18. Postoperative doppler evaluation of liver transplants

    Directory of Open Access Journals (Sweden)

    Rupan Sanyal

    2014-01-01

    Full Text Available Doppler ultrasound plays an important role in the postoperative management of hepatic transplantation, by enabling early detection and treatment of various vascular complications. This article describes the normal Doppler findings following liver transplantation and reviews the imaging appearances of various vascular complications associated with it. The article also discusses transient waveform abnormalities, often seen on a post-transplant Doppler examination, and the importance of differentiating them from findings suggestive of ominous vascular complications.

  19. Postoperative doppler evaluation of liver transplants

    Science.gov (United States)

    Sanyal, Rupan; Zarzour, Jessica G; Ganeshan, Dakshina M; Bhargava, Puneet; Lall, Chandana G; Little, Mark D

    2014-01-01

    Doppler ultrasound plays an important role in the postoperative management of hepatic transplantation, by enabling early detection and treatment of various vascular complications. This article describes the normal Doppler findings following liver transplantation and reviews the imaging appearances of various vascular complications associated with it. The article also discusses transient waveform abnormalities, often seen on a post-transplant Doppler examination, and the importance of differentiating them from findings suggestive of ominous vascular complications. PMID:25489129

  20. Tides and tidal harmonics at Umbharat, Gujarat

    Digital Repository Service at National Institute of Oceanography (India)

    Suryanarayana, A.; Swamy, G.N.

    A part of the data on tides recorded at Machiwada near Umbharat, Gulf of Cambay during April 1978 was subjected to harmonic analysis following the Admiralty procedure. The general tidal characteristics and the value of four major harmonic...