Rebolini, Elisa
2015-01-01
We present a range-separated linear-response time-dependent density-functional theory (TDDFT) which combines a density-functional approximation for the short-range response kernel and a frequency-dependent second-order Bethe-Salpeter approximation for the long-range response kernel. This approach goes beyond the adiabatic approximation usually used in linear-response TDDFT and aims at improving the accuracy of calculations of electronic excitation energies of molecular systems. A detailed derivation of the frequency-dependent second-order Bethe-Salpeter correlation kernel is given using many-body Green-function theory. Preliminary tests of this range-separated TDDFT method are presented for the calculation of excitation energies of four small molecules: N2, CO2, H2CO, and C2H4. The results suggest that the addition of the long-range second-order Bethe-Salpeter correlation kernel overall slightly improves the excitation energies.
Active laser ranging with frequency transfer using frequency comb
Energy Technology Data Exchange (ETDEWEB)
Zhang, Hongyuan; Wei, Haoyun; Yang, Honglei; Li, Yan, E-mail: liyan@mail.tsinghua.edu.cn [State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instruments, Tsinghua University, Beijing 100084 (China)
2016-05-02
A comb-based active laser ranging scheme is proposed for enhanced distance resolution and a common time standard for the entire system. Three frequency combs with different repetition rates are used as light sources at the two ends where the distance is measured. Pulse positions are determined through asynchronous optical sampling and type II second harmonic generation. Results show that the system achieves a maximum residual of 379.6 nm and a standard deviation of 92.9 nm with 2000 averages over 23.6 m. Moreover, as for the frequency transfer, an atom clock and an adjustable signal generator, synchronized to the atom clock, are used as time standards for the two ends to appraise the frequency deviation introduced by the proposed system. The system achieves a residual fractional deviation of 1.3 × 10{sup −16} for 1 s, allowing precise frequency transfer between the two clocks at the two ends.
Frequency ranges and attenuation of macroseismic effects
Tosi, Patrizia; De Rubeis, Valerio; Sbarra, Paola
2017-09-01
Macroseismic intensity is assessed on the basis of the effects caused by an earthquake. These effects reflect the expression of both the intensity and frequency of the ground motion, thus complicating prediction equation modelling. Here we analysed data of several macroseismic transitory effects caused by recent Italian earthquakes in order to study their attenuation as a function of magnitude and hypocentral distance and to obtain a specific prediction equation, of simple functional form, that could be applied to each of the effects under analysis. We found that the different attenuation behaviours could be clearly defined by the values of the specially formulated magnitude-distance scaling ratio (S), thus allowing to group the effects on the basis of the S value. The oscillation of hanging objects and liquids, together with the feeling of dizziness, were separated from most other variables, such as the effects of the earthquake on small objects, china and windows, which were caused by a vibration of higher frequency. Besides, the greater value of S, associated with the perception of the seismic sound, explained the peculiarity of this phenomenon. As a result, we recognized the frequency range associated with each effect through comparisons with the ground motion prediction equations and, in particular, with the 5 per cent damped horizontal response spectra. Here we show the importance of appropriately selecting the diagnostic elements to be used for intensity assessment in order to improve the correlation with ground motion.
On the validity range of piston theory
CSIR Research Space (South Africa)
Meijer, M-C
2015-06-01
Full Text Available as the analytical validity range for linear piston theory as based in potential flows. The range of validity of single-term nonlinear extensions to the linear potential equation into the transonic and hypersonic regions is treated. A brief review of the development...
Grounded theory: building a middle-range theory in nursing
Directory of Open Access Journals (Sweden)
Maria João Fernandes
2015-03-01
Full Text Available The development of nursing as a discipline results from a boom of investigations underway for nearly a century, and of the construction of theories that have arisen during the 1950’s, with greater relevance since the 1960’s. Giving continuation to the production of knowledge in nursing and seeking to contribute to the increase in the number of explanatory theories of the functional content of nurses, there is interest in answering the question: how can a middle-range theory in nursing be built that explains the nurse-elderly interaction in a successful aging process? As well, we address the goal of describing the process of building a middle-range theory in nursing. Middle-range theory refers to a qualitative paradigm study of inductive thinking, developed in the context of primary health care. The information was collected through participant observation and interviews. Method of analysis grounded theory by Corbin and Strauss(1 was followed, utilizing the triangulation of data and theoretical sampling. Grounded theory has become a method of analysis which facilitates the understanding and explanation of the phenomenon under study. By making clear the nature and process of the nurse-elderly interaction in the selected context and within the context of successful aging, a middle-range theory proposal emerged.
Characteristics of different frequency ranges in scanning electron microscope images
Energy Technology Data Exchange (ETDEWEB)
Sim, K. S., E-mail: kssim@mmu.edu.my; Nia, M. E.; Tan, T. L.; Tso, C. P.; Ee, C. S. [Faculty of Engineering and Technology, Multimedia University, 75450 Melaka (Malaysia)
2015-07-22
We demonstrate a new approach to characterize the frequency range in general scanning electron microscope (SEM) images. First, pure frequency images are generated from low frequency to high frequency, and then, the magnification of each type of frequency image is implemented. By comparing the edge percentage of the SEM image to the self-generated frequency images, we can define the frequency ranges of the SEM images. Characterization of frequency ranges of SEM images benefits further processing and analysis of those SEM images, such as in noise filtering and contrast enhancement.
Middle Range Theory: A Perspective on Development and Use.
Liehr, Patricia; Smith, Mary Jane
This replication and critique addresses ongoing development and use of middle range theory since considering this body of nursing knowledge 18 years ago. Middle range theory is appreciated as essential to the structure of nursing knowledge. Nine middle range theories that demonstrate ongoing use by the theory authors are analyzed using the criteria of theory name, theory generation, disciplinary perspective, theory model, practice use and research use. Critique conclusions indicate the importance of staying with the theory over time, naming and development consistent with the disciplinary perspective, movement to an empirical level, and bringing middle range theory to the interdisciplinary table.
Veysman, M; Winkel, M; Reinholz, H
2016-01-01
Fundamental properties of warm dense matter are described by the dielectric function, which gives access to the frequency-dependent electrical conductivity, absorption, emission and scattering of radiation, charged particles stopping and further macroscopic properties. Different approaches to the dielectric function and the related dynamical collision frequency are compared in a wide frequency range. The high-frequency limit describing inverse bremsstrahlung and the low-frequency limit of the dc conductivity are considered. Sum rules and Kramers-Kronig relation are checked for the generalized linear response theory and the standard approach following kinetic theory. The results are discussed in application to aluminum, xenon and argon plasmas.
Discrete-time model reduction in limited frequency ranges
Horta, Lucas G.; Juang, Jer-Nan; Longman, Richard W.
1991-01-01
A mathematical formulation for model reduction of discrete time systems such that the reduced order model represents the system in a particular frequency range is discussed. The algorithm transforms the full order system into balanced coordinates using frequency weighted discrete controllability and observability grammians. In this form a criterion is derived to guide truncation of states based on their contribution to the frequency range of interest. Minimization of the criterion is accomplished without need for numerical optimization. Balancing requires the computation of discrete frequency weighted grammians. Close form solutions for the computation of frequency weighted grammians are developed. Numerical examples are discussed to demonstrate the algorithm.
Long range ultra-high frequency (UHF) radio frequency identification (RFID) antenna design
Reynolds, Nathan D.
There is an ever-increasing demand for radio frequency identification (RFID) tags that are passive, long range, and mountable on multiple surfaces. Currently, RFID technology is utilized in numerous applications such as supply chain management, access control, and public transportation. With the combination of sensory systems in recent years, the applications of RFID technology have been extended beyond tracking and identifying. This extension includes applications such as environmental monitoring and healthcare applications. The available sensory systems usually operate in the medium or high frequency bands and have a low read range. However, the range limitations of these systems are being overcome by the development of RFID sensors focused on utilizing tags in the ultra-high frequency (UHF) band. Generally, RFID tags have to be mounted to the object that is being identified. Often the objects requiring identification are metallic. The inherent properties of metallic objects have substantial effects on nearby electromagnetic radiation; therefore, the operation of the tag antenna is affected when mounted on a metallic surface. This outlines one of the most challenging problems for RFID systems today: the optimization of tag antenna performance in a complex environment. In this research, a novel UHF RFID tag antenna, which has a low profile, long range, and is mountable on metallic surfaces, is designed analytically and simulated using a 3-D electromagnetic simulator, ANSYS HFSS. A microstrip patch antenna is selected as the antenna structure, as patch antennas are low profile and suitable for mounting on metallic surfaces. Matching and theoretical models of the microstrip patch antenna are investigated. Once matching and theory of a microstrip patch antenna is thoroughly understood, a unique design technique using electromagnetic band gap (EBG) structures is explored. This research shows that the utilization of an EBG structure in the patch antenna design yields
Energy based correlation criteria in the mid-frequency range
Biedermann, J.; Winter, R.; Wandel, M.; Böswald, M.
2017-07-01
Aircraft structures are characterized by their lightweight design. As such, they are prone to vibrations. Numerical models based on the Finite Element Method often show significant deviations when the mid-frequency range is considered, where strong interaction between vibrations and acoustics is present. Model validation based on experimental modal data is often not possible due to the high modal density that aircraft fuselage structures exhibit in this frequency range. Classical correlation criteria like the Modal Assurance Criterion require mode shapes and can therefore not be applied. Other correlation criteria using frequency response data, such as the Frequency Domain Assurance Criterion, are highly sensitive to even small structural modifications and fail to indicated the correlation between test and analysis data in the mid-frequency range. Nevertheless, validated numerical models for the mid- to high-frequency ranges are a prerequisite for acoustic comfort predictions of aircraft cabin. This paper presents a new method for the correlation of response data from test and analysis in the mid-frequency range to support model validation in the mid-frequency range and to enable the usage of finite element models in this frequency range. The method is validated on a stiffened cylindrical shell structure, which represents a scale-model of an aircraft fuselage. The correlation criterion presented here is inspired by Statistical Energy Analysis and is based on kinetic energies integrated over frequency bands and spatially integrated over surface areas of the structure. The objective is to indicate frequency bands where the finite element model needs to be adjusted to better match with experimental observations and to locate the areas where these adjustments should be applied.
Predicting Achievable Fundamental Frequency Ranges in Vocalization Across Species.
Directory of Open Access Journals (Sweden)
Ingo Titze
2016-06-01
Full Text Available Vocal folds are used as sound sources in various species, but it is unknown how vocal fold morphologies are optimized for different acoustic objectives. Here we identify two main variables affecting range of vocal fold vibration frequency, namely vocal fold elongation and tissue fiber stress. A simple vibrating string model is used to predict fundamental frequency ranges across species of different vocal fold sizes. While average fundamental frequency is predominantly determined by vocal fold length (larynx size, range of fundamental frequency is facilitated by (1 laryngeal muscles that control elongation and by (2 nonlinearity in tissue fiber tension. One adaptation that would increase fundamental frequency range is greater freedom in joint rotation or gliding of two cartilages (thyroid and cricoid, so that vocal fold length change is maximized. Alternatively, tissue layers can develop to bear a disproportionate fiber tension (i.e., a ligament with high density collagen fibers, increasing the fundamental frequency range and thereby vocal versatility. The range of fundamental frequency across species is thus not simply one-dimensional, but can be conceptualized as the dependent variable in a multi-dimensional morphospace. In humans, this could allow for variations that could be clinically important for voice therapy and vocal fold repair. Alternative solutions could also have importance in vocal training for singing and other highly-skilled vocalizations.
Inexpensive automatic ranging for digital voltmeters and frequency counters
Roller, R. F.
1970-01-01
Seven integrated circuits incorporated at very low cost into frequency counters and digital voltmeters performing a voltage-to-frequency conversion permit automatic range changing. Extra decades are switched into and out of the counting chain as a function of the counter during the previous counting period.
Chaotic Colpitts Oscillator for the Ultrahigh Frequency Range
DEFF Research Database (Denmark)
Tamasevicius, A.; Mykolaitis, G.; Bumeliene, S.
2006-01-01
. Simulations indicate that chaotic oscillations observed experimentally at higher frequencies, e.g., at about 1000MHz are caused by parasites, like wiring inductances, loss resistance appearing due to skin effect, and collector-emitter capacitance of the transistor. Reliable and reproducible chaos can......PSpice simulation and experimental results demonstrating chaotic performance of the Colpitts oscillator in the ultrahigh frequency (300–1000 MHz) range are presented.Various combinations of the resonance tank parameters are considered to achieve a fundamental frequency as high as possible...... be generated at fundamental frequencies up to about 500MHz with the single-stage Colpitts oscillator using the microwave 9 GHz bipolar junction transistors....
Bearing fault detection in the acoustic emission frequency range
Tavakoli, Massoud S.
The effectiveness of using bearing fault detection in the acoustic-emission frequency range is demonstrated using a vertical milling machine as the testbed. The experimental testbed is monitored by an accelerometer and an acoustic emission sensor, and the signals are demodulated by rms enveloping and then fast-Fourier-transformed. The analytical computation of the defect characteristic frequency is explained, and the time histories are given of the enveloped signal and its spectrum. The method is shown to be useful for extracting the repetition rate of the repetitive component of the general signal, and the signal generated by the bearing defect is identified in the frequency ranges of mechanical vibration and acoustic emission. The signal in the acoustic-emission frequency range is shown to be helpful for detecting bearing defects because it not affected by repetitive mechanical noise.
Cross-Linguistic Differences in Bilinguals' Fundamental Frequency Ranges
Ordin, Mikhail; Mennen, Ineke
2017-01-01
Purpose: We investigated cross-linguistic differences in fundamental frequency range (FFR) in Welsh-English bilingual speech. This is the first study that reports gender-specific behavior in switching FFRs across languages in bilingual speech. Method: FFR was conceptualized as a behavioral pattern using measures of span (range of fundamental…
Middle range theory evaluation: bridging the theory-practice gap ...
African Journals Online (AJOL)
The importance underlying the practice of nursing education must continue to be explored through theories to bring about refinement of educational strategies for nursing discipline. The involvement of students learning using this process will help create learning values that serve to retain inquisitive and reflective nursing ...
The middle-range theory of nursing intellectual capital.
Covell, Christine L
2008-07-01
This paper is a report of the development of the middle-range theory of nursing intellectual capital. Rising healthcare costs and advances in technology have contributed to the need for better understanding of the influence of nurses' knowledge, skills and experience on patient and organizational outcomes. The middle-range nursing intellectual capital theory was developed using the strategies of concept and theory derivation. The principles of research synthesis were used to provide empirical support for the propositions of the theory. The middle-range nursing intellectual capital theory was derived from intellectual capital theory to make it relevant and applicable to a specific aspect of nursing, continuing professional development. It proposes that the nursing knowledge available in healthcare organizations is influenced by variables within the work environment, and influences patient and organizational outcomes. The middle-range nursing intellectual capital theory should be tested in different healthcare systems and in different settings and countries to determine its effectiveness in guiding research.
Toward a Middle-Range Theory of Weight Management.
Pickett, Stephanie; Peters, Rosalind M; Jarosz, Patricia A
2014-07-01
The authors of this paper present the middle-range theory of weight management that focuses on cultural, environmental, and psychosocial factors that influence behaviors needed for weight control. The theory of weight management was developed deductively from Orem's theory of self-care, a constituent theory within the broader self-care deficit nursing theory and from research literature. Linkages between the conceptual and middle-range theory concepts are illustrated using a substruction model. The development of the theory of weight management serves to build nursing science by integrating extant nursing theory and empirical knowledge. This theory may help predict weight management in populations at risk for obesity-related disorders. © The Author(s) 2014.
Experimental Limits on Gravitational Waves in the MHz frequency Range
Energy Technology Data Exchange (ETDEWEB)
Lanza, Robert Jr. [Univ. of Chicago, IL (United States)
2015-03-01
This thesis presents the results of a search for gravitational waves in the 1-11MHz frequency range using dual power-recycled Michelson laser interferometers at Fermi National Accelerator Laboratory. An unprecedented level of sensitivity to gravitational waves in this frequency range has been achieved by cross-correlating the output fluctuations of two identical and colocated 40m long interferometers. This technique produces sensitivities better than two orders of magnitude below the quantum shot-noise limit, within integration times of less than 1 hour. 95% confidence level upper limits are placed on the strain amplitude of MHz frequency gravitational waves at the 10^{-21} Hz^{-1/2} level, constituting the best direct limits to date at these frequencies. For gravitational wave power distributed over this frequency range, a broadband upper limit of 2.4 x 10^{-21}Hz^{-1/2} at 95% confidence level is also obtained. This thesis covers the detector technology, the commissioning and calibration of the instrument, the statistical data analysis, and the gravitational wave limit results. Particular attention is paid to the end-to-end calibration of the instrument’s sensitivity to differential arm length motion, and so to gravitational wave strain. A detailed statistical analysis of the data is presented as well.
Dielectric characterization of materials at microwave frequency range
Directory of Open Access Journals (Sweden)
J. de los Santos
2003-01-01
Full Text Available In this study a coaxial line was used to connect a microwave-frequency Network Analyzer and a base moving sample holder for dielectric characterization of ferroelectric materials in the microwave range. The main innovation of the technique is the introduction of a special sample holder that eliminates the air gap effect by pressing sample using a fine pressure system control. The device was preliminary tested with alumina (Al2O3 ceramics and validated up to 2 GHz. Dielectric measurements of lanthanum and manganese modified lead titanate (PLTM ceramics were carried out in order to evaluate the technique for a high permittivity material in the microwave range. Results showed that such method is very useful for materials with high dielectric permittivities, which is generally a limiting factor of other techniques in the frequency range from 50 MHz to 2 GHz.
Long-range interactions in lattice field theory
Energy Technology Data Exchange (ETDEWEB)
Rabin, J.M.
1981-06-01
Lattice quantum field theories containing fermions can be formulated in a chirally invariant way provided long-range interactions are introduced. It is established that in weak-coupling perturbation theory such a lattice theory is renormalizable when the corresponding continuum theory is, and that the continuum theory is indeed recovered in the perturbative continuum limit. In the strong-coupling limit of these theories one is led to study an effective Hamiltonian describing a Heisenberg antiferromagnet with long-range interactions. Block-spin renormalization group methods are used to find a critical rate of falloff of the interactions, approximately as inverse distance squared, which separates a nearest-neighbor-antiferromagnetic phase from a phase displaying identifiable long-range effects. A duality-type symmetry is present in some block-spin calculations.
Tunable and Broadband Differential Phase Sections in Terahertz Frequency Range
Kosiak, O. S.; Bezborodov, V. I.; Kuleshov, Ye. M.; Nesterov, P. K.
2016-12-01
Purpose: Studying the quasioptical tunable and broadband differential phase section (DPS) consisting of several birefringent elements (BE) on the basis of form birefringence effect. Design/methodology/approach: Using the polarization scattering matrix method, the impact of the mutual rotation axis of anisotropy of several BE by the amount of phase shift and the position of the plane of anisotropy of resulting DPS is considered. Findings: The DPS tunable in a wide range are shown to be possibly implemented in the case of quarter- wave DPS of two, and in the case of half-wave DPS of three, identical non-tunable BE. The analysis has shown to the possibility of creating a broadband quarter-wave and half-wave DPS. Conclusions: Experimental research has confirmed the possibility of constructing a tunable and broadband DPS. On this basis, tunable and broadband polarization converters, rotators of polarization plane, polarization phase shifters and frequency shifters in the terahertz frequency range can be created.
Optical properties of human nails in THz frequency range
Guseva, Victoria A.; Gusev, Sviatoslav I.; Demchenko, Petr S.; Sedykh, Egor A.; Khodzitsky, Mikhail K.
2017-03-01
This work is devoted to investigation of optical properties (dispersion of refractive index, permittivity and absorption coefficient) of human nails in THz frequency range. These data were obtained by THz time-domain spectroscopy (TDS) technique in transmission mode. These results may be used to develop non-invasive technique of human pathologies control using nail as reference sample in reflection mode of THz TDS.
Range and Frequency of Africanized Honey Bees in California (USA.
Directory of Open Access Journals (Sweden)
Yoshiaki Kono
Full Text Available Africanized honey bees entered California in 1994 but few accounts of their northward expansion or their frequency relative to European honey bees have been published. We used mitochondrial markers and morphometric analyses to determine the prevalence of Africanized honeybees in San Diego County and their current northward progress in California west of the Sierra Nevada crest. The northernmost African mitotypes detected were approximately 40 km south of Sacramento in California's central valley. In San Diego County, 65% of foraging honey bee workers carry African mitochondria and the estimated percentage of Africanized workers using morphological measurements is similar (61%. There was no correlation between mitotype and morphology in San Diego County suggesting Africanized bees result from bidirectional hybridization. Seventy percent of feral hives, but only 13% of managed hives, sampled in San Diego County carried the African mitotype indicating that a large fraction of foraging workers in both urban and rural San Diego County are feral. We also found a single nucleotide polymorphism at the DNA barcode locus COI that distinguishes European and African mitotypes. The utility of this marker was confirmed using 401 georeferenced honey bee sequences from the worldwide Barcode of Life Database. Future censuses can determine whether the current range of the Africanized form is stable, patterns of introgression at nuclear loci, and the environmental factors that may limit the northern range of the Africanized honey bee.
Flight nursing expertise: towards a middle-range theory
Reimer, Andrew P.; Moore, Shirley M.
2010-01-01
Aim This paper presents a middle-range Theory of Flight Nursing Expertise. Background Rotary-wing (helicopter) medical transport has grown rapidly in the USA since its introduction, particularly during the past 5 years. Patients once considered too sick to transport are now being transported more frequently and over longer distances. Many limitations are imposed by the air medical transport environment and these require nurses to alter their practice. Data sources A literature search was conducted using Pubmed, Medline, CINAHL, secondary referencing and an Internet search from 1960 to 2008 for studies related to the focal concepts in flight nursing. Discussion The middle-range Theory of Flight Nursing Expertise is composed of nine concepts (experience, training, transport environment of care, psychomotor skills, flight nursing knowledge, cue recognition, pattern recognition, decision-making and action) and their relationships. Five propositions describe the relationships between those concepts and how they apply to flight nursing expertise. Implications for nursing After empirical testing, this theory may be a useful tool to assist novice flight nurses to attain the skills necessary to provide safe and competent care more efficiently, and may aid in designing curricula and programmes of research. Conclusion Research is needed to determine the usefulness of this theory in both rotary and fixed-wing medical transport settings, and to examine the similarities and differences related to expertise needed for different flight nurse team compositions. Curriculum and training innovations can result from increased understanding of the concepts and relationships proposed in this theory. PMID:20337803
Stepped-frequency radar sensors theory, analysis and design
Nguyen, Cam
2016-01-01
This book presents the theory, analysis and design of microwave stepped-frequency radar sensors. Stepped-frequency radar sensors are attractive for various sensing applications that require fine resolution. The book consists of five chapters. The first chapter describes the fundamentals of radar sensors including applications followed by a review of ultra-wideband pulsed, frequency-modulated continuous-wave (FMCW), and stepped-frequency radar sensors. The second chapter discusses a general analysis of radar sensors including wave propagation in media and scattering on targets, as well as the radar equation. The third chapter addresses the analysis of stepped-frequency radar sensors including their principles and design parameters. Chapter 4 presents the development of two stepped-frequency radar sensors at microwave and millimeter-wave frequencies based on microwave integrated circuits (MICs), microwave monolithic integrated circuits (MMICs) and printed-circuit antennas, and discusses their signal processing....
Middle-Range Theory: Coping and Adaptation with Active Aging.
Salazar-Barajas, Martha Elba; Salazar-González, Bertha Cecilia; Gallegos-Cabriales, Esther Carlota
2017-10-01
Various disciplines focus on a multiplicity of aspects of aging: lifestyles, personal biological factors, psychological conditions, health conditions, physical environment, and social and economic factors. The aforementioned are all related to the determinants of active aging. The aim is to describe the development of a middle-range theory based on coping and adaptation with active aging. Concepts and relationships derived from Roy's model of adaptation are included. The proposed concepts are hope, health habits, coping with aging, social relations, and active aging.
A wide-frequency-range air-jet shaker
Herr, Robert W
1957-01-01
This paper presents a description of a simple air-jet shaker. Its force can be calibrated statically and appears to be constant with frequency. It is relatively easy to use, and it has essentially massless characteristics. This shaker is applied to define the unstable branch of a frequency-response curve obtained for a nonlinear spring with a single degree of freedom.
Self-consistent many-body perturbation theory in range-separated density-functional theory
DEFF Research Database (Denmark)
Fromager, Emmanuel; Jensen, Hans Jørgen Aagaard
2008-01-01
In many cases, density-functional theory (DFT) with current standard approximate functionals offers a relatively accurate and computationally cheap description of the short-range dynamic electron correlation effects. However, in general, standard DFT does not treat the dispersion interaction...... effects adequately which, on the other hand, can be described by many-body perturbation theory MBPT. It is therefore of interest to develop a hybrid model which combines the best of both the MBPT and DFT approaches. This can be achieved by splitting the two-electron interaction into long-range and short...
Intensity autocorrelation measurements of frequency combs in the terahertz range
Benea-Chelmus, Ileana-Cristina; Rösch, Markus; Scalari, Giacomo; Beck, Mattias; Faist, Jérôme
2017-09-01
We report on direct measurements of the emission character of quantum cascade laser based frequency combs, using intensity autocorrelation. Our implementation is based on fast electro-optic sampling, with a detection spectral bandwidth matching the emission bandwidth of the comb laser, around 2.5 THz. We find the output of these frequency combs to be continuous even in the locked regime, but accompanied by a strong intensity modulation. Moreover, with our record temporal resolution of only few hundreds of femtoseconds, we can resolve correlated intensity modulation occurring on time scales as short as the gain recovery time, about 4 ps. By direct comparison with pulsed terahertz light originating from a photoconductive emitter, we demonstrate the peculiar emission pattern of these lasers. The measurement technique is self-referenced and ultrafast, and requires no reconstruction. It will be of significant importance in future measurements of ultrashort pulses from quantum cascade lasers.
Duan, Cun-li; Zhang, Su-juan; He, Jiang-long
2011-06-01
Q-switched Short pulse laser has been widely applied in many fields, such as optical ranging, remote sensing, communications, nonlinear optics and spectroscopy etc. Q-switched Nd3+: YAG laser, with its high thermal conductivity and resistance to damage threshold, longer energy levels were generally used especially. Second harmonics generation was usually obtained through optical nonlinear effects in crystal. To the frequency doubling technology, poor conversion efficiency and multi-output frequency are the main problems. Researchers focus more on phase and group velocity matching induced by nonlinear effects, but pays less attention on theoretical modeling and numerical calculation of factors affecting frequency doubling of pulsed laser. In this article, nonlinear effects of double frequency crystals in Q-switched Nd3+: YAG laser was first analyzed in theory, then we deduced the relation expressions between factors affecting the efficiency of frequency doubling( thickness of frequency doubling crystal, cross section area of incident beam, power of the fundamental field, phase matching of incidence light)and double frequency efficiency. Secondly, taken KTP Crystal for example; numerical results and theirs' corresponding curves on these relation expressions was calculated and drawn with MATLAB software. These findings can be used for processing the specific requests of frequency doubling crystal. Finally, Theory modeling and numerical calculation were tested in experiment. The experiment results are in good agreement with those obtained in theory.
Interactive Theory of Breastfeeding: creation and application of a middle-range theory.
Primo, Cândida Caniçali; Brandão, Marcos Antônio Gomes
2017-01-01
To describe a breastfeeding theory based on King's Conceptual System. Theoretical study that used analysis of concept, assertion synthesis, and derivation of theory for the creation of a new theory. King's system components were associated with elements of the breastfeeding process and a middle-range theory was created, which describes, explains, predicts, and prescribes breastfeeding by analyzing factors that precede and affect it, as well as their consequences on the breastfeeding process. The Breastfeeding Interactive Model is abstract enough to be applied in different social, cultural, political, and economic contexts, because it conceptualizes breastfeeding in systemic, dynamic, and procedural aspects. Based on a conceptual model of nursing, it contributes to the scientific construction of the subject; however it can also potentially be applied by other professionals involved in breastfeeding assistance.
Electron scattering from neon via effective range theory
Energy Technology Data Exchange (ETDEWEB)
Fedus, Kamil, E-mail: kamil@fizyka.umk.pl [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Torun (Poland)
2014-07-01
Elastic cross-sections for electron scattering on neon from 0 energy up to 16 eV are analyzed by an analytical approach to the modified effective range theory (MERT). It is shown that energy and angular variations of elastic differential, integral and momentum transfer cross sections can be accurately parameterized by six MERT coefficients up to the energy threshold for the first Feshbach resonance. MERT parameters are determined empirically by numerical comparison with large collection of available experimental data of elastic total (integral) cross-sections. The present analysis is validated against numerous electron beams and swarm experiments. The comparison of derived MERT parameters with those found for other noble gases, helium, argon and krypton, is done. The derived scattering length (for the s-partial wave) in neon, 0.227a0, agrees well with recent theories; it is small but, differently from Ar and Kr, still positive. Analogue parameters for the p-wave and the d-wave are negative and positive respectively for all the four gases compared. (author)
Building a Middle-Range Theory of Adaptive Spirituality.
Dobratz, Marjorie C
2016-04-01
The purpose of this article is to describe a Roy adaptation model based- research abstraction, the findings of which were synthesized into a middle-range theory (MRT) of adaptive spirituality. The published literature yielded 21 empirical studies that investigated religion/spirituality. Quantitative results supported the influence of spirituality on quality of life, psychosocial adjustment, well-being, adaptive coping, and the self-concept mode. Qualitative findings showed the importance of spiritual expressions, values, and beliefs in adapting to chronic illness, bereavement, death, and other life transitions. These findings were abstracted into six theoretical statements, a conceptual definition of adaptive spirituality, and three hypotheses for future testing. © The Author(s) 2016.
Effective field theory for long-range properties of bottomonium
Krein, Gastão
2017-03-01
In this communication we present selected results from a recent study [N. Brambilla, G. Krein, J. Tarrús Castellà and A. Vairo, Phys. Rev. D 93, 054002 (2016)] of long-range properties of bottomonium. An analytical expression for the chromopolarizability of 1S bottomonium states is derived within the framework of potential nonrelativistic QCD (pNRQCD). Next, after integrating out the ultrasoft scale associated with the binding energy of bottomonium, the QCD trace anomaly is used to obtain the two-pion production amplitude for the chromopolarizability operator and the result is matched to a chiral effective field theory having bottomonium states and pions as degrees of freedom. We present results for the leading chiral logarithm correction to the mass of the 1S bottomonium and the van der Waals potential between two bottomonium states.
Range-based covariance estimation using high-frequency data: The realized co-range
K. Bannouh (Karim); D.J.C. van Dijk (Dick); M.P.E. Martens (Martin)
2008-01-01
textabstractWe introduce the realized co-range, utilizing intraday high-low price ranges to estimate asset return covariances. Using simulations we find that for plausible levels of bid-ask bounce and infrequent and non-synchronous trading the realized co-range improves upon the realized covariance,
Orbit-averaged quasilinear diffusion operator in the ion-cyclotron range of frequencies
Belmondo, V.; Bilato, R.; Brambilla, M.; Maj, O.
2010-11-01
The absorption of radio-frequency waves in the ion-cyclotron range of frequencies (ICRF) in fusion plasmas is adequately described in the frame of the quasilinear theory. A peculiarity of ICRF heating is to increase the fraction of trapped particles, whose the guiding-center trajectories are typically banana orbits with finite width. One possible way to properly account for the effects due to the finite-width orbits is provided by the orbit-averaged quasilinear theory. Here, we propose a routine for the evaluation of the orbit-averaged quasilinear diffusion tensor, given the the wave fields from the full wave code TORIC. Particular care is taken in the evaluation of the contribution of each wave-particle resonance as well as for the transition between the two regimes of correlated and uncorrelated resonances along the orbit. We discuss the quasilinear diffusion coefficient thus obtained and validate the result by comparing the power deposition profile computed from the orbit-averaged quasilinear operator with the one determined by TORIC. For future applications, a novel algorithm for the calculation of the corresponding Monte Carlo operators is also presented.
Short-Range Correlation Models in Electronic Structure Theory
Goldey, Matthew Bryant
Correlation methods within electronic structure theory focus on recovering the exact electron-electron interaction from the mean-field reference. For most chemical systems, including dynamic correlation, the correlation of the movement of electrons proves to be sufficient, yet exact methods for capturing dynamic correlation inherently scale polynomially with system size despite the locality of the electron cusp. This work explores a new family of methods for enhancing the locality of dynamic correlation methodologies with an aim toward improving accuracy and scalability. The introduction of range-separation into ab initio wavefunction methods produces short-range correlation methodologies, which can be supplemented with much faster approximate methods for long-range interactions. First, I examine attenuation of second-order Moller-Plesset perturbation theory (MP2) in the aug-cc-pVDZ basis. MP2 treats electron correlation at low computational cost, but suffers from basis set superposition error (BSSE) and fundamental inaccuracies in long-range contributions. The cost differential between complete basis set (CBS) and small basis MP2 restricts system sizes where BSSE can be removed. Range-separation of MP2 could yield more tractable and/or accurate forms for short- and long-range correlation. Retaining only short-range contributions proves to be effective for MP2 in the small aug-cc-pVDZ (aDZ) basis. Using one range-separation parameter within either the complementary error function (erfc) or a sum of two error functions (terfc), superior behavior is obtained versus both MP2/aDZ and MP2/CBS for inter- and intra-molecular test sets. Attenuation of the long-range helps to cancel both BSSE and intrinsic MP2 errors. Direct scaling of the MP2 correlation energy (SMP2) proves useful as well. The resulting SMP2/aDZ, MP2(erfc, aDZ), and MP2(terfc, aDZ) methods perform far better than MP2/aDZ across systems with hydrogen-bonding, dispersion, and mixed interactions at a
Alternative theories of atmospheric telecommunications and low-frequency fluctuations
Frederiksen, Jorgen S.; Webster, Peter J.
1988-08-01
Observational studies have revealed a rich low-frequency structure in the atmosphere. A review of the theories, observations, and model studies of this low-frequency atmospheric variability is presented. On time scales of weeks or longer the atmosphere appears to possess distinct oscillatory behavior in well-defined and persistent "centers of action." This behavior is also an endemic feature of surrogate atmospheric data sets emerging from experiments with complicated climate models. Many theories have attempted to determine the dominant physical processes responsible for the low-frequency variance but have usually failed when compared carefully with observations. For example, simple linear steady state and Rossby wave dispersion theories have been used in an attempt to explain the observed global response to low-latitude perturbation. However, the observed structures of mature anomalies are often quite distinct from the vertical structures of disturbances predicted in these theories. Also, in general circulation and model studies, the sign of the nonlinear response is not simply related to the sign of the forcing as predicted by linear steady state theories. It is argued that the theories fail because either the full three-dimensional complexity of the basic state is not considered or its inherent instability structure is not recognized or is, in fact, ignored. It is shown that three-dimensional instability theory provides a natural generalization and marriage of the zonally averaged instability theory of Charney and Eady and the Rossby wave dispersion theory of Rossby and Yeh. As such, it provides a formalism which may be used to understand a wide variety of atmospheric fluctuations including the locations of eddy flux covariance maxima and storm tracks in both the tropics and extratropics and the generation of blocking, teleconnection patterns, and other quasi-stationary anomaly features. Attention is focused on two particular mechanisms within this formalism
Estimation of critical and viscous frequencies for Biot theory in cancellous bone.
Hughes, Elinor R; Leighton, Timothy G; Petley, Graham W; White, Paul R; Chivers, Robert C
2003-07-01
The use of Biot theory for modelling ultrasonic wave propagation in porous media involves the definition of a "critical frequency" above which both fast and slow compressional waves will, in principle, propagate. Critical frequencies have been evaluated for healthy and osteoporotic cancellous bone filled with water or marrow, using data from the literature. The range of pore sizes in bone gives rise to a critical frequency band rather than a single critical frequency, the mean of which is lower for osteoporotic bone than normal bone. However, the critical frequency is a theoretical concept and previous researchers considered a more realistic "viscous frequency" above which both fast and slow waves may be experimentally observed. Viscous frequencies in bone are found to be several orders of magnitude greater than calculated critical frequencies. Whereas two waves may well be observed at all ultrasonic frequencies for water-filled cancellous bone at 20 degrees C, it is probable megahertz frequencies would be needed for observation of two waves in vivo.
Theory of Inpatient Circadian Care (TICC): A Proposal for a Middle-Range Theory
Camargo-Sanchez, Andrés; Niño, Carmen L; Sánchez, Leonardo; Echeverri, Sonia; Gutiérrez, Diana P; Duque, Andrés F; Pianeta, Oscar; Jaramillo-Gómez, Jenny A; Pilonieta, Martin A; Cataño, Nhora; Arboleda, Humberto; Agostino, Patricia V; Alvarez-Baron, Claudia P; Vargas, Rafael
2015-01-01
The circadian system controls the daily rhythms of a variety of physiological processes. Most organisms show physiological, metabolic and behavioral rhythms that are coupled to environmental signals. In humans, the main synchronizer is the light/dark cycle, although non-photic cues such as food availability, noise, and work schedules are also involved. In a continuously operating hospital, the lack of rhythmicity in these elements can alter the patient’s biological rhythms and resilience. This paper presents a Theory of Inpatient Circadian Care (TICC) grounded in circadian principles. We conducted a literature search on biological rhythms, chronobiology, nursing care, and middle-range theories in the databases PubMed, SciELO Public Health, and Google Scholar. The search was performed considering a period of 6 decades from 1950 to 2013. Information was analyzed to look for links between chronobiology concepts and characteristics of inpatient care. TICC aims to integrate multidisciplinary knowledge of biomedical sciences and apply it to clinical practice in a formal way. The conceptual points of this theory are supported by abundant literature related to disease and altered biological rhythms. Our theory will be able to enrich current and future professional practice. PMID:25767632
Theory of Inpatient Circadian Care (TICC): A Proposal for a Middle-Range Theory.
Camargo-Sanchez, Andrés; Niño, Carmen L; Sánchez, Leonardo; Echeverri, Sonia; Gutiérrez, Diana P; Duque, Andrés F; Pianeta, Oscar; Jaramillo-Gómez, Jenny A; Pilonieta, Martin A; Cataño, Nhora; Arboleda, Humberto; Agostino, Patricia V; Alvarez-Baron, Claudia P; Vargas, Rafael
2015-01-01
The circadian system controls the daily rhythms of a variety of physiological processes. Most organisms show physiological, metabolic and behavioral rhythms that are coupled to environmental signals. In humans, the main synchronizer is the light/dark cycle, although non-photic cues such as food availability, noise, and work schedules are also involved. In a continuously operating hospital, the lack of rhythmicity in these elements can alter the patient's biological rhythms and resilience. This paper presents a Theory of Inpatient Circadian Care (TICC) grounded in circadian principles. We conducted a literature search on biological rhythms, chronobiology, nursing care, and middle-range theories in the databases PubMed, SciELO Public Health, and Google Scholar. The search was performed considering a period of 6 decades from 1950 to 2013. Information was analyzed to look for links between chronobiology concepts and characteristics of inpatient care. TICC aims to integrate multidisciplinary knowledge of biomedical sciences and apply it to clinical practice in a formal way. The conceptual points of this theory are supported by abundant literature related to disease and altered biological rhythms. Our theory will be able to enrich current and future professional practice.
Bendable, low-loss Topas fibers for the terahertz frequency range
DEFF Research Database (Denmark)
Nielsen, Kristian; Rasmussen, Henrik K.; Adam, Aurèle J.L.
2009-01-01
structure proves that the fiber is single-moded over a wide frequency range, and we see the onset of higher-order modes at high frequencies as well as indication of microporous guiding at low frequencies and high porosity of the fiber. Transmission spectroscopy demonstrates low-loss propagation (
Speckle Reduction in OCT using Massively-Parallel Detection and Frequency-Domain Ranging.
Desjardins, A E; Vakoc, B J; Tearney, G J; Bouma, B E
2006-05-29
Speckle noise significantly limits the information content provided by coherent optical imaging methods such as optical coherence tomography and its recent derivative, optical frequency-domain imaging (OFDI). In this paper, we demonstrate a novel OFDI system that simultaneously acquires hundreds of angularly resolved images, which can be compounded to reduce speckle noise. The system comprises an InGaAs line-scan camera and an interferometer, configured so that the elements of the detector array simultaneously capture light spanning a backscattering angular range of 32 degrees. On successive read-outs of the array, the wavelength of the laser source was stepped through a range of 130 nm centered at 1295 nm to concurrently generate 400 angle-resolved OFDI images. A theory of angle-resolved OFDI and the design equations of the system are presented. Incoherent averaging of the angle-resolved data is shown to yield substantial speckle reduction (as high as an 8 dB SNR improvement) in images of a tissue phantom and esophageal tissue ex vivo.
Oyeka, Dumtoochukwu O; Batchelor, John C; Ziai, Ali Mohamad
2017-04-01
This Letter presents an investigation of the effect of human tissue conductivity and permittivity on the performance of epidermal transfer tattoo ultra-high frequency radio-frequency identification (RFID) tags. The measurements were carried out on 20 individuals and the variations in the measured dielectric properties correlate well with variations in the measured tag read range on the individuals and to a lesser extent with their body mass index values. Simulation results also showed the effects of permittivity and conductivity on the designed resonance frequency of the RFID tag.
Batchelor, John C.; Ziai, Ali Mohamad
2017-01-01
This Letter presents an investigation of the effect of human tissue conductivity and permittivity on the performance of epidermal transfer tattoo ultra-high frequency radio-frequency identification (RFID) tags. The measurements were carried out on 20 individuals and the variations in the measured dielectric properties correlate well with variations in the measured tag read range on the individuals and to a lesser extent with their body mass index values. Simulation results also showed the effects of permittivity and conductivity on the designed resonance frequency of the RFID tag. PMID:28461902
Directory of Open Access Journals (Sweden)
Tong Wu
2016-11-01
Full Text Available We present a spatial frequency domain multiplexing method for extending the imaging depth range of a spectral domain optical coherence tomography (SDOCT system without any expensive device. This method uses two galvo scanners with different pivot-offset distances in two independent reference arms for spatial frequency modulation and multiplexing. The spatial frequency contents corresponding to different depth regions of the sample can be shifted to different frequency bands. The spatial frequency domain multiplexing SDOCT system provides an approximately 1.9-fold increase in the effective ranging depth compared with that of a conventional full-range SDOCT system. The reconstructed images of phantom and biological tissue demonstrate the expected increase in ranging depth. The parameters choice criterion for this method is discussed.
Buried Object Detection Method Using Optimum Frequency Range in Extremely Shallow Underground
Sugimoto, Tsuneyoshi; Abe, Touma
2011-07-01
We propose a new detection method for buried objects using the optimum frequency response range of the corresponding vibration velocity. Flat speakers and a scanning laser Doppler vibrometer (SLDV) are used for noncontact acoustic imaging in the extremely shallow underground. The exploration depth depends on the sound pressure, but it is usually less than 10 cm. Styrofoam, wood (silver fir), and acrylic boards of the same size, different size styrofoam boards, a hollow toy duck, a hollow plastic container, a plastic container filled with sand, a hollow steel can and an unglazed pot are used as buried objects which are buried in sand to about 2 cm depth. The imaging procedure of buried objects using the optimum frequency range is given below. First, the standardized difference from the average vibration velocity is calculated for all scan points. Next, using this result, underground images are made using a constant frequency width to search for the frequency response range of the buried object. After choosing an approximate frequency response range, the difference between the average vibration velocity for all points and that for several points that showed a clear response is calculated for the final confirmation of the optimum frequency range. Using this optimum frequency range, we can obtain the clearest image of the buried object. From the experimental results, we confirmed the effectiveness of our proposed method. In particular, a clear image of the buried object was obtained when the SLDV image was unclear.
Optimal frequency range for medical radar measurements of human heartbeats using body-contact radar.
Brovoll, Sverre; Aardal, Øyvind; Paichard, Yoann; Berger, Tor; Lande, Tor Sverre; Hamran, Svein-Erik
2013-01-01
In this paper the optimal frequency range for heartbeat measurements using body-contact radar is experimentally evaluated. A Body-contact radar senses electromagnetic waves that have penetrated the human body, but the range of frequencies that can be used are limited by the electric properties of the human tissue. The optimal frequency range is an important property needed for the design of body-contact radar systems for heartbeat measurements. In this study heartbeats are measured using three different antennas at discrete frequencies from 0.1 - 10 GHz, and the strength of the received heartbeat signal is calculated. To characterize the antennas, when in contact with the body, two port S-parameters(†) are measured for the antennas using a pork rib as a phantom for the human body. The results shows that frequencies up to 2.5 GHz can be used for heartbeat measurements with body-contact radar.
Directory of Open Access Journals (Sweden)
Kim Sun Ho
2017-01-01
Full Text Available An efficient current drive scheme in central or off-axis region is required for the steady state operation of tokamak fusion reactors. The current drive by using the fast wave in frequency range higher than two times lower hybrid resonance (w>2wlh could be such a scheme in high density, high temperature reactor-grade tokamak plasmas. First, it has relatively higher parallel electric field to the magnetic field favorable to the current generation, compared to fast waves in other frequency range. Second, it can deeply penetrate into high density plasmas compared to the slow wave in the same frequency range. Third, parasitic coupling to the slow wave can contribute also to the current drive avoiding parametric instability, thermal mode conversion and ion heating occured in the frequency range w<2wlh. In this study, the propagation boundary, accessibility, and the energy flow of the fast wave are given via cold dispersion relation and group velocity. The power absorption and current drive efficiency are discussed qualitatively through the hot dispersion relation and the polarization. Finally, those characteristics are confirmed with ray tracing code GENRAY for the KSTAR plasmas.
Motion Compensation of Moving Targets for High Range Resolution Stepped-Frequency Radar
Directory of Open Access Journals (Sweden)
Xiqin Wang
2008-05-01
Full Text Available High range resolution (HRR profiling using stepped-frequency pulse trains suffers from range shift and the attenuation/dispersion of range profiles while the target of interest is moving. To overcome these two drawbacks, a new algorithm based on the maximum likelihood (ML estimation is proposed in this paper. Without altering the conventional stepped-frequency waveform, this algorithm can estimate the target velocity and thereby compensate the phase errors caused by the targetÃ¢Â€Â™s motion. It is shown that the velocity can be accurately estimated and the range profile can be correctly reconstructed.
Suo, Dingjie; Guo, Sijia; Lin, Weili; Jiang, Xiaoning; Jing, Yun
2015-09-21
High intensity focused ultrasound (HIFU) based thrombolysis has emerged as a promising drug-free treatment approach for ischemic stroke. The large amount of acoustic power required by this approach, however, poses a critical challenge to the future clinical translation. In this study, multi-frequency acoustic waves at MHz range (near 1.5 MHz) were introduced as HIFU excitations to reduce the required power for treatment as well as the treatment time. In vitro bovine blood clots weighing around 150 mg were treated by single-frequency and multi-frequency HIFU. The pulse length was 2 ms for all experiments except the ones where the duty cycle was changed. It was found that dual-frequency thrombolysis efficiency was statistically better than single-frequency under the same acoustic power and excitation condition. When varying the acoustic power but fixing the duty cycle at 5%, it was found that dual-frequency ultrasound can save almost 30% power in order to achieve the same thrombolysis efficiency. In the experiment where the duty cycle was increased from 0.5% to 10%, it was shown that dual-frequency ultrasound can achieve the same thrombolysis efficiency with only half of the duty cycle of single-frequency. Dual-frequency ultrasound could also accelerate the thrombolysis by a factor of 2-4 as demonstrated in this study. No significant differences were found between dual-frequencies with different frequency differences (0.025, 0.05, and 0.1 MHz) and between dual-frequency and triple-frequency. The measured cavitation doses of dual-frequency and triple-frequency excitations were at about the same level but both were significantly higher than that of single-frequency.
Campbell, D L M; Hinch, G N; Dyall, T R; Warin, L; Little, B A; Lee, C
2017-01-01
The number and size of free-range laying hen (Gallus gallus domesticus) production systems are increasing within Australia in response to consumer demand for perceived improvement in hen welfare. However, variation in outdoor stocking density has generated consumer dissatisfaction leading to the development of a national information standard on free-range egg labelling by the Australian Consumer Affairs Ministers. The current Australian Model Code of Practice for Domestic Poultry states a guideline of 1500 hens/ha, but no maximum density is set. Radio-frequency identification (RFID) tracking technology was used to measure daily range usage by individual ISA Brown hens housed in six small flocks (150 hens/flock - 50% of hens tagged), each with access to one of three outdoor stocking density treatments (two replicates per treatment: 2000, 10 000, 20 000 hens/ha), from 22 to 26, 27 to 31 and 32 to 36 weeks of age. There was some variation in range usage across the sampling periods and by weeks 32 to 36 individual hens from the lowest stocking density on average used the range for longer each day (Paccessed the range with 2% of tagged hens in each treatment never venturing outdoors and a large proportion that accessed the range daily (2000 hens/ha: 80.5%; 10 000 hens/ha: 66.5%; 20 000 hens/ha: 71.4%). On average, 38% to 48% of hens were seen on the range simultaneously and used all available areas of all ranges. These results of experimental-sized flocks have implications for determining optimal outdoor stocking densities for commercial free-range laying hens but further research would be needed to determine the effects of increased range usage on hen welfare.
Kinetic theory and long range correlations in moderately dense gases
Energy Technology Data Exchange (ETDEWEB)
Petrosky, T.; Prigogine, I. [Univ. of Texas, Austin, TX (United States)
1997-01-01
The complex spectral representation of the Liouville operator is applied to moderately dense gases interacting through hard-core potentials in arbitrary d-dimensional spaces. It is shown that Markovian kinetic equations exist for all d. This provides an answer to the long standing question do kinetic equations exist in two dimensional systems. The non-Markovian effects, such as the long-time tails for arbitrary n-mode coupling, are estimated by superposition of the Markovian evolutions in each subspace as introduced in our spectral decomposition. The long-time tail effects invalidate the traditional kinetic theory based on a truncation of BBGKY hierarchy for d < 4, as well as the Green-Kubo formalism, as there appear contributions of order t{sup -1}, t{sup -{1/2}},... coming from multiple mode-mode couplings even for d = 3.
Ayrinhac, S; Devos, A; Le Louarn, A; Mante, P-A; Emery, P
2010-10-15
We show that the propagation of coherent acoustic phonons generated by femtosecond optical excitation can be clearly resolved using a probe laser in the middle UV (MUV) range. The MUV probe is easily produced from a high-repetition-rate femtosecond laser and a homemade frequency tripler. We present various experimental results that demonstrate efficient and high frequency detection of acoustic phonons. Thus, we show that the MUV range offers a unique way to reach higher frequencies and probe smaller objects in ultrafast acoustics.
Absorption properties of water-in-oil emulsions in the low THz frequency range
DEFF Research Database (Denmark)
Møller, Uffe; Folkenberg, Jacob Riis; Jepsen, Peter Uhd
We use transmission THz spectroscopy to investigate the absorption properties of water-in-oil emulsions with water content varying in the 0-20% range, relevant for a range of food products. We find that at low frequencies the effective absorption coefficient of the emulsion is suppressed compared...
Study on The Extended Range Weather Forecast of Low Frequency Signal Based on Period Analysis Method
Li, X.
2016-12-01
Although many studies have explored the MJO and its application for weather forecasting, low-frequency oscillation has been insufficiently studied for the extend range weather forecasting over middle and high latitudes. In China, low-frequency synoptic map is a useful tool for meteorological operation department to forecast extend range weather. It is therefore necessary to develop objective methods to serve the need for finding low-frequency signal, interpretation and application of this signal in the extend range weather forecasting. In this paper, method of Butterworth band pass filter was applied to get low-frequency height field at 500hPa from 1980 to 2014 by using NCEP/NCAR daily grid data. Then period analysis and optimal subset regression methods were used to process the low frequency data of 150 days before the first forecast day and extend the low frequency signal of 500hPa low-frequency high field to future 30 days in the global from June to August during 2011-2014. Finally, the results were test. The main results are as follows: (1) In general, the fitting effect of low frequency signals of 500hPa low-frequency height field by period analysis in the northern hemisphere was better than that in the southern hemisphere, and was better in the low latitudes than that in the high latitudes. The fitting accuracy gradually reduced with the increase of forecast time length, which tended to be stable during the late forecasting period. (2) The fitting effects over the 6 key regions in China showed that except filtering result over Xinjiang area in the first 10 days and 30 days, filtering results over the other 5 key regions throughout the whole period have passed reliability test with level more than 95%. (3) The center and scope of low and high low frequency systems can be fitted well by using the methods mentioned above, which is consist with the corresponding use of the low-frequency synoptic map for the prediction of the extended period. Application of the
The BDS Triple Frequency Pseudo-range Correlated Stochastic Model of Single Station Modeling Method
Directory of Open Access Journals (Sweden)
HUANG Lingyong
2017-05-01
Full Text Available In order to provide a reliable pseudo-range stochastic model, a method is studied to estimate the BDS triple-frequency pseudo-range related stochastic model based on three BDS triple-frequency pseudo-range minus carrier (GIF combinations using the data of a single station. In this algorithm, the low order polynomial fitting method is used to fit the GIF combination in order to eliminate the error and other constants except non pseudo noise at first. And then, multiple linear regression analysis method is used to model the stochastic function of three linearly independent GIF combinations. Finally the related stochastic model of the original BDS triple-frequency pseudo-range observations is obtained by linear transformation. The BDS triple-frequency data verification results show that this algorithm can get a single station related stochastic model of BDS triple-frequency pseudo-range observation, and it is advantageous to provide accurate stochastic model for navigation and positioning and integrity monitoring.
Floquet engineering of long-range p -wave superconductivity: Beyond the high-frequency limit
Li, Zeng-Zhao; Lam, Chi-Hang; You, J. Q.
2017-10-01
It has been shown that long-range p -wave superconductivity in a Kitaev chain can be engineered via an ac field with a high frequency [M. Benito et al., Phys. Rev. B 90, 205127 (2014), 10.1103/PhysRevB.90.205127]. For its experimental realization, however, theoretical understanding of Floquet engineering with a broader range of driving frequencies becomes important. In this paper, focusing on the ac-driven tunneling interactions of a Kitaev chain, we investigate effects from the leading correction to the high-frequency limit on the emergent p -wave superconductivity. Importantly, we find new engineered long-range p -wave pairing interactions that can significantly alter the ones in the high-frequency limit at long interaction ranges. We also find that the leading correction additionally generates nearest-neighbor p -wave pairing interactions with a renormalized pairing energy, long-range tunneling interactions, and, in particular, multiple pairs of Floquet Majorana edge states that are destroyed in the high-frequency limit.
Kassem, M.; Soize, C.; Gagliardini, L.
2011-02-01
In a recent work [ Journal of Sound and Vibration 323 (2009) 849-863] the authors presented an energy-density field approach for the vibroacoustic analysis of complex structures in the low and medium frequency ranges. In this approach, a local vibroacoustic energy model as well as a simplification of this model were constructed. In this paper, firstly an extension of the previous theory is performed in order to include the case of general input forces and secondly, a structural partitioning methodology is presented along with a set of tools used for the construction of a partitioning. Finally, an application is presented for an automotive vehicle.
UTag: Long-range Ultra-wideband Passive Radio Frequency Tags
Energy Technology Data Exchange (ETDEWEB)
Dowla, F
2007-03-14
Long-range, ultra-wideband (UWB), passive radio frequency (RF) tags are key components in Radio Frequency IDentification (RFID) system that will revolutionize inventory control and tracking applications. Unlike conventional, battery-operated (active) RFID tags, LLNL's small UWB tags, called 'UTag', operate at long range (up to 20 meters) in harsh, cluttered environments. Because they are battery-less (that is, passive), they have practically infinite lifetimes without human intervention, and they are lower in cost to manufacture and maintain than active RFID tags. These robust, energy-efficient passive tags are remotely powered by UWB radio signals, which are much more difficult to detect, intercept, and jam than conventional narrowband frequencies. The features of long range, battery-less, and low cost give UTag significant advantage over other existing RFID tags.
An atomic magnetometer with autonomous frequency stabilization and large dynamic range
Energy Technology Data Exchange (ETDEWEB)
Pradhan, S., E-mail: spradhan@barc.gov.in, E-mail: pradhans75@gmail.com; Poornima,; Dasgupta, K. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai 85 (India); Homi Bhabha National Institute, Department of Atomic Energy, Mumbai 85 (India); Mishra, S.; Behera, R. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai 85 (India)
2015-06-15
The operation of a highly sensitive atomic magnetometer using elliptically polarized resonant light is demonstrated. It is based on measurement of zero magnetic field resonance in degenerate two level systems using polarimetric detection. The transmitted light through the polarimeter is used for laser frequency stabilization, whereas reflected light is used for magnetic field measurement. Thus, the experimental geometry allows autonomous frequency stabilization of the laser frequency leading to compact operation of the overall device and has a preliminary sensitivity of <10 pT/Hz{sup 1/2} @ 1 Hz. Additionally, the dynamic range of the device is improved by feedback controlling the bias magnetic field without compromising on its sensitivity.
The frequency-temperature analysis equations of piezoelectric plates with Lee plate theory.
Wang, J
1999-01-01
Frequency-temperature analysis theory of crystal plates based on the incremental field theory (IFT) and the Mindlin plate theory have been widely used in the vibration analysis of crystal resonators subject to temperature change. As one of the two major plate theories for the resonator analysis, the Lee plate theory based on the trigonometric series expansion of displacements has been extensively used for both analytical and numerical analyses of quartz resonators, and efforts have also been made in correcting and perfecting the theory for much broader applications. In this paper, the earlier frequency-temperature analysis equations based on the IFT is further extended to the trigonometric series expansion in a systematic manner. By incorporating the frequency-temperature analysis into the Lee plate theory, the complete analysis of crystal resonators can be made in a consistent way. The thickness-shear and flexural vibration equations have been compared with the Mindlin plate theory to demonstrate the similarity and consistency.
Evaluation of the spectral fit algorithm as functions of frequency range and deltakaeff.
Bigelow, Timothy A; O'Brien, William D
2005-11-01
Considerable effort has been directed at quantifying the properties of the tissue microstructure (i.e., scatterer correlation length) to diagnose disease and monitor treatment. In vivo assessments have had limited success due to frequency-dependent attenuation along the propagation path (i.e., total attenuation) masking the frequency dependence of the scattering from the tissue microstructure. Previously, both total attenuation and scatterer correlation length, given by the effective radius, were solved simultaneously by a two-parameter minimization of the mean squared error between a reference spectrum, modified by the attenuation and scatterer effective radius, and the backscattered waveforms using an algorithm termed the spectral fit algorithm. Herein, the impact of frequency range (largest frequency minus smallest frequency) and deltakaeff (largest kaeff value minus smallest kaeff value; k is wave number and aeff is scatterer effective radius) used by the spectral fit algorithm on estimating the scatterer effective radius, and total attenuation was assessed by computer simulations while excluding frequencies of the backscattered power spectrum dominated by electronic noise. The simulations varied the effective radius of the scatterers (5 microm to 150 microm), the attenuation of the region (0 to 1 dB/cm-MHz), the bandwidth of the source, and the amount of electronic noise added to the radio frequency (rf) waveforms. The center frequency of the source was maintained at 8 MHz. Comparable accuracy and precision of the scatterer effective radius were obtained for all the simulations whenever the same deltakaeff was used to obtain the estimates. A deltakaeff of 1 gave an accuracy and precision of approximately 15% +/- 35%, and a width of 1.5 gave an accuracy and precision of approximately 5% +/- 15% consistently for all of the simulations. Similarly, the accuracy and precision of the total attenuation estimate were improved by increasing the frequency range used by
Frequency of negative differential resistance electrochemical oscillators: theory and experiments.
Kiss, István Z; Pelster, Lindsey N; Wickramasinghe, Mahesh; Yablonsky, Gregory S
2009-07-21
An approximate formula for the frequency of oscillations is theoretically derived for skeleton models for electrochemical systems exhibiting negative differential resistance (NDR) under conditions close to supercritical Hopf bifurcation points. The theoretically predicted omega infinity (k/R)1/2 relationship (where R is the series resistance of the cell and k is the rate constant of the charge transfer process) was confirmed in experiments with copper and nickel electrodissolution. The experimentally observed Arrhenius-type dependence of frequency on temperature can also be explained with the frequency equation. The experimental validity of the frequency equation indicates that 'apparent' rate constants can be extracted from frequency measurements of electrochemical oscillations; such method can aid future modeling of complex responses of electrochemical cells.
A Middle-Range Theory for Diabetes Self-management Mastery.
Fearon-Lynch, Jennifer A; Stover, Caitlin M
2015-01-01
Diabetes mellitus is the seventh leading cause of death in America and affects 382 million people worldwide. Individuals with diabetes must manage the complexity of the disease, its treatment, and complications to avert deleterious consequences associated with the illness. However, not all patients with diabetes successfully gain mastery to positively impact self-management. A new middle-range theory is proposed that merges 2 extant theories, theory of mastery and organismic integration theory, to better understand this human response. The theories' philosophical, theoretical, and conceptual perspectives were examined and relational properties synthesized to provide a conceptual representation of the phenomenon of interest.
The effects of tones on speaking frequency and intensity ranges in Mandarin and Min dialects
Chen, Sheng H.
2005-05-01
The differences of speaking frequency and intensity in different tonal dialects has not been widely investigated. The purposes of this study were (1) to compare the speaking frequency and speaking intensity ranges of Mandarin and Min and (2) to compare the speaking frequency and intensity ranges of Mandarin and Min to those of American English. The subjects were 80 normal Taiwanese adults divided into two dialect groups, Mandarin and Min. The speaking F0, the highest speaking F0, the lowest speaking F0, the maximum range of speaking F0, and the intensity counterpart were obtained from reading in their native dialects. Statistical analysis revealed that Min speakers had a significantly greater maximum range of speaking intensity and a smaller lowest speaking intensity than Mandarin speakers, which indicated tonal effects by speakers of the Min dialect. Moreover, Mandarin and Min speakers had a greater maximum range of speaking F0 and maximum range of speaking intensity than American English speakers. The data may provide an assessment tool for Mandarin speakers and Min speakers. .
Ding, Zhenyang; Yao, X Steve; Liu, Tiegen; Du, Yang; Liu, Kun; Han, Qun; Meng, Zhuo; Chen, Hongxin
2012-12-17
We present a novel method to achieve a space-resolved long- range vibration detection system based on the correlation analysis of the optical frequency-domain reflectometry (OFDR) signals. By performing two separate measurements of the vibrated and non-vibrated states on a test fiber, the vibration frequency and position of a vibration event can be obtained by analyzing the cross-correlation between beat signals of the vibrated and non-vibrated states in a spatial domain, where the beat signals are generated from interferences between local Rayleigh backscattering signals of the test fiber and local light oscillator. Using the proposed technique, we constructed a standard single-mode fiber based vibration sensor that can have a dynamic range of 12 km and a measurable vibration frequency up to 2 kHz with a spatial resolution of 5 m. Moreover, preliminarily investigation results of two vibration events located at different positions along the test fiber are also reported.
DEFF Research Database (Denmark)
Meyer, Steffen
2017-01-01
to picoseconds in the previous experiments. For the broad spectrum, the additional effect of group delay dispersion (GDD) has to be taken into account, since the Raman process relies on the coherent interaction of all frequency components of the spectrum, with GDD influencing the relative phase which leads......This thesis presents for the first time the experimental implementation of coherent Raman oscillations with a femtosecond frequency comb for transition frequencies in the THz range. The technique has been successfully demonstrated before to drive Raman transitions between hyperfine structure states...... to destructive interference. Therefore, GDD is compensated using a prism compressor and it is shown quantitatively that the measured GDD matches the theoretically predicted effect on the total Raman Rabi frequency. For the measurements and compensation of GDD, the techniques of interferometric autocorrelation...
Tuning Range Optimization of a Planar Inverted F Antenna for LTE Low Frequency Bands
DEFF Research Database (Denmark)
Barrio, Samantha Caporal Del; Pelosi, Mauro; Franek, Ondrej
2011-01-01
This paper presents a Planar Inverted F Antenna (PIFA) tuned with a fixed capacitor to the low frequency bands supported by the Long Term Evolution (LTE) technology. The tuning range is investigated and optimized with respect to the bandwidth and the efficiency of the resulting antenna. Simulations...
Semiannual Status Report. [excitation of electromagnetic waves in the whistler frequency range
1994-01-01
During the last six months, we have continued our study of the excitation of electromagnetic waves in the whistler frequency range and the role that these waves will play in the acceleration of electrons and ions in the auroral region. A paper entitled 'Electron Beam Excitation of Upstream Waves in the Whistler Mode Frequency Range' was listed in the Journal of Geophysical Research. In this paper, we have shown that an anisotropic electron beam (or gyrating electron beam) is capable of generating both left-hand and right-hand polarized electromagnetic waves in the whistler frequency range. Since right-hand polarized electromagnetic waves can interact with background electrons and left-hand polarized waves can interact with background ions through cyclotron resonance, it is possible that these beam generated left-hand and right-hand polarized electromagnetic waves can accelerate either ions or electrons (or both), depending on the physical parameters under consideration. We are currently carrying out a comprehensive study of the electromagnetic whistler and lower hybrid like waves observed in the auroral zone using both wave and particle data. Our first task is to identify these wave modes and compare it with particle observations. Using both the DE-1 particle and wave measurements, we can positively identify those electromagnetics lower hybrid like waves as fast magnetosonic waves and the upper cutoff of these waves is the local lower hybrid frequency. From the upper cutoff of the frequency spectrum, one can infer the particle density and the result is in very good agreement with the particle data. Since these electromagnetic lower hybrid like waves can have frequencies extended down to the local ion cyclotron frequency, it practically confirms that they are not whistler waves.
Instantaneous pair theory for high-frequency vibrational energy relaxation in fluids
Larsen, Ross E.; Stratt, Richard M.
1999-01-01
Notwithstanding the long and distinguished history of studies of vibrational energy relaxation, exactly how it is that high frequency vibrations manage to relax in a liquid remains somewhat of a mystery. Both experimental and theoretical approaches seem to say that there is a natural frequency range associated with intermolecular motion in liquids, typically spanning no more than a few hundred cm-1. Landau-Teller-type theories explain rather easily how a solvent can absorb any vibrational energy within this "band," but how is it that molecules can rid themselves of superfluous vibrational energies significantly in excess of these values? In this paper we develop a theory for such processes based on the idea that the crucial liquid motions are those that most rapidly modulate the force on the vibrating coordinate — and that by far the most important of these motions are those involving what we have called the mutual nearest neighbors of the vibrating solute. Specifically, we suggest that whenever there is a single solvent molecule sufficiently close to the solute that the solvent and solute are each other's nearest neighbors, then the instantaneous scattering dynamics of the solute-solvent pair alone suffices to explain the high-frequency relaxation. This highly reduced version of the dynamics has implications for some of the previous theoretical formulations of this problem. Previous instantaneous-normal-mode theories allowed us to understand the origin of a band of liquid frequencies, and even had some success in predicting relaxation within this band, but lacking a sensible picture of the effects of liquid anharmonicity on dynamics, were completely unable to treat higher frequency relaxation. When instantaneous-normal-mode dynamics is used to evaluate the instantaneous pair theory, though, we end up with a multiphonon picture of the relaxation which is in excellent agreement with the exact high-frequency dynamics — suggesting that the critical anharmonicity
A Frequency-Depth Explicit Interaction Theory Formulation
DEFF Research Database (Denmark)
Ruiz, Pau Mercadé; Ferri, Francesco; Kofoed, Jens Peter
2016-01-01
An alternative definition of the usual diffraction transfer matrix defined by Kagemoto and Yue (1986) has been developed. A method is thereby presented which enables the prediction of the diffraction transfer matrix for any desired wave frequency and water depth. The method has been tested...... been shown for the case of a fixed water depth condition and predicting for different wave frequencies. Furthermore, the investigations have shown promising results when only accounting for travelling wave modes....
Kim, Won J.
2012-01-01
Reliable measurements for effective teaching are lacking. In contrast, some theories of leadership (particularly transformational leadership) have been tested and found to have efficacy in a variety of organizational settings. In this study, the full-range leadership theory, which includes transformational leadership, was applied to the…
Excitation of Lamb waves over a large frequency-thickness product range for corrosion detection
Zeng, Liang; Luo, Zhi; Lin, Jing; Hua, Jiadong
2017-09-01
For corrosion detection, it is often desirable that a Lamb wave mode is highly sensitive to surface thinning and enjoys some degree of mode purity at a particular frequency. In view of this, this paper aims to generate a variety of Lamb wave modes over broad frequency bands to ensure an abundant supply of candidates for corrosion detection, and further, establish a strategy to find appropriate operation points efficiently and effectively. Firstly, a short-duration laser pulse is applied to generate Lamb waves over a large frequency-thickness product range. The selection of symmetric modes or anti-symmetric modes is obtained by addition or subtraction of signals captured by two identical transducers which are symmetrically coupled on both sides of the plate. Subsequently, the S0 mode at a non-dispersive frequency bandwidth is employed to improve the accuracy of the transmitter-receiver distance. Based on those, three selection criteria including mode separability, amplitude ratio and corrosion sensitivity, are presented to efficiently determine the suitable operation points (i.e., mode types and frequencies). The experimental results show that the simulated corrosion could be correctly detected and accurately localized at the chosen modes and frequencies.
Wide-range dynamic strain measurements based on K-BOTDA and frequency-agile technique
Zhou, Dengwang; Dong, Yongkang; Wang, Benzhang; Zhang, Hongying; Lu, Zhiwei
2017-04-01
We propose and demonstrate a novel fast Brillouin optical time-domain analysis system using the coefficient K spectrum which is defined as the ratio of phase-shift and gain of Brillouin amplification, where K features linear response, immune to the variation of pump power and a wide measure range. For a 30ns-square pump pulse, the frequency span of K spectrum can reach up to 200MHz. In dynamic strain experiment, a multi-slope assisted K-BOTDA with the measured strain of 5358.3μɛ and the vibration frequency of 6.01Hz and 12.05Hz are demonstrated.
Toward development of a middle-range theory of psychological adaptation in death and dying.
Dobratz, Marjorie C
2011-10-01
This paper presents a middle-range theory of psychological adaptation in death and dying that was abstracted from a series of quantitative and qualitative studies. The findings from these studies are described, a conceptual definition for end-of-life psychological adaptation is given, evidence is synthesized into a limited number of assumptions, testable hypotheses are derived, and the constructed middle-range theory is linked to the conceptual-theoretical framework of the Roy adaptation model.
An impedance bridge measuring the capacitance ratio in the high frequency range up to 1 MHz
Bee Kim, Dan; Kew Lee, Hyung; Kim, Wan-Seop
2017-02-01
This paper describes a 2-terminal-pair impedance bridge, measuring the capacitance ratio in the high frequency range up to 1 MHz. The bridge was configured with two voltage sources and a phase control unit which enabled the bridge balance by synchronizing the voltage sources with an enhanced phase resolution. Without employing the transformers such as inductive voltage divider, injection and detection transformers, etc, the bridge system is quite simple to set up, and the balance procedure is quick and easy. Using this dual-source coaxial bridge, the 1:1 and 10:1 capacitance ratios were measured with 1 pF-1 nF capacitors in the frequency range from 1 kHz to 1 MHz. The measurement values obtained by the dual-source bridge were then compared with reference values measured using a commercial precision capacitance bridge of AH2700A, the Z-matrix method developed by ourselves, and the 4-terminal-pair coaxial bridge by the Czech Metrological Institute. All the measurements agreed within the reference uncertainty range of an order of 10-6-10-5, proving the bridge ability as a trustworthy tool for measuring the capacitance ratio in the high frequency range.
Impact of energetic particle orbits on long range frequency chirping of BGK modes
Hezaveh, H.; Qu, Z. S.; Layden, B.; Hole, M. J.
2017-12-01
Long range frequency chirping of Bernstein-Greene-Kruskal modes, whose existence is determined by the fast particles, is investigated in cases where these particles do not move freely and their motion is bounded to restricted orbits. A nonuniform equilibrium magnetic field is included into the bump-on-tail instability problem of a plasma wave. The parallel field gradients account for the existence of different orbit topologies of energetic particles. With respect to fast particles dynamics, the extended model captures the range of particles motion (trapped/passing) with energy and thus represents a more realistic 1D picture of the long range sweeping events observed for weakly damped modes, e.g. global Alfven eigenmodes, in tokamaks. The Poisson equation is solved numerically along with bounce averaging the Vlasov equation in the adiabatic regime. We demonstrate that the shape and the saturation amplitude of the nonlinear mode structure depends not only on the amount of deviation from the initial eigenfrequency but also on the initial energy of the resonant electrons in the equilibrium magnetic field. Similarly, the results reveal that the resonant electrons following different equilibrium orbits in the nonuniform field lead to different rates of frequency evolution. As compared to the previous model (Breizman 2010 Nucl. Fusion 50 084014), it is shown that the frequency sweeps with lower rates. The additional physics included in the model enables a more complete 1D description of the range of phenomena observed in experiments.
A Rayleigh Doppler Frequency Estimator Derived from Maximum Likelihood Theory
DEFF Research Database (Denmark)
Hansen, Henrik; Affes, Sofiene; Mermelstein, Paul
1999-01-01
Reliable estimates of Rayleigh Doppler frequency are useful for the optimization of adaptive multiple access wireless receivers.The adaptation parameters of such receivers are sensitive to the amount of Doppler and automatic reconfiguration to the speed of terminalmovement can optimize cell...... capacities in low and high speed situations.We derive a Doppler frequency estimatorusing the maximum likelihood method and Jakes model [\\ref{Jakes}] of a Rayleigh fading channel. This estimator requires an FFT and simple post-processing only. Its performance is verifiedthrough simulations and found to yield...
Waveguiding Effect in the Gigahertz Frequency Range in Pillar-based Phononic-Crystal Slabs
Pourabolghasem, Reza; Dehghannasiri, Razi; Eftekhar, Ali Asghar; Adibi, Ali
2018-01-01
The waveguiding effect for a phononic-crystal (PnC)-based device operating in the gigahertz (GHz) frequency regime is experimentally demonstrated. To that end, a metallic pillar-based PnC membrane with a PnC band gap in the GHz frequency range is designed, and, based on that, an acoustic waveguide operating in the GHz regime is designed and fabricated. To characterize the fabricated PnC waveguide, a set of focusing interdigital transducers is designed and fabricated, enabling efficient excitation and detection of acoustic signals inside the PnC waveguide. The finite-element method is used to study the acoustic properties of the proposed structures and optimize their design. Experimental evidence supporting the existence of the waveguiding effect in the proposed structure in the GHz frequency regime is provided, showing reasonable agreement with the numerical calculations.
Electrodynamic properties of porous PZT-Pt films at terahertz frequency range
Energy Technology Data Exchange (ETDEWEB)
Komandin, Gennady A.; Porodinkov, Oleg E.; Spektor, Igor E.; Volkov, Alexander A. [Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Vorotilov, Konstantin A.; Seregin, Dmitry S.; Sigov, Alexander S. [Moscow Technological University (MIREA), Moscow (Russian Federation)
2017-01-15
Electrodynamics of Si-SiO{sub 2}-TiO{sub 2}-Pt-PZT heterostructures is studied in the frequency range from 5 to 5000 cm{sup -1} by monochromatic BWO (backward wave oscillator) and infrared Fourier-transform spectroscopy techniques to derive the dielectric characteristics of the sol-gel porous ferroelectric PbZr{sub 0.48}Ti{sub 0.52}O{sub 3} films. Broad frequency band dielectric response of PZT films with different density is constructed using the oscillator dispersion models. The main contribution to the film permittivity is found to form at frequencies below 100 cm{sup -1} depending strongly and non-linearly on the film medium density. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
A Rayleigh Doppler frequency estimator derived from maximum likelihood theory
DEFF Research Database (Denmark)
Hansen, Henrik; Affes, Sofiéne; Mermelstein, Paul
1999-01-01
capacities in low and high speed situations. We derive a Doppler frequency estimator using the maximum likelihood method and Jakes model (1974) of a Rayleigh fading channel. This estimator requires an FFT and simple post-processing only. Its performance is verified through simulations and found to yield good...
Propagation in a shearing plasma. II - Turbulence and the frequency range of pulsar microstructure
Harding, A. K.; Tademaru, E.
1980-01-01
Numerical calculations are presented which explore the propagation of radio waves and pulses through a turbulent shearing plasma. A stochastic model is used to describe the turbulent velocity field, in which random fluctuations are superposed on a mean profile. Both Gaussian wave packets and shot-noise pulses polarized in the plane of shearing acquire quasi-periodic intensity modulations above the rest-frame plasma frequency. The frequency range over which these modulations appear is shown to depend on the spatial correlation length of the turbulent fluctuations and on their standard deviation from the mean velocity. The period of the modulations is variable from one realization of the random process to the next, and the average period is frequency dependent. The results of these calculations lend further support to a model for pulsar microstructure in which periodic micropulses are pure temporal modulations of the emitted radiation due to propagation effects in magnetospheric shearing regions. It is shown that turbulence on a scale of approximately 10 cm can produce these quasi-periodic modulations over a frequency range comparable to that of observed microstructure.
Directory of Open Access Journals (Sweden)
Kolbunov V.R.
2015-06-01
Full Text Available Polymer composites with active fillers are recently considered to be promising materials for the design of new functional devices with controllable properties and are intensively investigated. Dielectric studies are one of the most effective methods for studying structural features and mechanisms of conductivity formation for this type of two-component systems. The paper presents research results of the dielectric characteristics in the range of radio frequency of 50 kHz — 10 MHz and temperature range of 30—60°C of polyethylene composites of vanadium dioxide with different volume fractions of filler. Two dispersion areas were found: a high-frequency area caused by the Maxwell charge separation on the boundaries of the polyethylene matrix — conductive filler of VI2 crystallites, and a low frequency area associated with the presence of the transition layer at this boundary. The relative permittivity of the composite has a tendency to a decrease in absolute value with increasing temperature. The analysis of the low-frequency dependence of the dielectric constant of the value of the filler’s volume fraction revealed that the investigated composite belongs to two-component statistical mixtures with a transition layer between the components.
An OFDM Carrier Frequency Offset Estimation Scheme with Wide Fractional Offset Estimation Range
Directory of Open Access Journals (Sweden)
C. Yu
2013-04-01
Full Text Available In this paper, we propose a carrier frequency offset (CFO estimation scheme which is robust to the fractional CFO variation for orthogonal frequency division multiplexing (OFDM systems. The proposed scheme first performs the envelope equalization process to convert the offset estimation problem to a carrier estimation problem, and then, estimates the integer and fractional parts of CFO by using periodogram of the received signal. Especially, in the estimation stage for fraction CFO, the ratio of the square-roots of periodograms is employed enlarging the estimation range of the stage than that of the conventional scheme. Numerical results demonstrate that the proposed scheme has better estimation performance than the conventional scheme for wider fractional CFO range in various channel conditions.
Artificial Temperature Anisotropy of Crystals in X-Ray Frequency Range
Mkrtchyan, Vahram P.; Gasparyan, Laura G.; Balyan, Minas K.
2010-04-01
The effect of artificial temperature anisotropy of crystals in X-ray frequency range was observed for the first time and an effort to theoretically interpret this effect in Bragg-Laue diffraction case was made. It was established that an isotropic crystal optically turns into an artificially anisotropic one with optical axis along the direction of applied external influence as a symmetry axis, giving rise to the double refraction.
Heberle, Dylan A; Levine, Zachary H
2013-01-01
We propose a method to extend the frequency range of polarization entanglement in periodically poled rubidium-doped potassium titanyl phosphate (Rb:KTP) waveguides. Our calculations predict that output wavelengths from 1130 nm to 1257 nm may be achieved using Rb:KTP by the appropriate selection of a direction of propagation for the waveguide. The fidelity using a poling period of 1 mm is approximately 0.98.
Low-power wide-locking-range injection-locked frequency divider for OFDM UWB systems
Energy Technology Data Exchange (ETDEWEB)
Yin Jiangwei; Li Ning; Zheng Renliang; Li Wei; Ren Junyan, E-mail: lining@fudan.edu.c [State Key Laboratory of ASIC and System, Fudan University, Shanghai 201203 (China)
2009-05-01
This paper describes a divide-by-two injection-locked frequency divider (ILFD) for frequency synthesizers as used in multiband orthogonal frequency division multiplexing (OFDM) ultra-wideband (UWB) systems. By means of dual-injection technique and other conventional tuning techniques, such as DCCA and varactor tuning, the divider demonstrates a wide locking range while consuming much less power. The chip was fabricated in the Jazz 0.18 mum RF CMOS process. The measurement results show that the divider achieves a locking range of 4.85 GHz (6.23 to 11.08 GHz) at an input power of 8 dBm. The core circuit without the test buffer consumes only 3.7 mA from a 1.8 V power supply and has a die area of 0.38 x 0.28 mm{sup 2}. The wide locking range combined with low power consumption makes the ILFD suitable for its application in UWB systems.
Frequency-Modulated, Continuous-Wave Laser Ranging Using Photon-Counting Detectors
Erkmen, Baris I.; Barber, Zeb W.; Dahl, Jason
2014-01-01
Optical ranging is a problem of estimating the round-trip flight time of a phase- or amplitude-modulated optical beam that reflects off of a target. Frequency- modulated, continuous-wave (FMCW) ranging systems obtain this estimate by performing an interferometric measurement between a local frequency- modulated laser beam and a delayed copy returning from the target. The range estimate is formed by mixing the target-return field with the local reference field on a beamsplitter and detecting the resultant beat modulation. In conventional FMCW ranging, the source modulation is linear in instantaneous frequency, the reference-arm field has many more photons than the target-return field, and the time-of-flight estimate is generated by balanced difference- detection of the beamsplitter output, followed by a frequency-domain peak search. This work focused on determining the maximum-likelihood (ML) estimation algorithm when continuous-time photoncounting detectors are used. It is founded on a rigorous statistical characterization of the (random) photoelectron emission times as a function of the incident optical field, including the deleterious effects caused by dark current and dead time. These statistics enable derivation of the Cramér-Rao lower bound (CRB) on the accuracy of FMCW ranging, and derivation of the ML estimator, whose performance approaches this bound at high photon flux. The estimation algorithm was developed, and its optimality properties were shown in simulation. Experimental data show that it performs better than the conventional estimation algorithms used. The demonstrated improvement is a factor of 1.414 over frequency-domainbased estimation. If the target interrogating photons and the local reference field photons are costed equally, the optimal allocation of photons between these two arms is to have them equally distributed. This is different than the state of the art, in which the local field is stronger than the target return. The optimal
Modeling of high‐frequency seismic‐wave scattering and propagation using radiative transfer theory
Zeng, Yuehua
2017-01-01
This is a study of the nonisotropic scattering process based on radiative transfer theory and its application to the observation of the M 4.3 aftershock recording of the 2008 Wells earthquake sequence in Nevada. Given a wide range of recording distances from 29 to 320 km, the data provide a unique opportunity to discriminate scattering models based on their distance‐dependent behaviors. First, we develop a stable numerical procedure to simulate nonisotropic scattering waves based on the 3D nonisotropic scattering theory proposed by Sato (1995). By applying the simulation method to the inversion of M 4.3 Wells aftershock recordings, we find that a nonisotropic scattering model, dominated by forward scattering, provides the best fit to the observed high‐frequency direct S waves and S‐wave coda velocity envelopes. The scattering process is governed by a Gaussian autocorrelation function, suggesting a Gaussian random heterogeneous structure for the Nevada crust. The model successfully explains the common decay of seismic coda independent of source–station locations as a result of energy leaking from multiple strong forward scattering, instead of backscattering governed by the diffusion solution at large lapse times. The model also explains the pulse‐broadening effect in the high‐frequency direct and early arriving S waves, as other studies have found, and could be very important to applications of high‐frequency wave simulation in which scattering has a strong effect. We also find that regardless of its physical implications, the isotropic scattering model provides the same effective scattering coefficient and intrinsic attenuation estimates as the forward scattering model, suggesting that the isotropic scattering model is still a viable tool for the study of seismic scattering and intrinsic attenuation coefficients in the Earth.
Directory of Open Access Journals (Sweden)
Laurent Segers
2015-07-01
Full Text Available This paper describes a new approach and implementation methodology for indoor ranging based on the time difference of arrival using code division multiple access with ultrasound signals. A novel implementation based on a field programmable gate array using finite impulse response filters and an optimized correlation demodulator implementation for ultrasound orthogonal signals is developed. Orthogonal codes are modulated onto ultrasound signals using frequency shift keying with carrier frequencies of 24.5 kHz and 26 kHz. This implementation enhances the possibilities for real-time, embedded and low-power tracking of several simultaneous transmitters. Due to the high degree of parallelism offered by field programmable gate arrays, up to four transmitters can be tracked simultaneously. The implementation requires at most 30% of the available logic gates of a Spartan-6 XC6SLX45 device and is evaluated on accuracy and precision through several ranging topologies. In the first topology, the distance between one transmitter and one receiver is evaluated. Afterwards, ranging analyses are applied between two simultaneous transmitters and one receiver. Ultimately, the position of the receiver against four transmitters using trilateration is also demonstrated. Results show enhanced distance measurements with distances ranging from a few centimeters up to 17 m, while keeping a centimeter-level accuracy.
Segers, Laurent; Van Bavegem, David; De Winne, Sam; Braeken, An; Touhafi, Abdellah; Steenhaut, Kris
2015-07-30
This paper describes a new approach and implementation methodology for indoor ranging based on the time difference of arrival using code division multiple access with ultrasound signals. A novel implementation based on a field programmable gate array using finite impulse response filters and an optimized correlation demodulator implementation for ultrasound orthogonal signals is developed. Orthogonal codes are modulated onto ultrasound signals using frequency shift keying with carrier frequencies of 24.5 kHz and 26 kHz. This implementation enhances the possibilities for real-time, embedded and low-power tracking of several simultaneous transmitters. Due to the high degree of parallelism offered by field programmable gate arrays, up to four transmitters can be tracked simultaneously. The implementation requires at most 30% of the available logic gates of a Spartan-6 XC6SLX45 device and is evaluated on accuracy and precision through several ranging topologies. In the first topology, the distance between one transmitter and one receiver is evaluated. Afterwards, ranging analyses are applied between two simultaneous transmitters and one receiver. Ultimately, the position of the receiver against four transmitters using trilateration is also demonstrated. Results show enhanced distance measurements with distances ranging from a few centimeters up to 17 m, while keeping a centimeter-level accuracy.
Kananenka, Alexei A; Zgid, Dominika
2017-11-14
We present a rigorous framework which combines single-particle Green's function theory with density functional theory based on a separation of electron-electron interactions into short- and long-range components. Short-range contribution to the total energy and exchange-correlation potential is provided by a density functional approximation, while the long-range contribution is calculated using an explicit many-body Green's function method. Such a hybrid results in a nonlocal, dynamic, and orbital-dependent exchange-correlation functional of a single-particle Green's function. In particular, we present a range-separated hybrid functional called srSVWN5-lrGF2 which combines the local-density approximation and the second-order Green's function theory. We illustrate that similarly to density functional approximations, the new functional is weakly basis-set dependent. Furthermore, it offers an improved description of the short-range dynamic correlation. The many-body contribution to the functional mitigates the many-electron self-interaction error present in many density functional approximations and provides a better description of molecular properties. Additionally, we illustrate that the new functional can be used to scale down the self-energy and, therefore, introduce an additional sparsity to the self-energy matrix that in the future can be exploited in calculations for large molecules or periodic systems.
Supplementary Golay pair for range side lobe suppression in dual-frequency tissue harmonic imaging.
Shen, Che-Chou; Wu, Chi; Peng, Jun-Kai
2015-02-01
In dual-frequency (DF) harmonic imaging, the second harmonic signal at second harmonic (2f0) frequency and the inter-modulation harmonic signal at fundamental (f0) frequency are simultaneously imaged for spectral compounding. When the phase-encoded Golay pair is utilized to improve the harmonic signal-to-noise ratio (SNR), however, the DF imaging suffers from range side lobe artifacts due to spectral cross-talk with other harmonic components at DC and third harmonic (3f0) frequency. In this study, a supplementary Golay pair is developed to suppress the range side lobes in combination with the original Golay pair. Since the phase code of the DC interference cannot be manipulated, the supplementary Golay is designed to reverse the polarity of the 3f0 interference and the f0 signal while keeping the 2f0 signal unchanged. For 2f0 imaging, the echo summation of the supplementary and the original Golay can cancel the 3f0 interference. On the contrary, the echo difference between the two Golay pairs can eliminate the DC interference for f0 imaging. Hydrophone measurements indicate that the range side lobe level (RSLL) increases with the signal bandwidth of DF harmonic imaging. By using the combination of the two Golay pairs, the achievable suppression of RSLL can be 3 and 14 dB, respectively for the f0 and 2f0 harmonic signal. B-mode phantom imaging also verifies the presence of range side lobe artifacts when only the original Golay pair is utilized. In combination with the supplementary Golay pair, the artifacts are effectively suppressed. The corresponding range side lobe magnitude reduces by about 8 dB in 2f0 imaging but remains unchanged in f0 imaging. Meanwhile, the harmonic SNR improves by 8-10 dB and the contrast-to-noise ratio of harmonic image increases from about 1 to 1.2 by spectral compounding. For DF tissue harmonic imaging, the spectral cross-talk in Golay excitation results in severe range side lobe artifacts. To restore the image quality, two particular
DEFF Research Database (Denmark)
Cornaton, Y.; Stoyanova, A.; Jensen, Hans Jørgen Aagaard
2013-01-01
An alternative separation of short-range exchange and correlation energies is used in the framework of second-order range-separated density-functional perturbation theory. This alternative separation was initially proposed by Toulouse and relies on a long-range-interacting wave function instead...... of the noninteracting Kohn-Sham one. When second-order corrections to the density are neglected, the energy expression reduces to a range-separated double-hybrid (RSDH) type of functional, RSDHf, where "f" stands for "full-range integrals" as the regular full-range interaction appears explicitly in the energy...... on the potential energy curves in the equilibrium region, improving the accuracy of binding energies and equilibrium bond distances when second-order perturbation theory is appropriate....
Zhang, Daimeng
intermodulation (IM) measurement over a broad range of tone frequencies and tone powers. A sharp onset followed by a surprising strongly suppressed IM region near the resonance is observed. This behavior can be understood employing methods in nonlinear dynamics; the sharp onset, and the gap of IM, are due to sudden state jumps during a beat of the two-tone sum input signal. The theory predicts that the IM can be manipulated with tone power, center frequency, frequency difference between the two tones, and temperature. This quantitative understanding potentially allows for the design of rf-SQUID metamaterials with either very low or very high IM response.
High-sensitivity operation of single-beam optically pumped magnetometer in a kHz frequency range
Savukov, I.; Kim, Y. J.; Shah, V.; Boshier, M. G.
2017-03-01
Optically pumped magnetometers (OPM) can be used in various applications, from magnetoencephalography to magnetic resonance imaging and nuclear quadrupole resonance (NQR). OPMs provide high sensitivity and have the significant advantage of non-cryogenic operation. To date, many magnetometers have been demonstrated with sensitivity close to 1 fT, but most devices are not commercialized. Most recently, QuSpin developed a model of OPM that is low cost, high sensitivity, and convenient for users, which operates in a single-beam configuration. Here we developed a theory of single-beam (or parallel two-beam) magnetometers and showed that it is possible to achieve good sensitivity beyond their usual frequency range by tuning the magnetic field. Experimentally we have tested and optimized a QuSpin OPM for operation in the frequency range from DC to 1.7 kHz, and found that the performance was only slightly inferior despite the expected decrease due to deviation from the spin-exchange relaxation-free regime.
Eto, Kumi; Koch, Pamela; Contento, Isobel R.; Adachi, Miyuki
2011-01-01
Objective: To examine associations between Theory of Planned Behavior variables and the family meal frequency. Methods: Fifth-through seventh-grade students (n = 236) completed a self-administered questionnaire in their classrooms. The relationships between Theory of Planned Behavior variables (intention, attitudes, subjective norms, and perceived…
A nonlinear model of magnetorheological elastomer with wide amplitude range and variable frequencies
Wang, Qi; Dong, Xufeng; Li, Luyu; Ou, Jinping
2017-06-01
To develop control algorithms that taking maximum advantage of rapidly varying rheological properties of MR elastomer devices, models must be developed that can adequately characterize the smart material’s intrinsic nonlinearity. However, most existing MRE models are only effective within a narrow strain amplitude range and under certain loading frequencies. To derive a MRE model with better applicability, MR elastomer samples were fabricated and their steady-state response under harmonic loading with different strain amplitudes, frequencies and magnetic fields were tested. Following a review of several existing models of MR elastomer, a new revised Bouc-Wen model is proposed that can effectively portray the behavior of the material. Comparison with experimental results indicates that the model is accurate over a wide range of frequencies, strain amplitudes and magnetic flux densities. A simplified model was then proposed after parametric study. As the magnetic field is the only determinant of the parameters, the simplified model is adequate for base isolation devices design and simulation.
Complex magnetic susceptibility setup for spectroscopy in the extremely low-frequency range.
Kuipers, B W M; Bakelaar, I A; Klokkenburg, M; Erné, B H
2008-01-01
A sensitive balanced differential transformer was built to measure complex initial parallel magnetic susceptibility spectra in the 0.01-1000 Hz range. The alternating magnetic field can be chosen sufficiently weak that the magnetic structure of the samples is only slightly perturbed and the low frequencies make it possible to study the rotational dynamics of large magnetic colloidal particles or aggregates dispersed in a liquid. The distinguishing features of the setup are the novel multilayered cylindrical coils with a large sample volume and a large number of secondary turns (55 000) to measure induced voltages with a good signal-to-noise ratio, the use of a dual channel function generator to provide an ac current to the primary coils and an amplitude- and phase-adjusted compensation voltage to the dual phase differential lock-in amplifier, and the measurement of several vector quantities at each frequency. We present the electrical impedance characteristics of the coils, and we demonstrate the performance of the setup by measurement on magnetic colloidal dispersions covering a wide range of characteristic relaxation frequencies and magnetic susceptibilities, from chi approximately -10(-5) for pure water to chi>1 for concentrated ferrofluids.
Performance Analysis of Frequency Shift Keyed Signals in a Sonar Ranging System
Kodama, Tetsuji; Nakahira, Kenji; Koyama, Yuu; Murakami, Junichi
Pulsed ultrasonic distance measurement systems are frequently used in robotics applications, thanks to their low cost and small size. The pulse compression techniques, originally developed by radar engineers, were adopted to eliminate frequent misreadings caused by crosstalk or external ultrasound sources. High-performance computing systems for the implementation of pulse compression techniques enable reliable and accurate distance measurement. In most cases however, they significantly increase the complexity of the total system, cutting down one of the advantages of ultrasonic systems. The ultrasonic ranging using a digital polarity correlator can overcome this drawback, because the cost of realizing delay and multiplication for each point on the polarity correlation function as a parallel operation is very low. This paper presents an analysis of the binary coded frequency shift keyed signals for the ultrasonic ranging using a digital polarity correlator. The spectra of the frequency shift keyed signals have been observed to be narrow compared with the spectra of the corresponding phase shift keyed signals. This suggests the possibility of a more reliable and accurate distance measurement with the frequency shift keyed signals in terms of occupied bandwidth.
Hematite from Natural Iron Stones as Microwave Absorbing Material on X-Band Frequency Ranges
Zainuri, Mochamad
2017-05-01
This study has been investigated the effect of hematite as microwave absorbing materials (RAM) on X-Band frequency ranges. Hematite was succesfully processed by coprecipitation method and calcined at 500 °C for 5 hour. It was synthesized from natural iron stones from Tanah Laut, South Kalimantan, Indonesia. The products were characterized by X-ray diffraxtion (XRD), conductivity measurement, Vibrating Sample Magnetometer (VSM), and Vector Network Analyzer (VNA). The result was shown that hematite has conductivity value on (2.5-3).10-7 S/cm and be included as dielectric materials. The hysterisis curve was shown that hematite was a super paramagnetic materials. The product was mixed on paint with procentage 10% of total weight and coated on steel grade AH36 with spray methods. Then, the maximum of reflection loss on x - band’s frequency range (8,2-12,4) GHz was -7 dB on frequency of 10.5 GHz. It mean that almost 50% electromagnetic energy was absorbed by hematite.
Jointly Optimal Design for MIMO Radar Frequency-Hopping Waveforms Using Game Theory
2016-04-01
Jointly Optimal Design for MIMO Radar Frequency-Hopping Waveforms Using Game Theory KEYONG HAN, Student Member, IEEE ARYE NEHORAI, Fellow, IEEE...matrices that result in improved performance over that of separate designs. We propose a game theory framework for the joint design. First, we present...badly when the function evaluation is expensive. In recent years, game theory has been used to solve multiobjective design problems, especially for
Harker, K. J.
1972-01-01
Two basic high-frequency ionospheric instabilities are discussed - i.e., the three-wave parametric interaction, and the oscillating two-stream instability. In the parametric instability, the ion-acoustic wave has a complex frequency, whereas in the oscillating two-stream instability the ion-acoustic frequency is purely imaginary. The parametric instability is shown to be the only one whose threshold depends on the ion collision frequency. A coupled-mode theory is proposed which permits study and classification of high-frequency instabilities on a unified basis.
Multi-configuration time-dependent density-functional theory based on range separation
DEFF Research Database (Denmark)
Fromager, E.; Knecht, S.; Jensen, Hans Jørgen Aagaard
2013-01-01
Multi-configuration range-separated density-functional theory is extended to the time-dependent regime. An exact variational formulation is derived. The approximation, which consists in combining a long-range Multi-Configuration- Self-Consistent Field (MCSCF) treatment with an adiabatic short......-range density-functional (DFT) description, is then considered. The resulting time-dependent multi-configuration short-range DFT (TD-MC-srDFT) model is applied to the calculation of singlet excitation energies in H, Be, and ferrocene, considering both short-range local density (srLDA) and generalized gradient...
An Emerging Integrated Middle-Range Theory on Asian Women's Leadership in Nursing.
Im, Eun-Ok; Broome, Marion E; Inouye, Jillian; Kunaviktikul, Wipada; Oh, Eui Geum; Sakashita, Reiko; Yi, Myungsun; Huang, Lian-Hua; Tsai, Hsiu-Min; Wang, Hsiu-Hung
2018-02-01
Asian cultures reflect patriarchal cultural values and attitudes, which likely have influenced women leaders in their countries differently from women in Western cultures. However, virtually no leadership theories have been developed to reflect the experiences and development of nursing leaders from Asian cultures. The purpose of this article is to present an emerging integrated middle-range theory on Asian women's leadership in nursing. Using an integrative approach, the theory was developed based on three major sources: the leadership frames of Bolman and Deal, literature reviews, and exemplars/cases from five different countries. The theory includes two main domains (leadership frames and leadership contexts). The domain of leadership frames includes human resources/networks, structure/organization, national/international politics, and symbols. The domain of leadership contexts includes cultural contexts, sociopolitical contexts, and gendered contexts. This theory will help understand nursing leadership in Asian cultures and provide directions for future nurse leaders in this ever-changing globalized world.
Estimation of the RF Characteristics of Absorbing Materials in Broad RF Frequency Ranges
Fandos, R
2008-01-01
Absorbing materials are very often used in RF applications. Their electromagnetic characteristics (relative permittivity Îµr, loss tangent tan Î´ and conductivity Ï) are needed in order to obtain a high-quality design of the absorbing pieces in the frequency range of interest. Unfortunately, suppliers often do not provide these quantities. A simple technique to determine them, based on the RF measurement of the disturbance created by the insertion of a piece of absorber in a waveguide, is presented in this note. Results for samples of two different materials, silicon carbide and aluminum nitride are presented. While the former has a negligible conductivity at the working frequencies, the conductivity of the latter has to be taken into account in order to obtain a meaningful estimation of Îµr and tan Î´. The equations of Kramers & Kronig have been applied to the data as a cross check, confirming the results.
Inoue, S.; Shiraishi, J.; Takechi, M.; Matsunaga, G.; Isayama, A.; Hayashi, N.; Ide, S.
2017-11-01
An active stabilization effect of a rotating control field against an error field penetration is numerically studied. We have developed a resistive magnetohydrodynamic code ‘AEOLUS-IT’, which can simulate plasma responses to rotating/static external magnetic field. Adopting non-uniform flux coordinates system, the AEOLUS-IT simulation can employ high magnetic Reynolds number condition relevant to present tokamaks. By AEOLUS-IT, we successfully clarified the stabilization mechanism of the control field against the error field penetration. Physical processes of a plasma rotation drive via the control field are demonstrated by the nonlinear simulation, which reveals that the rotation amplitude at a resonant surface is not a monotonic function of the control field frequency, but has an extremum. Consequently, two ‘bifurcated’ frequency ranges of the control field are found for the stabilization of the error field penetration.
Range-resolved interferometric signal processing using sinusoidal optical frequency modulation.
Kissinger, Thomas; Charrett, Thomas O H; Tatam, Ralph P
2015-04-06
A novel signal processing technique using sinusoidal optical frequency modulation of an inexpensive continuous-wave laser diode source is proposed that allows highly linear interferometric phase measurements in a simple, self-referencing setup. Here, the use of a smooth window function is key to suppress unwanted signal components in the demodulation process. Signals from several interferometers with unequal optical path differences can be multiplexed, and, in contrast to prior work, the optical path differences are continuously variable, greatly increasing the practicality of the scheme. In this paper, the theory of the technique is presented, an experimental implementation using three multiplexed interferometers is demonstrated, and detailed investigations quantifying issues such as linearity and robustness against instrument drift are performed.
Diversification Rates and the Evolution of Species Range Size Frequency Distribution
Directory of Open Access Journals (Sweden)
Silvia Castiglione
2017-11-01
Full Text Available The geographic range sizes frequency distribution (RFD within clades is typically right-skewed with untransformed data, and bell-shaped or slightly left-skewed under the log-transformation. This means that most species within clades occupy diminutive ranges, whereas just a few species are truly widespread. A number of ecological and evolutionary explanations have been proposed to account for this pattern. Among the latter, much attention has been given to the issue of how extinction and speciation probabilities influence RFD. Numerous accounts now convincingly demonstrate that extinction rate decreases with range size, both in living and extinct taxa. The relationship between range size and speciation rate, though, is much less obvious, with either small or large ranged species being proposed to originate more daughter taxa. Herein, we used a large fossil database including 21 animal clades and more than 80,000 fossil occurrences distributed over more than 400 million years of marine metazoans (exclusive of vertebrates evolution, to test the relationship between extinction rate, speciation rate, and range size. As expected, we found that extinction rate almost linearly decreases with range size. In contrast, speciation rate peaks at the large (but not the largest end of the range size spectrum. This is consistent with the peripheral isolation mode of allopatric speciation being the main mechanism of species origination. The huge variation in phylogeny, fossilization potential, time of fossilization, and the overarching effect of mass extinctions suggest caution must be posed at generalizing our results, as individual clades may deviate significantly from the general pattern.
Nanostructured composite layers for electromagnetic shielding in the GHz frequency range
Suchea, M.; Tudose, I. V.; Tzagkarakis, G.; Kenanakis, G.; Katharakis, M.; Drakakis, E.; Koudoumas, E.
2015-10-01
We report on preliminary results regarding the applicability of nanostructured composite layers for electromagnetic shielding in the frequency range of 4-20 GHz. Various combinations of materials were employed including poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), polyaniline, graphene nanoplatelets, carbon nanotubes, Cu nanoparticles and Poly(vinyl alcohol). As shown, paint-like nanocomposite layers consisting of graphene nanoplatelets, polyaniline PEDOT:PSS and Poly(vinyl alcohol) can offer quite effective electromagnetic shielding, similar or even better than that of commercial products, the response strongly depending on their thickness and resistivity.
Wideband Monopole Fractal Heptagonal Antenna Implementation in X-Band Frequency Range
Iqbal, Muhammad Naeem; Ur-Rahman, Hamood; Tauqeer, T.; Ramer, Rodica
2017-10-01
A wideband heptagonal fractal monopole antenna with coplanar waveguide feed is designed and fabricated in X-band frequency range. Comparison of heptagonal fractal monopole antennas with two different substrates to achieve optimum efficiency for UWB applications is presented. FR4 and RT/Duroid 5880 substrates are used for antenna design and fabrication. Four iterations of base shape are used. Fractal antenna has omni-directional radiation pattern. Simulated and measured results showed that monopole fractal antenna with RT/Duroid 5880 substrate has better performance than fractal antenna with FR4 substrate in terms of bandwidth and return loss. Major application area of proposed antenna is wireless body area networks.
A New Algorithm for Joint Range-DOA-Frequency Estimation of Near-Field Sources
Directory of Open Access Journals (Sweden)
Jian-Feng Chen
2004-03-01
Full Text Available This paper studies the joint estimation problem of ranges, DOAs, and frequencies of near-field narrowband sources and proposes a new computationally efficient algorithm, which employs a symmetric uniform linear array, uses eigenvalues together with the corresponding eigenvectors of two properly designed matrices to estimate signal parameters, and does not require searching for spectral peak or pairing among parameters. In addition, the proposed algorithm can be applied in arbitrary Gaussian noise environment since it is based on the fourth-order cumulants, which is verified by extensive computer simulations.
Dielectric properties of the lithium-titanium ferrite ceramics in a wide frequency range
Surzhikov, A. P.; Gyngazov, S. A.; Lysenko, E. N.; Frangul'yan, T. S.; Malyshev, A. V.
2015-06-01
Electrophysical properties of the Li-Ti ferrite ceramics with the spinel structure (Li0.649Fe1.598Ti0.5Zn0.2Mn0.051O4) are studied in the frequency interval 0.5-2.5 GHz at temperatures ranging from room temperature to 530 K. The thermal emf of the ferrite ceramic samples is studied. It is demonstrated that the sample under study exhibits electron conduction. The calculated results are used to interpret the conduction mechanism using the hopping model.
Rouseff, Daniel; Tang, Dajun; Williams, Kevin L; Wang, Zhongkang; Moum, James N
2008-09-01
Preliminary results are presented from an analysis of mid-frequency acoustic transmission data collected at range 550 m during the Shallow Water 2006 Experiment. The acoustic data were collected on a vertical array immediately before, during, and after the passage of a nonlinear internal wave on 18 August, 2006. Using oceanographic data collected at a nearby location, a plane-wave model for the nonlinear internal wave's position as a function of time is developed. Experimental results show a new acoustic path is generated as the internal wave passes above the acoustic source.
A Fixed-Frequency Bidirectional Resonant DC-DC Converter Suitable for Wide Voltage Gain Range
DEFF Research Database (Denmark)
Shen, Yanfeng; Wang, Huai; Blaabjerg, Frede
2017-01-01
. It is realized by configuring a full-bridge mode and a half-bridge mode operation during each switching cycle. The fixed-frequency phase-shift control schemes are applied and the normalized voltage gain can be always from 0.5 to 1, regardless of the load. The transformer root-mean-square (RMS) currents in both...... the forward and the reverse modes have a negligible variation with respect to the voltage gain, which is beneficial to low conduction losses throughout a wide voltage range. Moreover, the applied MOSFETs are soft-switched, allowing for minimum switching losses. Both the operation principles...
Theory of High Frequency Rectification by Silicon Crystals
Bethe, H. A.
1942-10-29
The excellent performance of British "red dot" crystals is explained as due to the knife edge contact against a polished surface. High frequency rectification depends critically on the capacity of the rectifying boundary layer of the crystal, C. For high conversion efficiency, the product of this capacity and of the "forward" (bulk) resistance R {sub b} of the crystal must be small. For a knife edge, this product depends primarily on the breadth of the knife edge and very little upon its length. The contact can therefore have a rather large area which prevents burn-out. For a wavelength of 10 cm. the computations show that the breadth of the knife edge should be less than about 10 {sup -3} cm. For a point contact the radius must be less than 1.5 x 10 {sup -3} cm. and the resulting small area is conducive to burn-out. The effect of "tapping" is probably to reduce the area of contact. (auth)
Bongers, W. A.; van Beveren, V.; Thoen, D. J.; Nuij, Pjwm; M.R. de Baar,; Donne, A. J. H.; Westerhof, E.; Goede, A. P. H.; Krijger, B.; van den Berg, M. A.; Kantor, M.; M. F. Graswinckel,; Hennen, B.A.; Schüller, F. C.
2011-01-01
An intermediate frequency (IF) band digitizing radiometer system in the 100-200 GHz frequency range has been developed for Tokamak diagnostics and control, and other fields of research which require a high flexibility in frequency resolution combined with a large bandwidth and the retrieval of the
Bongers, WA.; Van Beveren, V.; Thoen, D.J.; Nuij, P.J.W.M.; De Baar, M.R.; Donné, A.J.H.; Westerhof, E.; Goede, A.P.H.; Krijger, B.; Van den Berg, M.A.; Kantor, M.; Graswinckel, M.F.; Hennen, B.A.; Schüller, F.C.
2011-01-01
An intermediate frequency (IF) band digitizing radiometer system in the 100–200 GHz frequency range has been developed for Tokamak diagnostics and control, and other fields of research which require a high flexibility in frequency resolution combined with a large bandwidth and the retrieval of the
Nanostructured composite layers for electromagnetic shielding in the GHz frequency range
Energy Technology Data Exchange (ETDEWEB)
Suchea, M. [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Chemistry and Physics, “Al.I. Cuza” University of Iasi, Iasi (Romania); Tudose, I.V. [Chemistry and Physics, “Al.I. Cuza” University of Iasi, Iasi (Romania); Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Tzagkarakis, G. [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Electrical Engineering Department, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Kenanakis, G. [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Institute of Electronic Structure & Laser (IESL), Foundation for Research and Technology (FORTH) Hellas, Heraklion (Greece); Katharakis, M. [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Drakakis, E. [Electrical Engineering Department, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Koudoumas, E., E-mail: koudoumas@staff.teicrete.gr [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Electrical Engineering Department, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece)
2015-10-15
Graphical abstract: - Highlights: • Paint-like nanocomposite layers consisting of graphene nanoplatelets, PANI:HCl and PEDOT:PSS present very effective attenuation of electromagnetic radiation in the frequency range 4–20 GHz. • The shielding performance is based mostly on the graphene nanoplatelets and supported by PANI:HCl. In contrast, PEDOT:PSS plays mainly the role of the binder. • Increasing resistivity was observed to reduce the shielding effect, while increasing thickness to favor it. - Abstract: We report on preliminary results regarding the applicability of nanostructured composite layers for electromagnetic shielding in the frequency range of 4–20 GHz. Various combinations of materials were employed including poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), polyaniline, graphene nanoplatelets, carbon nanotubes, Cu nanoparticles and Poly(vinyl alcohol). As shown, paint-like nanocomposite layers consisting of graphene nanoplatelets, polyaniline PEDOT:PSS and Poly(vinyl alcohol) can offer quite effective electromagnetic shielding, similar or even better than that of commercial products, the response strongly depending on their thickness and resistivity.
flatFLIM: enhancing the dynamic range of frequency domain FLIM.
Schuermann, Klaus C; Grecco, Hernán E
2012-08-27
Fluorescence Lifetime Imaging Microscopy (FLIM) is a quantitative technique to probe the nanoenvironment of fluorescent molecules. It is the most robust way to quantify Förster Resonance Energy Transfer (FRET) as it allows reliable differentiation between concentration changes and quenching. In this way, molecular interactions can be imaged in single living cells. The most common wide-field implementation is homodyne Frequency Domain (FD) FLIM, which determines the fluorescence lifetime by measuring the phase and modulation changes of the fluorescence in each pixel upon excitation with a light source modulated at a high frequency. The fluorescence lifetimes are derived from a stack of images acquired at different phase shifts between excitation and detection. In this work we describe a simple method to enhance the dynamic range of FD-FLIM based on precompensating the expected fluorescence modulation by varying the laser power through the phase stack. We show theoretically and experimentally that most of the dynamic range of the camera can be recovered to quantify cells with different intensities. This improvement can be added to any FD-FLIM setup with minimal modifications, enhancing the throughput of information content.
Jung, Jae Woong; Kim, Jae Eun; Lee, Jin Woo
2018-01-01
We present the design, including an experimental demonstration, of an acoustic metamaterial panel aimed at reducing incoming broadband noise in the audible frequency range while allowing an incoming fluid to pass through the holes formed in the panel. The noise reduction performance of the proposed acoustic metamaterial panel is attributed to an array of annular cavities enclosing the fluid passage holes. The acoustic behavior of the acoustic metamaterial panel is theoretically analyzed by the transfer matrix method, and an equivalent acoustic impedance of each annular cavity is included with its effective length in the derived transfer matrix. The effective bulk modulus for the acoustic metamaterial panel is then extracted from the transmission and reflection coefficients by using the retrieval method. It is shown that the frequency range of the negative effective bulk modulus coincides with the stop band of the acoustic metamaterial panel. The underlying physical mechanism for the negative effective bulk modulus is attributed to the out-of-phase motion of vibrating particles in adjacent annular cavities. A calculated transmission coefficient curve of the acoustic metamaterial panel is shown to be in good agreement with the measured one. The findings presented in this work should be useful in the design of a holey soundproof panel.
A Novel Unit Cell for Active Switches in the Millimeter-Wave Frequency Range
Müller, Daniel; Scherer, Gunnar; Lewark, Ulrich J.; Massler, Hermann; Wagner, Sandrine; Tessmann, Axel; Leuther, Arnulf; Zwick, Thomas; Kallfass, Ingmar
2018-02-01
This paper presents a novel transistor unit cell which is intended to realize compact active switches in the high millimeter-wave frequency range. The unit cell consists of the combination of shunt and common gate transistor within a four-finger transistor cell, achieving gain in the amplifying state as well as good isolation in the isolating state. Gate width-dependent characteristics of the unit cell as well as the design of actual switch implementations are discussed in detail. To verify the concept, two switches, a single pole double throw (SPDT) switch and single pole quadruple throw (SP4T) switch, intended for the WR3 frequency range (220-325 GHz) were manufactured and characterized. The measured gain at 250 GHz is 4.6 and 2.2 dB for the SPDT and SP4T switch, respectively. An isolation of more than 24 dB for the SPDT switch and 12.8 dB for the SP4T switch was achieved.
Mitchell, Jason W.; Baldwin, Philip J.; Kurichh, Rishi; Naasz, Bo J.; Luquette, Richard J.
2007-01-01
The Formation Flying Testbed (FFTB) at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) provides a hardware-in-the-loop test environment for formation navigation and control. The facility is evolving as a modular, hybrid, dynamic simulation facility for end-to-end guidance, navigation and control (GN&C) design and analysis of formation flying spacecraft. The core capabilities of the FFTB, as a platform for testing critical hardware and software algorithms in-the-loop, have expanded to include S-band Radio Frequency (RF) modems for interspacecraft communication and ranging. To enable realistic simulations that require RF ranging sensors for relative navigation, a mechanism is needed to buffer the RF signals exchanged between spacecraft that accurately emulates the dynamic environment through which the RF signals travel, including the effects of the medium, moving platforms, and radiated power. The Path Emulator for Radio Frequency Signals (PERFS), currently under development at NASA GSFC, provides this capability. The function and performance of a prototype device are presented.
Clegg-Watkins, R. N.; Jolliff, B. L.; Lawrence, S. J.
2016-01-01
Boulders represent a landing hazard that must be addressed in the planning of future landings on the Moon. A boulder under a landing leg can contribute to deck tilt and boulders can damage spacecraft during landing. Using orbital data to characterize boulder populations at locations where landers have safely touched down (Apollo, Luna, Surveyor, and Chang'e-3 sites) is important for determining landing hazard criteria for future missions. Additionally, assessing the distribution of boulders can address broader science issues, e.g., how far craters distribute boulders and how this distribution varies as a function of crater size and age. The availability of new Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) images [1] enables the use of boulder size- and range frequency distributions for a variety of purposes [2-6]. Boulders degrade over time and primarily occur around young or fresh craters that are large enough to excavate bedrock. Here we use NAC images to analyze boulder distributions around Cone crater (340 m diameter) at the Apollo 14 site. Cone crater (CC) was selected because it is the largest crater where astronaut surface photography is available for a radial traverse to the rim. Cone crater is young (approximately 29 Ma [7]) relative to the time required to break down boulders [3,8], giving us a data point for boulder range-frequency distributions (BRFDs) as a function of crater age.
Analysis of the exactness of mean-field theory in long-range interacting systems.
Mori, Takashi
2010-12-01
Relationships between general long-range interacting classical systems on a lattice and the corresponding mean-field models (infinitely long-range interacting models) are investigated. We study systems in arbitrary dimension d for periodic boundary conditions and focus on the free energy for fixed value of the total magnetization. As a result, it is shown that the equilibrium free energy of the long-range interacting systems are exactly the same as that of the corresponding mean-field models (exactness of the mean-field theory). Moreover, the mean-field metastable states can be also preserved in general long-range interacting systems. It is found that in the case that the magnetization is conserved, the mean-field theory does not give correct property in some parameter region.
Reflecting and Polarizing Properties of Conductive Fabrics in Ultra-High Frequency Range
Directory of Open Access Journals (Sweden)
Oleg Kiprijanovič
2015-09-01
Full Text Available The system based on ultra-wide band (UWB signals was employed for qualitative estimation of attenuating, reflecting and polarizing properties of conductive fabrics, capable to prevent local static charge accumulation. Pulsed excitation of triangle monopole antenna of 6.5 cm height by rectangular electric pulses induced radiation of UWB signals with spectral density of power having maximum in ultra-high frequency (UHF range. The same antenna was used for the radiated signal receiving. Filters and amplifiers of different passband were employed to divide UHF range into subranges of 0.3-0.55 GHz, 0.55-1 GHz, 1-2 GHz and 2-4 GHz bands. The free space method, when conductive fabric samples of 50x50 cm2 were placed between transmitting and receiving antennas, was used to imitate a practical application. Received wideband signals corresponding to the defined range were detected by unbiased detectors. The fabrics made of two types of warps, containing different threads with conductive yarns, were investigated. It was estimated attenuation and reflective properties of the fabrics when electric field is collinear or perpendicular to thread direction. In the UHF range it was revealed good reflecting properties of the fabrics containing metallic component in the threads. The system has advantages but not without a certain shortcoming. Adapting it for specific tasks should lead to more effective usage, including yet unused properties of the UWB signals.
Yu, Xudong; Long, Xingwu; Wei, Guo; Li, Geng; Qu, Tianliang
2015-04-01
A finite element model of the hemispherical resonator gyro (HRG) is established and the natural frequencies and vibration modes are investigated. The matrix perturbation technology in the random finite element method is first introduced to analyze the statistical characteristics of the natural frequencies of HRG. The influences of random material parameters and dimensional parameters on the natural frequencies are quantitatively described based on the probability theory. The statistics expressions of the random parameters are given and the influences of three key parameters on natural frequency are pointed out. These results are important for design and improvement of high accuracy HRG.
Historic Frequency and Severity of Fire in Whitebark Pine Forests of the Cascade Mountain Range, USA
Directory of Open Access Journals (Sweden)
Michael P. Murray
2018-02-01
Full Text Available Whitebark pine (Pinus albicaulis Engelm. is a foundation species of high elevation forest ecosystems in the Cascade Mountain Range of Oregon, Washington, and British Columbia. We examined fire evidence on 55 fire history sites located in the Cascade Range. To estimate dates of historic fires we analyzed 57 partial cross-sections from fire-scarred trees plus 700 increment cores. The resulting 101 fire events indicate fire has been a widespread component of Cascadian whitebark pine stands. Results are site specific and vary considerably. Whitebark pine stands appear to burn in a variety of severities and frequencies. Sites where fire intervals were detected ranged from 9 to 314 years, with a median of 49 years, and averaging 67 years. Fire intervals shortened significantly with higher latitudes. In assessing the most recent fire event at each site, overall, 56 percent burned as stand replacing events. In the 20th century, the number of fires diminished significantly. Due to conservation imperatives, re-introducing fire should be undertaken with extreme care to avoid substantial mortality of this endangered species.
Park, SangWook; Kim, Minhyuk
2016-01-01
In this paper, a numerical exposure assessment method is presented for a quasi-static analysis by the use of finite-difference time-domain (FDTD) algorithm. The proposed method is composed of scattered field FDTD method and quasi-static approximation for analyzing of the low frequency band electromagnetic problems. The proposed method provides an effective tool to compute induced electric fields in an anatomically realistic human voxel model exposed to an arbitrary non-uniform field source in the low frequency ranges. The method is verified, and excellent agreement with theoretical solutions is found for a dielectric sphere model exposed to a magnetic dipole source. The assessment method serves a practical example of the electric fields, current densities, and specific absorption rates induced in a human head and body in close proximity to a 150-kHz wireless power transfer system for cell phone charging. The results are compared to the limits recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the IEEE standard guidelines.
Dynamics of r.f. production of Stellarator plasmas in the ion cyclotron range of frequency
Energy Technology Data Exchange (ETDEWEB)
Moiseenko, V.E. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Center; Lysoivan, A.I. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Center; Kasilov, S.V. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Center; Plyusnin, V.V. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Center
1995-01-01
The present study investigated numerically the process of r.f. production of plasma in the URAGAN-3M torsatron in the frequency range below the ion cyclotron frequency ({omega}<{omega}{sub ci}). The dynamics of r.f. plasma build-up at the stages of neutral gas burnout and plasma heating were studied using a zero-dimensional transport code, in which the plasma confinement law was determined by large helical device scaling. Two models for input r.f. power were used. In the first case, the r.f. power absorbed by the electrons was computed by a one-dimensional r.f. code solving Maxwell`s boundary problem equations. The mechanisms of electron heating through direct excitation of the slow wave (SW) by antennae as well as the conversion of fast wave (FW) into SW in the vicinity of Alfven resonance (scenario of Alfven heating) were taken into account in the computations. In the second case, an `ideal` model of r.f. power deposition onto the electrons as a linear function of plasma density was employed. A noticeable difference in plasma production dynamics computed for these two cases was found. Better agreement with experimental data obtained from the URAGAN-3M torsatron was found for the first case resulting from combination of the one-dimensional r.f. and zero-dimensional transport codes. ((orig.)).
Zero-range effective field theory for resonant wino dark matter. Part I. Framework
Braaten, Eric; Johnson, Evan; Zhang, Hong
2017-11-01
The most dramatic "Sommerfeld enhancements" of neutral-wino-pair annihilation occur when the wino mass is near a critical value where there is a zero-energy S-wave resonance at the neutral-wino-pair threshold. Near such a critical mass, low-energy winos can be described by a zero-range effective field theory in which the winos interact nonperturbatively through a contact interaction. The effective field theory is controlled by a renormalization-group fixed point at which the neutral and charged winos are degenerate in mass and their scattering length is infinite. The parameters of the zero-range effective field theory can be determined by matching wino-wino scattering amplitudes calculated by solving the Schrödinger equation for winos interacting through a potential due to the exchange of weak gauge bosons. If the wino mass is larger than the critical value, the resonance is a wino-pair bound state. The power of the zero-range effective field theory is illustrated by calculating the rate for formation of the bound state in the collision of two neutral winos through the emission of two soft photons.
Zero-Range Effective Field Theory for Resonant Wino Dark Matter
Johnson, Evan; Braaten, Eric; Zhang, Hong
2017-01-01
The most dramatic ``Sommerfeld enhancements'' of neutral-wino-pair annihilation occur when the wino mass is tuned to near critical values where there is a zero-energy S-wave resonance at the neutral-wino-pair threshold. If the wino mass is larger than the critical value, the resonance is a wino-pair bound state. If the wino mass is near a critical value, low-energy winos can be described by a zero-range effective field theory in which the winos interact nonperturbatively through a contact interaction. The parameters of the zero-range effective field theory can be determined by matching wino scattering amplitudes calculated by solving the Schrödinger equation for a nonrelativistic effective field theory in which the winos interact nonperturbatively through a potential due to the exchange of weak gauge bosons. The power of the zero-range effective field theory is illustrated by calculating the rate for formation of the bound state in the collision of two neutral winos through the emission of two soft photons. Supported in part by DOE grant DE-FG02-05ER15715.
Directory of Open Access Journals (Sweden)
H. Garbe
2008-05-01
Full Text Available Up to now most limits for radiated emission are given as values for the electrical field strength. Battermann, 2007 has shown that the frequency range extension for radiated emission measurements above 1 GHz generates a lot of problems while performing the test on a classical test site as depicted in Fig. 1. This paper will give a motivation to use an other measurand namely the total-radiated-power than electrical field strength by using alternative test sites like reverberation chambers, TEM-waveguides, Fully Anechoic Rooms (FAR etc. Nevertheless most of the existing standards still specify electrical field strength limits. This paper will show how to set the parameters in the given algorithm to establish a link between measured total radiated power and equivalent electrical field values.
Relaxations in metallic glasses investigated by a broad frequency and temperature range
Energy Technology Data Exchange (ETDEWEB)
Bedorf, Dennis; Koeppe, Thomas; Hachenberg, Joerg; Samwer, Konrad [I. Physikalisches Institut, Universitaet Goettingen, Friedrich-Hund-Platz 1, 37077 Goettingen (Germany); Kahl, Annelen [Keck Laboratories MS 138-78 Caltech, Pasadena CA 91125 (United States); Richert, Ranko [Department of Chemistry and Biochemistry, Arizona State University, Tempe AZ 85287-1604 (United States)
2007-07-01
We are interested in glassy dynamics and the atomistic processes leading to different relaxations in amorphous materials. To measure the complex elastic constants, two mechanical spectroscopy techniques were employed. The use of a double-paddle-oscillator (DPO) provides sufficient sensitivity to investigate the loss of even thin films. A DPO is driven in eigenfrequency mode at 5.4 kHz and an amorphous metallic film (PdCuSi) is evaporated onto it and measured under UHV conditions. Cooling and heating enables measurements in a broad temperature range with different heating rates. To survey the elastic constants at higher frequencies, an ultrasonic spectroscopy technique in the MHz regime is used. The pulse-echo method is applied to a bulk metallic glass in order to obtain the shear modulus and attenuation by monitoring shear wave propagation. The results are discussed in the framework of the Cooperative Shear Model.
Acoustic absorption measurement of human hair and skin within the audible frequency range.
Katz, B F
2000-11-01
Utilizing the two-microphone impedance tube method, the acoustic absorption of human skin and hair is measured in the frequency range 1-6 kHz. Various locations on a number of human subjects are measured to determine if the presence of bone or an air pocket affects the acoustic absorption of human skin. The absorption coefficient of human hair is also measured. Additional techniques are utilized to minimize errors due to sample mounting methods. Techniques are employed to minimize potential errors in sensor and sample locations. The results of these measurements are compared to relevant historical papers on similar investigations. Results for skin measurements compare well with previous work. Measured hair absorption data do not agree with previous work in the area but do coincide with expected trends, which previous works do not.
Studies for the ion cyclotron range of frequency heating in a tokamak fusion experimental device
Energy Technology Data Exchange (ETDEWEB)
Saigusa, Mikio [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment
1996-02-01
Ion cyclotron range of frequency heating has been investigated as an efficient additional plasma heating and non-inductive current driving methods in a tokamak type fusion experimental device. At first, an ICRF antenna coupling code was developed for the estimation of the coupling properties of phased antenna array, so that the ICRF antennas were designed for JT-60 and JT-60U ICRF heating systems using the coupling codes. The ICRF heating experiments had been performed in JT-60 and JT-60U. The coupling properties of ICRF antenna, the physics of peripheral plasma and energy confinement by ICRF heating in various heating regimes have been investigated. Next, the Toroidicity induced Alfven Eigen (TAE) mode have been studied using minority ICRF heating for producing energetic ions which can excite TAE mode. The TAE mode could be suppressed by current profile control using current ramp operation and lower hybrid current drive. (author) 74 refs.
Interaction of a relativistic electron beam with radiation in the THz frequency range
Sung, Chieh
0.5-3 THz range with a maximum of ˜2 kW of peak power in a 200 ns pulse suitable as a seed for an FEL microbuncher. These sources represent the most powerful and the most energetic narrowband THz sources currently reported using nonlinear optical technique to our knowledge. During the FEL microbunching process, the wiggling electrons in the undulator also emit radiation coherently at the resonant frequency; as a result, the THz FEL microbuncher can double as a single pass THz amplifier tunable in the 0.5-3 THz range. It is shown that when seeded with a ˜1 kW THz pulse and driven by an electron beam with a peak current of 60A, a 2 m-long undulator can amplify the radiation power to ˜20MW. The frequency range can be further expanded to up to 9 THz via the High Gain Harmonic Generation (HGHG) FEL configuration. The results of these simulations are used as a guide in designing a single-pass THz FEL microbuncher/amplifier which is currently under construction. In order to study THz microbunching and amplification, several original techniques and diagnostics were also developed. Guiding a THz pulse through a hollow waveguide, filtering a short THz pulse using a Fabry-Perot interferometer and measuring the frequency components using a diffraction grating spectrometer were demonstrated.
Georgiades, Nikos P.; Polzik, Eugene S.; Kimble, H. Jeff
1999-02-02
An opto-electronic system and technique for comparing laser frequencies with large frequency separations, establishing new frequency standards, and achieving phase-sensitive detection at ultra high frequencies. Light responsive materials with multiple energy levels suitable for multi-photon excitation are preferably used for nonlinear mixing via quantum interference of different excitation paths affecting a common energy level. Demodulation of a carrier with a demodulation frequency up to 100's THZ can be achieved for frequency comparison and phase-sensitive detection. A large number of materials can be used to cover a wide spectral range including the ultra violet, visible and near infrared regions. In particular, absolute frequency measurement in a spectrum from 1.25 .mu.m to 1.66 .mu.m for fiber optics can be accomplished with a nearly continuous frequency coverage.
On the effect of topography on surface wave propagation in the ambient noise frequency range
Köhler, Andreas; Weidle, Christian; Maupin, Valérie
2012-04-01
Due to the increasing popularity of analyzing empirical Green's functions obtained from ambient seismic noise, more and more regional tomographical studies based on short-period surface waves are published. Results could potentially be biased in mountainous regions where topography is not small compared to the wavelength and penetration depth of the considered waves. We investigate the effect of topography on the propagation of short-period Rayleigh waves empirically by means of synthetic data using a spectral element code and a 3-D model with real topography. We show that topography along a profile through the studied area can result in an underestimation of phase velocities of up to about 0.7% at the shortest investigated period (3 s). Contrary to the expectation that this bias results from the increased surface distance along topography, we find that this error can be estimated by local topographic contrasts in the vicinity of the receiver alone. We discuss and generalize our results by considering topographic profiles through other mountain ranges and find that southern Norway is a good proxy to assess the topography effect. Nevertheless, topographic bias on phase velocity measurements is in general not large enough to significantly affect recovered velocity variations in the ambient noise frequency range.
Mitchell, Jason W.; Baldwin, Philip J.; Kurichh, Rishi; Naasz, Bo J.; Luquette, Richard J.
2007-01-01
The Formation Flying Testbed (FFTB) at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) provides a hardware-in-the-loop test environment for formation navigation and control. The facility is evolving as a modular, hybrid, dynamic simulation facility for end-to-end guidance, navigation and. control (GN&C) design and analysis of formation flying spacecraft. The core capabilities of the FFTB, as a platform for testing critical hardware and software algorithms in-the-loop, have expanded to include S-band Radio Frequency (RF) modems for inter-spacecraft communication and ranging. To enable realistic simulations that require RF ranging sensors for relative navigation, a mechanism is needed to buffer the RF signals exchanged between spacecraft that accurately emulates the dynamic environment through which the RF signals travel, including the effects of medium, moving platforms, and radiated power. The Path Emulator for RF Signals (PERFS), currently under development at NASA GSFC, provides this capability. The function and performance of a prototype device are presented.
Trollinger, Valerie L.
This study investigated the relationship between acoustical measurement of singing accuracy in relationship to speech fundamental frequency, speech fundamental frequency range, age and gender in preschool-aged children. Seventy subjects from Southeastern Pennsylvania; the San Francisco Bay Area, California; and Terre Haute, Indiana, participated in the study. Speech frequency was measured by having the subjects participate in spontaneous and guided speech activities with the researcher, with 18 diverse samples extracted from each subject's recording for acoustical analysis for fundamental frequency in Hz with the CSpeech computer program. The fundamental frequencies were averaged together to derive a mean speech frequency score for each subject. Speech range was calculated by subtracting the lowest fundamental frequency produced from the highest fundamental frequency produced, resulting in a speech range measured in increments of Hz. Singing accuracy was measured by having the subjects each echo-sing six randomized patterns using the pitches Middle C, D, E, F♯, G and A (440), using the solfege syllables of Do and Re, which were recorded by a 5-year-old female model. For each subject, 18 samples of singing were recorded. All samples were analyzed by the CSpeech for fundamental frequency. For each subject, deviation scores in Hz were derived by calculating the difference between what the model sang in Hz and what the subject sang in response in Hz. Individual scores for each child consisted of an overall mean total deviation frequency, mean frequency deviations for each pattern, and mean frequency deviation for each pitch. Pearson correlations, MANOVA and ANOVA analyses, Multiple Regressions and Discriminant Analysis revealed the following findings: (1) moderate but significant (p pitches E, F♯, G and A in the study; (2) mean speech frequency also emerged as the strongest predictor of subjects' ability to sing the notes E and F♯; (3) mean speech frequency
Statistical testing of the full-range leadership theory in nursing.
Kanste, Outi; Kääriäinen, Maria; Kyngäs, Helvi
2009-12-01
The aim of this study is to test statistically the structure of the full-range leadership theory in nursing. The data were gathered by postal questionnaires from nurses and nurse leaders working in healthcare organizations in Finland. A follow-up study was performed 1 year later. The sample consisted of 601 nurses and nurse leaders, and the follow-up study had 78 respondents. Theory was tested through structural equation modelling, standard regression analysis and two-way anova. Rewarding transformational leadership seems to promote and passive laissez-faire leadership to reduce willingness to exert extra effort, perceptions of leader effectiveness and satisfaction with the leader. Active management-by-exception seems to reduce willingness to exert extra effort and perception of leader effectiveness. Rewarding transformational leadership remained as a strong explanatory factor of all outcome variables measured 1 year later. The data supported the main structure of the full-range leadership theory, lending support to the universal nature of the theory.
Li, Zhenglin; Zhang, Renhe; Li, Fenghua
2010-09-01
Ocean reverberation in shallow water is often the predominant background interference in active sonar applications. It is still an open problem in underwater acoustics. In recent years, an oscillation phenomenon of the reverberation intensity, due to the interference of the normal modes, has been observed in many experiments. A coherent reverberation theory has been developed and used to explain this oscillation phenomenon [F. Li et al., Journal of Sound and Vibration, 252(3), 457-468, 2002]. However, the published coherent reverberation theory is for the range independent environment. Following the derivations by F. Li and Ellis [D. D. Ellis, J. Acoust. Soc. Am., 97(5), 2804-2814, 1995], a general reverberation model based on the adiabatic normal mode theory in a range dependent shallow water environment is presented. From this theory the coherent or incoherent reverberation field caused by sediment inhomogeneity and surface roughness can be predicted. Observations of reverberation from the 2001 Asian Sea International Acoustic Experiment (ASIAEX) in the East China Sea are used to test the model. Model/data comparison shows that the coherent reverberation model can predict the experimental oscillation phenomenon of reverberation intensity and the vertical correlation of reverberation very well.
Recent studies of short-range order in alloys: The Cowley theory revisited
Energy Technology Data Exchange (ETDEWEB)
Reinhard, L. [Lawrence Livermore National Lab., CA (United States); Moss, S.C. [Houston Univ., TX (United States). Dept. of Physics
1993-02-08
We present comparisons of various statistical theories for effective pair interactions (EPI) in alloys. We then evaluate these EPI`s using the Cowley theory, the Krivoglaz-Clapp-Moss (KCM) approximation, the {gamma}-expansion method (GEM) of Tokar, Masanskii and coworkers, and the exact inverse Monte Carlo (IMC) method, introduced by Gerold and Kern. Via a series of model calculations on a hypothetical bcc alloy with a single nearest-neighbor interaction we show that the Cowley theory is successful in evaluating the EPI`s in more dilute alloys but tends to overestimate the magnitude of the nearest neighbor energy at higher concentrations, whereas the KCM expression becomes increasingly inaccurate at lower concentrations. In general, however, the approximate mean field theories are most accurate at higher concentrations and higher temperatures. Recent studies of short-range order in single crystals are discussed in which these EPI`s have been evaluated using the IMC, KCM, GEM and Cowley theories. Examples include the bcc alloy Fe{sub 0.53}Cr{sub 0.47} and the fcc alloys Cu{sub 3} Au, CU{sub 0.69}Zn{sub 0.31} and Ni{sub 0.89}BgCr{sub 0.11}. In all cases the approximate expressions do quite well, especially the GEM.
Kimura, Tomoki; Taki, Hirofumi; Sakamoto, Takuya; Sato, Toru
2009-07-01
We employed frequency domain interferometry (FDI) for use as a medical acoustic imager to detect multiple targets with high range resolution. The phase of each frequency component of an echo varies with the frequency, and target intervals can be estimated from the phase variance. This processing technique is generally used in radar imaging. When the interference within a range gate is coherent, the cross correlation between the desired signal and the coherent interference signal is nonzero. The Capon method works under the guiding principle that output power minimization cancels the desired signal with a coherent interference signal. Therefore, we utilize frequency averaging to suppress the correlation of the coherent interference. The results of computational simulations using a pseudoecho signal show that the Capon method with adaptive frequency averaging (AFA) provides a higher range resolution than a conventional method. These techniques were experimentally investigated and we confirmed the effectiveness of the proposed method of processing by FDI.
Revil, A
2013-01-01
A model combining low-frequency complex conductivity and high-frequency permittivity is developed in the frequency range from 1 mHz to 1 GHz. The low-frequency conductivity depends on pore water and surface conductivities. Surface conductivity is controlled by the electrical diffuse layer, the outer component of the electrical double layer coating the surface of the minerals. The frequency dependence of the effective quadrature conductivity shows three domains. Below a critical frequency fp , which depends on the dynamic pore throat size Λ, the quadrature conductivity is frequency dependent. Between fp and a second critical frequency fd , the quadrature conductivity is generally well described by a plateau when clay minerals are present in the material. Clay-free porous materials with a narrow grain size distribution are described by a Cole-Cole model. The characteristic frequency fd controls the transition between double layer polarization and the effect of the high-frequency permittivity of the material. The Maxwell-Wagner polarization is found to be relatively negligible. For a broad range of frequencies below 1 MHz, the effective permittivity exhibits a strong dependence with the cation exchange capacity and the specific surface area. At high frequency, above the critical frequency fd , the effective permittivity reaches a high-frequency asymptotic limit that is controlled by the two Archie's exponents m and n like the low-frequency electrical conductivity. The unified model is compared with various data sets from the literature and is able to explain fairly well a broad number of observations with a very small number of textural and electrochemical parameters. It could be therefore used to interpret induced polarization, induction-based electromagnetic methods, and ground penetrating radar data to characterize the vadose zone.
Revil, A
2013-01-01
A model combining low-frequency complex conductivity and high-frequency permittivity is developed in the frequency range from 1 mHz to 1 GHz. The low-frequency conductivity depends on pore water and surface conductivities. Surface conductivity is controlled by the electrical diffuse layer, the outer component of the electrical double layer coating the surface of the minerals. The frequency dependence of the effective quadrature conductivity shows three domains. Below a critical frequency fp, which depends on the dynamic pore throat size Λ, the quadrature conductivity is frequency dependent. Between fp and a second critical frequency fd, the quadrature conductivity is generally well described by a plateau when clay minerals are present in the material. Clay-free porous materials with a narrow grain size distribution are described by a Cole-Cole model. The characteristic frequency fd controls the transition between double layer polarization and the effect of the high-frequency permittivity of the material. The Maxwell-Wagner polarization is found to be relatively negligible. For a broad range of frequencies below 1 MHz, the effective permittivity exhibits a strong dependence with the cation exchange capacity and the specific surface area. At high frequency, above the critical frequency fd, the effective permittivity reaches a high-frequency asymptotic limit that is controlled by the two Archie's exponents m and n like the low-frequency electrical conductivity. The unified model is compared with various data sets from the literature and is able to explain fairly well a broad number of observations with a very small number of textural and electrochemical parameters. It could be therefore used to interpret induced polarization, induction-based electromagnetic methods, and ground penetrating radar data to characterize the vadose zone. PMID:23576823
Directory of Open Access Journals (Sweden)
Vida Zaroushani
2016-12-01
Full Text Available Introduction: Due to the importance of engineering controls for prevention of microwave exposure, this study was conducted to design and constract a novel electromagnetic shielding and also to examine the factors influencing shielding efficacy in X band frequency range. Material and Method: This study used Resin Epoxy as matrix and nano-Nickel Oxide as filler to prepare the composite plates with three different thicknesses (2,4, and 6 mm and four different weight percentages (5,7,9 and 11. The fabricated composites characterized using X-ray diffraction and Field Emission Scanning Electron microscopy. Shielding effectiveness, percolation depth, and percolation threshold were measured using Vector Network Analyzers. Thermal Gravimetric Analysis was conducted to study the temperature influence on weight loss for fabricated composites. Result: A maximum shielding effectiveness value of 84.18% was obtained for the 11%-6mm composite at 8.01 GHz and the 7%-4mm composite exhibits a higher average of shielding effectiveness of 66.72% at X- band frequency range. The 4mm thickness was optimum and critical diameter for composite plates; and percolation depth was obtained greater than thickness of composites. However, increasing the nickel oxide content did not show noticeable effect on the shielding effectiveness. Thermal Gravimetric Analysis showed that the study shields were resistant to temperature up to 150 °C without experiencing weight loss. What is more, the results indicated that Nickel oxide Nano particles had desirable distribution and dispersion in epoxy matrix and percolation threshold was appeared in low content of nickel oxide nanoparticles. Conclusion: A novel electromagnetic shield using low thickness and few content of nanoparticle with noticeable efficacy was properly designed and constructed in the field of occupational health. In addition, this shield has low cost, easy to manufacture, resistance to wet/corrosion, and low weight. Epoxy
Blood optical properties at various glucose level values in THz frequency range
Gusev, S. I.; Borovkova, M. A.; Strepitov, M. A.; Khodzitsky, M. K.
2015-07-01
the patients. Most biomolecules have characteristic signature frequencies in the terahertz (THz) range, which can reveal their presence and determine the concentration. Therefore, this paper is intended to study the blood optical properties in the THz frequency range in order to determine THz radiation effect on blood. The main aim of this investigation is to determine the effect of blood glucose concentration on the blood optical properties. In the case if blood optical properties vary at different glucose concentrations having a proportional relationship between them, these results will confirm the possibility of development of non-invasive procedures for blood glucose level diagnostics.
DEFF Research Database (Denmark)
Bumeliene, S.; Tamasevicius, A.; Mykolaitis, G.
2006-01-01
A hardware prototype of the two-stage Colpitts oscillator employing the microwave BFG520 type transistors with the threshold frequency of 9 GHz and designed to operate in the ultrahigh frequency range (300–1000 MHz) is described. The practical circuit in addition to the intrinsic two...
Effective theory and breakdown of conformal symmetry in a long-range quantum chain
Lepori, L.; Vodola, D.; Pupillo, G.; Gori, G.; Trombettoni, A.
2016-11-01
We deal with the problem of studying the symmetries and the effective theories of long-range models around their critical points. A prominent issue is to determine whether they possess (or not) conformal symmetry (CS) at criticality and how the presence of CS depends on the range of the interactions. To have a model, both simple to treat and interesting, where to investigate these questions, we focus on the Kitaev chain with long-range pairings decaying with distance as power-law with exponent α. This is a quadratic solvable model, yet displaying non-trivial quantum phase transitions. Two critical lines are found, occurring respectively at a positive and a negative chemical potential. Focusing first on the critical line at positive chemical potential, by means of a renormalization group approach we derive its effective theory close to criticality. Our main result is that the effective action is the sum of two terms: a Dirac action SD, found in the short-range Ising universality class, and an "anomalous" CS breaking term SAN. While SD originates from low-energy excitations in the spectrum, SAN originates from the higher energy modes where singularities develop, due to the long-range nature of the model. At criticality SAN flows to zero for α > 2, while for α theory, we compared the two-fermion static correlation functions and the von Neumann entropy obtained from them with the ones calculated on the lattice, finding agreement. These results explain two observed features characteristic of long-range models, the hybrid decay of static correlation functions within gapped phases and the area-law violation for the von Neumann entropy. The proposed scenario is expected to hold in other long-range models displaying quasiparticle excitations in ballistic regime. From the effective theory one can also see that new phases emerge for α 2). Close to this line, where the minimum of the spectrum coincides with the momentum where singularities develop, the critical exponents
Tuning the Polarization State of Light over a Broad Frequency Range with Metasurfaces
Wang, Mu; Jiang, Shang-Chi; Wang, Zheng-Han; Xiong, Xiang; Peng, Ru-Wen; Nanjing University Team
Controlling the polarization state, the transmission direction and the phase of light within a confined space is an important issue in optics. By integrating metallic metastructure and dielectric interlayer, it is possible to realize the dispersion-free broadband device on sub-wavelength scale, where the strong response of the metallic structures helps to decrease the device size while the dielectric interlayer helps to eliminate the dispersion simultaneously in both the amplitude and the phase difference of the reflected/transmitted light. As an examples to apply this concept, a broadband quarter-wave plate and a half-wave plate are experimentally demonstrated. By carefully selecting the structural parameters, the polarization state of light can be freely tuned across a broad frequency range, and all of the polarization states on the Poincaré sphere can be realized dispersion free. Some contents of this talk can be found in the following references: [1] S.-C. Jiang, et al., High-efficiency generation of circularly polarized light via symmetry-induced anomalous reflection,Physical Review B 91, 125421 (2015), [2] S.-C. Jiang, et al., Controlling the Polarization State of Light with a Dispersion-Free Metastructure, Physical Review X 4, 021026 (2014), [3] X. Xiong, et al., Metallic stereostructured layer: an approach for broadband polarization state manipulation,Applied Physics Letters 105, 201105 (2014).
Kuzhir, Polina P.; Paddubskaya, Alesia G.; Volynets, Nadezhda I.; Batrakov, Konstantin G.; Kaplas, Tommi; Lamberti, Patrizia; Kotsilkova, Rumiana; Lambin, Philippe
2017-07-01
The ability of thin conductive films, including graphene, pyrolytic carbon (PyC), graphitic PyC (GrPyC), graphene with graphitic islands (GrI), glassy carbon (GC), and sandwich structures made of all these materials separated by polymer slabs to absorb electromagnetic radiation in microwave-THz frequency range, is discussed. The main physical principles making a basis for high absorption ability of these heterostructures are explained both in the language of electromagnetic theory and using representation of equivalent electrical circuits. The idea of using carbonaceous thin films as the main working elements of passive radiofrequency (RF) devices, such as shields, filters, polarizers, collimators, is proposed theoretically and proved experimentally. The important advantage of PyC, GrI, GrPyC, and GC is that, in contrast to graphene, they either can be easily deposited onto a dielectric substrate or are strong enough to allow their transfer from the catalytic substrate without a shuttle polymer layer. This opens a new avenue toward the development of a scalable protocol for cost-efficient production of ultralight electromagnetic shields that can be transferred to commercial applications. A robust design via finite-element method and design of experiment for RF devices based on carbon/graphene films and sandwiches is also discussed in the context of virtual prototyping.
Fu, Fanrui; Xin, Sherman Xuegang; Chen, Wufan
2014-02-01
This study aimed to obtain the temperature- and frequency-dependent dielectric properties of tissues subjected to magnetic resonance (MR) scanning for MR imaging-guided focused ultrasound surgery (MRgFUS). These variables are necessary to calculate radio frequency electromagnetic fields distribution and specific radio frequency energy absorption rate (SAR) in the healthy tissues surrounding the target tumours, and their variation may affect the efficacy of advanced RF pulses. The dielectric properties of porcine uterus, liver, kidney, urinary bladder, skeletal muscle, and fat were determined using an open-ended coaxial probe method. The temperature range was set from 36 °C to 60 °C; and the frequencies were set at 42.58 (1 T), 64 (1.5 T), 128 (3 T), 170 (4 T), 298 (7 T), 400 (9 T), and 468 MHz (11 T). Within the temperature and frequency ranges, the dielectric constants were listed as follows: uterus 49.6-121.64, liver 44.81-127.68, kidney 37.3-169.26, bladder 42.43-125.95, muscle 58.62-171.7, and fat 9.2327-20.2295. The following conductivities were obtained at the same temperature and frequency ranges: uterus 0.5506-1.4419, liver 0.5174-0.9709, kidney 0.8061-1.3625, bladder 0.6766-1.1817, muscle 0.8983-1.3083, and fat 0.1552-0.2316. The obtained data are consistent with the temperature and frequency ranges typically used in MRgFUS and thus can be used as reference to calculate radio frequency electromagnetic fields and SAR distribution inside the healthy tissues subjected to MR scanning for MRgFUS.
Ion cyclotron range of frequencies heating of plasma with small impurity production
Ohkawa, Tihiro
1987-01-01
Plasma including plasma ions is magnetically confined by a magnetic field. The plasma has a defined outer surface and is intersected by resonance surfaces of respective common ion cyclotron frequency of a predetermined species of plasma ions moving in the magnetic field. A radio frequency source provides radio frequency power at a radio frequency corresponding to the ion cyclotron frequency of the predetermined species of plasma ions moving in the field at a respective said resonance surface. RF launchers coupled to the radio frequency source radiate radio frequency energy at the resonance frequency onto the respective resonance surface within the plasma from a plurality of locations located outside the plasma at such respective distances from the intersections of the respective resonance surface and the defined outer surface and at such relative phases that the resulting interference pattern provides substantially null net radio frequency energy over regions near and including substantial portions of the intersections relative to the radio frequency energy provided thereby at other portions of the respective resonance surface within the plasma.
Low frequency sound scattering from spherical assemblages of bubbles using effective medium theory.
Hahn, Thomas R
2007-12-01
The determination of the acoustic field scattered by an underwater assembly of gas bubbles or similar resonant monopole scatterers is of considerable theoretical and practical interest. This problem is addressed from a theoretical point of view within the framework of the effective medium theory for the case of spherically shaped assemblages. Although being valid more generally, the effective medium theory is an ideal instrument to study multiple scattering effects such as low frequency collective resonances, acoustically coupled breathing modes of the entire assembly. Explicit expressions for the scattering amplitude and cross sections are derived, as well as closed form expressions for the resonance frequency and spectral shape of the fundamental collective mode utilizing analytical S-matrix methods. This approach allows, in principle, a simultaneous inversion for the assembly radius and void fraction directly from the scattering cross sections. To demonstrate the validity of the approach, the theory is applied to the example of idealized, spherically shaped schools of swim bladder bearing fish. The analytic results of the theory are compared to numerical first-principle benchmark computations and excellent agreement is found, even for densely packed schools and frequencies across the bladder resonance.
DEFF Research Database (Denmark)
Fromager, Emmanuel; Jensen, Hans Jørgen Aagaard
2011-01-01
-cluster theories, self-consistency effects are introduced in the density functional part, which for an exact solution requires iterations. They are generally assumed to be small but no detailed study has been performed so far. Here, the authors analyze self-consistency when using Møller-Plesset-type (MP......Range-separated density-functional theory combines wave function theory for the long-range part of the two-electron interaction with density-functional theory for the short-range part. When describing the long-range interaction with non-variational methods, such as perturbation or coupled......) perturbation theory for the long range interaction. The lowest-order self-consistency corrections to the wave function and the energy, that enter the perturbation expansions at the second and fourth order, respectively, are both expressed in terms of the one-electron reduced density matrix. The computational...
Multi-configuration time-dependent density-functional theory based on range separation
Fromager, Emmanuel; Jensen, Hans Jørgen Aa
2012-01-01
Multi-configuration range-separated density-functional theory is extended to the time-dependent regime. An exact variational formulation is derived. The approximation, which consists in combining a long-range Multi-Configuration-Self-Consistent Field (MCSCF) treatment with an adiabatic short-range density-functional (DFT) description, is then considered. The resulting time-dependent multi-configuration short-range DFT (TD-MC-srDFT) model is applied to the calculation of singlet excitation energies in H2, Be and ferrocene, considering both short-range local density (srLDA) and generalized gradient (srGGA) approximations. In contrast to regular TD-DFT, TD-MC-srDFT can describe double excitations. As expected, when modeling long-range interactions with the MCSCF model instead of the adiabatic Buijse-Baerends density-matrix functional as recently proposed by Pernal [K. Pernal, J. Chem. Phys. 136, 184105 (2012)], the description of both the 1^1D doubly-excited state in Be and the 1^1\\Sigma^+_u state in the stretch...
GNSS single frequency ionospheric range delay corrections: NeQuick data ingestion technique
Oladipo, O. A.; Schüler, Torben
2012-11-01
A study of the performance of the NeQuick model and the Klobuchar model for GNSS single frequency range delay correction on a global scale was done using data for moderate solar activity. In this study NeQuick was used in the way intended for Galileo. This study is to assess the performance of the two models at each ionospheric geographic region during moderate solar activity as previously published studies were concentrated only on high solar activity. The results obtained showed that NeQuick outperformed Klobuchar for the whole year at the three geographical regions of the ionosphere. In terms of monthly root mean square of mismodeling, NeQuick outperformed Klobuchar by 15 TECU or more at low-latitudes, 5 TEC or more at mid-latitudes, and 1 TECU or more at high-latitudes. Also, a study on how the data ingestion technique already developed for NeQuick could be expanded in order to reduce the deviation of NeQuick TEC prediction from observation for a particular day based on the information from the previous day was done. Instead of obtaining a regularly spaced Az grid from monitoring stations spread across the region of interest, we obtained hourly Az coefficients from hourly Az from designated monitoring stations. The obtained hourly Az coefficients were then used to drive NeQuick for the next day at the test stations. The results obtained, in terms of daily RMS of mismodeling, showed a daily maximum improvement of 26.0% at low-latitudes, 54.9% at mid-latitudes, and 41.3% at high-latitudes.
Hartcher, K M; Hickey, K A; Hemsworth, P H; Cronin, G M; Wilkinson, S J; Singh, M
2016-05-01
Severe feather-pecking (SFP), a particularly injurious behaviour in laying hens (Gallus gallus domesticus), is thought to be negatively correlated with range use in free-range systems. In turn, range use is thought to be inversely associated with fearfulness, where fearful birds may be less likely to venture outside. However, very few experiments have investigated the proposed association between range use and fearfulness. This experiment investigated associations between range use (time spent outside), fearfulness, plumage damage, and BW. Two pens of 50 ISA Brown laying hens (n=100) were fitted with radio frequency identification (RFID) transponders (contained within silicone leg rings) at 26 weeks of age. Data were then collected over 13 days. A total of 95% of birds accessed the outdoor run more than once per day. Birds spent an average duration of 6.1 h outside each day over 11 visits per bird per day (51.5 min per visit). The top 15 and bottom 15 range users (n=30), as determined by the total time spent on the range over 13 days, were selected for study. These birds were tonic immobility (TI) tested at the end of the trial and were feather-scored and weighed after TI testing. Birds with longer TI durations spent less time outside (P=0.01). Plumage damage was not associated with range use (P=0.68). The small group sizes used in this experiment may have been conducive to the high numbers of birds utilising the outdoor range area. The RFID technology collected a large amount of data on range access in the tagged birds, and provides a potential means for quantitatively assessing range access in laying hens. The present findings indicate a negative association between fearfulness and range use. However, the proposed negative association between plumage damage and range use was not supported. The relationships between range use, fearfulness, and SFP warrant further research.
DEFF Research Database (Denmark)
Barrera Figueroa, Salvador; Torras Rosell, Antoni; Jacobsen, Finn
2013-01-01
Measurement microphones are typically calibrated in a free field at frequencies up to 50 kHz. This is a sufficiently high frequency for the most sound measurement applications related with noise assessment. However, other applications such as the measurement of noise emitted by ultrasound cleaning...... machines and failure detection in aeronautic structures require that the sensitivity of the microphone is known at frequencies up to 150 kHz. Another area of particular interest is the investigation of the perception mechanisms of ultrasound. In any of these applications, it is of fundamental importance...... to establish a well-defined traceability chain to support the measurement results. In order to extend the frequency range of free-field calibration the measurement system and measurement methods must undergo a series of changes and adaptations including the type of excitation signal, techniques for eliminating...
Flock, W. L.
1981-01-01
When high precision is required for range measurement on Earth space paths, it is necessary to correct as accurately as possible for excess range delays due to the dry air, water vapor, and liquid water content of the atmosphere. Calculations based on representative values of atmospheric parameters are useful for illustrating the order of magnitude of the expected delays. Range delay, time delay, and phase delay are simply and directly related. Doppler frequency variations or noise are proportional to the time rate of change of excess range delay. Tropospheric effects were examined as part of an overall consideration of the capability of precision two way ranging and Doppler systems.
The quasilinear theory in the approach of long-range systems to quasi-stationary states
Campa, Alessandro; Chavanis, Pierre-Henri
2017-05-01
We develop a quasilinear theory of the Vlasov equation in order to describe the approach of systems with long-range interactions to quasi-stationary states. The quasilinear theory is based on the assumption that, although the initial distribution is not Vlasov stable, nevertheless its evolution towards a Vlasov stable stationary state is such that it is always only slightly inhomogeneous. We derive a diffusion equation governing the evolution of the velocity distribution of the system towards a steady state. This steady state is expected to correspond to the space-averaged quasi-stationary distribution function reached by the Vlasov equation as a result of a collisionless relaxation. We compare the prediction of the quasilinear theory to direct numerical simulations of the Hamiltonian mean field model, starting from an unstable spatially homogeneous distribution, either Gaussian or semi-elliptical. In the Gaussian case, we find that the quasilinear theory works reasonably well for weakly unstable initial conditions (i.e. close to the critical energy ε_c=3/4=0.75 ) and that it is able to predict the energy ε_t≃ 0.735 marking the effective out-of-equilibrium phase transition between unmagnetized and magnetized quasi-stationary states found in the numerical simulations. Similarly, the quasilinear theory works well for energies close to the instability threshold of the semi-elliptical case ε^*c =5/8=0.625 , and it predicts an effective out-of-equilibrium transition at εt≃ 0.619 . In both situations, the quasilinear theory works less well at energies lower than the out-of-equilibrium transition, the disagreement with the numerical simulations increasing with decreasing energy. In that case, we observe, in agreement with our previous numerical study (Campa and Chavanis 2013 Eur. Phys. J. B 86 170), that the quasi-stationary states are remarkably well fitted by polytropic distributions (Tsallis distributions) with index n = 2 (Gaussian case) or n
Directory of Open Access Journals (Sweden)
S. Lalléchère
2017-05-01
Full Text Available The aim of this proposal is to demonstrate the ability of tridimensional (3-D electromagnetic modeling tool for the characterization of composite materials in microwave frequency band range. Indeed, an automated procedure is proposed to generate random materials, proceed to 3-D simulations, and compute shielding effectiveness (SE statistics with finite integration technique. In this context, 3-D electromagnetic models rely on random locations of conductive inclusions; results are compared with classical electromagnetic mixing theory (EMT approaches (e.g. Maxwell-Garnett formalism, and dynamic homogenization model (DHM. The article aims to demonstrate the interest of the proposed approach in various domains such as propagation and electromagnetic compatibility (EMC.
Charged particle behavior in localized ultralow frequency waves: Theory and observations
Li, Li; Zhou, Xu-Zhi; Zong, Qiu-Gang; Rankin, Robert; Zou, Hong; Liu, Ying; Chen, Xing-Ran; Hao, Yi-Xin
2017-06-01
The formation and variability of the Van Allen radiation belts are highly influenced by charged particles accelerated via drift-resonant interactions with ultralow frequency (ULF) waves. In the prevailing theory of drift resonance, the ULF wave amplitude is assumed independent of magnetic longitude. This assumption is not generally valid in Earth's magnetosphere, as supported by numerous observations that point to the localized nature of ULF waves. Here we introduce a longitude dependence of the ULF wave amplitude, achieved via a von Mises function, into the theoretical framework of ULF wave-particle drift resonance. To validate the revised theory, the predicted particle signatures are compared with observational data through a best fit procedure. It is demonstrated that incorporation of nonlocal effects in drift-resonance theory provides an improved understanding of charged particle behavior in the inner magnetosphere through the intermediary of ULF waves.
Irwansyah, Kuse, Naoyuki; Usagawa, Tsuyoshi
2017-08-01
Directivity pattern of an ordinary loudspeaker becomes more directive at higher frequencies. However, because a single loudspeaker tends to radiate uniformly in all directions at low frequencies, reverberation from surrounding building walls may affect speech intelligibility when installing a multiple-loudspeaker system at crossroads. As an alternative, a sharply directive sound source is recommended to be used, but in many cases the directivity of an ordinary loudspeaker is less sharp at lower frequencies. Therefore, in order to overcome such a limitation, this paper discusses the possibility of using four loudspeakers under active control to realize a quadrupole radiation pattern in low frequency range. In this study, the radiation pattern of a primary loudspeaker and three secondary loudspeakers has been modelled. By placing the loudspeakers close together in the direction of 0°, 90°, 180°, and 270°, it was theoretically demonstrated that a quadrupole radiation pattern can be shaped in the target frequency range up to 600 Hz by simply controlling the directivity in three of four directions which are 45°, 135°, 225°, and 315°. Although, the radiation pattern model is far from realistic configurations and conditions, it is possible to realize a quadrupole radiation pattern in the low frequency range.
Energy Technology Data Exchange (ETDEWEB)
Hariharan, K.; Ramesh, R.; Kathiravan, C.; Rajalingam, M. [Indian Institute of Astrophysics, Bangalore-560034 (India); Abhilash, H. N., E-mail: khariharan@iiap.res.in [Poornaprajna College, Udupi-576101 (India)
2016-02-15
A new antenna system with a digital spectro-correlator that provides high temporal, spectral, and amplitude resolutions has been commissioned at the Gauribidanur Observatory near Bangalore in India. Presently, it is used for observations of the solar coronal transients in the scarcely explored frequency range ≈30–15 MHz. The details of the antenna system, the associated receiver setup, and the initial observational results are reported. Some of the observed transients exhibited quasi-periodicity in their time profiles at discrete frequencies. Estimates of the associated magnetic field strength (B) indicate that B ≈ 0.06–1 G at a typical frequency such as 19.5 MHz.
Directory of Open Access Journals (Sweden)
Mohammad Hassan Moeini
2017-04-01
Full Text Available Microcellular thermoplastic polyurethane foams are examined as absorbing materials in the X-band (8.2-12.4 GHz frequency range by means of experiment. In this work, we aim to establish relationships between foam morphology including cell size and air volume fraction and electromagnetic properties including absorption, transmission and reflection quality. Nanocomposites based on thermoplastic polyurethane containing carbon black were prepared by coagulation method. In this procedure 15 wt% carbon black-containing nanocomposite was converted to microcellular foams using batch foaming process and supercritical carbon dioxide as physical foaming agent. The morphology of the foams was evaluated by scanning electron microscopy. S-parameters of the samples were measured by a vector network analyzer (VNA and the effect of morphological parameters such as cell size and air volume fraction on the absorbing properties was investigated. We also established structure/properties relationships which were essential for further optimizations of the materials used in the construction of radar absorbing composites. Foaming reduced the percolation threshold of the nanocomposites due to the reduction in the average distance between nanoparticles. Foaming and dielectric constant reduction dropped the reflection percentage significantly. The increase in air volume fraction in the foam increased absorption per its weight, because of multiple scattering in composite media. The sensitivity of electromagnetic wave toward the variation of cell size is strongly weaker than that toward the variation of air volume fraction. Electromagnetic properties of the microcellular foams deviated a little from effective medium theories (EMTs. Air volume fraction of the cells was a function of cell size and smaller cells showed higher absorption.
Golfinopoulos, Theodore; LaBombard, Brian; Burke, William; Parker, Ronald R; Parkin, William; Woskov, Paul
2014-04-01
A wide-frequency range (50-300 kHz) power system has been implemented for use with a new RF antenna - the "Shoelace" antenna - built to drive coherent plasma fluctuations in the edge of the Alcator C-Mod tokamak. A custom, dynamically tunable matching network allows two commercial 1 kW, 50-Ω RF amplifiers to drive the low-impedance, inductive load presented by the antenna. This is accomplished by a discretely variable L-match network, with 81 independently selected steps available for each of the series and parallel legs of the matching configuration. A compact programmable logic device provides a control system that measures the frequency with better than 1 kHz accuracy and transitions to the correct tuning state in less than 1 ms. At least 85% of source power is dissipated in the antenna across the operational frequency range, with a minimum frequency slew rate of 1 MHz/s; the best performance is achieved in the narrower band from 80 to 150 kHz which is of interest in typical experiments. The RF frequency can be run with open-loop control, following a pre-programmed analog waveform, or phase-locked to track a plasma fluctuation diagnostic signal in real time with programmable phase delay; the amplitude control is always open-loop. The control waveforms and phase delay are programmed remotely. These tools have enabled first-of-a-kind measurements of the tokamak edge plasma system response in the frequency range and at the wave number at which coherent fluctuations regulate heat and particle transport through the plasma boundary.
Human exposure to pulsed fields in the frequency range from 6 to 100 GHz
Laakso, Ilkka; Morimoto, Ryota; Heinonen, Juhani; Jokela, Kari; Hirata, Akimasa
2017-09-01
Restrictions on human exposure to electromagnetic waves at frequencies higher than 3-10 GHz are defined in terms of the incident power density to prevent excessive temperature rise in superficial tissue. However, international standards and guidelines differ in their definitions of how the power density is interpreted for brief exposures. This study investigated how the temperature rise was affected by exposure duration at frequencies higher than 6 GHz. Far-field exposure of the human face to pulses shorter than 10 s at frequencies from 6 to 100 GHz was modelled using the finite-difference time-domain method. The bioheat transfer equation was used for thermal modelling. We investigated the effects of frequency, polarization, exposure duration, and depth below the skin surface on the temperature rise. The results indicated limitations in the current human exposure guidelines and showed that radiant exposure, i.e. energy absorption per unit area, can be used to limit temperature rise for pulsed exposure. The data are useful for the development of human exposure guidelines at frequencies higher than 6 GHz.
Jennings, Jori Johnson; Kuehn, David P
2008-01-01
This study addresses two questions: (1) How much nasality is present in classical Western singing? (2) What are the effects of frequency range, vowel, dynamic level, and gender on nasality in amateur and classically trained singers? The Nasometer II 6400 by KayPENTAX (Lincoln Park, NJ) was used to obtain nasalance values from 21 amateur singers and 25 classically trained singers while singing an ascending five-tone scalar passage in low, mid, and high frequency ranges. Each subject sang the scalar passage at both piano and mezzo-forte dynamic loudness levels on each of the five cardinal vowels (/a/, /e/, /i/, /o/, /u/). A repeated mixed-model analysis indicated a significant main effect for the amateur/classically trained distinction, dynamic loudness level, and vowel, but not for frequency range or gender. The amateur singers had significantly higher nasalance scores than classically trained singers in all ranges and on all vowels except /o/. Dynamic loudness level had a significant effect on nasalance for all subject groups except for female majors in the mid- and high-frequency ranges. The vowel, /i/, received significantly higher nasalance than all of the other vowels. Although results of this study show that dynamic loudness level, vowel, and level of training in classical singing have a significant effect on nasality, nasalance scores for most subjects were relatively low. Only six of the subjects, all of whom were amateur singers, had average nasalance scores that could be considered hypernasal (ie, a nasalance average of 22 or above).
Ennis, C.; Auchettl, R.; Appadoo, D. R. T.; Robertson, E. G.
2017-11-01
Solid-state density functional theory code has been implemented for the structure optimization of crystalline methanol, acetaldehyde and acetic acid and for the calculation of infrared frequencies. The results are compared to thin film spectra obtained from low-temperature experiments performed at the Australian Synchrotron. Harmonic frequency calculations of the internal modes calculated at the B3LYP-D3/m-6-311G(d) level shows higher deviation from infrared experiment than more advanced theory applied to the gas phase. Importantly for the solid-state, the simulation of low-frequency molecular lattice modes closely resembles the observed far-infrared features after application of a 0.92 scaling factor. This allowed experimental peaks to be assigned to specific translation and libration modes, including acetaldehyde and acetic acid lattice features for the first time. These frequency calculations have been performed without the need for supercomputing resources that are required for large molecular clusters using comparable levels of theory. This new theoretical approach will find use for the rapid characterization of intermolecular interactions and bonding in crystals, and the assignment of far-infrared spectra for crystalline samples such as pharmaceuticals and molecular ices. One interesting application may be for the detection of species of prebiotic interest on the surfaces of Kuiper-Belt and Trans-Neptunian Objects. At such locations, the three small organic molecules studied here could reside in their crystalline phase. The far-infrared spectra for their low-temperature solid phases are collected under planetary conditions, allowing us to compile and assign their most intense spectral features to assist future far-infrared surveys of icy Solar system surfaces.
Filter-free photonic frequency sextupler operated over a wide range of modulation index
Zhu, Zihang; Zhao, Shanghong; Li, Xuan; Qu, Kun; Lin, Tao
2017-05-01
An integrated dual-polarization modulator is proposed to generate frequency-sextupled microwave signal without an optical filter. The dual-polarization modulator can achieve even-order optical sidebands suppression modulation along the orthogonal polarization directions with different modulation index. By properly adjusting the power relationship of the orthogonal polarization directions, two optical first-order sidebands will cancel each other out. Thus, a pure frequency-sextupled signal with an optical sideband suppression ratio (OSSR) exceeding 38 dB and a radio frequency spurious suppression ratio (RFSSR) higher than 32 dB is generated, which match well with the theoretical analysis. Since there is no requirement to carefully adjust the modulation index to achieve correct operation of the sextupler, it is much easy to implement. Furthermore, it is also proved to be valid that even if the extinction ratios of the MZMs, the polarization angle of the polarizer, and the direct current (DC) bias phase shift deviate from the ideal values to a certain degree, the performance of the generated frequency-sextupled microwave signal is still acceptable.
Proof of long range order in 4-d SU(N) lattice gauge theory
Grady, Michael
2013-01-01
An extended version of 4-d SU(2) lattice gauge theory is considered in which different inverse coupling parameters are used, $\\beta_H=4/g_{H}^2$ for plaquettes which are purely spacelike, and $\\beta_V$ for those which involve the Euclidean timelike direction. It is shown that when $\\beta_H = \\infty$ the partition function becomes, in the Coulomb Gauge, exactly that of a set of non-interacting 3-d O(4) classical Heisenberg models. Long range order at low temperatures (weak coupling) has been rigorously proven for this model. It is shown that the correlation function demonstrating spontaneous magnetization in the ferromagnetic phase is a continuous function of $g_H$ at $g_H =0$ and therefore that the spontaneously broken phase enters the ($\\beta_H$, $\\beta_V$) phase plane (no step discontinuity at the edge). Once the phase transition line has entered, it can only exit at another identified edge, which requires the SU(2) gauge theory within also to have a phase transition at finite $\\beta$. A phase exhibiting sp...
Investigation of hopped frequency waveforms for range and velocity measurements of radar targets
CSIR Research Space (South Africa)
Kathree, U
2015-10-01
Full Text Available In the field of radar, High Range Resolution (HRR) profiles are often used to improve target tracking accuracy in range and to allow the radar system to produce an image of an object using techniques such as inverse synthetic aperture radar (ISAR...
Saito, Takahiro; Maehara, Shinya; Doi, Kohei; Sato, Takashi; Ohdaira, Yasuo; Sakamoto, Shuichi; Ohkawa, Masashi
2017-06-01
An optical range finder system that relies on laser diodes' frequency noise, instead of intensity or frequency modulations, and its improvement in resolution are reported. The distance to the target is measured by calculating the cross-correlation of two signals reflected from the target and reference mirrors. These two signals are converted from the laser diodes' frequency noise signals by frequency/intensity converters, such as a Fabry-Perot etalon. We obtained the distance to the target by checking time lags between the target and reference beams at the highest correlation coefficient. We also measured the change in the correlation coefficient around the peak sampling point by adjusting the reference-path length, achieving a resolving power of ±3 mm.
Energy Technology Data Exchange (ETDEWEB)
Drakakis, E. [Electrical Engineering Department, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Kymakis, E. [Electrical Engineering Department, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Tzagkarakis, G.; Louloudakis, D.; Katharakis, M. [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Kenanakis, G. [Institute of Electronic Structure & Laser (IESL), Foundation for Research and Technology (FORTH) Hellas, Heraklion (Greece); Suchea, M.; Tudose, V. [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Chemistry Faculty, “Al.I.Cuza” University of Iasi, Iasi (Romania); Koudoumas, E., E-mail: koudoumas@staff.teicrete.gr [Electrical Engineering Department, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece)
2017-03-15
Highlights: • Optimum paint contents should be chosen so that homogeneous and uniform nanocomposite layers exist exhibiting effective electromagnetic shielding. • The electromagnetic shielding in the frequency range studied comes mainly from absorption and increases with frequency. • Reflection reduces with increasing frequency, the decrease rate being smaller than that of the increase in absorption. • The shielding efficiency depends on both conductivity and thickness, the first dependence being more pronounced. - Abstract: We report on the mechanisms of the electromagnetic interference shielding effect of graphene based paint like composite layers. In particular, we studied the absorption and reflection of electromagnetic radiation in the 4–20 GHz frequency of various dispersions employing different amounts of graphene nanoplatelets, polyaniline, and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), special attention given on the relative contribution of each process in the shielding effect. Moreover, the influence of the composition, the thickness and the conductivity of the composite layers on the electromagnetic shielding was also examined.
Measurement of Ion Motional Heating Rates over a Range of Trap Frequencies and Temperatures
Bruzewicz, C D; Chiaverini, J
2014-01-01
We present measurements of the motional heating rate of a trapped ion at different trap frequencies and temperatures between $\\sim$0.6 and 1.5 MHz and $\\sim$4 and 295 K. Additionally, we examine the possible effect of adsorbed surface contaminants with boiling points below $\\sim$105$^{\\circ}$C by measuring the ion heating rate before and after locally baking our ion trap chip under ultrahigh vacuum conditions. We compare the heating rates presented here to those calculated from available electric-field noise models. We can tightly constrain a subset of these models based on their expected frequency and temperature scaling interdependence. Discrepancies between the measured results and predicted values point to the need for refinement of theoretical noise models in order to more fully understand the mechanisms behind motional trapped-ion heating.
Effects of laser frequency chirp on modal noise in short-range radio over multimode fiber links
DEFF Research Database (Denmark)
Visani, Davide; Tartarini, Giovanni; Petersen, Martin Nordal
2010-01-01
An important effect of the frequency chirp of the optical transmitter in radio over multimode fiber links is put into evidence experimentally and modeled theoretically for the first time, to our knowledge. This effect can have an important impact in short-range connections, where, although...
DEFF Research Database (Denmark)
Lindelöw, Per Jonas Petter; Mohr, Johan Jacob
2007-01-01
Range unambiguous high duty cycle coherent lidars can be constructed based on frequency stepped pulse train modulation, even continuously emitting systems could be envisioned. Such systems are suitable for velocity sensing of dispersed targets, like the atmosphere, at fast acquisition rates...
Lucke, K.; Hastie, Gordon D.; Ternes, Kerstin; McConnell, Bernie; Moss, Simon; Russell, Deborah J.F.; Weber, Heike; Janik, Vincent M.
2016-01-01
The hearing sensitivity of 18 free-ranging and 10 captive harbour seals (Phoca vitulina) to aerial sounds was measured in the presence of typical environmental noise through auditory brainstem response measurements. A focus was put on the comparative hearing sensitivity at low frequencies. Low-
CMOS radio frequency circuits for short-range direct-conversion receivers
Kaukovuori, Jouni
2008-01-01
The research described in this thesis is focused on the design and implementation of radio frequency (RF) circuits for direct-conversion receivers. The main interest is in RF front-end circuits, which contain low-noise amplifiers, downconversion mixers, and quadrature local oscillator signal generation circuits. Three RF front-end circuits were fabricated in a short-channel CMOS process and experimental results are presented. A low-noise amplifier (LNA) is typically the first amplifying b...
Historic Frequency and Severity of Fire in Whitebark Pine Forests of the Cascade Mountain Range, USA
Michael P. Murray; Joel Siderius
2018-01-01
Whitebark pine (Pinus albicaulis Engelm.) is a foundation species of high elevation forest ecosystems in the Cascade Mountain Range of Oregon, Washington, and British Columbia. We examined fire evidence on 55 fire history sites located in the Cascade Range. To estimate dates of historic fires we analyzed 57 partial cross-sections from fire-scarred trees plus 700 increment cores. The resulting 101 fire events indicate fire has been a widespread component of Cascadian whitebark pine stands. Res...
A finite range pairing force for density functional theory in superfluid nuclei
Tian, Y.; Ma, Z. Y.; Ring, P.
2009-06-01
The problem of pairing in the S10 channel of finite nuclei is revisited. In nuclear matter forces of separable form can be adjusted to the bare nuclear force, to any phenomenological pairing interaction such as the Gogny force or to exact solutions of the gap equation. In finite nuclei, because of translational invariance, such forces are no longer separable. Using well-known techniques of Talmi and Moshinsky we expand the matrix elements in a series of separable terms, which converges quickly preserving translational invariance and finite range. In this way the complicated problem of a cut-off at large momenta or energies inherent in other separable or zero range pairing forces is avoided. Applications in the framework of the relativistic Hartree-Bogoliubov approach show that the pairing properties are depicted on almost the same footing as by the original pairing interaction not only in nuclear matter, but also in finite nuclei. This simple separable force can be easily applied for the investigation of pairing properties in nuclei far from stability as well as for further investigations going beyond mean field theory.
Resolution theory and static- and frequency dependent cross-talk in piezoresponse force microscopy
Energy Technology Data Exchange (ETDEWEB)
Jesse, Stephen [ORNL; Guo, Senli [ORNL; Kumar, Amit [ORNL; Rodriguez, Brian [University College, Dublin; Proksch, Roger [Asylum Research, Santa Barbara, CA; Kalinin, Sergei V [ORNL
2010-01-01
Probing materials functionality locally by scanning probe microscopy requires reliable framework for identifying the target signal and separating it from the effects of surface morphology and instrument non-idealities, i.e. instrumental and topographical cross-talk. Here we develop the linear resolution theory framework to describe the cross-talk effects, and apply it for elucidation of frequency dependent cross-talk mechanisms in the Piezoresponse Force Microscopy. The use of band excitation method allows electromechanical/electrical and mechanical/topographic signals to be unambiguously separated. The applicability of functional fit approach and multivariate statistical analysis methods for data identification in band excitation SPM is explored.
DEFF Research Database (Denmark)
Thomsen, Jon Juel
2003-01-01
, as was done in a few related studies¿¿unless the system has very low modal density or heavy damping; thus first-order consideration to resonance effects is included. Using the specific example with experimental support to put confidence on the proposed theory, expressions for predicting the stiffening effect...... for a more general class of continuous systems in differential operator form are also provided.......One effect of strong mechanical high-frequency excitation may be to apparently "stiffen" a structure, a well-described phenomenon for discrete systems. The present study provides theoretical and experimental results on this effect for continuous elastic structures. A laboratory experiment is set up...
Wu, Tong; Ding, Zhihua; Wang, Chuan; Chen, Minghui
2011-12-01
A high speed swept source optical coherence tomography (SS-OCT) system capable of full-range imaging is presented. Wave-number carrier frequency is introduced into the spectral interference signal by a transmissive dispersive optical delay line (TDODL). High carrier frequency in the spectral interference signal corresponding to an equivalent distance-shift is exploited to obtain full-range OCT imaging. Theoretical development is conducted with the instantaneous coherence function introduced for a complete description of a spectral interference signal. Performance advantage of the TDODL-based method over the conventional approach where only one side (positive or negative path length difference) is used for imaging to avoid overlaying mirror artifacts is confirmed by the measured envelopes of spectral interference signal. Feasibility of the proposed method for full-range imaging is validated in a custom-built SS-OCT system by in vivo imaging of a biological sample.
High resolution kilometric range optical telemetry in air by radio frequency phase measurement
Energy Technology Data Exchange (ETDEWEB)
Guillory, Joffray; García-Márquez, Jorge; Truong, Daniel; Wallerand, Jean-Pierre [Laboratoire Commun de Métrologie LNE-Cnam (LCM), LNE, 1 rue Gaston Boissier, 75015 Paris (France); Šmíd, Radek [Laboratoire Commun de Métrologie LNE-Cnam (LCM), LNE, 1 rue Gaston Boissier, 75015 Paris (France); Institute of Scientific Instruments of the CAS, Kralovopolska 147, 612 64 Brno (Czech Republic); Alexandre, Christophe [Centre d’Études et de Recherche en Informatique et Communications (CEDRIC), Cnam, 292 rue St-Martin, 75003 Paris (France)
2016-07-15
We have developed an optical Absolute Distance Meter (ADM) based on the measurement of the phase accumulated by a Radio Frequency wave during its propagation in the air by a laser beam. In this article, the ADM principle will be described and the main results will be presented. In particular, we will emphasize how the choice of an appropriate photodetector can significantly improve the telemeter performances by minimizing the amplitude to phase conversion. Our prototype, tested in the field, has proven its efficiency with a resolution better than 15 μm for a measurement time of 10 ms and distances up to 1.2 km.
Accuracy of finite-difference harmonic frequencies in density functional theory.
Liu, Kuan-Yu; Liu, Jie; Herbert, John M
2017-07-15
Analytic Hessians are often viewed as essential for the calculation of accurate harmonic frequencies, but the implementation of analytic second derivatives is nontrivial and solution of the requisite coupled-perturbed equations engenders a sizable memory footprint for large systems, given that these equations are not required for energy and gradient calculations in density functional theory. Here, we benchmark the alternative approach to harmonic frequencies based on finite differences of analytic first derivatives, a procedure that is amenable to large-scale parallelization. Not only for absolute frequencies but also for isotopic and conformer-dependent frequency shifts in flexible molecules, we find that the finite-difference approach exhibits mean errors finite-difference error can be larger, but even in these cases the errors can be reduced below 0.1 cm-1 by judicious choice of the displacement step size and a higher-order finite-difference approach. The surprising accuracy and robustness of the finite-difference results suggests that availability of the analytic Hessian is not so important in today's era of commodity processors that are readily available in large numbers. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.
Study of transmission line attenuation in broad band millimeter wave frequency range
Energy Technology Data Exchange (ETDEWEB)
Pandya, Hitesh Kumar B. [ITER-India, IPR, Gandhinagar, Gujarat (India); Austin, M. E. [Institute for Fusion Studies, the University of Texas at Austin, Austin, Texas (United States); Ellis, R. F. [Laboratory for Plasma and Fusion Energy Studies, University of Maryland, College Park, Maryland 20742 (United States)
2013-10-15
Broad band millimeter wave transmission lines are used in fusion plasma diagnostics such as electron cyclotron emission (ECE), electron cyclotron absorption, reflectometry and interferometry systems. In particular, the ECE diagnostic for ITER will require efficient transmission over an ultra wide band, 100 to 1000 GHz. A circular corrugated waveguide transmission line is a prospective candidate to transmit such wide band with low attenuation. To evaluate this system, experiments of transmission line attenuation were performed and compared with theoretical loss calculations. A millimeter wave Michelson interferometer and a liquid nitrogen black body source are used to perform all the experiments. Atmospheric water vapor lines and continuum absorption within this band are reported. Ohmic attenuation in corrugated waveguide is very low; however, there is Bragg scattering and higher order mode conversion that can cause significant attenuation in this transmission line. The attenuation due to miter bends, gaps, joints, and curvature are estimated. The measured attenuation of 15 m length with seven miter bends and eighteen joints is 1 dB at low frequency (300 GHz) and 10 dB at high frequency (900 GHz), respectively.
Range Detection of the Extremely Low-Frequency Magnetic Field Produced by Laptop's AC Adapter
Brodić, Darko; Amelio, Alessia
2017-02-01
Human exposure to extremely low frequency magnetic field represents a risk to their health. This paper takes into consideration the level of an extremely low-frequency magnetic field between 30 and 300 Hz emitted by an AC laptop adapter. The experiment consists of testing 17 different AC adapters for laptops. During the testing, laptops are operated in a normal operating conditions as well as under heavy load. The magnetic field measurement is conducted in the area around the AC adapter. Obtained data is evaluated according to the critical level of the magnetic field proposed by safety standards. Furthermore, data is classified by a K-medians method in order to determine the critical levels of the magnetic field exposure in the nearby area of the AC adapter. Obtained classifications are evaluated according to safety standards, giving a critical analysis of magnetic field areas at risk. Due to emission of a very strong magnetic field in certain areas, a recommendation for safety use of the AC adapter is proposed.
Study of transmission line attenuation in broad band millimeter wave frequency range.
Pandya, Hitesh Kumar B; Austin, M E; Ellis, R F
2013-10-01
Broad band millimeter wave transmission lines are used in fusion plasma diagnostics such as electron cyclotron emission (ECE), electron cyclotron absorption, reflectometry and interferometry systems. In particular, the ECE diagnostic for ITER will require efficient transmission over an ultra wide band, 100 to 1000 GHz. A circular corrugated waveguide transmission line is a prospective candidate to transmit such wide band with low attenuation. To evaluate this system, experiments of transmission line attenuation were performed and compared with theoretical loss calculations. A millimeter wave Michelson interferometer and a liquid nitrogen black body source are used to perform all the experiments. Atmospheric water vapor lines and continuum absorption within this band are reported. Ohmic attenuation in corrugated waveguide is very low; however, there is Bragg scattering and higher order mode conversion that can cause significant attenuation in this transmission line. The attenuation due to miter bends, gaps, joints, and curvature are estimated. The measured attenuation of 15 m length with seven miter bends and eighteen joints is 1 dB at low frequency (300 GHz) and 10 dB at high frequency (900 GHz), respectively.
Kari, Leif
2017-09-01
The constitutive equations of chemically and physically ageing rubber in the audible frequency range are modelled as a function of ageing temperature, ageing time, actual temperature, time and frequency. The constitutive equations are derived by assuming nearly incompressible material with elastic spherical response and viscoelastic deviatoric response, using Mittag-Leffler relaxation function of fractional derivative type, the main advantage being the minimum material parameters needed to successfully fit experimental data over a broad frequency range. The material is furthermore assumed essentially entropic and thermo-mechanically simple while using a modified William-Landel-Ferry shift function to take into account temperature dependence and physical ageing, with fractional free volume evolution modelled by a nonlinear, fractional differential equation with relaxation time identical to that of the stress response and related to the fractional free volume by Doolittle equation. Physical ageing is a reversible ageing process, including trapping and freeing of polymer chain ends, polymer chain reorganizations and free volume changes. In contrast, chemical ageing is an irreversible process, mainly attributed to oxygen reaction with polymer network either damaging the network by scission or reformation of new polymer links. The chemical ageing is modelled by inner variables that are determined by inner fractional evolution equations. Finally, the model parameters are fitted to measurements results of natural rubber over a broad audible frequency range, and various parameter studies are performed including comparison with results obtained by ordinary, non-fractional ageing evolution differential equations.
DEFF Research Database (Denmark)
Zhao, Ying; Deng, Lei; Pang, Xiaodan
2011-01-01
We present a W-band fiber-wireless transmission system based on a nonlinear frequency multiplier for high-speed wireless short range access applications. By implementing a baseband digital signal predistortion scheme, intensive nonlinear distortions induced in a sextuple frequency multiplier can...... be effectively pre-compensated. Without using costly W-band components, a transmission system with 26km fiber and 4m wireless transmission operating at 99.6GHz is experimentally validated. Adjacent-channel power ratio (ACPR) improvements for IQ-modulated vector signals are guaranteed and transmission...
Korolev, A M; Shnyrkov, V I; Shulga, V M
2011-01-01
We have presented theory and experimentally demonstrated an efficient method for drastically reducing the power consumption of the rf/microwave amplifiers based on HEMT in unsaturated dc regime. Conceptual one-stage 10 dB-gain amplifier showed submicrowatt level of the power consumption (0.95 μW at frequency of 0.5 GHz) when cooled down to 300 mK. Proposed technique has a great potential to design the readout amplifiers for ultra-deep-cooled cryoelectronic quantum devices.
Complex magnetic susceptibility setup for spectroscopy in the extremely low-frequency range
Kuipers, B.W.M.; Bakelaar, I.A.; Klokkenburg, M.; Erne, B.H.
2008-01-01
A sensitive balanced differential transformer was built to measure complex initial parallel magnetic susceptibility spectra in the 0.01–1000 Hz range. The alternating magnetic field can be chosen sufficiently weak that the magnetic structure of the samples is only slightly perturbed and the low
Frequency and fitness consequences of bacteriophage φ6 host range mutations.
Directory of Open Access Journals (Sweden)
Brian E Ford
Full Text Available Viruses readily mutate and gain the ability to infect novel hosts, but few data are available regarding the number of possible host range-expanding mutations allowing infection of any given novel host, and the fitness consequences of these mutations on original and novel hosts. To gain insight into the process of host range expansion, we isolated and sequenced 69 independent mutants of the dsRNA bacteriophage Φ6 able to infect the novel host, Pseudomonas pseudoalcaligenes. In total, we found at least 17 unique suites of mutations among these 69 mutants. We assayed fitness for 13 of 17 mutant genotypes on P. pseudoalcaligenes and the standard laboratory host, P. phaseolicola. Mutants exhibited significantly lower fitnesses on P. pseudoalcaligenes compared to P. phaseolicola. Furthermore, 12 of the 13 assayed mutants showed reduced fitness on P. phaseolicola compared to wildtype Φ6, confirming the prevalence of antagonistic pleiotropy during host range expansion. Further experiments revealed that the mechanistic basis of these fitness differences was likely variation in host attachment ability. In addition, using computational protein modeling, we show that host-range expanding mutations occurred in hotspots on the surface of the phage's host attachment protein opposite a putative hydrophobic anchoring domain.
Chandrayadula, Tarun K; Colosi, John A; Worcester, Peter F; Dzieciuch, Matthew A; Mercer, James A; Andrew, Rex K; Howe, Bruce M
2013-10-01
Second order mode statistics as a function of range and source depth are presented from the Long Range Ocean Acoustic Propagation EXperiment (LOAPEX). During LOAPEX, low frequency broadband signals were transmitted from a ship-suspended source to a mode-resolving vertical line array. Over a one-month period, the ship occupied seven stations from 50 km to 3200 km distance from the receiver. At each station broadband transmissions were performed at a near-axial depth of 800 m and an off-axial depth of 350 m. Center frequencies at these two depths were 75 Hz and 68 Hz, respectively. Estimates of observed mean mode energy, cross mode coherence, and temporal coherence are compared with predictions from modal transport theory, utilizing the Garrett-Munk internal wave spectrum. In estimating the acoustic observables, there were challenges including low signal to noise ratio, corrections for source motion, and small sample sizes. The experimental observations agree with theoretical predictions within experimental uncertainty.
An Efficient Framework for Analysis of Wire-Grid Shielding Structures over a Broad Frequency Range
Directory of Open Access Journals (Sweden)
A. Karwowski
2016-12-01
Full Text Available A computationally efficient MoM-based framework for broadband electromagnetic simulation of wire-grid shielding structures is presented in the paper. Broadband capability of the approach is attained through supporting MoM by an adaptive frequency sweep combined with rational interpolation of the observable implemented via Stoer-Bulirsch algorithm. The performance increase is gained by employing CUDA-enabled CPU+GPU co-processing. For large-size problems exceeding the amount of memory available on the GPU device, a hybrid out-of-GPU memory LU decomposition algorithm is employed. The demonstration examples are provided to illustrate the the accuracy and high efficiency of the approach.
Controlled X-ray pumping in a wide range of piezo-electric oscillation frequencies
Navasardyan, M A; Galoyan, K G
1986-01-01
In case of Laue diffraction the transmitted X-ray reflection in shown to be effectively controllable in the perfect quartz single crystal when it generates ultrasonic oscillations at the resonance frequency or in its vicinity. The maximum effective amplitude of applied sinusoidal oscillations is equal to 70 V. The pumping degree depends on the voltage amplitude. In this work monochromatic K subalpha sub 1 and K subalpha sub 2 molybdenum lines satisfying the thin crystal condition, mu t<=1, are used (mu is the linear absorption coefficient of the sample for the given wavelength and t is its thickness). The radiation was reflected from different planes such as (1011), (1011), (2022) etc. The complete pumping strongly restricts the structural factor possibilities in estimating the intensity of diffracted X-rays in case of considerable deformations in the bulk of perfect single crystal.
Directory of Open Access Journals (Sweden)
Ashish Saini
2016-06-01
Full Text Available In the present study, indium doped nano sized nickel zinc cobalt based ferrite ceramics with composition Ni0.5Zn0.3Co0.2InxFe2-xO4 (x = 0.2 and 0.4 were synthesized by a co-precipitation technique. Powdered sample has been pre-sintered at 800 °C, pressed into toroids and finally sintered at 1000 °C. The single phase formation of the presintered powder has been confirmed by X ray diffraction (XRD. The average particle size of the presintered powder has been estimated by field emission scanning electron microscope (FESEM and found to be about ~60 nm for x = 0.2 and ~80 nm at x = 0.4. The electromagnetic characterization has been made using vector network analyzer. High value of permeability (17.3 and 15.2 for x = 0.2 and 0.4 respectively with low magnetic loss tangent of 10−1 order were obtained. Permittivity of 8.2 and 10, and dielectric loss tangent of the order of 10−2 were also achieved. With the measured electromagnetic parameters, miniaturization factor of 12.32 and normalized characteristic impedance close to unity (1.23 were obtained up to 100 MHz frequency. These fascinating parameters definitely propose Ni0.5Zn0.3Co0.2In0.4Fe1.6O4 ceramics as a substrate material for miniaturized antenna in very high frequency band. Possible reasons and mechanisms of electromagnetic properties for different concentrations of indium are discussed in the paper.
Spike-frequency adapting neural ensembles: beyond mean adaptation and renewal theories.
Muller, Eilif; Buesing, Lars; Schemmel, Johannes; Meier, Karlheinz
2007-11-01
We propose a Markov process model for spike-frequency adapting neural ensembles that synthesizes existing mean-adaptation approaches, population density methods, and inhomogeneous renewal theory, resulting in a unified and tractable framework that goes beyond renewal and mean-adaptation theories by accounting for correlations between subsequent interspike intervals. A method for efficiently generating inhomogeneous realizations of the proposed Markov process is given, numerical methods for solving the population equation are presented, and an expression for the first-order interspike interval correlation is derived. Further, we show that the full five-dimensional master equation for a conductance-based integrate-and-fire neuron with spike-frequency adaptation and a relative refractory mechanism driven by Poisson spike trains can be reduced to a two-dimensional generalization of the proposed Markov process by an adiabatic elimination of fast variables. For static and dynamic stimulation, negative serial interspike interval correlations and transient population responses, respectively, of Monte Carlo simulations of the full five-dimensional system can be accurately described by the proposed two-dimensional Markov process.
Silva, Walter A.
1993-01-01
A methodology for modeling nonlinear unsteady aerodynamic responses, for subsequent use in aeroservoelastic analysis and design, using the Volterra-Wiener theory of nonlinear systems is presented. The methodology is extended to predict nonlinear unsteady aerodynamic responses of arbitrary frequency. The Volterra-Wiener theory uses multidimensional convolution integrals to predict the response of nonlinear systems to arbitrary inputs. The CAP-TSD (Computational Aeroelasticity Program - Transonic Small Disturbance) code is used to generate linear and nonlinear unit impulse responses that correspond to each of the integrals for a rectangular wing with a NACA 0012 section with pitch and plunge degrees of freedom. The computed kernels then are used to predict linear and nonlinear unsteady aerodynamic responses via convolution and compared to responses obtained using the CAP-TSD code directly. The results indicate that the approach can be used to predict linear unsteady aerodynamic responses exactly for any input amplitude or frequency at a significant cost savings. Convolution of the nonlinear terms results in nonlinear unsteady aerodynamic responses that compare reasonably well with those computed using the CAP-TSD code directly but at significant computational cost savings.
Low-frequency source for very long-range underwater communication.
Mosca, Frédéric; Matte, Guillaume; Shimura, Takuya
2013-01-01
Very long-range underwater acoustic communication (UAC) is crucial for long cruising (>1000 km) autonomous underwater vehicles (AUVs). Very long-range UAC source for AUV must exhibit high electro-acoustic efficiency (>60%) and compactness. This paper describes the Janus-Hammer Bell (JHB) transducer that has been designed for this purpose and meets those requirements. The transducer works on the 450-550 Hz bandwidth and reaches source level above 200 dB (ref. 1 μPa at 1 m) with 1 kW excitation and full immersion capability. JHB source has been used for communication experiments by the Japanese institute for marine technology (Japan Agency for Marine-Earth Science and Technology) achieving a baud rate of 100 bits/s at 1000 km.
Adiabatic perturbation theory for atoms and molecules in the low-frequency regime
Martiskainen, Hanna; Moiseyev, Nimrod
2017-12-01
There is an increasing interest in the photoinduced dynamics in the low frequency, ω, regime. The multiphoton absorptions by molecules in strong laser fields depend on the polarization of the laser and on the molecular structure. The unique properties of the interaction of atoms and molecules with lasers in the low-frequency regime imply new concepts and directions in strong-field light-matter interactions. Here we represent a perturbational approach for the calculations of the quasi-energy spectrum in the low-frequency regime, which avoids the construction of the Floquet operator with extremely large number of Floquet channels. The zero-order Hamiltonian in our perturbational approach is the adiabatic Hamiltonian where the atoms/molecules are exposed to a dc electric field rather than to ac-field. This is in the spirit of the first step in the Corkum three-step model. The second-order perturbation correction terms are obtained when i ℏ ω ∂/∂ τ serves as a perturbation and τ is a dimensionless variable. The second-order adiabatic perturbation scheme is found to be an excellent approach for calculating the ac-field Floquet solutions in our test case studies of a simple one-dimensional time-periodic model Hamiltonian. It is straightforward to implement the perturbation approach presented here for calculating atomic and molecular energy shifts (positions) due to the interaction with low-frequency ac-fields using high-level electronic structure methods. This is enabled since standard quantum chemistry packages allow the calculations of atomic and molecular energy shifts due to the interaction with dc-fields. In addition to the shift of the energy positions, the energy widths (inverse lifetimes) can be obtained at the same level of theory. These energy shifts are functions of the laser parameters (low frequency, intensity, and polarization).
Chelpanov, Maksim A.; Mager, Olga V.; Mager, Pavel N.; Klimushkin, Dmitri Yu.; Berngardt, Oleg I.
2018-01-01
A statistical study of waves in the magnetosphere registered with the midlatitude coherent decameter radar located near Ekaterinburg (EKB), Russia is presented. The radar monitors ionospheric flow velocities whose small-scale variations are evoked by magnetosphere ultra low frequency (ULF) waves of Pc5-range. Data from 16 events observed during 7 months in 2014 and 2015 underwent wavelet analysis. Frequencies of the oscillating components were compared with Alfvén eigenfrequencies, which were inferred from THEMIS and Van Allen spacecraft data. The comparison showed that only a minor part of the oscillations registered with the radar in the nightside ionosphere could be attributed to the Alfvén mode. A majority of the waves have lower frequencies, which do not show dependence on Alfvén eigenfrequency of a field line.
Directory of Open Access Journals (Sweden)
Adriana Medeiros Gama
2010-04-01
Full Text Available The complex dielectric permittivity (e and magnetic permeability (m of Radar Absorbing Materials (RAM based on metallic magnetic particles (carbonyl iron particles embedded in a dielectric matrix (silicon rubber have been studied in the frequency range of 2 to 18 GHz. The relative permeability and permittivity of carbonyl iron-silicon composites for various mass fractions are measured by the transmission/reflection method using a vector network analyzer. The concentration dependence of permittivity and permeability on the frequency is analyzed. In a general way, the results show that e´ parameter shows a more significant variation among the evaluated parameters (e”, m”, m’. The comparison of dielectric and magnetic loss tangents (e”/e” and m”/m’, respectively shows more clearly the variation of both parameters (e and m according to the frequency. It is also observed that higher carbonyl iron content fractions favor both dielectric and magnetic loss tangents.
Blok, Amanda C
2017-04-01
To report an analysis of the concept of self-management behaviors. Self-management behaviors are typically associated with disease management, with frequent use by nurse researchers related to chronic illness management and by international health organizations for development of disease management interventions. A concept analysis was conducted within the context of Orem's self-care framework. Walker and Avant's eight-step concept analysis approach guided the analysis. Academic databases were searched for relevant literature including CIHAHL, Cochrane Databases of Systematic Reviews and Register of Controlled Trials, MEDLINE, PsycARTICLES and PsycINFO, and SocINDEX. Literature using the term "self-management behavior" and published between April 2001 and March 2015 was analyzed for attributes, antecedents, and consequences. A total of 189 journal articles were reviewed. Self-management behaviors are defined as proactive actions related to lifestyle, a problem, planning, collaborating, and mental support, as well as reactive actions related to a circumstantial change, to achieve a goal influenced by the antecedents of physical, psychological, socioeconomic, and cultural characteristics, as well as collaborative and received support. The theoretical definition and middle-range explanatory theory of self-management behaviors will guide future collaborative research and clinical practice for disease management. © 2016 Wiley Periodicals, Inc.
Predicting Short-Range Order in Multicomponent Alloys from an Improved Mean-Field Theory
Ong, Zhun-Yong; Johnson, Duane
2007-03-01
In alloys the atomic short-range order (SRO) indicates the nascent ordering to which the disordered alloy is tending at high temperatures. Direct first-principles prediction based upon KKR-CPA and mean-field thermodynamics have been successful in predicting system-specific SRO [1], if, at a minimum, corrections are included to satisfy the diffuse scattering sum rule in k-space. However, such models do not account for k-dependence of the corrections. Here, we present an analytic generalization to multicomponent alloys that includes ``cyclic diagrams'' [2,3] for composition, temperature, and k-dependent corrections to SRO. We first explore the improvement to SRO in model fcc ternary alloys via the generalized Ising model. We find that there is much better agreement to Monte Carlo simulations than with standard Bragg-Williams with(out) Onsager corrections. Then we implement this within the KKR-CPA linear-response theory of SRO.Work was supported by DOE (Award DEFG02-03ER46026 and NSF (DMR-0325939). [1] J.B. Staunton, D.D. Johnson, and F.J. Pinski, Phys. Rev. Lett. 65, 1259 (1990); Phys. Rev. B 50, 1450 (1994); ibid, 57, 15177 (1998). [2] R. Brout, Phys. Rev. 115, 824-835 (1959). [3] R.V. Chepulski, et al, Phys. Rev. 65, 064201-7 (2002).
Jenni, Raoul; Oechslin, Mathias S; James, Clara E
2017-04-24
Processing western tonal music may yield distinct brain responses depending on the mode of the musical compositions. Although subjective feelings in response to major and minor mode are well described, the underlying brain mechanisms and their development with increasing expertise have not been thoroughly examined. Using high-density electroencephalography, the present study investigated neuronal activities in the frequency domain in response to polyphone musical compositions in major and minor mode in non-musicians, amateurs and experts. During active listening decrease of theta- and gamma-frequency range activities occurred with increasing expertise in right posterior regions, possibly reflecting enhanced processing efficiency. Moreover, minor and major compositions distinctively modulated synchronization of neuronal activities in high frequency ranges (beta and gamma) in frontal regions, with increased activity in response to minor compositions in musicians and in experts in particular. These results suggest that high-frequency electroencephalographic (EEG) activities carry information about musical mode, showing gradual increase of processing efficiency and sensitivity with musical expertise. Copyright © 2017 Elsevier B.V. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Atdaev, A.; Danilyuk, A. L.; Labunov, V. A.; Prischepa, S. L., E-mail: prischepa@bsuir.by [Belarusian State University of Informatics and Radioelectronics (Belarus); Pavlov, A. A. [Russian Academy of Sciences, Institute of Microelectronics Nanotechnologies (Russian Federation); Basaev, A. S.; Shaman, Yu. P. [SMC Technological Center (Russian Federation)
2016-12-15
The interaction of electromagnetic radiation with a magnetically functionalized nanocomposite based on carbon nanotubes (CNTs) is considered using the model of random distribution of ferromagnetic nanoparticles in the carbon matrix characterized by the presence of resistive–inductive–capacitive coupling (contours). The model is based on the representation of the nanocomposite as a system consisting of the CNT matrix, ferromagnetic nanoparticles, and the interfaces between CNTs and nanoparticles. The wide range of possible resonant phenomena caused both by the presence of contours and the properties of the CNT nanocomposite is shown.
Hwang, H. D.; Maxit, L.; Ege, K.; Gerges, Y.; Guyader, J.-L.
2017-04-01
Vibro-acoustic simulation in the mid-frequency range is of interest for automotive and truck constructors. The dissipative treatments used for noise and vibration control such as viscoelastic patches and acoustic absorbing materials must be taken into account in the problem. The Statistical modal Energy distribution Analysis (SmEdA) model consists in extending Statistical Energy Analysis (SEA) to the mid-frequency range by establishing power balance equations between the modes of the different subsystems. The modal basis of uncoupled-subsystems that can be estimated by the finite element method in the mid-frequency range is used as input data. SmEdA was originally developed by considering constant modal damping factors for each subsystem. However, this means that it cannot describe the local distribution of dissipative materials. To overcome this issue, a methodology is proposed here to take into account the effect of these materials. This methodology is based on the finite element models of the subsystems that include well-known homogenized material models of dissipative treatments. The Galerkin method with subsystem normal modes is used to estimate the modal damping loss factors. Cross-modal coupling terms which appear in the formulation due to the dissipative materials are assumed to be negligible. An approximation of the energy sharing between the subsystems damped by dissipative materials is then described by SmEdA. The different steps of the method are validated experimentally by applying it to a laboratory test case composed of a plate-cavity system with different configurations of dissipative treatments. The comparison between the experimental and the simulation results shows good agreement in the mid-frequency range.
Gu, Changgui; Yang, Huijie
2017-06-01
The rhythms of physiological and behavioral activities in mammals, which are regulated by the main clock suprachiasmatic nucleus (SCN) in the brain, can not be only synchronized to the natural 24 h light-dark cycle, but also to cycles with artificial periods. The range of the artificial periods that the animal can be synchronized to is called entrainment range. In the absence of the light-dark cycle, the animal can also maintain the circadian rhythm with an endogenous period close to 24 h. Experiments found that the entrainment range is not symmetrical with respect to the endogenous period. In the present study, an explanation is given for the asymmetry based on a Kuramoto model which describes the neuronal network of the SCN. Our numerical simulations and theoretical analysis show that the asymmetry results from the difference in the intrinsic frequencies between two subgroups of the SCN, as well as the entrainment range is affected by the difference.
Frequency-swept Light Sources for Optical Coherence Tomography in the 1060nm range
DEFF Research Database (Denmark)
Marschall, Sebastian
instrument in the biomedical eld, especially in ophthalmology, where it is used for diagnosing retinal diseases. Using light at 1060nm permits deep penetration into the retina and into the layers beneath, the choroid and the sclera. This wavelength range is also benecial for imaging in eyes affected...... by cataract. For the 1060nm band, rapidly tunable lasers|so-called swept sources|are available which enable ultra-high speed acquisition of large three-dimensional datasets. However, these light sources require further improvements: higher output power for sufficient signal quality and wider tuning bandwidth...... for better depth resolution in combination with high tuning speed. We investigate the performance of novel semiconductor laser gain media in fiber-based high-speed swept source prototypes. We demonstrate high output power using a tapered amplifier, and we achieve improved depth resolution with a broadband...
Theory and measurement of the soliton self-frequency shift and efficiency in optical microcavities.
Yi, Xu; Yang, Qi-Fan; Yang, Ki Youl; Vahala, Kerry
2016-08-01
Dissipative Kerr cavity solitons experience a so-called self-frequency shift (SFS) as a result of Raman interactions. The frequency shift has been observed in several microcavity systems. The Raman process has also been shown numerically to influence the soliton pumping efficiency. Here, a perturbed Lagrangian approach is used to derive simple analytical expressions for the SFS and the soliton efficiency. The predicted dependences of these quantities on soliton pulse width are compared with measurements in a high-Q silica microcavity. The Raman time constant in silica is also inferred. Analytical expressions for the Raman SFS and soliton efficiency greatly simplify the prediction of soliton behavior over a wide range of microcavity platforms.
Resolution theory, and static and frequency-dependent cross-talk in piezoresponse force microscopy
Energy Technology Data Exchange (ETDEWEB)
Jesse, S; Guo, S; Kumar, A; Kalinin, S V [The Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Rodriguez, B J [Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4 (Ireland); Proksch, R [Asylum Research, Santa Barbara, CA 93117 (United States)
2010-10-08
Probing the functionality of materials locally by means of scanning probe microscopy (SPM) requires a reliable framework for identifying the target signal and separating it from the effects of surface morphology and instrument non-idealities, e.g. instrumental and topographical cross-talk. Here we develop a linear resolution theory framework in order to describe the cross-talk effects, and apply it for elucidation of frequency-dependent cross-talk mechanisms in piezoresponse force microscopy. The use of a band excitation method allows electromechanical/electrical and mechanical/topographic signals to be unambiguously separated. The applicability of a functional fit approach and multivariate statistical analysis methods for identification of data in band excitation SPM is explored.
Low-frequency flute instabilities of a hollow cathode arc discharge - Theory and experiment.
Ilic, D. B.; Rognlien, T. D.; Self, S. A.; Crawford, F. W.
1973-01-01
The characteristics of two low-frequency electrostatic flute instabilities of a low-pressure hollow cathode arc discharge are reported. Mode I has azimuthal mode number m = 1, and occurs when the radial electric field is negative (directed inward), while mode II has m = - 1 and occurs when the field is positive. The radial electric field is controlled by varying the potential of a secondary anode cylinder located close to the outer discharge radius. A linear perturbation analysis, based on the two-fluid equations, is given for a low-beta, collisionless, cylindrical plasma column, immersed in a uniform axial magnetic field, having a Gaussian density profile and an arbitrary radial electric field profile. Reasonable correlation between theory and experiment is demonstrated for both modes.
Hodgson, Shirley-Anne; Herdering, Regina; Singh Shekhawat, Giriraj; Searchfield, Grant D
2017-01-01
It has been suggested that frequency lowering may be a superior tinnitus reducing digital signal processing (DSP) strategy in hearing aids than conventional amplification. A crossover trial was undertaken to determine if frequency compression (FC) was superior to wide dynamic range compression (WDRC) in reducing tinnitus. A 6-8-week crossover trial of two digital signal-processing techniques (WDRC and 2 WDRC with FC) was undertaken in 16 persons with high-frequency sensorineural hearing loss and chronic tinnitus. WDRC resulted in larger improvements in Tinnitus Functional Index and rating scale scores than WDRC with FC. The tinnitus improvements obtained with both processing types appear to be due to reduced hearing handicap and possibly decreased tinnitus audibility. Hearing aids are useful assistive devices in the rehabilitation of tinnitus. FC was very successful in a few individuals but was not superior to WDRC across the sample. It is recommended that WDRC remain as the default first choice tinnitus hearing aid processing strategy for tinnitus. FC should be considered as one of the many other options for selection based on individual hearing needs. Implications of Rehabilitation Hearing aids can significantly reduce the effects of tinnitus after 6-8 weeks of use. Addition of frequency compression digital signal processing does not appear superior to standard amplitude compression alone. Improvements in tinnitus were correlated with reductions in hearing handicap.
Frequency tripled 1542 nm telecom laser diode stabilized to iodine hyperfine line in the 10-15 range
Philippe, Charles; Holleville, David; Lours, Michel; Minh-Pham, Tuam; Hrabina, Jan; Burck, Frederic Du; Wolf, Peter; Acef, Ouali
2016-01-01
We report on telecom laser frequency stabilization to narrow iodine hyperfine line in the green range of the optical domain, after a frequency tripling process using two nonlinear PPLN crystals. We have generated up to 300 mW optical power in the green (P3w), from 800 mW of infrared power (Pw). This result corresponds to an optical conversion efficiency eta= P3w/Pw ~ 36 %. To our knowledge, this is the best value ever demonstrated for a CW frequency tripling process. We have used a narrow linewidth iodine hyperfine line (component a1 of the 127I2 R 35 (44-0) line) to stabilize the IR laser yielding to frequency stability of 4.8x10-14 t-1/2 with a minimum of 6x10-15 reached after 50 s of integration time. The whole optical setup is very compact and mostly optically fibered. This approach opens the way for efficient and elegant architecture development for space applications as one of several potential uses.
Oscillation center theory and ponderomotive stabilization of low-frequency plasma modes
Similon, Philippe L.; Kaufman, Allan N.; Holm, Darryl D.
1986-06-01
Nonlinear, nondissipative ponderomotive theory is developed in relation to recent experimental results showing that externally imposed rf fields can stabilize an axisymmetric mirror plasma. First, the ponderomotive force problem is reexamined, with emphasis on self-consistency of the interaction between the plasma and high-frequency field. The averaged action principle for the antenna-plasma system yields self-consistent plasma and electromagnetic field dynamics on the oscillation-center time scale. The plasma equilibrium condition is expressed as a balance among plasma and magnetic pressure forces, including interchange, ponderomotive, and magnetization forces. Next, the spectral stability of such static equilibria is studied in the low-frequency magnetohydrodynamic (MHD) approximation, with a ΔW principle that incorporates the various ponderomotive contributions: particle effects, magnetization effects, and self-consistent adjustment of the rf field resulting from displacements of the plasma away from equilibrium. The ponderomotive potential energy functional is related to the antenna inductance and antenna current amplitude. Finally, the noncanonical Hamiltonian formulation for the system's dynamics is given, in terms of Eulerian fields. It allows the construction of nonlinearly conserved functionals, which yield criteria for linearized Lyapunov stability, for both multifluid and MHD models. The Lyapunov stability conditions are related to the modified ΔW variational principle.
Theory of frequency and phase synchronization in a rocked bistable stochastic system.
Casado-Pascual, Jesús; Gómez-Ordóñez, José; Morillo, Manuel; Lehmann, Jörg; Goychuk, Igor; Hänggi, Peter
2005-01-01
We investigate the role of noise in the phenomenon of stochastic synchronization of switching events in a rocked, overdamped bistable potential driven by white Gaussian noise, the archetype description of stochastic resonance. We present an approach to the stochastic counting process of noise-induced switching events: starting from the Markovian dynamics of the nonstationary, continuous particle dynamics, one finds upon contraction onto two states a non-Markovian renewal dynamics. A proper definition of an output discrete phase is given, and the time rate of change of its noise average determines the corresponding output frequency. The phenomenon of noise-assisted phase synchronization is investigated in terms of an effective, instantaneous phase diffusion. The theory is applied to rectangular-shaped rocking signals versus increasing input-noise strengths. In this case, for an appropriate choice of the parameter values, the system exhibits a noise-induced frequency locking accompanied by a very pronounced suppression of the phase diffusion of the output signal. Precise numerical simulations corroborate very favorably our analytical results. The novel theoretical findings are also compared with prior ones.
Babbs, Charles F
2011-01-01
To explore the fundamental biomechanics of sound frequency transduction in the cochlea, a two-dimensional analytical model of the basilar membrane was constructed from first principles. Quantitative analysis showed that axial forces along the membrane are negligible, condensing the problem to a set of ordered one-dimensional models in the radial dimension, for which all parameters can be specified from experimental data. Solutions of the radial models for asymmetrical boundary conditions produce realistic deformation patterns. The resulting second-order differential equations, based on the original concepts of Helmholtz and Guyton, and including viscoelastic restoring forces, predict a frequency map and amplitudes of deflections that are consistent with classical observations. They also predict the effects of an observation hole drilled in the surrounding bone, the effects of curvature of the cochlear spiral, as well as apparent traveling waves under a variety of experimental conditions. A quantitative rendition of the classical Helmholtz-Guyton model captures the essence of cochlear mechanics and unifies the competing resonance and traveling wave theories.
Quantitative Reappraisal of the Helmholtz-Guyton Resonance Theory of Frequency Tuning in the Cochlea
Directory of Open Access Journals (Sweden)
Charles F. Babbs
2011-01-01
Full Text Available To explore the fundamental biomechanics of sound frequency transduction in the cochlea, a two-dimensional analytical model of the basilar membrane was constructed from first principles. Quantitative analysis showed that axial forces along the membrane are negligible, condensing the problem to a set of ordered one-dimensional models in the radial dimension, for which all parameters can be specified from experimental data. Solutions of the radial models for asymmetrical boundary conditions produce realistic deformation patterns. The resulting second-order differential equations, based on the original concepts of Helmholtz and Guyton, and including viscoelastic restoring forces, predict a frequency map and amplitudes of deflections that are consistent with classical observations. They also predict the effects of an observation hole drilled in the surrounding bone, the effects of curvature of the cochlear spiral, as well as apparent traveling waves under a variety of experimental conditions. A quantitative rendition of the classical Helmholtz-Guyton model captures the essence of cochlear mechanics and unifies the competing resonance and traveling wave theories.
Directory of Open Access Journals (Sweden)
Marie Gleizes
Full Text Available Neuronal activity is characterized by a diversity of oscillatory phenomena that are associated with multiple behavioral and cognitive processes, yet the functional consequences of these oscillations are not fully understood. Our aim was to determine whether and how these different oscillatory activities affect short-term synaptic plasticity (STP, using the olfactory system as a model. In response to odorant stimuli, the olfactory bulb displays a slow breathing rhythm as well as beta and gamma oscillations. Since the firing of olfactory bulb projecting neurons is phase-locked with beta and gamma oscillations, structures downstream from the olfactory bulb should be driven preferentially at these frequencies. We examined STP exhibited by olfactory bulb inputs in slices of adult mouse piriform cortex maintained in vitro in an in vivo-like ACSF (calcium concentration: 1.1 mM. We replaced the presynaptic neuronal firing rate by repeated electrical stimulation (frequency between 3.125 and 100 Hz applied to the lateral olfactory tract. Our results revealed a considerable enhancement of postsynaptic response amplitude for stimulation frequencies in the beta and gamma range. A phenomenological model of STP fitted to the data suggests that the experimental results can be explained by the interplay between three mechanisms: a short-term facilitation mechanism (time constant ≈160 msec, and two short-term depression mechanisms (recovery time constants <20 msec and ≈140 msec. Increasing calcium concentration (2.2 mM resulted in an increase in the time constant of facilitation and in a strengthening of the slowest depression mechanism. As a result, response enhancement was reduced and its peak shifted toward the low beta and alpha ranges while depression became predominant in the gamma band. Using environmental conditions corresponding to those that prevail in vivo, our study shows that STP in the lateral olfactory tract to layer Ia synapse allows
Ishihara, M.; Hirasawa, T.; Tsujita, K.; Kitagaki, M.; Bansaku, I.; Fujita, M.; Kikuchi, M.
2011-03-01
Photoacoustics has been widely studied as a combined imaging modality of both optical and acoustical methods. The merits of the photoacoustic imaging are realizing the full potentials of pulsed laser-tissue interaction. As the photoacoustic waves can be induced at chromophores by pulsed lased irradiation through a thermoelastic process, it covers a wide range of frequency. In order to take advantages of the wide range frequency characteristics, we employed not PZT, but piezoelectronic copolymer film, P(VDF/TrFE) film, with various thickness ranging from 20 to 100 μm as photoacoustic transducers. Because blood vessels play a key role in homeostasis, we experimentally demonstrated blood vessels phantom using second harmonic generation of Q-switched Nd:YAG laser and Ti:sapphire nanosecond laser pulses through optical fiber transmission. The detected photoacoustic waveforms showed distinctive time-of-flight signals. The photoacoustic signals were sensitive to temperature, absorption coefficients of chromophores, and diameters of the phantom vessels. Hemoglobin oxygen saturation could be easily derived from the multi wavelength photoacoustic signals using differential optical absorption characteristics. These results proved the functional quantitative photoacoustic imaging using the signal characteristics. A multivariate photoacoustic imaging approach must be promising to convenient diagnosis.
Ege, Kerem; Boutillon, Xavier; Rébillat, Marc
2013-03-01
The piano soundboard transforms the string vibration into sound and therefore, its vibrations are of primary importance for the sound characteristics of the instrument. An original vibro-acoustical method is presented to isolate the soundboard nonlinearity from that of the exciting device (here: a loudspeaker) and to measure it. The nonlinear part of the soundboard response to an external excitation is quantitatively estimated for the first time, at ≈-40 dB below the linear part at the ff nuance. Given this essentially linear response, a modal identification is performed up to 3 kHz by means of a novel high resolution modal analysis technique [K. Ege, X. Boutillon, B. David, High-resolution modal analysis, Journal of Sound and Vibration 325 (4-5) (2009) 852-869]. Modal dampings (which, so far, were unknown for the piano in this frequency range) are determined in the mid-frequency domain where FFT-based methods fail to evaluate them with an acceptable precision. They turn out to be close to those imposed by wood. A finite-element modelling of the soundboard is also presented. The low-order modal shapes and the comparison between the corresponding experimental and numerical modal frequencies suggest that the boundary conditions can be considered as blocked, except at very low frequencies. The frequency-dependency of the estimated modal densities and the observation of modal shapes reveal two well-separated regimes. Below ≈1 kHz, the soundboard vibrates more or less like a homogeneous plate. Above that limit, the structural waves are confined by ribs, as already noticed by several authors, and localised in restricted areas (one or a few inter-rib spaces), presumably due to a slightly irregular spacing of the ribs across the soundboard.
Siaki, Leilani A; Loescher, Lois J; Trego, Lori L
2013-03-01
This article presents a discussion of development of a mid-range theory of risk perception. Unhealthy behaviours contribute to the development of health inequalities worldwide. The link between perceived risk and successful health behaviour change is inconclusive, particularly in vulnerable populations. This may be attributed to inattention to culture. The synthesis strategy of theory building guided the process using three methods: (1) a systematic review of literature published between 2000-2011 targeting perceived risk in vulnerable populations; (2) qualitative and (3) quantitative data from a study of Samoan Pacific Islanders at high risk of cardiovascular disease and diabetes. Main concepts of this theory include risk attention, appraisal processes, cognition, and affect. Overarching these concepts is health-world view: cultural ways of knowing, beliefs, values, images, and ideas. This theory proposes the following: (1) risk attention varies based on knowledge of the health risk in the context of health-world views; (2) risk appraisals are influenced by affect, health-world views, cultural customs, and protocols that intersect with the health risk; (3) strength of cultural beliefs, values, and images (cultural identity) mediate risk attention and risk appraisal influencing the likelihood that persons will engage in health-promoting behaviours that may contradict cultural customs/protocols. Interventions guided by a culturally sensitive mid-range theory may improve behaviour-related health inequalities in vulnerable populations. The synthesis strategy is an intensive process for developing a culturally sensitive mid-range theory. Testing of the theory will ascertain its usefulness for reducing health inequalities in vulnerable groups. © 2012 Blackwell Publishing Ltd.
Corfman, Thomas A; Cooper, Rory A; Boninger, Michael L; Koontz, Alicia M; Fitzgerald, Shirley G
2003-01-01
The objective of this study was to examine the use and efficacy of a pushrim-activated power-assist wheelchair (PAPAW) in the reduction of upper extremity range of motion (ROM) and stroke frequency in manual wheelchair users. Ten manual wheelchair users were evaluated using a repeated-measures design with and without the use of a PAPAW for maximum ROM of shoulder flexion/extension, abduction/adduction, internal/external rotation, and horizontal flexion/extension; elbow flexion/extension; wrist flexion/extension, supination/pronation, and ulnar/radial deviation; and stroke frequency. Participants propelled a Quickie 2 manual wheelchair configured as a PAPAW and their own wheelchair on a computer-controlled dynamometer at 3 different resistance levels and 2 different speeds. The use of the PAPAW significantly (P wrist flexion/extension and ulnar/radial deviation for many speed and resistance combinations. Univariate analysis revealed that stroke frequency was unaltered in all cases. These findings provide the foundation for studying the utility of the PAPAW in reducing the risk of upper limb injury and neuropathy in the manual wheelchair user population.
Revealing Long-Range Interconnected Hubs in Human Chromatin Interaction Data Using Graph Theory
Boulos, R. E.; Arneodo, A.; Jensen, P.; Audit, B.
2013-09-01
We use graph theory to analyze chromatin interaction (Hi-C) data in the human genome. We show that a key functional feature of the genome—“master” replication origins—corresponds to DNA loci of maximal network centrality. These loci form a set of interconnected hubs both within chromosomes and between different chromosomes. Our results open the way to a fruitful use of graph theory concepts to decipher DNA structural organization in relation to genome functions such as replication and transcription. This quantitative information should prove useful to discriminate between possible polymer models of nuclear organization.
DEFF Research Database (Denmark)
Fromager, Emmanuel; Toulouse, Julien; Jensen, Hans Jørgen Aagaard
2007-01-01
) adequately which, on the other hand, can be described in wave-function theory (WFT), for example, with a multiconfigurational self-consistent field (MCSCF) model. It is therefore of high interest to develop a hybrid model which combines the best of both WFT and DFT approaches. The merge of WFT and DFT can......In many cases, the dynamic correlation can be calculated quite accurately and at a fairly low computational cost in Kohn-Sham density-functional theory (KS-DFT), using current standard approximate functionals. However, in general, KS-DFT does not treat static correlation effects (near degeneracy...
Rowihal, Said Soliman
Both voltage-source and current-source inverters are widely used for supplying three-phase power to induction motor drives, each having their advantages and disadvantages. For high power drives and applications requiring accurate speed and tracking coordination, the synchronous motors are the optimum choice. For constant speed applications of synchronous motor drives, current-source inverters tend to be favored as the motor can usually be operated in the overexcited leading power factor region, thus providing the inverter with sufficient electro-motive force to allow natural commutation. Generally speaking low speed operation of synchronous motors is not satisfactory from naturally commutated current-source inverters. To provide a dynamic range of speed and frequency would require expensive control circuitry and complicates the performance of the drive. The advantage of the voltage-source inverter for the wide range of speed and frequency control herein envisaged is that forced commutation is employed throughout the range and the commutating circuits have been well developed and established. On balance, voltage-source inverters represent a viable compromise for variable-speed three -phase synchronous motor drives including start-up. To investigate the transient response of the voltage -source fed-synchronous motor drives, a digital computer program is developed. The program is based on two models --machine model and inverter model. The machine is represented by a detailed two-axis model which includes the effects due to saliency, damper windings, and machine resistances. The inverter model represents a forced-commutated voltage-source inverter assuming ideal switching devices (thyristors and diodes). To cope with the wide variations of power factor during start-up, a thyristor with a reverse connected parallel diode are integrated as a bidirectional switch. The digital program provides the machine variables of interest (phase currents, field current, damper winding
Viscoelastic behavior over a wide range of time and frequency in tin alloys: SnCd and SnSb
Energy Technology Data Exchange (ETDEWEB)
Quackenbush, J.; Brodt, M.; Lakes, R.S. [Univ. of Iowa, Iowa City, IA (United States)
1996-08-01
All materials exhibit some viscoelastic response, which can manifest itself as creep, relaxation, or, if the load is sinusoidal in time, a phase angle {delta} between stress and strain. Recently, a study of pure elements with low melting points, Cd, In, Pb, and Sn disclosed that cadmium exhibited a substantial loss tangent of 0.03 to 0.04 over much of the audio range of frequencies, combined with a moderate stiffness G = 20.7 GPa. Lead, by contrast, exhibited tan {delta} of 0.005 to 0.016 in the audio range. Indium exhibited a high loss tangent exceeding 0.1 at very low frequency. A eutectic alloy of indium and tin was found to exhibit substantial damping exceeding 0.1 below 0.1 Hz, and this alloy was used to make a composite exhibiting high stiffness and high damping. It is the purpose of this communication to present viscoelastic properties of two additional low melting point alloys, SnCd and SnSb. Both InSn and SnSb are used as solders. Although the melting point of Sb is 630.74 C, T{sub H} > 0.55 at ambient temperature for the alloy of SnSb (95 wt% Sn/5 wt% Sb) which melts near 240 C. Eutectic SnCd melts at 177 C so T{sub H} {approx} 0.65 at room temperature.
Towards cosmopolitan middle-range theorizing: A metamorphosis in the practice of social theory?
DEFF Research Database (Denmark)
Blok, Anders
2015-01-01
, spurred as it is by the urgency of responding to the global risks of climate change via reworking key categories of social theory. More strongly than existing notions of world risk society and second modernity, his new concept of metamorphosis (‘Verwandlung’) captures the way contemporary social upheavals...
Directory of Open Access Journals (Sweden)
Satoshi Ota
2016-09-01
Full Text Available The dependence of magnetic relaxation on particle parameters, such as the size and anisotropy, has been conventionally discussed. In addition, the influences of external conditions, such as the intensity and frequency of the applied field, the surrounding viscosity, and the temperature on the magnetic relaxation have been researched. According to one of the basic theories regarding magnetic relaxation, the faster type of relaxation dominates the process. However, in this study, we reveal that Brownian and Néel relaxations coexist and that Brownian relaxation can occur after Néel relaxation despite having a longer relaxation time. To understand the mechanisms of Brownian rotation, alternating current (AC hysteresis loops were measured in magnetic fluids of different viscosities. These loops conveyed the amplitude and phase delay of the magnetization. In addition, the intrinsic loss power (ILP was calculated using the area of the AC hysteresis loops. The ILP also showed the magnetization response regarding the magnetic relaxation over a wide frequency range. To develop biomedical applications of magnetic nanoparticles, such as hyperthermia and magnetic particle imaging, it is necessary to understand the mechanisms of magnetic relaxation.
Counting statistics of chaotic resonances at optical frequencies: Theory and experiments
Lippolis, Domenico; Wang, Li; Xiao, Yun-Feng
2017-07-01
A deformed dielectric microcavity is used as an experimental platform for the analysis of the statistics of chaotic resonances, in the perspective of testing fractal Weyl laws at optical frequencies. In order to surmount the difficulties that arise from reading strongly overlapping spectra, we exploit the mixed nature of the phase space at hand, and only count the high-Q whispering-gallery modes (WGMs) directly. That enables us to draw statistical information on the more lossy chaotic resonances, coupled to the high-Q regular modes via dynamical tunneling. Three different models [classical, Random-Matrix-Theory (RMT) based, semiclassical] to interpret the experimental data are discussed. On the basis of least-squares analysis, theoretical estimates of Ehrenfest time, and independent measurements, we find that a semiclassically modified RMT-based expression best describes the experiment in all its realizations, particularly when the resonator is coupled to visible light, while RMT alone still works quite well in the infrared. In this work we reexamine and substantially extend the results of a short paper published earlier [L. Wang et al., Phys. Rev. E 93, 040201(R) (2016), 10.1103/PhysRevE.93.040201].
Long-range weight functions in fundamental measure theory of the non-uniform hard-sphere fluid.
Hansen-Goos, Hendrik
2016-06-22
We introduce long-range weight functions to the framework of fundamental measure theory (FMT) of the non-uniform, single-component hard-sphere fluid. While the range of the usual weight functions is equal to the hard-sphere radius R, the modified weight functions have range 3R. Based on the augmented FMT, we calculate the radial distribution function g(r) up to second order in the density within Percus' test particle theory. Consistency of the compressibility and virial routes on this level allows us to determine the free parameter γ of the theory. As a side result, we obtain a value for the fourth virial coefficient B 4 which deviates by only 0.01% from the exact result. The augmented FMT is tested for the dense fluid by comparing results for g(r) calculated via the test particle route to existing results from molecular dynamics simulations. The agreement at large distances (r > 6R) is significantly improved when the FMT with long-range weight functions is used. In order to improve agreement close to contact (r = 2R) we construct a free energy which is based on the accurate Carnahan-Starling equation of state, rather than the Percus-Yevick compressibility equation underlying standard FMT.
Directory of Open Access Journals (Sweden)
N. V. Yagova
2010-09-01
Full Text Available We analyze spectral parameters of the geomagnetic disturbances within the 1–4 mHz (Pc5/Pi3 frequency range for 29 observatories from polar to auroral latitudes. The main object of this study is the broadband (noise background under quiet and moderately disturbed conditions. To obtain a quantitative description of background high-latitude long period ULF activity the log-log dependence of the spectral power on frequency is expanded over Legendre polynomials, and the coefficients of this expansion (spectral moments are used to describe the most common features of these spectra. Not only the spectral power, but also the spectral slope and higher spectral moments, averaged over relatively long time intervals, demonstrate a systematic dependence on corrected geomagnetic (CGM latitude, Φ, and magnetic local time, MLT. The 2-D distributions of the spectral moments in Φ-MLT coordinates are characterized by existence of structures, narrow in latitude and extended in MLT, which can be attributed to the projections of different magnetospheric domains. Spatio-temporal distributions of spectral power of elliptically (P-component and randomly (N-component polarized signal are similar, but not identical. The N-component contribution to the total signal becomes non-negligible in regions with a high local activity, such as the auroral oval and dayside polar cusp. The spectral slope indicates a larger relative contribution of higher frequencies upon the latitude decrease, probably, as a result of the resonant effects in the ULF noise. The higher spectral moments are also controlled mostly by CGM latitude and MLT and are fundamentally different for the polarized and non-polarized components. This study is a step towards the construction of an empirical model of the ULF wave power in Earth's magnetosphere.
Digital Repository Service at National Institute of Oceanography (India)
Bayat, M.; Crasta, N.; Aguiar, A.P.; Pascoal, A.M.
This paper addresses the problem of range-based autonomous underwater vehicle (AUV) localization in the presence of unknown ocean currents. In the setup adopted, the AUV is equipped with an attitude and heading reference system, a depth sensor...
Energy Technology Data Exchange (ETDEWEB)
Garaio, E., E-mail: eneko.garayo@ehu.es [Elektrizitatea eta Elektronika Saila, UPV/EHU, P.K. 644, Bilbao (Spain); Collantes, J.M. [Elektrizitatea eta Elektronika Saila, UPV/EHU, P.K. 644, Bilbao (Spain); Garcia, J.A. [Fisika Aplikatua II Saila, UPV/EHU, P.K. 644, Bilbao (Spain); Plazaola, F. [Elektrizitatea eta Elektronika Saila, UPV/EHU, P.K. 644, Bilbao (Spain); Mornet, S. [Institut de Chimie de la Matière Condensée de Bordeaux, UPR 9048 CNRS / Université de Bordeaux, Bordeaux (France); Couillaud, F. [Résonance Magnétique des Systèmes Biologiques, UMR 5536 CNRS / Université de Bordeaux, Bordeaux (France); Sandre, O., E-mail: olivier.sandre@enscbp.fr [Laboratoire de Chimie des Polymères Organiques, UMR 5629 CNRS / Université de Bordeaux, Bordeaux (France)
2014-11-15
Measurement of specific absorption rate (SAR) of magnetic nanoparticles is crucial to assert their potential for magnetic hyperthermia. To perform this task, calorimetric methods are widely used. However, those methods are not very accurate and are difficult to standardize. In this paper, we present AC magnetometry results performed with a lab-made magnetometer that is able to obtain dynamic hysteresis-loops in the AC magnetic field frequency range from 50 kHz to 1 MHz and intensities up to 24 kA m{sup −1}. In this work, SAR values of maghemite nanoparticles dispersed in water are measured by AC magnetometry. The so-obtained values are compared with the SAR measured by calorimetric methods. Both measurements, by calorimetry and magnetometry, are in good agreement. Therefore, the presented AC magnetometer is a suitable way to obtain SAR values of magnetic nanoparticles. - Highlights: • We propose AC magnetometry as a method to measure the specific absorption rate (SAR) of magnetic nanoparticles suitable for magnetic hyperthermia therapy. • We have built a lab-made AC magnetometer, which is able to measure magnetic dynamic hysteresis-loops of nanoparticle dispersions. • The device works with AC magnetic field intensities up to 24 kA m{sup −1} in a frequency range from 75 kHz to 1 MHz. • The SAR values of maghemite nanoparticles around 12 nm in magnetic diameter dispersed in water are measured by the lab-made magnetometer and different calorimetric methods. • Although all methods are in good agreement, several factors (probe location, thermal inertia, losses, etc.) make calorimetric method less accurate than AC magnetometry.
Fredette, Luke; Singh, Rajendra
2017-02-01
A spectral element approach is proposed to determine the multi-axis dynamic stiffness terms of elastomeric isolators with fractional damping over a broad range of frequencies. The dynamic properties of a class of cylindrical isolators are modeled by using the continuous system theory in terms of homogeneous rods or Timoshenko beams. The transfer matrix type dynamic stiffness expressions are developed from exact harmonic solutions given translational or rotational displacement excitations. Broadband dynamic stiffness magnitudes (say up to 5 kHz) are computationally verified for axial, torsional, shear, flexural, and coupled stiffness terms using a finite element model. Some discrepancies are found between finite element and spectral element models for the axial and flexural motions, illustrating certain limitations of each method. Experimental validation is provided for an isolator with two cylindrical elements (that work primarily in the shear mode) using dynamic measurements, as reported in the prior literature, up to 600 Hz. Superiority of the fractional damping formulation over structural or viscous damping models is illustrated via experimental validation. Finally, the strengths and limitations of the spectral element approach are briefly discussed.
DEFF Research Database (Denmark)
Hedegård, Erik Donovan
2017-01-01
considered the large collection of organic molecules whose excited states were investigated with a range of electronic structure methods by Thiel et al. As a by-product of our calculations of oscillator strengths, we also obtain electronic excitation energies, which enable us to compare the performance......We have in a series of recent papers investigated electronic excited states with a hybrid between a complete active space self-consistent field (CASSCF) wave function and density functional theory (DFT). This method has been dubbed the CAS short-range DFT method (CAS–srDFT). The previous papers...
Energy Technology Data Exchange (ETDEWEB)
Stotland, Alexander; Peer, Tal; Cohen, Doron [Department of Physics, Ben-Gurion University, Beer-Sheva 84005 (Israel); Budoyo, Rangga; Kottos, Tsampikos [Department of Physics, Wesleyan University, Middletown, CT 06459 (United States)
2008-07-11
The calculation of the conductance of disordered rings requires a theory that goes beyond the Kubo-Drude formulation. Assuming 'mesoscopic' circumstances the analysis of the electro-driven transitions shows similarities with a percolation problem in energy space. We argue that the texture and the sparsity of the perturbation matrix dictate the value of the conductance, and study its dependence on the disorder strength, ranging from the ballistic to the Anderson localization regime. An improved sparse random matrix model is introduced to capture the essential ingredients of the problem, and leads to a generalized variable range hopping picture. (fast track communication)
DEFF Research Database (Denmark)
Hedegård, Erik D.; Olsen, Jógvan Magnus Haugaard; Knecht, Stefan
2015-01-01
-MC-srDFT is designed to combine efficient treatment of complicated electronic structures with inclusion of effects from the surrounding environment. The environmental effects encompass classical electrostatic interactions as well as polarization of both the quantum region and the environment. Using response theory......, molecular properties such as excitation energies and oscillator strengths can be obtained. The PE-MC-srDFT method and the additional terms required for linear response have been implemented in a development version of Dalton. To benchmark the PE-MC-srDFT approach against the literature data, we have...... investigated the low-lying electronic excitations of acetone and uracil, both immersed in water solution. The PE-MC-srDFT results are consistent and accurate, both in terms of the calculated solvent shift and, unlike regular PE-MCSCF, also with respect to the individual absolute excitation energies...
Novel methodology for wide-ranged multistage morphing waverider based on conical theory
Liu, Zhen; Liu, Jun; Ding, Feng; Xia, Zhixun
2017-11-01
This study proposes the wide-ranged multistage morphing waverider design method. The flow field structure and aerodynamic characteristics of multistage waveriders are also analyzed. In this method, the multistage waverider is generated in the same conical flowfield, which contains a free-stream surface and different compression-stream surfaces. The obtained results show that the introduction of the multistage waverider design method can solve the problem of aerodynamic performance deterioration in the off-design state and allow the vehicle to always maintain the optimal flight state. The multistage waverider design method, combined with transfiguration flight strategy, can lead to greater design flexibility and the optimization of hypersonic wide-ranged waverider vehicles.
Nikolova, Mila; Steidl, Gabriele
2014-07-16
Color image enhancement is a complex and challenging task in digital imaging with abundant applications. Preserving the hue of the input image is crucial in a wide range of situations. We propose simple image enhancement algorithms which conserve the hue and preserve the range (gamut) of the R, G, B channels in an optimal way. In our setup, the intensity input image is transformed into a target intensity image whose histogram matches a specified, well-behaved histogram. We derive a new color assignment methodology where the resulting enhanced image fits the target intensity image. We analyse the obtained algorithms in terms of chromaticity improvement and compare them with the unique and quite popular histogram based hue and range preserving algorithm of Naik and Murthy. Numerical tests confirm our theoretical results and show that our algorithms perform much better than the Naik-Murthy algorithm. In spite of their simplicity, they compete with well-established alternative methods for images where hue-preservation is desired.
Stefan, V. Alexander; IAPS Team
The novel study of the epileptogenesis mechanisms is proposed. It is based on the pulsed-operated (amplitude modulation) multi-photon (frequency modulation) fiber-laser interaction with the brain epilepsy-topion (the epilepsy onset area), so as to prevent the excessive electrical discharge (epileptic seizure) in the brain. The repetition frequency, Ω, matches the low frequency (epileptic) phonon waves in the brain. The laser repetition frequency (5-100 pulses per second) enables the resonance-scanning of the wide range of the phonon (possible epileptic-to-be) activity in the brain. The tunable fiber laser frequencies, Δω (multi photon operation), are in the ultraviolet frequency range, thus enabling monitoring of the electrical charge imbalance (within the 10s of milliseconds), and the DNA-corruption in the epilepsy-topion, as the possible cause of the disease. Supported by Nikola Tesla Labs., Stefan University.
Ho, Kevin Ming-Jiang
The thesis comprises of 3 projects; an L-band microstrip antenna with frequency agility and polarization diversity, X-band phased array antennas incorporating commercially packaged RFIC phased array chips, and studies for Ku/Ka-band shared aperture antenna array. The first project features the use of commercially packaged RF-MEMS SPDT switches, that boasts of high reliability, high linearity, low losses, hermetically packaged and fully compatible for SMTA processes for mass-assembly and production. Using the switches in a novel manner for the feed network, microstrip antennas with polarization diversity are presented. Frequency agility is achieved with the use of tuning diodes to provide capacitive loading to the antenna element. Additional inductance effects from surface-mounted capacitors, and its impact, is introduced. Theoretical cross-polarization of probe-fed antenna elements is presented for both linear and circular polarized microstrip antennas. Designs and measurements are presented, for microstrip antennas with polarization diversity, wide frequency tuning range, and both features. Replacement of the tuning diodes with commercially-packaged high Q RF MEMS tunable capacitors will allow for significant improvements to the radiation efficiency. In another project, multi-channel CMOS RFIC phased-array receiver chips are assembled in QFN packages and directly integrated on the same multi-layered PCB stack-up with the antenna arrays. Problems of isolation from the PCB-QFN interface, and potential performance degradation on antenna array from the use of commercial-grade laminates for assembly requirements, namely potential scan blindness and radiation efficiency, are presented. Causes for apparent drift of dielectric constant for microstrip circuits, and high conductor losses observed in measurements, are introduced. Finally, studies are performed for the design of a Ku/Ka-Band shared aperture array. Different approaches for developing dual-band shared apertures
Energy Technology Data Exchange (ETDEWEB)
Franz Gross, Alfred Stadler
2010-09-01
We present the effective range expansions for the 1S0 and 3S1 scattering phase shifts, and the relativistic deuteron wave functions that accompany our recent high precision fits (with \\chi^2/N{data} \\simeq 1) to the 2007 world np data below 350 MeV. The wave functions are expanded in a series of analytical functions (with the correct asymptotic behavior at both large and small arguments) that can be Fourier-transformed from momentum to coordinate space and are convenient to use in any application. A fortran subroutine to compute these wave functions can be obtained from the authors.
Biogeographic ranges do not support niche theory in radiating Canary Island plant clades
DEFF Research Database (Denmark)
Steinbauer, Manuel; Field, Richard; Fernández-Palacios, José María
2016-01-01
species in radiating clades in oceanic archipelagos, where closely related species exist in both sympatry and allopatry and the species’ entire ranges are known. We took advantage of this natural experimental system to test whether the climatic niche relationships predicted by the two hypotheses are found....... Location: Canary Islands. Methods: For the plant clades Aeonium, Argyranthemum, Descurainia, Echium, Lotus and Sonchus, separately, we tested relationships between phylogenetic distance and climatic niche differentiation (in temperature, precipitation and their combination), using a high-resolution dataset...
Perturbation theory for short-range weakly-attractive potentials in one dimension
Energy Technology Data Exchange (ETDEWEB)
Amore, Paolo, E-mail: paolo.amore@gmail.com [Facultad de Ciencias, CUICBAS, Universidad de Colima, Bernal Díaz del Castillo 340, Colima, Colima (Mexico); Fernández, Francisco M., E-mail: fernande@quimica.unlp.edu.ar [INIFTA (UNLP, CONICET), Division Química Teórica, Blvd. 113 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)
2017-03-15
We have obtained the perturbative expressions up to sixth order for the energy of the bound state in a one dimensional, arbitrarily weak, short range finite well, applying a method originally developed by Gat and Rosenstein Ref. [1]. The expressions up to fifth order reproduce the results already known in the literature, while the sixth order had not been calculated before. As an illustration of our formulas we have applied them to two exactly solvable problems and to a nontrivial problem.
DEFF Research Database (Denmark)
Stobbe, Søren; Johansen, Jeppe; Kristensen, Philip Trøst
2009-01-01
of the exciton wave function on quantum dot size. We derive the quantum optics theory of a solid-state emitter in an inhomogeneous environment and compare this theory to our experimental results. Using this model, we extract the frequency dependence of the overlap between the electron and hole wave functions. We......We analyze time-resolved spontaneous emission from excitons confined in self-assembled InAs quantum dots placed at various distances to a semiconductor-air interface. The modification of the local density of optical states due to the proximity of the interface enables unambiguous determination...
DEFF Research Database (Denmark)
Hubert, Mickaël; Hedegård, Erik D.; Jensen, Hans Jørgen Aa
2016-01-01
-srDFT for a selected benchmark set of electronic excitations of organic molecules, covering the most common types of organic chromophores. This investigation confirms the expectation that the MC-srDFT method is accurate for a broad range of excitations and comparable to accurate wave function methods such as CASPT2......Computational methods that can accurately and effectively predict all types of electronic excitations for any molecular system are missing in the toolbox of the computational chemist. Although various Kohn-Sham density-functional methods (KS-DFT) fulfill this aim in some cases, they become...... and double excitations have been promising, it is nevertheless important that the accuracy of MC-srDFT is at least comparable to the best KS-DFT methods also for organic molecules that are typically of single-reference character. In this paper we therefore systematically investigate the performance of MC...
Usuki, Tsuneo
2013-09-01
The moduli of conventional elastic structural materials are extended to one of the viscoelastic materials through a modification whereby the dynamic moduli converge to the static moduli of elasticity as the fractional order approaches zero. By plotting phase velocity curves and group velocity curves of plane waves and Rayleigh surface wave for a viscoelastic material (polyvinyl chloride foam), the influence of the fractional order of viscoelasticity is examined. The phase and group velocity curves in the high frequency range were derived for longitudinal, transverse, and Rayleigh waves inherent to the viscoelastic material. In addition, the equation for the phase velocity was mathematically derived on the complex plane, too, and graphically illustrated. A phenomenon was found that, at the moment when the fractional order of the time derivative reaches an integer value 1, the curve on the complex plane becomes completely different, exhibiting snap-through behavior. We examined the mechanism of the snap-through mathematically. Numerical calculation examples were solved, and good agreement was confirmed between the numerical calculation and the analytical expression mentioned above. From the results of the numerical example, regularities were derived for the absolute value of the complex phase and group velocities on the complex plane.
Directory of Open Access Journals (Sweden)
Roberta Gomes Carvalho/
2014-09-01
Full Text Available The geographical distribution of Aedes albopictus in Brazil was updated according to the data recorded across the country over the last eight years. Countrywide house indexes (HI for Ae. albopictus in urban and suburban areas were described for the first time using a sample of Brazilian municipalities. This mosquito is currently present in at least 59% of the Brazilian municipalities and in 24 of the 27 federal units (i.e., 26 states and the Federal District. In 34 Brazilian municipalities, the HI values for Ae. albopictus were higher than those recorded for Ae. aegypti, reaching figures as high as HI = 7.72 in the Southeast Region. Remarks regarding the current range of this mosquito species in the Americas are also presented. Nineteen American countries are currently infested and few mainland American countries have not confirmed the occurrence of Ae. albopictus. The large distribution and high frequency of Ae. albopictus in the Americas may become a critical factor in the spread of arboviruses like chikungunya in the new world.
Carvalho, Roberta Gomes; Lourenço-de-Oliveira, Ricardo; Braga, Ima Aparecida
2014-01-01
The geographical distribution of Aedes albopictus in Brazil was updated according to the data recorded across the country over the last eight years. Countrywide house indexes (HI) for Ae. albopictus in urban and suburban areas were described for the first time using a sample of Brazilian municipalities. This mosquito is currently present in at least 59% of the Brazilian municipalities and in 24 of the 27 federal units (i.e., 26 states and the Federal District). In 34 Brazilian municipalities, the HI values for Ae. albopictus were higher than those recorded for Ae. aegypti, reaching figures as high as HI = 7.72 in the Southeast Region. Remarks regarding the current range of this mosquito species in the Americas are also presented. Nineteen American countries are currently infested and few mainland American countries have not confirmed the occurrence of Ae. albopictus. The large distribution and high frequency of Ae. albopictus in the Americas may become a critical factor in the spread of arboviruses like chikungunya in the new world. PMID:25317707
Directory of Open Access Journals (Sweden)
Katsuya Kobayashi
Full Text Available Physiological high frequency activities (HFA are related to various brain functions. Factors, however, regulating its frequency have not been well elucidated in humans. To validate the hypothesis that different propagation modes (thalamo-cortical vs. cortico-coritcal projections, or different terminal layers (layer IV vs. layer II/III affect its frequency, we, in the primary somatosensory cortex (SI, compared HFAs induced by median nerve stimulation with those induced by electrical stimulation of the cortex connecting to SI. We employed 6 patients who underwent chronic subdural electrode implantation for presurgical evaluation. We evaluated the HFA power values in reference to the baseline overriding N20 (earliest cortical response and N80 (late response of somatosensory evoked potentials (HFA(SEP(N20 and HFA(SEP(N80 and compared those overriding N1 and N2 (first and second responses of cortico-cortical evoked potentials (HFA(CCEP(N1 and HFA(CCEP(N2. HFA(SEP(N20 showed the power peak in the frequency above 200 Hz, while HFA(CCEP(N1 had its power peak in the frequency below 200 Hz. Different propagation modes and/or different terminal layers seemed to determine HFA frequency. Since HFA(CCEP(N1 and HFA induced during various brain functions share a similar broadband profile of the power spectrum, cortico-coritcal horizontal propagation seems to represent common mode of neural transmission for processing these functions.
Trejos, Víctor M; Gil-Villegas, Alejandro
2012-05-14
Thermodynamic properties of quantum fluids are described using an extended version of the statistical associating fluid theory for potentials of variable range (SAFT-VR) that takes into account quantum corrections to the Helmholtz free energy A, based on the Wentzel-Kramers-Brillouin approximation. We present the theoretical background of this approach (SAFT-VRQ), considering two different cases depending on the continuous or discontinuous nature of the particles pair interaction. For the case of continuous potentials, we demonstrate that the standard Wigner-Kirkwood theory for quantum fluids can be derived from the de Broglie-Bohm formalism for quantum mechanics that can be incorporated within the Barker and Henderson perturbation theory for liquids in a straightforward way. When the particles interact via a discontinuous pair potential, the SAFT-VR method can be combined with the perturbation theory developed by Singh and Sinha [J. Chem. Phys. 67, 3645 (1977); and ibid. 68, 562 (1978)]. We present an analytical expression for the first-order quantum perturbation term for a square-well potential, and the theory is applied to model thermodynamic properties of hydrogen, deuterium, neon, and helium-4. Vapor-liquid equilibrium, liquid and vapor densities, isochoric and isobaric heat capacities, Joule-Thomson coefficients and inversion curves are predicted accurately with respect to experimental data. We find that quantum corrections are important for the global behavior of properties of these fluids and not only for the low-temperature regime. Predictions obtained for hydrogen compare very favorably with respect to cubic equations of state.
Riest, Jonas; Nägele, Gerhard; Liu, Yun; Wagner, Norman J; Godfrin, P Douglas
2018-02-14
Recently, atypical static features of microstructural ordering in low-salinity lysozyme protein solutions have been extensively explored experimentally and explained theoretically based on a short-range attractive plus long-range repulsive (SALR) interaction potential. However, the protein dynamics and the relationship to the atypical SALR structure remain to be demonstrated. Here, the applicability of semi-analytic theoretical methods predicting diffusion properties and viscosity in isotropic particle suspensions to low-salinity lysozyme protein solutions is tested. Using the interaction potential parameters previously obtained from static structure factor measurements, our results of Monte Carlo simulations representing seven experimental lysoyzme samples indicate that they exist either in dispersed fluid or random percolated states. The self-consistent Zerah-Hansen scheme is used to describe the static structure factor, S(q), which is the input to our calculation schemes for the short-time hydrodynamic function, H(q), and the zero-frequency viscosity η. The schemes account for hydrodynamic interactions included on an approximate level. Theoretical predictions for H(q) as a function of the wavenumber q quantitatively agree with experimental results at small protein concentrations obtained using neutron spin echo measurements. At higher concentrations, qualitative agreement is preserved although the calculated hydrodynamic functions are overestimated. We attribute the differences for higher concentrations and lower temperatures to translational-rotational diffusion coupling induced by the shape and interaction anisotropy of particles and clusters, patchiness of the lysozyme particle surfaces, and the intra-cluster dynamics, features not included in our simple globular particle model. The theoretical results for the solution viscosity, η, are in qualitative agreement with our experimental data even at higher concentrations. We demonstrate that semi
Neurone bioelectric activity under magnetic fields of variable frequency in the range of 0.1-80 Hz
Pérez Bruzón, R. N.; Azanza, María. J.; Calvo, Ana C.; del Moral, A.
2004-05-01
Intracellular recordings from single unit molluscan neurones under exposure to ELF-MF (1 mT, 0.1-80 Hz), show that neurone frequency activity, f, decreases with the applied magnetic field frequency, fM, a phenomenon which indicates a frequency-window effect for the neurone membrane response. The HMHW of the window amounts between 2-10 Hz. An explanation of this phenomenon is proposed.
Neurone bioelectric activity under magnetic fields of variable frequency in the range of 0.1-80 Hz
Energy Technology Data Exchange (ETDEWEB)
Perez Bruzon, R.N.; Azanza, M.J. E-mail: mjazanza@posta.unizar.es; Calvo, Ana C.; Moral, A. del
2004-05-01
Intracellular recordings from single unit molluscan neurones under exposure to ELF-MF (1 mT, 0.1-80 Hz), show that neurone frequency activity, f, decreases with the applied magnetic field frequency, f{sub M}, a phenomenon which indicates a frequency-window effect for the neurone membrane response. The HMHW of the window amounts between 2-10 Hz. An explanation of this phenomenon is proposed.
Bobkova, I. V.; Bobkov, A. M.; Silaev, M. A.
2017-09-01
We present the generalized quasiclassical theory of the long-range superconducting proximity effect in heterostructures with strong ferromagnets, where the exchange splitting is of the order of Fermi energy. In the ferromagnet the propagation of equal-spin Cooper pairs residing on the spin-split Fermi surfaces is shown to be governed by the spin-dependent Abelian gauge field which results either from the spin-orbital coupling or from the magnetic texture. This additional gauge field enters into the quasiclassical equations in superposition with the usual electromagnetic vector potential and results in the generation of spontaneous superconducting currents and phase shifts in various geometries which provide the sources of long-range spin-triplet correlations. We derive the Usadel equations and boundary conditions for the strong ferromagnet and consider several generic examples of the Josephson systems supporting spontaneous currents.
Directory of Open Access Journals (Sweden)
Urbanczyk Guillaume
2017-01-01
Full Text Available Waves in the Ion Cyclotron (ICRF and Lower Hybrid (LH Range of Frequencies are efficient techniques respectively to heat the plasma and drive current. Main difficulties come from a trade-off between good RF coupling and acceptable level of impurities release. The mutual influence of both systems makes such equilibrium often hard to reach [1]. In order to investigate those interactions based on Scrape-Off Layer (SOL plasma parameters, a new reciprocating probe was designed allying a three tips Langmuir probe with an emissive wire. The emissive filament provides a precise measure of plasma potential [2], which can be used to calibrate Langmuir probe's results. This paper reports on experimental results obtained on EAST, where there are two ICRF antennas and two LH launchers. Among others diagnostics, the new reciprocating probe enabled to evidence the deleterious influence of ICRF power on LHWs coupling in L-mode plasmas. In areas connected with an active ICRF antenna, SOL potentials increase while densities tend to decrease, respectively enhancing impurities release and deteriorating LHWs coupling. This phenomenon has mostly been attributed to RF sheath; the one that forms on top of Plasma Facing Components (PFCs and causes ExB density convections [3]. From those experiments it seems ICRF has a strong influence on magnetically connected areas, both in the near field – influencing ICRF waves coupling – and in farther locations such as in front of LH grills. Moreover, influence of ICRF on LH system was observed both in L and H modes. Those results are consistent with RF sheath rectification process. Concerning the influence of LHWs on ICRF coupling, nothing was observed in L-mode. Besides during H-mode experiments, LHWs have been identified as having a mitigating effect on ELMs [4], which on average lowers the pedestal, increasing edge densities to the profit of ICRF waves coupling.
Urbanczyk, Guillaume; Zhang, Xinjun; Qin, Chengming; Zhao, Yanping; Zhang, Tao; Zhang, Ling; Li, Jiangang; Yuan, Shuai; Chen, Liang; Zhang, Heng; Zhang, Jiahui; Wang, Jianhua; Yang, Xiuda; Qian, Jinping
2017-10-01
Waves in the Ion Cyclotron (ICRF) and Lower Hybrid (LH) Range of Frequencies are efficient techniques respectively to heat the plasma and drive current. Main difficulties come from a trade-off between good RF coupling and acceptable level of impurities release. The mutual influence of both systems makes such equilibrium often hard to reach [1]. In order to investigate those interactions based on Scrape-Off Layer (SOL) plasma parameters, a new reciprocating probe was designed allying a three tips Langmuir probe with an emissive wire. The emissive filament provides a precise measure of plasma potential [2], which can be used to calibrate Langmuir probe's results. This paper reports on experimental results obtained on EAST, where there are two ICRF antennas and two LH launchers. Among others diagnostics, the new reciprocating probe enabled to evidence the deleterious influence of ICRF power on LHWs coupling in L-mode plasmas. In areas connected with an active ICRF antenna, SOL potentials increase while densities tend to decrease, respectively enhancing impurities release and deteriorating LHWs coupling. This phenomenon has mostly been attributed to RF sheath; the one that forms on top of Plasma Facing Components (PFCs) and causes ExB density convections [3]. From those experiments it seems ICRF has a strong influence on magnetically connected areas, both in the near field - influencing ICRF waves coupling - and in farther locations such as in front of LH grills. Moreover, influence of ICRF on LH system was observed both in L and H modes. Those results are consistent with RF sheath rectification process. Concerning the influence of LHWs on ICRF coupling, nothing was observed in L-mode. Besides during H-mode experiments, LHWs have been identified as having a mitigating effect on ELMs [4], which on average lowers the pedestal, increasing edge densities to the profit of ICRF waves coupling.
Murray, Aja Louise; Booth, Tom; McKenzie, Karen; Kuenssberg, Renate
2016-06-01
It has previously been noted that inventories measuring traits that originated in a psychopathological paradigm can often reliably measure only a very narrow range of trait levels that are near and above clinical cutoffs. Much recent work has, however, suggested that autism spectrum disorder traits are on a continuum of severity that extends well into the nonclinical range. This implies a need for inventories that can capture individual differences in autistic traits from very high levels all the way to the opposite end of the continuum. The Autism-Spectrum Quotient (AQ) was developed based on a closely related rationale, but there has, to date, been no direct test of the range of trait levels that the AQ can reliably measure. To assess this, we fit a bifactor item response theory model to the AQ. Results suggested that AQ measures moderately low to moderately high levels of a general autistic trait with good measurement precision. The reliable range of measurement was significantly improved by scoring the instrument using its 4-point response scale, rather than dichotomizing responses. These results support the use of the AQ in nonclinical samples, but suggest that items measuring very low and very high levels of autistic traits would be beneficial additions to the inventory. (PsycINFO Database Record (c) 2016 APA, all rights reserved).
Sesek, Aleksander; Zemva, Andrej; Trontelj, Janez
2018-02-14
The THz sensors using microbolometers as a sensing element are reported as one of the most sensitive room-temperature THz detectors suitable for THz imaging and spectroscopic applications. Microbolometer detectors are usually fabricated using different types of the MEMS technology. The patent for the detection system presented in this paper describes a method for microbolometer fabrication using a standard CMOS technology with advanced micromachining techniques. The measured sensitivity of the sensors fabricated by the patented method is 1000 V/W at an optimal frequency and is determined by the performance of a double-dipole antenna and quarter-wavelength resonant cavity. The paper presents a patented method for fabrication of a microbolometer system for radiation detection in the THz frequency range (16). The method is divided into several stages regarding the current silicon micromachining process. Main stages are fabrication of supporting structures for micro bridge, creation of micro cavities and fabrication of Aluminum antenna and Titanium microbolometer. Additional method for encapsulation in the vacuum is described which additionally improves the performance of bolometer. The CMOS technology is utilized for fabrication as it is cost effective and provides the possibility of larger sensor systems integration with included amplification. At other wavelengths (e.g. IR region) thermistors are usually also the receivers with the sensor resistance change provoked by self-heating. In the THz region the energy is received by an antenna coupled to a thermistor. Depending on the specific application requirement, two types of the antenna were designed and used; a narrow-band dipole antenna and a wideband log-periodic antenna. With method described in the paper, the microbolometer detector reaches sensitivities up to 500 V/W and noise equivalent power (NEP) down to 10 pW/√Hz. Additional encapsulation in the vacuum improves its performance at least by a factor of 2
Pienkowski, Martin; Eggermont, Jos J
2010-09-01
Passive exposure of adult animals to a random ensemble of tone pips band limited between 4 and 20 kHz has been shown to suppress neural activity in primary auditory cortex (AI) to sounds in the exposure frequency range. In the long-term (>3 months), the suppressed neurons can be reactivated by frequencies above and below the exposure range, i.e., tonotopic map reorganization occurs. The suppression can be at least partially reversed after a long period of quiet recovery, as the moderate-level exposure does not impair peripheral hearing. Here we exposed adult cats, for 7-13 weeks without interruption, to two different moderate-level tone pip ensembles, in separate experiments. One exposure stimulus consisted of an octave-wide 2-4 kHz band, which overlaps substantially with the cat vocalization range; the other consisted of a pair of third-octave bands centered at 4 and 16 kHz. We again report a decrease in AI responsiveness in the exposure frequency range, irrespective of the exposure stimulus bandwidth or center frequency, and a slow, partial recovery over a 12-week post-exposure window. In contrast to our previous studies, the suppression in both of the present experiments extended well beyond the exposure frequency range. In particular, following the 4 and 16 kHz experimental acoustic environment, AI activity was strongly suppressed not only in response to frequencies close to the two exposure bands, but also in response to frequencies between the bands, i.e., the results resembled those to a single broadband stimulus spanning the 3-18 kHz range. On the other hand, responses in secondary auditory cortex (AII) were suppressed predominantly around 4 and 16 kHz, with little or no suppression in between. Copyright (c) 2010 Elsevier B.V. All rights reserved.
Quantum Theory of Conditional Phonon States in a Dual-Pumped Raman Optical Frequency Comb
Mondloch, Erin
In this work, we theoretically and numerically investigate nonclassical phonon states created in the collective vibration of a Raman medium by the generation of a dual-pumped Raman optical frequency comb in an optical cavity. This frequency comb is generated by cascaded Raman scattering driven by two phase-locked pump lasers that are separated in frequency by three times the Raman phonon frequency. We characterize the variety of conditioned phonon states that are created when the number of photons in all optical frequency modes except the pump modes are measured. Almost all of these conditioned phonon states are extremely well approximated as three-phonon-squeezed states or Schrodinger-cat states, depending on the outcomes of the photon number measurements. We show how the combinations of first-, second-, and third-order Raman scattering that correspond to each set of measured photon numbers determine the fidelity of the conditioned phonon state with model three-phonon-squeezed states and Schrodinger-cat states. All of the conditioned phonon states demonstrate preferential growth of the phonon mode along three directions in phase space. That is, there are three preferred phase values that the phonon state takes on as a result of Raman scattering. We show that the combination of Raman processes that produces a given set of measured photon numbers always produces phonons in multiples of three. In the quantum number-state representation, these multiples of three are responsible for the threefold phase-space symmetry seen in the conditioned phonon states. With a semiclassical model, we show how this three-phase preference can also be understood in light of phase correlations that are known to spontaneously arise in single-pumped Raman frequency combs. Additionally, our semiclassical model predicts that the optical modes also grow preferentially along three phases, suggesting that the dual-pumped Raman optical frequency comb is partially phase-stabilized.
Zaske, Sebastian; Lenhard, Andreas; Becher, Christoph
2011-06-20
We report on single photon frequency downconversion from the red part of the spectrum (738 nm) to the telecommunications C-band. By mixing attenuated laser pulses with an average photon number per pulse telecommunications wavelengths.
Wukitch, S. J.; Garrett, M. L.; Ochoukov, R.; Terry, J. L.; Hubbard, A.; Labombard, B.; Lau, C.; Lin, Y.; Lipschultz, B.; Miller, D.; Reinke, M. L.; Whyte, D.; Alcator C-Mod Team
2013-05-01
Ion cyclotron range of frequency (ICRF) heating is expected to provide auxiliary heating for ITER and future fusion reactors where high Z metallic plasma facing components (PFCs) are being considered. Impurity contamination linked to ICRF antenna operation remains a major challenge particularly for devices with high Z metallic PFCs. Here, we report on an experimental investigation to test whether a field aligned (FA) antenna can reduce impurity contamination and impurity sources. We compare the modification of the scrape of layer (SOL) plasma potential of the FA antenna to a conventional, toroidally aligned (TA) antenna, in order to explore the underlying physics governing impurity contamination linked to ICRF heating. The FA antenna is a 4-strap ICRF antenna where the current straps and antenna enclosure sides are perpendicular to the total magnetic field while the Faraday screen rods are parallel to the total magnetic field. In principle, alignment with respect to the total magnetic field minimizes integrated E|| (electric field along a magnetic field line) via symmetry. A finite element method RF antenna model coupled to a cold plasma model verifies that the integrated E|| should be reduced for all antenna phases. Monopole phasing in particular is expected to have the lowest integrated E||. Consistent with expectations, we observed that the impurity contamination and impurity source at the FA antenna are reduced compared to the TA antenna. In both L and H-mode discharges, the radiated power is 20%-30% lower for a FA-antenna heated discharge than a discharge heated with the TA-antennas. However, inconsistent with expectations, we observe RF induced plasma potentials (via gas-puff imaging and emissive probes to be nearly identical for FA and TA antennas when operated in dipole phasing). Moreover, the highest levels of RF-induced plasma potentials are observed using monopole phasing with the FA antenna. Thus, while impurity contamination and sources are indeed
Changming, Pi; Wei, Yan; Ke, Zhang; Wenhong, Li
2010-08-01
This paper presents a width controller, a dead time controller, a discontinuous current mode (DCM) controller and a frequency skipping modulation (FSM) controller for a high frequency high efficiency buck DC-DC converter. To improve the efficiency over a wide load range, especially at high switching frequency, the dead time controller and width controller are applied to enhance the high load efficiency, while the DCM controller and FSM controller are proposed to increase the light load efficiency. The proposed DC-DC converter controllers have been designed and fabricated in the Chartered 0.35 μm CMOS process, and the measured results show that the efficiency of the buck DC-DC converter is above 80% over a wide load current range from 8 to 570 mA, and the peak efficiency is 86% at 10 MHz switching frequency.
Energy Technology Data Exchange (ETDEWEB)
Pi Changming; Yan Wei; Zhang Ke; Li Wenhong, E-mail: wenhongli@fudan.edu.c [State Key Laboratory of ASIC and Systems, Fudan University, Shanghai 201203 (China)
2010-08-15
This paper presents a width controller, a dead time controller, a discontinuous current mode (DCM) controller and a frequency skipping modulation (FSM) controller for a high frequency high efficiency buck DC-DC converter. To improve the efficiency over a wide load range, especially at high switching frequency, the dead time controller and width controller are applied to enhance the high load efficiency, while the DCM controller and FSM controller are proposed to increase the light load efficiency. The proposed DC-DC converter controllers have been designed and fabricated in the Chartered 0.35 {mu}m CMOS process, and the measured results show that the efficiency of the buck DC-DC converter is above 80% over a wide load current range from 8 to 570 mA, and the peak efficiency is 86% at 10 MHz switching frequency. (semiconductor integrated circuits)
Stefan, V. Alexander; IAPS-team Team
2017-10-01
The novel study of the laser excitation-suppression of the brain waves is proposed. It is based on the pulsed-operated multi-photon fiber-laser interaction with the brain parvalbumin (PV) neurons. The repetition frequency matches the low frequency brain waves (5-100 Hz); enabling the resonance-scanning of the wide range of the PV neurons (the generators of the brain wave activity). The tunable fiber laser frequencies are in the ultraviolet frequency range, thus enabling the monitoring of the PV neuron-DNA, within the 10s of milliseconds. In medicine, the method can be used as an ``instantaneous-on-off anesthetic.'' Supported by Nikola Tesla Labs, Stefan University.
DEFF Research Database (Denmark)
Nilsson, Niels Christian; Serafin, Stefania; Nordahl, Rolf
2014-01-01
and virtual walking speeds. This paper details a study investigating the effects of movement type (treadmill walking and WIP) and step frequency (1.4, 1.8 and 2.2 steps per second) on the range of perceptually natural visual walking speeds. The results suggests statistically significant main effects of both...... movement type and step frequency but no significant interaction between the two variables....
Menn, Lise; Duffield, Cecily Jill
2013-11-01
Error and preservation patterns in aphasic speech show that the brain makes use of the frequencies of words, constructions, and collocations, as well as category membership and hierarchical structure, during language processing. Frequency effects are evident along two quasi-independent axes: syntagmatic (the sequential context, e.g., deploying correct functors, categories, and utterance-level intonation) and paradigmatic (the choice at any given linguistic level, e.g., selecting content words and modifying structures). Frequency along the syntagmatic axis is shown to play a role in errors involving idioms, constructions, and collocations that cross major phrasal boundaries. Along the paradigmatic axis, frequency affects errors involving lexical selection, competing functors and inflected forms (e.g., using plural where singular is required). An account of language representation and processing that encompasses frequency as well as categorization and structure is compatible with what we know about how the brain works: increased experience with a linguistic structure results in increased activation-and strengthening-of the neural networks involved in processing that structure. These claims are supported by the literature on experimental work in normal speakers. Parsimony, plus the unexamined assumption that mental representation is like a written record (entries either present or absent, structure displayable in two dimensions), has been a misleading guide to modeling language representation. The substantial redundancy in representations and processing that is introduced by incorporating both frequency-based and hierarchy-based information is in fact appropriate for the brain as a fast, reliable, massively parallel error-correcting network with very large storage capacity and gradient representation strength. WIREs Cogn Sci 2013, 4:651-663. doi: 10.1002/wcs.1257 CONFLICT OF INTEREST: The authors have declared no conflicts of interest for this article. For further
Romanov, A. N.; Kochetkova, T. D.; Suslyaev, V. I.; Shcheglova, A. S.
2017-09-01
Dielectric characteristics of some species of marsh vegetation: lichen Cladonia stellaris (Opiz) Pouzar, moss Sphagnum, and a representative of Bryidae mosses - Dicranum polysetum are studied in the frequency range from 100 MHz to 18 GHz. At a frequency of 1.41 GHz, the influence of temperature in the range from -12 to +20°C on the behavior of dielectric characteristics of mosses, lichens, and peat is studied. The dependences of the dielectric characteristics of vegetation on the volumetric wetness are established.
Tang, Martin
2017-01-01
Passenger demand for enhanced cabin comfort have made cabin noise to an important factor. The damping behaviour of the cabin must be understood in order to predict noise emission. Due to the high modal density and overlap, state-of-the-art methods are not able to accurately identify damping in the mid- and high-frequency range. However, these frequency ranges are relevant in the field of acoustics. 2016 a method was proposed for local damping identification, which was applied to an aircra...
Energy Technology Data Exchange (ETDEWEB)
Pavelyev, D. G., E-mail: pavelev@rf.unn.ru, E-mail: obolensk@rf.unn.ru [Lobachevsky State University of Nizhny Novgorod (Russian Federation); Vasilev, A. P., E-mail: vasiljev@mail.ioffe.ru [Russian Academy of Sciences, Submicron Heterostructures for Microelectronics, Research and Engineering Center (Russian Federation); Kozlov, V. A., E-mail: kozlov@ipm.sci-nnov.ru; Koschurinov, Yu. I.; Obolenskaya, E. S.; Obolensky, S. V. [Lobachevsky State University of Nizhny Novgorod (Russian Federation); Ustinov, V. M., E-mail: vmust@beam.ioffe.ru [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)
2016-11-15
The electron transport in superlattices based on GaAs/AlAs heterostructures with a small number of periods (6 periods) is calculated by the Monte Carlo method. These superlattices are used in terahertz diodes for the frequency stabilization of quantum cascade lasers in the range up to 4.7 THz. The band structure of superlattices with different numbers of AlAs monolayers is considered and their current–voltage characteristics are calculated. The calculated current–voltage characteristics are compared with the experimental data. The possibility of the efficient application of these superlattices in the THz frequency range is established both theoretically and experimentally.
Atdayev, Agylych; Danilyuk, Alexander L; Prischepa, Serghej L
2015-01-01
The interaction of electromagnetic radiation with a magnetic nanocomposite based on carbon nanotubes (CNT) is considered within the model of distributed random nanoparticles with a core-shell morphology. The approach is based on a system composed of a CNT conducting resistive matrix, ferromagnetic inductive nanoparticles and the capacitive interface between the CNT matrix and the nanoparticles, which form resonance resistive-inductive-capacitive circuits. It is shown that the influence of the resonant circuits leads to the emergence of specific resonances, namely peaks and valleys in the frequency dependence of the permeability of the nanocomposite, and in the frequency dependence of the reflection and transmission of electromagnetic radiation.
Directory of Open Access Journals (Sweden)
Agylych Atdayev
2015-04-01
Full Text Available The interaction of electromagnetic radiation with a magnetic nanocomposite based on carbon nanotubes (CNT is considered within the model of distributed random nanoparticles with a core–shell morphology. The approach is based on a system composed of a CNT conducting resistive matrix, ferromagnetic inductive nanoparticles and the capacitive interface between the CNT matrix and the nanoparticles, which form resonance resistive–inductive–capacitive circuits. It is shown that the influence of the resonant circuits leads to the emergence of specific resonances, namely peaks and valleys in the frequency dependence of the permeability of the nanocomposite, and in the frequency dependence of the reflection and transmission of electromagnetic radiation.
Richmond, J. H.
1974-01-01
Piecewise-sinusoidal expansion functions and Galerkin's method are employed to formulate a solution for an arbitrary thin-wire configuration in a homogeneous conducting medium. The analysis is performed in the real or complex frequency domain. In antenna problems, the solution determines the current distribution, impedance, radiation efficiency, gain and far-field patterns. In scattering problems, the solution determines the absorption cross section, scattering cross section and the polarization scattering matrix. The electromagnetic theory is presented for thin wires and the forward-scattering theorem is developed for an arbitrary target in a homogeneous conducting medium.
Chen, Jenn-Shyong; Furumoto, Jun-ichi; Su, Ching-Lun; Chu, Yen-Hsyang
Field-aligned irregularity (FAI) in the ionosphere is a topic of interest to atmospheric radar community. In addition to the field-aligned characteristic, quasi-periodic (QP) appearance of FAI echoes has been observed frequently by very-high-frequency (VHF) atmospheric radar. The occurrence range of QP FAI echoes changes with time, and the slope of range versus time can be positive or negative, depending on occurrence time of the echoes. Several mechanisms responsible for the QP FAI echoes have been proposed, e.g., modulation in altitude by a passing atmospheric gravity wave, semidiurnal neutral-wind variation, and so on. Owing to the finite pulse length of radar in observation, the range resolution of measurement is limited within hundreds of meters. In view of this, the range imaging (RIM) using multiple frequencies has been employed to improve the range resolution of measurement. The multi-frequency technique transmits a set of slightly different frequencies sequentially during each radar pulse, and the radar returns at different transmitting frequencies are received, respectively. With adaptive retrieval algorithms for these radar returns, it is capable of resolving the echo structures at meter scale in the range direction. RIM has been employed in the lower atmosphere successfully. In this study, the performance of RIM for FAI was first carried out with the Middle and Upper atmosphere Radar (46 MHz; 34.85(°) N, 136.10(°) N; Japan) and the Chung-Li VHF radar (52 MHz; 24.9(°) N, 121.1(°) E; Taiwan). Some initial results of high-resolution FAI echoes within the range gate will be shown.
High-Frequency Acoustics of Ocean Sediments and Biot’s Theory
1999-09-30
roughly divided into two groups, one in which the sediment is approximated as an elastic fluid (e.g. Moe and Jackson 1998) or solid (e.g. Jackson and Ivakin... Mecanique et d’Acoustique, France. REFERENCES Chotiros, Nicholas P. 1998: Biot’s theory and granular media. Poromechanics- A tribute to Maurice A...John E. and Jackson, Darrell R. 1998: Near-field scattering through and from a two-dimensional fluid – fluid rough interface. J. Acoust. Soc. Am. 103(1
Long-Range Prediction of Population by Sex and Age in Each DistrictBased on Fuzzy Theory
Pak, Pyong Sik; Kim, Gwan
This paper proposes a method of predicting the population by sex and age for each of 402 districts over a long-range period in the Kansai region, Japan, by applying fuzzy theories. First, to predict the total social increase for 402 districts by directly taking into consideration of differences in factors of migration in each district, nine rules or domains were set up by using the migration rate and the total social increase in each district as the premise variables. Regression models were constructed in the consequences which use various socioeconomic indicators as explaining variables. The future value of the total social increase in each district can be obtained by weighting the values calculated from the estimated regression models with the membership values denoting the degree of belonging to each rule. Second, a method to estimate the social increase by sex and age in each district is proposed based on fuzzy clustering method for dealing with long-range socioeconomic changes in population migration by sex, age and district. All the samples of the migration ratio were classified into the same nine domains. By applying Fuzzy c-Means on districts belonged to each domain, all samples were classified into 20 clusters. The future migration ratio in each district can be estimated by weighting the migration pattern in each cluster with the values of membership function denoting the degree of belonging to each cluster. Results of the validity test of the constructed population model based on the proposed methods are also presented. It has been shown that it becomes possible to predict the population by sex, age and district over a long-range period by using the proposed method.
Kirichuk, V F; Antipova, O N; Krylova, Ya A
2014-06-01
We studied the effect of terahertz waves (NO frequency range, 150.176-150.664 GHz) on stress-induced variations in behavioral reactions of male albino rats during hypokinetic stress. THz irradiation was followed by partial or complete normalization of behavioral reactions of male albino rats after hypokinetic stress. The most significant effect was observed after continuous irradiation for 30 min.
2016-08-01
LIST OF MATHEMATICAL SYMBOLS AND UNITS ................................................. iii 1 INTRODUCTION ...HYDROPHONES IN THE FREQUENCY RANGE 250 HZ TO 500 KHZ USING THREE-TRANSDUCER SPHERICAL WAVE RECIPROCITY 1. INTRODUCTION This document describes the...for algae , there is little aquatic vegetation. Calibration measurements were performed on 22 June 2016. Environmental conditions during the
Ma, H.; van der Zee, Ronan A.R.; Nauta, Bram
2015-01-01
This paper describes the power dissipation analysis and the design of an efficiency-improved high-voltage class-D power amplifier. The amplifier adaptively regulates its switching frequency for optimal power efficiency across the full output power range. This is based on detecting the switching
Ho, Kevin Ming-Jiang
2014-01-01
The thesis comprises of 3 projects; an L-band microstrip antenna with frequency agility and polarization diversity, X-band phased array antennas incorporating commercially packaged RFIC phased array chips, and studies for Ku/Ka- band shared aperture antenna array. The first project features the use of commercially packaged RF-MEMS SPDT switches, that boasts of high reliability, high linearity, low losses, hermetically packaged and fully compatible for SMTA processes for mass-assembly and prod...
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Fannin, P.C. [Department of Electronic and Electrical Engineering, Trinity College, University of Dublin, Dublin 2 (Ireland); Vekas, L. [Center for Fundamental Technical Research, Romanian Academy-Timisoara Branch, Timisoara (Romania); Marin, C.N., E-mail: catalin.marin@e-uvt.ro [West University of Timisoara, Faculty of Physics, V. Parvan Blv., no. 4, 300223 Timisoara (Romania); Malaescu, I. [West University of Timisoara, Faculty of Physics, V. Parvan Blv., no. 4, 300223 Timisoara (Romania)
2017-02-01
Complex susceptibility measurements provide a unique and efficient means for the investigation and determination of the dynamic properties of magnetic fluids. In particular, measurement of the frequency, f(Hz), and field, H(kA/m), dependent, complex susceptibility, χ(ω, Η)= χ′(ω, Η)−iχ″(ω, Η), of magnetic fluids has proven to be a valuable and reliable technique for investigating such properties. The experimental data presented here was obtained from measurements of a transformer oil based ferrofluid, with measurements being performed over the frequency range 0.1–20 GHz and polarising fields 0–168 kA/m. In the case of transformer oil magnetic fluids, the normal measurement emphasis has been on the investigation of their dielectric properties, including the effects which lightning may have on these properties. Little has been reported on the measurement of the corresponding magnetic susceptibility, χ(ω), of such fluids and in this paper we address this fact. Thus we consider it worthwhile, in the case of a transformer with magnetic fluid transformer oil, being affected as a result of a lightening occurrence, to have knowledge of the fluids dynamic properties, at the microwave frequencies. In the process of determining the sample susceptibility profiles, it was found that the peak value of the χ″(ω) component, was approximately constant over the frequency range 2.4–6.3 GHz. From this it was determined that the fluid was effectively operating as a wideband absorber over a bandwidth of 3.9 GHz. - Highlights: • Complex magnetic susceptibility measurements in the frequency range 0.1–20 GHz. • Determination of the dynamic properties of a transformer oil based ferrofluid. • Wideband attenuator ( Absorber) in the frequency range 2.4–6.3 GHz.
Sagaidachnyi, A. A.; Volkov, I. U.; Fomin, A. V.
2016-04-01
This paper describes limit possibilities of modern cooled thermal imaging cameras as a tool for estimation of blood flow oscillations at the surface of living body. Skin temperature oscillations, as we assumed, are a consequence of the blood flow oscillations. We considered the temperature sensitivity 0.01-0.02 °C as a typical for the most of modern cooled long wave thermal imaging cameras. Fourier filter used to investigate the temperature signal separately within endothelial, neurogenic, myogenic, respiratory and cardiac frequency ranges. The level of temporal noise has been estimated during measurements of no living body with stabilized temperature ~ 24°C. The level of temperature oscillations has been calculated for the group of healthy subjects within each frequency range. Thus, we were able to determine signal-to-noise ratio within frequency band [0.001, 1] Hz. As a result, we determine that skin temperature oscillations measured by thermal imaging camera with sensitivity 0.02°C have the upper frequency limit ~ 0.2 Hz. In other words, within the respiratory and cardiac frequency ranges of blood flow oscillations the noise level exceeds signal one, and temperature measurements at the skin surface are practically useless. The endothelial, neurogenic and myogenic components of the temperature oscillations contain ~98% of the total spectral power of the signal. We have plot the empirical extrapolated curve of sensitivity of thermal imaging camera vs. frequency of the temperature oscillations. The data analysis shows that measurements of skin temperature oscillations within respiratory and cardiac ranges require the temperature sensitivity at least ~ 0.01°C and 0.001°C, respectively.
Asbridge, Mark; Butters, Jennifer
2013-01-01
Road rage has been described as a key criminal justice and public health concern. Although research attention to this issue has expanded dramatically, most of this work has focused on the identification of predisposing individual factors. It is equally important to begin to assess those factors that may modify the likelihood of road rage including the broader structural opportunities that are connected with the propensity to be involved in a road rage incident. Drawing on opportunity theory, this article examines whether there is a relationship between increased opportunities to be involved in road rage and an increased likelihood of being a road rage victim or offender. The analysis is further extended to specifically test whether this relationship is linear, thereby examining the applicability of the opportunity saturation hypothesis. Using data from the Centre for Addiction and Mental Health (CAMH) Monitor, our findings support both the application of opportunity theory to understanding road rage and the presence of opportunity saturation. Although a clear relationship exists between kilometers driven and experiences of road rage, evidence emerged suggesting there may be a threshold whereby increased opportunities for road rage do not lead to road rage behavior.
Nikravan, Afsoun; Badali, Yosef; Altındal, Şemsettin; Uslu, İbrahim; Orak, İkram
2017-10-01
In order to interpret the electrical characteristics of fabricated Au/ZnO/n-Si structures as a function of frequency and voltage well, their capacitance-voltage ( C- V) and conductance-voltage ( G/ ω- V) measurements were carried out in a wide range of frequencies (0.7 kHz-2 MHz) and voltages (± 6 V) by 50 mV steps at room temperature. Both the C- V and G/ ω- V plots have reverse, depletion, and accumulation regions such as a metal-insulator/oxide semiconductor (MIS or MOS) structures. The values of doped-donor atoms ( N D), Fermi energy level ( E F), barrier height (ΦB), and series resistance ( R s) of the structure were obtained as a function of frequency and voltage. While the value of N D decreases with increasing frequency almost as exponentially, the value of depletion width ( W D) increases. The values of C and G/ ω increase with decreasing frequency because the surface states ( N ss) are able to follow the alternating current (AC) signal, resulting in excess capacitance ( C ex) and conductance ( G ex/ ω), which depends on their relaxation time and the frequency of the AC signal. The voltage-dependent profiles of N ss were obtained from both the high-low frequency capacitance and Hill-Colleman methods. The other important parameter R s of the structure was also obtained from the Nicollian and Brews methods as a function of voltage.
Willis, Elizabeth C; Kenny, Dianna T
2011-09-01
Assessment of the voice-change progress of 20 girls (12-13 years) over 1 year by observing changes in speaking fundamental frequency (SFo), voice range, and register pitch breaks in the context of weight, height, voice training, and self-perception. One-year longitudinal collective case study. Twenty girls were recorded at the beginning and end of a year; nine girls were recorded another three times. SFo, vocal range, and characteristics were analyzed and interactions between these data assessed against weight and height to indicate pubertal development, and to test the hypothesis that changes in weight, height, SFo, and pitch breaks were related. Effects of training and the girls' self-perception of their voice use were also assessed. Vocal characteristics changed as the girls passed through different weight ranges. During 47.5-52.4 kg (called band 2) and 52.4-57.5 kg (band 3), there was progressive contraction of vocal range and in some girls a slight rise in SFo between recording times 1 and 5. Both high- and low-pitch breaks were present in 45% of girls' voices. Girls in band 4 (pitch breaks in vocal-range areas that indicated the development of adult vocal registers. In this study, voice-trained girls were heavier, had higher SFo, used wider speech-range inflection, had a higher vocal range, and greater voice-use confidence; all girls lost confidence in their voice use over the year. In this longitudinal study of twenty 13-year-old girls, voice changes in SFo, vocal range, and pitch-break frequency were synchronous with certain weight ranges. Girls with training registered higher maximum phonational frequency and were more confident in their voice use than girls without training. Copyright © 2011 The Voice Foundation. Published by Mosby, Inc. All rights reserved.
Drakakis, E.; Kymakis, E.; Tzagkarakis, G.; Louloudakis, D.; Katharakis, M.; Kenanakis, G.; Suchea, M.; Tudose, V.; Koudoumas, E.
2017-03-01
We report on the mechanisms of the electromagnetic interference shielding effect of graphene based paint like composite layers. In particular, we studied the absorption and reflection of electromagnetic radiation in the 4-20 GHz frequency of various dispersions employing different amounts of graphene nanoplatelets, polyaniline, and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), special attention given on the relative contribution of each process in the shielding effect. Moreover, the influence of the composition, the thickness and the conductivity of the composite layers on the electromagnetic shielding was also examined.
Theory and experiment research for ultra-low frequency maglev vibration sensor
Energy Technology Data Exchange (ETDEWEB)
Zheng, Dezhi; Liu, Yixuan, E-mail: xuan61x@163.com; Guo, Zhanshe; Fan, Shangchun [School of Instrument Science and Opto-electronics Engineering, Beihang University, Beijing 100191 (China); Zhao, Xiaomeng [Laser Medicine Laboratory, Institute of Biomedical Engineering, Chinese Academy of medical Sciences and Peking Union Medical College, Tianjin 300192 (China)
2015-10-15
A new maglev sensor is proposed to measure ultra-low frequency (ULF) vibration, which uses hybrid-magnet levitation structure with electromagnets and permanent magnets as the supporting component, rather than the conventional spring structure of magnetoelectric vibration sensor. Since the lower measurement limit needs to be reduced, the equivalent bearing stiffness coefficient and the equivalent damping coefficient are adjusted by the sensitivity unit structure of the sensor and the closed-loop control system, which realizes both the closed-loop control and the solving algorithms. A simple sensor experimental platform is then assembled based on a digital hardware system, and experimental results demonstrate that the lower measurement limit of the sensor is increased to 0.2 Hz under these experimental conditions, indicating promising results of the maglev sensor for ULF vibration measurements.
Alatas, Husin; Falah, Ahmad K.; Alditia, Randika; Gunara, Bobby E.
2017-12-01
We discuss the existence of graviton in a Friedmann-Lemaitre-Robertson-Walker (FLRW) metric of isotropic and homogeneous universe based on de Rham-Gabadadze-Tolley (dRGT) nonlinear massive gravity theory. We consider a similar FLRW fiducial metric in the formulation that lead to a Friedmann-Lemaitre equation similar to the case of cosmological constant based dark energy model. We show that these equations can be constructed by considering a constraint equation found from varying the corresponding action with respect to the fiducial metric. Under a specific choice of fiducial metric lapse function, we determine the range of present cosmological time bare graviton mass in a parameter space by considering the observed cosmological constant density parameter and the related Higuchi bound for the lower dressed graviton mass value. The existence of an indefinite condition in the corresponding parameter space is also discussed and analyzed, as well as the characteristics of the related bare graviton mass and the strong-coupling scale quantity.
DEFF Research Database (Denmark)
Hedegård, Erik D.; Jensen, Hans Jørgen Aagaard; Knecht, Stefan
2013-01-01
Charge transfer excitations can be described within Time-Dependent Density Functional Theory (TD-DFT), not only by means of the Coulomb Attenuated Method (CAM) but also with a combination of wave function theory and TD-DFT based on range separation. The latter approach enables a rigorous formulat......Charge transfer excitations can be described within Time-Dependent Density Functional Theory (TD-DFT), not only by means of the Coulomb Attenuated Method (CAM) but also with a combination of wave function theory and TD-DFT based on range separation. The latter approach enables a rigorous...... formulation of multi-determinantal TD-DFT schemes where excitation classes, which are absent in conventional TD-DFT spectra (like for example double excitations), can be addressed. This paper investigates the combination of both the long-range Multi-Configuration Self-Consistent Field (MCSCF) and Second Order...... Polarization Propagator Approximation (SOPPA) ansätze with a short-range DFT (srDFT) description. We find that the combinations of SOPPA or MCSCF with TD-DFT yield better results than could be expected from the pure wave function schemes. For the Time-Dependent MCSCF short-range DFT ansatz (TD...
Energy Technology Data Exchange (ETDEWEB)
Kleismit, Richard A; Kozlowski, Gregory; Foy, Brent D [Department of Physics, Wright State University, 3640 Col. Glenn Hwy, Dayton, OH 45435-0001 (United States); Hull, Barbara E [Department of Biological Sciences, Wright State University, 3640 Col. Glenn Hwy, Dayton, OH 45435-0001 (United States); Kazimierczuk, Marian [Department of Electrical Engineering, Wright State University, 3640 Col. Glenn Hwy, Dayton, OH 45435-0001 (United States)], E-mail: richard.kleismit@wright.edu
2009-02-07
The near-field evanescent microwave microscope is based on a coaxial transmission line resonator with a silver plated tungsten tip protruding through an end-wall aperture. The sensor is used to measure the local dielectric properties of porcine skin in the frequency range from 1 GHz to 15 GHz. The dielectric property of the skin within the near field of the tip frustrates the electric field and measurably changes the transmission line's resonant frequency and quality factor (Q). The shift of the resonator's frequency and Q is measured as a function of tip-sample separation, and a quantitative relationship between the real and imaginary parts of the local dielectric constant using the method of images is established. The associated changes in quality factor image scans of subsurface tissue structure and dielectric properties of skin surface lesions are presented.
Structural Damage Detection Using Changes in Natural Frequencies: Theory and Applications
He, K.; Zhu, W. D.
2011-07-01
A vibration-based method that uses changes in natural frequencies of a structure to detect damage has advantages over conventional nondestructive tests in detecting various types of damage, including loosening of bolted joints, using minimum measurement data. Two major challenges associated with applications of the vibration-based damage detection method to engineering structures are addressed: accurate modeling of structures and the development of a robust inverse algorithm to detect damage, which are defined as the forward and inverse problems, respectively. To resolve the forward problem, new physics-based finite element modeling techniques are developed for fillets in thin-walled beams and for bolted joints, so that complex structures can be accurately modeled with a reasonable model size. To resolve the inverse problem, a logistical function transformation is introduced to convert the constrained optimization problem to an unconstrained one, and a robust iterative algorithm using a trust-region method, called the Levenberg-Marquardt method, is developed to accurately detect the locations and extent of damage. The new methodology can ensure global convergence of the iterative algorithm in solving under-determined system equations and deal with damage detection problems with relatively large modeling error and measurement noise. The vibration-based damage detection method is applied to various structures including lightning masts, a space frame structure and one of its components, and a pipeline. The exact locations and extent of damage can be detected in the numerical simulation where there is no modeling error and measurement noise. The locations and extent of damage can be successfully detected in experimental damage detection.
Viger, Louise; Ponomarev, Artem L.; Plante, Ianik; Evain, Trevor; Penninckx, Sebastien; Blattnig, Steve R.; Costes, Sylvain V.
2017-01-01
Exploration missions to Mars and other destinations raise many questions about the health of astronauts. The continuous exposure of astronauts to galactic cosmic rays is one of the main concerns for long-term missions. Cosmic ionizing radiations are composed of different ions of various charges and energies notably, highly charged energy (HZE) particles. The HZE particles have been shown to be more carcinogenic than low-LET radiation, suggesting the severity of chromosomal aberrations induced by HZE particles is one possible explanation. However, most mathematical models predicting cell death and mutation frequency are based on directly fitting various HZE dose response and are in essence empirical approaches. In this work, we assume a simple biological mechanism to model DNA repair and use it to simultaneously explain the low- and high-LET response using the exact same fitting parameters. Our work shows that the geometrical position of DNA repair along tracks of heavy ions are sufficient to explain why high-LET particles can induce more death and mutations. Our model is based on assuming DNA double strand breaks (DSBs) are repaired within repair domain, and that any DSBs located within the same repair domain cluster into one repair unit, facilitating chromosomal rearrangements and increasing the probability of cell death. We introduced this model in 2014 using simplified microdosimetry profiles to predict cell death. In this work, we collaborated with NASA Johnson Space Center to generate more accurate microdosimetry profiles derived by Monte Carlo techniques, taking into account track structure of HZE particles and simulating DSBs in realistic cell geometry. We simulated 224 data points (D, A, Z, E) with the BDSTRACKS model, leading to a large coverage of LET from 10 to 2,400 keV/µm. This model was used to generate theoretical RBE for various particles and energies for both cell death and mutation frequencies. The RBE LET dependence is in agreement with
Energy Technology Data Exchange (ETDEWEB)
Seemann, K. [Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft, Institut fuer Materialforschung I, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)]. E-mail: klaus.seemann@imf.fzk.de; Leiste, H. [Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft, Institut fuer Materialforschung I, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Bekker, V. [Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft, Institut fuer Materialforschung I, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)
2006-07-15
A new generation of CMOS-compatible micro-inductor prototypes with magnetic cores were realized, characterised as well as theoretically modelled in a frequency range up to 4 GHz, a frequency range where, e.g., mobile communication and global positioning systems (GPS) are operated. The micro-inductor's electrical magnitudes like inductance (L) and quality factor (Q) were theoretically described by means of an equivalent circuit model taking the frequency behaviour of the magnetic film core, expressed by the Landau-Lifschitz and Maxwell equations, into account. Six inch targets were used to deposit metallic layers (Al{sub 99}Si{sub 0.5}Cu{sub 0.5}), diffusion barriers (Si{sub 3}N{sub 4}), insulating layers (SiO{sub 2}) and magnetic films (Fe{sub 39}Co{sub 3}Ta{sub 8}N{sub 23}) by DC or reactive r.-f.-magnetron sputtering. All film materials were patterned by NUV-lithography (Near Ultra Violet), plasma beam milling and reactive ion etching to form the micro-inductors on 4-inch silicon wafers. The inductor windings are arranged in a way that they possess a low resistance and generate a quasi closed flux at the end of the cores to minimise eddy current losses in the silicon substrate. In order to diminish demagnetising effects in an efficient working core the magnetic films were patterned into micro squares with lateral dimensions of 20 and 100 {mu}m with 100 nm in thickness. More magnetic volume and a higher micro-inductor cross-section was achieved by producing 100 nm magnetic double layers separated by a 800 nm thick Si{sub 3}N{sub 4} inter-layer. To guarantee a sufficiently high cut-off frequency of the magnetic films, they were annealed in a static magnetic field at a temperature of 400 deg. C for uniaxial anisotropy induction. This represents a temperature treatment where aluminium CMOS processes take place. As a result of patterning, the magnetic film material exhibited a remarkable increase of the cut-off frequency from 2 GHz in laterally extended films up
Van Buren, Kendra L.; Ouisse, Morvan; Cogan, Scott; Sadoulet-Reboul, Emeline; Maxit, Laurent
2017-09-01
In the development of numerical models, uncertainty quantification (UQ) can inform appropriate allocation of computational resources, often resulting in efficient analysis for activities such as model calibration and robust design. UQ can be especially beneficial for numerical models with significant computational expense, such as coupled models, which require several subsystem models to attain the performance of a more complex, inter-connected system. In the coupled model paradigm, UQ can be applied at either the subsystem model level or the coupled model level. When applied at the subsystem level, UQ is applied directly to the physical input parameters, which can be computationally expensive. In contrast, UQ at the coupled level may not be representative of the physical input parameters, but comes at the benefit of being computationally efficient to implement. To be physically meaningful, analysis at the coupled level requires information about how uncertainty is propagated through from the subsystem level. Herein, the proposed strategy is based on simulations performed at the subsystem level to inform a covariance matrix for UQ performed at the coupled level. The approach is applied to a four-subsystem model of mid-frequency vibrations simulated using the Statistical Modal Energy Distribution Analysis, a variant of the Statistical Energy Analysis. The proposed approach is computationally efficient to implement, while simultaneously capturing information from the subsystem level to ensure the analysis is physically meaningful.
Chen, Hetuo; Fu, Xuewen; An, Qi; Tang, Bin; Zhang, Shuren; Yang, Hao; Long, Yin; Harfouche, Mark; Wang, Huolei; Li, Yingxiang
2017-10-26
Microwave dielectric ceramic materials are extensively utilized in microwave applications because of their high dielectric constants and quality factors. These applications also require ceramics of zero temperature coefficients at the resonant frequency (τ f ), which can be realized through mixing a ceramic that one is interested in with another ceramic with -τ f , or by performing the ionic substitution. With the mixing/ionic substitution, it is indispensable to compute the quality factors precisely. Previous study indicates that the quality factor depends on the grain size, porosity, internal strain, structure, phase evolution, and conductivity etc. Here we derive a quality factor formula based on the definition, which works very well for multiphase composites, single phase solid solutions, and equivalent ionic substituted single phase materials. Our formula calculation and fits to the previous experimental results demonstrate that the quality factor of the ceramic mixtures strongly depend on the dielectric constants and the dielectric constant variation index. Our results suggest that the impacts from grain size, porosity, and internal strain etc. can be summarized to the dielectric constant or dielectric constant variation index, which is of great importance for future design of high performance microwave dielectric ceramics.
Zafar, Haroon; Breathnach, Aedán; Subhash, Hrebesh M; Leahy, Martin J
2015-05-01
Photoacoustic imaging (PAI) with a linear-array-based probe can provide a convenient means of imaging the human microcirculation within its native structural context and adds functional information. PAI using a multielement linear transducer array combined with multichannel collecting system was used for in vivo volumetric imaging of the blood microcirculation, the total concentration of hemoglobin (HbT), and the hemoglobin oxygen saturation (sO₂) within human tissue. Three-dimensional (3-D) PA and ultrasound (US) volumetric scans were acquired from the forearm skin by linearly translating the transducer with a stepper motor over a region of interest, while capturing two-dimensional images using 15, 21, and 40 MHz frequency transducer probes. For the microvasculature imaging, PA images were acquired at 800- and 1064-nm wavelengths. For the HbT and sO₂ estimates, PA images were collected at 750- and 850-nm wavelengths. 3-D microcirculation, HbT, and sO₂ maps of the forearm skin were obtained from normal subjects. The linear-array-based PAI has been found promising in terms of resolution, imaging depth, and imaging speed for in vivo microcirculation imaging within human skin. We believe that a reflection type probe, similar to existing clinical US probes, is most likely to succeed in real clinical applications. Its advantages include ease of use, speed, and familiarity for radiographers and clinicians.
Hutchins, Tiffany L.; Allen, Lyndsey; Schefer, Maggie
2017-01-01
Traditional child-performance measures of theory of mind (ToM) are associated with several limitations. The Theory of Mind Inventory-2 (ToMI-2) is a new broadband caregiver-informant measure designed to tap children's ToM competence. The purposes of this pilot study were to (1) gather preliminary data to explore the scope of the ToM challenges…
Suarez, Adrian; Victoria, Jorge; Alcarria, Antonio; Torres, Jose; Martinez, Pedro A; Martos, Julio; Soret, Jesus; Garcia-Olcina, Raimundo; Muetsch, Steffen
2018-01-23
The gap of standardization for conducted and field coupled electromagnetic interferences (EMI) in the 2-150 kHz frequency range can lead to Electromagnetic Compatibility (EMC) problems. This is caused by power systems such as Pulse Width Modulation (PWM) controlled rectifiers, photovoltaic inverters or charging battery units in electric vehicles. This is a very important frequency spectral due to interferences generated in a wide range of devices and, specifically, communication problems in the new technologies and devices incorporated to the traditional grid to convert it into a Smart Grid. Consequently, it is necessary to provide new solutions to attenuate this kind of interference, which involves finding new materials that are able to filter the electromagnetic noise. This contribution is focused on characterizing the performance of a novel material based on nanocrystalline and comparing it to most common material compositions such as MnZn and NiZn. This research is carried out from the point of view of the manufacturing process, magnetic properties and EMI suppression ability. This last item is carried out through two analysis procedures: a theoretical method by determining the attenuation ratio by measuring impedance parameter and proposing a new empirical technique based on measuring directly the insertion loss parameter. Therefore, the main aim of this characterization process is to determine the performance of nanocrystalline compared to traditional cable ferrite compositions to reduce the interferences in this controversial frequency range. From the results obtained, it is possible to deduce that nanocrystalline cable ferrite provides the best performance to filter the electromagnetic noise in the 2-150 kHz frequency range.
Smolyanskaya, O. A.; Kravtsenyuk, O. V.; Panchenko, A. V.; Odlyanitskiy, E. L.; Guillet, J. P.; Cherkasova, O. P.; Khodzitsky, M. K.
2017-12-01
In the course of in vitro studies of blood of laboratory animals with progressing Ehrlich carcinoma, we have revealed the change of the blood plasma optical properties in the THz range, which can be used for developing the express diagnostics of the presence of oncological diseases. An applied software package is elaborated that allows the phantoms of biological samples having a complex structure to be numerically simulated and the parameters of the electromagnetic wave reflected from these samples in the THz frequency range to be calculated. Presented at the Fundamentals of Laser Micro- and Nanotechnologies (FLAMN-16) International Symposium (Pushkin, Leningrad oblast, 27 June to 1 July 2016).
Lin, Guoping; Chembo, Yanne K
2015-01-26
Optical whispering gallery mode (WGM) resonators have been very attracting platforms for versatile Kerr frequency comb generations. We report a systematic study on the material dispersion of various optical materials that are capable of supporting quality factors above 109. Using an analytical approximation of WGM resonant frequencies in disk resonators, we investigate the effect of the geometry and transverse mode order on the total group-velocity dispersion (GVD). We demonstrate that the major radii and the radial mode indices play an important role in tailoring the GVD of WGM resonators. In particular, our study shows that in WGM disk-resonators, the polar families of modes have very similar GVD, while the radial families of modes feature dispersion values that can differ by up to several orders of magnitude. The effect of these giant dispersion shifts are experimentally evidenced in Kerr comb generation with magnesium fluoride. From a more general perspective, this critical feature enables to push the zero-dispersion wavelength of fluorite crystals towards the mid-infrared (mid-IR) range, thereby allowing for efficient Kerr comb generation in that spectral range. We show that barium fluoride is the most interesting crystal in this regard, due to its zero dispersion wavelength (ZDW) at 1.93 μm and an optimal dispersion profile in the mid-IR regime. We expect our results to facilitate the design of different platforms for Kerr frequency comb generations in both telecommunication and mid-IR spectral ranges.
Boisvert, Jean-Sébastien; Margot, Joëlle; Massines, Françoise
2017-04-01
In this paper the recently reported hybrid mode (a dielectric barrier discharge (DBD) excited by an electric field oscillating at about 1 MHz) is investigated using space and time-resolved imaging together with electrical measurements. In contrast with the helium low-frequency DBD, at 1.6 MHz the light emission is desynchronized with the discharge current. It rather depends on the enhanced rate of stepwise excitation resulting from the massive secondary emission occurring 0.15Ƭ after the discharge current maximum (Ƭ is the excitation wave period). The consequence of ion impacts on the dielectric surfaces is a higher gas and dielectric temperatures as compared to typical helium DBDs. The electrical behavior and the gas temperature of a pulsed dielectric-barrier discharge operated at 1.6 MHz are also described in this paper as a function of the repetition rate (varying from 1 Hz to 10 kHz). The gas temperature is reduced when repetition rates higher or equal to 10 Hz is used. This is related to the gas renewal rate of 8.3 Hz, i.e., gas residence time of 120 ms in our conditions. In addition, due to the memory effect in the gas, the gas gap voltage decreases as the repetition rate increases. However, beyond 100 Hz, the power decreases and the gas gap voltage increases again. As a consequence, for a given power density, the optimal repetition rate is 100 Hz which minimizes the gas temperature without reducing the power density. Contribution to the topical issue "The 15th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XV)", edited by Nicolas Gherardi and Tomáš Hoder
Surface impedance of BaFe2-xNixAs2 in the radio frequency range
Directory of Open Access Journals (Sweden)
A. Abbassi
2012-08-01
Full Text Available We report measurements of the temperature dependence of the surface impedance in superconducting BaFe1.93Ni0.07As2 crystals using the radiofrequency reflection technique in the 5
Tamagawa, Hirohisa; Ikeda, Kota
2017-09-01
Donnan theory and Goldman-Hodgkin-Katz equation (GHK eq.) state that the nonzero membrane potential is generated by the asymmetric ion distribution between two solutions separated by a semipermeable membrane and/or by the continuous ion transport across the semipermeable membrane. However, there have been a number of reports of the membrane potential generation behaviors in conflict with those theories. The authors of this paper performed the experimental and theoretical investigation of membrane potential and found that (1) Donnan theory is valid only when the macroscopic electroneutrality is sufficed and (2) Potential behavior across a certain type of membrane appears to be inexplicable on the concept of GHK eq. Consequently, the authors derived a conclusion that the existing theories have some limitations for predicting the membrane potential behavior and we need to find a theory to overcome those limitations. The authors suggest that the ion adsorption theory named Ling's adsorption theory, which attributes the membrane potential generation to the mobile ion adsorption onto the adsorption sites, could overcome those problems.
Morimoto, Ryota; Hirata, Akimasa; Laakso, Ilkka; Ziskin, Marvin C.; Foster, Kenneth R.
2017-03-01
This study computes the time constants of the temperature elevations in human head and body models exposed to simulated radiation from dipole antennas, electromagnetic beams, and plane waves. The frequency range considered is from 1 to 30 GHz. The specific absorption rate distributions in the human models are first computed using the finite-difference time-domain method for the electromagnetics. The temperature elevation is then calculated by solving the bioheat transfer equation. The computational results show that the thermal time constants (defined as the time required to reach 63% of the steady state temperature elevation) decrease with the elevation in radiation frequency. For frequencies higher than 4 GHz, the computed thermal time constants are smaller than the averaging time prescribed in the ICNIRP guidelines, but larger than the averaging time in the IEEE standard. Significant differences between the different head models are observed at frequencies higher than 10 GHz, which is attributable to the heat diffusion from the power absorbed in the pinna. The time constants for beam exposures become large with the increase in beam diameter. The thermal time constant in the brain is larger than that in the superficial tissues at high frequencies, because the brain temperature elevation is caused by the heat conduction of energy absorbed in the superficial tissue. The thermal time constant is minimized with an ideal beam with a minimum investigated diameter of 10 mm this minimal time constant is approximately 30 s and is almost independent of the radiation frequency, which is supported by analytic methods. In addition, the relation between the time constant, as defined in this paper, and ‘averaging time’ as it appears in the exposure limits is discussed, especially for short intense pulses. Similar to the laser guidelines, provisions should be included in the limits to limit the fluence for such pulses.
Giner, Beatriz; Bandrés, Isabel; López, M Carmen; Lafuente, Carlos; Galindo, Amparo
2007-10-14
A study of the phase equilibrium (experimental and modeled) of mixtures formed by a cyclic ether and haloalkanes has been derived. Experimental data for the isothermal vapor liquid equilibrium of mixtures formed by tetrahydrofuran and tetrahydropyran and isomeric chlorobutanes at temperatures of 298.15, 313.15, and 328.15 K are presented. Experimental results have been discussed in terms of both molecular characteristics of pure compounds and potential intermolecular interaction between them using thermodynamic information of the mixtures obtained earlier. The statistical associating fluid theory for potential of variable range (SAFT-VR) approach together with standard combining rules without adjustable parameters has been used to model the phase equilibrium. Good agreement between experiment and the prediction is found with such a model. Mean absolute deviations for pressures are of the order of 1 kPa, while less than 0.013 mole fraction for vapor phase compositions. In order to improve the results obtained, a new modeling has been carried out by introducing a unique transferable parameter k(ij), which modifies the strength of the dispersion interaction between unlike components in the mixtures, and is valid for all the studied mixtures being not temperature or pressure dependent. This parameter together with the SAFT-VR approach provides a description of the vapor-liquid equilibrium of the mixtures that is in excellent agreement with the experimental data for most cases. The absolute deviations are of the order of 0.005 mole fraction for vapor phase compositions and less than 0.3 kPa for pressure, excepting for mixtures containing 2-chloro-2-methylpropane which deviations for pressure are larger. Results obtained in this work in the modeling of the phase equilibrium with the SAFT-VR equation of state have been compared to the ones obtained in a previous study when the approach was used to model similar mixtures with clear differences in the thermodynamic behavior
Xie, Yi; Kopeikin, Sergei Affiliaiton: AB(Department of Physics and Astronomy, University of Missouri, USA kopeikins@missouri.edu)
2010-08-01
We overview a set of post-Newtonian reference frames for a comprehensive study of the orbital dynamics and rotational motion of Moon and Earth by means of lunar laser ranging (LLR). We employ a scalar-tensor theory of gravity depending on two post-Newtonian parameters, and , and utilize the relativistic resolutions on reference frames adopted by the International Astronomical Union (IAU) in 2000. We assume that the solar system is isolated and space-time is asymptotically flat at infinity. The primary reference frame covers the entire space-time, has its origin at the solar-system barycenter (SSB) and spatial axes stretching up to infinity. The SSB frame is not rotating with respect to a set of distant quasars that are forming the International Celestial Reference Frame (ICRF). The secondary reference frame has its origin at the Earth-Moon barycenter (EMB). The EMB frame is locally-inertial and is not rotating dynamically in the sense that equation of motion of a test particle moving with respect to the EMB frame, does not contain the Coriolis and centripetal forces. Two other local frames geocentric (GRF) and selenocentric (SRF) have their origins at the center of mass of Earth and Moon respectively and do not rotate dynamically. Each local frame is subject to the geodetic precession both with respect to other local frames and with respect to the ICRF because of their relative motion with respect to each other. Theoretical advantage of the dynamically non-rotating local frames is in a more simple mathematical description. Each local frame can be aligned with the axes of ICRF after applying the matrix of the relativistic precession. The set of one global and three local frames is introduced in order to fully decouple the relative motion of Moon with respect to Earth from the orbital motion of the Earth-Moon barycenter as well as to connect the coordinate description of the lunar motion, an observer on Earth, and a retro-reflector on Moon to directly measurable
Energy Technology Data Exchange (ETDEWEB)
Pubby, Kunal; Narang, Sukhleen Bindra [Guru Nanak Dev University, Department of Electronics Technology, Amritsar (India); Kaur, Prabhjyot; Chawla, S.K. [Guru Nanak Dev University, Department of Chemistry, Centre for Advanced Studies-I, Amritsar (India)
2017-05-15
Hexaferrite nano-particles of stoichiometric composition Sr(CoZr){sub x}Fe{sub 12-2x}O{sub 19}, with x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 were prepared using sol-gel auto-combustion route owing to its advantages such as low sintering temperature requirement, homogeneity and uniformity of grains. Tartaric acid as a fuel was utilized to complete the chemical reaction. The goal of this study is to analyse the effect of co-substitution of cobalt and zirconium on the electromagnetic and absorption properties of pure SrFe{sub 12}O{sub 19} hexaferrite. The properties were measured on the rectangular pellets of thickness 2.5 mm for K-frequency band using Vector Network Analyzer. The doping of Co-Zr has resulted in increase in real as well as imaginary parts of permittivity. The values of real permittivity lie in the range 3.6-7.0 for all the composition. The real part of permeability remains in range 0.7-1.6 in the studied frequency band for all the samples and shows slightly increasing trend with frequency. The maximum values of dielectric loss tangent peak (3.04) and magnetic loss tangent peak (2.34), among all the prepared compositions, have been observed for composition x = 0.2. Compositions with x = 0.6 and x = 0.0 also have high dielectric and magnetic loss peaks. Dielectric loss peaks are attributed to dielectric resonance and magnetic loss peaks are attributed to natural resonance. Experimentally determined reflection loss results show that all six compositions of prepared series have high values of absorption to propose them as single-layer absorbers in 18-26.5 GHz frequency range. The composition with x = 0.2 has maximum absorption capacity with reflection loss peak of -37.2 dB at 24.3 GHz frequency. The undoped composition also has high absorption peak (-25.46 dB), but -10 dB absorption bandwidth is minimum (2.2 GHz) out of the present series. Maximum absorption bandwidth is obtained for x = 1.0 (4.1 GHz). Other doped compositions also have high absorption bandwidth
Pubby, Kunal; Narang, Sukhleen Bindra; Kaur, Prabhjyot; Chawla, S. K.
2017-05-01
Hexaferrite nano-particles of stoichiometric composition {{Sr}}{({{CoZr}})_x}{{F}}{{{e}}_{12 - 2x}}{{{O}}_{19}}, with x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 were prepared using sol-gel auto-combustion route owing to its advantages such as low sintering temperature requirement, homogeneity and uniformity of grains. Tartaric acid as a fuel was utilized to complete the chemical reaction. The goal of this study is to analyse the effect of co-substitution of cobalt and zirconium on the electromagnetic and absorption properties of pure {{SrF}}{{{e}}_{12}}{{{O}}_{19}} hexaferrite. The properties were measured on the rectangular pellets of thickness 2.5 mm for K-frequency band using Vector Network Analyzer. The doping of Co-Zr has resulted in increase in real as well as imaginary parts of permittivity. The values of real permittivity lie in the range 3.6-7.0 for all the composition. The real part of permeability remains in range 0.7-1.6 in the studied frequency band for all the samples and shows slightly increasing trend with frequency. The maximum values of dielectric loss tangent peak (3.04) and magnetic loss tangent peak (2.34), among all the prepared compositions, have been observed for composition x = 0.2. Compositions with x = 0.6 and x = 0.0 also have high dielectric and magnetic loss peaks. Dielectric loss peaks are attributed to dielectric resonance and magnetic loss peaks are attributed to natural resonance. Experimentally determined reflection loss results show that all six compositions of prepared series have high values of absorption to propose them as single-layer absorbers in 18-26.5 GHz frequency range. The composition with x = 0.2 has maximum absorption capacity with reflection loss peak of -37.2 dB at 24.3 GHz frequency. The undoped composition also has high absorption peak (-25.46 dB), but -10 dB absorption bandwidth is minimum (2.2 GHz) out of the present series. Maximum absorption bandwidth is obtained for x = 1.0 (4.1 GHz). Other doped compositions also
Tamulevičius, Tomas; Šimatonis, Linas; Ulčinas, Orestas; Tamulevičius, Sigitas; Žukauskas, Egidijus; Rekuvienė, Regina; Mažeika, Liudas
2016-10-01
Scanning acoustic microscopy (SAM) is used as a routine non-destructive test tool for different diagnostic examinations: detection of defects such as microcracks, delamination, disbonding, inclusions, subsurface features in materials such as pores and cracks. SAM can be operated in a wide frequency range from Megahertz to Gigahertz. SAM measurement spatial resolution is diffraction limited by the wavelength of the acoustic wave in particular medium and also depends on individual transducers geometry. Actual SAM spatial resolution can be determined by measuring calibrated lithographically formed microstructures in high acoustic impedance materials. Numerical acoustic signal simulation method, based on the diffraction approach, was employed for the selection of the calibration block pattern geometry and linear dimensions of the elements. Universal calibration block for SAM operating in a 20-230 MHz frequency range was micromachined in high acoustic impedance ceramic substrates. Differently spaced (from 18 to 185 µm) lines of the same width and different widths (from 17 to 113 µm) but similar spacing lines were imposed in alumina ceramics employing one step lithography process, i.e. femtosecond laser ablation. Proposed SAM calibration pattern linear dimensions were characterized employing optical and scanning electron microscopy. Finally the samples were measured with SAM employing different frequency transducers and results were compared with the numerical simulations. It was obtained that resolution of SAM operating with 230 MHz transducer is not worse than 40 µm. © The Author (2016). Published by Oxford University Press on behalf of Journal of Molecular Cell Biology, IBCB, SIBS, CAS. All rights reserved.
Sheeran, Paul S; Daghighi, Yasaman; Yoo, Kimoon; Williams, Ross; Cherin, Emmanuel; Foster, F Stuart; Burns, Peter N
2016-03-01
Phase-shift perfluorocarbon droplets are designed to convert from the liquid to the gas state by the external application of acoustic or optical energy. Although droplet vaporization has been investigated extensively at ultrasonic frequencies between 1 and 10 MHz, few studies have characterized performance at the higher frequencies commonly used in small animal imaging. In this study, we use standard B-mode imaging sequences on a pre-clinical ultrasound platform to both image and activate sub-micron decafluorobutane droplet populations in vitro and in vivo at center frequencies in the range of 20-40 MHz. Results show that droplets remain stable against vaporization at low imaging pressures but are vaporized at peak negative pressures near 3.5 MPa at the three frequencies tested. This study also found that a small number of size outliers present in the distribution can greatly influence droplet performance. Removal of these outliers results in a more accurate assessment of the vaporization threshold and produces free-flowing microbubbles upon vaporization in the mouse kidney. Copyright © 2016 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Lin, Y [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Wukitch, S J [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Bonoli, P T [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Marmar, E [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Mossessian, D [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Nelson-Melby, E [Centre de Recherches en Physique des Plasmas, Association EURATOM - Confederation Suisse, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Phillips, P [Fusion Research Center, University of Texas, Austin, Texas 78712 (United States); Porkolab, M [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Schilling, G [Plasma Physics Laboratory, Princeton, NJ 08543 (United States); Wolfe, S [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Wright, J [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)
2003-06-01
Localized direct electron heating (EH) by mode-converted (MC) ion cyclotron range of frequencies (ICRF) waves in D(H) tokamak plasmas has been clearly observed for the first time in Alcator C-Mod. Both on- and off-axis (high field side) mode conversion EH (MCEH) have been observed. The MCEH profile was obtained from a break-in-slope analysis of electron temperature signals in the presence of radio frequency shut-off. The temperature was measured by a 32-channel high spatial resolution ({<=}7 mm) 2nd harmonic heterodyne electron cyclotron emission system. The experimental profiles were compared with the predictions from a toroidal full-wave ICRF code TORIC. Using the hydrogen concentration measured by a high-resolution optical spectrometer, TORIC predictions were shown qualitatively in agreement with the experimental results for both on- and off-axis MC cases. From the simulations, the EH from MC ion cyclotron wave and ion Bernstein wave is examined.
Rdzanek, Wojciech P
2016-06-01
This study deals with the classical problem of sound radiation of an excited clamped circular plate embedded into a flat rigid baffle. The system of the two coupled differential equations is solved, one for the excited and damped vibrations of the plate and the other one-the Helmholtz equation. An approach using the expansion into radial polynomials leads to results for the modal impedance coefficients useful for a comprehensive numerical analysis of sound radiation. The results obtained are accurate and efficient in a wide low frequency range and can easily be adopted for a simply supported circular plate. The fluid loading is included providing accurate results in resonance.
Energy Technology Data Exchange (ETDEWEB)
Aguayo-Rodriguez, G; Zaldivar-Huerta, I E [Instituto Nacional de Astrofisica, Optica y Electronica (INAOE). Sta. Maria Tonantzintla, Pue. Mexico (Mexico); GarcIa-Juarez, A [Depto. de Investigacion en Fisica, Universidad de Sonora (UNISON) Hermosillo, Son. Mexico (Mexico); Rodriguez-Asomoza, J [Depto. de Ingenieria Electronica, Universidad de las Americas-Puebla (UDLA). San Andres Cholula, Pue. Mexico (Mexico); Larger, L; Courjal, N [Laboratoire d' Optique P. M. Duffieux, UMR 6603 CNRS, Institut des Microtechiques de Franche-Comte, FRW 0067, UFR Sciences et Techniques, Universite de Franche-Comte (UFC), Besancon cedex (France)
2011-01-01
We demonstrate experimentally the efficiency of tuning of a photonic filter in the frequency range of 0.01 to 20 GHz. The presented work combines the use of a multimode optical source associated with a dispersive optical fiber to obtain the filtering effect. Tunability effect is achieved by the use of a Fabry-Perot filter that allows altering the spectral characteristics of the optical source. Experimental results are validated by means of numerical simulations. The scheme here proposed has a potential application in the field of optical telecommunications.
Thakor, Sanketsinh; Rana, V. A.; Vankar, H. P.
2017-05-01
In present work, Bisphenol A-(epichlorhydrin); epoxy resin with hardener N(3-dimethylaminopropyl)-1,3-propylenediamine were used to determine the dielectric properties. Sample of the neat epoxy resin and nanoparticle loaded epoxy resin in the form of disc were prepared of different weight fraction. SiO2 and ZnO nanoparticles were taken as filler in the epoxy resin. Complex permittivity of the prepared samples was measured in the frequency range of 20 Hz to 2 MHz using precision LCR meter at room temperature. The charismatic change in dielectric behavior based on type and concentration of nanoparticle are discussed in detail.
Yedlin, Matthew; Virieux, Jean
2010-05-01
As data collection in both seismic data acquisition and radar continues to improve, more emphasis is being placed on data pre-processing and inversion, in particular frequency domain waveform inversion in seismology [1], and, for example, time-domain waveform inversion in crosshole radar measurements [2]. Complementary to these methods are the sensitivity kernel techniques established initially in seismology [3, 4]. However, these methods have also been employed in crosshole radar tomography [5]. The sensitivity kernel technique has most recently been applied to the analysis of diffraction of waves in shallow water [6]. Central to the sensitivity kernel techniques is the use of an appropriate Green's function in either two or three dimensions and a background model is assumed for the calculation of the Green's function. In some situations, the constant velocity Green's function is used [5] but in other situations a smooth background model is used in a ray-type approximation. In the case of the smooth background model, computation of a ray-tracing type Green's function is problematic since at the source point the rays convergence, creating a singularity in the computation of the Jacobian used in the amplitude calculation. In fact the source is an axial caustic in two dimensions and a point caustic in three dimensions [7]. To obviate this problem, we will create a uniform asymptotic ansatz [8], explaining in detail how it is obtained in two dimensions. We will then show how to extend the results to three dimensions. In both cases, the Green's function will be obtained in the frequency domain for the acoustic equation with smoothly varying density and bulk modulus. The application of the new Green's function technique will provide more flexibility in the computation of sensitivities, both in seismological and radar applications. References [1] R. G. Pratt. 1999, Seismic waveform inversion in the frequency domain, part 1: Theory and verification in a physical scale
Energy Technology Data Exchange (ETDEWEB)
Yun, Jae Hyun [Department of Physics and Institute for Basic Science Research, Sung Kyun Kwan University, Suwon 440-746 (Korea, Republic of)]. E-mail: ataxtr@hanmail.net; Kang, Hee Soo [Department of Physics and Institute for Basic Science Research, Sung Kyun Kwan University, Suwon 440-746 (Korea, Republic of); Jeon, Gun Sang [School of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Choi, Han-Yong [Department of Physics and Institute for Basic Science Research, Sung Kyun Kwan University, Suwon 440-746 (Korea, Republic of)]. E-mail: hychoi@skku.edu
2007-03-15
We study the interaction induced zero temperature metal-insulator transition of the Holstein model at half-filling employing the dynamical mean-field theory in combination with Wilson's numerical renormalization group. We calculate the transitions between the insulating and metallic states as coupling constant g and the bare phonon frequency {omega}{sub 0} are varied. For the electron-phonon coupling g smaller than the critical value g{sub c1} the ground state is a metallic state, and for g>g{sub c2} it is the bipolaron insulating state. Between g{sub c1}
1.55-μm mode-locked quantum-dot lasers with 300 MHz frequency tuning range
Energy Technology Data Exchange (ETDEWEB)
Sadeev, T., E-mail: tagir@mailbox.tu-berlin.de; Arsenijević, D.; Bimberg, D. [Institut für Festkörperphysik, Technische Universität Berlin, 10623 Berlin (Germany); Franke, D.; Kreissl, J.; Künzel, H. [Heinrich-Hertz-Institut, Einsteinufer 37, 10587 Berlin (Germany)
2015-01-19
Passive mode-locking of two-section quantum-dot mode-locked lasers grown by metalorganic vapor phase epitaxy on InP is reported. 1250-μm long lasers exhibit a wide tuning range of 300 MHz around the fundamental mode-locking frequency of 33.48 GHz. The frequency tuning is achieved by varying the reverse bias of the saturable absorber from 0 to −2.2 V and the gain section current from 90 to 280 mA. 3 dB optical spectra width of 6–7 nm leads to ex-facet optical pulses with full-width half-maximum down to 3.7 ps. Single-section quantum-dot mode-locked lasers show 0.8 ps broad optical pulses after external fiber-based compression. Injection current tuning from 70 to 300 mA leads to 30 MHz frequency tuning.
You, Weilong; Pei, Binbin; Sun, Ke; Zhang, Lei; Yang, Heng; Li, Xinxin
2017-10-01
This paper presents an oven controlled N++ [1 0 0] length-extensional mode silicon resonator, with a lookup-table based control algorithm. The temperature coefficient of resonant frequency (TCF) of the N++ doped resonator is nonlinear, and there is a turnover temperature point at which the TCF is equal to zero. The resonator is maintained at the turnover point by Joule heating; this temperature is a little higher than the upper limit of the industrial temperature range. It is demonstrated that the control algorithm based on the thermoresistor on the substrate and the lookup table for heating voltage versus chip temperature is sufficiently accurate to achieve a frequency stability of ±0.5 ppm over the industrial temperature range. Because only two leads are required for electrical heating and piezoresistive sensing, the power required for heating of this resonator can be potentially lower than that of the oscillators with closed-loop oven control algorithm. It is also shown that the phase noise can be suppressed at the turnover temperature because of the very low value of the TCF, which justifies the usage of the heating voltage as the excitation voltage of the Wheatstone half-bridge.
Energy Technology Data Exchange (ETDEWEB)
Schmid, Gernot [Austrian Research Centers GmbH-ARC, ITM, A-2444 Seibersdorf (Austria); Ueberbacher, Richard [Austrian Research Centers GmbH-ARC, ITM, A-2444 Seibersdorf (Austria); Samaras, Theodoros [Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Tschabitscher, Manfred [Center of Anatomy and Cell Biology, Medical University of Vienna, A-1090 Vienna (Austria); Mazal, Peter R [Department of Clinical Pathology, Medical University Vienna, A-1090 Vienna (Austria)
2007-09-07
In order to enable a detailed analysis of radio frequency (RF) absorption in the human pineal gland, the dielectric properties of a sample of 20 freshly removed pineal glands were measured less than 20 h after death. Furthermore, a corresponding high resolution numerical model of the brain region surrounding the pineal gland was developed, based on a real human tissue sample. After inserting this model into a commercially available numerical head model, FDTD-based computations for exposure scenarios with generic models of handheld devices operated close to the head in the frequency range 400-1850 MHz were carried out. For typical output power values of real handheld mobile communication devices, the obtained results showed only very small amounts of absorbed RF power in the pineal gland when compared to SAR limits according to international safety standards. The highest absorption was found for the 400 MHz irradiation. In this case the RF power absorbed inside the pineal gland (organ mass 96 mg) was as low as 11 {mu}W, when considering a device of 500 mW output power operated close to the ear. For typical mobile phone frequencies (900 MHz and 1850 MHz) and output power values (250 mW and 125 mW) the corresponding values of absorbed RF power in the pineal gland were found to be lower by a factor of 4.2 and 36, respectively. These results indicate that temperature-related biologically relevant effects on the pineal gland induced by the RF emissions of typical handheld mobile communication devices are unlikely.
Energy Technology Data Exchange (ETDEWEB)
Lysoivan, A.I. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Moiseenko, V.E. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Plyusnin, V.V. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Kasilov, S.V. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Bondarenko, V.N. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Chechkin, V.V. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Fomin, I.P. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Grigor`eva, L.I. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Konovalov, V.G. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Koval`ov, S.V. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Litvinov, A.P. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Mironov, Yu.K. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Nazarov, N.I. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Pavlichenko, O.S. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Pavlichenko, R.O. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Shapoval, A.N. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Skibenko, A.I. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center; Volkov, E.D. [Kharkov Inst. of Phys. and Tech. (Ukraine). Nat. Sci. Center
1995-01-01
Numerical and experimental results of Alfven wave heating of plasmas in the frequency range below the ion cyclotron frequency ({omega}<{omega}{sub ci}) are presented. Two different types of antenna were used for plasma production and heating: a frame type antenna (FTA) conventionally used in the URAGAN-3M device and a three-half-turn antenna (THTA) proposed recently to avoid the deleterious effects of conversion of fast wave to slow wave in the plasma periphery and to perform plasma core heating more effectively. Numerical modeling of electromagnetic field excitation in the URAGAN-3M plasma by the FTA and THTA was performed using a one-dimensional code. The results of calculations showed better performance of the compact THTA compared with the FTA for the case of a high density plasma (approximately 10{sup 13}cm{sup -3}). When using the THTA, the experiments performed showed the possibility of dense plasma production (more than 2x10{sup 13}cm{sup -3}) and heating, which had not been obtained earlier in the URAGAN-3M. Shifting the power deposition profile deeper inside the plasma body with the THTA resulted in modification of the plasma density profile and an improvement in plasma confinement. ((orig.)).
Energy Technology Data Exchange (ETDEWEB)
Tsujii, N.; Porkolab, M.; Bonoli, P. T.; Lin, Y.; Wright, J. C.; Wukitch, S. J. [MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Jaeger, E. F. [XCEL Engineering, Inc., Oak Ridge, Tennessee 37830 (United States); Green, D. L. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Harvey, R. W. [CompX, Del Mar, California 92014 (United States)
2012-08-15
Radio frequency waves in the ion cyclotron range of frequencies (ICRF) are widely used to heat tokamak plasmas. In ICRF heating schemes involving multiple ion species, the launched fast waves convert to ion cyclotron waves or ion Bernstein waves at the two-ion hybrid resonances. Mode converted waves are of interest as actuators to optimise plasma performance through current drive and flow drive. In order to describe these processes accurately in a realistic tokamak geometry, numerical simulations are essential, and it is important that these codes be validated against experiment. In this study, the mode converted waves were measured using a phase contrast imaging technique in D-H and D-{sup 3}He plasmas. The measured mode converted wave intensity in the D-{sup 3}He mode conversion regime was found to be a factor of {approx}50 weaker than the full-wave predictions. The discrepancy was reduced in the hydrogen minority heating regime, where mode conversion is weaker.
Tsujii, N.; Porkolab, M.; Bonoli, P. T.; Edlund, E. M.; Ennever, P. C.; Lin, Y.; Wright, J. C.; Wukitch, S. J.; Jaeger, E. F.; Green, D. L.; Harvey, R. W.
2015-08-01
Mode conversion of fast waves in the ion cyclotron range of frequencies (ICRF) is known to result in current drive and flow drive under optimised conditions, which may be utilized to control plasma profiles and improve fusion plasma performance. To describe these processes accurately in a realistic toroidal geometry, numerical simulations are essential. Quantitative comparison of these simulations and the actual experimental measurements is important to validate their predictions and to evaluate their limitations. The phase contrast imaging (PCI) diagnostic has been used to directly detect the ICRF waves in the Alcator C-Mod tokamak. The measurements have been compared with full-wave simulations through a synthetic diagnostic technique. Recently, the frequency response of the PCI detector array on Alcator C-Mod was recalibrated, which greatly improved the comparison between the measurements and the simulations. In this study, mode converted waves for D-3He and D-H plasmas with various ion species compositions were re-analyzed with the new calibration. For the minority heating cases, self-consistent electric fields and a minority ion distribution function were simulated by iterating a full-wave code and a Fokker-Planck code. The simulated mode converted wave intensity was in quite reasonable agreement with the measurements close to the antenna, but discrepancies remain for comparison at larger distances.
Energy Technology Data Exchange (ETDEWEB)
Tsujii, N., E-mail: tsujii@k.u-tokyo.ac.jp [Graduate School of Frontier Sciences, The University of Tokyo, Chiba 277-8561 (Japan); Porkolab, M.; Bonoli, P. T.; Edlund, E. M.; Ennever, P. C.; Lin, Y.; Wright, J. C.; Wukitch, S. J. [MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Jaeger, E. F. [XCEL Engineering, Inc., Oak Ridge, Tennessee 37830 (United States); Green, D. L. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Harvey, R. W. [CompX, Del Mar, California 92014 (United States)
2015-08-15
Mode conversion of fast waves in the ion cyclotron range of frequencies (ICRF) is known to result in current drive and flow drive under optimised conditions, which may be utilized to control plasma profiles and improve fusion plasma performance. To describe these processes accurately in a realistic toroidal geometry, numerical simulations are essential. Quantitative comparison of these simulations and the actual experimental measurements is important to validate their predictions and to evaluate their limitations. The phase contrast imaging (PCI) diagnostic has been used to directly detect the ICRF waves in the Alcator C-Mod tokamak. The measurements have been compared with full-wave simulations through a synthetic diagnostic technique. Recently, the frequency response of the PCI detector array on Alcator C-Mod was recalibrated, which greatly improved the comparison between the measurements and the simulations. In this study, mode converted waves for D-{sup 3}He and D-H plasmas with various ion species compositions were re-analyzed with the new calibration. For the minority heating cases, self-consistent electric fields and a minority ion distribution function were simulated by iterating a full-wave code and a Fokker-Planck code. The simulated mode converted wave intensity was in quite reasonable agreement with the measurements close to the antenna, but discrepancies remain for comparison at larger distances.
Kawai, Hiroki; Nagaoka, Tomoaki; Watanabe, Soichi; Saito, Kazuyuki; Takahashi, Masaharu; Ito, Koichi
2010-01-01
This paper presents calculated specific absorption rate (SAR) dosimetry in 4 and 8 week Japanese pregnant-woman models exposed to plane waves over the frequency range of 10 MHz-1.5 GHz. Two types of 2 mm spatial-resolution pregnant-woman models comprised a woman model, which is similar to the average-sized Japanese adult female in height and weight, with a cubic (4 week) embryo or spheroidal (8 week) one. The averaged SAR in the embryos exposed to vertically and horizontally polarized plane waves at four kinds of propagation directions are calculated from 10 MHz to 1.5 GHz. The results indicate that the maximum average SAR in the embryos exposed to plane waves is lower than 0.08 W kg-1 when the incident power density is at the reference level of ICNIRP guideline for general public environment.
Demontoux, François; Bircher, Simone; Ruffié, Gilles; Bonnaudiin, Fabrice; Wigneron, Jean-Pierre; Kerr, Yann
2017-04-01
Microwave remote sensing and non-destructive analysis are a powerful way to provide properties estimation of materials. Numerous applications using microwave frequency behavior of materials (remote sensing above land surfaces, non-destructive analysis…) are strongly dependent on the material's permittivity (i.e. dielectric properties). This permittivity depends on numerous parameters such as moisture, texture, temperature, frequency or bulk density. Permittivity measurements are generally carried out in the laboratory. Additionally, dielectric mixing models allow, over a restricted range of conditions, the assessment of a material's permittivity. in-situ measurements are more difficult to obtain. Some in situ measurement probes based on permittivity properties of soil exist (e.g. Time Domain Reflectometers and Transmissometers, capacitance and impedance sensors). They are dedicated to the acquisition of soil moisture data based on permittivity (mainly the real part) estimations over a range of frequencies from around 50 MHz to 1 or 2 GHz. Other Dielectric Assessment Kits exist but they are expensive and they are rather dedicated to laboratory measurements. Furthermore, the user can't address specific issues related to particular materials (e.g. organic soils) or specific measurement conditions (in situ long time records). At the IMS Laboratory we develop probes for in situ soil permittivity measurements (real and imaginary parts) in the 0.5 - 6 GHz frequency range. They are based on the end effect phenomenon of a coaxial waveguide and so are called end effect probes in this paper. The probes can be connected to a portable Vector Network Analyzer (VNA, ANRITSU MS2026A) for the S11 coefficient measurements needed to compute permittivity. It is connected to a PC to record data using an USB connection. This measurement set-up is already used for in situ measurement of soil properties in the framework of the European Space Agency's (ESA) SMOS space mission. However
Iijima, Hokuto; Nagai, Ryoji; Nishimori, Nobuyuki; Hajima, Ryoichi; Minehara, Eisuke J
2009-12-01
A second-harmonic generation frequency-resolved optical gating (SHG-FROG) system has been developed for the complete characterization of laser pulses in the wavelength range of 10-30 microm. A tellurium crystal is used so that spectrally resolved autocorrelation signals with a good signal-to-noise ratio are obtained. Pulses (wavelength approximately 22 microm) generated from a free-electron laser are measured by the SHG-FROG system. The SHG intensity profile and the spectrum obtained by FROG measurements are well consistent with those of independent measurements of the pulse length and spectrum. The pulse duration and spectral width determined from the FROG trace are 0.6 ps and 5.2 THz at full width half maximum, respectively.
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Carl Hopkins
Full Text Available Presentation of music as vibration to the skin has the potential to facilitate interaction between musicians with hearing impairments and other musicians during group performance. Vibrotactile thresholds have been determined to assess the potential for vibrotactile presentation of music to the glabrous skin of the fingertip, forefoot and heel. No significant differences were found between the thresholds for sinusoids representing notes between C1 and C6 when presented to the fingertip of participants with normal hearing and with a severe or profound hearing loss. For participants with normal hearing, thresholds for notes between C1 and C6 showed the characteristic U-shape curve for the fingertip, but not for the forefoot and heel. Compared to the fingertip, the forefoot had lower thresholds between C1 and C3, and the heel had lower thresholds between C1 and G2; this is attributed to spatial summation from the Pacinian receptors over the larger contactor area used for the forefoot and heel. Participants with normal hearing assessed the perception of high-frequency vibration using 1s sinusoids presented to the fingertip and were found to be more aware of transient vibration at the beginning and/or end of notes between G4 and C6 when stimuli were presented 10dB above threshold, rather than at threshold. An average of 94% of these participants reported feeling continuous vibration between G4 and G5 with stimuli presented 10dB above threshold. Based on the experimental findings and consideration of health effects relating to vibration exposure, a suitable range of notes for vibrotactile presentation of music is identified as being from C1 to G5. This is more limited than for human hearing but the fundamental frequencies of the human voice, and the notes played by many instruments, lie within it. However, the dynamic range might require compression to avoid the negative effects of amplitude on pitch perception.
Hopkins, Carl; Maté-Cid, Saúl; Fulford, Robert; Seiffert, Gary; Ginsborg, Jane
2016-01-01
Presentation of music as vibration to the skin has the potential to facilitate interaction between musicians with hearing impairments and other musicians during group performance. Vibrotactile thresholds have been determined to assess the potential for vibrotactile presentation of music to the glabrous skin of the fingertip, forefoot and heel. No significant differences were found between the thresholds for sinusoids representing notes between C1 and C6 when presented to the fingertip of participants with normal hearing and with a severe or profound hearing loss. For participants with normal hearing, thresholds for notes between C1 and C6 showed the characteristic U-shape curve for the fingertip, but not for the forefoot and heel. Compared to the fingertip, the forefoot had lower thresholds between C1 and C3, and the heel had lower thresholds between C1 and G2; this is attributed to spatial summation from the Pacinian receptors over the larger contactor area used for the forefoot and heel. Participants with normal hearing assessed the perception of high-frequency vibration using 1s sinusoids presented to the fingertip and were found to be more aware of transient vibration at the beginning and/or end of notes between G4 and C6 when stimuli were presented 10dB above threshold, rather than at threshold. An average of 94% of these participants reported feeling continuous vibration between G4 and G5 with stimuli presented 10dB above threshold. Based on the experimental findings and consideration of health effects relating to vibration exposure, a suitable range of notes for vibrotactile presentation of music is identified as being from C1 to G5. This is more limited than for human hearing but the fundamental frequencies of the human voice, and the notes played by many instruments, lie within it. However, the dynamic range might require compression to avoid the negative effects of amplitude on pitch perception.
Nishigaki, Shinsuke M.
2012-12-01
Schierenberg [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.85.061130 85, 061130 (2012)] recently applied the Wigner surmise, i.e., substitution of ∞×∞ matrices by their 2×2 counterparts for the computation of level spacing distributions, to random matrix ensembles in transition between two universality classes. I examine the accuracy and the range of validity of the surmise for the crossover between the Gaussian orthogonal and unitary ensembles by contrasting them with the large-N results that I evaluated using the Nyström-type method for the Fredholm determinant. The surmised expression at the best-fitting parameter provides a good approximation for 0≲s≲2, i.e., the validity range of the original surmise.
Song, Jong-Won; Hirao, Kimihiko
2015-10-14
Since the advent of hybrid functional in 1993, it has become a main quantum chemical tool for the calculation of energies and properties of molecular systems. Following the introduction of long-range corrected hybrid scheme for density functional theory a decade later, the applicability of the hybrid functional has been further amplified due to the resulting increased performance on orbital energy, excitation energy, non-linear optical property, barrier height, and so on. Nevertheless, the high cost associated with the evaluation of Hartree-Fock (HF) exchange integrals remains a bottleneck for the broader and more active applications of hybrid functionals to large molecular and periodic systems. Here, we propose a very simple yet efficient method for the computation of long-range corrected hybrid scheme. It uses a modified two-Gaussian attenuating operator instead of the error function for the long-range HF exchange integral. As a result, the two-Gaussian HF operator, which mimics the shape of the error function operator, reduces computational time dramatically (e.g., about 14 times acceleration in C diamond calculation using periodic boundary condition) and enables lower scaling with system size, while maintaining the improved features of the long-range corrected density functional theory.
Shimoda, K.; Wang, T. C.; Townes, C. H.
1956-03-01
The theory of the molecular transitions which are induced by the microwave field in a maser and the effects of various design parameters are examined in detail. It is shown that the theoretical minimum detectable beam intensity when the maser is used as a spectrometer for the 3-3 line of ammonia is about 10{sup 9} molecules/sec under typical experimental conditions. Various systematic frequency shifts and random frequency fluctuations of the maser oscillator are discussed and evaluated. The most prominent of the former are the "frequency-pulling" effect which arises from detuning of the cavity and the Doppler shift due to the asymmetrical coupling of the beam with the two travelling wave components of the standing waves which are set up in the cavity. These two effects may produce fractional shifts as large as one part in 10{sup 9}. If adequate precautions are taken, however, they can be reduced to one part in 10{sup 10} or possibly less. The random fluctuations are shown to be of the order of one part in 10{sup 13} under typical operating conditions. For molecular beams in which the electric-dipole transition is used the TM{sub 010} mode is usually the most suitable for the maser which atomic beams in which magnetic transitions are utilized, the TE{sub 011} mode is to be preferred.
Ikegami, Seiji
2017-09-01
The switching model (PSM) developed in the previous paper is extended to obtain an ;extended switching model (ESM). In the ESM, the mixt electronic-and-nuclear energy-loss region, in addition to the electronic and nuclear energy-loss regions in PSM, is taken into account analytically and appropriately. This model is combined with a small-angle multiple scattering range theory considering both nuclear and electronic stopping effects developed by Marwick-Sigmund and Valdes-Arista to formulate a improved range theory. The ESM is also combined with the multiple scattering theory with non-small angle approximation by Goudsmit-Saunderson. Furthermore, we applied ESM to lateral spread model of Marwick-Sigmund. Numerical calculations of the entire distribution functions including one of the mixt region are roughly and approximately possible. However, exact numerical calculation may be impossible. Consequently, several preliminary numerical calculations of the electronic, mixt, and nuclear regions are performed to examine their underlying behavior with respect to the incident energy, the scattering angle, the outgoing projectile intensity, and the target thickness. We show the numerical results not only of PSM and but also of ESM. Both numerical results are shown in the present paper for the first time. Since the theoretical relations are constructed using reduced variables, the calculations are made only on the case of C colliding on C.
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VIKAS RAINA
2017-11-01
Full Text Available Time synchronization between the sensor nodes to reduce end to end delay for critical and real time data monitoring can be achieved by cautiously monitoring the mobility of the mobile sink node in underwater wireless sensor networks. The proposed Alive-in-Range (AR-MAC medium access control protocol monitors delay sensitive, critical and real time data. The idea evolves as a reduction in duty cycle, precise time scheduling of active/sleep cycles of the sensors, monitoring the mobility of the sink node along-with the selection of appropriate queues and schedulers can reduce the end to end delay enhancing other performance metrics too. The algorithms effective path determination and optimum throughput path determination are proposed. It is assumed that the sensors are properly anchored to limit their movement due to waves within the permissible limits to follow these algorithms. This paper attempts to utilize electromagnetic waves at resonance frequency of 2.4 GHz for underwater communication. The results verify that the implementation of Alive-in-Range MAC protocol has reduced the average end to end delay significantly making it appropriate for critical and real time data monitoring. This work proves the suitability of electromagnetic waves as an effective alternative for underwater wireless communication. The main objective is to mitigate sink neighbourhood problem, distance constrained mobile sink problem and to reduce the average end to end delay by implementing Alive-in-Range (AR-MAC medium access control protocol in underwater sensor networks and to draw the attention of researchers in this area.
Dongqing Peng; Haijian Zhang; Wei Guo; Wen Yang
2016-01-01
Based on Time-Frequency (TF) analysis and a-contrario theory, this paper presents a new approach for extraction of linear arranged power transmission tower series in Polarimetric Synthetic Aperture Radar (PolSAR) images. Firstly, the PolSAR multidimensional information is analyzed using a linear TF decomposition approach. The stationarity of each pixel is assessed by testing the maximum likelihood ratio statistics of the coherency matrix. Then, based on the maximum likelihood log-ratio image,...
Chen, J.-S.; Chu, Y.-H.
2001-01-01
The thickness and position of an atmospheric layer embedded in the radar volume can be resolved by using the frequency-domain interferometry (FDI) technique in accordance with an analytical expression, in which a single layer with Gaussian shape is assumed. However, the FDI experimental results obtained from the Chung-Li VHF radar show that the layer thickness is usually dependent on the layer position. In view of this, an attempt is made in this paper to interpret the observations. With the help of numerical simulation, we examine three FDI models: (1) a non-Gaussian layer, (2) single layer in company with background scatterers, and (3) multiple layers. The analytical FDI expression derived from the Gaussian-layer model is employed in the numerical study to calculate the layer position and layer thickness on the basis of the coherence and phase estimated from the examined layer model. It shows that the resultant thickness and position of the FDI layer are dependent on each other, which is in agreement with the observed thickness-position relations shown in this paper. Moreover, the numerical results can also provide a reasonable interpretation of the observations reported by earlier scientific workers, such as the discrepancy between the vertical displacement velocity of the layer and the vertical Doppler velocity, the difference in thickness between the FDI-derived layer and in situ observed temperature//humidity sheets, etc. We finally illustrate that the range weighting effect of the radar system plays a crucial role in the FDI-derived thickness-position relations.
Siegel, JH; Cerka, AJ; Recio-Spinoso, A; Temchin, AN; van Dijk, P; Ruggero, MA
2005-01-01
When stimulated by tones, the ear appears to emit tones of its own, stimulus-frequency otoacoustic emissions (SFOAEs). SFOAEs were measured in 17 chinchillas and their group delays were compared with a place map of basilar-membrane vibration group delays measured at the characteristic frequency. The
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A.T. Archibald
2015-09-01
Full Text Available AbstractHere we present high frequency long-term observations of ethane, benzene and methyl chloride from the AGAGE Ragged Point, Barbados, monitoring station made using a custom built GC-MS system. Our analysis focuses on the first three years of data (2005–2007 and on the interpretation of periodic episodes of high concentrations of these compounds. We focus specifically on an exemplar episode during September 2007 to assess if these measurements are impacted by long-range transport of biomass burning and biogenic emissions. We use the Lagrangian Particle Dispersion model, NAME, run forwards and backwards in time to identify transport of air masses from the North East of Brazil during these events. To assess whether biomass burning was the cause we used hot spots detected using the MODIS instrument to act as point sources for simulating the release of biomass burning plumes. Excellent agreement for the arrival time of the simulated biomass burning plumes and the observations of enhancements in the trace gases indicates that biomass burning strongly influenced these measurements. These modelling data were then used to determine the emissions required to match the observations and compared with bottom up estimates based on burnt area and literature emission factors. Good agreement was found between the two techniques highlight the important role of biomass burning. The modelling constrained by in situ observations suggests that the emission factors were representative of their known upper limits, with the in situ data suggesting slightly greater emissions of ethane than the literature emission factors account for. Further analysis was performed concluding only a small role for biogenic emissions of methyl chloride from South America impacting measurements at Ragged Point. These results highlight the importance of long-term high frequency measurements of NMHC and ODS and highlight how these data can be used to determine sources of emissions
Moukhtar, Julien; Faivre-Moskalenko, Cendrine; Milani, Pascale; Audit, Benjamin; Vaillant, Cedric; Fontaine, Emeline; Mongelard, Fabien; Lavorel, Guillaume; St-Jean, Philippe; Bouvet, Philippe; Argoul, Françoise; Arneodo, Alain
2010-04-22
Sequence dependency of DNA intrinsic bending properties has been emphasized as a possible key ingredient to in vivo chromatin organization. We use atomic force microscopy (AFM) in air and liquid to image intrinsically straight (synthetic), uncorrelated (hepatitis C RNA virus) and persistent long-range correlated (human) DNA fragments in various ionic conditions such that the molecules freely equilibrate on the mica surface before being captured in a particular conformation. 2D thermodynamic equilibrium is experimentally verified by a detailed statistical analysis of the Gaussian nature of the DNA bend angle fluctuations. We show that the worm-like chain (WLC) model, commonly used to describe the average conformation of long semiflexible polymers, reproduces remarkably well the persistence length estimates for the first two molecules as consistently obtained from (i) mean square end-to-end distance measurement and (ii) mean projection of the end-to-end vector on the initial orientation. Whatever the operating conditions (air or liquid, concentration of metal cations Mg(2+) and/or Ni(2+)), the persistence length found for the uncorrelated viral DNA underestimates the value obtained for the straight DNA. We show that this systematic difference is the signature of the presence of an uncorrelated structural intrinsic disorder in the hepatitis C virus (HCV) DNA fragment that superimposes on local curvatures induced by thermal fluctuations and that only the entropic disorder depends upon experimental conditions. In contrast, the WLC model fails to describe the human DNA conformations. We use a mean-field extension of the WLC model to account for the presence of long-range correlations (LRC) in the intrinsic curvature disorder of human genomic DNA: the stronger the LRC, the smaller the persistence length. The comparison of AFM imaging of human DNA with LRC DNA simulations confirms that the rather small mean square end-to-end distance observed, particularly for G
Ucun, Fatih; Sağlam, Adnan; Güçlü, Vesile
2007-06-01
The molecular structures, vibrational frequencies and corresponding vibrational assignments of xanthine and its methyl derivatives (caffeine and theobromine) have been calculated using ab initio Hartree-Fock (HF) and density functional theory (B3LYP) methods with 6-31G(d, p) basis set level. The calculations were utilized to the CS symmetries of the molecules. The obtained vibrational frequencies and optimised geometric parameters (bond lengths and bond angles) were seen to be well agreement with the experimental data. The used scale factors which have been obtained the ratio of the frequency values of the strongest peaks in the calculated and experimental spectra seem to cause the gained vibrations well corresponding to the experimental ones. Theoretical infrared intensities and Raman activities are also reported.
Ganapolskii, E M; Eremenko, Z E; Tarasov, Yu V
2009-04-01
The influence of random axially homogeneous surface roughness on spectral properties of dielectric resonators of circular disk form is studied both theoretically and experimentally. To solve the equations governing the dynamics of electromagnetic fields, the method of eigenmode separation is applied previously developed with reference to inhomogeneous systems subject to arbitrary external static potential. We prove theoretically that it is the gradient mechanism of wave-surface scattering that is highly responsible for nondissipative loss in the resonator. The influence of side-boundary inhomogeneities on the resonator spectrum is shown to be described in terms of effective renormalization of mode wave numbers jointly with azimuth indices in the characteristic equation. To study experimentally the effect of inhomogeneities on the resonator spectrum, the method of modeling in the millimeter wave range is applied. As a model object, we use a dielectric disk resonator (DDR) fitted with external inhomogeneities randomly arranged at its side boundary. Experimental results show good agreement with theoretical predictions as regards the predominance of the gradient scattering mechanism. It is shown theoretically and confirmed in the experiment that TM oscillations in the DDR are less affected by surface inhomogeneities than TE oscillations with the same azimuth indices. The DDR model chosen for our study as well as characteristic equations obtained thereupon enable one to calculate both the eigenfrequencies and the Q factors of resonance spectral lines to fairly good accuracy. The results of calculations agree well with obtained experimental data.
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Anđić A.
2006-01-01
Full Text Available High frequency acoustic oscillations were suggested as the source of mechanical heating in the chromosphere. In this work the radial component of the oscillations in the frequency interval 3 mHz to 22 mHz are investigated. The observations were performed using "D spectrometry on the Fe I neutral spectral line at 543:45 nm. The high frequency oscillations of different frequencies appear to be associated with different spatial scales. It seems that different sources produce high and low frequency acoustic oscillations.
Poletto, Rosangela; Janczak, Andrew M; Marchant-Forde, Ruth M; Marchant-Forde, Jeremy N; Matthews, Donald L; Dowell, Carol A; Hogan, Daniel F; Freeman, Lynetta J; Lay, Donald C
2011-05-03
Understanding autonomic nervous system functioning, which mediates behavioral and physiological responses to stress, offers great potential for assessing farm animal stress and welfare. Evaluation of heart rate variability (HRV) and blood pressure variability (BPV), using time and frequency domain analyses may provide a sensitive and reliable measure of affective states and stress-mediated changes in sympathetic and parasympathetic tones. The aim of this research was to define low (LF) and high frequency (HF) power spectral ranges using pharmacological autonomic blockade, and to examine HRV and BPV parameter changes in response to atropine and propranolol in swine. Ten, 13-week old, barrows (n=6) and gilts (n=4) underwent surgery to place an intra-cardiac electrode and a blood pressure catheter attached to a biotelemetric transmitter; pigs had a 3-week recovery period prior to data collection. Each pig was subjected to administration of 4 intravenous (i.v.) drug treatments: a control treatment, 3 mL of saline, and 3 blockade treatments; 0.1 mg/kg of atropine, 1.0 mg/kg of propranolol, and .1 mg/kg of atropine together with 1.0 mg/kg of propranolol. All treatments were delivered by injection in the jugular vein with a minimum of 48 h between individual treatments. Behavior, ECG and blood pressure data were recorded continuously for a total of 1h, from 30 min pre-injection to 30 min post-injection. For data analyses, two 512-beat intervals were selected for each treatment while the pig was lying and inactive. The first interval was selected from the pre-injection period (baseline), and the second was selected between 10 and 30 min post-injection. Time and frequency domain (power spectral density) analyses were performed on each data interval. Subsequent, LF and HF bands from the power spectral densities were defined based on general linear and regression analyses. The HRV and BPV were computed with a covariate (baseline) factorial analysis of treatment by sex
Energy Technology Data Exchange (ETDEWEB)
Pande, Anu; Gairola, Preeti [Uttaranchal University, Prem Nagar, Dehradun (India); Sambyal, Pradeep [National Physical Laboratory (CSIR), K, S. Krishnan Marg, New Delhi (India); Gairola, S.P., E-mail: spgairola10@gmail.com [Uttaranchal University, Prem Nagar, Dehradun (India); Kumar, Vinod [Centre for Energy Studies, Indian Institute of Technology, New Delhi (India); Singh, Kuldeep [Central Electrochemical Research Institute (CSIR), Karaikudi, Tamilnadu (India); Dhawan, S.K. [National Physical Laboratory (CSIR), K, S. Krishnan Marg, New Delhi (India)
2017-03-01
In today’s times where pollution of all kinds is at its peak, numerous efforts are being made to find proper waste disposal methods. Moving on the same lines, this paper presents an economical and environmentally safe method of disposal of red mud to control electromagnetic pollution by using it as an electromagnetic shielding material. Composites of PANI/RM have been prepared by in-situ chemical oxidative polymerization and have been tested for structural analysis, thermal stability and magnetization by XRD, TGA and VSM techniques respectively. Further, the composites have shown shielding effectiveness of 33–41 dB (>99.99% attenuation) in 8.2–12.4 GHz frequency range (X-band) at a thickness of 3 mm which is absorption dominated. Thus, the results conclude that the incorporation of red mud into polymer matrix can serve two purposes – firstly, it can provide a good alternative as a shielding material and secondly, it can prove to be a feasible way of waste disposal. - Highlights: • An attempt to find out application of red mud in controlling electromagnetic pollution. • Waste utilization for technology: Red mud is an insoluble industrial waste used for EMI Shielding application. • Using and testing of Red Mud as filler instead of the other widely used fillers. • Characterization of materials (Red Mud/Polyaniline composite) for EMI shielding Application. • EMI Shielding results discussions of new material (Red Mud/Polyaniline).
Energy Technology Data Exchange (ETDEWEB)
Fraboulet, D.; Becoulet, A.; Nguyen, F
1998-11-01
To maintain the ignition state in a tokamak fusion reactor, a control must be performed on the population of alpha-products, and this implies the ability to diagnose those {alpha}-particles. It is studied here whether the detection of emission radiated in the ion cyclotron range of frequency be a reactor plasma can provide useful information concerning fusion products, especially concerning their density profile. It is shown that the detection of the radiation emitted by the fast alpha particles along their cyclotron motion can give access to moments of their distribution function. This requires to compute the phase of the emitted field, using a full-wave approach. Such a technique allows to set in a convenient way the inverse problem of the determination of the emitting {alpha}-particles distribution through the radiation detection. A brief analysis of the expected situation in a reactor-relevant plasma is given. In parallel, the 1-D full-wave code developed in this frame is also useful for studying the physics of Fast Wave plasma heating. It enables to take into account the mode conversion of the Fast Wave into the Ion Bernstein Wave that appears near each ion cyclotron resonance. Results show that higher order terms may significantly alter the energy partitioning, in hot plasma cases involving mode conversion heating and/or ion cyclotron high harmonics heating. (author) 47 refs.
Sudhyadhom, Atchar
2017-11-01
The accurate determination of mean ionization potential (I m) has the potential to reduce range uncertainty based margins and therefore allow for more focal treatments in proton radiotherapy. Many methods have been proposed to reduce uncertainty in I m and stopping power ratios (SPR), each with varying degrees of accuracy and issues. In this work, we present a simple parameterized model to determine I m in human biological tissue, allowing for the computation of patient-specific I m at the voxel level using magnetic resonance imaging (MRI). The model requires the measurement of three parameters by MRI, with only two parameters, mass percent water content and mass percent hydrogen content in organic molecules, required for the special case of soft tissues. The accuracy of this I m determination method was evaluated in available ‘standard’ (ICRU Report #44, (ICRU 1989 Tissue Substitutes in Radiation Dosimetry and Measurement (Bethesda, MD: International Commission on Radiation Units and Measurements))) human tissues. The sensitivity of this I m determination method to in vivo perturbations was also tested by calculating the effect of 10% variations in the experimentally measurable parameters on I m and SPR. For the human tissues modeled in this work, a high level of accuracy with low susceptibility to perturbations in measurement error was achieved in the prediction of I m. Root-mean-square errors in I m were within 0.77% and 1.8% for both soft and bony tissues, and were 0.09% and 0.2% for the SPR of soft and bony tissues, respectively, assuming knowledge of electron density. Proof of principle MR measurements and model-based computations of I m and SPR were taken in phantom for a series of hydrogenous solutions and compared against expected I m and SPR calculations from known elemental composition. MR determined I m and SPR values in a known composition solution were determined to within 5% and 0.52%, respectively. We present a novel model to accurately
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Winthrop J. Brown
2004-06-01
Full Text Available The generation of high intensity, ultrashort x-ray pulses enables exciting new experimental capabilities, such as femtosecond pump-probe experiments used to temporally resolve material structural dynamics on atomic time scales. Thomson backscattering of a high intensity laser pulse with a bright relativistic electron bunch is a promising method for producing such high-brightness x-ray pulses in the 10–100 keV range within a compact facility. While a variety of methods for producing subpicosecond x-ray bursts by Thomson scattering exist, including compression of the electron bunch to subpicosecond bunch lengths and/or colliding a subpicosecond laser pulse in a side-on geometry to minimize the interaction time, a promising alternative approach to achieving this goal while maintaining ultrahigh brightness is the production of a time-correlated (or chirped x-ray pulse in conjunction with pulse slicing or compression. We present the results of a complete analysis of this process using a recently developed 3D time and frequency-domain code for analyzing the spatial, temporal, and spectral properties an x-ray beam produced by relativistic Thomson scattering. Based on the relativistic differential cross section, this code has the capability to calculate time and space dependent spectra of the x-ray photons produced from linear Thomson scattering for both bandwidth-limited and chirped incident laser pulses. Spectral broadening of the scattered x-ray pulse resulting from the incident laser bandwidth, laser focus, and the transverse and longitudinal phase space of the electron beam were examined. Simulations of chirped x-ray pulse production using both a chirped electron beam and a chirped laser pulse are presented. Required electron beam and laser parameters are summarized by investigating the effects of beam emittance, energy spread, and laser bandwidth on the scattered x-ray spectrum. It is shown that sufficient temporal correlation in the scattered
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M.O. Kurtukova
2009-12-01
Full Text Available The effect of electromagnetic radiation of terahertz range at frequency of emission and absorption molecular spectrum of 150+0,75GHz nitric oxide on morphofunctional changes of microcirculation and tissue structure in animals in condition of acute and prolonged immobilization stress has been studied. It has shown that the influence of electromagnetic waves at these frequencies causes activity decrease of hypothalamic-pituitary-adrenal and tireoyd axis of stress reaction. It has been determined that terahertz range waves at frequency of nitric oxide are liable to restore disturbances of intravascular, vascular and extravascular components of microcirculation and also have histoprotective effect
Gao, Jianbo; Hu, Jing; Mao, Xiang; Perc, Matjaž
2012-01-01
Culturomics was recently introduced as the application of high-throughput data collection and analysis to the study of human culture. Here, we make use of these data by investigating fluctuations in yearly usage frequencies of specific words that describe social and natural phenomena, as derived from books that were published over the course of the past two centuries. We show that the determination of the Hurst parameter by means of fractal analysis provides fundamental insights into the nature of long-range correlations contained in the culturomic trajectories, and by doing so offers new interpretations as to what might be the main driving forces behind the examined phenomena. Quite remarkably, we find that social and natural phenomena are governed by fundamentally different processes. While natural phenomena have properties that are typical for processes with persistent long-range correlations, social phenomena are better described as non-stationary, on–off intermittent or Lévy walk processes. PMID:22337632
Ribay, Guillemette; Catheline, Stefan; Clorennec, Dominique; Ing, Ros Kiri; Fink, Mathias
2007-08-01
When a plane acoustic wave reaches a medium with an impedance infinite or null, it experiences a phase shift of zero or pi and its amplitude on the edge is maximum or vanishes. The case of a flexion wave (A0 Lamb wave) at a free end is also simple; its amplitude is multiplied by a factor 2 square root 2 and the phase shift is pi/2. The evanescent wave at the origin of these phenomena, perfectly described by the classical flexural plate theory, is identified as the imaginary A1 mode of the exact Rayleigh-Lamb theory. The experiences confirm the theoretical predictions.
DEFF Research Database (Denmark)
Judge, Alexander C.; Bang, Ole; de Sterke, Martin
2010-01-01
We extend the analytical theory explaining the trapping of normally dispersive waves by a Raman soliton in an axially uniform optical fiber to include axially nonuniform fibers. It is shown how a changing group velocity in such a fiber leads to the same trapping mechanism as for a decelerating...
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Yu. S. Аlyapkinа
2017-01-01
Full Text Available Based on real-time allele-specific polymerase chain reaction, the ranges of potential mutations in codons of 306 and 405 of the embBgene in Mycobacterium tuberculosis associated with resistance to ethambutol were investigated. 5 different mutations were detected in codon 306 and 3 mutations were found in codon 406 of the embB gene. The detected mutations were confirmed by sequencing and mass spectrometry. By analyzing the frequency of detected mutations of , the set of reagents was developed for rapid testing of susceptibility tuberculous mycobacteria to ethambutol by multi-competitive allele-specific real-time PCR. Out of 107 tested specimens of clinical isolates, mutations of the embB gene of M. tuberculosis were detected in 49 (45.8% specimens, and no mutations were found in 58 (52.2% specimens. 39 (36.4% specimens had mutations in codon 306 of the embB gene, and 9 (8.4% specimens had a mutation in codon 406, and 1 (0.9% specimen had mutations in both codons 306 and 406. The high level of agreement in the results of molecular genetic and bacteriological tests (84% proved the significance of mutations in codons 306 and 406 of the embB gene in M. tuberculosis and the need for their identification in order to detect ethambutol resistant strains of M. tuberculosis. When using molecular genetic tests, the sensitivity level made 75.8%, while the specificity of standard culture-based methods makes 95.6%.
Tomovski, Boyan; Gräbner, Frank; Hungsberg, Axel; Kallmeyer, Christian; Linsel, Mario
2011-11-01
Within only the last decade, usage of mobile phones and many other electronic devices with high speed wireless RF connection is rapidly increasing. Modern life requires reliable, quick and high-quality information connections, which explains the widely spreading craze for electronic mobile devices of various types. The vast technological advances we are witnessing in electronics, electro-optics, and computer science have profoundly affected our everyday lives. Meanwhile, safety concerns regarding the biological effects of electromagnetic (EM) radiation have been raised, in particular at a low level of exposure which we everyday experience. A variety of waves and signals have to be considered such as different sine waves, digital signals used in radio, television, mobile phone systems and other information transfer systems. The field around us has become rather complicated and the "air space is getting more and more dense with RF. The establishing of safety recommendations, law norms and rules augmented by adequate measurements is very important and requires quite an expertise. But as many scientific researches suggest, what we are currently witnessing is very likely to generate a great public danger and a bad influence over the human body. There are many health organisations warning the public for possible development of cancer, mental and physical disorders etc [7, 8]. These suggestions are quite serious and should not be neglected by the official bodies and the test laboratories. In the following work, the effects of electromagnetic field over a virtual model of a human head have been simulated in the frequency range from 900 MHz to 1800 MHz (commonly created in the real life by mobile GSM system) with the help of the program MEFiSTo 2D Classic [1]. The created virtual models using the 2D simulation & computation software proved that the use of new high tech nanotextile materials for shielding layers around the human body can reduce the effects of EM fields
Energy Technology Data Exchange (ETDEWEB)
Liu, P.; Wu, D.; Sun, L.Y.; Zhao, D.Y.; Hai, R.; Li, C. [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Chinese Ministry of Education, School of Physics and Optical Electronic Technology, Dalian University of Technology, Dalian, 116024 (China); Ding, H., E-mail: hding@dlut.edu.cn [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Chinese Ministry of Education, School of Physics and Optical Electronic Technology, Dalian University of Technology, Dalian, 116024 (China); Hu, Z.H.; Wang, L.; Hu, J.S.; Chen, J.L.; Luo, G.N. [Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, Anhui 230031 (China)
2017-05-15
Highlights: • LIBS was applied to EAST for monitoring the cleaning performance of the first wall using He-ICRF cleaning. • The cleaning performance is effective under helium ambient gas and some measurements have been obtained. • The results also indicate that the influence of magnetic field on LIBS signal is much stronger in helium ambient gas. • The effect of delay time and laser fluence on the LIBS signal has been investigated. - Abstract: In this paper, laser-induced breakdown spectroscopy (LIBS) under magnetic field condition has been studied in laboratory and EAST tokamak. The experimental results reveal that in helium ambient gas, the magnetic field significantly enhances the LIBS signal intensity (∼3 times). The effect of time delay and laser fluence on the intensity of LIBS has been investigated for optimizing the signal to background ratio (S/B). The developed LIBS approach has been applied to monitor the cleaning performance of the first wall in the fusion device of EAST using the ion cyclotron range of frequency (ICRF). The experimental results demonstrate that the cleaning performance for Li/D co-deposition layer is effective under helium ambient gas. The removing rate of Li on the surface of W tile is faster than that on Mo tile in He-ICRF cleaning and the D/(D + H) ratio on Mo tile is higher by ∼1.2 times than that on W tile. This work would indicate the feasibility of using LIBS to monitor the wall cleaning processes in EAST tokamak.
Roeters, S.J.; van Dijk, C.N.; Torres Knoop, A.; Backus, E.H.G.; Campen, R.K.; Bonn, M.; Woutersen, S.
2013-01-01
Vibrational sum-frequency generation (VSFG) spectra of the amide-I band of proteins can give detailed insight into biomolecular processes near membranes. However, interpreting these spectra in terms of the conformation and orientation of a protein can be difficult, especially in the case of complex
Directory of Open Access Journals (Sweden)
Dongqing Peng
2016-11-01
Full Text Available Based on Time-Frequency (TF analysis and a-contrario theory, this paper presents a new approach for extraction of linear arranged power transmission tower series in Polarimetric Synthetic Aperture Radar (PolSAR images. Firstly, the PolSAR multidimensional information is analyzed using a linear TF decomposition approach. The stationarity of each pixel is assessed by testing the maximum likelihood ratio statistics of the coherency matrix. Then, based on the maximum likelihood log-ratio image, a Cell-Averaging Constant False Alarm Rate (CA-CFAR detector with Weibull clutter background and a post-processing operator is used to detect point-like targets in the image. Finally, a searching approach based on a-contrario theory is applied to extract the linear arranged targets from detected point-like targets. The experimental results on three sets of PolSAR data verify the effectiveness of this approach.
Mandelis, Andreas; Feng, Chris
2002-02-01
A three-dimensional theory of the frequency-domain thermal-wave field generated inside a turbid medium with optical and thermal properties of human tissue is presented. The optical source is treated as a three-dimensional harmonically modulated diffuse-photon-density wave (DPDW) field in the diffusion approximation of the radiative transfer theory. Unlike earlier Green-function-based theoretical models, exact boundary conditions are used based on the requirement that there should be no diffuse photon intensity entering the turbid medium from the outside. Explicit analytical expressions for the DPDW field and for the dependent thermal-wave field are obtained in the spatial Hankel-transform domain. The formalism is further extended to the calculation of the infrared photothermal radiometric signal arising from the nonradiatively generated thermal-wave distribution in turbid media with instantaneous nonradiative deexcitation as well as in media with nonzero fluorescence relaxation lifetimes. Numerical inversions have been performed and presented as examples of selected special cases of the theory. It is found that the present theory with exact DPDW-field boundary conditions is valid throughout the entire domain of the turbid medium, with the exception of the very near-surface ballistic photon "skin layer" (7-50 microm). Photothermal radiometric signals were found to be more reliably predicted than DPDW signals within this layer, due to the depth-integration nature of this detection methodology.
DEFF Research Database (Denmark)
Fromager, Emmanuel; Réal, Florent; Wåhlin, Pernilla
2009-01-01
the universality of this value by considering "extreme" study cases, namely, neutral and charged isoelectronic f0 actinide compounds (ThO2, PaO2+, UO22+, UN2, CUO, and NpO23+). We find for these compounds that μ(opt)=0.3 a.u. but show that 0.4 a.u. is still acceptable. This is a promising result...... in the investigation of a universal range separation. The accuracy of the currently best MC-srDFT (μ=0.3 a.u.) approach has also been tested for equilibrium geometries. Though it performs as well as wave function theory and DFT for static-correlation-free systems, it fails in describing the neptunyl (VII) ion NpO23......+ where static correlation is significant; bending is preferred at the MC-srDFT (μ=0.3 a.u.) level, whereas the molecule is known to be linear. This clearly shows the need for better short-range functionals, especially for the description of the short-range exchange. It also suggests that the bending...
Experiment-theory comparison for low frequency BAE modes in the strongly shaped H-1NF stellarator
Haskey, S. R.; Blackwell, B. D.; Nührenberg, C.; Könies, A.; Bertram, J.; Michael, C.; Hole, M. J.; Howard, J.
2015-09-01
Recent advances in the modeling, analysis, and measurement of fluctuations have significantly improved the diagnosis and understanding of Alfvén eigenmodes in the strongly shaped H-1NF helical axis stellarator. Experimental measurements, including 3D tomographic inversions of high resolution visible light images, are in close agreement with beta-induced Alfvén eigenmodes (BAEs) calculated using the compressible ideal MHD code, CAS3D. This is despite the low β in H-1NF, providing experimental evidence that these modes can exist due to compression that is induced by the strong shaping in stellarators, in addition to high β, as is the case in tokamaks. This is confirmed using the CONTI and CAS3D codes, which show significant gap structures at lower frequencies which contain BAE and beta-acoustic Alfvén eigenmodes (BAAEs). The BAEs are excited in the absence of a well confined energetic particle source, further confirming previous studies that thermal particles, electrons, or even radiation fluctuations can drive these modes. Datamining of magnetic probe data shows the experimentally measured frequency of these modes has a clear dependence on the rotational transform profile, which is consistent with a frequency dependency due to postulated confinement related temperature variations.
Energy Technology Data Exchange (ETDEWEB)
Chamati, H; Tonchev, N S [Institute of Solid State Physics, 72 Tzarigradsko Chaussee, 1784 Sofia (Bulgaria)
2006-01-20
The difficulties arising in the investigation of finite-size scaling in d-dimensional O(n) systems with strong anisotropy and/or long-range interaction, decaying with the interparticle distance r as r{sup -d-{sigma}}(0 < {sigma} {<=} 2), are discussed. Some integral representations aiming at the simplification of the investigations are presented for the classical and quantum lattice sums that take place in the theory. Special attention is paid to a more general form allowing to treat both cases on an equal footing and in addition cases with strong anisotropic interactions and different geometries. The analysis is simplified further by expressing this general form in terms of a generalization of the Mittag-Leffler special functions. This turned out to be very useful for the extraction of asymptotic finite-size behaviours of the thermodynamic functions.
Lee, Seung Min; Sung, Kyung Mi
2017-06-01
The purpose of this study was to examine the effects of a violence coping program (VCP) based on Polk's middle-range theory of resilience on nursing competency, resilience, burnout, and the ability to cope with violence in nurses working in emergency rooms. A quasi-experimental study, with a nonequivalent control group and a pretest-posttest design, was conducted. Participants were 36 nurses who worked in emergency rooms and had experienced violence; 18 nurses from D hospital and 18 nurses from C hospital were assigned to the experimental and control groups, respectively. The experimental group received the VCP twice per week for 8 weeks. Levels of resilience, F=59.41, pburnout, F=52.74, pburnout and improving resilience, active coping behavior, and nursing competency. Therefore, it would be a useful intervention for improving the quality of nursing care provided in emergency rooms.
Energy Technology Data Exchange (ETDEWEB)
Idehara, T.; Saito, T.; Ogawa, I.; Mitsudo, S.; Tatematsu, Y. [Research Center for Development of Far Infrared Region, University of Fukui, 3-9-1 Bunkyo, 910-8507 Fukui (Japan); Sabchevski, S. [Research Center for Development of Far Infrared Region, University of Fukui, 3-9-1 Bunkyo, 910-8507 Fukui (Japan); Institute of Electronics of the Bulgarian Academy of Sciences, 72 Tzarigradsko Shose Blvd., 1784 Sofia (Bulgaria)], E-mail: sabch@ie.bas.bg
2008-12-31
Some recent advancements in the development of powerful high frequency gyrotrons that generate coherent radiation in the sub-terahertz and terahertz regions of the electromagnetic spectrum as well as their typical and novel applications are presented and discussed.
Understanding autonomic nervous system functioning, which mediates behavioral and physiological responses to stress, offers great potential for evaluation of farm animal stress and welfare. Evaluation of heart rate variability (HRV) and blood pressure variability (BPV), using time and frequency doma...
DEFF Research Database (Denmark)
Mackeprang, Kasper; Kjærgaard, Henrik Grum
2017-01-01
The local mode perturbation theory (LMPT) model was developed to improve the description of hydrogen bonded XH-stretching transitions, where X is typically O or N. We present a modified version of the LMPT model to extend its application from hydrated bimolecular complexes to hydrogen bonded...... bimolecular complexes with donors such as alcohols, amines and acids. We have applied the modified model to a series of complexes of different hydrogen bond type and complex energy. We found that the differences between local mode (LM) and LMPT calculated fundamental XH-stretching transition wavenumbers...
Parkinson, William A.; Oddershede, Jens
1991-06-01
The quadratic response function (QRF) is evaluated within the random phase approximation (RPA), to compute frequency-dependent first hyperpolarizabilities β(ω,ω). The method treats electron correlation consistent through first order, so the computed values are equivalent to coupled-perturbed Hartree-Fock (CPHF) results. The QRF is obtained by solving systems of linear equations, thus circumventing the RPA eigenvalue problem. The QRF equation of motion is used to develop hyperpolarizability identities in the dipole length and mixed-velocity representations. The two forms of β are equivalent at the RPA level, and provide a useful measure of completeness of basis. The method is applied to the hyperpolarizability of HF and H2O. It is found that basis sets used in previous studies were not saturated for all β components, and that basis sets which satisfy length-velocity sum rules for linear response properties are not sufficient for agreement of quadratic response properties. The calculated dispersion ratios are in good agreement with experimental measurement, indicating that dispersion effects are properly described by frequency-dependent calculations in the RPA at field energies which are small compared to vertical excitation energies.
DEFF Research Database (Denmark)
Fromager, Emmanuel; Cimiraglia, Renzo; Jensen, Hans Jørgen Aagaard
2010-01-01
A rigorous combination of multireference perturbation theory and density functional theory (DFT) is proposed. Based on a range separation of the regular two-electron Coulomb interaction, it combines a short-range density functional with second-order strongly contracted n-electron valence state pe...... zero. The method yields very promising results for the van der Waals systems Be2, Mg2, and Ca2; including the multireference system Be2....
Teng, Da; Cao, Qing; Wang, Kai
2017-05-01
We present an extension of the generalized nonlocal (GNL) optical response theory for the mode analysis of several plasmonic waveguides. We show that, compared with the local description, the imaginary part of the effective mode index is enlarged using the GNL response model. We ascribe this enlargement to the ‘effective’ surface modification and the induced charge diffusion. This result is quite different from that of the hydrodynamic model, where the imaginary part becomes smaller compared with that of the local model. Further, we investigate the influence of geometry parameters on propagation properties and find that the nonlocal effects are much more remarkable for smaller gap and sharper tip. Although the introduction of diffusion has a negative impact on the propagation length, it reveals the true physical insight and should be taken care when dealing with nanoplasmonic waveguide for photonic integration applications.
Mackeprang, Kasper; Kjaergaard, Henrik G.
2017-04-01
The local mode perturbation theory (LMPT) model was developed to improve the description of hydrogen bonded XH-stretching transitions, where X is typically O or N. We present a modified version of the LMPT model to extend its application from hydrated bimolecular complexes to hydrogen bonded bimolecular complexes with donors such as alcohols, amines and acids. We have applied the modified model to a series of complexes of different hydrogen bond type and complex energy. We found that the differences between local mode (LM) and LMPT calculated fundamental XH-stretching transition wavenumbers and oscillator strengths were correlated with the strength of the hydrogen bond. Overall, we have found that the LMPT model in most cases predicts transition wavenumbers within 20 cm-1 of the experimental values.
Roeters, S J; van Dijk, C N; Torres-Knoop, A; Backus, E H G; Campen, R K; Bonn, M; Woutersen, S
2013-07-25
Vibrational sum-frequency generation (VSFG) spectra of the amide-I band of proteins can give detailed insight into biomolecular processes near membranes. However, interpreting these spectra in terms of the conformation and orientation of a protein can be difficult, especially in the case of complex proteins. Here we present a formalism to calculate the amide-I infrared (IR), Raman, and VSFG spectra based on the protein conformation and orientation distribution. Based on the protein conformation, we set up the amide-I exciton Hamiltonian for the backbone amide modes that generate the linear and nonlinear spectroscopic responses. In this Hamiltonian, we distinguish between nearest-neighbor and non-nearest-neighbor vibrational couplings. To determine nearest-neighbor couplings we use an ab initio 6-31G+(d) B3LYP-calculated map of the coupling as a function of the dihedral angles. The other couplings are estimated using the transition-dipole coupling model. The local-mode frequencies of hydrogen-bonded peptide bonds and of peptide bonds to proline residues are red-shifted. To obtain realistic hydrogen-bond shifts we perform a molecular dynamics simulation in which the protein is solvated by water. As a first application, we measure and calculate the amide-I IR, Raman, and VSFG spectra of cholera toxin B subunit docked to a model cell membrane. To deduce the orientation of the protein with respect to the membrane from the VSFG spectra, we compare the experimental and calculated spectral shapes of single-polarization results, rather than comparing the relative amplitudes of VSFG spectra recorded for different polarization conditions for infrared, visible, and sum-frequency light. We find that the intrinsic uncertainty in the interfacial refractive index--essential to determine the overall amplitude of the VSFG spectra--prohibits a meaningful comparison of the intensities of the different polarization combinations. In contrast, the spectral shape of most of the VSFG
DEFF Research Database (Denmark)
Han, Loc A; Poulsen, Torben
1998-01-01
Equivalent Threshold Sound Pressure Levels (ETSPLs) have been determined for the Sennheiser HDA 200 earphone and the Etymotic Research ER-2insert earphone. Thirty-one young normal-hearing test subjects participated and the thresholds were determined for all recommended frequencies in thefrequency...
DEFF Research Database (Denmark)
Poulsen, Torben; Oakley, Sebastian
2009-01-01
Hearing threshold sound pressure levels were measured for the Sennheiser HDA 280 audiometric earphone. Hearing thresholds were measured for 25 normal hearing test subjects at the 11 audiometric test frequencies from 125 Hz to 8000 Hz. Sennheiser HDA 280 is a supra-aural earphone that may be seen ...
Schreckenberg, Jens M. A.; Dufal, Simon; Haslam, Andrew J.; Adjiman, Claire S.; Jackson, George; Galindo, Amparo
2014-09-01
An improved formulation of the extension of the statistical associating fluid theory for potentials of variable range to electrolytes (SAFT-VRE) is presented, incorporating a representation for the dielectric constant of the solution that takes into account the temperature, density and composition of the solvent. The proposed approach provides an excellent correlation of the dielectric-constant data available for a number of solvents including water, representative alcohols and carbon dioxide, and it is shown that the methodology can be used to treat mixed-solvent electrolyte solutions. Models for strong electrolytes of the metal-halide family are considered here. The salts are treated as fully dissociated and ion-specific interaction parameters are presented. Vapour pressure, density, and mean ionic activity coefficient data are used to determine the ion-ion and solvent-ion parameters, and mixed-salt electrolyte solutions (brines) are then treated predictively. We find that the resulting intermolecular potential models follow physical trends in terms of energies and ion sizes with a close relationship observed with well-established ionic diameters. A good description is obtained for the densities, mean ionic activity coefficients, and vapour pressures of the electrolyte solutions studied. The theory is also seen to provide excellent predictions of the osmotic coefficient and of the depression of the freezing temperature, and provides a qualitative estimate of the solvation free energy. The vapour pressure of aqueous brines is predicted accurately, as is the density of these solutions, although not at the highest pressures considered. Calculations for the vapour-liquid and liquid-liquid equilibria of salts in water+methanol and water+n-butan-1-ol are presented. In addition, it is shown that the salting-out of carbon dioxide in sodium chloride solutions is captured well using a predictive model.
Lin, Guoping
2015-01-01
Optical whispering gallery mode (WGM) resonators have been very attracting platforms for versatile Kerr frequency comb generations. We report a systematic study on the material dispersion of various optical materials that are capable of supporting quality factors above $10^9$. Using an analytical approximation of WGM resonant frequencies in disk resonators, we investigate the effect of the geometry and transverse mode order on the total group-velocity dispersion ($GVD$). We demonstrate that the major radii and the radial mode indices play an important role in tailoring the $GVD$ of WGM resonators. In particular, our study shows that in WGM disk-resonators, the polar families of modes have very similar $GVD$, while the radial families of modes feature dispersion values that can differ by up to several orders of magnitude. The effect of these giant dispersion shifts are experimentally evidenced in Kerr comb generation with magnesium fluoride. From a more general perspective, this critical feature enables to pus...
Patrick Reilly, J
2014-10-01
Differences between IEEE C95 Standards (C95.6-2002 and C95.1-2005) in the low-frequency (1 Hz-100 kHz) and the ICNIRP-2010 guidelines appear across the frequency spectrum. Factors accounting for lack of convergence include: differences between the IEEE standards and the ICNIRP guidelines with respect to biological induction models, stated objectives, data trail from experimentally derived thresholds through physical and biological principles, selection and justification of safety/reduction factors, use of probability models, compliance standards for the limbs as distinct from the whole body, defined population categories, strategies for central nervous system protection below 20 Hz, and correspondence of environmental electric field limits with contact currents. This paper discusses these factors and makes the case for adoption of the limits in the IEEE standards.
Fuks, Johanna I
2014-01-01
We explore an asymmetric two-fermion Hubbard dimer to test the accuracy of the adiabatic approximation of time-dependent density functional theory in modelling time-resolved charge transfer. We show that the model shares essential features of a ground state long-range molecule in real-space, and by applying a resonant field we show that the model also reproduces essential traits of the CT dynamics. The simplicity of the model allows us to propagate with an "adiabatically-exact" approximation, i.e. one that uses the exact ground-state exchange-correlation functional, and compare with the exact propagation. This allows us to study the impact of the time-dependent charge-transfer step feature in the exact correlation potential of real molecules on the resulting dynamics. Tuning the parameters of the dimer allows a study both of charge-transfer between open-shell fragments and between closed-shell fragments. We find that the adiabatically-exact functional is unable to properly transfer charge, even in situations ...
Xu, Fuming; Wang, Bin; Wei, Yadong; Wang, Jian
2013-10-01
Orbital-free density functional theory (OFDFT) replaces the wavefunction in the kinetic energy by an explicit energy functional and thereby speeds up significantly the calculation of ground state properties of the solid state systems. So far, the application of OFDFT has been centered on closed systems and less attention is paid on the transport properties in open systems. In this paper, we use OFDFT and combine it with non-equilibrium Green's function to simulate equilibrium electronic transport properties in silicon nanostructures from first principles. In particular, we study ac transport properties of a silicon atomic junction consisting of a silicon atomic chain and two monoatomic leads. We have calculated the dynamic conductance of this atomic junction as a function of ac frequency with one to four silicon atoms in the central scattering region. Although the system is transmissive with dc conductance around 4 to 5 e2/h, capacitive-like behavior was found in the finite frequency regime. Our analysis shows that, up to 0.1 THz, this behavior can be characterized by a classic RC circuit consisting of two resistors and a capacitor. One resistor gives rise to dc resistance and the other one accounts for the charge relaxation resistance with magnitude around 0.2 h/e2 when the silicon chain contains two atoms. It was found that the capacitance is around 5 aF for the same system.
Directory of Open Access Journals (Sweden)
Zi Ping Wu
2015-06-01
Full Text Available The electromagnetic interference (EMI shielding effectiveness (SE of carbon nanotube (CNT macro-film that is adhered to common cloth to maintain the light weight, silk-like quality, and smooth surface of the material for EMI shielding is investigated. The results show that a high and stable EMI SE of 48 dB to 57 dB at 40 GHz to 60 GHz was obtained by the macro-film with a thickness of only ∼4 μm. The composite CNT macro-film is easily manipulated, and its EMI property is significantly different from that of traditional electromagnetic shielding materials that show a lower EMI SE with increasing frequency. For example, the EMI SE of Cu foils decrease from 75 dB to 35 dB as frequency increases from 25 GHz to 60 GHz. Considering their stable and outstanding EMI SE and easy manipulation, the composite CNT macro-films are expected to have potential applications in shielding against millimeter waves.
Nadaud, Kevin; Borderon, Caroline; Renoud, Raphaël; Ghalem, Areski; Crunteanu, Aurelian; Huitema, Laure; Dumas-Bouchiat, Frédéric; Marchet, Pascal; Champeaux, Corinne; Gundel, Hartmut W.
2017-05-01
Domain wall motions in ferroelectrics participate to the material's complex permittivity and are responsible for their sensitivity of the dielectric properties to the driving electric field and thus to the incident power at microwave frequencies. In the present study, the dependence of the permittivity, the dielectric losses, and the tunability of Ba2/3Sr1/3TiO3 (BST) thin films on the incident power and on the bias fields is examined at a frequency of 500 MHz. While the domain wall motion participates only slightly to the permittivity (influences the losses due to its very dissipative behavior. As a consequence, the Figure of Merit (FoM, the ratio between tunability and dielectric losses) of the material depends on the applied microwave power. In the present study, a decrease in the FoM from 29 to 21 is observed for an incident power varying from -20 dBm to 5 dBm. When characterizing ferroelectric materials, the incident power has to be considered; moreover, domain wall motion effects should be limited in order to achieve a high FoM and less power sensitivity.
Khatun, Mahfuza; Mehrpouyan, Hani; Matolak, David; Guvenc, Ismail
2017-01-01
Millimeter-wave (mmWave) communications will play a key role in enhancing the throughput, reliability, and security of next generation wireless networks. These advancements are achieved through the large bandwidth available in this band and through the use of highly directional links that will be used to overcome the large pathloss at these frequencies. Although the terrestrial application of mmWave systems is advancing at a rapid pace, the use of mmWave communication systems in aviation systems or airports is still in its infancy. This can be attributed to the challenges related to radio technology and lack of development, and characterization of mmWave wireless channels for the aviation field and the airport environment. Consequently, one of our goals is to develop methodologies that support mmWave air to ground links, and various links at airports, by applying new localization schemes that allow for application of highly directional links that can be deployed over longer distances despite the high path loss at mmWave frequencies. However, a very thorough understanding of the mmWave channel models are needed to enable such new applications. To this end, in this paper, we present a survey of the current channel models in the mmWave band. The 3-dimensional statistical channel model is also reviewed and its parameters and typical characteristics for this model are identified and computed through simulation for the Boise metropolitan area.
Klimov, A. N.; Kulik, S. P.; Molotkov, S. N.; Potapova, T. A.
2017-03-01
In the paper by Gleim et al (2016 Opt. Express 24 2619), it was declared that the system of quantum cryptography, exploiting quantum key distribution (QKD) protocol BB84 with the additional reference state and encoding in a sub-carrier, is able to distribute secret keys at a distance of 210 km. The following shows that a simple attack realized with a beam splitter results in a loss of privacy of the keys over substantially smaller distances. It turns out that the actual length of the secret key transmission for the QKD system encoding in the sub-carrier frequency is ten times less than that declared in Gleim et al (2016 Opt. Express 24 2619). Therefore it is impossible to safely use the keys when distributed at a larger length of the communication channel than shown below. The maximum communication distance does not exceed 22 km, even in the most optimistic scenario.
Energy Technology Data Exchange (ETDEWEB)
Kazakov, Ye. O.; Ongena, J.; Van Eester, D.; Lerche, E.; Messiaen, A. [Laboratory for Plasma Physics, LPP-ERM/KMS, EUROfusion Consortium Member, Brussels (Belgium); Bilato, R. [Max-Planck-Institut für Plasmaphysik, Garching (Germany); Dumont, R. [CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France); Mantsinen, M. [Catalan Institution for Research and Advanced Studies, Barcelona (Spain); Barcelona Supercomputing Center (BSC), Barcelona (Spain)
2015-08-15
A fusion reactor requires plasma pre-heating before the rate of deuterium-tritium fusion reactions becomes significant. In ITER, radio frequency (RF) heating of {sup 3}He ions, additionally puffed into the plasma, is one of the main options considered for increasing bulk ion temperature during the ramp-up phase of the pulse. In this paper, we propose an alternative scenario for bulk ion heating with RF waves, which requires no extra {sup 3}He puff and profits from the presence of intrinsic Beryllium impurities in the plasma. The discussed method to heat Be impurities in D-T plasmas is shown to provide an even larger fraction of fuel ion heating.
A high-efficiency low-voltage class-E PA for IoT applications in sub-1 GHz frequency range
Zhou, Chenyi; Lu, Zhenghao; Gu, Jiangmin; Yu, Xiaopeng
2017-10-01
We present and propose a complete and iterative integrated-circuit and electro-magnetic (EM) co-design methodology and procedure for a low-voltage sub-1 GHz class-E PA. The presented class-E PA consists of the on-chip power transistor, the on-chip gate driving circuits, the off-chip tunable LC load network and the off-chip LC ladder low pass filter. The design methodology includes an explicit design equation based circuit components values' analysis and numerical derivation, output power targeted transistor size and low pass filter design, and power efficiency oriented design optimization. The proposed design procedure includes the power efficiency oriented LC network tuning, the detailed circuit/EM co-simulation plan on integrated circuit level, package level and PCB level to ensure an accurate simulation to measurement match and first pass design success. The proposed PA is targeted to achieve more than 15 dBm output power delivery and 40% power efficiency at 433 MHz frequency band with 1.5 V low voltage supply. The LC load network is designed to be off-chip for the purpose of easy tuning and optimization. The same circuit can be extended to all sub-1 GHz applications with the same tuning and optimization on the load network at different frequencies. The amplifier is implemented in 0.13 μm CMOS technology with a core area occupation of 400 μm by 300 μm. Measurement results showed that it provided power delivery of 16.42 dBm at antenna with efficiency of 40.6%. A harmonics suppression of 44 dBc is achieved, making it suitable for massive deployment of IoT devices. Project supported by the National Natural Science Foundation of China (No. 61574125) and the Industry Innovation Project of Suzhou City of China (No. SYG201641).
Crist, Michele R.; Knick, Steven T.; Hanser, Steven E.
2017-01-01
The delineation of priority areas in western North America for managing Greater Sage-Grouse (Centrocercus urophasianus) represents a broad-scale experiment in conservation biology. The strategy of limiting spatial disturbance and focusing conservation actions within delineated areas may benefit the greatest proportion of Greater Sage-Grouse. However, land use under normal restrictions outside priority areas potentially limits dispersal and gene flow, which can isolate priority areas and lead to spatially disjunct populations. We used graph theory, representing priority areas as spatially distributed nodes interconnected by movement corridors, to understand the capacity of priority areas to function as connected networks in the Bi-State, Central, and Washington regions of the Greater Sage-Grouse range. The Bi-State and Central networks were highly centralized; the dominant pathways and shortest linkages primarily connected a small number of large and centrally located priority areas. These priority areas are likely strongholds for Greater Sage-Grouse populations and might also function as refugia and sources. Priority areas in the Central network were more connected than those in the Bi-State and Washington networks. Almost 90% of the priority areas in the Central network had ≥2 pathways to other priority areas when movement through the landscape was set at an upper threshold (effective resistance, ER12). At a lower threshold (ER4), 83 of 123 priority areas in the Central network were clustered in 9 interconnected subgroups. The current conservation strategy has risks; 45 of 61 priority areas in the Bi-State network, 68 of 123 in the Central network, and all 4 priority areas in the Washington network had ≤1 connection to another priority area at the lower ER4threshold. Priority areas with few linkages also averaged greater environmental resistance to movement along connecting pathways. Without maintaining corridors to larger priority areas or a clustered group
Donner, Reik V.; Potirakis, Stelios M.; Barbosa, Susana M.; Matos, Jose A. O.
2015-04-01
The presence or absence of long-range correlations in environmental radioactivity fluctuations has recently attracted considerable interest. Among a multiplicity of practically relevant applications, identifying and disentangling the environmental factors controlling the variable concentrations of the radioactive noble gas Radon is important for estimating its effect on human health and the efficiency of possible measures for reducing the corresponding exposition. In this work, we present a critical re-assessment of a multiplicity of complementary methods that have been previously applied for evaluating the presence of long-range correlations and fractal scaling in environmental Radon variations with a particular focus on the specific properties of the underlying time series. As an illustrative case study, we subsequently re-analyze two high-frequency records of indoor Radon concentrations from Coimbra, Portugal, each of which spans several months of continuous measurements at a high temporal resolution of five minutes. Our results reveal that at the study site, Radon concentrations exhibit complex multi-scale dynamics with qualitatively different properties at different time-scales: (i) essentially white noise in the high-frequency part (up to time-scales of about one hour), (ii) spurious indications of a non-stationary, apparently long-range correlated process (at time scales between hours and one day) arising from marked periodic components probably related to tidal frequencies, and (iii) low-frequency variability indicating a true long-range dependent process, which might be dominated by a response to meteorological drivers. In the presence of such multi-scale variability, common estimators of long-range memory in time series are necessarily prone to fail if applied to the raw data without previous separation of time-scales with qualitatively different dynamics. We emphasize that similar properties can be found in other types of geophysical time series (for
Miyahara, Yasunori; Ishikawa, Keisuke; Kuroda, Tadahiro
2017-04-01
We use a simple directly modulated closed loop to develop a 2.1-mW, 2.4-GHz frequency-shift keying (FSK) transmitter that operates on 400-mV DC supply. Connecting a capacitor bank switch via a transformer in the voltage control oscillator (VCO) to the frequency-divider circuit expands the frequency tuning range without reducing VCO performance. A prototype was fabricated using the 65-nm standard CMOS process with a chip size of 1.65 × 1.85 mm2. A modulation output signal spectrum of -42 dBc at 1.5 MHz with -6 dBm at the PA buffer output terminal; moreover, a VCO phase noise of -101 dBc/Hz at 1 MHz is achieved. The FSK transmitter can readily use voltages supplied by harvested energy because of the low power consumption of the sensor network.
Jenke, T; Geltenbort, P; Ivanov, A N; Lauer, T; Lins, T; Schmidt, U; Saul, H; Abele, H
2012-01-01
The evidence for the observation of the Higgs spin-0-boson as a manifestation of a scalar field provides the missing corner stone for the standard model of particles (SM). However, the SM fails to explain the non-visible but gravitationally active part of the universe. Its nature is unknown but the confirmation of a scalar Higgs is giving a boost to scalar-field-theories. So far gravity experiments and observations performed at different distances find no deviation from Newton's gravity law. Therefore dark energy must possess a screening mechanism which suppresses the scalar-mediated fifth force. Our line of attack is a novel gravity experiment with neutrons based on a quantum interference technique. The spectroscopic measurement of quantum states on resonances with an external coupling makes this a powerful search for dark matter and dark energy contributions in the universe. Quantum states in the gravity potential are intimately related to other scalar field or spin-0-bosons if they exist. If the reason is ...
Energy Technology Data Exchange (ETDEWEB)
Möller, S., E-mail: s.moeller@fz-juelich.de [Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), 52425 Jülich (Germany); Wauters, T. [Laboratory for Plasma Physics, ERM/KMS, TEC Partner, 1000 Brussels (Belgium); Kreter, A. [Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), 52425 Jülich (Germany); Petersson, P.; Carrasco, A.G. [Fusion Plasma Physics, KTH Royal Institute of Technology, Teknikringen 31, 10044 Stockholm (Sweden)
2015-08-15
Plasma impact removal using radio frequency heated plasmas is a candidate method to control the co-deposit related tritium inventory in fusion devices. Plasma parameters evolve according to the balance of input power to losses (transport, radiation, collisions). Material is sputtered by the ion fluxes with impact energies defined by the plasma sheath. H{sub 2}, D{sub 2} and {sup 18}O{sub 2} plasmas are produced in the carbon limiter tokamak TEXTOR. Pre-characterised a-C:D layers are exposed to study local removal rates. The D{sub 2} plasma exhibits the highest surface release rate of 5.7 ± 0.9 ∗ 10{sup 19} D/m{sup 2}s. Compared to this the rate of the O{sub 2} plasma is 3-fold smaller due to its 11-fold lower ion flux density. Re-deposition of removed carbon is observed, indicating that pumping and ionisation are limiting the removal in TEXTOR. Presented models can explain the observations and allow tailoring removal discharges. An integral application scenario using ICWC and thermo-chemical removal is presented, allowing to remove 700 g T from a-C:DT co-deposits in 20 h with fusion compatible wall conditions using technical specifications similar to ITER.
Energy Technology Data Exchange (ETDEWEB)
Batou, A., E-mail: anas.batou@univ-paris-est.fr [Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallee (France); Soize, C., E-mail: christian.soize@univ-paris-est.fr [Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallee (France); Brie, N., E-mail: nicolas.brie@edf.fr [EDF R and D, Département AMA, 1 avenue du général De Gaulle, 92140 Clamart (France)
2013-09-15
Highlights: • A ROM of a nonlinear dynamical structure is built with a global displacements basis. • The reduced order model of fuel assemblies is accurate and of very small size. • The shocks between grids of a row of seven fuel assemblies are computed. -- Abstract: We are interested in the construction of a reduced-order computational model for nonlinear complex dynamical structures which are characterized by the presence of numerous local elastic modes in the low-frequency band. This high modal density makes the use of the classical modal analysis method not suitable. Therefore the reduced-order computational model is constructed using a basis of a space of global displacements, which is constructed a priori and which allows the nonlinear dynamical response of the structure observed on the stiff part to be predicted with a good accuracy. The methodology is applied to a complex industrial structure which is made up of a row of seven fuel assemblies with possibility of collisions between grids and which is submitted to a seismic loading.
Energy Technology Data Exchange (ETDEWEB)
Belyaeva, A.A.; Golubev, Y.M.
1987-09-01
The matrix isolation method is used to obtain the spectra of molecules in solid neon in the 1000--400-nm range. All the recorded bands are referred to transitions within the 5f /sup 2/ configuration of U/sup 4 +/ ion in the field of four fluorine ions. The interpretation assumes the case of a weak crystal field in which the terms of U/sup 4 +/ ion with different J are not mixed up. It is concluded that the UF/sub 3/ molecule has the structure of either a tetrahedron or a slightly distorted tetrahedron.
Borucki, W. J.; Koch, D. G.; Dunham, E. W.; Jenkins, J. M.; Young, Richard E. (Technical Monitor)
1997-01-01
The surprising discovery of giant planets in inner orbits around solar-like stars has brought into question our understanding of the development and evolution of planetary systems, including our solar system. To make further progress, it is critical to detect and obtain data on the frequency and characteristics of Earth-class planets. The Kepler Mission is designed to be a quick, low-cost approach to accomplish that objective. Transits by Earth-class planets produce a fractional change in stellar brightness of 5 x 10(exp -5) to 40 x 10(exp -5) lasting for 4 to 16 hours, From the period and depth of the transits, the orbit and size of the planets can be calculated. The proposed instrument is a one-meter aperture photometer with a 12 deg field-of-view (FOV). To obtain the required precision and to avoid interruptions caused by day-night and seasonal cycles, the photometer will be launched into a heliocentric orbit. It will continuously and simultaneously monitor the flux from 80,000 dwarf stars brighter than 14th magnitude in the Cygnus constellation. The mission tests the hypothesis that the formation of most stars produces Earth-class planets in inner orbits. Based on this assumption and the recent observations that 2% of the stars have giant planets in inner orbits, several types of results are expected from the mission: 1. From transits of Earth-class planets, about 480 planet detections and 60 cases where two or more planets are found in the same system. 2. From transits of giant planets, about 160 detections of inner-orbit planets and 24 detections of outer-orbit planets. 3. From the phase modulation of the reflected light from giant planets, about 1400 planet detections with periods less than a week, albedos for 160 of these giant planets, and densities for seven planets.
Borucki, W. J.; Koch, D. G.; Dunham, E. W.; Jenkins, J. M.
1997-01-01
The surprising discovery of giant planets in inner orbits around solar-like stars has brought into question our understanding of the development and evolution of planetary systems, including our solar system. To make further progress, it is critical to detect and obtain data on the frequency and characteristics of Earth-class planets. The Kepler Mission is designed to be a quick, low-cost approach to accomplish that objective. Transits by Earth-class planets produce a fractional change. in stellar brightness of 5 x 10(exp -5) to 40 x 10(exp -5) lasting for 4 to 16 hours. From the period and depth of the transits, the orbit and size of the planets can be calculated. The proposed instrument is a one-meter aperture photometer with a 12 deg. field-of-view (FOV). To obtain the required precision and to avoid interruptions caused by day-night and seasonal cycles, the photometer will be launched into a heliocentric orbit. It will continuously and simultaneously monitor the flux from 80,000 dwarf stars brighter than 14th magnitude in the Cygnus constellation. The mission tests the hypothesis that the formation of most stars produces Earth-class planets in inner orbits. Based on this assumption and the recent observations that 2% of the stars have giant planets in inner orbits, several types of results are expected from the mission: 1. From transits of Earth-class planets, about 480 planet detections and 60 cases where two or more planets are found in the same system. 2. From transits of giant planets, about 160 detections of inner-orbit planets and 24 detections of outer-orbit planets. 3. From the phase modulation of the reflected light from giant planets, about 1400 planet detections with periods less than a week, albedos for 160 of these giant planets, and densities for seven planets.
Li, M.; Jiang, Y. S.
2014-11-01
Micro-Doppler effect is induced by the micro-motion dynamics of the radar target itself or any structure on the target. In this paper, a simplified cone-shaped model for ballistic missile warhead with micro-nutation is established, followed by the theoretical formula of micro-nutation is derived. It is confirmed that the theoretical results are identical to simulation results by using short-time Fourier transform. Then we propose a new method for nutation period extraction via signature maximum energy fitting based on empirical mode decomposition and short-time Fourier transform. The maximum wobble angle is also extracted by distance approximate approach in a small range of wobble angle, which is combined with the maximum likelihood estimation. By the simulation studies, it is shown that these two feature extraction methods are both valid even with low signal-to-noise ratio.
Hou, Xiaoyan; Lee, Heow Pueh; Ong, Chong Jin; Lim, Siak Piang
2013-07-01
The purpose of this research is to present a new design of standing-wave ultrasonic motor. This motor uses three piezoelectric actuating blocks which deform appropriately when powered up. The deformations of the blocks in ultrasonic range are internally amplified via the design of the motor by about 80 times and collectively yield an elliptical trajectory for the driving head of the motor. Finite Element Analysis using ANSYS was performed for both dynamic analysis and optimization of a prototype motor. The numerical results verified that at steady state, the motor can achieve vibrations in micro-meter level and the velocity can reach decimeter scale, satisfying the fast speed requirement as a positioning actuator. Copyright © 2012 Elsevier B.V. All rights reserved.
Bhattacharya, A.; Lora, J. M.; Pollen, A.; Vollmer, T.; Thomas, M.; Leithold, E. L.; Mitchell, J.; Tripati, A.
2016-12-01
contribution. Most importantly, we find that during the Last Glacial Maximum (LGM) the Great Plains may not have witnessed an increase in the incidence of tornado frequency. Acknowledgements: James Sigman, Jacob Ashford, Jason Neff and Amato Evan
Directory of Open Access Journals (Sweden)
Ion N.Chiuta
2009-05-01
Full Text Available The paper determines relations for shieldingeffectiveness relative to several variables, includingmetal type, metal properties, thickness, distance,frequency, etc. It starts by presenting some relationshipsregarding magnetic, electric and electromagnetic fieldsas a pertinent background to understanding and applyingfield theory. Since literature about electromagneticcompatibility is replete with discussions about Maxwellequations and field theory only a few aspects arepresented.
Donner, R. V.; Potirakis, S. M.; Barbosa, S. M.; Matos, J. A. O.; Pereira, A. J. S. C.; Neves, L. J. P. F.
2015-05-01
The presence or absence of long-range correlations in the environmental radioactivity fluctuations has recently attracted considerable interest. Among a multiplicity of practically relevant applications, identifying and disentangling the environmental factors controlling the variable concentrations of the radioactive noble gas radon is important for estimating its effect on human health and the efficiency of possible measures for reducing the corresponding exposition. In this work, we present a critical re-assessment of a multiplicity of complementary methods that have been previously applied for evaluating the presence of long-range correlations and fractal scaling in environmental radon variations with a particular focus on the specific properties of the underlying time series. As an illustrative case study, we subsequently re-analyze two high-frequency records of indoor radon concentrations from Coimbra, Portugal, each of which spans several weeks of continuous measurements at a high temporal resolution of five minutes.Our results reveal that at the study site, radon concentrations exhibit complex multi-scale dynamics with qualitatively different properties at different time-scales: (i) essentially white noise in the high-frequency part (up to time-scales of about one hour), (ii) spurious indications of a non-stationary, apparently long-range correlated process (at time scales between some hours and one day) arising from marked periodic components, and (iii) low-frequency variability indicating a true long-range dependent process. In the presence of such multi-scale variability, common estimators of long-range memory in time series are prone to fail if applied to the raw data without previous separation of time-scales with qualitatively different dynamics.
Steber, Amanda; Pate, Brooks
2014-06-01
Advances in chip-level microwave technology in the communications field have led to the possibilities of low cost alternatives for current Fourier transform microwave (FTMW) spectrometers. Many of the large, expensive microwave components in a traditional design can now be replaced by robust, mass market monolithic microwave integrated circuits (MMICs). "Spectrometer on a board" designs are now feasible that offer dramatic cost reduction for microwave spectroscopy. These chip-level components can be paired with miniature computers to produce compact instruments that are operable through USB. A FTMW spectrometer design using the key MMIC components that drive cost reduction will be presented. Two dual channel synthesizers (Valon Technology Model 5008), a digital pattern generator (Byte Paradigm Wav Gen Xpress), and a high-speed digitizer/arbitrary waveform generator combination unit (Tie Pie HS-5 530 XM) form the key components of the spectrometer for operation in the 18-26.5 GHz range. The design performance is illustrated using a spectrometer that is being incorporated into a museum display for astrochemistry. For this instrument a user interface, developed in Python, has been developed and will be shown.
von Lilienfeld, O Anatole
2013-01-01
Generalized gradient approximated (GGA) density functional theory (DFT) typically overestimates polarizability and bond-lengths, and underestimates force constants of covalent bonds. To overcome this problem we show that one can use empirical frequency correcting atom centered potentials (FCACPs), parameterized for every nuclear species. Parameters are obtained through minimization of a penalty functional that explicitly encodes hybrid DFT geometries and static polarizabilities of reference molecules. For hydrogen, fluorine, chlorine, and carbon the respective reference molecules consist of H$_2$, F$_2$, Cl$_2$, and CH$_4$. The transferability of this approach to other systems and properties is assessed for harmonic frequencies of a small set of molecules. Numerical evidence, gathered for CCl$_3$F, HF, HCl, CFH$_3$, and CHCl$_3$, indicates that the GGA+FCACP level of theory yields significantly improved harmonic frequencies at the desired hybrid DFT geometry minima, as well as systematically reduced molecular...
Radio Frequency Ranging for Swarm Relative Localization
2017-10-01
Path Loss GPS Global Positioning System ID identification IDE integrated development environment IO input/output ISM industrial, scientific, and...information. This is particularly important in GPS-denied environments where there are limited positioning options. Many applications exist for relative...4 Fig. 3 Atmel sampling rate tests results .......................................................... 6 Fig. 4 Zoomed medium and slow
Static electromagnetic frequency changers
Rozhanskii, L L
1963-01-01
Static Electromagnetic Frequency Changers is about the theory, design, construction, and applications of static electromagnetic frequency changers, devices that used for multiplication or division of alternating current frequency. It is originally published in the Russian language. This book is organized into five chapters. The first three chapters introduce the readers to the principles of operation, the construction, and the potential applications of static electromagnetic frequency changers and to the principles of their design. The two concluding chapters use some hitherto unpublished work
Fang, Cong; Ma, Jiashuai; Yao, Meng; Di, Wenning; Lin, Di; Xu, Haiqing; Wang, Wei; Luo, Haosu
2017-02-01
In this paper, we investigate the responsivities and output voltage noise power spectral densities of magnetoelectric (ME) laminate sensors, consisting of length magnetized Terfenol-D alloys and transverse/width poled Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMNT) crystals (i.e. L-T mode and L-W mode respectively), which are directly integrated with custom-build low noise charge amplifier circuits. Both the theoretical analyses and experimental results prove that the L-W mode sensor with the optimized polarized direction of the PMNT plate possesses lower magnetic detection limit at the interested high frequency range of 10 kHz≤f≤50 kHz. The equivalent magnetic noise (EMN) of the L-W mode sensor is 0.78 pT/Hz1/2 at 30 kHz, which is about 1.7 times lower than the 1.35 pT/Hz1/2 for conventional L-T mode sensor. Furthermore, an effective method of using operational amplifiers with low equivalent input noise voltage and employing ME laminate composites with high voltage coefficient to reduce the EMNs of the ME laminate sensors at high frequency range has been established.
Loring, FH
2014-01-01
Summarising the most novel facts and theories which were coming into prominence at the time, particularly those which had not yet been incorporated into standard textbooks, this important work was first published in 1921. The subjects treated cover a wide range of research that was being conducted into the atom, and include Quantum Theory, the Bohr Theory, the Sommerfield extension of Bohr's work, the Octet Theory and Isotopes, as well as Ionisation Potentials and Solar Phenomena. Because much of the material of Atomic Theories lies on the boundary between experimentally verified fact and spec
Ryliskyte, Ligita; Ghiadoni, Lorenzo; Plantinga, Yvonne; Janaviciene, Silvija; Petrulioniene, Zaneta; Laucevicius, Aleksandras; Gintautas, Jonas
2004-01-01
High-frequency ultrasonographic imaging of flow-mediated dilatation (FMD) in a brachial artery, as non-invasive technique, was used for the clinical evaluation of endothelial function (EF) in 115 subjects (ages 44.19+/-12.23 (26 to 83) free of coronary heart disease or its equivalents. Our aim was to study the normative ranges for FMD in subjects of different age groups with low cardiovascular risk factors. The mean FMD was 8.23+/-4.51% (0 to 20.9). Multivariate analysis revealed that there were only two independent predictors of FMD: resting vessel diameter (r = -0.45, pFMD = 25.5-0.17 x age-2.6 x resting vessel diameter. Our study demonstrates that FMD in low cardiovascular risk patients inversely correlates with age as well as brachial artery diameter. Normative ranges of FMD could be predicted for different age groups. In addition to conventional methods for the assessment of cardiovascular risk by using a population-based approach (score indexes such as SCORE, FRAMINGH, PROCAM), high-frequency ultrasonographic imaging of flow-mediated dilatation (FMD) in the brachial artery is now becoming an accepted method for the assessment of an individual patient's cardiovascular risk. Although preliminary guidelines have been published, this technique has interpretive limitations. In a study that was published earlier, the authors estimated diameter-related normal ranges of FMD. Several articles reported cut points between control and diseased groups. Data about the impact of age on FMD are also available in the literature. However, this is the first attempt to classify normal values into groups according to age and diameter.
Kinetic theory of plasma waves: Part II homogeneous plasma
Westerhof, E.
2000-01-01
The theory of electromagnetic waves in a homogeneous plasma is reviewed. The linear response of the plasma to the waves is obtained in the form of the dielectric tensor. Waves ranging from the low frequency Alfven to the high frequency electron cyclotron waves are discussed in the limit of the cold
KINETIC THEORY OF PLASMA WAVES: Part II: Homogeneous Plasma
Westerhof, E.
2010-01-01
The theory of electromagnetic waves in a homogeneous plasma is reviewed. The linear response of the plasma to the waves is obtained in the form of the dielectric tensor. Waves ranging from the low frequency Alfven to the high frequency electron cyclotron waves are discussed in the limit of the cold
Kinetic theory of plasma waves - Part II: Homogeneous plasma
Westerhof, E.
2008-01-01
The theory of electromagnetic waves in a homogeneous plasma is reviewed. The linear response of the plasma to the waves is obtained in the form of the dielectric tensor. Waves ranging from the low frequency Alfven to the high frequency electron cyclotron waves axe discussed in the limit of the cold
Digital repetitive control under varying frequency conditions
Ramos, Germán A; Olm, Josep M
2013-01-01
The tracking/rejection of periodic signals constitutes a wide field of research in the control theory and applications area. Repetitive Control has proven to be an efficient way to face this topic. However, in some applications the frequency of the reference/disturbance signal is time-varying or uncertain. This causes an important performance degradation in the standard Repetitive Control scheme. This book presents some solutions to apply Repetitive Control in varying frequency conditions without loosing steady-state performance. It also includes a complete theoretical development and experimental results in two representative systems. The presented solutions are organized in two complementary branches: varying sampling period Repetitive Control and High Order Repetitive Control. The first approach allows dealing with large range frequency variations while the second allows dealing with small range frequency variations. The book also presents applications of the described techniques to a Roto-magnet plant and...
Younis, Mohammad I.
2016-03-10
Embodiments of multi-frequency excitation are described. In various embodiments, a natural frequency of a device may be determined. In turn, a first voltage amplitude and first fixed frequency of a first source of excitation can be selected for the device based on the natural frequency. Additionally, a second voltage amplitude of a second source of excitation can be selected for the device, and the first and second sources of excitation can be applied to the device. After applying the first and second sources of excitation, a frequency of the second source of excitation can be swept. Using the methods of multi- frequency excitation described herein, new operating frequencies, operating frequency ranges, resonance frequencies, resonance frequency ranges, and/or resonance responses can be achieved for devices and systems.
Giuntoli, Gianfranco; Hughes, Skye; Karban, Kate; South, Jane
2015-07-01
This article builds upon previous theoretical work on job loss as a status passage to help explain how people's experiences of involuntary unemployment affected their mental well-being during the 2009-2010 economic recession. It proposes a middle-range theory that interprets employment transitions as status passages and suggests that their health and well-being effects depend on the personal and social meanings that people give to them, which are called properties of the transitions. The analyses, which used a thematic approach, are based on the findings of a qualitative study undertaken in Bradford (North England) consisting of 73 people interviewed in 16 focus groups. The study found that the participants experienced their job losses as divestment passages characterised by three main properties: experiences of reduced agency, disruption of role-based identities, for example, personal identity crises, and experiences of 'spoiled identities', for example, experiences of stigma. The proposed middle-range theory allows us to federate these findings together in a coherent framework which makes a contribution to illuminating not just the intra-personal consequences of unemployment, that is, its impact on subjective well-being and common mental health problems, but also its inter-personal consequences, that is, the hidden and often overlooked social processes that affect unemployed people's social well-being. This article discusses how the study findings and the proposed middle-range theory can help to address the theoretical weaknesses and often contradictory empirical findings from studies that use alternative frameworks, for example, deprivation models and 'incentive theory' of unemployment. © The Author(s) 2014.
Chen, Bingxin; Wang, Jiamin; Qi, Hongxin; Zhang, Jie; Chen, Shude; Wang, Xianghui
2017-03-01
As electromagnetic exposure experiments can only be performed on small animals, usually rats, research on the characteristics of specific absorption rate (SAR) distribution in the rat has received increasing interest. A series of calculations, which simulated the SAR in a male rat anatomical model exposed to electromagnetic plane waves ranging from 0.05 to 5 GHz with different incidence and polarization, were conducted. The whole-body-averaged SAR (SARwb) and the tissue-averaged SAR (SARavg) in 20 major tissues were determined. Results revealed that incidence has great impact on SAR in the rat at higher frequencies owing to the skin effect and the effect on SARavg in tissues is much more apparent than that on SARwb; while polarization plays an important role under lower frequencies. Not only the incidence, but also the polarization in the rat keeps changing when the rat is in free movement. Thus, this article discussed a convenient way to obtain relatively accurate SARwb in a free-moving rat.
Kawamori, E.; Igami, H.
2017-11-01
A diagnostic technique for detecting the wave numbers of electron density fluctuations at electron gyro-scales in an electron cyclotron frequency range is proposed, and the validity of the idea is checked by means of a particle-in-cell (PIC) numerical simulation. The technique is a modified version of the scattering technique invented by Novik et al. [Plasma Phys. Controlled Fusion 36, 357-381 (1994)] and Gusakov et al., [Plasma Phys. Controlled Fusion 41, 899-912 (1999)]. The novel method adopts forward scattering of injected extraordinary probe waves at the upper hybrid resonance layer instead of the backward-scattering adopted by the original method, enabling the measurement of the wave-numbers of the fine scale density fluctuations in the electron-cyclotron frequency band by means of phase measurement of the scattered waves. The verification numerical simulation with the PIC method shows that the technique has a potential to be applicable to the detection of electron gyro-scale fluctuations in laboratory plasmas if the upper-hybrid resonance layer is accessible to the probe wave. The technique is a suitable means to detect electron Bernstein waves excited via linear mode conversion from electromagnetic waves in torus plasma experiments. Through the numerical simulations, some problems that remain to be resolved are revealed, which include the influence of nonlinear processes such as the parametric decay instability of the probe wave in the scattering process, and so on.
Crisco, Joseph J; Schwartz, Joel B; Wilcox, Bethany; Brideau, Holly; Basseches, Benjamin; Kerman, Karen
2015-08-20
Upper extremities affected by hemiplegic cerebral palsy (CP) and other neuromuscular disorders have been demonstrated to benefit from therapy, and the greater the duration of the therapy, the greater the benefit. A great motivator for participating in and extending the duration of therapy with children is play. Our focus is on active motion therapy of the wrist and forearm. In this study we examine the wrist motions associated with playing with two toys and three computer games controlled by a specially-designed play controller. Twenty children (ages 5-11) with no diagnosis of a muscular disorder were recruited. The play controller was fitted to the wrist and forearm of each child and used to measure and log wrist flexion and extension. Play activity and enjoyment were quantified by average wrist range of motion (ROM), motion frequency measures, and a discrete visual scale. We found significant differences in the average wrist ROM and motion frequency among the toys and games, yet there were no differences in the level of enjoyment across all toys and games, which was high. These findings indicate which toys and games may elicit the greater number of goal-directed movements, and lay the foundation for our long-term goal to develop and evaluate innovative motion-specific play controllers that are engaging rehabilitative devices for enhancing therapy and promoting neural plasticity and functional recovery in children with CP. Copyright © 2015 Elsevier Ltd. All rights reserved.
Meinhardt, Hans
2012-08-06
In his pioneering work, Alan Turing showed that de novo pattern formation is possible if two substances interact that differ in their diffusion range. Since then, we have shown that pattern formation is possible if, and only if, a self-enhancing reaction is coupled with an antagonistic process of longer range. Knowing this crucial condition has enabled us to include nonlinear interactions, which are required to design molecularly realistic interactions. Different reaction schemes and their relation to Turing's proposal are discussed and compared with more recent observations on the molecular-genetic level. The antagonistic reaction may be accomplished by an inhibitor that is produced in the activated region or by a depletion of a component that is used up during the self-enhancing reaction. The autocatalysis may be realized by an inhibition of an inhibition. Activating molecules can be processed into molecules that have an inhibiting function; patterning of the Wnt pathway is proposed to depend on such a mechanism. Three-component systems, as discussed in Turing's paper, are shown to play a major role in the generation of highly dynamic patterns that never reach a stable state.
Zagidullin, M V; Pershin, A A; Azyazov, V N; Mebel, A M
2015-12-28
Experimental and theoretical studies of collision induced emission of singlet oxygen molecules O2(a(1)Δg) in the visible range have been performed. The rate constants, half-widths, and position of peaks for the emission bands of the (O2(a(1)Δg))2 collisional complex centered around 634 nm (2) and 703 nm (3) have been measured in the temperature range of 90-315 K using a flow-tube apparatus that utilized a gas-liquid chemical singlet oxygen generator. The absolute values of the spontaneous emission rate constants k2 and k3 are found to be similar, with the k3/k2 ratio monotonically decreasing from 1.1 at 300 K to 0.96 at 90 K. k2 slowly decreases with decreasing temperature but a sharp increase in its values is measured below 100 K. The experimental results were rationalized in terms of ab initio calculations of the ground and excited potential energy and transition dipole moment surfaces of singlet electronic states of the (O2)2 dimole, which were utilized to compute rate constants k2 and k3 within a statistical model. The best theoretical results reproduced experimental rate constants with the accuracy of under 40% and correctly described the observed temperature dependence. The main contribution to emission process (2), which does not involve vibrational excitation of O2 molecules at the ground electronic level, comes from the spin- and symmetry-allowed 1(1)Ag←(1)B3u transition in the rectangular H configuration of the dimole. Alternatively, emission process (3), in which one of the monomers becomes vibrationally excited in the ground electronic state, is found to be predominantly due to the vibronically allowed 1(1)Ag←2(1)Ag transition induced by the asymmetric O-O stretch vibration in the collisional complex. The strong vibronic coupling between nearly degenerate excited singlet states of the dimole makes the intensities of vibronically and symmetry-allowed transitions comparable and hence the rate constants k2 and k3 close to one another.
Compact ranges in antenna and RCS measurements
Audone, B.
1989-09-01
With the increased complexity and extended frequency range of operation model measurements and far field test ranges are no longer suitable to satisfy the demand of accurate testing. Moreover plane wave test conditions are required for Radar Cross Section (RCS) measurements which represent a key point in stealth technology. Compact ranges represent the best test facilities available presently since they allow for indoor measurements under far field conditions in real time without any calculation effort. Several types of compact ranges are described and compared discussing their relevant advantages with regard to RCS and antenna measurements. In parallel to measuring systems sophisticated computer models were developed with such a high level of accuracy that it is questionable whether experiments give better results than theory. Tests performed on simple structures show the correlation between experimental results and theoretical ones derived on the basis of GTD computer codes.
Chesi, Stefano; Coish, W. A.
2015-06-01
We have theoretically analyzed coherent nuclear-spin dynamics induced by electron transport through a quantum-dot spin valve. The hyperfine interaction between electron and nuclear spins in a quantum dot allows for the transfer of angular momentum from spin-polarized electrons injected from ferromagnetic or half-metal leads to the nuclear spin system under a finite voltage bias. Accounting for a local nuclear-spin dephasing process prevents the system from becoming stuck in collective dark states, allowing a large nuclear polarization to be built up in the long-time limit. After reaching a steady state, reversing the voltage bias induces a transient current response as the nuclear polarization is reversed. Long-range nuclear-spin coherence leads to a strong enhancement of spin-flip transition rates (by an amount proportional to the number of nuclear spins) and is revealed by an intense current burst, analogous to superradiant light emission. The crossover to a regime with incoherent spin flips occurs on a relatively long-time scale, on the order of the single-nuclear-spin dephasing time, which can be much longer than the time scale for the superradiant current burst. This conclusion is confirmed through a general master equation. For the two limiting regimes (coherent/incoherent spin flips), the general master equation recovers our simpler treatment based on rate equations, but is also applicable at intermediate dephasing. Throughout this work, we assume uniform hyperfine couplings, which yield the strongest coherent enhancement. We propose realistic strategies, based on isotopic modulation and wave-function engineering in core-shell nanowires, to realize this analytically solvable "box-model" of hyperfine couplings.
Shi, Zhenzhi; Fan, Ying; Zhao, Huijuan; Xu, Kexin
2012-06-01
Accurate determination of the optical properties (the absorption coefficient μ(a) and the reduced scattering coefficient μ(s) (')) of tissues is very important in a variety of diagnostic and therapeutic procedures. Optical diffusion theory is frequently used as the forward model for describing the photon transfer in media with large reduced albedos (a(')) and in large source-detector separations (SDS). Several other methods (PN approximation, hybrid diffusion-P3 approximation) have also been published that describe photon transfer in media with low a(') or small SDSs. We studied the theoretical models for the steady-state spatially resolved diffuse reflectance measurement to accurately determine μ(a) and μ(s) (') at large a(') range but small SDSs. Instead of using a single model, a joint derivation method is proposed. The developed method uses one of the best aforementioned theoretical methods separately in five ranges of a(') determined from several forward models. In the region of small SDSs (the range between 0.4 and 8 mm) and large a(') range (between 0.5 and 0.99), the best theoretical derivation model was determined. The results indicate that the joint derivation method can improve the derivation accuracy and that a(') range can be determined by the steady-state spatially resolved diffuse reflectance measurement.
Fundamentals of sum-frequency spectroscopy
Shen, Y R
2016-01-01
The first book on the topic, and written by the founder of the technique, this comprehensive resource provides a detailed overview of sum-frequency spectroscopy, its fundamental principles, and the wide range of applications for surfaces, interfaces, and bulk. Beginning with an overview of the historical context, and introductions to the basic theory of nonlinear optics and surface sum-frequency generation, topics covered include discussion of different experimental arrangements adopted by researchers, notes on proper data analysis, an up-to-date survey commenting on the wide range of successful applications of the tool, and a valuable insight into current unsolved problems and potential areas to be explored in the future. With the addition of chapter appendices that offer the opportunity for more in-depth theoretical discussion, this is an essential resource that integrates all aspects of the subject and is ideal for anyone using, or interested in using, sum-frequency spectroscopy.
Microwave balanced oscillators and frequency doublers
Siripon, N
2002-01-01
The research presented in this thesis is on the application of the injection-locked oscillator technique to microwave balanced oscillators. The balanced oscillator design is primarily analysed using the extended resonance technique. A transmission line is connected between the two active devices, so that the active device resonate each other. The electrical length of the transmission line is also analysed for the balanced oscillation condition. The balanced oscillator can be viewed with the negative resistance model and the feedback model. The former model is characterised at a circuit plane where the feedback network is cut. By using both the negative-resistance oscillator model and the feedback model, the locking range of the oscillator is analysed by extending Kurokawa's theory. This analysis demonstrates the locking range of the injection phenomenon, where the injection frequency is either close to the free-running frequency, close to (1/n) x free-running frequency or close to n x the free-running frequen...
Nel, R.; Avison, J.; Harris, P.; Blabla, M.; Hämäläinen, J.
2017-01-01
The degrees of equivalence of the AFRIMETS.AUV.A-K5 regional key comparison are reported here as the final report. The scope of the comparison covered the complex pressure sensitivities of two LS1P microphones over the frequency range 2 Hz to 10 kHz in accordance with IEC 61094-2: 2009. Four national metrology institutes from two different regional metrology organisations participated in the comparison. Two LS1P microphones were circulated simultaneously to all the participants in a circular configuration. One of the microphones sensitivity shifted and all results associated with this microphone were subsequently excluded from further analysis and linking. The AFRIMETS.AUV.A-K5 comparison results were linked to the CCAUV.A-K5 comparison results via dual participation in the CCAUV.A-K5 and AFRIMETS.AUV.A-K5 comparisons. The degrees of equivalence, linked to the CCAUV.A-K5 comparison, were calculated for all participants of this comparison. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
De Naeghel, Jessie; Van Keer, Hilde; Vansteenkiste, Maarten; Rosseel, Yves
2012-01-01
Research indicates the need to further examine the dimensions of reading motivation. A clear theoretical basis is necessary for conceptualizing reading motivation and considering contextual differences therein. The present study develops and validates the SRQ-Reading Motivation, a questionnaire measuring recreational and academic reading motivation based on self-determination theory. The study clarifies the relation among reading motivation, reading self-concept, reading behavior (i.e., engag...
Frequency Standards and Metrology
Maleki, Lute
2009-04-01
Preface / Lute Maleki -- Symposium history / Jacques Vanier -- Symposium photos -- pt. I. Fundamental physics. Variation of fundamental constants from the big bang to atomic clocks: theory and observations (Invited) / V. V. Flambaum and J. C. Berengut. Alpha-dot or not: comparison of two single atom optical clocks (Invited) / T. Rosenband ... [et al.]. Variation of the fine-structure constant and laser cooling of atomic dysprosium (Invited) / N. A. Leefer ... [et al.]. Measurement of short range forces using cold atoms (Invited) / F. Pereira Dos Santos ... [et al.]. Atom interferometry experiments in fundamental physics (Invited) / S. W. Chiow ... [et al.]. Space science applications of frequency standards and metrology (Invited) / M. Tinto -- pt. II. Frequency & metrology. Quantum metrology with lattice-confined ultracold Sr atoms (Invited) / A. D. Ludlow ... [et al.]. LNE-SYRTE clock ensemble: new [symbol]Rb hyperfine frequency measurement - spectroscopy of [symbol]Hg optical clock transition (Invited) / M. Petersen ... [et al.]. Precise measurements of S-wave scattering phase shifts with a juggling atomic clock (Invited) / S. Gensemer ... [et al.]. Absolute frequency measurement of the [symbol] clock transition (Invited) / M. Chwalla ... [et al.]. The semiclassical stochastic-field/atom interaction problem (Invited) / J. Camparo. Phase and frequency noise metrology (Invited) / E. Rubiola ... [et al.]. Optical spectroscopy of atomic hydrogen for an improved determination of the Rydberg constant / J. L. Flowers ... [et al.] -- pt. III. Clock applications in space. Recent progress on the ACES mission (Invited) / L. Cacciapuoti and C. Salomon. The SAGAS mission (Invited) / P. Wolf. Small mercury microwave ion clock for navigation and radioScience (Invited) / J. D. Prestage ... [et al.]. Astro-comb: revolutionizing precision spectroscopy in astrophysics (Invited) / C. E. Kramer ... [et al.]. High frequency very long baseline interferometry: frequency standards and
Directory of Open Access Journals (Sweden)
Radu BOGATEANU
2009-09-01
Full Text Available The low frequency damper is an autonomous equipment for damping vibrations with the 1-20Hz range.Its autonomy enables the equipment to be located in various mechanical systems, without requiring special hydraulic installations.The low frequency damper was designed for damping the low frequency oscillations occurring in the circuit controls of the upgraded IAR-99 Aircraft.The low frequency damper is a novelty in the aerospace field ,with applicability in several areas as it can be built up in an appropriate range of dimensions meeting the requirements of different beneficiaries. On this line an equipment able to damp an extended frequency range was performed for damping oscillations in the pipes of the nuclear power plants.This damper, tested in INCAS laboratories matched the requirements of the beneficiary.The low frequency damper is patented – the patent no. 114583C1/2000 is held by INCAS.
Miliordos, Evangelos; Aprà, Edoardo; Xantheas, Sotiris S.
2013-09-01
We report the first optimum geometries and harmonic vibrational frequencies for the ring pentamer and several water hexamer (prism, cage, cyclic and two book) at the coupled-cluster including single, double, and full perturbative triple excitations (CCSD(T))/aug-cc-pVDZ level of theory. All five examined hexamer isomer minima previously reported by Møller-Plesset perturbation theory (MP2) are also minima on the CCSD(T) potential energy surface (PES). In addition, all CCSD(T) minimum energy structures for the n = 2-6 cluster isomers are quite close to the ones previously obtained by MP2 on the respective PESs, as confirmed by a modified Procrustes analysis that quantifies the difference between any two cluster geometries. The CCSD(T) results confirm the cooperative effect of the homodromic ring networks (systematic contraction of the nearest-neighbor (nn) intermolecular separations with cluster size) previously reported by MP2, albeit with O-O distances shorter by ˜0.02 Å, indicating that MP2 overcorrects this effect. The harmonic frequencies at the minimum geometries were obtained by the double differentiation of the CCSD(T) energy using an efficient scheme based on internal coordinates that reduces the number of required single point energy evaluations by ˜15% when compared to the corresponding double differentiation using Cartesian coordinates. Negligible differences between MP2 and CCSD(T) frequencies are found for the librational modes, while uniform increases of ˜15 and ˜25 cm-1 are observed for the bending and "free" OH harmonic frequencies. The largest differences between CCSD(T) and MP2 are observed for the harmonic hydrogen bonded frequencies, for which the former produces larger absolute values than the latter. Their CCSD(T) redshifts from the monomer values (Δω) are smaller than the MP2 ones, due to the fact that CCSD(T) produces shorter elongations (ΔR) of the respective hydrogen bonded OH lengths from the monomer value with respect to MP2
Santos, M. R. P.; Freire, F. N. A.; Sohn, R. S. T. M.; Almeida, J. S.; Sancho, E. O.; Costa, A. D. S. B.; Medeiros, A. M. L.; Sombra, A. S. B.
2008-12-01
In this paper, a new electroceramic composite [Pb(Fe0.5Nb0.5) O3 (PFN)]Z [Cr0.75Fe1.25O3 (CRFO)]100-Z (Z = 0, 10) is investigated in the microwave (MW) frequency range. The dielectric permittivity and loss in the region of 4-8 GHz (G and H MW bands) were studied. The performance of cylindrical resonator antennas based on CRFO100 and on PFN10 was examined. The experimental and theoretical results of the dielectric resonator antenna (DRA) such as return loss, bandwidth, input impedance and radiation patterns are in good agreement for both composites: PFN10 (10% PFN + 90% CRFO) and CRFO100 (100% CRFO). A numerical validation was made considering an air gap between the dielectric resonator and the metallic conductors. The PFN10 matrix composite PFN10 (10% PFN + 90% CRFO) presents the highest dielectric permittivity (9.9 at 4.44 GHz) and the lowest bandwidth (9.9%). The CRFO100 phase (100% CRFO) presents a dielectric permittivity of 8.35 at 4.67 GHz and a bandwidth of 11.8%. The Hakki-Coleman procedure was also used in this study. The dielectric permittivity of 8.35 (tan δ = 1 × 10-3) at 7.94 GHz was obtained for CRFO100. The PFN10 presents a dielectric permittivity of 10.17 (tan δ = 4.9 × 10-3) at 7.05 GHz. These measurements confirm the possible use of such material for small DRAs.
Kinetic Scale Structure of Low-frequency Waves and Fluctuations
Energy Technology Data Exchange (ETDEWEB)
López, Rodrigo A.; Yoon, Peter H. [Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742 (United States); Viñas, Adolfo F. [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, MD 20771 (United States); Araneda, Jaime A., E-mail: rlopezh@umd.edu, E-mail: yoonp@umd.edu [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Concepción (Chile)
2017-08-10
The dissipation of solar wind turbulence at kinetic scales is believed to be important for the heating of the corona and for accelerating the wind. The linear Vlasov kinetic theory is a useful tool for identifying various wave modes, including kinetic Alfvén, fast magnetosonic/whistler, and ion-acoustic (or kinetic slow), and their possible roles in the dissipation. However, the kinetic mode structure in the vicinity of ion-cyclotron modes is not clearly understood. The present paper aims to further elucidate the structure of these low-frequency waves by introducing discrete particle effects through hybrid simulations and Klimontovich formalism of spontaneous emission theory. The theory and simulation of spontaneously emitted low-frequency fluctuations are employed to identify and distinguish the detailed mode structures associated with ion-Bernstein modes versus quasi-modes. The spontaneous emission theory and simulation also confirm the findings of the Vlasov theory in that the kinetic Alfvén waves can be defined over a wide range of frequencies, including the proton cyclotron frequency and its harmonics, especially for high-beta plasmas. This implies that these low-frequency modes may play predominant roles even in the fully kinetic description of kinetic scale turbulence and dissipation despite the fact that cyclotron harmonic and Bernstein modes may also play important roles in wave–particle interactions.
Low profile frequency agile MIMO slot antenna with TCM characterization
Ghalib, Asim
2017-06-07
In this paper, a frequency reconfigurable multiple-input-multiple-output (MIMO) slot antenna is presented. The proposed design is low profile and compact with wide tunability range, covering several well-known frequency bands from 1800 MHz to 2450 MHz. The frequency reconfigurability is achieved by loading the annular slot with varactor diodes. The antenna system is also analyzed for MIMO performance metrics. Moreover, the effect of circular slot antenna on the chassis modes is also investigated using the theory of characteristic modes (TCM). The physical principle behind frequency reconfigurability is also investigated using TCM analysis. An interesting finding is observed using varactor diodes for frequency reconfigurability, that is the reactive impedance loading does not alter the modal significance (MS) plots but only aid in the input impedance matching at different frequency bands.
Tsai, Tsung-Han; Zhou, Chao; Adler, Desmond C; Fujimoto, James G
2009-11-09
We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep rate of 1kHz and 120kHz, respectively over a 135nm tuning range centered at 1310nm with average output powers of 50mW. A 25GHz free spectral range frequency comb filter in the swept lasers causes the lasers to generate a series of well defined frequency steps. The narrow bandwidth (0.015nm) of the frequency comb filter enables a approximately -1.2dB sensitivity roll off over approximately 3mm range, compared to conventional swept source and FDML lasers which have -10dB and -5dB roll offs, respectively. Measurements at very long ranges are possible with minimal sensitivity loss, however reflections from outside the principal measurement range of 0-3mm appear aliased back into the principal range. In addition, the frequency comb output from the lasers are equally spaced in frequency (linear in k-space). The filtered laser output can be used to self-clock the OCT interference signal sampling, enabling direct fast Fourier transformation of the fringe signals, without the need for fringe recalibration procedures. The design and operation principles of FC swept lasers are discussed and designs for short cavity lasers for OCT and interferometric measurement applications are proposed.
Foundations for radio frequency engineering
Geyi, Wen
2015-01-01
The book provides a comprehensive coverage of the fundamental topics in microwave engineering, antennas and wave propagation, and electromagnetic compatibility, including electromagnetic boundary value problems, waveguide theory, microwave resonators, antennas and wave propagation, microwave circuits, principles of electromagnetic compatibility designs, information theory and systems. Deals systematically with fundamental problems in radio frequency engineering, this important volume provides an updated treatment of radio frequency theory and techniques. The book can be used as a one-semester course for senior and first-year graduate students or as a reference for radio frequency engineers and applied physicists.
Larionov, Igor A
2011-06-22
We explore for all wavevectors through the Brillouin zone the dynamic spin susceptibility χ(total)(+,-)(ω, q) that takes into account the interplay of localized and itinerant charge carriers. The imaginary part, Imχ(total)(+,-)(ω, q), has peaks at the antiferromagnetic wavevector Q = (π, π) and a diffusive-like, extremely narrow and sharp peak (symmetric ring of maxima |q| = q(0)) at very small wavevectors Q(0) is proportional to w/J ≈ 10(-6) with the nuclear magnetic/quadrupole resonance frequency ω and the superexchange coupling constant J. We demonstrate the capability of Imχ(total)(+,-)(ω, q) for plane copper (63)(1/T(1)) and oxygen (17)(1/T(1)) nuclear spin-lattice relaxation rate calculations from carrier free right up to optimally doped La(2 - x)Sr(x)CuO(4) and obtain the basic features of temperature and doping behavior for (63)(1/T(1)) in agreement with experimental observations.
Energy Technology Data Exchange (ETDEWEB)
Miliordos, Evangelos; Aprà, Edoardo; Xantheas, Sotiris S.
2013-01-01
We report the first optimum geometries and harmonic vibrational frequencies for the ring pentamer and several water hexamer (prism, cage, cyclic and two book) at the CCSD(T)/aug-cc-pVDZ level of theory. All five hexamer isomer minima previously reported by MP2 are also minima on the CCSD(T) potential energy surface (PES). In addition, all CCSD(T) minimum energy structures for the n=2-6 cluster isomers are quite close to the ones previously obtained by MP2 on the respective PESs, as confirmed by a modified Procrustes analysis that quantifies the difference between any two cluster geometries. The CCSD(T) results confirm the cooperative effect of the homodromic ring networks (systematic contraction of the nearest-neighbor (nn) intermolecular separations with cluster size) previously reported by MP2, albeit with O-O distances shorter by ~0.02 Å, indicating that MP2 overcorrects this effect. The harmonic frequencies at the minimum geometries were obtained by the double differentiation of the CCSD(T) energy using an efficient scheme based on internal coordinates that reduces the number of required single point energy evaluations by ~15% when compared to the corresponding double differentiation using Cartesian coordinates. Negligible differences between MP2 and CCSD(T) are found for the librational modes, while uniform increases of ~15 and ~25 cm^{-1} are observed for the bending and “free” OH harmonic frequencies. The largest differences between MP2 and CCSD(T) are observed for the harmonic hydrogen bonded frequencies. The CCSD(T) red shifts from the monomer frequencies (Δω) are smaller than the MP2 ones, due to the fact that the former produces shorter elongations (ΔR) of the respective hydrogen bonded OH lengths from the monomer value with respect to the latter. Both the MP2 and CCSD(T) results for the hydrogen bonded frequencies were found to closely follow the relation - Δω = s · ΔR, with a rate of s = 20.3 cm^{-1} / 0.001 Å. The CCSD
Frequency selectivity at very low centre frequencies
DEFF Research Database (Denmark)
Orellana, Carlos Andrés Jurado; Pedersen, Christian Sejer; Marquardt, Torsten
2010-01-01
measurements based on OAE suppression techniques and notched-noise masking data psychophysically measured for centre frequencies in the range 50-125 Hz, this study examines how individual differences in frequency selectivity, as well as in masking, may occur at very low CFs due to individual differences...... in the shape of the METFs, thought to be affected by the helicotrema impedance. Preliminary analysis indicates that individual differences in the METFs might underlay the observed individual differences in frequency selectivity. Main effects predicted by the calculations are a pronounced flattening off...
Theory, the Final Frontier? A Corpus-Based Analysis of the Role of Theory in Psychological Articles
Beller, Sieghard; Bender, Andrea
2017-01-01
Contemporary psychology regards itself as an empirical science, at least in most of its subfields. Theory building and development are often considered critical to the sciences, but the extent to which psychology can be cast in this way is under debate. According to those advocating a strong role of theory, studies should be designed to test hypotheses derived from theories (theory-driven) and ideally should yield findings that stimulate hypothesis formation and theory building (theory-generating). The alternative position values empirical findings over theories as the lasting legacy of science. To investigate which role theory actually plays in current research practice, we analyse references to theory in the complete set of 2,046 articles accepted for publication in Frontiers of Psychology in 2015. This sample of articles, while not representative in the strictest sense, covers a broad range of sub-disciplines, both basic and applied, and a broad range of article types, including research articles, reviews, hypothesis & theory, and commentaries. For the titles, keyword lists, and abstracts in this sample, we conducted a text search for terms related to empiricism and theory, assessed the frequency and scope of usage for six theory-related terms, and analyzed their distribution over different article types and subsections of the journal. The results indicate substantially lower frequencies of theoretical than empirical terms, with references to a specific (named) theory in less than 10% of the sample and references to any of even the most frequently mentioned theories in less than 0.5% of the sample. In conclusion, we discuss possible limitations of our study and the prospect of theoretical advancement. PMID:28642728
Theory, the Final Frontier? A Corpus-Based Analysis of the Role of Theory in Psychological Articles
Directory of Open Access Journals (Sweden)
Sieghard Beller
2017-06-01
Full Text Available Contemporary psychology regards itself as an empirical science, at least in most of its subfields. Theory building and development are often considered critical to the sciences, but the extent to which psychology can be cast in this way is under debate. According to those advocating a strong role of theory, studies should be designed to test hypotheses derived from theories (theory-driven and ideally should yield findings that stimulate hypothesis formation and theory building (theory-generating. The alternative position values empirical findings over theories as the lasting legacy of science. To investigate which role theory actually plays in current research practice, we analyse references to theory in the complete set of 2,046 articles accepted for publication in Frontiers of Psychology in 2015. This sample of articles, while not representative in the strictest sense, covers a broad range of sub-disciplines, both basic and applied, and a broad range of article types, including research articles, reviews, hypothesis & theory, and commentaries. For the titles, keyword lists, and abstracts in this sample, we conducted a text search for terms related to empiricism and theory, assessed the frequency and scope of usage for six theory-related terms, and analyzed their distribution over different article types and subsections of the journal. The results indicate substantially lower frequencies of theoretical than empirical terms, with references to a specific (named theory in less than 10% of the sample and references to any of even the most frequently mentioned theories in less than 0.5% of the sample. In conclusion, we discuss possible limitations of our study and the prospect of theoretical advancement.
Theory, the Final Frontier? A Corpus-Based Analysis of the Role of Theory in Psychological Articles.
Beller, Sieghard; Bender, Andrea
2017-01-01
Contemporary psychology regards itself as an empirical science, at least in most of its subfields. Theory building and development are often considered critical to the sciences, but the extent to which psychology can be cast in this way is under debate. According to those advocating a strong role of theory, studies should be designed to test hypotheses derived from theories (theory-driven) and ideally should yield findings that stimulate hypothesis formation and theory building (theory-generating). The alternative position values empirical findings over theories as the lasting legacy of science. To investigate which role theory actually plays in current research practice, we analyse references to theory in the complete set of 2,046 articles accepted for publication in Frontiers of Psychology in 2015. This sample of articles, while not representative in the strictest sense, covers a broad range of sub-disciplines, both basic and applied, and a broad range of article types, including research articles, reviews, hypothesis & theory, and commentaries. For the titles, keyword lists, and abstracts in this sample, we conducted a text search for terms related to empiricism and theory, assessed the frequency and scope of usage for six theory-related terms, and analyzed their distribution over different article types and subsections of the journal. The results indicate substantially lower frequencies of theoretical than empirical terms, with references to a specific (named) theory in less than 10% of the sample and references to any of even the most frequently mentioned theories in less than 0.5% of the sample. In conclusion, we discuss possible limitations of our study and the prospect of theoretical advancement.
Parametric effects of word frequency effect in memory for mixed frequency lists
Lohnas, Lynn J.; Kahana, Michael J.
2013-01-01
The word frequency paradox refers to the finding that low frequency words are better recognized than high frequency words yet high frequency words are better recalled than low frequency words. Rather than comparing separate groups of low and high frequency words, we sought to quantify the functional relation between word frequency and memory performance across the broad range of frequencies typically used in episodic memory experiments. Here we report that both low frequency and high frequenc...
Broadband frequency conversion
DEFF Research Database (Denmark)
Sanders, Nicolai; Jensen, Ole Bjarlin; Tidemand-Lichtenberg, Peter
We present a simple, passive and static setup for broadband frequency conversion. By using simple optical components like lenses, mirrors and gratings, we obtain the spectral angular dispersion to match the second harmonic generation phasematching angles in a nonlinear BiBO crystal. We are able...... to frequency double a single-frequency diode laser, tunable in the 1020-1090 nm range, with almost equal efficiency for all wavelengths. In the experimental setup, the width of the phasematch was increased with a factor of 50. The method can easily be extended to other wavelength ranges and nonlinear crystals...
Wavelets theory, algorithms, and applications
Montefusco, Laura
2014-01-01
Wavelets: Theory, Algorithms, and Applications is the fifth volume in the highly respected series, WAVELET ANALYSIS AND ITS APPLICATIONS. This volume shows why wavelet analysis has become a tool of choice infields ranging from image compression, to signal detection and analysis in electrical engineering and geophysics, to analysis of turbulent or intermittent processes. The 28 papers comprising this volume are organized into seven subject areas: multiresolution analysis, wavelet transforms, tools for time-frequency analysis, wavelets and fractals, numerical methods and algorithms, and applicat
Energy Technology Data Exchange (ETDEWEB)
Lai, N.D.
2003-07-15
We explored some new features of single- and dual-frequency solid-state lasers oscillating in continuous-wave or pulsed regimes. First, we have developed some techniques to optimise the characteristics of pulsed lasers. A weak modulation of the pump power made it possible to obtain a stable repetition rate with a relative stability of 10{sup -6}. The pulse duration was continuously controlled from ten nanoseconds to a few hundreds nanoseconds by three different methods: adjustment of the laser beam diameter in the absorber, adjustment of the pump beam diameter in the active medium, and, in particular, the use of forked eigenstates in a two-axis laser. Moreover, the forked eigenstates allows to increase the pulse energy by coherent addition of the pulses. A compact two-frequency Nd:YAG-Cr:YAG laser with a beat note frequency continuously adjustable up to 2,7 GHz was demonstrated. The two-frequency pulses are ideal sources to meet various needs of applications such as the Doppler lidar-radar. Moreover, we show that two-frequency pulses at 1,55 {mu}m can be obtained by using a new c-cut Co:ASL saturable absorber in an Er-Yb:glass laser. These pulses are perfectly adapted to free-space detection systems requiring eye safety. The coherence time of the beat note in these lasers was also studied: it is limited by the pulse duration. A new technique of modulating the pump power of a solid-state laser at frequencies close to its relaxation oscillation frequency was studied and made it possible to generate a beat note coherence from pulse to pulse. Frequency conversion techniques using the nonlinear optical effects make it possible to obtain tunable two-frequency sources in the visible spectrum. Green and red two-frequency pulses were obtained by using different conversion techniques, intra-cavity or extra-cavity. A two-frequency THz source in the red spectrum was also obtained by doubling the frequencies of a two-frequency THz Er-Yb:glass laser using a mixed fan-out PPLN
DEFF Research Database (Denmark)
Javadi, Hossein; Forouzbakhsh, Farshid; Daei Kasmaei, Hamed
2016-01-01
is the mechanism of increasing in the photon energy that causes increase in its frequency growth? So, in CPH theory (Creative particles of Higgs Theory), it has been attempted to scrutinize the interface between classical mechanics, relativity and quantum mechanics through a novel approach to the established...
Riehle, Fritz
2006-01-01
Of all measurement units, frequency is the one that may be determined with the highest degree of accuracy. It equally allows precise measurements of other physical and technical quantities, whenever they can be measured in terms of frequency.This volume covers the central methods and techniques relevant for frequency standards developed in physics, electronics, quantum electronics, and statistics. After a review of the basic principles, the book looks at the realisation of commonly used components. It then continues with the description and characterisation of important frequency standards
Energy Technology Data Exchange (ETDEWEB)
Macrae, K.I.; Riegert, R.J. (Maryland Univ., College Park (USA). Center for Theoretical Physics)
1984-10-01
We consider a theory in which fermionic matter interacts via long-range scalar, vector and tensor fields. In order not to be in conflict with experiment, the scalar and vector couplings for a given fermion must be equal, as is natural in a dimensionally reduced model. Assuming that the Sun is not approximately neutral with respect to these new scalar-vector charges, and if the couplings saturate the experimental bounds, then their strength can be comparable to that of gravity. Scalar-vector fields of this strength can compensate for a solar quadrupole moment contribution to Mercury's anomalous perihelion precession.
Drago, S.; Sebastiano, Fabio; Leenaerts, Dominicus Martinus Wilhelmus; Breems, Lucien Johannes; Nauta, Bram
2010-01-01
A low power frequency synthesiser circuit (30) for a radio transceiver, the synthesiser circuit comprising: a digital controlled oscillator configured to generate an output signal having a frequency controlled by an input digital control word (DCW); a feedback loop connected between an output and an
Demma, D.J.; Mech, L.D.
2009-01-01
We tested whether Wolf (Canis lupus) visits to individual female White-tailed Deer (Odocoileus virginianus) summer ranges during 2003 and 2004 in northeastern Minnesota were in accord with optimal-foraging theory. Using GPS collars with 10- to 30-minute location attempts on four Wolves and five female deer, plus eleven VHF-collared female deer in the Wolves' territory, provided new insights into the frequency of Wolf visits to summer ranges of female deer. Wolves made a mean 0.055 visits/day to summer ranges of deer three years and older, significantly more than their 0.032 mean visits/day to ranges of two-year-old deer, which generally produce fewer fawns, and most Wolf visits to ranges of older deer were much longer than those to ranges of younger deer. Because fawns comprise the major part of the Wolf's summer diet, this Wolf behavior accords with optimal-foraging theory.
Nonlinear Frequency Compression
Scollie, Susan; Glista, Danielle; Seelisch, Andreas
2013-01-01
Frequency lowering technologies offer an alternative amplification solution for severe to profound high frequency hearing losses. While frequency lowering technologies may improve audibility of high frequency sounds, the very nature of this processing can affect the perceived sound quality. This article reports the results from two studies that investigated the impact of a nonlinear frequency compression (NFC) algorithm on perceived sound quality. In the first study, the cutoff frequency and compression ratio parameters of the NFC algorithm were varied, and their effect on the speech quality was measured subjectively with 12 normal hearing adults, 12 normal hearing children, 13 hearing impaired adults, and 9 hearing impaired children. In the second study, 12 normal hearing and 8 hearing impaired adult listeners rated the quality of speech in quiet, speech in noise, and music after processing with a different set of NFC parameters. Results showed that the cutoff frequency parameter had more impact on sound quality ratings than the compression ratio, and that the hearing impaired adults were more tolerant to increased frequency compression than normal hearing adults. No statistically significant differences were found in the sound quality ratings of speech-in-noise and music stimuli processed through various NFC settings by hearing impaired listeners. These findings suggest that there may be an acceptable range of NFC settings for hearing impaired individuals where sound quality is not adversely affected. These results may assist an Audiologist in clinical NFC hearing aid fittings for achieving a balance between high frequency audibility and sound quality. PMID:23539261
Frequency selective terahertz retroreflectors
Williams, Richard James
The use of novel optical structures operating at terahertz frequencies in industrial and military applications continues to grow. Some of these novel structures include gratings, frequency selective surfaces, metamaterials and metasurfaces, and retroreflectors. A retroreflector is a device that exhibits enhanced backscatter by concentrating the reflected wave in the direction of the source. Retroreflectors have applications in a variety of diverse fields such as aviation, radar systems, antenna technology, communications, navigation, passive identification, and metrology due to their large acceptance angles and frequency bandwidth. This thesis describes the design, fabrication, and characterization of a retroreflector designed for terahertz frequencies and the incorporation of a frequency selective surface in order to endow the retroreflector with narrow-band frequency performance. The radar cross section of several spherical lens reflectors operating at terahertz frequencies was investigated. Spherical lens reflectors with diameters ranging from 2 mm to 8 mm were fabricated from fused silica ball lenses and their radar cross section was measured at 100 GHz, 160 GHz, and 350 GHz. Crossed-dipole frequency selective surfaces exhibiting band-pass characteristics at 350 GHz fabricated from 12 um-thick Nickel screens were applied to the apertures of the spherical lens reflectors. The radar cross section of the frequency selective retroreflectors was measured at 160 GHz and 350 GHz to demonstrate proof-of-concept of narrow-band terahertz performance.
2006-02-06
and a reverberation time of approximately 5 ms. 3. In the marina facing FAU SeaTech, keeping source and receiver static at 20 to 50 m range [9...Both source and receiver can move. In each case, the ambient noise level, bathymetry, channel impulse response, reverberation time , Doppler shift and...in the marina and the turning basin confirmed this statement. Overall, the reverberation time tends to remain within 1 ms, and very occasionally
Brinca, Armando L.; Tsurutani, Bruce T.
1988-01-01
Cometary heavy ions can resonantly excite hydromagnetic wave activity with spacecraft frequency spectra strongly deviating from the ion cyclotron frequency. The influence of the newborn particle temperature on this effect is assessed, its relevance to the interpretation of the observations is discussed, and an alternative, more efficient mechanism to generate spacecraft frequencies of the order of the proton cyclotron frequency is suggested.
DEFF Research Database (Denmark)
Wæver, Ole
2009-01-01
Kenneth N. Waltz's 1979 book, Theory of International Politics, is the most influential in the history of the discipline. It worked its effects to a large extent through raising the bar for what counted as theoretical work, in effect reshaping not only realism but rivals like liberalism and refle......Kenneth N. Waltz's 1979 book, Theory of International Politics, is the most influential in the history of the discipline. It worked its effects to a large extent through raising the bar for what counted as theoretical work, in effect reshaping not only realism but rivals like liberalism...... and reflectivism. Yet, ironically, there has been little attention to Waltz's very explicit and original arguments about the nature of theory. This article explores and explicates Waltz's theory of theory. Central attention is paid to his definition of theory as ‘a picture, mentally formed' and to the radical anti......-empiricism and anti-positivism of his position. Followers and critics alike have treated Waltzian neorealism as if it was at bottom a formal proposition about cause-effect relations. The extreme case of Waltz being so victorious in the discipline, and yet being consistently mis-interpreted on the question of theory...
Directory of Open Access Journals (Sweden)
Kathy Lay
2007-05-01
Full Text Available Objective: Feminism has grown rapidly in the last 40 years as both a multidisciplinary voice advocating for change and an area of scholarship and theory building. A review of empirical articles describes 17 studies that indicate a wide range of applications of feminist theory, but theory is applied primarily as a lens for other issues, rather than to expand theory development. Advocacy and philosophical views seem to overshadow theory development. Suggestions for improving feminist theory are offered.
Reinventing Grounded Theory: Some Questions about Theory, Ground and Discovery
Thomas, Gary; James, David
2006-01-01
Grounded theory's popularity persists after three decades of broad-ranging critique. In this article three problematic notions are discussed--"theory," "ground" and "discovery"--which linger in the continuing use and development of grounded theory procedures. It is argued that far from providing the epistemic security promised by grounded theory,…
Arbitrary optical frequency synthesis traced to an optical frequency comb
Cai, Zihang; Zhang, Weipeng; Yang, Honglei; Li, Yan; Wei, Haoyun
2016-11-01
An arbitrary optical frequency synthesizer with a broad tuning range and high frequency accuracy is presented. The system includes an external cavity diode laser (ECDL) as the output laser, an Erbium-doped optical frequency comb being a frequency reference, and a control module. The optical frequency from the synthesizer can be continuously tuned by the large-scale trans-tooth switch and the fine intra-tooth adjustment. Robust feedback control by regulating the current and PZT voltage enables the ECDL to phase-lock to the Erbium-doped optical frequency comb, therefore to keep stable frequency output. In the meanwhile, the absolute frequency of the synthesizer is determined by the repetition rate, the offset frequency and the beat frequency. All the phase lock loops in the system are traced back to a Rubidium clock. A powerful and friendly software is developed to make the operation convenient by integrating the functions of frequency setting, tuning, tracing, locking and measuring into a LabVIEW interface. The output frequency tuning span and the uncertainty of the system are evaluated as >6 THz and <3 kHz, respectively. The arbitrary optical frequency synthesizer will be a versatile tool in diverse applications, such as synthetic wavelength based absolute distance measurement and frequency-stabilized Cavity Ring-Down Spectroscopy.
Dew, M.; Harrison, F.
1980-02-01
Field strength measurements over 10 to 110 MHz were made using a tracking generator counter, a spectrum analyzer, and a biconal antenna. The dimensions of the shielded enclosure were 6.1 x 3.66 x 3.0 m, and the concrete floored, metal hangar 80 x 40 x 10 m. It was found that in each polarization the hangar performance deviated much less from that in the open air than did the shielded enclosure performance. The latter shows deviations with modulus as great as 38 dB (certical pol) and 26 dB (horizontal pol). For any electric field strength measured in the shielded enclosure (in 10 kHz bandwidth in the range 10 to 110 MHz) the probability that the result would be at least 6 dB different from that similary obtained in the open air was 38% or 43.5% according to polarization and that when similarly measured in the hangar the corresponding probabilities were 0% and 1%. Hangar results were shown to lie much closer to the open air results than do the shielded enclosure results. This is further demonstrated by the rms deviations of the shielded enclosure and hangar readings from those of the open air.
Friedrich, Harald
2016-01-01
This corrected and updated second edition of "Scattering Theory" presents a concise and modern coverage of the subject. In the present treatment, special attention is given to the role played by the long-range behaviour of the projectile-target interaction, and a theory is developed, which is well suited to describe near-threshold bound and continuum states in realistic binary systems such as diatomic molecules or molecular ions. It is motivated by the fact that experimental advances have shifted and broadened the scope of applications where concepts from scattering theory are used, e.g. to the field of ultracold atoms and molecules, which has been experiencing enormous growth in recent years, largely triggered by the successful realization of Bose-Einstein condensates of dilute atomic gases in 1995. The book contains sections on special topics such as near-threshold quantization, quantum reflection, Feshbach resonances and the quantum description of scattering in two dimensions. The level of abstraction is k...
Asynchronous BCI control using high-frequency SSVEP
National Research Council Canada - National Science Library
Diez, Pablo F; Mut, Vicente A; Avila Perona, Enrique M; Laciar Leber, Eric
2011-01-01
...) and high frequency (> 30 Hz). SSVEP-based Brain-Computer Interfaces (BCI) are principally focused on the low and medium range of frequencies whereas there are only a few projects in the high-frequency range...
Energy Technology Data Exchange (ETDEWEB)
Lo, W.-C.; Sposito, G.; Majer, E.
2007-02-01
An analytical theory is presented for the low-frequency behavior of dilatational waves propagating through a homogeneous elastic porous medium containing two immiscible fluids. The theory is based on the Berryman-Thigpen-Chin (BTC) model, in which capillary pressure effects are neglected. We show that the BTC model equations in the frequency domain can be transformed, at sufficiently low frequencies, into a dissipative wave equation (telegraph equation) and a propagating wave equation in the time domain. These partial differential equations describe two independent modes of dilatational wave motion that are analogous to the Biot fast and slow compressional waves in a single-fluid system. The equations can be solved analytically under a variety of initial and boundary conditions. The stipulation of 'low frequency' underlying the derivation of our equations in the time domain is shown to require that the excitation frequency of wave motions be much smaller than a critical frequency. This frequency is shown to be the inverse of an intrinsic time scale that depends on an effective kinematic shear viscosity of the interstitial fluids and the intrinsic permeability of the porous medium. Numerical calculations indicate that the critical frequency in both unconsolidated and consolidated materials containing water and a nonaqueous phase liquid ranges typically from kHz to MHz. Thus engineering problems involving the dynamic response of an unsaturated porous medium to low excitation frequencies (e.g. seismic wave stimulation) should be accurately modeled by our equations after suitable initial and boundary conditions are imposed.
Theory of heterogeneous viscoelasticity
Schirmacher, Walter; Ruocco, Giancarlo; Mazzone, Valerio
2016-03-01
We review a new theory of viscoelasticity of a glass-forming viscous liquid near and below the glass transition. In our model, we assume that each point in the material has a specific viscosity, which varies randomly in space according to a fluctuating activation free energy. We include a Maxwellian elastic term, and assume that the corresponding shear modulus fluctuates as well with the same distribution as that of the activation barriers. The model is solved in coherent potential approximation, for which a derivation is given. The theory predicts an Arrhenius-type temperature dependence of the viscosity in the vanishing frequency limit, independent of the distribution of the activation barriers. The theory implies that this activation energy is generally different from that of a diffusing particle with the same barrier height distribution. If the distribution of activation barriers is assumed to have the Gaussian form, the finite-frequency version of the theory describes well the typical low-temperature alpha relaxation peak of glasses. Beta relaxation can be included by adding another Gaussian with centre at much lower energies than that is responsible for the alpha relaxation. At high frequencies, our theory reduces to the description of an elastic medium with spatially fluctuating elastic moduli (heterogeneous elasticity theory), which explains the occurrence of the boson peak-related vibrational anomalies of glasses.
Surfing in tortoises? Empirical signs of genetic structuring owing to range expansion
Graciá, Eva; Botella, Francisco; Anadón, José Daniel; Edelaar, Pim; Harris, D. James; Giménez, Andrés
2013-01-01
Much of our current knowledge about the genetic dynamics in range expansions originates from models, simulations and microcosm experiments that need to be corroborated by field data. Here, we report a neutral genetic pattern that matches the predictions of the genetic surfing theory. Genetic surfing occurs when repeated founding events and genetic drift act on the wave of advance of an expanding population, promoting strong spatial structure. In the range expansion of the tortoise Testudo graeca from North Africa to southeastern Spain, we found several genetic signatures consistent with surfing: a decrease of genetic diversity with distance from the initial founder area, clinal patterns in allele frequencies, rare African alleles which have become common at distal sites in the Spanish range, and stronger spatial differentiation in the expanded range than in the original one. Our results provide support for the theory that genetic drift can be an important force in shaping the genetic structure of expanding populations. PMID:23554278
Term frequency inverse document frequency (TF-IDF) technique and ...
African Journals Online (AJOL)
Term frequency inverse document frequency (TF-IDF) technique and artificial neural network in email classification system. ... This has inspired attention for urgent need to manage and maintain e-mail. Email messages are expected to be sent and gathered in a warehouse for recurring use as it ranges from inert institutional ...
Variable frequency iteration MPPT for resonant power converters
Zhang, Qian; Bataresh, Issa; Chen, Lin
2015-06-30
A method of maximum power point tracking (MPPT) uses an MPPT algorithm to determine a switching frequency for a resonant power converter, including initializing by setting an initial boundary frequency range that is divided into initial frequency sub-ranges bounded by initial frequencies including an initial center frequency and first and second initial bounding frequencies. A first iteration includes measuring initial powers at the initial frequencies to determine a maximum power initial frequency that is used to set a first reduced frequency search range centered or bounded by the maximum power initial frequency including at least a first additional bounding frequency. A second iteration includes calculating first and second center frequencies by averaging adjacent frequent values in the first reduced frequency search range and measuring second power values at the first and second center frequencies. The switching frequency is determined from measured power values including the second power values.
Efficient Generation of Frequency-Multiplexed Entangled Single Photons
Qiu, Tian-Hui; Xie, Min
2016-12-01
We present two schemes to generate frequency-multiplexed entangled (FME) single photons by coherently mapping photonic entanglement into and out of a quantum memory based on Raman interactions. By splitting a single photon and performing subsequent state transfer, we separate the generation of entanglement and its frequency conversion, and find that the both progresses have the characteristic of inherent determinacy. Our theory can reproduce the prominent features of observed results including pulse shapes and the condition for deterministically generating the FME single photons. The schemes are suitable for the entangled photon pairs with a wider frequency range, and could be immune to the photon loss originating from cavity-mode damping, spontaneous emission, and the dephasing due to atomic thermal motion. The sources might have significant applications in wavelength-division-multiplexing quantum key distribution.
Representation theory of finite monoids
Steinberg, Benjamin
2016-01-01
This first text on the subject provides a comprehensive introduction to the representation theory of finite monoids. Carefully worked examples and exercises provide the bells and whistles for graduate accessibility, bringing a broad range of advanced readers to the forefront of research in the area. Highlights of the text include applications to probability theory, symbolic dynamics, and automata theory. Comfort with module theory, a familiarity with ordinary group representation theory, and the basics of Wedderburn theory, are prerequisites for advanced graduate level study. Researchers in algebra, algebraic combinatorics, automata theory, and probability theory, will find this text enriching with its thorough presentation of applications of the theory to these fields. Prior knowledge of semigroup theory is not expected for the diverse readership that may benefit from this exposition. The approach taken in this book is highly module-theoretic and follows the modern flavor of the theory of finite dimensional ...
Directory of Open Access Journals (Sweden)
Yanghai Li
2016-01-01
Full Text Available Through the analysis of the control theory for steam turbine, the transfer function of the steam turbine control modes in the parallel operation was obtained. The frequency domain analysis indicated that different control modes of turbine control system have different influence on the damping characteristics of the power system. The comparative analysis shows the direction and the degree of the influence under the different oscillation frequency range. This can provide the theory for the suppression of the low-frequency oscillation from turbine side and has a guiding significance for the stability of power system. The results of simulation tests are consistent with the theoretic analysis.
Simple Models of EMI Filters for Low Frequency Range
Directory of Open Access Journals (Sweden)
Z. Raida
2008-09-01
Full Text Available This paper deals with mathematical simulations of EMI filtersÃ¢Â€Â™ performance. These filters are commonly used for the suppressing of electromagnetic interference which penetrates through the power supply networks. The performance of these filters depends on terminating impedances which are plugged to the inputs and outputs clamps of the EMI filters. This paper describes the method by which it is possible to calculate the insertion loss of the filters. The method is based on the modified nodal voltage method. The circuitry of the EMI filters is used for their description. The effect of spurious components is not taken into account. The filter itself is described by set of admittance parameters, which makes the presented method more universal. The calculated results were compared with measured data of several filters for several impedance combinations. Different test setups, like asymmetrical, symmetrical, etc. were taken into account. The simplicity and accuracy of the presented method is discussed in the conclusion. The achieved accuracy is on high level. The described method is universal, but for filters with more than one current compensated inductor, the mentioned method is complicated. The size of the final equation for calculating the insertion loss rapidly increases with the number of current compensated inductors.
High force vibration testing with wide frequency range
Romero, Edward F.; Jepsen, Richard A.; Gregory, Danny Lynn
2013-04-02
A shaker assembly for vibration testing includes first and second shakers, where the first shaker includes a piezo-electric material for generating vibration. A support structure permits a test object to be supported for vibration of the test object by both shakers. An input permits an external vibration controller to control vibration of the shakers.
Vibration of railway bridges in the audible frequency range
Herron, David
2009-01-01
The noise level associated with a train travelling on a bridge is normally greater than that for a train travelling on plain track. It is sometimes the bridge noise that causes the highest levels of disturbance to people in the vicinity or triggers action underregulations such as the Environmental Noise Directive. Consequently, there is a need to study means of predicting noise levels from proposed bridges, noise controlmeasures for existing structures and principles of low-noise bridge desig...
Radio frequency modulation made easy
Faruque, Saleh
2017-01-01
This book introduces Radio Frequency Modulation to a broad audience. The author blends theory and practice to bring readers up-to-date in key concepts, underlying principles and practical applications of wireless communications. The presentation is designed to be easily accessible, minimizing mathematics and maximizing visuals.
Radio frequency propagation made easy
Faruque, Saleh
2015-01-01
This book introduces Radio Frequency Propagation to a broad audience. The author blends theory and practice to bring readers up-to-date in key concepts, underlying principles and practical applications of wireless communications. The presentation is designed to be easily accessible, minimizing mathematics and maximizing visuals.
Energy Technology Data Exchange (ETDEWEB)
Huang, Houbing, E-mail: hbhuang@ustb.edu.cn; Zhao, Congpeng; Ma, Xingqiao, E-mail: xqma@sas.ustb.edu.cn
2017-03-15
We investigated stress-modulated magnetization precession frequency in Heusler-based spin transfer torque oscillator by combining micromagnetic simulations with phase field microelasticity theory, by encapsulating the magnetic tunnel junction into multilayers structures. We proposed a novel method of using an external stress to control the magnetization precession in spin torque oscillator instead of an external magnetic field. The stress-modulated magnetization precession frequency can be linearly modulated by externally applied uniaxial in-plane stress, with a tunable range 4.4–7.0 GHz under the stress of 10 MPa. By comparison, the out-of-plane stress imposes negligible influence on the precession frequency due to the large out-of-plane demagnetization field. The results offer new inspiration to the design of spin torque oscillator devices that simultaneously process high frequency, narrow output band, and tunable over a wide range of frequencies via external stress. - Highlights: • We proposed stress-modulated magnetization precession in spin torque oscillator. • The magnetization precession frequency can be linearly modulated by in-plane stress. • The stress also can widen the magnetization frequency range 4.4–7.0 GHz. • The stress-modulated oscillation frequency can simplify STO devices.
Marino Beiras, Marcos
2011-01-01
We give an overview of the relations between matrix models and string theory, focusing on topological string theory and the Dijkgraaf--Vafa correspondence. We discuss applications of this correspondence and its generalizations to supersymmetric gauge theory, enumerative geometry and mirror symmetry. We also present a brief overview of matrix quantum mechanical models in superstring theory.
DEFF Research Database (Denmark)
Game Theory is a collection of short interviews based on 5 questions presented to some of the most influential and prominent scholars in game theory. We hear their views on game theory, its aim, scope, use, the future direction of game theory and how their work fits in these respects....
Jara, Pascual; Torrecillas, Blas
1988-01-01
The papers in this proceedings volume are selected research papers in different areas of ring theory, including graded rings, differential operator rings, K-theory of noetherian rings, torsion theory, regular rings, cohomology of algebras, local cohomology of noncommutative rings. The book will be important for mathematicians active in research in ring theory.
Energy Technology Data Exchange (ETDEWEB)
Kondo, Koichi [NEC Tokin Corporation, 6-7-1 Koriyama, Taihaku-ku, Sendai, Miyagi 982-8510 (Japan)]. E-mail: kondok@nec-tokin.com; Chiba, Tatsuya [NEC Tokin Corporation, 6-7-1 Koriyama, Taihaku-ku, Sendai, Miyagi 982-8510 (Japan); Ono, Hiroshi [NEC Tokin Corporation, 6-7-1 Koriyama, Taihaku-ku, Sendai, Miyagi 982-8510 (Japan); Yoshida, Shigeyoshi [NEC Tokin Corporation, 6-7-1 Koriyama, Taihaku-ku, Sendai, Miyagi 982-8510 (Japan); Shimada, Yutaka [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Sendai, Miyagi 980-8577 (Japan); Matsushita, Nobuhiro [Department of Physical Electronics, Tokyo Institute of technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552 (Japan); Abe, Masanori [Department of Physical Electronics, Tokyo Institute of technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552 (Japan)
2006-06-15
In order to apply to a novel, flexible type of GHz noise suppressors, we prepared Ni{sub 0.2}Zn{sub x}Fe{sub 2.8-x}O{sub 4} films with x=0.3 and 0.6 and thicknesses of 2 and 5{mu}m, by spin spray ferrite plating from an aqueous solution on polyimide sheets at 90 deg. C. Placing the films onto a microstrip line, we measured transmission loss {delta}P{sub loss} and reflection parameter S{sub 11} at 10MHz-10GHz. As x increased from 0.3 to 0.6, f{sub r} (natural resonance frequency) decreased from 350 to 50MHz, which resulted in decreasing f{sub c} (a frequency from which {delta}P{sub loss} begins rising) from 400 to 100MHz. This means we can tune f{sub c} of the films by changing the Zn concentration x. At 8GHz, {delta}P{sub loss} obtained by the ferrite films increased from 40% to 70% when their thickness increased from 2 to 5{mu}m. We obtained S{sub 11}<10%, irrespective of Zn concentration, in the whole measurement frequency range. By the films with x=0.3 and 2{mu}m thickness we obtained {delta}P{sub loss}=40%, which was as strong as that obtained by a commercially available composite sheet type noise suppressor of 25{mu}m thickness that are made of ferromagnetic metal flakes embedded in a flexible polymer matrix. Moreover, {delta}P{sub loss} by the ferrite film increased to 70% when the thickness was increased to 5{mu}m. Therefore, our NiZn ferrite films are promising to be actually used as GHz noise suppressors with tunable working frequencies that exhibit stronger noise suppression than the commercialized composite type of noise suppressors.
Karlin, Anna R
2016-01-01
This book presents a rigorous introduction to the mathematics of game theory without losing sight of the joy of the subject. This is done by focusing on theoretical highlights (e.g., at least six Nobel Prize winning results are developed from scratch) and by presenting exciting connections of game theory to other fields, such as computer science, economics, social choice, biology, and learning theory. Both classical topics, such as zero-sum games, and modern topics, such as sponsored search auctions, are covered. Along the way, beautiful mathematical tools used in game theory are introduced, including convexity, fixed-point theorems, and probabilistic arguments. The book is appropriate for a first course in game theory at either the undergraduate or graduate level, whether in mathematics, economics, computer science, or statistics. Game theory's influence is felt in a wide range of disciplines, and the authors deliver masterfully on the challenge of presenting both the breadth and coherence of its underlying ...
Design of multi-frequency CW radars
Jankiraman, Mohinder
2007-01-01
This book deals with the basic theory for design and analysis of Low Probability of Intercept (LPI) radar systems. The design of one such multi-frequency high resolution LPI radar, PANDORA, is covered.
THEORY IN RELIGION AND AGING: AN OVERVIEW
Levin, Jeff; Chatters, Linda M.; Taylor, Robert Joseph
2011-01-01
This paper provides an overview of theory in religion, aging, and health. It offers both a primer on theory and a roadmap for researchers. Four “tenses” of theory are described—distinct ways that theory comes into play in this field: grand theory, mid-range theory, use of theoretical models, and positing of constructs which mediate or moderate putative religious effects. Examples are given of both explicit and implicit uses of theory. Sources of theory for this field are then identified, emphasizing perspectives of sociologists and psychologists, and discussion is given to limitations of theory. Finally, reflections are offered as to why theory matters. PMID:20087662
Lovász, László
2009-01-01
This book surveys matching theory, with an emphasis on connections with other areas of mathematics and on the role matching theory has played, and continues to play, in the development of some of these areas. Besides basic results on the existence of matchings and on the matching structure of graphs, the impact of matching theory is discussed by providing crucial special cases and nontrivial examples on matroid theory, algorithms, and polyhedral combinatorics. The new Appendix outlines how the theory and applications of matching theory have continued to develop since the book was first publish
Discrete frequency slice wavelet transform
Yan, Zhonghong; Tao, Ting; Jiang, Zhongwei; Wang, Haibin
2017-11-01
This paper introduces a new kind of Time-Frequency Representation (TFR) method called Discrete Frequency Slice Wavelet Transform (DFSWT). It is an improved version of Frequency Slice Wavelet Transform (FSWT). The previous researches on FSWT show that it is a new efficient TFR in an easy way without strict limitation as traditional wavelet theory. DFSWT as well as FSWT are defined directly in frequency domain, and still keep its properties in time-frequency domain as FSWT decomposition, reconstruction and filter design, etc. However, the original signal is decomposed and reconstructed on a Chosen Frequency Domains (CFD) as need of application. CFD means that the decomposition and reconstruction are not completed on all frequency components. At first, it is important to discuss the necessary condition of CFD to reconstruct the original signal. And then based on norm l2, an optimization algorithm is introduced to reconstruct the original signal even accurately. Finally, for a test example, the TFR analysis of a real life signal is shown. Some conclusions are drawn that the concept of CFD is very useful to application, and the DFSWT can become a simple and easy tool of TFR method, and also provide a new idea of low speed sampling of high frequency signal in applications.
Johnstone, PT
2014-01-01
Focusing on topos theory's integration of geometric and logical ideas into the foundations of mathematics and theoretical computer science, this volume explores internal category theory, topologies and sheaves, geometric morphisms, other subjects. 1977 edition.
Multifrequency radio frequency sensing with photonics-assisted spectrum compression.
Yin, Feifei; Gao, Yuyang; Dai, Yitang; Zhang, Junyi; Xu, Kun; Zhang, Ziping; Li, Jianqiang; Lin, Jintong
2013-11-01
We propose and demonstrate a multifrequency radio frequency (RF) spectrum estimation technology. With photonic assistance, a multifrequency RF signal ranging from 0 to 1 GHz is highly spectrally compressed and sensed using a single analog-to-digital converter with analog bandwidth of 42.6 MHz. By calculating the cross correlation of pseudo random binary sequence and the encoded signal, up to 40 RF tones are precisely recognized without large computational load. The employment of optical mixing decreased the cost and increased the performance compared to its electrical counterpart. The theory and performance are also discussed.
Harris, Tina
2014-01-01
Grounded theory is a popular research approach in health care and the social sciences. This article provides a description of grounded theory methodology and its key components, using examples from published studies to demonstrate practical application. It aims to demystify grounded theory for novice nurse researchers, by explaining what it is, when to use it, why they would want to use it and how to use it. It should enable nurse researchers to decide if grounded theory is an appropriate app...
Predicting fire frequency with chemistry and climate
Richard P. Guyette; Michael C. Stambaugh; Daniel C. Dey; Rose-Marie. Muzika
2012-01-01
A predictive equation for estimating fire frequency was developed from theories and data in physical chemistry, ecosystem ecology, and climatology. We refer to this equation as the Physical Chemistry Fire Frequency Model (PC2FM). The equation was calibrated and validated with North American fire data (170 sites) prior to widespread industrial influences (before ...
Experiments and theory on parametric instabilities excited in HF heating experiments at HAARP
Energy Technology Data Exchange (ETDEWEB)
Kuo, Spencer [New York University-Polytechnic School of Engineering, 5 Metrotech Center, Brooklyn, New York 11201 (United States); Snyder, Arnold [NorthWest Research Associates, P.O. Box 530, Stockton Springs, Maine 04981 (United States); Lee, M. C. [Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215 (United States); Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
2014-06-15
Parametric instabilities excited by O-mode HF heater and the induced ionospheric modification were explored via HAARP digisonde operated in a fast mode. The impact of excited Langmuir waves and upper hybrid waves on the ionosphere are manifested by bumps in the virtual spread, which expand the ionogram echoes upward as much as 140 km and the downward range spread of the sounding echoes, which exceeds 50 km over a significant frequency range. The theory of parametric instabilities is presented. The theory identifies the ionogram bump located between the 3.2 MHz heater frequency and the upper hybrid resonance frequency and the bump below the upper hybrid resonance frequency to be associated with the Langmuir and upper hybrid instabilities, respectively. The Langmuir bump is located close to the upper hybrid resonance frequency, rather than to the heater frequency, consistent with the theory. Each bump in the virtual height spread of the ionogram is similar to the cusp occurring in daytime ionograms at the E-F2 layer transition, indicating that there is a small ledge in the density profile similar to E-F2 layer transitions. The experimental results also show that the strong impact of the upper hybrid instability on the ionosphere can suppress the Langmuir instability.
Energy Technology Data Exchange (ETDEWEB)
Pires, G.F.M.; Rodrigues, H.O. [Departamento de Engenharia de Teleinformatica (DETI), Universidade Federal do Ceara (UFC), CEP 60455-760, Fortaleza, Ceara (Brazil); Laboratorio de Telecomunicacoes e Ciencias e Engenharia de Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara (UFC), Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceara (Brazil); Almeida, J.S.; Sancho, E.O.; Goes, J.C. [Laboratorio de Telecomunicacoes e Ciencias e Engenharia de Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara (UFC), Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceara (Brazil); Costa, M.M. [Departamento de Fisica, Universidade Federal de Mato Grosso (UFMT), Cuiaba (Brazil); Denardin, J.C. [Universidad de Santiago de Chile, Departamento de Fisica, Avenida Ecuador 3493, Estacion Central, Santiago (Chile); Sombra, A.S.B., E-mail: sombra@ufc.b [Laboratorio de Telecomunicacoes e Ciencias e Engenharia de Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara (UFC), Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceara (Brazil)
2010-03-18
In this paper the magnetic and dielectric properties of Y-type hexaferrite (Co{sub 2}Y:Ba{sub 2}Co{sub 2}Fe{sub 12}O{sub 22}) added with 3, 5 and 10 wt.% of PbO and Bi{sub 2}O{sub 3}, obtained in a new procedure of the solid-state method, is presented. The analysis by X-ray diffraction (XRD) using the Rietveld refinement confirmed the formation of single-phase compound with a hexagonal crystal structure (a = b = 5.8560 A and c = 43.4977 A; {alpha} = {beta} = 90{sup o} and {gamma} = 120{sup o}). SEM micrograph of the material shows an uniform distribution of grains throughout the surface of the samples. Detailed studies of the dielectric properties of Co{sub 2}Y, investigated in a wide frequency range (100 Hz to 100 MHz) at room temperature by complex impedance spectroscopy (CIS) technique, showed that these properties are strongly dependent on frequency and on the added level of the impurity. The effect of polyvinyl alcohol (PVA) and tetraethyl orthosilicate (TEOS) on the properties of Co{sub 2}Y hexaferrite was also studied.
Non-Relativistic Superstring Theories
Energy Technology Data Exchange (ETDEWEB)
Kim, Bom Soo
2007-12-14
We construct a supersymmetric version of the 'critical' non-relativistic bosonic string theory [1] with its manifest global symmetry. We introduce the anticommuting bc CFT which is the super partner of the {beta}{gamma} CFT. The conformal weights of the b and c fields are both 1/2. The action of the fermionic sector can be transformed into that of the relativistic superstring theory. We explicitly quantize the theory with manifest SO(8) symmetry and find that the spectrum is similar to that of Type IIB superstring theory. There is one notable difference: the fermions are non-chiral. We further consider 'noncritical' generalizations of the supersymmetric theory using the superspace formulation. There is an infinite range of possible string theories similar to the supercritical string theories. We comment on the connection between the critical non-relativistic string theory and the lightlike Linear Dilaton theory.
Digital frequency control of satellite frequency standards. [Defense Navigation Satellites
Nichols, S. A.
1973-01-01
In the Frequency and Time Standard Development Program of the TIMATION System, a new miniaturized rubidium vapor frequency standard has been tested and analyzed for possible use on the TIMATION 3A launch, as part of the Defense Navigation Satellite Development Program. The design and construction of a digital frequency control was required to remotely control this rubidium vapor frequency standard as well as the quartz oscillator in current use. This control must be capable of accepting commands from a satellite telemetry system, verify that the correct commands have been sent and control the frequency to the requirements of the system. Several modifications must be performed to the rubidium vapor frequency standard to allow it to be compatible with the digital frequency control. These include the addition of a varactor to voltage tune the coarse range of the flywheel oscillator, and a modification to supply the C field current externally. The digital frequency control for the rubidium vapor frequency standard has been successfully tested in prototype form.
High-frequency magnetic components
Kazimierczuk, Marian K
2013-01-01
A unique text on the theory and design fundaments of inductors and transformers, updated with more coverage on the optimization of magnetic devices and many new design examples The first edition is popular among a very broad audience of readers in different areas of engineering and science. This book covers the theory and design techniques of the major types of high-frequency power inductors and transformers for a variety of applications, including switching-mode power supplies (SMPS) and resonant dc-to-ac power inverters and dc-to-dc power converters. It describes eddy-current phenomena (su
Rowen, Louis H
1991-01-01
This is an abridged edition of the author's previous two-volume work, Ring Theory, which concentrates on essential material for a general ring theory course while ommitting much of the material intended for ring theory specialists. It has been praised by reviewers:**""As a textbook for graduate students, Ring Theory joins the best....The experts will find several attractive and pleasant features in Ring Theory. The most noteworthy is the inclusion, usually in supplements and appendices, of many useful constructions which are hard to locate outside of the original sources....The audience of non
Harris, Tina
2015-04-29
Grounded theory is a popular research approach in health care and the social sciences. This article provides a description of grounded theory methodology and its key components, using examples from published studies to demonstrate practical application. It aims to demystify grounded theory for novice nurse researchers, by explaining what it is, when to use it, why they would want to use it and how to use it. It should enable nurse researchers to decide if grounded theory is an appropriate approach for their research, and to determine the quality of any grounded theory research they read.
Microwave Frequency Multiplier
Velazco, J. E.
2017-02-01
High-power microwave radiation is used in the Deep Space Network (DSN) and Goldstone Solar System Radar (GSSR) for uplink communications with spacecraft and for monitoring asteroids and space debris, respectively. Intense X-band (7.1 to 8.6 GHz) microwave signals are produced for these applications via klystron and traveling-wave microwave vacuum tubes. In order to achieve higher data rate communications with spacecraft, the DSN is planning to gradually furnish several of its deep space stations with uplink systems that employ Ka-band (34-GHz) radiation. Also, the next generation of planetary radar, such as Ka-Band Objects Observation and Monitoring (KaBOOM), is considering frequencies in the Ka-band range (34 to 36 GHz) in order to achieve higher target resolution. Current commercial Ka-band sources are limited to power levels that range from hundreds of watts up to a kilowatt and, at the high-power end, tend to suffer from poor reliability. In either case, there is a clear need for stable Ka-band sources that can produce kilowatts of power with high reliability. In this article, we present a new concept for high-power, high-frequency generation (including Ka-band) that we refer to as the microwave frequency multiplier (MFM). The MFM is a two-cavity vacuum tube concept where low-frequency (2 to 8 GHz) power is fed into the input cavity to modulate and accelerate an electron beam. In the second cavity, the modulated electron beam excites and amplifies high-power microwaves at a frequency that is a multiple integer of the input cavity's frequency. Frequency multiplication factors in the 4 to 10 range are being considered for the current application, although higher multiplication factors are feasible. This novel beam-wave interaction allows the MFM to produce high-power, high-frequency radiation with high efficiency. A key feature of the MFM is that it uses significantly larger cavities than its klystron counterparts, thus greatly reducing power density and arcing
Number theory via Representation theory
Indian Academy of Sciences (India)
2014-11-09
Number theory via Representation theory. Eknath Ghate. November 9, 2014. Eightieth Annual Meeting, Chennai. Indian Academy of Sciences1. 1. This is a non-technical 20 minute talk intended for a general Academy audience.