Antenna impedance matching with neural networks.
Hemminger, Thomas L
2005-10-01
Impedance matching between transmission lines and antennas is an important and fundamental concept in electromagnetic theory. One definition of antenna impedance is the resistance and reactance seen at the antenna terminals or the ratio of electric to magnetic fields at the input. The primary intent of this paper is real-time compensation for changes in the driving point impedance of an antenna due to frequency deviations. In general, the driving point impedance of an antenna or antenna array is computed by numerical methods such as the method of moments or similar techniques. Some configurations do lend themselves to analytical solutions, which will be the primary focus of this work. This paper employs a neural control system to match antenna feed lines to two common antennas during frequency sweeps. In practice, impedance matching is performed off-line with Smith charts or relatively complex formulas but they rarely perform optimally over a large bandwidth. There have been very few attempts to compensate for matching errors while the transmission system is in operation and most techniques have been targeted to a relatively small range of frequencies. The approach proposed here employs three small neural networks to perform real-time impedance matching over a broad range of frequencies during transmitter operation. Double stub tuners are being explored in this paper but the approach can certainly be applied to other methodologies. The ultimate purpose of this work is the development of an inexpensive microcontroller-based system.
Theory of fractional order elements based impedance matching networks
Radwan, Ahmed G.
2011-03-01
Fractional order circuit elements (inductors and capacitors) based impedance matching networks are introduced for the first time. In comparison to the conventional integer based L-type matching networks, fractional matching networks are much simpler and versatile. Any complex load can be matched utilizing a single series fractional element, which generally requires two elements for matching in the conventional approach. It is shown that all the Smith chart circles (resistance and reactance) are actually pairs of completely identical circles. They appear to be single for the conventional integer order case, where the identical circles completely overlap each other. The concept is supported by design equations and impedance matching examples. © 2010 IEEE.
Directory of Open Access Journals (Sweden)
Jianfei An
2014-01-01
Full Text Available A new method that is based on genetic algorithm (GA is developed to design electrical impedance matching network for broadband piezoelectric ultrasound transducer. The new method can both optimize the topology of the matching network and perform optimization on the components at the same time. Results of classical algorithms are referenced to reduce the number of candidate topologies and greatly simplify the calculation process. Some calculation strategies, such as elitist strategy and clearing niche method, are adopted during optimization to make sure that the algorithm can convergence to global optimal result. Simulation results show that the new method has advantages over designing complex impedance matching network.
Electronically Tunable Impedance-Matching Networks for Intelligent RF Power Amplifiers
Directory of Open Access Journals (Sweden)
Liang Li
2013-11-01
Full Text Available This paper presents the simulation and optimization design of the electronically tunable impedance-matching networks for intelligent RF power amplifiers in a cognitive radio system. Reconfigurable elements, such as varactors and RF switches are utilized to achieve the dynamic impedance matching both in the input and output matching circuit, providing coarse and fine tuning of the target impedances with low loss and excellent impedance coverage from 500MHz to 800MHz. The topology of varactor model is illustrated to ensure the precision of simulation. In addition, high-precision bias voltage controlling system is designed to improve the nonlinear problem caused by the varactor. The simulation results demonstrate the excellent performance of the tunable networks, satisfying the requirement of the cognitive radio systems.
Wideband Tuning of Impedance Matching for actual RF Networks using AQPSO
Directory of Open Access Journals (Sweden)
Yin Xin
2013-11-01
Full Text Available An adaptive wideband impedance matching technique using a passive PI-network is presented in the paper on the basis of adaptive quantum particle swarm optimization algorithms (AQPSO, which avoiding the drawbacks of the standard particle swarm optimization (PSO algorithm. The Wideband Tuning technique is for actual RF chips. So on-chip models for RF capacitors and inductors are considered. And the effects of the parasitic component loss in the PI-network are analyzed. Then the circuit is simplified according to the sensitivities of the elements. Therefore, the computational complexity is dramatically reduced. Finally, the AQPSO algorithm is adopted to maximize the power transmission efficiency. Simulation results show that the proposed tuning technique can achieve good accuracy of impedance matching and load power. The reflection coefficient and VSWR obtained are also satisfactory. Moreover, the proposed method can be useful for software defined radio systems using a single antenna for multiple mobile and wireless bands.
Influence of the Antenna Impedance Variation and Input Matching Network Q on LNA Key Figures
DEFF Research Database (Denmark)
Ruaro, Andrea; Kvist, Søren Helstrup; Gülstorff, Steen;
2012-01-01
In this paper we present an analysis of the behaviour of a 2:4 GHz Low Noise Amplifier (LNA) for Wireless Body Area Network (WBAN) applications facing antennadetuning issue. An amplifier with ultra-low power, low voltage, and with reduced component count is prototyped to validate simulation results......, then the behaviour is analyzed through simulations based on data measured on real users. The analysis shows that the designed LNA is stable to the antenna impedance variation expectable in most cases, while highlights the possible risks associated to a high-Q input matching network when used in a context prone...... to antenna detuning risk....
Impedance matching network for high frequency ultrasonic transducer for cellular applications.
Kim, Min Gon; Yoon, Sangpil; Kim, Hyung Ham; Shung, K Kirk
2016-02-01
An approach for the design of an impedance matching network (IMN) for high frequency ultrasonic transducers with large apertures based on impedance analysis for cellular applications is presented in this paper. The main objectives were to maximize energy transmission from the excitation source to the ultrasonic transducers for cell manipulation and to achieve low input parameters for the safe operation of an ultrasonic transducer because the piezoelectric material in high frequency ultrasonic transducers is prone to breakage due to its being extremely thin. Two ultrasonic transducers, which were made of lithium niobate single crystal with the thickness of 15 μm, having apertures of 4.3 mm (fnumber=1.23) and 2.6mm (fnumber=0.75) were tested. L-type IMN was selected for high sensitivity and compact design of the ultrasonic transducers. The target center frequency was chosen as the frequency where the electrical admittance (|Y|) and phase angle (θz) from impedance analysis was maximal and zero, respectively. The reference center frequency and reference echo magnitude were selected as the center frequency and echo magnitude, measured by pulse-echo testing, of the ultrasonic transducer without IMN. Initial component values and topology of IMN were determined using the Smith chart, and pulse-echo testing was analyzed to verify the performance of the ultrasonic transducers with and without IMN. After several iterations between changing component values and topology of IMN, and pulse-echo measurement of the ultrasonic transducer with IMN, optimized component values and topology of IMN were chosen when the measured center frequency from pulse-echo testing was comparable to the target frequency, and the measured echo magnitude was at least 30% larger than the reference echo magnitude. Performance of an ultrasonic transducer with and without IMN was tested by observing a tangible dent on the surface of a plastic petridish and single cell response after an acoustic pulse was
Broadband electrical impedance matching for piezoelectric ultrasound transducers.
Huang, Haiying; Paramo, Daniel
2011-12-01
This paper presents a systematic method for designing broadband electrical impedance matching networks for piezoelectric ultrasound transducers. The design process involves three steps: 1) determine the equivalent circuit of the unmatched piezoelectric transducer based on its measured admittance; 2) design a set of impedance matching networks using a computerized Smith chart; and 3) establish the simulation model of the matched transducer to evaluate the gain and bandwidth of the impedance matching networks. The effectiveness of the presented approach is demonstrated through the design, implementation, and characterization of impedance matching networks for a broadband acoustic emission sensor. The impedance matching network improved the power of the acquired signal by 9 times.
Directory of Open Access Journals (Sweden)
Jianfei An
2014-04-01
Full Text Available An improved method based on a genetic algorithm (GA is developed to design a broadband electrical impedance matching network for piezoelectric ultrasound transducer. A key feature of the new method is that it can optimize both the topology of the matching network and perform optimization on the components. The main idea of this method is to find the optimal matching network in a set of candidate topologies. Some successful experiences of classical algorithms are absorbed to limit the size of the set of candidate topologies and greatly simplify the calculation process. Both binary-coded GA and real-coded GA are used for topology optimization and components optimization, respectively. Some calculation strategies, such as elitist strategy and clearing niche method, are adopted to make sure that the algorithm can converge to the global optimal result. Simulation and experimental results prove that matching networks with better performance might be achieved by this improved method.
An, Jianfei; Song, Kezhu; Zhang, Shuangxi; Yang, Junfeng; Cao, Ping
2014-04-16
An improved method based on a genetic algorithm (GA) is developed to design a broadband electrical impedance matching network for piezoelectric ultrasound transducer. A key feature of the new method is that it can optimize both the topology of the matching network and perform optimization on the components. The main idea of this method is to find the optimal matching network in a set of candidate topologies. Some successful experiences of classical algorithms are absorbed to limit the size of the set of candidate topologies and greatly simplify the calculation process. Both binary-coded GA and real-coded GA are used for topology optimization and components optimization, respectively. Some calculation strategies, such as elitist strategy and clearing niche method, are adopted to make sure that the algorithm can converge to the global optimal result. Simulation and experimental results prove that matching networks with better performance might be achieved by this improved method.
Impedance-matched Marx generators
Directory of Open Access Journals (Sweden)
W. A. Stygar
2017-04-01
Full Text Available We have conceived a new class of prime-power sources for pulsed-power accelerators: impedance-matched Marx generators (IMGs. The fundamental building block of an IMG is a brick, which consists of two capacitors connected electrically in series with a single switch. An IMG comprises a single stage or several stages distributed axially and connected in series. Each stage is powered by a single brick or several bricks distributed azimuthally within the stage and connected in parallel. The stages of a multistage IMG drive an impedance-matched coaxial transmission line with a conical center conductor. When the stages are triggered sequentially to launch a coherent traveling wave along the coaxial line, the IMG achieves electromagnetic-power amplification by triggered emission of radiation. Hence a multistage IMG is a pulsed-power analogue of a laser. To illustrate the IMG approach to prime power, we have developed conceptual designs of two ten-stage IMGs with LC time constants on the order of 100 ns. One design includes 20 bricks per stage, and delivers a peak electrical power of 1.05 TW to a matched-impedance 1.22-Ω load. The design generates 113 kV per stage and has a maximum energy efficiency of 89%. The other design includes a single brick per stage, delivers 68 GW to a matched-impedance 19-Ω load, generates 113 kV per stage, and has a maximum energy efficiency of 90%. For a given electrical-power-output time history, an IMG is less expensive and slightly more efficient than a linear transformer driver, since an IMG does not use ferromagnetic cores.
DEFF Research Database (Denmark)
Siwakoti, Yam Prasad; Loh, Poh Chiang; Blaabjerg, Frede;
2014-01-01
This letter introduces a new versatile Y-shaped impedance network for realizing converters that demand a very high-voltage gain, while using a small duty ratio. To achieve that, the proposed network uses a tightly coupled transformer with three windings, whose obtained gain is presently not matched...... by existing networks operated at the same duty ratio. The proposed impedance network also has more degrees of freedom for varying its gain, and hence, more design freedom for meeting requirements demanded from it. This capability has been demonstrated by mathematical derivation, and proven in experiment...
基于 L型网络的高效无源阻抗匹配研究%High-Efficiency Passive Impedance Matching Research Base on L Network
Institute of Scientific and Technical Information of China (English)
邵蕊娜; 张峻梓; 李风光; 闫钧
2015-01-01
In order to maximize the efficiency of passive impedance matching network, taking L network as the basic unit, this paper derives the approximate expression of the efficiency of L network by defining the impedance conversion factor.Based on this, the conditions for the efficiency maximization of the impedance matching network by cascading multiple L network is put forward, that is, the formulae of the number of the cascaded L network and the impedance ratio of every L network are presen-ted.Experimental results show that under 2.6MHz, the impedance matching network designed according to the proposed method has high efficiency, which verifies the validity of the proposed theory and design method.%为了研究无源阻抗匹配网络的效率最大化问题，以L型网络为基本单元，通过定义阻抗变换因数，推导出L型网络效率的近似表达式；以此为基础，提出了多个L型网络级联构成阻抗匹配网络时，实现效率最大化的条件，即级联L型网络的个数和每级L型网络阻抗变比的计算方法。2．6 MHz下的实验结果表明，根据笔者所提出方法设计的阻抗匹配网络具有较高效率，验证了所提出理论和设计方法的有效性。
Impedance matching at arterial bifurcations.
Brown, N
1993-01-01
Reflections of pulse waves will occur in arterial bifurcations unless the impedance is matched continuously through changing geometric and elastic properties. A theoretical model is presented which minimizes pulse wave reflection through bifurcations. The model accounts for the observed linear changes in area within the bifurcation, generalizes the theory to asymmetrical bifurcations, characterizes changes in elastic properties from parent to daughter arteries, and assesses the effect of branch angle on the mechanical properties of daughter vessels. In contradistinction to previous models, reflections cannot be minimized without changes in elastic properties through bifurcations. The theoretical model predicts that in bifurcations with area ratios (beta) less than 1.0 Young's moduli of daughter vessels may be less than that in the parent vessel if the Womersley parameter alpha in the parent vessel is less than 5. Larger area ratios in bifurcations are accompanied by greater increases in Young's moduli of branches. For an idealized symmetric aortic bifurcation (alpha = 10) with branching angles theta = 30 degrees (opening angle 60 degrees) Young's modulus of common iliac arteries relative to that of the distal abdominal aorta has an increase of 1.05, 1.68 and 2.25 for area ratio of 0.8, 1.0 and 1.15, respectively. These predictions are consistent with the observed increases in Young's moduli of peripheral vessels.(ABSTRACT TRUNCATED AT 250 WORDS)
Fractional Order Element Based Impedance Matching
Radwan, Ahmed Gomaa
2014-06-24
Disclosed are various embodiments of methods and systems related to fractional order element based impedance matching. In one embodiment, a method includes aligning a traditional Smith chart (|.alpha.|=1) with a fractional order Smith chart (|.alpha.|.noteq.1). A load impedance is located on the traditional Smith chart and projected onto the fractional order Smith chart. A fractional order matching element is determined by transitioning along a matching circle of the fractional order Smith chart based at least in part upon characteristic line impedance. In another embodiment, a system includes a fractional order impedance matching application executed in a computing device. The fractional order impedance matching application includes logic that obtains a first set of Smith chart coordinates at a first order, determines a second set of Smith chart coordinates at a second order, and determines a fractional order matching element from the second set of Smith chart coordinates.
Active impedance matching of complex structural systems
Macmartin, Douglas G.; Miller, David W.; Hall, Steven R.
1991-01-01
Viewgraphs on active impedance matching of complex structural systems are presented. Topics covered include: traveling wave model; dereverberated mobility model; computation of dereverberated mobility; control problem: optimal impedance matching; H2 optimal solution; statistical energy analysis (SEA) solution; experimental transfer functions; interferometer actuator and sensor locations; active strut configurations; power dual variables; dereverberation of complex structure; dereverberated transfer function; compensators; and relative power flow.
Impedance-matched cavity quantum memory
Afzelius, Mikael
2010-01-01
We consider an atomic frequency comb based quantum memory inside an asymmetric optical cavity. In this configuration it is possible to absorb the input light completely in a system with an effective optical depth of one, provided that the absorption per cavity round trip exactly matches the transmission of the coupling mirror ("impedance matching"). We show that the impedance matching results in a readout efficiency only limited by irreversible atomic dephasing, whose effect can be made very small in systems with large inhomogeneous broadening. Our proposal opens up an attractive route towards quantum memories with close to unit efficiency.
Design of an impedance matching acoustic bend
Yang, Yuzhen; Jia, Han; Lu, Wenjia; Sun, Zhaoyong; Yang, Jun
2017-01-01
We propose the design of an impedance matching acoustic bend in this article. The bending structure is composed of sub-wavelength unit cells with perforated plates and side pipes, whose mass density and bulk modulus can be tuned simultaneously. So the refraction index and the impedance of the acoustic bend can be modulated simultaneously to guarantee both the bending effect and the high transmission. The simulation results of sound pressure field distribution show that the bending effect of t...
Matching network for RF plasma source
Pickard, Daniel S.; Leung, Ka-Ngo
2007-11-20
A compact matching network couples an RF power supply to an RF antenna in a plasma generator. The simple and compact impedance matching network matches the plasma load to the impedance of a coaxial transmission line and the output impedance of an RF amplifier at radio frequencies. The matching network is formed of a resonantly tuned circuit formed of a variable capacitor and an inductor in a series resonance configuration, and a ferrite core transformer coupled to the resonantly tuned circuit. This matching network is compact enough to fit in existing compact focused ion beam systems.
Impedance-matched drilling telemetry system
Normann, Randy A.; Mansure, Arthur J.
2008-04-22
A downhole telemetry system that uses inductance or capacitance as a mode through which signal is communicated across joints between assembled lengths of pipe wherein efficiency of signal propagation through a drill string, for example, over multiple successive pipe segments is enhanced through matching impedances associated with the various telemetry system components.
Impedance matching between ventricle and load.
Piene, H
1984-01-01
Impedance matching in the cardiovascular system is discussed in light of two models of ventricle and load: a Thevenin equivalent consisting of a hydromotive pressure source and an internal, source resistance and compliance in parallel; and a time-varying compliance filled from a constant pressure source and ejecting into a load of three components, a central resistor, a compliance, and a peripheral resistance. According to the Thevenin analog, the energy source and the load are matched when the load resistance is T/t times the internal source resistance (T is total cycle length, t is systolic time interval). Both from this model and from the variable compliance model it appears that optimum matching between source and load depends on the compliance of the Windkessel, as low compliance shifts the matching load resistance to a low value. Animal experiments (isolated cat hearts) indicated that both left and right ventricles at normal loads work close to their maxima of output hydraulic power, and, according to experiments in the right ventricle, maximum power output is related to load resistance and compliance as predicted by the above models. From an experimentally determined relationship among instantaneous ventricular pressure and volume (right ventricle of isolated cat hearts), an optimum load impedance was calculated on the basis of the assumption that the ratio between stroke work and static, potential energy developed in the ventricular cavity is maximum. The optimum load impedance found by this procedure closely resembles the normal input impedance of the cat lung vessel bed.
DEFF Research Database (Denmark)
Siwakoti, Yam Prasad; Blaabjerg, Frede; Galigekere, Veda Prakash;
2016-01-01
A novel A-source impedance network is proposed in this letter. The A-source impedance network uses an autotransformer for realizing converters for any application that demand a very high dc voltage gain. The network utilizes a minimal turns ratio compared to other Magnetically Coupled Impedance S...... with an example single-switch 400 W dc-dc converter. For the closed-loop control design and stability assessment, a small signal model and its analysis of the proposed network are also presented in brief.......A novel A-source impedance network is proposed in this letter. The A-source impedance network uses an autotransformer for realizing converters for any application that demand a very high dc voltage gain. The network utilizes a minimal turns ratio compared to other Magnetically Coupled Impedance...
Impedance Matched Absorptive Thermal Blocking Filters
Wollack, E J; Rostem, K; U-Yen, K
2014-01-01
We have designed, fabricated and characterized absorptive thermal blocking filters for cryogenic microwave applications. The transmission line filter's input characteristic impedance is designed to match $50\\,\\Omega$ and its response has been validated from 0-to-50\\,GHz. The observed return loss in the 0-to-20\\,GHz design band is greater than $20\\,$dB and shows graceful degradation with frequency. Design considerations and equations are provided that enable this approach to be scaled and modified for use in other applications.
阻抗匹配及调配网络参数设计%Design of Impedance Matching and Deployment of Network Parameters
Institute of Scientific and Technical Information of China (English)
李俊学; 李湛宇
2011-01-01
在信息传输系统中，不论是超高频、高频还是低频，阻抗匹配都是一个极为重要的环节。为了能使能量得到有效地传输，使负载得到最大的有效功率，文中给出了阻抗匹配的方法及网络计算公式，同时给出了抑制射频倒送的主要方法。%In the information transmission system, whether it is ultra-high frequency, high frequency or low frequency, impedance matching is an extremely important part. In order to enable the effective transmission of energy, and to maximize the effective power of load, methods of impedance matching and formulas of network computation are proposed, and the inhibition of RF down the main method of delivery is provided.
Energy Technology Data Exchange (ETDEWEB)
Lee, Seung Hyun; Song, Ho Seung; Kim, Jeong Hwan; Cong, Truong Van; Kim, Hui Su; Yeon, Yeong Heum; Lee, Yong seok; Chai, Jong Seo, E-mail: jschai@skku.edu
2015-01-21
The SKKUCY-9 is a compact cyclotron for radioactive isotopes (RI) production of positron emission tomography (PET). Charged particles such as H-ions are accelerated azimuthally within a high intensity electric field (E-field) generated from a radio frequency (RF) system in cyclotron. A high power RF signal is transmitted from an RF amplifier to an RF resonating cavity. The RF system of the SKKUCY-9 operates in continuous wave (CW) mode. If an ion beam were accelerated in the cyclotron, the vacuum level and permittivity would be changed because of beam loading. It causes an impedance shift of the RF resonating cavity. This impedance mismatch generates reflected power that decreases the RF transmitting power. To prevent this situation, an impedance matching system is necessary. This paper describes the impedance matching system of a 20 kW RF amplifier in an SKKUCY-9 compact cyclotron. The impedance matching circuit was designed using both an input stage and output stage, which are divided between the cathode and anode in a vacuum tube that is used as an amplifying device. The equivalent circuit of the matching system is made of passive elements. The characteristic results of designed circuit were calculated using a Smith chart. In assembling, the inductors were replaced by movable stub-line structures. The dimensions of the stub-line structures were optimized with equations and the measurement results. The experiment was performed to find the result values of matching circuit impedance and RF power amplitude.
Impedance matched thin metamaterials make metals absorbing.
Mattiucci, N; Bloemer, M J; Aközbek, N; D'Aguanno, G
2013-11-13
Metals are generally considered good reflectors over the entire electromagnetic spectrum up to their plasma frequency. Here we demonstrate an approach to tailor their absorbing characteristics based on the effective metamaterial properties of thin, periodic metallo-dielectric multilayers by exploiting a broadband, inherently non-resonant, surface impedance matching mechanism. Based on this mechanism, we design, fabricate and test omnidirectional, thin ( 99%) over a frequency range spanning from the UV to the IR. Our approach opens new venues to design cost effective materials for many applications such as thermo-photovoltaic energy conversion devices, light harvesting for solar cells, flat panel display, infrared detectors, stray light reduction, stealth and others.
Impedance matching with an adjustable segmented transmission line.
Qian, Chunqi; Brey, William W
2009-07-01
A capability for impedance matching between the RF probe and the spectrometer is a standard requirement for NMR. Both lumped element and branched transmission line methods are widely used for this purpose. Here, we propose to use the segmented transmission line structure which is well known in wireless communications. It relies upon reflections between transmission lines of different characteristic impedances that are serially connected to match the impedance of a coil or resonator to the characteristic impedance of the NMR spectrometer. In our implementation, two quarter wave length dielectric slugs are placed within a coaxial transmission line. Adjustment of the positions of the slugs allows the variable tuning and matching needed for NMR probes, eliminating the need for variable capacitors and inductors. As a demonstration of the usefulness of this approach, we have incorporated a variable segmented transmission line into a home-built Variable Angle Spinning probe. Finally, we discuss the range of possible application for segmented transmission line networks in NMR probe design.
Novel method for planar microstrip antenna matching impedance
Ali, Mahdi; Samet, Mounir
2010-01-01
Because all microstrip antennas have to be matched to the standard generator impedance or load, the input impedance matching method for antenna is particularly important. In this paper a new methodology in achieving matching impedance of a planar microstrip antenna for wireless application is described. The method is based on embedding an Interdigital capacitor. The fine results obtained by using a microstrip Interdigital capacitor for matching antenna impedance led to an efficient method to improve array antenna performance. In fact, a substantial saving on the whole surfaces as well as enhancement of the gain, the directivity and the power radiated was achieved.
Hybrid-Source Impedance Networks
DEFF Research Database (Denmark)
Li, Ding; Gao, Feng; Loh, Poh Chiang;
2010-01-01
the cascaded networks would have a higher output voltage gain and other unique advantages that currently have not been investigated yet. It is anticipated that these advantages would help the formed inverters find applications in photovoltaic and other renewable systems, where a high voltage gain is usually......Hybrid-source impedance networks have attracted attention among researchers because of their flexibility in performing buck-boost energy conversion. To date, three distinct types of impedance networks can be summarized for implementing voltage-type inverters with another three types summarized...
A Frequency-Tracking and Impedance-Matching Combined System for Robust Wireless Power Transfer
Directory of Open Access Journals (Sweden)
Yanting Luo
2017-01-01
Full Text Available One of the greatest challenges to power embedded devices using magnetically coupled resonant wireless power transfer (WPT system is that the amount of power delivered to the load is very sensitive to load impedance variations. Previous adaptive impedance-matching (IM technologies have drawbacks because adding IM networks, relay coils, or other compensating components in the receiver-side will significantly increase the receiver size. In this paper, a novel frequency-tracking and impedance-matching combined system is proposed to improve the robustness of wireless power transfer for embedded devices. The characteristics of the improved WPT system are investigated theoretically based on the two-port network model. Simulation and experimental studies are carried out to validate the proposed system. The results suggest that the frequency-tracking and impedance-matching combined WPT system can quickly find the best matching points and maintain high power transmission efficiency and output power when the load impedance changes.
Study on electrical impedance matching for broadband ultrasonic transducer
Energy Technology Data Exchange (ETDEWEB)
Kim, Geon Woo [University of Science and Technology, Daejeon (Korea, Republic of); Kim, Ki Bok [Korea Research Institute of Standards and Science, Center for Safety Measurement, Daejeon (Korea, Republic of); Baek, Kwang Sae [Elache Co., Busan (Korea, Republic of)
2017-02-15
Ultrasonic transducers with high resolution and resonant frequency are required to detect small defects (less than hundreds of μm) by ultrasonic testing. The resonance frequency and resolution of an ultrasonic transducer are closely related to the thickness of piezo-electric materials, backing materials, and the electric impedance matching technique. Among these factors, electrical impedance matching plays an important role because it can reduce the loss and reflection of ultrasonic energy differences in electrical impedance between an ultrasonic transducer and an ultrasonic defects detecting system. An LC matching circuit is the most frequently used electric matching method. It is necessary for the electrical impedance of an ultrasonic transducer to correspond to approximately 50 Ω to compensate the difference in electrical impedance between both connections. In this study, a 15 MHz immersion ultrasonic transducer was fabricated and an LC electrical impedance circuit was applied to that for having broad-band frequency characteristic.
Induced optical metric in the non-impedance-matched media
Mousavi, S. A.; Roknizadeh, R.; Sahebdivan, S.
2016-11-01
In non-magnetic anisotropic media, the behavior of electromagnetic waves depends on the polarization and direction of the incident light. Therefore, to tame the unwanted wave responses such as polarization dependent reflections, the artificial impedance-matched media are suggested to be used in optical devices like invisibility cloak or super lenses. Nevertheless, developing the impedance-matched media is far from trivial in practice. In this paper, we are comparing the samples of both impedance-matched and non-impedance-matched (non-magnetic) media regarding their electromagnetic response in constructing a well-defined optical metric. In the case of similar anisotropic patterns, we show that the optical metric in an impedance-matched medium for unpolarized light is the same as the optical metric of an electrical birefringent medium when the extraordinary mode is concerned. By comparing the eikonal equation in an empty curved space-time and its counterparts in the medium, we have shown that a non-impedance-matched medium can resemble an optical metric for a particular polarization. As an example of non-impedance-matched materials, we are studying a medium with varying optical axis profile. We show that such a medium can be an alternative to impedance-matched materials in various optical devices.
On the minimum number of states for switchable matching networks
Firrao, E.L.; Annema, A.J.; Vliet, F.E. van; Nauta, B.
2015-01-01
The impedance of an antenna changes heavily with changing EM environments, while RF power amplifiers (PAs) are optimized for driving a well-defined load impedance. As a solution, switchable matching networks are used in automatic antenna tuners to match the antenna impedance to (about) the desired P
Experiences with active damping and impedance-matching compensators
Betros, Robert S.; Alvarez, Oscar S.; Bronowicki, Allen J.
1993-09-01
TRW has been implementing active damping compensators on smart structures for the past five years. Since that time there have been numerous publications on the use of impedance matching techniques for structural damping augmentation. The idea of impedance matching compensators came about by considering the flow of power in a structure undergoing vibration. The goal of these compensators is to electronically dissipate as much of this flowing power as possible. This paper shows the performance of impedance matching compensators used in smart structures to be comparable to that of active damping compensators. Theoretical comparisons between active damping and impedance matching methods are made using PZT actuators and sensors. The effects of these collocated and non-collocated PZT sensors and actuators on the types of signals they sense and actuate are investigated. A method for automatically synthesizing impedance matching compensators is presented. Problems with implementing broad band active damping and impedance matching compensators on standard Digital Signal Processing (DSP) chips are discussed. Simulations and measurements that compare the performance of active damping and impedance matching techniques for a lightly damped cantilevered beam are shown.
Institute of Scientific and Technical Information of China (English)
李引凡
2013-01-01
The structure and matching range of Γ-section impedance matching network of antenna tuner were introduced at first. Then the Γ-section impedance matching network was analyzed in matching HF tactical whip antenna with different parameters, and the matching curve of inputting resistance and capacitive reactance of antenna can be got with different frequencies and threshold VSWR in various parameters. These analysis can be referenced in designing impedance matching network of antenna tuner and in deciding antenna type matched by antenna tuner.%介绍了天线调谐器Г形阻抗匹配网络的结构形式和匹配区域,分析了Г形网络各参数取不同值时对HF战术鞭状天线的适配性,给出了当参数变化随频率、VSWR门限变化时对HF战术鞭状天线输入电阻和输入容抗的适配曲线,为设计天线调谐器阻抗匹配网络和决定天线调谐器适配天线类型提供了参考.
Impedance Matching of Tapered Slot Antenna using a Dielectric Transformer
Simons, R. N.; Lee, R. Q.
1998-01-01
A new impedance matching technique for tapered slot antennas using a dielectric transformer is presented. The technique is demonstrated by measuring the input impedance, Voltage Standing Wave Ratio (VSWR) and the gain of a Vivaldi antenna (VA). Measured results at Ka-Band frequencies are presented and discussed.
Impedance Conjugate Matching of Plasmonic Nanoantenna in Optical Nanocircuits
DEFF Research Database (Denmark)
Sachkou, Yauhen; Andryieuski, Andrei; Lavrinenko, Andrei
2011-01-01
nanocircuitry to nanoscale optical microscopy and ultra-sensing. The coupling efficiency between nanoantenna and other elements in integrated optical nanocircuit strongly depends on its properties where the impedance matching plays a crucial role. We investigate the dependence of impedance of the T...
基于归一化网络的多枝节阻抗匹配仿真%Simulation Based on Normalized Network of Multi-side Impedance Matching
Institute of Scientific and Technical Information of China (English)
陶喆; 林财兴; 何绪兰
2011-01-01
Impedance matching problem that how to make microwave circuit or system without reflection, let the moving standing wave as close to moving wave as possible to make the maximum power load is generally used the double side match solution. But the strict requirements of conduct may occur match failed. Using the normalized network to compute the multiple side issues, the calculation of the Lossless transmission line matching problem doesn't need to consider the system's characteristic impedance and wavelength, just need to consider the network matrix after the cascade calculations for impedance matching, overcome the inaccuracy of graphical method and the dead zone of the double-side match.%为使微波电路或系统无反射,行驻波尽最接近行波状态,从而使得负载功率达到最大的阻抗匹配问题一般采用双枝节阻抗匹配;但是双枝节匹配对于负载阻抗的电导有严格要求,可能会出现匹配失败.通过归一化网络计算多枝节问题,使计算无耗传输线的匹配问题时无需考虑系统的特性阻抗和波长,只需考虑网络矩阵进行级联计算后的阻抗匹配,弥补了图解法的繁琐、不精确等问题,并且避免了双枝节匹配的死区问题.
Impedance matching through a single passive fractional element
Radwan, Ahmed Gomaa
2012-07-01
For the first time, a generalized admittance Smith chart theory is introduced to represent fractional order circuit elements. The principles of fractional order matching circuits are described. We show that for fractional order α < 1, a single parallel fractional element can match a wider range of load impedances as compared to its series counterpart. Several matching examples demonstrate the versatility of fractional order series and parallel element matching as compared to the conventional approach. © 2012 IEEE.
Zemin Liu; Yu-Pin Hsu; Hella, Mona M
2016-08-01
This paper presents a high-efficiency RF powering system, suitable for individual health monitoring applications. The system is composed of an antenna, an impedance matching network, and a two-stage full-wave RF-DC rectifier. A novel tuning mechanism is proposed to automatically adjust the impedance of the matching network. This mechanism can effectively improve the power efficiency of the system by 47% compared to the case without tuning. For the adaptive impedance, only a 5-bits binary weighted capacitor bank is required in the matching network. The complete system, designed in a standard 0.13μm CMOS technology, converts a -6dBm 915MHz RF signal to a 1.7V DC voltage with an output current of 85μA. The simulated maximum power efficiency of the complete RF harvester is 66%.
Directory of Open Access Journals (Sweden)
Jun He
2015-08-01
Full Text Available A novel compact rat-race ring coupler with meander high-impedance transmission line and port impedance matching is presented in this Letter. First, a ring coupler with high port impedance is designed using meander lines. Secondly, an impedance matching section is designed to match the high port impedance to ordinary 50 Ω. The proposed coupler effectively reduces occupied area to 16.8% of conventional one. The design is validated both by simulation and measurement.
Maximizing switching current of superconductor nanowires via improved impedance matching
Zhang, Labao; Yan, Xiachao; Jia, Xiaoqing; Chen, Jian; Kang, Lin; Wu, Peiheng
2017-02-01
The temporary resistance triggered by phase slips will result in the switching of a superconductor nanowire to a permanent normal state, decreasing the switching current. In this letter, we propose an improved impedance matching circuit that releases the transition triggered by phase slips to the load resistor through the radio frequency (RF) port of a bias tee. The transportation properties with different load resistors indicate that the switching current decreases due to the reflection caused by impedance mismatching, and it is maximized by optimized impedance matching. Compared to the same setup without the impedance matching circuit, the switching current was increased from 8.0 μA to 12.2 μA in a niobium nitride nanowire after releasing the temporary transition triggered by phase slips. The leakage process with impedance matching outputs a voltage pulse, which enables the user to directly register the transition triggered by phase slips. The technique for maximizing the switching current has a potential practical application in superconductor devices, and the technique for counting phase slips may be applied to explore the behavior of phase slips.
Back-action evasion as an alternative to impedance matching.
Yurke, B
1991-04-26
Back-action evasion is a measurement technique originally devised to overcome certain limits imposed by quantum mechanics on the sensitivity of gravitational radiation detectors. The technique is, however, more generally applicable and can be used to improve the sensitivity of instrumentation with noise floors much greater than the quantum noise floor. The principle of back-action evasion is described here by means of a simple example. A comparison of back-action evasion with impedance matching is made to clarify when back-action evasion may be useful. Back-action evasion allows one to achieve a sensitivity comparable to that achieved by impedance matching.
Manipulate acoustic waves by impedance matched acoustic metasurfaces
Wu, Ying; Mei, Jun; Aljahdali, Rasha
We design a type of acoustic metasurface, which is composed of carefully designed slits in a rigid thin plate. The effective refractive indices of different slits are different but the impedances are kept the same as that of the host medium. Numerical simulations show that such a metasurface can redirect or reflect a normally incident wave at different frequencies, even though it is impedance matched to the host medium. We show that the underlying mechanisms can be understood by using the generalized Snell's law, and a unified analytic model based on mode-coupling theory. We demonstrate some simple realization of such acoustic metasurface with real materials. The principle is also extended to the design of planar acoustic lens which can focus acoustic waves. Manipulate acoustic waves by impedance matched acoustic metasurfaces.
Impedance matching, optimum velocity, and ideal middle ears.
Peake, W T; Rosowski, J J
1991-05-01
One way to assess an ear's performance as a receiver of acoustic power is to consider impedance matching at the tympanic membrane. Assumptions about some of the impedances involved have lead to the idea of an optimum velocity magnitude (per unit pressure), which has been used as a test of middle-ear performance. We show that this approach is not a realistic way to assess effectiveness of power absorption at the tympanic membrane. More generally, we suggest that, if the performance of the combined external-and-middle ear in collecting acoustic power and delivering it to the inner ear is considered, the external- and middle-ear power-transfer efficiencies, as well as impedance matching, are involved in relating performance to an ideal.
Enhancement of antenna-coupled microbolometers response by impedance matching
Directory of Open Access Journals (Sweden)
Jorge Simón
2015-10-01
Full Text Available Metallic structures were evaluated to determine the one best matches impedance between lithographic antennas and microbolometers. The best was a 0.28λ transmission line section between the antenna and the microbolometer, 12% longer than what RF theory sets, whose behaviour was compared with other structures. The response was 360% higher.
Quadratic Boost A-Source Impedance Network
DEFF Research Database (Denmark)
Siwakoti, Yam Prasad; Blaabjerg, Frede; Chub, Andrii
2016-01-01
A novel quadratic boost A-source impedance network is proposed to realize converters that demand very high voltage gain. To satisfy the requirement, the network uses an autotransformer where the obtained gain is quadratically dependent on the duty ratio and is unmatched by any existing impedance ...
Institute of Scientific and Technical Information of China (English)
黄蕾
2016-01-01
针对可靠保证电源分配网络的时域瞬态响应、全频域稳态响应、极低目标阻抗、电源及信号完整性设计目标的问题，提出一种基于目标阻抗匹配的电源分配网络设计优化的方法。以低功耗Zigbee遥控器为例，从目标阻抗分配、寄生参数预估、蒙特卡罗分析、回流路径规划、结果对比分析及工程实施探讨这6个方面阐述低功耗大动态电流电路 PDN的设计与优化。基于2级共模电感(双 T型网络)搭建目标 PDN，实现 VRM输出端与 PDN输入端及PDN输入端与输出端的阻抗匹配。结果表明：该方法能够成功指导PDN的设计优化，可以提高实际的PCB设计质量，降低设计风险，减少设计修改和制作的次数，从而缩短市场开发周期、减少开发成本，在工程上是可行的，并具有良好的应用推广价值。%Aiming at the problem of the time domain transient response, steady state response of full frequency domain, low target impedance, power and signal integrity design of the power distribution network, this paper brought forward one kind of the method that design and optimization of power distribution net which is based on matching target impedance. Taking a low-power consumption Zigbee remote as example, this paper discussed the method from 6 aspect which were distribution of target impedance, estimate parasitism parameter, Monte Carlo analysis, back-flow route plan, comparative analysis of simulation result and the project implement. This paper had build the target PDN based on common mode transformer of 2-stair (pair of T types network), realized matching output impedance of VRM to input impedance of PDN, and matching input impedance to output impedance of PDN. Result is indicated, this method is able to guide the design and optimization of PDN successfully, can rise quality of actual PCB design, lessening design risk, cut down the times of designing modification and fabrication, shorten the
Beam steering and impedance matching of plasmonic horn nanoantennas
Afridi, Adeel; Kocabaş, Şükrü Ekin
2016-10-01
In this paper, we study a plasmonic horn nanoantenna on a metal-backed substrate. The horn nanoantenna structure consists of a two-wire transmission line (TWTL) flared at the end. We analyze the effect of the substrate thickness on the nanoantenna's radiation pattern, and demonstrate beam steering in a broad range of elevation angles. Furthermore, we analyze the effect of the ground plane on the impedance matching between the antenna and the TWTL, and observe that the ground plane increases the back reflection into the waveguide. To reduce the reflection, we develop a transmission line model to design an impedance matching section which leads to 99.75% power transmission to the nanoantenna.
Causal impedance matching for broadband hybrid noise absorption.
Yuan, Jing
2003-06-01
The complementary strengths and weaknesses of passive and active noise control (ANC) methods have motivated many researchers to develop hybrid noise absorbers that integrate both control strategies. The impedance matching technique (IMT) is the most effective for such a purpose. An unsolved problem with available IMT schemes is the a priori reference signal that limits IMT applications. This study proposes the use of the forward wave, available by the two-microphone method, as the reference signal. Due to inevitable errors in wave separation and inlet reflection of the control signal, the absorber becomes a feedback system. A simple and stable ANC is developed for impedance matching without the a priori reference signal. The proposed absorber has an absorption coefficient of 0.9 or above in a frequency range of 60-850 Hz. It is stable in the presence of sensor mismatch and robust with respect to significant variation of inlet boundary conditions.
Impedance matching wireless power transmission system for biomedical devices.
Lum, Kin Yun; Lindén, Maria; Tan, Tian Swee
2015-01-01
For medical application, the efficiency and transmission distance of the wireless power transfer (WPT) are always the main concern. Research has been showing that the impedance matching is one of the critical factors for dealing with the problem. However, there is not much work performed taking both the source and load sides into consideration. Both sides matching is crucial in achieving an optimum overall performance, and the present work proposes a circuit model analysis for design and implementation. The proposed technique was validated against experiment and software simulation. Result was showing an improvement in transmission distance up to 6 times, and efficiency at this transmission distance had been improved up to 7 times as compared to the impedance mismatch system. The system had demonstrated a near-constant transfer efficiency for an operating range of 2cm-12cm.
Beam steering and impedance matching of plasmonic horn nanoantennas
Afridi, Adeel
2016-01-01
In this paper, we study a plasmonic horn nanoantenna on a metal-backed substrate. The horn nanoantenna structure consists of a two-wire transmission line (TWTL) flared at the end. We analyze the effect of the substrate thickness on the nanoantenna's radiation pattern, and demonstrate beam steering in a broad range of elevation angles. Furthermore, we analyze the effect of the ground plane on the impedance matching between the antenna and the TWTL, and observe that the ground plane increases the back reflection into the waveguide. To reduce the reflection, we develop a transmission line model to design an impedance matching section which leads to 99.75% power transmission to the nanoantenna.
Bonding and impedance matching of acoustic transducers using silver epoxy.
Son, Kyu Tak; Lee, Chin C
2012-04-01
Silver epoxy was selected to bond transducer plates on glass substrates. The properties and thickness of the bonding medium affect the electrical input impedance of the transducer. Thus, the thickness of the silver epoxy bonding layer was used as a design parameter to optimize the structure for the transducer input impedance to match the 50 Ω output impedance of most radio frequency (RF) generators. Simulation and experimental results show that nearly perfect matching is achieved without using any matching circuit. At the matching condition, the transducer operates at a frequency band a little bit below the half-wavelength resonant frequency of the piezoelectric plate. In experiments, lead titanate (PT) piezoelectric plates were employed. Both full-size, 11.5 mm × 2 mm × 0.4 mm, and half-size, 5.75 mm × 2 mm × 0.4 mm, can be well matched using optimal silver epoxy thickness. The transducer assemblies demonstrate high efficiency. The conversion loss from electrical power to acoustic power in soda-lime glass is 4.3 dB. This loss is low considering the fact that the transducers operate at off-resonance by 12%. With proper choice of silver epoxy thickness, the transducer can be matched at the fundamental, the 3rd and 5th harmonic frequencies. This leads to the possible realization of triple-band transducers. Reliability was assessed with thermal cycling test according to Telcordia GR-468-Core recommendation. Of the 30 transducer assemblies tested, none broke until 2900 cycles and 27 have sustained beyond 4050 cycles.
Micro-Horn Arrays for Ultrasonic Impedance Matching
Rao, Shanti; Palmer, Dean
2009-01-01
Thin-layered structures containing arrays of micromachined horns, denoted solid micro-horn arrays (SMIHAs), have been conceived as improved means of matching acoustic impedances between ultrasonic transducers and the media with which the transducers are required to exchange acoustic energy. Typically, ultrasonic transducers (e.g., those used in medical imaging) are piezoelectric or similar devices, which produce small displacements at large stresses. However, larger displacements at smaller stresses are required in the target media (e.g., human tissues) with which acoustic energy is to be exchanged. Heretofore, efficiencies in transmission of acoustic energy between ultrasonic transducers and target media have been severely limited because substantial mismatches of acoustic impedances have remained, even when coupling material layers have been interposed between the transducers and the target media. In contrast, SMIHAs can, in principle, be designed to effect more nearly complete acoustic impedance matching, leading to power transmission efficiencies of 90 percent or even greater. The SMIHA concept is based on extension, into the higher-frequency/ lower-wavelength ultrasonic range, of the use of horns to match acoustic impedances in the audible and lower-frequency ultrasonic ranges. In matching acoustic impedance in transmission from a higher-impedance acoustic source (e.g., a piezoelectric transducer) and a lowerimpedance target medium (e.g., air or human tissue), a horn acts as a mechanical amplifier. The shape and size of the horn can be optimized for matching acoustic impedance in a specified frequency range. A typical SMIHA would consist of a base plate, a face plate, and an array of horns that would constitute pillars that connect the two plates (see figure). In use, the base plate would be connected to an ultrasonic transducer and the face plate would be placed in contact with the target medium. As at lower frequencies, the sizes and shapes of the pillars
Consideration of impedance matching techniques for efficient piezoelectric energy harvesting.
Kim, Hyeoungwoo; Priya, Shashank; Stephanou, Harry; Uchino, Kenji
2007-09-01
This study investigates multiple levels of impedance-matching methods for piezoelectric energy harvesting in order to enhance the conversion of mechanical to electrical energy. First, the transduction rate was improved by using a high piezoelectric voltage constant (g) ceramic material having a magnitude of g33 = 40 x 10(-3) V m/N. Second, a transducer structure, cymbal, was optimized and fabricated to match the mechanical impedance of vibration source to that of the piezoelectric transducer. The cymbal transducer was found to exhibit approximately 40 times higher effective strain coefficient than the piezoelectric ceramics. Third, the electrical impedance matching for the energy harvesting circuit was considered to allow the transfer of generated power to a storage media. It was found that, by using the 10-layer ceramics instead of the single layer, the output current can be increased by 10 times, and the output load can be reduced by 40 times. Furthermore, by using the multilayer ceramics the output power was found to increase by 100%. A direct current (DC)-DC buck converter was fabricated to transfer the accumulated electrical energy in a capacitor to a lower output load. The converter was optimized such that it required less than 5 mW for operation.
Cascaded impedance networks for NPC inverter
DEFF Research Database (Denmark)
Li, Ding; Gao, Feng; Loh, Poh Chiang;
2010-01-01
would have a higher output voltage gain. It is anticipated that it would help the formed inverters find applications in photovoltaic and other renewable systems, where a high voltage gain is usually requested. Experimental testing has already been conducted and verifies the theory. ©2010 IEEE....... they are subject to the renewable sources. To date, three distinct types of impedance networks can be summarized for implementing a hybrid source impedance network, which can in principle be combined and cascaded before connected to a NPC inverter by proposed two ways. The resulting cascaded impedance network NPC...
Insect sound production: transduction mechanisms and impedance matching.
Bennet-Clark, H C
1995-01-01
The chain of sound production in insects can be summarised as: (1) muscle power-->(2) mechanical vibration of the sound-producing structure-->(3) acoustic loading of this source-->(4) sound radiation. At each link (-->) optimal impedance matching is desirable but, to meet other acoustic requirements, each stage has special properties. The properties of sound waves are discussed in the context of impedance matching between sources of different sizes or configurations and the surrounding fluid medium. Muscles produce high pressures over small areas, but sound sources produce low pressures over large areas. Link 1-->2 requires a change in the force: area ratio between the muscle and the sound source. Because the source size is necessarily small, sounds tend to be produced at a higher frequency than that of the driving muscle contraction, so link 1-->2 may involve a frequency multiplication mechanism. This can also be regarded as a mechanism of impedance matching between the aqueous muscle and the structure from which the insect produces sound. Stage 2 typically involves a resonant structure that determines the song frequency and is excited by link 1-->2. If link 2-->3 provides good impedance matching, the mechanical resonance is likely to be damped, with loss of song purity. So it is desirable for the stage 2 resonance to be sustained by coherent excitation and for the acoustic loading (link 2-->3) to maintain the dominant frequency between stages 2 and 4. Examples where this occurs are cricket wings and cicadas. At stage 3, the source size or configuration should allow impedance matching between the sound source (3) and its load (4). A variety of acoustic devices are exploited, leading to loud, efficient sound production. Examples that use resonant loads, tuned to the insects' song frequency, are the burrows of mole crickets and the abdomens of cicadas. Overall, the mechanisms of sound production of many insects are capable of producing songs of high species
Invisible plasmonic meta-materials through impedance matching to vacuum.
Lee, J W; Seo, M A; Sohn, J Y; Ahn, Y H; Kim, D S; Jeoung, S C; Lienau, Ch; Park, Q-Han
2005-12-26
We report on perfect transmission in two-dimensional plasmonic matamaterials in the terahertz frequency range, in which zeroth order transmittance becomes essentially unity near specific resonance frequencies. Perfect transmission may occur when the plasmonic metamaterials are perfectly impedance matched to vacuum, which is equivalent to designing an effective dielectric constant around epsilonr = -2. When the effective dielectric constant of the metamaterial is tuned towards epsilonr and the hole coverage is larger than 0.2, strong evanescent field builds up in the near field, making perfect transmission possible.
Acoustic impedance matching of piezoelectric transducers to the air.
Gómez Alvarez-Arenas, Tomás E
2004-05-01
The purpose of this work is threefold: to investigate material requirements to produce impedance matching layers for air-coupled piezoelectric transducers, to identify materials that meet these requirements, and to propose the best solution to produce air-coupled piezoelectric transducers for the low megahertz frequency range. Toward this end, design criteria for the matching layers and possible configurations are reviewed. Among the several factors that affect the efficiency of the matching layer, the importance of attenuation is pointed out. A standard characterization procedure is applied to a wide collection of candidate materials to produce matching layers. In particular, some types of filtration membranes are studied. From these results, the best materials are identified, and the better matching configuration is proposed. Four pairs of air-coupled piezoelectric transducers also are produced to illustrate the performance of the proposed solution. The lowest two-way insertion loss figure is -24 dB obtained at 0.45 MHz. This increases for higher frequency transducers up to -42 dB at 1.8 MHz and -50 at 2.25 MHz. Typical bandwidth is about 15-20%.
DEFF Research Database (Denmark)
Siwakoti, Yam P.; Loh, Poh Chiang; Blaabjerg, Frede
2014-01-01
operated at the same duty ratio. This capability has been demonstrated by mathematical derivation for the proposed network in comparison with other recently reported networks. To further prove the network performance, a single-switch dc-dc converter has been implemented with the network, before testing...
Quadratic Boost A-Source Impedance Network
DEFF Research Database (Denmark)
Siwakoti, Yam Prasad; Blaabjerg, Frede; Chub, Andrii
2016-01-01
A novel quadratic boost type A-source impedance network is proposed in this paper for realizing converters that demand a very high voltage gain. To achieve that, the proposed network uses an auto-transformer, whose obtained gain is quadratically dependent on the duty ratio and is presently not ma...
Improved phonocardiogram system based on acoustic impedance matching.
Schwartz, R S; Reeves, J T; Sodal, I E; Barnes, F S
1980-04-01
We considered that phonocardiographic recording could be improved 1) by minimizing the acoustic impedance mismatch between the precordial tissue and transducer, 2) by optimizing the configuration of the impedance-matching medium and transducer design, and 3) by storing signals in digital form through analog-to-digital conversion of analog recordings made at the bedside. The use of an aqueous coupling medium to improve energy transmission increased signal voltage approximately 100-fold over presently used commercial devices. Further match to the crystal was achieved by a concentrating horn configuration for the aqueous medium. Measured frequency response of the device in the range 1 Hz to 1 kHz was better than two other commercially tested microphones. Inspection of comparative phonocardiograms showed more information from the new device than from the two other commercial devices. Unfiltered digitized signals, using our microphone in normal subjects, demonstrated good beat-to-beat repeatability, but analog filtering to obtain the conventional phonocardiogram showed significant loss of information. The new instrument appears to be superior to those commercial devices tested in recording heart sounds.
Phonon impedance matching: minimizing interfacial thermal resistance of thin films
Polanco, Carlos; Zhang, Jingjie; Ghosh, Avik
2014-03-01
The challenge to minimize interfacial thermal resistance is to allow a broad band spectrum of phonons, with non-linear dispersion and well defined translational and rotational symmetries, to cross the interface. We explain how to minimize this resistance using a frequency dependent broadening matrix that generalizes the notion of acoustic impedance to the whole phonon spectrum including symmetries. We show how to ``match'' two given materials by joining them with a single atomic layer, with a multilayer material and with a graded superlattice. Atomic layer ``matching'' requires a layer with a mass close to the arithmetic mean (or spring constant close to the harmonic mean) to favor high frequency phonon transmission. For multilayer ``matching,'' we want a material with a broadening close to the geometric mean to maximize transmission peaks. For graded superlattices, a continuous sequence of geometric means translates to an exponentially varying broadening that generates a wide-band antireflection coating for both the coherent and incoherent limits. Our results are supported by ``first principles'' calculations of thermal conductance for GaAs / Gax Al1 - x As / AlAs thin films using the Non-Equilibrium Greens Function formalism coupled with Density Functional Perturbation Theory. NSF-CAREER (QMHP 1028883), NSF-IDR (CBET 1134311), XSEDE.
Application of an impedance matching transformer to a plasma focus.
Bures, B L; James, C; Krishnan, M; Adler, R
2011-10-01
A plasma focus was constructed using an impedance matching transformer to improve power transfer between the pulse power and the dynamic plasma load. The system relied on two switches and twelve transformer cores to produce a 100 kA pulse in short circuit on the secondary at 27 kV on the primary with 110 J stored. With the two transformer systems in parallel, the Thevenin equivalent circuit parameters on the secondary side of the driver are: C = 10.9 μF, V(0) = 4.5 kV, L = 17 nH, and R = 5 mΩ. An equivalent direct drive circuit would require a large number of switches in parallel, to achieve the same Thevenin equivalent. The benefits of this approach are replacement of consumable switches with non-consumable transformer cores, reduction of the driver inductance and resistance as viewed by the dynamic load, and reduction of the stored energy to produce a given peak current. The system is designed to operate at 100 Hz, so minimizing the stored energy results in less load on the thermal management system. When operated at 1 Hz, the neutron yield from the transformer matched plasma focus was similar to the neutron yield from a conventional (directly driven) plasma focus at the same peak current.
A general theory to analyse and design wireless power transfer based on impedance matching
Liu, Shuo; Chen, Linhui; Zhou, Yongchun; Cui, Tie Jun
2014-10-01
We propose a general theory to analyse and design the wireless power transfer (WPT) systems based on impedance matching. We take two commonly used structures as examples, the transformer-coupling-based WPT and the series/parallel capacitor-based WPT, to show how to design the impedance matching network (IMN) to obtain the maximum transfer efficiency and the maximum output power. Using the impedance matching theory (IMT), we derive a simple expression of the overall transfer efficiency by the coils' quality factors and the coupling coefficient, which has perfect accuracy compared to full-circuit simulations. Full-wave electromagnetic software, CST Microwave Studio, has been used to extract the parameters of coils, thus providing us a comprehensive way to simulate WPT systems directly from the coils' physical model. We have also discussed the relationship between the output power and the transfer efficiency, and found that the maximum output power and the maximum transfer efficiency may occur at different frequencies. Hence, both power and efficiency should be considered in real WPT applications. To validate the proposed theory, two types of WPT experiments have been conducted using 30 cm-diameter coils for lighting a 20 W light bulb with 60% efficiency over a distance of 50 cm. The experimental results have very good agreements to the theoretical predictions.
Analog Video Line Driver with Adaptive Impedance Matching
Nauta, Bram; Dijkstra, Marcel B.
1998-01-01
A new principle for an adaptive line driver is presented. This type of line driver can adapt its output impedance automatically to the applied load. This results in automatically corrected output impedance for different cables with terminations. Also, the line-driver output impedance becomes insensi
Resistor network approaches to electrical impedance tomography
Borcea, Liliana; Vasquez, Fernando Guevara; Mamonov, Alexander V
2011-01-01
We review a resistor network approach to the numerical solution of the inverse problem of electrical impedance tomography (EIT). The networks arise in the context of finite volume discretizations of the elliptic equation for the electric potential, on sparse and adaptively refined grids that we call optimal. The name refers to the fact that the grids give spectrally accurate approximations of the Dirichlet to Neumann map, the data in EIT. The fundamental feature of the optimal grids in inversion is that they connect the discrete inverse problem for resistor networks to the continuum EIT problem.
Optical impedance matching using coupled plasmonic nanoparticle arrays.
Spinelli, P; Hebbink, M; de Waele, R; Black, L; Lenzmann, F; Polman, A
2011-04-13
Silver nanoparticle arrays placed on top of a high-refractive index substrate enhance the coupling of light into the substrate over a broad spectral range. We perform a systematic numerical and experimental study of the light incoupling by arrays of Ag nanoparticle arrays in order to achieve the best impedance matching between light propagating in air and in the substrate. We identify the parameters that determine the incoupling efficiency, including the effect of Fano resonances in the scattering, interparticle coupling, as well as resonance shifts due to variations in the near-field coupling to the substrate and spacer layer. The optimal configuration studied is a square array of 200 nm wide, 125 nm high spheroidal Ag particles, at a pitch of 450 nm on a 50 nm thick Si(3)N(4) spacer layer on a Si substrate. When integrated over the AM1.5 solar spectral range from 300 to 1100 nm, this particle array shows 50% enhanced incoupling compared to a bare Si wafer, 8% higher than a standard interference antireflection coating. Experimental data show that the enhancement occurs mostly in the spectral range near the Si band gap. This study opens new perspectives for antireflection coating applications in optical devices and for light management in Si solar cells.
Gordy, R. S.
1972-01-01
An improved broadband impedance matching technique was developed. The technique is capable of resolving points in the waveguide which generate reflected energy. A version of the comparison reflectometer was developed and fabricated to determine the mean amplitude of the reflection coefficient excited at points in the guide as a function of distance, and the complex reflection coefficient of a specific discontinuity in the guide as a function of frequency. An impedance matching computer program was developed which is capable of impedance matching the characteristics of each disturbance independent of other reflections in the guide. The characteristics of four standard matching elements were compiled, and their associated curves of reflection coefficient and shunt susceptance as a function of frequency are presented. It is concluded that an economical, fast, and reliable impedance matching technique has been established which can provide broadband impedance matches.
Impedance Matching and Emission Properties of Nanoantennas in an Optical Nanocircuit
Huang, Jer-Shing; Feichtner, Thorsten; Biagioni, Paolo; Hecht, Bert
2009-05-01
An experimentally realizable prototype nanophotonic circuit consisting of a receiving and an emitting nano antenna connected by a two-wire optical transmission line is studied using finite-difference time- and frequency-domain simulations. To optimize the coupling between nanophotonic circuit elements we apply impedance matching concepts in analogy to radio frequency technology. We show that the degree of impedance matching, and in particular the impedance of the transmitting nano antenna, can be inferred from the experimentally accessible standing wave pattern on the transmission line. We demonstrate the possibility of matching the nano antenna impedance to the transmission line characteristic impedance by variations of the antenna length and width realizable by modern microfabrication techniques. The radiation efficiency of the transmitting antenna also depends on its geometry but is independent of the degree of impedance matching. Our systems approach to nanophotonics provides the basis for realizing general nanophotonic circuits and a large variety of derived novel devices.
Online impedance matching system for ICRH-RF experiments on SST-1 tokamak
Energy Technology Data Exchange (ETDEWEB)
Joshi, R.; Singh, M.; Jadav, H.M.; Mishra, K.; Singh, Raj; Kulkarni, S.V.; Bora, D.
2015-11-15
High-power radio frequency (RF) heating system in the frequency range of ion cyclotron range of frequencies (ICRF) on tokamak needs a mechanism for matching impedance seen by the antenna in presence of plasma to the generator output impedance for maximum transfer of RF power to the plasma with minimum reflections to avoid damage to the generator. The impedance of the antenna is strongly dependent on edge plasma parameters and the impedance sometimes changes as fast as 10{sup −4} s, while the RF generators used can deliver full power only into constant load impedance. Hence, the matching system with dynamic response in between generator and antenna is very much essential for high power ICRF experiments when the plasma is of longer duration with variable load impedance. For ICRF system on SST-1 tokamak, two automatic matching systems are employed each for one transmission line, which consists of motorized stub tuners and phase shifters to match the antenna impedance in the time scale of 120 ms. As a part of initial testing, online impedance matching system is tested with individual transmission lines and then both the lines are matched simultaneously on a variable dummy load which simulates the plasma load. In order to deliver power to both the lines from a single RF generator, hybrid coupler is used which also protects RF generator from reflections up to certain extent. However for hybrid coupler has to work properly and both the lines should see same load impedance. The automatic matching system is installed on tokamak state super-conducting tokamak (SST-1) and is tested up to 140 kW power in the vacuum vessel of the tokamak. Here we present the details of the online matching system and its testing results. The significant result is that we could match the variable load impedance with the generator impedance within 120 ms by suitably adjusting the step counts of the motor controller.
Input impedance matching of acoustic transducers operating at off-resonant frequencies.
Son, Kyu Tak; Lee, Chin C
2010-12-01
The input impedance matching technique of acoustic transducers at off-resonant frequencies is reported. It uses an inherent impedance property of transducers and thus does not need an external electric matching circuit or extra acoustic matching section. The input electrical equivalent circuit includes a radiation component and a dielectric capacitor. The radiation component consists of a radiation resistance and a radiation reactance. The total reactance is the sum of the radiation reactance and the dielectric capacitive reactance. This reactance becomes zero at two frequencies where the impedance is real. The transducer size can be properly chosen so that the impedance at one of the zero-crossing frequencies is close to 50 Ω, the output impedance of signal generators. At this off-resonant operating frequency, the reflection coefficient of the transducer is minimized without using any matching circuit. Other than the size, the impedance can also be fine tuned by adjusting the thickness of material that bonds the transducer plate to the substrates. The acoustic impedance of the substrate and that of the bonding material can also be used as design elements in the transducer structure to achieve better transducer matching. Lead titanate piezoelectric plates were bonded on Lucite, liquid crystal polymer (LCP), and bismuth (Bi) substrates to produce various transducer structures. Their input impedance was simulated using a transducer model and compared with measured values to illustrate the matching principle.
Impedance matching and emission properties of nanoantennas in an optical nanocircuit.
Huang, Jer-Shing; Feichtner, Thorsten; Biagioni, Paolo; Hecht, Bert
2009-05-01
An experimentally realizable prototype optical nanocircuit consisting of a receiving and an emitting nanoantenna connected by a two-wire optical transmission line is studied using finite-difference time- and frequency-domain simulations. To optimize the coupling between optical nanocircuit elements we apply impedance matching concepts in analogy to radio frequency technology. We show that the degree of impedance matching, and in particular the impedance of the emitting nanoantenna, can be inferred from the experimentally accessible standing wave pattern on the transmission line. We demonstrate the possibility of matching the nanoantenna impedance to the transmission line by variations of the antenna length and width realizable by modern microfabrication techniques. The radiation efficiency of the emitting antenna also depends on its geometry but is independent of the degree of impedance matching. The case study presented here provides the basis for experimental realizations of general optical nanocircuits based on readily available gold nanostructures and a large variety of derived novel devices.
Kaymaksüt, Ercan; Kaymaksut, Ercan
2008-01-01
In this thesis a 5.2 GHz combined power amplifier is designed for Wireless Local Area Network (WLAN) application. A new on-chip power combining technique by using impedance matching Wilkinson power divider circuits will be presented. Two impedance matching Wilkinson power dividers are employed for matching the input and output impedances of the amplifier to 50 (omega)Ω as well as splitting the input power into two amplifiers and combining their output powers. A 5.2 GHz fully integrated class-...
A New Impedance Matching Method for an Ultra-Wide Band and Dual Circularly Polarised Feed
Li, Sha; Yan, Yi Hua; Wang, Wei; Chen, Zhi Jun; Liu, Dong Hao; Zhang, Fu Shun; Jeffrey, Natasha
2016-12-01
In traditional antenna design, metal components are not placed in the central part of the antenna as they change the characteristics of near field radiation. However, we show that placing a metal ring in the centre of the strip lines, which connect the ends of folded high-frequency dipoles, does not damage the performance of the feed. Instead it significantly improves the voltage standing wave ratio of the feed whilst other performance indicators are not compromised. Thus, our findings show an excellent way of improving the wide band feed. Based on this foundation, a new circularly polarised feed for operation between 0.4 to 2 GHz is introduced for the Chinese Spectral Radioheliograph in this paper. The issue of a feed impedance matching network is investigated. By optimising the impedance matching, the performance of the feed is enhanced with respect to the previous realisations of the Eleven feed. The simulation and experimental results show that the gain of the feed is about 10 dBi, and the VSWR is less than 2:1. In addition, the feed has a low axial ratio, fixed phase centre location, and constant beam width in the range of 0.4 to 2 GHz.
Shindo, Y; Kato, K; Hirashima, T; Yabuhara, T
2008-01-01
In this paper, we discuss a new system to make impedance matching automatically for a re-entrant resonant cavity applicator for brain tumor hyperthermia treatment non-invasively. We have already discussed about the effectiveness of the heating method using manual type impedance matching controller, with experiments of heating an agar phantom and computer simulations. However, it becomes difficult to perform an accurate impedance matching as resonant frequency becomes high. Here, in order to make a more accurate impedance matching, we developed the automatic impedance matching system (AIMS). We noticed that the reflected power was generated when the impedance matching was not complete. In this system, therefore, to reduce the reflected power fed back, the stepping motor to turn the dial of variable capacitors is controlled by developed software. To evaluate the developed AIMS, the experiments of heating the agar phantom were performed. From these results, we found that the temperature rise of the agar phantom by using AIMS was about 180% of using manual type controller under the same heating condition. It was found that the proposed system was very effective for hyperthermia treatment using resonant cavity applicator even when the resonant frequency was high.
Printed circuit board impedance matching step for microwave (millimeter wave) devices
Pao, Hsueh-Yuan; Aguirre, Jerardo; Sargis, Paul
2013-10-01
An impedance matching ground plane step, in conjunction with a quarter wave transformer section, in a printed circuit board provides a broadband microwave matching transition from board connectors or other elements that require thin substrates to thick substrate (>quarter wavelength) broadband microwave (millimeter wave) devices. A method of constructing microwave and other high frequency electrical circuits on a substrate of uniform thickness, where the circuit is formed of a plurality of interconnected elements of different impedances that individually require substrates of different thicknesses, by providing a substrate of uniform thickness that is a composite or multilayered substrate; and forming a pattern of intermediate ground planes or impedance matching steps interconnected by vias located under various parts of the circuit where components of different impedances are located so that each part of the circuit has a ground plane substrate thickness that is optimum while the entire circuit is formed on a substrate of uniform thickness.
Narrowband impedance matching layer for high efficiency thickness mode ultrasonic transducers.
Toda, Minoru
2002-03-01
A new matching layer design concept has been proposed for narrowband continuous wave (CW) devices. Analysis has shown that the mechanical impedance of a resonant-type transducer in thickness mode CW operation does not equal its acoustic impedance rhoVs but roughly equals rhoVs/Q, where p is density, Vs is acoustic velocity, and Q is the mechanical quality factor. The value of rhoVs/Q is much lower than the acoustic impedance of water for any transducer material, including lead zirconium titanate (PZT), single crystals, or polyvinylidene fluoride (PVDF). With this new approach, the impedance of the matching layer must also be between water and pVs/Q, but there are few such practical low impedance materials. To realize equivalent low impedance structure, a novel double layer design is presented: a relatively low impedance material (such as polyethylene or polyurethane) on the inside and a relatively high impedance material (such as polyester or metal) on the outside. A high power CW transducer structure was designed and fabricated with PVDF-TrFE (polyvinylidene fluoride trifluoroethylene) to operate at 1.4 MHz. The basic quarter wavelength resonator structure is 0.7-mm alumina/0.2-mm piezo-polymer/0.25-mm polyester, and the matching section is 0.2-mm polyurethane and 0.25-mm polyester. A maximum power output of 6 to 9 W/cm2 with conversion efficiency of 30 to 35% was observed. For the transducer without matching section, the observed power was 3 to 4 W/cm2. Mason's model analyses (1) predict that the traditional matching layer is for broadband purposes and reduces output power both for PZT and PVDF-TrFE (2); this new matching scheme can be applied to PZT high power transducer. This high efficiency technique has application in various CW systems, such as Doppler sensors, interferometry, phase-sensitive imaging, or high energy focused beam systems.
DEFF Research Database (Denmark)
Yoon, Ick-Jae; Christensen, S.; Zhurbenko, Vitaliy
2016-01-01
condition is proposed. It is observed that the improvement ratio of the BW is limited in practical situation. Nevertheless, the measured reflection coefficient of the 3D-printed SSR antenna loaded with the designed active matching circuit shows two-times wider impedance BW than passive matching, verifying...
Matching theory for wireless networks
Han, Zhu; Saad, Walid
2017-01-01
This book provides the fundamental knowledge of the classical matching theory problems. It builds up the bridge between the matching theory and the 5G wireless communication resource allocation problems. The potentials and challenges of implementing the semi-distributive matching theory framework into the wireless resource allocations are analyzed both theoretically and through implementation examples. Academics, researchers, engineers, and so on, who are interested in efficient distributive wireless resource allocation solutions, will find this book to be an exceptional resource. .
Polyimide Aerogels and Porous Membranes for Ultrasonic Impedance Matching to Air
Swank, Aaron J.; Sands, Obed S.; Meador, Mary Ann B.
2014-01-01
This work investigates acoustic impedance matching materials for coupling 200 kHz ultrasonic signals from air to materials with similar acoustic properties to that of water, flesh, rubber and plastics. Porous filter membranes as well as a new class of cross-linked polyimide aerogels are evaluated. The results indicate that a single impedance matching layer consisting of these new aerogel materials will recover nearly half of the loss in the incident-to-transmitted ultrasound intensity associated with an air/water, air/flesh or air/gelatin boundary. Furthermore, the experimental results are obtained where other uncertainties of the "real world" are present such that the observed impedance matching gains are representative of real-world applications. Performance of the matching layer devices is assessed using the idealized 3-layer model of infinite half spaces, yet the experiments conducted use a finite gelatin block as the destination medium.
Optimized Wideband Impedance Matching Balun for Conducting Two-Arm Antennas
Directory of Open Access Journals (Sweden)
Khalid F. A. Hussein
2014-01-01
Full Text Available A split coaxial balun with a step transition of the inner conductor diameter is introduced to satisfy impedance matching between unbalanced feeder and balanced antennas. The location of the step transition along the axis of the balun and the diameter change are two dimensional parameters that are not present in the conventional split coaxial balun. These additional parameters, together with the double slot width, provide more flexibility to design the balun for better impedance matching. The effects of the three dimensional parameters on the input impedance seen at the (unbalanced coaxial line side of the balun are investigated when it is terminated with specific lumped impedance at its (balanced split side. An optimization procedure is introduced to arrive at the balun dimensional parameters to give the best matching with specific load impedance. The proposed balun is designed to feed (balanced two-arm antennas such as the dipole and the bowtie antenna from 50 Ω-coaxial line. The electromagnetic simulation shows that the proposed balun results in a perfect impedance matching. A comparison with the performance of the conventional split balun used to feed a dipole antenna shows that the balun proposed in the present paper gives a much lower value of the return loss at the design frequency and a wider bandwidth for VSWR ≤ 1.5. The simulation results obtained using the MoM are compared with experimental measurements showing good agreement.
An impedance matching of femoral-popliteal arterial grafts: a theoretical study.
Hirayama, H; Nishimura, T; Fukuyama, Y
1997-05-01
We have proposed a mathematical method to investigate the matching conditions for an arterial graft in the femoral-popliteal region from a mechanical stand-point. Pulsatory blood flow, arterial wall motions, and conservation law are expressed by linear dynamical equations based on strict mechanical and constitutional considerations. To express the physiological blood flow in an actual arterial system, the tethering effects from the surrounding tissue and wall tensions were incorporated. The physiological parameters of arterial wall and tethering were utilized from reported experimental data. By complex analysis, mathematical expressions for the local impedance and reflection coefficient were obtained. They include not only blood properties such as viscosity and density, but also arterial properties including elastic modulus, radius, Poisson ratio, wall thickness, wall tension, frequency, and tethering effects from surrounding tissue. A matching condition was defined for minimizing the local impedance and reflection coefficient. The biophysical background was to reduce any mechanical mismatches, thus minimizing the disturbance of the flow velocity profile and shear stress distribution within the artery. Impedance matching in turn diminishes the negative factors for graft substitution represented by intimal hyperplasia and thrombosis. The calculated impedance and reflection coefficient inversed parabolically to functions of the resistance of the host artery, and there was one host arterial resistance that minimized the impedance and reflection coefficient. The present analysis revealed that for matching host artery with an elevated resistance, the dynamic elastic modulus of the wall of the graft that minimizes the impedance and reflection coefficient was increased. This indicates that for a host artery with a high resistance, an impedance matched stiff wall graft is preferable. For a large radius and a compliant host artery on the other hand, a large compliant graft
Wang, Haifeng; Cao, Wenwu
2004-02-01
The quarter-wavelength (lambda/4) acoustic matching layer is a vital component in medical ultrasonic transducers, which can compensate for the large acoustic impedance mismatch between the piezoelectric material and the human body. At high frequencies (approximately 100 MHz), the lambda/4 matching layers become extremely thin, and the characterization of their properties becomes very challenging. We report a method to measure the phase velocity and attenuation of ultra-thin layers using the lambda/4 matching principle, in which the acoustic impedance of the thin layer is between the substrate and water. The method has been successfully used to characterize epoxy films on glass substrate. The experimental results show good agreement in the phase-velocity measurement between our proposed method and the conventional ultrasonic spectroscopy method, but the attenuation measurement is sensitive to the properties of the substrate and water medium as well as the alignment of the sample.
ALD中射频阻抗匹配器的设计与研究%Design and research of RF impedance matching device in ALD
Institute of Scientific and Technical Information of China (English)
孙小孟; 李勇滔; 夏洋; 李超波; 李英杰; 陈盛云; 赵章琰; 秦威
2012-01-01
The design of RF impedance matching device in the atomic layer deposition (ALD) system is described. The impedance matching network was simulated with ADS. Through analyzing the load impedance characteristic before and after the plasma generating in the vacuum chamber, and combining with the simulation results, the control method of impedance matching network when the plasma produce is proposed. The experiment proves that impedance matching can be realized by this impedance matching device and the control method.%阐述原子层沉积系统(ALD)中射频阻抗匹配器的设计方案.利用ADS软件对阻抗匹配网络进行仿真,通过分析ALD真空腔室内等离子体产生前后的负载阻抗变化,结合仿真结果,提出等离子体产生过程中阻抗匹配网络的控制方法.经实验验证,该阻抗匹配器和控制方法可实现阻抗匹配.
Bhagat, M. S.; Biswas, A. K.; Rana, L. B.; Kukreja, L. M.
2012-10-01
Impedance matching in an indigenously developed 2 kW RF-excited fast axial flow (RF-FAF) CO2 laser was seen to be significantly influenced by the capacitance formed between the laser head and the electrodes. We find in the published literature that this capacitance is generally assumed to be negligible while designing the matching network in the RF-FAF CO2 lasers. It is shown that this capacitance could have a significant value and consequently would modify the design of the matching network remarkably for a specific laser design studied in the present case. The widely used discharge load model for capacitively coupled RF (CCRF) discharge excited CO2 laser plasma is extended to include this capacitance. The method of measurement of this capacitance using a bridge and the ANSYS software based simulation of its formation due to the laser head structure are discussed.
High transmission acoustic focusing by impedance-matched acoustic meta-surfaces
Al Jahdali, Rasha
2016-01-19
Impedance is an important issue in the design of acoustic lenses because mismatched impedance is detrimental to real focusing applications. Here, we report two designs of acoustic lenses that focus acoustic waves in water and air, respectively. They are tailored by acoustic meta-surfaces, which are rigid thin plates decorated with periodically distributed sub-wavelength slits. Their respective building blocks are constructed from the coiling-up spaces in water and the layered structures in air. Analytic analysis based on coupled-mode theory and transfer matrix reveals that the impedances of the lenses are matched to those of the background media. With these impedance-matched acoustic lenses, we demonstrate the acoustic focusing effect by finite-element simulations.
Impedance-matching analysis in IR leaky-wave antennas
Premkumar, Navaneeth; Xu, Yuancheng; Lail, Brian A.
2015-08-01
Planar leaky-wave antennas (LWA) that are capable of full-space scanning have long since been the pursuit for applications including, but not limited to, integration onto vehicles and into cameras for wide-angle of view beam-steering. Such a leaky-wave surface (LWS) was designed for long-wave infrared frequencies with frequency scanning capability. The LWS is based on a microstrip patch array design of a leaky-wave impedance surface and is made up of gold microstrip patches on a grounded zinc sulphide substrate. A 1D composite right/left-handed (CRLH) metamaterial made by periodically stacking a unit cell of the LWS in the longitudinal direction to form a LWA was designed. This paper deals with loading the LWA with a nickel bolometer to collect leaky-wave signals. The LWA radiates a backward leaking wave at 30 degrees at 28.3THz and scans through broadside for frequencies 20THz through 40THz. The paper deals with effectively placing the bolometer in order for the collected signal to exhibit the designed frequency regime. An effective way to maximize the power coupling into the load from the antenna is also explored. The benefit of such a metamaterial/holographic antennacoupled detector is its ability to provide appreciable capture cross-sections while delivering smart signals to subwavelength sized detectors. Due to their high-gain, low-profile, fast response time of the detector and ease of fabrication, this IR LWA-coupled bolometer harbors great potential in the areas of high resolution, uncooled, infrared imaging.
Improved Decoupling for 13C coil Arrays Using Non-Conventional Matching and Preamplifier Impedance
DEFF Research Database (Denmark)
Sanchez, Juan Diego; Johansen, Daniel Højrup; Hansen, Rie Beck
In this study, we describe a method to obtain improved preamplifier decoupling for receive-only coils. The method relies on the better decoupling obtained when coils are matched to an impedance higher than 50 . Preamplifiers with inductive imaginary impedance and low real impedance, increase...... the effectiveness of the decoupling. A 2-channel 13C array of 50 mm loop coils show an increase of Q-factor of the coils from 247 to 365. The measured SNR, using two small phantoms, demonstrated a similar improvement....
Fleury, Romain; Alù, Andrea
2014-12-01
Broadband impedance matching and zero reflection of acoustic waves at a planar interface between two natural materials is a rare phenomenon, unlike its optical counterpart, frequently observed for polarized light incident at the Brewster angle. In this article, it is shown that, by inserting a metamaterial layer between two acoustic materials with different impedance, it is possible to artificially realize an extremely broadband Brewster-like acoustic intromission angle window, in which energy is totally transmitted from one natural medium to the other. The metamaterial buffer, composed of acoustically hard materials with subwavelength tapered apertures, provides an interesting way to match the impedances of two media in a broadband fashion, different from traditional methods like quarter-wave matching or Fabry-Pérot resonances, inherently narrowband due to their resonant nature. This phenomenon may be interesting for a variety of applications including energy harvesting, acoustic imaging, ultrasonic transducer technology, and noise control.
Qian, Y; Harris, N R
2014-02-01
This work describes a new approach to impedance matching for ultrasonic transducers. A single matching layer with high acoustic impedance of 16 MRayls is demonstrated to show a bandwidth of around 70%, compared with conventional single matching layer designs of around 50%. Although as a consequence of this improvement in bandwidth, there is a loss in sensitivity, this is found to be similar to an equivalent double matching layer design. Designs are calculated by using the KLM model and are then verified by FEA simulation, with very good agreement Considering the fabrication difficulties encountered in creating a high-frequency double matched design due to the requirement for materials with specific acoustic impedances, the need to accurately control the thickness of layers, and the relatively narrow bandwidths available for conventional single matched designs, the new approach shows advantages in that alternative (and perhaps more practical) materials become available, and offers a bandwidth close to that of a double layer design with the simplicity of a single layer design. The disadvantage is a trade-off in sensitivity. A typical example of a piezoceramic transducer matched to water can give a 70% fractional bandwidth (comparable to an ideal double matched design of 72%) with a 3dB penalty in insertion loss.
Y junctions in photonic crystal channel waveguides: high transmission and impedance matching.
Boscolo, S; Midrio, M; Krauss, T F
2002-06-15
We investigate the efficiency of transmission through photonic crystal Y junctions and show the importance of matching mode symmetries. Furthermore, we show that by adding tuning holes to the input waveguide it is possible to achieve almost perfect impedance matching, leading ideally to unitary transmission through the junction. The model system is based on a triangular photonic lattice of holes in dielectrics to reflect experimental reality.
Boosting Local Field Enhancement by on-Chip Nanofocusing and Impedance-Matched Plasmonic Antennas
DEFF Research Database (Denmark)
Zenin, Vladimir A.; Andryieuski, Andrei; Malureanu, Radu
2015-01-01
-field enhancement that can advantageously be exploited in modern optical nanotechnologies, including signal processing, biochemical sensing, imaging, and spectroscopy. Here, we propose, analyze, and experimentally demonstrate on-chip nanofocusing followed by impedance-matched nanowire antenna excitation in the end...
Impedance-Matched Reduced Acoustic Cloaking with Realizable Mass and Its Layered Design
Institute of Scientific and Technical Information of China (English)
CHEN Huan-Yang; YANG Tao; LUO Xu-Dong; MA Hong-Ru
2008-01-01
We present an impedance-matched reduced version of acoustic cloaking whose mass is in a reasonable range. A layered cloak design with isotropic material is also proposed for the reduced cloak. Numerical calculations from the transfer matrix methods show that the present layered cloak can reduce the scattering of an air cylinder substantially.
Influence of errors in the dimensions of a switched parasitic array on gain and impedance match
CSIR Research Space (South Africa)
Mofolo, MRO
2012-09-01
Full Text Available of these variations on the antenna performance attributes (e.g. gain and impedance match) is estimated using a Monte Carlo simulation. The simulation results demonstrate that the combined effect of all variations in the structural parameters quantify the impact...
Two port network analysis for three impedance based oscillators
Said, Lobna A.
2011-12-01
Two-port network representations are applied to analyze complex networks which can be dissolved into sub-networks connected in series, parallel or cascade. In this paper, the concept of two-port network has been studied for oscillators. Three impedance oscillator based on two port concept has been analyzed using different impedance structures. The effect of each structure on the oscillation condition and the frequency of oscillation have been introduced. Two different implementations using MOS and BJT have been introduced. © 2011 IEEE.
A Low-Profile WLAN Antenna with Inductor and Tuning Stub for Broadband Impedance Matching
Directory of Open Access Journals (Sweden)
Woo-Su Kim
2014-01-01
Full Text Available This paper presents a low-profile multiband antenna suitable for wireless local area networks (WLANs, using a chip inductor and tuning stub for broadband impedance matching. The proposed antenna is compact 12×10×1 mm3 and covers three bands: 2.4-GHz (2.400–2.484 GHz, 5.2-GHz (5.150–5.350 GHz, and 5.8-GHz (5.725–5.825 GHz. The measured 10-dB bandwidths are 12.0% (2.28–2.57 GHz in the lower band for 2.4-GHz WLANs and 39.1% (4.81–7.15 GHz in the upper band for 5 GHz-WLANs. The measured peak gain of the antenna is between 2.7 and 4.39 dBi and the radiation patterns are omnidirectional.
Locating Impedance Change in Electrical Impedance Tomography Based on Multilevel BP Neural Network
Institute of Scientific and Technical Information of China (English)
彭源; 莫玉龙
2003-01-01
Electrical impedance tomography (EIT) is a new computer tomography technology, which reconstructs an impedance (resistivity, conductivity) distribution, or change of impedance, by making voltage and current measurements on the object's periphery.Image reconstruction in EIT is an ill-posed, non-linear inverse problem. A method for finding the place of impedance change in EIT is proposed in this paper, in which a multilevel BP neural network (MBPNN) is used to express the non-linear relation between theimpedance change inside the object and the voltage change measured on the surface of the object. Thus, the location of the impedance change can be decided by the measured voltage variation on the surface. The impedance change is then reconstructed using a linear approximate method. MBPNN can decide the impedance change location exactly without long training time. It alleviates some noise effects and can be expanded, ensuring high precision and space resolution of the reconstructed image that are not possible by using the back projection method.
Enhancing phonon flow through one-dimensional interfaces by impedance matching
Energy Technology Data Exchange (ETDEWEB)
Polanco, Carlos A., E-mail: cap3fe@virginia.edu; Ghosh, Avik W., E-mail: ag7rq@virginia.edu [Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States)
2014-08-28
We extend concepts from microwave engineering to thermal interfaces and explore the principles of impedance matching in 1D. The extension is based on the generalization of acoustic impedance to nonlinear dispersions using the contact broadening matrix Γ(ω), extracted from the phonon self energy. For a single junction, we find that for coherent and incoherent phonons, the optimal thermal conductance occurs when the matching Γ(ω) equals the Geometric Mean of the contact broadenings. This criterion favors the transmission of both low and high frequency phonons by requiring that (1) the low frequency acoustic impedance of the junction matches that of the two contacts by minimizing the sum of interfacial resistances and (2) the cut-off frequency is near the minimum of the two contacts, thereby reducing the spillage of the states into the tunneling regime. For an ultimately scaled single atom/spring junction, the matching criterion transforms to the arithmetic mean for mass and the harmonic mean for spring constant. The matching can be further improved using a composite graded junction with an exponential varying broadening that functions like a broadband antireflection coating. There is, however, a trade off as the increased length of the interface brings in additional intrinsic sources of scattering.
New Magnetically Coupled Impedance (Z-) Source Networks
DEFF Research Database (Denmark)
Siwakoti, Yam Prasad; Blaabjerg, Frede; Loh, Poh Chiang
2016-01-01
by their discontinuous currents drawn from the sources and/or high stresses experienced by their components. This paper thus proposes three new MCIS networks named respectively as quasi-Y-source, quasi-Γ-Z-source and quasi-T-source or quasi-Trans-Z-source networks. These new networks inherit all advantages....... Derivations of all two-winding MCIS networks, including existing and new networks, from the generalized three-winding MCIS networks are then systematically illustrated, before comparing them. Operational principles, mathematical derivations, simulation and experimental results of all studied networks have...
New Power Sharing Control for Inverter-Dominated Microgrid Based on Impedance Match Concept
Gu, Herong; Wang, Deyu; Shen, Hong; Zhao, Wei; Guo, Xiaoqiang
2013-01-01
Power flow control is one of the most important issues for operating the inverter-dominated autonomous microgrid. A technical challenge is how to achieve the accurate active/reactive power sharing of inverters. P-F and Q-V droop control schemes have been widely used for power sharing in the past decades. But they suffer from the poor power sharing in the presence of unequal line impedance. In order to solve the problem, a comprehensive analysis of the power droop control is presented, and a new droop control based on the impedance match concept is proposed in this paper. In addition, the design guidelines of control coefficients and virtual impedance are provided. Finally, the performance evaluation is carried out, and the evaluation results verify the effectiveness of the proposed method. PMID:24453910
New power sharing control for inverter-dominated microgrid based on impedance match concept.
Gu, Herong; Wang, Deyu; Shen, Hong; Zhao, Wei; Guo, Xiaoqiang
2013-01-01
Power flow control is one of the most important issues for operating the inverter-dominated autonomous microgrid. A technical challenge is how to achieve the accurate active/reactive power sharing of inverters. P-F and Q-V droop control schemes have been widely used for power sharing in the past decades. But they suffer from the poor power sharing in the presence of unequal line impedance. In order to solve the problem, a comprehensive analysis of the power droop control is presented, and a new droop control based on the impedance match concept is proposed in this paper. In addition, the design guidelines of control coefficients and virtual impedance are provided. Finally, the performance evaluation is carried out, and the evaluation results verify the effectiveness of the proposed method.
Directory of Open Access Journals (Sweden)
Thuc Phi Duong
2015-07-01
Full Text Available To enable the geometrical freedom envisioned for wireless power transfer (WPT, fast dynamic adaptation to unpredictable changes in receiver position is needed. In this paper, we propose an adaptive impedance-searching system that achieves good impedance matching quickly. For fast and robust operation, the proposed method consists of three steps: system calibration, coarse search, and fine search. The proposed WPT system is characterized using distance variation and lateral and angular misalignment between coils. The measured results indicate that the proposed method significantly reduces searching time from a few minutes to approximately one second. Furthermore, the proposed system achieves impedance matching with good accuracy. The robust impedance-searching capability of the proposed system significantly improves power transfer efficiency. At 6.78 MHz, we achieve a maximum efficiency of 89.7% and a high efficiency of >80% up to a distance of 50 cm. When the center-to-center misalignment is 35 cm, the efficiency is improved from 48.4% to 74.1% with the proposed method. At a distance of 40 cm, the efficiency is higher than 74% for up to 60° of angular rotation. These results agree well with the simulated results obtained using a lumped-element circuit model.
A low-loss SAW-TV-IF filter with an extended impedance matching range.
Yamada, J; Fujita, Y; Shiba, T; Toyama, T
1988-01-01
A novel low-loss SAW (surface acoustic wave) filter for an intermediate frequency (IF) circuit in a color TV receiver has been developed. It consists of an apodized bidirectional and an unapodized group-type unidirectional transducer. The unidirectional transducer is designed to use different numbers of finger pairs in sending and reflecting electrodes for extension of the impedance-matching range. A thin-film capacitor for use as a phase shifter is monolithically fabricated on a 128 degrees Y-X LiNbO(3) substrate. A low insertion loss (11.3 dB) and impedance matching without adjustment are achieved at the same time without increasing the device chip size or number of electrical parts.
Roussy, Georges; Kongmark, Nils
2003-01-01
It is shown that a bi-directional waveguide launcher can be used advantageously for reducing the reflection coefficient mismatch of an input impedance of an applicator. In a simple bi-directional waveguide launcher, the magnetron is placed in the waveguide and generates a nominal field distribution with significant output impedance in both directions of the waveguide. If a standing wave is tolerated in the torus, which connects the launcher and the applicator, the power transfer from the magnetron to the applicator can be optimal, without using special matching devices. It is also possible to match the bi-directional launcher with two inductance stubs near the antenna of the magnetron and use them for supplying a two-input applicator without reflection.
Metallic wave-impedance matching layers for broadband terahertz optical systems.
Kröll, Josef; Darmo, Juraj; Unterrainer, Karl
2007-05-28
We examine the potential of ultra-thin metallic layers for broadband wave-impedance matching in the terahertz frequency range. The metallic layer is modeled using Fresnel formulae for stratified optical medium. Experimental data for chromium and indium-tin-oxide layers, measured using time-domain terahertz spectroscopy over the frequency range 0.4 - 4.5 THz, are compared with theoretical results.
Impedance matching in photonic crystal microcavities for second-harmonic generation.
Di Falco, Andrea; Conti, Claudio; Assanto, Gaetano
2006-01-15
By numerically integrating the three-dimensional Maxwell equations in the time domain with reference to a dispersive quadratically nonlinear material, we study second-harmonic generation in planar photonic crystal microresonators. The proposed scheme allows efficient coupling of the pump radiation to the defect resonant mode. The outcoupled generated second harmonic is maximized by impedance matching the photonic crystal cavity to the output waveguide.
Impedance-Source Networks for Electric Power Conversion Part II
DEFF Research Database (Denmark)
Siwakoti, Yam P.; Peng, Fang Zheng; Blaabjerg, Frede
2015-01-01
Impedance-source networks cover the entire spectrum of electric power conversion applications (dc-dc, dc-ac, ac-dc, ac-ac) controlled and modulated by different modulation strategies to generate the desired dc or ac voltage and current at the output. A comprehensive review of various impedance-source......-network-based power converters has been covered in a previous paper and main topologies were discussed from an application point of view. Now Part II provides a comprehensive review of the most popular control and modulation strategies for impedance-source network-based power converters/inverters. These methods...... topology at a certain power level, switching frequency and demanded dynamic response....
Impedance-Source Networks for Electric Power Conversion Part I
DEFF Research Database (Denmark)
Siwakoti, Yam P.; Peng, Fang Zheng; Blaabjerg, Frede;
2015-01-01
Impedance networks cover the entire of electric power conversion from dc (converter, rectifier), ac (inverter), to phase and frequency conversion (ac-ac) in a wide range of applications. Various converter topologies have been reported in the literature to overcome the limitations and problems...... of the traditional voltage source, current source as well as various classical buck-boost, unidirectional, and bidirectional converter topologies. Proper implementation of the impedance-source network with appropriate switching configurations and topologies reduces the number of power conversion stages in the system...... power chain, which may improve the reliability and performance of the power system. The first part of this paper provides a comprehensive review of the various impedance-source-networks-based power converters and discusses the main topologies from an application point of view. This review paper...
Plasmonic transmission lines: from micro to nano scale with lambda/4 impedance matching.
Ginzburg, Pavel; Orenstein, Meir
2007-05-28
The downscaling of conventional RF transmission lines methodologies to subwavelength plasmonic circuits is discussed and demonstrated for a lambda/4 transformer impedance matching. The nano-size transformer, matching between 0.5mum and 50nm wide plasmonic transmission lines, enhances the coupling efficiency by more than 285% compared to the direct ("end fire") coupling - i.e. harvesting more than 86% of total incident power. The influence of the transverse resonances induced by the metal claddings of the input transmission line on the light harvesting is discussed as well.
Hybrid-source impedance network and its generalized cascading concepts
DEFF Research Database (Denmark)
Li, Ding; Gao, Feng; Loh, Poh Chiang;
2009-01-01
. It is anticipated that these concepts and their formed inverters can find applications in photovoltaic and other renewable systems, which in turn motivate the investigation initiated here on two-level and three-level generalized cascading concepts. In addition to their theoretical performance merits, practical......Hybrid-source impedance networks have attracted attention among researchers because of their flexibility in performing buck-boost energy conversion. To date, three distinct types of impedance networks can be summarized for implementing voltage-type inverters, with another three types summarized...
Optimal Workloop Energetics of Muscle-Actuated Systems: An Impedance Matching View
Farahat, Waleed A.; Herr, Hugh M.
2010-01-01
Integrative approaches to studying the coupled dynamics of skeletal muscles with their loads while under neural control have focused largely on questions pertaining to the postural and dynamical stability of animals and humans. Prior studies have focused on how the central nervous system actively modulates muscle mechanical impedance to generate and stabilize motion and posture. However, the question of whether muscle impedance properties can be neurally modulated to create favorable mechanical energetics, particularly in the context of periodic tasks, remains open. Through muscle stiffness tuning, we hypothesize that a pair of antagonist muscles acting against a common load may produce significantly more power synergistically than individually when impedance matching conditions are met between muscle and load. Since neurally modulated muscle stiffness contributes to the coupled muscle-load stiffness, we further anticipate that power-optimal oscillation frequencies will occur at frequencies greater than the natural frequency of the load. These hypotheses were evaluated computationally by applying optimal control methods to a bilinear muscle model, and also evaluated through in vitro measurements on frog Plantaris longus muscles acting individually and in pairs upon a mass-spring-damper load. We find a 7-fold increase in mechanical power when antagonist muscles act synergistically compared to individually at a frequency higher than the load natural frequency. These observed behaviors are interpreted in the context of resonance tuning and the engineering notion of impedance matching. These findings suggest that the central nervous system can adopt strategies to harness inherent muscle impedance in relation to external loads to attain favorable mechanical energetics. PMID:20532203
Hedlin, Michael A H; Alcoverro, Benoit
2005-04-01
Rosette spatial filters are used at International Monitoring System infrasound array sites to reduce noise due to atmospheric turbulence. A rosette filter consists of several clusters, or rosettes, of low-impedance inlets. Acoustic energy entering each rosette of inlets is summed, acoustically, at a secondary summing manifold. Acoustic energy from the secondary manifolds are summed acoustically at a primary summing manifold before entering the microbarometer. Although rosette filters have been found to be effective at reducing infrasonic noise across a broad frequency band, resonance inside the filters reduces the effectiveness of the filters at high frequencies. This paper presents theoretical and observational evidence that the resonance inside these filters that is seen below 10 Hz is due to reflections occuring at impedance discontinuities at the primary and secondary summing manifolds. Resonance involving reflections at the inlets amplifies noise levels at frequencies above 10 Hz. This paper further reports results from theoretical and observational tests of impedance matching capillaries for removing the resonance problem. Almost total removal of resonant energy below 5 Hz was found by placing impedance matching capillaries adjacent to the secondary summing manifolds in the pipes leading to the primary summing manifold and the microbarometer. Theory and recorded data indicate that capillaries with resistance equal to the characteristic impedance of the pipe connecting the secondary and primary summing manifolds suppresses resonance but does not degrade the reception of acoustic signals. Capillaries at the inlets can be used to remove resonant energy at higher frequencies but are found to be less effective due to the high frequency of this energy outside the frequency band of interest.
Optimal workloop energetics of muscle-actuated systems: an impedance matching view.
Directory of Open Access Journals (Sweden)
Waleed A Farahat
2010-06-01
Full Text Available Integrative approaches to studying the coupled dynamics of skeletal muscles with their loads while under neural control have focused largely on questions pertaining to the postural and dynamical stability of animals and humans. Prior studies have focused on how the central nervous system actively modulates muscle mechanical impedance to generate and stabilize motion and posture. However, the question of whether muscle impedance properties can be neurally modulated to create favorable mechanical energetics, particularly in the context of periodic tasks, remains open. Through muscle stiffness tuning, we hypothesize that a pair of antagonist muscles acting against a common load may produce significantly more power synergistically than individually when impedance matching conditions are met between muscle and load. Since neurally modulated muscle stiffness contributes to the coupled muscle-load stiffness, we further anticipate that power-optimal oscillation frequencies will occur at frequencies greater than the natural frequency of the load. These hypotheses were evaluated computationally by applying optimal control methods to a bilinear muscle model, and also evaluated through in vitro measurements on frog Plantaris longus muscles acting individually and in pairs upon a mass-spring-damper load. We find a 7-fold increase in mechanical power when antagonist muscles act synergistically compared to individually at a frequency higher than the load natural frequency. These observed behaviors are interpreted in the context of resonance tuning and the engineering notion of impedance matching. These findings suggest that the central nervous system can adopt strategies to harness inherent muscle impedance in relation to external loads to attain favorable mechanical energetics.
Optimal workloop energetics of muscle-actuated systems: an impedance matching view.
Farahat, Waleed A; Herr, Hugh M
2010-06-03
Integrative approaches to studying the coupled dynamics of skeletal muscles with their loads while under neural control have focused largely on questions pertaining to the postural and dynamical stability of animals and humans. Prior studies have focused on how the central nervous system actively modulates muscle mechanical impedance to generate and stabilize motion and posture. However, the question of whether muscle impedance properties can be neurally modulated to create favorable mechanical energetics, particularly in the context of periodic tasks, remains open. Through muscle stiffness tuning, we hypothesize that a pair of antagonist muscles acting against a common load may produce significantly more power synergistically than individually when impedance matching conditions are met between muscle and load. Since neurally modulated muscle stiffness contributes to the coupled muscle-load stiffness, we further anticipate that power-optimal oscillation frequencies will occur at frequencies greater than the natural frequency of the load. These hypotheses were evaluated computationally by applying optimal control methods to a bilinear muscle model, and also evaluated through in vitro measurements on frog Plantaris longus muscles acting individually and in pairs upon a mass-spring-damper load. We find a 7-fold increase in mechanical power when antagonist muscles act synergistically compared to individually at a frequency higher than the load natural frequency. These observed behaviors are interpreted in the context of resonance tuning and the engineering notion of impedance matching. These findings suggest that the central nervous system can adopt strategies to harness inherent muscle impedance in relation to external loads to attain favorable mechanical energetics.
Wong, Yan Chiew
2014-01-01
Tunability and adaptability for radio frequency (RF) front-ends are highly desirable because they not only enhance functionality and performance but also reduce the circuit size and cost. This thesis presents a number of novel design strategies in DC-DC converters, impedance networks and adaptive algorithms for tunable and adaptable RF based mobile telecommunication systems. Specifically, the studies are divided into three major directions: (a) high voltage switch controller ba...
Anatomy Ontology Matching Using Markov Logic Networks
Directory of Open Access Journals (Sweden)
Chunhua Li
2016-01-01
Full Text Available The anatomy of model species is described in ontologies, which are used to standardize the annotations of experimental data, such as gene expression patterns. To compare such data between species, we need to establish relationships between ontologies describing different species. Ontology matching is a kind of solutions to find semantic correspondences between entities of different ontologies. Markov logic networks which unify probabilistic graphical model and first-order logic provide an excellent framework for ontology matching. We combine several different matching strategies through first-order logic formulas according to the structure of anatomy ontologies. Experiments on the adult mouse anatomy and the human anatomy have demonstrated the effectiveness of proposed approach in terms of the quality of result alignment.
Impedance matching vertical optical waveguide couplers for dense high index contrast circuits.
Sun, Rong; Beals, Mark; Pomerene, Andrew; Cheng, Jing; Hong, Ching-Yin; Kimerling, Lionel; Michel, Jurgen
2008-08-04
We designed and demonstrated a compact, high-index contrast (HIC) vertical waveguide coupler for TE single mode operation with the lowest coupling loss of 0.20 dB +/- 0.05 dB at 1550 nm. Our vertical coupler consists of a pair of vertically overlapping inverse taper structures made of SOI and amorphous silicon. The vertical coupler can suppress power oscillation observed in regular directional couplers and guarantees vertical optical impedance matching with great tolerance for fabrication and refractive index variations of the waveguide materials. The coupler furthermore shows excellent broadband coupling efficiencies between 1460 nm and 1570 nm.
Impedance Matching Antenna-Integrated High-Efficiency Energy Harvesting Circuit.
Shinki, Yuharu; Shibata, Kyohei; Mansour, Mohamed; Kanaya, Haruichi
2017-08-01
This paper describes the design of a high-efficiency energy harvesting circuit with an integrated antenna. The circuit is composed of series resonance and boost rectifier circuits for converting radio frequency power into boosted direct current (DC) voltage. The measured output DC voltage is 5.67 V for an input of 100 mV at 900 MHz. Antenna input impedance matching is optimized for greater efficiency and miniaturization. The measured efficiency of this antenna-integrated energy harvester is 60% for -4.85 dBm input power and a load resistance equal to 20 kΩ at 905 MHz.
Antenna-load interactions at optical frequencies: impedance matching to quantum systems.
Olmon, R L; Raschke, M B
2012-11-09
The goal of antenna design at optical frequencies is to deliver optical electromagnetic energy to loads in the form of, e.g., atoms, molecules or nanostructures, or to enhance the radiative emission from such structures, or both. A true optical antenna would, on a qualitatively new level, control the light-matter interaction on the nanoscale for controlled optical signal transduction, radiative decay engineering, quantum coherent control, and super-resolution microscopy, and provide unprecedented sensitivity in spectroscopy. Resonant metallic structures have successfully been designed to approach these goals. They are called optical antennas in analogy to radiofrequency (RF) antennas due to their capability to collect and control electromagnetic fields at optical frequencies. However, in contrast to the RF, where exact design rules for antennas, waveguides, and antenna-load matching in terms of their impedances are well established, substantial physical differences limit the simple extension of the RF concepts into the optical regime. Key distinctions include, for one, intrinsic material resonances including quantum state excitations (metals, metal oxides, semiconductor homo- and heterostructures) and extrinsic resonances (surface plasmon/phonon polaritons) at optical frequencies. Second, in the absence of discrete inductors, capacitors, and resistors, new design strategies must be developed to impedance match the antenna to the load, ultimately in the form of a vibrational, electronic, or spin excitation on the quantum level. Third, there is as yet a lack of standard performance metrics for characterizing, comparing and quantifying optical antenna performance. Therefore, optical antenna development is currently challenged at all the levels of design, fabrication, and characterization. Here we generalize the ideal antenna-load interaction at optical frequencies, characterized by three main steps: (i) far-field reception of a propagating mode exciting an antenna
On the Design of Conical Antennas for Broadband Impedance Matching Performance
Directory of Open Access Journals (Sweden)
Francisco Estêvão Simão Pereira
2017-01-01
Full Text Available In the scope of broadband radiators, the biconical antenna, or its monopole conical counterpart, is long known to be a proper choice. One common form of such radiator, the spherically capped conical antenna (SCCA, has closed-form solution to its input impedance, from which the broadband performance potential is easily verified. Nonetheless, from the design perspective, apart from a few clues inferred from existing solutions, little is found to accurately guide the choice of the main geometrical parameters of the antenna that will enable it to comply with a set of imposed bandwidth requirements. This paper proposes a simple 10-step sequence to derive conical or biconical antenna design charts. These charts provide straightforward information on the geometrical limits within which the required antenna impedance matching broadband performance is achieved. The method is assessed for the SCCA and the open conical antenna (OCA using theoretical and simulated estimates of the input impedance. A discussion on the impact of the cap and the feed gap is included.
Broadband gradient impedance matching using an acoustic metamaterial for ultrasonic transducers
Li, Zheng; Yang, Dan-Qing; Liu, Shi-Lei; Yu, Si-Yuan; Lu, Ming-Hui; Zhu, Jie; Zhang, Shan-Tao; Zhu, Ming-Wei; Guo, Xia-Sheng; Wu, Hao-Dong; Wang, Xin-Long; Chen, Yan-Feng
2017-02-01
High-quality broadband ultrasound transducers yield superior imaging performance in biomedical ultrasonography. However, proper design to perfectly bridge the energy between the active piezoelectric material and the target medium over the operating spectrum is still lacking. Here, we demonstrate a new anisotropic cone-structured acoustic metamaterial matching layer that acts as an inhomogeneous material with gradient acoustic impedance along the ultrasound propagation direction. When sandwiched between the piezoelectric material unit and the target medium, the acoustic metamaterial matching layer provides a broadband window to support extraordinary transmission of ultrasound over a wide frequency range. We fabricated the matching layer by etching the peeled silica optical fibre bundles with hydrofluoric acid solution. The experimental measurement of an ultrasound transducer equipped with this acoustic metamaterial matching layer shows that the corresponding ‑6 dB bandwidth is able to reach over 100%. This new material fully enables new high-end piezoelectric materials in the construction of high-performance ultrasound transducers and probes, leading to considerably improved resolutions in biomedical ultrasonography and compact harmonic imaging systems.
Antennas with non-foster matching networks
Aberle, James T
2007-01-01
Most antenna engineers are likely to believe that antennas are one technology that is more or less impervious to the rapidly advancing semiconductor industry. However, as demonstrated in this lecture, there is a way to incorporate active components into an antenna and transform it into a new kind of radiating structure that can take advantage of the latest advances in analog circuit design. The approach for making this transformation is to make use of non-Foster circuit elements in the matching network of the antenna. By doing so, we are no longer constrained by the laws of physics that apply
Franek, James; Brandt, Steven; Berger, Birk; Liese, Martin; Barthel, Matthias; Schüngel, Edmund; Schulze, Julian
2015-05-01
We present a novel radio-frequency (RF) power supply and impedance matching to drive technological plasmas with customized voltage waveforms. It is based on a system of phase-locked RF generators that output single frequency voltage waveforms corresponding to multiple consecutive harmonics of a fundamental frequency. These signals are matched individually and combined to drive a RF plasma. Electrical filters are used to prevent parasitic interactions between the matching branches. By adjusting the harmonics' phases and voltage amplitudes individually, any voltage waveform can be approximated as a customized finite Fourier series. This RF supply system is easily adaptable to any technological plasma for industrial applications and allows the commercial utilization of process optimization based on voltage waveform tailoring for the first time. Here, this system is tested on a capacitive discharge based on three consecutive harmonics of 13.56 MHz. According to the Electrical Asymmetry Effect, tuning the phases between the applied harmonics results in an electrical control of the DC self-bias and the mean ion energy at almost constant ion flux. A comparison with the reference case of an electrically asymmetric dual-frequency discharge reveals that the control range of the mean ion energy can be significantly enlarged by using more than two consecutive harmonics.
Controllable transmission and total reflection through an impedance-matched acoustic metasurface
Mei, Jun
2014-12-02
A general design paradigm for a novel type of acoustic metasurface is proposed by introducing periodically repeated supercells on a rigid thin plate, where each supercell contains multiple cut-through slits that are filled with materials possessing different refractive indices but the same impedance as that of the host medium. When the wavelength of the incident wave is smaller than the periodicity, the direction of the transmitted wave with nearly unity transmittance can be chosen by engineering the phase discontinuities along the transverse direction. When the wavelength is larger than the periodicity, even though the metasurface is impedance matched to the host medium, most of the incident energy is reflected back and the remaining portion is converted into a surface-bound mode. We show that both the transmitted wave control and the high reflection with the surface mode excitation can be interpreted by a unified analytic model based on mode-coupling theory. Our general design principle not only supplies the functionalities of reflection-type acoustic metasurfaces, but also exhibits unprecedented flexibility and efficiency in various domains of wave manipulation for possible applications in fields like refracting, collimating, focusing or absorbing wave energy.
What middle ear parameters tell about impedance matching and high frequency hearing.
Hemilä, S; Nummela, S; Reuter, T
1995-05-01
Acoustic energy enters the mammalian cochlea aided by an anatomical impedance matching performed by the middle ear. The purpose of this paper is to analyse the functional consequences of changes in scale of the middle ear when going from the smallest mammals to the largest. Our anatomical measurements in mammals of different sizes ranging from bats to elephants indicate that middle ear proportions are largely isometric. Thus the calculated transformer ratio is basically independent of animal size, a typical value lying between 30 and 80. Similarly, the calculated specific acoustic input impedance of the inner ear is independent of animal size, the average value being about 140 kPa s/m. We show that if the high frequency hearing limit of isometric ears is limited by ossicle inertia, it should be inversely proportional to the cubic root of the ossicular mass. This prediction is in reasonable agreement with published audiogram data. We then present a three-parameter model of the middle ear where some obvious deviations from perfect isometry are taken into account. The high frequency hearing limits of different species generally agree well with the predictions of this simple model. However, the hearing limits of small rodents clearly deviate from the model calculation. We interpret this observation as indicating that the hearing limit towards very high frequencies may be set by cochlear transduction mechanisms. Further we discuss the exceptional high frequency hearing of the cat and the amphibious hearing of seals.
Boosting local field enhancement by on-chip nanofocusing and impedance-matched plasmonic antennas
Zenin, Vladimir A; Malureanu, Radu; Radko, Ilya P; Volkov, Valentyn S; Gramotnev, Dmitri K; Lavrinenko, Andrei V; Bozhevolnyi, Sergey I
2016-01-01
Strongly confined surface plasmon-polariton modes can be used for efficiently delivering the electromagnetic energy to nano-sized volumes by reducing the cross sections of propagating modes far beyond the diffraction limit, i.e., by nanofocusing. This process results in significant local-field enhancement that can advantageously be exploited in modern optical nanotechnologies, including signal processing, biochemical sensing, imaging and spectroscopy. Here, we propose, analyze, and experimentally demonstrate on-chip nanofocusing followed by impedance-matched nanowire antenna excitation in the end-fire geometry at telecom wavelengths. Numerical and experimental evidences of the efficient excitation of dipole and quadrupole (dark) antenna modes are provided, revealing underlying physical mechanisms and analogies with the operation of plane-wave Fabry-P\\'erot interferometers. The unique combination of efficient nanofocusing and nanoantenna resonant excitation realized in our experiments offers a major boost to t...
Degree mixing in multilayer networks impedes the evolution of cooperation.
Wang, Zhen; Wang, Lin; Perc, Matjaž
2014-05-01
Traditionally, the evolution of cooperation has been studied on single, isolated networks. Yet a player, especially in human societies, will typically be a member of many different networks, and those networks will play different roles in the evolutionary process. Multilayer networks are therefore rapidly gaining on popularity as the more apt description of a networked society. With this motivation, we here consider two-layer scale-free networks with all possible combinations of degree mixing, wherein one network layer is used for the accumulation of payoffs and the other is used for strategy updating. We find that breaking the symmetry through assortative mixing in one layer and/or disassortative mixing in the other layer, as well as preserving the symmetry by means of assortative mixing in both layers, impedes the evolution of cooperation. We use degree-dependent distributions of strategies and cluster-size analysis to explain these results, which highlight the importance of hubs and the preservation of symmetry between multilayer networks for the successful resolution of social dilemmas.
Sudhir, Dass; Bandyopadhyay, M; Kraus, W; Gahlaut, A; Bansal, G; Chakraborty, A
2014-01-01
Impedance matching circuit between radio frequency (RF) generator and the plasma load, placed between them, determines the RF power transfer from RF generator to the plasma load. The impedance of plasma load depends on the plasma parameters through skin depth and plasma conductivity or resistivity. Therefore, for long pulse operation of inductively coupled plasmas, particularly for high power (∼100 kW or more) where plasma load condition may vary due to different reasons (e.g., pressure, power, and thermal), online tuning of impedance matching circuit is necessary through feedback. In fusion grade ion source operation, such online methodology through feedback is not present but offline remote tuning by adjusting the matching circuit capacitors and tuning the driving frequency of the RF generator between the ion source operation pulses is envisaged. The present model is an approach for remote impedance tuning methodology for long pulse operation and corresponding online impedance matching algorithm based on RF coil antenna current measurement or coil antenna calorimetric measurement may be useful in this regard.
Chow, Jong H; Littler, Ian C M; Rabeling, David S; McClelland, David E; Gray, Malcolm B
2008-05-26
We introduce a closed-loop feedback technique to actively control the coupling condition of an optical cavity, by employing amplitude modulation of the interrogating laser. We show that active impedance matching of the cavity facilitates optimal shot-noise sensing performance in a cavity enhanced system, while its control error signal can be used for intra-cavity absorption or loss signal extraction. We present the first demonstration of this technique with a fiber ring cavity, and achieved shot-noise limited loss sensitivity. We also briefly discuss further use of impedance matching control as a tool for other applications.
Wang, Lei; Yang, Shuaisai; Tang, Zhixiang; Shu, Weixing
2016-10-01
We propose a three-dimensional (3D) phase transformation method by an impedance-matched dielectric slab and apply it to generating hollow beams. We first employ transformation optics to establish a method for the transformation between two arbitrary 3D wavefronts through a flat dielectric and impedance-matched material. Then the method is used to convert a solid beam into a hollow beam with desired wavefront. By tuning the transformation surface, different hollow beams can be produced. The results are further validated by 3D finite-difference time-domain simulations.
Study on the Impedance Matching Design of Planar Slot Antenna%平板裂缝天线阻抗匹配设计的研究
Institute of Scientific and Technical Information of China (English)
金林; 何国瑜
2000-01-01
The design method of impedance matching for planar slot antenna is discussed in this paper. The impedance matching criterion that the sum of all the radiating slot normalized conductances is equal to 2 for the inner feed, and also the sum of all the coupling slot normalized impedances for the series-shunt inner feeder is equal to 2 are verified by using microwave network theory. According to this method , a new matching criterion of coupling slots is derived for the series-series feeder and the shunt-series feeder.%本文对平板裂缝天线阻抗匹配设计方法进行了讨论。采用微波网络理论，在内部馈电情况下，分别对一条辐射波导上辐射裂缝的归一化导纳和为2的匹配设计准则，以及对串－并形式馈电装置，对耦合裂缝的归一化阻抗和为2的匹配设计准则进行了证明。按照同样方法，对串－串、并－串形式的馈电装置，导出了新的耦合裂缝匹配设计准则。
High aspect ratio MEMS capacitor for high frequency impedance matching applications
DEFF Research Database (Denmark)
Yalcinkaya, Arda Deniz; Jensen, Søren; Hansen, Ole
2003-01-01
We present a microelectromechanical tunable capacitor with a low control voltage, a wide tuning range and adequate electrical quality factor. The device is fabricated in a single-crystalline silicon layer using deep reactive ion etching (DRIE) for obtaining high-aspect ratio (> 20) parallel comb-...... response and it was found that the device is a suitable passive component to be used in impedance matching applications, band-pass filtering or voltage controlled oscillators in the Very High Frequency (VHF) and Ultra High Frequency (UHF) bands.......We present a microelectromechanical tunable capacitor with a low control voltage, a wide tuning range and adequate electrical quality factor. The device is fabricated in a single-crystalline silicon layer using deep reactive ion etching (DRIE) for obtaining high-aspect ratio (> 20) parallel comb......-drive structures with vertical sidewalls. The process sequence for fabrication of the devices uses only one lithographic masking step and can be completed in a short time. The fabricated device was characterized with respect to electrical quality factor, tuning range, self-resonance frequency and transient...
Boosting Local Field Enhancement by on-Chip Nanofocusing and Impedance-Matched Plasmonic Antennas.
Zenin, Vladimir A; Andryieuski, Andrei; Malureanu, Radu; Radko, Ilya P; Volkov, Valentyn S; Gramotnev, Dmitri K; Lavrinenko, Andrei V; Bozhevolnyi, Sergey I
2015-12-09
Strongly confined surface plasmon-polariton modes can be used for efficiently delivering the electromagnetic energy to nanosized volumes by reducing the cross sections of propagating modes far beyond the diffraction limit, that is, by nanofocusing. This process results in significant local-field enhancement that can advantageously be exploited in modern optical nanotechnologies, including signal processing, biochemical sensing, imaging, and spectroscopy. Here, we propose, analyze, and experimentally demonstrate on-chip nanofocusing followed by impedance-matched nanowire antenna excitation in the end-fire geometry at telecom wavelengths. Numerical and experimental evidence of the efficient excitation of dipole and quadrupole (dark) antenna modes are provided, revealing underlying physical mechanisms and analogies with the operation of plane-wave Fabry-Pérot interferometers. The unique combination of efficient nanofocusing and nanoantenna resonant excitation realized in our experiments offers a major boost to the field intensity enhancement up to ∼12000, with the enhanced field being evenly distributed over the gap volume of 30 × 30 × 10 nm(3), and promises thereby a variety of useful on-chip functionalities within sensing, nonlinear spectroscopy and signal processing.
'GAIM' - Gas-addition, impedance-matched arc driver. [shock tube gas dynamics
Dannenberg, R. E.
1980-01-01
A conceptual view for a GAIM energy/driver system to maximize shock-tube performance through efficient interfacing of the energy source with the gas dynamics of the arc driver is presented. Electrical and arc-chamber requirements are evaluated utilizing two new computer codes. One code calculates the shock wave generated for a selected time rate and magnitude of arc-energy input; the other computes the values of external circuit elements required to produce the selected energy input, with the driver represented as the load element of the electrical discharge circuit. Results indicate that the energy-storage capability and the driver arrangement needed to produce the highest shock Mach number can be achieved by means of driver gas addition and by impedance matching (GAIM). Design criteria are presented for arc energy requirements necessary to produce given shock-wave speeds. Shock velocities as high as the 70 km/sec required for simulating Jovian entry now seem possible in shock-tube operation. Practical implementation of a GAIM system is discussed.
Low-loss impedance-matched optical metamaterials with zero-phase delay.
Yun, Seokho; Jiang, Zhi Hao; Xu, Qian; Liu, Zhiwen; Werner, Douglas H; Mayer, Theresa S
2012-05-22
Metamaterials have dramatically expanded the range of available optical properties, enabling an array of new devices such as superlenses, perfect absorbers, and ultrafast switches. Most research has focused on demonstrating negative- and high-index metamaterials at terahertz and optical wavelengths. However, far less emphasis has been placed on low-loss near-zero-index metamaterials that exhibit unique properties including quasi-infinite phase velocity and infinite wavelength. Here, we experimentally demonstrate a free-standing metallodielectric fishnet nanostructure that has polarization-insensitive, zero-index properties with nearly ideal transmission at 1.55 μm. This goal was achieved by optimizing the metamaterial geometry to allow both its effective permittivity and permeability to approach zero together, which simultaneously produces a zero index and matched impedance to free space. The ability to design and fabricate low-loss, near-zero-index optical metamaterials is essential for new devices such as beam collimators, zero-phase delay lines, and transformation optics lenses.
Murata, T; Akagi, K; Ostapenko, V V; Isoda, H; Nagata, K; Nasu, R; Shiga, T; Tanaka, Y; Yamamoto, I
1998-01-01
Capacitive heating is widely used in hyperthermic treatment of human malignancies. However, the pain on the body surface or thermoesthesia in the subcutaneous fatty layer may prevent an elevation of temperature in the tumors. Impedance matching is improved by a subtrap method entailing the application of two copper plates (10 x 850 x 0.06 mm) as a subtrap circuit to each of two capacitive electrodes. In a clinical trial the Tmax, Tave, Tmin for the subtrap method were all higher in comparison with those for the conventional technique (42.5 +/- 0.7 degrees C, 41.9 +/- 1.0 degrees C, 41.3 +/- 1.1 degrees C vs. 41.1 +/- 1.5 degrees C, 40.6 +/- 1.3 degrees C, 40.0 +/- 1.3 degrees C). Although the maximal radiofrequency (RF) power applied to patients was higher with the subtrap method (875 +/- 189 W vs. 763 +/- 200 W), the incidence of surface pain was reduced dramatically. It is concluded that the subtrap method substantially improves the RF capacitive heating of deep-seated tumors.
Sudhir, Dass; Bandyopadhyay, M.; Chakraborty, A.
2016-02-01
Plasma characterization and impedance matching are an integral part of any radio frequency (RF) based plasma source. In long pulse operation, particularly in high power operation where plasma load may vary due to different reasons (e.g. pressure and power), online tuning of impedance matching circuit and remote plasma density estimation are very useful. In some cases, due to remote interfaces, radio activation and, due to maintenance issues, power probes are not allowed to be incorporated in the ion source design for plasma characterization. Therefore, for characterization and impedance matching, more remote schemes are envisaged. Two such schemes by the same authors are suggested in these regards, which are based on air core transformer model of inductive coupled plasma (ICP) [M. Bandyopadhyay et al., Nucl. Fusion 55, 033017 (2015); D. Sudhir et al., Rev. Sci. Instrum. 85, 013510 (2014)]. However, the influence of the RF field interaction with the plasma to determine its impedance, a physics code HELIC [D. Arnush, Phys. Plasmas 7, 3042 (2000)] is coupled with the transformer model. This model can be useful for both types of RF sources, i.e., ICP and helicon sources.
Energy Technology Data Exchange (ETDEWEB)
Sudhir, Dass, E-mail: dass.sudhir@iter-india.org; Bandyopadhyay, M.; Chakraborty, A. [ITER-India, Institute for Plasma Research, A-29 GIDC, Sec-25, Gandhinagar, 382016 Gujarat (India)
2016-02-15
Plasma characterization and impedance matching are an integral part of any radio frequency (RF) based plasma source. In long pulse operation, particularly in high power operation where plasma load may vary due to different reasons (e.g. pressure and power), online tuning of impedance matching circuit and remote plasma density estimation are very useful. In some cases, due to remote interfaces, radio activation and, due to maintenance issues, power probes are not allowed to be incorporated in the ion source design for plasma characterization. Therefore, for characterization and impedance matching, more remote schemes are envisaged. Two such schemes by the same authors are suggested in these regards, which are based on air core transformer model of inductive coupled plasma (ICP) [M. Bandyopadhyay et al., Nucl. Fusion 55, 033017 (2015); D. Sudhir et al., Rev. Sci. Instrum. 85, 013510 (2014)]. However, the influence of the RF field interaction with the plasma to determine its impedance, a physics code HELIC [D. Arnush, Phys. Plasmas 7, 3042 (2000)] is coupled with the transformer model. This model can be useful for both types of RF sources, i.e., ICP and helicon sources.
Sudhir, Dass; Bandyopadhyay, M; Chakraborty, A
2016-02-01
Plasma characterization and impedance matching are an integral part of any radio frequency (RF) based plasma source. In long pulse operation, particularly in high power operation where plasma load may vary due to different reasons (e.g. pressure and power), online tuning of impedance matching circuit and remote plasma density estimation are very useful. In some cases, due to remote interfaces, radio activation and, due to maintenance issues, power probes are not allowed to be incorporated in the ion source design for plasma characterization. Therefore, for characterization and impedance matching, more remote schemes are envisaged. Two such schemes by the same authors are suggested in these regards, which are based on air core transformer model of inductive coupled plasma (ICP) [M. Bandyopadhyay et al., Nucl. Fusion 55, 033017 (2015); D. Sudhir et al., Rev. Sci. Instrum. 85, 013510 (2014)]. However, the influence of the RF field interaction with the plasma to determine its impedance, a physics code HELIC [D. Arnush, Phys. Plasmas 7, 3042 (2000)] is coupled with the transformer model. This model can be useful for both types of RF sources, i.e., ICP and helicon sources.
Toda, Minoru; Thompson, Mitchell
2010-12-01
This paper presents a novel design principle for designing multilayer polymer-metal structures which are well suited for front surface impedance conversion (matching) and for back surface acoustic absorption. It is shown that a polymer layer with an outer metal layer, when loaded by a low impedance propagation medium, acts as an efficient impedance converter. The resulting impedance seen at the inner polymer surface is increased and the structure provides the same performance as a traditional quarter-wavelength matching layer. Experimental evidence is also shown for a double-matching scheme for a lead zirconate titanate (PZT) transducer using an inner polymer-metal multilayer and an outer polymer quarterwavelength layer, resulting in a 55% bandwidth at 2.6 MHz with air backing. Also, it is theoretically shown that multiple layers of a lossy polymer adhesive-metal structure produce low propagation velocity and high absorption. Experimental proof of this ultrasonic multilayer backing absorber is provided. Design theories based on both a simplified mass and spring model and a rigorous one-dimensional wave model have been developed and show fair agreement.
Uncertainty quantification for electrical impedance tomography with resistor networks
Borcea, Liliana; Mamonov, Alexander V
2011-01-01
We present a Bayesian statistical study of the numerical solution of the two dimensional electrical impedance tomography problem, with noisy measurements of the Dirichlet to Neumann (DtN) map. The inversion uses parametrizations of the conductivity on optimal grids that are computed as part of the problem. The grids are optimal in the sense that finite volume discretizations on them give spectrally accurate approximations of the DtN map. The approximations are DtN maps of special resistor networks, that are uniquely recoverable from the measurements. We present a statistical study of the noise effects on the inversion on optimal grids for both the linearized and the nonlinear inverse problem. The linearization is about a constant conductivity. We take three different parametrizations of the unknown conductivity perturbations, with the same number of degrees of freedom. We obtain that the parametrization induced by the inversion on optimal grids is the most efficient of the three, because it gives the smallest...
阻抗匹配电路原理与应用%Impedance Matching Circuit Principle and its Application
Institute of Scientific and Technical Information of China (English)
田亚朋; 张昌民; 仲维伟
2012-01-01
阻抗匹配基本原理与概念，阻抗匹配常见于各级放大电路之间，放大电路与负载之间，信号与传输电路之间。微波电路与系统的设计中，无论是有源还是无源，都必须考虑匹配问题，其根本原因是低频电路中为电压与电流，而高频中导行电磁波不匹配就会发生严重的反射，损坏仪器和设备，文中阐述相应的解决方法。%The basic principles and concepts of impedance matching are presented. Impedance matching is ~mmonly used between the amplifiers at all levels, amplifier and load, signal and transmission circuit, and even etween microwave circuit and system design. The fundamental reason is that mis-matching of voltage and current in te low-frequency circuit and electromagnetic wave in the high frequency circuit may lead to serious reflection and amage instruments and equipment. Impedance matching is the solution, which is discussed in this paper.
Effects of leakage inductances on magnetically-coupled impedance-source networks
DEFF Research Database (Denmark)
Siwakoti, Yam P.; Loh, Poh Chiang; Blaabjerg, Frede
2014-01-01
Coupled inductors have lately been used with impedance-source networks for keeping their shoot-through times short, while providing higher voltage boosts. The parameter that is critical to the operation of such impedance network based converter with coupled inductors is the leakage inductances. H...
Matching Community Structure Across Online Social Networks
Li, Lin
2016-01-01
The discovery of community structure in networks is a problem of considerable interest in recent years. In online social networks, often times, users are simultaneously involved in multiple social media sites, some of which share common social relationships. It is of great interest to uncover a shared community structure across these networks. However, in reality, users typically identify themselves with different usernames across social media sites. This creates a great difficulty in detecting the community structure. In this paper, we explore several approaches for community detection across online social networks with limited knowledge of username alignment across the networks. We refer to the known alignment of usernames as seeds. We investigate strategies for seed selection and its impact on networks with a different fraction of overlapping vertices. The goal is to study the interplay between network topologies and seed selection strategies, and to understand how it affects the detected community structu...
Application of Impedance Matching Circuit in Filter Measure%阻抗匹配电路在滤波器测试中的应用
Institute of Scientific and Technical Information of China (English)
汶迎春
2012-01-01
To solve the problem of some type nonstandard impedance filter measure owing to sweep generator＇s aging, an impedance matching circuit is designed to measure filters by network analyzer. In this paper, measuring principles of sweep generator and network analyzer are introduced as well as their differences. The implement of net- work analyzer HP E5100B instead of sweep generator JW1252W in filter measure is given, and the principles of impedance matching circuit and its application in filter measure are expatiated. Experiments show that the use of the network analyzer can guarantee the consistency of numerical values to be measured. This method also has the advantages of easy operation and high precision and it can save labor and cost.%为解决扫频仪日趋老化带来的某型非标准阻抗滤波器测试问题，通过设计阻抗转换器实现了用网络分析仪对滤波器的测试。介绍了扫频仪与网络分析仪的测试原理和它们之间的区别，阐述了网络分析仪HPE5100B替代扫频仪JW1252W测试滤波器的实现方法，以及阻抗匹配电路的原理及其在滤波器测试中的应用。实验证明，用网络测试仪测试数值一致性好、操作简单、精度高、减少了工作量、降低了成本。
Vein matching using artificial neural network in vein authentication systems
Noori Hoshyar, Azadeh; Sulaiman, Riza
2011-10-01
Personal identification technology as security systems is developing rapidly. Traditional authentication modes like key; password; card are not safe enough because they could be stolen or easily forgotten. Biometric as developed technology has been applied to a wide range of systems. According to different researchers, vein biometric is a good candidate among other biometric traits such as fingerprint, hand geometry, voice, DNA and etc for authentication systems. Vein authentication systems can be designed by different methodologies. All the methodologies consist of matching stage which is too important for final verification of the system. Neural Network is an effective methodology for matching and recognizing individuals in authentication systems. Therefore, this paper explains and implements the Neural Network methodology for finger vein authentication system. Neural Network is trained in Matlab to match the vein features of authentication system. The Network simulation shows the quality of matching as 95% which is a good performance for authentication system matching.
The noise factor of receiver coil matching networks in MRI.
Cao, Xueming; Fischer, Elmar; Gruschke, Oliver; Korvink, Jan G; Hennig, Jürgen; Maunder, Adam M; De Zanche, Nicola; Zaitsev, Maxim
2017-04-01
In typical MRI applications the dominant noise sources in the received signal are the sample, the coil loop and the preamplifier. We hypothesize that in some cases (e.g. for very small receiver coils) the matching network noise has to be considered explicitly. Considering the difficulties of direct experimental determinations of the noise factor of matching networks with sufficient accuracy, it is helpful to estimate the noise factor by calculation. A useful formula of the coil matching network is obtained by separating commonly used coil matching network into different stages and calculating their noise factor analytically by a combination of the noise from these stages. A useful formula of the coil matching network is obtained. ADS simulations are performed to verify the theoretical predictions. Thereafter carefully-designed proof-of-concept phantom experiments are carried out to qualitatively confirm the predicted SNR behavior. The matching network noise behavior is further theoretically investigated for a variety of scenarios. It is found that in practice the coil matching network noise can be improved by adjusting the coil open port resonant frequency.
Matching Community Structure Across Online Social Networks
Lin LI; Campbell, W. M.
2016-01-01
The discovery of community structure in networks is a problem of considerable interest in recent years. In online social networks, often times, users are simultaneously involved in multiple social media sites, some of which share common social relationships. It is of great interest to uncover a shared community structure across these networks. However, in reality, users typically identify themselves with different usernames across social media sites. This creates a great difficulty in detecti...
Institute of Scientific and Technical Information of China (English)
MA Zhi; CAO Chen-Tao; LIU Qing-Fang; WANG Jian-Bo
2012-01-01
A delta-function method is proposed to quantitatively evaluate the electromagnetic impedance matching degree.Measured electromagnetic parameters of α-Fe/Fe3B/V2O3 nanocomposites are applied to calculate the matching degree by the method.Compared with reflection loss and quarter-wave principle theory,the method accurately reveals the intrinsic mechanism of microwave transmission and reflection properties.A possible honeycomb structure with promising high-performance microwave absorption,devised according to the method,is also proposed.
Rahman, Airul Azha Abd; Jamil, Wan Adil Wan; Umar, Akrajas Ali
2016-07-01
Multivariate energy harvesting system, solar and thermal energies, with configurable impedance matching features is presented. The system consists of a tuneable mechanism for peak performance tracking. The inputs are voltages ranging from 20 mV to 3.1 V. The matching load is individually tuned for photovoltaic and thermoelectric power efficiency not less than 80% and 50% of the open circuit voltage respectively. Of experimentation and analysis has been done, the time it takes to fully charge up to 3.4 V is 23 minutes with the rate of charging is 1.8 mV/sec. Empirical data is presented. [Figure not available: see fulltext.
Gholipur, Reza; Khorshidi, Zahra; Bahari, Ali
2017-04-12
Metamaterials have surprisingly broadened the range of available practical applications in new devices such as shielding, microwave absorbing, and novel antennas. More research has been conducted related to tuning DNG frequency bands of ordered or disordered metamaterials, and far less research has focused on the importance of impedance matching behavior, with little effort and attention given to adjusting the magnitude of negative permittivity values. This is particularly important if devices deal with low-amplitude signals such as radio or TV antennas. The carbon/hafnium nickel oxide (C/Hf0.9Ni0.1Oy) nanocomposites with simultaneously negative permittivity and negative permeability, excellent metamaterial performance, and good impedance matching could become an efficient alternative for the ordered metamaterials in wave-transparent, microwave absorbing, and solar energy harvesting fields. In this study, we prepared C/Hf0.9Ni0.1Oy nanocomposites by the solvothermal method, and we clarified how the impedance matching and double-negative (DNG) behaviors of C/Hf0.9Ni0.1Oy can be tuned by an external AC electric field created by an electric quadrupole system. An external electric field allows for the alignment of the well-dispersed nanoparticles of carbon with long-range orientations order. We believe that this finding broadens our understanding of moderate conductive material-based random metamaterials (MCMRMs) and provides a novel strategy for replacing high-loss ordered or disordered metamaterials with MCMRMs.
Privacy‐Preserving Friend Matching Protocol approach for Pre‐match in Social Networks
DEFF Research Database (Denmark)
Ople, Shubhangi S.; Deshmukh, Aaradhana A.; Mihovska, Albena Dimitrova
2016-01-01
that a secure match can achieve at least one order of accuracy and better computational performance than the techniques that use homomorphic encryption.It can handle and tackle new characteristics and an environment for a particular application in a mobile social network....... for use in social networks due to its data sharing problems and information leakage. In this paper, we propose a novel framework for privacy–preserving profile matching. We implement both the client and server portion of the secure match and evaluate its performance network dataset. The results show......Social services make the most use of the user profile matching to help the users to discover friends with similar social attributes (e.g. interests, location, age). However, there are many privacy concerns that prevent to enable this functionality. Privacy preserving encryption is not suitable...
基于PSO的射频天线自适应阻抗匹配%RF Antenna Adaptive Impedance Matching Based on PSO
Institute of Scientific and Technical Information of China (English)
韩涛
2016-01-01
Due to the variability of the field distribution of the antenna, the impedance mismatch will be destroyed easily. This will also reduce the power transmission efficiency and the output signal power. Therefore, a new method of particle swarm op-timization based on adaptive impedance matching of RF antenna is presented in this paper. Between the RF antenna and the ex-citation source, we add to the-type passive network. According to the real time variation of the load impedance, we can achieve the conjugate matching by adjust the variable capacitance and the inductance in the network,. The system obtains the maximum transmission power. In other words, it also increases the maximum reading distance of the RFID system reader.%由于天线的场分布的易变性容易导致阻抗失配，从而会降低功率传输效率和输出信号功率。文章提出了一种射频天线自适应阻抗匹配的粒子群方法，在射频天线和激励源中间加入无源型匹配网络，根据负载阻抗实时变化快速，通过调节网络中可变电容和电感来实现共轭匹配，射频天线负载获得最大传输功率，从而提高RFID系统读写器的最大读取距离。
Impedance Matching for Discrete, Periodic Media and Application to Two-Scale Wave Propagation Models
Thirunavukkarasu, Senganal
This dissertation introduces the idea of an equivalent continuous medium (ECM) that has the same impedance as that of an unbounded discrete periodic medium. Contrary to existing knowledge, we constructively show that it is indeed possible to achieve perfect matching for periodic and discrete media. We present analytical results relating the propagation characteristics of periodic media and the corresponding ECM, leading to the development of numerical methods for wave propagation in these media. In this dissertation, we present the main idea of ECM and apply it, with mixed results, to seemingly different problems requiring effective numerical methods for modeling wave propagation in unbounded media. An immediate application of ECM is in developing absorbing boundary conditions (ABCs) for wave propagation in unbounded discrete media. Using the idea of ECM, and building on class of continuous ABCs called perfectly matched discrete layers (PMDL), we propose a new class of discrete ABCs called discrete PMDL and develop frequency domain formulations that are shown to be superior to continuous ABCs. Another application that is explored in this dissertation is the design of interface conditions for concurrent coupling of two-scale wave propagation models, e.g. Atomistic-to-Continuum (AtC) coupling. We propose a domain-decomposition (DD) approach and develop accurate interface conditions that are critical for the concurrent coupling of the two-scale models. It turns out that time-domain discrete ABCs are key to the the accuracy of these interface conditions. Since discrete PMDL is well-posed and accurate for the model problem, we build on it to propose an efficient and accurate interface condition for two-scale wave propagation models. Although many open problems remain with respect to implementation, we believe that the proposed DD based approach is a good first step towards achieving efficient coupling of two-scale wave propagation models. Time-domain discrete PMDL can
Wang, Yonggang; Tong, Liqing; Liu, Kefu
2017-06-01
The purpose of impedance matching for a Marx generator and DBD lamp is to limit the output current of the Marx generator, provide a large discharge current at ignition, and obtain fast voltage rising/falling edges and large overshoot. In this paper, different impedance matching circuits (series inductor, parallel capacitor, and series inductor combined with parallel capacitor) are analyzed. It demonstrates that a series inductor could limit the Marx current. However, the discharge current is also limited. A parallel capacitor could provide a large discharge current, but the Marx current is also enlarged. A series inductor combined with a parallel capacitor takes full advantage of the inductor and capacitor, and avoids their shortcomings. Therefore, it is a good solution. Experimental results match the theoretical analysis well and show that both the series inductor and parallel capacitor improve the performance of the system. However, the series inductor combined with the parallel capacitor has the best performance. Compared with driving the DBD lamp with a Marx generator directly, an increase of 97.3% in radiant power and an increase of 59.3% in system efficiency are achieved using this matching circuit.
An Analysis of the Matching Hypothesis in Networks
Jia, Tao; Szymanski, Boleslaw; Korniss, Gyorgy
2015-01-01
The matching hypothesis in social psychology claims that people are more likely to form a committed relationship with someone equally attractive. Previous works on stochastic models of human mate choice process indicate that patterns supporting the matching hypothesis could occur even when similarity is not the primary consideration in seeking partners. Yet, most if not all of these works concentrate on fully-connected systems. Here we extend the analysis to networks. Our results indicate that the correlation of the couple's attractiveness grows monotonically with the increased average degree and decreased degree diversity of the network. This correlation is lower in sparse networks than in fully-connected systems, because in the former less attractive individuals who find partners are likely to be coupled with ones who are more attractive than them. The chance of failing to be matched decreases exponentially with both the attractiveness and the degree. The matching hypothesis may not hold when the degree-att...
A blind matching algorithm for cognitive radio networks
Hamza, Doha R.
2016-08-15
We consider a cognitive radio network where secondary users (SUs) are allowed access time to the spectrum belonging to the primary users (PUs) provided that they relay primary messages. PUs and SUs negotiate over allocations of the secondary power that will be used to relay PU data. We formulate the problem as a generalized assignment market to find an epsilon pairwise stable matching. We propose a distributed blind matching algorithm (BLMA) to produce the pairwise-stable matching plus the associated power allocations. We stipulate a limited information exchange in the network so that agents only calculate their own utilities but no information is available about the utilities of any other users in the network. We establish convergence to epsilon pairwise stable matchings in finite time. Finally we show that our algorithm exhibits a limited degradation in PU utility when compared with the Pareto optimal results attained using perfect information assumptions. © 2016 IEEE.
Personalized trajectory matching in spatial networks
Shang, Shuo
2013-07-31
With the increasing availability of moving-object tracking data, trajectory search and matching is increasingly important. We propose and investigate a novel problem called personalized trajectory matching (PTM). In contrast to conventional trajectory similarity search by spatial distance only, PTM takes into account the significance of each sample point in a query trajectory. A PTM query takes a trajectory with user-specified weights for each sample point in the trajectory as its argument. It returns the trajectory in an argument data set with the highest similarity to the query trajectory. We believe that this type of query may bring significant benefits to users in many popular applications such as route planning, carpooling, friend recommendation, traffic analysis, urban computing, and location-based services in general. PTM query processing faces two challenges: how to prune the search space during the query processing and how to schedule multiple so-called expansion centers effectively. To address these challenges, a novel two-phase search algorithm is proposed that carefully selects a set of expansion centers from the query trajectory and exploits upper and lower bounds to prune the search space in the spatial and temporal domains. An efficiency study reveals that the algorithm explores the minimum search space in both domains. Second, a heuristic search strategy based on priority ranking is developed to schedule the multiple expansion centers, which can further prune the search space and enhance the query efficiency. The performance of the PTM query is studied in extensive experiments based on real and synthetic trajectory data sets. © 2013 Springer-Verlag Berlin Heidelberg.
Zhen, L.; Gong, Y. X.; Jiang, J. T.; Xu, C. Y.; Shao, W. Z.; Liu, P.; Tang, J.
2011-04-01
CoFe/Al2O3 composite nanoparticles were successfully prepared by hydrogen-thermally reducing cobalt aluminum ferrite. Compared with CoFe alloy nanoparticles, the permeability of CoFe/Al2O3 composite nanoparticles was remarkably enhanced and an improved impedance characteristic was achieved due to the introduction of insulated Al2O3. A multilayer absorber with CoFe/Al2O3 composite nanoparticles as the impedance matching layer and CoFe nanoflake as the dissipation layer was designed by using genetic algorithm, in which an ultrawide operation frequency bandwidth over 2.5-18 GHz was obtained. The microwave absorption performance in both normal and oblique incident case was evaluated by using electromagnetic simulator. The backward radar cross-section (RCS) was decreased at least 10 dB over a wide frequency range by covering the multilayer absorber on the surface of perfect electrical conductive plate.
Efficient target control of complex networks based on preferential matching
Zhang, Xizhe; Lv, Tianyang
2016-01-01
Controlling a complex network towards a desire state is of great importance in many applications. Existing works present an approximate algorithm to find the driver nodes used to control partial nodes of the network. However, the driver nodes obtained by this algorithm depend on the matching order of nodes and cannot get the optimum results. Here we present a novel algorithm to find the driver nodes for target control based on preferential matching. The algorithm elaborately arrange the matching order of nodes in order to minimize the size of the driver nodes set. The results on both synthetic and real networks indicate that the performance of proposed algorithm are better than the previous one. The algorithm may have various application in controlling complex networks.
一种DDR信号阻抗匹配的新方法%New method of DDR signal impedance matching
Institute of Scientific and Technical Information of China (English)
王征
2012-01-01
There are two ways of DDR signal impedance marching:add the series-resistance in the source or add the shunt-resistance in the terminal.The two methods have their advantages and disadvantages.Source matching will increase the PCB plate area.Terminal matching will increase the power.This paper uses the shunt-capacitor to replace the shunt-resistance,which can solve the problem of PCB layout area,and the problem of single board power increased.It is a new method of DDR signal impedance matching.%DDR信号的阻抗匹配一般有两种方法：源端增加串联电阻和终端增加并联电阻。这两种方法各有利弊。其中源端串阻匹配会增加单板PCB的布板面积,终端并联匹配则会增加单板的功耗。本文则采用并联电容来替代并联电阻,这样即可以解决PCB布板面积的问题,也可以解决单板机功耗增加的问题,是DDR信号匹配的一种新方法。
Low-Loss Matching Network Design for Band-Switchable Multi-Band Power Amplifier
Fukuda, Atsushi; Furuta, Takayuki; Okazaki, Hiroshi; Narahashi, Shoichi; Nojima, Toshio
This paper presents a novel design scheme for a band-switchable multi-band power amplifier (BS-MPA). A key point of the design scheme is configuring multi-section reconfigurable matching networks (MR-MNs) optimally in terms of low loss matching in multiple frequency bands from 0.7 to 2.5GHz. The MR-MN consists of several matching sections, each of which has a matching block connected to a transmission line via a switch. Power dissipation at an actual on-state switch results in the insertion loss of the MR-MN and depends on how the impedance is transformed by the MR-MN. The proposed design scheme appropriately transforms the impedance of a high power transistor to configure a low loss MR-MN. Numerical analyses show quantitative improvement in the loss using the proposed scheme. A 9-band 3-stage BS-MPA is newly designed following the proposed scheme and fabricated on a multi-layer low temperature co-fired ceramic substrate for compactness. The BS-MPA achieves a gain of over 30dB, an output power of greater than 33dBm and a power added efficiency of over 40% at the supply voltage of 4V in each operating band.
Directory of Open Access Journals (Sweden)
Johannes Müller
Full Text Available BACKGROUND: Insights into the onset of evolutionary novelties are key to the understanding of amniote origins and diversification. The possession of an impedance-matching tympanic middle ear is characteristic of all terrestrial vertebrates with a sophisticated hearing sense and an adaptively important feature of many modern terrestrial vertebrates. Whereas tympanic ears seem to have evolved multiple times within tetrapods, especially among crown-group members such as frogs, mammals, squamates, turtles, crocodiles, and birds, the presence of true tympanic ears has never been recorded in a Paleozoic amniote, suggesting they evolved fairly recently in amniote history. METHODOLOGY/PRINCIPAL FINDINGS: In the present study, we performed a morphological examination and a phylogenetic analysis of poorly known parareptiles from the Middle Permian of the Mezen River Basin in Russia. We recovered a well-supported clade that is characterized by a unique cheek morphology indicative of a tympanum stretching across large parts of the temporal region to an extent not seen in other amniotes, fossil or extant, and a braincase specialized in showing modifications clearly related to an increase in auditory function, unlike the braincase of any other Paleozoic tetrapod. In addition, we estimated the ratio of the tympanum area relative to the stapedial footplate for the basalmost taxon of the clade, which, at 23:1, is in close correspondence to that of modern amniotes capable of efficient impedance-matching hearing. CONCLUSIONS/SIGNIFICANCE: Using modern amniotes as analogues, the possession of an impedance-matching middle ear in these parareptiles suggests unique ecological adaptations potentially related to living in dim-light environments. More importantly, our results demonstrate that already at an early stage of amniote diversification, and prior to the Permo-Triassic extinction event, the complexity of terrestrial vertebrate ecosystems had reached a level that
Design of Wireless Coupling Signal Transmission Antenna and Impedance Matching%无线耦合信号传输天线的设计和阻抗匹配
Institute of Scientific and Technical Information of China (English)
李凯丽; 梁庭; 洪应平; 杨芳; 秦丽; 熊继军
2013-01-01
In the occasion of no direct contact measured signal, the wireless coupling transmitting is used and the signal is tested, and the transmission antenna's parameters are calculated Trie ADS software is used to match the antenna impedance for the inductance of 4 u,H at the center frequency of 7. 812 MHz, and the impedance matching circuit is structured, and the test voltage changes before is compared with after the antenna impedance matching. The antenna impedance matching network is optimized.%在无法直接接触测量信号的场合,采用无线耦合方式进行信号传输与测试,对无线耦合信号传输天线进行参数设计,通过ADS软件对电感为4μH、中心频率为7.812 MHz的天线阻抗匹配设计进行仿真,搭建阻抗匹配电路,比较匹配前后天线端测试信号变化,优化天线阻抗匹配网络.
A Self-Complementary 1.2 to 40 GHz Spiral Antenna with Impedance Matching
Directory of Open Access Journals (Sweden)
M. Mazanek
2006-09-01
Full Text Available This paper describes a design of the Self- Complementary Spiral Antenna (SCSA which consists of a spiral antenna and a wideband impedance transformer. The spiral antenna and the transformer are designed separately due to computing demands. New knowledge about current distribution on the spiral antenna and influence of higher numbers of wavelength in circumference is presented. The novel transition between feeding and radiating antenna structure are optimized in the frequency range 1.2 to 40 GHz. The meaning of the transition in the paper includes the impedance as well as the geometry transforming of the structure. The antenna is suitable for wideband illuminating of a parabolic reflector due to relatively constant phase center and radiation pattern with frequency.
Yu, Zhang; Xiaohui, Song; Jianfang, Li; Fei, Gao
2017-05-01
Cable overheating will lead to the cable insulation level reducing, speed up the cable insulation aging, even easy to cause short circuit faults. Cable overheating risk identification and warning is nessesary for distribution network operators. Cable overheating risk warning method based on impedance parameter estimation is proposed in the paper to improve the safty and reliability operation of distribution network. Firstly, cable impedance estimation model is established by using least square method based on the data from distribiton SCADA system to improve the impedance parameter estimation accuracy. Secondly, calculate the threshold value of cable impedance based on the historical data and the forecast value of cable impedance based on the forecasting data in future from distribiton SCADA system. Thirdly, establish risks warning rules library of cable overheating, calculate the cable impedance forecast value and analysis the change rate of impedance, and then warn the overheating risk of cable line based on the overheating risk warning rules library according to the variation relationship between impedance and line temperature rise. Overheating risk warning method is simulated in the paper. The simulation results shows that the method can identify the imedance and forecast the temperature rise of cable line in distribution network accurately. The result of overheating risk warning can provide decision basis for operation maintenance and repair.
Optimal Grouping and Matching for Network-Coded Cooperative Communications
Energy Technology Data Exchange (ETDEWEB)
Sharma, S; Shi, Y; Hou, Y T; Kompella, S; Midkiff, S F
2011-11-01
Network-coded cooperative communications (NC-CC) is a new advance in wireless networking that exploits network coding (NC) to improve the performance of cooperative communications (CC). However, there remains very limited understanding of this new hybrid technology, particularly at the link layer and above. This paper fills in this gap by studying a network optimization problem that requires joint optimization of session grouping, relay node grouping, and matching of session/relay groups. After showing that this problem is NP-hard, we present a polynomial time heuristic algorithm to this problem. Using simulation results, we show that our algorithm is highly competitive and can produce near-optimal results.
Optimizing Transmission Line Matching Circuits
Novak, S.
1996-01-01
When designing transmission line matching circuits, there exist often overlooked, additional, not much used, degree of choice in the selection of the transmission line impedance. In this work are presented results of CAD analysis for the two element transmission line matching networks, demonstrating that selecting matching circuits transmission lines with higher impedance, than usually used 50 or 75 ohms, can in most cases substantially decrease the physical dimension of the final matching ci...
Institute of Scientific and Technical Information of China (English)
汪洪波; 黄稳; 陈长琦
2011-01-01
针对真空磁控溅射射频电源阻抗匹配问题,设计射频L型阻抗匹配网络结构.在负载阻抗不同速率变化时,基于遗传算法优化反射系数指标,通过调节匹配网络中两个电容值以达到与射频源的阻抗匹配.大量仿真结果表明,遗传算法的阻抗匹配过程,反射系数能够很快地被调节到最佳值；即使负载阻抗产生较大突变,匹配网络亦能使反射系数快速恢复到最佳匹配点.匹配过程速度快、在最佳匹配点处反射系数波动小、匹配系统精度高.%The impedance matching of the radio-frequency ( RF) power supply used in magnetron sputtering equipment was simulated based on genetic algorithm. A dedicated L-type RF impedance matching network,the two capacitors of which, C1 and C2,can be automatically regulated to match the impedances of the power supply and the load, was designed , constructed and installed in the control unit of the magnetron sputtering equipment. Hhe simulated results show that when the load impedance changes at different rates, especially at an abrupt, large rate, the reflection coefficient can be rapidly optimized. The test results confirmed that the newly-developed impedance matching network is capable of rapidly reducing the fluctuation below 0.05 and providing a high precision regulation.
Tittl, Andreas; Harats, Moshe G; Walter, Ramon; Yin, Xinghui; Schäferling, Martin; Liu, Na; Rapaport, Ronen; Giessen, Harald
2014-10-28
Plasmonic devices with absorbance close to unity have emerged as essential building blocks for a multitude of technological applications ranging from trace gas detection to infrared imaging. A crucial requirement for such elements is the angle independence of the absorptive performance. In this work, we develop theoretically and verify experimentally a quantitative model for the angular behavior of plasmonic perfect absorber structures based on an optical impedance matching picture. To achieve this, we utilize a simple and elegant k-space measurement technique to record quantitative angle-resolved reflectance measurements on various perfect absorber structures. Particularly, this method allows quantitative reflectance measurements on samples where only small areas have been nanostructured, for example, by electron-beam lithography. Combining these results with extensive numerical modeling, we find that matching of both the real and imaginary parts of the optical impedance is crucial to obtain perfect absorption over a large angular range. Furthermore, we successfully apply our model to the angular dispersion of perfect absorber geometries with disordered plasmonic elements as a favorable alternative to current array-based designs.
Cellular neural networks for the stereo matching problem
Energy Technology Data Exchange (ETDEWEB)
Taraglio, S. [ENEA, Centro Ricerche Casaccia, Rome (Italy). Dipt. Innovazione; Zanela, A. [Rome Univ. `La Sapienza` (Italy). Dipt. di Fisica
1997-03-01
The applicability of the Cellular Neural Network (CNN) paradigm to the problem of recovering information on the tridimensional structure of the environment is investigated. The approach proposed is the stereo matching of video images. The starting point of this work is the Zhou-Chellappa neural network implementation for the same problem. The CNN based system we present here yields the same results as the previous approach, but without the many existing drawbacks.
Cellular neural networks for the stereo matching problem
Energy Technology Data Exchange (ETDEWEB)
Taraglio, S. [ENEA, Centro Ricerche Casaccia, Rome (Italy). Dipt. Innovazione; Zanela, A. [Rome Univ. `La Sapienza` (Italy). Dipt. di Fisica
1997-03-01
The applicability of the Cellular Neural Network (CNN) paradigm to the problem of recovering information on the tridimensional structure of the environment is investigated. The approach proposed is the stereo matching of video images. The starting point of this work is the Zhou-Chellappa neural network implementation for the same problem. The CNN based system we present here yields the same results as the previous approach, but without the many existing drawbacks.
On the impedance of infinite LC ladder networks
Klimo, Paul
2017-01-01
The subject of electrical impedance is on the syllabi of most undergraduate courses in physics and electrical engineering. For example, Richard Feynman in his famous undergraduate text Lectures on Physics shows how to calculate the impedance of an infinite LC ladder. However, the formula he obtains has no useful physical interpretation if considered in the steady state frequency domain. In fact the value of this impedance becomes infinite unless one assumes that the energy flow along the infinite LC ladder is spatially uniform and in one direction only. This ad-hoc assumption, which renders the solution non-causal, is entirely unnecessary if the problem is considered in the time domain. It is important for students to appreciate that the concept of impedance works well only in dissipative circuits where the effects of transients are largely short lived. The purpose of this paper is to show that the same problem treated in the time domain by the Laplace transform method provides a qualitatively different and more satisfying explanation. We show that the current response of an infinite LC ladder, which is in the zero state before a causal harmonic driving voltage is applied, contains a significant non-harmonic component. This component, which is present in addition to the forced harmonic waveform, decays only very slowly and extracts an infinite amount of energy from the source.
Stereo Matching Based on Immune Neural Network in Abdomen Reconstruction
Directory of Open Access Journals (Sweden)
Huan Liu
2015-01-01
Full Text Available Stereo feature matching is a technique that finds an optimal match in two images from the same entity in the three-dimensional world. The stereo correspondence problem is formulated as an optimization task where an energy function, which represents the constraints on the solution, is to be minimized. A novel intelligent biological network (Bio-Net, which involves the human B-T cells immune system into neural network, is proposed in this study in order to learn the robust relationship between the input feature points and the output matched points. A model from input-output data (left reference point-right target point is established. In the experiments, the abdomen reconstructions for different-shape mannequins are then performed by means of the proposed method. The final results are compared and analyzed, which demonstrate that the proposed approach greatly outperforms the single neural network and the conventional matching algorithm in precise. Particularly, as far as time cost and efficiency, the proposed method exhibits its significant promising and potential for improvement. Hence, it is entirely considered as an effective and feasible alternative option for stereo matching.
Contribution to classification of buried objects based on acoustic impedance matching.
Stepanić, J; Wüstenberg, H; Krstelj, V; Mrasek, H
2003-03-01
Determination of material the buried objects are made of could contribute significantly to their recognition, or classification. This is important in detecting buried antipersonnel landmines within the context of humanitarian demining, as well as in a variety of other applications. In this article the concept has been formulated of the approach to buried object's material determination starting with ultrasonic impulse propagation analysis in a particular testing set configuration. The impulse propagates through a characterized transfer material in such a way that a part of it, a reflected wave, carries the information about the buried object's surface material acoustic impedance. The limit of resolution capability is theoretically analyzed and experimentally evaluated and the influencing factors described. Among these, the contact between clean surfaces of the transfer material and buried object is emphasized.
Matching Theory for Channel Allocation in Cognitive Radio Networks
Directory of Open Access Journals (Sweden)
L. Cao
2016-12-01
Full Text Available For a cognitive radio network (CRN in which a set of secondary users (SUs competes for a limited number of channels (spectrum resources belonging to primary users (PUs, the channel allocation is a challenge and dominates the throughput and congestion of the network. In this paper, the channel allocation problem is first formulated as the 0-1 integer programming optimization, with considering the overall utility both of primary system and secondary system. Inspired by matching theory, a many-to-one matching game is used to remodel the channel allocation problem, and the corresponding PU proposing deferred acceptance (PPDA algorithm is also proposed to yield a stable matching. We compare the performance and computation complexity between these two solutions. Numerical results demonstrate the efficiency and obtain the communication overhead of the proposed scheme.
A Low Cost BLE Transceiver with RX Matching Network Reusing PA Load Inductor for WSNs Applications
Liang, Zhen; Li, Bin; Huang, Mo; Zheng, Yanqi; Ye, Hui; Xu, Ken; Deng, Fangming
2017-01-01
In this work, a low cost Bluetooth Low Energy (BLE) transceiver for wireless sensor network (WSN) applications, with a receiver (RX) matching network reusing power amplifier (PA) load inductor, is presented. In order to decrease the die area, only two inductors were used in this work. Besides the one used in the voltage control oscillator (VCO), the PA load inductor was reused as the RX impedance matching component in the front-end. Proper controls have been applied to achieve high transmitter (TX) input impedance when the transceiver is in the receiving mode, and vice versa. This allows the TRX-switch/matching network integration without significant performance degradation. The RX adopted a low-IF structure and integrated a single-ended low noise amplifier (LNA), a current bleeding mixer, a 4th complex filter and a delta-sigma continuous time (CT) analog-to-digital converter (ADC). The TX employed a two-point PLL-based architecture with a non-linear PA. The RX achieved a sensitivity of −93 dBm and consumes 9.7 mW, while the TX achieved a 2.97% error vector magnitude (EVM) with 9.4 mW at 0 dBm output power. This design was fabricated in a 0.11 μm complementary metal oxide semiconductor (CMOS) technology and the front-end circuit only occupies 0.24 mm2. The measurement results verify the effectiveness and applicability of the proposed BLE transceiver for WSN applications. PMID:28422068
Analysis of acoustic impedance matching in dual-band ultrasound transducers.
Myhre, Ola Finneng; Johansen, Tonni Franke; Johan Angelsen, Bjørn Atle
2017-02-01
Dual-frequency band probes are needed for ultrasound (US) reverberation suppression and are useful for image-guided US therapy. A challenge is to design transducer stacks that achieve high bandwidth and efficiency at both operating frequencies when the frequencies are widely separated with a frequency ratio ∼6:1-20:1. This paper studies the loading and backing conditions of transducers in such stacks. Three stack configurations are presented and analyzed using one-dimensional models. It is shown that a configuration with three layers of material separating the transducers is favorable, as it reduces high frequency ringing by ∼20 dB compared to other designs, and matches the low frequency (LF) transducer to the load at a lower frequency. In some cases, the LF load matching is governed by a simple mass-spring interaction in spite of having a complicated matching structure. The proposed design should yield improved performance of reverberation suppression algorithms. Its suitability for reduction of probe heating, also in single-band probes, should be investigated.
Kaatee, R S; Crezee, J; Kanis, A P; Lagendijk, J J; Levendag, P C; Visser, A G
1997-06-01
In interstitial heating one of the main requirements for achieving a certain elevated temperature in a tumour is that the effective power per applicator (Peff), i.e. the power which is actually deposited in the tissue, is sufficiently high. In this paper this requirement is discussed for the applicators of the 27 MHz multielectrode current source (MECS) interstitial hyperthermia (IHT) system. To minimize power reflection, the applicator impedance was matched with the generator impedance by adjusting the length of the coaxial cable in between. Transmission line losses, applicator efficiency and subsequently Peff were computed for several applicator types. The actual Peff per electrode was obtained from calorimetric measurements. Experiments with RC loads, which can be seen as perfect applicators, were performed to investigate the effect of mismatching on Peff. Applicator losses were measured for clinically used applicators, both single- and dual-electrode, utilizing saline phantoms. A simple spherical tumour model, using the effective heat conductivity (keff) to account for heat transport, was used to estimate Peff for a given tumour size, implant size and applicator density. Computations of Peff of various MECS-IHT electrodes were in close agreement with the phantom measurements. Most of the initial generator power was absorbed in the transmission line (60-65%). The efficiency of the applicators was about 65%. For both single- and dual-electrode applicators the effective electrode power was found to be about 1 W. Model calculations show that Peff of 1 W is sufficient to reach a minimum tumour temperature of 43 degrees C in well perfused tumours (keff = 3 W m-1 degree C-1), using a typical implant with 2 cm electrodes and 1.5 cm spacing. Mismatching can considerably affect Peff. Both a reduction to almost zero and a two-fold increase are possible. However, because the matching theory is well understood, mismatching is not a serious problem in clinical practice and
Lin, Yo-Sheng; Lee, Tai-Hsing
2004-10-01
The realization of matched-impedance wide-band amplifier fabricated by 0.18 μm complementary metal oxide semiconductor (CMOS) process is reported. The technique of multiple feedback loops was used in the amplifier for terminal impedance matching and wide bandwidth simultaneously. The experimental results show that 3-dB bandwidth of 3 GHz and a gain of 10.7 dB with in-band input/output return loss more than 10 dB are obtained. These values agree well with those predicted from the analytic expressions derived for voltage gain, trans-impedance gain, bandwidth, and input/output return loss and impedance. In addition, the use of source capacitive peaking technique can improve the intrinsic over-damped characteristic of this amplifier.
Active network alignment: a matching-based approach
Malmi, Eric; Gionis, Aristides
2016-01-01
Network alignment is the problem of matching the nodes of two graphs, maximizing the similarity of the matched nodes and the edges between them. This problem is encountered in a wide array of applications - from biological networks to social networks to ontologies - where multiple networked data sources need to be integrated. Due to the difficulty of the task, an accurate alignment can rarely be found without human assistance. Thus, it is of great practical importance to develop network alignment algorithms that can optimally leverage experts who are able to provide the correct alignment for a small number of nodes. Yet, only a handful of existing works address this active network alignment setting. The majority of the existing active methods focus on absolute queries ("are nodes $a$ and $b$ the same or not?"), whereas we argue that it is generally easier for a human expert to answer relative queries ("which node in the set $\\{b_1, \\ldots, b_n\\}$ is the most similar to node $a$?"). This paper introduces a nov...
Impedance matching of a coaxial antenna for microwave in-situ processing of polluted soils.
Pauli, Mario; Kayser, Thorsten; Wiesbeck, Werner; Komarov, Vyacheslav
2011-01-01
The present paper is focused on the minimization of return loss of a slotted coaxial radiator proposed for a decontamination system for soils contaminated by volatile or semi-volatile organic compounds such as oils or fuels. The antenna upgrade is achieved by coating it with a 5 mm thick Teflon layer. The electromagnetic characteristics reflection coefficient and power density distribution around the antenna surrounded by soils with different moisture levels are analyzed numerically. Simplified analytical approaches are employed to accelerate the optimization of the given antenna for microwave heating systems. The improved antenna design shows a good matching of the antenna to the surrounding soil with varying moisture levels. This ensures a high efficiency of the proposed in-situ soil decontamination system.
A network approach in analysis of the matching hypothesis
Jia, Tao; Spivey, Robert; Korniss, Gyorgy; Szymanski, Boleslaw
2014-03-01
The matching hypothesis in social psychology claimed that people are more likely to form a committed relationship with someone who is equally attractive. This phenomenon can be well interpreted by the principle of homophily that people are apt to get in touch with others similar to them. Yet, social experiments indicate that people in general tend to prefer more attractive individuals regardless of their own attractiveness. Here study the stochastic matching process for different underlying networks and different attractiveness distributions. We showed that the correlation of attractiveness within couples could purely due to the limited number of acquaintance each person has and such correlation decreases as the network becomes more sparse. We also analyzed the effect of the degree distribution and the attractiveness on the number of individuals that can not find their partners. This work is supported by ARL NS-CTA, ARO, and ONR.
Memory Efficient String Matching Algorithm for Network Intrusion Management System
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
As the core algorithm and the most time consuming part of almost every modern network intrusion management system (NIMS), string matching is essential for the inspection of network flows at the line speed. This paper presents a memory and time efficient string matching algorithm specifically designed for NIMS on commodity processors. Modifications of the Aho-Corasick (AC) algorithm based on the distribution characteristics of NIMS patterns drastically reduce the memory usage without sacrificing speed in software implementations. In tests on the Snort pattern set and traces that represent typical NIMS workloads, the Snort performance was enhanced 1.48%-20% compared to other well-known alternatives with an automaton size reduction of 4.86-6.11 compared to the standard AC implementation. The results show that special characteristics of the NIMS can be used into a very effective method to optimize the algorithm design.
Structural controllability of complex networks based on preferential matching.
Zhang, Xizhe; Lv, Tianyang; Yang, XueYing; Zhang, Bin
2014-01-01
Minimum driver node sets (MDSs) play an important role in studying the structural controllability of complex networks. Recent research has shown that MDSs tend to avoid high-degree nodes. However, this observation is based on the analysis of a small number of MDSs, because enumerating all of the MDSs of a network is a #P problem. Therefore, past research has not been sufficient to arrive at a convincing conclusion. In this paper, first, we propose a preferential matching algorithm to find MDSs that have a specific degree property. Then, we show that the MDSs obtained by preferential matching can be composed of high- and medium-degree nodes. Moreover, the experimental results also show that the average degree of the MDSs of some networks tends to be greater than that of the overall network, even when the MDSs are obtained using previous research method. Further analysis shows that whether the driver nodes tend to be high-degree nodes or not is closely related to the edge direction of the network.
示波器阻抗匹配及探头选择问题研究%Research of Impedance Matching of Oscilloscope and Probe Selection
Institute of Scientific and Technical Information of China (English)
张秀华
2013-01-01
简要介绍了阻抗匹配的原理，分析了示波器测试通道输入阻抗匹配问题以及测试探头的选择问题，为测试人员在进行系统信号测试时提供了参考依据。%It introduces principle of impedance matching , analyses impedance matching of oscilloscope channel and probe selection.References are given to testing personnel during signal of system tested .
Institute of Scientific and Technical Information of China (English)
宋建立; 谭阳红; 张海霞; 贾庸; 于辉
2015-01-01
Power Line Communication(PLC)technology is an important communication method which has been extensively used in power system. In order to solve the impedance mismatch of PLC system, an adaptive impedance matching model for power line communication based on Quantum Particle Swarm Optimization(QPSO)has been proposed. With the help of Õ type matching network, PLC system can effectively eliminate matching restricted areas and get very accuracy matching results and fast matching speed. Dealing with the asymmetrical region by the variation, an improved quantum particle swarm optimization algorithm is proposed. Compared with GA(Genetic Algorithm), QPSO is employed in the impedance match because of fast convergence and satisfactory solutions. Test results indicate that the accuracy and the velocity of impedance match for PLC have been greatly improved, which effectively overcome the impedance mismatch of PLC system. Therefore, it will provide a perfect significance and application value in the engineering practice.%电力载波通信技术是电力系统中的重要通信手段，针对电力载波通信中阻抗失配问题，提出一种基于量子粒子群算法的电力载波通信自适应阻抗匹配模型。采用Õ型网络结构，有效地消除了匹配禁区问题，能够快速精准地获得匹配结果。针对遗传算法收敛速度慢、优化精度不高的缺陷，对量子粒子群算法在非对称区间进行分层变异改进处理，并将其应用于自适应阻抗匹配元件参数值的优化。测试结果表明此方案在阻抗匹配的精度和时间方面都有很大的提高，解决了电力线阻抗变化的问题，满足了电力载波通信在精准性、高效性和实时性的要求，在工程实践中具有一定的理论意义和应用价值。
三支节液态调配器ICRH时的阻抗匹配分析%Analysis of Impedance Matching of Three Liquid Stub Tuner for ICRH
Institute of Scientific and Technical Information of China (English)
尹陈艳; 龚学余; 杜丹; 向东; 胡凌志; 谭清懿
2014-01-01
In the paper ,the impedance matching between RF source and antenna load was studied by adopting the three liquid stub tuner for ion cyclotron resonance heating (ICRH) on Tokamak based on the transmission line theory .The impedance matching process was analyzed ,and the optimized parameters of three liquid stub tuner for the changeable antenna input impedance were obtained according to impedance matching condition .The numerical simulation results show that optimized parameters of three liquid stub tuner can make the antenna system obtain good matching w hen the other experimental conditions are same .%基于传输线理论，采用三支节液态调配器以达到托卡马克离子回旋共振加热（ICRH）时射频源和天线负载间的阻抗匹配。分析了其阻抗匹配过程，并根据阻抗匹配条件得到天线输入阻抗变化时，三支节液态调配器的优化调配参数。利用数值模拟验证了在其他实验参数相同的条件下，三支节液态调配器的优化调配参数能使天线系统获得良好的匹配状态。
Microwave Impedance Matching of A 2.45 GHz ECR Ion Source%2.45 GHz ECR离子源的微波阻抗匹配
Institute of Scientific and Technical Information of China (English)
钱程; 陈志; 马鸿义; 武启; 张文慧; 王云; 杨尧; 方兴; 孙良亭
2013-01-01
ECR离子源的等离子体阻抗对其微波传输与阻抗匹配设计至关重要.在中国科学院近代物理研究所现有的2.45 GHz ECR质子源上,对等离子体阻抗进行了测量.首先用水吸收负载代替等离子体负载测量得到了所用微波窗阻抗,然后根据质子源测量数据,推算得到了等离子体阻抗.实验结果表明,脊波导输出端阻抗与后续负载不完全匹配,等离子体阻抗随微波功率变化呈非线性.这些结果为ECR离子源过渡匹配和微波窗的设计提供了参考依据.%Plasma impedance of an ECR ion source is important for microwave transmission and impedance matching design. Plasma impedance was measured indirectly with the 2.45 GHz ECR proton source at the Institute of Modern Physics, Chinese Academy of Sciences. In the test, we got microwave window impedance by using water absorption load instead of plasma load, and the source plasma impedance was derived from the test data with the 2.45 GHz ECR proton source and microwave window impedance. The experimental results show that ridge waveguide output impedance and the subsequent load does not exactly match, plasma impedance variation is nonlinear with microwave power. The achieved result is useful in the design of ridged waveguide and microwave window.
Bora, Pritom J.; Porwal, Mayuri; Vinoy, K. J.; Ramamurthy, Praveen C.; Madras, Giridhar
2016-09-01
In this work, a promising, polyvinyl butryl (PVB)-MnO2 decorated Fe composite was synthesised and microwave absorption properties were studied for the most important frequency ranges i.e., X-band (8.2-12.4 GHz) and Ku-band (12.4-18 GHz). The microwave absorption of Fe nano cauliflower structure can be enhanced by MnO2 nanofiber coating. 10 wt% Fe-MnO2 nano cauliflower loaded PVB composite films (2 mm thick) shows an appreciable increase in microwave absorption properties. In X-band, the reflection loss (RL) of this composite decreases almost linearly to -7.5 dB, whereas in the Ku-band the minimum RL was found to be -15.7 dB at 14.7 GHz. Here it was observed that impedance matching is the primarily important factor responsible for enhanced microwave absorption. Further, enhancement of EM attenuation constant (α), dielectrics, scattering attenuation also bolsters the obtained results. This polymer composite can be considered as a novel microwave absorbing coating material.
Moya, A A
2016-02-01
The Gerischer impedance, i.e., the diffusion-reaction impedance of an ionic species in semi-infinite space, has been modelled by means of a novel simple equivalent ladder electric circuit constituted by a finite number of resistors and capacitors, which corresponds to the Cauer structure obtained from development into continued fractions. The Nyquist plots of the impedance of the ladder network or Cauer circuit and the deviation with respect to the Gerischer impedance have been originally analysed as a function of the number of circuit elements. From the Cauer equivalent circuit, a new and simple expression modelling the Gerischer impedance at the limit of the lowest frequencies has been derived.
Directory of Open Access Journals (Sweden)
Cunfu He
2014-01-01
Full Text Available Truss structure is widely used in civil engineering. However, it is difficult to quantitatively monitor the state of truss structures because of the connection diversity and complexity of truss structures. In this paper, electromechanical impedance (EMI technique was proposed to measure impedance spectra by using PZT elements and backpropagation (BP neural network was used as an effective nonlinear conversion tool to quantify the health state of truss structures. Firstly, frequency band of the spectrum was experimentally determined by the trial-and-error approach. Then four connection rods of this truss structure were selected for experimental research. These connection rods were loosened gradually with a small angle increment and the impedance spectra were recorded. Then, the measured data were compressed through dividing the frequency range into multiple subbands. And RMSD values of these bands showed that data points were reduced while damage features remained. Finally, one four-layered BP neural network model was constructed based on these compressed data. The research results showed that compressed impedance data could retain their damage features. After the training, the developed neural network model could not only determine the location of loosened rod, but also quantify the loosening levels.
Elasticity on Ontology Matching of Folksodriven Structure Network
Mas, Massimiliano Dal
2012-01-01
Nowadays folksonomy tags are used not just for personal organization, but for communication and sharing between people sharing their own local interests. In this paper is considered the new concept structure called "Folksodriven" to represent folksonomies. The Folksodriven Structure Network (FSN) was thought as folksonomy tags suggestions for the user on a dataset built on chosen websites - based on Natural Language Processing (NLP). Morphological changes, such as changes in folksonomy tags chose have direct impact on network connectivity (structural plasticity) of the folksonomy tags considered. The goal of this paper is on defining a base for a FSN plasticity theory to analyze. To perform such goal it is necessary a systematic mathematical analysis on deformation and fracture for the ontology matching on the FSN. The advantages of that approach could be used on a new interesting method to be employed by a knowledge management system.
Three-Level Z-Source Inverters Using a Single LC Impedance Network
DEFF Research Database (Denmark)
Loh, Poh Chiang; Lim, Sok Wei; Gao, Feng
2007-01-01
two LC impedance networks and two isolated dc sources, which can significantly increase the overall system cost and require a more complex modulator for balancing the network inductive voltage boosting. Offering a number of less costly alternatives, this letter presents the design and control of two...... three-level Z-source inverters, whose output voltage can be stepped down or up using only a single LC impedance network connected between the dc input source and either a neutral-point-clamped (NPC) or dc-link cascaded inverter circuitry. Through careful design of their modulation scheme, both inverters...... can function with the minimum of six device commutations per half carrier cycle (similar to that needed by a traditional buck three-level NPC inverter), while producing the correct volt-sec average and inductive voltage boosting at their ac output terminals. Physically, the designed modulation scheme...
Evolutionary matching-pennies game on bipartite regular networks
Szabó, György; Varga, Levente; Borsos, István
2014-04-01
Evolutionary games are studied here with two types of players located on a chessboard or on a bipartite random regular graph. Each player's income comes from matching-pennies games played with the four neighbors. The players can modify their own strategies according to a myopic strategy update resembling the Glauber dynamics for the kinetic Ising model. This dynamical rule drives the system into a stationary state where the two strategies are present with the same probability without correlations between the nearest neighbors while a weak correlation is induced between the second and the third neighbors. In stationary states, the deviation from the detailed balance is quantified by the evaluation of entropy production. Finally, our analysis is extended to evolutionary games where the uniform pair interactions are composed of an anticoordination game and a weak matching-pennies game. This system preserves the Ising type order-disorder transitions at a critical noise level decreasing with the strength of the matching-pennies component for both networks.
Comparison of the Impedance-Source Networks for Two and Multilevel Buck-Boost Inverter Applications
DEFF Research Database (Denmark)
Husev, Oleksandr; Blaabjerg, Frede; Roncero-Clemente, Carlos
2016-01-01
Impedance-source networks are an increasingly popular solution in power converter applications, especially in single-stage buck–boost power conversion to avoid additional front-end dc–dc power converters. In the survey papers published, no analytical comparisons of different topologies have been...... described, which makes it difficult to choose the best option. Thus, the aim of this paper is to present a comprehensive analytical comparison of the impedance-source-based buck–boost inverters in terms of passive component count and semiconductor stress. Based on the waveform of the input current, i...... in the inductors and the voltage ripple across the capacitors. Two-level and multilevel solutions are described. The conclusions provide a “one-stop” information source and a selection guide of impedance-source-based buck–boost inverters for different applications....
Institute of Scientific and Technical Information of China (English)
唐金元; 王翠珍; 于潞
2011-01-01
阻抗匹配电路是电子测量仪器前端模拟通道中的关键电路.在介绍电子测量仪器前端模拟通道组成、功能的基础七,阐述了阻抗匹配的作用,即实现信号最大功率传输和实现信号无反射传输.分析了选频匹配网络中常用的倒L型网络、T型网络和Ⅱ型网络的电路模型和电路参数设计计算方法,给出了实现阻抗变换的各种电压跟随器的电路结构形式,并对电子测量仪器前端T型阻抗匹配电路参数的计算进行了举例说明.%Impedance matching circuit is the key circuit in analog input channels of electronic measuring instruments.The paper firstly introduced the composition and functions of analog input channels in instruments, and expounded the roles of impedance matching, that is, it can transmit signal with maximum power or without reflecting.In the same time, it also analyzed the circuit models and the calculating methods of overturning L, T and Ⅱ style network, and proposed the circuits of each voltage follower to realize impedance change.Finally, the paper illustrate the parameter calculation of T impedance matching circuit in analog input channels of electronic measuring instruments.
Institute of Scientific and Technical Information of China (English)
魏海潮; 张记龙; 陈友华; 王艳超; 陈媛媛; 王志斌
2013-01-01
According to the principle of photoelastic modulated interfermeter, the impedance matching features of piezoelectric crystal has been analyzed and calculated firstly based on the equivalent circuit method,then the ideal matching condition between the piezoelectric crystal and the signal source has been derived.and finally the theoretical relation of inductance and capacitance in the impedance matching network has been obtained. In order to validate the proposed theory, some impedance matching experiments are designed and implemented. The experiment results indicate that the vibration performance of photoelastic modulated interfemeter has been optimized after using the impedance matching network. Meanwhile, the electronic quality factor of the driving controller is raised so that it leads to 40% increase of optical path difference, which improves the spectral resolution of the photoelastic modulated Fourier transform spectrometer.%根据弹光调制干涉具的工作原理,利用等效电路的方法,对压电晶体的阻抗特性进行了分析与计算,推导出了压电晶体与信号源间的理想匹配条件,得出了匹配网络中电感、电容的理论关系.根据理论关系,在信号源与压电晶体间作相应的阻抗匹配,搭建系统并进行相关实验验证.实验结果表明,通过该阻抗匹配网络,可使弹光调制干涉具的振动性能达到最佳,提高了驱动控制器的电品质因数,进而将弹光调制干涉具调制光程差提高了40％,达到了提高弹光调制傅里叶变换光谱仪光谱分辨率的目的.
File Detection On Network Traffic Using Approximate Matching
Directory of Open Access Journals (Sweden)
Frank Breitinger
2014-09-01
Full Text Available In recent years, Internet technologies changed enormously and allow faster Internet connections, higher data rates and mobile usage. Hence, it is possible to send huge amounts of data / files easily which is often used by insiders or attackers to steal intellectual property. As a consequence, data leakage prevention systems (DLPS have been developed which analyze network traffic and alert in case of a data leak. Although the overall concepts of the detection techniques are known, the systems are mostly closed and commercial.Within this paper we present a new technique for network trac analysis based on approximate matching (a.k.a fuzzy hashing which is very common in digital forensics to correlate similar files. This paper demonstrates how to optimize and apply them on single network packets. Our contribution is a straightforward concept which does not need a comprehensive conguration: hash the file and store the digest in the database. Within our experiments we obtained false positive rates between 10-4 and 10-5 and an algorithm throughput of over 650 Mbit/s.
Simulation of stochastic network dynamics via entropic matching.
Ramalho, Tiago; Selig, Marco; Gerland, Ulrich; Ensslin, Torsten A
2013-02-01
The simulation of complex stochastic network dynamics arising, for instance, from models of coupled biomolecular processes remains computationally challenging. Often, the necessity to scan a model's dynamics over a large parameter space renders full-fledged stochastic simulations impractical, motivating approximation schemes. Here we propose an approximation scheme which improves upon the standard linear noise approximation while retaining similar computational complexity. The underlying idea is to minimize, at each time step, the Kullback-Leibler divergence between the true time evolved probability distribution and a Gaussian approximation (entropic matching). This condition leads to ordinary differential equations for the mean and the covariance matrix of the Gaussian. For cases of weak nonlinearity, the method is more accurate than the linear method when both are compared to stochastic simulations.
Perfect Match: Biometrics and Body Patterning in a Networked World
Directory of Open Access Journals (Sweden)
Gillian Fuller
2003-01-01
Full Text Available Bodies are increasingly becoming collectively integrated into informational processes which are open to biotechnical forms of regulation. Biometrics, the use of body measurements such as retina scanning, face recognition and fingerprinting is now being uncontroversially introduced throughout the world under the aegis of security and efficient traffic management. Fields that once molded the individual through bodily confinement and observation are dispersing and converging into the regimes of logistics and control. This paper looks at the operations of biometrics to consider the biopolitical ramifications of body measurement as power is made operational by controlling movement via the haptic techniques of information architecture rather than the more familiar modes of discipline and panoptical vision machines. Biometrics is the perfect control for the networked individual as we divide across infinite planes and dimensions, reconfiguring endlessly to become pattern matches in expanding databases of everyday life.
DEFF Research Database (Denmark)
Kouchaki, Alireza; Nymand, Morten
2016-01-01
This paper presents LCL filter design method for three-phase two-level power factor correction (PFC) using line impedance stabilization network (LISN). A straightforward LCL filter design along with variation in grid impedance is not simply achievable and inevitably lead to an iterative solution...
Institute of Scientific and Technical Information of China (English)
陈鑫; 刘祥萱
2013-01-01
采用Smith圆图对尖晶石镍铁氧体的输入阻抗进行表征，并根据传输线理论计算不同涂层厚度下尖晶石镍铁氧体的反射率。结果表明，Smith圆图中输入阻抗越接近点（α=1，β=0），阻抗匹配性越好，反射率也越小。这为基于Smith圆图的吸波材料阻抗匹配设计应用奠定了基础。%The input impedance of spinel nickel ferrite was characterized by Smith circle diagram,and the reflectivity of spinel nickel ferrite with different coating thicknesses was calculated by transmission line theory. The results show that the closer the input impedance in the Smith circle diagram is to the point(α=1,β=0),the better the impedance matching is,and the smaller the reflectance is,which lays the foundation for application of Smith circle diagram in impedance matching design of absorbing materials.
Power Network impedance effects on noise emission of DC-DC converters
Esteban, M. C.; Arteche, F.; Iglesias, M.; Gimeno, A.; Arcega, F. J.; Johnson, M.; Cooper, W. E.
2012-01-01
The characterization of electromagnetic noise emissions of DC-DC converters is a critical issue that has been analyzed during the desing phase of CMS tracker upgrade. Previous simulation studies showed important variations in the level of conducted emissions when DC-DC converters are loaded/driven by different impedances and power network topologies. Several tests have been performed on real DC-DC converters to validate the Pspice model and simulation results. This paper presents these test results. Conducted noise emissions at the input and at the output terminals of DC-DC converters has been measured for different types of power and FEE impedances. Special attention has been paid to influence on the common-mode emissions by the carbon fiber material used to build the mechanical structure of the central detector. These study results show important recommendations and criteria to be applied in order to decrease the system noise level when integrating the DC-DC.
Research of impedance matching based on Matlab simulation%基于Matlab仿真的阻抗匹配问题的研究
Institute of Scientific and Technical Information of China (English)
王月爱; 侯艳红; 冯向莉
2013-01-01
阻抗匹配在高频设计中是一个常用的概念.对于不同特性的电路,匹配条件是不一样的.在纯电阻电路中,当负载电阻等于激励源内阻时,则输出功率为最大,这种工作状态称为匹配,否则称为失配.为了实现射频电路信号传输的完整性,使“信号质量奇迹般的改善”,必须做好电路的阻抗匹配.利用Matlab仿真解决阻抗匹配问题,设计了一套调节可调电容的算法,编写了算法和仿真的可视化Matlab程序,通过程序验证了算法的可行性；详细介绍了射频电路数学模型的建立,确定分段调节和同步调节两种阻抗匹配方案,并对四种参数情况下的仿镇结果和算法进行比较和讨论,得出算法存在的不足及改进方向.%Impedance matching in the high frequency design is a commonly used concept. For the circuits with different characteristics, their matching conditions are not the same. In the pure resistance circuit, when the load resistance is equal to the excitation source resistance, the output power is maximum. This state is called matching, otherwise known as mismatch. In order to realize the integrity of RF signal transmission and make "signal quality improvement like the miracle", the circuit im-pedance matching must be done. Matlab simulation is used in this paper to solve the impedance matching problem. A set of algo-rithms used for adjusting the adjustable capacitor is designed. A visual Matlab program for the algorithm and simulation is com-piled. The feasibility of the algorithm is verified by the program. The mathematical model establishment of RF circuit is intro-duced in detail. Two impedance matching schemes for the segmentation adjustment and synchronization regulation was deter-mined. The algorithms and emulating results obtained with four different parameters are compared and discussed. The deficiency of the algorithm and its improvement direction are pointed out.
Negative autoregulation matches production and demand in synthetic transcriptional networks.
Franco, Elisa; Giordano, Giulia; Forsberg, Per-Ola; Murray, Richard M
2014-08-15
We propose a negative feedback architecture that regulates activity of artificial genes, or "genelets", to meet their output downstream demand, achieving robustness with respect to uncertain open-loop output production rates. In particular, we consider the case where the outputs of two genelets interact to form a single assembled product. We show with analysis and experiments that negative autoregulation matches the production and demand of the outputs: the magnitude of the regulatory signal is proportional to the "error" between the circuit output concentration and its actual demand. This two-device system is experimentally implemented using in vitro transcriptional networks, where reactions are systematically designed by optimizing nucleic acid sequences with publicly available software packages. We build a predictive ordinary differential equation (ODE) model that captures the dynamics of the system and can be used to numerically assess the scalability of this architecture to larger sets of interconnected genes. Finally, with numerical simulations we contrast our negative autoregulation scheme with a cross-activation architecture, which is less scalable and results in slower response times.
一种用于无源UHF RFID应答器的阻抗匹配方法%A Novel Impedance Matching Approach for Passive UHF RFID Transponder ICs
Institute of Scientific and Technical Information of China (English)
陈力颖; 毛陆虹; 吴顺华; 郑轩
2008-01-01
This paper presents a novel impedance matching approach for passive UHF RFID transponder ICs, which are compatible with the ISO/IEC 18000-6B standard and operate in the 915MHz ISM band. The passive UHF RFID transpon- der with complex impedances is powered by received RF energy. The approach uses the parasitic inductance of the antenna to implement ASK modulation by adjusting the capacitive reactance of the matching network, which changes with the backscatter circuit. The impedance matching achieves maximum power transfer between the reader, antenna, and tran- sponder. The transponder IC, whose operating distance is more than 4m with the impedance matching approach, is fabrica- ted using a Chartered 0. 35μm two-poly four-metal CMOS process that supports Schottkv diodes and EEPROM.%提出了一种可以在915MHz ISM频带下工作的、符合ISO/IEC 18000-6B标准的无源UHF RFID应答器的阻抗匹配方法.该UHF RFID应答器具有复数阻抗并从射频电磁场接收能量.该阻抗匹配方法利用天线的寄生电感,通过调整反向散射电路的电容来改变匹配网络的容抗,从而实现ASK调制.而且,该阻抗匹配方法在阅读器、天线与应答器之间达到了最大的功率传输.采用该阻抗匹配方法的应答器芯片通过支持肖特基二极管和EEPROM的Chartered 0.35μm 2P4M CMOS工艺进行流片,经测试其工作距离约为4m.
Theory and design of broadband matching networks applied electricity and electronics
Chen, Wai-Kai
1976-01-01
Theory and Design of Broadband Matching Networks centers on the network theory and its applications to the design of broadband matching networks and amplifiers. Organized into five chapters, this book begins with a description of the foundation of network theory. Chapter 2 gives a fairly complete exposition of the scattering matrix associated with an n-port network. Chapter 3 considers the approximation problem along with a discussion of the approximating functions. Chapter 4 explains the Youla's theory of broadband matching by illustrating every phase of the theory with fully worked out examp
频率调制对ICRH天线阻抗匹配的影响研究%Influence of frequency modulation on the impedence matching of ICRH antenna
Institute of Scientific and Technical Information of China (English)
谭清懿; 龚学余; 杜丹; 郭征荣
2015-01-01
采用三支节液态调配器使离子回旋加热(ICRH)天线系统达到阻抗匹配，在阻抗匹配的条件下结合频率调制技术来减小由天线输入阻抗变化所引起的反射功率。数值模拟了频率调制前后天线负载与反射系数的变化关系，用来验证频率调制对ICRH天线中阻抗匹配装置的影响。模拟结果表明：三支节液态调配器结合频率调制方法，能更好地降低天线传输系统的反射系数，使得发射机的功率通过天线辐射更加有效地耦合到等离子体中去。%The liquid triple-stub tuner was adopted to obtain the impedance matching for antenna load of ion cyclotron resonance heating. Under the condition of impedance matching, the frequency modulation technique was used to reduce the reflected power caused by the change of antenna loading. The relationship between reflection coefficient and antenna loading before and after frequency modulation was numerically simulated to everify the effect of frequency modulation on ICRH system impedance matching device. The numerical simulation results show that the liquid triple-stub tuner combine with frequency modulation technique can better reduce the reflection coefficient of transmission system and make the RF power transit antenna radiation coupled to plasma more effectively.
Liang, Zhen; Li, Bin; Huang, Mo; Zheng, Yanqi; Ye, Hui; Xu, Ken; Deng, Fangming
2017-04-19
In this work, a low cost Bluetooth Low Energy (BLE) transceiver for wireless sensor network (WSN) applications, with a receiver (RX)-matching network-reusing power amplifier (PA) load inductor, is presented. In order to decrease the die area, only two inductors were used in this work. Besides the one used in the voltage control oscillator (VCO), the PA load inductor was reused as the RX impedance matching component in the front-end. Proper controls have been applied to achieve high transmitter (TX) input impedance when the transceiver is in the receiving mode, and vice versa. This allows the TRX-switch/matching network integration without significant performance degradation. The RX adopted a low-IF structure and integrated a single-ended low noise amplifier (LNA), a current bleeding mixer, a 4th complex filter and a delta-sigma continuous time (CT) analog-to-digital converter (ADC). The TX employed a two-point PLL-based architecture with a non-linear PA. The RX achieved a sensitivity of -93 dBm and consumes 9.7 mW, while the TX achieved a 2.97% error vector magnitude (EVM) with 9.4 mW at 0 dBm output power. This design was fabricated in a 0.11 μm complementary metal oxide semiconductor (CMOS) technology and the front-end circuit only occupies 0.24 mm². The measurement results verify the effectiveness and applicability of the proposed BLE transceiver for WSN applications.
多层介质阻抗匹配对隔爆效果的影响%Influence of multilayered media impedance matching on explosion interruption effect
Institute of Scientific and Technical Information of China (English)
陈闯; 王晓鸣; 李文彬; 贾方秀; 殷婷婷
2014-01-01
为了有效提升隔爆结构衰减爆炸冲击波的性能，将45＃钢、铝和有机玻璃进行不同组合，设计了顺序波阻抗梯度、逆序波阻抗梯度以及硬软硬三种多层隔爆结构。利用锰铜压阻传感器测压实验和数值计算对多层介质阻抗匹配特性对隔爆效果的影响进行了研究，获得了多层介质的不同组合引起的冲击波在传播过程中各层介质压力，理论分析、数值计算与实验结果吻合较好，并分析了第三层介质能量与冲量的变化规律。从不同方面得到的结果表明：逆序波阻抗梯度的输出冲击波压力最小，其第三层的能量与冲量最小，隔爆效果最佳。%In order to improve the performance of explosion interruption structures to attenuate explosion shock wave effectively,the explosion interruption structures with sequential impedance matching gradient, reverse impedance matching gradient and hard-soft-hard layers were designed through different combinations of 45 #steel,Aluminum and PMMA.The influence of multilayered media impedance matching property on the explosion interruption effect was studied by using a manganin pressure-resistance sensor and numerical calculation.The pressure of each layer media was obtained due to shock wave caused with different combinations of multilayered media in a process of shock wave transmission.The test results were consistent with those of the theoretical analysis and numerical calculation,the change rules of energy and impulse in the third layer were analyzed as well.The results from different aspects showed that the structures with reverse impedance matching gradient have an optimal explosion interruption effect,their output shock wave pressure is the minimum,their third layer's energy and impulse are the minimum too.
A Linkage Matching Method for Road and Habitation by Using Urban Skeleton Line Network
Directory of Open Access Journals (Sweden)
LIU Chuang
2016-12-01
Full Text Available Obvious data consistency degree is not high in roads or habitation data, often in the presence of large geometric position deviation, which is not conducive to improve the accuracy and efficiency of road or habitation matching. A linkage matching method for road and habitation by using urban skeleton line network is proposed to solve this problem. The linkage matching imitates the human thinking process of searching for target objects by the signal features and spatial correlation when reading maps, regarding matching as a reasoning process of goal feature searching and information association transmitting. Firstly, urban skeleton line network is constructed by constraint Delaunay triangulation network; then, the topological relationship among road, skeleton line, skeleton line mesh, habitation is constructed; last, matching transmission model is established by the topological relationship. According to this matching transmission model, linkage matching is fulfilled, which contains road matching drives habitation matching or habitation matching drives road matching. The advantage of this method is that as long as there is an element of data consistency is good, can drive another element to obtain a very good matching effect, at the same time conform to the human cognitive process.
Institute of Scientific and Technical Information of China (English)
刘鑫鑫; 张鹏飞; 李刚; 张天才
2013-01-01
电光调制器在量子光学、原子物理、激光光谱、光学控制和测量等许多方面具有广泛的应用,其射频阻抗匹配是重要的技术问题.文章在现有常用的射频匹配方法的基础上,运用Smith圆图,提出了一套简单快速实现电光调制器射频阻抗匹配的方法,包括网络构建的分析、设计并完成了在Labview环境下运用Smith图对电光调制器射频阻抗匹配网络设计的程序等.在此基础上,采用Newfocus 4002和Thorlabs公司的两种不同的电光调制器进行了实验.实验结果表明,在设计频率53.047 MHz和97.977 MHz处,匹配效率可以达到99.05％和95.6％.%Electro-optic modulator (EOM) has been widely used in many fields,such as optical communications, optical control and measurement and it is also used for quantum optics,atomic physics,laser spectros-copy,etc. The RF impedance matching of the EOM is an important technical issue. Based on the usual RF matching principle and method,and by using the Smith Chart,we propose a set of reliable and rapid method of RF impedance matching for an EOM,which includes the analysis of a network construction,the design procedures by using Smith chart in LABVIEW environment. We demonstrate the method on two EOMs from New Focus 4002 and Thorlabs The results show that the impedance matching efficiencies are 99. 5% and 95. 6% at the design frequency of 53. 047 MHz and 97. 977 MHz,respectively.
IMPROVED FINGER PRINT MATCHING USING MINUTIAE SINGULAR POINTS NETWORK
Prof. Vikas Goyal*, Himanshu Jindal
2017-01-01
Fingerprints are considered as a unique identification of a person and due to easy access its the best and one of the fastest method used in biometric identification systems. They are unique, so secure and reliable to use and doesnt change for one in a lifetime. And beside these things fingerprint recognition specially using minutiae matching technique is cheap, reliable and accurate up to a satisfactory limits. In this thesis work, we propose a method for fingerprint matching based...
Analysis of Impedance Matching Influence on Signal Transmission Quality%阻抗匹配对信号传输质量影响的分析
Institute of Scientific and Technical Information of China (English)
简钊
2012-01-01
Base on the common fault phenomenon in daily maintenance of digital television, this article intro- duces some technical problems often ignored and analyses special troubles made by coaxial cables in CATV system connecting theory with practice. Then the basic principles and concepts of impedance matching be- tween signal and transmission line are presented, to prove the consequence of signal transmission quality by impedance matching or not. With the purpose to give some references in maintenance work, a number of com- mon factors, which probable generate the fault phenomenon have summarized in the last place.%针对数字电视日常维护中常见的故障现象，从实践到理论分析了有线电视系统中由同轴电缆引起的一些特殊故障，阐述了信号与传输线路之间阻抗匹配的基本原理与概念，进一步验证阻抗的匹配与否直接关系到信号传输质量的优劣，最后总结了导致该类故障的常见因素，给相关维护工作提供参考。
Dawson, Michael R W; Dupuis, Brian; Spetch, Marcia L; Kelly, Debbie M
2009-08-01
The matching law (Herrnstein 1961) states that response rates become proportional to reinforcement rates; this is related to the empirical phenomenon called probability matching (Vulkan 2000). Here, we show that a simple artificial neural network generates responses consistent with probability matching. This behavior was then used to create an operant procedure for network learning. We use the multiarmed bandit (Gittins 1989), a classic problem of choice behavior, to illustrate that operant training balances exploiting the bandit arm expected to pay off most frequently with exploring other arms. Perceptrons provide a medium for relating results from neural networks, genetic algorithms, animal learning, contingency theory, reinforcement learning, and theories of choice.
Three-Level Z-Source Inverters Using a Single LC Impedance Network
DEFF Research Database (Denmark)
Loh, Poh Chiang; Lim, Sok Wei; Gao, Feng
2007-01-01
Three-level Z-source inverters are recent single-stage topological solutions proposed for buck-boost energy conversion with all favorable advantages of three-level switching retained. Despite their effectiveness in achieving voltage buck-boost conversion, existing three-level Z-source inverters use...... three-level Z-source inverters, whose output voltage can be stepped down or up using only a single LC impedance network connected between the dc input source and either a neutral-point-clamped (NPC) or dc-link cascaded inverter circuitry. Through careful design of their modulation scheme, both inverters...... can conveniently be implemented using a generic "alternative phase opposition disposition" carrier-based modulator with the appropriate triplen offset and time advance/delay added. The designed inverters, having a reduced passive component count, are lastly tested in simulation and experimentally...
Network-level accident-mapping: Distance based pattern matching using artificial neural network.
Deka, Lipika; Quddus, Mohammed
2014-04-01
The objective of an accident-mapping algorithm is to snap traffic accidents onto the correct road segments. Assigning accidents onto the correct segments facilitate to robustly carry out some key analyses in accident research including the identification of accident hot-spots, network-level risk mapping and segment-level accident risk modelling. Existing risk mapping algorithms have some severe limitations: (i) they are not easily 'transferable' as the algorithms are specific to given accident datasets; (ii) they do not perform well in all road-network environments such as in areas of dense road network; and (iii) the methods used do not perform well in addressing inaccuracies inherent in and type of road environment. The purpose of this paper is to develop a new accident mapping algorithm based on the common variables observed in most accident databases (e.g. road name and type, direction of vehicle movement before the accident and recorded accident location). The challenges here are to: (i) develop a method that takes into account uncertainties inherent to the recorded traffic accident data and the underlying digital road network data, (ii) accurately determine the type and proportion of inaccuracies, and (iii) develop a robust algorithm that can be adapted for any accident set and road network of varying complexity. In order to overcome these challenges, a distance based pattern-matching approach is used to identify the correct road segment. This is based on vectors containing feature values that are common in the accident data and the network data. Since each feature does not contribute equally towards the identification of the correct road segments, an ANN approach using the single-layer perceptron is used to assist in "learning" the relative importance of each feature in the distance calculation and hence the correct link identification. The performance of the developed algorithm was evaluated based on a reference accident dataset from the UK confirming that
DEFF Research Database (Denmark)
Wang, Xiongfei; Blaabjerg, Frede; Chen, Zhe
2012-01-01
This paper proposes a harmonic impedance synthesis technique for voltage-controlled distributed generation inverters in order to damp harmonic voltage distortion on a distribution network. The approach employs a multiloop control scheme, where a selective harmonic load current feedforward loop ba...
DEFF Research Database (Denmark)
Wang, Xiongfei; Blaabjerg, Frede; Chen, Zhe
2012-01-01
This paper proposes a harmonic impedance synthesis technique for voltage-controlled distributed generation inverter in order to damp harmonic voltage distortion on a distribution network. The approach employs a multiloop control scheme, where a selective load harmonic current feedforward loop bas...
Directory of Open Access Journals (Sweden)
Rutger Goekoop
Full Text Available INTRODUCTION: Human personality is described preferentially in terms of factors (dimensions found using factor analysis. An alternative and highly related method is network analysis, which may have several advantages over factor analytic methods. AIM: To directly compare the ability of network community detection (NCD and principal component factor analysis (PCA to examine modularity in multidimensional datasets such as the neuroticism-extraversion-openness personality inventory revised (NEO-PI-R. METHODS: 434 healthy subjects were tested on the NEO-PI-R. PCA was performed to extract factor structures (FS of the current dataset using both item scores and facet scores. Correlational network graphs were constructed from univariate correlation matrices of interactions between both items and facets. These networks were pruned in a link-by-link fashion while calculating the network community structure (NCS of each resulting network using the Wakita Tsurumi clustering algorithm. NCSs were matched against FS and networks of best matches were kept for further analysis. RESULTS: At facet level, NCS showed a best match (96.2% with a 'confirmatory' 5-FS. At item level, NCS showed a best match (80% with the standard 5-FS and involved a total of 6 network clusters. Lesser matches were found with 'confirmatory' 5-FS and 'exploratory' 6-FS of the current dataset. Network analysis did not identify facets as a separate level of organization in between items and clusters. A small-world network structure was found in both item- and facet level networks. CONCLUSION: We present the first optimized network graph of personality traits according to the NEO-PI-R: a 'Personality Web'. Such a web may represent the possible routes that subjects can take during personality development. NCD outperforms PCA by producing plausible modularity at item level in non-standard datasets, and can identify the key roles of individual items and clusters in the network.
Matching-centrality decomposition and the forecasting of new links in networks
Rohr, Rudolf P; Mazza, Christian; Bersier, Louix-Félix
2013-01-01
Networks play a prominent role in the study of complex systems of interacting entities in biology, sociology, and economics. Despite this diversity, we demonstrate here that a statistical model decomposing networks into matching and centrality components provides a comprehensive and unifying quantification of their architecture. First we show, for a diverse set of networks, that this decomposition provides an extremely tight fit to observed networks. Consequently, the model allows very accurate prediction of missing links in partially known networks. Second, when node characteristics are known, we show how the matching-centrality decomposition can be related to this external information. Consequently, it offers a simple and versatile tool to explore how node characteristics explain network architecture. Finally, we demonstrate the efficiency and flexibility of the model to forecast the links that a novel node would create if it were to join an existing network.
A Four-color Matching Method Combining Neural Networks with Genetic Algorithm
Institute of Scientific and Technical Information of China (English)
Su Xiaohong(苏小红); Wang Yadong; Zhang Tianwen
2003-01-01
A brief review of color-matching technology and its application of printing RGB images by CMY or CMYK ink-jet printers is presented, followed by an explanation to the conventional approaches that are commonly used in color-matching. Then, a four-color matching method combining neural network with genetic algorithm is proposed. The initial weights and thresholds of the BP neural network for RGB-to-CMY color conversion are optimized by the new genetic algorithm based on evolutionarily stable strategy. The fourth component K is generated by using GCR (Gray Component Replacement) concept. Simulation experiments show that it is well behaved in both accuracy and generalization performance.
The prediction in computer color matching of dentistry based on GA+BP neural network.
Li, Haisheng; Lai, Long; Chen, Li; Lu, Cheng; Cai, Qiang
2015-01-01
Although the use of computer color matching can reduce the influence of subjective factors by technicians, matching the color of a natural tooth with a ceramic restoration is still one of the most challenging topics in esthetic prosthodontics. Back propagation neural network (BPNN) has already been introduced into the computer color matching in dentistry, but it has disadvantages such as unstable and low accuracy. In our study, we adopt genetic algorithm (GA) to optimize the initial weights and threshold values in BPNN for improving the matching precision. To our knowledge, we firstly combine the BPNN with GA in computer color matching in dentistry. Extensive experiments demonstrate that the proposed method improves the precision and prediction robustness of the color matching in restorative dentistry.
Botwicz, Jakub; Buciak, Piotr; Sapiecha, Piotr
2006-03-01
Intrusion Prevention Systems (IPSs) have become widely recognized as a powerful tool and an important element of IT security safeguards. The essential feature of network IPSs is searching through network packets and matching multiple strings, that are fingerprints of known attacks. String matching is highly resource consuming and also the most significant bottleneck of IPSs. In this article an extension of the classical Karp-Rabin algorithm and its implementation architectures were examined. The result is a software, which generates a source code of a string matching module in hardware description language, that could be easily used to create an Intrusion Prevention System implemented in reconfigurable hardware. The prepared module matches the complete set of Snort IPS signatures achieving throughput of over 2 Gbps on an Altera Stratix I1 evaluation board. The most significant advantage of the proposed architecture is that the update of the patterns database does not require reconfiguration of the circuitry.
Institute of Scientific and Technical Information of China (English)
彭源; 莫玉龙
2003-01-01
Electrical impedance tomography (EIT) is a new computer tomography technology, which reconstructs an impedance (resistivity, conductivity) distribution, or change of impedance, by making voltage and current measurements on the object's periphery. Image reconstruction in EIT is an ill-posed, non-linear inverse problem. A method for finding the place of impedance change in EIT is proposed in this paper, in which a multilevel BP neural network (MBPNN) is used to express the non-linear relation between the impedance change inside the object and the voltage change measured on the surface of the object. Thus, the location of the impedance change can be decided by the measured voltage variation on the surface. The impedance change is then reconstructed using a linear approximate method. MBPNN can decide the impedance change location exactly without long training time. It alleviates some noise effects and can be expanded, ensuring high precision and space resolution of the reconstructed image that are not possible by using theback projection method.
An inkjet-printed UWB antenna on paper substrate utilizing a novel fractal matching network
Cook, Benjamin Stassen
2012-07-01
In this work, the smallest reported inkjet-printed UWB antenna is proposed that utilizes a fractal matching network to increase the performance of a UWB microstrip monopole. The antenna is inkjet-printed on a paper substrate to demonstrate the ability to produce small and low-cost UWB antennas with inkjet-printing technology which can enable compact, low-cost, and environmentally friendly wireless sensor network. © 2012 IEEE.
Gao, Zhong-Ke; Dang, Wei-Dong; Xue, Le; Zhang, Shan-Shan
2017-03-01
Characterizing the flow structure underlying the evolution of oil-in-water bubbly flow remains a contemporary challenge of great interests and complexity. In particular, the oil droplets dispersing in a water continuum with diverse size make the study of oil-in-water bubbly flow really difficult. To study this issue, we first design a novel complex impedance sensor and systematically conduct vertical oil-water flow experiments. Based on the multivariate complex impedance measurements, we define modalities associated with the spatial transient flow structures and construct modality transition-based network for each flow condition to study the evolution of flow structures. In order to reveal the unique flow structures underlying the oil-in-water bubbly flow, we filter the inferred modality transition-based network by removing the edges with small weight and resulting isolated nodes. Then, the weighted clustering coefficient entropy and weighted average path length are employed for quantitatively assessing the original network and filtered network. The differences in network measures enable to efficiently characterize the evolution of the oil-in-water bubbly flow structures.
Plummer, MD
1986-01-01
This study of matching theory deals with bipartite matching, network flows, and presents fundamental results for the non-bipartite case. It goes on to study elementary bipartite graphs and elementary graphs in general. Further discussed are 2-matchings, general matching problems as linear programs, the Edmonds Matching Algorithm (and other algorithmic approaches), f-factors and vertex packing.
A novel hybrid-maximum neural network in stereo-matching process.
Laskowski, Lukasz
2013-01-01
In the present paper, the completely innovative architecture of artificial neural network based on Hopfield structure for solving a stereo-matching problem-hybrid neural network, consisting of the classical analog Hopfield neural network and the Maximum Neural Network-is described. The application of this kind of structure as a part of assistive device for visually impaired individuals is considered. The role of the analog Hopfield network is to find the attraction area of the global minimum, whereas Maximum Neural Network is finding accurate location of this minimum. The network presented here is characterized by an extremely high rate of work performance with the same accuracy as a classical Hopfield-like network, which makes it possible to use this kind of structure as a part of systems working in real time. The network considered here underwent experimental tests with the use of real stereo pictures as well as simulated stereo images. This enables error calculation and direct comparison with the classic analog Hopfield neural network as well as other networks proposed in the literature.
Directory of Open Access Journals (Sweden)
Meng Zhan
Full Text Available The structure-dynamics-function has become one of central problems in modern sciences, and it is a great challenge to unveil the organization rules for different dynamical processes on networks. In this work, we study the vibration spectra of the classical mass spring model with different masses on complex networks, and pay our attention to how the mass spatial configuration influences the second-smallest vibrational frequency (ω2 and the largest one (ωN. For random networks, we find that ω2 becomes maximal and ωN becomes minimal if the node degrees are point-to-point-positively correlated with the masses. In these cases, we call it point-to-point matching. Moreover, ω2 becomes minimal under the condition that the heaviest mass is placed on the lowest-degree vertex, and ωN is maximal as long as the lightest mass is placed on the highest-degree vertex, and in both cases all other masses can be arbitrarily settled. Correspondingly, we call it single-point matching. These findings indicate that the matchings between the node dynamics (parameter and the node position rule the global systems dynamics, and sometimes only one node is enough to control the collective behaviors of the whole system. Therefore, the matching rules might be the common organization rules for collective behaviors on networks.
Shah, R.G.; Salafia, C.M.; Girardi, T.; Conrad, L.; Keaty, K.
2015-01-01
Variability in placental chorionic surface vessel networks (PCSVNs) may mark developmental and functional changes in fetal health. Here we report a protocol of manually tracing PCSVNs from digital 2D images of post-delivery placentas and its validation by a shape matching method to compare the similarity between paint-injected and unmanipulated (uninjected and deflated vessels) tracings of PCSVNs. We show that tracings of unmanipulated vessels produce networks that are very comparable to the networks obtained by tracing paint-injected PCSVNs. We suggest that manual tracings of unmanipulated PCSVNs can extract features of PCSVN growth and structure that may impact fetal wellbeing. PMID:26100723
Institute of Scientific and Technical Information of China (English)
马水生; 张亮; 李延军; 徐冰
2011-01-01
介绍了电气化铁道阻抗匹配平衡变压器的平衡匹配机制原理,并进一步就平衡匹配关系数学模型的搭建和变压器高低压侧电流变化的规律进行了推理分析.解析了差动保护在阻抗匹配平衡变压器中如何实现以及铁路电气化差动保护在实现过程中为防止误动作所增加的一些判据.阻抗匹配平衡变压器在电气化铁路建设中广泛应用,其差动保护逻辑和判据已完全由微机来实现,所提的计算方法和理论研究对于阻抗匹配平衡变压器保护设备的开发和应用具有较高的实用价值.%This paper introduces the principle of balance matching mechanism of the electric railway impedance matching balance transformer, and for further, the building of the mathematical model of balance matching relations and the law of current change between high and low pressure side, how to achieve differential protection in impedance matching balance transformer and some criterion added in the realization of railway electrification process in order to prevent malfunction are analyzed.Impedance matching balance transformer is widely used in electrification of railway construction, and its logic and criteria of differential protection has been achieved entirely by computer.The proposed calculation method and theoretical study have high practical value for the development and application of impedance matching balance transformer protection equipment.
A novel matching network employing surface acoustic wave devices for W-CDMA power amplifiers.
Li, Honglang; He, Songbai; Hashimoto, Ken-ya; Omori, Tatsuya; Yamaguchi, Masatsune
2006-12-22
This paper describes a new approach of designing high Q surface acoustic wave (SAW) resonators as an inductive element in the matching network for W-CDMA power amplifiers (PAs). Spiral inductors based on CMOS/BiCMOS technologies presently possess relatively low Q (typically <10) and occupy a considerably large area. In order to break through the limitations of the spiral inductors, the authors attempt to apply higher Q and wideband SAW resonators employing Cu-grating/15 degrees YX-LiNbO(3)-substrate structure to the matching network for improved PA performance. An analysis was made on SAW resonators in detail, and an SAW resonator having a very small capacitance ratio of 3.28 and moderate Q of 147.8 was developed. After discussing the frequency dependence of the effective inductances, SAW resonators, which are used to be as inductive elements in the matching networks of PAs, were designed and fabricated. The PA including the matching circuit was simulated using the characteristics of the fabricated SAW resonators. The result showed that with better shape factor and good out-of-rejection, the SAW resonators definitely work as an inductive element and could replace widely used spiral inductors.
McLean, James; Sutton, Robert; Post, John
2003-10-01
One useful method of acoustic impedance measurement involves the measurement of the electrical impedance ``looking into'' the electrical port of a reciprocal electroacoustic transducer. This reaction on the source method greatly facilitates the measurement of acoustic impedance by borrowing highly refined techniques to measure electrical impedance. It is also well suited for in situ acoustic impedance measurements. In order to accurately determine acoustic impedance from the measured electrical impedance, the characteristics of the transducer must be accurately known, i.e., the characteristics of the transducer must be ``removed'' completely from the data. The measurement of acoustic impedance via the measurement of the reaction on the source is analogous to modern microwave measurements made with an automatic vector network analyzer. The action of the analyzer is described as de-embedding the desired data (such as acoustic impedance) from the raw data. Such measurements are fundamentally substitution measurements in that the transducer's characteristics are determined by measuring a set of reference standards. The reaction on the source method is extended to take advantage of improvements in microwave measurement techniques which allow calibration via imperfect standard loads. This removes one of the principal weaknesses of the method in that the requirement of high-quality reference standards is relaxed.
Institute of Scientific and Technical Information of China (English)
何新; 夏加宽; 李文瑞; 张健
2016-01-01
In order to obtain maximum electric power output for torus topology thermoacoustic electric generation system (TOTAEGS), an acoustic impedance matching design was proposed on spring mechanical impedance and load impedance of the moving permanent magnet linear generator (TMPMLG). Two mathematical models were built about capturing acoustic power and outputting electric power by the acoustic-mechanical-electro analogism. Then combining the features for mechanical structure and gas medium in the travelling-wave thermoacoustic engine(TWTE), and analyzing the acoustic impedance influence from the spring mechanical and load, an acoustic impedance matching method of TMPMLG was proposed on the optimal dual power. The method makes improve capturing acoustic power as the constrained condition, in order to achieve maximum electric power output. Finally, MATALAB simulation and experiment verifies the acoustic impedance matching design on the optimal dual power is correct by the TOTAEGS experimental platform. The acoustic impedance matching design based on the optimal dual power is simple, which provides theoretical guidance for the controller of TOTAEGS.%为获得圆环体拓扑结构的热声发电系统最大电功输出，提出带有可变电负载的动磁式直线发电机声学阻抗匹配设计方法。通过声力电类比方法建立系统捕获声功和输出电功的数学模型。结合热声发动机机械结构和气体工作介质特征，分析弹簧机械阻抗和电负载阻抗对系统声学阻抗的影响，给出双功率优化运行的发电机声学阻抗匹配设计方法。该方法以提高声功捕获为约束条件，实现热声发电系统输出电功最大。用MATLAB程序和热声发电系统模拟实验平台验证双功率优化运行阻抗匹配方法。双功率优化运行的发电机声学阻抗匹配设计方法简单易行，为热声发电系统控制器的设计提供理论指导。
DEFF Research Database (Denmark)
Canali, Chiara; Mohanty, Soumyaranjan; Heiskanen, Arto
2015-01-01
We present the application of electrochemical impedance spectroscopy (EIS) as a method for discriminating between different polydimethylsiloxane (PDMS) scaffolds for three-dimensional (3D) cell cultures. The validity of EIS characterisation for scaffolds having different degree of porosity...... serve as means of single-frequency measurements for fast scaffold characterization combined with in vitro monitoring of 3D cell cultures....
User Matching with Relation to the Stable Marriage Problem in Cognitive Radio Networks
Hamza, Doha R.
2017-03-20
We consider a network comprised of multiple primary users (PUs) and multiple secondary users (SUs), where the SUs seek access to a set of orthogonal channels each occupied by one PU. Only one SU is allowed to coexist with a given PU. We propose a distributed matching algorithm to pair the network users, where a Stackelberg game model is assumed for the interaction between the paired PU and SU. The selected secondary is given access in exchange for monetary compensation to the primary. The PU optimizes the interference price it charges to a given SU and the power allocation to maintain communication. The SU optimizes its power demand so as to maximize its utility. Our algorithm provides a unique stable matching. Numerical results indicate the advantage of the proposed algorithm over other reference schemes.
Analysis of the Optimum Gain of a High-Pass L-Matching Network for Rectennas
Directory of Open Access Journals (Sweden)
Manel Gasulla
2017-07-01
Full Text Available Rectennas, which mainly consist of an antenna, matching network, and rectifier, are used to harvest radiofrequency energy in order to power tiny sensor nodes, e.g., the nodes of the Internet of Things. This paper demonstrates for the first time, the existence of an optimum voltage gain for high-pass L-matching networks used in rectennas by deriving an analytical expression. The optimum gain is that which leads to maximum power efficiency of the rectenna. Here, apart from the L-matching network, a Schottky single-diode rectifier was used for the rectenna, which was optimized at 868 MHz for a power range from −30 dBm to −10 dBm. As the theoretical expression depends on parameters not very well-known a priori, an accurate search of the optimum gain for each power level was performed via simulations. Experimental results show remarkable power efficiencies ranging from 16% at −30 dBm to 55% at −10 dBm, which are for almost all the tested power levels the highest published in the literature for similar designs.
Analysis of the Optimum Gain of a High-Pass L-Matching Network for Rectennas.
Gasulla, Manel; Jordana, Josep; Robert, Francesc-Josep; Berenguer, Jordi
2017-07-25
Rectennas, which mainly consist of an antenna, matching network, and rectifier, are used to harvest radiofrequency energy in order to power tiny sensor nodes, e.g., the nodes of the Internet of Things. This paper demonstrates for the first time, the existence of an optimum voltage gain for high-pass L-matching networks used in rectennas by deriving an analytical expression. The optimum gain is that which leads to maximum power efficiency of the rectenna. Here, apart from the L-matching network, a Schottky single-diode rectifier was used for the rectenna, which was optimized at 868 MHz for a power range from -30 dBm to -10 dBm. As the theoretical expression depends on parameters not very well-known a priori, an accurate search of the optimum gain for each power level was performed via simulations. Experimental results show remarkable power efficiencies ranging from 16% at -30 dBm to 55% at -10 dBm, which are for almost all the tested power levels the highest published in the literature for similar designs.
Institute of Scientific and Technical Information of China (English)
张喆斯; 马延鋆; 宋振华; 马宏伟
2015-01-01
针对基于磁致伸缩式纵向超声导波传感器的管道无损检测问题，介绍了磁致伸缩式纵向超声导波传感器的检测原理及其结构。在此基础上，对接收传感器与接收源之间的阻抗匹配问题进行了讨论，阐述了实现阻抗匹配的条件与方法，并且通过理论计算得到最佳匹配条件与匹配电路的最佳电容。最后，设计了验证试验，验证了阻抗匹配问题的存在，讨论了阻抗匹配角、匹配电容值与导波信号幅值之间的关系，并且利用试验方法得到了真实条件下匹配电路的最佳电容值。%Aiming at the problems of nondestructive testing of pipelines based on longitudinal guided wave magnetostrictive sensor, in this article, the testing principle and structure of the longitudinal guided wave magnetostrictive sensor was introduced.Based on it,the problem of the impedance matching between the receiving transducer and the receiving source was discussed deeply.The conditions of implementation and methods of impedance matching are elaborated.Optimal matching condition and the optimal capacitor of the matching circuit is obtained from theoretical calculations.Finally,experiment was designed to verify the existence of the problems of impedance matching,and the relationships among the impedance matching angle,the matching capacitance and the guided wave signal amplitude was discussed,and the best capacitance value of matching circuit under real conditions was obtained by experimental method.
A dual band high impedance antenna for RF Harvest applications
Medina, Andres J.
A design for a compact dual band very high impedance antenna for RF Harvest applications is presented. The antenna is designed to present a very high input impedance at its feed point at 900 MHz and 1.8 GHz. The design incorporates the folding concept into a customized bowtie antenna to achieve high input impedance. The design methodology and simulations are presented, as well as a comparison of the measured results against the simulation results. A rectifier circuit and dual band matching network are also simulated and presented.
Institute of Scientific and Technical Information of China (English)
张燕; 尚中选; 吕印定; 顾彪
2013-01-01
The fairly homogeneous plasma was generated by dielectric barrier discharge(BDB)in the 3 mm gap filled with atmospheric pressure nitrogen, and regulated with the impedance matching network. The impacts of the discharge conditions on plasma characteristics were evaluated.The discharge was found to be Townsend mode. The results show that at a given frequency and gas-gap width, as the amplitude of driving voltage increased, the discharge current and discharge power increased at different rates,a fairly slow increase,followed by a linear increase after the discharge area covered the entire electrode. Besides, an increase of frequency resulted in an observable resonance of the discharge current and power. However, the experimentally optimized driving frequency was found to disagree with the simulated result reported by Chen et al.%在介质阻挡放电装置中,使用阻抗匹配网络后,当气体间隙为3mm时,在大气压氮气中获得了均匀介质阻挡放电等离子体,放电模式为汤森放电.在其他放电参数不变的情况下,放电电流和放电功率随着外加电压峰峰值的增大先非常缓慢增加,然后当放电面积铺满整个电极后呈线性增加.而放电电流和放电功率随驱动频率的增加呈现出非常明显的谐振现象,实验所得到的最佳匹配频率和Chen给出的理论计算结果存在差异.
Directory of Open Access Journals (Sweden)
Kentaro Inoue
Full Text Available BACKGROUND: For visualizing large-scale biochemical network maps, it is important to calculate the coordinates of molecular nodes quickly and to enhance the understanding or traceability of them. The grid layout is effective in drawing compact, orderly, balanced network maps with node label spaces, but existing grid layout algorithms often require a high computational cost because they have to consider complicated positional constraints through the entire optimization process. RESULTS: We propose a hybrid grid layout algorithm that consists of a non-grid, fast layout (preprocessor algorithm and an approximate pattern matching algorithm that distributes the resultant preprocessed nodes on square grid points. To demonstrate the feasibility of the hybrid layout algorithm, it is characterized in terms of the calculation time, numbers of edge-edge and node-edge crossings, relative edge lengths, and F-measures. The proposed algorithm achieves outstanding performances compared with other existing grid layouts. CONCLUSIONS: Use of an approximate pattern matching algorithm quickly redistributes the laid-out nodes by fast, non-grid algorithms on the square grid points, while preserving the topological relationships among the nodes. The proposed algorithm is a novel use of the pattern matching, thereby providing a breakthrough for grid layout. This application program can be freely downloaded from http://www.cadlive.jp/hybridlayout/hybridlayout.html.
Matching Parasitic Antenna for Single RF MIMO
DEFF Research Database (Denmark)
Han, Bo; Kalis, A; Nielsen, Rasmus Hjorth
2012-01-01
Single RF MIMO communication emerges a novel low cost communication method which does not consume as much power as the conventional MIMO. The implementation of such single RF MIMO system is done by mapping the weighting factors to the polarizations or the radiation patterns of the antennas....... In order to have such performance, an antenna with rich pattern modes is required by the system, thus the ESPAR antenna is investigated. The critical part on such antenna is parasitic element impedance matching. Unlike the conventional smith-chart matching method which assumes the minimal resistance...... is zero and with goal of 50 ohm or 75 ohm matching, matching on such parasitic antenna will adopt negative value as well. This paper presents a matching network with controllable impedance even to the range of negative values....
Predicting Football Matches Results using Bayesian Networks for English Premier League (EPL)
Razali, Nazim; Mustapha, Aida; Yatim, Faiz Ahmad; Aziz, Ruhaya Ab
2017-08-01
The issues of modeling asscoiation football prediction model has become increasingly popular in the last few years and many different approaches of prediction models have been proposed with the point of evaluating the attributes that lead a football team to lose, draw or win the match. There are three types of approaches has been considered for predicting football matches results which include statistical approaches, machine learning approaches and Bayesian approaches. Lately, many studies regarding football prediction models has been produced using Bayesian approaches. This paper proposes a Bayesian Networks (BNs) to predict the results of football matches in term of home win (H), away win (A) and draw (D). The English Premier League (EPL) for three seasons of 2010-2011, 2011-2012 and 2012-2013 has been selected and reviewed. K-fold cross validation has been used for testing the accuracy of prediction model. The required information about the football data is sourced from a legitimate site at http://www.football-data.co.uk. BNs achieved predictive accuracy of 75.09% in average across three seasons. It is hoped that the results could be used as the benchmark output for future research in predicting football matches results.
Institute of Scientific and Technical Information of China (English)
SONG Tian; WANG DongSheng; TANG ZhiZhong
2009-01-01
Pattern matching is one of the most performance-critical components for the content inspection based applications of network security, such as network intrusion detection and prevention. To keep up with the increasing speed network, this component needs to be accelerated by well designed custom coprocessor. This paper presents a paremeterized multilevel pattern matching architecture (MPM) which is used on FPGAs. To achieve less chip area, the architecture is designed based on the idea of selected character decoding (SCD) and multilevel method which are analyzed in detail. This paper also proposes an MPM generator that can generate RTL-level codes of MPM by giving a pattern set and predefined parameters. With the generator, the efficient MPM architecture can be generated and embedded to a total hardware solution. The third contribution is a mathematical model and formula to estimate the chip area for each MPM before it is generated, which is useful for choosing the proper type of FPGAs. One example MPM architecture is implemented by giving 1785 patterns of Snort on Xilinx Virtex 2 Pro FPGA.The results show that this MPM can achieve 4.3 Gbps throughput with 5 stages of pipelines and 0.22 slices per character, about one half chip area of the most area-efficient architecture in literature. Other results are given to show that MPM is also efficient for general random pattern sets. The performance of MPM can be scalable near linearly, potential for more than 100 Gbps throughput.
DEFF Research Database (Denmark)
Guo, Xiaoqiang; Zhang, Xue; Wang, Baocheng;
2014-01-01
This letter presents a new control strategy of threephase grid-connected inverter for the positive sequence voltage recovery and negative sequence voltage reduction under asymmetrical grid faults. Unlike the conventional control strategy based on an assumption that the network impedance is mainly...... inductive, the proposed control strategy is more flexible and effective by considering the network impedance impact, which is of great importance for the high penetration of grid-connected renewable energy systems into low-voltage grids. The experimental tests are carried out to validate the effectiveness...
NetMatchStar: an enhanced Cytoscape network querying app [version 1; referees: 2 approved
Directory of Open Access Journals (Sweden)
Fabio Rinnone
2015-08-01
Full Text Available We present NetMatchStar, a Cytoscape app to find all the occurrences of a query graph in a network and check for its significance as a motif with respect to seven different random models. The query can be uploaded or built from scratch using Cytoscape facilities. The app significantly enhances the previous NetMatch in style, performance and functionality. Notably NetMatchStar allows queries with wildcards.
DEFF Research Database (Denmark)
Jensen, Kåre Jean; Munk, Steen M.; Sørensen, John Aasted
1998-01-01
processes and communication systems lead to demands for improved monitoring of power distribution networks so that the quality of power delivery can be kept at a controlled level. The ground fault localization method for each feeder in a network is based on the centralized frequency broadband measurement...... of three phase voltages and currents. The method consists of a feature extractor, based on a grid description of the feeder by impulse responses, and a neural network for ground fault localization. The emphasis of this paper is the feature extractor, and the detection of the time instance of a ground fault...
Zhang, K.; Sheng, Y. H.; Li, Y. Q.; Han, B.; Liang, Ch.; Sha, W.
2006-10-01
In the field of digital photogrammetry and computer vision, the determination of conjugate points in a stereo image pair, referred to as "image matching," is the critical step to realize automatic surveying and recognition. Traditional matching methods encounter some problems in the digital close-range stereo photogrammetry, because the change of gray-scale or texture is not obvious in the close-range stereo images. The main shortcoming of traditional matching methods is that geometric information of matching points is not fully used, which will lead to wrong matching results in regions with poor texture. To fully use the geometry and gray-scale information, a new stereo image matching algorithm is proposed in this paper considering the characteristics of digital close-range photogrammetry. Compared with the traditional matching method, the new algorithm has three improvements on image matching. Firstly, shape factor, fuzzy maths and gray-scale projection are introduced into the design of synthetical matching measure. Secondly, the topology connecting relations of matching points in Delaunay triangulated network and epipolar-line are used to decide matching order and narrow the searching scope of conjugate point of the matching point. Lastly, the theory of parameter adjustment with constraint is introduced into least square image matching to carry out subpixel level matching under epipolar-line constraint. The new algorithm is applied to actual stereo images of a building taken by digital close-range photogrammetric system. The experimental result shows that the algorithm has a higher matching speed and matching accuracy than pyramid image matching algorithm based on gray-scale correlation.
Coalition-based multimedia peer matching strategies for P2P networks
Park, Hyunggon; van der Schaar, Mihaela
2008-01-01
In this paper, we consider the problem of matching users for multimedia transmission in peer-to-peer (P2P) networks and identify strategies for fair resource division among the matched multimedia peers. We propose a framework for coalition formation, which enables users to form a group of matched peers where they can interact cooperatively and negotiate resources based on their satisfaction with the coalition, determined by explicitly considering the peer's multimedia attributes. In addition, our proposed approach goes a step further by introducing the concept of marginal contribution, which is the value improvement of the coalition induced by an incoming peer. We show that the best way for a peer to select a coalition is to choose the coalition that provides the largest division of marginal contribution given a deployed value-division scheme. Moreover, we model the utility function by explicitly considering each peer's attributes as well as the cost for uploading content. To quantify the benefit that users derive from a coalition, we define the value of a coalition based on the total utility that all peers can achieve jointly in the coalition. Based on this definition of the coalition value, we use an axiomatic bargaining solution in order to fairly negotiate the value division of the upload bandwidth given each peer's attributes.
Institute of Scientific and Technical Information of China (English)
李龙; 余楚中; 王鹏飞
2011-01-01
Impedance matching balance transformer is tion substation transformer. In order to solve the puzzle often used as the main electrified railway tracthat could not accurately identify the failure in internal or external impedance matching transformer by traditional fauh diagnosis method, based on that the winding resistance and short circuit reactance value have not been changed in normal opera- tion for impedance matching balance transformer or external fault, the paper proposed an identification algorithm of recursive least square parameter estimation on line to distinguish the fault. The curve of experimental simulation demonstrated that it could effectively distinguish to be internal failure or external fault. The research result shows its feasibility to distinguish two sorts of different faults.%阻抗匹配平衡变压器常被用作电气化铁道牵引变电所的主变压器。为解决传统故障诊断方式难以准确鉴别该变压器内外故障，基于正常运行或发生外部故障时绕组电阻和短路电抗值不产生变化，而当出现内部故障时将产生变化的问题，提出了利用最小二乘参数估计递推算法在线辨识其变化以鉴别内外故障。实验仿真曲线证实了采用该算法能有效区分其内外故障，研究结果验证了用该方法鉴别2种不同类型故障的可行性。
Profile-Matching Techniques for On-Demand Software Management in Sensor Networks
Directory of Open Access Journals (Sweden)
Falko Dressler
2007-03-01
Full Text Available The heterogeneity and dynamics in terms of hardware and software configurations are steadily increasing in wireless sensor networks (WSNs. Therefore, software management is becoming one of the most prominent challenges in this domain. This applies especially for on-demand updates for improved redundancy or adaptive task allocation. Methodologies for efficient software management in WSN need to be investigated for operating and maintaining large-scale sensor networks. We developed a profile-based software management scheme that consists of a dynamic profile-matching algorithm to identify current hardware and software configurations, an on-demand code generation module, and mechanisms for dynamic network-centric reprogramming of sensor nodes. We exploit the advantages of robot-based reconfiguration and reprogramming methods for efficient and secure software management. The mobile robot system is employed for decision processes and to store the source code repository. The developed methods are depicted in detail. Additionally, we demonstrate the applicability and advantages based on a scenario that we implemented in our lab.
Profile-Matching Techniques for On-Demand Software Management in Sensor Networks
Directory of Open Access Journals (Sweden)
Dressler Falko
2007-01-01
Full Text Available The heterogeneity and dynamics in terms of hardware and software configurations are steadily increasing in wireless sensor networks (WSNs. Therefore, software management is becoming one of the most prominent challenges in this domain. This applies especially for on-demand updates for improved redundancy or adaptive task allocation. Methodologies for efficient software management in WSN need to be investigated for operating and maintaining large-scale sensor networks. We developed a profile-based software management scheme that consists of a dynamic profile-matching algorithm to identify current hardware and software configurations, an on-demand code generation module, and mechanisms for dynamic network-centric reprogramming of sensor nodes. We exploit the advantages of robot-based reconfiguration and reprogramming methods for efficient and secure software management. The mobile robot system is employed for decision processes and to store the source code repository. The developed methods are depicted in detail. Additionally, we demonstrate the applicability and advantages based on a scenario that we implemented in our lab.
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.
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.
Energy Technology Data Exchange (ETDEWEB)
Golfinopoulos, Theodore, E-mail: golfit@mit.edu; LaBombard, Brian; Burke, William; Parker, Ronald R.; Parkin, William; Woskov, Paul [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139 (United States)
2014-04-15
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.
Analysis of oversized sliding waveguide by mode matching and multi-mode network theory
Energy Technology Data Exchange (ETDEWEB)
Ohkubo, K.; Kubo, S.; Idei, H.; Shimozuma, T.; Yoshimura, Y.; Sato, M.; Takita, Y. [National Inst. for Fusion Science, Toki, Gifu (Japan); Leuterer, F. [Max-Planck Institut fuer Plasmaphysik, Garching (Germany)
2000-12-01
Transmission and reflection coefficients of HE{sub 11} hybrid modes in the sliding waveguide are discussed on the basis of mode matching method and multi-mode network theory. The sliding waveguide is composed of the corrugated waveguide with 88.9 mm{phi} and the smooth-wall waveguide with 110 mm{phi} in inner diameter. It is confirmed that the decrease in power of <0.2% at 84 GHz is obtained for 2 cm in gap of the sliding waveguide. At the sliding length near multi-half-wavelength in vacuum, transmission and reflection powers in the sliding waveguide change slightly, because the very small amount of standing wave of higher-order TE or TM modes is produced resonantly. (author)
Color matching of fabric blends: hybrid Kubelka-Munk + artificial neural network based method
Furferi, Rocco; Governi, Lapo; Volpe, Yary
2016-11-01
Color matching of fabric blends is a key issue for the textile industry, mainly due to the rising need to create high-quality products for the fashion market. The process of mixing together differently colored fibers to match a desired color is usually performed by using some historical recipes, skillfully managed by company colorists. More often than desired, the first attempt in creating a blend is not satisfactory, thus requiring the experts to spend efforts in changing the recipe with a trial-and-error process. To confront this issue, a number of computer-based methods have been proposed in the last decades, roughly classified into theoretical and artificial neural network (ANN)-based approaches. Inspired by the above literature, the present paper provides a method for accurate estimation of spectrophotometric response of a textile blend composed of differently colored fibers made of different materials. In particular, the performance of the Kubelka-Munk (K-M) theory is enhanced by introducing an artificial intelligence approach to determine a more consistent value of the nonlinear function relationship between the blend and its components. Therefore, a hybrid K-M+ANN-based method capable of modeling the color mixing mechanism is devised to predict the reflectance values of a blend.
Detecting network intrusions by data mining and variable-length sequence pattern matching
Institute of Scientific and Technical Information of China (English)
Tian Xinguang; Duan Miyi; Sun Chunlai; Liu Xin
2009-01-01
Anomaly detection has been an active research topic in the field of network intrusion detection for many years. A novel method is presented for anomaly detection based on system calls into the kernels of Unix or Linux systems. The method uses the data mining technique to model the normal behavior of a privileged program and uses a variable-length pattern matching algorithm to perform the comparison of the current behavior and historic normal behavior, which is more suitable for this problem than the fixed-length pattern matching algorithm proposed by Forrest et al. At the detection stage, the particularity of the audit data is taken into account, and two alternative schemes could be used to distinguish between normalities and intrusions. The method gives attention to both computational efficiency and detection accuracy and is especially applicable for on-line detection. The performance of the method is evaluated using the typical testing data set, and the results show that it is significantly better than the anomaly detection method based on hidden Markov models proposed by Yan et al. and the method based on fixed-length patterns proposed by Forrest and Hofmeyr. The novel method has been applied to practical hosted-based intrusion detection systems and achieved high detection performance.
Directory of Open Access Journals (Sweden)
Claudia Cioli
Full Text Available We explore the relationships between the cortex functional organization and genetic expression (as provided by the Allen Human Brain Atlas. Previous work suggests that functional cortical networks (resting state and task based are organized as two large networks (differentiated by their preferred information processing mode shaped like two rings. The first ring--Visual-Sensorimotor-Auditory (VSA--comprises visual, auditory, somatosensory, and motor cortices that process real time world interactions. The second ring--Parieto-Temporo-Frontal (PTF--comprises parietal, temporal, and frontal regions with networks dedicated to cognitive functions, emotions, biological needs, and internally driven rhythms. We found--with correspondence analysis--that the patterns of expression of the 938 genes most differentially expressed across the cortex organized the cortex into two sets of regions that match the two rings. We confirmed this result using discriminant correspondence analysis by showing that the genetic profiles of cortical regions can reliably predict to what ring these regions belong. We found that several of the proteins--coded by genes that most differentiate the rings--were involved in neuronal information processing such as ionic channels and neurotransmitter release. The systematic study of families of genes revealed specific proteins within families preferentially expressed in each ring. The results showed strong congruence between the preferential expression of subsets of genes, temporal properties of the proteins they code, and the preferred processing modes of the rings. Ionic channels and release-related proteins more expressed in the VSA ring favor temporal precision of fast evoked neural transmission (Sodium channels SCNA1, SCNB1 potassium channel KCNA1, calcium channel CACNA2D2, Synaptotagmin SYT2, Complexin CPLX1, Synaptobrevin VAMP1. Conversely, genes expressed in the PTF ring favor slower, sustained, or rhythmic activation (Sodium
Fagnoni, Nicolas
2016-01-01
The Hydrogen Epoch of Reionization Array (HERA) is a new powerful radio-telescope, dedicated to the study of the early universe. Its main goal is to characterise the period of the universe where the first galaxies and stars started to form, by studying the evolution of the 21-cm emission signal from neutral hydrogen, during the Epoch of Reionization. In this article, we present an electromagnetic and electrical co-simulation of the antenna performed with CST. We focus our analysis on the characterisation of the chromatic effects caused by the antenna, in particular multiple reflections of the received signal between the feed and the dish. These reflections can have an important impact on the scientific results, and it is crucial to keep them as low as possible. Therefore, we are currently developing a matching circuit which aims to improve the impedance matching between the feed and the front end.
Impedance Scaling and Impedance Control
Energy Technology Data Exchange (ETDEWEB)
Chou, W.; Griffin, J.
1997-06-01
When a machine becomes really large, such as the Very Large Hadron Collider (VLHC), of which the circumference could reach the order of megameters, beam instability could be an essential bottleneck. This paper studies the scaling of the instability threshold vs. machine size when the coupling impedance scales in a ``normal`` way. It is shown that the beam would be intrinsically unstable for the VLHC. As a possible solution to this problem, it is proposed to introduce local impedance inserts for controlling the machine impedance. In the longitudinal plane, this could be done by using a heavily detuned rf cavity (e.g., a biconical structure), which could provide large imaginary impedance with the right sign (i.e., inductive or capacitive) while keeping the real part small. In the transverse direction, a carefully designed variation of the cross section of a beam pipe could generate negative impedance that would partially compensate the transverse impedance in one plane.
Microwave Impedance Measurement for Nanoelectronics
Directory of Open Access Journals (Sweden)
M. Randus
2011-04-01
Full Text Available The rapid progress in nanoelectronics showed an urgent need for microwave measurement of impedances extremely different from the 50Ω reference impedance of measurement instruments. In commonly used methods input impedance or admittance of a device under test (DUT is derived from measured value of its reflection coefficient causing serious accuracy problems for very high and very low impedances due to insufficient sensitivity of the reflection coefficient to impedance of the DUT. This paper brings theoretical description and experimental verification of a method developed especially for measurement of extreme impedances. The method can significantly improve measurement sensitivity and reduce errors caused by the VNA. It is based on subtraction (or addition of a reference reflection coefficient and the reflection coefficient of the DUT by a passive network, amplifying the resulting signal by an amplifier and measuring the amplified signal as a transmission coefficient by a common vector network analyzer (VNA. A suitable calibration technique is also presented.
Institute of Scientific and Technical Information of China (English)
陈航; 张允孟; 李志舜
2001-01-01
The article study widening band of longitudinal mode piezoelectric transducers.The non-single resonance characteristics appear by forming proper impedance matching layers on the radiative surface of longitudinal mode piezoelectric transducer.The places of resonance points can be adjusted,and the radiated characteristic of transducer with single matching layers was improved by choosing the length of matching layer reasonably.The research on the transducer having mechanical quality factor Qm＝6,bandwidth of transmitting sensitivity △f＝4kHz presents that,using quarter matching layer,two times bandwidth was achieved in same transmitting sensitivity.%本文研究纵向振动压电换能器的频带展宽问题。在复合棒纵向换能器的辐射端加上适当材料的阻抗匹配层，可以使其工作在非单谐振状态下。在单层阻抗匹配层的情况下，合理地选择匹配层的厚度可以调整其谐振点之间的位置，从而改善换能器的辐射特性。本研究结果表明，对于机械品质因素Qm＝6，发射响应带宽△f＝4kHz的纵向振子，采用四分之一波长厚度的匹配层，在不降低发射响应的条件下，可展宽频带一倍以上。
Institute of Scientific and Technical Information of China (English)
郑颖楠; 王俊平; 张霞
2011-01-01
A new method which can linearize the nonlinear internal impedance was proposed. Based on the concept of dynamic equivalent impedance error, the engineering significance of dynamic equivalent impedance matching and the validity of dynamic equivalent impedance error control method were discussed. According to the thought of equivalent impedance matching, the self-optimizing maximum power point tracking (MPPT) control structure and algorithm in the photovoltaic power generation were developed, which can be achieved by digital. The experimental results show that the dynamic equivalent impedance matching algorithm has more obvious advantages, compared with the classic MPPT control algorithms.%提出1种非线性内阻抗的线性化处理方法.基于动态等效阻抗误差的概念,论述动态等效阻抗适配的L程意义:阐述动态等效阻抗误差控制的有效性.根据等效阻抗适配思想,构造出数字实现的光伏发电最大功率点跟踪(maximum power point tracking,MPPT)自寻优控制系统结构和算法.最后的实验结果证明,与几种经典MPPT控制算法相比,动态等效阻抗匹配控制算法具有更明显的优点.
A Multi-View Dense Image Matching Method for High-Resolution Aerial Imagery Based on a Graph Network
Directory of Open Access Journals (Sweden)
Li Yan
2016-09-01
Full Text Available Multi-view dense matching is a crucial process in automatic 3D reconstruction and mapping applications. In this paper, we present a robust and effective multi-view dense matching algorithm for high-resolution aerial images based on a graph network. The overlap ratio and intersection angle between image pairs are used to find candidate stereo pairs and build the graph network. A Coarse-to-Fine strategy based on an improved Semi-Global Matching algorithm is applied for disparity computation across stereo pairs. Based on the constructed graph, point clouds of base views are generated by triangulating all connected image nodes, followed by a fusion process with the average reprojection error as a priority measure. The proposed method was successfully applied in experiments on aerial image test dataset provided by the ISPRS of Vaihingen, Germany and an oblique nadir image block of Zürich, Switzerland, using three kinds of matching configurations. The proposed method was compared to other state-of-art methods, SURE and PhotoScan. The results demonstrate that the proposed method delivers matches at higher completeness, efficiency, and accuracy than the other methods tested; the RMS for average reprojection error reached the sub pixel level and the actual positioning deviation was better than 1.5 GSD.
Institute of Scientific and Technical Information of China (English)
袁义坤; 赵增辉; 王育平; 赵向东
2012-01-01
The series inductance of driving circuit was matched by analyzing equivalent circuit and considering the e-lectrical characteristics of capacitive load for ultrasonic motor. The output efficiency of driving power was improved and the voltage waveform was ameliorated. The impedance matching was verified by experiment. The ultrasonic motor can be controlled and driven effectively.%从分析超声波电动机定子等效电路模型人手,考虑电机容性负载特性,对驱动电路进行了串联电感匹配,改善了驱动电源与电机之间的耦合程度,提高了驱动电源的输出效率,同时匹配电感后电压波形有了明显的改善,并通过实验测试了阻抗匹配的驱动效果,为进一步有效驱动控制超声波电动机提供可靠的依据.
Sun, Hokeun; Wang, Shuang
2013-05-30
The matched case-control designs are commonly used to control for potential confounding factors in genetic epidemiology studies especially epigenetic studies with DNA methylation. Compared with unmatched case-control studies with high-dimensional genomic or epigenetic data, there have been few variable selection methods for matched sets. In an earlier paper, we proposed the penalized logistic regression model for the analysis of unmatched DNA methylation data using a network-based penalty. However, for popularly applied matched designs in epigenetic studies that compare DNA methylation between tumor and adjacent non-tumor tissues or between pre-treatment and post-treatment conditions, applying ordinary logistic regression ignoring matching is known to bring serious bias in estimation. In this paper, we developed a penalized conditional logistic model using the network-based penalty that encourages a grouping effect of (1) linked Cytosine-phosphate-Guanine (CpG) sites within a gene or (2) linked genes within a genetic pathway for analysis of matched DNA methylation data. In our simulation studies, we demonstrated the superiority of using conditional logistic model over unconditional logistic model in high-dimensional variable selection problems for matched case-control data. We further investigated the benefits of utilizing biological group or graph information for matched case-control data. We applied the proposed method to a genome-wide DNA methylation study on hepatocellular carcinoma (HCC) where we investigated the DNA methylation levels of tumor and adjacent non-tumor tissues from HCC patients by using the Illumina Infinium HumanMethylation27 Beadchip. Several new CpG sites and genes known to be related to HCC were identified but were missed by the standard method in the original paper. Copyright © 2012 John Wiley & Sons, Ltd.
Abbasi Hoseini, Afshin; Zavareh, Zahra; Lundell, Fredrik; Anderson, Helge I.
2014-04-01
A matching algorithm based on self-organizing map (SOM) neural network is proposed for tracking rod-like particles in 2D optical measurements of dispersed two-phase flows. It is verified by both synthetic images of elongated particles mimicking 2D suspension flows and direct numerical simulations-based results of prolate particles dispersed in a turbulent channel flow. Furthermore, the potential benefit of this algorithm is evaluated by applying it to the experimental data of rod-like fibers tracking in wall turbulence. The study of the behavior of elongated particles suspended in turbulent flows has a practical importance and covers a wide range of applications in engineering and science. In experimental approach, particle tracking velocimetry of the dispersed phase has a key role together with particle image velocimetry of the carrier phase to obtain the velocities of both phases. The essential parts of particle tracking are to identify and match corresponding particles correctly in consecutive images. The present study is focused on the development of an algorithm for pairing non-spherical particles that have one major symmetry axis. The novel idea in the algorithm is to take the orientation of the particles into account for matching in addition to their positions. The method used is based on the SOM neural network that finds the most likely matching link in images on the basis of feature extraction and clustering. The fundamental concept is finding corresponding particles in the images with the nearest characteristics: position and orientation. The most effective aspect of this two-frame matching algorithm is that it does not require any preliminary knowledge of neither the flow field nor the particle behavior. Furthermore, using one additional characteristic of the non-spherical particles, namely their orientation, in addition to its coordinate vector, the pairing is improved both for more reliable matching at higher concentrations of dispersed particles and
BLMA: A Blind Matching Algorithm with Application to Cognitive Radio Networks
Hamza, Doha R.
2017-01-26
We consider a two-sided one-to-one abstract matching problem with a defined notion of pairwise stability. The formulated problem is shown to encompass the ordinal and cardinal utility markets. We propose a distributed blind matching algorithm (BLMA) to solve the problem. BLMA is characterized by random activations of agents, and by generic negotiation and aspiration (utility) update processes. We prove the solution produced by BLMA will converge to an
Saito, Kotaro; Kihara, Mitsuru; Shimizu, Tomoya; Yoneda, Keisuke; Kurashima, Toshio
2015-06-01
We performed environmental and accelerated aging tests to ensure the long-term reliability of solid type refractive index matching material at a splice point. Stable optical characteristics were confirmed in environmental tests based on an IEC standard. In an accelerated aging test at 140 °C, which is very much higher than the specification test temperature, the index matching material itself and spliced fibers passing through it had steady optical characteristics. Then we performed an accelerated aging test on an index matching material attached to a built-in fiber before splicing it in the worst condition, which is different from the normal use configuration. As a result, we confirmed that the repeated insertion and removal of fiber for splicing resulted in failure. We consider that the repetition of adhesion between index matching material and fibers causes the splice to degrade. With this result, we used the Arrhenius model to estimate a median lifetime of about 68 years in a high temperature environment of 60 °C. Thus solid type index matching material at a splice point is highly reliable over long periods under normal conditions of use.
Input impedance characteristics of microstrip structures
Directory of Open Access Journals (Sweden)
A. I. Nazarko
2015-06-01
Full Text Available Introduction. Electromagnetic crystals (EC and EC-inhomogeneities are one of the main directions of microstrip devices development. In the article the input impedance characteristics of EC- and traditional microstrip inhomogeneities and filter based on EC-inhomogeneities are investigated. Transmission coefficient characteristics. Transmission coefficient characteristics of low impedance EC- and traditional inhomogeneities are considered. Characteristics are calculated in the software package Microwave Studio. It is shown that the efficiency of EC-inhomogeneity is much higher. Input impedance characteristics of low impedance inhomogeneities. Dependences of input impedance active and reactive parts of EC- and traditional inhomogeneities are given. Dependences of the active part illustrate significant low impedance transformation of nominal impedance. The conditions of impedance matching of structure and input medium are set. Input impedance characteristics of high impedance inhomogeneities. Input impedance characteristics of high impedance EC- and traditional inhomogeneities are considered. It was shown that the band of transformation by high impedance inhomogeneities is much narrower than one by low impedance inhomogeneities. Characteristics of the reflection coefficient of inhomogeneities are presented. Input impedance characteristics of narrowband filter. The structure of narrowband filter based on the scheme of Fabry-Perot resonator is presented. The structure of the filter is fulfilled by high impedance EC-inhomogeneities as a reflectors. Experimental and theoretical amplitude-frequency characteristics of the filter are presented. Input impedance characteristics of the filter are shown. Conclusions. Input impedance characteristics of the structure allow to analyse its wave properties, especially resonant. EC-inhomogeneity compared with traditional microstrip provide substantially more significant transformation of the the input impedance.
Goekoop, R.; Goekoop, J.G.; Scholte, H.S.
2012-01-01
Introduction: Human personality is described preferentially in terms of factors (dimensions) found using factor analysis. An alternative and highly related method is network analysis, which may have several advantages over factor analytic methods. Aim: To directly compare the ability of network comm
Institute of Scientific and Technical Information of China (English)
郑颖楠; 王俊平; 刘旭圆
2012-01-01
从阻抗视角分析光伏系统MPPT问题.基于对含源单调连续型非线性一端口网络的研究,引入误差调节的概念,提出一种光伏发电MPPT控制的自寻优算法.该算法可将非线性极值跟踪控制问题转化为线性误差调节问题.在1kW光伏发电实验平台上的实验证实了该算法的有效性.%The subject of the maximum power point tracking of PV system from the impedance angle was analyzed. Based on the study of the monotonous continuous nonlinear network with source and one port, leads into a concept of error adjustment, a self-optimizing algorithm of PV MPPT control was presented. The algorithm can transform nonlinear extreme value tracking control problem into regulation of the linear error. The experiment that completed in the 1 kW experimental platform confirms the validity of the algorithm.
Institute of Scientific and Technical Information of China (English)
杨琳; 刘德喜; 祝大龙
2016-01-01
The multi-layer substrate based on low temperature co-fired ceramic(LTCC)is an effective way to manufacture milli-meter modules with miniature size and light weight.The vertical transition structure is widely used in the LTCC multi-layer sub-strate,which is very important for the transmission of radio frequency signal.In this paper a three-dimensional model is established by HFSS software.A high impedance transmission line is adopted for well match.The transmission performance of the vertical tran-sition structure is improved.At the same time,the parasitic inductance of the circuit is reduced.The return loss is reduced by 10dB on average in the frequency range of 30GHz to 40GHz.%LTCC（低温共烧陶瓷）多层介质基板是实现毫米波组件小型化、轻量化的有效途径，设计良好的垂直过渡结构，实现低插损的射频信号传输尤为重要。利用三维电磁场仿真软件 HFSS 建立垂直过渡结构的仿真模型，采用高阻抗线进行阻抗匹配，在优化垂直过渡结构传输特性的同时，降低了电路的寄生电感。在30GHz －40GHz 频率范围内，垂直过渡结构的回波损耗平均降低了10dB。
Institute of Scientific and Technical Information of China (English)
Lixia Kang; Yongzhong Liu
2015-01-01
Multi-period heat exchanger network (HEN) retrofit is usually performed by targeting and matching heat trans-fer areas. In this paper, based on the reverse order matching method we proposed previously, three strategies of matching heat transfer areas are proposed to minimize the investment cost for the retrofit of HEN in multi-period, in which replacement of heat exchangers, addition of heat exchangers and addition of heat transfer areas are performed. We demonstrate the procedures through three scenarios, including maximum number of substituted heat exchangers after retrofit, minimum additional heat transfer areas in the retrofitted HEN, and minimum investment cost for retrofit. The strategies are extended to a single period HEN retrofit problem. The results of multi-period and single period HEN retrofit problems indicate the effectiveness of the strategies. More-over, these results are better than those reported in literature. The strategies are simple and easy to implement, which are of great benefit to large-scale HEN retrofit in practice.
A Collaborative Algorithm for Ontological Matching in E-Learning Courseware Domain Knowledge Network
Directory of Open Access Journals (Sweden)
Akanbi C. Olufisoye
2011-11-01
Full Text Available Domain Knowledge is the content repository of a courseware system consisting of a series of learning objects. However, the unstructured and inconsistent naming of domain knowledge components does not permit knowledge transfer across diverse collaborative systems due to differences in architecture, format and representations. To address this identified problem, we formulate an ontological matching algorithm that provides a sharable knowledge in collaborative learning environment in this paper. The Algorithm employs Hybrid Similarity Measure to compute both Concept and Relational similarity values of the various input graphs-learning objects .
National Research Council Canada - National Science Library
Hsieh, Kuen-Chang; Chen, Yu-Jen; Lu, Hsueh-Kuan; Lee, Ling-Chun; Huang, Yong-Cheng; Chen, Yu-Yawn
2013-01-01
...) of the elderly by using non-linear Back Propagation Artificial Neural Network (BP-ANN) model and to compare the predictive accuracy with the linear regression model by using energy dual X-ray absorptiometry (DXA...
Pattern matching in high energy physics by using neural network and genetic algorithm
Castellano, M G; Bevilacqua, V; Nappi, E
2000-01-01
In this paper two different approaches to provide information from events by high energy physics experiments are shown. Usually the representations produced in such experiments are spot-composed and the classical algorithms to be needed for data analysis are time consuming. For this reason the possibility to speed up pattern recognition tasks by soft computing approach with parallel algorithms has been investigated. The first scheme shown in the following is a two-layer neural network with forward connections, the second one consists of an evolutionary algorithm with elitistic strategy and mutation and cross-over adaptive probability. Test results of these approaches have been carried out analysing a set of images produced by an optical ring imaging Cherenkov (RICH) detector at CERN. (10 refs).
Rulaningtyas, Riries; Suksmono, Andriyan B.; Mengko, Tati L. R.; Saptawati, Putri
2016-03-01
Pulmonary tuberculosis is a deadly infectious disease which occurs in many countries in Asia and Africa. In Indonesia, many people with tuberculosis disease are examined in the community health center. Examination of pulmonary tuberculosis is done through sputum smear with Ziehl - Neelsen staining using conventional light microscope. The results of Ziehl - Neelsen staining will give effect to the appearance of tuberculosis (TB) bacteria in red color and sputum background in blue color. The first examination is to detect the presence of TB bacteria from its color, then from the morphology of the TB bacteria itself. The results of Ziehl - Neelsen staining in sputum smear give the complex color images, so that the clinicians have difficulty when doing slide examination manually because it is time consuming and needs highly training to detect the presence of TB bacteria accurately. The clinicians have heavy workload to examine many sputum smear slides from the patients. To assist the clinicians when reading the sputum smear slide, this research built computer aided diagnose with color image segmentation, feature extraction, and classification method. This research used K-means clustering with patch technique to segment digital sputum smear images which separated the TB bacteria images from the background images. This segmentation method gave the good accuracy 97.68%. Then, feature extraction based on geometrical shape of TB bacteria was applied to this research. The last step, this research used neural network with back propagation method to classify TB bacteria and non TB bacteria images in sputum slides. The classification result of neural network back propagation are learning time (42.69±0.02) second, the number of epoch 5000, error rate of learning 15%, learning accuracy (98.58±0.01)%, and test accuracy (96.54±0.02)%.
Institute of Scientific and Technical Information of China (English)
熊芝耀; 程敏胜; 张志文; 刘福生
2001-01-01
The Balance Transformer Accroding to Impedance Matching which has been widely used in electric railway is a kind of three-phase to two-phase power supply equipment.The single phase load is generally not considered as balance,but its balance transformation can be realized by compensation.When the capacity of power supply network is not so large compared with that of the single phase loads that it can not bear the negative influence,the theory discussed in this paper render the primary three phase system symmetry.This paper analyses and calculates the related condition of single phase transformation of balance in details.The test of practical model proves its feasibility.%阻抗匹配平衡变压器，是一种三相变两相的供电设备，已广泛用于我国电气化铁道。对于单相负荷，通常原方三相电流是不平衡的，但通过补偿，也可实现平衡变换。这一新的发现，对有的单相负荷容量较大，且电网容量不大，经受不了较大负序干扰的地方，能使原方三相系统保持对称运行。本文对单相平衡变换的条件进行了较详细的分析和计算并通过模型机试验，验证了其可行性。
Yari, Abdollah; Saeidikhah, Marzieh
2015-11-01
In this work, a gold electrode (GE) was modified by coating with two dimensional silica network/citrate capped gold nanoparticles-poly(diallyldimethylammonium chloride) (GE-TDSN-CGNP-PDDA) for ultra-sensitive determination of Bovine Serum Albumin (BSA). After covalently binding of a silica network (in two-dimensional form) on the surface of a gold electrode, via twice in situ hydrolysis of 3-mercaptopropyl-tri-ethoxysilane, citrate capped gold nanoparticles (CGNP) were chemically adsorbed on the silica cage. Subsequently, PDDA was bonded to CGNP via electrostatic interaction of positively charged polymer and negatively charged stabilizer of CGNP. Analytical properties of GE-TDSN-CGNP-PDDA were studied by Electrochemical Impedance Spectroscopy (EIS). The detection limit for measured BSA was found to be 8.4×10(-13) mol L(-1) and the measuring linear concentration range of the proposed sensor was 9.9×10(-12)-1.6×10(-10) mol L(-1) of BSA. In addition, GE-TDSN-CGNP-PDDA exhibited good stability with high selectivity and was applied for determination of BSA in some samples with satisfactory results.
Definition of the characteristic impedance
Institute of Scientific and Technical Information of China (English)
徐云生; Abbas Sayed OMAR
1996-01-01
Currently available definitions of the characteristic impedance are ambiguous andior inaccurate.A general definition,based on the description of discontinuities between adjacent waveguides,is given.This definition is accurate and independent of the structure concerned.So it can be applied to the design of passive components in any type of transmission lines.Using this definition,a given structure can be uniquely characterized,but the absolute value of the characteristic impedance has no sense any more.As an example,the design of a microstrip impedance transformer using this new definition is presented.Numerical results using the mode-matching method prove the accuracy of the theory.
Salehi, Mohammad Reza; Noori, Leila; Abiri, Ebrahim
2016-11-01
In this paper, a subsystem consisting of a microstrip bandpass filter and a microstrip low noise amplifier (LNA) is designed for WLAN applications. The proposed filter has a small implementation area (49 mm2), small insertion loss (0.08 dB) and wide fractional bandwidth (FBW) (61%). To design the proposed LNA, the compact microstrip cells, an field effect transistor, and only a lumped capacitor are used. It has a low supply voltage and a low return loss (-40 dB) at the operation frequency. The matching condition of the proposed subsystem is predicted using subsystem analysis, artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS). To design the proposed filter, the transmission matrix of the proposed resonator is obtained and analysed. The performance of the proposed ANN and ANFIS models is tested using the numerical data by four performance measures, namely the correlation coefficient (CC), the mean absolute error (MAE), the average percentage error (APE) and the root mean square error (RMSE). The obtained results show that these models are in good agreement with the numerical data, and a small error between the predicted values and numerical solution is obtained.
Institute of Scientific and Technical Information of China (English)
李阳; 张雅希; 闫卓; 杨庆新; 薛明; 张献
2016-01-01
Impedance mismatch in wireless power transfer system may lead to the problems of low efficiency or burnout power amplifier. Taken the coupling factor, resistance of power and coil into account, this paper analyzed the power amplifier load impedance of four-coil model wireless power transfer system via coupled magnetic resonances, based on mutual inductance coupling theory. Since the impedance is difficult to achieve the ideal effect by changing the system mutual inductance, the impedance matching circuit was proposed and designed. Matching circuit ofπ type was designed, the calculating method and its results were given. In the end, the experiment device of wireless power transfer via coupled magnetic resonances was developed. Experimental results were consistent with the theoretical analysis. Thus it provides a useful reference for further studies on adaptive impedance matching and the improvement of the wireless power transfer power and efficiency.%针对无线电能传输系统中阻抗失配引起的效率低和烧毁射频功放等问题，综合考虑耦合因数、电源和线圈内阻，利用互感耦合理论对四线圈结构的磁耦合谐振式无线电能传输系统中射频功放的负载阻抗进行等效分析；并针对通过改变系统互感系数来调整阻抗难以达到理想效果的缺陷，提出和设计阻抗匹配电路方法来调整阻抗。根据阻抗特性设计了π型结构的阻抗匹配电路，给出了系统器件参数的计算方法和结果。最后设计了基于磁耦合谐振技术的无线电能传输装置，并进行了阻抗匹配实验，实验结果与理论分析具有较好的一致性，证明了理论分析的正确性。也为进一步研究自适应阻抗匹配，提高无线电能传输功率和效率提供了有益的参考。
Institute of Scientific and Technical Information of China (English)
桂存兵; 刘洋; 何业军
2013-01-01
为实现光伏发电应用中LCC谐振电路的最大功率点跟踪(MPPT),首先,基于傅里叶级数的动态相量法对LCC谐振电路建立了稳态数学模型.然后,基于阻抗匹配的思想,在其数学模型的基础上提出了一种以开关频率为控制变量的MPPT阻抗匹配方法.最后,根据已有文献提供的最大功率点测量矩阵为依据进行了仿真和实验,通过仿真和实验结果验证了这种阻抗匹配方法的正确性.与其它几种经典的MPPT算法比较,验证了以阻抗匹配思想为基础的MPPT方法有明显的优点.%In order to realize the maximum power point tracking (MPPT) of the series-parallel resonant converter ( LCC) with capacitive output filter in the photovoltaic power generation, firstly, based on Fourier series, a steady-state mathematical model of the LCC resonant circuit is established using dynamic phasor. Then, according to the thought of equivalent impedance matching, a MPPT algorithm is obtained based on the mathematical model of LCC converter. Finally, in terms of measurement matrix of the maximum power which has been provided by the existing literatures, this method of equivalent impedance matching is verified by the results of simulation and experiment. Compared with the classic MPPT algorithm, the MPPT algorithm which accords to the thought of equivalent impedance matching has more obvious advantages.
A Study on the Optimal Receiver Impedance for SNR Maximization in Broadband PLC
Directory of Open Access Journals (Sweden)
Massimo Antoniali
2013-01-01
Full Text Available We consider the design of the front-end receiver for broadband power line communications. We focus on the design of the input impedance that maximizes the signal-to-noise ratio (SNR at the receiver. We show that the amplitude, rather than the power, of the received signal is important for communication purposes. Furthermore, we show that the receiver impedance impacts the amplitude of the noise term. We focus on the background noise, and we propose a novel description of the noise experienced at the receiver port of a PLC network. We model the noise as the sum of four uncorrelated contributions, that is, the active, resistive, receiver, and coupled noise components. We study the optimal impedance design problem for real in-home grids that we assessed with experimental measurements. We describe the results of the measurement campaign, and we report the statistics of the optimal impedance. Hence, we study the best attainable performance when the optimal receiver impedance is deployed. We focus on the SNR and the maximum achievable rate, and we show that power matching is suboptimal with respect to the proposed impedance design approach.
Best matching theory & applications
Moghaddam, Mohsen
2017-01-01
Mismatch or best match? This book demonstrates that best matching of individual entities to each other is essential to ensure smooth conduct and successful competitiveness in any distributed system, natural and artificial. Interactions must be optimized through best matching in planning and scheduling, enterprise network design, transportation and construction planning, recruitment, problem solving, selective assembly, team formation, sensor network design, and more. Fundamentals of best matching in distributed and collaborative systems are explained by providing: § Methodical analysis of various multidimensional best matching processes § Comprehensive taxonomy, comparing different best matching problems and processes § Systematic identification of systems’ hierarchy, nature of interactions, and distribution of decision-making and control functions § Practical formulation of solutions based on a library of best matching algorithms and protocols, ready for direct applications and apps development. Design...
三角网约束下的层次匹配方法%Hierarchical Matching Method with Triangle Network Constraint
Institute of Scientific and Technical Information of China (English)
郑顺义; 马电; 王晓南
2014-01-01
Focusing on dense matching in photogrammetry ,an image matching method by combing the triangle network constraint with pyramid strategy has been proposed in this paper .Firstly ,feature points are extracted in each layer ,and then image matching is done under the constraint of a Delaunay triangle network ,which has been constructed by the matching result of a higher layer .The pyramid strategy itself shows a coarse‐to‐fine process and meanwhile Delaunay triangle network can pass a powerful match control from the higher layer to the lower layer .Experiments shows that the proposed method can get a reliable ,high‐accuracy and dense match result and the generated point cloud can describe the topography well .%针对数字摄影测量中密集匹配问题，提出一种三角网约束与金字塔策略相结合的影像匹配方法。该方法在每层金字塔影像中提取特征点，利用金字塔上层影像的匹配结果构建Delaunay三角网，约束和指导金字塔下层影像的匹配；金字塔策略本身体现由粗到精的匹配过程，而Delaunay三角网能有效地将上层匹配结果作为约束传递到下层影像。实验结果证明，文中方法生成的密集匹配点云密度大、误匹配少、精度高，能有效地反映地貌特征。
Cheng, Jianlin; Saigo, Hiroto; Baldi, Pierre
2006-03-15
The formation of disulphide bridges between cysteines plays an important role in protein folding, structure, function, and evolution. Here, we develop new methods for predicting disulphide bridges in proteins. We first build a large curated data set of proteins containing disulphide bridges to extract relevant statistics. We then use kernel methods to predict whether a given protein chain contains intrachain disulphide bridges or not, and recursive neural networks to predict the bonding probabilities of each pair of cysteines in the chain. These probabilities in turn lead to an accurate estimation of the total number of disulphide bridges and to a weighted graph matching problem that can be addressed efficiently to infer the global disulphide bridge connectivity pattern. This approach can be applied both in situations where the bonded state of each cysteine is known, or in ab initio mode where the state is unknown. Furthermore, it can easily cope with chains containing an arbitrary number of disulphide bridges, overcoming one of the major limitations of previous approaches. It can classify individual cysteine residues as bonded or nonbonded with 87% specificity and 89% sensitivity. The estimate for the total number of bridges in each chain is correct 71% of the times, and within one from the true value over 94% of the times. The prediction of the overall disulphide connectivity pattern is exact in about 51% of the chains. In addition to using profiles in the input to leverage evolutionary information, including true (but not predicted) secondary structure and solvent accessibility information yields small but noticeable improvements. Finally, once the system is trained, predictions can be computed rapidly on a proteomic or protein-engineering scale. The disulphide bridge prediction server (DIpro), software, and datasets are available through www.igb.uci.edu/servers/psss.html.
A. Hak (Tony); J. Dul (Jan)
2009-01-01
textabstractPattern matching is comparing two patterns in order to determine whether they match (i.e., that they are the same) or do not match (i.e., that they differ). Pattern matching is the core procedure of theory-testing with cases. Testing consists of matching an “observed pattern” (a pattern
Paoluzzi, M; Marques-Balula, J; Nisbet, D
2010-01-01
In the LINAC4 H- source and the SPL plasma generator at CERN, the plasma is heated by a 100 kW, 2 MHz RF system. Matching of the load impedance to the final amplifier is achieved with a resonant network. The system implements a servo loop for power stabilization and frequency hopping to cope with the detuning effects induced by the plasma. This paper provides a detailed description of the system, including the pulse rate increase to 50 Hz for use in the SPL plasma generator. The performances, measurements of RF power coupling, contribution of the plasma to the impedance as well as first operation are reported.
Electrical Impedance Measurements of PZT Nanofiber Sensors
Directory of Open Access Journals (Sweden)
Richard Galos
2017-01-01
Full Text Available Electrical impedance measurements of PZT nanofiber sensors were performed using a variety of methods over a frequency spectrum ranging from DC to 1.8 GHz. The nanofibers formed by electrospinning with diameters ranging from 10 to 150 nm were collected and integrated into sensors using microfabrication techniques. Special matching circuits with ultrahigh input impedance were fabricated to produce low noise, measurable sensor outputs. Material properties including resistivity and dielectric constant are derived from the impedance measurements. The resulting material properties are also compared with those of individual nanofibers being tested using conductive AFM and Scanning Conductive Microscopy.
Hierarchical model of matching
Pedrycz, Witold; Roventa, Eugene
1992-01-01
The issue of matching two fuzzy sets becomes an essential design aspect of many algorithms including fuzzy controllers, pattern classifiers, knowledge-based systems, etc. This paper introduces a new model of matching. Its principal features involve the following: (1) matching carried out with respect to the grades of membership of fuzzy sets as well as some functionals defined on them (like energy, entropy,transom); (2) concepts of hierarchies in the matching model leading to a straightforward distinction between 'local' and 'global' levels of matching; and (3) a distributed character of the model realized as a logic-based neural network.
Hak, Tony; Dul, Jan
2009-01-01
textabstractPattern matching is comparing two patterns in order to determine whether they match (i.e., that they are the same) or do not match (i.e., that they differ). Pattern matching is the core procedure of theory-testing with cases. Testing consists of matching an “observed pattern” (a pattern of measured values) with an “expected pattern” (a hypothesis), and deciding whether these patterns match (resulting in a confirmation of the hypothesis) or do not match (resulting in a disconfirmat...
Kalaiselvi, P; Raj, S Alfred Cecil; Jagannathan, K; Vijayan, N; Bhagavannarayana, G; Kalainathan, S
2014-11-11
Nonlinear optical single crystal of L-Proline trichloroacetate (L-PTCA) was successfully grown by Slow Evaporation Solution Technique (SEST). The grown crystals were subjected to single crystal X-ray diffraction analysis to confirm the structure. From the single crystal XRD data, solid state parameters were determined for the grown crystal. The crystalline perfection has been evaluated using high resolution X-ray diffractometer. The frequencies of various functional groups were identified from FTIR spectral analysis. The percentage of transmittance was obtained from UV Visible spectral analysis. TGA-DSC measurements indicate the thermal stability of the crystal. The dielectric constant, dielectric loss and ac conductivity were measured by the impedance analyzer. The DC conductivity was calculated by the cole-cole plot method.
Institute of Scientific and Technical Information of China (English)
张胜凯; 黄文娟; 韩高峰
2012-01-01
To improve the utilization of branch roads and reduce the traffic pressure on arterial roads, the optimization approach of one-way traffic organization is proposed from the view of reducing network impedance and improving traffic efficiency. The bievel programming model is developed with the objective of minimizing network impedance and travel time. The minimum objectixie value of the upper model is obtained by optimizing one-way traffic, and the lower one adopts the capacity limitation-incremental loading method to distribute traffic flow. Through establishing virtual road network, the effectiveness of one-way traffic organization is proved by comparing the network impedance and travel time before and after optimization.%为提高支路的利用率，以降低主干道的交通压力，从降低路网阻抗及提高交通效率的角度出发，提出单向交通组织的优化方法。建立以路网阻抗及出行时间最小化为目标的双层优化模型，其中上层模型通过优化支路的单向交通组织方案使得目标值达到最小，下层模型按照容量限制——增量加栽方法进行交通量的重分配。通过建立虚拟路网，类比分析单向交通组织优化前后的路网阻抗及出行时间，验证单向交通组织的优化效果。
Institute of Scientific and Technical Information of China (English)
夏加宽; 李文瑞; 何新; 张健
2015-01-01
为获得热声发电系统最大电能输出和声功捕获，该文以横向磁通永磁直线发电机为例，采用力–电类比法建立热声发电系统等效模型，研究电磁力、次级速度与阻抗之间的关系，推导热声发电系统等效阻尼的表达式，并分析电抗对等效阻尼的影响。在此基础上，基于最大电能输出进行阻抗匹配，并采用相量法分析阻抗匹配对机械谐振条件的影响，推导出谐振弹簧劲度系数表达式。最后，通过直线振荡系统实验平台验证阻抗匹配及弹簧谐振劲度系数理论推导的准确性，为热声发电系统直线发电机的设计提供理论指导。%In order to obtain maximum captured acoustic and electric power output of thermoacoustic electric generation systems (TAEGS), an electro-mechanical analogic model was built using an appropriate transverse flux PM linear machine (TFPMLM). The relationship among electromagnetic force, velocity of mover and reactance was analyzed, and expression of TAEGS equivalent damping was deduced. The effect of the reactance on equivalent damping was analyzed, and the parameter of reactance was deduced for getting impedance matching. The influence of impedance matching on conditions of mechanical resonance was researched using phasor diagram. Expression of the spring stiffness factor was deduced. Experimental results through a linear oscillatory platform verify the validity of the impedance matching and theoretically derivate equivalent resonance stiffness factor. The achievements in this paper provide theoretical guidance for the linear generator design of TAEGS.
DEFF Research Database (Denmark)
Bak, Christen Kjeldahl; Dalsgaard, Erik
1967-01-01
An ac measuring technique devised primarily for measuring galvanomagnetic effects in metals is presented. The instrument may, however, be useful whenever it is desired to measure and record continuously impedances in the range 10−3 to 10−8 Omega. The sample assembly is disscussed in some detail...
Battery impedance spectroscopy using bidirectional grid connected converter
Indian Academy of Sciences (India)
SHIMUL KUMAR DAM; VINOD JOHN
2017-08-01
Battery impedance can provide valuable insight into the condition of the battery. Commercially available impedance measurement instruments are expensive. Hence their direct use in a battery management system is not justifiable. In this work, a 3-kW bi-directional converter for charging and discharging a batterybank has been implemented with the capability of impedance measurement. The converter is grid connected and controlled to operate at unity power factor. Additional requirements on filter design and control structure of battery converter for impedance measurement are discussed. An algorithm has been developed to measure impedance by frequency sweep, avoiding transients. The measured impedance has been compared to that from a commercially available impedance measurement equipment and is shown to have a good match.
Lafleur, T.; Delattre, P. A.; Booth, J. P.; Johnson, E. V.; Dine, S.
2013-01-01
A broad-band, inline current-voltage probe, with a characteristic impedance of 50 Ω, is presented for the measurement of voltage and current waveforms, impedance, and power in rf systems. The probe, which uses capacitive and inductive sensors to determine the voltage and current, respectively, can be used for the measurement of single or multi-frequency signals into both matched and unmatched loads, over a frequency range of about 1-100 MHz. The probe calibration and impedance/power measurement technique are described in detail, and the calibrated probe results are compared with those obtained from a vector network analyzer and other commercial power meters. Use of the probe is demonstrated with the measurement of power into an unmatched capacitively coupled plasma excited by multi-frequency tailored voltage waveforms.
Lafleur, T; Delattre, P A; Booth, J P; Johnson, E V; Dine, S
2013-01-01
A broad-band, inline current-voltage probe, with a characteristic impedance of 50 Ω, is presented for the measurement of voltage and current waveforms, impedance, and power in rf systems. The probe, which uses capacitive and inductive sensors to determine the voltage and current, respectively, can be used for the measurement of single or multi-frequency signals into both matched and unmatched loads, over a frequency range of about 1-100 MHz. The probe calibration and impedance/power measurement technique are described in detail, and the calibrated probe results are compared with those obtained from a vector network analyzer and other commercial power meters. Use of the probe is demonstrated with the measurement of power into an unmatched capacitively coupled plasma excited by multi-frequency tailored voltage waveforms.
Wakefields and coupling impedances
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S. (Superconducting Super Collider Laboratory, 2550 Beckleymeade Ave., Dallas, Texas 75237 (United States))
1995-02-01
After a short introduction of the wake potentials and coupling impedances, a few new results in impedance calculations are discussed. The first example is a new analytical method for calculating impedances of axisymmetric structures in the low frequency range, below the cutoff frequency of the vacuum chamber. The second example demonstrates that even very small discontinuities on a smooth waveguide can result in appearance of trapped modes, with frequencies slightly below the waveguide cutoff frequency. The high-frequency (above the cutoff) behavior of the coupling impedance of many small discontinuities is discussed in the third example. [copyright] 1995 [ital American] [ital Institute] [ital of] [ital Physics
Wakefields and coupling impedances
Kurennoy, Sergey
1995-02-01
After a short introduction of the wake potentials and coupling impedances, a few new results in impedance calculations are discussed. The first example is a new analytical method for calculating impedances of axisymmetric structures in the low frequency range, below the cutoff frequency of the vacuum chamber. The second example demonstrates that even very small discontinuities on a smooth waveguide can result in appearance of trapped modes, with frequencies slightly below the waveguide cutoff frequency. The high-frequency (above the cutoff) behavior of the coupling impedance of many small discontinuities is discussed in the third example.
Impedance plethysmography of thoracic region: impedance cardiography.
Directory of Open Access Journals (Sweden)
Deshpande A
1990-10-01
Full Text Available Impedance plethysmograms were recorded from thoracic region in 254 normal subjects, 183 patients with coronary artery disease, 391 patients with valvular heart disease and 107 patients with congenital septal disorder. The data in 18 normal subjects and 55 patients showed that basal impedance decreases markedly during exercise in patients with ischaemic heart disease. Estimation of cardiac index by this technique in a group of 99 normal subjects has been observed to be more consistent than that of the stroke volume. Estimation of systolic time index from impedance plethysmograms in 34 normal subjects has been shown to be as reliable as that from electrocardiogram, phonocardiogram and carotid pulse tracing. Changes in the shape of plethysmographic waveform produced by valvular and congenital heart diseases are briefly described and the role of this technique in screening cardiac patients has been highlighted.
Energy Technology Data Exchange (ETDEWEB)
Maschio, Celio; Nakajima, Lincoln; Schiozer, Denis J. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil)
2008-07-01
The purpose of this work is to present a methodology for production history matching using proxy models generated through artificial neural networks. Optimization processes through genetic algorithm using the proxy models and the flux simulator area compared. The methodology was tested in three reservoir models with 4, 8 and 16 variables, and one realistic synthetic model with 20 parameters, in order to evaluate the performance of the technique with the increasing of the number of variable. The results obtained with the proxy models are very similar compared to the results obtained with the simulator, showing as main advantage the reduction of the number of simulations allowed by the proposed methodology. (author)
An impedance grasping strategy
Muñoz Arias, Mauricio; Scherpen, Jacqueline M.A.; Macchelli, Alessandro
2014-01-01
This work is devoted to an impedance grasping strategy for a class of standard mechanical systems in the port- Hamiltonian framework. The presented control strategy re- quires a set of coordinate transformations, since the impedance control in the port-Hamiltonian framework with structure preservati
2010-01-01
N1 FY10 Research Project Research Sponsor: Navy Recruiting Command POC M J h N bl H d f R h DISE : r. o n o e, ea o esearc Matching Navy Recruiting...Naval Postgraduate SchoolDistributed Information Systems Experimentation ( DISE ) Dr. Douglas J. MacKinnon Dr. Shelley P. Gallup Research Associate...Experimentation ( DISE ),Monterey,CA,93943 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S
Directory of Open Access Journals (Sweden)
Raimo Virkkala
Full Text Available National reserve networks are one of the most important means of species conservation, but their efficiency may be diminished due to the projected climatic changes. Using bioclimatic envelope models and spatial data on habitats and conservation areas, we studied how efficient the reserve network will be in preserving 100 forest, mire, marshland, and alpine bird species of conservation concern in Finland in 2051-2080 under three different climate scenarios. The occurrences of the studied bird species were related to the amount of habitat preferred by each species in the different boreal zones. We employed a novel integrated habitat suitability index that takes into account both the species' probability of occurrence from the bioclimatic models and the availability of suitable habitat. Using this suitability index, the distribution of the topmost 5% suitability squares ("hotspots" in the four bird species groups in the period 1971-2000 and under the three scenarios were compared with the location of reserves with the highest amounts of the four habitats to study the efficiency of the network. In species of mires, marshlands, and Arctic mountains, a high proportion of protected habitat was included in the 5% hotspots in the scenarios in 2051-2080, showing that protected areas cover a high proportion of occurrences of bird species. In contrast, in forests in the southern and middle boreal zones, only a small proportion of the protected habitat was included in the 5% hotspots, indicating that the efficiency of the protected area network will be insufficient for forest birds in the future. In the northern boreal zone, the efficiency of the reserve network in forests was highly dependent on the strength of climate change varying between the scenarios. Overall, there is no single solution to preserving biodiversity in a changing climate, but several future pathways should be considered.
Virtual Impedance Based Stability Improvement for DC Microgrids with Constant Power Loads
DEFF Research Database (Denmark)
Lu, Xiaonan; Sun, Kai; Huang, Lipei
2014-01-01
. To validate the stability with the above stabilizers in a DC microgrid with parallel interfacing converters and CPL, the impedance matching approach is employed. The output impedance of the source converter and input impedance of the load are calculated respectively, and the influence of droop control...
Line Impedance Estimation Using Active and Reactive Power Variations
DEFF Research Database (Denmark)
Timbus, Adrian Vasile; Rodriguez, Pedro; Teodorescu, Remus;
2007-01-01
This paper proposes an estimation method of power system impedance based on power variations caused by a distributed power generation system (DPGS) at the point of common coupling (PCC). The proposed algorithm is computationally simple and uses the voltage variations at the point of common coupling...... (PCC) caused by the variations of the power delivered to utility network to derive the value of grid impedance. Accurate estimation of both resistive and inductive part of the impedance is obtained, as the results presented show....
Impedance and Collective Effects
Metral, E; Rumolo, R; Herr, W
2013-01-01
This document is part of Subvolume C 'Accelerators and Colliders' of Volume 21 'Elementary Particles' of Landolt-Börnstein - Group I 'Elementary Particles, Nuclei and Atoms'. It contains the Chapter '4 Impedance and Collective Effects' with the content: 4 Impedance and Collective Effects Introduction 4.1 Space Charge 4.2 Wake Fields and Impedances 4.3 Coherent Instabilities 4.4 Landau Damping 4.5 Two-Stream Effects (Electron Cloud and Ions) 4.6 Beam-Beam Effects 4.7 Numerical Modelling
A transcutaneous energy transmission system for artificial heart adapting to changing impedance.
Fu, Yang; Hu, Liang; Ruan, Xiaodong; Fu, Xin
2015-04-01
This article presents a coil-coupling-based transcutaneous energy transmission system (TETS) for wirelessly powering an implanted artificial heart. Keeping high efficiency is especially important for TETS, which is usually difficult due to transmission impedance changes in practice, which are commonly caused by power requirement variation for different body movements and coil-couple malposition accompanying skin peristalsis. The TETS introduced in this article is designed based on a class-E power amplifier (E-PA), of which efficiency is over 95% when its load is kept in a certain range. A resonance matching and impedance compressing functions coupled network based on parallel-series capacitors is proposed in the design, to enhance the energy transmission efficiency and capacity of the coil-couple through resonating, and meanwhile compress the changing range of the transmission impedance to meet the load requirements of the E-PA and thus keep the high efficiency of TETS. An analytical model of the designed TETS is built to analyze the effect of the network and also provide bases for following parameters determination. Then, according algorithms are provided to determine the optimal parameters required in the TETS for good performance both in resonance matching and impedance compressing. The design is tested by a series of experiments, which validate that the TETS can transmit a wide range of power with a total efficiency of at least 70% and commonly beyond 80%, even when the coil-couple is seriously malpositioned. The design methodology proposed in this article can be applied to any existing TETS based on E-PA to improve their performance in actual applications.
Fletcher, Martyn; Liang, Bojian; Smith, Leslie; Knowles, Alastair; Jackson, Tom; Jessop, Mark; Austin, Jim
2008-10-01
In the study of information flow in the nervous system, component processes can be investigated using a range of electrophysiological and imaging techniques. Although data is difficult and expensive to produce, it is rarely shared and collaboratively exploited. The Code Analysis, Repository and Modelling for e-Neuroscience (CARMEN) project addresses this challenge through the provision of a virtual neuroscience laboratory: an infrastructure for sharing data, tools and services. Central to the CARMEN concept are federated CARMEN nodes, which provide: data and metadata storage, new, thirdparty and legacy services, and tools. In this paper, we describe the CARMEN project as well as the node infrastructure and an associated thick client tool for pattern visualisation and searching, the Signal Data Explorer (SDE). We also discuss new spike detection methods, which are central to the services provided by CARMEN. The SDE is a client application which can be used to explore data in the CARMEN repository, providing data visualization, signal processing and a pattern matching capability. It performs extremely fast pattern matching and can be used to search for complex conditions composed of many different patterns across the large datasets that are typical in neuroinformatics. Searches can also be constrained by specifying text based metadata filters. Spike detection services which use wavelet and morphology techniques are discussed, and have been shown to outperform traditional thresholding and template based systems. A number of different spike detection and sorting techniques will be deployed as services within the CARMEN infrastructure, to allow users to benchmark their performance against a wide range of reference datasets.
Impedance and component heating
Métral, E; Mounet, N; Pieloni, T; Salvant, B
2015-01-01
The impedance is a complex function of frequency, which represents, for the plane under consideration (longitudinal, horizontal or vertical), the force integrated over the length of an element, from a “source” to a “test” wave, normalized by their charges. In general, the impedance in a given plane is a nonlinear function of the test and source transverse coordinates, but it is most of the time sufficient to consider only the first few linear terms. Impedances can influence the motion of trailing particles, in the longitudinal and in one or both transverse directions, leading to energy loss, beam instabilities, or producing undesirable secondary effects such as excessive heating of sensitive components at or near the chamber wall, called beam-induced RF heating. The LHC performance limitations linked to impedances encountered during the 2010-2012 run are reviewed and the currently expected situation during the HL-LHC era is discussed.
Energy Technology Data Exchange (ETDEWEB)
Zotter, B. [European Organization for Nuclear Research, Geneva (Switzerland)
1996-08-01
This report describes a number of measurements and computations of the impedance of the Large Electron Positron collider LEP at CERN. The work has been performed over several years, together with D. Brandt, K. Cornelis, A. Hofmann, G. Sabbi and many others. The agreement between measurements of single bunch instabilities on the machine and computer simulations is in general excellent and gives confidence in the impedance model used. (author)
Torregrosa, Adrián J; Maestre, Haroldo; Capmany, Juan
2013-11-18
The availability of reconfigurable all-optical wavelength converters for an efficient and flexible use of optical resources in WDM (wavelength division multiplexing) networks is still lacking at present. We propose and report preliminary results on a versatile active technique for multiple and tunable wavelength conversions in the 1500-1700 nm spectral region. The technique is based on combining broadband quasi-phase matched intra-cavity parametric single-pass difference-frequency generation close to degeneracy in a diode-pumped tunable laser. A periodically poled stoichiometric lithium tantalate crystal is used as the nonlinear medium, with a parametric pump wave generated in a continuous-wave self-injection locked Cr3+:LiCAF tunable laser operating at around 800 nm.
Directory of Open Access Journals (Sweden)
Abu Bakar Ibrahim
2012-01-01
Full Text Available This paper presents the design of low noise amplifier with cascode and cascaded techniques using T-matching network applicable for IEEE 802.16 standards. The amplifier use FHX76LP Low Noise SuperHEMT FET. The design simulation process is using Advance Design System (ADS software. The cascode and cascaded low noise amplifier (LNA produced gain of 53.4dB and noise figure (NF of 1.2dB. The input reflection (S11 and output return loss (S22 are -24.3dB and -23.9dB respectively. The input sensitivity is compliant with the IEEE 802.16 standards.
Directory of Open Access Journals (Sweden)
J. Staufer
2013-08-01
Full Text Available Ozone, an important greenhouse gas, has the largest climate forcing in the tropopause region, meaning that knowledge of long-term ozone changes in the upper troposphere/lower stratosphere (UTLS is particularly important. Here, we perform a 16 yr comparison (1994–2009 of UTLS ozone measurements from balloon-borne ozonesondes and MOZAIC (measurements of ozone, water vapor, carbon monoxide and nitrogen oxides by in-service Airbus aircraft. The analysis uses trajectories computed from ERA-Interim wind fields to find matches between the two measurement platforms. Ozonesonde data quality is most critical in the UTLS, where natural variability is high, particularly close to the tropopause. On average, at the 28 launch sites considered, ozone mixing ratios measured by the sondes exceed MOZAIC data by 5–15%, with differences being smaller in the LS than in the UT at many launch sites. For most sites, sondes and MOZAIC data are in close agreement after 1998. Before 1998 ozone mixing ratios measured by the Brewer–Mast (BM sondes and Electrochemical Concentration Cell (ECC sondes are systematically (up to 20% higher than the MOZAIC UV photometers. The reason for this large difference remains unclear. Results also show that after 1998 large background current signals may affect ozonesonde performance, limiting the determination of reliable ozone trends in the UTLS. Sonde measurements appear to be insensitive to changing the type of ECC ozonesonde, provided the cathode sensing solution strength remains unchanged. Only Scoresbysund (Greenland showed systematically higher readings after changing from Science Pump Corporation sondes to ENSCI Corporation sondes, while keeping a 1.0% KI cathode electrolyte. This suggests that ECC sondes, provided their background current and sensing solutions are properly monitored, are robust and reliable tools for ozone trend studies in the UTLS.
Resonant impedance matchers for Mario Schenberg detector
Energy Technology Data Exchange (ETDEWEB)
Frajuca, Carlos; Bortoli, Fabio S. [Centro Federal de Educacao Tecnologica de Sao Paulo, SP (Brazil)
2006-07-01
'Mario Schenberg' is a spherical resonant-mass gravitational wave (GW) detector that will be part of a GW detection array of two detectors, the other one is been built in The Netherlands. Their resonant frequencies will be around 3.2 kHz with a bandwidth of about 200 Hz. This range of frequencies is new in a field where the typical frequencies lay below 1 kHz, making the transducer development much more complex. Some studies indicated that using low mass mechanical resonators (used for impedance matching to the parametric transducer, in a cold damping regime), allow the detector to reach the standard quantum limit. In this work we describe the study of mechanical impedance matcher resonators used to obtain a better coupling between the sphere and the transducers and keeping the same calibration for all transducers, this has been show to be not a easy task since the differential motions of the sphere surface propagates to the motions of the resonant mechanical impedance matchers, when it can be done then the next step is to calculate the effective mass of the resonating mechanical impedance matcher and then, calculate the detector sensitivity, this is also complicated because there is a spread in the resonant mechanical impedance matcher frequencies. (author)
Frequency Bandwidth of Half-Wave Impedance Repeater
Directory of Open Access Journals (Sweden)
Marek Dvorsky
2012-01-01
Full Text Available This article brings in the second part general information about half-wave impedance repeater. The third part describes the basic functional principles of the half-wave impedance repeater using Smith chart. The main attention is focused in part four on the derivation of repeater frequency bandwidth depending on characteristics and load impedance of unknown feeder line. Derived dependences are based on the elementary features of the feeder lines with specific length. The described functionality is proved in part 4.3 by measurement of transformed impedance using vector several unbalanced feeder lines and network analyzer VNWA3+.
Coupled Transmission Lines as Impedance Transformer
DEFF Research Database (Denmark)
Jensen, Thomas; Zhurbenko, Vitaliy; Krozer, Viktor
2007-01-01
A theoretical investigation of the use of a coupled line section as an impedance transformer is presented. We show how to properly select the terminations of the coupled line structures for effective matching of real and complex loads in both narrow and wide frequency ranges. The corresponding....... Wideband matching performance with relative bandwidth beyond 100% and return loss > 20 dB is demonstrated both theoretically and experimentally. Good agreement is achieved between the measured and predicted performance of the coupled line transformer section....
Freitas, Ayres; Plehn, Tilman
2016-01-01
Effective Lagrangians are a useful tool for a data-driven approach to physics beyond the Standard Model at the LHC. However, for the new physics scales accessible at the LHC, the effective operator expansion is only relatively slowly converging at best. For tree-level processes, it has been found that the agreement between the effective Lagrangian and a range of UV-complete models depends sensitively on the appropriate definition of the matching. We extend this analysis to the one-loop level, which is relevant for electroweak precision data and Higgs decay to photons. We show that near the scale of electroweak symmetry breaking the validity of the effective theory description can be systematically improved through an appropriate matching procedure. In particular, we find a significant increase in accuracy when including suitable terms suppressed by the Higgs vacuum expectation value in the matching.
Finemet cavity impedance studies
Persichelli, S; Migliorati, M; Salvant, B
2013-01-01
The aim of the study is to evaluate the impedance of the Finemet kicker cavity to be installed in the PS straight section 02 during LS1, under realistic assumptions of bunch length. Time domain simulations with CST Particle Studio have been performed in order to get the impedance of the cavity and make a comparison with the longitudinal impedance measured for a single cell prototype. The study has been performed on simplified 3D geometries imported from a mechanical CATIA drawing, assuming that the simplications have small impact on the nal results. Simulations confirmed that the longitudinal impedance observed with measurements can be excited by bunches circulating in the PS. In the six-cells Finemet cavity, PS bunches circulating in the center can excite a longitudinal impedance, the real part of which has a maximum of 2 kOhm at 4 MHz. This mode does not seem to have any transverse component. All the eigenmodes of the cavity are strongly damped by the Finemet rings: we predict to have no issues regarding tr...
Creasy, M. Austin
2016-03-01
Impedance models of pipes can be used to estimate resonant frequencies of standing waves and model acoustic pressure of closed and open ended pipes. Modelling a pipe with impedance methods allows additional variations to the pipe to be included in the overall model as a system. Therefore an actuator can be attached and used to drive the system and the impedance model is able to include the dynamics of the actuator. Exciting the pipe system with a chirp signal allows resonant frequencies to be measured in both the time and frequency domain. The measurements in the time domain are beneficial for introducing undergraduates to resonances without needing an understanding of fast Fourier transforms. This paper also discusses resonant frequencies in open ended pipes and how numerous texts incorrectly approximate the resonant frequencies for this specific pipe system.
Kopp, Joachim; Slatyer, Tracy R; Wang, Xiao-Ping; Xue, Wei
2016-01-01
We consider a new class of thermal dark matter models, dubbed "Impeded Dark Matter", in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. We demonstrate that either case can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonstrate that the annihilation cross-section for Impeded Dark Matter depends linearly on the dark matter velocity or may even be kinematically forbidden, making this scenario almost insensitive to constraints from the cosmic microwave background and from observations of dwarf galaxies. Accordingly, it may be possible for Impeded Dark Matter to yield observable signals in clusters or the Galactic center, with no corresponding signal in dwarfs. For positive mass splitting, we show that the annihilation cross-section is suppress...
Small Signal Modeling and Comprehensive Analysis of Magnetically Coupled Impedance Source Converters
DEFF Research Database (Denmark)
Forouzesh, Mojtaba; Siwakoti, Yam Prasad; Blaabjerg, Frede
2016-01-01
Magnetically coupled impedance-source (MCIS) networks are recently introduced impedance networks intended for various high-boost applications. It employs coupled magnetic in the circuit to achieve higher voltage gain. Various MCIS networks have been proposed in the literature for myriad applicati...
Tuning and Matching of Constant Impedance Travelling Wave Accelerating Structure
Institute of Scientific and Technical Information of China (English)
YANG; Jing-he; ZHU; Zhi-bin; WU; Qing-feng; ZENG; Zi-qiang; WANG; Xiu-long; ZHOU; Wen-zhen
2015-01-01
As the penetration depth of electron accelerated by 10MeV electron irradiating accelerator is deep,and the accelerator has broad application prospects.The performance of the accelerator is influenced,to a great extent,by the traveling wave accelerating tube,which is the core component of the accelerator.To develop the accelerator
Best Wideband Impedance Matching Bounds for Lossless 2-Ports
2001-09-01
SIAM, Philadelphia. [31] Henrici , Peter [1974] Applied and Computational Complex Analysis , Volume 1, John Wiley & Sons, New York, NY. [32] Hintzman...emerged as the analysis tools in this effort. 3 1.1 H’ Notation The real numbers are denoted by R. The complex numbers are denoted by C. The set of...research topic focuses on completing the analysis of the preceeding section regarding the existence of s 2 (Question 5) Computing inf{flAP(s 2,sL)II
Force-free black hole jet power from impedance matching
Penna, Robert F
2015-01-01
The standard model of spin-powered black hole jets is the Blandford-Znajek (BZ) model. Unfortunately, the BZ jet power depends on an arbitrary function, $\\Omega_F(\\theta)$, which controls the angular distribution of field line velocities at the horizon. In practice, this function is fixed by finding exact solutions of force-free electrodynamics (FFE) and reading off $\\Omega_F(\\theta)$. We prove that all stationary, axisymmetric solutions of FFE with roughly uniform distributions of field lines at the horizon and at infinity have $\\Omega_F/\\Omega_H\\approx 0.5$, where $\\Omega_H$ is the angular velocity of the horizon. We derive a formula for $\\Omega_F(\\theta)$ that depends only on the angular distribution of field lines at the horizon and at infinity (the full FFE solution is not needed). We give a physical interpretation of our results using the black hole membrane paradigm and a recent extension which treats future null infinity as a resistive membrane. We show that $\\Omega_F/\\Omega_H$ is controlled by impeda...
Impedance of rigid bodies in one-dimensional elastic collisions
Santos, Janilo; Nelson, Osman Rosso
2012-01-01
In this work we study the problem of one-dimensional elastic collisions of billiard balls, considered as rigid bodies, in a framework very different from the classical one presented in text books. Implementing the notion of impedance matching as a way to understand eficiency of energy transmission in elastic collisions, we find a solution which frames the problem in terms of this conception. We show that the mass of the ball can be seen as a measure of its impedance and verify that the problem of maximum energy transfer in elastic collisions can be thought of as a problem of impedance matching between different media. This approach extends the concept of impedance, usually associated with oscillatory systems, to system of rigid bodies.
Field-aligned-impedance-transforming ICRF antenna in the LHD
Energy Technology Data Exchange (ETDEWEB)
Saito, K., E-mail: saito@nifs.ac.jp; Seki, T.; Kasahara, H.; Seki, R.; Kamio, S.; Nomura, G.; Mutoh, T.
2015-10-15
Newly developed ion cyclotron range of frequencies (ICRF) antennas were fabricated and installed in the Large Helical Device (LHD). The antennas, called field-aligned-impedance-transforming (FAIT) antennas, were designed based on former handshake form (HAS) antennas for high power and steady-state operation. The FAIT antennas demonstrated higher loading resistance and lower temperature on ceramic feed-through than HAS antennas. Antenna impedance and injected power were measured precisely using a directional coupler installed between the impedance matching device and antenna. It was shown that an injection power of 1.8 MW or a power density of 15 MW/m{sup 2} would be possible for short-pulse discharges. The mutual coupling between two FAIT antennas is small enough, since any current phase is possible without adjusting the impedance matching device. Although the FAIT antennas are aligned in a poloidal direction, a high heating efficiency of 85% was achieved with the proper minority concentration ratio.
Energy Technology Data Exchange (ETDEWEB)
Chou, W.
1989-06-12
Recently, measurements in the SPS show that the coherent tune shift in the horizontal direction has positive values whereas that in the vertical direction has negative ones. Thus the existence of negative transverse impedance gets confirmed in a real machine. This stimulates us to start a new round of systematic studies on this interesting phenomenon. The results obtained from our computer simulations are presented in this note. Our simulations demonstrate that the negative transverse impedance may appear when the rotational symmetry embedded in a discontinuity is broken, and that the geometries that we have studies may be the source of the positive horizontal tune shift measured in the SPS.
Impedance of accelerator components
Energy Technology Data Exchange (ETDEWEB)
Corlett, J.N. [Center for Beam Physics, Lawrence Berkeley National Laboratory, I Cyclotron Road, Berkeley, California 94720 (United States)
1997-01-01
As demands for high luminosity and low emittance particle beams increase, an understanding of the electromagnetic interaction of these beams with their vacuum chamber environment becomes more important in order to maintain the quality of the beam. This interaction is described in terms of the wake field in time domain, and the beam impedance in frequency domain. These concepts are introduced, and related quantities such as the loss factor are presented. The broadband Q=1 resonator impedance model is discussed. Perturbation and coaxial wire methods of measurement of real components are reviewed. {copyright} {ital 1997 American Institute of Physics.}
A Review of Galvanically Isolated Impedance-Source DC–DC Converters
DEFF Research Database (Denmark)
Chub, Andrii; Vinnikov, Dmitri; Blaabjerg, Frede
2016-01-01
Impedance-source converters, an emerging technology in electric energy conversion, overcome limitations of conventional solutions by the use of specific impedance-source networks. Focus of this paper is on the topologies of galvanically isolated impedance-source dc-dc converters. These converters...... research directions in this field....
Longitudinal impedance of RHIC
Energy Technology Data Exchange (ETDEWEB)
Blaskiewicz, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Brennan, J. M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Mernick, K. [Brookhaven National Lab. (BNL), Upton, NY (United States)
2015-05-03
The longitudinal impedance of the two RHIC rings has been measured using the effect of potential well distortion on longitudinal Schottky measurements. For the blue RHIC ring Im(Z/n) = 1.5±0.2Ω. For the yellow ring Im(Z/n) = 5.4±1Ω.
Impedance plethysmography: basic principles.
Directory of Open Access Journals (Sweden)
Babu J
1990-04-01
Full Text Available Impedance Plethysmography technique has been discussed with explanation of two compartment model and parallel conductor theory for the estimation of peripheral blood flow and stroke volume. Various methods for signal enhancement to facilitate computation of blood flow are briefly described. Source of error in the estimation of peripheral blood flow is identified and the correction has been suggested.
Implantable Impedance Plethysmography
2014-01-01
We demonstrate by theory, as well as by ex vivo and in vivo measurements that impedance plethysmography, applied extravascularly directly on large arteries, is a viable method for monitoring various cardiovascular parameters, such as blood pressure, with high accuracy. The sensor is designed as an implant to monitor cardiac events and arteriosclerotic progression over the long term.
Implantable Impedance Plethysmography
Directory of Open Access Journals (Sweden)
Michael Theodor
2014-08-01
Full Text Available We demonstrate by theory, as well as by ex vivo and in vivo measurements that impedance plethysmography, applied extravascularly directly on large arteries, is a viable method for monitoring various cardiovascular parameters, such as blood pressure, with high accuracy. The sensor is designed as an implant to monitor cardiac events and arteriosclerotic progression over the long term.
Oehlschlägel, Jens
2007-01-01
Cluster matching by permuting cluster labels is important in many clustering contexts such as cluster validation and cluster ensemble techniques. The classic approach is to minimize the euclidean distance between two cluster solutions which induces inappropriate stability in certain settings. Therefore, we present the truematch algorithm that introduces two improvements best explained in the crisp case. First, instead of maximizing the trace of the cluster crosstable, we propose to maximize a chi-square transformation of this crosstable. Thus, the trace will not be dominated by the cells with the largest counts but by the cells with the most non-random observations, taking into account the marginals. Second, we suggest a probabilistic component in order to break ties and to make the matching algorithm truly random on random data. The truematch algorithm is designed as a building block of the truecluster framework and scales in polynomial time. First simulation results confirm that the truematch algorithm give...
Han, B. X.; Stockli, M. P.; Kang, Y.; Piller, C.; Murray, S. N.; Pennisi, T. R.; Santana, M.; Welton, R. F.
2016-02-01
The Spallation Neutron Source H- ion source is operated with a pulsed 2-MHz RF (50-60 kW) to produce the 1-ms long, ˜50 mA H- beams at 60 Hz. A continuous low power (˜300 W) 13.56-MHz RF plasma, which is initially ignited with a H2 pressure bump, serves as starter plasma for the pulsed high power 2-MHz RF discharges. To reduce the risk of plasma outages at lower H2 flow rates which is desired for improved performance of the following radio frequency quadrupole, the 13.56-MHz RF matching network was characterized over a broad range of its two tuning capacitors. The H-α line intensity of the 13.56-MHz RF plasma and the reflected power of the 13.56-MHz RF were mapped against the capacitor settings. Optimal tunes for the maximum H-α intensity are consistent with the optimal tunes for minimum reflected power. Low limits of the H2 flow rate not causing plasma outages were explored within the range of the map. A tune region that allows lower H2 flow rate has been identified, which differs from the optimal tune for global minimum reflected power that was mostly used in the past.
Lai, Chang-Jiang-Sheng; Zha, Liangping; Liu, Da-Hui; Kang, Liping; Ma, Xiaojing; Zhan, Zhi-Lai; Nan, Tie-Gui; Yang, Jian; Li, Fajie; Yuan, Yuan; Huang, Lu-Qi
2016-07-22
Rapid discovery of novel compounds of a traditional herbal medicine is of vital significance for pharmaceutical industry and plant metabolic pathway analysis. However, discovery of unknown or trace natural products is an ongoing challenge. This study presents a universal targeted data-independent acquisition and mining strategy to globally profile and effectively match novel natural product analogues from an herbal extract. The famous medical plant Gastrodia elata was selected as an example. This strategy consists of three steps: (i) acquisition of accurate parent and adduct ions (PAIs) and the product ions data of all eluting compounds by untargeted full-scan MS(E) mode; (ii) rapid compound screening using diagnostic product ions (DPIs) network and in silico analogue database with SUMPRODUCT function to find novel candidates; and (iii) identification and isomerism discrimination of multiple types of compounds using ClogP and ions fragment behavior analyses. Using above data mining methods, a total of 152 compounds were characterized, and 70 were discovered for the first time, including series of phospholipids and novel gastroxyl derivatives. Furthermore, a number of gastronucleosides and phase II metabolites of gastrodin and parishins were discovered, including glutathionylated, cysteinylglycinated and cysteinated compounds, and phosphatidylserine analogues. This study extended the application of classical DPIs filter strategy and developed a structure-based screening approach with the potential for significant increase of efficiency for discovery and identification of trace novel natural products. Copyright © 2016 Elsevier B.V. All rights reserved.
Impedance calculation for ferrite inserts
Energy Technology Data Exchange (ETDEWEB)
Breitzmann, S.C.; Lee, S.Y.; /Indiana U.; Ng, K.Y.; /Fermilab
2005-01-01
Passive ferrite inserts were used to compensate the space charge impedance in high intensity space charge dominated accelerators. They study the narrowband longitudinal impedance of these ferrite inserts. they find that the shunt impedance and the quality factor for ferrite inserts are inversely proportional to the imaginary part of the permeability of ferrite materials. They also provide a recipe for attaining a truly passive space charge impedance compensation and avoiding narrowband microwave instabilities.
Acoustic ground impedance meter
Zuckerwar, A. J. (Inventor)
1984-01-01
A method and apparatus are presented for measuring the acoustic impedance of a surface in which the surface is used to enclose one end of the chamber of a Helmholz resonator. Acoustic waves are generated in the neck of the resonator by a piston driven by a variable speed motor through a cam assembly. The acoustic waves are measured in the chamber and the frequency of the generated acoustic waves is measured by an optical device. These measurements are used to compute the compliance and conductance of the chamber and surface combined. The same procedure is followed with a calibration plate having infinite acoustic impedance enclosing the chamber of the resonator to compute the compliance and conductance of the chamber alone. Then by subtracting, the compliance and conductance for the surface is obtained.
2010-11-30
ELECTROMAGNEETIC SURFACE IMPEDANCE PROPERTIES FA9550-09-C-0198 DR. ADOUR KABAKIAN HUGHES RESEARCH LABS AFOSR / RSE 875 North Randolph Street, Suit...325 Room 3112 Arlington, Virginia 22203-1768 AFOSR / RSE AFRL-OSR-VA-TR-2012-0770 Distribution A We have investigated and determined how the tensor...the case of a TM wave, which favors propagation along the shorter principal axis. Standard terms apply U U U UU Arje Nachman RSE (Program Manager
Kopp, Joachim; Liu, Jia; Slatyer, Tracy R.; Wang, Xiao-Ping; Xue, Wei
2016-01-01
We consider a new class of thermal dark matter models, dubbed "Impeded Dark Matter", in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. We demonstrate that either case can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonst...
Acoustic impedances of ear canals measured by impedance tube
DEFF Research Database (Denmark)
Ciric, Dejan; Hammershøi, Dorte
2007-01-01
During hearing sensitivity tests, the sound field is commonly generated by an earphone placed on a subject ear. One of the factors that can affect the sound transmission in the ear is the acoustic impedance of the ear canal. Its importance is related to the contribution of other elements involved...... in the transmission such as the earphone impedance. In order to determine the acoustic impedances of human ear canals, the standardized method for measurement of complex impedances used for the measurement of the audiometric earphone impedances is applied. It is based on the transfer function between two microphone...... locations in an impedance tube. The end of the tube representing the measurement plane is placed at the ear canal entrance. Thus, the impedance seen from the entrance inward is measured on 25 subjects. Most subjects participated in the previous measurement of the ratio between the pressures at the open...
Longitudinal Impedance Measurements of the Components for the BEPCII
Zhou, Demin; Kang, Wen; Wang Jiu Qing; Zhou, Lijuan
2005-01-01
A longitudinal impedance measurement system was established for the BEPCII. The measurements, done in the frequency domain, are based on the coaxial wire method using HP/Agilent 8720ES network analyzer. The applications of the TRL calibration technique and absorbers were investigated to find a good approach for impedance measurements. The impedance, larger than 20 Ohm and below 6 GHz, can be measured using the TRL calibration technique in the experiment. And better measurement results were got using the reference pipes with the absorbers. So, this system satisfies the requirements of the BEPCII. This paper gives a review on this impedance measurements system for the BEPCII. The measurements results show that there are no serious impedance problems for BEPCII bellows and injection kickers, agreeing well with the numerical simulations. More improvements on this system are in progress.
Modified impedance source inverter for power conditioning system
Indian Academy of Sciences (India)
J SUGANTHI; M RAJARAM
2017-03-01
Based on classical impedance source inverter concept, this paper presents a modified impedance source inverter controlled by different pulse width modulation control strategies for solar PV/battery-powered applications. A brief topology analysis, generalized discussion and design of impedance network elements are presented. Comparison with the classical impedance source inverter is presented. Using simulation, analytical results are presented that ensure stability. The proposed voltage type inverter has reduced inrush current at startup, less capacitor voltage stress and minimum inductor current ripples. DC link voltage boost, reduced total harmonic distortion of output current and voltage, better voltage gain and wide range of output voltage controlcan be achieved easily with improved power quality. Experimental set-up of the modified impedance source inverter with Field Programmable Gate Array (FPGA) controller has been constructed to ascertain the results.
Observations involving broadband impedance modelling
Energy Technology Data Exchange (ETDEWEB)
Berg, J.S. [Stanford Linear Accelerator Center, Menlo Park, CA (United States)
1996-08-01
Results for single- and multi-bunch instabilities can be significantly affected by the precise model that is used for the broadband impedance. This paper discusses three aspects of broadband impedance modelling. The first is an observation of the effect that a seemingly minor change in an impedance model has on the single-bunch mode coupling threshold. The second is a successful attempt to construct a model for the high-frequency tails of an r.f. cavity. The last is a discussion of requirements for the mathematical form of an impedance which follow from the general properties of impedances. (author)
BP网络在阻抗式原油含水率测量仪中的应用%Application of BP Network in Impedance Crude Oil Watercut Meter
Institute of Scientific and Technical Information of China (English)
黄家才; 李宏胜; 滕福林; 刘毅
2011-01-01
阻抗法测原油含水率时,测量结果受温度影响很大.由于含水率与温度之间具有复杂的非线性关系,因此很难建立精确的温度补偿模型.针对该问题,建立一个BP神经网络模型,并将其用于原油含水率的测量.现场实验表明:当温度变化时,该方法提高了原油含水率的测量精度,具有一定推广价值.%In impedance crude oil watercut measuring, the result is impacted greatly by the temperature, and it is hard to describe the precise model for temperature compensation, because of the complex nonlinear relation between the watercut and the temperature. To solve the above problem,a BP artificial neural networks model was established and used in the crude oil watercut measuring. The practical experiments show that the method is effective and increases the measuring precision.
Institute of Scientific and Technical Information of China (English)
赵晨飞; 韩卿; 兀旦晖
2012-01-01
计算机配色可提高油墨配色的速度和精度,具有重要作用.基于两种颜色空间和BP神经网络的计算机配色系统被研究,实验结果表明基于光谱颜色空间配色系统的配色精度更高,可应用于目前的各种印刷方式中,基于BP神经网络的配色系统具有很强的适用性,推进了印刷的数字化流程.%Computer color matching can improve the ink s color matching speed and accuracy, which plays an important role. In this paper the two kinds of computer color matching system based on two color spaces and BP neural network are disscussed. The experimental results show that the color matching system based on the spectral color space is of higher accuracy which can be applied to the current various printing way. The color matching system based on BP neural network has strong applicability, can improve the printing's digital workflow.
Institute of Scientific and Technical Information of China (English)
唐君; 杨云
2014-01-01
为了提高计算机网络入侵检测的效率和性能，采用多模式匹配算法来实现入侵检测。首先对网络入侵检测模型进行了分析，接着对多模式匹配算法基本定义进行阐述，提出了典型多模式匹配算法最后进行实例仿真，并从匹配时间和内存消耗两个方面对常见的三种多模式匹配算法性能进行了分析比较，实验证明，多模式匹配算法适用于计算机网络入侵检测，具有一定的研究价值。%In order to improve the efficiency and performance of network intrusion detection, the paper uses multiple pattern matching algorithms to realize the intrusion detection. Firstly, the paper analyzes the network intrusion detection model, and then elaborates the basic definition of multiple pattern matching algorithm, puts forward the typical multiple pattern matching algorithm, finally carries out the instance simulation, and compares the performances of the common three multi-ple matching algorithms from the two aspects of matching time and memory consumption, experiments show that multiple pattern matching algorithm is suitable for computer network intrusion detection, which has certain research value.
一种结构化P2P网络拓扑匹配的通用算法%Generic Topology Matching Method Based on Structured P2P Network
Institute of Scientific and Technical Information of China (English)
殷苗苗; 陈世平
2012-01-01
Compared with the unstructured P2P networks, structured P2P networks have good expansibility and robustness. But structured P2P overlay network is directly based on logic network, not too much above the underlying physical network topology structure, which causes a serious topology mismatching between logical topology structure and physical topology structure. About the question, this paper proposed a protocol-independent topology matching method, by combining the existing beacons node, adaptive matching algorithm with IP distribution strategy to construct the initial topological structure, and by optimizing node switching to maintenance the network topology. Simulation experiments show that the algorithm improve the matching degree of the network topology, and meanwhile with lower traffic cost.%与非结构化P2P网络相比,结构化P2P网络具有良好的可扩展性、鲁棒性.但是结构化P2P覆盖网络是直接建立在逻辑网络之上,没有过多地考虑底层物理网络拓扑结构,导致逻辑拓扑结构与物理拓扑结构严重不匹配.本文提出一种新的协议无关的拓扑匹配算法,将现有的界标节点、自适应匹配算法与IP分配策略相结合构建初始拓扑结构,优化节点交换算法来维护拓扑结构.模拟实验表明,本算法提高了网络的拓扑匹配度,具有更低的通信开销.
Blaskiewicz, M.; Dooling, J.; Dyachkov, M.; Fedotov, A.; Gluckstern, R.; Hahn, H.; Huang, H.; Kurennoy, S.; Linnecar, T.; Shaposhnikova, E.; Stupakov, G.; Toyama, T.; Wang, J. G.; Weng, W. T.; Zhang, S. Y.; Zotter, B.
1999-12-01
The impedance working group was charged to reply to the following 8 questions relevant to the design of high-intensity proton machines such as the SNS or the FNAL driver. These questions were first discussed one by one in the whole group, then each ne of them assigned to one member to summarize. On the lst morning these contributions were publicly read, re-discussed and re-written where required—hence they are not the opinion of a particular person, but rather the averaged opinion of all members of the working group. (AIP)
Low profile conformal antenna arrays on high impedance substrate
Singh, Hema; Jha, Rakesh Mohan
2016-01-01
This book presents electromagnetic (EM) design and analysis of dipole antenna array over high impedance substrate (HIS). HIS is a preferred substrate for low-profile antenna design, owing to its unique boundary conditions. Such substrates permit radiating elements to be printed on them without any disturbance in the radiation characteristics. Moreover HIS provides improved impedance matching, enhanced bandwidth, and increased broadside directivity owing to total reflection from the reactive surface and high input impedance. This book considers different configurations of HIS for array design on planar and non-planar high-impedance surfaces. Results are presented for cylindrical dipole, printed dipole, and folded dipole over single- and double-layered square-patch-based HIS and dogbone-based HIS. The performance of antenna arrays is analyzed in terms of performance parameters such as return loss and radiation pattern. The design presented shows acceptable return loss and mainlobe gain of radiation pattern. Thi...
Broadband matching of dual-linear polarisation stacked probe-fed microstrip patch antenna
DEFF Research Database (Denmark)
Jaworski, G.; Krozer, Viktor
2004-01-01
A novel approach for impedance matching of probe-fed, stacked microstrip patch antenna elements is demonstrated. The matching structure is compact and enables more than doubling of the operational bandwidth. A circuit model for the feeding probes is developed and its impact on antenna impedance...
Outdoor ground impedance models.
Attenborough, Keith; Bashir, Imran; Taherzadeh, Shahram
2011-05-01
Many models for the acoustical properties of rigid-porous media require knowledge of parameter values that are not available for outdoor ground surfaces. The relationship used between tortuosity and porosity for stacked spheres results in five characteristic impedance models that require not more than two adjustable parameters. These models and hard-backed-layer versions are considered further through numerical fitting of 42 short range level difference spectra measured over various ground surfaces. For all but eight sites, slit-pore, phenomenological and variable porosity models yield lower fitting errors than those given by the widely used one-parameter semi-empirical model. Data for 12 of 26 grassland sites and for three beech wood sites are fitted better by hard-backed-layer models. Parameter values obtained by fitting slit-pore and phenomenological models to data for relatively low flow resistivity grounds, such as forest floors, porous asphalt, and gravel, are consistent with values that have been obtained non-acoustically. Three impedance models yield reasonable fits to a narrow band excess attenuation spectrum measured at short range over railway ballast but, if extended reaction is taken into account, the hard-backed-layer version of the slit-pore model gives the most reasonable parameter values.
Broadband metamaterial for nonresonant matching of acoustic waves.
D'Aguanno, G; Le, K Q; Trimm, R; Alù, A; Mattiucci, N; Mathias, A D; Aközbek, N; Bloemer, M J
2012-01-01
Unity transmittance at an interface between bulk media is quite common for polarized electromagnetic waves incident at the Brewster angle, but it is rarely observed for sound waves at any angle of incidence. In the following, we theoretically and experimentally demonstrate an acoustic metamaterial possessing a Brewster-like angle that is completely transparent to sound waves over an ultra-broadband frequency range with >100% bandwidth. The metamaterial, consisting of a hard metal with subwavelength apertures, provides a surface impedance matching mechanism that can be arbitrarily tailored to specific media. The nonresonant nature of the impedance matching effectively decouples the front and back surfaces of the metamaterial allowing one to independently tailor the acoustic impedance at each interface. On the contrary, traditional methods for acoustic impedance matching, for example in medical imaging, rely on resonant tunneling through a thin antireflection layer, which is inherently narrowband and angle specific.
Frequency-Tunable antenna by input-impedance-tunable CMOS RF-Frontend
Haider, Nadia; Oude Alink, Mark S.; Caratelli, Diego; Klumperink, Eric A.M.; Yarovoy, Alexander G.
2013-01-01
Variable-impedance matching between the antenna and the RF-frontend provides several potential advantages, including changing operational frequency, compensating for unintentional mismatch, improving scanning capability, and reducing noise and interference signal levels. In this article a concept of
面向骨干网NIDS的细粒度并行多模式匹配方法%Fine-grained Parallel Multi-pattern Matching for Backbone Network NIDS
Institute of Scientific and Technical Information of China (English)
邵宗有; 刘兴奎; 刘新春; 孙凝晖
2013-01-01
As the network bandwidth continuously increases, the network security has been seriously threatened by malicious behaviors and risks. Network intrusion detection system (NIDS) is one of the efficient measures to cope with intrusion threats and protect information security, which employs pattern matching techniques to analyze incoming packets and detect potential threats. However,pattern matching is such a compute-intensive task that most current techniques can't meet the demand of NIDS for backbone networks over lOGbps speed. We proposed a novel Bloom filter based approach for pattern matching,called PBPM (Parallel-Bloom-filter-based multi-Pattern Matching). PBPM employs multiple copies of the same Bloom filter to carry out parallel matching on different positions of the input text at the same time. The fine-grained parallel approach is able to skip multiple characters per clock when implemented on FPGAs,dramatically improving pattern matching performance. Experimental results on the rule set from Snort 2. 9 show that the throughput of PBPM exceeds more than 20Gbps.%随着网络带宽的快速增长,互联网正面临着日益严重的安全威胁.网络入侵检测系统(NIDS)利用模式匹配等技术对网络报文进行分析和检测,是防范网络威胁、保护网络安全的一种有效手段.但模式匹配消耗巨大的计算量,现有的技术难以满足10Gbps以上骨干网络NIDS的需求.提出了基于Bloom filter的细粒度并行模式匹配技术PBPM(Parallel-Bloom-filter-based multi-Pattern Matching),PBPM利用多个相同的Bloom filter分别从输入文本的不同位置处并行匹配,每个周期可完成多个字符的匹配,显著提高了匹配速率.详细讨论了在FPGA上的实现方式,在Snort 2.9规则集上的测试结果表明,PBPM能够提供超过20Gbps的模式匹配需求.
A Topology-Matching P2P Overlay Network Model Based on Hilbert Curve%基于Hilbert曲线的拓扑匹配的P2P覆盖网模型
Institute of Scientific and Technical Information of China (English)
李永; 余镇危
2013-01-01
针对P2P网络中由于逻辑网络和物理网络的拓扑结构不匹配导致物理路由效率低下的问题,提出一种新的拓扑匹配的P2P覆盖网模型.首先基于Vivaldi网络坐标系统对网络节点进行聚类,划分成K个聚集,且在每个聚集内选出头节点；然后利用Hilbert空间填充曲线的局部保持特性,把K个聚集的头节点构成环状拓扑结构；最终得到一个拓扑匹配的Hilbert-Ring覆盖网模型.仿真实验表明,该模型具有良好的性能,可以有效地降低网络延迟,减少网络开销.%Aiming at the unmatched topology problem between overlay network and physical network which result in inefficient routing, a new topology-matching P2P overlay network model is presented. Firstly, network nodes are clustered into K groups based on the network coordinates system Vivaldi, and selecting a leader node for each group. Then, using the proximity-aware nature of hilbert space filing curve, the K leader nodes are formed into ring topology. Finally a topology-matching Hilbert-Ring overlay network model is obtained. Simulating experiment shows that this model has the good performance, and it is effective in lowering the network delay and decreasing the network load.
Alba Avilés, Manuel
2015-01-01
WhereIsTheMatch is a very ambitious project that consists of developing my own social network mobile app for Android. This app is focused on easily finding people and places to play sports. The main idea of this project is create a first step to a final product and my own developing style. I knew from the beginning that this would be a very hard and a very demanding task because of the several areas that are involved in the development of a mobile app, such as database implementation, interfa...
Optically stimulated differential impedance spectroscopy
Maxey, Lonnie C; Parks, II, James E; Lewis, Sr., Samuel A; Partridge, Jr., William P
2014-02-18
Methods and apparatuses for evaluating a material are described. Embodiments typically involve use of an impedance measurement sensor to measure the impedance of a sample of the material under at least two different states of illumination. The states of illumination may include (a) substantially no optical stimulation, (b) substantial optical stimulation, (c) optical stimulation at a first wavelength of light, (d) optical stimulation at a second wavelength of light, (e) a first level of light intensity, and (f) a second level of light intensity. Typically a difference in impedance between the impedance of the sample at the two states of illumination is measured to determine a characteristic of the material.
IMPEDANCE OF FINITE LENGTH RESISTOR
Energy Technology Data Exchange (ETDEWEB)
KRINSKY, S.; PODOBEDOV, B.; GLUCKSTERN, R.L.
2005-05-15
We determine the impedance of a cylindrical metal tube (resistor) of radius a, length g, and conductivity {sigma}, attached at each end to perfect conductors of semi-infinite length. Our main interest is in the asymptotic behavior of the impedance at high frequency, k >> 1/a. In the equilibrium regime, , the impedance per unit length is accurately described by the well-known result for an infinite length tube with conductivity {sigma}. In the transient regime, ka{sup 2} >> g, we derive analytic expressions for the impedance and wakefield.
Analyzing Impedance Spectroscopy Results
Institute of Scientific and Technical Information of China (English)
Yoed Tsur; Sioma Baltianski
2006-01-01
In this contribution we briefly discuss several analysis techniques for impedance spectroscopy experiments. A number of different approaches, which differ even by the definition of the problem, are used in the literature. Some aimed towards finding an equivalent circuit. Others aimed towards finding directly dielectric properties of the material under an assumed model. Others towards finding distribution of relaxation times, either parametric or point-by point. No matter what the approach is, this will always be an ill-posed problem in the sense that there exist a large number of possible solutions that solve the problem (mathematically) equally well. Therefore some a-priori knowledge about the system must be used. In addition, we should remember that the ultimate goal is to get physical insight about the system.
Institute of Scientific and Technical Information of China (English)
颜无瑕; 曹宝香
2011-01-01
Towards the difficulty of the schema matching in Deep Web and according to the features of the existing schema matching,we proposes a new approach using different groups of the ontology with the same meaning to establish the relationship between schemas, in this way the complexity can be reduced, at the same time by using the self-study ability of neural network the automation of the matching has been improved too. The experimental results show that this approach can improve the precision ratio and recall ratio of the schema matching obviously, and it can effectively improve the quality of the schema matching.%针对Deep Web中模式匹配难度大的问题,根据目前模式匹配的特点,提出一种基于本体和BP网络相融合的的模式匹配新方法.该方法利用具有相同含义的本体分组来确立模式之间的对应关系,降低匹配的复杂度;利用BP网络的自我学习能力提高匹配的自动化程度.实验结果表明该方法能明显提高模式匹配的精确度和召回率,有效地提高了匹配质量.
Short-circuit impedance measurement
DEFF Research Database (Denmark)
Pedersen, Knud Ole Helgesen; Nielsen, Arne Hejde; Poulsen, Niels Kjølstad
2003-01-01
Methods for estimating the short-circuit impedance in the power grid are investigated for various voltage levels and situations. The short-circuit impedance is measured, preferably from naturally occurring load changes in the grid, and it is shown that such a measurement system faces different...
Impedance of Finite Length Resistor
Krinsky, Samuel; Podobedov, Boris
2005-01-01
We determine the impedance of a cylindrical metal tube (resistor) of radius a and length g, attached at each end to perfect conductors of semi-infinite length. Our main interest is in the behavior of the impedance at high frequency (k>>1/a). In the equilibrium regime, ka2
Impedance source power electronic converters
Liu, Yushan; Ge, Baoming; Blaabjerg, Frede; Ellabban, Omar; Loh, Poh Chiang
2016-01-01
Impedance Source Power Electronic Converters brings together state of the art knowledge and cutting edge techniques in various stages of research related to the ever more popular impedance source converters/inverters. Significant research efforts are underway to develop commercially viable and technically feasible, efficient and reliable power converters for renewable energy, electric transportation and for various industrial applications. This book provides a detailed understanding of the concepts, designs, controls, and application demonstrations of the impedance source converters/inverters. Key features: Comprehensive analysis of the impedance source converter/inverter topologies, including typical topologies and derived topologies. Fully explains the design and control techniques of impedance source converters/inverters, including hardware design and control parameter design for corresponding control methods. Presents the latest power conversion solutions that aim to advance the role of pow...
Institute of Scientific and Technical Information of China (English)
夏汉铸; 刘辉元
2015-01-01
针对无线Mesh网络的网络特性,分析现有的队列管理策略,提出一种基于匹配因子的积极队列管理策略MFAQM.MFAQM算法通过网络的实际情况确定匹配因子MF,根据匹配因子来调整队列管理策略中丢包率和ECN标记概率,从而实现动态的积极队列管理. 详细讨论MFAQM算法的实现过程和相关参数的计算方法,通过仿真分析验证了该算法对无线Mesh网络性能的提高.%In light of the network property of wireless Mesh networks ( WMNs ) , we analyse existing queue management strategies and present a match factor-based active queue management strategy MFAQM.The algorithm determines the match factor MF through actual condition of networks, and adjusts packet loss rate and ECN marking probability in queue management strategy based on MF, so as to realise the dynamically active queue management.The paper thoroughly discusses the implementation process of MFAQM algorithm and the computation method for correlated parameters, by simulation we verify the improvement of the algorithm in performance of wireless Mesh net-works.
Measurement of Phase Dependent Impedance for 3-phase Diode Rectifier
DEFF Research Database (Denmark)
Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth
2016-01-01
This paper presents a new method to measure the phase dependent impedance from an experimental set up. Though most of power electronics based system is gradually migrating to IGBT based voltage source converter due to their controllability, the rectifier composed of diode or thyristor components...... are still widely used in AC-DC applications because of their cost effectiveness and reliability. However, these topologies generate harmonic problems in their network due to their switching instant variation caused by the frequency and phase of grid voltage. Hence, a lot of solutions have been proposed...... application. It is found that the phase dependent impedance shows different properties with the impedance profiles, which have been proposed in the research. This paper explains a method to measure the phase dependent impedance profile from an experimental set up. Furthermore, the results are compared...
Impedance of rigid bodies in one-dimensional elastic collisions
Santos, Janilo; de Oliveira, Bruna P. W.; Nelson,Osman Rosso
2012-01-01
In this work we study the problem of one-dimensional elastic collisions of billiard balls, considered as rigid bodies, in a framework very different from the classical one presented in text books. Implementing the notion of impedance matching as a way to understand efficiency of energy transmission in elastic collisions, we find a solution which frames the problem in terms of this conception. We show that the mass of the ball can be seen as a measure of its impedance and verify that the probl...
Bioelectric impedance phase angle in breast carcinoma
Directory of Open Access Journals (Sweden)
Ruchi Tyagi
2014-01-01
Full Text Available Context: Worldwide breast cancer is the most frequently diagnosed life threatening cancer and the leading cause of death in women. Bioelectric impedance analysis (BIA affords an emerging opportunity to assess prognosis because of its ability to non invasively assess cell and plasma membrane structure and function by means of phase angle. Aims: To compare the phase angle between patients of breast cancer and their matched control with the help of BIA. Settings and Design: After taking clearance from ethical committee, a total of 34 female cases of histologically proven infiltrating ductal breast carcinoma were included from the surgery IPD, department of surgery. Equal numbers of the matched controls were recruited from the friends and relatives of cases. Materials and Methods: Bio Electrical Impedance Analyzer (BIA BODY STAT QUAD SCAN 4000 was used to measure resistance (R and reactance (Xc by recording a voltage drop in applied current. Phase angle is the ratio of reactance to resistance and is a measure of cell vitality. Statistical analysis used: Unpaired "t" test was applied. Results: In control group, the phase angle showed a mean of 5.479 whereas in test group, it showed a mean value of 4.726. The P value showed a significant difference (P < 0.0001. The smaller the phase angle values were higher was the tumor, nodes, metastases (TNM staging. The phase angles differed significantly from the healthy age matched control values. Conclusions: This study demonstrated that phase angle is a strong predictor of severity of breast cancer and differed significantly between the two groups.
Mayer, Anke; Kratz, Karl; Hiebl, Bernhard; Lendlein, Andreas; Jung, Friedrich
2012-03-01
The cell population of peripheral blood monocytes/macrophages (MO) is heterogeneous: The majority of the MO are CD14++ CD16- and named "classical" (= MO1). Furthermore, two other subpopulations were described: CD14++ CD16+ ("intermediate" = MO2) and CD14+ CD16++ ("non-classical" = MO3). It is reported that MO2 possess anti-inflammatory properties and express the MO lineage marker CD163. On a hydrophilic neutrally charged acrylamide-based hydrogel human intermediate (CD14++ CD16+ ), angiogenically stimulated CD163++ monocytes/macrophages (aMO2) maintained a proangiogenic and noninflammatory status for at least 14 days. Here, we explored whether this aMO2 subset adhered to hydrophobic poly(n-butyl acrylate) networks (cPnBA) and also remained in its proangiogenic and noninflammatory status. Because substrate elasticity can impact adherence, morphology, and function of cells, cPnBAs with different Young's modulus (250 and 1100 kPa) were investigated, whereby their elasticity was tailored by variation of the cross-linker content and matched to the elasticity of human arteries. The cPnBAs exhibited similar surface properties (e.g., surface roughness), which were maintained after ethylene oxide sterilization and exposure in serum-free cell culture medium for 18 h at 37°C. aMO2 were seeded on cPnBA samples (1.7 × 10(5) cells/1.33 cm(2) ) in Dulbecco's modified Eagle medium (DMEM high glucose) supplemented with vascular endothelial growth factor 165 (VEGF-A(165) , 10 ng/mL) and fetal calf serum (10 vol%) for 3 and 72 h. On both polymeric samples (n = 3 each), the numbers of adherent cells per unit area were significantly higher (P glass, 3 h: 6 ± 3 cells/mm(2) , 72 h: 130 ± 83 cells/mm(2) ) and showed a typically spread morphology. The mRNA expression profile of the aMO2 was not influenced by the substrate elasticity. In the supernatant of aMO2 on cPnBA0250, significantly less VEGF-A(165) product was found than expected based on
Electrical impedance spectroscopy and the diagnosis of bladder pathology.
Keshtkar, Ahmad; Keshtkar, Asghar; Smallwood, Rod H
2006-07-01
Bladder pathology is usually investigated visually by cystoscopy. At present, definitive diagnosis of the bladder can be made by biopsy only, usually under general anaesthesia. This is a relatively high-cost procedure in terms of both time and money and is associated with discomfort for the patient and morbidity. Thus, we used an electrical impedance spectroscopy technique for differentiating pathological changes in the urothelium and improving cystoscopic detection. For ex vivo study, a whole or part of the patient's urinary bladder was used to take the readings less than half an hour after excision at room temperature, about 27 degrees C, using the Mk3.5 Sheffield System (2-384 kHz in 24 frequencies). In this study, 145 points (from 16 freshly excised bladders from patients) were studied in terms of their biopsy reports matching to the electrical impedance measurements. For in vivo study, a total of 106 points from 38 patients were studied to take electrical impedance and biopsy samples. The impedance data were evaluated in both malignant and benign groups, and revealed a significant difference between these two groups. The impedivity of the malignant bladder tissue was significantly higher than the impedivity of the benign tissue, especially at lower frequencies (p < 0.001). In addition, the receiver operating characteristic (ROC) curve for impedance measurements indicated that this technique could provide diagnostic information (individual classification is possible). Thus, the authors have investigated the application of bio-impedance measurements to the bladder tissue as a novel and minimally invasive technique to characterize human bladder urothelium. Therefore, this technique, especially at lower frequencies, can be a complementary method for cystoscopy, biopsy and histopathological evaluation of the bladder abnormalities.
Zhang, Jin; Cheng, Ying; Liu, Xiaojun
2017-06-01
The effective impedance modulation of artificial acoustic metamaterials is crucial in application scenarios. Here, a Mie-resonator dimer is proposed as a tunable mutual inductive coupled unit to drive a mismatched to matched impedance transition, which can achieve a wide impedance modulation range. We have demonstrated a widely tunable impedance modulation to realize an extraordinary acoustic transmission at low frequency by using the metasurface with a Mie-resonator dimer. Based on full-wave simulations, a two-port equivalent circuit model is made to explain the mechanism of the impedance modulation. Moreover, the proposal metasurface can be tuned to exhibit any desired transmittance.
Richardson, John G.
2009-11-17
An impedance estimation method includes measuring three or more impedances of an object having a periphery using three or more probes coupled to the periphery. The three or more impedance measurements are made at a first frequency. Three or more additional impedance measurements of the object are made using the three or more probes. The three or more additional impedance measurements are made at a second frequency different from the first frequency. An impedance of the object at a point within the periphery is estimated based on the impedance measurements and the additional impedance measurements.
Scattering patterns of dihedral corner reflectors with impedance surface impedances
Balanis, Constantine A.; Griesser, Timothy; Liu, Kefeng
The radar cross section patterns of lossy dihedral corner reflectors are calculated using a uniform geometrical theory of diffraction for impedance surfaces. All terms of up to third order reflections are considered for patterns in the principal plane. The surface waves are included whenever they exist for reactive surface impedances. The dihedral corner reflectors examined have right, obtuse, and acute interior angles, and patterns over the entire 360 deg azimuthal plane are calculated. The surface impedances can be different on the four faces of the dihedral corner reflector; however, the surface impedance must be uniform over each face. Computed cross sections are compared with a moment method technique for a dielectric/ferrite absorber coating on a metallic corner reflector. The analysis of the dihedral corner reflector is important because it demonstrates many of the important scattering contributors of complex targets including both interior and exterior wedge diffraction, half-plane diffraction, and dominant multiple reflections and diffractions.
GB-R impedances: new approach to impedance simulation
Serrano, L.; Carlosena, A.
1995-04-01
A new design procedure is presented for obtaining simulated inductors and large capacitors from classical opamp circuits. Such impedances exploit almost all of the available bandwidth of the operational amplifier.
A Wireless Multi-Sensor Dielectric Impedance Spectroscopy Platform
Directory of Open Access Journals (Sweden)
Seyed Alireza Ghaffari
2015-09-01
Full Text Available This paper describes the development of a low-cost, miniaturized, multiplexed, and connected platform for dielectric impedance spectroscopy (DIS, designed for in situ measurements and adapted to wireless network architectures. The platform has been tested and used as a DIS sensor node on ZigBee mesh and was able to interface up to three DIS sensors at the same time and relay the information through the network for data analysis and storage. The system is built from low-cost commercial microelectronics components, performs dielectric spectroscopy ranging from 5 kHz to 100 kHz, and benefits from an on-the-fly calibration system that makes sensor calibration easy. The paper describes the microelectronics design, the Nyquist impedance response, the measurement sensitivity and accuracy, and the testing of the platform for in situ dielectric impedance spectroscopy applications pertaining to fertilizer sensing, water quality sensing, and touch sensing.
Institute of Scientific and Technical Information of China (English)
LI Bi-Xin; CHEN Jiang-Shan; ZHAO Yong-Biao; MA Dong-Ge
2011-01-01
Frequency-dependent electrical transport properties of 4, 4′, 4″-tri (N-carbazolyl)-triphenylamine (TCTA ) are analyzed by impedance spectroscopy (IS) as functions of bias and temperature. The Cole-Cole plot shows a single semicircle which indicates that the equivalent circuit can be designed as a single parallel resistor Rp and capacitor Cp network with a series resistance Rs. The bulk capacitance Cp remains unchanged while the resistance Rp decreases along with bias voltage. Conduction mechanism matches well with the space-charge-limited current (SCLC) model with exponential trap charge distributions. The temperature-dependent impedance studies reveal the activation energy of 0.246eV with no phase change in the temperature range 220-320K. These results indicate that the IS method is applicable for organic semiconductors having a wide band gap.%@@ Frequency-dependent electrical transport properties of 4,4′,4″-tri(N-carbazolyl)-triphenylamine(TCTA ) are analyzed by impedance spectroscopy(IS) as functions of bias and temperature.The Cole-Cole plot shows a single semicircle which indicates that the equivalent circuit can be designed as a single parallel resistor Rp and capacitor Cp network with a series resistance Rs.The bulk capacitance Cp remains unchanged while the resistance Rp decreases along with bias voltage.Conduction mechanism matches well with the space-charge-limited current (SCLC) model with exponential trap charge distributions.The temperature-dependent impedance studies reveal the activation energy of 0.246eV with no phase change in the temperature range 220-320K.These results indicate that the IS method is applicable for organic semiconductors having a wide band gap.
HDR reservoir flow impedance and potentials for impedance reduction
Energy Technology Data Exchange (ETDEWEB)
DuTeau, R.; Brown, D.
1993-06-01
The data from flow tests which employed two different production zones in a well at Fenton Hill indicates the flow impedance of a wellbore zone damaged by rapid depressurization was altered, possibly by pressure spallation, which appears to have mechanically propped the joint apertures of outlet flow paths intersecting the altered wellbore. The rapid depressurization and subsequent flow test data derived from the damaged well has led to the hypothesis that pressure spallation and the resultant mechanical propping of outlet flow paths reduced the outlet flow impedance of the damaged wellbore. Furthermore, transient pressure data shows the largest pressure drop between the injection and production wellheads occurs near the production wellbore, so lowering the outlet impedance by increasing the apertures of outlet flow paths will have the greatest effect on reducing the overall reservoir impedance. Fenton Hill data also reveals that increasing the overall reservoir pressure dilates the apertures of flow paths, which likewise serves to reduce the reservoir impedance. Data suggests that either pressure dilating the wellbore connected joints with high production wellhead pressure, or mechanically propping open the outlet flow paths will increase the near-wellbore permeability. Finally, a new method for calculating and comparing near-wellbore outlet impedances has been developed. Further modeling, experimentation, and engineered reservoir modifications, such as pressure dilation and mechanical propping, hold considerable potential for significantly improving the productivity of HDR reservoirs.
Refraction and wave matching in hyperbolic thermoelasticity
Directory of Open Access Journals (Sweden)
Józef Rafa
2015-03-01
Full Text Available The subject of the publication concerns the propagation of thermoelastic waves with a particular emphasis on the refraction of waves at the boundary of a layer laying (resting on a halfspace. Analogously to the effect of wave matching, which appears in the case of acoustic and electromagnetic waves, the impedance of a thermoelastic wave has been introduced and its influence and the reflection andrefraction on the boundary at media has been investigated. The model of the medium describes a mutual coupling of mechanical and thermalinteractions with a wave type propagation of heat in media taken into account.[b]Keywords[/b]: hyperbolic thermoelasticity, wave impedance of a thermoelastic medium,refraction and wave matching
Impedance Source Power Electronic Converters
DEFF Research Database (Denmark)
Liu, Yushan; Abu-Rub, Haitham; Ge, Baoming
Impedance Source Power Electronic Converters brings together state of the art knowledge and cutting edge techniques in various stages of research related to the ever more popular impedance source converters/inverters. Significant research efforts are underway to develop commercially viable...... and technically feasible, efficient and reliable power converters for renewable energy, electric transportation and for various industrial applications. This book provides a detailed understanding of the concepts, designs, controls, and application demonstrations of the impedance source converters/inverters. Key...... control methods. Presents the latest power conversion solutions that aim to advance the role of power electronics into industries and sustainable energy conversion systems. Compares impedance source converter/inverter applications in renewable energy power generation and electric vehicles as well...
IMPEDANCE CHARACTERISTICS OF POLYFURAN FILMS
Institute of Scientific and Technical Information of China (English)
Liang Li; Xiao-bo Wan; Gi Xue
2002-01-01
Electrochemical impedance spectroscopy (EIS) was first used for the characterization of polyfuran (PFu) films that had been formed electrochemically on an Au electrode. The polyfuran was measured in high oxidation state, intermediate oxidation state and reduction state, respectively. As the oxidation level is increased, the ionic conductivity of PFu/BF4-increases. And impedance studies on PFu show that the anion BF4- appears to be mobile with a high diffusion coefficient of approximately 10-8 cm2 @ s-1.
Energy Technology Data Exchange (ETDEWEB)
Xie Jian [Ulm Univ. (Germany). Inst. fuer Energiewandlung und -speicherung; Krap, Norbert; Keiper, Heiko [DB Energie GmbH (Germany)
2008-08-15
Electric power supply grids today are subject to voltage and current harmonics. Frequency converters contribute to this effect. The frequency curves of the grid impedances are important parameters for assessing the feedback effects of frequency converters. Network impedance in HV grids can be measured by various methods. (orig.)
Institute of Scientific and Technical Information of China (English)
王敏; 黄心汉; 魏武; 李炜
2001-01-01
A method of characters in vehicle number-plate using pattern match and neural networks is presented. This method integrates the advantages of pattern match and neural networks recognizing characters in vehicle number-plate. It can be used to solve at the same time the problem that only pattern match or neural network is difficult to recognize the characters. The recognition rate can be improved with the recognition time reduced and the adaptable ability of recognition method increased. The experimental results show that, for a vehicle number-plate, recognition rate of characters is more than 90% and the recognition time of characters is less than 1.2 second by using this method. It is obvious that this method is of more effective recognition ability than other methods.%提出了一种基于模板匹配和神经网络的车牌识别方法.该方法集成了模板匹配识别车牌字符和神经网络识别车牌字符的优势，可有效地提高车牌字符的识别率、识别速度和识别系统的泛化能力.实验结果表明：大多数情况下，该方法的识别率超过90?%，识别时间不超过1?200?ms，能有效地识别各种车牌中的字符，满足实际系统的要求.
Leydesdorff, L.; de Moya-Anegón, F.; de Nooy, W.
2016-01-01
We compare the network of aggregated journal–journal citation relations provided by the Journal Citation Reports (JCR) 2012 of the Science Citation Index (SCI) and Social Sciences Citation Index (SSCI) with similar data based on Scopus 2012. First, global and overlay maps were developed for the 2 se
Leydesdorff, L.; de Moya-Anegón, F.; de Nooy, W.
We compare the network of aggregated journal–journal citation relations provided by the Journal Citation Reports (JCR) 2012 of the Science Citation Index (SCI) and Social Sciences Citation Index (SSCI) with similar data based on Scopus 2012. First, global and overlay maps were developed for the 2
An Impedance-Based Stability Analysis Method for Paralleled Voltage Source Converters
DEFF Research Database (Denmark)
Wang, Xiongfei; Blaabjerg, Frede; Loh, Poh Chiang
2014-01-01
This paper analyses the stability of paralleled voltage source converters in AC distributed power systems. An impedance-based stability analysis method is presented based on the Nyquist criterion for multiloop system. Instead of deriving the impedance ratio as usual, the system stability...... is assessed based on a series of Nyquist diagrams drawn for the terminal impedance of each converter. Thus, the effect of the right half-plane zeros of terminal impedances in the derivation of impedance ratio for paralleled source-source converters is avoided. The interaction between the terminal impedance...... of converter and the passive network can also be predicted by the Nyquist diagrams. This method is applied to evaluate the current and voltage controller interactions of converters in both grid-connected and islanded operations. Simulations and experimental results verify the effectiveness of theoretical...
Report of the SSC impedance workshop
Energy Technology Data Exchange (ETDEWEB)
NONE
1985-10-28
This workshop focused attention on the transverse, single-bunch instability and the detailed analysis of the broadband impedance which would drive it. Issues discussed included: (1) single bunch stability -- impact of impedance frequency shape, coupled-mode vs. fast blowup regimes, possible stopband structure; (2) numerical estimates of transverse impedance of inner bellows and sliding contact shielded bellows; (3) analytic estimates of pickup and kicker impedance contributions; and (4) feasibility studies of wire and beam measurements of component impedance.
Transverse Impedance of LHC Collimators
Métral, E; Assmann, Ralph Wolfgang; Boccardi, A; Bracco, C; Bohl, T; Caspers, Friedhelm; Gasior, M; Jones, O R; Kasinski, K; Kroyer, T; Redaelli, S; Robert-Demolaize, R; Roncarolo, F; Rumolo, G; Salvant, B; Steinhagen, R; Weiler, T; Zimmermann, F
2007-01-01
The transverse impedance in the LHC is expected to be dominated by the numerous collimators, most of which are made of Fibre-Reinforced-Carbon to withstand the impacts of high intensity proton beams in case of failures, and which will be moved very close to the beam, with full gaps of few millimetres, in order to protect surrounding super-conducting equipments. We present an estimate of the transverse resistive-wall impedance of the LHC collimators, the total impedance in the LHC at injection and top energy, the induced coupled-bunch growth rates and tune shifts, and finally the result of the comparison of the theoretical predictions with measurements performed in 2004 and 2006 on a prototype collimator installed in the SPS.
Impedances of Laminated Vacuum Chambers
Energy Technology Data Exchange (ETDEWEB)
Burov, A.; Lebedev, V.; /Fermilab
2011-06-22
First publications on impedance of laminated vacuum chambers are related to early 70s: those are of S. C. Snowdon [1] and of A. G. Ruggiero [2]; fifteen years later, a revision paper of R. Gluckstern appeared [3]. All the publications were presented as Fermilab preprints, and there is no surprise in that: the Fermilab Booster has its laminated magnets open to the beam. Being in a reasonable mutual agreement, these publications were all devoted to the longitudinal impedance of round vacuum chambers. The transverse impedance and the flat geometry case were addressed in more recent paper of K. Y. Ng [4]. The latest calculations of A. Macridin et al. [5] revealed some disagreement with Ref. [4]; this fact stimulated us to get our own results on that matter. Longitudinal and transverse impendances are derived for round and flat laminated vacuum chambers. Results of this paper agree with Ref. [5].
Microfabricated Thin Film Impedance Sensor & AC Impedance Measurements
Directory of Open Access Journals (Sweden)
Jinsong Yu
2010-06-01
Full Text Available Thin film microfabrication technique was employed to fabricate a platinum based parallel-electrode structured impedance sensor. Electrochemical impedance spectroscopy (EIS and equivalent circuit analysis of the small amplitude (±5 mV AC impedance measurements (frequency range: 1 MHz to 0.1 Hz at ambient temperature were carried out. Testing media include 0.001 M, 0.01 M, 0.1 M NaCl and KCl solutions, and alumina (~3 μm and sand (~300 μm particulate layers saturated with NaCl solutions with the thicknesses ranging from 0.6 mm to 8 mm in a testing cell, and the results were used to assess the effect of the thickness of the particulate layer on the conductivity of the testing solution. The calculated resistances were approximately around 20 MΩ, 4 MΩ, and 0.5 MΩ for 0.001 M, 0.01 M, and 0.1 M NaCl solutions, respectively. The presence of the sand particulates increased the impedance dramatically (6 times and 3 times for 0.001 M and 0.1 M NaCl solutions, respectively. A cell constant methodology was also developed to assess the measurement of the bulk conductivity of the electrolyte solution. The cell constant ranged from 1.2 to 0.8 and it decreased with the increase of the solution thickness.
Institute of Scientific and Technical Information of China (English)
李伟明; 王鹏; 陈天浩; 徐幸莲; 周光宏
2014-01-01
temperature of the meat was kept within 0-4℃during the measurement. The location of each test was the same and measurement time was 1-2 sec at every frequency. The experimental results showed that changes in the tissue structure caused by freezing and thawing could be reflected by the impedance magnitude and phase. The impedance magnitude of both fresh and frozen-thawed meat would decrease as the frequencies increased and the impedance magnitude of fresh meat was significantly higher (P The impedance phase angle of both fresh and frozen-thawed meat would increase as the frequencies increase. Compared with frozen-thawed meat, fresh meat had a higher (P After freezing-thawing cycles, low-frequency impedance magnitude would decrease significantly (P0.05). High-frequency phase angle would increase (P From the quality aspect, the increasing of freezing-thawing cycles lead to inevitable decline in meat quality. More thawing loss, cooking loss and higher TBARS value are found after freezing-thawing cycles. The precise calculation of the quality by impedance measurement could not be obtained for no accordant significant correlation (P>0.05) was found between impedance properties and quality parameters in different groups. Radial Basis Function (RBF) Neural Networks that are built up based on impedance magnitude and phase angle of specific frequencies from 50 Hz to 200 kHz (Total 12 frequencies) could give a solution to estimate the freezing-thawing cycles of meat without complex mathematics modeling, and the prediction accuracy satisfies the requirement. Accuracy of the testing samples of fresh chicken meat was up to 100 percent, one time freezing-thawing cycle samples also had a high degree of distinction from two and three times. These results reflect that electrical impedance measurement is a simple innocuous tool for frozen meat characterization. For improving the measurement accuracy, a dadatabase with a big enough data volume needs to be built in future work.
Yoo, Hyun Deog; Jang, Jong Hyun; Ryu, Ji Heon; Park, Yuwon; Oh, Seung M.
2014-12-01
Electrochemical impedance analysis is performed to predict the rate capability of two commercial activated carbon electrodes (RP20 and MSP20) for electric double-layer capacitor. To this end, ac impedance data are fitted with an equivalent circuit that comprises ohmic resistance and impedance of intra-particle pores. To characterize the latter, ionic accessibility into intra-particle pores is profiled by using the fitted impedance parameters, and the profiles are transformed into utilizable capacitance plots as a function of charge-discharge rate. The rate capability that is predicted from the impedance analysis is well-matched with that observed from a charge-discharge rate test. It is found that rate capability is determined by ionic accessibility as well as ohmic voltage drop. A lower value in ionic accessibility for MSP20 is attributed to smaller pore diameter, longer length, and higher degree of complexity in pore structure.
Acoustic boundary conditions at an impedance lining in inviscid shear flow
Khamis, Doran; Brambley, Edward James
2016-01-01
This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by Cambridge University Press. The accuracy of existing impedance boundary conditions is investigated, and new impedance boundary conditions are derived, for lined ducts with inviscid shear flow. The accuracy of the Ingard–Myers boundary condition is found to be poor. Matched asymptotic expansions are used to derive a boundary condition accurate to second order in the boundary layer thic...
Wideband impedance spectrum analyzer for process automation applications
Doerner, Steffen; Schneider, Thomas; Hauptmann, Peter R.
2007-10-01
For decades impedance spectroscopy is used in technical laboratories and research departments to investigate effects or material characteristics that affect the impedance spectrum of the sensor. Establishing this analytical approach for process automation and stand-alone applications will deliver additional and valuable information beside traditional measurement techniques such as the measurement of temperature, flow rate, and conductivity, among others. As yet, most of the current impedance analysis methods are suited for laboratory applications only since they involve stand-alone network analyzers that are slow, expensive, large, or immobile. Furthermore, those systems offer a large range of functionality that is not being used in process control and other fields of application. We developed a sensor interface based on high speed direct digital signal processing offering wideband impedance spectrum analysis with high resolution for frequency adjustment, excellent noise rejection, very high measurement rate, and convenient data exchange to common interfaces. The electronics has been implemented on two small circuit boards and it is well suited for process control applications such as monitoring phase transitions, characterization of fluidal systems, and control of biological processes. The impedance spectrum analyzer can be customized easily for different measurement applications by adapting the appropriate sensor module. It has been tested for industrial applications, e.g., dielectric spectroscopy and high temperature gas analysis.
Ozekes, Serhat; Osman, Onur; UCAN, Osman N.
2008-01-01
Objective The purpose of this study was to develop a new method for automated lung nodule detection in serial section CT images with using the characteristics of the 3D appearance of the nodules that distinguish themselves from the vessels. Materials and Methods Lung nodules were detected in four steps. First, to reduce the number of region of interests (ROIs) and the computation time, the lung regions of the CTs were segmented using Genetic Cellular Neural Networks (G-CNN). Then, for each lu...
Acoustic Ground-Impedance Meter
Zuckerwar, A. J.
1983-01-01
Helmoltz resonator used in compact, portable meter measures acoustic impedance of ground or other surfaces. Earth's surface is subject of increasing acoustical investigations because of its importance in aircraft noise prediction and measurment. Meter offers several advantages. Is compact and portable and set up at any test site, irrespective of landscape features, weather or other environmental condition.
Small Signal Loudspeaker Impedance Emulator
DEFF Research Database (Denmark)
Iversen, Niels Elkjær; Knott, Arnold
2014-01-01
Specifying the performance of audio amplifiers is typically done by playing sine waves into a pure ohmic load. However real loudspeaker impedances are not purely ohmic but characterized by the mechanical resonance between the mass of the diaphragm and the compliance of its suspension which vary...
Magnetically Coupled Impedance-Source Inverters
DEFF Research Database (Denmark)
Loh, Poh Chiang; Blaabjerg, Frede
2013-01-01
input-to-output gain and the presence of an impedance network. The former means a high dc-link voltage, which can stress the semiconductor switches unnecessarily. The latter leads to increases in cost and size, which similarly are undesirable. To lessen these concerns, an interesting approach is to use......Z-source inverters are a new class of inverters proposed with output voltage or current buck-boost ability. Despite their general attractiveness, there are some present limitations faced by existing Z-source inverters, most of which are linked to their requirement for low modulation ratio at high...... magnetically coupled transformers or inductors to raise the gain and modulation ratio simultaneously, while reducing the number of passive components needed. A study of the approach is now presented to show how various existing magnetically coupled inverters can be derived by applying a generic methodology...
Magnetically coupled impedance-source inverters
DEFF Research Database (Denmark)
Loh, Poh Chiang; Blaabjerg, Frede
2012-01-01
input-to-output gain, and the presence of an impedance network. The former means a high dc-link voltage, which can stress the semiconductor switches unnecessarily. The latter leads to increases in cost and size, which similarly are undesirable. To lessen these concerns, an interesting approach is to use......Z-source inverters are a new class of inverters proposed with output voltage or current buck-boost ability. Despite their general attractiveness, there are some present limitations faced by existing Z-source inverters. Most of which are linked to their requirement for low modulation ratio at high...... magnetically coupled transformers or inductors to raise the gain and modulation ratio simultaneously, while reducing the number of passive components needed. A study of the approach is now presented to show how various existing magnetically coupled inverters can be derived by applying a generic methodology...
Institute of Scientific and Technical Information of China (English)
张淯舒; 王慧强; 冯光升; 吕宏武
2016-01-01
Opportunistic social networks can provide message dissemination service through encounters created by nodes’ movement in intermittently connected or completely disconnected wireless networks ,but there are still some shortcomings in message dissemination efficiency and user experience .In order to promote the performance of dissemination system and improve the user experience ,an opportunistic social network message dissemination mechanism based on node interest matching is proposed .A kind of opportunistic social networks with hybrid architecture is introduced to avoid problems such as incomplete information of network topology and low computing ability of nodes .Considering the fact that node behaviors and interests can both affect the performance of dissemination , the analytical method designed takes both of them as reference factors , and an improved co‐clustering algorithm for data with complex relationship is proposed .In addition , the interest matching rate for nodes is used to show what percentage of buffer is occupied by the useful messages to user ,and a novel message dissemination strategy is proposed to raise the rate .Simulation results show that the proposed scheme can both improve the capability of opportunistic social networks in terms of delivery rate ,latency and buffer usage ,and promote the performance of message dissemination systems in terms of efficiency ,coverage rate and interest matching rate .%机会社会网络（opportunistic social networks）能够利用节点移动创造的相遇机会，在缺乏持续端到端连接的网络中，为用户提供稳定的消息分发途径，但在消息分发效率以及用户体验方面存在不足。为提高消息分发系统的性能、改善网络用户体验，提出一种基于节点兴趣匹配的机会社会网络分发机制。通过引入混合结构的机会社会网络分发系统解决网络拓扑信息获取不全与节点计算能力不足的问题；
Statistics of polarisation matching
Naus, H.W.L.; Zwamborn, A.P.M.
2014-01-01
The reception of electromagnetic signals depends on the polarisation matching of the transmitting and receiving antenna. The practical matching differs from the theoretical one because of the noise deterioration of the transmitted and eventually received electromagnetic field. In other applications,
Matching Through Position Auctions
Terence Johnson
2009-01-01
This paper studies how an intermediary should design two-sided matching markets when agents are privately informed about their quality as a partner and can make payments to the intermediary. Using a mechanism design approach, I derive sufficient conditions for assortative matching to be profit- or welfare-maximizing, and then show how to implement the optimal match and payments through two-sided position auctions. This sharpens our understanding of intermediated matching markets by clarifying...
ANALYSIS OF MONOPOLE ANTENNA ON CIRCULAR DISC BY MODE MATCHING
Institute of Scientific and Technical Information of China (English)
Sun Baohua; Zhang Fushun; Liu Qizhong
2001-01-01
Mode matching is used for the analysis of monopole antenna on circular disc, which is achieved by developing a novel model consisting of two artificial ground planes above and bellow the monopole antenna. Using this model, the input impedance is computed and compared with measured data reported in literatures, and excellent agreement is observed.
Bladder Cancer Detection Using Electrical Impedance Technique (Tabriz Mark 1
Directory of Open Access Journals (Sweden)
Ahmad Keshtkar
2012-01-01
Full Text Available Bladder cancer is the fourth most common malignant neoplasm in men and the eighth in women. Bladder pathology is usually investigated visually by cystoscopy. In this technique, biopsies are obtained from the suspected area and then, after needed procedure, the diagnostic information can be taken. This is a relatively difficult procedure and is associated with discomfort for the patient and morbidity. Therefore, the electrical impedance spectroscopy (EIS, a minimally invasive screening technique, can be used to separate malignant areas from nonmalignant areas in the urinary bladder. The feasibility of adapting this technique to screen for bladder cancer and abnormalities during cystoscopy has been explored and compared with histopathological evaluation of urinary bladder lesions. Ex vivo studies were carried out in this study by using a total of 30 measured points from malignant and 100 measured points from non-malignant areas of patients bladders in terms of their biopsy reports matching to the electrical impedance measurements. In all measurements, the impedivity of malignant area of bladder tissue was significantly higher than the impedivity of non-malignant area this tissue (<0.005.
Bladder cancer detection using electrical impedance technique (tabriz mark 1).
Keshtkar, Ahmad; Salehnia, Zeinab; Keshtkar, Asghar; Shokouhi, Behrooz
2012-01-01
Bladder cancer is the fourth most common malignant neoplasm in men and the eighth in women. Bladder pathology is usually investigated visually by cystoscopy. In this technique, biopsies are obtained from the suspected area and then, after needed procedure, the diagnostic information can be taken. This is a relatively difficult procedure and is associated with discomfort for the patient and morbidity. Therefore, the electrical impedance spectroscopy (EIS), a minimally invasive screening technique, can be used to separate malignant areas from nonmalignant areas in the urinary bladder. The feasibility of adapting this technique to screen for bladder cancer and abnormalities during cystoscopy has been explored and compared with histopathological evaluation of urinary bladder lesions. Ex vivo studies were carried out in this study by using a total of 30 measured points from malignant and 100 measured points from non-malignant areas of patients bladders in terms of their biopsy reports matching to the electrical impedance measurements. In all measurements, the impedivity of malignant area of bladder tissue was significantly higher than the impedivity of non-malignant area this tissue (P < 0.005).
Time-domain fitting of battery electrochemical impedance models
Alavi, S. M. M.; Birkl, C. R.; Howey, D. A.
2015-08-01
Electrochemical impedance spectroscopy (EIS) is an effective technique for diagnosing the behaviour of electrochemical devices such as batteries and fuel cells, usually by fitting data to an equivalent circuit model (ECM). The common approach in the laboratory is to measure the impedance spectrum of a cell in the frequency domain using a single sine sweep signal, then fit the ECM parameters in the frequency domain. This paper focuses instead on estimation of the ECM parameters directly from time-domain data. This may be advantageous for parameter estimation in practical applications such as automotive systems including battery-powered vehicles, where the data may be heavily corrupted by noise. The proposed methodology is based on the simplified refined instrumental variable for continuous-time fractional systems method ('srivcf'), provided by the Crone toolbox [1,2], combined with gradient-based optimisation to estimate the order of the fractional term in the ECM. The approach was tested first on synthetic data and then on real data measured from a 26650 lithium-ion iron phosphate cell with low-cost equipment. The resulting Nyquist plots from the time-domain fitted models match the impedance spectrum closely (much more accurately than when a Randles model is assumed), and the fitted parameters as separately determined through a laboratory potentiostat with frequency domain fitting match to within 13%.
Smart Multi-Frequency Bioelectrical Impedance Spectrometer for BIA and BIVA Applications.
Harder, Rene; Diedrich, Andre; Whitfield, Jonathan S; Buchowski, Macie S; Pietsch, John B; Baudenbacher, Franz J
2016-08-01
Bioelectrical impedance analysis (BIA) is a noninvasive and commonly used method for the assessment of body composition including body water. We designed a small, portable and wireless multi-frequency impedance spectrometer based on the 12 bit impedance network analyzer AD5933 and a precision wide-band constant current source for tetrapolar whole body impedance measurements. The impedance spectrometer communicates via Bluetooth with mobile devices (smart phone or tablet computer) that provide user interface for patient management and data visualization. The export of patient measurement results into a clinical research database facilitates the aggregation of bioelectrical impedance analysis and biolectrical impedance vector analysis (BIVA) data across multiple subjects and/or studies. The performance of the spectrometer was evaluated using a passive tissue equivalent circuit model as well as a comparison of body composition changes assessed with bioelectrical impedance and dual-energy X-ray absorptiometry (DXA) in healthy volunteers. Our results show an absolute error of 1% for resistance and 5% for reactance measurements in the frequency range of 3 kHz to 150 kHz. A linear regression of BIA and DXA fat mass estimations showed a strong correlation (r(2)=0.985) between measures with a maximum absolute error of 6.5%. The simplicity of BIA measurements, a cost effective design and the simple visual representation of impedance data enables patients to compare and determine body composition during the time course of a specific treatment plan in a clinical or home environment.
Beam Coupling Impedances of Small Discontinuities
Kurennoy, S S
2000-01-01
A general derivation of the beam coupling impedances produced by small discontinuities on the wall of the vacuum chamber of an accelerator is reviewed. A collection of analytical formulas for the impedances of small obstacles is presented.
Tapping mode microwave impedance microscopy
Lai, K.
2009-01-01
We report tapping mode microwave impedance imaging based on atomic force microscope platforms. The shielded cantilever probe is critical to localize the tip-sample interaction near the tip apex. The modulated tip-sample impedance can be accurately simulated by the finite-element analysis and the result agrees quantitatively to the experimental data on a series of thin-film dielectric samples. The tapping mode microwave imaging is also superior to the contact mode in that the thermal drift in a long time scale is totally eliminated and an absolute measurement on the dielectric properties is possible. We demonstrated tapping images on working nanodevices, and the data are consistent with the transport results. © 2009 American Institute of Physics.
Impedance analysis of acupuncture points and pathways
Teplan, Michal; Kukučka, Marek; Ondrejkovičová, Alena
2011-12-01
Investigation of impedance characteristics of acupuncture points from acoustic to radio frequency range is addressed. Discernment and localization of acupuncture points in initial single subject study was unsuccessfully attempted by impedance map technique. Vector impedance analyses determined possible resonant zones in MHz region.
A spatial impedance controller for robotic manipulation
Fasse, Ernest D.; Broenink, Jan F.
1997-01-01
Mechanical impedance is the dynamic generalization of stiffness, and determines interactive behavior by definition. Although the argument for explicitly controlling impedance is strong, impedance control has had only a modest impact on robotic manipulator control practice. This is due in part to the
Impedance effect of manganite thin film-based photodetectors
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
We report on the photodetector structures based on perovskite manganite La0.67Ca0.33MnO3 thin films on tilted SrTiO3 (001) substrates. The photovoltaic effect has been observed in response to excitation by 308 nm ultraviolet laser pulse irradiation in duration of 20 ns at room temperature. The outputs obtained required no amplification. To reduce the deformation of the signal detected, a series of testing measurements were made to investigate the impedance effect. When the impedance at the oscilloscope end matched to the co-axis cable, the signal trace was almost triangular and symmetrical, with response time equal to the excitation laser. In addation, the response linearly depends on the irradiated area for low on-sample energy. The devices work well under unbiased conditions and so are simple to configure for practical applications.
Probe impedance measurements for millimeter-wave integrated horn antennas
Guo, Yong; Chiao, Jung-Chih; Potter, Kent A.; Rutledge, David B.
1993-01-01
In order to achieve an impedance-matched millimeter-wave integrated horn antenna mixer array, the characteristics of the antenna probes inside the horn must be known. This paper describes impedance measurements for various probes in low-frequency model horns of two different types: (1) a 3 x 3 array made of aluminum by electric discharge machining and (2) a half horn made of copper sheet placed on a big copper-clad circuit board that was used as an image plane. The results of measurements indicate that the presence of the horn increases the effective length of the probe element, in agreement with reports of Guo et al. (1991) and theoretical analysis of Eleftheriades et al. (1991). It was also found that the resonant frequencies can be controlled by changing the length of the probes or by loading the probes.
Energy Technology Data Exchange (ETDEWEB)
Ozekes, Serhat; Osman, Onur; Ucan, N. [Istanbul Commerce University, Ragip Gumuspala Cad. No: 84 34378 Eminonu, Istanbul (Turkmenistan)
2008-02-15
The purpose of this study was to develop a new method for automated lung nodule detection in serial section CT images with using the characteristics of the 3D appearance of the nodules that distinguish themselves from the vessels. Lung nodules were detected in four steps. First, to reduce the number of region of interests (ROIs) and the computation time, the lung regions of the CTs were segmented using Genetic Cellular Neural Networks (G-CNN). Then, for each lung region, ROIs were specified with using the 8 directional search; +1 or -1 values were assigned to each voxel. The 3D ROI image was obtained by combining all the 2-Dimensional (2D) ROI images. A 3D template was created to find the nodule-like structures on the 3D ROI image. Convolution of the 3D ROI image with the proposed template strengthens the shapes that are similar to those of the template and it weakens the other ones. Finally, fuzzy rule based thresholding was applied and the ROI's were found. To test the system's efficiency, we used 16 cases with a total of 425 slices, which were taken from the Lung Image Database Consortium (LIDC) dataset. The computer aided diagnosis (CAD) system achieved 100% sensitivity with 13.375 FPs per case when the nodule thickness was greater than or equal to 5.625 mm. Our results indicate that the detection performance of our algorithm is satisfactory, and this may well improve the performance of computer aided detection of lung nodules.
Institute of Scientific and Technical Information of China (English)
王加钢; 吴小燕; 王琳; 王学伟
2012-01-01
以住宅小区载波抄表信道为测试对象,构建了低压电力线载波阻抗自动测试系统并开发了相应的系统主站管理软件。该系统长期稳定运行,可实现远程多载波频率阻抗自动连续测试及现场USB连接自动扫频阻抗测试等功能。本文根据长期采集的阻抗测试结果,着重分析了阻抗模值、相位在冬季受供暖设备影响下的变化规律,为低压电力线载波通信信道阻抗特性研究和阻抗匹配提供了参考。%In order to test the residential meter-reading channel, an automatic impedance test system for low-voltage power line carrier communication network was set up and management software was developed. This system can be used for remote automatic continuous impedance testing in the condition of multi-carrier frequency, and for automatic sweep impedance testing by local USB connection, and also capable of operate stably in long term, The variation of impedance modulus and phase under the influence of heating equipment in the winter was analyzed based on long-term test results of the system, and the impedance for low-voltage power line carrier communication channel was provided for impedance matching and characteristics analysis.
Institute of Scientific and Technical Information of China (English)
吴旭婧; 许勇; 张亚楠
2015-01-01
With the widely application of the Wireless Sensor Network( WSN) ,the security problem is more and more prominent. The distribution and management of WSN receive more and more attention. This paper proposes a key pre-distribution scheme which matches patterns according to the fingerprint identification by dividing the network after collecting the deployment information. The scheme divides the network into several domains,and the seed pool is divided into multiple sub-seed pools relatively. Nodes select seeds from relative areas to generate patterns and texts, and use fingerprint function values as communication keys when match successfully. The performance and security analysis shows that the scheme can substantially improve a network’ s connectivity and reduce storage consumption compared with the traditional random key pre-distribution scheme.%随着无线传感器网络( WSN)的广泛应用,其安全问题尤其突出,WSN的密钥分配和管理受到越来越多研究者的重视。通过收集节点的部署信息对区域进行划分,提出一种根据指纹识别进行模式匹配的密钥预分配方案。该方案将网络划分成多个较小区域,同时将密钥种子池分成多个与其对应的子密钥种子池。节点通过挑选相应区域内种子生成模式和文本,根据匹配成功时生成的指纹函数值建立通信密钥。安全性分析结果表明,与传统的随机密钥预分配方案相比,该方案具有较高的网络连通率及较低的存储能耗。
Impedance Discontinuity Reduction Between High-Speed Differential Connectors and PCB Interfaces
Navidi, Sal; Agdinaoay, Rodell; Walter, Keith
2013-01-01
High-speed serial communication (i.e., Gigabit Ethernet) requires differential transmission and controlled impedances. Impedance control is essential throughout cabling, connector, and circuit board construction. An impedance discontinuity arises at the interface of a high-speed quadrax and twinax connectors and the attached printed circuit board (PCB). This discontinuity usually is lower impedance since the relative dielectric constant of the board is higher (i.e., polyimide approx. = 4) than the connector (Teflon approx. = 2.25). The discontinuity can be observed in transmit or receive eye diagrams, and can reduce the effective link margin of serial data networks. High-speed serial data network transmission improvements can be made at the connector-to-board interfaces as well as improving differential via hole impedances. The impedance discontinuity was improved by 10 percent by drilling a 20-mil (approx. = 0.5-mm) hole in between the pin of a differential connector spaced 55 mils (approx. = 1.4 mm) apart as it is attached to the PCB. The effective dielectric constant of the board can be lowered by drilling holes into the board material between the differential lines in a quadrax or twinax connector attachment points. The differential impedance is inversely proportional to the square root of the relative dielectric constant. This increases the differential impedance and thus reduces the above described impedance discontinuity. The differential via hole impedance can also be increased in the same manner. This technique can be extended to multiple smaller drilled holes as well as tapered holes (i.e., big in the middle followed by smaller ones diagonally).
A compact broadband nonsynchronous noncommensurate impedance transformer
DEFF Research Database (Denmark)
Zhurbenko, Vitaliy; Kim, Kseniya; Narenda, Kumar
2012-01-01
Nonsynchronous noncommensurate impedance transformers consist of a combination of high‐ and low‐impedance transmission lines. High‐impedance lines have narrow tracks in strip and microstrip technology, which allows for high flexibility and miniaturization of the layout in comparison to the tradit......Nonsynchronous noncommensurate impedance transformers consist of a combination of high‐ and low‐impedance transmission lines. High‐impedance lines have narrow tracks in strip and microstrip technology, which allows for high flexibility and miniaturization of the layout in comparison...... to the traditional tapered line transformers. This flexibility of the broadband nonsynchronous noncommensurate impedance transformers is experimentally demonstrated in this article allowing the length reduction by almost three times. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1832–1835, 2012; View...
Gal, Avigdor
2011-01-01
Schema matching is the task of providing correspondences between concepts describing the meaning of data in various heterogeneous, distributed data sources. Schema matching is one of the basic operations required by the process of data and schema integration, and thus has a great effect on its outcomes, whether these involve targeted content delivery, view integration, database integration, query rewriting over heterogeneous sources, duplicate data elimination, or automatic streamlining of workflow activities that involve heterogeneous data sources. Although schema matching research has been o
Impedance studies of 2D azimuthally symmetric devices of finite length
Biancacci, N; Métral, E; Salvant, B; Migliorati, M; Palumbo, L
2014-01-01
In particle accelerators, the beam quality can be strongly affected by the interaction with self-induced electromagnetic fields excited by the beam in the passage through the elements of the accelerator. The beam coupling impedance quantifies this interaction and allows predicting the stability of the dynamics of high intensity, high brilliance beams. The coupling impedance can be evaluated with finite element methods or using analytical approaches, such as field matching or mode matching. In this paper we present an application of the mode matching technique for an azimuthally uniform structure of finite length: a cylindrical cavity loaded with a toroidal slab of lossy dielectric, connected with cylindrical beam pipes. In order to take into account the finite length of the structure, with respect to the infinite length approximation, we decompose the fields in the cavity into a set of orthonormal modes. We obtain a complete set of equations using the magnetic field matching and the nonuniform convergence of ...
Doubly Fed Induction Generator System Resonance Active Damping through Stator Virtual Impedance
DEFF Research Database (Denmark)
Song, Yipeng; Wang, Xiongfei; Blaabjerg, Frede
2017-01-01
The penetration of wind power has been increasing in the past few decades all over the world. Under certain non-ideal situations where the wind power generation system is connected to the weak grid, the Doubly Fed Induction Generator (DFIG) based wind power generation system may suffer High...... Frequency Resonance (HFR) due to the impedance interaction between the DFIG system and the weak grid network whose impedance is comparative large. Thus, it is important to implement an active damping for the HFR in order to ensure a safe and reliable operation of both the DFIG system and the grid connected...... converters/loads. This paper analyzes and explains first the HFR phenomenon between the DFIG system and a parallel compensated weak network (series RL + shunt C). Then on the basis of the DFIG system impedance modeling, an active damping control strategy is introduced by inserting a virtual impedance...
Directory of Open Access Journals (Sweden)
E. J. Farrell
1987-01-01
Full Text Available Explicit recurrences are derived for the matching polynomials of the basic types of hexagonal cacti, the linear cactus and the star cactus and also for an associated graph, called the hexagonal crown. Tables of the polynomials are given for each type of graph. Explicit formulae are then obtained for the number of defect-d matchings in the graphs, for various values of d. In particular, formulae are derived for the number of perfect matchings in all three types of graphs. Finally, results are given for the total number of matchings in the graphs.
Characteristic Impedance of a Microstrip-Like Interconnect Line in Presence of Ground Plane Aperture
Directory of Open Access Journals (Sweden)
Rohit Sharma
2007-01-01
Full Text Available We propose new empirical expressions for the characteristic impedance of a microstrip-like interconnect line in presence of ground plane aperture. The existing characteristic impedance expressions are modified so as to include the effect of the ground plane aperture. The variation in the characteristic impedance vis-à-vis the aperture size is established. The proposed expressions are general and valid for a range of dielectric materials concerning MICs, RFICs, and PCBs. The results are validated by measurements performed on a vector network analyzer.
Impedance-Based High Frequency Resonance Analysis of DFIG System in Weak Grids
Song, Yipeng; Wang, Xiongfei; Blaabjerg, Frede
2017-01-01
The impedance-based model of Doubly Fed Induction Generator (DFIG) systems, including the rotor part (Rotor Side Converter (RSC) and induction machine), and the grid part (Grid Side Converter (GSC) and its output filter), has been developed for analysis and mitigation of the Sub- Synchronous Resonance (SSR). However, the High Frequency Resonance (HFR) of DFIG systems due to the impedance interaction between DFIG system and parallel compensated weak network is often overlooked. This paper thus...
Avolio, Alberto
2009-02-01
By definition, vascular impedance is described in the frequency domain as the ratio of sinusoidal functions of pressure and flow, yielding spectral values of impedance modulus and phase. The impedance spectrum is determined by the structure and physical properties of the vascular system, such that for a given system the relation between pressure and flow can be modified by alteration of the geometric or mechanical properties of the vascular segments. Whereas input impedance of an arterial system can be readily determined by simultaneous measurement of just two time varying signals of blood pressure and flow, the production of the same impedance spectrum from the physical properties of the system would require information of inordinate complexity and magnitude. Hence, arterial models with a tractable number of parameters or explicit mathematical description are used to approximate the physiological impedance of a vascular structure, which in all animal species consists of distributed branching arterial networks. Although models are a necessary approximation, the strong similarity between the impedance spectra of models and physiological arterial systems enables investigations of fundamental concepts. This is illustrated by examining the effect of the branching structure on the decoupling of the high peripheral resistance from the ejecting ventricles and how physical parameters derived from the impedance spectrum can be used to investigate concepts of optimal design and features related to body size across a broad range of animal species.
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba; Christopher J. Ziolkowski
2004-06-30
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba
2003-10-01
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba
2003-04-01
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a thin film sensor conformal with the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is capacitively coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba; Christopher J. Ziolkowski
2005-01-17
This project aimed at developing a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GTI. GTI proposed to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or non-metallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba
2003-01-30
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a thin film sensor conformal with the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is capacitively coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba; Christopher J. Ziolkowski
2004-10-29
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or non-metallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba
2002-08-30
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a thin film sensor conformal with the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is capacitively coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba
2004-02-01
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba
2002-11-27
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a thin film sensor conformal with the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is capacitively coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba
2004-05-03
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging
Impedance spectroscopy of food mycotoxins
Bilyy, Oleksandr I.; Yaremyk, Roman Ya.; Kotsyumbas, Ihor Ya.; Kotsyumbas, Halyna I.
2012-01-01
A new analytical method of high-selective detection of mycotoxins in food and feed are considered. A method is based on optical registration the changes of conduct of the electric polarized bacterial agents in solution at the action of the external gradient electric fields. Measuring are conducted in integrated electrode-optical cuvette of the special construction, which provides the photometric analysis of forward motion of the objects registration in liquid solution under act of the enclosed electric field and simultaneous registration of kinetics of change of electrical impedance parameters solution and electrode system.
Observations involving broadband impedance modelling
Energy Technology Data Exchange (ETDEWEB)
Berg, J.S.
1995-08-01
Results for single- and multi-bunch instabilities can be significantly affected by the precise model that is used for the broadband impendance. This paper discusses three aspects of broadband impendance modeling. The first is an observation of the effect that a seemingly minor change in an impedance model has on the single-bunch mode coupling threshold. The second is a successful attempt to construct a model for the high-frequency tails of an r.f cavity. The last is a discussion of requirements for the mathematical form of an impendance which follow from the general properties of impendances.
RETIRED MATCHES AMONG MALE PROFESSIONAL TENNIS PLAYERS
Directory of Open Access Journals (Sweden)
Kristijan Breznik
2012-06-01
Full Text Available The aim of this study was to explore the effect of characteristics of various games and players on the proportion of retired tennis matches in the Open Era of tennis. The data included over 420,000 matches played among 17,553 tennis players in the period from 1968 to the end of 2010. The influence of the surface type was clearly confirmed, with the proportion of retired matches being higher on hard and clay courts compared to grass and carpet surfaces. Similarly, more retired matches were observed in outdoor venues than in indoor ones. The impact of other variables, tournament types, rounds at which the game was played and both players' ranks, is more ambiguous. Our interpretation of the obtained results is presented in the paper. Network analytic methods were applied to extract players with the most retired matches in their careers. Eventually, we defined a group of top tennis players and gave a more precise insight into retired matches in that group. Correspondence analysis was used to visually display the two-mode network of top players and the proportion of retired matches by surface type
Cascaded Network Body Channel Model for Intrabody Communication.
Wang, Hao; Tang, Xian; Choy, Chiu Sing; Sobelman, Gerald E
2016-07-01
Intrabody communication has been of great research interest in recent years. This paper proposes a novel, compact but accurate body transmission channel model based on RC distribution networks and transmission line theory. The comparison between simulation and measurement results indicates that the proposed approach accurately models the body channel characteristics. In addition, the impedance-matching networks at the transmitter output and the receiver input further maximize the power transferred to the receiver, relax the receiver complexity, and increase the transmission performance. Based on the simulation results, the power gain can be increased by up to 16 dB after matching. A binary phase-shift keying modulation scheme is also used to evaluate the bit-error-rate improvement.
Ontology Matching Across Domains
2010-05-01
matching include GMO [1], Anchor-Prompt [2], and Similarity Flooding [3]. GMO is an iterative structural matcher, which uses RDF bipartite graphs to...AFRL under contract# FA8750-09-C-0058. References [1] Hu, W., Jian, N., Qu, Y., Wang, Y., “ GMO : a graph matching for ontologies”, in: Proceedings of
Journal bearing impedance descriptions for rotordynamic applications
Childs, D.; Moes, H.; Van Leeuwen, H.
1976-01-01
The paper deals with the development of analytic descriptions for plain circumferentially-symmetric fluid journal bearings, which are suitable for use in rotor dynamic analysis. The bearing impedance vector is introduced, which defines the bearing reaction force components as a function of the bearing motion. Impedances are derived directly for the Ocvirk (short) and Sommerfeld (long) bearings, and the relationships between the impedance vector and the more familiar mobility vector are developed and used to derive analytic impedance for finite-length bearings. The static correctness of the finite-length cavitating impedance is verified. Analytic stiffness and damping coefficient definitions are derived in terms of an impedance vector for small motion around an equilibrium position and demonstrated for the finite-length cavitating impedance. Nonlinear transient rotordynamic simulations are presented for the short pi and 2-pi impedances and the finite-length cavitating impedance. It is shown that finite-length impedance yields more accurate results for substantially less computer time than the short-bearing numerical-pressure-integration approach.
Estimation of Elastic Parameters Using Two-Term Fatti Elastic Impedance Inversion
Institute of Scientific and Technical Information of China (English)
Jin Zhang; Huaishan Liu; Siyou Tong; Lei Xing; Xiangpeng Chen; Chaoguang Su
2015-01-01
Elastic impedance (EI) inversion has been widely used in industry to estimate kinds of elastic parameters to distinguish lithology or even fluid. However, it is found that conventional three-term elastic impedance formula is unstable even with slight random noise in seismic data, due to the ill-conditioned co-efficient matrix of elastic parameters. We presented two-term Fatti elastic impedance inversion method, which is more robust and accurate than conventional three-term elastic impedance inversion. In our method, density is ignored to increase the robustness of inversion matrix. Besides, P-impedance and S-impedance, which are less sensitive to random noise, are inverted instead of VP and VS in conventional three-term elastic impedance. To make the inversion more stable, we defined the range of K value as a con-straint. Synthetic tests claim that this method can obtain promising results with low SNR (signal noise ratio) seismic data. With the application of the method in a 2D line data, we achievedλρ,μρand VP/VS sections, which matched the drilled well perfectly, indicating the potential of the method in reservoir prediction.
Caetano, Tiberio S; Cheng, Li; Le, Quoc V; Smola, Alex J
2008-01-01
As a fundamental problem in pattern recognition, graph matching has applications in a variety of fields, from computer vision to computational biology. In graph matching, patterns are modeled as graphs and pattern recognition amounts to finding a correspondence between the nodes of different graphs. Many formulations of this problem can be cast in general as a quadratic assignment problem, where a linear term in the objective function encodes node compatibility and a quadratic term encodes edge compatibility. The main research focus in this theme is about designing efficient algorithms for approximately solving the quadratic assignment problem, since it is NP-hard. In this paper we turn our attention to a different question: how to estimate compatibility functions such that the solution of the resulting graph matching problem best matches the expected solution that a human would manually provide. We present a method for learning graph matching: the training examples are pairs of graphs and the `labels' are ma...
Energy Technology Data Exchange (ETDEWEB)
Theiler, James P [Los Alamos National Laboratory
2009-01-01
Following an analogous distinction in statistical hypothesis testing, we investigate variants of machine learning where the training set comes in matched pairs. We demonstrate that even conventional classifiers can exhibit improved performance when the input data has a matched-pair structure. Online algorithms, in particular, converge quicker when the data is presented in pairs. In some scenarios (such as the weak signal detection problem), matched pairs can be generated from independent samples, with the effect not only doubling the nominal size of the training set, but of providing the structure that leads to better learning. A family of 'dipole' algorithms is introduced that explicitly takes advantage of matched-pair structure in the input data and leads to further performance gains. Finally, we illustrate the application of matched-pair learning to chemical plume detection in hyperspectral imagery.
Institute of Scientific and Technical Information of China (English)
徐富新; 王晶; 黄玉秀; 王洲
2015-01-01
为提高实验教学中实验报告成绩的录入效率，设计了一个基于图像处理技术的手写字符识别系统。以VISUAL C++6.0为编译环境，MFC为图形界面开发平台，通过CCD摄像头进行图像采集，根据图像识别原理对图片进行预处理，并分别采用BP神经网络和模板匹配两种不同方法对实验报告成绩及学号字符进行识别，比较了两种方法在识别准确率和速度方面的优劣。测试结果表明，BP神经网络法比模板匹配法识别的准确率更高，而后者识别速度较后者快10倍左右，自动打分系统较传统的手工录入法大幅度提高了数据输入速度。该系统可以应用于各类实验报告成绩的快速录入。%In order to improve the input efficiency of the experiment report grades in experiment teaching, this paper designs a handwritten character recognition system based on image processing technology, which is able to identify and save stu-dent id with VISUAL C++ 6.0 being the compiler environment, MFC as graphics interface development platform, CCD camera for image acquisition, and preprocessing of image based on image recognition theory. This paper also tests both methods of BP neural network and template matching to identify report grades and student’s id and compares the pros and cons of their recognition accuracy and speed. The results show that template matching methods have a lower accuracy rate than BP neural network methods, but are almost 10 times faster, and both of them improve the data input speed greatly compared with the traditional method of manual entry. This system can be applied to quick entry of various types of experi-mental report grades.
Stability Enhancement Based on Virtual Impedance for DC Microgrids with Constant Power Loads
DEFF Research Database (Denmark)
Lu, Xiaonan; Sun, Kai; Guerrero, Josep M.
2015-01-01
the overall stability of the above DC microgrid with constant power loads (CPLs), a comprehensive small-signal model is derived by analyzing the interface converters in each stage. The instability issue induced by the CPLs is revealed by using the criteria of impedance matching. Meanwhile, virtual...
Spheromak Impedance and Current Amplification
Energy Technology Data Exchange (ETDEWEB)
Fowler, T K; Hua, D D; Stallard, B W
2002-01-31
It is shown that high current amplification can be achieved only by injecting helicity on the timescale for reconnection, {tau}{sub REC}, which determines the effective impedance of the spheromak. An approximate equation for current amplification is: dI{sub TOR}{sup 2}/dt {approx} I{sup 2}/{tau}{sub REC} - I{sub TOR}{sup 2}/{tau}{sub closed} where I is the gun current, I{sub TOR} is the spheromak toroidal current and {tau}{sub CLOSED} is the ohmic decay time of the spheromak. Achieving high current amplification, I{sub TOR} >> I, requires {tau}{sub REC} <<{tau}{sub CLOSED}. For resistive reconnection, this requires reconnection in a cold zone feeding helicity into a hot zone. Here we propose an impedance model based on these ideas in a form that can be implemented in the Corsica-based helicity transport code. The most important feature of the model is the possibility that {tau}{sub REC} actually increases as the spheromak temperature increases, perhaps accounting for the ''voltage sag'' observed in some experiments, and a tendency toward a constant ratio of field to current, B {proportional_to} I, or I{sub TOR} {approx} I. Program implications are discussed.
Damage Diagnosis in Semiconductive Materials Using Electrical Impedance Measurements
Ross, Richard W.; Hinton, Yolanda L.
2008-01-01
Recent aerospace industry trends have resulted in an increased demand for real-time, effective techniques for in-flight structural health monitoring. A promising technique for damage diagnosis uses electrical impedance measurements of semiconductive materials. By applying a small electrical current into a material specimen and measuring the corresponding voltages at various locations on the specimen, changes in the electrical characteristics due to the presence of damage can be assessed. An artificial neural network uses these changes in electrical properties to provide an inverse solution that estimates the location and magnitude of the damage. The advantage of the electrical impedance method over other damage diagnosis techniques is that it uses the material as the sensor. Simple voltage measurements can be used instead of discrete sensors, resulting in a reduction in weight and system complexity. This research effort extends previous work by employing finite element method models to improve accuracy of complex models with anisotropic conductivities and by enhancing the computational efficiency of the inverse techniques. The paper demonstrates a proof of concept of a damage diagnosis approach using electrical impedance methods and a neural network as an effective tool for in-flight diagnosis of structural damage to aircraft components.
Institute of Scientific and Technical Information of China (English)
张霞; 张岐山
2012-01-01
A new distribution network optimization problem in the supply chain background was studied. In the design of transportation network we adopted the matching mode in which a supplier and a customer are merged. The model was built with soft time windows constraint, vehicle maximum driving distance constraint and capacity constraints. Discrete particle swarm optimization algorithm based on integer number coding and random swap sequence was applied to solve the problem. Finally the validity of the model and the algorithm was tested through operating and comparing three different algorithms on numerical examples. Results show that DPSO can reduce the iteration number,and get the optimal solution of the problem.%针对客户和供应商匹配运输下的供应链配送网络优化问题,在模型中加入客户软时间窗约束、车辆最大行驶距离约束以及设施容量约束,建立了全新的0-1整数规划模型,采用基于整数编码和交换序的离散粒子群优化算法来求解.通过算例将标准粒子群算法( PSO)、局部版粒子群算法(LPSO)和离散粒子群算法(DPSO)的运行结果进行比较,结果表明,DPSO算法可以减少迭代次数,并获得问题的最优解.
Pumping slots: impedances and power losses
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S. [Maryland Univ., College Park, MD (United States). Dept. of Physics
1996-08-01
Contributions of pumping slots to the beam coupling impedances and power losses in a B-factory ring are considered. While their leading contribution is to the inductive impedance, for high-intensity machines with short bunches like e{sup +}e{sup -} B-factories the real part of the impedance and related loss factors are also important. Using an analytical approach we calculate the coupling impedances and loss factors due to slots in a ring with an arbitrary cross section of the vacuum chamber. Effects of the slot tilt on the beam impedance are also considered, and restrictions on the tilt angle are derived from limitations on the impedance increase. The power leakage through the slots is discussed briefly. The results are applied to the KEK B-factory. (author)
Caetano, Tibério S; McAuley, Julian J; Cheng, Li; Le, Quoc V; Smola, Alex J
2009-06-01
As a fundamental problem in pattern recognition, graph matching has applications in a variety of fields, from computer vision to computational biology. In graph matching, patterns are modeled as graphs and pattern recognition amounts to finding a correspondence between the nodes of different graphs. Many formulations of this problem can be cast in general as a quadratic assignment problem, where a linear term in the objective function encodes node compatibility and a quadratic term encodes edge compatibility. The main research focus in this theme is about designing efficient algorithms for approximately solving the quadratic assignment problem, since it is NP-hard. In this paper we turn our attention to a different question: how to estimate compatibility functions such that the solution of the resulting graph matching problem best matches the expected solution that a human would manually provide. We present a method for learning graph matching: the training examples are pairs of graphs and the 'labels' are matches between them. Our experimental results reveal that learning can substantially improve the performance of standard graph matching algorithms. In particular, we find that simple linear assignment with such a learning scheme outperforms Graduated Assignment with bistochastic normalisation, a state-of-the-art quadratic assignment relaxation algorithm.
Jain, Anil K; Feng, Jianjiang
2011-01-01
Latent fingerprint identification is of critical importance to law enforcement agencies in identifying suspects: Latent fingerprints are inadvertent impressions left by fingers on surfaces of objects. While tremendous progress has been made in plain and rolled fingerprint matching, latent fingerprint matching continues to be a difficult problem. Poor quality of ridge impressions, small finger area, and large nonlinear distortion are the main difficulties in latent fingerprint matching compared to plain or rolled fingerprint matching. We propose a system for matching latent fingerprints found at crime scenes to rolled fingerprints enrolled in law enforcement databases. In addition to minutiae, we also use extended features, including singularity, ridge quality map, ridge flow map, ridge wavelength map, and skeleton. We tested our system by matching 258 latents in the NIST SD27 database against a background database of 29,257 rolled fingerprints obtained by combining the NIST SD4, SD14, and SD27 databases. The minutiae-based baseline rank-1 identification rate of 34.9 percent was improved to 74 percent when extended features were used. In order to evaluate the relative importance of each extended feature, these features were incrementally used in the order of their cost in marking by latent experts. The experimental results indicate that singularity, ridge quality map, and ridge flow map are the most effective features in improving the matching accuracy.
Optimal Packed String Matching
DEFF Research Database (Denmark)
Ben-Kiki, Oren; Bille, Philip; Breslauer, Dany
2011-01-01
In the packed string matching problem, each machine word accommodates – characters, thus an n-character text occupies n/– memory words. We extend the Crochemore-Perrin constantspace O(n)-time string matching algorithm to run in optimal O(n/–) time and even in real-time, achieving a factor – speedup...... over traditional algorithms that examine each character individually. Our solution can be efficiently implemented, unlike prior theoretical packed string matching work. We adapt the standard RAM model and only use its AC0 instructions (i.e., no multiplication) plus two specialized AC0 packed string...
Cartesian impedance control of dexterous robot hand
Institute of Scientific and Technical Information of China (English)
JIANG Li; LIU Hong; CAI He-gao
2005-01-01
Presents a novel compliant motion control for a robot hand using the Cartesian impedance approach based on fingertip force measurements. The fingertip can accurately track desired motion in free space and appear as mechanical impedance in constrained space. In the position based impedance control strategy, any switching mode in contact transition phase is not needed. The impedance parameters can be adjusted in a certain range according to various tasks. In this paper, the analysis of the finger's kinematics and dynamics is given. Experimental results have shown the effectiveness of this control strategy.
Infographic explaining NCI-COG Pediatric MATCH, a cancer treatment clinical trial for children and adolescents, from 1 to 21 years of age, that is testing the use of precision medicine for pediatric cancers.
Data Matching Imputation System
National Oceanic and Atmospheric Administration, Department of Commerce — The DMIS dataset is a flat file record of the matching of several data set collections. Primarily it consists of VTRs, dealer records, Observer data in conjunction...
Brooks, Martin; And Others
1983-01-01
The Cognitive Levels Matching Project trains teachers to guide students' skill acquisition and problem-solving processes by assessing students' cognitive levels and adapting their teaching materials accordingly. (MLF)
Impedance Spectroscopy of Human Blood
Mesa, Francisco; Bernal, José J.; Sosa, Modesto A.; Villagómez, Julio C.; Palomares, Pascual
2004-09-01
The blood is one of the corporal fluids more used with analytical purposes. When the blood is extracted, immediately it is affected by agents that act on it, producing transformations in its elements. Among the effects of these transformations the hemolysis phenomenon stands out, which consists of the membrane rupture and possible death of the red blood cells. The main purpose of this investigation was the quantification of this phenomenon. A Solartron SI-1260 Impedance Spectrometer was used, which covers a frequency range of work from 1 μHz to 10 MHz, and its accuracy has been tested in the accomplishment of several applications. Measurements were performed on 3 mL human blood samples, from healthy donors. Reactive strips for sugar test of 2 μL, from Bayer, were used as electrodes, which allow gathering a portion of the sample, to be analyzed by the spectrometer. Preliminary results of these measurements are presented.
Lorentz Force Electrical Impedance Tomography
Grasland-Mongrain, Pol; Chapelon, Jean-Yves; Lafon, Cyril
2014-01-01
This article describes a method called Lorentz Force Electrical Impedance Tomography. The electrical conductivity of biological tissues can be measured through their sonication in a magnetic field: the vibration of the tissues inside the field induces an electrical current by Lorentz force. This current, detected by electrodes placed around the sample, is proportional to the ultrasonic pressure, to the strength of the magnetic field and to the electrical conductivity gradient along the acoustic axis. By focusing at different places inside the sample, a map of the electrical conductivity gradient can be established. In this study experiments were conducted on a gelatin phantom and on a beef sample, successively placed in a 300 mT magnetic field and sonicated with an ultrasonic transducer focused at 21 cm emitting 500 kHz bursts. Although all interfaces are not visible, in this exploratory study a good correlation is observed between the electrical conductivity image and the ultrasonic image. This method offers...
Electrical impedance tomography of electrolysis.
Meir, Arie; Rubinsky, Boris
2015-01-01
The primary goal of this study is to explore the hypothesis that changes in pH during electrolysis can be detected with Electrical Impedance Tomography (EIT). The study has relevance to real time control of minimally invasive surgery with electrolytic ablation. To investigate the hypothesis, we compare EIT reconstructed images to optical images acquired using pH-sensitive dyes embedded in a physiological saline agar gel phantom treated with electrolysis. We further demonstrate the biological relevance of our work using a bacterial E.Coli model, grown on the phantom. The results demonstrate the ability of EIT to image pH changes in a physiological saline phantom and show that these changes correlate with cell death in the E.coli model. The results are promising, and invite further experimental explorations.
Electrical impedance tomography of electrolysis.
Directory of Open Access Journals (Sweden)
Arie Meir
Full Text Available The primary goal of this study is to explore the hypothesis that changes in pH during electrolysis can be detected with Electrical Impedance Tomography (EIT. The study has relevance to real time control of minimally invasive surgery with electrolytic ablation. To investigate the hypothesis, we compare EIT reconstructed images to optical images acquired using pH-sensitive dyes embedded in a physiological saline agar gel phantom treated with electrolysis. We further demonstrate the biological relevance of our work using a bacterial E.Coli model, grown on the phantom. The results demonstrate the ability of EIT to image pH changes in a physiological saline phantom and show that these changes correlate with cell death in the E.coli model. The results are promising, and invite further experimental explorations.
Architecture, modeling, and analysis of a plasma impedance probe
Jayaram, Magathi
Variations in ionospheric plasma density can cause large amplitude and phase changes in the radio waves passing through this region. Ionospheric weather can have detrimental effects on several communication systems, including radars, navigation systems such as the Global Positioning Sytem (GPS), and high-frequency communications. As a result, creating models of the ionospheric density is of paramount interest to scientists working in the field of satellite communication. Numerous empirical and theoretical models have been developed to study the upper atmosphere climatology and weather. Multiple measurements of plasma density over a region are of marked importance while creating these models. The lack of spatially distributed observations in the upper atmosphere is currently a major limitation in space weather research. A constellation of CubeSat platforms would be ideal to take such distributed measurements. The use of miniaturized instruments that can be accommodated on small satellites, such as CubeSats, would be key to achieving these science goals for space weather. The accepted instrumentation techniques for measuring the electron density are the Langmuir probes and the Plasma Impedance Probe (PIP). While Langmuir probes are able to provide higher resolution measurements of relative electron density, the Plasma Impedance Probes provide absolute electron density measurements irrespective of spacecraft charging. The central goal of this dissertation is to develop an integrated architecture for the PIP that will enable space weather research from CubeSat platforms. The proposed PIP chip integrates all of the major analog and mixed-signal components needed to perform swept-frequency impedance measurements. The design's primary innovation is the integration of matched Analog-to-Digital Converters (ADC) on a single chip for sampling the probes current and voltage signals. A Fast Fourier Transform (FFT) is performed by an off-chip Field-Programmable Gate Array (FPGA
Map Matching for Intelligent Speed Adaptation
DEFF Research Database (Denmark)
Tradisauskas, Nerius; Juhl, Jens; Lahrmann, Harry;
2007-01-01
The availability of Global Navigation Satellite Systems enables sophisticated vehicle guidance and advisory systems such as Intelligent Speed Adaptation (ISA) systems. In ISA systems, it is essential to be able to position vehicles within a road network. Because digital road networks as well as GPS...... positioning are often inaccurate, a technique known as map matching is needed that aims to use this inaccurate data for determining a vehicle's real road-network position. Then, knowing this position, an ISA system can compare the vehicle's speed with the speed limit in effect and react appropriately...
Power flow analysis for droop controlled LV hybrid AC-DC microgrids with virtual impedance
DEFF Research Database (Denmark)
Li, Chendan; Chaudhary, Sanjay; Vasquez, Juan Carlos
2014-01-01
The AC-DC hybrid microgrid is an effective form of utilizing different energy resources and the analysis of this system requires a proper power flow algorithm. This paper proposes a suitable power flow algorithm for LV hybrid AC-DC microgrid based on droop control and virtual impedance. Droop...... and virtual impedance concepts for AC network, DC network and interlinking converter are reviewed so as to model it in the power flow analysis. The validation of the algorithm is verified by comparing it with steady state results from detailed time domain simulation. The effectiveness of the proposed...
New OTRA-Based Generalized Impedance Simulator
Ashish Gupta; Raj Senani; Bhaskar, D. R.; Singh, A. K.
2013-01-01
Operational transresistance amplifier (OTRA) has attracted considerable attention in the recent literature in several applications such as impedance simulation, universal biquad filter realization, realization of sinusoidal oscillators and multivibrators. However, to the best knowledge of the authors, any OTRA-based generalized impedance simulator circuits have not been reported so far. The purpose of this paper is to present such a circuit.
Quantification of coating aging using impedance measurements
Westing, E.P.M. van; Weijde, D.H. van der; Vreijling, M.P.W.; Ferrari, G.M.; Wit, J.H.W. de
1998-01-01
This chapter shows the application results of a novel approach to quantify the ageing of organic coatings using impedance measurements. The ageing quantification is based on the typical impedance behaviour of barrier coatings in immersion. This immersion behaviour is used to determine the limiting c
Impedance of a slotted-pipe kicker
Energy Technology Data Exchange (ETDEWEB)
Feng Zhou [Academia Sinica, Beijing, BJ (China). Inst. of High Energy Physics
1996-08-01
This paper introduces the principle of a new slotted kicker simply, which is made by using vacuum pipe itself with proper slits as current conductors, and then, presents a rough estimation of its longitudinal and transverse impedance, respectively. Calculation shows that its impedance is reduced significantly compared to our present air-coil kicker. (author)
Possibilities of electrical impedance tomography in gynecology
V, Trokhanova O.; A, Chijova Y.; B, Okhapkin M.; V, Korjenevsky A.; S, Tuykin T.
2013-04-01
The paper describes results of comprehensive EIT diagnostics of mammary glands and cervix. The data were obtained from examinations of 170 patients by EIT system MEM (multi-frequency electrical impedance mammograph) and EIT system GIT (gynecological impedance tomograph). Mutual dependence is discussed.
Approaches for Stereo Matching
Directory of Open Access Journals (Sweden)
Takouhi Ozanian
1995-04-01
Full Text Available This review focuses on the last decade's development of the computational stereopsis for recovering three-dimensional information. The main components of the stereo analysis are exposed: image acquisition and camera modeling, feature selection, feature matching and disparity interpretation. A brief survey is given of the well known feature selection approaches and the estimation parameters for this selection are mentioned. The difficulties in identifying correspondent locations in the two images are explained. Methods as to how effectively to constrain the search for correct solution of the correspondence problem are discussed, as are strategies for the whole matching process. Reasons for the occurrence of matching errors are considered. Some recently proposed approaches, employing new ideas in the modeling of stereo matching in terms of energy minimization, are described. Acknowledging the importance of computation time for real-time applications, special attention is paid to parallelism as a way to achieve the required level of performance. The development of trinocular stereo analysis as an alternative to the conventional binocular one, is described. Finally a classification based on the test images for verification of the stereo matching algorithms, is supplied.
Impedance Spectroscopy of Dielectrics and Electronic Conductors
DEFF Research Database (Denmark)
Bonanos, Nikolaos; Pissis, Polycarpos; Macdonald, J. Ross
2013-01-01
Impedance spectroscopy is used for the characterization of materials, such as electroceramics, solid and liquid electrochemical cells, dielectrics and also fully integrated devices, such as fuel cells. It consists of measuring the electrical impedance - or a closely related property, such as admi......Impedance spectroscopy is used for the characterization of materials, such as electroceramics, solid and liquid electrochemical cells, dielectrics and also fully integrated devices, such as fuel cells. It consists of measuring the electrical impedance - or a closely related property......, and procedures for the correction of measurement errors. The applications of impedance spectroscopy are illustrated with examples from electroceramics and polymer-based dielectric systems. The way in which the technique is applied to the two classes of materials is compared with reference to the different models...
Update of the SPS Impedance Model
Salvant, B; Zannini, C; Arduini, G; Berrig, O; Caspers, F; Grudiev, A; Métral, E; Rumolo, G; Shaposhnikova, E; Zotter, B; Migliorati, M; Spataro, B
2010-01-01
The beam coupling impedance of the CERN SPS is expected to be one of the limitations to an intensity upgrade of the LHC complex. In order to be able to reduce the SPS impedance, its main contributors need to be identified. An impedance model for the SPS has been gathered from theoretical calculations, electromagnetic simulations and bench measurements of single SPS elements. The current model accounts for the longitudinal and transverse impedance of the kickers, the horizontal and vertical electrostatic beam position monitors, the RF cavities and the 6.7 km beam pipe. In order to assess the validity of this model, macroparticle simulations of a bunch interacting with this updated SPS impedance model are compared to measurements performed with the SPS beam.
Impedance-Based High Frequency Resonance Analysis of DFIG System in Weak Grids
DEFF Research Database (Denmark)
Song, Yipeng; Wang, Xiongfei; Blaabjerg, Frede
2017-01-01
The impedance-based model of Doubly Fed Induction Generator (DFIG) systems, including the rotor part (Rotor Side Converter (RSC) and induction machine), and the grid part (Grid Side Converter (GSC) and its output filter), has been developed for analysis and mitigation of the Sub- Synchronous...... Resonance (SSR). However, the High Frequency Resonance (HFR) of DFIG systems due to the impedance interaction between DFIG system and parallel compensated weak network is often overlooked. This paper thus investigates the impedance characteristics of DFIG systems for the analysis of HFR. The influences...... of the rotor speed variation, the machine mutual inductance and the digital control delay are evaluated. Two resonances phenomena are revealed, i.e., 1) the series HFR between the DFIG system and weak power grid; 2) the parallel HFR between the rotor part and the grid part of DFIG system. The impedance...
Note: Characterization and test of a high input impedance RF amplifier for series nanowire detector
Wan, Chao; Pei, Yufeng; Jiang, Zhou; Kang, Lin; Wu, Peiheng
2016-09-01
We designed a high input impedance RF amplifier based on Tower Jazz's 0.18 μm SiGe BiCMOS process for series nanowire detector. The characterization of its gain and input impedance with a vector network analyzer is described in detail for its specificity. The actual 15 dB gain should be the measured value subtracts 6 dB, which is easy to be ignored. Its input impedance can be equivalent to 6.7 kΩ ∥ 3.4 pF though fitting the measurement, whose accuracy is verified. The process of measurement provides a good reference to characterize the similar special amplifier with unmatched impedance.
Matrix solution for the wall impedance of infinitely long multilayer circular beam tubes
Directory of Open Access Journals (Sweden)
H. Hahn
2010-01-01
Full Text Available The coupling impedance of beam tubes is a long-standing important topic for particle accelerators that many authors have addressed. The present study was initiated in view of a specific problem, but its novel approach is broadly applicable to the longitudinal and transverse coupling impedances of coated beam tubes or multilayer tubes. The matrix method presented here derives the wall impedance by treating the radial wave propagation of the beam-excited electromagnetic fields in full analogy to longitudinal transmission lines. Starting from the Maxwell equations, the radially transverse magnetic field components are described for monopole and dipole modes by a 2×2 matrix. Assuming isotropic material properties within one layer, the transverse field components at the inner boundary of a layer uniquely are determined by matrix transfer of the field components at its outer boundary. By imposing power-flow constraints on the matrix, wave impedance mapping and field matching between layers is enforced and replaced by matrix multiplication. The longitudinal and transverse coupling impedances are derived from the wall impedance at the innermost boundary, and the different procedures for its determination are discussed. The matrix method is demonstrated via selected yet representative examples of the well-documented cases of a stainless-steel tube, and of a graphite collimator.
Institute of Scientific and Technical Information of China (English)
逄德明; 胡罡; 徐明
2011-01-01
频谱感知是无线认知网络有效工作的基础,现有研究主要集中在提高频谱检测的效率,对于如何保证在不可信的网络环境中实现安全可靠的频谱感知还没有理想的解决方案.针对频谱感知过程中存在的一种典型攻击行为一仿冒主用户攻击,提出了一种基于能量指纹匹配的检测方案.认知用户利用自身的位置分布特征,使用能量检测生成主用户的能量指纹,以此作为节点的身份标识,分析不同用户对频谱资源的使用方式,最终实现对仿冒行为的检测.理论分析以及模拟测试表明,该方案在误检概率较低的前提下,可以有效地检测仿冒攻击行为,提高频谱感知的准确率.%Spectrum sensing is an essential mechanism in cognitive radio networks. While so many works have been done or being carried on upon improving the efficiency of the sensing process,there is no appropriate scheme to realize security sensing in untrustworthy environments. We proposed a mechanism based on Energy Fingerprint(EF) matching to address a typical attack in CR networks,the Primary User Emulation Attack(PUEA). Based on the distribution of their positions and through energy detection,the secondary users can create PU's EF which is used as an identification of node to analyze the spectrum accessing mode of different users,and finally detect the PUEA. Through analysis and simulation, it can be demonstrated that while keeping the probability of missing the return of the primary low,it is possible to detect the emulation attack effectively.
Design of Matched Absorbing Layers for Surface Plasmon-Polaritons
Directory of Open Access Journals (Sweden)
Sergio de la Cruz
2012-01-01
Full Text Available We describe a procedure for designing metal-metal boundaries for the strong attenuation of surface plasmon-polaritons without the introduction of reflections or scattering effects. Solutions associated with different sets of matching materials are found. To illustrate the results and the consequences of adopting different solutions, we present calculations based on an integral equation formulation for the scattering problem and the use of a nonlocal impedance boundary condition.
Non-foster matching of an RFID antenna
Mohamed Hassan Salem, Nedime Pelin
2011-07-01
Novel designs of radio-frequency identification (RFID) tag antennas with better matching characteristics to achieve extended range for passive tags are investigated in ultra-high frequency (UHF) band. A microstrip dipole antenna with or without an integrated negative impedance converter designed to cancel out the antenna\\'s input capacitance at resonance frequency was designed, simulated, constructed and measured for implementation in RFID applications. © 2011 IEEE.
Matching of Energy Provisions in Multihop Wireless Infra-Structures
Directory of Open Access Journals (Sweden)
Rui Teng
2016-01-01
Full Text Available Recently there have been large advances in energy technologies for battery-operated systems, including green energy resources and high capacity batteries. The effective use of battery energy resources in wireless infrastructure networks to improve the versatility and reliability of wireless communications is an important issue. Emerging applications of smart cities, Internet of Things (IoT, and emergency responses highly rely on the basic communication network infrastructures that enable ubiquitous network connections. However, energy consumption by nodes in a wireless infrastructure network depends on the transmissions of other nodes in the network. Considering this inter-dependence is necessary to achieve efficient provision of energy in wireless networks. This paper studies the issue of energy provision for wireless relay nodes in Wireless Multihop Infrastructures (WMI assuming constraints on the total energy provision. We introduce a scheme of Energy Provision Matching (Matching-EP for WMI which optimizes energy provision based on matching of energy provision with estimates of differentiated position-dependent energy consumption by wireless nodes distributed in the network. The evaluation results show that Matching-EP with 4%–34% improvement in energy matching degree enables 10%–40% improvement of the network lifetime, and 5%–40% improvement of packet delivery compared with conventional WMI networks.
Bellahsene, Zohra; Rahm, Erhard
2011-01-01
Requiring heterogeneous information systems to cooperate and communicate has now become crucial, especially in application areas like e-business, Web-based mash-ups and the life sciences. Such cooperating systems have to automatically and efficiently match, exchange, transform and integrate large data sets from different sources and of different structure in order to enable seamless data exchange and transformation. The book edited by Bellahsene, Bonifati and Rahm provides an overview of the ways in which the schema and ontology matching and mapping tools have addressed the above requirements
DEFF Research Database (Denmark)
Hartelius, Karsten; Carstensen, Jens Michael
2003-01-01
A method for locating distorted grid structures in images is presented. The method is based on the theories of template matching and Bayesian image restoration. The grid is modeled as a deformable template. Prior knowledge of the grid is described through a Markov random field (MRF) model which...... nodes and the arc prior models variations in row and column spacing across the grid. Grid matching is done by placing an initial rough grid over the image and applying an ensemble annealing scheme to maximize the posterior distribution of the grid. The method can be applied to noisy images with missing...
Middle matching mining algorithm
Institute of Scientific and Technical Information of China (English)
GUO Ping; CHEN Li
2003-01-01
A new algorithm for fast discovery of sequential patterns to solve the problems of too many candidate sets made by SPADE is presented, which is referred to as middle matching algorithm. Experiments on a large customer transaction database consisting of customer_id, transaction time, and transaction items demonstrate that the proposed algorithm performs better than SPADE attributed to its philosophy to generate a candidate set by matching two sequences in the middle place so as to reduce the number of the candidate sets.
Impedance adaptation methods of the piezoelectric energy harvesting
Kim, Hyeoungwoo
In this study, the important issues of energy recovery were addressed and a comprehensive investigation was performed on harvesting electrical power from an ambient mechanical vibration source. Also discussed are the impedance matching methods used to increase the efficiency of energy transfer from the environment to the application. Initially, the mechanical impedance matching method was investigated to increase mechanical energy transferred to the transducer from the environment. This was done by reducing the mechanical impedance such as damping factor and energy reflection ratio. The vibration source and the transducer were modeled by a two-degree-of-freedom dynamic system with mass, spring constant, and damper. The transmissibility employed to show how much mechanical energy that was transferred in this system was affected by the damping ratio and the stiffness of elastic materials. The mechanical impedance of the system was described by electrical system using analogy between the two systems in order to simply the total mechanical impedance. Secondly, the transduction rate of mechanical energy to electrical energy was improved by using a PZT material which has a high figure of merit and a high electromechanical coupling factor for electrical power generation, and a piezoelectric transducer which has a high transduction rate was designed and fabricated. The high g material (g33 = 40 [10-3Vm/N]) was developed to improve the figure of merit of the PZT ceramics. The cymbal composite transducer has been found as a promising structure for piezoelectric energy harvesting under high force at cyclic conditions (10--200 Hz), because it has almost 40 times higher effective strain coefficient than PZT ceramics. The endcap of cymbal also enhances the endurance of the ceramic to sustain ac load along with stress amplification. In addition, a macro fiber composite (MFC) was employed as a strain component because of its flexibility and the high electromechanical coupling
Adaptive Matching of the Scanning Aperture of the Environment Parameter
Choni, Yu. I.; Yunusov, N. N.
2016-04-01
We analyze a matching system for the scanning aperture antenna radiating through a layer with unpredictably changing parameters. Improved matching has been achieved by adaptive motion of a dielectric plate in the gap between the aperture and the radome. The system is described within the framework of an infinite layered structure. The validity of the model has been confirmed by numerical simulation using CST Microwave Studio software and by an experiment. It is shown that the reflection coefficient at the input of some types of a matching device, which is due to the deviation of the load impedance from the nominal value, is determined by a compact and versatile formula. The potential efficiency of the proposed matching system is shown by a specific example, and its dependence on the choice of the starting position of the dielectric plate is demonstrated.
A review on compressed pattern matching
Directory of Open Access Journals (Sweden)
Surya Prakash Mishra
2016-09-01
Full Text Available Compressed pattern matching (CPM refers to the task of locating all the occurrences of a pattern (or set of patterns inside the body of compressed text. In this type of matching, pattern may or may not be compressed. CPM is very useful in handling large volume of data especially over the network. It has many applications in computational biology, where it is useful in finding similar trends in DNA sequences; intrusion detection over the networks, big data analytics etc. Various solutions have been provided by researchers where pattern is matched directly over the uncompressed text. Such solution requires lot of space and consumes lot of time when handling the big data. Various researchers have proposed the efficient solutions for compression but very few exist for pattern matching over the compressed text. Considering the future trend where data size is increasing exponentially day-by-day, CPM has become a desirable task. This paper presents a critical review on the recent techniques on the compressed pattern matching. The covered techniques includes: Word based Huffman codes, Word Based Tagged Codes; Wavelet Tree Based Indexing. We have presented a comparative analysis of all the techniques mentioned above and highlighted their advantages and disadvantages.
Zhou, Feng; de la Torre, Fernando
2015-11-19
Graph matching (GM) is a fundamental problem in computer science, and it plays a central role to solve correspondence problems in computer vision. GM problems that incorporate pairwise constraints can be formulated as a quadratic assignment problem (QAP). Although widely used, solving the correspondence problem through GM has two main limitations: (1) the QAP is NP-hard and difficult to approximate; (2) GM algorithms do not incorporate geometric constraints between nodes that are natural in computer vision problems. To address aforementioned problems, this paper proposes factorized graph matching (FGM). FGM factorizes the large pairwise affinity matrix into smaller matrices that encode the local structure of each graph and the pairwise affinity between edges. Four are the benefits that follow from this factorization: (1) There is no need to compute the costly (in space and time) pairwise affinity matrix; (2) The factorization allows the use of a path-following optimization algorithm, that leads to improved optimization strategies and matching performance; (3) Given the factorization, it becomes straight-forward to incorporate geometric transformations (rigid and non-rigid) to the GM problem. (4) Using a matrix formulation for the GM problem and the factorization, it is easy to reveal commonalities and differences between different GM methods. The factorization also provides a clean connection with other matching algorithms such as iterative closest point; Experimental results on synthetic and real databases illustrate how FGM outperforms state-of-the-art algorithms for GM. The code is available at http://humansensing.cs.cmu.edu/fgm.
Institute of Scientific and Technical Information of China (English)
彭硕
2002-01-01
It was a Saturday morning, our school football team was going to have a match with the No. 28 Middle Schooh They were really a strong team. But we weren't afraid of them. We had many mare good players on our team, so we were stronger than ever before.
Herrnstein, R. J.
1979-01-01
The matching law for reinforced behavior solves a differential equation relating infinitesimal changes in behavior to infinitesimal changes in reinforcement. The equation expresses plausible conceptions of behavior and reinforcement, yields a simple nonlinear operator model for acquisition, and suggests a alternative to the economic law of…
Claesson, Anders
2010-01-01
We show that there are n! matchings on 2n points without, so called, left (neighbor) nestings. We also define a set of naturally labeled (2+2)-free posets, and show that there are n! such posets on n elements. Our work was inspired by Bousquet-M\\'elou, Claesson, Dukes and Kitaev [arXiv:0806.0666]. They gave bijections between four classes of combinatorial objects: matchings with no neighbor nestings (due to Stoimenow), unlabeled (2+2)-free posets, permutations avoiding a specific pattern, and so called ascent sequences. We believe that certain statistics on our matchings and posets could generalize the work of Bousquet-M\\'elou et al.\\ and we make a conjecture to that effect. We also identify natural subsets of matchings and posets that are equinumerous to the class of unlabeled (2+2)-free posets. We give bijections that show the equivalence of (neighbor) restrictions on nesting arcs with (neighbor) restrictions on crossing arcs. These bijections are thought to be of independent interest. One of the bijections...
'Wiggle matching' radiocarbon dates
Ramsey, CB; van der Plicht, J; Weninger, B
2001-01-01
This paper covers three different methods of matching radiocarbon dates to the 'wiggles' of the calibration curve in those situations where the age difference between the C-14 dates is known. These methods are most often applied to tree-ring sequences. The simplest approach is to use a classical Chi
Jeuring, J.T.
2007-01-01
The pattern matching problem can be informally specified as follows: given a pattern and a text, find all occurrences of the pattern in the text. The pattern and the text may both be lists, or they may both be trees, or they may both be multi-dimensional arrays, etc. This paper describes a general p
Rotor damage detection by using piezoelectric impedance
Qin, Y.; Tao, Y.; Mao, Y. F.
2016-04-01
Rotor is a core component of rotary machinery. Once the rotor has the damage, it may lead to a major accident. Thus the quantitative rotor damage detection method based on piezoelectric impedance is studied in this paper. With the governing equation of piezoelectric transducer (PZT) in a cylindrical coordinate, the displacement along the radius direction is derived. The charge of PZT is calculated by the electric displacement. Then, by the use of the obtained displacement and charge, an analytic piezoelectric impedance model of the rotor is built. Given the circular boundary condition of a rotor, annular elements are used as the analyzed objects and spectral element method is used to set up the damage detection model. The Electro-Mechanical (E/M) coupled impedance expression of an undamaged rotor is deduced with the application of a low-cost impedance test circuit. A Taylor expansion method is used to obtain the approximate E/M coupled impedance expression for the damaged rotor. After obtaining the difference between the undamaged and damaged rotor impedance, a rotor damage detection method is proposed. This method can directly calculate the change of bending stiffness of the structural elements, it follows that the rotor damage can be effectively detected. Finally, a preset damage configuration is used for the numerical simulation. The result shows that the quantitative damage detection algorithm based on spectral element method and piezoelectric impedance proposed in this paper can identify the location and the severity of the damaged rotor accurately.
Tracking of electrochemical impedance of batteries
Piret, H.; Granjon, P.; Guillet, N.; Cattin, V.
2016-04-01
This paper presents an evolutionary battery impedance estimation method, which can be easily embedded in vehicles or nomad devices. The proposed method not only allows an accurate frequency impedance estimation, but also a tracking of its temporal evolution contrary to classical electrochemical impedance spectroscopy methods. Taking into account constraints of cost and complexity, we propose to use the existing electronics of current control to perform a frequency evolutionary estimation of the electrochemical impedance. The developed method uses a simple wideband input signal, and relies on a recursive local average of Fourier transforms. The averaging is controlled by a single parameter, managing a trade-off between tracking and estimation performance. This normalized parameter allows to correctly adapt the behavior of the proposed estimator to the variations of the impedance. The advantage of the proposed method is twofold: the method is easy to embed into a simple electronic circuit, and the battery impedance estimator is evolutionary. The ability of the method to monitor the impedance over time is demonstrated on a simulator, and on a real Lithium ion battery, on which a repeatability study is carried out. The experiments reveal good tracking results, and estimation performance as accurate as the usual laboratory approaches.