碳纳米颗粒悬浮液光限幅性能理论分析和数值模拟

碳纳米颗粒悬浮液作为一种宽带光限幅材料,在光限幅领域有很好的应用前景。为提高碳纳米颗粒悬浮液的光限幅性能,研究了其光限幅机理。基于等效球的米氏散射理论和介质的激光传输理论,在忽略多重散射情况下建立了碳纳米颗粒悬浮液散射系数和透过率理论模型。采用Matlab数值模拟了微气泡膨胀过程中微气泡的散射、消光和吸收效率因子的变化情况和散射光强随着散射角的变化规律,并研究了微气泡尺寸和悬浮液浓度对碳纳米颗粒悬浮液光散射的影响,样品厚度和悬浮液浓度对光限幅特性的影响。研究发现微气泡尺寸的增加可以显著增大散射系数,微气泡尺寸是影响碳纳米颗粒悬浮液光限幅性能的关键因素,研究结果为实验研究提供了理论指导。     

色散平坦光子晶体光纤中实现光波变换的研究

基于四波混频(FWM)效应,在色散平坦光于品体光纤(PCF)中实现了全光波长变换.采用长度为30 m、具有小的反常色散值的高非线性色散平坦PCF对10 Gbit/s的信号进行了波长变换,当平均泵浦功率为26dBm时,在20 nm转换带宽内得到了-19.5 dB的转换效率;用具有小的正常色散值的高非线性色散平坦PCF替代原光纤,进行了实验与理论比较.研究结果表明:利用两种不同的光纤得到了儿乎相同的转换效率和转换带宽.     

Power module stray inductance extraction: Theoretical and experimental analysis

We propose a stray inductance extraction method on power modules of the few-kilovolts/several-hundred-amperes class using only low voltages and low currents. The method incorporates a double-pulse generator, a level shifter, a switching device, and a load inductor. The conventional approach generally requires a high voltage of more than half the power module's rated voltage and a high current of around half the rated current. In contrast, the proposed method requires a low voltage and low current environment regardless of the power module's rated voltage because the module is measured in a turn-off state. Both theoretical and experimental results are provided. A physical circuit board was fabricated, and the method was applied to three commercial power modules with EconoDUAL3 cases. The obtained stray inductance values differed from the manufacturer-provided values by less than 1.65 nH, thus demonstrating the method's accuracy. The greatest advantage of the proposed approach is that high voltages or high currents are not required.     

Theoretical and experimental analysis of wire segment holograms forstatistical interconnect metrology

Theoretical and experimental results using computer generated wire segment holograms for statistical interconnect metrology are presented. Test structures have been constructed using a process capable of imaging 1-μm features and consist of arrays of wire segments illuminated by a He-Ne Laser. Since the holograms are fabricated at the same time as actual wires on the wafer, the quality of the projected image correlates with the emergence of global feature patterning errors. Specifically, this paper presents data on the effect of varied exposure time on the intensity of the projected image. An initial statistical analysis indicates that the test structures are capable of detecting variations in wire geometry which are approximately 1.0% of the nominal wire width. It is anticipated that significant improvements to this level of sensitivity can be obtained by optimization of the holographic encoding process and test image selection     

半导体激光器实现波长转换的理论和实验分析

作为自动交换光网络中的核心器件,全光波长转换器在网络中发挥着重要作用。建立了半导体激光器实现波长转换的理论模型,利用速率方程,数值求解了半导体激光器进行波长转换的特性;自行搭建了一套利用光纤光栅外腔半导体激光器进行全光波长转换的实验平台,并对实验结果进行了研究。发现试验结果和理论分析结果是相当吻合的。分析表明,降低光子寿命,优化外腔结构将是该器件在未来智能光网中实用的关键。     

LD泵浦准三能级系统的理论分析及实验优化设计

从速率方程的理论出发 ,推导出了LD端泵准三能级系统的输出功率及斜效率的表达式 ,讨论了泵浦光及振荡光的空间分布变量及晶体长度和透射率对输出功率的影响 ,由此可得到在一定条件下的实验优化设计方案。     

Theoretical and experimental analysis of air cooling forintracavitary microwave hyperthermia applicators

An intracavitary microwave antenna array system has been developed and tested for the hyperthermia treatment of prostate cancer at Thayer School of Engineering and Dartmouth-Witchcock Medical Center. The antenna array consists of a choked dipole antenna inserted into the urethra and a choked dipole antenna eccentrically embedded in a Teflon obturator inserted into the rectum. To prevent unnecessary heating of the healthy tissue that surrounds each applicator, an air cooling system has been incorporated into the rectal applicator. The air cooling system was designed and modeled theoretically using a numerical solution of heat and momentum equations within the applicator, and an analytical solution of the Pennes bioheat equation in tissue surrounding the applicator. The 3D temperature distribution produced by the air-cooled rectal applicator was measured in a perfused canine prostate     

Theoretical and experimental analysis of influence of phase-to-intensity noise conversion in interferometric systems

The noise power spectral density in interferometric systems was studied theoretically and experimentally. The influence of 1/f frequency modulation noise, white noise, and source dispersion are shown in the conversion of phase noise into intensity noise. The direct relative intensity noise (RIN) is compared with the RIN caused by phase-to-intensity noise conversion, and the root mean square of equivalent interferometer phase error was studied. The influence of the interferometer operating point is shown on the noise power spectrum. The results can be employed to estimate the influence of the these effects in phase-to-intensity noise conversion in radio-frequency-modulated optical links, which use either self-delayed interferences or interferometers. These results can be applied to optical signal processing, radar signal processing, etc., which often use interferometers.     

Theoretical and experimental analysis of a pel-recursive Wiener-based motion estimation algorithm

This paper analyses a pel-recursive Wiener-based motion estimation algorithm. An accurate estimation approach and then some methods for calculating the parameters of the estimation algorithm are derived. A theoretical convergence analysis is also performed. Some simulation results are presented that show the convergence abilities of the proposed algorithms.     

Theoretical and experimental analysis of right ventricular bypassand univentricular circulatory support

In this paper we examine the dynamic coupling between cardiac pump events and vascular arterial-venous factors that regulate the rate of blood flow around the circulation. A series of experiments were designed to test the feasibility of maintaining vascular and pulmonary function in the absence of the right heart and to characterize the physiologic and hemodynamic consequence of such an exclusion. Theoretical analysis of the cardiovascular system (excluding neuro-humoral factors) using both lumped time invariant and distributed compartmental mathematical equivalent representations, demonstrated that a change in cardiac output (Q) has an inverse-linear effect on venous and direct-linear effect on arterial pressure. A single blood-pump, in a form of a mechanical substitute or the biologic left-heart, alone can support the circulation. Cardiac output reserve is limited (50 percent of normal) because of the rapidly diminishing pulmonary venous-pressure as outflow is increased, irrespective of the pump's specific characteristics. Experiments in animals combined with mock-circulatory studies and computer modeling confirm that near normal flow can be sustained by increasing the stressed blood volume or reducing selectively the systemic venous compliance (i.e., inflatable pressure suit, venous constriction, intra-abdominal compression maneuvers, etc.). The right heart is not essential for normal pulmonary circulation but serves to maintain low systemic venous pressure and relatively high left-heart flow reserve. Purely mechanical properties of the vascular system determine the control and stability of the circulation.     

Theoretical and experimental analysis of clipping-induced impulsivenoise in AM-VSB subcarrier multiplexed lightwave systems

A new theoretical and experimental analysis of clipping-induced impulsive noise in directly modulated AM-VSB/digital hybrid lightwave systems is presented. The theoretical model is based on asymptotic clipping and shot noise theories, and the probability density of combined Gaussian and impulsive noise is obtained by performing a numerical inverse Fourier transform on the closed-form characteristic function. Similar analyzes in previously published work have resulted in closed-form expressions for the BER in hybrid AM-VSB/QAM systems, but these models, which do not use the numerical inverse Fourier transform, have either required the use of an experimentally measured clipping rate using a spectrum analyzer or have had limited BER prediction accuracy. Application of our theory to experimental results for the BER in a hybrid AM-VSB/64 QAM system demonstrates that the performance of the model if better than the models of previously published works. Theoretical analysis of a similar hybrid system employing the N-VSB HDTV digital modulation format rather than QAM indicates that an improvement in BER is achieved if 8-VSB at double the symbol rate is used instead of 64 QAM. We also present the first experimental characterization of the amplitude and time distribution of (1) low-frequency bandpass and (2) down-converted impulsive noise and we show that the time interval between clipping events has a high probability of being 167 μs, 1.5 μs, or 4 ms in an NTSC system with unmodulated carriers. These results have potential impact on forward error correcting codes used to ameliorate the degrading effects of clipping     

Theoretical and experimental study of the analysis and modeling ofintegrated optical components

Using a mode-matching technique, a modular microwave equivalent circuit incorporating both guided and continuum spectra has been developed to model open guided-wave integrated optical components accurately with limited computational effort. The accuracy of the analysis is verified by comparison with other methods of analysis, and by experiments performed on GaAs homojunction rib waveguides, directional couplers, and three-guide couplers. The limitations of approximate theories for the analysis of coupled structures are also identified     

单级磁压缩网络理论分析与实验研究

脉冲电源具有广泛的应用价值,而磁压缩技术是脉冲电源的关键技术.本文分析了单级磁压缩电路的结构和工作原理,设计并搭建了一种单级磁压缩电路,对其进行了仿真分析与实验研究,仿真结果和实验结果具有很好的一致性.实验结果表明,所设计的磁压缩电路可有效陡化电流波形.     

基于线性插值的RF-导频插入DDO-OFDM系统的仿真分析与实验验证

RF-导频（RF-pilot）插入的直接探测光正交频分复用（DDO-OFDM）系统通过调节载信比（CSPR）可以有效对系统传输性能进行优化,是高速短距离局域网传输的备选方案之一。在该系统下,利用导频子载波处信道估计结果,提出一种基于线性插值与时域平均的信道估计方法,用于实现非导频子载波处信道响应的估计。本文方法可以实时跟踪信道变化,有效抑制噪声影响。仿真中,13个导频子载波用于信道估计,采用线性插值与时域平均的方法估计出非导频子载波处的信道响应,传输4-QAM映射的20 Gbit/s信号在光纤中传输400 km。与背靠背相比,在误码率（EBR）为1×10^-3时,几乎没有光信噪比（OSNR）损伤。通过原理验证性实验,验证了本文方法在RF-pilot插入DDO-OFDM系统中用于信道估计的可行性。     

基于等离子体镜的太赫兹单脉冲选择方法

研究了一种用于中国工程物理研究院太赫兹自由电子激光装置(CTFEL)输出的太赫兹的单脉冲选择方法,以满足一些对太赫兹脉冲的时间分辨率和峰值强度提出较高要求同时要保证较低平均功率的实验的需要。利用自诱导等离子体开关技术,太赫兹能够被短脉冲激光打靶产生的等离子体镜反射,从而使等离子体镜可以作为门控开关,选出单个太赫兹微脉冲。通过理论分析计算出等离子体临界密度和激光功率密度阈值,采用辐射流体模拟软件对激光打靶过程进行数值模拟。模拟结果表明,激光激发出的等离子体密度远大于临界密度。由此证明了实验的可行性,进而给出实验所需装置的参数指标以及实验光路设计。     

Theoretical and experimental analysis of a—Si:H logic circuits

Expressions of the static behavior of a-Si-H TFT's previously established in our laboratory are used in order to calculate the theoretical transfer characteristics of enhanced/enhanced (E/E) inverters. These characteristics are shown to be strongly influenced by the parameters of the band-tail distribution of localized states (especially its critical temperature Tc), and consequently by the quality of the semiconductor thin film. Several experimental results are presented to confirm the obtained expressions.     

Theoretical and experimental analysis of leakage current in InGaAsPBH lasers with p-n-p-n current blocking layers

The dependence of the leakage current in 1.3-μm InGaAsP buried heterostructure (BH) lasers with p-n-p-n current blocking layers on well number, mesa width, and carrier density has been analyzed using a two-dimensional device simulator and compared with the electroluminescence (EL) emitted from InP layers. The analysis of the minority carrier flow reveals that the electron current flowing through the p-n-p-n current blocking layers is the dominant component of the leakage current. The measured EL intensity has two peaks at both sides of the n-blocking layer apart from the active layer. The EL intensity decreases with increasing well number and carrier density of the p-blocking layer, and increases with increasing mesa width. These results are consistent with the simulations     

Theoretical and experimental analysis of waveguide containing transversally magnetized strongly gyrotropic dissipative semiconductor layer

In this paper we present the Maxwell equations' solution method enabling to electrodynamically rigorously compute opened and screened waveguides containing transversally magnetized gyrotropic material. There have been theoretically and experimentally analysed a rectangular metal waveguide having along the narrow wall a gyrotropic dissipative layer ofn-InSb. There has been found the resonant waveguide losses' dependence on the magnitude of the biasing magnetic field. The correspondence of computed and experimental data is fairly good.     

Theoretical and experimental study of transverse-horizontal convolver

The letter presents the results of theoretical and experimental studies for the transverse-horizontal convolver (THC) fabricated on LiNbO3. First, the definition of the figure of merit for the THC is proposed and, secondly, the existence of the crystal orientation and the direction of propagation with high efficiency and large electromechanical coupling coefficient for an LiNbO3 SAW THC is shown.     

Theoretical and experimental analysis of a venting clip to reduce stray inductance in high-power conversion applications

In this study, we present a venting clip for high-power applications that is intended to reduce stray inductance. To reduce the stray inductance of packages in high-power applications, the proposed venting clip features slots are inserted onto a conventional clip. A conventional clip and the proposed venting clip were designed and fabricated to compare the respective stray inductance. The inductance of the proposed venting clip was approximately 15.8% than that of the conventional clip at a frequency of 100 kHz. Through a comparison between the conventional and venting clips, it is confirmed that the proposed venting clip is superior for high-power applications in terms of decreasing inductance. With reduced inductance, the switching-loss for such applications is also expected to decrease. Moreover, the impedance of the venting clip decreased by approximately 15.5% compared with that of the conventional clip at a frequency of 100 kHz. The venting clip, which has reduced resistive component, is also expected to decrease conduction loss in high-power applications.