Effect of height on power density in spiral-wound power-pot-coretransformers

The effect of height on power density in spiral-wound power-pot-core transformers is examined for the practical range of power, frequency, loss, and volt-per-turn. Relevant mechanical and electrical equations are derived and applied to an optimization algorithm that searches for the design that maximizes the power density at a given height. It has been found that the curves of power density versus height exhibit a peak (on the order of 1000 W/in³ in several cases) at a critical height between 0.25 and 0.3 in. Below this critical height, the power density decreases drastically     

直流偏置下高频磁性材料铁芯损耗的研究

对具有直流偏置、正弦电压激磁的功率铁氧体铁芯损耗进行有效测量的基础上,分析了直流偏置对铁氧体材料的性能的影响和磁损与交直流磁感应强度的关系,在一定的交流激磁范围内,为磁性元件的设计提供了一定的参考。     

Low-loss fusion splices of optical fibers

A low-loss splicing method, based on discharge fusion of optical fibers by a simple apparatus and by applying pressure between fibers before fusion, was developed. Average splice losses of about 0.07 and 0.15 dB for single-mode (SM) fibers having core diameters of 10 and 7μm, respectively, and 0.02 dB for 50-μm core diameter graded-index (GI) fibers are obtained. Fusion loss and fusion time are obtained minimum for better end preparation having low initial alignment losses at critical pressure and temperature. Mathematical expressions for the variation of fusion time and splice loss with effect of applied pressure between the fibers, for different practical axis alignment, showing the optimum condition to have minimum splice loss are made. Experimental fusion losses are analyzed in terms of residual misalignment of off axis, angular tilt of the fibers during aligning, and air gaps in the splicing zone. Optimum fusion time is obtained by considering the forces due to applied pressure, thermal expansion, and surface tension in the viscous melted glass of the fiber. Theoretical curves of fusion times and splicing losses versus applied pressure agree with the experimental results. The decrease of fusion time to about 1.3 times and splice loss to about two times were found when applied pressure is varried from low to its critical value of 20-25 g. The splice losses are found at a minimum for the operating temperature range of 1980°C to 2140°C for silica fibers. Experimental results of the histogram of bar chart of splice losses agree with the derived mathematical expressions assuming a statistical distribution function of splice losses.     

Temperature dependence of optical gain, quantum efficiency, andthreshold current in GaAs/GaAlAs graded-index separate-confinementheterostructure single-quantum-well lasers

The temperature dependence of the optical gain in graded-index separate-confinement heterostructure single-quantum-well lasers with different quantum-well widths were investigated. The observed dependence of the kink temperature on cavity loss and quantum-well width and the differential quantum efficiency minimum at the kink temperature were analyzed in terms of the temperature variation of the gain spectra and peak gain curves. Dependences of the characteristic temperature T ₀ on the quantum-well width, cavity loss, and temperature range are discussed in terms of the variation of the peak modal gain versus current relation with temperature and quantum-well width     

Properties of the PbSe diode laser

Diode laser action has been obtained at 8.5μ with PbSe. This laser is of potential interest for terrestrial communications since its emission is in the 8-to-14-μ atmospheric window, a spectral region of high atmospheric transparency where attenuation due to scattering by haze is low. Fabrication techniques are described which are based on controlling carrier type and concentration by adjusting the Pb:Se ratio. Below threshold for laser action, the emission exhibits two spectral peaks, one near 8.5μ which increases superlinearly with current and another near 10.1μ which increases slowly with current. Laser action associated with the 8.5μ peak is observed above a threshold Current density of 2000 A cm^-2. From measurements which did not resolve the cavity mode structure, the emission peak was found to shift to higher energies in a [100] oriented magnetic field at the rate of7.1 times 10^{-8}eV per gauss, or 17 Mc/s per gauss. This is the expected shift if the emission is associated with band-to-band transitions. The threshold current decreased to a fraction of its zero field value in a magnetic field of approximately 10 kilogauss, then increased slowly with higher fields.     

Prediction of magnetic flux-controlled gate voltage insuperconducting field-effect transistors

The undirectional model to the superconducting field-effect transistor (SFET) is shown to be thermodynamically unsound. A gate voltage which is controlled by the magnetic flux difference in a Josephson weak link is predicted by energy arguments. For a passive SFET model to be consistent with recent experimental observations of a charge-controlled critical current, a back-reaction from the DC drain-to-source flux (phase difference) to the DC gate voltage is required. As this effect is important in large devices and occurs at V_DS=0, it does not appear to be directly related to charge-space energy bands or quasiparticle interference     

CLADISS-a longitudinal multimode model for the analysis of thestatic, dynamic, and stochastic behavior of diode lasers withdistributed feedback

A computer model called CLADISS is presented for the analysis of multisection diode lasers. The model allows for the analysis of a wide variety of multisection devices with discrete or distributed internal reflections. The simulator can carry out a threshold, DC, AC, and a noise analysis. The threshold analysis determines the threshold of the various longitudinal modes of the laser. The power versus current and the wavelength versus current characteristics are found with the self-consistent DC analysis. CLADISS includes all of the longitudinal variations by dividing each laser section in many short segments. Both the optical field and carrier density are discretized according to this segmentation. To demonstrate the capabilities of CLADISS some nonlinear effects in DFB lasers are treated. Instabilities induced in the side-mode suppression ratio by spatial hole burning are considered. The effects of spatial hole burning and side modes on the FM response on the linewidth are discussed     

Magnetization Loss in a Striated YBCO Coated Conductor Considering the Intrinsic Critical Current Distribution

In this work we present numerical analysis results of the magnetization loss in a perpendicular AC magnetic field. The numerical analysis is based on the relation of the linkage magnetic flux to current distribution, and takes into account the$J_ c-B$characteristic, and$n$value-$B$characteristic. We discuss the relation between the magnetization losses with striated superconducting tape and the semicylindrical intrinsic critical current density distribution across the width of the superconducting tape. The result shows that the magnetization loss of monocore superconducting tape in a low magnetic field is affected by the intrinsic semicylindrical critical current density distribution. With a striated structure, the influence of the intrinsic critical current density distribution is reduced.     

Influence of growth conditions on deep levels in molecular-beam-epitaxial GaAs

Molecular-bearn-epitaxially grown undoped GaAs layers are studied with regard to the relation between growth conditions and deep-level trap generation. Both carrier concentration and electron trap density have a minimum value in samples grown at close to the minimum As/Ga flux ratio under As-stabilised conditions. Growth under these conditions leads to suppression of defect generation and unintentional impurity incorporation.     

高斯激光束闭孔Z-扫描曲线特征研究

从理论上研究了材料的非线性折射和非线性吸收同时存在时 ,闭孔Z 扫描透过率曲线的特征 ,结果表明峰 谷或谷 峰结构特征取决于材料的三阶非线性极化率的虚部与实部的比值 ρ。给出了高斯光束情况下决定峰 谷或谷 峰结构存在与否的精确临界值 ρc 和曲线的某些特征参量与ρ的关系以及本理论的适用范围。CS2 的Z 扫描实验与理论结果符合得很好。     

Gain characteristics of 1.55-μm high-speed multiple-quantum-welllasers

We describe the important characteristics of high-speed p-doped compressively strained MQW lasers obtained from comprehensive below-threshold DC measurements. Results of gain and differential gain versus wavelength and carrier density are verified by above-threshold resonance measurements. Measurement-derived design curves of gain, differential gain, and linewidth enhancement factor allow device optimization for high speed and low chirp     

Temperature sensitivity of injection-locked vertical-cavity surface-emitting lasers

The dynamics of injection-locked vertical-cavity surface-emitting lasers (VCSELs) are studied as a function of temperature. The temperature dependence of the slave VCSEL's parameters is used in a rate-equation analysis and parametric maps in the injection strength K- and frequency detuning /spl omega/-planes are calculated in order to investigate the temperature dependence of the system's stability. We demonstrate that, as we increase temperature for the range where the linewidth enhancement factor /spl alpha/ starts to stabilize, approximately 10 K above the temperature of where the minimum of the threshold carrier density occurs, the locking region tends to be suppressed and the nonlinearities to grow due to the increase of the relaxation resonance frequency /spl omega//sub R/ and the total loss rate /spl Gamma//sub 0/. Below that range, the opposite route is followed due to the enhanced value of the linewidth enhancement factor /spl alpha/, and the results are sensitive to the intraband relaxation time /spl tau/. It is finally concluded that, to take advantage of the stable locking region and to avoid the nonlinearities, it is better for the VCSEL device to have a minimum carrier density of 40 K-50 K below room temperature, thus allowing a good operating tolerance in the range /spl plusmn/20 K around room temperature.     

Resistance transients in Al-based thin films and activation energymeasurements

In this work, we present a study of resistance transients (pulses) observed during noise measurements in Al-based thin films at high current densities and/or high temperatures. It was found that the maximum pulse height M gradually increases with film current density until it reaches a peak at a critical film temperature, T_c. Above the critical temperature, M decreases to a value close to its initial value then increases with the film current density. It was also found that the critical temperature is 254°C for the Al-Si(0.75%)-Cu(0.5%) samples used in this study. In addition, it was found that the number of pulses detected per measurement period increases with increasing film current density. A new technique for determining the electromigration activation energy from the Arrhenius plot of M versus film temperature is also presented. The activation energy values determined using this new technique were between 0.58 and 0.77 eV for the Al-Si(0.75%)-Cu(0.5%) samples     

Flexible Liquid-Based Continuous Direct-Current Tribovoltaic Generators Enable Self-Powered Multi-Modal Sensing

Flexible tribovoltaic direct-current (DC) generators are urgently expected by wearable applications. Traditional rigid contact-separation type tribovoltaic DC generators normally have non-ignorable friction loss and cannot sustain outstanding outputs. This hinders their serviceability in continuous motion scenarios. Here, flexible liquid-based DC generators (FLGs) with metal-liquid-semiconductor indium gallium zinc oxide (IGZO) stack structures are reported. The FLG with Pt/H₂O/IGZO structure delivers a peak short-circuit current density up to 2.3 µA cm⁻², a peak open-circuit voltage up to 620 mV, and a power density up to 0.1 µW cm⁻². The differences in the properties of different liquid–solid interfaces are studied by density functional theory, showing that the bond formation, charge-transfer-induced dipole electric field at the solid-liquid interface, and the built-in electric field are responsible for the generation and separation of electron-hole pairs to form continuous DC. The proposed FLG can keep excellent performance even after >5 × 10⁴ shaking cycles or exposing to ambient conditions for 30 days, showing extraordinary stability. Besides charging capacitors or driving LEDs, the FLG is further demonstrated to work for self-powered multifunctional sensing, enabling pressure, position-posture, or temperature detections. This design offers potential solutions and novel possibilities for next-generation self-powered wearable electronics.     

采用有限元方法分析直流电磁铁吸合过程

本文建立了直流电磁铁电磁吸力计算的有限元模型,模型中考虑了漏磁通和铁磁材料的非线性。本文还计算了衔铁处于不同位置时的磁场分布及漏磁率,得到了铁心中、衔铁中的磁密以及衔铁受到的电磁吸力随气隙变化的规律。有限元方法的分析结果对学生掌握＂电工学＂课程中电磁铁的吸力计算及吸合过程中的电磁规律有一定的帮助。     

Characterization of an experimental ferrite LTCC tape system for microwave and millimeter-wave applications

An experimental-low temperature cofired ceramic (LTCC) ferrite tape system is characterized using circuits that are fabricated from the very material under test. Such in situ circuits provide data that are thought to be more representative of the performance obtainable by more complicated circuitry that will eventually be made from the same material using the same fabrication method. Emphasis is placed on simple measurements that can be performed using a minimum amount of equipment. For the first time, a compact in situ LTCC solenoid transformer is used to measure the magnetostatic properties of the ferrite, yielding a measured saturation flux density of 230 mT, a remanence of 136 mT, and a coercivity of 688 A/m. The peak linear relative permeability of the ferrite is 97 and its Curie temperature is low, only 117/spl deg/C. A novel two-port line-connected ring resonator is used to characterize the material in the 6-40 GHz range. At frequencies above 20 GHz, the relative permittivity of the ferrite is 11.0, whereas its loss tangent ranges from 0.002 to 0.004, demonstrating the ferrite's suitability for use in microwave and millimeter-wave circuitry.     

Establishing the minimum reverse bias for a p-i-n diode in ahigh-power switch

An important circuit design parameter in a high-power p-i-n diode application is the selection of an appropriate applied DC reverse bias voltage. Until now, this important circuit parameter has been chosen either conservatively, using the magnitude of the peak RF voltage, or by empirical trials to determine a possible lower value. The reverse bias requirement for a p-i-n diode operating in a high-power RF and microwave environment is explored. It is demonstrated that the minimum reverse bias voltage is equivalent to the p-i-n diode's self-generated DC voltage under similar RF conditions. A concise expression for this self-generated voltage is developed and experimentally verified and should assist the design engineer in more accurately selecting an appropriate minimum value for the applied reverse bias voltage setting     

Design of gain-clamped doped-fiber amplifiers for optimal dynamicperformance

This paper provides a detailed analysis of gain-clamped doped-fiber amplifiers and design guidelines in a wavelength division multiplexed (WDM) networking environment. A simple dynamic model of the doped-fiber amplifier allows us to derive explicit expressions for the small-signal response, which help identify and optimize the most critical parameters for best dynamic performance. The most important parameter is the pump power, which should be chosen 1-2 dB's above its required open-loop value, with all channels present, for the required signal gain. In an all-optical networking scenario with input power per channel as high as -3 dBm the required pump power may well exceed 20 dBm. Thus optimization of other parameters such as laser wavelength and loop loss are important. For best dynamic performance either the loop loss should be extremely small, implying a very large laser flux, or the laser gain variation in response to a perturbation should be large. Accordingly, the laser wavelength should be placed either close to the unity-gain region of the clamped gain profile, or at its peak. Finally, the small signal model for a chain of clamped amplifiers is provided, and it is shown that long chains are vulnerable to low-frequency input signal perturbations     

A niobium nitride-based analog to digital converter using rapidsingle flux quantum logic operating at 9.5 K

An analog to digital converter (ADC) using the rapid single flux quantum (RSFQ) logic family implemented in niobium nitride (NbN) technology is described. The circuit was originally developed and demonstrated in niobium technology. An identical circuit was then laid out, fabricated and demonstrated in NbN technology. The chips were fabricated using an eight-layer NbN-based process with Josephson junction critical current density of 500 A/cm². In this paper, we report on the measurement results for a 6-bit flux quantizing ADC which exhibited proper operation and good DC bias margins. We also demonstrate results from an ADC chip operating up to 9.5 K     

Polar Quantization of a Complex Gaussian Random Variable

We solve numerically the optimum fixed-level non-uniform and uniform quantization of a circularly symmetric complex (or bivariate) Gaussian random variable for the mean absolute squared error criterion. For a given number of total levels, we determine its factorization into the product of numbers of magnitude and phase levels that produces the minimum distortion. We tabulate the results for numbers of "useful" output levels up to 1024, giving their optimal factorizations, minimum distortion, and entropy. For uncoded quantizer outputs, we find that the optimal splitting of rate between magnitude and phase, averaging to 1.52 and 1.47 bits more in the phase angle than magnitude for optimum and uniform quantization, respectively, compares well with the optimal polar coding formula Of 1.376 bits of Pearlman and Gray [3]. We also compare the performance of polar to rectangular quantization by real and imaginary parts for both uncoded and coded output levels. We find that, for coded outputs, both polar quantizers are outperformed by the rectangular ones, whose distortion-rate curves nearly coincide with Pearlman and Gray's polar coding bound. For uncoded outputs, however, we determine that the polar quantizers surpass in performance their rectangular counterparts for all useful rates above 6.0 bits for both optimum and uniform quantization. Below this rate, the respective polar quantizers are either slightly inferior or comparable.