A hybrid method combining the multitemporal resolution time-domain method of moments with the time-domain geometrical theory of diffraction for thin-wire antenna problems

In this paper, a hybrid method combining a multitemporal resolution (MTR) enhanced time-domain method of moments (TD-MoM) with the TD geometrical theory of diffraction (GTD) is presented, which allows to efficiently calculate the transient fields radiated by antennas in presence of large objects. The MTR scheme tailors the time step size-and thus implicitly the duration of the temporal basis function-on the basis of the distance between source and test element. Additionally, the voltage induced by source elements far away from the test element is interpolated in time. The hybrid method is applied to calculate the radiation properties of thin-wire antennas in presence of perfectly conducting flat scatterers to demonstrate its basic features and advantages.     

Mechanically Programmable Dip Molding of High Aspect Ratio Soft Actuator Arrays

This work presents multiple methods of creating high aspect ratio fluidic soft actuators that can be formed individually or in large arrays via dip coating. Within this methodology, four strategies are provided to mechanically program the motion of these actuators, including the use of fiber inclusions, gravity, surface tension, and electric fields. The modular nature of this dip coating fabrication technique is inexpensive, easy to modify, and scalable. These techniques are used to demonstrate the fabrication of soft actuators with aspect ratios up to 200:1 and integrated arrays of up to 256 actuators. Furthermore, these methods have the potential to achieve higher aspect ratios and larger array sizes. Operating pressure, curvature, and curling strength tests reveal the design space in which fabrication parameters can be selected to tune the input and output parameters of soft bending actuators. An individual bending actuator made with these methods weighs between 0.15 and 0.5 g, can hold up to 2 N, and can be designed to work in groups to increase curling strength with distributed contact forces. Arrays of these actuators may be useful in atypical grasping and manipulation tasks, fluid manipulation, and locomotion.     

GaAs-AlGaAs quantum cascade lasers: physics, technology, andprospects

In recent years, the performance of GaAs-AlGaAs-based quantum cascade (QC) lasers has improved markedly. These devices are capable of pulsed room temperature operation and can deliver respectable average powers (11 mW at λ~9 μm) operating on a Peltier cooler. This performance has been achieved by the suppression of thermally activated carrier leakage through increases in the heterobarrier band offset. We demonstrate that QC lasers, with wavelengths λ⩾9 μm, can operate using heterostructures encompassing the entire composition range of Al_xGa_1-xAs, without encountering potential problems-of the satellite X-minima for x>45%. Furthermore, we present particular characteristics of these devices, such as a phonon-limited temperature dependence, electrical and optical self-oscillations, and novel design concepts that exploit this closely lattice matched material system. Finally, we discuss improvements in device fabrication to lower the operating current through a reduction of the area of current injection. Using this technology, devices can be designed to selectively pump the fundamental lateral mode. We, therefore, observe single spatial-mode operation over the entire current range of operation     

改进光电晶体管线性运行的反馈电路

当设计者用光电晶体管将一个调制后的光信号转换成电信号时,如果有高亮度的背光使光电晶体管饱和,就会遇到麻烦.当光电晶体管基极端悬浮时,其集电极/射极电压只取决于信号与背光重叠而产生的光电流.光电晶体管增益及其作用区范围由R1阻值(见图1)确定.R1阻值较高时,电路的增益增加,但光电晶体管会很快饱和.图1中没有背光照射时,晶体管工作在其线性区的偏置点φ2,Q1的集电极电压围绕VCE作线性变化.其输出VOUT准确地重复使调制光信号产生幅度波动.当施加外部稳定的背光照明时,电路的工作点移至偏置点φ3,输出电压被压缩并出现失真.     

Modeling Feedback Bridging Faults with Non-Zero Resistance

We study the behavior of feedback bridging faults with non-zero bridge resistance in both combinational and sequential circuits. We demonstrate that a test vector may detect the fault, not detect the fault or lead to oscillation, depending on bridge resistance. Moreover, the resistance intervals in which a particular behavior is observed are not necessarily contiguous. We demonstrate non-trivial behavior for situations in which a detection seems impossible, namely disabled loops going through a gate with controlling values on its side inputs.We outline the multiple strengths problem which arises due to the fact that a critical bridge resistance depends on the strengths of the signals driving the bridge, which in turn are functions of the number of the on-transistors, these again depending on the bridge resistance, making such a fault very hard to resolve. For sequential circuits, we describe additional difficulties caused by the need to account for implications on bridge behavior, which have originated in the previous time frames. We conclude that the complexity of resistive feedback bridging fault simulation accurate enough to resolve such situations will probably be prohibitively high and propose possible simplifying assumptions. We present simulation results for ISCAS benchmarks using these assumptions with and without taking oscillation into account.This revised version was published online in March 2005 with corrections to the cover date.     

Flight Test Results of a Thermoelectric Energy Harvester for Aircraft

The idea of thermoelectric energy harvesting for low-power wireless sensor systems in aircraft and its practical implementation was recently published. The concept of using a thermoelectric generator (TEG) attached to the aircraft inner hull and a thermal storage device to create an artificial temperature gradient at the TEG during take-off and landing from the temperature changes of the fuselage has passed initial tests and is now subject to flight testing. This work presents preflight test results, e.g., vibration and temperature testing of the harvesters, the practical installation of two harvesting devices inside a test plane, and the first test flight results. Several flight cycles with different flight profiles, flight lengths, and outside temperatures have been performed. Although the influence of different flight profiles on the energy output of the harvester can be clearly observed, the results are in good agreement with expectations from numerical simulations with boundary conditions evaluated from initial climate chamber experiments. In addition, the flight test demonstrates that reliable operation of thermoelectric energy harvesting in harsh aircraft environments seems to be feasible, therefore paving the way for realization of energy-autonomous, wireless sensor networks.     

Extraction and analysis of T waves in electrocardiograms during atrial flutter

Analysis of T waves in the ECG is an essential clinical tool for diagnosis, monitoring, and follow-up of patients with heart dysfunction. During atrial flutter, this analysis has been so far limited by the perturbation of flutter waves superimposed over the T wave. This paper presents a method based on missing data interpolation for eliminating flutter waves from the ECG during atrial flutter. To cope with the correlation between atrial and ventricular electrical activations, the CLEAN deconvolution algorithm was applied to reconstruct the spectrum of the atrial component of the ECG from signal segments corresponding to TQ intervals. The locations of these TQ intervals, where the atrial contribution is presumably dominant, were identified iteratively. The algorithm yields the extracted atrial and ventricular contributions to the ECG. Standard T-wave morphology parameters (T-wave amplitude, T peak-T end duration, QT interval) were measured. This technique was validated using synthetic signals, compared to average beat subtraction in a patient with a pacemaker, and tested on pseudo-orthogonal ECGs from patients in atrial flutter. Results demonstrated improvements in accuracy and robustness of T-wave analysis as compared to current clinical practice.     

Design and development of multicolor MWIR/LWIR and LWIR/VLWIR detector arrays

Multicolor infrared (IR) focal planes are required for high-performance sensor applications. These sensors will require multicolor focal plane arrays (FPAs) that will cover various wavelengths of interest in mid wavelength infrared/long wavelength infrared (MWIR/LWIR) and long wavelength infrared/very long wavelength infrared (LWIR/VLWIR) bands. There has been significant progress in HgCdTe detector technology for multicolor MWIR/LWIR and LWIR/VLWIR FPAs.^1–3 Two-color IR FPAs eliminate the complexity of multiple single-color IR FPAs and provide a significant reduction of weight and power in simpler, reliable, and affordable systems. The complexity of a multicolor IR detector MWIR/LWIR makes the device optimization by trial and error not only impractical but also merely impossible. Too many different geometrical and physical variables need to be considered at the same time. Additionally, material characteristics are only relatively controllable and depend on the process repeatability. In this context, the ability of performing “simulation experiments” where only one or a few parameters are carefully controlled is paramount for a quantum improvement of a new generation of multicolor detectors for various applications.     

锁存继电器的CMOS电路

控制应用经常要求将一只继电器锁存定位,直到需要改变其状态时为止。完成这个任务的是锁存继电器。当给它们发送一个脉冲时,它们可能保持在当前状态,也可能改变状态,具体取决于脉冲的极性以及继电器当前状态。图1中电路会根据一