Weighted-coupling Y-branch optical switch in InGaAs/InGaAlAsquantum well electron transfer waveguides

We demonstrate the first weighted-coupling Y-branch switch in semiconductors. The active waveguide core contains an InGaAs/InGaAlAs chopped quantum well electron transfer structure which provides large voltage-controlled refractive index changes near 1.55 μm with high speed capability. We obtain polarization-independent switching over a wide operating range, from 1.52 to 1.58 μm wavelength. We show that shaping the Y-branch results in significant improvements in voltage-length product and crosstalk performance over conventional, non-shaped Y-branches. In push-pull configuration, the drive voltage requirement is only 3.5 V for a 550 μm active length switch     

Output-buffer switch architecture for asynchronous transfer mode

This paper proposes a new asynchronous transfer mode (ATM) switch architecture for the broadband ISDN. The ATOM switch ATM output-buffer modular switch has a multi-stage network structure, and is highly modular to facilitate capacity expansion. The ATOM switch element is of the output-buffer type with a time-division multiplexed bus and FIFO buffer for each outgoing line. Bit-slice techniques are used to implement the high-speed time-division bus and buffer memories. The output buffer switch has the advantages of no throughput degradation since internal contention is eliminated, and a simple control structure for providing priority and multi-point connections. This paper also deals with switching delay and buffer overflow probabilities for mixed (bursty and non-bursty) traffic.     

Round-robin selection with adaptable-size frame in a combined input-crosspoint buffered switch

As an alternative to input-buffered switches, combined input-crosspoint buffered switches relax arbitration timing and provide high-performance switching for packet switches with high-speed ports. It has been shown that these switches, with one-cell crosspoint buffer and round-robin (RR) arbitration at input and output ports, provide 100% throughput under uniform traffic. However, under admissible traffic patterns with nonuniform distributions, only weight-based selection schemes are reported to provide high throughput. We propose an RR based arbitration scheme for a combined input-crosspoint buffered packet switch that provides nearly 100% throughput for several admissible traffic patterns, including uniform and unbalanced traffic, using one-cell crosspoint buffers. The presented scheme uses adaptable-size frames, so that the frame size adapts to the traffic pattern.     

The scanning electron microscope as a means of investigating "Second breakdown" and similar phenomena

This paper illustrates the ability of the scanning electron microscope to contribute to the understanding of breakdown phenomena. In particular, we stress the use of this instrument as a very fine probe with an ability to make high resolution "maps" of the charge collection efficiency of a diode, and to detect very small regions of avalanche breakdown. By means of recently obtained pictures, the voltage sensitivity and spatial resolution of this technique is discussed. The range of experimental conditions over which this method can be used is described. The inherent limitations and the possible extensions are also given. Finally, the application to "second breakdown" is suggested.     

高帧频低拖尾帧转移CCD驱动技术

帧转移CCD在先进高光谱遥感技术中具有非常重要的应用价值,而拖尾问题是其在高光谱成像等高帧频应用中存在的最大障碍之一。为了减小拖尾的影响,建立了驱动器、PCB传输线及CCD内部结构一体化的驱动信号传输模型,比传统模型能更准确地预测CCD内部和外部的驱动信号波形;仿真对比了各种典型参数对CCD驱动信号波形的影响,仿真与实测结果具有很好的一致性。根据仿真结果进行了高帧频帧转移CCD驱动电路的优化设计,实现了100 ns的行转移时间,在500 fps的帧频下获得了拖尾系数小于1%的驱动效果,为进一步提高CCD的工作帧频提供了保障。     

A thermally-actuated latching MEMS switch matrix and driver chip for an automated distribution frame

This paper presents a thermally-actuated latching MEMS switch matrix together with an integrated driver chip for controlling these switches. The novel thermal actuators are heated by making use of a polysilicon heater underneath the structure, which results in a more stable actuation and a facilitated driving. The designed driver can generate adjustable latching waveforms which are needed to latch the switch into a closed or open state. As the thermal actuators in the MEMS switch require voltages up to 24 V, the high-voltage 0.35 µm  I3T50 technology of ON Semiconductor was used to fabricate the device. The driver, measuring 2 × 2 mm², contains 32 output drivers and can control a 4 × 4 latching switch matrix. This driver chip together with the latching MEMS switches were combined to create a prototype 2 × 2 double-pole single-throw latching MEMS switch matrix. The proposed MEMS switch matrix could be used in the fixed-access telecommunication network in which it can implement a compact automated distribution frame for connecting twisted pairs.     

Static memory element based on electron Y-branch switch

A compact memory element, based on an electron Y-branch switch, has been realised. Memory operation is a result of bilateral feedback coupling of each of the branches to the opposing side-gate. D-flip-flop in addition to RS-flip-flop operation is demonstrated.     

Color reproduction of a single chip color camera with a frame transfer CCD

A single chip color camera of phase separation type employing a 512 V/spl times/486 H element frame transfer CCD with a high color fidelity has been fabricated. The horizontal color crosstalk is successfully suppressed by using a color stripe filter array in which optically opaque stripes are vertically aligned on the channel stop regions of the CCD.     

Characteristics of a photoconductive detector as an optoelectronic switch

Measurements of the wavelength, signal frequency, and position sensitivities of GaAs field effect transistors used as photoconductive detectors are presented. Switching of the optical sensitivity by means of both the drain and gate voltages are demonstrated. The former method can provide the basis for employing such photoconductive detectors as optoelectronic wide-band switches. The observed properties of the field effect transistor (FET) devices studied shows that the design of photoconductive optoelectronic switches will involve compromises between sensitivity and isolation in choosing the operating wavelength, and among frequency response, power consumption, and physical size in choosing the physical layout of the device.     

Tester architecture for a time-division switch

A tester architecture for time-space switches as well as the appropriate testing method are proposed. This architecture makes it possible to detect all stuck-type faults in a digital switch in a reasonable time.     

Unusual loss of electron mobility upon furan for thiophene substitution in a molecular semiconductor

Furan has often been considered as a more sustainable alternative to thiophene in organic electronics. Herein we demonstrate that replacing thiophene with furan in a phthalimide based molecular semiconductor results in a complete loss of electron mobility when evaluated using organic thin film transistors (OTFTs). Although optical, electronic, thermal, and structural characterization show subtle effects substituting furan for thiophene, theoretical dimer modeling employing the respective single crystal structures of the two molecules reveals a loss of degeneracy between the lowest unoccupied molecular orbital (LUMO) and LUMO+1 molecular orbitals in the bifuran-containing molecule. These results demonstrate that minor changes to molecular structure can result in large differences in device performance.     

Landscape phage as a molecular recognition interface for detection devices

Filamentous phages are thread-shaped bacterial viruses. Their outer coat is a tube formed by thousands equal copies of the major coat protein pVIII. Libraries of random peptides fused to pVIII domains were used for selection of phages probes specific for a panel of test antigens and biological threat agents. Because the viral carrier in the phages borne bio-selective probes is infective, they can be cloned individually and propagated indefinitely without needs of their chemical synthesis or reconstructing. As a new bioselective material, landscape phages combine unique characteristics of affinity reagents and self-assembling proteins. Biorecognition layers formed by the phage-derived probes bind biological agents with high affinity and specificity and generate detectable signals in analytical platforms. The performance of phage-derived materials as biorecognition interface was illustrated by detection of Bacillus anthracis spores and Salmonella typhimurium cells. With further refinement, the phage-derived analytical platforms for detecting and monitoring of numerous threat agents may be developed, since phage interface against any bacteria, virus or toxin may be readily selected from the landscape phage libraries. As an interface in the field-use detectors, they may be superior to antibodies, since they are inexpensive, highly specific and strong binders, resistant to high temperatures and environmental stresses.     

Selective electron transfer between quantum dots induced by a resonance pulse

A theoretical study of the effect of a resonance electromagnetic pulse on the coherent electron dynamics in a system of tunneling-coupled quantum dots (QDs) arranged in a closed-ring configuration is carried out. It is shown that selective electron transfer between two arbitrary QDs is possible. The transfer probability is calculated as a function of the parameters that characterize the QDs and the electromagnetic pulse. It is shown that this probability can be close to unity. Factors leading to a reduction of the transfer probability in a realistic system are considered. The results obtained can be used for the development of new types of nanoelectronic devices for performing operations with quantum bits.     

Theoretical model for a microsctip optoelectronic switch

A theoretical model is given to represent the active part of either an optoelectronic switch, similar to those described by Auston el al., or an optoelectronic gate such as the one we developed. These devices consist mainly of a microstrip line, with a characteristic impedance of 50 ?, which is deposited on a high-resistivity semiconductor. The centre strip has a break, creating a gap which can be illuminated by an optical laser pulse. The latter generates an electron-hole plasma of high density at the surface of the semiconductor, allowing the transmission of a signal across the gap.     

Novel architecture for a time division switch

A layout for a single-chip implementation of a time switch for a digital switching system is described. Using only a few simple cell types, a complete switch can be designed by connecting the cells in regular arrays. Interconnect wiring is incorporated into the cells, so the effort required to design a time switch of any size is minimised.     

Dextran particles as a carrier for Giardia lamblia for scanning electron microscopy.

Giardia lamblia trophozoites attach readily to dextran particles after which they can be conveniently processed for scanning electron microscopy. As the particles are spherical in shape, G. lamblia can be viewed from various directions and their morphology studied.     

对扫描电镜观察微生物样品出现磷酸盐结晶现象的改良

制备常规扫描电镜生物样品时,通常使用磷酸缓冲液来进行漂洗,其结果是容易产生结晶,沉积在样品表面.针对微生物具有坚韧的细胞壁的特性,作者使用去离子水替代磷酸缓冲液来漂洗固定液.结果显示,扫描电镜下样品形态完好,无磷酸盐结晶,提高了样品制备的成功率.     

Mailbox switch: a scalable two-stage switch architecture for conflict resolution of ordered packets

Traditionally, conflict resolution in an input- buffered switch is solved by finding a matching between inputs and outputs per time slot, which incurs unscalable computation and communication overheads. The main objective of this paper is to propose a scalable solution, called the mailbox switch, that solves the out-of-sequence problem in the two-stage switch architecture. The key idea of the mailbox switch is to use a set of symmetric connection patterns to create a feedback path for packet departure times. With the information of packet departure times, the mailbox switch can schedule packets so that they depart in the order of their arrivals. Despite the simplicity of the mailbox switch, we show via both the theoretical models and simulations that the throughput of the mailbox switch can be as high as 75%. With limited resequencing delay, a modified version of the mailbox switch achieves 95% throughput. We also propose a recursive way to construct the switch fabrics for the set of symmetric connection patterns. If the number of inputs, N, is a power of 2, we show that the switch fabric for the mailbox switch can be built with y log2 N 2 x 2 switches.