K-band MMIC active band-pass filters

Two K-band active band-pass filters using 0.15-/spl mu/m GaAs pHEMT technology, with one fixed-frequency and the other tunable, are designed, fabricated, and tested. The fixed-frequency filter has its central frequency at 22.6 GHz, with 900-MHz bandwidth (4%). The tunable filter can be tuned from 19.5 to 21.5 GHz with the same bandwidth. Both circuits have a common size of 1 mm /spl times/ 1 mm. To our knowledge, the tunable filter is the highest frequency tunable active filter ever reported.     

嵌入式系统中USB总线的应用

详细阐述了一种用于嵌入式系统中的USB总线接口电路,该电路是基于USB专用芯片CH375实现的,并给出了系统硬件实现和应用程序。实验结果表明,该电路具有成本低、可靠性高等特点,可方便地集成到各种嵌入式系统中。     

Biomimetic Lamellar Chitosan Scaffold for Soft Gingival Tissue Regeneration

Mucogingival surgery has become a common procedure for soft gingival tissue reparation in dental clinical practice, which mainly relies on autograft or commercial collagen membranes (CM). However, the autograft faces grand challenges in source availability and long-term post-surgery pain management, and the CM is restricted by its poor mechanical properties in an aqueous environment. Here, it is reported that a bio-inspired lamellar chitosan scaffold (LCS) with long range ordered porous structure, manufactured through a bidirectional freezing method, can serve as a promising gingival tissue engineering material. The LCS not only exhibits excellent mechanical properties in the hydrated state but also accelerates vessel formation and soft tissue regeneration in vivo. Most interestingly, the LCS is found to be capable of inducing macrophage differentiation to M2 macrophages, which is thought to play an important role in tissue regeneration. These advantages combined with its easy and low-cost preparation process make the LCS a promising candidate for dental clinical applications.     

分叉管内爆轰波传播特性实验研究

为了研究爆轰波在分叉管内的传播特性,对以H_2/O_2为燃料的分叉式脉冲爆轰发动机进行了实验研究。分别测试了不同工况条件下管内不同采样点爆轰波压力,并对其变化过程进行了深入分析。实验结果表明:爆轰波在分叉管内传播过程中,分叉口下游主管道内爆轰波在经过6倍管径长度的过渡区后恢复稳定,爆轰强度不变。爆轰波绕射进入分叉支管2,并且在管壁发生多次碰撞和反射,形成过驱爆轰,在燃料充分填充的条件下可以恢复稳定爆轰,爆轰强度与主管道内爆轰波强度相同。在分叉支管2内加装扰流片对加快形成爆轰的影响甚小,分叉支管2内燃料填充率是形成稳定爆轰的关键。     

CE/SE方法在点火管一维两相流数值计算中的应用

介绍了CE／SE方法。该方法不同于以往的一些计算格式，在计算中它把时间和空间同等对待，具有格式构造简单、计算方便和对激波间断分辨率高等优点。运用适合点火管一维两相流控制方程的CE／SE方法来计算点火管内的一维两相流流动，源项采用四阶Runge-Kutta方法进行处理。数值计算的结果与实验数据的比较表明，CE／SE方法能对两相流进行有效的数值模拟。     

Realization of nth-order series impedance function using only (n-1) current-feedback amplifiers

A new configuration for realizing a higher-order series impedance function using current-feedback amplifiers (CFAs) is presented. The nth-order series impedance function employs only (n–1) CFAs and (2n–1) passive elements. The higher order series impedance function can be applied to realize various higher-order highpass and lowpass filters. The passive element values can be easily decided from the coefficients of the filter transfer functions. The use of CFAs simplifies the circuit implementation and makes the proposed circuit attractive for application. Experiments and simulation results are given to confirm the theoretical analysis.     

Accurate model of arbitrary wire antennas in free space, above orinside ground

An accurate model of wire antennas in free space, above or inside lossy ground is presented in which the current is assumed to flow on the surface of the wire and the testing is also performed on the surface. To replace the traditional delta-gap source, a more accurate source model is developed by using the Huygens' principle. From this principle and reciprocity theorem, a variational formulation of the input admittance is derived. When the triangle function is chosen as both basis and weighting functions, all the elements of impedance matrix and source vector are formulated in closed forms, which can be rapidly computed. Several numerical results are given. Comparing with measured data, both the current distribution and input impedance by this model are more accurate than those of delta-gap model     

Minimum time control of conductive heating systems formicroelectronics processing

A minimum time control scheme is designed to improve repeatability by minimizing the loading effects induced by the common processing condition of placement of a semiconductor wafer at ambient temperature on a large thermal-mass bake plate at processing temperature. The minimum time control strategy provides an optimal solution for minimizing the worst case deviation from a nominal temperature set-point during the load disturbance condition. This results in a predictive controller that performs a predetermined heating sequence prior to the arrival of the wafer as part of the resulting feedforward/feedback strategy to eliminate the load disturbance. The controller is easy to design and implement and makes it more suitable for online implementation such as automatic online tuning of a feedforward controller. Experimental results depict an order-of-magnitude improvement in the settling time and the integral-square temperature error between the optimal predictive controller and a feedback controller for a typical load disturbance     

ATM网络中VBR复用器的硬件实现

提出了一种用于ＡＴＭ网络中ＶＢＲ业务的复用器设计方案,探讨了如何将一种基于令牌 桶控制的ＵＰＣ算法用于ＡＴＭ统计复用器的信源接入控制,并用“在系统编程技术”加以硬件实现。     

Physical parameters extraction from current–voltage characteristic for diodes using multiple nonlinear regression analysis

In this work, the two-step iteration combined with the nonlinear multiple regression technique to extract physical parameters for diodes, using a simple physical-based current–voltage (I–V) model is demonstrated. This statistical method can be applied for sampling for a wide variety of diodes including light-emitting diodes (LEDs) and Schottky diodes. Our results show the technique is an accurate and systematic approach for extracting diode parameters. The calculated recombination currents indicate the recombination efficiency for LEDs and the quality for Schottky diodes.