ATM网络中CBR业务连接允许控制机制

该文提出了一种基于有限容量缓冲区下CBR业务信元丢失率和最小速率替换的线性近似连接允许控制机制，与原有的CAC机制相比，该文的CAC机制存在两个方面的改进：一方面，使用更合理、精确的CLR表达式，从而能够作出更为准确的连接允许判断：另一方面，能够提供服务质量服务。     

Theoretical Study on the Gain and Tuning Characteristics of Miniature Optically Pumped NH3 Submillimeter Laser

The gain and the tuning characteristics of miniature optically pumped super-radiant NH₃ submillimeter-wave gas laser have been studied theoretically based on the quantum density matrix equations. The density matrix equations of three-level quantum system have been solved, and the gain and the output density versus different frequency detuning of submillimeter laser and infrared pumping laser have been calculated respectively by means of iteration method. The characteristic curves corresponding to ideal monochromatic IR pumping model and broadened IR pumping model have been obtained. Meanwhile, the tuning and the nonlinear properties of the system have been revealed.     

Thermally induced variation in barrier height and ideality factor of Ni/Au contacts to p-GaN

In this paper, we describe the change in barrier heights (ϕ_B) and ideality factors (n) of Ni/Au contacts to p-GaN determined from current-voltage measurements as a result of (a) rapid thermal annealing between 400–700°C under flowing nitrogen, and (b) testing at temperatures of 20–300°C. The lowest barrier height and ideality factor values were obtained from samples annealed at 500–600°C. These results provide supporting evidence that thermal processing helps to remove contaminants at the contact-GaN interface, thus decreasing effective barrier height and consequently, contact resistance.     

防病毒安全网关技术在数据交换中的应用

1.概述 随着信息化高速发展和高科技时代的到来,恶意软件和非法内容也随之增多,危害严重的蠕虫等恶意代码能够在短时间内传遍全球,感染上万台主机,并造成无法估量的经济损失、数据丢失,同时还会大量消耗网络和系统修复的时间、人力成本.     

Simulation and Experimental Method for Microwave Oven

The simulation software, HFSS （high frequency structure simulator）, is introduced in microwave oven design. In the cold test, a network analyzer is used to measure the reflection coefficient （S11） of the cavity under empty and loaded states over the frequency range from 2.448 GHz to 2.468 GHz. In the hot test, a piece of wet thermal paper and an infrared thermal imaging camera are used to measure the electric field distributions on the mica and turntable. In the cold test, the simulation agrees well with the experiment no matter in empty state or loaded state. In the hot test, the simulation agrees well with the experiment in general in empty state and approximately in loaded state. The little difference in both cold and hot test may be due to that the model in simulation is not absolutely identical with that in experiment or the inadequate precision of infrared thermal imaging camera.     

MOCVD生长的GaN 薄膜中缺陷团引起的X射线漫散射研究

采用高分辨X射线衍射对在蓝宝石(0001)面生长的GaN外延膜的漫散射进行了研究.结果表明,GaN薄膜中存在缺陷团,其浓度随着穿透位错密度的增加而增加,其平均半径呈相反趋势.基于位错是点缺陷的聚集区,缺陷团优先在位错附近形成的效应对结果进行了解释.同时发现电子迁移率随缺陷团浓度的增加而减少.     

Junction Temperature Measurements and Thermal Modeling of GaInN/GaN Quantum Well Light-Emitting Diodes

We present a junction temperature analysis of GaInN/GaN quantum well (QW) light-emitting diodes (LEDs) grown on sapphire and bulk GaN substrate by micro-Raman spectroscopy. The temperature was measured up to a drive current of 250 mA (357 A/cm²). We find better cooling efficiency in dies grown on GaN substrates with a thermal resistance of 75 K/W. For dies on sapphire substrates we find values as high as 425 K/W. Poor thermal performance in the latter is attributed to the low thermal conductivity of the sapphire. Three-dimensional finite-element simulations show good agreement with the experimental results, validating our thermal model for the design of better cooled structures.     

GaN1-xPx三元合金的红外谱

对GaN1-xPx三元合金进行了红外谱的测试和拟合. 分析结果表明在GaN1-xPx三元合金中存在两个彼此竞争的机制制约着载流子浓度的变化. 一个是来自等电子陷阱的影响，它将减少三元合金中载流子的浓度；另一个来自缺陷的影响，它将增加三元合金中载流子的浓度. 对合金介电函数的倒数的虚部进行了计算，其结果显示，随着合金中P组分比的增加，纵向光学声子-等离激元（LPP）耦合模式向高频方向移动，同时LPP模式线宽逐渐增宽，说明随着合金中P组分比的增加，LPP模式的耦合作用增加，阻尼增强.     

GaN外延材料中持续光电导的光淬灭

研究了非故意掺杂和掺Si的n型GaN外延材料持续光电导的光淬灭.实验发现,非故意掺杂GaN的持续光电导淬灭程度远大于掺Si的n型GaN;撤去淬灭光后前者的持续光电导几乎没有变化,后者却明显减小;稍后再次加淬灭光,前者的持续光电导仍无变化,而后者却明显增加.作者认为两者持续光电导的形成都与空穴陷阱有关,用空穴陷阱模型解释了非故意掺杂GaN持续光电导的形成以及淬灭过程;掺Si的n型GaN的持续光电导是电子陷阱(杂质能级)和空穴陷阱共同作用的结果,并且在持续光电导发生的不同阶段其中一种陷阱的作用占主要地位.     

End-to-End Rate Adaptation to Support Heterogeneous Services for Infrastructure-Based Vehicular Networks

Vehicle to Infrastructure(V2I) communications aim to provide mobile users on the road low-cost Internet and driver safety services.However, to meet Quality of Service(QoS) requirements of various applications and efficiently utilize limited wireless channel resourc-es, the transport layer protocol has to perform effective rate control in low channel quality and frequent changing topology communica-tion environment. In this paper, we propose a novel rate-control scheme in infrastructure based vehicular networks that avoids conges-tion and starvation and promotes fairness in end-to-end V2I communications. In vehicular networks, a bottleneck roadside unit(RSU)keeps track of its buffer size, aggregate incoming rate, and link throughput, and appropriately allocates bandwidth to traversing flows.With feedback information from the RSU, source nodes dynamically adjust their sending rates to avoid buffer overflow or starvation atthe bottleneck RSU. Simulation results show that the proposed scheme can reduce not only packet losses owing to buffer overflow butalso buffer starvation time, which improves the utilization efficiency of wireless channel resource.