基于变分法的光子超导波基态分析

利用一般的电磁辐射与晶格振动的相互作用模型，研究了强光场与晶格振动的非线性相互作用导致光子对形成这一基本问题，导出了光子．光子有效相互作用。然后利用变分法求得了超导波态系统的基态能量表达式，并讨论了光子对的形成条件。     

单模光纤的传输衰减随温度变化的研究

本文从实验上测量了单模石英光纤在－50～120℃范围内的损耗。随着温度升高，光纤的损耗随之降低，在常温附近达到最小。其后损耗随着温度的继续升高而增加。损耗的变化主要是由于杂质的吸收和微弯损耗。本文对杂质的吸收以及微弯损耗进行了数值模拟，并且从理论上定性地解释了损耗对温度的依赖关系。     

All-active monolithic InP-based HBT VCO with tunable HEMT inductor

A novel HEMT-HBT VCO is presented; it is the first all-active analogue VCO demonstrated using InP HEMT-HBT integrated MMIC technology. The MMIC monolithically integrates an InP common-collector HBT oscillator with a tunable InP HEMT active inductor using selective MBE. The novel HEMT-HBT VCO can provide performance advantages over analogue VCOs such as the multi-vibrator, and has direct implications for high speed clock recovery circuits needed in InP based optoelectronic IC applications     

Random switching techniques for inverter control

New techniques which dramatically reduce acoustic noise by randomising the inverter switching frequency for inverter control are presented. It is shown that the proposed techniques combine the advantages of conventional pulsewidth modulation (PWM) techniques based on regular-sampling techniques and random PWM techniques     

气体钻井岩屑运移机理研究

气体钻井由于其机械钻速快，能有效防止水敏性泥页岩坍塌，杜绝井漏。然而在气体钻井中井筒内岩屑的运移机理还不是十分清楚，为此，从气固两相流基本理论出发，对气体钻井过程中岩屑的重复破碎和细岩屑聚团过程进行了分析，并对接单根后岩屑的运移模式进行了描述，指出由于岩屑聚团的崩裂速度远远超过理论计算的相应初始运移速度，在接完单根后为使井底得到清洁，应增大注气量。另外，还提出了气体钻井过程中岩屑间协同作用的物理模型，指出从含少量细岩屑时的粗岩屑表面改性向大量细岩屑聚团过渡中，存在一个最佳点，该点携岩效率最好。通过研究，对气体钻井过程中岩屑的运移机理有了更进一步的认识。     

浅析硫磺回收装置中的自动控制设计

大规模高含硫原油的炼制工艺必须配套设置脱硫和硫磺回收装置。笔者针对硫磺回收装置的特点,为确保装置的安全平稳运行,提出了该装置自动控制设计中需要严格监控的工艺参数及重点部位,叙述了仪表选型原则和精确测量与控制的原理和方法。     

Influences of Connecting Unit Architecture on the Performance of Tandem Organic Light‐Emitting Devices

The present work investigates the influence of the n‐type layer in the connecting unit on the performance of tandem organic light‐emitting devices (OLEDs). The n‐type layer is typically an organic electron‐transporting layer doped with reactive metals. By systematically varying the metal dopants and the electron‐transporting hosts, we have identified the important factors affecting the performance of the tandem OLEDs. Contrary to common belief, device characteristics were found to be insensitive to metal work functions, as supported by the ultraviolet photoemission spectroscopy results that the lowest unoccupied molecular orbitals of all metal‐doped n‐type layers studied here have similar energy levels. It suggests that the electron injection barriers from the connecting units are not sensitive to the metal dopant used. On the other hand, it was found that performance of the n‐type layers depends on their electrical conductivities which can be improved by using an electron‐transporting host with higher electron mobility. This effect is further modulated by the optical transparency of constituent organic layers. The efficiency of tandem OLEDs would decrease as the optical transmittance decreases.     

Hiding data in multitone images for data communications

Two novel data-hiding schemes for secure data communications are presented. These two schemes perform on the pixel differences between the original (host) image and the decompressed image, which is inspired from Wu's and Chao's methods. The first scheme, referred to as 'scheme-1', utilises the differences between two similar images and then embeds the secret data into the different parts. In the embedding process, two auxiliary techniques, zero-replacement and complement-bit, will also be incorporated. In addition, to enhance the hiding efficiency of scheme-1, the authors have followed the bit-plane hiding strategy and created scheme-2. The proposed schemes have two advantages. First, the error distortion can be measured before the hiding process begins. Second, there is no complex computation, which means the hiding process can be executed very efficiently. The experimental results show that the two proposed schemes can achieve better image quality than other data-hiding schemes. At the same time, the new schemes can also satisfy the three basic requirements a data hiding scheme should live up to: invisibility, capacity and data security.     

基于CORDIC的一种高速实时定点FFT的FPGA实现

本文论述了一种利用CORDIC算法在FPGA上实现高速实时定点FFF的设计方案。利用CORDIC算法来实现复数乘法，与使用乘法器相比降低了系统的资源占用率，提高了系统速度[1]。设计基于基4时序抽取FFT算法，采用双端口内置RAM和流水线串行工作方式。本设计针对256点、24位长数据进行运算，在XilnxSpartan2E系列的xc2s300e器件下载验证通过，完成一次运算约为12μs，可运用于高速DSP、数字签名算法等对速度要求高的领域。