一种结合人脸检测的小波图像编码方法

本文基于人脸检测的基础上，提出了一种结合矢量量化（ＶＱ）的小波图像编码方法。该方法充分利用人眼的视觉特性，高压缩比时恢复图像仍能保持较好的主观质量。     

Growth and optical investigation of quaternary GaInAsSb/AlGaAsSb quantum wells

Infrared photoluminescence and high sensitive absorption measurements were performed on a quaternary GaInAsSb/AlGaAsSb strained multiple quantum well (MQW), as well as single quantum well (SQW) structures grown by molecular-beam epitaxy, to investigate its band offsets and subband behavior. Strong luminescence and well-resolved excitonic absorption peaks are observed even at room temperature, which is indicative of the good quality of our quaternary sample. By fitting the experimental results to the theoretical calculations, we find that the light holes are confined in well regions for Ga_0.75In_0.25As_0.04Sb_0.96/Al_0.22Ga_0.78As_0.02Sb_0.98 QWs (type I MQW) with a conduction-band offset ratio of Q_c = 0.66 ± 0.01. The transition from type I to type II for light holes is predicted theoretically and demonstrated directly by photoluminescence spectra in the SQW structures.     

The CEO problem [multiterminal source coding]

We consider a new problem in multiterminal source coding motivated by the following decentralized communication/estimation task. A firm's Chief Executive Officer (CEO) is interested in the data sequence {X(t)} _t=1^∞ which cannot be observed directly, perhaps because it represents tactical decisions by a competing firm. The CEO deploys a team of L agents who observe independently corrupted versions of {X(t)}_t=1^∞. Because {X(t)} is only one among many pressing matters to which the CEO must attend, the combined data rate at which the agents may communicate information about their observations to the CEO is limited to, say, R bits per second. If the agents were permitted to confer and pool their data, then in the limit as L→∞ they usually would be able to smooth out their independent observation noises entirely. Then they could use their R bits per second to provide the CEO with a representation of {X(t)} with fidelity D(R), where D(·) is the distortion-rate function of {X(t)}. In particular, with such data pooling D can be made arbitrarily small if R exceeds the entropy rate H of {X(t)}. Suppose, however, that the agents are not permitted to convene, Agent i having to send data based solely on his own noisy observations {Y_i(t)}. We show that then there does not exist a finite value of R for which even infinitely many agents can make D arbitrarily small. Furthermore, in this isolated-agents case we determine the asymptotic behavior of the minimal error frequency in the limit as L and then R tend to infinity     

一种基于PLL的CBR业务时钟恢复方案

信元在 ATM 网内传输时,由于网内缓存的存在,造成了信元延时变化。信元延时变化对基于锁相环(PLL)的恒定比特率业务时钟的恢复有很大影响,即时钟的抖动和漂移比较明显。从而使这种基于 PLL 的CBR 业务时钟恢复方案在某些场合不能应用。本文提出了一种基于 PLL 的时钟恢复新方案,该方案可以明显地降低由于信元延时变化而造成的 CBR 业务时钟的抖动和漂移,同时不增加缓存的容量。     

一种基于SBC技术的16kbit/s高效语音编译码器

本文介绍一种基于SBC技术的16kbit／s高效语音编译码器．在该编码方案中，IIR型正义镜象滤波器（QMF）用于实现语音分带，而基于快速搜索技术的矢量量化（FVQA）用于对除基带（采用ADPCM技术）外的其余高频带语音编码。一片TMS320C25芯片实现了两路16kbit／s语音编译码器，并借此实现了两人双向实时通信。得到良好的语音可懂度、自然度及客观评测结果。     

不同跨接模型对临界区域热力性质计算的影响

经典状态方程虽然能够描述远临界区域的热力学性质,但由于临界区密度涨落的影响,无法精确描述流体在近临界的热力学性质。在简单的经典状态方程基础上引入跨接模型,使得跨接方程能够较好地描述流体近临界区和远临界区的热力学性质。以较为常用的PR方程为基础,比较了引入不同跨接模型（跨接正弦模型‐1（CSM ）、跨接解析正弦模型（ASM ）和跨接正弦模型‐2（NSM ））后的跨接方程对丁烷、戊烷及己烷的相平衡和单相区性质的计算效果,发现PR／CSM方程和PR／ASM方程相平衡计算精度相当,优于PR／NSM 方程,对于单相区性质,PR／ASM方程计算偏差最小,优于PR／CSM方程和PR／NSM方程,而且PR／ASM方程的跨接函数为显式函数的形式,简化了计算过程,使用更方便。     

颗粒流重力增加法的改进研究

针对土坡安全系数数值分析中运用颗粒流重力增加法计算结果偏大的问题,对颗粒流重力增加法进行了改进,即通过降低颗粒摩擦系数,抵消土体抗剪强度因重力增加而提高的不利影响,使计算出的土坡安全系数更加合理。计算结果表明,采用改进的重力增加法计算的土坡安全系数与其他方法计算结果相近;同时结合模型颗粒间的接触和作用力的变化,可以准确确定粘性土坡的滑动面。可见改进的重力增加法有效改善了重力增加法的不足,在计算粘性土坡的安全系数中具有一定的参考价值。     

抗垢减焦增液剂的合成及效果评价

根据抗垢减焦机理,以醇胺脂和脂肪酸进行反应得到无灰非金属分散剂,并添加热裂解引发剂、抑制剂、抗焦剂、溶剂等多种组分复配成抗垢减焦增液剂。实验室模拟评价结果表明：在不同减压渣油中添加质量分数为300μg／g的抗垢减焦增液剂,可使反应管结垢结焦率相对降低25．7％～29．7％、焦化反应的生焦率降低0．38％～1．07％、液体收率提高1．11％～2．72％。抗垢减焦增液剂合成调配容易,添加操作简便,有利于装置长周期运转。     

MoO_3/HZSM-5催化剂上重芳烃加氢脱烷基反应

采用等体积浸渍法制备了不同负载量的MoO3/HZSM-5催化剂,考察了MoO3/HZSM-5催化剂上MoO3负载量和工艺条件对重芳烃(C9+)加氢脱烷基反应的影响;并用X射线衍射、吡啶吸附红外光谱、氨程序升温脱附等技术对催化剂进行了表征。实验结果表明,重芳烃在MoO3/HZSM-5催化剂上的反应性能与HZSM-5分子筛上MoO3的分散状态、催化剂的酸性和酸量及工艺条件有关;当MoO3/HZSM-5催化剂中MoO3的负载量(质量分数)接近15%时,MoO3在HZSM-5分子筛表面呈单层分散。采用15%MoO3/HZSM-5催化剂,在550℃、3.0MPa、重时空速3.62h-1及V(H2)∶V(C9+)=800的反应条件下,重芳烃转化率达55.94%,苯、甲苯、二甲苯(BTX)收率大于50%,BTX总选择性达90%以上。     

氟化氢/USY分子筛催化合成对叔丁基苯酚

以USY负载HF为催化剂,以甲基叔丁基醚(MTBE)、苯酚为原料,在微型反应器上催化合成了对叔丁基苯酚。考察了HF负载量、反应温度、空速及原料配比对烷基化反应的影响及催化剂的稳定性。结果表明,HF改性后USY的L酸中心增加,B酸中心减少,苯酚转化率增大。L酸中心是烷基化反应的主要活性中心。在反应温度160℃、HF负载量1%、反应空速1.7h~(-1)、n(MTBE):n(苯酚)=1.5:1条件下,苯酚的转化率为91%,对叔丁基苯酚的选择性为79.05%。催化剂使用120h后,仍保持较好的催化活性。