Detection of incoherent broadband terahertz light using antenna-coupled high-electron-mobility field-effect transistors

The sensitivity of direct terahertz detectors based on self-mixing of terahertz electromagnetic wave in field-effect transistors is being improved with noise-equivalent power close to that of Schottky-barrier-diode detectors. Here we report such detectors based on AlGaN/GaN two-dimensional electron gas at 77~K are able to sense broadband and incoherent terahertz radiation. The measured photocurrent as a function of the gate voltage agrees well with the self-mixing model and the spectral response is mainly determined by the antenna. A Fourier-transform spectrometer equipped with detectors designed for 340, 650 and 900~GHz bands allows for terahertz spectroscopy in a frequency range from 0.1 to 2.0~THz. The 900~GHz detector at 77~K offers an optical sensitivity about $1~\mathrm{pW/\sqrt{Hz}}$ being comparable to a commercial silicon bolometer at 4.2~K. By further improving the sensitivity, room-temperature detectors would find applications in active/passive terahertz imaging and terahertz spectroscopy.Comment: 4.5 pages, 5 figure

Research on the Product Policy for High-tech Products in the Introduction stage

摘要本文以市场引入期的高科技产品作为研究对象，在对产品策略内涵、特征和国内外研究现状进行简要概述的基础上，分析了引入期高科技产品的特点，并结合市场营销的相关理论及作者毕业实习的社会实践经验，指出高科技产品在引入期的根本任务及实现这一任务的有关措施。本文的安排如下。第一章：产品策略概述。本章首先阐述了产品及产品策略的内涵，接着分析总结了产品策略的特征，最后介绍了产品策略、产品生命周期及高科技产品营销的研究现状。第二章：产品策略的构成要素。产品策略作为营销策略的基础部分，在其理论发展过程中，已经形成了一套成熟的研究框架，其内容有：产品线决策，产品组合策略，品牌策略，包装策略，服务策略，新产品开发策...Abstract This Paper takes the high-tech product in the introducing stage as the research object. It summarizes briefly the product policy, the product characteristics and the overseas and the domestic correlative research status. On the basis of the brief summary, the paper has analyzed the characteristics of the high-tech product in the introduction stage. Through connecting the above summary,...学位：管理学硕士院系专业：管理学院企业管理系_企业管理(含财务管理、市场营销、人力资源管理)学号：20031404

深度学习在电力负荷预测中的应用

针对电力负荷预测中存在的随机性、不确定性的问题,结合深度学习算法具有很强的自适应感知能力等特点,采用目前较为主流的深度学习方法,如长短时记忆(LSTM)网络、门循环单元(GRU)神经网络和栈式自编码器(SAE),分别研究其应用于电力负荷预测时的效果。研究发现,将历史负荷数据作为三种深度学习预测模型的输入时,三种预测模型的负荷预测精度指标评估结果各有不同。因此,为了全面评估三种预测模型的预测效果,提出将不同时间段内的相同历史负荷数据作为预测模型输入对比各模型的负荷预测精度,从中找出最佳的预测模型。仿真结果验证了三种预测模型在电力负荷预测应用中的可行性,且发现在单输入因素时LSTM模型的预测精度相对较高。因此,在后续研究中,可以考虑以LSTM预测模型作为基础预测模型,结合更多的负荷影响因素进行改进,以提高负荷预测精度

Topological structure evolvement of flow and temperature fields in deformable drop Marangoni migration in microgravity

Using the level-set method and the continuum interface model, the axisymmetric thermocapillary migration of a deformable liquid drop immerged in an immiscible bulk liquid with a temperature gradient is simulated numerically with constant material properties of the two phases. Steady terminal state of the motion can always be reached. The dimensionless terminal migration velocity decreases monotonously with the increase of the Marangoni number. Good agreements with space experimental data and most of previous numerical studies in the literature are evident. The terminal topological structure of flow field, in which a recirculation identical to Hill's vortex exists inside the drop, does not change with the Marangoni number. Only slight movement of the location of vortex center can be observed. On the contrary, bifurcations of the terminal topological structure of temperature field occur twice with increasing Marangoni number. At first, the uniform and straight layer-type structure of temperature field at infinitesimal Reynolds and Marangoni numbers wraps inside of the drop due to convective transport of heat as the Marangoni number increases, resulting in the emergence of an onion-type local cooler zone around the center of the drop beyond a lower critical Marangoni number. Expanding of this zone, particularly in the transverse direction, with the increasing of the Marangoni number leads to a cap- or even shell-type structure. The coldest point within the liquid drop locates on the axis. There is a middle critical Marangoni number, beyond which the coldest point will jump from the rear stagnation into the drop, though the topological structure of the temperature field does not change. The second bifurcation occurs at an upper critical Marangoni number, where the shell-type cooler zone inside drops ruptures from the central point and then a torus-type one emerges. The coldest point departs from the axis, and the so-called "cold-eye" appears in the meridian. It is also found that the inner and outer thermal boundary layers along the interface may exist both inside and outside the drop if Ma > 70. But the thickness decreases with the increasing Marangoni number more slowly than the prediction of potential flow at large Marangoni and Reynolds numbers. A velocity shear layer outside the drop is also introduced formally, of which modality may be affected by the convective transports of heat and/or momentum. (C) 2011 Elsevier Ltd. All rights reserved

Research on DiffSev Performance Evaluation by Simulation

中文文摘：：Internet 越来越多的多媒体实时传输业务对网络服务质量提出了更高的要求。在分析传统 的尽力而为服务不足的基础上，剖析了区分服务的体系结构和工作机制，并运用NS2 网络仿真器 构建DiffServ 的仿真模型，进行性能评价研究。DiffServ 的端到端QoS 特性难以用精确的数学模 型加以刻画，模拟方法是评价这种服务性能的有效途径。 [英文文摘]Internet real time multimedia communication issues a further challenge to IP QoS. The authors discuss some problems of current network service, and analyze the architecture of DiffServ. We focus on the research into the DiffServ performance evaluation though simulation, and present the results to check DiffServ module versatility in services definition. Keywords: IP QoS; DiffServ; RED; simulation; performance evaluation国家自然科学基金 (60175008); 国家“九七三”信息与高性能 软件的子项目 (G199803040803)

有机光波导放大器最新进展

稀土掺杂平面光波导放大器是一类重要的光子学元件,它是光通信密集波分复用(DWDM)传输系统的重要组成部分,可以和调制器、光开关、隔离器、阵列波导光栅等任何有损耗的器件集成在一起,补偿光传输过程中的各类损耗。综述了应用于第二(1.33μm)、第三(1.53μm)标准通信窗口的有机光波导放大器的研究现状,阐述了不同类型材料制备的器件存在的优缺点、制备过程中存在的问题,并对其发展前景进行了展望

探针熔解分析法快速检测结核分枝杆菌链霉素耐药突变

目的评价探针熔解分析法快速检测结核分枝杆菌链霉素耐药突变的应用价值,为临床应用提供依据。方法首先用中国药品生物制品检定所提供的含37份标准非结核分枝杆菌的标准盘进行特异性评价,然后将野生型结核分枝杆菌H37Rv基因组DNA梯度稀释进行灵敏度考察,最后对906株结核分枝杆菌临床分离株(其中37份有药物敏感性试验结果)的链霉素耐药相关基因进行检测,并对突变菌株、有药敏结果的菌株以及疑似杂合的菌株进行测序分析。结果标准盘评价结果证实该体系特异检测H37Rv结核分枝杆菌。分析灵敏度为5～50拷贝每反应。在所有的906份结核分枝杆菌培养标本中,103份标本发生突变且与测序结果一致,18份标本存在杂合信号,17份标本无信号。37份有药敏结果的标本中,敏感的标本用探针熔解分析法所得结果均为野生型,耐药的16份标本仅检测到7份突变,另有9份耐药的标本实时检测为野生型,与测序结果相符。结论探针熔解分析技术特异性好,可以快速、准确地检测结核分枝杆菌链霉素耐药常见突变,有望直接用于临床标本链霉素耐药性检测

CT评价经皮左室分区术对心尖部室壁瘤形成的缺血性心肌病患者心功能的影响

心尖部室壁瘤是临床上常见的疾病,发病早期如果得不到及时有效的治疗,将会引起心力衰竭、心脏破裂、缺血性心肌病及栓塞等并发症,主要是由于冠状动脉粥样硬化引起的心肌梗死造成[1]。文献[2,3]报道显示:部分冠状动脉正常患者也可以引发心肌梗死后室壁瘤。数据报道显示[4,5]:每年全球约有1 700万人死于心血管疾病,并且一半以上死于急性心肌梗死,对于存活患者液容易演变为慢性心力衰竭。目前