收视价值的迷失 高端人群在远离卫视 2008目睹中国电视之怪现状

近两个月来,本刊网站的论坛里又不太安静。有个叫"高清迷"的香港网友遭到了广东一些网友的质疑。彼此论战的焦点大部分在说香港电视好看或不好看。"高清迷"网友说大陆电视越来越好,水平已经超过香港的电视节目。广东网友们则是缅怀香港电视的辉煌历史。这原本是简单的我说你好你说我好,互相捧场的事情,但是网络的奇妙性在于事情并没有朝积极的方向发展,其结果是吵架不可避免的发生了。外来的和尚是不是会念经,我们先不去管他。重要的是我们要弄清楚自己是怎么回事。本文,是专业电视人对我国各省卫视台做的调查评估。让我们了解一下我国的电视台的现状吧。     

上海慕尼黑电子展暨同期展会见闻

2007年3月21日～23日的上海新国际博览中心是格外的热闹,超过2万名来自电子行业的专业观众汇聚与此.吸引他们来到这里的原因就是慕尼黑上海电子展,慕尼黑上海激光、光电展(LASER. World of Photonics China)、中国国际半导体设备、材料、生产和服务展览暨研讨会(SEMICON China),以及中国国际电子电路展览会(CPCA Show)四大电子业权威品牌展联合在此举行.     

ADSL服务

现在使用ADSL上宽带网的用户是越来越多了,对ADSL设备的维护也成了一个不容忽视的问题.只有维护保养好它,不但让你的"宽带之旅"省心又省力,还能延长其寿命.ADSL的维护可分为软件和硬件两个方面来分析,软件主要是PPPOE协议的问题,和计算机本身的气操作系统,和网卡方面的事情.硬件主要是局端的节点设备,和用户端猫的问题.还有通信的线路等一些因素.     

命题逻辑中代数学的影子

命题逻辑是一个以命题为基本研究对象的数学化的逻辑系统,命题逻辑是数理逻辑的基础,也是计算机科学与技术的理论基础.为了深入理解命题逻辑,将命题逻辑与一般的代数学进行比较,从6个方面简要总结和论述命题逻辑中代数学的一些思想和方法,使得读者能从中体会到代数学的一些思想和方法在命题逻辑中的应用.     

不一样的热插拔(hot swap)控制器

引言 热插拔(hot swapping)的定义是从一块正在通电运作中的背板(backplane)上插入或移除电路板.这项技术被广泛应用在电信服务器(telecom servers)、USB界面、火线(firewire)界面和 CompactPCI应用等[参考1].这种技术可在维持系统背板的电压下,更换发生故障的电路板,而同时系统中其它正常的电路板仍可保持运作.     

从跨国公司CEO扎堆访华说起

11月1日,似乎是个好日子!来自英特尔、EMC、思科的3位跨国公司CEO均选在这一天访华,并宣布其在中国市场大手笔的战略投入. 11月2日,来自全球最大显卡芯片厂商NVIDIA公司的联合创始人、总裁兼CEO黄仁勋借访华之际,在清华大学美术学院报告厅进行了"GPU--还原一个真世界"的演讲.     

FEW-NNN: A Fuzzy Entropy Weighted Natural Nearest Neighbor Method for Flow-Based Network Traffic Attack Detection

Attacks such as APT usually hide communication data in massive legitimate network traffic, and mining structurally complex and latent relationships among flow-based network traffic to detect attacks has become the focus of many initiatives. Effectively analyzing massive network security data with high dimensions for suspicious flow diagnosis is a huge challenge. In addition, the uneven distribution of network traffic does not fully reflect the differences of class sample features, resulting in the low accuracy of attack detection. To solve these problems, a novel approach called the fuzzy entropy weighted natural nearest neighbor(FEW-NNN) method is proposed to enhance the accuracy and efficiency of flowbased network traffic attack detection. First, the FEW-NNN method uses the Fisher score and deep graph feature learning algorithm to remove unimportant features and reduce the data dimension. Then, according to the proposed natural nearest neighbor searching algorithm(NNN_Searching), the density of data points, each class center and the smallest enclosing sphere radius are determined correspondingly. Finally, a fuzzy entropy weighted KNN classification method based on affinity is proposed, which mainly includes the following three steps: 1、 the feature weights of samples are calculated based on fuzzy entropy values, 2、 the fuzzy memberships of samples are determined based on affinity among samples, and 3、 K-neighbors are selected according to the class-conditional weighted Euclidean distance, the fuzzy membership value of the testing sample is calculated based on the membership of k-neighbors, and then all testing samples are classified according to the fuzzy membership value of the samples belonging to each class;that is, the attack type is determined. The method has been applied to the problem of attack detection and validated based on the famous KDD99 and CICIDS-2017 datasets. From the experimental results shown in this paper, it is observed that the FEW-NNN method improves the accuracy and efficiency of flow-based network traffic attack detection.     

追日

去年10月一个温暖的早晨,在澳大利亚内陆深处,14名麻省理工学院的学生和校友上午6点就爬出了他们的睡袋,准备车队,进行又一天的艰苦驾驶,在护卫队的护送下,他们驶过一段平坦、笔直、炎热、灰尘弥漫的道路.领头的车辆迎着其他车流,形成了一个缓冲带,一辆货车断后以监测整个队伍的进程.     

Design of Diode Type Un-Cooled Infrared Focal Plane Array Readout Circuit

The diode infrared focal plane array uses the silicon diodes as a sensitive device for infrared signal measurement. By the infrared radiation, the infrared focal plane can produces small voltage signals. For the traditional readout circuit structures are designed to process current signals, they cannot be applied to it. In this paper,a new readout circuit for the diode un-cooled infrared focal plane array is developed. The principle of detector array signal readout and small signal amplification is given in detail. The readout circuit is designed and simulated by using the Central Semiconductor Manufacturing Corporation (CSMC) 0.5 μm complementary metal-oxide-semiconductor transistor (CMOS) technology library. Cadence Spectre simulation results show that the scheme can be applied to the CMOS readout integrated circuit (ROIC) with a larger array, such as 320×240 size array.     

抓住流动性机遇推动多层次资本市场建设

到2007年第一、二季度,积累已久的"流动性过剩"问题在中国经济生活中凸现,特别是对中国国内股市产生了巨大影响.由于对中国汇率的失重预期以及外贸顺差等双重因素,导致了"流动性过剩".其初始的"泄洪"渠道从投资房地产业转向主板A股市场.在这场被热炒的"流动性过剩"盛宴中,代表创新与可持续性发展的高新技术产业巨头企业们开始纷纷回归A股上市.     

掺氮ZnSe外延层的光致发光研究

报导了掺氮ＺｎＳｅ外延层的光致发光,研究了与氮受主有关的发光峰随温度和激发强度的变化关系．１０Ｋ下施主－受主对发光峰随激发强度的增加向高能方向移动,且峰强呈现饱和趋势．在１０～３００Ｋ温度范围光致发光谱表明,随着温度增加,由于激子在受主束缚激子态和施主束缚激子态之间转移,施主束缚激子发光峰强度相对受主束缚激子发光峰强度增加     

GaP：N液相外延层中杂质对PL谱的影响

借助低温光致发光方法测量了ＧａＰＮ双液相外延材料ＰＬ谱，结果表明：辐射复合效率高的材料ＰＬ谱基本上由孤立Ｎ和ＮＮｉ等束缚激子尖锐峰组成；发光效率较低的ＰＬ谱含有ＤＡ对辐射跃迁的钟形谱上迭加ＮＮｉ峰．分析了谱峰的性质，阐明了提高ＧａＰＮ外延片发光效率的制备工艺途径     

多层In_(0.55)Al_(0.45)As/A_(0.5)Ga_(0.5)As量子点的变温光致发光研究

测量了自组织多层In0.55Al0.45As/Al0.5Ga0.5As量子点的变温光致发光谱,同时观察到来自浸润层和量子点的发光,首次直接观察到了浸润层和量子点之间的载流子热转移.分析发光强度随温度的变化发现浸润层发光的热淬灭包括两个过程:低温时浸润层的激子从局域态热激发到扩展态,然后被量子点俘获;而温度较高时则通过势垒层的X能谷淬灭.利用速率方程模拟了激子在浸润层和量子点间的转移过程,计算结果与实验符合得很好     

细菌视紫红质三阶非线性光感应超快过程研究

用前向立体筒并四波混频实验对光能转换生物分子细菌视紫红质（bR)作三阶非线性光学超快过程研究,观察到时间响应由快成份和慢成份组成,用激子们相空间充满理论和构形变化模型分别给予动力学机制解释,快成份对应于自由电子－空穴对形成的激子,慢居份对应于无辐射衰变形成的极化子,通过对实验曲线的数学拟合,得到激子饱和密度和激子长度,激子和极化子寿命,以及极化子形成效率等动力学参数。     

ZnSeTe／ZnSe量子阱中Te等电子陷阱的静压光子发光谱研究

测量了ZnSe0.92Te0.08/ZnSe超晶格量子阱材料在77K时0-7.8GPa静压下的光致发光谱。观察到ZnSe0.92Te0.08阱层中Te等电子陷阱上的束缚洋鬼子发光，发现它的压力系数比ZnSe带边发光的压力系数小的约50%，表明Te等电子陷阱对激子的束缚势是相当局域的。还观察到了激子在ZnSe0.92Te0.08阱层中的Te等电子陷阱能级与相邻（CdSe)1/(ZnSe)3短周期超晶格之间的转移现象。     

Direct and Indirect Exciton Dynamics in Few‐Layered ReS2 Revealed by Photoluminescence and Pump‐Probe Spectroscopy

Atomically thin‐layered ReS₂ with a distorted 1T structure has attracted attention because of its intriguing optical and electronic properties. Here, the direct and indirect exciton dynamics of a three‐layered ReS₂ is investigated by polarization‐resolved transient photoluminescence (PL) and ultrafast pump‐probe spectroscopy. The various time scales of the decay signals of the time‐resolved PL (<10 ps), with monitoring of the populations of electron–hole pairs (exciton), and the transient differential reflectance (≈1 and 100 ps), with monitoring of the populations of electrons and/or holes in the excited states, are observed. These results reveal the characteristic exciton dynamics: rapid relaxation of direct excitons (electron–hole pairs) and slow relaxation of the momentum‐mismatched indirect excitons accompanied by a one‐phonon emission process. These findings provide important information regarding the indirect bandgap nature of few‐layered ReS₂ and its characteristic exciton dynamics, boosting the understanding of the novel electronic and optical properties of atomically thin‐layered ReS₂.     

Temperature dependent optical properties of self-organized InAs/GaAs quantum dots

We report photoluminescence (PL), time-resolved PL, and PL excitation experiments on InAs/GaAs quantum dots (QDs) of different size as a function of temperature. The results indicate that both the inhomogeneous properties of the ensemble and the intrinsic properties of single QDs are important in understanding the temperature-dependence of the optical properties. With increasing temperature, excitons are shown to assume a local equilibrium distribution between the localized QD states, whereas the formation of a position-independent Fermi-level is prevented by carrier-loss to the barrier dominating thermally stimulated lateral carrier transfer. The carrier capture rate is found to decrease with increasing temperature and, at room temperature, long escape-limited ground state lifetimes of some 10 ps are estimated. PL spectra excited resonantly in the ground state transition show matching ground state absorption and emission, indicating the intrinsic nature of exciton recombination in the QDs. Finally, the PL excitation spectra are shown to reveal size-selectively the QD absorption, demonstrating the quantum-size effect of the excited state splitting.     

Recombination of self-trapped excitons in silicon nanocrystals grown in silicon oxide

The kinetics of photoluminescence (PL) and steady-state PL from silicon nanocrystals formed in the SiO₂ matrix by silicon ion implantation were studied experimentally for the first time in the temperature range from liquid-helium to room temperature. A dramatic increase in the photoluminescence decay time, accompanied by PL intensity quenching, is observed below 70 K. The results obtained indicate that the silicon nanocrystal PL arises from radiative recombination of excitons self-trapped at the silicon nanocrystal-SiO₂ interface.     

Photoexcitation dynamics in polythiophene/fullerene blends for photovoltaic applications

We used the transient and steady state photomodulation spectroscopies for studying the photoexcitations dynamics in blends of regio-regular poly(3-hexylthiophene) (RR-P3HT) and fullerene in a broad spectral range from 0.13 to 2.25 eV. We found that both localized polarons and singlet excitons are instantaneously photogenerated in the blends. However the photogeneration process of delocalized polarons which contribute to the photocurrent proceeds in two steps: first, within a couple of ps the excitons generated in the polymer domains populate the charge transfer complex states at the RR-P3HT/fullerene interfaces; this is followed by the charge transfer ionization into delocalized charge polarons in the polymer and fullerene constituents within ～20 ps. In contrast, the localized polaron dynamics are unrelated with the excitons and delocalized polarons dynamics. We also report on the occurrence of ultrafast quantum interference anti-resonances between photoinduced infrared-active vibrations and the delocalized polaron band in the blends, which shows the delocalization character of the photogenerated charges that contribute to the photocurrent.     

Photoluminescence of silicon nanocrystals under the effect of an electric field

The effect of an electric field on photoluminescence (PL) of silicon nanocrystals formed in silicon dioxide by ion implantation with subsequent annealing has been studied. Application of an electric field leads to an increase in PL intensity by ～10% at low temperatures and an electric field strength of 12 kV/cm and to its decrease at temperatures above 20 K. The increase in exciton PL intensity in an electric field is inconsistent with the model of recombination of quantum-confined excitons in nanocrystals. The effect can be described in terms of a model of recombination of self-trapped excitons formed at the interface between a Si nanocrystal and SiO₂.