A Parallel Hill Climbing Algorithm for Pushing Dependent Data in Clients–Providers–Servers Systems

The up-link bandwidth in satellite networks and in advanced traffic wireless information system is very limited. A server broadcasts data files provided by different independent providers and accessed by many clients in a round-robin manner. The clients who access these files may have different patterns of access. Some clients may wish to access several files in any order (AND), some wish to access one out of several files (OR), and some clients may access a second file only after accessing another file (IMPLY). The goal of the server is to order the files in a way that minimizes the access time of the clients given some a priori knowledge of their access patterns. An appropriate clients–servers model was recently proposed by Bay-Noy, Naor and Schieber. They formulated three separate problems and proposed an algorithm that evaluates certain number of random permutations and chooses the one whose access time is minimized. In this paper, we formulate a combined AOI (AND-OR-IMPLY) problem, and propose to apply a parallel hill climbing algorithm (to each of the four problems), which begins from certain number of random permutations, and then applies hill climbing technique on each of them until there is no more improvement. The evaluation time of neighboring permutations generated in hill climbing process is optimized, so that it requires O(n) time per permutation instead of O(n ²) time required for evaluating access time of a random permutation, where n is the number of files the server broadcasts. Experiments indicate that the parallel hill climbing algorithm is O(n) times faster that random permutations method, both in terms of time needed to evaluate the same number of permutations, and time needed to provide a high quality solution. Thus the improvement is significant for broadcasting large number of files.     

Li掺杂量对Li-N共掺ZnO薄膜光学性能的影响

本文利用溶胶-凝胶旋涂法在玻璃衬底上制备了 本征、N单掺和Li-N共掺的ZnO薄膜。 研究Li掺杂量的改变对薄膜的晶体结构、表面形貌、透过性能和发光性能的影响。采用了紫 外-可见分光光度计(UV-VIS)、光致发光谱(PL)、扫描电子显微镜(SEM)和X射线衍 射 仪(XRD)等表征手段对样品进行了测试。结果表明:Li掺杂量的改变对薄膜的结构和性能 都有一定的影响,随着Li掺杂量的增加,(002)衍射峰强度增大,晶 粒尺寸先增加后减小, 紫外发射峰的强度和薄膜的透过性能同样是先增强后减弱。当Li元素的原子比为6at%时, 薄膜的c轴择优取向明显,结晶性能最好,薄膜紫外发光最强,透过率最大。     

有线数字电视机顶盒高清交互终端软件统一平台的构建与实现

“有线数字电视机顶盒高清交互终端软件统一平台”是一种建立在不同类型机顶盒硬件基础上的系统软件,向下提供跨硬件平台的接口,实现对硬件平台的操作;向上提供应用程序开发接口,实现与上层应用程序的对接。该平台实现了机顶盒软硬件的分离,解决了机顶盒软件升级难度大、成本高、周期长和部署新业务困难的难题,同时支持高清交互业务的实现,提高了广电网络技术应用水平和服务质量。该平台通过在山西晋中、长治等地有线电视网络近三年的规模应用,取得了良好的经济效益和社会效益。     

The measurement of carbon dioxide transmission of edible films by a static method

A static method is proposed for the measurement of CO₂ transmission of edible films. It is based on the absorption of CO₂ transmitted through the film on an absorbent ascarite II. Water is evolved during absorption of CO₂ by ascarite II and that is absorbed by a desiccant, anhydrous CaCl₂. Total CO₂ transmission is determined from the increase in weight of the absorbents. The transmission parameters, CO₂ transmission rate (CO₂TR), CO₂ permeance and CO₂ permeability (CO₂P), are also calculated. The edible film used was composed of methyl cellulose and polyethylene glycol. An attempt was made to determine the optimum amounts of ascarite II and CaCl₂ to be used. Finally, the effect of CO₂ pressure on the transmission parameters was also examined. CO₂TR was found to increase with increasing pressure while CO₂ permeance and CO₂P values were found to decrease with increasing pressure. © 1999 Society of Chemical Industry     

A generalized correlation attack on a class of stream ciphers based on the Levenshtein distance

A statistical approach to cryptanalysis of a memoryless function of clock-controlled shift registers is introduced. In the case of zero-order correlation immunity, an algorithm for a shift register initial state reconstruction based on the sequence comparison concept is proposed. A constrained Levenshtein distance relevant for the cryptanalysis is defined and a novel recursive procedure for its efficient computation is derived. Preliminary experimental results are given and open theoretic problems are discussed.Following [11], a Boolean function f(x ₁,..., x _n) is said to be mth-order correlation immune if m is the maximum integer such that the random variable f(X ₁,..., X _n) is statistically independent of every set of m random variables chosen from the balanced and independent binary random variables X ₁,..., X _n.     

New neural method for bias dependent noise modelling of microwave transistors

A new method for accurate determination of noise parameters of microwave transistors for various bias conditions is proposed in this paper. The proposed model consists of a transistor empirical noise model (modification of Pospieszalski’s noise model) and two artificial neural networks. With the aim to avoid extraction of the empirical model parameters for each bias point, an artificial neural network is used to introduce bias-dependence of the equivalent circuit parameters. Accuracy of such bias-dependent model is further improved by using an additional neural network aimed to correct the noise parameters’ values. The proposed modeling approach is exemplified by modelling of a MESFET device in packaged form. The noise parameters obtained by the simulation agree well with the measured data.     

The application of Ramo's theorem to the impulse response calculation of a reach-through avalanche photodiode

A method for calculation the impulse response of a depletion layer of a semiconductor device based on Ramo's theorem is described. Using this method the impulse response of a reach-through avalanche photodiode is derived.     

A multimodal hand-based verification system with an aliveness-detection module

This paper presents a multimodal biometrie verification system based on the following hand features: palmprint, four digitprints and four fingerprints. The features are obtained using the Karhunen-Loève transform based approach, and information fusion at the matching-score level was applied. We experimented with different resolutions of the regions of interest, different numbers of features and several normalization and fusion techniques at the matching-score level. To increase the reliability of the system to spoof attacks we included an aliveness-detection module based on thermal images of the hand dor sa. The verification performance when using a system configuration with optimum parameters, i.e., resolution, number of features, normalization and fusion technique, showed an equal error rate (EER) of 0.0020%, which makes the system appropriate for the implementation of high-security biometric systems.     

Error probability analysis of bit-interleaved coded modulation

This correspondence presents a simple method to accurately compute the error probability of bit-interleaved coded modulation (BICM). Thanks to the binary-input output-symmetric (BIOS) nature of the channel, the pairwise error probability (PEP) is equal to the tail probability of a sum of random variables with a particular distribution. This probability is in turn computed with a saddlepoint approximation. Its precision is numerically validated for coded transmission over standard Gaussian noise and fully interleaved fading channels for both convolutional and turbo-like codes.