Multi-Strategy Dynamic Spectrum Access in Cognitive Radio Networks: Modeling, Analysis and Optimization

Dynamic spectrum access(DSA) based on cognitive radios(CR) technique is an effective approach to address the "spectrum scarcity" issue. However, traditional CR-enabled DSA system employs only single DSA strategy, which might not be suited to the dynamic network environment. In this paper, we propose a multi-strategy DSA(MS-DSA) system, where the primary and the secondary system share spectrum resources with multiple DSA strategies simultaneously. To analyze the performance of the proposed MS-DSA system, we model it as a continuous-time Markov chain(CTMC) and derive the expressions to compute the corresponding performance metrics. Based on this, we define a utility function involving the concerns of effective throughput, interference quantity on primary users, and spectrum leasing cost. Two optimization schemes, named as spectrum allocation and false alarm probability selection, are proposed to maximize the utility function. Finally, numerical simulations are provided to validate our analysis and demonstrate that the performance can be significantly improved caused by virtues of the proposed MS-DSA system.

A Review in the Core Technologies of 5G: Device-to-Device Communication, Multi-Access Edge Computing and Network Function Virtualization

5G is a new generation of mobile networking that aims to achieve unparalleled speed and performance. To accomplish this, three technologies, Device-to-Device communication (D2D), multi-access edge computing (MEC) and network function virtualization (NFV) with ClickOS, have been a significant part of 5G, and this paper mainly discusses them. D2D enables direct communication between devices without the relay of base station. In 5G, a two-tier cellular network composed of traditional cellular network system and D2D is an efficient method for realizing high-speed communication. MEC unloads work from end devices and clouds platforms to widespread nodes, and connects the nodes together with outside devices and third-party providers, in order to diminish the overloading effect on any device caused by enormous applications and improve users’ quality of experience (QoE). There is also a NFV method in order to fulfill the 5G requirements. In this part, an optimized virtual machine for middle-boxes named ClickOS is introduced, and it is evaluated in several aspects. Some middle boxes are being implemented in the ClickOS and proved to have outstanding performances.

A distributed role-based access control model for multi-domain environments

Access control in multi-domain environments is an important question in building coalition between domains. Based on the RBAC access control model and the concepts of secure domain, the role delegation and role mapping are proposed, which support the third-party authorization. A distributed RBAC model is then presented. Finally implementation issues are discussed.

Accessing Multi-Source Geological Data through Network in MORPAS Software System

MORPAS is a special GIS (geographic information system) software system, based on the MAPGIS platform whose aim is to prospect and evaluate mineral resources quantificationally by synthesizing geological, geophysical, geochemical and remote sensing data. It overlays geological database management, geological background and geological abnormality analysis, image processing of remote sensing and comprehensive abnormality analysis, etc.. It puts forward an integrative solution for the application of GIS in basic-level units and the construction of information engineering in the geological field. As the popularization of computer networks and the request of data sharing, it is necessary to extend its functions in data management so that all its data files can be accessed in the network server. This paper utilizes some MAPGIS functions for the second development and ADO (access data object) technique to access multi-source geological data in SQL Server databases. Then remote visiting and congruous management will be realized in the MORPAS system.

A Random Multi-Access Method for Data Services in CDMA Cellular System

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New strategies for collision resolution of multi-access channel

The truncated binary exponential back-off algorithm is one of the most effective methods applied in collision resolution process of random multi-access channel.In this study,two new strategies are presented to improve the capability of the truncated binary exponential back-off algorithm.In the new strategies,the sizes of the initial window size or the operating window sizes are adjusted dynamically,which always bring a significant improvement for the self-adaptability of the original algorithm.A series of experiments are simulated and the results verify that the new strategies can make the implementation more stable and effective than the original algorithm.

Centralized Role-Based Access Control for Federated Multi-Domain Environments

The secure interaction among multiple security domains is a major concern. In this paper, we highlight the issues of secure interoperability among multiple security domains operating under the widely accepted Role Based Access Control （RBAC） model. We propose a model called CRBAC that easily establishes a global policy for roles mapping among multiple security domains. Our model is based on an extension of the RBAC model. Also, multiple security domains were composed to one abstract security domain. Also roles in the multiple domains are translated to permissions of roles in the abstract security domain. These permissions keep theirs hierarchies. The roles in the abstract security domain implement roles mapping among the multiple security domains. Then, authorized users of any security domain can transparently access resources in the multiple domains.

Access化学发光仪测定尿液β-人绒毛膜促性腺激素的实验评价

目的 探讨Access化学发光仪测定尿液 β 人绒毛膜促性腺激素 ( β HCG)的可行性。 方法 对测定尿液 β HCG的精密度、线性作实验观察 ,并与血清 β HCG测定作比较。对同一浓度 β HCG在不同尿中所测结果的准确性及影响因素作初步探讨。结果 混合尿液 β HCG测定的批内重复性 <3 .5 0 % ,批间 <6.0 0 % ,线性范围 0 .8～ 912IU/L ,与血清同水平HCG标本的相关性Y =0 .87X + 1.0 8,r =0 .993 7。结论 Access化学发光仪可用于测定尿液 β HCG ,但准确度比血清标本稍差。

基于主体-主导的Access程序设计教学策略研究

本文首先分析了以"教"和以"学"为中心的教学模式的学习理论和教学设计理论,在对它的可行性及必要性等进行研究的基础上,结合高校Access程序设计教学的具体情况,提出在高校Access程序设计教学中运用"双主"教学的主要策略,并在实践中进行运用,获得了较好的教学效果。

一种通用的Beyond 3G Multi-Radio接入架构

下一代移动通信网(Beyond 3G)是多种无线接入(Multi-Radio)共存的融合网络.如何有效集成异构无线网络,优化使用全部的无线资源是B3G研究领域内关键课题之一.在分析目前多种异构无线网络整合方案的基础上,借鉴欧洲IST 6th框架中Multi-Radio接入架构的基本思想,考虑在链路层实现异构无线网络之间的整合,从而提出一种通用B3G Multi-Radio接入架构模型,该模型可以无缝融合多种无线接入技术、有效利用全网无线资源.

Multi-features Based Approach for Moving Shadow Detection

In the video-based surveillance application, moving shadows can affect the correct localization and detection of moving objects. This paper aims to present a method for shadow detection and suppression used for moving visual object detection. The major novelty of the shadow suppression is the integration of several features including photometric invariant color feature, motion edge feature, and spatial feature etc. By modifying process for false shadow detected, the averaging detection rate of moving object reaches above 90% in the test of Hall-Monitor sequence.

An Overview of Non.Orthogonal Multiple Access

In recent years, non-orthogonal multiple access(NOMA) has attracted a lot of attention as a novel and promising power-domain us-er multiplexing scheme for Long-Term Evolution(LTE) enhancement and 5G. NOMA is able to contribute to the improvement ofthe tradeoff between system capacity and user fairness(i.e., cell-edge user experience). This improvement becomes in particularemphasized in a cellular system where the channel conditions vary significantly among users due to the near-far effect. In this arti-cle, we provide an overview of the concept, design and performance of NOMA. In addition, we review the potential benefits and is-sues of NOMA over orthogonal multiple access(OMA) such as orthogonal frequency division multiple access(OFDMA) adoptedby LTE, and the status of 3GPP standardization related to NOMA.

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST)

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST, also called the Guo Shou Jing Telescope) is a special reflecting Schmidt telescope. LAMOST’s special design allows both a large aperture (effective aperture of 3.6 m–4.9 m) and a wide field of view (FOV) (5°). It has an innovative active reflecting Schmidt configuration which continuously changes the mirror’s surface that adjusts during the observation process and combines thin deformable mirror active optics with segmented active optics. Its primary mirror (6.67m×6.05 m) and active Schmidt mirror (5.74m×4.40 m) are both segmented, and composed of 37 and 24 hexagonal sub-mirrors respectively. By using a parallel controllable fiber positioning technique, the focal surface of 1.75 m in diameter can accommodate 4000 optical fibers. Also, LAMOST has 16 spectrographs with 32 CCD cameras. LAMOST will be the telescope with the highest rate of spectral acquisition. As a national large scientific project, the LAMOST project was formally proposed in 1996, and approved by the Chinese government in 1997. The construction started in 2001, was completed in 2008 and passed the official acceptance in June 2009. The LAMOST pilot survey was started in October 2011 and the spectroscopic survey will launch in September 2012. Up to now, LAMOST has released more than 480 000 spectra of objects. LAMOST will make an important contribution to the study of the large-scale structure of the Universe, structure and evolution of the Galaxy, and cross-identification of multiwaveband properties in celestial objects.

Recovery of single event upset in advanced complementary metal-oxide semiconductor static random access memory cells

Using computer-aided design three-dimensional （3D） simulation technology, the recovery mechanism of single event upset and the effects of spacing and hit angle on the recovery are studied. It is found that the multi-node charge collection plays a key role in recovery and shielding the charge sharing by adding guard rings. It cannot exhibit the recovery effect. It is also indicated that the upset linear energy transfer （LET） threshold is kept constant while the recovery LET threshold increases as the spacing increases. Additionally, the effect of incident angle on recovery is analysed and it is shown that a larger angle can bring about a stronger charge sharing effect, thus strengthening the recovery ability.

基于Mi-Fi的多终端Access VPN接入研究与实现

为了解决多个Wi-Fi终端同时接入Access VPN的问题,采用运营商提供的专用APN技术,利用Mi-Fi和专用APN相结合设计了一种新型实现方案。通过双向NAT转换技术,不改变原网络结构和数据配置。实验结果表明,网络组建快捷,系统运行稳定,通过Mi-Fi实现的多终端接入与单机APN接入效果完全一致。

A Comparative Study of Acute Hemodynamic Effects of Multi -site Cardiac Pacing in patients with cardiac function NYHA class ⅠtoⅡ without bundle branch block

Objective To compare the acute hemodynamic effects of five different pacing modes in patients with cardiac function NYHA class Ⅰ to Ⅱ without bundle branch block (BBB). Methods This study included 12 patients (SSS 7, Ⅲ°AVB 5) undergoing pacemaker implantation. Right ventricular apex (RVA), right ventricular outflow tract (RVOT), right ventricular bifocal (RV-Bi), left ventricular base (LVB) and bi -ventricular (Bi-Ⅴ) pacing at 60 -80 ppm were done in VVI mode prior to implantation of DDD pacemaker. The cardiac index (CI), mean pulmonary artery pressure (mPAP) and pulmonary capillary wedge pressure (PCWP) were measured with Swan - Ganz thermodilution catheter after 5 minutes of each pacing mode. Results (1) Comparing to pacing at RVA (CI: 2. 41± 0. 38 L/min per m2, PCWP: 16. 7 ±3.3 mmHg), the CI increased and the PCWP decreased significantly in pacing at RVOT(CI: 2. 63 ± 0.46, PCWP: 13. 8±2. 3), LVB(CI: 2. 78±0.52, PCWP: 14. 4±3.1), RV-Bi(CI: 2. 83±0.57, PCWP: 12. 8± 2. 5) and Bi -Ⅴ pacing (CI: 2. 94± 0.60, PCWP: 12. 7±2. 5), P < 0. 01, respectively. (2) The CI of RV-Bi and Bi-Ⅴ pacing was higher than that of RVOT and LVB pacing, the PCWP was lower, P < 0. 05, respectively. (3) There was no significant difference between RV - Bi pacing and Bi-Ⅴ pacing in CI and PCWP. Conclusion There is no significant difference between RV - Bi pacing and Bi -V pacing in the acute hemodynamic effects; however,dual - site pacing is much better than single site pacing in that aspect for patients with cardiac function NYHA class Ⅰ to Ⅱ without BBB. Among single site pacing, the RVOT and LVB pacing is better than RVA pacing in cardiac function.

Ensuring Security, Confidentiality and Fine-Grained Data Access Control of Cloud Data Storage Implementation Environment

With the development of cloud computing, the mutual understandability among distributed data access control has become an important issue in the security field of cloud computing. To ensure security, confidentiality and fine-grained data access control of Cloud Data Storage (CDS) environment, we proposed Multi-Agent System (MAS) architecture. This architecture consists of two agents: Cloud Service Provider Agent (CSPA) and Cloud Data Confidentiality Agent (CDConA). CSPA provides a graphical interface to the cloud user that facilitates the access to the services offered by the system. CDConA provides each cloud user by definition and enforcement expressive and flexible access structure as a logic formula over cloud data file attributes. This new access control is named as Formula-Based Cloud Data Access Control (FCDAC). Our proposed FCDAC based on MAS architecture consists of four layers: interface layer, existing access control layer, proposed FCDAC layer and CDS layer as well as four types of entities of Cloud Service Provider (CSP), cloud users, knowledge base and confidentiality policy roles. FCDAC, it’s an access policy determined by our MAS architecture, not by the CSPs. A prototype of our proposed FCDAC scheme is implemented using the Java Agent Development Framework Security (JADE-S). Our results in the practical scenario defined formally in this paper, show the Round Trip Time (RTT) for an agent to travel in our system and measured by the times required for an agent to travel around different number of cloud users before and after implementing FCDAC.

MODELING MULTI-TRAFFIC ADMISSION CONTROL IN OFDMA SYSTEM USING COLORED PETRI NET

Call Admission Control (CAC) is one of the key traffic management mechanisms that must be deployed in order to meet the strict requirements for dependability imposed on the services provided by modern wireless networks. In this paper, we develop an executable top-down hierarchical Colored Petri Net (CPN) model for multi-traffic CAC in Orthogonal Frequency Division Multiple Access (OFDMA) system. By theoretic analysis and CPN simulation, it is demonstrated that the CPN model is isomorphic to Markov Chain (MC) assuming that each data stream follows Poisson distribution and the corresponding arrival time interval is an exponential random variable, and it breaks through MC's explicit limitation, which includes MC's memoryless property and proneness to state space explosion in evaluating CAC process. Moreover, we present four CAC schemes based on CPN model taking into account call-level and packet-level Quality of Service (QoS). The simulation results show that CPN offers significant advantages over MC in modeling CAC strategies and evaluating their performance with less computational complexity in addition to its flexibility and adaptability to different scenarios.

Research on A Master - slave Multi - microcomputers Control System for Hollow Spindle Fancy Yarn Spinning Machine

In this paper, a successfully studied and developed master - slave muld - microcomputers control system based on PC - BUS for hollow spindle fancy yarn spinning machine, mainly Its overall scheme, software and hardware construction, is introduced. Spinning experiments show that the system achieves satisfactory result. This system can solve the diftkultles of mechatronical fusion between domestic hollow splndk fancy yarn spuming muchine and its microcomputer control technology.

On the Representation of Multi-layer Woven Structure

A quantitative method is developed to identify the structures of multi-layer woven fabric in this study. Six structural parameters are selected to represent the fabric structure. With some design criteria for the reinforcement of textile composites, the relationships among the structural parameters are derived for different binding patterns of the fabric structure. The conditions, which meet the requirements of structural cell stability,are also discussed.