Analysis and Simulation for Capacity of Time Division-Synchronous Code Division Multiple Access System

Capcity both in uplink and downlink of TD-SCDMA (time division-synchronous code division multiple access) system is studied in a multi-cell environment. The theoretical expressions of the mean of intercell interference in uplink and the mean of sum of power allocation in downlink are given, by which uplink and downlink capacity is analyzed. Furthermore, we give the simulation models for both uplink and downlink capacity. The results from theoretical analysis and simulation fit very well. In the end, the maximum number of users that TD-SCDMA system can serve for 12.2 k speech service is given.

Implementing Discretionary Access Control with Time Character in Linux and Performance Analysis

DAC （Discretionary Access Control Policy） is access control based on ownership relations between subject and object, the subject can discretionarily decide on that who, by what methods, can access his owns object. In this paper, the system time is looked as a basic secure element. The DAC_T （Discretionary Access Control Policy with Time Character） is presented and formalized. The DAC_T resolves that the subject can discretionarily decide that who, on when, can access his owns objects. And then the DAC_T is implemented on Linux based on GFAC （General Framework for Access Control）, and the algorithm is put forward. Finally, the performance analysis for the DAC T Linux is carried out. It is proved that the DAC T Linux not only can realize time constraints between subject and object but also can still be accepted by us though its performance have been decreased.

A 65-nm 1-Gb NOR floating-gate flash memory with less than 50-ns access time

This paper presents a 65-nm 1-Gb NOR-type floating-gate flash memory,in which the cell device and chip circuit are developed and optimized.In order to solve the speed problem of giga-level NOR flash in the deep submicron process,the models of long bit-line and word-line are first given,by which the capacitive and resistive loads could be estimated.Based on that,the read path and key modules are optimized to enhance the chip access property and reliability.With the measurement results,the flash memory cell presents good endurance and retention properties,and the macro is operated with 1-ls/byte program speed and less than 50-ns read time under 3.3 V supply.

Accessibility Comparison and Spatial Differentiation of Xi’an Scenic Spots with Different Modes Based on Baidu Real-time Travel

A study of the accessibility of a city’s scenic spots via different travel modes can contribute to optimization of tourism-related transportation while improving tourists’ travel-related satisfaction levels and advancing tourism. We systematically analyzed the accessibility of 56 scenic spots in Xi’an City, China, via car and public transport travel modes using the real-time travel function of the Baidu Maps API(Application Programming Interface) along with spatial analysis methods and the modal accessibility gap index of scenic spots. We obtained the following results. First, maximum and minimum travel times using public transport exceeded those using cars. Moreover, the accessibility of scenic spots via cars and public transport presented a circular spatial pattern of increasing travel time from the center to the periphery. Contrasting with travel by public transport, car travel showed a clear time-space compression effect. Second, accessibility of the scenic spots via cars and public transport showed some spatial heterogeneity, with no clear advantages of car accessibility in the central urban area. However, advantages of car accessibility were increasingly evident moving from the center to the periphery. Third, whereas the correlation of the modal accessibility gap index of scenic spots in Xi’an with global space was significantly positive, local spatial interdependence was only evident in some inner city areas and in marginal areas. Moreover, spatial heterogeneity was evident in two regions but was insignificant in other areas, indicating that the spatial interdependence of the modal accessibility gap index in most scenic spots was not apparent in terms of the overall effect of public transport routes, road networks, and the distribution of scenic spots. The improvement of public transport coverage in marginal areas and the optimization of public transport routes in central urban areas are essential tasks for improving travel using public transport in the future.

User-Based Discrete-Time Queuing Analysis for Opportunistic Spectrum Access in Cognitive Radio Networks

In cognitive radio networks, the spectrum utilization can be improved by cognitive users opportunistically using the idle channels licensed to the primary users. However, the new arrived cognitive users may not be able to use the channel immediately since the channel usage state is random. This will impose additional time delay for the cognitive users. Excessive waiting delay can make cognitive users miss the spectrum access chances. In this paper, a discrete-time Markov queuing model from a macro point of view is provided. Through the matrix-geometric solution theory, the average sojourn time for cognitive users in the steady state before accessing the spectrum is obtained. Given the tolerant delay of cognitive users, the macro-based throughput is derived and an access control mechanism is proposed. The numerical results show the effects of service completion probability on average sojourn time and throughput. It is confirmed that the throughput can be obviously improved by using the proposed access control mechanism. Finally, the performance evaluations based on users are compared to that based on data packets.

A passive optical network based on optical code division multiplexing and time division multiple access technology

A passive optical network （PON） scheme based on optical code division multiplexing （OCDM） for the downstream traffics is proposed and analyzed in detail. In the PON, the downstream traffics are broadcasted by OCDM technology to guarantee the security, while the upstream traffics pass through the same optical fiber by the common time division multiple access （TDMA） technology to decrease the cost. This schemes are denoted as OCDM/TDMA-PON, which can be applied to an optical access network （OAN） with full services on demand, such as Internet protocol, video on demand, tele-presence and high quality audio. The proposed OCDM/TDMA-PON scheme combines advantages of PON, TDMA, and OCDM technology. Simulation results indicate that the designed scheme improves the OAN performance, and enhances flexibility and scalability of the system.

Role of Time-Domain Based Access Control Model

While Role-Based Access Control Model (RBAC) is being analyzed, the concept of Role of Time-domain Based Access Control Model (T-RBAC) is put forward. With time-domain added, both time-domain and authority control roles. The basic idea of T-RBAC is introduced and described formally, and the safely of this model is analyzed. The research shows that T-RBAC fulfills both rules of information security, which are principle of least privilege and separation of duties. With practical application of T-RBCA, it can handle most of the time-related or authority-related problems. What’s more, it also increases the security level, flexibility and dynamic adaptation of the system and has lower complexity than system only handled by authority. This model also can solve conflicts caused by authority.

Digital compass for multi-user beam access in mmWave cellular networks

Beamforming in stand-alone Millimeter-Wave(mmWave)communications results in prolonged access times and latencies due to the increased number of measurements required to determine the optimal beam directions at the Mobile Station(MS)and Base Station(BS),returning the highest received signal level.Therefore,dynamic and fast access schemes that meet the Third-Generation Partnership Project(3GPP)specifications are required here.Therefore,in this paper,a novel initial access scheme is proposed for multiple MS users by leveraging for the first time a digital compass in the access procedure.Namely,when a new MS joins the footprint of a BS,it probes the channel for beacon signaling about the BS direction,i.e.,broadcasted by a neighboring MS that completed beam association at previous time steps.Then,a digital compass is utilized to adjust the coordinates of the BS according to the location of the new MS.The proposed scheme is applied for a single and multi-user settings at various broadcasting approaches.This includes a single associated MS user that broadcasts information to a single incoming MS user,a single user that broadcasts signals to multiple incoming users,or all multiple associated users broadcast to multiple incoming users.Overall,the proposed schemes yield in notable efficiency in terms of the computational complexity,access times,power and energy consumption as compared to existing access schemes.Further,high success rates are achieved at the detriment of relatively higher cost.

基于Access数据库的护理部办公系统设计与应用

[目的]探讨基于Access数据库的护理部办公系统的设计及应用情况,以提升护理管理效能。[方法]将护理管理人员标准、护理部年度SWOT分析、目标管理及计划、个人ABC时间管理、工作实施与监控等内容通过Access数据库进行编程、整合,形成系统化、整体化的信息管理平台,利用区域共享等技术支持,进行护理部办公信息化管理。[结果]开发的护理部办公系统具有信息录入、分类、修改、删除、查询以及统计筛选功能,软件系统界面清晰、美观,操作简单,存储安全,试用5个月,运行状态稳定。系统使用前后护理管理人员工作任务按时完成率、护理部工作满意度比较差异有统计学意义(P<0.05)。[结论]基于Access数据库的护理部办公系统实现了信息化管理,目标管理指标监控及时,系统数据分析支持护理决策,有效提高了管理效能。

Fiber-based multiple access timing signal synchronization technique

A fiber-based,multiple access timing signal synchronization scheme is demonstrated.By coupling out the bidirectional transmission signals,a highly stable timing signal can be recovered at arbitrary points along the fiber with the help of the loop delay message broadcasted via ethernet from the local module.The experiment is carried out on a 30-km fiber placed in a temperature-controlled box.In one-day period,when the round trip fiber transfer delay fluctuation is60 ns,the fluctuations of the stabilized timing signal from the download and the remote modules were only ±125 ps and±100 ps,respectively.Also,the system error caused by transmission path asymmetry and thermal drift is calibrated,and a100-ps magnitude synchronization accuracy is realized.This method could provide new insights into the construction of a fiber-based time transfer network.

基于ACCESS的产品实时库存及质量检验管理系统

为使产品库存和产品质量检验数据管理规范化、便捷化,并且在企业内部局域网实现数据共享,对企业的库存管理方式和产品质检过程进行充分调研,针对中小型机械制造类企业的实际需求,利用Microsoft Access 2003开发了产品实时库存及质量检验管理系统。实践证明,该数据库系统解决了企业旧的台账管理方式中数据处理机械化、低效率问题。

A timeslot assignment scheme for cluster-tree based wireless sensor network

Many efforts have been made to develop time division multiple access （TDMA） slots allocation in a multi-hop converge-cast wireless sensor network （WSN）, however, most of them either use complex algorithm or concern frames only without simultaneous transmission in a single slot. In this paper, we present a timeslot assignment scheme for cluster-tree-based TDMA WSN, co：＇ering three frequently used working modes in practical applications. The shortest frame formed can guarantee real-time conununication and is also facilitated for message and slot integration, since timeslots allocated to a single node are continuous. During allocation processes, the algorithms are distributed and light-weighted. The experiment resulted from a WSN prototype system shows that our scheme can achieve a good reliability.

Multi-Threat Real-Time Separating System

This paper describes a multi-threat real-time separating system for broadband anti-radiation missile seeker. It presents a method, with a dual-port memory as comparer, to perform PF and PW hardware real-time separation and to determine the time-of-arrival (TOA) by use of sequential difference histogram (SDIF). The method has been applied to practice, which has achieved good results.

The effect of urine pregnancy testing on timing of accessing antenatal care and abortion services in Western Nigeria

Objective: Effective confirmation of pregnancy is a basic component of reproductive health services. It is a determinant for accessing antenatal care (ANC) if the pregnancy is wanted and abortion services if the pregnancy is unwanted. This study examined the effect of urine pregnancy testing in the timing of presentation for pregnancy care. Method: A cross-sectional study was conducted among 320 women presenting for antenatal care and 300 women presenting for abortion at private sector clinics in Western Nigeria. Results: The median age at first presentation was 20 weeks for ANC clients and 8 weeks for abortion clients. Obtaining urine pregnancy test of one’s accord was associated with a decrease in the gestational age at presentation of 3.7 weeks and 1.5 weeks for antenatal and abortion clients, respectively, independent of all other factors. Conclusion: Bearing in mind that the clinical benefit and public health impact of early presentation for antenatal and abortion services are unequivocal, strategies aimed at decreasing gestational age at presentation for pregnancy care should be given priority. “Fast-track” urine pregnancy testing services should be promoted in the private and public clinics in Nigeria.

考虑综合经济性的风光配电网储能优化配置

在配电网中配置储能系统可以有效缓解风光接入对配电网产生的影响,提升对风光的消纳能力、减少电压偏差等,而储能接入的位置和容量不同会对配电网产生不同的影响。首先分析储能建设过程中的主要费用,考虑基于分时电价下的网损成本和峰谷差收益,以年综合成本、配电网的日节点电压偏差和最小为目标,建立配电网储能选址定容模型,采用改进多目标遗传二代算法(improved multi-objective nondominated sorting genetic Ⅱ algorithm, INSGA-Ⅱ)对模型进行求解,利用改进理想点决策法(improved ideal point based decision, IIPBD)来选取最优配置方案,最后在IEEE-33节点模型中对方案进行验证。仿真结果表明:使用INSGA-Ⅱ算法进行求解时最终决策出的储能配置方案实现了成本最小,并且显著提升了电压的稳定性,验证了改进后算法的优良性和所提出的储能优化配置方案的有效性。

Hybrid Deep Learning-Based Adaptive Multiple Access Schemes Underwater Wireless Networks

Achieving sound communication systems in Under Water Acoustic(UWA)environment remains challenging for researchers.The communication scheme is complex since these acoustic channels exhibit uneven characteristics such as long propagation delay and irregular Doppler shifts.The development of machine and deep learning algorithms has reduced the burden of achieving reli-able and good communication schemes in the underwater acoustic environment.This paper proposes a novel intelligent selection method between the different modulation schemes such as Code Division Multiple Access(CDMA),Time Divi-sion Multiple Access(TDMA),and Orthogonal Frequency Division Multiplexing(OFDM)techniques using the hybrid combination of the convolutional neural net-works(CNN)and ensemble single feedforward layers(SFL).The convolutional neural networks are used for channel feature extraction,and boosted ensembled feedforward layers are used for modulation selection based on the CNN outputs.The extensive experimentation is carried out and compared with other hybrid learning models and conventional methods.Simulation results demonstrate that the performance of the proposed hybrid learning model has achieved nearly 98%accuracy and a 30%increase in BER performance which outperformed the other learning models in achieving the communication schemes under dynamic underwater environments.

Joint power control based on service factor for code division multiple access system

An important feature of the traffic in mobile networks is burstiness. Drawbacks of conventional power control algorithms for time division duplex （TDD）-code division multiple access （CDMA） systems are analyzed. A joint power control algorithm based on service factor is presented to address the TDD-CDMA mobile services in the burst mode according to the Markov modulated Bernoulli process. The joint power control equation is derived. A function model is developed to verify the new algorithm and evaluate its performance. Simulation results show that the new power control algorithm can estimate interference strength more precisely, speed up convergence of power control, and enhance power efficiency and system capacity. It is shown that the proposed algorithm is more robust against link gain changes, and outperforms the reference algorithms.

Space-division multiple access for CDMA multiuser underwater acoustic communications

Time reversal mirror （TRM） can use the physical characteristics of the underwater acoustic （UWA） channel to focus on the desired user in multi-user UWA communication. The active average sound intensity （AASI） detector can estimate all azimuths of users with the same frequency band at the same time in order to achieve directional communication by vector combination. Space-division multiple access （SDMA） based on TRM combined with the AASI detector is proposed in this paper, which can make the capacity of the code division multiple access （CDMA） UWA system significantly increase. The simulation and lake test results show that the 7-user UWA multi-user system can achieve low bit error communication.

心临其境——“云旅游”中临场感对旅游意愿的影响研究

“云旅游”是一个受众广、效果佳的营销渠道,“心临其境”的临场感对旅游意愿具有重要的影响。基于S-O-R(Stimuli-Organism-Response,S-O-R)模型,引入临场感理论,探究临场感对旅游意愿的作用,并将感知收益作为中介变量,上网时长作为调节变量,研究临场感对旅游意愿的影响路径。文章依据375份调查问卷,采用结构方程模型进行实证研究,研究发现:临场感间接影响旅游意愿,社会临场感对旅游意愿的影响大于物理临场感;临场感对感知收益具有显著正向影响,感知收益在临场感对旅游意愿的影响中发挥完全中介作用;上网时长在临场感对旅游意愿的影响中发挥负向调节作用,即上网时长越长,临场感对旅游意愿的影响越弱。将临场感引入“云旅游”情景中,解释了“云旅游”过程中旅游意愿形成的具体过程,为旅游目的地设计“云旅游”产品提供理论依据与实践指导。

Practical Solutions for Reducing Container Ships' Waiting Times at Ports Using Simulation Model

The main challenge for container ports is the planning required for berthing container ships while docked in port.Growth of containerization is creating problems for ports and container terminals as they reach their capacity limits of various resources which increasingly leads to traffic and port congestion.Good planning and management of container terminal operations reduces waiting time for liner ships.Reducing the waiting time improves the terminal’s productivity and decreases the port difficulties.Two important keys to reducing waiting time with berth allocation are determining suitable access channel depths and increasing the number of berths which in this paper are studied and analyzed as practical solutions.Simulation based analysis is the only way to understand how various resources interact with each other and how they are affected in the berthing time of ships.We used the Enterprise Dynamics software to produce simulation models due to the complexity and nature of the problems.We further present case study for berth allocation simulation of the biggest container terminal in Iran and the optimum access channel depth and the number of berths are obtained from simulation results.The results show a significant reduction in the waiting time for container ships and can be useful for major functions in operations and development of container ship terminals.