稀有气体的制取及工艺研究

对稀有气体的市场和发展进行了简述,对稀有气体的制取工艺进行了简单介绍,并对其进行了研究和探讨。结合国内外发展状况,提出了具体流程方案并进行了详细阐述,希望能促进气体分离行业的发展与进步。     

标准化概念定义的评论

本文阐述了标准概念定义的状况,总结了国际标准化组织和中国对标准化概念定义的历程,重点分析了国际标准化组织的标准化定义存在的问题,对国际标准化组织的标准化定义进行了分析和检验,对标准化的概念和定义的特性进行了理论性比较,对如何定义标准化概念进行了理性的讨论。     

监督工作在实验室管理体系运行中的作用

本文从认可准则对实验室监督工作的要求入手,对监督的意义和作用进行了阐述,同时对实验室监督工作现状进行了分析,并对监督工作的内容、方式和要求进行了论述。     

探究标准高分子分离膜材料及其研究进展

本篇论文就对高分子分离膜材料的运用和理论两方面进行了分析和探讨,对分离膜的性能,机理和类型进行介绍并对较为常见的一些高分子分离膜材料性能特征和适用特点进行了总结与分析,对近些年的高分子分离膜材料的制备与合成,应用和改变性能等的研发成果进行了阐述。     

工件偏载情况对双柱立车的影响分析

该文通过有限元分析及其理论计算2个方向对双柱立车工件偏载现象,对加工精度和使用寿命的影响进行了分析,对采用有限元分析方法解决实际问题的思路进行了剖析,对主轴系统受力状态进行了分析,指出了影响加工精度和机床使用寿命的关键参数,并从设计人员和使用人员的角度对偏载情况的注意事项进行了阐述,对于机床设计与维护具有一定的参考意义。     

某油田钻具失效统计分析

对某油田2002-2004年钻具失效情况进行了系统调查,查清了不同钻具的失效形式和失效次数。通过统计分析发现钻铤断裂次数最多,占钻具失效总数的比例最大。对钻铤断裂机理和受力状态进行了分析,认为钻铤断裂性质主要属于早期疲劳失效。对钻铤标准和实际使用状况进行了分析,找出了钻铤标准中存在的问题。对钻铤断裂原因从螺纹接头结构应力、残余应力和材料韧性等方面进行了分析,指出了导致钻铤断裂的产品质量问题。通过使用工况和钻井参数对钻铤的受力状态进行了分析,指出了使用操作对钻铤断裂的影响。最后对该油田依据上述结论采取措施后2009-2011年钻具失效情况进行了统计分析,发现钻具失效事故大幅度减少。     

高精度电阻测量方法及其应用

本文对电阻量测量中的电压电流法和比例测量法进行了比较和分析;对小电阻和大电阻测量方法进行了探讨,对电阻测量方法在铂电阻温度传感器测量中的应用进行了简要的介绍。     

某型车辆驾驶室内部噪声分析研究

建立了某型车辆驾驶室结构的三维有限元模型,对驾驶室进行了试验模态分析,得到了模态参数,检验和修正了结构的三维有限元模型,对驾驶室结构进行了动态响应分析.采用边界元法进行了驾驶室内部声学特性研究,对驾驶员耳旁的声压和声学灵敏度进行了分析,得出了驾驶室内声场的声学特性,对驾驶室结构提出改进措施,有效地降低了车内噪声.     

冰蓄冷专用风机盘管的研制

对自行研制的冰蓄冷系统专用风机盘管进行了阐述。对送风口附近存在的结雾和滴水现象进行了分析,提出了新的冰蓄冷系统专用风机盘管的设计方案,进而针对第一种方案进行了理论分析和设计计算。对相关工作进行了初步的展望。     

试述高分子压电复合材料研究进展标准

本文章就对一直以来高分子复合材料所进行研发的进展情况进行了介绍和分析,同时对高分子复合材料的优势和缺陷进行了分析和探讨。     

Delivery of pre‐stored videos for mobile clients with insufficient playback buffer and bounded delay guarantee

Abstract

A deterministic service model assisted by a sufficiently large playback buffer space can provide bounded delay guarantees for video packets and simplify network resource management. However, many popular mobile terminals do not have sufficient memory capacity for deterministic video services since the embedded memory is limited and needs to be shared by numerous software programs and masses of personal data. This paper improves the traditional deterministic modeling approach for delivering pre‐stored videos to mobile clients with QoS guarantees. The limitation of playback buffer space, the network delay jitter, the processing load of resource management, and the QoS guarantee are considered in the proposed mechanism. Some traffic smoothing operations are integrated into the proposed mechanism for reducing the playback buffer demand and data rate variation. This paper further proposes a smart video frame skip algorithm, originating at the sender for preventing possible overflow problems due to insufficient playback buffer space. The algorithm can determine the most suitable temporal range for skipping frames and prevent arbitrary discarding from inappropriate video frames such as I‐frames on the client side. Simulation results reveal that the proposed mechanism can effectively remedy situations of insufficient playback buffer space while still maintaining the advantages of deterministic services.     

IP网络服务质量管理体系研究

在对IP网络QoS管理现状进行客观分析的基础上,提出了新一代IP网络的QoS管理体系结构。新体系加强了业务管理,并将QoS部署、测量和管理有效地融合为一体。进一步讨论了QoS管理体系的设计原则和体系的逻辑结构。该体系结构已在863项目中得到应用。     

QoS Model of a Router with Feedback Control

The Internet has evolved into a shared, integrated platform of a broad range of applications with different Quality‐of‐Service (QoS) requirements. Routers are an important part of the Internet and play a critical role in assuring QoS. A router is usually placed between two networks to receive data packets from one network and then transmit those data packets to another network if necessary. Data packets are the actual units of data traveling on computer networks. A data packet has two parts: header and data. The data carries messages, such as e‐mail text, from computer applications. The header carries information that is required to control and manage the transmission of the data packet on computer networks. Existing approaches for providing QoS involve prediction or estimation for traffic characterization to determine parameters required of static traffic admission control. However, prediction or estimation inaccuracy in traffic characterization can result in inappropriate parameter settings for static admission control and, in turn, compromise QoS or resource utilization. This study presents a QoS model of a router with feedback control that monitors the state of resource usage and adaptively adjusts parameters of traffic admission control to overcome prediction or estimation inaccuracy and achieve a balance between QoS and resource utilization. The QoS model of a router with feedback control is simulated to test its performance on QoS and resource utilization in both heavy and light traffic conditions. The performance of the QoS model of a router with feedback control is also compared with that of two basic QoS models of a router with static admission control using admission control parameters resulting from over‐ and under‐characterization of traffic, respectively. The simulation results show that the QoS model of a router with feedback control achieves a better balance between QoS and resource utilization than the basic QoS models with over‐ and under‐characterizations of traffic in the heavy traffic condition. This study also shows that the three models of routers demonstrate similar QoS performances and resource utilization in the light traffic condition. Copyright © 2005 John Wiley & Sons, Ltd.     

Performance evaluation of bufferless optical packet switches supporting quality of service

The author evaluates the performance of bufferless optical packet switches equipped with shared tuneable optical wavelength converters (TOWC) and supporting the quality of service (QoS). The TOWCs are shared per output fibre and, hence each output fibre has a dedicated pool of TOWCs. The TOWCs are not completely shared within the node. The QoS, expressed in terms of the packet loss probability, is differentiated by giving the packets different priorities in accessing both the output wavelengths and the TOWCs. A scheduling algorithm is proposed and its complexity is evaluated. The QoS technique?s effectiveness is studied by means of an analytical model based on a probabilistic approach and validated by simulation results. The results show that the proposed technique to support the QoS facilitates a good differentiation of the QoS offered to packets.     

一种基于域的IP QoS分类方法

回顾了IP QoS的发展,总结了IP网中不同QoS技术的特征,提出了一种基于域的QoS分类方法,将各种QoS技术归结为时域、空域、逻辑域和层域。通过该方法可以更加深入地分析采用不同QoS技术对网络引入的代价,对构建一个合理的具有QoS保证的IP网具有一定的指导意义。     

Cross-layer cooperation for accurate admission control decisions in mobile ad hoc networks

Mobile ad hoc networks (MANETs) are unpredictable by nature. Providing any kind of reliability for quality of service (QoS) in such networks is challenging. Quantifying available resources accurately, avoiding interference with ongoing QoS traffic and adapting to QoS violations caused by nodes' mobility are the main concerns for the design of an efficient admission control protocol in MANETs. Adaptive admission control (AAC), a novel admission control protocol which uses robust and accurate resource estimation and prediction techniques for relevant admission decisions has been proposed. Furthermore, AAC uses statistical QoS provision to counteract the QoS threatening mobility. Through simulations, we show that our proposed scheme outperforms existing approaches in terms of correctness and overall performance.     

Mobile agent based approach for QoS routing

A mobile agent based on-demand quality of service (QoS) unicast routing scheme for supporting multimedia applications is proposed that considers bandwidth, delay and packet loss as QoS metrics for feasible path computation. A mobile agent is employed to find multiple QoS paths and select a best path among them to preserve resources so as to increase call success ratio and network bandwidth utilisation as well as adapt to network dynamics. The scheme is simulated in various network scenarios (sparse and dense networks) to verify performance and operation effectiveness, and compared with RSVP-based QoS routing by using an internet routing protocol. The results demonstrate significant improvements in call success ratio and network bandwidth utilisation compared with RSVP-based QoS routing, both in case of sparse and dense networks. Benefits of the agent-based scheme are adaptability, flexibility, and support for component-based software engineering features such as software reuse, customisation and maintainability     

天基多媒体移动通信网的QoS综合评判模型

简要分析了天基网上多媒体通信的QoS要求，阐述了其QoS的主要参数指标。基于多元信息处理技术与层次判决提出了天基多媒体移动通信网（MWAN）的QoS综合评判模型，结合实例说明了具体的评判过程，该模型具有简洁、可操作性强的特点，可供从事卫星移动通信、多媒本通信相关人员参考。     

Prediction of Cloud Ranking in a Hyperconverged Cloud Ecosystem Using Machine Learning

Cloud computing is becoming popular technology due to its functional properties and variety of customer-oriented services over the Internet. The design of reliable and high-quality cloud applications requires a strong Quality of Service QoS parameter metric. In a hyperconverged cloud ecosystem environment, building high-reliability cloud applications is a challenging job. The selection of cloud services is based on the QoS parameters that play essential roles in optimizing and improving cloud rankings. The emergence of cloud computing is significantly reshaping the digital ecosystem, and the numerous services offered by cloud service providers are playing a vital role in this transformation. Hyperconverged software-based unified utilities combine storage virtualization, compute virtualization, and network virtualization. The availability of the latter has also raised the demand for QoS. Due to the diversity of services, the respective quality parameters are also in abundance and need a carefully designed mechanism to compare and identify the critical, common, and impactful parameters. It is also necessary to reconsider the market needs in terms of service requirements and the QoS provided by various CSPs. This research provides a machine learning-based mechanism to monitor the QoS in a hyperconverged environment with three core service parameters: service quality, downtime of servers, and outage of cloud services.     

Quality of service supporting downlink scheduling scheme in worldwide interoperability for microwave access wireless access systems

IEEE 802.16 is a standardisation for a broadband wireless access in metropolitan area networks (MAN). Since the IEEE 802.16 standard defines the concrete quality of service (QoS) requirement, a scheduling scheme is necessary to achieve the QoS requirement. Many scheduling schemes are proposed with the purpose of throughput optimisation and fairness enhancement, however, few scheduling schemes support the delay requirement. In this study, the authors propose a new scheduling scheme reflecting the delay requirement. Specifically, the authors add the delay requirement term in the proportional fair scheduling scheme and the scheduling parameters are optimised with respect to the QoS requirement. Therefore the QoS requirement is achieved without the excessive resource consumption.