Access probability optimization for streaming media transmission in heterogeneous cellular networks

FemtoCaching technology, aiming at maximizing the access probability of streaming media transmission in heterogeneous cellular networks, is investigated in this paper. Firstly, five kinds of streaming media deployment schemes are proposed based on the network topology and the relationship between users and streaming media. Secondly, a matching algorithm for adaptive streaming media deployment is proposed, where the FemtoCaching can be adjusted dynamically. Thirdly, a joint problem is formulated combined with the channel assignment, the power allocation, and the caching deployment. To address this problem, we propose a joint optimization algorithm combining matching algorithm and genetic algorithm to maximize the access probability of streaming media transmission. Simulation experiments demonstrate that: (1) the average access probability of all users accessing streaming media in the network based on the proposed algorithm compared with recent works can be greatly improved, and (2) the performance increases with increasing the number of channels and the storage capacity of micro base stations, but decreases with increasing the number of users.

     

基于S3C2410和Linux2.6的无线网络数据采集终端

传统的基于单片机的数据采集终端在对所采集数据的实时显示分析方面需要额外的PC支持,不具备便携性。设计出基于嵌入式技术的无线网络传输数据采集终端。该终端采用S3C2410处理器,支持大屏幕LCD显示,移植支持无线网络的最新Linux内核,实现了Linux2.6下基于SPI接口的A/D驱动,并提供接口给上层Qt应用程序。应用表明,该终端界面友好,便携性好,运行稳定,具有良好的可扩充性,具有很好的推广价值。     

通道压裂裂缝铺砂影响因素实验评价

通道压裂铺砂形态是显示通道压裂效果的重要指标。文中采用可视化变角度缝网支撑剂铺置装置,研究了通道压裂裂缝铺砂形态影响因素,分析了压裂液黏度、支撑剂质量浓度、纤维质量浓度、排量、射孔数、脉冲时间对铺砂通道率的影响,并采用混合水平正交试验及拟水平法研究了各因素对通道率的影响程度。结果表明:支撑剂质量浓度越低,脉冲时间越短,纤维质量浓度越大,则通道率越高;注入排量过高或过低均对支撑剂铺置形态不利,最优排量为4 m3/min;分簇射孔的通道率要明显大于连续射孔;较大的压裂液黏度能获得更大的通道率。通过混合水平正交试验,得出各因素的影响程度大小顺序依次为:支撑剂质量浓度、脉冲时间、纤维质量浓度、布孔方式、排量、压裂液黏度。     

Synthesis and Performance Characterization of a Low Adsorption Clay-resistant Polycarboxylate Superplasticizer

A low adsorption clay-resistant polycarboxylate superplasticizer (KN-PC) was synthesized using acrylic acid and isopentenol polyoxyethylene ether as the main reaction materials.The structural characterization and clay-resistant mechanism of the KN-PC were explored using Fourier transform infrared spectroscopy and X-ray diffraction,and the effect of the KN-PC on the performance of composite paste with various montmorillonite (MMT) contents was analyzed.Compared with ordinary polycarboxylate superplasticizer (PC),the KN-PC has a low sensitivity to the MMT.By the action of the MMT,the adsorption dosage of the KN-PC on the MMT is much smaller than that of the PC.     

水下不分散混凝土性能的研究进展

水下不分散混凝土能够在水中直接浇筑,不易发生分散与离析,对施工环境几乎无污染,被国内外学者称为"全新的、理想的、划时代的混凝土".然而,我国水下不分散混凝土整体技术与国外先进技术相比还存在一定差距,主要是施工性能差、配套施工技术落后、整体强度偏低以及耐久性相对差.施工性能差的重要原因是对水下混凝土抗分散性能影响因素的系统研究较少.抗分散性研究既要考虑混凝土组成材料、抗分散剂自身组成影响因素,还需考虑施工方法和施工环境影响.现有的《水下不分散混凝土施工规范》中对混凝土抗分散性能的评价是在静水环境下测试分析,适合于静水环境下混凝土的抗分散性与实际环境施工的高压或者高水流速环境要求有较大差距,建立动水作用下混凝土抗分散性能的评价方法、指标以及开发新型高效抗分散剂尤为重要.抗分散混凝土的试配、调整以及一系列宏观测试工作量大、周期长,建立水下不分散混凝土性能预测模型是未来的发展趋势.本文从上述存在问题的四个方面进行了综述,并对水下不分散混凝土未来的研究重点进行了展望.其中为适应动水环境施工,新型抗分散剂及其抗分散机理方面:对于由水玻璃和黄原胶絮凝剂组成的高效抗分散剂,因黄原胶结构中的羟基和羧基与水泥颗粒中的Ca2+、Fe3+、Al3+形成化学配位键,将水化产物连接在一起,与纤维素对水泥粒子的物理吸附效应相比,浆液的抗分散性显著提高;纳米纤维素(CF)具有高比表面积和高宽比,在含量达到一定程度时可在空间上以三维尺度不断形成桥键,抗分散效果显著.为提高水下混凝土的浇筑质量和抗分散能力,通过数理统计以及因子优化设计法建立了综合考虑胶凝材料含量、水胶比、砂胶比、抗分散剂和高效减水剂浓度等参数的数学模型,可直接预测水下混凝土坍落度、流动度、冲刷质量损失以及抗压强度发展;通过砂子取代混凝土中的粗骨料,所用砂子的表面积与粗骨料表面积相等的方法,建立了统计回归模型,该模型可预测混凝土抗冲刷损失以及所能承受的临界水压.