西宁至成都铁路勘察阶段XCDCSZ-3-1号深孔突发高压CO2气体,具有压力大、持续喷发时间长、对环境影响大、气体封堵专业性强及现场处置麻烦的特点.在收集、分析区域地质、深孔钻探、气体样品资料的基础上,认为高压CO2气体为无机成因,基底大理岩受热分解产生,主要聚集在基底不整合面界面,主控因素为基底构造.以1-1′为标准物探剖面,通过综合地球物理勘探手段和合理的物探测线布置,快速、有效、安全的查明基底构造分布规律.研究认为:采用二维地震反射法、音频大地电磁法两种物探手段相互验证、综合解译,查明海东南山特长隧道发育走向近东西、枢纽东倾的鼻状隆起构造,是高压CO2气体存储、运移的主控构造,分析鼻状隆起构造与线路的关系,达到优化线路方案绕避高压气体的目的.

MIMO/OFDM is an effective architecture for future wireless communication systems. An adaptive cross-layer spatial subchannel allocation algorithm based on multiuser MIMO/OFDM systems is proposed in this paper. With the goal of maximizing overall data throughput in the physical layer we derive the criteria of subcarrier allocation and develop the adaptive allocation approach by using the T-ARQ technology in the link layer. The simulation results show that our proposed algorithm can achieve good performance and high total transmission rate efficiently.

The effect of grain size on plasticity was investigated based on the theories of dislocation pile-up and Frank–Read (FR) source activation in ultrafine grained materials. The possible reason of the experimental phenomena of decrease in plasticity as grain size refined in ultrafine grained materials was theoretically analyzed and the critical grain size for plasticity decrease was proposed. The results predicted that there was a critical grain size of about 4–5μm with the present parameters of X80 microalloyed steel where the plasticity would shift from increase to decrease as grain refined, which well agreed with the experimental data described in the references in ultrafine grained materials. The mechanism of decreasing in plasticity as grain size refined was dominantly due to the decrease of probability of activation of FR source. The modeling for predicting the critical grain size has been built up which would be very helpful to optimize microstructure for obtaining excellent combination of strength and plasticity.

In this paper, we investigate the performance of Signal to Leakage and Noise Radio (SLNR) based user scheduling in uplink of multi-cell with large-scale antenna system. Large antenna array is desired to improve the performance in future system by providing better beamforming capability. However, some studies have found that the signal channel is 'hardened' (becomes invariant) when the antenna number goes extremely large, which implies that the signal channel aware user scheduling may have no gain at all. With the mathematic tool of order statistics, we analyzed the signal and interference terms of SLNR in a homogeneous multicell network. The derived distribution function of signal and interference shows that the leakage channel's variance is much more influential than the signal channel's variance in large-scale antenna regime. So even though the signal channel is hardened, the SLNR-based scheduling can achieve remarkable multiuser diversity (MUD) gain due to the fluctuation of the uplink leakage channel. By providing the final SINR distribution, we verify that the SLNR-based scheduling can leverage MUD in a better way than the signal channel based scheduling. The Monte Carlo simulations show that the throughput gain of SLNR-based scheduling over signal channel based scheduling is significant.

Femtocells may coexist with macrocells in the same band and significantly improve the spatial reuse (SR) of spectrum. To avoid high interference to the scheduled macrocell users (MUs), femtocell base stations (BSs) sense and access the channel opportunistically. When massive MIMO is deployed at macrocell BS, we find that this cognitive behavior forms too many guard zones scattered over macrocell's coverage area and seriously degrades spatial reuse efficiency. In this work, we consider not only the inter-user channel orthogonality, but also geographic locations for massive MIMO user scheduling in cognitive two-tier networks. We propose to choose MUs not far from each other as receivers of the macrocell's downlink spatial multiplexing streams, such that guard zones can be aligned spatially and more SR opportunities can be provided to femtocells. Simulations show that our scheme can significantly improve femto-tier throughput while only slightly sacrificing macro-tier throughput.

This work presents two speed based mobility models for gossip algorithms in wireless sensor networks. The corresponding upper bounds on the convergence time are derived, which show the relationship between speed of agents and convergence rate of gossip algorithms. The influences of speed are examined under both mobility models. Simulation results indicate that the speed based mobility model can offer more precise estimates of communication cost, which provide useful references for large-scale sensor network planning.

The effect of volume fraction of ferrite on the mechanical properties including strength, plasticity and wok hardening was systematically investigated in X80 pipeline steel in order to improve the plasticity. The microstructures with different volume fraction of ferrite and bainite were obtained by heat-treatment processing and the mechanical properties were tested. The work hardening behavior was analyzed by C-J method. The results show that the small amount of ferrite could effectively improve the plasticity. The work hardening ability and the ratio of yield/tensile strength with two phases of ferrite/bainite would be obviously better than that with single phase of bainite. The improvement of plasticity could be attributed to the ferrite in which more plastic deformation was afforded.

A Gossip algorithm with fast convergence was proposed ,and the broadcast nature of wire-less networks was exploited to accelerate convergence .By superposition coding ,the nodes that cannot decode the original information completely are able to obtain partial information w hich is helpful to the diffusion of message .T heoretical analysis and simulation results show that superposition coding based Gossip algorithm can achieve a fast convergence .Meanwhile ,through adjusting the communication radius ,the tradeoff between the rate of convergence and accuracy of the computation can be achieved .

With the rapid growth of the scale, complexity, and heterogeneity of Peer-to-Peer (P2P) systems, it has become a great challenge to deal with the peer's network-oblivious traffic and self-organization problems. A potential solution is to deploy servers in appropriate locations. However, due to the unique features and requirements of P2P systems, the traditional placement models cannot yield the desirable service performance. To fill this gap, we propose an efficient server placement model for P2P live streaming systems. Compared to the existing solutions, this model takes the Internet Service Provider (ISP) friendly problem into account and can reduce the cross-network traffic among ISPs. Specifically, we introduce the peers' contribution into the proposed model, which makes it more suitable for P2P live streaming systems. Moreover, we deploy servers based on the theoretical solution subject to practical data and apply them to practical live streaming applications. The experimental results show that this new model can reduce the amount of cross-network traffic and improve the system efficiency, has a better adaptability to Internet environment, and is more suitable for P2P systems than the traditional placement models.

Mobile video networking develops rapidly during the past few decades,and is becoming the indispensable part of people's life.Mobile video netw orking has been in constant development and in innovation w ith the continuous change of user needs.This paper categorized the evolution process of mobile video netw orking into three stages based on the changes of its architectures,including client / server architecture stage,overlay architecture stage and the content-oriented netw ork stage,and then elaborates the driving force and key technologies of each stage.In the end,this paper made comprehensive comparisons and analysis for the three stages and discussed the future trend of mobile video netw orking.

Machine-type communication emerges recently as a solution to cater for ubiquitous connections between a diversity of devices and the public wireless data networks. Long Term Evolution Advanced system introduces machinetomachine M2M communication as an important part of realising the blueprint of smart cities. To bring M2M communication into reality, the access procedure is a key problem. Massive access requests on the air interface in M2M communication make the communication scenarios significantly different from the traditional communications, which challenges the cellular access mechanism greatly. In this paper, the challenges of applying M2M through Long Term Evolution Advanced system are discussed. We model the access on the air interface as a queuing system. The queuing theory indicates that the system is not stable when the occupation rate is high. The access performance of M2M is evaluated by system level simulation, which shows that the congestion on the air interface is very serious in some application cases. To ease the congestion on the air interface, this paper proposes a bundling transmission scheme. Copyright © 2013 John Wiley & Sons, Ltd.

We consider the distributed channel allocation problem in an asymmetrical opportunistic spectrum access (OSA) system where each secondary user possibly has different channel reward even in the same channel due to geographic dispersion. We formulate this problem as a Gale-Shapley stable theorem using game theory to optimize the sum reward of all secondary users. It is challenging to achieve the stable matching of user-channel pairs without centralized control and prior knowledge of channel availability statistics. In this paper, we present a novel decentralized order-optimal learning Gale-Shapley scheme (OLGS) in which secondary users learn from their local history data and individually adjust their behaviors in a time-varying OSA system. The proposed scheme eliminates collisions among secondary users by a one-to-one user-channel matching policy. It also achieves stable spectral allocations using learning method without assuming known channel parameters and independent of information exchange among secondary users. Simulation results show that the system regret of the OLGS solution grows with time at the logarithmic order with low complexity.

This paper introduces a novel two-step interference alignment beamforming algorithm for a multiple-antenna interference channel with uncoordinated interference. The proposed algorithm performs subspace division of the signal space by using the total least squares method to use all available degrees of freedom in the system. The algorithm also uses the minimum mean square error as a criterion to maximize the sum rate of the system. Simulation results indicate that the sum rate of the proposed algorithm outperforms the sum rates of previous works in the context of a network with uncoordinated interference. The performance levels of these algorithms are also compared for different uncoordinated interference strengths. Almost the same trend is obtained for the sum rate performance.

This paper proposes triplewise gossip algorithm (TGA), a novel gossip algorithm for fast convergence in wireless sensor networks. During the operation of TGA, the active node selects two of its neighbors to perform triplewise averaging at each iteration. Compared with pairwise gossip algorithms, more transmissions are required at each iteration, however the total number of radio transmissions is reduced because fewer iterations are needed to get to convergence. The convergence rate of TGA is studied theoretically and verified by simulations. Similar to pairwise gossip algorithms, the proposed algorithm is a fundamental gossip algorithm. Many optimization methods that are designed for pairwise gossip algorithms can also be applied to triplewise gossip algorithms and would usually achieve better performance. Greedy TGA is presented as an improvement of the proposed algorithm, which is proved to be able to significantly accelerate convergence by numerical simulation results.

Delay-bounded multimedia services,like audio/video conferencing,are important aspects of overlay network multicast.With the development of mobile Internet,more and more users are expecting to access to these services through mobile terminal equipment;however,existing spanning tree algorithm for overlay network multicasting can't satisfy the heterogeneity of mobile terminals and service delay constraint concurrently.To this end,this paper puts forward a heuristic delay-bounded overlay multicasting algorithm,which takes both bandwidth demand of mobile terminals and service delay into consideration and as well satisfies the constraint of link bandwidth and transcode capability of serving node.Simulation results show that compared to the Transcasting algorithm proposed by Tamai et al,the proposed algorithm could obviously bring down the average serving delay and enhance the robustness at the cost of slight bandwidth consumption.

This paper presents a novel way to improve Transmission Control Protocol (TCP) performance of the users at the edge areas of the macro cells in Long Term Evolution Advanced (LTE-A) systems. Previous works on improving wireless TCP performance are reviewed and current considerations on TCP in LTE-A are explained. However, those solutions are neither too complex nor limited to some presuppositions which are too restricting for the deployment of LTE-A networks. In this paper a substituted TCP acknowledgement transmission scheme based on Automatic Repeat reQuest (ARQ) information in layer 2 is proposed. The simulation result shows that the proposed method can reduce the delay and improve the throughput of the edging users of the cell, as well as reducing radio resources in LTE-A macro cells.

This paper explores the problem of how a secondary transmitter could serve several users simultaneously by utilizing the spectrum of a primary system while imposing no impact on it (i.e. satisfying the coexistence constraint), even if the primary system keeps active all the time. The difficulty of this problem lies in that how the secondary system should tackle the interference encountered at multiple secondary receivers. In the cognitive transmission framework, the core of the above problem include two aspects: 1) How to learn quickly the message(s) of the primary system? 2) How to efficiently address the interference at multiple secondary receivers with the knowledge of the primary message? To solve these two problems, our main idea is to fully exploit the advantages of multiple antennas and the potential of transmitter cognition of the interfered message, in order to achieve the goal of fast exploration and full exploitation. In information theoretic terms, the above problem is equivalent to studying the achievable rate of the causally cognitive MISO broadcast channel under the so-called coexistence constraint. For this problem, we propose an efficient achievable scheme which is essentially based on the dirty paper coding and the zero-forcing beamforming and proves to be capable of realizing rather considerable sum rate and degrees of freedom for the secondary system. Our scheme exploits an interesting result regarding the capacity region of the MIMO Gaussian broadcast channel with states known only to the encoders.

With the popularization of mobile Internet,more and more users get access to Internet applications through mobile terminal equipment.Although traditional content delivery network can improve the mobile service quality to a certain extent,it still can′t adapt to the mobility of users and meet the demand of higher experience of service.To this end,this paper puts forward a Mobility-Aware Multimedia System(MAMS),and on this basis further proposes a Client-Driven QoS-Oriented Server Selection Scheme(CQS3),in which mobile terminals measure service quality of mobile multimedia periodically,and take both the loads and comprehensive service quality grades of edge servers into consideration when selecting the best edge servers.Simulation results show that compared with closest surrogate scheme,this scheme could ensure a similar delay performance while significantly improves PSNR,and it is also well adapt to user mobility.