Preventing Data Leakage in a Cloud Environment

Despite the multifaceted advantages of cloud computing,concerns about data leakage or abuse impedes its adoption for security-sensi tive tasks.Recent investigations have revealed that the risk of unauthorized data access is one of the biggest concerns of users of cloud-based services.Transparency and accountability for data managed in the cloud is necessary.Specifically,when using a cloudhost service,a user typically has to trust both the cloud service provider and cloud infrastructure provider to properly handling private data.This is a multi-party system.Three particular trust models can be used according to the credibility of these providers.This pa per describes techniques for preventing data leakage that can be used with these different models.

共轭多孔聚合物应用于近红外光热转换材料

近红外光热转换材料在光热治疗、光驱动智能器件等医学和能源领域受到广泛重视.本文以商业化芳香小分子为单体,通过一步简单的交联聚合方法制得了四种共轭多孔聚合物,并首次系统研究了它们的光热转换性能.结果表明,它们均具有灵敏的近红外光热响应性,且材料的光热转换效率与单体结构中共轭苯环数有很大关系,其中两种聚合物的光热转换效率可高达47%以上.同时,该类共轭多孔聚合物可作为光热转换填料,将其少量填充于热敏型形状记忆材料基体中,可实现远程、快速、定点调控材料形状的回复,且其对基材的热性质和力学性能影响很小.研究表明,由于其合成简单、原料易得、光热转换效率高,该共轭多孔聚合物是一类很有应用前景的光热转换材料.

Alleviating the crosstalk effect via a fine-moulded light-blocking matrix for colour-converted micro-LED display with a 122% NTSC gamut

One of the major challenges when fabricating high gamut colour-converted micro-light-emitting diodes(LEDs)displays is severe crosstalk effect among adjacent pixels because of the wide view-angle feature of micro-LED chips.In this study,potential factors that contribute to the crosstalk effect were systematically simulated.We observed that precisely filling the space between each micro-LED chip with a light blocking matrix(LBM)can be a promising solution to alleviate this risk.After careful investigations,a press-assisted moulding technique was demonstrated to be an effective approach of fabricating the LBM.Nevertheless,experimental observations further revealed that residual black LBM on the surface of micro-LEDs severely reduces the brightness,thereby compromising the display performance.This problem was successfully addressed by employing a plasma etching technique to efficiently extract the trapped light.Eventually,a top-emitting blue micro-LED-based backlight fine-moulded with a black LBM was developed and combined with red and green quantum dot colour-conversion layers for full-colour display.The colour gamut of our manufactured display prototype can cover as high as 122%that of the National Television Standards Committee.

Estimation of Cloud Node Acquisition

Over the past decade, there has been a paradigm shift leading consumers and enterprises to the adoption of cloud computing services. Even though most cases are still in the early stages of transition, there has been a steady increase in the implementation of the pay-as-you-go or pay-as-you-grow models offered by cloud providers. Whether applied as an extension of virtual infrastructure, software, or platform as a service, many users are still challenged by the estimation of adequate resource allocation and the wide variations in pricing. Customers require a simple method of predicting future demand in terms of the number of nodes to be allocated in the cloud environment. In this paper, we review and discuss existing methodologies for estimating the demand for cloud nodes and their corresponding pricing policies. Based on our review, we propose a novel approach using the Hidden Markov Model to estimate the acquisition of cloud nodes.

Multi-Clock Snapshot Isolation Concurrency Control for NVM Database

Multi-Clock Snapshot Isolation(MCSI)is a concurrency control mechanism that implements snapshot isolation on a single-layer Non-Volatile Memory(NVM)database.It stores a single copy of data by using multi-version storage to ensure durability and runtime access.With multi-clock transaction timestamp assignment,MCSI can efficiently generate snapshots with vector clocks and use per-thread transaction status arrays to identify uncommitted versions in NVM.For evaluation,we compared MCSI with the PostgreSQL-style concurrency control used in the single-layer NVM database N2DB.The maximum transaction throughput of MCSI is 101%–195%higher than that of N2DB for the YCSB workloads,and 25%–49%higher for the TPC-C workloads.Moreover,the transaction latency of MCSI remains relatively stable as the thread count increases.With 18 worker threads,the average transaction latency of MCSI is 65%–84%lower than that of N2DB for the YCSB workloads and 16%–43%lower for the TPC-C workloads.

Garbage Collection and Data Recovery for N2DB

Non-Volatile Memory(NVM) offers byte-addressability and persistency. Because NVM can be plugged into memory and provide low latency, it offers a new opportunity to build new database systems with a single-layer storage design. A single-layer NVM-Native DataBase(N2 DB) provides zero copy and log freedom. Hence, all data are stored in NVM and there is no extra data duplication and logging during execution. N2 DB avoids complex data synchronization and logging overhead in the two-layer storage design of disk-oriented databases and in-memory databases. Garbage Collection(GC) is critical in such an NVM-based database because memory leaks on NVM are durable. Moreover, data recovery is equally essential to guarantee atomicity, consistency, isolation, and durability properties. Without logging, it is a great challenge for N2 DB to restore data to a consistent state after crashes and recoveries. This paper presents the GC and data recovery mechanisms for N2 DB. Evaluations show that the overall performance of N2 DB is up to 3:6 higher than that of InnoDB. Enabling GC reduces performance by up to 10%,but saves storage space by up to 67%. Moreover, our data recovery requires only 0:2% of the time and half of the storage space of InnoDB.