Replication Strategy with Comprehensive Data Center Selection Method in Cloud Environments

As the amount of data continues to grow rapidly,the variety of data produced by applications is becoming more affluent than ever.Cloud computing is the best technology evolving today to provide multi-services for the mass and variety of data.The cloud computing features are capable of processing,managing,and storing all sorts of data.Although data is stored in many high-end nodes,either in the same data centers or across many data centers in cloud,performance issues are still inevitable.The cloud replication strategy is one of best solutions to address risk of performance degradation in the cloud environment.The real challenge here is developing the right data replication strategy with minimal data movement that guarantees efficient network usage,low fault tolerance,and minimal replication frequency.The key problem discussed in this research is inefficient network usage discovered during selecting a suitable data center to store replica copies induced by inadequate data center selection criteria.Hence,to mitigate the issue,we proposed Replication Strategy with a comprehensive Data Center Selection Method(RS-DCSM),which can determine the appropriate data center to place replicas by considering three key factors:Popularity,space availability,and centrality.The proposed RS-DCSM was simulated using CloudSim and the results proved that data movement between data centers is significantly reduced by 14%reduction in overall replication frequency and 20%decrement in network usage,which outperformed the current replication strategy,known as Dynamic Popularity aware Replication Strategy(DPRS)algorithm.

A novel method for geometric quality assurance of rock joint replicas in direct shear testing-Part 2:Validation and mechanical replicability

Each rock joint is unique by nature which means that utilization of replicas in direct shear tests is required in experimental parameter studies.However,a method to acquire knowledge about the ability of the replicas to imitate the shear mechanical behavior of the rock joint and their dispersion in direct shear testing is lacking.In this study,a novel method is presented for geometric quality assurance of replicas.The aim is to facilitate generation of high-quality direct shear testing data as a prerequisite for reliable subsequent analyses of the results.In Part 1 of this study,two quality assurance parameters,smf and V_(Hp100),are derived and their usefulness for evaluation of geometric deviations,i.e.geometric reproducibility,is shown.In Part 2,the parameters are validated by showing a correlation between the parameters and the shear mechanical behavior,which qualifies the parameters for usage in the quality assurance method.Unique results from direct shear tests presenting comparisons between replicas and the rock joint show that replicas fulfilling proposed threshold values of σ_(mf)<0.06 mm and
|V_(Hp100)|
<0.2 mm have a narrow dispersion and imitate the shear mechanical behavior of the rock joint in all aspects apart from having a slightly lower peak shear strength.The wear in these replicas,which have similar morphology as the rock joint,is in the same areas as in the rock joint.The wear is slightly larger in the rock joint and therefore the discrepancy in peak shear strength derives from differences in material properties,possibly from differences in toughness.It is shown by application of the suggested method that the quality assured replicas manufactured following the process employed in this study phenomenologically capture the shear strength characteristics,which makes them useful in parameter studies.

A novel method for geometric quality assurance of rock joint replicas in direct shear testing-Part 1:Derivation of quality assurance parameters and geometric reproducibility

Since each rock joint is unique by nature,the utilization of replicas in direct shear testing is required to carry out experimental parameter studies.However,information about the ability of the replicas to simulate the shear mechanical behavior of the rock joint and their dispersion in direct shear testing is lacking.With the aim to facilitate generation of high-quality direct shear test data from replicas,a novel component in the testing procedure is introduced by presenting two parameters for geometric quality assurance.The parameters are derived from surface comparisons of three-dimensional(3D)scanning data of the rock joint and its replicas.The first parameter,smf,captures morphological deviations between the replica and the rock joint surfaces.smf is derived as the standard deviation of the deviations between the coordinate points of the replica and the rock joint.Four sources of errors introduced in the replica manufacturing process employed in this study could be identified.These errors could be minimized,yielding replicas with smf
0.06 mm.The second parameter is a vector,VHp100,which describes deviations with respect to the shear direction.It is the projection of the 100 mm long normal vector of the best-fit plane of the replica joint surface to the corresponding plane of the rock joint.

VHp100

was found to be less than or equal to 0.36 mm in this study.Application of these two geometric quality assurance parameters demonstrates that it is possible to manufacture replicas with high geometric similarity to the rock joint.In a subsequent paper(part 2),smf and VHp100 are incorporated in a novel quality assurance method,in which the parameters shall be evaluated prior to direct shear testing.Replicas having parameter values below established thresholds shall have a known and narrow dispersion and imitate the shear mechanical behavior of the rock joint.

网格环境下基于多Replica的数据传输

数据密集型应用需要在广域、分布式计算环境中高效地传输大量的信息。提出了一种在网格环境下基于多Replica的并行传输方法来实现GridFtp中的条状传输,以提高网络传输的效率及其安全性,并实现了一个适用于网格环境的数据传输客户端工具(MFTP)。实验表明,MFTP具有较好的数据传输性能和可靠性。

AdpReplica:自适应副本管理机制

本文提出一种自适应副本管理机制—AdpReplica。AdpReplica将期望可用性和一致性维护开销看成副本数的函数,并建立自适应模型。该模型动态管理副本,使文件副本数维持在一个合理的水平,既满足用户的期望可用性,提高访问效率和平衡负载,又减少带宽消耗,保证系统稳定,为用户提供满意的存储QoS。

Novel algorithm for distributed replicas management based on dynamic programming

Replicas can improve the data reliability in distributed system. However, the traditional algorithms for replica management are based on the assumption that all replicas have the uniform reliability, which is inaccurate in some actual systems. To address such problem, a novel algorithm is proposed based on dynamic programming to manage the number and distribution of replicas in different nodes. By using Markov model, replicas management is organized as a multi-phase process, and the recursion equations are provided. In this algorithm, the heterogeneity of nodes, the expense for maintaining replicas and the engaged space have been considered. Under these restricted conditions, this algorithm realizes high data reliability in a distributed system. The results of case analysis prove the feasibility of the algorithm.

Research on Distributed Dynamic Replication Management Policy

This paper introduces replication management policies in distributed file system, and presents a novel decentralized dynamic replication management mechanism based on accessing frequency detecting named FDRM. In FDRM, in order to provide better system performance and reduce network traffic, system nodes scan their local replicas to monitor replicas’ access pattern, and makes decision independently to add, delete or migrate replicas. In addition, the scanning interval of a replica is variable according to the accessing frequency to that replica, which makes FDRM more sensitive to the change of system behaviors, so that one can get better performance with less system overhead. Experiments show the efficiency and performance improvement of FSRM.

Comparison between visual clinical examination and the replica method for assessments of sealant retention over a 2-year period

To compare the levels of agreement and the survival rates of sealant retention for different sealing materials over a 2-year period assessed using the visual clinical examination and replica methods, sealant retention data were obtained by visual clinical examination and from replicas of the same sealed tooth at baseline and at 0.5-, 1- and 2-year evaluation points in 407 children and were compared for agreement using kappa coefficients. Survival curves of retained sealants on occlusal surfaces were created using modified categorisation （fully retained sealants and those having all pits and fissures partly covered with the sealant material versus completely lost sealants that included pit and fissure systems that had /〉 1 pit re-exposed） according to the Kaplan-Meier method. The kappa coefficient for the agreement between both assessment methods over the three evaluation time points combined was 0.38 （95% confidence interval （CI）： 0.35-0.41）. More sealant retention was observed from replicas than through visual clinical examination. Cumulative survival curves at the three evaluation times were not statistically significantly higher when assessed from replicas （P=0.47）. Using the replica method, more retained sealant material was observed than through visual clinical examination during the 2-year period. This finding did not result in a difference in the survival rates of sealants assessed by the two assessment methods. When replicas cast in die stone are used for assessing sealant retention, the level of reliability of the data is higher than that of data obtained through the commonly used visual clinical examination, particularly if such assessments are conducted over time.

Studies on Artificial Replica of Eperythrozoonosis

Twenty one health hybrid dogs weighted （7±3.2） kg were intramuscularly injected with tetracyclinum in a dose of 10 mg/kg body weight for continuous 5 days while the blood eperythrozoon test showing negative reaction and divided randomly into three groups. The treating methods were respectively GroupⅠ, lienectomy, Group Ⅱ, both lienectomy and injection of immunosuppressor and Group Ⅲ, control. All dogs were intraperitoneal injected with 4ml anticoagulative blood from dog with eperythrozoonosis (the erythrozoon infection rate was 94 %, erythrocyte was 3.8×106/mm3). The result shown the eperythrozoon infection rate in GroupⅠ and Ⅱ were respectively 1.5 % and 2.1 % on the first day after administration. On the sixth day, the infection rate of GroupⅠ, Ⅱ and Ⅲ were 81.3 %, 86.5 % and 75.2 % respectively. The hematological changes in GroupⅠ and Ⅱ included both decrease in packed cell volume （HCT PCV）, hemoglobin, total erythrocyte, acidocyte number and lymphocyte, and rise in total leukocyte, neutrocyte and monocyte. Five dogs in GroupⅠ and seven dogs in Group Ⅱ showed apparent symptoms of anaemia, icterus, high fever, anorexia, diarrhea and emesis,etc. The morbidity in GroupⅠ and Ⅱ were respectively 71 % and 100 %, and two dogs in Group Ⅱdied. The changes in clinical symptoms, the hemogram and the physiological indexes in GroupⅠ and Ⅱ were the same as those in natural eperythrozoonosis.

Two phase decision algorithm of replica allocation

In distributed parallel server system, location and redundancy of repficas have great influence on availability and efficiency of the system. In order to improve availability and efficiency of the system, two phase decision algorithm of replica allocation is proposed. The algorithm which makes use of auto-regression model dynamically predicts the future count of READ and WRITE operation, and then determines location and redundancy of replicas by considering availability, CPU and bands of the network. The algorithm can not only ensure the requirement of availability, but also reduce the system resources consumed by all the operations in a great scale. Analysis and test show that communication complexity and time complexity of the algorithm satisfy O（n）, resource optimizing scale increases with the increase of READ count.

Correlation-Aware Replica Prefetching Strategy to Decrease Access Latency in Edge Cloud

With the number of connected devices increasing rapidly,the access latency issue increases drastically in the edge cloud environment.Massive low time-constrained and data-intensive mobile applications require efficient replication strategies to decrease retrieval time.However,the determination of replicas is not reasonable in many previous works,which incurs high response delay.To this end,a correlation-aware replica prefetching(CRP)strategy based on the file correlation principle is proposed,which can prefetch the files with high access probability.The key is to determine and obtain the implicit high-value files effectively,which has a significant impact on the performance of CRP.To achieve the goal of accelerating the acquisition of implicit highvalue files,an access rule management method based on consistent hashing is proposed,and then the storage and query mechanisms for access rules based on adjacency list storage structure are further presented.The theoretical analysis and simulation results corroborate that CRP shortens average response time over 4.8%,improves average hit ratio over 4.2%,reduces transmitting data amount over 8.3%,and maintains replication frequency at a reasonable level when compared to other schemes.

Let Us Enjoy Self-made Ammonite Accessories:A Self-learning Practice of Replica-making of Fossils,A Dissemination Activity of the Fukada Geological Institute Since Seven Years Ago

Elaborate and precise replicas taken from real fossils are used for academic researches in place of originals. They are often exhibited in museums in order to avoid demolition of the fragile originals.Replicas not only increase the number of specimens but also expand the chances for people to get direct observation of scientifically valuable materials.Up to now。

Analysis and Comparison of Time Replica and Time Linear Interpolation for Pilot Aided Channel Estimation in OFDM Systems

This paper analyzes and compares two time interpolators, i.e., time replica and time linear interpolator, for pilot aided channel estimation in orthogonal frequency division multiplexing (OFDM) systems. The mean square error (MSE) of two interpolators is theoretically derived for the general case. The equally spaced pilot arrangement is proposed as a special platform for these two time interpolators. Based on this proposed platform, the MSE of two time interpolators at the virtual pilot tones is derived analytically;moreover, the MSE of per channel estimator at the entire OFDM symbol based on per time interpolator is also derived. The effectiveness of the theoretical analysis is demonstrated by numerical simulation in both the time-invariant frequency-selective channel and the time varying frequency-selective channel.

Tree Automata for Extracting Consensus from Partial Replicas of a Structured Document

In an asynchronous cooperative editing workflow of a structured document, each of the co-authors receives in the different phases of the editing process, a copy of the document to insert its contribution. For confidentiality reasons, this copy may be only a partial replica containing only parts of the (global) document which are of demonstrated interest for the considered co-author. Note that some parts may be a demonstrated interest over a co-author;they will therefore be accessible concurrently. When it’s synchronization time (e.g. at the end of an asynchronous editing phase of the process), we want to merge all contributions of all authors in a single document. Due to the asynchronism of edition and to the potential existence of the document parts offering concurrent access, conflicts may arise and make partial replicas unmergeable in their entirety: they are inconsistent, meaning that they contain conflictual parts. The purpose of this paper is to propose a merging approach said by consensus of such partial replicas using tree automata. Specifically, from the partial replicas updates, we build a tree automaton that accepts exactly the consensus documents. These documents are the maximum prefixes containing no conflict of partial replicas merged.

Carbon Replicas of Porous Concrete Obtained by Chemical Vapor Deposition—Some Aspects of the Synthesis Mechanism

In this contribution, the template assisted synthesis of porous carbons by chemical vapor deposition in porous concrete templates has been described for the first time. Porous concrete made templates can be obtained in almost any geometrical shape and are therefore attractive templates to prepare porous carbon monoliths. The carbon deposition process in porous concrete follows a three-stage-course consisting in an initial period, a period of fast carbon deposition and a period of slow carbon deposition. The carbon growth within the template pores occurs obviously plug-like from the inner to the outer sphere. Any continuous covering of the template pore walls by carbon could not be observed. In difference to porous concrete, the carbon deposition in silica gel is strongly accompanied by mass transfer limitations. For porous concrete, such strong effect has not been observed obviously due to its hierarchical pore system. The template materials have been loaded with carbon by chemical vapor deposition in a flow reactor. The process of the template pore filling has been characterized by the time dependence of the template mass gain. The materials have been characterized by means of X-ray tomography and nitrogen adsorption at 77 K, respectively.

A CORBA Replication Voting Mechanism for Maintaining the Replica Consistent

Nowadays, more and more applications are being developed through distributed object computing middleware, such as CORBA, their requirements for fault-tolerance, especially real time and critical system, become more and more critical. Despite almost ten years have passed since the earliest FT-CORBA standard was promulgated by Object Management Group (OMG), CORBA is still facing many challenges when it is used for distributed applications developing, as the standard is complex and lack of understanding. This paper focus on the consistency of the replicated object and the network partition problem, it incorporates a CORBA Replication Voting Mechanism (CRVM) to meet the challenge which makes a good performance.

The "Replica of Marco Polo's Will" is Donated to WTA

The donation of the"Replica of Marco Polo's Will"opens the comprehensive cooperation between the two countries in China-Italy Year of Culture and Tourism.More than 700 years ago,Marco Polo came to Hangzhou,China from Ven ice,Italy.His Travels of Marco Polo built a bridge to promote cultural exchanges between the East and the West;Today,in the 21 st century.

PRS:Predication-Based Replica Selection Algorithm for Key-Value Stores

The tail latency of end-user requests,which directly impacts the user experience and the revenue,is highly related to its corresponding numerous accesses in key-value stores.The replica selection algorithm is crucial to cut the tail latency of these key-value accesses.Recently,the C3 algorithm,which creatively piggybacks the queue-size of waiting keys from replica servers for the replica selection at clients,is proposed in NSDI 2015.Although C3 improves the tail latency a lot,it suffers from the timeliness issue on the feedback information,which directly influences the replica selection.In this paper,we analysis the evaluation of queuesize of waiting keys of C3,and some findings of queue-size variation were made.It motivate us to propose the Prediction-Based Replica Selection(PRS)algorithm,which predicts the queue-size at replica servers under the poor timeliness condition,instead of utilizing the exponentially weighted moving average of the state piggybacked queue-size as in C3.Consequently,PRS can obtain more accurate queue-size at clients than C3,and thus outperforms C3 in terms of cutting the tail latency.Simulation results confirm the advantage of PRS over C3.

意大利Aprilia RS125 REPLICA

Aprilia RS 125 REPLICA车是著名的意大利Aprilia公司生产的一款仿赛车。它移植了多项由赛场累积下来的优异技术,如前浮动式单碟。