“军卫1号”工程中“死锁”的判断及处理方法

系统运行中常会遇到用户反映系统运行速度慢 ,好像是系统死机了 ,有时重启也不能进入系统 ,但有时等会儿又能进入系统的现象。与此同时如果数据库管理员在服务器端查看系统的性能监测程序 ,可看到系统 CPU的使用率几乎达到了百分之百。这种现象我们称之为“死锁”,但这种“死锁”与真正意义上的死锁不同 。

A Deadlock-Avoidance Dispatching Method for Multiple-Load AGVs Based Transportation System

In recent years,multiple-load automatic guided vehicle(AGV)is increasingly used in the logistics transportation fields,owing to the advantages of smaller fleet size and fewer occurrences of traffic congestion.However,one main challenge lies in the deadlock-avoidance for the dispatching process of a multiple-load AGV system.To prevent the system from falling into a deadlock,a strategy of keeping the number of jobs in the system(NJIS)at a low level is adopted in most existing literatures.It is noteworthy that a low-level NJIS will make the processing machine easier to be starved,thereby reducing the system efficiency unavoidably.The motivation of the paper is to develop a deadlock-avoidance dispatching method for a multiple-load AGV system operating at a high NJIS level.Firstly,the deadlock-avoidance dispatching method is devised by incorporating a deadlock-avoidance strategy into a dispatching procedure that contains four sub-problems.In this strategy,critical tasks are recognized according to the status of workstation buffers,and then temporarily forbidden to avoid potential deadlocks.Secondly,three multiattribute dispatching rules are designed for system efficiency,where both the traveling distance and the buffer status are taken into account.Finally,a simulation system is developed to evaluate the performance of the proposed deadlock-avoidance strategy and dispatching rules at different NJIS levels.The experimental results demonstrate that our deadlock-avoidance dispatching method can improve the system efficiency at a high NJIS level and the adaptability to various system settings,while still avoiding potential deadlocks.

A distributed deadlock detection algorithm for mobile computing system

The mode of mobile computing originated from distributed computing and it has the un-idempotent operation property, therefore the deadlock detection algorithm designed for mobile computing systems will face challenges with regard to correctness and high efficiency. This paper attempts a fundamental study of deadlock detection for the AND model of mobile computing systems. First, the existing deadlock detection algorithms for distributed systems are classified into the resource node dependent (RD) and the resource node independent (RI) categories, and their corresponding weaknesses are discussed. Afterwards a new RI algorithm based on the AND model of mobile computing system is presented. The novelties of our algorithm are that: 1) the blocked nodes inform their predecessors and successors simultaneously; 2) the detection messages (agents) hold the predecessors information of their originator; 3) no agent is stored midway. Additionally, the quit-inform scheme is introduced to treat the excessive victim quitting problem raised by the overlapped cycles. By these methods the proposed algorithm can detect a cycle of size n within n-2 steps and with (n^2-n-2)/2 agents. The performance of our algorithm is compared with the most competitive RD and RI algorithms for distributed systems on a mobile agent simulation platform. Experiment results point out that our algorithm outperforms the two algorithms under the vast majority of resource configurations and concurrent workloads. The correctness of the proposed algorithm is formally proven by the invariant verification technique.

Application of modified banker’s algorithm in FMS deadlock problem

Presents a method for deadlock avoidance algorithm used in Flexible Manufacturing System(FMS). This method is an improvement of the Banker algorithm. The Banker algorithm is commonly used in the Operating System (OS), but some improvements will have to be made on the algorithm if this algorithm is used in FMS. The difference between the process in operating system and the job in the FMS is fully discussed. Based on this difference, the improvement is made. In order to improve the algorithm, formal methods are adopted to the manufacturing systems. The simulation model is translated into a format suitable for model checking. That is, the model is written into PROMELA, the input language of the popular model checker SPIN. After that, SPIN is used to verify that the model does not have deadlock. This algorithm proves to be highly effective in practice.

Azerbaijan is in the TANAP, TAP, and South Stream Project Triangle at the Deadlock of Nabucco

This study has been investigated some pipeline lines after collapsing process of Union of Soviet Socialist Republics from Azerbaijan to Europe and another alternative ways from Russia. As we know Russia is a big power as from economic, defensive, and political aspects, as that＇s in ruler position in the region. So, USA from another side of the world as a super power of the world could make dimension of those pipelines from transit of Turkey. That＇s why new Nabucco project has been also cancelled by Russia＇s power. This article has been studied newly established project of Trans Anatolian Natural Gas Line Project （TANAP） from Azerbaijan＇s oil and gas department; Ministry＇s State Petroleum Company＇s （SOCAR） project has not been cancelled by Turkish Petroleum Company （TPAO）. So TANAP＇s advantages and disadvantages have been researched in this article.

Research on efficient edge-chasing deadlock detection/resolution for distributed systems

Numerous edge-chasing deadlock detection algonthms were developed lor the cycle detection in distributed systems, but their detections had the n steps speed limitation and n （ n- 1） overhead limitation to detect a cycle of size n under the one-resource request model. Since fast deadlock detection is critical, this paper proposed a new algorithm to speed up the detection process. In our algorithm, when the running of a transaction node is blocked, the being requested resource nodes reply it with the waiting or being waited message simultaneously, so the blocked node knows both its predecessors and successors, which helps it detecting a cycle of size 2 directly and locally. For the cycle of size n （ n 〉 2）, a special probe is produced which has the predecessors information of its originator, so the being detected nodes know their indirect predecessors and direct successors, and can detect the cycle within n - 2 steps. The proposed algorithm is formally proved to be correct by the invariant verification method. Performance evaluation shows that the message overhead of our detection is （ n^2 - n - 2）/2, hence both the detection speed and message cost of the proposed algorithm are better than that of the existing al gorithms.

Optimization of Waterway with Multiple Locks and Canals by Integration of Petri Net and Genetic Algorithm

This paper presents the possibilities of job optimization in waterway with multiple locks and canals, in order to increase the system productivity. Safe navigation in such complex waterway system is very demanding. Some of the problems that need to be solved are： How to control traffic in a way that vessels move in opposite directions; How to resolve possible conflicts in case that more vessels try to acquire particular lock at the same time; How to avoid possible deadlocks; How to ensure the vessel passage in the shortest possible time？ It is necessary to apply adequate control policy to avoid deadlocks and blocks the vessels＇ moving only in the case of dangerous situation. The motion of vessels can be described as the set of discrete events and states. Herein we propose deadlock avoidance algorithm for complex waterway system with multiple key resources and we use multiple re-entrant flowlines class of Petri net （MRF^PN）. The solution represents deadlock prevention supervisor in a sense that vessels are stopped only in a case of immediate dangerous situation in dense traffic. The goal of this paper is to find optimal, conflict and deadlock free job schedule in CWS. In this sense, the authors developed the algorithm which integrates MRF^PN with a genetic algorithm. The algorithm deals with multi-constrained scheduling problem with shared resources. The final goals are minimization the total travel time of vessels through the waterway system.

Comparison of outcomes following three surgical techniques for patients with severe jejunoileal atresia

Background:Severe jejunoileal atresia is associated with prolonged parenteral nutrition,higher mortality and secondary surgery.However,the ideal surgical management of this condition remains controversial.This study aimed to compare the outcomes of patients with severe jejunoileal atresia treated by three different procedures.Methods:From January 2007 to December 2016,105 neonates with severe jejunoileal atresia were retrospectively reviewed.Of these,42 patients(40.0%)underwent the Bishop–Koop procedure(BK group),49(46.7%)underwent primary anastomosis(PA group)and 14(13.3%)underwent Mikulicz double-barreled ileostomy(DB group).Demographics,treatment and outcomes including mortality,morbidity and nutrition status were reviewed and were compared among the three groups.Results:The total mortality rate was 6.7%,showing no statistical difference among the three groups(P=0.164).The BK group had the lowest post-operative complication rate(33.3%vs 65.3%for the PA group and 71.4%for the DB group,P=0.003)and re-operation rate(4.8%vs 38.8%for the PA group and 14.3%for the DB group,P<0.001).Compared with the BK group,the PA group showed a positive correlation with the complication rate and re-operation rate,with an odds ratio of 4.15[95%confidence interval(CI):1.57,10.96]and 12.78(95%CI:2.58,63.29),respectively.The DB group showed a positive correlation with the complication rate when compared with the BK group,with an odds ratio of 7.73(95%CI:1.67,35.72).The weight-for-age Z-score at stoma closure was–1.22(95%CI:–1.91,–0.54)in the BK group and–2.84(95%CI:–4.28,–1.40)in the DB group(P=0.039).Conclusions:The Bishop–Koop procedure for severe jejunoileal atresia had a low complication rate and re-operation rate,and the nutrition status at stoma closure was superior to double-barreled enterostomy.The Bishop–Koop procedure seems to be an appropriate choice for severe jejunoileal atresia.