An optimistic locking technique for concurrency control indistributed databases

A method called optimistic method with dummy locks (ODL) is suggested for concurrency control in distributed databases. It is shown that by using long-term dummy locks, the need for the information about the write sets of validated transactions is eliminated and, during the validation test, only the related sites are checked. The transactions to be aborted are immediately recognized before the validation test, reducing the costs of restarts. Usual read and write locks are used as short-term locks during the validation test. The use of short-term locks in the optimistic approach eliminates the need for the system-wide critical section and results in a distributed and parallel validation test. The performance of ODL is compared with strict two-phase locking (2PL) through simulation, and it is found out that for the low conflict cases they perform almost the same, but for the high conflicting cases, ODL performs better than strict 2PL     

Multi-Agent System-Based Fuzzy Controller Design with Genetic Tuning for a Mobile Manipulator Robot in the Hand Over Task

This paper presents an application of the multi-agent system approach to a service mobile manipulator robot that interacts with a human during an object delivery and hand-over task in two dimensions. The base, elbow and shoulder of the robot are identified as three different agents, and are controlled using fuzzy control. The control variables of the controllers are linear velocity of the base, angular velocity of the elbow, and angular velocity of the shoulder. Main inputs to the system are the horizontal and vertical distances between the human and robot hands. These are input to all three agents. In developing the fuzzy control rules, effective delivery and avoidance of contact with humans, not to cause physical damage, are considered. The membership functions of the fuzzy controllers are tuned by using genetic algorithms. In tuning, the performance is calculated considering the distance deviation from the direct path, time spent to reach the human hand and energy consumed by the actuators. The proposed multi-agent system structure based on fuzzy control for the object delivery task succeeded in both effective and safe delivery.     

Formalization of Workflows and Correctness Issues in the Presence of Concurrency

In this paper, main components of a workflow system that are relevant to the correctness in the presence of concurrency are formalized based on set theory and graph theory. The formalization which constitutes the theoretical basis of the correctness criterion provided can be summarized as follows:-Activities of a workflow are represented through a notation based on set theory to make it possible to formalize the conceptual grouping of activities.-Control-flow is represented as a special graph based on this set definition, and it includes serial composition, parallel composition, conditional branching, and nesting of individual activities and conceptual activities themselves.-Data-flow is represented as a directed acyclic graph in conformance with the control-flow graph.The formalization of correctness of concurrently executing workflow instances is based on this framework by defining two categories of constraints on the workflow environment with which the workflow instances and their activities interact. These categories are:-Basic constraints that specify the correct states of a workflow environment.-Inter-activity constraints that define the semantic dependencies among activities such as an activity requiring the validity of a constraint that is set or verified by a preceding activity.Basic constraints graph and inter-activity constraints graph which are in conformance with the control-flow and data-flow graphs are then defined to represent these constraints. These graphs are used in formalizing the intervals among activities where an inter-activity constraint should be maintained and the intervals where a basic constraint remains invalid.A correctness criterion is defined for an interleaved execution of workflow instances using the constraints graphs. A concurrency control mechanism, namely Constraint Based Concurrency Control technique is developed based on the correctness criterion. The performance analysis shows the superiority of the proposed technique. Other possible approaches to the problem are also presented.     

Application of Genetic Algorithms to Geometry Optimization of Microclusters: A Comparative Study of Empirical Potential Energy Functions for Silicon

Evolutionary computation techniques (in particular, genetic algorithms) have been applied to optimize the structure of microclusters. Various empirical potential energy functions have been used to describe the interactions among the atoms in the clusters. A comparative study of silicon microclusters has been performed.     

Fingerprint classification through self-organizing feature mapsmodified to treat uncertainties

In this paper, a neural network structure based on self organizing feature maps (SOFM) is proposed for fingerprint classification. In order to be able to deal with fingerprint images having distorted regions, the SOFM learning and classification algorithms are modified. For this purpose, the concept of “certainty” is introduced and used in the modified algorithms. This fingerprint classifier together with a fingerprint identifier, constitute subsystems of an automated fingerprint identification system, named HALafis. Our results show that a network that is trained with a sufficiently large and representative set of samples can be used as an indexing mechanism for a fingerprint database, so that it does not need to be retrained for each fingerprint added to the database     

Alpha‐Lipoic Acid Protects against Indomethacin‐Induced Gastric Oxidative Toxicity by Modulating Antioxidant System

Abstract: Gastroprotective effects of α‐lipoic acid (ALA) against oxidative gastric damage induced by indomethacin (IND) have been investigated. All doses (50, 75, 100, 150, 200, and 300 mg/kg body weight) of ALA reduced the ulcer index with 88.2% to 96.1% inhibition ratio. In biochemical analyses of stomach tissues, ALA administration decreased the level of lipid peroxidation (LPO) and activities of myeloperoxidase (MPO) and catalase (CAT) in gastric tissues, which were increased after IND application. ALA also increased the level of glutathione (GSH) and activities of superoxide dismutase (SOD) and glutathione S‐transferase (GST) that were decreased in gastric damaged stomach tissues. In conclusion, the gastroprotective effect of ALA could be attributed to its ameliorating effect on the antioxidant defense systems.     

Concurrency control in distributed databases through time intervalsand short-term locks

A method for concurrency control in distributed database management systems that increases the level of concurrent execution of transactions, called ordering by serialization numbers (OSN), is proposed. The OSN method works in the certifier model and uses time-interval techniques in conjunction with short-term locks to provide serializability and prevent deadlocks. The scheduler is distributed, and the standard transaction execution policy is assumed, that is, the read and write operations are issued continuously during transaction execution. However, the write operations are copied into the database only when the transaction commits. The amount of concurrency provided by the OSN method is demonstrated by log classification. It is shown that the OSN method provides more concurrency than basic timestamp ordering and two-phase locking methods and handles successfully some logs which cannot be handled by any of the past methods. The complexity analysis of the algorithm indicates that the method works in a reasonable amount of time