Showing papers by "Aletheia University published in 2001"

Active route-maintenance protocol for signal-based communication path in ad-hoc networks

Abstract: Ad-hoc wireless networks consist of mobile hosts in a network without of base stations and are characterized by a highly dynamic network topology. The network topology changes frequently due to host migration, signal interference and power outages. This makes routing maintenance challenging for routing protocol design. We present an active route maintenance protocol to prevent the existing route from disconnecting. By monitoring the status of signal strength and the stability of individual hosts, an active node that causes the route to have a weak connection actively issues a route reestablishing process in which the active host selects one of its neighbors as the candidate for partial reconstruction of the weak connection. An enhanced active route maintenance protocol is also proposed to reduce the probability of route breakage and enhance the route efficiency. Performance simulation results show that the proposed route maintenance protocol effectively reduces both the overhead and route maintenance, as well as alleviating the route-break phenomenon.

Employing data flow testing on object-oriented classes

Abstract: At the class testing level, state-based testing and data flow testing techniques have been employed. However, while the former only involves the variables that have an effect on the behaviour of the object under test, it is possible for errors to occur in variables, which do not define an object’s state. Data flow testing has been applied to generate test cases for testing classes using data flow criteria, but this is a difficult task. Moreover, some of data flow test cases thus generated may be unworkable. Selecting data flow test cases based on sequences of specification messages is a way to reduce the effort of generating feasible intra-class data flow test cases. However, some test cases cannot be selected, if data flow anomalies exist within the sequences. The data flow testing technique in this research is divided into two stages; first detecting data flow anomalies and then computing data flow test cases.

Additive subgroups generated by polynomial values on right ideals

Abstract: Let R be a prime ring with extended centroid C, ρ a nonzero right ideal of R and f(X 1,…,Xt ) a nonzero polynomial over C. We determine the additive subgroup of RC generated by all elements f(x 1,…,xt ) for x 1,…,xt ∈ ρ C and obtain a result concerning an independence property of polynomials in prime rings.

Hierarchical cellular-based management for mobile hosts in ad-hoc wireless networks

Abstract: We propose a hierarchical cellular-based management model for mobile ad hoc network. Under the proposed management model, the mobile host can construct a stable communication path with fewer flooding messages and a smaller number of hop count. In the first level management, we select a host as a manager to take the responsibility of constructing the communication path and managing the mobile hosts in a specific cellular region such that the number of flooding packets can be largely reduced. The second level management is also proposed to reduce the number of hop count and improve the efficiency for constructing a QoS routing path. We compare the cellular-based management model with triangular and zone based management models. The performance evaluation shows that hierarchical cellular-based management has a better behavior in reducing the number of flooding messages and hop count of the routing paths.

A distribution free newsboy problem under shortage-level constraints

Abstract: Since order quantity has only been decided at a spot selling time in the classical newsboy problem, both the purchase timing and the time-variant variance of the forecasted demand are neglected When the buyer purchases seasonal commodity by changing, his pre-planned schedule for more purchase discount, it is necessary for the buyer to forecast the demand of spot selling time, which may increase the variance of the demand This paper deals simultaneously with optimal purchase timing, and order quantity under a specified shortage-level limit in a distribution free newsboy problem Besides, a numerical example is used to illustrate the largest amount called Expectled Value of Additional Information, which decision-maker will be willing to pay for the knowledge of the normal distribution. Furthermore, the effects of parameters and economical meanings are also included. The resultant outcomes could apply to some cases in futures commodity contracth.

Improved one-to-all broadcasting algorithms on faulty SIMD hypercubes

Abstract: Consider an n–dimensional SIMD hypercube Hn with � 3n/2 �− 1 faulty nodes. With n +3l og(n − 1) + 7, n +2 log(n − 1) + 9, n +l og(n − 1) + O(log log(n − 1)), n +l og(n − 1) + 12, and n +1 9 steps, this paper presents some one–to–all broadcasting algorithms on the faulty SIMD Hn .Th e sequence of dimensions used for broadcasting in each algorithm is the same regardless of which node is the source. The proposed one–to–all broad

Lead time reduction in continuous review inventory model

Abstract: The Japanese successful experiences of using Just-In-Time (JIT) production show that the advantages and benefits associated with the efforts to control the lead-time. The goal of JIT inventory management philosophies is the focus that emphasizes high quality. keeps low inventory level and lead-time to a practical minimum. Thus, lead time can be reduced. the expense of an additional investment cost, so as to improve customer service level. This article combines the concept of capital investment allocated to reducing lead time. A continuous review inventory model is developed and a procedure is provided to find the optimal order quantity and optimal lead time reduction investment.