Improving responsiveness of soft aperiodic tasks using proportional slack time

In a real-time system with both hard real-time periodic jobs and soft real-time aperiodic jobs, it is important to guarantee that the deadline of each periodic job is met, as well as to provide a fast response time for each aperiodic job. We propose an algorithm, called Proportional Slack Reserve (PSR), that produces an efficient schedule for such an environment. For every execution unit of a periodic job, the PSR algorithm reserves time which can be used for execution of aperiodic jobs. If reserved time is not available, the algorithm assigns a deadline to an aperiodic job for achieving better responsiveness of aperiodic jobs. The proposed algorithm can fully utilize processing power while meeting all deadlines of periodic jobs. It can also easily reclaim the time unused by the periodic job. We analytically show that for each aperiodic job, the response time in a PSR schedule is no longer than that in a TBS schedule, which is known to be efficient for servicing aperiodic jobs. We also present simulation results in which the response time of PSR is significantly improved over that of TBS, and moreover the performance of PSR compares favorably with TB(N) considering scheduling overhead.     

Forgery attacks on Kang et al.’s identity-based strong designated verifier signature scheme and its improvement with security proof

Recently, Kang et al. proposed a new identity-based strong designated verifier signature scheme (ID-SDVS) and identity-based designated verifier proxy signature scheme (ID-DVPS). They claimed that their schemes are unforgeable. However, we found out that their schemes are universally forgeable in the sense that anyone can forge valid ID-SDVS and ID-DVPS on an arbitrary message without the knowledge of the secret key of either the signer or the designated verifier. Finally, we propose an improved ID-SDVS which is unforgeable. We give formal security proof of universal unforgeability of our scheme. We also give an improved ID-DVPS.     

Multiple change-point detection of multivariate mean vectors with the Bayesian approach

Bayesian multiple change-point models are proposed for multivariate means. The models require that the data be from a multivariate normal distribution with a truncated Poisson prior for the number of change-points and conjugate priors for the distributional parameters. We apply the stochastic approximation Monte Carlo (SAMC) algorithm to the multiple change-point detection problems. Numerical results show that SAMC makes a significant improvement over RJMCMC for complex Bayesian model selection problems in change-point estimation.     

Hybrid Simulation of Miscible Mixing with Viscous Fingering

By modeling mass transfer phenomena, we simulate solids and liquids dissolving or changing to other substances. We also deal with the very small‐scale phenomena that occur when a fluid spreads out at the interface of another fluid. We model the pressure at the interfaces between fluids with Darcy's Law and represent the viscous fingering phenomenon in which a fluid interface spreads out with a fractal‐like shape. We use hybrid grid‐based simulation and smoothed particle hydrodynamics (SPH) to simulate intermolecular diffusion and attraction using particles at a computable scale. We have produced animations showing fluids mixing and objects dissolving.     

Effectiveness of MMORPG‐based instruction in elementary English education in Korea

This study investigated the effectiveness of massive multiplayer online role‐playing game (MMORPG)‐based (massive multiplayer online role‐playing game) instruction in elementary English education. The effectiveness of the MMORPG program was compared with face‐to‐face instruction and the independent variables (gender, prior knowledge, motivation for learning, self‐directed learning skills, computer skills, game skills, computer capacity, network speed, and computer accessibility) were examined to see how accurately achievement was predicted in MMORPG instruction. The results indicated that students studying English utilizing online role‐playing games showed higher scores in areas of listening, reading, and writing than those who attended face‐to‐face instruction classes. It was also found that prior knowledge, motivation for learning, and network speed were factors affecting achievement in English learning. These findings suggest that MMORPGs can play an important role in improving English communicative skills.     

Coordinating decisions by supply chain partners in a vendor-managed inventory relationship

We look into the linked decision making in the vendor-managed inventory (VMI) relationship. It is a supply chain management model, where the retailer decides the retail price while the vendor determines its capacity commitment. In this model, the retailer and the vendor should coordinate their decisions in order to maximize their individual profit or the total profit combining the two participants together. The vendor has to take into account the demand pattern throughout the product life cycle (PLC) when it decides its capacity commitment, which will affect its inventory management cost during the PLC, while the retailer should change the retail price over the PLC so as to maximize the revenues and minimize the inventory cost at the same time. Employing a system dynamics simulation approach based on differential game theory, which also takes into account the product characteristics such as the demand’s innovation and imitation effects, we analyze and confirm the dynamic coordination of key decision variables by the supply chain partners in the VMI relationship.     

Outsourcing strategy in two-stage call centers

This paper considers ‘two-stage’ call centers where some incoming calls are completed by first service while others require an additional second service. Although this type of call center is not uncommon, it has not been dealt with, if any, in the call center literature. In this paper, we introduce the concept of the ‘two-stage’ call center and discuss its features. Furthermore, we develop an effective outsourcing strategy in ‘two-stage’ call centers. To this end, we model ‘two-stage’ service system and propose several call routing structures. The structures are compared through numerical test and conventional queueing theories form the theoretical basis of our study.     

Laser marking system for light guide panel using design of experiment and web-based prototyping

A light guide panel (LGP) is an element of the liquid crystal display (LCD) back light unit (BLU), which is used for display devices. In this study, the laser marking process is applied to the fabrication of light guide panels as the new fabrication process. In order to obtain a light guide panel which has high luminance and uniformity, four principal parameters such as power, scanning speed, ratio of line gap, and number of line were selected. A web-based design tool was developed to generate patterns of light guide panel via the network, and the tool may assist the designer to develop various prototype patterns. Topcon-BM7 was used for luminance measurement of each specimen with 100 mm×100 mm area. By Taguchi method, optimized levels of each parameter were found, and luminance of 3523 cd/cm² and uniformity of 92% were achieved using the laser machined BLU.