• KIISE Transactions on Computing Practices
• /
• v.21 no.3
• /
• pp.269-274
• /
• 2015

As smart device companies such as Google or Apple develop competitive mobile-based automotive operating systems and navigation systems, the range of choice for users in such markets is expanding. Navigation systems equipped with mobile operating systems have increased convenience for users. However, since an API for the POI databases used in navigation systems doesn't exist, the number of applications using POI data is insufficient. In this paper, we designed and implemented system calls for navigation operating systems with a focus on POI search, in order to resolve such limitations. The system calls support set-based POI search functions, and therefore provides solutions to search performance degradation problems caused by false inputs. As a result of performance evaluation, not only did the search performance improve, but there was also no problem in applying APIs in applications.

• Journal of KIISE:Computing Practices and Letters
• /
• v.8 no.4
• /
• pp.450-456
• /
• 2002

Open source web service softwares are usually running on UNIX-based operating systems. Choosing an operating system can affect web system performance. In this paper, we describe a source - code-level time measurement tool and measure a service time of each system call that Squid - open source web proxy cache - makes. We run Squid 2.4.STABLEl on Linux 2.4.2 and Solaris 8, and we compare the measured time. As a result, Linux 2.4.2 performs better than Solaris 8. It can be used as a guide for selecting system software on building web service using open source software, and also be used as a basis for enhancing the operating system performance of supporting web service software.

• Proceedings of the KSR Conference
• /
• 2011.05a
• /
• pp.904-909
• /
• 2011

The development of train control system shall operate a series of processes like system designing, system production and system performance evaluation as a result of various requirements analysis presented in operation rules, operating guidelines for railway organizations etc, notified by the nation. Therefore, considering operation conditions, operation plan, linkage to railway network etc, the major document like system functional specifications, system development specifications, system test plans etc must be drawn up. In this paper we classify system operating scenarios required to prepare for system standard specification and system performance evaluation report of CBTC system for urban subways supporting unmanned automatic operation, and adjust each of the operating status.

• Journal of Advanced Marine Engineering and Technology
• /
• v.35 no.7
• /
• pp.881-890
• /
• 2011

Analyses of performance and behavior of the individual PEM fuel cells (PEMFC) under different operating conditions are of importance optimally to design and efficiently to operate the stack. The paper focuses on experimental analyses of a two-cell stack under different operating conditions, which performance and behavior are measured by the voltage of a cell as well as the stack. Experimental parameters include stoichiometric ratio, temperature of the air supplied under different working stack temperatures and loads. Results showed that the cell voltages are dominantly influenced by the temperature of the air supplied among others. In addition, an inherent difference between the first and the second cell voltage exists because of the tolerances of the cell components and the resulting different over-potentials at different equilibrium states. Furthermore, it is shown that the proton conductivity in the membranes conditioned by the humidity in the cathode channel highly affects the voltage differences of the two cells.

• Proceedings of the KSME Conference
• /
• 2001.06d
• /
• pp.703-707
• /
• 2001

A performance analysis of a SOFC/MGT hybrid system has been carried out for concept design. Thermo-dynamic models for each component being able to describe electrochemical characteristics and heat and mate-rial balance are proposed. Estimated is the power capacity of a SOFC suitable for the hybrid operation with a 5kW class MGT. Effects of current density and operating pressure are also investigated. Electric efficiency showed weak dependence on operating pressure and current density. It is desirable that the SOFC operates at high current density in manufacturing cost's point of view though operating with high current density slightly decreases the electric efficiency find specific power.

• Proceedings of the KIEE Conference
• /
• 2003.04a
• /
• pp.53-55
• /
• 2003

It is indispensable to compensate the switching characteristic variation of circuit breakers in use due to the change of operating conditions in order to get the reliable performance of controlled switching. In this paper the compensation measures against main factors such as temperature, control voltage, idle time and operating number are described. And the performance of the proposed measure is verified through the experimental results.

• International Journal of Contents
• /
• v.10 no.1
• /
• pp.23-28
• /
• 2014

When developing a classifier using various objective functions, it is important to compare the performances of the classifiers. Although there are statistical analyses of objective functions for classifiers, simulation results can provide us with direct comparison results and in this case, a comparison criterion is considerably critical. A Receiver Operating Characteristics (ROC) graph is a simulation technique for comparing classifiers and selecting a better one based on a performance. In this paper, we adopt the ROC graph to compare classifiers trained by mean-squared error, cross-entropy error, classification figure of merit, and the n-th order extension of cross-entropy error functions. After the training of feed-forward neural networks using the CEDAR database, the ROC graphs are plotted to help us identify which objective function is better.

• Industrial Engineering and Management Systems
• /
• v.6 no.1
• /
• pp.83-93
• /
• 2007

This paper gives an attempt to build a decision support tool linked with a simulation software called ARENA for evaluating and comparing the performance of the push and pull material driven strategies operating in the flow shop environment with a bottleneck resource as the shop's constraint. To be fair for such evaluation, the comparison must be made fairly under the optimal setting of both systems' operating parameters. In this study, an optimal-seeking heuristic algorithm, Genetic Algorithm (GA), is employed to suggest a systems' best design based on the economic consideration, which is the profit generated from the system. Results from the study have revealed interesting outcomes, letting us know the strength and weakness of the push and pull mechanisms as well as the effect of each operating parameter to the overall system's financial performance.

• 제어로봇시스템학회:학술대회논문집
• /
• 1996.10b
• /
• pp.347-350
• /
• 1996

With only the classical PID controller applied to control of a DC motor, a good (target) performance characteristic of the controller can be obtained, if all the model parameters of DC motor and operating conditions such as external load torque, disturbance, etc. are exactly known. However, in case when some of system parameters or operating conditions are uncertain or unknown, the fixed PID controller does not guarantee the good performance which is assumed with precisely known system parameters and operating conditions. In view of this and robustness enhancement of DC motor control system, we propose a PID learning controller which consists of a set of learning rules for PID gain tuning and learning of an auxiliary input. The proposed PID learning controller is shown to drive the state of uncertain DC motor system with unknown system parameters and external load torque to the desired one globally asymptotically. Computer simulation results are given to demonstrate the effectiveness of the proposed PID learning controller, thereby showing whose superiority to the conventional fixed PID controller.

• The KSFM Journal of Fluid Machinery
• /
• v.14 no.2
• /
• pp.11-16
• /
• 2011

This paper presents a numerical study of casing treatments on a centrifugal compressor stage to improve stability and the surge margin. High efficiency, a high pressure ratio, and a wide operating range are required for a high performance centrifugal compressor. In the present study, a ring groove arrangement was applied to the transonic centrifugal compressor. According to the numerical analysis using a commercial code ANSYS-CFX, the unstable phenomena limiting the range of the centrifugal compressors were compared with and without a ring groove. Although the ring groove decreased the efficiency, but increased the operating range by suppressing a flow separation at the leading-edge of the impeller especially near shroud part. Newly designed ring groove arrangement improved the compressor performance and increased the operating range of the compressor.