• Proceedings of the IEEK Conference
• /
• 2003.07a
• /
• pp.461-464
• /
• 2003

This paper explains the impact of frequency error on the performance of WCDMA mobile communication systems and what brings about the frequency error between the base station and the mobile station, and then presents automatic frequency error correction method in mobile receiver. On the basis of system requirement related to frequency stability, the integration test between the base station and the mobile station was accomplished. After applying automatic frequency error correction to mobile receiver, 4 Hz of frequency error at transmitting frequency was obtained. The result met frequency error requirement of 0.1ppm(about 200 Hz). Performance degradation due to frequency error was measured by means of Error Vector Magnitude (EVM)

• Journal of the Korea Society of Computer and Information
• /
• v.8 no.4
• /
• pp.132-137
• /
• 2003

Due to the advances of the Internet technologies and web-based applications, the demand for wide distributed processing is increased. Mobile Agents have been proposed as a model to meet with the requirement for such environment. But current mobile agent system has the technical restriction. The requirement of mobile agent for the wide distributed processing is analysed in mobile agent system architecture, programming paradigm and technologies.

• Journal of the Korean Society for Railway
• /
• v.9 no.4 s.35
• /
• pp.482-486
• /
• 2006

The Systems Engineering Management Plan (SEMP) is the primary, top level technical management document for the integration of all engineering activities at the project plan phase. This document defined the activities to plan, control, and perform overall engineering integration. To develop the SEMP for Railway Safety System, several standards are reviewed and analyzed. And then a common requirement for SEMP preparation is derived from the results of analysis. Also, the SEMP example available practically applies to Railway Safety System. In particular, The SEMP focused on controling technical program management has been organized so far, but in this study the detailed contents of SEMP put stress on project management is derived. And it is related to each other between project management and technical engineering management. At the end, to continuously manage the items and contents of the SEMP, a database management and an automatic document generation system is presented using Computer-Aided Systems Engineering (CASE) tool.

• Proceedings of the KSR Conference
• /
• 2007.05a
• /
• pp.1000-1007
• /
• 2007

Recently, many critical control systems are developed using formal methods. When software applied to such systems is developed, the employment of formal methods in the software requirements specification and verification will provide increased assurance for such applications. Earlier error of overlooked requirement specification can be detected using formal specification method. Also the testing and full verification to examine all reachable states using model checking to undertake formal verification are able to be completed. In the comparison of other formal specification methods, we choose the Z formal language for applying to the train control system. Using Z is able to realize higher correctness in the requirement specification, and we propose the Statemate of the best solution in formal verification tools for the system modeling and verification. The Statemate makes it possible to prove thoroughly the system execution from the simple graphical modeling of the complicated train control system. Then we can expect that the model-based formal method combining Z with Statemate will be utilized widely for the railway systems due to various strong points.

• Journal of Institute of Control, Robotics and Systems
• /
• v.17 no.12
• /
• pp.1273-1277
• /
• 2011

This paper proposes a control-based approach for duty cycle adaptation in wireless sensor networks. The proposed method, QCon, controls duty cycle through queue management in order to achieve high performance under variable traffic rates. To minimize energy consumption while meeting delay requirement, we design a feedback controller, which adapts the sleeping time according to dynamically changing traffic by constraining the queue length at a predetermined value. Based on control theory, we analyze the adaptive behavior of QCon and derive conditions for system stability. Results from asymptotic analysis and simulations indicate that QCon outperforms existing scheduling protocol by achieving more energy savings while satisfying delay requirement.

• Asian-Australasian Journal of Animal Sciences
• /
• v.5 no.1
• /
• pp.75-79
• /
• 1992

Fourteen Sahiwal ${\times}$ Friesian crossbred heifers were used in a 10-wk feeding trial to determine maintenance energy requirements and efficiency of gain. The heifers were individually fed with a diet consisting of 30% dry grass and 70% concentrates at either 110, 140 or 180% of the anticipated maintenance requirement ($494kJ\;ME/kg^{0.75}/day$). Liveweight of individual heifers was measured weekly to calculate diet requirements and average daily gain (ADG). Diet digestibility was determined for all heifers to determine ME intake. Retained energy (RE) of individual heifers was determined from changes in total body fat and protein using a TOH isotope dilution procedure and, assuming calorific values of 39.3 and 23.6 kJ/g for fat and protein respectively. The estimated ME for maintenance was 433 and $470kJ/kg^{0.75}/day$ by liveweight (ADG) equilibrium and energy (RE) equilibrium analysis respectively. ME requirement for one g of liveight gain was 28 kJ.

• Proceedings of the KSRS Conference
• /
• 2007.10a
• /
• pp.105-108
• /
• 2007

The COMS LRIT/HRIT broadcast service should satisfy the 15 minutes timeliness requirement. The timeliness requirement is an important enough to impact on the overall performance of LHGS. Therefore, the simulation for the LHGS processing was performed with the LHGS prototype in this paper. First, processing time is measured for each process (per modules) of the LHGS without I/O time. Then, the LHGS processing is performed with worst scenario and the processing time is measured. Finally, analyses for processing time and time constraint are performed.

• Nuclear Engineering and Technology
• /
• v.31 no.1
• /
• pp.58-67
• /
• 1999

The purpose is to produce a model of nuclear reactor trip logic caused by the steam generator water level of Wolsong 2/3/4 unit through an activity chart and a statechart and to produce C language automatically using Statechart-based Formalism and Stalemate MAGNUM toolset suggested by David Harel Formalism. It was worth attempting auto-generation of C language though we manually made Software Requirement Specification(SRS) for safety-critical software using statechart-based formalism. Most of the phases of the software life-cycle except the software requirement specification of an analysis phase were generated automatically by Computer Aided Software Engineering (CASE) tools. It was verified that automatically produced C language has high productivity, portability, and quality through the simulation.

• International Journal of Reliability and Applications
• /
• v.3 no.1
• /
• pp.25-35
• /
• 2002

This paper presents a dynamic reliability assessment methodology for use in the safety assessment of a complex system such as a nuclear power plant. The method is applied to a dynamic analysis of the potential accident sequences that may occur during mid-loop operation in a nuclear power plant. The idea behind this approach consists of both the use of the concept of the performance achievement/requirement correlation and of a dynamic event tree generation method. The assessment of the system reliability depends on the determination of both the required performance distribution and the achieved performance distribution. The quantified correlation between requirement and achievement represents a comparison between two competing variables. It is demonstrated that this method is easily applicable and flexible in that it can be applied to any kind of dynamic reliability problem.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.03a
• /
• pp.211-215
• /
• 2004

For design of cryogenic propellant feeding system, one of the main requirements is to meet temperature requirement for satisfying turbo-pump NPSH requirement. In this paper improved method of estimating the thermal stratification in liquid oxygen tank is presented to help design. In the case of liquid rocket using turbo-pump, the inner pressure of liquid oxygen tank is maintained low, so vaporization of liquid oxygen is generally occurred. In this paper, inner process of LOX tank is analyzed by two phase flow modeling. The vaporization rate and required helium mass is investigated.