• The KIPS Transactions:PartC
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• v.8C no.1
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• pp.1-11
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• 2001

There are several traditional factors of software quality. Some of them are such as correctness, reliability, efficiency, compatibility, portability, etc. In addition to them, security is required as another factor of software quality nowadays because some application programs are used as a way to attack information systems by stack frame manipulation. Each processor has its own peculiar stack frame mechanism and C language uses the characteristics of them. This paper explains the concept of security problem caused by stack frame manipulation, and the stack frame mechanism of Pentium, Alpha and SP ARC processor in detail. And then it examines the effect of stack frame mechanism on the security of programs in C language.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.4
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• pp.1-7
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• 2015

A cavitation venturi is a device that allows a liquid flow rate to be fixed or locked independent of a downstream pressure and has been successfully used in a liquid rocket engine system which requires a stable propellant flow rate. In the present research, four cavitation venturis which have same dimensions except for converging inlet angle and diverging outlet angle, were designed and manufactured. Flow rates through each venturi and upstream/downstream pressures were measured by changing the pressures. From the experimental data, the discharge coefficients and critical pressure ratios were calculated for each venturi. It was found that the inlet and outlet angles of the cavitation venturi affected the discharge coefficient, and the outlet angle influenced on the critical pressure ratio.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06a
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• pp.328-330
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• 2006

동적 전력 관리 기법을 활용한 프로세서의 등장은 고성능 임베디드 장치들의 저전력 설계에 있어서 큰 영향을 주고 있다 특히, XSCALE과 같은 고성능 프로세서의 소비전력은 동작 클럭의 속도와 비례하여 빠르게 증가하고 있으며, 이를 극복하기 위한 다양한 기법이 제시되었다. 동적 전력 관리 기법은 크게 1) 동적 전압 관리 기법과 동적 프리퀀시 관리 기법으로 구분된다. 동적 프리퀀시 관리 기법을 사용한 프로세서는 필요에 따라 프로세서의 동작 클럭 속도를 변경한다. 이는 전체적인 프로세서 성능의 저하를 수반하게 된다 특히, 주변 장치들의 전력 관리가 동시에 이루어지지 않을 경우에는 시스템의 전체적인 성능에 큰 영향을 끼치게 된다. I/O 장치의 인터럽트는 CPU의 현재 실행을 잠시 멈추고, 인터럽트 처리를 우선적으로 수행하도록 한다. 따라서 CPU가 처리할 수 있는 양보다 많은 인터럽트 발생은 인터럽트 처리 이후에 실제 응용 프로그램들이 동작할 시간을 줄이게 되어 CPU는 살아있으나, 인터럽트 이외의 실제 프로세스 실행을 진행할 수 없는 라이브륵(livelock) 현상이 발생한다. 동적 프리퀀시 스케일링을 사용하는 경우, 프로세서의 동작 속도 저하로 인한 livelock 현상이 발생할 수 있으며 이를 막기 위하여, 인터럽트 처리를 제한하는 기법을 제시한다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.1
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• pp.168-174
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• 2022

In a wave power generation system, the overtopping system is known as an overtopping wave energy converter (OWEC). The performance of an OWEC is affected by wave characteristics such as height and period because its power generation system is sensitive to those characteristics; these, as well as wave direction, depend on the sea. As these characteristics vary, it is hard for the OWEC to produce power in a stable manner. Therefore, it is necessary to find an appropriate shape for an OWEC, according to the characteristics of the sea it is in. This research verified the effect of the design of the OWEC ramp on the hydraulic efficiency using the smoothed particle hydrodynamics (SPH) particle method. A total of 10 models were designed and used in simulations performed by selecting the design parameters of the ramp and changing the attack angle based on those parameters. The hydraulic efficiency was calculated based on the rate of discharged water obtained from the analysis result. The effect of each variable on the overtopping performance according to the shape of the ramp was then confirmed. In this study, we present suggestions for determining the direction for an appropriately shaped OWEC ramp, based on a specific sea area.

• Korean Journal of Construction Engineering and Management
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• v.16 no.4
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• pp.89-97
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• 2015

This paper analyzes the duration of the construction document (CD) phase of 42 large public building projects delivered by the total solution service of Public Procurement Services in Korea from 2009 to 2014. The quality of construction documents significantly affects the quality of construction and facility management. Thus, securing appropriate time for the CD phase during project planning is important for the quality of a project. Currently, the duration of the CD phase is planned based on the construction costs of a project following a notice of the Ministry of Land, Infrastructure and Transport. However, our analysis results showed that the correlation between the actual duration of the CD phase and construction costs is very weak. The actual CD phase takes 1.33-1.79 times longer than the planned duration. The practitioners who were interviewed, were already aware that the correlation between the duration of the CD phase and the construction costs is weak. They identified the complexity of the project, the extent of the design changes, project type, client characteristics, and others as more influential factors on the CD phase than the construction costs. To improve the quality of CDs, a new guideline for determining an adequate CD phase duration should be studied and developed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.5
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• pp.383-390
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• 2013

The reduction of the maximum acceleration which causes shock for a missile is very important to prevent abnormal operation of a missile and decrease size and cost of missile components. Because the maximum acceleration created by operation of an ejection gas generator occurs in the initial ejection stage, the design parameters which affect initial ejection stage were examined. The igniter and the nozzle closure were selected as design parameters of a gas generator. The maximum acceleration created by the gas generator was examined experimentally by changing of the design parameters. Finally the reduction effect of the maximum acceleration was compared quantitatively by static fire test of a gas generator. The maximum acceleration of the best model which was applied to each optimal design parameter was about 68% reduced than that of the reference model.

• Journal of Korean Society of Transportation
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• v.27 no.5
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• pp.195-208
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• 2009

A network design problem (NDP) formulated as a mathematical program is generally used to find an optimum value to minimize or to maximize some objectives such as total travel time, social benefit, or others. NDP has, however, some limits of describing components of travel patterns like activities and trip generation due to its modeling simplicity, and also it has difficulty in including attributes of regional planning. In order to cope with such limits, this paper extends NDP to the urban planning field and proposes a mathematical program which can describe the interactions between urban social activities and transportation planning. Based on this model the authors try to optimize both urban activities and the transportation system. The model developed in this paper is tested to assess its application with a real-size regional transportation network.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.6
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• pp.879-885
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• 2018

The highway weaving section is a point where there is a conflict caused by entry and exit vehicles. In order to minimize the impact on the main line, an accumulation line should be installed. The design speed of the collecting part is 50 km/h, but the actual driver does not have proper deceleration according to the design speed. In this study, considering the driving behaviors, the design specification, and the driver 's viewing angle, the appropriate separation distance for safe entry and exit of collecting, connecting, and collecting roads was examined. As a result of the analysis, it is found that a distance of 60m is required from the point where the merging starts. The results of this study are expected to contribute to the improvement of driver safety due to the conflict between entry and exit vehicles when applied to the weaving section where collecting roads are installed.

• Korean Journal of Construction Engineering and Management
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• v.6 no.5 s.27
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• pp.89-101
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• 2005

The early phase of construction projects, communication among the related participants has great influence on the further transaction of the projects. However, important decision making are made by the experience of the field managers in practice without the method for systematic analysis. For example, in building construction project, selection process for construction method has been executed by decision making of some architects dependent on their experience. As a result, there have been frequent construction method alterations during the construction process and delay of duration, addition of cost, etc have followed accordingly. The main reasons of such a mal-functional transaction are due to the absent of the reasonal procedure of decision making reflecting the characteristics of construction project. Therefore, there is a need for an supporting tool and production design for the selection of rational construction method. The objective of this study is to propose production design process and decision making model in relation to various influent factors at the early phase of construction projects. To achieve these objectives, this study 1)analyzes the prior theory about production design, 2)we have studied about selection process for optimal construction method through constraint analysis in structural works, 3)performs a case study to embody the problems of the production design, and 4)proposes a cooperative committee model for supporting production design by analyzing the results of case study and interviewing experts. It is anticipated that the effective tool of proposed model would be able to improve communication among the related participants and systematically accumulate data that might be used in similar construction projects.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.12
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• pp.76-82
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• 2005

An experimental study on an axial-type micro turbine which consists of maximum 6 stages is conducted to measure aerodynamic characteristics on each stage. This turbine has a 2.0 flow coefficient, 3.25 loading coefficient and 25.8mm mean diameter. The solidity of stators and rotors is within a 0.67~0.75, and the off-design performance is measured by changing the load after adjusting the mass flowrate and the total pressure to constant at inlet. A maximum specific output power of 2kW/kg/sec is obtained in one stage, but the increment of the specific output power with increasing stages is alleviated. In case of torque, the increment of the torque maintains to constant at low RPM region, but its increment become dull at high RPM region. The efficiency of the micro turbine becomes low because the tip gap effect is great due to the small blade, but it could be improved by increasing the stages.