• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.1
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• pp.1-6
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• 1999

Nearshore and offshore pipelines are often applied to carry oil, gas, water and combined products. The thermal and pressure gradients of the fluid inside pipeline cause pipeline expansion. This expansion produces stress to connecting structures with pipeline. Should this stress exceeds the yield strength of connecting components or the allowable displacement of the system, a damage can occur. As most pipelines contain hazardous and toxic fluids, the damage usually leads to fatal accidents involving great economic loss as well. Even subsea pipelines can be easily applied to transport liquid type fluid without time and space constraint, they should be designed and maintained carefully to be functional safely during design lifetime. In this paper, various theories estimating pipeline thermal expansion are investigated and the effects of pipe components to expansion are studied.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.269-273
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• 2005

A practical, 30-tonf-class fullscale thrust chamber has been combustion tested using real propellants for the first time in the domestic technology scene. The very first combustion test was conducted at a low mass flow rate condition for the preliminary assessment of any problems associated with its function and performance while reducing risks from a high chamber pressure never achieved before. A test for the design condition achieved through a low-pressure stage shows stable characteristics of all the static pressures and thrust. Dynamic pressures measured in the manifolds and the chamber did not reveal any distinct wave coupled to a specific frequency and their intensities reside in the allowable range. Moreover, it is encouraging to find no physical failures with a thrust chamber hardware.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.5
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• pp.127-133
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• 2002

The general requirements to achieve the structural integrity of the airframe are described in the military specification, MIL-STD-1530A. One of these requirements is the durability and damage tolerance of the airframe, which should be shown through the analysis and test based on the related specifications. This paper introduces the full scale durability test to evaluate the structural safety and durability of the basic trainer, KT-1. The test was performed according to the procedure in the military specification. The flight by flight load spectrum was developed by KT-1 fatigue load criteria and used for the durability test. The durability test had been performed for 4 service lives and was completed successfully. Therefore, it was shown that KT-1 airframe satisfied the durability requirements.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.1
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• pp.77-84
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• 2022

A submarine power cable is a transmission cable for carrying electric power below the surface of the water. Recently, submarine cables transfer power from offshore renewable energy schemes to shore, e.g. wind, wave and tidal systems, and these cables are either buried in the seabed or lie on the ocean floor, depending on their location. Since these power cables are used in the extreme environments, they are made to withstand in harsh conditions and temperatures, and strong currents. However, undersea conditions are severe enough to cause all sorts of damage to offshore cables, these conditions result in cable faults that disrupt power transmission. In this paper, we explore the design criteria for such cables and the procedures and challenges of installation, and cable transfer splicing system. The specification of submarine cable designed with 3 circuits of 154kV which is composed of the existing single circuit and new double circuits, and power capacity of 100MVA per cable line. The determination of new submarine cable burial depth and cable arrangement method with both existing and new cables are studied. We have calculated the permission values of cable power capacity for underground route, the values show the over 100MW per cable line.

• Journal of Internet Computing and Services
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• v.7 no.6
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• pp.157-174
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• 2006

Ajax interaction model changes the posture of web application to become a stateful over HTTP. Ajax applications are long-lived inthe browser. XMLHTTPRequest (XHR) is used to facilitate the data exchange. Using HTTPS over this interaction is not viable because of the frequency of data exchange. Moreover, switching of protocols form HTTP to HTTPS for sensitive information is prohibited because of server-of-origin policy. The longevity, constraint, and asynchronous features of Ajax application need to hove a different authentication and session fondling mechanism that invoke re-authentication. This paper presents an authentication and session management scheme using Ajax. The scheme is design lo invoke periodic and event based re-authentication in the background using digest authentication with auto-generated password similar to OTP (One Time Password). The authentication and session management are wrapped into a framework called AWASec (Ajax Web Application Security) for coupling to avoid broken authentication and session management.

• Spatial Information Research
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• v.21 no.6
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• pp.43-55
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• 2013

Recently, the research to visualize and to reproduce evacuation situations such as terrorism, the disaster and fire indoor space has been come into the spotlight and designing a model for interior space and reliable analysis through safety evaluation of the life is required. Therefore, this paper aims to develop simulation model which is able to suggest evacuation route guidance and safety analysis by considering the major risk factor of fire in actual building. First of all, we designed 3D-based fire and evacuation model at a subway station building in Incheon and performed fire risk analysis through thermal parameters on the basis of interior materials supplied by Incheon Transit Corporation. In order to evaluate safety of a life, ASET (Available Safe Egress Time), which is the time for occupants to endure without damage, and RSET (Required Safe Egress Time) are calculated through evacuation simulation by Fire Dynamics Simulator. Finally, we can come to the conclusion that a more realistic safety assessment is carried out through indoor space model based on 3-dimension building information and simulation analysis applied by safety guideline for measurement of fire and evacuation risk.

• Journal of Korean Society of Steel Construction
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• v.9 no.3 s.32
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• pp.363-375
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• 1997

This study encompasses the performance of static and fatigue test for the 8 large scale test specimens to clarify the fatigue behavior of coped stringer and the effect of the repair and strengthening on the damaged stringer of the floor system in steel railway bridges. For the purpose of the research, the actual stress wave for the existing bridge was measured, the basic stress range frequency histogram was made and the equivalent stress range was calculated. Using the result from the equivalent stress range made by adjusting the stress range, the static and fatigue test was carried out by identifying the previous rehabilitation and after. As the result of the static tests, it was revealed that the level of local stress under the S1 specimen test of the real equivalent stress range was similar to tensile strength of the test material, and it was consistent with the requirement of the initiation condition of the fatigue crack. Through the various rehabilitation methods to the damaged specimens, the effects of the repair and reinforcement were analyzed. According to the results of the repair of effect, bolting the high tension bolt over the stop hole was confirmed to be more adequate method than drilling only stop hole to delay the fatigue crack growth. Futhermore, in case of the stringer subjected by bending moment, the reinforcement over the upper flange side was determined to be a useful strengthening method, and the reinforcement to the web of the stringer was not appropriate to accomodate as a adequate strengthening method. Also it was confirmed that the category of the fatigue design for the coped stringer met with the category E specified on the fatigue design criteria of the Highway Standard Specification in Korea.

• Aerospace Engineering and Technology
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• v.2 no.2
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• pp.105-114
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• 2003

It is conducted to analyze vibration loads on the 1st stage of KSR-III(KSR : Korea Sounding Rocket) during their ground transportation and various handling process. These loads may be different from the real flight environment. Inadequate assessment of these loads can cause not only local damages on the rocket system but also the critical problem like flight mission failure. Therefore, transportation and handling loads must be considered during design and attenuated to ensure that the rocket structural damage does not occur. This work is concerned with the generation of criteria and prediction of transportation and handling loads for KSR-III. The results show that the shipping container is well designed to satisfy the design requirements. The maximum vibration level recorded during whole transportation and handling for KSR-III is less than 2g, the criteria of KSR-III movement condition.

• Journal of the Korean Society of Marine Environment & Safety
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• v.11 no.2 s.23
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• pp.77-82
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• 2005

Previously sailing yachts or leisure yachts were mainly made from FRP(Fiber glass reinforced plastic) in the small shipbuilding, but recently there is a trend to replace it for steel or aluminum to substitute FRP for environmental friendly materials. Although It have to need a many checked item in case of hull girder strength and transverse strength normally evaluate base on calculation of class guideline so called direct calculation method. Otherwise. this method of initial structural design considered enough for safety margin on the structure. But, case of small craft must consider for evaluating local strength through rational method. In this paper, check the bow structure members for satisfying results base on allowable stress criterion of damaged bow structure by dynamic load due to slamming and bottom impact load due to pitching motion through finite element analysis. and investigate engine bed structure considering engine weight load and transverse wave load.

• Journal of Aerospace System Engineering
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• v.11 no.1
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• pp.1-7
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• 2017

While a satellite is carried into orbit by a launch vehicle, it is exposed to the severe launch environment with random vibrations and shock. Accordingly, these vibration sources affect electronic equipment, particularly the printed circuit board (PCB) in the satellite. When the launch load impacts the PCB, it causes negative behavior. This causes perpendicular bending around the boundary of fixation points that finally leads to the failure of solder joints, lead wires, and PCB cracks. To overcome these issues, the electronic equipment design must meet reliability requirements. In this paper, Steinberg's method is used to derive allowable and maximum deflection to verify design from a life perspective concerning the control board of the Antenna Pointing Driver (APD) mounted on KOMPSAT-3.