• Journal of the Korean GEO-environmental Society
• /
• v.8 no.3
• /
• pp.11-18
• /
• 2007

This paper studied the economical efficiency of ground source heat pump system under various conditions in apartments which have important effects on the housing market. And this study analysed the initial cost increase, saved managing cost and recovery time of initial cost. Analysis result showed as time of heating-cooling and water heating increases, the amount of saved managing cost increased much than the initial construction cost, so recovery time shortened. And as the net area of apartment increases, the recovery time increased. The study of the relation between the installation type and recovery time of initial construction cost showed when heat-cooling system adapted ground source heat and water heating system adapted waste heat, the initial construction cost was recovered most quickly. When Ground Source Heating system was used for the heating-cooling and water heating system, ground source heating system was used for the heating-cooling and waste heat used for water heating, and ground source heating system was used for the heating-cooling and LNG used for water heating, the construction cost increased 72,000, 66,900 and 62,300 won each per $m^2$ compared to the current system (package air-conditioner, heating and water heating using LNG).

• Journal of the Korean Society of Propulsion Engineers
• /
• v.14 no.3
• /
• pp.69-78
• /
• 2010

Korea Aerospace Research Institute started on design and development of a hypersonic air-breathing engine test facility from 2000 and completed the test facility installation in July 2009. This facility, designated as Scramjet engine test facility(SeTF), is a blow-down type high enthalpy wind tunnel which has a pressurized air supply system, air heater system, free-jet test chamber, fuel supply system, facility control/measurement system and exhaust system. In this paper, details of the specifications, and configuration of the SeTF are described. For verifying characteristics of the SeTF, wind tunnel tests are now on progress and some of the data are also described.

• Journal of KIISE:Software and Applications
• /
• v.32 no.12
• /
• pp.1238-1246
• /
• 2005

This thesis is written with web security module for safe data transmission between heterogeneous systems(ex. OS). Web system has allowed users to have great convenience and a lot of information. Though web service business has been progressed much, because of the limitation of it's own system, lots of loss, derived from data spillage which is the weakest point of security, has also followed. Suggested security module is realized by two module. One for server security module for web server, the other is client security module for client. The security structure, suggested on this thesis guarantee safe data transmission by only simple installation of modules in clients and servers. for speed sensitive transmission between web server and browser, Triple-DES, symmetric encryption system suitable for fast encryption communication, is adapted. To solve problems caused from key management, Diffie-Hellman's key exchange algorithm is adapted. By this method, all symmetric encryption troubles from key distribution and management, speed could be work out a solution. And Diffie-Hellman type algorithm secures Authentication for safe data Protection.

• Korean Journal of Construction Engineering and Management
• /
• v.10 no.2
• /
• pp.132-144
• /
• 2009

In this study, the basic data for calculating the proper construction cost as minimizing the uncertainty at the stage of forecasting construction cost with the basis of the analysis on the actual construction cost within completed domestic public apartment house. In this regard, 23 public apartment houses by each region which were ordered by the Korea National Housing Corporation and completed from 2004 to 2007 were selected as the objects of study. Four works such as common temporary installation, construction work, civil work and machine/equipment work which are the important direct cost items based on the actually inputted and settled construction costs were classified by completion year, region, architectural area, and the distribution type considering inflation rate. The sequent actual construction costs per 3.3m2 were compared and analyzed by each work, the proper construction costs were analogized and the calculating formula were presumed with the basis of average actual construction costs to be analyzed and presented.

• Korean Journal of Construction Engineering and Management
• /
• v.11 no.1
• /
• pp.130-141
• /
• 2010

Poor expertise in equipment operation and installation, coupled with unpredictable natural disaster, usually directly leads to disastrous accidents of large lifting equipment such as tower cranes. For example, 52 tower cranes fell down due to the unstable support in Korea at the attack of Typhoon "Maemi" in 2003, which damaged property and caused loss of life. In high-rise construction projects, top-slewing or luffing-jib tower cranes needs checking the stability of lateral-support in addition to the bottom support such as the foundation. In this study, the optimization algorithm for lateral-support of tower cranes is conducted, which is expected to enhance the structural stability of tower cranes and save the cost in conflict with the safety.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2006.03a
• /
• pp.527-534
• /
• 2006

A real-time hybrid method, in which the experimental implementation and the numerical computation of a structure are simultaneously carried out in real-time and combined on-line, has been used as a dynamic testing technique of structure to investigate its dynamic behaviors. In this paper, an experimental hybrid method, which implements the earthquake response control of a building structure with a TLD by using only a TLD as an experimental part, is proposed and is experimentally verified through a shaking table test. In the proposed methodology, the whole building structure with a TLD is divided into the upper TLD and the lower structural parts as experimental and numerical substructures, respectively. At the moment, the control force acting between their interface is measured from the experimental TLD with shear-type load-cell which is mounted on shaking table. Shaking table vibrates the upper experimental TLD with the response calculated from the numerical substructure, which is subjected to the excitations of the measured interface control force at its top story and an earthquake input at its base. The experimental results show that the conventional method, in which both a TLD and a building model are physically manufactured and are tested, can be replaced by the proposed methodology with a simple experimental installation and a good accuracy for evaluating the control performance of a TLD.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.3
• /
• pp.56-64
• /
• 2019

Various defects that occur in the maintenance stage are connected to all kinds of wasted resources and economic losses as additional investments are made. Residents are harmed temporally, materially, and psychologically, and businesses suffer not only monetary losses but also reduced credit ratings. The aim of this study was to increase the efficiency of quality management and minimize defect disputes by estimating the importance of the defect type considering the defect frequency and severity in apartment buildings. For this, 7,548 defect items for 48 apartment buildings were examined. The analysis confirmed that defects are concentrated on RC, finishing and MEP work. In addition, defects with high importance are identified as broken, incorrect installation, missing tasks, and water problems. In addition, the exterior wall/roof, the Internal wall, ceiling, and floor, which are constructed in the field, are more important than the furniture and MEP equipment installed in the field.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.42 no.6
• /
• pp.775-786
• /
• 2022

In the plant structures including nuclear power plants, penetrations are frequently installed in walls and slabs to reinforce facilities during operation, and reinforcing bars are sometimes cut off during concrete coring. Since these penetrations are not considered at the design or construction stage, cutting of reinforcing bar during opening installation is actually damage to the structure, structural integrity evaluation considering the stress transition range or effective width around the new penetration is necessary. In this study, various nonlinear analyses and static loading experiments are performed to evaluate the effect of reinforcing bar cutting that occurs when a penetration is newly installed in the shear wall of wall-type building of operating nuclear power plant. In addition, the decrease in wall stiffness due to the installed new penetration and cutting of reinforcing bars is evaluated and the stress and strain distributions of rebars around penetration are also measured.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.4B
• /
• pp.421-428
• /
• 2008

For last decades, the rapid coastal erosion process spreading along Korean peninsular has become a nuisance especially for tourism and local economy. Global warming and sea-level rise demand persistently new coastal protection strategies against the conventional methods using armored structures. In a view of this, Kweon et al. (2007) has proposed a new type of horizontal steel plates for an ideal candidate as eco-friendly detached breakwater systems for global warming era. The breakwater is composed of piles and horizontal porous plates that was devised for the optimized blockage effects and wave energy dissipations. This system provides outstanding performances as wave barrier and added advantages such as a rapid installation, an easy relocation, a perfect water circulation for the stagnation of pollutions in sheltered regions. The present experimental study focuses on the performance evaluations of the proposed system in wind wave conditions as a wave dissipator and reflector. The reflection, transmission, and energy dissipation of the random waves has been discussed in detail based on a newly proposed relation between wave steepness and a plate width normalized by wave length that are major factors affecting the wave transmission.

• Journal of the Korean Geotechnical Society
• /
• v.20 no.7
• /
• pp.25-32
• /
• 2004

This paper examines the results of full-scale field tests on micropiles and side resistance is evaluated with respect to axial displacements and soil properties. Both cohesive and cohesionless soils are included in this evaluation. For all practical purposes, the developed load-displacement relationship and the geotechnical soil properties for each micropile and soil type can be used to represent the available data well through normalized average values and empirical correlations. There is a significant difference in load-carrying capacity between micropiles and drilled shafts that results primarily from the micropile pressure-grouting installation effects on the state of stress in the ground. The results show that micropiles can have a significant increase of capacity over larger-diameter drilled shafts at shallower depths with D/B < 100 or so. In cohesive soils, the typical increase is on the order of 1.5 with values as high as 2.5. For cohesionless soils, the typical increases are in the range of 1.5 to 2.5 with values as high as 6.