• KIEAE Journal
• /
• v.9 no.6
• /
• pp.51-56
• /
• 2009

The most important advantages of atrium buildings are to allow the abundant natural lighting and outside views. However, the abundant lighting frequently causes to increase a cooling load in summer. The roof watering systems are useful to reduce the cooling load and save the energy. This study aims to investigate the effects of the roof watering system in atrium through the scaled model experiments. For the study, the 1/20 scaled model was made and tests were performed under the clear sky conditions through August 24 to september 7 in 2008. The model size was $45{\times}45{\times}60(cm)$ and depth of roof water was 3(cm). As results, the thermal effects of two types of atrium(roof opening, and roof and front opening,) were evaluated through the experimental points and conditions. It is expected to use the results for the next research to develop the practical roof watering systems for atrium.

• 전자공학회논문지 IE
• /
• v.45 no.4
• /
• pp.74-79
• /
• 2008

The paper represented central management system of dual direction that does opening and shutting, real-time check of various doors of the prison in the on-line network. To remove a fault of 125kHz RFID technology, we use 13.56MHz RFID technology, can solve the problem of the maintenance and trust, development of on-line control and management system that ring the alarm in the abnormal opening and shutting doors.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.8 no.3 s.22
• /
• pp.11-17
• /
• 2005

In this paper, the mathematical model of the underwater discharge system using a linear pump is derived and the suitable opening pattern of a flow control valve which satisfies the discharge performance requirements is obtained through the underwater discharge simulations. The simulation results show that the dynamic characteristics of a projectile are greatly affected by the opening pattern of the flow control valve, however, hardly by the diving depth. It is anticipated that the simulation model can be used to derive the design parameters and analyze the performance of the designed underwater discharge system using a linear pump.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.11a
• /
• pp.751-754
• /
• 2004

This paper presents a design of the directional radiation pattern by using the structural-acoustic interaction. For this purpose, prediction of the pressure distribution of the field points and radiation pattern of the structural-acoustic coupling system is shown. In order to get a strong coupling, coupled system that has a finite space and a semi-infinite space separated by two flexible walls and an opening is selected. A volume interaction can be occurred in structure boundary and a pressure interaction can be happened in the opening boundary. The coupled system is maximized the radiation power on the main axis and minimized the side lobe level.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.3
• /
• pp.517-532
• /
• 2017

The transverse ventilation system, commonly applied to urban tunnel, is necessary to be distributed with airflow uniformly. In this study, we developed a program that can optimize the opening ratio of ports to ensure ventilation performance of design criteria through a uniform airflow distribution even though ventilation interval becomes longer. And program's prediction performance was verified by comparison with TUNVEN DUCT program. For comparison, Semi-transverse ventilation system was applied. Both programs predicted a similar port size and air flow distribution, and the variation range of the calculated values was 11.71% and 1.36%, respectively. This program is very useful for port optimization design of transverse and semi-transverse ventilation system, because it is possible to analyze various tunnel lengths and supply/exhaust port installation conditions.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.15 no.5 s.98
• /
• pp.527-535
• /
• 2005

This paper explains a general coupling system in terms of the system parameters. impedance of a cavity or mobility of a structure. To easily access the mechanism of the structural-acoustic coupled system, a simple expression is derived. A general coupled equation is also derived of a general coupled problem constituted a flexible structure and an opening boundary in terms of vector and matrix notation, and is analyzed the coupling phenomena using the understanding acquired simple coupled system. The paper shows that the general coupled equation is expanded version of the simple coupled equation by some limiting checks. The paper also shows that the degree of coupling is proportioned to a stiffness of the acoustic system and a modal coupling coefficient, but is in inverse proportion to a mass of the structural system and the difference of the excitation frequency and resonant frequency of the acoustic or structural system.

• Wind and Structures
• /
• v.16 no.1
• /
• pp.93-115
• /
• 2013

This paper describes a study of the influence of a dynamically flexible building structure on pressures inside and net pressures on the roof of low-rise buildings with a dominant opening. It is shown that dynamic interaction between the flexible roof and the internal pressure results in a coupled system that is similar to a two-degree-of-freedom mechanical system consisting of two mass-spring-damper systems with excitation forces acting on both the masses. Two resonant modes are present, the natural frequencies of which can readily be obtained from the model. As observed with quasi-static building flexibility, the effect of increased dynamic flexibility is to reduce the first natural frequency as well as the corresponding peak value of the admittance, the latter being the result of increased damping effects. Consequently, it is found that the internal and net roof pressure fluctuations (RMS coefficients) are also reduced with dynamic flexibility. This model has been validated from experiments conducted using a cylindrical model with a leeward end flexible diaphragm, whereby good match between predicted and measured natural frequencies, and trends in peak admittances and RMS responses with flexibility, were obtained. Furthermore, since significant differences exist between internal and net roof pressure responses obtained from the dynamic flexibility model and those obtained from the quasi-static flexibility model, it is concluded that the quasi-static flexibility assumption may not be applicable to dynamically flexible buildings. Additionally, since sensitivity analyses reveal that the responses are sensitive to both the opening loss coefficient and the roof damping ratio, careful estimates should therefore be made to these parameters first, if predictions from such models are to have significance to real buildings.

• Tunnel and Underground Space
• /
• v.28 no.5
• /
• pp.457-475
• /
• 2018

For increase of reality in numerical analysis, a blasting vibration waveform obtained from field blast operations has been directly used for input parameters of dynamic analysis in the form of vibration velocity. A numerical model was built considering the geological characteristics of underground limestone opening as well as the mining stages in this opening, and the effect of blast operations on stability of underground limestone opening was investigated by dynamic numerical analysis. The adequacy of applying the real vibration waveform to dynamic analysis has been approved from the preliminary analysis, and the dynamic numerical analysis results show that the continuous mining operation can cause the collapse of roof in openings and the active yield zone around openings. Therefore, the additional reinforcements should be applied for ensuring the stability of underground limestone openings.

• Journal of Biosystems Engineering
• /
• v.20 no.4
• /
• pp.351-359
• /
• 1995

In pressure cooling system, produce were packed in vented box and cooled rapidly by producing a difference in air pressure on opposite faces of stacks of vented box. So, energy requirements and performance of pressure cooling system depended upon the air flow rate and the static pressure drop through packed produce in vented box. The static pressure drop across packed produce in vented box normally depended upon air flow rate, vent area of box and conditions of produce bed (depth, porosity, stacking patterns, size and shape of products) in box. The objectives of this study were to investigate the effect of vent area and air flow rate on airflow resistance of empty box and packed produce in vented box, and to investigate the relationship between the air flow resistance of packed products in vented box and sum of air flow resistance of empty box only and products in bulk only. Mandarins and tomatoes were used in the experiment. The airflow rate were in the range of 0.02~1.0$m^3$/s.$m^2$, the opening ratio of vent hole were in the range of 2.5~20% of the side area. The results were summerized as follows. 1. The pressure drops across vented box increased in proportion to superficial air velocity and decreased in proportion to opening ratio of vent hole. A regression equation to calculate airflow resistance of vented box was derived as a function of superficial air velocity and opening ratio of vent hole. 2. The pressure drops across packed produce in vented box increased in proportion to superficial air velocity and decreased in proportion to opening ratio of vent hole. 3. Because of the air velocity increase in the vicinity of vent hole in box, the airflow resistances of packed products in vented box were always higher than sum of air flow resistance of empty box only and products in bulk only. 4. Based on the airflow resistance of empty box and products in bulk, a regression equation to calculate airflow resistance of packed products in vented box was derived.

• Journal of the Korean Society of Industry Convergence
• /
• v.25 no.6_3
• /
• pp.1183-1190
• /
• 2022

Recently, the Ministry of Strategy and Finance announced a plan to reduce the proportion of economic evaluation in non-metropolitan areas and strengthen balanced development evaluation through the reorganization of the preliminary feasibility study system. In addition, the social value of the quality of life, such as job, environment, and safety, which may be affected by the implementation of transportation facility investment projects, was reflected as the main item of policy evaluation. In this study, the ripple effect of the project in terms of social value was reviewed for the Gangil-Chuncheon. The effect of highway opening was investigated by reviewing the feasibility report, post-evaluation report, and statistical indicators. Recently, the Gangil-Chuncheon highway is getting used by around 110,000 people per day. The number of tourists in Chuncheon rapidly has increased from 5 million a year to more than 11 million now. In addition, it was confirmed to produce effects such as population migration, net inflow and land price increase, improvement of living convenience, and expansion of emergency medical care. Although this ripple effect was influenced by various socio-economic factors as well as the opening of the highway, it is clear that it is difficult to occur without the opening of the highway. It is judged that the evaluation of indirect benefits and social values due to the opening of the highway can be quantified through continuous research and data construction. Post-evaluation of construction works, including project efficiency evaluation and ripple effect evaluation, is performed for construction works with a construction cost of more than 50 billion won. In the future, we will continuously improve the evaluation system in order to evaluate the indirect benefits and social values of public investment projects.