• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.66-66
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• 2011

중위도 이북의 건물에서 고층건물의 혹한기 연돌효과는 건물의 여러 가지 기능에 큰 영향을 미치며, 승강기 승강로는 화재시 차압 때문에 연기의 주된 전파통로가 된다. 외피의 밀폐성능을 높여 건물 내부의 연도효과를 줄일 수 있으나, 외피의 밀폐기능은 비상시 피난을 위해 피난경로를 개방하는 순간 일시에 무력화된다. 또한 건물 외피의 밀폐성능이 우수할수록 연돌효과 그 자체로써 건물외피에 미치는 구조적 영향이 커진다. 고층부의 연돌효과는 외피를 밖으로 밀어내는 작용이므로 풍하측에서는 마이너스 풍압에 더하여 건물 외피에 부담을 증가시킨다. 그러므로 고층건물에 발생하는 혹한기 연돌효과의 영향을 정리하자면 다음과 같다. ${\bullet}$ 건물 외벽 및 창문에 미치는 구조적 영향 ${\bullet}$ 제연 시스템의 기능 저해 ${\bullet}$ 승강기 문 개폐 장애와 소음 등 설비 기능의 부정적 영향 ${\bullet}$ 공조기능 장애 ${\bullet}$ 화재시 승강기 승강로 등 수직 샤프트를 통한 연기 전파 혹한기 건물 안팎의 온도차가 40K일 때 높이 600m인 초고층 건물 최상층에 발생하는 연돌효과에 의한 차압은 풍속으로 환산할 때 32m/s에 달한다. 그러므로 초고층 건물 설계시에는 최상층의 풍하측에 설계상의 예상 최대풍속에다 이러한 환산풍속을 더한 고속 풍력이 창문을 밖으로 밀어내는 것으로 보아야 한다. 또한 공조 및 환기시스템에서는 이러한 차압을 고려하지 않으면 고층부에서 환기 성능이 무력화될 수 있다. 다음과 같은 방법들을 이용하여 고층건물의 연돌효과를 효과적으로 줄일 수 있다. 1) 계단실의 연돌효과 저감 방법 계단실에 발생하는 연돌효과에 의한 차압은 계단실에 상승기류를 발생시킨다. 이러한 차압과 상승기류는 계단실 상하부를 개방하면 자연적으로 평형을 이루게 되므로 별도의 제어가 필요 없게 된다. 또한 화재감지기와 연동하여 상하부 외벽의 개구부를 열어두게 되면 피난상황에 따라 문이 여닫힘으로써 발생하는 압력상태의 변화를 고려할 필요가 없게 된다. 2) 승강기 승강로의 연돌효과 승강로의 상하부에 대규모 개구를 두면 대규모의 외기가 도입되어 상승 유동 후 배출되므로 승강로 내부 온도 저하로 연돌효과가 저감되고, 승강로로 유입된 연기는 대규모의 외기에 희석되어 농도가 낮아지고 대부분 외부로 배출된다. 3) 샤프트 복합효과를 이용하는 방법 거실 평면적에 비해 승강기나 계단이 아주 많고 누설틈새 등 개구의 면적 합계가 크면 샤프트들이 서로 복합효과를 이루어 연돌효과에 의한 차압이 줄어든다. 연돌효과 제어용 샤프트를 하나 더 보조적으로 설치함으로써, 보조샤프트에 의해 발생하는 차압으로 거실을 가압 혹은 감압하여 문제가 되는 차압을 어느 정도 상쇄할 수 있다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.85-91
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• 2018

Recently, there have been a lot of casualties due to fires in high-rise buildings. The toxic gases and smokes generated by fires in high-rise buildings spread rapidly through the elevator shaft and stairwell, due to the stack effect, and can cause critical casualties. To reduce the number of casualties, smoke control systems have been introduced. Smoke control systems play an essential role in preventing the spread of smoke in high-rise buildings and securing the evacuation route. Also, in high-rise buildings, evacuation by an elevator is considered to be indispensable. However, the pressure field in the shaft is strongly disturbed when the elevator is moving and this can affect the performance of the smoke control system. Therefore, in this study, we experimentally and numerically analyzed the effect of elevator movement on the pressure difference between the vestibule and living room by building a model using the sandwich pressurization method based on the performance based design. To consider the leakage areas in high-rise buildings, e.g. the windows, fire door and elevator, the National Fire Safety Codes and area ratio were used. The elevator speed in the model building was varied between 20 m/s and 100 m/s corresponding to a real elevator speed of 7 m/s~17 m/s. As a result, the relationship between the pressure difference and elevator speed was found to be ${\Delta}P=40{\cdot}{\exp}$(-Ves /-104.7)-23.735. This result can be used to take into consideration the effect of elevator movement when designing smoke control systems.

• Proceedings of KOSOMES biannual meeting
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• 2005.05a
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• pp.147-154
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• 2005

The ship plating is generally subjected to combined in-plane load and lateral pressure loads. In-plane loads include axial load and edge shear, which are mainly induced by overall hull girder bending and torsion of the vessel. Lateral pressure is due to water pressure and cargo. These load components are not always applied simultaneously, but more than one can normally exist and interact Hence, for more rational and safe design of ship structures, it is of crucial importance to better understand the interaction relationship of the buckling and ultimate strength for ship plating under combined loads. Actual ship plates are subjected to relatively small water pressure except for the impact load due to slamming and panting etc. The present paper describes an accurate and fast procedure for analyzing the elastic-plastic large deflection behavior up to the ultimate limit state of ship plates under combined loads. In this paper, the ultimate strength characteristics of plates under axial compressive loads and lateral pressure loads are investigated through ANSYS elastic-plastic large deflection finite element analysis with varying lateral pressure load level.

• Korean Journal of Food Science and Technology
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• v.46 no.5
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• pp.588-592
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• 2014

Under optimized condition mild pressure in combination with specific temperature for heat treatment transform the 6-gingerol into 6-shogaol. The purpose of this study was to optimize the conditions used for heat treatment under pressure for increasing 6-shogaol content in ginger (Zingiber officinale Roscoe). A central composite experimental design was used to evaluate the effects of application temperature ($70-130^{\circ}C$) and temperature-holding time (95-265 min) on the transformation of 6-shogaol. The experimental values were shown to be in significantly good agreement with the predicted values (adjusted determination coefficient, $R^2{_{Adj}}=0.9857$). 6-Shogaol content increased as the application temperature and temperature-holding time increased. By analyzing the response surface plots, the optimum conditions of heat treatment (temperature and time) for increasing 6-shogaol content were found to be $127^{\circ}C$ and 109 min, respectively. Under these optimal conditions, the predicted 6-shogaol content was 3.98 mg/g dried ginger. The adequacy of the model equation for predicting the optimum response values was effectively verified by the validation data.

• The Journal of the Acoustical Society of Korea
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• v.40 no.1
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• pp.55-63
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• 2021

In this study, a numerical methodology is proposed for evaluating valve flow noise in a pipe conveying high pressure gas, and the effects of perforated plates on reduction of such valve flow noise are quantitatively analyzed. First, high-accurate unsteady compressible Large Eddy Simulation techniques are utilized to predict flow and flow noise by a valve in a high-pressure pipe. The validity of the numerical result is confirmed by comparing the predicted wall pressure spectrum with the measured one. Next, the acoustic power of downstream-propagating acoustic waves due to the valve flow is analyzed using an acoustic power formula for acoustic waves propagating on mean flow in a pipe. Based on the analysis results, perforated plates are designed and installed downstream of the valve to suppress the valve flow noise and the acoustic power of downstream-going acoustic waves is predicted by using the same numerical procedure. The reduction by 9.5 dB is confirmed by comparing the predicted result with that of the existing system. Based on these results, the current numerical methodology is expected to be used to reduce valve flow noise in an existing system as well as in a design stage.

• Journal of the Korea Concrete Institute
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• v.25 no.5
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• pp.485-496
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• 2013

In recent years, frequent terror or military attacks by explosion or impact accidents have occurred. Examplary case of these attacks were World Trade Center collapse and US Department of Defense Pentagon attack on Sept. 11 of 2001. These attacks of the civil infrastructure have induced numerous casualties and property damage, which raised public concerns and anxiety of potential terrorist attacks. However, a existing design procedure for civil infrastructures do not consider a protective design for extreme loading scenario. Also, the extreme loading researches of prestressed concrete (PSC) member, which widely used for nuclear containment vessel, gas tank, bridges, and tunnel, are insufficient due to experimental limitations of loading characteristics. To protect concrete structures against extreme loading such as explosion and impact with high strain rate, understanding of the effect, characteristic, and propagation mechanism of extreme loadings on structures is needed. Therefore, in this paper, to evaluate the impact resistance capacity and its protective performance of bi-directional unbonded prestressed concrete member, impact tests were carried out on $1400mm{\times}1000mm{\times}300mm$ for reinforced concrete (RC), prestressed concrete without rebar (PS), prestressed concrete with rebar (PSR, general PSC) specimens. According to test site conditions, impact tests were performed with 14 kN impactor with drop height of 10 m, 5 m, 4 m for preliminary tests and 3.5 m for main tests. Also, in this study, the procedure, layout, and measurement system of impact tests were established. The impact resistance capacity was measured using crack patterns, damage rates, measuring value such as displacement, acceleration, and residual structural strength. The results can be used as basic research references for related research areas, which include protective design and impact numerical simulation under impact loading.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.4
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• pp.7-11
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• 2006

In this paper, it is reported that film-bulk-acoustic resonator with high c-axis oriented AIN film on $Mo/SiO_2/Si(100)$ using metal-organic-chemical-vapor deposition was fabricated. The resonant frequency and anti-resonant frequency of the fabricated resonator were observed with 3.189[GHz] and 3.224[GHz], respectively. The quality factor and the effective electromechanical coupling coefficient(${k_{eff}}^2$) were measured with 24.7 and 2.65[%], respectively. The conditions of AIN deposition were substrate temperature of $950[^{\circ}C]$, pressure of 20Torr, and V-III ratio of 25000. A high c-axis oriented AIN film with $4{\times}10^{-5}[\Omega{cm}]$ resistivity of Mo bottom electrode and $4[^{\circ}]$ of AIN(0002) full-width at half-maximum(FWHM) on $Mo/SiO_2/Si(100)$ was grown successfully. The FWHM value of deposited AIN film is useful for the RF band pass filter specification for GHz-band wireless local area network.

• Journal of the Korea Organic Resources Recycling Association
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• v.26 no.2
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• pp.95-103
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• 2018

As a guideline for desulfurization and dehumidification pretreatment facility for optimizing utilization of biogas, the $H_2S$ concentration is set at 150 % which can be treated with iron salts, dehumidification is the optimum value for generator operation, and the relative humidity applied at the utilization of biogas in EU is set at 60 %. We have set up the generator facility guidelines to optimize utilization of biogas. The appropriate amount of biogas should be at least 90 % of the total gas generation, and the capacity of generator facility should be set at 20~30 %. In order to equalize the pressure of the incoming gas the generator, a gas equalization tank should be installed and the generator room average temperature should be kept at $45^{\circ}C$ or less. Since the gas is not produced at a certain methane concentration in the digester, the efficiency is lowered. Therefore, it is required to install an air fuel ratio control system according to the change in methane concentration. Therefore, it is necessary to compensate for the disadvantages of biogasification facilities of organic waste resources and optimize utilization of biogas and improve operation of facilities. This study was conducted to optimize biogas utilization of type of organic waste(containing sewage sludge and food waste, animal manure), investigate the facilities problem and propose design, operation guidelines such as pre-treatment facilities and generators.

• Tunnel and Underground Space
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• v.26 no.2
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• pp.59-67
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• 2016

In this paper, we perform a numerical analysis to evaluate the potential of fault reactivation during gas production from hydrate bearing sediments and the moment magnitude of induced seismicity. For the numerical analysis, sequential coupling of TOUGH+Hydrate and FLAC3D was used and the change in effective stress and consequent geomechanical deformation including fault reactivation was simulated by assuming that Mohr-Coulomb shear resistance criterion is valid. From the test production simulation of 30 days, we showed that pore pressure reduction as well as effective stress change hardly induces the fault reactivation in the vicinity of a production well. We also investigated the influence of stress state conditions to a fault reactivation, and showed that normal fault stress regime, where vertical stress is relatively greater than horizontal, may have the largest potential for the reactivation. We tested one simulation that earthquake can be induced during gas production and calculated the moment magnitude of the seismicity. Our calculation presented that all the magnitudes from the calculation were negative values, which indicates that induced earthquakes can be grouped into micro-seismic and as small as hardly perceived by human beings. However, it should be noted that the current simulation was carried out using the highly simplified geometric model and assumptions such that the further simulations for a scheduled test production and commercial scale production considering complex geometric conditions may produce different results.

• Journal of the Korean Geotechnical Society
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• v.27 no.2
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• pp.53-62
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• 2011

During the construction of vertical cutoff walls, filtration of bentonite slurry into the adjacent soil formation fabricates a layer of bentonite filter cake on the wall surface. The bentonite filter cake possesses much lower hydraulic conductivity compared to that of backfill materials in the cutoff wall. Hydraulic conductivity of bentonite filter cakes formed with three different types of bentonites has been measured by performing the modified fluid loss test under various pressure levels. Three different mixture ratios, 4, 6, and 8%, were selected for fabricating bentonite filter cakes to represent common field conditions. Two analysis methods for interpreting the experimental data from the modified fluid loss tests were employed to estimate hydraulic conductivity of the bentonite cakes. The range of hydraulic conductivities of the three bentonite cakes is between $2.15{\times}10^{-11}\;m/s$ and $2.88{\times}10^{-10}\;m/s$ which is 1 to 2.7 orders of magnitude lower than that of the design cutoff wall backfill. The stress distribution and thickness of the bentonite cakes were also evaluated in this paper.