• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.31 no.5
• /
• pp.235-241
• /
• 2018

The internal pressure is a critical parameter for designing a pressure vessel. The static pressure that a pressure vessel must withstand is usually determined according to the various codes and standards with simple formula or numerical simulations considering the geometric parameters such as diameter and thickness of a vessel. However, there is no specific codes or technical standards we can use practically for designing of pressure vessels which have to endure the detonation pressure. Detonation pressure is a kind of dynamic pressure which causes an impulsive pressure on the vessel wall in a extremely short time duration. In addition, it is known that the magnitude of reflected pressure at the vessel wall due to the explosion can be over twice the incident pressure. Therefore, if we only consider the reflected pressure, the design of the pressure vessel can be too conservative from the economical point of view. In this study, we suggest a practical method to evaluate the magnitude of maximum allowable pressure that the pressure vessel can withstand against the detonation inside a vessel. As an example to validate the proposed method, we consider the pressure vessel containing hydrogen gas.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.46 no.6
• /
• pp.39-47
• /
• 2009

This paper presents implementation of two types of the 802.11 MAC engine for the next generation WLAN, 802.11n. The first version of MAC engine consists of hardwired logic and embedded firmware. Hardwired logic includes Tx block, Rx block, Backoff block, and ChannelManage block. Embedded firmware contains Protocol Control block, MLME block, and MSDU processing block. The first version has a time-critical fault during the atomic transmission caused by software overhead, so it can not be applied to 802.11n MAC. For that reason, the second version has additional blocks with hardwired logic modules to reduce software overhead of the first version. This enhanced version has 73Mbps throughput and it is expected to be further improved up to 129 Mbps with frame aggregation which is one of the key additional features of 802.11n. As a result, the second version of MAC engine can be applied to 802.11n MAC.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.19 no.1
• /
• pp.29-36
• /
• 2015

Base isolation is considered as a seismic protective system in the design of next generation Nuclear Power Plants (NPPs). If seismic isolation devices are installed in nuclear power plants then the safety under a seismic load of the power plant may be improved. However, with respect to some equipment, seismic risk may increase because displacement may become greater than before the installation of a seismic isolation device. Therefore, it is estimated to be necessary to select equipment in which the seismic risk increases due to an increase in the displacement by the installation of a seismic isolation device, and to perform research on the seismic performance of each piece of equipment. In this study, modified NRC-BNL benchmark models were used for seismic analysis. The numerical models include representations of isolation devices. In order to validate the numerical piping system model and to define the failure mode, a quasi-static loading test was conducted on the piping components before the analysis procedures. The fragility analysis was performed by using the results of the inelastic seismic response analysis. Inelastic seismic response analysis was carried out by using the shell finite element model of a piping system considering internal pressure. The implicit method was used for the direct integration time history analysis. In addition, the collapse load point was used for the failure mode for the fragility analysis.

• Journal of Radiation Protection and Research
• /
• v.28 no.2
• /
• pp.79-85
• /
• 2003

This study was intended to estimate Hp(10) recommended by the ICRU using the $CaSO_4:Dy,P$ element developed in the KAERI. For the estimation of Hp(10), TL response should be compensated properly through the energy range using filter materials since $CaSO_4:Dy,P$ is of severe photon energy dependent response. Various experiments and computations using Monte Carlo Code were carried out for designing filter satisfying the performance requirements of the ISO related to TL dosimeter. Under the completed filter, the relative response of $CaSO_4:Dy,P$ showed $0.75{\sim}1.0$ for photons in the range of $20{\sim}662keV$. Especially it was possible to reduce the thickness of front filter and simplify the filter combination with rear filter of larger diameter and to considerably improve angular dependence by introducing taper to the filler.

• Journal of the Korea Society of Computer and Information
• /
• v.25 no.2
• /
• pp.59-66
• /
• 2020

In this paper, we propose a pipe leak detection system through data collection using low-power wireless acoustic sensor modules and data analysis using deep auto-encoder. Based on the Fourier transform, we propose a low-power wireless acoustic sensor module that reduces data traffic by reducing the amount of acoustic sensor data to about 1/800, and we design the system that is robust to noise generated in the audible frequency band using only 20kHz~100kHz frequency signals. In addition, the proposed system is designed using a deep auto-encoder to accurately detect pipe leaks even with a reduced amount of data. Numerical experiments show that the proposed pipe leak detection system has a high accuracy of 99.94% and Type-II error of 0% even in the environment where high frequency band noise is mixed.

• Korean Journal of Materials Research
• /
• v.8 no.8
• /
• pp.678-684
• /
• 1998

By means of constant- pressure molecular dynamics simulations, we studied the liquid- glass- crystalline transition of a system composed of Lennard- Jones particles with periodic boundary conditions. Atomic volume and enthalpy were calculated as functions of temperature during heating and cooling processes. The Wendt- Abraham ratio derived from radial distribution function and the angular distribution function characterizing short range order were analyzed to distinguish between liquid, glass and crystalline states. A liquid phase resulting from a slow heating of an initial fee crystal amorphized on fast quench, but it crystallized on slow quench. When slowly heated, the amorphous phase from fast quench crystallized into an fee structure. A system with free surface was shown to melt from the surface inward at a lower temperature than bulk system and to have a strong tendency for crystallization even during a fast quench from a liquid state.

• Journal of Microbiology and Biotechnology
• /
• v.26 no.8
• /
• pp.1428-1438
• /
• 2016

In the present work, Arthrobacter sp. 25, a lead-tolerant bacterium, was assayed to remove lead(II) from aqueous solution. The biosorption process was optimized by response surface methodology (RSM) based on the Box-Behnken design. The relationships between dependent and independent variables were quantitatively determined by second-order polynomial equation and 3D response surface plots. The biosorption mechanism was explored by characterization of the biosorbent before and after biosorption using atomic force microscopy (AFM), scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The results showed that the maximum adsorption capacity of 9.6 mg/g was obtained at the initial lead ion concentration of 108.79 mg/l, pH value of 5.75, and biosorbent dosage of 9.9 g/l (fresh weight), which was close to the theoretically expected value of 9.88 mg/g. Arthrobacter sp. 25 is an ellipsoidal-shaped bacterium covered with extracellular polymeric substances. The biosorption mechanism involved physical adsorption and microprecipitation as well as ion exchange, and functional groups such as phosphoryl, hydroxyl, amino, amide, carbonyl, and phosphate groups played vital roles in adsorption. The results indicate that Arthrobacter sp. 25 may be potentially used as a biosorbent for low-concentration lead(II) removal from wastewater.

• Applied Biological Chemistry
• /
• v.11
• /
• pp.167-171
• /
• 1969

Gartic bulblets were planted to investigate the effect of some different cultivating conditions on the growth and bulb formation of the garlic plants (Allium sativum L.) Two different conditions namely perfect and imperect aerobic condition, and 3 different fertilizer levels was made. The split plot design was adopted for this experiment. 1) For the growth rate, under the imperfect aerobic condition, the plant height was more increased than that of perfect aerobic condition no relation to the fertilizer levels. 2) With respect to the fresh weight of garlic, the similar tendency to the growth rate was observed, but dry weight was did not. 3) The uptake of phosphorus was found to be increased in the imperfect condition. It could there be concluded that imperfect aerobic condition seems to be much favorable condition than the perfect aerobic condition to the development of garlic bulbs.

• Geomechanics and Engineering
• /
• v.33 no.1
• /
• pp.101-112
• /
• 2023

When a submerged floating tunnel is connected to the ground, there is a risk of stress concentration at the shore connection owing to the displacement imbalance caused by low confinement pressures in water and high confinement pressures in the ground. Here, the effects of the boundary condition and stiffness of the joints installed at the shore connection on the behaviors of a submerged floating tunnel and its shore connection were analyzed using a numerical method. The analysis results obtained with fixed and ground boundaries were similar due to the high stiffness of the ground boundary. However, the stability of the shore connection was found to be improved with the ground boundary as a small displacement was allowed at the boundary. The effect of the joint stiffness was evaluated by investigating the dynamic behavior of the submerged floating tunnel, the magnitude of the load acting on the bored tunnel, and the stress distribution at the shore connection. A lower joint stiffness was found to correspond to more effective relief of the stress concentration at the shore connection. However, it was confirmed that joints with low stiffness also increase the submerged floating tunnel displacement and decrease the frequency of the dynamic behavior, causing a risk of increased resonance when wave loads with low frequency are applied. Therefore, it is necessary to derive the optimal joint stiffness that can achieve both stress concentration relief and resonance prevention during the design of shore connections to secure their dynamic stability.

• Geomechanics and Engineering
• /
• v.33 no.1
• /
• pp.1-9
• /
• 2023

The unconfined compression strength (UCS) of soils is commonly used either before or during the construction of geo-structures. In the pre-design stage, UCS as a mechanical property is obtained through a laboratory test that requires cumbersome procedures and high costs from in-situ sampling and sample preparation. As an alternative way, the empirical model established from limited testing cases is used to economically estimate the UCS. However, many parameters affecting the 1D soil compression response hinder employing the traditional statistical analysis. In this study, gene expression programming (GEP) is adopted to develop a prediction model of UCS with common affecting soil properties. A total of 79 undisturbed soil samples are collected, of which 54 samples are utilized for the generation of a predictive model and 25 samples are used to validate the proposed model. Experimental studies are conducted to measure the unconfined compression strength and basic soil index properties. A performance assessment of the prediction model is carried out using statistical checks including the correlation coefficient (R), the root mean square error (RMSE), the mean absolute error (MAE), the relatively squared error (RSE), and external criteria checks. The prediction model has achieved excellent accuracy with values of R, RMSE, MAE, and RSE of 0.98, 10.01, 7.94, and 0.03, respectively for the training data and 0.92, 19.82, 14.56, and 0.15, respectively for the testing data. From the sensitivity analysis and parametric study, the liquid limit and fine content are found to be the most sensitive parameters whereas the sand content is the least critical parameter.