• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.957-972
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• 2018

Tunnels constructed in cold regions can cause serious defects such as cracks and leaks due to external temperature changes in the portals and vents. In order to prevent the freezing damage of the tunnel, appropriate measures should be applied to the section where the freeze damage is concerned. However, the specific criteria and contents for judging whether or not the anti-freeze measures are applied are not presented. In this study, the laboratory freezing tests on the temperature changes of the concrete specimens under freezing conditions were carried out. And the freeze-thaw repetition cycle (F), which can judge the possibility of freezing damage, were presented based on the heat transfer quantity (W) by experimental results of case studies. Also, we propose a classification of cold regions considering the climatic characteristics of Korea for using it to efficient design and maintenance.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.4
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• pp.753-762
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• 2024

Tunnels have limited evacuation areas, and It is difficult for cars coming from behind to recognize the accident situation in front. Since an accident is very likely to lead to a serious secondary accident, a IoT-based smart tunnel accident warning system was studied to prepare for traffic accidents that occur in tunnels. If the measured values from the flame detection sensor, gas detection sensor, and shock detection sensor in the tunnel exceed the standard, it is judged to be an emergency situation and an alert system is designed to operate. The accident information message was designed to be displayed on the LCD and transmitted to drivers inside and outside the tunnel through a Wi-Fi communication network. A performance test system was established and performance evaluation was performed for several accident scenarios. As a result of the test, it was confirmed that the accident alert system can accurately detect accidents based on given reference values, perform alert procedures, and transmit alert messages to smart phones through Wi-Fi wireless communication. And through this, its effectiveness could be confirmed.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.3
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• pp.361-365
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• 2005

For the EXP 1, the objective of this study was to determine the effect of MSM (methyl sulfonyl methane) supplementation on growth performance and nutrient digestibility in pigs. Sixty crossbred (Landrace × Yorkshire × Duroc) pigs (48.15±0.15㎏ average initial body weight) were used in a 35 days growth assay. Dietary treatments included 1) Control (basal diet), 2) T1 (basal diet＋0.01% MSM) and 3) T2 (basal diet＋0.02% MSM). For overall period, average daily gain, average daily feed intake and feed efficiency were not significantly different among the treatments (p＆gt;0.05). Digestibilies of DM, N, Ca and P were not significant defferences (p＆gt;0.05). For the EXP 2, the objective of this study was to determine the effect of MSM and antibiotic supplementation on growth performance and nutrient digestibility in pigs. One hundred crossbred (Landrace × Yorkshire × Duroc) pigs (33.85±0.15㎏ average initial body weight) were used in a 42 days growth assay. Dietary treatments included 1) Control (basal diet), 2) T1 (basal diet＋0.05% neomycin sulfate, 0.055% oxytetracycline), 3) T2 (Con diet＋0.01% MSM) and T3 (T1＋0.01% MSM). For overall period, average daily gain and average daily feed intake of pigs fed T3, T2 diets were higher than those of CON diet (p＆lt;0.05). Average daily gain was not significantly different between T2 and T3. However, food efficiency of pigs fed CON was the highest among the treatments (p＆lt;0.05). Pigs fed T3 diet increased nutrient digestibility compared to other treatments (p＆lt;0.05). In conclusion, the results suggest that the dietary addition of MSM and antibiotics into diets for pigs affect growth performance and nutrient digestibility.

• Journal of Venture Innovation
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• v.4 no.1
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• pp.51-65
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• 2021

The HR policy in the public sector was closed and operated mainly on written tests, but in 2006, a new evaluation, promotion and education system based on competence was introduced in the promotion and selection system of civil servants. In particular, the seniority-oriented promotion system was evaluated based on competence by operating an Assessment Center related to promotion. Competency evaluation is known to be the most reliable and valid evaluation method among the evaluation methods used to date and is also known to have high predictive feasibility for performance. In 2001, 19 government standard competency models were designed. In 2006, the competency assessment was implemented with the implementation of the high-ranking civil service team system. In the public sector, the purpose of the competency evaluation is mainly to select third-grade civil servants, assign fourth-grade civil servants, and promotion fifth-grade civil servants. However, competency assessments in the public sector differ in terms of competency assessment objectives, assessment processes and competency assessment programmes compared to those in the private sector. For the purposes of competency assessment, the public sector is for the promotion of candidates, and the private sector focuses on career development and fostering. Therefore, it is not continuously developing capabilities than the private sector and is not used to enhance performance in performing its duties. In relation to evaluation items, the public sector generally operates a system that passes capacity assessment at 2.5 out of 5 for 6 competencies, lacks feedback on what competencies are lacking, and the private sector uses each individual's competency score. Regarding the selection and operation of evaluators, the public sector focuses on fairness in evaluation, and the private sector focuses on usability, which is inconsistent with the aspect of developing capabilities and utilizing human resources in the right place. Therefore, the public sector should also improve measures to identify outstanding people and motivate them through capacity evaluation and change the operation of the capacity evaluation system so that they can grow into better managers through accurate reports and individual feedback

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.6
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• pp.533-540
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• 2012

Rubber laminated bearings with lead core are highly affected by changes in temperature because key materials which are rubber and lead have temperature dependencies. In this study, two full scale LRB(D800, S=5) are manufactured and temperature dependency tests on shear properties are accomplished. The shear properties at the 3rd cycle are used at $-10^{\circ}C$, $0^{\circ}C$, $10^{\circ}C$, $20^{\circ}C$, $30^{\circ}C$, $40^{\circ}C$ respectively. The double shear configuration, simultaneously testing two pieces, is applied for compression shear test in order to minimize the friction effects due to the test machine, described in ISO 22762-1:2010. Characteristic strength, post-yield stiffness, effective stiffness, equivalent damping ratio are estimated and presented coefficient due to the temperature changes.

• Fire Science and Engineering
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• v.31 no.3
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• pp.63-72
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• 2017

This study fabricated a low-voltage 10 circuit distribution board based on the KEMC (Korea Electrical Manufacturers Cooperative) 2102-610 standard and performed a characteristics assessment of the developed 10 circuit distribution board to secure product stability. The developed 10 circuit distribution board is designed to have the characteristics of insulation materials, as well as resistance to corrosion ultraviolet radiation and mechanical impact. The developed distribution board is fabricated to have an appropriate protection class of enclosure, electric shock prevention and protection circuits, switchgear and its components, internal electrical circuits and connectors, external conduct terminal, insulation characteristics, temperature rise test, heat resistance, etc. The developed 10 circuit distribution board consists of a single phase circuit and 3-phase circuits. It is possible to measure in real time the leakage current generated from the load distribution line by installing a sensor module at the load side of each of the branched switchgears. In addition, it is possible to increase a circuit according to the use and purpose of the load and to also manage and check the load in real time. Temperature rise tests were performed on the developed 10 circuit distribution board at 18 places including the inlet connection, main circuit and distribution circuit bus bars and bus bar supports, etc. The highest temperature of $65.3^{\circ}C$ was measured at the R-Phase of the connection of the MCCB power supply for the branch circuit bus bar and a temperature rise of $61.6^{\circ}C$ was measured at the T-Phase of the load side. When applying thermal stress to an MCCB for 6 hours at $180^{\circ}C$ using a heat resistant experimental device, it was found that the actuator lever was transformed and moved in the tripped state.

• The Journal of Engineering Geology
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• v.29 no.4
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• pp.509-529
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• 2019

This study performs to evaluate the role of filter material at alluvial well for intake of riverbank filtration and the applicability and improvement effect of dual filter well. To achieve this objective, dual filter intake well and single filter intake well were installed with different filter conditions at riverbank free surface aquifer in soil layer then we evaluated filter material condition, permeability, optimum yield and well efficiency according to yield in drawdown test. As a results, we assumed forming dual filter layer minimizes sudden speed changes at boundary between aquifer and filter layer by cushioning of groundwater flow. This suppresses warm current then intake groundwater efficiently, therefore it seems decreasing peripheral groundwater level changes in spite of higher intake water amount than single filter intake well. Furthermore, we confirmed by test, installing dual filter improves permeability, optimum yield and well efficiency. The result will be used by combining with former study to set up standard of design/construction of dual filter intake well at alluvial aquifer layer. Furthermore, we expect this result will be used to prove application effect of dual filter intake well compared to single filter one and radial collector well which are mainly applied on riverbank filtration.

• Journal of the Korean Society for Railway
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• v.16 no.1
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• pp.7-13
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• 2013

A scaled version of a roller rig is developed to demonstrate the dynamic characteristics of a railway vehicle for academic purposes. This rig is designed based on Jaschinski's similarity law. It is scaled to 1/10 of actual size and allows 9-DOF motion to examine the up and down vibration of a train set. The test rig consists of three sub-hardware components: (i) a driving roller mechanism with a three-phase AC motor and an inverter, (ii) a bogie structure with first and second suspensions, and (iii) the vehicle body. The motor of the rig is capable of 3,600rpm, allowing the test to simulate a vehicle up to a maximum speed of 400Km/hr. Because bearings and joints are properly connected to the sub-structures, various motion analyses, such as a lateral, pitching, and yawing motion, are allowed. The slip motion between the rail and the wheel set is also monitored by several sensors mounted in the rig. After the construction of the hardware, an experiment is conducted to obtain the natural frequencies of the dynamic behavior of the specimen. First, the test rig is run and data are collected from six sets of accelerometers. Then, a numerical analysis of the model based on the ADAMS program is derived. Finally, the measurement data of the first three fundamental frequencies are compared to the analytical result and the validation of the test rig is conducted. The results show that the developed roller rig provides good accuracy in simulating the dynamic behavior of the vehicle motion. Although the roller rig designed in this paper is intended for academia, it can easily be implemented as part of a dynamic experiment of a bogie and a vehicle body for a high-speed train as part of the research efforts in this area.

• Journal of the Korean Geotechnical Society
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• v.32 no.4
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• pp.41-49
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• 2016

Pile foundations used as offshore support structures are dominantly subjected to cyclic lateral loads due to wind and waves. In this study, a series of cyclic lateral load tests were performed on a pre-installed aluminum flexible pile in sandy soil with three different relative densities (40%, 70% and 90%) in order to evaluate the effect of cyclic lateral loads on lateral load capacity of a pile. The cyclic lateral loads increased the lateral load capacity of a pile at 40% relative density, whereas they decreased it at 70% and 90% relative densities. This can be explained by the fact that the cyclic lateral loads slightly densified the surrounding soil in relatively loose sand (40%), while the surrounding soil was disturbed in relatively dense sand (70% and 90%). These effects were more obvious as the cyclic lateral load amplitude increased, being independent with the saturation. Also, from the test results, an empirical equation for the lateral load capacity of a cyclic laterally loaded pile in sandy soil was developed in terms of relative density of the soil and the cyclic lateral load amplitude.

• Journal of the Korean Institute of Gas
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• v.2 no.1
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• pp.99-106
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• 1998

In order to investigate the impact properties of structural materials for LNG tank, instrumented Charpy impact tests were carried out at cryogenic temperatures. $9\%$ Ni steel showed a superior fracture resistance because of less degradation in toughness until 77 K. From the load-deflection curve obtained by an instrumented methods it was found that with the decrease of temperature from 173 K to 77 K, the peak load in the curve increased, but the total absorbed energy decreased. In addition, the energy absorbed during the crack growth was larger than one absorbed in the process of crack initiation. In SUS304L material, the energy absorbed in the process of the crack initiation was relatively large, but the energy absorbed in the process of crack growth was small, the behavior of absorbed energy was well agreed with the observations of the fracture surface which showed a relatively smooth fracture surface. The absorbed Charpy impact energy in the case of A5083 alloy was lower as compared with other steels, and some cracks were observed along the crack propagation direction at the fracture surface of 77 K.