• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.917-930
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• 2018

A quantitative risk assessment method for quantitatively evaluating the fire risk in designing a road tunnel disaster prevention facilities has been introduced to evaluate the appropriateness of a disaster prevention facility in a large tunnel through which all vehicle types pass. However, since the quantitative risk assessment method of the developed can be applied only to the large sectional area tunnels (large tunnels), it is necessary to develop a quantitative risk assessment method for road tunnels passing only small cars which has recently been constructed or planned. In this study, fire accidents scenarios and quantitative risk assesment method for small road tunnels through small cars only which is based on the methods for existing road tunnels (large tunnels). And the risk according to the distance between cross passage is evaluated. As a result, in order to satisfy the societal risk assessment criteria, the distance of the appropriate distance between cross passages was estimated to be 200 m, and the effect of the ventilation system of the large port exhaust ventilation system was quantitatively analyzed by comparing the longitudinal ventilation system.

• Structural Engineering and Mechanics
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• v.48 no.6
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• pp.879-914
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• 2013

In part I of the article, formulation and characteristics of the several well-known structural geometrical nonlinear solution techniques were studied. In the present paper, the efficiencies and capabilities of residual load minimization, normal plane, updated normal plane, cylindrical arc length, work control, residual displacement minimization, generalized displacement control and modified normal flow will be evaluated. To achieve this goal, a comprehensive comparison of these solution methods will be performed. Due to limit page of the article, only the findings of 17 numerical problems, including 2-D and 3-D trusses, 2-D and 3-D frames, and shells, will be presented. Performance of the solution strategies will be considered by doing more than 12500 nonlinear analyses, and conclusions will be drawn based on the outcomes. Most of the mentioned structures have complex nonlinear behavior, including load limit and snap-back points. In this investigation, criteria like number of diverged and complete analyses, the ability of passing load limit and snap-back points, the total number of steps and analysis iterations, the analysis running time and divergence points will be examined. Numerical properties of each problem, like, maximum allowed iteration, divergence tolerance, maximum and minimum size of the load factor, load increment changes and the target point will be selected in such a way that comparison result to be highly reliable. Following this, capabilities and deficiencies of each solution technique will be surveyed in comparison with the other ones, and superior solution schemes will be introduced.

• KIEAE Journal
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• v.17 no.2
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• pp.29-34
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• 2017

Purpose: Recently, significant heat loss through the window takes place in buildings. Nevertheless, there exists little literature concerning the exterior horizontal shading devices and the design criteria are not clearly settled yet. Applying the exterior horizontal shading devices is more efficient as compared to the interior shading devices in that solar radiation can be directly blocked before passing through the window or the envelope. The purpose of this study is to reduce the internal load by designing the exterior horizontal shading devices and verify the degree of reduction in energy consumption. Method: This study aims to reduce energy consumption in cooling and heating through proposing proper length and shape of the exterior horizontal shading devices in public buildings. In the process, actual energy data and the Design Builder simulation program are utilized. In addition, economic aspect is considered to figure out the optimal length of the exterior horizontal shading devices that maximizes efficiency. Result: As a result, the proper length and shape of the exterior horizontal shading devices are provided as follows: 1) Energy consumption in cooling and heating is minimized when the exterior horizontal shading devices are designed as 0.5m*2. 2) Electricity bill is the lowest when the exterior horizontal shading devices are designed as 3.3m*2. The gap between maximum and minimum electricity bill is about 7.8~14%.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.11
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• pp.2577-2596
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• 2013

In this paper, we present an Energy-Aware Self-Stabilizing Distributed Clustering protocol based on message-passing model for Ad Hoc networks. The latter does not require any initialization. Starting from an arbitrary configuration, the network converges to a stable state in a finite time. Our contribution is twofold. We firstly give the formal proof that the stabilization is reached after at most n+2 transitions and requires at most $n{\times}log(2n+{\kappa}+3)$ memory space, where n is the number of network nodes and ${\kappa}$ represents the maximum hops number in the clusters. Furthermore, using the OMNeT++ simulator, we perform an evaluation of our approach. Secondly, we propose an adaptation of our solution in the context of Wireless Sensor Networks (WSNs) with energy constraint. We notably show that our protocol can be easily used for constructing clusters according to multiple criteria in the election of cluster-heads, such as nodes' identity, residual energy or degree. We give a comparison under the different election metrics by evaluating their communication cost and energy consumption. Simulation results show that in terms of number of exchanged messages and energy consumption, it is better to use the Highest-ID metric for electing CHs.

• Journal of the Korean Institute of Landscape Architecture
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• v.33 no.5 s.112
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• pp.104-113
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• 2005

This landscape design proposal was presented for a competition for mixed-use development project by project financing in Asan Baebang which was held by the Korea National Housing Corporation in July of 2005. The site is a center of Asan Baebang New Town Development District and has a commercial area of $57,929m^{2}$. Design guidelines and judging criteria of this competition were to build a symbolic center and cultural core for district, to elevate positive image and identity of Asan New Town by attractive place making, to link with separated block in the site and regional context, and to make environmentally sustainable design by creating an attractive waterfront of Jang Jae stream passing through the site. This is the most important condition for the design. Therefore, the authors developed design concept and strategy within the guidelines and this conditions. The schema of the design was introduced by the water in the site. To evolve design concept, we reinterpreted water and context in the site combining with landscape design strategy. So the proposal set the main design concept as 'all that is solid melt into water' as if Marshall Berman said. By doing that, design concept of the proposal evolved as follows: 'extension' of water and greer, 'a joint' of space,'newness' of experience, 'breath' of consensus with each other. The spatial concept of this project was developed by expressing five theme spaces; eco zone, entertainment zone, art zone, culture zone, leisure zone. These theme spaces were consecutively placed along the pedestrian path and to consists of vertical layer in each level and diverse design technique and spatial effects are used.

• Journal of Mechanical Science and Technology
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• v.19 no.2
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• pp.634-648
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• 2005

Performed here is a comparative assessment study for the probabilistic fracture mechanics approach of the pressurized thermal shock of the reactor pressure vessel. A round robin consisting of one prerequisite deterministic study and five cases for probabilistic approaches is proposed, and all organizations interested are invited. The problems are solved by the participants and their results are compared to issue some recommendation of best practices and to assure an understanding of the key parameters in this type of approach, like transient description and frequency, material properties, defect type and distribution, fracture mechanics methodology etc., which will be useful in the justification through a probabilistic approach for the case of a plant over-passing the screening criteria. Six participants from 3 organizations responded to the problem and their results are compiled and analyzed in this study.

• Journal of Korean Tunnelling and Underground Space Association
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• v.2 no.2
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• pp.62-71
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• 2000

The abandoned mines causing settlement of the surface above and collapse of the cavities are the major influencing factor on the stability of the nearby underground structures. To prevent the harmful effect, the backfill methods are commonly applied to the cavities although the design criteria and the analysis method are not properly addressed in some cases. An approximate analytical method together with the numerical technique is considered in this study to simulate the gradual deterioration of the rock masses around the cavities and, therefore, the influential zone to the underground structures passing through the cavities. Also considered in this study is the backfill effect on the stability of the rock masses around the cavities. Specifically, the incomplete backfill effect is compared with that of the idealized backfill method by adopting elasto-plastic analysis involving a strain softening material law.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.30 no.2
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• pp.124-133
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• 2020

Objectives: Mask fit is a crucial factor in preventing respiratory infections among healthcare workers. The current coronavirus(COVID-19) pandemic calls for the replacement of imported N95 medical masks with domestic N95 versions. In this study, we aimed to determine whether these masks provide proper protection. Methods: Thirty-five participants from three healthcare institutions donned four types of masks and Quantitative Fit Tests(Portacount, USA) were performed. The order of fit test for the four types of masks was randomized, and a three-minute washout period was applied between test times(2 min 29 sec) to reduce potential error stemming from physical exhaustion. Results: There were no significant differences in the Fit Factor for the four types of masks, and there were no gender differences. However, the Fit Factor significantly differed across the three healthcare institutions (p=0.007). With eight of the 35 participants passing, the pass rate with the criteria of 100 or higher was 21%. Conclusions: The mask used in this study was a new domestic N95 medical mask, and the participants were unfamiliar with how to wear it. They reported difficulties with mask fitting. In light of a previous finding that mask fit improved with frequently used masks, wearer preferred masks, or when masks that are regularly worn are used during fit training, the fact that participants were unfamiliar with the mask used in this study is a limitation that should not be overlooked.

• Korean Journal of Environmental Agriculture
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• v.26 no.3
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• pp.204-209
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• 2007

Agricultural area in the vicinity of the ${\triangle}{\triangle}$ smelting factory in Kyeongbuk province, the third largest zinc smelting factory in the world, was contaminated by high concentration of heavy metals. However, the heavy metals source was not yet directly traced and thus, resulted to a conflict between the factory and residents within its vicinity. In order to determine the level of heavy metal contamination in the arable lands located at the north eastern part of the factory, soils were sampled systematically. To find out the major reason for the occurrence of this problem, waters and aerosols were sampled with constant intervals to the upward and downward direction from the factory and were analyzed to find out the heavy metal concentrations. Cadmium (Cd) and zinc (Zn) of the heavy metals were highly accumulated more than the Korean warning criteria (Cd 1.5, Zn 300 mg $kg^{-1}$) with mean values 1.7 and 407 mg $kg^{-1}$, respectively, at the surface soils (0-20 cm), and heavy metal concentration significantly decreased with increasing soil depth In addition, the concentration of both metals slightly decreased with increasing distance from the factory to the surface soils. Cadmium and Zn were detected in the upward stream water with low concentration and concentrations increased significantly in the downstream after passing across the factory. Aerosol samples also showed traces of Cd and Zn which could be attributed to the contamination of the water system and the surface soils. Conclusively, Cd and Zn emitted from the ${\triangle}{\triangle}$ smelting factory moved with the aerosol in the atmosphere and thus, contaminated the agricultural areas and the water system within it vicinity.

• Journal of the Korean Geotechnical Society
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• v.29 no.9
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• pp.55-69
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• 2013

An alternative design method of existing methods based on elastic theory the design method of roadbed considering plastic deformation of roadbed and stress-strain at roadbed materials with the cyclic loading of trains passing. The characteristics of the developed design method considering traffic load, number of cyclic loading and resilience modulus of roadbed materials can evaluate elastic strain as well as plastic settlement with allowable design criteria. The proposed design method is applied to standard roadbed section drawing of HONAM high-speed railway considering design conditions such as allowable elastic and plastic settlement, train speed, the tonnage of trains. As a result, required levels of resilience modulus model parameter ($A_E$), unconfined compressive strength, types of soil material were evaluated.