• 한국방재학회:학술대회논문집
• /
• 2011.02a
• /
• pp.159-159
• /
• 2011

수자원 공급의 시 공간적 편차가 큰 우리나라에서는 수자원을 이용하기 위해서 다수의 댐을 건설하고 있다. 특히, 생활수준의 향상으로 용수 수요가 급증하였기 때문에 용수가 부족한 곳에는 광역상수도 사업 등을 통하여 용수를 공급하고 있다. 댐에서 용수가 공급되기까지의 과정은 일종의 관수로 흐름으로 생각할 수 있다. 관수로 내를 흐르는 유체가 갑자기 정지하게 되면, 유체 운동 에너지의 변화가 유발되고, 그로 인해 관내에 급격한 압력의 상승이 일어나게 된다. 반대로 정지하고 있던 유체가 빠른 속도로 흐르게 되면 압력 감소가 급격하게 발생한다. 이와 같이 유체 운동 상태의 급변에 의한 압력변화와 그에 따른 압력파가 음속의 속도로 상 하류로 전파되는 현상을 수격작용(waterhammer)이라 한다. 통상적으로 수격작용은 밸브 개폐 정도가 갑자기 바뀔 때, 펌프의 급격한 기동이나 정지 시, 터빈 내 전력소요가 갑자기 바뀔 때, 댐 수위의 갑작스런 변화, 펌프 임펠러의 진동, 물 수요의 급격한 변화 등에 의해 발생하며, 수격작용은 유체의 질량과 운동량 때문에 관 벽에 큰 힘을 가하게 되어 정상적인 동수압 보다 몇 배나 큰 압력을 발생시킴으로 관 자체는 물론 펌프, 밸브, 터빈 등 관 시설물을 파손시키거나 진동, 소음 등을 야기시킴으로 대규모 건물, 공장, 발전소 등을 설계할 경우 그에 대한 적절한 대책을 강구하여야 한다. 특히 댐에 연결된 저수지 또는 조정지로부터의 도수로가 압력수로이며 그 길이가 상당히 크면 수차가 급정지했을 경우 수격작용에 의해서 압력터널 내에 과도한 압력상승이 일어난다. 이 압력상승을 방지함과 함께 발전소 부하의 증감에 따라서 수량을 공급하거나, 흡수할 목적으로 압력도수로와 수압관과의 접합부에 자유수면이 있는 수조를 설치한다. 이것을 조압수조(surge tank)라 한다(최영박, 1979). 조압수조에서 부하의 급속한 차단에 의해서 수차로 유입될 수량이 차단되면 도수로 내로 흘러 들어온 물은 관성 때문에 수조 내의 수위를 상승시키고, 수조 수위가 어느 정도 이상으로 되어 저수지 수위 보다 상승하면 수조로의 유입이 정지하고 반대로 수조에서 저수지로 역류하여 수조수위는 하강한다. 즉, 조압수조는 도수로 내에 발생한 과도한 압력을 수조 내 수면의 승강운동을 이용하여 감소시키고 원래의 안정적인 수위로 회복시킨다. 본 연구에서는 수격작용에 대한 댐 안정성을 확보하는 수단 중의 하나인 조압수조에 대해 살펴보았다. 연구대상으로 용담댐을 선정하였다. 용담댐에 대한 기존의 검토결과 수직 갱의 지름이 5m 이상이면 조압수조의 동적안정조건을 만족 시키는 것으로 조사되었다. 댐의 설계홍수위인 EL. 265.5m를 기준으로 조압수조의 안정성을 감소시키지 않는 범위 내에서 조압수조 내 격벽 설치 유 무에 따른 수조의 최적 크기를 산정하였다. 산정결과를 분석한 결과 동일 조건에서 격벽을 설치한 경우가 격벽을 설치하지 않은 경우에 비해서 조압수조의 면적이 약 21% 감소하는 것으로 나타났다.

• Korean Journal of Construction Engineering and Management
• /
• v.23 no.6
• /
• pp.30-42
• /
• 2022

OSC is a type of supply chain and value chain that spans the entire process of construction production (planning, design, construction, maintenance, etc.). It is a method of producing the final object by manufacturing it in a factory, transporting it to the site, installing and construction. This research as is the construction cost was compared for each case A, which applied the PC method, and case B, which applied the RC method. In the case of applying the PC method (excluding the PC design cost), compared to the case where only the RC method was applied, the frame construction cost per unit quantity (m³) increased by about 70% (50% based on the total RC construction type). Of the total frame construction cost of PC method application, PC accounted for 90.2%, 'PC manufacturing cost' 54.8%, 'PC assembly cost' 28.5%, and 'transportation cost' accounted for 6.89%. Also a decision-making framework that can consider both costs and benefits was established. In the case of benefits, the construction period, defect repair, disaster occurrence, energy efficiency, noise/dust/waste, and greenhouse gas emission indicators reflecting OSC technical advantages were presented. It can contribute to providing a basis for helping decision-making on the introduction of PC apartment houses using OSC.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.24 no.7
• /
• pp.848-857
• /
• 2018

Recently, around the world, active development of new renewable energy sources including solar power, waves, and fuel cells, etc. has taken place. Particularly, floating offshore wind farms have been developed for saving costs through large scale production, using high-quality wind power and minimizing noise damage in the ocean area. The development of floating wind farms requires an evaluation of the Maritime Safety Audit Scheme under the Maritime Safety Act in Korea. Floating wind farms shall be assessed by applying the line and area concept for systematic development, management and utilization of specified sea water. The development of appropriate evaluation methods and standards is also required. In this study, proper standards for marine traffic surveys and assessments were established and a systemic treatment was studied for assessing marine spatial area. First, a marine traffic data collector using AIS or radar was designed to conduct marine traffic surveys. In addition, assessment methods were proposed such as historical tracks, traffic density and marine traffic pattern analysis applying the line and area concept. Marine traffic density can be evaluated by spatial and temporal means, with an adjusted grid-cell scale. Marine traffic pattern analysis was proposed for assessing ship movement patterns for transit or work in sea areas. Finally, conceptual design of a Marine Traffic and Safety Assessment Solution (MaTSAS) was competed that can be analyzed automatically to collect and assess the marine traffic data. It could be possible to minimize inaccurate estimation due to human errors such as data omission or misprints through automated and systematic collection, analysis and retrieval of marine traffic data. This study could provides reliable assessment results, reflecting the line and area concept, according to sea area usage.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.45 no.6
• /
• pp.62-75
• /
• 2017

This study analyzes the multiple effects of the following three aspects of waterscape facilities within apartment complexes: planning/designing, maintenance/management, and use of the facilities and suggests primary documents that will be fundamental for the methods to accelerate the implementation of waterscape facilities. A survey and analysis was conducted among a few of the most representative private apartment complexes in Seoul in accordance with the management and operation of waterscape facilities. The analysis used frequency analysis, descriptive statistics, reliability test, t-test, and PLS regression analysis. The research findings are as follows: first, the degree of use of waterscape facilities was found to be low regardless of the levels of operation, but residents' preference for the facilities was shown to be high, thus indicating there are still high expectations on the part of residents. Second, regardless of whether the facilities are being operated efficiently, the two items of location and display method under the section of planning and designing and the two items of aptitude and convenience under the section of use were found to positively affect the operation and use of waterscape facilities. Particularly, the item of freshness, cleanliness was shown to be directly and indirectly correlated with obsolescence, administration costs, and noise, which negatively affect the operation. Third, it was found that the administration costs itself that had been shown as the most negative factor of operating landscaping facilities in previous research did not cause problems in the residential area where the facilities are not operated efficiently. The finding suggests that the administration costs do not matter but that in the case of experience- and entertainment-typed facilities that residents want, they are linked to problems that do not introduce the desired facilities. Fourth, it was found that various aspects of planning, designing, maintaining, and using facilities interconnect and affect one another in the process of operating and using waterscape facilities resulting in the need to have a comprehensive approach to these three factors of planning, design, maintenance, management, and utilization. This study proposes that the needs and values of residents should be reflected to activate the introduction of landscaping facilities in the apartment complexes.

• The Korean Journal of Nuclear Medicine Technology
• /
• v.14 no.1
• /
• pp.61-66
• /
• 2010

Purpose: Recently, Department of Nuclear Medicine have an interest in Video Display Terminals (VDT) syndrome including musculoskeletal disorders, ophthalmologic disorders, trouble of electromagnetic waves and stress disorders occur to VDT workers as the growing number of users and rapid pace of service period supply in large amount. This study research on the actual condition for VDT syndrome in Nuclear Medicine, Seoul National University Hospital (SNUH), discover the problem and draw a plan of upcoming improvement. The aim of this study establish awareness about VDT syndrome and is to prevent for it in the long run. Materials and Methods: Department of Nuclear Medicine, SNUH is composed Principle part, Pediatric part and PET center. We estimated risk factors visit in each part directly. Estimation method use "Check list for VDT work" of Wonjin working environment health laboratory and check list is condition of VDT work, condition of work tables, condition of chairs, condition of keyboards, condition of monitors, working position, character of health management and other working environment. Analysis result is verified in Department of Occupational and Environment, Hallym University Sacred Heard Hospital. Results: As a result of analysis, VDT condition of Department of Nuclear Medicine, SNUH is rule good. In case of work tables, recent of things are suitable to users upon the ergonomical planning, but 15% of existing work tables are below the standard value. In case of chairs are suitable, but 5% of theirs lost optimum capacity become superannuated. The keyboards are suitable for 98% of standard value. In case of monitors, angle control of screen is possible of all, but positioning control is impossible for 38%. In case of working position, 10% is fixed positioning for long time and some of the items researched unsuitable things for standard. At health management point, needed capable of improvement. Also, other working condition as lighting, temperature, noise and ventilation, discovered the problem, but is sufficient to advice value. Conclusion: VDT syndrome is occurrences of possibility continuously, come economical expensive about improvement, is inherent in various causes and originate without your knowledge. So, there is need systematic management system. In Nuclear Medicine, VDT syndrome make it better that constant interest and effort as improvement of ergonomical working environment, improvement of working procedure, regular exercise and steady stretching, and can be prevented fairly. This promote physical and mental condition of worker in top form in comfortable working environment, so this is judged by enlargement of operations efficiency and rising of satisfaction ratings of the inside client.

• Journal of the Korean Geosynthetics Society
• /
• v.18 no.4
• /
• pp.115-127
• /
• 2019

The low-flow grouting injection technique, the target construction method for this study, is a method of pouring mortar into the ground by non-emission replacement principle, which can be expected to increase the density of the ground, and, in some cases, be used as a base file using the strength of the high injection solids, along with low noise, low pollution, and high durability. To verify that the dynamic characteristics of the ground are improved by the low-flow injection technique, the test work was conducted on the site and physical tests were performed, and the quality of the improvement formed in the ground was verified through the indoor test on the core and core recovery rate was analyzed. The density logs test layer calculated the volume density of the ground layer by using the Compton scattering of gamma-rays, and the sonic logs was tested on the ground around the drill hole using a detector consisting of sonar and receiver devices inside the drill hole. As a result of the measurement of the change in physical properties (density and sonic logs) before and after grouting, both properties were basically increased after infusion of grout agent. However, the variation in density increase was greater than the increase in speed after grouting, and the ground density measurement method was thought to be effective in measuring the fill effect of the filler. Strength and core recovery rates were measured from specimens taken after the age of 28 days, and the results of the test results of the diffusion and strength test of the improved products were verified to satisfy the design criteria, thereby satisfying the seismic performance reinforcement.

• Resources Recycling
• /
• v.19 no.3
• /
• pp.24-32
• /
• 2010

In the present work, a new separation system with rotating rakes has been developed to separate the film-based plastics from the recyclable materials, and environment assessment is also carried out during operation of the device. Capacity of the device was about 5.3 ton/hr at a rakes rotation speed of 26.0 rpm (the number of rakes in the 1st, 2nd and 3rd trials were 39, 52 and 48, respectively) and a belt conveyor speed of 38.5m/min, which satisfied the initial design capacity (5.0 ton/hr). Recovery ratio and purity of the plastic films were 92.6% and 96.5%, respectively at a rotation speed of 28 rpm. The levels of noise, vibration and particulate emission were below material standard regulatory limits. Plastic refused fuel (RPF) was also prepared with the recovered films. The calorific value and chlorine content of the prepared RPF were 9,740 kcal/kg and 0.18%, respectively which satisfy the first grade quality specification of the Korean RPF standard. As a result of this work, recovery of energy resources from the municipal solid waste is possible by adopting the developed separation device.

• Proceedings of the Korean Society for Rock Mechanics Conference
• /
• 2008.03a
• /
• pp.51-68
• /
• 2008

When the train enters into a tunnel a high speed, pressure waves are generated inside the tunnel. The pressure waves at propagate in a form of compression wave toward the tunnel exit and a fraction of the compression waves that arrives at the exit of the tunnel are discharged to outside of the tunnel and the remainder is reflected into the tunnel as expansion waves. The compression waves emitted from the tunnel does not radiate in a specific direction but in all directions. If the amplitude of the compression wave is great, it causes noise and vibration, and it is called "Micro-Pressure Wave." "Micro-Pressure Wave" must be considered as a decision for the optimum tunnel cross-section as the amplitude of the compression wave depends on train speed, tunnel length, area of tunnel and train. Therefore, this paper introduces the case study of Micro-Pressure Wave characteristics for determination of tunnel cross section in Honam high speed railway, the pressure inside the tunnel and the micro-pressure waves at tunnel exit were measured at Hwashin 5 tunnel in Kyungbu HSR line. At the same time. a test of train operation model was performed and then the measurement results and test results were compared to verify that the various parameters used as input conditions for the numerical simulations, which were appropriate. Also a model test was performed, in order to analysis of the Micro-Pressure Wave Mitigation Performance by Type of Hood at Entrance Portal.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.42 no.6
• /
• pp.751-762
• /
• 2022

Welded head studs are mainly used as shear connectors to bond steel girders and concrete slabs in steel-concrete composite bridges. For welded shear connectors, environmental problems include noise and scattering dust which are generated during the removal of damaged or aged slabs. Therefore, it is necessary to develop demountable shear connectors that can easily replace aged concrete slabs for efficient maintenance and thus for better management of environmental problems and life cycle costs. The buried nut method is commonly studied in relation to bolted shear connectors, but this method is not used in civil structures such as bridges due to low rigidity, low shear resistance, and increased initial slip. In this study, in order to mitigate these problems, a demountable bolted shear connector is proposed in which the buried nut is integrated into the stud column and has a tapered shape at the bottom of an enlarged column shank. To verify the performance of the proposed demountable stud bolts in terms of static shear strength and slip displacement, a horizontal shear test was conducted, with the performance outcomes compared to those of conventional welded studs. It was confirmed that the proposed demountable bolted shear connector is capable of excellent shear performance and that it satisfies the slip displacement and ductility design criteria, meaning that it is feasible as a replacement for existing welding studs.

• The Korean Journal of Air & Space Law and Policy
• /
• v.30 no.2
• /
• pp.3-36
• /
• 2015

As of end of 2014, the population engaging in aviation activities for leisure has reached approximately 13 million, where approximately 356 cases involve a general aircraft, 200 cases involve light aircraft, and 636 cases involve an ULM. The industry for leisure has become a very promising industry in line with rapidly rising living standards which are expected to further increase in the future. The demand for such services is expected to increase over time. The purpose of this paper is to review the development and site selection of airfields in anticipation of these developments in the industry. While the government also has experience in the review of airfield location and candidate sites, it is not the government that carries out the actual construction. As such, the feasibility of the site needs to be verified in terms of actual construction. This study identified factors for Site Selection of factors through a review of related documents and existing research reports. A questionnaire was also used to collect the views of experts in the field, which was then analyzed. The Research model was confirmed in the layered form for an AHP analysis. The factors for Site Selection were identified as the technical / operational factors and economic / political elements for a two-stage configuration. The third step consisted of technical and operational elements. The final step is was constructed a total of 11 elements (weather, surface conditions, obstacle limitation surface, airspace conditions, operating procedures, noise problems, environmental issues, availability of facilities, construction and investment costs, contribution to the local economy, accessibility, demand / the proximity of demand). The surveys are conducted for more than 10 General and light aircraft pilots, professionals, and instructor. The analysis results showed a higher level in the technical / operating elements (73.2%) in the first step, while the next step sawa higher level of the operational elements (30.9%) than the other. The factors for Site Selection were any particular elements did not appear high, the weather conditions (17.5%), noise problems (19.8%), the proximity of demand (6%), accessibility (5.7%), environmental issues (11.1%), availability of facilities (8%), airspace conditions (7.9%), obstacle limitation surface (12%), construction and investment costs (4.2%) and to operating procedures (4.9%), contribution to the local economy (3.8%).