• 한국지반신소재학회논문집
• /
• 제12권3호
• /
• pp.75-79
• /
• 2013

동결깊이는 영구 동토지역 및 계절성 동토지역에서 도로의 동상방지층, 매설관의 깊이 및 건물의 기초를 설계하는데 중요한 고려사항이다. methylene blue 동결깊이 측정장치는 지중 온도센서를 이용한 계측시스템과 비교하여 저렴하고 유지관리와 측정이 용이한 장점을 지니고 있다. 그러나 지반공학적 관점에서 지중에 매설된 methylene blue 동결깊이 측정장치의 신뢰성을 검토한 연구는 미미하다. 본 논문에서는 실내실험과 현장실험을 통해 methylene blue 동결깊이 측정장치의 신뢰성을 검토하고, 나아가 국내 현장에서 검증된 측정장치로 장기간 측정된 동결깊이 실측 데이터를 이용하여 최대 동결깊이 분포도를 작성하였다. 본 연구를 바탕으로 실측된 동결깊이는 향후 국내 지반구조물 설계에 중요한 자료로 활용될 수 있을 것으로 판단된다.

• 한국생활과학회지
• /
• 제20권5호
• /
• pp.1075-1091
• /
• 2011

The purposes of this study were to investigate the actual state of indoor air quality in semi-underground multi-family housing units in early summer, to analyze the influencing factors, and to make suggestions for improvement. A series of field investigations were conducted in four target units between June 22, 2010, and June 28, 2010. The field investigations included measurements of indoor air quality as well as the observation of architectural characteristics and living conditions. In addition to the field investigation, on-site questionnaire surveys were administrated to residents in 90 units. The findings are summarized as follows: (1) The average $CO_2$ levels in each of the four units ranged from 759ppm to 1885ppm. $CO_2$ levels in three units exceeded the evaluation standard (1000ppm), and one unit was lower than the standard. This unit had smaller number of staying person and a large amount of ventilation than others; (2) the average CO levels in each unit were almost 0ppm, but 0.1~1.1 levels of CO were revealed at several times; (3) the average PM-10 levels ranged from $8{\mu}g/m^3$ to $40{\mu}g/m^3$, which distributes within the standard ($150{\mu}g/m^3$). The influencing factors of PM-10 levels were analyzed as inflow from outside, the use of a gas range, and the residents' activities; (4) therefore, it was evaluated to be necessary to improve ventilation for the indoor air quality of semi-underground housing in aspect of $CO_2$ levels.

• 한국산업보건학회지
• /
• 제31권3호
• /
• pp.266-273
• /
• 2021

Objective: The objective of this study was to suggest improvement methods for investigations and systems through a review of musculoskeletal risk factor investigation reports conducted in the workplace. Methods: A total of 34 reports on musculoskeletal risk factor investigations were reviewed. To confirm the appropriateness of the evaluation, reevaluation was conducted through a field investigation using other evaluation tools. In order to understand the effectiveness of the improvement plan, a survey was conducted with those in charge of tasks with ergonomic burdens. Results: As a result of performing a field survey using the work sampling method recommended by the KOSHA (Korea Occupational Safety and Health Agency) for ten tasks, eight tasks were determined to pose an ergonomic burden. When 30 tasks were evaluated with RULA (rapid entire body assessment), 90% of them were evaluated at a higher level than the results of the workplace survey. Among the improvement measures, only 36% of the field workers affirmed them, and in only 19% of the workplaces were actual improvements made. Conclusions: In order to improve the ergonomic investigation system for risk factors in the ergonomic burden task, it is necessary to secure the objectivity of the evaluation performed by the institution and enable the active participation of workers in improvement activities.

• Journal of Advanced Research in Ocean Engineering
• /
• 제1권3호
• /
• pp.186-197
• /
• 2015

In summer 2010, field measurements of local ice loads were carried out in the Arctic Ocean using the Korean first icebreaking research vessel, ARAON. In some previous studies by the authors, several investigations for the data measured at 2010 including the relationship between the measuring points and ice loads, the possibility for observation of higher ice load and the relationship between the ship speed and ice loads were reported. During 10 days in August 2013, new field measurements were performed in similar waters of the Arctic Ocean using the same vessel, ARAON. The aim of this study is to investigate the statistical properties of 2013 measurements and compare results by two periods.

• 융합보안논문지
• /
• 제7권3호
• /
• pp.31-37
• /
• 2007

유비쿼터스 환경에서 개인 프라이버시를 보호하기 위한 RFID 시스템 보안에 대한 많은 연구가 이루어지고 있다. RFID 시스템 보안 중 상호인증 방법으로 XOR 기반, 해쉬기반, 그리고 재암호화 기반의 프로토콜을 사용한다. 그러나 인증과 프라이버시를 보호하기 위한 프로토콜은 좀 더 강화된 암호 시스템을 사용해야 한다. 공개키는 강력한 보안성을 제공하나, 비용이 많이 요구되어 RFID 시스템에서 사용하기에는 적합하지 않다. 따라서 본 논문에서는 상호 인증과 안전성을 위하여 유한체 GF($2^n$)을 이용한 인증 프로토콜을 제안하고 RFID 시스템에서의 여러 공격에 대하여 안전성 분석을 하였다.

• 농촌계획
• /
• 제7권2호
• /
• pp.3-11
• /
• 2001

A portable GPS receiver and a navigation software were used to investigate land application practices of manure composts. The field investigation indicated that most of the land application of manure composts were observed before April. Plowing for incorporation of manure with soil were continued from the middle of April. The results also revealed that over 60% of the farms were within 1 km from livestock farms from which manure composts were transported. Most of the farms having land application were dry field rather than paddies, Some of fields located near livestock farms frequently experience over-application of manure composts. It seems to have been difficult to complete the investigation in this study without the Gps/navigation system. The GPS/navigation system will become an essential tool in field investigations such as ecological/environmental monitoring works that require repeated observation at a number of sites.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
• /
• pp.657-662
• /
• 1997

In these day, there have been shortage of construction workers and an increase of labor cost in our county. In order to overcome these problems, prefabricated and mechanized system of bar placing have been used in the construction fields. As a part of this tendency, welded wire fabric(WWF) reinforcement were studied several years ago. In this study, the required working hour. the labor power and the construction process of WWF reinforcement for the apartment building slabs are reported. From the result of field investigations, it is showed that the WWF reinforcement facilitates the field placing and the working time of WWF placing is saved, and then the labor cost of WWF reinforcement is less than that of the conventional bar reinforcement.

• Structural Engineering and Mechanics
• /
• 제35권4호
• /
• pp.409-430
• /
• 2010

The present paper will be concerned to the investigation of the stress-strain field around the cavity that is loaded or partially loaded at the inner surface by the rotationally symmetric loading. The cavity of the spherical, cylindrical or elliptical shape is situated in a stressed elastic continuum, subjected to the gravitation field. As the contribution to the similar investigations, the paper introduces the new function of loading in the form of the infinite sine series. Besides, in this paper the solution of stresses around an oblong ellipsoid cavity, has been obtained using appropriate curvilinear elliptical coordinates. This analytical approach avoids the solutions of the same problem that lead to expressions that contain rather complex integrations. Thus the presented solutions provide the applicable and explicit expressions for stresses and strains developed in infinite series with easily determinable coefficients by the use of contemporary mathematical packages. The numerical examples are also included to confirm the convergence of the obtained solutions.

• Structural Engineering and Mechanics
• /
• 제77권3호
• /
• pp.395-406
• /
• 2021

Near-field underwater explosion (UNDEX) phenomena were investigated by experiments and numerical simulations. The UNDEX experiments were performed in a water tank using a ship-like model. One kilogram of TNT, one of the most widely used military high explosives, was used for the experiments. Numerical simulations were performed under the same conditions as in the experiments using the commercial software LS-DYNA. Underwater pressures, accelerations, velocities, and strains by shock waves were measured at multiple locations. Further, the bubble pulsation period and the whipping deformations of the ship-like model were explored. The experimental results are presented and examined through comparison with the results obtained from widely used empirical equations and numerical simulations.

• 한국소음진동공학회논문집
• /
• 제23권11호
• /
• pp.973-981
• /
• 2013

The main role of an acoustic diffuser is to diffuse reflected sound field spatially. Since the pioneering work of Schroeder, there have been investigations to improve its performance by using shape/sizing optimization methods. In this paper, a gradient-based topology optimization algorithm is newly presented to find the optimal distribution of reflecting materials for maximizing diffuser performance. Time-harmonic acoustic analysis in a two-dimensional acoustic domain is carried out where the domain is discretized by finite elements. Perfectly matched layers are placed to surround the domain to simulate non-reflecting boundary conditions. Design variables are assigned to each element of which material properties are interpolated between those of air and those of a rigid body. An approach to extract the reflected field from the total acoustic field is employed. To validate the effectiveness of the proposed method, design problems are solved at different frequencies. The performance of the optimized diffusers obtained by the proposed method is compared against that of the conventional Schroeder diffusers.