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        A Study of a Mobile Launch Platform Effect on Bi-folded Wing Deployment

        이영환,이재은,김민규,정석영 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.3

        This study considers a mobile platform effect on a bifolded wing deployment. An additional velocity induced by a mobile launch platform was applied. Therefore, aerodynamic moments on a deploying bi-folded wing were calculated with wind-over-deck velocity, a vector sum of the platform velocity and the wind velocity. In the calculation, the panel method is applied to obtain the moments for quick aerodynamic prediction. Then, wind tunnel tests were conducted to measure the aerodynamic moments. As a result, considering the velocity of the mobile launch platform as a vector quantity provides more realistic and reasonable aerodynamic moments for the design criteria of deploying devices.

      • 복지전달체계의 효율성 제고를 위한 법·제도적 연구

        이영환 한국경제연구원 2013 한국경제연구원 정책연구 Vol.2013 No.2

        '스콜라' 이용 시 소속기관이 구독 중이 아닌 경우, 오후 4시부터 익일 오전 7시까지 원문보기가 가능합니다.

      • KCI등재

        공기중 유기용제 농도 측정에 있어서 수동식 시료채취기의 성능평가 및 한국산 수동식 시료채취기의 개발에 관한 연구 : 제2부 : 한국산 수동식 시료채취기의 개발 Part 2 : Development of New Passive Samplers

        이영환,백남원,박정임,공상휘 한국산업위생학회 1996 한국산업보건학회지 Vol.6 No.1

        A new type of passive samplers were designed and produced by authors. After evaluating the quality of activated carbon by measuring recovery rate of organic vapors and steadiness of sampling rate, activated carbon with 30 - 35 mesh produced by Company S in Korea was selected. In each passive sampler, an amount of 400 ㎎ of the activated carbon was filled in 25-㎜ cassette and covered by fixed screen (or wire screen with 100 mesh). In addition to the fixed screen, a wind screen (or wire screen with 300 mesh) was also attached at outer face. The sampling rate of the new Korean passive samplers was estimated. Conclusions obtained in the study are as follows. 1 Sampling rates of the newly developed Korean passive samplers were affected by sampling time. For n-hexane, sampling rates of 15- and 60-minute samples were 70.92 and 37.45 ㎖/min, respectively. Sampling rate of both 200- and 450-minute samples was 25.96 ㎖/min. It is concluded that, when passive samplers are used for measuring organic vapors, samples be collected longer than 60 minutes. 2. Sampling rate of the passive samplers was also affected by airborne concentration of organic vapors. Lower sampling rates were determined at Level of 1/2 threshold limit values (TLVs) recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). It is recommended that sampling rate of the passive samplers be obtained at site by measuring concentrations using both the NIOSH Method and passive samplers simultaneously. 3. When the passive samplers, which collected organic vapors, were exposed to clean air for five hours, there was no significant loss of organic vapors due to reverse diffusion. 4. When samples were stored at room temperature (21.8 ± 0.7℃) and refrigerator (3.8 0.7℃), there was no significant difference in the accuracy of results. For trichloroethylene and n-hexane, accuracies were within 25 % at both temperatures until seven days. However, poor accuracy exceeding 25 % was indicated in toluene from the first day. It is recommended that samples be stored at freezing temperature below 0 ℃. 5. Sampling efficiency was significantly affected by direction of the passive samplers. Results of samplers facing wind and down, respectively, were compared. Lower amount of organic vapors were collected when the sampler was oriented down. It is recommended that, when air velocity is low in plants, the passive samplers be oriented to the wind. However, when air velocity is high, the passive samplers be oriented down.

      • KCI등재

        용융가압함침공정으로 제조된 TiC 세라믹 입자 강화 철강복합재의 염수환경에서의 부식 특성

        이영환,고성민,신상민,조승찬,김양도,김정환,이상관,이상복 한국복합재료학회 2020 Composites research Vol.33 No.5

        In this study, TiC ceramic particulate reinforced steel composites was fabricated using a liquid pressing infiltration process. Studies were conducted on microstructure analysis and basic physical properties such as hardness and corrosion characteristics in salt water environment for comparison with commercial nodular cast iron. As a result of comparison of corrosion characteristics in a salt water environment, both corrosion potential and corrosion current density were lower than that of ductile graphite cast iron. The lower calculated corrosion rate confirms that the TiC-Fe metal composite has superior corrosion resistance than the cast iron. 본 연구에서는 용융가압함침공정을 이용하여 제조된 TiC 세라믹 입자강화 철강복합재를 제조하고 상용구상흑연주철과 비교를 위하여 미세조직 분석 및 경도 등 기초물성과 선박 해양 분야등의 적용가능성 검토를 위하여 염수환경에서의 부식 특성에 관한 연구를 진행하였다. 염수환경에서의 부식특성 비교 결과 구상흑연주철 대비 부식전위와 부식전류밀도 모두 낮은 값을 나타내었고, 낮은 연간부식률을 통하여 TiC-Fe 금속복합재의 내식성이 더 뛰어난 것을 확인하였다.

      • 도로 건설 현장 인력ㆍ업무 실태 분석 및 최적화 방안

        이영환,장철기,구본상 한국건설산업연구원 2006 한국건설산업연구원 연구보고서 Vol.2006 No.12

        '스콜라' 이용 시 소속기관이 구독 중이 아닌 경우, 오후 4시부터 익일 오전 7시까지 원문보기가 가능합니다.

        제1장 서론 - 국내 건설기업은 여러 가지 급변하는 대내ㆍ외 환경 변화에 적응하고 있으며, 이런 변화는 현장조직의 운영 조직의 운영 체계에도 많은 영향을 끼치고 있음. ㆍ건설기업의 인당 매출액 목표치의 상향 조정과 외주비 비중의 증가 추세 지속. ㆍ공공 발주기관 및 건설기업의 지속적인 업무 프로세스 혁신 수행과 IT 기술을 활용한 현장관리 업무의 정보화 촉진. ㆍ건설산업 구조개편에 따른 현장 생산체계의 변화가 불가피. ㆍ대형 건설기업을 중심으로 한 현장조직 슬림화를 위한 시범사업 시행. - 건설기업의 현장조직 최적화에 대해서 다음과 같은 문제점을 제기하고 있음. ㆍ인당 매출액 목표치를 달성하기 위해서 ‘Top-Down’ 방식으로 추진되고 있는 ‘현장 슬림화’가 최적화 방안인가? ㆍ‘현장 슬림화’가 국내 건설기업의 현장조직의 최적화 방안으로 자리 매김을 하기 위해서는 현상 분석과 제반 전제조건에 대한 해결방안을 강구해야 하는데 이에 대한 준비가 미흡하다는 지적. ㆍ국내 건설산업 전반에 대한 실태분석이 없어서 우리 회사가 운용하고 있는 현장조직 운영방안이 적정한가? ㆍ급변하는 대내ㆍ외 환경을 고려한 현장조직 최적화에 대한 방향성 제시가 필요한 시점. - 따라서, - 본 연구는 대형 및 중견 건설기업의 국내 도로 건설공사의 현장조직 운영에 대한 다양한 관점에서의 실태 조사 및 분석을 통해 현장조직 운영 현황과 향후 전개 방향을 파악하며, 이를 토대로 하여 국내 도로 건설공사 현장조직의 최적화 방안을 제안하고자 함. 제2장 국내 도로 건설공사 현장 생산체계 분석 - 국내 도로 건설공사의 현장 업무 수행체계는 발주기관, 건설사업소(고속국도의 경우), 현장감리단(현장감독관), 시공계약자, 하도급계약자 등으로 구성함. - 고속도로 현장 조직 체계는 현장(공구)별로 3~4명의 현장 주재 감독원을 파견하여 공사를 관리하며, 검측원을 활용하는 자체 감독 체계를 채택함. ㆍ물량이 초과되는 부분에는 자문감리단을 활용하는 경우와 책임감리단이 현장관리 업무를 수행하는 사례도 존재. - 국도 건설공사는 공사관리관이 여러 개의 공구로 구성된 노선을 담당하고, 공구별 책임감리단이 시공계약자의 업무를 관리함. - 시공자(원도급업체)의 일반적인 현장조직 체계는 소장을 정점으로 하여 공사, 공무, 관리, 품질 분야를 하부조직으로 구성하나, 안전은 하부조직과의 업무 독립성을 고려하여 소장의 직할조직으로 배치함. ㆍ시공계약자의 현장조직에서 소장(현장대리인), 품질관리자, 안전관리자, 환경관리자(해당되는 경우에만 선임) 등은 관련법의 기준(첨부1 참조 에 의하여 자격을 갖춘 자를 선임하여 배치. ㆍ품질 분야는 「건설기술관리법」의 건설공사 품질관리를 위한 시설 및 품질관리자 배치기준을 충족시키는 인원수를 배치하며, 일반적으로 고속국도 현장의 품질관리 인원이 국도 건설 현장보다 많이 배치. - 장기계속계약에서 전체 계약금액을 기준으로 투입인원을 규정하는 현행의 방식보다 연도별 예산 규모를 고려한 배치 기준 적용이 타당하다는 의견 제시. - 대부분의 업체에서 도로 현장 인원 투입과 관련하여 일정한 기준은 있으며, 여러 가지 제반 요소를 고려하여 인력 투입 정도를 결정하나, 투입인력의 최소화를 목표로 함. ㆍ제반 요소는 해당 공사의 연도별 매출 기준 인당 생산성, 공 Recent policy changes in general to specialty contract regulations, innovations in process improvements and implementation of IT applications, and pressures to improve per capita income of construction companies has made imperative the need to change how general contractors manage and control their sites. One aspect of change in particular is to ‘slim’ down general contractors’ site office personnel, by reducing the total number of workforce on site and streamlining or delegating to other parties daily site management activities. However, initiatives to improve organizational effectiveness of site office personnel have been performed in an ad hoc fashion without an objective study of the roles and responsibilities of site personnel. In addition, there is an absence of a thorough analysis of the prerequisite conditions that make such initiatives feasible. Needless to day, results of such efforts to date has been met with mixed success. The goal of this researchis to take an objective view of how general contractors manage sites today, determine the minimum and optimal number of field personnel, identify site management activities that may be outsourced or delegated to minimize field personnel, and provide recommendations that allow a more structured and transitional approach to optimizing field personnel. The study is limited to road construction, as it comprises the largest part of public sector civil construction, and is notoriously less productive compared to other sectors (e.g., building construction). A survey was designed based on a preliminary review of site personnel regulations and an independent effects analysis. Specifically, the survey inquired on the main factors (e.g., construction budget, type of road, etc.) that affected the number of site personnel general contractors employed, and the criteria they used to make such decisions. In addition, the survey also inquired on the roles and responsibilities site personnel performed and which activities could be delegated or outsourced to the main office or subcontractors. This survey was distributed to the top 200 Korean contractors, from which 181 site surveys were retrieved. Analysis of the results showed that the average productivity of field personnel, in terms of revenue ""per man-month,"" was 88.9 million won, which is translated to approximately 1.06 billion won/year per capita. As expected, this figure is much lower than the average of the rest of civil construction, which is typically 1.44 billion won/year per capita. The major factors ofstatistical relevance that influenced the average number of site personnel include the size of the company, type of road construction (highways, state and local), type of contract (public versus private), budget appropriation method, subcontract method and ratio between permanent and temporary hires. Analysis into daily site activities revealed that while some of the work could be delegated to the main office, the majority of the work was site specific. Instead, results of the survey showthat the overload in general contractors’ daily activities could be improved by allocating many of the tasks to subcontractors. While currently most of the subcontractors work portion is limited to on-site construction work, delegating additional activities such as scheduling, cost control, safety and quality inspections would ease the burden of general contractors. However, the contractors also noted that for this to be feasible, subcontractors need to be educated first and foremost in everyday construction management skills, such as schedule management, cost control and quality procedures. In addition,the analysis indicated that anotherway to decrease the contractor’s burden was to package individual construction tasks into a single contract, which would alleviate general contractors from managing contracts individually.  

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