• 제목/요약/키워드: Electric machines

검색결과 266건 처리시간 0.019초

가변피치 프로펠러의 축기전력 특성에 관한 연구 - 세계로호를 중심으로 - (A Study on the Characteristics of Shaft Electric Motive Force of Controllable Pitch Propeller - Focusing on the M/V Segero -)

  • 박경민;임명환;최상범;안병원
    • 해양환경안전학회지
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    • 제28권1호
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    • pp.135-140
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    • 2022
  • 대부분의 기계는 여러 종류의 금속으로 구성된다. 특히 선박의 축계는 프로펠러 날개의 황동과 스테인리스로 된 축으로 이루어져 있다. 이 이종금속이 바닷물의 전해액에 들어가면 볼타 전지를 이루고, 기전력이 발생된다. 이 기전력은 축계를 받치고 있는 베어링과 축을 전기부식 시키는 원인이 된다. 선박에서는 이 부식을 막기 위해 선박에서는 축 접지 시스템을 설치하여 운용하고 있다. 본 연구는 가변피치 프로펠러의 축기전력을 측정하기 위하여 추진축의 전압과 주기관의 회전수를 동시에 측정하였다. 측정장치는 내셔널인스트루먼트사의 24bit A/D컨버터를 사용하여 측정하였고, 프로그램은 LabVIEW를 사용하였다. 주기관의 회전수와 축기전력의 발생, 블레이드 각도에 따른 기전력과, 배의 항해 방향에 따른 축기전력을 측정하고 분석하였다.

Full-scale TBM excavation tests for rock-like materials with different uniaxial compressive strength

  • Gi-Jun Lee;Hee-Hwan Ryu;Gye-Chun Cho;Tae-Hyuk Kwon
    • Geomechanics and Engineering
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    • 제35권5호
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    • pp.487-497
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    • 2023
  • Penetration rate (PR) and penetration depth (Pe) are crucial parameters for estimating the cost and time required in tunnel construction using tunnel boring machines (TBMs). This study focuses on investigating the impact of rock strength on PR and Pe through full-scale experiments. By conducting controlled tests on rock-like specimens, the study aims to understand the contributions of various ground parameters and machine-operating conditions to TBM excavation performance. An earth pressure balanced (EPB) TBM with a sectional diameter of 3.54 m was utilized in the experiments. The TBM excavated rocklike specimens with varying uniaxial compressive strength (UCS), while the thrust and cutterhead rotational speed were controlled. The results highlight the significance of the interplay between thrust, cutterhead speed, and rock strength (UCS) in determining Pe. In high UCS conditions exceeding 70 MPa, thrust plays a vital role in enhancing Pe as hard rock requires a greater thrust force for excavation. Conversely, in medium-to-low UCS conditions less than 50 MPa, thrust has a weak relationship with Pe, and Pe becomes directly proportional to the cutterhead rotational speed. Furthermore, a strong correlation was observed between Pe and cutterhead torque with a determination coefficient of 0.84. Based on these findings, a predictive model for Pe is proposed, incorporating thrust, TBM diameter, number of disc cutters, and UCS. This model offers a practical tool for estimating Pe in different excavation scenarios. The study presents unprecedented full-scale TBM excavation results, with well-controlled experiments, shedding light on the interplay between rock strength, TBM operational variables, and excavation performance. These insights are valuable for optimizing TBM excavation in grounds with varying strengths and operational conditions.

인천항 하역장비 대기오염물질 배출량 산정 연구 (An Study on Estimating Cargo Handling Equipment Emission in the Port of Incheon)

  • 조정정;범태황;이향숙
    • 한국항만경제학회지
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    • 제36권3호
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    • pp.21-38
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    • 2020
  • 최근들어 항만도시에서의 대기오염이 심각한 문제로 대두되고 있다. 그러나 항만의 하역기계에서 배출되는 온실가스는 선박, 트럭 등 타 수단에 비해 상대적으로 주목받지 못하였다. 본 연구에서는 인천항에서 디젤엔진으로 가동되는 하역기계로부터 배출되는 대기오염물질 배출량을 산정하였다. 이를 위해 각 항만하역사로부터 2017년 기준 하역장비의 대수, 제원, 가동시간 등 활동자료를 수집하였다. 분석 결과, CO 105.6톤, NOX 243.2톤, SOX 0.005톤, PM 22.8톤, VOC 26.0톤, NH3 0.2톤이 발생한 것으로 나타났다. CO와 NOX의 배출은 하역기계 전체 배출량의 87.71%를 차지하였으며, 크레인, 지게차, 트랙터, 로더의 배출량이 하역기계 전체 배출량의 84.79%를 차지하였다. 또한 노후화된 디젤엔진을 장착한 하역기계가 주 배출원임을 규명하였다. 분석된 대기오염물질 배출량 수치는 하역기계에 의한 항만 대기 오염의 심각성을 나타내며, 다음과 같은 친환경장비 도입이 시급함을 시사한다. 첫째, 오래된 디젤 장비의 LNG연료 또는 전기장비로의 교체가 필요하다. 둘째, NOX의 배출을 감소시킬 수 있는 선택적환원촉매(SCR)와 같은 후처리장비의 사용이 필요하다. 향후 체계적이고 공식적인 국가 대기오염배출 인벤토리 정립 방법을 설정하고, 매년 하역기계에서 배출되는 대기오염물질 배출량을 모니터링 및 평가하는 것이 필요하다.

익산 제 1 공단 토양의 중금속 함량 분포 조사 (Distribution of Heavy metals in Soil at Iksan 1st Industrial Complex Area)

  • 김성조;백승화;문광현;장광호;김수진
    • 한국환경농학회지
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    • 제17권1호
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    • pp.48-53
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    • 1998
  • 1975년부터 산업활동이 시작된 익산 제1공단내 토양 중에 중금속함량을 비오염지 자연토양 중의 이들 함량과 비교하고 산업활동의 종류에 따른 토양 중 중금속 함량 변화와의 관계를 구명하기 위하여 주로 표층토를 중심으로 $0{\sim}3$$3{\sim}6cm$ 토양층에 있는 Cd, Cu, Ni, Pb 및 Zn의 함량을 조사 분석한 결과는 다음과 같다. 공단 내 토양 중 중금속별 함량변화는 Cd와 Cu는 시료의 $16{\sim}25%$, Pb와 Zn은 93% 이상이 비오염지 자연토양 중 이들 중금속함량 평균치 이상의 토양 중 축적현상을 보였고, Ni함량은 산업활동에 의한 토양 중 변화를 인정할 수 없었다. Cd의 분포는 $0{\sim}3cm$ 토양층은 섬유산업지역에서 5ppm이상의 최고치를 나타내었고, 그 다음이 화학약품 및 식품산업지역에서 높은 것으로 나타났다. $3{\sim}6cm$ 토양층에서는 금속가공지역에서 5ppm 이상의 최고치를 보였고, 다음이 섬유산업지역에서 높은 것으로 나타나 토양층위에 따라 Cd의 축적분포가 조금씩 달랐다. Cu함량은 $0{\sim}3cm$의 토양층에서는 전선류를 제조하는 지역에서 400ppm 이상의 최고치를 나타냈으며, $3{\sim}6cm$ 토양층에서는 전기 저항기, 기계제작 및 전선류 제조지역에서 400ppm이상의 토양축적현상을 보였다. Ni은 도금 및 금속가공지역에서 시료채취 토양층과 관계없이 35ppm이상의 함량을 보였고, 그 다음으로 석재 및 반도체 산업지역에서 25ppm이상의 토양 중 함량을 나타냈다. Pb는 화학약품 및 견직물공장에서 시료채취 토층과 관계없이 $400{\sim}1000ppm$이상의 토양 중 함량을 보였다. Zn은 화학약품과 견직물공장지역에서 토양 깊이와 관계없이 1200ppm이상의 가장 높은 함량분포를 보이는 곳도 있었으며, 그 다음이 도금 및 금속가공, 그리고 피혁공장순으로 Zn함량이 많은 것으로 나타났다. 결과적으로 산업활동의 형태 및 종류는 토양 중의 중금속의 종류 및 함량변화의 원인이 되고 있었고 이 지역에서는 Pb 및 Zn 토양중 함량변화가 뚜렷하였다.

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Moire 영상을 이용한 근골격계 질환의 한의학적 진단에 관한 연구 (A Study on Oriental Medical Diagnosis of Musculoskeletal Disorders using Moire Image)

  • 이은경;유승현;이수경;강성호;한종민;정명수;천은주;송용선;이기남
    • 대한예방한의학회지
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    • 제4권2호
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    • pp.72-92
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    • 2000
  • This research has conducted studies on an Oriental medicine-based method of diagnosing of occupational musculoskeletal system diseases. This researcher has searched through existing relevant medical literature. Also, this researcher has worked on a moire topography using moire topography. In this course, this researcher has reached the following conclusion in relation to the possibility of using a moire topography as a diagnosing device of musculoskeletal system diseases under Oriental medicine . 1 The Western medicine outlines its criteria of screening occupational musculoskeletal system diseases as follows A. The occupational musculoskeletal diseases must clearly include one or more of the subjective symptoms characterized by pain, hypoesthesia dysaesthesia, anaesthesia. etc . B, There should be clinically admitted objective observations and diagnosis outlining that the disease concerned shows symptoms such as tenderness, induration. and edema that can appear with occupational musculoskeletal system diseases. dyscinesia should be admitted with the disease concerned, or there should be observations and diagnosis outlining that abnormality exists in electric muscular or nervous diagnosis and examination . C. It should be admitted that prior to the occurrence of symptoms or observations and diagnosis on musculoskeletal system-related diseases, a patient has been engaged in works with conditions requiring improper work posture or work movement. That is, this is an approach whereby they see abnormality in the musculoskeletal system come from material and structural defect, and adjust and control abnormality in the musculoskeletal system and secreta . 2. The Oriental medicines sees that a patient develops the pain of occupational musculoskeletal diseases as he cannot properly activate the flow of his life force and blood thus not only causing formation of lumps in the body and blocking the flow of life force and blood in some parts of the body. Hence, The Oriental medicine focuses on resolving the cause of weakening the flow of life force and blood, instead of taking material approach of correcting structural abnormality Furthermore , Oriental medicine sees that when muscle tension builds up, this presses blood vessels and nerves passing by, triggering circulation dyscrasia and neurological reaction and thus leading to lesion. Thus, instead of taking skeletal or neurophysiological approach. it seeks to fundamentally resolve the cause of the flow of the life force and blood in muscles not being activated. As a result Oriental medicine attributes the main cause of musculoskeletal system diseases to muscle tension and its build-up that stem from an individual's long formed chronicle habit and work environment. This approach considers not only the social structure aspect including companies owners and work environment that the existing methods have looked at, but also individual workers' responsibility and their environmental factors. Hence, this is a step forward method. 3 The diagnosis of musculoskeletal diseases under Oriental medicine is characterized by the fact that an Oriental medicine doctor uses not only photos taken by himself, but also various detection devices to gather information and pass comprehensive judgment on it. Thus, it is the core of diagnosis under Oriental medicine to develop diagnosing devices matching the characteristics of information to be induced and to interpret information so induced from the views of Oriental medicine. Diagnosis using diagnosing devices values the whole state of a patient and formal abnormality alike, and the whole balance and muscular state of a patient serves as the basis of diagnosis. Hence, this method, instead of depending on the information gathered from devices under Western medicine, requires devices that provide information on the whole state of a patient in addition to the local abnormality information that X-ray. CT, etc., can offer. This method sees muscle as the central part of the abnormality in the musculoskeletal system and thus requires diagnosing devices enabling the muscular state. 4. The diagnosing device using moire topography under Oriental medicine has advantages below and can be used for diagnosing musculoskeletal system diseases with industrial workers . First, the device can Provide information on the body in an unbalanced state. and thus identify the imbalance and difference of height in the left and right stature that a patient can not notice at normal times. Second, the device shows the twisting of muscles or induration regions in a contour map. This is not possible with existing shooting machines such as X-ray, CT, etc., thus differentiating itself from existing machines. Third, this device makes it possible for Oriental medicine to take its unique approach to the abnormality in the musculoskeletal system. Oriental medicine sees the state and imbalance state in muscles as major factors in determining the lesion of musculoskeletal system, and the device makes it possible to shoot the state of muscles in detail. In this respect, the device is significant. Fourth, the device has an advantage as non-aggression diagnosing device.

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우리나라 양곡가공공장의 현황분석 (The Profile of Milling Plants in Korea)

  • 정창주;금동혁;강화석
    • Journal of Biosystems Engineering
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    • 제3권1호
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    • pp.47-63
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    • 1978
  • This study was conducted to obtain a basic information necessary to assess present rice milling technology in Korea The profiles for milling plants was analyzed by survey work.For the private custom-work mills, which process about 80 percent of domestic rice consumption ,their actual milling test for the identical samples as used for filed mills was conducted. Two rice varieties Japonica and Tongil-type were associated with the experiments. The results are summarized as follows: 1. Analyses for private custom-work mills showed their general aspects as; about 91 percent of the mills belonged to an individual owner ship ; more than 93 percent of the mills was established earlier than 1950 ; about 80 percent of the mills was powered with electric motor; mills having less than two employees were about 75 percent; about 45 percent of the mills provided for warehouse in storing customers cereal grains. 2. The polishers installed in 1,255mills within the surveyed area (7 counties) have been supplied by 44 different domestic manufacturers ;in but about 60 percent of which was supplied by 6major manufacturers. The polishers could be classified into two categories in terms of principles of their polishing actions ;jet-pearler and friction types. About 51 percent of the mills was equipped with the former which has been recognized as giving greater milling recovery than the friction types. 3. Reason for owners of private mills to supplement new machines was due mainly to pgrading their mills to meet the requirements that established by the Government. However, about 60 percent of the mill owners intended to replace with new pearler by their own needs to meet with new high yielding varieties. 4. Processing systems of each previate rice mills surveyed could be classified into three categories, depending upon whether the systems posessed such components as precleaner and paddy separator or not. Only 36.7 percent of mills was installed with both precleanr ad paddy seperrator, 5.0 percent of mills did have neither percleaner nor paddy seperator, and rest of them equipped only one of the two. Hence,it is needed for about 63% of rice miils to be supplemented with these basic facilities to meet with the requirements for the standaized system. 5. Actual milling capacity measured at each field rice mills was shown a wide variation, having range from about 190 to 1,210 kg/hr. The percentages of mills classified according to daily milling capacity based on this hourly capacity were 24.3% for the capacity less than 3 M/T a day; 20.0% for 3-4 M/T; 15.6% for 4-5 M/T; 6.7% for 5-6 M/T; 22.3% for 6-7 M/T; and 11.0% for more than 7 M/T a day. 6. Actual amount of rice processed was about 310 M/T a year in average. About 42% of total milled rice was processed during October to Decembear, which formed a peak demand period for rice mills. The amount of rice milled during January to May was relatively small, but it had still a large amount compared to that during June to September. 7. Utilization rate of milling facility, i. e., percentage of the actual amount of milled rice to the capacity of rice mills, was about 18% on the year round average, about 41% in the peak demand season, and about 10% during June to September. Average number of operating days for mills surveyed was about 250 days a year, and about 21 days a month. 8. Moisture contents of paddy at the time of field mill tests were ranged 14.5% to 19.5% for both Japonica and Tong-i] varieties, majority of paddy grains having moisture level much higher than 1530. To aviod potential reduction of milling recovery while milling and deterioration of milled rice while storage due to these high grain mJisture contents, it may be very important for farmers holding rice to dry by an artificial drying method. 9. Milling recovery of JapJnica varieties in rice mills was 75.0% in average and it was widely ranged from 69.0% to 78.0 % according to mills. Potential increase in milJing recovery of Japonica variety with improvement of mill facilities was estimated to about 1.9%. On the other hand, milling recovery of Tong-il varieties in the field mill tests was 69.8% in average and it ranged from 62% to 77 %, which is much wider than that of Japonica varieties. It is noticed that the average milling recovery of Tong-il variety of 69.8% was much less than that of the Japonica-type. It was estimated th3.t up to about 5.0% of milling recovery for Tong-il variety could be improved by improving the present lo'.ver graded milling technology. 10. Head rice recoveries, as a factor of representing the quality of commercial goods, of Japonica and Tong-il varieties were 65.9% and 53.8% in average, and they were widely ranged from 52% to 73% and from 44% to 65% , respectively. It was assessed that head rice recovery of Japonica varieties can be improved up 3.3% and that of Tong-il varieties by 7.0% by improving mill components and systems.

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