• 제목/요약/키워드: smooth tube

검색결과 223건 처리시간 0.026초

설비공학 분야의 최근 연구 동향 : 2013년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2013)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
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    • 제26권12호
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    • pp.605-619
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    • 2014
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.

고려홍어 Hongeo koreana의 난각(연골어강: 홍어목: 홍어과) (Egg Capsule of Hongeo koreana (Chondrichthyes: Rajiformes: Rajidae))

  • 정충훈;김진구
    • 한국어류학회지
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    • 제21권4호
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    • pp.283-286
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    • 2009
  • 고려홍어의 모식산지인 한반도 남서해안에서 포획한 암컷개체의 자궁에서 직접 적출한 난각 2개를 새롭게 기재하였다. 본종의 난각은 다른 종과 비교하여 보통 크기이고, 뿔(horn)을 포함한 전장은 124.5~133.7 mm, 뿔을 제외한 주부(main portion)의 체장은 102.8~109.4 mm, 최대폭은 41.0~42.2 mm이다. 측면에서 볼 때 배쪽으로 불룩한 비대칭이고, 표면은 비교적 부드러운 편이지만 세로로 미세한 고랑(longitudinal striations)은 뚜렷하고, 매우 발달한 섬유다발(견상사(絹狀絲) silky fibers)로 덥혀 있다. 앞뒤의 apron은 뚜렷하며, 네 뿔은 짧고 튜브모양이고 그 횡단면은 타원형이고, 앞쪽 뿔은 안쪽으로 심하게 구부러져 있으며, 호흡공(respiratory fissure)은 네 뿔의 끝부분에 위치한다. 신선한 상태에서 밝은 갈색이다.

Behavior of improved through-diaphragm connection to square tubular column under tensile loading

  • Qin, Ying;Zhang, Jing-Chen;Shi, Peng;Chen, Yi-Fu;Xu, Yao-Han;Shi, Zuo-Zheng
    • Structural Engineering and Mechanics
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    • 제68권4호
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    • pp.475-483
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    • 2018
  • Square tubular columns are commonly used in moment resisting frames, while through-diaphragm connection is the most typical configuration detail to connect the H-shaped beam to the column. However, brittle fracture normally occurs at the complete joint penetration weld between the beam flange and the through-diaphragm due to the stress concentration caused by the geometrical discontinuity. Accordingly, three improved types of through-diaphragm are presented in this paper to provide smooth force flow path comparing to that of conventional connections. Tensile tests were conducted on four specimens and the results were analyzed in terms of failure modes, load-displacement response, yield and ultimate capacity, and initial stiffness. Furthermore, strain distributions on the through-diaphragm, the beam flange plate, and the column face were comprehensively evaluated and discussed. It was found that all the proposed three types of improved through-diaphragm connections were able to reduce the stress concentration in the welds between the beam flange and the through-diaphragm. Furthermore, the stress distribution in connection with longer tapered through-diaphragm was more uniform.

미만성 폐림프관종증과 동반된 양측성유미흉 -수술치험 1례 보고- (Bilateral chylothorax with diffuse pulmonary Iymphangiomatosis)

  • 김경렬;최세영
    • Journal of Chest Surgery
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    • 제29권3호
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    • pp.360-364
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    • 1996
  • 유미흉이란 유미액이 유출되는 현상이다. 그리고 드물게 미만성 폐림프관종증도유미흥을유발하나 이에 대해서는 잘 알려져 있지 않다. 본 교실에서는 유미흥을 동반한미만성 폐림프관종증을경험하였기에 보고하는바이다. 환자는 3세된 여자로 기 침과 발열감을 주소로 내원하였다. 단순 흉부 될영상 양측성 흥막 유출 소견과 간질성 침윤 소견을 보였다. 검사실 소견상흥막 유출은유미액으로밝혀 졌으며,폐쇄식 흥강내 삽관술로조절되지않아흥관결찰술을시행하였다. 병리 조직 검사상흥막과 소엽간중격에서 림프관을따라내퍼세포들이 연결되어 있었으며 림프관이 증식된간질부위에평활근조직을관찰할수있었다. 술후, 수차례의 화학적 홍막 유착술을 시행하여 유미흥을 치료하였으며 환자는 퇴원후 10개월동안 특별한 문제없이 잘 지내고 있다.

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헬리컬 코일형 가스냉각기 내 CO2의 냉각 열전달 특성 (Cooling Heat Transfer Characteristics of CO2 in Helical Coil Type Gas Coolers)

  • 손창효;전민주;오후규
    • Journal of Advanced Marine Engineering and Technology
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    • 제31권6호
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    • pp.699-706
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    • 2007
  • The cooling heat transfer coefficient and pressure drop of $CO_2$(R-744) in helical coil copper tubes were investigated experimentally The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter. a pre-heater and a inclined helical coil type gas cooler (test section). The test section consists of a smooth copper tube of 2.45 and 4.55mm inner diameter The refrigerant mass fluxes were varied from 200 to $600 [kg/m^2s]$ and the inlet pressures of 9as cooler were 7.5 to 10.0 [MPa]. The heat transfer coefficients of $CO_2$ in helical coil tubes increase with the increase of mass flux and gas cooling pressure of $CO_2$. The pressure drop of $CO_2$ in the gas cooler shows a relatively food agreement with those Predicted by Ito's correlation developed for single-phase in helical coil tubes. Though a few correlation available with the data. the local heat transfer coefficient of $CO_2$ agrees well with those presented by Pitla et al. among the predictions. However at the region near pseudo-critical temperature. the experiment data indicate higher values than the Pitla et al. correlation.

초소형 디플렉터 타입 볼스크류 개발을 위한 해석에 관한 연구 (A Study on the Analysis for Development of a Deflector Type Miniature Ball Screw)

  • 이춘만;문성호;이영훈;김준환
    • 한국정밀공학회지
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    • 제33권12호
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    • pp.979-984
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    • 2016
  • Recently, ball screws have been used in machine tools, robot parts, and medical instruments. The demand for ball screws of high precision and reduced size is increasing because of the growth of high value-added industries. Three types of ball screws are typically used: deflector type, end-cap type, and tube type. They are also classified from C0 to C9 according to the precision level. A deflector type ball screw can reduce the variation of rotational torque and the size of the nut of the ball screw is minimized. To ensure the reliable design of ball screws, it is important to perform a structural analysis. The purpose of this study is to perform a stability evaluation through analysis of a deflector type miniature ball screw for weapon systems. The analysis is performed through Finite Elements Method (FEM) simulation to predict characteristics such as deformation, stress, and thermal effects. The interference between the shaft and the deflector for smooth rotation are also studied. Based on the results of the analysis, the development of the deflector type miniature ball screw for weapon systems is performed.

하이브리드 플립드 러닝과 플립드 러닝의 학습 효과 비교 (Comparison of learning effects between hybrid flipped learning and flipped learning)

  • 최보람
    • 대한물리치료과학회지
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    • 제31권2호
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    • pp.90-104
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    • 2024
  • Background: Hybrid learning is an educational approach that combines the teaching methods of online and lecture-style classes to compensate for each method's strengths and weaknesses. Compared to lecture-style classes, flipped learning improves overall class satisfaction and self-directed learning but is associated with lower learning motivation. It is necessary to determine whether hybrid flipped learning can solve the learning motivation problem of flipped learning by incorporating flipped learning into hybrid learning. The purpose of this study is to compare the effects of hybrid flipped learning and flipped learning on students' learning ability. Design: Cross-sectional study Methods: For students in the Department of Physical Therapy, classes were conducted using both flipped learning and hybrid flipped learning. In both learning methods, students took online classes first and participated in them every week. Flipped learning classes was conducted offline at school every week, while hybrid flipped learning alternated between live classes on YouTube and offline classes at school every other week. Results: Hybrid flipped learning resulted in significantly lower learning satisfaction and course evaluation than flipped learning, with no significant difference in grades. Conclusion: Hybrid flipped learning was able to cope with the situation well with the non-face-to-face teaching method caused by COVID-19, but it was difficult to improve learning ability because there were restrictions on activities that could interact with students. Flipped learning is a smooth offline activity that enables two-way activities between professors and students to improve learning ability, but the effect of improving test scores is still unclear.

투시 검사 시 장비에 따른 환자와 시술자의 입사표면선량 연구 (Fluoroscopic the equipment study in accordance with the entrance surface dose study of patients and practitioners)

  • 양해두;홍선숙;성민숙;하동윤
    • 대한디지털의료영상학회논문지
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    • 제15권2호
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    • pp.13-18
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    • 2013
  • Purpose : Fluoroscopy equipment, depending on the type of changes that occur in the patient's position ESD and study the patient's scatter ray of ESD Practitioners considered a comparative analysis was to evaluate the correct dose. Materials and Methods : HITACHI four overtube type TU-8000 Flat Detector and Under tube C-Arm Philips' Multi Diagnost Eleva with Flat Detector type were measured by. Each devices is a measure of the patient's esd randophantom position in tabel unfors Xi multi funtion then fixed to the abdomen fluoroscopy and 10 seconds, spot was measured three times, practitioners of the incident surface dose by considering the patient's scatter ray of the table for each device in the average human stomach 21cm thickness acrylic phantom ($25cm{\times}25cm$) Place the practitioner position after position randophantom unfors Xi multi funtion in the thyroid and stomach 1 minute by a fixed one-time fluoroscopy and measured. Results : 10 seconds and the patient perspective of the c-arm ESD 1.2 times smaller on the AP and oblique measurements were measured in the 6-13 times smaller. spot positions to changes in the measured three times on the AP of the abdomen, ESD is 18 times smaller c-arm measurements and the oblique measurement was 19-30 times smaller. And 1 minute at practitioners fluoroscopy esd in the thyroid 2.12 times the c-arm, chest 1.75 times less the dose was measured. On the AP, depending on the device, but the lack of dose difference oblique positions of the two devices depending on changes in the area due to changes in both the AP than on the dose increased, the difference in dose between the two devices, the maximum difference was approximately 27 times. Conclusion : Fluoroscopic equipment at the time of inspection in accordance with changes in dose according to the patient and the patient's positions changes, because the area of the scatter ray considering the change of dose measurements be made, and study of the equipment according to the characteristics of the efficiency and the exposure of the patient and practitioner is considered smooth study equipment manufacturers that can be done is to build the system and think that is also important. Various fluoroscopy when you check future changes in many factors of change in dose for the equipment in the laboratory system by considering the scatter ray radiation shielding for the management to take advantage of reckless undertube have been utilized as more exposure Reduction activities can help is considered as the direction.

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주사전자현미경을 이용한 토마토에 발생하는 아메리카잎굴파리(Liriomyza trifolii)의 외부형태적 특징 (External Morphology of the American Leafminer, Liriomyza trifolii (Diptera: Agromyzidae), on Tomato with Scanning Electron Microscope)

  • 윤영남;김기덕;박수진;김남성;서미자;채순용
    • 농업과학연구
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    • 제27권1호
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    • pp.13-19
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    • 2000
  • SEM을 이용하여 아메리카잎굴파리 (Liriomyza trifoljj) 의 암 수컷 성충의 외부형태적 특정을 살펴보았다. 더듬이에 있어 감각모의 3가지 형태는 더듬이가는마디(funicle)에서 관찰되었으며, 모상감각기(trichoid sensillum)는 말단 부위가 뽀족한 특정적인 형태를 하고 있고 감각기들 중에서 가장 많이 분포하고 있다. 원추상 감각기(basiconic sensillum)는 길이가 $13{\mu}m$, 지름이 $1.4{\mu}m$에서 $1.2{\mu}m$인 원형곡선형이다. 홈형 감각기 (grooved sensillum)는 간상 (peg) 끝에서 나온 손 모양을 하고 있으며, 이 모든 감각기들은 후각과 연관되어져 있는 것으로 추정된다. 구기는 흡즙형으로 작고 펼쳐진 윗입술(labrum) 과 합쳐져서 하나의 연결된 주둥이(rostrum)을 형성하고 있다. 가느다란 한 쌍의 작은턱수염 (maxillary palp)은 긴 관 모양으로 각각의 세로로 이어져 있다. 발마디는 5마디로 이루어져 있으며 그 한가운데에는 패드모양의 흡착반(pulvillus)과 가시모양의 발톱사이돌기(empodium)가 있다. 아메리카잎굴파리는 흡착반과 발톱사이돌기에서 미끄러운 표변에 부착할 수 있는 물질을 분비한다. 수컷의 생식기는 매우 복잡하며 삽입구(aedeagus)는 생식기관으로서 가장 일반적인 모양이다. 반면에 암컷의 생식기는 상대적으로 간단한데 이 구조는 외부로 돌출된 관모양이었다. 또한 이러한 결과를 이미 발표된 다른 여러 종의 파리와 비교하였다.

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PVD-Be와 비정질 Zr-Be 합금을 용가재로 사용한 Zircaloy-4의 브레이징 접합부의 비교 연구 (A Study on the Comparison of Brazed Joint of Zircaloy-4 with PVD-Be and Zr-Be Amorphous alloys as Filler Metals)

  • 황용화;김재용;이형권;고진현;오세용
    • 한국산학기술학회논문지
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    • 제7권2호
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    • pp.113-119
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    • 2006
  • 중수로형 핵연료 제조공정 중 연료봉 피복관에 간격체와 지지체 등의 부착물이 브레이징으로 접합된다. 본 연구에서는 베릴륨을 물리 증착법(PVD)으로 접합될 부착물의 표면에 증착한 것과 비정질 용가재[$Zr_{1-x}Be_{x}(0.3{\le}x{\le}0.5)$]를 사용하여 브레이징된 접합부의 미세조직과 경도 등의 특성을 비교하고 브레이징 온도가 접합부에 미치는 영향 조사하였다. 비정질 용가재에 의한 접합층의 두께는 PVD-Be의 경우와 비교하여 더 얇았고, Be 함량이 감소할수록 접합층의 두께는 감소하였으며 모재의 침식은 거의 없었다. PVD-Be의 경우 공정 반응, 액상 출현, 모세관 현상과 확산으로 브레이징 되나 비정질 합금은 용가재 만이 용융되어 액상 접합되는 것으로 사료된다. PVD-Be 접합부의 미세조직은 계면에서 수지상이 형성되어 내부로 성장하나, 비정질 합금에 의한 접합부는 석출된 제2상들이 구상으로 구성되며 브레이징 온도가 증가할수록 구상은 더욱 커졌다. 비정질 합금 접합부의 경도는 Be 함량이 감소할수록 경도는 증가하였다. 본 연구에 사용된 비정질 합금 중 $Zr_{0.7}Be_{0.3}$ 합금은 접합부에서 Be의 모재로의 확산이 적어 부드러운 계면과 모재의 침식이 없었고 높은 경도 때문에 핵연료 피복재 접합에 가장 적합한 용가재로 사료된다.

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