• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.258-263
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• 2010

An experimental study was performed to understand spray characteristics of the V type rotating fuel nozzle with orifice diameters by using high speed rotational system. The experimental apparatus consist of a high speed rotational system, fuel injection system and acrylic case. The droplet size and velocity were measured by PDPA(Phase Doppler Particle Analyzer) and spray was visualized by using Nd-Yag laser-based flash photography. From the test results, droplet diameters are reduced with increasing orifice diameter and the optimum injection orifice diameter is 2.6 mm. When increasing orifice diameter over than 2.6 mm, droplet diameter is not decreased with increasing orifice diameter. This is due to the irregular distribution of the liquid sheet around the inner surface of injection orifice.

• Journal of the Korean Arthroscopy Society
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• v.10 no.2
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• pp.148-152
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• 2006

Purpose: The purpose of this study was to investigate the distribution of the diameter of four strand autologous hamstring tendon and to identify the factors related to the diameter. Materials and Methods: Between December 2004 and July 2006, 66 patients underwent anterior cruciate ligament reconstruction using autologous hamstring tendon. Sixty one patients were male and the other 5 patients were female. Both semitendinosus and gracilis tendon were harvested in every case. Harvested two tendons were folded once together to create a four strand double loop graft and were passed through cylindrical sizer to measure their diameter. Parameters such as sex, age, height and weight were analyzed for their correlation with the diameter of the graft. Results: The diameter of the graft ranged from 6 mm to 10 mm. The graft with the diameter of 8 mm was most common and the average diameter of all the grafts was $7.85{\pm}0.92mm$. Seven patients (10.6%) had a graft with the diameter of 6 mm, which is considered too thin to be ideal one. No statistically significant correlation was found between age of the patient and the diameter of the graft. However, the diameter of the graft was significantly correlated with sex, height and weight of the patient. Female patients had a significant tendency to have thinner hamstring tendons. Both small height and light weight of the patients were correlated with thinner hamstring tendons significantly. Conclusion: Sex, height and weight of the patients were the factors that had a statistically significant correlation with the diameter of the graft. Being aware of the risk factors related with harvesting exceedingly thin hamstring tendon prior to anterior cruciate ligament reconstruction, one can utilize wide range of options in selecting an optimal graft.

• Journal of Korean Society of Forest Science
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• v.81 no.1
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• pp.21-29
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• 1992

This study was conducted to provide basic information for deciding silvicultural system appropriate to a natural mixed stand in Jindong-Ri. For this, the stand structure such as DBH distribution, height distribution, and volume per DBH class were analyzed and the possibility of selection cutting as a silvicultural system was discussed. The DBH structure of the stand has reverse J-shaped diameter distribution which is typical in a selection cutting stand. The possibility of selection cutting is also accepted in the height structure by showing multi-storied height distribution of the stand. On the other hand, volume structure per DBH class did not show the mature stand of selection cutting due mainly to the lack of number of trees at 30cm DBH class and above. It seems that the unclear part of stand structure should be solved by further studies. Also, the rate of increment for DBH and volume should be estimated to predict the future stand structure.

• Journal of agriculture & life science
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• v.52 no.6
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• pp.111-125
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• 2018

In this study, we evaluated the uniformity of deposition rate and particle size distributions of the variable rate application technique using the unmanned rotorcraft by measuring the spray pattern according to path location in the range of spraying flight. The coefficient of variation (CV) of the lateral coverage rate for the overlapped distribution with the spray swath of 3.6 m in both guidance and auto-pilot flight modes maintaining constant flight speed was about 30% and the CV of the coverage rate by the flight path location was extremely small. Therefore, it was assessed that the variable rate application technology compensating for the variation of ground speed was superior in terms of spray uniformity. In addition, the droplet size distributions in both volume median diameter(VMD) and number median diameter(NMD) were adequate for aerial application and uniform in terms of lateral distribution. Thereafter, we intend to contribute to a precise application on small-scaled fields using the unmanned agricultural rotorcraft by the variable rate application.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.317-323
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• 2020

In this study, the correlations between flow rate, exhaust pressure, and droplet mean diameter with the shape factor of a water curtain nozzle were investigated. To analyze the flow coefficient and the distribution constant on the effects of the hydraulic diameter, five nozzles (D5W3, D5W6, D5W8, D4W6, and D7W6) were mocked up with a consideration of the internal diameter and width. The results showed that the flow coefficient increased in proportion to the constant 0.79 and 62.8 of the hydraulic diameters according to the diameter. As the nozzle width increased, the average droplet size decreased to the -0.235 exponential of the pressure. The average volume was reduced, in which the size distribution of the volume indeterminate decreased with increasing pressure for the same nozzle of the water-curtain. The distribution constants of droplet increased in proportion to the 0.258 exponential of the hydraulic diameter and 244.21. These results are expected to be useful to the design of pressure, flow meter, and average droplet size from a water curtain nozzle to predict the flow characteristics.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.4
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• pp.699-721
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• 1996

브로네마르크가 골유착성 임플랜트를 소개한 이래로, 현재 골유착성 임플랜트에 의한 치료는 안전하고 안정적인 방법으로 여겨지고 있다. 골유착성 임플랜트를 이용한 초기의 치료는 무치악 환자의 저작기능 회복에 중점을 두어 왔다. 그러나 현재는 환자와 시대의 요구에 따라서 심미성이 주요한 관심사가 되었다. 그래서 표준 지대주보다 더 심미적인 지대주 시스템들이 개발되었다. 다양한 직경의 임플랜트 고정체에 관한 임상가들의 요구에 의해 직경 이 큰 고정체가 생산되기 시작했으며, 5mm의 직경을 갖는 고정체가 그 예이다. 골유착성 임플랜트를 사용하여 보철치료를 할 때, 골과 고정체의 계면은 보철물과 지대주에 가해지는 교합력을 인접골에 전달하게 되며, 이것은 계면에 생물학적인 반응을 야기할 수 있다. 임플랜트의 형태는 골흡수와 같은 바람직하지 않은 반응을 일으키지 않도록 고안되어야 하며, 임플랜트 자체가 교합력을 견딜 수 있어야 한다. 그러므로 골유착성 임플랜트 시스템을 임상에 사용하려고 할 때 이것의 생역학적 분석은 반드시 필요하다. 본 연구에서는 삼차원 유한요소분석적 방법을 사용하여 3.75mm직경을 갖는 고정체에 표준 지대주, 이세티콘 지대주, 마이러스콘 지대주를 연결한 모델과 5mm 직경을 갖는 고정체에 표준 지대주를 연결한 모델에 각각 수직하중, 경사하중, 수평하중을 가했을 때의 응력분포를 비교하였다. 본 연구의 결과는 다음과 같다. 1. 모든 모델에서 금나사의 경부, 금원주, 지대주에 응력의 집중이 일어났다. 2. 임플랜트 고정체에서는 고정체 상방 2/3, 그리고 지대주와 접촉하는 고정체 상면에서 응력의 집중이 관찰되었다. 3. 골에서는 상부 피질골에 응력의 집중이 관찰되었으며, 해면골에서는 두드러진 응력의 집중을 보인 부위는 없었으나 고정체의 근단부 주위 해면골에서의 응력값이 비교적 높았다. 4. 5mm 직경의 고정체를 사용하지 않은 모델 중에서, 표준 지대주를 사용한 경우가 가장 응력분산에 유리하였으며 마이러스콘 지대주를 사용한 경우가 가장 불리하였다. 5. 3가지 하중 조건하에서 수평하중과 경사하중의 경우가 수직하중의 경우보다 더 높은 응력값이 관찰되었다. 6. 응력값은 골에서보다 임플랜트 내부에서 훨씬 높았다.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.11a
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• pp.296-297
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• 2002

입자상 오염물질은 공기역학적 직경 2.5$\mu\textrm{m}$를 기준으로 미세입자와 거대입자로 나누어지는 쌍극분포의 형태(Whitby et at., 1972)를 나타내며, 분진이 인체에 미치는 영향에 관한 많은 연구를 통해 10$\mu\textrm{m}$ 이하의 입자가 호흡성 분진으로 인체에 더 유해한 영향을 미치고 있음이 밝혀졌다(Emison, 1988). 이러한 특징은 동일 질량의 분진을 가정할 때 입자의 직결이 작아질수록 저감효율이 떨어지며, 분진의 표면적이 커져 중금속이나 가스상 오염물질의 흡착이 상대적으로 용이해지기 때문이다(Saffiotti, 1965). (중략)

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.10
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• pp.859-864
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• 2014

This experimental study investigates the effects of a downstream cylinder in the wake change on upstream object's diameter. A V-shaped object is placed in the upstream of the test section and a circular cylinder containing a load-cell is placed in the downstream. The velocity distribution of the wake generated from the upstream object with a change in its diameter is investigated. Further, the fluctuation in the lift coefficient and Karman-vortex emission frequency with a change in the position of the downstream cylinder is examined. The study results reveal the following. i) The flow velocity in the wake is smaller than that in the main stream. ii) The lock-in phenomenon occurs when the diameter of the upstream object is larger than that of the downstream cylinder. iii) To generate maximum fluctuating lift force of the downstream cylinder in the wake, the position of the downstream cylinder must be moved with changing diameter of the upstream object together.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.3
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• pp.253-267
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• 2008

The purpose of this study was to evaluate the pattern and the magnitude of stress distribution in the supporting tissues surrounding implant fixture with different diameter of implant fixtures(3i implant, Ø4.0, Ø5.0, Ø6.0mm and UCLA abutments(Ø4.1, Ø5.0, Ø6.0mm using photoelastic stress analysis. Photoelastic model was made with PL-2 resin(Measurements Group, Raleigh, USA) and three implants of each diameter were placed in the mandibular posterior edentulous area distal to the canine. Individual crowns were fabricated using UCLA abutments. Photoelastic stress analysis was carried out to measure the fringe order around the implant supporting structure under simulated loading conditions(15 lb, 30 lb). The results were as follows; 1. The more the diameter of implant fixture was increased, the less the stress concentration on cervical area of fixture was observed under loading. 2. Increasing mesiodistal diameter of implant superstructure had no much influence on stress distribution around implant fixture. 3. The use of smaller abutment had no influence on stress distribution around implant fixture. The use of smaller abutment diameter than that of implant fixture had no favorable effect on implant supporting tissue at biomechanical consideration.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.517-517
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• 2012

높은 전력 효율과 간단한 매칭 네트워크의 구조 등 많은 장점을 갖고 있는 직경 560 mm 페라이트 챔버가 대면적 웨이퍼에 대응하기 위해 개발 되었다. 플라즈마 소스원이 챔버 외곽에 위치해 있는 구조적 특성으로 인하여 아르곤 가스 방전 시 플라즈마 밀도 분포는 챔버 중앙부가 낮게 나타나는 볼록한 모양으로 형성 되는데 헬륨 가스를 적절히 혼합할 시에 밀도 분포가 변화가 관찰된다. 헬륨 가스 혼합 비에 따라 플라즈마 밀도 분포는 균일도가 매우 높아 질 수 있으며 60% 이상의 혼합비에서는 중앙 부분의 밀도가 최대치로 역전되는 오목한 밀도 분포가 나타나기도 한다. 이는 헬륨 가스의 대표적인 특징인 가벼운 질량과 높은 이온화 에너지 등에 기인하는데 이러한 특징을 갖는 헬륨 가스를 주입하게 되면 전자의 energy relaxation length가 늘어나게 되며 ambipolar diffusion 계수가 증가하게 된다. 랑뮈어 프로브를 이용하여 측정된 플라즈마 밀도 분포 변화는 앞서 계산 된 energy relaxation length 및 ambipolar diffusion 계수들의 변화로 설명된다.