• Journal of Welding and Joining
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• 제21권1호
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• pp.60-65
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• 2003

At present. welding of most pipes with large diameter is carried out by the manual process. Automation of the welding process is necessary f3r the sake of consistent weld quality and improvement in productivity. In this study, two vision sensors, based on the optical triangulation, were used to obtain the information for seam tracking and detecting the weld defects. Through utilization of the vision sensors, noises were removed, images and 3D information obtained and positions of the feature points detected. The aforementioned process provided the seam and leg position data, calculated the magnitude of the gap, fillet area and leg length and judged the weld defects by ISO 5817. Noises in the images were removed by using the gradient values of the laser stripe's coordinates and various feature points were detected by using an algorithm based on the iterative polygon approximation method. Since the process time is very important, all the aforementioned processes should be conducted during welding.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 추계 학술대회논문집
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• pp.185-188
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• 2006

An investigation of the ejector-jets focusing on its flow properties was carried out by varying the geometric parameters. The area ratio of the primary nozzle, AR that was tested in the present measurement was 2.17 and 3.18, while the ratio of the length to the diameter of the duct downstream the primary nozzle inlet, L/D had values of 3.41, 6.82, and 10.23. For the frame work of flow characteristics, the wall pressures distribution of ejector-jet was investigated by experiment for basic study of ejector-jet performance. In result, terminal shock location and existence of series of oblique shocks are recognized. In this study, CFD analysis was conducted at the same time. And as a result of comparison experiment data with CFD analysis, the physical phenomena of ejector-jets were estimated.

• 한국전산유체공학회지
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• 제12권2호
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• pp.46-52
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• 2007

An experimental and numerical investigation of the ejector-jets focusing on its geometric parameters that effect on thrust performance was carried out. The area ratio of the primary nozzle that was tested in the present study was 2.17 and 3.18, while the ratio of the length to the diameter of the duct downstream the primary nozzle inlet had values of 3.41, 6.82, and 10.23. Internal flow properties of ejector-jet were estimated by comparison experiment data and CFD analysis for basic study of ejector-jet thrust performance. For examination of thrust performance, the thrust ratios increased with increase in L/D. Especially at AR=2.17, the maximum thrust augmentation was 33 percent for the shortest L/D. It is expected that the increase of mixing duct length of ejector-jet will be helpful in a thrust performance by improving mixing efficiency.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 춘계 학술대회논문집
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• pp.166-170
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• 2007

An experimental and numerical investigation of the ejector-jets focusing on its geometric parameters that effect on thrust performance was carried out. The area ratio of the primary nozzle that was tested in the present studywas 2.17 and 3.18, while the ratio of the length to the diameter of the duct downstream the primary nozzle inlet had values of 3.41, 6.82, and 10.23. Internal flow properties of ejector-jet were estimated by comparison experiment data and CFD analysis for basic study of ejector-jet thrust performance. For examination of thrust performance, the thrust ratios increased with increase in L/D. Especially at AR=2.17, the maximum thrust augmentation was 34 percent for the shortest L/D. It is expected that the increase of mixing duct length of ejector-jet will be helpful in a thrust performance by improving mixing efficiency.

• Computers and Concrete
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• 제28권6호
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• pp.559-566
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• 2021

In this paper, frequency analysis has been done for functionally graded cylindrical shell with ring supports using Sander's shell theory. The vibrations of rotating cylindrical shells are analyzed for different physical factors. The fundamental natural frequency is investigated for different parameters such as: ratios of length-to-diameter ring supports. By increasing different value of height-to-radius ratio, the resulting backward and forward frequencies increase and frequencies decrease on increasing height-to-radius ratio. The frequencies for different position of ring supports are obtained in the form of bell shaped. The backward frequencies increases and forward frequencies decrease on increasing the rotating speed. The results generated furnish the evidence regarding applicability of present shell model and also verified by earlier published literature.

• 한국안광학회지
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• 제4권2호
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• pp.1-16
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• 1999

주기적으로 변하는 압력이 탈수상태의 HEMA 콘택트 렌즈에 작용하여 진동이 발생하는 경우, 렌즈상의 임의의 위치에서 파형과 평균진폭을 예측할 수 있는 미분방정식과 컴퓨터 프로그램을 유도하였다. 중심부분의 두께 0.08mm, 직경 14mm, 곡율반경 8mm 렌즈의 고유 공진진동수는 추가질량감소법에 의해 5730 Hz으로 측정되었다. 진동에 주로 관여하는 렌즈의 유효반경의 측정값과 고유 공진 진동수값으로부터 base curve를 가지고 있는 상태에서 렌즈의 탄성율(Young's modulus)을 구할 수 있었으며, 본 실험에 사용한 렌즈에서는 그 값이 $4{\times}10^9$ Pa으로 구해졌다. 파동방정식과 탄성이론에 기초를 두고 유도한 컴퓨터 모델을 작동하여 렌즈의 유효 반경, 렌즈두께, damping, 압력진폭, driving 압력의 진동수 등의 변수가 진동에 미치는 영향을 모사하였다. 렌즈의 유효반경이 클수록, 렌즈의 두께가 얇아 질수록 공진진동수는 낮아지며, 공진진동수 감소에 따라 평균진폭의 급격한 증가가 예측되었다. 외부 압력의 진동수가 렌즈의 고유진동수의 정배수에 접근하는 경우 diaphram의 진동 파형은 원호형에서 파도 또는 종(bell)형으로 전환되며 결과적으로 중심부근의 진폭이 갑자기 상승하게 될 것으로 예상된다.

• Asian-Australasian Journal of Animal Sciences
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• 제14권4호
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• pp.507-514
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• 2001

Two experiments were carried out to investigate whether duckweed is useful as a dietary protein source for fine-wool Merino sheep and to evaluate its effects on wool yield and characteristics. In Experiment 1, the sheep were given one of three maintenance diets consisting of oaten chaff (520-700 g/d) supplemented with 16-32 g crude protein/d in the form of fresh (1 kg/d) or sun-dried (50-100 g/d) duckweed. Each ration was estimated to provide 5.4 MJ (1.3 Mcal)/d of metabolisable energy (ME). The sheep readily ingested the fresh or dried duckweed. None of the wool measures (yield, rate of fibre elongation, fibre diameter) differed (p>0.05) between dietary treatments. In Experiment 2, oaten-chaff-based diets (800 g/d) supplying 6.5-7.2 MJ (1.6-1.7 Mcal)/d of ME were supplemented with iso-nitrogenous amounts (4-5 g N) either of urea (8 g), cottonseed meal (60 g) or dried duckweed (100 g). In this experiment, the rate of wool fibre elongation, thought to be related to intestinal amino acid absorption, was lower (p<0.05) for sheep given the oaten chaff/urea diet than for those given either oaten chaff/cottonseed meal or oaten chaff/duckweed for which the rates did not differ (p>0.05). Fibre diameter, which ranged from 16.0-16.7 mm, did not differ (p>0.05) between diets, but tended to be lower on the oaten chaff/urea diet so that volume of wool produced was also significantly lower (p<0.05) on this diet than on the diets containing duckweed or cottonseed meal. Rumen ammonia concentrations at 4.5 and 7.5 h after feeding were higher (p<0.05) for sheep given the oaten chaff/urea diet than for those given the other two diets. A comparison of the rumen ammonia concentrations, wool growth rate and predicted flows of amino acids from the rumen of sheep supplemented with duckweed rather than cottonseed meal suggested that duckweed is a valuable source of 'escape protein' for ruminants.

• 한국산림과학회지
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• 제98권5호
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• pp.576-583
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• 2009

Based on the stem analysis and biomass measurement of 36 trees and 1,576 branches in Pinus sylvestris var. mongolica (Mongolian pine) plantations of Northeast China, this study was conducted to develop estimation model equation for leaf biomass of a single tree and branch, to examine the vertical distribution of leaf biomass in the crown, and to evaluate the proportional ratios of biomass by tree parts, stem, branch, and leaf. The results indicated that DBH and crown length were quite appropriate to estimate leaf biomass. The biomass of single branch was highly correlated with branch collar diameter and relative height of branch in the crown, but not much with stand density, site quality, and tree height. Weibull distribution function would have been appropriate to express vertical distribution of leaf biomass. The shape parameters from 29 sample trees out of 36 were less than 3.6, indicating that vertical distribution of leaf biomass in the crown was displayed by bell-shaped curve, a little inclined toward positive side. Apparent correlationship was obtained between leaf biomass and branch biomass having resulted in linear function equation. The stem biomass occupied around 80% and branch and leaf made up about 20% of total biomass in a single tree. As the level of tree class was increased from class I to class V, the proportion of the stem biomass to total biomass was gradually increased, but that of branch and leaf became decreased.

• 생물환경조절학회지
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• 제6권1호
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• pp.15-25
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• 1997

피망(Capsicum annuum L.) 플러그 육묘시 초장 조절을 위해 주야간 온도차(DIF)에 따른 16조합 처리를 50일간 실시한 뒤 각각의 묘소질에 따른 정식후 생육에 관하여 실험하였다. 주야간 온도차 처리에 따른 피망 플러그묘의 초장은 주간온도가 증가함에 따라 증가하였고, 같은 일평균 온도에서는 -DIF에 의해 억제되고, +DIF에 의해 촉진되었다. 엽전개 속도는 DIF처리 효과보다는 일평균 온도에 의해 좌우되었고, 생체중 및 건물중은 일평균 온도가 증가할수록 증가하였고 야간온도에 비해 주간온도가 크게 영향을 미쳤다. 엽면적과 줄기직경은 주야간온도가 16$^{\circ}C$부터 24$^{\circ}C$로 증가할 때까지 증가하다가 그 이상의 온도에서는 감소하였다. 육묘시 온도처리에 따른 제 1번화의 착생 절위는 일평균 온도가 증가할수록 낮아졌으나 화뢰의 퇴화는 오히려 증가하였다. 이상의 결과를 종합해 볼 때 피망육묘시 DIF를 조절하여 육묘시 초장조절이 가능하며 -DIF 처리로 초장이 억제된 유묘일지라도 정식후 +DIF 조건에서 재배함으로써 생육을 촉진시킬 수 있었다. 또한 엽전개 속도(생육속도)와 제 1번 화의 화아 분화도 일평균 온도를 조절함으로써 조절이 가능하며, 적온 범위 내에서 일평균 온도를 증가시킴으로써 화아 분화를 촉진시킬 수 있다고 판단된다.

• 한국산림과학회지
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• 제99권1호
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• pp.153-162
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• 2010

본 연구는 경기도 용인 지역 전나무(Abies holophylla Maxim.) 임분의 구조를 분석하고, 이 지역 전나무 임분의 지속가능성을 알아보기 위하여 수행되었다. 용인시의 정수리, 대대리, 호동 지역 전나무 임분에서 매목조사를 실시하고, 관목층의 구조와 치수의 발생을 조사하였다. 산림 관리나 작업이 이루어지지 않았던 정수리와 대대리 임분에서 전나무는 중요도 40%로 임분을 우점하고 있었으며, 연속적인 연령과 직경분포를 보이고 있었다. 반면 호동 지역 임분은 간벌과 택벌 등의 산림 작업이 이루어졌던 지역으로 전나무가 흉고직경 10-45 cm 범위에 분포하나 대부분 25-30 cm 직경급에 몰려 있고, 단일수관층을 가지고 있었다. 전나무의 연령과 흉고직경의 상관 관계는 유의한 것으로 나타나긴 하였으나 높지 않았고($R^2$=0.2, P=0.03), 비슷한 연령대라도 다양한 흉고직경 값을 가졌다. 정수리 임분의 연속적인 직경 분포와 다층수관구조는 전나무가 조림 후 지속적으로 갱신이 이루어져 왔음을 보여주었다. 전나무의 치수는 ha당 2000-33000본까지 발생하였으나, 2-5 cm 직경급의 전나무는 ha당 70-150본 정도로 치수 단계에서 유령목으로 자라나는 동안의 생존율은 낮았다. 지속적인 천연갱신과 연간 약 0.6 cm의 직경생장율은 조사 지역의 환경이 전나무 서식에 비교적 적합한 지역임을 나타낸다. 또한 전나무 임분은 향후에도 지속적으로 유지될 것으로 보여 내음성 수종인 전나무를 대상으로 한 택벌림 경영의 가능성을 제시해주고 있다.