• 한국재료학회지
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• 제30권6호
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• pp.308-314
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• 2020

A commercial AA1070 alloy for electrical wire is severely deformed by drawing process in which a rod with an initial diameter of 9mm into is reduced to a wire of 2mm diameter. The drawn AA1070 wire is then annealed at various temperatures from 200 to 450 ℃ for 2h. Changes in microstructure, mechanical properties and electrical properties of the specimens with annealing temperature are investigated in detail. The specimen begins partially to recrystallize at 250 ℃; above 300 ℃ it is covered with equiaxed recrystallized grains over all regions. Fiber textures of {110}<111> and {112}<111> components are mainly developed, and {110}<001> texture is partially developed as well. The tensile strength tends to decrease with annealing temperature due to the occurrence of recovery or/and recrystallization. On the other hand, the elongation of the annealed wire increases with the annealing temperature, and reaches a maximum value of 33.3 % at 300 ℃. Electric conductivity of the specimens increases with annealing temperature, and reaches a maximum value of 62.6 %IACS after annealing at 450 ℃. These results are discussed in comparison with those for the other aluminum alloy.

• 한국수정란이식학회지
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• 제12권2호
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• pp.203-209
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• 1997

This study was carried out to compare the actual size(length and height) of ovaries, follicles and corpora lutea of Korean native cow with those on sonograms. We used 3 different probes(3.5 MHz abdominal probe, 6.5 MHz transvaginal probe and 5.0 MHz transrectal probe) and a calipher for measurements of ovaries, follicles and corpora lutea on sonograms and actual size. Under water immersion, 157 ovaries were scanned with 3 probes and measured in actual size and compared each other. The average height and width of ovaries of Korean native cows were 17.40$\pm$3.99 and 34.23$\pm$6.02mm, respectively. In comparison of height, length of ovaries and preovulation follicles, we found that image with a transvaginal probe was nearly the same as the actual size(p<0.01), but with an abdominal probe the image was appeared larger than the actual size. In measurement(diameter) of preovulation follicles the transvaginal probe was proven to be more accurate to the actual size than other probes and in corpus luteum measurement all probes were accurate. In the comparison of number of follicles by different size ranges, there was no statistical difference in the count of follicles over 10 mm in diameter between the transvaginal probe and naked eyes.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.302-307
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• 2005

The discharge coefficient in segmental wedge having ninety degrees vertex angle for the five kinds of opening ratio with differential pressure taps located at both upstream and downstream of one diameter of pipe was measured main purpose of this work is placed on developing the proper form of an equation for the discharge coefficient of a segmental wedge used as a primary element of flow metering devices, and from thata six-term equation which can express the variability of opening ratios was developed. The same assumption and hypotheses were used and tested for all procedures as conventional differential producers; however, the range of the opening ratio over this work is more expanded than previous studies. The opening ratios of segmental wedge, namely 0.3, 0.4, 0.5, 0.6 and 0.7 were investigated the Reynolds number based on the spool inside diameter ranges from 12,000 to 380,000, the resulting equation for the discharge coefficient is relatively simple; it contains only one variable-opening ratio because the characteristic of discharge coefficient of segmental wedge has little connection with the Reynolds number as shown by previous studies.

• 한국가시화정보학회지
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• 제4권2호
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• pp.69-75
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• 2006

The microbubbles were used in various fields, such as turbulent control, drag reduction, material science and life science. The X-ray PTV using X-ray micro-imaging technique was employed to mea-sure the size and velocity of micro-bubbles moving in an opaque tube simultaneously. Micro-bubbles of $10{\sim}60{\mu}m$ diameter moving upward in an opaque tube (${\phi}$=2.7mm) were tested. Due to the different refractive indices of water and air, phase contrast X-ray images clearly show the exact size and shape of over-lapped microbubbles. In all of the working fluids tested (deionized water, tap water, 0.01 and 0.10M NaCl solutions), the measured terminal velocity of the microbubbles rising through the solution was proportional to the square of the bubble diameter. The rising velocity was increased with increasing mole concentration. The microbubble can be useful as contrast agent or tracer in life science and biology. The X-ray PTV technique should be able to extract useful information on the behavior of various bio/microscale fluid flows that are not amenable to analysis using conventional methods.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1359-1364
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• 2008

It is well known that the standard penetration test (SPT) has been used in all over the world to get geotechnical properties of the ground. However, it is difficult to apply the SPT to the dense sand, gravel, weathered rock, etc. For the application of the SPT in these grounds, it is necessary to change in the diameter and the impact energy of the SPT. For the improvement of site investigation technology, Large Penetration Testing device (KICT-type LPT) was developed and applied to the in situ condition. The drop height and weight of the hammer in developed system were decided as 760mm and 150kg, respectively. And the developed sampler has the inner diameter of 63 mm and the length of 500 mm with the adjustment of energy ratio to the SPT of 1.5. In this study, the performance of KICT-type LPT was evaluated by using a calibration chamber system and pile driving analyzer (PDA)

• 한국압력기기공학회 논문집
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• 제8권3호
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• pp.23-27
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• 2012

A seawater pumps in the nuclear power plant is responsible for providing cooling water to other components all the time. Because of the depreciation, the seawater pump with current impeller consumes too much power for maintaining the total head. Therefore the objective of this study is to reduce power with maintaining certain the total head by cutting the current impeller. By using a commercial CFD code, FLUENT, the overall performance of seawater pump with current and modified impeller was simulated. Also Affinity law was applied at pumps with various impeller diameter and evaluated the validity of the affinity law. The numerical results show that the pump efficiency is quite irrelevant to the diameters of the impellers and the pump efficiency becomes worse over the designed flow rate. And affinity law result and numerical one show good agreements at small change of impeller diameter. One of the impeller diameters was decided to modify and was applied to the nuclear power plant with the numerical study above.

• International Journal of Aeronautical and Space Sciences
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• 제18권3호
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• pp.395-402
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• 2017

The local heat transfer and total pressure drops of developed turbulent flows in the ribbed rectangular convergent/divergent channels with ${\Lambda}/V-shaped$ ribs have been investigated experimentally. The channels have the exit hydraulic diameter ($D_{ho}$) to inlet hydraulic diameter ($D_{hi}$) ratios of 0.67 for convergence and 1.49 for divergence, respectively. The ${\Lambda}/V-shaped$ ribs with three different flow attack angles of $30^{\circ}$, $45^{\circ}$, and $60^{\circ}$ are manufactured with a fixed rib height (e) of 10 mm and the ratio of rib spacing (S) to height (e) of 10 on the walls. Thermal performances of the ribbed rectangular convergent/divergent channels are compared with the smooth straight tube under identical pumping power. The results show that the flow attack angle of $45^{\circ}$ with ${\Lambda}-shaped$ rib has the greatest thermal performance at all the Reynolds numbers studied in the convergent channel; whereas, the flow attack angle of $60^{\circ}$ with V-shaped rib has the greatest thermal performance over Reynolds number of 30,000 in the divergent channel.

• Journal of Ecology and Environment
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• 제48권1호
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• pp.49-59
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• 2024

Background: The present study aims to identify the pattern and size of Juniperus species (Juniperus phoenicea and J. procera) in the natural forests in terms of tree dimension, size structure and density, discussing the existing both species in Sarrawat Mountains for suggesting the preservation, conservation, and sustainable development. For achieving this, the height and mean crown diameter of each individual was measured based on 2-4 diameter measurements per ind. (506 ind. for J. phoenicea and 322 ind. for J. procera). Results: The size index of both species was classified into 7 classes: the first (< 100 cm) and the second (100-200 cm) classes were chosen to represent the juvenile stage. The total mean of the J. phoenicea population increased with the increase of altitude, while the whole population decreased after altitude of 2,000 m. The total mean of the J. procera population increased with the increase of altitude till altitude of 2,000-2,100 m. Conclusions: The present study indicated that both of species grow at low altitudes, they only grow at altitude above 1,700 m above sea level. The present study indicated that the study area has the two Juniperus spp. (J. phoenicea and J. procera) associated together all over the area. The results were discussed and compared with other related studies.

• 생물환경조절학회지
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• 제27권2호
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• pp.103-110
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• 2018

본 연구는 하절기 '매향' 딸기 자묘의 삽목 번식에 적절한 관수 방법을 구명하기 위해 수행되었다. 딸기 자묘의 삽수는 24구 딸기 전용 포트(24구, $60{\times}34{\times}10cm$)에 상업용 혼합 상토(Tosilee)를 이용하여 삽목하고, 반 밀폐형 소형비닐터널에 위치시켰다. 각각의 반 밀폐형 소형터널의 처리는 다음과 같이 처리했다; 대조구(무처리), 두상관수(하루 두 번), 매트관수(하루 두 번), 그리고 안개관수(8:00시부터 18:00시까지 30분 온/오프 설정). 딸기 자묘는 반 밀폐형 소형터널 내에서 8일 동안 발근을 하였고, 그 이후 플라스틱 필름을 제거 하였다. 삽목 후 61일째에 초장, 근장, 1차 근수, 엽병장, 엽장, 엽폭, 크라운 직경, 엽록소 값, 엽면적, 지상부와 지하부의 생체중 및 건물중을 측정하였다. 터널 내의 하루 평균 상대습도는 각각 안개관수, 두상관수, 매트관수, 대조구 순으로 72.5, 56.3, 45.8, 그리고 29%를 나타냈다. 그러나 공기온도는 모든 처리에서 유사하였다. 딸기 자묘의 4일째와 8일째 발근율은 두상관수와 안개관수 처리에서 유의적으로 높았다. 초장, 엽병장, 크라운 직경, 엽면적은 두상관수와 안개관수 처리에서 높은 값을 나타냈다. 게다가 지상부의 생체중 및 건물중은 다른 처리에 비해 두상관수와 안개관수 처리에서 무거웠다. 지하부의 건물중은 안개관수 처리에서 유의적으로 무거웠다. 하지만 근장, 1차 근수, 엽록소 값, 지하부의 생체중은 모든 처리구에서 유의적인 차이를 나타내지 않았다. 결과적으로, '매향' 딸기의 삽목 번식 시 생육과 발근율은 두상관수와 안개관수 처리에서 가장 효과적인 것으로 나타났다.

• 한국추진공학회지
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• 제13권5호
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• pp.21-28
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• 2009

본 연구는 초음속 축소형 디퓨저의 설계 및 시동 특성에 영향을 주는 변수를 파악하기 위하여 상온의 공기와 질소 가스를 사용하여 실험을 수행하였다. 1차 노즐의 목 면적의 변화, 1차 노즐 전단의 압력 변화, 디퓨저 길이와 직경의 비($L_d/D_d$) 그리고 디퓨저의 팽창부 유 무에 따른 디퓨저의 시동 특성을 알아보았다. 실험 결과 1차 노즐의 직경이 감소할수록 디퓨저 시동압력은 증가하였으며, 디퓨저의 예측 모델과 비교하여 90~98%의 장치 효율을 확인하였다. 또한 $L_d/D_d$가 8.4이상인 디퓨저와 팽창부의 유 무에 관계없이 디퓨저는 정상적으로 시동하였다. 본 실험 결과는 실물형 고고도 환경 모사 장치의 개발에 있어서 기초 자료로 활용될 것이다.