• International Journal of Aeronautical and Space Sciences
• /
• 제18권4호
• /
• pp.797-806
• /
• 2017

In this study, the reflection coefficient (RC) and the flame transfer function (FTF) were measured by applying acoustic excitation to a duct-type model combustor and were used to predict the frequency of the combustion instability (CI). The RC is a value that varies with the excitation frequency and the geometry of the combustor as well as other factors. Therefore, in this study, an experimentally measured RC was used to improve the accuracy of prediction in the cases of 25% and 75% hydrogen in a mixture of hydrogen and methane as a fuel. When the measured RCs were used, an unstable condition was correctly predicted, which had not been predicted when the RCs had been assumed to be a certain value. The reason why the CI occurred at a specific frequency was also examined by comparing the peak of the FTF with the resonance frequency, which was calculated using Helmholtz's resonator analysis and a resonance frequency equation. As the CI occurred owing to the interaction between the perturbation in the rate of heat release and that in the pressure, the CI was frequent when the peak of the FTF was close to the resonance frequency such that constructive interference could occur.

• 한국방사선학회논문지
• /
• 제7권6호
• /
• pp.433-439
• /
• 2013

본 연구에서는 집속형 초음파를 이용하는 뇌 질환 치료의 연구를 위한 인체 두부 유사 팬텀을 개발하였다. 문헌 연구를 통하여 피부 조직, 두개골, 뇌 조직의 음향학적 및 물리적 특성을 조사하였으며 근사한 값을 가지는 적합한 각 조직 대체 물질을 제시하였다. 피부 조직의 경우 글리세롤 기반 연부 조직 유사 팬텀의 성분비를 조정하여 실제 조직과 유사한 음향학적 특성을 가지도록 하였으며 고분자 합성수지의 음향학적 특성을 측정하여 두개골 유사 물질로써의 적합성을 평가하였다. 뇌 조직은 투명한 egg white 팬텀을 이용하여 집속형 초음파의 가열 특성을 확인할 수 있도록 하였다. 또한 뇌 질환 치료 프로토콜 개발을 위한 시험 조사가 가능하도록 대체 물질들을 결합한 두부 유사 팬텀을 제작하였고 제작된 팬텀의 유효성 및 활용성 평가를 위해 초음파 조사 조건에 따른 팬텀의 변성을 관찰하였다.

• 한국항공우주학회지
• /
• 제37권9호
• /
• pp.916-922
• /
• 2009

우주공간에서 임무를 수행하는 인공위성의 열설계는 열모델을 활용한 열해석 결과를 바탕으로 수행되므로, 열모델의 정확성은 매우 중요하며 이것은 보정과정을 통하여 향상된다. 열모델의 보정은 인공위성이 열진공 챔버에 장착된 형상을 모사하는 모델링에서 시작하여 실제형상과 열모델간의 일치성에 대한 검증, 거시적 변수에서부터 미시적 변수에 이르기까지 열모델 변수에 대한 조정 등을 거쳐 주어진 성공 조건을 만족할 때까지 열모델을 지속적으로 수정하는 과정으로 이루어진다. 본 연구에서는 열모델 보정의 성공 기준을 수립하고 인공위성 열-구조 모델 열진공 시험결과를 활용한 열모델 보정을 수행하여 보정 기준을 충족시켰다. 본 연구에서 보정이 완료된 열모델은 저궤도 인공위성 상세 열설계에 적용될 수 있었다.

• 대한물리의학회지
• /
• 제2권2호
• /
• pp.101-112
• /
• 2007

Purpose : The purpose of this study was to evaluate influence of sacroiliac joint mobilization on lower extremity muscle strength. Methods : The subjects were consisted of thirty patients who had Leg length inequality(LLI) of more than 10mm(16 females. 14 males) from 21 to 41 years of age(mean aged 24.87). All subjects randomly assigned to sacroiliac joint mobilization group(n=15), control group(n=15). sacroiliac joint mobilization group received sacroiliac joint mobilization about 10 minutes for 3 times per week during 4 weeks period. Control group not received intervention during 4 weeks period. The tape measure method(TMM) was used to measure functional Leg length inequality. Biodex System 3 Pro was used to measure strength of Knee extension & flexion. All measurements of each subjects were measured at pre-test, 2weeks post-test and 4weeks post-test. Results : 1. The LLI of sacroiliac joint mobilization group was significantly reduced according to within treatment period(p<.05), most significantly reduced between pre-test and post-test(p<.05). sacroiliac joint mobilization group significantly more reduced than control group(p<.05). 2. The knee extension strength of sacroiliac joint mobilization group was significantly increased according to within treatment period(p<.05), most significantly increased between pre-test and post-test(p<.05). sacroiliac joint mobilization group significantly more increased than control group(p<.05). 3. The knee flexion strength of sacroiliac joint mobilization group was significantly increased according to within treatment period(p<.05), most significantly increased between pre-test and post-test(p<.05). sacroiliac joint mobilization group significantly more increased than control group(p<.05). Conclusion : sacroiliac joint mobilization can reduce LLI and increased lower extremity muscle strength.

• 대한물리의학회지
• /
• 제2권2호
• /
• pp.183-194
• /
• 2007

Purpose : The purpose of this study was to evaluate influence of therapeutic exercise on functional leg length inequality(LLI). Methods : The subjects were consisted of thirty patients who had Leg length inequality(LLI) of more than 10mm(l6 females. 14 males) from 20 to 35 years of age(mean aged 24.23). All subjects randomly assigned to contract-relax exercise of proprioceptive neuromuscular facilitation(PNF) group(n=15), control group(n=15). Contract-relax exercise group received contract-relax exercise about 10 minutes with therapeutic massage about 15 minutes for 3 times per week during 4 weeks period. Control group not received intervention during 4 weeks period. The tape measure method(TMM) was used to measure functional Leg length inequality. Biodex System 3 Pro was used to measure strength of Knee extension & flexion. All measurements of each subjects were measured at pre-test, 2weeks post-test and 4weeks post-test. Results : 1. The LLI of contract-relax exercise group was significantly reduced according to within treatment period(p<.05), most significantly reduced between pre-test and post-test(p<.05). Contract-relax exercise group significantly more reduced than control group(p<.05). 2. The knee extension strength of contract-relax exercise group was significantly increased according to within treatment period(p<.05), most significantly increased between pre-test and post-test(p<.05). Contract-relax exercise group significantly more increased than control group(p<.05). 3. The knee flexion strength of contract-relax exercise group was significantly increased according to within treatment period(p<.05), most significantly increased between pre-test and post-test(p<.05). Contract-relax exercise group significantly more increased than control group(p<.05). Conclusion : Contract-relax exercise applied with therapeutic massage can reduce LLI and increased lower extremity muscle strength.

• 대한전자공학회논문지SD
• /
• 제43권5호
• /
• pp.25-33
• /
• 2006

전달 행렬 방법과 capacitance-voltage 특성, 그리고 측정된 광응답 스펙트럼을 이용하여 Schottky 다이오드 UV-A와 B 광검출기에 사용되는 GaN, $Al_{0.2}Ga_{0.8}N$ 등의 반도체 및 Schottky 접촉 금속 Ni의 물질특성인 흡수계수(absorption coefficient)를 추출하였다. 입사된 빛이 반도체의 공핍영역에서 흡수되는 양을 구하고, 이로부터 각 파장에서의 광응답 특성을 얻는 과정을 컴퓨터 프로그램으로 구현하였다. 그리고, 계산 값을 측정치와 비교하여 각 파장에서 GaN, $Al_{0.2}Ga_{0.8}N$, Ni의 흡수계수를 얻을 수 있었다. 추출된 흡수계수를 이용하여 자외선 광검출기의 광응답을 높이는 설계 방안을 모색하였다. Ni의 흡수계수가 크기 때문에 광응답을 결정하는 주요 요소는 Ni 전극의 두께이다. 따라서 Schottky 접촉 금속 Ni의 두께를 줄이고, 공핍 영역의 크기를 늘릴 수 있다면 광응답 특성이 더욱 향상된 광검출기의 실현이 가능해질 것이다.

• Mycobiology
• /
• 제35권2호
• /
• pp.54-61
• /
• 2007

Two isolates of Tricholoma matsutake T-008 and T-034, preserved in Entomopathogenic Fungal Culture Collection (EFCC) of Korea, were used in the present study. The isolates had 100% Bootstrap homology with Tricholoma matsutake U62964 and T. matsutake AB188557 and AF309538 preserved in Gene Bank of NCBI. Mycelial growth of T. matsutake was highest in TMM and MYA at $25^{\circ}C$. The highest dry wt. of mycelium was obtained after 65 days of culture, when 6 mycelial discs were inoculated in 100 ml of broth in 250 ml shaking flask. Mycelial mats were observed in clumped condition at the inoculation sites of pine forest after two weeks of inoculation. After 5 months of inoculation, mycelia mats were observed growing inside soil and walls of a few inoculation sites, while mycelial mats growth up to $5{\sim}8$ cm were observed in the roots of pine tree after 6 months. The survival rate of the inoculum was about 40% of the total inoculation sites. The survival rate was found below 20% when the mycelium was inoculated in the summer. The reasons for low survival rates of the mycelium were mainly due to dry season and the soil-borne small animals such as earthworm and mole. After one year of inoculation, no external difference was observed between the artificially inoculated mycelia and the naturally existing mycelia of T. matsutake. The present study showed that fruiting bodies of T. matsutake could be produced by artificial inoculation under the appropriate environmental conditions.

• 센서학회지
• /
• 제18권5호
• /
• pp.377-384
• /
• 2009

The ultrasonic hyperthermia for oncology has been developed and studied. The HIFU(high intensity focused ultrasound) is the most recent method to treat the tumor by using ultrasound. In this study, an insertion-type transducer for treating a prostate cancer, which can focus the ultrasonic beam mechanically and electrically, was designed and developed. The developed transducer was composed of three arrays, and each array has 32 elements. For the purpose of the mechanical focusing, both side arrays are slanted to the center array by $15^{\circ}$. With this structure, NFL(near field length) was set up as 30 mm. The PZT-4 and two matching layers were used, and the backing layer was excepted to prevent energy losses. The acoustic field analysis and the heating test were performed to evaluate the performance of developed transducer. The shape of an acoustic field, peak pressure, and acoustic pressure distribution were compared with numerical simulation. The NFL was 32 mm, the beam width was 5 mm, focal area was $40\;mm^2$, and peak pressure was 5.5 MPa. With heating by using developed transducer, the temperature increased up to $33^{\circ}C$ at focal zone. As a result of this study, the usefulness of suggested transducer for prostate cancer hyperthermia was confirmed by the acoustic field analysis and the heating test with TMM(tissue mimicking) phantom.

• 대한조선학회지
• /
• 제27권3호
• /
• pp.31-37
• /
• 1990

선박의 방향안정성 등을 논할 때 필요하게 되는 선형조종미계수에 대해서는 이론적, 실험적으로 그 추정법이 제안되고 있다. 이중, 실험적 방법은 모형선에 규칙적인 강제동요를 시켜서 원하는 값들을 구하고 있으나, 한규칙 동요에 대해서 그 주파수에 대한 값만 나오므로 넓은 범위의 운동주파수에 걸쳐 미계수의 값들을 얻고자 할 때는 방대한 회수의 실험을 행해야 한다, 이러한 단점을 개선하기 위해 고안된 것이 본 논문에서 취급하는 Transient Maneuvering Method(TMM)로서, 기본원리는 모형에게 과도적 운동을 시켜 그로 인한 동유체력을 계측하고 이를 Fourier 변환하므로서 여러가지 주파수에 대한 미계수의 값을 얻게 되는 것이다. 종래의 이 분야 연구자들은 모형을 움직일 때 전동모터를 사용했으나 모터를 사용할 경우 원하는 과도 운동을 충분히 시킬 수 없으므로 본 논문에서는 유압 펌프를 사용하여 좋은 효과를 얻었다. 그 외에도 입력신호를 다소 개량하여 최종결과의 S/N비를 개선하는데 성공하였다. 실험에 사용한 모델은 Todd의 계열 60(Cb=0.7) 2M급이고, 이 결과를 종래의 PMM 시험결과와 비교하였다.

• PNF and Movement
• /
• 제12권4호
• /
• pp.201-207
• /
• 2014

Purpose: The purpose of this study was functional leg length inequality effect on COP(Center Of Pressure) and LOS(limits Of Stability) and EMG activation. Methods: The participants were consisted of fourteen. Subjects were distributed 2 groups; control group, leg length inequality ${\leq}3mm$, n=8), experimental group(leg length inequality${\geq}10mm$, n=8). The participants were measured leg length wearing comfortable clothes through tape measure method(TMM). All subjects was measured COP(Center Of Pressure), LOS(limits of stability) using by Balance Trainer BT4(HUR, Finland). Results: The results COP was not exist statistical significant differences(p>0.05). LOS was not exist statistical significant difference(p>0.05). Conclusion: The results was not statistical significant differences COP and LOS depending on Leg Length Inequality. But between experimental group and comparison group was exist mean differences on COP, LOS(COP:Ex.>Com, LOS:Ex.