The Effects of Antihypertensive Drugs on Bone Mineral Density in Ovariectomized Mice

Kang, Kwi Young,Kang, Yoongoo,Kim, Mirinae,Kim, Youngkyun,Yi, Hyoju,Kim, Juryun,Jung, Hae-Rin,Park, Sung-Hwan,Kim, Ho-Youn,Ju, Ji Hyeon,Hong, Yeon Sik The Korean Academy of Medical Sciences 2013 JOURNAL OF KOREAN MEDICAL SCIENCE Vol.28 No.8

<P>The effects of several antihypertensive drugs on bone mineral density (BMD) and micro-architectural changes in ovariectomized (OVX) mice were investigated. Eight-week-old female C57/BL6 mice were used for this study. Three days after ovariectomy, mice were treated intraperitoneally with nifedipine (15 mg/kg), telmisartan (5 mg/kg), enalapril (20 mg/kg), propranolol (1 mg/kg) or hydrochlorothiazide (12.5 mg/kg) for 35 consecutive days. Uterine atrophy of all mice was confirmed to evaluate estrogen deficiency state. BMD and micro-architectural analyses were performed on tibial proximal ends by micro-computed tomography (micro-CT). When OVX mice with uterine atrophy were compared with mice without atrophy, BMD decreased (<I>P</I> < 0.001). There were significant differences in BMD loss between different antihypertensive drugs (<I>P</I> = 0.005). Enalapril and propranolol increased BMD loss in mice with atrophied uteri compared with control mice. By contrast, thiazide increased BMD in mice with uterine atrophy compared with vehicle-treated mice (<I>P</I> = 0.048). Thiazide (<I>P</I> = 0.032) and telmisartan (<I>P</I> = 0.051) reduced bone loss and bone fraction in mice with uterine atrophy compared with the control. Thiazide affects BMD in OVX mice positively. The reduction in bone loss by thiazide and telmisartan suggest that these drugs may benefit menopausal women with hypertension and osteoporosis.</P>

연소관 내열고무의 내열성능평가를 위한 시험장치 개발

강윤구(YoonGoo Kang),박종호(JongHo Park) 한국추진공학회 2016 한국추진공학회지 Vol.20 No.3

Test equipment was designed and manufactured to evaluate thermal reaction characteristic of internal insulators of solid rocket motor. Test is allowed up to chamber pressure 2,500 psi, burn-time 100 s. A cross section of test sample part is quadrature, and various test samples can be comparable at the same time. Inner temperature of test sample can be measured by thermocouples during burning. Test was executed in condition of efficient average chamber pressure 1,000 psi, efficient burn-time 10 s and safety of equipment was confirmed. Basic data for understanding thermal characteristics of internal insulator, that is, pressure-time curve, temperature-time curve in the test sample, and thermal destruction thickness of test sample was gained successfully.

Kevlar/EPDM 내열고무의 압력 변화에 따른 열반응 비교

강윤구(YoonGoo Kang),박종호(JongHo Park) 한국추진공학회 2016 한국추진공학회지 Vol.20 No.3

Characteristic of thermal reaction of Kevlar/EPDM internal insulator used in a solid rocket motor chamber was investigated at 1,030 psi, 35.86 s and 1,406 psi, 36.63 s. Surface status after test was similar each other and thermal destruction depth was 4.10 mm and 4.18 mm, respectively. Kinetic constant ξ, ζ and thermal destruction velocity V<SUB>TD</SUB> were also similar. It was concluded that characteristics of thermal reaction of Kevlar/EPDM internal insulator were not affected by change of chamber pressure.

고체로켓 추진기관용 연소관단열재의 내열성능평가를 위한 시험장치 개발

강윤구(Yoongoo Kang),윤덕진(Deokjin Yun),김수영(Suyoung Kim),이종성(Jongsung Lee),권태하(Taeha Kwon) 한국추진공학회 2017 한국추진공학회 학술대회논문집 Vol.2017 No.5

고체로켓 추진기관의 연소관 내부에 사용되는 연소관단열재의 열반응 특성을 평가하기 위한 모사시험장치를 개발하였다. 연소실 압력 2,500 psi, 연소시간 40 s까지 시험을 할 수 있으며, 삭마가 일어나는 조건에 대해 재료의 열반응 특성을 확인할 수 있고, 여러 시편을 동시에 상대 비교할 수 있다. 시험장치의 안전성을 확인하기 위하여 연소실 유효평균압력 878 psi, 유효연소시간 10.7 s, 연소가스속도 100 m/s 조건에서 각기 다른 시편 4 종을 동시에 장착하여 시험을 수행하였으며, 열반응 특성 분석에 필요한 기본 데이터들, 즉 연소실의 압력-시간 선도, 재료 내부에서의 온도-시간 선도, 재료의 열파괴두께를 획득하였다. Test equipment was designed and manufactured to evaluate thermal reaction characteristic of internal insulators of solid rocket motor. Test is allowed up to chamber pressure 2,500 psi, burn-time 40 s. It is possible to observe and to compare thermal reaction characteristic for a few materials simultaneously, under the condition that the ablation occurs. In efficient average chamber pressure 878 psi, efficient burn-time 10.7 s and gas velocity 100 m/s, test was executed for confirming safety of equipment, being 4 test materials inserted simultaneously. Basic data for understanding thermal characteristic of internal insulator, that is, pressure-time curve, temperature-time curve in the test sample, and thermal destruction depth of test samples was gained successfully.

압력과 산화몰분율이 그라파이트 목삽입재의 삭마율에 미치는 영향

함희철(Heecheol Hahm),강윤구(Yoongoo Kang) 한국추진공학회 2014 한국추진공학회지 Vol.18 No.1

The ablation characteristics of graphite nozzle throat insert is analyzed for the use in solid rocket propulsion system. The propulsion system is composed of three types of conventional nozzles, such as De-Laval type, blast tube type, and submerged type. Various kinds of propellants are used in the thirteen kinds of propulsion system that has different shapes of each other. Total thirty seven tests are performed. From the results of the analysis, it is found that the ablation rate is higher for the higher average chamber pressure and the higher concentration of oxidizing species in combustion gas.

그라파이트 목삽입재의 삭마율에 미치는 영향 인자 연구

함희철(Heecheol Hahm),강윤구(Yoongoo Kang),서상규(Sangkyu Seo) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.12

고체 로켓 추진기관의 노즐목 삽입재에 적용하는 그라파이트의 삭마율 특성을 분석하였다. 지상연소시험은 3종류의 일반적인 노즐형태를 갖는 추진기관을 사용하여 수행하였다. 즉, De-Laval 형태, 토출관 형태, 내삽 형태이다. 10종류의 서로 다른 형상의 추진기관에 다양한 추진제를 적용하였고, 노즐목 위치에 그라파이트를 적용하여 총 48회의 연소시험을 수행하였다. 분석결과 그라파이트의 삭마율은 연소실 평균압력이 상승함에 따라, 산화제 몰분율이 증가함에 따라 증가함을 알 수 있었다. 또한, 연소실 압력, 산화제 몰분율, 노즐목 크기의 3가지 영향인자를 고려한 노즐목 삭마율 관계식을 유도하였으며, 측정 결과와 비교하여 ± 0.10 mm/s 이내로 일치하였다. The ablation characteristics of graphite nozzle throat insert was analyzed for the use in solid rocket propulsion system. The propulsion system was composed of three types of conventional nozzles, such as De-Laval type, blast tube type, and submerged type. Various kinds of propellants were used in the ten kinds of propulsion system that had different shapes of each other. Total forty eight tests were performed. From the results of the analysis, it was found that the ablation rate was higher for the higher average chamber pressure and the higher oxidizer mole fraction. A useful correlation for nozzle throat ablation rate was developed in three terms of the chamber pressure, oxidizer mole fraction, and throat size. The calculated ablation rates from the correlation showed agreement within ± 0.10 mm/s of the experimentally determined values.

연소 전 고체 추진기관의 내부 온도변화 특성에 관한 실험적 연구

송기혁(Keehyeok Song),강윤구(Yoongoo Kang),구송회(Songhoe Koo) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.5

고체 추진기관 개발 과정에서 운용조건에서의 성능을 확인하기 위해 일반적으로 저온(-40℃), 상온(20℃), 고온(60℃)의 조건에서 지상연소시험이 수행된다. 온도챔버 내부에서 운용온도 조건으로 조정된 추진기관은 온도챔버 외부에 위치한 시험시설로 이동되고 신속한 설치 후 연소시험에 사용된다. 연소 전 설치과정에서 추진기관은 대기온도에 의해 열손실 혹은 열취득이 발생하게 되며 노출시간이 길어짐에 따라 원하는 시험목표 온도와 상이해질 수 있다. 본 연구에서는 HTPB계 추진제를 사용하는 추진기관을 대상으로 실험을 통해 얻은 내부 온도변화 특성을 제시하였다. Ground combustion test is generally implemented to verify the performance of the motor on the three different operation temperatures(-40, 20, 60℃). The internal temperature of the motor is adjusted to operation temperature by temperature chamber, and the motor is moved out to test facility. After rapid setting, the motor is tested for combustion. In this process, heat loss or heat gain may happen and the long exposure time at outside can cause unintended results. This paper shows internal temperature characteristics of solid propulsion motor using HTPB propellant before combustion.

흑연 노즐목 삽입재의 삭마율에 미치는 영향 인자 연구

함희철(Heecheol Hahm),강윤구(Yoongoo Kang),서상규(Sangkyu Seo) 한국추진공학회 2017 한국추진공학회지 Vol.21 No.4

The ablation characteristics of graphite nozzle throat insert was analyzed for the use in solid rocket propulsion system. The propulsion system was composed of three types of conventional nozzles, such as De-Laval type, blast tube type, and submerged type. Various kinds of propellants were used in ten kinds of propulsion system that had different shapes with each other. Total forty eight tests were performed. From the results of the analysis, it was found that the ablation rate was increased for the higher average chamber pressure and the higher oxidizer mole fraction. A useful correlation for nozzle throat ablation rate was developed in terms of the chamber pressure, oxidizer mole fraction, and throat size. The calculated ablation rates from the correlation showed agreement within ± 0.10 mm/s with the experimentally determined values.

고체추진기관의 Al₂O₃가 고무내열재에 미치는 영향을 평가하는 시험방법 연구

이형식(Hyungsik Lee),강윤구(Yoongoo Kang),임수용(Sooyong Lim),오종윤(Jongyun Oh),이경훈(Kyunghoon Lee) 한국추진공학회 2011 한국추진공학회지 Vol.15 No.3

In solid propellant rocket motors, Al₂O₃, one of combustion products, can be accumulated inside a combustion chamber. A special rocket motor was designed and tested to simulate thermal reaction of rubber insulator affected by the deposited slag. We successfully demonstrated through a dynamic radioscopy that the slag was deposited at the location as designed. In this paper we present a new test method which can simulate a high temperature and pressure environment in combustion chamber to evaluate material characteristics of rubber insulator and can provide design data to decide its thickness for a new solid rocket motor. The solid rocket motor, which has an average chamber pressure of 770 psia and a burning time of 50 seconds, was tested. The results show that erosion of EPDM insulator is more affected by a gas velocity rather than by the thermal reaction of slag with a high thermal capacity.

로켓 노즐의 열전달계수 비교 연구

함희철(Heecheol Hahm),강윤구(Yoongoo Kang) 한국추진공학회 2012 한국추진공학회지 Vol.16 No.2

The goal of heat transfer studies is the accurate prediction of temperature and heat flux distribution on material boundaries. To this purpose, general-purpose computational fluid dynamics(CFD) code is used : FLUENT. Mass fluxes and pressure ratio are calculated for two types of nozzle. The comparative studies reveal that the computational results are in agreement with the experimental data. Also, heat transfer coefficients from FLUENT for one type of nozzle are very similar and agree well with the experimental data in the diverging part of the nozzle, but the calculated results are large in the converging part. The heat transfer coefficients from Bartz equation are over-predicted. We can consider various reasons for these differences, i.e., laminarization by the highly accelerated flow in the nozzle, turbulent flow model and grid generation.