SHS 공정에 의해 제조된 Mo_xW_1-xSi₂ 발열체의 열화메커니즘

이동원,이상헌,김용남,이성철,구상모,오종민,Lee, Dong-Won,Lee, Sang-Hun,Kim, Yong-Nam,Lee, Sung-Chul,Koo, Sang-Mo,Oh, Jong-Min 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.10

The degradation mechanism of $Mo_xW_{1-x}Si_2$ ultrahigh-temperature heating elements fabricated by self-propagating high-temperature synthesiswas investigated. The $Mo_xW_{1-x}Si_2$ specimens (with and without post-annealing) were subjected to ADTs (accelerated degradation tests) at temperatures up to $1,700^{\circ}C$ at heating rates of 3, 4, 5, 7, and $14^{\circ}C/min$. The surface loads of all the specimen heaters were increased with the increase in the target temperature. For the $Mo_xW_{1-x}Si_2$ specimens without annealing, many pores and secondary-phase particles were observed in the microstructure; the surface load increased to $23.9W/cm^2$ at $1,700^{\circ}C$, while the bending strength drastically reduced to 242 MPa. In contrast, the $Mo_xW_{1-x}Si_2$ specimens after post-annealing retained $single-Mo_xW_{1-x}Si_2$ phases and showed superior durability after the ADT. Consequently, it is thought that the formation of microcracks and coarse secondary phases during the ADT are the main causes for the degraded performance of the $Mo_xW_{1-x}Si_2$ heating elements without post-annealing.

SHS 공정으로 제조된 Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si₂ 발열체의 가속수명시험과 고장분석

이동원(Dong-Won Lee),이상헌(Sang-Hun Lee),김용남(Yong-Nam Kim),이희수(Heesoo Lee),이성철(Sung-Chul Lee),구상모(Sang-Mo Koo),오종민(Jong-Min Oh) 한국전기전자학회 2017 전기전자학회논문지 Vol.21 No.3

고온자전합성과 후열처리 공정으로 MoxW1-xSi₂ 발열체를 제조하였다. MoxW1-xSi₂ 발열체의 신뢰성을 검증하기 위해 가속수명시험을 수행하였으며, 수명시간을 Minitab 프로그램으로 추정하였다. 또한, 가속수명시험 후의 MoxW1-xSi₂ 발열체의 고장분석을 전기적과 구조적 특성으로부터 수행하였다. 그 결과, MoxW1-xSi₂ 발열체의 지배적인 고장 유형은 발열체 내부의 크랙 형성과 SiO₂ 보호층의 박리임을 확인하였다. MoxW1-xSi₂ heaters were fabricated by self-propagating high-temperature synthesis (SHS) process and post sintering process. To validate the reliability of the MoxW1-xSi₂ heaters, the accelerated life test (ALT) was conducted, and then lifetime to MoxW1-xSi₂ heaters was estimated by using Minitab programs. Also, the failure analysis of MoxW1-xSi₂ heaters after ALT was performed through electrical and structural properties. As the results, it was confirmed that the dominant failure mode of MoxW1-xSi₂ heaters is the crack formation in heaters and the delamination of protective SiO₂ layers.

고 사구체전 저항의 신장에서 수출소동맥 이완에 대한 신혈역학적 반응 : 수학적 접근

양훈모,주명찬 순천향의학연구소 1998 Journal of Soonchunhyang Medical Science Vol.4 No.1

To progressive increases in efferent arteriolar resistance (RE), GFR responds with an initial increase followed by a decrease. The biphasic response implies that the response of GFR to RE varies depending on the renal hemodynamic conditions. We studied, with a glomerular model, the mechanism of deterioration of renal function during angiotensin I converting enzyme inhibitor (ACEI) in the kidney with renal artery stenosis. The glomerular model was based on a simulation of flow along a glomerular capillary with negligible resistance and uniform ultrafiltration coefficient (kf, 0.09 nl·sec-1·mmHg-1). The control preglomerular resistance (RPRE) and RE were 0.071 and 0.081 mmHg·min·ml-1, respectively. The effect of renal artery stenosis is to increase RPRE by inserting a fixed stenotic resistance in series with the afferent arteriolar resistance, and RPRE which is the sum of the resistances of stenosed renal artery and afferent arteriole is increased in the kidney with stenosed renal artery. Since the higher RPRE is associated with greater reduction in GFR in response to reduction in RE, the kidney with stenosed renal artery will respond with severer decrease in GFR to postglomerular vasodilation. In addition, the preglomerular vasodilation which accounts for the major compensatory response to renal hypotension in the normal kidney becomes less and less effective in recovering PG and GFR during a decrease in renal artery pressure as the resistance caused by the stenosis becomes greater. The model has shown that these two factors contributed to the greater reduction in GFR (34ml·min-1 during renal artery stenosis vs. 46.5ml·min-1 during control) despite an increase in kf (40%) during ACEI in the kidney with renal artery stenosis (resistance; 0.082 mmHg·min·ml-1). In conclusion, severer deterioration of renal function in response to ACEI administration in the kidney with renal artery stenosis results from the reduced ability of RPRE to decrease in response to hypotension and the increased sensitivity of GFR to a decrease in RE when RPRE is increased.

근육세뇨관 수분 및 이온 이동에 대한 모델

양훈모,송혜섭,민영기 순천향의학연구소 1999 Journal of Soonchunhyang Medical Science Vol.5 No.2

본 연구는 세뇨관 벽을 통하여 물과 이온이 이동하는 현상을 수학적 모델에 근거하여 수행하였다. 세포측막, tight junction, 기저막으로 구성된 측간질 공간으로의 염분이동은 삼투현상에의해 동시에 수분이동을 유발한다. 이로인한 수분에 공간내 증가는 정수합을 증가시켜 Na, Cl, HCO3 에 대한 반사계수가 0 이고 투과성이 매우 높은 기저막을 통해 용액이 유출된다. 동반이동 가능성과 비평형 열역학 이론을 포함한 본 모델을 이용하여 tight junction의 이온투과성과 반사계수가 물과 이온 이동에 미치는 영향을 조사해 본 결과는 다음과 같다. 1. 수분의 전도성(Lp)은 100배 이상하여야 삼투압에 의한 수분이동이 전체 수분이동에 영향을 미칠 수 있다. 2. 관강 측과 기저측 세포막은 반사계수가 1이기 때문에 세포를 관통하는 convective ion flux에는 영향이 없었다. 3. 관강내 액과 측공간 액사이에는 높은 HCO3 농도 경사가 유지되고 있기 때문에 HCO3에 대한 높은 반사계수는 삼투적 수분 흡수에 필수적이다. 4. Cl의 반사계수의 감소는 수분흡수를 증가시켜 Cl 재흡수도 증가시켰다. 동시에 전기적 확산에 의해 Na 재흡수도 증가하였다. 5. 전반적인 반사계수의 감소는 수분 재흡수는 감소 시켰으나 용질 재흡수는 증가시켰다.

수입소동맥 저항과 수출소동맥 저항의 상호 작용에 대한 연구

양훈모,민영기,이정범 순천향의학연구소 2004 Journal of Soonchunhyang Medical Science Vol.10 No.1

It has generally been accepted that efferent arteriolar constriction increase GFR. However, it has also been shown in mathematical studies that increases in efferent arteriolar resistance beyond some extent causes GFR to decrease. The aim of the present study is to investigate the occurrence of physiological and/or pathophysiological conditions in which GFR is decreased by efferent constriction. The renal hemodynamic data obtained by several investigators were analyzed with a mathematical model of single nephron GFR (SNGFR). The glomerular model is based on a simulation of flow along a glomerular capillary with negligible resistance and uniform ultrafiltration coefficient (K_(f), 0.09 nl · sec^(-1) · mmHg^(-1)). The data analyzed are from rats which have been shown to achieve filtration pressure equilibrium(FPE) during filtration along the glomerular capillary. The hemodynamic states of rat kidney is characterized by a high K_(f), low RBF, and high vascular resistance. In these animals, inhibition of the renin-angiotensin system was associated with increases in GFR. This was mainly contributed to the increase in K_(f). Analysis with the present model has shown that lowered efferent arteriolar resistance during angiotensin inhibition augmented GFR response to K_(f). The analysis of the data obtained by manipulating efferent resistance during aortic constriction demonstrated the importance of pregiomerular resistance(R_(PRE)) related to efferent resistance (R_(E)). in this hemodynamic condition. The FPE which determines the sensitivity of SNGFR to SNBF and K_(f) is attained nearer the afferent end as R_(PRE) increases further: On the other hand, R_(PRE) had no effect on FPE. In conclusion, certain physiological manipulation affects R_(PRE) and K_(f) in such fashion that a decrease in R_(E) may have a beneficial effect on GFR and vice versa. This analysis indicates that it is not limited to theoretical importance; it demonstrated that in rat kidneys which have low flow and high afferent resistance the efferent arteriolar dilation can be associated with the promotion of GFR.

개에서 17-ODYA가 신혈류량 자동 조절에 미치는 영향

양훈모,민영기,박중섭 순천향의학연구소 1999 Journal of Soonchunhyang Medical Science Vol.5 No.1

17-ODYA is a potent inhibitor of the formation of 20-hydroxyeicosatetraenoic acid, epoxyeicosatrienoic acids and dihydroeicosatetraenoic acids by renal cortical microsomes. This study characterized the effects of intrarenal infusion of 17-ODYA on renal blood flow (RBF) and autoregulation of RBF. Seven dogs were prepared for the measurements of RBF, mean systemic and renal perfusion pressure. The renal perfusion pressure was able to be adjusted to desired levels by an inflatable supra-aortic occluder. Intrarenal infusion of 17-ODYA produced a diuresis and a natriuresis but no change in RBF. 17-ODYA had no effect on autoregulation of RBF: Both the plateau and steep portrions. of the autoregulatory curves were identical to control. Thesholds for lower limit of autoregulation were 72±4 and 72±5 mmHg during control and 17-ODYA and not significantly different from each other. These results suggest that endogenous cytochrome P-450 metabolites of AA do not influence RBF autoregulatory capacity in dogs.

편측 하악 과두골절의 관혈적 치료에 있어서 예후에 영향을 줄 수 있는 인자들에 관한 임상 통계학적 연구

성현모,이동근,민승기,오승환,장관식 대한악안면성형재건외과학회 2001 Maxillofacial Plastic Reconstructive Surgery Vol.23 No.1

The purpose of this study is to reveal the factors leading to the problem of unilateral condylar fractures and suggest a treatment guideline of treatment for good prognosis in surgical treatment, The factors can be age, sex, fracture site, degree of displacement, posterior occlusion loss, post-operative alteration of condylar head position, post-operatlve condylar head resorption, and maxillomandibular fixation period. One hundred and eleven patients with unilateral condylar fractures, who were treated by surgical method from 1990 Feb. to 2000 Feb., were studied. Minimum follow-up period was 6 months. The results were as follows ; 1. In the age group of 41 ∼60, females had significantly higher complication rate than males, therefore we must be careful about treatment of female in this age group 2 In level I fractures of the mandibular condyle, because there were abundant complications when the patients were treated with fragment removal, conservative treatment is recommended over the surgical approach. 3. There were no differences in the complication rate, in the level Ⅱ, Ⅲ fractures. but were severe complications in the cases of patients treated by Dr.Nam's method or fragment removal. Therefore, open reduction and internal fixation is recommended over Dr.Nam's method or fragment removal. 4. In level Ⅳ fractures, open reduction and internal fixation is recommended 5. Although there was a higher complication rate depending on the degree of deviation, there was no correlation between the degree of deviation and development of complications in each level of fracture 6. Because the complication rate was higher in cases of condylar resorption, vertical dimension loss, and alteration of condylar head position, we must make an effort to prevent such complications during treatment

신장내 국소혈류량 조절에 대한 신교감신경의 영향

양훈모,민영기,김동진,송호연,송윤섭 순천향의학연구소 2001 Journal of Soonchunhyang Medical Science Vol.7 No.2

Control of blood pressure is affected by regulation of intrarenal blood flow. Renal sympathetic nerve simulation inhibits pressure-depressor mechanism of kidney. This antidepressor mechanism was known as happening to due to a decrease the blood supply of renal medulla. It is not known whether renal sympathetic nerve innervation of renal medulla is and it affects regulation of medullary blood flow. We tried to measure total renal blood flow(TRBF), cortical blood flow(CBF), papillary blood flow(PBF) by ultrasonic and laser Doppler techniques in Wistar rats during 3 kinds of renal sympathetic nerves stimulation. The simulation orders are tried randomly and each stimulation period is 15 minute. TRBF and CBF decreased at 1 Hz by 2 and 2%, 3Hz by 18 and 15%, 5Hz by 49 and 44%, respectively as similar to each other. But PBF increased by 1% at 1 Hz and 4% at 3 Hz, while it decreased by 4% at 5 Hz. Therefore, it seems superficial renocortical and total renal blood flows are closely regulated by renal sympathetic nerves with increasing vasoconstriction at 5 Hz, onthe other hand while medullary blood flow seems to be under strong local control, tending to offset neurogenic flows restrictions.

뇌 해마의 복측 또는 배측 부분이 제거된 흰쥐 중격핵의 신경전달물질

양훈모,김종규,한영길,민영기 순천향의학연구소 1999 Journal of Soonchunhyang Medical Science Vol.5 No.1

This study was planned to analyze amino acids in the septal nucleus of dorsal and ventral hippocampectomized rats by high performance liquid chromatography (HPLC). Male albino rats were used. Under chloral hydrate anesthesia (20%, 2 ml/kg body weight), a hole was made in each parietal bone about 4 mm lateral to the sagittal suture, and 4 mm rostral to the lambda suture. The cortical tissue on each side was removed and, through this opening, the hippocampal tissue anterodorsal and posteroventral to the hippocampal flexures on both sides was removed by aspiration. This preparation served as the dorsal and the ventral hippocampal animals, respectively. The cortical control animal received the same surgery short of hippocampectomy. The normal rats served as normal control animal. One day later, the animals were sacrificed by decapitation in the cold room. Two to three milligrams of tissue was obtained form the septal nucleus in one side of the brain. The tissue samples were homogenized and centrifuged. Then content of each amino acid was measured by HPLC form the brain tissue. The contents of aspartate and glutamate were decreased significantly more in the dorsal and ventral hippocampal groups than in the normal and the cortical control groups. The contents of glutamate were decreased significantly more in the ventral hippocampal group than in the dorsal hippocampal, while there were no significant differences between the two control groups. It is inferred form the above mentioned results that glutamate and aspartate may be used as excitatory transmitters in septal nucleus, and that the dorsal hippocampus may be facilitatory to the septal nucleus, but the ventral hippocampus would be inhibitory/facilitatory to the cortex.

Norepinephrine에 의한 신자율 조절 변화의 Prostaglandin의 역활

배원경,양훈모,심동원 순천향대학교 1994 논문집 Vol.17 No.2

We investigated whether indomethacin, a prostaglandin (PG) synthesis inhibitor, modulates the effect of norepinephrine on the autoregulation of the renal blood flow(RBF) in anesthetized dogs. A silastic inflatable occluder was placed around the aorta cephalad to the bifurcation of thee renal artery, and an electromagnetic flow probe was placed around the renal artery for the measurement of RBF. RBF autoregulatory curves were determined during intravenous infusion of NE(0.3 & 0.8 ㎍/㎏/min) before and after the blockade of PG synthesis with indomethacin(1-2 ㎎/㎏). During control, we observed a precise autoregulation of RBF until RAP decreased to 69±3mmHg. The higher dose(0.8 ㎍/㎏/min) of NE shifted the curve to the right increasing the lower limit of RBF autoregulation to 79±5 mmHg while the lower dose had no effect on the curve. Inhibition of PG synthesis with indomethacin decreased RBF 8-10% during basal condition. However, the autoregulatory curves determind after the inhibition of PG synthesis were not significantly different from those determined before the inhibition. These data indicate that PG does not modulate the effect of norepinephrine on the autoregulation of RBF.