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.

Tight Junction의 투과성 변화가 근위세뇨관 재흡수에 미치는 영향

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

The proximal tubular model is based on a simulation of fluid and ion transport across the tubular wall. This model includes a space between the basolateral cell membrane, tight junction and the basement membrane as lateral interstitial space. Salt transport into the interspace would induce an osmotic water flow across this membrane. The accumulation of salt and water solute within the interspace would create a sufficient hydrostatic pressure to drive this solution out across the permeable basement membrane ( σ, reflection coefficient = 0). We tested with this model the influence of σ and permeability characteristics (Pi) of the proximal tubular epithelium on transmembrane volume(Jv) and ion(Ji) fluxes and potential difference. Epithelial transport mechanism specifically included the possibility of coupled transport processes and the linear theory of nonequilibrium thermodynamics. The model predicted the following results. An increase in PNa decreased the reabsorption of all the major ions and water due to diffusion of Na into the lumen. An increase in Pa had an opposite effect: The electrochemical gradient favoring chloride reabsorption was established shortly after the initial segment. PHCO3 was ineffective in affecting proximal tubular transport of water and ions. While σNa, and σcl had very little effect on the proximal tubular transport, σHCO3 had a significant effect on JNa, Ja but not on JHCO3. It was due to an increase in convective flow of sodium and chloride secondary to an increase in Jv. It is concluded that the changes in σi or Pi for specific ions can have a differential effect on tubular transport since ion fluxes are the sum of both diffusive and convective components; the electrochemical gradient affects the former, and water flux and σi between which there is a kind of reciprocal relation affect the latter.

요관압 상승이 신혈류량 자동조절에 미치는 영향

김영준,민영기,양훈모 순천향의학연구소 1997 Journal of Soonchunhyang Medical Science Vol.3 No.1

To investigate the effect of acute elevation of ureteral pressure (UP) on autoregulation of renal blood flow(RBF), RBF autoregulation curves were determined in 6 anesthetized dogs equipped with electromagnetic flow probes around the renal artery, at UP occuring during spontaneous urine flow and UP of 40 cmH₂O. The desired UP was achieved by vertically elevating the water-filled syringe connected to a ureteral catheter to 40 cm above the kidney level. In response to the elevation of UP to 40 cmH₂O, RBF increased from 182±11 to 204±11 mL/min, and MAP didn't change significantly by the maneuver (114±6 vs 116±6 mmHg). While the autoregulation of RBF was well observed until the renal artery pressure(RAP) was lowered to 60±3 mmHg at spontaneous urine flow, at the elevated ureteral pressure RBF began to decrease with RAP as RAP decreasd below 72±2 mmHg. Elevated RBF at normal RAP associated with earlier loss of autoregulatory capacity during UP elevation suggests that tubuloglomerular feedback mechanism is involved in the renal response to increased UP.

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.

엔지오텐신이 Norepinephrine의 신혈관 반응에 미치는 영향

이석호,김종규,양훈모,민영기,임한혁 순천향의학연구소 1999 Journal of Soonchunhyang Medical Science Vol.5 No.2

To determine the effect of angiotensin Ⅱ(ANG Ⅱ)-induced hypertension on the renal hemodynamic response of norepinephrine(NE), mongrel dog instrumented for checking of renal blood flow(RBF) was followed as the step increases every 2 minutes in the rate of norepinephrine infusion into the renal artery during 5 conditions (C : control, C+PD : control+pressure decompression of aorta, ACEI : angiotensin converting enzyme inhibitor, ACEI+ANG Ⅱ : angiotensin converting enzyme inhibitor+ANG Ⅱ, ACEI+ANG Ⅱ+PD : angiotensin converting enzyme inhibitor+ANG Ⅱ+pressure decompression of aorta) Without relation of increase (C, C+PD) or decrease (ACEI+ANG Ⅱ, ACEI+ANG Ⅱ+PD) of the plasma ANG Ⅱ level when NE is infused into vessel, there were no differences in RBF response to NE infusion between C and C+PD and between ACEI+ANG Ⅱ and ACEI+ANG Ⅱ+PD, which implies that renal arterial pressure(RAP) does not play an important role in controling the renal hemodynamic response to NE. When renin angiotensin system was blocked by captopril without adding to ANG Ⅱ supply (ACEI), RBF can be severe decreased to approximately 90% at much lower rates of NE infusion than occurred when the sufficient concentration of ANG Ⅱ were present in the plasma. As the increased sensitivity of NE did not occur at lower renal arterial pressure, when ANGⅡ was present in the plasma in sufficient concentrations, it seems that protective effect on renal function is possible by ANGⅡ during renal sympathetic stimulation.

흰쥐 중격핵의 아미노산 함량에 대한 해마 제거의 영향

한영길,김종규,양훈모 순천향의학연구소 1995 Journal of Soonchunhyang Medical Science Vol.1 No.2

A study was planned to analyze amino acid in target structure -the septal mucleus-of hippocampectomized rats by high-performance liquid chromatograph (HPLC). 33 female rats were divided into 3 groups, of which 8 rats had their hippocampal tissue on both sides removed through an opening in the parieto-occipital cortex (hippocampal group), 7 rats received damage to the parieto-occipital cortex only (cortical control group), and 8 rats serveed as normal control animals. One week later, the animals were sacrificed by decapitationin the cold room. Two to three mg of tissue was obtained from the septal nucleus in one side of the brain. The tissue three mg of tissue was obtained from the septal nucleus in one side of the brain. The tissue samples were homogenized in 200 of 0.5M perchloric acid in 1mM EDTA with ground-glass homogenizers. After centrifugation at 3.500 rpm for 15 min, an aliquot of 80 supernatant was neutralized with 40㎕ of 2.0M KHCO and then centrifuged again at 3,500 rpm for 10min. An aliquot of 20㎕ was taken and diluted with 350㎕ β-mercaptopropionic acid in 10 ml of 100 mM sodium borate buffer (Ph 9.1) and 350㎕ of OPA solved in ethanol which was diluted with 10ml of 100 mM sodium borate buffer (Ph 9.1) Then 400㎕ of the resulting sample was injected auto injector. Peak areas were automatically integrated and calculated by chromatopac. In the septal nucleus, aspartate increased a little in the hippocampla group and the cortical control group than in the normal control group . while there were no significant difference between the 3 groups. Glutamate decreased significantly in the hippocampla group than in the normal control group (P<0.001) and the cortical control group (P<0.005), while there were no significant difference between the 2 control groups. In the serine, glycine, threonine and alanine, the differences among 3 group values were nonsignificant. It is inferred from the above mentioned results that excitatory transmitter substances employ the glutamate in the septal nucleus, and that the hippocampus was facilitatory to the septal nucleus.

세포질 Na+에 의한 Na+ channel 억제작용이 원위세뇨관 상피세포 재흡수에 미치는 영향 : Mathematical Approach

민영기,김영준,양훈모 순천향의학연구소 2001 Journal of Soonchunhyang Medical Science Vol.7 No.2

1. The epithelial cells of frog skin and the early distal tulule were modeled to test the Na^(+) concentration dependence of Na^(+) permeability. Model variables include concentrations of Na^(+), K^(+), Cl^(-), cellular impermeants. The model equations specify mass conservation, electroneutrality constraints and Goldman constant field equation. 2. Phenomenological expressions described the relations between luminal Na^(+) or cellular Na^(+) and apical Na^(+) permeability. In response to an increase in luminal concentration, the initial rise of short-circuit curreni Isc simulated by this model was very steep and formed a spike as Isc began to decline. This is contrasted by the experimental result by Huchs et al.: Isc increased relatively slowly, and the peak appeared blunted. This behavior could be simulated by including hysteresis phenomenon that is likely to be induced by the saturation of Na^(+) channel. 3. When both Na^(+) dependency of channel and hysteresis were included in the simulation, time course of Isc to step changes in luminal Na^(+) was similar to that obtained from the real experiment. 4. When the unstirred layer effect was included in this model instead of hyteresis, the time course of Isc to step change in luminal Na^(+) could also be simulated. 5. Conclusion : The delayed rise of Isc instantaneouly after switching to luminal solution with high Na^(+) was the result of the transient but strong inhibition of apical Na^(+) permeability. The delayed inhibition observed after the initial inhibition had almost disappeared appears to result from another mechanism and was simulated close to the actual curve with the regulatory formula based on cell Na^(+) concentration.

신혈역학적 상황에 따른 수출소동맥 저항의 사구체여과율에 미치는 영향

민영기,김태웅,양훈모 순천향의학연구소 2001 Journal of Soonchunhyang Medical Science Vol.7 No.2

It is generally known that efferent arteriolar constriction increases GFR. However, it has been shown in methemadical studies that increases in efferent arteriolar resistance beyond some extent causes GFR to decrease. The aim of the present study was to investigate the possibility that the deterioration of GFR by efferent constriction occurs in physiological and/or pathophysiological conditions. The renal hemodynamic data obtained by several investigators were analyzed with a mathematical model of single nephron GFR (SNGFR). The data analyzed are from rats which has been shown to achieve filtration pressure equilibrium (FPE) during filtration along the glomerular capillary. The glomerular model is based on a simulation of flow along a glomerular capillary with negligible resistance and uniform ulitrafiltration coefficient (Kf, 0.09 nl·sec-1·mmHg-1). The hemodynamic states of rat kidney is characterized by a high Kf and 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 by the increase in Kf. Analysis with the present model has shown that lowered efferent arteriolar resistance during angiotensin inhibition augmented GFR response to Kf. The analysis of the data obtained by manipulating efferent resistance during aortic constriction demonstrated the important of pregiomerular resistance(RPRE) relative to efferent resistance(RE). in this hemodynamic condition. The FPE which determines the sensitivity of SNGER to SNBF and Kf is attained nearer the afferent end as RPRE increases further: On the other hand, RPRE had no effect on FPE. In conclusion, certain physiological manipulation affects RPRE and Kf in such fashion that a decrease in RE 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 kidney which has low flow and high afferent resistance the efferent arteriolar dilation can be associated with the promotion of GFR.