Fabrication and High-Temperature Compressive Behavior of Unique Multi-Sheet Stacked Block Ni–Cr–Al Metallic Foam

Kyu‑Sik Kim,Tae‑Hoon Kang,박만호,Kee‑Ahn Lee 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5

Large unique block Ni–Cr–Al superalloy foam was fabricated using a combination method of powder-alloying, multi-sheetstacking, and hot compression processes. Subsequently, the compressive properties and deformation behaviors of multi-sheetstacked block metallic foam were investigated from room temperature to 1073 K. The analysis of the resulting structuralcharacteristics of the block foam showed that the interfaces between the sheets have complex strut interactions, such ascontacted (deformed) and intersected struts. The relative density was measured as 2.93% for sheet foam and 4.90% for blockfoam. The compressive deformation of sheet and block Ni–Cr–Al foams showed the typical compressive stress–strain curvesof plastically deformable metallic foams regardless of foam type. However, different deformation behaviors in the plateauregions were detected based on the type of foam. It is noteworthy that the yield strength of block foam showed a relativelylower value than that of sheet foam, even though the block foam had higher relative density. The existence of unique interfacesin the multi-sheet stacked block foam may have affected strength and plastic deformation. Finally, distinct compressivebehaviors related to the structural and microstructural characteristics of block Ni–Cr–Al foam are discussed.

쿠싱증후군 환자에서 당 대사 이상 정도에 따른 인슐린 감수성과 인슐린 저항성의 변화

정인경,김성훈,정재훈,민용기,이명식,이문규,유형준,안규정,노정현,김동준,김광원 대한내분비학회 2003 Endocrinology and metabolism Vol.18 No.4

연구배경 당질 코르티코이드는 당 대사에 매우 중요한 호르몬으로 내인성 당질 코르티코이드 과다상태인 쿠싱증후군에서는 말초조직에서 인슐린 저항이 증가하고 이를 보상하고자 인슐린 분비의 증가로 고인슐린혈증이 동반된다고 보고되고 있다. 하지만 생체 내에서와 달리 시험관내에서는 췌도세포에 당질 코르티코이드를 장시간 처리하면, 인슐린 분비 및 생합성이직접적으로 억제됨이 확인된 바 있어 쿠싱증후군 환자에서 당뇨병의 원인으로는 아마도 말초조직에서 증가된 인슐린 저항성 뿐 아니라 이를 충분히 보상하지 못하는 췌장에서의 인슐린 분비 저하가 같이 동반되어있지 않을까 하는 가설을 세우게 되었고, 아직까지 당질코르티코이드가 당대사 이상을 일으키는 기전에 대해 쿠싱증후군을 당대사 정도에 따라 인슐린 감수성과 분비능을 분석한 연구는 없었기에 이를 알아보고자 하였다. 방법: 삼성서울병원에서 쿠싱증후군으로 진단 받은 환자 15명을 대상으로 하였다. 이에 대한 대조군으로는 쿠싱증후군 환자와 같은 성별 그리고 체질량지수를 갖은 15명의 건강한 성인을 대상으로 비교 하였다 쿠싱증후군 환자를 대상으로 경구당부하 검사를 통해 당대사 정도를 정상군, 내당능장애군, 그리고 당뇨병군으로 나눈 후 정맥 당부하 검사를 시행하여 각군의 인슐린 저항성과 인슐린 분비능의 지표를 비교하고, 수술 후 쿠싱증후군이 완치된 상태에서 수술 전후의 당대사 지표의 변화를 조사하였다. 결과: 1) 쿠싱증후군 환자 중 정상인은 20%, 내당능 장애는 27%, 그리고 당뇨병은 53%였다. 체질량지수, 나이, 그리고 발병 기간은 세 군간에 의미 있는 차이가 없었으나, 24시간 소변검사의 코르티솔 농도는 당뇨병군에서 의미있게 높았다. 2) 정맥당부하 검사 결과, 인슐린 감수성 지표인 Sl는쿠싱증추린」서 1.58±0.10[×10^(-4)(min^(-1)(μU/mL)^(-1)]로 정상 대조군의 3.37±0.49[×10^(-4)(min^(-1)(μU/mL)^(-1)]에 비해 의미있게 낮았으나(P=0.024), 쿠싱증후군 환자 중 NGT, IGT, DM 군간에 서로 통계적인 차이는 없었다. 3) SG는 정상 대조군과 쿠싱증후군 환자간에는 의미있는 차이가 없었고, 쿠싱 증후군에 있어서 당대사가 악화될수록 감소하는 경향을 보였으나 의미있는 차이는 없었다. 4) 인슐린 분비능의 지표인 AIRg는 정상인에 비해 전체 쿠싱증후군 환자의 경우 증가하는 경향을 보였으나 의미있는 차이는 없었다. 하지만 쿠싱증후군 환자중에서 당대사 상태에 따라 NGT군은 1299 (1297∼1310)(mu/g/min ×10^(-2))로 정상 대조군(368.9±98.6[mu/g/min ×10^(-2)]) 보다도 의미있게 높았고, DM군{202.2 (91.1~371.4) [mu/g/min ×10^(-2)}은 NGT군에 비해 의미있게 낮았다(P=0.0031). 5) 15명중 현재 완치 상태에 있는 6명에 대해 수술전과 후로 비교하였다. 수술 전 당대사 상태가 1명은정상, 1명은 내당능 장애, 그리고 4명은 당뇨병이었으나 수술 후 시행한 경구 당부하 검사상 모두 정상 당대사 상태를 보였다. 6) 수술 후 완치된 환자 6명에 있어 인슐린 감수성지표인 Sl는 수술전에 중앙값이 1.22[×10^(-4)(min^(-1)(μU/mL)^(-1)]로 대조군에 비해 의미있게 감고』어 있었으나(p.0.05), 수술후 10.95 [×10^(-4)(min^(-1)(μU/mL)^(-1)]로 정상 수준으로 회복되었고(P=0.0022), 인슐린 분비능을 나타내는 AIRg [mu/g/min ×10^(-2)] 값도 정상수준으로 회복되었다. 특히 인슐린 분비능의 회복양상은 혈당농도에 따라 판이하게 나타나서, 정상과 내당능장애 상태에 있던 2명은 수술전에 1201 [mu/g/min ×10^(-2)]로 증가되어 있던 AIRg 값이 수술 후 정상 수준으로 감소하였고, 수술 전에 당뇨병 상태에 있던 4명의 경우 245.9 [mu/g/min ×10^(-2)]로 인슐린 분비능이 감고il어 있었는데 이들은 수술 후 모두 정상 수준으로 증가되었다 (P=0.0286). 결론: 쿠싱증후군 환자에서 당대사 이상은 80%로 높은 유병률을 보였다. 모든 쿠싱증후군환자에서 인슐린 감수성은 정상인에 비해 저하되어 있어 말초조직의 인슐린 저항이 선행됨을 시사하며, 인슐린 분비능은 당대사의 정도에 따라 다르게 나타났는데, 정상 당대사군에서는 인슐린의 저항성을 극복할 만큼 정상 대조군보다 더 많은 양의 인슐린 분비를 하다가 고코르티솔혈증이 심할수록 인슐린 분비능의 감소로 당뇨병으로 진행됨을 확인할 수 있었고, 이런 인슐린 저항성과 인슐린 분비장애는 수술 후 다시 회복되는 가역적인변화를 보였다. Background: Glucocorticoid plays an important role in the control of carbohydrate metabolism. Patients with Cushing's syndrome have been reported to have an increased incidence of carbohydrate intolerance due to peripheral insulin resistance and hyperinsulinemia, although the exact incidence and nature of this disorder have remained unclear. Few results have been published about insulin resistance and insulin secretion according to the level of glucose concentration, or about the reversibility of such defects in patients with Cushing's syndrome. Methods: To assess the effect of glucocorticoid on the insulin sensitivity and insulin secretion in Cushing's syndrome, 15 patients with Cushing's syndrome were classified into 3 groups (normal glucose tolerance: NGT, impaired glucose tolerance: IGT, diabetes: DM) according to the degree of glucose tolerance based on the oral glucose tolerance test (OGTT). Insulin modified, frequently sampled, intravenous glucose tolerance test (FSIGT) was performed before and after curative surgery on these patients and on 15 healthy control subjects. Data were evaluated by non-parametric statistical analysis. Results: 1) Among the 15 patients with Cushing's syndrome, 3 (20%) were NGT, 4 (27%) IGT, and 8 (53%) DM, based on OGTT. Twenty-four hour urinary free cortisol (UFC) was significantly higher in the DM group. 2) Insulin sensitivity index (SI) of Cushing's syndrome was significantly lower than that of the control group p=0.0024), but was not significantly different among the three Cushing's syndrome groups of NGT, IGT and DM. 3) Glucose mediated glucose disposal (SG) (Ed- confirm this abbreviation; it does not seem to match the definition) of Cushing's syndrome was not significantly different from that of the control group. 4) Insulin secretion (AIRg) of Cushing's syndrome tended to be high, but it was not significantly different from that of control. However, according to the level of glucose concentration there was significant difference in AlRg among the three Cushing's syndrome groups p=0.0031); AIRg of DM was significantly lower than that of NGT. 5) After surgical treatment, parameters of insulin sensitivity and insulin secretion were normalized in 6 cured patients; 1 with NGT, 1 with IGT, and 4 with DM, preoperatively. Median SI of all 6 patients was significantly improved up to the normal range postoperatively p=0.0022). Median AIRg of these 6 patients was balanced around that of normal control postoperatively p=0.0286). Conclusion: Eighty percent of patients with Cushing's syndrome had abnormality of carbohydrate metabolism. Insulin sensitivity was significantly decreased in Cushing's syndrome. Insulin secretion was significantly higher only in the NGT and IGT groups of Cushing's syndrome. As the hypercortisolemia is exacerbated, insulin secretion is significantly decreased and causes DM, suggesting that glucocorticoid has a direct or indirect toxic effect on the pancreatic beta cell (J Kor SOC Endocrinol 18:392-403, 2003).

선천성 수근관 증후군 1례 보고

이규훈,황치문,김민석,김희상,안경회 大韓再活醫學會 1998 Annals of Rehabilitation Medicine Vol.22 No.3

혈행화된 두개골 피판을 이용한 안와저 및 안와하연의 재건술 치험례

정윤규,이훈범,김석원,봉정표,김균태,김주봉 大韓成形外科學會 1998 Archives of Plastic Surgery Vol.25 No.5

A number of methods have been introduced for support the orbital floor following a maxillectomy without orbital exenteration or severe facial trauma. These methods including skin graft and muscular sling provided the unsatisfactory results, like as diplopia, orbital ptosis, enophthalmos and severe facial deformity. Therefore the bone and soft tissue reconstructions using microvascular free flaps were performed recently by many surgeons, but long time operation, donor site morbidity, postoperative large scar, and ptosis of the flap were pointed out as disadvantages of free flap reconstruction. Vascularized calvarial bone flap, a modified method of free calvarial bone graft, was adequate for reconstruction of the orbital floor and the infraorbital rim as a horizontal buttress, especially in case of poor vascular bed and postradiated state. The authors introduced the vascularized calvarial bone flap for the orbital floor and the infraorbital rim reconstruction in 3 cases of maxillectomy, and could be obtained satisfactory results aesthetically and functionally.

강모단 하방에 용수철이 부착된 칫솔의 치태 제거 효과에 관한 임상적 연구

조성훈,양규호,오종석 전남대학교 치과대학 2000 전남치대논문집 Vol.12 No.1

Oral examinations were conducted before the experiment started. The students were given common toothbrushes (control group) or spring-attached toothbrushes (experimental group) and instructed to brush their teeth by scrubbing method. Measurement of plaque index and count of salivary bacteria were done at 0, 1, 3, and 5 weeks. 1. Mean plaque index was significantly reduced at week 1 compared with at week 0 in both groups. (P<0.05) 2. Mean plaque index was significantly reduced at week 3 compared with at week 1 in the experimental group. (P<0.05) 3. Mean plaque index was significantly reduced at week 5 compared with at week 3 in the experimental group. (P<0.05) 4. There were no significant differences of mean plaque index among week 1, week 3, and week 5 in control group. (P>0.05) 5. The number of salivary bacteria was slightly reduced during the experiment, however there was no statistical significance. (P>0.05) To reduce the plaque effectively, the use of spring-attached toothbrush should be recommended, and adequeate instruction for children is needed.

조직이 불균질화된 Al₂O₃-Zr₂O 복합체의 열-기계적 성질

김의훈,황규홍 국립경상대학교 공과대학 부설 첨단소재연구소 1991 尖端素材 Vol.1 No.-

The thermo-mechanical properties of Al₂O₃-ZrO₂ ceramics having dual microstructure were studied. The Al₂O₃-ZrO₂composites having dual microstructure were fabricated by dry mixing the sieve-granulated Al₂O₃vol.% (t)ZrO₂ granule and 15 to 30 vol.% Al₂O₃-20 vol.% (m) ZrO₂granule, followed by isostatic pressing and sintering at 1600℃ for 1 hr. So Al₂O₃-20 vol.% (t)ZrO₂part was become to matrix region and Al₂O₃-20 vol.% (m)ZrO₂part was become to dispersed region as irregular sieve-shaked granule shape. When weak granule was used for dispersed region, initial strength was slightly decreased than the matrix composite, but retained strength after thermal shock was increased. And if weak granule have been used for dispersed region smaller than that for matrix region, critical temperature and strength was slightly increased due to the different existing shape of dispersed region in the duplex composites. But strong granule made by high temperature calicination was used for dispersed region, thermal shock behavior showed stable crack growth because the dispersed region had lower density than matrix.

ATM망에서 Fair Queueing 알고리즘에 관한 연구

문규춘,김훈,한상엽,박광채 조선대학교 에너지.자원신기술연구소 1999 에너지·자원신기술연구소 논문지 Vol.21 No.2

B-ISDN using ATM should provide QoS of various service and also fair control for each source. In this paper, we suggested the Virtual-Time-based Round Robin(VTRR), fair scheduling algorithm guaranteeing demanded QoS. We searched the characteristic and required points possessing proper fair scheduling algorithm in high speed network. And we analyzed the performance character and simulation. The result is that VTRR is much simpler in algorithm and is better than WFQ or GPS in performance.

朝鮮時代 鄕校建築의 樣式에 關한 硏究 : 忠南地方 鄕校의 大成殿을 中心으로

李達勳,金賢錫,姜圭敏 대전대학교 산업기술연구소 1999 산업기술연구소 論文集 Vol.10 No.1

This paper, studying about Taesongjeon (the great shrine) which is in 11 Hyang-kyo (local school annexed to the confucian shrine) Architecture in Chung Nam local province, understands the meaning of 'Taesongjeon' from inspecting the specific regional feature of its construction type by analyzing various peculiarities and proposes the preservation of Hyang-gyo Architecture. The results of this paper are as following : 1) Generally, the placement types of Hyang-gyo Architecture in Chung Nam local province is 'School in the front and shrine in the back' 2) The shape of Taesongjeon plane has a open plane figure to worship and can be divided into 3 kans in front and 3 kans on sides. 3) The type of Gong-po of Taesongjeon is Mu-Chul-Mok Yi-Ikkong system and the form of the frame has been built with a higher pillar type.

감염 조절용 차단막의 두께가 광중합기의 중합광에 미치는 영향

장훈상,이석련,홍성옥,류현욱,송창규,민경산 大韓齒科保存學會 2010 Restorative Dentistry & Endodontics Vol.35 No.5

연구목적: 본 연구는 감염 조절용 차단막을 여러 겹으로 사용했을 때 광중합기의 광강도와 파장, light diffusion 등에 미치는 영향에 대해 조사하였다. 연구 재료 및 방법: 감염 조절용 차단막은 투명 랩 (크린랩)을 사용하였고 광중합기는 할로겐 광중합기 (Optilux 360)와 LED 광중합기 (Elipar FreeLight 2)를 사용하였다. 차단막을 1겹, 2겹, 4겹, 8겹으로 광중합기의 광섬유말단을 감싸고 휴대용 광강도 측정기 (Cure Rite)로 광중합기의 광강도를 측정하였다. 광중합기를 주문제작한 optical breadboard에 고정시킨 후 휴대용 spectroradiometer (CS-1000)를 이용하여 광중합기의 파장을 측정하였고, DSLR (Nikon D70s)을 이용하여 광중합기의 light diffusion을 사진 촬영하였다. 결과: 광강도 측정 결과는 차단막의 두께가 증가할수록 광강도가 유의하게 감소하였으나 할로겐 광중합기에서 1겹과 2겹 사이에는 유의차가 없었으며, 4겹 이상의 차단막을 투과할 때 광강도가 더 많이 감소하였다. 여러 겹의 차단막을 투과한 광중합기의 전체적인 파장 형태와 peak wavelength의 변화는 관찰되지 않았다. Light diffusion 사진 촬영 시, LED 광중합기에서는 차단막의 두께가 미치는 영향이 없었으나 할로겐 광중합기에서는 차단막을 4겹 사용했을 때부터 중합광이 조사되는 각도가 감소하기 시작하여 8겹 사용했을 때 통계적으로 유의하게 감소하는 것을 볼 수 있었다 (p < 0.05). 결론: 광중합형 복합레진을 광중합할 경우 감염 조절용 차단막이 찢어지는 경우를 대비하여 1겹으로 사용하기 보다는 2겹으로 사용하는 것이 환자간의 교차감염을 예방하는데 유리할 것으로 사료된다. Objectives: This study investigated the effect of infection control barrier thickness on power density, wavelength, and light diffusion of light curing units. Materials and Methods: Infection control barrier (Cleanwrap) in one-fold, two-fold, four-fold, and eightfold, and a halogen light curing unit (Optilux 360) and a light emitting diode (LED) light curing unit (Elipar FreeLight 2) were used in this study. Power density of light curing units with infection control barriers covering the fiberoptic bundle was measured with a hand held dental radiometer (Cure Rite). Wavelength of light curing units fixed on a custom made optical breadboard was measured with a portable spectroradiometer (CS-1000). Light diffusion of light curing units was photographed with DSLR (Nikon D70s) as above. Results: Power density decreased significantly as the layer thickness of the infection control barrier increased, except the one-fold and two-fold in halogen light curing unit. Especially, when the barrier was four-fold and more in the halogen light curing unit, the decrease of power density was more prominent. The wavelength of light curing units was not affected by the barriers and almost no change was detected in the peak wavelength. Light diffusion of LED light curing unit was not affected by barriers, however, halogen light curing unit showed decrease in light diffusion angle when the barrier was four-fold and statistically different decrease when the barrier was eight-fold (p < 0.05). Conclusions: It could be assumed that the infection control barriers should be used as two-fold rather than one-fold to prevent tearing of the barriers and subsequent cross contamination between the patients.

有機絶緣物과 半導電性돌기 사이의 트리 現象에 關한 硏究

蔡奎炘,金東弼 全北大學校 1989 論文集 Vol.31 No.-

여러가지 트리 발생 모델중에서 導電性 돌기를 모의하는 것으로는 일반적으로 금속 針電極을 사용하지만 실제 CV 케이블 등의 半導電性 돌기에서 발생하는 劣化現象에 대한 규명은 불명확하다. 本論文에서는 半導電性 돌기를 모의하기 위해 半導電性複合體로 만든 SCC針電極을 제작하여 트리의 발생과 진전에 대하여 검토하였다. 이 실험에서 트리의 진전은 放電電流의 급증시간 T_i에 따르며 T_i는 印加電壓의 영향이 크다는 것을 알았으며 半導電性 돌기에서 발생한 트리는 導電性 돌기에서 발생한 것보다 진전이 느리다. 또한 有害한 半導電性 돌기의 曲率半經은 약 10um 이하로 나타난다. Among sevral tree generation models, in making simulation conductive protrusion, metal needle electrode is generally used, but it is not clear a searching examination about deterioration phenomenon which apperars in the semiconductive protrusion of CV cable etc. In this paper, it is examined generation and growth of tree turning out SCC needle electrode made of semiconductive compound in order to make simulation the semiconductive protrusion. In this experiment, it is known that growth of tree is in proportion to interrup time Ti of discharge current and test voltage affects Ti very much, growth of tree appeared in semiconductive protrusion is more slow than that generated in conductivity protrusion. Moreover, the tip radius of noxious semiconductive protrusion shows approximately under 10um.