Microstructures and Mechanical Properties of Multiphase‑Reinforced In Situ Aluminum Matrix Composites

Ju‑Hye Kim,Jae‑Gil Jung,Eun‑Ji Baek,최윤석,Kwangjun Euh 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.2

We investigated the microstructures and mechanical properties of multiphase-reinforced in situ aluminum matrix composites(AMCs) prepared with various combinations and contents of Li, Mg, Si, Cu, Zn, Sn, and Ni. The area fractions of thesecondary phases in the as-cast AMCs ranged from 26% to 58%, and the types of secondary phases depended on the alloychemical compositions. The type and amount of secondary phases were more important than matrix strengthening in determiningthe alloy mechanical properties. Composite hardness and compressive stress increased while fracture strain decreasedwith increasing total area fraction of the secondary phases up to 40%. The formation of coarse primary and soft/heavySn-containing phases significantly deteriorated the alloy mechanical properties. Annealing also influenced the mechanicalproperties of the AMCs by changing the microstructures of the secondary phases and Al matrices.

야생 설치류의 한타바이러스 감염에 대한 연구

백락주,송진원,송기준,박광숙,최영주,강주일,이용주 대한감염학회 1997 감염 Vol.29 No.6

목적:국내 야서중에 한타바이러스의 숙주는 등줄쥐와 집쥐로 알려져 있으나, 한국에 서식하고 있는 다양한 야생 설치류를 채집하여 한타바이러스에 대한 항체검사를 실시하여 새로운 혈청형의 한타바이러스가 있는지를 혈청학적으로 규명하고자 하였다. 방법:국내에 서식하고 있는 야생 설치류를 1995년 10월부터 1996년 10월까지 7종 551수의 야시와 4종 97수의 소형동물을 채집하여 한타바이러스에 대한 항체검사를 간접형광항체법으로 실시하였다. 결과: 1) 야서 7종 551수와 소형동물 4종 97수를 대상으로 한탄바이러스의 감염율은 등줄쥐 17.2%(29/162), 흰넓적다리붉은쥐 8.7%(2/23), 대륙밭쥐는 25%(2/8), 그리고 땃쥐는 7.1%(1/14)이었다. 그리고 야생토끼는 8.8%(7/80)가 서울바이러스에 대한 항체를 가지고 있었다. 등줄쥐의 양성혈청중 대부분은 서울바이러스와 일부는 푸말라바이러스, 프로스펙트힐바이러스, 뉴욕바이러스와도 교차반응이 있었다. 흰넓적다리붉은쥐 2수와 대륙밭쥐 2수는 5가지 한타바이러스 모두에 교차 반응이 있었다. 2) 다람쥐는 9.5%(28/283)가 채집지역에 관계없이 한탄바이러스에 대한 항체를 가지고 있었고 항체기는 1:16 내지 1:256으로 비교적 낮았으며 서울바이러스, 푸말라바이러스, 프로스켁트힐바이러스와 뉴욕바이러스에 각각 반응하는 것도 일부는 교차반응을 보이는것도 있다. 청설모는 10.3%(7/68)가 한탄바이서르에 대한 항체를 가지고 있었으며 항체가는 1:16 내지 1:1,024이었으며 일부는 교차반응이 있었다. 3) 야생토끼의 서울바이러스에대한 항체양성율은 8.8%(7/80)이었으며 이중에 2수는 한탄바이러스와 교차반응이 있었고, 푸말라바이러스, 프로스켁트힐바이러스, 뉴욕바이러스와는 교차반응이 없었다. 항체가는 1:16 내지 1:64로 비교적 낮았다. 결론:등줄쥐는 한탄바이러스에 의한 감염이지만 흰넓적다리붉은쥐, 대륙밭쥐, 다람쥐 그리고 청설모의 일부는 한탄바이러스가 보다 다른 한타바이러스에 대한 항체가가 높았고 특히 일부 다람쥐 혈청은 푸말라바이러스 혹은 프로스켁트힐바이러스에만 반응하였다. 그리고 야생토끼는 서울바이러스에 대한 감염율이 높은 것으로 보아 국내에 한탄바이러스와 서울 바이러스 이외에 새로운 혈청형의 한타바이러스가 있는 것을 사료된다. Background: Hantavirus are widley distributed in rodents populations even in geographical areas where hemorrhagic fever with renal syndrome(HFRS) has not been reported. Multiple species of Murid and Arvicolid rodents serve as the natural reserviors of hantaviruses. Serologic diagnosis using hantaviral antigens indicates that hantaviruses are widley distibuted in wild rodents. This study were designed to find the distribution of hantaviruses among wild rodents and small mammals in Korea, 1995-1996. Methods: Rodents were trapped alive in selected areas. A total of 551 wild rodents from 7 species and 97 small mammals from 4 species were captured in Korea. Serologic evidence for hantavirus infection were tested using five hantavirus antigens by indirect immunofluorescent antibody technique(IFA). Among 162 Apodemus agrarius, 23 Apodemus peninsulae, 8 Clethrionomys regulus, 6 Microtus fortis, 1 Mus musculus, 283 Tamias sibiricus, 68 Sciurus vulgaris, 14 Crocidura laciura, 80 Lepus sinensis, 2 Capereolus capereolus and 1 Nyctereutes procyonoides. Results: 29 A. agrarius, 2 A. peninsulae, 1 C. laciura, 2 C. regulus, 27 T. sibiricus and 7 S. vulgaris were sero positive agaist hantaan virus and 7 L. sinensis were IF antibody positive against Seoul virus. Some of Tamias sibiricus were only seropositive against puumala virus or prospect hill virus. Conclusion: This data suggests that new serotypes of hantavirus might distribute among rodents in Korea.

이하선 종양에 관한 임상적 연구

백승,하주원,오희균,유선열,김원재 大韓顎顔面成形再建外科學會 2002 Maxillofacial Plastic Reconstructive Surgery Vol.24 No.5

This is clinical study on 113 patients who were treated for parotid tumors at Chonnam National University Hospital over a period of 5 years from January 1996 to December 2000. The results were as follows ; The mean ages were 42.6 years old (12∼73 years) for benign parotid tumor patients and 43.9 years old (2∼74 years) for malignant patients. The ratio of male to female was 1:2 in malignant parotid tumors, but there was no difference in benign tumors. There was no difference in mean mass size and duration of illness between benign and malignant tumor patients. The combined usage of fine needle aspiration biopsy and computed tomogram was common as the diagnostic methods of parotid tumor. The parotid tumors were commonly located in the superficial lobe (69%). The ratio of benign and malignant tumors was 4:1. The most common benign tumor was pleomorphic adenoma (72% of benign tumor), followed by Warthin's tumor and monomorphic adenoma. The most common malignant tumor was mucoepidermoid carcinoma (45% of malignant tumor), followed by adenoid cystic carnoma, carcinoma ex pleomorphic adenoma, and adenocarcinoma. The most common operations were superficial parotidectomy (72%) for benign parotid tumor and total parotidectomy (45%) for malignant tumor. The most common postoperative complication was temporary facial nerve weakness (82%), followed by Frey's syndrome (14%) and permanent facial palsy (4%). Postoperative radiation therapy was done in 12 patients (60%) and the mean radiation dose was 5550±620 cGy. Of 113 cases, tumor recurrence developed in 12 cases (10%). These results suggest that the successful management of parotid gland tumors needs adequate surgical treatment on the basis of knowledge of parotid gland anatomy and preoperative diagnosis.

광중합형 수복용 복합레진의 인장강도에 미치는 thermal cycling과 시효 처리의 영향

백상현,채민수,이주형,김태조,배태성 대한치과기재학회 1998 대한치과재료학회지 Vol.25 No.1

The improvement in the mechanical properties of restorative composites has contributed to their increased use in recent years. In spite of their growing popularity, composites still have low resistance to fracture and wear in oral environments. This study was performed to examine whether the tensile strengths of light-cured restorative composites were affected by thermal cycling and aging in water. Five commerically available light-activated composites(Heliomolar : HM, Aelitefil : AF, Amelogen : AG, Clearfil AP-X : CF, Z100 : ZH) were used. Rectangular tension test specimens were fabricated in a teflon mold giving 5 mm in gauge length and 2mm in thickness. All samples were divided into 3 groups. Group 1 was stored in a desiccator for 10 days. Group 2 was immersed in a 37℃ distilled water for 10 days. Group 3 was subjected to 10,000 thermal cycles between 5℃ and 55℃, and the immersion time in each bath was 15 seconds per cycle. Tensile testing was carried out at a crosshead speed of 0.5 mm/min and fracture surfaces were observed with scanning electron microscope. The results obtained were summarized as follows; 1. The strength data fit to single-mode Weibull distribution(r²> 0.86) and Weibull parameters decreased after thermal cycling test. 2. The highest characteristics strength was observed in the CF group but the highest Weibull modulus was obtained in the AF group after thermal cycling test. 3. The highest tensile strength value of 83.92 MPa was obtained in the CF group and the lowest value of 13.91 MPa was obtained in the AG group. Tensile strengths showed no significant difference between HM and AG groups but other groups showed the significant differences in each group(p<0.05). 4. According to the microscopic observation of the fracture surfaces, fractures of large fillers were observed in the hybrid composites of the AF and CF groups.

스퍼터링 조건에 따른 Co 박막의 증착속도 및 미세구조의 변화

백주열,박창만,최영근,이기암,황도근 단국대학교 신소재기술연구소 1992 신소재 Vol.2 No.-

DC 마그네트론 스퍼터링법으로 제조된 코발트 박막에 대해 증착속도 및 미세구조에 미치는 스퍼터링조건의 영향을 조사하였다. 증착속도는 투입전력이 커질수록 증가하였으며, 아르곤 압력이 커질수록 감소하였는데, 이는 투입전력의 증가로 인한 타게트 표면의 이온전류 밀도의 상승과 Ar 압력증가에 따른 비산효과의 증대로 인한 타게트 표면의 이온 전류 밀도의 감소로 고찰되었다. 투입전력이 커질수록 결정립의 크기가 감소하였으며, 투입 전력에 관계없이 특정한 면이 발달하지 않는 비정실 구조를 나타내었다. Ar 압력에 관계없이 비정질 구조를 나타내었다. We have investigated the influence of sputtering condition on deposition rate and microstructure of Co thin film produced by the method of DC Magnetron Sputtering. Deposition rate increased with the input power due to the rise in ionic current density on the surface of target, and decreased with the pressure of Ar gas due to the decrement of ionic current density by the effect of diffusion. Microstructure of the Co thin film became a finer structure with the increase in the input power, and showed amorphous irrespective of the charge of the input power and the pressure of Ar gas.

가토에서 Pentoxifylline, Asprin 및 Heparin이 피부피판의 생존 및 출혈 경향에 미치는 영향

하주원,백승,박홍주,오희균,유선열 大韓顎顔面成形再建外科學會 2002 Maxillofacial Plastic Reconstructive Surgery Vol.24 No.5

The skin flap, which has been frequently used in the maxillofacial soft tissue defects, can be failed due to insufficient blood supply to the flap. To increase its survival rate, antithrombotic agents has been used. The agents have, however, been restrictly used because of their side effects, such as bleeding tendency or hematoma formation on the operation site. The present study aimed to the effect of pentoxifylline, aspirin, and heparin on the skin flap survival rate and bleeding tendency. Twelve adult white rabbits, weighing about 2.0 ㎏, were used. Five random skin flaps, which is 1㎜ thickness, were prepared on the dorsal surface of each rabbit by using 1.5×7.5㎝ prefabricated template. The animals were divided into 4 groups on the basis of drugs used: Control group, animals in which no drug was given (n=3); Pentoxifylline group, animals in which pentoxifylline was given intraorally (n=3); Aspirin group, animals in which aspirin was given intravenously (n=3), and Heparin group, animals in which heparin was given intravenously (n=3). On the 3rd and 7th day after operation, prothrombin time (PT) and activated partial thromboplastin time (aPTT) were measured to evaluate the bleeding tendency. The animals were sacrificed on the 7th day and the mean skin falp survival rate of each group was measured. The results obtained were as follows : The skin flap survival rates of pentoxifylline (84.3±7.9%) and heparin (79.5±10.9%) groups were significantly increased, compared with control group (68.0±10.8%)(P<0.05). The survival rate of aspirin group (73.0±11.1%) was not increased. In bleeding tendency, the PT values were prolonged in heparin and aspirin groups at the 3rd day after operation (P<0.05), and prolonged in order of heparin group, aspirin group, and pentoxifylline group at the 7th day after operation. The aPPT values in heparin and aspirin groups were also prolonged at the 3rd day after operation (P<0.05), and prolonged in order of Aspirin group, Heparin group, and Pentoxifylline group at the 7th day after operation. These results suggest that pentoxifylline may be the most useful drug among three drugs to increase skin falp survival rate and less increase the bleeding tendency.

가토에서 Pentoxifylline, Aspirin 및 Heparin이 피부피판의 생존 및 출혈 경향에 미치는 영향

하주원,백승,박홍주,오희균,유선열 전남대학교 치의학연구소 2002 구강과학 Vol.14 No.2

The skin flap, which has been frequently used in the maxillofacial soft tissue defects, can be failed due to insufficient blood supply to the flap. To increase its survival rate, antithrombotic agents has been used. The agents have, however, been restrictly used because of their side effects, such as bleeding tendency or hematoma formation on the operation site. The present study aimed to the effect of pentoxifylline, aspirin, and heparin on the skin flap survival rate and bleeding tendency. Twelve adult white rabbits, weighing about 2.0 kg, were used. Five random skin flaps, which is 1mm thickness, were prepared on the dorsal surface of each rabbit by using 1.5 X 7.5 cm prefabricated template. The animals were divided into 4 groups on the basis of drugs used: Control group, animals in which no drug was given (n=3); Pentoxifylline group, animals in which pentoxifylline was given intraorally (n=3); Aspirin group, animals in which aspirin was given intravenously (n=3). On the 3rd and 7th day after operation, prothrombin time (PT) and activated partial thromboplastin time (aPTT) were measured to evaluate the bleeding tendency. The animals were sacrificed on the 7th day and the mean skin flap survival rate of each group was measured. The results obtained were as follows : 1. The skin flap survival rates of pentoxifylline (84.3±7.9%) and heparin (79.5±10.9%) groups were significantly increased, compared with control group (68.0±10.8%)(ㅔ<0.05). The survival rate of aspirin group (73.0±11.1%) was not increased. 2. In bleeding tendency, the PT values were prolonged in heparin and aspirin groups at the 3rd day after operation (p<0.05), and prolonged in order of heparin group, aspirin group, and pentoxifylline group at the 7th day after operation. The aPPT values in heparin and aspirin groups were also prolonged at the 3rd day after operation (p<0.05), and prolonged in order of Aspirin group. Heparin group, and Pentoxifylline group at the 7th day after operation. These results suggest that pentoxifylline may be the most useful drug among three drugs to increase skin flap survival rate and less increase the bleeding tendency.

한국근현대사에서 고구려와 발해에 관한 인식 : 역사교과서를 중심으로 Published in the Modern and Contemporary Periods of Korean History

신주백 한국역사연구회 2005 역사와 현실 Vol.- No.55

In this article, how the perceptions toward ancient dynasties such as Koguryo or Balhae have changed, in terms of historical mentioning included inside the official History textbooks published or released during the modern and contemporary time periods of the Korean history, are examined. And total of three distinctive time periods have been suggested by this researcher as essential eras, in terms of tracing such changes. The contents of most of the History textbooks that were published or released around the time when the country was being opened to the rest of the world for the first time, were influenced by the discussions of the 'Three Han entities being One(the Sam-Han Il-Tong-ron/三韓一統論 discussions), which were mainly based upon the idea of Shilla being the most prominent and legitimate entity of them all, as mentioned in the classic Korean history text 'Samguk Sagi/三國史記'. Within this frame of reference, dynasties like Koguryo and Baekjae were considered to be subordinate('附') states to Shilla. Historians who eventually overcame this kind of academic attitude were Shin Chae Ho and Park Eun Shik. These two considered Balhae and Shilla as two dynasties which have co-existed at the time, and refused to accept the concept of the so-called 'Unified Shilla'. They also tried to elicit a line of legitimacy for the Korean Ancient history from a specific succession line which was theorized by them to have started with the Dangun Kingdom, then continued to Buyeo and Koguryo, and finally ended with Balhae. The Joseon Governor General office, responding to such historical perspectives and also to thwart them overall, attempted to document the ancient history of events that happened on the Korean peninsula within the context of the Japanese ancient history, and also deliberately based their historical perspective upon favorably embracing Shilla's alleged unification of the peninsula. And after that, when Japan invaded the Manchu region in 1931 and later also the Chinese mainland in 1937, they decided to highlight the history of Koguryo and Balhae, and also the alleged fact that those two dynasties maintained a submissive position to Japan for a long time. After 1945, there have been attempts to review the history of Shilla and Balhae without any kind of discrimination, yet ancient Korean history based upon Shilla-based perspectives soon resurfaced and again became a dominant perspective throughout the country. It should also be noted that the political intrigues and shifts which continued inside both the South and North Korean governments during the 1960s forced the overall school education to harbor a primary objective emphasizing the importance of historical perspective based upon the concept of independent actions and thinking. Coming into the year 2000, an attempt to review Shilla and Balhae indiscriminately, and also to refer to the era as the 'South and North dynasties period', appeared in the official textbooks for the first time, but the actual contents of those sections in textbooks still remained practically unchanged from mainly being defined by the 'Unified Shilla dynasty'mentality, thus resulting in a compromised state of the relevant mentions in textbooks.

정신분열증환자의 혈장 Homovanillic Acid 농도와 치료반응과의 관계

조주연,기백석,박두병 大韓神經精神醫學會 1996 신경정신의학 Vol.35 No.3

In order to see whether the plasma homovanillic acid(HVA) levels can be adopted as a predictive biological marker reflecting therapeutic response of haloperidol, the authors measured HVA levels in 10 shchizophrenic patient and analyzed their relationship to therapeutic response. The measurement of plasma HVA level were carried out with high performance liquid chromatography(HPLC) before and after 7, 28days of treatment and the therapeutic response were assessed with Brief Psychiatric Rating Scale(BPRS) before and after 28days of treatment. The results of this study were as follows. 1) Plasma HVA levels after 7 days of treatment were significantly increased as compared to baseline plasma HVA levels and plasma HVA levels after 28 days of treatment were significantly decreased compared to levels after 7 days of treatment. 2) Significant correlation was found between baseline plasma HVA levels and clinical improvement after 28 days of treatment. 3) There was significant correlation between increase in plasma HVA level after 7 days and clinical improvement after 28 days of treatment. But there was no significant correlations between decrement in plasma HVA level from 7 days to 28 days and clinical improvement after 28 days of treatment. Hence theses observations have led us to propose that the early changes in plasma HVA levels are predictive of eventual treatment response.

구개부에 발생한 다형선종의 처치

하주원,백승,송종운,박충열,이용욱,박홍주,오희균,유선열,김옥준 大韓顎顔面成形再建外科學會 2001 Maxillofacial Plastic Reconstructive Surgery Vol.23 No.6

Pleomorphic adenoma of the palate is the most common of all intraoral salivary tumors. It can occur at any age but it presents most commonly in the 40∼60 age group, and there is no significant sex preponderance. It grows slowly and is usually painless, firm, well-circumscribed nodule. Because of high rate of recurrence, extra-capsular excision including the overlying mucosa and margin of normal tissue is recommended. We report 10 cases of palatal pelomorphic adenoma which have been successfully treated by extra-capsular excision. The surgical defects smaller than 3㎝ in diameter were covered with palatal acrylic splint for the secondary healing. The larger defects were repaired using palatal island flap in 3 cases, rotation flap and buccal fat graft in each 1 case. No patient showed any recurrence or malignant change during the mean follow-up period of 4 years and 9 months. These repair methods seem to be simple, reliable and uncomplicated procedures in the palatal surgical defects.