重硏削加工에서 硏削깊이가 表面層에 미치는 影響

閔宅基 충남대학교 공업교육연구소 1985 論文集 Vol.8 No.1

This is an experimental study on the surface layer for surface grinding with grinding depth and work speed as variables. Followings are the results of experiment 1. Surface roughness was abrutly increased at 0.07 mm grinding depth. 2. Hardness was increased from surface to the depth of 1∼1.4 mm.

수종 음료수의 법랑질과 상아질 침식에 관한 연구

장기택 大韓小兒齒科學會 1997 大韓小兒齒科學會誌 Vol.24 No.4

The aim of this study was to evaluate the in vitro effects of exposure to acidic beverages on microhardness of enamel and dentin. Thirty enamel specimens and thirty dentin specimens were obtained from extracted bovine maxillay incisiors. Enamel and dentin specimens were divided into three groups and treated with acidic beverages as follows ; Group 1 : cola(pH 2.52), Group 2 : plain soda water(pH 2.93) and Group 3 : orange juice(pH 3.75). Erosive treatment was performed by storing each specimens for 5 min in 50ml solution of cola, soda water and orange juice. Average microhardness values(VHN) were determined before and after erosive treatment. All beverages produced significant loss of microhardness of enamel and dentin. Microhardness of enamel was reduced in the following order : Group 1 :42.71±4.36(%), Group 2 : 37.09±6.25(%), Group 3 : 35.46±4.98(%). Microhardness of dentin was reduced in the following order : Group 1 : 17.14±3.42(%), Group 2 : 13.89±3.18(%), Group 3 : 13.82±3.50(%). The differences between group 1 and group 2,3 were statistically significant(p<0.05).

입원치료를 요하는 소아의 급성복증

배택환,김준식,유인술,조준필,이철주,민영기 大韓應急醫學會 1996 대한응급의학회지 Vol.7 No.1

The acute abdomen defined as an acute abdominal condition which needs immediate decision for treatment is one of the most common cause for emergency care. One thound six hundreds nine patients were visited to pediatric emergency center due to acute abdomen. To aid in early diagnosis and proper treatment, a clinical review was made on 278 cases of acute abdomen under 15 yrs old which admitted to Pediatrics and General surgery via emergency center from June of 1994 to May of 1995. The results as follows: It was 17.3% of total visiting to pediatric emergency center due to gastrointestinal sysmptoms. The sex ratio(Male: Female) was 2.35:1. Acute gastroenteristis was the most common acute abdominal condition(54%) and followed by acute appendicitis(17.9%), and intussusception(13.9%). The most common chief commplaint was vomiting(58%) and followed by abdominal pain(39.4%), diarrhea(35.8%), and fever(42.1%). One hundred fifty-five patients were visited to pediatric emergency center via local clinic and thirty patients via OPDs. The operations were done in 75 patients. Among them, immediate operation were done in 60 patients and delayed operations were done in 15 patients, but there is no difference in complication.

아르곤 레이저와 가사광선의 복합레진 및 Glass ionomer 중합에 관한 연구

장기택,이상훈,이광수 大韓小兒齒科學會 1996 大韓小兒齒科學會誌 Vol.23 No.1

Following results were obtained after measuring microhardness value of top and bottom surface of the specimens, which were made of either light curing glass ionomer or composite resin, polymerized with visible light and argon laser varying curing time. 1. In Fuji Ⅱ-LC and Vitremer, significant difference was found in microhardness value, only in less than 10 seconds of curing time between using visible light and argon laser, and in the basis of microhardness value of the bottom surface, curing time of the argon laser takes only a half than that of visible light. 2. In Prisma, significant difference was found in microhardness value, only in less than 20 seconds of curing time between using of visible light and argon laser, and in the basis of microhardness value of the bottom surface, curing time of the argon laser takes only a half than that of visible light. 3. In Z-100, significant difference was found in microhardness value, only in less than 30 seconds of curing time between using of visible light and argon laser, and curing time of the argon laser takes only a quater than that of visible light. 4. In Clearfil, significant difference was found in microhardness value, in every each curing time between using of visible light and argon laser, and curing time of the argon laser takes only a quater than that of visible light.

중합시간과 중합방법에 따른 자가중합형 상교정용 레진의 중합률의 비교에 관한 연구

장기택,김종철,유종욱 大韓小兒齒科學會 1999 大韓小兒齒科學會誌 Vol.26 No.2

가찰성 상교정 장치에 많이 사용되는 자가중합형 상교정용 레진의 미반응 단량체는 레진의 물성과 생물학적인 면에 많은 영향을 끼친다. 다라서 미반은 단량체를 최소화하고 중합률을 최대로 하는 중합방법에 대한 연구는 중요한 의의를 갖는다. 저자는 자가중합형 상교정용 레진의 중합시간과 중합방법에 따른 중합률을 비교해보기 위해 시편을 다음과 같이 5군으로 나누어 연구를 진행하였다. 상교정용 레진의 분말과 용액을 혼합하여 제 1군은 28℃의 공기중에 보관하였고, 제 2군은 28℃의 물에, 제 3군은 28℃의 물과 30psi의 압력에, 제 4군은 43℃의 물에, 제 5군은 43℃의 물과 30psi 의 압력하에 각각 보관하였고, 10분, 1시간, 12시간, 1일, 3일 경과 후에 각 시편을 Fourier 변환적외선분광법을 이용하여 중합률을 측정하여 다음과 같은 결론을 얻었다. 1. 모든 군에서 중합시간이 경과함에 따라 중합률도 지속적으로 증가하는 양상을 보였다. 10분경과 후의 결과와 비교하여 볼 때, 제 1군은 12시간 경과 후부터 중합률의 증가가 유의성이 있었고, 제 2군과 3군, 4군, 5군은 1시간 경과 후부터 유의성이 있었다.(p<0.05) 2. 10분과 1일, 3일 경과 후에는 제 5군, 제 4군, 제 3군, 제 2군, 제 1군의 순서대로 중합률이 높았다. 3. 중합시 온도에 따른 비교에서, 1일 경과 후를 제외하고는 모든 시간에서 43℃에서 중합시킨 군의 중합률이 28℃에서 중합시킨 군의 중합률보다 유의성 있게 높았다.(p<0.05) 4. 압력은 12시간 경과 후를(p<0.05) 제외하고는 중합률에 영향을 주지 못했다. 5. 보관방법은 1시간 경과 후를(p<0.05) 제외하고는 중합률에 영향을 주지 못했다. Autopolymerized resin facilitates a more rapid and easier means for the construction of removable orthodonic appliances than heat cured resin. But many reports reveal that more unreacted monomer is found in autopolymerized resin. It is very important to achieve maximum degree of polymerization because if polymerization is inadequate, high level of unreacted monomer has been shown to adversely affect mechanical and physical properties, and also the question of allergy or toxicity to methylmethacrylate must be considered. The purpose of this study was to compare the degree of polymerization according to curing method and curing time. Five groups were desinged ; Group 1 was polymerizied at room temperature(28℃) ; Group 2 in 28℃ water ; Group 3 in 28℃ water under 30psi pressure ; Group 4 in 43℃ water ; Group 5 in 43℃ water under 30psi pressure for 10 minutes. 1 hour, 12 hour, 1 day and 3 day. The degree of polymerization was meaured by means of Fourier Transform Infrared spectroscopy. The results were as follows : 1. The degree of polymerization increased constantly in accordance with curing time in all groups and after curing for 10 minutes. Group 1 showed significantly higher degree of polymerization after 12 hours and Group 2, Group 3, Group 4, Group 5 after 1 hour (p<0.05). 2. The degree of polymerization decreased in the order of Group 5, Group 4, Group 3, Group 2, Group 1 except when the curing time was 1 hour and 12 hours(p<0.05). 3. The degree of polymerization Group 4, Group 5 cured at 43℃ showed significantly higher degree of polymerization than Group 2, Group 3 at 28℃ except when the curting time was 1 day(p<0.05) 4. Among Group 2, Group 3 and Group 4, Group 5, the pressure had no effect on polymerization except when the curing time was 12 hours(p<0.05) 5. Between Group 1 and Group 2, the method of storage had no effect on polymerization except when the curing time was 1 hour(p<0.05)

Air abrasive technique 을 이용한 복합레진 수복 증례

장기택,이상훈,한세현,이창우 大韓小兒齒科學會 1997 大韓小兒齒科學會誌 Vol.24 No.4

The air abrasive technique is a non-mechanical method by which teeth are treated before restoration and stains and calculi are removed from tooth surfaces using the kinetic energy of small particles. The air abrasive technique in dentistry was first introduced in the 1950's with as instrument called 'Airdent'. But, as the main restorative materials of the period were amalgam and gold, and the instrument's inability to control the flow of particles caused the particles to be spread throughout the clinics, widespread use was not possible. In the 1990's, as these techincal problems were solved and more interest in new restorative materials rose in an effort to preserve sound tooth structure, new developments took place in instruments related to the air abrasive technique. The air abrasive technique produces less pressure, vibration and heat that might cause patient discomfort and facilitates the preservation of sound tooth structure. It also reduces the need for anesthesia and is less harmful to the pulp. Other advantages include increase in dentin bonding strength of composite resin, lower possibility of saliva contamination and maintenance of a dry field. But there is not direct contact between the nozzle and the tooth, the operator cannot use his or her tactile sense and must rely solely upon visual input. Other disadvantages are : the tooth preparation depends on the operator's ability ; alpha-alumina particles, after bouncing off the tooth surface, cause damage to dental mirrors ; the equipment is expensive and takes up a certain amount of space in the clinic. The author conducted case report using the air abrasive technique on patient visiting the Department of Pediatric Dentistry at Seoul National University Dental Hospital and arrived at the following conclusions. 1. The tooth preparation capability of different air abrasive devices varied widely among manufacturers. 2. It was more effective in treating early caries lesions and stains compared to lesions where caries had already progressed to produce soft dentin. 3. The cold stream and noise caused by the evacuation system was a major cause of discomfort to pediatric patients. 4. As there is no direct contact with tooth surface when using the air abrasive technique for tooth preparation, considerable experience and skill is required for proper tooth preparation.

WWW상에서 음란물 검색기법 : Obscene Material Searching Method in WWW

노경택,김경우,이기영,김규호 韓國컴퓨터情報學會 1999 韓國컴퓨터情報學會論文誌 Vol.4 No.2

WWW은 기존의 인터넷이 단순 문자 자료 중심의 데이타 교환을 멀티미디어화 하기 위한 프로토콜이며, 자료들을 하이퍼텍스트 형태로 저장함으로써 초보자들도 쉽게 원하는 자료를 찾고, 접근할 수 있도록 되어 있다. 이러한 WWW의 멀티미디어 데이타의 검색 및 접근의 용이성은 음란물 데이타가 보편화, 멀티미디어화 되는데 결정적인 역할을 하였으며 음란물의 상업화를 가능케 하는 사회적 문제를 야기하였다. 한편, 이러한 문제를 해결하기 위해 음란물을 제공하는 사이트를 효율적으로 차단하기 연구가 활발하게 진행되고 있다. 본 논문에서는 이러한 음란물을 제공하는 사이트를 효율적으로 검색하여, 미성년자의 음란성 사이트 접근을 차단하기 위한 기법을 제시하고 이를 구현하였다. 제안된 기법은 링크를 기반으로 정보 검색 기능을 수행하며, 가장 정확한 결과를 보여 주는 것으로 알려진 확률 모델과 비교한 결과 제안된 모델(Link-Based Model)이 확률 모델보다 평균 재현율과 정확율에서 12%와 8% 성능이 우수하였다. 특히 텍스트 이외의 데이타와 적은 링크를 가진 문서들을 검색하는데 크게 효율성이 향상되었다. World-Wide Web(WWW) is a protocol for changing information exchanges which is central to text documents in the existing network to make a multimedia data exchanges. It is possible for a beginner to search and access data which he wants to find as data were stored in the form of hypertext. The easiness for searching and accessing the multimedia data in WWW makes a important role for obscene materials to be toward generalization and multimedia and occurs social problems for them to be commercialized, while other researchers have actively studied the way to block effectively the site providing obscene materials for solving such problems. This paper presents and implements the blocking method for the sites having obscene material as it effectively search them. The proposed model was based on Link-Based information retrieval method and proved that it accomplished more efficient retrieval of relevant documents than probabilistic model when compared the one with the other which is known to generate the most correct results. The improvements in the average recall and precision ratio were shown as 12% and 8% respectively. Especially, the retrieval capability of relevant documents which include non-text data and have a few links increased high]y.

가시광선과 아르곤 레이저로 복합레진 중합시 미세누출에 관한 비교 연구

장기택,정태련,김종철 大韓小兒齒科學會 1996 大韓小兒齒科學會誌 Vol.23 No.4

For the purpose of evaluation of microleakage of class V resin restoration, 64 extracted bovine teeth were filled with two kinds of light curing composite resins(Z-100, Clearfil) and polymerized with 40 seconds of visible light and with 10 seconds of argon laser. After 1000 thermocycling(5℃/55℃), specimens were placed in 1% methylen blue dye solution for 72 hours in 37℃ water bath. The specimens were sectioned at center of filling body and the degree of dye penetration was observed with a stereomicroscope. The following results were obtained, 1. Differences of the microleakage of resin restorations polymerized with 10 seconds of argon laser and 40 seconds of visible light were statistically insignificant. 2. There was more microleakage in Z-100 than clearfil and there was a statistical significancy (p<0.05).

편도체 중심핵 손상이 갈등 스트레스에 의해 유발되는 위궤양에 미치는 영향

이종택,김기석 한국심리학회 1990 한국심리학회지 생물 및 생리 Vol.2 No.1

본 연구에서는 흰쥐를 대상으로 편도체 중심핵의 손상이 갈등 스트레스에 의해 유발되는 위궤양 발생을 억제하는 가를 살펴보고자 하였다. 피험동물을 편도체 중심핵 손상집단과 모의시술 통제집단으로 나누어 각각 20마리씩 시술하였다. 시술 1주일 후, 피험동물을 스키너 상자에 넣고 갈등 스트레스 인자로 전기쇼크를 48시간동안 주었다. 실험결과 행동지표인 지렛대 누르기, 체중 및 물섭취량에는 두 집단간에 차이가 없었다. 그러나 편도체 중심핵을 손상한 집단의 피험동물에게서는 모의시술 통제집단의 피험동물보다 유의미하게 위궤양의 수, 위궤양의 길이 및 미란발생이 억제되었다. 이러한 결과는 편도체 중심핵이 갈등 스트레스에 관여하는 뇌의 신경실체임을 시사한다. This experiment was conducted to answer the question whether or not the lesion of central amygdaloid nucleus inhibites the development of a conflict stress induced stomach ulcer, 40 rats were randomly assigned into two groups, that is, a central amygdaloid nucleus lesion group and a sham-operationed group. One week after surgery, they were put in Skiner Box and received electric shock as a conflict stress. After the experiment, the stomach was removed as soon as possible. The lesion group had inhibited significantly the development of stomach ulcer, whereas the sham-operated group did not inhibit the development of the ulcer. The results suggest that the central amygdaloid nucleus is a neural substrate that responds to the conflict stress as well as any other type of stress.

TCP-RLDM:Congestion losses과 Wireless losses 구별을 통한 수신측 기반 혼잡제어 방안 : TCP-RLDM:Receiver-oriented Congestion Control by Differentiation for Congestion and Wireless Losses

노경택,이기영 韓國컴퓨터情報學會 2002 韓國컴퓨터情報學會論文誌 Vol.7 No.4

본 논문은 수신측이 네트워크 혼잡도를 측정 참여하여 송신측으로 하여금 네트워크 상태에 따른 윈도우 크기를 조절하는데 있다. TCP-RLDM은 기존 TCP의 Additive Increase/Multiplicative Decrease 방법의 단점을 보완하는 데이터 수신율을 기초로 하는 측정기반 전송 전략을 채택하였다. 이는 유무선 망에서나 지연에 민감하거나 용인하는 응용들로 구성된 이질적 환경에서 동적으로 대응하기 위해 에러손상의 성질에 따른 즉, 혼잡에 의한 손실인지 전송상 일시적 손실인지에 따라서 적절히 대처 함으로써 성능을 높일 수 있게 되었다. 수신측으로부터의 데이터 수신율과 에러발생 원인에 대한 정보를 이용, 송신측의 wave 전송방식과 가급적 혼잡이 발생하기 이전에 혼잡회피전략을 적용함으로써 가변적인 네트워크환경에 잘 대처하도록 하였다. This paper aims to adjust the window size according to the network condition that the sender determines by making the receiver participating in the congestion levels. TCP-RLDM has the measurement-based transmission strategy based on the data-receiving rate complementing TCP with the property of Additive Increase / Multiplicative Decrease. The protocol can make an performance improvement by responding differently according to the property of errors whether congestion losses or transient transmission errors - to confront dynamically in heterogeneous environments with wired or wireless networks and delay-sensitive or - tolerant applications. By collecting data-receiving rate and the cause of errors from the receiver and by enabling sender to use the congestion avoidance strategy before occuring congestion possibly, the protocol works well at variable network environments.