유산균의 배양 및 건조조건에 관한 연구 : 제1보 유산균의 배양조건에 관한 연구 partⅠ.Optimum Cultural Conditions of Lactic Acid Bacteria

신원철,윤주천,김갑수,최승락,이근억,유주현 江原大學校 産業科學硏究所 1981 産業技術硏究 Vol.1 No.-

In order to use as a starter after drying, optimum growth conditions of Str. thermophilus and L. bulgaricus were investigated. The results were as follows. The growth of Str. thermophilus was reached at stationary phase after 12 hours incubation and L. bulgaricus was after 6 hours. Str. thermophilus was grown well, in the medium containing 10% of skim milk, 2%5 of sucrose, 0.1% of KCl and 0.015%(v./v.) of soy-sauce. In the case of L. bulgaricus, 10% of skim milk, 2% of glucose, 0.5% of bacto-peptone, 0.1% of K₂HPO₄ and 0.02% of pyridoxine was suitable for the maximum growth.

광원 및 광조사 방법에 따른 심미충전재의 중합수축

이용근,윤태호,임범순,김철위 대한치과기재학회 2000 대한치과재료학회지 Vol.27 No.4

The polymerization shrinkage of dental esthetic filling materials of five kinds of resin composite and three kinds of compomer was measured with a thermal dilatometer (Thermal Dilatometer, DIL 402C, TASC 414/3A Controller, Netzche, Germany) during polymerization with a halogen lamp curing unit (VIP, Bisco, U.S.A.) or a plasma arc curing unit (Flipo, Serial No. P03G02221, Lokki, France). The irradiation time of the halogen lamp was 40, 80 and 120 s with the intensity of 400 ㎽/㎠, and that of the plasma arc was 9 s. The pulse-cure mode with a halogen lamp was 5 s pre-polymerization at 200 ㎽/㎠, 3 minutes wait and then 120 s irradiation at 400 ㎽/㎠. From this experiment, the following results were obtained : 1.Depending on the irradiation source and mode, the amount of polymerization shrinkage after 14 minutes from the start of irradiation was significantly different in some materials. However, there was no significant difference in most of materials (p>0.05). 2.Most of the polymerization shrinkage occurred within two minutes from the start of irradiation except for pulse-cure. 3.In all the materials studied, the amount of polymerization shrinkage after 14 minutes from the start of irradiation was not different between the results from 120 seconds irradiation with the halogen lamp and these from pulse-cure (p> 0.05), and the amounts of shrinkage from a plasma arc was generally lower than those from other curing modes. 4.The amount of polymerization shrinkage after 14 minutes from the start of irradiation was not different between the results from 120 seconds irradiation with a halogen lamp and those from plasma arc (p>0.05) in all the eight materials studied.

치과생체재료 분야의 연구현황 및 전망

김철위,이용근 대한치과기재학회 1999 대한치과재료학회지 Vol.26 No.1

치과생체재료학의 연구현황을 분석하고 새로운 천년을 전망하여 연구방향을 모색하기 위한 본 글에서는 현재까지의 치과생체재료학 분야의 연구성과를 검토하고, 이어 향후 방향을 예측한 여러 의견을 모아 제시하고자 한다. 이어 각 재료와 특성별로 앞으로의 연구방향을 설정하여 보고자 한다.

샘플데이타 제어시스템 설계를 위한 새로운 고전기법

하철근 울산대학교 1994 공학연구논문집 Vol.25 No.2

본 논문은 샘플데이타 제어시스템을 위한 새로운 직접설계방법(Direct Design method)을 제안한다. 그 제안된 기법은 아날로그 제어기설계 방법을 직접적으로 디지탈 제어기설계에 응용한 것으로 이는 w-Domain에서의 근궤적법을 이용한 하나의 고전기법이다. 고전기법으로 부터 얻은 아날로그 제어기설계 경험을 살려 샘플데이타 제어시스템을 설계하기 위해 우선 w-Domain이라는 새로운 복소수 영역과 안정성 판별기준을 정의하고그 영역에서 상태방정식으로 표현된 샘플데이타 시스템을 제안한다. 또한 그 영역에서 근궤적법으로 설계된 제어기를 디지탈 제어기로 구현하기 위해 이득변환식(Gain Transformation Formulus)이 고안된다. 본 논문에서 제안된 방법을 안테나 방위각 제어문제에 적용해 보임으로써, 아날로그 제어기설계 경험과 기술이 디지탈 제어기 설계를 위한 직접설계방법에 응용될 수 있음을 보여준다. This paper presents a new direct design method for sampled-data control systems. The proposed synthesis method utilizes a design method of analog control system to design a digital controller using direct design method, which is a classical root-locus method in the w-domain. To adopt the valuable experiences obtained from design of analog controllers in classical design methods to design of sampled-data control systems, first of all, in this paper a new complex domain, what we call w-domain, and stability criterion in the domain are defined. Then a sampled-data system in the w-domain is proposed, which is represented in state space. To realize a unique digital controller synthesized in the w-domain, exact gain transformation formulus is invented. Through an illustrative example of antenna azimuth control in the proposed approach, any experts to analog designs can easily take advantage of their valuable knowledge and skill to design sampled-data control systems in direct design method.

사지의 급성동맥 색전증에 대한 응급동맥 색전제거술

박철완,원형섭,박정배,이근,조상훈,표창해,김상일 대한응급의학회 1996 대한응급의학회지 Vol.7 No.2

Acute arterial occlusion of the extremities is often a surgical emergency and is due mostly to arterial embolus. It has infrequently been reported in the emergency department. Cardiac embolism is most commonly the result of atrial fibrillation secondary to valvular heart disease followed by ischemic heart disease. The emergency arterial embolectomy by Fogarty balloon catheter works well when the cause of occlusion is cardiac embolus obstructing normal vessels in a patient with valvular heart disease. Recently we met some patients with acute critical ischemia of the extremities due to arterial emboli in our emergency department. On physical examination, they all had symptoms of 5"P"s(pain, pallor, pulselessness, paresthesia, paralysis). After emergency arterial embolect omy, immediate improvement was observed in all patients. They were discharged within 1 week. We report our experiences with the review of literatures.

제1회 한국물리탐구토론대회에 출제된 문제 풀이에 대한 분석 : 『Adhesive tape』와 『Fractal Diffraction』을 중심으로 centering around problems on "adhesive tape" and "fractai diffraction"

육근철,김용복,이희복,정기주,김준태 공주대학교 과학교육연구소 2003 과학교육연구 Vol.34 No.-

제1회 한국물리탐구토론대회에는 10개의 문제가 출제되었는데 본 연구에서는 이들 10개의 문제 중 『접착테이프(Adhesive tape)』 문제를 해결한 5개 팀의 보고서와 『Fractal Diffraction』 문제들 해결한 고등학생부 3개 팀과 중학생부 1개 팀의 보고서를 비교 분석하였다. 그 결과 학생들은 접착테이프를 갑자기 뗄 때 빛이 발생하는 원인을 정전기 발생, 전자의 이동, 에너지의 변환 등으로 해석하였다. 그리고 Fractal 문제의 경우 학생들은 Fractal 이라는 개념을 제대로 이해하지 못하여 잘못된 방향으로 문제를 해결한 팀이 많았다. 특히 『Fractal Diffraction』문제는 출제된 10문제 중 가장 까다로운 문제로 학생들이 생각하고 있는 것으로 조사되었다. 본 대회는 탐구 토론대회이므로 탐구의 과정별로 새로운 아이디어를 제안하여 결론에 이르는 창의적 탐구 과정이 제안되어야 한다. We have analyzed students' reports on two problems such as "adhesive tape" and "fractal diffraction" among ten assigned-problems in the first Korean youth physics tournament. (KYPT). There were five team's reports on "adhesive tape" and four team's reports on "fractal diffraction". Students analyzed that the reason for lightening coming out from the stripping down adhesive tape ma be caused by electrostatic friction, electron transfer, energy transformation, etc. However, many students failed to solve the "fractal diffraction" problem correctly. This pro blem is found to be most difficult one among ten problems in the first KYPT for the reports should include the creative investigations by their own ideas in every steps of inquiries.

치과용 저금계 합금의 조성 및 열처리에 따른 경도 및 변색에 관한 연구

김철위,김명국,백기석,이용근,윤태호 대한치과기재학회 2000 대한치과재료학회지 Vol.27 No.1

Discoloration of dental alloys results from several reasons such as chemical tarnish, precipitation of chromatic substance on the alloy surface. In this study, the discoloration of 20 kinds of dental casting alloys was measured after immersion in various solutions, and the results were analyzed by the composition of the alloys and solutions. The effects of constitutional elements of the alloys on the color and discoloration of alloys were evaluated also. Cast specimens were polished with #400 silicons carbide paper, and were washed and dried. Vickers hardness of the alloys specimens was measured before and after heat treatment. Color of specimens was measured with the Spectrophotometer (Minolta CM-3500d, Japan.) with the CIELAB scale. Illumination C was used with SCE. Five kinds of aqueous solutions of HP (10% H₂O₂), NS (5% Na₂S), NC (5% NaCL), AS (mucin-added artificial saliva) and SF (10% SnF₂) were used, and the specimens were immersed at 37℃ for one and three days. ΔE* of the mostly discolored alloy for three days in HP was very high as 26.6, 10.27 in NS, 7.88 in AS, 4.23 in SF, and 4.18 in NC. Multiple regression analysis among CIE L*, a*, b* before immersion and the alloy composition showed that each CIE L*, a*, b* was negatively correlated with palladium content, and R value was -0.623, -0.365, -0.674 respectively. Multiple regression analysis among ΔE*, ΔL*, Δa*, and Δb* after there days and the alloy composition showed that silver was positively correlated with ΔE* (R = 0.510, p<0.01), and CIE L* was influenced by silver and copper content, CIE a* was influenced by copper and indium content, CIE b* was influenced by silver content (p<0.01). VHN number was 146.00∼347.60 before heat treatment, and 161.20∼331.20 after heat treatment.

치과교정용 탄선의 전기화학적 부식평가

이용근,김철위 大韓齒科器材學會 1994 대한치과재료학회지 Vol.21 No.2

The corrosion of dental orthodontic appliances can have serious clinical implications ranging from loss of dimension to stress corrosion failure of the appliances. The production of possible toxic corrosion products and their absorption by the surrounding tissue is undesirable. The study on the toxicity of corrosion products is carried out actively nowadays. And it is the standard practice of biocompatibility test that the elucidation of reaction mechanism between wire and electrolyte using electrochemical corrosion test. In this study, five kinds of stainless steel orthodontic wires, four kinds of cobalt-chromium orthodontic wires and two kinds of nickel-titanium wires were studied using electrochemical method. The results were as follows : 1. The corrosion potentials of orthodontic wires did not change much after altering the measuring condition, but the zero current potentials of those had great variation after altering the measuring condition. 2. Stainless steel orthodontic wires showed apparent passivation within the oral potential range. In the rescan procedure, the current density was reduced than the first scan and the transformation of oxide layer was observed around -100 mV(SCE) in some wires. 3. Cobalt-chromium orthodontic wires showed passivation starting from -800∼-700mV(SCE), and maintained upto +700mV(SCE). In the rescan procedure, the current density was reduced apparently than the first scan and similar potentiodynamic polarization curve as first scan was obtained after rescan procedure. 4. Nickel-titanium orthodontic wire showed increase of current density in the range of -100∼+100 mV(SCE) and showed passivation in the range of +200∼+800 mV(SCE). In the rescan procedure, the current density was higher than in the first scan in some potential range.

지연제어동작을 갖는 샘플데이타 시스템의 최적제어

하철근 울산대학교 1994 공학연구논문집 Vol.25 No.2

본 논문에서는 지연제어동작을 갖는 샘플데이타 시스템의 제어문제를 다루고자 한다. 그 문제는 전적으로 이산시간 영역에서 명확히 설명되고 선형최적확률제어기법 (LQG approach) 에 의하여 해결된다. 또한 본 논문에서 제안된 제어기법(LQG approach)으로 설계된 선형최적 확률보상기 (LQG compensator) 가 지연제어입력을 가지는 경우에도 분리원리 (Separation Principle) 가 성립됨을 증명한다. 본 연구의 이론적인 결과를 Two-Mass-Spring 시스템에 적용하여 검증하였다. 결과로부터 알 수 있는 사실은 지연제어동작으로 야기된 시스템의 안정성 (stability) 과 강건성 (robustness) 그리고 제어시스템의 성능 (performance) 저하는 본 논문에서 제어된 방법을 통하여 회복 또는 향상될 수 있다는 것이다. 특히 그 최적확률보상기는 시간지연으로 발생하는 제어동작 포화 (saturation) 로부터 샘플데이타 시스템을 보호할 수 있다. In this paper, we treat the sampled-data control problem that accounts for time-delay in the contril action. The problem is formulated entirely in discrete-time domain, and the optimal design is achieved in Linear Quadratic Gaussian(LQG) approach. It is shown in this approach that 'Separation Principle' is valid with an additional feedback of delayed control input to the LQG compensator proposed in this paper. The method is applied to a benchmark problem of two-mass-spring system. Design results obtained indicate that degradation of stability, robustness and performance due to the delayed control action may get recovered to (or even better than) level of the system with no delay time through the design method proposed. Especially, the LQG approach shows the fact that the LQG compensation may prevent the sampled-data control system from saturation of control action due to the time-delay.

레진기질과 생체활성 필러에 따른 콤포짓트레진의 특성

이용근,임범순,김철위 大韓齒科器材學會 2003 대한치과재료학회지 Vol.30 No.2

In dentistry, since composite resins are used to restore teeth, their chemical and physico-mechanical characteristics should be similar to those of natural tooth. The mineral phase of bone and teeth is mainly hydroxyapatite. Therefore, synthetic hydroxyapatite would seem a good choice as an inorganic filler to he used in dental restoration or bone implant. The purpose of this study was to gain more insight into the possibility of the bioactive filler incorporated composite resin as restorative material, limns; material or pulp capping material through the evaluation of mechanical properties and cytotoxicity. Bioactive fillers such as apatite-wollastonite (AW) glass ceramic, bioglass (BG) and hydroxyapatite (HA) powders, and conventional glass fillers were incorporated into light-curing resin matrices composed of Bis-GMA and TEGDMA (6:4 by wt.), Bis-GMA and HEMA (6:4 by wt.), Bis-GMA, HEMA and TEGDMA (3:4:3 by wt.). and UDMA and TEGDMA (6:4 by wt.). Compressive, diametral tensile and flexural strength of light-cured specimens immersed in 37℃ DW for 24 hours was measured. Cytotoxicity by MTT method was also evaluated. When Bis-GMA and TEGDMA mixture was used as the resin matrix, compressive, diametral tensile and flexural strength of bioactive filler incorporated composite resin was 17.72∼128.22 ㎫. 39.57∼84.46 ㎫ and 21.35∼57.36 ㎫, respectively. When Bis-GMA and HEMA mixture was used as the resin matrix, BG filler incorporated composite resin did not cure, and the highest compressive and diametral tensile strength of bioactive filler incorporated composite resins was 40.24 ㎫ and 35.30 ㎫, respectively. When Bis-GMA, HEMA and TEGDMA mixture was used as the resin matrix, BG filler incorporated composite resin did not cure, and three strength values were highest after incorporating HA filler. When UDMA and TEGDMA mixture was used as the resin matrix, compressive, diametral tensile and flexural strength of bioactive filler incorporated composite resin was 38.61∼137.31 ㎫, 32.59∼110.47 ㎫ and 17.10∼48.70 ㎫, respectively. Generally, cytotoxicity of bioactive filler incorporated composite resin was higher than those of conventional glass filler incorporated resins. From the above result, mechanical properties of bioactive filler incorporated composite resins made of conventional Bis-GMA, UDMA and TEGDMA matrices were moderate; however, those of HEMA-incorporated matrices were low.