• 전기의세계
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• v.39 no.4
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• pp.10-18
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• 1990

우리나라 전기전자공학과는 완전히 분리되어 있고 그 외에도 제어계측공학과, 전산기공학과, 전자통신공학과 등으로 분리되어 있으나 선진국에서는 하나의 학과로 되어 있다. 그리고 우리나라의 교과과정은 졸업에 필요한 과목수가 지나치게 많아서 한과목을 깊게 공부하는대산 여러과목을 훑어보는 식으로 운용되어 왔다. 전공과목수가 9개(실제로는 미분방정식과 졸업논문을 제외하면 7개) 밖에 안된다고 해서 M.I.T.의 전기전자공학 교육이 우리나라보다 못하다고 말 할 수는 없다. MIT의 교과과정이 오늘과 같이 된데에는 오랜 연구와 경험이 필요하였다. 즉 기술 과목만을 많이 가르쳐서 졸업시키면 졸업생의 대부분이 인문사회 출신 사장 아래에서 기술자 역할밖에 못한다는 것을 알았던 것이다. 2차 대전 당시 레이다를 포함한 각종 신형전자장비를 개발한 것은 공대출신보다는 물리학과 수학과 출신의 역할이 컸던 것이다. 특히, SPUTNIK이 1957년에 발사된 이후 미국의 공대들은 과학과목에 큰 비중을 두게 되었던 것이다. 최근에는 그 반작용으로 설계과목에 비중을 두기 시작하였다. 졸업후 2-3년 지나면 별로 쓸모없는 과목들을 많이 가르치는 것보다는 기초적인 과목만을 충실하게 가르치는 것이 훨씬 좋다고 본다.

• Korean Journal of Environmental Agriculture
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• v.15 no.1
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• pp.19-24
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• 1996

To investigate the alterations of ultrastructure of leaves by acid rain, 10mm of SAR(Simulated Acid Rain, pH 2.0, 2.5, 2.7, 3.0, 6.0) were applied to 4 crops(rice, soybean, barley, and radish) at the two day interval. The symptoms of leaf damage by SAR were observed by naked eyes and SEM(Scanning Electron Microscope). The results are summarized as follow: Visible leaf injury were more serious in dicots than monocots such as rice and barley with the order of bean, radish, rice, barley. With the SAR treatment of pH 2.0, histological perturbation of trichome were developed in bean and radish. And with the SAR treatment of pH 2.5, stomata of all tested crops except rice were deshaped.

• Journal of Technologic Dentistry
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• v.37 no.4
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• pp.205-212
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• 2015

Purpose: The objective of this study was to compare the surface roughness according to polishing process in conventional laboratory techniques used for polishing three different acrylic denture base resins. Materials and methods: Specimen preparation and surface polishing procedures were conducted to manufacturer's recommendation with three heat-polymerized denture base resins. Surface roughness and gloss were measured by a contact type tester and a LED gloss checker using thickness 2 mm and diameter 10 mm. There were five specimens for each acrylic resin material and polishing procedures. Mean average surface roughness (Ra) values of each specimen group were analyzed using a one-way ANOVA analysis of variance and Scheffe's post hoc test. Surfaces after surface roughness and gloss testing according to each polishing process were evaluated under a stereoscopic microscope. Results: The highest mean average surface roughness was measured($Ra=2.43{\pm}0.47$) for surfaces finished with a denture tungsten carbide bur in Triplex. The lowest surface roughness values ($Ra=0.11{\pm}0.07$) were determined in Vertex polished with a lathe. In addition, all materials revealed that surface roughness determined highly in HP1 and HP2 than other procedures. All correlation between surface roughness and gloss showed highly with three heat-polymerized resins. Specially, topmost correlation revealed than other material in Triplex. Significant differences in mean average surface roughness were found between polishing process used high speed lathe and low speed hand-piece. Conclusion: Laboratory polishing used to high speed was found to produce the smoothest surface of heat-polymerized denture base acrylic resin. Therefore, we recommended that high polishing process need to get smooth surface.

• Journal of Technologic Dentistry
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• v.41 no.4
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• pp.263-269
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• 2019

Purpose: The purpose of this study was to evaluate the internal fitness of prostheses fabricated with non-contact extra-oral scanner and those fabricated with intra-oral video scanner, with a comparative accuracy analyses of their precision and trueness. Methods: A polymethyl methacrylate (PMMA) model was fabricated by replicating a master model. The prostheses in the first group were fabricated based on the PMMA model with an intra-oral video scanner (IVS group). Following the fabrication of work models with Type IV Stone that were based on the PMMA model, the prostheses in the second group were fabricated with a non-contact extra-oral scanner (ENB group). The precision and trueness of the prostheses were calculated from comparisons of the three-dimensional images of the internal surfaces of the prostheses and those of the master model. Kruskal-Wallis tests were used to determine the statistical significance, with the level of type 1 error set at 0.05. Results: Trueness (P < 0.009) and precision (P < 0.001) did not differ significantly between the ENB and IVS groups. The IVS group exhibited lower trueness values and larger precision values than the ENB group. Conclusion: Although no significant differences were found in the internal fitness of the prostheses that were fabricated by the two different scanners, the intraoral video scanner-fabricated prostheses had better trueness, whereas the non-contact extra-oral scanner-fabricated prostheses had better precision.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.880-883
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• 2009

석탄가스화복합발전(IGCC) 시스템에서 합성가스 중에 포함된 황화수소($H_2S$)는 후단의 가스 터빈과 같은 장치의 부식을 방지하고, 합성가스를 이용하는 연료전지 등의 연계 공정에서 요구하는 수준에 맞추어 정제되어야 한다. 본 연구에서는 $H_2S$ 정제공정 추가에 따른 IGCC 시스템의 효율저하를 최소화하기 위하여 고온고압에서 사용가능한 탈황제를 분무건조법을 이용하여 제조하고 제조된 탈황제에 대해 물성 및 황 흡수능 시험을 실시하였다. 형상, 내마모도, 평균입자크기, 충진밀도와 함께 제조된 탈황제가 적용되는 유동층 공정에 적합한 강도를 보유하는지 여부를 미국표준시험방법에 의하여 측정하였다. 황 흡수능은 열중량분석기를 반응기로 사용하여 모사 합성 가스 분위기에서 측정하였다. 분무건조 성형된 탈황제의 일부가 구형이 아닌 타원형 또는 도넛 형태를 나타내고 있어 형상 개선을 위한 제조방법 개선이 필요한 것으로 나타났다. 제조된 탈황제는 기공도가 65% 이상으로 macropore가 기공부피의 대부분을, mesopore가 비표면적의 대부분을 제공하고 있었다. 소성온도를 650 $^{\circ}C$에서 750 $^{\circ}C$로 증가시킴에 따라 대체로 강도가 감소하는 경향을 나타내었다. 열중량분석기로 측정된 황 흡수능은 약 10 wt%로 나타났다. 제조된 탈황제 중 일부는 유동층 공정에 적합한 물성을 보유하고 있었으며 반응성 또한 기존에 개발된 탈황제에 버금가는 성능을 나타내어 향후 공정 적용이 가능할 것으로 분석되었다.

• Polymer(Korea)
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• v.25 no.6
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• pp.774-781
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• 2001

In order to reuse the waste matters, the polyester hybrid composites were fabricated with the waste stone (WSP) and waste tire (WTC). Before mixing, the waste fillers were treated with the silane coupling agent [${\gamma}$-methacryloxy propyl trimethoxy silane(${\gamma}$-MPS)] for enhancing the dispersion of the fillers and interfacial bonding with polymer matrix. Mechanical properties and morphologies of the resulted hybrid composites were investigated with the filler content. The hybrid composites containing surface treated fillers have high initial thermal decomposition temperature and low weight loss compared to the untreated one. The highest mechanical properties of composites were obtained with the ${\gamma}$-MPS (2 wt%) treated fillers. The porosity of composite increased with the content of organic filler which can be reduced by the silane surface treatment of fillers. The pore size distribution of the composites varied with the waste filler content.

• Journal of Technologic Dentistry
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• v.23 no.2
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• pp.179-188
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• 2002

With regard to the manufacture of dental prosthesis, all the dental mechanism is of vital significance at the aspect of activating its function by fixing the prosthesis to Patient's oral cavity. However, if there we will take our immediate action without the discretion about its process none the less for the importance of dental mechanism, then we might have a serious problem. Accordingly, there need to pay attention to the dilatability makes up for the shrinkage state occurring by the feature of metal materials and manufacturing process which appeared in the process of dental mechanism, which eventually is expected to playa very important role in casting a dental prosthesis appropriate to one's oral tissue. This study was designed to take into account of the effects on margin consistency of prosthesis according to the continued time of casting-ring in the course of the casting of dental alloy. For this, the researcher made an experiment on the casting of dental alloy, its dilatability, and the change of phase. The results of this study were as follows: First, the researcher could see that the sample which was cast under the condition of $650^{\circ}C/20$ Minutes(the continued time) was far superior to others at the aspect of margin consistency. Second, according to the measurement of expansion coefficient by Dilatometer, the researcher perceived the fact that the expansion-coefficient showed a maximum of $37.1{\mu}m$ considering the sample's length which was cast with ordinary temperature under the condition of $650^{\circ}C/20$ Minutes. Third, from the result of X-ray diffraction under the condition of $650^{\circ}C/20$ Minutes(the continued time), the researcher could find that there's no difference between the change of phase and its intensity. As mentioned above, the researcher could ascertain the fact that its contraction don't give rise to the change of phase.

• Journal of Technologic Dentistry
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• v.30 no.1
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• pp.73-82
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• 2008

This study has been analyzed to write an ideal training evaluation table after analyzing validity of content organization and assigning score of evaluating elements of clinical practice of Dept. of dental technology. 220 junior students who are studying dental technology in D university in Daegu were questioned to analyze the relationship of content organization and score of clinical practice evaluation table. The corrected material has been inspected by SAS V8 for Windows. The results are as following. 1. The validity of content organization of clinical practice evaluation table has a result which can be reliable over than 70% but the validity of score shows low reliance. c 2. The validity of content organization of detail elements of clinical practice evaluation shows that overuse of material and attentiveness(3.78) and responsibility (3.60) are high response but in score organization, the validity shows that safety measure(2.36) when controling machines, arrangement(2.98) after use and ability (2.98) of solving problems are very low. 3. In the elements without interpersonal relation, it shows that those are related to each other. its grading is p < 0.01 so it appears to be meaningful. 4. In result of analyzing the effect to 'studying amount' mark in clinical practice evaluation mark, it appears the element of attitude for job to affect it. And in result of analyzing the effect to 'training attitude' mark, it appears the element of 'controling machines' to affect it. For these results, to be a better evaluation tool, it should be modified by continuous research with arranging evaluation elements to be marked differently in between elements.

• Journal of Technologic Dentistry
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• v.39 no.2
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• pp.83-91
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• 2017

Purpose: The objective of this study was to evaluate influence of mechanical properties of gingival shade composite resins(GSCRs) according to thermocycling treatment. Methods: The material utilized in this study was Crea.lign(CGR), Twiny flow(TGF) and Twiny(TGP). Total sixty specimens were fabricated with a dimension of $25{\times}2{\times}2mm$ according to the ISO 4049. After fabrications, specimens of before and after thermocycling(to $55^{\circ}C$ from $5^{\circ}C$) were stored in the distilled water for 24 hours at the $37^{\circ}C$. Three-point flexural test was performed in universal testing machine(Instron 5966, USA) at a crosshead speed of 1 mm/min. Flexural strength, flexural modulus and work of fracture according to the thermocycling were analyzed using a one-way ANOVA analysis. Surface analysis of GSCRs after thermocycling evaluated using the scanning electron microscope. Results: : The highest FS was measured in TGP group of NTC group and lowest in CGR group after TC. After TC, FS and FM decreased in CGR and TGP groups, but TGF increased. There was a statistically significant difference between FS and WOF in GSCRs(p<0.05). But FM did not show any significant difference after TC (p>0.05). The strength of the characteristic exceeded the flexural strength required by ISO 4049(> 80 MPa). Weibull modulus(m) showed the highest reliability in the TGP group (m = 14.22), and the reliability of the TGF and TGP groups after TC decreased. Conclusion: Thermocycling treatment is important factor influence of mechanical properties with gingival shade composite resins. Therefore, we recommended that mechanical properties need to get useful information and accuracy for life-span expectancy according to the thermocycling treatment.

• Journal of Technologic Dentistry
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• v.32 no.4
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• pp.359-367
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• 2010

Purpose: This study was conducted to investigate the wearing dentures status of the elderly and understand the relationship between demographic sociological properties, oral health care habits, lifestyle, and whether they wears dentures or not. Methods: In a surveying of 349 elderly who lives in Daegu and Kyung-pook, following results are obtained. Results: Wearing dentures rates of the aged are 58.5%. The more the aged is female(p=0.025), elderly(p=0.000), a low education level(p=0.000), no job(p=0.006), and a solitary person(p=0.016) the higher rate they wears dentures. The more the aged brushes their teeth after each meal(p=0.029) and uses the oral health devices(p=0.000) the lower rate they wears dentures. The more the aged have dinner alone(p=0.009), do not kept up with the exercises (p=0.000), and would like to dine off a soft food(p=0.000) the higher rate they wears dentures. Conclusion: This study showed that an old people's condition of oral health care who live in Daegu Kyungpook is very serious. Therefor not only an elderly but other aged people is need of constant and organized education for taking their oral health care habits and changing their lifestyle. Because wearing dentures rates of the aged by demographic sociological properties, oral health care habits, and lifestyle is lower.