• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1018-1021
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• 2006

Powdered metal parts and components may be carburized successfully in a vacuum furnace by combining carburizing technology $VacCarb^{TM}$ with a hi-tech control system. This approach is different from traditional carburizing methods, because vacuum carburizing is a non-equilibrium process. It is not possible to set the carbon potential as in a traditional carburizing atmosphere and control its composition in order to obtain a desired carburized case. This paper presents test results that demonstrate that vacuum carburizing system $VacCarb^{TM}$ carburized P.M. materials faster than traditional steel with acceptable results. In the experiments conducted, PM samples with the lowest density and open porosity showed a dramatic increase in the surface carbon content up to 2.5%C and a 3 times deeper case. Currently the boost-diffusion technique is applied to control the surface carbon content and distribution in the case. In the first boost step, the flow of the carburizing gas has to be sufficient to saturate the austenite, while avoiding soot deposition and formation of massive carbides. To accomplish this goal, the proper gas flow rate has to be calculated. In the case of P.M. parts, more carbon can be absorbed by the part's surface because of the additional internal surface area created by pores present in the carburized case. This amount will depend on the density of the part, the densification grade of the surface layer and the stage of the surface. "as machined" or "as sintered". It is believed that enhanced gas diffusion after initial evacuation of the P.M. parts leads to faster carburization from within the pores, especially when pores are open . surface "as sintered" and interconnected . low density. A serious problem with vacuum carburizing is delivery of the carbon in a uniform manner to the work pieces. This led to the development of the different methods of carburizing gas circulation such as the pulse/pump method or the pulse/pause technique applied in SECO/WARWICK's $VacCarb^{TM}$ Technology. In both cases, each pressure change may deliver fresh carburizing atmosphere into the pores and leads to faster carburization from within the pores. Since today's control of vacuum carburizing is based largely on empirical results, presented experiments may lead to better understanding and improved control of the process.

• Restorative Dentistry and Endodontics
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• 제38권3호
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• pp.154-159
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• 2013

Objectives: The aim of this study was to compare the cleaning efficacy of different final irrigation regimens in canal and isthmus of mandibular molars, and to evaluate the influence of related variables on cleaning efficacy of the irrigation systems. Materials and Methods: Mesial root canals from 60 mandibular molars were prepared and divided into 4 experimental groups according to the final irrigation technique: Group C, syringe irrigation; Group U, ultrasonics activation; Group SC, VPro StreamClean irrigation; Group EV, EndoVac irrigation. Cross-sections at 1, 3 and 5 mm levels from the apex were examined to calculate remaining debris area in the canal and isthmus spaces. Statistical analysis was completed by using Kruskal-Wallis test and Mann-Whitney U test for comparison among groups, and multivariate linear analysis to identify the significant variables (regular replenishment of irrigant, vapor lock management, and ultrasonic activation of irrigant) affecting the cleaning efficacy of the experimental groups. Results: Group SC and EV showed significantly higher canal cleanliness values than group C and U at 1 mm level (p < 0.05), and higher isthmus cleanliness values than group U at 3 mm and all levels of group C (p < 0.05). Multivariate linear regression analysis demonstrated that all variables had independent positive correlation at 1 mm level of canal and at all levels of isthmus with statistical significances. Conclusions: Both VPro StreamClean and EndoVac system showed favorable result as final irrigation regimens for cleaning debris in the complicated root canal system having curved canal and/or isthmus. The debridement of the isthmi significantly depends on the variables rather than the canals.

• 대한방사선치료학회지
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• 제18권2호
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• pp.89-96
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• 2006

목 적: 방사선치료를 목적으로 촬영된 CT영상을 이용하여 조직내 불균질 물질 및 체위고정 기구에 대한 보정이 선량계산 결과에 미치는 영향을 알아보고자 한다. 대상 빛 방법: 체내불균질 물질의 다양한 사례를 알아보기 위하여 본원에서 제작한 물팬텀($250{\times}250{\times}250mm^3$) 내부에 (1) 뼈 (2) 금속 (3) 조영제 (4) 고정기구(Head holder/Vac-lok) 등 CT Number를 변화시킬 수 있는 물질을 삽입하여 CT촬영을 시행 하였다. 각기 다른 형태의 불균질 CT영상을 전산화치료계획장치(RTP)에 입력하여 동일한 조건(SAD=100 cm 조사야=$10{\times}10cm^2$, 깊이=10cm, 1문조사)으로 에너지별(4, 6, 10 MV X-선) 처방선량 100 cGy를 얻기 위한 선량계산(MU)을 시행하여 비교, 분석하였다. 결 과: 물로만 구성된 팬텀을 기준값으로, 불균질 보정계수 차이는 뼈조직 상태인 경우는 $2.7{\sim}5.3%$, 금속물질인 경우 $2.7{\sim}3.8%$, 조영제인 경우 $0.9{\sim}2.3%$, Head holder $0.9{\sim}2.3%$, Head holder와 Pillow인 경우 $3.5{\sim}6.9%$, 그리고 Vac-lok인 경우 $0.9{\sim}1.5%$의 차이로 나타났다. 결 론: 체내의 불균질 보정계수 차이는 임상적으로 그 적용 형태가 다양하고, 일관성을 보이지 않으며, 조사문수가 증가함에 따라 그 차이가 1%미만으로 허용 가능할 것이나, 고정 기구등에 의한 불균질 보정은 충분히 고려하여 선량계산의 부정확도를 최소화 시켜야 할 것으로 사료된다.

• 대한미생물학회지
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• 제35권5_6호
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• pp.363-363
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• 2000

• 대한족부족관절학회:학술대회논문집
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• 대한족부족관절학회 2008년도 추계학술대회 및 총회
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• pp.21-21
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• 2008

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1563-1565
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• 1999

Linear and nonliear complex permittivities have been measured for amorphous copolymers of vinylidene cyanide (VDCN) with vinyl acetate (VAc), vinyl propionate (VPr), vinyl benzoate (VBz), styrene (St) and methyl methacrylate (MMA). It is found that the third order permittivity ${\varepsilon}_3$ depends upon frequency according to a function ${\Delta}_{{\varepsilon}_3}/(1+i{\omega}{\tau}_^3)$ while the linear permittivity obeys a Debye function ${\Delta}_{{\varepsilon}_1}/(1+i{\omega}{\tau}_1)$. Experimental results are well fitted by the above predicted functions except at low frequencies where dc conduction dominates. The ${\tau}_1$ and ${\tau}_3$ are nearly equal, and depend upon temperature according to a WLF form. The relaxation strength ${\Delta}_{{\varepsilon}_1}$ depends upon comonomers ranging from $130_{{\varepsilon}_0}$(VAc) to $20{{\varepsilon}_0}$(MMA). The ${\Delta}_{{\varepsilon}_3}$ is negative and depends more strongly upon comonomers. Combined knowledge about linear and nonlinear permittivities predicts very large correlation factors which indicates strongly cooperative dipolar motions in those amorphous copolymers.

• 한국인터넷방송통신학회논문지
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• 제12권2호
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• pp.77-83
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• 2012

진공 시스템의 성능에 대한 밸브 컨덕턴스의 영향은 진공시스템의 설계 최적화를 위해 전산모사 되었다. 본 연구에서는, 전산모사기인 VacSimMulti에 의한 모델링기구가 제시되었다. 진공 시스템의 설계는 진공 장비의 다양한 산업적 구현을 위해 특정한 프로세스 조건을 충족해야 한다. 진공 밸브의 구조, 길이, 직경 등은 컨덕턴스 영향의 전산모사 변수로서 모델링 되었으며, 직렬 진공 시스템의 배기 밸브 또한, 다양한 크기와 구조로 모델링하여 전산모사되었다. 밸브 직경의 변화는 도관의 길이의 변화보다 진공특성에 있어 더 유의미한 효과를 보여주었으며 슬릿형의 밸브도관 시스템은 모델링된 밸브구조 중 가장 뛰어난 진공특성을 가지는 것으로 관찰 되었다.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XII)
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• pp.582-586
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• 2003

There has been interest in developing gene therapy based on naked plasmid DNA for treating serum protein deficiencies and human erythropoietin (hEPO) is one of the candidate for gene therapy being Investigated most enthusiastically. We constructed novel plasmid DNA vectors pVAC-hEPOI/II/III which contain one, two, three hEPO gene(s) respectively for producing high level expression and secretion of hEPO in vitro and in vivo. NIH3T3 and COS7 cells were transfected transiently with these vectors and increase in hEPO expression in medium reached 2-5 fold in comparison with pSecTagB-hEPO. Intra muscular administrations of pVAC-hEPOI/II/III vectors into mice resulted in high level secretion of hEPO in the serum and corresponding increases in hematocrit level. In conclusion the transduction efficiency of naked plasmid vectors is one of the critical factors of a gene delivery system and these novel plasmid vectors will contribute to various gene therapy based on naked plasmid DNA.

• 한국대기환경학회지
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• 제21권2호
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• pp.155-160
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• 2005

Removal of methyl mercaptan was investigated using adsorption on virgin activated carbon (VAC) and modified activated carbons with acidic chemicals in the present work. CAC, NAC, AAC and SAC were represented as activated carbons modified with HCI, HNO$_{3}$, CH$_{3}$COOH and H$_{2}$S0$_{4}$ ,respectively The pore structures were evaluated using nitrogen isotherm. The surface properties of virgin activated carbon and modified activated carbons were characterized by EA, pH of carbon surface and acid value from Boehm titration. The modification of activated carbon with acidic chemicals resulted in a decrease in BET surface area, micropore volume and surface pH, but an increase in acid value. The order of the adsorption capacity of activated carbons was NAC>AAC>SAC>CAC>VAC, and in agreement with that of acid value of activated carbons, whereas in disagreement with that of micropore volume of activated carbons. It appeared that chemical adsorption played an important role in methyl mercaptan on modified activated carbons with acidic chemicals compared to virgin activated carbon. Modifying activated carbon with acidic chemicals enabled to significantly enhance removal of methyl mercaptan.

• Journal of Trauma and Injury
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• 제27권2호
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• pp.29-32
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• 2014

Pelvic bone fracture with hemodynamic instability is fatal and the mortality rate can range up to 40%. Despite the big advances in the treatment of massive bleeding and hemorrhagic shock, the mortality associated with hemodynamically unstable pelvic bone fractures remains high. The gold standard of treatment for pelvic bone fracture with hemodynamic instability has not yet been determined and is an issue of main discussion among many doctors. Retroperitoneal packing is not yet wide spread in Korea, but is a good modality for managing of massive bleeding from pelvic bone fractures when an angiography suite or an expert surgeon is not available. A vacuum-assisted closure (VAC) system can also be applied with retroperitoneal packing in the manner of damage control surgery and open abdomen surgery. We present the case of a 51-year-old male who had a pelvic bone fracture with massive bleeding. We performed retroperitoneal gauze packing with a VAC system for the first time. The postoperative vital signs of patient were immediately stable, the massive bleeding was easily and quickly controlled, and the amount of transfusion of blood components was reduced.