저항을 이용한 프로판-공기 혼합가스의 점화한계 개선에 관한 연구

이춘하,오종용,옥경재,지승욱,이광식,심광렬 한국화재소방학회 2004 한국화재소방학회논문지 Vol.18 No.1

본 논문은 IEC형 불꽃점화 시험장치를 이용하여 저압 유도회로의 최소 점화한계를 프로판-공기 5.25 Vol.%의 혼합 가스에 대하여 실험적으로 구하였으며, 또한 유도회로의 인덕턴스 L에 안전소자로서 저항을 병렬접속하였을 경우 프로판-공기 5.25 Vol.%의 혼합 가스에 대한 점화한계 개선효과를 관찰하였다. 그 결과, 최소 점화한계는 전류의 크기에 따라 좌우되었다 또한, 전원으로부터 공급되는 에너지는 인덕턴스에 우선 축적되고. 그 초과분의 에너지가 폭발성 가스의 점화원으로 작용하였다. 점화한계 개선효과는 인덕턴스가 300 mH일 때, 최고 330%의 개선효과가 나타났으며 인덕턴스가 클수록 점화한계 개선효과가 크게 나타났다. 또한 병렬로 접속한 저항의 크기가 적을수록 점화한계 개선 효과가 크다. 본 연구결과는 본질안전 방폭형 전기기기의 연구개발을 위한 기본자료로 활용할 수 있을 뿐만 아니라 이들 기기의 방폭성능에 대한 시험자료로도 활용이 가능할 것으로 사료된다. This paper describes the minimum ignition limits for propane-air 5.25 Vol.% mixture gases in low voltage inductive circiuts. The improved effects on the ignition limit are studied by parallel safety components(resistors) for propane-air 5.25 Vol.% mixture gas in low voltage inductive circuits. The experimental devices used in this test are the IEC type spark ignition test apparatus. The minimum ignition limits are controlled by the values of current in inductive circuit. Energy supplied from elect source is first accumulated at the inductance, it's extra energy is working as ignition source of the explosive gas. The improved effects on the ignition limit are respectively obtained as the maximum rising rate of 330% by composing parallel circuits between inductance and resistor as compared with disconnecting inductance with the safety components. The more values of inductance increase the higher improved effects of ignition limit rise. The less values of resistor the higher improved effects of ignition limit rise. It is considered that the result can be used for not only data for researches and development of intrinsically safe explosion-proof machines which are applied equipment and detectors used in dangerous areas but also for datum for its equipment tests.

Biomechanical three-dimensional finite element analysis of monolithic zirconia crown with different cement type

Ha, Seung-Ryong The Korean Academy of Prosthodonitics 2015 The Journal of Advanced Prosthodontics Vol.7 No.6

PURPOSE. The objective of this study was to evaluate the influence of various cement types on the stress distribution in monolithic zirconia crowns under maximum bite force using the finite element analysis. MATERIALS AND METHODS. The models of the prepared #46 crown (deep chamfer margin) were scanned and solid models composed of the monolithic zirconia crown, cement layer, and prepared tooth were produced using the computer-aided design technology and were subsequently translated into 3-dimensional finite element models. Four models were prepared according to different cement types (zinc phosphate, polycarboxylate, glass ionomer, and resin). A load of 700 N was applied vertically on the crowns (8 loading points). Maximum principal stress was determined. RESULTS. Zinc phosphate cement had a greater stress concentration in the cement layer, while polycarboxylate cement had a greater stress concentration on the distal surface of the monolithic zirconia crown and abutment tooth. Resin cement and glass ionomer cement showed similar patterns, but resin cement showed a lower stress distribution on the lingual and mesial surface of the cement layer. CONCLUSION. The test results indicate that the use of different luting agents that have various elastic moduli has an impact on the stress distribution of the monolithic zirconia crowns, cement layers, and abutment tooth. Resin cement is recommended for the luting agent of the monolithic zirconia crowns.

Comparison of polymer-based temporary crown and fixed partial denture materials by diametral tensile strength

Ha, Seung-Ryong,Yang, Jae-Ho,Lee, Jai-Bong,Han, Jung-Suk,Kim, Sung-Hun 대한치과보철학회 2010 The Journal of Advanced Prosthodontics Vol.2 No.1

PURPOSE. The purpose of this study was to investigate the diametral tensile strength of polymer-based temporary crown and fixed partial denture (FPD) materials, and the change of the diametral tensile strength with time. MATERIAL AND METHODS. One monomethacrylate-based temporary crown and FPD material (Trim) and three dimethacrylate-based ones (Protemp 3 Garant, Temphase, Luxtemp) were investigated. 20 specimens (Ø 4 mm × 6 mm) were fabricated and randomly divided into two groups (Group Ⅰ: Immediately, Group Ⅱ: 1 hour) according to the measurement time after completion of mixing. Universal Testing Machine was used to load the specimens at a cross-head speed of 0.5 mm/min. The data were analyzed using one-way ANOVA, the multiple comparison Scheffe′test and independent sample t test (α= 0.05). RESULTS. Trim showed severe permanent deformation without an obvious fracture during loading at both times. There were statistically significant differences among the dimethacrylate-based materials. The dimethacrylate-based materials presented an increase in strength from 5 minutes to 1 hour and were as follows: Protemp 3 Garant (23.16 - 37.6 MPa), Temphase (22.27 - 28.08 MPa), Luxatemp (14.46 - 20.59 MPa). Protemp 3 Garant showed the highest value. CONCLUSION. The dimethacrylate-based temporary materials tested were stronger in diametral tensile strength than the monomethacrylate-based one. The diametral tensile strength of the materials investigated increased with time.

The influence of various core designs on stress distribution in the veneered zirconia crown: a finite element analysis study

Ha, Seung-Ryong,Kim, Sung-Hun,Han, Jung-Suk,Yoo, Seung-Hyun,Jeong, Se-Chul,Lee, Jai-Bong,Yeo, In-Sung The Korean Academy of Prosthodonitics 2013 The Journal of Advanced Prosthodontics Vol.5 No.2

PURPOSE. The purpose of this study was to evaluate various core designs on stress distribution within zirconia crowns. MATERIALS AND METHODS. Three-dimensional finite element models, representing mandibular molars, comprising a prepared tooth, cement layer, zirconia core, and veneer porcelain were designed by computer software. The shoulder (1 mm in width) variations in core were incremental increases of 1 mm, 2 mm and 3 mm in proximal and lingual height, and buccal height respectively. To simulate masticatory force, loads of 280 N were applied from three directions (vertical, at a $45^{\circ}$ angle, and horizontal). To simulate maximum bite force, a load of 700 N was applied vertically to the crowns. Maximum principal stress (MPS) was determined for each model, loading condition, and position. RESULTS. In the maximum bite force simulation test, the MPSs on all crowns observed around the shoulder region and loading points. The compressive stresses were located in the shoulder region of the veneer-zirconia interface and at the occlusal region. In the test simulating masticatory force, the MPS was concentrated around the loading points, and the compressive stresses were located at the 3 mm height lingual shoulder region, when the load was applied horizontally. MPS increased in the shoulder region as the shoulder height increased. CONCLUSION. This study suggested that reinforced shoulder play an essential role in the success of the zirconia restoration, and veneer fracture due to occlusal loading can be prevented by proper core design, such as shoulder.

Biomechanical three-dimensional finite element analysis of monolithic zirconia crown with different cement type

Seung-Ryong Ha 대한치과보철학회 2015 The Journal of Advanced Prosthodontics Vol.7 No.6

PURPOSE. The objective of this study was to evaluate the influence of various cement types on the stress distribution in monolithic zirconia crowns under maximum bite force using the finite element analysis. MATERIALS AND METHODS. The models of the prepared #46 crown (deep chamfer margin) were scanned and solid models composed of the monolithic zirconia crown, cement layer, and prepared tooth were produced using the computer-aided design technology and were subsequently translated into 3-dimensional finite element models. Four models were prepared according to different cement types (zinc phosphate, polycarboxylate, glass ionomer, and resin). A load of 700 N was applied vertically on the crowns (8 loading points). Maximum principal stress was determined. RESULTS. Zinc phosphate cement had a greater stress concentration in the cement layer, while polycarboxylate cement had a greater stress concentration on the distal surface of the monolithic zirconia crown and abutment tooth. Resin cement and glass ionomer cement showed similar patterns, but resin cement showed a lower stress distribution on the lingual and mesial surface of the cement layer. CONCLUSION. The test results indicate that the use of different luting agents that have various elastic moduli has an impact on the stress distribution of the monolithic zirconia crowns, cement layers, and abutment tooth. Resin cement is recommended for the luting agent of the monolithic zirconia crowns.

A pilot study using machine learning methods about factors influencing prognosis of dental implants

Ha, Seung-Ryong,Park, Hyun Sung,Kim, Eung-Hee,Kim, Hong-Ki,Yang, Jin-Yong,Heo, Junyoung,Yeo, In-Sung Luke The Korean Academy of Prosthodonitics 2018 The Journal of Advanced Prosthodontics Vol.10 No.6

PURPOSE. This study tried to find the most significant factors predicting implant prognosis using machine learning methods. MATERIALS AND METHODS. The data used in this study was based on a systematic search of chart files at Seoul National University Bundang Hospital for one year. In this period, oral and maxillofacial surgeons inserted 667 implants in 198 patients after consultation with a prosthodontist. The traditional statistical methods were inappropriate in this study, which analyzed the data of a small sample size to find a factor affecting the prognosis. The machine learning methods were used in this study, since these methods have analyzing power for a small sample size and are able to find a new factor that has been unknown to have an effect on the result. A decision tree model and a support vector machine were used for the analysis. RESULTS. The results identified mesio-distal position of the inserted implant as the most significant factor determining its prognosis. Both of the machine learning methods, the decision tree model and support vector machine, yielded the similar results. CONCLUSION. Dental clinicians should be careful in locating implants in the patient's mouths, especially mesio-distally, to minimize the negative complications against implant survival.

Implant-supported overdenture with prefabricated bar attachment system in edentulous mandibular patient

Seung-Ryong Ha,Sung-Hun Kim,Seung-Il Song,Seong-Tae Hong,Gy-Young Kim 대한치과보철학회 2012 The Journal of Advanced Prosthodontics Vol.4 No.4

Implant-supported overdenture is a reliable treatment option for the patients with edentulous mandible when they have difficulty in using complete dentures. Several options have been used for implant-supported overdenture attachments. Among these, bar attachment system has greater retention and better maintainability than others. SFI-Bar(R) is prefabricated and can be adjustable at chairside. Therefore, laboratory procedures such as soldering and welding are unnecessary, which leads to fewer errors and lower costs. A 67-year-old female patient presented, complaining of mobility of lower anterior teeth with old denture. She had been wearing complete denture in the maxilla and removable partial denture in the mandible with severe bone loss. After extracting the teeth, two implants were placed in front of mental foramen, and SFI-Bar(R) was connected. A tube bar was seated to two adapters through large ball joints and fixation screws, connecting each implant. The length of the tube bar was adjusted according to inter-implant distance. Then, a female part was attached to the bar beneath the new denture. This clinical report describes two-implant-supported overdenture using the SFI-Bar(R) system in a mandibular edentulous patient.

동적수질예측결과의 확률분포특성을 이용한 목표수질 달성가능성 평가

하성룡 ( Sung Ryong Ha ),이지헌 ( Ji Heon Lee ),서세덕 ( Se Deok Seo ),이승철 ( Seung Chul Lee ),박정하 ( Jung Ha Park ) 한국환경영향평가학회 2008 환경영향평가 Vol.17 No.1

The Role of p53 in Marijuana Smoke Condensates-induced Genotoxicity and Apoptosis

Ha Ryong Kim,Bo Hee Son,Soo Yeun Lee,Kyu Hyuck Chung,Seung Min Oh 환경독성보건학회 2012 환경독성보건학회지 Vol.27 No.-

Objectives: Marijuana is one of the most frequently abused drug in Korea and its adverse health effects are controversial. p53 is known to be crucial in regulating the DNA damage responses, and adverse effects can occur when it is regulated by marijuana smoke. We evaluated a role of p53 on genotoxic effect and apoptosis in lung cancer cells exposed to marijuana smoke condensates (MSCs). Methods: The p53-related genotoxicity and apoptosis of MSCs were evaluated using in vitro bioassay, viz., comet assay, cytokinesis-block micronucleus assay and apoptosis assay. We used two cell lines with differential p53 expression (p53-wildtype (WT) H460 and p53-null H1299). Results: MSCs significantly increased DNA breakages and chromosomal changes in p53-WT H460 and p53-null H1299 cells. The genotoxicity induced by MSCs in p53-null H1299 cells showed greater sensitivity than p53-WT H460 cells. Moreover, MSCs showed a significant increase in reactive oxygen species production and apoptosis. The apoptotic responses induced by MSCs were higher in p53-WT H460 cells than in p53-null H1299 cells. Significantly increased mRNA expression or apoptosis related genes, including p53, caspase-3, and Bax/Bcl-2 ratio were observed in the p53-WT H460 cells exposed to MSCs. Conclusions: These results suggest that MSCs induce DNA/chromosomal damages and apoptosis in human lung cancer cells and p53 plays an important role in the cellular response to MSCs. The present study may have border implications for our understanding of pulmonary diseases.

홍수터 여과 모형을 이용한 하천수종의 유기물과 질소 제거

하현수,김상태,김승현,정종배,정병룡,이영득,엄진섭,지승환 한국농화학회 2002 Applied Biological Chemistry (Appl Biol Chem) Vol.45 No.2

유기물과 질소 함량이 높은 하천수가 대하천에 유입되기전 소하천의 잡초가 자라는 홍수터에 살포하여 사질 토층을 수직 이동하는 도안 잡초의 근권에서 유기물의 분해와 함께 탈질에 의해 질소가 제거되도록 하는 홍수터여과공법을 개발하였다. 직경 15㎝,길이 150㎝의 PVC pipe에 실제 흥수터에서 채취한 사질의 토양을 층진하여 제작된 흥수터 모형에 하천수물 27.2,40.8,68.0 ㎖/day^1/㎡의 유량으로 연속적으로 살포라고 정상상태에 이른 후 토양 깊이별로 토양 용액을 체취하여 유기물과 NO_3-N을 비롯한 무기질소의 이동과 제거 현상을 조사하였고 토양 기체를 체취하여 N_2와 N_2O의 발생 현상을 측정하였다. 포화상태에 가까운 수준으로 유량을 조절할 경우 하천수에 포함된 유기물만을 이용하더라도 매우 효과적인 탈질 환경이 5㎝ 깊이 부근의 표층 토양에서부터 형성되었으며 유기물의 제거와 함께 질소도 효과적으로 제거할 수 있는 것으로 나타났다. 90㎝ 깊이의 흥수터 토양을 통과하는 동안 평균적으로 COD는 18.7에서 5㎎/l로 무기질소함량은 2.7에서 0.4㎎/l로 정화되었다. 탈질 기체는 대부분 N_2형태로 발생되었으며 온실효과와 오존층 파괴를 유발하는 N_2O발생량은 매우 적었다.표층 토양에 잡초의 근권이 형성되어 있는 실제 홍수터에 이와 같은 기법을 적용할 경우 모형 실험에서 나타난 결과보다 더욱 활발한 탈진 현상이 유발될 수 있을 것으로 판단된다. 이러한 흥수터 여과는 부지과 따로 필요하지 않으므로 시설 및 운영비가 경쟁기술에 비해 싸고, 화학약품 처리나 슬러지 발생이 없는 환경친화적인 하천수 처리방법이 될 것으로 기대하며, 하천수 외에도 도시하수나 산업폐수의 3차 처리에도 응용되어 하폐수의 재활용을 통한 수자원으 절약과 하천수량의 중대에도 기여할 수 있을 것이다. If contaminated river water is sprayed over the floodplain, organic matter and nitrogen would be removed by microbial in the rhizosphere of vegetation during the filtration through soil.In this study we tested the organic matter and nitrogen removal from contaminated river water by the floodplain.Model system of floodplain was constructed using a PVC pipe (15 ㎝ i.d ×150 ㎝ L) which was packed with a loamy sand soil collected from a floodplain in Nakdong river. The model system was instrumented with soil solution samlers and gas samplers. A river water collected from Omogcheon in Kyongsan was sprayed from top of the model system at three different rates. The model system was instrumented with soil solution samplers and gas samplers. A rier water collected from Omaogcheom in Kyongsan was sprayed from top of the model system at three differednt rates. The concentration of organic matter. DO,NO_3-,NH_4+,N_2 and N_2O, and redox potential were measured as a function of soil depth for 24 days after the system steady state. When river water was sprayed at the rates of 40.8 and 68.0 ㎛^2/day, a significant reductive condition for denitrification was developed at below 5-cm depth of the soil. When the water reached at 90~cm depth of the soil, COD and concentration of inorganic nitrogen were lowered, on an average, from 18.7 to 5㎎/l and from 2.7 to 0.4 ㎎/l, respectively. N_2 comprised most of the N gas evolved from denitrification and N_2O concentrations emitted at the surface of soil were less than 1 ㎕/l. The effective removal of organic matter and nitrogen by the filtrtion in the model system of floodplain demonstrates that the native floodplains, which include rhizosphere of vegetation at the top soil, could be more effective in the treatment of contarninated river waters and other industrial waste waters containing high concentration of organic matter and nitrogen.