• 구강회복응용과학지
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• 제26권2호
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• pp.121-143
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• 2010

본 연구의 목적은 임플란트 형태 및 골 흡수가 피로 파절에 미치는 효과를 평가하는 것이다. 오스탬 임플란트 4가지 형태 즉 외부 연결 평행형, 내부 연결 평행형, 외부 연결 첨형, 내부 연결 첨형 선정하고, 8개 군으로 분류하였다. 또한 식립 높이에 따른 피로 수명 변화 조사하기 위하여 시료 고정 지그 표면으로부터 고정체를 각각 2mm, 4mm 노출시켜 피로 시험을 시행하였다. 피로 파절 실험은 하중 조건을 최대 하중 600N, 최소 하중 60N으로 하였으며, 스테인리스 스틸로 지그 제작하여 동적 하중 피로 시험기에 연결하고 고정 후 실온에서 14Hz로 실험하였다. 고정체, 지대주 나사 파절 양상, 파절 위치 등 관찰하기 위해 주사전자현미경 사용하였으며, 유한 요소 분석 하여 고정체, 지대주 나사에 나타나는 응력 분포, 파절면 양상 비교 분석하여 다음의 결과를 얻었다. 1. 고정체를 2mm 노출시켜 피로 시험시 첨형 임플란트 피로 수명이 평행형보다 높고, 외부 연결형이 내부 연결형보다 높았다. 2. 고정체를 4mm씩 노출시켜 피로 시험시 평행형 임플란트 피로 수명이 첨형보다 높고, 외부 연결형 임플란트 피로수명이 내부 연결형보다 높았다. 3. 고정체 노출 높이가 2mm인 경우 내부 연결형은 모두 지대주 몸체, 고정체 육각부 접하는 경계부에서 수평으로 피로 파절 발생하였고, 외부 연결형은 고정체 육각부에서 고정체 나사부 방향으로 경사지게 또는 고정체 사공 간부에서 피로 파절 발생하였다. 고정체가 4mm 노출된 경우 임플란트 종류 무관하게 지대주 나사 첨부 고정체 사공간부에서 주로 발생하였다. 4. 피로 파절면 관찰은 모든 군에서 피로 줄무늬를 보였으며 취성파괴 특징인 벽개파면, 연성파괴 특징인 딤플무늬 등이 혼재되어 나타났다. 5. 압축력 받는 협측 유효 응력이 인장력 받는 설측보다 높고, 고정체에 작용하는 유효 응력이 지대주 나사에 작용하는 것보다 높았으며, 고정체에 작용하는 최대 유효 응력은 평행형에서 높았다. 따라서 교합력 많이 받는 구치부에서 내부 연결형 임플란트 식립시 각별한 주의 필요하다고 사료된다.

• Current Research on Agriculture and Life Sciences
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• 제8권
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• pp.107-113
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• 1990

본(本) 연구(硏究)는 고성능(高性能) 농약(農藥) 살포기인 스피드 스프레이어에 있어서 농약(農藥)살포 시(時) 인체(人體)에 해로운 농약(農藥)으로부터 오퍼레이터를 보호(保護)하기 위하여 무인(無人) 운전(運轉) 연구(硏究)의 일환(一環)으로 원칩 마이크로 컴퓨터를 이용(利用)하여 원격조종(遠隔操縱) 변속장치(變速裝置)를 개발(開發)할 목적(目的)으로 수행(遂行)한 연구(硏究)에서 얻어진 결과(結果)를 要約(요약)하면 다음과 같다. 1. 시작(試作)한 원칩 마이크로 컴퓨터를 이용(利用)한 원격조종(遠隔操縱) 변속장치(變速裝置)는 변속조작(變速操作) 100회(回) 중(中) 오동작(吳動作)이 전무(全無)하여 조작성(操作性)이 정확(正確)하였다. 2. 使用된 원칩 마이크로 컴퓨터의 프로그램은 기계어(機械語)로 작성(作成)되었으며, 변속조작(變速操作) 시간(時間)이 3초(初) 이내(以內)로 사람에 의한 변속조작(變速操作) 시간(時間)과 거의 같았다. 3. 본(本) 연구(硏究)에 사용(使用)한 원칩 마이크로 컴퓨터는 지금까지 자동화(自動化) 장치(裝置)에 많이 도입(導入) 사용(使用)하던 퍼스널 컴퓨터, 랩탑 컴퓨터, 원 보오도 컴퓨터 등과 비교하여 볼 때 극소형(極小型)으로 소비전력(消費電力)이 작으며 염가(廉價)이기 때문에 농업용(農業用)으로 적합(適合)하다고 사료(思料)된다. 4. 본(本) 연구(硏究)에 사용(使用)된 변속장치(變速裝置)는 승용(乘用) 농업기계(農業機械)와 같은 형식(形式)의 것이므로 농업용(農業用) 트렉터 및 포장기계(圃場機械)의 자동화(自動化) 기계(機械)에도 적용(適用)될 것으로 판단(判斷)된다. 5. 본(本) 실험장치(實驗裝置)는 직접(直接)레버조작(操作) 및 원격조종(遠隔操縱)이 동시(同時)에 이루어지도록 제작(製作)하였기 때문에 구조적(構造的)으로 복잡(複雜)하나 직접(直接)레버 조작부(操作部)를 제거(除去)하고 원격조종부(遠隔操縱部)만 스피드 스프레이어에 장착(裝着)하면 더욱더 소형화(小型化) 되고 중량(重量)도 더 가벼워져 사용(使用)하기에 편리(便利)한 장치(裝置)가 될 것으로 사료(思料)된다.

• 산업경영시스템학회지
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• 제40권4호
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• pp.164-170
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• 2017

The CNC machine tool field is showing a growing trend with the recent rapid development of manufacturing industries such as semiconductors, automobiles, medical devices, various inspection and test equipment, mechanical metal processing equipment, aircraft, shipbuilding and electronic equipment. However, small and medium-sized machining companies that use CNC machine tools are experiencing difficulties in increasingly intense competition. Especially, small companies which are receiving orders from 3rd or 4th venders are very difficult in business management. In recent years, company S experienced difficulty to make product quality and delivery time due to the ignorance of the processing method when manufacturing cooling plate jig made of SUS304 material used for cell phone liquid crystal glass processing. In order to solve these problems, we redesigned the process according to the size of our company and tried to manage all processes with quantified data. In the meantime, we have found that there is a need to improve the cutter process, which accounts for most of the machining process. Therefore, we have investigated the correlation between RPM and FEED of three cutters that have been used in the past. As a result, we found that it is the most urgent problem to solve the roughing process during the cutter operation which occupies more than 70% of the total machining. In order to shorten the machining time and improve the quality in machining of SUS304 cooling plate jig, we select the main factors such as price, tool life, maintenance cost, productivity, quality, RPM, and FEED and use AHP to find the most suitable milling cutter. We also tried to solve the problem of delivery, quality and production capacity which was a big problem of S company through experiment operation with selected cutter tool. As a result, the following conclusions were drawn. First, the most efficient of the three cutters currently available in the machining center has proven to be an M-cutter. Second, although one additional facility was required, it was possible to produce the existing facilities without additional investment by supplementing the lack of production capacity due to productivity improvement. Third, the Company's difficulties in delivery and capacity shortfalls have been resolved. Fourth, annual sales increased by KRW 109 million and profits increased by KRW 32 million annually. Fifth, it can confirm the usefulness of AHP method in corporate decision making and it can be utilized in various facility investment and process improvement in the future.

• 정보과학회 논문지
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• 제43권5호
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• pp.531-540
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• 2016

최근 모바일 환경의 다양한 센서 정보를 이용한 상황인지 서비스가 활발히 연구되고 있다. 본 논문에서는 모바일 및 웨어러블 센서 데이터를 사용해 다양한 맥락에서 나타날 수 있는 사용자의 식사상황을 효과적으로 인식할 수 있는 확률모델을 제안한다. 식사행위와 관련된 상황들을 체계적으로 모델링하기 위해 행위이론의 4가지 행위 요소 및 육하원칙의 5가지 구성 요소들을 모바일 및 웨어러블의 저수준 센서 데이터로 추론 가능한 범위에 맞게 통합하여 인식모델을 구축하고, 트리구조의 베이지안 네트워크 모델링 방식을 사용하여 인식의 경량화를 시도하였다. 제안하는 시스템의 유용성을 입증하기 위하여 1주일간 다양한 배경의 4명 사용자로부터 식사상황 및 일상생활에 대한 383분의 데이터를 수집하였다. 실험결과 기존의 대표적인 분류기들과 비교하여 상대적으로 우수한 인식률(93.21%)이 도출되는 것을 확인하였다. 또한 실제 시나리오를 통한 내부 분석을 수행하여 인식에 사용되는 각 요소들의 유용성을 검증하였다.

• 대한치과기공학회지
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• 제39권2호
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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.

• 대한기계학회논문집A
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• 제39권6호
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• pp.597-602
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• 2015

고장력 Cr-Mo강은 이온질화와 연질화 두가지 질화처리를 수행하였다. 각 질화처리의 특징을 비교하기 위해서 30분의 공정시간을 가지고 질화처리를 하였다. 표면강도의 변화를 비교하기 위해서 비커스 경도 시험이 수행되었으며 피로시험은 켄틸레버 회전굽힘 피로시험기(Yamamoto, YRB 200)를 이용하여 수행되었다. 초고주기영역($N>10^7cycle$)의 특징을 알아보기 위해서 피로시험은 피로한도 이후까지 진행하였다. 피로 시험 후 주사전자현미경(SEM)을 이용해서 파단면을 분석하였으며 고주기영역과 초고주기 영역의 파괴기구를 관찰하였다.

• 한국재료학회지
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• 제23권7호
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• pp.353-358
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• 2013

To improve coating ability and the life of the coating, Ti based composite materials with hydroxyapatite(HA) should be developed. The raw materials of Ti-26wt%, Nb-1wt%, and Si with 10wt% HA were mixed for 24 h by a mixing machine and milled for 1 h to 6 h by planetary mechanical ball milling. Ti-26%Nb-1%Si-(10%HA) composites, composed of nontoxic elements, were fabricated successfully by spark plasma sintering(SPS) at $1000^{\circ}C$ under 70MPa. The relative density of the sintered Ti-Nb-Si-HA composites using the 24 h mixed powder, and the 6 h milled powder, was 91% and 97 %, respectively. The effects of HA contents and milling time on microstructure and mechanical properties were investigated by SEM and hardness tester, respectively. The Vickers hardness of the composites increased with increasing milling time and higher HA content. The Young's modulus of the sintered Ti-26%Nb-1%Si-10%HA composite using the 6 h-milled powder was 55.6 GPa, as obtained by compression test. Corrosion resistance of the Ti-26wt%Nb-1wt%Si composite was increased by milling and by the addition of 10wt%HA. Wear resistance was improved with increasing milling time. Biocompatibility of the Ti-Nb-Si alloys was improved by the addition of HA.

• Food Science and Biotechnology
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• 제15권1호
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• pp.5-12
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• 2006

Degradation performance of environmentally friendly plastics that can be disintegrated by combination of sunlight, microbes in soil, and heat produced in landfills was evaluated for use in industries. Two multi-degradable master batches (MCC-101 and MCC-102 were manufactured, separately mixed with polyethylene using film molding machine to produce 0.025 mm thick films, and exposed to sunlight, microbes, and heat. Low- and high-density polyethylene (LDPE and HDPE) films containing MCC-101 and MCC-102 became unfunctional by increasing severe cleavage at the surface and showed high reduction in elongation after 40 days of exposure to ultraviolet light. LDPE and HDPE films showed significant physical degradation after 100 and 120 days, respectively, of incubation at $68{\pm}2^{\circ}C$. SEM images of films cultured in mixed mold spore suspension at $30^{\circ}C$ and 85% humidity for 30 days revealed accelerated biodegradation on film surfaces by the action of microbes. LDPE films containing MCC-l01 showed absorption of carbonyls, photo-sensitive sites, at $1710\;cm${-1}$ when exposed to light for 40 days, whereas those not exposed to ultraviolet light showed no absorption at the same frequency. MCC-101-based LDPE films showed much lower $M_w$ distribution after exposure to UV than its counterpart, due to agents accelerating photo-degradation contained in MCC-101.

• Restorative Dentistry and Endodontics
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• 제47권2호
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• pp.16.1-16.9
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• 2022

Objectives: This study compared the cyclic fatigue resistance of One Curve (C wire) and F6 Skytaper (conventional austenite nickel-titanium [NiTi]), and 2 instruments with thermos-mechanically treated NiTi: Protaper Next X2 (M wire) and Hyflex CM (CM wire). Materials and Methods: Ten new instruments of each group (size: 0.25 mm, 6% taper in the 3 mm tip region) were tested using a rotary bending machine with a 60° curvature angle and a 5 mm curvature radius, at room temperature. The number of cycles until fracture was recorded. The length of the fractured instruments was measured. The fracture surface of each fragment was examined with a scanning electron microscope (SEM). The data were analyzed using one-way analysis of variance and the post hoc Tukey test. The significance level was set at 0.05. Results: At 60°, One Curve, F6 Skytaper and Hyflex CM had significantly longer fatigue lives than Protaper Next X2 (p < 0.05). No statistically significant differences were found in the cyclic fatigue lives of One Curve, F6 Skytaper, and Hyflex CM (p > 0.05). SEM images of the fracture surfaces of the different instruments showed typical features of fatigue failure. Conclusions: Within the conditions of this study, at 60° and with a 5 mm curvature radius, the cyclic fatigue life of One Curve was not significantly different from those of F6 Skytaper and Hyflex CM. The cyclic fatigue lives of these 3 instruments were statistically significantly longer than that of Protaper Next.

• 대한의용생체공학회:의공학회지
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• 제45권2호
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• pp.95-100
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• 2024

Vitiligo is a condition characterized by the destruction or dysfunction of melanin-producing cells in the skin, resulting in a loss of skin pigmentation. Facial vitiligo, specifically affecting the face, significantly impacts patients' appearance, thereby diminishing their quality of life. Evaluating the efficacy of facial vitiligo treatment typically relies on subjective assessments, such as the Facial Vitiligo Area Scoring Index (F-VASI), which can be time-consuming and subjective due to its reliance on clinical observations like lesion shape and distribution. Various machine learning and deep learning methods have been proposed for segmenting vitiligo areas in facial images, showing promising results. However, these methods often struggle to accurately segment vitiligo lesions irregularly distributed across the face. Therefore, our study introduces a framework aimed at improving the segmentation of vitiligo lesions on the face and providing an evaluation of vitiligo lesions. Our framework for facial vitiligo segmentation and lesion evaluation consists of three main steps. Firstly, we perform face detection to minimize background areas and identify the face area of interest using high-quality ultraviolet photographs. Secondly, we extract facial area masks and vitiligo lesion masks using a semantic segmentation network-based approach with the generated dataset. Thirdly, we automatically calculate the vitiligo area relative to the facial area. We evaluated the performance of facial and vitiligo lesion segmentation using an independent test dataset that was not included in the training and validation, showing excellent results. The framework proposed in this study can serve as a useful tool for evaluating the diagnosis and treatment efficacy of vitiligo.