열가소성 직물탄소복합소재 사출 성형품의 표면 함침 개선에 관한 연구

정의철,윤경환,이성희,Jeong, Eui-Chul,Yoon, Kyung-Hwan,Lee, Sung-Hee 한국금형공학회 2021 한국금형공학회지 Vol.15 No.3

In molding of continuous fiber-reinforced thermoplastic composites, it is very difficult to impregnate between the reinforcements and the matrix since the matrix has a high melting temperature and high viscosity. Therefore, most of composite molding processes are divided in the manufacturing processes of intermediate materials called prepreg and the forming of products from intermediate materials. The divided process requires additional facilities and thermoforming, and they increase the cycle time and cost of composite products. These problems can be resolved by combining the continuous fiber-reinforced composite molding process with injection molding. However, when a composite material is manufactured by inserting woven fabric into the injection mold, poor impregnation occurs on the surface of the molded product. It affects the properties of the composites. In this paper, through an impregnation experiment using cores with different heat transfer rates and pore densities, the reason for the poor impregnation was confirmed, and molding experiments were conducted to produce composite with improved surface impregnation by inserting the mesh. And also, the surface impregnation and deformation of composites molded using different types of mesh were compared with each other.

손목 움직임 추정을 위한 Gaussian Mixture Model 기반 표면 근전도 패턴 분류 알고리즘

정의철,유송현,이상민,송영록,Jeong, Eui-Chul,Yu, Song-Hyun,Lee, Sang-Min,Song, Young-Rok 대한의용생체공학회 2012 의공학회지 Vol.33 No.2

In this paper, the Gaussian Mixture Model(GMM) which is very robust modeling for pattern classification is proposed to classify wrist motions using surface electromyograms(EMG). EMG is widely used to recognize wrist motions such as up, down, left, right, rest, and is obtained from two electrodes placed on the flexor carpi ulnaris and extensor carpi ulnaris of 15 subjects under no strain condition during wrist motions. Also, EMG-based feature is derived from extracted EMG signals in time domain for fast processing. The estimated features based in difference absolute mean value(DAMV) are used for motion classification through GMM. The performance of our approach is evaluated by recognition rates and it is found that the proposed GMM-based method yields better results than conventional schemes including k-Nearest Neighbor(k-NN), Quadratic Discriminant Analysis(QDA) and Linear Discriminant Analysis(LDA).

사출/압축 공정과 인서트 오버몰딩을 이용한 탄소복합소재 성형에 대한 연구

정의철,윤경환,홍석관,이상용,이성희,Jeong, Eui-Chul,Yoon, Kyung-hwan,Hong, Seok-Kwan,Lee, Sang-Yong,Lee, Sung-Hee 한국금형공학회 2020 한국금형공학회지 Vol.14 No.4

In this study, forming of carbon composite parts was performed using an injection/compression molding process. An impregnation of matrix is determined by ability of wet and flow rate between the matrix and reinforcement. The flow rate of matrix passing through the reinforcements is a function of permeability of reinforcement, a viscosity of matrix and pressure gradient on molding, and the viscosity of the matrix depends on the mold temperature, molding pressure and shear strain of matrix. Therefore, compression molding experiment was conducted using a heating mold in order to confirm the possibility of matrix impregnation. The impregnation of the matrix through the porosities between the woven yarns was confirmed by the cross-sectional SEM image of compression molded parts. An injection molding process was also performed at a short cycle time, high molding pressure and low mold temperature than those of compression experiment conditions. Deterioration of impregnation on the surface of molded parts were caused by these injection conditions and it could be the reason of decreasing the maximum tensile strength. In order to improve impregnation of matrix on the surface, injection/compression molding and insert-over molding were applied. As a result of applying injection/compression molding and insert-over molding, it was shown that the improvement of impregnation on the surface and the maximum tensile strength was increased about 2.8 times than the virgin matrix.

남성 비임균성요도염 환자에서 질트리코모나스증 진단을 위한 소변배양 및 혈청학적 검사

정의철(Eui Chul Jeong),김재홍(Jae Hong Kim),노영석(Young Suck Ro),이창우(Chang Woo Lee) 대한피부과학회 1993 大韓皮膚科學會誌 Vol.31 No.1

Trichomoniasis, a common and sometimes distressing condition in women, is caused by infection of the genitourinary tract by the pathogenic protozoan Trichomonris aginalis(T. vaginalis). Men may also be infected, although frequently without any symptoms, and most cases of trichomoniasis are sexually transmitted. The best evidence for an etiologic role for T. vaginalis is in nongonococcal urethritis(NGU). In epidemiologic studies, T,ginalis has been isolated from 1 to 68 percent in men with NGU. The nurnber of NGU is increasing rapidly than gonorrhea in deeloped nations, and in some developing countries, especially in Korea, In view of the difficulties in findng trichomonads by direct microsco by in men, urine culture and serodiagnosis plays an important role in the diagnostic work. Urine culture, indirect fluorescent antibody test(IFAT) and enzyme-linked immunosorbent assay (ELISA) were used to elecect T.vaginalis in 221 patients with male NGU. These patients visited the VD Clinic of ChoongKu Public Health Center in Seoul from May to August, 1989 and from March, 1990 to December, 1991. The results obtained were as follows.: 1. T. vaginalis was grown from only one of the 221 samples on TPS-1 meida. 2. In 208 NGU patients, there were 10(4.8%) positive reactions on IgG antibody in IFAT. 3. In 208 NGU patient, there were 14(6.7%) positive reactions to IgG antibody in ELISA. 4. No statistical significant correlation was found between then sults of IFAT and ELISA in individual patients. In conclusion, 1. Male trichomoniasis in patients with NGU was detected at a, significantly low rate. Due to the small number of patients in the test, further epidemiologic stidies of trichomoniasis in male NGU patient are necessary. 2. Serologic studies (IFAT and ELISA) have detected sorre trichomoniasis in male patients with NGU. These tests seem to be helpful in the diagnosis of male t-ichomoniasis. (Kor J Dermatol 1993; 31 (1): 47-57)

임질후 요도염에 관한 고찰

정의철(Eui Chul Jeong),김재홍(Jae Hong Kim),김중환(Joong Hwan Kim) 대한피부과학회 1986 대한피부과학회지 Vol.24 No.2

The subject were 653 male patients with uncomplicated gonorrhea at the VD Clinic of Choong Ku Public Health Center in Seoul from January to November 1985. 653 male patients with uncomplicated gonococcal infection were treated one of the following regimens. Five treatment regimens used were 2, 0 gm spectinomycin single 1M, 4 0 mega unit fortified procain penicillin G+2. 0 gm kanamycin sulfate IM preceded by 1 pgm probenecid PO, 6.0 mega unit fortified procain penicillin G+2 pgm kanamycin sulfate IM preceded by 1. 0 gm probenecid PO, 5, 0 rnega unit aqueous crystaline penicillin+2. 0 gm kanamycin sulfate irn preceded by 1, 0 gm probenecid PO and 9 tablets of cotrimoxazole+ 2. 0 gm kanamycin sulfate IM. There were no significant differences in the incidence of PGU among the five treatment groups. The overall PGU rate was 67.3% 59.2% and 53.6% at 3~5, 7~10 and 14 days after treatment respectively. The incidence of PGU at 7-10 days was not significantly higher than that of at 14 days after treatment. It is suggested that it is best to test PGU at 7 days after treatment. Because the longer one waits, the harder to follow the patients, and in earlier period, post-inflammatory irritation might be too frequent. It is also suggested that at 3 5 days after treatment examination of urethritis might serve to compare the effect of treatment regimens on the incidence of PGU.

경화부종

정의철(Eui Chul Jeong),최광호(Kwang Ho Choi),김재홍(Jae Hong Kim),김중환(Joong Hwan Kim) 대한피부과학회 1985 대한피부과학회지 Vol.23 No.5

Scleredema is a rare scleradematosis of unknown cause involving the face, neck, upper portion of the trunk, and proximal upper extremities. The clinical features of the disease are nonpitting indurated edema or stiffness of the neck, which may be sudden or insidious in onset. Diabetes mellitus and its complications have been frequently described to be associated with this disease. We present a case of scleredema developed on the nape, upper portion of the back and shoulder in 60-year-old man who had been suffered from diabetes mellitus for the past ten years.

유리섬유 및 하니콤 리브가 사출성형품의 강도에 미치는 영향

정의철(Eui-chul Jeong),김용대(Yong-Dae Kim),이준희(June-Hee Lee),이성희(Sung-Hee Lee) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.6

COMPARATIVE ANALYSIS OF TOILETRIES DESIGN IN KOREA, CHINA, AND JAPAN - FROM LATE 17TH TO 19TH CENTURY -

정의철 ( Jung Eui-chul ),박영순 ( Park Young-soon ),신지혜 ( Shin Ji-hye ),김은정 ( Kim Eun-jeong ) 한국디자인트렌드학회 2012 한국디자인포럼 Vol.34 No.-

This research describes the design characteristics in Korea, China, and Japan by investigating makeup culture and toiletries. To find unique design characteristics, the toiletries of upper class women from the late 17th to 19th centuries were compared. The research methods included both reviewing previous publications and field studies. The three countries developed their own forms, proportions, materials and surfaces. Korean toiletries could be diverse and stable in forms and proportions, because they had various shapes and lower centroid. Korean women thought the symbolic meanings significant for their daily necessities, and preferred planar painting and engraving to decorate the patterns. The materials and surfaces of Korean toiletries were practical, soft, and gave less artificial process to reveal their natural material texture. Chinese toiletries had complex forms and were tall. For the patterns, symbolic meanings were significant as Korea. The patterns were carved in three-dimensional forms. Chinese women preferred rare materials. Japanese toiletries had simple lines and were easily stackable. Japanese women often used patterns for decorative purposes instead of symbolic meanings, and the patterns were mostly decorated with planar paintings. For the materials and surfaces, the Japanese preferred wood with lacquers and luxurious materials such as gold. In summary, the design characteristics of Korean toiletries had diverse forms, flexible proportions, painted patterns with symbolic meanings, practical materials and soft surface, while those of China had a complicated structure and carved patterns. Japan had simple forms, sharp edges, and layered structure with colorful lacquers.

폴리머코어 게이트 크기 변화가 두께 방향 수축률에 미치는 영향에 대한 연구

최한솔,정의철,박준수,김미애,채보혜,김상윤,김용대,윤경환,이성희,Choi, Han-Sol,Jeong, Eui-Chul,Park, Jun-Soo,Kim, Mi-Ae,Chae, Bo-Hye,Kim, Sang-Yun,Kim, Yong-Dae,Yoon, Kyung-Hwan,Lee, Sung-Hee 한국금형공학회 2020 한국금형공학회지 Vol.14 No.1

In this study, the variation of the shrinkage in the thickness direction of the molded parts according to the gate size of the polymer core fabricated through the 3D printer using the SLS method was studied. The polymer cores are laser sintered and the powder material is nylon base PA2200. The polymer cores have lower heat transfer rate and rigidity than the metal core due to the characteristics of the material. Therefore, the injection molding test conditions are set to minimize the deformation of the core during the injection process. The resin used in the injection molding test is a PP material. The packing condition was set to 80, 90 and 100% of the maximum injection pressure for each gate size. The runner diameter used was ∅3mm, and the gates were fabricated in semicircle shapes with cross sections 1, 2, and 3 ㎟, respectively. Thickness measurement was performed for 10 points at 2.5 mm intervals from the point 2.5 mm away from the gate, and the shrinkage to thickness was measured for each point. The shrinkage rate according to the gate size tends to decrease as the cross-sectional area decreases as the maximum injection pressure increases. The average thickness shrinkage rate was close to 0% when the packing pressure was 90% for the gate area of 1mm2. When the holding pressure was set to 100%, the shrinkage was found to decrease by 3% from the standard dimension due to the over-packing phenomenon. Therefore, the smaller the gate, the more closely the molded dimensions can be molded due to the high pressure generation. It was confirmed that precise packing process control is necessary because over-packing phenomenon may occur.

연결된 사물인터넷 환경에서의 CMF 디자인 모델 제안

허정철(Jeong-Cheol Heo),정의철(Eui-Chul Jung) 한국HCI학회 2020 한국HCI학회 학술대회 Vol.2020 No.2

제품들이 인터넷을 통해 연결되어 지능적 관계를 형성하는 사물인터넷 환경에서 연결성은 중요한 키워드이다. 독립된 제품과 달리 사물인터넷 환경에서의 제품은 개별적인 기능 외에도 주고받는 데이터를 통해 사용자의 니즈를 충족시킨다. CMF 디자인은 제품의 색상, 재료, 마감(Color, Material, Finish)을 통해서 제품에 기능적, 감성적 특징을 지원하는 디자인 과정이다. 제품들이 인터넷을 통해 연결되어 있는 사물인터넷 환경에서, CMF 디자인 역시 연결성을 고려할 필요가 있다. 본 연구는 연결된 사물 환경에서 사용자의 상황에 따라 다양한 이미지를 생성할 수 있는 CMF 디자인 연구 모델 제안을 목적으로 한다. 연구방법으로 첫째, 사물인터넷의 개념 및 사례, 사물인터넷 환경을 분석하여 연결성을 통한 사물인터넷과 환경의 특성을 이해한다. 둘째, CMF 디자인의 방법론 조사를 통해 현재 독립된 제품의 CMF 디자인 연구 현황을 탐색한다. 셋째, 사례 분석을 통해 연결성에 의해 변화하는 실험적 CMF 가 적용된 디자인을 분석하여 새로운 가능성을 이해하고, CMF 디자인을 설명할 수 있는 모델을 구축한다. 결과적으로, 이 모델을 바탕으로 스마트홈과 자율주행자 실내 환경에서, 연결된 사물의 CMF 디자인의 역할을 설명할 수 있는 시나리오를 제시하여, 모델의 적용 가능성을 논의한다. 이 연구를 통하여, 연결성을 고려한 사물인터넷 CMF 디자인의 컨셉을 제시하고 평가할 수 있는 연구 기반을 수립할 수 있을 것으로 기대한다.