• 한국분말재료학회지
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• 제29권5호
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• pp.382-389
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• 2022

A typical trade-off relationship exists between strength and elongation in face-centered cubic metals. Studies have recently been conducted to enhance strength without ductility reduction through surface-treatment-based ultrasonic nanocrystalline surface modification (UNSM), which creates a gradient microstructure in which grains become smaller from the inside to the surface. The transformation-induced plasticity effect in Fe-Mn alloys results in excellent strength and ductility due to their high work-hardening rate. This rate is achieved through strain-induced martensitic transformation when an alloy is plastically deformed. In this study, Fe-6%Mn powders with different sizes were prepared by high-energy ball milling and sintered through spark plasma sintering to produce Fe-6%Mn samples. A gradient microstructure was obtained by stacking the different-sized powders to achieve similar effects as those derived from UNSM. A compressive test was performed to investigate the mechanical properties, including the yielding behavior. The deformed microstructure was observed through electron backscatter diffraction to determine the effects of gradient plastic deformation.

• The Plant Pathology Journal
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• 제39권3호
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• pp.275-289
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• 2023

Fungal isolates from infected Chinese quince trees were found to cause black rot in Yeongcheon, Gyeongsangbuk Province, Korea. The quince leaves withered and turned reddish-brown and fruits underwent black mummification. To elucidate the cause of these symptoms, the pathogen was isolated from infected leaf and fruit tissues on potato dextrose agar and Levan media. Several fungal colonies forming a fluffy white or dark gray mycelium and two types of fungi forming an aerial white mycelium, growing widely at the edges, were isolated. Microscopic observations, investigation of fungal growth characteristics on various media, and molecular identification using an internal transcribed spacer, β-tubulin, and translation elongation factor 1-α genes were performed. The fungal pathogens were identified as Diplodia parva and Diplodia crataegicola. Pathogenicity tests revealed that the pathogen-inoculated fruits exhibited a layered pattern, turning brown rotting; leaves showed circular brown necrotic lesions. The developed symptoms were similar to those observed in the field. Fungal pathogens were reisolated to fulfill Koch's postulates. Apples were inoculated with fungal pathogens to investigate the host range. Strong pathogenicity was evident in the fruits, with browning and rotting symptoms 3 days after inoculation. To determine pathogen control, a fungicidal sensitivity test was conducted using four registered fungicides. Thiophanate-methyl, propineb, and tebuconazole inhibited the mycelial growth of pathogens. To the best of our knowledge, this is the first report on the isolation and identification of the fungal pathogens D. parva and D. crataegicola from infected fruits and leaves of Chinese quince, causing black rot disease in Korea.

• 소성∙가공
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• 제33권2호
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• pp.103-111
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• 2024

With the increasing global interest in carbon neutrality, the automotive industry is also transitioning to the production of eco-friendly cars, specifically electric vehicles. In order to achieve comparable driving distances to internal combustion engine vehicles, the application of high-capacity battery packs has led to an increase in vehicle weight. To achieve light-weighting and durability requirements of automotive components simultaneously, there is a demand for research on the application of Ultra-High Strength Steel (UHSS). However, when manufacturing chassis components using UHSS, there are challenges related to fracture defects due to lower elongation compared to regular steel sheets, as well as spring-back issues caused by high tensile strength. In this study, a simulated specimen that is not affected by the property changes of four materials was designed to improve formability of the rear cross member, which is the most challenging automotive chassis component. The influence and correlation of material-specific variables were analyzed through finite element analysis (FEA) for each material with tensile strength of 440, 590, 780, and 980 MPa grades, resulting in the development of a predictive equation. To validate the equation, the simulated specimens of 980 MPa grade were produced from the test molds. Then the reliability of the FEA and predictive equation was verified with measured specimen data using a 3D scanner. The results of this study can be proposed to improve the formability of UHSS chassis components in future researches.

• Safety and Health at Work
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• 제15권2호
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• pp.228-235
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• 2024

Background: Glove reuse poses risks, as chemicals can persist even after cleaning. Decontamination methods like thermal aeration, recommended by US OSHA, vary in effectiveness. Some studies show promising results, while others emphasize the importance of considering both permeation and tensile strength changes. This research advocates for informed glove reuse, emphasizing optimal thermal aeration temperatures and providing evidence to guide users in maintaining protection efficiency. Methods: The investigation evaluated Neoprene and Nitrile gloves (22 mils). Permeation tests with toluene and acetone adhered to American Society for Testing Materials (ASTM) F739 standards. Decontamination optimization involved aeration at various temperatures. The experiment proceeded with a maximum of 22 re-exposure cycles. Tensile strength and elongation were assessed following ASTM D 412 protocols. Breakthrough time differences were statistically analyzed using t-test and ANOVA. Results: At room temperature, glove residuals decreased, and standardized breakthrough time (SBT)₂ was significantly lower than SBT₁, indicating reduced protection. Higher temperature decontamination accelerated residual removal, with ∆SBT (SBT₂/SBT₁) exceeding 100%, signifying restored protection. Tensile tests showed stable neoprene properties postdecontamination. Results underscore thermal aeration's efficacy for gloves reuse, emphasizing temperature's pivotal role. Findings recommend meticulous management strategies, especially post-breakthrough, to uphold glove-protective performance. Conclusions: Thermal aeration at 100℃ for 1 hour proves effective, restoring protection without compromising glove strength. The study, covering twenty cycles, suggests safe glove reuse with proper decontamination, reducing costs significantly. However, limitations in chemical-glove combinations and exclusive focus on specific gloves caution against broad generalization. The absence of regulatory directives on glove reuse highlight the importance of informed selection and rigorous decontamination validation for workplace safety practices.

• 대한한방내과학회지
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• 제31권3호
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• pp.578-585
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• 2010

Objectives : Coldness of hands and feet has been regarded to be associated with blood circulation. This study was performed to assess the correlation between erythrocyte deformability and coldness of hands and feet. Methods : 145 patients who had taken an erythrocyte deformability test were selected for this study among hospitalized patients within 4 weeks after their cerebral infarction at the Internal Medical Department at Kyunghee Oriental Medical Center from August 2008 to August 2009. We divided the selected patients into two groups, with and without of coldness of hands and feet groups. The two groups were compared on risk factors for atherosclerosis and examined for variables including erythrocyte deformability. Results : 1. On demographic variables of the patients, only body mass index was significantly lower in the coldness of hands and feet group than the control group. There was no significant difference of the rate of hypertension, diabetes mellitus, hyperlipidemia, ischemic heart disease, smoking, drinking and carotid artery stenosis between the two groups. 2. According to blood test, the coldness of hands and feet group showed significantly lower erythrocyte deformability index than the control group. 3. Body mass index and erythrocyte deformability index showed a close relationship with coldness of hands and feet in multivariate analysis. Conclusions : The correlation between the erythrocyte deformability and coldness of hands and feet in cerebral infarction patients were decreased erythrocyte deformability participated in the mechanism of coldness of hands and feet.

• Toxicological Research
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• 제22권3호
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• pp.221-228
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• 2006

Bonogen shampoo is composed of several plant extracts which are known to be used in oriental medicine. This study was carried out to investigate the effects of Bonogen shampoo on hair growth in an alopecia model of C57BL/6 mice. There were eight male and female experimental groups including distilled water(DW: negative control), a commercial shampoo[M], 3% minoxidil (MXD) and Bonogen shampoo(BNG). Dorsal skin hair of six-week-old mice was trimmed with an electric clipper carefully not to damage the skin. The next day, mice without skin scratch were selected, randomized and separated in 10 mice per group. The test compounds were topically treated with 0.15 ml per mouse or dorsal skin for 21 days daily and then washed thoroughly with DW. The hair regrowth was determined photographically at 0, 4, 7, 10, 15, 18, and 21 days and histologically at day 21. No clinical signs were observed in all mice. Although body weight was slightly increased in 3% MXD group than other groups, it was not significant. Hair regrowth began to be promoted after 14 days and appeared a distinct regrowth pattern in all animals by topical treatment of test compounds at 18 days. In particular, the topical treatment of bonogen shampoo or 3% MXD for 21 days to dorsal skin accelerated hair regrowth faster than DW or M shampoo. At 21 days, the hair regrowth promotion speed was in order of 3% MXD>BNG>M>DW. The bonogen shampoo or 3% MXD also promoted hair follicle elongation compared to the negative control. These results suggest that bonogen shampoo has hair growth promoting activities and may be useful for treatment of bald or alopecia.

• 한국미생물·생명공학회지
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• 제27권6호
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• pp.427-432
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• 1999

농산물의 증산을 위한 과도한 농약 사용으로 인한 토양 생태계의 파괴를 줄이기 위하여 맹독성 농약을 대신할 수 있는 생물학적 방제제 개발의 일환으로 식물병원성 진균의 생육을 억제하는 siderophore를 생산하는 생물학적 방제균을 선발하여, 이를 동정하고 근부병균억제기작을 연구하여 향후 다기능 생물학적 방제제 개발의 기초자료를 활용하고자 하였다. 이를 위해 저병해 경작지 토양에 장기간 우점화 되어 있는 siderophore 생산 가능성이 높은 토착 길항미생물을 전국 각지의 저병해 경작지에서 분리하였고, 이들 중 siderophore 생산능이 높은 길항미생물 4종의 균주를 chrome azurol S(CAS) agar를 이용하여 선발하였다. 그 중 최고의 길항성을 나타내는 GL7 균주를 최종 선발하였고, API diagnostic test와 지방산 분석, 그리고 각종 생리학적 특성 및 형태학적 특성을 통해 동정한 결과 Pseudomonas fluoresceus의 한 균주임을 확인하였다. 최종 선발된 siderophore 생산균주 P. fluorescens GL7의 길항기작을 병원성 진균인 Fusarium solani를 대상으로 균사 생장과 포자 발아 등의 억제율을 조사한 결과 균사 생장 억제율은 75% 이상이며, 포자 발아억제율은 97% 이상으로 우수한 방제능을 확인할 수 있었다. 선발된 siderophore 생산능이 높은 길항균주 P. fluo-rescens GL7을 대상으로 토양 내에서 실제로 근부병에 방제력이 있는가를 조사하기 위해 강낭콩 종자(Phaseolus vulgaris L.)를 발병 기주식물로 사용하여 방제시험을 한 결과 F. solam만 처리한 경우는 30%의 성장율을, P. fluorescens GL7 균주와 F. solani와 함께 처리한 경우는 95% 정도의 성장율을 나타내어 약 65% 정도의 발병율을 줄일 수 있었다. 또한 F. solani와 P. fluorescens GL7을 처리하지 않은 무처리구에 비해 식물 물게가 147% 정도로 증가하여 식물의 생육도와 뿌리의 발육상태가 양호하였고, 근부병 발생도 거의 볼 수 없었으므로 아주 우수한 siderophore 생산성 생물학적 방제균을 선발할 수 있었다.

• 폴리머
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• 제30권3호
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• pp.259-265
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• 2006

손상된 조직의 재생을 촉진시키는 여러가지 성장인자를 함유한 소장점막하조직(small intestinal subucosa, SIS)과 드레싱 교체시 손상된 피부로부터 박리가 용이한 수화젤 특성을 갖는 PVA를 이용하여 창상 치유를 촉진시키고 박리가 용이한 드레싱을 제조하였다. SIS 시트를 2, 4 및 10 wt%로 제조한 PVA 용액에 침지시킨 후 각기 다른 몰드에서 동결건조함으로써 PVA가 코팅된 SIS 시트를 제조하였다. 제조한 시트는 인장시험을 통해 기본 물성을 평가하였고, 분해도, 물 흡수성, 그리고 in vitro 실험을 통해 그 특성을 조사하였다. PVA를 코팅한 SIS(PVA-SIS) 시트의 인장강도와 신장률은 PVA의 함량이 증가함에 따라 각각 감소, 증가하였으며, 분해도는 본래의 SIS에 비해 감소하였고, SIS에 2 및 4 wt%의 PVA가 코팅되었을 때 물 흡수성이 증가하였다. 또한 전 PVA-SIS 시트에서 세포부착도가 본래의 SIS 시트에 비해 낮음을 확인하였다. 이로써 PVA를 코팅한 SIS 시트가 창상 치료를 위한 드레싱제와 생분해성 이식 제제로서 사용가능하리라 판단되었다.

• 폴리머
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• 제33권5호
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• pp.446-451
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• 2009

신뢰성 평가 시험법인 RS M 0042에 따라, 열화시간 경과에 따른 선형저밀도 폴리에틸렌 파이프의 신뢰성 평가를 수행하였다. 열화시간이 증가함에 따라, 인장강도는 250일 열화시점까지 비례적으로 증가하였고, 경도는 비교적 미소한 증가를 보였으며, 연신율은 점진적으로 감소하는 경향을 보였다. 이러한 결과는 열화시간이 증가함에 따른, 결정화도의 증가와 열산화에 의한 가교밀도의 증가, 사슬 전단 및 사슬 운동성의 감소 등에 기인한 것으로 판단된다. 장기정수압시험 결과는 초기의 연성파괴에서 차후 취성파괴로 전환되는 시점이 존재함을 확인하였다. 산화유도시간 측정은 선형저밀도폴리에틸렌 파이프의 열산화 정도를 관찰하기 위해 도입되었다. 측정 결과는 250일 이후 선형저밀도폴리에틸렌 파이프에 첨가된 산화방지제가 거의 고갈되었음을 보여준다. $100^{\circ}C$ 열화 조건에서 산화방지제의 잔존량을 계산할 수 있는 실험식을 열화시간의 함수로 표현하여 제안하였다. 적외선분광분석 결과는 열화된 선형저밀도폴리에틸렌 파이프 표면상에 카르보닐 및 하드록실 관능기가 증가하였음을 보여준다. 이는 선형저밀도폴리에틸렌 표면의 탄화수소 그룹의 산화가 국부적으로 발생하였음을 나타낸다.

• 구강회복응용과학지
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• 제19권4호
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• pp.269-279
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• 2003

This study investigated the mechanical properties of precious metal-ceramic alloy joined by the laser-welding and the soldering compared with the parent metal. Twenty-four tensile specimens were cast in precious metal-ceramic alloy and divided into three groups of eight. All specimens in the control group(group 1) were left in the as-cast condition. Group 2 and 3 were the test specimens, which were sectioned at the center. Eight of sectioned specimens were joined by soldering with a propane-oxygen torch, and the remaining specimens were joined by laser-welding. After joining, each joint diameter was measured, and then tested to tensile failure on an Instron machine. Failure loads were recorded, and then fracture stress(ultimate tensile strength), 0.2% yield strength and % elongation calculated. These data for three groups were subjected to a one-way analysis of variance(ANOVA). Neuman-Keuls post hoc test was then used to determine any significant differences between groups. The fracture locations, fracture surfaces were examined by SEM(scanning electron microscope). The results were as follows: 1) The tensile strength and 0.2% yield strength of the soldered group($280.28{\pm}49.35MPa$, $160.24{\pm}26.67MPa$) were significantly less than both the as-cast group($410.99{\pm}13.07MPa$, $217.82{\pm}17.99MPa$) and the laser-welded group($383.56{\pm}59.08MPa$, $217.18{\pm}12.96MPa$). 2) The tensile strength and 0.2% yield strength of the laser-welded group were about each 98%, 99.7% of the as-cast group. There were no statistically significant differences in these two groups(p<0.05). 3) The percentage elongations of the soldered group($3.94{\pm}2.32%$) and the laser-welded group($5.06{\pm}1.08%$) were significantly less than the as-cast group($14.25{\pm}4.05%$) (p<0.05). 4) The fracture of the soldered specimens occurred in the solder material and many porosities were showed at the fracture site. 5) The fracture of the laser-welded specimens occurred also in the welding area, and lack of fusion and a large void was observed at the center of the fracture surface. However, the laser-welded specimens showed a ductile failure mode like the as- cast specimens. The results of this study indicated that the tensile strengths of the laser-welded joints were comparable to those of the as-cast joints and superior to those of the soldered joints.