Deformation Behaviors of Flat Rolled Wire in Twinning‑Induced Plasticity Steel

Joong‑Ki Hwang 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.5

The influence of room temperature flat rolling on microstructure, mechanical properties, and shape change in twinninginducedplasticity (TWIP) steel wire has been investigated to understand the deformation behaviors of flat rolled wire inTWIP steel and to apply TWIP steels to flat rolled wire products. Numerical simulation, hardness test, and EBSD techniqueswere used to analyze the distribution of strain, mechanical properties, and microstructure of flat rolled TWIP steel wire. Theshape of flat rolled TWIP steel wire was also evaluated and compared with plain carbon steels having low strain hardeningrate. A very different behavior of hardness, strain, twinning, and KAM value was observed with area of flat rolled wire dueto the different stress state and strain with area of wire. The center area had the maximum twin density, KAM value, effectivestrain, and hardness; whereas free surface area had the minimum values. The hardness inhomogeneity factor (HIF) along thehorizontal direction was much higher in comparison with that of the vertical direction. The maximum HIF value occurredat the specific reduction in height, i.e., 27%. This means HIF value gradually increased and then decreased with reduction inheight, which is inconsistent with the results of plain carbon steel and Cu wire. The lateral spread and width of contact areaof flat rolled TWIP steel wire were lower than those of plain carbon steels, indicating that material properties such as strainhardening exponent are crucial parameters that influence the shape of flat rolled wire products.

프리캐스트 포스트텐션 콘크리트 넓은 보-기둥 내부 접합부의 비탄성 거동

황재환,최윤철,김영찬,김대중,임재형,권기혁,문정호,이리형 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.2(구조계)

The purpose of this paper is to evaluate the response of Precast Prestressed Concrete Interior Wide Beam-Column Joint subjected to cyclic lateral loading. To this end, the experimental investigation was performed with six half-scale specimens of interior connection. The design parameters are the beam to column depth ratio, and the number of tendons within column core. One of the specimens, IJH-6, is modeled for the connection at the top floor of a structure. The test results showed that the specimens sufficiently resist up to limiting drift ratio of 0.035 in accordance with the provisional standard by ACI of acceptance criteria for concrete special moment frames.

골격성 제Ⅲ급 부정교합 환자에 대한 상악골 전방견인 장치의 치료효과

황충주,임중기,경승현 대한치과교정학회 1994 대한치과교정학회지 Vol.24 No.4

Before 1970, mandibular overgrowth was known as main cause of skeletal Class Ⅲ malocclusion in growing children; however, recent study reports that many skeletal Class Ⅲ malocclusion patients also show maxillary deficiency. Since 1972, when Delaire re-accommodated Protraction Head Gear (P.H.G). many researchers have reported that skeletal Class Ⅲ discrepancies could be corrected through use of P.H.G., which induces anterior movement of maxilla and change in mandibular growth pattern into infero-posterior direction ; nevertheless, it is very difficult to predict resultant changes of orofacial region. The purpose of this study was to find out what treatment effect P.H.G., has on different study samples. Author divided 51 skeletal Class Ⅲ malocclusion patients with maxillary deficiency who were treated with P.H.G. into different study groups depending on sex, treatment beginning age, intraoral appliance, and facial growth pattern. By doing so, following results were obtained. 1. Treatment beginning age and Sex Four age groups (5.8 to 8 year-old, 8 to 10 year-old, 10 to 12 year-old, 12 year-old, 12 to 14 year-old) were compared, and no significant difference was observed. (p<0.05) There was no significant difference between the sex groups, either. (p<0.05) 2. Intraoral appliance Treatment effects of study groups that used R.P.E(mean age of 10.2) and Labio- Lingual appliance(mean age of 8.9) were compared. There was no significant difference depending on the type of intraoral appliance that was used. (p<0.05) 3. Facial growth pattern 1) Amounts of SNB and ANB corrections were smaller in clockwise growth pattern group than those in normal or counterclockwise growth pattern group. (p<0.05) 2) Amounts of increase in wits appraisal and mandibular plane angle were greater in counterclockwise growth pattern group than those in normal or clockwise growth pattern group. (p<0.05) 3) Amounts of increase in articular angle were greater in counter clockwise growth pattern group than those in clockwise growth pattern group. (p<0.05).

치면세균막에서 분리한 뮤탄스 연쇄상구균 및 Streptococcus anginosus의 수종 항생제에 대한 감수성 조사

국중기,임상수,유소영,황호길 大韓齒科保存學會 2004 Restorative Dentistry & Endodontics Vol.29 No.5

The aim of this study was to investigate the susceptibility of mutans streptococci (S. mutans and S. sobrinus) and Streptococcus anginosus, for seven antibiotics, penicillin G, amoxicillin, ciprofloxacin, cefuroxime, erythromycin, bacitracin, and vancomycin. The minimum inhibitory concentration (MIC) of seven antibiotics against 3 species (type strains) of mutans streptococci and S. anginosus, 10 strains (wild type) of S. mutans, 7 strains (wild type) of S. sobrinus, and 11 strains (wild type) of S. anginosus, were measured by broth dilution method. All of the type strains of mutans streptococci and S. anginosus had the same susceptibility for penicillin G, amoxicillin, cefuroxime and bacitracin. Type strain of S. anginosus was sensitive in ciprofloxacin, but those of mutans streptococci were not. All of the clinical isolates of mutans streptococci and S. anginosus had the same susceptibility for the seven antibiotics. Our data reveal that mutans streptococci and S. anginosus have similar antibiotic-resistant character. In addition. these results may offer the basic data to verify the antibiotic-resistant mechanism of mutans streptococci and S. anginosus.

좌골신경 손상 후 스트렙토조토신 유도성 당뇨병에 의한 축사재생의 지연 효과

황진연,김기중,남궁욱 大田大學校 附屬 韓方病院 2020 惠和醫學 Vol.29 No.1

Objective: The goal of this study is to investigate whether peripheral axonal regeneration is affected by diabetes in experimental animals. Method: Sprague Dawely rat was injected with 45~50 mg/kg of streptozotocin (STZ) to generate an animal model of diabetes. Three months after STZ injection, sciatic nerve (2 cm length) was removed and the same length of nerve segments from STZ-injected animal or from control animal (CTL) was transplanted into STZ-injected animals (STZ-STZ and STZ-CTL respectively). Similarly, sciatic nerve segments from STZ-injected animal or from control animal were grafted into the control animals (CTL-STZ and CTL-CTL respectively). All animals were sacrificed 2 weeks after transplantation. Sciatic nerve sections were prepared and subjected to immunofluorescence staining analysis. Results: Immunofluorescence staining for NF-200 showed that distal elongation of regenerating axons reached 40~80% of proximal neve in both CTL-STZ and CTL-CTL groups. However, distal elongation in both STZ-STZ and STZ-CTL groups were 20~60% of proximal nerve. Furthermore, measurement of axonal regeneration after immuno-staining with SCG10 showed that the scores of distal elongation relative to proximal nerve were 50~90% in CTL-CTL and CTL-STZ groups and 10-60% in STZ-CTL and STZ-STZ. Conclusions: Our data showed that the levels of axonal regeneration were not affected irrespective of whether they were from STZ- or CTL graft, but were greatly reduced when the nerves were transplanted into the STZ host.

師範系 體育敎育科 志望生의 一般運動能力檢査 基準値 設定에 關한 硏究

梁點紅,高基俊,黃喆文,金泰運,金重雄,白永鎬,表內淑,黃太相,徐國雄 釜山大學校 附設 體育科學硏究所 1989 體育科學硏究所 論文集 Vol.5 No.-

This study was analyzed the validity and the reliability of evaluation norm. which was used in choosing and grading events of the General Motor Ability Test. The General Motor Ability Test has been done for applicants for entrance to the department of physical education, college of education, Pusan National University. The subjects of this study were 433 applicants(men :387, women :46) for three years. They were tested in seven events : 1) 100m Dash, 2) 1500m Run(man), 800m Run (woman), 3) Throwing Hand-Ball, 4) Broad Jump, 5) Chinning(man), Flexed-Arm Hang(woman), 6) Zig-Zag Run, 7) Trunk Flexion. The results could be summerized as follows ; 1. In 100m Dash, 1500m Run, and Throwing Hand-Ball, man's average records were shown normal distribution which was inclined toward low ll grade. Therefore, the interval size of those three events must be regulated to lower. 2. Average records of Broad Jump in man were distributed into high (1) grade. So, the interval size must be adjusted to higher. 3. In Chinning, Zig-Zag Run, ad Trunk Flexion, man's average records were shawn normal distribution, and the interval size was similar to present records. 4. For woman, it was impossible to analyze correctly in all seven events because of the small number of subjects. So, it was for the sake of the reference. 5. The record of applicants for three years were operated to the variable quantity analysis. And the restults were these ; 100m Dash was F=3.0865(p<0.05), Chinning F=3.9309(p<0.05), Broad Jump F=14.7338(p<0.001), Throwing Hand-Ball F=4.9716(p<0.01), and Zig-Zag Run F=6.8297(p<0.001). Then, it was shown statistical meaningful difference in three groups. 6. In investigating the validity in choosing seven events, it was concluded that the events have been chosen reasonably. Because all events except for 100m Dash, and Zig-Zag Run in man were independent. From the analysis of the General Motor Ability Test, we could realized the necessity of regulating the standard and the interval size in several events. Then, we proposed the new evaluation norm which was suitable to present situation.

서울의 PPNG 발생 빈도(1991-1992)

김재홍,윤기범,박평원,김영진,전경민,김영태,김중환,곽호,구상완,송민석,유옥,지혜구,김동원,문상은,박영립,정승호,성범진,성순제,엄주용,황정열,이기홍,이주협,전태진 대한화학요법학회 1994 대한화학요법학회지 Vol.12 No.1

The prevalence of PPNG among pretreated gonorrhea cases isolated at the STD clinic of Choong-Ku Public Health Center in Seoul has been studied and reported annually since 1981. In 1991, 123 strains of N.gonorrhoeae were isolated, among which 58(47.1%) were PPNG. In 1992, 98 starains of N.gonorrhoeae were isolated, among which 51(52.0%) were PPNG. In all, 109(49.3%) strains were found to be PPNG among 221 strains isolated between 1991-1992. The prevalence of PPNG in Seoul showed increased tendency till 1989, thereafter, it has been stationary or slightly decreasing.

중합효소연쇄반응법을 이용한 급성 치수 및 치근단 질환의 병원성 세균의 동정

김지훈,유소영,임선아,국중기,임상수,박슬희,황호길 大韓齒科保存學會 2003 Restorative Dentistry & Endodontics Vol.28 No.2

The purpose of this study was to investigate the frequency of 7 putative pathogens in endodontic infections. The specimens were collected from infected pulpal tissue of patients who were referred for root canal treatment to the department of conservative dentisty, Chosun University. Samples were collected aseptically using a barbed broach and a paper point. The cut barbed broaches and paper points were transferred to an eppendorf tube containing 500 ml of 1 X PBS. DNAs were extracted from the samples by direct DNA extraction method using lysis buffer (0.5% EDTA, 1% Triton X-100). Identification of 7 putative pathogens was performed by PCR based on 16S rDNA. The target species were as follows: Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, Bacteroides forsythus, Actinobacillus actinomycetemcomitans, and Treponema denticola. Our data revealed that the prevalence of P.endodontalis was found in 88.6% (39 / 54), P.gingivalis 52.3% (23 / 44), P.nigrescens 18.2%(8 / 44), P.intermedia 15.9% (7 / 44), B.forsythus 18.2% (8 / 44), A.actinomycetemcomitans 2.3% (1 / 44), T.denticola 25% (11 / 44) of the samples. The high prevalence of P. endodontalis and P.gingivalis suggests that they may play an important role in the etiology of endodontic infections.

Direct formed high-strength bolt with hot-rolled TWIP steel

Joong-Ki Hwang(황중기) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.5

Evaluation of Material and Characteristic for Alkali-Metal based High Temperature Heat Pipe and TEC (Thermal-to-Electric Convertor)

Joong-Ki HWANG(황중기),Min-Soo SUH(서민수) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.06

Heat pipe generally transfer thermal energy from one regime to another essentially evaporator to condenser. Superalloy envelope with alkali-metal (sodium, potassium) working fluid for high temperature heat pipe (HP). Na-AMTEC convert between thermal energy and electrical energy, in specific terms, the static energy conversion subjected to electrochemical reaction mainly depending on its chemical kinetics and temperature. In particular, Na-AMTEC convert energy between heat and electricity transpired via ionization of natrium as known as reduction and oxidation (REDOX) which is differentiate it from the dynamic energy conversion. In specific terms, 1) the input of thermal energy is converted into electrical energy as same as a thermoelectric cell, 2) the input of thermal energy is converted into the sum of electrical energy P_e and thermal energy P_th, as same as a combined heat & power (CHP) and 3) the input of electrical energy is converted into thermal energy as same as an electrochemical heat pump. Na-AMTEC could highly utilized in aforementioned objectives with efficiencies potentially near Carnot theorem. In case of thermal energy in both of Na HP and Na-AMTEC, the alkali-metal is an energy medium of heat transfer (HF) and heat transfer fluid (HTF). The purpose of Na HP is transferring thermal energy from source to sink with maximizing heat transfer rate and minimizing the heat loss to ambient surroundings. Similarly, the purpose of Na-AMTEC, alkali-metal based thermopower HP, is to convert thermal source into electricity in order to reduce several conventional stages of conversion processes e.g. thermal energy loss during phase change of HTF, energy loss in terms of temperature and pressure during the energy transportation and energy loss during relative mechanical motion results from energy loss and materials squander due mainly to friction and wear. This study is to report the development efforts of Na HP and thermopower HP fabricated for high grade to low grade temperature power generation.