Effect of Mn and C on Age Hardening of Fe–Mn–Al–C Lightweight Steels

Sung‑Won Park,Jun Young Park,Kyong Mox Cho,Jae Hoon Jang,Seong‑Jun Park,Joonoh Moon,Tae‑Ho Lee,Jong‑Ho Shin 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.3

The effects of Mn and C content on the age hardening of Fe–Mn–Al–C lightweight steels, which have austenitic or duplex(austenite and ferrite) microstructures, were investigated. An increase in Mn content induced a delay of the age hardeningthat is caused by the formation of intra-granular κ-carbides. In order to interpret the effect of Mn content, first-principlescalculations were conducted using the supercells of Fe24Al8C8,Fe24Al8C7,Fe24(Al7Mn)C8, and Fe24(Al7Mn)C7. The calculationsshowed that an increase in Mn content could be the source of the delay of the intra-granular κ-carbide formation bysuppressing C atom’ occupation of the vacancy at the body-centered site of L12. An increase in C content accelerated theformation of intra-granular κ-carbides, which induced the intense age hardening, and coarse inter-granular κ-carbides, whichresulted in significant decrease in impact absorbed energy due to inter-granular fracture.

Age-dependent differences of treadmill exercise on spatial learning ability between young- and adult-age rats

Jun-Jang Jin,Il-Gyu Ko,Sung-Eun Kim,Lakkyong Hwang,Man-Gyoon Lee,Dae-Young Kim,Sun-Young Jung 한국운동재활학회 2017 JER Vol.13 No.4

Aluminum-free low-modulus Ti–C composites that exhibit reduced image artifacts during MRI

Kim, Sung-Chul,Lee, Hong-Jun,Son, Seong-Guk,Seok, Hyun-Kwang,Lee, Kang-Sik,Shin, Seung-Young,Lee, Jae-Chul Elsevier 2015 ACTA BIOMATERIALIA Vol.12 No.-

<P><B>Abstract</B></P> <P>Feasibility studies were performed to determine the suitability of a novel synthesis technique for fabricating multifunctional composite materials for orthopedic implants. By blending paramagnetic Ti powder with diamagnetic graphite and consolidating the resulting mixtures, Ti–C composites that cannot be feasibly obtained via conventional alloying techniques or ingot metallurgy were synthesized. The synthesized composite material exhibited extremely low magnetic susceptibility (χ=67.6×10<SUP>−6</SUP>), and, as a result, exhibited fewer artifacts during magnetic resonance imaging. The strength of the composite material (σ=770MPa) was such that it could support external loads to which the human body is subjected, but its Young’s modulus was low (<I>E</I> =81.9 GPa) such that it could mitigate the stress-shielding effect. The material was also free from toxic elements such as Al and V and, thus, can be considered less harmful.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Fabrication of Al₂O₃ nano-micro patterns by Al₂O₃ dispersion resin using UV imprint lithography

Park, Jaemin,Sung, Young Hoon,Son, Soomin,Jun, Junho,Huh, Daihong,Lee, Heon Elsevier 2018 THIN SOLID FILMS - Vol.660 No.-

<P><B>Abstract</B></P> <P>Aluminum oxide (Al<SUB>2</SUB>O<SUB>3</SUB>) has excellent properties in terms of hardness, abrasion resistance, refractive index, electrical insulation and chemical stability; therefore, it has been used in various optical applications such as for resistance random access memory active layers and nano-micro polishing. In this study, a functional Al<SUB>2</SUB>O<SUB>3</SUB> nanoparticle resin with refractive index control was developed and various nano-micro structures were formed using UV-nanoimprint lithography. It is also possible to adjust and measure the desired optical properties by controlling the specifications of the formed Al<SUB>2</SUB>O<SUB>3</SUB> structures. It was confirmed that imprinting is possible not only on traditional rigid substrates but also on flexible ones. Furthermore, scanning electron microscopy showed that the various Al<SUB>2</SUB>O<SUB>3</SUB> nano-micro structures were well formed. The effect of annealing temperature on the phase change and crystallinity was investigated by X-ray diffraction. The hardness and Young's modulus were also measured by using a nanoindenter. The refractive index of Al<SUB>2</SUB>O<SUB>3</SUB> dispersion resin composition was examined using an ellipsometer. Moreover, the optical characteristics of each Al<SUB>2</SUB>O<SUB>3</SUB> nano-micro structure were measured by UV–visible spectroscopy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Manufacture of Al<SUB>2</SUB>O<SUB>3</SUB> dispersion solution with adjustable refractive index </LI> <LI> Fabrication of nano-micro structures using Al<SUB>2</SUB>O<SUB>3</SUB> dispersion resin </LI> <LI> Characterization of Al<SUB>2</SUB>O<SUB>3</SUB> dispersion resin and Al<SUB>2</SUB>O<SUB>3</SUB> nano-micro structure </LI> </UL> </P>

소아 전풍 환자에 대한 임상적 고찰

강효준,왕한영,성호석 ( Hyo Jun Kang,Han Young Wang,Ho Suk Sung ) 대한피부과학회 1997 大韓皮膚科學會誌 Vol.35 No.3

Background: Pityriasis versicolor(PV) is a superficial mycosis, theoretically unusual in children. Epidemiologic and clinical data for children with PV under 14 years were collected. Objective . The purpose of this study was to evaluate the clinical features of PV in the young. Method: We included all cases of PV in patients under 14 years of age observed in our department from 1981 to 1995. All cases were diagnosed on the basis of clinical criteria and were confirmed by microscopic examination. Results : From 1981 to 1995 we encountered 32 cases of PV in children, compared with 637 cases in adults; thus children represented 4.7% of all cases. The ratio of male to female was l. 7:1. Among the age groups, the incidence was the highest in the 10-14 years(43%). The monthly prevalence was the highest in August. Distribution of the lesions were the face(40.9%), neck (25%), chest(13.6%), back(11.3%), extremities(6.8%) and abdomen(2.2%). The incidence of hypopigmented lesions was 70.4% and that of hyperpigmented lesions was 29.6%. Conclusion : This study confirms that the face is a predilectionl site for PV in children and all facial lesions are hypopigmented. Other clinical features are variable and similar to those of adults. (Kor J .Dermatol 1997;35(3): 431-434)

Crucial Role of Oxidation Debris of Carbon Nanotubes in Subsequent End-Use Applications of Carbon Nanotubes

Kim, Yern Seung,Oh, Jun Young,Kim, Jae Ho,Shin, Min Ho,Jeong, Yo Chan,Sung, Sae Jin,Park, Jisoo,Yang, Seung Jae,Park, Chong Rae American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.20

<P>A facile purification method for oxidized carbon nanotubes (CNTs) is developed to preserve acidic carbon compounds (ACCs) for achieving high-quality dispersion of CNTs. The remaining ACCs, which originated from the surface destruction of CNTs during the oxidation process, are considered to play a crucial role in the dispersion of CNTs in water and various polar protic solvents. To elucidate the concrete role of ACCs, a direct titration method is applied to quantitatively investigate the degree of ionization of both CNTs and ACCs in their aqueous dispersion. While ACCs with strong carboxylic groups (pK(a) of around 2.9) are easily removed by the neutral or base washing of oxidized CNTs, which is common in the purification process, ACC-selective purification using acid washing preserves the ACCs attached to CNTs, thereby effectively stabilizing CNT dispersions in aqueous solutions. Additionally, the Hansen solubility parameters of ACC-preserved and ACC-removed CNTs were determined by the inverse gas chromatography method to estimate their miscibility in various solvents. The preserved ACCs significantly influenced the dispersibility of CNTs in polar protic solvents, which may widen the possible application of CNTs. Specifically, the ACC-preserved high-quality CNT dispersion produces high-performance CNT buckypaper with densely packed nanostructures. The Young's modulus and tensile strength of these buckypapers reach up to 12.0 and 91.0 MPa, respectively, which exceed those of ACC-removed CNTs in previous reports.</P>

Possible Involvement of Photoperiodic Regulation in Reproductive Endocrine System of Female Olive Flounder Paralichthys olivaceus

Kim, Hyun Chul,Lee, Chi Hoon,Hur, Sung Pyu,Kim, Byeong Hoon,Park, Jun Young,Lee, Young Don The Korean Society of Developmental Biology 2015 발생과 생식 Vol.19 No.1

This study investigated possible involvement of photoperiodic regulation in reproductive endocrine system of female olive flounder. To investigate the influence on brain-pituitary axis in endocrine system by regulating photoperiod, compared expression level of Kisspeptin and sbGnRH mRNA in brain and FSH-${\beta}$, LH-${\beta}$ and GH mRNA in pituitary before and after spawning. Photoperiod was treated natural photoperiod and long photoperiod (15L:9D) conditions from Aug. 2013 to Jun. 2014. Continuous long photoperiod treatment from Aug. (post-spawning phase) was inhibited gonadal development of female olive flounder. In natural photoperiod group, the Kiss2 expression level a significant declined in Mar. (spawning period). And also, FSH-${\beta}$, LH-${\beta}$ and GH mRNA expression levels were increasing at this period. However, in long photoperiod group, hypothalamic Kiss2, FSH-${\beta}$, LH-${\beta}$ and GH mRNA expression levels did not show any significant fluctuation. These results suggest that expression of hypothalamic Kiss2, GtH and GH in the pituitary would change in response to photoperiod and their possible involvement of photoperiodic regulation in reproductive endocrine system of the BPG axis.

수종의 실란처리 유리섬유를 첨가한 의치상용 레진의 강도변화 및 마모전.후 표면성상분석

이상일,김창회,임영준,김명주,윤석대,Lee, Sang-Il,Kim, Chang-Whe,Lim, Young-Jun,Kim, Myung-Joo,Yun, Suk-Dae 대한치과보철학회 2007 대한치과보철학회지 Vol.45 No.4

Statements of problem: The fracture of acrylic resin dentures remains an unsolved problem. Therefore, many investigations have been performed and various approaches to strengthening acrylic resin, for example, the reinforcement of heat-cured acrylic resin using glass fibers, have been suggested over the years. Silane is important for bonding between glass fiber and resin. Purpose: The aim of the present study was to investigate the effect of various silane on the strength of PMMA resin and roughness of resin-glass fiber complex after abrasion test. Material and methods: 3mm glass fiber (Chopped strand, Hankuk fiber Co., Milyang, Korea) was treated with 3 kinds of silane (MPS, EPS, APS) (Sila-ace, Chisso chemical, Tokyo, Japan) and mixed with PMMA resin(Vertex RS, Vertex Dental B.V., Zeist, Netherlands). Transverse strength and Young's modulus was measured using Instron (Instron model 4466, Instron, Massachusetts, USA). After abrasion test (The 858 Mini Bionix II Test System, MTS System Co., Minnesota, USA) surface roughness was evaluated using tester (Form Talysurf plus, Taylor Hopson Ltd., Leicester England). Examination of scanning electron microscope was also performed. Results: Within this study, the following conclusions were drawn. 1. Surface treatment of glass fiber with MPS and APS increased transverse strength of PMMA resin complex, but surface treatment with EPS decreased transverse strength of PMMA resin complex (p<0.05). 2. Silane treated glass fiber increased Young's modulus of PMMA resin complex compared to desized glass fiber (p<0.05). 3. Roughness increased after abrasion test in case of PMMA resin reinforced with desized glass fiber (p<0.05). 4. Roughness change was not observed after abrasion test in case of PMMA resin reinforced with silane treated glass fiber (p>0.05).

Effect of DREAMMO<SUP>®</SUP> Scalp Lotion on Hair Growth Promotion in an Alopecia Model of C57BL/6 Mice

Seung Ho Lee,Hwa Jeung Lee,In Jeoung Baek,Jung Min Yon,Sang Yoon Nam,Beom Jun Lee,Young Won Yun,Yun-Bae Kim,Seock Yeon Hwang,Jin Tae Hong 한국실험동물학회 2006 Laboratory Animal Research Vol.22 No.1

Scalp hair loss has increased recently in young-aged people as well as middle-aged people, and although there are no serious in health problems, scalp hair loss may significantly affect a variety of psychological and social experiences and the individual's quality of life. DREAMMO scalp lotion is composed of several plant extracts which are known to be used as oriental medicine to prevent hair loss or promote hair growth in alopecia. This study was carried out to investigate the effect of DREAMMO scalp lotion on hair growth in an alopecia model of C57BL/6 mice. Mice were divided into three experimental groups including control, DREAMMO scalp lotion and 3% Minoxidil (MXD). The test compounds were topically treated with 0.2 ㎖ per mouse per day for 4 weeks. The hair growth was determined photographically and histologically in an alopecia model of C57BL/6 mice. After 3-4 weeks, DREAMMO scalp lotion significantly increased hair growth compared to the controls in the dorsal skin of C57BL/6 mice. DREAMMO scalp lotion also promoted the elongation of hair follicles than the controls. These results suggest that DREAMMO scalp lotion has a hair growth activity and can be useful for the treatment of alopecia.

Possible Involvement of Photoperiodic Regulation in Reproductive Endocrine System of Female Olive Flounder Paralichthys olivaceus

Hyun Chul Kim,Chi Hoon Lee,Sung Pyu Hur,Byeong Hoon Kim,Jun Young Park,Young Don Lee 한국발생생물학회 2015 발생과 생식 Vol.19 No.1

This study investigated possible involvement of photoperiodic regulation in reproductive endocrine system of female olive flounder. To investigate the influence on brain-pituitary axis in endocrine system by regulating photoperiod, compared expression level of Kisspeptin and sbGnRH mRNA in brain and FSH-β, LH-β and GH mRNA in pituitary before and after spawning. Photoperiod was treated natural photoperiod and long photoperiod (15L:9D) conditions from Aug. 2013 to Jun. 2014. Continuous long photoperiod treatment from Aug. (post-spawning phase) was inhibited gonadal development of female olive flounder. In natural photoperiod group, the Kiss2 expression level a significant declined in Mar. (spawning period). And also, FSH-β, LH-β and GH mRNA expression levels were increasing at this period. However, in long photoperiod group, hypothalamic Kiss2, FSH-β, LH-β and GH mRNA expression levels did not show any significant fluctuation. These results suggest that expression of hypothalamic Kiss2, GtH and GH in the pituitary would change in response to photoperiod and their possible involvement of photoperiodic regulation in reproductive endocrine system of the BPG axis.