Effects of Pilger Rolling and Heat Treatment on Microstructure and Corrosion Resistance of Ag-electroplated 304 Stainless Steel Tubes

Hyun Park,Woo‑Jin Lee,Jae‑Han Son,Han‑Kyun Shin,Sung‑Kyu Hong,Hyo‑Jong Lee 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8

We introduce a cost-effective method that combines electroplating with metal cold working processes to manufacture compositetubes with robust corrosion resistance. First, a 3-step electroplating process was developed to form an adhesive anduniform Ag coating on the outer wall of a 304 stainless steel tube. The process consisted of a Ni-strike step for removing thepassivation layer of the initial 304 tube, Cu deposition for smoothing the surface by adding a buffer layer, and Ag deposition. To reinforce the interfacial adhesion between the electroplated layers and the 304 tube and increase the area of the Ag coating,a pilger rolling or pilger rolling + heat-treatment process was performed after the Ag electroplating process. Scanningelectron microscopy of the composite tubes after each process indicated that the as-deposited Ag coating changed fromhaving a rough to smooth surface after only pilger rolling and with additional heat treatment. Electron backscatter diffractionanalysis of the microstructures and textures of the tubes revealed that dynamic recrystallization occurred extensively duringpilger rolling, resulting in the formation of a relatively defect-free grain structure without heat treatment. Furthermore,electrochemical polarization curves determined that the Ag-coated composite tubes are superior to the uncoated 304 tubein terms of corrosion resistance under Cl−atmosphere, owing to the formation of a AgCl passivation layer during testing. Surface analysis of the composite tubes suggests that the properties of the AgCl passivation layer are related to the grainsize of the Ag coating and the density of plastic-deformation-induced defects.

골격성 Ⅲ 급 부정교합자의 악골 부조화가 구치부 치성보상에 미치는 영향

성지현,김성식,손우성 대한치과교정학회 2003 대한치과교정학회지 Vol.33 No.1

골격성 Ⅲ 급 부정교합자는 부적절한 악골 위치에서 기능 교합을 유지하기 위해 치아의 경사도와 수직적 위치가 변화하게 된다. 이러한 치성보상은 전치부 및 구치부 전반에 걸쳐 일어나며, 현재 보편적으로 시행되고 있는 악교정수술을 위한 술전교정시 이를 제거하여 각 골격 구조내에서 치아들이 적절히 위치되도록 하여야 한다. 전치부 치성보상에 관한 측모 두부방사선 사진을 이용한 연구는 많이 시행되어졌으나, 구치부 경사도에 관한 연구는 미미한 실정이다. 이에 본 연구는 성인 골격성 Ⅲ 급 부정교합자의 전후방적, 수직적 악골 부조화에 따른 폭경 부조화 및 구치 경사도 변화를 알아보기 위해 진단 모형상에서 상하악 견치, 제1소구치, 제1대구치 부위의 기저골 폭경을 측정하여 상악에 대한 하악의 비율을 구하였으며, 모형을 삭제하여 좌우 구치간 경사도를 측정하였다. 악골 부조화 심화에 따른 기저골 폭경 비율과 제1대구치 협설 경사도 변화의 상관관계를 조사하여 다음과 같은 결론을 얻었다. 1. 골격성 Ⅲ 급 부정교합자의 악공의 전후방적 부조화가 심화될수록 상하악 구치간 각도합이 증가하여 치성보상이 많이 일어났으며, 특히 하악 구치가 설측 경사되는 치성보상을 보였다(p<0.001). 2. 골격성 Ⅲ 급 부정교합자의 악골의 수직적 부조화 및 폭경 부조화와 구치부 치성부상 간에는 유의할만한 상관성이 없었다. 3. 골격성 Ⅲ 급 부정교합자의 전후방적, 수직적 부조화의 심화와 기저골 폭경 부조화는 유의할만한 상관성이 없었다. This study examined the relations between degree of posterior dental compensation and skeletal discrepancy in Class Ⅲ malocclusion. The pretreatment lateral cephalograms and dental casts of 87 skeletal Class Ⅲ adults were selected to provide a random sampling of skeletal Class Ⅲ malocclusion. Skeletal discrepancy was described with ANB angle, Wits appraisal, Sn-Mn plane angle, FMA and ratios of basal arch width. Degree of posterior dental compensation was described with macillary intermolar angle, mandibular intermolar angle and sum of intermoloar angle. The relationships between skeletal discrepancy and degree of posterior dental compensation were analyzed with simple correlation analysis, stepwise multiple regression analysis. The results were as follows : 1. A strong association was found between the variation in the anteroposterior measure, ANB angle and the variation of posterior dental compensation measures, sum of intermolar angle and mandibular angle and mandibular intermolar angle in skeletal Class Ⅲ malocclusion. 2. There was no statistically significant relationship between the variation in the vertical measures and the variation of posterior dental compensation measures in skeletal Class Ⅲ malocclusion. 3. There was no statistically significant relationship between the variation in the anteroposterior and vertical measures and degree of basal arch width discrepancy.

Tuberculosis risk is associated with genetic polymorphisms in the LRP2, CUBN, and VDR genes

Sung‑Soo Kim,Sang In Lee,Hyun‑Seok Jin,Sangjung Park 한국유전학회 2020 Genes & Genomics Vol.42 No.10

Background Vitamin D (Vit. D) is used extensively during tuberculosis treatment. Low levels of serum Vit. D increase the risk of active tuberculosis development. Altered expression of the proteins involved in Vit. D metabolism impairs cathelicidin production, thereby increasing the host susceptibility to tuberculosis. Objective We are trying to investigate whether single nucleotide polymorphisms (SNPs) in LRP2, CUBN, and VDR genes could afect tuberculosis development. Methods We included participants of the Korean Association Resource (KARE), part of the Korean Genome and Epidemiology Study (KoGES), and used their recorded data. A total of 8840 people (4182 men and 4658 women) were eligible subjects. The 5-kb regions from the ends of transcripts of GC, LRP2, CUBN, and VDR genes were amplifed to select 13, 47, 70, and 15 SNPs, respectively. For association analysis and statistical analysis, PLINK version 1.07 and PASW Statistics version 18.0 were used. Results Signifcant correlation was observed in 11, 2, and 1 SNPs in LRP2, CUBN, and VDR genes. The efect of rs6747692 of LRP2 on transcription factor binding was confrmed using RegulomeDB. We confrmed that rs2239182 of VDR is located in the genomic eQTL region and can afect transcription factor binding and gene expression. Conclusions Genetic polymorphisms in genes encoding proteins involved in Vit. D metabolism infuence immune system components. Therefore, such polymorphisms may infuence the susceptibility to Mycobacterium tuberculosis invasion and alter the defense mechanisms against Mycobacterium tuberculosis infection. The correlation between genetic variation and tuberculosis development can provide new guidelines for the management of tuberculosis.

OVERSHOOT를 제거한 개선된 큐빅 스플라인 보간법에 관한 연구

김성현,김진만,조상현,주동현,김두영 東亞大學校附設情報技術硏究所 2005 情報技術硏究所論文誌 Vol.12 No.2

This study presents the improvement of cubic spline interpolation without overshoot. The o-riginal cubic spline interpolation has overshoots between two data. They are noises in still image zoom because of getting out of the pixel value. But the improvement of cubic spline in-terpolation removes them and proffers better quality still image than other interpolations.

평면형 Bi-Sb 다중접합 열전변환기의 특성

이현철,유호종,김진섭,함성호,신장규,이종현,이정희,권성원,박세일 경북대학교 센서기술연구소 1997 센서技術學術大會論文集 Vol.8 No.1

A planar Bi-Sb multijunction thermal converter for the precise measurements of ac voltage and current has been fabricated and its characteristics was discussed. In order to convert ac power into heat, a bifilar thin film Pt-heater, which could cancel its Thomson and Peltier effects, was prepared on the Si_(3)N_(4)/SiO_(2)/Si_(3)N_(4) diaphragm for the thermal isolation between heater and silicon substrate. To convert the temperature or the heat generated by the heater into dc voltage and current, hot and cold junctions of the Bi-Sb thermopile, which has a large difference in Seebeck coefficients, were formed on the dielectric diaphragm and the silicon substrate, respectively. The respective thermal sensitivity of the thermal converter with a bifilar heater was about 10.1 mV/mW and 14.8 mV/mW in the air and vacuum, which is about eight times higher than that of commercial 3-dimensional thermal converter. In the case of ac 2 V-input voltage, the ac-dc voltage transfer difference was about ±2.0 ppm, and in the case of ac 10 mA-input current, the ac-dc current transfer difference was about ± 0.6 ppm, in the frequency range from 10 Hz to 10 kHz.

SPHIT 알고리즘의 개선을 통한 JPEG2000 정지영상 부호화에서의 압축효율 개선

조상현,김성현,김진만,주동현,김두영 東亞大學校附設 情報技術硏究所 2004 情報技術硏究所論文誌 Vol.12 No.1

With the increasing use of multimedia technologies, image compression requires higher performance as well as new functionality. Specially, in the specific area of still image encoding, a new standard, JPEG2000 was developed. This paper proposed SPHIT Algorithm that uses a method to optimized selection of threshold from feature of wavelet transform coefficients and to removes sign bit in LL area on JPEG2000. Experimental results show the proposed algorithm achieves more improved bit rate.

비외상성 두개내 출혈 환자에서 심근손상의 발생과 예후에 미치는 영향

강구현,황성호,이강현,조준휘,김성환,문중범,박해상,이서영,이성수,김헌주 대한응급의학회 2000 대한응급의학회지 Vol.11 No.4

Objective: The aim of this study was to investigate the clinical significance of myocardial injuries in patients with nontraumatic intracranial hemorrhage by identifying the occurrence of myocardial injury and defining its correlation with subsequent cardiovascular events. Subjects and methods: One hundred twenty-four patients with nontraumatic intracraninal hemorrhage presented to the emergency department within six hours from onset of symptoms were enrolled. Brain CT, serial electrocardiography, and echocardiography were done at the emergency center. Blood samples for troponin I and creatine kinase(CK)-MB were drawn immediately and eight hours after admission, Troponin I and CK-MB were measured using a chemiluminescent immunoassay, respectively. Results: Electrocardiographic and echocardiography abnormalities were found in 65 cases(52.4%) and 21 cases(17%), respectively. Serum troponin I and creative kinase-MB were increased in 35 cases (28.2%) and in 58 cases(46.8%), respectively. Abnormal findings of echocardiography and ECG, as well as elevated levels of serum troponin I and creative kinase-MB, were associated with an increased risk of cardiovascular event and survival. Logistic regression analysis revealed that an abnormal echcocardiographic finding and elevation of serum troponin I were factors associated with the occurrence an adverse cardiovascular event and that electrocardiographic abnormalities and initial mental status were factors associated with poor prognosis. Conclusion: This study reveals that actual myocardial injury develops in a significant proportion of patients with nontraumatic intracranial hemorrhage and that the development of the myocardial injury is associated with an adverse cardiovascular event that occurs during admission.

주산기 백서에서 혈중 에스트로겐 농도와 공간 기억력과의 상관관계

박민성,박제민,신성현,한귀원,김명정,김성곤 大韓神經精神醫學會 2006 신경정신의학 Vol.45 No.5

Objectives : This study was designed to find possible effect of pregnancy and parturition on spatial memory, especially in relation to levels of estrogen during the third trimester and postpartal period in rats. Methods : 25 female Sprague Dawley rats were divided into pregnant group (N= 14) and control group (N= 11). Changes in spatial memory during 6 weeks including third trimester and postpartal period were measured using Morris water maze. Time to reach the platform in the maze was indicator of spatial memory. Serum estrogen level was measured on 1 week before delivery, postpartal day 1, and day 14. Results : Both groups showed gradual improvement in performance by trial days and weeks, but no significant difference was found between the two groups. However in the third trimester, pregnant group showed a trend of less achievement on 3 days of learning than control group. Serum estrogen levels did not differ significantly between groups over the 6 weeks of period. However there was positive correlation between serum estrogen level on postpartum day 1 and time to reach platform on postpartum week 2, and negative correlation between estrogen level on postpartum day 14 and latency to the platform on postpartum week 5. Conclusion : These results imply that changes in the serum estrogen level may have dual effects on the spatial learning in peripartal period. It is suggested that decline in cognitive function might occur either by failure of rapid decrease of estrogen, immediately after parturition, or retarded restoration of estrogen in later postpartal period.

입력전류 파형 개선형 단상 정류기의 토폴로지

이상현(Sang-Hyun Lee),박진민(Jin-Min Park),문상필(Sang-Pil Mun),서기영(Ki-Young Suh) 한국조명·전기설비학회 2003 한국조명·전기설비학회 학술대회논문집 Vol.2003 No.-

For small capacity rectifier circuits such as these for consumer electronics and appliances, capacitor input type rectifier circuits are generally used. Consequently, various harmonics generated within the power system become a serious problem. Various studies of this effect have been presented previously. However, most of these employ switching devices, such as FETs and the like. The absence of switching devices makes systems more tolerant to over-load, and brings low radio noise benefits. We propose a power factor correction scheme using a LC resonant in commercial frequency without switching devices. In this method, it makes a sinusoidal wave by widening conduction period using the current resonance in commercial frequency, Hence the harmonic characteristics can be significantly improved, where the lower order harmonics, such as the fifth and seventh order are much reduced. The result are confirmed by the theoretical and experiment implementations.

The impact of blowflies on pig cadaver decomposition on Yeongdo Island, Busan, South Korea

Park Sang‐Hyun,Baek Seung‐Ho,Moon Tae‐Young 한국곤충학회 2021 Entomological Research Vol.51 No.11

The decomposition process is an important factor in forensics, and flies play a crucial role in the decomposition of animals and humans. However, there remains limited information on the effect of flies that attend death scenes. This study assesses the effect of the presence or absence of blowflies on the rate and process of cadaver decomposition in the spring, summer, and autumn from 2016 to 2020 on Yeongdo Island, Busan, South Korea. Nine blowfly species belonging to four genera in two subfamilies were sampled. The blowflies that approached the cadavers differed between seasons, but Chrysomya pinguis (Walker) was the dominant species regardless of the season. Blowfly presence on cadavers significantly affected the duration of the decomposition stage and the pattern of weight loss in nearly all scenarios. With the presence of blowflies, the decomposition rate was four times faster in spring, three times faster in summer, and nine times faster in autumn. These results show that the presence or absence of blowflies is an essential factor in the decomposition process of cadavers. Therefore, it should be taken into account when estimating postmortem intervals in medicolegal forensic entomology.