Omphalocele–Exstrophy–Imperforate Anus–Spinal Defect Complex in an Infant from Monozygotic Twins Conceived by In Vitro Fertilization: A Case Report

백경윤,조혜정,김은진,김석영,손동우 대한주산의학회 2022 Perinatology Vol.33 No.4

The omphalocele–exstrophy–imperforate anus–spinal defect (OEIS) complex is a combination of congenital birth defects. This disease is rare and difficult to diagnose during pregnancy. However, if omphalocele, lumbosacral meningomyelocele, and difficulty in visualizing the bladder are observed on prenatal ultrasonography, the OEIS complex should be suspected. Prenatal diagnosis is important because this disease requires sophisticated multidisciplinary management to avoid excessive morbidity. We report a prenatally suspected case of OEIS complex in a fetus of monozygotic twins conceived by in vitro fertilization, which was later diagnosed after birth with omphalocele, bladder exstrophy, vesicointestinal fistula, imperforate anus, meningomyelocele, and club feet.

Effects of Substrate Preheating During Direct Energy Deposition on Microstructure, Hardness, Tensile Strength, and Notch Toughness

백경윤,이기용,박상후,심도식 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.6

This study examined the effects of substrate preheating for the hardfacing of cold-press dies using the high-speedtool steel AISI M4. The preheating of the substrate is a widely used technique for reducing the degree of thermaldeformation and preventing crack formation. We investigated the changes in the metallurgical and mechanicalproperties of the high-speed tool steel M4 deposited on an AISI D2 substrate with changes in the substrate preheatingtemperature. Five preheating temperatures (100-500 °C; interval of 100 °C) were selected, and the changesin the temperature of the substrate during deposition were observed. As the preheating temperature of the substratewas increased, the temperature gradient between the melting layer and the substrate decreased; this prevented theformation of internal cracks, owing to thermal stress relief. Field-emission scanning electron microscopy showedthat a dendritic structure was formed at the interface between the deposited layer and the substrate while a cellularmicrostructure was formed in the deposited layer. As the preheating temperature was increased, the sizes of thecells and precipitated carbides also increased. Furthermore, the hardness increased slightly while the strength andtoughness decreased. Moreover, the tensile and impact properties deteriorated rapidly at excessively high preheatingtemperatures (greater than 500 °C). The results of this study can be used as preheating criteria for achieving thedesired mechanical properties during the hardfacing of dies and molds.

단부처리시설물의 충격흡수구조설계에 따른 방호성능 개선 연구

백경윤,우수성,심도식,박원균,송대빈 한국기계가공학회 2022 한국기계가공학회지 Vol.21 No.11

In the event of a collision with the end of a vehicle guardrail, the high rigidity continues to pose a threat to the safety of passengers; hence, an end treatment facility must be mandatorily installed. This requires a shock-absorbing mechanism design to reduce the impact on the occupant and a shock-absorbing structure that can protect the occupant from an abrupt deceleration movement. In this study, the structure of a guardrail was improved. For a head-on collision of a vehicle with an end treatment facility, the impact absorption performance owing to the structure of the guardrail was observed by a simulation using ABAQUS, a finite element analysis program. To improve the impact absorption performance of the end treatment facility, we designed a structure in which a groove is formed in the guardrail, pressed in the longitudinal direction, and then pushed backward according to the groove shape to absorb the impact. The calculation of the reaction force of the collision member according to the guardrail groove shape showed that the wave shape had the lowest reaction force. The actual crash test report also satisfied the absorption performance evaluation with excellent results for the passenger protection performance evaluation criteria (THIV((Theoretical Head Impact Velocity)) 15.7% and PHD (Post-impact Head Deceleration) 21.17%).

Mechanical Characteristics of a Tool Steel Layer Deposited by Using Direct Energy Deposition

백경윤,신광용,이은미,심도식,이기용,윤희석,김명호 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.4

This study focuses on the mechanical characteristics of layered tool steel deposited using direct energydeposition (DED) technology. In the DED technique, a laser beam bonds injected metal powder and a thin layerof substrate via melting. In this study, AISI D2 substrate was hardfaced with AISI H13 and M2 metalpowders for mechanical testing. The mechanical and metallurgical characteristics of each specimen wereinvestigated via microstructure observation and hardness, wear, and impact tests. The obtained characteristicswere compared with those of heat-treated tool steel. The microstructures of the H13- and M2-depositedspecimens show fine cellular-dendrite solidification structures due to melting and subsequent rapid cooling. Moreover, the cellular grains of the deposited M2 layer were smaller than those of the H13 structure. Thehardness and wear resistance were most improved in the M2-deposited specimen, yet the H13-depositedspecimen had higher fracture toughness than the M2-deposited specimen and heat-treated D2.

RUS법에 의한 Micro-Crack을 가진 Ferrule의 주파수 특성 평가

백경윤,이길성,양순호,김성훈,조영재,민한기,양인영 朝鮮大學校 機械技術硏究所 2003 機械技術硏究 Vol.6 No.2

광섬유 정렬부품으로 사용되는 페롤은 극히 높은 정밀도를 요하는 제품으로서, 높은 치수 정밀도와 결함이 포함되지 않는 등 높은 신뢰성이 요구되는 제품이다. 이러한 페롤의 형상결함평가에 종래의 광학현미경 평가법과는 달리. 본 논문에서는 공명초음파법(ResonantUltrasound Spectroscopy)을 이용하고자 한다. 공명초음파법이란 결함이 없는 시험편을 기계적으로 진동시켰을 때의 공진 주파수와 시험편 내에 결함을 가지고 있을 때의 공명 주파수 양상을 비교 분석하여 결함유무를 검출해내는 방법이다. 본 연구에서는 양품과 크랙을 가진 시험편을 현장에서 직접 사용되고 있는 광학현미경에 의해 분류를 한 다음, 더욱 정확한 측정을 위해 SEM에 의해 다시 분류하였다. 각각에 대해 공진 주파수를 측정하였고, 이 데이터의 검증을 위해 FEM해석을 수행하였다. 실험으로부터 얻는 양품의 공진 주파수와 FEM해석을 통해 얻었던 양품의 공진 주파수의 오차는 1∼2%정도의 범위를 벗어나지 않음을 알 수 있었다. 또한 크랙에 대한 공진 주파수를 측정하여서, 양품의 공진 주파수와 비교를 행하였고, 이 데이터를 가지고 모드별로 히스토그램을 그려서, 그것으로부터 현장에서 실제로 이용 가능한 모드를 존재함을 확인하였다. The Ferrule which is used as the product optical fiber very precisely, is required high to set the optical axes of an dimensional precision, lack of defect and high expectation. Up to now the optical instrument has been used for the defect and shape inspection of the Ferrule, but in this paper we examined the detectable defect and expectation by using the Resonant Ultrasound Spectroscopy (RUS). The RUS is the measurement' which is to excite specimen and to inspect the difference of natural frequency pattern between acceptable specimen and specimen has some defects. In this paper, we classified specimens into three groups by using She optical instrument; acceptable specimen A-type, 3-type and specimen A-type which has crack. And we reclassified by Scanning Microscope to carry out the more exact measurement. We surveyed the resonant frequency of every specimen, and carried out the simulation from the explicit finite elements code, NasEran t o verify the experiment data. The average error between the resonant frequency of acceptable specimens which is obtained from experiment and that from FEM analysis is in the range of 1-2 percentage. Also, we measured the resonant frequency of specimen which has crack, and compared that of acceptable specimen. We drew histogram by using these data, and confirmed the available mode in the plant.

[소설 당선작] 푸른피

백경윤 숙명문학인회 2016 숙명문학 Vol.- No.4

FE Simulation-based Process Design for Manufacturing Structural Members of Commercial Vehicle using Pipes with Rectangular Cross-Sections

백경윤,심도식 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

Bent pipes are key components employed in vast quantities and diversities for satisfying the increasing demand for lightweight andhigh-strength products. Consequently, pipe bending has become an attractive manufacturing technology for lightweight productforming. This study examined the roll-bending process using a computer numerically controlled (CNC) profile bending machineequipped with three driving rolls. In this process, process design variables should be precisely designed to obtain smoothly curvedpipes with high precision and without defects. Specifically, the central roller position must be precisely determined by consideringspringback?which is inevitable in the cold-forming process. A numerical approach was applied to calculate the central roller positionfor producing the required curvature. The established FE model was compared with experimental results for validation and then usedto obtain the relationship between the central roller stroke and the final curvature of the bent pipe for various pipe material propertiesand cross-sections. The central roller position for producing the desired curvature was determined using a pipe deformation databaseobtained from a series of forming simulations, and the usefulness of the proposed numerical approach was evaluated.

창작 발표회 날

백경윤 성균관대학교 체육대학 1996 체육대학 학회지 Vol.12 No.1

Directed energy deposition (DED) 공정 연구개발 동향

백경윤,오욱진,심도식 대한금속재료학회(구 대한금속학회) 2019 재료마당 Vol.32 No.5

지형분류에 따른 구제역 발생 지역 유형분석

백경윤,이상윤,김명훈,김태형,손원근,김기연,김현태 경상대학교 농업생명과학연구원 2013 농업생명과학연구 Vol.47 No.6

The study was conducted to investigate the type analysis of foot and mouth disease area according to terrain classification. This study was analyzed Foot-and-mouth disease occurred 58 farmers and sampled 58 farms of non-occurrence farmers were classified terrain according to elevation, slope bearing, slope, stable bearing, adjacent road and adjacent town in Gyeongbuk area. Similar trend terrain elements between FMD farm and non-occurrence farm(items: Slope direction, farms direction, adjacent road and adjacent village). Different trend terrain elements between FMD farm and non-occurrence farm(items: Elevation, slope and adjacent river). Through this study, considering the many variables should be utilized to prevent the spread of foot-and-mouth disease estimation as a basis for classification but did not know the special terrain of foot-and-mouth disease outbreak farms. 2010년 구제역으로 많은 농가들이 피해를 입었으며, 발생원인과 바이러스 전파 과정에 대해서 명확한 원인과 근거를 찾을 수 없는 상태이다. 본 연구에서는 구제역의 발생에 있어서 불명확한 살처분 방지와 감염경로의 예측을 위한 지형적인 특성을 구명하고자, 2010년 경북지역을 대상으로 구제역이 발생한 농가 58개의 지형을 분류하였다. 분류요소는 농가가 위치한 고도, 경사도, 축사의 방향, 도로인접도, 마을인접도와 경사방향을 설정하여 발생농가의 지형적 자료를 각 항목에 분류하였다. 각 요소별 분류에서 고도와 경사도, 하천인접도에서는 차이점을 나타내었으나, 축사방향 및 경사방향, 도로인접도, 마을인접도에서는 유사한 지형적인 특성을 보였다. 본 연구를 통하여 구제역 발생 농가만의 특수한 지형은 알 수가 없었지만, 많은 변수들을 고려한 지형분류가 구제역 확산 방지와 예찰을 하기 위한 기초자료로 활용 될 수 있을 것으로 판단된다.