• Wind and Structures
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• 제36권3호
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• pp.201-213
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• 2023

In this study, the effect of sea surface temperature (SST) on the distribution of vertical wind speed in the atmospheric boundary layer of coastal areas was analyzed. In general, coastal areas are known to be more susceptible to various meteorological factors than inland areas due to interannual changes in sea surface temperature. Therefore, the purpose of this study is to analyze the relationship between sea surface temperature (ERA5) and wind resource data based on the meteorological mast of Høvsøre, the test bed area of the onshore wind farm in the coastal area of Denmark. In addition, the possibility of coastal disasters caused by abnormal vertical wind shear due to changes in sea surface temperature was also analyzed. According to the analysis of the correlation between the wind resource data at met mast and the sea surface temperature by ERA5, the wind speed from the sea and the vertical wind shear are stronger than from the inland, and are vulnerable to seasonal sea surface temperature fluctuations. In particular, the abnormal vertical wind shear, in which only the lower wind speed was strengthened and appeared in the form of a nose, mainly appeared in winter when the atmosphere was near-neutral or stable, and all occurred when the wind blows from the sea. This phenomenon usually occurred when there was a sudden change in sea surface temperature within a short period of time.

• Steel and Composite Structures
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• 제51권4호
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• pp.441-456
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• 2024

This paper aims to develop Machine Learning (ML) algorithms to predict the buckling resistance of cold-formed steel (CFS) channels with restrained flanges, widely used in typical CFS sheathed wall panels, and provide practical design tools for engineers. The effects of cross-sectional restraints were first evaluated on the elastic buckling behaviour of CFS channels subjected to pure axial compressive load or bending moment. Feedforward multi-layer Artificial Neural Networks (ANNs) were then trained on different datasets comprising CFS channels with various dimensions and properties, plate thicknesses, and restraining conditions on one or two flanges, while the elastic distortional buckling resistance of the elements were determined according to the Finite Strip Method (FSM). To develop less biased networks and ensure that every observation from the original dataset has the chance of appearing in the training and test set, a K-fold cross-validation technique was implemented. In addition, the hyperparameters of the ANNs were tuned using a grid search technique to provide ANNs with optimum performances. The results demonstrated that the trained ANNs were able to predict the elastic distortional buckling resistance of CFS flange-restrained elements with an average accuracy of 99% in terms of coefficient of determination. The developed models were then used to propose a simple ANN-based design formula for the prediction of the elastic distortional buckling stress of CFS flange-restrained elements. Finally, the proposed formula was further evaluated on a separate set of unseen data to ensure its accuracy for practical applications.

• 한국항행학회논문지
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• 제28권2호
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• pp.178-184
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• 2024

항공기 탑재 레이다는 전술 목적에 따라 다양한 운용 모드를 가지며, 각 모드별 운용 목적에 맞게 탐색 영역을 설정할 수 있도록 설계된다. 일반적인 AESA 레이다는 조종사가 탐색 영역을 지정하면 지정된 영역내 표적을 탐지하기 위해 사전 정의된 탐색빔 그리드에 따라 차례로 탐색빔을 방사하여 표적을 탐지하게 된다. 이때 자항공기의 자세가 변하더라도 사전에 조종사가 탐지하고자 하는 영역을 안정적으로 탐색할 수 있어야 한다. 본 논문은 항공기 탑재 레이다의 공대공 운용 모드에서 탐색 패턴 안정화를 통해 자항공기의 Roll과 Pitch 기동시에도 표적을 안정적으로 탐지할 수 있는 방안에 관한 것으로, 시스템 통합 시험 (SIL; system integration laboratory) 환경에서 자항공기의 기동과 표적을 모의하여 그 성능을 입증하였다.

• 대한방사선치료학회지
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• 제26권2호
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• pp.313-320
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• 2014

목 적 : Spine SBRT 치료 시 보편적인 치료방법인 콜리메이터 각도 $30^{\circ}$와 $330^{\circ}$를 각각 사용한 2회전 치료계획 (이하 Universal MLC VMAT)과 MLC 운동 방향과 척수 또는 마미 (이하 OAR)의 장축을 일치시킨 콜리메이터 각도 $273^{\circ}$와 $350^{\circ}$를 사용한 2회전 치료계획 (이하 Coaxial MLC VMAT) 유용성을 비교, 평가하고자 한다. 대상 및 방법 : 본원에서 Varian TBX을 이용하여, Coaxial MLC VMAT 치료 계획으로 치료 받은 spine SBRT환자 10명을 대상으로 하였다. 전산화치료계획은 Eclipse (ver 10.0.42, Varian, USA), PRO3 (Progressive Resolution Optimizer 10.0.28), AAA (Anisotropic Analytic Algorithm Ver 10.0.28) 알고리즘을 이용하였다. 치료계획은 VMAT로 겐트리 회전반경이 각각 $360^{\circ}$인 두 개의 ARC, 10MV FFF (Flattening Filter Free)를 이용하여 수립하였고, 각 ARC는 콜리메이터 각도 $273^{\circ}$, $350^{\circ}$로 설정하였다. 기존 치료계획을 바탕으로 실험군인 Universal MLC VMAT 치료계획을 수립하였다. 콜리메이터 각도를 제외한 모든 조건은 동일하게 설정하였으며, 특히 최적화 (VMAT optimization) 과정에서 무작위하게 나타나는 선량차이를 최소화하기 위해 각각 2회의 최적화, 선량 계산 과정을 거쳤다. 계산 grid 는 0.2 cm, normalization은 타겟 $V_{100%}=90%$로 설정하였다. OAR의 선량 $V_{10Gy}$, $D_{0.03cc}$, Dmean, 타겟의 H.I (Homogeneity index) 그리고 각 치료 계획의 Total MU를 평가 지표로 설정하였고, Mapcheck2 (Sun Nuclear Co., USA) 와 Mapphan (Sun Nuclear Co., USA) 그리고 SNC patient (Sun Nuclear Co., USA Ver 6.1.2.18513) 를 이용하여 Coaxial MLC VMAT 계획의 임상 적용 가능 여부 확인을 위한 IMRT verification QA (gamma test)를 실시하였다. 결 과 : 두 치료계획을 비교한 결과 OAR의 $V_{10Gy}$차이는 최대 4.1%, 최소 0.4%, 평균 1.9%로, $D_{0.03cc}$ 는 최대 83.5 cGy, 최소 2.2 cGy, 평균 33.3 cGy로 Coaxial MLC VMAT plan 이 더 낮은 것으로 나타났다. Dmean 또한 최대 34.8 cGy, 최소 -13.0 cGy, 평균 9.6 cGy로 Coaxial MLC VMAT plan 이 낮은 것으로 나타났다. H.I. 는 최대 0.04, 최소 0.01로 Coaxial MLC VMAT plan 이 평균 0.02 낮은 것으로 나타났으며, Total MU의 평균값을 비교한 결과 Coaxial MLC VMAT plan 이 평균 74.1 MU 더 낮게 나타났다. Coaxial MLC VMAT plan에 대한 IMRT verification gamma test 결과는 1 mm / 2%, pass rate 90.0% 기준을 모두 통과하였다. 결 론 : Coaxial MLC VMAT 치료계획은 Universal MLC VMAT 치료계획에 비해 대부분의 평가지표에서 유리한 것으로 나타냈으며 특히 OAR의 선량 $V_{10Gy}$을 낮추는데 있어 탁월한 것으로 사료된다. 실험결과를 바탕으로 두 치료 계획을 비교해 볼 때, 같은 MU를 사용한다면 Coaxial MLC VMAT 치료계획이 Universal MLC VMAT 치료계획에 비해 효율적이라 사료된다.

• Archives of Plastic Surgery
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• 제36권3호
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• pp.283-288
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• 2009

Purpose: Frey's syndrome is a common complication after parotid surgery and characterized by gustatory sweating and flushing in the periauricular area during meals. Although a variety of methods have been proposed to prevent this postoperative problem but they have been unsatisfactory. In this article, therefore, botulinum toxin A was used to treat nine patients with Frey's syndrome and its duration effect after injection was investigated. Methods: Nine patients became the object of study about the effect of botulinum toxins as treatment of Frey's syndrome. Age of patients ranged from 25 to 78 years (mean, 43.7 years). Six of nine patients had both symptoms of gustatory sweating and flushing. And the others had only gustatory sweating symptom. Using Minor starch iodine test, the affected skin area was detected, and it was marked by $1cm^2$ sized grid appearance. After application of EMLA cream on the gustatory sweating area, botulinum toxin A was injected intracutaneously into the affected skin area ($2.5U/cm^2$). Patients were followed up from six to fifteen months (mean, about 12 months) and asked about improvement of their symptoms. Results: The treatement with botulinum toxin A took effective within two days after injection. Six months after injection, gustatory sweating disappeared completely in all patients, and five of six patients who had gustatory flushing improved in their symptom. Last follow-up, no patients complained of recurrent gustatory sweating and flushing except one. One patient, seven months after initial injection, was retreated with botulinum toxin A because of recurrence, and the result was successful. The duration of the effect after botulinum toxin A treatment was ranged from seven to thirteen months. One patient in our series experienced the upper eyelid weakness as adverse effect, but it improved spontaneously. Conclusion: Local injection of botulinum toxin A is an effective, safe and long - lasting method for treatment of Frey's syndrome. Hereafter, however, additional study will be required to evaluate the duration effect of botulinum toxin A according to frequency in use and dosage.

• 한국산학기술학회논문지
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• 제19권5호
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• pp.184-189
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• 2018

최근에 안전기준과 환경규제 강화의 증대로 인해, 차체의 경량화에 대한 연구가 지속적으로 증가하고 있다. 고강도강의 응용은 가장 보편화 된 차체 경량화의 효과적인 방법 중에 하나이다. TWB(Tailor Welded Blank)는 다양한 두께와 용접을 사용하여 부분적인 강도와 경량화를 만족시키는 주요한 공법으로 활용되고 있다. 그러나 추가적인 용접공정으로 인해 판재간의 용접성이 중요하고 용접부에 대한 품질관리가 중요하다. 이점을 개선하기 위해, TRB(Tailor Rollded Blank)공법이 제안되었다. TRB는 롤러 압력을 조절하여 판재의 두께를 다르게 하고, 용접을 사용하는 TWB 공법보다 추가적인 용접공정이 없기 때문에 생산 비용적인 측면에서 훨씬 더 효율적이다. 본 연구에서는 Blank의 압연 영향을 조사하기 위해 스탬핑용 고강도강 TRB 판재의 성형성을 분석하였다. 성형성을 분석하기 위해, TRB 판재에서 0.8 mm, 1 mm의 두께를 갖는 부분을 채취하여 시험하였다. 시편에 새겨진 그리드마킹의 변형도를 분석하여 변형률을 조사하였고, 0.8 mm와 1.0 mm의 두께를 갖는 TRB 시편으로 Erichsen 시험을 한 후에 FE분석을 활용하여 성형성과 고유진동수를 비교하였다.

• 마이크로전자및패키징학회지
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• 제22권1호
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• pp.69-74
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• 2015

첨단 전자기기에 사용되는 전자부품의 크기와 접속피치가 감소하면서 리플로우 공정 후 플럭스 잔사의 세정이 어려워짐에 따라 무세정 솔더 페이스트에 대한 요구가 증가하고 있다. 본 연구에서는 SAC305 솔더분말과 에폭시 레진을 주성분으로 하는 경화성 플럭스를 혼합하여 제조한 에폭시 경화형 솔더 페이스트에 대하여 리플로우 공정성, 플럭스 잔사의 부식성, 솔더볼 및 보드레벨 BGA 패키지 솔더 접합부의 기계적 거동을 기존 로진계 솔더 페이스트와 비교하여 평가하였다. 에폭시 경화형 솔더 페이스트는 솔더 접합부 주변에 경화물 필렛을 형성한 것으로 보아 플럭싱 작용에 의해 솔더 접합부가 형성된 이후에 경화반응이 진행되는 것을 확인할 수 있었으며, 동판에 대한 젖음성 시험을 통해 기존상용 솔더 페이스트 정도의 납퍼짐성을 갖는 것을 알 수 있었다. 리플로우 후 동판에 대한 고온 고습 시험을 통해 에폭시 경화형 솔더 페이스트는 동판 부식을 전혀 발생시키지 않는 것으로 나타났는데, 이는 FT-IR 분석결과 에폭시 경화반응을 통해 단단히 고정된 결과로 생각되었다. 볼전단, 볼당김 및 다이전단 시험 결과, 솔더 접합부 주변에 형성된 경화물 필렛은 솔더 표면과 접착본딩을 형성하며, 다이전단강도를 15~40% 정도 향상시키는 것으로 보아 에폭시 경화형 솔더 페이스트는 플럭스 잔사 세정공정의 생략과 함께 솔더 접합부 보강효과를 통해 패키지 신뢰성 향상에도 기여할 수 있을 것으로 생각되었다.

• 한국조경학회지
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• 제24권3호
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• pp.96-108
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• 1996

This study aimed at choosing the urban community parks such as D Kjin, Chungang, Dosan Park as the target place for this study, and at analyzing the damage level of the pavement surfaces focusing on the spaces and the materials. We devided the damage level within $1.5\times$1.5m grid int the grade from one to five points, and made use of the method of giving marks to get hold of the damage level of the pavement surfaces. Especially we took and analyze Duncan test for the spaces suffering severe damage. The result is as follows : 1. The damage of unenenness turned out to be a most excessive damage in the damage level according to the pavement materials in case of D kjin, and Chunggnag Park. Especially the concrete blocks proved to be the exessive damage in comparison with the other pavement materials, and the demolitional damage of the damage types to the most severe damage. The corner damage turned relatively out to be a heavy damage in case of Dosan Park in Seoul. 2. In the event of the damage level of pavement surfaces according to the spaces, the space which was made the more use of and which was the more concentrated, turned out to be the degree of the more excessive damage. 3. We took the Duncan test to verify the deference of the damage type between the spaces and the pavement materials of the target places for survey. The result of verification was that there was no difference of the damage type between the corner and block damage itself in case of the enterance area and the square of D kjin Park in Ch nju, and that the damage level of the pavement materials proved to be the more execssive damage than that of the spaces. The corner damage of Chungang Park in Hj ngju, showed the same result as D kjin Park in Ch nju and the uneveness didn't have any difference of damage type in all spaces. In case of Dosan in Seoul, the damage of crevice, demolition, and pumping didn't have any difference of damage type and the damage of the cross area was the most high. In conclusion, we proposed that we should get hold of whether the cause of pavement damage is caused by the defect of materials of by the construction problem including the foundation, or the unsuitableness of the method for using the pavement materials, and also that we should take a sensus of the user type and should decide a suitable design load and the necessary thickness of the pavement materials. In this study, not only we aimed at the external damage of the materials, but we tried to propose rather reasonable and developed construction method by studying the material experiment, the foundation state, and the type of using the spaces and materials, and by examining into the fundamental damaged cause.

• 한국안광학회지
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• 제19권1호
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• pp.17-22
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• 2014

목적: 시력검사거리에 따른 원거리 시력검사의 신뢰성을 평가하고자 하였다. 방법: 5 m 거리에서 교정시력이 1.0 이상이 되었던 성인 39명(78안)을 대상으로 하였다. 각각의 검사거리(5 m, 4 m, 그리고 3 m)에서 대상자의 교정굴절력을 측정하였다. 시시력표는 자동 챠트(LCD-700, Hyeseong Optic. Co., Korea)를, 타각적 굴절검사는 검영기(Beta 200, Heine, Germany)와 자동굴절검사기(RK-5, Canon, Japan)를 사용하였다. 조절력검사는 (-)렌즈 부가법으로, 조절래그 검사는 근거리 격자시표를 사용하였다. 결과: 구면교정굴절력은 5 m에 비하여 3 m에서 평균 $0.10{\pm}0.38$ D 감소하였고 난시도는 $0.05{\pm}0.10$ D 감소하였으며, 난시축은 우좌안이 귀방향으로 각각 $2.64{\pm}18.75$ 도, $11.43{\pm}48.55$ 도 회전하였다. 교정굴절력의 변동과 난시도의 변동은 최대교정굴절력과의 약한 음의 상관관계를 보였다(r=-0.31, r=-0.29). 결론: 검사거리에 따라 구면교정굴절력과 난시도는 5 m에 비하여 3 m에서 감소하며, 난시축은 귀방향으로 회전하는 경향이 있기 때문에, 안경원에서 원거리 시력검사를 위한 검사거리는 5 m로 개선되어져야 할 것이다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.431-432
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• 2012

In the era of 20 nm scaled semiconductor volume manufacturing, Microelectronics Manufacturing Engineering Education is presented in this paper. The purpose of microelectronic engineering education is to educate engineers to work in the semiconductor industry; it is therefore should be considered even before than technology development. Three Microelectronics Manufacturing Engineering related courses are introduced, and how undergraduate students acquired hands-on experience on Microelectronics fabrication and manufacturing. Conventionally employed wire bonding was recognized as not only an additional parasitic source in high-frequency mobile applications due to the increased inductance caused from the wiring loop, but also a huddle for minimizing IC packaging footprint. To alleviate the concerns, chip bumping technologies such as flip chip bumping and pillar bumping have been suggested as promising chip assembly methods to provide high-density interconnects and lower signal propagation delay [1,2]. Aluminum as metal interconnecting material over the decades in integrated circuits (ICs) manufacturing has been rapidly replaced with copper in majority IC products. A single copper metal layer with various test patterns of lines and vias and $400{\mu}m$ by $400{\mu}m$ interconnected pads are formed. Mask M1 allows metal interconnection patterns on 4" wafers with AZ1512 positive tone photoresist, and Cu/TiN/Ti layers are wet etched in two steps. We employed WPR, a thick patternable negative photoresist, manufactured by JSR Corp., which is specifically developed as dielectric material for multi- chip packaging (MCP) and package-on-package (PoP). Spin-coating at 1,000 rpm, i-line UV exposure, and 1 hour curing at $110^{\circ}C$ allows about $25{\mu}m$ thick passivation layer before performing wafer level soldering. Conventional Si3N4 passivation between Cu and WPR layer using plasma CVD can be an optional. To practice the board level flip chip assembly, individual students draw their own fan-outs of 40 rectangle pads using Eagle CAD, a free PCB artwork EDA. Individuals then transfer the test circuitry on a blank CCFL board followed by Cu etching and solder mask processes. Negative dry film resist (DFR), Accimage$^{(R)}$, manufactured by Kolon Industries, Inc., was used for solder resist for ball grid array (BGA). We demonstrated how Microelectronics Manufacturing Engineering education has been performed by presenting brief intermediate by-product from undergraduate and graduate students. Microelectronics Manufacturing Engineering, once again, is to educating engineers to actively work in the area of semiconductor manufacturing. Through one semester senior level hands-on laboratory course, participating students will have clearer understanding on microelectronics manufacturing and realized the importance of manufacturing yield in practice.