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Hybrid Friction Stir Welding of High-carbon Steel

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Journal of Materials Science & Technology 2011年第2期27卷 127-130页

作者： Don-Hyun Choi Chang-Yong Lee byung-wook ahn Jung-Hyun Choi Yun-Mo Yeon Keun Song Seung-Gab Hong Won-Bae Lee Ki-Bong Kang Seung-Boo Jung School of Advanced Materials Science and Engineering Sungkyunkwan University 300 Cheoncheon-dongJangan-guSuwonGyeonggi-do 440-746South Korea Department of Mechanical Engineering Korea Advanced Institute of Science and Technology 335 GwahangnoYuseong-guDaejeon 305-701South Korea Department of Advanced Materials Application Suwon Science College 9-10Botong-liJeongnam-myeonHwasungGyeonggi-do 445-742South Korea Technical Research Lab POSCO Corp.Goedong-dongNam-guPohangGyeongbuk790-785South Korea

A high-carbon steel joint,SK5（0.84 wt% C）,was successfully welded by friction stir welding（FSW）,both without and with a gas torch,in order to control the cooling rate during *** welding,the weld zone comprised gray and black regions,corresponding to microstructural variation：a martensite structure and a duplex structure of ferrite and cementite,*** volume fraction of the martensite structure and the Vickers hardness in the welds were decreased with the using of the gas torch,which was related with the lower cooling rate.

关键词： Friction stir welding High-carbon steel Transformation Martensite

Microstructure and mechanical property of A356 based composite by friction stir processing

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Transactions of Nonferrous Metals Society of China 2013年第2期23卷 335-340页

作者： Don-Hyun CHOI Yong-Hwan KIM byung-wook ahn Yong-Il KIM Seung-Boo JUNG School of Advanced Materials Science and Engineering Sungkyunkwan University300 Cheoncheon-dong Jangan-gu Suwon Gyeonggi-do 440-746 Korea MEPL Sungkyunkwan University 300 Cheoncheon-dong Jangan-gu Suwon Gyeonggi-do 440-746 Korea

Friction stir processing （FSP） was used to incorporate SiC particles into the matrix of A356 Al alloy to form composite material. Constant tool rotation speed of 1800 r/min and travel speed of 127 mm/min were used in this study. The base metal （BM） shows the hypoeutectic Al-Si dendrite structure. The microstructure of the stir zone （SZ） is very different from that of the BM. The eutectic Si and SiC particles are dispersed homogeneously in primary Al solid solution. The thermo-mechanically affected zone （TMAZ）, where the original microstructure is greatly deformed, is characterized by dispersed eutectic Si and SiC particles aligned along the rotational direction of the tool. The hardness of the SZ shows higher value than that of the BM because some defects are remarkably reduced and the eutectic Si and SiC particles are dispersed over the SZ.

关键词： friction stir processing A356 alloy SiC powder eutectic Si

Regression tree ensemble learning-based prediction of the heating and cooling loads of residential buildings

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Building Simulation 2022年第11期15卷 2003-2017页

作者： Nikhil Pachauri Chang wook ahn Al Graduate School Gwangju Institute of Science and Technology123 Cheomdangwagi-roBuk-guGwangju 61005R.O.Korea

Building energy consumption is heavily dependent on its heating load(HL)and cooling load(CL).Therefore,an efficient building demand forecast is critical for ensuring energy savings and improving the operating efficacy of the heating,ventilation,and air conditioning(HVAC)*** and specialized energy-efficient building modeling technologies may offer a fair estimate of the influence of different construction ***,deploying these tools could be time-consuming and complex for the ***,in this article,an ensemble model based on decision trees and the least square-boosting(LS-boosting)algorithm known as the regression tree ensemble(RTE)is proposed for the accurate prediction of HL and *** hyper parameters of the RTE are optimized by shuffled frog leaping optimization(SFLA),which leads to *** regression(STR)and Gaussian process regression(GPR)based on different kernel functions are also designed for comparison *** demonstrate that the value of root mean squared error is reduced by 37%–68%and 30%–41%for HL and CL of residential buildings,respectively,by the proposed SRTE in comparison to other ***,the findings from the real dataset support the proposed model’s effectiveness in predicting HVAC energy *** can be concluded that the proposed SRTE is more effective and accurate than other methods for predicting the energy consumption of HVAC systems.

关键词： energy heating load cooling load decision tree LS-boosting shuffled frog leaping optimization

UEs Power Reduction Evolution with Adaptive Mechanism over LTE Wireless Networks

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Journal of Electronic Science and Technology 2018年第1期16卷 79-83页

作者： Ruchi Sachan Chang wook ahn Department of Computer Engineering Sungkyunkwan UniversityGyeonggi-do 16419

At present, the major drawback for mobile phones is the issue of power consumption. As one of the alternatives to decrease the power consumption of standard, power-hungry location-based services usually require the knowledge of how individual phone features consume power. A typical phone feature is that the applications related to multimedia streaming utilize more power while receiving, processing, and displaying the multimedia contents, thus contributing to the increased power consumption. There is a growing concern that current battery modules have limited capability in fulfilling the long-term energy need for the progress on the mobile phone because of increasing power consumption during multimedia streaming processes. Considering this, in this paper, we provide an offline meaning sleep-mode method to compute the minimum power consumption comparing with the power-on solution to save power by implementing energy rate adaptation(RA) mechanism based on mobile excess energy level purpose to save battery power use. Our simulation results show that our RA method preserves efficient power while achieving better throughput compared with the mechanism without rate adaptation(WRA).

关键词： Green communication 4 generation long term evolution(4G LTE) networks rate adaptation(RA) power consumption model

Holographic memory-based Bayesian optimization algorithm (HM-BOA) in dynamic environments

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Science China(Information Sciences) 2013年第9期56卷 110-126页

作者： KAEDI Marjan GHASEM-AGHAEE Nasser ahn Chang wook Department of Information technology Engineering University of Isfahan Department of Computer Engineering University of Isfahan Department of Computer Engineering Sungkyunkwan University

This paper presents a new evolutionary dynamic optimization algorithm, holographic memory-based Bayesian optimization algorithm (HM-BOA), whose objective is to address the weaknesses of sequential memory-based dynamic optimization approaches. To this end, holographic associative neural memory is applied to one of the recent successful memory-based evolutionary methods, DBN-MBOA (memory-based BOA with dynamic Bayesian networks). Holographic memory is appropriate for encoding environmental changes since its stimulus and response data are represented by a vector of complex numbers such that the phase and the magnitude denote the information and its confidence level, respectively. In the learning process in HM-BOA, holographic memory is trained by probabilistic models at every environmental change. Its weight matrix contains abstract information obtained from previous changes and is used for constructing a new probabilistic model when the environment changes. The unique features of HM-BOA are: 1) the stored information can be generalized, and 2) a small amount of memory is required for storing the probabilistic models. Experimental results adduce grounds for its effectiveness especially in random environments.

关键词： dynamic optimization Bayesian optimization algorithm holographic memory dynamic Bayesian networks.

^(27)Al MAS-NMR study of inorganic polymer formation at ambient temperature

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Transactions of Nonferrous Metals Society of China 2011年第A1期21卷 182-187页

作者： Sang-wook ahn Hee-Soo LEE Wan-Hee YANG Jung-Woo LEE Young-Keun JEONG National Core Research Center for Hybrid Materials Solution Pusan National University School of Material Science and Engineering Pusan National University INTChem Co. Ltd.

Inorganic polymers are a novel class of materials formed by the polymerization of silicon, aluminium and oxygen species to form an amorphous three-dimensional framework structure. The basis of this process is the alkaline solutions to induce a certain amount of Si and AI atoms to dissolve from a feedstock such as aluminosilicate. A study of 27A1 MAS-NMR was carried out in an attempt to understand the reaction mechanism of the inorganic polymerization at ambient temperature. Scanning electron microscopy （SEM） and X-ray diflYactometry （XRD） were also employed to establish the composition and microstructure of the inorganic polymerization. Specimens were prepared with different A1/Si mole ratios from the starting materials. The higher the AI content, the more sufficient the AI atoms that can combine with SiO4, and the longer the reaction time, the more the bonded Si--O--A1--O polymer structure, and then the higher the A1 content, the fewer the octahedral A1 with a uniform Si--O--A1--O structure in four directions, because four AI atoms are combined with SiO4, resulting in a uniform Si--O--AI--O structure in four directions. The results show that they have an amorphous microstructure.

关键词： inorganic polymer amorphous tetrahedral

Metastatic liver cancer: A rare case

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World Journal of Gastroenterology 2005年第27期11卷 4281-4284页

作者： Bong-Wan Kim Hee-Jung Wang In-Ho Jeong Sang-Ick ahn Myoung-wook Kim Department of Surgery

Hemangioperioltoma is a rare tumor especially when it rises in the peritoneal cavity. We present a case of a 60-year-old woman with an isolated recurrent hemangiopericytoma of the liver. The patient presented with a palpable right upper quadrant abdominal mass, which occurred 7 years after undergoing resection of a malignant hemangiopericytoma arising from the greater omentum. She had not followed up 6 mo after surgery. Various imaging studies showed a single large, well-capsulated liver tumor with central necrosis, accompanied by hypervascularity typical of a vascular tumor. Preoperative laboratory HBsAg and anti-HCV workup were both negative. Under the impression of recurrent malignant hemangiopericytoma, right trisegmentectomy was performed to completely resect the tumor. Pathological examination confirmed the diagnosis of recurrent hemangiopericytoma. Even though the incidence of the hemangiopericytoma is relatively low, malignant hemangiopericytoma has a tendency to recur frequently after a long-term disease-free interval. Also, the recurrent hemangiopericytoma is not easily detected early during follow-up until it becomes symptomatic because there are no specific tumor markers, and because of the diversity with regard to site of recurrence. The authors suggest that Positron Emission Tomogram （PET） may be a useful tool for the detection of recurrent hemangioperioltoma. We describe herein some characteristics and behaviors of malignant hemangiopericytoma, particularly after surgical resection.

关键词： Hemangiopericytoma Greater omentum Hepatic metastasis Follow-up Positron emission tomography

Ischemic colitis after enema administration: Incidence, timing, and clinical features

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World Journal of Gastroenterology 2020年第41期26卷 6442-6454页

作者： Yura ahn Gil-Sun Hong Ju Hee Lee Choong wook Lee Seon-Ok Kim Department of Radiology and Research Institute of Radiology University of Ulsan College of Medicine&Asan Medical CenterSeoul 05505South Korea Department of Clinical Epidemiology and Biostatistics Asan Medical CenterUniversity of Ulsan College of MedicineSeoul 05505South Korea

BACKGROUND Enema administration is a common procedure in the emergency department(ED). However, several published case reports on enema-related ischemic colitis(IC) have raised the concerns regarding the safety of enema agents. Nevertheless, information on its true incidence and characteristics are still *** To investigate the incidence, timing, and risk factors of IC in patients receiving *** We consecutively collected the data of all adult patients receiving various enema administrations in the ED from January 2010 to December 2018 and identified patients confirmed with IC following enema. Of 8320 patients receiving glycerin enema, 19 diagnosed of IC were compared with an age-matched control group without *** The incidence of IC was 0.23% among 8320 patients receiving glycerin enema;however, there was no occurrence of IC among those who used other enema agents. The mean age ± standard deviation(SD) of patients with glycerin enemarelated IC was 70.2 ± 11.7. The mean time interval ± SD from glycerin enema administration to IC occurrence was 5.5 h ± 3.9 h(range 1-15 h). Of the 19 glycerin enema-related IC cases, 15(79.0%) were diagnosed within 8 h. The independent risk factors for glycerin-related IC were the constipation score [Odds ratio(OR), 2.0;95% confidence interval(CI): 1.1-3.5, P = 0.017] and leukocytosis(OR, 4.5;95%CI: 1.4-14.7, P = 0.012).CONCLUSION The incidence of glycerin enema-related IC was 0.23% and occurred mostly in the elderly in the early period following enema administration. Glycerin enemarelated IC was associated with the constipation score and leukocytosis.

关键词： Enema Glycerin Ischemic colitis Incidence Timing Risk factors

Efficacy of Seprafilm~ graft with adhesiolysis in experimentally induced lid adhesion in rabbits

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International Journal of Ophthalmology(English edition) 2013年第1期6卷 44-49页

作者： Sang wook Jin Hee Bae ahn Mi Sook Roh Yoon Hyung Kwon Won Yeol Ryu Department of Ophthalmology College of MedicineDong-A University Department of Pathology College of MedicineDong-A University

AIM:To evaluate the efficacy of Seprafilm transplantation following adhesiolysis for preventing postoperative readhesion and improving surgical outcomes. METHODS:Primary blepharoplasty was carried out on both eyelids of 18 albino rabbits. After 2 weeks, a new skin incision was made, and adhesiolysis was performed on both eyelids. The rabbits were categorized into two groups, one with adhesiolysis alone in the left eyelid (control group), and the other with adhesiolysis with a Seprafilm graft in the right eyelid (Seprafilm group). The degrees of inflammation and fibrosis were examined with hematoxylin-eosin (HE) and Masson’s trichrome stains. Expression of α-smooth muscle actin (α-SMA) was also immunohistochemically examined. RESULTS:Eyelid examination immediately after the operation revealed mild swelling and hemorrhage in both groups, but these symptoms resolved after 1 week-2 weeks, and eyelid shape had recovered completely in both groups. Microscopic assessments demonstrated that the Seprafilm group showed less inflammation and fibrosis than the control group. The Seprafilm group also exhibited fewer α-SMA-positive cells than the control group. CONCLUSION:Based on these findings, we conclude that Seprafilm graft with adhesiolysis is an effective method for preventing postoperative readhesions after eyelid surgery.

关键词： Seprafilm adhesion adhesiolysis