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Byte Frequency Based Indicators for Crypto-Ransomware Detection from Empirical Analysis

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Journal of Computer Science & Technology 2022年第2期37卷 423-442页

作者： Geun Yong Kim joon-young Paik Yeongcheol Kim Eun-Sun cho Department of Computer Science and Engineering Chungnam National UniversityDaejeon 34134South Korea School of Computer Science and Technology Tiangong UniversityTianjin 300387China

File entropy is one of the major indicators of crypto-ransomware because the encryption by ransomware increases the randomness of file ***,entropy-based ransomware detection has certain limitations;for example,when distinguishing ransomware-encrypted files from normal files with inherently high-level entropy,misclassification is very *** addition,the entropy evaluation cost for an entire file renders entropy-based detection impractical for large *** this paper,we propose two indicators based on byte frequency for use in ransomware detection;these are termed EntropySA and DistSA,and both consider the interesting characteristics of certain file subareas termed“sample areas”(SAs).For an encrypted file,both the sampled area and the whole file exhibit high-level randomness,but for a plain file,the sampled area embeds informative structures such as a file header and thus exhibits relatively low-level randomness even though the entire file exhibits high-level *** and DistSA use“byte frequency”and a variation of byte frequency,respectively,derived from sampled *** indicators cause less overhead than other entropy-based detection methods,as experimentally proven using realistic ransomware *** evaluate the effectiveness and feasibility of our indicators,we also employ three expensive but elaborate classification models(neural network,support vector machine and threshold-based approaches).Using these models,our experimental indicators yielded an average Fl-measure of 0.994 and an average detection rate of 99.46%for file encryption attacks by realistic ransomware samples.

关键词： computer security cryptography machine learning ransomware

Preliminary experimental study of a supercritical CO2 power cycle test loop with a high-speed turbo-generator using R134a under similarity conditions

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Frontiers in Energy 2017年第4期11卷 452-460页

作者： Junhyun cho Hyungki SHIN Jongjae cho young-Seok KANG Ho-Sang RA Chulwoo ROH Beomjoon LEE Gilbong LEE Byunghui KIM young-Jin BAIK Thermal Energy System Laboratory Korea Institute of Energy Research 152 Gajeong-ro Yusung-gu Daejeon 34129 Republic of Korea Engine Component Research Team Korea Aerospace Research Institute (KARl) 169-84 Gwahak-ro Yusung-gu Daejeon 34133 Republic of Korea InGineers 21 Saman-ro 16 Beon-gil Gimhae-si Gyeongsangnam-do 621-220 Republic of Korea

Research on applying a supercritical carbon dioxide power cycle （S-CO2） to concentrating solar power （CSP） instead of a steam Rankine cycle or an air Brayton cycle has been recently conducted. An S-CO2 system is suitable for CSP owing to its compactness, higher efficiency, and dry-cooling capability. At the Korea Institute of Energy Research （KIER）, to implement an S-CO2 system, a 10 kWe class test loop with a turbine- alternator-compressor （TAC） using gas foil bearings was developed. A basic sub-kWe class test loop with a high- speed radial type turbo-generator and a test loop with a capability of tens of kWe with an axial type turbo- generator were then developed. To solve the technical bottleneck of S-CO2 turbomachinery, a partial admission nozzle and oil-lubrication bearings were used in the turbo- generators. To experience the closed-power cycle and develop an operational strategy of S-CO2 operated at high pressure, an organic Rankine cycle （ORC） operating test using a refrigerant as the working fluid was conducted owing to its operational capability at relatively low- pressure conditions of approximately 30 to 40 bar. By operating the sub-kWe class test loop using R134a as the working fluid instead of CO2, an average turbine power of 400 W was obtained.

关键词： supercritical CO2 power cycle turbomachin-ery compressor turbine

Nitrile Electrolyte Strategy for 4.9 V-Class Lithium-Metal Batteries Operating in Flame

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Energy & Environmental Materials 2023年第3期6卷 229-237页

作者： Hyunseok Moon Sung-Ju cho Dae-Eun Yu Sang-young Lee Department of Chemical and Biomolecular Engineering Yonsei UniversitySeoul 03722Korea Molecular Foundry Lawrence Berkeley National LaboratoryBerkeley CA USA Batteries R&D Center LG Energy SolutionDaejeon 34122Korea

Challenges facing high-voltage/high-capacity cathodes,in addition to the longstanding problems pertinent to lithium(Li)-metal anodes,should be addressed to develop high-energy-density Li-metal *** issue mostly stems from interfacial instability between electrodes and *** carbonate-or ether-based liquid electrolytes suffer from not only volatility and flammability but also limited electrochemical stability ***,we report a nitrile electrolyte strategy based on concentrated nitrile electrolytes(CNEs)with *** CNE consists of high-concentration lithium bis(fluorosulfonyl)imide(LiFSI)in a solvent mixture of succinonitrile(SN)/acetonitrile(AN).The SN/AN solvent mixture is designed to ensure high oxidation stability along with thermal stability,which are prerequisites for high-voltage Li-metal *** CNE exhibits interfacial stability with Li metals due to the coordinated solvation *** nitrate(LiNO_(3))and indium fluoride(InF_(3))are incorporated in the CNE as synergistic co-additives to further stabilize solid-electrolyte interphase(SEI)on Li *** resulting electrolyte(CNE+LiNO_(3)/InF_(3))enables stable cycling performance in Li||LiNi_(0.8)Co_(0.1)Mn_(0.1)and 4.9 V-class Li||LiNi_(0.5)Mn_(1.5)O_(4)***,the Li||LiNi_(0.5)Mn_(1.5)O_(4)cell maintains its electrochemical activity at high temperature(100℃)and even in flame without fire or explosion.

关键词： 4.9 V-class cathodes electrolyte-electrode interfaces lithium-metal batteries nitrile electrolytes safety

Spontaneous resolution of multiple lymphangiomas of the colon:A case report

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World Journal of Gastroenterology 2011年第11期17卷 1515-1518页

作者： Ji Min Lee Woo Chul Chung Kang-Moon Lee Chang Nyol Paik Yeon-Ji Kim Bo-In Lee young Seok cho Hyun joo choi Department of Internal Medicine College of Medicine the Catholic University of KoreaSt.Vincent's Hospital 93-6Ji dongPaldal-guSuwonGyeonggi-do442-723South Korea

Lymphangioma of the colon is a relatively rare nonepithelial tumor and usually presents as a submucosal polypoid *** cases incidentally discovered are usually ***,they may present as abdominal pain or bleeding,and their resection is normally *** itself is generally recognized as a benign tumor and no cases of malignant transformation have yet been reported,although its natural history is currently *** the best of our knowledge,this study is the first to describe a case of spontaneous resolution in multiple colonic lymphangiomas without any specific treatment.

关键词： Lymphangioma Colon Natural history

High-temperature Oxidation Behavior of Zircaloy-4 and Zirlo in Steam Ambient

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Journal of Materials Science & Technology 2010年第9期26卷 827-832页

作者： Hyung Hoon Kim Jun Ho Kim Jin young Moon Ho Seong Lee Jeong joo Kim young Suck Chai School of Materials Science and Engineering Kyungpook National University School of Mechanical Engineering Yeungnam University214-1 Dae-dongGyeongsan-si

The oxidation characteristics for Zircaloy-4 and Zirlo in the temperature range of 700-1200°C under steam supply condition were investigated by using a modified thermo-gravimetric *** specimens were oxidized for 3600 s at each temperature and then quenched in a *** oxidation rate constants were measured from the weight gains to evaluate the oxidation behavior in Zircaloy-4 and *** weight gain rates of Zirlo were lower than those of Zircaloy-4,leading to the low rate *** different oxidation behaviors between both cladding materials were considered to be due to the difference in their chemical compositions.

关键词： Zircaloy-4 Zirlo Oxidation

White matter changes in 80 mild cognitive impairment patients using magnetic resonance imaging

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Neural Regeneration Research 2009年第9期4卷 654-658页

作者： Hyun cho Jee-Hyun Kwon Sun-young Kim Department of Neurology Ulsan University Hospital

BACKGROUND： Many studies have suggested that one possible etiology of mild cognitive impairment is small vessel cerebrovascular disease, which is associated with small subcortical infarcts and white matter abnormalities. These white matter changes have been detected as white matter hyperintensity （WMH） using magnetic resonance imaging. WMH may be associated with frontal lobe dysfunction. OBJECTIVE： To examine white matter changes in mild cognitive impairment patients of different subtypes, and to evaluate the correlation between white matter changes and neuropsychological characteristics, demographic information, vascular risk factors, and mild cognitive impairment subtypes. DESIGN, TIME AND SETTING： The neurophysiological, comparison study was performed at the Department of Neurology Memory Clinic, Ulsan University Hospital, South Korea, between March 2007 and March 2008. PARTICIPANTS： Out of a total of 83 subjects with clinically diagnosed mild cognitive impairment at the out-patient clinic, 3 subjects with severe WMH were excluded. A total of 80 subjects were included in this study. No patients suffered from cognitive impairment induced by neurological diseases, mental disorders, or somatic diseases. In accordance with magnetic resonance imaging results, the patients were assigned to two subtypes： 56 subjects without WMH and 24 subjects with WMH. METHODS： All patients were subjected to a standard neuropsychological battery using the Korean version of the Mini-Mental State Examination, Clinical Dementia Rating, and comprehensive Seoul Neuropsychological Screening Battery. The Clinical Dementia Rating reflected general cognitive function of patients. Results from the Seoul Neuropsychological Screening Battery reflected attention, language function, visuospatial function, verbal memory, nonverbal memory, long-term memory, and frontal/executive function. Magnetic resonance imaging was used to map changes in the brain. MAIN OUTCOME MEASURES： The association between va

关键词： mild cognitive impairment cerebrovascular disease white matter hyperintensity frontal/executive dysfunction

Adaptive Model Predictive Control for Yaw System of Variable-speed Wind Turbines

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Journal of Modern Power Systems and Clean Energy 2021年第1期9卷 219-224页

作者： Dongran Song Qing Chang Songyue Zheng Sheng Yang Jian Yang young Hoon joo the School of Automation Central South Universityand Hunan Provincial Key Laboratory of Power Electronics Equipment and GridChangsha 410083China the School of Energy Science and Engineering Central South UniversityChangsha 410083China the School of IT Information and Control Engineering Kunsan National UniversityKunsan 54150Korea

Due to varying characteristics of the wind condition, the performance of the wind turbines can be optimized by adapting the parameters of the control system. In this letter, an adaptive technique is proposed for the novel model predictive control(MPC) for the yaw system of the wind turbines. The control horizon is adapted to the one with the best predictive performance among multiple control horizons. The adaptive MPC is demonstrated by simulations using real wind data, and its performance is compared with the baseline MPC at fixed control horizon. Results show that the adaptive MPC provides better comprehensive performance than the baseline ones at different preview time of wind directions. Therefore, the proposed adaptive technique is potentially useful for the wind turbines in the future.

关键词： Wind turbine yaw system wind direction adaptive model predictive control

Security Analysis of Smart Speaker: Security Attacks and Mitigation

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Computers, Materials & Continua 2019年第9期61卷 1075-1090页

作者： youngseok Park Hyunsang choi Sanghyun cho young-Gab Kim Naver Corp. 6 Buljeong-roJeongja-dongBundang-guGyeonggi-doKorea Sejong University 209Neungdong-roGwangjin-guSeoul05006Korea

The speech recognition technology has been increasingly common in our ***,a number of commercial smart speakers containing the personal assistant system using speech recognition came *** the smart speaker vendors have been concerned about the intelligence and the convenience of their assistants,but there have been little mentions of the smart speakers in security *** the smart speakers are becoming the hub for home automation,its security vulnerabilities can cause critical *** this paper,we categorize attack vectors and classify them into hardware-based,network-based,and *** the attack vectors,we describe the detail attack scenarios and show the result of tests on several commercial smart *** addition,we suggest guidelines to mitigate various attacks against smart speaker ecosystem.

关键词： Smart speaker personal assistant system IoT security

A case of hypereosinophilic syndrome presenting with intractable gastric ulcers

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World Journal of Gastroenterology 2009年第48期15卷 6129-6133页

作者： Tae young Park Chang Hwan choi Suh Yoon Yang InSoo Oh In-Do Song Hyun Woong Lee Hyung joon Kim Jae Hyuk Do Sae Kyung Chang Ah Ra cho young joo Cha Department of Internal Medicine Chung-Ang University College of Medicine Department of Laboratory Medicine Chung-Ang University College of Medicine

We report a rare case of hypereosinophilic syndrome （HES） presenting with intractable gastric ulcers. A 71-year-old man was admitted with epigastric pain. Initial endoscopic findings revealed multiple, active gastric ulcers in the gastric antrum. He underwent Helicobacterpylori （Hpylon） eradication therapy followed by proton pump inhibitor （PPI） therapy. However, follow- up endoscopy at 4, 6, 10 and 14 mo revealed persistent multiple gastric ulcers without significant improvement. The proportion of his eosinophil count increased to 43% （total count： 7903/mm3）. Abdominal-pelvic and chest computed tomography scans showed multiple small nodules in the liver and both lungs. The endoscopic biopsy specimen taken from the gastric antrum revealed prominent eosinophilic infiltration, and the liver biopsy specimen also showed eosinophilic infiltration in the portal tract and sinusoid. A bone marrow biopsy disclosed eosinophilic hyperplasia as well as increased cellularity of 70%. The patient was finally diagnosed with HES involving the stomach, liver, lung, and bone marrow. When gastric ulcers do not improve despite H pylon eradication and prolonged PPI therapy, infiltrative gastric disorders such as HES should be considered.

关键词： Gastric ulcer Hypereosinophilic syndrome