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Anomaly Detection in Imbalanced Encrypted Traffic with Few Packet Metadata-Based Feature Extraction

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Computer Modeling in Engineering & Sciences 2024年第10期141卷 585-607页

作者： Min-Gyu kim Hwankuk kim Department of Financial Information Security Kookmin UniversitySeoul02707Republic of Korea Department of Information Security Cryptography Mathematics Kookmin UniversitySeoul02707Republic of Korea

In the IoT(Internet of Things)domain,the increased use of encryption protocols such as SSL/TLS,VPN(Virtual Private Network),and Tor has led to a rise in attacks leveraging encrypted *** research on anomaly detection using AI(Artificial Intelligence)is actively progressing,the encrypted nature of the data poses challenges for labeling,resulting in data imbalance and biased feature extraction toward specific *** study proposes a reconstruction error-based anomaly detection method using an autoencoder(AE)that utilizes packet metadata excluding specific node *** proposed method omits biased packet metadata such as IP and Port and trains the detection model using only normal data,leveraging a small amount of packet *** makes it well-suited for direct application in IoT environments due to its low resource *** experiments comparing feature extraction methods for AE-based anomaly detection,we found that using flowbased features significantly improves accuracy,precision,F1 score,and AUC(Area Under the Receiver Operating Characteristic Curve)score compared to packet-based ***,for flow-based features,the proposed method showed a 30.17%increase in F1 score and improved false positive rates compared to Isolation Forest and ***,the proposedmethod demonstrated a 32.43%higherAUCwhen using packet features and a 111.39%higher AUC when using flow features,compared to previously proposed oversampling *** study highlights the impact of feature extraction methods on attack detection in imbalanced,encrypted traffic environments and emphasizes that the one-class method using AE is more effective for attack detection and reducing false positives compared to traditional oversampling methods.

关键词： One-class anomaly detection feature extraction auto-encoder encrypted traffic CICIoT2023

Ag-GST/HfO_(x)-based unidirectional threshold switching selector with low leakage current and threshold voltage distribution for high-density cross-point arrays

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Rare Metals 2024年第1期43卷 280-288页

作者： Kyoung-Joung Yoo Dae-Yun Kang Nahyun kim Ho-Jin Lee Ta-Hyeong kim Taeho kim Tae Geun kim School of Electrical Engineering Korea UniversitySeoul 02841Republic of Korea

The use of electrochemical-metallization-based volatile threshold switching selectors in cross-point arrays has been widely explored owing to their high on-off ratios and simple ***,these devices are unsuitable for cross-point architectures because of the difficulty in controlling the random filament formation that results in large fluctuations in the threshold voltage during *** this study,we investigated the unidirectional threshold transition characteristics associated with an Ag/GST/HfO_(x)/Pt-based bilayer selector and demonstrated the occurrence of a low leakage current(<1×10^(-11) A) and low distribution of the threshold voltage(Δ0.11 V).The bilayer structure could control the filament formation in the intermediate state through the insertion of an HfO_(x) tunneling *** stacking a bilayer selector with NiO_(x)based resistive random-access memory,the leakage and programming currents of the device could be significantly *** the crossbar array configuration,we performed equivalent circuit analysis of a one-selector oneresistor(1S1R) devices and estimated the optimal array size to demonstrate the applicability of the proposed *** maximum acceptable crossbar array size of the 1S1R device with the Ag/GST/HfO_(x)/Pt/Ti/NiO_(x)/Pt structure was 5.29×10^(14)(N^(2),N=2.3×10^(7)).

关键词： Selector device Tunneling barrier Threshold switching Sputtering 1S1R Cross-point array

EFFECT OF SPECIMEN ASPECT RATIO ON FATIGUE LIFE OF CLOSED CELL Al-Si-Ca ALLOY FOAM

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Acta Mechanica Solida Sinica 2008年第4期21卷 354-358页

作者： Amkee kim Ilhyun kim Division of Mechanical and Automotive Engineering Kongju National University275Budae-dongCheonanChungnam 330-717Korea

Quasi-static and compressive fatigue tests on the closed cell Al-Si-Ca alloy foam specimens with three different aspect ratios were performed. It turned out that the onset of cyclic shortening of foam with a lower aspect ratio took place earlier and the fatigue strength was lower compared with the specimen with a higher aspect ratio, although all the dimensions of specimen satisfied the seven times the cell size criterion, while the quasi-static stress-strain curves were almost same having same Young＇s modulus, yield stress and plateau stress. Therefore, the seven times the cell size criterion for the quasi-static compression behavior was not applicable to the fatigue analysis of Al-Si-Ca alloy foam.

关键词： aluminum foam aspect ratio fatigue behavior compressive strength

Phase-pure Na3V2(PO4)2F3 embedded in carbon matrix through a facile polyol synthesis as a potential cathode for high performance sodium-ion batteries

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Nano Research 2019年第4期12卷 911-917页

作者： Sohyun Park Jinju Song Seyeon kim Balaji Sambandam Vinod Mathew Sungjin kim Jeonggeun Jo Seokhun kim Jaekook kim Department of Materials Science and Engineering Chonnam National University 300 Ybngbong-dong Buk-gu Gwangju 500-757 Republic of Korea Gwangju Bio/Energy R&D Center Korea Institute of Energy Research (KIER) 270-25 Samso-ro Buk-gu Gwangju 61003 Republic of Korea

In this study,a pseudo-layered Na super-ionic conductor of Na3V2(PO4)2F3 (NVPF)/C cathode for sodium-ion batteries is prepared successfully using a facile polyol refluxing process without any impurity *** X-ray diffraction and Rietveld refinement results confirm that NVPF possesses tetragonal NASICON-type lattice with a space group of P42/*** this preparative method,polyol is utilized as a solvent as well as a carbon *** presence of nanosized NVPF particles in the carbon network is confirmed by field-emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM).The existence of carbon is analyzed by Raman scattering and elemental *** applied as a Na-storage material in a potential window of 2.0-4.3 V,the electrode exhibits two flat voltage plateaus at 3.7 and 4.2 V with an electrochemically active V^3+/V^4+ redox *** addition,Na3V2(PO4)2F3/C composite achieved a retention capacity of ~ 88% even after 1,500 cycles at 15 ***,at high current densities of 30 and 50 C,Na3V2(PO4)2F3/C cathode retains the specific discharge capacities of 108.4 and 105.9 mAh·g-1,respectively,revealing the structural stability of the material prepared through a facile polyol refluxing method.

关键词： fluorophosphate Na3V2(PO4)2F3 polyol process sodium ion batteries long life stability

The Effect of Diffuser Angle on the Discharge Coefficient of a Miniature Critical Nozzle

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Journal of Thermal Science 2010年第3期19卷 222-227页

作者： Jae Hyung kim Heuy Dong kim Toshiaki Setoguchi School of Mechanical Engineering Andong National UniversityAndong760-749Korea Department of Mechanical Engineering Saga University1HonjoSagaJapan

Many researches on critical nozzles have been performed to accurately measure the mass flow rate of gas flow,and to standardize the performance as a flow ***,much interest is being paid on the measurement of very small mass flow rate in industry fields such as MEMS ***,the design and performance data of the critical nozzles obtained so far have been applied mainly to the critical nozzles with comparatively large diameters,and the works available on miniature critical nozzles are *** the present study,a computational fluid dynamics method has been applied to investigate the influence of the diffuser angle on discharge coefficient of the miniature critical *** computations,the throat diameter of critical nozzle is varied from 0.2 mm to 5.0 mm and the diffuser angle is changed from 2 deg to 8 *** computational results are validated with some experimental data *** results show that the present computational results predict appropriately the discharge coefficient of the gas flows through miniature critical *** is known that the discharge coefficient is considerably influenced by the diffuser angle,as the throat diameter of nozzle becomes small below a certain *** implies that the miniature critical nozzles should be carefully designed.

关键词： Compressible Flow Critical Nozzle Compressible Flow Discharge Coefficient Diffuser Configuration Reynolds Number

Silicon nanowire CMOS NOR logic gates featuring onevolt operation on bendable substrates

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Nano Research 2018年第5期11卷 2625-2631页

作者： Jeongje Moon Yoonjoong kim Doohyeok Lim Sangsig kim Department of Electrical Engineering Korea University 145 Anam-ro Seongbuk-gu Seoul 02841 Republic of Korea LED PKG Development Group Samsung Electronics Co. Ltd. 1 Samsung-ro Yongin-si Gyeonggi-do 17113 Republic of Korea

In this study, we propose complementary metal-oxide-semiconductor （CMOS） NOR logic gates consisting of silicon nanowire （NW） arrays on bendable substrates. A circuit consisting of two p-channel NW field-effect transistors （NWFETs） in series and two n-channel NWFETs in parallel is constructed to operate a two- input CMOS NOR logic gate. The NOR logic gates operate at a low supply voltage of 1 V with a rail-to-rail logic swing and a high voltage gain of approximately -3.0. The exact NOR logic functionality is achieved owing to the superior electrical characteristics of the well-aligned p- and n-NWFETs, which are obtained using conventional Si-based CMOS technology. Moreover, the NOR logic gates exhibit stable characteristics and have good mechanical properties. The proposed bendable NW CMOS NOR logic gates are promising building blocks for future bendable integrated electronics.

关键词： field-effect transistor silicon nanowire NOR logic gate bendable substrate

Measurements of Formaldehyde and TVOC Emission from Paints and Coating Materials using Small Chamber Method for Building Composites

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Journal of Wuhan University of Technology(Materials Science) 2012年第1期27卷 120-125页

作者： Jin-A kim Sumin kim Hyun-Joong kim Janghoo SEO National Instrumentation Center for Environmental Management Seoul National University Seoul 151-921 Republic of Korea Laboratory of Adhesion & Bio-Composites Program in Environmental Materials Science Seoul National University Seoul 151-921 Republic of Korea Building Environment & Materials Lab School of Architecture Soongsil University Seoul 156-743 Republic of Korea School of Architecture Chosun University Gwangju 507-759 Korea

An optimal test method for paint is proposed; additionally, the Field and Laboratory Emission Cell （FLEC） method used in Europe is applied as a substitute for the 20 L small chamber method. The emission factors of total volatile organic compounds （TVOC） and formaldehyde from oil-based paint, emulsion paint, and water-dispersion paint with a coating weight of 300 g/m2, cured for 24/48 hours, were measured using the 20 L small chamber method. The emission rate of TVOC and formaldehyde from all paints began to stabilize after approximately 7 days after 24/48 hours of curing even though Korean standards stipulate that paint should be measured and analyzed after the third day of application. The emission factor of TVOC and formaldehyde from oil-based, emulsion, and water-dispersion paints were also measured using the FLEC method. There was good correlation between the 20 L small chamber method and the FLEC method for oil-based, emulsion, and water-dispersion paint emissions. With the FLEC method, using paints prepared under identical conditions, the emission rate was stable 24 hours after installation of samples because the air flow rate of FLEC is much higher than that of a 20 L small chamber, and the relative cell volume of FLEC is much smaller than that of a 20 L small chamber.

关键词： formaldehyde TVOC paints coating materials FLEC

Analytical analysis of pullout resistance of the hydraulic expansion rockbolts on a frictionally coupled model

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Journal of Mountain Science 2016年第12期13卷 2249-2259页

作者： Sejin kim Heejung YOUN Kyoungchul kim Department of Civil Engineering Hongik University R&D Center Kolon Global Corporation

This paper proposes an empirical formula to estimate the shear strength of hydraulic expansion *** field experimental results were obtained from eleven pullout tests to evaluate the results computed by the proposed *** was found that shear resistance of hydraulic expansion rockbolts significantly depends on the uniaxial compressive strength and elastic modulus of rock,with high correlation coefficients of 0.7651 and0.8587,*** developed formula enables estimation of the maximum pullout load in an analytical process without pullout tests in the ***,due to the poor interlocking at the initial pullout load,the measured displacements were higher than the estimated *** reduce the interlocking effects between bolt and rock,we recommend preloading of 29.4 *** allows reducing the distance between the measured and estimated displacement and making two load-displacement curves practically identical with marginal differences of 1.1 to 1.5 mm at the maximum pullout load.

关键词： Expansion rockbolt Pullout resistance Pullout load Shear strength

A nanofilter composed of carbon nanotube-silver composites for virus removal and antibacterial activity improvement

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Journal of Environmental Sciences 2016年第4期28卷 275-283页

作者： Jun Pyo kim Jae Ha kim Jieun kim Soo No Lee Han-Oh Park Nano Development Team Bioneer Corporation Daejeon 306-220 Republic of Korea

We have developed a new nanofilter using a carbon nanotube-silver composite material that is capable of efficiently removing waterborne viruses and *** nanofilter was subjected to plasma surface treatment to enhance its flow rate,which was improved by approximately 62%.Nanoscale pores were obtained by fabricating a carbon nanotube network and using nanoparticle fixation technology for the removal of *** pore size of the nanofilter was approximately 38 nm and the measured flow rate ranged from 21.0 to 97.2 L/（min·m^2）under a pressure of 1–6 kgf/cm^2 when the amount of loaded carbon nanotube-silver composite was 1.0 mg/cm^*** nanofilter was tested against Polio-,Noro-,and Coxsackie viruses using a sensitive real-time polymerase chain reaction assay to detect the presence of viral particles within the *** trace of viruses was found to flow through the nanofilter with carbon nanotube-silver composite loaded above 0.8 mg/cm^***,the surface of the filter has antibacterial properties to prevent bacterial clogging due to the presence of 20-nm silver nanoparticles,which were synthesized on the carbon nanotube surface.

关键词： Carbon nanotube Silver nanoparticle Virus removal Nanofilter Water purification