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Flexible and disposable paper-based gas sensor using reduced graphene oxide/chitosan composite

Journal of Materials Science & Technology 2022年第6期101卷 165-172页

作者： hyunjun park Woong Kim Sang Won Lee Joohyung park Gyudo Lee Dae Sung yoon Wonseok Lee Jinsung park Department of Control and Instrumentation Engineering Korea UniversitySejong 30019Republic of Korea School of Biomedical Engineering Korea UniversitySeoul 02841Republic of Korea Department of Biotechnology and Bioinformatics Korea UniversitySejong 30019Republic of Korea Department of Electrical Engineering Korea National University of TransportationChungju 27469Republic of Korea

Nitrogen dioxide(NO_(2))is a representative toxicant in air pollution that mostly arises from the exhaust gas released by *** is related to various respiratory diseases such as pneumonia and sudden infant death ***,because the toxicity of nitrogen dioxide is high in overpopulated areas(i.e.,a capital or metropolis),the development of simple,practical,and facile sensors is highly *** work presents a flexible and disposable paper-based NO_(2)sensor based on a reduced graphene oxide/chitosan(r GO/CS)*** synthesized r GO/CS composite can be easily flexed and deformed into various shapes,which are attributed to chitosan molecules that function as a dispersion and reduction agent and support *** addition,this composite can be attached to paper owing to its adhesive property;hence it can be utilized in versatile applications in a disposable *** analyzing the conductive change of the r GO/CS composite when it reacts with NO_(2),we can detect nitrogen dioxide in a concentration range of 0–100 ppm with a detection limit of 1 ***,we performed NO_(2)detection in the exhaust gas released by automobiles using the r GO/CS composite for practical *** results indicated that the r GO/CS composite has the potential to be used in feasible gas sensing as a facile and disposable sensor under various conditions.

关键词： Reduced graphene oxide Chitosan Composite material Nitrogen dioxide Paper-based gas sensor Flexible and disposable sensor

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An in-situ Raman spectroscopic study on potential-pO^(2-) phase diagram of lanthanum in LiCl-KCl eutectic melt

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Journal of Rare Earths 2020年第7期38卷 793-800,I0004页

作者： Seung park Jong-IL yun Department of Nuclear and Quantum Engineering.KAIST Yuseong-guDaejeon 34141Republic of Korea

The oxidative reaction between lanthanum trichloride and oxide ion was studied in the molten LiCl-KCl eutectic at 773 K by in-situ Raman spectroscopy using an yttria-stabilized zirconia electrode in conjunction with electrochemical *** formation of lanthanum oxychloride,LaOCl(s),was confirmed by studying the vibrational properties of crystalline LaOCl and X-ray diffraction *** solubility product of LaOCl in the LiCl-KCl molten eutectic at 773 K is found to be pKsp(LaOCl)=7.569±0.100,by combining the results of Raman spectroscopy and potentiometric titration with the addition of barium *** use of Raman spectroscopic quantitation of dissolved lanthanum ions in the system allows faster and more accurate determination of the stable phase of lanthanum as well as the solubility product of LaOCl compared with that measured by potentiometric titration *** on experimentally obtained pKsp and standard equilibrium potentials,the potentialpO2- phase diagram of lanthanum in the molten LiCl-KCl eutectic was reported.

关键词： Lanthanum Solubility product E-pO2-diagram Raman spectroscopy Chloride molten salt Rare earths

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Electrochemically Deposited CZTSSe Thin Films for Monolithic Perovskite Tandem Solar Cells with Efficiencies Over 17%

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Energy & Environmental Materials 2024年第1期7卷 147-152页

作者： Sun Kyung hwang Ik Jae park Se Won Seo Jae hyun park So Jeong park Jin young Kim Department of Materials Science and Engineering Seoul National UniversitySeoul 08826Korea Department of Applied Physics Sookmyung Women's UniversitySeoul 04310Korea Research Institute of Advanced Materials and Systems Sookmyung Women's UniversitySeoul 04310Korea Research Institute of Advanced Materials(RIAM) Seoul National UniversitySeoul 08826Korea

In spite of the high potential economic feasibility of the tandem solar cells consisting of the halide perovskite and the kesterite Cu2ZnSn(S,Se)4(CZTSSe),they have rarely been demonstrated due to the difficulty in implementing solution-processed perovskite top cell on the rough surface of the bottom ***,we firstly demonstrate an efficient monolithic two-terminal perovskite/CZTSSe tandem solar cell by significantly reducing the surface roughness of the electrochemically deposited CZTSSe bottom *** surface roughness(R_(rms))of the CZTSSe thin film could be reduced from 424 to 86 nm by using the potentiostatic mode rather than using the conventional galvanostatic mode,which can be further reduced to 22 nm after the subsequent ion-milling *** perovskite top cell with a bandgap of 1.65 eV could be prepared using a solution process on the flattened CZTSSe bottom cell,resulting in the efficient perovskite/CZTSSe tandem solar *** the current matching between two subcells involving the thickness control of the perovskite layer,the best performing tandem device exhibited a high conversion efficiency of 17.5%without the hysteresis effect.

关键词： CZTSSe monolithic tandem solar cells perovskite solution process surface roughness control

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Efficiency of enhanced oil recovery by injection of low-salinity water in barium-containing carbonate reservoirs

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Petroleum Science 2018年第4期15卷 772-782页

作者： hyemin park yongjun park yeonkyeong Lee Wonmo Sung Department of Earth Resources and Environmental Engineering Hanyang University

When low-salinity water containing sulfate ions is injected into carbonate reservoirs, rock dissolution and in situ precipitation occur, altering rock permeability and wettability. Particularly, when barium ions are present in formation water,they react chemically with SO;, and BaSO;is precipitated. These reactions can cause a serious impact on the efficiency of enhanced oil recovery（EOR）. Therefore, the main purpose of this study was to identify EOR efficiency induced by lowsalinity waterflooding（LSWF） when Ba;is present in carbonate reservoirs. From the experimental results, it was confirmed that the permeability calculated by the measured pressure difference was improved because of rock dissolution predominating over in situ precipitation for the case of low Ba;concentrations. In the analysis of wettability alteration through the measurements of relative permeabilities before and after LSWF, the higher Ba;concentration case consumed more SO;in precipitating the BaSO;, resulting in weaker wettability alteration due to the reduction of sulfate *** phenomena ultimately influenced EOR efficiency, i.e., the oil recovery was greater for the lower Ba;concentration.

关键词： Low-salinity water flooding Barium Sulfate Oil recovery Carbonate

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Cluster-Based Stable BSM Dissemination System for Safe Autonomous Platooning

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Computers, Materials & Continua 2022年第4期71卷 321-338页

作者： Jaehwan Lee Suhwan Kwak Seungwoo park Sangoh park School of Computer Science and Engineering Chung-Ang UniversityDongjak-guSeoul06974Korea

Recently,the importance of vehicle safety supporting system has been highlighted as autonomous driving and platooning has attracted the *** ensure driving safety,each vehicle must broadcast a basic safety message(BSM)every 100 ***,stable BSM exchange is difficult because of the changing environment and limited bandwidth of vehicular wireless *** increasing number of vehicles on the road increases the competition to access wireless networks for BSM exchange;this increases the packet collision *** increased packet collision rate impairs the transmission and reception of BSM information,which can easily cause a traffic *** propose a solution,the vehicular safety support system(V3S),which exchanges BSMs reliably even when many vehicles are on the *** V3S uses a clustering scheme to decrease network traffic by reducing the amount of data exchanged between a vehicle and the roadside unit(RSU).In addition,the V3S reduces the collision rate of wireless network packets by broadcasting the vehicle’s BSM in an allocated timeslot using the time division multiple access(TDMA)MAC *** V3S also deals with insufficient bandwidth for dedicated short-range communications(DSRC)by changing DSRC channels according to traffic *** evaluating the packet error rate for stable BSM packet delivery,the V3S demonstrates an excellent packet error rate of less than 1%,compared to the 802.11p with its packet error rate of 82%.

关键词： Road vehicles communication systems clustering methods vehicular networks basic safety message dedicated short-range communication

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Parameter estimation for building energy models using GRcGAN

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Building Simulation 2023年第4期16卷 629-639页

作者： hansol Shin Cheol-Soo park Department of Architecture and Architectural Engineering College of EngineeringSeoul National UniversitySeoul08826R.O.Korea Institute of Construction and Environmental Engineering Institute of Engineering ResearchCollege of EngineeringSeoul National UniversitySeoul08826R.O.Korea

Parameter estimation methods can be classified into(1)manual(trial-and-error),(2)numerical optimization(optimization,sampling),(3)Bayesian inference(Bayes filter,Bayesian calibration),and(4)machine learning(generative model).Bayesian calibration has been widely used because it can capture stochastic nature of uncertain ***,the results of Bayesian calibration could be biased by(1)the prior distribution assumed by the expert’s subjective judgment;(2)the likelihood function that cannot always describe the true likelihood;and(3)the posterior distribution approximation method,such as the Markov Chain Monte Carlo,which requires significant computation *** overcome this,a new approach using a generator-regularized continuous conditional generative adversarial network(GRcGAN)is presented in this *** target parameters of the DOE reference building model were *** was trained to estimate uncertain parameters using simulated monthly electricity and gas *** can successfully estimate five uncertain parameters based on 1,000 training data *** proposed approach presents a potential for stochastic parameter estimation.

关键词： generative adversarial networks generative model parameter estimation inverse problem model calibration parameter uncertainty

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highly efficient reduction of aqueous Cr(VI) with novel ZnO/SnS nanocomposites through the piezoelectric effect

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Journal of Environmental Sciences 2022年第8期34卷 57-66页

作者： hao Sun Soo-Jin park Department of Chemistry and Chemical Engineering Inha UniversityIncheon 22212South Korea

In this work, novel ZnO/SnS nanocomposites were successfully synthesized via a hydrothermal approach, which is developed for piezoelectric catalytic reduction of hexavalent chromium(Cr(VI)) in an aqueous solution. The constructed ZnO/SnS nanocomposites exhibited higher catalytic efficiency for Cr(VI) reduction under a mechanical force(e.g., ultrasonic vibration) compared to pristine ZnO and SnS. In particular, the ZnO/SnS(with 30 wt.% of SnS) heterojunctions revealed an optimal degradation activity among all the prepared samples, which completely removed the Cr(VI)(20 mg/L) solution within 35 min. Moreover, the piezoelectric catalytic activity of ZnO/SnS remained stable after four consecutive cycling experiments. The results of the morphology observations indicated that the SnS nanoparticles adhere to the surface of the ZnO nanorods. The improved piezoelectric catalytic performance of the ZnO/SnS heterojunctions can be attributed to the formation of an intimate interfacial between ZnO and SnS, which effectively inhibits the electron-hole recombination and speeds up the rate of charge transfer. The study reveals a new design of ZnO/SnS heterojunctions as a high-performance and eco-friendly piezoelectric catalyst and provides a promising strategy for addressing environmental problems and energy crises.

关键词： Cr(VI)reduction ZnO/SnS Piezoelectric effect

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Using Speaker-Specific Emotion Representations in Wav2vec 2.0-Based Modules for Speech Emotion Recognition

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Computers, Materials & Continua 2023年第10期77卷 1009-1030页

作者： Somin park Mpabulungi Mark Bogyung park hyunki hong College of Software Chung-Ang UniversitySeoul06973Korea Department of AI Chung-Ang UniversitySeoul06973Korea

Speech emotion recognition is essential for frictionless human-machine interaction,where machines respond to human instructions with context-aware *** properties of individuals’voices vary with culture,language,gender,and *** variations in speaker-specific properties may hamper the performance of standard representations in downstream tasks such as speech emotion recognition(SER).This study demonstrates the significance of speaker-specific speech characteristics and how considering them can be leveraged to improve the performance of SER *** the proposed approach,two wav2vec-based modules(a speaker-identification network and an emotion classification network)are trained with the Arcface *** speaker-identification network has a single attention block to encode an input audio waveform into a speaker-specific *** emotion classification network uses a wav2vec 2.0-backbone as well as four attention blocks to encode the same input audio waveform into an emotion *** two representations are then fused into a single vector representation containing emotion and speaker-specific *** results showed that the use of speaker-specific characteristics improves SER ***,combining these with an angular marginal loss such as the Arcface loss improves intra-class compactness while increasing inter-class separability,as demonstrated by the plots of t-distributed stochastic neighbor embeddings(t-SNE).The proposed approach outperforms previous methods using similar training strategies,with a weighted accuracy(WA)of 72.14%and unweighted accuracy(UA)of 72.97%on the Interactive Emotional Dynamic Motion Capture(IEMOCAP)*** demonstrates its effectiveness and potential to enhance human-machine interaction through more accurate emotion recognition in speech.

关键词： Attention block IEMOCAP dataset speaker-specific representation speech emotion recognition wav2vec 2.0

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GENERAL DECAy OF A TRANSMISSION PROBLEM FOR KIRChhOFF TyPE WAVE EQUATIONS WITh BOUNDARy MEMORy CONDITION

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Acta Mathematica Scientia 2014年第5期34卷 1395-1403页

作者： Sun hye park Center for Education Accreditation Pusan National University

In this paper, we investigate the influence of boundary dissipation on the de-cay property of solutions for a transmission problem of Kirchhoff type wave equation with boundary memory condition. By introducing suitable energy and Lyapunov functionals, we establish a general decay estimate for the energy, which depends on the behavior of relaxation function.

关键词： transmission problem Kirchhoff type general decay memory term relaxationfunction

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LENTICULAR NONCOMMUTATIVE TORI

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Acta Mathematica Scientia 2003年第1期23卷 83-94页

作者： Chun-Gil park Department of Mathematics Chungnam National University Daejeon 305-764 Korea

All C*-algebras of sections of locally trivial C* -algebra bundles over ∏i=1sLki(ni) with fibres Aw Mc(C) are constructed, under the assumption that every completely irrational noncommutative torus Aw is realized as an inductive limit of circle algebras, where Lki (ni) are lens spaces. Let Lcd be a cd-homogeneous C*-algebra over whose cd-homogeneous C*-subalgebra restricted to the subspace Tr × T2 is realized as C(Tr) A1/d Mc(C), and of which no non-trivial matrix algebra can be factored *** lenticular noncommutative torus Lpcd is defined by twisting in by a totally skew multiplier p on Tr+2 × Zm-2. It is shown that is isomorphic to if and only if the set of prime factors of cd is a subset of the set of prime factors of p, and that Lpcd is not stablyisomorphic to if the cd-homogeneous C*-subalgebra of Lpcd restricted to some subspace LkiLki (ni) is realized as the crossed product by the obvious non-trivial action of Zki on a cd/ki-homogeneous C*-algebra over S2ni+1 for ki an integer greater than 1.

关键词： Lens space homogeneous C*-algebra C*-algebra bundle twisted group C*-algebra noncommutative torus K-theory UhF-algebra Cuntz algebra

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