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Multi-objective optimization of a flow straightener in a large capacity firefighting water cannon

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Journal of Hydrodynamics 2019年第1期31卷 137-144页

作者： Qing-jiang Xiang Lin Xue kwang-yong kim Zhe-fu Shi National Research Centre of Pumps Jiangsu UniversityZhenjiang 212013China Department of Mechanical Engineering Inha UniversityIncheonKorea Shanghai Fire Research Institute of Ministry of Emergency Management Shanghai 200032China

In the present study,a multi-objective optimization of a flow straightener in a firefighting water cannon is performed by using the surrogate modeling and a hybrid multi-objective genetic algorithm to increase the jet range of the water *** on analysis using the three-dimensional Reynolds-averaged Navier-Stokes equations,the optimization is carried with a surrogate model and the radial basis neural *** geometric design variables,i.e.,the lengt扎 the thickness of the blade,and the radius of the outer pipe of the flow straightener,are selected for the *** pressure drop through the water can non and the area-averaged turbulent kinetic energy at the outlet of the water cannon,which are closely related to the jet range of the water cannon,are selected as the objective functions to be *** design space is determined through a parametric study,and the Latin hypercube sampling method is used to select the design points in the design *** Pareto-optimal solutions are obtained through the *** representative Pareto-optimal solutions are selected to study the trade-off between two objectives.

关键词： Firefighting water cannon multi-objective optimization surrogate model turbulence kinetic energy hydraulic loss

Submicron Ag-coated Cu particles as filler in sintering paste: Suppression of Ag dewetting and improvement of sinterability by surface modification using stearic acid

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Transactions of Nonferrous Metals Society of China 2024年

作者： Yeongjung kim yong-Sung Eom kwang-Seong Choi Jong-Hyun Lee Department of Materials Science and Engineering， Seoul National University of Science and Technology， 232 Gongneung-ro Low-Carbon Integration Tech， Creative Research Section， ETRI， 218 Gajeong-ro Materials Research Institute for Future Convergence， Seoul National University of Science and Technology， 232 Gongneung-ro

Four types of submicron Ag-coated Cu particles with different Ag contents were prepared as sintering paste fillers， and the Ag contents of the particles were measured to be 10， 20， 30， and 40 wt%. Four types of particles （in order of increasing Ag content: A10， A20， A30， and A40） were surface-modified with stearic acid， to suppress the Ag shell dewetting and improve sinterability. The surface-modified particles were mixed with a polyol-based solvent to fabricate a resin-free paste. Subsequently， the pastes were screen-printed onto a slide glass and sintered at 250 ℃ in a nitrogen atmosphere for 1–10 min to form an electrode. The electrical resistivity of the sintered film as a function of sintering time was measured using a four-point probe. All the four surface-modified Cu@Ag particles with different Ag contents exhibited decreased electrical resistivity. Particularly， the largest difference in values after and before the surface modification was observed for A40 with the highest Ag content; the electrical resistivities of the initial and surface-modified particles were 1.51×10-4and 6.67×10-5Ω·cm， respectively， after sintering for 10 min. The findings of this study confirmed that the surface modification using stearic acid effectively suppressed the dewetting of the Ag shell and improved the sinterability of the submicron Cu@Ag particles.

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Surface-functionalized hole-selective monolayer for high efficiency single-junction wide-bandgap and monolithic tandem perovskite solar cells

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Journal of Energy Chemistry 2024年第1期88卷 317-326,I0008页

作者： Devthade Vidyasagar Yeonghun Yun Jae Yu Cho Hyemin Lee Kyung Won kim yong Tae kim Sung Woong Yang Jina Jung Won Chang Choi Seonu kim Rajendra Kumar Gunasekaran Seok Beom Kang kwang Heo Dong Hoe kim Jaeyeong Heo Sangwook Lee School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Department of Materials Science and Engineering and Optoelectronics Convergence Research CenterChonnam National UniversityGwangju 61186Republic of Korea Department of Materials Science and Engineering Korea UniversitySeoul 02841Republic of Korea Department of Nanotechnology and Advanced Materials Engineering Sejong UniversitySeoul 05006Republic of Korea

Carbazole moiety-based 2PACz([2-(9H-carbazol-9-yl)ethyl]phosphonic acid)self-assembled monolayers(SAMs)are excellent hole-selective contact(HSC)materials with abilities to excel the charge-transferdynamics of perovskite solar cells(PSCs).Herein,we report a facile but powerful method to functionalize the surface of 2PACz-SAM,by which reproducible,highly stable,high-efficiency wide-bandgap PSCs can be *** 2PACz surface treatment with various donor number solvents improves assembly of 2PACz-SAM and leave residual surface-bound solvent molecules on 2PACz-SAM,which increases perovskite grain size,retards halide segregation,and accelerates hole *** surface functionalization achieves a high power conversion efficiency(PCE)of 17.62%for a single-junction wide-bandgap(~1.77 e V)*** also demonstrate a monolithic all-perovskite tandem solar cell using surfaceengineered HSC,showing high PCE of 24.66%with large open-circuit voltage of 2.008 V and high fillfactor of 81.45%.Our results suggest this simple approach can further improve the tandem device,when coupled with a high-performance narrow-bandgap sub-cell.

关键词： Perovskite solar cells 2PACz Monolithic tandem solar cells Wide bandgap

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Emission wavelength selection via anomalous polarized fluorescence in ZnO-C nanowires

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Nano Research 2024年第5期17卷 4489-4497页

作者： Joon Kiat Kang kim yong Lim Chorng Haur Sow Department of Physics National University of SingaporeSingapore 117542Singapore

Defect fluorescence from high aspect ratio semiconductor nanowires typically displays a weak polarization parallel to the nanowire’s long axis due to dielectric mismatch in high aspect ratio ***,anomalous 2.2 eV defect fluorescence distinctly polarized perpendicular to the nanowire is observed and measured from carbon-incorporated zinc oxide *** observations are significant because polarized defect emissions with consistent polarization on a mesoscopic scale are *** a systematic study and comparison of experimental results with density functional theory calculations,an oriented defect complex comprising carbon substituting on an oxygen site and an oxygen vacancy(CO-VO)is deduced to be responsible for the anomalous yellow fluorescence,demonstrating a method for relating atomic-scale defect geometry to mesoscopic *** anomalous emission can appear in both green-and red-fluorescing nanowires grown with different carbon concentrations,verifying the independence and uniqueness of the 2.2 eV *** allows for polarization-dependent emission wavelength selection from a single nanowire.

关键词： anomalous polarization defects fluorescence zinc oxide carbon

Depolarization mitigated in ferroelectric Hf_(0.5)Zr_(0.5)O_(2)ultrathin films(<5 nm)on Si substrate by interface engineering

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Journal of Advanced Ceramics 2024年第3期13卷 282-292页

作者： Se Hyun kim Younghwan Lee Dong Hyun Lee Geun Hyeong Park Hyun Woo Jeong Kun Yang yong Hyeon Cho Young yong kim Min Hyuk Park Department of Materials Science and Engineering College of EngineeringSeoul National UniversitySeoul 08826Republic of Korea Research Institute of Advanced Materials College of EngineeringSeoul National UniversitySeoul 08826Republic of Korea Inter-university Semiconductor Research Center College of EngineeringSeoul National UniversitySeoul 08826Republic of Korea Pohang Accelerator Laboratory Pohang University of Science&TechnologyPohang 790784Republic of Korea

(Hf,Zr)O_(2)offers considerable potential for next-generation semiconductor devices owing to its nonvolatile spontaneous polarization at the ***,scaling this material to sub-5 nm thickness poses several challenges,including the formation of an interfacial layer and high trap *** particular,a low-k SiO_(2)interfacial layer is naturally formed when(Hf,Zr)O_(2)films are directly grown on a Si substrate,leading to high depolarization fields and rapid reduction of the remanent *** address these issues,we conducted a study to significantly improve ferroelectricity and switching endurance of(Hf,Zr)O_(2)films with sub-5 nm thicknesses by inserting a TiO_(2)interfacial *** deposition of a Ti film prior to Hf_(0.5)Zr_(0.5)O_(2)film deposition resulted in a high-k TiO_(2)interfacial layer and prevented the direct contact of Hf_(0.5)Zr_(0.5)O_(2)with *** findings show that the high-k TiO_(2)interfacial layer can reduce the SiO_(2)/Si interface trap density and the depolarization field,resulting in a switchable polarization of 60.2μC/cm^(2)for a 5 nm thick Hf_(0.5)Zr_(0.5)O_(2)***,we propose that inserting a high-k TiO_(2)interfacial layer between the Hf_(0.5)Zr_(0.5)O_(2)film and the Si substrate may offer a promising solution to enhancing the ferroelectricity and reliability of(Hf,Zr)O_(2)grown on the Si substrate and can pave the way for next-generation semiconductor devices with improved performance.

关键词： ferroelectric charge trapping hafnia depolarization

Removal of intrahepatic bile duct stone could reduce the risk of cholangiocarcinoma: A single-center retrospective study in South Korea

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World Journal of Clinical Cases 2024年第5期12卷 913-921页

作者： Tae In kim Sung yong Han Jonghyun Lee Dong Uk kim Division of Gastroenterology Biomedical Research InstitutePusan National University HospitalBusan 49241South Korea Department of Internal Medicine Pusan National UniversityCollege of MedicineYangsan 50612South Korea

BACKGROUND Intrahepatic duct(IHD)stones are among the most important risk factors for cholangiocarcinoma(CCC).Approximately 10%of patients with IHD stones develop CCC;however,there are limited studies regarding the effect of IHD stone removal on CCC *** To investigate the association between IHD stone removal and CCC *** We retrospectively analyzed 397 patients with IHD stones at a tertiary referral center between January 2011 and December *** CCC occurred in 36 of the 397 enrolled *** univariate analysis,chronic hepatitis B infection(11.1%vs 3.0%,P=0.03),carbohydrate antigen 19-9(CA19-9,176.00 vs 11.96 II/mL,P=0.010),stone located in left or both lobes(86.1%vs 70.1%,P=0.042),focal atrophy(52.8%vs 26.9%,P=0.001),duct stricture(47.2%vs 24.9%,P=0.004),and removal status of IHD stone(33.3%vs 63.2%,Pupper normal limit,carcinoembryonic antigen>upper normal limit,stones located in the left or both lobes,focal atrophy,and complete removal of IHD stones without recurrence were independent factors influencing CCC ***,the type of removal method was not associated with CCC *** Complete removal of IHD stones without recurrence could reduce CCC risk.

关键词： Intrahepatic bile duct stone Cholangiocarcinoma Percutaneous transhepatic cholangioscopy Endoscopic retrograde cholangiopancreatography Carbohydrate antigen 19-9

Tidal effects based on a GUP-induced effective metric

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Communications in Theoretical Physics 2024年第9期76卷 65-74页

作者： Soon-Tae Hong yong-Wan kim Young-Jai Park Center for Quantum Spacetime and Department of Physics Sogang University Department of Physics and Research Institute of Physics and Chemistry Jeonbuk National University Department of Physics Sogang University

In this paper, we study tidal forces in the Schwarzschild black hole, whose metric explicitly includes a generalized uncertainty principle(GUP) effect. We also investigate interesting features of the geodesic equations and tidal effects that are dependent on the GUP parameter αrelated to a minimum length. Then, by solving the geodesic deviation equations explicitly with appropriate boundary conditions, we show that α in the effective metric affects both the radial and angular components of the geodesic equation, particularly near the singularities.

关键词： effective metric generalized uncertainty principle geodesic deviation equation

Ionizing terahertz waves with 260 MV/cm from scalable optical rectification

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Light(Science & Applications) 2024年第6期13卷 1075-1087页

作者： Hyeongmun kim Chul Kang Dogeun Jang Yulan Roh Sang Hwa Lee Joong Wook Lee Jae Hee Sung Seong Ku Lee Ki-yong kim Advanced Photonics Research Institute GISTGwangju61005Korea Department of Physics and Optoelectronics Convergence Research Center Chonnam National UniversityGwangju61186Korea Pohang Accelerator Laboratory POSTECHPohang37673Korea Center for Relativistic Laser Science Institute for Basic ScienceGwangju61005Korea Institute for Research in Electronics and Applied Physics Department of PhysicsUniversity of MarylandCollege ParkMaryland20742USA

Terahertz(THz)waves,known as non-ionizing radiation owing to their low photon energies,can actually ionize atoms and molecules when a sufficiently large number of THz photons are concentrated in time and ***,we demonstrate the generation of ionizing,multicycle,15-THz waves emitted from large-area lithium niobate crystals via phase-matched optical rectification of 150-terawatt laser pulses.A complete characterization of the generated THz waves in energy,pulse duration,and focal spot size shows that the field strength can reach up to 260 megavolts per *** particular,a single-shot THz interferometer is employed to measure the THz pulse duration and spectrum with complementary numerical *** intense THz pulses are irradiated onto various solid targets to demonstrate THz-induced tunneling ionization and plasma *** study also discusses the potential of nonperturbative THz-driven ionization in gases,which will open up new opportunities,including nonlinear and relativistic THz physics in plasma.

关键词： optical interferometer matched

Effects of mesenchymal stem cell on dopaminergic neurons,motor and memory functions in animal models of Parkinson's disease:a systematic review and meta-analysis

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Neural Regeneration Research 2024年第7期19卷 1584-1592页

作者： Jong Mi Park Masoud Rahmati Sang Chul Lee Jae Il Shin yong Wook kim Department and Research Institute of Rehabilitation Medicine Yonsei University College of MedicineSeoulSouth Korea Department of Physical Education and Sport Sciences Faculty of Literature and Human SciencesLorestan UniversityKhoramabadIran Department of Pediatrics Yonsei University College of MedicineSeoulSouth Korea

Parkinson’s disease is chara cterized by the loss of dopaminergic neurons in the substantia nigra pars com pacta,and although restoring striatal dopamine levels may improve symptoms,no treatment can cure or reve rse the disease *** cell therapy has a regenerative effect and is being actively studied as a candidate for the treatment of Parkinson’s *** stem cells are considered a promising option due to fewer ethical concerns,a lower risk of immune rejection,and a lower risk of *** performed a meta-analysis to evaluate the therapeutic effects of mesenchymal stem cells and their derivatives on motor function,memory,and preservation of dopamine rgic neurons in a Parkinson’s disease animal *** searched bibliographic databases(PubMed/MEDLINE,Embase,CENTRAL,Scopus,and Web of Science)to identify articles and included only pee r-reviewed in vivo interve ntional animal studies published in any language through J une 28,*** study utilized the random-effect model to estimate the 95%confidence intervals(CI)of the standard mean differences(SMD)between the treatment and control *** use the systematic review center for laboratory animal expe rimentation’s risk of bias tool and the collaborative approach to meta-analysis and review of animal studies checklist for study quality assessment.A total of 33studies with data from 840 Parkinson’s disease model animals were included in the *** with mesenchymal stem cells significantly improved motor function as assessed by the amphetamine-induced rotational *** the stem cell types,the bone marrow MSCs with neurotrophic factor group showed la rgest effect size(SMD[95%CI]=-6.21[-9.50 to-2.93],P=0.0001,I^(2)=0.0%).The stem cell treatment group had significantly more tyrosine hydroxylase positive dopamine rgic neurons in the striatum([95%CI]=1.04[0.59 to 1.49],P=0.0001,I^(2)=65.1%)and substantia nigra(SMD[95%CI]=1.38[0.89 to 1.87],P=0.0001,I^(2)=75.3%),indicating a

关键词： animal animal experimentation mesenchymal stem cells models Parkinson’s disease stem cell transplantation

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