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Review of Computational Approaches to Optimization Problems in Inhomogeneous Rods and Plates

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Communications on Applied Mathematics and Computation 2024年第1期6卷 236-256页

作者： Weitao Chen chiu-Yen Kao Department of Mathematics University of California at Riverside900 University AveRiversideCA92521USA Department of Mathematical Sciences Claremont McKenna College850 Columbia AveClaremontCA91711USA

In this paper,we review computational approaches to optimization problems of inhomogeneous rods and *** consider both the optimization of eigenvalues and the localization of *** problems are motivated by physical problems including the determination of the extremum of the fundamental vibration frequency and the localization of the vibration *** demonstrate how an iterative rearrangement approach and a gradient descent approach with projection can successfully solve these optimization problems under different boundary conditions with different densities given.

关键词： Inhomogeneous rods and plates Bi-Laplacian Optimization of eigenvalues Localization of eigenfunctions Rearrangement

A High Power-Added-Efficiency 2.5-GHz Class-F Power Amplifier Using 0.5 μm GaN on SiC HEMT Technology

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Journal of Computer and Communications 2016年第3期4卷 74-78页

作者： Chia-Han Lin hsien-chin chiu Min-Li Chou Hsiang-Chun Wang Ming-Feng Huang Department of Electronic Engineering Chang Gung University No. 259 Wenhua 1st Rd. Guishan Dist. Taoyuan City 33302 Taiwan JMIC 16F. No.44 Sec. 2 Zhongshan N. Rd. Zhongshan Dist. Taipei City 104 Taiwan

This paper proposed the high-frequency, multi-harmonic-controlled, Class-F power amplifier (PA) implemented with 0.5 μm GaN Hetrojunction Electron Mobility Transistor (HEMT). For PA design at high frequencies, parasitics of a transistor significantly increase the difficulty of harmonic manipulation, compared to low-frequency cases. To overcome this issue, we propose a novel design methodology based on a band-reject, low-pass, output matching network, which is realized with passive components. This network provides optimal fundamental impedance and allows harmonic control up to the third order to enable an efficient Class-F behavior. The implemented PA exhibits performance at 2.5 GHz with a 50% PAE, 14 dB gain, and 10 W output power.

关键词： GaN High Power Class-F

“If Somebody Needed Help, I Went Over”: Social Capital and Therapeutic Communities of Older Adult Farmers in British Columbia Floods

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International Journal of Disaster Risk Science 2024年第2期15卷 290-301页

作者： Kyle Breen Siyu Ru Luna Vandeweghe Jenna chiu Lindsay Heyland Haorui Wu School of Social Work Dalhousie UniversityHalifaxNS B3H 1S2Canada

Older adults in disaster contexts are often thought of as a passive, vulnerable population that lacks agency and capacities to cope in the aftermath. However, it can be argued that older adults may have underrecognized strengths that can be utilized pre-, peri-, and post-disaster. One of these strengths is older adults' unique social capital that stems from long-standing connections with other members of their respective communities. Using data from in-depth, semistructured interviews with farmers in British Columbia 3–11 months after the 2021 floods, this research explored the experiences of older adult farmers' recovery. The farmers discussed how they leveraged their social capital to aid in their recovery efforts from the flood event. By using their bonding social capital, older adult farmers transformed their existing, deep-rooted connections into post-disaster assistance. This, in turn, generated the idea of the therapeutic community, helping community members cope in the aftermath. This research indicated the need to further examine how older adults in disaster settings can be viewed as assets with community knowledge and skills as opposed to solely as a vulnerable population.

关键词： British Columbia Flood disaster Older adults Qualitative research Social capital Therapeutic community

Detecting fake reviewers in heterogeneous networks of buyers and sellers:a collaborative training-based spammer group algorithm

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Cybersecurity 2024年第2期7卷 44-67页

作者： Qi Zhang Zhixiang Liang Shujuan Ji Benyong Xing Dickson K.W.chiu Shandong Provincial Key Laboratory of Wisdom Mine Information Technology Shandong University of Science and TechnologyQingdao 266590ShandongChina Zhejang University-University of linois at Urbana-Champaign Institute Haining 314499ZhejiangChina School of Civil Engineering Beijing Jiaotong UniversityBeijing 100044China Faculty of Education The University of Hong KongPok Fu LamHong KongChina

It is not uncommon for malicious sellers to collude with fake reviewers(also called spammers)to write fake reviews for multiple products to either demote competitors or promote their products'reputations,forming a gray industry *** detect spammer groups in a heterogeneous network with rich semantic information from both buyers and sellers,researchers have conducted extensive research using Frequent Item Mining-based and graph-based ***,these methods cannot detect spammer groups with cross-product attacks and do not jointly consider structural and attribute features,and structure-attribute correlation,resulting in poorer detection ***-fore,we propose a collaborative training-based spammer group detection algorithm by constructing a heterogene-ous induced sub-network based on the target product set to detect cross-product attack spammer *** jointly consider all available features,we use the collaborative training method to learn the feature representations of *** addition,we use the DBSCAN clustering method to generate candidate groups,exclude innocent ones,and rank them to obtain spammer *** experimental results on real-world datasets indicate that the overall detection performance of the proposed method is better than that of the baseline methods.

关键词： Spammer group Heterogeneous network Collaborative training DBSCAN

Phase-Noise Improvement of GaAs pHEMT K-Band Voltage Controlled Oscillator Using Tunable Field-Plate Voltage Technology

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Phase-Noise Improvement of GaAs pHEMT K-Band Voltage Control...

Introduction of rare-earth element Sc in alloy design to modify wear features of dual-phase high-entropy alloy

2008 9th International Conference on Solid-State and Integrated-Circuit Technology

作者： hsien-chin chiu Shao Wei Lin Chien-Cheng Wei Chia-Shih Cheng Yu-Fei Wu Jeffrey.S.Fu Department of Electronic Engineering Chang Gung University

This paper presents a voltage-controlled oscillator(VCO) with low phase noise performance by applying tunable field-plate(FP) voltage on 0.15μm gate length GaAs pseudomorphic high electron mobility transistors(pHEMTs).In this study,the FP metal between gate and drain terminals was connected to a single pad and was controlled by an extra voltage supplier(V).Owing to the depth modulation of fieldplate induced depletion region at various field-plate voltages,the device flicker noise were also improved by applying negative *** technique is easy to apply,based on standard pHEMT fabrication,and especially attractive for reducing the phase noise of VCO design without extra power consumption.A tunable phase noise inductor-capacitor(L-C) feedback 21 GHz VCO was fabricated in a standard 0.15 urn GaAs pHEMT *** measured phase-noise of this novel design is -95 dBc/Hz at an offset frequency of 1 MHz and this value can be improved to -99.6 dBc/Hz at V of -5.5 *** core dc power consumption of this circuit is 30.8 mW.

关键词： Voltage-controlled oscillators(VCOs) GaAs RFIC low phase-noise field-plate pHEMT CPW

来源： cnki会议评论

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Rare Metals 2024年第2期43卷 817-828页

作者： Hao Ren Rui-Run Chen Xue-Feng Gao Tong Liu Gang Qin Yu-Lung chiu Shi-Ping Wu Jing-Jie Guo Guo National Key Laboratory for Precision Hot Processing of Metals School of Materials Science and EngineeringHarbin Institute of TechnologyHarbin150001China School of Metallurgy and Materials University of BirminghamBirminghamB152TTUK

Tailoring the alloy composition,which induces the hard secondary phase to increase hardness and strength to improve the wear features,is a feasible approach for developing wear-resistant metal ***,a group of(AlCoCrFeNi)_(100–x)Sc_(x)(x=0–2.0,at%)high-entropy alloys(HEAs)are designed and the phase compositions and wear behaviors are ***-doped HEA series contain the primary body-centered cubic(BCC)and eutectic phases,in which the eutectic phase is composed of the alternately grown BCC and Laves *** addition promotes the diffusion of Ni atoms from BCC phase to form the Sc-rich Laves phase at the grain *** hardness increases due to solid solution strengthening and second phase *** the second phase strengthening plays a more significant role relative to solid solution *** phase and the oxides caused by wear heating prevent the direct contact between friction pair and HEAs,thus inducing a decreased wear rate from 6.82×10^(−5) to 3.47×10^(−5)m^(3)·N^(−1)·m^(−1).Moreover,the wear mechanism changes from adhesive wear,abrasive wear and oxidative wear to abrasive wear and oxidative wear.

关键词： High entropy alloy(HEA) Laves phase Hardness Wear mechanism

A Hf-doped dual-phase high-entropy alloy: phase evolution and wear features

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Rare Metals 2024年第1期43卷 324-333页

作者： Hao Ren Rui-Run Chen Xue-Feng Gao Tong Liu Gang Qin Yu-Lung chiu Shi-Ping Wu Jing-Jie Guo National Key Laboratory for Precision Hot Processing of Metals School of Materials Science and EngineeringHarbin Institute of TechnologyHarbin 150001China School of Metallurgy and Materials University of BirminghamEdgbastonBirmingham B152TTUK

Initially defined high entropy alloys(HEAs)usually exhibit a single-phase solid-solution ***,two and/or more types of phases in HE As possibly induce the desired microstructure features,which contribute to improving the wear properties of HE ***,we prepare a series of(AlCoCrFeNi)_(100-x)Hf_(x)(x=0,2,4and 6;at%) HEAs and concern their phase compositions,micro structures and wear *** leads to the formation of(Ni,Co)_(2)Hf-type Laves phase and tailors the microstructure from a body-centered cubic(BCC) singlephase structure to a hypoeutectic *** increased hardness from~HV 512.3 to~HV 734.1 is due to solid-solution strengthening,grain refinement strengthening and precipitated phase *** a few oxides(Al_(2)O_(3)+Cr_(2)O_(3)) caused by the wear heating contribute to an 85.5% decrease in wear rate of the HEA system from6.71×10^(-5) to 0.97×10^(-5) m^(3)·N^(-1)·m^(-1).In addition,Hf addition changes the wear mechanism from abrasive wear,mild oxidative wear and adhesive wear to oxidative wear and adhesive wear.

关键词： High entropy alloy Laves phase Hardness Wear mechanism

Can You Help Me,Please?

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空中英语教室（初级版．大家说英语） 2024年第9期 35-38,54,55,56页

作者： Maria chiu 不详

Everyone needs help *** can ask,"Can you give me a hand?"Maybe you have to finish a *** need *** can ask,"Can you hand those scissors to me?"Or perhaps you need some advice or want someone's *** you have to solve a **... 详细信息

关键词： something someone You

Classification of high-ordered topological nodes towards Moiré flat bands in twisted bilayers

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Science china(Physics,Mechanics & Astronomy) 2024年第9期Mechanics & Astronomy) .卷 137-151页

作者： Fan Cui Congcong Le Qiang Zhang Xianxin Wu Jiangping Hu ching-Kai chiu Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of Sciences School of Physical Sciences University of Chinese Academy of Sciences RIKEN Interdisciplinary Theoretical and Mathematical Sciences(iTHEMS) CAS Key Laboratory of Theoretical Physics Institute of Theoretical PhysicsChinese Academy of Sciences Kavli Institute of Theoretical Sciences University of Chinese Academy of Sciences New Cornerstone Science Laboratory

At magic twisted angles, Dirac cones in twisted bilayer graphene(TBG) can evolve into flat bands, serving as a critical playground for the study of strongly correlated physics. When chiral symmetry is introduced, rigorous mathematical proof confirms that the flat bands are locked at zero energy in the entire Moiré Brillouin zone(BZ). Yet, TBG is not the sole platform that exhibits this absolute band flatness. Central to this flatness phenomenon are topological nodes and their specific locations in the BZ. In this study, considering twisted bilayer systems that preserve chiral symmetry, we classify various ordered topological nodes in base layers and all possible node locations across different BZs. Specifically, we constrain the node locations to rotational centers,such as Γ and M points, to ensure the interlayer coupling retains equal strength in all directions. Using this classification as a foundation, we systematically identify the conditions under which Moiré flat bands emerge. Additionally, through the extension of holomorphic functions, we provide proof that flat bands are locked at zero energy, shedding light on the origin of the band flatness. Remarkably, beyond Dirac cones, numerous twisted bilayer nodal platforms can host flat bands with a degeneracy number of more than two, such as four-fold, six-fold, and eight-fold. This multiplicity of degeneracy in flat bands might unveil more complex and enriched correlation physics.

关键词： twisted bilayer systems high-ordered topological nodes Morié flat bands high degeneracy

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