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Smoothed online convex optimization via online balanced descent

Smoothed online convex optimization via online balanced desc...

2018 Workshop on MAthematical performance Modeling and Analysis, MAMA 2018 and Workshop on Critical Infrastructure Network Security, CINS 2018

作者： Goel, Gautam Chen, Niangjun Wierman, Adam Department of Computing and Mathematical Sciences California Institute of Technology United States Institute for High Performance Computing United States

We study smoothed online convex optimization, a version of online convex optimization where the learner incurs a penalty for changing her actions between rounds. Given a (pd) lower bound on the competitive ratio of any online algorithm, where d is the dimension of the action space, we ask under what conditions this bound can be beaten. We introduce a novel algorithmic framework for this problem, Online Balanced Descent (OBD), which works by iteratively projecting the previous point onto a carefully chosen level set of the current cost function so as to balance the switching costs and hitting costs. We demonstrate the generality of the OBD framework by showing how, with dierent choices of "balance," OBD can improve upon state-of-the-art performance guarantees for both competitive ratio and regret;in particular, OBD is the first algorithm to achieve a dimension-free competitive ratio, 3 + O(1/), for locally polyhedral costs, where measures the "steepness" of the costs. We also prove bounds on the dynamic regret of OBD when the balance is performed in the dual space that are dimension-free and imply that OBD has sublinear static regret. © 2018 Copyright held by the owner/author(s).

关键词： Cost functions

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Enabling QoE-aware Mobile Cloud Video Recording over Roadside Vehicular Networks

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China Communications 2016年第8期13卷 63-73页

作者： Tongtong Jiang Zhaobin Deng Weiwei Huang Guoqing Zhang Department of Computer Science Sun Yat-sen University Guangdong Province Key Laboratory of Big Data Analysis and Processing Sun Yat-sen University Collaborative Innovation Center of High Performance Computing National University of Defense Technology Institute of Computing Technology Chinese Academy of Sciences

Most of previous video recording devices in mobile vehicles commonly store captured video contents locally. With the rapid development of 4G/Wi Fi networks, there emerges a new trend to equip video recording devices with wireless interfaces to enable video uploading to the cloud for video playback in a later time point. In this paper, we propose a QoE-aware mobile cloud video recording scheme in the roadside vehicular networks, which can adaptively select the proper wireless interface and video bitrate for video uploading to the cloud. To maximize the total utility, we need to design a control strategy to carefully balance the transmission cost and the achieved QoE for users. To this purpose, we investigate the tradeoff between cost incurred by uploading through cellular networks and the achieved QoE of users. We apply the optimization framework to solve the formulated problem and design an online scheduling algorithm. We also conduct extensive trace-driven simulations and our results show that our algorithm achieves a good balance between the transmission cost and user QoE.

关键词： mobile cloud video vehicular networks quality-of-experience

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Bulk superconductivity in pressurized trilayer nickelate Pr4Ni3O10 single crystals

arXiv

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arXiv 2025年

作者： Zhang, Enkang Peng, Di Zhu, Yinghao Chen, Lixing Cui, Bingkun Wang, Xingya Wang, Wenbin Zeng, Qiaoshi Zhao, Jun State Key Laboratory of Surface Physics Department of Physics Fudan University Shanghai200433 China Shanghai Research Center for Quantum Sciences Shanghai201315 China Shanghai201203 China Shanghai Synchrotron Radiation Facility Shanghai Advanced Research Institute Chinese Academy of Sciences Shanghai201204 China Institute of Nanoelectronics and Quantum Computing Fudan University Shanghai200433 China Center for High Pressure Science and Technology Advanced Research Shanghai201203 China Hefei National Laboratory Hefei230088 China

The discovery of superconductivity in pressurized bilayer and trilayer nickelates has generated significant interest. However, their superconducting properties are often dependent on sample quality and pressure conditions, complicating the interpretation of the underlying physics. Finding new systems with optimized bulk superconducting properties is therefore important for advancing our understanding of these materials. Unlike cupates, where trilayer compounds typically exhibit the highest transition temperature (Tc), the bilayer nickelate La3Ni2O7 has thus far outperformed the trilayer La4Ni3O10 in reported Tc. Whether the trilayer nickelates have achieved the optimal Tc remains unclear, with various scenarios suggesting different possibilities. Here, we report the discovery of bulk superconductivity in pressurized Pr4Ni3O10 single crystals, achieving a maximum onset Tc of 40.5 K at 80.1 GPa, significantly exceeding the 30 K observed in La4Ni3O10. The bulk nature of superconductivity is confirmed by zero resistance and a strong diamagnetic response below Tc with a superconducting volume fraction exceeding 80%. These findings establish trilayer nickelates as genuine bulk high-temperature superconductors, provide new insights into the mechanisms driving superconductivity, and point to a promising route toward further enhancing superconducting properties in nickelates. © 2025, CC BY-NC-ND.

关键词： Single crystals

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Developing axisymmetric parametric model for electrostatic force balance

Developing axisymmetric parametric model for electrostatic f...

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2004 Conference on Precision Electromagnetic Measurements Digest, CPEM 2004

作者： Ku, Y.S. Lee, M.H. Center for Measurement Standards Industrial Technology Research Institute Taiwan National Center for High-Performance Computing Taiwan

ISBN: (纸本)0780384938

An axisymmetric parametric model, based on a 2-dimensional finite element method (FEM), was developed in order to calculate both electric field around a charged coaxial cylindrical capacitor and force between its electrodes. It enables us to optimize design and structure of an electrostatic force balance. This model will be used as a crosscheck by comparing the force derived from its deadweight with the calculated one, especially in the range of from micro-Newton to nano-Newton. © 2004 IEEE.

关键词： Electrostatic force

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high performance event trace visualization

High performance event trace visualization

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13th Euromicro Conference on Parallel, Distributed and Network-Based Processing 2005, PDP 2005

作者： Knüpfer, Andreas Brunst, Holger Nagel, Wolfgang E. Center for High Performance Computing Dresden University of Technology 01062 Dresden Germany

ISBN: (纸本)0769522807

This paper presents a joint effort to make huge event traces accessible for interactive program analysis. It combines a distributed software architecture with compressible data structures and customized query algorithms. The advanced technologies are discussed both theoretically and practically. Based on a proof-of-concept implementation the response times for typical queries are presented to show the practical relevance of this combined approach.

关键词： Computer programming

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performance tuning on parallel systems: All problems solved? 5th

Performance tuning on parallel systems: All problems solved?

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5th International Workshop on Applied Parallel computing, PARA 2000

作者： Brunst, Holger Nagel, Wolfgang E. Seidl, Stephan Center for High Performance Computing Dresden University of Technology Dresden01062 Germany

ISBN: (纸本)354041729X

performance tuning of parallel programs, considering the current status and future developments in parallel programming paradigms and parallel system architectures, remains an important topic even if the single CPU performance is doubling every 18 months. Based on a brief summary of state of the art parallel programming techniques, new performance tuning aspects will be identified. The main part of the paper concentrates on how to deal with these aspects by means of new performance analysis and tuning concepts. First tool developments are presented where part of these concepts are already implemented. Finally, an existing scientific parallel application will be presented with respect to its performance tuning stages which were carried out at our center. © Springer-Verlag Berlin Heidelberg 2001.

关键词： Parallel programming

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EXTENSION OF THE PIECEWISE PARABOLIC METHOD TO MULTIDIMENSIONAL IDEAL MAGNETOHYDRODYNAMICS

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JOURNAL OF COMPUTATIONAL PHYSICS 1994年第2期115卷 485-514页

作者： DAI, WL WOODWARD, PR School of Physics and Astronomy Supercomputer Institute Army High Performance Computing Research Center University of Minnesota 1100 Washington Avenue South Minneapolis Minnesota 55415

An extension of the piecewise parabolic method to treat multi-dimensional ideal magnetohydrodynamical equations is presented in this paper. The multidimensional scheme is constructed from a one-dimensional functioning code based on the dimensional splitting method originally suggested by Strang. The functioning code is built upon a nonlinear Riemann solver for ideal MHD equations recently developed by the authors. The correctness of the scheme is tested in the steepening of waves in both one- and two-dimensional situations and in Various MHD shock-tube problems which involve all the discontinuities in ideal MHD. The robust character of the scheme is demonstrated in the shock-tube problems and in the interaction between MHD shocks and a cloud. The results of these problems show that the scheme keeps the principal advantages of a high-order Godunov scheme: robust operation in the presence of very strong waves, thin shock fronts with little attendant noise generation, and thin contact discontinuity, (C) 1994 Academic Press. Inc.

关键词： Magnetohydrodynamics

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Galaxy populations of ProtoClusters in cosmological hydrodynamical simulations

arXiv

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arXiv 2025年

作者： Esposito, Michela Borgani, Stefano Strazzullo, Veronica Pannella, Maurilio Granato, Gian Luigi Ragone-Figueroa, Cinthia Saro, Alex Nonino, Mario Valentini, Milena Department of Physics University of Trieste via G. Tiepolo 11 TriesteI-34131 Italy INAF - Observatory of Trieste via G. Tiepolo 11 TriesteI-34143 Italy IFPU - Institute for Fundamental Physics of The Universe via Beirut 2 TriesteI-34014 Italy INFN - Istituto Nazionale di Fisica Nucleare via Valerio 2 TriesteI-34127 Italy ICSC - Italian Research Center on High Performance Computing Big Data and Quantum Computing via Magnanelli 2 Casalecchio di Reno40033 Italy Universidad Nacional de Córdoba Laprida 854 CórdobaX5000BGR Argentina

Context. The study of protoclusters at cosmic noon is essential for understanding the impact on galaxy properties of the environment and of the transformational processes occurring during this epoch. Aims. This work tests the predictions on galaxy evolution of the DIANOGA cosmological hydrodynamical simulations of cluster progenitors at z = 2.2, comparing them with observations, and investigates the environmental effects on galaxy populations by comparing simulated protoclusters with an average volume of the Universe. Methods. We analyze 14 DIANOGA protoclusters and a cosmological box of 49 cMpc/h per side, simulated with OpenGADGET3. We compare predictions and observations of the galaxy stellar mass function (GSMF), the star-forming Main Sequence (MS), the fraction of star-forming gas, gas depletion times, and the fraction of quenched galaxies. We also compute the rest-frame UV-to-NIR colors of galaxies with the SKIRT-9 radiation transfer code, to analyze UVJ diagrams. Results. We showed that the DIANOGA simulations produce a GSMF in broad agreement with observations. The simulated GSMF shows a higher fraction of high-mass galaxies (M∗ > 1010 M☉) in massive halos in protoclusters, compared to the cosmological box. The same signal, albeit with lower significance, is also observed in the wide-field protocluster structures, indicating an accelerated evolution of galaxies before their infall into massive halos. Our simulations underestimate star formation rates of galaxies both in protoclusters and in the cosmological box, compared to observed counterparts, due to an underestimation of the star-forming gas reservoirs. We find a weak suppression of SFRs in protocluster galaxies (∼ 0.05 dex), compared to the cosmological box, increasing up to ∼ 0.25 dex in massive halos, reflecting suppressed cold gas reservoirs. The quenched galaxy fraction varies significantly across different protocluster halos, consistent with observations at z ∼ 2 − 2.5. The simulations show a stron

关键词： Cosmology

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A Weighted E-Voting Scheme with Secret Weights

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电子学报(英文版) 2006年第3期15卷 413-416页

作者： ZHONG Hong HUANG Liusheng XIONG Yan Department of Computer Science University of Science and Technology of China Hefei 230027 China National High Performance Computing Center at Hefei Hefei 230027 China

The weighted threshold E-voting has great value in many e-commerce applications, whose votes are tallied in proportion with voters' secret weights. It's necessary to design a scheme that satisfies the security requirements of commonly e-voting scheme and preserve the privacy of weights since the privacy of investor will be revealed if the weight is leaked. The previous solutions are mostly based on homomorphic threshold ElGamal cryptosystem and zero-knowledge proofs protocol that suffers from O(n) exponentiation when preparing proofs. This paper describes a secure and practical scheme that adopts novel secure two-party scalar product and private comparison protocol with untrusted third party. The computational cost can be O(n) by selecting reasonable security parameter. Our solution meets all security requirements of weighted voting including the privacy of vote and weight, Dispute-freeness, Fairness and Receipt-Freeness. It's worthwhile for practical applications.

关键词：密码安全策略安全需求域值

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INTERACTIONS BETWEEN MAGNETOHYDRODYNAMIC DISCONTINUITIES

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PHYSICS OF PLASMAS 1994年第11期1卷 3662-3675页

作者： DAI, WL WOODWARD, PR University of Minnesota School of Physics and Astronomy Army High Performance Computing Research Center Supercomputer Institute 1100 Washington Avenue South Minneapolis Minnesota 55415

Interactions between magnetohydrodynamical (MHD) discontinuities are studied through numerical simulations for the set of one-dimensional MHD equations. The interactions include the impact of a shock on a contact discontinuity, the collision of two shocks, and the catchup of a shock over another shock. The shocks involved in the interactions may be very strong. Each shock in an interaction may be either a fast or a slow shock.

关键词： SHOCK WAVES MAGNETOHYDRODYNAMICS NUMERICAL SOLUTION INTERACTIONS

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