检索结果-内蒙古大学图书馆

作者： Mihai lulian Florea Aalto University

学位级别：博士

A wide range of inverse problems and various machine learning tasks can be expressed as large- scale optimization problems with a composite objective structure, where the gradient of the smooth part has a global Lipschitz constant that is either impractical to compute or considerably larger than the local values. The smooth part may be strongly convex as well, especially in certain medical imaging applications. The only fast methods that are able to address this entire class of problems are similar to or based on the black-box algorithms developed and analyzed by Nesterov using the estimate sequence mathematical framework. In this work, we introduce the augmented estimate sequence framework, a relaxation of the estimate sequence. When the lower bounds incorporated in the augmented estimate functions are hyperplanes or parabolae, this framework generates a conceptually simple gap sequence. We use this gap sequence to construct the Accelerated Composite Gradient Method (ACGM), a versatile ﬁrst-order scheme applicable to the entire composite problem class. ACGM is endowed with an efﬁcient dynamic Lipschitz constant estimation (line-search) procedure and features monotonicity. Motivated by the absence of an accurate complexity measure applicable to all ﬁrst-order methods, we also introduce the wall-clock time unit (VVTU). The WTU accounts for variations in algorithmic per-iteration complexity and more consistently reﬂects the performance of ﬁrst-order methods in practical implementations. When analyzed using WTU, ACGM has the best provable convergence rate on the composite problem class, both in the strongly and non-strongly convex cases. We conﬁrm the superiority of ACGM within its class using an extensive simulation benchmark. ACGM also excels in terms of robustness and usability. In particular, ACGM is guaranteed to converge without requiring any quantitative prior information on the problem. Additional information, if available, leads to an improvement in performanc

关键词： Acceleration composite objective estimate sequence Fast Gradient Method ﬁrst-order method FISTA large-scale optimization line-search Nesterov method matrix-free optimization algorithm point-spread function spatially varying ultrasound

来源：评论

学校读者我要写书评

暂无评论

Analysis and Application of Discrete Halbach Magnet Array With Unequal Arc Lengths and Unequally Changed Magnetization Directions

引用

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 2018年第3期28卷 1-5页

作者： Huang, Hailin Jing, Libing Qu, Ronghai Li, Dawei Huazhong Univ Sci & Technol Coll Elect & Elect Engn State Key Lab Adv Electromagnet Engn & Technol Wuhan 430074 Hubei Peoples R China

This paper presents a general process to analyze and optimize the performance for an arbitrary discrete Halbach magnet array which is "unnormal" on magnetization direction and arc length of each segment. Besides the original type, a new arrangement of Halbach array is proposed, which does not have main PM segments. Two-dimensional field analytical models for predicting the air-gap field distribution of both arrangements are offered and validated by an FEA method. Then, a multi-objective optimizer was applied for different requirements, and comparison between normal and optimized 3-segment Halbach array is given to verify the effect of optimization. At last, some potential applications and follow-up study are discussed.

关键词： Analytical model Halbach PM array magnetic fields optimization algorithm

来源：评论

学校读者我要写书评

暂无评论

Weapon-Target Assignment algorithm for Simultaneous and Sequenced Arrival

引用

JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2018年第11期41卷 2361-2373页

作者： Volle, Kyle Rogers, Jonathan Georgia Inst Technol Sch Mech Engn Atlanta GA 30332 USA

Weapon-target assignment is a multi-agent control problem in which each weapon is assigned to a target to minimize the expected survival value of the targets. In this work, a multi-objective version of the weapon-target assignment problem is considered in which the quality of an assignment is dependent on both the total effectiveness of the weapons assigned to each target and the relative timing of agents' arrival. Such timing constraints may be important in real-world scenarios in which a mission planner wishes to enforce an element of surprise on each target. Building on previous work, a new modified cost function is presented that couples weapon effectiveness and timing metrics into a combined cost. In cases where weapon-target closing speeds are limited to a certain range, this combined cost allows the inclusion of arrival time constraints in the assignment decision process. The performance of this new cost function is demonstrated through theoretical analysis and simulation. Results show that the proposed cost function balances the dual goals of optimizing effectiveness and arrival time considerations under closing speed limitations and that a user-defined tuning parameter can be used to adjust the priority of the dual goals of sequenced arrival and achieving the desired probability of kill.

关键词： Weapon Target Assignment algorithm Weapon Target Assignment Branch and Bound algorithm Monte Carlo Simulation algorithm Performance optimization algorithm Mobile Robotic System Damage Assessment Annealing Computing

来源：评论

学校读者我要写书评

暂无评论

Economic and environmental costs of replacing nuclear fission with solar and wind energy in Sweden

引用

ENERGY POLICY 2018年第Jan.期112卷 56-66页

作者： Hong, Sanghyun Qvist, Staffan Brook, Barry W. Univ Tasmania Fac Sci Engn & Technol Private Bag 55 Hobart Tas 7001 Australia Uppsala Univ Dept Phys & Astron Uppsala Sweden

Nuclear power is facing an uncertain future in Sweden due to political directives that are seeking to phase out this energy source over coming decades. Here we examine the environmental and economic costs of hypothetical future renewable-energy-focused cases compared with the current nuclear and hydroelectricity-centred mix in Sweden. We show that if wind and photovoltaics replace entire nuclear power while maintaining the current level of dispatchable backup capacity including hydroelectric power and peak gas power, 154 GW of wind power will be required and will generate 427.1 TWh (compared with the actual demand of 143.7 TWh) to reliably meet demand each hour of the year. As a consequence, the annual spending on electricity systems will be five times higher than the status quo. Increasing dispatchable power, increasing transmission capacities to other countries, and generating electricity from combined heat and power plants even when there is no heat demand, will together reduce the required capacities of wind and solar photovoltaic by half, but it will double the greenhouse gas emissions during the combustion process. In conclusion, our economic and greenhouse-gas emissions analyses demonstrate that replacing nuclear power with renewables will be neither economic nor environmentally friendly with regards to the climate.

关键词： Nuclear power Renewable Sustainability assessment Alternative cases optimization algorithm

来源：评论

学校读者我要写书评

暂无评论

Analog active filter design using a multi objective genetic algorithm

引用

AEU-INTERNATIONAL JOURNAL OF ELECTRONICS AND COMMUNICATIONS 2018年 93卷 83-94页

作者： Mostafa, Sheikh Shanawaz Horta, Nuno Ravelo-Garcia, Antonio G. Morgado-Dias, Fernando Polo Cient & Tecnol Madeira Madeira Interact Technol Inst Floor 2Caminho Penteada P-9020105 Funchal Portugal Univ Lisbon Inst Super Tecn Inst Telecomunicacoes Av Rovisco Pais 1 P-1049001 Lisbon Portugal Univ Las Palmas Gran Canaria Inst Technol Dev & Innovat Commun Las Palmas Gran Canaria 35017 Spain Univ Madeira Praca Municipio 17 P-9000034 Funchal Portugal

The selection of the correct values for passive elements, resistors, and capacitors, is an important task in analog active filter design. The classic method of choosing passive elements is a difficult task and can lead to errors. To reduce the incidence of error and human effort evolutionary optimization techniques are used to select the values of capacitors and resistors. However, due to the single objective optimization technique, these are not well suited to optimize different filter parameters. For this reason, the performance of a multi-objective genetic algorithm named non-dominated sorting genetic algorithm II (NSGA-II) against the different single objective algorithms is evaluated. Two analog active filters: A fourth order Butterworth and a second order state variable filter with the operational amplifiers in their cores are used for testing purposes. In both cases two different objects are chosen along with eight components as variables to be optimized. The component values are compatible with the E12, E24 and E96 series using NSGA-II. The computation results are better in terms of design error and allow for better resistor and capacitor choice. To reach the same or better results the NSGA-II needs fewer generations compared with other genetic algorithms for this problem.

关键词： Evolutionary optimization Technique optimization algorithm Analog active filter Butterworth filter NSGA-II

来源：评论

学校读者我要写书评

暂无评论

Improved Differential Evolution algorithm and Its Applications to Orbit Design

引用

JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2018年第4期41卷 936-943页

作者： Yao, Wei Luo, Jianjun Macdonald, Malcolm Wang, Mingming Ma, Weihua Northwestern Polytech Univ Xian 710072 Shaanxi Peoples R China Northwestern Polytech Univ Natl Key Lab Aerosp Flight Dynam Xian 710072 Shaanxi Peoples R China Univ Strathclyde Strathclyde Space Inst Glasgow G1 1XJ Lanark Scotland Natl Key Lab Aerosp Flight Dynam Xian Shaanxi Peoples R China

A double self-adaptive differential evolution algorithm with a random mutant was proposed. When a random mutant and a double self-adaptive scaling factor are introduced into the traditional differential evolution algorithm, the scaling factors of the proposed algorithm can adjust with the optimization procedure, and the algorithm can jump out of the local optimal. When the algorithms are applied to several test function studies including low dimension and high dimension and compared with the other algorithms, the simulations demonstrated that the advanced algorithm can give a better performance in solution accuracy, convergence, and the results' standard deviation. The case studies prove that the novel self-adaptive algorithm with random mutant can provide a better performance on multitarget, maneuver optimal problems than others.

关键词： Earth optimization algorithm Transfer Orbit Satellites Particle Swarm optimization Lambert's Problem Orbital Eccentricity Aerodynamic Shape optimization Interplanetary Trajectories Monte Carlo Simulation

来源：评论

学校读者我要写书评

暂无评论

Computational analysis of non-invasive deep brain stimulation based on interfering electric fields

引用

PHYSICS IN MEDICINE AND BIOLOGY 2019年第23期64卷 235010-235010页

作者： Karimi, Fariba Attarpour, Ahmadreza Amirfattahi, Rassoul Nezhad, Abolghasem Zeidaabadi Isfahan Univ Technol Dept Elect & Comp Engn Esfahan *** Iran

Neuromodulation modalities are used as effective treatments for some brain disorders. Non-invasive deep brain stimulation (NDBS) via temporally interfering electric fields has emerged recently as a non-invasive strategy for electrically stimulating deep regions in the brain. The objective of this study is to provide insight into the fundamental mechanisms of this strategy and assess the potential uses of this method through computational analysis. Analytical and numerical methods are used to compute the electric potential and field distributions generated during NDBS in homogeneous and inhomogeneous models of the brain. The computational results are used for specifying the activated area in the brain (macroscopic approach), and quantifying its relationships to the stimulation parameters. Two automatic algorithms, using artificial neural network (ANN), are developed for the homogeneous model with two and four electrode pairs to estimate stimulation parameters. Additionally, the extracellular potentials are coupled to the compartmental axon cable model to determine the responses of the neurons to the modulated electric field in two developed models and to evaluate the precise activated area location (microscopic approach). Our results show that although the shape of the activated area was different in macroscopic and microscopic approaches, it located only at depth. Oura* optimization algorithms showed significant accuracy in estimating stimulation parameters. Moreover, it demonstrated that the more the electrode pairs, the more controllable the activated area. Finally, compartmental axon cable modeling results verified that neurons can demodulate and follow the electric field modulation envelope amplitude (MEA) in our models. The results of this study help develop the NDBS method and eliminate some limitations associated with the nonautomateda* optimization algorithm.

关键词： non-invasive deep brain stimulation temporally interfering electric fields optimization algorithm axon modeling

来源：评论

学校读者我要写书评

暂无评论

A heuristic method to determine traffic bottlenecks based on ant colony: A case study of Iran

引用

CASE STUDIES ON TRANSPORT POLICY 2018年第4期6卷 716-721页

作者： Mahpour, Alireza Amiri, Amir Mohammadian Deldar, Milad Saffarzadeh, Mahmoud Nazifi, Amin Rd Housing & Dev Res Ctr BHRC Tehran Iran Univ Calif Berkeley Berkeley CA 94720 USA Islamic Azad Univ Sci & Res Branch Tehran Iran TMU Tehran Iran

The increase of density at bottlenecks enhances the probability of accident occurrence, delay, fuel consumption and pollution. For predicting the exact location of bottlenecks in the abnormal demand situation, such as holidays, national rituals, religious ceremonies or important sports events, is of great importance that has been evaluated in the present study. Despite the enormous amount of effort has been devoted to identifying the existing bottlenecks, there is still no consensus how the location of bottlenecks in the abnormal demand situation can be projected. To tackle this problem, the present study investigates the Kerman province road network, the largest province of Iran, to identify the existing bottlenecks. Moreover, Ant Colonya* optimization algorithm has been used to predict the location of potential bottlenecks. The results of the research indicated that the proposed approach not only has the ability to identify existing bottlenecks, but it also can be used for prediction the potential bottlenecks in the future.

关键词： Ant Colony Bottleneck optimization algorithm Metaheuristic Iran

来源：评论

学校读者我要写书评

暂无评论

Development of a Method for Improving the Electric Field Distribution in Patients Undergoing Tumor-Treating Fields Therapy

引用

JOURNAL OF THE KOREAN PHYSICAL SOCIETY 2018年第10期73卷 1577-1583页

作者： Sung, Jiwon Seo, Jaehyeon Jo, Yunhui Yoon, Myonggeun Hwang, Sang-Gu Kim, Eun Ho Korea Univ Dept Bioconvergence Engn Seoul 02841 South Korea Korea Inst Radiol & Med Sci Seoul 01812 South Korea

Tumor-treating fields therapy involves placing pads onto the patient's skin to create a low-intensity (1 - 3 V/cm), intermediate frequency (100 - 300 kHz), alternating electric field to treat cancerous tumors. This new treatment modality has been approved by the Food and Drug Administration in the USA to treat patients with both newly diagnosed and recurrent glioblastoma. To deliver the prescribed electric field intensity to the tumor while minimizing exposure of organs at risk, we developed an optimization method for the electric field distribution in the body and compared the electric field distribution in the body before and after application of thisa* optimization algorithm. To determine the electric field distribution in the body before optimization, we applied the same electric potential to all pairs of electric pads located on opposite sides of models. We subsequently adjusted the intensity of the electric field to each pair of pads to optimize the electric field distribution in the body, resulting in the prescribed electric field intensity to the tumor while minimizing electric fields at organs at risk. A comparison of the electric field distribution within the body before and after optimization showed that application of thea* optimization algorithm delivered a therapeutically effective electric field to the tumor while minimizing the average and the maximum field strength applied to organs at risk. Use of thisa* optimization algorithm when planning tumor-treating fields therapy should maintain or increase the intensity of the electric field applied to the tumor while minimizing the intensity of the electric field applied to organs at risk. This would enhance the effectiveness of tumor-treating fields therapy while reducing dangerous side effects.

关键词： Tumor-treating fields Alternating electric field optimization algorithm Cancer therapy Electric field calculation

来源：评论

学校读者我要写书评

暂无评论

A Novel Method for Physical-Layer Authentication via Channel State Information 12

A Novel Method for Physical-Layer Authentication via Channel...

引用

12th International Conference on Signal Processing and Communication Systems (ICSPCS)

作者： Lord, Scott Roth, John McEachen, John Tummala, Murali Naval Postgrad Sch Dept Elect & Comp Engn Monterey CA 93943 USA

ISBN: (纸本)9781538656020

The channel response between a wireless transmitter node and a receiver node changes as the nodes move and the environment changes. Recent studies have suggested several approaches to leverage such changes in channel response as an attribute for authenticating a communication node's claimed identity. We propose a specular reflector mapping approach to enable authentication of a communication node's reported location by comparing measured transmission channel characteristics to those expected for emissions from the reported location. This work focuses on how a specular reflecting plane can be estimated from the multipath time delay measurements over multiple transmitter positions presenting theoretical limits to estimating such a reflecting plane. Additionally, we provide a brief example to illustrate the value such a reflecting plane can bring in regards to authenticating a transmission's claimed position of origin.

关键词： Physical-layer security authentication single bounce reflection optimization algorithm multipath

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：