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Achievable degrees of freedom of MIMO two-way X relay channel with delayed CSIT

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Science China(Information Sciences) 2016年第8期59卷 193-203页

作者： Qingyun LI Gang WU Hongxiang LI Shaoqian LI National Key Laboratory of Science and Technology on Communications University of Electronic Science and Technology of China Department of Electrical and Computer Engineering University of Louisville

The previous work on interference alignment for multiple-input-multiple-output(MIMO) two-way X relay channel assumes perfect channel state information at the transmitter(CSIT), which is reasonable in slow fading channel. However, in fast fading scenario, this assumption is impractical. In this paper, assuming that each node has delayed CSIT, we study the achievable degrees of freedom(DOF) for MIMO two-way X relay channel in frequency division duplex(FDD) systems. Specifically, in the broadcast(BC) phase, we propose a new multiple-stage transmission(MST) scheme, which utilizes retrospective interference alignment for physical layer network coding(PLNC). We show that MST can achieve significant DOF gain and tremendous power gain over other schemes. When the number of antennas for each user, N, is smaller than the number of the relays, M, the time division multiple access(TDMA) scheme can only achieve an ergodic sum-rate increase by N bps/Hz for every increasing of 3 d B of signal-to-noise power ratio(SNR), while the proposed MST scheme can achieve an ergodic sum-rate increase by M bps/Hz.

关键词： degrees of freedom physical layer network coding interference alignment delayed CSIT multiplestage transmission

Impact vibration reduction for flexible manipulators via controllable local degrees of freedom

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Chinese Journal of Aeronautics 2013年第5期26卷 1303-1309页

作者： Bian Yushu Gao Zhihui Deng Yuchun School of Mechanical Engineering and Automation Beihang University

When performing operation tasks, the interaction between a flexible manipulator and a grasped object usually results in an impact. In this paper, a new way is suggested to alleviate impact vibration of a flexible manipulator via its structural characteristic when capturing a moving object. Controllable local degrees of freedom are introduced to the topological structure of the flexible manipulator, and used as an effective tool to combat impact vibration through dynamic coupling. A corresponding method is put forward to reduce impact vibration responses of the flexible manip- ulator via the controllable local degrees of freedom. By planning motion of the controllable local degrees of freedom, appropriate control force can be constructed to increase the modal damping and stiffness and eliminate the exciting force simultaneously, thereby reducing impact vibration responses of the flexible manipulator. Simulations are conducted and results are shown to prove the presented method.

关键词： degrees of freedom Dynamics Flexible manipulators Impact Vibration control

Breakdown of Landau Fermi liquid theory： Restrictions on the degrees of freedom of quantum electrons

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Frontiers of physics 2018年第2期13卷 119-137页

作者： Yue-Hua Su Han-Tao Lu Department of Physics Yantai University Yantai 264005 China Center for Interdisciplinary Studies Lanzhou University Lanzhou 730000 China

One challenge in contemporary condensed matter physics is to understand unconventional electronic physics beyond the paradigm of Landau Fermi-liquid theory. Here, we present a perspective that posits that most such examples of unconventional electronic physics stem from restrictions on the degrees of freedom of quantum electrons in Landau Fermi liquids. Since the degrees of freedom are deeply connected to the system＇s symmetries and topology, these restrictions can thus be realized by external constraints or by interaction-driven processes via the following mechanisms：（i） symmetry breaking, （ii） new emergent symmetries, and （iii） nontrivial topology. Various examples of unconventionM elec- tronic physics beyond the reach of traditional Landau Fermi liquid theory are extensively investigated from this point of view. Our perspective yields basic pathways to study the breakdown of Landau Fermi liquids and also provides a guiding principle in the search for novel electronic systems and devices.

关键词： breakdown of the Landau Fermi liquids degrees of freedom symmetry topology

How Initial degrees of freedom May Contribute to Initial Effective Mass, i.e. Effective Mass of the Universe Proportional to (D.O.F.) to the 1/4^th Power by an Enormous Initial Degree of freedom Value

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Journal of High Energy Physics, Gravitation and Cosmology 2022年第4期8卷 1127-1133页

作者： Andrew Walcott Beckwith Physics Department College of Physics Chongqing University Huxi Campus Chongqing China

Using a relationship between Hubble’s “parameter”, Temperature, Energy and effective mass, from there obtain in 3 + 1 dimensions a relationship between effective mass, and the initial degrees of freedom, to the 1/4th power, we will discuss candidates for entry into this, assuming for a start that initial universe conditions are similar to a black hole, i.e. a nearly singular start to inflationary expansion;this would necessitate a HUGE initial degree of freedom value as outlined in our argument.

关键词： degrees of freedom Effective Mass Hubbles Parameter

Empowerment in chronic wound care——exploring the scope for patient contribution

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Frontiers of Nursing 2024年第1期11卷 1-16页

作者： Benedikt Hackert Ewa Klara Stürmer Ulrich Weger Department of Psychology and Psychotherapy University of Witten/HerdeckeAlfred-Herrhausen-Straße 5058448 WittenGermany Department for Vascular Medicine University Heart and Vascular Center HamburgUniversity Medical Center Hamburg-EppendorfMartinistreet 5220246 HamburgGermany

Objective:In this study,we investigated the concept of empowerment in chronic wound care and propose to facilitate patient control by making use of degrees of freedom(DOF):that is,shaping of everyday wound care tasks initiated by patients and based on their wishes,mostly in terms of patients executing treatment steps,requesting or directing health care professionals to under take changes,or modifications of internal states.Methods:As a first step,we conducted a systematic literature search,followed by an inductive form of qualitative content analysis,which resulted in the identification of 5 dimensions as main elements of empowerment:education and shared decision making,adherence to self-care behaviors,responsibility and control,general call for empowerment,and DOF.However,the latter are noticeably absent in the literature.To investigate patients'freedom in shaping the wound care process,we conducted a second literature search.Results:A number of possibilities for patients to influence the wound care process could be identified,but experimental or clinical evidence about their effects is missing,their variety is limited,and they are only inadequately described.Conclusions:However,DOF should be an indispensable aspect of genuine empowerment,since they allow patients to occupy the role of the agent in the treatment process and give rise to the subjective experience of feeling empowered.Thus,in the third part,we develop a research proposal on how to investigate and include DOF in the clinical practice of wound care.Finally,limitations about implementations are discussed(e.g.,patients being reluctant to overcome their passive role,resulting in frustration for health care professionals).

关键词： adherence chronic wounds control degrees of freedom empowerment shared decision making

On degrees of freedom of the cellular network

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Science China(Information Sciences) 2010年第5期53卷 1034-1043页

作者： SUN Jun 1,2 , LIU YingZhuang 1,2 & ZHU GuangXi 1,2 1 Department of Electronics and Information Engineering, Huazhong University of Science and Technology, Wuhan 430074, China 2 Division of Optical Network and Intelligent Communication, Wuhan National Laboratory for Optoelectronics, Wuhan 430074, China Department of Electronics and Information Engineering Huazhong University of Science and Technology Wuhan China Division of Optical Network and Intelligent Communication Wuhan National Laboratory for Optoelectronics Wuhan China

In this paper, we consider the capacity limits of the cellular network by modeling it as consisting of two mutually interfering multiple access channels with multiple antennas at each receiver (e.g., base station). By developing a tight outerbound as well as an achievable scheme which exploits the idea of interference alignment, we are able to exactly characterize the sum degrees of freedom (DoF) of the network when the channel coefficients are timeor frequency-varying, which equals KM K+min(M,K) (where M and K denote the number of receiver antennas and number of users in per cell, respectively) per cell. From the DoF result, it can be observed that in addition to the multi-user gain which has been reported for the network with single-antenna BSs, there also exists the multi-antenna gain in the cellular network. In particular, when the number of users is large, we can nearly achieve the interference-free DoF of a cellular network with multiple-antenna BSs, which is a somewhat surprising result.

关键词： capacity degrees of freedom cellular network interference alignment interference channel MIMO

A New Sparser Nested Array Configuration with Increased degrees of freedom

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A New Sparser Nested Array Configuration with Increased Degr...

作者： Mohammed Abdulrahman Abdulwadood Abdullah 华南理工大学

学位级别：硕士

Array signal processing concentrates on sensor arrays that receive signals in spatial domain.The application of array signal processing includes source number recognition and direction of arrival estimation（DOA）and so on.These applications often use the uniform linear array（ULA）,that are often costly and difficult to provide large aperture,since the maximum number of resolvable sources for a ULA ofsensors is-1.Recently,increasing the degree of freedom（DOF）based on the concept of Khatri-Rao（KR）product has attracted much attention in array signal processing.One typical array is nested array,which can achieve（~2）degrees-of-freedom（DOFs）by using only（）sensors.The nested array is obtained from a combination of two ULAs,one ULA is a dense sub-array,that utilizes the classical inter-sensor spacing,while the other ULA is a sparse array,as it employs a sparser inter-inter-element spacing.A preferable sparse array usually has a closed-form expression for sensors locations,and a long central uniform linear array segment in difference co-array（DCA）.All those lead to more resolvable sources and high estimation accuracy.In this thesis,a novel nested array configuration is proposed.The proposed array has a closed-form expression for its sensor locations,it extends the concept of the two-level nested array and exploits the difference co-array to increase the achievable DOFs.The spacing between the dense and sparse array,and the spacing between the sensors of sparse array change according to the total number of physical sensors.The holes in the difference co-array are interpolated by using nuclear norm to exploit a full difference co-array.The proposed array structure can improve the accuracy and achieve a higher resolution in direction-of-arrival（DOA）estimation.The numerical simulation results eventually validate the efficacy of the proposed array.

关键词： Nested arrays difference co-arrays DOA estimation degrees of freedom nuclear norm minimization

A multiscale view in functional materials

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Progress in Natural Science:Materials International 2022年第6期32卷 674-683页

作者： Guoqiang Shi Dongfeng Xue Multiscale Crystal Materials Research Center Shenzhen Institute of Advanced Technology Chinese Academy of Sciences

Functional materials show various highly demanded performances originating from intrinsic features related to degrees of freedom in a lattice framework.Presently,deep physical or chemical insights of quantum materials stimulate researchers to clarify multiscale processes within both materials and devices,which may be understood as functional materials that possess energy origin beyond electron contribution.It is of great significance for the design of functional materials to understand the sources of properties of functional materials from the perspective of multi degrees of freedom via multiscale research methods.This short review illustrates the importance and explores the energy source of functional materials from multiple degrees of freedom perspectives.Moreover,we analyzed the multiple degrees of freedom within lithium niobate single crystals to clarify their multiscale features.This short review may,in some cases,provide a perspective for enhancing research scopes of functional materials and recommending some methodologies from multiple degrees of freedom perspectives.

关键词： degrees of freedom Functional crystals Lithium niobate

Hierarchical Self-organization of Complex Systems

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Chemical Research in Chinese Universities 2004年第4期20卷 440-445页

作者： CHAILi-he WENDong-sheng SchoolofEnvironmentalScienceandEngineering TianjinUniversityTianjin300072P.R.China InstituteofParticleScienceandEngineering UniversityofLeedsLeedsLS29JTUK

Researches on organization and structure in complex systems are academic and industrial fronts in modern sciences. Though many theories are tentatively proposed to analyze complex systems, we still lack a rigorous theory on them. Complex systems possess various degrees of freedom, which means that they should exhibit all kinds of structures. However, complex systems often show similar patterns and structures. Then the question arises why such similar structures appear in all kinds of complex systems. The paper outlines a theory on freedom degree compression and the existence of hierarchical self-organization for all complex systems is found. It is freedom degree compression and hierarchical self-organization that are responsible for the existence of these similar patterns or structures observed in the complex systems.

关键词： Complex systems degrees of freedom Hierarchical Self-organization