The basic function of the Internet is to delivery data(what) to serve the needs of all applications. IP names the attachment points(where) to facilitate ubiquitous interconnectivity as the current way to deliver data....The basic function of the Internet is to delivery data(what) to serve the needs of all applications. IP names the attachment points(where) to facilitate ubiquitous interconnectivity as the current way to deliver data. The fundamental mismatch between data delivery and naming attachment points leads to a lot of challenges, e.g., mapping from data name to IP address, handling dynamics of underlying topology, scaling up the data distribution, and securing communication, etc. Informationcentric networking(ICN) is proposed to shift the focus of communication paradigm from where to what, by making the named data the first-class citizen in the network, The basic consensus of ICN is to name the data independent from its container(space dimension) and session(time dimension), which breaks the limitation of point-to-point IP semantic. It scales up data distribution by utilizing available resources, and facilitates communication to fit diverse connectivity and heterogeneous networks. However, there are only a few consensuses on the detailed design of ICN, and quite a few different ICN architectures are proposed. This paper reveals the rationales of ICN from the perspective of the Internet evolution, surveys different design choices, and discusses on two debatable topics in ICN, i.e.,self-certifying versus hierarchical names, and edge versus pervasive caching. We hope this survey helps clarify some mis-understandings on ICN and achieve more consensuses.展开更多
Machine learning(ML) has been widely applied to the upper layers of wireless communication systems for various purposes, such as deployment of cognitive radio and communication network. However, its application to the...Machine learning(ML) has been widely applied to the upper layers of wireless communication systems for various purposes, such as deployment of cognitive radio and communication network. However, its application to the physical layer is hampered by sophisticated channel environments and limited learning ability of conventional ML algorithms. Deep learning(DL) has been recently applied for many fields, such as computer vision and natural language processing, given its expressive capacity and convenient optimization capability. The potential application of DL to the physical layer has also been increasingly recognized because of the new features for future communications, such as complex scenarios with unknown channel models, high speed and accurate processing requirements; these features challenge conventional communication theories. This paper presents a comprehensive overview of the emerging studies on DL-based physical layer processing, including leveraging DL to redesign a module of the conventional communication system(for modulation recognition, channel decoding, and detection) and replace the communication system with a radically new architecture based on an autoencoder. These DL-based methods show promising performance improvements but have certain limitations, such as lack of solid analytical tools and use of architectures that are specifically designed for communication and implementation research, thereby motivating future research in this field.展开更多
It is extensively approved that Channel State Information(CSI) plays an important role for synergetic transmission and interference management. However, pilot overhead to obtain CSI with enough precision is a signific...It is extensively approved that Channel State Information(CSI) plays an important role for synergetic transmission and interference management. However, pilot overhead to obtain CSI with enough precision is a significant issue for wireless communication networks with massive antennas and ultra-dense cell. This paper proposes a learning- based channel model, which can estimate, refine, and manage CSI for a synergetic transmission system. It decomposes the channel impulse response into multiple paths, and uses a learning-based algorithm to estimate paths' parameters without notable degradation caused by sparse pilots. Both indoor measurement and outdoor measurement are conducted to verify the feasibility of the proposed channel model preliminarily.展开更多
We propose a pilot domain non-orthogonal multiple access(NOMA)for uplink massive devices grant-free random access scenarios in massive multiple-input multiple-output(MIMO)maritime communication systems.These scenarios...We propose a pilot domain non-orthogonal multiple access(NOMA)for uplink massive devices grant-free random access scenarios in massive multiple-input multiple-output(MIMO)maritime communication systems.These scenarios are characterized by numerous devices with sporadic access behavior,and therefore only a subset of them are active.Due to massive potential devices in the network,it is infeasible to assign a unique orthogonal pilot to each device in advance.In such scenarios,pilot decontamination is a crucial problem.In this paper,the devices are randomly assigned non-orthogonal pilots which are constructed by a linear combination of some orthogonal pilots.We show that a bipartite graph can conveniently describe the interference cancellation(IC)processes of pilot decontamination.High spectrum efficiency(SE)and low outage probability can be obtained by selecting the numbers of orthogonal pilots according to the given probability distribution.Numerical evaluatioDs show that the proposed pilot domain NOMA decreases the outage probability from 20%to 2 e-12 at the SE of 4 bits/s/Hz for a single device,compared to the conventional method of slotted ALOHA with 1024 antennas at the BS,or increases the spectrum efficiency from 1.2 bits/s/Hz to 4 bit/s/Hz at the outage probability of2 e-12 in contrast with the Welch bound equality(WBE)non-orthogonal pilots.展开更多
In this paper a low-density pairwise check(LDPC) coded three-way relay system is considered, where three user nodes desire to exchange messages with the help of one relay node. Since physical-layer network coding is a...In this paper a low-density pairwise check(LDPC) coded three-way relay system is considered, where three user nodes desire to exchange messages with the help of one relay node. Since physical-layer network coding is applied, two time slots are sufficient for one round information exchange. In this paper, we present a decode-and-forward(DF) scheme based on joint LDPC decoding for three-way relay channels, where relay decoder partially decodes the network code rather than fully decodes all the user messages. Simulation results show that the new DF scheme considerably outperforms other common schemes in three-way relay fading channels.展开更多
The network resource allocation in SDN for control applications is becoming a key problem in the near future because of the conflict between the need of the flow-level flexibility control and the limited capacity of f...The network resource allocation in SDN for control applications is becoming a key problem in the near future because of the conflict between the need of the flow-level flexibility control and the limited capacity of flow table.Based on the analysis of the difference of the definition of network resource between SDN and traditional IP network,the idea of the integrated allocation of link bandwidth and flow table for multiple control applications in SDN is proposed in this paper.Furthermore,a price-based joint allocation model of network resource in SDN is built by introducing the price for each of the resources,which can get the proportional fair allocation of link bandwidth and the minimum global delay at the same time.We have also designed a popular flow scheduling policy based on the proportional fair allocation of link bandwidth in order to achieve the minimum global delay.A flow scheduling module has been implemented and evaluated in Floodlight,named virtual forwarding space(VFS).VFS can not only implement the fair allocation of link bandwidth and minimum delay flow scheduling in data plane but also accelerate packet forwarding by looking up control rules in control plane.展开更多
Detecting target echo in the existence of self-screen jamming is a challenging work for radar system, especially when digital radio frequency memory(DRFM) technique is employed that mixes the jamming and target echo b...Detecting target echo in the existence of self-screen jamming is a challenging work for radar system, especially when digital radio frequency memory(DRFM) technique is employed that mixes the jamming and target echo both in spatial and time-frequency domain. The conventional way to solve this problem would suffer from performance degradation when physical target(PT) and false target(FT) are superposed in time. In this paper, we propose a new spatial filter according to the different correlation characteristic between PT and FT. The filter takes the ratio of expected signal power to expected jamming and noise power as the objective function under the constant filter modulus constraint. The optimal filter coefficients are derived with a generalized rayleigh quotient approach. Moreover, we analytically compute the target detection probability and demonstrate the applicability of the proposed method to the correlation coefficient. Monte Carlo simulations are provided to corroborate the proposed studies. Furthermore, the proposed method has simple architecture and low computation complexity, making it easily applied in modern radar system.展开更多
Rapid developments in quantum information processing have been made, and remarkable achievements have been obtained in recent years, both in theory and experiments. Coherent control of nuclear spin dynamics is a power...Rapid developments in quantum information processing have been made, and remarkable achievements have been obtained in recent years, both in theory and experiments. Coherent control of nuclear spin dynamics is a powerful tool for the experimental implementation of quantum schemes in liquid and solid nuclear magnetic resonance(NMR) system,especially in liquid-state NMR. Compared with other quantum information processing systems, the NMR platform has the advantages such as the long coherence time, the precise manipulation, and well-developed quantum control techniques,which make it possible to accurately control a quantum system with up to 12-qubits. Extensive applications of liquid-state NMR spectroscopy in quantum information processing such as quantum communication, quantum computing, and quantum simulation have been thoroughly studied over half a century. This article introduces the general principles of NMR quantum information processing, and reviews the new-developed techniques. The review will also include the recent achievements of the experimental realization of quantum algorithms for machine learning, quantum simulations for high energy physics, and topological order in NMR. We also discuss the limitation and prospect of liquid-state NMR spectroscopy and the solid-state NMR systems as quantum computing in the article.展开更多
In device-to-device(D2D)underlay cellular networks with downlink spectrum sharing,massive MIMO seems promising as the large number of antennas at the base station(BS) can be utilized to suppress interference.However,t...In device-to-device(D2D)underlay cellular networks with downlink spectrum sharing,massive MIMO seems promising as the large number of antennas at the base station(BS) can be utilized to suppress interference.However,the channel state information(CSI) from the BS to D2D receivers is required to obtain this advantage.In this paper,we first propose a novel time division duplex(TDD) scheme for D2D users to acquire this CSI,without additional pilot overhead.Moreover,we propose an interference-aware MMSE precoder utilizing the acquired CSI from the BS to not only cellular users but also D2D users to suppress the cellular-to-D2D interference.Simulation results show that our proposed TDD scheme and precoder can significantly improve the achievable sum spectral efficiency(SE) and D2D SE,compared to the classical MMSE precoder.Compared with the interferenceaware ZF precoder,whose performance severely degrades for large user numbers,our proposed interference-aware MMSE precoder can always guarantees a high and stable performance in terms of achievable SE.展开更多
With the advance of smart material science,robotics is evolving from rigid robots to soft robots.Compared to rigid robots,soft robots can safely interact with the environment,easily navigate in unstructured fields,and...With the advance of smart material science,robotics is evolving from rigid robots to soft robots.Compared to rigid robots,soft robots can safely interact with the environment,easily navigate in unstructured fields,and be minimized to operate in narrow spaces,owning to the new actuation and sensing technologies developed by the smart materials.In the review,different actuation and sensing technologies based on different smart materials are analyzed and summarized.According to the driving or feedback signals,actuators are categorized into electrically responsive actuators,thermally responsive actuators,magnetically responsive actuators,and photoresponsive actuators;sensors are categorized into resistive sensors,capacitive sensors,magnetic sensors,and optical waveguide sensors.After introducing the principle and several robotic prototypes of some typical materials in each category of the actuators and sensors.The advantages and disadvantages of the actuators and sensors are compared based on the categories,and their potential applications in robotics are also presented.展开更多
In this paper, Cu–Cu interconnects with ultrafine pad pitches of 6 μm, 8 μm, and 15 μm are implemented on the12 inch wafers by a direct bonding process. Defects are not found by traditional non-destructive(NDT) c-...In this paper, Cu–Cu interconnects with ultrafine pad pitches of 6 μm, 8 μm, and 15 μm are implemented on the12 inch wafers by a direct bonding process. Defects are not found by traditional non-destructive(NDT) c-mode scanning acoustic microscopy(c-SAM). However, cross sectional observation of bonding interfaces reveals that micro-defects such as micro seams are located at SiO_2 bonding interfaces. In order to examine the micro-defects in the ultra-fine pitch direct bonding process by the NDT technology, a novel "defect-enlarged approach" is proposed. The bonded dies are first annealed in an N_2 oven at 300?C for a few hours and then cooled quickly in air. The c-SAM scanning images show large defects at the place where nothing can be detected by c-SAM before this treatment. Cross sectional observation of the bonding interfaces indicates that these defects consist of large size micro seams at the SiO_2 bonding interface, especially near Cu pads with an ultrafine pitch of 6 μm. However, these large defects disappear after several hours at room temperature, observed by c-SAM. It is inferred that the disappearance of these defects inspected by the "defect-enlarged approach" results from the combination of intrinsic micro seams and "weak" bonds in the silicon oxide layer. Then the underlying physical mechanism of these micro-defects is proposed, which is influenced by Cu pad surface topology and bonding models.展开更多
Dipole coupled nanomagnets controlled by the static Zeeman field can form various magnetic logic interconnects.However, the corner wire interconnect is often unreliable and error-prone at room temperature. In this stu...Dipole coupled nanomagnets controlled by the static Zeeman field can form various magnetic logic interconnects.However, the corner wire interconnect is often unreliable and error-prone at room temperature. In this study, we address this problem by making it into a reliable type with trapezoid-shaped nanomagnets, the shape anisotropy of which helps to offer the robustness. The building method of the proposed corner wire interconnect is discussed,and both its static and dynamic magnetization properties are investigated. Static micromagnetic simulation demonstrates that it can work correctly and reliably. Dynamic response results are reached by imposing an ac microwave field on the proposed corner wire. It is found that strong ferromagnetic resonance absorption appears at a low frequency. With the help of a very small ac field with the peak resonance frequency, the required static Zeeman field to switch the corner wire is significantly decreased by ~21 m T. This novel interconnect would pave the way for the realization of reliable and low power nanomagnetic logic circuits.展开更多
An electro-absorption(EA)modulator is one of key components for optical fiber communications due to the high speed,small size,low voltage and integration ability with other semiconductor devices.A 40 Gb/s InGaAsP/InP ...An electro-absorption(EA)modulator is one of key components for optical fiber communications due to the high speed,small size,low voltage and integration ability with other semiconductor devices.A 40 Gb/s InGaAsP/InP multiplequantum-well(MQW)EA modulator monolithically integrated with a semiconductor optical amplifier(SOA)was fabricated for digital communications.The modulator capacitance was reduced to obtain 40 GHz bandwidth,and the SOA section helped reduce the insertion loss from 18 dB to 3 dB.InGaAlAs/InP MQW EA modulators have also been fabricated and characterized for analog optical fiber communications.A low driving voltage of 2.7 V and high spurious free dynamic range of 107 dB·Hz2/3 were estimated by static and dynamic measurements.展开更多
We present the solid model edit distance(SMED),a powerful and flexible paradigm for exploiting shape similarities amongst CAD models.It is designed to measure the magnitude of distortions between two CAD models in bou...We present the solid model edit distance(SMED),a powerful and flexible paradigm for exploiting shape similarities amongst CAD models.It is designed to measure the magnitude of distortions between two CAD models in boundary representation(B-rep).We give the formal definition by analogy with graph edit distance,one of the most popular graph matching methods.To avoid the expensive computational cost potentially caused by exact computation,an approximate procedure based on the alignment of local structure sets is provided in addition.In order to verify the flexibility,we make intensive investigations on three typical applications in manufacturing industry,and describe how our method can be adapted to meet the various requirements.Furthermore,a multilevel method is proposed to make further improvements of the presented algorithm on both effectiveness and efficiency,in which the models are hierarchically segmented into the configurations of features.Experiment results show that SMED serves as a reasonable measurement of shape similarity for CAD models,and the proposed approach provides remarkable performance on a real-world CAD model database.展开更多
基金supported by the National High-tech R&D Program("863"Program)of China(No.2013AA013505)the National Science Foundation of China(No.61472213)State Scholarship Fund from China Scholarship Council(No.201406210270)
文摘The basic function of the Internet is to delivery data(what) to serve the needs of all applications. IP names the attachment points(where) to facilitate ubiquitous interconnectivity as the current way to deliver data. The fundamental mismatch between data delivery and naming attachment points leads to a lot of challenges, e.g., mapping from data name to IP address, handling dynamics of underlying topology, scaling up the data distribution, and securing communication, etc. Informationcentric networking(ICN) is proposed to shift the focus of communication paradigm from where to what, by making the named data the first-class citizen in the network, The basic consensus of ICN is to name the data independent from its container(space dimension) and session(time dimension), which breaks the limitation of point-to-point IP semantic. It scales up data distribution by utilizing available resources, and facilitates communication to fit diverse connectivity and heterogeneous networks. However, there are only a few consensuses on the detailed design of ICN, and quite a few different ICN architectures are proposed. This paper reveals the rationales of ICN from the perspective of the Internet evolution, surveys different design choices, and discusses on two debatable topics in ICN, i.e.,self-certifying versus hierarchical names, and edge versus pervasive caching. We hope this survey helps clarify some mis-understandings on ICN and achieve more consensuses.
文摘Machine learning(ML) has been widely applied to the upper layers of wireless communication systems for various purposes, such as deployment of cognitive radio and communication network. However, its application to the physical layer is hampered by sophisticated channel environments and limited learning ability of conventional ML algorithms. Deep learning(DL) has been recently applied for many fields, such as computer vision and natural language processing, given its expressive capacity and convenient optimization capability. The potential application of DL to the physical layer has also been increasingly recognized because of the new features for future communications, such as complex scenarios with unknown channel models, high speed and accurate processing requirements; these features challenge conventional communication theories. This paper presents a comprehensive overview of the emerging studies on DL-based physical layer processing, including leveraging DL to redesign a module of the conventional communication system(for modulation recognition, channel decoding, and detection) and replace the communication system with a radically new architecture based on an autoencoder. These DL-based methods show promising performance improvements but have certain limitations, such as lack of solid analytical tools and use of architectures that are specifically designed for communication and implementation research, thereby motivating future research in this field.
基金Supported by the National Natural Science Foundation of China Grant No.10874098the National Basic Research Program of China under Grant Nos.2009CB929402 and 2011CB9216002
基金supported by National Basic Research Program of China (NO 2012CB316002)China’s 863 Project (NO 2014AA01A703)+2 种基金National Major Projec (NO. 2014ZX03003002-002)Program for New Century Excellent Talents in University (NCET-13-0321)Tsinghua University Initiative Scientific Research Program (2011THZ02-2)
文摘It is extensively approved that Channel State Information(CSI) plays an important role for synergetic transmission and interference management. However, pilot overhead to obtain CSI with enough precision is a significant issue for wireless communication networks with massive antennas and ultra-dense cell. This paper proposes a learning- based channel model, which can estimate, refine, and manage CSI for a synergetic transmission system. It decomposes the channel impulse response into multiple paths, and uses a learning-based algorithm to estimate paths' parameters without notable degradation caused by sparse pilots. Both indoor measurement and outdoor measurement are conducted to verify the feasibility of the proposed channel model preliminarily.
基金Supported by the National Natural Science Foundation of China Grant Nos 10775076 and 10874098, the National Basic Research Program of China under Grant No 2009CB929402, the Specialized Research Fund for the Doctoral Program of Education Ministry of China.
基金supported by Key R&D Program of China under Grant 2018YFB1801102National Natural Science Foundation of China(U1736108)+1 种基金Foundation for Innovative Research Groups of the National Natural Science Foundation of China(61621091)Tsinghua University Initiative Scientific Research Program 20193080005。
文摘We propose a pilot domain non-orthogonal multiple access(NOMA)for uplink massive devices grant-free random access scenarios in massive multiple-input multiple-output(MIMO)maritime communication systems.These scenarios are characterized by numerous devices with sporadic access behavior,and therefore only a subset of them are active.Due to massive potential devices in the network,it is infeasible to assign a unique orthogonal pilot to each device in advance.In such scenarios,pilot decontamination is a crucial problem.In this paper,the devices are randomly assigned non-orthogonal pilots which are constructed by a linear combination of some orthogonal pilots.We show that a bipartite graph can conveniently describe the interference cancellation(IC)processes of pilot decontamination.High spectrum efficiency(SE)and low outage probability can be obtained by selecting the numbers of orthogonal pilots according to the given probability distribution.Numerical evaluatioDs show that the proposed pilot domain NOMA decreases the outage probability from 20%to 2 e-12 at the SE of 4 bits/s/Hz for a single device,compared to the conventional method of slotted ALOHA with 1024 antennas at the BS,or increases the spectrum efficiency from 1.2 bits/s/Hz to 4 bit/s/Hz at the outage probability of2 e-12 in contrast with the Welch bound equality(WBE)non-orthogonal pilots.
基金supported in part by the National Natural Science Foundation of China under Grant 61201187by the Importation and Development of High-Caliber Talents Project of Beijing Municipal Institutions under Grant YETP0110+2 种基金by the Tsinghua University Initiative Scientific Research Program under Grant 20121088074by the Foundation of Zhejiang Educational Committee under Grant Y201121579by the Visiting Scholar Professional Development Project of Zhejiang Educational Committee under Grant FX2014052
文摘In this paper a low-density pairwise check(LDPC) coded three-way relay system is considered, where three user nodes desire to exchange messages with the help of one relay node. Since physical-layer network coding is applied, two time slots are sufficient for one round information exchange. In this paper, we present a decode-and-forward(DF) scheme based on joint LDPC decoding for three-way relay channels, where relay decoder partially decodes the network code rather than fully decodes all the user messages. Simulation results show that the new DF scheme considerably outperforms other common schemes in three-way relay fading channels.
基金Supported by the National High-tech R&D Program("863" Program) of China (No.2013AA013505)the National Science Foundation of China(No.61472213)National Research Foundation of Korea(NRF 2014K1A1A2064649)
文摘The network resource allocation in SDN for control applications is becoming a key problem in the near future because of the conflict between the need of the flow-level flexibility control and the limited capacity of flow table.Based on the analysis of the difference of the definition of network resource between SDN and traditional IP network,the idea of the integrated allocation of link bandwidth and flow table for multiple control applications in SDN is proposed in this paper.Furthermore,a price-based joint allocation model of network resource in SDN is built by introducing the price for each of the resources,which can get the proportional fair allocation of link bandwidth and the minimum global delay at the same time.We have also designed a popular flow scheduling policy based on the proportional fair allocation of link bandwidth in order to achieve the minimum global delay.A flow scheduling module has been implemented and evaluated in Floodlight,named virtual forwarding space(VFS).VFS can not only implement the fair allocation of link bandwidth and minimum delay flow scheduling in data plane but also accelerate packet forwarding by looking up control rules in control plane.
文摘Detecting target echo in the existence of self-screen jamming is a challenging work for radar system, especially when digital radio frequency memory(DRFM) technique is employed that mixes the jamming and target echo both in spatial and time-frequency domain. The conventional way to solve this problem would suffer from performance degradation when physical target(PT) and false target(FT) are superposed in time. In this paper, we propose a new spatial filter according to the different correlation characteristic between PT and FT. The filter takes the ratio of expected signal power to expected jamming and noise power as the objective function under the constant filter modulus constraint. The optimal filter coefficients are derived with a generalized rayleigh quotient approach. Moreover, we analytically compute the target detection probability and demonstrate the applicability of the proposed method to the correlation coefficient. Monte Carlo simulations are provided to corroborate the proposed studies. Furthermore, the proposed method has simple architecture and low computation complexity, making it easily applied in modern radar system.
基金Project supported by the National Natural Science Foundation of China(Grants Nos.11175094 and 91221205)the National Basic Research Program of China(Grant No.2015CB921002)
文摘Rapid developments in quantum information processing have been made, and remarkable achievements have been obtained in recent years, both in theory and experiments. Coherent control of nuclear spin dynamics is a powerful tool for the experimental implementation of quantum schemes in liquid and solid nuclear magnetic resonance(NMR) system,especially in liquid-state NMR. Compared with other quantum information processing systems, the NMR platform has the advantages such as the long coherence time, the precise manipulation, and well-developed quantum control techniques,which make it possible to accurately control a quantum system with up to 12-qubits. Extensive applications of liquid-state NMR spectroscopy in quantum information processing such as quantum communication, quantum computing, and quantum simulation have been thoroughly studied over half a century. This article introduces the general principles of NMR quantum information processing, and reviews the new-developed techniques. The review will also include the recent achievements of the experimental realization of quantum algorithms for machine learning, quantum simulations for high energy physics, and topological order in NMR. We also discuss the limitation and prospect of liquid-state NMR spectroscopy and the solid-state NMR systems as quantum computing in the article.
基金supported by National Basic Research Program of China under Grants No. 2013CB329002Science Fund for Creative Research Groups of NSFC under Grants No.61321061+3 种基金China's 863 Project under Grants No.2015AA01A706National Major Project under Grants No.2016ZX03001023-003Program for New Century Excellent Talents in University under Grants No.NCET-130321Tsinghua-Qualcomm Joint Research Program,and Tsinghua University Initiative Scientific Research Program under Grants No. 2011THZ02-2
文摘In device-to-device(D2D)underlay cellular networks with downlink spectrum sharing,massive MIMO seems promising as the large number of antennas at the base station(BS) can be utilized to suppress interference.However,the channel state information(CSI) from the BS to D2D receivers is required to obtain this advantage.In this paper,we first propose a novel time division duplex(TDD) scheme for D2D users to acquire this CSI,without additional pilot overhead.Moreover,we propose an interference-aware MMSE precoder utilizing the acquired CSI from the BS to not only cellular users but also D2D users to suppress the cellular-to-D2D interference.Simulation results show that our proposed TDD scheme and precoder can significantly improve the achievable sum spectral efficiency(SE) and D2D SE,compared to the classical MMSE precoder.Compared with the interferenceaware ZF precoder,whose performance severely degrades for large user numbers,our proposed interference-aware MMSE precoder can always guarantees a high and stable performance in terms of achievable SE.
基金Supported by National Key Research and Development Program of China(Grant No.2019YFB 1309800)National Natural Science Foundation of China(Grant Nos.62173197,91848206)Beijing Science&Technology Project(Grant No.Z191100008019008).
文摘With the advance of smart material science,robotics is evolving from rigid robots to soft robots.Compared to rigid robots,soft robots can safely interact with the environment,easily navigate in unstructured fields,and be minimized to operate in narrow spaces,owning to the new actuation and sensing technologies developed by the smart materials.In the review,different actuation and sensing technologies based on different smart materials are analyzed and summarized.According to the driving or feedback signals,actuators are categorized into electrically responsive actuators,thermally responsive actuators,magnetically responsive actuators,and photoresponsive actuators;sensors are categorized into resistive sensors,capacitive sensors,magnetic sensors,and optical waveguide sensors.After introducing the principle and several robotic prototypes of some typical materials in each category of the actuators and sensors.The advantages and disadvantages of the actuators and sensors are compared based on the categories,and their potential applications in robotics are also presented.
基金supported by the National Natural Science Foundation of China(Grant No.61274111)the National Basic Research Program of China(Gran No.2015CB057205)
文摘In this paper, Cu–Cu interconnects with ultrafine pad pitches of 6 μm, 8 μm, and 15 μm are implemented on the12 inch wafers by a direct bonding process. Defects are not found by traditional non-destructive(NDT) c-mode scanning acoustic microscopy(c-SAM). However, cross sectional observation of bonding interfaces reveals that micro-defects such as micro seams are located at SiO_2 bonding interfaces. In order to examine the micro-defects in the ultra-fine pitch direct bonding process by the NDT technology, a novel "defect-enlarged approach" is proposed. The bonded dies are first annealed in an N_2 oven at 300?C for a few hours and then cooled quickly in air. The c-SAM scanning images show large defects at the place where nothing can be detected by c-SAM before this treatment. Cross sectional observation of the bonding interfaces indicates that these defects consist of large size micro seams at the SiO_2 bonding interface, especially near Cu pads with an ultrafine pitch of 6 μm. However, these large defects disappear after several hours at room temperature, observed by c-SAM. It is inferred that the disappearance of these defects inspected by the "defect-enlarged approach" results from the combination of intrinsic micro seams and "weak" bonds in the silicon oxide layer. Then the underlying physical mechanism of these micro-defects is proposed, which is influenced by Cu pad surface topology and bonding models.
基金Supported by the National Natural Science Foundation of China under Grant No 61302022
文摘Dipole coupled nanomagnets controlled by the static Zeeman field can form various magnetic logic interconnects.However, the corner wire interconnect is often unreliable and error-prone at room temperature. In this study, we address this problem by making it into a reliable type with trapezoid-shaped nanomagnets, the shape anisotropy of which helps to offer the robustness. The building method of the proposed corner wire interconnect is discussed,and both its static and dynamic magnetization properties are investigated. Static micromagnetic simulation demonstrates that it can work correctly and reliably. Dynamic response results are reached by imposing an ac microwave field on the proposed corner wire. It is found that strong ferromagnetic resonance absorption appears at a low frequency. With the help of a very small ac field with the peak resonance frequency, the required static Zeeman field to switch the corner wire is significantly decreased by ~21 m T. This novel interconnect would pave the way for the realization of reliable and low power nanomagnetic logic circuits.
基金supported by National ScienceFoundation Programs(60536020,60723002)"973"State Key Basic Research Programs(2006CB302800,2006CB921106)
文摘An electro-absorption(EA)modulator is one of key components for optical fiber communications due to the high speed,small size,low voltage and integration ability with other semiconductor devices.A 40 Gb/s InGaAsP/InP multiplequantum-well(MQW)EA modulator monolithically integrated with a semiconductor optical amplifier(SOA)was fabricated for digital communications.The modulator capacitance was reduced to obtain 40 GHz bandwidth,and the SOA section helped reduce the insertion loss from 18 dB to 3 dB.InGaAlAs/InP MQW EA modulators have also been fabricated and characterized for analog optical fiber communications.A low driving voltage of 2.7 V and high spurious free dynamic range of 107 dB·Hz2/3 were estimated by static and dynamic measurements.
基金Acknowledgment This work was supported by Beijing Natural Science Foundation Funded Project （No.4110001）, National S＆T Major Project （No. 2011ZX03003-002）, Tsinghua Independent Research （No. 2010TH203-02） and Samsung Company.
基金Supported by National Science Foundation of China(61373071)
文摘We present the solid model edit distance(SMED),a powerful and flexible paradigm for exploiting shape similarities amongst CAD models.It is designed to measure the magnitude of distortions between two CAD models in boundary representation(B-rep).We give the formal definition by analogy with graph edit distance,one of the most popular graph matching methods.To avoid the expensive computational cost potentially caused by exact computation,an approximate procedure based on the alignment of local structure sets is provided in addition.In order to verify the flexibility,we make intensive investigations on three typical applications in manufacturing industry,and describe how our method can be adapted to meet the various requirements.Furthermore,a multilevel method is proposed to make further improvements of the presented algorithm on both effectiveness and efficiency,in which the models are hierarchically segmented into the configurations of features.Experiment results show that SMED serves as a reasonable measurement of shape similarity for CAD models,and the proposed approach provides remarkable performance on a real-world CAD model database.
