We have carried out an experimental study of liquid drop impact on superhydrophobic substrates covered by a carpet of chemically coated nano-wires.The micro-structure of the surface is similar to some biological ones(...We have carried out an experimental study of liquid drop impact on superhydrophobic substrates covered by a carpet of chemically coated nano-wires.The micro-structure of the surface is similar to some biological ones(Lotus leaf for example).In this situation the contact angle can then be considered as equal to 180 degrees,with no hysteresis.Due to its initial inertia,the drop experiences a flattening phase after it hits the surface,taking the shape of a pancake.Once it reaches its maximal lateral extension,the drop begins to retract and bounces back.We have extracted the lateral extension of the drop,and we propose a model that explains the trend.We find a limit initial velocity beyond which the drop protrudes into the nano-wire carpet.We discuss the relevance of practical issues in terms of self-cleaning surfaces or spray-cooling.展开更多
MnO2/MnO cathode material with superior Zn^2+storage performance is prepared through a simple physical mixing method.The MnO2/MnO nanocomposite with a mixed mass ratio of 12:1 exhibits the highest specific capacity(36...MnO2/MnO cathode material with superior Zn^2+storage performance is prepared through a simple physical mixing method.The MnO2/MnO nanocomposite with a mixed mass ratio of 12:1 exhibits the highest specific capacity(364.2 mA·h/g at 0.2C),good cycle performance(170.4 mA·h/g after 100 cycles)and excellent rate performance(205.7 mA·h/g at 2C).Analysis of cyclic voltammetry(CV)data at various scan rates shows that both diffusioncontrolled insertion behavior and surface capacitive behavior contribute to the Zn2+storage performance of MnO2/MnO cathodes.And the capacitive behavior contributes more at high discharge rates,due to the short paths of ion diffusion and the rapid transfer of electrons.展开更多
This work presents our understanding of insect wings, and the design and micromachining of artificial wings with golden ratio-based and tapered veins. The geometric anisotwpy of Leading Edge Veins （LEVs） selected by...This work presents our understanding of insect wings, and the design and micromachining of artificial wings with golden ratio-based and tapered veins. The geometric anisotwpy of Leading Edge Veins （LEVs） selected by Diptera has a function able to evade impact. As a Diptera example, the elliptic hollow-LEVs of cranefly wings are mechanically and aerodynamically significant. In this paper, an artificial wing was designed to be a fractal structure by mimicking cranefly wings and incorporating cross-veins and discal cell. Standard technologies of Microelectromechanical Systems （MEMS） were employed to materialize the design using the selected material. One SU-8 wing sample, light and stiffenough to be comparable to fresh cranefly wings, was presented. The as-prepared SU-8 wings are faithful to real wings not only in weight and vein pattern, but also in flexural stiffness and mass distribution. Thus our method renders possible mimickine with good lidelity of natural wings with complex geometry and morphology.展开更多
Usually a buffer layer of cadmium sulphide is used in high efficiency solar cells based on Cu(In,Ga)Se2(CIGS). Because of cadmium toxicity, many in-vestigations have been conducted to use Cd-free buffer layers. Our wo...Usually a buffer layer of cadmium sulphide is used in high efficiency solar cells based on Cu(In,Ga)Se2(CIGS). Because of cadmium toxicity, many in-vestigations have been conducted to use Cd-free buffer layers. Our work focuses on this type of CIGS-based solar cells where CdS is replaced by a ZnS buffer layer. In this contribution, AFORS-HET software is used to simulate n-ZnO: Al/i-ZnO/n-ZnS/p-CIGS/Mo polycrystalline thin-film solar cell where the key parts are p-CIGS absorber layer and n-ZnS buffer layer. The characteristics of these key parts: thickness and Ga-content of the absorber layer, thickness of the buffer layer and doping concentrations of absorber and buffer layers have been investigated to optimize the conversion efficiency. We find a maximum conversion efficiency of 26% with a short-circuit current of 36.9 mA/cm2, an open circuit voltage of 824 mV, and a fill factor of 85.5%.展开更多
The halogenated boron-doped diamond （BDD） surfaces were reacted with sodium azide through a nucle- ophilic substitution reaction. The resulting azide-terminated BDD surfaces were used to trigger the ＂click＂ reacti...The halogenated boron-doped diamond （BDD） surfaces were reacted with sodium azide through a nucle- ophilic substitution reaction. The resulting azide-terminated BDD surfaces were used to trigger the ＂click＂ reaction. Because of the attractive electrochemical properties of ferrocene-containing molecules, such as fast electron transfer rates, reversible redox activities, and favorable redox potentials, we show that ferrocene derivatives can be grafted onto non-oxidized diamond surfaces by ＂click chemistry＂. These redox-active ferrocene-containing layers on a BDD surface, because of their ability to store and release charges reversibly, have the potential to be used as hybrid molecular/semiconductor memory devices.展开更多
Orthogonal frequency division multiplexing-interleave division multiple access (OFDM-IDMA) systems may suffer from serious inter-carrier interference (ICI) in time-and frequency-selective (doubly selective) channels. ...Orthogonal frequency division multiplexing-interleave division multiple access (OFDM-IDMA) systems may suffer from serious inter-carrier interference (ICI) in time-and frequency-selective (doubly selective) channels. In such case, the conventional OFDM-IDMA detection algorithm for quasi-static channels will result in significantly performance degradation. In this paper, signal detection is investigated for OFDM-IDMA uplink over doubly selective channels. Firstly, the impact of time-varying channels for OFDM-IDMA uplink is analyzed, which leads to the failure of the conventional algorithm. Secondly, a novel iterative detection algorithm is developed based on an integrated interference canceller, which can iteratively estimate and mitigate the ICI as well as multiple access interference (MAI) simultaneously. In addition, an improved detection algorithm is derived for reducing the complexity using an approximation to the mean and variance of the interference. Simulation results indicate that the proposed algorithm can significantly enhance the system performance to the conventional case, and the improved algorithm can strike a balance between performance and complexity.展开更多
In this paper, the problem of channel estimation for superposition coded modulation-orthogonal frequency division multiplexing (SCM-OFDM) systems over frequency selective channels is investigated. Assuming that the pa...In this paper, the problem of channel estimation for superposition coded modulation-orthogonal frequency division multiplexing (SCM-OFDM) systems over frequency selective channels is investigated. Assuming that the path delays are known, a new channel estimator based on modified Kalman filter algorithms is introduced for the estimation of the multipath Rayleigh channel complex gains (CG). In the simulation, the mean square error (MSE) and bit-error-rate (BER) performances are given to verify the effectiveness of the Kalman estimation algorithms for SCM-OFDM systems.展开更多
WSNs （wireless sensor networks） can be used for railway infrastructure inspection and vehicle health monitoring. SHM （structural health monitoring） systems have a great potential to improve regular operation, secu...WSNs （wireless sensor networks） can be used for railway infrastructure inspection and vehicle health monitoring. SHM （structural health monitoring） systems have a great potential to improve regular operation, security and maintenance routine of structures with estimating the state of its health and detecting the changes that affect its performance. This is vital for the development, upgrading, and expansion of railway networks. The work presented in this paper aims at the possible use of acoustic sensors coupled with ZigBee modules for health monitoring of rails. The detection principle is based on acoustic noise correlation techniques. Experiments have been performed in a rail sample to confirm the validity of acoustic noise correlation techniques in the rail. A wireless communication platform prototype based on the ZigBee/IEEE 802.15.4 technology has been implemented and deployed on a rail sample. Once the signals from the structure are collected, sensor data are transmitted through a ZigBee solution to the processing unit.展开更多
Radars and their applications were, for a long time, reserved to national defense, air security or weather service domains. For a few years, with the emergence of new technologies, radar applications have been develop...Radars and their applications were, for a long time, reserved to national defense, air security or weather service domains. For a few years, with the emergence of new technologies, radar applications have been developed and have become known in the civil domain. In particular, the arrival of UWB—Ultra-Wideband technology allows the design of compact and low-cost radars with multiple fields of application. In this paper, we focus on road applications, such as driving assistance with the objective of increasing safety and reducing accidents. In classical UWB radar systems, Gaussian and monocycle pulses are commonly used. In previous works, original waveforms based on orthogonal functions (Hermite and Gegenbauer) were proposed. These provide a good spatial resolution, suitable for radar detection. Another advantage of these waveforms is their multiple access capability, due to their orthogonality. The aim of the study presented in this article is to compare simulation and experimental results obtained, especially for short-range anticollision radar application, using these waveforms in one part and Gaussian and monocycle pulses in the other part. The originality of this paper relies on the new approach. Indeed, this comparison study using these waveforms has never been done before. Finally, some examples of real experiments in a real road environment with different waveforms are presented and analysed.展开更多
In this paper, a transmission system based on OFDM (Orthogonal Frequency Division Multiplexing) technique and channel estimation is proposed. The idea is to enhance the assisted channel estimation without data rate lo...In this paper, a transmission system based on OFDM (Orthogonal Frequency Division Multiplexing) technique and channel estimation is proposed. The idea is to enhance the assisted channel estimation without data rate loss. A solution based on frequency diversity is proposed. With the same number of pilots, the global system performances are better for higher mobility speed. The main results will be presented in the case of high mobility context.展开更多
Nowadays, because of its wide bandwidth and high communication capability, the optical fiber is more and more used for high data rate transmission of information in railway environments. Conventionally, only one servi...Nowadays, because of its wide bandwidth and high communication capability, the optical fiber is more and more used for high data rate transmission of information in railway environments. Conventionally, only one service is sent over the fiber at a time. However, many different services can be simultaneously conveyed in railway stations such as passenger information service, cellular phone, Wi-Fi... The objective of the work proposed in this paper is to demonstrate the potential benefits of transmitting radio signals over fiber in a railway environment. The main idea is to exploit the full capacity of the fiber by transmitting multiple services using the same fiber. Since, different services are operating in different frequency bands; we propose a new multiplexing technique called Mode Group Diversity Multiplexing （MGDM） to ensure the transmission of multiple services using the same fiber, without additional infrastructure. There are numerous advantages of the proposed technique, e.g., faster and reliable data exchange, high resolution video surveillance capability, high data rate information exchange in railway stations. We present, in this paper, the physical characteristics of optical fibers, performance of MGDM multiplexing technique, and the influence of the laser excitation conditions at the entrance of the fiber on the performances of the system.展开更多
The deployment of wireless technologies in the radiology field requires development of radiolucent materials allowing wireless communication. In this paper, both the radiolucency (X-rays) and Electro-Magnetic (EM) pro...The deployment of wireless technologies in the radiology field requires development of radiolucent materials allowing wireless communication. In this paper, both the radiolucency (X-rays) and Electro-Magnetic (EM) properties of the conductive polymer poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) are investigated to address wireless applications in the field of the radiology. A model was developed to predict the PEDOT:PSS performance and assess the interest of this material in terms of radiolucency characteristics and Electro Magnetic (EM) radiation efficiency. A PEDOT:PSS antenna operating in the Radio-Frequency Identification (RFID) Ultra High Frequency (UHF) band, was realized to experimentally validate abilities of PEDOT:PSS. These performances are compared with those produced by a similar antenna made of conventional materials such as copper. Experimental results validate the numerical model of the designed structure. This paper demonstrates the potential of polymer materials in the field of x-ray imaging.展开更多
In the railway application, in order to establish the communication between wagons, some technologies are proposed such as the ZigBee and HTN (Hybrid Networking Technology). However, these techniques have some limitat...In the railway application, in order to establish the communication between wagons, some technologies are proposed such as the ZigBee and HTN (Hybrid Networking Technology). However, these techniques have some limitations such as: the low data rate, non-secured transmission and interferences. The Ultra Wide Band (UWB) technology presents a good alternative and a good candidate for this application. In recent years, UWB communication systems have received significant attention from both the industry and the academia. In February 2002, the Federal Communications Commission (FCC) allocated 7500 MHz of spectrum (from 3.1 GHz to 10.6 GHz) for use by UWB devices. This ruling has helped to create new standardization efforts, like IEEE 802.15.3a, which focus on developing high speed wireless communication systems. The application of the UWB radio technique in the transport is a more recent topic that is thoroughly researched considering several factors including the nature of the transport propagation environment;the use of adequate transmitting/receiving duty cycle (LDC);the number of devices using UWB technology, the types and levels of interferences. Regulation bodies have considered these railway applications. Impulse Radio Ultra Wideband (IR-UWB) systems have been studied for their inherent advantages of coexistence with narrowband systems with high data rate over short distances with sufficiently small amount of transmitted power. The UWB systems are highly susceptible to interference between the coexisting narrowband systems because of very low transmission power. This paper considers the use of the UWB radio technology for railway application. In this paper, we evaluate the communication performance in constrained environment for the railway application.展开更多
We investigate the electronic transport in a simple mesoscopic cross structure made of two wires(stubs)grafted at the same point along a quantum waveguide.We show that the structure may exhibit important phenomena suc...We investigate the electronic transport in a simple mesoscopic cross structure made of two wires(stubs)grafted at the same point along a quantum waveguide.We show that the structure may exhibit important phenomena such as bound in continuum(BIC)states.These states are transformed into electromagnetically induced transparency(EIT)resonance by detuning slightly the lengths of the stubs.The last phenomenon is used to propose and study a mesoscopic demultiplexer device with an input waveguide and two output waveguides.We give closed-form expressions of the geometrical parameters that allow a selective transfer of a given state in the first waveguide without perturbing the second waveguide.The effect of temperature on the transmission resonances is also examined by using Landauer-Büttiker formula.The analytical results of the dispersion relation and transmission and reflection coefficient are obtained using the Green's function method.展开更多
Recent studies using BSIM3 models have suggested that noise depends on the transconductance-to-drain ratio gm/ID of a transistor. However, to the best of our knowledge, no experimental result demonstrating gm/ID depen...Recent studies using BSIM3 models have suggested that noise depends on the transconductance-to-drain ratio gm/ID of a transistor. However, to the best of our knowledge, no experimental result demonstrating gm/ID dependent noise previously observed in simulation is available in the literature. This paper examines the underlying principles that make it possible to analyze noise using gm/ID based noise analysis. Qualitative discussion of normalized noise is presented along with experimental results from a 130 nm CMOS process. A close examination of the experimental results reveals that the device noise is width independent from 1 Hz to 10 kHz. Moreover, noise increases as gm/ID is reduced. The experiment observation that noise is width independent makes it possible for circuit designers to generate normalized parameters that are used to study noise intuitively and accurately.展开更多
In this paper, a biosensor based on photonic crystal fiber (PCF) is proposed and designed using Full-Vectorial Finite Element Method (FVFEM). The proposed PCF sensor consists of three concentric circles surrounding th...In this paper, a biosensor based on photonic crystal fiber (PCF) is proposed and designed using Full-Vectorial Finite Element Method (FVFEM). The proposed PCF sensor consists of three concentric circles surrounding the core. The key optical sensor characteristics such as sensitivity, the field profiles and real part of the refractive index of the proposed PCF structure are investigated by employing the FVFEM. The proposed sensor can be deployed for environmental sensing when the PCF active region is filled with either analytes such as liquids or gas. By careful selection of the design parameters such as the radius of the sensing circle, the diameter of air holes in the core region and hole to hole spacing, Λ, the sensitivity analytes is determined. Our simulation results show that, the electric field distribution is primary localized in the third concentric circle with a radius of 16 μm. Effects of PCF bending on the sensitivity is also studied and reported.展开更多
This paper presents a basic block for building large-scale single-electron neural networks. This macro block is completely composed of SET inverter circuits. We present and discuss the basic parts of this device. The ...This paper presents a basic block for building large-scale single-electron neural networks. This macro block is completely composed of SET inverter circuits. We present and discuss the basic parts of this device. The full design and simulation results were done using MATLAB and SIMON, which are a single-electron tunnel device and circuit simulator based on a Monte Carlo method. Special measures had to be taken in order to simulate this circuit correctly in SIMON and compare results with those of SPICE simulation done before. Moreover, we study part of the network as a memory cell with the idea of combining the extremely low-power properties of the SET and the compact design.展开更多
<span style="font-family:Verdana;">The aim of this work is to analyze the influence of the interfacial MoSe</span><sub><span style="font-family:Verdana;">2</span></...<span style="font-family:Verdana;">The aim of this work is to analyze the influence of the interfacial MoSe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> layer </span><span style="font-family:Verdana;">on </span><span style="font-family:Verdana;"><span>the performance of a /n-ZnO/i-ZnO/n-Zn(O,S)/p-CIGS/p</span><sup><span>+</span></sup><span>-MoSe</span><sub><span>2</span></sub><span>/Mo/SLG</span></span><span style="font-family:Verdana;"> solar cell. In this investigation, the numerical simulation software AFORS-</span><span style="font-family:Verdana;">HET is used to calculate the electrical characteristics of the cell with and</span><span style="font-family:Verdana;"> without this MoSe</span><span style="font-family:Verdana;"><sub>2</sub></span><span style="font-family:Verdana;"> layer. Different reported experimental works have highlighted the presence of a thin-film MoSe</span><span style="font-family:Verdana;"><sub>2</sub></span><span style="font-family:Verdana;"> layer at the CIGS/Mo contact interface. Under a tunneling effect, this MoSe</span><span style="font-family:Verdana;"><sub>2</sub></span><span style="font-family:Verdana;"> layer transforms the Schottky CIGS/Mo contact nature into a quasi-ohmic one. Owing to a heavily p-doping, the MoSe</span><span style="font-family:Verdana;"><sub>2</sub></span><span style="font-family:Verdana;"> thin layer allows better transport of majority carrier, tunneling them from CIGS to Mo. Moreover, the bandgap of MoSe</span><span style="font-family:Verdana;"><sub>2</sub></span><span style="font-family:Verdana;"> is wider than that of the CIGS absorbing layer, such that an electric field is generated close to the back surface. The presence of this electric field reduces carrier recombination at the interface. Under these conditions, we examined the performance of the cell with and without MoSe</span><span style="font-family:Verdana;"><sub>2</sub></span><span style="font-family:Verdana;"> layer. When the thickness of the CIGS absorber is in the range from 3.5 μm down to 1.5 μm, the efficiency of the cell with a MoSe</span><span style="font-family:Verdana;"><sub>2</sub></span><span style="font-family:Verdana;"> interfacial layer remains almost constant, about 24.6%, while that of the MoSe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">-free solar cell decreases from 24.6% to 23.4%. Besides, a Schottky barrier height larger than 0.45 eV severely affects the fill factor and open circuit voltage of the solar cell with MoSe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> interface layer compared to the MoSe</span><span style="font-family:Verdana;"><sub>2</sub></span><span style="font-family:Verdana;">-free solar cell.</span>展开更多
This paper studies a new positioning beacon for railway transport using Ultra Wideband (UWB) radio and Time Reversal (TR) techniques. UWB radio has the potential to offer a good level of performance in terms of locali...This paper studies a new positioning beacon for railway transport using Ultra Wideband (UWB) radio and Time Reversal (TR) techniques. UWB radio has the potential to offer a good level of performance in terms of localization accuracy. Time Reversal channel pre-filtering facilitates signal detection and also helps increasing the received energy in the targeted area. In this paper, we evaluate the characteristics of TR technique in terms of temporal focusing. The theoretical and simulation results for Power Delay Profile, equivalent channel model and focusing gain of TR-UWB are given. We analyze the contribution of Time Reversal associated with UWB technology to enhance the localization resolution. The IEEE 802.15.3achannel models are used to evaluate the performance of this system. In terms of localization error, the theoretical and simulation results show that TR-UWB technique delivers improved performance over the UWB localization approach.展开更多
文摘We have carried out an experimental study of liquid drop impact on superhydrophobic substrates covered by a carpet of chemically coated nano-wires.The micro-structure of the surface is similar to some biological ones(Lotus leaf for example).In this situation the contact angle can then be considered as equal to 180 degrees,with no hysteresis.Due to its initial inertia,the drop experiences a flattening phase after it hits the surface,taking the shape of a pancake.Once it reaches its maximal lateral extension,the drop begins to retract and bounces back.We have extracted the lateral extension of the drop,and we propose a model that explains the trend.We find a limit initial velocity beyond which the drop protrudes into the nano-wire carpet.We discuss the relevance of practical issues in terms of self-cleaning surfaces or spray-cooling.
基金Project(21905304)supported by the National Natural Science Foundation of ChinaProject(ZR2019BEM031)supported by the Natural Science Foundation of Shandong Province,ChinaProjects(18CX02158A,19CX05001A)supported by the Fundamental Research Funds for the Central Universities,China。
文摘MnO2/MnO cathode material with superior Zn^2+storage performance is prepared through a simple physical mixing method.The MnO2/MnO nanocomposite with a mixed mass ratio of 12:1 exhibits the highest specific capacity(364.2 mA·h/g at 0.2C),good cycle performance(170.4 mA·h/g after 100 cycles)and excellent rate performance(205.7 mA·h/g at 2C).Analysis of cyclic voltammetry(CV)data at various scan rates shows that both diffusioncontrolled insertion behavior and surface capacitive behavior contribute to the Zn2+storage performance of MnO2/MnO cathodes.And the capacitive behavior contributes more at high discharge rates,due to the short paths of ion diffusion and the rapid transfer of electrons.
文摘This work presents our understanding of insect wings, and the design and micromachining of artificial wings with golden ratio-based and tapered veins. The geometric anisotwpy of Leading Edge Veins （LEVs） selected by Diptera has a function able to evade impact. As a Diptera example, the elliptic hollow-LEVs of cranefly wings are mechanically and aerodynamically significant. In this paper, an artificial wing was designed to be a fractal structure by mimicking cranefly wings and incorporating cross-veins and discal cell. Standard technologies of Microelectromechanical Systems （MEMS） were employed to materialize the design using the selected material. One SU-8 wing sample, light and stiffenough to be comparable to fresh cranefly wings, was presented. The as-prepared SU-8 wings are faithful to real wings not only in weight and vein pattern, but also in flexural stiffness and mass distribution. Thus our method renders possible mimickine with good lidelity of natural wings with complex geometry and morphology.
文摘Usually a buffer layer of cadmium sulphide is used in high efficiency solar cells based on Cu(In,Ga)Se2(CIGS). Because of cadmium toxicity, many in-vestigations have been conducted to use Cd-free buffer layers. Our work focuses on this type of CIGS-based solar cells where CdS is replaced by a ZnS buffer layer. In this contribution, AFORS-HET software is used to simulate n-ZnO: Al/i-ZnO/n-ZnS/p-CIGS/Mo polycrystalline thin-film solar cell where the key parts are p-CIGS absorber layer and n-ZnS buffer layer. The characteristics of these key parts: thickness and Ga-content of the absorber layer, thickness of the buffer layer and doping concentrations of absorber and buffer layers have been investigated to optimize the conversion efficiency. We find a maximum conversion efficiency of 26% with a short-circuit current of 36.9 mA/cm2, an open circuit voltage of 824 mV, and a fill factor of 85.5%.
基金The National Nature Science Foundation of China(Nos.51002090 and 50972078)the Outstanding Young Scientist Research Award Fund of Shandong Province(No.BS2010CL028)were gratefully acknowledged for financial support
文摘The halogenated boron-doped diamond （BDD） surfaces were reacted with sodium azide through a nucle- ophilic substitution reaction. The resulting azide-terminated BDD surfaces were used to trigger the ＂click＂ reaction. Because of the attractive electrochemical properties of ferrocene-containing molecules, such as fast electron transfer rates, reversible redox activities, and favorable redox potentials, we show that ferrocene derivatives can be grafted onto non-oxidized diamond surfaces by ＂click chemistry＂. These redox-active ferrocene-containing layers on a BDD surface, because of their ability to store and release charges reversibly, have the potential to be used as hybrid molecular/semiconductor memory devices.
文摘Orthogonal frequency division multiplexing-interleave division multiple access (OFDM-IDMA) systems may suffer from serious inter-carrier interference (ICI) in time-and frequency-selective (doubly selective) channels. In such case, the conventional OFDM-IDMA detection algorithm for quasi-static channels will result in significantly performance degradation. In this paper, signal detection is investigated for OFDM-IDMA uplink over doubly selective channels. Firstly, the impact of time-varying channels for OFDM-IDMA uplink is analyzed, which leads to the failure of the conventional algorithm. Secondly, a novel iterative detection algorithm is developed based on an integrated interference canceller, which can iteratively estimate and mitigate the ICI as well as multiple access interference (MAI) simultaneously. In addition, an improved detection algorithm is derived for reducing the complexity using an approximation to the mean and variance of the interference. Simulation results indicate that the proposed algorithm can significantly enhance the system performance to the conventional case, and the improved algorithm can strike a balance between performance and complexity.
文摘In this paper, the problem of channel estimation for superposition coded modulation-orthogonal frequency division multiplexing (SCM-OFDM) systems over frequency selective channels is investigated. Assuming that the path delays are known, a new channel estimator based on modified Kalman filter algorithms is introduced for the estimation of the multipath Rayleigh channel complex gains (CG). In the simulation, the mean square error (MSE) and bit-error-rate (BER) performances are given to verify the effectiveness of the Kalman estimation algorithms for SCM-OFDM systems.
文摘WSNs （wireless sensor networks） can be used for railway infrastructure inspection and vehicle health monitoring. SHM （structural health monitoring） systems have a great potential to improve regular operation, security and maintenance routine of structures with estimating the state of its health and detecting the changes that affect its performance. This is vital for the development, upgrading, and expansion of railway networks. The work presented in this paper aims at the possible use of acoustic sensors coupled with ZigBee modules for health monitoring of rails. The detection principle is based on acoustic noise correlation techniques. Experiments have been performed in a rail sample to confirm the validity of acoustic noise correlation techniques in the rail. A wireless communication platform prototype based on the ZigBee/IEEE 802.15.4 technology has been implemented and deployed on a rail sample. Once the signals from the structure are collected, sensor data are transmitted through a ZigBee solution to the processing unit.
文摘Radars and their applications were, for a long time, reserved to national defense, air security or weather service domains. For a few years, with the emergence of new technologies, radar applications have been developed and have become known in the civil domain. In particular, the arrival of UWB—Ultra-Wideband technology allows the design of compact and low-cost radars with multiple fields of application. In this paper, we focus on road applications, such as driving assistance with the objective of increasing safety and reducing accidents. In classical UWB radar systems, Gaussian and monocycle pulses are commonly used. In previous works, original waveforms based on orthogonal functions (Hermite and Gegenbauer) were proposed. These provide a good spatial resolution, suitable for radar detection. Another advantage of these waveforms is their multiple access capability, due to their orthogonality. The aim of the study presented in this article is to compare simulation and experimental results obtained, especially for short-range anticollision radar application, using these waveforms in one part and Gaussian and monocycle pulses in the other part. The originality of this paper relies on the new approach. Indeed, this comparison study using these waveforms has never been done before. Finally, some examples of real experiments in a real road environment with different waveforms are presented and analysed.
文摘In this paper, a transmission system based on OFDM (Orthogonal Frequency Division Multiplexing) technique and channel estimation is proposed. The idea is to enhance the assisted channel estimation without data rate loss. A solution based on frequency diversity is proposed. With the same number of pilots, the global system performances are better for higher mobility speed. The main results will be presented in the case of high mobility context.
文摘Nowadays, because of its wide bandwidth and high communication capability, the optical fiber is more and more used for high data rate transmission of information in railway environments. Conventionally, only one service is sent over the fiber at a time. However, many different services can be simultaneously conveyed in railway stations such as passenger information service, cellular phone, Wi-Fi... The objective of the work proposed in this paper is to demonstrate the potential benefits of transmitting radio signals over fiber in a railway environment. The main idea is to exploit the full capacity of the fiber by transmitting multiple services using the same fiber. Since, different services are operating in different frequency bands; we propose a new multiplexing technique called Mode Group Diversity Multiplexing （MGDM） to ensure the transmission of multiple services using the same fiber, without additional infrastructure. There are numerous advantages of the proposed technique, e.g., faster and reliable data exchange, high resolution video surveillance capability, high data rate information exchange in railway stations. We present, in this paper, the physical characteristics of optical fibers, performance of MGDM multiplexing technique, and the influence of the laser excitation conditions at the entrance of the fiber on the performances of the system.
文摘The deployment of wireless technologies in the radiology field requires development of radiolucent materials allowing wireless communication. In this paper, both the radiolucency (X-rays) and Electro-Magnetic (EM) properties of the conductive polymer poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) are investigated to address wireless applications in the field of the radiology. A model was developed to predict the PEDOT:PSS performance and assess the interest of this material in terms of radiolucency characteristics and Electro Magnetic (EM) radiation efficiency. A PEDOT:PSS antenna operating in the Radio-Frequency Identification (RFID) Ultra High Frequency (UHF) band, was realized to experimentally validate abilities of PEDOT:PSS. These performances are compared with those produced by a similar antenna made of conventional materials such as copper. Experimental results validate the numerical model of the designed structure. This paper demonstrates the potential of polymer materials in the field of x-ray imaging.
文摘In the railway application, in order to establish the communication between wagons, some technologies are proposed such as the ZigBee and HTN (Hybrid Networking Technology). However, these techniques have some limitations such as: the low data rate, non-secured transmission and interferences. The Ultra Wide Band (UWB) technology presents a good alternative and a good candidate for this application. In recent years, UWB communication systems have received significant attention from both the industry and the academia. In February 2002, the Federal Communications Commission (FCC) allocated 7500 MHz of spectrum (from 3.1 GHz to 10.6 GHz) for use by UWB devices. This ruling has helped to create new standardization efforts, like IEEE 802.15.3a, which focus on developing high speed wireless communication systems. The application of the UWB radio technique in the transport is a more recent topic that is thoroughly researched considering several factors including the nature of the transport propagation environment;the use of adequate transmitting/receiving duty cycle (LDC);the number of devices using UWB technology, the types and levels of interferences. Regulation bodies have considered these railway applications. Impulse Radio Ultra Wideband (IR-UWB) systems have been studied for their inherent advantages of coexistence with narrowband systems with high data rate over short distances with sufficiently small amount of transmitted power. The UWB systems are highly susceptible to interference between the coexisting narrowband systems because of very low transmission power. This paper considers the use of the UWB radio technology for railway application. In this paper, we evaluate the communication performance in constrained environment for the railway application.
文摘We investigate the electronic transport in a simple mesoscopic cross structure made of two wires(stubs)grafted at the same point along a quantum waveguide.We show that the structure may exhibit important phenomena such as bound in continuum(BIC)states.These states are transformed into electromagnetically induced transparency(EIT)resonance by detuning slightly the lengths of the stubs.The last phenomenon is used to propose and study a mesoscopic demultiplexer device with an input waveguide and two output waveguides.We give closed-form expressions of the geometrical parameters that allow a selective transfer of a given state in the first waveguide without perturbing the second waveguide.The effect of temperature on the transmission resonances is also examined by using Landauer-Büttiker formula.The analytical results of the dispersion relation and transmission and reflection coefficient are obtained using the Green's function method.
文摘Recent studies using BSIM3 models have suggested that noise depends on the transconductance-to-drain ratio gm/ID of a transistor. However, to the best of our knowledge, no experimental result demonstrating gm/ID dependent noise previously observed in simulation is available in the literature. This paper examines the underlying principles that make it possible to analyze noise using gm/ID based noise analysis. Qualitative discussion of normalized noise is presented along with experimental results from a 130 nm CMOS process. A close examination of the experimental results reveals that the device noise is width independent from 1 Hz to 10 kHz. Moreover, noise increases as gm/ID is reduced. The experiment observation that noise is width independent makes it possible for circuit designers to generate normalized parameters that are used to study noise intuitively and accurately.
文摘In this paper, a biosensor based on photonic crystal fiber (PCF) is proposed and designed using Full-Vectorial Finite Element Method (FVFEM). The proposed PCF sensor consists of three concentric circles surrounding the core. The key optical sensor characteristics such as sensitivity, the field profiles and real part of the refractive index of the proposed PCF structure are investigated by employing the FVFEM. The proposed sensor can be deployed for environmental sensing when the PCF active region is filled with either analytes such as liquids or gas. By careful selection of the design parameters such as the radius of the sensing circle, the diameter of air holes in the core region and hole to hole spacing, Λ, the sensitivity analytes is determined. Our simulation results show that, the electric field distribution is primary localized in the third concentric circle with a radius of 16 μm. Effects of PCF bending on the sensitivity is also studied and reported.
文摘This paper presents a basic block for building large-scale single-electron neural networks. This macro block is completely composed of SET inverter circuits. We present and discuss the basic parts of this device. The full design and simulation results were done using MATLAB and SIMON, which are a single-electron tunnel device and circuit simulator based on a Monte Carlo method. Special measures had to be taken in order to simulate this circuit correctly in SIMON and compare results with those of SPICE simulation done before. Moreover, we study part of the network as a memory cell with the idea of combining the extremely low-power properties of the SET and the compact design.
文摘<span style="font-family:Verdana;">The aim of this work is to analyze the influence of the interfacial MoSe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> layer </span><span style="font-family:Verdana;">on </span><span style="font-family:Verdana;"><span>the performance of a /n-ZnO/i-ZnO/n-Zn(O,S)/p-CIGS/p</span><sup><span>+</span></sup><span>-MoSe</span><sub><span>2</span></sub><span>/Mo/SLG</span></span><span style="font-family:Verdana;"> solar cell. In this investigation, the numerical simulation software AFORS-</span><span style="font-family:Verdana;">HET is used to calculate the electrical characteristics of the cell with and</span><span style="font-family:Verdana;"> without this MoSe</span><span style="font-family:Verdana;"><sub>2</sub></span><span style="font-family:Verdana;"> layer. Different reported experimental works have highlighted the presence of a thin-film MoSe</span><span style="font-family:Verdana;"><sub>2</sub></span><span style="font-family:Verdana;"> layer at the CIGS/Mo contact interface. Under a tunneling effect, this MoSe</span><span style="font-family:Verdana;"><sub>2</sub></span><span style="font-family:Verdana;"> layer transforms the Schottky CIGS/Mo contact nature into a quasi-ohmic one. Owing to a heavily p-doping, the MoSe</span><span style="font-family:Verdana;"><sub>2</sub></span><span style="font-family:Verdana;"> thin layer allows better transport of majority carrier, tunneling them from CIGS to Mo. Moreover, the bandgap of MoSe</span><span style="font-family:Verdana;"><sub>2</sub></span><span style="font-family:Verdana;"> is wider than that of the CIGS absorbing layer, such that an electric field is generated close to the back surface. The presence of this electric field reduces carrier recombination at the interface. Under these conditions, we examined the performance of the cell with and without MoSe</span><span style="font-family:Verdana;"><sub>2</sub></span><span style="font-family:Verdana;"> layer. When the thickness of the CIGS absorber is in the range from 3.5 μm down to 1.5 μm, the efficiency of the cell with a MoSe</span><span style="font-family:Verdana;"><sub>2</sub></span><span style="font-family:Verdana;"> interfacial layer remains almost constant, about 24.6%, while that of the MoSe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">-free solar cell decreases from 24.6% to 23.4%. Besides, a Schottky barrier height larger than 0.45 eV severely affects the fill factor and open circuit voltage of the solar cell with MoSe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> interface layer compared to the MoSe</span><span style="font-family:Verdana;"><sub>2</sub></span><span style="font-family:Verdana;">-free solar cell.</span>
文摘This paper studies a new positioning beacon for railway transport using Ultra Wideband (UWB) radio and Time Reversal (TR) techniques. UWB radio has the potential to offer a good level of performance in terms of localization accuracy. Time Reversal channel pre-filtering facilitates signal detection and also helps increasing the received energy in the targeted area. In this paper, we evaluate the characteristics of TR technique in terms of temporal focusing. The theoretical and simulation results for Power Delay Profile, equivalent channel model and focusing gain of TR-UWB are given. We analyze the contribution of Time Reversal associated with UWB technology to enhance the localization resolution. The IEEE 802.15.3achannel models are used to evaluate the performance of this system. In terms of localization error, the theoretical and simulation results show that TR-UWB technique delivers improved performance over the UWB localization approach.
