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It has been found that, as a main mechanism for diabetes, insulin resistance may have appeared more than a decade before the onset of diabetes. Therefore, early detection of insulin resistance has vital significance for the early prevention, diagnosis, and treatment of diabetes. The content of intramyocellular lipid (IMCL) in human calf muscle has close and complex relationship with insulin resistance and metabolic disorders and, therefore, is associated with type 2 diabetes mellitus and even a variety of mental diseases. However, the current “gold standard” for IMCL measurement is the invasive biopsy technology, which is not suitable for large-scale basic research and long-term clinical applications. IMCL measurement technology based on proton magnetic resonance spectroscopy and spectroscopic imaging (1H MRSI) provides a radiation-free, non-invasive, and high-precision detection method. More than this, 1H MRSI has been expected to clarify the relationship between IMCL content and insulin resistance, as well as the relationship between insulin resistance and type 2 diabetes mellitus, and has the potential to be applied in clinical practice. This paper describes and summarizes the technical development of 1H MRSI-based IMCL content measurement. It also points out the challenges and the latest solutions of this technique from the aspects of physiological and structural characteristics of calves, muscle fiber direction, the bulk fat distribution, and the demand for precise quantification of IMCL content. In addition to reviewing the latest technical solutions to these problems, we particularly discuss the combination of 1H MRSI with some new technologies such as multi-mode magnetic resonance imaging (MRI) and magnetic resonance fingerprinting spectroscopy (MRFS), which will synergically provide more diversified, multi-dimensional and multi-scale measurement method for high-precision measurement of IMCL.

In recent years, the advantages of wireless communication systems assisted by intelligent reflecting surface (IRS) have attracted great attention in the field of mobile communication. However, due to IRS is a passive device with a large number of reflecting array sources, channel estimation (CE) is somewhat challenging. To solve this problem, this paper designs a CE scheme for large IRS-assisted multi-user wireless communication systems. The main idea is to reduce training overhead for CE by exploiting the spatial correlation of IRS channels and the correlation between users’ channels. The simulation results show that compared with the traditional CE scheme, proposed CE scheme requires fewer pilot symbols. And when users send pilot symbols of the same length, the mean square error (MSE) is smaller.

Given the vulnerability of deep neural network to adversarial attacks, the application of deep learning in the wireless physical layer arouses comprehensive security concerns. In this paper, we consider an autoencoder-based communication system with a full-duplex (FD) legitimate receiver and an external eavesdropper. It is assumed that the system is trained from end-to-end based on the concepts of autoencoder. The FD legitimate receiver transmits a well-designed adversary perturbation signal to jam the eavesdropper while receiving information simultaneously. To defend the self-perturbation from the loop-back channel, the legitimate receiver is re-trained with the adversarial training method. The simulation results show that with the scheme proposed in this paper, the block-error-rate (BLER) of the legitimate receiver almost remains unaffected while the BLER of the eavesdropper is increased by orders of magnitude. This ensures reliable and secure transmission between the transmitter and the legitimate receiver.

By adopting a GaAs based semiconductor saturable absorber mirror (SESAM), we have demonstrated a ~3.5 μm passively Q-switched Er3+:ZBLAN fiber laser. The recorded highest repetition rate is 58.71 kHz with a pulse width of 2.4 μs and pulse energy of ~1 pJ. The results prove that the GaAs based SESAM has the capacity to extend the operation wavelength to midinfrared region beyond 3.0 μm.

In this paper, we consider simultaneous wireless information and power transfer (SWIPT) in a multiple-input-single-output (MISO) channel with a full-duplex (FD) receiver and an energy-harvesting (EH) receiver which is a potential eavesdropper, where the receivers adopt the power splitting approach to decode information and harvest energy simultaneously. The FD receiver decodes the information that should be kept secret from the EH receiver and sends jamming signals to degrade the eavesdropper simultaneously using the energy it harvests from the source. Taking into account the eavesdropper channel uncertainties, we attempt to maximize the worst-case secrecy rate (WCSR) at the receiver by jointly optimizing the information beamforming and energy covariance at the transmitter and the artificial noise (AN) covariance at the FD receiver, subject to the power constraint at the transmitter and the minimum energy required at the EH receiver. In order to solve this non-convex optimization problem, semidefinite relaxation (SDR) approach and extended S-procedure are explored to convert the original non-convex optimization problem to a convex one which can be solved efficiently. Numerical results are given to show the superiority of our proposed scheme.

In this paper, we study a multiuser wireless powered communication system, where an energy-constrained full-duplex information transmitter (IT), powered by wireless energy from a dedicated energy transmitter (ET), intends to send confidential information to the information receiver (IR) in the presence of multiple idle users that could be the potential eavesdroppers. In the practical scenario of imperfect channel state information and assuming that the idle users need to harvest energy from the ET, we aim to maximize the worst-case secrecy rate at the IR by jointly optimizing the transmit covariance matrix at the ET as well as the information beamforming and artificial noise covariance at the IT, subject to their individual transmit power constraints and the minimum required power transferred to the idle users. We employ the semidefinite relaxation (SDR) and extended S -procedure approaches to transform the original nonconvex optimization problem into convex problem, which can be efficiently solved by solving a sequence of semidefinite programs. Furthermore, we show that the SDR is tight since there always exists a rank-one optimal solution. For performance comparison, two heuristic schemes for ease of implementation are also developed. Numerical results are presented to show the effectiveness of our proposed schemes.

In this paper, we study a simultaneous wireless information and power transfer (SWIPT) system aided by the intelligent reflecting surface (IRS) technology, where an AP transmits confidential information to the legitimate information receiver (IR) in the presence of an energy harvesting (EH) receiver that could be a potential eavesdropper. We aim to maximize the secrecy rate at the legitimate IR by jointly optimizing the information beamforming vector and the energy transfer beamforming vector at the access point (AP), and the phase shift matrix at the IRS, subject to the minimum harvested power required by the EH receiver. The semi-definite relaxation (SDR) approach and the alternating optimization (AO) method are proposed to convert the original non-convex optimization problem to a series of semi-definite programs (SDPs), which are solved iteratively. Numerical results show that the achievable secrecy rate of the proposed IRS-assisted SWIPT system is higher than that of the SWIPT system without the assistance of the IRS.

Accurate load forecasting guarantees the stable and economic operation of power systems. With the increasing integration of distributed generations and electrical vehicles, the variability and randomness characteristics of individual loads and the distributed generation has increased the complexity of power loads in power systems. Hence, accurate and robust load forecasting results are becoming increasingly important in modern power systems. The paper presents a multi-layer stacked bidirectional long short-term memory (LSTM)-based short-term load forecasting framework, the method includes neural network architecture, model training, and bootstrapping. In the proposed method, reverse computing is combined with forward computing, and a feedback calculation mechanism is designed to solve the coupling of before and after time-series information of the power load. In order to improve the convergence of the algorithm, deep learning training is introduced to mine the correlation between historical loads, and the multi-layer stacked style of the network is established to manage the power load information. Finally, actual data are applied to test the proposed method, and a comparison of the results of the proposed method with different methods shows that the proposed method can extract dynamic features from the data as well as make accurate predictions, and the availability of the proposed method is verified with real operational data.

In this letter, we study a novel multi-antenna wireless powered communication (WPC) system consisting of an energy source (ES), a full-duplex self-energy recycling information source (IS), an information receiver (IR), and an energy receiver (ER) (potential eavesdropper). The energy-constrained IS, powered by ES, sends the confidential information to IR over the wiretap channel. Our goal is to maximize the secrecy rate for IR by jointly optimizing the energy and information beamforming vectors, under the constraints of the transmit power at ES and IS and the harvested energy at ER. To solve the formulated non-convex problem, a partial Lagrange dual method coupled with two-stage optimization method is proposed, which derives the optimal solution in semi-closed form. Numerical results show the superiority of our proposed design compared with the existing schemes.

In this letter, a transmit power control architecture based on the recurrent neural network (RNN) is proposed to solve the power allocation problem for the interference channel to maximize the weighted sum-rate. Compared with the conventional power control schemes, such as weighted minimization mean squared error (WMMSE), which require a considerable number of computations, the RNN-based scheme not only requires much lower computational complexity, but also can well learn and characterize inter-user relationship in the interference channel. The simulation results show that the proposed scheme achieves the sum-rate close to the WMMSE-based scheme with much lower complexity and obtains higher sum-rate than the deep neural network (DNN)-based scheme with much less model parameters.

Breathing solitons, as localized wave packets with a periodic evolution in amplitude and duration, are able to model extreme wave events in complex nonlinear dispersive systems. We have numerically studied the formation and manipulation of graded-index breathing solitons embedded in nonlinear multimode fibers based on a single nonlinear Schrödinger equation that includes the spatial self-imaging effect through a periodically varying nonlinear parameter. Through changing specific parameters of the input optical field, we can manipulate the period and depth of graded-index breathing soliton dynamics under different relative strengths between the dispersion length and the self-imaging period of the multimode fiber. Our study can explicitly derive a robust mechanism to control the behavior of the breathing localized structure directly and contribute to a better understanding of the much more complex nonlinear graded-index soliton dynamics in multimode fibers.

Ad click prediction is a task to estimate the click-through rate(CTR) in sponsored ads, the accuracy of which impacts user search experience and businesses' revenue. This challenging problem plays a key role in online advertising system and has to deal with several hard issues. State-of-the-art sponsored search systems generally formulate it as a supervised classification problem and employ machine learning approaches to predict the CTR per ad. However, the large-scale number of data leads to memory busy when training model on a single machine. Constantly, data scientists sample the huge data to scale down the calculating time which may circumvent the fitting result. In this paper, we propose a embedded model named XG-FwFMs which use less parameters calculating and prevent the model from over-fitting. Experimental results on real advertising data sets show that this approach has better prediction accuracy, parameter sensitivity and effectiveness than traditional nonlinear models.

The intelligent reflecting surface (IRS), which consists of a large number of reflecting units, can adjust the phase shifts of its reflecting units to strengthen the desired signal and/or suppress the undesired signal. In this paper, we consider an IRS-assisted wireless surveillance system where an IRS is deployed to assist the legal surveillance receiver E to monitor the information transmission of the suspicious link from AP to the suspicious receiver B. Two communication scenarios assuming whether the suspicious link is aware of the existence of the monitor are considered. The optimization problem under the constraint that the achievable rate at the monitor E is larger than that at the suspicious receiver B is proposed to jointly optimize the beamforming vector at the AP and the phase shift matrix at the IRS to maximize the achievable eavesdropping rate. To solve this non-convex problem, we introduce the semi-definite relaxation (SDR) approach and the alternating optimization (AO) method to convert the non-convex optimization problem to a series of semi-definite programs (SDPs) and solve the SDPs iteratively. Simulation results show that the assistance of IRS can greatly improve the performance of the surveillance, and achieves significant advantages over the traditional relay-assisted wireless surveillance system.

We have investigated the propagation characteristics of anisotropic a-axis hollow lithium niobate nanowire based on a three-layer-dielectric circular waveguide structure by exactly solving Maxwell's equations. The modal characteristics, waveguide dispersion, and nonlinear parameters of the hollow nanowire have been numerically investigated. The numerical results show that the lithium niobate hollow nanowires have some excellent and unique properties, such as the enhanced evanescent field, large dispersion, and high nonlinearity, which are favorable for nonlinear optics applications, such as supercontinuum generation. The results may make inroad toward the miniaturized high-performance linear or nonlinear photonic devices.

We propose a manipulation approach to vary the wave speed, as well as the grayness, of dark solitons under the optical event horizon arising from the interaction between a dark soliton and a probe wave. To the best of our knowledge, the optical event horizon effect is demonstrated for the first time to be capable of inducing a reversible conversion between a black soliton and a gray one. This reversible soliton transformation and control process originates from the intrinsic competition between the probe-induced nonlinear phase shift and the internal phase of the dark soliton. In a cascaded system consisting of two optical event horizons, we also observe the new optical soliton tunneling phenomena where a dark soliton can be reset longitudinally purposely. The results may find applications in information cloaking such as effectively hiding the presence of intermediate fiber section to the receiver.

We demonstrate that the optical event horizon can provide an effective technique to actively control the propagation properties of a dark soliton with another weak probe wave. Careful power adjustment of the probe wave enables the black soliton converted into a gray one with varying grayness through the nonlinear interaction, corresponding to a nearly adiabatic variation of the soliton’s speed. The sign of the phase angle for the newly formed gray soliton at optical event horizon is significantly dependent on the frequency of the launched probe wave. Linear-stability analysis of dark solitons under the perturbation of a weak probe wave is performed to clarify the intrinsic mechanism of the nonlinear interaction. The probe wave manipulated collisional dynamics between both dark solitons are investigated as an analogue of the combined white-hole and black-hole horizons which provides some insights into exploring the transition between integrable and non-integrable systems.

In this paper, we exploit the potential benefits of machine learning in enhancing physical layer security in cooperative wireless networks. We focus on the case where multiple relays adopt amplify-and-forward (AF) relaying to forward information from the source to the destination. It is assumed that the global channel state information (CSI) of the legitimate links and wiretap links is available to the source. The optimal relay is selected to improve physical layer security against eavesdropping. By modeling the problem of the relay selection as a multi-class classification problem, a neural network (NN) based scheme is proposed to select the optimal relay which guarantees the perfect secrecy performance of the relay cooperative communication system. Compared with the conventional relay selection scheme, the simulation results show that our proposed scheme not only achieves almost the same secrecy performance, but also has advantage of relatively small feedback overhead. The work presented here provides insights into the new design of relay selection based on machine learning.

In this paper, we illustrate how the periodically modulated nonlinear parameter induced by the spatial beam oscillation can be used to generate broadband resonant radiations, through a train of dark pulses in normally dispersive graded-index multimode fibers under the efficient quasi-phase-matching schemes. More precisely, we demonstrate that two co-propagating waves with equal intensities and certain temporal delays can induce the formation of a train of dark solitons, with each emitting multiple resonant radiation lines, which can possibly form multiple radiation continuums based on vast amount of excited dark solitons. The nonlinear-interaction-aided excitation of dark pulses and their radiations appear to occur through a deterministic pathway, in sharp contrast to the situation for bright pulses in the anomalous dispersion region. The quasi-phase-matching condition via periodic oscillation of spatial beam in the normal-dispersion regime adds a unique dimension to the physical design of multimode waveguides, allowing the spectrum to be engineered for specific applications.

In this paper, we consider a secrecy wireless powered communication network, where an information source (IS) transmits message to a legitimate information receiver (IR) with the energy it harvests from the energy source (ES) and a full-duplex (FD) active eavesdropper (AE) performs eavesdropping and jamming simultaneously with the energy it harvests from the ES. With a goal to maximize the achievable secrecy rate, we jointly optimize the energy beamforming and the artificial noise (AN) beamforming at the ES, the information beamforming at the IS and the energy transfer time at the ES. Numerical results are given to show the superiority of our proposed scheme.

The evolution of the ring Airy Gaussian beams with a modulated vortex in free space is numerically investigated. Compared with the unmodulated vortex, the unique property is that the beam spots first break up, and then gather. The evolution of the beams is influenced by the parameters of the vortex modulation, and the splitting phenomenon gets enhanced with multiple rings becoming light spots if the modulation depth increases. The symmetric branch pattern of the beam spots gets changed when the number of phase folds increases, and the initial modulation phase only impacts the angle of the beam spots. Moreover, a large distribution factor correlates to a hollow Gaussian vortex shape and weakens the splitting and gathering trend. By changing the initial parameters of the vortex modulation and the distribution factor, the peak intensity is greatly affected. In addition, the energy flow and the angular momentum are elucidated with the beam evolution features being confirmed.

In this paper, we consider a simultaneous wireless information and power transfer (SWIPT) system with a full-duplex (FD) receiver and an energy-harvesting (EH) eavesdropper. The FD receiver decodes the information that should be kept secret from the EH eavesdropper and sends jamming signals to degrade the eavesdropper simultaneously using the energy it harvests from the source. An optimization problem is formulated to maximize the worst-case secrecy rate taking into account the eavesdropper channel uncertainties. A SDR-based method is proposed to solve this problem. Numerical results are given to show the superiority of our proposed scheme.

To ensure the quality monitoring of a thin film transistor (TFT) - Liquid Crystal Display (LCD) panel and detect the defective products in the whole production process, this paper presents a pattern generation system for functionality test of TFT-LCD panels, which is composed of a PC-based graphic user interface (GUI) and a test signal generator. PC is mainly used to provide the GUI, which allows users to edit timing and patterns required by multiple functionality tests. Then, the edited timing and patterns are downloaded to the test signal generator in the form of test files. After downloading the test file, the test signal generator can implement the generation of LVDS signal independently out of PC. Finally, using the LVDS interface, the test signal generator can be connected to the TFT-LCD in the production line to perform the functionality test.

The absence of Raman and unique pressure-tunable dispersion is the characteristic feature of gas-filled photonic crystal fiber (PCF), and its zero dispersion points can be extended to the near-infrared by increasing gas pressure. The generation of dispersive wave (DW) in the normal group velocity dispersion (GVD) region of PCF is investigated. It is demonstrated that considering the self-steepening (SS) and introducing the chirp of the initial input pulse are two suitable means to control the DW generation. The SS enhances the relative average intensity of blue-shift DW while weakening that of red-shift DW. The required propagation distance of DW emission is markedly varied by introducing the frequency chirp. Manipulating DW generation in gas-filled PCF by the combined effects of either SS or chirp and three-order dispersion (TOD) provides a method for a concentrated transfer of energy into the targeted wavelengths.

Space-time duality and time-to-frequency mapping bring a lot of analogies. We apply the concept of optical reflection and refraction, for the first time, to the spectral domain. The optical reflection and refraction phenomena are addressed in the spectral domain across a dispersion discontinuity boundary, where a weak probe pulse is co-propagating with a strong perpendicularly polarized parabolic pulse. The total internal reflection behavior in the spectral domain is analytically determined. Our results can complete the theory of the optical wave confinement in the spatial, temporal and spectral domains, which can be a guide for spectrum engineering and characterization.

In this paper, an adaptive cooperation scheme is presented for bidirectional communication between two nodes, where the non-relay direct transmission and the one- or two-way relaying diversity transmission are jointly considered. The results show that the proposed scheme obtains lower outage probability than the conventional bidirectional communication methods.

Based on the extended Huygens-Fresnel principle, we have derived the analytical expression of the average intensity of optical coherence lattices (OCLs) in oceanic turbulence with anisotropy, and then the beam quality parameters including the Strehl ratio (SR) and the power-in-the-bucket (PIB) are obtained. One can find that the OCLs will eventually evolve into Gaussian shape with the periodicity reciprocity gradually breaking down when propagating through the anisotropic ocean water, and that the trend of evolving into Gaussian can be accelerated for increasing the ratio of temperature and salinity contributions to the refractive index spectrum ω, the lattice constant a and the rate of dissipation of mean square temperature χT or decreasing the anisotropic factor ξ and the rate of dissipation of turbulent kinetic energy per unit mass of fluid ε. Further, the SR and PIB in the target plane under the effects of oceanic parameters are discussed in detail, and the SR and PIB can be increased for the larger ξ and ε or the smaller χT and ω, namely, the beam quality becomes better. Our results can find potential application in the future optical communication system in an oceanic environment.

The dynamics of Airy beams modeled by the fractional Schrodinger equation (FSE) with the potential barrier are numerically investigated. Adjusting the Levy index provides a convenient way to control the diffraction of Airy beams which presents the non-diffraction and splitting property. It has been found that the total reflection of beams occurs when the depth of the single potential barrier exceeds the threshold, and that the number of reflected waves is influenced by the Levy index and the location of potential barrier. However, the periodic self-imaging phenomenon of Airy beams is shown under a symmetric potential barrier when the Levy index is equal to one, and the self-imaging period of the asymmetric Airy beams is analytically demonstrated and is as twice as that of symmetric Gaussian beams, moreover, the chaoticon of light field is formed during propagation as the Levy index increases. All the properties of Airy beams modeled by FSE confirm the potential application in optical manipulation.

We show that the group-velocity-led optical event horizon (OEH) in optical fibers provides a convenient way to actively control the propagation property of higher-order solitons by a comparatively weak dispersive wave (DW) pulse. It has been found numerically that clean soliton breakup, a process by which a second-order soliton completely splits into a pair of constituent solitons with vastly different power proportions after interacting with the weak DW pulse, will occur while external DWs become polychromatic. The temporal separation between both constituent solitons can be controlled by adjusting the power of the external DW. The more energetic main soliton is advanced/trailed in time depending on the selected frequency of input DW pulse. We have developed an analytic formalism describing the external acting-force (AF) perturbation. These results provide a fundamental explanation and physical scaling of optical pulse evolution in optical fibers and can find applications in improved supercontinuum sources.

In underwater acoustic networks (UANs), the “hidden terminal” and “exposed terminal” problems greatly restrict their capacity due to the characteristics of the underwater acoustic channel, such as very limited bandwidth, time-varying multipath propagation, and large propagation delay. However, it is still possible to achieve reasonably good performance if we smartly leverage large propagation delay. In this paper, we propose a multi-channel MAC protocol for UANs (called UA-MCMA). UA-MCMA divides the available channel into a control channel and several traffic channels, each of which will be uniquely used by one node within its single-hop scope. Unlike conventional handshaking-based schemes that tend to suffer from low throughput and high transmission delay in UANs due to the long propagation delay, the UA-MCMA combats this problem by allowing a sender to start transmitting data packets on its traffic channel periodically after it has sent a request-to-send frame on the control channel, without waiting for the clear-to-send frame from the receiver. By doing so, some data can be transmitted during the channel reservation period, which notably improves the performance of UANs. Simulation results confirm its good performance in terms of throughput and average packet delay.

Converter valve possesses the function of AC-DC voltage conversion and power transmission. It is an important device in the valve hall of UHVDC converter station. Since the corona discharge has a serious impact on the safe and stable operation of converter valve, it is necessary to analyze its surface electric field (E-field) distribution. In this paper, the structure characteristics of three typical double valve designs have been analyzed, which were respectively used in three high voltage (400-800kV) valve halls of one ±800kV UHVDC transmission project in China. Based on the project drawings, the equivalent model of each type of double valve with shielding structure was built with three-dimensional (3D) finite-element method (FEM) software ANSYS. Considering the interaction of double valves in actual valve hall, three double valve FEM models of same type in one hall, which formed the upper 6-pulse bridge in the 12-pulse converter unit, were built for the analysis of E-field distribution. Due to the hybrid AC-DC operating voltage, the transient E-field analysis with discrete loading voltage waveforms was adopted in these models. After calculation, the E-field distribution characteristic of different double valve types were summarized and compared under the normal operating condition. The results showed that the surface E-field strength on the shielding structure of all the double valves was lower than the critical value of corona inception and could meet the project requirements. This research could provide valuable references for shielding structure design and optimization of converter valve in the UHVDC transmission project.

GIS disconnector contains various special components, such as moving electrode, insulated pull rod, basin-type insulator, which are sensitive to the electric field. Due to the mechanical movement, which is realized when the conversion between open and closed states of circuit, it's possible to produce some metal, nonmetal particles, or mechanical damage on components, etc. This paper mainly focuses on the impacts of foreign materials with diverse factors which can affect the electric field distribution in GIS disconnector. First, with a common 550kV GIS disconnector structure and its operating condition parameters, the typical distribution of potential and electric field have been calculated. Then, based on further calculation, comparisons and analysis of defects have been done, including surface defects and foreign material with different size, properties, and locations. Influence on electric field by internal defects in the insulated pull rod, was also concerned. At last, the correlation between defects and the electric field distribution have been systematically analyzed. The research achievements will provide references and guidance for structural design, manufacturing, and field assembly of GIS disconnector, to help improve the safety and long-term stability of the equipment.

In this paper, we consider a state-dependent relay channel with orthogonal components where the message must be kept secret from the relay node and the channel state information is known non-causally at the source node. A lower bound on the secrecy capacity is derived by the state description scheme proposed in this paper. The source node transmits a description of the channel state information (CSI) to the destination. The message that passes through the relay node is encrypted by a key which is generated from this state description and shared between the source and destination nodes. This scheme enables the relay node to cooperate with the source node to send messages to the destination without getting any information of the message. We show that the achievable secrecy rate by the scheme in this paper is larger than that by the scheme of X. He who showed that the relay is useless in the state-independent untrusted relay channel with orthogonal components.

The divorce between management research and management practice has attracted intensive attention. It means that the findings or theories developed in management research are not used effectively in practices. This paper describes the divorce between management research and management practice, analyzes its causes, and presents the solutions to "upholding heaven and standing on earth" research as well as reform and improvement of academic appraisal system. It is found in related researches that although many scholars undertake and complete various research projects in the field of management, they are seldom granted theoretical research projects directing at practical management issues proposed and funded by enterprises. Some scholars may participate in management consultation projects funded by large enterprises, which, however, seldom involve the field of theoretical research. Meanwhile, few doctoral dissertations funded or entrusted by enterprises to study the practical problems they are faced with cover the field of management research. Besides, under the circumstance that the international trend leans towards empirical researches on management, the management research issues and hypotheses in many doctoral dissertations in mainland China are essentially "common sense" or "hypotheses", which reflects the divorce between management theory and management practice. The relationship between management research and management practice has attracted the attention of many scholars in mainland China.

Broadcast channels with correlated sources are considered from a joint source-channel coding perspective, where each receiver is kept in ignorance of the source intended for the other receiver. This setting can be seen as a generalization of Han- Costa's broadcast channel with correlated sources under addi- tional secrecy constraints on both receivers. General outer and inner bounds for this reliable and secure communication are de- termined. The joint source-channel coding is proved to be optimal for two special cases, including the sources satisfying a certain Markov property sent over semi-deterministic broadcast channels, and arbitrary correlated sources sent over less-noisy broadcast channels.

We have numerically investigated the propagation properties of ring Airy beams modeled by a fractional Schrodinger equation (FSE). Beam splitting is exhibited and clarified from the view of group delay. Compared with the case of the condition in free space, the focal intensity is greatly enhanced and presents a trend from increasing to decreasing with the decrement of the Levy index, while the focal length largely increases; in addition, the parabolic trajectory is distorted with the Bessel pattern gradually disappearing. However, both the focal intensity and its length get decreased due to the absence of the initial phase of ring Airy beams; simultaneously, the size of the focal spot decreases for a larger Levy index. The changes of focusing properties are clearly clarified. Moreover, without initial phase, the ratio of focal intensity under the Levy index to the condition in free space is given to show the faster growth of focal intensity when the Levy index is lower than 1.25; otherwise, the trend gets reversed. The autofocusing properties of ring Airy beams modeled by FSE can find applications in optical trapping and manipulation.

In this paper, a class of state-dependent relay channel with orthogonal channels from the source to the relay and from the source and the relay to the destination is studied. The two orthogonal channels are corrupted by two independent channel states S R and S D, respectively, which are known to both the source and the relay. The lower bounds on the capacity are established for the channel either with non-causal channel state information or with causal channel state information. Further, we show that the lower bound with non-causal channel state information is tight if the receiver output Y is a deterministic function of the relay input X r, the channel state S D, and one of the source inputs X D, i.e., Y = f(X D, X r, S D), and the relay output Y r is restricted to be controlled by only the source input X R and the channel state S R, i.e., the channel from the source to the relay is governed by the conditional probability distribution P Y r | X R , S R . The capacity for this class of semi-deterministic orthogonal relay channel is characterized exactly. The results are then extended to the Gaussian cases, modeling the channel states as additive Gaussian interferences. The capacity is characterized for the channel when the channel state information is known non-causally. However, when the channel state information is known causally, the capacity cannot be characterized in general. In this case, the lower bound on the capacity is established, and the capacity is characterized when the power of the relay is sufficiently large. Some numerical examples of the causal state information case are provided to illustrate the impact of the channel state and the role of the relay in information transmission and in cleaning the channel state.

In this paper, we investigate the one-way relaying assisted secondary user information exchange, i.e., cognitive one-way relaying scheme, and the two-way relaying assisted secondary user information exchange, i.e., cognitive two-way relaying scheme, in cognitive radio networks. The exact closed-form expressions of outage probability for the proposed schemes are derived with imperfect spectrum sensing over Rayleigh fading channels. Considering the effect of the interference from the primary user on secondary data transmissions performance, we further give the closed-form expressions of outage probability floor. Numerical results show that the cognitive two-way relaying scheme outperforms the cognitive one-way relaying scheme in terms of outage probability performance.

The four-terminal relay-eavesdropper channel with orthogonal receive components (i.e. the signals transmitted from the source and relay do not interfere each other) is studied in this paper. As the relay node merely repeats the received noisy signal with the conventional amplify-and-forward (AF) relaying strategy, AF is suboptimal. A piecewise linear AF (PLAF) relaying scheme is utilized to the channel model in this paper. Achievable secrecy rate with PLAF is derived and computed numerically. Numerical examples are given to show the performance improvement of PLAF compared with AF. Simulation results show that PLAF outperforms AF and achieves a higher secrecy rate than decode-and-forward (DF) in some certain cases but without complex encoding and decoding.

In this paper, a class of state-dependent relay channel with orthogonal channels from the source to the relay and from the source and the relay to the destination is studied. The two orthogonal channels are corrupted by common channel state which is known to both the source and the relay non-causally. The lower bound on the capacity for the channel is derived firstly. Then, we show that if the receiver output Y is a deterministic function of the relay input Xr, the channel state S and one of the source inputs XD, i.e. Y = f(Xr, XD, S), the explicit capacity can be characterized.

We have numerically studied the effect of mutual interactions between soliton and dispersive waves and the possibility to create a solitonic well consisting of initial twin-solitons moving away from each other to trap the incident dispersive wave. Different from the case of the solitonic cage formed by the velocity-matched twin-solitons, the intense dispersive wave can break up into small pulses, which are almost completely trapped within the solitonic well. Moreover, the corresponding spectrum of the trapped dispersive wave can be narrowed firstly and then expanded, and a new dispersive wave can be generated as the twin-solitons collision occurred. By adjusting either the peak power or temporal width of incident dispersive wave, both the intensity of the collision-induced dispersive wave and the position where it is generated can be controlled.

The controlling optical frequency in the regime of an optical event horizon by the collision between a soliton and a probe pulse is investigated, and the process by which the probe is converted into the generated pulse (idler) with new optical frequency is reversible. For the two cases in which the probe wave interacts with a bright/dark soliton, a unified analytical formula governing the reversible frequency conversion process is derived that can predict the frequency of the idler very well. This reversible frequency-conversion process is validated by cascaded four-wave mixing (FWM) triggered by a set of quasi-CW fields, strongly suggesting that the process arose from cascaded Bragg scattering. It establishes a link between the nonlinear interactions of a soliton with the probe and FWM of monochromatic quasi-CWs.

The Gaussian orthogonal untrusted relay channel is investigated in this paper. We assume that there is an eavesdropper at the relay node which can access everything that the relay node knows. The source node transmits signals to the relay node and the destination node in channel 1, the relay node transmits signals to destination node in channel 2, channel 1 and channel 2 are orthogonal. The achievable secrecy rate is derived firstly. Under the limit of the total channel resource, the maximum achievable secrecy rate is obtained through optimizing the resource allocation. Of the Gaussian orthogonal untrusted relay channel, there exists a unique optimum bandwidth or power to achieve the maximum secrecy rate and a higher secrecy rate can be achieved using this optimal resource allocation strategy than the maximum resource allocation strategy.

The orthogonal relay-eavesdropper channel is investigated. The source communicates with the relay and the destination in channel 1, the relay communicates with the destination in channel 2, channel 1 and channel 2 are orthogonal with each other. The secrecy rate is derived based on the analysis of parallel relay- eavesdropper channel. Under the limit of the total channel resource, the maximal secrecy rate is obtained through optimizing the resource allocation parameter a. In the Gaussian channel, when eavesdropper listen the signals of channel 1, it is proved that there exists the unique a to reach the maximum secrecy rate and a higher secrecy rate can be achieved using the optimal resource allocation strategy than the equal resource allocation strategy.

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