Joint SIC and power allocation for a multi-user paired UWOC-NOMA system in a turbulence environment.

This paper proposes a staircase joint optimization scheme (SJOS) with alternating diagonal interference cancellation and power allocation in an underwater wireless optical communication system based on nonorthogonal multiple access (UWOC-NOMA) with the multi-user paired. The scheme employs the directional iteration to alternatively optimize the subproblems of the interference cancellation and the power allocation. Furthermore, a one-way sorting algorithm based on the alternating diagonal interference cancellation and power allocation subalgorithm based on the conjugate gradient method are presented to solve the two subproblems, respectively. Simulation results show that the algorithm effectively reduces the average outage probability of the system with fast convergence, even with an increase in the number of paired users.

Modeling and performance analysis of underwater wireless optical absorption, scattering, and turbulence channels employing Monte Carlo-multiple phase screens.

The absorption, scattering, and turbulence effects have a significant impact on the performance of underwater wireless optical communication (UWOC). Therefore, it is crucial to consider seawater's optical parameters comprehensively when designing UWOC systems. So far, most studies on the UWOC channel have separately modeled the absorption and scattering, and turbulence of seawater, and furthermore, the continuous phase perturbations caused by turbulence are neglected to simplify the model when modeling turbulence channels. Hence, this paper simultaneously considers the absorption, scattering, and turbulence effects of seawater and proposes a UWOC channel modeling method that combines Monte Carlo simulation with multiple phase screen approaches. Subsequently, the impacts of different systems and channel conditions on system performance are explored, and simulation results indicate that as the turbidities and turbulence intensities of the seawater increase, the probability density function of received light signal intensity becomes more dispersed. The turbulence introduces an increase in path loss of approximately 5 dB compared to its absence. Furthermore, the channel impulse response (CIR) is obtained, where the turbulence effects cause a 50% decrease in the CIR peak and the noticeable temporal spread.

Disrupted topological organization of the motor execution network in Wilson's disease.

Objective: There are a number of symptoms associated with Wilson's disease (WD), including motor function damage. The neuropathological mechanisms underlying motor impairments in WD are, however, little understood. In this study, we explored changes in the motor execution network topology in WD. Methods: We conducted resting-state functional magnetic resonance imaging (fMRI) on 38 right-handed individuals, including 23 WD patients and 15 healthy controls of the same age. Based on graph theory, a motor execution network was constructed and analyzed. In this study, global, nodal, and edge topological properties of motor execution networks were compared. Results: The global topological organization of the motor execution network in the two groups did not differ significantly across groups. In the cerebellum, WD patients had a higher nodal degree. At the edge level, a cerebello-thalamo-striato-cortical circuit with altered functional connectivity strength in WD patients was observed. Specifically, the strength of the functional connections between the cerebellum and thalamus increased, whereas the cortical-thalamic, cortical-striatum and cortical-cerebellar connections exhibited a decrease in the strength of the functional connection. Conclusion: There is a disruption of the topology of the motor execution network in WD patients, which may be the potential basis for WD motor dysfunction and may provide important insights into neurobiological research related to WD motor dysfunction.

Modeling and performance analysis of oblique underwater optical communication links considering turbulence effects based on seawater depth layering.

Underwater wireless optical communication (UWOC) has been introduced to support emerging high-speed and low latency underwater communication applications. Most of the current studies on UWOC assume that the water temperature and salinity are constant, which can be justified only for horizontal links. In fact, as the temperature and salinity of seawater change with increasing depth, the seawater at different depths is bound to exhibit different optical properties. This implies that for the same link length, the communication system with the transmitter and receiver at different depths, will exhibit different performances. This paper first proposes an oblique optical link model considering turbulence effects, which is based on the layering of temperature and salinity with depth in realistic ocean water. Subsequently, the performance of the optical communication system with vertical and oblique links is analysed by adopting the oceanic power spectrum and seawater data from different ocean areas measured by the global ocean observation buoy, Argo. Our simulation shows that the performance of the underwater optical communication system is worse when the optical transmitter is located at the mixed layer than at the thermocline. When the transmitter is at the thermocline, the communication quality of the system will be worse at environments that temperature and salinity vary more slowly. When the tilt angle of the optical link in the vertical direction is less than 10°, the oblique link can be treated as a vertical link with the same link length.

Characterization and Performance Enhancement of Cement-Based Thermoelectric Materials.

Thermoelectric materials enable the direct conversion of thermal to electrical energy. One application of this is ambient heat energy harvesting where relatively stable temperature gradients existing between the inside and outside of a building could be utilized to produce electricity. Buildings can thus change from energy consumers to energy generators. This could ultimately help reduce the surface temperatures and energy consumption of buildings, especially in urban areas. In this paper, research work carried out on developing and characterizing a cement-based thermoelectric material is presented. Cement-based samples are doped with different metal oxides (Bi2O3 and Fe2O3) to enhance their thermoelectric properties, which are defined through their Seebeck coefficient, electrical conductivity and thermal conductivity. The study also discusses the positive impact of moisture content on the electrical conductivity.

Iterative adaptive frequency-domain equalization based on sliding window strategy over time-varying underwater acoustic channels.

This letter provides a novel iterative adaptive frequency-domain equalization for time-varying underwater acoustic (UWA) channels. The proposed scheme adopts a modified frequency-domain block least mean square algorithm to update the filter weights. A sliding window strategy is developed to deal with the rapid time-varying characteristics of UWA channels. The proposed method enhances the performance through an iterative structure. Experimental results show that the bit error rates of the proposed method can be one order of magnitude lower than those of conventional schemes.

A Multiple-Input Multiple-Output Reservoir Computing System Subject to Optoelectronic Feedbacks and Mutual Coupling.

In this paper, a multiple-input multiple-output reservoir computing (RC) system is proposed, which is composed of multiple nonlinear nodes (Mach-Zehnder modulators) and multiple mutual-coupling loops of optoelectronic delay lines. Each input signal is added into every mutual-coupling loop to implement the simultaneous recognition of multiple route signals, which results in the signal processing speed improving and the number of routes increasing. As an example, the four-route input and four-route output RC is simultaneously realized by numerical simulations. The results show that this type of RC system can successfully recognize the four-route optical packet headers with 3-bit, 8-bit, 16-bit, and 32-bit, and four-route independent digital speeches. When the white noise is added to the signals such that the signal-to-noise ratio (SNR) of the optical packet headers and the digital speeches are 35 dB and 20 dB respectively, the normalized root mean square errors (NRMSEs) of the signal recognition are all close to 0.1. The word error rates (WERs) of the optical packet header recognition are 0%. The WER of the digital speech recognition is 1.6%. The eight-route input and eight-route output RC is also numerically simulated. The recognition of the eight-route 3-bit optical packet headers is implemented. The parallel processing of multiple-route signals and the high recognition accuracy are implemented by this proposed system.

Efficient optoelectronic reservoir computing with three-route input based on optical delay lines.

In the reservoir computing (RC) system based on delay line structure, the dynamical reservoir has short-term memory capability and can map instantaneous time signals to a high-dimensional space, so that it can effectively classify and recognize complicated time signals. A new RC system is proposed in this paper, where three-way signals are simultaneously input into the dynamical reservoir, and simultaneously processed and classified. Therefore, the information processing speed of the RC system is promoted manyfold. The reservoir is composed of a semiconductor laser and two optical feedback loops, in which two input signals are injected into two optical feedback loops, and another input signal is added to the driving current of the semiconductor laser. The computation efficiency of the RC system is validated by two tasks of the optical packet header recognition and digital speech recognition. By optimizing the parameters, the multi-input RC system can simultaneously recognize three-way 3-bit, 8-bit, 16-bit, and 32-bit optical packet headers with the optimal word error rate (WER) of 0%, and recognize three-way digital speech signals with the optimal WER of 0.2%. It is proven that this multi-input system outperforms the single-inputting RC system based on delay line structure.

Flexible TWDM-RoF system with good dispersion tolerance for downlink and uplink based on additional SCS.

A high-efficiency full-duplex radio-over-fiber (RoF) system incorporating time- and wavelength-division multiplexing technology is proposed in this paper, which is more flexible for the wavelength assignment based on an additional subcentral station (SCS). The periodic power fading effect resulting from a radio frequency signal transmitted over an optical fiber is effectively eliminated for the downlink and uplink. Colorless base stations are achieved by a centralized allocation strategy of upstream light sources. At the SCS, an optical cross-connect unit is employed to enhance the utilization of light sources and the flexibility of the proposed RoF system. Simultaneously, the requirements of high-bandwidth modulators and photodetectors are significantly reduced with a centralized optical carrier suppressed modulation and an all-optical frequency downconversion at the SCS. On the basis of the additional SCS, a 26 GHz full-duplex experiment system is demonstrated, and two 1.25 Gbps baseband data signals for downlink and uplink are successfully transmitted over a 40 km standard single-mode fiber.

Experimental demonstration of polarization-division multiplexing of chaotic laser secure communications.

Optical polarization-division multiplexing (PDM) can double the capacity of a communication system. In this paper, PDM between a conventional fiber-optic channel and a chaos-encrypted channel, and between two chaos-encrypted channels, is proposed and experimentally investigated. The bit rate for each channel is 1.25 Gb/s, while the transmission in the standard single-mode fiber can be up to 22.54 km. The effect of the mutual power leakages on the receiver quality is experimentally explored, which is induced by the variation in polarization direction during the propagating process. In addition, the effect of optical launched power at the transmitter side on the Q-factor is tested and analyzed.

Long-haul dense wavelength division multiplexing between a chaotic optical secure channel and a conventional fiber-optic channel.

The purpose of this paper is to numerically investigate dense wavelength division multiplexing (DWDM) transmission between a chaotic optical secure channel and a conventional fiber-optic channel. A 2.5 Gbits/s secure message masked by the chaotic optical secure channel and a 10 Gbits/s message sequence carried by the conventional fiber-optic channel can be realized simultaneously when the channel spacing is 0.8 nm. The results show that the Q-factors of the recovered messages can be increased significantly when the launched optical power is reduced appropriately. The deterioration of the quality of communication caused by fiber dispersion can be compensated noticeably on the condition that the symmetrical dispersion compensation scheme is adopted. In addition, the secure message is masked by chaos shift keying in the chaotic optical secure channel. The multiplexing distance between the chaotic optical secure channel and the conventional fiber-optic channel is up to 500 km.

Synthesis, characterization, interaction with DNA and cytotoxicity in vitro of dinuclear Pd(II) and Pt(II) complexes dibridged by 2,2'-azanediyldibenzoic acid.

The dinuclear complexes [Pd(2)(L)(2)(bipy)(2)] (1), [Pd(2)(L)(2)(phen)(2)] (2), [Pt(2)(L)(2)(bipy)(2)] (3) and [Pt(2)(L)(2)(phen)(2)] (4), where bipy=2,2'-bipyridine, phen=1,10-phenanthroline and L=2,2'-azanediyldibenzoic dianion) dibridged by H(2)L ligands have been synthesized and characterized. The binding of the complexes with fish sperm DNA (FS-DNA) were investigated by fluorescence spectroscopy. The results indicate that the four complexes bound to DNA with different binding affinity, in the order complex 4>complex 3>complex 2>complex 1, and the complex 3 binds to DNA in both coordination and intercalative mode. Gel electrophoresis assay demonstrates the ability of the complexes to cleave the pBR 322 plasmid DNA. The cytotoxic activity of the complexes was tested against four different cancer cell lines. The four complexes exhibited cytotoxic specificity and significant cancer cell inhibitory rate.

A novel binuclear palladium complex with benzothiazole-2-thiolate: synthesis, crystal structure and interaction with DNA.

The novel Pd(II) complex, [Pd(2)(micro-bzta)(4)].1.5DMSO (where bzta=benzothiazole-2-thiolate) has been synthesized and structurally characterized by element analysis, IR and single-crystal X-ray diffractometry. In the binuclear complex, two palladium(II) are bridged by four deprotonated benzothiazole-2-thialate in a head to tail disposition and the distance of the two Pd(II) is 2.747 A. Three-dimensional structure of the complex was constructed though S...S (3.339 A) weak interaction and pi...pi stack. The binding of the title complex with fish sperm DNA (FS-DNA) has been investigated by absorption and fluorescence spectra. The results indicate that the complex bind to FS-DNA in an intercalative mode and the intrinsic binding constant K of the title complex with FS-DNA is about 1.2 x 10(4)M(-1). Gel electrophoresis assay demonstrates the ability of the complex to cleave the pUC19 plasmid DNA.