A New Multiuser Detector for Synchronous DS/CDMA System

1IntroductionInaCode-DivisionMultiple-Access(CDMA)system,severalindependentusersaccesssimulboeouslyacommonchannelbymodulatingpreassignedsignatUrewaveforms.Inthemobileradiochannels,MultipleAccessinterference(MAI)arises.Therefore,muchattelltionhasbeend...     

Domain decomposition FDTD algorithm for the analysis of a new type of E-plane sectorial horn with aperture field distribution optimization

In this paper, a universal and efficient approach of domain decomposition finite-difference time-domain FDTD (DD-FDTD) is presented for the analysis of a new type of horn antenna-E-plane sectorial horn with field amplitude taper and phase correction in the aperture. The power fed into the horn is redistributed to achieve the optimal field amplitude distribution in the aperture, and meanwhile the field phase is corrected by metal lens. Compared with conventional E-plane sectorial horns, the new horn antenna takes the advantages of low sidelobe level, short physical length and wide flare angle etc. Moreover, the most important property of this horn is the weak coupling with each other when it is used as the element of a phased array antenna. The field analysis of such a horn antenna is an extremely complicated three-dimensional EM boundary value problem. The domain decomposition FDTD method is presented in this paper to break through the drawback. The whole horn is decomposed into several subdomains and the meshes are created in local coordinates. In the iteration procedure of FDTD, the data are exchanged between adjacent subdomains with overlapped meshes. The aperture field distribution, voltage standing-wave ratio and pattern calculated by the DD-FDTD method are in good agreement with the experimental data.     

An Efficient Distributed Control Scheme for Lightpath Establishment in Dynamic WDM Networks

An adaptive hybrid reservation protocol (AHRP) is proposed for the purpose of quickly and efficiently establishing a lightpath in dynamic wavelength routed networks. This protocol uses a special reservation-and-probe (RESV_PROB) packet and extends the signaling to integrate forward reservation and backward reservation into one monolithic process. To decrease the blocking probability that happens in cases where two end nodes associated with a specific link simultaneously reserve the same wavelength, an adaptive wavelength selection policy is specially employed in AHRP. A discrete-event simulation tool based on ns-2 is developed to investigate AHRP's performance, including its blocking probability, average lightpath setup delay, and signaling overhead. AHRP is also compared with existing protocols. Results show that during highly dynamic traffic conditions, AHRP possesses the lowest blocking probability, shorter setup delay, and less signaling overhead.     

Realizing High Thermoelectric Performance in Earth-Abundant Bi2S3 Bulk Materials via Halogen Acid Modulation

Bi₂S₃-based thermoelectric materials without toxic and expensive elements have a high Seebeck coefficient and intrinsic low thermal conductivity. However, Bi₂S₃ suffers from low electrical conductivity, which makes it a less-than-perfect thermoelectric material. In this work, halogen elements F, Cl, and Br from halogen acid are successfully introduced into the Bi₂S₃ lattice using a hydrothermal procedure to efficiently improve the carrier concentration. Compared with the pure sample, the electron concentration of the Bi₂S₃ sample treated with HCl is increased by two orders of magnitude. An optimal power factor of 470 µW m⁻¹ K⁻² for the Bi₂S_2.96Cl_0.04 sample at 673 K is obtained. Density functional theory calculations reveal that an effective delocalized electron conductive network forms after Cl doping, which raises the Fermi level into the conduction bands, thus generating more free electrons and improving the conductivity of the Bi₂S₃-based materials. Ultimately, an excellent ZT of ≈0.8 is achieved at 673 K for the Bi₂S_2.96Cl_0.04 sample, which is one of the highest values reported for a state-of-the-art Bi₂S₃ system. The energy conversion efficiency of the module reaches 2.3% at 673 K with a temperature difference of 373 K. This study offers a new method for enhancing the thermoelectric properties of Bi₂S₃ by adding halogen acid in the hydrothermal process for powder synthesis.     

Multifunctional Superelastic Cellulose Nanofibrils Aerogel by Dual Ice-Templating Assembly

A superelastic aerogel with fast shape recovery performance from large compressive strain is highly desired for numerous applications such as thermal insulation in clothing, high-sensitive sensors, and oil contaminant removal. Fabrication of superelastic cellulose nanofibrils (CNF) aerogels is challenging as the CNF can assemble into non-elastic sheet-like cell walls. Here, a dual ice-templating assembly (DITA) strategy is proposed that can control the assembly of CNF into sub-micrometer fibers by extremely low temperature freezing (–196 °C), which can further assemble into an elastic aerogel with interconnected sub-micron fibers by freezer freezing (−20 °C) and freeze drying. The CNF aerogel from the DITA process demonstrates isotropic superelastic behavior that can recover from over 80% compressive strain along both longitudinal and cross-sectional directions, even in an extremely cold liquid nitrogen environment. The elastic CNF aerogel can be easily modified by chemical vapor deposition of organosilane, demonstrating superhydrophobicity (164° water contact angle), high liquid absorption (489 g g⁻¹ of chloroform absorption capacity), self-cleaning, thermal insulating (0.023 W (mK)⁻¹), and infrared shielding properties. This new DITA strategy provides a facile design of superelastic aerogels from bio-based nanomaterials, and the derived high performance multifunctional elastic aerogel is expected to be useful for a wide-range of applications.     

Synergistic Manipulation of Zn2+ Ion Flux and Nucleation Induction Effect Enabled by 3D Hollow SiO2/TiO2/Carbon Fiber for Long-Lifespan and Dendrite-Free Zn–Metal Composite Anodes

Aqueous rechargeable zinc–metal batteries are a promising candidate for next-generation energy storage devices due to their intrinsic high capacity, low cost, and high safety. However, uncontrollable dendrite formation is a serious problem, resulting in limited lifespan and poor coulombic efficiency of zinc–metal anodes. To address these issues, a 3D porous hollow fiber scaffold with well-dispersed TiO₂, SiO₂, and carbon is used as superzincophilic host materials for zinc anodes. The amorphous TiO₂ and SiO₂ allow for controllable nucleation and deposition of metal Zn inside the porous hollow fiber even at ultrahigh current densities. Furthermore, the as-fabricated interconnected conductive hollow SiO₂ and TiO₂ fiber (HSTF) possess high porosity, high conductivity, and fast ion transport. Meanwhile, the HSTF exhibits remarkable mechanical strength to sustain massive Zn loading during repeated cycles of plating/stripping. The HSTF with interconnected conductive network can build a uniform electric field, redistributing the Zn²⁺ ion flux and resulting in smooth and stable Zn deposition. As a result, in symmetrical cells, the Zn@HSTF electrode delivers a long cycle life of over 2000 cycles at 20 mA cm⁻² with low overpotential (≈160 mV). The excellent cycling lifespan and low polarization are also realized in Zn@HSTF//MnO₂ full cells.     

Interfacial engineering of printable bottom back metal electrodes for full-solution processed flexible organic solar cells

Printing of metal bottom back electrodes of flexible organic solar cells (FOSCs) at low temperature is of great significance to realize the full-solution fabrication technology.However,this has been difficult to achieve because often the interfacial properties of those printed electrodes,including conductivity,roughness,work function,optical and mechanical flexibility,cannot meet the device requirement at the same time.In this work,we fabricate printed Ag and Cu bottom back cathodes by a low-temperature solution technique named polymer-assisted metal deposition (PAMD) on flexible PET substrates.Branched polyethylenimine (PEI) and ZnO thin films are used as the interface modification layers (IMLs) of these cathodes.Detailed experimental studies on the electrical,mechanical,and morphological properties,and simulation study on the optical properties of these IMLs are carried out to understand and optimize the interface of printed cathodes.We demonstrate that the highest power conversion efficiency over 3.0％ can be achieved from a full-solution processed OFSC with the device structure being PAMDAg/PEI/P3HT:PC61BM/PH1000.This device also acquires remarkable stability upon repeating bending tests.     

Fast super-resolution estimation of DOA and DOD in bistatic MIMO Radar with off-grid targets

In this paper, we focus on the problem of joint DOA and DOD estimation in Bistatic MIMO Radar using sparse reconstruction method. In traditional ways, we usually convert the 2D parameter estimation problem into 1D parameter estimation problem by Kronecker product which will enlarge the scale of the parameter estimation problem and bring more computational burden. Furthermore, it requires that the targets must fall on the predefined grids. In this paper, a 2D-off-grid model is built which can solve the grid mismatch problem of 2D parameters estimation. Then in order to solve the joint 2D sparse reconstruction problem directly and efficiently, three kinds of fast joint sparse matrix reconstruction methods are proposed which are Joint-2D-OMP algorithm, Joint-2D-SL0 algorithm and Joint-2D-SOONE algorithm. Simulation results demonstrate that our methods not only can improve the 2D parameter estimation accuracy but also reduce the computational complexity compared with the traditional Kronecker Compressed Sensing method.     

Using mobile phones to enhance computing platform trust

This paper presents a new method to enhance the trust of traditional computing device by using the popular mobile phone. We first propose a formal method to analyze the platform trust establishment process based on trusted computing technology, and the formal results reveal possible attack and suggest potential solutions. Then, we design an improved solution, in which the mobile phone is extended to support three trusted computing functions: using mobile phone as a root of trust instead of Trusted Platform Module, as a local investigator to obtain evidences from the local computing platform, and as a trusted agent to build a secure communication channel with an external entity in the remote attestation applications. Finally, to describe the feasibility and efficiency, a prototype of the trusted mobile phone is implemented and evaluated based on an ARM development board.     

Simultaneous wireless information and power transfer for relay assisted energy harvesting network

The simultaneous wireless information and power transfer in an energy harvesting system is investigated, where a relay is self-sustained by harvesting radio-frequency (RF) energy from the transmitter and multiple user devices are distributed according to a homogeneous Poisson point process. A joint time switching and power splitting protocol for relay-assisted transmission is proposed, in which each time slot is split into two stages. In the first stage, the relay utilizes a portion of received RF signal power for energy harvesting and the remaining power for information processing. In the second stage, information is delivered from the relay to its closest destination node with the harvested energy. The outage probability, network throughput and energy efficiency are derived and analyzed in closed form. On this basis, the optimal power splitting and time switching ratio which maximizes network throughput is obtained. Simulation results are also provided to validate our theoretical analysis.