arXiv subjects

Bin Li

Publications and source records attributed to Bin Li.

At least 685 records · Page 38Linked to original sources

arXiv2016

A Survey of Multi-Objective Optimization in Wireless Sensor Networks: Metrics, Algorithms and Open Problems

Wireless sensor networks (WSNs) have attracted substantial research interest, especially in the context of performing monitoring and surveillance tasks. However, it is challenging to strike compelling trade-offs amongst the various conflicting optimization criteria, such as the network's energy dissipation, packet-loss rate, coverage and lifetime. This paper provides a tutorial and survey of recent research and development efforts addressing this issue by using the technique of multi-objective optimization (MOO). First, we provide an overview of the main optimization objectives used in WSNs. Then, we elaborate on various prevalent approaches conceived for MOO, such as the family of mathematical programming based scalarization methods, the family of heuristics/metaheuristics based optimization algorithms, and a variety of other advanced optimization techniques. Furthermore, we summarize a range of recent studies of MOO in the context of WSNs, which are intended to provide useful guidelines for researchers to understand the referenced literature. Finally, we discuss a range of open problems to be tackled by future research.

cs.NI↗

arXiv2016

Charged Lepton Flavor-violating Transitions in Color Octet Model

We study charged lepton flavor-violating (LFV) transitions in the color octet model that generates neutrino mass and lepton mixing at one loop. By taking into account neutrino oscillation data and assuming octet particles of TeV scale mass, we examine the feasibility to detect these transitions in current and future experiments. We find that for general values of parameters the branching ratios for LFV decays of the Higgs and $Z$ bosons are far below current and even future experimental bounds. For LFV transitions of the muon, the present bounds can be satisfied generally, while future sensitivities could distinguish between the singlet and triplet color-octet fermions. The triplet case could be ruled out by future $μ-e$ conversion in nuclei, and for the singlet case the conversion and the decays $μ\to 3e,~eγ$ play complementary roles in excluding relatively low mass regions of the octet particles.

hep-ph↗

arXiv2016

Hierarchy, dimension, attractor and self-organization -- dynamics of mode-locked fiber lasers

Mode-locked fiber lasers are one of the most important sources of ultra-short pulses. However, A unified description for the rich variety of states and the driving forces behind the complex and diverse nonlinear behavior of mode-locked fiber lasers have yet to be developed. Here we present a comprehensive theoretical framework based upon complexity science, thereby offering a fundamentally new way of thinking about the behavior of mode-locked fiber lasers. This hierarchically structured frame work provide a model with and changeable variable dimensionality resulting in a simple and elegant view, with which numerous complex states can be described systematically. The existence of a set of new mode-locked fiber laser states is proposed for the first time. Moreover, research into the attractors' basins reveals the origin of stochasticity, hysteresis and multistability in these systems. These findings pave the way for dynamics analysis and new system designs of mode-locked fiber lasers. The paradigm will have a wide range of potential applications in diverse research fields.

physics.optics↗

arXiv2016

TMRT Observations of Carbon-chain molecules in Serpens South 1A

We report Shanghai Tian Ma Radio Telescope detections of several long carbon-chain molecules at C and Ku band, including HC3N, HC5N, HC7N, HC9N, C3S, C6H and C8H toward the starless cloud Serpens South 1a. We detected some transitions (HC9N J=13-12 F=12-11 and F=14-13, H13CCCN J=2-1 F=1-0 and F=1-1, HC13CCN J=2-1 F=2-2, F=1-0 and F=1-1, HCC13CN J=2-1 F=1-0 and F=1-1) and resolved some hyperfine components (HC5N J=6-5 F=5-4, H13CCCN J=2-1 F=2-1) for the first time in the interstellar medium. The column densities of these carbon-chain molecules in a range of 10^{12}-10^{13} cm^{-2} are comparable to two carbon-chain molecule rich sources, TMC-1 and Lupus-1A. The abundance ratios are 1.00:(1.11\pm0.15):(1.47\pm0.18) for [H13CCCN]:[HC13CCN]:[HCC13CN]. This result implies that the 13C isotope is also concentrated in the carbon atom adjacent to the nitrogen atom in HC3N in Serpens south 1a, which is similar to TMC-1. The [HC3N]/[H13CCCN] ratio of 78\pm9, the [HC3N]/[HC13CCN] ratio of 70\pm8, and the [HC3N]/[HCC13CN] ratio of 53\pm4 are also comparable to those in TMC-1. In any case, Serpens South 1a proves a testing ground for understanding carbon-chain chemistry.

astro-ph.GA↗

arXiv2016

Origin of the superconductivity of WTe2 under pressure

Tungsten ditelluride (WTe2) has attracted significant attention due to its interesting electronic properties, such as the unsaturated magnetoresistance and superconductivity. Recently, it has been proposed to be a new type of Weyl semimetal, which is distinguished from other transition metal dichalcogenides (TMDs) from a topological prospective. Here, we study the structure of WTe2 under pressure with a crystal structure prediction and ab initio calculations combined with high pressure synchrotron X-ray diffraction and Raman spectroscopy measurements. We find that the ambient orthorhombic structure (Td) transforms into a monoclinic structure (1T') at around 4-5 GPa. As the transition pressure is very close to the critical point in recent high-pressure electrical transport measurements, the emergence of superconductivity in WTe2 under pressure is attributed to the Td-1T' structure phase transition, which associates with a sliding mechanism of the TMD layers and results in a shorter Te-Te interlayer distance compared to the intralayer ones. These results highlight the critical role of the interlayer stacking and chalcogen interactions on the electronic and superconducting properties of multilayered TMDs under hydrostatic strain environments.

cond-mat.mtrl-sci↗

arXiv2015

Single-pulse radio observations of the Galactic Center magnetar PSR J1745-2900

In this paper, we report radio observations of the Galactic Center magnetar PSR J1745-2900 at six epochs between June and October, 2014. These observations were carried out using the new Shanghai Tian Ma Radio Telescope at a frequency of 8.6 GHz. Both the flux density and integrated profile of PSR J1745-2900 show dramatic changes from epoch to epoch showing that the pulsar was in its "erratic" phase. On MJD 56836, the flux density of this magnetar was about 8.7 mJy, which was ten times large than that reported at the time of discovery, enabling a single-pulse analysis. The emission is dominated by narrow "spiky" pulses which follow a log-normal distribution in peak flux density. From 1913 pulses, we detected 53 pulses whose peak flux density is ten times greater than that of the integrated profile. They are concentrated in pulse phase at the peaks of the integrated profile. The pulse widths at the 50% level of these bright pulses was between 0.2 to 0.9 deg, much narrower than that of integrated profile (~12 deg). The observed pulse widths may be limited by interstellar scattering. No clear correlation was found between the widths and peak flux density of these pulses and no evidence was found for subpulse drifting. Relatively strong spiky pulses are also detected in the other five epochs of observation, showing the same properties as that detected in MJD 56836. These strong spiky pulses cannot be classified as "giant" pulses but are more closely related to normal pulse emission.

astro-ph.HE↗

arXiv2015

Low-complexity Non-coherent Signal Detection for Nano-Scale Molecular Communications

Nano-scale molecular communication is a viable way of exchanging information between nano-machines. In this letter, a low-complexity and non-coherent signal detection technique is proposed to mitigate the inter-symbol-interference (ISI) and additive noise. In contrast to existing coherent detection methods of high complexity, the proposed non-coherent signal detector is more practical when the channel conditions are hard to acquire accurately or hidden from the receiver. The proposed scheme employs the concentration difference to detect the ISI corrupted signals and we demonstrate that it can suppress the ISI effectively. The concentration difference is a stable characteristic, irrespective of the diffusion channel conditions. In terms of complexity, by excluding matrix operations or likelihood calculations, the new detection scheme is particularly suitable for nano-scale molecular communication systems with a small energy budget or limited computation resource.

cs.ET↗

arXiv2015

Capacity-Achieving Rateless Polar Codes

A rateless coding scheme transmits incrementally more and more coded bits over an unknown channel until all the information bits are decoded reliably by the receiver. We propose a new rateless coding scheme based on polar codes, and we show that this scheme is capacity-achieving, i.e. its information rate is as good as the best code specifically designed for the unknown channel. Previous rateless coding schemes are designed for specific classes of channels such as AWGN channels, binary erasure channels, etc. but the proposed rateless coding scheme is capacity-achieving for broad classes of channels as long as they are ordered via degradation. Moreover, it inherits the conceptual and computational simplicity of polar codes.

cs.IT↗

arXiv2015

Reduce the Complexity of List Decoding of Polar Codes by Tree-Pruning

Polar codes under cyclic redundancy check aided successive cancellation list (CA-SCL) decoding can outperform the turbo codes and the LDPC codes when code lengths are configured to be several kilobits. In order to reduce the decoding complexity, a novel tree-pruning scheme for the \mbox{SCL/CA-SCL} decoding algorithms is proposed in this paper. In each step of the decoding procedure, the candidate paths with metrics less than a threshold are dropped directly to avoid the unnecessary computations for the path searching on the descendant branches of them. Given a candidate path, an upper bound of the path metric of its descendants is proposed to determined whether the pruning of this candidate path would affect frame error rate (FER) performance. By utilizing this upper bounding technique and introducing a dynamic threshold, the proposed scheme deletes the redundant candidate paths as many as possible while keeping the performance deterioration in a tolerant region, thus it is much more efficient than the existing pruning scheme. With only a negligible loss of FER performance, the computational complexity of the proposed pruned decoding scheme is only about $40\%$ of the standard algorithm in the low signal-to-noise ratio (SNR) region (where the FER under CA-SCL decoding is about $0.1 \sim 0.001$), and it can be very close to that of the successive cancellation (SC) decoder in the moderate and high SNR regions.

cs.IT↗

arXiv2015

Molecular Communications: Channel Model and Physical Layer Techniques

This article examines recent research in molecular communications from a telecommunications system design perspective. In particular, it focuses on channel models and state-of-the-art physical layer techniques. The goal is to provide a foundation for higher layer research and motivation for research and development of functional prototypes. In the first part of the article, we focus on the channel and noise model, comparing molecular and radio-wave pathloss formulae. In the second part, the article examines, equipped with the appropriate channel knowledge, the design of appropriate modulation and error correction coding schemes. The third reviews transmitter and receiver side signal processing methods that suppress inter-symbol-interference. Taken together, the three parts present a series of physical layer techniques that are necessary to producing reliable and practical molecular communications.

cs.ET↗

arXiv2015

A Decision-Aided Parallel SC-List Decoder for Polar Codes

In this paper, we propose a decision-aided scheme for parallel SC-List decoding of polar codes. At the parallel SC-List decoder, each survival path is extended based on multiple information bits, therefore the number of split paths becomes very large and the sorting to find the top L paths becomes very complex. We propose a decision-aided scheme to reduce the number of split paths and thus reduce the sorting complexity.

cs.IT↗

arXiv2015

Multilayer C2N: Effect of Stacking Order and Number of Layers on Bandgap and Its Controlled Electronic Properties by External Electric Field

Successful synthesis of the nitrogenated holey two-dimensional structures C2N (Nat. Commun. 2015, 6, 1-7) using simply wet-chemical reaction offer a cost-effective way to generate other 2D materials with novel optical and electronic properties. Using the few-layer C2N as models, we have performed an ab initio study of electronic properties of layered C2N. Band gaps of this system exhibit monotone decreasing as the number of layers increase. And a direct-gap to indirect-gap transition at the bulk C2N. Besides, when we apply an out-of-plane electric field on few-layer C2N, the band gap of multilayer C2N will be decreased as the electric field increased and a semiconductor-semimetal transition will happen for five-layer C2N under an appropriate electric field, whereas the band gap of monolayer C2N is unchanged under electric field. Owing to their tunable bandgaps in a wide range, layers C2N will have tremendous opportunities to be applied in nanoscale electronic and optoelectronic devices.

cond-mat.mtrl-sci↗

arXiv2015

Molecular Communications with Longitudinal Carrier Waves: Baseband to Passband Modulation

Traditional molecular communications via diffusion (MCvD) systems have used baseband modulation techniques by varying properties of molecular pulses such as the amplitude, the frequency of the transversal wave of the pulse, and the time delay between subsequent pulses. In this letter, we propose and implement passband modulation with molecules that exhibit longitudinal carrier wave properties. This is achieved through the oscillation of the transmitter. Frequency division multiplexing is employed to allow different molecular information streams to co-exist in the same space and time channel, creating an effective bandwidth for MCvD.

cs.ET↗

arXiv2015

Low-latency List Decoding Of Polar Codes With Double Thresholding

For polar codes with short-to-medium code length, list successive cancellation decoding is used to achieve a good error-correcting performance. However, list pruning in the current list decoding is based on the sorting strategy and its timing complexity is high. This results in a long decoding latency for large list size. In this work, aiming at a low-latency list decoding implementation, a double thresholding algorithm is proposed for a fast list pruning. As a result, with a negligible performance degradation, the list pruning delay is greatly reduced. Based on the double thresholding, a low-latency list decoding architecture is proposed and implemented using a UMC 90nm CMOS technology. Synthesis results show that, even for a large list size of 16, the proposed low-latency architecture achieves a decoding throughput of 220 Mbps at a frequency of 641 MHz.

cs.AR↗

arXiv2015

Towards Data-Driven Hierarchical Surgical Skill Analysis

This paper evaluates methods of hierarchical skill analysis developed in aerospace to the problem of surgical skill assessment and modeling. The analysis employs tool motion data of Fundamental of Laparoscopic Skills (FLS) tasks collected from clinicians of various skill levels at three different clinical teaching hospitals in the United States. Outcomes are evaluated based on their ability to provide relevant information about the underlying processes across the entire system hierarchy including control, guidance and planning.

cs.HC↗

arXiv2014

Experimental demonstration of longitudinal beam phase space linearizer in a free-electron laser facility by corrugated structures

Removal of residual linear energy chirp and intrinsic nonlinear energy curvature in the relativistic electron beam from radiofrequency linear accelerator is of paramount importance for efficient lasing of a high-gain free-electron laser. Recently, it was theoretically and experimentally demonstrated that the longitudinal wakefield excited by the electrons itself in the corrugated structure allows for precise control of the electron beam phase space. In this Letter, we report the first utilization of a corrugated structure as beam linearizer in the operation of a seeded free-electron laser driven by a 140 MeV linear accelerator, where a gain of ~10,000 over spontaneous emission was achieved at the second harmonic of the 1047 nm seed laser, and a free-electron laser bandwidth narrowing by about 50% was observed, in good agreement with the theoretical expectations.

physics.acc-ph↗

arXiv2014

First-principles Study of the Interactions of Electron Donor and Acceptor Molecules with Phosphorene

Density functional theory calculations have been carried out to investigate single-layer phosphorene functionalized with two kinds of organic molecules, i.e. an electrophilic molecule tetracyano-p-quinodimethane (TCNQ) as electron acceptor and a nucleophilic molecule tetrathia-fulvalene (TTF) as electron donor. The TCNQ molecule introduces shallow acceptor states in the gap of phosphorene close to the valence band edge (VBE), which makes the doped system a p-type semiconductor. However, when the TTF molecule is adsorbed on the phosphorene, the occupied molecular states introduced into the gap are of deep donor states so that effective n-doping for transport cannot be realized. This disadvantageous situation can be amended by applying an external electric field perpendicular to the phosphorene surface with direction from the phosphorene to the TTF molecule, under which the TTF-introduced donor states move closer to conduction band edge (CBE) of the phosphorene and then the TTF-doped phosphorene system becomes an n-type semiconductor. The effective bipolar doping of single-layer phosphorene via molecular adsorption predicted above, especially n-doping against its native p-doping propensity, would broaden the way to the application of this new type of two-dimensional material in nanoelectronic and optoelectronic devices.

cond-mat.mes-hall↗

arXiv2014

A RM-Polar Codes

In this letter we propose a new hybrid code called "RM-Polar" codes. This new codes are constructed by combining the construction of Reed-Muller (RM) code and Polar code. It has much larger minimum Hamming distance than Polar codes, therefore it has much better error performance than Polar codes.

cs.IT↗