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Qiang Li

Publications and source records attributed to Qiang Li.

At least 487 records · Page 27Linked to original sources

High-mass outflows identified from COHRS CO\,(3 - 2) Survey

An unbiased search of molecular outflows within the region of the COHRS survey has identified 157 high-mass outflows from a sample of 770 ATLASGAL clumps with a detection rate of 20\%. The detection rate of outflows increases for clumps with higher M$_{clump}$, L$_{bol}$, L$_{bol}$/M$_{clump}$, N$_{H_{2}}$, and T$_{dust}$ compared to the clumps with no outflow. The detection rates of the outflow increases from protostellar (8\%) to YSO clump (17\%) and to MSF clump (29\%). The detection rate 26\% for quiescent clump is preliminary, because the sample of quiescent clumps is small. A statistical relation between the outflow and clump masses for our sample is $\log(M_{out}/M_{\bigodot}) = (-1.1\pm0.21) + (0.9\pm0.07)\log(M_{clump}/M_{\bigodot})$. The detection rate of outflows and the outflow mass-loss rate show an increase with increasing M$_{clump}$, L$_{bol}$, N$_{H_{2}}$, and T$_{dust}$, which indicates that clumps with outflow with higher parameter values are at a more advanced evolutionary stage. The outflow mechanical force increases with increasing bolometric luminosities. No clear evidence has yet been found that higher mass outflows have different launching conditions than low-mass outflows.

astro-ph.GA↗

Electron and hole contributions to normal-state transport in the superconducting system Sn$_{1-x}$In$_x$Te

Indium-doped SnTe has been of interest because the system can exhibit both topological surface states and bulk superconductivity. While the enhancement of the superconducting transition temperature is established, the character of the electronic states induced by indium doping remains poorly understood. We report a study of magneto-transport in a series of Sn$_{1-x}$In$_x$Te single crystals with $0.1\le x \le 0.45$. From measurements of the Hall effect, we find that the dominant carrier type changes from hole-like to electron-like at $x\sim0.25$; one would expect electron-like carriers if the In ions have a valence of $+3$. For single crystals with $x = 0.45$, corresponding to the highest superconducting transition temperature, pronounced Shubnikov-de Haas oscillations are observed in the normal state. In measurements of magnetoresistance, we find evidence for weak anti-localization (WAL). We attribute both the quantum oscillations and the WAL to bulk Dirac-like hole pockets, previously observed in photoemission studies, which coexist with the dominant electron-like carriers.

cond-mat.supr-con↗

Strong Decays of the Orbitally Excited Scalar $D^{*}_{0}$ Mesons

We calculate the two-body strong decays of the orbitally excited scalar mesons $D_0^*(2400)$ and $D_J^*(3000)$ by using the relativistic Bethe-Salpeter (BS) method. $D_J^*(3000)$ was observed recently by the LHCb Collaboration, the quantum number of which has not been determined yet. In this paper, we assume that it is the $0^+(2P)$ state and obtain the transition amplitude by using the PCAC relation, low-energy theorem and effective Lagrangian method. For the $1P$ state, the total widths of $D_0^*(2400)^{0}$ and $ D_0^*(2400)^+$ are 226 MeV and 246 MeV, respectively. With the assumption of $0^+(2P)$ state, the widths of $D_J^*(3000)^0$ and $D_J^*(3000)^+$ are both about 131 MeV, which is close to the present experimental data. Therefore, $D_J^*(3000)$ is a strong candidate for the $2^3P_0$ state.

hep-ph↗

Boundary Element Method for non-adhesive and adhesive contacts of a coated elastic half-space

We present a new formulation of the Boundary Element Method (BEM) for simulating the non-adhesive and adhesive contact between an indenter of arbitrary shape and an elastic half-space coated with an elastic layer of different material. We use the Fast Fourier Transform based formulation of BEM, while the fundamental solution is determined directly in the Fourier space. Numerical tests are validated by comparison with available asymptotic analytical solutions for axisymmetric flat and spherical indenter shapes.

cond-mat.soft↗

Indentation of concave power law profiles with arbitrary exponents

We study analytically and numerically the process of indentation of cylindrical rigid indenter with concave face in form of a power-law function. In the well-known case of a parabolic concave indenter, the contact starts at sharp edges of the indenter and spreads inwards with increasing indentation depth. For all profiles with the exponent larger than 2, the contact area first spreads from the boarder inwards, but then a contact is established in the center of the indenter. Finally, the outer ring spreads inwards and the central contact area outwards until the complete contact is achieved. The critical indentation depth for the full contact is calculated ones proceeding from the full contact and looking for the condition of vanishing pressure and also proceeding from incomplete contact (in this case numerically, using Boundary Element Method). The results of both approaches coincide.

cond-mat.soft↗

The evolving networks of debtor-creditor relationships with addition and deletion of nodes: a case of P2P lending

P2P lending activities have grown rapidly and have caused the huge and complex networks of debtor-creditor relationships. The aim of this study was to study the underlying structural characteristics of networks formed by debtor-creditor relationships. According attributes of P2P lending, this paper model the networks of debtor-creditor relationships as an evolving networks with addition and deletion of nodes. It was found that networks of debtor-creditor relationships are scale-free networks. Moreover, the exponent of power-law was calculated by an empirical study. In addition, this paper study what factors impact on the exponent of power-law besides the number of nodes. It was found that the both interest rate and term have significantly influence on the exponent of power-law. Interest rate is negatively correlated with the exponent of power-law and term is positively correlated with the exponent of power-law. Our results enriches the application of complex networks

q-fin.GN↗

Energy-resolved fast neutron resonance radiography at CSNS

The white neutron beamline at the China Spallation Neutron Source will be used mainly for nuclear data measurements. It will be characterized by high flux and broad energy spectra. To exploit the beamline as a neutron imaging source, we propose a liquid scintillator fiber array for fast neutron resonance radiography. The fiber detector unit has a small exposed area, which will limit the event counts and separate the events in time, thus satisfying the requirements for single-event time-of-flight (SEToF) measurement. The current study addresses the physical design criteria for ToF measurement, including flux estimation and detector response. Future development and potential application of the technology are also discussed.

physics.ins-det↗

Minimum Symbol Error Rate-Based Constant Envelope Precoding for Multiuser Massive MISO Downlink

This paper considers the problem of constant envelope (CE) precoder designs for multiuser massive MISO downlink channels. The use of CE signals allows one to employ low-cost radio frequency chains and thereby facilitates the implementation of massive MIMO. However, the subsequent CE precoder designs are usually challenging owing to the non-convex CE constraints. The existing CE precoder designs consider minimization of some measures on the distortion levels of the received symbols, and they usually aim at improving the symbol-error rate (SER) performances. In this paper we formulate a minimum SER-based design for CE precoding. The design formulation is non-convex and we propose two low-complexity first-order algorithms using gradient projection. Curiously, our simulation results show that the proposed designs can achieve bit-error rate performance close to that of zero-forcing beamforming without CE signaling restrictions.

cs.IT↗

Adhesion-assisted nanoscale rotary locomotor in non-liquid environments

Rotation in micro/nanoscale provides extensive applications in mechanical actuation$^{1, 2}$, cargo delivery$^{3, 4}$, and biomolecule manipulation$^{5, 6}$. Light can be used to induce a mechanical rotation remotely, instantly and precisely$^{7-13}$, where liquid throughout serves as a must-have enabler to suspend objects and remove impact of adhesion. Achieving light-driven motion in non-liquid environments faces formidable challenges, since micro-sized objects experience strong adhesion and intend to be stuck to contact surfaces. Adhesion force for a usual micron-sized object could reach a high value$^{14, 15}$ (nN - μN) which is several orders of magnitude higher than both its gravity (~ pN) and typical value of optical force (~ pN) in experiments$^{16}$. Here, in air and vacuum, we show counter-intuitive adhesion-assisted rotary locomotion of a micron-sized metal nanoplate with ~30 nm-thickness, revolving around a microfiber. This locomotor is powered by pulsed light guided into the fiber, as a coordinated consequence of photothermally induced surface acoustic wave on the nanoplate and favorable configuration of plate-fiber geometry. The locomotor crawls stepwise with sub-nanometer locomotion resolution actuated by designed light pulses. Furthermore, we can control the rotation velocity and step resolution by varying the repetition rate and pulse power, respectively. A light-actuated micromirror scanning with 0.001° resolution is then demonstrated based on this rotary locomotor. It unfolds unprecedented application potential for integrated micro-opto-electromechanical systems, outer-space all-optical precision mechanics and controls, laser scanning for miniature lidar systems, etc.

physics.optics↗

Evidence for magnetic-field-induced decoupling of superconducting bilayers in La$_{2-x}$Ca$_{1+x}$Cu$_{2}$O$_{6}$

We report a study of magnetic susceptibility and electrical resistivity as a function of temperature and magnetic field in superconducting crystals of La$_{2-x}$Ca$_{1+x}$Cu$_{2}$O$_{6}$ with $x=0.10$ and 0.15 and transition temperature $T_{c}^{\rm m} = 54$ K (determined from the susceptibility). When an external magnetic field is applied perpendicular to the CuO$_2$ bilayers, the resistive superconducting transition measured with currents flowing perpendicular to the bilayers is substantially lower than that found with currents flowing parallel to the bilayers. Intriguingly, this anisotropic behavior is quite similar to that observed for the magnetic irreversibility points with the field applied either perpendicular or parallel to the bilayers. We discuss the results in the context of other studies that have found evidence for the decoupling of superconducting layers induced by a perpendicular magnetic field.

cond-mat.supr-con↗

Initial State Radiation Simulation with MadGraph

Initial State Radiation (ISR) effect is implemented in Madgraph using photon structure functions. Detailed examinations are performed against other generators including Whizard, BabayagaNLO and KKMC, for various physics processes at linear colliders such as 240GeV CEPC and 10.58GeV Belle II. ISR effects on new physics searches are also discussed, taking anomalous gauge boson coupling and dark photon as examples. An ISR plugin is made public for wide usage.

hep-ph↗

The Strong Decays of $P-$wave Mixing Heavy-Light $1^+$ States

Many $P-$wave mixing heavy-light $1^+$ states have not been discovered by experiment, some of them have been discovered but without the information of width, or with large uncertainty widths. In this paper, we study the strong decays of $P-$wave mixing heavy-light $1^+$ states $D^0$, $D^\pm$, $D_s^\pm$, $B^0$, $B^\pm$ and $B_s$ by the improved Bethe-Salpeter(B-S) method in two conditions of mixing angle $θ$: one is $θ=35.3^\circ$; another is considering the correction to mixing angle $θ=35.3^\circ+θ_1$. And we get some valuable predictions of the strong decay widths: $Γ(D_1^{\prime0})=232$ MeV, $Γ(D_1^0)=21.5$ MeV, $Γ(D_1^{\prime\pm})=232$ MeV, $Γ(D_1^\pm)=21.5$ MeV, $Γ(D_{s1}^{\prime\pm})=0.0101$ MeV, $Γ(D_{s1}^{\pm})=0.950$ MeV, $Γ(B_1^{\prime\pm})=263$ MeV, $Γ(B_1^{\pm})=16.8$ MeV, $Γ(B_{s1}^{\prime})=0.01987$ MeV and $Γ(B_{s1})=0.412$ MeV. We find that the decay widths of $D_{s1}^{\pm}$ and $B_{s1}$ are very sensitive to the mixing angle. And our results will provide the theoretical assistance by the future experiments.

hep-ph↗

Computer-aided diagnosis of lung carcinoma using deep learning - a pilot study

Aim: Early detection and correct diagnosis of lung cancer are the most important steps in improving patient outcome. This study aims to assess which deep learning models perform best in lung cancer diagnosis. Methods: Non-small cell lung carcinoma and small cell lung carcinoma biopsy specimens were consecutively obtained and stained. The specimen slides were diagnosed by two experienced pathologists (over 20 years). Several deep learning models were trained to discriminate cancer and non-cancer biopsies. Result: Deep learning models give reasonable AUC from 0.8810 to 0.9119. Conclusion: The deep learning analysis could help to speed up the detection process for the whole-slide image (WSI) and keep the comparable detection rate with human observer.

cs.CV↗

One-bit massive MIMO precoding via a minimum symbol-error probability design

Massive multiple-input multiple-output (MIMO) has the potential to substantially improve the spectral efficiency, robustness and coverage of mobile networks. However, such potential is limited by hardware cost and power consumption associated with a large number of RF chains. Recently, one-bit quantization is proposed to address this issue by replacing high-resolution digital-to-analog converters (DACs) with one-bit DACs, thereby simplifying the RF chains. Despite low system cost, advanced signal processing techniques are needed to compensate for quantization distortions caused by low resolution DACs. In this paper, a symbol-error-rate (SER)-based one-bit precoding scheme is proposed to minimize the detection error probability of all users under one-bit constraints. The problem is recast as a continuous optimization problem with a biconvex objective. By applying the block coordinate descent (BCD) method and the FISTA method, we develop an efficient iterative algorithm to obtain a one-bit precoding solution. Simulation results demonstrate its superiority over state-of-the-art algorithms in terms of bit error rate performance in high-order modulation cases.

cs.IT↗

Strong decays of $D_J(3000)$ and $D_{sJ}(3040)$

In this paper, we systematically calculate two-body strong decays of newly observed $D_J(3000)$ and $D_{sJ}(3040)$ with 2P$(1^+)$ and 2P$(1^{+\prime})$ assignments in an instantaneous approximation of the Bethe-Salpeter equation method. Our results show that both resonances can be explained as the 2P$(1^{+'})$ with broad width via $^3P_1$ and $^1P_1$ mixing in $D$ and $D_s$ families. For $D_J(3000)$, the total width is 229.6 MeV in our calculation, close to the upper limit of experimental data, and the dominant decay channels are $D_2^*π$, $D^*π$, and $D^*(2600)π$. For $D_{sJ}(3040)$, the total width is 157.4 MeV in our calculation, close to the lower limit of experimental data, and the dominant channels are $D^*K$ and $D^*K^*$. These results are consistent with observed channels in experiments. Given the very little information that has been obtained from experiments and the large error bars of the total decay widths, we recommend the detection of dominant channels in our calculation.

hep-ph↗

Optimize transfer learning for lung diseases in bronchoscopy using a new concept: sequential fine-tuning

Bronchoscopy inspection as a follow-up procedure from the radiological imaging plays a key role in lung disease diagnosis and determining treatment plans for the patients. Doctors needs to make a decision whether to biopsy the patients timely when performing bronchoscopy. However, the doctors also needs to be very selective with biopsies as biopsies may cause uncontrollable bleeding of the lung tissue which is life-threaten. To help doctors to be more selective on biopsies and provide a second opinion on diagnosis, in this work, we propose a computer-aided diagnosis (CAD) system for lung diseases including cancers and tuberculosis (TB). The system is developed based on transfer learning. We propose a novel transfer learning method: sentential fine-tuning . Compared to traditional fine-tuning methods, our methods achieves the best performance. We obtained a overall accuracy of 77.0% a dataset of 81 normal cases, 76 tuberculosis cases and 277 lung cancer cases while the other traditional transfer learning methods achieve an accuracy of 73% and 68%. . The detection accuracy of our method for cancers, TB and normal cases are 87%, 54% and 91% respectively. This indicates that the CAD system has potential to improve lung disease diagnosis accuracy in bronchoscopy and it also might be used to be more selective with biopsies.

cs.CV↗

Probing the Dark Sector through Mono-Z Boson Leptonic Decays

Collider search for dark matter production has been performed over the years based on high pT standard model signatures balanced by large missing transverse energy. The mono-Z boson production with leptonic decay has a clean signature with the advantage that the decaying electrons and muons can be precisely measured. This signature not only enables reconstruction of the Z boson rest frame, but also makes possible recovery of the underlying production dynamics through the decaying lepton angular distribution. In this work, we exploit full information carried by the leptonic Z boson decays to set limits on coupling strength parameters of the dark sector. We study simplified dark sector models with scalar, vector, and tensor mediators and observe among them different signatures in the distribution of angular coefficients.Specifically, we show that angular coefficients can be used to distinguish different scenarios of the spin-0 and spin-1 models, including the ones with parity-odd and charge conjugation parity-odd operators. To maximize the statistical power, we perform a matrix element method study with a dynamic construction of event likelihood function. We parametrize the test statistic such that sensitivity from the matrix element is quantified through a term measuring the shape difference. Our results show that the shape differences provide significant improvements in the limits, especially for the scalar mediator models. We also present an example application of a matrix-element-kinematic-discriminator, an easier approach that is applicable for experimental data.

hep-ph↗

Tradeoff between Delay and Physical Layer Security in Wireless Networks

Exchange of crucial and confidential information leads to the unprecedented attention on the security problem in wireless networks. Though the security has been studied in a number of works, the joint optimization of the physical layer security and the end-to-end delay management, which requires a meticulous cross-layer design, has seldom been evaluated. In this work, by combining the tools from stochastic geometry and queueing theory, we analyze the tradeoff between the delay and the security performance in large wireless networks. We further propose a simple transmission mechanism which splits a message into two packets and evaluate its effect on the mean delay and the secrecy outage probability. Our numerical results reveal that the security performance is better for larger path loss exponent when the density of legitimate nodes is large, and it is reverse when the density is small. Moreover, it is observed that by introducing the simple mechanism of message split, the security performance is greatly improved in the backlogged scenario and slightly improved in the dynamic scenario when the density of legitimate transmitters is large. In summary, this work provides an understanding and a rule-of-thumb for the practical design of wireless networks where both the delay and the security are key concerns.

cs.IT↗