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The electromagnetic induction quenching approach has been widely applied in the engine industry, especially in relation to parts made of metal materials, such as crankshafts. To this end, the reinforcing effect of this technique has been quantitatively studied. Using this approach, we first performed multi-physics simulations to obtain key information, such as the temperature and residual stress distributions. Then, the fatigue limit load was predicted according to the simulation results and the indirect-defined theory of critical distance (ITCD) model. Finally, the feasibility of this prediction method was verified by standard bending fatigue experiments. The results of the prediction method were accurate and consistent with the experimental results, with wide popularization and application prospects.

Crankshaft is one of the most important parts in modern diesel engine. Usually, the strength of this part is improved by the electromagnetic induction quenching approach. In this paper, the high cycle bending fatigue property of the steel crankshaft after this treatment was selected as the object of study. First, a simplified 2D finite element model was built based on the structural features of the crankshaft to simulate the electromagnetic induction quenching process of a given type of steel crankshaft. In this way, the temperature and residual stress distribution property of the crankshaft can be determined at any time node during the process. Then the fatigue limit load of this crankshaft was predicted based on the results obtained in the previous chapter and the selected mean stress models. Finally, corresponding experimental verifications were conducted to check the accuracy of the predictions. Validations between the experimental results and the prediction showed that this that the combination of the simulation results and the Gerber mean stress model can obtain the fatigue property of this type of crankshaft accurately, thus was suitable for actual engineering applications.

PurposeBamboo scrimber is a new natural fiber-reinforced composite material in the modern industry. In this paper, the strength characteristics of this material were chosen as the object of study.Design/methodology/approachFirst, axial tensile fracture experiments were conducted on different test specimens to determine the corresponding strength data. Then three commonly used distribution models were applied to analyze the relationship between the strength and survival rate.FindingsThe results show that the tensile data demonstrate obvious dispersion. In addition, the three-parameter Weibull model fits the data best and may be used as the fundamental model for future analysis.Originality/valueSpecial statistical analysis research of the bamboo material experimental results has rarely been discovered. This paper provides a solid foundation for better understanding the mechanism of the bamboo scrimber strength phenomenon.

In recent years, 1.3 μm lasers have been widely used in laser medical treatment, optical fiber communication and optoelectronic countermeasures, etc. In this paper, the unstable cavity structure with double pump cavity connected in series and the method to optimize the thermal lens effect are used to obtain a maximum 41 W average power of continuous-wave laser. Meanwhile, the pulsed laser is realized through an acousto-optic Q switch and the repetition rate can be adjusted in the range of 1~10 kHz. The maximum single pulse energy can reach 8.44 mJ with the repetition frequency of 1 kHz, corresponding to 65 kW peak power. In the future, the output power will be further improved by optimizing the laser, which will be beneficial to expand the applications in related fields.

We mainly study the conversion efficiency of Erbium/Ytterbium (Er/Yb) co-doped silicate glass fiber (Nufern PM-EYDF-12/130-HE) under different pump wavelengths, pump methods, gain fiber length and input signal power. Through a series of experimental studies, it is found that the hybrid pump mode of multi-mode pump diodes at 976 nm and 915 nm/940 nm are more efficient than that of single-wavelength pumping. When the input signal power is 85 mW, the fiber length is 3.9 m, the hybrid pump power of 976 nm and 940 nm is 10 W respectively, the output optical power can reach 6.41 W, and the optical-to-optical conversion efficiency is 33.7 %, and the signal-to-noise ratio (SNR) is more than 45 dB. When the hybrid pump power of 976 nm and 915 nm is 10 W respectively, the output power can reach 6.31 W, and the PPCE is 33 %. Under the condition of 20 W reverse pump power, the optical-to-optical efficiency of 976 nm, 915 nm and 940 nm single-wavelength pump is 30.7 %, 25.2 % and 21.7 % respectively.

Two dimensional materials have been regarded as promising candidates for photocatalytic water splitting. Herein, we systematically investigated the potential of a novel two dimensional penta-X2C (X = P, As, Sb) family for photocatalytic water splitting by means of density functional theory. The penta-X2C family consists of semiconductors with indirect band gaps of 2.64 eV, 2.09 eV and 1.35 eV for X = P, As and Sb, respectively. Notably, the band edge positions of penta-P2C and penta-As2C can perfectly satisfy the redox potentials of photocatalytic water splitting via strain engineering, whereas penta-Sb2C only meets the reduction potential. The ultrahigh (up to 103–105 cm2 V−1 s−1) and anisotropic carrier mobilities are crucial to suppressing the photogenerated electron-hole pair recombination. Meanwhile, the penta-X2C family exhibits excellent light absorption in the visible-ultraviolet region, favorable for the utilization of sunlight. In addition, compared with other common 2D materials such as graphene and h-BN, the penta-X2C family possesses a relatively smaller Young's modulus and larger critical strain, while penta-X2C have large negative Poisson's ratios of −0.103, −0.079 and −0.077, respectively. These results testify that the penta-X2C family has potential applications not only in photocatalytic water splitting but also in designing 2D electromechanical and optoelectronic devices.

Based on an all-fiber master oscillator power amplifier (MOPA) structure, a 1950-nm narrow-linewidth, single-mode, high peak power nanosecond pulsed fiber laser was developed. The seed source is a distributed feedback (DFB) semiconductor laser with a linewidth of 0.5 MHz. A precise and stable closed-loop temperature control technology is used to design the driving circuit of the seed laser, which ensures the stability of the laser wavelength and power, and greatly reduces the frequency and intensity noise of the laser. The continuous seed laser is modulated by an acousto-optic modulator (AOM). At the same time, the high-frequency control technology of acousto-optic modulator and cascade amplification technology are used to realize the continuous adjustable of laser pulse shape (Gaussian pulse or square wave pulse), repetition rate (1 kHz ~ 300 kHz) and pulse width (50 ns ~ 500 ns) of 2.0 μm band single frequency laser. This laser is very suitable for coherent lidar applications

Recently, excitonic solar cells (XSCs) with high photovoltaic performance have raised research interests because of their high power conversion efficiencies (PCEs). Herein, by using first-principles calculations, we predict that γ-BX (X = S, Se, Te) monolayers are direct semiconductors with the band gaps of 2.94, 2.71, and 1.32 eV, respectively, and maintain semiconduction in the broad strain range of 0% ≤ δ ≤ 5%. The moderate direct band gap, high transport property, dramatically high absorption from visible to the ultraviolet region, and extraordinary excitonic behavior of monolayer γ-BTe, render it promising for next-generation optoelectronic and photovoltaic devices. By choosing monolayer GeP

We report a high-energy narrow-linewidth SBS-free high-efficiency polarization-maintaining fiber laser based on MOPA at 1572 nm for CO2 coherent remote sensing. The Lorentz linewidth of the seed laser is 150 μJ, with tunable repetition rate of 1 k~1 MHz and tunable pulse width of 100~500 ns.

This study aimed to investigate the prevalence and molecular characteristics of Listeria monocytogenes in cooked products in Zigong City, China. The overall occurrence of the L. monocytogenes in the ready-to-eat (RTE) shops and mutton restaurants surveyed was 16.2% (141/873). An occurrence of 13.5% was observed in RTE pork, 6.5% in RTE vegetables, and more than 24.0% in either cooked mutton or cooked haggis. Serotype 1/2b (45.4%), 1/2a (33.3%), and 1/2c (14.2%) were the predominant types. By comparing the clonal complexes (CCs) based on multilocus sequence typing (MLST) of the L. monocytogenes from cooked foods in Zigong City and 33 listeriosis cases from different districts of China, CC87, CC9, CC8, and CC3 were showed to be prevalent in cooked products and CC87 and CC3 were the first two frequent types in the 33 clinic-source strains. All CC87 stains harbored the newly reported Listeria pathogenicity island 4 (LIPI-4) gene fragment ptsA, and all CC3 strains possessed the Listeria pathogenicity island 3 (LIPI-3) gene fragment llsX. These may increase the occurrence of the strains belonging to CC87 and CC3 in listeriosis cases in China and also underline the risk of infection owing to the consumption of the cooked products from Zigong. ST619 (serotype 1/2b) harbored both llsX and ptsA, indicating a potential hypervirulent sequence type in Zigong.

We propose a novel two-dimensional crystal based on layered bulk metallic SnP3 using first-principles calculations. The obtained low cleavage energy of monolayer and bilayer SnP3 implies the possibility of their exfoliation from layered bulk SnP3 experimentally. Monolayer and bilayer SnP3 are structurally stable with 0.72 eV and 1.02 eV indirect band gaps, respectively, at the HSE06 functional level. Tunable bandgaps can be achieved by strain engineering. With a compressive strain of 4%, the valence band maximum of bilayer SnP3 varies from the high symmetry point K to point Γ, resulting in transformation from an indirect to a direct semiconductor. Analogous to phosphorene, remarkably high carrier mobilities are predicted for monolayer SnP3, which is several times higher than that of monolayer GeP3. The hole mobilities of bilayer SnP3 can reach as high as 104 cm2 V−1 s−1. Moreover, an excellent absorption coefficient in the range of solar spectrum was predicted. These results qualify monolayer and bilayer SnP3 as promising novel 2D materials for applications in microelectronics, optoelectronics and field-effect transistors.

The groundbreaking works in graphene and graphene nanoribbons (GNRs) over the past decade, and the recent discovery of borophene draw immediate attention to the underexplored borophene nanoribbons (BNRs). We herein report a density functional theory (DFT) study of the geometric, electronic and magnetic properties of BNRs as a function of orientation (denoted as BxNRs and ByNRs with the orientation along x- and y-axis, respectively), ribbon width (Nx, Ny = 4 to 15), and hydrogenation effects. We found that the anisotropic quasi-planar geometric structure of BNRand its edge states profoundly govern the electronic and magnetic properties. Pristine ByNRs adopt a magnetic ground state, anti-ferromagnetic (AFM) or ferromagnetic (FM) depending on the ribbon width, while pristine BxNRs are non-magnetic (NM). Upon hydrogenation, all BNRs become NM. Interestingly, both pristine and hydrogenated ByNRs undergo a metal-semiconductor-metal transition at Ny = 7, while BxNRs remain metallic., Comment: 33 pages, 9 figures

Listeria monocytogenes is a foodborne pathogen frequently isolated from raw pork meat. This study was designed to investigate the prevalence and molecular characteristics of L. monocytogenes in raw pork from open markets in China. The survey was conducted monthly over a 12-month period in Zigong, China. L. monocytogenes was isolated from 262 of 1641 samples collected (16.0%) including minced meat samples (131/608, 21.5%), pork pieces samples (111/857, 13.0%) and environmental swabs (20/176, 11.4%). The isolation rates in spring and winter were significantly higher than those in summer and autumn ( X 2 = 68.85, P AscI pulsed-field gel electrophoresis (PFGE). The 262 isolates were subtyped into five serotypes: 1/2b (43.1%), 1/2c (35.5%), 1/2a (19.1%), 4b (1.1%), 3a (1.1%); 20 sequence types (STs) with four most frequent STs, being ST9 (35.9%), ST87 (19.8%), ST3 (16.0%) and ST8 (14.1%); and 39 pulsotypes (PTs) with PT4 (26.3%), PT30 (14.5%) and PT11 (12.6%) being most frequent. Two primary pulsotypes from pork pieces were previously isolated from clinical listeriosis cases in the local hospitals. The six markets from different districts differed in the level of contamination and strain types. Persistent contamination of L. monocytogenes was found in the markets especially in meat mincers, which were found to be one likely source of continuous cross contamination. These findings will help develop strategies to reduce L. monocytogenes contamination in open markets for better public health control and prevention of foodborne L. monocytogenes infections.

In recent years, high-brightness picosecond lasers have been widely used in high-end precision processing, spectroscopy and high harmonic generation. To obtain higher power and excellent beam quality, it is an ideal solution to add a high-gain amplifier to the back end of the high-stability picosecond fiber or solid seed. In this article, a fiber-solid hybrid end-pumped Nd:YVO4 picosecond laser system with high beam quality is demonstrated. The influence of the self-developed picosecond fiber seed output characteristics on solid amplifiers has been studied in detail, including the energy, repetition rate and spectrum. After two-stage traveling wave amplifiers, the maximum 155 μJ single pulse energy is obtained with 20 kHz repetition rate, and the corresponding peak power reaches 14.9 MW with 10.4 ps pulse duration. Meanwhile, the beam quality factors under the maximum 18.4 W average power are measured to be M x 2 = 1.27 and M y 2 = 1.25, respectively.

Linewidth measurement of single-frequency laser using self-heterodyne method is studied. 1/f noise and the noise caused by double Rayleigh scattering in delayed fiber can affect the shape of linewidth, which introduces inaccuracy in linewidth measurement.

SUMMARYEscherichia albertiiis a newly emerging enteric pathogen that has been associated with gastroenteritis in humans. Recently,E. albertiihas also been detected in healthy and sick birds, animals, chicken meat and water. In the present study, the prevalence and characteristics of theeae-positive, lactose non-fermentingE. albertiistrains in retail raw meat in China were evaluated. Thirty isolates of such strains ofE. albertiiwere identified from 446 (6·73%) samples, including duck intestines (21·43%, 6/28), duck meat (9·52%, 2/21), chicken intestines (8·99%, 17/189), chicken meat (5·66%, 3/53), mutton meat (4·55%, 1/22) and pork meat (2·44%, 1/41). None was isolated from 92 samples of raw beef meat. Strains were identified asE. albertiiby phenotypic properties, diagnostic PCR, sequence analysis of the 16S rRNA gene, and housekeeping genes. Five intimin subtypes were harboured by these strains. All strains possessed the II/III/V subtype group of thecdtBgene, with two strains carrying another copy of the I/IV subtype group. Pulsed-field gel electrophoresis showed high genetic diversity ofE. albertiiin raw meats. Our findings indicate thatE. albertiican contaminate various raw meats, posing a potential threat to public health.

In this paper, three reverse link access protocols (AP) enabling discontinuous transmission (DTX) in DS-CDMA personal communication systems are introduced and discussed. The first protocol is synchronous (SDTX-AP), and it uses a so-called synchronous reservation channel to accommodate access requests in a time slotted frame structure. The second uses an asynchronous approach (ADTX-AP) with a spread slotted ALOHA protocol for access requests; access request messages consist of a synchronizing preamble and a user identifier appendix. The third one employs a synchronous structure of overlapping slots, offset in time by a minimum interval (mini-slot) necessary to enable resolution of overlapping access probes sent by different mobile users (MSDTX-AP). Instead of using different spreading codes for different mobile transmitters, all transmitters are assigned the same spreading code to send their access request messages on the access reservation channel. Analysis considers the mean access delay and throughput of the protocols in a multipath fading channel. Numerical results indicate that at high values of offered traffic of access requests mean access delays of ADTX-AP and SDTX-AP are comparable. The mean access delay for the MSDTX-AP depends on the number of minislots or users within each frame, but its throughput is much higher than that of either SDTX-AP or ADTX-AP.

Introduction: for realizing detection of drowsiness, a method based on Tsallis entropy of EEG signal is proposed. Materials and Methods: EEG signals with bipolar montage C4-P4 and T4-T6 were collected from 20 healthy subjects during wake and drowsiness. After four kinds of EEG rhythms were extracted, the each rhythm complexity for the EEG signals was analyzed with Tsallis entropy. Results and Discussion: the results show that the Tsallis entropy of EEG theta rhythms either C4-P4 or T4-T6 in wake is obviously higher than drowsiness. So the drowsiness could be reliably detected in real-time by the Tsallis entropy of theta rhythm on C4-P4 or T4-T6.

A dual-wavelength, all-fiber, passively Q-switched Erbium laser based on a SWNT saturable absorber is demonstrated, which can simultaneously generate ~μs pulses with ~kHz repetition rate at 1532 nm and 1558 nm wavelength.

In order to discuss the unity of heart rate variability (HRV) and pulse rate variability (PRV) and explore the relationship between HRV/PRV and the autonomic nervous. R-R intervals and P-P intervals were obtained from ECG and pulse signals of 17 healthy volunteers by synchronous acquisition system. HRV and PRV were analyzed offline by spectral analysis. And PRV derived from pulse wave corresponds well to traditional HRV derived from ECG. The results indicate that PRV and HRV had the same features which synchronous acquisition ECG and pulse wave, and the PRV may replace HRV to estimate the excitement of autonomic nervous.

The paper considers optimal forward link power allocation for data transmission in DS-CDMA systems. Acceptable quality voice communications in DS-CDMA can be achieved through the application of the forward error correction (FEC). Due to stringent requirements on signal delay, no retransmission is allowed in voice only systems. Highly reliable data transmission over wireless channels, however, can be achieved with hybrid automatic-repeat-request (ARQ) schemes. The average power allocated to data users then needs to be calculated as the actual link transmitted power times the average number of times that a data packet must be transmitted before it is accepted. Since a base station's total power available to mobiles is limited, there is an optimum power allocated to every data user in the cell, which maximizes the system capacity. The optimal power allocation can be described as the stochastic nonlinear programming optimization problem. Numerical results are presented to illustrate the problem. The powers allocated to data users are location dependent, but the numerical results demonstrate that the mean signal-to-interference ratio (SIR) is location independent when the optimal power allocation is achieved.

Capacity analysis of a multi-service CDMA communication system when both continuous and discontinuous transmission schemes are employed, is presented. Data messages treated in this paper include long ones for which closed loop power control can be implemented, and short ones for which only open loop power control is feasible. The effect of the discontinuous transmission's overhead on the system Erlang capacity is evaluated. For data transmission, when a negative-acknowledgment ARQ protocol is employed, its impact on the call admission control (CAC) is also investigated. The concept of equivalent bandwidth has been introduced which makes the analysis of an interference-limited system similar to that of a bandwidth-limited system without fixed channel assignment. The proposed CAC algorithms can be employed in a system supporting multi-rate data services. Simulations are conducted to validate the analysis.

This paper considers two types of digital matched filter-based synchronizers. One is applied with biphase spreading, and the other with quadri-phase spreading. The synchronizers are primarily designed for application on reverse links of the IS-95 type systems, but with minor modifications they can also be used in other DS-CDMA systems. Probabilities of correct acquisition and false alarm for both Gaussian and Rayleigh fading channels are derived. The differential approach is considered to reduce the number of required operations. Numerical results are presented when a specially designed packet synchronization preamble is used, and the mean acquisition time is evaluated.

Combined error correction and detection techniques, or hybrid automatic-repeat-request (ARQ) schemes with negative acknowledgment are considered for highly reliable reverse link data transmission in direct sequence code division multiple access (DS-CDMA) personal communication systems. In this paper a coherent link using OQPSK and continuous pilot signal assisted radio channel estimation is analyzed. The proposed selective repeat hybrid ARQ scheme employs an inner convolutional code for error correction and an outer shortened BCH code for error detection. Accepted packet error rate and throughput are derived as a function of the error correction encoded frame error rate. An optimum signal-to-interference ratio (SIR) assignment maximizing the system's capacity is also found. Analysis and simulations show that by applying the proposed type I hybrid ARQ scheme with properly selected system parameters, virtually error free and highly efficient data transmission in CDMA personal communication systems is possible.

Several important characteristics of the magnetic-field-enhanced terahertz radiation from InAs and InSb emitters pumped at 1550?nm wavelength are experimentally investigated. The emission efficiency, pump saturation power and emission spectrum from these two different materials are compared side by side. With the external magnetic field, while the InSb crystal shows a higher THz emission efficiency, it has a lower saturation pump power (0.42??J?cm?2) than that of InAs (0.86??J?cm?2). They are shown to be much easier to saturate compared to the InAs emitter pumped at 800?nm reported previously. The THz spectrum from InAs has a broader bandwidth than that of InSb, and its shape also varies significantly under higher pump powers with an interesting increase at frequencies above 1?THz. The results could be very helpful in designing and implementing compact, high-efficiency THz sources using low-cost, high-power fiber ultrafast lasers.