bluuebunny/crossref_metadata_2025 huggingface dataset:
Winding number statistics for chiral random matrices: Averaging ratios of determinants with parametric dependence
Authors: Hahn Nico , Kieburg Mario , Gat Omri , Guhr Thomas
Published: February 2023

Topological invariance is a powerful concept in different branches of physics as they are particularly robust under perturbations. We generalize the ideas of computing the statistics of winding numbers for a specific parametric model of the chiral Gaussian unitary ensemble to other chiral random matrix ensembles. In particular, we address the two chiral symmetry classes, unitary (AIII) and symplectic (CII), and we analytically compute ensemble averages for ratios of determinants with parametric dependence. To this end, we employ a technique that exhibits reminiscent supersymmetric structures, while we never carry out any map to superspace.
Continuously and widely tunable frequency-stabilized laser based on an optical frequency comb
Authors: Shen Ze-Min , Zhou Xiao-Long , Huang Dong-Yu , Pan Yu-Hao , Li Li , Wang Jian , Li Chuan-Feng , Guo Guang-Can
Published: February 2023

Continuously and widely tunable lasers, actively stabilized on a frequency reference, are broadly employed in atomic, molecular, and optical (AMO) physics. The frequency-stabilized optical frequency comb (OFC) provides a novel optical frequency reference, with a broadband spectrum that meets the requirement of laser frequency stabilization. Therefore, we demonstrate a frequency-stabilized and precisely tunable laser system based on it. In this scheme, the laser frequency locked to the OFC is driven to jump over the ambiguity zones, which blocks the wide tuning of the locked laser, and tuned until the mode hopping happens with the always-activated feedback loop. Meanwhile, we compensate the gap of the frequency jump with a synchronized acoustic optical modulator to ensure the continuity. This scheme is applied to an external cavity diode laser (ECDL), and we achieve tuning at a rate of about 7 GHz/s, with some readily available commercial electronics. Furthermore, we tune the frequency-stabilized laser only with the feedback of diode current, and its average tuning speed can exceed 100 GHz/s. Due to the resource-efficient configuration and the simplicity of completion, this scheme can be referenced and can find wide applications in AMO experiments.
A reconfigurable ladder-shaped THz metamaterial integrated with a microelectromechanical cantilever array
Authors: Huang Ying , Okatani Taiyu , Inomata Naoki , Kanamori Yoshiaki
Published: February 2023

We experimentally demonstrate a microelectromechanically reconfigurable ladder-shaped metamaterial (LS-MM) operating in a terahertz (THz) range. Ultrasmall cantilever actuators with a beam length of 14 μm are employed to independently reshape each unit cell of the LS-MM, correspondingly switching the transmission response of THz waves. The microelectromechanically driven LS-MM achieves a tuning contrast of 60.1% in transmittance at 0.78 THz and a 0.9-rad delay in the transmission phase shift at 1.35 THz through the off-to-on reconfiguration. In particular, the cantilever actuator has a high mechanical resonant frequency of 585 kHz owing to its small size. The microelectromechanically driven LS-MM advantageously offers a pathway for applications requiring fast tunable transmission modulations, such as high-resolution THz imaging and wireless communications.
Transient conduction of ZnO varistors under moderate time-varying voltages: Dynamics of interfacial charges of the double Schottky barrier
Authors: Cheng Zhuolin , Hou Zongke , Wu Tong , Wang Yao , Li Rou , Lin Ying , Li Jianying , Li Shengtao , Wu Kangning
Published: February 2023

ZnO varistors are widely employed for overvoltage protections and surge absorptions due to their excellent nonlinear current–voltage characteristics originating from double Schottky barriers (DSBs). In most cases, they are operating under moderate ac voltages, while calculating the transient current responses of DSBs remains a challenge, impeding the development of condition assessments. In this paper, a transient conducting model for the DSB is proposed by quantifying the charge trapping processes of the interface states. The DSB is found to quickly reach a quasi-steady state, where the interfacial charge stabilizes with only small modulations at a relatively high level above the dc equilibrium value, even though the applied ac voltage varies in time and polarity. This is the result of efficient charge trapping and slow de-trapping by grain boundary interface states. For charge compensation under the time-varying voltage, the width of the two depletion regions of the DSB shows periodic changes. The proposed model is validated by a satisfying agreement between experimentally measured current responses and simulation results of ZnO varistors. The findings of this study provide a perspective on investigating the time-varying conducting systems and open avenues for condition assessments of nonlinear conducting devices.
Dynamics and microrheology of colloidal clay-polymer glasses and gels: Size-dependent phenomena and re-entrant behavior at early aging times
Authors: Shen Jiachun , Bhatia Surita R.
Published: February 2023

Colloidal clay Laponite forms a variety of arrested states that display interesting aging behavior. Microrheology has been applied to Laponite-based glasses and gels, but few studies evaluate the influence of probe particle size. In this work, we report the dynamics and microrheology of Laponite-polymer dispersions during aging using passive microrheology with three different probe particle sizes. At early aging times, the neat Laponite dispersion forms an arrested state; the nature of this state (e.g., a repulsive glass or gel) has remained the subject of debate. The addition of polymer retards gelation and melts the arrested state. While this melting has been observed at the macroscale and has been attributed to a re-entrant transition of a repulsive glass to a liquid state, to our knowledge, it has not been observed at the microscale. The delay of the gelation time needed to form an arrested state was found to depend on the polymer concentration and could vary from ∼24 h for neat Laponite to seven days for some Laponite-polymer samples. Significant effects of probe particle sizes are observed from the mean-squared displacement (MSD) curves as small and intermediate probe particles show diffusive motion, while the motion of large particles is restricted. By examining the factor of ⟨Δr2 (τ)⟩a, structural heterogeneity can be confirmed through the strong size-dependence displayed. Different MSD trends of probe particles are obtained at longer aging times, but no significant changes occur after 30 days of aging. Our microrheology results also reveal significant effects of probe particle size.
On the application of statistical turbulence models to the simulation of airflow inside a car cabin
Authors: Djeddou Mokhtar , Mehel Amine , Fokoua Georges , Tanière Anne , Chevrier Patrick
Published: February 2023

Computational fluid dynamics simulations of airflow inside a full-scale passenger car cabin are performed using the Reynolds averaged Navier–Stokes equations. The performance of a range of turbulence models is examined by reference to experimental results of the streamwise mean velocity and turbulence intensity profiles, obtained using the hot-wire anemometry technique at different locations inside the car cabin. The models include three linear eddy-viscosity-based variants, namely, the realizable k–ε, the renormalization group k–ε, and the shear-stress transport k–ω models. The baseline Reynolds stress model (BSL-RSM), a second-moment-closure variant, and an Explicit Algebraic Reynolds Stress Model (BSL-EARSM) are also investigated. Visualization of velocity vectors and streamlines in different longitudinal planes shows a similar airflow pattern. The flow topology is mainly characterized by jet flows developing from the dashboard air vents and extending to the back-seats compartment resulting in a large vortex structure. Additionally, a comparison between numerical and experimental results shows a relatively good agreement of the mean velocity profiles. However, all models exhibit some limitations in predicting the correct level of turbulence intensity. Moreover, the realizability of the modeled Reynolds stresses and the structure of turbulence are analyzed based on the anisotropy invariant mapping approach. All models reveal a few amounts of non-realizable solutions. The linear eddy-viscosity-based models return a prevailing isotropic turbulence state, while the BSL-RSM and the BSL-EARSM models display pronounced anisotropic turbulence states.
Frequency dependence of effective conductivity induced by spatial variance in isotropic heterogeneous media
Authors: Deng Changyu , Epureanu Bogdan , Popa Bogdan-Ioan , Lu Wei
Published: February 2023

It is an essential and challenging task to determine effective conductivity of heterogeneous media. Different from homogeneous media, heterogeneity causes the effective conductivity to behave as a function of frequency under an alternating current (AC). There have been few reports to quantify this function despite the wide applications of AC on heterogeneous media. This Letter derives the analytical form of the effective conductivity as a function of frequency caused by heterogeneity, where the local properties of the media are isotropic and independent of frequency. We use simulation and experiment data to validate our formulation and find that our form shows better agreement with the data than other models. This research provides a practical guidance on the interpretation and application of impedance and conductivity data.
Assessment of kinetic theories for moderately dense granular binary mixtures: Shear viscosity coefficient
Authors: Chamorro Moisés García , Garzó Vicente
Published: February 2023

Two different kinetic theories [J. Solsvik and E. Manger (SM), Phys. Fluids 33, 043321 (2021) and Garzó et al. (GDH), Phys. Rev. E 76, 031303 (2007)] are considered to determine the shear viscosity η for a moderately dense granular binary mixture of smooth hard spheres. The mixture is subjected to a simple shear flow and heated by the action of an external driving force (Gaussian thermostat) that exactly compensates the energy dissipated in collisions. The set of Enskog kinetic equations is the starting point to obtain the dependence of η on the control parameters of the mixture: solid fraction, concentration, mass and diameter ratios, and coefficients of normal restitution. While the expression of η found in the SM-theory is based on the assumption of Maxwellian distributions for the velocity distribution functions of each species, the GDH-theory solves the Enskog equation by means of the Chapman–Enskog method to first order in the shear rate. To assess the accuracy of both kinetic theories, the Enskog equation is numerically solved by means of the direct simulation Monte Carlo method. The simulation is carried out for a mixture under simple shear flow, using the thermostat to control the cooling effects. Given that the SM-theory predicts a vanishing kinetic contribution to the shear viscosity, the comparison between theory and simulations is essentially made at the level of the collisional contribution ηc to the shear viscosity. The results clearly show that the GDH-theory compares with simulations much better than the SM-theory over a wide range of values of the coefficients of restitution, the volume fraction, and the parameters of the mixture (masses, diameters, and concentration).
Flexoelectric aging effect in ferroelectric materials
Authors: Zhang Zhen , Wen Zhaokuan , Li Ting , Wang Zhiguo , Liu Zhiyong , Liao Xiaxia , Ke Shanming , Shu Longlong
Published: February 2023

In spite of the flexoelectric effect being a universal phenomenon in the ferroelectric perovskites, the current understanding of flexoelectric aging in ferroelectrics is, actually, rather incomplete. In this paper, we have fabricated a series of Mn-doped BaTiO3 perovskite ceramics (BaTi1–xMnxO3, x = 0.1% and 1%, BTMO) to systematically investigate the corresponding flexoelectric aging behavior by controlling the concentration of Mn. We found that the variation of Mn dopant significantly effects the Curie temperature, dielectric constant, flexoelectric aging, and flexoelectric coefficient of the BTMO ceramics. Especially for the BTMO (0.1%) ceramics, obvious ferroelectric aging and flexoelectric aging phenomenon are observed at room temperature. The main reason for aging of BTMO ceramics is that the doping of Mn introduces oxygen vacancies, which tend to be stable under the action of strain gradient and electric field. Therefore, the results presented in this paper verify that the flexoelectric aging in Mn-doped BTO ceramics is closely related to ferroelectric fatigue.
Learning time-averaged turbulent flow field of jet in crossflow from limited observations using physics-informed neural networks
Authors: Huang Weichen , Zhang Xu , Zhou Wenwu , Liu Yingzheng
Published: February 2023

Physics-informed neural networks (PINNs) are becoming popular in solving fluid mechanics problems forwardly and inversely. However, under limited observations, the application of PINNs was found to be difficult in solving the inverse problems of three-dimensional Reynolds-averaged Navier–Stokes (RANS) equations. In this study, the classical turbulent case of jet in crossflow was representatively adopted into the investigation. The dataset was obtained from a high-fidelity large-eddy simulation. The tensor-basis eddy viscosity (t-EV) model was imported first into the structure of PINNs as prior knowledge. Observations of five measured planes were preliminarily used to reconstruct the time-averaged turbulent flow field. After embedding the t-EV model, the highest absolute error and the relative L2 error of streamwise velocity were reduced by 11.1% and 31.4%, respectively. To cut down the volume of limited observations, a more effective training dataset containing only two planes and two pairs of lines was determined based on the flow characteristics (e.g., shear layer and counter-rotating vortex pair). Compared with those of five planes, the highest absolute error and the relative L2 error of streamwise velocity were further reduced by 30.0% and 6.4%, respectively. The investigation in this study provided an alternative to resolve the inverse problems of three-dimensional RANS equations with limited observations, which extended the deep learning application in fluid mechanics.
Numerical study on flow dynamics in the supercritical water circulating fluidized bed riser
Authors: Xi Kenan , Wang Hao , Lu Youjun
Published: February 2023

There are a few reports about supercritical water circulating fluidized beds (SCWCFBs), and simulations were conducted via a two-fluid model to investigate flow dynamics in a riser of SCWCFB across different flow velocities, solid circulation rates, pressures, and temperatures. The investigated characteristics include the void fraction distributions, fluid velocities, particle velocities, and drag forces. The results show that the flow characteristics in the SCWCFB riser are similar to those in the traditional gas–solid riser. In the supercritical water fluidized bed riser, the void fractions are mainly in the range of 0.85–0.95. They are low at the bottom but high at the top and low near the wall but high at the center. Particle velocities are mainly distributed between 0 and 1 m s−1. They are upward near the axis of the riser and downward near the walls, showing the annular-core flow structures. Fluid paths are tortuous at low fluid velocities but straight at high fluid velocities. Particle drag forces are mainly around 0.7–0.8 times particle weights. The effects of pressures on flow dynamics in the SCWCFB riser can be ascribed to the changes in density and viscosity of supercritical water, affecting the ability of fluid to carry particles.
Sunspots and their cycle
Authors: Pasachoff Jay M. , Seaton Daniel B. , Reardon Kevin P.
Published: February 2023

These dark blemishes on stars are key to understanding the interaction of strong magnetic fields and dynamic plasma.
Losartan controls immune checkpoint blocker-induced edema and improves survival in glioblastoma mouse models
Authors: Datta Meenal , Chatterjee Sampurna , Perez Elizabeth M. , Gritsch Simon , Roberge Sylvie , Duquette Mark , Chen Ivy X. , Naxerova Kamila , Kumar Ashwin S. , Ghosh Mitrajit , Emblem Kyrre E. , Ng Mei R. , Ho William W. , Kumar Pragya , Krishnan Shanmugarajan , Dong Xinyue , Speranza Maria C. , Neagu Martha R. , Iorgulescu J. Bryan , Huang Raymond Y. , Youssef Gilbert , Reardon David A. , Sharpe Arlene H. , Freeman Gordon J. , Suvà Mario L. , Xu Lei , Jain Rakesh K.
Published: February 2023

Immune checkpoint blockers (ICBs) have failed in all phase III glioblastoma trials. Here, we found that ICBs induce cerebral edema in some patients and mice with glioblastoma. Through single-cell RNA sequencing, intravital imaging, and CD8
+
T cell blocking studies in mice, we demonstrated that this edema results from an inflammatory response following antiprogrammed death 1 (PD1) antibody treatment that disrupts the blood–tumor barrier. Used in lieu of immunosuppressive corticosteroids, the angiotensin receptor blocker losartan prevented this ICB-induced edema and reprogrammed the tumor microenvironment, curing 20% of mice which increased to 40% in combination with standard of care treatment. Using a bihemispheric tumor model, we identified a “hot” tumor immune signature prior to losartan+anti-PD1 therapy that predicted long-term survival. Our findings provide the rationale and associated biomarkers to test losartan with ICBs in glioblastoma patients.
An intelligent vision recognition method based on deep learning for pointer meters
Authors: Chen Leisheng , Wu Xing , Sun Chao , Zou Ting , Meng Kai , Lou Peihuang
Published: February 2023

Nowadays, pointer instruments remain the main state monitoring devices in the power industry, because they have strong mechanical stability to resist electromagnetic interferences compared with digital instruments. Although the object detection algorithms based on deep learning have widely been used in the field of instrument detection, the meter recognition process still relies on threshold segmentation to recognize object points and on Hough transform to extract the meter pointer. An intelligent vision recognition method based on YOLOv5 and U2-Net network (YLU2-Net) is proposed to improve the accuracy and efficiency of meter recognition in a complex environment. Firstly, the pointer meter is located in the instrument images by using the YOLOv5 network as a region of interest (RoI). Then, the instrument RoI is processed by means of perspective transformation and image resizing. Thirdly, an improved U2-Net image segmentation method with the deep separable convolution and the focal loss function is devised to distinguish the pointers and scales from the background in the instrument RoI. Further, a dimension reduction reading method with the polar coordinate transformation is developed to calculate the meter reading accurately and efficiently. Finally, the ablation experiment is conducted to test the performance of each algorithm module in our method, and the competition experiment is completed to compare our method with other state-of-the-art ones. The experimental results verify the accuracy and efficiency of the YLU2-Net recognition method proposed.
High responsivity of VIS-NIR photodetector based on Ag2S/P3HT heterojunction
Authors: Zhang Haiting , Wei Dongdong , Song Xiaoxian , Xu Ze , Wang Fuguo , Li Hongwen , Sun Wenbao , Dai Zijie , Ren Yunpeng , Ye Yunxia , Ren Xudong , Yao Jianquan
Published: February 2023

Ag2S quantum dot (QD) photodetectors (PDs) have attracted a lot of attention in the field of imaging system and optical communication. However, the current Ag2S PDs mainly works in the near-infrared band, and its detection ability in the visible band remains to be strengthened. In this paper, we used poly(3-hexylthiophene) (P3HT) with high carrier mobility and Ag2S QDs to construct heterojunction PD. Stronger absorption in blends with polymer P3HT compared to single Ag2S QDs. The optical absorption spectra show that the Ag2S/P3HT has strong light absorption peak at 394 and 598 nm. The results show that P3HT significantly enhances the absorption of Ag2S QDs from the visible to near-infrared band. The output characteristics, transfer characteristics and fast switching capability of the device at 405 nm, 532 nm and 808 nm were tested. The device has the responsivity of 6.05 A W−1, 83.72 A W−1 and 37.31 A W−1 under 405 nm, 532 nm and 808 nm laser irradiation. This work plays an important role in improving the detection performance of Ag2S QDs and broadening its applications in photoelectric devices for weak light and wide spectrum detection.
Foundations of plasma standards
Authors: Alves Luís L , Becker Markus M , van Dijk Jan , Gans Timo , Go David B , Stapelmann Katharina , Tennyson Jonathan , Turner Miles M , Kushner Mark J
Published: February 2023

The field of low-temperature plasmas (LTPs) excels by virtue of its broad intellectual diversity, interdisciplinarity and range of applications. This great diversity also challenges researchers in communicating the outcomes of their investigations, as common practices and expectations for reporting vary widely in the many disciplines that either fall under the LTP umbrella or interact closely with LTP topics. These challenges encompass comparing measurements made in different laboratories, exchanging and sharing computer models, enabling reproducibility in experiments and computations using traceable and transparent methods and data, establishing metrics for reliability, and in translating fundamental findings to practice. In this paper, we address these challenges from the perspective of LTP standards for measurements, diagnostics, computations, reporting and plasma sources. This discussion on standards, or recommended best practices, and in some cases suggestions for standards or best practices, has the goal of improving communication, reproducibility and transparency within the LTP field and fields allied with LTPs. This discussion also acknowledges that standards and best practices, either recommended or at some point enforced, are ultimately a matter of judgment. These standards and recommended practices should not limit innovation nor prevent research breakthroughs from having real-time impact. Ultimately, the goal of our research community is to advance the entire LTP field and the many applications it touches through a shared set of expectations.
Full-wave and plasma simulations of microstrip excited, high-frequency, atmospheric pressure argon microdischarges
Authors: Kourtzanidis Konstantinos
Published: February 2023

Two-dimensional fully coupled electromagnetic (EM) wave-plasma simulations are used to study the formation, early transient and quasi-steady state of the argon plasma excited by a two-dimensional discontinuous microstrip line. The EM waves that normally propagate in the microstrip transmission line, radiate and scatter at the position of the gap and the electric field is enhanced primarily at the corner of the gap. The microdischarge is preferentially formed at this position of the EM field hotspot and in low frequencies propagates on the dielectric surface, much like a microwave surface streamer. In longer times, diffusion dominates and the whole gap is filled with plasma of maximum density in the order of 1020

m

−
3

while it occupies a volume larger than the gap. Cycle-averaged mean electron temperatures range from 2.8 to 3.9 eV, while the plasma reaches a quasi-static regime in approximately 2 µs having reconfigured the transmission and radiation patterns of the slitted microstrip line. The tunability of the microstrip due to plasma formation provides means for sustaining the discharge in a stable regime. For the same input EM power, the electron temperature increases with increasing excitation frequency while electron densities found to decrease. For the same wave frequency, a decrease of the electron densities with increasing gap is also found in addition to a restriction of the discharge expansion. Finally, thicker dielectrics result to higher electron densities and electron temperatures as well as absorbed power from the plasma. These findings are attributed to the dependence of absorbed EM power and skin depth on the EM wave angular frequency, the critical for shielding electron density as well as the restructuring of the S-parameters due to the changes in operational parameters.
Unified mechanism behind the even-parity ground state and neutron halo of 11Be*
Authors: Geng Jing , Niu Yi Fei , Long Wen Hui
Published: February 2023

Using the axially deformed relativistic Hartree-Fock-Bogoliubov (D-RHFB) model, we explore the mechanism behind the parity inversion and halo occurrence in 11Be, which are well reproduced by the RHF Lagrangian PKA1. It is illustrated that evidently enhanced deformation effects by the π-pseudo-vector and ρ-tensor couplings in PKA1 are crucial for correctly describing both the even-parity ground state (GS) and the neutron halo of 11Be. Coupling with the deformation, the intrude

component largely enhances the couplings between the even-parity orbit

and the nuclear core to ensure an even-parity GS, whereas the

component therein dominates the halo formation in 11Be. Moreover, the deformed halo in 11Be is found to be stabilized by the attractive inherent correlations between the

and

components of the halo orbit

, instead of pairing correlations, which paves a new way for understanding the halo pictures in deformed unstable nuclei.
The European Muon Collaboration effect from short-range correlated nucleons in a x-rescaling model*
Authors: Wang Rong , Ma Na-Na , Wang Tao-Feng
Published: February 2023

In this paper, we examine the hypothesis that the nuclear EMC effect arises merely from the N-N SRC pairs inside the nucleus and that the properties of the N-N SRC pair are universal among the various nuclei, using the conventional x-rescaling model for the EMC effect. With the previously determined effective mass of the short-range correlated nucleon and the number of N-N SRC pairs estimated, we calculated the EMC effect of various nuclei within the x-rescaling approach. According to our calculations, the nuclear EMC effect due to the mass deficits of the SRC nucleons is not sufficient to reproduce the observed EMC effect in experiments. We speculate that the internal structure of the mean-field single nucleon is also clearly modified. Alternatively, there can be more origins of the EMC effect beyond the N-N SRC configuration (such as the α cluster), or the universality of N-N SRC pair is significantly violated from light to heavy nuclei.
Pulse Detonation Engine Performance Analysis
Authors: Xiao Zhiyi , Zheng Longxi , Lu Jie , Tan Wenhao
Published: February 2023

A brief retroversion is conducted on the developments of pulse detonation engines over these decades. Attempts are made to cover performance analysis, nozzle effects, partial filling, and cooperating work. Researchers have spared no effort to establish accurate models to describe the unsteady nature of pulse detonation engines while the accuracy is relatively just as it comes at the price of more or less simplification. Nozzle design would make a great difference to the ultimate performance as numerical simulations have proved nozzle shape, as well as expansion ratio, needs precisely devised. The partial filling has an impact on specific impulses by altering the pressure relaxation process which is testified by numerical simulations and experiments. Component matching brings a challenge to engineering practice due to the comprehensive and complicated co-reaction between every part of the engine. How to reconcile different components remains a fatal issue as many institutes have done amounts of work to demonstrate the feasibility of such a novel propulsion option.
Thermal Performance Analysis of Solar Seawater Desalination System Based on Heat Pump Cycle
Authors: Zhang Xiaoman , Leng Bo
Published: February 2023

Mathematical model of the solar seawater desalination system based on heat pump cycle was established, which was solved by programming with MATLAB language. The system performance was analyzed by changing four variables, including the initial temperature of water tank, drive hot water temperature drop, the mass concentration of LiBr dilute solution and the system startup temperature. The results show that increasing the initial temperature of water tank is conducive to reducing the heat consumption of the auxiliary heat source and increasing the solar energy supply ratio; Increasing drive hot water temperature drop is beneficial to increase the fresh water production, but the heat of the auxiliary heat source required increases, and the solar energy supply ratio decreases; Increasing the mass concentration of LiBr dilute solution will not change the total heat consumption of the system, the heat consumption of auxiliary heat sources and the solar energy supply ratio, but the fresh water production will decrease; Increasing the system startup temperature will increase the heat consumption of the auxiliary heat source, reduce the solar energy supply ratio, and slightly reduce the fresh water production.
Simulation Study on NO and PM Emission Reduction of Engine by Coupled Miller Cycle with Butanol Blending
Authors: Ye Zixiao , Huang Jialiang , Fan Jinyu , Li Pinfang , Zhang Feifei , Lin Hang , Wang Qiwei
Published: February 2023

Trade-off effect of engine emission, that is, NO emission reduction will lead to increase of PM emission. In order to alleviate the contradiction between NO and PM emission, coupling miller cycle with burning butanol was proposed. The simulation model was built by using AVL-FIRE software. The coupling scheme is optimized by changing intake pressure with power performance as constraint condition and emission reduction as evaluation index. Simulation results show that the mixing ratio B30 combined with miller degree M20 scheme matches the intake pressure 0.213MPa well. On a constant power basis, the simultaneous reduction of NO and PM is achieved.
Influence of Nozzle Structure of Oxygen Lance on Impact Dynamic Characteristics of Supersonic Jet
Authors: Jia Hongbin , Liu Xiang , Gui Lin , Han Peng , Liu Kun
Published: February 2023

In order to realize the smelting effect of high oxygen supply intensity in large and medium-sized converters, a new six hole oxygen lance nozzle with double angle, double flow and staggered double structure is designed in this paper, and the jet characteristics are compared with those of the traditional structure oxygen lance. According to the theory of fluid dynamics and the principle of similarity, the velocity attenuation of the centerline of the jet and the longitudinal section of the oxygen jet are tested by using the oxygen gun jet detection experimental system. The results show that the jet performance of the staggered double structure six hole oxygen lance nozzle is better than that of the traditional structure oxygen lance nozzle. When the ratio of large hole flow is 55%-65%, the angle of large hole is 12°-14°and the angle of small hole is 16°-18°, the ratio of hole flow plays a leading role in the size of jet velocity. The greater the flow distribution, the greater the jet velocity. Using staggered double structure six hole oxygen lance can improve the stirring force of the jet to the molten pool.
Simulation of Sequential Turbocharging Switching Control System for Low Speed Diesel Engines
Authors: Han Yuliang , Yang Chuanlei , Wang Hechun , Wang Yinyan , Hu Deng , Wang Binbin , Duan Baoying
Published: February 2023

In order to study the sequential turbocharging switching process of low-speed diesel engine, this paper uses GT-power software to establish a simulation model of sequential turbocharging low-speed diesel engine. It is enhanced and improved into a model of a sequential supercharged diesel engine. Modules such as load, governor, valve control, and surge margin are set up in the simulation model. Then parameters such as switching speed, valve opening time and response time are set in the model. Through the above preparations, the thesis has carried out the simulation calculation of the sequential supercharging transient switching process and verified the rationality of the setting parameters and the accuracy of the module setting. This provides a certain reference for the valve control strategy of the sequential supercharging switching system of low-speed diesel engines.
Study of Flow Field Characteristics During the Impact of a High-pressure Gas Jet on a Bulk-loaded Liquid
Authors: Wang Jian , Jiang Kun , Cheng Shenshen , Wang Hao
Published: February 2023

A visual experiment platform for high-pressure gas jet impacting the bulk-loaded liquid was designed and built in order to investigate the real law of the interaction between the high-pressure gas jet and the liquid medium during the liquid-balance launch of rocket launcher. The experiments of single-phase gas jet injection and the high-pressure gas jet at different temperatures impacting the bulk-loaded liquid were carried out, and the effects of gas temperature on the characteristics of the gas-liquid flow field have been revealed. The results show that the turbulent mixing between the high-pressure gas jet and the liquid medium leads to the appearance of pressure fluctuations in the gas chamber connected to the nozzle. The higher the gas temperature, the greater the amplitude of the pressure fluctuations. Under the impact of high-pressure gas jet, a gas cavity with an arc-shaped head is formed inside the bulk-loaded liquid. The higher the gas temperature, the faster and more unstable the development of the gas cavity and the flow field. The displacement equation of the gas cavity confirms to the first-order exponential decay function, and the error between the fitting value of the established mathematical model and the measured value is within 2%.
Research and Application of Automatic Crude Oil Metering System
Authors: Zhang Liwen , Yang Xiliang , Li Genchen , Zhang Xing , Qiu Rupei
Published: February 2023

At present, China’s crude oil metering still adopts manual reading (temperature, pressure and flow), manual compensation and correction methods. The workload is heavy, and the calculation results are easy to make mistakes and difficult to manage. In order to change this situation, this paper studies and proposes an automatic compensation calculation method for crude oil metering, and develops an automatic metering and management system for crude oil. The system has the functions of automatic collection and storage of on-site data (temperature, pressure and flow), offline metering, online metering, real-time monitoring of metering process flow, query and analysis of historical data, etc., which greatly reduces the workload of workers. At the same time, through the analysis of the system uncertainty and the comparative analysis of the field experimental data, the accuracy of the automatic metering system is verified, which provides a theoretical support for the system parameter selection and operation.
Research on the Anti-Disturbance Performance of Concrete
Authors: Wang Yuan , Zheng Xinxin , Zhang Jinhong , He Rui , Wang Ke
Published: February 2023

In order to speed up the construction progress of the project, the pouring of concrete is often carried out at the same time as blasting and excavation, resulting in various vibration interference to the concrete. These vibrations damage the performance and service time of the concrete. Therefore, it is especially important to study the anti-disturbance performance of concrete. By analyzing the research results of domestic and foreign, the influence law of disturbance on concrete was summarized and its action mechanism was discussed. The evaluation methods and improvement measures for the anti-disturbance performance of concrete were summarized. In addition, the deficiencies in the previous studies were pointed out in this paper.
Study of PLA-based Wood-Plastic Composites
Authors: Li Xiangrui , Yu Jiaming , Meng Lingyu , Li Chunfeng , Liu Mingli , Meng Lipeng
Published: February 2023

In order to cope with the environmental problems of plastic pollution and greenhouse gas emission, the development and utilization of environmentally friendly materials is urgent. Polylactic acid (PLA) is a completely degradable thermoplastic aliphatic polyester, but the high cost and poor toughness of PLA limit its wide application. PLA-based wood-plastic composites (WPC), prepared by laminating PLA with wood fibers, can reduce production costs and compensate for the deficiencies of PLA mechanical properties, while still retaining biodegradability. The synthesis of PLA, the preparation of PLA-based WPC, and the performance enhancement achieved by different wood fibers prepared WPC are presented. It is hoped that this will provide guidance for the early promotion of PLA-based WPCs.
Study of ZrO2 Content on Hardness and Wear Characteristic of Coatings
Authors: Feng Pei , Shi Yuhua , Shang Peng , Peng Tongtong , Feng Rongrong , Li Bin , Zhao Xinsheng
Published: February 2023

Aluminum alloy has limited its application due to low hardness and poor wear resistance. Therefore, surface modification by electroplating is beneficial to improving hardness and wear resistance properties. Hence, Ni/W–ZrO2 coating was organized on aluminum alloy by electro-deposition method in this paper. The optimum organization parameters were obtained. The impact of different ZrO2 additions on the hardness and friction wear properties of Ni/W–ZrO2 coatings were further investigated. The SEM, Vickers examiner and wear examination are used to analyze the micromorphology, micro-hardness as well as friction and wear resistance properties, respectively. The results show that when the addition of ZrO2 was 40g/L in the deposition bath, the Ni/W–ZrO2 coating possesses the optimum micro-hardness of 384HV. This is mainly attribute to the dispersion-enhancing effect of ceramic particles. This work offers a new approach to surface strengthening technology for aluminum alloys.
Characterization and Imaging of Damage during Creep Crack Growth in 2219 Aluminum Alloy
Authors: Guo Qi , Guo Zhimin , Fu Kang , Cao Yuling , Geng Xihui , Wang Xi , Tang Shengming
Published: February 2023

Aluminum alloys have been extensively applied in aerospace field due to their light weight. Some research results show that creep crack growth is one of the main reasons for the failure of aluminum alloys in high temperature service environment. Micro-CT is a novel method to obtain damage information inside materials, which can quantitatively characterize the volume, quantity and distribution of damage. In this paper, the characterization method based on X-ray micro-CT is utilized to study the growth behavior of damage during creep crack growth of 2219 aluminum alloy. The results indicate that the growth of creep cracks requires the existence of small-volume of damages at the crack tip. And creep crack growth rate in the centre of the sample is greater than that on the surface. The existence of large-volume independent branch cracks creates conditions for the unstable propagation of creep cracks. When the crack grows locally, it does not follow the direction vertical to the stress, but preferentially connects with the surrounding damage. Whereas, the creep crack growth will eventually return to the direction perpendicular to the stress under the influence of stress.
Improving the Radon Adsorption Capacity of Activated Carbon by Liquid Nitrogen Modification
Authors: Yu Bo , Deng Xiangyuan , Wu Haibiao , Yue Chengtao , Xiao Detao
Published: February 2023

Radon is a naturally occurring radioactive inert gas that poses a significant threat to the human health. Coconut shell activated carbon has been verified to be the best radon adsorbing material, but its radon adsorption capacity still cannot meet the requirement of industrial applications. Activated carbon modification using liquid nitrogen is an effective method for improving the radon adsorption capacity, but it is necessary to determine the conditions for large-scale production. In this study, the influence of environmental temperature, container geometry, and amount of activated carbon and liquid nitrogen on the modification effect are examined. The results show that the activated carbon has the best modification effect when the container is placed in a water bath at 50 °C. The container geometry and activated carbon mass have a minor influence on the modification effect. Further, the radon adsorption capacity is increased by 36% when 6.5 L of liquid nitrogen is added to 1 kg of activated carbon. The characterization results reveal that the chemical structure and elemental content of the activated carbon do not change after modification, but the number of micropores is significantly increased, especially the micropores with a size of 0.5-0.6 nm, which is related to the radon adsorption capacity of the modified activated carbon. Overall, the liquid-nitrogen-based modification is a simple, environment-friendly, and low-cost method to improve the radon adsorption capacity of activated carbon, which can be used in the large-scale production of highly efficient radon adsorbents.
Civil Aircraft Conceptual Design for CO2 and NOx Emission Reduction
Authors: Mu Tengfei , Tao Li
Published: February 2023

With the rapid development of the air transport industry and the continuous increase of fuel consumption, the environmental problems caused by the emission of civil aircraft have been paid more attention by public. In the future, the aircraft with global market competitiveness should not only meet the indicators of economy and reliability, but also consider the requirements of environmental protection, especially the negative impact of CO2 and NOX emissions. In this research, an assessment model of aircraft emissions is established to calculate the impact of CO2 and NOX emissions on global temperature changes. Further, an optimization framework for aircraft conceptual design is established combined with the analysis models of traditional disciplines such as aerodynamics and cost. Then, aiming at the low emission of the aircraft under the condition of satisfying the performance constraints, objective optimization design studies are conduct, and the design parameter could be valuable reference for the aircraft preliminary design.
Application of Conical Surface Brakes in Cranes
Authors: Wang Songlei , Liu Fang , Jin Hui
Published: February 2023

Both drum brakes and disc brakes have their own structural limitations and advantages. As a new type of industrial brake, cone brake combines the advantages of electric hydraulic drum brake and electric hydraulic disc brake, makes up for the shortcomings of drum brake and disc brake, and greatly improves the service performance and safety performance of the brake. This paper introduces the structure composition and working principle of the conical surface brake, analyzes the advantages of the conical surface brake through the comparison with the drum brake, carries out experimental research, analyzes the test results, gives optimization suggestions for the existing shortcomings, and explores the application prospect of the new brake combined with the introduction of application examples. This paper provides a reference for the technical innovation of brake and a new choice for brake users.
Optimization Application of Deep Belief Network in Gear Fault Diagnosis
Authors: Liu Haotao , Wang Jingjing
Published: February 2023

Deep belief networks (DBNs) in the process of the application of the gear vibration signal fault diagnosis, vector network depth, the number of neurons in hidden layer, set the initial parameters, such as there is a certain blindness, and for different data sets, the influence of initial parameters is different also, in order to get ideal fault recognition rate, the initial parameters have to be repeatedly debugging, This process is not only time-consuming and laborious, but also disadvantageous to its universal application in fault diagnosis. To solve this problem, this paper mainly optimizes the number of hidden layer neurons and learning rate of DBNs. The diagnosis example shows that after optimization, the initial parameter setting is more accurate and efficient, and the fault identification rate is significantly improved.
Design of High-Precision Micro-Capacitance Detection System
Authors: Kang Jianbing , Li Jing , Liu Xuefeng , Lian Huadong , Zhang Ai
Published: February 2023

The focus of this paper is on the development of micro-displacement measurement system of Beam Steering Mechanism (BSM) and Fast Sweeping Mirror (FSM) using in space remote sensor. The main objective is to design a micro-capacitance measuring technology based on Pcap01. In the proposed approach, first, the principle of capacitance measurement and the design of hardware and software of the system are introduced; then, the system is implemented to high-precision results below 3.5nF. The experiment results show that under the 1KHz output data rate, the system can achieve a resolution of 1.4fF in the range of 1pF~30pF, which can meet the system requirements of range and accuracy ratio of 20000.
Evaluation of Electromechanical Transmission System at Vehicle Level
Authors: Xu Baorong , Wan Li , Wu Haoyang , Liu Cheng
Published: February 2023

With the rapid development and maturity of new energy technologies, electromechanical transmission systems, which deeply integrate electric transmission and mechanical transmission technologies, have been widely used in various vehicles and equipment. To ensure high efficiency and reliability of electromechanical transmission systems, this study investigated the vehicle-level comprehensive performance evaluation index system for an electromechanical transmission while focusing on the electrical properties of the transmission system. An evaluation index was constructed for the vehicle-level electromechanical transmission system. An expert investigation method was used to select and optimize the evaluation indicators, and the evaluation index system for the electromechanical transmission system was obtained. Based on an analytic hierarchy process and the grey relational algorithm, a vehicle-level evaluation method was established for the electromechanical transmission system. This study provides a theoretical basis and guidance for the validation, development, and design finalization of electromechanical hybrid vehicles.
Simulation Analysis of Personnel Evacuation Environment in Fire at Subway Platform with Different Suspended Ceiling Forms
Authors: Zhu Changlin , Li Fuyuan , Li Xiaqing , Zhang Rongguo
Published: February 2023

Taking the island platform layer of a subway station in Xi’an as the research object, the dynamic simulation sortware FDS is used to constructs the physical model of the platform layer with three different suspended ceiling forms (flat, square concave and grille). Under the condition of 5 MW fire source intensity at the platform layer, The parameters related to the personnel evacuation environment, such as the smoke spreading process, the temperature distribution of the ceiling layer, the temperature distribution at human eye characteristic height layer, the CO concentration distribution and the wind speed at the stairway, were simulated under each model, and the smoke emission effect under three different ceiling forms was compared and analyzed when the platform layer in the subway station was in fire. The results show that the square concave ceiling form can effectively slow down the flue gas spreading process and reduce the flue gas concentration outside the stairway, but it will cause local fluctuation of temperature and CO concentration distribution. The grille ceiling form can enhance the height of the smoke layer and make the evacuation in a safer environment before and during the middle stage of the fire, but too high smoke layer is not conducive to smoke exhaust.