bluuebunny/crossref_metadata_2025 huggingface dataset:
Indoor air disinfection by non thermal atmospheric pressure plasma: a comparative study of performance in low and high humidity environments
Authors: Jangra Ramavtar , Ahlawat Kiran , Mohan Medicherla Krishna , Prakash Ram
Published: July 2024

Atmospheric pressure plasma (APP) has intrigued the interest of researchers for various applications such as disinfection, air purification, etc. In this context, a deeper understanding of the correlation between APP’s characteristics like discharge parameters, active species composition, and eradication of airborne microorganisms with varying relative humidity (RH) has been examined using a dielectric barrier discharge based atmospheric pressure plasma (DBD-APP) source. One of the electrodes of the developed DBD-APP source has been coated with TiO2 nanoparticles to enhance the generation of reactive species during the discharge process. The results show that, even with the same peak-to-peak applied voltage, the peak-to-peak current and discharge power decrease with increasing RH. Optical emission spectroscopy (OES) is used to determine the relative emission intensity of the reactive species, whereas spectrophotometry is used to quantify the reactive species produced by the plasma at various parameters. Instead of UV radiation, the plasma-produced highly energetic electrons activates the TiO2 nanoparticles for electron–hole pair generation. The geometry of the plasma device has played an important role in generating high energy electrons. From the developed DBD-APP source, the airborne microorganism’s disinfection efficiency of ∼95.8% and ∼98.7% has been achieved in the total bacterial counts (TBCs) and total fungal counts (TFCs) at an RH range of 70%–90%, in just 20 min of continuous operation. However, in the RH range of 20%–40%, the inactivation efficiency dropped to ∼78.8% and ∼87.5% for the TBCs and TFCs, respectively. The outcome indicates that higher humidity levels are better for indoor air purification using DBD-APP sources and that plasma with a circulation system can effectively disinfect indoor environments.
Change in nonlinear optical response of C24 nanocage upon doping with lithium based superalkalis
Authors: Kosar Naveen , Safdar Ayesha , Imran Muhammad , Younis Adnan , Mahmood Tariq
Published: July 2024

Density functional theory (DFT) calculations are used to analyze the change in nonlinear optical (NLO) response, electronic and geometric properties of the Li based superalkalis doped C24 nanocage. It was observed that the adsorption of Li4N, Li3O and Li2F superalkalis on C24 nanocage results in thermodynamically stable isomers (A-F). The energy gap between the highest occupied and the lowest unoccupied molecular orbitals (GH-L) is reduced after superalkalis doping on carbon (C24) nanocage. Density of states spectra depict the strong contribution of superalkalis in HOMOs of the considered complexes. Natural bond orbital (NBO) charge analysis showed that the charge is being transferred from superalkali toward C24 nanocage. The values of polarizability (α

o
) and hyperpolarizability (β

o
) showed that doping of superalkalis on C24 has a significant effect on its NLO response, resulting in a considerable increase in values of α

o
and β

o
. Li4N@C24 isomer E showed the highest β

o
value of 6470.74 au. Time dependent density functional theory (TD-DFT) calculations are implemented to analyze the absorption spectra. This research provides unique and highly efficient superalkalis doped C24 isomers for their applications in future electronic devices.
Performance analysis of perovskite solar cell in presence and absence of defects
Authors: De Sarkar Pratik , Ghosh K K
Published: July 2024

Studies of the effect of defects in any solar cell are important in achieving a satisfactory level of its performance. A comparative study with a defect-free against the defect-induced cell carries instant and ready information on laboratory/industry-based fabricated cell performance, which is prone to unavoidably induced defects. In spite of good deal of works on defects of cells such a study in an organized and comparative way remains absent to the knowledge of the authors. Ready and classified presentation of such a study, therefore, is considered to be significant. Present work is a result of motivation to fulfil this gap. This article presents a study of the effects of bulk and interface defects in perovskite solar cells. On examining the effects of deep and shallow defect levels on key performance metrics such as open-circuit voltage, short-circuit current density, and fill factor, the resulting study discusses an analysis of the impact of the defects on cell efficiency. A defect-free cell with optimal perovskite, hole-transport layer (HTL), and electron-transport layer (ETL) dimensions are analysed simultaneously to assess the level at which the defects can degrade the performance of a defect-free cell. It is observed that the defects, particularly in the deep levels, significantly impair the performance of a cell, including the open circuit voltage, short circuit current density, fill factor, and efficiency, compared to those in shallow levels.
Statistical inference for marshall-olkin bivariate Kumaraswamy distribution under adaptive progressive hybrid censored dependent competing risks data
Authors: Haghverdi Vardani Mohsen , Panahi Hanieh , Behzadi Mohammad Hassan
Published: July 2024

The statistical inference under competing risks model is of great significance in reliability analysis and it is more practical to assume that they have dependent competing causes of failure in actual situations. In this article, we make inference for unknown parameters of a Marshall-Olkin bivariate Kumaraswamy distribution under adaptive progressive hybrid censoring mechanism. The maximum likelihood estimations of the unknown parameters are derived, and the Fisher information matrix is then employed to construct asymptotic confidence intervals. Bayes estimates are evaluated against squared error and linex loss functions assuming ordered Gamma-Dirichlet and Gamma-Dirichlet prior distributions for order restriction and without order restriction cases respectively. The Metropolis-Hasting and Lindley techniques are applied to acquire the estimates of all unknown parameters. A thorough simulation analysis is demonstrated to assess the performance of the supplied approaches across various sample sizes. The usefulness of the techniques is illustrated using real engineering data to prove their versatility in practical applications.
A numerical aproach to dispersion-dissipation-reaction model: third order KdV-Burger-Fisher equation
Authors: Esen Alaattin , Karaagac Berat , Yagmurlu Nuri Murat , Ucar Yusuf , Manafian Jalil
Published: July 2024

In this study, an efficient numerical method is applied to KdV-Burger-Fisher equation which is one of the dispersion-dissipation–reaction model. The present method is based on the collocation method whose weight functions are taken from the family of the Dirac delta functions in finite element methods. The element functions are selected as quintic trigonometric B-spline basis. The error norms L
2 and L
∞ are calculated to measure the efficiency of the method. Numerical solutions and error norms which are obtained via collocation method and trigonometric basis are presented in tables and simulations of the solutions are exhibited as well. Additionally, stability analysis is investigated.
Image encryption scheme based on pseudo-DWT and cubic S-box
Authors: Qiao Linhao , Mei Qixiang , Jia Xingxing , Ye Guodong
Published: July 2024

Combining a pseudo-Discrete Wavelet Transform (pseudo-DWT) and a novel cubic S-box technique, an image encryption scheme using a newly-developed four-dimensional hyperchaotic system (NewHS) is presented in this paper. The principal advantage of this method resides in its enhanced security, with hash values (computed by SHA-256) of the plaintext, thereby bolstering resistance to chosen-plaintext attack. Initially, a novel three-dimensional cubic S-box is designed via chaotic sequence, increasing the complexity and randomness. Subsequently, the proposed scheme employs a Ladder permutation for image scrambling, achieving a one-time pad encryption effect. Finally, a pseudo-DWT is devised to segment and reconstruct the image, implementing scrambling and diffusion encryption. Moreover, experiments and security analysis also prove that the proposed encryption scheme can show good performance.
Use of Nash equilibrium in finding game theoretic robust security bound on quantum bit error rate
Authors: Dutta Arindam , Pathak Anirban
Published: July 2024

Nash equilibrium is employed to find a game theoretic robust security bound on quantum bit error rate (QBER) for DL04 protocol which is a scheme for quantum secure direct communication that has been experimentally realized recently. The receiver, sender and eavesdropper (Eve) are considered to be quantum players (players having the capability to perform quantum operations). Specifically, Eve is considered to have the capability of performing quantum attacks (e.g., Wójcik’s original attack, Wójcik’s symmetrized attack and Pavičić attack) and classical intercept and resend attack. Game theoretic analysis of the security of DL04 protocol in the above scenario is performed by considering several game scenarios. The analysis revealed the absence of a Pareto optimal Nash equilibrium point within these game scenarios. Consequently, mixed strategy Nash equilibrium points are identified and employed to establish both upper and lower bounds for QBER. Further, the vulnerability of the DL04 protocol to Pavičić attack in the message mode is established. In addition, it is observed that the quantum attacks performed by Eve are more powerful than the classical attack, as the QBER value and the probability of detecting Eve’s presence are found to be lower in quantum attacks compared to classical ones.
Dynamical analysis of high-order Hopfield neural network with application in WBANs
Authors: Liu Dingfa , Zhang Juan , Njitacke Zeric Tabekoueng , Jean De Dieu Nkapkop , Jiang Donghua , Ruben Mouangue
Published: July 2024

Given the increasing demand for privacy preservation of medical data, a novel medical image encryption scheme is proposed based on Invertible Neural Network (INN) in this paper. Firstly, a new High-Order Hopfield Neural Network (HOHNN) is designed to yield a cipher flow as the conditional input, thereby regulating the encryption process. Moreover, its intrinsic properties as well as various dynamic behaviors are both demonstrated through theoretical analysis and two-parameter Lyapunov exponential charts. Secondly, guided by a multi-objective loss function and a known prior distribution, the original medical image is encrypted into a noise-like cipher image through the proposed encryption scheme. Besides, it is worth mentioning that unlike the existing deep learning-based data encryption schemes, the decryption network shares the identical weight matrix and network structure with the corresponding encryption one in this work. Finally, extensive simulation experiments have validated the feasibility as well as the security of the proposed scheme.
Dependence of thermodynamic quantities at freeze-out on pseudorapidity and collision energy in p-p collisions at LHC energies*
Authors: Badshah Murad , Obaidat Yahia A.H. , Alrebdi Haifa I. , Waqas M. , Ajaz Muhammad , Ghodhbani Refka
Published: July 2024

The transverse momentum distributions of charged hadrons produced in proton-proton collisions at center-of-mass energies (

) of 0.9 TeV and 2.36 TeV, as measured by the CMS detector at the Large Hadron Collider (LHC), have been analyzed within various pseudorapidity classes utilizing the thermodynamically consistent Tsallis distribution. The fitting procedure resulted in the key parameters, namely, effective temperature (T), non-extensivity parameter (q), and kinetic freezeout volume (V). Additionally, the mean transverse momentum (

) and initial temperature (Ti
) of the particle source are determined through the fit function and string percolation method, respectively. An alternative method is employed to calculate the kinetic freezeout temperature (

) and transverse flow velocity (

) from T. Furthermore, thermodynamic quantities at the freezeout, including energy density (ε), particle density (n), entropy density (s), pressure (P), and squared speed of sound (

), are computed using the extracted T and q. It is also observed that, with a decrease in pseudorapidity, all thermodynamic quantities except V and q increase. This trend is attributed to greater energy transfer along the mid pseudorapidity. q increases towards higher values of pseudorapidity, indicating that particles close to the beam axis are far from equilibrium. Meanwhile, V remains nearly independent of pseudorapidity. The excitation function of these parameters (q) shows a direct (inverse) correlation with collision energy. The ε, n, s, and P show a strong dependence on collision energies at low pseudorapidities. Explicit verification of the thermodynamic inequality

suggests the formation of a highly dense droplet-like Quark-Gluon Plasma (QGP). Additionally, the inequality

is explicitly confirmed, aligning with the evolution of the produced fireball.
Inner fission barriers of uranium isotopes in the deformed relativistic Hartree-Bogoliubov theory in continuum*
Authors: Zhang 张 Wei 炜 , Huang 黄 Jin-Ke 靳岢 , Sun 孙 Ting-Ting 亭亭 , Peng 彭 Jing 婧 , Zhang 张 Shuang-Quan 双全
Published: July 2024

The inner fission barriers of the even-even uranium isotopes from the proton to the neutron drip line are examined using the deformed relativistic Hartree-Bogoliubov theory in continuum. A periodic-like evolution for the ground state shapes is shown with respect to the neutron number, i.e., spherical shapes at shell closures

126, 184, 258, and prolate dominated shapes between them. Analogous to the shape evolution, the inner fission barriers also exhibit a periodic-like behavior: peaks at the shell closures and valleys in the mid-shells. The triaxial effect on the inner fission barrier is evaluated using triaxial relativistic mean field calculations combined with a simple BCS method for pairing. When the triaxial correction is included, the inner barrier heights show good consistency with available empirical data. Additionally, the evolution from the proton to the neutron drip line aligns with results from the multi-dimensionally constrained relativistic mean field theory. A flat valley in the fission barrier height is predicted around the neutron-rich nucleus

U which may play a role of fission recycling in astrophysical r-process nucleosynthesis.
Current-collapse suppression and leakage-current decrease in AlGaN/GaN HEMT by sputter-TaN gate-dielectric layer
Authors: Liu Bosen , Yu Guohao , Jia Huimin , Zhu Jingyuan , Zhou Jiaan , Li Yu , Zhang Bingliang , Du Zhongkai , Guo Bohan , Wang Lu , Huang Qizhi , Jiang Leifeng , Zeng Zhongming , Wei Zhipeng , Zhang Baoshun
Published: July 2024

In this paper, we explore the electrical characteristics of high-electron-mobility transistors (HEMTs) using a TaN/AlGaN/GaN metal insulating semiconductor (MIS) structure. The high-resistance tantalum nitride (TaN) film prepared by magnetron sputtering as the gate dielectric layer of the device achieved an effective reduction of electronic states at the TaN/AlGaN interface, and reducing the gate leakage current of the MIS HEMT, its performance was enhanced. The HEMT exhibited a low gate leakage current of 2.15 × 10−7 mA/mm and a breakdown voltage of 1180 V. Furthermore, the MIS HEMT displayed exceptional operational stability during dynamic tests, with dynamic resistance remaining only 1.39 times even under 400 V stress.
Implementation of sub-100 nm vertical channel-all-around (CAA) thin-film transistor using thermal atomic layer deposited IGZO channel
Authors: Chen Yuting , Duan Xinlv , Ma Xueli , Yuan Peng , Jiao Zhengying , Shen Yongqing , Chai Liguo , Luan Qingjie , Xiang Jinjuan , Geng Di , Wang Guilei , Zhao Chao
Published: July 2024

In–Ga–Zn–O (IGZO) channel based thin-film transistors (TFT), which exhibit high on–off current ratio and relatively high mobility, has been widely researched due to its back end of line (BEOL)-compatible potential for the next generation dynamic random access memory (DRAM) application. In this work, thermal atomic layer deposition (TALD) indium gallium zinc oxide (IGZO) technology was explored. It was found that the atomic composition and the physical properties of the IGZO films can be modulated by changing the sub-cycles number during atomic layer deposition (ALD) process. In addition, thin-film transistors (TFTs) with vertical channel-all-around (CAA) structure were realized to explore the influence of different IGZO films as channel layers on the performance of transistors. Our research demonstrates that TALD is crucial for high density integration technology, and the proposed vertical IGZO CAA-TFT provides a feasible path to break through the technical problems for the continuous scale of electronic equipment.
Memristive feature and mechanism induced by laser-doping in defect-free 2D semiconductor materials
Authors: Du Xiaoshan , Wang Shu , Zhang Qiaoxuan , Chen Shengyao , Yang Fengyou , Liu Zhenzhou , Fan Zhengwei , Ma Lijun , Wang Lei , Du Lena , Wang Zhongchang , Wang Cong , Chen Bing , Liu Qian
Published: July 2024

Memristors as non-volatile memory devices have gained numerous attentions owing to their advantages in storage, in-memory computing, synaptic applications, etc. In recent years, two-dimensional (2D) materials with moderate defects have been discovered to exist memristive feature. However, it is very difficult to obtain moderate defect degree in 2D materials, and studied on modulation means and mechanism becomes urgent and essential. In this work, we realized memristive feature with a bipolar switching and a configurable on/off ratio in a two-terminal MoS2 device (on/off ratio ~100), for the first time, from absent to present using laser-modulation to few-layer defect-free MoS2 (about 10 layers), and its retention time in both high resistance state and low resistance state can reach 2 × 104 s. The mechanism of the laser-induced memristive feature has been cleared by dynamic Monte Carlo simulations and first-principles calculations. Furthermore, we verified the universality of the laser-modulation by investigating other 2D materials of TMDs. Our work will open a route to modulate and optimize the performance of 2D semiconductor memristive devices.
Assembly of functional carboxymethyl cellulose/polyethylene oxide/anatase TiO2 nanocomposites and tuning the dielectric relaxation, optical, and photoluminescence performances
Authors: Ismail Asmaa M. , Reffaee Abeer A. , El Desouky Fawzy G.
Published: July 2024

Nanocomposite films consisting of carboxymethyl cellulose, polyethylene oxide (CMC/PEO), and anatase titanium dioxide (TO) were produced by the use of sol-gel and solution casting techniques. TiO2 nanocrystals were effectively incorporated into CMC/PEO polymers, as shown by X-ray diffraction (XRD) and attenuated total reflectance fourier transform infrared (ATR-FTIR) analysis. The roughness growth is at high levels of TO nanocrystals (TO NCs), which means increasing active sites and defects in CMC/PEO. In differential scanning calorimetry (DSC) thermograms, the change in glass transition temperature (T
g) values verifies that the polymer blend interacts with TO NCs. The increment proportions of TO NCs have a notable impact on the dielectric performances of the nanocomposites, as observed. The electrical properties of the CMC/PEO/TO nanocomposite undergo significant changes. The nanocomposite films exhibit a red alteration in the absorption edge as the concentration of TO NCs increases in the polymer blend. The decline in the energy gap is readily apparent as the weight percentage of TO NCs increases. The photoluminescence (PL) emission spectra indicate that the sites of the luminescence peak maximums show slight variation; peaks get wider, while their intensities decrease dramatically as the concentration of TO increases. These nanocomposite materials show potential for multifunctional applications including optoelectronics, antireflection coatings, photocatalysis, light emitting diodes, and solid polymer electrolytes.
Identifying alterations in hand movement coordination from chronic stroke survivors using a wearable high-density EMG sleeve
Authors: Tacca Nicholas , Baumgart Ian , Schlink Bryan R , Kamath Ashwini , Dunlap Collin , Darrow Michael J , Colachis IV Samuel , Putnam Philip , Branch Joshua , Wengerd Lauren , Friedenberg David A , Meyers Eric C
Published: July 2024

Objective. Non-invasive, high-density electromyography (HD-EMG) has emerged as a useful tool to collect a range of neurophysiological motor information. Recent studies have demonstrated changes in EMG features that occur after stroke, which correlate with functional ability, highlighting their potential use as biomarkers. However, previous studies have largely explored these EMG features in isolation with individual electrodes to assess gross movements, limiting their potential clinical utility. This study aims to predict hand function of stroke survivors by combining interpretable features extracted from a wearable HD-EMG forearm sleeve. Approach. Here, able-bodied (N = 7) and chronic stroke subjects (N = 7) performed 12 functional hand and wrist movements while HD-EMG was recorded using a wearable sleeve. A variety of HD-EMG features, or views, were decomposed to assess alterations in motor coordination. Main Results. Stroke subjects, on average, had higher co-contraction and reduced muscle coupling when attempting to open their hand and actuate their thumb. Additionally, muscle synergies decomposed in the stroke population were relatively preserved, with a large spatial overlap in composition of matched synergies. Alterations in synergy composition demonstrated reduced coupling between digit extensors and muscles that actuate the thumb, as well as an increase in flexor activity in the stroke group. Average synergy activations during movements revealed differences in coordination, highlighting overactivation of antagonist muscles and compensatory strategies. When combining co-contraction and muscle synergy features, the first principal component was strongly correlated with upper-extremity Fugl Meyer hand sub-score of stroke participants (R
2 = 0.86). Principal component embeddings of individual features revealed interpretable measures of motor coordination and muscle coupling alterations. Significance. These results demonstrate the feasibility of predicting motor function through features decomposed from a wearable HD-EMG sleeve, which could be leveraged to improve stroke research and clinical care.
Ion heating/transport characteristics of the merging startup plasma scenario in the TS-6 spherical tokamak
Authors: Tanabe H. , Cai Y. , Tanaka H. , Ahmadi T. , Inomoto M. , Ono Y.
Published: July 2024

Here we report the ion heating/transport characteristics of the merging startup scenario in the TS-6 spherical tokamak. In addition to the previously investigated impulsive heating process during magnetic reconnection, here we also focus on a longer time scale response of the ion temperature profile both during and after merging, including the semi-steady plasma confinement phase. During magnetic reconnection, (i) the ion temperature profile forms a poloidally asymmetric profile around the X-point in the initiation phase and (ii) radially asymmetric higher deposition is obtained at the high field side. After merging, (iii) the radially asymmetric double-peak structure is affected by parallel heat conduction and is aligned with field lines, but it does not simply become a flux function on a microsecond time scale—inboard/outboard asymmetry lasts even in the semi-steady confinement phase. (iv) Under the influence of the low-aspect-ratio configuration, there is a two to three times higher toroidal field on the high-field side on the same closed flux surface: characteristic asymmetry of inboard/outboard ion temperature has been found experimentally for the first time.
An active fractional Ornstein–Uhlenbeck particle: diffusion and dissipation
Authors: Rangaig Norodin A
Published: July 2024

In this work, we consider a particle subjected to active fluctuations due to the presence of an active bath. The active fluctuation driving the particle is modeled as an Ornstein–Uhlenbeck process with memory, due to the recent experimental result in that a bacterial bath under a chemotactic mechanism exhibits a large distribution of persistence time, which may result in long-range persistence of a probe particle that cannot be captured by the conventional Ornstein–Uhlenbeck model for active noise. As a paradigmatic model, we consider introducing a fractional Ornstein–Uhlenbeck process with a power-law kernel, which includes a fractional order variable

0
<
α
⩽
1

, to model an active noise acting on a particle. We present the relevant properties of the active noise and its implications for the diffusion of free and harmonically confined single particles. This is also supported by the derived active Smoluchowski description. More importantly, we find that the effect of α can either reduce or increase the effective temperature at long time, depending on the competition between the harmonic timescale and persistence time. Lastly, the effects of presented active noise on the spectral density of the energy dissipation rate and the dissipation energy from both the thermal and active bath are explored.
Power-law relaxation of a confined diffusing particle subject to resetting with memory
Authors: Boyer Denis , Majumdar Satya N
Published: July 2024

We study the relaxation of a Brownian particle with long range memory under confinement in one dimension. The particle diffuses in an arbitrary confining potential and resets at random times to previously visited positions, chosen with a probability proportional to the local time spent there by the particle since the initial time. This model mimics an animal which moves erratically in its home range and returns preferentially to familiar places from time to time, as observed in nature. The steady state density of the position is given by the equilibrium Gibbs–Boltzmann distribution, as in standard diffusion, while the transient part of the density can be obtained through a mapping of the Fokker–Planck equation of the process to a Schrödinger eigenvalue problem. Due to memory, the approach at late times toward the steady state is critically self-organised, in the sense that it always follows a sluggish power-law form, in contrast to the exponential decay that characterises Markov processes. The exponent of this power-law depends in a simple way on the resetting rate and on the leading relaxation rate of the Brownian particle in the absence of resetting. We apply these findings to several exactly solvable examples, such as the harmonic, V-shaped and box potentials.
Monte Carlo study of frustrated Ising model with nearest- and next-nearest-neighbor interactions in generalized triangular lattices
Authors: Jang Hoseung , Yu Unjong
Published: July 2024

We investigate the frustrated J
1–J
2 Ising model with nearest-neighbor interaction J
1 and next-nearest-neighbor interaction J
2 in two kinds of generalized triangular lattices (GTLs) employing the Wang–Landau Monte Carlo method and finite-size scaling analysis. In the first GTL (GTL1), featuring anisotropic properties, we identify three kinds of super-antiferromagnetic ground states with stripe structures. Meanwhile, in the second GTL (GTL2), which is non-regular in next-nearest-neighbor interaction, the ferrimagnetic 3×3 and two kinds of partial spin liquid (PSL) ground states are observed. We confirm that residual entropy is proportional to the number of spins in the PSL ground states. Additionally, we construct finite-temperature phase diagrams for ferromagnetic nearest-neighbor and antiferromagnetic next-nearest-neighbor interactions. In GTL1, the transition into the ferromagnetic phase is continuous, contrasting with the first-order transition into the stripe phase. In GTL2, the critical temperature into the ferromagnetic ground state decreases as antiferromagnetic next-nearest-neighbor interaction intensifies until it meets the 3×3 phase boundary. For intermediate values of the next-nearest-neighbor interaction, two successive transitions emerge: one from the paramagnetic phase to the ferromagnetic phase, followed by the other transition from the ferromagnetic phase to the 3×3 phase.
A scaling region identification method for the divider dimension of urban thermal environments
Authors: Tao Sulin , Li Yuhong
Published: July 2024

A scaling region identification method for divider dimensions using the coefficient of determination is proposed to improve the estimation accuracy of the divider dimension in the study of urban thermal environment differentiation characteristics. The effectiveness of this method was verified by analyzing the urban surface thermal field differentiation characteristics by applying the estimated divider dimensions of Nanjing’s thermal environment surfaces and transect lines. The research results show that the urban thermal environment has fractal characteristics only within a certain temperature threshold range. When the constraint of scaling regions is considered, the calculated divider dimension of the surface thermal field surface increases, reflecting the more complex fractal structure of the thermal field. For each temperature grade, the “trough” position of the thermal field divider dimension surface estimated by the line-divider method is near the determination level of the high-temperature region based on robust statistics, allowing the spatial extent of the urban heat island (UHI) to be determined based on the “trough” feature of the thermal field divider dimension surface.
Analysis of wheel-rail contact under oil lubrication conditions
Authors: Li Yaojie , Tian Chun , Zhou Jiajun , Zhai Gengwei
Published: July 2024

This investigation centers on the characteristics of the contact between the wheel and rail when lubricated with oil, with a consideration of the impact of surface roughness. Confronting significant challenges related to low adhesion, a thorough examination is undertaken to analyze the changes in film thickness under oil lubrication, investigating trends at varying vehicle speeds and axle loads. Employing detailed modeling based on micro-elastohydrodynamic theory, the distribution of oil film thickness under diverse operational conditions is determined. The findings indicate that, under oil lubrication, a film thickness in the range of several tens of micrometers is established, effectively insulating the surfaces of the wheel and rail, thereby reducing adhesion. With increasing vehicle speed, the thickness of the oil film also rises, whereas an elevation in axle load results in a marginal decrease in film thickness. This research contributes to a comprehensive comprehension of the wheel-rail contact mechanism in oil lubrication scenarios, providing theoretical backing to address concerns related to low adhesion. The implications are substantial for improving the safety and economic efficiency of efficient railway transportation.
Research on the progress of particle-bubble transport
Authors: Liang Zihao , Wang Jinfeng , Sun Weihua , Ye Guosen , Jiang Jilin , Han Xinrong
Published: July 2024

Due to the pressing need for efficient and environmentally friendly utilization of low-quality mineral resources in the field of mineral processing, there has been a growing focus on investigating the flotation method. Foam flotation is widely employed as a means to separate different valuable minerals. The underlying mechanism involves numerous buoyant bubbles within the fluid that come into contact with and transport target mineral particles towards the upper apex of the fluid, resulting in the formation of a foam layer. This foam layer serves as a collection point for valuable target minerals, thereby facilitating their separation and recovery. This paper reviews the research progress of flotation to the present, and the source, purpose, and significance of flotation research are discussed first. Secondly, the great changes brought by the simulation method to the optimization of flotation performance are demonstrated. Finally, the sub-process mechanism of flotation is discussed. Through the above investigation on the progress of particle-bubble transport, the importance of bubbles and particles to the improvement or reduction of flotation performance is clarified, and the follow-up research and engineering practice are guided.
Numerical investigation of elliptical trailing edge on cascade loss of transonic turbine airfoils
Authors: Wei Shuang , Wang Jinhuo , Chen Yipeng , Geng Zhangnan , Liu Qinglong
Published: July 2024

The shape and thickness of the trailing edge are important factors in the supersonic loss in transonic cascades. To investigate the influence of trailing edge shape, a prismatic turbine cascade and a three-dimensional cascade with an elliptic trailing edge were analyzed with numerical simulation by changing different elliptic axis ratios ER. It was indicated that the shock wave and its mixing with the wake were the important sources of loss in the transonic prismatic cascade. With the increase of exit Mach number, shock waves are generated rapidly and migrate downstream, and the shock loss and the total loss of the prismatic cascade are both accrescent. Increasing the elliptical axis ratio could weaken shock waves and delay shock waves. In the loss state region 3, the cascade loss of the ER3 blade is reduced by 8% compared with the round trailing edge cascade. As the elliptical axis ratio of the three-dimensional cascade is increasing, the profile loss and secondary loss are reduced. However, an excessive elliptical axis ratio could lead to an increase in tip leakage loss. Within the range of ER values from 0 to 3, the total loss of the transonic three-dimensional cascade reached minimization when ER was 3.0.
Research on simulation calculation method of local strength of swath ship stabilizing fins based on sub-model method
Authors: Jiang Xueyun , Zhang Song , Chen Kezhong , Li Xiangyuan
Published: July 2024

At present, there is little research on the strength simulation calculation method of local steel structure at the joint between the fin stabilizer and hull of SWATH at home and abroad. Aiming at the problems of high-stress levels and difficult local strength of the local structure at the joint of SWATH submersible and stable fin, this paper, based on APDL language, takes a SWATH ship as an example, establishes a whole ship simulation model, analyses and studies the modeling scope, modeling requirements, boundary conditions, and loading methods of the local calculation model of stable fin, and puts forward an efficient simulation calculation and analysis method, namely sub-model method, which is suitable for the local strength calculation of stable fin, and provides guidance for the structural design method of the stable fin of SWATH catamaran.
Numerical simulation of response behavior and damage regularity of human lower limbs under axial impact load
Authors: Wang Yuhong , Wang Xianhui , Ma Ning , Zhou Qiang , Wang Jianguo , Sun Xiaowang
Published: July 2024

Axial impacts to the lower extremities of personnel in events such as explosions and falls on the underside of vehicles, which are extremely hazardous to personnel, may result in serious injuries. Most of the current studies on human lower limb injuries from axial loading have not considered the restraining effect of the knee joint. In this paper, based on the THUMS human finite element model, the failure parameters of the tibia, calcaneus, and talus of the lower limb are added and verified. On this basis, the response behavior of the lower limbs of personnel under different axial loads is investigated, and the damage law is further analyzed and studied. It is found that the motion of human lower limbs under axial impact is divided into two phases: the axial motion phase and the rotation phase around the knee joint, and the lower limbs are mainly subjected to compression and bending loads, respectively. The duration of the axial motion phase is related to the impact velocity and the rate of change of velocity and affects the magnitude of tibial force.
Simulation study of jet trajectory based on Runge-Kutta method
Authors: Tang Yaling , Zhao Lei , Zhang Xuefeng
Published: July 2024

To solve the problem of not being able to accurately spray to the designated target point due to wind and distance factors when firefighting at a long distance, this paper adopts the Runge-Kutta algorithm to simulate the trajectory of the fire cannon, and establishes the mathematical model of the trajectory of the jet under the ideal state and the trajectory of the jet under the influence of the wind. We carry out three-dimensional visualization research and compare the results of the simulation experiment with the real experimental data, and the range, height, and trajectory have a high degree of fit. Comparing the simulation results with the real experimental data, the range and height of the jet and the trajectory have a high degree of affinity, and adding the wind power value panel in the visualization interface can simulate the changes of the jet trajectory under different wind speeds and wind power and effectively simulate the trajectory of the jet under natural conditions.
Simulation research of the influence of different representative wavelengths on colorimetric temperature measurement accuracy
Authors: Qi Bowei , Jiang Zhiwei
Published: July 2024

Colorimetric temperature measurement can achieve greater accuracy by obtaining data on the spectral radiance at two representative wavelengths. As color CCD cameras have three pairs of color combinations, the research would explore the accuracy of these three combinations in temperature measurement by simulation research. The stimulation values of the CCD camera for the three primary colors often differ from the three primary color wavelengths specified by the CIE. Therefore, through conducting comparative temperature measurement experiments on simulated objects, the research assesses the accuracy of color temperature measurement by comparing the performance of the CIE-specified wavelengths for the three primary colors with the stimulus values of a color CCD camera. Additionally, this research would also investigate the impact of differences in representative wavelengths on the accuracy of non-grey body temperature measurements.
Exploration of the effect of hot smoke generated by tunnel fire on the ventilation flow field of jet fan
Authors: Peng Xinyi , Zhao Weifeng , Zhang Xinyue
Published: July 2024

To reduce the hazard of hot smoke from tunnel fires, ventilation becomes a necessary control strategy. Uniform ventilation is the main method used in the study of tunnel fires, but it has obvious differences from the widely used jet fan ventilation in practice, and the two have different performances in controlling smoke. Therefore, the distribution of the upstream flow field with jet fan ventilation will be studied in a tunnel fire. Considering several parameters such as the HRR and the velocity of fan exit, numerical simulations were conducted to monitor the fire development by using a Fire dynamics simulator (FDS). The results suggest that the center-line velocity decay of a jet fan can be categorized into three regions: linear decay, power function decay, and stabilization. The decay coefficient (n) related to power function decay correlates with HRR, and therefore, a new prediction for the center-line velocity distribution of the jet fan is proposed. The predicted results correlate well with the available experimental data.
Simulation study on the effect of liquid ammonia spray on the heat transfer performance of multiple heat exchange tubes
Authors: Zhao Shouzheng , Zhao Songsong , Shi Yaoguang , Zhu Zongsheng , Liu Jianyu
Published: July 2024

In this paper, aiming at the problems of low heat transfer efficiency and uneven heat transfer of heat exchange tubes in refrigeration and air conditioning chillers, a liquid ammonia spray cooling method is proposed, and a flow and heat transfer model is established. The distribution of refrigerant droplets in the fluid domain and the heat transfer on the surface of the heat exchange tube are simulated under different spray speeds, spray directions, and double nozzle sprays. The results show that with the increase of spray velocity, the heat transfer performance of heat exchange tubes decreases first and then increases. The effect of spray velocity on the heat transfer performance of each row of heat exchange tubes is not consistent. The farther away it is from the nozzle, the greater the speed corresponding to the peak value of the heat transfer performance improvement of the heat exchange tube will be; the spray direction (gravity) has little influence on the heat transfer performance of the heat exchange tube, which is within 5.1%. Compared with single-nozzle spray, double-nozzle spray greatly improves the heat transfer performance of multi-row heat exchange tubes.
Geometry-based multi-beam survey line layout problem
Authors: Li Chuangqi , Wang Yuhang , Hu Fan
Published: July 2024

The multi-beam measurement system plays a crucial role in ocean mapping and underwater terrain detection. By simultaneously transmitting multiple beams, the system can accurately receive sound waves reflected from the seabed, providing more precise and comprehensive water depth information while effectively revealing the complexity and characteristics of underwater terrain. Under the background and application provided by Question B of the 2023 National Mathematical Contest in Modeling for College Students, this paper investigates the relationship between ocean floor width measurement and factors such as beam position, angle, and slope. Utilizing geometric relations, trigonometric similarity, and sine theorem, a mathematical model is established to determine adjacent strip coverage width and overlap ratio. Furthermore, an optimal strategy is determined by using a greedy algorithm, while binary search backtracking is employed to derive the interval of the next adjacent survey line with the required overlap ratio to obtain an optimal terrain detection strategy.
Simulation and verification of cylinder head’s temperature field for marine low-speed engine
Authors: Hu Lei , Chen Yangfan , Luo Qiang
Published: July 2024

The high load capacity of marine low-speed engines poses a challenge to the thermal load of the cylinder head and temperature field simulation can guide its structural design and optimization. The 3-dimensional models of the fluid domain for the cooling water and the solid domain for the cylinder head are established and meshed, the fluid domain model is simulated to research the heat transfer pattern by Fluent software, and the surface temperature and heat transfer coefficient of the cooling water is calculated. The thermal boundary conditions of the gas in the cylinder are simulated through the analysis of the engine working process. The temperature of the cylinder head is calculated based on the fluid-structure interaction model with the thermal boundary conditions by Workbench software. The validation of the model is carried out by comparing the simulated and measured temperature data in the heated inner wall of the cylinder head. The research results show that compared with the measured value, the error of simulation results is small, which shows that the model and method are reasonable. The temperature in the inner wall of the combustion chamber is low, which can provide possibilities to appropriately improve the power density of the low-speed engine and reduce the risk of low-temperature corrosion.
Investigation of geometrical hopper and initial packing state on the inter-phase momentum transfer with granular flow in vertical packed bed
Authors: Fu Chunpeng
Published: July 2024

For the specific application of vertical packed bed design, the main task is to optimize and improve the granular flow pattern, since a worse granular flow pattern is detrimental to the performance of heat transfer and flow in vertical packed bed. To improve the uniformity of granular flow profiles, an application of the discrete element method is used to investigate the granular flow pattern in a vertically packed bed under the condition of different tapered hopper angles and initial packing states. The uniformity of granular dramatically decreases with an increase in the fluctuation of granular velocity distribution. The variation of structural parameters has a positive influence on enhancing the stability of the granular layer. Coefficient of variation and relative fluctuation kinetic energy are introduced as criteria to describe the stability of the granular layer. This study numerically reveals the evolution of initial packing states has a slight influence on improving the stability of granular flow.
Simulation calculation and optimization of hydraulic buffer device based on Simulink
Authors: Wang Lliuhuo , Hu Sukai , Qi Han , Sun Qiang
Published: July 2024

When the hydraulic cylinder moves at high speed to the end of the stroke, it usually produces severe pressure, shock, and vibration, and makes the system very unstable, so the buffer device is often used to buffer the deceleration process of the hydraulic cylinder. In this paper, the cushioning process of a high-pressure hydraulic cylinder buffer device is modeled mathematically, the motion parameters in the cushioning process are calculated based on Simulink, and different structural parameters of the cylinder block are optimized and compared, to study the influence of structural parameters of the cushioning device on the cushioning process.
Research on the influence of cutting surface characteristics on the cutting load of the conical pick
Authors: Liu Jinxia , Zeng Fanchang , Zhang Chao
Published: July 2024

A coal rock cutting model was established using ANSYS/LS-DYNA and the influence of different cutting surfaces was studied. By using the control variable method, simulation experiments are conducted on single and multiple conical picks cutting under the different ratios of cutting spacing to the cutting thickness. The variation pattern of the cutting correlation is obtained. The conclusion is that when the ratio is 2-2.5, there is a significant cutting correlation between adjacent picks, and the conical picks have the best cutting performance. As the ratio increases, the cutting correlation between adjacent picks weakens, which is not conducive to the cutting of the pick. This conclusion has important guiding significance for the design of cutting parameters.
Dynamic response analysis of ship reef hard grounding
Authors: Liang Enqiang , Kong Jiali , Zheng Minghui , Li Shengtao
Published: July 2024

With the rapid growth of the world economy, the shipping industry has developed rapidly on a global scale, and the water traffic has become increasingly busy. Therefore, the risk of ship transportation has become bigger and bigger, and ship grounding and collision occupy about 50% of the total number of all accidents, among which the consequences of oil tanker grounding accidents are more serious, which not only jeopardize the safety of the personnel but also cause a large area of pollution to the sea. Therefore, it is particularly important to study the ship grounding and collision of oil tankers. Based on the nonlinear finite element software ABAQUS, a calculation model for oil tanker grounding is established, and simplified boundary conditions that can be used for grounding simulation analysis are determined. At the same time, material strain rate sensitivity and material hardening properties are considered. Based on the quasi-static tensile test data of Q235 steel used in ships, material parameters that meet the requirements of collision simulation calculation are calibrated and calculated. The dynamic response of hard grounding is analyzed from both external and internal mechanisms. The research results can provide a reference for improving the grounding collision performance of oil tankers.