bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal enhancement of couple stress fluid flow through anisotropic porous media
Authors: Bhargavi D. , Aich Rishav , Gupta Nitish
Published: April 2024

This study examines forced convective heat transfer via an anisotropic porous channel in a couple stress flow. The flow field is assumed to be fully developed and governed by the Darcy Brinkman Forchheimer equation. The thermal field is assumed to be developing. The channel walls are subjected to constant heat flux. Since the momentum equation is non-linear and the thermal energy equation is linear, coupled equations are solved numerically using the finite difference method. The variation in the bulk mean temperature is linear with the axial distance for all values of the couple stress parameter and Darcy number. In the absence of axial conduction and heat sources or sinks in the flow field, it is easy to see that the energy gained by the fluid up to an axial distance is twice the axial distance. The parameters, anisotropic permeability ratio, and anisotropic angle enhance the heat transfer. The couple stress parameter lessens the enhancement in heat transfer. Anisotropy is critical in heat transmission for Darcy number, DaH≤0.8. The heat transfer rate decreases by more than 40% due to couple stress fluid and anisotropic effects in the channel, as opposed to the Newtonian isotropic situation. This investigation's findings have been compared with previous experimental and numerical research.
Multichannel Doppler fiber-imager spectrometer for spatiotemporal characterization of high-intensity laser-driven plasmas
Authors: Zeraouli G. , Marconi M. , Sullivan B. , Wang S. , Anaraki S. Zahedpour , Hollinger R. , Shlyaptsev S. , Mariscal D. , Rocca J. J.
Published: April 2024

We demonstrate a flexible multichannel fiber-based imaging Doppler spectrometer to characterize plasmas in high intensity (≥1 × 1018 W/cm2) laser-plasma experiments at high repetition rates. This instrument collects data from ×21 different plasma locations combining optical fibers and a single imaging spectrometer. This diagnostic maps the plasma velocity evolution as a function of time with sub-pico-second resolution. Experimental results showing 2D velocity measurements of plasma with 20 μm spatial resolution are presented. Intensities of the order of 1018 W/cm2 were used to generate a plasma, while a much less intense, frequency doubled (400 nm), probe beam (1011 W/cm2) was used to measure the Doppler shift from the plasma critical surface. The instrument can be scaled to a larger number of channels (e.g., 100) still using a single spectrometer.
Predicting thermal transport properties in phononic crystals via machine learning
Authors: Dong Liyuan , Li Wei , Bu Xian-He
Published: April 2024

Although anisotropic phononic crystals (PnCs) could be utilized to control the phonon dispersions and thermal transports, rapidly discovering their properties presents a significant challenge due to the enormous consumption of traditional computational methods. In this study, we have developed machine learning techniques to forecast the thermal conductance of anisotropic PnCs (GPnC and GPnC/Gmem) based on the elastic constants, taking conventional inorganic and halide perovskites as examples for their thermoelectric applications. Our findings suggest that predicting GPnC/Gmem is more challenging than predicting GPnC attribute to the complex influence factors and spatial distribution patterns of the former. The GPnC and GPnC/Gmem of the weakest thermal anisotropic materials—all hexagonals are invariants in the (0 0 1) plane, because the velocities in this plane are direction-independent. The GPnC and GPnC/Gmem of the strongest thermal anisotropic material FAPbI3 reaches the minimum and maximum values in [1 1 0] and [1 0 0] directions, respectively. Ultimately, our machine learning models can map the hidden complex nonlinear relationships between target thermal properties and mechanical features to provide valuable insight for accurate and efficient prediction and analysis of the thermal behaviors of PnCs at a mesoscopic level under low temperatures.
Probing rotated Weyl points on one-dimensional sonic crystals
Authors: Zhang Xu , Deng Chengxin , Yang Yiqin , Li Jin , Yu Yingjian , Yang Hai
Published: April 2024

Recently, researchers have devoted their intense efforts to investigating Weyl physics in synthetic space. In this Letter, we study the intriguing topological rotated Weyl physics in a three-dimensional parameter space, which consists of two extra structural parameters and the wave vector of a simple one-dimensional sonic crystal. In our ultrasonic experiments, we observe that the topological interface states propagate along the interface formed by two sonic crystals of distinct chirality caused by the rotated Weyl points. We detect the rotated synthetic Weyl points and measure the singularities of the reflection phase, which results in the robustness of the interface states. At the same time, it also shows the advantages of synthetic dimensions in exploring high-dimensional physics problems in low-dimensional systems.
Switchable Faraday laser with frequencies of 85Rb and 87Rb 780 nm transitions using a single isotope 87Rb Faraday atomic filter
Authors: Qin Xiaomin , Liu Zijie , Shi Hangbo , Wang Zhiyang , Guan Xiaolei , Shi Tiantian , Chen Jingbiao
Published: April 2024

In the development of atomic physics, laser sources with Frequencies corresponding to atomic transition and high stability are essential. The Faraday laser is a special diode laser using the Faraday anomalous dispersion optical filter (FADOF) to realize frequency selection, so the output laser frequency is automatically limited to the atomic Doppler broadening. However, the frequency of a Faraday laser corresponds to the range around only one atomic hyperfine transition. Here, we realize a switchable Faraday laser with two isotopes laser frequencies corresponding to 85Rb 52S1/2 (F=3)→52P3/2 and 87Rb 52S1/2 (F=2)→52P3/2 transitions based on a single isotope 87Rb-FADOF. The laser has good robustness against the fluctuation of diode current and temperature, with wavelength fluctuating within 0.8 pm from 16 to 30 °C of diode temperature, and has a free-running linewidth of 18 kHz. We also lock the laser frequency to the two cycling transitions of 85Rb 52S1/2 (F=3)→52P3/2 (F′=4) and 87Rb 52S1/2 (F=2)→52P3/2 (F′=3) by the modulation transfer spectroscopy technique. The Allan deviation of the residual error signal is 3×10−14/τ, and the frequency stability of the beat detection reaches 2.8×10−12 at 1 s integration time. This 780 nm switchable Faraday laser expands the application scenarios of Faraday lasers, which can be used in laser cooling atoms, optical frequency standards, and other quantum precision measurement fields.
A multidimensional examination of phase separation in single-component fluids
Authors: Das Sandip , Mussel Matan
Published: April 2024

A thermodynamic instability in a homogeneous fluid can lead to spontaneous formation of distinct domains within the fluid. This process involves not only the spatial redistribution of fluid density but also transient exchanges of pressure, temperature, and energy. However, classical theoretical frameworks, such as the Ginzburg–Landau and Cahn–Hilliard models, lack incorporation of these essential thermodynamic aspects. To investigate the dynamics of multiple physical fields during phase separation, we numerically solve a two-dimensional van der Waals fluid model. Thermodynamic consistency is demonstrated by verifying the coexistence curve. While the equilibrium pressure remains similar across the unstable region of the isotherm, we demonstrate that the energy in the system depends on the initial density. Although the majority of energy is stored as heat at typical values of the heat capacity, high-density domains contain less specific energy compared to their low-density counterparts due to interparticle attraction. Consequently, the transition of low-density domains into high-density through the process of coalescence releases excess energy, which redistributes in the form of longitudinal waves and heat. We also highlight the role of parameters, such as heat capacity and thermal conductivity, in less intuitive phenomena, including elevated temperature fluctuations and memory preservation.
Quantum metaphotonics: Recent advances and perspective
Authors: Zhang Jihua , Kivshar Yuri
Published: April 2024

Quantum metaphotonics has emerged as a cutting-edge subfield of meta-optics employing subwavelength resonators and their planar structures, such as metasurfaces, to generate, manipulate, and detect quantum states of light. It holds a great potential for the miniaturization of current bulky quantum optical elements by developing a design of on-chip quantum systems for various applications of quantum technologies. Over the past few years, this field has witnessed a surge of intriguing theoretical ideas, groundbreaking experiments, and novel application proposals. This Perspective aims to summarize the most recent advancements and also provides a perspective on the further progress in this rapidly developing field of research.
Parametric study of large-eddy simulation to capture scaling laws of velocity fluctuations in neutral atmospheric boundary layers
Authors: Feng Dachuan , Gupta Vikrant , Li Larry K. B. , Wan Minping
Published: April 2024

The development of digital twins for wind farms often involves the use of large-eddy simulation (LES) to model atmospheric boundary layers. Existing LES solvers primarily focus on accurately capturing streamwise fluctuations. They, however, overlook the less energetic cross-stream fluctuations, which play a crucial role in wind turbine wake evolution. In this study, we conduct a systematic parametric study and incorporate changes in an open-source LES solver. The improved solver is able to predict all three components of velocity fluctuations in alignment with the scaling laws derived from the attached-eddy hypothesis. In particular, we examine the impact of (i) the subgrid-scale model, (ii) the wall model, (iii) the von Kármán constant, and (iv) the grid-cell aspect ratio. We find that although all these factors influence the prediction of velocity fluctuations, the grid-cell aspect ratio has the greatest effect on the spanwise and vertical velocity components. Notably, utilizing nearly isotropic grid cells leads to the best alignment of all three velocity component fluctuations with the scaling laws. Spectral analysis further demonstrates that the present LES solver accurately predicts the characteristic length scales for all velocity fluctuation components, making it a reliable tool for obtaining turbulent inflow conditions for wind farm modeling.
Highly distinctive linear and nonlinear rheological behaviors of mucin-based protein solutions as simulated normal and asthmatic human airway mucus
Authors: Liu Zhiwei , Seto Ryohei , Zhang Hailin , Che Bo , Liu Lei , Deng Linhong
Published: April 2024

Mucus on the human airway surface normally provides a fluid barrier to trap and remove inhaled hazardous particulates such as viruses and bacteria, a physiological function known as mucus clearance. This function, however, can fail if the mucus has abnormal rheological properties, as in the case of certain lung diseases such as asthma. Despite its importance, airway mucus rheology has not been well studied so far, largely because of its complex nature and limited availability. Therefore, in this study, we prepared mucin-based protein solutions as simulated normal and asthmatic airway mucus (NM and AM, respectively) and subsequently studied them in both linear and nonlinear rheological conditions using either conventional steady-state or large amplitude oscillatory shear experiments together with nonlinear multi-mode Giesekus model analysis. We also examined the microscopic structure of the simulated airway mucus by optical or atomic force microscopy. We found that both NM and AM exhibited typical nonlinear rheological behaviors of protein solutions. However, as compared to NM, AM was much more solid-like, and the viscosity, yield stress, and dynamic modulus were more than ten times that of NM. These differences in macroscopic rheological behaviors between NM and AM could be attributed to their different microstructures. Taken together, this study provides evidence that airway mucus may dramatically change its rheological behaviors with changing chemical composition and microstructure as occurring in diseased conditions such as AM. Thus, the presented rheological assessment and modeling analysis, together with the microscopic characterization of simulated airway mucus, may have important values for better understanding the critical roles of mucus rheology in the determination of the mucus clearance function in health and disease as well as the development of pulmonary drug delivery systems.
Reappraisal of plane wall jet self-similarity
Authors: Djenidi L. , Agrawal Amit
Published: April 2024

There is a general consensus that the characteristic velocity and length scales for a plane wall jet exhibit power law with distance downstream of the jet nozzle/slot, x; however, no definitive values are given for the power-law exponents. In view of this, plane wall jet self-similarity is reappraised using a compilation of experimental and direct numerical data of plane wall jets. The plots of compensated distributions of the maximum velocity Umax and length y1/2, the location where the velocity is equal to Umax/2 in the outer part of the flow, reveal that these variables follow the power laws Umax∼y1/2n and y1/2∼xm, where n∼−1/2 and m∼1, which comply with self-similarity solutions. While n∼−1/2 is in agreement with the existing results, the linear growth of y1/2 contrasts with the common belief that m should be less than 1. It is argued that the limited ranges of x and Reynolds numbers (Re) used in the previous studies prevent this latter behavior to be observed. This behavior emerges when these data are compiled into a single set, allowing a reasonable range of x and Re. It is further observed that only one velocity scale, either Umax or uτ, the friction velocity, is needed for the outer region, which complies with a requirement imposed by self-similarity under a linear growth y1/2. In the inner region, either ν/uτ or y1/2,in (the location where the velocity is equal to Umax/2 in the inner part) can be used as a scaling velocity, while uτ should be the adequate scaling velocity. The present analysis provides some support to the argument that scaling could be universal, at least when the Reynolds number is large enough and the flow is allowed to evolve over a very long distance.
Plasma assisted remediation of SiC surfaces
Authors: Mathews M. A. , Graves A. R. , Boris D. R. , Walton S. G. , Stinespring C. D.
Published: April 2024

This paper describes a three-step process to remediate surface and sub-surface defects on chemo-mechanically polished SiC surfaces. In this process, a CF4-based inductively coupled plasma with reactive ion etch was used to remove material to a depth, which is unaffected by surface and subsurface polishing damage. This produced a planarized but carbon-rich fluorinated surface. This surface was then exposed to a 2 min rapid thermal oxidation in air at 1000 °C to oxidize and volatilize the excess carbon and fluorinated species, respectively. The resulting surface oxide was then stripped using a dilute hydrofluoric acid in water solution. This process, referred to as plasma assisted remediation, reproducibly yielded planarized, stoichiometric surfaces with low levels of carbon and oxygen contamination suitable for subsequent device fabrication. In the supporting studies described here, 4H- and 6H-SiC(0001) surfaces were remediated and characterized by x-ray photoelectron spectroscopy and atomic force microscopy at each stage of the process. Experimental studies under ion-rich and radical-dominant conditions are also reported which provide greater insight into the underlying chemistry and physics of the process.
Bulk fluidity and apparent wall slip of deflocculated kaolin suspensions
Authors: Pěnkavová V. , Tihon J.
Published: April 2024

The influence of different electrolytes on the apparent wall slip (AWS) of aqueous kaolin suspensions is studied experimentally. The fluidity and AWS characteristics of purely aqueous and deflocculated kaolin suspensions are measured by gap-dependent rotational viscometry using unconventional cone–cone geometry. The applied sensors are made of different materials: stainless steel (smooth and sandblasted), titanium, and duralumin (with an anodized surface). Both the quality of the sensor surface and the presence of electrolytes strongly influence the observed AWS behavior. In the case of a purely aqueous 40% kaolin suspension, positive AWS (depleted layer formation) is measured on the stainless steel and titanium sensors, while negative AWS (stagnant layer formation) is observed on the anodized duralumin sensor. In the case of fully deflocculated suspensions, Newtonian flow behavior is observed with almost no measurable AWS effects. In the case of partially deflocculated suspensions, the type of deflocculant becomes important. While the presence of Na2CO3 or NaOH does not qualitatively change the AWS trends and only slightly increases them, the presence of SHMP (sodium hexametaphosphate) leads to positive AWS on anodized duralumin. However, the addition of NaCMC (sodium salt of carboxymethylcellulose) induces negative AWS on all the surfaces studied.
Magnetic proximity effect on the spin-valley coupling in two-dimensional Cr2Ge2Te6/2H-TMD van der Waals heterostructures
Authors: Zhao Yanzhe , Huang He , Zhang Zeyu , Wang Liming , Wu Yanfei , Liu Chuang , Zhang Jingyan , Zheng Xinqi , Zhou Shiming , Wang Shouguo
Published: April 2024

Two-dimensional (2D) transition metal dichalcogenides with 2H-phases, as a unique platform of valleytronics, display valley polarization and the well-known anomalous valley Hall effect when stacking with 2D magnetic substrates. In this study, we employ first-principles calculations to investigate the magnetic states, band structures, and magnetic proximity-dependent valley properties of 2D van der Waals heterostructures Cr2Ge2Te6/2H-MX2 (M = Mo, W, and X = S, Se, Te). Our findings reveal that the heterostructures possess stacking-dependent spontaneous valley polarization as well as pristine perpendicular magnetic anisotropy. Additionally, the Berry curvature and circular polarization demonstrate the presence of spin–momentum coupling characteristics, while the calculated non-zero Hall voltage indicates that the anomalous valley Hall effect can be achieved in valley-polarized systems. Furthermore, due to the strain effect and the electronic polarization at the interface, Cr2Ge2Te6/2H-MX2 heterostructures undergo the transition from semiconductors to semimetals upon substitution of early chalcogen elements. These calculations provide valuable insights for practical applications of valleytronics in 2D van der Waals heterostructure systems.
Study on the performance of a floating horizontal-axis tidal turbine with pitch motion under wave–current interaction
Authors: Jing Fengmei , Mei Yunlei , Lu Qiang , Yang Lele , Guo Bin
Published: April 2024

Waves can induce motion in the floating platforms that support tidal turbines, affecting their hydrodynamic loads. To study the non-constant hydrodynamic of floating tidal turbines in a wave condition, this paper investigates the effect of pitch motion on the power coefficient (CP), thrust coefficient (CT), and wake flow of a tidal turbine using computational fluid dynamics. A pitch motion experiment is designed to verify the validity of the numerical method. The results show that the CP and CT exhibit periodic fluctuations under pitch motion, with the fluctuation period being consistent with the pitch period. Waves do not change the overall fluctuation trend of the CP and CT, but they do complicate the fluctuations and increase the likelihood of blade fatigue damage. Pitch motion reduces the mean power, with large-amplitude pitch motions particularly likely to result in severe power loss. The low-velocity region of the wake under pitch motion exhibits significant periodic oscillations. The wake is more susceptible to the pitch period than the pitch amplitude, and small-period pitch motions force the wake to deform earlier, accelerating wake vortex dissipation and velocity recovery. Increasing the immersion depth reduces the effect of waves on tidal turbine performance, but is not conducive to wake recovery. In summary, the rational design of the immersion depth and limiting the movement amplitude of the floating platform have the potential to prolong the working life of tidal turbines and increase their power output.
Versatile Cu2ZnSnS4-based synaptic memristor for multi-field-regulated neuromorphic applications
Authors: Dong Xiaofei , Sun Hao , Li Siyuan , Zhang Xiang , Chen Jiangtao , Zhang Xuqiang , Zhao Yun , Li Yan
Published: April 2024

Integrating both electrical and light-modulated multi-type neuromorphic functions in a single synaptic memristive device holds the most potential for realizing next-generation neuromorphic systems, but is still challenging yet achievable. Herein, a simple bi-terminal optoelectronic synaptic memristor is newly proposed based on kesterite Cu2ZnSnS4, exhibiting stable nonvolatile resistive switching with excellent spatial uniformity and unique optoelectronic synaptic behaviors. The device demonstrates not only low switching voltage (−0.39 ± 0.08 V), concentrated Set/Reset voltage distribution (<0.08/0.15 V), and long retention time (>104 s) but also continuously modulable conductance by both electric (different width/interval/amplitude) and light (470–808 nm with different intensity) stimulus. These advantages make the device good electrically and optically simulated synaptic functions, including excitatory and inhibitory, paired-pulsed facilitation, short-/long-term plasticity, spike-timing-dependent plasticity, and “memory-forgetting” behavior. Significantly, decimal arithmetic calculation (addition, subtraction, and commutative law) is realized based on the linear conductance regulation, and high precision pattern recognition (>88%) is well achieved with an artificial neural network constructed by 5 × 5 × 4 memristor array. Predictably, such kesterite-based optoelectronic memristors can greatly open the possibility of realizing multi-functional neuromorphic systems.
An analytical model for water entry cavity of bodies of revolution in two-dimensional background flow
Authors: Hong Yao , Liu Hua , Liu Yunqiao , Wang Benlong
Published: April 2024

The dynamics of the cavity created by water entry of a body of revolution into two-dimensional background flow is investigated in this paper. The background flow, whether quiescent or moving, is the undisturbed flow by the water entry cavity. It is assumed to have a larger characteristic length, and a smaller characteristic velocity than the cavity. The cavity attached behind an impact body is regarded as a slender, deformable air cylinder. To consider the azimuthal disturbance in the cavity surface, the potential flow is described using the mode decomposition method in a moving coordinate system. The deduced approximate model suggests that the azimuthal disturbance of the initial conditions, the pressure gradient or the movement of background flow, results in the non-uniform three-dimensional deformation of the cavity. Moreover, the approximate model can reduce to several cavity models proposed for different types of water entry problems. The model is further validated by the favorable comparison with the available experimental results measured in quiescent and moving background flow.
Simulation method for filling stage in liquid composite molding based on a two-phase flow volume of fluid model
Authors: Yang Wenkai , Chen Wengang
Published: April 2024

Liquid composite molding (LCM) is a process for manufacturing fiber-reinforced resin matrix composites. The chemical rheological properties of resin in the filling stage of LCM will produce a non-isothermal flow process that includes multi-field coupling of thermal field, flow field, and chemical field. During the filling stage, the resin is injected into a closed mold pre-laid with a fiber at a certain temperature and pressure to flow continuously and undergo a curing chemical reaction. The viscosity of resin changes constantly under the influence of temperature and the curing reaction, which affects the flow of resin. The simulation of this multi-field coupling filling stage in LCM can provide an effective reference for the design of process parameters. The simulation method of the filling stage in LCM is studied in this paper. The mathematical model of the filling stage is derived based on the air–resin two-phase flow volume of the fluid model. Based on the secondary development of the ANSYS FLUENT software, the mathematical model is solved to realize the simulation. The parameters of an alkali-free glass fiber plain weave fabric are measured and the calculation model of thermosetting resin viscosity is established by designed experiments, which are applied in simulation. The filling stage experiment of LCM is designed to verify the accuracy of simulation results. Meanwhile, by comparing with the traditional simulation method, it is found that the data error obtained by the simulation method in this paper is significantly reduced.
A revision of Derris and Brachypterum (Leguminosae subfamily Papilionoideae) in Australia
Authors: Cooper Wendy E. , Zich Frank A. , Nauheimer Lars , Harrison Melissa J. , Crayn Darren M.
Published: April 2024

Derris Lour. and Brachypterum (Wight & Arn.) Benth. (Leguminosae subfamily Papilionoideae) in Australia are revised on the basis of examination of fresh, dried and spirit-preserved specimens and phylogenetic analysis of plastid matK and nuclear internal transcribed spacer (ITS) sequence data. Three species of Derris and four species of Brachypterum are recognised as occurring in Australia. Two new Brachypterum species, namely Brachypterum nitidum W.E.Cooper and Brachypterum opacum W.E.Cooper, are described and illustrated. Notes on habitat, distribution and an identification key are presented for all species of both genera that occur in Australia.
Spherical warp-based bubble with non–trivial lapse function and its consequences on matter content
Authors: Abellán G , Bolívar N , Vasilev I
Published: April 2024

In the present work, we study the consequences of including the lapse function as an additional degree of freedom for a general spherical warp-based geometry. By allowing a non-uniform lapse function to evolve, we find that it is possible to accommodate a fluid that includes heat flow. This broadens the range of fluid types that have been studied in these systems and is consistent with the spherical warp metric. Having added the lapse function, we solved the system of equations using an anisotropic fluid with heat flow. In this way, we can examine the different characteristics of the variables of the system. Next, we study the energy conditions and establish how these are modified by including heat flux for an appropriate generic observer in a locally flat spacetime. Finally, we explore all energy conditions using the numerical solutions and verify the regions where they are satisfied.
Dynamic transient response measurement method for parity-time-symmetric LC telemetry sensors
Authors: Zhang Chi , Li Jie , Wu Jianhui , Wang Haobin , Zhang Kaihang , Kuang Haoze , Chen Jinkai , Hao Jin , Dong Shurong , Fu Yongqing , Luo Jikui
Published: April 2024

Parity-time symmetry concept has been utilized to develop high precision LC passive wireless sensors. However, they often use the traditional frequency sweeping method for measurements, thus the measurement precision and speed are strongly influenced by the performance of the frequency domain analysis instrument. To solve this issue, herein we proposed a time domain measurement method and extracted sensing information from the transient response signals of the reader. Its measurement speed was much faster than that using the frequency domain analysis instrument. A distance sensing system was developed to demonstrate the feasibility of the new method. It showed a resolution of less than 300 nm for detections of centimeter range, and the measurement time was as short as 100 μs, which was at least 1000 times faster than that using the traditional method. This technology can be explored as an innovative strategy for LC passive telemetry sensing.
Neural networks for turbulent transport prediction in a simplified model of tokamak plasmas
Authors: Pomârjanschi L M
Published: April 2024

The method of using neural networks (NNs) for turbulent transport prediction in a simplified model of tokamak plasmas is explored. The NNs are trained on a database obtained via test-particle simulations of a transport model in the slab-geometrical approximation. It consists of a five-dimensional input of transport model parameters, and the radial diffusion coefficient as output. The NNs display fast and efficient convergence, a validation error below 2

%

, and predictions in excellent agreement with the real data, obtained orders of magnitude faster than test-particle simulations. In comparison to a spline interpolation, the NN outperforms, exhibiting better predicting and extrapolating capabilities. We demonstrate the preciseness and efficiency of this method as a proof-of-concept, establishing a promising approach for future, more comprehensive research on the use of NNs for transport predictions in tokamak plasmas.
A practical main frame for convex-deformable mobile devices
Authors: Kim Jeongil , Yu Changmin , Jeong Jaehyun , Jeong Yoon Chang , Kang Kiju
Published: April 2024

In the existing mobile devices, such as iPads, the touchscreen & display assembly and the rear cover account for at least 60% of the total device weight. Therefore, device weight can be reduced significantly only by replacing these glass and metallic components with non-glass and polymeric equivalents. Recently, the authors’ research group demonstrated a monolithically polymeric sandwich plate that is convex-deformable, even with solid chips embedded in its cores. In this study, a new design of this sandwich plate is proposed to facilitate its use as a practical main frame of a mobile device. This design is validated by conducting finite element analyses and experiments involving three-dimensionally printed prototype of the proposed sandwich plate design. The plate is fabricated as two separate halves that are then assembled using snap-fits to form a single body. A flexible printed-circuit board with regularly arranged elliptical holes and many solid chips embedded on its upper and lower surfaces is accommodated within the core of the proposed plate. In addition, rib-like side covers and an overall latex coating are used to protect all four sides and the entire outer surface, respectively, without adversely affecting the overall convex deformation of the proposed plate design.
Compression and fretting wear studies of γ/α
2 duplex TiAl alloys at the nanoscale
Authors: Zheng Min , Han Jianfeng , Qu Dingfeng , Chen Weihua , Sun Yuhang , Chen Jie , Zhu Zongxiao
Published: April 2024

The study investigated the nanofabrication behavior of TiAl alloys with a duplex structure of γ/α
2. The process included downward pressure followed by reciprocating friction with diamond grinding balls and was simulated using molecular dynamics (MD). It was found that a certain number of dislocations in the workpiece was low, and the resilience was high during the initial pressing stage. The dislocations increased, the resilience decreased, and the plastic deformation capacity was enhanced under continuous pressing. The α
2 phase did not deform significantly during the compression process. The presence of the α
2 phase increases the overall hardness of the material, and elastic-plastic deformation occurs mainly where the γ phase is present; the endowment layer dislocations generated during the intrinsic stacking fault rebound via the phase boundary to form V-shaped dislocations. During the reciprocating friction of the workpiece, forward friction produces V-shaped dislocations, and reverse friction makes the dislocations disappear. This process results in the forward average friction force being more significant than the reverse average. γ/α
2 phase boundary has an impeding effect on the downward proliferation of defects, and the phase boundary makes the temperature transfer appear discontinuous. During friction, the specific number of vacancy atoms in the γ-phase increases, and the transition between FCC and HCP occurs.
Genetic optimization of terahertz metamaterial absorber for improved absorption and quality factor
Authors: Sun Zhenci , Liang Chao , Zhao Xiaoguang , Zhao Jiahao
Published: April 2024

Terahertz metamaterial absorbers are typically comprised of an array of sub-wavelength meta-atoms, a dielectric spacer layer and a ground plane. The absorption and quality factor are two of the most important performance metrics for various advanced applications, such as THz communication, sensing, and imaging. However, a large number of structural parameters in the meta-atom make the design approach based on physical intuition and parameter sweep impractical and difficult. In this paper, we report an intelligent design methodology based on the genetic algorithm that facilitates the optimization of an air-spaced terahertz metamaterial absorber to improve its absorption and quality factor. The presented approach starts by randomly generating the size parameters of the meta-atom, and it iteratively obtains the optimized design of the dual narrow band terahertz metamaterial perfect absorber. The quality factor for the two near unity-absorption peaks are 23.8 at 0.5 THz and 60.3 at 0.7 THz, respectively. The device was fabricated using the surface and bulk-micromachining processes, and the measured absorption spectra agrees well with the simulated results. Not limited to this proof-of-concept demonstration, this methodology can be applied to all metamaterial-based photonic systems achieving efficient forward optimization design.
Synthesis of a fluorescent probe for rhodamine B and determination of Zn2+ content in pharmaceutical zinc gluconate
Authors: Cao Pan , Ren Zhixin , Huang Siying , Zhang Yiying , Lv Yuguang
Published: April 2024

The intermediate LBXJ was prepared by Rhodamine B, hydrazine hydrate and HCl, and then the probe Y2ST was prepared by LBXJ, chromone 3-formaldehyde and absolute ethanol. NMR characterized the structures of the intermediate and probe, IR and MS. Compared the fluorescence selectivity of ions after the system was determined and tested the response time, pH value, cation interference, reversibility, linearity, detection limit, accuracy, coordination ratio, and recovery rate of the samples. The detection limit of Y2ST was 0.7×10-6 mol/L, and the detection rate of Zn2+ in zinc gluconate was 96.1% at 5×10-6 mol/L--5×10-5 mol/L. It can be used for the content determination of Zn2+.
NV color center fluorescence signal measurement based on FPGA architecture
Authors: Zeng Seng , Yang Shuqiang , Shang Zhengguo , He Xianming
Published: April 2024

Nitrogen-vacancy (NV) quantum defects in diamond are sensitive detectors of magnetic fields. Then, the existing sensing technologies based on diamond NV centers rely on bulky and expensive instruments, which must be replaced by a more compact design. Here we combine NV quantum sensing technology with integrated circuit technology to create a compact and easy-to-operate platform. Using the existing integrated circuit technology, we integrate the lock-in amplifier, microwave generator and TTL modulator together. with this platform, we can obtain a magnetic sensitivity of 5.72μT/Hz
1/2.
Self-calibration performance analysis of sheet micro-components based on droplet array
Authors: Yan Hu , Qin Zhang , Shen Jin
Published: April 2024

The droplet array-based micro-component self-calibration method features simple operation, easy batch control implementation, and holds great promise in the field of micro-assembly. The paper investigates the self-calibration process, analyzes the factors influencing self-calibration performance, discusses self-calibration errors, self-calibration range, and their relationship with micro-component parameters, droplet array parameters, and fluid parameters, and proposes a construction method suitable for droplet arrays suitable for micro-components. The research results indicate that the self-calibration error and calibration range of micro-components are related to micro-component parameters, substrate array parameters, and droplet parameters. When the micro-component size is greater than or equal to the droplet array size, the self-calibration error is relatively small. Constructing an appropriate droplet array based on the size and shape of the micro-components can reduce self-calibration errors and meet the self-calibration accuracy requirements for micro-components of varying sizes and shapes.
Numerical simulation of the lubrication characteristics of bionic surface textures on mechanical sealing rings
Authors: Chen Hao , Yan Zhen , Dai Wan , Zheng Zhu , Bie YuFeng , Chen YunFei
Published: April 2024

Inspired by the shark scale surface in natural world, five different bionic surface textures were designed. Through numerical simulation, the influence mechanism of the geometrical parameters on the lubrication characteristics of the bionic surface textures on the mechanical sealing rings under refrigerant conditions was investigated. The results revealed that the lubrication characteristics of the bionic surface textures is jointly influenced by the texture shape, arrangement, vortex phenomenon, and hydrodynamic pressure effect. The lubrication characteristics of all five bionic surfaces designed in this study was superior to those of the smooth surface. The effects of density and texture depth on the lubrication characteristics of the surface textures exhibits criticality. The results provide valuable insights into the effective design of bionic surface textures on mechanical seal rings, especially in improving their lubrication characteristics under refrigerant conditions. The effectiveness of numerical simulation techniques in evaluating and optimizing the performance of bionic texture design in various micro- and nanofabrication processes is further validated.
Design and simulation of capacitive sensor for grain moisture detection
Authors: Wang Xiang , Chen Yuxuan , Jiang Jiaxin , Zheng Gaofeng , Zhang Runyang , Li Shufan , Lv Wenlong , Song Yunkang , Wang Lingyun , Li Wenwang
Published: April 2024

The high moisture content of grain would result in quality deteriorations such as mold and mildew during storage and transportation. For effective detection of grain moisture, a forked-finger capacitive sensor in the form of triangular prism is proposed. The effect of the sensor structural parameters on its capacitance, electric field distribution, sensitivity and penetration depth are investigated using finite element simulations. The results show that an optimised effective penetration depth of 2.73 mm for grain moisture detection can be achieved when the finger width, number, length and spacing are 50 μm, 25.4 mm and 50 μm, respectively. This work may provide a new approach for the structural design of capacitive grain moisture sensors.
Preparation and anticorrosion performance of graphene composited waterborne coatings
Authors: Zhang Han , Miao Raoliang , Xie Xuefeng , Ma Hanjun , Feng Fang , Jiang Li
Published: April 2024

Waterborne coatings are safe and environmentally friendly and widely used in automobile, construction and other fields. The low hardness of films formed by water-based anticorrosion coatings and their poor anticorrosion effect can be resulted from the addition of hydrophilic substances, which make it easy for water penetration. In this experiment, glycidyl methacrylate (GMA), butyl acrylate (BA), methyl methacrylate (MMA), and acrylic acid (AA) were used as the polymerization monomers to enhance the hardness, adhesion, and film-forming properties of the coatings by introducing the epoxy bond of GMA in the synthesis. The appropriate formula ratios for the waterborne coatings were determined by conditioning the content of wetting agent, thickener, levelling agent, defoamer, and modified acrylic-based resin. Based on this formula, suitable additive ratios of graphene were determined by condition experiments. When the addition ratio of graphene was 0.6wt% - 0.8wt%, the obtained coatings exhibited satisfactory hardness, film-forming properties, strong adhesion and anticorrosive properties. The results of salt spray tests and potentiodynamic polarization experiments verified that graphene in a certain proportion can effectively block the penetration of water, so that the coating presented excellent properties.
Analysis of excitation and detection capability of hemispherical resonator based on interdigital electrodes
Authors: Liu Pingyuan , Zhu Feng , Xi Xiang , Lu Kun , Shi Yan
Published: April 2024

In this paper, a theoretical model of excitation and detection is established based on the excitation and detection method of the uncoated hemispherical resonator with interdigital electrodes, which proves the feasibility of the excitation and detection of the interdigital electrodes in principle. The simulation and analysis of its influence parameters are also carried out to provide theoretical support for the design and optimization of the interdigital electrode to realize the excitation and detection of the hemispherical resonator. Finally, the excitation and detection of uncoated hemispherical resonators by interdigital electrodes were successfully verified through experiments.
Design of multi-band flexible microstrip antenna based on micro drop jetting
Authors: Zhidong Zhong , Xiayun Shu , Xuefeng Chang , Yiquan Tang , Sai Cheng
Published: April 2024

Due to the high compatibility of micro-droplet jetting 3D printing technology within the realm of printed electronics, a flexible and miniaturized multi-band microstrip antenna was designed. The purpose of this is to extend the wireless signal response range of wearable devices and to investigate the feasibility of producing wearable devices with high efficiency. The antenna uses polydimethylsiloxane (PDMS) as the dielectric substrate and nanosilver as the conductive material for the radiating patch, demonstrating remarkable flexibility. The antenna’s structure underwent simulation and analysis through frequency sweeping using ANSYS HFSS simulation software. The outcomes illustrate the antenna operating within three frequency bands at 2.5GHz, 3.5GHz, and 5.8GHz, and the return loss is kept below -18dB for each central frequency. Simultaneously, it displays favorable flexibility. The radiation pattern of the antenna indicates that it has good directivity and no extra side lobes are generated. Ultimately, Antennas were fabricated using microdroplet spraying technology, and the final product’s characteristics and morphology were analyzed. The aforementioned findings demonstrate that micro-droplet jetting technology’s remarkable precision and efficiency render it a viable approach for the processing and production of flexible microstrip antennas.
Review of RF microsystem packaging process technology
Authors: Cui Jing , Cui Suning , Yuan Xiaoming , Kang Nan , Liu Dexi , Shi Lei , Liu Yawei
Published: April 2024

The 3-D heterogeneous integration technology of microsystem is the best technical means to achieve higher integration, higher performance and higher working frequency of radio frequency (RF) electronic system. RF microsystem integration technology is categorized into three main types based on the packaging substrate: silicon-based, ceramic-based, and resin-based. In this work, the principle of RF microsystem integration technology is demonstrated in detail, and the process routes and characteristics of different packaging structures are clarified. Moreover, through the multi-dimensional comparison of different packaging structures, the application conditions of specific packaging structures are obtained. According to the comprehensive evaluation, the resin-based embedded chip package shows outstanding potentials in RF performance, integration capability, batch production capability and process cost. However, there are three shortcomings that limit its application in RF microsystems: Firstly, in terms of the universality of RF chips, metal grounding on the back of RF chips cannot be realized by this packaging, and special design of RF chips is required. At present, however, the universal chip with gold back grounding on the market cannot meet the requirements of the packaging process. Secondly, because of the high cost of customized chips, this packaging process is not suitable for small-scale production. Thirdly, the resin-based package does not have the sealing function, thus reliability of the product still needs to be verified. Ceramic-based RF microsystems do not require customized chips and have advantages in chip versatility compared to resin-based systems, with integration capabilities comparable to resin-based systems. However, its batch production capacity is much lower than resin based. In contrast, the silicon-based embedded chip package is as excellent as the resin-based products in chip versatility, RF performance, integration capability, batch production capability, etc., except that the manufacturing cost is high, and the yield should be effectively guaranteed in the manufacturing process. The conclusion provides a guidance for the future research of RF microsystem integration technology.
Design of a charge-sensitive amplifier for MEMS piezoelectric hydrophone
Authors: Huang Z. , Liu Y. , Fang S. , Wang L. , Liu K.
Published: April 2024

Hydrophone is an important part of sonar system and convert acoustic signal into electrical signal. However, the electrical signal generated by the hydrophone is relatively weak and cannot be directly used for underwater detection and communication. Therefore, it is necessary to preprocess the generated electrical signal. In this paper, a switched capacitor charge-sensitive amplifier for MEMS piezoelectric hydrophone is designed. In the structure, two single-channel charge amplifiers are used for time-division multiplexing. The noise sampling and charge amplification are performed separately in the same half cycle to achieve the effect of alternating output, thereby increasing the sampling rate and solving the problem of discontinuous output of the switched capacitor circuit. In the circuit design, virtual switch and two-phase non-overlapping clock are adopted to reduce the error caused by charge injection and clock feedthrough effect of CMOS switch. What’s more, the correlated double sampling technique is used to reduce the offset and low frequency noise of the circuit. The gain of the charge-sensitive amplifier designed in this study is 26 dB, the bandwidth is 0.8Hz∼17.6kHz, the equivalent input noise power spectral density is 115.6

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/

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at 0.1Hz, and the charge sensitivity is 2 mV / pC. The fitting line between the input charge and the amplitude of the output curve is similar to the theory. The simulation results show that the charge-sensitive amplifier proposed in this study meets the design requirements of the MEMS piezoelectric hydrophone readout circuit.