bluuebunny/crossref_metadata_2025 huggingface dataset:
Potential Risk Factors for Ventriculoperitoneal Shunt Implantation in Paediatric Patients with Posthemorrhagic Hydrocephalus of Prematurity Treated with Subcutaneous Reservoir: An Institutional Experience
Authors: Bębenek Adam K. , Kwiatkowski Stanisław , Milczarek Olga
Published: July 2021

Background Posthemorrhagic hydrocephalus of prematurity (PHHP) is a result of intraventricular hemorrhage (IVH). IVH occurs in 6 to 23% of the preterms in countries with advanced medical health care. Most of these patients will eventually require the use of ventriculoperitoneal shunt (VPS). The purpose of this study is to assess the risk factors of VPS implantation in patients with PHHP who have been treated with ventricular catheter with subcutaneous reservoir (VCSR).

Methods The retrospective study was conducted evaluating 35 premature patients who suffered from severe IVH. Their mean gestational age was 28 weeks. The assessment included antenatal factors such as gestational age, birth weight, and intrauterine and perinatal infection. Postparturient period factors such as the IVH grade, time between diagnosis, and VCSR implantation and body weight on VCSR implantation were also considered in the study. Postprocedural complications, such as bacterial cerebrospinal fluid (CSF) infection, sepsis, and skin lesions, were evaluated. Data were calculated with R program, version 4.04.

Results From among 35 evaluated patients, 23 (65.71%) required a VPS. Median of birth weight was 1,190 g. Infections were observed in 11 (31.43%) cases. Mean time between IVH diagnosis and VCSR implantation was 2.6 weeks. Postprocedural complications occurred in 19 (54.29%) patients. None of the evaluated factors has proven its statistical significance (p > 0.05) for being a potential risk factor for VPS implantation.

Conclusion External factors seem to not affect the necessity of VPS implantation in patients after the severe IVH. Ostensibly, there seems to be no difference between the grades III and the IV of Papile's IVH scale regarding VPS implantation necessity.
Characterizing the microscale thermal conductivity of industrial filler materials for thermal composites
Authors: Lim Alane
Published: July 2021

Method shows some deviations between bulk and microscale thermal conductivity for inorganic particles embedded in epoxy resin.
Modeling electrical conduction in resistive-switching memory through machine learning
Authors: Periasamy Karthekeyan , Wang Qishen , Fu Yi , Go Shao-Xiang , Jiang Yu , Bajalovic Natasa , Wang Jer-Chyi , Loke Desmond. K.
Published: July 2021

Traditional physical-based models have generally been used to model the resistive-switching behavior of resistive-switching memory (RSM). Recently, vacancy-based conduction-filament (CF) growth models have been used to model device characteristics of a wide range of RSM devices. However, few have focused on learning the other-device-parameter values (e.g., low-resistance state, high-resistance state, set voltage, and reset voltage) to compute the compliance-current (CC) value that controls the size of CF, which can influence the behavior of RSM devices. Additionally, traditional CF growth models are typically physical-based models, which can show accuracy limitations. Machine learning holds the promise of modeling vacancy-based CF growth by learning other-device-parameter values to compute the CC value with excellent accuracy via examples, bypassing the need to solve traditional physical-based equations. Here, we sidestep the accuracy issues by directly learning the relationship between other-device-parameter values to compute the CC values via a data-driven approach with high accuracy for test devices and various device types using machine learning. We perform the first modeling with machine-learned device parameters on aluminum-nitride-based RSM devices and are able to compute the CC values for nitrogen-vacancy-based CF growth using only a few RSM device parameters. This model may now allow the computation of accurate RSM device parameters for realistic device modeling.
Further compactifying linear optical unitaries
Authors: Bell B. A. , Walmsley I. A.
Published: July 2021

Quantum integrated photonics requires large-scale linear optical circuitry, and for many applications, it is desirable to have a universally programmable circuit, able to implement an arbitrary unitary transformation on a number of modes. This has been achieved using the Reck scheme, consisting of a network of Mach–Zehnder interferometers containing a variable phase shifter in one path as well as an external phase shifter after each Mach–Zehnder. It subsequently became apparent that with symmetric Mach–Zehnders containing a phase shifter in both paths, the external phase shifters are redundant, resulting in a more compact circuit. The rectangular Clements scheme improves on the Reck scheme in terms of circuit depth, but it has been thought that an external phase-shifter was necessary after each Mach–Zehnder. Here, we show that the Clements scheme can be realized using symmetric Mach–Zehnders, requiring only a small number of external phase-shifters that do not contribute to the depth of the circuit. This will result in a significant saving in the length of these devices, allowing more complex circuits to fit onto a photonic chip, and reducing the propagation losses associated with these circuits. We also discuss how similar savings can be made to alternative schemes, which have robustness to imbalanced beam-splitters.
Origin invariant full optical rotation tensor in the length dipole gauge without London atomic orbitals
Authors: Caricato Marco , Balduf Ty
Published: July 2021

We present an origin-invariant approach to compute the full optical rotation tensor (Buckingham/Dunn tensor) in the length dipole gauge without recourse to London atomic orbitals, called LG(OI). The LG(OI) approach is simpler and less computationally demanding than the more common length gauge (LG)-London and modified velocity gauge (MVG) approaches, and it can be used with any approximate wave function or density functional method. We report an implementation at the coupled cluster with single and double excitations level (CCSD), for which we present the first simulations of the origin-invariant Buckingham/Dunn tensor in the LG. We compare LG(OI) and MVG results on a series of 22 organic molecules, showing good linear correlation between the approaches, although for small tensor elements, they provide values of opposite sign. We also attempt to decouple the effects of electron correlation and basis set incompleteness on the choice of gauge for specific rotation calculations on simple test systems. The simulations show a smooth convergence of the LG(OI) and MVG results with the basis set size toward the complete basis set limit. However, these preliminary results indicate that CCSD may not be close to a complete description of the electron correlation effects on this property even for small molecules and that basis set incompleteness may be a less important cause of discrepancy between choices of gauge than electron correlation incompleteness.
High-conductivity polarization-induced 2D hole gases in undoped GaN/AlN heterojunctions enabled by impurity blocking layers
Authors: Chaudhuri Reet , Chen Zhen , Muller David A. , Xing Huili Grace , Jena Debdeep
Published: July 2021

High-conductivity undoped GaN/AlN 2D hole gases (2DHGs), the p-type dual of the AlGaN/GaN 2D electron gases (2DEGs), have offered valuable insights into hole transport in GaN and enabled the first GaN GHz RF p-channel FETs. They are an important step toward high-speed and high-power complementary electronics with wide-bandgap semiconductors. These technologically and scientifically relevant 2D hole gases are perceived to be not as robust as the 2DEGs because structurally similar heterostructures exhibit wide variations of the hole density over Δps>7×1013 cm−2, and low mobilities. In this work, we uncover that the variations are tied to undesired dopant impurities such as silicon and oxygen floating up from the nucleation interface. By introducing impurity blocking layers (IBLs) in the AlN buffer layer, we eliminate the variability in 2D hole gas densities and transport properties, resulting in a much tighter control over the 2DHG density variations to Δps≤1×1013 cm−2 across growths, and a 3× boost in the Hall mobilities. These changes result in a 2–3× increase in hole conductivity when compared to GaN/AlN structures without IBLs.
Ferroelectric control of the perpendicular magnetic anisotropy in PtCoRu/Hf0.5Zr0.5O2 heterostructure
Authors: Zhang Bao , Li Chunlong , Hong Peizhen , Huo Zongliang
Published: July 2021

The magneto-electric coupling (MEC) effect has been considered an effective method for the voltages controlled magnetic anisotropy in traditional ferroelectric/ferromagnetic structures. Unlike traditional perovskite ferroelectrics, the ferroelectric hafnium-based oxides hold great potential for use in the complementary metal oxide semiconductors (CMOS) circuit with the advantages of CMOS compatibility and easy scaled-down and lower leakage current. In this article, the MEC effects in the PtCoRu/Hf0.5Zr0.5O2 (HZO) heterostructure have been investigated using the polar magneto-optical Kerr effect microscopy and anomalous Hall effect. The major modification of perpendicular magnetic anisotropy of the PtCoRu thin film was controlled obviously within the ±4 V polarized voltages of the Hf0.5Zr0.5O2 (HZO) film, accompanying with the coercivity field and remnant magnetization significantly decreased. The Hall voltages of PtCoRu in Hall bar devices were also controlled effectively under ±3 V polarized voltages. Such a finding proposes a more optimized method for the magnetic logic gates and memories based on voltage-controlled magnetic anisotropy in future.
Microfluidic devices fitted with “flowver” paper pumps generate steady, tunable gradients for extended observation of chemotactic cell migration
Authors: Baldwin Scott A. , Van Bruggen Shawn M. , Koelbl Joseph M. , Appalabhotla Ravikanth , Bear James E. , Haugh Jason M.
Published: July 2021

Microfluidics approaches have gained popularity in the field of directed cell migration, enabling control of the extracellular environment and integration with live-cell microscopy; however, technical hurdles remain. Among the challenges are the stability and predictability of the environment, which are especially critical for the observation of fibroblasts and other slow-moving cells. Such experiments require several hours and are typically plagued by the introduction of bubbles and other disturbances that naturally arise in standard microfluidics protocols. Here, we report on the development of a passive pumping strategy, driven by the high capillary pressure and evaporative capacity of paper, and its application to study fibroblast chemotaxis. The paper pumps—flowvers (flow + clover)—are inexpensive, compact, and scalable, and they allow nearly bubble-free operation, with a predictable volumetric flow rate on the order of μl/min, for several hours. To demonstrate the utility of this approach, we combined the flowver pumping strategy with a Y-junction microfluidic device to generate a chemoattractant gradient landscape that is both stable (6+ h) and predictable (by finite-element modeling calculations). Integrated with fluorescence microscopy, we were able to recapitulate previous, live-cell imaging studies of fibroblast chemotaxis to platelet derived growth factor (PDGF), with an order-of-magnitude gain in throughput. The increased throughput of single-cell analysis allowed us to more precisely define PDGF gradient conditions conducive for chemotaxis; we were also able to interpret how the orientation of signaling through the phosphoinositide 3-kinase pathway affects the cells’ sensing of and response to conducive gradients.
Complementary study of anisotropic ion conduction in (110)-oriented Ca-doped BiFeO3 films using electrochromism and impedance spectroscopy
Authors: Suh Jeonghun , Lim Ji Soo , Park Heung-Sik , Yang Chan-Ho
Published: July 2021

Oxygen vacancies are ubiquitous in oxides, and taking advantage of their mobility is the cornerstone for a variety of future applications. The visualization and quantification of collective defect flow based on electrochromism is a powerful approach to explore oxygen kinetics and electrochemical reaction even in cases that electronic conduction is considerably mixed, but whether or not the measured kinetic properties harmonize with those obtained by the conventional impedance spectroscopy remains veiled. Here, we identify complementary relationships between the two methods by investigating the oxygen vacancy transport in Ca 30%-doped bismuth ferrite thin films epitaxially grown on SrTiO3 (110) substrates. We find that the activation energy of ionic hopping is 0.78 (or 0.92 eV) for the application of an electric bias along [001] (or [11¯0]) due to the grain elongation along [001]. We anneal the films in an N2 gas environment at high temperatures to suppress the electronic contribution for access to standard impedance spectroscopy. The oxygen kinetic properties obtained from the two methods are consistent with each other, complementarily revealing the collective phase evolution as well as the ionic impedance of the bulk, grain boundary, and interfacial regions. These comparative works provide useful insights into ionic defect conduction in oxides in an intuitive and quantitative manner.
Direct measurements of thermal transport in glass and ceramic microspheres embedded in an epoxy matrix
Authors: Thompson Matthew F. , Wu Xuewang , Huang Dingbin , Zhang Yingying , Seaton Nicholas C. A. , Zhang Chi , Johnson Matthew T. , Podkaminer Jacob P. , Ho Victor , Wang Xiaojia
Published: July 2021

The time-domain thermoreflectance metrology is applied to evaluate the thermal conductivities of filler particles embedded in a composite matrix. Specifically, a system of glass and ceramic microspheres with a diameter of 100 to 150 μm embedded in an epoxy matrix was used as a representation of a typical composite thermal interface material (TIM) suitable for microelectronics applications. These measurements provide a direct characterization of the thermal properties of filler materials. The measured thermal conductivities of both borosilicate glass and yttria stabilized zirconia microspheres agree well with literature values for bulk materials, whereas the thermal conductivity of the alumina microspheres is nearly 50% lower than that of bulk crystals. The reduction in thermal conductivity of the alumina microspheres highlights how important this level of understanding is for TIM development and is attributed to enhanced phonon scattering due to structural heterogeneity, such as defects induced by phase mixing and microvoids. Combining sample preparation, structural characterization, and direct thermal measurements, our study reveals the structure–thermal property relationship for individual microspheres. The results of this work can facilitate the design and engineering of composite-based thermally conductive materials for thermal management applications.
Robust liquid repellency by stepwise wetting resistance
Authors: Sun Jing , Zhu Pingan , Yan Xiantong , Zhang Chao , Jin Yuankai , Chen Xuan , Wang Zuankai
Published: July 2021

Maintaining both high static liquid repellency and large dynamic pressure resistance is highly preferred for a myriad of applications, such as energy conversion, anti-icing, and antifouling. However, these two merits are mutually exclusive in conventional surface design: Sparse structures with reduced solid–liquid contact area yield high static liquid repellency, which in turn inevitably suffer from poor dynamic wetting properties as exemplified by low wetting resistance and easy Cassie-to-Wenzel transition. Here, we circumvent this trade-off by designing a springtail cuticle-inspired surface consisting of multilayered, doubly reentrant posts with increasing diameter from top to bottom, which simultaneously imparts high static wetting and multiple energy barriers for the gradual liquid penetration in a stepwise mode. Particularly, the synergy between the doubly reentrant structure, which increases the breakthrough pressure, and the multilayered architecture sustains a robust liquid repellency in a broad range of conditions otherwise challenging on conventional structures. Our findings provide an important insight for the rational design of robust superliquid-repellent surfaces.
Hybrid lattice-Boltzmann finite-difference simulation of ternary fluids near immersed solid objects of general shapes
Authors: Huang Jun-Jie
Published: July 2021

In this paper, a hybrid lattice-Boltzmann finite-difference method is developed for the simulation of ternary fluids near immersed solid objects of general shapes. The flow equations are solved by the lattice-Boltzmann method and the coupled Cahn–Hilliard equations for interface evolutions are solved by the finite-difference method. A special implementation of the wetting boundary condition on a surface of general shapes immersed inside the domain was extended for ternary fluids within the phase-field framework with no need to use complicated interpolations. Several two and three dimensional problems with three immiscible fluids were studied by using the proposed method and the results agree well with analytical predictions and/or previous numerical and experimental studies. In particular, the inclusion of properly chosen free energy to handle total spreading enabled us to numerically reproduce the encapsulation of a small droplet by another bigger one of different component on a round fiber. The proposed method is expected to be useful to investigate a variety of multiphase problems involving ternary fluids and surfaces with different configurations, including the challenging total spreading regime.
Nonreciprocal thermal radiation of nanoparticles via spin-directional coupling with reciprocal surface modes
Authors: Dong Jian , Zhang Wenjie , Liu Linhua
Published: July 2021

We demonstrate nonreciprocal far-field thermal emission and nonreciprocal near-field radiative heat transfer of Weyl semimetal nanoparticles when the circular thermal emission of the particles directionally couples with the spin of the surface modes supported by a reciprocal substrate. Our work can be applied to the development of nonreciprocal and directional thermal emitters and to the nanoscale routing of a radiative heat flux.
Accurate prediction of hydration free energies and solvation structures using molecular density functional theory with a simple bridge functional
Authors: Borgis Daniel , Luukkonen Sohvi , Belloni Luc , Jeanmairet Guillaume
Published: July 2021

This paper assesses the ability of molecular density functional theory to predict efficiently and accurately the hydration free energies of molecular solutes and the surrounding microscopic water structure. A wide range of solutes were investigated, including hydrophobes, water as a solute, and the FreeSolv database containing 642 drug-like molecules having a variety of shapes and sizes. The usual second-order approximation of the theory is corrected by a third-order, angular-independent bridge functional. The overall functional is parameter-free in the sense that the only inputs are bulk water properties, independent of the solutes considered. These inputs are the direct correlation function, compressibility, liquid–gas surface tension, and excess chemical potential of the solvent. Compared to molecular simulations with the same force field and the same fixed solute geometries, the present theory is shown to describe accurately the solvation free energy and structure of both hydrophobic and hydrophilic solutes. Overall, the method yields a precision of order 0.5 kBT for the hydration free energies of the FreeSolv database, with a computer speedup of 3 orders of magnitude. The theory remains to be improved for a better description of the H-bonding structure and the hydration free energy of charged solutes.
High-contrast level-crossing resonances in a small cesium vapor cell for applications in atomic magnetometry
Authors: Brazhnikov D. V. , Vishnyakov V. I. , Ignatovich S. M. , Mesenzova I. S. , Andreeva C. , Goncharov A. N.
Published: July 2021

Level-crossing (LC) resonances in alkali-metal vapors are widely used for atomic magnetometry. One of the most simple and robust techniques involves a single circularly polarized light wave, while a transverse magnetic field (Bx⊥k) is scanned around zero to observe the subnatural-linewidth resonance of electromagnetically induced transparency (EIT) in the light wave transmission. This technique allows miniaturization of the magnetic field sensor to a great extent, maintaining high sensitivity of measurements. To obtain a high quality factor of the LC resonance and, therefore, high performance of the sensor, either a high temperature (>120 °C) or an extended volume of the vapor cell (V≫1 cm3) is usually required. Here, we propose a slight modification to the commonly used configuration, which can provide high-quality LC resonances in small (≪1 cm3) vapor cells at a relatively low temperature of 60 °C or less. The modification consists in adding the second (pump) counterpropagating light wave with opposite circular polarization (σ+σ− configuration). In our experiments, the waves excite the D1-line ground-state level Fg=4 in cesium atoms in the presence of a buffer gas (Ne, 130 Torr). In the proposed scheme, a subnatural-linewidth electromagnetically induced absorption (EIA) resonance is observed. We compare parameters of the EIA resonance with those obtained in the single-wave scheme to show benefits of using the proposed σ+σ− configuration. The results have good prospects for developing a low-power miniaturized atomic magnetometer with a wide operating range.
Acoustic shielding and interaction effects for strongly heated supersonic twin jets
Authors: Pineau P. , Bogey C.
Published: July 2021

The effects of jet interactions and acoustic shielding on the noise of strongly heated supersonic twin jets are studied using large-eddy simulations. For that purpose, one single jet and three twin jets separated by distances of 2, 2.4, and 2.8 jet diameters are considered at a Mach number of 3.1 and a stagnation temperature of 2000 K. The twin jets interact and merge near the end of their potential cores at a position that is shifted downstream when the nozzle spacing increases. For larger nozzle spacing, the turbulence rates in the plane containing the jets are higher whereas those in the jet midplane are lower. In the near pressure field, the overall acoustic power radiated by the twin jets is lower than that for two non-interacting single jets, which indicates that some of the sound sources are weakened by jet interactions. A maximum noise reduction of 2 dB is reached in the jet plane, where the acoustic waves produced by one jet are shielded by the other one. Despite the overall noise reduction, some noise components are stronger for the twin jets, suggesting that they generate additional interaction noise. This is the case for the broadband shock-associated noise component and for the noise radiated at low polar angles in the jet midplane. The intensity of interaction noise increases with the nozzle spacing and varies with the turbulence rates in the inner shear layers at the axial position where the twin jets interact.
Theorising translation as a process of ‘cultural repatriation’
Authors: Pasmatzi Kalliopi
Published: July 2021

This article scrutinises instances where translation corresponds to what I call ‘cultural repatriation’, through the examination of two Anglophone novels about the Greek civil war and their transfer into Greece. Translation as repatriation concentrates on works which are, effectively, repatriated into their original context and made vulnerable to its aesthetic and socio-ideological encounters. The translation of Gage’sEleni(1983a) and de Bernières’sCaptain Corelli’s Mandolin(1994) into Greek constitutes cultural repatriation as cultural representations in the works are constructed through a ‘foreign gaze’ and rendered problematic upon transfer. Within this context, I examine how specific strategies in the promotion, translation, and consumption of these works challenge or reinforce hegemonic versions and narrative modes of the historical narrative and lead to a renegotiation of the cultural categories constructed in them. Methodologically, the article combines Bourdieu’s sociology and narrative theory creating a robust framework for the study of cultural repatriation.
Spatiotemporal stability of periodic travelling waves in a heteroclinic-cycle model
Authors: Hasan Cris R , Osinga Hinke M , Postlethwaite Claire M , Rucklidge Alastair M
Published: July 2021

We study a rock–paper–scissors model for competing populations that exhibits travelling waves in one spatial dimension and spiral waves in two spatial dimensions. A characteristic feature of the model is the presence of a robust heteroclinic cycle that involves three saddle equilibria. The model also has travelling fronts that are heteroclinic connections between two equilibria in a moving frame of reference, but these fronts are unstable. However, we find that large-wavelength travelling waves can be stable in spite of being made up of three of these unstable travelling fronts. In this paper, we focus on determining the essential spectrum (and hence, stability) of large-wavelength travelling waves in a cyclic competition model with one spatial dimension. We compute the curve of transition from stability to instability with the continuation scheme developed by Rademacher et al (2007 Physica D 229 166–83). We build on this scheme and develop a method for computing what we call belts of instability, which are indicators of the growth rate of unstable travelling waves. Our results from the stability analysis are verified by direct simulation for travelling waves as well as associated spiral waves. We also show how the computed growth rates accurately quantify the instabilities of the travelling waves.
Piecewise linear maps with heterogeneous chaos
Authors: Saiki Yoshitaka , Takahasi Hiroki , Yorke James A
Published: July 2021

Chaotic dynamics can be quite heterogeneous in the sense that in some regions the dynamics are unstable in more directions than in other regions. When trajectories wander between these regions, the dynamics is complicated. We say a chaotic invariant set is heterogeneous when arbitrarily close to each point of the set there are different periodic points with different numbers of unstable dimensions. We call such dynamics heterogeneous chaos (or hetero-chaos). While we believe it is common for physical systems to be hetero-chaotic, few explicit examples have been proved to be hetero-chaotic. Here we present two explicit dynamical systems that are particularly simple and tractable with computer. It will give more intuition as to how complex even simple systems can be. Our maps have one dense set of periodic points whose orbits are 1D unstable and another dense set of periodic points whose orbits are 2D unstable. Moreover, they are ergodic relative to the Lebesgue measure.
Complex oscillatory motion of multiple spikes in a three-component Schnakenberg system
Authors: Xie Shuangquan , Kolokolnikov Theodore , Nishiura Yasumasa
Published: July 2021

In this paper, we introduce a three-component Schnakenberg model, whose key feature is that it has a solution consisting of N spikes that undergoes Hopf bifurcations with respect to N distinct modes nearly simultaneously. This results in complex oscillatory dynamics of the spikes, not seen in typical two-component models. For parameter values beyond the Hopf bifurcations, we derive reduced equations of motion which consist of coupled ordinary differential equations (ODEs) of dimension 2N for spike positions and their velocities. These ODEs fully describe the slow-time evolution of the spikes near the Hopf bifurcations. We then apply the method of multiple scales to the resulting ODEs to derive the long-time dynamics. For a single spike, we find that its long-time motion consists of oscillations near the steady state whose amplitude can be computed explicitly. For two spikes, the long-time behavior can be either in-phase or out-of-phase oscillations. Both in-phase and out-of-phase oscillations are stable, coexist for the same parameter values, and the fate of motion depends solely on the initial conditions. Further away from the Hopf bifurcation points, we offer numerical experiments indicating the existence of highly complex oscillations.
Fast flavor oscillations of astrophysical neutrinos with 1, 2, …, ∞ crossings
Authors: Bhattacharyya Soumya , Dasgupta Basudeb
Published: July 2021

In the early Universe, as well as in supernovae and merging neutron stars, neutrinos have such high densities that they affect each other and exhibit collective flavor oscillations. A crucial ingredient for fast collective flavor oscillations is that the electron lepton number (ELN) distribution changes its sign as a function of direction, i.e., has a zero crossing. We present a study in two spatial dimensions and time, focussing on the fast and linear regime, and show how fast flavor oscillations depend on the ELN and its crossings. We show that a large number of crossings can inhibit flavor oscillations. This may be a natural self-limiting mechanism that stabilizes the flavor content of the dense neutrino gas in a vast majority of scenarios, especially the early Universe, where the angular distributions for all flavors are very similar and crossings occur mainly due to fluctuations.
Correction of calculated dynamic scheme of unmanned aerial vehicle based on results of ground modal tests
Authors: Parafes’ S , Turkin I
Published: July 2021

The problem of correcting of the calculated dynamic scheme of an unmanned aerial vehicle (UAV) based on the results of ground modal tests is considered. The provisions that allow achieving satisfactory results when the UAV calculated dynamic scheme correcting are formulated. Correction criteria are considered. Features of the calculated dynamic scheme correction in the study of the flutter and the aeroelastic stability of the UAV with the automatic control system (ACS) are presented. It is noted that along with the provisions that are universal for dynamical aeroelasticity tasks related to the correction of natural frequencies, forms, and coefficients of structural damping of the UAV on the results of ground modal tests, in the study of aeroelastic stability of the UAV with the ACS is also crucial to correct the transfer function of the UAV body from section, in which the rudder rotation axes are located, up to the cross-section, where ACS sensors are installed. This is because the UAV body is directly part of the UAV stabilization loop and significantly affects to its stability reserves. An example of correcting of the UAV calculated dynamic scheme is given.
Assessment of aircraft prospects using a combined method of identifying preferences
Authors: Sudakov V , Sivakova T
Published: July 2021

Recently, the task of replacing the aircraft fleet has been in demand. The aim of the work is a multi-criteria assessment of aircraft and further decisions on their use. To solve this problem, it is proposed to use a combined method for identifying preferences, which is well algorithmic and allows you to take into account dependences on preferences in the multidimensional system of values of the decision maker. An algorithm based on the method of enumeration on a vector lattice has been developed. This algorithm helps the decision maker to take into account a large number of criteria and decide on the need to replace the aircraft. The advantages include a reduction in the calculation time. An interface for entering editing and preferences is proposed, which makes it possible to assess the feasibility of introducing new and withdrawing old aircraft.
Research on the Application of Machine Vision in Tea Autonomous Picking
Authors: Tian Jun , Zhu Honglin , Liang Wenjiang , Chen Jingshan , Wen Feijuan , Long Zhang
Published: July 2021

As a non-destructive, real-time, fast, objective, and economical detection method, machine vision technology has been widely used in target recognition and positioning in various fields in recent years. Selective picking of tea buds is an important prerequisite for high-quality and efficient tea production. Autonomous picking of tea based on machine vision has become a research hotspot at home and abroad. At present, many scholars have studied the visual recognition and positioning methods in the process of intelligent tea picking, but the effect has not yet reached the actual picking requirements. In order to give everyone a comprehensive understanding of the existing research methods, this article systematically reviews the tea bud segmentation and bud picking point positioning methods based on machine vision technology, and prospects the application prospects and directions of machine vision technology in tea picking.
A Pose Transformation Estimation Method Based on Feature Extraction and Matching in Ceramic Green Body Bonding Process
Authors: Ma Qihang , Zhang Jian
Published: July 2021

Bonding the ceramic green-bodies of the seat ring to the cup body is an important step in the production process of the toilet. This paper proposes a pose transformation estimation method based on feature extraction and matching in ceramic green body bonding process. This method uses a Local Feature Statistics Histogram (LFSH) to extract the features of the bonding surfaces and find the corresponding point sets. Then, a Sample Consensus Initial Aligment (SAC-IA) algorithm combined with LFSH features is used to perform coarse registration calculation. Finally, using the Iterative Cloest Point (ICP) algorithm, the result of the coarse registration is used as the initial value to complete the fine registration and obtain the pose transformation matrix. Before registration, the relative poses of the two point clouds are randomly transformed. This method is tested on the point cloud data of the cup body and the seat ring. Experimental results show that the role of SAC-IA can increase the speed of registration compared to using ICP alone.
Research on driving force of electric four-wheel drive rodless aircraft tractor when crossing obstacles
Authors: Zhang Mingyang , Liu Huan
Published: July 2021

In this paper, the static analysis of an electric four-wheel drive rodless aircraft tractor over obstacle with load is carried out. Based on MATLAB, all combination of front and rear wheel driving forces are calculated, and the minimum driving force required for obstacle surmounting under different parameters is obtained. The above work provides necessary theoretical basis for tractor design.
Parametric design of inner teeth of center wheel in electromagnetic harmonic movable teeth transmission
Authors: Yubo Ren , Yaoyang MA , Rui Wan
Published: July 2021

In order to improve the rationality and design efficiency of the structural parameters of the electromagnetic harmonic movable teeth drive system, the rationality of the set parameters is judged based on theoretical calculation, and visual programming is carried out by using VB. The designer only needs to input the set parameters into the specified dialog box to get the corresponding output results, which makes the design of the inner teeth of the center wheel more convenient and fast.
Design and analysis of permanent magnet synchronous servo motor with low rotational inertia and high torque density
Authors: Chenwei Yang , Fei Dong , Yi An , Fengqing Zhu
Published: July 2021

Aerospace servo motor has the characteristics of strong load capacity, fast response and high control accuracy. To satisfy the design target of high dynamic performance and low weight, the high magnetic loading ironless-core array rotor structure is applied to balance the low rotational inertia and high torque density of permanent magnet servo system.
Study on critical condition of dynamic recrystallization of large back-up roll steel
Authors: Qi Peng , Ren Facai , Xu Jinsha
Published: July 2021

70Cr3Mo alloy steel is mainly used to produce large back-up roll for cold rolling mill, which has higher processing quality requirements. In this paper, the hot compression test of 70Cr3Mo large back-up roll steel was carried out, and the flow stress curves under different deformation temperatures and strain rates were obtained. The critical condition of dynamic recrystallization of the steel was determined by calculation and fitting, and the critical stress formula of dynamic recrystallization was obtained.
The structure design of the end picker for the automobile control arm stamping production line
Authors: Xiaogang Liu , Junchen WU
Published: July 2021

In the process of stamping, production and transportation of automobile control arm, the surface of the workpiece can not be adsorbed due to the oil stains on the surface of the workpiece. The traditional vacuum chuck can not be adsorbed. The electromagnetic chuck will generate heat for a long time and cause the magnetic force to decline, resulting in reduced reliability and causing the workpiece to fall off. The principle uses NdFeB material to design a new type of electric permanent magnet end picker. When the power is cut off, it relies on the magnetic force of the permanent magnet to adsorb. After the robot transfers the workpiece, the coil around the reversible material is passed through an electric current to generate an electromagnetic field opposite to the permanent magnet. To counteract the magnetic force, the workpiece is separated, the end suction cup of the end picker is designed according to the quality of the workpiece and the contact area, and ANSYS ELECTRONICS is used for modeling analysis and verification. The data shows that the device can meet the needs of the car control arm grasping and handling work. It provides a new idea for automatic production line of automobile control arm.
Finite element simulation of plough cone cutter
Authors: Li Guangqiao , Liu Xiaomin , Bai Zongxi
Published: July 2021

In order to improve the ROP of the PDC bit, a plough cone cutter was designed and finite element simulation was performed. Compared with conventional cutter, plough cone cutter has smaller stress field and strain field in the rock breaking process. The largest tangential rock breaking force and maximum axial rock breaking force is higher, but the average tangential rock breaking force and the average axial rock breaking force are smaller, and the rock breaking effect is better; the back dip angle has a significant impact on the rock breaking effect. Under the same plough cone cutter, with the increase of the inclination angle, the stress field and strain field of the rock after rock breaking will become smaller, and the rock breaking effect will be better. Therefore, the plough cone cutter with a backward inclination angle of 22° has an advantage in the rock breaking process.
Artificial vascular implants with unidirectional drug release and mechanical properties imitating natural blood vessels
Authors: Bin Wang , Yi Zhang , Junchao Hu , Yuanyuan Liu
Published: July 2021

Small-diameter artificial vessels require a combination of a range of material properties, including high strength, compliance, sutureability, and kink resistance in specific situations. We combined electrospinning technology with thermally induced separation technology to prepare composite three-layer artificial vessels using a PCL/gelatin co-blended material and a hybrid hydrogel enhanced gel structure to achieve high strength, flexibility and kink resistance, as well as excellent water tightness. The electrospun fibers in the artificial vessel provide mechanical stability, while the gelatin blended material enhances hydrophilicity. The results show that the three-layer composite structure is well bonded together, provides sufficient rupture strength and sutureability, and exhibits arterial-like compliance and resistance to kinking. The hydrogel layer drug release rate can also be adjusted by adjusting the PCL/gelatin co-blended layer ratio. This composite vascular scaffold is expected to play an important role in tissue engineering.
Lipschitz discrete observer design for HCCI engine mixed gas temperature at intake valve closed
Authors: Zheng Taixiong , Yang Xinqing , Li Yongfu , Ma Ying
Published: July 2021

The gas temperature for Homogeneous Charge Compression Ignition engine at intake valve closed is difficult to measure; so a Lipschitz discrete observer is designed. In particular, a single cylinder engine model is proposed. And, a thermodynamic process based state equation is presented considering the heat loss of residual exhaust gas. Consequently, a discrete nonlinear state observer is designed using Lipschitz condition. Finally, the numerical experiments are performed. The results demonstrate the effectiveness of the proposed observer in terms of the accuracy and robustness.
Design of a New Engine Hood based on Lattice Structure for Pedestrian Protection
Authors: Liu Meng , Sun Fuzhen , Wang Baoming , Wang Jianfeng , Yang Na
Published: July 2021

This paper designs four kinds of three-dimensional negative Poisson’s ratio lattice structures, based on the two-dimensional concave hexagonal negative Poisson’s ratio honeycomb structure. Different parameters are designed for simulation analysis and experimental research, and the influence of different parameters on Poisson’s ratio is studied respectively. The main contents are as follows: Firstly, the three-dimensional solid model of lattice structure is established by modeling software, and the different structural parameters are determined, and the equivalent mechanical model is established. And according to the relevant structural parameters to establish the test scheme. Then, the finite element software is used to simulate the test core material with different parameters. According to the simulation results, the influence of different parameters on Poisson’s ratio is found out. Then the crashworthiness of the test board with different parameters is simulated and analyzed. According to the results, the most suitable structure is selected and applied to the engine hood. Finally, the simulation experiment of collision between pedestrian head and engine hood is carried out. The results of this paper compare the performance of lattice sandwich panels with different parameter structures in different tests and select the optimal combination of structural parameters. The adjustment and optimization direction of the structure is put forward according to the test results.
Pattern Recognition of Quality Control Chart of Multi-variety and Small-batch Production Mode Based on MC-GA Optimized BP
Authors: Meng Lili , Ji Kun , Zheng Lei , Sun XiaoWei
Published: July 2021

To solve the problem of product quality control in multi-variety and small-batch production mode, a quality control chart recognition model of MC-GA optimized BP was established by using Monte Carlo method to simulate the product quality data characteristics of different varieties and combining the data processing capability of neural network and the adaptive global optimization search capability of genetic algorithm; then the MC(Monte Carlo method)-GA(Genetic Algorithm) optimized BP(Back Propagation Neuron Network) was compared with the traditional MC-BP is compared and analyzed in terms of accuracy, time and error in quality control graph pattern recognition, and it is concluded that the former is better in quality control graph pattern recognition. It can be seen that the MC-GA optimized BP model is more effective in identifying the quality status of products in the multi-variety and small-batch production mode, and can accurately predict the stability of the manufacturing process, so as to enhance the competitiveness of enterprises.
Research on compliant path planning of two-machine cooperation of industrial robots
Authors: Zhao Wei
Published: July 2021

Since its invention, industrial robots have developed into intelligent automation equipment that integrates multi-disciplinary technologies and are widely used in manufacturing and other industries. With the increasing requirements for the development of productivity, the application research of multi-robot cooperative work unit highlights its importance. In order to realize the safe and stable operation of robots, it is necessary to carry out collision-free and compliant path planning. This paper analyzes the related theories of industrial robot two-machine cooperation, combines the key points of industrial robot two-machine cooperation compliant path planning, and establishes a simulation experiment to simulate the application process. Its purpose is to accumulate reliable application data and lay the foundation for the continuous optimization of the cooperation system.
Grinding machine CNC with noble integrated motion control system
Authors: Qinghua Wang , Yanhua Hu , Renxuan Fu , Junyong He
Published: July 2021

According to research progress and applying technology of CNC control system architecture, this paper discusses three kinds of CNC control systems: Open CNC system, embedded CNC system and PLC CNC system, and a new architecture is proposed. The paper illuminates that integrated motion control system architecture is a new concept of CNC, by which it has high precision and low cost. In this paper, a grinding machining controller using this structure is described and verified by software.
Research of Mechanical Interface Control Model for Aircraft Digital Mock up
Authors: Jian Xu , Xinai Zhang , Hao Su
Published: July 2021

Mechanical interface design is used to clarify the design division and interface of all parties, and is one of the important tasks of aircraft design. The mechanical interface control model is a digital representation of the mechanical interface characteristics between one aircraft system (including structure) and another. It is a model carrier for mechanical interface design collaboration. This article introduces the definition and classification of the mechanical interface control model of the aircraft digital mock up, focuses on the general design process, requirements, application and management of the mechanical interface control model, it provides relevant reference and help for the design and management of the mechanical interface of the aircraft digital mock up.
A Novel 5G Band Filter Based on Ceramic Dielectric
Authors: Luo Bing , Zhan Zhong-shan , Fang Bo , Zhang Jian-bao
Published: July 2021

The construction of 5G system is in the works. In order to improve the anti-interference and reduce the volumes of 5G system, it is important to design a filter with better filtering performance and smaller volume. At present, the research of 5G filter is almost base on metal resonator. This paper designs a ceramic dielectric resonator, and on the basis of the designed dielectric resonator, a 5G band dielectric filter is designed after theoretical calculation and analysis by using rf/microwave simulation software HFSS. The coefficients are realized by the distance between two resonators, and the Q value is realized by the distance between the input port and the first resonator. The results show that in the pass-band (3.4 ∼ 3.5GHz), the return loss is more than 15dB, the insertion loss is less than 0.35dB, and the VSWR is 1.62. The filter has the advantages of small insertion loss, small size and good rejection out of pass-band, which can be applied to 5G band wireless communication system with better suppression performance to improve the communication quality of the communication system.
Dynamic Performance study of Giant Magnetostrictive Actuator
Authors: Yan Wu , Yong He , Haoran Song , Zhijuan Ding , Xuhui Liu
Published: July 2021

Optimized design problems for giant magnetostrictive actuator (GMA) structures, the effects of structural dimensions on dynamic properties of GMA were analyzed. In this paper, an equivalent dynamic model of GMA was established, and the step response and frequency response of GMA were simulated and analyzed. The results show that the length of the giant magnetostrictive rod and the mass of the load have great influence on the dynamic performance of the GMA system.