bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of moderate and vigorous walking exercise on reducing depression in middle‐aged and older adults: A pilot randomized controlled trial
Authors: Yu Danny J. , Yu Angus P. , Leung Chit K. , Chin Edwin C. , Fong Daniel Y. , Cheng Calvin P. , Yau Suk Y. , Siu Parco M.
Published: May 2022

The optimal intensity of physical activity for alleviating depression in middle‐aged and older adults remains unclear. The World Health Organization (WHO) physical activity guidelines recommend adults and older adults to accumulate at least 150–300 minutes of moderate or 75–150 minutes of vigorous aerobic‐type physical activity weekly or an equivalent combination of both for health benefits including reduced risk of depression. This parallel, assessor‐blinded, pilot randomized controlled trial preliminarily compared the effectiveness of the minimal volume of aerobic‐type physical activity at different intensities as recommended by WHO (150 minutes of moderate walking exercise and 75 minutes of vigorous walking exercise weekly) on alleviating depression in middle‐aged and older adults. Thirty‐five participants were randomized to the control group (CON), moderate walking exercise group (MOD), or vigorous walking exercise group (VIG). The exercise frequency was three times a week and the intervention duration was 12 weeks. The primary outcome was the severity of depression assessed by Beck Depression Inventory. Secondary outcomes included severity of anxiety, sleep quality, quality of life, and cardiorespiratory fitness. Thirty participants completed the study (CON: n = 10, MOD: n = 10, VIG: n = 10). Participants in both MOD and VIG had significantly decreased depression severity after the intervention compared to CON (both p < 0.001). There was no significant difference between MOD and VIG (p = 0.92). Both MOD and VIG interventions also mitigated anxiety severity, improved quality of life and cardiorespiratory fitness. The minimum volume of walking exercise at either moderate or vigorous intensity was found to alleviate depression in middle‐aged and older adults.

Trial registration: ClinicalTrials.gov identifier: NCT04403373.

Highlights

The 12‐week 150‐minute moderate walking exercise and 75‐minute vigorous walking exercise (the minimal weekly volumes of aerobic‐type physical activity recommended by WHO guidelines) similarly reduced the severity of depression in middle‐aged and older adults.

The 12‐week walking exercise interventions significantly reduced anxiety severity concomitant with improved quality of life and cardiorespiratory fitness in middle‐aged and older adults with depression.
Bound states of central force system in special relativity
Authors: Setiawan Iwan , Sugihakim Ryan , Gunara Bobby Eka
Published: May 2022

In this paper we consider the central force problem in the special theory of relativity. We derive the special relativistic version of the Binet equation describing the orbit of a massive body. Then, the motion of a planet in a solar-like system where the gravitational potential is modified by adding a term that is proportional to the inverse of the square of the radial coordinate is discussed. Using perturbative method, we obtain the explicit orbital function. At the end, the orbital precession of the planet and its relation to the result from general relativity are also discussed.
The transverse magnetic electromagnetic bound mode in a black phosphorene inserted multilayer dielectric structure
Authors: Yang C H , Yang J T , Peng K K , Li Q F
Published: May 2022

The electromagnetic wave of the bound mode along the black phosphorene (BP) interface and the field distribution in a BP inserted planar multilayer dielectric structure have been investigated. The dispersion results indicate that the transverse magnetic surface plasmon wave is a bound mode and anisotropic with different electric field polarization directions. The effective refractive index increases as a function of the incident optical energy. It can also be tuned by the chemical potential and the thickness of the middle dielectric layer. The variable coupling strength between the light and matter based on the BP intraband optical conductivity makes the influence of the thickness of the middle dielectric layer significant or negligible in the lower and higher frequency regimes, respectively. The presented results can be applied to design BP-based promising optoelectronic devices.
Quasinormal modes of Schwarzschild black holes in projective invariant Chern-Simons modified gravity
Authors: Boudet S. , Bombacigno F. , Olmo G.J. , Porfírio P.J.
Published: May 2022

We generalize the Chern-Simons modified gravity to the metric-affine case and impose projective invariance by supplementing the Pontryagin density with homothetic curvature terms which do not spoil topologicity. The latter is then broken by promoting the coupling of the Chern-Simons term to a (pseudo)-scalar field. The solutions for torsion and nonmetricity are derived perturbatively, showing that they can be iteratively obtained from the background fields. This allows us to describe the dynamics for the metric and the scalar field perturbations in a self-consistent way, and we apply the formalism to the study of quasinormal modes in a Schwarzschild black hole background. Unlike in the metric formulation of this theory, we show that the scalar field is endowed with dynamics even in the absence of its kinetic term in the action. Finally, using numerical methods we compute the quasinormal frequencies and characterize the late-time power law tails for scalar and metric perturbations, comparing the results with the outcomes of the purely metric approach.
Multivariate analysis reveals topography dependent relationships amongst neurite morphological features from dorsal root ganglia neurons
Authors: Nelson Derek W , Puhl Devan L , Funnell Jessica L , Kruger Uwe , Gilbert Ryan J
Published: May 2022

Objective. Nerve guidance scaffolds containing anisotropic architectures provide topographical cues to direct regenerating axons through an injury site to reconnect the proximal and distal end of an injured nerve or spinal cord. Previous in vitro cultures of individual neurons revealed that fiber characteristics such as fiber diameter and inter-fiber spacing alter neurite morphological features, such as total neurite length, the longest single neurite, branching density, and the number of primary neurites. However, the relationships amongst these four neurite morphological features have never been studied on fibrous topographies using multivariate analysis. Approach. In this study, we cultured dissociated dorsal root ganglia on aligned, fibrous scaffolds and flat, isotropic films and evaluated the univariate and multivariate differences amongst these four neurite morphological features. Main results. Univariate analysis showed that fibrous scaffolds increase the length of the longest neurite and decrease branching density compared to film controls. Further, multivariate analysis revealed that, regardless of scaffold type, overall neurite length increases due to a compromise between the longest extending neurite, branching density, and the number of primary neurites. Additionally, multivariate analysis indicated that neurite branching is more independent of the other neurite features when neurons were cultured on films but that branching is strongly related to the other neurite features when cultured on fibers. Significance. These findings are significant as they are the first evidence that aligned topographies affect the relationships between neurite morphological features. This study provides a foundation for analyzing how individual neurite morphology may relate to neural regeneration on a macroscopic scale and provide information that may be used to optimize nerve guidance scaffolds.
Identifying oscillations under multi-site sensory stimulation for high-level peripheral nerve injured patients: a pilot study
Authors: Geng Yanjuan , Qin Liuni , Li Yongcheng , Yu Zhebin , Li Linling , Asogbon Mojisola Grace , Zhan Yang , Yan Nan , Guo Xin , Li Guanglin
Published: May 2022

Objective. For high-level peripheral nerve injuryed (PNI) patients with severe sensory dysfunction of upper extremities, identifying the multi-site tactile stimulation is of great importance to provide neurorehabilitation with sensory feedback. In this pilot study, we showed the feasibility of identifying multi-site and multi-intensity tactile stimulation in terms of electroencephalography (EEG). Approach. Three high-level PNI patients and eight non-PNI participants were recruited in this study. Four different sites over the upper arm, forearm, thumb finger and little finger were randomly stimulated at two intensities (both sensory-level) based on the transcutaneous electrical nerve stimulation. Meanwhile, 64-channel EEG signals were recorded during the passive tactile sense stimulation on each side. Main results. The spatial-spectral distribution of brain oscillations underlying multi-site sensory stimulation showed dominant power attenuation over the somatosensory and prefrontal cortices in both alpha-band (8–12 Hz) and beta-band (13–30 Hz). But there was no significant difference among different stimulation sites in terms of the averaged power spectral density over the region of interest. By further identifying different stimulation sites using temporal-spectral features, we found the classification accuracies were all above 89% for the affected arm of PNI patients, comparable to that from their intact side and that from the non-PNI group. When the stimulation site-intensity combinations were treated as eight separate classes, the classification accuracies were ranging from 88.89% to 99.30% for the affected side of PNI subjects, similar to that from their non-affected side and that from the non-PNI group. Other performance metrics, including specificity, precision, and F1-score, also showed a sound identification performance for both PNI patients and non-PNI subjects. Significance. These results suggest that reliable brain oscillations could be evoked and identified well, even though induced tactile sense could not be discerned by the PNI patients. This study have implication for facilitating bidirectional neurorehabilitation systems with sensory feedback.
Dynamics of charge-imbalance-resolved entanglement negativity after a quench in a free-fermion model
Authors: Parez Gilles , Bonsignori Riccarda , Calabrese Pasquale
Published: May 2022

The presence of a global internal symmetry in a quantum many-body system is reflected in the fact that the entanglement between its subparts is endowed with an internal structure, namely it can be decomposed as a sum of contributions associated to each symmetry sector. The symmetry resolution of entanglement measures provides a formidable tool to probe the out-of-equilibrium dynamics of quantum systems. Here, we study the time evolution of charge-imbalance-resolved negativity after a global quench in the context of free-fermion systems, complementing former works for the symmetry-resolved entanglement entropy. We find that the charge-imbalance-resolved logarithmic negativity shows an effective equipartition in the scaling limit of large times and system size, with a perfect equipartition for early and infinite times. We also derive and conjecture a formula for the dynamics of the charged Rényi logarithmic negativities. We argue that our results can be understood in the framework of the quasiparticle picture for the entanglement dynamics, and provide a conjecture that we expect to be valid for generic integrable models.
Numerical simulation of hovering flow field and interference characteristics of rotor system
Authors: Wang Yu , Sun Mao , Yan Chao
Published: May 2022

In order to investigate the aerodynamic interference characteristics of tandem rotor, this paper simulates the hovering flow field of single rotor and tandem rotor based on the dynamic structure overset grid method and unsteady Navier-Stokes equations in computational fluid dynamics (CFD). In the study of hover state of single rotor with twist, the trajectory of the blade vortex and the change pattern are briefly analyzed. Subsequently, the flow field disturbance of tandem rotor, the vortex structure, the pull coefficient and the downwash flow are investigated. The results show that there is obvious blade vortex interference in the overlapping area of the tandem rotor, where the downwash flow reduces the effective angle of attack of the blade and thus has a significantly effect on the pull coefficient. The rotor is less disturbed when it is far from the overlapping area, and the tension coefficient does not change significantly. After integrating the pull coefficient of the upper and lower rotors in one cycle, it was found that the loss of pull coefficient of the two rotors reached 5.7% and 10.7% respectively, which proved that the aerodynamic interference between the tandem rotor in hovering condition had an important effect on the aerodynamic performance of the vehicle.
Aircraft Condition Detection Based on Distributed Optical Fiber Sensing Technology
Authors: Zhang Zhen , Tian Zhenzi
Published: May 2022

This paper describes the principle of distributed optical fiber sensing technology and its application in the field of aircraft condition detection. Firstly, the differences between two kinds of distributed fiber sensing technologies are introduced, and the characteristics of the existing typical distributed fiber Bragg grating sensing system and the system type selection need system coverage, parameter sampling rate and reflected light demodulation mode. Then it introduces the principle and steps of using wavelet transform algorithm to analyze the aircraft state information. Finally, the system architecture suitable for the aircraft state detection environment is analyzed and proposed, and the integration scheme of the system with the state detection information acquisition system is discussed based on the characteristics of the system, and the problems needing attention such as time synchronization, data frame format and system interface are summarized.
Design and Research of Double-Wheeled Helicopter Tractor
Authors: Li Jing , Zheng Naibo
Published: May 2022

Due to the limited wheel size, existing domestic helicopter tractors are only applicable to some small and medium-sized single-wheeled helicopters. This paper introduces a double-wheeled helicopter tractor. The wheel holding mechanism can maximally hold a helicopter with a wheel diameter of 500mm, thus suitable for most common types of general aviation airports, such as Z-9, AS-365N, EC-155, AW -139, AS-332, etc. By improving stable torque output of the motor at low speed, self-developed reducer greatly increases the applicability and safety of helicopter traction.
Research on Simulation Method of Aircraft Design Based on Apriori Algorithm Analysis Research
Authors: Wang Hongsong
Published: May 2022

Aiming at the optimization problem of the aircraft design simulation method, in order to solve related problems, a new optimization method using gradient algorithm is proposed, and it is combined with Apriori algorithm analysis. Apriori algorithm analysis has advantages as well as some disadvantages. The advantage lies in its global optimization processing, while the limitation lies in its early maturity, and the local optimization performance needs to be improved. For this problem, this article adds the gradient algorithm to the experimental process. By accelerating the implementation of the gradient algorithm and retaining the optimal solution of the iterative process, global convergence is achieved, thereby increasing the calculation speed to a certain extent.
Numerical investigation of non-premixed H2-Air rotating detonation combustor with different equivalence ratios
Authors: Jiang Hanyu , Huang Yue
Published: May 2022

The initiation and propagation of rotating detonation waves (RDWs) are key techniques for the engineering application of rotating detonation engine (RDE). In this paper, the Naiver-Stokes equation of the three-dimensional unsteady reaction flow has been solved using one step hydrogen/air reaction mechanism to investigate the formation and propagation processes of RDWs under the non-premixed condition with different inlet equivalence ratios. The numerical results show that compared with RDWs generated by premixed propellants, less stable propagation processes and lower detonation fronts can be observed in RDWs generated under the non-premixed condition. It can be also concluded that the equivalence ratio has a great effect on the formation and propagation of RDWs. The formation time of stable RDWs increases when the ER changes from 1.0 to 1.3. However, under the conditions of the two ERs, similar re-initiation phenomena is observed in the evolution process of RDWs and a three-wave mode has been established.
Numerical Investigation on the Height of Detonation Wave in Rotating Detonation Engine
Authors: Xue Sainan , Ma Hu , Wang Fengming , Zhang Cuizhen , Xu Can , Zhuo ChangFei , Zhou Changsheng
Published: May 2022

Three-dimensional numerical simulations were conducted on a non-premixed rotating detonation engine (RDE) with different exhaust nozzles (i.e. without a nozzle, with a divergent nozzle, with a convergent nozzle, and with a Laval nozzle). Aside from describing the flow-field structure inside the chamber, the detonation wave height of the detonation wave, and the outlet Mach number were also investigated. It is found that the convergent and Laval nozzles make the flow-fields more complex in chamber by the reflected shock waves. The height rises with the increase of air mass flow rate when detonation chamber exit is in choke state, but it decrease when detonation chamber exit is not in choke state.
Design of a fuel-efficient scheme for space debris removal
Authors: Hu Wenjun , Yang Yueneng
Published: May 2022

In view of the growing threat of space debris and the limitation of current debris removal method. A novel conceptual solution for multiple space debris removal is proposed, and a low-cost and miniaturized removal system is designed in this paper. And the structural composition of this removal system is designed and the space debris removal process is introduced, the system can be divided into two components including satellite platform and many mission CubeSats. The mission CubeSats can be re-launched into the transfer orbits of different space debris through a push-launch method, and the fuel consumptions on the removal mission for three space debris, using the proposed multiple removal system and traditional removal system are calculated and compared. The compared results demonstrated that the proposed solution for multiple space debris removal and the designed removal system can decrease the fuel consumptions effectively.
Adaptive Fault-tolerant and Anti-disturbance Attitude Control of the Reconfigurable Modular CubeSat
Authors: Shi Jian-Cai , Song Xiao-Dong , Yan Ming-Zheng , Shen Xiao-Peng
Published: May 2022

This paper addresses the dynamical coupling and attitude control problems caused by the large-scale abrupt changes of the system mass characteristics and the relative motion of the sub-body during the autonomous reconfiguration of the modular satellite in orbit, the attitude dynamics equations of the reconfigurable modular CubeSat system with time-varying mass characteristics parameters are derived. An improved adaptive fault-tolerant anti-disturbance control algorithm that does not rely on an accurate dynamics model and converges quickly in finite time is also proposed based on the composite control idea. In the attitude control of modular CubeSat with large external disturbances and large range of moment of inertia time variation, the method has a faster convergence speed and higher accuracy than the traditional sliding mode control. Without any fault detection and diagnostic information, the method is able to achieve fast and highly accurate attitude adaptive fault-tolerant control in the presence of large disturbances and actuator time-varying, stochastic-type faults through real-time observation of total disturbances inside and outside the system. The final simulation results verify the effectiveness and reliability of the method.
Star spot centroid extraction method in high dynamic condition based on difference hash algorithm
Authors: Di PAN , Qi ZHOU , Weizhi QU , Bing LIU , Pingchuan REN
Published: May 2022

In high dynamic conditions, star spot exhibits a tailing phenomenon, which makes it impossible to accurately extract the star centroid. Adjusting the exposure time can shorten the tail length but it will reduce the energy received by the detector, which also makes it difficult to extract the star target. Aiming at the above two problems, this paper proposes a star spot centroid extraction method under high dynamic conditions based on different hash algorithm. The method is divided into three steps. Firstly, establish a mathematical model of dynamic star spots. Then using difference hash algorithm and Hamming distance to realize coarse positioning of star targets in star tracking window. Finally, adopt threshold segmentation and connected domain method to extract star spot centroid in the coarse location area. The experimental results show that the proposed method can adapt to various exposure time, making the star sensor realize the stable tracking at the angular velocity of 3°/s. When the exposure time is 50ms and the angular velocity is 3°/s, the angular distance error is 13 arcseconds, the average extraction rate is 96%, which is 29.6% and 29.7% better than the traditional method.
Three-dimensional low-altitude flight trajectory planning technology based on digital map
Authors: Zerui CHAO , Ying NAN , Xin WANG
Published: May 2022

Aiming at the intricate terrain of Yunnan, a three-dimensional low-altitude flight trajectory planning technology based on digital maps is proposed. First, divide the map of Yunnan into 36 digital maps, use VC++ to write a program to read the longitude and latitude coordinates of each point in the digital map and the height of each point into the memory, generate a grid coordinate system based on the start and end points, and find the grid from the memory The height data corresponding to each point in the coordinate system; then, the dynamic planning algorithm and the simple method are used to perform terrain avoidance and terrain following in the grid coordinate system, and finally, use MATLAB to draw the planning path map in the geographic coordinate system.
A numerical Investigation on Schardin’s Problem Using a Quasi-DNS Solver
Authors: Li Weixuan , Li Yingkun , Li Chunlei , Zhu Liang , Chen Xiong
Published: May 2022

In the present research, Schardin’s problem is numerically investigated using a FORTRAN based quasi-DNS solver, the numerical results are validated using the experimental result and the shock impinges process is analyzed in detail. During the shock impinges process, we noticed that the periodical vortex shedding phenomena could be observed, thus, the proper orthogonal decomposition (POD) is utilized to shed light on the flow features during the vortex shedding process.
Construction of an Smart Progress Production Unit Based on Paddle Boring
Authors: Guan Xiang , Sun Jinhao , Hou Zhixia , Xiao Qingdong , Chen Long , Gan Lu
Published: May 2022

With the continuous improvement of hardware product performance and data processing capability and the rapid development of network communication technology, the intelligent technology of computer systems is becoming more and more mature, and the intelligence of manufacturing has become the focus of people's attention. The intelligent performance of manufacturing is to use the knowledge obtained from data analysis to make inferences and decisions to solve problems, and the Cyber-Physical System (CPS) supports the deep integration of informationization and industrialization by integrating advanced information technology and automatic control technology, such as perception, computation, communication, control, etc. Although there has been great progress in the research of CPS, it has been widely used in the development of computer systems. Despite significant progress in CPS research, some key issues have yet to be fully addressed at the shop floor level, including dynamic reorganization and local intelligence. These issues have hindered the research on the intelligence of complex processes. For progress units of complex processes, this study proposes a CPS-based smart progress unit (SPU) construction method. In order to improve machining efficiency and quality consistency, this study proposes a multi-source data acquisition technique and a multi-objective optimization algorithm to process the data within the machining unit. Finally, this study takes the paddle boring process as an example, and designs hardware and software systems to automate the paddle boring process and meet the needs of automation and intelligent transformation of the paddle boring process.
Design of X-axis Feed System of Cradle Five Axis CNC Machine Tool and its Computer Finite Element Analysis
Authors: Zhu Xiurong
Published: May 2022

For the design of the x-axis feed system of the cradle five axis CNC machine tool, the entity modeling is carried out by using CATIA P3 v5r21 and Auto CAD; the x-axis design of the cradle five axis CNC machine tool is carried out and the accuracy and strength are checked; the CAE analysis of the structural strength and stability is carried out by using the general structural analysis module. The DMU kinematics module is used to eliminate the interference. Optimize the structural parameters to improve the stability and accuracy of machine tools.
Dynamic simulation of flap mechanism considering assembly error
Authors: Xue Xiaofeng , He Zhiyu , Feng Yunwen , Cui Weijun
Published: May 2022

The existence of assembly error will have an impact on the kinematic accuracy and dynamic performance of mechanical system, which can not be ignored. Therefore, a dynamic simulation method of flap mechanism considering assembly error is established. Firstly, the motion digital prototype of flap mechanism and the rigid flexible coupling dynamic model considering the deformation of flap wing surface are established, and then when the error direction is fixed, by setting the deviation values of the two driving shafts, the influence on the driving torque of the flap mechanism and the load of key components under the working conditions of 2mm, 4mm and 6mm is explored. Then, through the eight error directions defined by the deviation function, the influence of the direction error of the drive shaft assembly on the driving torque of the flap mechanism is obtained when the error size is 6mm fixed. The results show that when the assembly deviation of the two driving shafts is in the three working conditions with the selected size, the flap trajectory basically coincides, and the driving torque of the inner mechanism increases by 10.19% when the error is 6 mm; When the size of the assembly error remains fixed, the change of the error direction will increase the driving torque of the flap mechanism. The dynamic simulation study can provide some theoretical guidance for the manufacturing and assembly of this type of high-lift device.
Optimal Design and Research on the Structure of Tripod Constant Velocity Universal Joint
Authors: Lu Yujun , Wang Wei , Feng Chanjing , Zhao Zhichang
Published: May 2022

In order to reduce the problems of wear between the internal structures of the universal joints and short service life, a new track contact structure was designed based on the original type of universal joint structure, and a mechanical model of the structure was established. In the ANSYS Workbench, the material properties, contact pair settings, universal joint force and other parameters are analyzed, the contact stress changes between the original structure and the optimized structure are studied, and the torsional fatigue life experiment is carried out in conjunction with the experimental workbench. The results show that the optimized new structure can effectively reduce wear and increase durability in the service process, thus extending its service life.
Evaluation of flow and heat transfer performance of spiral coil jacket with different cross sections
Authors: Wang Lv , Liao Xiaoping , Li Hongjun
Published: May 2022

The flow and heat transfer performance of the spiral coil jacket for a reactor with five different cross-section shapes was evaluated. The comprehensive performance of five jacket models was analyzed through PEC and JF evaluation factors, which provided a basis for jacket design in industrial application. The results showed that at certain Reynolds number, the Nusselt number of the arcuate cross-section jacket was lower than that of the half-pipe jacket, but the flow resistance coefficient was lower and the resistance loss was smaller. The secondary flow generated by the half pipe jacket made the temperature gradient in the corner of the cross section far less than that of the center, thus affecting the heat transfer of the jacket. The vortex structure analysis showed that the edges and corners of the inner wall of the jacket were prone to generate vortex structure. The comprehensive evaluation factors of PEC and JF showed that the arcuate jacket of 140° had the best comprehensive performance.
Numerical Investigation on Aerodynamic and Electromagnetic Influence of Shape of The Grilles in a Rectangular Duct
Authors: Wang Xufei , Yang Qingzhen , He Yubo , Zhang Saile
Published: May 2022

The electromagnetic scattering characteristics of the inlet with grilles are calculated to verify the feasibility to reduce the radar cross section by installation of grilles. The Method of Moment (MOM) is used to calculate the models. According to its complicated structures, the inlet with grilles is simplified and the structured mesh is applied to specify the minor features of a large quantity of grilles to obtain aerodynamic characteristics of these models. The SST k-ω turbulence model based on the RANS method is utilized to simulate the air flow through the inlet. A clear duct with the geometric parameters (180mm 180mm 400mm) as well as the duct with grilles involving different parameters (shapes, thickness) is applied for the numerical simulation at the speed of 0.6 Mach at a certain range of angles of attack. Grilles in different parameters are simulated separately and compared with the clear inlet and the inlet with grilles, to find an approximate but simple method to estimate the aerodynamic influence taken by the different grilles. The results implicate that grille installation in the inlet has a significant positive influence on electromagnetic stealth performance. RCS drops by 4.80dBsm at an angle of attack of 0°. Meanwhile, substantial RCS reduction at range of angle of attack from 0°to 20° is found. Thickness and shape have remarkable influence on aerodynamic performance instead of electromagnetic scattering characteristics (f=1GHz, VV). The couple of grilles and inlet duct shows a little effect on aerodynamic characteristics compared with the single-element grille. It is acceptable to simulate grilles with inlet by numerically calculating the single-element grille.
Design of 2×250kN large-span hoist hydraulic automatic grabbing beam
Authors: Cheng Tanghua , Ren Tao , Chai Xu , Yao Kun , Jia Jiangming
Published: May 2022

In water conservancy projects, automatic grabbing beams, as an important supporting equipment of mobile hoisting equipment, are widely used to improve the performance of operating gates and trash racks. This paper takes the hydraulic automatic grabbing beam of the 2 × 250kN large-span hoist at Baihetan Hydropower Station as an example. The design of the hydraulic automatic grabbing beam for the hoist is systematically analyzed, combined with engineering examples, and the most unfavorable conditions are used. As a result of the calculation, some design parameters of the long-span grab beam were obtained. The test results show that all performance indicators can meet the design requirements and relevant standard requirements.
Energy consumption and mechanical proprietaries of Hybrid Deposition & Micro-Rolling
Authors: Huang Cheng , Zhang Haiou , Wang Guilan
Published: May 2022

The traditional forging process involves high energy consumption due to the giant equipment, long process, and low material utilization. Recently, metal additive manufacturing technology has developed rapidly with the advantage of high utilization. However, looseness and defects caused by the anisotropy of layer forming would result in low mechanical properties and fatigue properties. The hybrid deposition and micro rolling (HDMR) combined in-situ rolling with additive manufacturing, which applies a forging force to the built part by a micro-roller. A comparison is carried out with the conventional forging approach in terms of energy consumption and mechanical properties. It was found that components of Ti-6Al-4V made by HDMR showed a better strength performance in tensile strength and impact toughness with lower energy consumption than the traditional forging approach. Additionally, HDMR realizes integrated manufacture instead of the distributed manufacturing of large-scale equipment in a lengthy process, which is a promising substitute for conventional forging.
Microstructure and Mechanical Properties of C10100 Copper/304 Stainless Steel Electron Beam Welded Joint
Authors: Sun Wenjun , Wang Shanlin , Hong Min
Published: May 2022

Copper-steel dissimilar welded structural components are widely used in heat exchangers of nuclear power equipment. Electron beam welded dissimilar joints of C10100 copper/304 stainless steel sheets were investigated in this research. The experimental results for the microstructure and mechanical properties proved that optimizing welding process parameters could be used to get a well-formed weld without defects and the microstructure of weld was consisted of a mixture of two finite solid solutions in austenite matrix. The grain orientation was random, with dominating high-angle grain boundaries. The microhardness dropped along the 304SS / weld/C10100 copper interfaces, and the tensile strength reached 310 MPa. The heat-affected zone on the C10100 copper side appeared as the weakest part due to the largest austenite size and the least number of high-angle grain boundaries.
Feedforward Model-Based Intelligent Compensation System for Spindle Dynamic Thermal Error
Authors: Tang Jiangwen , Jiang Li , Xue Liang , Yang Zhuang
Published: May 2022

Among spindle dynamic errors, thermal error is an important factor affecting machining precision, the most convenient and economical solution for which is dynamic compensation of thermal error. In view of defects of complicated system, complex debugging, poor stability, high cost, etc., in the existing compensation approaches, thermal error compensation technology is investigated with compensation model established to complete the system design. The system is tested on the spindle of precise horizontal machining center. In the experiment, multiple linear regression, BP neural network, etc. are taken for technical analysis with dynamic feedforward model established. The experimental results indicate that the compensation system under study has dynamic compensation rate of over 90%, while the spindle has greatly shorter warm-up time, which can operate normally before entering the thermal steady state. The finally completed feedforward model-based intelligent compensation control system has good steady-state and dynamic compensation performance. In particular, its self-correction function greatly improves system adaptability and simplifies operation in use.
Three-dimensional cooperative guidance law for multiple missile based on sliding mode control
Authors: Zheng Zhongxu , Jiang Zhenyu , Sun XiaoDong , Fan XiaoShuai , Ma Rundong
Published: May 2022

Based on the missile-target three-dimensional relative motion model, a multi-missile coordinated three-dimensional guidance law with attack time constraints is designed for attacking stationary targets. The sliding mode variable structure control is adopted in the pitch channel, and the dynamic inverse control is adopted in the yaw channel. By maneuvering in the yaw channel, adjusting the missile's attack time and comparing with the results of using augmented proportional guidance, the simulation results show that the algorithm designed in this article can achieve coordinated attack and high hitting accuracy, which verifies the correctness and superiority of the algorithm.
Design of High Precision Semiconductor Laser System
Authors: Zhou Mengyuan , Wang Gaojie
Published: May 2022

In PCR technology, the suitability and stability of the light source used to excite fluorescence is particularly important. Semiconductor laser not only plays an important role in medical, science and technology, aerospace, transportation, communications and other fields, but also brings great changes to society. In this paper, the research background and the overall design architecture of the laser are described first, and then the circuit design of the key modules of the system is described in detail, the optical control closed-loop feedback system ensures the stability of laser drive current, and the temperature control closed-loop and PID algorithm reduce the adverse effects of temperature on laser power. At the same time, the sparrow search algorithm is used to optimize the three parameters of PID, the simulation results and test data show that: The whole design fully meets the needs of the application scene.
Energy Estimation and Testing Verification on Ignition of a Torch Ignition System
Authors: Xu Jiabao , Zhuo Danchen , Xing Lixiang , Gao Yushan , Jin Ping
Published: May 2022

The torch type electric ignition system is a desirable choice for reusable liquid vehicle engine. It is generally believed that the ignition and start-up process of engine are crucial and high-risk. However, due to the complexity of combustion experiments, the ignition and start-up process can be efficiently analysed from the perspective of energy exchange. By building the energy analysis equations of electric spark plug, ignition chamber and thrust chamber, the energy estimation method of torch type electric ignition system is established. Furthermore, the time scheduling and examining method for multi-injector ignition and start-up process of large flow liquid rocket engine with multi-injector are established. The hot-firing test of LOX/CH4 rocket engine is carried out according to the design parameters to validate the effectiveness of the energy estimation method.
Design and verification of small solid rockets navigation algorithm test platform
Authors: Fan Xiaoshuai , Bai Xibin , Jiang Zhenyu , Zhang Shifeng , Zheng Zhongxu
Published: May 2022

Aiming at the navigation system of small solid rockets, a navigation algorithm test platform with real time simulator and flight control computer is designed. The inertial navigation algorithm is taken as an example to test the effectiveness of the platform. The flight dynamic model of a small solid rocket is established in a real time simulator, and the test is carried out in the working environment of a small test rocket to simplify the model. The acceleration and angular velocity data generated by the simulation is sent to the onboard computer to calculate the attitude of the rocket in real time, which verifies the correctness of the data communication link, real time solution and navigation algorithm between the onboard computer and the real time simulator. The test results show that the test platform is easy to use and can test the rocket navigation algorithm quickly and effectively.
Aircraft/Engine Integrated Design for an Air-superiority Unmanned Aerial Vehicle
Authors: Jianzhi DENG , Wenyan SONG , Guangjun YANG , Feng JIANG , Neng XIONG
Published: May 2022

Aiming at the demand of efficient energy management for wide flight envelope of air-superiority unmanned aerial vehicle (UAV), an conceptual and preliminary design of air-superiority UAV with oil-electric hybrid power was proposed based on the idea of integrated aircraft and engine modelling. The evaluation model of the UAV aerodynamic performance and the thrust requirements of full flight envelope were determined, then the matching configuration of target turbofan engine was proposed. According to general design parameters of UAV, the simulation model and constraint relations for aircraft-engine integration performance calculation were established, parameters were optimized for typical multi-mission conditions, the tactical performance of future advanced air superiority UAV was predicted. The integrated design method of air superiority UAV upon hybrid electric turbofan can also be applied to improve the performance of UAVs in service, which established in this paper has good engineering practical value.
Modeling Investigation of Liquid Oxygen Flashing Spray with CFD
Authors: Luo Meng , Zhu Pingping , Rana Usman , Ma Hu , Yu Zhendong , Haidn Oskar J.
Published: May 2022

Injection of cryogenic propellants (e.g. liquid oxygen) into low-pressure environment (e.g. upper-stage rocket engine) may trigger flashing phenomenon, which severely affects the propellants’ mixing and combustion. In order to unveil the characteristics of flashing sprays, numerical models of flashing sprays were developed and validated. First, a developed model based on Adachi-correlation was employed for the flashing spray simulation. The results show good agreements with the experiments, both for the flashing spray morphology and temperature distribution. In the near-injector region, the flashing evaporation dominates the spray vaporization with the evaporation mass flow rate of about 2 orders of magnitude higher than that by the other heat transfers, whereas downstream the injector, the external heat transfer (i.e. heat conduction and convection) does. Furthermore, a new flashing spray model based on the nucleate boiling theory was proposed, which shows an improved agreement of the droplet temperature between the simulation and test data.
Experimental research on weathercock interference characteristics of weathercock airspeed tube
Authors: Chengchuan Yang , Zheng Gong , Yongliang Chen , Wei Zhong , Yalei Bai
Published: May 2022

Pitot tube is one of the most important airborne devices on the aircraft. The airspeed tube can not only provide the pilot with the airspeed of the aircraft, but also the rate of climb of the aircraft. In this paper, the wind tunnel test method is used to test the weathercock type airspeed tube used on a domestic supersonic tailless layout aircraft and it obtains the airspeed tube's angle of attack and sideslip angle weathercock interference characteristics and total static pressure aerodynamic characteristics. In this process, we find that the sideslip angle begins to offset with the angle of attack increasing and the offset is about -1° when the airspeed exceeds 1.5 Ma. Subsequently, CFD calculations are used to compare and supplement the wind vane characteristics obtained from the wind tunnel test. It is found that the pressure data collected by the airspeed tube has a certain error due to the interference characteristics of the wind vane. Finally, the pressure error is corrected by BP neural network prediction model. It provides a reference to calibrating air-data-sensors for researchers.
Aerodynamic of a probe using an inflatable braking device during its descent in mars atmosphere
Authors: Koryanov Vsevolod V. , Menetrier–Hacquemand Nathan
Published: May 2022

For reentry in Mars atmosphere, inflatable braking devices are interesting as they do not use rigid heat shields, parachutes, or retrorockets which limits the mass to send into space. This paper focuses on one MetNet probe, to validate the use of inflatable braking device geometry. This study shows the results on aerodynamic coefficients determined using different solvers from OpenFOAM software in distinct configurations exposing that small deformations of the braking device in the stages of the probe’s reentry should not threatens the mission. Finally, this study shows final velocity determined using a Python program and compared with expected values on different locations on Mars’s surface to ensure that the probe survives its descent.
Gas-Solid Interface Interactions Based on Molecular Dynamics Simulations
Authors: Zongyang Li , Lin Bi , Jianqiang Chen
Published: May 2022

Gas-solid interface interaction as the key point and difficult point of dilute gas flow, understanding the mechanism of it, to have a clearer understanding of the gas molecules in the solid near-wall surface motion law. This paper combines the molecular dynamics method and particle beam method to simulate the interaction between argon molecules and solid platinum wall surface, to study the scattering law after the collision between gas molecules and solid surface at different incidence angles and the mechanism of energy conversion between them, the results show that the tangential kinetic energy is lost after the collision between gas molecules and wall surface, while the change of normal kinetic energy is determined by the magnitude of the incident velocity; the incident velocity is small, the reflected tangential velocity distribution basically fits the Maxwell reflection distribution when the incident velocity reaches a high speed, and the reflected tangential velocity distribution appears head-and-shoulder or even bimodal distribution, which is helpful for future research on the tangential momentum adaptation coefficient of the scattering nucleus model.
Echo Doppler Frequency Compensation Analysis of Space-based Radars
Authors: Hongjian Wang , Yong Yu , Zhibin Zheng , Zhiyong Lei , Yao Wei , Gang Wu
Published: May 2022

Based on the geometric model between space-based radar (SBR) and the Earth, Earth’s rotation adds an additional component to the echo Doppler frequency. The result is as follows, when the orbit inclination is fixed, the crab magnitude has an offset effect on the clutter Doppler frequency, and the fluctuation of the offset value is very small, so the echo data can be uniformly compensated. However, the effect of the crab angle on the clutter Doppler frequency is two orders of magnitude larger than that of the crab magnitude and changes with time, so real-time compensation is needed. The maximum compensation interval is also related to the radar pulse repetition time and the number of accumulated pulses. Compensation interval needs to be less than 6s under a typical scene. The above conclusions lay the foundation for effective detection of SBR.
Study of bipedal locomotion considering property of toe mechanism
Authors: Nguyen Van-Tinh , Tao Ngoc-Linh , Nguyen Thanh-Trung , Bui Ngoc-Tam
Published: May 2022

Walking behaviour of the humanoid robot depends on many parameters of body structure, in which, the foot structure is one of the most important factors since it directly interacts with the environment in the locomotion. In this paper, joint characteristics of the robot’s foot have been investigated for our further understanding of biped motion. These properties are stiffness and damping factor of spring of passive toe joints. The subject of this paper is a small humanoid robot named Kondo KHR-3HV belonging to the Kondo Kagaku company. The foot structure of the robot consists of a big toe and a tiptoe with passive joints using torsion spring. The effect of the structure property is collected and evaluated through dynamic simulation on Adams and analysis of variance (ANOVA).
Aerodynamic Studies of Small Box-Wing Unmanned Aerial Vehicle Using CFD
Authors: Sutthison Danupol , Wongkamchang Prasatporn , Sukuprakarn Nukul
Published: May 2022

This paper presents a computational fluid dynamics (CFD) simulation study of a small unmanned aerial vehicle (UAV) with airfoil s3010 and 245 mm chord length at a cruising speed of 17.5 m/s, compared with the aerodynamic characteristics of a 3D conventional fixed-wing UAV from a commercial RC airplane modified with a box-wing configuration. Simulation results showed that at an angle of attack of 0°, the lift coefficient increased by 60.005%, drag coefficient increased by 58.3299% and L/D ratio increased 1.0578%. The box-wing UAV had higher lift-to-drag ratio than the fixed-wing UAV. However, weight increased by 46.5%. The fuselage shape of the box-wing UAV in this study can be redesigned to shorten the rear area for drag and weight reduction.