bluuebunny/crossref_metadata_2025 huggingface dataset:
Potential of CRISPR/Cas13 System in Treatment and Diagnosis of COVID-19
Authors: Khodavirdipour Amir , Piri Motahareh , Jabbari Sarvin , Khalaj-kondori Mohammad
Published: February 2021

The novel coronavirus disease 2019 (COVID-19) belongs to coronaviridae families like sarbecovirus (SARS), and causes pyrexia, pertussis, and acute respiratory distress syndrome (ARDS) in major. Started from Wuhan, China, COVID-19 now forced the World Health Organization (WHO) call it a global pandemic. These dreadful figures elevate the need for rapid action for a rapid diagnostic tool, an efficacious therapy, or vaccine for such widespread disease. In this article, we reviewed all the latest research and trials including conventional antiviral medicines that have a narrow and finite effect on COVID-19. Recently, some advances were made by a nucleotide/nucleoside analogues (NUC) inhibitor (remdesivir), ivermectin (antiparasitic drug), and convalescent plasma; the later one has more recently been approved by the Food and Drug Administration (FDA). Additionally, a clinical-grade soluble human angiotensin-converting enzyme (ACE2), named hrsACE2, was able to inhibit the infection of human blood vessel organoids, as well as the human kidney organoids, by the virus. As of now, innovative therapeutics based on the CRISPR/Cas13d might overcome the challenge of COVID-19 either as a treatment option or precise and rapid diagnostic tool due to its rapid and precise nature. In this updated comprehensive rapid review, we tried to cover all recent findings in terms of genomics, diagnosis, prevention, and treatment.
Low-Intensity Pulsed Ultrasound Therapy: A Nonsurgical Treatment Modality for Mandible Fracture Nonunion?
Authors: Abel Adam R. , Reeve Gwendolyn S.
Published: February 2021

Standard treatment of mandibular nonunion includes debridement and application of maxillomandibular or rigid internal fixation techniques, with adjunctive bone grafting when necessary. Frequently described in the orthopaedic literature, low-intensity pulsed ultrasound therapy (LIPUS) is a noninvasive treatment modality used to accelerate healing of fresh fractures and established nonunions. The purpose of this study was to conduct a systematic review to determine the extent of LIPUS study in the treatment of mandibular nonunions to identify whether LIPUS represents an effective nonsurgical alternative or adjunct for nonunion management. A literature review was conducted to investigate published reports on the utilization of LIPUS in treating mandible fracture nonunions. The search yielded two randomized controlled trials demonstrating favorable healing parameters in fresh human mandible fractures treated with LIPUS, two randomized controlled trials demonstrating osteogenic differentiation in human mandibular fracture cellular components, and one study reporting improved healing at rabbit mandibular osteotomy sites. No articles published reports studying LIPUS in facial fracture nonunion were identified. This report reviews published literature on mandibular nonunions, and the evidence of LIPUS use in long bone nonunions. There are no known studies presenting LIPUS treatment of mandible fracture nonunions. However, on the basis of published orthopaedic data, LIPUS therapy could be considered as an adjunct or alternative to traditional surgical management of select mandible fracture nonunions.
Demedicalisation of HIV interventions to end HIV in the Asia–Pacific
Authors: Janamnuaysook Rena , Green Kimberly Elizabeth , Seekaew Pich , Ngoc Vu Bao , Van Ngo Huu , Anh Doan Hong , Pengnonyang Supabhorn , Vannakit Ravipa , Phanuphak Praphan , Phanuphak Nittaya , Ramautarsing Reshmie Ashmanie
Published: February 2021

Despite the challenges to the HIV response in the Asia–Pacific, a demedicalisation of HIV intervention has been demonstrated to be an important strategy to maximise the uptake of HIV prevention tools among key populations in this region. Demedicalisation of HIV interventions translates medical discourse and shifts the paradigm from a disease-focused to a people-centred approach. It also recognises real-life experiences of key populations in the HIV response by empowering them to voice their needs and be at the forefront of the epidemic control. We further categorise a demedicalisation approach into three frameworks: (1) the demystification of clinical or medical concerns; (2) the destigmatisation of people living with HIV; and (3) the decentralisation of healthcare services. This article reviewed the demedicalisation framework by looking at the HIV intervention examples from countries in the Asia–Pacific, which included: (1) a study on drug–drug interaction between pre-exposure prophylaxis and feminising hormone treatment for transgender women; (2) the roles of key population-led health services; and (3) certification of key population lay providers.
Lexical evidence for ancestral communication in Black South
African English
Authors: Peters Arne
Published: February 2021

The present chapter derives from a comprehensive
project on culture-specific conceptualizations in Black South
African English. It carries out a lexico-semantic analysis of
conceptualizations of ancestral communication in Black South African
English and is based on a 66,634-word corpus of 424 unedited
classifieds published in 48 consecutive editions of the South
African Daily Sun newspaper as well as on a
54,000-word corpus of ethnographic interviews with meso-/acrolectal
Pedi, Sotho, Swati, Tswana, Xhosa and Zulu L1-speakers of English.
The chapter addresses the central role of the ancestors in
traditional and retraditionalized Black South African communities
and the importance of intact communicative bonds between the
physical and the spiritual parts of the community. In addition, the
analysis produces lexico-semantic evidence for the processes of
nativization and contextualizations in Black South African English
by examining the ritualized communicative act of throwing
bones as conducted by diviner-diagnosticians in mediated
ancestral communication. Finally, the chapter proposes a model
representation of the vertical organization of ancestral
communication schemas in Black South African English. The present
chapter communicates with Peters (2021), which
provides a more detailed account of the cultural-conceptual
background of witchcraft and traditional healing
as represented in Black South African English herbalist
classifieds.
Food safety and methods to ensure food security in the face of climate change.
Authors: Tripathi Jyoti
Published: February 2021

Serious social, economic, and ecological consequences of climate change due to the high levels of greenhouse gases (GHGs) in our atmosphere resulting from a wide range of human activities including the burning of fossil fuels and land use have impacted weather events world over. Extreme weather events and warmer global temperatures are likely to be more frequent with an adverse overall effect on agricultural production unless there is an urgent reduction in GHG emissions. There is thus an immediate need for increasing adaptive capacity in agriculture to long-term climatic trends and increasing variability in weather patterns. Climate change also poses significant challenges to global food safety due to the emergence of new pathogens, insect pests, and toxicants. Food safety threats cause an enormous burden on economies due to disruptions or restrictions in global and regional agrifood trade, food loss, and associated income. Food safety thus plays a critical role across the four pillars of food security-availability, access, utilization, and stability. Climate change is likely to create new safety issues entailing reassessing our tolerance to risk and safety limits presently established for the human food chain. The present review focuses on the factors affecting food security and safety as a consequence of climate change and the pre- and postharvest strategies that need to be adopted to mitigate these effects for enhancing food safety and global food sufficiency in future.
Self-powered and high responsivity photodetector based on a n-Si/p-GaTe heterojunction
Authors: Liu Yali , Wu Xiaoxiang , Guo Wenxuan , Li Mengge , Niu Xinyue , Yao Jiadong , Yu Ying , Xing Boran , Yan Xiaoyuan , Zhang Shucheng , Sha Jian , Wang Yewu
Published: February 2021

Heterojunction integrated by two-dimensional/three-dimensional materials has shown great potential applications in optoelectronic devices because of its fast response speed, high specific detectivity and broad spectral response. In this work, the vertical n-Si/p-GaTe heterojunction has been designed and fabricated, which shows a high responsivity up to 5.73 A W−1 and a fast response time of 20 μs at zero bias benifitting from the high efficiency of light absorption, internal photocurrent gain and strong built-in electrical field. A specific detectivity of 1012 Jones and a broad spectral response ranging from 300 to 1100 nm can also be achieved. This work provides an alternative strategy for high-performance self-powered optoelectronic devices.
Measuring muscle quality: associations between echo intensity and normalized strength and power
Authors: Giuliani Hayden K , Laffan Megan R , Trivisonno Abigail J , Gerstner Gena R , Mota Jacob A , Arieta Luke R , Ryan Eric D
Published: February 2021

Objective. Muscle quality has received considerable attention within the literature due to its influence on health and performance. However, it has been assessed by various measures (e.g. ultrasound imaging, normalized strength), contributing to a lack of a consensus definition. The purpose of this study was to investigate the association between common muscle quality measures: vastus lateralis echo intensity (EI) and peak torque (PT) and power (PP) normalized to thigh lean mass (TLM) and thigh fat mass (TFM). Approach. Participants’ (n = 39; age = 32.7 ± 8.2 years; %BF = 24.1% ±8.1%) whole body and leg composition was assessed via dual-energy x-ray absorptiometry and custom thigh analyses. Subcutaneous fat-corrected muscle EI was assessed via ultrasonography. Maximal PT and PP of the dominant leg extensors were examined on a calibrated dynamometer and were normalized to both TLM and TFM, respectively. Pearson product-moment correlations were used to examine the associations between EI and PT/TLM, PT/TFM, PP/TLM, and PP/TFM. Main results. Greater muscle EI was significantly related with lower PT/TFM and PP/TFM (r = −0.74 to −0.70, P < 0.001), but unrelated to PT/TLM or PP/TLM (P ≥ 0.205). Significance. These findings suggest that ultrasound imaging (muscle EI) and normalized strength and power may not be used interchangeably to define muscle quality, and muscle EI may be more sensitive to the adiposity of the limb than TLM. Future research should consider using separate and consistent definitions when referring to imaging-derived or normalized strength and power values of muscle quality.
Nonlinear harmonic excitations in collisional, asymmetrically-driven capacitive discharges
Authors: Liu Jian-Kai , Kawamura Emi , Lieberman Michael A , Lichtenberg Allan J , Wang You-Nian
Published: February 2021

The standing wave effect, which may lead to center-high density profiles in high frequency capacitive discharges, can be enhanced by nonlinearly excited harmonics. In this work, a nonlinear transmission line model, which solves for the electromagnetic fields in the time domain, is coupled to a two-dimensional bulk plasma fluid model to study nonlinear effects in asymmetric cylindrical capacitive argon discharges. An analytical collisional or collisionless (ion) sheath model is used to determine the stochastic and ohmic sheath heating and the nonlinear dependence of sheath voltage on sheath charge. We first examine a base case of a 20 mTorr argon discharge driven with an electron power P
e = 40 W at a frequency f = 60 MHz, using collisionless and collisional sheath models. For the collisionless sheath model, the nonlinearly excited harmonics near the series and spatial resonance frequencies significantly enhance the on-axis power deposition and lead to a sharp peak of electron density at the discharge center. The collisional sheath model gives a smaller sheath width, leading to lower series and spatial resonance frequencies and a smaller source voltage for the fixed electron power. As a result, lower harmonics with broader spatial profiles and decreased magnitude are excited, reducing the center-high plasma nonuniformity. Then, we examine the discharge in a pressure range of 20–100 mTorr at fixed P
e = 40 W and f = 60 MHz, using the collisional sheath model. As pressure increases, the harmonics gradually damp out, and the enhancement of on-axis power deposition becomes less significant. At the same time, more power is localized near the powered electrode edge due to decreased skin depth and smaller energy diffusion. As a result, the density peak shifts from the radial center to the powered electrode edge.
Heat pulse propagation and anomalous electron heat transport measurements on the optimized stellarator W7-X
Authors: Weir G.M. , Xanthopoulos P. , Hirsch M. , Höfel U. , Stange T. , Pablant N. , Grulke O. , Äkäslompolo S. , Alcusón J. , Bozhenkov S. , Beurskens M. , Dinklage A. , Fuchert G. , Geiger J. , Landreman M. , Langenberg A. , Lazerson S. , Marushchenko N. , Pasch E. , Schilling J. , Scott E.R. , Turkin Y. , Klinger T.
Published: February 2021

The optimized stellarator Wendelstein 7-X (W7-X) is designed to have an approximately quasi-isodynamic magnetic configuration with reduced neoclassical transport in comparison to a classical stellarator, and turbulent transport is expected to be a significant source of anomalous heat transport across the plasma minor radius. The ion temperature gradient driven mode and the trapped electron mode (TEM) are thought to be responsible for the ion-scale turbulence in W7-X plasmas with volume averaged pressure below 1%. In this work, the electron temperature gradient driven turbulence is shown to be a good candidate for the explanation of the observed electron heat flux, in the inner plasma region where the density gradient is weak (in the outer region, a relatively stronger density gradient would drive additional TEM turbulence). The experimental electron heat transport measured during electron cyclotron resonant heating power and plasma density scans is compared to neoclassical predictions, and the stiffness in the electron heat transport measured during transient transport experiments is presented in three common magnetic configurations of W7-X. In low-⟨β⟩ plasma discharges, the stiffness in the electron heat flux, quantified by the ratio of the heat pulse to power balance diffusivity,

χ

e

H
P

/

χ

e

P
B

, is measured to be less than 2, and trend downwards with increasing collisionality.
Measurements and modelling of diamagnetic flux in ASDEX Upgrade
Authors: Giannone L. , Fischer R. , Kappatou A. , Tardini G. , Weiland M. , Angioni C. , Fable E. , Griener M. , McDermott R.M. , Sieglin B. , Jansen van Vuuren A. , Bilato R. , Dunne M. , Gude A. , Kallenbach A. , Kurz J.M. , Maraschek M. , Rittich D.M. , Ryter F. , Schneider P.A. , Schuhbeck K.H. , Stroth U. , Zohm H. , the ASDEX Upgrade Team
Published: February 2021

The reproducibility of diamagnetic flux measurements in vacuum field shots for the internal and external diamagnetic flux measurements in the ASDEX Upgrade tokamak is investigated. A comparison of diamagnetic flux measurements and predictions from equilibrium reconstruction, including pressure constraints from thermal and fast-ion contributions, is reported. The ideal magnetohydrodynamic model involved in interpreting diamagnetic flux measurements in a tokamak with anisotropic pressure is summarised. The plasma energy calculated from equilibrium reconstruction and inferred from diamagnetic flux measurements is compared with the respective values calculated by modelling with TRANSP and IDE/RABBIT. It is found that at low densities, in discharges with parallel neutral beam sources, the plasma energy inferred from the diamagnetic flux measurements is smaller than the plasma energy calculated from the equilibrium reconstruction. In addition, details of the modelling are discussed to stress the interdependence of the various modelling inputs and the interpretation of the results. A comparison of diamagnetic flux measurements with calculations from equilibrium reconstruction by IDE and fast-ion profiles from RABBIT and TRANSP simulations can identify anisotropic plasma discharges and provide a consistency check of the input data for modelling.
Evaluation of dynamic Localization System Based on UWB and Wi-Fi for Indoor Environments
Authors: Mosleh Mahmood F , Daraj A K
Published: February 2021

Due to limitations and complexity in indoor communications, many wireless technologies deployed to correspond with those challenges. The Ultra-Wideband (UWB) wireless communication for indoor environments is one of the widespread bands developed for convey high data rate. The other widespread band is 2.4GHz based on Wi-Fi technology. Each of the mentioned bands could be convenient for specific areas and not for others based on long or short-range communications. In this paper, both bands are applied for indoor environments to find the target’s locations. A new technique based on Multi-Scale Bands with Dynamic approach (MSBD) is applied to implement an optimum system. The three dimensional (3D) case study building designed based on Wireless Insite Package with real building geometric measurements. It is worth to mention that both bands are applied based on dynamic parameters to assign specific parameters for specific environments. The average error in the whole building based on static parameters using UWB is (1.023m) while (0.452m) based on individual 2.4GHZ. The obtained results confirm that the proposed MSBD technique is significantly outperformed individual band with static parameters. The enhancement is noted from error range which improved from (1.023m) to (0.08m) for UWB and (0.452m) to (0.15m) for 2.4GHz. For optimum system, the UWB was deployed for a distance under (10m) and Wi-Fi for other distance. By deploying both technologies and using the dynamic system, the performance of the proposed system worked with accurate measurements in short and long-distance in addition to both LOS and NLOS scenarios identify relevant articles in literature searches, great care should be taken in constructing both.
Controlling of Induction Motor Using Grey Wolf Optimization Algorithm
Authors: Fadhil Ghaith M. , Abed Issa A. , Jasim Rasheed S.
Published: February 2021

This paper introduces the improved Direct Torque Control (DTC) of the Induction Motor (IM) to enhance its performance. The DTC method is generally used to control electrical machinery. The traditional Proportional Integral (PI) speed controller parameters are manually adjusted to match the speed with the given reference. However, traditional PI has a drawback such that it does not fit all error limits. Thus, the intelligent DTC has been discussed with the proposed Grey Wolf (GWO). The grey wolf algorithm is used to adjust PI speed controller parameters as well the results are compared with those of genetic algorithm. Simulation results show that the GWO algorithm is exceptionally successful for improving induction motor with a fast-tracking response.
A Proposed Linear Multi-Controller Architecture to Improve the Performance of Software Defined Networks
Authors: Noman Haeeder Munther , Jasim Mahdi Nsaif
Published: February 2021

In the last few years, there has been a growing interest in the rise of demand for moving from traditional networks towards software-defined networks, this has raised a lot of challenges. Software-defined networks are continually evolving, which include the need to address issues such as scalability, and packet loss, transmission delay and network congestion. accordingly, researchers introduced the concept of multi-controller architectures, although it will not assist to balance the load between them, it will tackle the network congestion issue through the distribution of load between them. the present study proposes a linear multi-controller architecture to explore the impact of increasing the number of controllers connected in a linear style on network performance. The study was based on the generation of simultaneous multi-flows with different sizes using Distributed Internet Traffic Generator(D-ITG). From the outcomes of our investigation, it is possible to conclude that the performance-enhanced uniformly with the number of controllers while preserving the same number of Open Vswitches. as the number of controllers reached four, The Quad-controller architecture recorded the best results related to improving the reduction of average delay and average jitter to 62% and 64% as well as increasing the throughput, bytes received, average packet rate to 32%, 32% and 31.8%.
A Comparative Performance Analysis for Static and Dynamic Load Balancing Techniques in Software Defined Network Environment
Authors: Noman Haeeder Munther , Jasim Mahdi Nsaif
Published: February 2021

Traditional load balancer suffers from inflexibility, high cost and the difficulty to manage the network. Software-Defined Network (SDN) gives a promising solution for traditional load balancer limitations through enabling programmability and centralized control over the network, which offers inexpensive and scalable solutions. This paper investigates the impact of increasing the workload requests from 0 up to 180 requests per second (req/sec) in order to explore average network throughput under the deployment of static as well as dynamic load balancing algorithms by the POX controller. The study was based on the utilization of HTTPerf based on the fact that it provides a flexible facility for the generation of various HTTP workloads as well for the measurement of server performance. Our experiments revealed that as the number of requests increases the throughput increases as well. Dynamic least bandwidth-based load balance scheme has shown a remarkable improvement in terms of average network throughput up to 8%, 3.3% and 2.56 %, as compared with static load balancing schemes like random, round-robin and weighted round-robin. However, Dynamic least bandwidth recorded a slight ineffective improvement less than 1 % was recorded when a comparison was carried out dynamic least connections, this directed us to the fact that their performance was almost the same. Based on what dynamic least bandwidth scheme has achieved in terms of average network throughput, more efforts should be driven by the researchers on algorithm development like introducing static weight for each server as well as the application of the algorithm on several POX controllers to avoid a single point of failure.
Parabolic solar water heater performance with optimum tracking system: Baghdad city case study
Authors: Al-Sayyab Ali K Shaker , Aabdul Wahid Mohammed
Published: February 2021

The energy extracted from the solar is changing cording to seasons and the way of tracking. In this study, have been five tracking modes are North-South and East-West, which have been rotating over the seasons of the year. Also, the Baghdad city has been chosen to select the optimum tracking mode. A mathematical pattern has been used to solve numerically. From this study, deduced that all the tracking models performance is converging at the noon period of the North-South tracking mode. These will allow the highest solar energy collected is 34.15% from the East-West tracking rotating mode.
Corrosion protection of zinc alloy ZA12 using anodizing process in acidic media
Authors: Abdulhussein Basheer A. , Ajeel Sami A. , Ali Alaa M.
Published: February 2021

Zinc alloys are used in very wide industrial applications due to their excellent physical and mechanical properties. To improve the corrosion resistance, anodizing process is used. Anodizing of Zinc Alloy ZA12 is investigated in 1 M H2SO4 solution for 10, 20 30,40 and 50 mins at a constant voltage of 5V. Atomic force microscope (AFM) used to study the surface roughness of the anodic film. The results show that the surface roughness of anodic film is primarily depending on the anodizing time and coating average thickness. Furthermore, the microhardness also increases with the anodizing time. The corrosion performances in sea water of both anodized and non-anodized zinc specimens are acquired by potentiostatic polarization. Corrosion current density (iCorr) and corrosion potential (ECorr) are obtained from potentiostatic polarization studies. The studies show that the corrosion current density and corrosion rate were reduced with increasing the anodizing time which enlarges anodic film average thickness. The results of corrosion rates indicate an enhancement in corrosion resistance of anodized Zinc Alloy ZA12 in the sea water. Contact angle test measurements for ZnO layer formation on zinc alloy AZ12 were detected which indicate that the contact angle of un-anodized film seems to be elevated than that of anodized film after sealing the anodic film.
Research on Electrical Automation Metal Pipe Cutting Device
Authors: Zheng Hui , Tang Lin
Published: February 2021

This article analyzes the key points in the design of electrical automation metal pipe cutting devices. The content of this article includes cutting principle analysis, power supply structure design, transducer design, horn design, controller selection, touch control screen circuit design, sensor circuit design, emergency stop control circuit design, executive circuit design, etc. The author studied the amplitude detection experiment, process parameter experiment, cutting experiment analysis, etc., whose purpose is to improve the orderliness of the metal pipe cutting process and improve the final construction quality of the pipe.
Design of a diamond tool for laser in situ assistance
Authors: Mingqiang Xia , Guangfeng SHI , Jiaolong BI , Jiyu GAO , Dawei YU , Guoquan SHI
Published: February 2021

Abstract Laser in-situ auxiliary processing is an advanced hard and brittle material processing method. In order to improve the utilization rate of the laser in the processing process and better realize the thermal softening effect on hard and brittle materials, the transmission model of the laser and diamond tools was established by COMSOL, and the laser transmission through the rake face of the ordinary arc-edged diamond tool was analyzed. A diamond tool with laser incident surface parallel to the rake surface is designed. The laser incident surface of this diamond tool is parallel to the rake surface, so that the laser can penetrate the diamond rake surface perpendicularly, which is compared with the ordinary circle. The arc turning tool can significantly improve the beam quality, increase the power density of the laser penetrating the tool, and obtain the temperature field change of the diamond tool during laser irradiation and the rule of tool tip deformation. The research is to improve the laser in-situ assisted diamond tool Machining accuracy provides theoretical basis.
Enhanced Physical Properties of PEO /GRAPHENE Composites
Authors: Hua Lei
Published: February 2021

PEO/graphene composites were prepared by a simple and green method in presence of graphite oxide (GO) reduced by Vitamin C (VC) in aqueous. The resultant PEO/RG-VC composites exhibited excellent thermal and outstanding mechanical properties. When loading about 7 wt.% RG-VC graphene sheets, the Youngs modulus of PEO/RG-VC 7 was improved as two times as that of the neat PEO. However, the crystallization behaviour of the composites could not be improved as expected.
Intelligent Control System for Corn Harvester
Authors: Wang Chen , Cao Shukun , Gao Kuizeng , Cao Wenlong , Cui Shoubo
Published: February 2021

Based on the traditional corn harvester, this paper optimizes the basic structure of the harvester, analyzes the transmission mode and working principle of each mechanism, and designs and selects the electric devices and sensors needed in the optimization process. Combined with PLC control theory and output signal processing of sensors, the hydraulic components of walking hydraulic system of electric devices and harvesters are controlled.
Process design of BS15-1602001 clutch withdrawal fork
Authors: Sang Zhenyuan , Sun Shuguang
Published: February 2021

BS15-1602001 clutch withdrawal fork is one of the main components produced for certain enterprise. The special shape and the complicated conversion among design datum, positioning datum and measuring datum lead to difficulty in detecting the machining parts. This article focuses on the design and determination of the part process route from several aspects, such as the machining processability of the part material and structure, the selection of the rough positioning reference and the precision reference, the machining allowance and the determination of the dimensional tolerances, in which content involves knowledge of metal materials, machining, cutting tools, fixtures, equipment, heat treatment, etc.
Analysis on Vibration Characteristics of Flexible Rotating Manipulator
Authors: Yue Pengfei , Zhao Yang , Zhu Yongyong , Wang Deshi
Published: February 2021

Aiming at the problem that the inertia effect of the tip mass causes the accuracy decrease of the manipulator’s movement, the floating coordinate system was utilized to describe the manipulator’s elastic deformation displacement, and the nonlinear coupling term caused by the transverse deformation was taken into account. According to Lagrange equation of the second type, the system dynamics equation expressed by the modal function was derived. Combined with numerical simulation, the influence of the tip mass on the vibration characteristics of the system was analyzed. Studies have shown that the tip load of the flexible manipulator increases the vibration response amplitude of the system and reduces the response frequency. Reducing the length of the manipulator is beneficial to improve its motion accuracy. Research results have application value for manipulator optimization design and reliability evaluation.
Study on the influence of tube surface notch on crack initiation during blanking
Authors: Zhao R F , Xiao X D , Guo L , Gao W C , Liu Y W
Published: February 2021

In the process of precision tube separation, according to the prefabricated notches on the outer surface of the tube, the notch effects of different types of notches are studied, and the influence of the stress field at the root of the annular V-shaped notch is analyzed. It is determined that the notch angle, notch depth and the radius of the bottom angle of the notch root are the three main parameters that affect the stress field at the root of the notch, and the mathematical expression of the V-notch parameters suitable for tube separation is derived. The design of tube precision separation notch is put forward, and four different notches are numerically simulated. It is concluded that 45° asymmetric V-shaped notch and annular V-shaped notch facing the cutting end are the two notches which are more suitable for the blanking method in this paper. An experimental study is carried out on the crack propagation caused by the notch, and the experimental results are consistent with the numerical simulation results.
Research progress on selective laser melting of hard composite materials
Authors: Xie Y X
Published: February 2021

Composite materials are made of multiphase materials composed of two or more materials with different properties. Hard composite materials are often used as alloy materials for tool production due to their high hardness, high strength and good wear resistance. This paper briefly introduces the domestic and foreign research progress and technical status of hard composite materials by laser area melting, summarizes the influence of forming powder and process parameters on the forming performance characteristics of hard composite materials, as well as selective laser melting area of hard composite materials. The quality inspection and molding process simulation of the company, and prospects for the future development, provide a reference for the laser melting “3D printing” of hard composite materials.
Research on the Numerical Model of Solvent Diffusion Based on Fick’s Law and Free Volume Theory
Authors: Xu Haibo , Li Peixuan , Wen Litao , Wang Zewei
Published: February 2021

The release of acetone solvent from the adhesive layer is an important part of the curing of DW-1 adhesive, and this process is mainly affected by its diffusion behavior. In order to predict the volatile residual amount of acetone in the adhesive layer, the diffusion phenomenon of acetone solvent was studied. Based on Fick’s law, a numerical model of solvent diffusion is established, and a calculation method of mutual diffusion coefficient suitable for the system of acetone and DW-1 glue is proposed; a simulation model is constructed to reveal the competition mechanism of volatilization phenomenon and diffusion phenomenon, and analyzes the acetone in the diffusion process Distribution status. The theoretical guidance for reducing the residual amount of acetone is provided by this research in the adhesive layer.
The influence of process parameters on the performance of nylon 6 selective laser sintering parts
Authors: Si Liang , Han Yuchen , Zhou Mengyuan , Li Maoyuan
Published: February 2021

During the selective laser sintering process, the sintering behavior between powders is mainly affected by thermal effect. There are a large number of process parameters influencing the variation of temperature and molten pool, of which the laser density and scanning speed play a crucial role in determining the performance of the parts. In this paper, the effects of laser density and scanning speed on the precision and strength of polyamide 6 selective laser sintering parts were systematically investigated. The results show that with the increase of energy density, the positive dimensional deviation of the parts in three directions increases gradually, and the tensile strength increases at beginning and then decreases. When the laser power and scanning speed were changed, the tensile strength of the parts varied between 5.62 MPa and 58.74 MPa.
Effect of Equal Channel Angular Pressing on Microstructure and Mechanical Properties of ZK60 Alloy
Authors: Ling Zhang , Yinglong Li , Chengtao Yu , Zongli Pi , Qi Shao
Published: February 2021

Approaches of optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction, electron backscattered diffraction (EBSD), transmission electron microscopy (TEM) and mechanical property testing have been used to study the microstructure and mechanical properties of Mg-6.1Zn-0.7Zr alloys before and after equal channel angular pressing (ECAP) investigated in detail using. The study demonstrates that the microstructure comprises of fine-grained equiaxed dynamic recrystallization. The size of various grains is in the range 2.3-5.2 μm along the boundaries of unrecrystallized grains after 6 passes of ECAP. Meanwhile, the Mg-Zn and Mg-Zn-Zr compounds gradually crush into fine dispersed particles and the dislocation density increases. With increase of pass the average (0001)<11-20> basal slip Schmid factor gradually increases to 0.41. The strength and ductility have improved with increasing of ECAP pass. Notably, after 6 passes, due to decrease of grain size and the strengthening effects of fragmentized secondary phase particles, the ultimate tensile strength increases to 260 MPa, and the elongation at break exceeds 28.6%.
Laser SLAM optimization based on resampling
Authors: Xu Shuyang , Cao Shukun , Gao Kuizeng , Cao Wenlong , Ma Jianzhong , Chen Song , Wang Chen
Published: February 2021

In order to solve the particle degradation and particle exhaustion in the simultaneous positioning and map construction method of Rao-Blackwellized particle filter, an optimization method for simultaneous positioning and map construction is proposed. In order to alleviate the need for too much data in the re-sampling stage, the calculation time is longer, and the calculation amount is reduced by dropping some low-weight particles and reducing the number of particles. The experimental results show that compared with the traditional RBPF-SLAM method, the improved method can obtain a more accurate map with fewer particles, reduce the number of Kalman particle filtering, and reduce the amount of calculation to meet the needs of actual use.
Standard and verification regulation of asphalt wax content measuring instrument
Authors: Zhang Jinning , Zhou Yishu , Liu Yue , Chen Liuqing , Wang Pengfei
Published: February 2021

Asphalt wax content measuring instrument is a key equipment used to measure the wax content in petroleum asphalt. It is mainly used to measure the wax content of road asphalt, and is widely used in transportation industry and petroleum industry. This project focuses on the research of asphalt wax content meter, investigates the practicability of the current measurement verification regulation, excavates the deep-seated reasons in the process of metrological verification, corrects the deficiencies existing in the existing measurement verification regulations, and adds new requirements in line with the construction of transportation power, so as to make the measurement verification regulations meet the requirements of current engineering construction. Based on the above reasons, the research on asphalt wax content meter is carried out. According to the existing measurement verification regulations, combined with the characteristics of equipment value and the requirements of transportation power, it can guide the production of such equipment, improve the quality, and guide the test and detection personnel have a clear understanding of the status of the equipment in the daily detection process. The measurement verification regulations can ensure the wax content of asphalt in the construction process of high-grade highway It has a positive effect on promoting the construction of transportation power.
Research Status and Prospect of Residual Plastic Film Pickup Mechanism in China
Authors: Zhang Yaxin , Zhang Jiahua , Li Shaohua , Zhang Yumei , Li Hang
Published: February 2021

Plastic film mulching technology not only improves the yield, but also brings white pollution. In order to solve the problem of residual film recovery, a large number of plastic film collecting machines have been designed in China. The film picking mechanism is the key part of the residual film recovery machine. Its mechanism form and operation quality play an important role in improving the recovery rate of the residual film. This paper analyzes the development status of the film collecting mechanism of the residual film recycling machine at home and abroad, briefly introduces the structure and working principle of seven kinds of residual film collecting mechanisms, including Winding type, telescopic rod type, elastic tooth type, gear teeth type, drum type and pneumatic type. This study provides relevant suggestions for the optimization and improvement of the film collecting mechanism in the future.
An improved hybrid genetic algorithm for holes machining path optimization using helical milling operation
Authors: Li Z Q , Liu X , Duan L S , Liu L
Published: February 2021

Helical milling is capable of fabricating a lot of holes with only one cutting tool under one clamping. As the holes machining efficiency is determined by the holes machining time and the airtime, and when the cutting conditions of helical milling operation is determined, holes machining path optimization will have a great effect on holes machining efficiency. Based on the TSP model, an improved hybrid genetic algorithm is proposed to solve holes machining path optimization model to get the optimized processing path. By comparing the path length of the optimized machining path and the simulation time with that obtained using the basic GA and the basic ACO, the optimization algorithm proposed in this paper can effectively reduce the machining path length and thus improve the efficiency of holes machining operation.
Analysis on Influencing Factors of Grinding Aid Effect of Cement Grinding Aids
Authors: Zhao Hui
Published: February 2021

In the cement industry, grinding aids can be used to improve the efficiency, promote the realization of the concept of energy saving and emission reduction, and reduce the production cost to a great extent. Cement grinding aid is a kind of material which can promote cement grinding, and it is an important part of energy-saving development of industry at present. It can not be ignored in improving cement technology. Based on this, this paper analyzes the influencing factors of grinding aid effect in cement grinding process.
The Development Status of Selective Laser Melting Technology (SLM)
Authors: Tian Qiwen
Published: February 2021

With the development of manufacturing technology, traditional manufacturing methods can no longer meet the needs of modern society. Additive manufacturing technology (AM) is a new type, which bases on the principle of layered manufacturing and uses the method of accumulating materials layer by layer to directly manufacture digital models into solid parts. In recent years, AM has been greatly developed and applied. Selective Laser Melting technology (SLM) is a very widely used technology in AM. SLM uses a high-energy laser beam to scan the metal powder on a predetermined path. It first melts the metal powder completely, then after cooling, the melted metal powder solidfies into a part. This article first describes the characteristics and equipment development of SLM technology, then summarizes the application of SLM technology, finally discusses the shortcomings of SLM technology.
Research on 3D Printing Resource cloud Platform Technology based on dynamic Service Composition
Authors: Lv Wenyan
Published: February 2021

To improve the improve the management and matching of 3D printing resources, a 3Dprinting cloud platform based on dynamic service composition technology is established, and the 3D printing composite service is optimized. First, cloud computing is combined with 3D printing to establish cloud manufacturing mode. According to the characteristics of each stage, the dynamic service composition technology under cloud manufacturing mode is divided into three stages. Then, dynamic service composition technology of 3D printing resource is established. Based on the logical relationship between services, breadth algorithm and depth algorithm are used to find the optimal service composition path in the search graph to meet the different needs of users. The experimental results show that the relationship between user requirements and services can be obtained by calculating the quality of service. In the case, the service quality required by users is less than 20, and service 1 and 3 can meet the needs of users. This exploration provides a reference for the study of 3D printing resources dynamic service composition.
Research and Optimization of Inverter Electromagnetic Compatibility System
Authors: Changkai Xia , Xiangli Lin , Chunwei Shao , Mingpeng Ding
Published: February 2021

Modern electrical and electronic equipment has increasingly higher requirements on the reliability of its performance, especially the electromagnetic compatibility of the equipment. According to the working environment of the inverter cabinet and the design requirements of the cabinet, this paper widely combines the practical experience of the project, mainly from the aspects of gaps, ventilation holes, sealing, electrical layout, etc. It puts forward measures to improve the electromagnetic compatibility performance of the cabinet structure design. It achieves the purpose of meeting the requirements of GJB151A, and effectively improves the electromagnetic compatibility of the inverter.
On mechanisms of mixing by forced and natural convection in microfluidic devices
Authors: Bratsun Dmitry , Mizev Alexey , Mosheva Elena , Pismen Len , Siraev Ramil , Shmyrov Andrey
Published: February 2021

Continuous-flow microfluidic devices are applied in the study of microorganisms, in genetic research, production of pharmaceutical substances, lab-on-a-chip technology, biomedicine etc. Some applications require continuous mixing of the solutions that flow through the devices. However, straight-line mechanical mixing methods cannot be used due to the small size of the channels. In this paper, we discuss from a theoretical and experimental point of view the prospects of using various mechanisms of natural or forced convection for efficient mixing of solutions entering a microfluidic chip. Different designs of micromixers operating on gravity-dependent instabilities of the Rayleigh-Taylor type, double diffusion convection, and surface-dependent Marangoni instability are considered. Micromixers, in which the fluid flow is controlled by an electro-osmotic mechanism and directional deformations of the channel walls, are considered as examples of forced convection. For each case, we will provide the assessment of the range of chip sizes in which this mixing mechanism works effectively. The examples of experimental implementation of different mixing principles are given.
Revisiting the need to combine educational and scientific-research processes in teaching CFD modelling to students
Authors: Fedyushkin A I , Puntus A A
Published: February 2021

Using the example of many years of experience in cooperation between Institute No. 8 “Information Technologies and Applied Mathematics” of the Moscow Aviation Institute and Ishlinsky Institute for Problems in Mechanics of RAS points out the need for cooperation between the university and specialists of academic institutions in the preparation of highly qualified specialists in the field of CFD, stages of training, examples of qualification work and the use of software CFD products for training are presented. The difficulties of teaching CFD modeling are discussed, achievements and examples of solving the problems of hydrodynamics and heat and mass transfer by students of the Moscow Aviation Institute are given.
On the effect of reversing the direction of convection in a two-component fluid
Authors: Ingel L Kh
Published: February 2021

The theoretical problem of convection in a two-component medium (for example, in salt water) after “switching on” the sources/sinks of heat and admixture on an infinite vertical boundary is considered. Generally speaking, the degree of influence of the two components on convection is different due to the difference in their diffusion velocities. We suppose that heat diffuses much faster than the admixture and then the heated/cooled region at the lateral boundary is much thicker than the region of propagation of the impurity concentration disturbance. Therefore, convection due to temperature deviations is less affected by viscosity than due to deviations in admixture concentration. As a result, even a relatively weak “thermal” source of buoyancy can determine the direction of convection for some time in spite of the action of a more intense “concentration” source of buoyancy of a different sign. But if a vertical layer of a medium of finite thickness is considered, then a stationary regime is established over time, in which the direction of convection is determined by the total source of buoyancy, so that the direction of convection can change sign.