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Research on the Dynamic Responses of Simply Supported Horizontal Pipes Conveying Gas-Liquid Two-Phase Slug Flow
Gang Liu, Zongrui Hao, Yueshe Wang, Wanlong Ren
October 14, 2021 (v1)
Subject: Other
Keywords: dynamic responses, intermittent, simply supported pipe, two-phase slug flow
The dynamic responses of simply supported horizontal pipes conveying gas-liquid two-phase slug flow are explored. The intermittent characteristics of slug flow parameters are mainly considered to analyze the dynamic model of the piping system. The results show that the variations of the midpoint transverse displacement could vary from periodic-like motion to a kind of motion whose amplitude increases as time goes on if increasing the superficial gas velocity. Meanwhile, the dynamic responses have certain relations with the vibration acceleration. By analyzing the parameters in the power spectrum densities of vibration acceleration such as the number of predominant frequencies and the amplitude of each peak frequency, the dynamic behaviors of the piping system like periodicity could be calculated expediently.
The Influence of Hydrodynamic Changes in a System with a Pitched Blade Turbine on Mixing Power
Jacek Stelmach, Czesław Kuncewicz, Szymon Szufa, Tomas Jirout, Frantisek Rieger
October 14, 2021 (v1)
Subject: Other
Keywords: impeller, Mixing, pitched blade turbine, power consumption
This paper presents an analysis of hydrodynamics in a tank with a 45° and 60° pitched blade turbine impeller operating while emptying the mixer and with an axial agitator working during axial pumping-down of water at different water levels above the impeller. Measurements made with the PIV method confirmed the change in direction of pumping liquid after the level dropped below the critical value, with an almost unchanged liquid stream flowing through the mixer. It was found that an increase in the value of the tangential velocity in the area of the impeller took place and the quantity of this increase depended on the angle of the blade pitch and the rotational frequency of the impeller. Change in this velocity component increased the mixing power.
Advances and Gaps in Natech Quantitative Risk Analysis
Adriana Mesa-Gómez, Joaquim Casal, Mauricio Sánchez-Silva, Felipe Muñoz
September 22, 2021 (v1)
Subject: Other
Keywords: area-wide, Natech, natural event, process safety, risk
The occurrence of Natech (natural hazard triggering technological disasters) accidents has generated a reflection about the need to manage adequately the risk to people, to the environment, and to the infrastructures subjected to natural events. For this reason, academia and industry have increased research in the process safety area in the last decade, strengthening quantitative risk analysis (QRA) methodologies for Natech events. However, these methodologies have some gaps that must be closed for a better decision-making process. In this communication a comparative analysis of the existing Natech QRA approaches is done, to highlight features and differences and to identify main gaps that should be addressed in future research. It can be mentioned that all the analyzed methodologies, which have been applied to floods, earthquakes, and lightning, are based on an initial one developed in 2007. The critical gap is that in all these methodologies, the final step is the risk calculation ba... [more]
Direct Growth of Carbon Nanotubes on Aluminum Foil by Atmospheric Pressure Microwave Plasma Chemical Vapor Deposition
Dashuai Li, Ling Tong
September 22, 2021 (v1)
Subject: Other
Keywords: aluminum foil, AMPCVD, CNTs, microwave plasma
This paper is about the research that carbon nanotubes (CNTs) grow on aluminum foils without additional catalysts by atmospheric pressure microwave plasma chemical vapor deposition (AMPCVD) with the precursor of argon-hydrogen-ethanol. At different temperatures, a series of experiments that CNTs grow on aluminum foils were done with and without the alumina layer. The EDS results showed that iron impurities in aluminum foils catalyze the growth of CNTs. By measurements of SEM and HRTEM, tens of microns long and multi-walled CNTs are grown. The CNTs’ content in the sample changes more with the increase in temperature. The Raman measuring shows that CNTs have fewer defects with higher temperature. Finally, by measurements of EDS mapping and XRD on aluminum foil, the growth mechanism of CNTs was discussed.
Degradation of 2,4-Dichlorophenol by Ethylenediamine-N,N′-disuccinic Acid-Modified Photo-Fenton System: Effects of Chemical Compounds Present in Natural Waters
Wenyu Huang, Ying Huang, Shuangfei Wang, Hongfei Lin, Gilles Mailhot
September 21, 2021 (v1)
Subject: Other
Keywords: 2,4-DCP, EDDS, inorganic ions, natural water bodies, organic matter, photo-Fenton
This paper describes a study of the treatment of 2,4-dichlorophenol (2,4-DCP) with an ethylenediamine-N,N′-disuccinic-acid (EDDS)-modified photo-Fenton system in ultrapure water and different natural waters. The results showed that the EDDS-modified photo-Fenton system is adequate for 2,4-DCP degradation. Compared with a medium containing a single organic pollutant, the removal of pollutants in a more complex medium consisting of two organic compounds is slower by around 25 to 50% as a function of the organic pollutant. Moreover, 2,4-DCP can be further effectively degraded in the presence of organic materials and various inorganic ions. However, the photodegradation of 2,4-DCP in different natural waters, including natural lake water, effluent from domestic sewage treatment plants, and secondary effluent from pulp and paper mill wastewaters, is inhibited. Chemical compounds present in natural waters have different influences on the degradation of 2,4-DCP by adopting the EDDS-modified p... [more]
Optimizing the Axial Resistance Profile of Submerged Hollow Fiber Membranes
Michael Kuhn, Heiko Briesen
September 21, 2021 (v1)
Subject: Other
Keywords: filter design, mechanistic model, membrane filtration, optimal control, process optimization
Submerged hollow fiber membranes (SHFMs) are used for a wide variety of applications. Their applicability and their advantages, however, depend crucially on the prevailing hydrodynamics within single fibers. In this respect, the non-uniform distribution of transmembrane flux is a known problem related to inhomogeneous membrane fouling and disadvantages for cleaning. To address this problem, we propose an approach to homogenize transmembrane flux by varying the local membrane resistance using optimal control methods for the first time in SHFM research. Based on an established model, different scenarios are optimized, namely with different fiber lengths and inner radii. In addition, a double-end setup is explored. It is shown that the optimization goal is reached very well in all tested cases, which underlines the general validity of our strategy. Further uses and extensions of the optimization method are provided, as well as hints for the practical implementation of the suggested measur... [more]
Ultrasonic Intensification of Mass Transfer in Organic Acid Extraction
Oleg M. Gradov, Yulia A. Zakhodyaeva, Inna V. Zinov’eva, Andrey A. Voshkin
September 16, 2021 (v1)
Subject: Other
Keywords: acoustics, aqueous two-phase system, eco-friendly extraction, intensification, interphase distribution, nonlinearity, poly (ethylene)glycol, pressure drop, resonance frequency, ultrasonic irradiation
The mechanism of ultrasonic extraction was discovered and analyzed in detail for the liquid membrane technique from the consideration of the specific features of the radial vibrations of a droplet of the dispersed phase placed into an immiscible continuous phase subjected to ultrasonic irradiation. Analytical formulas were derived for the rate of mass transfer as a function of the amplitude of acoustic pressure oscillations and the time of ultrasonic treatment of an extraction system. Conditions for achieving the maximum efficiency of the extraction of a substance under the stimulating effect of ultrasound were analyzed. A nonlinear equation was derived for the radial vibrations of a spherical droplet of the dispersed phase in an immiscible continuous phase under forcing in the form of acoustic pressure periodically changing with time. Experimental study of the dependence of sulfosalicylic acid distribution on time in an aqueous two-phase system with ultrasound shows good agreement of... [more]
The Effect of Slurry Wet Mixing Time, Thermal Treatment, and Method of Electrode Preparation on Membrane Capacitive Deionisation Performance
Ebrahiem Botha, Nafeesah Smith, Bongibethu Hlabano-Moyo, Bernard Bladergroen
August 2, 2021 (v1)
Subject: Other
Keywords: capacitive deionisation, contact angle, maximum salt adsorption capacity, thermal treatment, wet mixing
Capacitive deionisation (CDI) electrodes with identical composition were prepared using three deposition methods: (1) slurry infiltration by calendering (SIC), (2) ink infiltration dropwise (IID), and (3) ink deposition by spray coating (IDSC). The SIC method clearly showed favourable establishment of an electrode with superior desalination capacity. Desalination results showed that electrodes produced from slurries mixed longer than 30 min displayed a significant reduction in the maximum salt adsorption capacity, due to the agglomeration of carbon black. The electrodes were then thermally treated at 130, 250, and 350 °C. Polyvinylidene difluoride (PVDF) decomposition was observed when the electrodes were treated at temperatures higher than 180 °C. The electrodes treated at 350 °C showed contact angles of θ = 0°. The optimised electrodes showed a salt adsorption capacity value of 24.8 mg/g (130 °C). All CDI electrodes were analysed using specific surface area by N2 adsorption, contact... [more]
Flow and Diffusion Characteristics of Typical Halon Extinguishing Agent Substitute under Different Release Pressures
Jiaming Jin, Renming Pan, Ruiyu Chen, Xiaokang Xu, Quanwei Li
July 29, 2021 (v1)
Subject: Other
Keywords: aircraft weight reduction, diffusion, flow, Halon candidate substitute, HFC-125, release pressure
To provide guidance towards reducing the weight of the HFC-125 storage vessel by reducing the release pressure and to reveal the effects of release pressure on the extinguishing efficiency of HFC-125, we investigated the flow and diffusion characteristics of HFC-125 under six release pressures in the present study. The influence of release pressure on the degree of superheat, injection duration, pressure loss, jet angle, and concentration distribution were analyzed. Results show that the degree of superheat and the injection duration both decreased with the release pressure. The bubble expansion in the HFC-125 could slow down the pressure decrease in the storage vessel. The flow process in the pipeline can be divided into three phases: pipeline filling, stable flow, and mixed gases release. Both of the maximum and mean values of the pipeline pressure loss increased with the release pressure. The maximum concentration value decreased with the increase of the distance from the nozzle. Th... [more]
The Dynamics of Globally Unstable Air-Helium Jets and Its Impact on Jet Mixing Intensity
Agnieszka Pawlowska, Andrzej Boguslawski
July 29, 2021 (v1)
Subject: Other
Keywords: Mixing, mixing length scales, turbulence
The paper presents experimental investigations of the low-density air-helium jets. The paper is aimed at the analysis of the flow conditions promoting the local absolute instability leading to global flow oscillations. A number of the test cases are analysed with a wide range of the shear layer thickness showing conditions favorable for the global modes and also mixing intensity triggered by such a regime. It is shown that high mixing intensity is determined not only by the global regime but also by the vortex pairing process. The results are compared with a recently proposed universal scaling law for an onset into the global mode. The results turn out to be far from this scaling law and the reasons for such discrepancies are discussed. The measurements show also that if the shear layer at the nozzle exit is thin enough the global modes are suppressed. The mechanism leading to the global mode suppression under such conditions is carefully analysed.
Abrasive Water Jet Cutting of Hardox Steels—Quality Investigation
Tibor Krenicky, Milos Servatka, Stefan Gaspar, Jozef Mascenik
July 29, 2021 (v1)
Subject: Other
Keywords: abrasive water jet, cutting, quality prediction, surface quality
The paper aims to study the surface quality dependency on selected parameters of cuts made in Hardox™ by abrasive water jet (AWJ). The regression process was applied on measured data and the equations were prepared for both the Ra and Rz roughness parameters. One set of regression equations was prepared for the relationship of Ra and Rz on cutting parameters—pumping pressure, traverse speed, and abrasive mass flow rate. The second set of regression equations describes relationships between the declination angle in kerf as the independent variable and either the Ra or the Rz parameters as dependent variables. The models can be used to predict cutting variables to predict the surface quality parameters.
The Concept of Sustainable Development of Modern Dentistry
Leszek A. Dobrzański, Lech B. Dobrzański, Anna D. Dobrzańska-Danikiewicz, Joanna Dobrzańska
July 19, 2021 (v1)
Subject: Other
Keywords: caries, dental implantology, dental interventionistic treatment, dental prophylaxis, dental prosthetics, dentist ethics, dentist safety, Dentistry 4.0, dentistry sustainable development, endodontics, periodontology, toothlessness
This paper concerns the assessment of the current state of dentistry in the world and the prospects of its sustainable development. A traditional Chinese censer was adopted as the pattern, with a strong and stable support on three legs. The dominant diseases of the oral cavity are caries and periodontal diseases, with the inevitable consequence of toothlessness. From the caries 3.5−5 billion people suffer. Moreover, each of these diseases has a wide influence on the development of systemic complications. The territorial range of these diseases and their significant differentiation in severity in different countries and their impact on disability-adjusted life years index are presented (DALY). Edentulousness has a significant impact on the oral health-related quality of life (OHRQoL). The etiology of these diseases is presented, as well as the preventive and therapeutic strategies undertaken as a result of modifying the Deming circle through the fives’ rules idea. The state of developme... [more]
Grey-Taguchi-Based Optimization of Wire-Sawing for a Slicing Ceramic
Yao-Yang Tsai, Jihng-Kuo Ho, Wen-Hao Wang, Chia-Chin Hsieh, Chung-Chen Tsao, Chun-Yao Hsu
July 19, 2021 (v1)
Subject: Other
Keywords: Grey-Taguchi method, material removal rate, slurry concentration, surface roughness, wire-sawing
Slicing ceramic (SC) is well-known as difficult-to-cut material. It is a hard and brittle material. The Grey-Taguchi method, which converts multiple response problems into a single response, is used to determine the effect of the process parameters for wire-sawing on multiple quality characteristics. The wire-sawing parameters include the wire tension (T), the slurry concentration (C), mixed grains mesh size (G), the wire speed (S), and the working load (P). The machining quality characteristics include a material removal rate (MRR), machined surface roughness (SR) of SC, kerf width (KW), wire wear (WW), and flatness (FT). An analysis of variance (ANOVA) is used to identify the mixed grains and slurry concentration that have a significant effect on multiple quality characteristics. The results of the ANOVA using the Grey-Taguchi method show that the optimum conditions are T2C1G1S2P1 (wire tension of 24 N, slurry concentration of 10% wt., mixed grains of #600 + #1000 mesh size, wire spe... [more]
Novel Study for Energy Recovery from the Cooling−Solidification Stage of Synthetic Slag Manufacturing: Estimation of the Potential Energy Recovery
Francisco M. Baena-Moreno, Mónica Rodríguez-Galán, Benito Navarrete, Luis F. Vilches
July 12, 2021 (v1)
Subject: Other
Keywords: energy recovery, fixed bed regenerator, metal spheres, sustainable synthetic slag production, waste and energy nexus
Herein, a novel method for energy recovery from molten synthetic slags is analyzed. In this work, the potential energy that could be recovered from the production of synthetic slag is estimated by means of an integrated experimental−theoretical study. The energy to be recovered comes from the cooling−solidification stage of the synthetic slag manufacturing. Traditionally, the solidification stage has been carried out through quick cooling with water, which does not allow the energy recovery. In this paper, a novel cooling method based on metal spheres is presented, which allows the energy recovery from the molten slags. Two points present novelty in this work: (1) the method for measuring the metal spheres temperature (2) and the estimation of the energy that could be recovered from these systems in slag manufacturing. The results forecasted that the temperature achieved by the metal spheres was in the range of 295−410 °C in the center and 302−482 °C on the surface. Furthermore, we est... [more]
Whispering-Gallery-Mode for Coherent Random Lasing in a Dye-Doped Polystyrene Encapsulated Silica-Glass Capillary
Kai Nie, Yueqi Wang, Zhenzhen Zhang, Gang Zou, Xiaolong Xu, Zhijia Hu, Qijin Zhang
June 29, 2021 (v1)
Subject: Other
Keywords: coherent random lasing (RL), random lasers, whispering gallery modes
Dye-doped polystyrene (DDPS) encapsulated in a silica-glass capillary with a diameter of 300 μm was fabricated through radical polymerization of styrene within the capillary. The coherent random lasing (RL) with full width at half maximum (FWHM) of 0.36 nm and a quality factor of 1608 was produced in the DDPS with the capillary when pumping at 532 nm. However, the incoherent RL with FWHM of 6.62 nm and a quality factor of 92 was produced in the DDPS without the capillary. A detailed investigation on this phenomenon by changing the diameter of the capillary and core refractive index (RI) reveals that there exists a strong whispering gallery mode (WGM) resonance in the capillary, which helps generate the coherent RL. The findings may open up a new approach for the fabrication of highly efficient photonic devices.
Water-Soluble Carbon Quantum Dots Modified by Amino Groups for Polarization Fluorescence Detection of Copper (II) Ion in Aqueous Media
Anastasia Yakusheva, Dmitry S. Muratov, Dmitry Arkhipov, Gopalu Karunakaran, Sergei A. Eremin, Denis Kuznetsov
June 29, 2021 (v1)
Subject: Other
Keywords: carbon quantum dots, copper cation, fluorescence properties, polarization fluorescent analysis, water samples
Industrialization is serious for changing the environment and natural water composition, especially near cities and manufacturing areas. Logically, the new ultrasensitive technology for precise control of the quality and quantity of water sources is needed. Herein, an innovative method of polarization fluorescence analysis (FPA) was developed to measure the concentration of heavy metals in water. The approach was successfully applied for precise tests with reduced analysis time and increased measurement efficiency among laboratory methods. Based on this work, the investigations established the new type of carbon quantum dots (CQDs) with controllable fluorescence properties and functionalized amino—groups, which is appropriate for FPA. The parameters of one and two-step microwave synthesis routes are adjusted wavelength and fluorescence intensity of CQDs. Finally, under optimized conditions, the FPA is showed the detection of copper (2+) cations in water samples below European Union sta... [more]
Thermal Stress and Deformation of Hollow Paddle-Shaft Components with Internal High Temperature Molten Salt Flow
Taha Rajeh, Basher Hassan Al-Kbodi, Houlei Zhang
June 21, 2021 (v1)
Subject: Other
Keywords: deformation, heat transfer, hollow paddle, molten salt, pressure drop, stress distribution, thermal stress
Excessive thermal stress and deformation are important reasons causing disservice of high temperature heat exchangers. This paper presents thermal stress and expansion analysis of single-leaf type hollow paddle-shaft components with internal high temperature molten salt flow based on three-dimensional numerical simulations. The results show that the hollow paddles enhance the heat transfer and decrease the maximum thermal stress simultaneously with the expense of a much higher pressure drop than that of solid paddles. The cumulative von Mises stress distribution curve shows that the stress distribution of the component with hollow paddles is more uniform than that with solid paddles. The radial and axial deformations do not differ much for the components with hollow and solid paddles. A larger volume of the fluid space in the hollow paddles leads to stronger heat transfer, smaller maximum thermal stress, and more uniform stress distribution. The effects of the paddle height, the diamet... [more]
A Study on Fiber Laser Welding of High-Manganese Steel for Cryogenic Tanks
Jaewoong Kim, Jisun Kim, Changmin Pyo
June 21, 2021 (v1)
Subject: Other
Keywords: bead on plate, cryogenic impact strength, high-manganese steel, tensile strength, yield strength
As the environmental regulations on ship emissions by the International Maritime Organization (IMO) become stricter, the demand for a ship powered by liquefied natural gas (LNG) is rapidly increasing worldwide. Compared to other materials, high-manganese steel has the advantages of superior impact toughness at cryogenic temperatures, a low thermal expansion coefficient, and a low-cost base material and welding rod. However, there is a limitation that the mechanical properties of a filler material are worse than those of a base material that has excellent mechanical properties. To solve these shortcomings, a basic study was performed to apply fiber laser welding with little welding deformation and no filler material to high-manganese steel. The relationship between laser welding parameters and penetration shapes was confirmed through cross-section observation and analysis by performing a bead on plate (BOP) test by changing laser power and welding speed, which are the main parameters of... [more]
Optimization of Oxidative Leaching for Vanadium Extraction from Low-Grade Stone Coal Using Response Surface Methodology
Zulv Huang, Tao Chen, Yang Zhou, Wenbin Xu, Hanzhi Lin, Bo Yan
June 21, 2021 (v1)
Subject: Other
Keywords: kinetics, Optimization, oxidation leaching, stone coal, vanadium
The feasibility and kinetics of vanadium (V) recovery from oxidative leaching of low-grade stone coal using MnO2 were investigated. Oxidative leaching processes (OLPs) were designed using response surface methodology (RSM) based on the central composite design (CCD) model. The results show that the order of factors that influence OLPs is leaching temperature > H2SO4 concentration > leaching time > MnO2 dosage. The interaction between leaching temperature and H2SO4 concentration on the OLP is the most significant. Vanadium leaching efficiency was 89.3% using 31% H2SO4 and 3% MnO2 at 90 °C for 7.9 h. The kinetics of V leaching from stone coal show that the leaching rate is controlled by chemical reaction through a layer according to the shrinking core model and the activation energy is 55.62 kJ/mol. A comparison of the SEM-EDS results of minerals before and after leaching confirms that the muscovite structure was significantly destroyed and V and aluminum (Al) were effectively dissolved... [more]
Theoretical Evaluation of the Melting Efficiency for the Single-Screw Micro-Extrusion Process: The Case of 3D Printing of ABS
Andrea La Gala, Rudinei Fiorio, Mustafa Erkoç, Ludwig Cardon, Dagmar R. D’hooge
June 10, 2021 (v1)
Subject: Other
Keywords: additive manufacturing, melting, micro-extrusion, polymer melting model, process design, rapid prototyping, single screw extrusion
One of the challenges for single-screw micro-extrusion or additive manufacturing (AM), thus 3D printing, of polymers is controlling the melting efficiency so that energy and equipment costs can be minimized. Here, a numerical model is presented for AM process design, selecting acrylonitrile−butadiene−styrene (ABS) as viscoelastic reference polymer. It is demonstrated that AM melting is different compared to conventional melting due to variation in extrusion dimensions, leading to a different balance in heating by conduction and viscous heat dissipation as caused by the shearing between the melt layers in the associated film layer near the barrel. The thickness of this melt film layer is variable along the screw length, and it is shown that simplified models assuming an overall average value are too approximate. It is highlighted that the screw frequency, pitch angle and compression ratio are important process parameters to control the point of melt finalization. In addition, the power-... [more]
Auto-Aspirated DAF Sparger Study on Flow Hydrodynamics, Bubble Generation and Aeration Efficiency
Dmitry Vladimirovich Gradov, Andrey Saren, Janne Kauppi, Kari Ullakko, Tuomas Koiranen
June 10, 2021 (v1)
Subject: Other
Keywords: dissolved air flotation, gas–liquid ejector, gas–liquid mass transfer, high-speed camera, particle image velocimetry, water treatment
A novel auto-aspirated sparger is examined experimentally in a closed-loop reactor (CLR) at lab scale using particle image velocimetry, high-speed camera and oxygen mass transfer rate measurements. State-of-the-art 3D printing technology was utilized to develop the sparger design in stainless steel. An insignificant change in the bubble size distribution was observed along the aerated flow, proving the existence of a low coalescence rate in the constraint domain of the CLR pipeline. The studied sparger created macrobubbles evenly dispersed in space. In pure water, the produced bubble size distribution from 190 to 2500 μm is controlled by liquid flow rate. The bubble size dynamics exhibited a power-law function of water flow rate approaching a stable minimum bubble size, which was attributed to the ratio of the fast-growing energy of the bubble surface tension over the kinetic energy of the stream. Potentially, the stream energy can efficiently disperse higher gas flow rates. The oxygen... [more]
Starting Conditions of Particle Migration in Tight Sandstone Reservoir Development
Jie Shan, Xiaojun Zhou
June 2, 2021 (v1)
Subject: Other
Keywords: extended DLVO, hydrodynamics, non-Newtonian fluid, particle migration, starting conditions
In the tight sandstone oil production stage, the migration of particles will not only block the oil path and throat, but also block the wellbore and damage the equipment. Based on the theory of non-Newtonian fluid, hydrodynamics, the extended Derjaguin Landau Verwey Overbeek (DLVO) theory and the JKR (the model of Johnson−Kendall−Roberts) contact theory, the mathematical model and quantitative analysis of the critical condition of the particle separation from the surface due to the influence of oil flow in the fracture environment are presented in this paper. A theoretical model with pressure gradient as the core parameter and particle size, crack size and various contact forces as variables is established. By adding the formula of non-Newtonian fluid and taking the consistency coefficient and fluidity index as the contrast relation, the change rule of particle migration under the influence of non-Newtonian fluid is obtained. Effective prevention and control measures for the purpose of... [more]
Multiple Criteria Decision-Making: A Novel Applications of Network DEA Model
Chang-Hsu Chen, Wen-Bin Lin, Shih-Chieh Yang, Richard Hsiao
May 28, 2021 (v1)
Subject: Other
Keywords: aboriginals, efficiency, ex-member, multi-criteria decision making, Taiwanese coaches
Do retired professional baseball players become effective coaches? Are Taiwanese coaches up to the job of coaching in the Chinese Professional Baseball League (CPBL)? What are the key coaching factors affecting a CPBL team’s performance in the regular-season? In this study, we examine the key coaching factors affecting the efficiency of CPBL teams from the perspective of efficiency and productivity, using network data envelopment analysis, truncated regression analysis, and bootstrapping methods to provide specific recommendations. We calculated the efficiency of each CPBL team from the 2014 to 2016 regular-seasons. First, the “ex-member” indicator had a significant negative impact on team performance, indicating that a coaching team consisting of coaches with different backgrounds or experience is advantageous to a team’s performance in games; and second, the “ex-professional player” indicator had a significant impact on team performance in the regular season, indicating that the valu... [more]
Analysis of Dynamic Engaged Characteristics of Wet Clutch in Variable Speed Transmission of a Helicopter
Heyun Bao, Tongjing Xu, Guanghu Jin, Wei Huang
May 27, 2021 (v1)
Subject: Other
Keywords: characteristics of dynamic engagement, oil film thickness, spring preload, variable speed helicopter transmission, wet clutch
The working principle and motion process of an aviation wet clutch are analyzed. The initial velocity before the friction pair engaged is solved. The transient Reynolds equation is modified, and an oil film bearing capacity model and a micro-convex bearing capacity model are derived. The film thickness equation between N friction pairs and a pressure-plate is derived. A dynamic engaged model of springs, pistons, friction pairs, and pressure plates are established. The torque balance equation is established of two pairs of friction pairs. The friction torque, rate of change in the oil film, and law of relative change in speed are obtained. The results demonstrate that the spring preload and the viscosity of the lubricating oil have a significant influence on the engagement characteristics. Increasing the quality of the friction plate will reduce the time of engagement, whereas the quality of the friction plate has slight effect on the friction torque characteristics and oil film thickne... [more]
Effect of Strain Hardening Laws on Solution Behavior Near Frictional Interfaces in Metal Forming Processes: A Simple Analytical Example
Sergei Alexandrov, Elena Lyamina, Pierre-Yves Manach
May 27, 2021 (v1)
Subject: Other
Keywords: friction, metal forming processes, plasticity, singularity, work hardening
The main objective of the present paper is to compare, by means of a problem leading to a closed-form solution, the qualitative behavior of solutions based on three strain hardening laws: Swift’s law, Ludwik’s law, and Voce’s law. The boundary value problem involves the maximum friction law as one of the boundary conditions. Such features of the solutions as nonexistence and singularity are emphasized. An important feature of Swift’s and Ludwik’s laws is that the equivalent stress approaches infinity as the equivalent strain approaches infinity. On the contrary, Voce’s law involves saturation stress as one of the constitutive parameters. This qualitative difference in the equivalent stress behavior as the equivalent strain approaches infinity results in the qualitative difference in solutions’ behavior. In particular, Swift’s and Ludwik’s hardening laws are compatible with the regime of sticking independently of other conditions. In the case of Voce’s law, the solution under sticking c... [more]
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