Sintering of CoO: I, Initial Stage

The initial-sintering kinetics of compacts of uniform spheres of CoO were investigated at various temperatures and O₂ partial pressures. Volume-diffusion kinetics were exhibited initially, followed by retardation of sintering and deviation from the sintering model as a result of faceting of the spheres. The calculated volume diffusivities lie between those measured for Co and O in CoO.     

Strength characteristics of illinois coal combustion by‐product: PCC dry bottom ash

The coal combustion by‐product, dry bottom ash, originates from the burning of pulverized coal to produce electricity. Currently, almost all of the pulverized coal combustion (PCC) dry bottom ash is being dumped into ash ponds and landfills. Some of the ash ponds are reaching their maximum capacity and there is an immediate need for alternative measures to either dispose of or utilize the coal combustion by‐products for construction purposes. Within the past five years, several studies have investigated the use of PCC dry bottom ash in concrete and concrete products. However, its use in geotechnical applications is very limited. The physical properties of Illinois PCC dry bottom ash are similar to that of natural sand with particle sizes ranging from fine gravel to fine sand. Shear strength characteristics of soils, or materials similar to soils, are the most important parameters needed for the design of any geotechnical engineering project. Therefore, this study was initiated to develop understanding of the shear behavior of Illinois PCC dry bottom ash so that its potential use in geotechnical engineering applications could be accessed. This paper presents the results of an experimental study conducted to develop the technical data on shear strength characteristics of Illinois PCC dry bottom ash amended with bentonite.     

AA5083铝合金的搅拌摩擦焊接工艺参数对搅拌头受力和热输入的影响(英文)

采用系统实验设计方法研究AA5083铝合金搅拌摩擦焊接工艺参数对搅拌头受力和热量输入的影响,得到了用来设计搅拌摩擦焊搅拌头和焊机的经验模型。当采用计算机来控制搅拌摩擦焊接时,这些模型可用来确定AA5083这类铝合金的摩擦焊接工艺参数、编制焊接程序及工艺参数控制。结果表明:影响轴向力和热量输入的重要参数是搅拌头转速、焊接速度和搅拌头轴肩直径,而影响纵向应力的重要参数是焊接速度和探头直径。     

COVID-19: Review on Its Etiology,Pathogenesis, and Existence in Humans

The world is facing a new healthcare crisis with the rise and spread of novel coronavirus since December 2019.Also known as Severe Acute Respiratory Syndrome Corona Virus-2 (SARS-CoV-2), the disease associated with SARSCoV-2 is even called COVID-19. The infection is said to have originated from the bat community and transmitted tohumans through an intermediate host (yet unknown) in Wuhan, in the Hubei region of China. COVID-19 is havinga pulverizing impact on the scientific community. As of August 13, 2020, the number of confirmed cases had reachedup to 20,439,814 and the death toll to 744,385, affecting more than 188 territories across the globe. In these difficulttimes, the world is looking towards research and clinical work from different scientific communities to lead the wayto a solution to the issue. In this review, we are focusing on COVID-19 emergence, pathogenicity, and existence inhumans, as well as the SARS-CoV-2 infection mechanism and its similarities to previous coronavirus strains.     

Study of optical characteristics of tin oxide thin film prepared by sol–gel method

In this paper, we present details of preparation of tin oxide (SnO $_{{2}})$ thin film by sol–gel process. The film was synthesized on a glass (Corning 7059) plate by dip coating method. Here, we used tin (II) chloride as precursor and methanol as solvent. Optical characteristics and physical properties like refractive index, absorption coefficient and thickness of thin film were calculated from the study of transmission spectrum (wavelength vs transmission curve) data given by UV/VIS Spectrophotometer. Effect of number of coatings on transmittance and refractive index was also examined. It was observed that refractive index decreases with the number of coating and transmission value was more than 80% at wavelength greater than 450 nm in all cases. Structural analysis was studied by XRD measurement by using diffractometer which confirms tetragonal rutile structure of SnO ₂ . Surface morphology was analysed from SEM micrograph and change in morphology on number of coat was discussed.     

Wear monitoring of single point cutting tool using acoustic emission techniques

This paper examines the flank and crater wear characteristics of coated carbide tool inserts during dry turning of steel workpieces. A brief review of tool wear mechanisms is presented together with new evidence showing that wear of the TiC layer on both flank and rake faces is dominated by discrete plastic deformation, which causes the coating to be worn through to the underlying carbide substrate when machining at high cutting speeds and feed rates. Wear also occurs as a result of abrasion, as well as cracking and attrition, with the latter leading to the wearing through the coating on the rake face under low speed conditions. When moderate speeds and feeds are used, the coating remains intact throughout the duration of testing. Wear mechanism maps linking the observed wear mechanisms to machining conditions are presented for the first time. These maps demonstrate clearly that transitions from one dominant wear mechanism to another may be related to variations in measured tool wear rates. Comparisons of the present wear maps with similar maps for uncoated carbide tools show that TiC coatings dramatically expand the range of machining conditions under which acceptable rates of tool wear might be experienced. However, the extent of improvement brought about by the coatings depends strongly on the cutting conditions, with the greatest benefits being seen at higher cutting speeds and feed rates. Among these methods, tool condition monitoring using Acoustic Techniques (AET) is an emerging one. Hence, the present work was carried out to study the stability, applicability and relative sensitivity of AET in tool condition monitoring in turning.     

Indigenous development and airworthiness certification of 15–5 PH precipitation hardenable stainless steel for aircraft applications

In this paper, we discuss the optimization of chemical composition, processing (forging and rolling) and heat treatment parameters to obtain the best combination of mechanical properties in case of a Fe–15Cr–5Ni–4Cu precipitation hardenable stainless steel. The ε-copper precipitates that form during aging are spherical in shape and coherent with the matrix and principally provide strengthening in this alloy. The orientation relationship is found to be Kurdjumov–Sachs (K–S), which is common in fcc–bcc systems. Results obtained from metallurgical evaluation (mechanical property and metallography) on 15–5 PH alloy during type certification on 3 different melts were used for the optimization, attempted in this study. The mechanical properties following strain deformation has been carried out using optical microscope, scanning electron microscope (SEM) and transmission electron microscope (TEM). In the aged conditions, the 15–5 PH alloy exhibited brittle failure with extensive cleavage and/or quasicleavage fracture. This paper reports all results and also factually shows that indigenously developed and produced 15–5 PH stainless steel matches in its properties with the equivalent aeronautical grade precipitation hardening stainless steels globally produced by internationally renowned manufactures.     

Space vector-based analysis of overmodulation in triangle-comparison based PWM for voltage source inverter

The equivalence of triangle-comparison-based pulse width modulation (TCPWM) and space vector based PWM (SVPWM) during linear modulation is well-known. This paper analyses triangle-comparison based PWM techniques (TCPWM) such as sine-triangle PWM (SPWM) and common-mode voltage injection PWM during overmodulation from a space vector point of view. The average voltage vector produced by TCPWM during overmodulation is studied in the stationary (a–b) reference frame. This is compared and contrasted with the average voltage vector corresponding to the well-known standard two-zone algorithm for space vector modulated inverters. It is shown that the two-zone overmodulation algorithm itself can be derived from the variation of average voltage vector with TCPWM. The average voltage vector is further studied in a synchronously revolving (d-q) reference frame. The RMS value of low-order voltage ripple can be estimated, and can be used to compare harmonic distortion due to different PWM methods during overmodulation. The measured values of the total harmonic distortion (THD) in the line currents are presented at various fundamental frequencies. The relative values of measured current THD pertaining to different PWM methods tally with those of analytically evaluated RMS voltage ripple.     

AN MILP FORMULATION FOR LOAD-SIDE DEMAND CONTROL

ABSTRACT

This paper presents a mixed integer linear programming formulation for load-side control of electrical energy demand. The formulation utilizes demand prediction to determine if control actions are necessary, and it schedules both shedding and restoration times based on an optimization model that minimizes the net cost of load shedding. Operational constraints are satisfied through the use of minimum/maximum uptimes/downtimes, which depend upon the current state of the system. The algorithm is evaluated using a simulation model of an underground coal mining operation where, (i) its performance is compared with a traditional static, priority-based, load-shedding schedule, and, (ii) its potential is established for producing net savings through demand control.