Equivalent Circuit Models: An Effective Tool to Simulate Electric/Dielectric Properties of Ores-An Example Using Granite.

The equivalent circuit model is widely used in high-voltage (HV) engineering to simulate the behavior of HV applications for insulation/dielectric materials. In this study, equivalent circuit models were prepared in order to represent the electric and dielectric properties of minerals and voids in a granite rock sample. The HV electric-pulse application shows a good possibility of achieving a high energy efficiency with the size reduction and selective liberation of minerals from rocks. The electric and dielectric properties were first measured, and the mineral compositions were also determined by using a micro-X-ray fluorescence spectrometer. Ten patterns of equivalent circuit models were then prepared after considering the mineral distribution in granite. Hard rocks, as well as minerals, are dielectric materials that can be represented as resistors and capacitors in parallel connections. The values of the electric circuit parameters were determined from the known electric and dielectric parameters of the minerals in granite. The average calculated data of the electric properties of granite agreed with the measured data. The conductivity values were 53.5 pS/m (measurement) and 36.2 pS/m (simulation) in this work. Although there were some differences between the measured and calculated data of dielectric loss (tanδ), their trend as a function of frequency agreed. Even though our study specifically dealt with granite, the developed equivalent circuit model can be applied to any other rock.

Simulation of Electrical and Thermal Properties of Granite under the Application of Electrical Pulses Using Equivalent Circuit Models.

Since energy efficiency in comminution of ores is as small as 1% using a mechanical crushing process, it is highly demanded to improve its efficiency. Using electrical impulses to selectively liberate valuable minerals from ores can be a solution of this problem. In this work, we developed a simulation method using equivalent circuits of granite to better understand the crushing process with high-voltage (HV) electrical pulses. From our simulation works, we calculated the electric field distributions in granite when an electrical pulse was applied. We also calculated other associated electrical phenomena such as produced heat and temperature changes from the simulation results. A decrease in the electric field was observed in the plagioclase with high electrical conductivity and void space. This suggests that the void volume in each mineral is important in calculating the electrical properties. Our equivalent circuit models considering both the electrical conductivity and dielectric constant of a granite can more accurately represent the electrical properties of granite under HV electric pulse application. These results will help us better understand the liberation of minerals from granite by electric pulse application.

Role of SiOx in rice-husk-derived anodes for Li-ion batteries.

The present study investigated the role of SiOx in a rice-husk-derived C/SiOx anode on the rate and cycling performance of a Li-ion battery. C/SiOx active materials with different SiOx contents (45, 24, and 5 mass%) were prepared from rice husk by heat treatment and immersion in NaOH solution. The C and SiOx specific capacities were 375 and 475 mAh g-1, respectively. A stable anodic operation was achieved by pre-lithiating the C/SiOx anode. Full-cells consisting of this anode and a Li(Ni0.5Co0.2Mn0.3)O2 cathode displayed high initial Coulombic efficiency (~ 85%) and high discharge specific capacity, indicating the maximum performance of the cathode (~ 150 mAh g-1). At increased current density, the higher the SiOx content, the higher the specific capacity retention, suggesting that the time response of the reversible reaction of SiOx with Li ions is faster than that of the C component. The full-cell with the highest SiOx content exhibited the largest decrease in cell specific capacity during the cycle test. The structural decay caused by the volume expansion of SiOx during Li-ion uptake and release degraded the cycling performance. Based on its high production yield and electrochemical benefits, degree of cycling performance degradation, and disadvantages of its removal, SiOx is preferably retained for Li-ion battery anode applications.

Suitable binder for Li-ion battery anode produced from rice husk.

Rice husk (RH) is a globally abundant and sustainable bioresource composed of lignocellulose and inorganic components, the majority of which consist of silicon oxides (approximately 20% w/w in dried RH). In this work, a RH-derived C/SiOx composite (RHC) was prepared by carbonization at 1000 °C for use in Li-ion battery anodes. To find a suitable binder for RHC, the RHC-based electrodes were fabricated using two different contemporary aqueous binders: polyacrylic acid (PAA) and a combination of carboxymethyl cellulose and styrene butadiene rubber (CMC/SBR). The rate and cycling performances of the RHC electrodes with respect to the insertion/extraction of Li ions were evaluated in a half-cell configuration. The cell was shorted for 24 h to completely lithiate the RHC. Impedance analysis was conducted to identify the source of the increase in the resistance of the RHC electrodes. The RHC electrode fabricated using PAA exhibited higher specific capacity for Li-ion extraction during the cycling test. The PAA binder strengthened the electrode and alleviated the increase in electrode resistance caused by the formation of the interphase film. The high affinity of PAA for SiOx in RHC was responsible for the stabilization of the anodic performance of Li-ion batteries.

A modified measurement method of electrical properties for ZnO microvaristors by direct measurements.

Zinc oxide (ZnO) materials are fine ceramics with non-linear electrical properties. Their non-linear electrical properties appear from a double Schottky barrier formed in the grain boundaries (GBs). These microparticles are not easy to measure directly with electrical microprobes due to their small size (i.e., 50-100 µm). We developed a direct measurement process with two Cu cables of small diameter. In this paper, we have developed an amplified method of the previous measurement system, which can measure not only one ZnO microvaristor directly but also a group of microvaristors in a series connection. The I-V characteristics of the microvaristors were measured with the modified method, and we found non-linear properties in each particle while measuring I-V characteristics. Their fine structures were also investigated, and the non-linear I-V characteristics showed a direct relationship with the number of the GBs of the samples. Moreover, varistor voltage was calculated for a single GB for the I-V measurements for ZnO microvaristors connected in a series connection.

Assessment of clinical and biochemical profile of prediabetic subject in Bangladesh, attending in BIRDEM and results of intervention by lifestyle modification, metformin, and DPP4 inhibitor.

Prediabetes increases an individual's risk for progress to diabetes. The aim of the study is to assess prediabetic profile before and after life style modification only, lifestyle with metformin and lifestyle with DPP-4 inhibitor. This study was carried out at BIRDEM. The subjects were IGT, IFG or combined. In Group A 50 subjects were advised with lifestyle, 42 were follow up with the results showed that highly significant change in BMI, Fasting & 2 h plasma glucose, serum triglyceride, and reduced HbA1c level, reduction rate of DM is 43%. In Group B 50 subjects were advised with lifestyle plus metformin, 44 were follow up with the results showed that significant change in BMI, Fasting, 2 h plasma glucose, triglyceride, and reduced HbA1c, reduction rate of DM is 58%. In Group C 50 subjects were advised with lifestyle plus DPP4i, 37 were follow up with the results showed that significantly change in BMI, Fasting, 2 h plasma glucose, triglyceride and reduced HbA1c level, reduction rate of DM is 43%. There is significant outcome difference in BMI in between A vs. B and A vs. C group. More mean changed in 2hrs after blood glucose level in group A vs. group B and B vs. C group. There is significant outcome difference in TG level in A vs. B, B vs. C group but no difference in A vs. C group.