Experimental and Numerical Study on the Electrical and Thermal Characteristics of High Energy Density Lithium-ion Battery Cell for Application of Battery Electric Vehicle

In this paper, the electrical and thermal characteristics of the high-energy density of 100 Ah (over 350 Wh/L) pouch-type lithium-ion battery (LIB) cell are analyzed experimentally. To determine the effects of applying current-rate (crate) on its behavior, the battery is charged and discharged in different c-rate ranging from 0.5C to 1.2C. The changes in discharged capacity and heat generation rates of battery cells are examined and its mechanism is analyzed deeply in the view of variations on internal resistance. The battery heat generation is considered with two heat sources, joule and entropic heat. A newly developed inverse calculation method is adopted to derive the entropic coefficient in the function of the state of charge. The heat capacity of the battery cell is determined from the convective cooling experiment of battery cell with aluminum block and the combined heat transfer coefficient to calculate the cooling rates of battery cells is also determined appropriately from the Nusselt number correlation. It is confirmed that the numerical model based on the above methods is well suited as a whole from the experiments. In addition, the cell is discharged in different ambient temperature ranging from -15℃ to 45℃ to find out the temperature effects on LIBs. The decrease of capacity and more heat generation of LIB is found under both low and high ambient temperature. As a result, the optimum operating temperature range is redefined as 25℃-35℃ through analyzing the change of electrical and thermal performances of the battery cells

Fabrication of poly(vinyl alcohol)-polyaniline nanofiber/graphene hydrogel for high-performance coin cell supercapacitor

Electroactive polymer hydrogel offers several advantages for electrical devices, including straightforward synthesis, high conductivity, excellent redox behavior, structural robustness, and outstanding mechanical properties. Here, we report an efficient strategy for generating polyvinyl alcohol-polyaniline-multilayer graphene hydrogels (PVA-PANI-MLGHDGs)with excellent scalability and significantly improved mechanical, electrical, and electrochemical properties; the hydrogels were then utilized in coin cell supercapacitors. Production can proceed through the simple formation of boronate (-O-B-O-) bonds between PANI and PVA chains; strong intermolecular interactions between MLG, PANI, and PVA chains contribute to stronger and more rigid HDGs. We identified the optimal amount of PVA (5 wt.%) that produces a nanofiber-like PVA-PANI HDG with better charge transport properties than PANI HDGs produced by earlier approaches. The PVA-PANI-MLG HDG demonstrated superior tensile strength (8.10 MPa) and higher specific capacitance (498.9 F/cm2, 166.3 F/cm3, and 304.0 F/g) than PVA-PANI HDGs without MLG. The remarkable reliability of the PVA-PANI-MLG HDG was demonstrated by 92.6% retention after 3000 cycles of galvanostatic charge-discharge. The advantages of this HDG mean that a coin cell supercapacitor assembled using it is a promising energy storage device for mobile and miniaturized electronics. © 2020 by the authors.1

Fabrication of Conducting Polyacrylate Resin Solution with Polyaniline Nanofiber and Graphene for Conductive 3D Printing Application

Three-dimensional printing based on the digital light processing (DLP) method offers solution processability, fast printing time, and high-quality printing through selective light curing of photopolymers. This research relates to a method of dispersing polyaniline nanofibers (PANI NFs) and graphene sheets in a polyacrylate resin solution for optimizing the conductive solution suitable for DLP-type 3D printing. Dispersion and morphology of the samples with different filler contents were investigated by field emission scanning electron microscope (FE-SEM) and optical microscope (OM) analyses. The polyacrylate composite solution employing the PANI NFs and graphene was printed well with various shapes and sizes through the 3D printing of DLP technology. In addition, the electrical properties of the printed sculptures have been investigated using a 4-point probe measurement system. The printed sculpture containing the PANI NFs and graphene sheets exhibited electrical conductivity (4.00 × 10−9 S/cm) up to 107 times higher than the pure polyacrylate (1.1 × 10−16 S/cm). This work suggests potential application of the PANI NF/graphene cofiller system for DLP-type 3D printing

Analysis of Fine Crack Images Using Image Processing Technique and High-Resolution Camera

Visual inspections are performed to investigate cracks in concrete infrastructure. These activities require manpower or equipment such as articulated ladders. Additionally, there are health and safety issues because some structures have low accessibility. To deal with these problems, crack measurement with digital images and digital image processing (DIP) techniques have been adopted in various studies. The objective of this experimental study is to evaluate the optical limit of digital camera lenses as working distance increases. Three different lenses and two digital cameras were used to capture images of lines ranging from 0.1 to 0.5 mm in thickness. As a result of the experiments, it was found that many elements affect width measurement. However, crack width measurement is dependent on the measured pixel values. To accurately measure width, the measured pixel values must be in decimal units, but that is theoretically impossible. According to the results, in the case of 0.3 mm wide or wider cracks, a working distance of 1 m was secured when the focal length was 50 mm, and working distances of 3 m and 4 m were secured when the focal length was 100 mm and 135 mm, respectively. However, for cracks not wider than 0.1 mm, focal lengths of 100 mm and 135 mm showed measurability within 1 m, but a focal length of 50 mm was judged to hardly enable measurement except for certain working positions. Field measurement tests were conducted to verify measurement parameters identified by the results of the indoor experiment. The widths of actual cracks were measured through visual inspection and used for the analysis. From the evaluation, it was confirmed that the number of pixels corresponding to the working distance had a great influence on crack width measurement accuracy when using image processing. Therefore, the optimal distance and measurement guidelines required for the measurement of the size of certain objects was presented for the imaging equipment and optical equipment applied in this study

Development of Bonded Natural Stone Pavement Using Ultra-Rapid-Hardening Mortar

Bonded natural stone pavement has been typically used in historical neighborhoods to satisfy functional and architectural aesthetic standards. Despite its advantages, it has been barely applied to places for heavy traffic volume or high travelling speed because of various structural failures in joints and bedding courses. Ultra-rapid-hardening mortar for natural stone pavement was considered as an alternative to minimize these failures. The objective of this study is to develop bound stone pavement using the ultra-rapid-hardening mortar for high traffic volume and evaluate throughout by carrying out material tests, plate load test, accelerated pavement test (APT), and falling weight deflectometer (FWD) test. For the tests, four types of pavements, asphalt, concrete block, and two bound stone pavements, were produced in a testing facility. The bearing capacity of the sub-base course, which was asphalt and concrete, showed values 1.62 and 2.64 times higher than deemed satisfactory. Additionally, rut depth was measured using a transverse profile logger during the APT test and the test was terminated at 1.97 million cumulative equivalent single axle loads (ESALs). In the rut depth measurements, the deepest deflection (16.0 mm) was made in the asphalt pavement and the depth of the concrete block pavement was 4.5 mm. Vertical displacements of 3.0 and 1.5 mm were obtained in stone pavements A and B, respectively. The maximum pavement vertical deflection response was recorded at 0, 0.4, and 1.97 million ESALs. The response results revealed that they were influenced by the material types of either bedding or sub-base courses. With these outcomes, it would be possible to apply the baseline data for designing rigid small element pavement for heavy traffic volume or high travelling speed roads

Exploiting Bacterial Genera as Biocontrol Agents: Mechanisms, Interactions and Applications in Sustainable Agriculture

The rising demand for sustainable agriculture necessitates alternative methods to using chemical pesticides for controlling plant pathogens. Biocontrol involves the use of natural antagonists, such as bacteria, as an alternative to synthetic chemical pesticides, which can be harmful to human health and the environment. This review discusses the potential of Bacillus, Streptomyces, Pseudomonas and Serratia as biocontrol agents (BCAs) against various plant pathogens. These bacteria suppress pathogen growth via various mechanisms, such as antibiosis, nutrient and space competition and systemic resistance, and significantly contribute to plant growth. We provide an overview of the secondary metabolites, plant interactions and microbiota interactions of these bacteria. BCAs offer a promising and sustainable solution to plant pathogens and help maintain the one-health principle.11Nsciescopuskc