Influence of reflected waves at the bonded boundary in double-layered thickness-shear resonator using α-quartz

The influence of the reflected waves at the bonding boundary on the resonance waveform and temperature characteristics was investigated using α-quartz (QZ). The double-layered resonator specimen was fabricated using 129.55°Y- and 0°Y-cut QZ substrates with the thickness ratio x=0.520. The temperature characteristic at the range from 100°C to 300°C was deviated from the calculated values estimated by the equations considering thickness and electric flux density ratio proposed in the previous work, and the resonant waveform of the specimen was deteriorated as compared with that of single-layer resonators. In order to clarify these phenomena, the phase matching conditions and total amplitude in the specimen were examined. As a result, it was clarified that increase of the amplitude in the layer with lower acoustic impedance was affected to the temperature characteristic, and acoustic losses due to reflection / transmission at the bonding boundary was affected to the total amplitude of resonance.

Classification of Non-Infected and Infected with Basal Stem Rot Disease Using Thermal Images and Imbalanced Data Approach

Basal stem rot (BSR) disease occurs due to the most aggressive and threatening fungal attack of the oil palm plant known as Ganoderma boninense (G. boninense). BSR is a disease that has a significant impact on oil palm crops in Malaysia and Indonesia. Currently, the only sustainable strategy available is to extend the life of oil palm trees, as there is no effective treatment for BSR disease. This study used thermal imagery to identify the thermal features to classify non-infected and BSR-infected trees. The aims of this study were to (1) identify the potential temperature features and (2) examine the performance of machine learning (ML) classifiers (naïve Bayes (NB), multilayer perceptron (MLP), and random forest (RF) to classify oil palm trees that are non-infected and BSR-infected. The sample size consisted of 55 uninfected trees and 37 infected trees. We used the imbalance data approaches such as random undersampling (RUS), random oversampling (ROS) and synthetic minority oversampling (SMOTE) in these classifications due to the different sample sizes. The study found that the Tmax feature is the most beneficial temperature characteristic for classifying non-infected or infected BSR trees. Meanwhile, the ROS approach improves the curve region (AUC) and PRC results compared to a single approach. The result showed that the temperature feature Tmax and combination feature TmaxTmin had a higher correct classification for the G. boninense non-infected and infected oil palm trees for the ROS-RF and had a robust success rate, classifying correctly 87.10% for non-infected and 100% for infected by G. boninense. In terms of model performance using the most significant variables, Tmax, the ROS-RF model had an excellent receiver operating characteristics (ROC) curve region (AUC) of 0.921, and the precision–recall curve (PRC) region gave a value of 0.902. Therefore, it can be concluded that the ROS-RF, using the Tmax, can be used to predict BSR disease with relatively high accuracy.

Silk Powder from Cocoons and Woven Fabric as a Potential Bio-Modifier

Silk, as a protein fiber characterized by high biocompatibility, biodegradability, and low toxicity, is mainly used as textile structures for various purposes, including for biological applications. The key issue for unlimited silk applicability as a modifier is to prepare its relevant form to cover or introduce to other materials. This study presents silk powder fabrication from Bombyx mori cocoons and non-dyed silk woven fabric through cryogenic milling. The cocoons were milled before and after the degumming process to obtain powders from raw structures and pure fibroin. The powder morphology and composition were analyzed using scanning electron microscopy and energy dispersive spectroscopy. The influence of the milling on the silk structure was studied using infrared and Raman spectroscopies, indicating that silk powders retained dominant β-sheet structure. The powders were also analyzed by differential scanning calorimetry and thermogravimetric techniques. The thermal endothermic peak and onset temperature characteristic for silk decomposition shifted to the lower values for all powders, indicating less thermal stability. However, the process was found to be an efficient way to obtain silk powders. The new milled form of silk can allow its introduction into different matrices or form coatings without using any harsh solvents, enriching them with new features and make more biologically friendly.

Analysis of the Influence of Continuous-Drive Friction Welding on the Microstructure and Mechanical Properties of the UNS C64200 Bronze-Aluminum-Silicon Alloy

Friction welding (FRW) is an important commercial solid-state welding process in which coalescence is achieved by frictional heat combined with pressure. The objective of this work is to analyze the microstructure and the mechanical behavior of the copper alloy UNS C64200 – bronze-aluminum-silicon, as well as to raise the ideal welding parameters so that there is adequate weldability after process of continuous-drive friction welding. Regarding the analysis of the microstructure, scanning electron microscopy was used to characterize phases. The mechanical properties were evaluated by means of a hardness test of the center of the welded joint, traversing the entire extent of the thermally affected zone. Results show that the UNS C64200 alloy, when subjected to conventional friction welding, behaves satisfactorily in terms of weldability, without the appearance of cracks or defects arising from the temperature characteristic of this process, as well as good hardness with values above the minimum established in norm and higher than the base material.

The utilization of lignocellular bio-mass as green building thermal insulation material

In new residential structures and green architecture, it is necessary to maintain the heat of the internal environment to an appropriate level throughout winter conditions with low electricity usage. This work is thus intended to produce environmentally acceptable isolation substances (organic material). Lignocellular biomass, which is also referred to as Poaceae common reed and Phragmites australis and straw, were used as organic material in this study. During testing of its performance under controlled settings, the insulating effectiveness of these organic compounds was assessed. The exploratory project comprises three forms of isolation: organic made from straw and reed, industrial isolation (fibreglass), and brickwork without insulation. An infrared sensor was used to calculate the quality of isolation. For each isolation situation, the temperature characteristic was produced. The findings show that fibreglass was equivalent to the effectiveness of the organic isolation. Furthermore, the efficiency difference was 0. 84 percent comparing the industrial and organic isolation substances, which shows that Lignocellusic Biomass is a viable environmental-friendly replacement to industrial isolation substances.

Non-isothermal rarefied gas flow in microtube with constant wall temperature

In this paper, pressure-driven gas flow through a microtube with constant wall temperature is considered. The ratio of the molecular mean free path and the diameter of the microtube cannot be negligible. Therefore, the gas rarefaction is taken into account. A solution is obtained for subsonic as well as slip and continuum gas flow. Velocity, pressure, and temperature fields are analytically attained by macroscopic approach, using continuity, Navier-Stokes, and energy equations, with the first order boundary conditions for velocity and temperature. Characteristic variables are expressed in the form of perturbation series. The first approximation stands for solution to the continuum flow. The second one reveals the effects of gas rarefaction, inertia, and dissipation. Solutions for compressible and incompressible gas flow are presented and compared with the available results from the literature. A good matching has been achieved. This enables using proposed method for solving other microtube gas flows, which are common in various fields of engineering, biomedicine, pharmacy, etc. The main contribution of this paper is the integral treatment of several important effects such as rarefaction, compressibility, temperature field variability, inertia, and viscous dissipation in the presented solutions. Since the solutions are analytical, they are useful and easily applicable.

Tunable Temperature Characteristic of Terahertz Bragg Fiber Filled with Liquid Water

Hollow-core terahertz (THz) fibers have attracted a lot of research interest due to the low loss and easy inner modification with functional materials. Liquid water has unique properties in the THz region and has been widely investigated in THz emission, sensing, and devices. In this paper, a hollow-core THz Bragg fiber with a water defect layer is proposed. The finite element method is used to verify and analyze the tunable temperature characteristic of the water-filled THz fiber. The numerical analysis results show that the confinement loss and the low-frequency side of the dip near 0.5 THz can be controlled by the temperature of the liquid water. The temperature sensitivity of the THz fiber is obtained at 0.09614 dB·m−1/K at 0.45 THz with a high core power fraction up to 98%. The proposed THz fiber has potential applications in THz interaction with liquid and THz tunable devices.