Plasma measurement by optical visualization and triple probe method under high-speed impact

Transient temperature, another source to provide reservoir information besides transient pressure, has been received much attention in recent years. Different from the immediate response of transient pressure due to flow rate change, there are obvious time lags between the transient temperature change and flow rate change. In this paper, the nonsynchrony between PDG transient temperature, pressure and flow-rate data was quantitatively investigated with wavelet transform (WT). Field PDG data analysis show that transient pressure changes nearly at the same time of flow rate change. However, due to the adiabatic expansion/compression effect, the time lags between transient temperature and flow rate are significant and cannot be neglected. Field PDG data demonstrates that averagely transient temperature changes about 0.225 hours later than the flow rate. Accurately identifying the time of flow events from PDG temperature data is difficult. The identified flow event time from PDG temperature is the time when Joule-Thomson effect dominates the reservoir temperature change. The flow events with time periods less than the time lags cannot be identified from PDG temperature data due to the adiabatic expansion/compression effect. Compared with the Haar wavelet, the the second derivative of the Gaussian wavelet can more accurately identify flow events from PDG temperature data. This study will be useful for improving the accuracy of transient identification from PDG data, and can benefit transient temperature analysis by clarifying the time lags due to adiabatic expansion/compression effect, and synchronize PDG transient temperature, pressure and flow-rate data for better data processing and analysis.

Radiative characteristic of N_2-CO_2 mixture afterglow plasma generated by microwave discharge changes by mixture ratio of N_2 and CO_2 gases. In order to investigate the cause of the change, the electron temperature and electron density were measured using triple probe method. The triple probe was inserted in the afterglow plasma and was set at 10mm intervals at the point of 40 to 100mm from the downstream end of the cavity resonator. From the measured probe voltage and current, the electron temperature and density were calculated. The profiles of the electron temperature and density were changed by the mixture ratio of N_2 and CO_2 gases. For the CO_2 mixture ratio of larger than 6%, the electron temperature and density decreased steadily along with the flow, however, for the CO_2 mixture ratio of less than 4%, increased temporarily in the lower region of 50 to 90mm.

When the temperature changes, the stress produced by the external constraint and the mutual constraint between the internal parts of the object, which makes it unable to expand and contract freely, is called thermal stress. The thermal stress is caused by the steady temperature field. When the transient temperature changes to zero and the temperature distribution reaches a stable state, the temperature distribution can be obtained from the heat conduction equation and temperature boundary conditions, and then the displacement and stress can be obtained from the elastic equation including the temperature term.

By developing a thermo-mechanical coupled model, we quantitatively analyzed the effect of thermo-oxidative ageing on the temperature, thermal strain and thermal stress histories of braided composites during high-speed impact. We also considered temperature dependence of elastic modulus during impact in this model. The proposed model was first applied to the unaged composites, then the results were compared to the impact responses captured by the split Hopkinson bar and the high-speed camera. The comparisons of the experimental and numerical results show that the proposed model could capture the adiabatic temperature rise, stress-strain responses and failure process of braided composites during high-speed impact. The validated model was subsequently employed to thermo-oxidative aged composites. Results show that the temperature rise, thermal strain and thermal stress all depend on the mechanical properties of resin, and they decreased with the increase of ageing temperature since the performance of resin is compromised by thermo-oxidation ageing. The change of resin performance after ageing leads to the change in the temperature rise during impact, so the stiffness of composites will decrease in varying degrees after ageing.

Exploration adsorption characteristics of zeolite 13X depending on humidity and flow rate in sorption thermal energy storage applications

Gridlike patterns of differing cell density were observed in evenly seeded cell monolayers. Such patterns were obtained in five of six cell lines tested, suggesting widespread occurrence. The mechanism appears to involve small, transient temperature changes related to incubator tray structure. The very short time course of appearance of the patterns implicates attachment rather than growth as the critically affected factor. Impaired adhesion or directed sedimentation resulting from thermally induced microcurrents in the medium are the two most likely mechanisms.

Thermal acclimation following changes from 6 °C to 15 °C and from 15 °C to 25 °C was investigated in the diatom Chaetoceros calcitrans. Cell division rate increased with temperature. Cellular carbon showed a slight decrease with an increase in temperature from 6 °C to 15 °C but showed no further change with an increase to 25 °C. Cells grown at 6 °C had low levels of light-harvesting components and a high carotenoid to chlorophyll a (Chla) ratio due to an increase in abundance of photoprotective pigments. The abundance of light-harvesting pigments increased with temperature and this was mirrored by a decrease in carotenoid: Chla ratio. All pigments showed an immediate change in abundance following each temperature shift. However, changes in photoprotective pigments reached a plateau after 12 h, in contrast to the lightharvesting pigments that took 4 days to become acclimated. Light-saturated rates of photosynthesis were at a minimum at 6 °C and increased twofold with temperature between 6 °C and 25 °C. Light-limited photosynthesis showed little change with temperature. It is suggested that, at low temperatures, the rate of carbon fixation is impaired due to a decrease in the activity of photosynthetic enzymes. This imparts an increase in excitation pressure due to an imbalance between light absorption and utilization. Cells respond to this by decreasing their light-harvesting capacity and increasing their ability to dissipate the excess energy. This fairly rapid regulation may be ecologically advantageous in areas where there are transient temperature changes.

This paper describes a method combining Bayesian optimization (BO) and a lumped-capacitance thermal network model that is effective for speeding up the thermal design optimization of an electronic circuit board layout with transient heating chips. As electronic devices have become smaller and more complex, the importance of thermal design optimization to ensure heat dissipation performance has increased. However, such a thermal design optimization is difficult because various trade-offs associated with packaging and transient temperature changes of heat-generating components must be considered. This study aims to improve the performance of thermal design optimization by artificial intelligence. BO using a Gaussian process was combined with the lumped-capacitance thermal network model, and its performance was verified. As a result, BO successfully found the ideal circuit board layout as well as particle swarm optimization (PSO) and genetic algorithm (GA) could. The CPU time for BO was 1/5 and 1/4 of that for PSO and GA. In addition, BO found a non-intuitive optimal solution in approximately 7 min from 10 million layout patterns. It was estimated that this was 1/1000 of the CPU time required for analyzing all layout patterns.

We measured the principal thermal conductivities and the principal axis angle of a 0.1-mm-thick pyrolytic graphite sheet (PGS), by the integrated multi-temperature probe method. To determine its principal thermal conductivities, a sample is heated using a point heat source places on the sample surface and the transient temperature changes of nine points with radii of r1 = 2.5, r2 = 5.0, and r3 = 7.5 mm on three axes with β= 120° are measured by the integrated multi-temperature probe method. The two measured principal thermal conductivities are λp1 = 746 W/(m·K) and λp2 = 925 W/(m·K). The geometrical mean of the two measured principal thermal conductivities of PGS is λ= (λp1·λp2)1/2 = 831 W/(m·K). The relative errors in this measurement are 7.1% for λp1 and 8.7% for λp2. The calculated anisotropic factor ξ, which is the ratio of λp2 to λp1, is 1.24. The measured data of PGS showed a strong anisotropy of thermal conductivity. This suggests that there is a possibility for PGS to become a standard two-dimensional anisotropic material.

In the processing of titanium alloys, high temperatures at cutting interfaces lead to poor machinability and reduced machining efficiency. High-speed ultrasonic vibration cutting (HUVC) offers an improvement in heat dissipation compared to conventional cutting (CC), yet it loses its cooling advantage as cutting speeds further increase. To optimize efficiency, this study investigated transient cutting temperature variations using experimental measurements and finite element method (FEM) simulations to elucidate the cooling mechanisms in HUVC. An eroding junction thermocouple, along with stringent electromagnetic insulation measures, was employed to capture transient temperature changes with microseconds. The maximum discrepancy between measured and simulated temperatures in CC was found to be 13.8%, validating the feasibility of the FEM method for experimental supplementation and theoretical analysis in HUVC. The results indicated that HUVC reduced cutting temperatures by up to 40.7% compared to CC, with minimal differences in peak temperatures between HUVC and CC at identical cutting speeds. The cooling advantage in HUVC is attributed to temperature declines observed during the interface separation. The maximum temperature reduction ratio increased significantly from 40.9% to 77.1% with the rise in vibration amplitudes. Besides, an increase in tool clearance was found to improve cooling conditions in both CC and HUVC. This study introduced a novel method for ultrasonic temperature measurement in metal cutting, thereby advancing the understanding of cooling mechanisms at cutting interfaces in HUVC. Furthermore, modified process parameters were provided to achieve high-performance HUVC in machining difficult-to-cut alloys.

The basic function of friction clutches is to transfer the torque in the conditions of its smooth engagement without vibrations. Hard working conditions under high thermal and mechanical loads, leading to high temperature in the contact area, intense wear, and instability of the coefficient of friction impose restrictive criteria in the design of friction materials. In this paper, the results of experimental research of the effect of ceramic and intermetallic additives to the copper-based material of the friction disc of the clutch on the thermophysical and frictional properties were presented. Next, these properties were incorporated in the proposed contact 3D numerical model of the clutch to carry out computer simulations of the heating process and subsequent cooling. Based on the obtained experimental data and transient temperature changes of the friction and steel discs, the relations between the powder additives, thermophysical properties of the five friction materials, and coefficients of friction, wear, and temperature reached were discussed. Among these, it was found that when working with the lubrication, the largest values of the coefficient of friction 0.068 and wear were reached when using the 3 wt.% SiC additive.

The granular flow induced by high-speed impact was experimentally and numerically investigated. A sheet of free-falling small glass beads was formed in the test chamber at low pressure. A spherical projectile or a slender puff of particle cloud launched by the ballistic range collided with the particle sheet in the in-plane direction to obtain a quasi- two-dimensional situation. The observation by the high-speed camera revealed that the shock-layer-like compressed zone and the void zone were formed on the forward side and the backward side, respectively. To describe such phenomena in the framework of the continuum fluid dynamics, the compressible and non-expanding (CNE) fluid model was applied and the two-dimensional Euler equations were numerically solved by the finite volume method with the Riemann solver formulated for the CNE fluid model. Finding an appropriate set of the parameters in the equation of state, qualitatively good agreement was obtained between the experimental and the computational results.

Noninvasive therapies such as focused ultrasound were developed to be used for cancer therapies, vessel bleeding, and drug delivery. The main purpose of focused ultrasound therapy is to affect regions of interest (ROI) of tissues without any injuries to surrounding tissues. In this regard, an appropriate monitoring method is required to control the treatment. This study is aimed to develop a noninvasive monitoring technique of focused ultrasound (US) treatment using sparse representation of US radio frequency (RF) echo signals. To this end, reasonable results in temperature change estimation in the tissue under focused US radiation were obtained by utilizing algorithms related to sparse optimization as orthogonal matching pursuit (OMP) and accompanying Shannon's entropy. Consequently, ex vivo tissue experimental tests yielded two datasets, including low-intensity focused US (LIFU) and high-intensity focused US (HIFU) data. The proposed processing method analyzed the ultrasonic RF echo signal and expressed it as a sparse signal and calculated the entropy of each frame. The results indicated that the suggested approach could noninvasively estimate temperature changes between 37°C and 47°C during LIFU therapy. In addition, it represented temperature changes during HIFU ablation at various powers, ranging from 10 to 130 W. The normalized mean square error of the proposed method is 0.28, approximately 2.15 on previous related methods. These results demonstrated that this novel proposed approach, including the combination of sparsity and Shanoon's entropy, is more feasible and effective in temperature change estimation than its predecessors.

Ultrasound can be used as a feasible method for estimating temperature changes during hyperthermia therapies due to its high capability of tissue penetration and relative ease of signal processing. During hyperthermia therapies, the proportionality constant between echo-shift and temperature is determined by the local change in the speed of sound due to temperature and the linear coefficient of thermal expansion of the material. A model of the interaction of an ultrasonic pulse with the displacement of a muscle tissue scatterer is presented in this work using the Finite Element Method to estimate temperature changes in a non-invasive way. The method is based on quantifying the time-delays of an ultrasonic pulse passing through a section of muscle tissue with ideal characteristics that has a 1 mm diameter glass scatterer inside; this latter is displaced due to the tissue thermal expansion phenomenon that appears as a result of heat application (37- $61^{\circ}C)$ during hyperthermia therapies. A time-delay of 0.913 ns/°C is quantified in this paper by comparing seven ultrasonic signals that represent the scatterer displacement.

Fast temperature estimation from undersampled k-space with fully-sampled center for MR guided microwave ablation