Behavioral Interactions between a Native and an Invasive Fish Species in a Thermally Heterogeneous Experimental Chamber

Mechanisms of the displacement of native fish by nonnative fish can include agonistic behaviors that push native fish species out of their preferred habitat, including their thermal optima. To examine these interactions, we built an experimental thermal preference chamber to evaluate: (1) the thermal preference of native, glacial relict northern redbelly dace Chrosomus eos; (2) if the thermal preference and movement changed in the presence of the invasive western mosquitofish Gambusia affinis; and (3) the direction of agonistic interactions. We hypothesized that G. affinis would express agonistic behavior toward C. eos, because G. affinis is widely recognized as an aggressive invader. Given the temperature range of the experimental chamber, i.e., 20–30 °C, C. eos selected an average of 24.3 °C as its thermal preference. After G. affinis’ introduction, the thermal preference of C. eos increased by 1.7 °C and the movement, given by distance (cm) travelled, increased by 21%. Contrary to our prediction, more agonistic interactions were observed in C. eos toward G. affinis. These results indicate that agonistic behavior of G. affinis toward native fish species may be species- and condition-specific, and may not always be the primary mechanism of native species’ displacement. Biological invasions are a global issue and altered thermal regimes are expected to continue. This study provided the novel approach using of a thermally heterogeneous thermal chamber to examine thermal preferences and aggressive interactions between a native and an invasive species. Future research should examine other life history traits that may be conveying the competitive advantage to G. affinis.

Basis of rational design of mineral wool product polymerization furnace on conveyor horizontal dryer

The structural features of the thermal unit for the production of molded heat insulation materials and their technological parameters must be in full compliance with the properties of the initial materials and are determined by the production program of the enterprise. Based on the peculiarities of gas dynamics formation, the structural parameters of the thermal chamber are determined: dimensions, shape of the internal surface, presence of longitudinal and transverse seals, extent and parameters of heat treatment. Method of thermal calculation including separate consideration of conditions of mineral wool carpet heating in heat chamber and formation of heat carrier flow in furnace is proposed.

In-Place Characterization of On-State Voltage for SiC MOSFETs: Controlled Shoot-Through vs. Film Heater

The on-state voltage of MOSFETs is a convenient and powerful temperature-sensitive electric parameter (TSEP) to determine the junction temperature, thus enabling device monitoring, protection, diagnostics and prognostics. The main hurdle in the use of the on-state voltage as a TSEP is the per-device characterization procedure, to be carried out in a controlled environment, with high costs. In this paper, we compare two novel techniques for MOSFET junction temperature estimation: controlled shoot-through and direct heating by resistive heaters embedded in two Kapton (polyimide) films. Both allow in-place characterization of the TSEP curve with the device mounted in its final circuit and assembly, including the working heat sink. The two methods are also validated against the conventional procedure in a thermal chamber.

In-place Characterization of On-state Voltage for SiC MOSFETs: Controlled Shoot-through vs. Film Heater

The on-state voltage of MOSFETs is a convenient and powerful temperature-sensitive electric parameter (TSEP) to determine the junction temperature, thus enabling device monitoring, protection, diagnostics and prognostics. The main hurdle in the use of the on-state voltage as a TSEP is the per-device characterization procedure, to be carried out in a controlled environment, with high costs. In this paper we compare two novel techniques for MOSFET junction temperature estimation: controlled shoot-through and direct heating by resistive heaters embedded in two Kapton (polyimide) films. Both allow in-place characterization of the TSEP curve with the device mounted in its final circuit and assembly, including the working heat sink. The two methods are also validated against the conventional procedure in a thermal chamber.

Mechanical properties of unmodified and montmorillonite-modified epoxy compounds. Part I: compression test

The aim of the article was to determine the compressive strength and compressive strain of an unmodified and a modified epoxy compounds containing a montmorillonite filler, as well as to determine the effect of temperature and an aging time on the mechanical parameters of the considered epoxy compounds. The subject of the research was both the unmodified and the modified adhesive compounds. The unmodified epoxy compounds were made in four variants, which included the epoxy resins based on a bisphenol A as well as the curing agents: a triethylenetetramine and a polyamide curing agent. The modified compounds containing the montmorillonite filler, were also made in four variants. The samples were subjected in a thermal chamber at 80 °C for 1 and 2 months and in a thermal shock chamber in the temperature range from − 40 °C to 80 °C for 1 and 2 months. The reference samples were seasoned at room temperature 20–25 °C. The epoxy compounds samples were subjected to the compression strength tests in accordance with ISO 604 standard. The compressive strength is influenced by the environment and temperature, the aging time and the presence of the modifying agent. The epoxy compounds subjected at elevated or variable temperatures have higher compressive strength than the reference epoxy compounds. The operation of the climatic chamber or the thermal shock chamber makes the samples more deformable than the reference samples.

EFFECT OF IMPACTOR MASS ON CFRP IN ARCTIC CONDITION UNDER LOW-VELOCITY IMPACT

This study investigates the impact response and damage characterization of carbon fiber reinforced polymer (CFRP) under low-velocity impact by impactors of different masses and velocities at 62J. Low-velocity impacts are conducted at room temperature (23ºC) as well as low temperature (-70ºC) conditions in the thermal chamber of the drop tower testing machine, Instron CEAST 9350. The aim is to observe composite behavior in the cold Arctic environment due to equal energy impacts. Moreover, a 3mm thickness of ice is created on the CFRP samples at -12ºC after 24 hours of freezing and impacted at -70ºC. The goal is to elucidate the contribution of surface ice on the overall impact damage of composites. X-ray micro-computed tomography is utilized to reveal the inner damages of the composite structures. Intralaminar damage in the form of fiber breakage is found as the dominant failure mode on the CFRP samples from 62J impacts. But differences in the delamination and matrix crack formation are identified for different mass-velocity configurations and environmental conditions. Results show that low mass impactors produce a larger damage initiation force on the composites at all temperatures, whereas no specific trend is observed in the peak force values due to severe fiber failure. Although higher mass impactors show longer impact duration, lower mass impactors develop greater damage on the CFRP, as seen by a greater reduction in specimen stiffness. Furthermore, the presence of ice is observed to have a minimal effect on the damage behavior of composites. But ice layer assists to reduce the amplitude of initial load drop by the low mass impactor and as such, less permanent displacement is identified in the CFRP specimens than both room temperature and low-temperature conditions. This study explores the understanding of the dynamic behavior of composites under low-temperature icy conditions.

Heating rates are more strongly influenced by near-infrared than visible reflectance in beetles

Adaptations to control heat transfer through the integument are a key component of temperature regulation in animals. However, there remain significant gaps in our understanding of how different optical and morphological properties of the integument affect heating rates. To address these gaps, we examined the effect of reflectivity in both ultraviolet-visible and near-infrared wavelengths, surface micro-sculpturing, effective area (area subjected to illumination) and cuticle thickness on radiative heat gain in jewel beetles (Buprestidae). We measured heating rate using a solar simulator to mimic natural sunlight, a thermal chamber to control the effects of conduction and convection, and optical filters to isolate different wavelengths. We found that effective area and reflectivity predicted heating rate. The thermal effect of reflectivity was driven by variation in near-infrared rather than ultraviolet-visible reflectivity. By contrast, cuticle thickness and surface rugosity had no detectable effect. Our results provide empirical evidence that near-infrared reflectivity has an important effect on radiative heat gain. Modulating reflectance of near-infrared wavelengths of light may be a more widespread adaptation to control heat gain than previously appreciated.

40 GHz VCO and Frequency Divider in 28 nm FD-SOI CMOS Technology for Automotive Radar Sensors

This paper presents a 40 GHz voltage-controlled oscillator (VCO) and frequency divider chain fabricated in STMicroelectronics 28 nm ultrathin body and box (UTBB) fully depleted silicon-on-insulator (FD-SOI) complementary metal-oxide–semiconductor (CMOS) process with eight metal layers back-end-of-line (BEOL) option. VCOs architecture is based on an LC-tank with p-type metal-oxide–semiconductor (PMOS) cross-coupled transistors. VCOs exhibit a tuning range (TR) of 3.5 GHz by exploiting two continuous frequency tuning bands selectable via a single control bit. The measured phase noise (PN) at 38 GHz carrier frequency is −94.3 and −118 dBc/Hz at 1 and 10 MHz frequency offset, respectively. The high-frequency dividers, from 40 to 5 GHz, are made using three static CMOS current-mode logic (CML) Master-Slave D-type Flip-Flop stages. The whole divider factor is 2048. A CMOS toggle flip-flop architecture working at 5 GHz was adopted for low frequency dividers. The power dissipation of the VCO core and frequency divider chain are 18 and 27.8 mW from 1.8 and 1 V supply voltages, respectively. Circuit functionality and performance were proved at three junction temperatures (i.e., −40, 25, and 125 °C) using a thermal chamber.

Effect of Artificial Aging on Mechanical and Tribological Properties of CAD/CAM Composite Materials Used in Dentistry

With easy-to-process 3D printing materials and fast production, the quality of dental services can be improved. In the conventional procedure, the dentist makes temporary crowns directly in the patient’s mouth, e.g., from the most commonly used bis-acrylic composites. Temporary crowns made directly in the office without the use of CAD/CAM are often of inferior quality, which directly results in impaired hygiene, poorer masticatory mechanics, greater deposition of plaque, calculus and sediment, and may adversely affect periodontal and gum health. The mechanical strength, resistance to aging and abrasion of 3D printing materials are higher than those of the soft materials used in conventional methods. This translates into durability. The patient leaves the surgery with a restoration of higher utility quality compared to the conventional method. The objective of the paper was to determine the influence of aging in artificial saliva of AM (additive manufacturing) orthodontic composites on their functional properties. For the purpose of the study, fillings well-known worldwide were selected. These were traditional UV-curable resins (M I, M II, M III, M V) and a hybrid material based on a UV-curable resin (M VI). Samples were stored in artificial saliva at 37 ± 1 °C in a thermal chamber for 6 months. Indentation hardness, frictional tests and sliding wear measurements were conducted. A comparison between various materials was made. Descriptive statistics, degradation coefficients, H2E, Archard wear and specific wear rate were calculated. The Weibull statistical test for indentation hardness was performed and Hertzian contact stresses for the frictional association were calculated for unaged (M I, M II, M III, M V, M VI) and aged (M I AS, M II AS, M III AS, M V AS, M VI AS) samples. M I exhibited the lowest average hardness among the unaged materials, while M III AS had the lowest average hardness among the aged materials. Comparably low hardness was demonstrated by the M I AS material. The coefficient of friction values for the aged samples were found to be higher. The lowest wear value was demonstrated by the M I material. The wear resistance of most of the tested materials deteriorated after aging. The M VI AS material had the highest increase in wear. According to the results provided, not only the chemical composition and structure, but also aging have a great impact on the indentation hardness and wear resistance of the tested orthodontic materials.

Accurate estimation of temperatures in a cryogenic space cooled by a Stirling cryocooler

The experimental analysis of cryogenic chambers coupled with Stirling cryocoolers has received scant attention in the research literature. This work provides a novel contribution by developing and experimentally validating an analytical model of the coupling to predict temperatures in the system. The paper unifies the Stirling cryocooler equation previously derived by Otaka et al. and the thermal-electrical analogy for the chamber. The analytical formula predicts steady-state temperatures in the chamber as a function of the system's controllable design and operational parameters. The model was validated with experimental data from 15 tests of an alpha-type Stirling cryocooler coupled with a thermal chamber. The resulting model showed an accurate prediction of temperatures with an average coefficient of variance of 5%, mean biased error of 2%, and R² value of 0.95. The findings are relevant because of the urgent need to learn how to control cryogenic spaces using electricity-based systems. Such spaces will be of high significance in the future because advanced solutions and products in biomedicine, electronics, computing and other fields use cryogenic spaces.