Sample Temperature Research Articles

An Experimental Study on Deuterium Production from Titanium Hydride Powders Subjected to Thermal Cycles

An extensive multi-year experimental study was conducted to investigate the potential production of deuterium from titanium hydride TiHx powders subjected to specific thermal cycles. Mass spectrometry was performed, focusing on the variation in signal intensities at m/z = 2, 3, 4, 18, 19, 20, and 21, corresponding to fragments primarily involving deuterium, during the degassing of titanium hydride powders as the sample temperature was raised from room temperature to approximately 1100 °C. The results reveal an anomaly in the deuterium-to-hydrogen ratios, with the analysis indicating an increase in deuterium concentration by a factor of approximately 280 compared to its natural concentration on Earth. Three independent methods confirmed the excess deuterium. Simultaneously, flow calorimetry was performed during the degassing process, which did not show any measurable excess heat produced in the configuration used. This study was motivated by our novel theoretical predictions, based on the standard electroweak theory with gauge symmetry, suggesting the generation of slow neutrons within metal hydrides when exposed to coherent excitations. Our findings align with direct measurements of neutron emission by TiHx powders under cavitation in liquid water, as recently published by Fomitchev-Zamilov.

Abstract A069: Effect of different voided urine sample storage time and temperature, and preservatives, on analysis with the multiplex bead-based Oncuria® bladder cancer immunoassay

Abstract Urinalysis accuracy requires reliable sample stability that is dependent on the chosen collection and storage conditions. If urine sample storage at room temperature (20°C) does not affect sample quality, this may reduce laboratory handling time and expense. This study evaluated whether different voided urine sample collection and storage parameters affected subsequent biomarker analysis by the multiplex Oncuria® bladder cancer immunoassay. The Oncuria® immunoassay simultaneously quantifies 10 protein analytes in urine to generate a bladder cancer diagnostic signature. Samples were stored at varied temperatures (20°C, 4°C, -80°C) for up to 1 month. The effects of adding two commercial urine sample stabilizers and antibiotics (trimethoprim) were also assessed. Subsequently, multiple potential biospecimen stabilizers were added to urine samples and evaluated with Oncuria® in hopes of allowing the urine sample to remain at room temperature for extended periods of time. First, it was demonstrated that voided urine samples stored at room temperate without such stabilizers had different levels of the 10 analytes associated with the Oncuria® test compared to voided urine samples stored at 4°C. Next, we evaluated the effects of commercially available biospecimen stabilizers. Despite the addition of these stabilizers, the levels of the 10 analytes were altered when the samples were stored at room temperature for prolonged periods of time. Therefore, we could not identify a suitable biospecimen stabilizer that would not require sample refrigeration. In conclusion, to minimize sample degradation/alteration after collection, voided urine samples should be refrigerated until analyzed with Oncuria® as the refrigeration is advantageous for the storage and the transport of these urine samples. Citation Format: Sunao Tanaka, Kaoru Murakami, Toru Sakatani, Riko Lee, Wayne Hogrefe, Fernando Siguencia, Steven M Smith, Charles J Rosser, Hideki Furuya. Effect of different voided urine sample storage time and temperature, and preservatives, on analysis with the multiplex bead-based Oncuria® bladder cancer immunoassay [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr A069.

Effect of stabilizers on the detection of swine influenza A virus (swIAV) in spiked oral fluids over time.

Aggregated samples such as oral fluids (OFs) display an animal friendly and time and cost-efficient sample type for swine Influenza A virus (swIAV) monitoring. However, further molecular and biological characterization of swIAV is of particular significance. The reportedly inferior suitability of aggregated samples for subtyping of swIAV presents a major drawback compared to nasal swabs, still considered the most appropriate sample type for this purpose (Garrido-Mantilla et al. BMC Vet Res 15(1):61, 2019). In addition, the viral load in the original sample, storage conditions and characteristics of different swIAV strains might further compromise the eligibility of aggregated samples for molecular detection and subtyping. Therefore, the present study aimed to evaluate the suitability of stabilizing media to minimize the degradation of viral RNA and thus increase the detection and subtyping rate of swIAV by RT-qPCR in spiked OFs under different conditions (virus strain, storage temperature and viral load in the original sample) over a time span of 14days. The use of stabilizing media in spiked OFs resulted in a significant higher probability to detect swIAV RNA compared to OFs without stabilizers (OR = 46.1, p < 0.001). In addition,swIAV degradation over time was significantly reduced in samples suspended with stabilizer (OR = 5.80, p < 0.001), in samples stored at 4°C (OR = 2.53, p < 0.001) and in samples spiked with the avian derived H1N2 subtype (OR = 2.26, p < 0.01). No significant differences in swIAV RNA detection and degradation of swIAV RNA in spiked OFs over time were observed between the three different stabilizing media. Addition of stabilizers and storage of samples under cooled conditions significantly improved detection and subtyping of swIAV in spiked OFs.

RBIO-08. INVESTIGATING THE EFFICACY AND MECHANISMS OF TUMOR TREATING FIELDS IN RADIATION-RESISTANT GLIOBLASTOMA MODELS

Abstract Glioblastoma (GBM) is an aggressive malignant brain tumor with poor prognosis despite current treatment regimens involving surgical resection, radiation, temozolomide, and the newly approved use of Tumor Treating Fields (TTFields; a noninvasive, transdermal, administration of alternating low-intensity, intermediate-frequency electrical fields). Acquired radiation resistance, thought to be partially driven by brain tumor-initiating cells (BTICs), underscores therapeutic challenges in GBM. While clinical evidence supports the therapeutic benefit of TTFields, its precise mechanisms of action are poorly understood, and TTFields impact on radiation-resistant GBM is unknown. To better understand the effect and mechanism of TTFields in radiation-resistant GBM, we utilized patient-derived xenolines (PDX) and their acquired radio-resistant pairs to assess changes in viability and molecular signaling. PDX were previously developed by subcutaneous implantation of patient GBM cells into immunodeficient (nu/nu) mice. Acquired radiation-resistant PDX were generated through serial in vivo radiation. TTFields were administered with the Novocure inovitroTM device in a cooling incubator to maintain 37oC sample temperature in the ceramic well plates of the device. PDX were cultured on geltrex-coated coverslips under serum-free conditions. Cytotoxicity was quantified 72h post TTFields with crystal violet. Molecular signaling was captured with PamChip peptide-based kinase activity arrays and RayBiotech proteomic arrays. We found that TTFields inhibit cell growth in both parental and acquired radiation-resistant PDX. Differences in molecular signatures between the PDX lines suggest molecular mechanisms of TTFields sensitivity signatures and interactions with acquired radio-resistant PDX. We are currently trying to generate TTFields-resistant PDX lines through serial treatment with plans to examine BTIC populations relative to TTFields efficacy. We also plan to explore targetable TTFields-induced alterations in the future.

Development of neutron self-indication thermometry at J-PARC

ABSTRACT Determining temperatures with small uncertainties is important for neutron thermometry, required for both fundamental science and industrial applications. Conventionally, neutrons transmitted through a sample in shielded materials are detected. The sample temperature is then derived by analyzing the energy dependence of the transmission neutrons at resonances influenced by the Doppler-broadening effect. However, reducing the temperature-determination uncertainty is extremely hard with the conventional method, because it is determined only by the small changes at the resonances, i.e. temperature-sensitive components, compared to the primary neutrons. Therefore, we propose a new thermometry named neutron self-indication thermometry (NSIT), which combines the Doppler-broadening effect with a self-indication technique that irradiates the sample and an indicator containing the same nuclide as the sample. The NSIT can enhance temperature sensitivity by measuring prompt gamma-rays to indirectly obtain the temperature-sensitive components at resonances by employing the same resonance twice. The temperature sensitivity and uncertainty of the NSIT were compared with those of the conventional method by varying the sample temperatures from 23.0°C to 492.6°C. The results demonstrated that the NSIT was approximately 1.6 times more sensitive and had lower uncertainty in determining temperature. These findings highlight the potential of the NSIT as an effective alternative to remote thermometry.

Study on temperature evolution law of coal containing gas under uniaxial loading process with different loading rates

AbstractIn order to investigate the evolution law of coal temperature during the gestation process of coal and gas outburst, laboratory experiments and numerical simulation approaches were employed. Infrared thermal radiation experiments on the surface of outburst coal during uniaxial loading and failure of coal were conducted. A coal and gas thermal‐hydromechanical coupling model considering the endothermic effect of desorption was established. Numerical simulation of uniaxial loading of gas‐containing coal was implemented to study the influences of deformation energy, frictional heat, and adsorption/desorption endothermic effects on coal temperature. The results indicate that the temperature of coal samples during the uniaxial loading and failure process generally exhibits a stepwise temperature increase. In the initial stage, the elastic thermal effect leads to a slow and fluctuating rise in the temperature of coal samples. During the yield and plastic deformation stages, frictional heat causes a rapid increase in the temperature of coal samples. With the increase of the loading rate, the increment of the temperature of coal samples gradually decreases and reaches the peak when the loading stress is 70% of the peak stress. According to the numerical calculation results, with the increase of the loading rate, the temperature reduction caused by gas desorption relatively decreases. By comparing the experimental results and numerical simulation results, it is found that the temperature reduction caused by desorption is greater than the temperature increments caused by deformation energy and frictional heat. The desorption endothermic effect and frictional heat effect are the dominant factors controlling the temperature variation of coal during the gestation process of outburst. The research achievements have significant theoretical significance and practical value for revealing the temperature evolution mechanism during the gestation process of coal and gas outburst, predicting coal and gas outburst, and protecting the atmospheric environment.

Effect of sample temperature and laser ablation angle on optical emission and acoustic signals from laser-induced zirconium plasma

A fiber-coupled, acoustic-wave-assisted (AW) microchip laser-induced breakdown spectroscopy (mLIBS) system was developed to analyze the elemental composition and surface imaging. In this study, we measured the dependence of sample temperature and laser ablation angle (LAA) on the laser-induced plasma–optical emission (LIP–OE) and LIP–acoustic signal (LIP–AS). The intensity of the LIP–OE and ablated mass at three different temperatures and eight different LAAs were estimated using a zirconium sample. Simultaneously, we investigated the LIP–AS amplitude, propagation speed, and shape by synchronizing the AW-mLIBS system with a high-speed camera. The results revealed that the LIP–OE increases with increasing temperature and is unaffected by LAA up to 40° because the amount of the ablated mass was similar to the plasma. Additionally, no considerable variation in plasma temperature was obtained using the Boltzmann method over the sample temperature. However, the propagation speed of the LIP–AS differs with temperature but has marginal angular dependence because the LIP–AS propagates as semispherical. Furthermore, no considerable changes were observed in the LIP–AS amplitude up to 100°C, and the LAA showed a similar tendency to that of the LIP–OE.

Влияние структуры и состава технически чистой бескислородной меди различных производителей на ее электропроводность и механические свойства

The composition, structure, electrical conductivity and mechanical properties of oxygen-free copper grade C10100 with a purity of 99.997% produced by Sichuan Huazi Technology Co., Ltd (China) intended for use in the production of niobium-titanium superconductors as a stabilizing component of a multi-filament composite were studied. It was shown that the recrystallization onset temperature of deformed copper samples in the form of wire is about 150 °C, and as a result of collective recrystallization at temperatures above 300 °C, the grain size reaches a value of more than 180 μm. The RRR parameter characterizing the electrical conductivity of copper at the cryogenic temperature of samples in a fully recrystallized state reaches a value of 1300 units, which is three times higher than the level typical for copper grade C10100 produced by leading manufacturers of cryogenic copper for superconductors. Maximum plasticity (up to 50%) of copper wire samples is achieved after short annealing (less than 5 minutes) at a temperature of 300°C. Increasing the annealing temperature to 600°C leads to a decrease in mechanical properties due to grain growth and the well-known effect of temperature plasticity failure.

ZnO/Organic superlattice with phase composite structure for enhanced thermoelectric performance at low temperature

Semiconducting metal oxides, such as zinc oxide (ZnO), are gaining recognition for thermoelectric applications due to their temperature stability, availability, eco-friendliness, and cost-effectiveness. However, ZnO faces challenges in achieving high ZT value due to its low carrier concentration and high thermal conductivity. Traditional methods, like doping and defect engineering, have shown limited success in overcoming these challenges. In this study, we introduce a unique superlattice structure with a phase-composite composition that significantly decreases thermal conductivity through enhanced phonon scattering while maintaining the power factor by inducing new resonant conducting states near the mobility edge. By optimizing nanolayer thickness and doping concentration, we achieved a remarkable power factor of 14.6 μW cm−1 K−2 and reduced thermal conductivity to ∼1.97 W m−1 K−1 at room temperature in samples with 6 nm-thick ZnO nanolayers fabricated at 100 °C. This leads to a ZT value of ∼0.22 at 300 K, the highest among metal oxide thermoelectric materials at low temperatures, which further increases to ∼0.55 at 510 K. These findings demonstrate the potential of hybrid superlattices for efficient low-temperature thermoelectric applications.

Epoxy/Phenolic Nanocomposite based Adhesives: Non-isothermal Cure Kinetic Study

The curing behavior of an epoxy/phenolic-based system containing graphene oxide (GO), and rubber powder as a toughening agent has been studied using differential scanning calorimetry (DSC) under non-isothermal conditions at a temperature from 0 to 200°C. So, to better dispersion of GO nanoplates in the resin media, the surface of the GOs was modified by 1,12-diaminododecane and subsequently aforementioned reaction was confirmed by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric techniques (TGA). DSC results show that rubber powders despite toughening properties prohibited resin-curing reactions. On the other hand, modified GO led to the promotion of curing reactions. The results of differential and integral iso conversional approaches indicated low activation energy for nanocomposite containing modified GO. Furthermore, thermal stability results reveal that the maximum decomposition temperature and char yield values of samples were increased gradually by the addition of GO and rubber powder to the system.

Cerium doped superparamagnetic Mn-Zn ferrite as a promising material for self-regulated magnetic hyperthermia

Recently, cubic ferrites (CF) have been widely explored in biomedical applications, especially those that display superparamagnetism behavior due to the desirable absence of remanent field. In this study, we report the self-stabilization of the magnetic fluid hyperthermia (MFH) temperature in the cancer therapy range (42 - 48 ºC) by Ce3+ substitution in superparamagnetic Mn0.8Zn0.2Fe2-xCexO4 ferrite with x = 0.0; 0.015; 0.030; 0.050 and 0.100. A comprehensive characterization was performed in order to investigate the influence of this replacement on the magnetic and structural properties of the ferrite. The samples were synthesized by the sol-gel auto-combustion method and the properties were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), Raman spectroscopy (RS), Mössbauer spectroscopy (MS), vibrational sample magnetometry (VSM), and ferromagnetic resonance (FMR). Magnetic hyperthermia essays were used to obtain the heat induction curves and calculate energy dissipation. We refined the XRD data by the Rietveld method to determine the cation distribution and calculate interionic parameters. Magnetic characterization confirms the superparamagnetic behavior at 300 K, which is expected from the TEM results that show a narrow distribution of particle sizes, with a mean size of about 6.5 nm for all samples. The VSM results show a consistent decrease in magnetization saturation with cerium content that result in a weaker self-heating induction capacity for the cerium-doped samples. FMR results also show a smaller relaxation time T2 for these samples, suggesting a slower energy dissipation rate. These conclusions are confirmed by the heat induction curves and the values of the specific absorption rate (SAR), which are smaller for cerium-doped samples. For the a field with an amplitude of 35.33 kA/m and a frequency of 222 kHz, the temperature of the cerium-doped samples saturates in the optimum interval for cancer treatment, between 42 and 48 ºC. These results suggest that Ce3+ is a promising doping ion to optimize the heating rate behavior of Mn-Zn ferrite for cancer treatment by hyperthermia.

Molecular dynamics simulation study to investigate electrical properties of plumbene

ABSTRACT Plumbene, the new 2D structure of lead, single-layered with a hexagonal arrangement of atoms draws the attention of researchers around the globe. We have designed a plumbene sheet using multi-scale modelling i.e. nonequilibrium molecular dynamics (NEMD) simulation methods to determine the electrical properties of plumbene. The effects of varying sample sizes and temperatures on the electrical properties of plumbene using NEMD are studied here. It is observed from 298 K to 318 K electrical conductivity of plumbene ranges from 2.7792 × 10−14 S/m to 1.2012 × 10−13 S/m, with a dwindling nature. Almost static electrical resistivity from 298 K to 378 K is noticed, afterwards a sudden sharp increase till 398 K. The Lorenz number of plumbene from 298 K to 318 K shows reverse results with its electrical conductivity under similar experimental conditions. The electrical conductivity of plumbene sheets at 298 K with 600Å to 1050Å ranges from 0.17794 × 10−14 S/m to 4.7696 × 10−14 S/m. Only at 750Å sample size is a sharp jump is noticed. A reverse trajectory is observed for both electrical resistivity and Lorenz number of plumbene sheet samples. In these two cases, the sharp jump is observed at 1000Å. Our results will be helpful for the effective utilisation of plumbene in targeted applications of electrical engineering fields.

Design of an atomic layer deposition system with in situ reflection high energy electron diffraction.

We report the design, fabrication, and testing of an atomic layer deposition (ALD) system that is capable of reflection high energy electron diffraction (RHEED) in a single chamber. The details and specifications of the system are described and include capabilities of RHEED at varied accelerating voltages, sample rotation (azimuthal) control, sample height control, sample heating up to set temperatures of 1050 °C, and either single- or dual-differential pumping designs. Thermal and flow simulations were used to justify selected system dimensions as well as carrier gas/precursor mass flow rates. Temperature calibration was conducted to determine actual sample temperatures that are necessary for meaningful analysis of thermally induced transitions in ALD thin films. Several demonstrations of RHEED in the system are described. Calibration of the camera length was conducted using a gold thin film by analyzing RHEED images. Finally, RHEED conducted at a series of increasing temperatures was used to monitor the crystallization of an ALD HfO2 thin film. The crystallization temperature and the ring pattern were consistent with the monoclinic structure as determined by separate x-ray diffraction-based measurements.

Enhancing accuracy and reproducibility in asphalt VOCs qualitative and quantitative analysis: Insights from laboratory studies on emission characteristics

Asphalt pavement will emit Volatile Organic Compounds (VOCs) during life cycle, posing environmental and health risks. Precise understanding of the emission characteristics of asphalt VOCs will facilitate the formulation of targeted measures for reducing emissions. Simulating the emission characteristics of VOCs from asphalt under laboratory conditions is an effective method for predicting asphalt VOCs pollution and implementing effective control measures. In this study, a quality control method for qualitative and quantitative detection of asphalt VOCs in laboratory settings was established based on sample storage time, asphalt sources, and temperature sensor positions. Furthermore, the study investigated the influence of mixing speed and sampling pump speed during asphalt VOCs generation on the emission characteristics. The results demonstrate that the quality control methods exhibit excellent reproducibility and reliability, making them valuable for future research and emission control strategies. Furthermore, the total concentration of asphalt VOCs increases with higher mixing speeds, but stabilizes when the mixing speed reaches 750–1250 r/min. As mixing speed increases, the proportion of alkane groups significantly decreases, while the proportion of aldehydes markedly increases, with the overall proportion remaining relatively stable. Decreasing sampling pump speed leads to a gradual increase in asphalt VOCs concentration. At lower pump speeds, a nonlinear increase in concentration occurs due to VOCs enrichment effects. Asphalt VOCs concentrations exhibit a proportional increase with sampling pump speeds exceeding 1000 ml/min. Finally, based on the results of the three-level analysis of "total concentration-group-substance" and taking into account the energy consumption, it is recommended that the mixing speed be set at 1000 r/min and the sampling pump speed be set at 1000 ml/min for the generation and collection of asphalt-related VOCs. This study can provide a reliable method for generating and collecting asphalt-related VOCs and offer critical insights for optimizing VOCs emission reduction strategies.

Distect: automatic sample-position tracking for X-ray experiments using computer vision algorithms.

Soft X-ray spectroscopy is an important technique for measuring the fundamental properties of materials. However, for measurements of samples in the sub-millimetre range, many experimental setups show limitations. Position drifts on the order of hundreds of micrometres during thermal stabilization of the system can last for hours of expensive beam time. To compensate for drifts, sample tracking and feedback systems must be used. However, in complex sample environments where sample access is very limited, many existing solutions cannot be applied. In this work, we apply a robust computer vision algorithm to automatically track and readjust the sample position in the dozens of micrometres range. Our approach is applied in a complex sample environment, where the sample is in an ultra-high vacuum chamber, surrounded by cooled thermal shields to reach sample temperatures down to 2.5 K and in the center ofa superconducting split coil. Our implementation allows sample-position tracking and adjustment in the vertical direction since this is the dimension where drifts occur during sample temperature change in our setup. The approach can be easily extended to 2D. The algorithm enables a factor of ten improvement in the overlap of a series of X-ray absorption spectra in a sample with a vertical size down to 70 µm. This solution can be used in a variety of experimental stations, where optical access is available and sample access by other means is reduced.

Impact of high‐intensity ultrasound, cooling rate, and storage temperature on physical properties and oil binding capacity in fully hydrogenated palm‐kernel lipid matrices

AbstractThe ability of a fat crystal network to entrap liquid oil is known as oil binding capacity (OBC) and is an imperative property in semi‐solid fats for use in confectionary, bakery, and snack products. Understanding the factors that increase the OBC of fats is crucial for developing fat‐based foods that are more resistant to unwanted oil migration. In this study, fully hydrogenated palm‐kernel based (FHPKO) lipid matrices were crystallized under different processing conditions to generate samples with a wide range of physical properties and OBC. Three dilutions were created by combining FHPKO with soybean oil (SBO)—75% FHPKO (containing 25% SBO), 50% FHPKO (50% SBO), and 20% FHPKO (80% SBO) and were crystallized at 33, 30, and 22°C; respectively. All the samples were crystallized using fast (FCR; 4.6°C/min) and slow (SCR; 0.1°C/min) cooling rates, as well as with (w) and without (wo) high‐intensity ultrasound (HIU; 20 kHz). These processing conditions resulted in four different sets of samples—FCR wo HIU, FCR w HIU, SCR wo HIU, SCR w HIU. Immediately after processing, the sample's hardness, solid fat content (SFC), viscoelasticity (G′, G″, δ), microstructure, melting behavior (Tpeak, enthalpy), and OBC using a centrifuge method (labeled OBCc) were analyzed. Samples were then stored at 22 and 5°C for 48 h and the aforementioned properties were measured again as well as OBC using a filter paper method (labeled OBCp). Results show that both OBCc and OBCp were positively correlated with the sample's SFC (rs = 0.912, p &lt; 0.001; rs = 0.777, p &lt; 0.001), storage moduli (G′) (rs = 0.674, p &lt; 0.001; rs = 0.526, p = 0.017), hardness (rs = 0.793, p &lt; 0.001; rs = 0.812, p &lt; 0.001), enthalpy (rs = 0.842, p &lt; 0.001; rs = 0.812, p &lt; 0.001), and the number of crystals (rs = 0.655, p &lt; 0.001; rs = 0.728, p &lt; 0.001); respectively. While no correlation between OBCp and the sample's peak melting temperature and microstructure was recorded, a negative association between the sample's peak melting temperature (rs = −0.782, p &lt; 0.001), phase angle (δ) (rs = −0.801, p &lt; 0.001), and crystal diameter (rs = −0.470, p = 0.004) was documented for OBCc. These results suggest oil binding capacity of palm‐kernel based crystallized fats can be increased by formulating harder fats that are elastic, contain more crystals, and have higher SFC and enthalpy. Additionally, the FCR with HIU processing conditions was the most effective in increasing the OBC.

Signature of the Kondo effect in superparamagnetic GO incorporated Cobalt substituted Ni/NiO nanoparticles

The study reports on the magnetization, magnetoresistance, and transport properties of superparamagnetic 10% Co-doped Ni/NiO (C10-NN), Graphene Oxide (GO) incorporated 10% Co-doped Ni/NiO (C10-NNG), and 15% Co-doped Ni/NiO (C15-NN) nanoparticles synthesized via a microwave-assisted sol-gel auto-combustion method. All samples show hysteresis in negative Magnetoresistance (M-R) at different temperatures. Resistivity ρ(T) versus temperature plots of samples C10-NN and C15-NN show metallic behavior with applied fields of 0, 1, 5, 8 T, and at 0 T, 1 T respectively. However, the plot of R-T of the C15-NN sample shows a significant difference at 0 T and 1 T. At 0 T for this sample, the metallic behavior is observed for temperature T > TM, with the resistivity falling abruptly at and above TM = 246 K. The resistivity decreases with increasing temperature, exhibiting metallic behavior again above TMM < 276 K. This jump at 276 K, indicating a metal-to metal transition. The Kondo effect is observed for the first time in C10-NNG sample. The upturn of resistivity ρ(T) towards low temperature in the C10-NNG sample is well described by the power series equation and Kondo term. This sample exhibits the upturn resistivity along with a metal–insulator transition above and below the Kondo temperature TK≈ 93.51(2) K at the 0 T, 1 T, 5 T, and 8 T fields.

Analysis of Thermal Isotropy of Parallelepiped Shape of Bronze Samples for Mechanical Engineering Applications

Objective: The need to find out whether the specimens are ‘thermally thin’ or not is the basis for applying the law of conservation of energy or the Fourier differential equation of heat conduction in finding the time dependence of the specimen temperature. The aim of this study is to find out the thermal field distribution in a parallelepiped shaped bronze specimen and to verify the Bio number. Methods: A number of external variables make it difficult to maintain a monotonic change in sample temperature during the ‘heating’ stage. These factors led to the use of the cooling method to study tiny samples with low inertia of the thermal process. We used the cooling method to experimentally verify the isotropy of the thermal field in the sample and to study the kinetics of cooling relative to the sample axes over a wide range of temperatures. Results: It was found out that in natural air cooling the main mechanisms are conductive, convective and radiative heat transfer. The contribution of thermal radiation to the cooling process is noticeable at high temperatures. It was found that the typical cooling time increases with sequential radiative, conductive and convective heat transfer. By extending the temperature study area to, for the first time, we were able to observe each component of the heat transfer process independently. The values of the typical cooling time on all axes correspond to the experimental error bounds. It was found that the temperature value of the sample is independent of the coordinates and depends only on time. In this case, the law of conservation of energy can be used to explain the dependence of body temperature on cooling time. Conclusion: It is shown that the sample under study is ‘thermally thin’, i.e. the thermal field is constant in all directions. In this situation, the thermal balance equation should be applied rather than the Fourier differential equation of heat conduction, since the temperature gradient inside the body is practically zero. The results obtained are of great importance for the study of cooling processes of metallic products in thermal power engineering, heat engineering and thermophysics.

PHOTOELECTRICAL PROPERTIES OF CdMnSe THIN FILMS

The studied semiconductor structure for photovoltaic cells is composed of SnO2-coated glass and CdMnSe thin film. A study is made by examining the photoluminescence from the surface of the CdMnSe thin film with laser power and sample temperature for an as-grown, then an air-annealed thin film and undergone CdCl2 treatment. Thin films of Cd1-xMnxSe (x=0.02) were grown on a glass substrate. The lifetime of charge carriers under pulsed illumination was determined from the kinetic decay of the photocurrent. The study of relaxation curves of nonequilibrium photoconductivity under the influence of laser radiation confirmed the presence of two recombination channels - intrinsic and impurity. Photocurrent relaxation occurs through fast and slow recombination channels. The fast relaxation time τ = 6 μs associated with the intrinsic transition and the slow relaxation time is due to impurity excitation and τ = 22 μs. The photoluminescence spectra of thin films of Cd1-xMnxSe (x=0.02) were studied. In the photoluminescence study, two maxima are observed due to donor-acceptor recombination and intracenter transition of Mn atom.

Performance evaluation of solar dryer integrated with solar panel for drying of carrot (Daucus carota) vegetable

ABSTRACT Solar energy is a well-known and economically efficient energy source. Solar energy is harvested in two modes: one is direct and another is indirect. In the direct type, the global radiation is used directly to dry the food samples, while in indirect mode, solar energy is converted into electricity to operate the integrated exhaust fan for enhancement of the drying rate. Thermal analyses of the various components of the PVT hybrid dryer have been incorporated into this performance evaluation. Carrot has been chosen as a food sample because it has good moisture content and is used for nutritive purposes. The maximum ambient temperature has been monitored as 41°C at maximum global radiation conditions. The effect of the PVT system with solar dryer in both cases i.e. natural convection and forced convection have also been discussed in terms of temperature profiles of the drying chamber, sample temperature, and thermal efficiency. The thermal efficiency has been found as 55.3% for forced convection and 53.4% for natural convection. Similarly, a 3°C temperature increment has been found in food samples. Results have been supported and analyzed by the comparison between outcomes of natural and induced convection.