Thermal Con Research Articles

A multiclass classification model for predicting the thermal conductivity of uranium compounds

ABSTRACT Advanced nuclear fuels are designed to offer improved performance and accident tolerance, with an emphasis on achieving higher thermal conductivity. While promising fuel candidates like uranium nitrides, carbides, and silicides have been widely studied, the majority of uranium compounds remain unexplored. To search for potential candidates among these unexplored uranium compounds, we incorporated machine learning to accelerate the material discovery process. In this study, we trained a multiclass classification model to predict a compound’s thermal conductivity based on 133 input features derived from element properties and temperature. The initial training data consist of over 160,000 processed thermal conductivity records from the Starrydata2 database, but a skewed data class distribution led the trained model to underestimate compound’s thermal conductivity. Consequently, we addressed the issue of class imbalance by applying Synthetic Minority Oversampling TEchnique and Random UnderSampling, improving the recall for materials with thermal conductivity higher than 15 W/mK from 0.64 to 0.71. Finally, our best model is used to identify 119 potential advanced fuel candidates with high thermal conductivity among 774 stable uranium compounds. Our results underscore the potential of machine learning in the field of nuclear science, accelerating the discovery of advanced nuclear materials.

Experimental investigation on thermal conductivity and thermal degredation of Honge oil methyl ester with B-20 blend.

Honge oil methyl ester (HOME) with B-20 blend is considered to examine thermal con- ductivity and thermal degredation of the biodiesel. Transient hot wire method is adopted to determine thermal conductivity of the samples.Heat source is clubbed with C-DAQ and LAB-VIEW software is utilized to record temperature and time. Following Sastry’s power law model, an improved emperical relation is developed for thermal conductivity of HOME with B-20 blend. Thermogravitometry (TG-DTG) analysis is performed under atmospheric condi- tions with 10°C/min heating rate of pure air flow.Diesel is exhibited one mass loss event from 55–334°C, whereas two mass loss event in case of biodiesel. Maximum decoposition tem- perature noticed for diesel,HOME andB-20 blend are 195°C, 227°C and 175°C respectively. Complete mass degradation takes place for diesel and HOME at 498°C, in case of HOME with B-20 blend complete mass degradation occurred at 377°C.

Optimization and Controlled Systems: A Case Study on Thermal Aware Workload Dispatching

Although successfully employed on many industrial problems, Combinatorial Optimization still has limited applicability on several real-world domains, often due to modeling difficulties. This is typically the case for systems under the control of an on-line policy: even when the policy itself is well known, capturing its effect on the system in a declarative model is often impossible by conventional means. Such a difficulty is at the root of the classical, sharp separation between off- line and on-line approaches. In this paper, we investigate a general method to model controlled systems, based on the integration of Machine Learning and Constraint Programming (CP). Specifically, we use an Artificial Neural Network (ANN) to learn the behavior of a controlled system (a multicore CPU with thermal con- trollers) and plug it into a CP model by means of Neuron Constraints. The method obtains significantly better results compared to an approach with no ANN guidance. Neuron Constraints were first introduced in [Bartolini et al., 2011b] as a mean to model complex systems: providing evidence of their applicability to controlled systems is a significant step forward, broadening the application field of combinatorial methods and disclosing opportunities for hybrid off-line/on-line optimization.

Flexible Nanotwinned Graphene/Copper Composites as Thermal Management Materials

The flexible nanotwinned graphene/copper (Gr/Cu) composite is successfully fabricated by pulse electrodeposition (PED). Microstructure, nanoindentation hardness, tensile properties, and thermal con...

Acute physiological and perceptual responses to wearing additional clothing while cycling outdoors in a temperate environment:A practical method to increase the heat load

ABSTRACTThis investigation assessed the acute physiological and perceptual responses to wearing additional clothing during outdoor cycling to determine if this strategy could increase the heat load while training in temperate environments. Seven male cyclists (age: 32 ± 13 y, height: 179 ± 10 cm, body mass: 74 ± 10 kg, body fat percentage: 10.3 ± 1.0%) completed 2 randomized outdoor (∼17°C and ∼82% RH), 80 min cycling sessions at moderate-hard intensities (CR10 RPE = 3–5). They wore spandex shorts and a short sleeve top (CON) or additional clothing including full-length spandex pants and a ‘winter’ cycling jacket and gloves (AC). Core temperature, heart rate, sweat rate, thermal sensation and thermal comfort were measured across the trials. Moderate increases were observed in AC vs. CON for the change in mean core temperature (0.4 ± 0.3°C, effect size, ES = 1.16 ± 0.55), change in maximum core temperature (0.5 ± 0.3°C, ES = 1.07 ± 0.48) and sweat rate (0.24 ± 0.16 L.h−1, ES = 1.04 ± 0.59). A small increase in mean heart rate (3 ± 3 bpm, ES = 0.32 ± 0.28) was observed as well as a ‘very likely’ (percentage difference = 22.4 ± 7.1) and ‘most likely’ (percentage difference = 42.9 ± 11.9) increase in thermal sensation and thermal comfort, respectively, in AC vs. CON. Dressing in additional clothing while cycling outdoors in a temperate environment increased physiological strain and sensations of warmth and discomfort. Training in additional clothing during outdoor cycling represents a practical alternative to increasing the heat load of a training session.

Effective thermal conductivity of dispersed materials with contrast inclusions

The results of numerical and experimental studies of the effective thermal conductivity of dis� persed materials with contrast inclusions are presented. The numerical analysis was based on using the mul� tiscale finite element method making it possible to calculate heat transport in media with ordered and chaotic location of the inclusions. The influence of the concentration of inclusions and the manner of their packing on the value of the effective coefficient of thermal conductivity was analyzed. The coefficient of thermal con� ductivity was studied experimentally for two media, gypsum and plexiglass with inclusions of steel balls (d = 3 mm) with different packing. The comparison of the results of measurements and numerical simulation makes it possible to verify the elaborated program complex and determine the boundaries of application of the available analytical dependences.

The Effect of Ice Slushy Ingestion and Mouthwash on Thermoregulation and Endurance Performance in the Heat

The purpose of this study was to establish whether sensory factors associated with cold-beverage ingestion exert an ergogenic effect on endurance performance independent of thermoregulatory or cardiovascular factors. Ten males performed three trials involving 90 min of steady state cycling (SS; 62% VO2max) in the heat (32.1 ± 0.9 °C, 40 ± 2.4% relative humidity) followed by a 4 kJ/kg body mass time trial (TT). During SS, participants consumed an identical volume (260 ± 38 g) of sports beverage (7.4% carbohydrate) every 15 min as either ice slushy (-1 °C; ICE), thermoneutral liquid (37 °C; CON), or thermoneutral liquid consumption with expectorated ice slushy mouthwash (WASH). Rectal temperature, hydration status, heart rate, and skin blood flow were not different between trials. Gastrointestinal (pill) temperature was lower in ICE (35.6 ± 2.7 °C) versus CON (37.4 ± 0.7 °C, p = .05). Heat storage tended to be lower with ICE during SS (14.7 ± 8.4 W.m(-2), p = .08) and higher during TT (68.9 ± 38.6 W.m(-2), p = .03) compared with CON (22.1 ± 6.6 and 31.4 ± 27.6 W.m(-2)). ICE tended to lower the rating of perceived exertion (RPE, 12.9 ± 0.6, p = .05) and improve thermal comfort (TC, 4.5 ± 0.2; p = .01) vs. CON (13.8 ± 1.0 and 5.2 ± 0.2 respectively). WASH RPE (13.0 ± 0.8) and TC (4.8 ± 0.2) tended to be lower versus CON (p = .07 and p = .09 respectively). ICE improved performance (18:28 ± 1:03) compared with CON (20:24 ± 1:46) but not WASH (19:45 ± 1:43). Improved performance with ICE ingestion likely resulted from the creation of a gastrointestinal heat sink, reducing SS heat storage. Although the benefits of cold-beverage consumption are more potent when there is ingestion, improved RPE, TC, and meaningful performance improvement with WASH supports an independent sensory effect of presenting a cold stimulus to the mouth.

Influence of TiO2 nanoparticles on the optical and structural properties of PPV thin films converted at low temperatures

In this work we studied the optical properties of poly(p-phenylene vinylene) (PPV) produced by the thermal con- version of a precursor polymer blended with a synthetic dye (Reactive Black 5). The production of PPV by this method decreases the overall time and cost of the process. We observed that the introduction of the dye resulted in an additional absorbance band near 550-700 nm, which can be beneficial to the photon harvesting capacity of the polymer if it is used as the donor material in a photovoltaic device. We studied how the optical and structures properties of this blend change when different quantities of TiO2 nanoparticles are introduced. For that, thin films were produced by the cast deposition of pre- PPV:dye:TiO2. The scanning electronic microscopic images showed that the inorganic semiconductor form large agglomer- ates of approximately 200 nm, indicating a very rough surface where the dye can be adsorbed. The analysis of photolumi- nescence and Raman peaks indicated a reduction of the mean conjugation length of the polymer chains in the presence of TiO2 nanoparticles.

Working Conditions in Carpet Weaving Workshops and Muscu-loskeletal Complaints among Workers in Tabriz - Iran.

Carpet weaving operations usualy involve poor working conditions that can lead to the development of musculoskeletal disorders (MSDs). This study investigated MSDs among car¬pet weavers in relation to working conditions from workers' view in Tabriz City, Northwest Iran. This cross-sectional and descriptive study was conducted in city of Tabriz, Iran. Data were col¬lected using interviews and questionnaires. The study population consisted of 200 randomly selected healthy weavers from twenty five active carpet weaving workshops. The results showed a high prevalence of musculoskeletal problems among the study population. The most commonly affected body areas were neck, lower back, ankles/feet, hands/wrists, upper back, shoulders and knees, respectively. More than half of the weavers were not satisfied with the thermal con¬dition, noise level and cleanliness of the air in the workshops. The result indicated a significant relation¬ship between upper back symptoms and daily working time and between lower back symptoms and the numbers of rows of knots woven in a day. Weavers' satisfaction with hand tools shape and thermal condi¬tion of the workshops were associated with lower back symptoms, whereas satisfaction with weaving looms were associated with upper back complaints. The poor working condition of hand-woven carpet workshops such as environmental con¬ditions and work station design and tools should be the subject of ergonomics interventions.

Simple glucose reduction route for one-step synthesis of copper nanofluids

One-step method has been employed in the synthesis of copper nanofluids. Copper nitrate is reduced by glucose in the presence of sodium lauryl sulfate. The synthesized particles are characterized by X-ray diffraction technique for the phase structure; electron diffraction X-ray analysis for chemical composition; transmission electron microscopy and field emission scanning electron micros- copy for the morphology; Fourier-transform infrared spectroscopy and ultraviolet-visible spectroscopy for the analysis of ingredients of the solution. Thermal conduc- tivity, sedimentation and rheological measurements have also been carried out. It is found that the reaction param- eters have considerable effect on the size of the particle formed and rate of the reaction. The techniques confirm that the synthesized particles are copper. The reported method showed promising increase in the thermal con- ductivity of the base fluid and is found to be reliable, simple and cost-effective method for preparing heat transfer fluids with higher stability.

Anisotropic thermal transport in a crosslinked polyisoprene rubber subjected to uniaxial elongation

AbstractAnisotropic thermal transport in a crosslinked polyisoprene (natural rubber) subjected to uniaxial elongation is investigated experimentally. Using a novel optical technique based on forced Rayleigh scattering, two components of the thermal diffusivity tensor are measured as a function of stretch ratio. The thermal diffusivity is found to increase in the direction parallel, and decrease in the direction perpendicular, to the stretch direction. The level of anisotropy for the natural rubber is substantially lower than that reported by Tautz 50 years ago but comparable to that found in our previous studies on molten polymers, quenched thermoplastics, and other crosslinked elastomers. Thermal diffusivity data along with measurements of the tensile stress were used to evaluate the stress‐thermal rule, which was found to be valid over the entire range of stretch ratios. In contrast, failure of the stress‐optic rule was observed at stretch ratios well below the largest value at which the stress‐thermal rule was valid. This suggests that the degree of anisotropy in thermal conductivity depends on both orientation and stretch of polymer chain segments. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012

Thermal conductivity enhancement of Ag nanowires on an organic phase change material

One of the greatest challenges in the applica- tion of organic phase change materials (PCMs) is to increase their thermal conductivity while maintaining high phase change enthalpy. 1-Tetradecanol/Ag nanowires composite PCM containing 62.73 wt% (about 11.8 vol%) of Ag nanowires showed remarkably high thermal con- ductivity (1.46 W m -1 K -1 ) and reasonably high phase change enthalpy (76.5 J g -1 ). This behavior was attributed to the high aspect ratio of Ag nanowires, few thermal conduct interfaces, and high interface thermal conductivity of Ag nanowires in the composite PCM. These results indicated that Ag nanowires might be strong candidates for thermal conductivity enhancement of organic PCMs.

Phonon Transport and Thermal Conductivity Percolation in Random Nanoparticle Composites

In this paper, we investigated the effective thermal conductivity of three dimen- sional nanocomposites composed of randomly distributed binary nanoparticles with large differ- ences (contrast ratio) in their intrinsic (bulk) ther- mal conductivity. When random composites are made from particles with very different thermal conductivity (large contrast ratio), a continuous phase of high thermal conductivity constituent is formed when itsvolumetric concentrationreaches beyond the percolation threshold. Such a contin- uous phase of material can provide a potentially low resistance pathway for thermal transport in random composites. The percolation theory pre- dicts the thermal conductivityof the random com- positesto increase according to a scaling law with increasing concentration of the high thermal con- ductivity constituent after percolation. However, when the characteristic size of the particles in the nanocomposites is comparable to or smaller than the phonon mean free path, the phonon scattering at interfaces between two materials can introduce significant thermal resistance in the highly con- ductive phononpathway. Such interfacial thermal resistance can reduce the thermal conductivity of the nanoparticle composites. The thermal con- ductivity of the random nanoparticle composites thus deviates significantly from the predictions of the percolation theory. In this study, the Monte Carlo simulation was employed to generate ran- dom distribution of nanoparticles and to simulate the phonontransportinrandomnanoparticlecom- posites. The effects of particle size, thermal con-

Effect of interfacial treatment on the thermal properties of thermal conductive plastics

In this paper, ZnO, which is processed by different surface treatment approaches, is blended together with polypropylene to produce thermal conductive polymer composites. The composites are analyzed by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) to investigate the surface modification of filler, their distribution in the matrix and the condition of two-phase interface. Optimized content of filler surface modifier is investigated as well. The results showed that using low-molecular coupling agent produces positive effect to improve the interface adhesion between filler and matrix, and the thermal conductivity of the composite as well. Macro-molecular cou- pling agent can strongly improve two-phase interface, but it is not beneficial at obtaining a high thermal conductivity. The blend of ZnO without modification and polypropylene has many defects in the two-phase interface, and the thermal con- ductivity of the composite is between those of composites produced by previous two approaches. The surface treatment of the filler also allowed producing the composites with lower coefficient of thermal expansion (CTE). As for the content of low-molecular coupling agent, it obtains the best effect at 1.5 wt%.

Reproduction and life-cycle of the beachflea (Orchestia gammarellus (Pallas) (Crustacea: Amphipoda) at thermal and non-thermal sites in the intertidal of Iceland: how important is temperature?

The littoral fringe beachflea Orchestia gammarellus (Pallas) is a seasonal breeder over much of its range. Previous studies indicated that tempera- ture was the most important factor initiating breeding while photoperiod appeared inconsequential. We tes- ted the effect of temperature by comparing two pop- ulations at non-thermal sites with two populations at thermal sites in Iceland. At the non-thermal sites the species is probably close to its lower temperature tol- erance limits, while potentially able to choose optimal temperatures at all times of the year at the thermal sites. The species was a seasonal breeder at all sites, but the breeding season started 2-3 months earlier at thermal sites. Breeding ended at about the same time at all sites. We conclude that photoperiod probably governs breeding season under constant thermal con- ditions, and this is also supported by observations on laboratory stocks. At the thermal sites the animals became sexually mature in a year or less, as is the case where the species has been studied at lower latitudes, while at the non-thermal sites Icelandic animals, apparently uniquely, need 2 years to become sexually mature.

Fiber optic microampere dc current sensor

A microampere dc current is measured by a fiber optic sen- sor. The phase change of the guided light induced by ohm's heat over a golden-coated fiber is detected by an interferometer. The thermal con- duction of the optical fiber and the relation of the temperature-induced phase change of the guided light are explored. A Michelson interferom- eter plus a Faraday rotator mirror enable system immunity from the polarization-induced signal fading due to the environmental disturbance, especially by vibration and temperature. A passive phase-generated car- rier (PGC) demodulation scheme enables the system to demodulate the interference signal stably by shifting the signal away from the high-noise, low-frequency band through a carrier. The sensitivity of the sensing sys- tem is improved by a biased method. The minimum measurable dc cur- rent is 3.416310 27 A with a dynamic range of 89.33 dB. © 2003 Society of

Progress in Controlled Breeding of Summer Flounder, Paralichthys dentatus, and Southern Flounder, P. lethostigma

ABSTRACT The sum mer floun der, Paralichthys dentatus, and the south ern floun der, P. lethostigma, are high value flat fish spe cies and im -por tant can di dates for com mer cial aquaculture in the east ern U.S. Wild-caught adults of both spe cies have been spawned ei ther nat u rally or by hor mone-in duc tion dur ing their first year in cap tiv ity, but spawn ing suc -cess and fre quency of vo li tional spawnings im proves with size/age and ha bit u a tion (>1.5 year) to cap tiv ity. Con trolled-en vi ron ment tanks (2.5-10 m3) sup plied with re cir cu lat ing sea wa ter (32-36 ppt) are used for photo -thermal con di tion ing of broodstock to fa cil i tate en vi ron men tal con trol, ob ser va tion, han dling, and feed ing. Stocking den si ties of 1.7-4.11 kg/m3and sex ra tios of 1-2 males:1 fe male are rec om mended, but op tima have not been de ter mined. In the sum mer floun der, com mer cial hatch er ies use hor mone-in duced spawn ing of photothermally con di tioned fish to sup -ply fingerlings year round. In tra mus cu lar im plan ta tion of a slow-re lease LHRHa pel let (dose ∼100 μg/kg) into fe males with max i mum fol li cle diameters >500 μm or with mean oocyte di am e ters rang ing from 258-456 μm in duces re pet i tive ovu la tion and spawn ing. Com mer cial culturists pres ently opt for strip spawn ing, us ing a “light ta ble” to es ti -mate time of ovu la tion, but hor mone-in duced vol un tary spawn ing and nat u ral spawn ing with out hor mone in duc tion could be come more prev a -lent with lon ger-term ac cli ma tion and do mes ti ca tion. In the south ern floun der, im plan ta tion of a slow-re lease LHRHa pel let (∼100 μg) has also in duced re pet i tive ovu la tion and spawn ing, al low ing mul ti ple strip spawn ing or vo li tional spawn ing in fe males with max i mum fol li cle di -am e ters > 500 μm. Large num bers of vi a ble em bryos have also been pro -duced through nat u ral spawn ing with out hor mone in duc tion. Through photothermal ma nip u la tion, the nat u ral spawn ing pe riod has been ex -tended by 2-3 months, but ad di tional stud ies are needed to pro duce fingerlings year round. A fun da men tal prob lem in the con trolled re pro -duc tion of both the sum mer floun der and south ern floun der is the vari -abil ity in num ber of eggs and the fer til ity rates among fe males and among con sec u tive spawns from the same fe male. More pre dict able rates of ovu la tion, as well as of fer til iza tion and hatch ing, are needed to lower costs of seed pro duc tion. Vari able spawn ing suc cess can be at trib -uted in large part to in con sis tent male per for mance and in ad e quate spermiation. Hor mone treat ments used to in duce ovu la tion in fe males have been in ef fec tive in in duc ing spermiation in males, and al ter na tive ther a pies are needed. In fe males, egg qual ity may pre sum ably be im -proved by op ti miz ing nutri tions, en vi ron men tal con di tion ing, and hor -mone doses and re lease rates. To date, adult broodstock are ob tained from the wild, and the po ten tial for se lec tive breed ing or for pro duc ing interspecific hy brids re mains un tapped.

Energetics and Thermoregulation by Small Passerines of the Humid, Lowland Tropics

Birds of the open, humid lowland tropics encounter challenging thermal con- ditions-high temperatures, high humidity, and intense solar radiation. I examined how one such species, the Variable Seedeater (Sporophila aurita, Emberizidae), responds to tempera- ture by measuring its body temperature (Tb), metabolic heat production (Hm calculated from oxygen consumption), and evaporative heat loss (HIf calculated from evaporative water loss) at stable air temperatures (Ta) between 14 and 460C. I also measured basal metabolic rate (BMR) and Tb of the Variable Seedeater's diminutive (7.5 g) congener, the Ruddy-breasted Seedeater (S. minuta). All measurements utilized fasted, active-phase birds that were resting in the dark. BMR was lower than expected allometrically in both species, averaging 76% of predicted (or 0.718 kJ/h) in the 9.8-g Variable Seedeater (n = 11) and 67% of predicted (or 0.525 kJ/h) in the Ruddy-breasted Seedeater (n = 3). The Variable Seedeater's thermoneutral zone (TNZ) was relatively high (28.9 to 39.2'C). Below the TNZ, Hm was linearly related to Ta as follows: Hm (kJ/h) = 2.22 - 0.052 Ta. Thermal conductance, as indicated by the slope of this relation, was 12% lower than predicted allometrically. Data for 14 tropical bird species show BMR and thermal conductance to be linked; species with relatively high thermal con- ductance have a high BMR and vice versa. Evaporative cooling is relatively ineffective in the humid tropics, and compared with most birds Variable Seedeaters have a blunted evapo- rative response to heat. They dissipate evaporatively a maximum of 127% of their metabolic heat production at high Ta, even when measured in air only half as humid as that of their native habitat. Consequently, Variable Seedeaters employ hyperthermia (elevated Tb ) to cope with heat. They are more tolerant of hyperthermia than most bird species and survive Tbs that are among the highest recorded for birds (46.8 to 47.0?C). Tolerance of hyperthermia is advantageous because it allows Variable Seedeaters to maintain an unusually large Tb-T, gradient in hot environments (0.8 to 1.4'C at Ta = 43?C), and thereby to dissipate heat pas- sively. Variable Seedeaters are able to circumvent partially the well-known temperature de- pendency of chemical reactions (i.e. the Arrhenius-van't Hoff effect). This enables them to become progressively hyperthermic at Tas above 35'C with relatively little increase in met- abolic heat production, their Hm increasing at only 52% of the allometrically predicted rate above the TNZ. Variable Seedeaters possess several traits that enhance their tolerance of high Ta, yet because of their small size and limited thermal inertia their principal response to heat stress in the field is to avoid it behaviorally rather than to overcome it physiologically.

The Effect of Fiber Concentration on the Thermal Conductivity of a Polycarbonate/Pitch-Based Carbon Fiber Composite

Results of measurements of the thermal and electrical conductivities of polycarbonate samples as a function of chopped pitch-based carbon fiber concentration are reported. The fibers, roughly 500 μm long, were found to be strongly oriented in the composite leading to a highly anisotropic thermal conductivity. Longitudinal thermal con ductivities comparable to that of metallic alloys are obtained in the direction of the fibers, while in the transverse direction only a small increase in the thermal conductivity is observed. We proposed a new model which is a derivation of equations used for con tinuous fibers composites. This model is quite well in accordance with the linear de pendence of the longitudinal thermal conductivity on the fiber concentration of our data. Taking into account the effect of the polymeric matrix, the importance of contact resis tances between fibers and their maximum packing as well as the qualitative differences be tween thermal and electrical conduction is discussed.

Developments at the institute of atomic energy, China

Abstract During the past year a ceremony was held to celebrate the completion of the installation of acold source in one of the beam tubes of the heavy water research reactor, (10 – 15 MW, ≈ 2.8 × 10l4 n cm−2s-−1), at the Institute of Atomic Energy, Beijing, China. The essential com- ponent is a liquid hydrogen container of φ10mm × 50mm volume located at the inner end of the beam tube next to the reactor core. A thermal siphon con- nected to a helium compressor system is used to keep the container of liquid hydrogen cooled. Preliminary meas- urements show a gain of 12 is obtained for 5A, neutrons. Two beams of 22 mm × 52 mm area will be extracted from the cold source and transported to another hall by a 32 m guide tube. Initially, a small angle neutron scattering spec- trometer with a 64 × 64 element position sensitive BF3 area detector will be in- stalled and topics of interest to materials sciences will be studied. Topics of interest to biology will be investigated later.