Large Temperature Fluctuations Research Articles

A new design of dual-constituent triangular lattice metamaterial with unbounded thermal expansion

Triangular lattice metamaterials composed of bi-layer curved rib elements (called the Lehman–Lakes lattice) possess unbounded thermal expansion, high stiffness and impossibility of thermal buckling, which are highly desirable in many engineering structural applications subjected to large fluctuations in temperature. However, the requirement of such lattice metamaterial is that it must be a hinged joint in order to achieve the bending deformation upon heating freely, which directly leads to poor manufacturability, especially in small dimensions. In this study, a new design of dual-constituent triangular lattice metamaterial (DTLM) with good manufacturability is proposed to achieve the identical unbounded thermal expansion. In this lattice, a special bi-layer curved rib element where layer one is partially covered by layer two is presented, where the hinge joints are not necessary because the flexural rigidity in the single-layer part is much smaller than that in the bi-layer part, and the desirable thermal bending deformation can be achieved. A sample fabricated by additive manufacturing is given in order to show the good manufacturability; simultaneously, the multifunctional performance of the tailored DTLM with zero, large positive or negative coefficient of thermal expansion (CTE) can remain excellent, as well as the Lehman–Lakes lattice. Examples illustrate that the DTLM with zero CTE has about 34.2% improvement in stiffness and meanwhile has 17% reduction in weight compared with the Lehman–Lakes lattice. The stiffness of the DTLM has a moderate reduction when achieving the same large positive or negative CTE. In addition, the thermomechanical properties of the DTLM are given by the closed-form analytical solution and their effectiveness is verified by the detailed numerical simulation.

Temporally resolved two dimensional temperature field of acoustically excited swirling flames measured by mid-infrared direct absorption spectroscopy.

The detailed understandings of temperature profiles and flow-flame interaction in unsteady premixed swirling flames are crucial for the development of low emission turbine engines. Here, a phase-locked tomographic reconstruction technique measuring the large absorption cross section of CO2 at its mid-infrared fundamental band around 4.2 μm is used to acquire the flame temperature and in situ CO2 volume fraction distribution in a turbulent premixed swirling flame under different levels of external acoustic forcing amplitude. The temporally resolved temperature field variation reveals large temperature fluctuation in unsteady premixed swirling flames produced near the nozzle exit due to vortex-driven mixing of surrounding cold gas. The temperature fluctuation quickly dissipates when moving downstream of the flame with the flow velocity of the burnt gas. The accurate high temporal resolution thermodynamic measurements of the phase-locked tomographic thermometry technique reported in this work can be generally applied to periodic reacting flows.

Temperature decoupled viscosity-density product measurement in liquid by utilizing a dual-mode AlN-based acoustic wave resonator

In this letter, we report a two-in-one acoustic wave resonator with Rayleigh and Lamb modes for temperature decoupled viscosity-density product sensing. The Lamb mode of the resonator is sensitive to both the viscosity-density product and the ambient temperature, while the Rayleigh mode only responds to the ambient temperature and is not affected by liquid properties. These unique characteristics of the two modes are due to the different spatial distributions of the acoustic energy. Taking advantage of the aforementioned features, a beat frequency strategy is proposed to decouple the temperature influence from the viscosity-density product measurement, thus realizing temperature independent viscosity-density product sensing in a single acoustic wave resonator chip. Experimental results show that the accurate measurement of the viscosity-density product can be achieved in Newtonian liquids with a sensitivity of −0.36 MHz/kg m−2 s−0.5 within a wide temperature range from 20 °C to 80 °C. Our work holds great promise for liquid property measurement occasions with large fluctuations in ambient temperature, such as oil and gas exploration, automobile, and aeronautic applications.

Probing of Local Multifield Coupling Phenomena of Advanced Materials by Scanning Probe Microscopy Techniques.

The characterization of the local multifield coupling phenomenon (MCP) in various functional/structural materials by using scanning probe microscopy (SPM)-based techniques is comprehensively reviewed. Understanding MCP has great scientific and engineering significance in materials science and engineering, as in many practical applications, materials and devices are operated under a combination of multiple physical fields, such as electric, magnetic, optical, chemical and force fields, and working environments, such as different atmospheres, large temperature fluctuations, humidity, or acidic space. The materials' responses to the synergetic effects of the multifield (physical and environmental) determine the functionalities, performance, lifetime of the materials, and even the devices' manufacturing. SPM techniques are effective and powerful tools to characterize the local effects of MCP. Here, an introduction of the local MCP, the descriptions of several important SPM techniques, especially the electrical, mechanical, chemical, and optical related techniques, and the applications of SPM techniques to investigate the local phenomena and mechanisms in oxide materials, energy materials, biomaterials, and supramolecular materials are covered. Finally, an outlook of the MCP and SPM techniques in materials research is discussed.

Reducing dust deposition and temperature fluctuations in the laying hen houses of Northwest China using a surge chamber

For the poultry houses in Northwest China, the local aeolian sandy soil which is carried into by the ventilated air and large air temperature fluctuations have multiple adverse environmental and bird health effects, resulting in considerable losses in egg production. New approaches are desired for these poultry houses to mitigate the air temperature differences and reduce dust deposition rates. A novel ventilation system is developed to make the fresh air go through a surge chamber before entering the houses. The surge chamber can be considered as a particle separator that reduces suspended particulate matter in the air stream using gravity and inertial forces. It can also provide a thermally comfortable intermediate environment, which has cooler air in the summer than the atmospheric air. The performance of a poultry house with the new ventilation system and a house with the standard ventilation system were evaluated, examining the air temperature difference, dust deposition rates, and layer performance. The results showed that the new ventilation system had much lower maximum horizontal and vertical air temperature differences (1.4 °C and 0.9 °C), compared to the standard house (6.4 °C and 5.4 °C). The new ventilation system with a surge chamber effectively reduced the amount of aeolian sandy soil carried into the houses by ventilation, reaching an efficiency of 95%. Egg production rates and hen body mass were greater in the modified house and feed consumption and mortality were lower in modified house than the standard house.

Resonant Temperature Fluctuations in Nebulae Ionized by Short-period Binary Stars

Abstract A prevailing open problem in planetary nebulae (PNe) research, and photoionized gaseous nebulae research at large, is the systematic discrepancies in electron temperatures and ionic abundances as derived from recombination and collisionally excited lines. Peimbert proposed the presence of “temperature fluctuations” in these nebulae, but the apparent amplitude of such fluctuations, as deduced from spectral diagnostics and/or abundance discrepancy factors (ADFs), remain unexplained by standard photoionization modeling. While this and other alternative models to explain the temperature and abundance discrepancies remain inconclusive, recent observations seem to point at a connection between nebular ADFs and a binary nature of photoionizing stars. In this paper, we show that large amplitude temperature fluctuations are expected to form in PNe photoionized by short-period binary stars. Resonant temperature fluctuations (RTFs) are first formed along the orbital disk around the binary stars, as the periodically varying ionizing radiation field induces periodic oscillations in the heating-minus-cooling function. Then, the temperature fluctuations propagate vertically to the disk as thermal waves that later steepen into radiative shocks. The binary period of the ionizing stars is determinant in the formation and propagation of temperature fluctuations, as well as in associated density fluctuations. Fluctuations propagate efficiently only in systems with binary periods significantly shorter than the gas thermalization time, of the order of 10 days. Furthermore, we propose temperature diagnostic line ratios that combine [O iii] collisionally excited lines and O ii recombination lines to determine the equilibrium temperature and the magnitude of RTFs in nebulae.

The Global Dispersal of the Non-Endemic Invasive Red Alga Gracilaria vermiculophylla in the Ecosystems of the Euro-Asia Coastal Waters Including the Wadden Sea Unesco World Heritage Coastal Area: Awful or Awesome?

Gracilaria vermiculophylla (Ohmi) Papenfu AŸ 1967 (Rhodophyta, Gracilariaceae) is a red alga and was originally described in Japan in 1956 as Gracilariopsis vermiculophylla. It is thought to be native and widespread throughout the Northwest Pacific Ocean. G. vermiculophylla is primarily used as a precursor for agar, which is widely used in the pharmaceutical and food industries. It has been introduced to the East Pacific, the West Atlantic and the East Atlantic, where it rapidly colonizes new environments. It is highly tolerant of stresses (nutrient, salinity, temperature) and can grow in an extremely wide variety of conditions; factors which contribute to its invasiveness. It invades estuarine areas where it out-competes native algae species and modifies environments. The following European coastal and brackish water seas are already invaded: Atlantic, North Sea, Mediterranean and Baltic Sea. The Euro-Asian brackish Black-Sea have not yet been invaded but are very vulnerable to intense invasion with G. vermiculophylla because they are isolated from direct marine influences and have a harsh environment with large salinity, nutrient and temperature fluctuations.

Cyclic plastic behavior of unidirectional SiC fibre-reinforced copper composites under uniaxial loads: An experimental and computational study

Silicon carbide continuous fiber-reinforced copper matrix composites (Cu/SiCf) offer huge potential as heat sink material for high-heat-flux applications at elevated temperatures (>300 °C) owing to the beneficial combination of strong, stiff and refractory SiC fibers with a highly conductive and ductile copper matrix. As high-heat-flux components are normally subjected to large temperature fluctuations combined with thermal strain variations, degradation of the Cu/SiCf composites caused by fatigue damages under cyclic loads may affect the structural integrity of the component. In this study, the robustness of the Cu/SiCf composites under cyclic loads at different temperatures was evaluated by means of uniaxial cyclic loading tests. The stability of the cyclic deformation hysteresis curves was used as a measure of material’s durability. The experimentally observed global deformation behavior was interpreted with the help of a micromechanics-based theoretical model. It was shown that the Mori-Tanaka type mean field theory could describe the cyclic loading behavior of the composite quite well with a good fitting quality between the measured and simulated saturated cyclic curves. The effects of fiber content, applied strain range and test temperature are discussed.

Highly durable, coking and sulfur tolerant, fuel-flexible protonic ceramic fuel cells.

Protonic ceramic fuel cells, like their higher-temperature solid-oxide fuel cell counterparts, can directly use both hydrogen and hydrocarbon fuels to produce electricity at potentially more than 50 per cent efficiency1,2. Most previous direct-hydrocarbon fuel cell research has focused on solid-oxide fuel cells based on oxygen-ion-conducting electrolytes, but carbon deposition (coking) and sulfur poisoning typically occur when such fuel cells are directly operated on hydrocarbon- and/or sulfur-containing fuels, resulting in severe performance degradation over time3-6. Despite studies suggesting good performance and anti-coking resistance in hydrocarbon-fuelled protonic ceramic fuel cells2,7,8, there have been no systematic studies of long-term durability. Here we present results from long-term testing of protonic ceramic fuel cells using a total of 11 different fuels (hydrogen, methane, domestic natural gas (with and without hydrogen sulfide), propane, n-butane, i-butane, iso-octane, methanol, ethanol and ammonia) at temperatures between 500 and 600 degrees Celsius. Several cells have been tested for over 6,000 hours, and we demonstrate excellent performance and exceptional durability (less than 1.5 per cent degradation per 1,000 hours in most cases) across all fuels without any modifications in the cell composition or architecture. Large fluctuations in temperature are tolerated, and coking is not observed even after thousands of hours of continuous operation. Finally, sulfur, a notorious poison for both low-temperature and high-temperature fuel cells, does not seem to affect the performance of protonic ceramic fuel cells when supplied at levels consistent with commercial fuels. The fuel flexibility and long-term durability demonstrated by the protonic ceramic fuel cell devices highlight the promise of this technology and its potential for commercial application.

Qualitative criteria and thresholds for low noise asphalt mixture design

Low noise asphalt pavements are cost efficient and cost effective alternative for road traffic noise mitigation comparing with noise barriers, façade insulation and other known noise mitigation measures. However, design of low noise asphalt mixtures strongly depends on climate and traffic peculiarities of different regions. Severe climate regions face problems related with short durability of low noise asphalt mixtures in terms of considerable negative impact of harsh climate conditions (frost-thaw, large temperature fluctuations, hydrological behaviour, etc.) and traffic (traffic loads, traffic volumes, studded tyres, etc.). Thus there is a need to find balance between mechanical and acoustical durability as well as to ensure adequate pavement skid resistance for road safety purposes. Paper presents analysis of the qualitative criteria and design parameters thresholds of low noise asphalt mixtures. Different asphalt mixture composition materials (grading, aggregate, binder, additives, etc.) and relevant asphalt layer properties (air void content, texture, evenness, degree of compaction, etc.) were investigated and assessed according their suitability for durable and effective low noise pavements. Paper concluded with the overview of requirements, qualitative criteria and thresholds for low noise asphalt mixture design for severe climate regions.

Chilling units and chilling hours for southern region of Brazil and Aomori in Japan

The brazilian apple production are located in the southern region, with the best areas in altitudes ranging from 800 to 1400 m, with great variability in the number of Chilling Hours (CH) and Chilling Units (CU) in the different regions and years. The objective of this study was to compare CH equal or below 7.2°C and CU by the North Carolina Modified model in different regions of southern Brazil, comparing with Aomori region in Japan. In Brazil was used historical data of the CH and CU from 2000 to 2016 in the municipalities of Caçador (960 m), Videira (774 m), São Joaquim (1376 m), Fraiburgo (1038 m) and Vacaria (986 m). In Aomori (2.8 m) the historical data used was from 2000 to 2011. The results shows that in southern Brazil there is a variation in the number of CH between sites and years, being greater in the sites of higher altitude, with an average of 880 CH in São Joaquim and 411 CH in Videira. When compared the brazilian regions with Aomori, the japanese region have a greater CH accumulation. Once CU have the same behavior of CH in respect to altitudes, but shows a larger variability between years in the different regions of southern Brazil, is possible to affirm that the North Carolina Modified method is more accurate to quantify the chilling in regions with large temperature fluctuations in the autumn and winter, while for regions with low thermal amplitude, the model of CH presents a better adherence.

Phenotypic and transcriptomic responses to salinity stress across genetically and geographically divergent Tigriopus californicus populations.

Species inhabiting the North American west coast intertidal must tolerate an extremely variable environment, with large fluctuations in both temperature and salinity. Uncovering the mechanisms for this tolerance is key to understanding species' persistence. We tested for differences in salinity tolerance between populations of Tigriopus californicus copepods from locations in northern (Bodega Reserve) and southern (San Diego) California known to differ in temperature, precipitation and humidity. We also tested for differences between populations in their transcriptomic responses to salinity. Although these two populations have ~20% mtDNA sequence divergence and differ strongly in other phenotypic traits, we observed similarities in their phenotypic and transcriptomic responses to low and high salinity stress. Salinity significantly affected respiration rate (increased under low salinity and reduced under high salinity), but we found no significant effect of population on respiration or a population by salinity interaction. Under high salinity, there was no population difference in knock-down response, but northern copepods had a smaller knock-down under low salinity stress, corroborating previous results for T.californicus. Northern and southern populations had a similar transcriptomic response to salinity based on a principle components analysis, although differential gene expression under high salinity stress was three times lower in the northern population compared to the southern population. Transcripts differentially regulated under salinity stress were enriched for "amino acid transport" and "ion transport" annotation categories, supporting previous work demonstrating that the accumulation of free amino acids is important for osmotic regulation in T.californicus.

Comparison of thermal tolerance and standard metabolic rate of two Great Lakes invasive fish species

Abstract Round goby (Neogobius melanostomus) and western tubenose goby (Proterorhinus semilunaris) invaded the Laurentian Great Lakes at approximately the same time and area yet have shown substantial differences in their post-invasion success with more rapid establishment and development of much larger abundances of round goby populations throughout the invaded habitat. In this study, we compared differences in physiological performance (thermal tolerance and standard metabolic rate) between round and tubenose goby collected from the Huron-Erie corridor. Tubenose goby were observed to have lower thermal tolerance but exhibited similar standard metabolic rate across environmental temperatures compared to round goby. At temperatures exceeding 31 °C, tubenose goby demonstrated significantly higher mortalities and shorter times to death relative to round goby. The observed differences in thermal tolerance were consistent with differences in the native geographic ranges observed for each species at their southern ranges. The observed differences in physiological performance combined with species differences in other life history traits such body size, reproduction, feeding ecology and habitat affiliation may also explain differences in the invasiveness experienced by these two Great Lakes invasive fish including a greater ability of round gobies to occupy extreme habitats with large water temperature fluctuations.

Three dimensional lightweight lattice structures with large positive, zero and negative thermal expansion

Tailoring thermal expansion of structures is in urgent need in engineering applications where the structures are susceptible to suffer large temperature fluctuation. Here, a method to reconstruct 3D truss structures is developed to obtain large positive, zero and even negative coefficient of thermal expansion (CTE). As the basis, theoretical analysis and numerical verification of the bi-material pyramid and tetrahedron lattice cells explicitly reveal that with thick members, the influence of the cross section on the CTEs should be well considered, and the CTEs should be accurately calculated by the solid model. Furthermore, two kinds of 3D lattice structures with isotropic tailorable CTEs are originally devised. Moreover, bi-pyramid and bi-tetrahedron units are devised, and a reconstruction method, which can reconstruct an arbitrary 3D truss structures to obtain specific target CTE, is originally developed. Typical supporting structure and platform used in satellites are reconstructed by the proposed method, and near zero thermal expansion, which is urgent needed in satellite, can be flexibly obtained. The analysis and proposal of three dimensional lattice structures and reconstruction method provide a new approach to develop structures with light weight and tailorable CTEs.

Temperature Effects on Rheological Properties of Fresh Thickened Copper Tailings that Contain Cement

Cemented paste backfill (CPB) is an economic and environmental friendly technique applied in underground mining for supporting surrounding rock and replacing the pillar. However, little is known about the temperature effects on CPB in mines having a large temperature fluctuation. The main purpose of this research was to investigate the effect of temperature change on the rheological properties (e.g., shear stress and apparent viscosity) of CPB with copper mine tailings. Specifically, a series of rheological tests were conducted on 6 CPB samples using a Brookfield R/S+ Rheometer under various temperatures (2°C, 10°C, 20°C, 30°C, 40°C, and 60°C). Our results showed that both shear stress and apparent viscosity of these tailing samples increased with temperature rising from 2 to 60°C. Likewise, temperature has a significant impact on the Bingham yield stress of thickened tailings. The yield stress decreased from 122 Pa (2°C) to 112 Pa (20°C) and then increased to 152 Pa (60°C). Moreover, the pipeline transport pressure drop of CPB at various temperatures was calculated, illustrating an obvious effect on the paste pipeline transport. Compared with 20°C, the pressure drop under 2°C and 60°C increased by 11% and 22%, respectively. The results of this study indicate that the temperature plays an essential role in determining rheological properties of CPB and its engineering application in mines particularly with naturally fluctuating temperatures.

Exploring the Environmental Physiology of the Indo-Pacific Reef Coral <em>Seriatopora hystrix</em> with Differential Proteomics

Although reef-building corals are threatened by a number of anthropogenic impacts, certain scleractinian-dinoflagellate (genus Symbiodinium) endosymbioses have proven markedly resilient to environmental change. For instance, corals from upwelling habitats of Southern Taiwan withstand both short- and long-term increases in temperature, potentially due to their routine exposure to highly variable temperature regimes in situ. To gain a greater understanding of the proteomic basis for such acclimatization to unstable environmental conditions, specimens of the Indo-Pacific reef-building coral Seriatopora hystrix Dana 1846 were sampled during a period of stable temperature conditions from 1) a site characterized by frequent upwelling events in Southern Taiwan and 2) a nearby, non-upwelling control site in the Taiwan Strait. Two-dimensional gel electrophoresis followed by sequencing of differentially concentrated proteins with mass spectrometry unveiled significantly more proteins involved in the cellular stress response in coral hosts of the upwelling site. Although such stress protein signatures could be indicative of sub-lethal levels of cellular stress, especially given the relatively higher sediment loads characteristic of the upwelling site, these proteins may, in contrast, have been constitutively maintained at high levels in preparation for large fluctuations in temperature and other abiotic parameters (e.g., nutrient levels) brought upon by upwelling events.

Stability test of TCRP1201+ total station parameters and its setup

Monitoring systems utilising automated electronic total stations are an important element of controlling safety levels of numerous engineering structures. In order to ensure appropriate credibility of the obtained data, it is crucial to maintain the stability of both the parameters of the used instrument as well as of its setup. This study presents the results of research on the stability of the Leica TCRP1201+ instrument’s basic parameters and three selected tripods manufactured using different materials. In the case of the total station the inspected values included Hz-collimation, V-collimation, and tilt compensation errors. Two of the head tilt components and torsion were examined for each of the tripods. The research was carried out in three-day sessions in conditions of large temperature fluctuations. Graphs presenting the changes in the studied values were supplemented with analysis of correlation between the said changes and the changes in temperature. The conclusions section of the study includes suggestions on how to avoid the negative effects of changes in the geometry of the measuring device.

Stability test of TCRP1201+ total station parameters and its setup

Monitoring systems utilising automated electronic total stations are an important element of controlling safety levels of numerous engineering structures. In order to ensure appropriate credibility of the obtained data, it is crucial to maintain the stability of both the parameters of the used instrument as well as of its setup. This study presents the results of research on the stability of the Leica TCRP1201+ instrument’s basic parameters and three selected tripods manufactured using different materials. In the case of the total station the inspected values included Hz-collimation, V-collimation, and tilt compensation errors. Two of the head tilt components and torsion were examined for each of the tripods. The research was carried out in three-day sessions in conditions of large temperature fluctuations. Graphs presenting the changes in the studied values were supplemented with analysis of correlation between the said changes and the changes in temperature. The conclusions section of the study includes suggestions on how to avoid the negative effects of changes in the geometry of the measuring device.

A hybrid strain and thermal energy harvester based on an infra-red sensitive Er3+ modified poly(vinylidene fluoride) ferroelectret structure

In this paper, a novel infra-red (IR) sensitive Er3+ modified poly(vinylidene fluoride) (PVDF) (Er-PVDF) film is developed for converting both mechanical and thermal energies into useful electrical power. The addition of Er3+ to PVDF is shown to improve piezoelectric properties due to the formation of a self-polarized ferroelectric β-phase and the creation of an electret-like porous structure. In addition, we demonstrate that Er3+ acts to enhance heat transfer into the Er-PVDF film due to its excellent infrared absorbance, which, leads to rapid and large temperature fluctuations and improved pyroelectric energy transformation. We demonstrate the potential of this novel material for mechanical energy harvesting by creating a durable ferroelectret energy harvester/nanogenerator (FTNG). The high thermal stability of the β-phase enables the FTNG to harvest large temperature fluctuations (ΔT ~ 24 K). Moreover, the superior mechanosensitivity, SM ~ 3.4 VPa−1 of the FTNG enables the design of a wearable self-powered health-care monitoring system by human-machine integration. The combination of rare-earth ion, Er3+ with the ferroelectricity of PVDF provides a new and robust approach for delivering smart materials and structures for self-powered wireless technologies, sensors and Internet of Things (IoT) devices.

Warm northern river temperatures increase post‐exercise fatigue in an Arctic migratory salmonid but not in a temperate relative

Abstract The Arctic is warming at twice the global average rate; how native and non‐native anadromous fishes will respond remains largely unknown. Some native Arctic salmonids are already experiencing warm (>21°C), physically challenging migratory river conditions and large diurnal temperature fluctuations (>10°C). We conducted field and laboratory experiments to determine how these extreme conditions may affect the capacity for migration in Arctic and temperate salmonids. In adult migratory Arctic char, reflex impairment following a handling challenge increased with temperature, indicating more extensive fatigue. In Arctic char smolts, temperature did not affect initial critical swimming performance (Umax1), however, there was a threshold for repeat swimming performance (Umax2) near 20°C, above which recovery was impaired. Following a simulated diurnal warming scenario (11–21°C), Umax1 increased in rainbow trout and remained constant in Arctic char as in the field while Umax2 remained constant in rainbow trout it was drastically reduced in Arctic char. Furthermore, at warm temperatures, Arctic char were unable to recover to routine levels of oxygen uptake after exercise, while rainbow trout were. Warming also had more pronounced effects on blood composition and plasma glucose and lactate concentration in Arctic char than in rainbow trout. In general, rainbow trout, a temperate salmonid, had superior swimming performance, aerobic capacity, and warm tolerance than Arctic char, an Arctic salmonid. The present flow and temperature regimes in some Arctic rivers may restrict migration of native salmonids by limiting their ability to recover from fatiguing exercise. Non‐native, temperate salmonids are likely better suited to overcome these particular physical and thermal challenges. A plain language summary is available for this article.