scholarly journals The Influence of Thermal Protection on Winter Den Selection by Porcupines, Erethizon dorsatum, in Second-Growth Conifer Forests

2005 ◽  
Vol 119 (2) ◽  
pp. 159
Author(s):  
Todd N. Zimmerling
Keyword(s):  
Selection Criteria ◽  
Thermal Protection ◽  
Energetic Cost ◽  
Ambient Conditions ◽  
Erethizon Dorsatum ◽  
Ambient Temperatures ◽  
Type Selection ◽  
Second Growth ◽  
Lower Critical Temperature ◽  
Thermal Cover

I investigated den type selection by Porcupines (Erethizon dorsatum), in relation to the thermal cover provided by the den type, over a period of four winters. Porcupines used log dens, stump dens and rock dens in proportion to the thermal cover provided by each den type. Based on behavioural observations of Porcupines, I assumed that the lower critical temperature for porcupines in my study area was -4°C. Both stump and rock dens provided adequate thermal protection, under most ambient conditions, to allow Porcupines to maintain their body temperature, without increasing basal metabolic rate. In most cases rock and stump dens maintained den temperatures above -4°C until ambient temperatures reached -12°C or lower. In contrast log dens provided poor thermal protection, even in years of thick snowcover. When ambient temperatures dropped below -4°C, den temperatures within log dens were also recorded below -4°C. Log dens were used least often by Porcupines, whereas stump and rock dens were used most often. Despite the large number of potential dens available to Porcupines within the study area, den use was generally limited to three dens per porcupine per winter. The limited use of dens by an individual porcupine during winter may be related to the energetic cost of finding a new den or it may be related to specific selection criteria used by Porcupines.

Using Thermoelectric Cooling With Tourniquets for Nerve Preservation

2016 ◽  
Author(s):  
M. Trupiano ◽  
S. Aarabi ◽  
A. F. Emery
Keyword(s):  
Thermal Conditions ◽  
Ambient Conditions ◽  
Transfer Coefficients ◽  
Thermoelectric Coolers ◽  
Ambient Temperatures ◽  
Nerve Preservation ◽  
Heat Transfer Coefficients ◽  
Surface Temperatures ◽  
Element Simulation ◽  
Free And Forced Convection

The use of a tourniquet leads to nerve damage, even if applied for short periods of time. This damage can be minimized if the limb is cooled. Because of the low conductivities of human tissue, core limb cooling is slow unless the surface temperature is very cool. Subzero surface temperatures can lead to skin injury (i.e., frostbite). Ideally one would adjust the limb surface temperatures as a function of time to maximize the cooling rate while avoiding permanent tissue damage. One possible approach is to use a thermoelectric cooler (TEC) in conjunction with a programmable power supply. TEC performance varies strongly with heat absorption rate, a function of limb thermal properties, and hot side temperatures that are strongly affected by the surface conditions on the hot side, i.e., overall heat transfer coefficients and ambient conditions. The paper describes the use of finite element simulation to predict the usefulness of using thermoelectric coolers applied to the surface of a limb when compared to the standard approach of using ice packs. Since the TEC performance is strongly influenced by its warm side thermal conditions, experimental results are presented for different ambient temperatures, free and forced convection, and evaporation of water from a wickable covering.

scholarly journals Performance Analysis of Heat Pump Dryer with Unit-Room in Cold Climate Regions

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3125 ◽  
Author(s):  
Yuan ◽  
Lin ◽  
Mao ◽  
Li ◽  
Yang ◽  
...  
Keyword(s):  
Heat Pump ◽  
Ambient Air ◽  
Open Loop ◽  
Cold Climate ◽  
Coefficient Of Performance ◽  
Ambient Conditions ◽  
Total Energy Consumption ◽  
Ambient Temperatures ◽  
Moisture Extraction ◽  
Modelling System

This study presents the development and evaluation of a novel partially open-loop heat pump dryer with a unit-room (HPDU). The unit-room was designed to enable the ambient air to be mixed with the return air, thereby reducing the influence of the ambient air on the system performance, while maintaining a high system thermal efficiency. A modelling system for the HPDU was developed and validated based on a real-scale experimental study. By using the modelling system, the system characteristics under different ambient conditions and bypass factors were analyzed. The energy benefit of the proposed HPDU was quantified through a comparative study with a closed-loop heat pump dryer (CHPD). It is evident that a maximal specific moisture extraction rate (SMER) and a minimal total energy consumption (TEC) existed when changing the bypass factor of the HPDU under certain ambient temperatures. Compared to the CHPD, the coefficient of performance (COP) of the HPDU increased by up to 39.56%, presenting a significant energy benefit for the application of HPDU.

scholarly journals Thermally induced torpor in fullterm lizard embryos synchronizes hatching with ambient conditions

2006 ◽  
Vol 2 (3) ◽  
pp. 415-416 ◽  
Author(s):  
Rajkumar Radder ◽  
Richard Shine
Keyword(s):  
Environmental Conditions ◽  
Low Temperatures ◽  
Access To Information ◽  
Ambient Conditions ◽  
Thermally Induced ◽  
Ambient Temperatures ◽  
Ground Conditions ◽  
Soil Temperatures ◽  
Bassiana Duperreyi ◽  
Do So

Eggs inside an underground nest have limited access to information about above-ground conditions that might affect the survival of emerging hatchlings. Our measurements of heart rates of embryos inside the intact eggs of montane lizards ( Bassiana duperreyi , Scincidae) show that low temperatures induce torpor in fullterm embryos, but do not do so during earlier embryogenesis or later, post-hatching. Because above-ground conditions affect soil temperatures, this stage-dependent torpor effectively restricts hatching to periods of high ambient temperatures above ground. Torpor thus can function not only to synchronize activity with suitable environmental conditions during post-hatching life (as reported for many species), but also can occur in embryos, to synchronize hatching with above-ground conditions that facilitate successful emergence from the nest.

Transport near a vertical ice surface melting in saline water: some numerical calculations

1982 ◽  
Vol 117 ◽  
pp. 379-402 ◽  
Author(s):  
Van P. Carey ◽  
Benjamin Gebhart
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Flow ◽  
Saline Water ◽  
Interface Temperature ◽  
Ambient Conditions ◽  
Interface Motion ◽  
Ambient Temperatures ◽  
Thermal Buoyancy ◽  
Ice Surface ◽  
Layer Flow

Computed numerical results are presented for the laminar buoyancy-induced flows driven by combined thermal and saline transport near a vertical melting ice surface in saline water. Results are presented which indicate that conventional boundary-layer flow occurs for some combinations of ambient salinity and temperature in the ranges 0 to 31‰ and −1 to 20°C, respectively. These conditions are very common in terrestrial waters. The analysis used herein is the first to model fully the many complicated aspects of these flows. The present analysis includes simultaneous transport of salt and thermal energy as well as the effect of interface motion. The formulation uses the most recently available transport properties and a very accurate equation of state for the density of pure and saline water. The interface temperature and salinity, which are not known a priori, are here determined jointly from the transport equations, and from species-conservation and phase-equilibrium relations at the ice surface. At low ambient temperatures, the flow is found to be dominated by the upward saline buoyancy, resulting in upward flow. However, at high temperatures and low salinities, the downward thermal buoyancy overcomes the upward saline buoyancy near the surface to cause downward flow. For choices of ambient conditions between these extremes, the opposing saline and thermal buoyancy are about equal in strength. The resulting tendency for bi-directional flow at these intermediate circumstances caused numerical stability problems which made it impossible to obtain convergent solutions for some cases. However, calculated solutions were obtained at ambient salinities below 5‰, for ambient temperatures between 8 and 20°C, and at temperatures below 4°C, for ambient salinities between 0 and 31‰. These solutions indicate the limits of the range of conditions for which laminar boundary layer flow occurs. They further suggest that outside these ranges, the flow may be laminar and bi-directional. The very strong buoyancy which characterizes some of these conditions suggests that they may become turbulent at short downstream distances. The computed results are seen to be in excellent agreement with the limited experimental data and observations of previous studies.

Investigation Of Pozzolanic Binders Using Sulpho-Calcic Fly Ashes

1988 ◽  
Vol 136 ◽  
Author(s):  
J. Pera ◽  
A. Sadr Momtazi ◽  
J. Dejean
Keyword(s):  
Blast Furnace Slag ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Fly Ashes ◽  
Hydrothermal Conditions ◽  
X Ray ◽  
Ambient Temperatures ◽  
Slaked Lime ◽  
Hydrated Product ◽  
Furnace Slag

ABSTRACTBecause of their high SO3 content (∼11%), sulfo-calcic fly ashes cannot be used as a cement admixture without pretreatment. The fly ashes contain mainly quicklime (CaO), anhydrite (CaSO4) and larnite (BC2S). At ambient temperatures and at normal consistency, their hydration leads to the formation of ettringite, slaked lime and gypsum. As a result, cracking and splitting of the hydrated product quickly occurs due to the crystallization of the ettringite.The ability of these fly ashes to produce Portlandite, Ca(OH)2, led the authors to investigate pozzolanic binders by the addition of artificial pozzolans — siliceous fly ashes, slag and clay minerals — which had been calcined at moderate temperatures.The sulfo-calcic fly ashes are ground, then slaked either in ambient or hydrothermal conditions (2 or 6 hours at 130°C). In the case of slaking under ambient conditions, ettringite is quickly produced with a definitive crystallographical structure. As a result, no volume change is observed after re-hydration of the material. By comparison, autoclave slaking does not lead to this phenomenon, and only slaked lime is produced.The rate of hydration is studied through the development of compressive strength and by analyses of the products by differential thermal analysis (DTA) and X-ray diffraction (XRD) at various hydration times. The best results are obtained using calcined laterite or blast furnace slag.

Body temperature and rate of O2 consumption in Chinese pangolins

1986 ◽  
Vol 250 (3) ◽  
pp. R377-R382 ◽  
Author(s):  
M. E. Heath ◽  
H. T. Hammel
Keyword(s):  
New York ◽  
Metabolic Response ◽  
Co2 Production ◽  
O2 Consumption ◽  
Metabolic Rates ◽  
Short Term ◽  
Ambient Temperatures ◽  
Lower Critical Temperature ◽  
Manis Pentadactyla ◽  
The Relationship

Body temperatures and rates of O2 consumption and CO2 production were measured in four Chinese pangolins (Manis pentadactyla) during short-term exposures (2-4 h) to ambient temperatures (Ta) of 10-34 degrees C. At Ta less than 27 degrees C the pangolins curled into a sphere. At Ta greater than 28 degrees C the animals laid on their backs with their soft abdominal skin exposed. Rectal temperatures between 33.4 and 35.5 degrees C were recorded from animals exposed to Ta of 10-32 degrees C. At Ta greater than or equal to 32 degrees C the animals appeared to be markedly heat stressed, rate of breathing was elevated, and core temperature rose somewhat. Resting metabolic rates averaged 3.06 ml O2 X kg-1 X min-1. This is significantly lower than would be predicted from the relationship between body mass and metabolic rate established by Kleiber (The Fire of Life: an Introduction to Animal Energetics. New York: Wiley, 1975) for other eutherian mammals. The magnitude of the metabolic response to Ta below the lower critical temperature was inversely correlated to the mass of the pangolin, the slope being greatest for the smallest animals. Respiratory quotients of 0.85-1.0 were observed.

scholarly journals The effects of oscillating boundary conditions on thermal ignition

2020 ◽  
Vol 61 ◽  
pp. C45-C58
Author(s):  
Matthew Berry ◽  
Mark Nelson ◽  
Brian Monaghan ◽  
Ben Whale
Keyword(s):  
Temperature Variation ◽  
Filter Cake ◽  
Seasonal Temperature ◽  
Ambient Conditions ◽  
Ambient Temperatures ◽  
Temperature Oscillations ◽  
Seasonal Temperature Variation ◽  
Oscillating Boundary ◽  
Diurnal Temperature Variation ◽  
Ignition Times

We investigate the effect that oscillating ambient temperatures have on the ignition times of supercritical stockpiles. Large stockpiles are exposed to seasonal and diurnal temperature variation. We analyse the effects of seasonal temperature variation. When considering ignition within a year of construction, stockpiles built in spring ignited with a lower critical parameter than those built at other times. Consequently, seasonal temperature variation needs to be accounted for when predicting stockpile ignition times. References P. C. Bowes. Self-heating: evaluating and controlling the hazards. Dept. of the Environment, Building Research Establishment, 1984. R. J. Longbottom, B. J. Monaghan, G. Zhang, D. J. Pinson, and S. J. Chew. Self-sintering of BOS filter cake for improved recyclability. ISIJ Int., 59(3):432–441, 2019. doi:10.2355/isijinternational.ISIJINT-2018-627. V. Novozhilov. Thermal explosion in oscillating ambient conditions. Sci. Rep., 6:29730, 07 2016. doi:10.1038/srep29730. N. C. Roy. Convection characteristics in a closed vessel in the presence of exothermic combustion and ambient temperature oscillations. Int. J. Heat Mass Trans., 116:655–666, 2018. doi:10.1016/j.ijheatmasstransfer.2017.09.058.

scholarly journals Resource Selection by Porcupines: Winter Den Site Location and Forage Tree Choices

2001 ◽  
Vol 16 (2) ◽  
pp. 53-57 ◽  
Author(s):  
Todd N. Zimmerling ◽  
Chad D. Croft
Keyword(s):  
Resource Selection ◽  
Sitka Spruce ◽  
Size Class ◽  
Western Hemlock ◽  
Site Location ◽  
Tree Species Composition ◽  
Erethizon Dorsatum ◽  
Size Classes ◽  
Second Growth ◽  
Conifer Tree

Abstract We examined the importance of tree species composition and tree size-class distribution in determining the selection of winter den sites and forage trees by porcupines (Erethizon dorsatum). Porcupines selected winter den sites with a higher composition of sitka spruce, in all diameter size classes. However, statistically significant selection was found only for the 15.0–19.9 cm dbh size classes of sitka spruce. Porcupines displayed a statistically significant avoidance of 5.0–9.9 cm dbh and 10.0–14.9 cm dbh western hemlock trees when selecting winter den sites. When foraging around the den sites, porcupines showed a statistical avoidance of amabilis fir in all size classes and selected western hemlock, except the smallest size class (5.0–9.9 cm dbh). The results of this study indicate that porcupines do not choose winter den site locations based on the availability of preferred forage resources. Porcupines appear to choose den sites based on within-stand, patch variation in the proportion of sitka spruce and small dbh western hemlock. Forage trees are then selected, nonrandomly from specific resource categories around the den site. Porcupines in this study were found to feed on a mean of 0.54 new forage trees/day. Regression analysis revealed a positive linear relationship between new forage trees used/day and porcupine midwinter weight (y = 0.15x–0.54; r2 = 0.73). The results indicate that larger porcupines may produce a larger proportion of observed conifer tree feeding damage in second growth stands, as compared to smaller porcupines. West. J. Appl. For. 16(2):53–57.

Cooling Technique for Outdoor Electronic Enclosures Using Phase Change Materials

2000 ◽  
Author(s):  
Hamid A. Hadim ◽  
Igbal Mehmedagic
Keyword(s):  
Phase Change ◽  
Thermal Management ◽  
Heat Sink ◽  
Phase Change Materials ◽  
Theoretical Study ◽  
Peak Load ◽  
Ambient Conditions ◽  
Moderate Amount ◽  
Ambient Temperatures ◽  
Cooling Technique

Abstract A theoretical study is conducted to investigate a new cooling technique for thermal management of outdoor telecommunication equipment enclosures. The technique consists of using a phase change material (PCM) combined with a heat sink to dissipate the heat to the ambient. The main advantages of using the PCM include: fully passive technique with no maintenance, no power is required, and relatively low cost. The use of the PCM for more effective thermal management of electronic enclosures is investigated for both the high end cooling (i.e. when the enclosure is exposed to high ambient temperatures) and the low end cooling (i.e. when the enclosure is exposed to very low ambient temperatures). The results from this preliminary theoretical study showed that with the use of a moderate amount of a properly selected PCM combined with the heat sink, the temperature within the enclosure can be maintained within the specified operating range. Potential applications with the use of the PCM include: peak load usage (e.g. during high communications traffic periods), extreme ambient conditions, reduced temperature fluctuations (to improve reliability), and more efficient implementation in smaller size enclosures.

scholarly journals Unsteady Pressure Measurement in a High Temperature Environment Using Water Cooled Fast Response Pressure Transducers

1995 ◽  
Author(s):  
D. G. Ferguson ◽  
P. C. Ivey
Keyword(s):  
High Temperature ◽  
Elevated Temperatures ◽  
Thermal Protection ◽  
Dynamic Pressure ◽  
Fast Response ◽  
Ambient Conditions ◽  
Pressure Transducers ◽  
Unsteady Pressure ◽  
Temperature Environment ◽  
High Temperature Environment

Measurement of unsteady pressure is a requirement in many proposed aero-engine active control systems. In the high temperature environment associated with the engine, thermally unprotected transducers may not measure accurately or even survive. This paper reports an examination of two water cooled, commercially available unsteady pressure transducers, which assesses the ability of the transducer to accurately measure unsteady pressure when mounted in a water cooling adapter and the effectiveness of the thermal protection at high temperatures. Mounting the transducer in a cooling adapter was shown to have no adverse effect upon its ability to measure dynamic pressure. Deliberately recessing the adapter back from the flow provided the most stable and predictable output at all flow conditions tested. Thermal protection allowed the transducer to survive at flow temperatures of up to 500°C with a potential to survive at higher temperatures. No reduction in performance is shown at elevated temperatures relative to performance at ambient conditions.

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