Search

A flow microcalorimeter operating in mixing mode generates a type of “continuous titration” when one of the feeding pumps is connected to a continuous gradient generating device. The proper correction of the instrumental signal for the thermal lag of the calorimeter can be performed by chemical calibration, through an evaluation of the parameters of Tian's equation, modified for the microcalorimeter. This equation relates the instrumental signal to the actual power developed by the reaction. This paper shows how a continuous exponential gradient method can be applied to the determination of the enthalpy changes of metal-ligand-proton equilibrium reaction in solution. The enthalpies obtained for the protonation of D-cycloserine and for the formation of CuL and CuL2 complexes in the Cu(II)-Glycine system are in substantial agreement with published values. The computer programs, in BASIC language on an IBM-XT PC, used to process gradient data, are presented.

Differential scanning calorimetry (DSC) was used to study the effect of chlorine treatment of wheat flour on the heat of gelatinization of the wheat flour and starch. The DSC thermograms were corrected for heat capacity changes and thermal lag. An endothermic transition occurred in both flours and starches at a temperature commonly associated with starch gelatinization. The enthalpy (ΔH) for the starches was concentration dependent. The chlorine treatment did not affect significantly the transition temperatures nor enthalpies of either the flour or the starch isolated from it. Addition of sucrose delayed the onset of gelatinization and increased the ΔH for both treated and untreated wheat flours and starches.

A comparison is made between the performance of constant‐current (C.C.A.) and constant‐temperature (C.T.A.) anemometers in measuring various characteristics of turbulence in supersonic flows. The two systems are comparable, with regard to the bandwidth and to the signal‐to‐noise ratio, provided that the overheat is not too low in the case of the C.T.A. system, and that suitable corrections be applied to the C.C.A. system. Besides, the two types of apparatus are similar in that their use is very time consuming, a separate adjustment being required for each point of measurement in the flow and each overheat, especially adjustment of the C.T.A. bandwidth, using a sine wave technique, and adjustment of the thermal lag compensating circuit of the C.C.A. system. They differ in that rigorous corrections, dealing for example with electrical noise and insufficiency of the bandpass, are more easily determined in situ and applied with the last system, while the former is better adapted to rapid measurements in blow‐down facilities, or when only high overheats are required. As for the level of the electronic noise, it seems to be equivalent in the two systems. Besides, when turbulent intensities and spectral densities are measured in a continuously running tunnel, the results are more reliable if they are obtained with the C.C.A. system, except for measurements of transverse fluxes of heat or momentum performed using an inclined hot wire. Hence the two types of apparatus appear to be complementary.

In order to evaluate and implement a widely used DSC method for purity determination, a commercial thermal analysis instrument was “interfaced” by means of an analog-to-digital converter and a communication terminal to a time-sharing computer. A computer program specifically designed for this system evaluates data for calibration purposes or calculates the purity. The program includes steps to detect the peak opening and closing, determine the area, evaluate the partial energies at various temperatures, linearize the 1/ F vs. T plot, and calculate mole % purity. The analysis (or calibration) proceeds without intervention, or at the operator's control, provides complete versatility by accommodating a choice of instrumental or computational factors, including thermal lag, heat capacity, iteration increment, and the portion of the curve (1/ F limits) to be considered. This automated and computerized system permits data accumulation and rapid purity calculation without human error, facilitating the systematic evaluation of theoretical and practical factors in the determination of purity.

Techniques for measuring the enthalpy change during isothermal aging of polymer glasses are discussed. Critical analysis of conventional scanning calorimetry reveals that its accuracy may be suspect under certain circumstances due to the thermal lag inherent in a temperature scanning experiment. An additional problem is that the conventional technique is restricted to certain kinds of paths for reaching the aging temperature. It is proposed that both problems can be overcome by analyzing the output of a scanning calorimeter not only during steady heating but also during the transients at the beginning and end of a heating scan. This data analysis method represents an extension of a method used previously by others in accurate measurements of the much larger heat of fusion of crystalline polymers. Practical feasibility of the improved technique is demonstrated by preliminary measurements of enthalpy relaxation during aging of well-characterized polystyrene at 80°C. In particular, the initial departure from equilibrium of a glass prepared by 5°C/min cooling from the liquid state is found to be 6.9 ± 0.6 J/g. This measured value agrees with a value calculated on the basis of the glass transition temperature corresponding to 5°C/min cooling and heat-capacity data from the literature.

Experiments were performed to study the effects of using a thermal storage-mass to enhance woodstove combustion-efficiency. The relation between thermal storage-mass spacing and combustion-zone temperature has been established. The results demonstrate that mass enhances combustion-efficiency. The stove may be operated at high temperatures that reduce pollution. Combustion-efficiency enhancement is inversely proportional to the mass spacing. The added mass moderates the frequency of room-temperature fluctuations without imposing a significant thermal lag, while providing a safety shield. However, use of the mass may cause a slight increase in energy consumption.

This paper examines methods of measuring the thermal time constants of reptiles under ramp-function conditions. It is found that the “thermal lag” method, previously reported in the literature, can be used only under certain very limited conditions. A second method, referred to as the “ramp-compensation” method, is introduced and shown to be superior in many ways, particularly in telemetric applications.

The thermal status of an animal is the result of a combination of physical and physiological factors. In poikilotherms, it may be possible to separate these more easily than in homeotherms, where the presence of control mechanisms can mask the processes occurring. The thermal time constant of a poikilotherm has been shown to be a useful measure of its thermal behaviour, and to vary with the physiological status of the animal. A simple model is developed to show how the thermal time constant is related to the physics of heat exchange. The derived thermal time constant is shown to scale as body mass raised to the power 2/3, and this is compared with results on lizards heating and cooling in water, taken from the literature. When heat exchange in air is considered, the concept of boundary layer resistance leads to a useful simplification. The thermal time constants in air taken from the literature show that the boundary layer resistance is approximately constant.

An increasing number of interesting new heterojunction structures rely on compositional gradients rather than abrupt heterojunctions. The use of rapid shuttering with a variable duty cycle is currently the most commonly used way of achieving the desired grading in molecular beam epitaxial (MBE) growth since thermal source ramping to achieve such grading suffers from problems of thermal lag and non-steady-state temperature distributions in the evaporation sources. In this work, we get around these obstacles by using reflective high energy electron diffraction (RHEED) oscillations to measure actual compositions during trial gradings and then use rhis direct data to fine tune the thermal ramps to achieve the desired compositional profile. The result is a graded layer with a precise reproducible profile grown without the complications of multiple interfaces and possible non-linear effective average properties inherent in the rapid shuttering Technique. These layers can then later be inserted during actual growth runs within more complex structures.

The authors attempted to clarify, compare, and contrast some previously unpublished difficulties encountered in the operation of deep-level transient spectroscopy (DLTS) systems, and describe corrective measures where applicable, including instrumentation and deep level anomalies which may affect capture cross section designations, such as pulse squaring and degeneracy factor effects. Thermal lag between sample and sensor has been demonstrated to cause the apparent peak temperatures of deep levels to be in error by several degrees. In addition, analysis of deep level data from a single Delta C-vs.-T plot has been achieved from half-peak-height points of the graph, for use where no other data are available from the sample under test. Trap depth determination from a single thermal scan of fragile Schottky barriers was considered. >

The temperature distribution of an outer wall of an internal space subjected to the solar radiation goes through a transient state until it reaches its final thermal equilibrium state. The temperature profiles on the wall cross-section and the time lag needed to reach thermal equilibrium depend on the structural characteristics of the wall and on the thermal parameters of the space-environment system. In the present work, analytical expressions yielding the duration of the transient state as a function of the thermal and structural characteristics, have been developed.

1. An adhesive bond between a strain gauge and the measured object can be formed by direct vacuum depsition of the sensitive layer on the object. 2. Replacement of the viscoelastic glue layer by an adhesive direct-deposition bond affords several advantages for strain gauge measurements: a higher conversion coefficient, reduced moisture sensitivity, increased range and stability of high-temperature measurements, and eliminates the effect of the gauge on the object deformation. The very low thermal lag of such a gauge is especially useful for measurements in nonstationary heating conditions. 3. Direct deposition of the strain gauge on the object with the aid of integrated-circuit technology makes it possible to reduce the gauge base and the grid dimensions by one to two orders of magnitude in comparison with commercial glued-on strain gauges, while improving the accuracy of their positioning on the object.

The effect of a spatial variation of the thermal conductivity on the magnitude of the maximum tensile thermal stress in a solid circular cylinder subjected to sudden convective heating was calculated by finite element methods. The general results show that by lowering the thermal conductivity in the surface region of the cylinder, the magnitude of the maximum tensile thermal stress at the center of the cylinder is reduced significantly. The negative temperature dependence of the thermal conductivity in dielectric materials, which indirectly creates a spatial variation in thermal conductivity, also causes a significant decrease in the magnitude of the tensile thermal stresses, as demonstrated by a numerical example for aluminum oxide. It is also shown that a spatial variation in thermal conductivity can significantly affect the time to maximum tensile stress as well.

An increase in the accuracy and precision of thermal diffusivity (α) was observed when estimated from thermal process data using the analytical heat conduction equation as compared to using the process fh value. Differences in α for the two methods ranged from 2.4 to 3.5%. Correcting for the presence of the thermocouple probe became more important with smaller can sizes. The analytical solution to the heat conduction equation proved to be a very sensitive model with regard to prolonged retort come-up time and heat conduction along the thermocouple probe.

We have employed a heat-pulse technique to study thermal properties at low temperatures. In the course of these studies we have identified a number of significant aspects of thermal transients which are not normally taken into account. These include finite-time effects for thermal diffusion, a modified equation in the presence of boundary scattering, and the role of thermal boundary resistance at the sample holder. We have used a steady-state, two-heater thermal conductivity measurement in conjunction with the heat-pulse studies to elucidate the latter effect. The result is that pulse measurements using a single thermometer can be used to determine both the boundary resistance and the heat capacity and thermal conductivity of a sample.

FromKing's linear equation a simple and universally valid expression for the sensitivity of hot-wires is derived.King's complete equation differs from the linear one by two correction terms, one of which is neglected as small. Using a result derived from the linear equation, the complete equation and its derivative are linearized. From this corrections are derived which are rather widely valid and which, when applied to the results obtained from the linear equation, lead to the more accurate ones corresponding toKing's complete equation. The measurements necessary to obtain the data for these corrections for a given kind of wire are easily made in still air without forced heat convection. The relation between pressure and temperature which in air influence the measurements without flow are explained on the basis of experimental results in connection with the similarity law for heat transfer by free convection. The curves given include the influence of the heating circuit upon the sensitivity and the thermal lag of the hot-wire.

Changes of length of a lead rod due to thermal expansion have been measured between 4.2° k and 10° k by a heterodyne-beat method in which the changes modify the capacity of a condenser in a resonant circuit. The variation with temperature of the Gfuneison constant y was deduced; the accuracy was just insufficient to show up the jump in thermal expansion coefficient at the superconducting transition.

This paper investigates the burning-rate response of a condensed-phase fuel plate adjacent to a reacting gaseous boundary layer, where the external flow has a longitudinal oscillation. The purpose is to simulate the unsteady droplet burning in a liquid-propellant rocket and to try to isolate a physical mechanism which leads to instability. The nonsteady process treated here is the heat transfer in the condensed phase. The results show that the velocity-sensitive responses exhibit resonant phenomena at the proper frequency range, and indicate that, in favorable conditions, a liquid-propellant rocket can be driven to instability because of the thermal lag in the droplets. Experiments to test this theory, and remedies to this type of instability, are suggested.

A brief history of solar stills in Chile is presented. Theoretical studies of solar stills in that country are described. These deal with efficiency, thermal balance, thermal intertia, thermal capacity, thermal conductance, thermal lag and distillation lag with regard to solar irradiation maximum, and time constant. Chilean solar still designs with evaporating trays of wood, metal, cement, and plastic, and evaporating cloths of various designs have been tested by the authors. Tests were made with glass and plastic covers in the Solar Energy Laboratory of the Universidad Santa Maria (Valparaiso) and in the Atacama Desert (Quillagua). Their purpose was to make theoretical predictions of still characteristics under different environmental conditions.

The coefficient of thermal expansion of a fluid can be measured by determining the critical temperature difference for the onset of thermal convection in a fluid layer heated from below. This method is particularly useful for fluids of very low thermal expansion because its accuracy is independent of the magnitude of the thermal expansion. It is easily adapted to measurement at elevated pressures. Accuracy of 0.5% is obtainable with care.

By use of the time-dependent diffusion equation it is shown that a heat-balance equation for an evaporating raindrop based on the “quasi-stationary” assumption (∂//t = 0) is accurate. This equation is then used to obtain the expression T = θw + zRdθw/dz for the steady-state temperature T of an evaporating drop in an atmosphere having linear vertical gradients of temperature and relative humidity, where θw is the equilibrium drop temperature in a uniform atmosphere (approximately the environmental wet-bulb temperature), dθw/dz is its vertical gradient, and zR is the thermal relaxation distance of the drop (falling at terminal velocity). The term zRdθw/dz is the thermal lag in the drop's response to the varying environment. Computations show that the ratio of the drop evaporation rate with the tag term to the rate without the tag departs significantly from unity for large drops and high humilities.

The problem discussed in this paper arose out of the need for accurately determining the temperature of a barometer under conditions of varying air temperature. A method for computing the thermal lag of simple and complex bodies of cylindrical form, when the ambient temperature is changing steadily, is given and formulae derived for determining the lagging times of such bodies in liquid and in gaseous media. Values calculated from the formulae are compared with results obtained experimentally.

In view of the complexity of the exact solution to the variational problem of constructing an optimum nozzle for gas-particle flow (see, for example, [1]) its solution in the one-dimensional approximation is of interest. In certain studies of this sort, by Marble [2] and Sternin [3], in addition to the assumption of one-dimensionality, an important role is also played by additional assumptions of smallness in the differences of the gas and particle velocities (and temperatures), which characterize the dynamic and thermal lag. The resulting linearization, used in [2, 3], not only narrows still further the region of validity of the one-dimensional approximation, but also leads to certain qualitative characteristics which do not correspond to the actual flow. For example, it is found [3] that variation of the contour curvature at only a single point may yield a finite thrust increment.

Since the results of the measurement of the X-ray-excited radioluminescence as a function of temperature (Part I of this paper) of TL dosimetry materials were difficult to interpret in terms of quenching of thermoluminescence, the direct measurement was made of the TL light sum and the glow-peak height as a function of heating rate. In order to overcome the problem of thermal lag between the heating planchet and the phosphor, a method was developed to achieve a high degree of thermal coupling by mixing powdered phosphor and gold and pressing the mixture to the surface of a gold disk. The glow curves from these gold plaques were recorded with a reader that produced heating programs which were linear to a few percent from rates of 4°C/min up to 640°C/min. By this technique glow-peak heights and light sums were measured for CaF2:Mn, natural fluorite, LiF(TLD-100), CaSO4:Mn, Li2B4O7:Mn, and terbium-activated lithium aluminosilicate glass over the full range of heating rates. Considerable variability was found in the thermal quenching characteristics of the various phosphors. All but the fluorite and the Li2B4O7:Mn showed some decrease in light output at high heating rates. LiF exhibited a decrease for low heating rates as well, with a broad maximum in the light output at about 100°C/min.

T USE of metallic fuel constituents in modern rocket engines has brought attention to nonequilibrium aspects of two-phase nozzle expansion processes. Since condensed metal oxide combustion products (which comprise 30 to 40% by weight of the total products of contemporary solid rockets) can do no expansion work, their presence in the rocket nozzle can only be deleterious to the effectiveness of the nozzle expansion process in converting thermal to kinetic energy. The condensed particles are accelerated in a nozzle almost exclusively by drag forces associated with lag or slippage of the particles relative to the expanding gas. Some performance loss relative to the calculated ideal no-slip expansion process must always be associated with macroscopic size particles, and experience has shown that the magnitude of the loss increases with the weight fraction of particles. Significant velocity and thermal lags thus have been suspected as a prime cause of rocket performance losses, and a number of studies have been directed toward delineation of the mechanism and magnitude of these lag effects. Early studies were summarized and extended in the review of Altman and Carter (l). Primarily, these early studies served to place bounds on the performance losses by examining the limiting cases of no-lag and complete lag. They demonstrated that thermal lag ordinarily has a lesser effect on specific impulse than does velocit}^ lag. Gilbert, Davis, and Altman (2) were the first to relate the losses to particle size. They solved the linear equation that results from assuming the drag force to be proportional to the velocity difference (Stokes' law) for the case of linearly accelerated nozzle gas. They demonstrated that, typically, a 1-ju diam particle follows the gas velocity closely, whereas a IQ-fj, diam particle has a significant lag. All of these early studies treated the nozzle expansion processes as though they are uncoupled, i.e., the thermal lag

Amorphous polymers thermal conductivity measured at 0.4-4 K, observing similar temperature dependences

A combined finger-plethysmograph and gradient calorimeter has been devised, especially to study cold-induced vasodilation in the finger. By using an electrical heater and a flow-heater it was shown that the thermal lag depends on thermal capacities, conductivities and temperature distribution, so that heat loss and flow are correlated only in the steady state. The actual drop of blood temperature from inflow to outflow was calculated. Results were: a) skin temperature was a better estimate of outflow than bath temperature, b) with general vasodilation, the inflow temperature was close to deep body temperature, but c) with vasoconstriction, digital arterial temperature might be as low as 14°C, and the calculated minimum blood flow (Greenfield) 70% too low. Plethysmography was possible during the hunting reaction in spite of a 30% decrease in venous distensibility. When the subject was cold, blood flow and heat loss, both in constriction and dilation phases, were reduced two or three times, probably due to the increased viscosity of blood. Submitted on August 3, 1959

In the previous part of the paper (1)' we discussed the fundamentals of cooling of a hot-wire and proposed a methed to compensate its thermal lag. Then in this paper, taking foundation on these theoretical results, we will show several methods to measure turbulent velocity fluctuations. We use the same symbols as in the previous paper (1) .

IN MISSILE applications, electric equipment is required to function for a relatively short period of time in a hot ambient atmosphere, but is deprived of external cooling media such as air or oil. The dependability of the equipment depends on its ability to absorb its own heat losses or to transmit these losses by conduction to cooler surroundings. The general purpose of this paper is to present a method for predicting simultaneously the transient temperatures in two heat-generating solids such that both materials store some heat, while some heat is transmitted from one to the other and thence possibly to a third region at a fixed temperature. In particular, mean transient temperatures are predicted in the field winding and laminations of an a-c generator which is bolted to a support, but otherwise insulated from the ambient atmosphere. Application of this method to temperature prediction in solid-state devices is natural.

An experimental investigation of the characteristics of thermistors, when used as anemometers, has been made. The various modes of operating thermistor micro-anemometers are studied, and the sensitivity and errors discussed. A variable-temperature, variable-speed wind tunnel was constructed for this investigation, to determine the power dissipated in the thermistor as a function of wind speed, wind direction, and air temperature. The thermal lag of the thermistor to environmental changes was studied. It was concluded that operating the thermistor at constant resistance, by means of a specially designed bridge, showed the greatest promise in that this mode of operation was the most sensitive to wind-speed changes, the least sensitive to ambient-temperature changes, and eliminated lag to a great extent. Operated at constant resistance, the lag time of the response of the thermistor to a “step-function” air-speed change was about 0.085 sec, the error in air-speed indication due to a degree change in...

A two-velocity and two-temperature model is considered for a continuous medium in relation to the flow of a mixture of gas and particles in the subsonic, transsonic, and supersonic parts of a Laval nozzle. It is assumed that the particles are small, and hence that the coefficients ϕf and ϕq, which define the interaction with the gas, are large (these coefficients are inversely proportional to the square of the particle radius for a Stokes mode of flow). This means that the velocity or thermal lag of the particles relative to the gas is small. The solution is sought as expansions with respect to the small parameters ɛ1=1/ϕf and ɛ2=1/ϕq.

The theory of programmed temperature gas chromatography, particularly in relationship to the spreading of peaks as measured by the plate height is expanded. The significance of the plate height in programmed temperature operations is examined. The close relationship of this with - the plate height in isothermal chromatography is discussed. Two phenomena which are unique to the programmed methods are treated theoretically. First is the zone compression at the head of the column which is a result of temperature being initially low followed by continual heating. Second is the effect of thermal lag which is responsible for a higher zone velocity at the wall than at the center of the column. This effect is treated in terms of the nonequilibrium theory which was developed for various plate height calculations in chromatography.

A method for measuring the thermal characteristics of natural rocks at low temperature is developed. The advantage of the experimental technique is that both thermal conductivity and thermal diffusivity are obtained from the same run by interpreting two parts of the temperature profiles. The quasi-steady state is used for thermal conductivity, and the thermal diffusivity is obtained from the asymptotic transient state (Fourier transient state).

The aim of this paper is to evaluate the thermal behaviour of a massive building during summer period. Experimental investigations were carried out on “ Caserma Gaetano Abela ”, an historical building located in Siracusa (Italy). The researchers have investigated the variation of both walls and indoor air temperatures in two rooms located on the east and west-facing sides. Two different experimental set-up were conducted, the first without allowing nocturnal ventilation, while the second with nocturnal ventilation obtained by opening the windows from 8:00 pm to 8:00 am. Based on the measurements of several physical parameters, the thermal lag and the decrement factor were calculated for the two ways of building ventilation management. The thermal comfort in the two offices was evaluated using the PMV and PPD indices. Results show that the high thermal inertia mass combined with natural ventilation reduces the indoor temperature during the nocturnal period, however the passive strategies resulted insufficient to obtain thermal comfort conditions during the following daytime hoursic correction. Globally it is possible to obtain an improvement of RT 60 from 7.3 to 2.5 s at 1 kHz and STI increases from 33.0% to 40.0%, at 1000 Hz.

The problem of computing the area under the thermodilution curve to determine the cardiac output by the thermodilution method is discussed. The circuit of an analog integrator is developed that outputs continuously a current area value. Recommendations for the choice of main integrator elements and methods of computing the cardiac output with the analog integrator are given. Two thermosensitive probes with different thermal lag have been tested by using a physical model of the circulation system, and some experimental results are presented. When defining the integration threshold for the area under the thermodilution curve the thermal lag of the probe should be taken into consideration.

Thermal compensation of quartz SAW oscillators through electronic control of a phase shift element in the feedback loop has been demonstrated as a promising technique to obtain significant improvement over the usual ST-cut stability. tion of several design considerations limiting ultimate compensation accuracy is presented. SAW delay line these include deviations from the theoretically predicted parabolic temperature dependence as a result of mounting-induced crystal strains, surface moisture, and multiple acoustic signal interference. factors which limit the ability to produce a parabolic phase shift versus temperature that exactly mirrors the SAW dependence are discussed including thermal lag and undesired phase variations with temperature of the electronic components. An examinaFor the

Kinetics is of fundamental importance in the understanding of the mechanism of thermal decomposition of high polymers. Since most thermal decomposition reactions are associated with weight changes, thermogravimetry is being employed to a great degree in kinetic studies of polymer decomposition. Two approaches are commonly used to obtain the various kinetic Chapaumeters of these reactions. The static method or “isothermal thermogravimetry” produces precise weight loss curves for various single temperatures as a function of time. Thus the rate Chapaumeters are obtained directly. This method is inherently time consuming and the results are sometimes questionable due to experimental uncertainities arising from the initial thermal lag of the sample. More recently, “dynamic thermogravimetry” data has been used for kinetic studies. In these, a single weight loss curve obtained by means of programmed heating is used to provide information equivalent to an entire family of isothermal weight loss curves. The new approach is time saving, being able to cover a wide range of temperatures in a relatively short time. For this work the kinetics evaluation procedure by Freeman and Carroll1 and its extension by Anderson and Freeman2, is applied to dynamic thermogravimetric data in order to evaluate the rate Chapaumeters.

During the 50-year history of laboratory and atmospheric experimental turbulence studies the preferred method of detecting small scale velocity and temperature fluctuations has beeen to observe the fluctuations in resistance of small elements which are temperature sensitive, such as platinum wires and films or metal oxide thermistors. Large electrical heating of such elements causes them to be sensitive to fluctuations in fluid velocity since the temperature, and therefore resistance, depends on the convective heat transfer. If the electric current through the sensing element is small, its temperature will adjust to the fluctuating ambient value, although with the thermal lag depending on the size of the element, the thickness of the fluid boundary layer, and their thermal diffusivities.

A sample cell, capable of supporting standard 13 mm diameter pressed pellets, and suitable for mounting in a commercial cryostat, has been constructed of Invar, and fitted with two thermocouple sensors for operating in the range 4.2 < T < 300 K. The thermal lag between the temperature of the experimental sample and the sensor reading has been determined by monitoring four phase changes in covalent solids which can be used as "infrared thermometers". In the temperature range 77 < T < 300 K this thermal lag is less than 0.5 degrees.

A portable version of the algorithm for finding the maximum of Gaussian-Markov weather variates has been obtained employing cubic B-splines. Efforts to model and predict equipment response to temperature modified by the thermal lag of the equipment are described. (Author)

All parts of plants have temperatures determined by their environmental conditions. The energy status of a plant or a plant leaf is manifested by its temperature. The leaves and stems of plants have small masses and are generally of low heat capacity. Because of this, the temperatures of these plant parts respond quickly to changes of environmental conditions. Trunks of trees, tree limbs, and other massive plant parts have much greater heat capacities and respond slowly to environmental variations, sometimes with a thermal lag of several hours, as shown in the study of tree trunks by Derby and Gates (1966).

Heat flow rates through 60-mm-thick rigid mineral fiber insulation mounted in the flat roof of an outdoor test facility were measured with heat flux transducers. The temperature differences across the insulation were measured simultaneously with thermocouples. Three different analytical procedures were used to calculate the thermal conductance of the insulation: (a) the ratio of heat flow rate to temperature difference; (b) the slope of heat flow rate as a function of temperature difference and mean temperature; and (c) transfer functions. The results obtained with these three methods are compared. The effect of ignoring thermal lag was estimated for the first two methods., Proceedings of a Symposium on Building Applications of Heat Flux Transducers: 22 September 1983, Philadelphia, PA, USA

REPTILES reportedly possess physiological mechanisms for the increase or decrease in the rate of heat exchange with their environments. This the animal could do by changing either its metabolic rate or its effective insulation. Both sorts of mechanisms have been postulated responsible for this capability.

Conventional structural cables (wire ropes) are composed of steel wires helically wound into strands that are then wound around a core. Cables made from shape memory alloy (SMA) wires are a new structural element with promising properties for a broad range of applications. Among the many potential advantages of this form are increased bending flexibility for spooling/packaging, better fatigue performance, energy absorption and damping, reduced thermal lag, redundancy, and significant design flexibility. Currently there are few studies of SMA cables in the literature. This paper describes exploratory thermomechanical experiments that were performed on two commercially available cable designs.