Temperature Control Mechanism Research Articles

Computational fluid dynamics model of avian tracheal temperature control as a model for extant and extinct animals

Respiratory evaporative cooling is an important mechanism of temperature control in bird. A computational simulation of the breathing cycle, heat and water loss in anatomical avian trachea/air sac model has not previously been conducted. We report a first attempt to simulate a breathing cycle in a three-dimensional model of avian trachea and air sacs (domestic fowl) using transient computational fluid dynamics. The airflow in the trachea of the model is evoked by changing the volume of the air sacs based on the measured tidal volume and inspiratory/expiratory times for the domestic fowl. We compare flow parameters and heat transfer results with in vivo data and with our previously reported results for a two-dimensional model. The total respiratory heat loss corresponds to about 13–19% of the starvation metabolic rate of domestic fowl. The present study can lend insight into a possible thermoregulatory function in species with long necks and/or a very long trachea, as found in swans and birds of paradise. Assuming the structure of the sauropod dinosaur respiratory system was close to avian, the simulation of the respiratory temperature control (using convective and evaporative cooling) in the extensively experimentally studied domestic fowl may also help in making simulations of respiratory heat control in these extinct animals.

Performance analysis of the air-conditioning system in Xi’an Xianyang International Airport

Reducing the energy consumption of air-conditioning systems is becoming increasingly important. This paper focuses on the air-conditioning system in Terminal 3 in Xi’an Xianyang International Airport, the first airport terminal to adopt radiant cooling in China. In the large spaces of this airport terminal, a temperature and humidity independent control (THIC) system has been adopted instead of a conventional nozzle air supply method, which significantly reduces the energy consumption of the air supply. The radiant floor is the main mechanism for indoor temperature control, while a liquid desiccant outdoor air processor combined with displacement ventilation is responsible for humidity control. Ice storage is adopted to reduce operating costs, and the supplied chilled water temperature can be as low as 3°C. This paper examines the performance of the THIC system in detail. The indoor environment is determined through measurements to be comfortable, and the on-site performances of key components in both the airport terminal and the cooling plant are investigated. The outdoor air processor supplies air of appropriate temperature and humidity ratio; two kinds of radiant floors are used for temperature control, both with measured cooling capacities of about 30–40W/m2; and the energy efficiency ratio (EER) of the cooling plant is 2.62.

Does wet hair in cold weather cause sinus headache and posterior eye pain? A possible mechanism through selective brain cooling system

As a general observation, wet hair in cold weather seems to be a predisposing factor for sinus headache and posterior eye pain. We offer a mechanism through selective brain cooling system for this observation. Selective brain cooling (SBC) is a mechanism to protect brain from hyperthermia. Components of SBC are head skin and upper respiratory tract (nose and paranasal sinuses). Cool venous blood from head skin and mucous membranes of nose and paranasal sinuses drains to intracranial dural sinuses and provide brain cooling. Brain will be cooled very much when head skin exposes to hypothermia such a condition like wet hair in cold weather. We suggest that, in order to reduce brain cooling activity, some alterations are being occurred within paranasal sinuses. For this purpose, sinus ostiums may close and mucus may accumulate to reduce air within sinuses. Also there may be some vasomotor changes to prevent heat loss. We hypothesize that this possible alterations may occur within paranasal sinuses as a control mechanism for brain temperature control during exposure of head skin to hypothermia. Paranasal sinuses may also cool brain directly by a very thin layer of bone separates the posterior ethmoid air sinus from the subarachnoid space and only thin plates of bone separate the sphenoidal sinuses from internal carotid artery and cavernous sinuses. Because of their critical role in the SBC, posterior ethmoid air sinus and sphenoidal sinuses may be affected from this alterations more than other paranasal sinuses. This situation may cause posterior eye pain. This mechanism can explain why a person who expose to hypothermia with wet hair or a person who don’t use a beret or a hat during cold weather gets sinus headache and posterior eye pain. These symptoms could lead to an incorrect diagnosis of sinusitis.

Investigation of electronic flow regulated J-T cooling system for detector cooling applications

An improved fixed orifice Joule Thomson cooling system has been obtained to provide a viable alternative to self-regulating Joule Thomson (J-T) coolers. It is based on the fact that Joule Thomson coolers require sufficiently lower gas flow for continued liquid formation. The inherent problem of high gas consumption of the system is solved electronically by reducing the gas flow to a sufficient level. Normally, in a self-regulated Joule Thompson cooling system, the flow reduction is achieved by reducing expansion orifice area through temperature-controlled mechanical bellow mechanism or flow area control mechanisms. In this article, an effort has been made to provide a gas-independent alternative to a self-regulating system which is always fluid specific.

Aluminium triflate catalysed O-glycosidation: temperature-switched selective Ferrier rearrangement or direct addition with alcohols

A temperature-controlled mechanism switch between the Al(OTf)(3)-catalysed direct addition of alcohols or the Ferrier rearrangement reactions in some glycals is presented. The scope and limitations are investigated as are the influence of the stereochemistry and nature of the protecting groups on the glycal substrate.

Integration of nanoparticle cell lysis and microchip PCR for one-step rapid detection of bacteria

This paper describes an integrated microchip system as an efficient and cost-effective solution involving Nanotechnology and Lab-on-a-Chip technology for the rapid detection of bacteria. The system is based on using surface-modified gold nanoparticles for efficient cell lysis followed by microchip PCR without having to remove the nanoparticles from the PCR solution. Poly(quaternary ammonium) modified gold nanoparticles are used to provide a novel and efficient cell lysis method without the need to go through time-consuming, expensive and complicated microfabrication processes as most of current cell lysis methods for Lab-on-a-Chip applications do. It also facilitates the integration of cell lysis and PCR by sharing the same reaction chamber as PCR uses. It is integrated with a prototype microchip PCR system consisting of a physical microchip PCR device and an automated temperature control mechanism. The research work explores solutions for the problem of PCR inhibition caused by gold nanoparticles as well as for the problem of non-specific PCR amplification in the integrated microchip system. It also explores the possibility of greatly reducing PCR cycling time to achieve the same result compared to the protocol for a regular PCR machine. The simplicity of the setup makes it easy to be integrated with other Lab-on-a-Chip functional modules to create customized solutions for target applications.

An overview and classification of thermal-aware scheduling techniques for multi-core processing systems

Thermal-aware scheduling of parallel jobs is becoming an increasingly critical issue in software design for computing platforms ranging from embedded systems to large servers and entire data centers. In addition to the obvious implications of unrestricted temperature, such as thermal emergencies resulting in hardware failure, effective thermal management reduces the cost of thermal packaging for processors while achieving long-term savings from reduced secondary cooling costs. In embedded systems, hardware temperature control mechanisms in conjunction with software and other dynamic thermal management (DTM) techniques have been effectively utilized to avoid overheating. Server systems can also optimally take advantage of advanced DTM and efficient task scheduling to exert a positive impact on overall cooling costs as well as on prolonging the life of system components. The aim of this paper is to provide a comprehensive survey of recent research on thermal-aware task scheduling techniques for multi-core systems. The paper starts with the motivation behind managing temperature through task mapping and scheduling and then addresses the problems faced in such an approach, while providing commonly used thermal and task models as well as contemporary temperature control mechanisms of modern multi-core processors. A number of objectives of optimization with different combinations of temperature and performance constraints are elaborated. Also described in the context of above mentioned issues is a structured coverage of recently published research work. This leads to grouping of existing techniques in a taxonomical manner as well as to some conclusive observations that can help in identifying possible new research directions.

The earliest high-fired glazed ceramics in China: the composition of the proto-porcelain from Zhejiang during the Shang and Zhou periods (c. 1700–221 BC)

Bodies and glazes of 54 proto-porcelain sherds and 18 non proto-porcelain samples from Shang and Zhou periods production sites in Deqing, Zhejiang province were analysed by EPMA-WDS. The results indicate that the bodies of all samples were made from local raw material – porcelain stone, with the proto-porcelain samples being made from clay of higher quality. Wood ashes, high in lime and low in potash, were intentionally applied to the proto-porcelain samples, resulting in the formation of lime-rich glazes whose compositions were determined by a temperature-controlled mechanism. In contrast, kiln fragments and furniture show a potash-rich fuel vapour glaze, which formed unintentionally during use of the kiln. The firing temperature for most of the proto-porcelain glazes is around the maturing temperature for typical more recent lime glazes, showing that the potters were already at such an early time able to attain sufficiently high temperature in their kilns.

Optimization of Phase Change Materials Used in Asphalt Pavement to Prevent Rutting

Rutting is a common and serious phenomenon in asphalt pavement especially in high temperature areas. Phase change material (PCM) can adjust temperature through storing and releasing thermal energy during phase change process and has been used in thermal energy storage areas and building materials. However, the use of PCM to regulate the temperature of asphalt pavement has not been widely studied. In this paper, the feasibility of temperature self-control asphalt pavement using PCM was studied for preventing rutting. The temperature-control mechanism of asphalt pavement with PCM has been presented. The selection criteria of PCM used in asphalt pavement have been made. Meanwhile, a paraffin/expanded graphite shape-stabled phase change material with a phase change temperature range of 40°C~50°C has been used in this study. The temperature rising test of asphalt concrete showed that sample with PCM exhibited a lower temperature than the control sample, which indicates that it is feasible to use PCM in asphalt pavement for lowering temperature and preventing rutting.

On the significance of structural vegetation elements for caterpillar thermoregulation in two peat bog butterflies: Boloria eunomia and B. aquilonaris

Purpose Temperature profoundly impacts on distribution and habitat-use of organisms. The development of ectothermous caterpillars does not depend on host plant quality only, but also on the availability of suitable thermal conditions. Selection for thermally favorable microclimates (i.e. behavioral thermoregulation) is a primary mechanism of temperature control, and caterpillars can be either (or alternately) temperature conformers (i.e. passively adopting ambient temperature conditions) or thermoregulators (i.e. able to some extent to elevate or decrease their body temperature relative to ambient temperature). Here, we addressed the functional significance of different structural vegetation elements for the behavioral thermoregulation by caterpillars of two butterfly species. Results Weather conditions influenced the caterpillar detection probability within host plant patches, indicating that caterpillars can hide and use suitable microclimates provided by vegetation structures to cope with weather variations. This is why we (1) evaluated the heterogeneity in temperature conditions provided by these structures, (2) quantified the influence of ambient temperature and light intensity on caterpillar body temperature, and (3) tested how position on structure, substrate color and exposition influenced caterpillar body temperature. As expected, vegetation structures provided heterogeneous temperature and sun exposition conditions, while caterpillar body temperature was dependent on ambient temperature and light intensity. But body temperature was additionally influenced by the position on vegetation structures, substrate color and exposition. Conclusions These results suggest that there is no unique and fixed structure in the vegetation subsuming the best thermal conditions for caterpillars. We argue that a better understanding of the thermal properties of vegetation structures is essential for correctly understanding caterpillar habitat-use and the behavioral mechanisms driving their body thermoregulation. Conceptually this means that thermal conditions should be included in the definition of a species' functional habitat. Practically this may influence the choice of appropriate habitat management for species of conservation concern.

A computational study of non-premixed flame extinction by water spray

The interaction of turbulent non-premixed flames with fine water spray is studied using direct numerical simulations (DNS) with detailed chemistry. The study is of practical importance in fire safety devices that operate in the mist regime, as well as in their use as an inexpensive temperature control mechanism for gas turbines. Dynamics of water spray is represented by the Lagrangian particle-in-cell method, coupled with an Eulerian gas-phase reacting flow solver. The model configuration is a two-dimensional ethylene–air counterflow diffusion flame at moderate strain rates. Laminar and turbulent flame simulations are performed at various water loading conditions. Comparison of various simulation cases highlights the flame weakening characteristics due to aerodynamic stretch and heat loss due to water spray evaporation. Local flame extinction is identified by a flame weakness factor derived based on an asymptotic model under non-adiabatic environments. A statistical analysis of the cumulative turbulent flame data shows that a large heat release enhancement is observed during the flame quenching due to the occurrence of edge flames, while such effects are substantially reduced in the presence of water spray. Findings from this study provide a better understanding of interaction between thermal and aerodynamic quenching in turbulent flame dynamics.

Applying back propagation network to cold chain temperature monitoring

Recently, the enhancement of contactless, real-time features and high data transmission rates in supply chain management has been widely discussed. Notably, the cold chain is a part of the supply chain in which temperature monitoring plays a vital role in the system while automatic data collection is an essential aspect of cold chain management. As such, automatic data collection methods, such as radio frequency identification (RFID) techniques, are used to collect temperature data in order to track and trace all manner of products. In this paper, we evaluate an exponentially weighted moving average (EWMA) control chart and artificial neural network technologies in order to monitor collected temperature data in the context of cold chain management. The back-propagation neural network is used to predict temperature shifts and trends. The EWMA control chart is adopted to monitor temperature variations. Using this strategy, as anomalies occur, the control center of an enterprise can perform certain actions immediately to prevent further disaster. Finally, we construct a system using a back-propagation neural network and statistical process control chart. A simulated environment using LEGO® bricks is also implemented to demonstrate the feasibility of this study. This temperature control mechanism is found to be useful for a real-time temperature data collection environment, as with using active RFID tags with temperature sensors for cold chain management.

AN IMPROVED COMPACT INTEGRATED ANALYTICAL SWATCH TESTING SYSTEM

A compact swatch testing system has been developed to precisely quantify the permeation and penetration of a chemical weapons agent simulant while reducing the system footprint, improving safety and usability, enhancing automation, and maintaining measurement precision comparable to its predecessor. With the addition of a new test cell design and temperature control mechanism, the improved system demonstrated higher steady-state permeation rates and shorter breakthrough times. In comparison to the earlier prototype, the compact configuration's footprint and volume are reduced substantially, thereby allowing for use inside a 6-foot laboratory hood. A reference device for assessing test cell performance was also developed.

Effects of α-Glucosylhesperidin on the Peripheral Body Temperature and Autonomic Nervous System

We studied the effects of alpha-glucosylhesperidin (G-Hsp) on the peripheral body temperature and autonomic nervous system in humans. We first conducted a survey of 97 female university students about excessive sensitivity to the cold; 74% of them replied that they were susceptible or somewhat susceptible to the cold. We subsequently conducted a three-step experiment. In the first experiment, G-Hsp (500 mg) was proven to prevent a decrease in the peripheral body temperature under an ambient temperature of 24 degrees C. In the second experiment, a warm beverage containing G-Hsp promoted blood circulation and kept the finger temperature higher for a longer time. We finally used a heart-rate variability analysis to study whether G-Hsp changed the autonomic nervous activity. The high-frequency (HF) component tended to be higher, while the ratio of the low-frequency (LF)/HF components tended to be lower after the G-Hsp administration. These results suggest that the mechanism for temperature control by G-Hsp might involve an effect on the autonomic nervous system.

Insect eggs protected from high temperatures by limited homeothermy of plant leaves

Virtually all aspects of insect biology are affected by body temperature, and many taxa have evolved sophisticated temperature-control mechanisms. All insects, however, begin life as eggs and lack the ability to thermoregulate. Eggs laid on leaves experience a thermal environment, and thus a body temperature, that is strongly influenced by the leaves themselves. Because plants can maintain leaf temperatures that differ from ambient, e.g. by evapotranspiration, plant hosts may protect eggs from extreme ambient temperatures. We examined the degree to which leaves buffer ambient thermal variation and whether that buffering benefits leaf-associated insect eggs. In particular, we: (1) measured temperature variation at oviposition sites in the field, (2) manipulated temperatures in the laboratory to determine the effect of different thermal conditions on embryo development time and survival, and (3) tested embryonic metabolic rates over increasing temperatures. Our results show that Datura wrightii leaves buffer Manduca sexta eggs from fatally high ambient temperatures in the southwestern USA. Moreover, small differences in temperature profiles among leaves can cause large variation in egg metabolic rate and development time. Specifically, large leaves were hotter than small leaves during the day, reaching temperatures that are stressfully high for eggs. This study provides the first mechanistic demonstration of how this type of leaf-constructed thermal refuge interacts with egg physiology.

Inducing Hypothermia After Cardiac Arrest

Inducing Hypothermia After Cardiac Arrest

Optical Disk Recorder (ODR) for Satellite Use

An earth-observing satellite flies at an altitude of 800 km. The data acquired while the satellite flies at the opposite side of the earth from a telemetry station has to be stored in the satellite because it is difficult to establish a communication channel between the telemetry station and the satellite. The use of the first optical disk recorder (ODR) in space has been planned [H. Anegawa, T. Fukuda, S. Yamamoto, D. Maeusli and M. Kasuya: Proc. Int. Symp. Optical Memory '91, (1991) p. 115; H. Anegawa, K. Tanaka and N. Tsuya: Proc. Optical Data Storage '92 p. 1 MD4 (1992)]. To make the optical disk drive work in space, the following measure was taken. The large acceleration during launching was solved using the launch lock mechanism. The temperature control mechanism was used to cope with a wide temperature change. Optical components were carefully selected for cosmic ray. ADEOS-II at which the ODR was installed was launched on December 14, 2002. The ODR had worked correctly for about ten months until the solar cell of the satellite stopped functioning. It was proved that the optical disk drive can work in space when an appropriate measure is taken.

SIZE MATTERS

SIZE MATTERS

Thermal and temporal response of ionization chambers in radiation dosimetry.

The temporal and thermal response of various commonly used ion chambers (NEL, Exradin, PTW) with different wall and electrode materials is studied in a water phantom. Measurements were taken in heating water bath having an automatic temperature control mechanism. All chambers were submersed at 3 cm depth in water phantom and connected to separate electrometers for simultaneous readings for a given dose from a 6 MV beam. The temporal response was studied at approximately +/- 10 degrees C from room temperature, i.e., 10 degrees C and 30 degrees C. Temporal results show that all chambers reach quick equilibrium response within < 2 minutes of submersion in water. The steady-state thermal response was dependent upon the water temperature and wall and electrode compositions. The temperature and pressure corrected response of the NEL chamber was least affected by the changes in water temperature, where as the Exradin chamber has positive and PTW has negative slope with water temperature. The response varied within +/-1.5% between 10 degrees C-50 degrees C temperature and is mainly dependent on volume changes rather than the humidity. A correction factor based on thermal coefficients is derived for each chamber. It is concluded that ion chamber correction factors can be divided into first order; temperature and pressure connection, second order; volume correction for thermal expansion, and third order; humidity correction. To eliminate dosimetric error, the temporal and thermal response should be known for a chamber or water phantom temperature should be maintained close to room temperature.

Design and development of a geothermal temperature control system for broodstock management of channel catfish Ictalurus punctatus

A control system was designed to raise and maintain water temperatures within ∼0.03-ha earthen ponds to a range conducive for spawning (24–30 °C) channel catfish Ictalurus punctatus. Heating was done during February 2001 to April 2001, when temperatures would have otherwise prohibited spawning (<24 °C). Temperature was increased from ∼10 °C (ambient) by ∼2 °C per day, and maintained at ∼27 °C, by the addition of geothermally warmed water (∼36 °C). The control system substantially increased the controllability and precision of heating ponds compared to manual operation. Systems were designed to control sets of four ponds. In designing this control system, consideration of biological constraints was essential. Reproduction in channel catfish is most strongly influenced by temperature. Because cold fronts are common during the winter and early spring (January–March), it was essential to ensure that pond temperatures did not fall below the range for spawning. Constraints on the heating rate and temperature variability to maintain fish health and stimulate spawning behavior were considered. Components of the control system included temperature measurement devices (type-T thermocouples), a central electronic control unit, electronic switches and electrically actuated ball valves. In response to the temperature sensed by each thermocouple, the controller sent a message to close or open the valve. When the valve was opened, warm water was added to the pond to increase the average pond temperature. Hardware and algorithm design and initial system testing were the major components of this project. The final design incorporated information on relevant biological parameters and safety features including peak pond temperature, independent aeration and water pressure control mechanisms. Initial results indicate successful control of this biological system, and ongoing studies suggest similar mechanisms may be used for additional control objectives. In particular, this system could be used to vary pond temperatures to study biological responses and to cool ponds by addition of well water during summer months.