Temperature-controlled Enclosure Research Articles

Characterising and tackling thermally induced zero-drift in displacement measuring interferometry using temperature-controlled enclosure

Abstract Our research efforts in displacement measurement interferometry focused on long-term drifts initiated an extended experimental investigation in the interferometric assemblies of our design. We aimed to analyze, characterize and tackle the long-term measurement stability, expressed as the zero-drift, with particular attention to the thermal effects. For the experimentation, we developed a thermostatic chamber equipped with active temperature regulation, an array of sensors and control electronics. With either the finely stabilized temperature or with the thermal cycling, we can carry out a range of investigations: verification of modified design or prototype interferometers, testing of production pieces, characterization of integrated assemblies and units in terms of the zero drift and the susceptibility to thermal effects—the temperature sensitivity ( δ L / δ T , expressed in nm ⋅ K−1). With these experimental studies, we demonstrate the potential of the zero drift studies to contribute to the development and broader expansion of interferometric instrumentation.

Characterization Of The Electrothermal Conversion Mechanisms Of A Plasma Actuator For Icing Control

The characterization of a new icing protection system, specifically a dielectric barrier discharge (DBD) plasma actuator, is conducted in this study. The system operates by establishing an AC high voltage between two electrodes arranged on opposite sides of a dielectric material. This setup generates a plasma on the dielectric surface, which in turn induces a significant temperature rise (about 30°C) in both the dielectric surface and the surrounding air. To gain a comprehensive understanding of the electrothermal conversion mechanisms involved in the discharge, a Planar Laser Induced Fluorescence technique is employed. Using a two-colour one-dye ratiometric method (PLIF2c1d), the technique provides measurements of the temperature evolution of an ice droplet deposited on the actuator during its melting process by the discharge. An annular actuator configuration is chosen to minimise the effect of the generated ionic wind and maintain the droplet in the discharge. A pyranine and sucrose solution is identified and temperature calibrated. The calibration process involves depositing a droplet of the solution in a temperature-controlled enclosure capable of reaching temperatures as low as -22°C. Through detailed spectral analysis, two specific detection spectral bands are selected for the imaging applications. These bands enable measurements of the ice temperature with a sensitivity of 7.61%/°C. The effects of laser light scattering by ice and fluorescence reabsorption are also investigated by varying the ice thickness. They are found to have limited influence on the fluorescence emission when the solution in ice form. Finally, the capacity of the technique is evaluated by measuring the ice temperature evolution during the melting induced by a plasma discharge. Droplets are deposited on two dielectric materials, namely PTFE and Sapphire, which possess distinct thermal and dielectric properties. Comparisons under varying plasma discharge power levels provide valuable insights into the optimization of DBD plasma actuators for effective icing protection.

Low-drift-rate external cavity diode laser

We present the design, construction, and simulation of a simple, low-cost external cavity diode laser with a measured free-running frequency drift rate of 1.4(1) MHz/h at 852 nm. This performance is achieved in a compact aluminum structure held inside an airtight, temperature-controlled enclosure. The high thermal conductivity of the laser cavity and the stable temperature environment inside the enclosure minimize the time-varying, spatial temperature gradients across the laser cavity. We present thermal finite element method simulations, which quantify the effects of temperature gradients, and suggest that the drift rate is likely limited by the laser-diode and piezo-aging.

Design and characterization of a smog chamber for studying gas-phase chemical mechanisms and aerosol formation

Abstract. We describe here characterization of a new state-of-the-art smog chamber facility for studying atmospheric gas-phase and aerosol chemistry. The chamber consists of a 30 m3 fluorinated ethylene propylene (FEP) Teflon film reactor housed in a temperature-controlled enclosure equipped with black lamps as the light source. Temperature can be set in the range from −10 to 40 °C at accuracy of ±1 °C as measured by eight temperature sensors inside the enclosure and one just inside the reactor. Matrix air can be purified with non-methane hydrocarbons (NMHCs) < 0.5 ppb, NOx/O3/carbonyls < 1 ppb and particles < 1 cm−3. The photolysis rate of NO2 is adjustable between 0 and 0.49 min−1. At 298 K under dry conditions, the average wall loss rates of NO, NO2 and O3 were measured to be 1.41 × 10−4 min−1, 1.39 × 10−4 min−1 and 1.31 × 10−4 min−1, respectively, and the particle number wall loss rate was measured to be 0.17 h−1. Auxiliary mechanisms of this chamber are determined and included in the Master Chemical Mechanism to evaluate and model propene–NOx–air irradiation experiments. The results indicate that this new smog chamber can provide high-quality data for mechanism evaluation. Results of α-pinene dark ozonolysis experiments revealed secondary organic aerosol (SOA) yields comparable to those from other chamber studies, and the two-product model gives a good fit for the yield data obtained in this work. Characterization experiments demonstrate that our Guangzhou Institute of Geochemistry, Chinese Academy Sciences (GIG-CAS), smog chamber facility can be used to provide valuable data for gas-phase chemistry and secondary aerosol formation.

A newly developed STM-based coordinate measuring machine

A novel coordinate measuring machine (CMM) with nanometer spatial resolution and larger than 10 mm scale measuring range. ► The STM-based CMM based on an ideal structural concept was developed. ► The developed system provides high measuring stability. ► The system has a nanometer scale measuring resolution. ► The variation of the measured height among 20 measurements was 4.6 nm. ► Shapes of a steel sphere and an aspheric lens mold could be obtained by the system. Demands for precision measurement of three dimensional micro-geometries over a large area have recently increased in a variety of industries. In order to meet such requirements, it is necessary to develop a novel coordinate measuring machine (CMM) which has high resolution together with larger than 10 mm scale measuring range. This paper presents a newly developed CMM with nanometer spatial resolution based on a scanning tunneling microscopy principle. The developed CMM is composed of a planar nano-motion control system driven by voice coil motors and a vertical nano-motion system driven by a hybrid actuator. Furthermore, in order to achieve long-term stability and repeatability, the machine is installed on an active vibration isolating system inside a temperature-controlled enclosure. Performance evaluation results confirm that the CMM has nanometer spatial resolution, large measuring range and high structural stability.

The effects of ambient temperature on the compaction of pharmaceutical powders

This article presents an experimental study of the effects of raised ambient temperature in dies and punches on the compaction of pharmaceutical powders. The experiments use an instrumented hydraulic press having a temperature-controlled enclosure allowing the ambient temperature of die and punch to be varied from 20 to 57 °C. A pharmaceutical powder was compacted at temperatures in this range and mechanical parameters, such as stress transfer ratio, stress transmission ratio, and die-wall friction, were analysed to examine the effects of heat transfer between tools and powder. In particular, it is shown that increasing the environmental temperature of die and punch increases the transfer ratio and the die-wall friction. The radial pressure is also slightly increased at the first stages of the compaction. However, the stress transmission is reduced by increasing the temperature. This may indicate an increase of shear stress. It is also observed that the particles undergoing compaction are ‘softened’ by increase of the temperature. This softening is certainly due to rise in temperature of the powder generated by the compaction and by the heat flux transfer between the die and the tablet. It is suggested that these effects could be important in industrial tablet production installations without air conditioning and thus subject to variations in ambient temperature.

A new environmental chamber for evaluation of gas-phase chemical mechanisms and secondary aerosol formation

A new state-of-the-art indoor environmental chamber facility for the study of atmospheric processes leading to the formation of ozone and secondary organic aerosol (SOA) has been constructed and characterized. The chamber is designed for atmospheric chemical mechanism evaluation at low reactant concentrations under well-controlled environmental conditions. It consists of two collapsible 90 m 3 FEP Teflon film reactors on pressure-controlled moveable frameworks inside a temperature-controlled enclosure flushed with purified air. Solar radiation is simulated with either a 200 kW Argon arc lamp or multiple blacklamps. Results of initial characterization experiments, all carried out at ∼300–305 K under dry conditions, concerning NO x and formaldehyde offgasing, radical sources, particle loss rates, and background PM formation are described. Results of initial single organic–NO x and simplified ambient surrogate–NO x experiments to demonstrate the utility of the facility for mechanism evaluation under low NO x conditions are summarized and compared with the predictions of the SAPRC-99 chemical mechanism. Overall, the results of the initial characterization and evaluation indicate that this new environmental chamber can provide high quality mechanism evaluation data for experiments with NO x levels as low as ∼2 ppb, though the results indicate some problems with the gas-phase mechanism that need further study. Initial evaluation experiments for SOA formation, also carried out under dry conditions, indicate that the chamber can provide high quality secondary aerosol formation data at relatively low hydrocarbon concentrations.

Detector based calibration of solar UV radiometers in laboratory environments with high accuracy

A detector based measurement system was designed and established in UME optics laboratory for the calibration of solar UV radiometers. Filter radiometer, made up of a silicon trap detector, band-pass filters and precision aperture in a temperature-controlled enclosure was constructed for this purpose. Spectral responsivity of trap detector was evaluated to be traceable to the cryogenic radiometer and electrically calibrated pyroelectric detector. Uncertainties in the filter radiometer’s responsivities at 291 nm, 296 nm, 313 nm, 357 nm, and 378 nm wavelengths were calculated as 1.6%, 1.3%, 0.8%, 0.6% and 0.2% respectively. Relative uncertainities in irradiance measurements were found to be between 3.4% and 0.9% in the region of 291–378 nm.

Secondary Organic Aerosol Formation by Irradiation of 1,3,5-Trimethylbenzene−NOx−H2O in a New Reaction Chamber for Atmospheric Chemistry and Physics

A new environmental reaction smog chamber was built to simulate particle formation and growth similar to that expected in the atmosphere. The organic material is formed from nucleation of photooxidized organic compounds. The chamber is a 27 m3 fluorinated ethylene propylene (FEP) bag suspended in a temperature-controlled enclosure. Four xenon arc lamps (16 kW total) are used to irradiate primary gas components for experiments lasting up to 24 h. Experiments using irradiations of 1,3,5-trimethylbenzene-NOx-H2O at similar input concentrations without seed particles were used to determine particle number and volume concentration wall loss rates of 0.209+/-0.018 and 0.139+/-0.070 h(-1), respectively. The particle formation was compared with and without propene.

Development of filter radiometer based high accurate calibration facility for solar UV meters

Summary A reference filter radiometer based measurement system was established in the laboratory to calibrate solar UV radiometers. Filter radiometer was constructed from three-element silicon photodiode based reflection type trap detector, band-pass filters and precision aperture in a temperature-controlled enclosure. Spectral responsivity of trap detector was determined as traceable to the cryogenic radiometer and electrically calibrated pyroelectric detector. Relative uncertainties in the filter radiometer's responsivities at six wavelengths between 291 nm and 434 nm were calculated. In order to engage this radiometer in various types of implementations, filter(s) having previously known spectral transmittance was used in the radiometer housing. Calibration of solar UV meters can be achived accurately by using the developed system.

Detection of Staphylococcus aureus enterotoxin B at femtomolar levels with a miniature integrated two-channel surface plasmon resonance (SPR) sensor

Surface plasmon resonance (SPR) biosensors offer the capability for continuous real-time monitoring. The commercial instruments available have been large in size, expensive, and not amenable to field applications. We report here an SPR sensor system based on a prototype two-channel system similar to the single channel Spreeta™ devices. This system is an ideal candidate for field use. The two-channel design provides a reference channel to compensate for bulk refractive index (RI), non-specific binding and temperature variations. The SPR software includes a calibration function that normalizes the response from both channels, thus enabling accurate referencing. In addition, a temperature-controlled enclosure utilizing a thermo-electric module based on the Peltier effect provides the temperature stability necessary for accurate measurements of RI. The complete SPR sensor system can be powered by a 12V battery. Pre-functionalized, disposable, gold-coated thin glass slides provide easily renewable sensor elements for the system. Staphylococcus aureus enterotoxin B (SEB), a small protein toxin was directly detectable at sub-nanomolar levels and with amplification at femtomolar levels. A regeneration procedure for the sensor surface allowed for over 60 direct detection cycles in a 1-month period.

200 kΩ ac resistance transfer standard

A resistance standard, comprising three 200 k resistors mounted in a temperature-controlled enclosure, has been constructed from commercial high-precision metal-foil resistors. The standard is intended for transfer of resistance value between a multifrequency resistance-capacitance (R-C) bridge and an ac quantum Hall resistance (QHR) bridge. The three resistors were fully characterized for their voltage dependence.

An experimental investigation of incremental reactivities of volatile organic compounds

California has adopted a set of VOC reactivity factors for regulatory purposes that is based on a model of the ozone formation process. These incremental reactivity factors (derived by Carter) describe the amount of ozone each exhaust VOC will form under a certain set of conditions in an urban atmosphere. The main objective of this study is to measure reactivity factors using smog chamber experiments, and to compare the measurements to the Carter factors. A new facility was constructed explicitly for this study. The facility has four identical smog chambers and a temperature-controlled enclosure for the chambers. The chambers are irradiated using a set of filtered xenon arc lamps to approximate “sunlight”. The reactivities of 14 individual VOCs representative of those found in automobile exhaust and several mixtures of VOCs have been measured. The measured and Carter-reactivity factors were highly correlated, suggesting that the chemical model used by Carter accounts for the reactivities of a wide range of compounds with dramatically different uncertainties in their mechanisms. The measured results, in general, are consistent with the Carter-reactivity factors for comparing the relative reactivities of VOCs in the atmosphere. However, additional kinetic and mechanistic studies of many VOC species including aromatic isomers are needed to improve reactivity scales.

Ccreening Onions (Allium cepa L.) and Other Allium spp. for Botrytis Leaf Blight Resistance

Greenhouse and field methods were developed to screen Allium spp. for resistance to Botrytis leaf blight (caused by Botrytis squamosa Walker). In the green-house, plants were sprayed with laboratory-grown inoculum and incubated in a temperature-controlled enclosure containing an atomizing mist system. For field inoculations, a portable misting system with windbreaks was erected, and the plants were sprayed with laboratory-grown inoculum. Greenhouse and field incubation conditions maintained leaf wetness without washing inoculum from the leaves. Botrytis leaf blight symptoms in greenhouse and field evaluations were identical to symptoms in commercial onion fields. A total of 86 selected USDA Allium collection accessions were evaluated using these methods. All A. fistulosum accessions and A. roytei were highly resistant to immune, as were most accessions of A. altaicum, A. galanthum, A. pskemense, and A. oschaninii. Nearly all of the A. vavilovii and A. cepa accessions were susceptible. However, one A. cepa accession (PI 273212 from Poland) developed only superficial lesions, which did not expand to coalesce and blight leaves. This work confirms previous reports of Botrytis leaf blight resistance in Allium spp., and suggests that strong resistance exists with A. cepa.

Ccreening Onions (Allium cepa L.) and Other Allium spp. for Botrytis Leaf Blight Resistance

Greenhouse and field methods were developed to screen Allium spp. for resistance to Botrytis leaf blight (caused by Botrytis squamosa Walker). In the green-house, plants were sprayed with laboratory-grown inoculum and incubated in a temperature-controlled enclosure containing an atomizing mist system. For field inoculations, a portable misting system with windbreaks was erected, and the plants were sprayed with laboratory-grown inoculum. Greenhouse and field incubation conditions maintained leaf wetness without washing inoculum from the leaves. Botrytis leaf blight symptoms in greenhouse and field evaluations were identical to symptoms in commercial onion fields. A total of 86 selected USDA Allium collection accessions were evaluated using these methods. All A. fistulosum accessions and A. roytei were highly resistant to immune, as were most accessions of A. altaicum, A. galanthum, A. pskemense, and A. oschaninii. Nearly all of the A. vavilovii and A. cepa accessions were susceptible. However, one A. cepa accession (PI 273212 from Poland) developed only superficial lesions, which did not expand to coalesce and blight leaves. This work confirms previous reports of Botrytis leaf blight resistance in Allium spp., and suggests that strong resistance exists with A. cepa.

Ambient temperature effects on taste aversion conditioned by ethanol: contribution of ethanol-induced hypothermia.

Six experiments examined the effects of low (5-10 degrees C), normal (21 degrees C), or high (32 degrees) ambient temperature on conditioned taste aversion and body temperature changes produced by ethanol, lithium chloride, or morphine sulfate. Fluid-deprived rats received five to seven taste conditioning trials at 48-hr intervals. On each trial, access to saccharin at normal ambient temperature was followed by injection of drug or saline and placement for 6 hr into a temperature-controlled enclosure. Exposure to low ambient temperature facilitated, whereas exposure to high ambient temperature retarded acquisition of ethanol-induced conditioned taste aversion. The ability of an alteration in ambient temperature to influence conditioned taste aversion varied as a function of ethanol dose and was related to ambient temperature's effect on ethanol-induced hypothermia. More specifically, strength of conditioned taste aversion was negatively correlated with core body temperature after ethanol injection. Alterations in ambient temperature alone did not affect ingestion of a paired flavor solution in the absence of drug. Moreover, alterations in ambient temperature did not appear to influence conditioned taste aversion by changing ethanol pharmacokinetics. Finally, high and low ambient temperature did not affect development of taste aversion conditioned by lithium chloride or morphine sulfate. The overall pattern of data presented by these experiments supports the hypothesis that ambient-temperature influences strength of ethanol-induced conditioned taste aversion by altering the hypothermic response to ethanol. More generally, these data support the suggestion that body temperature change induced by ethanol is related to ethanol's aversive motivational effects and may be involved in modulating ethanol intake.

A Brillouin scattering study of sound velocity in single-component liquids up to 800 bar

Describes the results of Rayleigh-Brillouin scattering experiments performed on a set of 10 single-component liquids. This set comprised associated and non-associated liquids. The samples were contained in a precision high-pressure cell mounted inside a temperature-controlled enclosure. This sample chamber provides excellent long-time pressure ( Delta P=0.05%) and temperature ( Delta T=+or-1 mK) stability. The Rayleigh-Brillouin spectra of the scattered light were studied at room temperature (20 degrees C), with the pressure acting on the samples varied from 1 to 800 bar. A home-made, piezoelectric-scanned, multipass Fabry-Perot interferometer was used to measure the Brillouin shift, which determines the hypersonic sound velocity (vs) of the thermally generated sound waves propagating in the scattering medium as a function of externally applied pressure. The authors have found that as the pressure was raised from 1 to 800 bar, vs(P) increased by more than 25% (typically) in most of the liquids considered in this study. They found that the vs(P) could be least-square fitted to a parabolic equation in P given by vs(P)=A0+A1P+AsP2 within experimental error. This equation is a manifestation of Tait's modified equation of state and the linear pressure dependence of the adiabatic bulk modulus in the modest-pressure regime.

An exposure facility for examining the physiological basis of air pollutant effects on plant growth

It is widely believed that regional declines in forest productivity are, at least in part, due to air pollutant exposure; however, the physiological basis for the declines is not clear, and the extent to which air pollutants are actually involved in the declines remains unresolved. This paper describes the design, construction and testing of a facility that monitors physiological responses to plants during exposure to various air pollutants. The facility consists of twelve continuous-stirred tank reactors (CSTRs) in a temperature-controlled enclosure, an air purification system, CO 2, H 2O, and pollutant ( NO x , O 3 and SO 2) analyzers and automated sampling, flow control and data acquisition systems. The facility is unique in the degree of computer control of gas flows and concentrations and in its ability to monitor physiological processes at low air flow rates. With these low flow rates, we will be able to productively explore the effects of air pollutants on maintenance respiration and photosynthesis and thereby explain effects on growth.

The principle of reversed lag applied to on-off temperature control

Cyclic fluctuations of temperature in an enclosure with a simple on-off control system are discussed. It is shown that such a system can be improved by using two control elements completely immersed in the fluid of the enclosure, and therefore not subject to datum error. The output signal of one of the control elements is required to have a lagging phase angle, and a theoretical analysis is made in which the thermal frequency responses of various configurations are compared. Conclusions are reached about the relative merits of different configurations, and a description is given of the application of the theoretical principles to an experimental temperature-controlled enclosure.