Accurate Temperature Control Research Articles

Device for the detection of short trace gas pulses

Abstract A device for detection of short gas pulses at very low concentrations is presented. The approach is based on a special temperature modulation technique enabling a differential surface reduction (DSR) measurement of a metal oxide semiconductor (MOS) gas sensor. With this method, the sensor surface is highly covered with oxidized surface states at high temperature (e. g. 400 °C) initially. The temperature is then reduced abruptly to, e. g., 100 °C resulting in a state with strong excess of negative surface charge. Reactions of these surface charges with reducing gases are prevailing and lead to very high sensitivity. For the measurement a dedicated detector (electronics and fluidic system) is presented. The electronics allows a high-resolution conductance measurement of the sensitive layer and accurate temperature control. The fluidic system is examined in terms of peak shape and optimal sensor response via FEM simulations.

Gold Nanoparticle-Functionalized Surface Plasmon Resonance Optical Fiber Biosensor: In Situ Detection of Thrombin With 1 n·M Detection Limit

We present an optical fiber biosensor that employs both long-range and localized surface plasmon resonances (SPRs) to sensitively detect very small changes in the resonances due to the surrounding refractive index. A tilted optical fiber Bragg grating inscribed in standard single-mode fiber couples light into the fiber's cladding, where it induces micrometer-scale SPRs in a 50-nm-thick gold coating. The limit of detection of the targeted protein, thrombin, is enhanced by resonance between the long-range SPRs and localized SPRs induced in 13-nm-diameter gold nanoparticles bonded via aptamers to the protein molecules. The sensor demonstrates stable and reproducible response to thrombin concentration down to a limit of detection of 1 n·M, which is three orders of magnitude more sensitive than previous optical fiber protein sensors. Meanwhile, it does not require accurate temperature control because of the elimination of the temperature cross-sensitivity inherent in TFBG devices (core mode). The high sensitivity, simplicity, compact size, and remote monitoring capability of the sensor open many new opportunities for environmental, biological, and medical sensing.

Paper-based resistive heater with accurate closed-loop temperature control for microfluidics paper-based analytical devices

Accurate temperature controlling system is essential for temperature-sensitive applications of microfluidics technology. In this paper, for the first time, we implemented a low-cost temperature controlling system on paper to be used in paper-based microfluidics. A resistive heater was fabricated by screen-printing of conductive electric paint on paper substrate. The temperature was measured by a non-contact temperature sensor to suppress the effect of contact sensors’ thermal mass on the measured temperature. By utilizing PID controller in a closed-loop system, the accuracy of temperature is below 0.22 °C which is suitable for biological temperature-sensitive applications. A microfluidics paper-based analytical device (µPAD) is fabricated by screen-printing on filter paper and attached to the heater to be used as device under test. The fabrication and implementation procedures of the whole system including the heater, the temperature controller and the µPAD are very low-cost, fast and simple. The operation of the fabricated heater and the temperature controlling system were validated by a temperature-sensitive colorimetric test of cholesterol.

Hydrogen-deuterium exchange mass spectrometry reveals folding and allostery in protein-protein interactions.

Hydrogen-deuterium exchange mass spectrometry (HDXMS) has emerged as a powerful approach for revealing folding and allostery in protein-protein interactions. The advent of higher resolution mass spectrometers combined with ion mobility separation and ultra performance liquid chromatographic separations have allowed the complete coverage of large protein sequences and multi-protein complexes. Liquid-handling robots have improved the reproducibility and accurate temperature control of the sample preparation. Many researchers are also appreciating the power of combining biophysical approaches such as stopped-flow fluorescence, single molecule FRET, and molecular dynamics simulations with HDXMS. In this review, we focus on studies that have used a combination of approaches to reveal (re)folding of proteins as well as on long-distance allosteric changes upon interaction.

Hydrogen peroxide and glucose concentration measurement using optical fiber grating sensors with corrodible plasmonic nanocoatings.

We propose and demonstrate hydrogen peroxide (H2O2) and glucose concentration measurements using a plasmonic optical fiber sensor. The sensor utilizes a tilted fiber Bragg grating (TFBG) written in standard single mode communication fiber. The fiber is over coated with an nm-scale film of silver that supports surface plasmon resonances (SPRs). Such a tilted grating SPR structure provides a high density of narrow spectral resonances (Q-factor about 105) that overlap with the broader absorption band of the surface plasmon waves in the silver film, thereby providing an accurate tool to measure small shifts of the plasmon resonance frequencies. The H2O2 to be detected acts as an oxidant to etch the silver film, which has the effect of gradually decreasing the SPR attenuation. The etching rate of the silver film shows a clear relationship with the H2O2 concentration so that monitoring the progressively increasing attenuation of a selected surface plasmon resonance over a few minutes enables us to measure the H2O2 concentration with a limit of detection of 0.2 μM. Furthermore, the proposed method can be applied to the determination of glucose in human serum for a concentration range from 0 to 12 mM (within the physiological range of 3-8 mM) by monitoring the H2O2 produced by an enzymatic oxidation process. The sensor does not require accurate temperature control because of the inherent temperature insensitivity of TFBG devices referenced to the core mode resonance. A gold mirror coated on the fiber allows the sensor to work in reflection, which will facilitate the integration of the sensor with a hypodermic needle for in vitro measurements. The present study shows that Ag-coated TFBG-SPR can be applied as a promising type of sensing probe for optical detection of H2O2 and glucose detection in human serum.

Temperature control scheme using hot-gas bypass for a machine tool oil cooler

Accurate temperature control that addresses heat generation is crucial given the development of high-accuracy high-speed machining process. Heat generation leads to a thermal error of machine tools. Therefore, developing high-accuracy machining without appropriate temperature control scheme is challenging. Machine tool coolers for forced convection cooling can effectively control heat generation. However, temperature control accuracy cannot be achieved because the temperature control scheme for machine tool oil cooler encounters nonlinear and time-varying problems with time delay characteristic. This study presents a novel temperature control scheme, namely, Proportional–integral–derivative (PID) control logic based on Smith predictive method. MATLAB simulation software was utilized to determine the specifications of outlet temperature control using hot-gas bypass scheme of high-precision oil cooler with refrigerant R-32. Simulation results revealed that the proposed control scheme present better temperature control accuracy than the traditional PID control. The proposed control scheme can also effectively solve the abovementioned problems through on-site experimental results. The steadystate error of the oil outlet temperature of the high-precision-type machine tool oil cooler can be controlled within 0.1 °C by using the proposed control hot-gas bypass scheme.

Design of PID temperature control system based on STM32

A rapid and high-accuracy temperature control system was designed using proportional-integral-derivative (PID) control algorithm with STM32 as micro-controller unit (MCU). The temperature control system can be applied in the fields which have high requirements on the response speed and accuracy of temperature control. The temperature acquisition circuit in system adopted Pt1000 resistance thermometer as temperature sensor. Through this acquisition circuit, the monitoring actual temperature signal could be converted into voltage signal and transmitted into MCU. A TLP521-1 photoelectric coupler was matched with BD237 power transistor to drive the thermoelectric cooler (TEC) in FTA951 module. The effective electric power of TEC was controlled by the pulse width modulation (PWM) signals which generated by MCU. The PWM signal parameters could be adjusted timely by PID algorithm according to the difference between monitoring actual temperature and set temperature. The upper computer was used to input the set temperature and monitor the system running state via serial port. The application experiment results show that the temperature control system is featured by simple structure, rapid response speed, good stability and high temperature control accuracy with the error less than ±0.5°C.

Design and Analysis of Hot Core Box Mold for New Energy Vehicle Motor Shell

To achieve rapid batch production with high-quality stability for the integral molding process of sand cores in low-pressure casting for the water-cooled aluminum alloy shell of new energy vehicle motors many process parameters were measured. The forming process and die structure of a circumferential sand core were analyzed. In addition, the electric heating power of each core box mold was accurately calculated using thermodynamic calculations. These details, combined with the three-dimensional shape of the core mold, the layout of the electric heating rod and the hole position for temperature measuring as well as the entire cylindrical waterway of a hot core box mold and the core way were designed to realize accurate control of the box temperature by adjusting the curing temperature and time parameters. Thus, improving the sand core curing quality and production efficiency, which will meet the casting specifications for mass production of the water-cooled motor shell.

How reproducible are kinetic parameter constraints of quartz luminescence? An interlaboratory comparison for the 110 °C TL peak

Knowledge of the kinetic parameters E (thermal activation energy) and s (frequency factor) of charge-trapping defects in the quartz crystal lattice is of paramount importance to assessing the thermal stability of associated luminescence signals used for dosimetry and dating. Since methods proposed for constraining thermoluminescence (TL) kinetics usually make use of the signal response to thermal treatments, accurate temperature control is required to obtain valid E and s values. In an attempt to check the extent to which consistent kinetic parameters could be obtained using routine luminescence measurement equipment, we have investigated three methods (isothermal decay, initial rise and the Hoogenstraaten method) in an inter-comparison study involving eight laboratories using Risø and Freiberg Instruments systems. The target signal was the so-called 110 °C TL peak of a sample of Oligocene coastal dune quartz sand from the Fontainebleau sand formation (France).TL glow curves recorded with heating rates in the range 0.02–5 K s−1 showed peak positions varying up to 60 °C between systems at the highest heating rates, attributed to temperature calibration errors and/or thermal lag. Kinetic parameters derived from the complete data set show a large spread, covering the ranges ∼0.5–1.2 eV and 106–1017 s−1 for E and s. In most cases, interlaboratory variations exceeded those of replicate measurements within individual laboratories. Signal lifetimes at 20 °C derived from the isothermal decay (∼59 min) and initial rise methods (at low heating rates; ∼60–80 min) most closely match the value directly measured at 20 °C from within two luminescence readers (∼70 min). Finally, we discuss the consequences of these findings for dosimetry and dating using luminescence signals and possible ways to reduce systematic errors in laboratory measurements of kinetic parameters.

Critical current measurements of high-temperature superconducting short samples at a wide range of temperatures and magnetic fields.

High-Temperature Superconductors (HTS) are potential materials for high-field magnets, low-loss transmission cables, and Superconducting Magnetic Energy Storage (SMES) due to their high upper critical magnetic field (Hc2) and critical temperature (Tc). The critical current (Ic) of HTS, which is one of the most important parameters for superconductor application, depends strongly on the magnetic fields and temperatures. A new Ic measurement system that can carry out accurate Ic measurement for HTS short samples with various temperatures (4.2-80 K), magnetic fields (0-14 T), and angles of the magnetic field (0°-90°) has been developed. The Ic measurement system mainly consists of a measurement holder, temperature-control system, background magnet, test cryostat, data acquisition system, and DC power supply. The accuracy of temperature control is better than ±0.1 K over the 20-80 K range and ±0.05 K when measured below 20 K. The maximum current is over 1000 A with a measurement uncertainty of 1%. The system had been successfully used for YBa2Cu3O7-x(YBCO) tapes Ic determination with different temperatures and magnetic fields.

Research on Temperature Control Technology of Thermal Vacuum Test in Aerospace Field

The temperature control system is an indispensable key system for the thermal vacuum test. It is used to simulate the infrared heat flow environment of the spacecraft in orbit. In order to improve the stability and reliability of temperature control, this paper designs and develops a thermal vacuum test temperature control system based on the Modbus RTU serial communication protocol on the LabVIEW platform. The system combines the flexibility of software development on LabVIEW platform and combines the stability of serial communication with controller. This temperature control system has been used in thermal vacuum test, the control effect of overshooting within 1°C and temperature control accuracy within ±0.2°C. The system has high stability, which achieves the expected goal.

Cold-Tip Temperature Control of Space-borne Satellite Stirling Cryocooler: Mathematical Modeling and Control Investigation

IR (Infra-Red) detectors are widely used in Space-borne remote sensing satellites. In order to achieve a high signal to noise ratio, the IR detectors need to be operated at cryogenic temperatures. Traditionally, the cryogenic cooling of these detectors is achieved using passive cooling techniques. However recent trend is to employ Stirling-cycle based miniaturized active cryocoolers. An accurate and stringent control of active cryocooler cold-tip temperature is essential to accomplish high signal & image quality from the IR detectors. This paper presents work on investigations and comparison of performance of proposed 2-DOF (2-Degrees-of-Freedom) versus traditional 1-DOF feedback-control structures for the control of cryocooler cold-tip temperature used in IR (Infra-Red) detectors of Space Satellites. Towards this, first-principle based control oriented mathematical model simulated in Matlab/Simulink is proposed to support such investigation and controller tuning. Open-loop (system) and closed-loop (controls) simulation results are tuned & validated with the experimental data obtained from the Lab-scale test-setup of a commercial Stirlingcryocooler. The performance of 2-DOF feedback control structures are analyzed with the help of experiment results offering a better cold-tip temperature control performance.

Prediction of Indoor Temperature and Relative Humidity Based on Cloud Database by Using an Improved BP Neural Network in Chongqing

For continuous improvement of productivity, accurate, stable, and reliable control of temperature and humidity is important in industrial production. Accurate prediction of air temperature and humidity can improve the predictability and stability of air conditioning control systems. In this paper, based on the cloud database of industry settings, an improved prediction model based on backpropagation (BP) neural networks was established to forecast indoor air temperature (IT) and relative humidity (IH) every 10 min and 6–72 h in advance. The experimental building was in Chongqing, a typical humid, hot-summer, and cold-winter area in China. The test data were used to determine the optimal parameters of the neural network model. The experimental results showed that the IT and IH predictions by our model have strong correlations with the actual data, with the coefficients of determination being 0.9897 and 0.9778, respectively. Compared with other literature, our model was more effective in temperature prediction. The presented method can be used for the prediction and control of the indoor temperature and relative humidity in industrial production.

On the InGaAs-based Photodetection Circuit for Scanning Near-Infrared Signal in the Wavelength Range of 1.0-2.0μm

Detection of scanning long wave near-infrared (NIR) signal is critical in numerous applications spanning the fields of military, industry, agriculture, environment, and medicine. In this paper, we present a low cost, high performance InGaAs-based photoelectric conversion and amplification circuit for detecting scanning NIR signal in the wavelength range of 1.0-2.0 μm. With a special focus on reducing the influence of dark current and dark current noise for improved detector efficiency and precision, this proposed circuit features a photovoltaic preamplifier, a low-pass filter, and a temperature control unit; the signal gain, the bandwidth and the noise of the entire circuit is tuned for the signal spectrum of interest. In particular, to make the InGaAs detector operate at the target temperature with little fluctuation, a low-cost closed-loop temperature control circuit is designed that delivers temperature control accuracy of ±0.1°C. Both simulation and experimental results have confirmed that the proposed detection circuit meets the specific performance requirements for its intended use in spectrometer.

Optimization design of the tuning method for FBG spectroscopy based on the numerical analysis of all-fiber Raman temperature lidar

Abstract All fiber Raman temperature lidar for space borne platform has been proposed for profiling of the temperature with high accuracy. Fiber Bragg grating (FBG) is proposed as the spectroscopic system of Raman lidar because of good wavelength selectivity, high spectral resolution and high out-of-band rejection rate. Two sets of FBGs at visible wavelength 532 nm as Raman spectroscopy system are designed for extracting the rotational Raman spectra of atmospheric molecules, which intensities depend on the atmospheric temperature. The optimization design of the tuning method of an all-fiber rotational Raman spectroscopy system is analyzed and tested for estimating the potential temperature inversion error caused by the instability of FBG. The cantilever structure with temperature control device is designed to realize the tuning and stabilization of the central wavelengths of FBGs. According to numerical calculation of FBG and finite element analysis of the cantilever structure, the center wavelength offset of FBG is 11.03 nm/°C with the temperature change in the spectroscopy system. By experimental observation, the center wavelength offset of surface-bonded FBG is 9.80 nm/°C with temperature changing when subjected to certain strain for the high quantum number channel, while 10.01 nm/°C for the low quantum number channel. The tunable wavelength range of FBG is from 528.707 nm to 529.014 nm for the high quantum number channel and from 530.226 nm to 530.547 nm for the low quantum number channel. The temperature control accuracy of the FBG spectroscopy system is up to 0.03 °C, the corresponding potential atmospheric temperature inversion error is 0.04 K based on the numerical analysis of all-fiber Raman temperature lidar. The fine tuning and stabilization of the FBG wavelength realize the elaborate spectroscope of Raman lidar system. The conclusion is of great significance for the application of FBG spectroscopy system for space-borne platform Raman lidar.

Depolarization currents in illite

In ceramic materials, depolarization effects take place when an external electrical field is removed. Therefore, an understanding of mechanisms of polarization and depolarization is important for a more accurate control of furnace temperature and DC or pulse electrical field in flash sintering. In this paper, depolarization currents were measured in illitic clay samples in the temperature range 450–1100 °C for 150–300 min. The ionic component was dominant in these depolarization currents. Time dependences of depolarization currents suggested several depolarization mechanisms took place. They were caused by localized hopping or migration of K+, Na+, H+, and OH− ions, which were the dominant charge carriers in various temperature ranges, in the internal electric field induced by space charges at electrodes. Depolarization is a long-lasting process at high temperatures and influences the internal electrical field in ceramics.

Design of Water Temperature Control System Based on Single Chip Microcomputer

In this paper, we mainly introduce a multi-function water temperature controller designed with 51 single-chip microcomputer. This controller has automatic and manual water, set the water temperature, real-time display of water and temperature and alarm function, and has a simple structure, high reliability, low cost. The current water temperature controller on the market basically use bimetal temperature control, temperature control accuracy is low, poor reliability, a single function. With the development of microelectronics technology, monolithic microprocessor function is increasing, the price is low, in all aspects of widely used. In the water temperature controller in the application of single-chip, with a simple design, high reliability, easy to expand the advantages of the function. Is based on the appeal background, so this paper focuses on the temperature controller in the intelligent control of the discussion.

NMR Quantification of Carbohydrates in Complex Mixtures. A Challenge on Honey.

The knowledge of carbohydrate composition is greatly important to determine the properties of natural matrices such as foodstuff and food ingredients. However, because of the structural similarity and the multiple isomeric forms of carbohydrates in solution, their analysis is often a complex task. Here we propose an NMR analytical procedure based on highly selective chemical shift filters followed by TOCSY, which allows us to acquire specific background-free signals for each sugar. The method was tested on raw honey samples dissolved in water with no other pretreatment. In total, 22 sugars typically found in honey were quantified: 4 monosaccharides (glucose, fructose, mannose, rhamnose), 11 disaccharides (sucrose, trehalose, turanose, maltose, maltulose, palatinose, melibiose and melezitose, isomaltose, gentiobiose nigerose, and kojibiose), and 7 trisaccharides (raffinose, isomaltotriose, erlose, melezitose, maltotriose, panose, and 1-kestose). Satisfactory results in terms of limit of quantification (0.03-0.4 g/100g honey), precision (% RSD: 0.99-4.03), trueness (bias % 0.4-4.2), and recovery (97-104%) were obtained. An accurate control of the instrumental temperature and of the sample pH endows an optimal chemical shift reproducibility, making the procedure amenable to automation and suitable to routine analysis. While validated on honey, which is one of the most complex natural matrices in terms of saccharides composition, this innovative approach can be easily transferred to other natural matrices.

Numerical study of heat transfer and thermal homogenization in a helical reactor

A fast and accurate control of the flow temperature by heating or cooling through the wall is essential for many chemical applications, in particular to achieve optimal reaction intensification. A numerical study based on computational fluid dynamics (CFD) has been done to investigate thermal homogenization within a horizontally-coiled helical pipe. The main target is to examine and compare the flow and mixing characteristics when heating different axial parts of the coil. The entrance region and two other locations within the fully-developed flow region have been investigated for that purpose; the first, the third and the fifth turn of a ten-turn coil have been heated individually. In each case, temperature field and thermal homogenization were assessed. The performance was quantified in terms of the required axial length for the temperature profile to become uniform again after heating. The investigations were performed for water as a working fluid, and for a wide range of Reynolds numbers between 2000 and 16,000, covering both the laminar range and transition to turbulence in the helical pipe. The thermal mixing performance in the entrance region was found to be noticeably better than that in the fully-developed region, increasingly so at higher Reynolds numbers. Therefore, it is recommended to systematically use the entrance region of a coil reactor for a fast and efficient step rise of the flow temperature.

Energy-Saving Benefits of Adiabatic Humidification in the Air Conditioning Systems of Semiconductor Cleanrooms

This paper aimed to evaluate the applicability of adiabatic humidification in the heating, ventilation, and air conditioning (HVAC) systems of semiconductor cleanrooms. Accurate temperature and humidity control are essential in semiconductor cleanrooms and high energy consumption steam humidification is commonly used. Therefore, we propose an adiabatic humidification system employing a pressurized water atomizer to reduce the energy consumption. The annual energy consumption of three different HVAC systems were analyzed to evaluate the applicability of adiabatic humidification. The studied cases were as follows: (1) CASE 1: a make-up air unit (MAU) with a steam humidifier, a dry cooling coil (DCC), and a fan filter unit (FFU); (2) CASE 2: a MAU with the pressurized water atomizer, a DCC, and a FFU; and (3) CASE 3: a MAU, a DCC, and a FFU, and the pressurized water atomizer installed in the return duct. The energy saving potential of adiabatic humidification over steam humidification has been proved, with savings of 8% and 23% in CASE 2 and CASE 3 compared to CASE 1, respectively. Furthermore, the pressurized water atomizer installed in the return duct exhibits greater energy saving effect than when installed in the MAU.