Compensation Of Temperature Effects Research Articles

Signal-based nonlinear modelling for damage assessment under variable temperature conditions by means of acousto-ultrasonics

Damage assessment can be considered as the main task within the context of structural health monitoring (SHM) systems. This task is not only confined to the detection of damages in its basic algorithms but also in the generation of early warnings to prevent possible catastrophes in the daily use of the structures ensuring their proper functioning. Changes in environmental and operational conditions (EOC), in particularly temperature, affect the performance of SHM systems that constitutes a great limitation for their implementation in real world applications. This paper describes a health monitoring methodology combining the advantages of guided ultrasonic waves together with the compensation for temperature effects and the extraction of defect-sensitive features for the purpose of carrying out a nonlinear multivariate diagnosis of damage. Two well-known methods to compensate the temperature effects, namely optimal baseline selection and optimal signal stretch, are investigated within the proposed methodology where the performance is assessed using receiver operating characteristic curves. The methodology is experimentally tested in a pipeline. Results show that the methodology is a robust practical solution to compensate the temperature effects for the damage detection task. Copyright © 2015 John Wiley & Sons, Ltd.

The circadian rhythms of photosynthesis, ATP content and cell division in Microcystis aeruginosa PCC7820

Microcystis aeruginosa is one of the most common blue-green algae species that forms harmful water bloom, which frequently causes serious ecological pollution and poses a health hazard to animals and humans. To understand the progression of algal blooms and to provide a theoretical basis for predicting and preventing the occurrence of algal blooms and reducing the harm of algal bloom to environment, we investigated the diurnal variation of photosynthesis, ATP content and cell division in M. aeruginosa PCC7820. The results showed that the photosynthesis and ATP content of M. aeruginosa PCC7820 exhibited clear circadian rhythm with a period of approximately 24 h and that the periodic rhythms continued for at least three cycles under continuous light conditions. Furthermore, the period length showed that a temperature compensation effect and changes in light cycle or temperature could reset the phase of circadian rhythm. These results indicate that the circadian rhythms of physiological process in M. aeruginosa PCC7820 are controlled by the endogenous circadian clock. Examinations of the number, size and cytokinin content of cells also reveal that the cell division of M. aeruginosa PCC7820 with the generation time of 38.4 h exhibits robust circadian rhythms with a period close to 24 h. The circadian rhythms of cell division may be generated by a biological clock through regulation of the cell division phase of M. aeruginosa PCC7820 via a gating mechanism. The phases in which cell division slows or stop recur with a circadian periodicity of about 24 h.

Temperature effect compensation for fast differential pressure decay testing

To avoid the long temperature recovery period with differential pressure decay for leak detection, a novel method with temperature effect compensation is proposed to improve the testing efficiency without full stabilization of temperature. The mathematical model of conventional differential pressure decay testing is established to analyze the changes of temperature and pressure during the measuring period. Then the differential pressure is divided into two parts: the exponential part caused by temperature recovery and the linear part caused by leak. With prior information obtained from samples, parameters of the exponential part can be identified precisely, and the temperature effect will be compensated before it fully recovers. To verify the effect of the temperature compensated method, chambers with different volumes are tested under various pressures and the experiments show that the improved method is faster with satisfactory precision, and an accuracy less than 0.25 cc min−1 can be achieved when the compensation time is proportional to four times the theoretical thermal-time constant.

An adaptive filter–based temperature compensation technique for structural health monitoring

Temperature variations have significant effects on guide wave propagation and therefore increase the detection uncertainty of the guided wave–based structural health monitoring system. A novel temperature compensation technique combining an adaptive filter and optimal baseline selection is developed to enhance the robustness and effectiveness of guided wave–based damage detection. The adaptive filter is the finite length unit impulse response digital filter based on adaptive linear neuron network. This article focuses on three main issues for practically implementing the proposed method: (a) establishment of temperature compensation standard, (b) parameter design of compensation filter, and (c) determination of temperature gradient to reduce the number of selected baselines. Experiments are conducted on two stiffened composite plates to verify the proposed method for effective and robust temperature compensation under a large temperature range from −40°C to 80°C. Results show that temperature interval for baselines of low-frequency signals, such as 50 kHz, can be up to 20°C to provide good temperature compensation with the proposed method, while temperature interval for baselines of high-frequency signals, such as 450 kHz, can be up to 12°C.

EFPI-FBG hybrid sensor for simultaneous measurement of high temperature and large strain

We report an extrinsic Fabry-Perot interferometer-fiber Bragg grating (EFPI-FBG) hybrid sensor in this letter. The interferometric cavity of the proposed hybrid sensor is composed of a glass capillary tube, a section of single-mode fiber, and a section of single-mode metal fiber with one FBG. The FBG processed by high-temperature annealing is used to measure temperature, whereas the fiber EFPI is adopted for strain measurement. One of the two aligned fibers is free along the axial direction, which is different from the traditional structure that both the fibers are fixed to glass capillary tube. Experimental results show that the sensor can measure high temperature and large strain simultaneously. The measuring range of temperature and strain for the hybrid sensor is up to 500 °C and 10,000 µ.., respectively. Effective temperature compensation of the hybrid sensor is realized, too.

A sub‐1 V nanopower temperature‐compensated sub‐threshold CMOS voltage reference with 0.065%/V line sensitivity

AbstractWe present the design of a nanopower sub‐threshold CMOS voltage reference and the measurements performed over a set of more than 70 samples fabricated in 0.18 µm CMOS technology. The circuit provides a temperature‐compensated reference voltage of 259 mV with an extremely low line sensitivity of only 0.065% at the price of a less effective temperature compensation. The voltage reference properly works with a supply voltage down to 0.6 V and with a power dissipation of only 22.3 nW. Very similar performance has been obtained with and without the inclusion of the start‐up circuit. Copyright © 2013 John Wiley & Sons, Ltd.

Cointegration approach for temperature effect compensation in Lamb-wave-based damage detection

Lamb waves are often used in smart structures with integrated, low-profile piezoceramic transducers for damage detection. However, it is well known that the method is prone to contamination from a variety of interference sources including environmental and operational conditions. The paper demonstrates how to remove the undesired temperature effect from Lamb wave data. The method is based on the concept of cointegration that is partially built on the analysis of the non-stationary behaviour of time series. Instead of directly using Lamb wave responses for damage detection, two approaches are proposed: (i) analysis of cointegrating residuals obtained from the cointegration process of Lamb wave responses, (ii) analysis of stationary characteristics of Lamb wave responses before and after cointegration. The method is tested on undamaged and damaged aluminium plates exposed to temperature variations. The experimental results show that the method can: isolate damage-sensitive features from temperature variations, detect the existence of damage and classify its severity.

Thermotolerance Responses in Ripening Berries of Vitis vinifera L. cv Muscat Hamburg

Berry organoleptic properties are highly influenced by ripening environmental conditions. In this study, we used grapevine fruiting cuttings to follow berry ripening under different controlled conditions of temperature and irradiation intensity. Berries ripened at higher temperatures showed reduced anthocyanin accumulation and hastened ripening, leading to a characteristic drop in malic acid and total acidity. The GrapeGen GeneChip® combined with a newly developed GrapeGen 12Xv1 MapMan version were utilized for the functional analysis of berry transcriptomic differences after 2 week treatments from veraison onset. These analyses revealed the establishment of a thermotolerance response in berries under high temperatures marked by the induction of heat shock protein (HSP) chaperones and the repression of transmembrane transporter-encoding transcripts. The thermotolerance response was coincident with up-regulation of ERF subfamily transcription factors and increased ABA levels, suggesting their participation in the maintenance of the acclimation response. Lower expression of amino acid transporter-encoding transcripts at high temperature correlated with balanced amino acid content, suggesting a transcriptional compensation of temperature effects on protein and membrane stability to allow for completion of berry ripening. In contrast, the lower accumulation of anthocyanins and higher malate metabolization measured under high temperature might partly result from imbalance in the expression and function of their specific transmembrane transporters and expression changes in genes involved in their metabolic pathways. These results open up new views to improve our understanding of berry ripening under high temperatures.

Continuous baseline growth and monitoring for guided wave SHM

It has been shown by many authors that temperature effect compensation is a necessity for the realization of a reliable structural health monitoring (SHM) system. However, there exist practical issues related to the acquisition of baseline signals, required for temperature compensation methods to work effectively, such as degenerate baseline signals recorded at the same temperature and a long acquisition period before monitoring is started. An alternative approach for the acquisition of baseline signals is presented in this paper. The algorithm makes the acquisition an evolutionary process, integrated in the damage detection procedures. The algorithm is shown to be successful in generating a concise set of baselines that guarantees efficient performance of temperature compensation methods, leading to computation time and computer memory savings. Its capabilities in detecting simulated abrupt and slowly evolving damages have also been tested.

Temperature Behavior and Compensation of Diode-Based Pre-Distortion Linearizer

This letter presents temperature behavior and compensation technique of Schottky diode and p-i-n diode based pre-distortion linearizer operating at microwave frequency. We have theoretically analyzed and experimentally demonstrated the temperature behavior of the linearizer and proposed a simple but effective temperature compensation technique. The proposed temperature compensation technique provides temperature dependent control bias to the diodes to achieve temperature invariant amplitude and phase expansion of the linearizer. Here design, simulation and test results of a temperature compensated linearizer is presented that compensates amplitude and phase variation from 6 dB and 50° to less than 0.7 dB and 4.5°, respectively, over a temperature range of -20 °C to +80 °C.

Analysis of Deformation of Reflector for RF-Excited CO<sub>2</sub> Laser

The paper aims to study the deformation and compensation of the reflector for RF-excited diffusion-cooled CO2 laser. Based on ANSYS, the thermal deformation and compensation of the reflector have been calculated, It has been proved that the effect of temperature compensation is obvious, and can correct the thermal deformation of the reflector to the tolerance of the parameter of optical cavity.

Measurement of Radius of Curvature by Coordinate Measurement Machine

Radius of curvature is one of the key parameters of optical components. A variety of methods have been developed for this measurement. This paper describes a novel way, named “CMM spherometry by probe compensation”, to measure the radius of curvature of optical surfaces by coordinate measuring machine (CMM). The measurement combines CMM measurement and iteration calculation scheme is presented. The measurement results of CMM and the trace samples are compared. The effect of temperature compensation is discussed.

Investigation of a Pressure Sensor with Temperature Compensation Using Two Concentric Wheatstone-Bridge Circuits

This study presents a silicon-based pressure sensor with temperature compensation. The eight piezoresistors were designed on the polycrystalline silicon membrane and constructed by two concentric Wheatstone-bridge circuits to perform two sets of sensors. The sensor in the central circuit measures the membrane deflection caused by the combined effects of pressure and temperature, while the outer one measures only the deflection caused by the working temperature. From this arrangement, it is reliable and accurate to measure the pressure by comparing the output signals from the two concentric Wheatstone-bridge circuits. The optimal positions of the eight piezoresistors were simulated by simulation software ANSYS. The investigated pressure sensor was fabricated by the micro electro-mechanical systems (MEMS) techniques. The measuring performance and an indication of the conventional single Wheatstone-bridge pressure sensor is easily affected under variation of different working temperature and causes a maximum absolute error up to 45.5%, while the double Wheatstone-bridge pressure sensor is able to compensate the error, and reduces it down to 1.13%. The results in this paper demonstrate an effective temperature compensation performance, and have a great performance and stability in the pressure measuring system as well.

Temperature-independent and enhanced dielectric properties for two-layer structure capacitors with 0.8Pb(Fe2/3W1/3)O3–0.2PbTiO3–MnO and 0.7Pb(Fe2/3W1/3)O3–0.3PbTiO3–MnO ceramics

This study fabricates capacitors with two-layer structure and different compositions, 0.8Pb(Fe2/3W1/3)O3–0.2PbTiO3–MnO and 0.7Pb(Fe2/3W1/3)O3–0.3PbTiO3–MnO, by using the conventional solid state oxide reaction method. By using the temperature compensation effect and adjusting the thickness ratio of the two layers with different compositions, the temperature–dielectric peak is enhanced and smoothed. The dielectric loss, space charge polarization and dc conduction are suppressed at the highest temperature region. Furthermore, the Maxwell–Wagner model is used to fit and explain the dielectric behaviors. This study also provides suggestions and discussion related to the effect of the interfacial region based on the experimental data and fitting results.

Auto-calibration of drive condition for cholesteric liquid crystal displays

Dynamic drive scheme (DDS) is known widely as passive matrix addressing that obtains both high-speed re-writing and a high contrast ratio in the field of cholesteric liquid crystal displays (LCDs). However, DDS has a serious problem in that the proper drive condition is very narrow and it is largely influenced by individual differences in LCDs that arise during their production. We have developed a new auto-calibration system that adjusts both the contrast ratio and color balance automatically using capacitances of effective pixels and temperature compensation models that utilize the physical properties of cholesteric LCDs. We have managed to optimize the driving conditions between 5 and 35 °C with this method, and obtained both stable and high-quality color images where the reflectance is 36%, contrast ratio is 8, and NTSC ratio is 20%. This auto-calibration system has been able to greatly improve the production yield of cholesteric LCDs and made it possible to make practical use of cholesteric LCDs.

석유류제품 토출온도 보정에 따른 경제성 분석

석유제품(휘발유, 경유 등)은 온도의 변화에 따라 부피가 변하기 때문에 기온이 높은 여름철에는 팽창된 부피로 공급받고, 기온이 낮은 겨울철에는 수축된 부피로 공급받는 특성이 있다. 따라서 여름철과 겨울철에 동일량을 주유하더라도 기준온도(<TEX>$15^{\circ}C$</TEX>)로 환산하면 주유량에 차이가 발생한다. 본 연구에서는 자동온도 보정장치를 부착함에 따른 경제적 편익과 이에 따라 수반되는 경제적 비용을 분석하였다. 분석결과 이론적으로 온도보정장치 부착에 따른 경제적 비용과 경제적 편익이 동일한 효과를 낳지만 부피변화의 한계비용곡선이 불확실성하에 있다면 상이한 결과를 초래할 수 있으므로 미래에 대한 불확실성 및 다양한 평가기준에 입각하여 적정한 정책수단을 선택하는 것 또한 중요한 과제가 될 것이다. The importance of physical changes in volume due to changes in temperature has been known for more than a century by the petroleum industry. To examine whether there are any differences between the economic effect of automatic temperature compensation and that of installation cost. The results of the analysis show that there are no ineffective in automatic temperature compensation installation. Analysis showed the increase of price oil will impact negatively on the automatic temperature compensation, appropriate level of economic cost and economic benefit should be calculated for the policy implementation in the future's study.

The effect of temperature compensation on the circadian rhythmicity of photosynthesis in Symbiodinium, coral-symbiotic alga

Circadian rhythms, which are found in most eukaryotes, are defined as rhythms that persist under constant conditions with a periodicity close to 24 h. One central key characteristic of all circadian rhythms is “temperature compensation”, which allows organisms to maintain robust rhythms with a period close to a diel cycle over a broad range of physiological temperatures. To better understand the response of the circadian clock in corals to temperature elevation, photosynthesis as an output process of the circadian clock was studied both in Stylophora pistillata corals and in cultured Symbiodinium algae. The time period of photosynthesis was not affected by temperature elevation in the cultured algae or in the corals harbouring Symbiodinium. However, the photosynthetic system responded to temperature elevations by adjusting the photosynthetic apparatus. These findings suggest that the endogenous algal circadian clock regulates the photosynthetic rhythm and compensates for temperature elevations that occur in the natural environment.

Miniature Fabry-Perot pressure sensor created by using UV-molding process with an optical fiber based mold

We present a miniature Fabry-Perot pressure sensor fabricated at the tip of an optical fiber with a pre-written Bragg grating by using UV-molding polymer process. The mold is constructed by integrating an optical fiber of 80 μm diameter with a zirconia ferrule. The optical fiber based mold makes it possible to use optical aligning method to monitor the coupled intensity between the mold-side and replica-side fibers, rendering a maskless alignment process with a submicrometer accuracy. A polymer-metal composite thin diaphragm is employed as the pressure transducer. The overall sensor size is around 200 μm in diameter. Experimental study shows that the sensor exhibits a good linearity over a pressure range of 1.9-7.9 psi, with a sensitivity of 0.0106 μm/psi. The fiber Bragg grating is exploited for simultaneous temperature measurements or compensation for temperature effects in pressure readings. The sensor is expected to benefit many fronts that require miniature and inexpensive sensors for reliable pressure measurement, especially biomedical applications.

CMOS Transistor Amplifier Temperature Compensation: Modeling and Analysis

The effect of temperature variations on a cascode low-noise MOS amplifier is analyzed. A gate biasing scheme for temperature compensation is illustrated. RF circuit simulation results show that the low-noise amplifier with temperature compensation can reduce temperature variation effect on the noise figure of the amplifier over a wide range of temperatures. Analytical equations to predict temperature compensation effect are also presented.

Temperature Frequency Characteristics of Hexamethyldisiloxane (HMDSO) Polymer Coated Rayleigh Surface Acoustic Wave (SAW) Resonators for Gas-Phase Sensor Applications

Temperature induced frequency shifts may compromise the sensor response of polymer coated acoustic wave gas-phase sensors operating in environments of variable temperature. To correct the sensor data with the temperature response of the sensor the latter must be known. This study presents and discusses temperature frequency characteristics (TFCs) of solid hexamethyldisiloxane (HMDSO) polymer coated sensor resonators using the Rayleigh surface acoustic wave (RSAW) mode on ST-cut quartz. Using a RF-plasma polymerization process, RSAW sensor resonators optimized for maximum gas sensitivity have been coated with chemosensitive HMDSO films at 4 different thicknesses: 50, 100, 150 and 250 nm. Their TFCs have been measured over a (−100 to +110) °C temperature range and compared to the TFC of an uncoated device. An exponential 2,500 ppm downshift of the resonant frequency and a 40 K downshift of the sensor’s turn-over temperature (TOT) are observed when the HMDSO thickness increases from 0 to 250 nm. A partial temperature compensation effect caused by the film is also observed. A third order polynomial fit provides excellent agreement with the experimental TFC curve. The frequency downshift due to mass loading by the film, the TOT and the temperature coefficients are unambiguously related to each other.