Effect Of Ambient Temperature Variation Research Articles

Structural damage identification under ambient temperature variations based on CNN and normalized modal flexibility-autoregressive coefficients hybrid index

This study proposes a novel method to identify structural damage considering ambient temperature variations. In this method, the normalized modal flexibility based index (nMFBI) and autoregressive (AR) coefficients are combined to form the nMFBI-AR hybrid index, and convolutional neural networks (CNN) are exploited to locate and quantify the damage. Moreover, the effects of ambient temperature variations and measurement noise are not considered in the training dataset, which is preferable in practical engineering. To verify the effectiveness of the proposed method, firstly, a numerical structure of a simply supported beam is investigated, and the performance of the nMFBI-AR index is evaluated by making a comparison with the nMFBI and AR indexes. Then, the proposed method is further verified by a test model of a three-story frame and a practical engineering example of a continuous rigid frame bridge. The results demonstrate that although the influence of ambient temperature variations and measurement noise are only considered in the test datasets, this approach has the best performance in locating and quantifying structural damage, and the errors are less than 16%, which is promising. In addition, this paper provides a guideline and a new idea for the study of damage index based on time-frequency hybrid information.

Significance of slight ambient temperature variation on the electrocatalyst performance toward oxygen evolution reaction

Hundreds of oxygen evolution reaction (OER) electrocatalysts have been developed over the past few decades, and their performances are evaluated and compared at ambient temperature. However, the effect of ambient temperature variation on OER electrocatalyst performance has received less attention, which may play a remarkable role in the electrocatalytic activity. In this work, we systematically investigated the influence of ambient temperature variation on electrocatalyst performance toward OER. The results show that the slight ambient temperature variation has a significant effect on OER catalyst performance based on the changes of overpotential (10 mA cm−2) and Tafel slope. Both remarkable chances are observed on transition metal (Ni) and noble metal (IrO2) electrocatalysts, and the overpotentials decrease around 81 mV with a temperature increase by 20 °C (from 10° to 30°C) for both Ni and IrO2 electrocatalysts with the Tafel slope drops of 36.9 and 29.5 mV dec−1, respectively. A similar trend is also found in the electrochemically active surface (ECSA) normalized performance and the charge transfer resistance. This study demonstrates that reporting the actual operating temperature for OER is not only recommended but also necessary to evaluate and compare electrocatalyst activities from different materials systems properly, and neglecting the ambient temperature variation effect can highly mislead conclusions.

CONCENTRATING SOLAR POWERED TRANSCRITICAL CO2 POWER GENERATION CYCLE FOR THE UNION TERRITORY OF LADAKH, INDIA

High solar irradiation, cloud-free dry climate, abundant barren land, and low ambient temperature make the Union Territory of Ladakh, India, suitable for concentrating solar thermal power (CSP) plants. The present study comprehensively analyzes a 5 MW transcritical CO<sub>2</sub> Rankine cycle power tower CSP plant. Low ambient temperature of the region allows transcritical operation, which provides high cycle efficiency. The study focuses on five aspects: solar field and thermal energy storage (TES), thermodynamic cycle simulation, turbomachines, and off-design performance analysis. Modeling and optimization of the solar field are undertaken to capture the diurnal and annual variations of direct normal irradiation levels using System Advisor Model open source software. Molten salt TES is integrated to overcome the dynamic variations of solar energy by providing stable operations and additional hours. The effect of storage sizes, starting from no storage to 12 hours, on the solar field size and specifications is also assessed. An in-house algorithm is developed for thermodynamic cycle optimization, exergy analysis, and off-design operations. The turbomachines of the cycle are designed using in-house meanline codes, and 3D CFD simulations are conducted for efficiency estimations. The effects of ambient temperature variations on the low side saturation pressure, cycle efficiency, and power output are evaluated. The proposed plant offers annual optical efficiency of 54.1%, thermal efficiency of 36.5%, and overall efficiency of 19.7%.

Architecture of an Electrical Equivalence Pyranometer with Temperature Difference Analog Control.

In this paper, an architecture of an electrical equivalence pyranometer with analog control of the temperature difference is presented. The classical electrical equivalence pyranometer employs a Wheatstone bridge with a feedback amplifier to keep the sensor operating at a constant temperature to estimate the incident radiation through the sensor thermal balance employing the electrical equivalence principal. However, this architecture presents limitations under ambient temperature variation, such as sensitivity variation. To overcome those limitations, we propose an architecture that controls the temperature difference between the sensor and ambient via an analog compensating circuit. Analytical results show an improvement near five times in sensitivity over the ambient temperature span and 76.3% increase of useful output voltage. A prototype was developed and validated with a commercial pyranometer, showing a high agreement on the measurement results. It is verified that the use of temperature difference, rather than constant temperature, significantly reduces the effect of ambient temperature variation.

Impacts of Ambient Temperature Change on the Breakdown Voltage of a Distribution Transformer

The aim of this paper is to determine the effects of ambient temperature variation on the breakdown voltage of a distribution transformer. Three different insulation oil samples (naphtha mineral, paraffin mineral and silicon base transformer oil) were collected from six distribution transformers (300 – 500 kVA) across two business units (Asaba and Ugbowo) of Benin Electricity Distribution Company during May and June, 2017. The oil samples were analysed using the 60 kV Megger OST60PB portable oil tester, to determine the trend of breakdown voltage of the oil insulation under varying temperature. A 3rd order polynomial model was deduced for each sample type with coefficient of determination within the range of 96.99 – 99.95 %. The observed average breakdown voltage is 43.6 kV (for naphtha base mineral transformer oil), 42.2 kV (for paraffin base mineral transformer oil) and 46.8 kV (for silicon base transformer oil) within the temperature range (26˚C – 32˚C). The result indicates that the breakdown voltages of the considered transformer oil types are satisfactory but the silicon base transformer oil has the best breakdown voltage.

Effect of Ambient Temperature Variation on Pressure Drop During Condensation in Long Inclined Tubes

Abstract Two-phase flow pressure drop during condensation of steam inside inclined tube heat exchangers was investigated over a wide range of ambient temperature. The ambient temperature changes from 3 to 45 °C, the steam mass flux varies from 3 to 18 kg/(m2 · s), vapor quality ranges from 0.51 to 0.86. 608 data points were experimentally obtained and compared with eight commonly used correlations from the available literatures. Frictional pressure drop increases with increasing temperature difference and fan speed. For the full experimental dataset, the best overall performing correlation was obtained by using the Wallis correlation (MAPE = 17.60%, NRMSE = 14.87%). For cold ambient temperatures, (Tamb < 20 °C, N = 298), the best overall performing correlation was obtained by using the Carey correlation (MAPE = 11.02%, NRMSE = 14.71%). For hot ambient temperatures (Tamb > 30 °C, N = 196), the Lockhart and Martinelli correlation has shown the best performance (MAPE = 16.84%, NRMSE = 20.45%). An improved two-phase frictional pressure drop correlation based on the Wallis correlation (Wallis, 1969, One Dimensional Two-Phase Flow, McGraw-Hill, New York) is proposed.

Effect of ambient temperature variations on estimation of proximity of the voltage collapse point

Due to deforestation, greenhouse gases and increasing air conditioner systems, the temperatures are changing drastically and the effects are prominent in summer and winter seasons. These ambient temperature variations are affecting the transmission system parameters and also the voltages at various buses. Changes in the transmission line parameters have non-negligible impact on system performance and present Energy Management applications are not considering these temperature variations in the power system state estimation. In this paper, impact of temperature variations on the power system Voltage Stability assessment is considered. Voltage stability assessment methods make use of the load flow results. Load flow results without considering the temperature variations are inaccurate in the real-time and leading to the erroneous results in the voltage stability assessment. In view of this, studies have been carried out on IEEE 30-bus, 118-bus and 300-bus systems, incorporating the seasonal temperature variations on various types of conductors, and also demonstrated the impact with conventional and ZIP type load models. In this paper, four voltage stability indices NLVSI, L m n , FVSI and VCPI(power) are used for identifying the proximity of voltage collapse point, critical line, critical bus voltage, critical bus angle, total system active power loss, total system reactive power loss etc.

Effect of ambient temperature variations on an indigenous microalgae-nitrifying bacteria culture dominated by Chlorella

Two outdoor photobioreactors were operated to evaluate the effect of variable ambient temperature on an indigenous microalgae-nitrifying bacteria culture dominated by Chlorella. Four experiments were carried out in different seasons, maintaining the temperature-controlled PBR at around 25 °C (by either heating or cooling), while the temperature in the non-temperature-controlled PBR was allowed to vary with the ambient conditions. Temperatures in the range of 15–30 °C had no significant effect on the microalgae cultivation performance. However, when the temperature rose to 30–35 °C microalgae viability was significantly reduced. Sudden temperature rises triggered AOB growth in the indigenous microalgae culture, which worsened microalgae performance, especially when AOB activity made the system ammonium-limited. Microalgae activity could be recovered after a short temperature peak over 30 °C once the temperature dropped, but stopped when the temperature was maintained around 28–30 °C for several days.

Thermodynamic and thermoeconomic analysis of a 21 MW binary type air-cooled geothermal power plant and determination of the effect of ambient temperature variation on the plant performance

Abstract The thermodynamic and thermoeconomic performances of a 21 MW geothermal power plant with air-cooled two level binary type organic Rankine cycle was numerically investigated based on its design and operating data. The investigated plant is the Sinem Geothermal Power Plant in Germencik, Aydin, Turkey. The paper provides a detailed comparison of the exergetic performance of this plant with other eight similar type of plant units, which make use of geothermal resources with similar specific exergies. Results indicate that the exergetic efficiency of the Sinem Geothermal Power Plant is the highest with 48.2% and the others vary between 9.6% and 42.7%. This result is mainly related to the exergy losses due to suppression of heat transfer in this plant, via low temperature brine reinjection, small temperature difference in the heat exchangers and high efficiencies of the individual components. First and second law efficiencies, as well as the exergy losses and improvement potentials of each component in the plant are also calculated. In air-cooled geothermal power plants, since ambient temperature is a critical parameter for the plant performance, both thermal and economic analysis of the plant is performed based on variation in ambient air temperature. Specifically, thermoeconomic analysis of the plant is evaluated to determine the exergoeconomic factor, the relative cost difference and the sum unit cost of the product (SUCP) of the plant. The effect of ambient temperature on the SUCP of the power plant, power generation, energy and exergy efficiencies are also examined in the present study. The results showed that; when the ambient temperature increases from 5 °C to 35 °C the reduction in power generation is 6.8 MW, energy efficiency decreases from 13.7% to 9.2% while exergy efficiency decreases from 54.9% to 36.7 and SUCP of the plant increases from nearly 230 $/GJ to 330 $/GJ.

A Plasmonic Fiber Based Glucometer and Its Temperature Dependence.

We present the plasmonic fiber based optical glucometer. A thin gold layer is coated on clad-free core of multimode optical fiber along 3 cm length to excite surface plasmons at 632.8 nm wavelength. Glucose oxidase is immobilized on the metal surface for glucose sensing. The effective surface refractive index increases by gluconic acid and hydrogen peroxide that are generated upon glucose injection, leading to plasmonic condition change with a consequence of optical power change at the fiber output. We obtain limit of detection of glucose concentration of 6.75 mg/dL, indicating higher sensitivity than the wavelength interrogating SPR glucometer that uses a spectrometer of 1nm spectral resolution. The coefficient of variation is 8.6% at a glucose concentration of 80 mg/dL at room temperature. We also examine the effects of ambient temperature variations from −10 °C to 40 °C on the performance of the presented sensor and compared them with those on commercially available glucometers that are based on enzyme electrodes. We find that the presented fiber sensor produced standard deviation of 12.1 mg/dL at a glucose concentration of 80 mg/dL under such varying temperature, which is, even without additional temperature correction function, comparable to the commercialized ones.

PCA-based filtering of temperature effect on impedance monitoring in prestressed tendon anchorage

For the long-term structural health monitoring of civil structures, the effect of ambient temperature variation has been regarded as one of the critical issues. In this study, a principal component analysis (PCA)-based algorithm is proposed to filter out temperature effects on electromechanical impedance (EMI) monitoring of prestressed tendon anchorages. Firstly, the EMI monitoring via a piezoelectric interface device is described for prestress-loss detection in the tendon anchorage system. Secondly, the PCA-based temperature filtering algorithm tailored to the EMI monitoring of the prestressed tendon anchorage is outlined. The proposed algorithm utilizes the damage-sensitive features obtained from sub-ranges of the EMI data to establish the PCA-based filter model. Finally, the feasibility of the PCA-based algorithm is experimentally evaluated by distinguishing temperature changes from prestress-loss events in a prestressed concrete girder. The accuracy of the prestress-loss detection results is discussed with respect to the EMI features before and after the temperature filtering.

Cut Off Frequency Variation by Ambient Heating in Tunneling p-i-n CNTFETs

In this paper, we study the effects of ambient temperature variations on the high frequency behavior of tunneling carbon nanotube field effect transistors (T-CNTFETs). Device characteristics including transconductance, gate capacitance, and intrinsic cutoff frequency are extracted and their variations by temperature are investigated. To study and simulate a tunneling carbon nanotube field effect transistor we used self-consistent numerical solution of Poisson-Schrodinger equations and non-equilibrium Green's function method. The studies carried out on 20 nm channel length and in the range of 270 to 400°K. The results show that in T-CNTFETs by increasing the temperature, a simultaneous reduction in the transconductance (gm) and gate capacitance (Cg) is observed and there is a linear relation between them. The reduction in these two parameters causes to reduction in cutoff frequency which means the reduction in their ratio (gm/Cg) by temperature. By increasing the temperature from 270 to 400°K, at 20 nm channel length, about 33 GHz reduction in cutoff frequency is observed. Also, Simulation results show that the threshold voltage experiences slight increment, i.e. decrease in its ON-state current. In addition, the leakage current increases by increasing the ambient temperature.

Marked daily variation in spring temperature induces variation in Caspase-3, Bcl-2 and HSP60 in Asian Short-toed Larks: how do wild birds maintain cellular homeostasis to cope with the ambient temperature variation?

Daily variation in ambient temperature is marked during the spring at middle and high latitudes, when birds have to physiologically prepare for the subsequent breeding period. The ability of birds to maintain homeostasis during this period is important to survival and reproduction. We compared levels of the apoptotic proteins Caspase-3 and B cell lymphoma 2 (Bcl-2) and of the stress response heat shock protein 60 (HSP60) in peripheral blood cell samples of wild Asian Short-toed Larks (Calandrella cheleensis) collected on specific dates in the spring of 2014 and 2015 at different ambient temperatures. We also conducted a controlled temperature experiment to confirm the effect of temperature on the secretion of these proteins. Our results show that levels of Caspase-3, Bcl-2 and HSP60 in the blood of Asian Short-toed Larks varied with daily variations in temperature. Caspase-3 levels were higher but Bcl-2 levels were lower in blood samples collected on days when the mean daily temperature had dramatically increased or decreased, and this trend was confirmed by the results of our laboratory experiment on the effects of temperature on Caspase-3 and Bcl-2 levels. HSP60 levels in the blood of wild-caught Asian Short-toed Larks were higher in samples collected on days with higher temperatures in 2014 and in the high-temperature treatment group in our laboratory experiment. These results indicate that marked daily variation in ambient temperature may increase Caspase-3 levels to initiate apoptosis and that Bcl-2 and HSP60 maintain cellular homeostasis by inhibiting this increase in Caspase-3, suggesting a possible molecular mechanism by which birds cope with the effects of ambient temperature variation at the cellular level.

Effect of Ambient Temperature Variations on Particle Dimesions in Ultrasonic Nebulizers during Cold Vaporization

Effect of Ambient Temperature Variations on Particle Dimesions in Ultrasonic Nebulizers during Cold Vaporization

Effect of Ambient Temperature Variation on Triaxial Shear Testing of Sands

Abstract Triaxial shear tests are often carried out in a temperature controlled laboratory environment, and a few degrees change in ambient temperature are often neglected or considered to have negligible effect on the experiment. In this study, the effect of the ambient temperature fluctuation on volume and pore water pressure measurements is investigated for triaxial testing of sand samples. The experimental results show that even few degrees (±2°C) variation in temperature can produce relatively large pore water pressures in a saturated soil specimen in triaxial testing. These changes can particularly impact triaxial shear testing results of sands. An analytical procedure is also introduced that reasonably captures temperature-induced volume and pore pressure changes in a triaxial sample. The analytical method is then used for a parametric study of the mechanisms involved in temperature-induced effects.

环境温度变化对夏克-哈特曼波前传感器测量精度影响分析

环境温度变化对夏克-哈特曼波前传感器测量精度影响分析

Experimental and Numerical Investigation of a Single-Phase Square Natural Circulation Loop

Experimental and numerical analyses are carried out for a natural circulation loop (NCL) under low and moderate heater power. The effect of ambient temperature variation on the loop thermal behavior has been taken into account in present study. The effect of liquid inertia has a role in the initial transience, as revealed by the numerical and experimental observations. The steady-state results from the present analyses are validated with the reported dimensionless results for NCL. The experimental steady-state results are in fair agreement with the developed lumped numerical models. At moderate power, the numerical and experimental results indicate periodic oscillations.

Effect of Ambient Temperature Variations on Positivity of Manual Fecal Immunochemical Tests.

In the United States, many fecal occult blood tests are mailed by patients to a laboratory for analysis. Hemoglobin is not stable in feces and can be affected by the heat. Effects of season and ambient temperature on fecal immunochemical tests (FITs) have demonstrated a decrease in positivity rates during the hottest season. To investigate the potential effect of the average of 4-day ambient maximum temperature variations on the positivity of a single sample, one-time Clinical Laboratory Improvement Amendments (CLIA)-waived FIT. Midwestern tertiary care hospital. Individuals scheduled for a colonoscopy were invited to complete a qualitative FIT prior to their colonoscopy in 2010 and 2011. FITs were read as positive or negative. Valid FITs were received from 1026 individuals over 25 months. The positivity rate was 10.9%. The mean 4-day average of daily maximum ambient temperatures was calculated including the day of receipt for each sample. Fahrenheit temperatures ranged from 16.0 to 96.8. Based on the odds ratio of 1.04 with a confidence interval of 0.94 to 1.14 for a 10°F increase in temperature, there was no statistically significant evidence of an effect of the preceding maximum average 4-day ambient temperature on FIT positivity. No evidence was found that ambient temperature had an effect on positivity rate over a 25-month period using 4 different qualitative FIT products. Further analysis on effect of ambient temperatures is warranted for the automated FITs and CLIA-waived FITs, including liquid-vial and dry-slide FITs. Primary care providers need to be aware of potential adverse effects of FITs.

Measuring Near‐Surface Soil Thermal Properties with the Heat‐Pulse Method: Correction of Ambient Temperature and Soil–Air Interface Effects

Large temperature gradients and proximity to the soil–air interface affect the measurement accuracy of thermal properties with the heat‐pulse probe (HPP). The objective of this study is to improve the HPP methodology for measuring soil heat capacity (C) and thermal conductivity (λ) in the surface soil layer by reducing the effects of ambient temperature variation and the soil–air interface. Thermal properties of eight soil layers (0–6, 2–6, 6–12, 12–18, 18–24, 24–30, 30–36, and 36–42 mm) were measured with the HPP in a loamy sand soil in two experiments with varying moisture conditions. Results were compared with values estimated with the de Vries models. Temperature drift caused by natural warming and cooling was removed from the observed trend of ambient temperature change with time. The influence of the soil–air interface was taken into account with a new solution using pulsed infinite line source theory with adiabatic boundary conditions. When ambient temperature change was considered, the HPP were capable of providing reasonable thermal property results at soil depths greater than 6 mm. For the 0‐ to 6‐mm depth layer, the HPP signals were affected simultaneously by ambient temperature drift and the soil‐air interface, and mixed scenarios were produced. Around midday, the HPP temperature by time curves were distorted so seriously that the effect of ambient temperature drift could not be removed. At other times, large errors were observed in the estimated C and λ data, even when ambient temperature drift was removed. When the effect of the soil–air interface was accounted for, however, C and λ measurement accuracies in the 0‐ to 6‐mm layer were improved significantly. The RMSE of C was reduced from 0.43 MJ m−3 °C−1 to 0.29 MJ m−3 °C−1 in Exp. 1, and from 0.52 MJ m−3 °C−1 to 0.34 MJ m−3 °C−1 in Exp. 2. Significant error reduction was also observed in λ measurements. Thus, to obtain accurate field measurements of shallow soil thermal properties, the ambient temperature drift and the impact of the soil–air interface must be properly taken into account.

Effects of temperature variations on safety of reinforced concrete structures during construction

Since 1960s, many research works on the reinforced concrete structure have been published and some concise and practical calculation methods for safety control during construction have been achieved. The reinforced concrete structure during construction is a time-dependent structure which consists of a partly completed structure and a formwork-shore system. Experience shows that the most critical condition of the time-dependent structure may happen when the formwork-shore system is partly removed or reset and accidents may occur. In the present paper, effect of ambient temperature variation between day and night is considered, new structural models for reinforced concrete frames, slab-column systems and shear wall structures are proposed, and a new software named Safety Analysis During Construction Considering Temperature (SACT) is also introduced. Compared with on-site measurements, the software SACT is validated for application on construction site.