Effect Of Ambient Temperature Variation Research Articles

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.

Comparative Assessment of Two Thermodynamic Cycles of an aero-derivative Marine Gas Turbine

This paper explores the gas turbine potentials that are fully enhanced by the use of intercooling and thermal recuperation as an engineering option available in the design of gas turbines and offered for marine applications. It examines the off-design performance of two different cycle designs of a 25MW aero-derivative engine by modelling and simulating each of them to operate under conditions other than those of their design point. The simple cycle model consists of a single-spool dual shaft layout while the advanced model is represented by an intercooled-recuperated cycle that runs on a dual-spool and is driven through a three shaft configuration. In each case, the output shaft is coupled to a power turbine through which the propulsion power may be transmitted to the propeller of the vessel to operate in a virtual marine environment. An off-design performance simulation of both engines has been conducted in order to investigate and compare the effect of ambient temperature variation during their part-load operation and particularly when subjected to a variety of marine operating conditions. The study assesses the techno-economic impact of the complex design of the advanced cycle over its simple cycle counterpart and demonstrates its potential for improved operating cost through reduced fuel consumption as a significant step in the current drive for establishing the marine gas turbine engine as a viable alternative to traditional prime movers in the ship propulsion industry.

Temperature and Frequency Effects on Properties of Polymer-Modified Concrete

The dynamic elastic modulus and damping of concrete made from ordinary portland cement (OPC) remain relatively constant over the significant ranges of temperatures and frequencies that might be encountered in normal application. This is not the case, however, with polymer-modified concrete (PMC). This paper presents results of an experimental study examining the role of temperature and frequency with regard to PMC’s dynamic properties when certain polymers [ethyl-vinyl-acetate (EVA) and several varieties of styrene-butadiene rubber (SBR)] are introduced to OPC concrete. It is possible to increase the concrete damping by a factor of as much as 2.7 times, provided the ambient temperature is reasonably close to the polymer’s glass transition temperature. On the other hand, the elastic moduli at a given temperature may decrease by as much as 45%, depending on polymer concentration, though the effect of ambient temperature variation is much less dramatic—on the order of 15% for a given polymer concentration.

Ultra Wide Wavelength Multiplexing/Demultiplexing Conventional Arrayed Waveguide Grating (AWG) Devices for Multi Band Applications

This paper has proposed new materials based conventional arrayed waveguide grating (AWG) devices such as pure silica glass (SiO 2), Lithium niobate (LiNbO 3), and gallium aluminum arsenide (Ga (1-x) Al (x) As) materials for multiplexing and demultiplexing applications in interval of 1.45 µm to 1.65 µm wavelength band, which including the short, conventional, long, and ultra long wavelength band. Moreover we have taken into account a comparison between these new materials within operating design parameters of conventional AWG devices such as diffraction order, length difference of adjacent waveguides, focal path length, free spectral range or region, maximum number of input/output wavelength channels, and maximum number of arrayed waveguides. As well as we have employed these materials based AWG to include Multi band applications under the effect of ambient temperature variations.

The effects of ambient temperature variation on respiratory hospitalizations in summer, New York State

A time-series study was used to assess the effect of temperature variation during summer on respiratory disease in New York State. Daily respiratory admissions were linked with various meteorological indicators including daily and weekly temperature variation from June-August, 1991-2004. Two-stage Bayesian hierarchical models were used to first compute percent excess risks at the region level while controlling for air pollutants and time-varying variables using Poisson generalized additive models, and then to pool statewide estimates together after controlling for regional confounders. This study found that the daily temperature range between maximum and minimum temperature was associated with a 0·27-0·38% increased risk of admission. Minimum temperature (TMIN) above the previous 6-day average was associated with a 0·93% higher risk of respiratory morbidity. Multiday temperature ranges within 5 and 7 days were associated with 0·49 and 0·73% increases in admissions, respectively. We concluded that daily and multiday temperature variation may increase respiratory hospitalizations with a larger risk associated with TMIN.

Control-Theoretic Dynamic Thermal Management of Automotive Electronics Control Units

There has been a large body of research on dynamic thermal management (DTM) to manage the die temperature of integrated circuits against their high power density. Control-theoretic DTM is one of the most effective DTM schemes that guarantee stability criteria while meeting several performance requirements such as response time, steady-state error, overshoot, undershoot, phase margin, gain margin, and so forth. Conventional control-theoretic DTM schemes show reasonable stability and performance for general-purpose processors, but they may not fulfill those requirements for vehicle electronics control units (ECUs) primarily because the ambient temperature of an ECU is dependent on the associated unit temperature that often exceeds 100 °C. This results in a high steady-state die temperature and a very narrow temperature headroom. Furthermore, the unit temperature dynamically changes according to the driving condition that acts as a major disturbance to the DTM system. This paper introduces an advanced control-theretic DTM mechanism for high-performance vehicle ECUs. We model such ambient temperature variation as a disturbance, and adopt a disturbance predictor and compensator that effectively mitigates the effects of ambient temperature variations. We demonstrate that the proposed method is superior to the previous control-theoretic DTM in terms of RMS errors, peak temperature, and thermal violation.

Novel Remote Measurement Technique Using Resistive Sensor as Grounded Load in an Opamp Based V-to-I Converter

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This letter presents a simple and low-cost remote measurement technique, which consists of two almost identical diodes along with a resistive sensor as grounded load in an operational amplifier based conventional voltage to current converter. For a square wave input to the circuit, the mean value of the circuit output waveform that is measured with a digital storage oscilloscope is linearly proportional with the sensing resistance. This straightforward technique is not only independent of lead resistances but also compensates the effect of ambient temperature variation. The experimental results corroborate the theoretical assumptions. </para>

Effect of ambient temperature on the redistribution of loads during construction of multi-storey concrete structures

The purpose of the present work is to evaluate the influence of ambient temperature variations in the load distribution between shores and slabs of high-rise structures under construction. On-site measurements have been carried out at different construction sites. These measurements have allowed an analysis of the relationship between the evolution of loads transmitted by shores and recorded ambient temperature. The effect of ambient temperature variation has been determined to be the key factor in load redistribution between constructional steps. Furthermore, new modified methods for the prediction of shore and slab loads are proposed to take into account the response of shores and columns to ambient temperature changes. These methods are based on previously developed Refined and Improved Simplified Methods. Finally, experimental and theoretical results have been compared. It is concluded that temperature variations are the determining factor in load redistribution between any two consecutive construction steps and that those redistributions can be adequately estimated by means of the new methods.

Passivated thick film catalytic type H 2 sensor operating at low temperature

Thick film catalytic sensors operable at a temperature of 120 °C have been developed to measure hydrogen concentration (HC) in 0–10% (v/v) range. The sensors consists of a glass encapsulated Pt-heater coated with a catalytic thick film and a compensating element without the active film. An rf sputtered PTFE thin film on active element has been found to improve resistance of the sensors to poisoning due to hexamethyldisilazane (HMDS) and iodine etc. During operation, temperature of compensating element is held constant at 120 °C to offset the effect of ambient temperature variations. A simple circuit for control of sensor temperature and measurement of its response is described. The sensors showed linear response up to 10% (v/v) of hydrogen in ∼40 standard cm 3/min air flow with response and recovery times of ∼30 and 50 s, respectively. The sensors were found to have a stable response when operated continuously for a period of 1 year.

Dialable ampere current source with ovenless construction and ppm/h stability

This paper describes the design and construction of a highly stable, dialable current source developed for use with an electron beam transport system. The current regulator is ovenless and employs thermal feedback to cancel effects of ambient temperature variation and self-heating in the current-sensing resistor. The regulator is of modular design and incorporates remote control features to facilitate use in applications requiring many current channels. The output current can be modulated to permit Monte Carlo beam optimization. The output stability is better than ±1 ppm/h at an output current of 1 A, in an environment subject to ±1 °C temperature variation, measured using instrumentation having a nominal stability of ±1.5 ppm/h.

Transistorized Oscillator as a Magnetic Fluxmeter

Effect of magnetic field on the amplitude of voltage oscillation of a transistorized oscillator is studied. A magnetic fluxmeter based on this effect has been designed. Effect of ambient temperature variations on the sensitivity of such a fluxmeter has been investigated and a suitable circuit is designed to eliminate this. Important practical applications of the study are given.

Temperature and pressure effects in glow-discharge reference tubes

The effect of ambient-temperature variations on the running voltage of a glow-discharge reference tube is considered. Previous theories by Jurriaanse and Benson and Chalmers have been modified to provide a new and more accurate method of calculating temperature coefficients of running voltage. To verify the theory it has been necessary to determine running-voltage changes with tube current for different pressures and temperatures using pure neon and various neon-argon gas fillings. The results of these measurements are presented and discussed, and have formed a basis for numerical calculations of some temperature coefficients.