Variation Of Temperature Field Research Articles

Tunable hybrid Tamm-microcavity states

Spectral manifestations of hybrid Tamm-microcavity modes in a 1D photonic crystal bounded with a silver layer and containing a nematic liquid crystal layer working as a microcavity have been studied using numerical simulation. It is demonstrated that the hybrid modes can be effectively tuned owing to the high sensitivity of the liquid crystal to the temperature and external electric field variations. It is established that the effect of temperature on the transmission spectrum of the investigated structure is most pronounced at the point of the phase transition of the liquid crystal to the isotropic state, where the refractive index jump is observed.

The influence of scan length on fabricating thin-walled components in selective laser melting

As one of the advanced additive manufacturing (AM) processes, the selective laser melting (SLM) process provides the possibility of manufacturing almost any complex parts in a wide range of metal materials. In the SLM process, undesired distortion and shrinkage are much more likely to occur in forming Ti6Al4V thin-walled parts due to high-temperature gradients and thermal stresses. In this study, a three-dimensional (3D) finite element model based on indirect coupled thermal-structural analysis is applied to study the variations of temperature, stress and strain fields with different scan lengths. At the same time, the corresponding validation experiments were conducted. It was found that the scan length chiefly affects the second peak temperature rather than the highest temperature. The strain is majorly decided by stress generated during the SLM process. The deviations of thin-walled parts are approximately proportional to the scan lengths. The most suitable scan length is between 4 mm and 6 mm for thin-walled components with specified process parameters, in which case the shrinkage per unit is close to zero.

Deformation and Vibration-Induced Stress Intensity of a High-Temperature Turbine Rotor with a Breathing Transverse Crack

The vibrations of a double-seat weighty rotor of the steam turbine with a breathing transverse crack are examined in the field of operating environment temperatures. The 3D vibration model for the rotor with a breathing transverse crack is applied. The variable two-dimensional temperature field is found from the solution of nonstationary heat transfer problem. Its effect on the contact of crack edges on rotor vibrations was evaluated. The distribution of stress intensity factors along the crack front was established for different rotor positions. Fatigue crack extension modes are assessed.

The New Method to Analysis the Influence of Trapped Pressure on Casing Stress in Multi-stage Fracturing of Shale Gas

Currently, most of the shale gas development in China's Sichuan region adopts the large-displacement staged fracturing technology. Some of the shale gas wells undergo casing deformation during stimulation of the reservoir, where the trapped pressure of cementing section has a non-negligible effect on the casing stress in the multi-stage fracturing process. To this end, this paper constructs a finite element model of casing-cement sheath-formation assemblage under shale anisotropy based on the step-by-step finite element method by taking into account the whole construction process of drilling, completion and fracturing, in order to analyze the effect of trapped pressure on the casing stress under varying missing degrees, temperature field variations and cement sheath-formation property variations of cementing section in the multi-stage fracturing process. The results show that: 1) the larger the temperature drop in the wellbore during fracturing, the greater the effect of trapped pressure on casing stress during instantaneous pumping termination. 2) The smaller the missing degree of cementing section, the greater the effect of trapped pressure on casing stress under variations of cement sheath and formation. Therefore, optimization of cementing quality and reasonable optimization of relevant fracturing operation parameters are necessary in the future shale gas fracturing stimulation, so as to ensure the normal proceeding of subsequent well completion works.

Magnetosheath High‐Speed Jets: Internal Structure and Interaction With Ambient Plasma

AbstractFor the first time, we have studied the rich internal structure of a magnetosheath high‐speed jet. Measurements by the Magnetospheric Multiscale (MMS) spacecraft reveal large‐amplitude density, temperature, and magnetic field variations inside the jet. The propagation velocity and normal direction of planar magnetic field structures (i.e., current sheets and waves) are investigated via four‐spacecraft timing. We find structures to mainly convect with the jet plasma. There are indications of the presence of a tangential discontinuity. At other times, there are small cross‐structure flows. Where this is the case, current sheets and waves overtake the plasma in the jet's core region; ahead and behind that core region, along the jet's path, current sheets are overtaken by the plasma; that is, they move in opposite direction to the jet in the plasma rest frame. Jet structures are found to be mainly thermal and magnetic pressure balance structures, notwithstanding that the dynamic pressure dominates by far. Although the jet is supermagnetosonic in the Earth's frame of reference, it is submagnetosonic with respect to the plasma ahead. Consequently, we find no fast shock. Instead, we find some evidence for (a series of) jets pushing ambient plasma out of their way, thereby stirring the magnetosheath and causing anomalous sunward flows in the subsolar magnetosheath. Furthermore, we find that jets modify the magnetic field in the magnetosheath, aligning it with their propagation direction.

Versatile variable temperature and magnetic field scanning probe microscope for advanced material research.

We have built a variable temperature scanning probe microscope (SPM) that covers 4.6 K-180 K and up to 7 T whose SPM head fits in a 52 mm bore magnet. It features a temperature-controlled sample stage thermally well isolated from the SPM body in good thermal contact with the liquid helium bath. It has a 7-sample-holder storage carousel at liquid helium temperature for systematic studies using multiple samples and field emission targets intended for spin-polarized spectroscopic-imaging scanning tunneling microscopy (STM) study on samples with various compositions and doping conditions. The system is equipped with a UHV sample preparation chamber and mounted on a two-stage vibration isolation system made of a heavy concrete block and a granite table on pneumatic vibration isolators. A quartz resonator (qPlus)-based non-contact atomic force microscope (AFM) sensor is used for simultaneous STM/AFM operation for research on samples with highly insulating properties such as strongly underdoped cuprates and strongly correlated electron systems.

Temperature Dependence of Faraday Effect-Induced Bias Error in a Fiber Optic Gyroscope.

Improving the performance of interferometric fiber optic gyroscope (IFOG) in harsh environments, such as magnetic field and temperature field variation, is necessary for its practical applications. This paper presents an investigation of Faraday effect-induced bias error of IFOG under varying temperature. Jones matrix method is utilized to formulize the temperature dependence of Faraday effect-induced bias error. Theoretical results show that the Faraday effect-induced bias error changes with the temperature in the non-skeleton polarization maintaining (PM) fiber coil. This phenomenon is caused by the temperature dependence of linear birefringence and Verdet constant of PM fiber. Particularly, Faraday effect-induced bias errors of two polarizations always have opposite signs that can be compensated optically regardless of the changes of the temperature. Two experiments with a 1000 m non-skeleton PM fiber coil are performed, and the experimental results support these theoretical predictions. This study is promising for improving the bias stability of IFOG.

The study on temperature field variation and phase transition law after shutdown of buried waxy crude oil pipeline

In the buried waxy crude oil pipeline, considering the change of physical properties with temperature and the latent heat of wax precipitation, based on the pipeline-soil-atmosphere coupled heat transfer, the temperature drop model after shutdown is established by apparent heat capacity method. Taking a waxy crude oil transportation pipeline in Daqing Oilfield as an example, under different initial oil temperatures, different environmental temperatures and different soil thermal conductivities, the distribution of temperature field in pipeline and soil is simulated, the influence mechanism on temperature field of these three cases is analyzed. In addition, the phase transition interface of wax precipitation in crude oil is traced, the variation law of interface position after shutdown is analyzed. This research could provide a theoretical basis for the establishment of pipeline shutdown engineering scheme.

Single-shot lifetime-based PSP and TSP measurements on turbocharger compressor blades

Fast-responding pressure-sensitive paint (Fast PSP) and temperature-sensitive paint (TSP) measurements were conducted on two turbocharger compressors using a single-shot lifetime-based technique. The fast PSP and TSP were applied on separate blades of one compressor, and both paints were excited by a pulsed 532 nm Nd:YAG laser. The luminescent decay signals following the laser pulse were recorded by a CCD camera in a double-exposure mode. Instantaneous pressure and temperature fields on compressor blades were obtained simultaneously, for rotation speeds up to 150,000 rpm. The variations in pressure and temperature fields with rotation speed, flow rate and runtime were clearly visualized, showing the advantage of high spatial resolution. Severe image blurring problems and significant temperature-induced errors in the PSP results were found at high rotation speeds. The first issue was addressed by incorporating a deconvolution-based deblurring algorithm to recover the clear image from the blurred image using the combination of luminescent lifetime and rotation speed. The second issue was resolved by applying a pixel-by-pixel temperature correction based on the TSP results. The current technique has shown great capabilities in flow diagnostics of turbomachinery and can serve as a powerful tool for CFD validations and design optimizations.

Simulation and experiment on transient temperature field of a magnetorheological clutch for vehicle application

The unpredictable power fluctuation due to severe heating has been demonstrated to be a critical bottleneck technique restricting the application of magnetorheological (MR) clutches in vehicle industry. The aim of this study is to introduce a low-cost transient simulation approach for evaluating the heat build-up and dissipation of a liquid-cooled MR vehicle clutch. This paper firstly performs a detailed description of the developed MR clutch in terms of operation principle, material selection and configuration. Subsequently, transient temperature simulations are carried out under various conditions to reveal the distribution, variation and impact factors of the transient temperature field. Following these, an experimental setup is established for heating tests of the clutch prototype. Experimental results concerning the temperature variation of magnetorheological fluids and the maximum allowable transient slip power of the clutch prototype are presented, which in return verify the correctness and feasibility of the simulation.

Numerical investigation of the influence of process conditions on the temperature variation in fused deposition modeling

An adaptable three-dimensional transient mathematical model of temperature variation with respect to space and time, during and after the fused deposition modeling (FDM), is proposed and applied with a boundary-adjusting finite difference method. This model enables researchers to study the influence of almost all other parameters on the temperature field and gradient variation when constructing any cuboid at fixed raster angle of 0(90)° and filling ratio of 100%. Some predicted but significant conclusions are reached: reheating of a deposited raster by a newly deposited one is universal and happens mainly in the layer thickness direction; temperature settings are the primary and direct factors determining temperature field variation, while layer thickness and printing speed can still exert their own influence; printing speed is predicted to be positively correlated to mechanical properties of FDM constructed components through the mechanism of thermal coalescence; strict energy management is required if a FDM printer of higher resolution is to be invented and applied. The technique of such mathematical model can provide immediate insights in the understanding of FDM process from the perspective of energy balance, many of which have never been revealed from previous reports yet.

Rock mechanics and wellbore stability in Dongfang 1-1 Gas Field in South China Sea

Thermal effect has great influence on wellbore stability in Dongfang 1-1 (DF 1-1) gas field, a reservoir with high-temperature and high-pressure. In order to analyze the wellbore stability in DF1-1 gas field, the variation of temperature field after drilling was analyzed. In addition, the effect of temperature changing on formation strength and the thermal expansion coefficients of formation were tested. On this basis, a wellbore stability model considering thermal effect was developed and the thermal effect on fracture pressure and collapse pressure was analyzed. One of the main challenges in this gas field is the decreasing temperature of the wellbore will reduce fracture pressure substantially, resulting in the drilling fluid leakage. If the drilling fluid density was reduced, kick or blowout may happen. Therefore, the key of safe drilling in DF1-1 gas field is to predict the fracture pressure accurately.

On-sky performance of the QACITS pointing control technique with the Keck/NIRC2 vortex coronagraph

A vortex coronagraph is now available for high contrast observations with the Keck/NIRC2 instrument at L band. Reaching the optimal performance of the coronagraph requires fine control of the wavefront incident on the phase mask. In particular, centering errors can lead to significant stellar light leakage that degrades the contrast performance and prevents the observation of faint planetary companions around the observed stars. It is thus critical to correct for the possible slow drift of the star image from the phase mask center, generally due to mechanical flexures induced by temperature and/or gravity field variation, or to misalignment between the optics that rotate in pupil tracking mode. A control loop based on the QACITS algorithm for the vortex coronagraph has thus been developed and deployed for the Keck/NIRC2 instrument. This algorithm executes the entire observing sequence, including the calibration steps, initial centering of the star on the vortex center and stabilisation during the acquisition of science frames. On-sky data show that the QACITS control loop stabilizes the position of the star image down to 2.4 mas rms at a frequency of about 0.02 Hz. However, the accuracy of the estimator is probably limited by a systematic error due to a misalignment of the Lyot stop with respect to the entrance pupil, estimated to be on the order of 4.5 mas. A method to reduce the amplitude of this bias down to 1 mas is proposed. The QACITS control loop has been successfully implemented and provides a robust method to center and stabilize the star image on the vortex mask. In addition, QACITS ensures a repeatable pointing quality and significantly improves the observing efficiency compared to manual operations. It is now routinely used for vortex coronagraph observations at Keck/NIRC2, providing contrast and angular resolution capabilities suited for exoplanet and disk imaging.

Steam flooding and oil recovery by different types of horizontal well pattern

ABSTRACTScale physical simulation experiments on different types of horizontal well pattern (i.e., row pattern, five spot pattern, and inverted nine spot pattern) are conducted in steam flooding of heavy oil. According to similarity principle physical model is established. Reservoir geology and process parameters of Xinchun oilfield are transformed into the parameters of physical model. The following conclusions are obtained: (a) the temperature field variation characteristics have been cleared, (b) recovery of row pattern (51.85%) is highest, and (c) the main mechanisms are explicated (i.e., flowability increases, thermal expansion, vaporization, distillation and in situ upgrading, greater sweep efficiency, and steam overlap).

Numerical Simulation & Scene Experiment of Metro Tunnel with Crossover Interval under Fire Conditions

In this study, numerical simulation and scene experiment with metro crossover interval are performed to estimate the effect of ventilation model and the position of the most unfavorable smoke removal on passenger’s life safety under fire conditions. Firstly, based on STESS (Metro Thermal Environment Simulation Software), a network model of smoke removal is established with the crossover interval of metro line 10 (Between Wen De Road Station and Yu Shan Road Station), which discusses the effect on smoke flow and fire spread in different indicators, including fire source position and intensity, the number of platform and interval fan used as dealing with emergency. Secondly, combined with FDS (Fire Dynamics Simulator) technology, a three-dimensional field model of metro station with crossover interval is set up, which contributes to the smoke’s variation of temperature field and velocity field as well as concentration field can be simulated and analyzed under fire conditions. And then the model of fire conditions is measured and verified with crossover interval in scene experiment. On the basis of above all, the study puts forward where each opening fan is positioned and what the number is needed, satisfying the requirements of smoke removal and providing references in metro crossover interval at the same time.

Research of creep deformation in amorphous and nanocrystalline alloys at variable temperature field

Investigations of Co-based amorphous alloys and Fe-based nanocrystalline alloy failure strain at creep tests within a temperature range being from 300 to 1023 K have been performed. A creep curve analytical form for all investigated alloys has been established.

高密度観測に認められる夏季関東地方の気温と地上気圧の時空間変動の特徴―2014年7～9月の気温と地上気圧データを用いて―

関東地方で実施した高密度観測から得られた夏季の気温と気圧データに対して主成分分析を行い，これらの時空間変動にみられる特徴を明らかにした．気温場と気圧場それぞれの上位3主成分には，海陸風循環，ヒートアイランド現象，北東気流に関係した空間分布が認められ，相互の主成分間に有意な相関関係が存在する．これらの気温と気圧の関係は，いずれも相対的に気温が高い（低い）地域で気圧が低い（高い）傾向を示す．晴天日の気温と気圧の分布には明瞭な日変化が認められ，日中には海風の発達に伴い，関東平野の内陸部で相対的に高温低圧となり，日没後から夜間にかけては，ヒートアイランド現象が顕在化して東京都心から北側郊外にかけての都市部で相対的な高温低圧傾向が認められた．これらの観測事実に基づいた解析から，晴天日の気温と気圧の主要な日変化パターンに，内陸部の高温低圧に伴う海風循環とヒートアイランド現象に伴う高温低圧が認められた．

A modal interferometer based on single mode fiber-hollow core fiber-single mode fiber structure filled with alcohol and magnetic fluid for simultaneously measuring magnetic field and temperature

In many fields, such as aerospace and marine environmental monitoring, magnetic field measurement is an important link. In recent years, optical fiber magnetic field sensor has received much attention because of its advantages such as small size, electromagnetic immunity, resistance to erosion and capability of remote sensing. In that case, magnetic fluid as a kind of medium between photons and magnetic field is widely used in optical fiber magnetic field sensors. Moreover, in the process of magnetic field measurement, disturbance introduced by temperature fluctuation always happens and brings uncertainty to the sensor. Temperature is also an important parameter in production process and needs to be measured. Therefore, designing a high-sensitive optical fiber sensor for simultaneously measuring magnetic field and temperature is a valuable work. In this paper, we present a high-sensitive hollow core fiber (HCF) interferometer for simultaneously measuring magnetic field and temperature. A segment of HCF filled with alcohol is inserted into single mode fiber (SMF) with 50 m offset at two splicing joints to guide light into the wall of HCF. And then this SMF-HCF-SMF structure is packaged by a capillary tube with full magnetic fluid (MF) inside it. Since the modal field area is large enough, the silica wall can support a series of guiding modes among which modal interference occurs and the interference spectrum can be recorded by an optical spectrum analyzer. Besides thermo-optic effect and thermal expansion effect of silica itself, the RI variations caused by thermo-optic effect of alcohol and MF as well as the magneto-optic effect of MF can also cause the phase difference of the guiding modes to change, thereby rendering interference dips movable. Thus, the sensitivity of temperature or magnetic field is higher than those given in some other previous studies. In addition, it is calculated that the effective RI sensitivities of guiding modes for inside and outside liquid are different because of the peculiar non-circular symmetry structure of HCF. So there is a possibility to find two dips in interference spectrum, which are formed with different modes and have various sensitivities to the variations of temperature and magnetic field. Finally, a sensitivity matrix can be built to demodulate those two parameters simultaneously. Experimental results show that within 20-58℃, the temperature sensitivities are 112 pm/℃ and 468 pm/℃ for dip1 and dip 2 whose magnetic field sensitivities are 37 pm/Oe and 82 pm/Oe within 0-169 Oe, respectively. The proposed sensor possesses high sensitivity and good mechanical strength, and can effectively eliminate the cross disturbances between temperature and magnetic field.

Spatial and temporal variation of total electron content as revealed by principal component analysis

Abstract. Eleven years of global total electron content (TEC) data derived from the assimilated thermosphere–ionosphere electrodynamics general circulation model are analyzed using empirical orthogonal function (EOF) decomposition and the corresponding principal component analysis (PCA) technique. For the daily averaged TEC field, the first EOF explains more than 89 % and the first four EOFs explain more than 98 % of the total variance of the TEC field, indicating an effective data compression and clear separation of different physical processes. The effectiveness of the PCA technique for TEC is nearly insensitive to the horizontal resolution and the length of the data records. When the PCA is applied to global TEC including local-time variations, the rich spatial and temporal variations of field can be represented by the first three EOFs that explain 88 % of the total variance. The spectral analysis of the time series of the EOF coefficients reveals how different mechanisms such as solar flux variation, change in the orbital declination, nonlinear mode coupling and geomagnetic activity are separated and expressed in different EOFs. This work demonstrates the usefulness of using the PCA technique to assimilate and monitor the global TEC field.

Response of the capacitance and dielectric loss of the SrRuO3/SrTiO3/SrRuO3 film heterostructures to variations in temperature and electric field

Three-layer epitaxial heterostructures with a 750-nm-thick intermediate strontium titanate layer between two strontium ruthenate conductive thin-film electrodes have been grown by laser deposition. Photolithography and ion etching have been used to form film parallel-plate capacitors based on the grown heterostructures. The capacitance (C) and dielectric loss tangent (tanδ) of the parallel-plate capacitors have been measured in the temperature range T = 4.2–300 K at an applied bias voltage of up to ±2.5 V and without it. At T > 100 K, the temperature dependence of the dielectric permittivity (e) of the SrTiO3 intermediate layer is well approximated by the Curie–Weiss law taking into account the capacitance induced by the penetration of an electric field into the oxide electrodes. At T ≈ 20 K, the dielectric permittivity e of the SrTiO3 intermediate layer decreases by approximately 20% in an electric field of 25 kV/cm. The dielectric loss tangent of the film capacitor heterostructures decreases monotonically with a decrease in the temperature in the range from 300 to 80 K and almost does not depend on the electric field strength. However, in the range from 80 to 4.2 K, the dielectric loss tangent increases nonmonotonically (abruptly) with a decrease in the temperature and decreases significantly in an applied electric field.