Spatio-Temporal Variation Analysis of the Biological Boundary Temperature Index Based on Accumulated Temperature: A Case Study of the Yangtze River Basin

Active accumulated temperature is an important index of agricultural heat resources in a region. Based on the temperature data of the Yangtze River Basin from 1970 to 2014, this paper analyzed the characteristics of the temporal and spatial variations of the biological boundary temperature in the Yangtze River Basin. The main conclusions were drawn as follows: (1) since 1970, the accumulated temperature of ≥0 °C in the northern subtropical zone, mid-subtropical zone, and plateau climate zone showed overall increasing trends, and the trends were 122 (p < 0.001), 87.7 (p < 0.001), and 75.3 °C/10a (p < 0.001), respectively. The accumulated temperature of ≥5 °C showed an upward trend, and the change tendency rates were 122.6 (p < 0.001), 90.5 (p < 0.001), and 81.4 °C/10a (p < 0.001), respectively. The accumulated temperature of ≥10 °C showed overall increasing trends and the trends were 115.7 (p < 0.001), 92.5 (p < 0.001), and 78.9 °C/10a (p < 0.001). Accumulated temperatures of ≥0 °C, ≥5 °C, and ≥10 °C in the northern subtropical zone increased significantly higher than that in the mid-subtropical zone and plateau climate zone. (2) The accumulated temperatures of ≥0 °C, ≥5 °C, and ≥10 °C in the northern subtropical zone showed an abrupt change in 1997. In the mid-subtropical zone and plateau climate zone, there was an abrupt change in the accumulated temperatures of ≥0 °C and ≥5 °C in 1994, and in the northern subtropical zone, the abrupt change of the accumulated temperature ≥10 °C occurred in 1998. (3) There are obvious differences in the biological boundary temperature within the Yangtze River Basin, and the stations with large increases are mainly distributed in the middle and lower reaches, such as the Hanshui Basin, the Poyang Lake Basin, the Taihu Lake Basin, and the middle and lower reaches of the mainstream area. The initial day, final day, and continuous days showed a trend of advancement, postponement, and extension, respectively. Besides, the heat resources showed significant increasing trends, which is of guiding significance for the future production and development of agriculture in the region. With the increase of heat resources in the Yangtze River Basin, appropriate late-maturing varieties should be selected in variety breeding, to make full use of heat resources and improve the quality of agricultural products. Secondly, the planting system should be adjusted and the multiple cropping index improved to steadily increase agricultural output. This brings new opportunities to adjust the structure of the agricultural industry and increase farmers’ income, in the Yangtze River basin.

A non-iterative inverse method for the identification of time and space-dependent heat sources of multi-dimensional FGMs by boundary temperature data

Background: Detection of heat sources is frequently encountered in many fields of science and engineering and plays a significant role in monitoring and control of many engineering thermal systems. Objective: The objective of this paper is to estimate the space and time-dependent heat sources in multi-dimensional functionally graded materials using boundary temperature data. Methods: First, the dimensionless temperature at the measurement points on the boundary is obtained by a direct process. Then, the objective function is obtained by a series of matrix operations, and the relationship between the temperature at the measurement points and the unknown parameters is established. After that, the strength of the heat sources can be inversed directly by the least-square error method, then the location and number of the heat sources can be obtained directly from the strength distribution of heat sources. The coefficient expansion method and truncated singular value decomposition method are applied to reduce the ill-posed degree of the inverse process. Results: Through the analysis of typical 2-dimensional and 3-dimensional examples, the influence of various factors such as the type of basis functions, the circular supported radius and the measurement noise on the inversion results is discussed, which shows that this method can identify the strength, location and number of heat sources of FGMs well. Conclusion: A non-iterative inverse method based on precise integration finite element method and least-square error method is established to estimate the strength, location and number of the unknown heat sources of functionally graded materials using boundary temperature data.

Estimation of Dense Plasma Temperature Formed under Shock Wave Cumulation

The research was carried out by means of implosion plasma generators with conical and hemispherical compression chambers to conduct a quantitative assessment of the boundary temperature of super dense plasma jets. It was proved experimentally that nuclear transformations in metals are caused by the impact of super dense plasma jets (11, ..., 12) × 103 kg/m3. The boundary temperature of these jets was evaluated. It was estimated that the nominal boundary temperature of the studied implosion plasma generators is 106 К. The pressure in the target at the penetration of the super dense jet (~12,000 kg/m3) at the speed of 28,000 m / sec is more than 30 ТPa. The boundary temperature was estimated and proved to depend on the pre-determined values only slightly. It was experimentally established that stable isotopes of manganese Mn55 (up to 27%) are formed in iron targets as a result of high temperature plasma jet penetration. The appearance of manganese must be related to iron transformation into stable isotopes Fe56 and Fe54. The obtained results may be applied for investigating structural changes in metals under the conditions of impulsive super high temperatures and pressures. This method can be also used as a testing ground for studying the physical conditions of forming chemical elements as well as super dense plasma jets.

Effect of Thermal Boundary Condition on Tilting Pad Journal Bearing Behavior

This research presents the effect of the thermal boundary condition on the tilting pad journal bearing characteristics. The thermal boundary condition includes the temperature around the bearing pad, spinning journal, and lubricant supply temperature. Change in bearing performance according to the temperature around each element constituting the bearing was analyzed without paying attention to how the actual thermal boundary conditions around the bearing are configured. High fidelity numerical model of tilting pad journal bearing is presented for (1) the analysis of heat generation in the thin film, (2) heat transfer in the lubricant, (3) heat flux flowing into the journal and pad, (4) temperature change in the journal and bearing, (5) the resultant thermal deformation, (6) change in the lubricant film thickness arising from the thermal deformation of journal and bearing pads, and (7) the resulting change in the heat generation in the thin film. To reach the steady state of the bearing–journal system, the Runge–Kutta scheme with adaptive time step is adopted where the dynamic and thermal system are solved simultaneously in multi-physics model. Performance change of the bearing according to three changes: (a) boundary temperature around shaft, (b) boundary temperature around bearing pads, and (c) lubricant supply temperature were investigated.

Analysis of thermal dynamic micro-EHL considering bearing assembly temperature

To investigate thermal failure of dynamic oil film in cylindrical roller bearings(CRBs), based on the temperature field of CRBs, non-Newtonian dynamic thermal elastohydrodynamic (TEHL) lubricating performance in cylindrical roller bearings was conducted. A single surface bump was coupled with longitudinal waviness on the roller surface, and a dynamic non-Newtonian finite line contact TEHL model was established considering the boundary temperature of the bearing assembly. Effects of the roller boundary temperature, the surface bump amplitude, the rotational speed, and the viscosity-pressure coefficient on thermal failure were analyzed. Comparison of lubricating performance between Newtonian and non-Newtonian fluid was made as well. Results show that, when the roller boundary temperature increases, the pressure and the oil temperature become larger, and the film thickness and frictional coefficient decrease obviously for roller to outer race contact. As the surface amplitude is large enough, or the rotational speed is low enough, phenomenon of partial contact between the roller and the outer ring may be generated due to high boundary temperature of solids. In addition, when the rotational speed is very low, the temperature of the roller surface reaches the first critical temperature of the adsorbed film, so thermal film failure may occur for roller to outer race lubrication.

Reconstruction of the thermal properties in a wave-type model of bio-heat transfer

Purpose This study aims to at numerically retrieve five constant dimensional thermo-physical properties of a biological tissue from dimensionless boundary temperature measurements. Design/methodology/approach The thermal-wave model of bio-heat transfer is used as an appropriate model because of its realism in situations in which the heat flux is extremely high or low and imposed over a short duration of time. For the numerical discretization, an unconditionally stable finite difference scheme used as a direct solver is developed. The sensitivity coefficients of the dimensionless boundary temperature measurements with respect to five constant dimensionless parameters appearing in a non-dimensionalised version of the governing hyperbolic model are computed. The retrieval of those dimensionless parameters, from both exact and noisy measurements, is successfully achieved by using a minimization procedure based on the MATLAB optimization toolbox routine lsqnonlin. The values of the five-dimensional parameters are recovered by inverting a nonlinear system of algebraic equations connecting those parameters to the dimensionless parameters whose values have already been recovered. Findings Accurate and stable numerical solutions for the unknown thermo-physical properties of a biological tissue from dimensionless boundary temperature measurements are obtained using the proposed numerical procedure. Research limitations/implications The current investigation is limited to the retrieval of constant physical properties, but future work will investigate the reconstruction of the space-dependent blood perfusion coefficient. Practical implications As noise inherently present in practical measurements is inverted, the paper is of practical significance and models a real-world situation. Social implications The findings of the present paper are of considerable significance and interest to practitioners in the biomedical engineering and medical physics sectors. Originality/value In comparison to Alkhwaji et al. (2012), the novelty and contribution of this work are as follows: considering the more general and realistic thermal-wave model of bio-heat transfer, accounting for a relaxation time; allowing for the tissue to have a finite size; and reconstructing five thermally significant dimensional parameters.