In order to study the evolution of the freezing fringe and final lenses of frost susceptible soils and advance the understanding of frost heave and mechanism of frost heave control, we used an open one-dimensional fro...In order to study the evolution of the freezing fringe and final lenses of frost susceptible soils and advance the understanding of frost heave and mechanism of frost heave control, we used an open one-dimensional frost heave test system of infrared radiation technology, instead of a traditional thermistor method. Temperatures of the freezing fringe and segregated ice were measured in a non-contact mode. The results show that accurate and precise temperatures of ice segregation can be obtained by infrared thermal imaging systems. A self-developed inversion program inverted the temperature field of frozen soils. Based on our analysis of temperature variation in segregated ice and our study of the relationship between temperature and rate of ice segregation in cooling and warming processes during intermittent freezing, the mechanism of decreasing frost heave of frozen soils by controlling the growth of final lenses with an intermittent freezing mode, can be explained properly.展开更多
Several studies have demonstrated the effect of planting methods on rice yield, but information on the climate resources is limited. This study aims to reveal the effects of planting methods on climate resources assoc...Several studies have demonstrated the effect of planting methods on rice yield, but information on the climate resources is limited. This study aims to reveal the effects of planting methods on climate resources associated with rice yield in a rice-wheat rotation system in the lower reaches of the Yangtze River, China. Field experiments were conducted in 2014 and 2015 with two japonica, two indica hybrid, and two japonica-indica hybrid varieties grown under three mechanized planting methods： carpet seedling of mechanical transplanting（CT）, mechanical direct seeding（DS）, and pot-hole seedling of mechanical transplanting（PT）. The rice yield and total dry matter under PT were greater than those under CT and DS methods. Besides, the entire growth duration and daily production showed significant positive relations with rice yield. Compared with CT and DS, the effective accumulated temperature and cumulative solar radiation of rice under PT were higher in phenological phases. In addition, the dry matter/effective accumulated temperature and solar energy utilization of rice under CT and DS were higher during vegetative phase and lower during reproductive and grain filling phases in contrast to PT. The mean daily temperature and mean daily solar radiation in the entire growth duration showed significant positive correlation with rice yield, total dry matter, and harvest index. This study demonstrated that when the mean daily temperature is 〈25.1°C in vegetative phase and 〉20.1°C in grain filling phase, rice yield could be increased by selecting mechanized planting methods. Most varieties under PT method exhibited high yield and climate resources use efficiency compared with CT and DS. In conclusion, the PT method could be a better cultivation measure for high rice yield, accompanied with high temperature and solar radiation use efficiency in a rice-wheat rotation system in the lower reaches of the Yangtze River, China.展开更多
For the sake of a more accurate shell boundary and calculation of radiation heat transfer in the Directional Solidification(DS) process, a radiation heat transfer model based on the Finite Element Method(FEM)is develo...For the sake of a more accurate shell boundary and calculation of radiation heat transfer in the Directional Solidification(DS) process, a radiation heat transfer model based on the Finite Element Method(FEM)is developed in this study. Key technologies, such as distinguishing boundaries automatically, local matrix and lumped heat capacity matrix, are also stated. In order to analyze the effect of withdrawing rate on DS process,the solidification processes of a complex superalloy turbine blade in the High Rate Solidification(HRS) process with different withdrawing rates are simulated; and by comparing the simulation results, it is found that the most suitable withdrawing rate is determined to be 5.0 mm·min^(-1). Finally, the accuracy and reliability of the radiation heat transfer model are verified, because of the accordance of simulation results with practical process.展开更多
Nearfield acoustic holography(NAH)is a powerful tool for realizing source identification and sound field reconstruction.The wave superposition(WS)-based NAH is appropriate for the spatially extended sources and does n...Nearfield acoustic holography(NAH)is a powerful tool for realizing source identification and sound field reconstruction.The wave superposition(WS)-based NAH is appropriate for the spatially extended sources and does not require the complex numerical integrals.Equivalent source method(ESM),as a classical WS approach,is widely used due to its simplicity and efficiency.In the ESM,a virtual source surface is introduced,on which the virtual point sources are taken as the assumed sources,and an optimal retreat distance needs to be considered.A newly proposed WS-based approach,the element radiation superposition method(ERSM),uses piston surface source as the assumed source with no need to choose a virtual source surface.To satisfy the application conditions of piston pressure formula,the sizes of pistons are assumed to be as small as possible,which results in a large number of pistons and sampling points.In this paper,transfer matrix modes(TMMs),which are composed of the singular vectors of the vibro-acoustic transfer matrix,are used as the sparse basis of piston normal velocities.Then,the compressive ERSM based on TMMs is proposed.Compared with the conventional ERSM,the proposed method maintains a good pressure reconstruction when the number of sampling points and pistons are both reduced.Besides,the proposed method is compared with the compressive ESM in a mathematical sense.Both simulations and experiments for a rectangular plate demonstrate the advantage of the proposed method over the existing methods.展开更多
<span style="font-family:Verdana;">Soil bulk density and moisture content are dynamic properties that vary with changes in soil and field conditions and have many agricultural, hydrological and environ...<span style="font-family:Verdana;">Soil bulk density and moisture content are dynamic properties that vary with changes in soil and field conditions and have many agricultural, hydrological and environmental implications. The main objective of this study was to compare between a soil core sampling method (core) and the CPN MC-3 Elite<span style="white-space:nowrap;"><sup>TM</sup></span> nuclear gauge method (radiation) for measuring bulk density (<span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"></span><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span>) and volumetric moisture content (<span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<span style="font-size:10.9091px;">v</span></i></span></span></i></span>) in a clay loam soil. Soil <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> and <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"></span><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<span style="font-size:10.9091px;">v</span></i></span></span></i></span> measurements were determined using the core and radiation methods at 0 - 10 and 10 - 20 cm soil depths. The mean values of soil <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> obtained using the core method (1.454, 1.492 g<span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#f7f7f7;"="">·</span>cm<span style="white-space:nowrap;"><sup>−3</sup></span>) were greater than those obtained using the radiation method (1.343, 1.476 g<span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#f7f7f7;"="">·</span>cm<span style="white-space:nowrap;"><sup>−3</sup></span>) at the 0 - 10 and 10 - 20 cm depths, respectively. Mean <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> and <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<span style="font-size:10.9091px;">v</span></i></span></span></i></span> values averaged across both depths (referred to as the 0 - 20 cm depth) measured by the core method were 4.47% and 22.74% greater, respectively, than those obtained by the radiation method. The coefficients of variation (CV) of soil <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"></span><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> values measured by the core method were lower than the CV values of those measured by the radiation method at both depths;however, the CV’s of <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> values for both methods were larger at the 0 - 10 cm depth than those measured at the 10 - 20 cm depth. Similarly, the CV values of soil <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<sub>v</sub></i></span></span></i></span> values measured by the core method were lower than the CV values of those measured by the radiation method at both depths. There were significant differences between two methods in terms of <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> and <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<sub>v</sub></i></span></span></i></span>, with the core method generating greater values than the radiation method at the 0 - 20 cm depth. These discrepancies between the two methods could have resulted from soil compaction and soil disturbance caused by the core and radiation techniques, respectively, as well as by other sources of error. Nevertheless, the core sampling method is considered the most common one for measuring <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> for many agricultural, hydrological and environmental studies in most soils.</span>展开更多
In the measurement of liquid level in industrial site environment,noise interference can affect the measurement accuracy.In order to improve the measurement accuracy of liquid level in the viscous state,a nuclear radi...In the measurement of liquid level in industrial site environment,noise interference can affect the measurement accuracy.In order to improve the measurement accuracy of liquid level in the viscous state,a nuclear radiation level measurement system based on the least mean square(LMS)filtering correction method is designed.The system uses STM32F103 as the control core and adopts HART bus HT1200M chip for remote signal transmission and reception.The adaptive LMS algorithm can be used for more accurate filtering,calculating iterative weight vector,updating weighted coefficient,effectively removing system measurement noise and improving the measurement accuracy.The results show that the nuclear radiation level gauge based on normalized LMS can correct the measurement system accuracy in adaptive rules,improve the measurement accuracy to meet the requirements of industrial field environment for liquid level measurement and enhance the industrial automation control degree.展开更多
This paper discusses a statistical second-order two-scale（SSOTS） analysis and computation for a heat conduction problem with a radiation boundary condition in random porous materials.Firstly,the microscopic configur...This paper discusses a statistical second-order two-scale（SSOTS） analysis and computation for a heat conduction problem with a radiation boundary condition in random porous materials.Firstly,the microscopic configuration for the structure with random distribution is briefly characterized.Secondly,the SSOTS formulae for computing the heat transfer problem are derived successively by means of the construction way for each cell.Then,the statistical prediction algorithm based on the proposed two-scale model is described in detail.Finally,some numerical experiments are proposed,which show that the SSOTS method developed in this paper is effective for predicting the heat transfer performance of porous materials and demonstrating its significant applications in actual engineering computation.展开更多
This letter is concerned with the plane and axisymmetric stagnation-point flows and heat transfer of an electrically-conducting fluid past a stretching sheet in the presence of the thermal radiation and heat generatio...This letter is concerned with the plane and axisymmetric stagnation-point flows and heat transfer of an electrically-conducting fluid past a stretching sheet in the presence of the thermal radiation and heat generation or absorption. The analytical solutions for the velocity distribution and dimensionless temperature profiles are obtained for the various values of the ratio of free stream velocity and stretching velocity, heat source parameter, Prandtl number, thermal radiation parameter, the suction and injection velocity parameter and magnetic parameter and dimensionality index in the series form with the help of homotopy analysis method （HAM）. Convergence of the series is explicitly dis- cussed. In addition, shear stress and heat flux at the surface are calculated.展开更多
Color-tunable phosphors Sr0.94MoO4：xEu^3＋, （0.06 - x）Tb^3＋ were synthesized rapidly by microwave ra- diation method with active carbon particle as microwave absorbent. The synthesized phosphors were investigated ...Color-tunable phosphors Sr0.94MoO4：xEu^3＋, （0.06 - x）Tb^3＋ were synthesized rapidly by microwave ra- diation method with active carbon particle as microwave absorbent. The synthesized phosphors were investigated by X-ray powder diffraction （XRD） and fluorescence spec- trophotometer. The effects of the ratio of Eu^3＋ and Tb^3＋ on the phase structure and luminescent properties of the phos- phors were discussed. The results show that Eu^3＋,Tb^3＋-doped samples can be well indexed to the pure tetragonal scheelite- type SrMoO4, indicating that Eu^3＋ and Tb^3＋ are effectively doped into the SrMoO4 host lattices. The as-synthesized Sro.94MoO4：xEu^3＋,（0.06 - x）Tb^3＋ phosphors have two luminescent centers （Eu^3＋ and Tb^3＋）, which can show red and green emissions under ultraviolet light excitation, respec- tively. Doping concentration of Eu^3＋ and Tb^3＋ has great effect on the intensity of emission peaks and the chromaticity of the samples, and the full color between green and red light can be achieved by adjusting the relative concentration of Eu^3＋ and Tb^3＋.展开更多
The broadband diffuse radiation method is improved to retrieve the aerosol refractive index imaginary part （AIP） and broadband （400-1000 nm mean） single scattering albedo （SSA）. In this method, four sets of SSA ...The broadband diffuse radiation method is improved to retrieve the aerosol refractive index imaginary part （AIP） and broadband （400-1000 nm mean） single scattering albedo （SSA）. In this method, four sets of SSA selection criteria are proposed for quality control. The method is used to retrieve AIP, SSA and absorptive optical thickness （AbOT） from routine hourly-exposed pyrheliometer and paranometer measurements over 11 sites （meteorological observatories） in China during 1998-2003. Apart from one suburban site （Ejin Qi）, the other urban sites are all located around big or medium cities. As shown in the retrieval results, annual mean SSA during 1998-2003 changes from 0.941 （Wuhan） to 0.849 （Lanzhou）, and AIP from 0.0054 to 0.0203. The 11-site average annual mean SSA and AIP are 0.898 and 0.0119, respectively. SSA during winter is smaller for most sites. There is an evidently positive correlation between SSA and aerosol optical thickness （AOT） for all sites. There is also a positive correlation between SSA and relative humidity for most sites, but a negative correlation for a few sites, such as Kashi and ǚrǚmqi in Northwest China.展开更多
The article deals with special questions of some aspects of food safety and application of methods of food physics in food processing and also in food quality control and quality assurance. The role of food safety has...The article deals with special questions of some aspects of food safety and application of methods of food physics in food processing and also in food quality control and quality assurance. The role of food safety has developed significantly in the last 2 decades, so today the production and processing of safe and quality food is of primary importance. Modem food production is based on principles of GAP and GMP （including GHP） and different methods and tools for quality control and assurance （IFS, HACCP, ISO-9000, ISO-9000/2010, ISO-22000, TQM）. There are different techniques and methods to produce safe food and to control the quality of the foodstuffs. The modem, up-to-date technologies and measurement techniques involve the application of many physical methods - high pressure, pulsing electrical field, microwave, non-destructive techniques （e.g., INAA, NMR, NIR-NIT, PAS）, radiation treatments as well. Using radiation technologies （of course not only nuclear ones） it is possible to fulfil some very important expectations of modem food processing, e.g., decrease of microbial contamination, improvement of sensory properties, increase of storability of food products.展开更多
The paper deals with some questions of important aspects of food safety and application of principles of food physics in the food sector. Food production and processing of quality food and safe food are today of prima...The paper deals with some questions of important aspects of food safety and application of principles of food physics in the food sector. Food production and processing of quality food and safe food are today of primary importance. Food production is based on the principles of Good Agricultural Practice （GAP）, Good Manufactoring Practice （GMP） and Good Hygiene Practice （GHP）. Recently, the industrial food processing is focused dominantly on the quality, and one of the basic requirements of the quality is the safety. There are different methods and techniques to produce safe food. The up-to-date food technologies and quality measurements （quality control and quality assurance） involve the application of different physical methods, e.g., high pressure, pulsing electrical field, nondestructive techniques, e.g., nuclear magnetic resonance （NMR）, near infrared reflectance, near infrared transmittance （NIR-NIT）, photo acoustic spectroscopy （PAS） and instrumental neutron activation analysis （INAA） for chemical composition determination, radiation techniques, nanofiltration and reverse osmosis （RO） as well. Using ionizing radiation （nuclear methods） and non-ionizing radiation technologies, it is possible to fulfill a lot of expectations： decrease of microbial contamination, improve of sensory properties, increase of storability, etc..展开更多
Under the background of the energy saving and emission reduction, more and more attention has been placed on investigating the energy efficiency of ships. The added resistance has been noted for being crucial in predi...Under the background of the energy saving and emission reduction, more and more attention has been placed on investigating the energy efficiency of ships. The added resistance has been noted for being crucial in predicting the decrease of speed on a ship operating at sea. Furthermore, it is also significant to investigate the added resistance for a ship functioning in short waves of large modern ships. The researcher presents an estimation formula for the calculation of an added resistance study in short waves derived from the reflection law. An improved method has been proposed to calculate the added resistance due to ship motions, which applies the radiated energy theory along with the strip method. This procedure is based on an extended integral equation （EIE） method, which was used for solving the hydrodynamic coefficients without effects of the irregular frequency. Next, a combined method was recommended for the estimation of added resistance for a ship in the whole wave length range. The comparison data with other experiments indicate the method presented in the paper provides satisfactory results for large blunt ship.展开更多
A reconstruction method is proposed for the polyurethane foam and then a complete numerical method is developed to predict the effective thermal conductivity of the polyurethane foam. The finite volume method is appli...A reconstruction method is proposed for the polyurethane foam and then a complete numerical method is developed to predict the effective thermal conductivity of the polyurethane foam. The finite volume method is applied to solve the 2D heterogeneous pure conduction. The lattice Boltzmann method is adopted to solve the 1D homogenous radiative transfer equation rather than Rosseland approximation equation. The lattice Boltzmann method is then adopted to solve 1D homogeneous conduction-radiation energy transport equation considering the combined effect of conduction and radiation. To validate the accuracy of the present method, the hot disk method is adopted to measure the effective thermal conductivity of the polyurethane foams at different temperature. The numerical results agree well with the experimental data. Then, the influences of temperature, porosity and cell size on the effective thermal conductivity of the polyurethane foam are investigated. The results show that the effective thermal conductivity of the polyurethane foams increases with temperature; and the effective thermal conductivity of the polyurethane foams decreases with increasing porosity while increases with the cell size.展开更多
Observation and research on solar radio emission have unique scientific values in solar and space physics and related space weather forecasting applications, since the observed spectral structures may carry important ...Observation and research on solar radio emission have unique scientific values in solar and space physics and related space weather forecasting applications, since the observed spectral structures may carry important information about energetic electrons and underlying physical mechanisms. In this study, we present the design of a novel dynamic spectrograph that has been installed at the Chashan Solar Radio Observatory operated by the Laboratory for Radio Technologies, Institute of Space Sciences at Shandong University. The spectrograph is characterized by real-time storage of digitized radio intensity data in the time domain and its capability to perform off-line spectral analysis of the radio spectra. The analog signals received via antennas and amplified with a low-noise amplifier are converted into digital data at a speed reaching up to 32 k data points per millisecond. The digital data are then saved into a high- speed electronic disk for further off-line spectral analysis. Using different word lengths （1-32k） and time cadences （5 ms-10 s） for off-line fast Fourier transform analysis, we can obtain the dynamic spectrum of a radio burst with different （user-defined） temporal （5 ms-10 s） and spectral （3 kHz-320kHz） resolutions. This enables great flexibility and convenience in data analysis of solar radio bursts, especially when some specific fine spectral structures are under study.展开更多
This paper deals with the detailed analysis of frequency drift rates of solar ＂drift pair＂ （DP） bursts observed from 2015 July 10 to 12 during a type III burst storm. The observations were conducted by the UTR-2 r...This paper deals with the detailed analysis of frequency drift rates of solar ＂drift pair＂ （DP） bursts observed from 2015 July 10 to 12 during a type III burst storm. The observations were conducted by the UTR-2 radio telescope at 9-33 MHz with high frequency and time resolution. DPs were recorded drifting from higher to lower frequencies （forward DPs） as well as from lower to higher ones （reverse DPs）. Patterns on their dynamic spectrum had various inclines and occupied different bandwidths. The frequency drift rate versus frequency dependence of these bursts has been studied. The fitting model to describe the peak evolution of these bursts in the frequency-time plane is presented. The relationship between DPs and type III solar bursts is discussed.展开更多
The 21 centimeter （21 cm） line emission from neutral hydrogen in the intergalactic medium （IGM） at high redshifts is strongly contaminated by foreground sources such as the diffuse Galactic synchrotron emission an...The 21 centimeter （21 cm） line emission from neutral hydrogen in the intergalactic medium （IGM） at high redshifts is strongly contaminated by foreground sources such as the diffuse Galactic synchrotron emission and free-free emission from the Galaxy, as well as emission from extragalactic radio sources, thus making its observation very complicated. However, the 21 cm signal can be recovered through its structure in frequency space, as the power spectrum of the foreground contamination is expected to be smooth over a wide band in frequency space while the 21 cm fluctuations vary significantly. We use a simple polynomial fitting to reconstruct the 21 cm signal around four frequencies 50, 100, 150 and 200 MHz with an especially small channel width of 20 kHz. Our calculations show that this multifrequency fitting approach can effectively recover the 21 cm signal in the frequency range 100 - 200 MHz. However, this method doesn＇t work well around 50 MHz because of the low intensity of the 21 cm signal at this frequency. We also show that the fluctuation of detector noise can be suppressed to a very low level by taking long integration times, which means that we can reach a sensitivity of ≈ 10 mK at 150 MHz with 40 antennas in 120 hours of observations.展开更多
Accurate fitting formulae to the synchrotron function, F（x）, and its com- plementary function, G（x）, are performed and presented. The corresponding relative errors are less than 0.26% and 0.035% for F（x） and G（...Accurate fitting formulae to the synchrotron function, F（x）, and its com- plementary function, G（x）, are performed and presented. The corresponding relative errors are less than 0.26% and 0.035% for F（x） and G（x）, respectively. To this end we have, first, fitted the modified Bessel functions, Ks/3（x） and K2/3（x）. For all the fitted functions, the general fit expression is the same, and is based on the well known asymptotic forms for low and large values of z for each function. It consists of multi- plying each asymptotic form by a function that tends to unity or zero for low and large values of z. Simple formulae are suggested in this paper, depending on adjustable parameters. The latter have been determined by adopting the Levenberg-Marquardt algorithm. The proposed formulae should be of great utility and simplicity for com- puting spectral powers and the degree of polarization for synchrotron radiation, both for laboratory and astrophysical applications.展开更多
We introduce a mathematical model based on a concept of intrinsic mode in order to analyse and synthesise optical wave propagation and radiation occurring in a non-uniform optical waveguide used in integrated optics a...We introduce a mathematical model based on a concept of intrinsic mode in order to analyse and synthesise optical wave propagation and radiation occurring in a non-uniform optical waveguide used in integrated optics as optical coupler. The model is based on numerical evaluation of electromagnetic wave by applying an intrinsic field integral to evaluate the field behaviour inside the optical waveguide. To analyse the field distribution inside the non-uniform waveguide and predict the beam propagation of optical energy involved in the propagation process, it is necessary to track the motion of any observation point along the tapered waveguide itself. Physically, the rays of the spectrum undergo reflections on the waveguide boundaries until the cut-off occurs and the phenomena of radiation begin. The numerical results show good agreement with those obtained by classical methods of evaluation used bv other works.展开更多
The Volume Source Boundary Point Method (VSBPM) is greatly improved so that it will speed up the VSBPM's solution of the acoustic radiation problem caused by the vibrating body. The fundamental solution provided b...The Volume Source Boundary Point Method (VSBPM) is greatly improved so that it will speed up the VSBPM's solution of the acoustic radiation problem caused by the vibrating body. The fundamental solution provided by Helmholtz equation is enforced in a weighted residual sense over a tetrahedron located on the normal line of the boundary node to replace the coefficient matrices of the system equation. Through the enhanced volume source boundary point analysis of various examples and the sound field of a vibrating rectangular box in a semi-anechoic chamber, it has revealed that the calculating speed of the EVSBPM is more than 10 times faster than that of the VSBPM while it works on the aspects of its calculating precision and stability, adaptation to geometric shape of vibrating body as well as its ability to overcome the non-uniqueness problem.展开更多
基金supported by the Key Project of the National Natural Science Foundation of China (No. 50534040)the Project of the National Natural Science Foundation of China (No. 40471021)
文摘In order to study the evolution of the freezing fringe and final lenses of frost susceptible soils and advance the understanding of frost heave and mechanism of frost heave control, we used an open one-dimensional frost heave test system of infrared radiation technology, instead of a traditional thermistor method. Temperatures of the freezing fringe and segregated ice were measured in a non-contact mode. The results show that accurate and precise temperatures of ice segregation can be obtained by infrared thermal imaging systems. A self-developed inversion program inverted the temperature field of frozen soils. Based on our analysis of temperature variation in segregated ice and our study of the relationship between temperature and rate of ice segregation in cooling and warming processes during intermittent freezing, the mechanism of decreasing frost heave of frozen soils by controlling the growth of final lenses with an intermittent freezing mode, can be explained properly.
基金financially supported by grants from the Major Independent Innovation Project in Jiangsu Province,China(CX(15)1002)the Agricultural Science and Technology Innovation Fund in Jiangsu Province,China(CX(12)1003-09)+3 种基金the National Key Research Program of China(2016YFD0300503)the Science and Technology Plan of Jiangsu Province,China(BE2015340)the Research Innovation Program for College Graduates of Jiangsu Province,China(KYLX15_1369)Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘Several studies have demonstrated the effect of planting methods on rice yield, but information on the climate resources is limited. This study aims to reveal the effects of planting methods on climate resources associated with rice yield in a rice-wheat rotation system in the lower reaches of the Yangtze River, China. Field experiments were conducted in 2014 and 2015 with two japonica, two indica hybrid, and two japonica-indica hybrid varieties grown under three mechanized planting methods： carpet seedling of mechanical transplanting（CT）, mechanical direct seeding（DS）, and pot-hole seedling of mechanical transplanting（PT）. The rice yield and total dry matter under PT were greater than those under CT and DS methods. Besides, the entire growth duration and daily production showed significant positive relations with rice yield. Compared with CT and DS, the effective accumulated temperature and cumulative solar radiation of rice under PT were higher in phenological phases. In addition, the dry matter/effective accumulated temperature and solar energy utilization of rice under CT and DS were higher during vegetative phase and lower during reproductive and grain filling phases in contrast to PT. The mean daily temperature and mean daily solar radiation in the entire growth duration showed significant positive correlation with rice yield, total dry matter, and harvest index. This study demonstrated that when the mean daily temperature is 〈25.1°C in vegetative phase and 〉20.1°C in grain filling phase, rice yield could be increased by selecting mechanized planting methods. Most varieties under PT method exhibited high yield and climate resources use efficiency compared with CT and DS. In conclusion, the PT method could be a better cultivation measure for high rice yield, accompanied with high temperature and solar radiation use efficiency in a rice-wheat rotation system in the lower reaches of the Yangtze River, China.
基金financially supported by the Program for New Century Excellent Talents in University(No.NCET-13-0229,NCET-09-0396)the National Science & Technology Key Projects of Numerical Control(No.2012ZX04010-031,2012ZX0412-011)the National High Technology Research and Development Program("863"Program)of China(No.2013031003)
文摘For the sake of a more accurate shell boundary and calculation of radiation heat transfer in the Directional Solidification(DS) process, a radiation heat transfer model based on the Finite Element Method(FEM)is developed in this study. Key technologies, such as distinguishing boundaries automatically, local matrix and lumped heat capacity matrix, are also stated. In order to analyze the effect of withdrawing rate on DS process,the solidification processes of a complex superalloy turbine blade in the High Rate Solidification(HRS) process with different withdrawing rates are simulated; and by comparing the simulation results, it is found that the most suitable withdrawing rate is determined to be 5.0 mm·min^(-1). Finally, the accuracy and reliability of the radiation heat transfer model are verified, because of the accordance of simulation results with practical process.
基金Project supported by the National Natural Science Foundation of China(Grant No.61701133)。
文摘Nearfield acoustic holography(NAH)is a powerful tool for realizing source identification and sound field reconstruction.The wave superposition(WS)-based NAH is appropriate for the spatially extended sources and does not require the complex numerical integrals.Equivalent source method(ESM),as a classical WS approach,is widely used due to its simplicity and efficiency.In the ESM,a virtual source surface is introduced,on which the virtual point sources are taken as the assumed sources,and an optimal retreat distance needs to be considered.A newly proposed WS-based approach,the element radiation superposition method(ERSM),uses piston surface source as the assumed source with no need to choose a virtual source surface.To satisfy the application conditions of piston pressure formula,the sizes of pistons are assumed to be as small as possible,which results in a large number of pistons and sampling points.In this paper,transfer matrix modes(TMMs),which are composed of the singular vectors of the vibro-acoustic transfer matrix,are used as the sparse basis of piston normal velocities.Then,the compressive ERSM based on TMMs is proposed.Compared with the conventional ERSM,the proposed method maintains a good pressure reconstruction when the number of sampling points and pistons are both reduced.Besides,the proposed method is compared with the compressive ESM in a mathematical sense.Both simulations and experiments for a rectangular plate demonstrate the advantage of the proposed method over the existing methods.
文摘<span style="font-family:Verdana;">Soil bulk density and moisture content are dynamic properties that vary with changes in soil and field conditions and have many agricultural, hydrological and environmental implications. The main objective of this study was to compare between a soil core sampling method (core) and the CPN MC-3 Elite<span style="white-space:nowrap;"><sup>TM</sup></span> nuclear gauge method (radiation) for measuring bulk density (<span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"></span><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span>) and volumetric moisture content (<span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<span style="font-size:10.9091px;">v</span></i></span></span></i></span>) in a clay loam soil. Soil <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> and <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"></span><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<span style="font-size:10.9091px;">v</span></i></span></span></i></span> measurements were determined using the core and radiation methods at 0 - 10 and 10 - 20 cm soil depths. The mean values of soil <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> obtained using the core method (1.454, 1.492 g<span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#f7f7f7;"="">·</span>cm<span style="white-space:nowrap;"><sup>−3</sup></span>) were greater than those obtained using the radiation method (1.343, 1.476 g<span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#f7f7f7;"="">·</span>cm<span style="white-space:nowrap;"><sup>−3</sup></span>) at the 0 - 10 and 10 - 20 cm depths, respectively. Mean <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> and <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<span style="font-size:10.9091px;">v</span></i></span></span></i></span> values averaged across both depths (referred to as the 0 - 20 cm depth) measured by the core method were 4.47% and 22.74% greater, respectively, than those obtained by the radiation method. The coefficients of variation (CV) of soil <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"></span><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> values measured by the core method were lower than the CV values of those measured by the radiation method at both depths;however, the CV’s of <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> values for both methods were larger at the 0 - 10 cm depth than those measured at the 10 - 20 cm depth. Similarly, the CV values of soil <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<sub>v</sub></i></span></span></i></span> values measured by the core method were lower than the CV values of those measured by the radiation method at both depths. There were significant differences between two methods in terms of <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> and <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<sub>v</sub></i></span></span></i></span>, with the core method generating greater values than the radiation method at the 0 - 20 cm depth. These discrepancies between the two methods could have resulted from soil compaction and soil disturbance caused by the core and radiation techniques, respectively, as well as by other sources of error. Nevertheless, the core sampling method is considered the most common one for measuring <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> for many agricultural, hydrological and environmental studies in most soils.</span>
基金National Natural Science Foundation of China(Nos.61761027,61261029)
文摘In the measurement of liquid level in industrial site environment,noise interference can affect the measurement accuracy.In order to improve the measurement accuracy of liquid level in the viscous state,a nuclear radiation level measurement system based on the least mean square(LMS)filtering correction method is designed.The system uses STM32F103 as the control core and adopts HART bus HT1200M chip for remote signal transmission and reception.The adaptive LMS algorithm can be used for more accurate filtering,calculating iterative weight vector,updating weighted coefficient,effectively removing system measurement noise and improving the measurement accuracy.The results show that the nuclear radiation level gauge based on normalized LMS can correct the measurement system accuracy in adaptive rules,improve the measurement accuracy to meet the requirements of industrial field environment for liquid level measurement and enhance the industrial automation control degree.
基金Project supported by the China Postdoctoral Science Foundation(Grant Nos.2015M580256 and 2016T90276)
文摘This paper discusses a statistical second-order two-scale（SSOTS） analysis and computation for a heat conduction problem with a radiation boundary condition in random porous materials.Firstly,the microscopic configuration for the structure with random distribution is briefly characterized.Secondly,the SSOTS formulae for computing the heat transfer problem are derived successively by means of the construction way for each cell.Then,the statistical prediction algorithm based on the proposed two-scale model is described in detail.Finally,some numerical experiments are proposed,which show that the SSOTS method developed in this paper is effective for predicting the heat transfer performance of porous materials and demonstrating its significant applications in actual engineering computation.
基金supported by the National Natural Science Founda-tions of China (50936003)the Open Project of State Key Laboratory for Advanced Metals & Materials and the Research Foundation of Engineering Research Institute,University of Science and Technology Beijing (2009Z-02)
文摘This letter is concerned with the plane and axisymmetric stagnation-point flows and heat transfer of an electrically-conducting fluid past a stretching sheet in the presence of the thermal radiation and heat generation or absorption. The analytical solutions for the velocity distribution and dimensionless temperature profiles are obtained for the various values of the ratio of free stream velocity and stretching velocity, heat source parameter, Prandtl number, thermal radiation parameter, the suction and injection velocity parameter and magnetic parameter and dimensionality index in the series form with the help of homotopy analysis method （HAM）. Convergence of the series is explicitly dis- cussed. In addition, shear stress and heat flux at the surface are calculated.
基金financially supported by the National Natural Science Foundation of China (No.21301046)
文摘Color-tunable phosphors Sr0.94MoO4：xEu^3＋, （0.06 - x）Tb^3＋ were synthesized rapidly by microwave ra- diation method with active carbon particle as microwave absorbent. The synthesized phosphors were investigated by X-ray powder diffraction （XRD） and fluorescence spec- trophotometer. The effects of the ratio of Eu^3＋ and Tb^3＋ on the phase structure and luminescent properties of the phos- phors were discussed. The results show that Eu^3＋,Tb^3＋-doped samples can be well indexed to the pure tetragonal scheelite- type SrMoO4, indicating that Eu^3＋ and Tb^3＋ are effectively doped into the SrMoO4 host lattices. The as-synthesized Sro.94MoO4：xEu^3＋,（0.06 - x）Tb^3＋ phosphors have two luminescent centers （Eu^3＋ and Tb^3＋）, which can show red and green emissions under ultraviolet light excitation, respec- tively. Doping concentration of Eu^3＋ and Tb^3＋ has great effect on the intensity of emission peaks and the chromaticity of the samples, and the full color between green and red light can be achieved by adjusting the relative concentration of Eu^3＋ and Tb^3＋.
文摘The broadband diffuse radiation method is improved to retrieve the aerosol refractive index imaginary part （AIP） and broadband （400-1000 nm mean） single scattering albedo （SSA）. In this method, four sets of SSA selection criteria are proposed for quality control. The method is used to retrieve AIP, SSA and absorptive optical thickness （AbOT） from routine hourly-exposed pyrheliometer and paranometer measurements over 11 sites （meteorological observatories） in China during 1998-2003. Apart from one suburban site （Ejin Qi）, the other urban sites are all located around big or medium cities. As shown in the retrieval results, annual mean SSA during 1998-2003 changes from 0.941 （Wuhan） to 0.849 （Lanzhou）, and AIP from 0.0054 to 0.0203. The 11-site average annual mean SSA and AIP are 0.898 and 0.0119, respectively. SSA during winter is smaller for most sites. There is an evidently positive correlation between SSA and aerosol optical thickness （AOT） for all sites. There is also a positive correlation between SSA and relative humidity for most sites, but a negative correlation for a few sites, such as Kashi and ǚrǚmqi in Northwest China.
文摘The article deals with special questions of some aspects of food safety and application of methods of food physics in food processing and also in food quality control and quality assurance. The role of food safety has developed significantly in the last 2 decades, so today the production and processing of safe and quality food is of primary importance. Modem food production is based on principles of GAP and GMP （including GHP） and different methods and tools for quality control and assurance （IFS, HACCP, ISO-9000, ISO-9000/2010, ISO-22000, TQM）. There are different techniques and methods to produce safe food and to control the quality of the foodstuffs. The modem, up-to-date technologies and measurement techniques involve the application of many physical methods - high pressure, pulsing electrical field, microwave, non-destructive techniques （e.g., INAA, NMR, NIR-NIT, PAS）, radiation treatments as well. Using radiation technologies （of course not only nuclear ones） it is possible to fulfil some very important expectations of modem food processing, e.g., decrease of microbial contamination, improvement of sensory properties, increase of storability of food products.
文摘The paper deals with some questions of important aspects of food safety and application of principles of food physics in the food sector. Food production and processing of quality food and safe food are today of primary importance. Food production is based on the principles of Good Agricultural Practice （GAP）, Good Manufactoring Practice （GMP） and Good Hygiene Practice （GHP）. Recently, the industrial food processing is focused dominantly on the quality, and one of the basic requirements of the quality is the safety. There are different methods and techniques to produce safe food. The up-to-date food technologies and quality measurements （quality control and quality assurance） involve the application of different physical methods, e.g., high pressure, pulsing electrical field, nondestructive techniques, e.g., nuclear magnetic resonance （NMR）, near infrared reflectance, near infrared transmittance （NIR-NIT）, photo acoustic spectroscopy （PAS） and instrumental neutron activation analysis （INAA） for chemical composition determination, radiation techniques, nanofiltration and reverse osmosis （RO） as well. Using ionizing radiation （nuclear methods） and non-ionizing radiation technologies, it is possible to fulfill a lot of expectations： decrease of microbial contamination, improve of sensory properties, increase of storability, etc..
基金Supported by the National Natural Science Foundation of China under Grant No.51079032 the Outstanding Youth Science Foundation of Heilongjiang Province,No.200908
文摘Under the background of the energy saving and emission reduction, more and more attention has been placed on investigating the energy efficiency of ships. The added resistance has been noted for being crucial in predicting the decrease of speed on a ship operating at sea. Furthermore, it is also significant to investigate the added resistance for a ship functioning in short waves of large modern ships. The researcher presents an estimation formula for the calculation of an added resistance study in short waves derived from the reflection law. An improved method has been proposed to calculate the added resistance due to ship motions, which applies the radiated energy theory along with the strip method. This procedure is based on an extended integral equation （EIE） method, which was used for solving the hydrodynamic coefficients without effects of the irregular frequency. Next, a combined method was recommended for the estimation of added resistance for a ship in the whole wave length range. The comparison data with other experiments indicate the method presented in the paper provides satisfactory results for large blunt ship.
基金Funded by Key Project of International Joint Research of National Natural Science Foundation of China(No.51320105004)
文摘A reconstruction method is proposed for the polyurethane foam and then a complete numerical method is developed to predict the effective thermal conductivity of the polyurethane foam. The finite volume method is applied to solve the 2D heterogeneous pure conduction. The lattice Boltzmann method is adopted to solve the 1D homogenous radiative transfer equation rather than Rosseland approximation equation. The lattice Boltzmann method is then adopted to solve 1D homogeneous conduction-radiation energy transport equation considering the combined effect of conduction and radiation. To validate the accuracy of the present method, the hot disk method is adopted to measure the effective thermal conductivity of the polyurethane foams at different temperature. The numerical results agree well with the experimental data. Then, the influences of temperature, porosity and cell size on the effective thermal conductivity of the polyurethane foam are investigated. The results show that the effective thermal conductivity of the polyurethane foams increases with temperature; and the effective thermal conductivity of the polyurethane foams decreases with increasing porosity while increases with the cell size.
基金supported by the National Natural Science Foundation of China(41331068,11503014 and U1431103)the China Postdoctoral Science Foundation(2016M600538)
文摘Observation and research on solar radio emission have unique scientific values in solar and space physics and related space weather forecasting applications, since the observed spectral structures may carry important information about energetic electrons and underlying physical mechanisms. In this study, we present the design of a novel dynamic spectrograph that has been installed at the Chashan Solar Radio Observatory operated by the Laboratory for Radio Technologies, Institute of Space Sciences at Shandong University. The spectrograph is characterized by real-time storage of digitized radio intensity data in the time domain and its capability to perform off-line spectral analysis of the radio spectra. The analog signals received via antennas and amplified with a low-noise amplifier are converted into digital data at a speed reaching up to 32 k data points per millisecond. The digital data are then saved into a high- speed electronic disk for further off-line spectral analysis. Using different word lengths （1-32k） and time cadences （5 ms-10 s） for off-line fast Fourier transform analysis, we can obtain the dynamic spectrum of a radio burst with different （user-defined） temporal （5 ms-10 s） and spectral （3 kHz-320kHz） resolutions. This enables great flexibility and convenience in data analysis of solar radio bursts, especially when some specific fine spectral structures are under study.
基金partially supported by Research Grant 0117U002396 from the National Academy of Sciences of Ukraine
文摘This paper deals with the detailed analysis of frequency drift rates of solar ＂drift pair＂ （DP） bursts observed from 2015 July 10 to 12 during a type III burst storm. The observations were conducted by the UTR-2 radio telescope at 9-33 MHz with high frequency and time resolution. DPs were recorded drifting from higher to lower frequencies （forward DPs） as well as from lower to higher ones （reverse DPs）. Patterns on their dynamic spectrum had various inclines and occupied different bandwidths. The frequency drift rate versus frequency dependence of these bursts has been studied. The fitting model to describe the peak evolution of these bursts in the frequency-time plane is presented. The relationship between DPs and type III solar bursts is discussed.
文摘The 21 centimeter （21 cm） line emission from neutral hydrogen in the intergalactic medium （IGM） at high redshifts is strongly contaminated by foreground sources such as the diffuse Galactic synchrotron emission and free-free emission from the Galaxy, as well as emission from extragalactic radio sources, thus making its observation very complicated. However, the 21 cm signal can be recovered through its structure in frequency space, as the power spectrum of the foreground contamination is expected to be smooth over a wide band in frequency space while the 21 cm fluctuations vary significantly. We use a simple polynomial fitting to reconstruct the 21 cm signal around four frequencies 50, 100, 150 and 200 MHz with an especially small channel width of 20 kHz. Our calculations show that this multifrequency fitting approach can effectively recover the 21 cm signal in the frequency range 100 - 200 MHz. However, this method doesn＇t work well around 50 MHz because of the low intensity of the 21 cm signal at this frequency. We also show that the fluctuation of detector noise can be suppressed to a very low level by taking long integration times, which means that we can reach a sensitivity of ≈ 10 mK at 150 MHz with 40 antennas in 120 hours of observations.
基金supported by the National Administration of Scientific Research NASR-DZ, of Algeria, in the framework of National Projects of Research (NPR)
文摘Accurate fitting formulae to the synchrotron function, F（x）, and its com- plementary function, G（x）, are performed and presented. The corresponding relative errors are less than 0.26% and 0.035% for F（x） and G（x）, respectively. To this end we have, first, fitted the modified Bessel functions, Ks/3（x） and K2/3（x）. For all the fitted functions, the general fit expression is the same, and is based on the well known asymptotic forms for low and large values of z for each function. It consists of multi- plying each asymptotic form by a function that tends to unity or zero for low and large values of z. Simple formulae are suggested in this paper, depending on adjustable parameters. The latter have been determined by adopting the Levenberg-Marquardt algorithm. The proposed formulae should be of great utility and simplicity for com- puting spectral powers and the degree of polarization for synchrotron radiation, both for laboratory and astrophysical applications.
基金co-supported by the University of Sciences and Technology of Oran Mohamed Boudiaf(USTOMB)the Centre of Satellites Development(CDS),Oran,Algeria
文摘We introduce a mathematical model based on a concept of intrinsic mode in order to analyse and synthesise optical wave propagation and radiation occurring in a non-uniform optical waveguide used in integrated optics as optical coupler. The model is based on numerical evaluation of electromagnetic wave by applying an intrinsic field integral to evaluate the field behaviour inside the optical waveguide. To analyse the field distribution inside the non-uniform waveguide and predict the beam propagation of optical energy involved in the propagation process, it is necessary to track the motion of any observation point along the tapered waveguide itself. Physically, the rays of the spectrum undergo reflections on the waveguide boundaries until the cut-off occurs and the phenomena of radiation begin. The numerical results show good agreement with those obtained by classical methods of evaluation used bv other works.
基金This work is supported by the National Natural Science Foundation of China (59575017) and the Technical Developmental Foundation of Machinery Industry (97JA0104).
文摘The Volume Source Boundary Point Method (VSBPM) is greatly improved so that it will speed up the VSBPM's solution of the acoustic radiation problem caused by the vibrating body. The fundamental solution provided by Helmholtz equation is enforced in a weighted residual sense over a tetrahedron located on the normal line of the boundary node to replace the coefficient matrices of the system equation. Through the enhanced volume source boundary point analysis of various examples and the sound field of a vibrating rectangular box in a semi-anechoic chamber, it has revealed that the calculating speed of the EVSBPM is more than 10 times faster than that of the VSBPM while it works on the aspects of its calculating precision and stability, adaptation to geometric shape of vibrating body as well as its ability to overcome the non-uniqueness problem.
