边数很少时二部图度方和的次大值

研究了给定顶点和边数且边数很少时二部图度方和的次大值.在确定了给定顶点和边数且边数很少时度方和达到最大的所有二部图后,通过讨论顶点数和边数之间的关系得出度方和的次大值.对于度方和问题在二部图中的研究有一定的推动作用.

边数较少时度方和达到次大值的二部图

在给定顶点数和边数且边数较少的情况下,二部图度方和的次大值已经确定.通过讨论顶点数和边数之间的关系,确定了给定顶点数和边数且边数较少时度方和达到次大值所对应的二部图,对度方和问题在二部图中的研究有一定的推动作用.

The influences of canopy temperature measuring on the derived crop water stress index

Crop water stress index(CWSI)is widely used for efficient irrigation management.Precise canopy temperature(T_(c))measurement is necessary to derive a reliable CWSI.The objective of this research was to investigate the influences of atmospheric conditions,settled height,view angle of infrared thermography,and investigating time of temperature measuring on the performance of the CWSI.Three irrigation treatments were used to create different soil water conditions during the 2020-2021 and 2021-2022 winter wheat-growing seasons.The CWSI was calculated using the CWSI-E(an empirical approach)and CWSI-T(a theoretical approach)based on the T_(c).Weather conditions were recorded continuously throughout the experimental period.The results showed that atmospheric conditions influenced the estimation of the CWSI;when the vapor pressure deficit(VPD)was>2000 Pa,the estimated CWSI was related to soil water conditions.The height of the installed infrared thermograph influenced the T_(c)values,and the differences among the T_(c)values measured at height of 3,5,and 10 m was smaller in the afternoon than in the morning.However,the lens of the thermometer facing south recorded a higher T_(c)than those facing east or north,especially at a low height,indicating that the direction of the thermometer had a significant influence on T_(c).There was a large variation in CWSI derived at different times of the day,and the midday measurements(12:00-15:00)were the most reliable for estimating CWSI.Negative linear relationships were found between the transpiration rate and CWSI-E(R^(2)of 0.3646-0.5725)and CWSI-T(R^(2)of 0.5407-0.7213).The relations between fraction of available soil water(FASW)with CWSI-T was higher than that with CWSI-E,indicating CWSI-T was more accurate for predicting crop water status.In addition,The R^(2)between CWSI-T and FASW at 14:00 was higher than that at other times,indicating that 14:00 was the optimal time for using the CWSI for crop water status monitoring.Relative higher yield of winter wheat was obtained with average seasonal values of CWSI-E and CWSI-T around 0.23 and 0.25-0.26,respectively.The CWSI-E values were more easily influenced by meteorological factors and the timing of the measurements,and using the theoretical approach to derive the CWSI was recommended for precise irrigation water management.

Establishment and application of logging saturation interpretation equation in vuggy reservoirs

Vuggy reservoirs are the most common, albeit important heterogeneous carbonate reservoirs in China. However, saturation calculations using logging data are not well developed, whereas Archie method is more common. In this study, electrical conduction in a vuggy reservoir is theoretically analyzed to establish a new saturation equation for vuggy reservoirs. We found that vugs have a greater effect on saturation than resistivity, which causes inflection in the rock-electricity curve. Using single-variable exPeriments, we evaluated the effects of rug size, vug number, and vug distribution on the rock-electricity relation. Based on the general saturation model, a saturation equation for vuggy reservoirs is derived, and the physical significance of the equation parameters is discussed based on the seepage-electricity similarity. The equation parameters depend on the pore structure, and vugs and matrix pore size distribution. Furthermore, a method for calculating the equation parameters is proposed, which uses nuclear magnetic resonance （NMR） data to calculate the capillary pressure curve. Field application of the proposed equation and parameter derivation method shows good match between calculated and experimental results, with an average absolute error of 5.8%.

Preliminary Results of Assessing the Mixing of Wave Transport Flux Residualin the Upper Ocean with ROMS

The effects of the mixing of wave transport flux residual(Bvl) on the upper ocean is studied through carrying out the control run(CR) and a series of sensitive runs(SR) with ROMS model.In this study,the important role of Bvl is revealed by comparing the ocean temperature,statistical analysis of errors and evaluating the mixed layer depth.It is shown that the overestimated SST is improved effectively when the wave-induced mixing is incorporated to the vertical mixing scheme.As can be seen from the vertical structure of temperature 28℃ isotherm changes from 20 min CR to 35 m in SR3,which is more close to the observation.Statistic analysis shows that the root-mean-square errors of the temperature in 10 m are reduced and the correlation between model results and observation data are increased after considering the effect of Bvl.The numerical results of the ocean temperature show improvement in summer and in tropical zones in winter,especially in the strong current regions in summer.In August the mixed layer depth(MLD) which is defined as the depth that the temperature has changed 0.5℃ from the reference depth of 10 m is further analyzed.The simulation results have a close relationship with undetermined coefficient of Bvl,sensitivity studies show that a coefficient about 0.1 is reasonable value in the model.

Symmetries and Group-Invariant Solutions for Transonic Pressure-Gradient Equations

Lie symmetry group method is applied to study the transonic pressure-gradient equations in two-dimensionalspace.Its symmetry groups and corresponding optimal systems are determined,and several classes of irrotational groupinvariantsolutions associated to the symmetries are obtained and special case of one-dimensional rarefaction wave isfound.

Influence of water saturation on propagation of elastic waves in transversely isotropic nearly saturated soil

Biot' s two-phase theory for fluid-saturated porous media was applied in a study carried out to investigate the influence of water saturation on propagation of elastic wave in transversely isotropic nearly saturated soil. The characteristic equations for wave propagation were derived and solved analytically. The results showed that there are four waves: the first and second quasi-longitudinal waves (QP1 and QP2), the quasitransverse wave (QSV) and the anti-plane transverse wave (SH) . Numerical results are given to illustrate theinfluence of saturation on the velocity, dispersion and attenuation of the four body waves. Some typical numerical results are discussed and plotted. The results can be meaningful for soil dynamics and earthquake engineering.

Face mask detection algorithm based on HSV+HOG features and SVM

To automatically detecting whether a person is wearing mask properly,we propose a face mask detection algorithm based on hue-saturation-value(HSV)+histogram of oriented gradient(HOG)features and support vector machines(SVM).Firstly,human face and five feature points are detected with RetinaFace face detection algorithm.The feature points are used to locate to mouth and nose region,and HSV+HOG features of this region are extracted and input to SVM for training to realize detection of wearing masks or not.Secondly,RetinaFace is used to locate to nasal tip area of face,and YCrCb elliptical skin tone model is used to detect the exposure of skin in the nasal tip area,and the optimal classification threshold can be found to determine whether the wear is properly according to experimental results.Experiments show that the accuracy of detecting whether mask is worn can reach 97.9%,and the accuracy of detecting whether mask is worn correctly can reach 87.55%,which verifies the feasibility of the algorithm.

A DIAGNOSTIC ANALYSIS OF THE WEAKENING OF WEST PACIFIC SUBTROPICAL ANTICYCLONE DURING THE PERIOD OF SOUTH CHINA SEA SUMMER MONSOON ONSET IN 1998

The onset of South China Sea summer monsoon in 1998 occurred on May 21st. Using the U.S. National Centers for Environmental Prediction reanalysis data, this paper examines the physical process of the weakening of a subtropical anticyclone in West Pacific during the onset period using the Zwack-Okossi vorticity equation. Results show that during the pre-onset period, the positive vorticity advection in front of an upper tropospheric trough was the most dominant physical mechanism for the increase of the cyclonic vorticity on the 850-hPa layer over the South China Sea and its nearby region. The secondary contribution to the increase of the cyclonic vorticity was the warm-air advection. After the onset, the magnitude of the latent-heat warming term rapidly increased and its effect on the increase of the cyclonic vorticity was about the same as the positive-vorticity advection. The adiabatic term and divergence term contributed negatively to the increase of the cyclonic vorticity most of the time. Thus, the positive vorticity advection is the most important physical mechanism for the weakening of the West Pacific subtropical anticyclone over the South China Sea during the onset period.

The establishment of a new deliverability equation considering threshold pressure gradient

The flowing mechanism of a low permeability gas reservoir is different from a conventional gas reservoir,especially for that with higher irreducible water saturation the threshold pressure gradient exists. At present,in all the deliverability equation,the additional pressure drop caused by the threshold pressure gradient is viewed as constant,but this method has big error in the practical application. Based on the non-Darcy steady flow equation,the limited integral of the additional pressure drop is solved in this paper and it is realized that the additional pressure drop is not a constant but has something to do with production data,and a new deliverability equation is derived,with the relevant processing method for modified isochronal test data. The new deliverability equation turns out to be practical through onsite application.

Some Discussions on Parallel Bounded Batch Scheduling to Minimize the Sum of Squared Machine Loads

We sttidy the problem of scheduling n jobs on m parallel bounded batch machines to minimize the sum of squared machine loads. Each batch contains at most B jobs, and the processing time of a batch is equal to the longest processing time of the jobs in this batch. We prove this problem to be NP-hard. Furthermore, we present a polynomial time approximation scheme （PTAS） and a fully polynomial time approximation scheme （FPTAS） for this problem.

Correlations between direct and indirect strength test methods

The difficulties associated with performing direct compression strength tests on rocks lead to the development of indirect test methods for the rock strength assessment. Indirect test methods are simple, more economical, less time-consuming, and easily adaptable to the field. The main aim of this study was to derive correlations between direct and indirect test methods for basalt and rhyolite rock types from Carlin trend deposits in Nevada. In the destructive methods, point load index, block punch index, and splitting tensile strength tests are performed. In the non-destructive methods, Schmidt hammer and ultrasonic pulse velocity tests are performed. Correlations between the direct and indirect compression strength tests are developed using linear and nonlinear regression analysis methods. The results show that the splitting tensile strength has the best correlation with the uniaxial compression strength.Furthermore, the Poisson's ratio has no correlation with any of the direct and indirect test results.

New method for plugging channeling in oil field by nitrogen foam

In order to present a new method for plugging channeling in oil field,the injection modes and validity period of foam system which plugged the formation water layer were studied by means of the experimental model which simulated the real conditions of oil wells existing channeling.Above all,the influence factors including reservoir pressure,permeability,oil saturation and gas-to-liquid ratio were studied through dynamic experiment.Then,in light of the technology characteristics of foam injection in oil field,the comparison between gas-liquid and liquid-gas injection modes was studied.The result shows that the gas-liquid injection mode can ensure the foam injectivity and plugging performance.The plugging validity of nitrogen foam injected into the formation water layer was evaluated in different plugging pressure gradients by the dynamic method which is more reasonable than the static evaluation method in laboratory.The research demonstrates that the plugging validity period of foam decreases with plugging pressure gradient increasing.If the plugging pressure gradient is 0.15 MPa/m,the validity period is 160 h.Finally,a empirical equation and a plate about the plugging validity and the plugging pressure gradient were obtained for forecasting the validity period of foam.

Corrections for the Location Errors of Wenchuan Aftershocks Recorded by the Nagqu and Hotan Arrays

We use the slowness-azimuth station correction( SASC) method to improve the location accuracy of the Wenchuan aftershocks recorded by the Nagqu and Hotan seismic arrays.The results show that the standard deviations of back-azimuth and slowness errors of Wenchuan aftershocks recorded by the Nagqu array decreased by 32% and 58%respectively after correction. The decrease is 38% and 71% for the Hotan array. After the correction,the location accuracy of all Wenchuan aftershocks recorded by the Nagqu array is improved. For the Hotan array,the accuracy is improved in the slowness estimation for 78% of aftershocks and in back-azimuth estimation for all aftershocks.

Estimation of Design Sea Ice Thickness with Maximum Entropy Distribution by Particle Swarm Optimization Method

The maximum entropy distribution, which consists of various recognized theoretical distributions, is a better curve to estimate the design thickness of sea ice. Method of moment and empirical curve fitting method are common-used parameter estimation methods for maximum entropy distribution. In this study, we propose to use the particle swarm optimization method as a new parameter estimation method for the maximum entropy distribution, which has the advantage to avoid deviation introduced by simplifications made in other methods. We conducted a case study to fit the hindcasted thickness of the sea ice in the Liaodong Bay of Bohai Sea using these three parameter-estimation methods for the maximum entropy distribution. All methods implemented in this study pass the K-S tests at 0.05 significant level. In terms of the average sum of deviation squares, the empirical curve fitting method provides the best fit for the original data, while the method of moment provides the worst. Among all three methods, the particle swarm optimization method predicts the largest thickness of the sea ice for a same return period. As a result, we recommend using the particle swarm optimization method for the maximum entropy distribution for offshore structures mainly influenced by the sea ice in winter, but using the empirical curve fitting method to reduce the cost in the design of temporary and economic buildings.

Study of Thermal and Hydraulic Performances of Circular and Square Ribbed Rough Microchannels Using LBM

The effects of roughness geometries and relative roughness height at the slip flow regime to investigate the thermal and hydraulic performances of microchannel have been considered in the present article using a thermal Lattice Boltzmann Method(TLBM).A two dimensional 9-bit(D2Q9)single relaxation time(SRT)model is used to simulate this problem.In micro-flows,the local density variation is still relatively small,but the total density changes,therefore,in order to account this density variation and its effect on the kinematic viscosityν,a new relaxation time proposed by Niu et al.[13]is used.The roughness geometry is modeled as a series of square and circular riblets with a relative roughness height from 0%to 10%of the channel height.The friction coefficients in terms of Poiseuille number(Pn)and the dimensionless heat transfer rate in terms of Nusselt number(Nu)have been discussed in order to analyze the roughness effects.The thermal-hydraulic performance(η)is calculated considering the simultaneous effects of thermal and fluid friction(pressure drop)at the slip flow regime at Knudsen number,Kn,ranging from 0.01 to 0.10 with other controlling parameters for both kind of geometries.The results have been compared with previous published works and it is found to be in very good agreement.

Propagation of plane wave in non-homogeneously saturated soils

Based on Biot's model for fluid-saturated media,which takes the inertial,fluid viscous,mechanical couplings,compressibility of grains and fluid into account,the dispersion equations of plane waves in non-homogeneously saturated soil are established by using reverberation ray matrix method(RRMM) with the aid of Helmholtz theorem.The non-homogeneity considered is a gradient variation in material properties with depth.The propagation characteristic of elastic waves in non-homogeneously saturated soil is analyzed by numerical example in this paper.The results show that the wave number and dissipation change little for two kinds of compression along the variation direction of the material properties,however,the non-homogeneity has significant effect on the wave number and dissipation of shear wave.

Convection in the Rayleigh-Bénard Flow with all Fluid Properties Variable

In the present paper, the effect of variable fluid properties （density, viscosity, thermal conductivity and specific heat） on the convection in the classical Rayleigh-Benard problem is investigated. The investigation concerns water, air, and engine oil by taking into account the variation of fluid properties with temperature. The results are obtained by numerically solving the governing equations, using the SIMPLE algorithm and covering large temperature differences. It is found that the critical Rayleigh number increases as the temperature difference increases considering all fluid properties variable. However, when the fluid properties are kept constant, calculated at the mean temperature, and only density is considered variable, the critical Rayleigh number either decreases or remains constant.

Partial and Spectral-Viscosity Models for Geophysical Flows

Two models based on the hydrostatic primitive equations are proposed.The first model is the primitive equations with partial viscosity only,and is oriented towards large-scale wave structures in the ocean and atmosphere.The second model is the viscous primitive equations with spectral eddy viscosity,and is oriented towards turbulent geophysical flows.For both models,the existence and uniqueness of global strong solutions are established.For the second model,the convergence of the solutions to the solutions of the classical primitive equations as eddy viscosity parameters tend to zero is also established.