浅谈钢闸门制作过程焊接变形的预防和控制

为了有效的预防和控制钢闸门制作时的焊接变形,保证闸门制作质量,本文通过对金延安项目钢闸门制作过程中焊接变形预防和控制采取的各种工艺措施进行分析介绍,对各类水工钢闸门的制作有指导和借鉴意义。

Heat Resisting Mechanism of Heat-Resisting Aluminum Alloy Conductor and Its Application in Transmission Line

In this paper the heat withstanding mechanism of heat-resisting aluminum alloy conductor is discussed, the types and performance of the conductor and its application on transmission lines are analyzed and introduced, and suggestions on accelerating exploitation and application of the conductor are put forward.

Evolution of deformation property and strength component mobilization for thermally treated Beishan granite under compression

The cohesion weakening and friction strengthening(CWFS)model for rock reveals the strength components mobilization process during progressive brittle failure process of rock,which is very helpful in understanding mechanical properties of rock.However,the used incremental cyclic loading−unloading compression test for the determination of strength components is very complicated,which limits the application of CWFS model.In this paper,incremental cyclic loading−unloading compression test was firstly carried out to study the evolution of deformation and the strength properties of Beishan granite after various temperatures treated under different confining pressures.We found the axial and lateral unloading modulus are closely related to the applied stress and damage state of rock.Based on these findings,we can accurately determine the plastic strain during the entire failure process using conventional tri-axial compression test data.Furthermore,a strength component(cohesive and frictional strength)determination method was developed using conventional triaxial compression test.Using this method,we analyzed the variation of strength mobilization and deformation properties of Beishan granite after various temperatures treated.At last,a non-simultaneous strength mobilization model for thermally treated granite was obtained and verified by numerical simulation,which demonstrated the effectiveness of the proposed strength determination method.

Time Series Analysis on the Ratio for Pixels with Abnormal Brightness Temperature Increase and Its Variation Before Some Earthquakes with M_S≥5.0 in the Taiwan Region

In the study of the application of MODIS satellite remote sensing data to earthquake prediction, the paper puts forward for the first time a quantitative method to estimate the ratio for the pixels with abnormal brightness temperature (BT) increase and a preliminary scheme for cloud removal. The principle is that, firstly, the cloudless data observed by the same satellite at the same period of time but in different days (usually 1 day to 3 days) are mosaiced to get high ratio of clear sky, and then the BT variation curve and mean square difference (MSD) of each pixel are calculated with the data from the covered area to determine daily whether the BT data of the day is normal or not at a certain pixel by using double the MSD as the criterion. The ratio for the pixels with abnormal BT increase can be calculated by dividing the total number of abnormal pixels with the total pixels of the whole area. Analysis on a series of recent earthquakes in the Taiwan Region shows that the ratio for pixels with abnormal BT increase, which normally undulates around zero, has a sudden enhancement 1 day to 20 days before medium-strong earthquakes. It is expected that a new method for identifying earthquake auspice could be found through special studies in regions with frequent seismic activity by analyzing the change of the ratio for the pixels with abnormal BT increase from MODIS satellite remote sensing infrared (IR) information from which the effect of clouds has been removed to a certain extent.

Study on Potassium Fluoaluminate Eutectic Flux

In this study, Nocolok eutectic flux,used widely in the process of the brazing of aluminum and its alloy, was prepared by the reaction between Al(OH) 3/KOH resolution and HF. A series of KF-AlF 3 eutectic productions at various reaction temperatures were prepared. The melting points of the products were measured by differential thermal analysis (DTA), and the composites were characterized by X-ray diffraction (XRD). The results suggest that the temperature control is important to produce an ideal flux consisting of K 2AlF 5, H 2O and KAlF 4, with a low melting point of 560 ℃,which is suitable for the brazing of aluminum and its alloy as the aluminum fluxes.

Gravitational Collapse of a Spherical Star with Heat Flow as a Possible Energy Mechanism of Gamma-Ray Bursts

We investigate the gravitational collapse of a spherically symmetric, inhomogeneous star, which is described by a perfect fluid with heat flow and satisfies the equation of state p = p/3 at its center. In the process of the gravitational collapse, the energy of the whole star is emitted into space. And the remaining spacetime is a Minkowski one without a remnant at the end of the process. For a star with a solar mass and solar radius, the total energy emitted is at the order of 10^54 erg, and the time-scale of the process is about 8 s. These are in the typical values for a gamma-ray burst. Thus, we suggest the gravitational collapse of a spherical star with heat flow as a possible energy mechanism of gamma-ray bursts.

Isothermal extrusion speed curve design for porthole die of hollow aluminium profile based on PID algorithm and finite element simulations

The isothermal extrusion process of hollow aluminium profile was investigated using incremental proportional-integral-derivative(PID)control algorithm and finite element simulations.The range of extrusion speed was determined by considering the maximum extrusion load and production efficiency.By taking the optimal solution temperature of the secondary phase as the target temperature,the extrusion speed–stroke curve for realizing the isothermal extrusion of the aluminium profile was obtained.Results show that in the traditional constant extrusion speed process,the average temperature of the cross-section of the aluminium profile at the die exit rapidly increases and then slowly rises with the increase in ram displacement.As the extrusion speed increases,the temperature difference at the die exit of the profile along the extrusion direction increases.The exit temperature difference between the front and back ends of the extrudate along the extrusion direction obtained by adopting isothermal extrusion is about 6.9℃.Furthermore,the heat generated by plastic deformation and friction during extrusion is balanced with the heat transfer from the workpiece to the container,porthole die and external environment.

基于标定热箱法检测建筑外窗保温性能浅析

《建筑外门窗保温性能检测方法》GB/T 8484—2020于2021年3月1日实施,文章通过分析GB/T 8484—2020与《建筑外门窗保温性能分级及检测方法》GB/T 8484—2008主要技术变化,主要有:①新规范修改了检测原理,试件的传热系数的计算考虑了试件和填充板间的边缘线传热量,同时将边缘线传热量记入数据处理公式;②调整了检测装置,热箱增加了与试件保持规定距离的导流板;③调整了传感器数量及填充板要求等,并结合工程实例,浅析新版规范的应用,为同行业试验人员检测或研究提供参考。

Effect of ZrO_2 Crystalline Phase on the Performance of Ni-B/ZrO_2 Catalyst for the CO Selective Methanation

Amorphous Ni-B/ZrO2 catalysts were prepared by coprecipitation-chemical reduction with KBH4 aqueous solution,and various crystalline phase ZrO2(amorphous-ZrO2,tetragonal-ZrO2 and monoclinic-ZrO2) supported Ni-B catalysts were obtained by thermal treatment in 5%H2-N2 stream at different temperature.The effect of ZrO2 polymorphs and the treatment temperature on the catalytic performance for the CO selective methanation were investigated,and the catalysts were characterized by N2 physisorption,Powder X-ray diffraction(XRD), Temperature-Programmed Desorption(CO-TPD and H2-TPD),and Differential Scanning Calorimeter(DSC).The treatment temperature affected strongly the crystalline structure of ZrO2,and the CO methanation activity and selectivity of the Ni-B/ZrO2 catalysts were significantly influenced by the crystalline phase of ZrO2.Of the three forms of ZrO2 polymorphs(amorphou-ZrO2,tetragonal-ZrO2 and monoclinic-ZrO2),the amorphous-ZrO2 supported nickle catalyst showed highest CO methanation activity,attributing in large part to the largest specific surface area and the optimum CO/H2 absorption intensity of the Ni-B/amorphous-ZrO2 catalyst.

Nonequilibrium Thermodynamics of Dark Energy on Cosmic Apparent Horizon

In recent several years,some works have been done on cosmic thermodynamics.The apparent horizonwas regarded as the key characteristic supersurface where thermodynamics can be built on perfectly.However,if theirreversible process is considered,the proper position for building thermodynamics will not be the apparent horizonanymore.The new position is related to dark energy state equation and the irreversible process parameters.

Thermal Energy of Confined Gravitons can Vary Cold Geodesic Curves

Internal energy of real warm bodies can change their kinetic-potential energy balance on Keplerian orbits and relativistic geodesic. Chiral nature of the mass results in chirality of gravitons and their energy confinement within the constant energy charge of a moving thermodynamical body. Zero energy-momentum gravitons provide dissipative self-heating and spiral fall of massive stars on gravitating centers. Computed self-heating of the pulsar PSR B1913＋16 quantitatively describes its period decay without an outward emission of metric waves in question. Deviation of warm bodies from geodesic trajectories of cold point matter complies with Einstein＇s directives toward pure field physics of material space plenum without metric singularities.

Geostrophic meridional transport in tropical Northwest Pacific based on Argo profiles

Absolute geostrophic currents in the North Pacific Ocean were calculated using P-vector method from newly gridded Argo profiling float data collected during 2004-2009. The meridional volume transport of geostrophic currents differed significantly from the classical Sverdrup balance, with differences of 10×106 -20×106 m3 /s in the interior tropical Northwest Pacific Ocean. Analyses showed that errors of wind stress estimation could not explain all of the differences. The largest differences were found in the areas immediately north and south of the bifurcation latitude of the North Equatorial Current west of the dateline, and in the recirculation area of the Kuroshio and its extension, where nonlinear eddy activities were robust. Comparison of the geostrophic meridional transport and the wind-driven Sverdrup meridional transport in a high-resolution OFES simulation showed that nonlinear effects of the ocean circulation were the most likely reason for the differences. It is therefore suggested that the linear, steady wind-driven dynamics of the Sverdrup theory cannot completely explain the meridional transport of the interior circulation of the tropical Northwest Pacific Ocean.

Oxidative heat release intensity in coal at low temperatures measured by the hot-wire method

Directly measuring the oxidative heat release intensity at low temperatures is difficult at present.We developed a new method based on heat conduction theory that directly measures heat release intensity of loose coal at low temperatures.Using this method, we calculated the oxidative heat release intensity of differently sized loose coals by comparing the temperature rise of the coal in nitrogen or an air environment.The results show that oxidation heat release intensity of Shenhua coal sized 0～15 mm is 0.001～0.03 W/m3 at 30～90 °C and increases with increasing temperature.The heat release intensity at a given temperature is larger for smaller sized coal.The temperature effect on heat release intensity is muted as the coal size increases.At lower temperature the change in heat release intensity as a function of size becomes smaller.These results show that the test system is usable for practical applications and is easy to operate and is capable of measuring mass samples.

Microstructures and compressive properties of AZ91D/fly-ash cenospheres composites

Novel AZ91D Mg alloy/fly-ash cenospheres(AZ91D/FACs)composites were fabricated by melt stir technique.Fly-ash cenosphere particles with 4%,6%,8%,10%in mass fraction and 100μm in size were used.Hardness and compressive strength of the composites were measured.The effects of mass fraction of cenospheres on the microstructure and compressive properties were characterized.The results show that the cenospheres are uniformly distributed in the matrix and there is no sign of cenosphere cluster or residual pore.The densities of the composites are 1.85-1.92 g/cm 3 .By comparing with matrix,the compressive yield strength of the composites is improved,and the cenospheres is filled with Mg matrix alloy.SEM,XRD and EDX results of the composites show clear evidence of reaction product at cenosphere/matrix interface.On the basis of XRD and EDX,composition, structure and thermodynamic analysis,the main interfacial phase between the cenosphere and AZ91D Mg alloy was identified to be MgAl2O4.

Synthesis and thermoelectric properties of Mg_2Si_(1-x)Sn_x solid solutions by microwave irradiation

In order to reduce the oxidizing and volatilizing caused by Mg element in the traditional methods for synthesizing Mg2Sil-xSnx （x=0.2, 0.4, 0.6, 0.8） solid solutions, microwave irradiation techniques were used in preparing them as thermoelectric materials. Structure and phase composition of the obtained materials were investigated by X-ray diffraction （XRD）. The electrical conductivity, Seebeck coefficient and thermal conductivity were measured as a function of temperature from 300 to 750 K. It is found that Mg2Si1-xSnx solid solutions are well formed with excessive content of 5% （molar fraction） Mg from the stoichiometric MgESil.xSnx under microwave irradiation. A maximum dimensionless figure of merit, ZT, of about 0.26 is obtained for Mg2Si1-xSnx solid solutions at about 500 K for x=0.6.

A novel method based on entransy theory for setting energy targets of heat exchanger network

A T-Q diagram based on entransy theory is applied to graphically and quantitatively describe the irreversibility of the heat transfer processes.The hot and cold composite curves can be obtained in the T-Q diagram.The entransy recovery and entransy dissipation that are affected by temperature differences can be obtained through the shaded area under the composite curves.The method for setting the energy target of the HENs in T-Q diagram based on entransy theory is proposed.A case study of the diesel oil hydrogenation unit is used to illustrate the application of the method.The results show that three different heat transfer temperature differences is 10 K,15 K and 20 K,and the entransy recovery is 5.498×10~7k W·K,5.377×10~7k W·K,5.257×10~7k W·K,respectively.And the entransy transfer efficiency is 92.29%,91.63%,90.99%.Thus,the energy-saving potential of the HENs is obtained by setting the energy target based on the entransy transfer efficiency.

THERMAL AWARE FLOORPLANNING USING GAUSS-SEIDEL METHOD

The Gauss-Seidel method is effective to solve the traditional sparse linear system. In the paper, we define a class of sparse linear systems in iterative algorithm. The iterative method for linear system can be extended to the dummy sparse linear system. We apply the Gauss-Seidel method, which is one of the iterative methods for linear system, to the thermal model of floorplan of VLSI physical design. The experimental results of dummy sparse linear system are computed by using Gauss-Seidel method that have shown our theory analysis and extendibility. The iterative time of our incremental thermal model is 5 times faster than that of the inverting matrix method.

Study of drying of small diameter Larch lumbers with intermittent heating

Intermittent heating for drying of small diameter Larch lumbers is investigated experimentally. The lumbers were dried using an experimental drying schedule. Moisture content (MC) of the lumber was continuously recorded and final drying defects were examined. The drying curves showed that the drying rate was a constant in the early stage of intermittent heating drying and decreased evidently when the MC was about 18% (intermittent 2h) and 20% (intermittent 6h). The drying quality reached the second (intermittent 2h) and first grade (intermittent 6h) of the Chinese National Standard. The visual drying defects, especially the check extent along grains were reduced with intermittent heating. When the intermittent time increased, the effect was more obvious.

Effect of phosphite and epoxy soybean oil on heat stability of poly （vinylchloride） composite stabilizers

The influences ofphosphite and epoxy soybean oil in combination with liquid calcium/zinc isocaprylates on the thermal stability of flexible poly （vinyl chloride） were studied. The stabilizing effect of poly （vinyl chloride） was evaluated by Congo red method, thermoaging test and Thermogravimetric-differential Scanning Calorimetry （TG-DSC）. The results showed that the addition of the phosphite or epoxy soybean oil improved the thermal stability of PVC with the calcium/zinc isocaprylates stabilizing system, especially epoxidied soybean oil exhibited a remarkable effect, and the synergism on PVC thermal stability for 3：2 phenyl dioctyl phosphite to epoxidized soybean oil weight ratio was acquired. Accordingly, the rapid mass loss in TG curve occured between 258.9 ℃ and 334.4 ℃, which corresponded to the enthalpy of the pyrogenation of 609.2 J/g. It was also found that the stabilized PVC of the best ratio gave better mechanical and processing properties.

A Novel Technology for Generation of Electricity and Cold by Using Energy Potential of Transmission Line＇s High Pressure Gas

The main objective of this paper is to develop a novel technology for combined generation of electricity and cold by using energy potential of transmission line＇s high pressure gas. For this purpose, the reduction of high pressure of the gas in gas distribution station instead of useless expansion throttling process is suggested to realize by adiabatic expansion, which is executed in a gas expanding turbine. Herewith, the gas distribution station is turned into energy and cold generating plant. Simultaneous operation of energy and cold generating plant is described. A method and appropriate formulas for determination of design characteristics of considered plant are suggested. A new method for reveres order of calculation and design of the cold store based on the use of expanded cold gas as cooling agent is developed. Calculations and analysis prove high energy efficiency of suggested technology, the wide use of which will provide significant production of cheap electricity and cold and as well as reduction of fossil fuel consumption.