Application conditions for ester cured alkaline phenolic resin sand

Five organic esters with different curing speeds:propylene carbonate(i.e.high-speed ester A);1,4-butyrolactone;glycerol triacetate(i.e.medium-speed ester B);glycerol diacetate;dibasic ester(DBE)(i.e.lowspeed ester C),were chosen to react with alkaline phenolic resin to analyze the application conditions of ester cured alkaline phenolic resin.The relationships between the curing performances of the resin(including pH value,gel pH value,gel time of resin solution,heat release rate of the curing reaction and tensile strength of the resin sand)and the amount of added organic ester and curing temperature were investigated.The results indicated the following:(1)The optimal added amount of organic ester should be 25 wt.%-30 wt.%of alkaline phenolic resin and it must be above 20 wt.%-50 wt.%of the organic ester hydrolysis amount.(2)High-speed ester A(propylene carbonate)has a higher curing speed than 1,4-butyrolactone,and they were both used as high-speed esters.Glycerol diacetate is not a high-speed ester in alkaline phenolic resin although it was used as a high-speed ester in ester cured sodium silicate sand;glycerol diacetate and glycerol triacetate can be used as medium-speed esters in alkaline phenolic resin.(3)High-speed ester A,medium-speed ester B(glycerol triacetate)and low-speed ester C(dibasic ester,i.e.,DBE)should be used below 15°C,35°C and 50°C,respectively.High-speed ester A or lowspeed ester C should not be used alone but mixed with medium-speed ester B to improve the strength of the resin sand.(4)There should be a suitable solid content(generally 45 wt.%-65 wt.%of resin),alkali content(generally 10 wt.%-15 wt.%of resin)and viscosity of alkaline phenolic resin(generally 50-300 mPa·s)in the preparation of alkaline phenolic resin.Finally,the technique conditions of alkaline phenolic resin preparation and the application principles of organic ester were discussed.

Numerical investigation of positive dihedral application conditions in compressor cascades

This study attempts to make a contribution to the understanding of dihedral application conditions and their aerodynamic mechanisms.The present efforts have finished contrastive investigations on several dihedral blades to their corresponding straight ones with different geometric or aerodynamic conditions including aspect ratio,solidity,aerofoil turning angle,inlet boundary layer configuration and inlet Mach number.A dihedral with the angle between the suction side and the endwall to be obtuse,i.e.,positive dihedral,is chosen.The result reveals the dihedral application conditions consist of aerofoil turning angle,inlet boundary layer,inlet Mach number and so on.The further analysis indicates:in a transonic cascade,two considerations are needed on the contrastive relationship between intensities of the two shocks,namely detached shock and passage shock,and the interaction of the shocks with the corner separation.

PERFECT SPLINES WITH BOUNDARY CONDITIONS AND THEIR APPLICATION TO CERTAIN EXTREMAL PROBLEMS

In this paper we consider two problems. The first is connected with the optimal recovery of functions satisfyiog boundary conditions. The second is the characterization of the unique func- tion whose r-th derivative has minimum L_∞-norm, taking given values of alternating signs and satis fying boundary conditions.

Impact failure models and application condition of trees in debris-flow hazard mitigation

Forestry has played an important role in hazard mitigation associated with debris flows.Most forest mitigation measures refer to the experience of soil and water conservation,which disregard the destructive effect of debris flows,causing potentially serious consequences.Determination of the effect of a forest on reducing debris-flow velocity and even stopping debris flows requires distinguishing between when the debris flow will destroy the forest and when the trees will withstand the debris-flow impact force.In this paper,we summarized two impact failure models of a single tree: stem breakage and overturning.The influences of different tree sizes characteristics(stem base diameter,tree weight,and root failure radius) and debris-flow characteristics(density,velocity,flow depth,and boulder diameter) on tree failure were analyzed.The observations obtained from the model adopted in this study show that trees are more prone to stem breakage than overturning.With an increase in tree size,the ability to resist stem breakage and overturning increases.Debris-flow density influences the critical failure conditions of trees substantially less than the debrisflow velocity,depth,and boulder diameter.The application conditions of forests in debris-flow hazard mitigation were proposed based on the analysis of the model results.The proposed models were applied in the Xiajijiehaizi Gully as a case study,and the results explain the destruction of trees in the forest dispersing zone.This work provides references for implementing forest measures for debris-flow hazard mitigation.

Some Generalizations of Monotonicity Condition and Applications

0 Introduction It is well known that there axe a great number of interesting results in Fourier analysis established by assuming monotonicity of coefficients, and many of them have been generalized by loosing the condition to quasi-monotonicity, O-regularly varying quasi-monotonicity, etc..

Transformation Behaviour of Austenite in Steel under Condition of Stress-strain and Its Application

Austenite can be retained at ambient temperature in steels by alloying and processing control. The transformation from austenite to martensite occurs under a certain conditions : thermal or deformation. Stress-strain induced martensitic transformation is important to improve the plasticity of steels which is called transformation induced plasticity (TRIP). Strength-ductility balance of the steels is greatly superior to that of other high strength steels due to the TRIP effect. A new type of steels-TRIP steel is developed

An application of radiation boundary condition to scattering problem of acoustic waves in fluids

A numerical method of solving acoustic wave scattering pnblem in fluids is described. Radiation boundary condition (RBC) obtained by factorization method of Helmholtz equation is applied to transforming the exterior boundary value problem in unbounded region into one in a finite region. Combined with RBC and scatterer surface boundary condition, Helmholtz equation is solved numerically by the finite difference method. Computational results for sphere and prolate spheroidal scatterers are in excellent agreement with eigenfunction solutions and much better than the results of OSRC method.

Discussion on several statistical problems in establishing quality standards of standard decoctions

Since 2016,a number of studies have been published on standard decoctions used in Chinese medicine.However,there is little research on statistical issues related to establishing the quality standards for standard decoctions.In view of the currently established quality standard methods for standard decoctions,an improvement scheme is proposed from a statistical perspective.This review explores the requirements for dry matter yield rate data and index component transfer data for the application of two methods specified in‘‘Technical Requirements for Quality Control and Standard Establishment of Chinese Medicine Formula Granules,"which include the average value plus or minus three times the standard deviation (■±3SD) or 70%to 130%of the average value (■±30%■).The square-root arcsine transformation method is used as an approach to solve the problem of unreasonable standard ranges of standard decoctions.This review also proposes the use of merged data to establish a standard.A method to judge whether multiple sets of standard decoction data can be merged is also provided.When multiple sets of data have a similar central tendency and a similar discrete tendency,they can be merged to establish a more reliable quality standard.Assuming that the dry matter yield rate and transfer rate conform to a binomial distribution,the number of batches of prepared slices that are needed to establish the standard decoction quality standard is estimated.It is recommended that no less than 30 batches of prepared slices should be used for the establishment of standard decoction quality standards.