Overfitting is one of the important problems that restrain the application of neural network. The traditional OBD (Optima Brain Damage) algorithm uses information of second derivative to calculate sensitivities and overfitting is restrained by deleting low-sensitivity weight. However, training of the network is needed repeatedly and its efficiency is low. In this paper, the Marquardt algorithm is incorporated into the OBD algorithm,so that a new method for pruning network--Dynamic Optimal Brain Damage (DOBD) is introduced. This algorithm simplifies the network and obtains good generalization through deleting weight parameters with low sensitivities dynamically while training at the same time. An approximate method through which sensitivities can be calculated during training with little computation and a rule that uses lower limit of sensitivity to delete the unnecessary weights are presented. The new algorithm is applied to the model of estimating stabilizer gasoline RVP (Reid Vapor Pressure) for FCC (Fluidized Catalytic Cracking) unit in refinery and is compared with OBD and the non-pruning method. It is shown that DOBD can avoid overfitting effectively and has a much faster convergence speed than OBD algorithm.

It is hard to obtain derivative functions for branched modules in polycondensation process optimization problems with current differentiation approaches,such as symbolic differentiation,extended automatic differentiation (XAD), etc .In this paper,symbolic automatic differentiation (SAD) and numerical automatic differentiation (NAD),the two components of XAD,are integrated in a flexible way to solve this problem.The resulting derivative evaluation approach,named as hybrid automatic differentiation (HAD),is used to solve a polycondensation optimization problem.In the polycondensation model,a flash distillation process model is adopted to calculate the concentration of volatile species in the reaction mass,which is a typical branched module.So the specific module is taken apart from the main model and each of the two parts is managed in a different way.Accordingly,the derivative function obtained by HAD contains two parts:one is a NAD tool to compute the derivatives of the flash distillation process module,the other is a series of symbolic derivatives generated by SAD for derivative evaluation of the main model.Numerical results demonstrate that the HAD based optimization can significantly reduce the solution time,and is of great importance for on-line process optimization.

Fullerenes are prepared from three high rank coals by arc plasma evaporation in helium. The results show that Chinese coals are potential candidates for producing fullerenes,and the yields of fullerenes are related to the properties of raw coals,such as ash content in coal and carbon content in coke electrodes made from coals.Because coal contains weak covalent bonds linking macromolecular structural units with a number of aromatic rings,large fragments can coexist in the arc plasma together with C 1 and C 2 units.This implies that these large fragments may play an important role in forming fullerenes.It is also found that the fullerene yields decrease as the ash content in coal increases,and increase with increasing carbon content in coal-based coke electrodes.The demineralization treatment is of great help to fullerene formation.The fullerene yield from Fengfeng coal after demineralization treatment is 6.51%,which is comparable to that obtained by using graphite under similar experimental conditions.

Pyrolysis of Shenmu coal maceral concentrates under different conditions was systematically investigated in TG-151 pressurized thermal balance.The pyrolysis kinetics was analysed by using Distribution Activation Energy Model (DAEM).The results indicated that vitrinite has higher yield of volatile matter than fusinite.With increasing temperature,the yield of volatile matter of vitrinite and fusinite increased.Pyrolysis pressure and heating rate showed little effect on the yield of volatile matter of macerals.The kinetic result illustrated that vitrinite has lower activation energy than fusinite.

In this paper,calcination characteristics and desulfurization property of several kinds of shells are studied by using thermogravimetic analysis methods.On the basis of theoretical analysis and experimental study,the kinetic model of shell calcination reaction is obtained and apparent activation energy is calculated and compared with that of limestones.The results indicate that apparent activation energy of shells is approximately 100?kJ·mol ^-1 lower than that of limestone.By using SEM,the microstructure of shells can be observed.From SEM photos of shells and limestone,this paper compares shells with limestone in specific surface area and porosity.Finally the reason for better desulfurization with shells than with limestones can be explained.

By electron paramagnetic resonance spectroscopy, electron microscopy and energy spectrum, the transferring of physiological state of cells was studied when oligosaccharide from Fusarium oxysprum was added in suspension cultures of Taxus chenensis var. mairei. Cells before elicitation were in a good state of growth including integration of cells, abundance of organelle, stability of active oxygen system, low redox potential of cells,flourishing of primary metabolism and low rate of taxol biosynthesis. After elicitation the activity of superoxide dismutase was improved sharply at first, and the activity of catalase and peroxidase were inhibited severely, then the oxidative burst was caused in cells and reached a maximum at 4h. The redox potential of cells was promoted rapidly, and ion channels in cell membrane were activated leading to H ⁺, Ca ²⁺ influx and Cl ^- efflux which caused alkalization of medium. The observation by using optical microcopy and transmission electron microscopy showed that the high electron density body including Ca ²⁺ in vacuole changed regularly. Cell growth was inhibited, but productivity of taxol was increased 5.5 fold of that of control (76.1mg·L ^-1 ) and the system became the state of product synthesis.

Main factors affecting production of glycerol in shake flasks in a process of repeated batch fermentation were studied. The experiments indicated that optimal concentration of corn steep liquor in repeated batch fermentation was lower than that in conventional batch fermentation because of higher cell density. The favorable occasion for reuse is when residual glucose concentration decreased to about 10g·L ^-1 ,and cell viability was about 60%.The residual harmful metabolite among centrifuged cells that were not washed inhibited glycerol production in the process of repeated batch fermentation, however, washing cells before centrifuged cells were reused would eliminate inhibition.

A series of comb-shaped copolymers of polycarboxylic acid type were synthesised by copolymerizing polyoxyethylene allyl methyl diether(APEO- n ), maleic anhydride (MAn), and/or styrene (St). The effects of structure and composition of copolymers on dispersing capability were studied. The results showed that the properties of superplastisizer were affected by the length and density of graft chain. The superplasticizer has excellent dispersing capability as the length of graft chain is 20-60,and the St is 5%-20%(mol).

As a CFC-free and energy-saving refrigeration technology, the waste heat powered heat-regenerative adsorptive reversible heat pump seems to be attractive compared with traditional technologies. An experimental prototype for this kind of heat pump has been built.This study aims at its performance research, which can be used to guide the optimal running and design of the heat pump. It is also a key step for the real application of this kind of system. In this paper, the main simulation and experiment performance objectives for the heat pump are defined. Based on the practical three-heat-reservoir model, the influence of various parameters is studied, such as heat source temperature, fan-coil temperature, environment temperature, heat capacity ratio and final heat-recovery temperature difference, etc. Research indicates that the prototype performance is satisfactory if compared with other cycles and the experimental result is close to simulation. So the application of the heat-regenerative adsorptive reversible heat pump is achievable and beneficial.

In accordance with anisotropic feature of turbulent flow,an anisotropic k-ε turbulence model is used to predict the turbulent flow field and turbulent intensity generated by a Rushton disc turbine with the improved inner-outer iterative procedure considering the feature of flow swirl in the stirred tank.The predicted flow patterns are compared with experimental data and the simulation results with the standard k-ε turbulence model.The anisotropic k-ε turbulence model gives better prediction than the standard k-ε turbulence model.The predicted turbulent flow field is in agreement with to experimental data and the trend of the turbulence intensity can be effectively reflected in the simulation.

A model of mass transfer coefficients in liquid phase near free gas-liquid interface is developed based on the energy spectrum functions of isotropic turbulence.The calculated results for the mass transfer coefficients in pipe flows and stirrer tanks agree well with the measured data reported in articles.

The pervaporation of ethanol from dilute aqueous solution through a novel plate composite silicone rubber membrane was investigated.Based upon the well-known resistance-in-series model,the overall mass transfer coefficient across membrane was measured and split into two parts of liquid film mass transfer coefficient and diffusive mass transfer coefficient in membrane,by conducting an ingenious calculation from the experimental data with different skin layer thickness of membranes. This allowed the relative contributions of the liquid film boundary layer resistance and the membrane resistance to be elucidated. Especially,the effects of liquid flow status on the surface of membrane on mass transfer of membrane was revealed,from which the correlations between liquid film mass transfer coefficient and Reynolds number as well as feed temperature could be obtained.

A liquid crystal technique was used to investigate the temperature profile in an agitated tank equipped with a PBT impeller.Four sets of vertical tubes were symmetrically fixed in the agitated tank with diameter of 500?mm.A mixture of cholesteric liquid crystals was dispersed homogeneously in glycerol.The effects of time,rotation speeds on the temperature profile were discussed.The commercial CFD code CFX- 4.3 was used to simulate the axial and radial temperature profiles in the tank.And the results of the simulation were compared to the experimental data.The CFD predictions are in good with eperimental data.

A computational fluid dynamics (CFD) program FLUENT has been used to predict the fluid flow distribution in plate-fin heat exchanger.It is found that the fluid flow maldistribution is very serious in the direction of header length for the conventional header used in industry.Based on the analysis of the fluid flow maldistribution,two improved headers with a two-stage distributing configuration are recommended and predicted by CFD.The predictions indicate that the improved header configuration can effectively improve the performance of fluid flow distribution in the heat exchanger.The absolute degree of fluid flow nonuniformity in plate-fin heat exchanger has reduced from 3.47 to 0.71 by changing the header ocnfiguration.The computational results are in good agreement with experimental ones,which indicates that the CFD technology is capable of closely predicting the fluid flow distribution in plate-fin heat exchanger.

In-situ carbonization of pre-oxidized fibre mixed with green petroleum coke powders without any binder to prepare C/C composites is an effective method to manufacture advanced C/C composites in a shorter period and with lower cost.But just like other C/C composites,the oxidation resistance of the material produced by this kind of technology is not satisfying even with oxidation resistant coating because of the different thermal expansion coefficients between the coating and the matrix.,and the crack problem will occur.A mixture of green petroleum coke,B 4C and SiC together with short carbon fiber is used as starting materials.The mixture is then press-formed without binding agent after grinding,dense and homogeneous bindless Carbon/Ceramic composites are then obtained after sintering.Composites thus prepared have excellent anti-oxidation property between 900-1000℃.Anti-oxidation mechanism is also discussed from the viewpoint of thermodynamics.

Thermal conductivites of fibrous refractories at high temperature were investigated in this paper based on microstructure analysis with fractal theory.It was found that the fractal dimension and volume fraction of fiber material are two important parameters affecting heat conduction.According to the equivalent heat resistances,a model of heat transfer inside the fiber material was developed for prediction of effective conductivities of the material at high temperature.Model predicting are in good agreement with experimental data as well as with results from literature.

The desulfurization technology during coal combustion in furnace has been a competitive choice for middle and small industrial boilers to meet the environmental protection requirements,with the advantage of low cost and convenient operation.The ordinary calcium-based sorbents such as limestone and calcium carbide residue have low desulfurization efficiency during coal combustion because of CaSO ₄ decomposition.The sulphation product BaSO ₄ which don’t decompose until 1580℃ has much better thermal stability than CaSO ₄ which rapidly decompose at about 1300℃.A new type of barium-based sorbent with high desulfurization efficiency was developed.ZCS intelligent sulfur determination analyzer was used to study sulfur capture mechanism during the high temperature combustion process of coal.In addition the dynamic sulfur capture process of the mixture of barium-based sorbent and calcium-based sorbent was studied in detail.Industrial grate furnace experiment revealed that the desulfurization efficiency of barium-based sorbents could reach 35.5%, which is higher than 13.88% of calcium-based sorbent.It implied that the desulfurization effect of barium salt was much better than calcium salt during coal combustion at about 1200～1300℃.

A new method was developed to obtain a new kind of enhanced surface for pool boiling heat transfer.In this method the combined chemical plating (electroless plating) layer was obtained on common metal substrate.The layer was made of metal and nonmetal elements and consisted of polymer particles.By high temperature heat treatment the polymer particles were carbonized to form micropores.The size and density of micropores may vary with the size and density of the polymer particles in the plating solution. It was found that there was a noncrystal metal layer on this kind of surfaces and there were enough ideal cavities on the surface which promoted the initiation of bubbles of nucleate pool boiling.Pool boiling heat transfer measurements were made by using a plain copper surface and the enhanced surface with water at atmospheric pressure.

Ultrasound of frequency 1.8MHz,sound intensity 1-5 W·cm ^-2 was used to induce sonochemical reaction in a near field acoustic sonoreactor.It was found that the sonochemical yield is linearly related to sound intensity and irradiation time. The cavitational bubble’s amount and sonochemical reaction dynamic equation in cavitational sound field were also presented.

The properties of modified product of acrylic phenolic resin containing quaternary ammonium salt groups (APRQA),and the effect of chemical modification on solubility,thermal property,and photo-crosslinking property,were studied in this paper. The experiment results showed that the modified resin exhibits much lower decomposition temperature and has good solubility in water,ethanol,DMSO,and DMF. After 30?min,thermocured at 160℃,the product of modified resin becomes insoluble in water. The photo-crosslinked film of modified resin has good physical properties as that of APRQA

A polyvinylidene fluoride (PVDF)/polyvinyl acetate (PVAc) blend ultrafiltration(UF) membrane was prepared by phase inversion method.The experimental results showed that the blend membrane significantly increased the water flux of PVDF membrane as well as kept the excellent chemical stability and high rejection for vitamin B ₁₂ .

Modeling of batch distillation has been mostly based on equilibrium model in previous studies.It leads to a large-scale differential algebraic equations (DAEs) system.Due to its dynamic nature,initialization of the system has been a problem.Batch distillation columns are frequently started up with different initial reboiler charges.A model to express startup behavior of batch columns starting from an empty cold state is proposed to handle this issue.Each tray will be described from a non-equilibrium phase in which only mass and energy transfer are taking place to an equilibrium phase in which the vapor-liquid equilibrium is reached.The switching point between these two phases is decided by the relationship of bubble-point temperature at the operating pressure.The liquid holdup of each tray is related to the geometry of the trays.The model is verified through experiment on a pilot batch plant with a bubble-cap tray column to separate a methanol-water mixture.