Table of Content

25 December 2007, Volume 35 Issue 12

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Mechanical Engineering

Multivariable Fuzzy Decoupling Control of Precise Extrusion Processing

Wen Sheng-ping Zhao Guo-ping Qu Jin-ping

2007, 35(12):  1-5. 

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In the precise extrusion processing of polymers , the melt temperature and the pressure in the die constitute a key factor to the quality of the extruded product. In this paper , some dynamic characteristic experiments were carried out , and a transfer function matrix model was established according to the experimental data obtained via system identification. The model was used to describe the relationships between the input signals related to melt
temperature and die pressure and the output signals concerning heater power and screw speed. Then , a fuzzy decoupling control algorithm of melt temperature and die pressure for the precise extrusion processing was proposed and finally implemented on a programmable computer controller. Experimental results show that the proposed algorithm is effective and contributes significantly to the development of the control technology of precise extrusion processmg.

Topology Extraction ofCompliantMechanism Based on Wavelet and Cubic Spline Interpolation

Fu Yong-qing Zhang X ian-min

2007, 35(12):  6-10. 

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In order to remove the checkerboard patterns in an optim ized topo logy so lution, w avelet transform and cub ic spline interpo lation are combined to perform the topo logy ex traction of a comp liantmechan ism. In the extract ion, firs,t the optim ized topology so lu tion ism apped into intermed iate variab les v ia nonlinear transformation to ensure the side constraints imposed on the direct topo logy variab les. Then, the intermed iate variab les are decomposed into approx imated and detail coeffic ients v iaw ave let transform, and the approx im ated coeffic ients are further treated v ia cub ic sp line interpo lation. A fter tha,t the approx im ated coe ff icients are reconstructed by w avelet and the corresponding topo logy result is obtained by the ant-i non linear transformat ion o f the reconstructed coeffic ients. F inally,based on the vo lume restriction of topo logy optim ization, the obta ined resu lt is evaluated and thew avelet decomposi-tion scale is determ ined. Experimenta l results show that the proposed a lgorithm can effective ly remove the checkerboard patterns in an optim ized topo logy solution and ex tract the expected topo logy o f a comp lian tmechan ism.

Numer ical Analysis of Gas2L iquid Two2Phase Flow inMultiphase Rotodynam ic Pump and Pump Performance

Huang Si Wang Hong-jun Zheng Mao-xi

2007, 35(12):  11-16. 

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A three-dimension gas-liquid two-phase flow with a high gas volumetric ratio in a helico-axialmultiphase rotodynamic pump is numerically simulated using the Fluent software. In the simulation, the Eulermodel of a two-phase turbulent flow in a multip le reference frame is adop ted. The rule and mechanism of the two-phase turbulent flow in the pump are then investigated by analyzing the absolute velocity in the pump, the relative velocity in the
impeller, the static p ressure, the distribution of gas and liquid phases, and the slip velocity between two phases.The results indicate that the liquid phase in the impeller mainly flows near the flange while the gas phase mainly near the hub due to the existence of centrifugal force, and that the two-phase separation in the diffuser obviously imp roves. The comparison of the p redicted results with the experimental ones demonstrates that the proposed me-thod is effective in the computation and analysis of the gas-liquid two2phase rotodynamic pump.

Application of Ni-P Brush Plating to Deep Drawing D ie of Stainless SteelMater ials

Luo Jian-dong Ruan Feng

2007, 35(12):  17-22. 

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Adhesive abrasion is the main factor that influences the die operation in the deep drawing of stainless steelmaterials. In order to solve this p roblem, SEM, hardometer, abrasion-testingmachine, XRD, EDS and light microscope are adop ted to investigate the effects of the addition of NiSO₄·6H₂O、NaH₂ PO₂·H₂O、EDTA-2Na、C₆H₈O7·H₂O、C₃H₆O₃  on the phosphoric content, thickness, hardness, abradability, cohesion, phase, mor-phology and energy spectrum of the p lating layer. An op timized formula for brush p lating is also p roposed. The re-sults show that, by using the p roposed formula, a Ni-P layer with a phosphoric mass fraction of about 2% can be obtained. The layer effectively sticks to the surface of Cr12MoV and possesses excellent hardness and abrasion-re-sistance after heating at 400 ℃. Practical app lication in factories reveals that the strengthened p lating layer obtained by the p roposed formula effectively avoids the adhesive abrasion of the die.

Modeling and Prediction of Water-Assisted Injection Molding Based on GA-LMßP Inverse Neural Network

Huαng Han-xiong He Jian-min Liu Xu-hui Deng Zhi-wu

2007, 35(12):  23-27,33. 

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Water-assisted injection molding (W AIM) is a new injection molding technique whose mathematical model is difficult to establish by mathematical method due to the process complexity. In this work , an inverse neural network named GA-LMBP is proposed by combining the genetic algorithm (GA) with the Levenberg-Marquardt back-propagation (LMBP) neural network. Based on the proposed GA-LMBP , a model to predict the W AIM process is developed according to a series of experimental results. It is found from the cross-validation that there is a good agreement between the predicted results by the model and the experimental ones , and that , with the thickness at different locations of molded parts as the system input , the model can quickly and accurately predict such processing parameters as short-shot size , water pressure , water injection delay time , and melt temperature.

Numerical Analysis of Flying Static Performances for Ultra-Thin Gas Film Lubrication of Magnetic Heads

Huang Ping Wu Yan-hua Niu Rong-jun

2007, 35(12):  28-33. 

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In this paper , the finite difference theory is adopted to obtain a discrete modified Reynolds equation of the gas , and the shear flow is used as the iterative leading term to obtain the pressure distribution of an ultra-thin gas-film lubrication bearing. Then , by varying the initial working parameters of the magnetic head , such as the flying height of the gas film , the initial pitch angle and the rotational speed of the disk , the parameters describing the
static flying characteristics of the bearing are calculated , including the gas-floating force , the pitch moment , as well as the maximum and minimum gas-floating forces. Moreover , the influences of the initial working parameters on the static flying characteristics are analyzed in detail. Calculated results indicate that , with the decrease in the flying height and the initial pitch angle , the stiffness of the gas-film lubrication bearing improves , and that the effect of rotational speed on performance parameters in constant flying height is similar to that in constant pitch angle.

Adaptive NC Curve Gr inding Based on Curvature

X ie Jin Xu W ei-wei Chen Li-zhi Tang Yong

2007, 35(12):  34-38,50. 

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In order to imp rove the efficiency of curve grinding, the adap tive NC grinding of a curved surface is con-ducted by controlling the wheel path based on the equal-envelope height. During the grinding, an adap tive NC grinding mode is established according to the curvature of the curved surface, and the characteristics of the grind-ings at different curvatures are analyzed based on the comparison of the equal2interval NC grindings with different envelope heights. Then, a NC grinding experiment is carried out to investigate the effectiveness of the p roposed adap tive NC grindingmode bymeasuring the form error. Analytical results indicate that (1) the effect ofwheelwear on grinding p recision can be reduced by using a moving grinding point in the envelope2form grinding; (2) in the curve grinding with equal2envelope-height path, the moving interval between wheel paths can be regulated accord-ing to the actual curvature, thus imp lementing the adap tive NC curve grinding and imp roving the machining effi-ciency; (3) the imp rovement ofmachining accuracy can greatly decrease the path number in the p recise grinding of the curved surface with large curvature. Experimental results show that smooth curved surface can be p roduced by de-creasing the equal2envelope height to 1μm, with a form error PV of 0.1285mm within the range of 100mm ×40mm.

Dimensional Synthesis of a Novel 2-DOF High-Speed Parallel Manipulator

Yuan lian-feng Zhao Xian-min

2007, 35(12):  39-44. 

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The conceptual design of the 2-DOF (Degree of Freedom) translational parallel mechanism with passive limbs is investigated , and some potential structures of the passive limb are generalized. Then , the DOF of the passive limb is analyzed based on the screw theory， and a novel high-speed parallel manipulator containing two active limbs and two passive limbs is presented. The two passive limbs are used to restrict the rotation of the movable platform and to improve the stiffness of the parallel manipulator. Moreover , a dimensional synthesis of the parallel manipulator is carried out based on the kinematic analysis , with the weight values of the mean and maximum condition numbers of Jacobian matrix in the operation space as the performance measures. The results show that the presented manipulator can be combined with a 1-DOF feed mechanism to create a 3 -DOF translational hybrid manipulator for the pick-and-place operation in industrial fields.

Order-Disorder Measurement Theory of Manufacturing Information System

Gong Zhu-ping Sun Yan-ming Zheng Shi-xiong

2007, 35(12):  45-50. 

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In order to measure the order of a manufacturing information system , the relationship between the orderdisorder degree of the system and the manufacturing information is studied in this paper. In the investigation , the manufacturing information is divided into 5 layers including the equipment information in workshop , the manufacture executive information , the flow management information , the bùsiness decision information and the strategy decision information. And , the respective grading standards for the absolute information value and the information importance of manufacturing information are defined according to the 5 layers. Then , the uncertainty value of manufacturing information is obtained according to Shannon 's Information Theory , which is then combined with the two grading standards proposed above to assess the absolute information value of each information item. Moreover , the absolute information values are combined with the relative coefficient between two information items to determine the independent information value of each information item. The sum of all independent information values forms the total information value of the manufacturing information system. In addition , according to the total information value and its maximum and mllllmum in extreme conditions , a parameter named the system order degree is defined to evaluate the order-disorder of the manufacturing information system , which is finally used in practice , with a linear correlation to the order of the manufacturing information system.

Algorithm for Smooth B-Spline Surface Reconstruction Based on Mesh Model

Gu Bu-yun Zhou Lai-shui Liu Sheng-lan Sun Xiu-hui

2007, 35(12):  51-55. 

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This paper proposes and implements an approach to smooth B-Spline surface reconstruction based on the mesh model. In the investigation , a method to define and optimize the feature lines of the mesh model is studied and implemented. Then , a set of interactive editing tools are provided for users to freely construct the final quadrilateral patch topology model which suits the original design intent. Finally , a smooth B-spline surface is reconstructed by synthetically considering the fitting accuracy , the smoothness and the continuousness. Experimental results demonstrate that the proposed algorithm meets the requirements for reconstruction efficiency and surface fitting quality in reverse engineering.

Image-Splicing Technology for IC Chip Inspection Based on Direction-Predicting Operator of Grading 8 Neighborhoods

Liang Zhong-wei Ye Bαng-yan Peng Rui-tao Xu Lan-ying

2007, 35(12):  56-60. 

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In the accurate optical inspection of the IC chip , it is necessary to obtain complete and accurate images describing the surface features of the chip. For this purpose , a template matching method based on the directionpredicting operator of grading 8 neighborhoods is proposed and is then applied to the high-accuracy image splicing of the IC chip. By quickly and accurately searching the matching pixel in the overlapping part of the microscopic
image , high-speed splicing of IC chip images is implemented. Experimental results indicate that the proposed method helps to obtain clear microscopic surface images of the IC chip as well as display effectively its topography and micro-flaws.

Experimental Observation and Córresponding Analysis of Bubbles and Polymer Melt in Elongated Flow Field

Li Lin Wang Hong Peng Yu-cheng

2007, 35(12):  61-65. 

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In order to investigate the dynamics of the bubbles in polymer melt , a self-designed columniform visible flow channel was used , and CO2 gas was directly injected into the polymer melt to obsertre the dynamic characteristics such as shape , size , motion and deformation of the bubbles in different locations in a small-pore enlongated flow field. Moreover , the variations of shape , distribution and motion of the bubbles with the flow-field structural
parameters and the processing conditions were revealed based on the classic two-phase flow theory. Experimental results indicate that (1) the gas phase in the melt exists in the form of bubbles; (2) many small bubbles may form due to the breaking up of a large enlongated bubble , the size , distribution and density of the small bubbles being related to the precessing temperature , velocity and injectión pressure; and (3) the breaking up of bubbles after the enlongation may result in the mixing of the gas and the melt , which is helpful for the application of CO2 as an foaming agent to the production of foamed plastic products.

Materials Science & Technology

Influence of EDC/NHS Crosslinking on Physicochemical Properties of Collagen

Wang Ying-jun Yang Chun-rong Wang Ling-yun

2007, 35(12):  66-70,96. 

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In order to improve the physicochemical properties of collagen , l-ethyl-3 -( 3 -dimethyl aminopropyl) carbodiimide (EDC) /N -hydroxysuccinimide (NHS) was used as a crosslinking agent for collagen matrices , and the effect of crosslinking agent dosage on the physicochemical properties of collagen was investigated. Then , the measurements of FT -IR , DSC and SEM were performed and the water absorption , the swelling ratio and the collagenase resistance were tested to characterize the physicochemical properties of the collagen before and after the crosslinking. The results demonstrate that , after the crosslinking , the thermal stability , the morphological stability and the enzymatic resistance all improve significantly , and that the disordered microstructure of collagen changes to a dense and ordered state. It is thus concluded that the EDC/NHS crosslinking greatly improves the physicochemical properties of collagen.

Sintering Process via Solid-State Reaction of Ti/ AI Composite Powders Prepared by High -Energy Ball Milling

Li Xiao-qiang Qu Sheng-guan Zhang Zhong-rong Shao Ming Li Yuan-yuan

2007, 35(12):  71-75. 

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The solid -state diffusion reaction behavior between Ti and Al foils was studied by using optical microscopy and energy spectrometer , and an equation describing the growth of TiA13 phase layer was deduced. Moreover , a two-step solid-state sintering process of milled Ti/ Al composite powders was investigated. The results indicate that ( 1) the proposed two-step solid-state sintering effectively avoids the deformation of powders during the sintering process and helps to obtain dense TiAl alloys with typical microstructure; (2) in order to obtain highly dense TiAl alloy , a sintering at elevated temperature after the presintering for a prolonged time at low temperature is necessaη because the presintering only helps to form thermostable microstructure of TiAl and Ti3Al and the relative density is still low; (3) the high-energy ball milling leads to fine TiAl microstructure , the longer the milling time , the finer the sintered alloy; and (4) with the increase in milling time , the content of lamella colonies in the dual-phase sinter
first increases but then decreases due to non-CIγstallization.

Characterization of NRlSBRlBR Blends Reinforcedby Modified Nano-CaCO₃

Gu Ju Li Qi Jia De-min Luo Yuan-fang Cheng Rong-shi

2007, 35(12):  76-81. 

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In this paper , RH , the complex of resorcinoland hexamethylene , was added in commercial nano-CaCO₃ modified with stearic acid (CCR) to prepare modified CCR (M -CCR) via solid state method , and the composites of NRlSBRlBR blends respectively filled with M -CCR and CCR were prepared. Then , the dispersion ability , interfacial combination , processing ability and morphology of M-CCR and CCR in NRlSBRlBR blend matrix were characterized by using the rubber process analyzer (RPA) and the TEM. Moreover , the mechanical properties of the composites were investigated. The results indicate that the processing ability , the reinforcement effect , the dispersion ability and the interfacial adhesion of M-CCR in the blend matrix are all superior to those of CCR.

Influence of Ceria Superficial Coating on Oxidation Mechanism of Chromium at 900℃

Jin Hui-ming Zhou Xiao-wei Zhang Lin-nan Liu Xiao-jun

2007, 35(12):  82-86. 

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The isothermal and cyclic oxidation hehaviors of pure chromium and the chromium coated with CeO₂ were studied at 900 "C in air. The morphology and microstructure of the oxide films were then ohserved hy means of SEM , TEM and high-resolution electronic microscopy (HREM). Moreover , the cracking and spalling of the oxide films were mon山red on line hy using the acoustic emission (AE) technique , and the distrihution of AE signals in
the time and numher domains were respectively analyzed according to the related oxide cracking model. The internal stresses of the oxide films coated on Cr surfaces with and without ceria were finally measured using a Laser Raman spectrometer. The results show that (1) the ceria coating greatly improves the anti-oxidation. ahility of Cr in isothermal and cyclic oxidation conditions; (2) the main reason for the improvement of anti -oxidation ahility of Cr is that the ceria addition greatly decreases the growing speed and grain size of Cr₂O₃ films; (3) the fine-grained Cr₂O₃ film is of hetter high-temperature plasticity and can relieve a part of the internal compressive stress hy means of high-temperature creeping , thus resulting in ohvious ridge character and relatively low internal compressive stress level; and (4) the adhesion of Cr₂O₃ film on Cr suhstrate greatly improves as the size and numher of film/ suhstrate interfacial defects decrease due to the ceria coating.

Comparison of Conductive Properties Between BaPbO₃ and BaTiO₃ Ceramics

Wang Xin Lu Yu-dong Zhuang Zhi-qiang Liu Bao-ling

2007, 35(12):  87-90. 

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In order to investigate the effect of CIγstal defect on the electrical properties of ceramics in a microcosmic scale , BaPbO₃ and BaTiO₃ polycrystalline ceramics were used as two objects to investigate the relationship between their conductive properties and crystal defect structures by studying the defect structure and roonHemperature conductivity of the ceramics sintered in different firing atmospheres. The results show that the difference in electrical properties between BaPbO₃ and BaTiO₃ ceramics mainly results from the difference in the defect structure. As the BaPbO₃ sample is of a shallow acceptor energy level , high conductivity can be achieved after sintering in oxidizing condition because the cavities trapped in the acceptor center are easy to transit to the valence band to form conductive carriers. However , the BaTi03 sample with a deep acceptor energy level turns into an insulator after sintering in oxidizing condition.

Dissolution Behavior of Solid Nickel in Liquid Zinc Containing Fe

Kong Gang Lu Jin-tang

2007, 35(12):  91-96. 

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The dissolution behavior of solid nickel in static liquid zinc containing Fe at 450 ℃ was studied by using optical microscopy , SEM and EDS , and the controlling mechanism of dissolution rate of solid nickel was analyzed according to the dimensionless correlation for mass transfer with natural convection and the dissolution rate model which takes into account the formation of intermetallic compound layers. The results show that (1) similar to that in pure liquid Zn , the dissolution of solid Ni in liquid Zn containing Fe may result in the formation of γ-Ni₂ Zn₅ and δ-NiZn₈ phase layers; (2) some Γ₂ -Fe₅ Zn₆ Ni ₈₉particles may form in the liquid near the solidJliquid interface due to the existence of Fe; and (3) the dissolution process of Ni in the liquid Zn unsaturated with Fe is similar to that in pure liquid Zn and is governed by a mixed control mechanism involving the diffusion of nickel atom in Ni-Zn alloy layers and the chemical reaction at the interfaces , while the dissolution rate of Ni in the liquid Zn supersaturated with Fe is mainly controlled by the diffusion of Ni atom across a concentration boundary layer. It is thus concluded that the existence of Fe in liquid Zn accelerates the dissolution of solid Ni.

Effect of Polypropylene Fiber on Sound-Absorbing Property and Its Simulation by Neural Network

Jin Xue-li Zeng Ling-ke Li Ping Hou Lai-guang

2007, 35(12):  97-101. 

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A kind of environment-friendly sound-absorbing material was fabricated by means of concrete molding , with expended cement , light ceramisite , fly ash and polypropylene fiber as the raw materials. The effects of the fiber length and dosage on the sound-absorbing property were experimentally investigated , finding that the soundabsorbing property , especially that at a high frequency , improves significantly with the doping of polypropylene
fiber. Moreover , a prediction system based on back-propagation (BP) neural network was proposed by means of Matlab , which was further trained with the data of fiber length , fiber dosage , test frequency and practical absorption coefficient. Thus , an input-output nonlinear mapping relationship was presented for the fabricated material. The predicted results of the test data indicate that the proposed system is of high accuracy.

Design of Multifunctional Fire Test Furnace for Building Elements

Li Ping Zeng Ling-ke Li Ru-xiang

2007, 35(12):  102-106. 

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A horizontal fire test fumace and a vertical fire test fumace were designed according to the requirements of GB/T9978-1999 so as to adapt to the fire test of various building components with high test reliability. In the designed fumaces , the temperature distributes more uniformly due to the rational layout of bumers , and the temperature and pressure can be automatically controlled by the self-designed control system. Thus , the disadvantages of
the traditional manual control are removed and pollution is reduced. Moreover , the new design saves space and lowers both fuel and labor costs. Industrial application demonstrates that the two newly-designed fumaces are effective.

Hydrothermal Synthesis and Flame-Retardant Properties of 4ZnO • B₂O₃ • H₂ O Microrods

Zhou Jie Su Da -gen Zhong Ming-feng

2007, 35(12):  107-110. 

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Well-dispersed 4ZnO • B₂O₃ • H₂ Omicrorods were prepared via the hydrothermal synthesis from zinc nitrate and boric acid , with triethanolamine as the surfactant. The phase , composition , surface structure and morphology of the product were then analyzed by means of powder X-ray diffraction , TG-DSC , IR , SEM and TEM. The results indicate that (1) The diameter and length of the well-dispersed product are 0.2 - 0.5μm and 5 -10μm ，respectively; (2) as for the poplar wood powder treated with 10% of zinc borate microrods , the limit oxygen index reaches 43. 2 and the residual charcoal ratio increases by 18. 69%， as compared with that of the powder without zinc borate. The results clearly show that zinc borate microrods are of fine flame-retardant properties.

Food Science & Technology

Separation and Identification of B-Phycoerythrin Subunits by HPLC and LC-ESI-MS

Chen Feng Hu lin-mei Guo Si-yuan Wei Dong Zhang Xue-wu

2007, 35(12):  111-115. 

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In this paper , three kinds of suhunits of B-þhycoerythrin (B-PE) were tested and identified on line hy using inverse HPLC with photodiode array/UV -Vis and fluorescence detector , and hy using LC-electrospray ionization/MS. The results show that the α and β suhunits as well as three γ suhunits of B-PE are all successfully separated hy C4 column according to the on-line spectroscopic characteristics , and that hoth the α and the Bsuhunits have a maximum ahsorption at 555 nm , while the γ suhunit species show their maximum absorptions at 493 and 555 nm. Moreover , hy coupling with the MS ,α and β suhunits with respective relative molecular masses of 18977 and 20330 can he identified. It is thus concluded that a comhination of the techniques mentioned ahove helps to identify the suhunits of B-PE reliahly.

Composition and Antimicrobial Activity of Essential Oil from Phyllanthus emblica L. by Supercritical CO2 Extraction

Zhao Mou-ming Liu XiAo-li Cui Chun Luo Wei

2007, 35(12):  116-120. 

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The essential oils of emblica fruit were extracted by means of supercritical CO₂ extraction (SFE) , and the antimicrobial activity of the product was investigated by using the agar dilution technique , with potassium sorbate as the control. Then , GC-MS was adopted to identify the composition of the product. The results show that ( 1) the extracted oils have a high antimicrobial activity against the original contaminating bacteria such as Bαcillus
subtilis , Stαphylococcus aureus， Escherichia coli , Salmonella , Saccgaromyces cerevisiae and Aspergillus oryzae; (2) Bacillus subtilis , Staphylococcus aureus ， Salmonella， Saccgaromyces cerevisiae , Aspergillus oryzae and Aspergillus niger are more sensitive to the oils extracted at 20 MPa than to potassium sorbate; (3) there are thirty compounds in the oils extracted at 20 MPa , mainly including β-bourbonene (38. 23%)， hexacosane (17. 2% ), thymol (10.94% ) , pentacosane (8.51 % ) ，β-carγophyllene (5.39%)， 2 , 3-dihydroxypropanol (4.36%) , palmitic acid (2.65%) and methyl eugenol (1.25%) ; and (4) the antimicrobial activity of the oils mainly results from the existence of methyl eugenol ，β-caryophyllene ，β-bourbonene and thymol.

Inactivation of Yeast Cells by Ultrasound Disinfection and Related Influences

Zhou Li-zhen Li Bing Li Lin Zhang Xi-mei

2007, 35(12):  121-125. 

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As an emerging nonthermal disinfection technique , ultrasonic treatment is still in its infancy of industrial application due to the insufficient investigations into its inf1uencing rules on disinfection and its effects on cells. In order to solve this prohlem , Saccharomyces cerevisiae was chosen as the ohject to reveal the effects of three ultrasonic parameters on the inactivation of yeast cells. The parameters included the ulrasonic power , the irradiation time and the pulse ratio. Moreover , the selective medium method and the TEM were adopted to investigate the cell sublethal injmγcaused hy ultrasonic treatment and the cell ultramicrostructure after the treatment , respectively. The results show that (1) hoth the ultrasonic power and the irradiation time have significant positive effects on the inactivation of cells j (2) no s山letl叫injured cells are detected after the ultrasonic treatment j and (3) ultrasonic irradiation may result in great damage to cell ultramicrostructure. It is thus concluded that the damage of structural integrity could he the direct reason for the death of cells.

Freshness Evaluation of Refrigerated Southern Sheatfish (Silurus meridionalis) Fillets Using Quality Index Method (QIM) and Physicochemical Parameters

Li Bian-sheng Yu Yu-ming Zhu Zhi-wei Huang Juan Ruan Zheng Li Bin Huang Jian-qiang

2007, 35(12):  126-131. 

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The freshness of Silurus meridionalis fillets storaged at 2℃ was synthetically evaluated by using the Qualty Index Method (QIM) and the physicochemical parameters. The QIM results show that the quality of the fil- lets , whose maximum storage time at 2℃ is 10 d , obviously lowers in the 8th day , and that there is a linear correlation between the Quality Index (QI) values and the storage time. The storage time estimated by QIM is of an accuracy of ±1. 5 d. Moreover , the physicochemical analytical results show that , after being stored for 8 d , the freshness of the fillets changes from Grade One to Grade Two , and that the pH value increases to more than 6. 90 , the TVBN va1ue exceeds 150mg/kg , and the hardness value obtained from texture profile analysis (TPA) obviously decreases. It is thus concluded that both the QIM and the physicochemical parameters are suitable for evaluating the freshness of fillets due to the good accordance between them.

Compression Heating Characteristics of Pressure-Transmitting Fluids in High Hydrostatic Pressure Processing

Wang Biao-shi Li Bian-sheng Huang Juan Zeng Qing-xiao Li Lin

2007, 35(12):  132-136. 

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The compression heating characteristics of three pressure-transmitting f1uids such as dioctyl sebacate ,water and ethanol in high hydrostatic pressure processing were investigated via the on-line measurement of temperature by inserting the probe into the high-pressure cavity. The results show that ( 1) the compression heating value of dioctyl sebacate decreases from 0. 089 to 0. 068 ℃ IMPa with the increase in pressure , while that of water slightly changes from 0. 026 to 0.028 ℃ /MPa , and that of ethanoldecreases from 0.082 to 0. 075 ℃/100 MPa; (2) the influence of pressure on the compression heating value of ethanol is greater than that on water but slightly smaller than dioctyl sebacate; (3) with the increase in the initial temperature , the compression heating value of dioctyl sebacate decreases , while that of water slightly increases; (4) the effect of the initial temperature on the compression heating value of ethanol is greater than that of water , which increases with the mass fraction; and (5) teflon liner has
greater heat preservation effect on dioctyl sebacate than stainless steel liner during the pressure-holding process in different simulated heat loss conditions.