RESIDENCE TIME DISTRIBUTION (RTD) AND GOODNESS OF MIXING (GM) DURING CO2-INJECTION IN TWIN-SCREW EXTRUSION PART II: GM STUDIES

Experimental residence-time distribution (RTD) characteristics of an extrusion process may be used to estimate the extent of mixing experienced in the extruder. Using earlier theories of laminar mixing and striation thickness reduction, a new approach to estimate efficacy of mixing of two phases in the mixing zone of the extruder is proposed. Predicting the time required to achieve complete mixing and comparing it with the minimum time (plug flow time) that the extrudate spends in the mixing zone gives a ratio that can be used to evaluate the adequacy of extruder operating conditions for good mixing of gas/fluid injection and extrudate. Twin-screw extrusion of cornmeal with carbon dioxide injection were used to investigate the effect of CO₂ injection pressure and extruder screw speeds on mixing. Lower CO₂ injection pressures (25 bars) and lower screw speeds (150 rpm) were theoretically shown to enhance mixing. Scanning electron micrographs (SEMs) of experimental samples taken showed smaller and more uniform cell structures for those conditions which were predicted to favor better mixing.     

Phase Relations in the System Bi2O3-WO3

Phase relations in the system Bi₂O₃-WO₃ were studied from 500° to 1100°C. Four intermediate phases, 7Bi₂O₃· WO₃, 7Bi₂O₃· 2WO₃, Bi₂O₃· WO₃, and Bi₂O₃· 2WO₃, were found. The 7B₂O · WO₃ phase is tetragonal with a ₀= 5.52 Å and c ₀= 17.39 Å and transforms to the fcc structure at 784°C; 7Bi₂O₃· 2WO₃ has the fcc structure and forms an extensive range of solid solutions in the system. Both Bi₂O₃· WO₃ and Bi₂O₃· 2WO₃ are orthorhombic with (in Å) a ₀= 5.45, b ₀=5.46, c ₀= 16.42 and a ₀= 5.42, b ₀= 5.41, c ₀= 23.7, respectively. Two eutectic points and one peritectic exist in the system at, respectively, 905°± 3°C and 64 mol% WO₃, 907°± 3°C and 70 mol% WO₃, and 965°± 5°C and 10 mol% WO₃.     

High input impedance current conveyor filters

Two new active RC canonic band pass filters are presented. The new configurations offer a very high input impedance and employ single grounded resistors for independent adjustments of ω₀, Q and gain.     

基于深度卷积神经网络的两阶段肺结节检测

针对传统肺结节检测中存在灵敏度低、假阳性高、小结节难检测的问题,提出一种基于深度卷积神经网络的两阶段肺结节检测框架.第一阶段使用特征金字塔子网提取肺部影像的多层次特征,引入多尺度区域建议子网用于在高灵敏度下检测出所有的候选结节;第二阶段设计级联卷积神经网络模型减少假阳性,通过保留分类错误样本用于重新训练模型,将多个模型结果进行投票选出最终分类结果.LUNA16数据集上的实验结果表明,所提框架灵敏度达到95.9％,检测效果优于其它算法,能够有效实现肺结节的准确检测.     

B/H CURVE APPROXIMATION FOR COMPUTER AIDED DESIGNS OF ELECTROMAGNETIC DEVICES

ABSTRACT

Interpolation approximation for an entire B/H curve range can be obtained by a simple spline algorithm. This paper describes a simplified technique to employ a spline algorithm to approximate interpolated values. This technique minimizes time for computer applications, and is suitable for computer aided design of electromagnetic devices where the complete B/H curve is required to be read from a finite number of given points     

BIOCHEMICAL CHARACTERIZATION AND THERMOSTABLE CAPACITY OF PARVALBUMINS: THE MAJOR FISH-FOOD ALLERGENS

The major allergens in fish‐food are parvalbumins (PVs). Muscle PVs of four fish species of genus Channa: Channa gachua, Channa punctatus, Channa striatus and Channa marulius were purified, characterized and used to differentiate (heated) fish specimens. Two to three proteins have been detected as PV‐isoforms by immunological probing through Western blotting. They were purified to homogeneity on diethyl amino ethyl‐cellulose. Modified systems of nondenaturing and denaturing polyacrylamide gel electrophoresis were used to resolve low molecular weight proteins, distinctly. Isoelectric points (pIs) were determined on native isoelectric focusing gels, which lie in the pI range of 4.55–5.10. The electrophoretic profiles remained species‐specific even after heating the PVs for 3 h at 90C and would be of immense help in discerning cooked fish specimens. Further, the addition of 5 mM β‐mercaptoethanol in the PVs has showed protection against heat denaturation of the protein and resulted in more compatible protein patterns. This study also demonstrates the relevance of the thermostable capacity of PVs in the differentiation of heat‐processed fish through electrophoretic analysis of heated PVs. Also, they represent a promising and simple biochemical tool in discerning closely related species.     

Phase Equilibria and Distribution Coefficients of δ-Lactones in Supercritical Carbon Dioxide

A static method was used to measure the solubilities and distribution coefficients of δ-lactones (pure), inherent (natural levels) δ-lactones of anhydrous milk fat (AMF) and fortified (added) δ-lactones in AMF in supercritical carbon dioxide (SC-CO₂) at 40°C with pressures of 5–30 MPa. At 40°C distribution coefficients of δ-lactones increased with pressure and exhibited molecular weight-dependency. Using experimental data, a mathematical model based on thermodynamic equilibria and material balance was developed and used to predict the distribution of inherent δ-lactones of AMF in a continuous SC-CO₂ extraction system. At 24.1 MPa/40°C column conditions, AMF was separated into a raffinate and 5 fractions. Predicted δ-lactones distribution coefficients in the raffinate and extract were in good agreement with experimental data.     

COMPARISON OF TWO METHODS TO INCREASE TIP CLEARANCE AND ITS EFFECT ON PERFORMANCE OF TURBOCHARGER CENTRIFUGAL COMPRESSOR STAGE

Tip clearance between the blade tip and casing of a centrifugal compressor can be varied through two methods:by changing the blade height(M1)or by changing the casing diameter(M2). Numerical simulations are carried out to compare these two methods and their effect on the stage and impeller performance.The impeller and diffuser are connected through rotor stator boundary using frozen rotor approach.Overall stage performance and the flow configuration have been investigated for nine tip clearance levels from no gap to 1 mm.Impeller and diffuser performances are also pre- sented separately.It has been found that the overall and impeller performance are comparatively better for M1 below tip clearance of 0.5 mm whereas M2 is found advantageous above 0.5 mm of tip clear- ance.Both M1 and M2 show performance degradation with the increase in tip clearance.Two models have been proposed for the stage total pressure ratio and efficiency,which are found to be in agree- ment with experimental results.The impeller efficiency and the pressure ratio are found to be maxi- mum at tip clearance of 0.1 mm for both the cases however minimum diffuser effectiveness is also observed at the same clearance level.Diffuser effectiveness is found to be maximum at zero gap for both cases.As it is practically impossible to have zero gap for unshrouded impellers so it is concluded that the optimum thickness is 0.5 mm onwards for M1 and 0.5 mm for M2 in terms of diffuser effec- tiveness.Mass averaged flow parameters,entropy,blade loading diagram and relative pressure fields are presented,showing the loss production within the impeller passage with tip clearance.     

ANTI-OXIDANT EFFECT OF QUERCETIN ON TYPE 2 DIABETIC ERYTHROCYTES

There is much evidence that oxidative stress is involved in the etiology of several diabetic complications. Many in vitro and in vivo studies have demonstrated that several parameters of red blood cell function and integrity are negatively affected by increased oxidative stress. Quercetin (3,3', 4',5,7-pentahydroxyflavone) is one of the most abundant bioflavonoids commonly present in most edible fruits and vegetables. Quercetin has been reported to prevent oxidant damage and cell death by scavenging free radicals. The present study was undertaken to evaluate the antioxidant effect of quercetin on markers of oxidative stress in erythrocytes from type 2 diabetic patients. Quercetin (at micromolar concentration) shows significant antioxidant effect in protecting erythrocytes from tert- butylhydroperoxide induced oxidative changes. These results suggest that a diet rich in quercetin may provide protection to diabetic patients against some late complications.

PRACTICAL APPLICATIONS

In recent years, there has been heightened interest in the possible therapeutic role of plant polyphenols for large number of human diseases. Among other known biological effects, plant polyphenols are known to have strong antioxidant properties. Out of more than 4,000 different types of plant polyphenols, relatively few are known to be effectively absorbed in the human digestive system. Among this group is the flavonoid quercetin that is present in many fruits and vegetables. We present here experimental proof of the protecting effect of this bioflavonoid on erythrocytes subjected to increased oxidative stress. Since diabetic patients are known to have increased oxidative stress, our results add to the scientific knowledge that a higher intake of diet rich in quercetin may protect diabetic patients from some late complications arising due to oxidative stress.