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991.
A general numerical model is described for the dissolution kinetics of spherical particles in binary systems for any combination of first order reactions at the particle-matrix interface and long distance diffusion within the matrix. The model is applicable to both finite and infinite media and handles both complete and partial particle dissolution. It is shown that interfacial reactions can have a strong effect on the dissolution kinetics, the solute concentration at the particle-matrix interface and the solute concentration profile in the matrix. 相似文献
992.
Oommen B.J. Zgierski J.R. 《IEEE transactions on pattern analysis and machine intelligence》1993,15(2):185-192
Let Λ be a finite plaintext alphabet and V be a cypher alphabet with the same cardinality as Λ. In all one-to-one substitution cyphers, there exists the property that each element in V maps onto exactly one element in Λ and vice versa. This mapping of V onto Λ is represented by a function T *, which maps any v ∈V onto some λ∈Λ (i.e., T *(v )=λ). The problem of learning the mapping of T * (or its inverse (T *)-1) by processing a sequence of cypher text is discussed. The fastest reported method to achieve this is a relaxation scheme that utilizes the statistical information contained in the unigrams and trigrams of the plaintext language. A new learning automaton solution to the problem called the cypher learning automaton (CLA) is given. The proposed scheme is fast, and the advantages of the scheme in terms of time and space requirements over the relaxation method have been listed. Simulation results comparing both cypher-breaking techniques are presented 相似文献
993.
The coagulation system plays a major role in the formation of the infected endocardial vegetation in bacterial endocarditis. Since monocytes can express tissue factor (TF) on their surfaces, they are thought to be responsible for the extrinsic activation of the coagulation cascade during this disease. The present study used an in vitro model in which fibrin plates, isolated adherent monocytes, and Streptococcus sanguis were used as an analog for endocardial vegetations. Adherence to fibrin by itself was found to stimulate TF expression on the monocytes, but stimulation by S. sanguis significantly increased TF expression, which was found to be maximal at a bacterium-to-monocyte ratio of 9 or more. 相似文献
994.
Diot C. Dabbous W. Crowcroft J. 《Selected Areas in Communications, IEEE Journal on》1997,15(3):277-290
Group communication supports information transfer between a set of participants. It is becoming more and more relevant in distributed environments. For distributed or replicated data, it provides efficient communication without overloading the network. For some types of multimedia applications, it is the only way to control data transmission to group members. This paper surveys protocol functions and mechanisms for data transmission within a group, from multicast routing problems up to end-to-end multipoint transmission control. We provide a bibliography which is organized by topic 相似文献
995.
1. 45 myopes (-3.0 to -6.0 D) were examined before and 1 and 6 months after photorefractive keratectomy (PRK). Visual acuity (VA) was tested using Snellen and logMAR charts. Contrast sensitivity (CS) was measured using a computerized system. 2. Preoperative best corrected VA (BCVA) in myopes was significantly lower in comparison with a control group using logMAR charts only. A reduction of BCVA by both methods at 1. month and its return after 6 months nearly to original values was noted. 3. Significantly lower values of CS were found in patients before PRK compared to the control group. After 1 and 6 months stayed the values on preoperative level. 相似文献
996.
Directional solidification studies of gelatinized corn starch-water mixtures were undertaken in order to examine, in situ, the freezing behavior of this food model. The solidification rate was controlled by varying sample cell velocity as it moved from a 25°C hot stage to a -25°C cold stage. While freezing at cell velocities ≤7.5 μm/sec, starch granules were alternately pushed or entrapped by the advancing solid-liquid interface producing a segregated structure consisting of alternating high-starch and low-starch bands. At a cell velocity of 10 μm/sec, the frozen product was homogeneous. The relationship between the solid-liquid interface velocity and segregation behavior was quantified and compared to an existing model of particle-interface interactions. 相似文献
997.
The effect of storage temperature on rheological behaviour of four varieties of baby foods was studied. After 24-month storage at 15C and 25C, the constant A in Weltman model increased significantly for the vegetables, meat and fish samples, and decreased significantly for the fruit samples. After 24-month storage at 5C and 15C there were no significant changes in flow behavior index, consistency index and yield stress of the Herschel-Bulkley model for the vegetables, meat, fish and fruit samples. Increase in storage temperature decreased the consistency index and yield stress of the fruit samples. 相似文献
998.
W.L. KERR R.J. KAUTEN M. OZILGEN M.J. McCARTHY D.S. REID 《Journal of food process engineering》1996,19(4):363-384
Nuclear magnetic resonance imaging (MRI), calorimetry, and temperature measurements were used to monitor cylindrical potato sections frozen at -11C and -42C. MRI showed the advance of the nonsymmetric freezing zone and loss of signal intensity as liquid water turned to ice. Differential calorimetry was used to follow heat removal during transient freezing. Measured times to 95% enthalpy change were 24 min (-42C) and 49 min (-11C), as compared to modeled values of 29 min (-42C) and 100 min (-11C). Times to 95% change in the NMR signal, integrated over the area of the image, were 21 min (-42C) and 56 min (-11C). Changes in NMR signal intensity could be correlated with the amount of unfrozen water remaining after a steady-state had been reached. At -42C, NMR indicated 25% unfrozen water remaining as compared to 26% by calorimetry, and 22% by modeling. At -11C, NMR measured 67% unfrozen water remaining as compared to 48% by calorimetry, and 25% by equilibrium modeling. 相似文献
999.
1000.
César I. Beristain Ebner Azuara Hugo S. Garcia & Eduardo J. Vernon-Carter 《International Journal of Food Science & Technology》1996,31(5):379-386
The water and oil uptake of mesquite and arabic gums in powdered form was studied at temperatures of 23, 35 and 45°C. A previously proposed equation to predict osmotic equilibrium was tested using the experimental data with both gums and a good statistical fit was obtained. Mesquite gum showed the highest water and oil absorption at all temperatures studied. Temperature dependence of the reciprocal of the S1 and WL∞ were determined using an Arrhenius equation. The activation energy for water and oil absorption for gum arabic was 21.98 and 39.57 kJ mol−1 , compared to that of mesquite gum having values of 15.79 and 46.16 kJ mol−1 , respectively. A second order kinetic model was obtained for water and oil absorption for both gums. 相似文献