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排序方式: 共有435条查询结果,搜索用时 15 毫秒
1.
Xiaoming Zhou Martin Jacobsson Henk Uijterwaal Piet Van Mieghem 《International Journal of Communication Systems》2008,21(6):643-663
Although packet delay and loss are two important parameters of the Internet performance, to the best of our knowledge, the evolution of large‐scale IPv6 delay and loss performance has previously not been studied. In this paper, we analyze more than 600 end‐to‐end IPv6 paths between about 26 testboxes of RIPE Network Coordination Centre over two years, and compare the delay and loss performance over time with their IPv4 counterparts. We present and discuss the measurement methodologies and show that IPv6 paths have a higher delay and loss than their IPv4 counterparts. The main reason for the worse performance stems from IPv6‐in‐IPv4 tunnels rather than from native IPv6 paths and such tunnels are still widely used today. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
2.
Anton A. Kiss Costin S. Bildea Alexandre C. Dimian Piet D. Iedema 《Chemical engineering science》2002,57(4):535-546
This article continues earlier work (Comput. Chem. Eng. 24 (2000) 209) concerning the design and control of isothermal reactor-separator-recycle systems. The multiplicity behaviour of six reaction systems of increasing complexity, from one-reactant, first-order reaction to chain-growth polymerisation, is investigated. Below a critical value of the plant Damkohler number, Da<Dacr, the only steady state involves infinite flow rates. Feasible steady states become possible if the critical value is exceeded, Da>Dacr. For one-reaction systems, one stable steady state is born at a transcritical bifurcation. For consecutive-reaction systems, including polymerisation, a fold bifurcation can lead to two feasible steady states. Moreover, the transcritical bifurcation is destroyed when two reactants are involved. If the gel-effect is included, a maximum of four steady states are possible. When multiple steady states exist, the achievable conversion is constrained by the instability of the low-conversion branch. This has practical importance for polymerisation systems when the radicals’ quasi-steady state assumption is not valid or the gel effect is significant. 相似文献
3.
This paper discussed the application of the method of the simplex-lattice design for predicting the properties of cement-based composites. On the basis of the compressive strength, its use was demonstrated on ternary paste systems composed of cement, silica fume and fly ash with constant water to binder ratio and a mass fraction of mineral admixtures not exceeding 30%. The regression model between compressive strength of paste and binder proportion was built up. The F-test method was utilized for validation of the regression model. The nonlinear programming system with upper and lower bound was solved. This allowed assessment of optimum mixture proportions and corresponding maximum compressive strength. It was shown that: (1) the 3rd-order regression model constructed by using the simplex-lattice design method could accurately predict the compressive strength in ternary paste system made of cement, silica fume and fly ash (the total mass fraction of all mineral admixtures was up to 30%); (2) to solve the nonlinear programming with the constraints of upper and lower bound played an important role in getting the optimum compressive strength and its corresponding mixture proportion at different ages; (3) the combination of the simplex-lattice design method and the optimization theory could be valuable tool for optimization of cement-based composites' properties. 相似文献
4.
The crosslink reaction is in fact from a commercial perspective the most reward ing reacting there is.It is used to adjust viscosity or rheology parameter in a large number of applications like p.e.the food or adhesives and textile printing. 相似文献
5.
Marco A. Jonker Piet S. van Roon Joop M. P. den Hartog 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1987,185(5):402-405
Summary The purpose of this study was to find experimental conditions for the complete solubility of collagen-free muscle proteins (CFMP) using acetone powder of Guelders ring sausage. Preliminary experiments were carried out to choose the best procedure for preparing the acetone dry powder. Two different methods of acetone extraction of minced sausage were compared. The acetone dry mass (ADM) method using continuous extraction in a Soxhlet [2] apparatus gave better results than the acetone powder (ACP) method, which used a blender [1]. The ADM method was used for further investigations. ADM was extracted with two types of sodium dodecyl sulphate (SDS), containing solvents A and B. Solvent A contains a Tris-boric acid buffer (pH 8.2) with 1.5% (m/v) SDS and 0.05% (m/v) dithioerythreitol [3]. Solvent B is a borate-chloric acid buffer (pH 9.0) with 2.0% (m/v) SDS and 1.0% (m/v) mercapto-ethanol [2]. Both solvents showed a linear relationship between the quantities of CFMP in ADM and the dissolved CFMP. The linear relationships were found between quantities of 10.0 and 30.0 mg (solution A) and of 5.0 and 30.0 mg ADM (solution B) per ml solvent. The solubility of CFMP was better in solvent B than in solution A. Completely dissolved CFMP from ADM was only obtained in the case of 5.0 mg ADM in 1.0 ml solution B. These conditions will be used in liquid chromatography experiments, the results of which will be reported later.
Supported by a grant from the Hoofdinspectie Levensmiddelen of the Ministry of Welzijn, Volksgezondheid en Cultuur 相似文献
Quantitative Aspekte zweier Verfahren für das Auflösen kollagenfreier Muskelproteine aus acetontrockenen Pulvern der Gelderschen Rauchwurst
Zusammenfassung Der Zweck dieser Untersuchungen ist, die experimentellen Bedingungen für die vollstän-dige Löslichkeit des kollagenfreien Muskelproteins (CFMP) aus dem Acetonpulver der Gelderschen Rauchwurst zu finden. Durch Vorversuche wurde die beste Arbeitsweise für das Zubereiten des Acetonpulvers gewählt. Zwei verschiedene Extraktionsverfahren mit zerkleinertem Wurstmaterial wurden miteinander verglichen. Die Methode mit der Acetontrockenmasse (ADM) mittels kontinuierlicher Extraktion [2] führte zu besseren Ergebnissen als die Methode mit Acetonpulver (ACP), wozu ein Mischgerät [1] verwendet wurde. Die ADM-Methode wurde für weitere Untersuchungen angewendet. ADM wurde mit zwei verschiedenen Extraktionslösungen von Natrium-Dodecylsulfat (SDS) (A und B) extrahiert. Lösung A enthalt einen Tris-Borsäure Puffer (pH 8,2) mit SDS (1,5%) und Dithioerithritol (0,05%) [3]. Die Lösung B enthält einen Borat-Salzsäure Puffer (pH 9,0) mit SDS (2,0%) und Mercapto-Ethanol (1,0%) [2]. Beide Extraktionslösungen zeigen ein lineares Verhalten zwischen den Mengen vom CFMP in ADM und in aufgelöstem CFMP. Diese Linearität wurde von 10,030,0 mg ADM (Lösungsmittel A) und von 5,030,0 mg ADM (Lösungsmittel B) gefunden. Die Lös-lichkeit in Lösung B ist gegeniiber Lösung A besser. Ein vollständig gelöstes CFMP aus ADM wurde nur bei der Extraktion von 5,0 mg ADM in 1,0 ml der Losung B erhalten. Diese Bedingung soll in unseren künftigen flüssigchromatographischen Experimenten verwendet werden.
Supported by a grant from the Hoofdinspectie Levensmiddelen of the Ministry of Welzijn, Volksgezondheid en Cultuur 相似文献
6.
Zhou D Lagoja IM Rozenski J Busson R Van Aerschot A Herdewijn P 《Chembiochem : a European journal of chemical biology》2005,6(12):2298-2304
Oligonucleotides that contain up to three aminopropyl nucleoside analogues have been synthesized. Dimers of aminopropyl adenine and thymidine were prepared and used as building blocks by applying phosphoramidite chemistry. Both R and S isomers of the aminopropyl nucleosides were used. This incorporation led to a reduction of thermal stability of double-stranded DNA. Furthermore, the (R)-adenine analogue, which yielded (S)-APNA, can be considered as a candidate for universal base pairing. 相似文献
7.
Vinh Phu Nguyen Oriol Lloberas-Valls Martijn Stroeven Lambertus Johannes Sluys 《Computer Methods in Applied Mechanics and Engineering》2011,200(9-12):1220-1236
The existence of a representative volume element (RVE) for a class of quasi-brittle materials having a random heterogeneous microstructure in tensile, shear and mixed mode loading is demonstrated by deriving traction–separation relations, which are objective with respect to RVE size. A computational homogenization based multiscale crack modelling framework, implemented in an FE2 setting, for quasi-brittle solids with complex random microstructure is presented. The objectivity of the macroscopic response to the micro-sample size is shown by numerical simulations. Therefore, a homogenization scheme, which is objective with respect to macroscopic discretization and microscopic sample size, is devised. Numerical examples including a comparison with direct numerical simulation are given to demonstrate the performance of the proposed method. 相似文献
8.
9.
Liu D Cao Y Kim KH Stanek S Doungratanaex-Chai B Lin K Tavanapong W Wong J Oh J de Groen PC 《Computer methods and programs in biomedicine》2007,88(2):152-163
Colonoscopy is an endoscopic technique that allows physicians to inspect the inside of the human colon. During a colonoscopic procedure, a tiny video camera at the tip of the endoscope generates a video signal of the internal mucosa of the colon. In current practice, the entire colonoscopic procedure is not routinely captured. Software tools providing easy access to important contents of videos that are digitally captured during colonoscopy are not available. Hence, it is very time consuming to review an entire video, locate important contents, annotate them, and extract the annotated contents for research, teaching, and training purposes. Arthemis, a software application, was developed to facilitate this process. For convenient data sharing, Arthemis allows annotation according to the European Gastrointestinal Society for Endoscopy (ESGE) Minimal Standard Terminology (MST), an internationally accepted standard for digestive endoscopy. Arthemis is part of our integrated capturing and content analysis system for colonoscopy called Endoscopic Multimedia Information System (EMIS). This paper presents Arthemis as a component of EMIS, the design and implementation of Arthemis, and key lessons learned from the development process. 相似文献
10.
Lixin Ma Changmei Cheng Xiaohong Liu Yufen Zhao Anlin Wang Piet Herdewijn 《Chemometrics and Intelligent Laboratory Systems》2004,70(2):123-128
A back propagation (BP) neural network (NN) method has been developed to predict the stability of RNA/DNA duplex. Calculated Tm of hybrid formation with the present parameters fits the experimental values within reasonable errors (AD=1.2887 K, SEP=1.782, R2=0.9673 for NN1; AD=2.1388 K, SEP=3.506, R2=0.8889 for NN2). And it has the advantage that the determinations of thermodynamic parameters (TP) are not needed. 相似文献