A test lab for the performance analysis of TCP over ethernet LAN on windows operating system

A test laboratory for the performance analysis of the Transmission Control Protocol (TCP) and the teaching of its basic concepts is proposed. The laboratory environment is a small Ethernet local area network (LAN) with PCs running different versions of the Windows operating system (95/98/NT/2000). To support the Internet Protocol Version 6 (IPv6) for Windows and to improve flexibility, the Netperf TCP software tool has been modified. Based on the modified Netperf and a protocol analyzer, students perform traffic measurements on a real network. Various aspects of the Microsoft TCP implementation for Windows are discovered and clearly explained. The IPv6 for Windows 2000 is also examined, and comparisons with IPv4 are made.     

The discontinuity problem of a cylindrical dielectric post in a waveguide and its application on the dielectric constant measurements of liquids

Contents An exact solution of the discontinuity problem of a circular cylindrical dielectric post centered in a rectangular waveguide is presented. The waveguide is divided in three regions where the field is expressed in cylindrical waves or in waveguide modes. By point matching, a system of linear equations determining the reflection and transmission coefficients is found. — The structure of our interest includes a liquid column surrounded by a cylindrical glass tube. For this case, curves have been made showing the relationship between the coefficients of reflection and transmission and the permittivity of the rod. Such curves are used for measuring the dielectric properties of liquids.

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Das Problem der Diskontinuität einer zylindrischen dielektrischen Probe in einem Wellenleiter und seine Anwendung auf Messungen der dielektrischen Konstanten von Flüssigkeiten

Übersicht Für das Problem einer durch einen dielektrischen Stab in einem rechteckigen Wellenleiter verursachten Diskontinuität wird eine exakte Feldlösung angegeben. Der Wellenleiter wird dabei in drei Bereiche eingeteilt, in denen das Feld in Form von Zylinderwellen oder Wellenleitermoden ausgedrückt wird. — Durch punktförmige Anpassung wird ein System linearer Gleichungen gefunden, aus dem sich Reflexions- und Transmissionskoeffizienten bestimmen lassen. — Als Anwendungsbeispiel wird eine Flüssigkeitssäule in einem zylindrischen Glasrohr untersucht. Für diesen Fall werden Diagramme angegeben, aus denen die Beziehungen zwischen den Transmissions- und Reflexionsfaktoren zu den dielektrischen Konstanten der Probe entnommen werden können. — Solche Kurven werden zur Messung der dielektrischen Eigenschaften von Flüssigkeiten benutzt.

     

Parametric analysis of the heat evolution during hydration of a cementitious plug in a borehole

Parametric analysis by the computer program ATHENAN of the hydration of a cementitious plug in the borehole of a test rock, showed that the temperature rise within the plug is most sensitive to the size of the plug and moderately sensitive to the conductivities of the plug and the rock followed by less sensitive to the diffusivities of the plug and the rock and the heat transfer coefficient between the rock and the surrounding air. For a given heat of hydration of a mixture, a critical plug size exists given the environmental conditions.     

Batch grinding kinetics in the presence of two active zones

It is shown that the presence of two active zones in a grinding mill leads to apparent non-first-order breakage of the top feed size in batch grinding. The equations to describe the kinetics of the breakage of the top size and of the total size distribution are obtained, and an analytical solution is given. Parametric analysis shows the influences of the relative magnitudes of the two active zones, the rates of breakage and the rate of mass transfer between the two active zones on the mill product. The concepts may be applicable to any type of mill where two active zones can exist.     

The relation between rheological and mechanical properties of PA6 nano- and micro-composites

A series of nanocomposites was prepared with two different methods leading to different levels of exfoliation, and the dynamic properties were measured in the solid state and the melt. The results were compared with micro-composites containing various shapes of glass filler. The higher modulus of nanocomposites at higher concentrations is accompanied by an increase in melt viscosity and the occurrence of a yield stress in the melt. The modulus at room temperature and the melt viscosity are influenced by the aspect ratio and the concentration of the filler particles. These results were used to calculate the aspect ratios of the reinforcement using the Halpin-Tsai composite model and several modified Einstein viscosity models. The experiments showed that the Simha theory for oblate and prolate spheroids predicts platelet aspect ratios from melt viscosity data that are close to the results from the Halpin-Tsai composite model and from TEM observations. The results of the analysis show the advantages and disadvantages of the various shapes and sizes of fillers and the level of exfoliation, both from a processing and a mechanical properties point of view.     

Dielectric spectroscopy using dielectric probes: a new approach to study glass transition dynamics in immiscible apolar polymer blends

Dielectric relaxation spectroscopy using dielectric probes was applied to study the (glass transition) dynamics in binary blends of isotactic PP, PS and LDPE. The blends were prepared by melt-mixing and doped with 0.5% of the dielectric probe 4,4′-(N,N-dibutylamino)-(E)-nitrostilbene (DBANS) (van den Berg O, Sengers WGF, Jager WF, Picken SJ, Wübbenhorst M. Macromolecules 2004;37:2460. [17]). Due to the selective amplification of the dielectric relaxation processes related to the dynamic glass transition of the polymers, accurate relaxation data were obtained, even for the minor phases. No substantial influence of the blend composition and the blend morphology on the glass transition dynamics was found, indicating that both blend constituents behave like homogeneous bulk materials. The normalised relaxation strength of glass transition processes remained constant, regardless of the blend type and blend composition. This indicates that the probe molecule, DBANS, was equally distributed over the two blend components in all three polymer combinations PE-PP, PE-PS and PP-PS.     

Fiber composite thin shells subjected to thermal buckling loads

The results of parametric studies to assess the effects of various parameters on the buckling behavior of angle-ply, laminated thin shells in a hot environment are presented in this paper. These results were obtained by using a three-dimensional finite element analysis. An angle-ply, laminated thin shell with fiber orientation of [θ/ −θ]₂ was subjected to compressive mechanical loads. The laminated thin shell has a cylindrical geometry. The laminate contained T300 graphite fibers embedded in an intermediate-modulus, high-strength (IMHS) matrix. The fiber volume fraction was 55% and the moisture content was 2%. The residual stresses induced into the laminated structure during the curing were taken into account. Parametric studies were performed to examine the effect on the critical buckling load of the following parameters: cylinder length and thickness, internal hydrostatic pressure, different ply thicknesses, different temperature profiles through the thickness of the structure, and different layup configurations and fiber volume fractions. In conjunction with these parameters the ply orientation varied from 0° to 90°. Seven ply angles were examined: 0°, 15°, 30°, 45°, 60°, 75°, and 90°. The results show that the ply angle θ and the laminate thickness had significant effects on the critical buckling load. The fiber volume fraction and the internal hydrostatic pressure had important effects on the critical buckling load. The cylinder length had a moderate influence on the buckling load. The thin shell with [θ/−θ]₂ or [θ/−θ]^s angle-ply laminate had better buckling-load performance than the thin shell with [θ]₄ off-axis laminate. The temperature profiles through the laminate thickness and various laminates with the same thickness but with the different ply thickness had insignificant effects on the buckling behavior of the thin shells.     

Radio resource allocation algorithms for multi-service OFDMA networks: the uniform power loading scenario

Adaptive Radio Resource Allocation is essential for guaranteeing high bandwidth and power utilization as well as satisfying heterogeneous Quality-of-Service requests regarding next generation broadband multicarrier wireless access networks like LTE and Mobile WiMAX. A downlink OFDMA single-cell scenario is considered where heterogeneous Constant-Bit-Rate and Best-Effort QoS profiles coexist and the power is uniformly spread over the system bandwidth utilizing a Uniform Power Loading (UPL) scenario. We express this particular QoS provision scenario in mathematical terms, as a variation of the well-known generalized assignment problem answered in the combinatorial optimization field. Based on this concept, we propose two heuristic search algorithms for dynamically allocating subchannels to the competing QoS classes and users which are executed under polynomially-bounded cost. We also propose an Integer Linear Programming model for optimally solving and acquiring a performance upper bound for the same problem at reasonable yet high execution times. Through extensive simulation results we show that the proposed algorithms exhibit high close-to-optimal performance, thus comprising attractive candidates for implementation in modern OFDMA-based systems.     

Adaptive Power and Subchannel Allocation for Dual-Class OFDMA Packet Data Networks

Adaptive Radio Resource Allocation exploiting the inherent frequency selectivity of the wireless medium as well as the multi-user diversity effect is expected to play a crucial role in providing high QoS on emerging OFDMA-based wireless networks. Although a plethora of studies concerning exclusively constant bit rate (CBR) or variable bit rate/best effort (BE) traffic has been published to date, limited amount of work has been devoted to the more practical mixed CBR-BE data traffic scenario over OFDM radio access networks. In this paper we attempt to deal with the specific heterogeneous allocation problem, namely the maximization of elastic users’ sum-throughput while providing minimum data rate service to a subset of non-elastic users. The contribution of this work is twofold. First, due to the high complexity of the resource allocation problem, we propose a relaxation method based on the prioritization of CBR- over BE-class users during the subchannel allocation procedure. We devise a method for obtaining the exact performance penalty induced by the specific hypothesis when compared to the optimal (unprioritized) decision. Secondly, we develop a polynomial complexity approximation algorithm for allocating power and bandwidth, that employs the CBR-prioritization idea. The scheme is shown to experience a relatively low performance penalty compared to its upper bound and to outperform two representative algorithms from the literature.     

Proton magnetic resonance spectroscopy in patients with glial tumors: a multicenter study

Budding yeast (Saccharomyces cerevisiae) Rap1p has been expressed in fission yeast (Schizosaccharomyces pombe) under the control of the regulatable fructose bisphosphatase (fbp) promoter. When the fbp promoter was derepressed, cells containing the complete RAP1 gene failed to show any significant growth, suggesting that Rap1p is toxic. A derivative of Rap1p that has a temperature-sensitive mutation in the DNA-binding domain was not toxic in cells grown at 37 degrees C, a temperature at which DNA binding by rap1p(ts) is severely inhibited. Removal of a short region downstream of the DNA-binding domain, including a region previously shown to be essential for Rap1p toxicity in budding yeast, also abolished the toxic effect. The toxic effect of Rap1p has therefore been conserved between two distantly related yeasts. In budding yeast, overexpression of Rap1p also caused changes to the lengths of the telomeric repeats. No effects on telomeres were detected in fission yeast.