A connection control strategy for bursty sources in broadband packet networks

This paper proposes an admission strategy for connection-oriented services at the access node of a broadband integrated packet network based on asynchronous transfer mode. Based on an estimate of the probability of cell loss and in the absence of buffering, we determine the number of sources from different classes of bursty traffic which can be accepted. The parameters which are used to describe the traffic sources are average bit rate and peak bit rate. We will evaluate the cell loss estimate for homogeneous and heterogeneous cases. Furthermore, we will examine the variation of this estimate as the average to peak ratio changes. The estimate is an upper bound for the probability of cell loss. Based on this upper bound simple and robust allocation of resources to bursty sources can be developed. The proposed strategy can be implemented using simple computations or via a look-up table to determine admission or denial of an incoming call and therefore allocating the required capacity. The procedure results in efficient use of the bandwidth, ensuring the desired service quality for connection-oriented services and results in proactive control of network congestion.     

Fault-Based Attack on Montgomery��s Ladder Algorithm

In this paper we present invalid-curve attacks that apply to the Montgomery ladder elliptic curve scalar multiplication (ECSM) algorithm. An elliptic curve over the binary field is defined using two parameters, a and b. We show that with a different “value” for curve parameter a, there exists a cryptographically weaker group in nine of the ten NIST-recommended elliptic curves over \mathbbF_2^m\mathbb{F}_{2^{m}}. Thereafter, we present two attacks that are based on the observation that parameter a is not utilized for the Montgomery ladder algorithms proposed by López and Dahab (CHES 1999: Cryptographic Hardware and Embedded Systems, LNCS, vol. 1717, pp. 316–327, Springer, Berlin, 1999). We also present the probability of success of such attacks for general and NIST-recommended elliptic curves. In addition we give some countermeasures to resist these attacks.     

Dynamic provisioning of LightPath services for radio astronomy applications

A demonstration at iGRID 2005 used dynamic, deterministic, and dedicated LightPath network services to link radio telescopes from around the world with computational facilities at the MIT Haystack Observatory to create a single coherent instrument for real-time astronomical and geodetic research. The “electronic Very Long Baseline Interferometry” (e-VLBI) application provides ultra-high resolution images of very faint and very distant objects in the universe. The application-specific network topology carried 2 Gbps of VLBI data from radio telescopes in Europe, North America, and Japan to Haystack for real-time correlation processing. This paper describes the application, the network technologies employed for the demonstration, the results, challenges and future work.     

Synthesis of Silicon Carbide from Rice Husk in a Packed Bed Arc Reactor

Silicon carbide in the form of powder was prepared from boiler burnt rice husk in a new type of packed bed arc reactor where the raw materials were processed in briquette form. X-ray diffraction analysis identified the presence of both β and α SiC. Microstructural characterization revealed the presence of triangular, truncated triangular, and hexagonal crystallites, along with platelets.     

Hollow Fiber Liquid Phase Microextraction Method Combined with High-Performance Liquid Chromatography for Simultaneous Separation and Determination of Ultra-Trace Amounts of Naproxen and Nabumetone in Cow Milk,Water, and Biological Samples

A simple and highly sensitive method based on hollow fiber liquid phase microextraction combined with high-performance liquid chromatography and fluorescence detection has been developed for simultaneous separation, preconcentration, and determination of naproxen and nabumetone from water, wastewater, milk, and biological samples. Parameters affecting the microextraction efficiency were evaluated and optimized. Under optimum conditions (extractant (14 μL of 1-undecanol), sample pH (3.0), extraction time (20 min), stirring rate (600 rpm), temperature (45 °C), potassium chloride concentration (4.0 %) and sample volume (9 mL)), the limits of detection based on (S/N?=?3) were 1.3 ng L^?1 for naproxen and 2.9 ng L^?1 for nabumetone. The intra- and inter-assay relative standard deviations for naproxen and nabumetone were in the ranges of 3.2–6.1 % and 6.5–9.5 %, respectively. The calibration curves were linear in concentration ranges of 4.0–300.0 ng L^?1 and 9.0–300.0 ng L^?1 for naproxen and nabumetone, respectively, with good coefficient of determination (r ²?>?0.999). The method was successfully applied to the determination of naproxen and nabumetone in cow milk, water, wastewater, human plasma, and urine samples.     

Development and dynamic modelling of a flexure-based Scott–Russell mechanism for nano-manipulation

This paper presents the design methodology and dynamic modelling of a piezo-driven flexure-based Scott–Russell mechanism for nano-manipulations. Based on finite element analysis, the Scott–Russell mechanism is monolithically constructed to provide high positioning accuracy and long-term repeatability. With consideration for the effect of the driving circuit, the dynamic model of the flexure-based Scott–Russell mechanism is established. The influence of the time constant RC on the dynamic response is investigated. The transient responses of the flexure-based Scott–Russell mechanism to three typical signals are derived based on the Laplace transform method. It is noted that the cycloidal command signal can generate vibration-free motion, and thus improve the dynamic performance of the flexure-based mechanism. Experimental tests have been carried out to verify the developed Scott–Russell mechanism and the established models.     

辣木种子汁与聚合氯化铝比较对水浊度的去除效率的影响

混凝处理和絮凝处理在水处理厂中是必要工艺。金属盐如硫酸铝和氯化铁在伊朗常用于混凝处理。聚合氯化铝（PAC）最近已经用于Baba-Sheykhali水处理厂。合成的混凝剂对于人体健康有害,并且对于发展中国家使用成本不经济。在本研究中比较了PAC与辣木种子汁作为混凝剂的功效。辣木生长在伊朗南部。为了实现本研究的目的,使用稀释的含有合成高岭土的水进行实验室试验。     

Making e-Government systems workable: Exploring the evolution of frames

As with other IT projects, implementing workable e-Government systems requires bringing together different stakeholders and bridging their perspectives during implementation. These perspectives often take the form of competing technology frames consisting of differentiated beliefs, interests, technology evaluation routines and artifact characteristics that need to be recognized and reconciled in order to make e-Government systems workable. Prior research, while recognizing the importance of frame evolution in making systems workable, has rarely described the underlying processes. This paper builds on a 10-year e-Government implementation to describe and analyze the processes of frame evolution—namely, frame differentiation, frame adaptation, and frame stabilization—that can help translate and reconcile competing frames into a truce frame. The examined properties of these specific processes are described and their dynamics are analyzed, thereby extending the e-Government implementation literature through a deeper understanding of frame evolution processes.     

A Decomposable Random Walk Model for Mobility in Wireless Communications

In this paper we develop models to represent the time until boundary crossing and associated statistics in cellular wireless networks. We propose modeling the terminal movements within a cell by a discrete two-dimensional random walk process. We note that in such an environment mobile units tend to move in roughly a straight line, with occasional backtracking, for a significant period of time before changing direction. We determine the time until crossing an exit point from a circular cell by choosing a random direction from the starting point to an exit point. The user would actually be moving in fluctuating directions until reaching this exit point. Subsequently, we calculate the expected time to reach the exit point as a function of the constant speed of travel and the propensity to change direction en route. The model is rather general and has the potential to be used for highly irregular cell shapes when boundary crossing is not distance-based but determined by propagation attenuation-based criterion.     

Finite element fatigue propagation of induced cracks by stiffeners in repaired panels with composite patches

Fatigue crack growth analyses of aluminum panels with stiffeners repaired by composite patches have been rarely investigated. Generally, cracks may occur around the rivets which are capable to propagate under cyclic loadings. A composite patch can be used to stop or retard the crack growth rate. In this investigation, finite element method is used for the crack propagation analyses of stiffened aluminum panels repaired with composite patches. In these analyses, the crack-front can propagate in 3-D general mixed-mode conditions. The incremental 3-D crack growth of the repaired panels is automatically handled by a developed ANSYS Parametric Design Language (APDL) code. Effects of rivets distances and their diameters on the crack growth life of repaired panels are investigated. Moreover, the obtained crack-front shapes at various crack growth steps, crack trajectories, and life of the unrepaired and repaired panels with various glass/epoxy patch lay-ups and various patch thicknesses are discussed.