Deconstructing the semantics of big-step modelling languages

With the popularity of model-driven methodologies and the abundance of modelling languages, a major question for a requirements engineer is: which language is suitable for modelling a system under study? We address this question from a semantic point-of-view for big-step modelling languages (BSMLs). BSMLs are a class of popular behavioural modelling languages in which a model can respond to an input by executing multiple transitions, possibly concurrently. We deconstruct the operational semantics of a large class of BSMLs into eight high-level, mostly orthogonal semantic aspects and their common semantic options. We analyse the characteristics of each semantic option. We use feature diagrams to present the design space of BSML semantics that arises from our deconstruction, as well as to taxonomize the syntactic features of BSMLs that exhibit semantic variations. We enumerate the dependencies between syntactic and semantic features. We also discuss the effects of certain combinations of semantic options when used together in a BSML semantics. Our goal is to empower a requirements engineer to compare and choose an appropriate BSML from the plethora of existing BSMLs, or to articulate the semantic features of a new desired BSML when such a BSML does not exist.     

Novel Voltage-Mode All-Pass Filter Based on Using DVCCs

In this paper, a novel design for realizing a voltage-mode (VM) all-pass filter utilizing two differential voltage current conveyors (DVCCs) is proposed. Also, the suggested filter uses a canonical number of passive elements (one grounded capacitor and one resistor) without requiring any element matching condition. The proposed filter has high input and low output impedances, which make it suitable for cascading. The effects of the nonidealities of the DVCCs on the proposed design are investigated. As an application, a quadrature oscillator is designed using the proposed VM all-pass filter and an integrator. The proposed filter and oscillator circuits are simulated using the SPICE simulation program to confirm the theory.     

Thickness effects on the fatigue strength of welded steel cruciforms

Over 100 fatigue tests were conducted on high strength welded steel (HSLA-80) cruciforms of different thickness. Tests were conducted under both constant and random amplitude axial loads to characterize thickness effects on fatigue strength. Specimens were similar in size, except for the thickness which was varied between four nominal values. Examination of both experimental and analytical results (obtained using linear cumulative damage and Rayleigh approximation) indicates thicker specimens exhibit lower fatigue lives under both constant and random amplitude loadings. These results, when compared with the commonly used ‘fourth root rule' thickness correction formula, indicate the latter to be generally conservative, particularly at low stress levels.     

Refractive lens exchange for presbyopia

True presbyopia correction still remains one of the main challenges amongst eye professionals. Many corrective techniques exist including bifocal spectacle correction, monovision techniques both with corrective lenses and surgery, multifocal corneal excimer laser and refractive lens exchange with either accommodating or multifocal lenses. Refractive lens exchange was first described more than 10 years ago and has become more accepted in recent years with advancements in lens technology and improvements in surgical techniques. This article reviews developments in this field and current available lens options in the treatment of presbyopia.     

MMPP models for multimedia traffic

The paper presents a study on the use of Markov‐Modulated Poisson Processes (MMPP's) for characterizing multimedia traffic with short‐term and long‐term correlation. The applicability of the 2‐state MMPP and a refined moment‐based parameter‐matching technique to model an arbitrary ATM traffic stream in evaluating its queueing performance are examined by simulation. Following a discussion on the limitation of the 2‐state MMPP model, a model using a superposition of N homogeneous 2‐state MMPP to characterize bursty multimedia traffic is presented. The proposed model requires only five parameters which can be estimated from the samples of the traffic counting process by using a pdf‐based matching technique. The introduced pdf‐based parameter‐matching procedure uses the probability density function of the arrival rate and the IDC curve of the traffic samples. An approximation for the probability of loss in MMPP/D/1 queues is also obtained. The versatility and accuracy of the proposed model to characterize bursty multimedia traffic are shown by several case studies and test results. This revised version was published online in June 2006 with corrections to the Cover Date.     

Novel thermally stable poly(ether imide ester)s from 2,6‐bis (4‐aminophenoxy) pyridine

2,6‐Bis (4‐aminophenoxy) pyridine was prepared via reaction of 4‐aminophenol with 2,6‐dichloropyridine in the presence of potassium carbonate in N‐methyl‐2‐pyrrolidone (NMP). This pyridine‐based ether diamine was reacted with two moles of trimellitic anhydride to synthesize related diimide‐diacid (DIDA). A high temperature solution polycondensation reaction of DIDA with different diols in the presence of triethylamine hydrochloride in dichlorobenzene resulted in different poly(ether imide ester)s. The monomer and polymers were fully characterized, and the physical and thermal properties of the polymers were studied. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 570–576, 2005     

A survey of decorative materials on the energy consumption of mid-rise residential buildings in Mashad, Iran

Polyvinylchloride (PVC) panel is one of the most favorite decorative materials that has been popularly applied as finishing of ceiling in residential buildings. It is about five years that the people incline to redecorate the ceiling of old buildings with PVC panel in big cities of Iran, such as Mashad. In this study, the influence of ceiling PVC panel on the cooling and heating loads of studied apartment were determined by software DeST-h. In addition, the summer natural ventilation of the mentioned apartment is investigated by determining the wind speed into the apartment through the computational fluid dynamics (CFD) software. The evaluation of environment indoor wind velocity showed that most of the apartment space is a comfortable zone. The results of studied building analyses demonstrated that using PVC panel on the ceiling can decline the energy consumption of the penthouse (fifth level) of the investigated building, which is about 3.7% and 7% for studied methods of without and with air layer, respectively. In addition, although the existence of air layer can decline the cooling and heating loads, the increase in air layer thickness did not show significant decrease on building energy consumption. However, the PVC panel is expensive and is not suitable to be used for ceiling thermal insulation, but adding a thin layer of air between ceiling and PVC panel can be a good step toward sustainable building, when the people are inclined to utilize it as a decorative ceiling.     

Relevance of peat-draining rivers for the riverine input of dissolved iron into the ocean

Peat bogs have the ability to produce strong chelate ligands (humic and fulvic acids) which enhance the weathering rates of iron-silicate minerals and greatly increase the solubility of the essential trace metal iron in river water. Fluvial networks link peat bogs with the ocean, and thus terrestrial-derived fulvic-iron complexes fuel the ocean's biological productivity and biological carbon pump, but understanding this role is constrained by inconsistent observations regarding the behaviour of riverine iron in the estuarine mixing zone, where precipitation reactions remove iron from the water column. We applied a characterization of the colloidal iron carriers in peatland-draining rivers in North Scotland, using field-flow fractionation (FFF), in combination with end-member mixing experiments of river water sampled near the river mouth and coastal seawater using a ⁵⁹Fe radiotracer method. According to our results, the investigated river contributed “truly dissolved” Fe concentrations of about 3300 nmol L^− 1 to the ocean which is nearly two orders of magnitude higher than the dissolved iron contribution of the “average world” river (∼ 40 nmol L^− 1). Thus we conclude that peatland-draining rivers are important sources of dissolved iron to the ocean margins. We propose highly electrostatic and sterical stabilized iron-organic matter complexes in the size range of < 2 kDa to be responsible for iron transport across the estuarine mixing zone.     

Modified chitosan as a polymeric nanoreactor for fabrication of pure ZnO nano particles

ZnO nanoparticles have been prepared successfully by hydrogel decomposition method (HDM). Synthesized ZnO nanoparticles were characterized by X‐ray diffraction (XRD), fourier transforms infrared spectroscopy (FTIR), and transition electron microscopy (TEM) techniques. Narrow distribution of sizes with a 20–30 nm diameter and regular distribution of ZnO nanoparticles are attributed to the application of poly(acrylic acid‐co‐acrylamide) grafted chitosan hydrogel as coating agent. The results show that the polymer thermal decomposition technique is a perfect method for the synthesis of ZnO nanoparticles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010