Resilient modulus–moisture content relationships for pavement engineering applications

In recent years, there has been an increased interest in determining the influence of moisture changes on the resilient modulus (M_R) of subgrade soils beneath pavement structures. Efforts have also been made to develop mathematical models that predict the change in M_R values with moisture. These models are expected to account for seasonal variations in subgrade moisture content. This study evaluates the variation of resilient modulus with post-compaction moisture content of soils in the State of Oklahoma and the State of Pennsylvania. A series of specimens was compacted at optimum moisture content and then tested for resilient modulus; other series of specimens were prepared at optimum moisture content and then either wetted or dried prior to M_R testing. Employed wetting and drying procedures are time-efficient in developing the M_R–moisture relationships. Results showed that M_R–moisture content relationships varied with soil types and M_R values varied inversely with changes of moisture content. In addition, an M_R–moisture model predicting the variation of resilient modulus with moisture contents is proposed. This model can be used to predict changes in the bearing capacity of pavements due to seasonal variations of moisture content.     

Evaluation of position tracking technologies for user localization in indoor construction environments

Evolving technologies such as location-aware computing offer significant potential of improving important decision-making tasks on construction sites by providing support for tedious and time-consuming tasks associated with timely and accurate access to project information. For example, rapid and convenient access to contextual project information, through continuous position tracking of engineers, managers, and inspectors, can lead to significant cost and time savings due to the accuracy and immediacy with which relevant project information can be made available to field personnel. Considering the spatial expanse and dynamic nature of typical construction projects, mobile users need to be constantly tracked both outdoors as well as indoors. The Global Positioning System (GPS) is an attractive option for outdoor environments, but is not suitable for indoor applications because it needs a clear line-of-sight to orbital satellites in order to track position. As a result, alternate means of tracking users' location in indoor environments without relying on GPS is needed. This paper presents research that investigated the effectiveness of three wireless technologies for dynamic indoor user position tracking. In particular, Wireless Local Area Networks (WLAN), Ultra-Wide Band (UWB), and Indoor GPS positioning systems are evaluated and compared. Experimental results demonstrate the ability of Indoor GPS, in particular, to estimate a mobile user's location with relatively low uncertainty (1 to 2 cm).     

Which security policies are enforceable by runtime monitors? A survey

Runtime monitoring is a widely used approach to ensure code safety. Several implementations of formal monitors have been proposed in the literature, and these differ with respect to the set of security policies that they are capable of enforcing. In this survey, we examine the evolution of knowledge regarding the issue of precisely which security policies monitors are capable of enforcing. We identify three stages in this evolution. In the first stage, we discuss initial limits on the set of enforceable properties and various ways in which this set can be extended. The second stage presents studies that identify constraints to the enforcement power of monitors. In the third stage, we present a final series of studies that suggest various alternative definitions of enforcement, which specify both the set of properties the monitors can enforce as well as the manner by which this enforcement is provided.     

Efficient finite element formulation for geothermal heating systems. Part I: steady state

This paper presents the development of a computationally efficient finite element tool for the analysis of 3D steady state heat flow in geothermal heating systems. Emphasis is placed on the development of finite elements for vertical borehole heat exchangers and the surrounding soil layers. Three factors have contributed to the computational efficiency: the proposed mathematical model for the heat exchanger, the discretization of the spatial domain using the Petrov–Galerkin method and the sequential numerical algorithm for solving the resulting system of non‐linear equations. These have contributed in reducing significantly the required number of finite elements necessary for describing the involved systems. Details of the mathematical derivations and some numerical examples are presented. Copyright © 2005 John Wiley & Sons, Ltd.     

A computational model for fracturing porous media

This paper presents a new computational model for simulating a fracturing process in a porous medium using the finite element method. Two independent numerical techniques are used for describing this process. The partition of unity method is used for describing the fracturing process, and the double porosity model is used for describing the resulting fluid flow. A key feature of the model is the coupling of these two independent numerical techniques, which provide the means for a better simulation of the involved physical and mechanical processes. The paper focuses on the numerical formulation of the model. The capability of the model is illustrated by means of numerical examples, which examine the behaviour of a 1D porous medium under different boundary conditions. The numerical results show that the very complicated physical and mechanical processes of the fracturing porous media can be simulated properly and efficiently. Copyright © 2006 John Wiley & Sons, Ltd.     

Epoxy–lignin polyblends. III. Thermal properties and infrared analysis

Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and IR analysis were performed on a nonviscous epoxy polymer system (EP) with Kraft lignin (L) up to 20%. Mixtures of EP with similar amounts of silica (S) as in EP–L polyblends were used as a reference system for the analyses performed. EP–L polyblends cured at room temperature exhibit a single T_g, a fact characteristic for the monophasic systems. One-step tensile storage modulus vs. temperature curves, and related one-peak tensile loss modulus vs. temperature curves were found for all the EP–L polyblends. At about 30°C the tensile storage modulus of EP does not change in the presence of lignin in amounts up to 20% by weight. All these showed that L is miscible with EP and it does not affect the crosslinking at room temperature. IR spectra led to similar conclusions. The gradual decrease of the peak values of tan δ with the amount of L in polyblends is due to an increase in the tensile storage modulus and a decrease of the tensile loss modulus at temperatures close to T_g. This fact is explained by a stronger bond between EP and L, which could be formed at higher temperatures. The DSC and DMA data are in agreement with the mechanical properties of EP–L polyblends, which were reported previously.     

Effects of endotoxin on lung pericytes in vitro

Lipopolysaccharide released during bacterial sepsis causes acute lung injury and ARDS. Pulmonary microvascular injury is a feature of ARDS, and vascular remodeling develops, leading to pulmonary hypertension. Pericytes in the lung circulation proliferate and contribute to the remodeling seen in experimental sepsis. It is unknown whether endotoxin can directly stimulate pericyte growth or induce contraction. We show that lipopolysaccharide from Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae increases rat lung pericyte proliferation in vitro by up to 72% on day 7 of exposure (P < 0.001), with E. coli being most potent. Lipid A is the active portion of the lipopolysaccharide, with equal activity at one-tenth the dose of lipopolysaccharide. Endotoxin's mitogenic effect requires the presence of serum, consistent with the requirement for a soluble CD14 receptor in the serum. Using FACS analysis, the pericytes lack surface CD14 receptors. Lipopolysaccharide exposure rapidly increases intracellular calcium and induces contraction of pericytes plated onto silicone membranes. Thus, endotoxin is a direct mitogen for lung pericytes in vitro and also induces pericyte contraction. Endotoxin, present in lung tissue early during sepsis, might directly contribute to the vascular remodeling in sepsis-induced lung injury.     

Resection of a chest chondrosarcoma invading the spine and the aorta

A 34-year-old man presented with a large chondrosarcoma of the chest invading six ribs and the vertebral bodies of five adjacent thoracic vertebrae. En bloc resection of the tumor with six ribs, the anterior part of five vertebral bodies, and the thoracic aorta was performed through a thoracotomy and a paravertebral incision.     

Evaluation of patient dose for mammography in Pernambuco, Brazil

The aim of this study is to evaluate the incident air kerma (INAK) and the mean glandular dose (MGD) during mammography in Recife, North-east Brazil. The study was performed in three institutions: a private clinic (A), a public hospital (B) and a private hospital (C). The incident air kerma to mammography procedures were estimated using a standard breast phantom and the patient MGD, evaluated in the units B and C, was performed using the calibration of output method. This method involves the recording of the patient exposure parameters (kVp, mAs, filter) and the measurement of these parameters of the incident air kerma using a calibrated ionisation chamber. The results obtained showed that INAK for the standard breast phantom, in the institutions A, B and C, were 18.2, 9.4 and 8.5 mGy, respectively. The results of patient MGD values ranged from 0.23 to 7.46 mGy per film, and the MGD values per woman were between 8.23 and 40.6 mGy for the C institution and between 1.50 and 18.78 mGy for the B institution.