Effect of Safety and Environmental Variables on Task Durations in Steel Erection

In spite of the efforts by government agencies, labor organizations, and researchers in the field of health and safety, injuries and fatalities continue to affect the construction industry. In 2002 the construction industry had the undesirable distinction of having two of the most dangerous occupations in the United States, with fatalities among structural steel workers at 58.2 per 100,000 workers (fourth highest rate) and among construction laborers at 27.7 per 100,000 workers (ninth highest rate). Costs associated with construction accidents, such as increased insurance premiums and medical expenses, and loss of productivity are also concerns in the industry. It has not been demonstrated how unsafe working conditions affect worker performance, and the impact of unsafe work practices on worker performance has not been quantified. This paper describes a methodology that included direct observation of steel erection activities and statistical analysis of task duration data. The data collected at steel erection sites included safety conditions such as the use of personal protective equipment (PPE), elevation of the work area, environmental conditions such as temperature and humidity, and worker performance in the form of task durations. Analysis of variance (ANOVA) analysis of 186 of steel erection task durations collected over a six-month period showed that the use of personal protective equipment (PPE), the time of day during which the operation was being performed, the elevation at which the work was being performed, and the presence of decking below the work area had statistically significant effects on the durations of steel erection tasks.     

Dynamic Simulation of Multi-Body Systems on Internet Using CORBA,Java and XML

In this paper a prototype of a computer program for multi-bodysimulation based on the use of CORBA, Java and XML is presented. Thisprototype makes use of a recursive dynamic formalism which outperformsmany implementations based on global formulations. The prototypepresented has been implemented using distributed Object OrientedProgramming techniques. The definition of the multi-body system is donethrough a data file defined using XML (eXtendible Markup Language). Thisprototype implements a `simulation service' on a network of computers,following a client-server scheme. This `simulation service' can operatein two different ways: offering a remote simulation on the server, orproviding a Java compiled code for local simulation on the client. Thepaper describes the practical implementation of such a service. The useof recursive functions and OOP permits the implementation of ageneral-purpose simulation code, which is compact, clear, clean,re-usable and easy to maintain. Once this Java code is compiled, it isstored in less than 125 Kbytes (including the numerical integrators).The Java programming language is used in order to assure compatibilitybetween different platforms. Finally, practical examples which make useof this approach are shown.     

Statistical Pattern Modeling in Vision-Based Quality Control Systems

Machine vision technology improves productivity and quality management and provides a competitive advantage to industries that employ this technology. In this article, visual inspection and quality control theory are combined to develop a robust inspection system with manufacturing applications. The inspection process might be defined as the one used to determine if a given product fulfills a priori specifications, which are the quality standard. In the case of visual inspection, these specifications include the absence of defects, such as lack (or excess) of material, homogeneous visual aspect, required color, predetermined texture, etc. The characterization of the visual aspect of metallic surfaces is studied using quality control chars, which are a graphical technique used to compare on-line capabilities of a product with respect to these specifications. Original algorithms are proposed for implementation in automated visual inspection applications with on-line execution requirements. The proposed artificial vision method is a hybrid between the two usual methods of pattern comparison and theoretical decision. It incorporates quality control theory to statistically model the pattern for defect-free products. Specifically, individual control charts with 6-sigma limits are set so the inspection error is minimized. Experimental studies with metallic surfaces help demonstrate the efficacy and robustness of the proposed methodology.     

Boosting Search with Variable Elimination in Constraint Optimization and Constraint Satisfaction Problems

There are two main solving schemas for constraint satisfaction and optimization problems: i) search, whose basic step is branching over the values of a variables, and ii) dynamic programming, whose basic step is variable elimination. Variable elimination is time and space exponential in a graph parameter called induced width, which renders the approach infeasible for many problem classes. However, by restricting variable elimination so that only low arity constraints are processed and recorded, it can be effectively combined with search, because the elimination of variables may reduce drastically the search tree size.In this paper we introduce BE-BB(k), a hybrid general algorithm that combines search and variable elimination. The parameter k controls the tradeoff between the two strategies. The algorithm is space exponential in k. Regarding time, we show that its complexity is bounded by k and a structural parameter from the constraint graph. We provide experimental evidence that the hybrid algorithm can outperform state-of-the-art algorithms in constraint satisfaction, Max-CSP and Weighted CSP. Especially in optimization tasks, the advantage of our approach over plain search can be overwhelming.     

Nonlinear analysis for seismic upgrade studies of existing essential facilities

The need to perform cost-effective seismic upgrades of essential facilities has made the use of nonlinear finite-element techniques an attractive option. These techniques allow for the analysis of full buildings with large, nonlinear deformations. For reinforced concrete structures, this includes concrete crushing and cracking, and steel reinforcement yielding. These nonlinear models can predict the response of buildings subjected to strong motion earthquakes with a greater degree of accuracy than simple linear or ‘quasi’ nonlinear models.     

Measurement of three independent components in impedance sensors using a single square wave

Two-wire impedance-based sensors involving electrolytes add the impedance of the electrodes to the electrical impedance of the medium to measure. An equivalent circuit for the measured impedance is a resistance in series with the parallel combination of another resistance and a capacitance. If the two electrodes are modelled by equal impedances, the equivalent circuit for the complete set up consists of three impedance components, which can be determined from three independent measurements. This paper describes a novel method to obtain those three components using a single square wave voltage (period 2T) instead of several sine waves and provides the equations to calculate their value from the three current intensity amplitudes measured at T/8, 3T/8 and 5T/8. Other measurement times would need different equations, but the same procedure applies. Anyway, the proposed method keeps the advantages of synchronous detection and relies on analytical solutions instead of the customary curve fitting procedures. Computer simulation and experimental results obtained by measuring the conductivity of known electrolyte samples validate the proposed method.     

A Color Vision-Based Lane Tracking System for Autonomous Driving on Unmarked Roads

This work describes a color Vision-based System intended to perform stable autonomous driving on unmarked roads. Accordingly, this implies the development of an accurate road surface detection system that ensures vehicle stability. Although this topic has already been documented in the technical literature by different research groups, the vast majority of the already existing Intelligent Transportation Systems are devoted to assisted driving of vehicles on marked extra urban roads and highways. The complete system was tested on the BABIECA prototype vehicle, which was autonomously driven for hundred of kilometers accomplishing different navigation missions on a private circuit that emulates an urban quarter. During the tests, the navigation system demonstrated its robustness with regard to shadows, road texture, and weather and changing illumination conditions.     

Packet Video Broadcasting with General-Purpose Operating Systems in an Ethernet

Video transmission with general-purpose PCs poses a number of requirements that radically differ from those of high-end dedicated video servers. We analyze the scenario of an Ethernet local area network in which a number of PCs are transmitting video streams, while other TCP/IP applications are also running concurrently. Our findings show that since the operating system clock resolution cannot cope with the transmission timing requirements the following holds: if the video transmission is performed with exact timing accuracy to maintain a constant rate then CPU load grows to 100%, thus blocking the PC for other user applications; on the other hand, if transmission is performed in a bursty manner, i.e. with sleep system calls, then CPU load decreases dramatically but the increased burstiness of the video stream has a negative impact on network performance (for example, capture effect in the Ethernet). Furthermore, the impact of video transmission over the rest of TCP/IP applications running on the same network depends heavily on the packet size. We provide an integrated analysis of operating system and network parameters to achieve video broadcasting while preserving timing requirements and minimizing the impact on other applications.     

Immunohistochemistry of neuronal nitric oxide synthase and protein nitration in the striatum of the aged rat

To ascertain the possible implications of the nitric oxide (NO*) producing system in striatal senescence, and by using immunohistochemistry and image-processing approaches, we describe the presence of the enzyme nitric oxide synthase (NOS), the NADPH-diaphorase (NADPH-d) histochemical marker, and nitrotyrosine-derived complexes (N-Tyr) in the striatum of adult and aged rats. The results showed neuronal NOS immunoreactive (nNOS-IR) aspiny medium-sized neurons and nervous fibres in both age groups, with no variation in the percentage of immunoreactive area but a significant decrease in the intensity and in the number of somata with age, which were not related to the observed increase with age of the striatal bundles of the white matter. In addition, NADPH-d activity was detected in neurons with morphology similar to that of the nNOS-IR cells; a decrease in the percentage of area per field and in the number of cells, but an increase in the intensity of staining for the NADPH-d histochemical marker, were detected with age. The number of neuronal NADPH-d somata was higher than for the nNOS-IR ones in both age groups. Moreover, N-Tyr-IR complexes were observed in cells (neurons and glia) and fibres, with a significant increase in the percentage of the area of immunoreaction, related to the increase of white matter, but a decrease in intensity for the aged group. On the other hand, we did not detect the inducible isoform (iNOS) either in adult or in aged rats. Taken together, these results support the contention that NADPH-d staining is not such an unambiguous marker for nNOS, and that increased protein nitration may participate in striatal aging.