Experimental investigation of leaky lamb modes by an optically induced grating

By removing the symmetry of a free plate configuration, fluid loading significantly modifies the nature of acoustic waves travelling along a plate, and it even gives existence to new acoustic modes. We present theoretical predictions for the existence, dispersive behavior, and spatial distribution of leaky Lamb waves in a fluid-loaded film. Although Lamb modes are often investigated by studying the radiated fluid waves resulting from their leakage, here their properties are assessed by detecting the wave displacements directly using laser beam deflection. By using crossed laser beam excitation, the detection and analysis of the different modes is done at a fixed wavelength, allowing one to verify the existence, the velocity, and the damping of each predicted mode in a simple and unambiguous way. Our theoretical predictions for the nature of the modes in a water-loaded Plexiglas film, including parts of looping modes, are experimentally confirmed.     

Partitioning of chemicals—important factors in exposure assessment of offshore discharges

The CHARM (chemical hazard assessment and risk management) model was developed to give operators, chemical suppliers, and environmental authorities a scientific framework for analyzing the environmental hazard and risk of offshore chemicals used and discharged to the marine environment. This paper presents results from an R and D project carried out on partitioning of typical offshore chemicals where the objective was to validate the partitioning algorithms in CHARM. The work included further development and verification of the HPLC (OECD 117) method for determining oil/water partitioning, or fraction released of production chemicals, for evaluation of the applicability of the Shake Flask method (OECD 107) and modification of the sediment/water partitioning test methods, as well as establishment of a calculation method for determining the weighted average log P_ow for chemical mixtures of homologs. The calculation method was recommended adopted in CHARM. Based on the experimental partitioning results, the CHARM partitioning algorithms were evaluated. The test results showed that the HPLC technique is a “robust” method for determining the P_ow, but has limitations for surfactants and chemicals with high log P_ow-values, which are typical offshore chemicals. The traditional correlations reported between P_ow, the BCF, the fraction of a chemical released with produced water, and the P_sw is not valid for typical surfactants. Another approach is therefore used in CHARM, which also was evaluated in this project. There is, however, a need for further validation of the CHARM partitioning algorithms.     

eScience in the Social Cloud

Social networks offer great potential for fostering collaboration between individuals and amongst groups. This potential collaborative environment is not only applicable for recreation, but can also provide considerable value to diverse research communities. For this reason scientists are increasingly utilizing social networking concepts in projects to form groups, share information, publicize their work and communicate with their peers. This article describes two different approaches to supporting eScience, by providing scientific computing and collaboration within what we term the Social Cloud. In our first approach the social network is used as a collaborative overlay, in combination with the ad hoc creation of infrastructure composed of virtual machine clusters built from resources contributed, by the users, to the Social Cloud. Our second approach is based around the principle of volunteer computing, where the Social Cloud provides researchers with a platform to exploit social networks by reaching out to non technical users who would otherwise be unlikely to donate computational time for scientific and other research. In this article we specifically explore the motivations of users to contribute computational time and examine the various ways these motivations can be catered to through the use of incentives in existing social networks.     

Fatigue during prolonged intermittent overhead work: reliability of measures and effects of working height

Shoulder pain is prevalent among industrial workers and existing evidence supports that overhead work is an important specific risk factor. Existing guidelines are limited, with overhead work typically recommended to be avoided, and research on overhead work has been mixed in terms of the effects of increasing arm reach. A laboratory-based simulation of overhead work was conducted, at three working heights, in order to facilitate improved guidelines and to identify potential non-linear effects of overhead work height. Several indicators of shoulder fatigue served as outcome measures and a preliminary study was performed to assess the reliability of several of these measures. Fatigue measures based on electromyography (EMG) generally had low reliability, whereas excellent reliability was exhibited for ratings of perceived discomfort (RPD). Consistent with this, no effects of overhead work height were found on EMG-based measures, yet clear non-linear effects were found on RPD and task performance. The source of the effects of work height appeared to be related to a combination of muscle activation levels and demands on precision/control at the highest location. These results support the utility of subjective measures for relatively low-level intermittent exertions and demonstrate increasingly detrimental fatigue and performance effects at extremes in reach during overhead work.     

A simple method for fitting sphere-like surfaces

In this paper we present a new and simple method for fitting a sphere-like surface to a set of data points in 3-space. In comparison to the standard method that involves using spherical harmonics, this method is conceptually simpler and computationally less complex and intensive, especially when used to address problems in which data is sparse or nonuniform.     

The Pavement Enterprise at Michigan Technological University

A project-based student Enterprise program was established at Michigan Technological University as part of an effort, funded by the National Science Foundation, related to reform of engineering education. The Enterprise program represents a separate degree track available in all departments of the College of Engineering. The Pavement Design, Construction, and Materials (Pavement) Enterprise was established in the Department of Civil and Environmental Engineering in conjunction with the Thompson Scholars program. The Thompson Scholars program is an asphalt-paving-industry-supported scholarship program. The Pavement Enterprise is composed of a team of students that work in a businesslike setting on projects related to the asphalt paving industry. In addition to their project activities, students are required to participate in paid summer internships in associated industries and organizations. An Advisory Board composed of industry and government leaders meets three times a year to provide advice, guidance, and feedback to the students and associated faculty. The team project activities of the Pavement Enterprise prepares graduates for careers in the pavement engineering field with knowledge and skills well beyond their peers in the traditional civil engineering curriculum. These team projects incorporate “active learning” techniques into the program. The performance of the Pavement Enterprise is demonstrated using student attrition as well as a peer review. Lessons learned in the operation of the program are presented for those institutions considering a similar program.     

Polymer field-theory simulations on graphics processing units

We report the first CUDA™ graphics-processing-unit (GPU) implementation of the polymer field-theoretic simulation framework for determining fully fluctuating expectation values of equilibrium properties for periodic and select aperiodic polymer systems. Our implementation is suitable both for self-consistent field theory (mean-field) solutions of the field equations, and for fully fluctuating simulations using the complex Langevin approach. Running on NVIDIA^®  Tesla T20 series GPUs, we find double-precision speedups of up to 30×$30\times$ compared to single-core serial calculations on a recent reference CPU, while single-precision calculations proceed up to 60×$60\times$ faster than those on the single CPU core. Due to intensive communications overhead, an MPI implementation running on 64 CPU cores remains two times slower than a single GPU.     

Least-Squares Support Vector Machines for the identification of Wiener–Hammerstein systems

This paper considers the identification of Wiener–Hammerstein systems using Least-Squares Support Vector Machines based models. The power of fully black-box NARX-type models is evaluated and compared with models incorporating information about the structure of the systems. For the NARX models it is shown how to extend the kernel-based estimator to large data sets. For the structured model the emphasis is on preserving the convexity of the estimation problem through a suitable relaxation of the original problem. To develop an empirical understanding of the implications of the different model design choices, all considered models are compared on an artificial system under a number of different experimental conditions. The obtained results are then validated on the Wiener–Hammerstein benchmark data set and the final models are presented. It is illustrated that black-box models are a suitable technique for the identification of Wiener–Hammerstein systems. The incorporation of structural information results in significant improvements in modeling performance.