Influence of washing and of heat-treatment conditions on the thermal stability of VPI-5

Thorough washing of a VPI-5 synthesized with n-dipropylamine as template improves greatly its thermal stability while no major change is observed in the template content. A detailed study of the influence of the pretreatment conditions shows that in order to obtain a high thermal stability (up to at least 960 °C) two parameters are of importance. The removal of both the template and the adsorbed water requires either a low heating rate at atmospheric pressure or a low pressure (less than 3 Torr) when the heating rate is 300 ° per hour.     

Supported Molybdenum Carbides Lie Between Metallic and Sulfided Catalysts for Deep HDS

Hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene on alumina-supported Mo₂C has been studied. These catalysts are stable and active under deep HDS conditions (0-250 wt ppm S). However, although they are well known to have hydrogenation properties, they lead preferentially to a non-hydrogenated product of the HDS reaction: dimethylbiphenyl. For the same reaction, supported platinum and sulfided molybdenum oxide lead to the hydrogenated products dimethyldicyclohexyl and methylcyclohexyltoluene, respectively. The ranking of HDS activity is as follows: MoS₂/Al₂O₃ < Mo₂C/Al₂O₃ < Pt/SiO₂.     

Comparing the revised NIOSH lifting equation to the psychophysical,biomechanical and physiological criteria used in its development

The purpose of this study was to perform a systematic and comprehensive comparison between the recommended weights of lift (RWL) from the revised NIOSH lifting equation, and the specific biomechanical, psychophysical and physiological criteria that were stated to be used in the equation's development. A composite acceptable load (CAL) table was developed for the 216 conditions presented in the female lifting table of Snook and Ciriello (1991). Each CAL value was calculated to correspond to the most conservative load of the three design criteria. The RWLs caused lumbar compression forces close to the biomechanical limit of 3400 N for lifts below knuckle height, but resulted in compression forces that are much lower at higher lifting heights. At moderate lifting frequencies, the average RWL would be acceptable to more than 95% of female workers according to the psychophysical criterion. At the highest frequencies, the RWL was found to be an average of 63% of the CAL values based on the integration of the psychophysical and physiological criteria. It is recommended that ergonomists acknowledge the very conservative nature of the revised NIOSH lifting equation when using it to evaluate occupational lifting tasks.     

A modified version of the three-compartment model to predict fatigue during submaximal tasks with complex force-time histories

The three-compartment model (3CM) was validated previously for prediction of endurance times by modifying its fatigue and recovery rates. However, endurance times do not typically represent work demands, and it is unknown if the current version of the 3CM is applicable for ergonomics analysis of all occupational tasks. The purpose of this study was to add biological fidelity to the 3CM, and validate the model against a series of submaximal force plateaus. The fatigue and recovery rates were modified to represent graded physiological motor unit characteristics (termed 3CM_GMU). In nine experiments of submaximal efforts, the 3CM_GMU produced a root-mean squared difference (RMSD) of 4.1 ± 0.5% MVC over experiments with an average strength loss (i.e. fatigue) of 31.0 ± 1.1% MVC. The 3CM_GMU model performed poorly for endurance tasks. The 3CM_GMU model is an improvement for evaluating submaximal force patterns consisting of intermittent muscle contractions of the hand and forearm.

Practitioner Summary: We modified an existing fatigue model using known physiological properties in order to predict fatigue during nine different submaximal force profiles; consistent with efforts seen in industrial work. We expect this model to be included in digital human modelling software, for the assessment of repetitive work and muscle fatigue in repetitive tasks.

Social Media Summary: The proposed model has applications for estimating task fatigue in proactive ergonomic analyses of complex force patterns using digital human models.     

Characterization of New Bimetallic Oxycarbide (MoWC0.5O0.6) for Bifunctional Isomerization of n-Heptane

A new bimetallic oxycarbide was synthesized and characterized by XRD, TEM, EDS, XPS and adsorption–desorption of probe molecules. All the molybdenum was reduced and 35% of tungsten was present as WO_x. The number of metallic sites, Lewis and Br?nsted acid sites were estimated. A turnover rate of 0.1 s⁻¹ was measured at 300 °C for the first order n-heptane isomerization.     

Vehicle routing and scheduling with dynamic travel times

The field of dynamic vehicle routing and scheduling is growing at a fast pace nowadays, due to many potential applications in courier services, emergency services, truckload and less-than-truckload trucking, and many others. In this paper, a dynamic vehicle routing and scheduling problem with time windows is described where both real-time customer requests and dynamic travel times are considered. Different reactive dispatching strategies are defined and compared through the setting of a single “tolerance” parameter. The results show that some tolerance to deviations with the current planned solution usually leads to better solutions.     

A variable neighborhood descent heuristic for arc routing problems with time-dependent service costs

This paper proposes a variable neighborhood descent heuristic for solving a capacitated arc routing problem with time-dependent service costs. The problem is motivated by winter gritting applications where the timing of each intervention is crucial. The variable neighborhood descent is based on neighborhood structures that manipulate arcs or sequences of arcs. Computational results are reported on problems derived from classical capacitated arc routing problem instances. A comparison is also provided with an alternative approach where the arc routing problem is solved after being transformed into an equivalent node routing problem.     

A psychophysical study to determine acceptable limits for repetitive hand impact severity during automotive trim installation

The purpose of the current study was to use a psychophysical methodology to establish acceptable impact severity levels for this automotive trim installation. Two studies were conducted. In the first study, 17 male and 12 female subjects (6 assembly line workers and 23 students) performed 5 hand impacts/min on a device that simulated the process of seating push pins during door trim panel installation. In both studies, subjects were asked to impact the simulation device as hard as they found acceptable without causing injury, numbness or pain. Subjects were trained for 11 h. Force and hand acceleration time-histories were recorded from the simulation device and a hand-mounted accelerometer, respectively. The magnitude of each impact was quantified with eight dependent measures: peak, time-to-peak, load rate and impulse, from both the force and acceleration transducers. Statistics were used to determine the effects of gender, skill level and impact location on acceptable impact severity. In the second study, 8 male and 8 female subjects performed repeated hand impacts on a wall-mounted force plate at three different frequencies (2, 5 and 8 impacts/min) over three separate sessions. Force measures and statistics were the same as in Study 1. In the first study, impact location did not appear to have a consistent effect on the acceptable impact severities and there was no significant differences observed between male and female values. For both force and acceleration, impulse was the most reliable variable followed by the peak. In the second study an increase in impact frequency was observed to result in a significant decrease in the acceptable levels of peak force and force impulse. This effect was largest when going from 2 to 5 impacts/min and was less pronounced when going from 5 to 8 impacts/min (especially for force impulse). Male subjects demonstrated significantly higher acceptable impulse levels. Based on the combined results from both studies, acceptable limits were recommended for peak force and impulse that would be acceptable to 75% of the population for a range of frequencies. These limits were observed to range from 181 (8/min) to 259 N (2/min) for peak force and 2.53 (8/min) to 3.52 N s (2/min) for force impulse. It was concluded that force impulse and peak force were the variables most likely being controlled by the subjects.

Relevance to industry

Automotive assembly includes a number of tasks that involve hand impacts within the manufacturing process. One such task is the door trim panel installation process where the base of the hand is used to impact the door trim panel and drive fastening push pins through holes in the metal door frames. The current study provides tolerance limits so that industrial tasks involving hand impacts can be evaluated for their injury risk.     

Report of an IEEE Task Force?An IEEE Opinion on Research Needs for Biomedical Engineerng Systems

MORE than 200 years ago, our forefathers made note of man's inalienable rights to life, liberty, and the pursuit of happiness. To the engineering community (applied science in the service of man), these may be coincident with applications to medicine and biology (biomedical engineering), defense, and entertainment. Biomedical engineering research has the distinction, among these three missions, of not only contributing to the quality of human life through the industrial economy but also to life itself?the most fundamental concern of all people. It is through biomedical engineering research that we have been able to learn much concerning the functioning of living systems, and it is through such knowledge that we have been able to develop improved clinical diagnosis, monitoring, and treatment, including life-sustaining devices and aids to the handicapped. Each step represents an improvement in the quality of life, and each step forms the foundation upon which to gain new knowledge to improve upon earlier developments.