The relationship between age and major league baseball performance: Implications for development.

Lifetime performance data of 388 baseball players active in 1965 were analyzed to determine the age of peak performance for skills required to play baseball, to derive age-performance curves for athletic productivity, and to assess the magnitude of individual differences among elite and less able players. Cross-sectional and longitudinal analyses show that athletic performance on key indicators rises relatively quickly from age 19 to a peak age of 27 and then declines. The primary difference between elite and less able players is that performance of the elite players remains high for a longer period of time and decays more gradually. The performance of the most elite players is superior to that of less able players even at very early ages. These results parallel findings reported for other achievement domains and can be explained in terms of basic developmental processes involving the interaction of experience, physiological capacity, and motivation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Signal detection based on empirical mode decomposition and Teager–Kaiser energy operator and its application to P and S wave arrival time detection in seismic signal analysis

Neural Computing and Applications - Determining P and S wave arrival times while minimizing noise is a major problem in seismic signal analysis. Precise determination of earthquake onset arrival...     

A GA-HP Model for the Optimal Design of Sewer Networks

This paper illustrates the application of a new model combined Genetic Algorithm with Heuristic Programming (GA-HP) technique in order to establish the optimal design for sewer networks. The objective is to minimise the construction cost function, which is represented by the depth of excavation and pipe diameter. The proposed GA-HP model has achieved the optimum design task in two stages. Firstly, the Genetic Algorithm (GA) was applied to obtain the diameters of the pipes needed for the preliminary design of the network. Secondly, Heuristic Programming (HP) preliminary designs were used to obtain the optimal slope for those pipes and to determine other characteristics such as the velocity, relative depth of water, excavation depths and total cost of the network. A MATLAB code was used to perform the GA-HP optimisation modelling. The performance of three different selection methods, four different crossover methods and different population sizes is examined with the proposed model, to determine their impact on convergence behaviour. The proposed GA-HP model is tested using some benchmark examples of sewer networks from the literature. The results show that the GA-HP model is superior to all previous methods and may be more efficient in the design of large networks.     

The behavior of thermosetting compounds in injection molding cavities

The thermo-mechanical history of thermosetting compounds in injection molding cavities influences the ultimate properties of molded articles and affects both moldability and the productivity of the process. Mathematical modeling is an attractive approach for obtaining information regarding the thermo-mechanical history of the compound in the cavity. In order to obtain useful mathematical models of the thermoset injection molding process, it is necessary to have information regarding the kinetics and heats of reaction during cure; the rheological, thermal, and PVT properties of the thermosetting compound; and the variation of these properties with operating variables and the degree of cure. The paper outlines a model of the thermoset injection molding process in simple rectangular or semi-circular cavities. Methods are described for the experimental determination of the various physical and chemical properties of thermosets, which are required for modeling purposes. The results obtained in conjunction with the characterization of an epoxy system are illustrated. Finally, the paper demonstrates the results of mathematical modeling of the injection molding process for a commercial epoxy molding compound in a semi-circular cavity, and shows that reasonable agreement is obtained between model predictions and experimental data.     

Adsorption isotherm mechanism of amino organic compounds as mild steel corrosion inhibitors by electrochemical measurement method

The inhibition ability of 4-amino-5-phenyl-4H-1, 2, 4-trizole-3-thiol (APTT), ethylenediaminetetra-acetic acid (EDTA) and thiourea (TU) for mild steel corrosion in 1.0 mol/L HCl solution at 30 ℃ was investigated. Tafel polarization and electrochemical impedance spectroscopy (EIS) were used to investigate the influence of these organic compounds as corrosion inhibitors of mild steel in 1.0 mol/L HCl solution at 30 ℃. The inhibition mechanism was discussed in terms of Langmuir isotherm model. Results obtained...     

Thermoset characterization for moldability analysis

The injection molding of thermosetting compounds involves complex interactions between material parameters and molding conditions, on one hand, and moldability and the ultimate properties of molded parts, on the other hand. The main role of the molding variables may be related to their effects on the cure time and temperature and on the flow and thermal phenomena that affect orientation and residual stresses. These effects are manifested in the ultimate mechanical properties and shrinkage of the molded articles. Only scattered empirical data are available on the effects of material parameters, like the basic kinetic, thermal, rheological, and pressure-volume-temperature properties of thermosetting compounds. The lack of useful information in this area may be related to the unavailability of sufficient, satisfactory data on the above properties. This situation has also resulted in limitations on meaningful work towards the mathematical modelling of the molding process, which would be useful for the optimization of production rates and product quality. The paper summarizes the status of work in this area with emphasis on recent results relating to kinetic, thermal, and rheological characterization of thermosetting molding compounds.     

A force sensing tool for disassembly operations

This paper discusses the design and characterization of a prototype disassembly tool that was designed to handle a family of electronic devices whose plastic, cantilever snap-fit covers house AA or AAA batteries. The tool was designed with the ability to release the snap-fit covers and the batteries contained inside. The tool design is based on the use of a force sensing tool tip that utilizes three force sensing resistors (FSRs) for force feedback. Two FSRs were used to measure horizontal forces applied to the tool tip while the third FSR was used to measure forces along a direction normal to the tool tip. The tool tip is used to push and lift up the snap-fit cover as well as the spring-loaded batteries. By using the conductance of the FSR sensors, a linear model of the FSR output was calibrated to the force applied to the FSR. The disassembly tool was mounted on a three-axis translational motion robot, and the robot was programmed to perform disassembly operations. Sensor feedback from the FSRs was used to control the movement of the tool during these operations. The results showed that the robot was able to successfully use the disassembly tool to perform the necessary operations to remove the device's snap-fit cover and batteries. Force readings recorded from the FSRs indicated that the disassembly tool was able to react to force interactions at the disassembly tool tip such as a missing part or misaligned part. The use of FSRs resulted in a low-cost, flexible disassembly tool.     

Research in online learning environments: Priorities and methodologies

Due to increasing demand for education and training in the information age, online learning and teaching is becoming a necessity in our future. However, lack of research goals to understand impact of online learning environments on students is a problem in research on online learning environments. We identified four main research goals to pursue in online learning environments based on their impact on learner achievement, engagement, and retention (opposite of attrition). Those goals are (a) enhancing learner engagement & collaboration, (b) promoting effective facilitation, (c) developing assessment techniques, and (d) designing faculty development programs. Current promising work in those areas is presented. Four methods that are common in the instructional technology literature are recommended to pursue those goals. Formative research and developmental research are relevant for all four. Although appropriate for any of the goals, experimental research is a better fit for goals b and c, and activity theory is useful for goals a and b.     

Generalized preisach model for hysteresis nonlinearity of piezoceramic actuators

This paper presents a new approach for modeling the hysteresis nonlinearity of a piezoceramic actuator using a modified generalized Preisach model, and the use of this model in a linearizing control scheme. The developed generalized Preisach model relaxes the congruency requirement on the hysteresis loops of a piezoceramic actuator, which must be satisfied when using the classical Preisach model. The congruency property is experimentally proved to not hold when running the actuator on a minor hysteresis loop. A numerical expression of the model is derived in terms of first- and second-order reversal curve experimental datasets. Output prediction using this model is performed on both an exponentially decayed sinusoidal input signal and an arbitrary input signal, and the results show that the model can accurately reproduce the hysteresis response with an error of less than 2.7%. A tracking control system for a piezoceramic actuator is also developed by combining a PID feedback controller with a hysteresis linearizing scheme in a feed-forward loop. The results show that this new control system can achieve 0.25 μm tracking control accuracy, which is 80 and 50% less than that obtained when using an open-loop controller and a regular feedback control system, respectively.