CINEMATOGRAPHICAL EXAMINATION OF POWERLIFTING AIDS IN SQUATTING

Six experienced weight-lifters were compared in powerlifting squats with and without lifting aids. Lifting aids were commercial, competitive elastic lifting suits and knee wraps. Subjects were filmed with a 16mm Locam camera at 50 fps while performing 3 trials of 3 repetitions maximum under the two lifting conditions. Squats were divided into four phases (2 for descent, 2 for ascent) by trunk to hip and thigh to leg rotations. Postural torques about the hip and the knee were estimated from digitized images. Inertial torques were discounted as modulating contributors to performance due to their invariance across the lifting conditions

THE EFFECT OF SELECTED SPORT SURFACES ON VERTICAL LANDING FORCES IN JUMPING

Introduction: The jump for height has received much attention as an important element in many sport activities, but less attention is given to the impact of landing, which may result in injuries due to the large forces involved (Miller, 1976). Therefore, activities that involve landings are potentially more harmful to the joint when there is inefficient absorptive material within the shoes and/or the sport surface. Cavanagh and Lafortune (1980) found that vertical forces, with magnitudes 2.5 times those found in running, were generated when landing from a vertical jump. Nigg, Denoth and Neukomm (1981) reported a force of magnitude 3.5 times the body weight when landing from a vertical jump. Knowing the magnitude of the vertical reaction forces to human beings, when jumping on different sport surfaces, could assist surface manufacturers and shoe designers in producing products that will reduce impact and therefore reduce injuries

THE EFFECT OF SELECTED SPORT SURFACES ON GROUND REACTION FORCES IN WALKING AND RUNNING

Introduction During physical activity, the human body exerts force against its environment. Previous research indicates that the body is exposed to magnitudes of force equaling 2 to 3 times body weight in running (Bates, 1985 & Dickinson, Cook & Leinhardt, 1985) and 1.1 to 1.3 times body weight in walking (Cavanagh, 1980). The magnitude and duration of these forces are a potential source of physical injury. Most biomechanical research in locomotion has examined the role offootwear. However, there is not enough information on the absorption capacity of shoes to determine their safety limit and the ground reaction force is relatively unaffected by footwear changes (Clarke, Frederick & Hamill, 1984)

Complexity Science Applications to Dynamic Trajectory Management: Research Strategies

The promise of the Next Generation Air Transportation System (NextGen) is strongly tied to the concept of trajectory-based operations in the national airspace system. Existing efforts to develop trajectory management concepts are largely focused on individual trajectories, optimized independently, then de-conflicted among each other, and individually re-optimized, as possible. The benefits in capacity, fuel, and time are valuable, though perhaps could be greater through alternative strategies. The concept of agent-based trajectories offers a strategy for automation of simultaneous multiple trajectory management. The anticipated result of the strategy would be dynamic management of multiple trajectories with interacting and interdependent outcomes that satisfy multiple, conflicting constraints. These constraints would include the business case for operators, the capacity case for the Air Navigation Service Provider (ANSP), and the environmental case for noise and emissions. The benefits in capacity, fuel, and time might be improved over those possible under individual trajectory management approaches. The proposed approach relies on computational agent-based modeling (ABM), combinatorial mathematics, as well as application of "traffic physics" concepts to the challenge, and modeling and simulation capabilities. The proposed strategy could support transforming air traffic control from managing individual aircraft behaviors to managing systemic behavior of air traffic in the NAS. A system built on the approach could provide the ability to know when regions of airspace approach being "full," that is, having non-viable local solution space for optimizing trajectories in advance

Development of Complexity Science and Technology Tools for NextGen Airspace Research and Applications

The objective of this research by NextGen AeroSciences, LLC is twofold: 1) to deliver an initial "toolbox" of algorithms, agent-based structures, and method descriptions for introducing trajectory agency as a methodology for simulating and analyzing airspace states, including bulk properties of large numbers of heterogeneous 4D aircraft trajectories in a test airspace -- while maintaining or increasing system safety; and 2) to use these tools in a test airspace to identify possible phase transition structure to predict when an airspace will approach the limits of its capacity. These 4D trajectories continuously replan their paths in the presence of noise and uncertainty while optimizing performance measures and performing conflict detection and resolution. In this approach, trajectories are represented as extended objects endowed with pseudopotential, maintaining time and fuel-efficient paths by bending just enough to accommodate separation while remaining inside of performance envelopes. This trajectory-centric approach differs from previous aircraft-centric distributed approaches to deconfliction. The results of this project are the following: 1) we delivered a toolbox of algorithms, agent-based structures and method descriptions as pseudocode; and 2) we corroborated the existence of phase transition structure in simulation with the addition of "early warning" detected prior to "full" airspace. This research suggests that airspace "fullness" can be anticipated and remedied before the airspace becomes unsafe

Literacy Challenges for the Twenty-First Century: Introducing the Issue

Advanced literacy is a prerequisite to adult success in the twenty-first century, By advanced literacy we do not mean simply the ability to decode words or read a text, as necessary as these elementary skills are, Instead we mean the ability to use reading to gain access to the world of knowledge, to synthesize information from different sources, to evaluate arguments, and to learn totally new subjects, These higher-level skills are now essential to young Americans who wish to explore fields as disparate as history, science, and mathematics; to succeed in postsecondary education, whether vocational or academic; to earn a decent living in the knowledge-based globalized labor market; and to participate in a democracy facing complex problems, The literacy challenge confronting children, their families, and schools in the United States has two parts. The first is the universal need to better prepare students for twenty-first-century literacy demands. The second is the specific need to reduce the disparities in literacy outcomes between children from disadvantaged backgrounds and those from more privileged homes. This issue of the Future of Children explores the literacy of America's children and how to improve it. We begin this introductory essay by reviewing briefly why literacy is so important in today's world and why the concept of literacy needs to be broadened to include a set of competencies that go well beyond the ability to recognize words and decode text. We end with a summary of the other articles in the issue and briefly consider what steps policy makers might take to respond to the urgent needs we cit

Does Income Mobility Equalize Longer-term Incomes? New Measures of an Old Concept

This paper develops a new class of measures of mobility as an equalizer of longer-term incomes – a concept different from other notions such as mobility as time-independence, positional movement, share movement, income flux, and directional income movement. A number of properties are specified leading to a class of indices, one easily-implementable member of which is applied to data for the United States and France. Using this index, income mobility is found to have equalized longer-term earnings among U.S. men in the 1970s but not in the 1980s or 1990s. In France, though, income mobility was equalizing throughout, and it has attained its maximum in the most recent period

Systematic and Controllable Negative, Zero, and Positive Thermal Expansion in Cubic Zr1–xSnxMo2O8

We describe the synthesis and characterization of a family of materials, Zr1–xSnxMo2O8 (0 < x < 1), whose isotropic thermal expansion coefficient can be systematically varied from negative to zero to positive values. These materials allow tunable expansion in a single phase as opposed to using a composite system. Linear thermal expansion coefficients, αl, ranging from −7.9(2) × 10–6 to +5.9(2) × 10–6 K–1 (12–500 K) can be achieved across the series; contraction and expansion limits are of the same order of magnitude as the expansion of typical ceramics. We also report the various structures and thermal expansion of “cubic” SnMo2O8, and we use time- and temperature-dependent diffraction studies to describe a series of phase transitions between different ordered and disordered states of this material