THE ROTATIONAL ABILITY OF 'THE HUMAN BODY

In sports like gymnastics, trampolining and diving, attention is focussed on control and good execution. Like all general movements, the movements involved in such sports are motions that consist of translation and rotation. However in this case, proficiency depends dominantly on the rotational ability of the athlete while performing the movement. We analyze such a movement using parameters from anthropometry, dynamics, and posture. We recorded anthropometric data of top athletes in trampolining and compared them with those of ordinary people. With a computer program based on the Hanavan model together with mass density values given by Dempster, we use the data to calculate the inertia tensor. Further data pertaining to dynamics, timing and coordination are derived by video-cinematographic methods. With the aid of two cameras, we filmed simultaneously various trampoline performances during the international competition held in Dillenburg, Germany in 1991. The videos were then digitized and the data processed by computer. We obtain the results for momentum, body orientation, posture and the center of gravity of the trampolinists during a jump. We demonstrate how strongly body structure, dynamics, timing and coordination contribute to the ability of the human body to rotate. The important parameters are the inertia tensor and the momentum, the combination of which determines the rotating. While momentum remains constant during a jump, the inertia tensor may vary in time due to different postures. Our findings show what momentum is necessary and which posture have to be in sequence for athletes to excel

THE INFLUENCE OF TIMING IN MOVEMENT EFFICIENCY

INTRODUCTION The vertical movement of the human body is visible in almost all sports. Even in the case of sports like running, cycling, and long jumping where the aim is to achieve horizontal distance, vertical motion is obvious and highly essential in performing the movement. Components of vertical motion contribute to the total energy needed for the movement. In this study we analyze efficiency of the vertical motion components and discuss timing as one of the factors influencing the energy consumption of the movement. Efficiency is defined as the quotient of the work output divided by the energy needed to perform and given as η= Wout / Ein where Wout is work per formed on a mass. In both the ascending or descending motions. Ein is energy produced by muscles to do so. In classical mechanics efficiency is calculated as positive for ascent and negative for descent. METHOD A computer simulation of human motion beginning in a standing position, moving down to a squatting position and vice versa was performed. The motion was constructed symmetrically for upward and downward movements, so that a downward movement can be described as an upward movement with time reversed (t -> -t). For this simulation we used the commercial software SDS Version 3.5 of Solid Dynamics. The human body is approximated by the Hanavan model using anthropometric data of a male person. Similar simulations are also done in the following movements: a) raising the body off the ground with one leg on a bench b) alternate stepping with one leg then the other, keeping the same foot position when on the ground C) lifting weights with the arms flexed In the second stage of the study we obtained real movement data using 3 cameras and a 3D Peak Performance digitizing system. This data and the anthropometry of our subjects were included into an inverse dynamics analysis, using SDS to calculate the efficiency. RESULTS Figure 1 represents the efficiency simulation for a squatting motion at difference timings. The graph shows for a downward or upward movement with a duration of 0.75 seconds, which result in an efficiency of 0.674. For slower movements η Coverges below 0.9. Our experiment shows efficiencies in the same range as the simulation. A detailed analysis of the various simulations demonstrates that efficiency is dependent on timing. Conclusion The above results suggest that the optimizing of efficiency helps to reduce energy consumption of the vertical motion. This subsequently provides more energy needed for the horizontal motion and thus the complete performance. Such effects seem unimportant for a single movement, but with thousands of repetitions in a cyclic motion the minute energy conservation adds up to a substantial amount and consequently influences the performance

Extreme non-linear response of ultra-narrow optical transitions in cavity QED for laser stabilization

We explore the potential of direct spectroscopy of ultra-narrow optical transitions of atoms localized in an optical cavity. In contrast to stabilization against a reference cavity, which is the approach currently used for the most highly stabilized lasers, stabilization against an atomic transition does not suffer from Brownian thermal noise. Spectroscopy of ultra-narrow optical transitions in a cavity operates in a very highly saturated regime in which non-linear effects such as bistability play an important role. From the universal behavior of the Jaynes-Cummings model with dissipation, we derive the fundamental limits for laser stabilization using direct spectroscopy of ultra-narrow atomic lines. We find that with current lattice clock experiments, laser linewidths of about 1 mHz can be achieved in principle, and the ultimate limitations of this technique are at the 1 $\mu$ Hz level.Comment: 5 pages, 4 figure

Prediction of Customer Movements in Large Tourism Industries by the Means of Process Mining

Customer movements in large tourism industries (such as public transport systems, attraction parks or ski resorts) can be understood as business processes. Their processes describe the flow of persons through the networked systems, while Information Systems log the different steps. The prediction of how large numbers of customers will behave in the near future is a complex and yet unsolved challenge. However, the possible business benefits of predictive analytics in the tourism industry are manifold. We propose to approach this task with the yet unexploited appli-cation of predictive process mining. In a prototypical use case, we work together with two major European ski resorts. We implement a predictive process mining algorithm towards the goal of predicting near future lift arrivals of skiers within the ski resort in real-time. Furthermore, we present the results of our prototypical implementation and draw conclusions for future research in the area

TRUST MANAGEMENT – AN INFORMATION SYSTEMS PERSPECTIVE

The focus of the Information Systems (IS) research on trust has been on the perception of trust and explaining the concept in terms of its antecedents. The merits of this descriptive and explanatory knowledge notwithstanding, the usefulness and applicability of this knowledge for organizations that aim at actively influencing their trust position is limited. In light of recent public scandals in areas such as social media, car manufacturing or financial services, organizations require an understanding of how customer trust can be managed using contemporary information systems solutions. In this paper we propose trust management as an IS theme of increasing relevance and draw upon extant research in IS, psychology, and marketing to bridge the gap between topics such as risk management, compliance management and governance on the one hand and trust management on the other. We utilize Botsman’s concept of uncertainty as a proxy for customer trust to bring together organizational approaches that can objectively reduce uncertainty linked to an organization, its processes, products, and services with the customer’s perception of this uncertainty. We contribute to the further maturity of trust management by providing new foundations and providing explicit advice on how to improve trust in organizations

MUSCLE ENERGY OF TENNIS-STOPS WITH DIFFERENT MOVEMENT PATTERNS

INTRODUCTION: Fast runs starting with high accelerations and ending with abrupt stops are essential elements of tennis. While acceleration is achieved in a unique way without sliding, stops are performed in various ways. Depending on the surface, shoes and anthropometry, the stopping motion may or may not sliding. Stopping without sliding is a motion in which muscles are shortened or stretched while contracting. During sliding stops, muscles also contract, but almost no shortening or stretching of the muscles is involved. This has a major influence on energy consumption. Muscle energy becomes a limiting factor for the speed and quality of performance during prolonged matches or tournaments. The purpose of this study was to approximate the relative differences in the energy consumption of tennis stops with different stopping patterns. METHOD: Five male tennis players participated in this study. All played at either the state or national level. Their ages were between 23 and 28 years (24.2±1.9). For each subject, 38 anthropometric measurements were taken. Reflective markers were placed on 17 landmarks. Each participant performed three stops in the university gymnasium (almost no sliding) and three stops on an indoor tennis court with a floor of loose rubber granulate designed to permit sliding. Movements were filmed using three 50 Hz digital cameras with a shutter speed of 1/3500 sec. Digitizing was done using an automatic WinAnalyze system. The resulting marker coordinates and 38 anthropometric measurements per athlete were the input for the SDS-98 simulation system. SDS-98 created the Hanavan model and calculated the inverse dynamics in accordance with the filmed movements. Muscle energies were computed for the joints (neck, shoulder, elbow, hip, knee, ankle, spine) using the equation: [formula], which is the integral of the absolute of the scalar product between the relative angular velocity and the torque of the joint. The efficiency 0 of a stop was calculated as the quotient of muscle energy divided by the total mechanical energy change from the beginning of the movement to the stop. RESULTS AND DISCUSSION: Significant differences were found for muscle energy/efficiency between stopping motions with and without sliding (0stop/0slide between 1.3 and 4.0). CONCLUSIONS: Deviations between real world data and research calculations can occur. They may be caused by the simplicity of the body model, by digitizing errors, and by uncertainty in calculating the center of pressure for the feet during ground contact. However, the results show quantitatively that sliding stops are favorable for players with low endurance

Dynamic acoustic field activated cell separation (DAFACS)

Advances in diagnostics, cell and stem cell technologies drive the development of application-specific tools for cell and particle separation. Acoustic micro-particle separation offers a promising avenue for highthroughput, label-free, high recovery, cell and particle separation and isolation in regenerative medicine. Here, we demonstrate a novel approach utilizing a dynamic acoustic field that is capable of separating an arbitrary size range of cells. We first demonstrate the method for the separation of particles with different diameters between 6 and 45 μm and secondly particles of different densities in a heterogeneous medium. The dynamic acoustic field is then used to separate dorsal root ganglion cells. The shearless, label-free and low damage characteristics make this method of manipulation particularly suited for biological applications. Advantages of using a dynamic acoustic field for the separation of cells include its inherent safety and biocompatibility, the possibility to operate over large distances (centimetres), high purity (ratio of particle population, up to 100%), and high efficiency (ratio of separated particles over total number of particles to separate, up to 100%)

Locking Local Oscillator Phase to the Atomic Phase via Weak Measurement

We propose a new method to reduce the frequency noise of a Local Oscillator (LO) to the level of white phase noise by maintaining (not destroying by projective measurement) the coherence of the ensemble pseudo-spin of atoms over many measurement cycles. This scheme uses weak measurement to monitor the phase in Ramsey method and repeat the cycle without initialization of phase and we call, "atomic phase lock (APL)" in this paper. APL will achieve white phase noise as long as the noise accumulated during dead time and the decoherence are smaller than the measurement noise. A numerical simulation confirms that with APL, Allan deviation is averaged down at a maximum rate that is proportional to the inverse of total measurement time, tau^-1. In contrast, the current atomic clocks that use projection measurement suppress the noise only down to the level of white frequency, in which case Allan deviation scales as tau^-1/2. Faraday rotation is one of the possible ways to realize weak measurement for APL. We evaluate the strength of Faraday rotation with 171Yb+ ions trapped in a linear rf-trap and discuss the performance of APL. The main source of the decoherence is a spontaneous emission induced by the probe beam for Faraday rotation measurement. One can repeat the Faraday rotation measurement until the decoherence become comparable to the SNR of measurement. We estimate this number of cycles to be ~100 cycles for a realistic experimental parameter.Comment: 18 pages, 7 figures, submitted to New Journal of Physic

CHILDREN’S PLANTAR PRESSURE DISTRIBUTION MEASUREMENTS: INFLUENCE OF FOOTWEAR

INTRODUCTION: Several significant studies (Aharonson et al., 1989; Orlin et al., 1990; Hennig & Rosenbaum, 1991; Pisciotta et al., 1994) have increased interest in plantar pressure distribution parameters in childhood. All over the world the gait labs, with their ongoing research studies on gait kinetics, are beginning to look for pressure distribution values, as for example Bontrager et al. (1997). More than a hundred years ago, Marey in 1886 and Beeley in 1882 developed plantar pressure measurement techniques. These techniques have continued to be developed, and at present there are measurement systems based on such different principles as footprints, optical, acoustical, pneumatic, hydraulic, inductive, piezoelectric, capacitive and resistive. (Borges Machado, 1994