No description available.

No description available.

The research presented here retrieves the cloud optical thickness and particle effective size of cirrus clouds using surface radiation measurements obtained during the Atmospheric Radiation Measurement (ARM) field campaign. The algorithm used is based on a method proposed by Yang et al. (2005). The research examines single-layer ice clouds in the midlatitude and polar regions. The retrieved information in the midlatitudes is then verified using retrievals from the Moderate-resolution Imaging Spectroradiometer (MODIS) onboard the Terra and Aqua satellites.

Thesis (M.S.)--University of Wisconsin -- La Crosse, 2009. / Includes bibliographical references.

No description available.

Humans routinely make movements to targets that have different accuracy requirements in different directions. Examples extend from everyday occurrences such as grasping the handle of a coffee cup to the more refined instance of a surgeon positioning a scalpel. The attainment of accuracy in situations such as these might rest upon the nervous system's capacity to regulate the limb's resistance to displacement, or impedance. To test this idea, subjects made movements from random starting locations to targets that had shape dependant accuracy requirements. A robotic device was used to assess both limb impedance and patterns of movement variability just as the subject reached the target. Impedance was seen to increase in directions where required accuracy was high. Furthermore, independent of target shape patterns of limb stiffness were seen to predict spatial patterns of movement variability. The nervous system was thus seen to modulate limb impedance in wholly predictable environments to shape movement variability and achieve reaching accuracy.

This investigation examined the effects of 4 weeks of non-dominant arm suspension on the functional and structural characteristics of the triceps brachii muscle of 6 normo-active college age males (age: 23.3 ±0.8 yrs, height: 176.1 ±3.7 cm, weight: 75.9 ±5.8 kg). The primary intent of this study was to determine if arm suspension is an effective analogue for simulating the effects of weightlessness on human skeletal muscle. Subjects were tested 2-3 days preceding suspension in a standard arm sling and immediately following removal of the sling. To suspend the arm the sling was worn during waking hours. Subjects were allowed to remove the sling during sleep and bathing. Specific instructions were given to avoid use of the arm. Torque production (Nm) during maximal isometric extensions at 90° significantly declined (p<0.05) in response to arm suspension (53.93 ±5.07 to 47.90 ±5.92; 12%). There was no significant change (p>0.05) in the force-velocity attributes of the triceps over the other measured velocities (60, 90, 120, 180, 240, 300°/sec). Cross-sectional muscle area (CSA) of the upper arm diminished significantly (44.26 +2.66 to 42.43 ±2.54 cm2; 4%) following the 4 weeks of unloading (p<0.05). Histochemical analysis of individual muscle fibers demonstrated reductions in fiber CSA of 27 and 18% for type I and type II fibers, respectively, however these changes were not statistically significant (p>0.05). Amplitude of the IEMG signal during maximal isometric contraction of the long head of the triceps fell (p<0.05) by 21 in response to the 4 week suspension period. The changes in triceps muscle structure and function found with arm suspension are similar in magnitude and direction to data obtained from humans following exposure to real and simulated weightlessness. These findings suggest that arm suspension may provide a useful model for simulating the effects of microgravity on human skeletal muscle. / School of Physical Education

The kinematic and kinetic characteristics of arm movement during four activities of daily living: lifting a weight, driving a steering wheel, opening/closing a door and cutting were investigated in this study by using a human movement analysis system comprising a 6 camera Vicon motion analysis system, a 6 component strain-gauged transducer, a specially designed and instrumented steering wheel simulation system, a door and a cutting plate. The most important achievements of this study are: (1) Implementation of the residual analysis technique into a computer program to filter the noisy kinematic data at an autoselected cut-off frequency for each data sequence. (2) The development of a new method of representing the velocity and acceleration of points of interest using the phase plane presentation. It was found that driving is the most complicated activity investigated in this study according to the range of arm movement. From the kinetic results, it was found that the order of difficulty of the four activities can be arranged as cutting, door opening/closing, lifting, and driving according to the magnitude of the maximum resultant total shoulder moment. The difficulty of the lifting activity increased with the weight to be lifted and the height of lifting. It was also found that the major component of the shoulder moment is the flexion/extension moment for most of the activities except driving, therefore it is concluded that having sufficient shoulder flexion/extension strength is most important for conducting most upper limb activities of daily living. In addition, the results of this study provide information for improving the understanding of the biomechanics of the upper limb activities and for clinical reference.

It is becoming increasingly necessary to carry out manual operations in environments which are hazardous to humans - using remote manipulator systems that can extend the operators reach. However, manual dexterity can become severely impaired due to the complex relationship that exists between the operator, the remote manipulator system and the task. Under such circumstances, the introduction of force feedback is considered a desirable feature, and is particularly important when attempting to carry out complex assembly operations. The dynamic interaction in the manmachine system can significantly influence performance, and in the past evaluation has been largely by comparative assessment. In this study, an experimental remote manipulator system, or tele-manipulator system, has been developed which consists of three electrically linked planar manipulator arms, each with three degrees of freedom. An articulated 'master' arm is used to control an identical 'slave' arm, and independently, a second kinematically and dynamically dissimilar slave arm. Fully resolved Generalized Control has been demonstrated using a high speed computer to carry out the necessary position and force transformations between dissimilar master and slave arms in realtime. Simulation of a one degree of freedom master-slave system has also been carried out, which includes a simple model of the human operator and a task based upon a rigid stop. The results show good agreement with parallel experimental tests, and have provided a firm foundation for developing a fully resolved position/position control scheme, and a unique way of backdriving the master arm. Preliminary tests were based on a peg-in-hole transfer task, and have identified the effect on performance of force reflection ratio. More recently a novel crank-turning task has been developed to investigate the interaction of system parameters on overall performance. The results obtained from these experimental studies, backed up by simulation, demonstrate the potential of computer augmented control of remote manipulator systems. The directions for future work include development of real-time control of tele-robotic systems and research into the overall man-machine interaction.

These studies examined motion trajectories and electromyographic (EMG) activity patterns during human horizontal reaching movements towards single- and double-step visual targets. These data were used to test and elaborate a model of two-joint planar arm movement based on the equilibrium point (EP) hypothesis or $ lambda$ model of motor control. This work aims to understand how reaching movements are planned and controlled by the nervous system. To this end, simulated trajectories and EMG patterns, generated with hypothetical central commands, were compared to empirical trajectories and EMG patterns. In general, the model was able to predict trajectories but was less successful in predicting EMG patterns. The results indicated that, in general, motions to both single- and double-step targets are generated by shifting the EP of the hand in a straight line towards the present target. Thus, a common control strategy underlying movements to single-step targets and trajectory modifications to double-step targets is proposed. Whereas the direction of shift of the EP is specified at the level of the hand, the rate of shift may be limited at the joint level.