Programmable, multi-purpose opto-electronic sensor system

Optical fibre sensing is becoming increasingly attractive in both the smart structure sphere of interest as well as the medical and industrial concerns. Fibre-optic interferometric sensors can be designed as compact and robust transducers. In general, the transduction mechanism involves the phase modulation of coherent or monochromatic light propagating through a fibre-optic cable, and detecting the changes in the energy associated with this phase change. Sensors based on this technique can generally be configured to be quite sensitive and measurements of a wide variety of physical parameters are achievable. Intrinsic features of optical fibres, such as immunity to electromagnetic interference, flexibility, thinness, strength and weight, make this ideal for sensor technology. In the process of developing fibre-optic sensors for laboratory experimentation, as well as generalised research, an appropriate, easy to use opto-electronic drive and measurement system is required. This paper discusses the operation of a programmable opto-electronic drive and measurement system     

Risk-taking during wayfinding is modulated by external stressors and personality traits

ABSTRACT

Two experiments examined cue reliance and risk-taking during desktop virtual wayfinding, and how they might be modulated by personality traits and external stressors. Participants navigated a series of virtual buildings and we manipulated the strength of probabilistic cues available to guide turn decisions. Navigators frequently discounted probabilistic cues and instead took risks, particularly when costs were low and potential benefits were high. Risk-taking was predicted by higher sense of direction and lower need for structure. Introducing a time stressor lowered risk-taking, with a higher relative reliance on probability-based information. This was most pronounced in females and those with a high need for structure. Results provide novel evidence that spatial cue reliance is modulated by individual differences and contextual constraints.     

Detonation engine fed by acetylene–oxygen mixture

The advantages of a constant volume combustion cycle as compared to constant pressure combustion in terms of thermodynamic efficiency has focused the search for advanced propulsion on detonation engines. Detonation of acetylene mixed with oxygen in various proportions is studied using mathematical modeling. Simplified kinetics of acetylene burning includes 11 reactions with 9 components. Deflagration to detonation transition (DDT) is obtained in a cylindrical tube with a section of obstacles modeling a Shchelkin spiral; the DDT takes place in this section for a wide range of initial mixture compositions. A modified ka-omega turbulence model is used to simulate flame acceleration in the Shchelkin spiral section of the system. The results of numerical simulations were compared with experiments, which had been performed in the same size detonation chamber and turbulent spiral ring section, and with theoretical data on the Chapman–Jouguet detonation parameters.     

Navigation Solution to Maneuver a Spacecraft Relative to a Sphere Centered on a Cooperative Satellite

A differential correction algorithm is presented to deliver an impulsive maneuver to a satellite to place it within a sphere, with a user defined radius, centered around a non-maneuvering satellite within a constrained time. The differential correction algorithm develops and utilizes the State Transition Matrix along with the Equations of Motion and multiple satellite?s state information to determine the optimum trajectory to achieve the desired results. The results from the differential correction algorithm are very accurate for prograde orbits, as presented. The results allow for orbit design trade-offs, including satellites? initial inclinations, semi-major axes, as well as the ballistic coefficients. The results also provide an empirical method to determine the optimum ΔV$\mathrm{\Delta }V$ solution for the provided problem. Understanding that the minimum fuel solution lies with a semi-major axis ratio of 1, a very accurate empirical approximation is presented for semi-major axis ratio values less than and greater than 1. This work ultimately provides the generalized framework for applying the algorithm to a unique user defined maneuvering spacecraft scenario.     

Longitudinal structure of ballooning MHD disturbances in a model magnetosphere

Large-scale toroidal Pc5 pulsations are commonly treated as Alfven oscillations of a magnetic field line. According to observations, their longitudinal structure is described well by theory. At the same time, the longitudinal structure of azimuthal small-scale poloidal Pc5 pulsations is virtually unknown. These pulsations are associated with ballooning disturbances described by a system of coupled equations for Alfvenic and slow magnetosonic (SMS) modes. In this work, the Voigt model is used to describe the equilibrium finite-pressure plasma configuration in an inhomogeneous magnetosphere plasma in a curved magnetic field. Spectral characteristics and the spatial structure of natural ballooning modes are calculated for this model. The model calculations demonstrate the possibility of different longitudinal scales for transverse and longitudinal magnetic components of oscillations near the top of the field line.     

Spatial Thinking Across the College Curriculum: A Report on a Specialist Meeting

This report presents findings from a specialist meeting of spatially-minded researchers and administrators from education and industry to consider prospects for introducing courses and curricula on spatial thinking in higher education. More than 40 participants explored the rationale for expanding student exposure to concepts, tools, and applications of spatial reasoning across a range of science, engineering, and humanities disciplines. The focus was on what we know and what we need to know to make the case for space, underscoring basic research on what is meant by spatial thinking and on variations in the spatial reasoning skills required in different domains of knowledge. The need for rigorous assessments of learning outcomes associated with different approaches to teaching spatial thinking was emphasized.     

Effect of weightlessness on posture and movement control during a whole body reaching task

Here are reported preliminary results of the “Synergy” experiment performed aboard the Russian orbital station “MIR” in July 1993 (Altaïr Mission). The experiment was carried out before, during, and after the space flight of two astronauts (S1 and S2). The duration of the flight was 21 days for S1 and 6 month for S2. The subjects were tested during preflight, inflight and postflight. The astronaut subjects were fixed on the ground by the feet. They were asked to pick up a box in front of them on the ground. Two velocities of movement and two distances of the target to be reached were tested. The movement of several small markers placed on the body was recorded on video tape.

Results show that the shape of head and hand trajectories in the sagittal plane remains roughly the same during the flight in spite of the modification of mechanical constraints. Trajectory invariance does not result in joint angular displacement invariance. These data indicate that the planning of the movement takes place in terms of head and hand trajectories rather than joint rotations as it was previously suggested for simple arm reaching movement.     

Spatial orientation during locomotion [correction of locomation] following space flight

To investigate changes in spatial orientation ability and walking performance following space flight, 7 astronaut subjects were asked pre- and post-flight to perform a goal directed locomotion paradigm which consisted of walking a triangular path with and without vision. This new paradigm, involving inputs from different sensory systems, allows quantification of several critical parameters, like orientation performance, walking velocities and postural stability, in a natural walking task. The paper presented here mainly focusses on spatial orientation performance quantified by the errors in walking the previously seen path without vision. Errors in length and reaching the corners did not change significantly from pre- to post-flight, while absolute angular errors slightly increased post-flight. The significant decrease in walking velocity and a change in head-trunk coordination while walking around the corners of the path observed post-flight may suggest that during re-adaptation to gravity the mechanisms which are necessary to perform the task have to be re-accomplished.     

Effect of potassium and calcium loading on healthy subjects under hypokinesia and physical exercise with fluid and salt supplements

The objective of this investigation was to determine the acute responses to the electrolyte challenges under hypokinesia and physical exercise (PE) of different intensities with fluid and salt supplementation (FSS). The studies were performed on 12 physically healthy male volunteers aged 19-24 years under 364 days of hypokinesia (decreased number of steps per day) with a set of PE with FSS. The volunteers were divided into two equal groups. The first group was subjected to a set of intensive PE and the second group was submitted to a set of moderate PE. Both groups of subjects consumed daily water and salt supplements that aimed to increase the body hydration level. For simulation of the hypokinetic effect all subjects were kept under an average of 3000 steps per day. Functional tests with a potassium chloride (KCl) and calcium lactate (Cal) load were performed during the hypokinetic period of 364 days and the 60-day, prehypokinetic period that served as control, while both groups of subjects consumed daily calcium and potassium supplements. The concentration of electrolyte and hormone levels in the blood and their excretion rate in urine were determined. Renal excretion of calcium and potassium and the blood concentration thereof increased markedly in both groups of subjects. With the potassium chloride load tests the increased potassium excretion was accompanied by higher aldosterone and insulin blood levels, and with the calcium lactate load tests the increased calcium excretion was accompanied by a decreased parathyroid content in the blood. FSS and PE, regardless of intensity, failed to attenuate calcium and potassium losses. Additional intake of KCl and Cal also failed to normalize potassium and calcium abnormalities. It was concluded that during the KCl and Cal loading tests, the increased losses of potassium and calcium in the hypokinetic subjects were due to the inability of their bodies to retain these electrolytes, and that electrolyte abnormalities could not be reversed by PE or rehydration in individuals subjected to prolonged restriction of motor activity.     

Telerobotics: problems and research needs

With major emphasis on simulation, a university laboratory telerobotics facility permits problems to be approached by groups of graduate students. Helmet-mounded displays provide realism; the slaving of the display to the human operator's viewpoint gives a sense of `telepresence' that may be useful for prolonged tasks. Using top-down 3-D model control of distant images allows distant images to be reduced to a few parameters to update the model used for display to the human operator in a preview model to circumvent, in part, the communication delay. Also, the model can be used as a format for supervisory control and permit short-term local autonomous operations. Image processing algorithms can be made simpler and faster without trying to construct sensible images from the bottom. Control studies of telerobots lead to preferential manual control modes and, in this university environment, to basic paradigms for human motion and thence, perhaps, to redesign of robotic control, trajectory path planning, and rehabilitation prosthetics. Speculation as to future industrial drives for this telerobotic field suggests efficient roles for government agencies such as NASA