Design of a Particle Beam Satellite System for Lunar Prospecting

One potential use for neutral particle beam (NPB) technology is as an active orbital probe to investigate the composition of selected locations on the lunar surface. Because the beam is narrow and can be precisely directed, the NPB probe offers possibilities for high resolution experiments that cannot be accomplished using passive techniques. Rather, the combination of both passive and active techniques can be used to provide both full-coverage mapping (passively) at low resolution (tens of kilometers) and high-resolution information for discrete locations of special interest. A preliminary study of NPB applicability for this dual-use application was recently conducted. The study was completed in Feb. 1993. A novel feature was the consideration of the use of a Russian launch vehicle (e.g., the Proton). The use of other Russian space hardware and capabilities was also encouraged. This paper describes the lunar prospector system design. Other researchers discuss the issues and opportunities involving lunar scientific experimentation using an NPB. The NPB lunar prospector utilizes a modified design of the Far Field Optics Experiment (FOX). Like the Earth-orbiting FOX, the core capability of the NPB lunar prospector will be a pulsed RF LINAC that produces a 5-MeV proton beam that is projected to the target with a 30-micro-r beam divergence and a 10-micro-r beam-pointing accuracy. Upon striking the lunar surface, the proton beam will excite characteristic radiation (e.g., X-rays) that can be sensed by one or more detectors on the NPB platform or on a separate detector satellite

Kinematic Effects of Stride Length Perturbations on System COM Horizontal Velocity During Locomotion

PURPOSE: To investigate the kinematic effect on the systems’ center of mass horizontal velocity in response to stride length perturbations. METHODS: Twelve healthy adults (23.1±7.71 yrs; 1.69±0.1 m; 66.82±12.6 kg; leg length 894.7±66.1 mm) performed 5 trials of preferred speed walking (PW) and running (PR)followed by 5 stride length perturbations based on percentages of leg length (60%, 80%, 100%, 120% and 140%). 3D kinematic analysis was completed using a 12-camera infrared motion capture system (Vicon, 200hz). Dependent variables computer for each condition included: center of mass horizontal velocity at the highest vertical position (COMHVhi) and at the lowest vertical position (COMHVlo). Statistical analysis included correlation matrices across levels of perturbation for each dependent variable (α=.05). RESULTS: COMHVhi demonstrated significant correlations with greater than 50% shared variance for PR vs 100% (r=.742), 60% vs 80% (r=.824), 60% vs 100% (r=.748), 60% vs 120% (r=.709), 80% vs 100% (r=.896), 100% vs 120% (r=.887), and 100% vs 140% (r=.728), and 120% vs 140% (r=.895). COMHVlo demonstrated significant correlations with greater than 50% shared variance for PR vs 100% (r=.753), PW vs 80% (r=.794), 60% vs 80% (r=.814), 60% vs 100% (r=.735), 60% vs 120% (r=.748), 80% vs 100% (r=.902), 80% vs 120% (r=.751), 100% vs 120% (r=.892), and 120% vs 140% (r=.710). DISCUSSION: Results suggest PR and PW have a greater relationship to stride length less than or equal to leg length, and thus extending stride length begins to diminish mechanical efficiency. It is a well-established mechanical relationship that horizontal velocity is a product of stride length and stride rate. Study results suggest that increases in stride length beyond 100% of leg length may be less than optimal mechanically. CONCLUSION: Stride lengths greater than 100% leg length during walking may be inefficient, perhaps owing to changes in lower extremity stiffness

Step Length Perturbations Alter Variations in Center of Mass Horizontal Velocity

PURPOSE: The purpose of the study was to investigate the effects of SL perturbations on system COM forward velocity (vx) during walking gait. METHODS: Eight healthy adults (23.5±3.6 yrs; 1.72±0.18 m; 73.11±15.29 kg) performed 5 trials of preferred speed walking (PW) and running (PR) followed by 5 stride length perturbations based on percentages of leg length (LL: 60%, 80%, 100%, 120% and 140%). 3D kinematic analysis was completed using a 12-camera infrared motion capture system (Vicon MX T40-S, 200Hz). Data filtering and interpolation included a low pass, 4th order Butterworth filter (cutoff frequency 15Hz) and cubic (3rd order spline). Maximum and minimum system COMvx comparisons were made independently among stride conditions using one-way repeated measures ANOVA and Bonferroni post-hoc contrasts. Change in system COMvx across gait stride were evaluated using one-way repeated measures ANOVA and Bonferroni post-hoc contrasts (α=0.05). RESULTS: Differences in maximum COMvx were detected among stride conditions (F[1.847,59.105]=339.458, pdetected among stride conditions (F[2.118,65.666] =130.951, pdetected significantly greater ΔCOMvx at 140% LL, and significantly less ΔCOMvx at 60% LL (p≤.005). DISCUSSION: Differences in maximum COMvx were detected among stride conditions (F[1.847,59.105]=339.458,

Unsteady movement of ripples and dunes related to bed-load transport

CER65DBS-EVR-CFN2.At head of title: International Association for Hydraulic Research.Includes bibliographical references.Two methods for computing bed-load transport from dune movement are considered. An equation based on the mean forward velocity and mean height of ripples and dunes is applied to flume data, and yields satisfactory results where the average dune shapes, velocities and heights can be determined accurately, as it the case for uniform two-dimensional flow. For unsteady flow, or for three-dimensional flow, where the size, shape, and movement of dunes varies in time and space, the volume of material passing through a series of incremental widths during some total time can be determined from sonic records. Bed-load transport rates are then estimated by integrating across the width of the stream. Applications of these concepts to field conditions are considered

Investigating single-leg landing strategies and movement control across changes in task demands

Variability is an intrinsic characteristic of human movement, with hypothesized connections to neuromotor functioning and mechanisms of injury. The purpose of this study was to evaluate changes in movement variability among kinematic, kinetic, and electromyographic (EMG) variables following mechanical task demand manipulations during single-leg drop landings. Biomechanical outcome variables included 3 kinematic (sagittal, hip, knee, and ankle angles), 4 kinetic (sagittal hip, knee, ankle moments and vertical ground reaction force; GRFz), and 5 EMG variables (gluteus maximus, vastus medialis, biceps femoris, medial gastrocnemius, and tibialis anterior muscles). Mechanical task demands were altered using load and landing height manipulations, computed as percentages of participant anthropometrics (bodyweight: BW, BW+12.5%, BW+25%, and height: H12.5% and H25%, respectively). Fewer emergent strategies were identified under greater mechanical task demands, defined using the load accommodation strategies model, alongside decreased movement variability, assessed using principal component analysis (PCA). Joint-specific biomechanical adjustments were identified, highlighting mechanisms for the observed load accommodation strategies and changes in movement variability. An increasingly upright landing posture was observed under greater mechanical task demands, decreasing effective landing height and reducing landing impulse. Alterations in movement variability were interpreted in the context of the available functional degrees of freedom at each lower extremity joint, aligning with physiological predictions and theories from motor control. The holistic approach taken in this investigation provided a more complete understanding of mechanisms contributing to changes in movement variability and factors that may underlie landing injuries

Test-retest reliability of knee kinematics measurement during gait with 3D motion analysis system

Restoration of gait symmetry following anterior cruciate ligament reconstruction (ACLR) is crucial to minimize the risk of joint degeneration. To achieve this, it is essential that the chosen measurement method can accurately assess knee kinematics and detect the changes in multi-planes of motion. However to date, limited study is available on repeatability of the multi-planes knee angle measurements particularly among male patients post ACLR. The purpose of this study was to assess the test-retest reliability of knee kinematic measurements using three-dimensional (3D) motion analysis system during gait in post ACLR patients. Eight patients with mean (SD) age 28.89 (4.0) years, 5.82(4.07) months post ACLR were recruited from a tertiary hospital of Kuala Lumpur. All patients undergone two sessions of knee joint angles measurement during gait at four hours interval, for the injured and the non-injured knees. Angles in the sagittal, frontal and transverse planes during initial contact phase of gait that derived from the two measurement sessions were compared.  The results showed high test-retest reliability of the measurement in sagittal and transverse planes; the intraclass correlation coefficient (ICC) was 0.97(95% CI: 0.84-0.99) and 0.96 (95% CI: 0.83-0.99) respectively, and moderate test-retest reliability for the measurements in frontal planes, with ICC 0.44 (95% CI: -0.32-0.86). The study findings suggest that multi-planes knee angle measurements during initial contact phase of gait could reliably be measured using a 3D motion analysis system. Further research may focus on knee kinematics measurements at other phases of gait. Keywords: biomechanics, reliability, walking, knee, anterior cruciate ligament reconstructio

Effect of membrane performance including fouling on cost optimization in brackish water desalination process

Membrane selection is a crucial step that will affect the economic feasibility of the membrane water treatment process. A comprehensive evaluation consisting of Verberne Cost Model, assessment of membrane performance and fouling propensity, osmotic pressure differential (OPD) and specific energy consumption (SEC) was employed to determine the potential of nanofiltration (NF 270, NF 90 and TS 80) and low pressure reverse osmosis (XLE) membranes to be used in brackish water desalination process. The aim was to save costs by replacing the typical brackish water reverse osmosis (BW 30) membrane. Verberne Cost Model showed that higher flux NF membranes resulted in lower overall costs. However, after assessing the membrane performance, NF 270 and TS 80 were excluded due to their high fouling propensity and their failure to reduce total dissolved solids (TDS) in the solution. Instead, NF 90 membrane which produced water with acceptable TDS and has moderate permeability ended up to be more cost competitive compared to BW 30 membrane, with 17%-21% lower total costs and 13%-17% lower water costs. Apart from this, OPD and SEC were applied to justify the selection of optimal membrane recovery rate based on the water costs calculated. It was determined that the optimal recovery rate was 80% where the SEC and water costs were close to available water treatment plants. Overall, this study showed that the selection of membrane can be carried out by using Verberne Cost Model assisted by assessment of membrane performance and fouling propensity, OPD and SEC

Students’ Psychosocial Perception of Automobile Technology Learning Environment and Attitudinal Outcomes in North-eastern Nigeria Tertiary Institutions

AbstractStudents’ perception of their learning environment is a crucial factor in improving quality of learning. Several researches revealed that students’ perception of the learning environment has a significant impact on the students’ academic performance and attitude. This study investigated relationships between students’ perception of automobile technology learning environments and their attitude towards automobile technology in north-eastern tertiary institutions of Nigeria. The research design of the study was a correlational survey design and the sample comprised 474 students offering automobile technology as a course in the institutions. The data were collected using ATLEI and ATAQ and these were analyzed using descriptive statistics, simple correlation, and multiple correlation analysis. The findings revealed that the automobile technology learning environments remain traditional and students anxiety-dominated the learning environment in the north-eastern tertiary institutions of Nigeria. It was recommended that lecturers in the institutions of learning should be sensitized on the importance of students’ perception of learning environment and enhanced student-student and student-lecturer relationships in their institutions

Expanded stability of layered SnSe-PbSe alloys and evidence of displacive phase transformation from rocksalt in heteroepitaxial thin films

Bulk PbSnSe has a two-phase region or miscibility gap as the crystal changes from a Van der Waals-bonded orthorhombic 2D layered structure in SnSe-rich compositions to the related 3D-bonded rocksalt structure in PbSe-rich compositions with large contrast in the electrical, optical, and thermal properties across this transition. With an aim to understand and harness this transition in thin films devices, we epitaxially integrate PbSnSe on GaAs by molecular beam epitaxy using an in-situ PbSe surface treatment and show a significantly reduced two-phase region by stabilizing the Pnma layered structure out to Pb$_{0.45}$Sn$_{0.55}$Se, beyond the bulk-limit of Pb$_{0.25}$Sn$_{0.75}$Se. Pushing further, we directly access metastable two-phase epitaxial films of layered and rocksalt grains that are nearly identical in composition around Pb$_{0.5}$Sn$_{0.5}$Se and entirely circumvent the miscibility gap. We present microstructural evidence for an incomplete displacive transformation from rocksalt to layered structure in these films that we speculate occurs during the sample cool down to room temperature after synthesis. In-situ x-ray diffraction measurement of an as-grown Pb$_{0.56}$Sn$_{0.44}$Se rocksalt film under cryogenic cooling reproduces the key attributes of this transition and validates our hypothesis. Notably, we find well-defined orientation relationships between the phases forming in the process and unconventional strain-relief mechanisms involved in the crystal structure transformation by transmission electron microscopy. Overall, our work adds a scalable thin film integration route to harnessing metastable layered compositions as well as the dramatic contrast in material properties in PbSnSe across a potentially ultrafast structural transition.Comment: 26 pages, 10 figure

Effects of environmental factors on development of Pyrenopeziza brassicae (light leaf spot) apothecia on oilseed rape debris

Publication no. P-2001-0221-01R. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 2001The development of Pyrenopeziza brassicae (light leaf spot) apothecia was studied on petiole debris from artificially infected oilseed rape leaves incubated at temperatures from 6 to 22 degreesC under different wetness regimes and in 16 h light/8 h dark or continuous darkness. There was no significant difference between light treatments in numbers of apothecia that developed. Mature apothecia developed at temperatures from 5 to 18 degreesC but not at 22 degreesC. The rate of apothecial development decreased as temperature decreased from 18 to 5 degreesC; mature apothecia were first observed after 5 days at 18 degreesC and after 15 days at 6 degreesC. Models were fitted to estimates of the time (days) for 50% of the maximum number of apothecia to develop (t(1); model 1, t(1) = 7.6 + 55.8(0.839)(T)) and the time for 50% of the maximum number of apothecia to decay (t(2); model 2, t(2) = 24.2 + 387(0.730)(T)) at temperatures (T) from 6 to 18 degreesC. An interruption in wetness of the petiole debris for 4 days after 4, 7, or 10 days of wetness delayed the time to observation of the first mature apothecia for approximate to4 days and decreased the number of apothecia produced (by comparison with continuous wetness). A relationship was found between water content of pod debris and electrical resistance measured by a debris-wetness sensor. The differences between values of tl predicted by model 1 and observed values of t(1) were 1 to 9 days. Model 2 did not predict t(2); apothecia decayed more quickly under natural conditions than predicted by model 2.Peer reviewe