The paper presents a tension control law to stabilize the motions of a Tethered Space-Tug system during its deorbiting process by regulating the tension in the tether. The tension control law is ...designed on a basis of two straightforward ideas, i.e., the potential energy shaping and the damping injection. The law is expressed in an analytical feedback form in terms of only the tether length without the need of the feedback of full state information. Meanwhile, the requirements of measuring velocities are removed with the aid of a dynamic extension technique based on the feedback interconnection of Euler-Lagrange systems. The positive and bounded tension constraint is taken into consideration explicitly by including a pair of special saturation terms in the feedback control law. The relative motions of the space-tug and the debris are described with respect to a local non-inertial orbital frame of reference, whereas the orbital motion equations of the system are formulated in terms of the modified equinoctial elements of the orbit. Finally, the effectiveness of the proposed scheme is demonstrated via numerical case studies.
•The analytical control law requires only tether length feedback.•The positive and bounded tension constraint is explicitly accounted for.•The orbital motion is described by the modified equinoctial elements.
The purpose of this study was to evaluate the association between functional mobility performance and executive functions in older adults with the amnestic (aMCI) and nonamnestic (naMCI) type of mild ...cognitive impairment (MCI), as well as in a control group. A cross-sectional study was conducted among 800 older adults (147 with MCI) who participated in a longitudinal study consisting in an interdisciplinary geriatric assessment and rehabilitation program in Kraków. Motor performance was measured with the Timed Up and Go test (TUG), while standard neuropsychological tests were used to assess different cognitive domains. Analysis of the entire sample showed that almost all cognitive domains and the presence of MCI are associated with functional mobility. Executive functions, letter fluency, and working memory were associated with TUG in the MCI group. The MCI type was not a significant moderator of the relationship between cognitive and motor performance. In group analyses, various cognitive predictors for TUG in the aMCI group, naMCI, and control group were demonstrated. Our results suggest that executive functions and working memory in aMCI and letter fluency in naMCI are independently associated with functional mobility performance. Executive functions are important for gait control in MCI.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
According to the Global Exploration Roadmap, a Getaway in the lunar vicinity will enable the human exploration of the Moon, paving the way toward Mars and further in the deep space. A reusable ...transportation system, the Lunar Space Tug (LST), can be a key support transportation system to achieve a continuous and sustainable connection between the Earth and the orbital lunar outpost. Exploiting an electrical propulsion technology consisting in Hall Thrusters (HTs), this reusable space cargo system can maximize the delivered payload, with a lower propellant consumption with respect to a chemical-based platform. This significant improvement comes with two main throwbacks: a long transfer time between Earth and Moon and a complex multidisciplinary design of the overall LST. The first issue can be overcome with good mission planning in order to reduce the layover times and maximize the use of the LST. However, the peculiarities of the adopted propulsion technology shape the overall mass and power distribution of the space tug, as well as its transfer trajectory. The design complexity introduced by this subsystem can be effectively investigated if the mission analysis, trajectory generation and subsystem sizing are merged together in one software. In fact, the low-thrust transfer trajectories are highly affected by orbital perturbation and eclipse periods. At the same time, the high demand in power of the propulsion system puts constraints on the mass breakdown and power allocations of the LST, therefore on the reachable thrust level. The trajectory and subsystems sizing limitations call for a particular accurate mission analysis in order to succeed. Only combining all those elements, it is possible to define feasible design boundaries without performing countless simulations trying to optimize each element as a stand-alone part.
Politecnico di Torino, in collaboration with the European Space Research and Technology Centre (ESTEC), developed a MatLab-based preliminary design tool for electric propulsion space tug missions, called MultidisciplinAry desiGN Electric Tug tOol (MAGNETO). Starting from the mission analysis of the lunar space tug, the tool building blocks and capabilities are presented. Moreover, the build-in trajectory module will be analysed in-depth. The potentiality of the trajectory generation tool in MAGNETO enables a refined design of the initial design envelope of the LST. For this reason, the improved results will be confronted with the previous LST design tool developed by Politecnico di Torino.
•Conceptual design analysis tool of an electrically propelled space tug.•Mass and power breakdown allocations for a space tug main subsystems.•Generation of a preliminary sub-optimal low-thrust trajectory.•Analysis of a payload cargo mission toward the lunar gateway.
Timed Up and Go (TUG) Test Kear, Breelan M.; Guck, Thomas P.; McGaha, Amy L.
Journal of primary care & community health,
01/2017, Letnik:
8, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Purpose: The Timed Up and Go (TUG) test is a reliable, cost-effective, safe, and time-efficient way to evaluate overall functional mobility. However, the TUG does not have normative reference values ...(NRV) for individuals younger than 60 years. The purpose of this study was to establish NRV for the TUG for individuals aged between 20 and 59 years and to examine the relationship between the TUG and demographic, physical, and mental health risk factors. Methods: Two hundred participants, 50 per decade (ages 20-29, 30-39, 40-49, 50-59 years) were selected at their primary care visit, and timed as they performed the TUG by standing up out of a chair, walking 3 m, turning around, walking back to the chair, and sitting down. Information regarding the risk factors socioeconomic status, body mass index, an index of multimorbidities, perceptions of overall physical and mental health was obtained and used as predictors of TUG time independent of age. Results: TUG times were significantly different among the decades (F = 6.579, P = .001) with slower times occurring with the 50-year-old decade compared with the 20s (P = .001), 30s (P = .001), and 40s (P = .020). Slower TUG times were associated with lower SES, higher body mass index, more medical comorbidities, and worse perceived physical and mental health. Regression results indicated that perceived physical and mental health accounted for unique variance in the prediction of TUG time beyond age, gender, and socioeconomic status. Conclusions: This study provided TUG NRV for adults in their 20s, 30s, 40s, and 50s. The TUG may have utility for primary care providers as they assess and monitor physical activity in younger adults, especially those with physical and mental health risk factors.
The transverse upper gracilis (TUG) flap is easily harvested to recruit a fair volume of tissue from the inner upper thigh region, making it the second choice of certain authors. Hip replacement is ...deemed prohibitive due to positional requirements that predispose to anterior dislocation of prosthetic femoral heads.
In this report, we describe a simple and safe way to raise TUG flap in patients with existing hip prostheses, detailing patient assessments, and technical variations in a limited case series.
A retrospective single cohort study was conducted on patient who underwent TUG flap-based reconstruction after hip replacement. Hip joint instability was assessed clinically and with CT. Flap harvesting was performed to prevent the extra-rotation of the femoral head by the thigh flex or dissecting the pedicle keeping the thigh straight.
Eleven patients were qualified for the study, and the flap raising time was superimposable to the conventional technique. Six flaps were elevated, while the thigh was kept in the flexed position without any extra-rotation, and the pedicle dissection was completed in 5 cases by keeping the thigh in the straight position. No intra- or postoperative hip dislocations resulted. All patients ambulated on mornings after surgery, returning to daily activities within 4 weeks.
TUG flap is a viable alternative that is not necessarily prohibited by existing prosthetic hips. Careful patient assessment and positioning during surgery are key considerations for safe and successful procedures.
•HMD wear is associated with change in motor behavior across ages.•HMD wear is linked with decrease in trunk velocity in sit-to-stand in older adults.•The physical effects of HMD should be considered ...when used with virtual reality.
The use of virtual reality (VR) in clinical settings has increased with the introduction of affordable, easy-to-use head-mounted displays (HMDs). However, some have raised concerns about the effects that HMDs have on posture and locomotion, even without the projection of a virtual scene, which may be different across ages.
How does HMD wear impact the kinematic measures in younger and older adults?
Twelve healthy young and sixteen older adults participated in two testing conditions: 1) TUG with no HMD and 2) TUG with an HMD displaying a scene of the actual environment (TUGHMD). The dependent variables were the pitch, yaw, and roll peak trunk velocities (PTVs) in each TUG component, turning cadence, and the time to complete the TUG and its components – SIT-TO-STAND, TURN, WALK, and STAND-TO-SIT.
Wearing the HMD decreased turning cadence and pitch and yaw PTVs in all TUG components, decreased roll PTV in SIT-TO-STAND and TURN, and increased the time taken to complete all TUG components in all participants. Wearing the HMD decreased the pitch PTV in SIT-TO-STAND in older relative to younger adults.
Wearing an HMD affected TUG performance in younger and older adults, which should be considered when an HMD is used for VR applications in rehabilitation.
Our findings highlight the importance of considering the physical effect of HMD wear in clinical testing, which may not be present with non-wearable VR technologies.
The call for concerted global action against the climate change impact is well heard. 191 countries would communicate their progressive plans through Nationally Determined Contributions (NDC) to the ...United Nations Framework Convention on Climate Change (UNFCCC) as signatories to the Paris Agreement. Harbour crafts as part of the larger maritime ecosystem, can significantly contribute to reduced emissions. In this paper, HyForce, the next generation 2 MW hydrogen powered virtual tugboat was designed for a feasibility assessment for her techno-economic and environmental footprint to replace existing diesel-powered tugboats. The study compares the use of hydrogen fuel cells and an internal combustion engine to perform the same dynamic load profile for a typical tugboat mission. The results from the study show that a signpost for commercial competitiveness of HyForce is influenced primarily by the projected liquid hydrogen cost of 5.10 USD per kg in 2040 with a 2,000 USD/kW capital cost for the fuel cells.
Greenhouse Gas (GHG) emissions from a “well-to-wake” analysis for fossil-based hydrogen and renewable hydrogen supply chains were conducted, and the results show 26.9% and 75.6% reduction, respectively, compared to similar tug running on diesel fuel.
•Feasibility assessment of a hydrogen – fuelled harbour tug.•The use of hydrogen PEM fuel cells and an internal combustion engine for marine tug application.•Total cost of ownership comparative analysis against a traditional diesel tug for 2030 and 2040.•Signposts for hydrogen landed cost breakeven point for commercial viability.•Well-to-wake GHG emissions for different sources of hydrogen.
•The primary finding of this analysis is that quality of life improved after virtual reality-based exercise in older adults aged 60 years or over.•Virtual reality-based exercise caused improvements ...in depressive symptoms in older adults.•Some of the balance tests revealed significant improvement following virtual reality-based exercise.
The objective of this study was to investigate the impact of virtual reality-based exercise on the quality of life, some balance variables, and depression among older adults aged 60 years or older.
We systematically searched five electronic databases.
Twenty-seven articles met our inclusion criteria. Meta-analysis revealed that exercise using virtual reality had a significant positive effect on overall quality of life (p = 0.05), mental (p = 0.001) and physical component scores (p = 0.01), social relation (p = 0.0002), psychological health(p = 0.01), physical health(p = 0.04), and environmental health (p = 0.04). Additionally, depression significantly improved following virtual reality-based exercise (p = 0.01). However, there were significant improvements in the balance berg scale (p<0.00001) and ABC scale (p<0.00001) but not in timed-up-and-go(TUG) or 8-foot-up-and-go(8-FUG).
Virtual reality-based exercise has a positive impact on various aspects of quality of life, BBS and ABC scores, and depression. More studies with larger sample sizes and less heterogeneity in design and assessments are required.
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