19684 research outputs found
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The effectiveness of physiotherapy sitting balance treatments on sitting balance outcomes in early sub-acute stroke. A systematic review and meta-analysis
No full textBackground: Difficulties with sitting balance are common after stroke. The ability to sit unsupported is imperative for many daily tasks and correlated to more positive outcomes. There is limited research on “sitting balance” therapeutic interventions and their impact. This systematic review and meta-analysis aims to investigate the effectiveness of physiotherapy sitting balance treatments on sitting balance outcomes in people up to 3-months post-stroke. Methods: The PRISMA checklist was followed and the review registered on PROSPERO. Seven electronic databases were searched to October 2023 (updated in January 2025) for studies comparing treatments focussing on sitting balance in adults who had suffered a cerebral stroke in the last three months. Studies were included if treatment was predominantly completed in sitting postures and reported sitting balance outcomes. Studies were assessed for eligibility, and data extraction and risk of bias was completed by two independent reviewers. Results: Data from 16 studies (623 participants) was synthesised narratively. Sitting balance interventions were classified into four main categories: weight shift and reaching; core stability exercises; environmental modifications; and task practice. A random effects meta-analysis conducted on eight studies (342 participants) revealed interventions to be beneficial for sitting balance (primary outcome: mean difference Trunk Impairment Scale 3.02; 95% confidence interval 2.19 to 3.86). Four studies demonstrated low risk of bias; and four showed some concerns. Conclusions: The current sitting balance treatments offered to early sub-acute stroke patients show significant improvements in sitting balance primary outcome. Sitting balance treatments can be categorised into four sub-types, helping to standardise clinical application and ensure consistency in future research. Systematic Review Registration Number: PROSPERO CRD42023444050. Contribution of the Paper: • Sitting balance impairment is significantly improved with therapy interventions completed in sitting. • Four main categories of sitting balance treatments have been researched in the subacute stroke population.</p
When may age not be a barrier to entrepreneurial entry of senior people? The role of individual geographical mobility experience and village democratic governance in rural areas in emerging economies
No full textThis paper contributes to the senior entrepreneurship and rural entrepreneurship literature by developing a contingency view on the likelihood of entrepreneurial entry by senior individuals in rural areas in emerging economies. Drawing on utility maximization theory, we propose that multi-level factors and their joint effects help older individuals overcome barriers to entrepreneurial entry. Using data from the Chinese Labour-force Dynamics Surveys (CLDS), comprising 8,692 individual-year observations in 209 villages in 2012, 2014 and 2016, our results reveal that individual geographical mobility experience attenuates the negative effect of older age on entrepreneurial entry in rural areas. Although village democratic governance does not independently mitigate this negative effect, its interaction with individual geographical mobility experience does. Our research has theoretical and policy implications for understanding senior entrepreneurial entry in rural areas of emerging markets and addressing the challenges posed by an ageing society.</p
Phenomenological modeling of planetary gear trains considering corner contact meshing impact with different fault size
No full textStudying the vibrational generation mechanisms of planetary gear train (PGT) plays a vital role in monitoring its health conditions. The meshing stiffness is an important influencing factor for the generated vibrations. Due to the actual meshing line often not being aligned with the theoretical one, the corner contact phenomenon occurs during the meshing process, which leads to the generation of relative velocities along the meshing line, resulting in meshing impacts. Under fault states, the vibration caused by these impacts is more significant, with the impact forces varying according to the size of the fault. Previous phenomenological models fail to delineate the vibration characteristics under diverse fault sizes and local fault impulse. This study investigated the meshing stiffness and impact of PGT under both normal and malfunctioning conditions and developed a periodic meshing impact function. The relationship between fault impacts and the meshing process was analyzed, leading to the development of an improved vibration signal model capable of reflecting fault size. Simulation studies are carried out to compare the patterns of sideband distribution under three different sizes of sun gear crack faults. The results indicate that as the fault size increases, the amplitude of the sidebands around the meshing frequency increases significantly, while the amplitude of the meshing frequency changes slightly, which phenomenon is also validated experimentally. The experimental studies demonstrated that the proposed model has a superior ability to characterize the vibrations compared to the conventional model.</p
A comparative investigation on the freeze–thaw resistance between dry-cured alkali-activated fly ash/slag and portland cement mortars
No full textThe present investigation analyses the freeze–thaw resistance of alkali-activated fly ash and/or ground granulated blast furnace slag (GGBFS) binders compared to ordinary Portland cement (OPC). The experimental program included 20 series of mortars of alkali-activated fly ash, alkali-activated slag, alkali-activated fly ash/slag, CEM I 42.5, and CEM I 52.5. Fly ash and slag were activated with Sodium Hydroxide (NaOH) and Dry cured at 100 °C for 72 h whereas the OPC mortars were water-cured for 28 days. After completing their curing period, the mortars were subjected to 100, 200, and 300 freeze–thaw cycles followed by testing and analysis of water absorption, porosity, flexural strength, compressive strength, and mass loss. The results reveal that dry-cured alkali-activated mortars show lower resistance to freeze–thaw damage and higher water absorption, porosity, and mass loss than OPC mortars. GGBFS mortars demonstrated significant deterioration after prolonged exposure, whereas OPC mortars, particularly CEM I 52.5R, showed remarkable self-healing properties. These findings indicate that the use of alkali-activated mortars needs to be investigated further to address their low performance under cyclic freeze–thaw stress in order to enhance their usability in cold-weather environments.</p
Crystal-orientation-dependent nanoscale machining mechanisms in ultrasonic vibration-assisted scratching sapphire
No full textUltrasonic vibration-assisted grinding (UVAG) is a promising, low-damage, high-efficiency and environmentally friendly technique for machining sapphire, yet its atomistic mechanisms and orientation dependence remain poorly understood. In this work, we employ molecular dynamics (MD) simulations to compare ultrasonic vibration-assisted scratching (UVAS) with conventional scratching (CS) on the A/C/M/R-planes of sapphire. Applying ultrasonic vibration dramatically reduces the scratching force by redistributing the stress field and activating cyclic deformation mechanisms, with the force-reduction sequence A≈ M > C > R. Surface-topography analysis shows that chip pile-up modes depend on crystal orientation; ultrasonic vibration not only lowers the pile-up height but also makes it more uniform. Moreover, ultrasonic vibration mitigates subsurface damage by suppressing tangled dislocation networks on the A- and M-planes and by promoting the nucleation of dislocations and twinning on the C- and R-planes, with the C-plane experiencing the least damage. These results systematically clarify the coupled effects of ultrasonic vibration and sapphire anisotropy, providing valuable guidance for selecting crystal orientations and vibration parameters during ultra-precision grinding of electronic devices, such as sustainable clean-energy LEDs.</p
Advanced vibration control strategies for Electro-Hydraulic testing systems focus on sinusoidal Swept-Frequency techniques
No full textThis paper presents an advanced investigation into vibration control strategies for electro-hydraulic testing systems, with a specific emphasis on sinusoidal swept-frequency techniques. Electro-hydraulic shaking tables (EHSTs) are critical in replicating the dynamic conditions for applications in civil engineering, automotive testing, and seismic assessments. Although widely used, the nonlinear dynamics of EHSTs—characterised by factors such as oil flow friction and dead zones—frequently cause distortion in response signals, particularly during high-frequency vibration testing, thereby limiting system performance. To address these challenges, this study proposes a dual approach. The first method employs offline control through system identification coupled with iterative correction algorithms, while the second uses real-time predictive control based on the system’s frequency response function. A novel composite control strategy is developed, integrating the strengths of both approaches to achieve improved amplitude and phase compensation, thus enhancing both robustness and accuracy in vibration control. The proposed strategy is validated through both simulations and experimental testing on a six-degree-of-freedom electro-hydraulic shaking table, demonstrating significant improvements in phase lag reduction and amplitude tracking, particularly at higher frequencies. This control approach provides an optimised solution for precise vibration control in complex engineering applications
A novel bio-inspired compound restrictor for high-precision aerostatic bearings:design and evaluation
No full textCompound restrictors are widely adopted in aerostatic bearings due to their good static performance and ease of fabrication. However, further enhancement of their performance using surfaces with groove structures designed is still rarely researched. Inspired by the unique fluid controllability of the biomimetic hexagonal micro-pattern, this paper proposes a novel bio-inspired aerostatic bearing design to realize high stability without compromising load capacity and static stiffness. Air mass flow rate, another key factor affecting its static performance, is also considered. Computational fluid dynamics (CFD) simulation study reveals that setting suitable divergence angle enables better pressurized airflow controllability. The key structural parameters were calculated using the resistance network method (RNM). The results were further verified through experimental measurements. Performance tests of the prototyped aerostatic linear motion stage verified the theoretical modelling accuracy. A positioning accuracy (perpendicular to the stage feed direction) of less than 15 nm/10 mm was achieved, which was almost half of that of the conventional linear bearing stage under the same conditions (8 μm bearing clearance, 0.2 MPa supply pressure).</p
A new dynamic model of electromagnetic coupling in induction motors with dynamic eccentricity
No full textInduction motors are extensively used in renewable energy systems, manufacturing, and electric vehicles, making early-stage condition monitoring of dynamic eccentricity crucial to ensure its reliable and safe high-speed operation while preventing severe failures. Experimental studies have shown that control voltage significantly affects the characteristics of dynamic eccentricity faults and the amplitude of their associated harmonics. This influence limits the accuracy of current-based fault diagnosis. However, most existing electromagnetic coupling models do not consider the effects of control voltage on the dynamic behaviour of stator current. Consequently, the underlying mechanism governing the motor’s frequency response under dynamic eccentricity—especially when subjected to realistic control voltage excitation—remains inadequately understood. To address this problem, this paper proposes a novel multiple coupled circuit (MCC) model that simultaneously considers the time-varying mutual inductance induced by rotor eccentricity and realistic pulse width modulation (PWM) excitation from an open-loop inverter. By leveraging modified winding function theory, the model enables accurate computation of inductances and stator current response under varying eccentricity and load conditions. The model has been verified by the designed custom-built experimental test rig. Comparative analysis with experimental data confirms that the proposed model accurately reproduces both time-domain waveforms and spectral features of stator current, including eccentricity-induced sidebands masked by PWM harmonics. Results indicate that PWM excitation elevates the spectral noise floor, which obscures low- frequency fault components; however, modulation features around the principal slot harmonics remain detectable. The study further reveals that the amplification of sideband increases approximately linearly with the severity of eccentricity. They are also affected by load torque (due to slip variations) and by the carrier frequency of the PWM control, which modulates the spectral distribution of fault-related components. These findings clarify the interplay between control voltage, mechanical load, and fault-related spectral features, providing a solid foundation for effective condition monitoring under realistic operating conditions.<br/
Intelligent graph based visual approach for assessing and optimising energy performance in residential buildings
No full textOptimising house energy performance requires not only understanding individual attributes but also quantifying how their interdependencies govern overall efficiency. In our study of 36,534 UK dwellings from the Department for Levelling Up, Housing & Communities, each home was modelled as a directed network of seven core attributes (nodes) connected by six weighted edges with 0.25 network density. We applied min–max normalisation, proportional rule-based edge weighting, and an adapted Dijkstra algorithm to construct seven efficiency pathways. Polar bar charts revealed that the three highest-ranked paths achieved median cumulative impact scores above 0.75, while P-value distribution analysis confirmed that five attributes heating cost, lighting cost, CO2 emissions per floor area, and hot water cost significantly (p < 0.05) drive network dynamics. In our case studies of detached, semi-detached, and terraced homes, using typology-specific percentile cut-offs stopped features from clumping together and made it easier to spot which ones matter most. The colour-coded network views turn the tangle of relationships into a clear to-do list for retrofit, so homeowners and policymakers can focus on what works. Simple network measures, how many nodes, how many links, and how dense the graph is, scale from a single house to a whole city. Put together, the method connects fine-grained feature checks with the shape of the whole network, giving a practical, evidence-based way to target actions that cut energy use and emissions. The results showed that some attributes, such as heating and hot water costs, had stronger effects on overall efficiency, while others showed moderate or small effects. These moderate effect sizes suggest that improvements in energy performance depend on the combined influence of several factors rather than a single dominant attribute.</p
High-performance achromatic metalens in the long-wavelength infrared regime
No full textIn recent decades, metasurfaces have shown remarkable advancements in the development of integrated and miniaturized optical devices. Among these, metalenses have emerged as a prominent and significant area of research. In this paper, a broadband achromatic metalens is designed to operate across a wide wavelength range, specifically from 9.6 μm to 11.6 μm. To efficiently achieve the optimization of initial metalens parameters, we employ an envelope-based layering strategy that divides the sample space into multiple adjacent floors. This approach effectively reduces the loss rate and computational burden in a comprehensive manner. An enhanced Archimedes optimization algorithm is utilized to obtain the optimal solution. It incorporates the opposition-based learning with Sine map and elite retention strategy to enhance the search capability and avoid getting trapped in local optima. Following the optimization process, the proposed metalens achieves an average focusing efficiency of 53.64 %, with chromatic aberration correction accomplished at a coefficient of variation of only 2.27 %. This accomplishment signifies a substantial advancement in the field of achromatic metalenses.</p
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