Line Trajectory Research Articles

Self-propulsion droplet induced via periodic explosive boiling

When a droplet is placed on a surface with a temperature higher than Leidenfrost temperature, it will be levitated on its own vapor cushion, which makes the droplet have amazing mobility. Generally, the vapor flow under the droplet is corrected by constructing asymmetry micro/nano textured surfaces to realize the self-propulsion of the droplet. However, the control of droplet dynamics becomes uncertain due to the complicated interaction among liquid-vapor-solid phases, and the direction of droplet motion and droplet transport velocity (10－40 cm/s) have limitations. Leidenfrost heat transfer surface and impact surface are constructed in this experiment. When the surface of Leidenfrost heat transfer for droplet levitation contacts the droplet which the sufficient energy flows towards, the rough ring surface acts as an igniter. When a warm Leidenfrsot droplet (<i>fuel</i>) contacts skirt ring (<i>igniter</i>), abundant micro/nano cavities of rough skirt ring not only generate additional radiation heat flux towards droplet but also provide nucleation sites to trigger explosive boiling on a ～10 ms time scale. The thrust force <i>F</i><sub>th</sub> generated by periodic explosive boiling realizes the self-propulsion of droplets. In the initial stage of droplet motion, the inertial force <i>F</i><sub>i</sub> is dominant, and the droplet impact is mostly specular reflection, and the droplet trajectory is chaotic. With the decrease of droplet diameter, the pulsed thrust <i>F</i><sub>th</sub> is dominant, and the droplet trajectory passes through the center of the Leidenfrost heat transfer surface. Our experimental results show that the droplet passes through the center of the Leidenfrost heat transfer surface in a wide diameter range (<i>D</i> = 0.671－1.576 mm). For the last (150<sup>th</sup>) collision with the rough ring, the curved trajectory exists instead of line trajectory with <inline-formula><tex-math id="Z-20211217122516-1">\begin{document}$ D \sim 0.105 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20211386_Z-20211217122516-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20211386_Z-20211217122516-1.png"/></alternatives></inline-formula> mm. For a very small droplet, the drag force <i>F</i><sub>d</sub> is dominant, which prevents the droplet from continuing to move. The droplet is followed by sessile droplet evaporation until it totally disappears. At the same time, the droplet transport velocity is as high as 68.91 cm/s, which has not been realized before. The present work provides a new method to manipulate droplet motion at a high temperature. Our Leidenfrost system is simple, cost-effective and lasts long-term operation because it does not depend on complicated micro/nano fabrications, which is expected to be used in microfluidic and heat transfer two-phase systems.

A Multiple Baseline Approach to Face Multipath

The positioning of tagged objects by means of the phase of the backscattered RFID signal is a challenging problem. Several approaches have been conceived in the years to face the problem of the narrow bandwidth of the RFID signal, which produces a periodic, and hence ambiguous, measurement of the tag-reader distance. One possible strategy is to exploit the movement of either the tag or the reader to collect a set of phase measurements which allow to solve the aforementioned ambiguity: this is, e.g., the approach pursued by SAR (Synthetic Aperture Radar) methods. In this article we propose an alternative approach which elaborates the sequence of phase samples in order to discover additional indicators that allow to improve the effectiveness of synthetic aperture methods. In particular we develop a strategy that permits to identify, among a set of measurements, the ones more strongly affected by the multipath. If a pattern emerges among the measurements without significant multipath (and this occurs if a low to moderate level of multipath characterizes the environment), by exploiting the good subset of measurements, it is possible to achieve an improvement in the positioning estimation. The method has been developed for a straight line trajectory: numerical results are reported in this article to illustrate the approach, while experimental results confirm its effectiveness.

Circumnuclear regions of different BPT types in star-forming MaNGA galaxies: AGN detectability

We consider the circumnuclear regions of star-forming MaNGA galaxies. The spaxels spectra are classified as active-galactic-nucleus-like (AGN-like), H II-region-like (or SF-like), and intermediate (INT) spectra according to their positions on the Baldwin-Phillips-Terlevich (BPT) diagram. There are the following four configurations of the radiation distributions in the circumnuclear regions in (massive) galaxies: (1) AGN+INT, the innermost region of the AGN-like radiation is surrounded by a ring of radiation of the intermediate type; (2) INT, the central area of radiation of the intermediate type; (3) SF+INT, the inner region of the H II-region-like radiation is surrounded by a ring of radiation of the intermediate type; and (4) SF, the central area of the H II-region-like radiation only. The low ionization nuclear emission line regions (LINERs) of configurations 1 and 2 are examined. The spaxel spectra of the LINERs form a sequences on the BPT diagram, that is, they lie along the known AGN-SF mixing line trajectories. The diagnostic line ratios of the spaxels spectra change smoothly with radius, from AGN-like (or INT) line ratios at the galactic center to H II-region-like at larger galactocentric distances. This is in agreement with the paradigm that the LINERs are excited by AGN activity. We found that the AGN and INT radiation in the circumnuclear region is accompanied by an enhanced gas velocity dispersionσgas. The radius of the area of the AGN and INT radiation is similar to the radius of the area with enhancedσgas, and the centralσgas, ccorrelates with the luminosity of the AGN+INT area. We assume that the gas velocity dispersion can serve as an indicator of the AGN activity. An appreciable enhancement ofσgas, cwas also measured in the SF-type centers of massive galaxies. The values ofσgas, cfor the SF-type centers partly overlap with those of the AGN-type centers. This suggests that the manifestation of the circumnuclear region as AGN or as SF on the BPT diagram depends not only on the value ofσgas, c(the level of the AGN activity) but it is also governed by an additional parameter(s). We find that there is a demarcation line between the positions of the AGN-type and SF-type objects on the central gas velocity dispersion – central Hαsurface brightness diagram, in the sense that an object with a given value ofσgas, cis an AGN-type only if the central Hαsurface brightness is lower than some value.

A Wireless Trajectory Measurement System for Unicondylar Knee Arthroplasty

During unicondylar knee arthroplasty surgery, the tibial prosthesis is fixed and the angle of distal femoral prosthesis relative to the prosthetic gasket is changed to generate the force line trajectory, which is important for doctors to judge the appropriate position of the implants. In this article, we propose a wireless force line trajectory measurement system for unicondylar knee arthroplasty, which includes the pressure sensors array, the control and processing data circuits, the radio frequency transmitter, and the data recorder. Data from 20 sensors are processed and transmitted wirelessly, and the force line trajectory is displayed on the screen in real time. The least squares fitting algorithm is proposed, with which we obtain the pressure distribution, the maximum pressure points, and the force line trajectory. We adopt field programmable gate array to implement the algorithm with lower-upper decomposition to fit the trajectory faster and transmit less data to save power. The average current consumption of the system is 1.37 mA in the operating mode. Dimensions of the data transmission module are length 70 mm, width 35 mm, and height 4 mm. The total uncertainty of the system measurement force line trajectory is 0.92 mm. Experimental results show that the system meets the requirement of real-time measurement of the force line trajectory during the surgery.

Trajectory Planning and Tracking for Carrier Aircraft-Tractor System Based on Autonomous and Cooperative Movement

The solution of how to plan out the cooperative moving trajectory autonomously and control the motion of carrier-based aircraft timely and accurately is the key to helping improve the overall deck operation efficiency. The main problem discussed in this article is coordinated trajectory planning strategy for multicarrier aircraft and cooperative control between tractor and carrier aircraft. First, the kinematic model and three-degree-of-freedom dynamics model of the towbarless traction system are established. Then, a coevolution mechanism for aircraft systems is proposed to ensure coordinated trajectory planning among multiple aircraft and a trajectory adapted to the tractor-aircraft system is generated based on the hybrid RRT∗ algorithm. Next, a double-layer closed-loop controller is designed for the trajectory tracking of the tractor-aircraft system on the deck under the constraints of incomplete constraints and various physical conditions. It includes an outer model predictive controller which effectively controls the cooperative motion between the carrier aircraft and tractor and an inner torque control strategy based on adaptive fuzzy PID control which strictly ensures the stability of the system. Simulation results demonstrate that the controller is more rapid, more accurate, and more robust in tracking line trajectory with initial deviation, sine curve with large curvature, and complex trajectories on decks compared with backstepping control and LQR algorithm.

EXPERIMENT STUDY OF AUTONOMOUS SYSTEM FOR INTRA-ROW WEED CONTROL

The study is used to propose and test by experiment a procedure for autonomous hoeing system for intra-row weed control. The proposed system utilizes the RTK-GPS navigation system. The system consists of autonomous vehicle equipped with side-shifting frame and cycloid hoe. The navigation of the system is controlled using a pre-specified plan and implemented in the system internal computer. The internal computer is also attached to a field station using the wireless local area network (WLAN). The performance of the system was measured through an experiment consisted of making rows having small plants and soil conditions similar to the actual field. The results based on chi-square shows that transverse deviation had normal distribution indicating the performance of the side-shift control. The results related to the longitudinal deviation distance between plants and the nearest line trajectories showed good chi-square fit which is an indication of performance of the cycloid hoe control. The result shows that the system is promising and can be used at larger level with suitable adjustments

Multi years catch composition and abundance of Parrotfish landed at Makassar Fisheries Port

Parrotfishes have an important ecological role in the coral reef ecosystem of the Spermonde Islands. The Spermonde Islands is located in the Makassar Strait, who was Wallace’s line trajectory. The Spermonde Islands consist of 120 islands, which have an area of around 2,500 km2, consisting of 50 vegetated islands and 70 non-vegetated sand dunes. Vegetated islandswere inhabited around 50,000 people. The ecological role and economic value of Parrotfishes place Parrotfishes in a paradoxical situation. Economically, Parrotfishes are an important protein resource for coastal and highlands communities. The Socio-economic contribution of Parrotfish can be overlooked, especially after the call not to eat Parrotfishes. For this reason, it necessary to overview the species composition and abundance of the Parrotfishes catch in Spermonde Islands by a monthly sampling of Parrotfish landed at Makassar Fisheries Port. The study aims to analyze the species composition and abundance for two different sampling periods (20014 and 2018) and to analyze their annual similarities. The study was expected to provide a preliminary description of the Parrotfishes. The number of species found in 2014 was 31, and in 2018 was 34. The similarity index between 2014 and 2015 was 0.912. The similarities indexes for monthly catches were lower. It was between 0.423 (May) and 0.680 (December). The catch was randomly distributed; this result shows that there were no target species in the catch of Parrotfish; the fishermen caught whatever Parrotfish they found. The sample conditions prove that large-sized Parrotfish were captured using the spear, whereas the medium and small size of Parrotfish seems to be captured using the net. The net use was quite worrying because the net was generally not selective. In order to maintain a balance between Parrotfish’s ecological role and socio-economic functions, regulations should be made regarding the prohibition on parrotfish catch with nets. It is recommended that Parrotfish should only be caught using the spear regularly and orderly so as not to damage the coral reefs.

Design of an optimal hydraulic tank configuration

The fluid behavior in the tank of the cutting machine hydrostatic actuator is considered. The hydrodynamic simulation technique of such processes is described. The velocity magnitudes, temperature distribution fields and fluid flow lines trajectories in the tank volume analyzed. The tank configuration changes that allow to an increase its operational efficiency as the part of the hydraulic actuator are proposed. Recommendations for selecting tank optimal geometric dimensions in accordance with the criterion for the most even fluid flow rates distribution in the tank entire volume are presented.

Size at the maturity of sea cucumber Holothuria scabra. Is it an overfishing sign in Wallacea Region?

As the largest trepang producer in the world, Indonesian trepang product still depends on wild catches. This wild catch could cause overfishing. In many fishing areas, sea cucumber populations have decreased to the point where they can be considered as a rare species. The wild catch could lead to a negative impact on size at maturity. Biologically, there are two types of reproductive strategies at marine organisms, i.e. ‘r-selection’ and ‘K-selection’. The ‘r-selection’ type was found in organisms that are dominantly controlled by their environmental factors and tend to reach physical maturation faster, while the ‘K-selection’ type was controlled more by biological factors, such as the presence of competitors. This study aims to analyze the size at the maturity of sea cucumber Holothuria scabra for different years to find out if the size at maturity can be used as a reference of the overfishing sign in the Wallacea region. The H. scabra or sandfishes were taken from the catches of fishermen at the Sub-district Liukang Tupabbiring Utara, Pangkep Regency, South Sulawesi, Indonesia. The Liukang Tupabbiring area is in the Spermonde Islands region, which is part of the Wallace line trajectory. Samplings were carried out for four years, from 2016 to 2019. The parameters measured were a total length (TL), total weight (TW), and gutted body weight (BW). The parameters observed were the color and stage of the gonad. The sizes at maturities were defined as the percentage of sexually mature, which were the sandfish with gonad stages of III, IV, and V. The study reveals that the size at maturity of sandfish was reached at a smaller size than previously reported. Biologically, smaller sizes at maturity could be a sign that sandfish has overfishing. As one organism whose biological organ structure was still primitive, Sea cucumber probably maintains the continuity of its generation by adapting reproductive strategy “r-selection type”.

Variation of major elements and heavy metals occurrence in hybrid aspen (Populus tremuloides Michx. × P. tremula L.) tree rings in marginal land

Fast growing tree species such as Populus spp. in short rotation woody crop (SRWC) systems could be an environmentally friendly and cost-effective approach to ensure sustainable biomass production and mitigate the negative impacts on the environment caused by more intensive management aimed to promote additional biomass increment. Knowledge on variation of major biologically important elements’ and toxic heavy metals’ occurrence in fertilised hybrid aspen tree rings in marginal land may have important and relevant implications for the management practice and evaluation of element fluxes in SRWC ecosystems. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to determine the relative amount of major elements (K, Ca, Mg, P) and heavy metals (Cd, Hg, Pb) in stem wood plane on straight line trajectory starting from pith to bark with measurement step 0.1 mm. While inductively coupled plasma mass spectrometry (ICP-MS) was used to determine average content of the mentioned elements in mechanically separated tree rings to quantify data obtained using LA-ICP-MS method and expressed in relative units. Stem disc samples were collected from six year old hybrid aspen trees growing in marginal agricultural land in the central part of Latvia (hemi-boreal climate conditions) that were initially fertilised with biogas production residues, sewage sludge, and wood ash. We concluded that the content of analysed major elements and heavy metals in the hybrid aspen tree rings varied considerably not only within the analysed stem plane (across tree rings) of one sample tree, but also within one annual ring with significant differences between the content of major elements in earlywood and latewood. Nevertheless, the results of the content of major elements and heavy metals in hybrid aspen tree rings highlighted the significant impact of the initially used fertiliser (especially wood ash) on the average content of elements. Hybrid aspens can be considered bioindicators of both the management activities and general growing conditions even if soil pH is close to neutrality, suggesting a limited mobility of the heavy metals.

Path tracking and backstepping control for a wheeled mobile robot (WMR) in a slipping environment

This work studies the motion of a two-wheeled differential drive mobile robot by presenting the kinematic and dynamic model of a nonholonomic wheeled mobile robot (WMR) with and without slip effect. The traction forces are derived and a control law designed using the backstepping method to drive the WMR to the desired trajectory. The parameters of the kinematic and dynamic controllers are tuned and modified to reach the desired performance. In addition, the input torque is controlled to avoid slip occurring. Simulation results show the effectiveness of the proposed control algorithm that is demonstrated by applying these controllers at different case studies (circular trajectory, elliptical trajectory, sinusoidal trajectory, infinity trajectory, and line trajectory), these results show good matching between desired trajectory and simulation, while the errors converge to zero rapidly. It shows good performance in minimizing the overshoot and reducing energy and the transient response time.

Planar tool radius compensation for CNC systems based on NURBS interpolation

This paper introduces the realization of a tool radius compensation algorithm for NURBS trajectory. First, a single-segment NURBS trajectory tool radius compensation algorithm is developed. Different from the straight line and arc trajectory, the self-intersection phenomenon is prone to happen when calculating a single NURBS tool center trajectory, and the self-intersection will cause the overcut of workpiece. To avoid this situation, the algorithm introduced in this paper can detect whether the NURBS tool center track has caused overcut, and deal with the self-processing. Second, the tool radius compensation algorithm with multi-segment NURBS trajectory is implemented. The focus of this part is the tool radius compensation of the trajectory transfer, and the trajectory transfer is divided into two types: the extension type and the shortened type. For the shortened type transfer, cross-processing is needed to avoid the overcut of workpiece at the transfer. When calculating the tool radius compensation of the shortened type, we not only need to find the intersection of the tool center trajectory of two adjacent NURBS curves, but also need to select the intersection we need when a number of intersections exist. For the extension type transfer, in order to ensure the continuity of the tool center trajectory, we need to extend the tool center trajectory or add arc-segment at the transfer. The proposed algorithm can automatically decide where to extend the tool center trajectory or add arc-segment to achieve the best efficiency. Finally, the algorithm can output the calculated NURBS tool center trajectory in the form of linear segment interpolation G code or NURBS interpolation G code according to the processing needs. Simulations on VERICUT and experiments on three-axis CNC machine tool shows the effectiveness and validation of the tool path compensation algorithm.

Virtual Antenna Array and Multipath AOA-Delay Fingerprints Based Location for Moving Targets

Multipath effects are the major challenge to the accurate indoor wireless positioning technology and the most viable solutions for overcoming such multipath effects are received signal strength (RSS) or channel status information (CSI) based fingerprinting location methods. However, these fingerprinting methods are usually subject to the RSS/CSI fingerprints’ high variability over space. In this paper, a novel virtual antenna array and multipath angle of arrival (AOA)-delay fingerprints based location method has been proposed. The proposed method employs 2-dimensional inverse Fourier transform on the CFRs (Channel Frequency Responses) at equi-spaced positions on a quasi-straight line moving trajectory, i.e., the CFRs of a virtual uniform linear array (VULA), to extract the equivalent multipaths’ AOAs and delays as the radio fingerprints, which vary much more slowly than the RSS/CSI fingerprints in the space domain. By exploiting the geometric properties of the multipaths’ AOAs and delays, a complete fingerprint database containing fingerprints of moving trajectories in different directions with each RP (reference position) as their midpoints can be constructed based on just two fingerprints of two perpendicular line trajectories with the same RP as the midpoints. Further, a two-step online fingerprinting location method is developed, the multipath delay estimates are used to narrow the scope of positioning in the first step, a modified WKNN (Weighed K-Nearest Neighbors) fingerprinting method, with the reciprocals of the fingerprints’ Euclidean distances adopted as the weighting factors, is then employed on RPs in such a narrowed positioning scope to enhance the positioning accuracy. Experimental results verify that the proposed fingerprinting method outperforms the corresponding traditional RSS/CSI fingerprints based approach.

QDR: A Quadrotor Dead Reckoning Framework

Quadrotors are used for variety of applications both outdoors and indoors. Among them are - deliveries, surveillance, transportation, mapping and more. To accomplish its tasks an accurate navigation solution is required. To that end, most quadrotors apply fusion between an inertial navigation system and other external sensors, such as global navigation satellite systems (outdoors) or vision (indoors/outdoors). Due to environmental or sensor constraints, in some portion of the trajectory, the navigation solution relies only on the inertial navigation system solution. Consequently, the navigation solution drifts in time due to errors and noise in the inertial sensors measurements. Motivated from the pedestrian dead reckoning approach, we propose the quadrotor dead-reckoning framework to mitigate the navigation solution drift in situations of pure inertial navigation. There, instead of a straight line trajectory, the quadrotor is flown with a periodic motion to enable peak to peak distance estimation. Simulation and experiments results show that the proposed approach greatly improves the accuracy of the navigation solution.

Ruled surfaces with constant Disteli-axis

This work develops the kinematic-geometry for ruled surfaces by using the analogy with spherical kinematics. This provides the ability to compute set of curvature functions which define the local shape of ruled surfaces. Hence, the well known equation of the Plucker's conoid has been obtained and its kinematic-geometry are examined in details. Finally, a characterization for a line trajectory to be a constant Disteli-axis is derived, and investigated.

High-brightness source of energetic He atoms

In atom beam lithography, a beam of kilo-electron-volt helium atoms illuminates a stencil mask and transmitted beamlets transfer the mask pattern to resist on a substrate. It shares the advantages of masked ion beam lithography but is immune to charging artifacts that limit resolution and pattern fidelity. This paper describes a high-brightness source of energetic He atoms, where He+ ions are extracted from a multicusp ion source, focused by two-stage accelerating optics, and neutralized by charge-transfer scattering in a differentially pumped, He-filled cell. Since scattering angles are extremely small, the straight line trajectories of scattered atoms are essentially tangent to the (possibly curved) trajectories of the parent ions. Space-charge repulsion prevents the ion beam crossing over; instead, it converges to a waist of minimum cross section before diverging further downstream. Atom trajectories produced by a cell placed in the region of intense space charge near the waist are strongly affected by the curvature of ion trajectories within the cell. The flaring of the ion beam due to space charge can be used to increase the width of the atom beam, although to the detriment of resolution. In this paper, the authors study a configuration where the cell is placed in the converging ion beam as far as practicable from the ion-beam waist. The atom beam then converges to a crossover, which becomes the virtual source seen by the mask. The source diameter and angular flux density initially increase with increasing cell pressure but saturate at higher pressures; the respective saturation values at 50 keV are 125 μm (2σ) and 8.7 × 1017 particles/s sr. Under these conditions, the beam diameter is ∼2.5 cm, 7 m from the source. A practical system for subnanometer printing is discussed with 0.2 nm (2σ) penumbral blur and 1.25 × 1013 particles/s cm2 flux density over a 1 cm circular field.

On the one-parameter Lorentzian spatial motions

In this paper, differential properties of the one-parameter Lorentzian spatial motions are developed with explicit expressions independent of coordinates systems. In term of this, we calculate the Disteli formulae of a spacelike line trajectory and derive the connections with kinematic geometry of the axodes. Lastly, a theoretical expression of a spacelike inflection line congruence are investigated in detail.

Confinement induced trajectory of a squirmer in a two dimensional channel

Micro-swimmers in confinement are encountered in a variety of scenarios such as locomotion of sperm cells in female reproductive tract, targeted drug delivery and biofilm formation. Using a squirmer, a surface actuating model, we simulate the trajectory of swimmers in a two-dimensional channel confinement. Exploiting the simplicity of squirmer model and performing the study in two dimensions we restrict the analysis to minimum number of parameters and isolate and analyze the confinement induced swimmer trajectories. Using exact solutions of two dimensional disk squirmers we first show that they behave qualitatively similar to three dimensional spherical squirmers near a repulsive, planar wall. In a channel, fully resolved flow and thus hydrodynamic interaction between the squirmer and the channel walls are obtained using the lattice Boltzmann method. We find that strong pullers and pushers slide along the channel walls, a behavior determined by single wall. In contrast, swimmers with weak force dipoles break the symmetry in behavior between pushers and pullers, and this behavior is determined by both walls of the channel. Weak pullers stay at the channel center and weak pushers execute an oscillatory trajectory spanning the channel width. Straight line trajectories can be solely characterized by a fixed point on a phase plane spanned by its orientation angle and the distance from the channel centerline whereas oscillatory trajectories can be solely characterized using its escape angle from the wall. The nature of the trajectories is found to be robust to the details of higher modes and the size of the confinement.

Three-dimensional mapping of intertrochanteric fracture lines.

Available research about the anatomic patterns of intertrochanteric fractures is lacking, and fracture mapping has not previously been performed on intertrochanteric fractures. This study aimed to determine the major trajectories of intertrochanteric fracture lines using computed tomography data from a series of surgically treated patients. In this study, 504 patients with intertrochanteric fractures were retrospectively analyzed. Fracture patterns were graded according to Arbeitsgemeinschaft für Osteosynthesefragen (AO) classification. Fracture lines were transcribed onto proximal femoral templates and graphically superimposed to create a compilation of fracture maps that were subsequently divided into anterior, posterior, lateral, and medial fracture maps to create a three-dimensional (3D) pattern by reducing fragments in the 3D models. The fracture maps were then converted into frequency spectra. The major fracture patterns were assessed by focusing on the lateral femoral wall, lesser trochanter, intertrochanteric crest, and inner cortical buttress. Anterior, posterior, lateral, and medial fracture maps were created. The majority of fracture lines (85.9%, 433/504) on the anterior maps were along the intertrochanteric line where the iliofemoral ligament was attached. In the medial plane, the majority of fracture lines (49.0%, 247/504) shown on the frequency spectrum included the turning point involving the third quadrant. In the posterior plane, the majority of fracture lines (52.0%, 262/504) involved the intertrochanteric crest from the greater to the lesser trochanter. In the lateral plane, the majority of fracture lines (62.7%, 316/504) involved the greater trochanter at the gluteus medius attachment. The fracture patterns observed in the present study might be used to describe morphologic characteristics and aid with management strategies. Further classifications or modifications that incorporate the fracture patterns identified in this study may be used in future research.

Evaluation of two wheelchair hand rim models: contact pressure distribution in straight line and curve trajectories

Manual wheelchairs are essential for people with disabilities or limited mobility. However, manual propulsion causes biomechanical loads, including contact pressures on the palms of the hands. The hand rim design has received little attention over time, remaining almost unchanged since its creation. This study investigated how two different designs of such devices – one standard and another with a contoured design – influence the contact pressure on the surface of the hands. The procedures included a figure-of-eight shape propulsion task on a regular floor, using both models on a wheelchair. A pressure-mapping system coupled with a pair of fabric gloves recorded the data. The results show that the contoured hand rim provides lower pressure in most of the analysed regions. Considering that manual propulsion is performed during a considerable part of the day as a routine activity, improving the hand rim interface may benefit the user’s comfort and safety during wheelchair use. Practitioner summary: The design of the hand rim used in wheelchair propulsion influences the contact pressure on the hands. Conventional round tube rims tend to concentrate high levels of pressure on the distal phalanges and metacarpal regions. A contoured design generally provides better stability and promotes the distribution of pressure. Abbreviations: AT: assistive technology; kPa: kilopascal