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Made available in DSpace on 2022-05-01T10:18:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-02-01 This study examined changes in postural control and gaze performance of faller and non-faller older adults under conditions of visual tasks and optical flow manipulations. Fifteen older non-fallers (69.8 years, ± 3.2) and fifteen older fallers (71.1 years, ± 6.4) stood on a force platform inside a moving room wearing an eye tracker. Four tasks were performed: gaze fixation; predictable saccades; unpredictable saccades; and free-viewing. The stimuli appeared at a frequency of 1.1 Hz during conditions of predictable and unpredictable saccades. Sixteen trials were divided into two blocks. In the first block, the room remained stationary. In the second block, the room oscillated, without the participant’s awareness, with a 0.6 cm amplitude and 0.2 Hz frequency. Results showed postural sway attenuation in older fallers during the saccadic tasks compared to gaze fixation and free-viewing tasks, in both stationary and moving room conditions. Both groups showed increased center of pressure (CoP) magnitude during the moving room condition and CoP displacements strongly coupled to the room’s movement. The influence of the moving room on the postural sway was reduced during the saccadic tasks for both older groups. Older fallers exhibited higher variability compared to older non-fallers. Gaze behavior differences between groups were dependent on the goals of the visual tasks. Therefore, CoP displacements of older adults are reduced during saccadic tasks regardless of their falling history. However, postural and gaze performance of older fallers suggests increased deterioration of postural and oculomotor control which may be used as a predictor of fall risk. Faculty of Sciences Department of Physical Education Laboratory of Information Vision and Action (LIVIA) São Paulo State University (UNESP), Av. Eng. Luiz Edmundo Carrijo Coube, 14-01, Vargem Limpa, São Paulo Graduate Program in Movement Sciences São Paulo State University - UNESP, São Paulo Faculty of Sciences Department of Physical Education Human Movement Research Laboratory (MOVI-LAB) São Paulo State University (UNESP), São Paulo Institute of Bioscience Department of Physical Education Movement Studies Laboratory (LEM) São Paulo State University (UNESP), São Paulo Faculty of Sciences Department of Physical Education Laboratory of Information Vision and Action (LIVIA) São Paulo State University (UNESP), Av. Eng. Luiz Edmundo Carrijo Coube, 14-01, Vargem Limpa, São Paulo Graduate Program in Movement Sciences São Paulo State University - UNESP, São Paulo Faculty of Sciences Department of Physical Education Human Movement Research Laboratory (MOVI-LAB) São Paulo State University (UNESP), São Paulo Institute of Bioscience Department of Physical Education Movement Studies Laboratory (LEM) São Paulo State University (UNESP), São Paulo

Among the various solutions proposed for these structures are stepped dams, which despite effectively reducing the flow pattern, weaken the vortex and dramatically lower the risk of vortex formation by reducing the size of the deadly roller. At high tailwater depths, however, the dimensions and submerged roller current strength can still be dangerous. Using triangular wedges as a complementing structure topping the step to change the vortex flow pattern is one method that has been addressed in previous studies. The present study investigates the effectiveness of these wedges on the proposed stepped design in reducing drowning risk at the Salmon Dam, the most dangerous dam in a pest management system that controls the immigrant sea lamprey population in the Great Lake of Ontario, Canada. It is shown that installing wedges on the steps, despite falling short of eliminating vertical vortex flow entirely, by changing the pattern and flow direction from vertical vortex to horizontal vortex, poses a risk of drowning in a wide range of tailwater depth. This study found that optimal wedge placement reduces the dangerous vertical roller area from 27 to 83% of the tailwater depth area. Moreover, using wedges on continuous steps retains the positive effect of wedges but also expands the range. The distance between the wedges wields significant influence on the flow pattern, but reducing the distance between them does not necessarily reduce the viewing range of this vertical roller.

We analyse the dynamics of a basketball which rolls around the rim of a basketball hoop. The rolling steady motions are determined, and we investigate falling, slipping, and instability. The qualitative behaviour of the global dynamics is analysed and the possible trajectories are categorised. We investigate the effect of initial conditions which cause the basketball to fall inside or outside the basket or to remain on the rim.

Short wall mining technology is an important method to coal resource mining in the United States, Australia and other countries, and also one of important methods to boundary coal resource recovery in China. Short wall mining technology through leaving a large number of coal pillars to support and control roof, induces a series of accidents, such as large area roof suspended, collapse and shock, which restricts the further popularization and application of short wall mining technology seriously. By improving the existing short wall mining technology, the article proposed short wall continuous mining technology with full roof falling, and designed measures to control roof. The main research work is as follows: (1) By reducing and eliminating coal pillars in mining section as much as possible, including entry protecting pillar and pillar between caverns, also ensured stability of roof during mining period at the same time; after mining, roof can be collapse, to prevent large area roof suspended and collapsed inducing shock accidents; mining process and equipment of short wall continuous mining technology with full roof falling, were designed comprehensively. (2) Measures to control roof of short wall continuous mining technology with full roof falling are designed, using self-moving hydraulic support to control roof of mining cavern, anchor bolt and cable to ensure branch and cross entries stable during mining period, and forced caving technology to control large area roof suspended; (3) Short wall continuous mining technology with full roof falling and roof control measures were successfully industrialized in 42,210 boundary coal face of Yujialiang coal mine, which belong to Shenhua energy group in Inner Mongolia. The research result is significant to enrich and develop short wall mining technology.

In order to design the vertical falling film evaporators applied in the sewage source heat pump systems, a numerical study employing the VOF (Volume of Fluid) method has been carried out to determine the thickness and the wave behavior of falling liquid film outside a vertical tube. The effects of the annular gap, tube diameter, tube length, spray density, viscosity and surface tension are discussed. The simulation results demonstrate that spray density and the fluid viscosity are the two most influential factors affecting the film thickness. Besides, when spray density is larger than 0.100 kg/(m∙s), the film thickness decreases slightly with the increase of the flow distance. So the influence of tube length on film thickness cannot be ignored and it also should be considered in the film thickness prediction model. On the other hand, the tube diameter and the surface tension have little effect on the film thickness. It mainly have a significant impact on the wave amplitude of the liquid film at low flowrate. Besides, the annular gap provides a limited effect on the outlet section of the falling film. On the basis of the simulation results, a new correlation incorporating the tube length is developed to effectively predict the falling film thickness. Compared with the experimental data, it is found that the prediction accuracy of the correlation can be controlled within ±15%. The present research provides a theoretical basis for designing falling film evaporators.

Prices often react stronger to rising than to falling costs. This asymmetric cost pass-through is still not fully understood, but recent theories suggest that asymmetric adjustments of consumers’ search efforts to rising and to falling prices may be one explanation for this pattern. I use novel panel data to investigate the interaction of consumer search intensity, pricing and cost pass-through of residential electricity tariffs on online price comparison sites. I find that consumers search slightly more when prices rise but drastically decrease search efforts when they fall. Moreover, I find direct evidence that cost pass-through heavily depends on consumers’ search efforts in that cost increases are passed-through less to the consumer when search intensity is high while cost decreases are passed-through more when search intensity is high. This finding may help upstream firms to better understand how their price changes will translate into retail price adjustments.

The dripping of molten thermoplastics is a widely observed phenomenon in cable and facade fire, where the large drips can often carry a blue chain flame during the free fall to ignite other flammable materials and escalate the fire hazard. This work simulated the flame evolution behind a falling thermoplastic drip with the DNS model and finite-rate flame chemistry. The accelerated free-fall of drip was modeled by fixing the position of drip, increasing the upward airflow, and setting a fuel jet on the top of the drip. Modeling reproduces the dripping flame and reveals the flame shedding to be a combination of a lifted flame and a vortex street, where the lifted flame caused by the gravity acceleration of drip is identified as the critical factor that governs the shedding formation. As the diameter of drip decreases, the falling drip becomes difficult in forming a stable shedding structure in the wake region, so that the dripping extinction occurs due to the dilution and cooling of airflow, agreeing well with the experimental observation. This work reveals the underlying mechanism of stabilizing the dripping flame and helps evaluate the fire risk and hazard of dripping phenomena.

The impingement of a droplet on a rigid square obstacle in a microchannel is simulated numerically using a high-density-ratio pseudo-potential multi-relaxation time LBM. The effects of Reynolds (Re) number, Weber (We) number, contact angle, obstacle size and kinematic viscosity ratio on the droplet dynamics after impact are investigated. It was found that the formation of the liquid film around the obstacle, the expansion of the droplet and its rupture time are all affected by these factors. As the Re number increases, the process of droplet falling along the obstacle is faster and the droplet demonstrates a more intense dynamic behavior. Increasing the We number makes the liquid film around the obstacle thinner and more stretched. Hydrophilicity and hydrophobicity of the obstacle surface play a major role in its surface wetting. For the hydrophobic obstacle wall, the separated sub-droplets move more rapidly toward the channel walls. As the hydrophobicity increases, the small droplet left on the upper surface of the obstacle will bounce upward. The bouncing tendency increases as the kinematic viscosity ratio decreases. As the obstacle size increases, the droplet expands more around it and approaches the channel walls faster.

To promote better sleep, we designed a motion mattress producing slow and swaying movements by slow regional changes of height generated by 10 separated air cells underneath. The motion induces a stretching movement and a gentle swaying movement of the user’s body. In this study, we examined its sleep-improving effects. Subjects who were not fully satisfied with their sleep were recruited. The study was performed for three periods, each of which was a week with a distinct condition. The first period was assigned as pre-experimental (PRE) period when the subjects sleep using their own mattress. The other two periods were assigned as motion mattress active (MM1) period and motion mattress control period. All subjects were randomly divided into two groups for a cross-over study. The subjects recorded electroencephalograms at home for themselves during these 3 weeks. Subjects were asked to perform sleep questionnaires. We examined the effects of this motion mattress at home by measuring the subjective and objective sleep parameters of 11 subjects. As for the objective sleep parameters, Sleep efficiency, NREM sleep stage 3, and awakening index significantly improved during MM1 compared with PRE (p

We may be suddenly forced to use crutches when having injuries to our legs, and, at that time, are often unfamiliar with the use of the crutches. To prevent secondary accidents that are caused by the lack of the patient’s knowledge of using crutches, the authors proposed a training device with pendulum-mechanism that may have a trainee suffer a falling by providing an external torque to the trainee’s body. It is expected to present a sense to be falling and to perturb the crutch walking motion by swinging a motor-driven pendulum weight. Thus, patients will acquire an ability to cope with falling by the use of the proposed system. In this paper, it was clarified that the pendulum device was effective for tilting the crutch moreover with any weight masses through experiments. In addition, it is also confirmed that it succeeds in perturbing the walking motion of the participants.

The falling ice (snow) radiative effects (FIREs) have previously been shown to contribute substantially to reduced discrepancies in simulations of present-day climatology of radiation, skin temperatures and sea ice concentration and thickness over the Southern Ocean. This study extends to examine the impacts of FIREs on simulation of sea ice changes under a scenario of gradual increase of atmospheric CO2 concentration. We perform a pair of sensitivity experiments including (CESM1-SoN) and excluding (CESM1-NoS) FIREs using Community Earth System Model version 1. The differences in the annual and seasonal means between the initial and warmer periods are examined. Relative to CESM1-SoN, CESM1-NoS simulates more surface reflected shortwave and less downward longwave radiative warming, as well as colder surface temperature, resulting in larger annual-mean sea ice extent and thickness and slower seasonal and long-term sea ice melting and thinning. Over the Southern Ocean of CESM1-SoN, reduced downwelling longwave radiation in austral winter (June-July-August: JJA) leads to sea-ice growth with colder skin temperature while reduced net radiation resulting from increased shortwave reflection in austral summer reduces the melting of sea ice with little change in skin temperature. CESM1-NoS shows seasonal and long-term trends similar to those in CMIP5 models that exclude FIREs, hinting slower future warming-driven changes and larger amplitude of the annual cycle in sea ice concentration and thickness. The ice-free Southern Ocean in peak melting season is simulated at approximately year 130 for CESM1-NoS but year 100 for CESM1-SoN, about 30 years later than that of the Arctic.

The incidence of fall-related hip fractures in old patients aged over 85 years was reported to be higher than that in old patients aged between 65 and 84 years; however, there are no known studies that reported differences of these age groups with respect to the falling situation.This study investigated the association between age and falling direction in patients with hip fractures.This study analyzed the medical records of older patients with fall-related hip fractures who were hospitalized in 2011-2018. Demographic (sex, age, and body mass index, BMI), medical and clinical (body mineral density, type of fracture, and cognitive function), and lifestyle variables (use of assistive device for locomotion and place of residence) and characteristics of falling (direction and location) were extracted. These were compared between the patients aged between 65 and 84 years (65-84 group) and over 85 years (85+ group). Multivariable logistic regression analysis was conducted to investigate associations with each falling direction (forward, sideways, and backward) with other variables.Compared with the 65-84 group, the proportion of hip fractures due to sideways falls was lower in the 85+ group (P 0.05) while the proportion of hip fractures due to backward falls was higher in the 85+ group. The multivariable logistic regression analysis showed the sideways and backward falling were only associated with the age group.These results suggested that the falling direction was associated with age but not with other variables investigated in this study in older patients with hip fractures.HINTERGRUND: Es ist bekannt, dass die Inzidenz von sturzbedingten Hüftfrakturen bei Patienten ab 85 Jahren höher ist als bei Patienten im Alter zwischen 65 und 84. Uns ist jedoch keine Studie bekannt, die den Unterschied zwischen diesen Altersgruppen bei der konkreten Situation des Sturzes zum Thema hat. ZIEL: Unser Ziel war es, den Zusammenhang zwischen Alter und Richtung des Sturzes bei Patienten mit Hüftfrakturen zu untersuchen.Diese Studie analysiert die medizinischen Aufzeichnungen älterer Patienten mit sturzbedingten Hüftfrakturen, die in den Jahren 2011–2018 im Krankenhaus aufgenommen wurden. Demographische Variablen (Geschlecht, Alter und Body-Mass-Index, BMI), medizinische und klinische Variablen (Körpermineraldichte, Art der Fraktur und kognitive Funktion), Lebensstilvariablen (Verwendung von Hilfsmitteln zur Fortbewegung und Wohnort) sowie Sturzmerkmale (Richtung und Ort) wurden dafür extrahiert. Anschließend wurden diese zwischen zwei Gruppen, Patienten im Alter zwischen 65 und 84 (Gruppe 65–84) und Patienten über 85 (Gruppe 85+) Jahren verglichen. Schließlich wurde eine multivariable logistische Regressionsanalyse durchgeführt, um Assoziationen zwischen der Fallrichtung (vorwärts, seitwärts und rückwärts) und anderen Variablen zu untersuchen.Verglichen mit der Gruppe 65–84 war der Anteil der Hüftfrakturen infolge seitlicher Stürze in der Gruppe 85+ niedriger (p 0,05), während der Anteil der Hüftfrakturen infolge von Rückwärtsstürzen in der Gruppe 85+ höher war. Die Regressionsanalyse zeigte, dass der Seitwärts- und Rückwärtssturz jeweils nur mit der Altersgruppe assoziiert war.Diese Ergebnisse legen nahe, dass die Fallrichtung mit dem Alter assoziiert ist, aber nicht mit den anderen Variablen, die in dieser Studie über ältere Patienten mit Hüftfrakturen auch untersucht wurden.

Changes in EEG spectral characteristics during periods of recovery of performance in a psychomotor test during spontaneous short-term periods of waking in daytime sleep were studied in 17 healthy subjects. The test consisted of two sequentially alternating tasks: to count from 1 to 10 silently accompanied by synchronized pressing of a button, and silent counting only. The monotonous nature of the test led to a rapid decline in the level of consciousness and, in most cases, induced falling asleep. Presses serves as a behavioral indicator of the recovery of cognitive processes inhibited during sleep. Situations with small (2–5) and relatively large (6–10) numbers of button presses were compared. The start of pressing was preceded by the appearance of generalized α rhythm, which decreased during performance of psychomotor activity. The power of this rhythm was always greater in longer periods of observed behavioral activity. The end of pressing returned α-power indicators to levels seen before waking. The EEG α rhythm in decreased consciousness during short-term waking evidently characterized the action of the thalamocortical activatory mechanism and was a necessary condition for motor interaction of the body with the external environment. The absence of any differences in the frontal areas at the initial stage on performance of short-lived activity and longer-lasting activity, approaching performance of the complete cycle of presses, suggested that they are involved to the same extent during this period regardless of the number of presses. This result may provide indirect support for the notion that the observed psychomotor activity, even with a small number of presses, is not automatic and unconscious but is accompanied by reduced and fragmented consciousness.

In the present study, the effect of peak occurrence time and flood duration on the scour around the bridge pier installed in a sharply bended channel was investigated. For this purpose, several simple single-peaked hydrographs with the same durations and different peak occurrence times were produced in laboratory. In addition, hydrographs having two consecutive peaks with a steady flow discharge at the first peak and an unsteady-flow discharge at the second peak and vice versa were investigated. The flow velocity range began from incipient motion conditions and steeply increased to live bed conditions. In each experiment, the temporal variations of the maximum local scour depth were measured. In single-peaked experiments, by increasing hydrograph duration from 25 to 100 min, the maximum scour depth increased by 20%, and the progression of sediments along the downstream straight path increased by 150%. For hydrographs with two non-equal and the same duration peaks, at a constant discharge for the first peak and a decrease in the second peak discharge from 70 to 60, 50, and 45 (L s−1), the volume of the scour hole around the pier was decreasing 15, 40, and 60%. Its area fell by 10, 40, and 55%, respectively. When the rising and falling limb time of hydrographs were equal, the maximum sedimentation height increased by 2.7, 3.5, and 5 times, respectively by increasing test duration from 25 to 50, 75, and 100 min.

Effects of the flow pattern of intertubular liquid film on mass and heat transfer synergies in a falling-film dehumidification system with horizontal pipes are studied. A flow model of the dehumidifying solution between horizontal pipes is established using Fluent software, the rule of transitions of the flow pattern between pipes is studied, critical Reynolds numbers of flow pattern transitions are obtained, and the accuracy of the model is verified by experiments. The mass transfer synergy angle and heat transfer synergy angle are respectively used as evaluation criteria for the mass transfer synergy and heat transfer synergy, and distribution laws of the synergy angles for droplet, droplet columnar and curtain flow patterns are obtained. Simulation results show that the mass transfer synergy angles corresponding to droplet, droplet columnar and curtain flow patterns all rise to a plateau with time. The mean mass-transfer synergy angle is 98° for the droplet flow pattern, higher than 96.5° for the droplet columnar flow pattern and 95° for the curtain flow pattern. The results show that the mass transfer synergy of the droplet flow pattern is better than that of the droplet columnar flow pattern and that of the curtain flow pattern.

PURPOSE: Intra-limb and muscular coordination during gait are the result of the organisation of the neuromuscular system, which have been widely studied on a flat terrain. Environmental factors, such as the inclination of the terrain, is a challenge for the postural control system to maintain balance. Therefore, we hypothesised that the central nervous system flexibly modifies its control strategies during locomotion on slopes. METHODS: Ten subjects walked on an inclined treadmill at different slopes (from - 9° to + 9°) and speeds (from 0.56 to 2.22 m s-1). Intra-limb coordination was investigated via the Continuous Relative Phase, whereas muscular coordination was investigated by decomposing the coordinated muscle activation profiles into Basic Activation Patterns. RESULTS: A greater stride to stride variability of kinematics was observed during walking on slopes, as compared to walking on the level. On positive slopes, the stride period and width present a greater variability without modification of the time-pattern of the muscular activation and of the variability of intersegmental coordination. On negative slopes, the stride width is larger, the variability of the stride period and of the inter-segmental coordination is greater and the basic activation patterns become broader, especially at slow speeds. CONCLUSION: Our findings suggest that the control strategy of downhill walking corresponds to a more conservative gait pattern, which could be adopted to lower the risk of falling at the cost of a greater energy consumption. In uphill walking, where metabolic demands are high, the strategy adopted may be planned to minimise energy expenditure.

Moziyan is an area containing unstable rock masses located in Hechuan District, Chongqing, China and has constantly seen group-occurring rockfalls since 1964. The present study aims to investigate the damage of Moziyan rock mass and protect the mining areas and residential areas from rockfall phenomenon. Mohr–Coulomb model in FLAC–3D Program was built to find out the rockfall initiation position. RocFall program has been used to calculate the distribution curves of stopping positions, bounce height, total kinetic energy, and translational velocity of the falling blocks varying with horizontal distance. According to the simulation results, the stability of Moziyan rock mass is controlled by the unloading cracks behind the slope, and the falling blocks have a maximum bounce height and maximum total kinetic energy of 0 m and 2720.9 kJ respectively at the horizontal position of 461.6 m, where proper protection measures should be adopted to minimize the risk of the damage of the Moziyan rock mass. Conclusively, the results of simulation indicate that a barrier of 3 m height and 3000 kJ absorption capacity is enough to resist the falling stones with a maximum speed of 13.2 m/s at the horizontal position of 461.6 m.

Older adults with type 2 diabetes mellitus (DM) have high incidence of falls. The aim of this study was to compare sensorimotor functions, balance, mobility, fear of falling, and fall history in older people with DM (with and without neuropathy) and non-diabetic healthy controls. We enrolled 153 participants aged 50–70 years: 51 people with diabetic peripheral neuropathy (D-PN), 52 with diabetes without neuropathy (D-noPN), and 50 healthy controls (HC). Participants completed a fear of falling assessment and detailed test battery comprising sensorimotor functions, lower limb strength, contrast vision, reaction time, balance, and mobility from which a composite physiological fall risk score (PFRS) was derived. In addition, a fall history of the past 3 months was recorded. Post hoc comparisons of ANOVA test revealed the D-PN had significant deficits than the other two groups in tests of lower limb sensation, knee extension strength, reaction time, postural sway, one leg standing, sit-to-stand and the timed up and go test. The D-PN had the highest fear of falling (30.18 ± 6.75) and the highest PFRS (1.68 ± 1.13). PFRS for the D-noPN (0.74 ± 0.80) was intermediate between HC (0.49 ± 0.96) and DP-N groups. Thirty-four D-PN participants (66.7%), 19 D-noPN participants (36.5%), and 7 HC (14.0%) reported one or more falls in the past 3 months (Chi2 test for trend = 28.1, df = 2, p

When we imaginatively picture what might happen, we may take what we imagine to be either realistic or fantastic. A wine glass falling to the floor and shattering is realistic. A wine glass falling and morphing into a bird and flying away is fantastic. What does the distinction consist in? Two important necessary conditions are here defined. The first is a condition on the realistic representation of spatial configuration, grounded in an account of the imagistic representation of spatial configuration. The second is a condition on the manner in which realistic courses of mental imagery may be grounded in remembered perceptions. This is defined in terms of an account of the representation of comparative similarity.

A 59-year-old man presents with left shoulder pain after falling while playing with his dog at the park. He drove himself to the emergency department (ED). He reports 5/10 pain and has reduced range of motion of the shoulder. His shoulder looks normal on exam and is not squared off. You wonder if he might have a posterior shoulder dislocation.

Several studies use force sensitive resistors (FSR) to compute gait and balance parameters related to falls without investigating the number of sensor units required to produce useful information. We propose a model with minimal sensors for an instrumented insole by investigating and optimizing the location and variety of sensors required to efficiently detect people at risk of falling. Datasets previously recorded on twelve Parkinson’s disease (PD) participants (67.7 ± 10.07 years), nine healthy elderly (66.8 ± 8.0 years) and ten young healthy adults (28.27 ± 3.74 years) were used in this study. We compared the datasets obtained from the use of four FSRs with those of three, two, one and no FSR; each set was combined with an inertial measurement unit (IMU). During the walking activity, the risk of falling scores from four FSRs and IMU (acceleration in y-axis only) were not significantly different compared with two FSRs and IMU (p > 0.05), whereas significant difference was found for three FSRs and IMU and one FSR and IMU (p 0.05). We concluded that it is feasible to estimate the risk index after reducing the number of sensing units from four to two FSRs during walking test and from four to three FSRs during sit-to-stand and stand-to-sit tests. The FSRs should be placed at strategic positions to avoid information loss.

The use of critical slowing down as an early warning indicator for regime switching in observations from noisy dynamical systems and models has been widely studied and implemented in recent years. Some systems, however, have been shown to avoid critical slowing down prior to a transition between equilibria (Ditlevsen and Johnsen, Geophysical Research Letters, 37(19), 2010; Hastings and Wysham, Ecol Lett 13(4):464–472, 2010). Possible explanations include a non-smooth potential driving the dynamic (Hastings and Wysham, Ecol Lett 13(4):464–472, 2010) or large perturbations driving the system out of the initial basin of attraction (Boettiger and Batt 2020). In this paper, we discuss a phenomenon analogous to critical slowing down, where a slow parameter change leads to a high likelihood of a regime shift and creates signature warning signs in the statistics of the process’s sample paths. This effect, which we dub “critical speeding up,” is demonstrated using a simple population model exhibiting an Allee effect. In short, if a basin of attraction is compressed under a parameter change then the potential well steepens, leading to a drop in the time series’ variance and autocorrelation; precisely the opposite warning signs exhibited by critical slowing down. The fact that either falling or rising variance / autocorrelation can indicate imminent state change should underline the need for reliable modeling of any empirical system where one desires to forecast regime change.

For a model of decaying dark energy with a fermion (τ-lepton), additional corrections to the classical estimate of the time of falling of particles into a static uncharged black hole in Kramer’s coordinates have been obtained, along with corrections to the Kruskal coordinates determined by a prescribed velocity functional of the fifth dimension.

Arboreal habitats are characterized by a complex three-dimensional array of branches that vary in numerous characteristics, including incline, compliance, roughness, and diameter. Gaps must often be crossed, and this is frequently accomplished by leaping. Geckos bearing an adhesive system often jump in arboreal habitats, although few studies have examined their jumping biomechanics. We investigated the biomechanics of landing on smooth surfaces in crested geckos, Correlophus ciliatus, asking whether the incline of the landing platform alters impact forces and mid-air body movements. Using high-speed videography, we examined jumps from a horizontal take-off platform to horizontal, 45° and 90° landing platforms. Take-off velocity was greatest when geckos were jumping to a horizontal platform. Geckos did not modulate their body orientation in the air. Body curvature during landing, and landing duration, were greatest on the vertical platform. Together, these significantly reduced the impact force on the vertical platform. When landing on a smooth vertical surface, the geckos must engage the adhesive system to prevent slipping and falling. In contrast, landing on a horizontal surface requires no adhesion, but incurs high impact forces. Despite a lack of mid-air modulation, geckos appear robust to changing landing conditions.

Biped robots are expected to be able to work in complex environments. However, these robots will inevitably fall at times and such falls may cause injury to the robot itself or to people nearby. Therefore, it is necessary to detect that the robot is falling to be able to warn the robot in sufficient time when it is about to fall and to switch its controller to protect the vulnerable parts of the robot. Modeling and analysis of the biped robot falling problem cannot be fully accurate and many current learning-based methods rely on large quantities of fall data that are difficult to use to train fragile robots. A machine learning-based fall detection method is therefore proposed in this paper. This method requires only a small amount of training data to obtain good fall detection, making the training process on the robot platform much safer. A support vector machine is used to determine the state of the robot and the decision boundary of the stable state is updated during motion to enable the classifier to match the motion capability of the robot.

Labyrinth weirs are often a favorable design option for regulating the water surface level in irrigation channels and increasing the spillway discharge capacity of dams. Sedimentation in irrigation channels and around related hydraulic structures such as weirs and turnouts is a common problem that causes disruption in operation. In this research, the effects of upstream sedimentation levels (non-sedimentation, S= 30, 60 and 90% of P=weirs’ height) and downstream bed levels on hydraulic performance of trapezoidal labyrinth weirs with various cycle’s geometries were investigated experimentally. The result showed that increase of S up to 60%P did not have a significant effect on the discharge coefficients and related total upstream head labyrinth weirs but further increase of S to 90%P reduced the discharge coefficient of weirs 15% approximately. Comparison of results indicated that for S up to 60%P, reduction of cycle number and its length in flow direction decreased the weirs’ discharge coefficients. However, by increasing S to 90%P, reduction of the apex angle of cycles and increase of the length of weirs in flow direction decreased the discharge coefficients of weirs. Analysis of results indicated that increase of tailwater level to two-thirds of P changed the flow pattern of falling nappe and the discharge coefficients of weirs changed significantly especially at high flow discharges. Finally, statistical equations were developed for estimation of the discharge coefficient of the trapezoidal labyrinth weirs for different upstream sedimentation levels and tailwater levels.

The formation and dynamics of a single drop of liquid under the influence of gravity can be experienced as everyday phenomena, and have been the subject of scientific investigations since at least the work of Leonardo da Vinci in the early 1500s and Mariotte in the 1680s. Experiences with liquid drops in everyday life are captured by poets and artists as well as scientists, whose theoretical and experimental investigations develop fundamental understanding of drops with size 107 m. This paper presents observations of the formation of a single liquid drop of molten steel following bursting of a liquid film formed by illuminating a steel plate by a high energy laser. The hole morphology is analyzed with a proposed kinematic model of hole expansion for the very early stages in the bursting of the hole. Estimates of the hole eccentricity, area, perimeter, and circularity obtained from the model are presented and discussed. Experimental measurements show that a single drop of liquid steel detaches from the end of a neck that then cools to room temperature. Measurements also show that the liquid drop oscillates while falling under gravity. No satellite drops are observed.

Fractures associated with electrical injury are mainly caused by high voltage electricity. Electricity is able to damage tissue in many ways such as direct mechanical injury, heat production by the current, and muscle contraction. Spinal column fractures due to direct electrical shock are seen very rarely. When it is seen, it is mainly caused by a secondary event such as, falling after the shock. In this article, we presented a 49-year-old man who suffered from a very irritating low back pain after an accidental electrical shock. Investigations showed 12th thoracic compression fracture. Patients who apply to hospital, complaining about severe pain and with a history of electrical injury, have to be examined very detailed and required imaging have to be done to rule out the correct diagnosis.

Falling film liquid desiccant dehumidification technology is attracting more and more attention due to lower energy consumption, less pollution, and more flexible humidity control in recent years. This paper conducts a comprehensive review on falling film liquid desiccant dehumidification systems. Firstly, the working principles and features of the liquid desiccant dehumidification are introduced to describe the dehumidification process. The existing liquid desiccants including organic and inorganic desiccants are reviewed. Then, the structures of falling film dehumidifiers including both adiabatic dehumidifiers and internally-cooled dehumidifiers are described. Besides, the simulation models of falling film dehumidifiers, such as finite difference models, effectiveness NTU (e-NTU) models and simplified simulation models are summarized. Finally, the exiting performance enhancing methods of falling film dehumidifiers are collected, which provide valuable guidance to researchers and engineers to improve the dehumidification performance.

The temporal development of scour at both the side and the front of circular bridge piers is studied under clear-water conditions with artificially generated, linearly rising and falling, asymmetric triangular-shaped hydrographs categorized as highly unsteady with relatively short rising durations. The base flow conditions are kept well below the conditions for scour inception so as to investigate the hysteresis in initialization of the scour. A conceptual model consisting of an S-shaped time–depth relationship is generated, and actual and effective time of scour inception, duration and finalization parameters are defined. Both the effective and the actual time of scour inception decreased with increasing unsteadiness, either at the side or at the front nose of the piers; however, scour finalization does not depend on the hydrograph unsteadiness The effect of flow deceleration during the falling phase of the hydrograph on scouring was weaker than the effect of flow acceleration during the rising phase. A five-step procedure is proposed involving the calculation of (1) the densimetric Froude number corresponding to effective scour inception at piers side, (2) the final scour depth at piers side, (3) and at the front nose, (4) the exponent n and finally (5) the scour depth time evolution for both side and front nose of the piers. The method is verified both by experimental and literature data.

Objectives Threats to balance, and subsequent increases in fall-related anxiety, can disrupt attentional processing during gait in older adults, leading to behavioral adaptations which may increase fall risk. However, limited research has investigated what changes in attention occur to contribute to these disruptions. The aim of this research was to describe changes in attention that occur during gait when older adults’ balance is threatened, while exploring how previous fall history and trait movement reinvestment (conscious monitoring and control of movement) also influence attention. Methods Forty older adults reported where they focus their attention when walking during two scenarios: (1) when they are relaxed and there is little risk of falling, and; (2) when their balance is threatened and they are anxious of falling. Results During the high-threat condition, participants reported greater attention towards movement processes, threats to balance, worries/disturbing thoughts and self-regulatory strategies, with less attention directed towards task-irrelevant thoughts. However, fall history influenced attentional focus, with fallers directing greater attention towards worries/disturbing thoughts. Contrary to predictions, trait movement reinvestment was not associated with attention directed towards movement processes. Discussion As processing worries/disturbing thoughts will likely reduce attentional resources available for effective postural control, we highlight this as one potential area to target interventions aimed at reducing the likelihood of repeated falling.

Rock sizes and shapes influence the trajectories of rockfall. Thus, this study examined the bounce height and runout distance of falling rocks on the basis of different rock sizes, rock shapes, and ground surfaces. A laboratory experiment of rocks with various sizes falling from 35°, 45°, and 60° slope angles and vertically on different ground surfaces was conducted in this study to understand the mechanism of falling rocks. RocFall 5.0 (Rocscience), a 2D rockfall numerical simulation program, was used to perform the probable bounce height and runout distance for various rock shapes on different ground surfaces. The laboratory experiment and a numerical simulation were compared to validate the applicability of laboratory testing in rockfall assessment and calibrate the coefficient of restitution, which is a critical parameter in bouncing blocks. Results indicated that steep slopes and hard ground surfaces cause a high bounce height of falling rocks. Moreover, light rocks bounce higher than heavy rocks, and rocks with round shapes bounce high initially and then roll further away from the falling slope. Therefore, the influence of rock sizes and shapes and impact surface material must not be omitted in investigating rockfall protective measures.

The weakness of the lower leg muscles due to nerve damage or muscle weakness can result in foot drop, a change in gait that manifests as an inability to lift the toes of the foot when walking. Foot drop results in a decreased quality of life, with unassisted movement becoming difficult or impossible. The increased risk of falls is particularly problematic as foot drop often affects the elderly or infirm for whom falling already presents a great danger. Current treatment options include fixed ankle–foot orthosis (AFO) aiming to provide rigid support to the foot if the impairment is mild or surgical intervention and functional electrical stimulation (FES) devices if the weakness is more severe. FES intervention is effective for providing a non-invasive treatment in even severe cases of foot drop. Limitations of current models relate to the non-naturalistic recreation of gait in the affected leg and its unsuitability for patients with extensive peripheral nerve damage. Although there are attempts to enhance integration of sensory information and mimic natural stimulation patterns, the focus on restoring a natural feedback loop is still amiss. Without such a closed loop feedback, restoration of a natural gait pattern is unlikely to occur. We here recommend, integration of motor output from multiple muscles, information about the inputs from higher-order controllers, recorded from the intact leg with a closed loop system to improve the effectiveness of FES.

Simulation methods that can overcome the limitations of theory and experiment are widely used to predict disaster situations and analyze evacuation safety. To obtain more accurate and realistic simulation results, various situations that arise when people evacuate must be reflected. In this research, regression analysis is applied to existing research on walking speed changes according to crowd density, and we suggest a new equation for walking speed changes of people during evacuation. The suggested equation is applied to crowd evacuation simulations based on the actual viewing angle of a person. In addition, we developed a fallen person algorithm and applied it to examples from the Society of Fire Protection Engineers (SFPE) to analyze the effect a fallen person has on evacuation. Through this research, evacuation safety analysis can be performed for cases involving falling people, and it will be possible to design buildings that can minimize risk and evacuation time in case of an actual emergency situation by analyzing the optimum measures more strictly.

Rockfall often collides with the slope during the movement on a slope surface, and the energy dissipation of rockfall collision is used to quantify by the coefficient of restitution (COR) in analysing rockfall trajectory. The coefficient of restitution is one of the most crucial parameters in analysing rockfall hazard, and it can be obtained by field test or laboratory test. The main motion modes of rockfall on the slope are rolling, impact and bounce, and rockfall has angular velocity when it collides with the slope. To study the COR of rotational rockfall, a special experimental equipment is designed to simulate the process of motion and impact of rockfall, which consists of a rolling slope, an impact slope and steel pipe scaffolding. Spherical blocks made of concrete are rolled down from the rolling slope and then fall freely to collide with the impact slope. The trajectories of the spherical blocks are then recorded with a high-speed camera. Four main factors affecting the COR of rockfalls were studied in this paper. The results show that the sandy soil thickness of slope has significant on the COR of rotational rockfall. As the sandy soil thickness increases, normal COR first decreases and then increases, while vertical COR first increases and then decreases. Based on the ratio of the sandy soil thickness to the spherical block diameter, a method for calculating normal and tangential CORs is proposed. The correlation between the COR and the impact angle is very apparent. A mutual conversion between rotational and translational kinetic energy occurs during the collision. There are complex mass effects and falling height effects on the COR.

Mixing and segregation of binary mixtures of freely-falling grains are demonstrated in a cylindrical pipe with an obstacle. Previously, the same setup was used to spatially focus monodisperse granular materials. As each grain is dropped one at a time from a random position at the entrance of the cylindrical pipe, it may collide with a steady or oscillating obstacle and the wall. We performed a time-driven multi-scale simulation and use Routh’s impact model for collisions to show that the focusing of grains for monodisperse granular materials is dependent on the geometry of the pipe, the elastic properties of the grain, and the amplitude of oscillation of the obstacle. For binary granular mixtures, segregation may be achieved when the elastic properties of the grain species have a big difference. However, the efficiency of segregation is diminished when the amplitude of obstacle oscillation is increased, leading to granular mixing. Just as a high degree of segregation can be attained with a stationary obstacle, a high degree of mixing can be obtained with a moving obstacle.

Free-falling paper shapes exhibit rich, complex and varied behaviours that are extremely challenging to model analytically. Physical experimentation aids in system understanding, but is time-consuming, sensitive to initial conditions and reliant on subjective visual behavioural classification. In this study, robotics, computer vision and machine learning are used to autonomously fabricate, drop, analyse and classify the behaviours of hundreds of shapes. The system is validated by reproducing results for falling discs, which exhibit four falling styles: tumbling, chaotic, steady and periodic. A previously determined mapping from a non-dimensional parameter space to behaviour groups is shown to be consistent with these new experiments for tumbling and chaotic behaviours. However, steady or periodic behaviours are observed in previously unseen areas of the parameter space. More complex hexagon, square and cross shapes are investigated, showing that the non-dimensional parameter space generalizes to these shapes. The system highlights the potential of robotics for the investigation of complex physical systems, of which falling paper is one example, and provides a template for future investigation of such systems. The dynamics of paper shapes in free fall are still not fully understood, despite being discussed for more than 150 years. Collecting large amounts of data has the potential to give us new insights and a robotics system could generate and analyse data in large quantities.

Flow visualization and particle image velocimetry are applied to capture the flow fields generated by all three states of a falling plate in two dimensional passive flight—fluttering, chaotic, and tumbling. The vortical structures are recorded in considerable clarity. Classic vortex shedding from different flight states are observed. The causes of more energetic tumbling mixing and localized fluttering disturbances are discussed. Strong, but small trailing processions of Karman vortex pairs or Kelvin–Helmholtz instabilities are found. It is also found that their formations are dependent on the trajectory, distinguishing the unique flow structures that different flight paths leave behind. The falling plate also induces a significant downwards convective motion. Further investigation shows that the wake trail and the convection contribute to the complex formation and dissipation of large vortical structures.

The interaction between two falling droplets in the liquid–liquid two-phase flow has been investigated in detail with the aids of the index matching technique and PIV. It has been almost impossible to measure or even visualize the multiple phases simultaneously. This is because of the difference in the refractive indices of each phase. In this study, the refractive index of the water phase has been equalized to that of the oil phase by adjusting the concentration of the aqueous solution of glycerol and thus the simultaneous visualization of both phases and also the PIV measurement have been carried out. Presently, the interaction between two falling droplets has been intensively investigated. The interaction between two solid particles has been well known by the name of drafting–kissing–tumbling (DKT) motion. Similar motion to DKT is also observed for the droplets, which are found not to really kiss. It is found that the flows inside of the droplets are also affected by the interaction between two droplets while one droplet overtakes the other. The conditions for the initial relative positions of the two droplets to overtake have been summarized. It has been made clear that the chasing droplet is pulled by the wake of the preceding droplet.

BACKGROUND: Falling is a significant concern for many elderly adults but identifying individuals at risk of falling is difficult, and it is not clear how elderly adults adapt to challenging walking. AIMS: The aim of the current study was to determine the effects of walking at non-preferred speeds on the coordination between foot and trunk acceleration variability in healthy elderly adults with and without fall history compared to healthy young adults. METHODS: Subjects walked on a treadmill at 80% to 120% of their preferred walking speed while trunk and foot accelerations were recorded with wireless inertial sensors. Variability of accelerations were measured by root mean square, range, sample entropy, and Lyapunov exponent. The gait stability index was calculated using each variability metric in the frontal and sagittal plane by taking the ratio of trunk acceleration variability divided by foot acceleration variability. RESULTS: Healthy young adults demonstrated larger trunk accelerations relative to foot accelerations at faster walking speeds compared to elderly adults, but both young and elderly adults show similar adaption to their acceleration regularity. Between group differences showed that elderly adult fallers coordinate acceleration variability between the trunk and feet differently compared to elderly non-fallers and young adults. DISCUSSION: The current results indicate that during gait, elderly fallers demonstrate more constrained, less adaptable trunk movement relative to their foot movement and this pattern is different compared to elderly non-fallers and healthy young. CONCLUSIONS: Coordination between trunk and foot acceleration variability plays an important role in maintaining stability during gait.

This paper uses a classical one-dimensional single-DOF model of the falling U-chain as an analytical paradigm for the assessment of a recursive modular modeling methodology, in which constraints can be enforced a posteriori. A two-dimensional nonlinear FEM model for the falling of an inextensible folded string is derived, and a numerical simulation is compared with the adopted paradigm. The proposed model not only reproduces with great accuracy the results obtained from the analytical paradigm, but also shows interesting features of this strongly nonlinear problem that might not be revealed by classical single-DOF models.

Bodies freely falling in steady water or air are common scenes encountered in various scientific and engineering fields, including the flapping flight of birds and the reentry of a space shuttle. In this work, the freely falling annular thin disks with small dimensionless moments of inertia I* and Reynolds number Re are investigated experimentally in a water tank. We use stereoscopic vision to record the position and orientation of the disks. The flow structure behind the disks is studied by applying fluorescent dye visualization and PIV method. Varying the geometry dimensionless parameter (the inner to outer diameter ratio η and I*) of the disks reveals two new falling patterns. When ηcrit1=0.6 0.8, the circular vortex loops shed frequently from the disk, which causes a lengthways vibration superimposed onto straight vertical motion. We also observe another two falling patterns reported previously: hula-hoop and helical motion. By comparing the wake structure of the two motions, we find that the vortex layer twists more violently in the hula-hoop motion, which is the reason for the different trajectory between them. Further research on flow field reveals that the torque on the disk that causes the vibration is due to the formation, elongation and shedding of the vortex.

Secularly declining GDP investment shares are often explained by the widespread fall in the relative price of investment goods. Granger non-causality tests applied to longer-term time series for a large number of industrial countries tend to reject that explanation.

© 2018 Springer-Verlag GmbH Germany, part of Springer Nature. The aims of this study were to (1) characterize anticipatory and reactive postural strategies in typically developing (TD) children and adolescents; (2) determine if TD youth shift from reactive to anticipatory mechanisms based on knowledge of platform movement; and (3) determine whether TD youth further modify postural strategies when additional information about the perturbation is provided. Sixteen typically developing youth aged 7–17 years stood with eyes open on a movable platform that progressively translated anteroposteriorly (20 cm peak-to-peak) through four speeds (0.1, 0.25, 0.5, and 0.61 Hz). Participants performed two trials each of experimenter-triggered and self-triggered perturbations. Postural muscle activity (1000 Hz) of the tibialis anterior, gastrocnemius, quadriceps and hamstrings and 3D whole body kinematics (100 Hz) were recorded. The Anchoring Index and marker-pair trajectory cross-correlations were calculated as indications of body stabilization. The number of steps taken to regain balance/avoid falling were counted. Transition states and steady states were analyzed separately. Generally, the higher frequencies resulted in more steps being taken, lower correlations coupled with greater temporal lags between marker trajectories, and postural muscle activity similar to older adults. The provision of self-triggered perturbations allowed participants to make the appropriate changes to their balance by use of anticipatory postural control mechanisms.

Falls are considered as risky for the elderly people because it may affect the health of the people. So, in the recent years many elderly fall detection methods has been developed. In the present years many fall detection method had been developed but it uses only accelerometer sensor to detect the fall. It may fail in finding in the difference between actual fall and fall like activities such as sitting fast and jumping. In the proposed approach I have suggested a fall detection algorithm to detect the fall of elderly people. Daily human activities are divided into two parts such as static position and dynamic position. With the help of tri-axis accelerometer proposed fall detection can detect four kinds of positions such as falling front, front backward, jumping and sitting fastly. Acceleration and velocity is used to determine kind of fall. Our algorithm uses accelerometer and gyroscope sensor to predict the fall correctly and reduce the false positives and false negatives and increase the accuracy. In addition to that our method is made out of low cost and it can be used in real-time.

BACKGROUND: In older adults, musculoskeletal pain is associated with increased concerns of falling, reduced balance and increased occurrence of falls. In younger adults, the intensity of neck pain and low back pain is associated with increased postural sway. It is not known if pain further impairs balance and concerns of falling in mobility-limited older adults, and if so, whether this is associated with different intensities of pain.OBJECTIVE: This study examined whether mobility-limited older adults with mild or intense neck pain and/or low back pain have significantly increased postural sway as measured by centre of pressure (COP) changes and concerns of falling compared to those without pain.METHODS: 48 older adults with a gait speed of 5) neck pain or low back pain.RESULTS: Intense neck pain was associated with increased anterior-posterior sway range and area of sway. Intense low back pain was associated with increased concerns of falling.CONCLUSION: Intense neck pain in mobility-limited older adults is associated with significant changes in postural balance, and intense low back pain is associated with significantly higher concerns of falling.

The aim of this study is to investigate the dynamics of an accelerating skater–board system modeling downhill motion. The governing mathematical model is a system of time-varying neutral delay-differential equations. Stability analysis is performed based on the frozen-time method, and the results are verified via numerical simulations. It is shown that the varying longitudinal speed may result in loss of stability at high speeds, which explains the unpredictable falling often observed at real downhill skateboarding. The positive effect of large longitudinal acceleration on the stability is also demonstrated.

Falling water evaporation cooling could efficiently suppress the containment operation pressure during the nuclear accident, by continually removing the core decay heat to the atmospheric environment. In order to identify the process of large-scale falling water evaporation cooling, the water flow characteristics of falling film, film rupture and falling rivulet were deduced, on the basis of previous correlation studies. The influences of the contact angle, water temperature and water flow rates on water converge along the flow direction were then numerically obtained and results were compared with the data for AP1000 and CAP1400 nuclear power plants. By comparisons, it is concluded that the water coverage fraction of falling water could be enhanced by either reducing the surface contact angle or increasing the water temperature. The falling water flow with evaporation for AP1000 containment was then calculated and the feature of its water coverage fraction was analyzed. Finally, based on the phenomena identification of falling water flow for AP1000 containment evaporation cooling, the scaling-down is performed and the dimensionless criteria were obtained.

Background: In older adults, impaired control of standing balance in the lateral direction is associated with the increased risk of falling. Assessing the factors that contribute to impaired standing balance control may identify areas to address to reduce falls risk. Aim: To investigate the contributions of physiological factors to standing lateral balance control. Methods: Two hundred twenty-two participants from the Pittsburgh site of the Health, Aging and Body Composition Study had lateral balance control assessed using a clinical sensory integration balance test (standing on level and foam surface with eyes open and closed) and a lateral center of pressure tracking test using visual feedback. The center of pressure was recorded from a force platform. Multiple linear regression models examined contributors of lateral control of balance performance, including concurrently measured tests of lower extremity sensation, knee extensor strength, executive function, and clinical balance tests. Models were adjusted for age, body mass index, and sex. Results: Larger lateral sway during the sensory integration test performed on foam was associated with longer repeated chair stands time. During the lateral center of pressure tracking task, the error in tracking increased at higher frequencies; greater error was associated with worse executive function. The relationship between sway performance and physical and cognitive function differed between women and men. Discussion: Contributors to control of lateral balance were task-dependent. Lateral standing performance on an unstable surface may be more dependent upon general lower extremity strength, whereas visual tracking performance may be more dependent upon cognitive factors. Conclusions: Lateral balance control in ambulatory older adults is associated with deficits in strength and executive function.