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In this research, the damage mechanism applied by the projectile at the ballistic tip on the samples during the ballistic test of the samples consisting of different materials with the same wall thickness as the ballistic test was attempted to determine. Free falling low velocity ballistic test was performed in order to compare stainless steel, brass, copper, low carbon steel materials with the same wall thickness section. A jig consisting of sensitive force readings was set up and its principles were established. This study showed that the projectile tip creates a deformation zone as well as the state of absorbing the impact on the material which are possible to determine by sensitive measurements. Stainless steel and Brass showed better performance than low C steel and Copper due possibly to low work hardening property. K, strength coefficient, showed a significant correlation with the results.

Overfall spillways are important hydraulic structures for the release of overtopping water flows downstream of a dam. To reduce the effects of the impact of falling water in plunge pools, an overfall spillway outlet design that produces a longitudinally spreading jet is required. This study examined the effects of a triangular wedge placed at the end of an overfall spillway to deflect the water flow in the lateral direction, making the jet longitudinally diffuse before reaching the plunge pool. Laboratory data on the mean pressure coefficient were used to analyse the effects of various design parameters. An increase in the deflection ratio and a decrease in the weir crest length reduced the jet impact pressure. Compared with the impact of a rectangular jet falling into a plunge pool, an appropriate triangular wedge structure was found to improve the spreading of the impingement jet and reduce the mean dynamic pressure coefficient. By optimising the geometric design to accomplish jet impact control, the results of the present investigation may help engineers to design overfall spillways in high-head dam projects.

For two kinds of specially made enhanced tubes with outer diameters of 19mm and 25mm, the falling film evaporation experiment was carried out by using environmental refrigerant R1234ze (E) under the experimental condition that the water velocity in the tube was controlled from 1 to 3.5 ms−1. "The Wilson-Gnielinski Separation Method" and "The Wilson-Gnielinski-Heat Flux Correction Method" were used to process the experimental data. The comparative analysis showed that when the heat fluxes of all the test points outside the tube were constant, the results of two calculation methods were almost the same. When the heat fluxes of all the test points outside the tube were fluctuant, the results of two calculation methods were different and the heat flux correction method should be applied to reduce the error. The enhanced tube with outer diameter of 19mm was used to investigate the heat transfer performance of falling film evaporation, with spray density ranging from 0.03 to 0.1kgm−1s−1, heat flux ranging from 15 to 45 kWm−2 and evaporation temperature ranging from 0 to 25°C. And the enhancement rate inside the tube was obtained by using the heat flux correction method. Finally, the variation trends of the overall heat transfer coefficient and the outside tube heat transfer coefficient under different working conditions were both obtained experimentally and analyzed theoretically.

Background Postural sway during quiet standing has been shown as a useful task to assess risk of falling in older adults. While the risk of falling is consistently reported to be higher in older females than males, the sex-related differences in postural sway are not consistent across the studies. Research question What are the effects of age and sex on postural sway during quiet standing during different stance conditions? Methods We examined the effects of age (40 young and 34 older adults), sex (37 males and 37 females), and their interaction on the postural sway during different stance conditions. We compared the center of pressure (CoP) velocity, amplitude and frequency during parallel (eyes open and eyes closed) and semi-tandem (eyes open) stances. Results Our results suggest that postural sway is similar between sexes in young participants, while older males exhibit larger postural sway than older female participants (10/21 outcomes). Older female participants exhibited lower CoP amplitude (but larger total and anterior-posterior CoP velocity) compared to young female participants. We also found that the increase in the postural sway with increasing task difficulty is more pronounced in older vs. young adults. Significance This study shows that ageing-related changes in postural sway are sex- and task-specific. Researchers and clinicians need to be aware of these effects when comparing groups or monitoring changes in time.

Accurate description of wind speed probability distribution is an essential part of wind farm planning and dispatching. The two-parameter Weibull distribution is mostly used to fit unimodal wind speed probability distribution, but it suffers from low fitting accuracy and insufficient applicability. To solve these issues of the Weibull distribution, a novel distribution model, Falling Model, is proposed in this paper. In this model, the first Step is to “fall” the empirical wind speed distribution based on the Weibull. Then the probability distribution of falling form is fitted by a Cloud Model after segmentation. Finally, the segmented Cloud Models are superposed with Weibull to build the Falling Model. The goodness-of-fit (GoF) of the Falling Model, Weibull, Burr, and Gamma distributions was compared in a case study, and it showed that the Falling Model had the highest fitting accuracy. The sum of squared error of the GoF is 106 times better than the Weibull. Further, the applicability analysis of the Falling Model was performed using existing literature data, and it found that the Falling Model can be widely applied. The study shows that the unimodal distribution combines the advantages of both the Weibull and several Cloud Models.

The risk of criticality accidents by fuel debris in the decommissioning of Fukushima Dai-ichi Nuclear Power Station is unlikely to be negligible. Therefore, an estimation of the consequences of suc...

Acute, traumatic rotator cuff tears typically occur in younger patients with a fall on an outstretched hand, grabbing an object to catch oneself when falling, or a glenohumeral dislocation. These tears are best evaluated with MRI. Partial-thickness tears may be managed nonoperatively with physical therapy, NSAIDs, and injections. Full-thickness tears in most patients should be managed with surgical repair as soon as possible, with better outcomes shown when repaired within 4 months of injury.

Exoskeletons often allow limited movement of the ankle joint. This could increase the chance of falling while walking, particularly on challenging surfaces, such as lateral inclines. In this study, the effect of a mobility limiting ankle brace on gait stability in the frontal plane was assessed, while participants walked on lateral inclines. The brace negatively affected gait stability when it was worn on the leg that was on the vertically lower side or ‘valley side’ of the lateral incline, which would indicate an increased risk of falling in that direction.

An important health-related problem of obesity is reduced stance stability, leading to increased chance of falling. In the present experiment, we aimed to compare stability in quiet and in dynamic body balance between women with morbid obesity (n = 13, body mass index [BMI] > 40 Kg/m2, mean age = 38.85 years) and with healthy body weight (lean) (n = 13; BMI < 25 Kg/m2, mean age = 37.62 years), evaluating the extent to which quiet and dynamic balance stability are associated with plantar sensibility. Quiet stance was evaluated in different visual and support base conditions. The dynamic task consisted of rhythmic flexion—extension movements at the hip and shoulder, manipulating vision availability. The plantar sensibility threshold was measured through application of monofilaments on the feet soles. The results showed that the morbidly obese, in comparison with the lean women, had higher plantar sensibility thresholds, and a reduced balance stability in quiet standing. Mediolateral stance stability on the malleable surface was strongly correlated with plantar sensibility in the obese women. Analysis of dynamic balance showed no effect of obesity and weaker correlations with plantar sensibility. Our results suggest that reduced plantar sensibility in morbidly obese women may underlie their diminished stance stability, while dynamic balance control seems to be unaffected by their reduced plantar sensibility.

Fall detection techniques for helping the elderly were developed based on identifying falling states using simulated falls. However, some real-life falling states were left undetected, which led to this work on analysing falling states. The aim was to find the differences between active daily living and soft falls where falling states were undetected. This is the first consideration to be based on the threshold-based algorithms using the acceleration data stored in an activity database. This study addresses soft falls in addition to the general falls based on two falling states. Despite the number of false alarms being higher rising from 18.5% to 56.5%, the sensitivity was increased from 52% to 92.5% for general falls, and from 56% to 86% for soft falls. Our experimental results show the importance of state occurrence for soft fall detection, and will be used to build a learning model for soft fall detection.

In this study, we investigate the falling body problem with three different fractional derivatives. We acquire the solutions of the model by the Sumudu transform. We show the accuracy of the Sumudu transform by some theoretic results and implementations.

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

A hypothesis gaining increasing popularity is that laypeople's representations of physical phenomena might be driven by internalized physical laws. In three experiments, we tested if such hypothesis holds true for the representation of gravitational motion. Participants were presented with realistic, real-scale virtual spheres falling vertically downward from about 2 m high. The spheres appeared to be made of either polystyrene or wood. In Experiment 1, participants adjusted the falling motion pattern until it appeared to be natural. In Experiment 2, they compared the perceived naturalness of vertical free falls in a vacuum with the perceived naturalness of more realistic falls characterized by the presence of air drag. In Experiment 3, they estimated the position of the sphere after a variable interval of time from the beginning of the fall. Inconsistently with predictions from physics, results showed that representations of gravitational motion were strongly affected by the implied masses of the falling objects and did not account for air drag. This provides support for the hypothesis of weight-based heuristic representations of gravitational motion against the hypothesis of the internalization of physical laws. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Falling film evaporators consisting of bundles of horizonal tubes are widely used in many applications including refrigeration, chemical processing, desalination, etc. While many experimental studies have been done, as yet there is no well-verified method for the prediction of heat transfer. The research reported here was done to fulfil this need. A correlation is presented for heat transfer before occurrence of CHF which has been verified with a wide range of data from 12 sources. The data include plain and enhanced tubes of many types and materials, diameters 15.9 to 25.4 mm, P/D 1.1 to 2.0, liquid film Reynolds number from 43-6449, and heat flux from 1 to 94 kWm−2. Included are eight diverse fluids (water, halocarbon refrigerants) with reduced pressures from 0.000046 to 0.172. The correlation predicts 2708 data points with mean absolute deviation of 17.4%. The correlation and its verification are presented and recommendations are made for its use.

This study investigates changes in the concentration and types of free radicals in the process of coal heating, first rising and then falling. Hailar lignite, Panjiang bituminous coal, and Yangquan anthracite were selected as coal test samples. The results show that the lignite’s concentration of free radical changes during heating is greater than that of bituminous coal or anthracite. It clearly shows that lignite is more prone to spontaneous combustion. In the heating and cooling portion of the experiment, the concentration of free radicals during the cooling process was much more than that of free radicals at the same temperature during the heating process. These results obtained from this research study can provide a reference for the prevention and control of the spontaneous combustion of coal with changes in temperature. This study provides a theoretical basis for the prevention and control of spontaneous combustion of coal and the selection of retarding agents and methods in the process of flame retarding by testing the free radical changes of coal at different temperatures. Also, it provides a reference for preventing and controlling coal oxidation with the change in temperature, first rising and then falling.

Longtime readers of this column will recall that the proliferation of space debris in near-Earth orbits is an issue that I have previously expressed concern about. Last May, the inevitable happened when a piece of space debris too small to be tracked has hit and damaged part of the International Space Station, namely, the Canadarm2 robotic arm [1] . The object punctured the thermal blanket and damaged the boom underneath, but fortunately, the instrument is still operational [1] .

Рассматриваются способы научного изображения темпоральных явлений на примере чертежей Галилео Галилея, при помощи которых он описывает и исследует равноускоренное движение. Для анализа применяется концептуальная рамка теории изобразительной и неизобразительной репрезентации Грегори Карри. Показано, что в случае научных диаграмм и графиков, представляющих время как одно из измерений пространства, основанием для геометрической изобразимости времени становится полагаемый изоморфизм между временем как континуумом мгновений и линией как континуумом точек. Парадигму такого структурного сопоставления мы находим в математическом мышлении Галилея, наиболее ярко проявляющемся в доказательстве формулы равноускоренного движения, представленном в «Беседах и математических доказательствах». The textbook narrative of the scientific revolution of the 17th century says that the early modern transformation of physics and mechanics was grounded in mathematization, that is, the application of mathematical principles and procedures to physical entities and events. However, such a transformation faces a major obstacle: compared to geometry, mechanics includes an additional dimension, namely, time. When temporality of motion is to be represented geometrically, a question arises on how a temporal succession can be expressed by a static image. The problem of representation of temporal events is not limited to science. In my paper, I apply a conceptual tool elaborated by Gregory Currie for the analysis of temporal representations in art, especially in cinema, to the analysis of scientific diagrams. In his book Image and Mind. Film, Philosophy, and Cognitive Science (1995), Currie distinguishes depictive and nondepictive representations, arguing that depictive representation requires similarity and homomorphism between an object ant its representation. Thus, it seems that any non-temporal image of temporal processes would lack the required similarity and cannot be a depictive representation. However, taking into account explanations given by Galileo Galilei for his famous diagrams of accelerated motion, I argue that the representation of time in scientific diagrams as a geometrical line is grounded in isomorphism between time as a continuous structure and continuous structure of a geometrical line. The main temporal process studied by mechanics is motion. Motion can be represented in two main ways: as a trajectory of a body over some period of time or as a functional relation of various parameters of motion (speed, path, acceleration) versus time. In the latter case, time is usually represented in a diagram as a geometrical line. We can find the origin of this type of representation in the late medieval doctrine of ‘intensio et remissio qualitatum’, intension and remission of qualities, in the context of which first diagrams representing intensity and extension of velocity of nonuniform motion as a changing quality over time were produced (Nicolas Oresme). We can find very similar graphical schemes in Galileo Galilei’s works, especially in Discorsi e dimostrazioni matematiche intorno a due nuove scienze (1638). In this work, Galileo announces with all clarity that he considers time to be the same aggregate of temporal moments as a line is an aggregate of points: every moment of time has a corresponding point on the geometrical line. This allows us to establish a homomorphic similarity between temporal duration and spatial (geometrical) extension. Thus, the essential requirement for depictive representation is met. Concluding, I have to point out that the homomorphic relation in this case is established between not real but abstract entities. The visible line itself is a representation of non-visible abstract geometrical line; in the same way, time consisting of non-divisible moments is just an abstract construction which refers to physical of psychological time-duration. However, the established relation between abstract time and abstract geometrical lines is a grounding event of the modern physical science.

The article suggests the calculation and visualization of motion of the man by opened and closed parachutes. It contains the formulation of the problem, the physical analog and mathematical model of the motion by closed and opened parachutes, the study of the kinematics and dynamics of the motion, the conditions for safe landing. There are graphs of the height versus time of motion and velocity versus height. The graphs show that the man falls down without parachute he reaches the Earth surface with the speed more than 30 m/s or 100 km/h. This is a dangerous descending. Landing is safe when the landing speed is of about u » 5 m/s. Duration of the landing time by the opened parachute is 34 min, and by the closed parachute the landing time is 3 min. The article also presents the calculation and visualization of the parachutist’s motion during free-fall drop when parachute opens in 20 seconds after the free fall start and the graphs of the height versus time and velocity versus height. It is seen from the graphs that at first the parachutist falls down with increasing speed reaching its upper value of about 40 m/s with which he proceeds his falling down within certain duration of time and at the height of 5400 m where the parachute opens the speed of the parachute sharply decreases and then gradually and monotonically reaches its value that enables a safe landing of the parachutist. Results of this study are used in classes on “Theoretical mechanics” and “Simulation of physical processes”.

Images of jumpers represent an emotionally charged symbol of 9/11, yet just after 9/11 their circulation was quickly and dramatically censored. Yet twenty years later, the 9/11 archive continues to...

Fall recovery after falling over is a critical feature for biped robots that work in the real world. We propose a method by considering robot joint angle trajectory as a multivariable function of time and orientation of robot root links. Compared with the conventional method, our method required less time and human effort, as the joint trajectory was autonomously optimized via evolutionary search in a dynamic simulator. In addition, the gap between simulation and real-world experiments could be narrowed by adding push disturbances when performing evolutionary search in the dynamic simulator. Using the proposed method, we successfully realized the fall-recovery feature on life-sized biped robot that was equipped with shell protector CHIDORI-F as depicted in Fig. 1 . Combining the aforementioned fall-recovery feature and previously developed fall-tolerant robot hardware, fall detector and fall-damage-reduction motion, we realized a biped robot platform that could tolerate falling, recover from all the fallen states, and continue working for considerable time without a tether.

Empirical correlations are developed for rewetting velocity and maximum heat transfer coefficient during rewetting phase of single hot vertical Fuel Pin Simulator (FPS) by using radial jet impingement and falling film. Emergency Core Cooling System (ECCS) has been designed for Advance Heavy water Reactor (AHWR) to rewet the hot fuel pin under the loss of coolant accident. Coolant injection takes place from a water rod which is located at the center of the fuel bundle in form of jets to rewet hot surface of fuel pin under loss of coolant accident. This kind of design to reflood the fuel bundle is different than bottom and top spray reflooding practiced in PWR and BWR type of nuclear reactors. There are two different kinds of rewetting found during radial jet induced cooling. The first one is due to radial jet impingement and the second one is due to falling film which is below the jet impingement point. Rewetting velocity has been predicted along the length of fuel pin due to radial jet impingement cooling. Temperature of FPS has been varied from 400°C to 700°C with help of different powers supply, simulating decay heat of reactor. A variation of coolant radial jet mass flow rate is from 0.5 lpm to 1.8 lpm. It is considered during ECCS injection. It has been observed from the experiments that rewetting velocity decreases with increasing the clad surface temperature and increases with increasing the coolant mass flow rate. The rewetting velocity in falling film is found to be nearly 1.8 times higher than rewetting velocity predicted in circumferential direction. Further, it is found that maximum heat transfer coefficient increases with increasing the radial jet coolant mass flow rate. The maximum heat transfer coefficient in case of radial jet impingement is found to be nearly 1.5 times the falling film rewetting. Developed correlation predicts the maximum heat transfer coefficient with experimental data well within the error band of ±10%.

Tsunami generation due to a landslide has been simulated using various numerical models, and the resulting water surface displacements from the models, as well as the corresponding experimental data, are compared. The numerical models used in this study are a two-layer long-wave model, a two-level non-hydrostatic model, a three-dimensional model, a lattice-Boltzmann-type model, an SPH-type model, and an MPS-type model. Tsunamis generated by a fluid falling down a uniform slope are accurately reproduced by the models, especially when the wave height of the tsunami is not large. When using the two-layer long-wave model, in which the two layers of a falling fluid and seawater are assumed not to mix, the parameters including the seabed friction coefficient, adjusted in one case, are not appropriate for other mixing conditions. The two-level model with non-hydrostatic pressure exhibits wave disintegration owing to the effects of both nonlinearity and dispersion, although the second wave generated by the reflection of a wave traveling towards the shore is not simulated accurately. Tsunamis caused by a group of rigid cylinders falling down a uniform slope have also been simulated using two Lagrangian models, namely the SPH- and MPS-type models. Although the first peak at the water level is accurately reproduced by both models, the water level at the trough between the first and second crests is overestimated.

Cooperative behavior displayed by five steel disks falling in a low-density particle bed involves the formation of upward and downward convex configurations, which resembles the flying pattern of a flock of birds. In this study, we focused on overtaking behavior in two falling disks, which causes the cooperative behavior, and we investigated the effects of differences in the disk release time and the initial disk separation distance on the falling behavior of the disks experimentally. Expanded polystyrene (EPS) particles (diameter 5.08 mm, mass 1.45 mg) were used as the bed particles and steel disks (diameter 25.4 mm, thickness 5.22 mm, mass 20.2 g) were used as the falling disks. We released one to five disks with various disk release time differences (0–0.154 s) and initial separation distances (0–100 mm). We recorded the disk falling behavior in the particle bed with a high-speed video camera (500 fps) and analyzed the behavior with image analysis software. Five-disk cooperative behavior similar to that reported in the literature occurred in our experimental setup. In the two-disk experiments, we observed overtaking behavior for an initial separation distance of 10 mm and release time difference of ≤ 0.076 s, and for an initial separation distance of ≤ 60 mm and release time difference of 0.02–0.03 s. The overtaking behavior arose from the decrease in the falling velocity of the first disk released. The EPS particle packing fraction in the area above the disk one disk diameter wide and a quarter of the disk diameter high determined the disk falling velocity. This mechanism was explained by the displacement behavior of EPS particles around the disks as the disks fell.

An older patient who has had total knee replacement surgery may be afraid about falling. Fear of falling following TKR and its effects on physical activity have received little attention. The purpose of this study was to see if there was a link between physical activity and fear of falling in individuals with TKR. The PASE Scale is used to measure physical activity. The fall efficacy scale is reliable measure for assessing fear of falling. The objective of the current study was to assess physical activity and fear of fall and to find Correlation of physical activity with fear of fall in patients with TKR. This research was conducted in the Physiotherapy OPD, in AVBRH Hospital in Wardha. The results of 60 TKR patients were studied. The PASE scale and the FES were used to measure physical activity and fear of falling, respectively. This study significantly showed that the correlation between PASE and FES was negative which means that there is Fear of Fall among participants who undergone TKR which was associated with decrease in physical activity score. Most of the studies indicated that there is decrease in physical activity in patients with TKR but very few studies indicated fear of fall in the patients. Therefore, the current study is being carried out which could help to reach the conclusion to find whether there is any correlation between physical activity and fear of fall in patients undergone TKR.

Animals use diverse solutions to land on vertical surfaces. Here we show the unique landing of the gliding gecko, Hemidactylus platyurus. Our high-speed video footage in the Southeast Asian rainforest capturing the first recorded, subcritical, short-range glides revealed that geckos did not markedly decrease velocity prior to impact. Unlike specialized gliders, geckos crashed head-first with the tree trunk at 6.0 ± 0.9 m/s (~140 body lengths per second) followed by an enormous pitchback of their head and torso 103 ± 34° away from the tree trunk anchored by only their hind limbs and tail. A dynamic mathematical model pointed to the utility of tails for the fall arresting response (FAR) upon landing. We tested predictions by measuring foot forces during landing of a soft, robotic physical model with an active tail reflex triggered by forefoot contact. As in wild animals, greater landing success was found for tailed robots. Experiments showed that longer tails with an active tail reflex resulted in the lower adhesive foot forces necessary for stabilizing successful landings, with a tail shortened to 25% requiring over twice the adhesive foot force., Siddall, Byrnes, Full, and Jusufi observe the function of the Asian flat-tailed gecko tail in gliding and landing on tree trunks in the field, complemented with mathematical and robotic models made of soft active materials. Altogether, their models show how geckos use an active tail reflex to brace the impact and reduce the risk of falling from landings on tree trunks.

The dissolved oxygen (DO) concentration is an important index of water quality. It has a significant impact on the biodegradation process in water and the survival of aquatic organisms. Low DO concentrations often exist and may result in a deterioration in water quality and an increase in wastewater treatment expenses. An analysis of the oxygen transfer efficiency as correlated with the flow characteristics of a falling jet could help to solve these problems. Experiments related to oxygen transfer along a falling water jet were conducted, and the effects of the flowrate ( Q ), falling height ( H ) and initial DO concentration ( c u ) were considered. The results demonstrated that a falling jet in air could be an effective way of improving the DO concentration. The results also indicated that the oxygen transfer efficiency is linearly dependent on c u and has a negative exponential relation with H . To deeply analyze the oxygen transfer process, the jet disturbance process was divided into 3 parts for the first time based on flow features: a smooth zone, turbulent zone and breakup zone. The results showed that the jet outlet velocity had a limited influence on the smooth zone height but assisted in jet breakup. Thereafter, a correlation modeling DO reaeration along the falling jet considering jet disturbance characteristics was obtained. This correlation was also applied to predict the aeration efficiency in experimental cases from the literature and showed good agreement with the reported results.

The behavior of falling film over horizontal has significant impacts on the efficiency of heat and mass transfer for the horizontal tube evaporators and absorbers especially for intermittent droplet model at low spray density, which has lower heat and mass transfer resistance. Thus it is critical to illuminate transient and intermittent flow mechanism of droplet dynamic behavior and film thickness evolution regulation over horizontal tube falling film at low spray density. A two dimension multi-phase flow mode for superhydrophilic surface was established to capture the microscopic flow mechanism. The results indicated that droplet generation and growth stages accounted for more than half of the droplet life cycle and an obvious droplet retraction and pulsation were first observed during droplet generation due to surface tension and local additional pressure. Further, the whole life cycle transient and intermittent film thickness map of droplet mode was depicted. And found that the liquid film thickness transient evolution regulation of droplet mode could be split into two zones: impact zone and stable zone. For impact zone, the film thickness was rapidly decreased with the spreading of the liquid film from the millimeter level to 200 μ m within 0.2 s. While for stable zone, film thickness almost maintained stable over a long period time until the next droplet impacted. Because of the intermittent of droplet generation and movement, the change of film thickness of droplet mode with spray Reynolds was achieved by increasing impact frequency of droplet impact instead of the volume of a single droplet.

In this study, the interaction between a spherical solid particle descending in a fine-bubble plume and the fine-bubbles around the particle is investigated experimentally. The fine-bubbles, which are formed by water electrolysis and have an average diameter of 0.037 mm, rise via buoyancy to form bubble plumes. The average bubble velocity in the conduit is 0.05 mm/s. A spherical solid particle with a diameter of 11.1 mm and a density of 1130 kg/m3 is dropped into the fully-developed bubble plume. The particle falls in a meandering motion in the fine-bubble plume. In this process, the terminal velocity of the particles falling in the fine-bubble plume is almost identical to that of a particle falling in the quiescent water. Additionally, after the fine-bubbles have been separated from the particle surface, they flow into the wake of the particle, forming a stagnant region. The particle wake diameter increases threefold, as compared with its value in the downstream direction of the fine-bubble plume.

The falling shadow theory is applied to subhoops and filters in hoops. The notions of falling fuzzy subhoops and falling fuzzy filters in hoops are introduced, and several properties are investigated. Relationship between falling fuzzy subhoops and falling fuzzy filters are discussed, and conditions for a falling fuzzy subhoop to be a falling fuzzy filter are provided. Also conditions for a falling shadow of a random set to be a falling fuzzy filter are displayed.

Industrial grade 2-pyrrolidone with a purity of 99.5% is produced by aminolysis of γ-butyrolactone and subsequent fractional distillation, but it still contains trace amounts of γ-butyrolactone and...

In this paper, a coupled computational fluid dynamics and discrete element method (CFD-DEM) is used to numerically simulate the energy transfer of the ore falling process and the change law of impact airflow velocity under different influencing factors. The results are as follows: the total drag force is an important factor that determines the impact airflow velocity. The greater the total drag force, the greater the impact airflow velocity. The impact airflow velocity increases with the increase of mass flow rate and discharge height and decreases with the increase of ore size, and it is found that the discharge height has the greatest impact on the impact airflow velocity, the ore size is the second, and the mass flow rate is the smallest. Therefore, in the allowable range of mine production, the discharge height should be appropriately reduced. The mathematical model of the impact airflow velocity is obtained by multivariate nonlinear regression on the experimental results of orthogonal experiments.

Reliable cleaning processes are an absolute prerequisite to ensure the production of safe foods. In particular, the cleaning of heat exchangers is a crucial process step since temperature induces t...

Drum of Shearer undertakes the main function of coal falling and loading, and its performance directly affects the working efficiency of the shearer. Therefore, in order to realize the analysis of the performance of the shearer drum, the MG2 × 55/250-BW shearer drum was the engineered object. Combining the physical and mechanical properties experiment results of coal samples, the coupling model of the drum cutting in complex coal seam was established using discrete element method. The falling-coal characteristics of the spiral drum were studied under different working conditions, and the falling-coal trajectories of the coal and rock particles were fitted. Based on a virtual prototype, the variations of the coal loading rate and lump coal rate with different design parameters were determined by studying the falling-coal effect and loading performance of the drum. Considering the drum performance, multi-objective optimization theory was used to determine the optimal operating and structural parameters. The results indicate that, in the process of drum cutting, the cutting depth has the most significant effect on the coal loading rate, while, the blade spiral angle has the least significant. Moreover, with the increase of the cutting depth of drum and the traction speed, the lump coal rate increases. While, with the increase of the drum rotation speed and the blade spiral angle, the lump coal rate decreases. It is found that when the cutting depth of the drum is 597 mm, the traction speed is 5.4 m/min, the drum rotation speed is 104.8 r/min, and the blade spiral angle is 12° the performance of the drum is optimal. Compared with the falling-coal trajectories before optimization, the displacements of the coal and rock particles ejected along the optimal falling-coal trajectories increase in the coal loading direction. The loading rate and lump coal rate of the drum increase by 6.05% and 12.27%, respectively. The load fluctuation of the drum decreases, and the productivity increases.

Arboreal animals often leap through complex canopies to travel and avoid predators. Their success at making split-second, potentially life-threatening decisions of biomechanical capability depends on their skillful use of acrobatic maneuvers and learning from past efforts. Here, we found that free-ranging fox squirrels (Sciurus niger) leaping across unfamiliar, simulated branches decided where to launch by balancing a trade-off between gap distance and branch-bending compliance. Squirrels quickly learned to modify impulse generation upon repeated leaps from unfamiliar, compliant beams. A repertoire of agile landing maneuvers enabled targeted leaping without falling. Unanticipated adaptive landing and leaping "parkour" behavior revealed an innovative solution for particularly challenging leaps. Squirrels deciding and learning how to launch and land demonstrates the synergistic roles of biomechanics and cognition in robust gap-crossing strategies.

"The essay focuses on completing one of Husserl’s signitive theory with a new perspective. The discussion of the signitive theory is based more on the apperception’s function than to the perceptive one. We have observed that music produces for the ʻSelfʼ different feelings. But one of the most seductive feelings we want to discuss related to music is the perpetual floating-feeling, which is quite similar to the levitation process and it has connections with the idea of the lightness of the Being in some circumstances. Despite these, stays nostalgia. We are introducing a model based on two terms, as permanent {ʻintoʼ}-falling Self’s condition into the sounds and the signitive-apperceptive-intuition. The basic assumption is that music is a continuously phenomenological-fall which extenses the Husserlian theory more, completing it day by day. We hope that our concepts proposed here, signitive-apperceptive-intuition and the {ʻintoʼ}-falling will bring a new light in modelling the sound in a phenomenological manner. Keywords: music, consciousness, floating, levitation, falling, Pyotr Ilyich Tchaikovsky, Gustav Mahler, Max Richter, Jonathan Dawe, phenomenology, absorption, sounds, nostalgia, sadness, existentialism, existence. "

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.

Falling is the main cause of disability and fatality of elderly. In this work we used a 24 GHz continuous-wave Doppler radar to develop a low price and a highly accurate fall detection system aiming at observing indoor human activities and detecting fall accidents, thus limiting the consequences of undiscovered falls. A radar sensor was selected due to its capability of tracking human motions, passing through obstacles, and not being affected by light conditions. The sampled signals from the sensor were subjected to different feature engineering and machine learning techniques in order to determine the most characteristic features. Consequently, we were able to extract nontraditional radar features. Moreover, to improve the systems responsiveness and to lessen the hardware constraints, we added an additional pre-processing step to detect major physical activities with O(N) complexity. As part of fall detection, we also implemented vital signs monitoring to reduce false positives and to alert concerned authorities if necessary. Experimental results show that our proposed system has 90% recall rate for fall detection and 97.7% and 95.3% accuracy rates for respiration and heartbeat detection respectively.

One third of older adults and one half of people with a lower limb amputation fall each year. A hip exoskeleton capable of rapidly delivering high torques in frontal and sagittal planes could assist with fall recovery. Here we describe the design and testing of a hip exoskeleton emulator with actuation to adjust foot placement or center-of-mass state. The emulator was designed to be lightweight and comfortable while exceeding the torque and range of motion requirements of the hip joint during walking and fall recovery. We conducted tests to determine step response time, bandwidth, and torque tracking error. The emulator has a peak torque of 75 Nm in frontal and sagittal planes and has a worn mass of 10.9 kg. Benchtop tests demonstrated rise times in frontal and sagittal planes of 44 and 32 ms, respectively, and bandwidths of 14 and 17 Hz, respectively. During walking trials, the emulator demonstrated an average of 1.6 Nm of RMS torque tracking error (7.86% of commanded torque range) across three exoskeleton behaviors. Experiments conducted using this emulator could identify control behaviors and mechanical performance requirements of untethered devices designed for improving mobility and quality of life of populations prone to falling.

A new wind tunnel test method is proposed to measure the aerodynamic forces act on the tumbling plate and the tension of the tow string in the wind tunnel not by using force sensors but by measuring the tow position. The tumbling phenomenon is considered to be an important phenomenon for aircraft flight safety because of the possibility of falling objects from aircrafts reaching far away or for knowing the behavior of falling roof tiles blown off by strong winds. Therefore, many tests to measure the force act on the tumbling plate in wind tunnel have been conducted. However, since the rotation of the test piece is accompanied by difficulties ex. support interference, movement restrictions, etc. However, according to present method, the aerodynamic forces act on the tumbling plate in wind tunnel can be measured optically in a non-contact manner, and an expensive force sensor is not required. Furthermore, it is also effective under conditions such as low wind velocity, in which the aerodynamic forces are buried in the measurement accuracy of the force sensors. This paper explains this wind tunnel test method from the viewpoint of dynamic balance and reports the results of verification wind tunnel test in which the effectiveness of this method was confirmed.

Introduction. Driving at a speed exceeding the permitted and average speed of traffic flow often leads to a collision of vehicles with other road users or with elements of the arrangement of highways. As a result, it is necessary to establish whether the fact of this violation of the traffic rules, which led to the occurrence of an emergency-dangerous road traffic situation. The methods used to calculate the speed of vehicles based on the resulting deformations are quite accurate, but this fact is true in conditions of complete overlap (impact across the entire width of the front, rear or side parts of the body). But there is a scientific task of developing a methodology according to which an expert or investigator will be able to calculate the average statistical value of measuring the depth of deformation of a vehicle for a specific road traffic situation.Materials and methods. The paper proposes a method for evaluating the possibility of using the data available to the expert for calculation by introducing the coefficient of variation of the depth of penetration. With the help of the coefficient of variation, the specialist has a tool for selecting and ignoring individual measurements of the depth of penetration, depending on the degree of overlap and on the ‘spread’ of the deformation values.Conclusions. After studying a number of collisions with incomplete overlap and excluding the ‘extra’ values of penetration, the speed equivalent to the energy cost for the development of residual deformations and errors (the difference between the true collision speed and the established one without taking into account the ‘falling out’ values of deformations) was calculated and it was found that the use of the algorithm taking into account the coefficient of variation led to sufficiently accurate calculation results.Discussions. The proposed methodology regulates the use of the coefficient of variation as a criterion for the admissibility of the use of source data to determine the quality of the final result of the calculation. This mathematical device is applicable to all collisions, but is especially relevant when studying collisions with incomplete overlap of any part of the car body.