Effect Of Drop Height Research Articles

Collision simulation of potato tubers for mechanized harvesting

AbstractThe economic losses caused by collision damages during mechanical potato harvesting are significant. In this study, the simulation analysis method was used to investigate the factors affecting these mechanical damages. Taking the typical early maturing potato variety Zaodabai as an example, our test results indicated that its elastic modulus is 3.148 MPa, Poisson's ratio is 0.45, and biological yield stress is 1.183 MPa. An accurate three‐dimensional potato model was created using reverse engineering technology. On this basis, the effects of drop height, collision mode, and collision material on the mechanical potato damage were investigated using finite element analysis. The results indicated that the potato damage characteristics become more evident as the drop height increased. Analyzing the collision mode of mechanized potato harvesting revealed that the potato damage degree is the lowest in the double‐rod long axis collision mode. The collision damage degree between a potato and four common collision materials was determined from highest to lowest as follows: 65 Mn rod, 65 Mn rubber‐coated rod, potato, and soil. This research provides a data basis and reference for the design and development of potato harvester equipment, particularly for low‐damage potato harvesters.Practical applicationsAs the fourth largest food crop in the world, potatoes have high economic value and are of great importance for food security. Collision damage in mechanized harvesting seriously reduces the quality and value of potatoes and causes large economic losses. Therefore, we aim to clarify the key factors affecting collision damage in mechanized harvesting. The influence of motion mode, collision height, collision method, and collision material on potato damage characteristics was investigated through simulation experiments. This study provides a data basis and reference methods for developing key components of high‐performance and low‐damage potato harvesters and serves as a reference for researching damage characteristics of other tuber, root, and bulb crops.

Determination of the optimal drop height for male with different exercise level in drop jump by unilateral lower limb

Background: Drop jump (DJ) is a kind of plyometric training. There is little research on the effect of drop height (DH) on unilateral DJ. This study explored the optimal DH of DJ by unilateral lower limb, aiming to provide a reference for males with different exercise levels to avoid the imbalance between bilateral lower limbs and for coaches to develop accurate and effective unilateral DJ training programs. Methods: 18 college athletes and 13 physically active students were recruited to participate in this study and then asked to take three tests, namely “single-leg DJ at low height (L- SLDJ)”, “single-leg DJ at medium height (M-SLDJ)”, and “single-leg DJ at high height (H-SLDJ)”. Motion Capture System and Force Plate were used to synchronously collect motion parameters. Results: At M-SLDJ, both dominant and non-dominant legs performed significantly better than those at the other two types of DH in terms of leg stiffness and power for males with different exercise levels. At H-SLDJ, for males with different exercise levels, dominant leg had significantly better performance in leg stiffness, power etc. than non-dominant leg. Conclusions: The M-SLDJ designed in this study can be used by college athletes or students majoring in physical education for unilateral lower limb DJ training to maximize the performance of dominant or non-dominant leg. Due to the significant difference between two legs in the case of H-SLDJ, the eccentric contraction ability and stability of the non-dominant leg should be enhanced during the training to avoid bilateral imbalance.

Biomechanical characterization of the foot-ground interaction among Service members with unilateral transtibial limb loss performing unconstrained drop-landings: Effects of drop height and added mass

There exist limited data to guide the development of methodologies for evaluating impact resilience of prosthetic ankle–foot systems, particularly regarding human-device interaction in ecologically valid scenarios. The purpose of this study was to biomechanically characterize foot–ground interactions during drop-landings among Service members with and without unilateral transtibial limb loss. Seven males with, and seven males without, unilateral transtibial limb loss completed six drop-landing conditions consisting of all combinations of three heights (20 cm, 40 cm, 60 cm) and two loads (with and without a 22.2 kg weighted vest). Peak ground reaction forces (GRF), vertical GRF loading rate and impulse, as well as ankle–foot, knee, and hip joint negative (absorption) powers and work were compared across groups (i.e., contralateral side and prosthetic side vs. uninjured controls) by height and load conditions. Loading occurred primarily in the vertical direction, and increased with increasing drop height and/or with added load. Vertical GRFs were overall ~ 15% smaller on the prosthetic side (vs. controls) with similar loading rates across limbs/groups. From the most challenging condition (i.e., 60 cm with 22 kg load), ankle–foot absorption energies on the prosthetic side were 64.6 (7.2) J; corresponding values were 187.4 (8.9) J for the contralateral limb and 161.2 (6.7) J among uninjured controls. Better understanding biomechanical responses to drop-landings in ecological scenarios will help inform future iterations of mechanical testing methodologies for evaluating impact resilience of prosthetic ankle–foot systems (enhancing prescription criteria and return-to-activity considerations) as well as identifying and mitigating risk factors for long-term secondary complications within the contralateral limb (e.g., joint degeneration).

Effects of drop height, conveyor belt speed, and acceleration on the welfare of broiler chickens in early and later life

During automated processing in commercial hatcheries, day-old chicks are subjected to a range of possible mental and physical stressors. Three determinants of the processing line seem to have the potential to affect the birds in particular: drop height from one conveyor belt to another, conveyor belt speed, and acceleration. The aim of this study was to evaluate the effects of these 3 factors on chicken health and welfare in early and later life. In a first trial, chickens were tested on an experimental processing line that was adjusted to different levels of drop heights, belt speeds, and accelerations separately (n = 14 animals per factor and increment). Besides the assessment of several indicators for disorientation during the treatment, postmortem radiographic images were created and analyzed with focus on traumatic injuries. The number of chickens changing their orientation after the drop was affected by drop height (P < 0.01), whereas body posture changes were affected both by drop height (P < 0.01) and belt speed (P < 0.01). Traumatic injuries were found only sporadically and were not related to a certain treatment. In a second trial, chickens that were exposed to a combination of the 3 processing factors were compared with an untreated control group (n = 63 per group) until 15 d of age. There were no differences between the 2 groups regarding BW, welfare scores, and fear-related responses in a novel object and in a tonic immobility test. The present results suggest that the treatments on the experimental conveyor belts affected the birds' health, welfare, and behavior to a limited extend. However, starting at a drop height of 280 mm and a conveyor belt speed of 27 m/min, significantly more chickens were not able to maintain their initial body position on the belt. This indicates that there may be scope for discomfort and welfare impairment if commercial systems are operated with considerably larger drop heights and at higher speeds.

Breakage of green iron ore pellets

Mechanical degradation of green iron ore pellets prior to induration is a concern and can result in return of material to discs or drums or contamination of the feed to the induration furnace during pelletization. The work investigates the effects of pellet size, drop height, impact angle and type of surface on the response of pellets to multiple impacts, analyzing not only the critical condition for appearance of a surface crack, but also for their disintegration. It also analyzes the effect of deformation velocity during compression, showing that stiffness of green iron ore pellets remains relatively constant while pellet fracture energies significantly increase. It is observed that the effect of pellet size is limited, while the effects of drop height, velocity, angle and type of surface significantly influence degradation of such pellets. Finally, the effect of weakening due to repeated drops on the strength of pellets after firing is demonstrated.

Effects of Drop Height on Drop Jump Performance

Background: Drop jumps (DJ) are commonly implemented in plyometric training programs in an attempt to enhance jump performance. However, it is unknown how different drop heights (DH) affect reactive strength index (RSI), jump height (JH) and ground contact time (GCT). Objectives: The purpose of this study was to assess the effect of various DHs on RSI, JH, and GCT. Methods: Twenty volunteers with a history of plyometric training (Males = 13, Females = 7; age: 22.80 ± 2.69 yr, height: 175.65 ± 11.81 cm, mass: 78.32 ± 13.50 kg) performed DJs from 30 cm (DJ30), 45 cm (DJ45), 60 cm (DJ60), 76 cm (DJ76), and 91 cm (DJ91) and a countermovement jump (0 cm). A 16-camera Vicon system was used to track reflective markers to calculate JH; a Kistler force plate was used to record GCT. RSI was calculated by dividing JH by GCT. RSI and GCT were compared using a 2x5 (sex x DH) mixed factor repeated measures ANOVA, while JH was compared using a 2x6 (sex x DH) repeated measures ANOVA. Results: There were no interactions, but there was a main effect for sex for both JH (M&gt;F) and GCT (F&gt;M). JH demonstrated no main effect for DH: DJ30 (0.49 ± 0.11 m), DJ45 (0.50 ± 0.11 m), DJ60 (0.49 ± 0.12 m), DJ76 (0.50 ± 0.11 m), and DJ91 (0.48 ± 0.12 m). However, GCT showed a main effect where DJ30 (0.36 ± 0.10 s), DJ45 (0.36 ± 0.12 s), and DJ60 (0.37 ± 0.10 s) were not significantly different but were less than DJ76 (0.40 ± 0.12 s) and DJ91 (0.42 ± 0.12 s). Conclusions: Increasing DH beyond 60 cm increased GCT but did not affect JH, resulting in decreased RSI. Therefore, practitioners designing plyometric training programs that implement DJs may utilize DHs up to 60 cm, thereby minimizing GCT without compromising JH.

FEM explicit dynamics simulation and NIR hyperspectral reflectance imaging for determination of impact bruises of Lycium barbarum L.

A 3D scanner was used to reverse engineer a model to assess impact bruising of fresh Goji (Lycium barbarum L.) fruit. Based on the results of physical compression tests, an elastic-plastic model was selected as the material mechanics model for the fruit. A finite element method explicit dynamics simulation was performed to predict impact bruising using Abaqus software. Simulation results showed that fruit were not damaged at a drop height of 0.2-0.5 m, an impact angle of 10–30 °, and with an impact material of wood board, foam board, and nylon board. Using response surface methodology, the effects of drop height, impact material, and impact angle on the bruise rate of fruit were determined. The optimized parameters were a drop height of 0.24 m, foam board as the impact material, and an impact angle of 13.11°. Near infrared hyperspectral reflectance imaging was also applied to this problem, and visualization models were established in Matlab. The field experiment showed a bruise rate was 9.8%. These results provide a theoretical basis for future studies of harvesting, transporting, sorting, grading, and packaging machines designed for use with L. barbarum.

Drop Weight Impact Behaviour of Tube Filled Polymeric Syntactic Foam

Accidents are misfortune which could happen to anyone at any place at any time and it affects the vehicle as well as the occupants. Continuous research is being carried out for improving the crashworthiness of the vehicles with different materials. These materials plays important aspect in energy absorption and impact resistant design of the structure, wherein, presence of these materials highly affects the response of structures subjected to impact loading. In the present study, a non-linear finite element code LS-DYNA® is used for numerical simulation of drop weight impact hammer test. The material chosen for simulated testing is polymeric syntactic foam. In this study, effect of density of foam, foam material model, effect of drop height and effect of tube, filled with foam, on energy absorption of foam is studied. Herein, material model chosen for hammer is bilinear material model and crushable foam as well as piecewise linear plasticity model is used to model the foam. Behaviour of foam is compared in terms of reaction force, displacement time history and force-displacement variation. Energy absorption for each model is computed for different velocities considered in the present study and it is observed that tube plays an important role in enhancing the energy absorption of foam.

Effects of drop height and load on ground reaction force and joint kinetics of the lower extremity during the drop clean

Effects of drop height and load on ground reaction force and joint kinetics of the lower extremity during the drop clean

롤투롤 시스템에서 플렉시블 소재에 인가된 장력과 분사 높이가 액적 접촉각에 미치는 영향

This study proposes a method for identifying correlations between tension and drop height for sessile droplets in a roll-toroll processing system. The effect of tension and drop height on the contact angle of a sessile droplet is presented. Design of experiment (DOE) methodology and statistical analysis are used to define a correlation between the process parameters. The contact angle is decreased while increasing tension and drop height. The influence of the tension is less significant on the contact angle compared with the effect of the drop height. However, tension should be considered as a major parameter because it is not easy to fix with roll eccentricity and compensating speed of the driven roll. The results of this study show that the effect of tension on the contact angle of a sessile droplet is more important than drop height because the drop height is fixed when the process systems are determined.

The analysis of knee joint loading during drop landing from different heights and under different instruction sets in healthy males

BackgroundMechanical loading during exercise has been shown to promote tissue remodeling. Safe and accessible exercise may be beneficial to populations at risk of diminished bone and joint health. We examined the effect of drop height and instruction on knee loading during a drop-landing task and proposed a task that makes use of drop heights that may be appropriate for rehabilitation purposes and functional in daily life to examine transient knee joint loads.MethodsTwenty males (22.0 ± 2.8 years) performed drop landings from 22 cm (low) and 44 cm (high) heights, each under three instructions: “land naturally” (natural), “softly” (soft), and “stiffly” (stiff). Knee compression force and external flexion moment were estimated using three-dimensional inverse dynamics and normalized to body mass.ResultsPeak knee compression force was larger (p < 0.001) for high (17.8 ± 0.63 N/kg) than low (14.8 ± 0.61 N/kg) heights. There was an increase (p < 0.001) in the knee compression force across soft (11.8 ± 0.40 N/kg), natural (17.0 ± 0.62 N/kg), and stiff (20.2 ± 0.67 N/kg) instructions. Peak knee flexion moment in high-natural (2.12 ± 0.08 Nm/kg) was larger (p < 0.001) than in high-soft (1.88 ± 0.08 Nm/kg), but lower than in high-stiff (2.23 ± 0.08 Nm/kg). No differences in peak knee flexion moment were observed across instructions for the low height.ConclusionsWe propose a drop-landing task that creates a scalable increase in knee compression loading. The absence of increased knee flexion moment with drop from the low height, compared to high, suggests that individuals could perform the task without incremental risk of knee injury. This task could be used in future studies to examine the effect of acute bouts of mechanical loading on bone and cartilage metabolism.

Effects of drop height and surface instability on neuromuscular activation during drop jumps.

The purpose of this study was to examine whether drop height-induced changes in leg muscle activity during drop jumps (DJ) are additionally modulated by surface condition. Twenty-four healthy participants (23.7±1.8years) performed DJs on a force plate on stable, unstable, and highly unstable surfaces using different drop heights (i.e., 20cm, 40cm, 60cm). Electromyographic (EMG) activity of soleus (SOL), gastrocnemius (GM), tibialis anterior (TA) muscles and coactivation of TA/SOL and TA/GM were analyzed for time intervals 100ms prior to ground contact (preactivation) and 30-60ms after ground contact [short latency response (SLR)]. Increasing drop heights resulted in progressively increased SOL and GM activity during preactivation and SLR (P<0.01; 1.01 ≤ d ≤ 5.34) while TA/SOL coactivation decreased (P<0.05; 0.51 ≤ d ≤ 3.01). Increasing surface instability produced decreased activities during preactivation (GM) and SLR (GM, SOL) (P<0.05; 1.36 ≤ d ≤ 4.30). Coactivation increased during SLR (P<0.05; 1.50 ≤ d ≤ 2.58). A significant drop height×surface interaction was observed for SOL during SLR. Lower SOL activity was found on unstable compared to stable surfaces for drop heights ≥40cm (P<0.05; 1.25 ≤ d ≤ 2.12). Findings revealed that instability-related changes in activity of selected leg muscles are minimally affected by drop height.

The effect of drop height on bruising of selected apple varieties

This paper presents an analysis of fruit impact in time and the results of the relationships between the bruise size and various impact parameters. The measuring device allows simultaneously analysis of the three basic quantities: impact velocity, rebound velocity and force response in time, and testing the momentum conservation law for a body such as an apple. In the experiments, the impact velocity 0.25ms−1 was the maximum velocity at which bruises for all tested apple varieties did not develop. The parameters which were the most strongly correlated with apple bruise volume were maximum force response and dissipated energy, which can be used to predict direct impact effects.

Interpreting the formation of bloodstains on selected apparel fabrics

Bloodstain pattern analysis (BPA) is the investigation and interpretation of blood deposited at crime scenes. However, the interaction of blood and apparel fabrics has not been widely studied. In this work, the development of bloodstains (passive, absorbed and transferred) dropped from three different heights (500, 1,000, 1,500 mm) on two cotton apparel fabrics (1 × 1 rib knit, drill) was investigated. High-speed video was used to investigate the interaction of the blood and fabric at impact. The effect of drop height on the development of passive, absorbed and transferred bloodstains was investigated using image analysis and statistical tools. Visually, the passive bloodstain patterns produced on the technical face of fabrics from the different drop heights were similar. The blood soaked unequally through to the technical rear of both fabrics. Very little blood was transferred between a bloody fabric and a second piece of fabric. Statistically, drop height did not affect the size of the parent bloodstain (wet or dry), but did affect the number of satellite bloodstains formed. Some differences between the two fabrics were noted, therefore fabric structure and properties must be considered when conducting BPA on apparel fabrics.

Experiments and modeling of HMX granular explosives subjected to drop-weight impact

The drop-weight impacts on a thin layer of cyclotetramethylene tetranitramine (HMX) explosive particles have been performed. The drop-weight impact machine is equipped with high-speed photographic techniques. Effects of drop heights and the amount of particles on compaction, deformation, and thermal responses were investigated. Considering the contact plasticity, friction, melting, fracture, as well as chemical reaction, an analytical model based on heating and kinematics equations for a single layer of explosive particles has been developed. The calculated average pressure, loading time and time-to-ignition agree well with experimental measured ones. Threshold conditions for ignition can be derived from the predicted temperature history curves. Individual particles’ pressure–strain exhibited stress–strain-like relationships, from which close relations can be found between experimental phenomena and the material's softening/hardening characteristics.

A microscopic model for predicting hot-spot ignition of granular energetic crystals in response to drop-weight impacts

A micro-mechanics model describing hot-spot formation in the energetic crystal powders cyclotetramethylene tetranitramine (HMX) and pentaerythritol tetranitrate (PETN) subjected to drop-weight impact is developed. Considering contact deformation, friction and chemical reactions at the particle level during the impact loading process, three hot-spot sources are included, namely, the micro-particle contact deformation between two equal-sized particles with no relative sliding, the contact sites between the impacting surface and the particles, and the contacting zone between particles with a sliding velocity along the maximum shear-stress direction. Drop-weight impacts on samples composed of equal-sized particle layers are considered. The temperature rise due to plastic and frictional dissipation is estimated, and melting is included. Hot spot ignition is predicted via thermal explosion, using an Arrhenius thermochemical model. The effects of drop height and particle size on the ignition processes are analyzed. The hot-spot sources at the interface between the particles and the impacting surfaces play the most important role during the early ignition stage. The time-to-ignition of the three sources increases with decreasing drop height. Calculated results show that the HMX and PETN crystals demonstrate monotonously increasing time-to-ignition with a reduction in particle size. The effect of particlesize on the hot spot ignition threshold can be predicted. Samples with a smaller particle size undergo larger localized deformations and lower average pressures.

The effect of drop height and body mass on drop jump intensity

The effect of drop height and body mass on drop jump intensity

EVALUATION OF PFWD FACTORS ON STIFFNESS MODULUS DETERMINATION OF UNBOUND MATERIALS

Worldwide use of portable falling weight deflectometer (PFWD) for construction quality control of earthworks and unbound pavement layers and their stiffness determination is increasing rapidly. However there are still many unknown factors related to application of PFWD, precision of the test results that may affect the PFWD data quality and it is necessary to identify them. In this research, field testing was carried out on different unbound base and sub-base layers on several highway construction sites in Tehran. In addition, a laboratory testing box was built in which several layers of unbound materials were compacted using a portable vibrating compactor. The stiffness moduli of the compacted layers were determined using PFWD (TML model Japan). Then, factors affecting PFWD measurements such as drop weight, drop height, plate diameter, plate-surface contact, and distances of extra geophones were investigated. The results showed that the PFWD moduli increased with increasing drop weight for the considered values and a model was presented for prediction of PFWD stiffness modulus through increasing of the drop weight. But the effect of drop height on PFWD moduli was not significant. It was found that the E0 moduli from the 100 mm loading plate were about 1.85 times higher than those from the 300 mm loading plate. Also, it was shown that the plate-surface contact was important in PFWD results. Finally, distances of extra geophones were discussed and it was found that they don’t have any important effect on upper layer moduli.

Comparison Of Different Drop Jump Heights On Vertical Jump Performance In Elite Team Handball Players

INTRODUCTION: Studies have shown that when compared to other kinds of vertical jump, drop jumps (DJ) can increase maximal jump height. However, landing from high levels can be detrimental to bone and joint structures and cause long-lasting injuries. PURPOSE: To examine the effects of different drop heights on the performance of drop jump in Brazilian elite team handball players. METHODS: Nine male team handball players (body mass 90.7±12.1kg; body height 184.3±8.9cm) were asked to drop from boxes 40, 60, and 80 cm high, and immediately perform a vertical jump as higher as possible. No arm swing was allowed. A force plate (Kistler - Model 9286A) was used to measure the vertical component of ground reaction force (GRFV), recorded by a customized LabView, which was also employed to calculate landing peak force (LPF1) and time to peak (TPF1) after the drop, contact time (CT), jump height (JH), and landing peak force (LPF2) and time to peak (TPF2) after the subsequent vertical jump. RESULTS: Except for LPF1 there were no effect of dropping height (40, 60, and 80 cm) on TPF1, CT, JH, LFP2, and TPF2. The landing peak force (LFP1) after the drop jump was lesser when the participants dropped from 40 cm (DJ 40) when compared to dropping from other heights (DJ 60 and DJ 80).TABLECONCLUSION: The results indicate that, no matter from what height the participants dropped, the final outcome (jump height) is similar. However, dropping from a higher place generates more peak force, and consequently, more stress in bones and joints structures. In conclusion, dropping from 40 cm can be more effective (same performance outcome and lower bone and joints overloads) than from higher heights.

Factors Affecting Portable Falling Weight Deflectometer Measurements

Lower cost and better quality evaluations of pavement characteristics require precise quality assurance/control programs that relate test results to design practice. Rapid in situ stiffness testing enables transportation agencies to conduct reliable and defensible quality assurance programs. This study explores the feasibility of using a portable falling weight deflectometer (PFWD) to characterize pavement layer moduli. Efforts were made to investigate factors that may influence PFWD results. Field dynamic cone penetrometer as well as laboratory California bearing ratio tests were performed and compared with results obtained from PFWD. One of the most important factors concerning the PFWD modulus is the size of the PFWD loading plate. Our testing suggests that an appropriate plate size can be chosen from the measured modulus. The effects of drop height on PFWD moduli were found to be small as the moduli remained about the same regardless of the drop heights. Considering the personnel and skills required for data collection, result interpretation, speed of testing, and the quality of data produced, the PFWD is preferred. PFWD is an ideal device for quality control during compaction monitoring because it enables a rapid stiffness assessment of individual pavement layers.