Impact Magnitude Research Articles

Mechanical impacts analysis in judoists body of different weight categories

This study aimed to analyze the impacts generated in different body regions of judoists of different weight categories during falls cushioning. Four black belt judoist, with at least 14 years of experience, participated in this study: three “uke” half-light, half-middle and half-heavy categories were thrown in “ippon-seoi-nage” technique by a “tori” with 77 kg. A triaxial Bruel and Kjaer accelerometer was alternately fastened with straps in the “uke” fist, hip and ankle to verify the impacts. Descriptive statistics, one way ANOVA and Tukey test were applied, with p≤0.05. The bigger impact magnitudes occurred in vertical axis, in the fist and for the half-middle category judoist; the impact times were larger in the hip for all athletes and in vertical axis. According to Macaulay criteria, the impact values founded represents severe injury risks in fist and ankle and moderate risk in judoists hip. Initiatives should be taken to reduce the damage due to impact during judo training and competitions. Key words: Judo, impact, transitory, vibrations, injury.

The ‘heel impact’ force peak during running is neither ‘heel’ nor ‘impact’ and does not quantify shoe cushioning effects

It has been common practice in studies of running shoe cushioning to use the magnitude of the initial transient peak (Fz1) of the vertical ground reaction force (Fz(t)), as an index of heel impact severity. Frequently, the results of such studies have been inconsistent with impact attenuation theory, in vitro impact test results and other load measures. This paper concludes that such use of Fz1 as a measure of heel impact load is not valid. Fz(t) and in shoe-pressure distributions were recorded while 20 male subjects ran at 4.0 ± 0.2 m/s on a laboratory runway in three footwear conditions representing the approximate range of commercially available running shoes and a minimal, uncushioned control shoe. Pressure data were used to identify spatial (heel and distal foot) components of Fz(t) and spectral analysis was used to distinguish high and low frequency components. Consistent with previous reports, cushioned shoes attenuated Fz1 magnitude by less than 10% and the most compliant shoe produced significantly higher force peaks than shoes with stiffer cushioning. Analysis of the spatial and frequency components of Fz(t) revealed that Fz1 is a composite that includes high frequency (heel impact) loads but that low frequency force components originating both in the heel and distal forefoot contribute about half its magnitude. In contrast to Fz1, cushioned shoes attenuated the high frequency (impact) force component by 35%, and effects across shoe conditions were consistent with both theory and in vitro impact test results. Thus Fz1 is neither uniquely defined by heel impact, nor a reliable indicator of impact magnitude. It can be shown that the artifactual effects of cushioning on Fz1 magnitude are derived from the superimposition of low frequency (non-impact) and non-heel load components.

Magnitudes de impacto e cinemática dos membros inferiores no arremesso em suspensão no handebol

The purpose of this study was to investigate kinematic characteristics and impact of the handball jump throw. Nine male athletes of the university team participated of this study. A tri-axial accelerometer was used for identify the impact magnitude of the lower limb and the three-dimensional analysis system DMAS 5.0® was used for the analysis knee and hip angle of the jump throw. The kinematic and accelerometry dates were simultaneously collection. Reflective markers were placed on the anatomic landmarks of the athletes and the accelerometer was placed on the knee and ankle. For the date analyses, descriptive statistics, analysis of variance and Pearson correlate were used. The level of significance was set at 5% for all tests. The biggest impact magnitudes were acquired of the anterior-posterior axle on the ankle joint (58.81 g). Knee and hip angle in the contact with ground were lesser than knee and hip angle in the maximum flexion of the lower limb (27.24º and 33.75º for knee and 25.77º and 26.77º for hip), respectively. The impact magnitude in the knee of the anterior-posterior axle showed inverse correlate with the knee (r= -0.64; p= 0.05) and hip angle (r= -0.77; p= 0.01) in contact with ground. From results can be conclude that, although this team to be amateur, is necessary improvement of jump throw technique to decrease of cumulative effects of overload by long time of training.

Ultimate Impact Resistance and Residual Toughness of Pre-Stressed Concrete Railway Sleepers

The pre-stressed concrete sleepers (or railroad ties), which are installed in railway track systems as the crosstie beam support, are designed to carry and transfer the wheel loads from the rails to the ground. It is well known that railway tracks are subject to impact loading conditions, which are attributable to the train operations with either wheel or rail abnormalities such as flat wheels, dipped rails, etc. These loads are of very high magnitude but short duration. In addition, there exists the potential of repeated load experience during the design life of pre-stressed concrete sleepers. Pre-stressed concrete has played a significant role in maintaining the high endurance of sleepers subjected to low to moderate repeated impact loads. In spite of the common use of pre-stressed concrete sleepers in railway tracks, their impact response and behaviour under repetitions of severe impact loads are not deeply appreciated, nor taken into consideration in design. This experimental investigation was aimed at understanding the residual capacity of pre-stressed concrete sleepers in railway track structures under ultimate impact loading, in order to develop state of the art limit states design concepts for pre-stressed concrete sleepers. A high-capacity drop weight impact testing machine was constructed at the University of Wollongong to achieve this purpose. A series of severe impact tests on in-situ pre-stressed concrete sleepers was carried out, ranging from low to high impact magnitudes. The impact energy was evaluated in relation to the drop heights. The impact-damaged sleepers were re-tested under static conditions in order to evaluate the residual fracture toughness in accordance with the Australian Standard. It was found that a concrete sleeper damaged by an impact load could possess significant reserve capacity sufficient for resisting about 1.05 to 1.10 times the design axle loads. The impact behaviour and residual fracture toughness under different magnitudes of impacts are highlighted in this paper. The effects of track environment, including soft and hard tracks, are also presented together with a discussion related to the ultimate limit states design.

Evaluating uncertainty in climate change impacts on crop productivity in the Iberian Peninsula

Using a multi-model ensemble of climate-change impacts over the Iberian Peninsula, we identified regions and cropping options for which the uncertainty levels of projected impacts on crop productivity were either high or low. The ensemble consisted of 10 members per combination of scenario, climate model, location and cropping option, and was used to quantify the uncertainty of impacts on crop yield. CERES wheat and maize simulation models were linked to the control run and 1 scenario provided by 10 regional climate models (RCMs): control (1969-1990) and A2 future (2070-2100) climate. The contribution of RCMs, locations and cropping options to uncertainty on yield projections was analysed. Differences between the sign of the response and 30 yr time series of projections generated by each member of the ensemble were compared. The largest response to A2 scenarios also resulted in the smallest uncertainty, and vice versa. Low uncertainty was found for the sign of the yield response, which was mainly positive for spring and winter cropping options and neg- ative for the summer option. Uncertainty was lower for A2 than for control projections. Uncertainty was largest in northern, coastal and mountain regions, and smallest for inland southern regions, and depended on seasonal cropping options. Minimum and maximum uncertainty were found for maize and irrigated spring wheat, respectively. Water availability was the determinant for interannual vari- ability and its uncertainty. Choice of RCM contributed less to uncertainty than choice of location, and choice of cropping option contributed more to uncertainty than both of these factors. Interannual vari- ability showed larger uncertainty than mean impact magnitude, and this uncertainty was larger than that of the sign of the yield response. Regions with high uncertainty could benefit from higher-reso- lution simulations.

SIX LESSONS FROM HAITI: THE NEED FOR COOPERATION DEVELOPMENT

One of the defining events of 2010 took place at its start. On 12 January, the long suffering of the Haitian people took on a grave new dimension, one that will last for years. For a few days, news of the tragedy filled the mass media and the eyes and thoughts of men and women across the world, who from their homes felt the anguish of that population that has more than paid for the audacity of wanting to be independent and free from slavery. In one of the news stories, a mother asked, 'What has Haiti done to deserve this?' The reading that follows: on the event itself, its impact and the manner and magnitude of the response is performed with a gaze that starts from Haiti, but spreads to the Caribbean Basin, the hemisphere and the world. These notes reflect on the lessons that Haiti offers, what it shows and proves, because Haiti is now a mirror in which we must look not only at the Caribbean, but at all the underdeveloped world.

Caracterização das forças de impacto na execução do Jump Kick

This study aimed to identify the number of jumps in Jump Kick training (Mix 30), the magnitudes and duration time of the impacts generated in the knee and ankle during landing; compare the magnitudes and associate them with weight, height and practice time. Eight teachers with 28,12±6,46 years; height 171,0±6,12 m; weight 68,38±9,04 kg and 41±32,23 months of practice time in Body Combat participated in this study. Was used a semi-structured interview, a video camera, a digital balance and a tri-axial accelerometer. The teachers realized 1420 jumps per class; the biggest impact magnitudes occurred in the ankle (31,4g, 27,6 g e 21,6 g in axis x, y e z respectively); the biggest impact time occurred in the knee (0,028 s, x axis); there was difference in impact values between teachers; there was any correlation (p≤0,05) between variables. Even if the impact values are low, the high impact numbers during a day is a factor that can cause future injuries.

An Analysis of Head Impact Profiles and Safe Hockey Behaviors in Youth Hockey Players

Abstract Although injury risk factors can be described in biomechanical terms, previous research has not described the relationship between style of play and the frequency and magnitude of head impacts. This paper is focused on the analysis of head impact profiles and safe hockey behaviors demonstrated during contact situations in a cohort of 13 Bantam-aged minor hockey players. Head impacts sustained at 27 home games during the 2006–2007 season were measured using the Head Impact Telemetry System (HITS). Hockey helmets (Canadian Standards Association approved) were equipped with six linear accelerometers and a wireless system that transmitted data to a receiver interfaced with a computer. Nine games were recorded using a field videography system to capture player collisions. A HITS profile was determined, which included the number of impacts (>10 g) (“g”=m/sec2) by player, the total number of impacts, the average number of impacts per game, and the mean linear acceleration value for all impacts per player. Based on these results, ten taped trials for the players sustaining greater than 180 total impacts over the season were qualitatively analyzed using a checklist to examine the safe hockey behaviors associated with body contacts. We captured 2753 head impacts over the season, with the average number of impacts per player per game ranging from 3 to 16 with a mean linear acceleration of 15.8 g (standard deviation=13.76). The checklist of safe hockey behaviors was used to analyze skating performance for a group of five players who experienced more than 180 impacts, with some impact magnitudes exceeding 98 g. In general, differences in indicators of skating skill, body position prior to check/contact, and actions during the contact were observed. While specific players may be predisposed to head impacts of a greater frequency and magnitude because of their style of play, these characteristics can be changed to reduce risk of potential injury.

Dynamics of alpine grassland NPP and its response to climate change in Northern Tibet

Based on the remote sensing and meteorological data collected from the 1981-2004 period, we calculated the alpine grassland Net Primary Productivity (NPP) in Northern Tibet using the Carnegie-Ames-Stanford Approach (CASA), and subsequently analyzed the trend of grassland NPP changes and its response to climate change from 1981 to 2004. The results show that alpine grassland NPP in Northern Tibet was very low in the last 24 years with a relatively large yearly variation. Most of the grassland area (88.61%) in Northern Tibet did not show a significant annual NPP change. The area with a significant decrease of annual NPP variation accounted for only 11.30% of the total grasslands surface, whereas that with a significant increase accounted for 0.09%. In recent years, the precipitation variation in Northern Tibet resulted in an increase of grassland NPP, though solar radiation resulted in decreased grassland NPP. During the 1981-2004 period, total solar radiation, precipitation and temperature, with a decreasing impact magnitude factor, have impacted the grassland NPP in Northern Tibet. The impact of regional climate change on grassland NPP was overall more detrimental than positive.

Comparative Hazard Characterization in Food Toxicology

Historically, different approaches have been adopted for comparing and characterizing hazards that can be found in the very complex mixture of substances present in food. In this review a variety of prominent risk assessment models are evaluated in the context of food safety. In their current state of refinement, though, they show limited applicability for comparative hazard characterization and impact magnitude scoring of adverse effects of substances in food. Nonetheless, some existing models hold building blocks and modelling concepts that appear promising for further development and integration. Thus, a new, dedicated, and generally accepted model is needed that is capable of generating relevant “Impact Magnitude Score” (IMS) values for comparing potentially toxic substances in food. A brief outline of requirements for a model (Guided Toxicology-assessment of Health Impact; GTHI) is presented that considers “severity” (S), “duration” (D), and “proportion of population affected” (P). An important demand on such a model is to provide significantly improved food safety evaluation amenable to regulatory agencies and consumers. This review is based on a project entitled “Promoting food safety through a new integrated risk analysis approach for foods” (acronym: “SAFE FOODS”) that is under the subsidy of the European Commission.

Avaliação de linhas de beneficiamento e impactos de queda na qualidade de caqui "Rama Forte"

O manuseio inadequado e excessivo de frutas e de hortaliças causa alta incidência de danos físicos e, consequentemente, perdas pós-colheita. O objetivo deste trabalho foi avaliar a magnitude de impacto em linhas de beneficiamento e classificação para caqui "Rama Forte" e determinar, em laboratório, seus limites de impactos. Para a avaliação dos pontos críticos, foi utilizada uma esfera instrumentada de 76 mm de diâmetro (Techmark, Inc., Lansing, EUA), que registrou a magnitude dos impactos em sete equipamentos distintos de quatro unidades de beneficiamento. A determinação de danos físicos foi feita em testes laboratoriais, nos quais a queda dos frutos foi relacionada com a magnitude de impacto, incidência de danos físicos e perdas na qualidade do fruto. Nas linhas de beneficiamento, os valores de impactos encontrados variaram de 21 a 87 G nos pontos de transferência, e a maioria dos impactos registrados (acima de 94%) durante a passagem pela linha foram de valores de até 50 G. Alturas de queda a partir de 20 cm causaram aumento na perda de massa do caqui no sexto dia de armazenamento, em temperatura ambiente. As quedas de 20 e 30 cm causaram maior escurecimento da casca (menores valores de L), associada à redução da intensidade da cor (chroma). O impacto não causou efeito nas características químicas da polpa do fruto.

Diagnosis of ecosystem impairment in a multiple‐stress context—how to formulate effective river basin management plans

The Water Framework Directive (WFD) of the European Union requires member states to attain a good ecological status for all water bodies by the year 2015. This implies that the bioecological protection endpoint itself is upfront, next to abiotic chemical quality standards, as tools to protect those endpoints. Within the requirements of the Directive, ecological status and abiotic conditions will be monitored extensively. Based on the analysis of the monitoring data, authorities are required to derive Programs of Measures (PoMs) for impacted sites. Optimization of these programs requires diagnosis, to provide site-specific or catchment-specific information on the causes of observed deviations from a good ecological status. This article shows one pilot analysis of monitoring data (Scheldt River, Belgium) compiled in the scope of the EU MODELKEY project. Ecological, ecotoxicological, and statistical models are combined to quantify local ecological impact magnitudes and to identify site-specific factors that are associated with those impacts. Results show significant ecological effects in terms of taxa loss at study sites, which are highly variable among sites, with variable combinations of environmental factors associated with those effects. The results of the diagnostic approach are discussed, which appear to be complementary to the assessment of chemical status required by the Directive. Both types of assessment are useful to assist in the derivation of optimized PoMs. In addition, it could be concluded that the acute toxic pressure parameter relates to reduced taxon abundance for more than half of the studied taxa and that this parameter relates to the fraction of taxa lost under field conditions. Finally, various lessons for the execution of monitoring programs are derived because the Scheldt (bio)monitoring data set has its weaknesses, although it can be seen as typical for current monitoring programs.

The biotic effects of large bolide impacts: size versus time and place

AbstractIn estimating the biotic effects of large terrestrial impacts we are reliant upon apparent crater diameter as a proxy for impact magnitude. This underlies the ‘kill-curve’ approach which graphs crater diameter directly against likely percentage losses of taxa. However, crater diameter is a complex product of syn- and post-impact processes that can be site-dependent. Furthermore, location (global positioning) and timing (moment in geological history) also strongly influence biotic effects. We examine four of our largest and best-documented Phanerozoic impacts to explore this more holistic size–time–place relationship. Only the c. 180 km end-Cretaceous Chicxulub crater (Mexico) links to any substantial immediate extinction and some of the worst effects stem from where it struck the planet (a continental margin carbonate platform site) and when (a time of high regional and global biodiversity). Both the c. 100 km late Triassic Manicouagan crater in NE Canada (arid continental interior, low regional and world biodiversity) and the c. 35 Ma 100 km Popigai crater, Siberia (continental arctic desert) provide much less damaging scenarios. However the c. 90 km Chesapeake Bay crater, Eastern USA (also c. 35 Ma) marks a far more sensitive (Chicxulub-like) site but it also proved relatively benign. Here the rheologically varied shallow marine target site produced an anomalously broad crater, and the scale of the impact has evidently been overestimated. We offer a new approach to the graphical prediction of biotic risk in which both crater diameter and a generalised time/place factor we term ‘vulnerability’ are variables.

The role of the contact geometry in wheel–rail impact due to wheel flats: Part II

A classification of wheel flats according to the different stages of their growth is given, along with the characteristic features of the dynamic wheel–rail interaction for each category. Mathematical expressions and frequency spectra of the corresponding wheel mass trajectories are derived. Difference is made between the subcritical and the transcritical speed regime. A criterion is derived for contact loss for worn flats. Simulations show that the dynamic wheel–rail interaction is governed by the track stiffness for low train speeds or long flat lengths; for high speeds and/or short flat lengths the interaction is governed by the inertial properties of the wheel and the rail. For a given flat geometry, nonlinearities in the relationship between the impact magnitude and the train speed occur in the stiffness-dominated speed domain, whereas this relationship is approximately linear in the inertia-governed domain. In the latter domain, the impact magnitude is found to be linearly dependent upon the maximum trajectorial curvature or inversely linearly dependent on the minimum circumferential wheel tread curvature. The above relationships are valid for the subcritical speed regime, in which no contact loss occurs. Different contributions from the literature are compared with respect to the established relationship between impact magnitude and speed. Significant differences are found, due to insufficiently defined parameters and conditions. Conditions are derived for a consistent application of the so-called equivalent rail indentation in experiments with wheel flats, and the indirect strain registration method for measuring dynamic wheel–rail contact forces is reviewed.

Impact magnitudes applied by surgeons and their importance when applying the femoral head onto the Morse taper for total hip arthroplasty

This study was designed to test whether the number of impacts, the experience of the surgeon or impact force made significant difference in pull off forces. The forces applied by 10 orthopaedic surgeons (five residents and five attending staff) to impact the femoral head onto the trunnion of a femoral component were recorded. The resultant forces were then divided into four energy levels and compared to determine if the number of impacts would make a difference in pull off strength. No significant differences existed between the resident versus attending groups in magnitude of force applied. Through ANOVA testing, it was found that at each of the energy levels, multiple blows demonstrated a significant pull off strength difference compared to a single blow. Increased pull off force was also noted when the magnitude of force of the applied blows was increased. We recommend at least two firm, axially aligned blows to impact the femoral head onto the trunnion intra-operatively.

Bed load transport in a steep snowmelt-dominated mountain stream as inferred from impact sensors

The article reports results from bed load transport investigations using impact sensors in Vinstra, a steep snowmelt-dominated mountain stream in Central Norway. The impact sensors proved able to detect thresholds for bed load entrainment. With increasing discharges surpassing the threshold for entrainment, both the magnitude and variance in impact force increases, but also showing differing rating relationships on rising and falling flows. Substantial bed load transport was only observed during the snowmelt-dominated spring flood period and impact magnitude was observed on average to follow diurnal variations in discharge during the spring flood event, but with a clockwise hysteresis relationship.

White Certificates for energy efficiency improvement with energy taxes: A theoretical economic model

In this paper we analyze interactions of two energy policy instruments, namely a White Certificates (WhC) scheme as an innovative policy instrument for energy efficiency improvement and energy taxation. These policy instruments differ in terms of objectives and final impacts on the price of electricity. We examine the effect of these policy instruments in the electricity sector, focusing on electricity producers and suppliers in a competitive market. Using microeconomic theory, we identify synergies between market players and demonstrate the total effect on the electricity price when suppliers internalize the behaviour of producers in their decisions. This model refers to an ideal market situation of full liberalization. The cases we examine consist of electricity producers with and without a carbon tax, electricity suppliers with and without an electricity tax, and with WhC obligations. Furthermore, we present a parallel implementation of WhC for electricity suppliers with carbon tax on electricity producers and an electricity tax with WhC obligations to electricity suppliers. We demonstrate differences in optimization behaviour of producers and suppliers. Based on a couple of cases of WhC with carbon and electricity taxes, various positive and negative effects of both schemes in terms of target achievement and efficiency are present, which can lead to an added value of such schemes in the policy mix, although uncertainties of outcomes are quite high. A basic finding is that in a merit order several parameters can increase final electricity price after the implementation of different policies: demand for electricity and electricity supply cost at a large scale and then follow the level of level of obligation for energy saving, level of penalty, and price of WhC (representing the marginal costs of energy saving projects). The impact magnitude of parameters depends on the values chosen and on the initial position of suppliers (i.e. if their actual behaviour deviates from full compliance with targets).

Characteristics of head impacts sustained by youth ice hockey players

This study aimed to measure the magnitude of head impacts sustained by 14 male, youth (13 years old) ice hockey players wearing instrumented helmets, and to compare impacts across event type (practice, game), player position, and location. Head impact magnitudes were captured during 58 games and 51 practices. Mixed linear models were utilized to analyze differences by event type, player position, and location of impact. Game impact magnitudes were significantly greater than practice impacts. Impacts sustained by forwards were similar in magnitude to those sustained by defensemen. Significant differences between head impact locations across all player positions were observed. Impacts to the top of the head were significantly greater than impacts to the back, front, left, and right sides. Youth ice hockey players sustain helmet impacts nearing 20 g on average, similar to measured values in collegiate American football players, and of potential concern because this sample involves younger athletes. Future biomechanical studies are needed to better interpret the finding that there is an increased likelihood of higher magnitude head impacts to the top of the head. The authors' long-term goal is to improve the understanding of impacts that may lead to concussions in young athletes.

MEASUREMENT OF HEAD IMPACTS IN COLLEGIATE FOOTBALL PLAYERS

To determine the relationship between recorded head accelerations and impact locations and acute clinical outcome of symptomatology, neuropsychological, and postural stability tests after cerebral concussion in Division I collegiate football players. A prospective field study was used in which accelerometers were embedded in the football helmets of 88 collegiate football players. Linear and rotational accelerations of all head impacts sustained over the course of 2004 to 2006 National Collegiate Athletic Association football seasons were collected in real-time. Change scores were calculated on clinical measures from the players' preseason baseline to postinjury (within 48 h) and regressed against the recorded linear and rotational accelerations of the head at the time of the concussion. Thirteen concussions were recorded ranging in impact magnitudes of 60.51 to 168.71 g. Linear regression showed no significant relationships between impact magnitude (linear or rotational acceleration) or impact location and change scores for symptom severity, postural stability, or neurocognitive function (P > 0.05). Our findings suggest that football players are concussed by impacts to the head that occur at a wide range of magnitudes and that clinical measures of acute symptom severity, postural stability, and neuropsychological function all appear to be largely independent of impact magnitude and location. Because of the varying magnitudes and locations of impacts resulting in concussion as well as other factors such as the frequency of subconcussive impacts and number of previous concussions, it may be difficult to establish a threshold for concussive injury that can be applied to all football players.

User-Based Motion Sensing and Fuzzy Logic for Automated Fall Detection in Older Adults

More than one third of community-dwelling older adults and up to 60% of nursing home residents fall each year, with 10-15% of fallers sustaining a serious injury. Reliable automated fall detection can increase confidence in people with fear of falling, promote active safe living for older adults, and reduce complications from falls. The performance of a 2-stage fall detection algorithm using impact magnitudes and changes in trunk angles derived from user-based motion sensors was evaluated under laboratory conditions. Ten healthy participants were instrumented on the front and side of the trunk with 3D accelerometers. Participants simulated 9 fall conditions and 6 common activities of daily living. Fall conditions were simulated on a protective mattress. The experimental data set comprised 750 events (45 fall events and 30 nonfall events per participant) that were classified by the fall detection algorithm as either a fall or a nonfall using inputs from 3D accelerometers. Significant differences for impacts recorded, trunk angle changes (p<0.01), and detection performances (p<0.05) were found between fall and nonfall conditions. The proposed algorithm detected fall events during simulated fall conditions with a success rate of 93% and a false-positive rate of 29% during nonfall conditions. Despite a slightly superior identification performance for the accelerometer located on the front of the trunk, no significant differences were found between the two motion sensor locations. Automated detection of fall events based on user-based motion sensing and fuzzy logic shows promising results. Additional rules and optimization of the algorithm will be needed to decrease the false-positive rate.