Static Task Research Articles

The Framing Preference for Large and Increasing Components in Static and Dynamic Descriptions.

Describing sets in terms of a two-valued variable, either value can be chosen: exam results may be referred to by pass rates or fail rates. What determines such framing choices? Building on work by McKenzie and colleagues on reference points in the production and interpretation of framed information, we investigate two determinants of frame choice. One is that speakers tend to focus on the component that has increased vis-à-vis a previous state, the other is the tendency to choose the component larger than 50%. We propose to view reference points as pointing to different kinds of communicative relevance. Hence the use of the previous state and the 50% reference points by speakers is not just a function of the information, but is co-determined by a communicative cue in the context: the question being asked about this information. This line of thought is supported by two experiments containing items offering two-sided distribution information at two points in time. Our first experiment employs a static task, requiring a description of the most recent situation. The second experiment uses a dynamic task, asking participants to describe the development between the two time points. We hypothesize that in static tasks the component size is the strongest frame choice determinant, while in dynamic tasks frame choice is mainly driven by whether a component has increased. The experiments consist of 16 different scenarios, both with symmetrical contrasts (i.e., dogs vs. cats) and with asymmetrical ones (i.e., winning vs. losing). Both experiments support the hypotheses. In the static task, the size effect is the only consistent effect; in the dynamic task, the effect of direction of change is much larger than that of size. This pattern of differences between size and change effects applies across symmetrical and asymmetrical contrasts. Our experiments shed light on cognitive and communicative regularities involved in the production of framed messages: people do tend to prefer larger and increasing components when choosing a frame, but the relative strength of both these preferences depends on the communicative task.

Evaluating stability of human spine in static tasks: a combined in vivo-computational study

Various interpretations and parameters have been proposed to assess spinal stability such as antagonist muscle coactivity, trunk stiffness and spinal buckling load; however, the correlation between these parameters remains unknown. We evaluated spinal stability during different tasks while changing the external moment and load height and investigated likely relationships between different EMG- and model-based parameters (e.g., EMG coactivity ratio, trunk stiffness, force coactivity ratio) and stability margins. EMG and kinematics of 40 young healthy subjects were recorded during various quasi-static tasks. Muscle forces, trunk stiffness and stability margins were calculated by a nonlinear subject-specific EMG-assisted-optimization musculoskeletal model of the trunk. The load elevation and external moment increased muscle activities and trunk stiffness while all stability margins (i.e., buckling loads) decreased. The force coactivity ratio was strongly correlated with the hand-load stability margin (i.e., additional weight in hands to initiate instability; R 2 = 0.54) demonstrating the stabilizing role of abdominal muscles. The total trunk stiffness (Pearson’s r = 0.96) and the sum of EMGs of back muscles (Pearson’s r = 0.65) contributed the most to the T1 stability margin (i.e., additional required load at T1 for instability/buckling). Force coactivity ratio and trunk stiffness can be used as alternative spinal stability metrics.

Influence of different transcranial magnetic stimulation current directions on the corticomotor control of lumbar erector spinae muscles during a static task

Different directions of transcranial magnetic stimulation (TMS) can activate different neuronal circuits. While posteroanterior current (PA-TMS) depolarizes mainly interneurons in primary motor cor...

Changes in the distribution of muscle activity when using a passive trunk exoskeleton depend on the type of working task: A high-density surface EMG study

Exoskeleton effectiveness in reducing muscle efforts has been usually assessed from surface electromyograms (EMGs) collected locally. It has been demonstrated, however, muscle activity redistributes within the low back muscles during static and dynamic contractions, suggesting the need of detecting surface EMGs from a large muscle region to reliably investigate changes in global muscle activation. This study used high-density surface EMG to assess the effects of a passive trunk exoskeleton on the distribution of low back muscles’ activity during different working tasks. Ten, male volunteers performed a static and a dynamic task with and without the exoskeleton. Multiple EMGs were sampled bilaterally from the lumbar erector spinae muscles while the hip and knee angles were measured unilaterally. Key results revealed for the static task exoskeleton led to a decrease in the average root mean square (RMS) amplitude (∼10%) concomitantly with a stable mean frequency and a redistribution of muscle activity (∼0.5 cm) in the caudal direction toward the end of the task. For the dynamic task, the exoskeleton reduced the RMS amplitude (∼5%) at the beginning of the task and the variability in the muscle activity distribution during the task. Moreover, a reduced range of motion in the lower limb was observed when using the exoskeleton during the dynamic task. Current results support the notion the passive exoskeleton has the potential to alleviate muscular loading at low back level especially for the static task.

Comparison between two mobile applications measuring shoulder elevation angle–A validity and feasibility study

Pain in the shoulder complex affects the working population where work with elevated arms is a risk factor. The aim of the present study was to compare a mobile application for measurements of arm elevation, ErgoExposure, against an existing mobile application, ErgoArmMeter, in a laboratory setting and to test the feasibility in a field trial. Eleven persons performed three tasks in the laboratory setting: static, dynamic, and simulated work tasks, where the applications were validated against an optical tracking system (OTS). Also, ErgoExposure was tested by a teacher in a real-world situation. Limits of agreement for the static task varied between -6.1° to 4.2° (ErgoExposure) and between -7.6° to 5.2° (ErgoArmMeter). The average root mean square difference for dynamic and simulated work tasks was 3.4° (ErgoExposure) and 7.7° (ErgoArmMeter). From the field trial, different work tasks produced distinct exposure variation analysis patterns. Both apps showed similar results compared to OTS, but ErgoExposure was more accurate than ErgoArmMeter.

Effects of Arm-Support Exoskeletons on Kinematics and Subjective Assessments During a Static Task

Effects of Arm-Support Exoskeletons on Kinematics and Subjective Assessments During a Static Task

Dynamic assessment in spelling and morphological awareness in Greek: The case of a transparent orthography

BackgroundRecent research is in favor of the use of dynamic assessment as an important method of combining assessment and intervention in a unified framework for typically and non-typically developing children. However, research is still sparse, in the evaluation of morphological awareness, especially for phonologically regular languages. AimsThis study aimed to investigate the role of dynamic assessment in the evaluation of morphological awareness in Greek children. MethodsForty Greek participants (7–8 years old) allocated to an experimental (N = 21) and a control group (N = 19) were preliminary assessed on reading syllables/words, spelling words, vocabulary and morphological awareness. They were also evaluated on static assessments of spelling and word-formation of morphologically complex words, while only the experimental group was evaluated on dynamic assessments of the same tasks. ResultsChildren achieved significantly higher performance on the dynamic assessment tasks in comparison to their static ones. Correlations indicated that the degree of children's progress depended greatly on their initial literacy and language skills, while regression analyses revealed that static tasks made a unique contribution to their dynamic performance. ConclusionsThe results underline the role of dynamic assessment in the evaluation of morphological awareness in a phonologically regular language with rich morphology, such as Greek.

Motion disrupts dynamic visual search for an orientation change

Visual search in dynamic environments, for example lifeguarding or CCTV monitoring, has several fundamentally different properties to standard visual search tasks. The visual environment is constantly moving, a range of items could become targets and the task is to search for a certain event. We developed a novel task in which participants were required to search static and moving displays for an orientation change thus capturing components of visual search, multiple object tracking and change detection paradigms. In Experiment 1, we found that the addition of moving distractors slowed participants’ response time to detect an orientation changes in a moving target, showing that the motion of distractors disrupts the rapid detection of orientation changes in a moving target. In Experiment 2 we found that, in displays of both moving and static objects, response time was slower if a moving object underwent a change than if a static object did, thus demonstrating that motion of the target itself also disrupts the detection of an orientation change. Our results could have implications for training in real-world occupations where the task is to search a dynamic environment for a critical event. Moreover, we add to the literature highlighting the need to develop lab-based tasks with high experimental control from any real-world tasks researchers may wish to investigate rather than extrapolating from static visual search tasks to more dynamic environments.

DEFORMATION AND BUCKLING ANALYSIS OF SHALLOW CONICAL SHELLS BASED ON IMPROVED MODEL OF WIND LOAD USING ENVIRONMENT ANSYS

The process of deformation and buckling of shallow thin-walled elastic conical shells has been investigated for the case of significantly non-uniform stress-strain state due to the action of wind load based on improved model of pressure application schema to the surface of shallow shell and for hinged hedge of border. An improved model of wind load was based on data presented in terms [5, 6] and was a logical continuation of previous investigation of wind action on shallow conical shells based on model of first approach [3]. Deformation and buckling process investigation has been carried out using software ANSYS which effectivity was approved by the fact of being used by NASA for its aerospace projects. A model of shallow conical shell has been made using four-corner finite element SHELL 281 with 8 nodes that let us obtain not only symmetrical relatively to the axis of rotation buckling form but an asymmetrical too. Two types of computation have been made during numerical modeling – linear bifurcation computation with determination of linear pressure qcr value and corresponding to it buckling form, and computation of geometrically non-linear problem of deformation with determination of limit pressure qlim and corresponding buckling form. Obtained buckling forms have been compared to the deformed shape of shell surface when aerodynamic computations have been carried out using software ANSYS. An estimation analysis has been made for case of application of improved model of wind load in comparison to the previous investigation according to the values of baring capacity and buckling shape coherence during resolution of static tasks and comparison to the results of aerodynamic solution. An analysis of base parameter influence has been carried out for the model of first approach and current improved model according to the bearing capacity value and local extremums on schema of pressure intensity distribution of wind load. Specific moments of deformation process computations based on improved model using environment ANSYS have been mentioned and of further analysis on the basis of improved model with it specifics have been given too.

ADES: A New Ensemble Diversity-Based Approach for Handling Concept Drift

Beyond applying machine learning predictive models to static tasks, a significant corpus of research exists that applies machine learning predictive models to streaming environments that incur concept drift. With the prevalence of streaming real-world applications that are associated with changes in the underlying data distribution, the need for applications that are capable of adapting to evolving and time-varying dynamic environments can be hardly overstated. Dynamic environments are nonstationary and change with time and the target variables to be predicted by the learning algorithm and often evolve with time, a phenomenon known as concept drift. Most work in handling concept drift focuses on updating the prediction model so that it can recover from concept drift while little effort has been dedicated to the formulation of a learning system that is capable of learning different types of drifting concepts at any time with minimum overheads. This work proposes a novel and evolving data stream classifier called Adaptive Diversified Ensemble Selection Classifier (ADES) that significantly optimizes adaptation to different types of concept drifts at any time and improves convergence to new concepts by exploiting different amounts of ensemble diversity. The ADES algorithm generates diverse base classifiers, thereby optimizing the margin distribution to exploit ensemble diversity to formulate an ensemble classifier that generalizes well to unseen instances and provides fast recovery from different types of concept drift. Empirical experiments conducted on both artificial and real-world data streams demonstrate that ADES can adapt to different types of drifts at any given time. The prediction performance of ADES is compared to three other ensemble classifiers designed to handle concept drift using both artificial and real-world data streams. The comparative evaluation performed demonstrated the ability of ADES to handle different types of concept drifts. The experimental results, including statistical test results, indicate comparable performances with other algorithms designed to handle concept drift and prove their significance and effectiveness.

UMOTS: an uncertainty-aware multi-objective genetic algorithm-based static task scheduling for heterogeneous embedded systems

UMOTS: an uncertainty-aware multi-objective genetic algorithm-based static task scheduling for heterogeneous embedded systems

Investigating the effect of a passive trunk exoskeleton on local discomfort, perceived effort and spatial distribution of back muscles activity

This study aimed at determining the effect of a passive exoskeleton on local perceived discomfort, perceived effort and low back muscles’ activity. Thirteen volunteers performed two simulated working tasks with and without the exoskeleton. In the static task, the exoskeleton decreased the lumbar perceived discomfort, the perceived effort and the level of low back muscles’ activity (∼10%) while increasing discomfort in the chest and feet. The percent decrease in EMG amplitude was correlated with the percent increase in perceived effort with exoskeleton. For the dynamic task, the exoskeleton increased the discomfort in the chest and decreased the level of back muscle activity (∼5%). Current findings suggest exoskeleton is effective in reducing the back load while increasing the perceived discomfort at non-targeted body regions in both working tasks. The concurrent increase of discomfort in non-targeted areas probably led to a higher perceived effort despite the reduction of low back muscle activity. Practitioner summary: This study provided insights into exoskeleton effects on local discomfort, perceived effort and muscle activity. Overall, the potential benefits of passive exoskeleton should be considered alongside its adverse effects on the non-targeted body regions that can lead to an increase of perceived effort despite the reduction of back muscle activity.

Social brokerage: Encounters between Colombian coffee producers and Austrian Buyers – A research-based relational pathway

The usual economic analyses skip the web of social relations where economic but also social influences are equally relevant. Reinecke et al. (2018) offer a conceptual perspective to study social brokerage (the ‘social turn’) across global value chains. This paper aims: 1) to reveal how Colombian producers and Austrian roasters start social ties (i.e. through social brokerage) and eventually become business partners with the illustrative example of specialty coffee chains, 2) to propose a research-based relational pathway for social brokerage, and 3) to unpack how encounters between producers and roasters originated and developed as well as to identify the required knowledge and coordination devices used. The encounters follow an ethnographic approach relying on participant observation (e.g. in Vienna, Austria and in selected Colombian coffee regions). Coffee is one of the many commodities suitable to analyze social interactions across global chains. Colonial patterns are still embedded in the economic geography of global value chains. The involvement of researchers (including non-Europeans) was key to enhance social brokerage (e.g. structural holes, boundary work) and in that way allowed disadvantaged chain actors to uninhibitedly voice whatever discomfort resulted from those interactions. Although material quality is paramount in the trade of specialty coffee, it shall not be the only guiding coordination device and knowledge construct to be followed by chain actors. Building collaborative relationships is not an easy or static task. Nonetheless, it is key to encourage knowledge sharing, to yield a sense of fairness and humanity across global chains and to cope with opportunistic gatekeepers.

Activation patterns of shoulder internal and external rotators during pure axial moment generation across a postural range

Musculoskeletal risk is mediated by body posture, especially for static tasks. Workstations that require non-neutral postures can lead to increased load, muscular fatigue and injury risk. However, demands during simple axial rotation tasks are not well-defined. The purpose of this study is to quantify the muscular activity of during static axial rotation in a range of postures. Eighteen participants performed 76 axial rotation exertions in varying combinations of humeral elevation angles (30°-60°-90°-120°-150°), plane of elevation (30°-60°-90°-120°) and exertion intensity (20–40%). Six unilateral (right) muscles (pectoralis major (clavicular and sternal), posterior deltoid, teres major, infraspinatus, latissiumus dorsi) were monitored using surface electromyography (EMG). EMG was normalized and integrated over 2 s. The influences of elevation, plane, and intensity on activity levels were then tested with a 3-way ANOVAs (p < .05). During internal rotation, activity was highest at low elevation/high plane combinations for the internal rotators, but at high elevation/low plane combinations for the external rotators. During the 40% intensity exertions, activity levels were highest at lower elevations for internal rotator but at high elevations for the external rotators. During external rotation, as the degree of elevation increased, the activity of the external rotator muscles also increased while internal rotators were unaffected. Humeral muscles responsible for axial rotation are influenced by arm posture during axial rotation exertions. High elevation and plane combinations resulted in high demands for external rotator muscles and this should be considered for job design and injury risk.

Sleep efficiency and physical performance differences between pain-free individuals and individuals with chronic lower back pain

Within the United States, chronic low back pain (cLBP) is a leading cause of pain and the second leading cause of disability. Individuals with cLBP frequently report sleep disturbances—most commonly, cLBP impacts sleep efficiency and quality. Additionally, cLBP most visibly impacts physical functioning with individuals with cLBP being not able to perform physical function tasks as effectively as pain-free individuals. Emerging evidence indicates that sleep has a significant relationship on physical functioning, however whether pain exacerbates sleep disturbances and physical functioning of people with cLBP, relative to pain-free individuals (PF) has not been previously examined. This study quantified differences by pain-status (cLBP and PF) for an individual's actigraphic sleep variables (e.g. sleep efficiency) and physical function, and examined the influence of pain on actigraphic variables and physical function in cLBP. Participants (cLBP = 102, PF = 45) completed the Short Physical Performance Battery (SPPB), daily pain ratings, and home sleep monitoring for 7-consecutive days/nights. Analyses revealed that cLBP individuals had reduced objective sleep quality (p = .003), and SPPB dynamic performance (p = .000), but not for static tasks (p >.05) compared to PF. Sleep quality prior to SPPB was associated with SPPB tasks for cLBP individuals (total battery r=.23) but not for PF (r=-.08). Additionally, daily pain ratings influenced sleep efficiency (p = .003), and pain from the night prior to SPPB was associated with worse outcomes for the dynamic SPPB tasks, but not the balance tasks for cLBP. Our findings suggest that sleep and pain may influence physical performance tasks for cLBP, but not PF– this further reinforces the importance of further examination of identifying whether pain or sleep are antecedents to reduced performance and outcomes in cLBP or if a bilateral relationship exists with pain severity and sleep quality. This work was supported by Examining Racial And SocioEconomic Disparities in cLBP; ERASED; R01MD010441.

Exploration of shear wave elastography measures of the iliotibial band during different tasks in pain-free runners

ObjectivesTo determine whether shear wave velocity (SWV) of the iliotibial band (ITB): i) increases with active and passive static tasks, and a dynamic task, ii) differs between ITB regions, iii) changes after exposure to running. Additionally, it aimed to determine the between-day reliability. DesignCase series & test-retest. SettingHuman movement unit laboratory. ParticipantsFifteen runners. Main outcome measuresSWV was measured unilaterally in three regions of the ITB (proximal, middle and distal), during six tasks: rest and contraction (pre- and post-running), modified Ober test, standing, pelvic drop, and weight shift. ResultsCompared to rest, SWV was higher during contraction and Ober test in the distal and middle regions, and higher for the middle region in standing and pelvic drop. No differences were found between regions. A tendency of decreased SWV was observed after running. Compared to the start of the dynamic task, SWV was greater at the end of the movement. Reliability was moderate-to-good for the middle region in the standing tasks (ICCs = 0.68 to 0.84). ConclusionSVW of the ITB was higher under passive or active tension. Comparisons between tasks/regions need to be considered in light of the small sample size and poor repeatability of some regions/conditions.

Methodical approaches to assessing the effectiveness of animal husbandry

Economic efficiency of livestock production is determined using a system of indicators, among which the main (generalizing) indicator of economic efficiency of livestock production is the achieved level of labor productivity. This indicator has a significant impact on other derivative indicators. A comprehensive assessment of the efficiency of farming systems should be carried out using a generalized indicator of the efficiency of the used resources of the livestock enterprise and an indicator of the share of growth of livestock products. The matrix method is the most acceptable for the analysis and an estimation of efficiency of work of the livestock enterprises. It allows: to rank livestock enterprises according to the achieved level of efficiency (static task); to study changes in the level of efficiency of livestock enterprises during the analyzed period (dynamic task); determine the dependence of farm performance on intensive and extensive factors. To assess the economic efficiency of feed production in animal husbandry use the indicator “marginal productivity of feed (feed protein) unit”. Evaluation of productive use of dairy cows is carried out using the coefficient of productivity intensity, which is calculated by the ratio of the average milk yield per day to the lifetime milk yield of cows. The complexity of livestock mechanization, individual technological lines or specific machines and equipment is determined by the calculated technical and economic indicators, comparing them with the indicators obtained in practice of the existing facility or basic analogue, or with the best examples of domestic or world practice. The application of the above indicators of analysis and evaluation of livestock efficiency will provide: assessment of the effectiveness of production systems by livestock enterprises in modern conditions of their development; objective characteristics of farming and the main results of activities in animal husbandry; identification of the most rational options for improving the efficiency of animal husbandry; comparative assessment of the efficiency of livestock enterprises operating in the same natural and economic conditions; measuring production efficiency in livestock and related industries; identification and evaluation of a set of measures for the development of animal husbandry aimed at improving the efficiency of its operation.

Automatically Determining Lumbar Load during Physically Demanding Work: A Validation Study.

A sensor-based system using inertial magnetic measurement units and surface electromyography is suitable for objectively and automatically monitoring the lumbar load during physically demanding work. The validity and usability of this system in the uncontrolled real-life working environment of physically active workers are still unknown. The objective of this study was to test the discriminant validity of an artificial neural network-based method for load assessment during actual work. Nine physically active workers performed work-related tasks while wearing the sensor system. The main measure representing lumbar load was the net moment around the L5/S1 intervertebral body, estimated using a method that was based on artificial neural network and perceived workload. The mean differences (MDs) were tested using a paired t-test. During heavy tasks, the net moment (MD = 64.3 ± 13.5%, p = 0.028) and the perceived workload (MD = 5.1 ± 2.1, p < 0.001) observed were significantly higher than during the light tasks. The lumbar load had significantly higher variances during the dynamic tasks (MD = 33.5 ± 36.8%, p = 0.026) and the perceived workload was significantly higher (MD = 2.2 ± 1.5, p = 0.002) than during static tasks. It was concluded that the validity of this sensor-based system was supported because the differences in the lumbar load were consistent with the perceived intensity levels and character of the work tasks.

Getting a grip on the resilience to blur: The impact of simulated vision loss on a visually guided combat sports interaction

Research has shown that performance in highly visually demanding sports can be resilient to substantial levels of blur. This raises the question whether the need for high visual clarity might be reduced even more in less visually demanding sports such as combat sports, where athletes compete at relatively close distances. The aim of this study was to examine the resilience to blur in the grip fighting phase of judo as an exemplar of a visually guided combat sports task. The results were particularly relevant for the purposes of Paralympic judo for athletes with vision impairment (VI judo), because athletes are currently allowed to compete with a visual acuity (VA) of 1.0 logMAR or worse (i.e., 6/60 or 20/200 vision), suggesting this is the presumed level of impairment that decreases performance in able-sighted judo. We let 28 able-sighted judo athletes compete in pairs in a series of grip fighting tasks under increasing levels of simulated vision impairment. Visual function was tested in each condition by measuring VA and contrast sensitivity (CS). We found that VA was a better predictor than CS of grip fighting performance. VA needed to be reduced to at least 1.3 logMAR before a decrease in performance was found, with approximately twice as much blur needed to be applied when compared to visually demanding tasks such as cricket batting, but less than what has been found in static tasks such as basketball free-throw shooting and golf putting. These findings hold implications for VI judo regulations, suggesting that a more severe degree of impairment should be required to participate than is currently the case.

Glow in the dark: Using a heat-sensitive camera for blind individuals with prosthetic vision

To date, retinal implants are the only available treatment for blind individuals with retinal degenerations such as retinitis pigmentosa. Argus II is the only visual implant with FDA approval, with more than 300 users worldwide. Argus II stimulation is based on a grayscale image coming from a head-mounted visible-light camera. Normally, the 11°×19° field of view of the Argus II user is full of objects that may elicit similar phosphenes. The prosthesis cannot meaningfully convey so much visual information, and the percept is reduced to an ambiguous impression of light. This study is aimed at investigating the efficacy of simplifying the video input in real-time using a heat-sensitive camera. Data were acquired from four Argus II users in 5 stationary tasks with either hot objects or human targets as stimuli. All tasks were of m-alternative forced choice design where precisely one of the m≥2 response alternatives was defined to be “correct” by the experimenter. To compare performance with heat-sensitive and normal cameras across all tasks, regardless of m, we used an extension of signal detection theory to latent variables, estimating person ability and item difficulty in d' units. Results demonstrate that subject performance was significantly better across all tasks with the thermal camera compared to the regular Argus II camera. The future addition of thermal imaging to devices with very poor spatial resolution may have significant real-life benefits for orientation, personal safety, and social interactions, thereby improving quality of life.