Multi-level Task Research Articles

Implications of Alternative Multilevel Design Methods for Design Process Management

Multilevel design problems are typically decomposed into a hierarchy of distributed and strongly coupled sub-problems, each solved by design teams with specialized knowledge and tools. There are two contrasting approaches to formulating and solving such collaborative design problems: (1) highly iterative exchanges of single design solutions, as in point-based optimization approaches, and (2) minimally iterative exchanges of multiple solutions, as in set-based approaches. In this article, the effects of these alternative approaches on the overall lead time of a design process are explored. A discrete event simulation is developed to evaluate the lead times of highly iterative and minimally iterative multilevel design strategies and the sensitivity of those lead times to the level of noise in the design environment for a range of designer work loads. Designer work loads include not only the multilevel design task of interest, but also secondary design jobs that consume designer time. Noise is represented as variability in task processing times, arrival rates, and iteration levels. An example design process for an unmanned aerial vehicle is used to compare set-based and point-based design strategies. The results of the simulations indicate that the lead times of minimally iterative, set-based design processes are more robust to busy design environments than highly iterative, point-based alternatives. Accordingly, it may be advantageous to favor richer, but less frequent, exchanges of information in a multilevel design process, even if more effort is required to generate those sets of information.

Explaining how and explaining why: developmental and evolutionary explanations of dominance

There have been two different schools of thought on the evolution of dominance. On the one hand, followers of Wright [Wright S. 1929. Am. Nat. 63: 274–279, Evolution: Selected Papers by Sewall Wright, University of Chicago Press, Chicago; 1934. Am. Nat. 68: 25–53, Evolution: Selected Papers by Sewall Wright, University of Chicago Press, Chicago; Haldane J.B.S. 1930. Am. Nat. 64: 87–90; 1939. J. Genet. 37: 365–374; Kacser H. and Burns J.A. 1981. Genetics 97: 639–666] have defended the view that dominance is a product of non-linearities in gene expression. On the other hand, followers of Fisher [Fisher R.A. 1928a. Am. Nat. 62: 15–126; 1928b. Am. Nat. 62: 571–574; Bürger R. 1983a. Math. Biosci. 67: 125–143; 1983b. J. Math. Biol. 16: 269–280; Wagner G. and Burger R. 1985. J. Theor. Biol. 113: 475–500; Mayo O. and Reinhard B. 1997. Biol. Rev. 72: 97–110] have argued that dominance evolved via selection on modifier genes. Some have called these “physiological” versus “selectionist,” or more recently [Falk R. 2001. Biol. Philos. 16: 285–323], “functional,” versus “structural” explanations of dominance. This paper argues, however, that one need not treat these explanations as exclusive. While one can disagree about the most likely evolutionary explanation of dominance, as Wright and Fisher did, offering a “physiological” or developmental explanation of dominance does not render dominance “epiphenomenal,” nor show that evolutionary considerations are irrelevant to the maintenance of dominance, as some [Kacser H. and Burns J.A. 1981. Genetics 97: 639–666] have argued. Recent work [Gilchrist M.A. and Nijhout H.F. 2001. Genetics 159: 423–432] illustrates how biological explanation is a multi-level task, requiring both a “top-down” approach to understanding how a pattern of inheritance or trait might be maintained in populations, as well as “bottom-up” modeling of the dynamics of gene expression.

A System for Distributed Storage and Analysis of Genome Information

A distributed computing system is developed to search and analyze genetic databases using parallel computing technologies. Queries are processed by a local network PC cluster. A universal task and data exchange format is developed for effective query processing. A multilevel hierarchic task batching procedure is elaborated to generate multiple subtasks and distribute them over cluster units under dynamic priority levels and with dynamic distribution of replicated source data subbases. Primary source data preparation and generation of annotation word indices are used to significantly reduce query processing time.

“Dynamic Trendelenburg”: Single-Leg-Squat Test for Gluteus Medius Strength

UNCTIONAL TESTING is often used to assess components of multilevel tasks. Although functional tests are used regularly, the reliability and validity of the tests are often not thoroughly investigated. The single-leg squat is one such test that is used by clinicians and has been suggested to assess general leg strength and muscle endurance.1 The single-leg squat is described with various techniques including a single-leg squat with hand support, squatting with an external load, and a lunge activity.2 No standardized method is used, and no relationship has been documented to determine what the single-leg-squat test is actually assessing. It has been suggested that the single-legsquat test can be used to assess various dysfunctions affecting the kinetic chain.3 Zeller et al. used a three-dimensional camera system to report kinematic differences between men and women performing a single-leg squat.2 They reported that women had approximately 4° more hip adduction than men did when performing the singleleg squat.2 Zeller et al. suggest that the increased hip adduction might be caused by difficulty in controlling the hip musculature resulting from a weak gluteus medius muscle.2 No information presently exists on the relationship between hip-adduction angles and gluteus medius strength. The Trendelenburg sign is a very simple test that indicates gluteus medius weakness4 and can be used to identify injuries that result from an unlevel pelvis. The injuries and disorders that can be caused by a weak gluteus medius are numerous and include torn anterior cruciate ligaments, eversion ankle sprains, shin splints, scoliosis, and other malalignment injuries up and down the kinetic chain.4,5 Novice clinicians might find it hard to iden tify a weak gluteus medius because the underlying cause of these disorders might be caused by the hip but manifest elsewhere along the kinetic chain. Maintenance of a single-leg stance is necessary during running, cutting, and decelerating activities.2 If a weak gluteus medius is present during these dynamic activities, it might be difficult to observe the pelvic drop as a clinician would during Trendelenburg’s test. A single-leg-squat test includes the static Trendelenburg position but incorporates movement into the test to make it more dynamic. It is hoped that the “dynamic Trendelenburg” can be used to identify gluteus medius weakness during more dynamic tasks than in the original Trendelenburg test. As an athlete performs a single-leg-squat test, the clinician must visually observe the task and base decisions regarding the athlete’s strength on these subjective observations. These observational practices are commonly used but are rarely put under the scrutiny of scientific examination. Previous research of a clinician’s ability to identify deviations from a normal movement pattern has yielded only low to moderate reliability.6 Thus these tests should be used with caution by clinicians when making decisions regarding athlete care. Several functional tests are available for clinicians to evaluate their athletes. In order to make sound clini

Effects of sleep deprivation and user interface on complex performance: a multilevel analysis of compensatory control.

This study was carried out to test the compensatory control model, which predicts performance maintenance under stress at the expense of effort and increased selectivity. It examined the effects of sleep deprivation on performance in an automated process control task based on a simplified life support system with two types of operator control panel interface: machine centered (M-C), in which access to the system was scheduled by the computer, and human-centered (H-C), in which access was ad-lib. The task environment also permitted the analysis of changes in strategy and in subsidiary activities (alarm reaction time, prospective memory). In a 2 x 2 repeated-measures design, 16 participants carried out the task with each interface after both normal sleep and one night of sleep deprivation (SD). No effects of SD were observed on primary task performance. As predicted, SD effects were confined to strategy changes and subsidiary task impairment and occurred only under the (low control) M-C interface. Subjective effort was increased under SD, with greater increases of effort associated with high levels of performance protection. The findings provide strong evidence in favor of the compensatory control model and argue for the use of complex, multilevel tasks in the analysis of performance under stress. Actual or potential applications include the development of more sensitive performance-testing systems based on multilevel analysis of decrement, and the design of interfaces for shift work and other suboptimal work conditions.

ERP components elicited in response to warning stimuli: the influence of task difficulty

A series of experiments were conducted to systematically evaluate the relative contributions of task difficulty and stimulus probability to P300 amplitudes. Scalp event-related potentials (ERPs) were recorded and the topographic distributions were evaluated during a multi-level cognitive task with an antecedent warning. In three separate studies, task difficulty (five levels), probability or expectedness (10–60%), and randomness (random or blocked presentation) were manipulated. Response accuracy, subjective ratings, and reference-free averages of the P300 components elicited by the warning stimuli were evaluated. Statistical analysis indicated that significantly larger P300s were associated with the more difficult task warnings except when memory tasks were presented in a blocked design, suggesting that neither task difficulty nor probability alone can account for variations in the P300 in a multi-level task scenario. Results are discussed with regard to adaptation-level theory.

Structure from associative learning

It is frequently pointed out that a tabula rasa learning system needs constraints in order to extract structural information from its input-output sequence. We have been experimenting with a learning-system (PP) that incorporates a simple associative form of learning in a production system architecture. It is demonstrated that PP, implemented in a simulated robot, can learn the structure of a multi-level task with the help of speech and one or more auxiliary actions. Following a suggestion that structure could be acquired by a stress/nonstress distinction in the teacher's verbal presentation, we report briefly on an experiment that shows that stress can replace the auxiliary action.

A comparative analysis of participatory ergonomics programs in U.S. and Japan manufacturing plants

The use of a participative approach to ergonomics is growing in countries throughout the world. This paper compares and contrasts Participatory Ergonomics programs in two U.S. and two Japanese manufacturing plants. All four programs focused on the redesign of repetitive manufacturing jobs to reduce physical stress on workers. In all four cases, this traditional ergonomics concern was addressed in a non-traditional way-involving broad participation of many manufacturing functions who worked together as an ergonomics team and direct input from operators whose jobs were redesigned. The participatory ergonomics programs were successful in making significant numbers of job changes in both countries. A comparison of the ergonomics programs across countries revealed some significant differences in structure and process. An overarching difference was in how participation was managed. In the Japan cases, participation was a carefully controlled process by which upper management and staff specialists worked through first-line supervisors to get input from workers meeting in quality (or safety) circles. In the U.S., multi-functional and multi-level task forces (including union and worker representatives) were formed and operators were invited to meetings to give input. The U.S. plants gave the task force a great deal of autonomy and virtually all decisions were group decisions. The differences suggest that effective participatory ergonomics programs can take many forms. The best program for any particular plants in differing countries depends on their own unique history, structure, and culture.

Assessment of control ability in the physically handicapped

A tracking task was developed in order to obtain parameters relevant to the design of control interfaces for the physically handicapped. Principles of construction and operation are given, and methods for obtaining parameters are described. Results are presented from evaluator use with a number of subjects covering a wide range of control abilities. Overall performance in the tracking task is compared to general physical ability and experience with other control devices. One task required a response to a target which moved between two possible positions after a constant or variable time interval; correlation was observed between variables representing overall speed and accuracy. For multi-level tasks, scores equal to total time on target were obtained for tasks of differing complexity. Their values are shown to contain information on both speed and accuracy of control. Factors affecting performance are discussed and useful parameters suggested. In particular, information derived from the first, simpler task was shown to correlate well with that from the more complex tests. This type of test provides a useful general method for the interactive design and assessment of control interfaces.

The Multi-Level Classroom or The One Room Little Red Schoolhouse Revisited

ESL classes are often composed of students from different language groups who are at different levels of language proficiency. We need to adapt traditional methods and settings to accommodate this reality if we wish to provide our students with rich language input. This article proposes a listening activity: the use of multilevel tasks drawing from a common text using the resources of the language lab. As well as offering a rationale and guide to the use of the language lab, it features practical suggestions for structuring exercises and examples of exercise types.