Application of Advanced Early Warning Systems with Adaptive Protection

This project developed and field-tested two methods of Adaptive Protection systems utilizing synchrophasor data. One method detects conditions of system stress that can lead to unintended relay operation, and initiates a supervisory signal to modify relay response in real time to avoid false trips. The second method detects the possibility of false trips of impedance relays as stable system swings “encroach” on the relays’ impedance zones, and produces an early warning so that relay engineers can re-evaluate relay settings. In addition, real-time synchrophasor data produced by this project was used to develop advanced visualization techniques for display of synchrophasor data to utility operators and engineers

Subjectivity in Failure Mode Effects Analysis (FMEA) Severity Classification within a Reliability Centered Maintenance (RCM) Context

This research paper investigated subjectivity in the severity rating of failure modes within a risk analysis process. Although several risk analysis processes can be utilized, the study considered the application of Failure Modes Effects Analysis (FMEA) or Failure Modes Effects and Criticality Analysis (FMECA) due to its common use within the Aerospace Industry. The study investigated both differences in severity selection given varying amounts of experience as well as any association between severity selection and the provided input information. The main goal of the research was to investigate the impact of data quality on severity selection and to identify factors that impact the severity score, and thus greatly influence the overall risk reduction strategies both in new acquisition and fielded systems. Participants consisted of both experienced and inexperienced FMEA/FMECA users. Participants were tasked to select a severity rating for nine failure modes (across three trials) assuming a typical severity scale. Different input data sets were provided in each trial to ascertain if an association exits between severity class selection and the amount of information available during analysis. This study provided evidence that risk analysis participants are subjective during severity rating selection when utilizing FMEA/FMECA processes. Users who are provided with irrelevant failure and mishap data tend to select similar severity levels; however, when no information is provided to users, user selections will be dramatically more conservative. Participants appear to select similar severity ratings regardless of the relevancy of the provided data

Electromyography & Portable Computing Devices: What Forearm Muscles Should be Measured?

Portable computing devices have become more lightweight and mobile due to changes in the hardware of the devices. In many cases, hardware keyboards are being replacing virtual keyboards, raising concerns on changing ergonomic exposures as, for example, muscle activation patterns may vary with virtual keyboard use. The objective was to identify active forearm muscles across select computing devices. Twenty participants completed a single test session in which seven forearm muscles were evaluated using surface EMG whilst they typed on two portable computing devices (netbook and slate computer) for 5 minutes apiece. Mean normalized EMG was analyzed and indicated that slate computers resulted in significantly lower muscle activation levels than netbooks. The extensor carpi radialis, extensor carpi ulnaris, extensor digitorum communis had the highest muscle activation levels for both the slate and netbook computers. This indicates that the same muscles should be studied for both slate and netbook computers

Quantification of lower extremity physical exposures in various combinations of sit/stand time duration associated with sit-stand workstation

Background: Sit-stand workstations are available for office work purposes but there is a dearth of quantitative evidence to state benefits for lower limb outcomes while using them. And there are no guidelines on what constitutes appropriate sit/stand time duration. The primary aim of this study has been to compare muscle activity and perceived discomfort in the lower extremity during various combinations of sit/stand time duration associated with a sit-stand workstation separately and to evaluate the effects of the sit-stand workstation on the lower extremity during the text entry task. Material and Methods: During the 5 days, all participants completed a 2-h text entry task each day for various sit/stand time duration combinations as follows: 5/25 min, 10/20 min, 15/15 min, 20/10 min, 25/5 min. Lower extremity muscular exposure of 12 male and 13 female participants was collected at 8 sites by surface electromyography and body discomfort was calculated by a questionnaire under those 5 conditions. Results: Results have demonstrated that lower extremity muscle activity has been significantly varied among the 5 sit/stand time duration groups. Perceived level of discomfort (PLD) has not differed significantly for 9 out of 10 body parts. Conclusions: The muscle activity of the thigh region was influenced by sit/stand time duration significantly. Ergonomic exposures of lower extremity when using a sit-stand workstation were increased, particularly during the long time standing posture. Results indicate that body mass index (BMI) and gender were not significant factors in this study. Combination of sit/stand time duration 25/5 min appears to show positive effects on relief of muscle exposure of back of thigh in the shifts of sitting and standing work position. Med Pr 2017;68(3):315–32

Interaction Effects Of Wrist And Forearm Posture On The Prediction Of Carpal Tunnel Syndrome Cases Within A Fish-Processing Facility

Deviated wrist posture has been implicated as a risk factor for carpal tunnel syndrome (CTS), although alone it has not been found to have a causal relationship with CTS. Studies investigating deviated wrist posture have quantified posture in a single plane of motion and not interactions of wrist postures in multiple planes. The objective of this cross-sectional study was to investigate the ability of wrist and forearm posture interaction effects to predict CTS among a population of fish processing operators. A total of 53 participants performing five job tasks were evaluated using electrogoniometers. Due to task asymmetry, each hand was evaluated separately and treated independently, providing 106 hands as data observations. Using logistic regression analysis it was found that a model including flexed (F), extended (E), the interaction of length of employment (LE) by FE, and the interaction of LE by FE by pronation/supination (PS) accurately classified 78% of all hands as cases or non-cases. The sensitivity of the final model was approximately 48%. The developed model was found to have superior predictive ability when compared to models not considering interaction terms, indicating that posture interactions may in fact have a significant effect on CTS alone

Time Pressure and Mental Workload Effects on Perceived Workload and Key Strike Force during Typing

Although physical factors are accepted as risks in the development of work related musculoskeletal disorders (WMSDs), psychosocial factors may explain some of the remaining differences in susceptibility to WMSDs. The following study examined the effects of two psychosocial factors, mental workload and time pressure, on typing performance, perceived workload, and key strike force while typing. The majority of the key strike force measures increased with increases in time pressure and mental workload. Perceived overall workload (as measured using SWAT) increased with mental workload and time pressure, and typing performance decreased. Additionally, gender, locus of control, and perceived stress level did not influence outcomes. Physical risk factors may be mediated by psychosocial factors to increase risk for WMSD development in the upper extremities. Therefore, both physical and psychosocial aspects of work environments should be considered when designing jobs and work tasks to prevent injuries and improve productivity. </jats:p

Analysis of Subjective Body Discomfort Ratings during Simulated Prolonged Driving Tasks: What Measures are most Effective?

Subjective discomfort ratings are a common assessment technique in human factors and ergonomics, and there exist a number of different methods for analyzing ratings (e.g., mean, median, maximum rating, etc.). The objective of this research was to evaluate multiple methods for analyzing body discomfort ratings. Perceived discomfort of eight participants was measured across ten body parts (buttock, left buttock, right buttock, lower back, upper back, neck, shoulder, eye, thigh and whole body) during 2-hour simulated driving tasks at 3 backrest angles (105°, 120°, 135°). Discomfort ratings were collected every 15 minutes using a modified Borg CR-scale. The time weighted discomfort (TWD) average of was found to be more sensitive to backrest angle changes than other measures considered. In addition, factor analysis revealed different methods provided different groupings of body parts, and the method selected for analyzing subjective discomfort ratings should be selected based on the objective of the study. </jats:p