S. Keith Adams

A mixed-integer linear model for optimal processing and transport of secondary materials

In every area of materials recovery management, transportation is an important component of waste management systems. Affordable transportation methods to move material from seller to buyer should be carefully investigated. The current study examines the possibility of installing intermediate processing stations between sellers and buyers. Intermediate processing stations are needed to assure quality of the recycled paper and cardboard and to collect and densify these materials for economical transport by truck or rail. The approach used emphasizes the application of a mixed-integer linear programming model for transportation of recovered paper. The research was focused on expressing the transportation optimization problem as a linear programming problem. Determination of optimal locations for the processing stations is emphasized. For this study, the available modes of transportation to recycling markets included semi-trailer truck and rail. The computerized transportation model presented is a general model applicable to either mode and can be modified to evaluate relevant secondary materials. The result of this research is an optimal transportation system model for the movement of recovered paper from selected sources in the State of Iowa to anticipated markets within the state. In most cases, truck transportation is the most practical mode because of its flexibility in routing and unit hauling capacity.

Operating procedure automation to enhance safety of nuclear power plants

Abstract Use of logic statements and computer assist are explored as means for automation and improvement on design of operating procedures including those employed in abnormal and emergency situations. Operating procedures for downpower and loss of forced circulation are used for demonstration. Human-factors analysis is performed on generic emergency operating procedures for three strategies of control; manual, semi-automatic and automatic, using standard emergency operating procedures. Such preliminary analysis shows that automation of procedures is feasible provided that fault-tolerant software and hardware become available for design of the controllers. Recommendations are provided for tests to substantiate the promise of enhancement of plant safety. Adequate design of operating procedures through automation may alleviate several major operational problems of nuclear power plants. Also, automation of procedures is necessary for partial or overall automatic control of plants. Fully automatic operations are needed for space applications while supervised automation of land-based and offshore plants may become the thrust of new generation of nuclear power plants.

Designing a User Interface for a PDA-Based Campus Navigation Device

University campuses, like many other public and private institutional settings, pose challenges to visitors and newcomers finding their way from place to place. In some cases, such campuses have grown to the size of a small town. Maps and tour guides have traditionally been the means used to assist visitors find their way; however, the recent development of high-power, low-cost mobile computing opens the door to portable electronic navigational aids. This paper focuses on user interface concerns in a personal digital assistant (PDA) based campus guide. Cognitive and visual display engineering principles are used to develop a preferred preliminary design. Subjective feedback and quantitative data on the user interface are gathered in a small pilot study. The appropriateness of the design and its implications for future work are also discussed.

Maximum Voluntary Hand Grip Torque for Circular Electrical Connectors

A study employing twenty male and eleven female subjects was performed to determine maximum hand grip torque that can be exerted during tightening or loosening of circular electrical connectors. A static, sustained three-second exertion was used as the strength criterion. Torque was applied to simulated connector rings with diameters of 0.9, 1.5, and 2.0 inches and measured by means of a single-bridge torsional load cell. Other variables tested included the type of grip employed (full or fingertip), orientation of the connector (front, right side, or rear facing behind a barrier), the use of work gloves and chemical defense gloves, the height of the connectors (60% and 85% of the maximum reach height) and the direction of rotation. Hand grip torque strength was found to be directly related to connector diameters, with similar strength patterns exhibited for tightening and loosening. Higher torque was exerted when the connectors were on the subjects right side, and tightening and loosening effort corresponded to flexing and extending the wrist parallel to the forearms. The use of gloves resulted in higher torque in most situations. Connector height and direction of rotation had little effect on torque strength.

MARTIN: a midwest regional database for recycling materials from post-consumer solid waste

Abstract This article describes the design, development and implementation of MARTIN (Mid-America Recycling and Transportation Information Network), a project conducted under sponsorship from the US Environmental Protection Agency and the Iowa Department of Natural Resources from 1990 to 1994. MARTIN was designed, developed and implemented in response to the needs of solid waste officials and generators to access information on the most cost effective options for marketing recyclable commodities. The system provides basic information on markets, material specifications and transportation. The database with its modem and aural DECtalk ™ telephone line access, originally planned for Iowa and bordering states, and expanded to a fifteen state area with access to regional and international markets, received calls from all parts of the United States. Unique features of this system include its flexibility, low cost, DECtalk ™ capability and transportation resource access and selection. This system operated 4 years from April 1991 through April 1995. The technology derived from developing MARTIN can be adapted to a broad range of material logistics and resource management applications.

A Data Bank for Human Related Events in Nuclear Power Plants

The authors introduce a comprehensive survey and evaluation of presently available data sources in nuclear power plants. A newly developed classification format for human related events is proposed. The format presents all necessary information in a coded form to support human reliability analysis and the assessment of performance shaping factors. Recommendations are given for improving data sources to facilitate the evaluation of man-machine interfaces and human performance in nuclear power plants.

A Procedure for Evaluating Auditory Warning Signals

Auditory warning devices used on typical industrial vehicles or material handling devices are produced in quantity as standard items affording the equipment purchaser little or no choice of signal characteristics. Industrial experience has indicated that masking of auditory warning signals by industrial noise backgrounds occurs frequently, often presenting serious incidents or causing accidents. This paper presents statistical model and practical method whereby the effectiveness of auditory warning devices in industrial environments can be predicted based on spectral analyses of the signal and the background in which it is to be used.

Hand-Grip Torque for Circular Electrical Connectors: The Effect of Obstructions

The hand grips of 18 male and 16 female subjects were studied to determine the maximum, clockwise static torque that could be applied to circular electrical connectors under six defined levels of interference and four conditions of interference (types of obstruction) with and without work gloves. The diameters of connectors tested were 0.9, 1.5 and 2.0 in., respectively. Torque strength and required separation were found to be a function of level of interference, condition of interference, connector size, and glove usage. Interference from an adjacent surface to the right or below the grasped connector was less severe than interference from adjacent connectors to the left and right. The greatest interference occurred when adjacent connectors were located to the right, left, above and below the grasped connector. Large connectors permitted greater torque and required less surface-to-surface clearance than small connectors. The use of work gloves increased torque strength slightly but required much larger clearances. Limitations in hand torque strength and required clearances for exertions should be taken into account as ergonomic guidelines for maintainability.

Operational and economic aspects of municipal solid waste recovery systems: Shredding and air classification

Abstract This article examines the Ames Solid Waste Resource Recovery System which has been in operation since November of 1975. The shredding and air classification are each treated as a subsystem of the process. Labor and energy requirements and cost of processing a unit mass of refuse through each subsystem are examined. Observations are based on an analysis of the facilitys operation from July 1977 through June 1978.

Quantitative Evaluation of Human Reliability for Operating Tasks in Nuclear Power Plants

Human reliability can be computed quantitatively provided that the operational data are put in the proper format and several information matrices are available. Both one dimensional and multidimensional trends can be easily determined by counting the number of operational errors that belong to one or more specific categories. Two examples are given for one dimensional trends in the operational tasks in 65 nuclear plants over a period of ten years. In the first example, the classification of events is made according to the cue used in error discovery. The results show that observation of unannunciated displays represents 41% of the total number of discovery cues. The second example shows that by classification of events according to the human failure mode, 50% of the total operation errors are due to omission. Recommendations and restrictions are given in detail. Assuming a constant failure rate (w.r.t. time) and an exponential human reliability model, failure rates (per hour and per demand of frequency of use) for valve mispositioning in two nuclear systems are computed. Comparison of the results obtained with other estimates of human error probabilities is made. Also, the results show that the unavailability of valves in those systems where human errors involved mispositioning is not significantly greater than that due to mechanical causes.