External Interruptions Research Articles

A design-oriented framework for modelling the planning and control of multiple task work in secretarial office administration

Design-oriented frameworks are a type of Human-Computer Interaction (HCI) discipline knowledge. They are intended to support iterative 'specify-and-implement' design practice, by assisting designers to create models of specific design problems, within a class of design problem. This paper presents a design-oriented framework for a class of HCI design problem, expressed as a the planning and control of multiple task work in secretarial office administration. The planning and control of multiple task work refers generally to how interactive human-computer worksystems specify and select behaviours for performing multiple concurrent tasks. Secretarial office administration is a sub-class of design problem, in which the work supports communications of the organization commissioning the new worksystem. The framework is based on a conception proposed to support an engineering discipline of HCI. The framework conceptualizes the relationship between an interactive worksystem, its domain of work and the effectiveness, or performance, with which work is carried out. The framework was developed from cognitive science and HCI theory and an empirical case-study of an existing secretarial worksystem. The framework expresses the domain of secretarial work as the state transformation of hierarchies of abstract and physical objects, representing communications carried out by the organization. The description of the secretarial worksystem expresses the relationship between abstract processes of planning, controlling, perceiving and executing, and abstract representations of plans and knowledge-of-tasks. Planning heuristics and control rules reflect general properties of the dynamic work domain, such as external interruptions and temporary opportunities. The framework also expresses the relationship between these planning and control structures and performance. In its current form, the framework is incomplete, but illustrates an approach to the development of design-oriented knowledge. Using this type of knowledge, a designer may reason about potential solutions to HCI design problems concerning planning and control behaviours for carrying out multiple task work for secretarial office administration.

A revised control system for a semi-continuous flowing-solvent liquefaction reactor

An integrated control and measurement system based on a single host computer (PC) has been constructed for running a semi-continuous flowing-solvent coal liquefaction reactor. The system, composed of a mix of special circuits and commercially available units, provides accurate temperature and flow control, data acquisition, real time display, and safety interlock. The real-time job-conflict problems are solved by using the interrupt concept: the background basic feedback control loop working in external interrupt mode took priority, with a foreground service routine executing more time-consuming tasks, including data recording to disk, and real-time result display on screen. Improved computer reliability, ease of maintenance, increased flexibility in the design of individual experiments, suppression of temperature overshoots and closer control of the solvent flow rate, have all served to improve the quality of data required for evaluating kinetic parameters. The design is readily adaptable to experiments requiring temperature and flow (or other variable) control, data acquisition, real-time results display, and safety interlock (fail-safe) functions.

Dynamic performance of a directly coupled PV pumping system

Although directly coupled Photovoltaic (PV) pumping systems have been extensively studied under steady state conditions, much less attention has been paid to the study of their transient performance. Actually the system is performing dynamically all the time because the solar irradiance is varying continuously. Thus, the steady state solution for the system performance is only an approximation. In this work both dynamic and steady state models are developed for a directly coupled PV pumping system. The results obtained by a detailed computer simulation program based on the two models are compared. The system is studied under external interruptions caused by sudden appearance or disappearance of clouds. The study showed that there are overshoots of both current and voltage of the DC motor. However, the characteristics of the PV array limit the overshoots during the transient period. The motor speed creeps steadily towards its steady state value without overshoot.

On Realtime Operating Systems: How to Compare Performance?

To compare realtime operating systems one must often rely on specifications given by the manufacturers. These published data are often measured by so-called benchmarks. But with the help of benchmarks it is not possible to collect sufficient information to determine the system behaviour for worst cases. Therefore it must be clarified which latency times exist and how they arise. Of great significance is the additional latency time of the operating system, which is compulsory for the design of the application. In this paper it is investigated whether and how long a given task, activated by an external interrupt, is delayed until task completion. For that all latency times which can occur are discussed, specifically the worst cases. We are taking a closer look at real time operating systems which encourage so-called kernel-level threads. The advantage of these kernel-level threads systems in contrast to traditional systems are discussed referring to performance. At the moment we are testing two systems, LynxOS and HP-RT. We want to measure the worst-case latency times and therefore illustrate how this is done.

On realtime operating systems: How to compare performance ?

To compare realtime operating systems one must often rely on specifications given by the manufacturers. These published data are often measured by so-called benchmarks. But with the help of benchmarks it is not possible to collect sufficient information to determine the system behaviour for worst cases. Therefore it must be clarified which latency times exist and how they arise. Of great significance is the additional latency time of the operating system, which is compulsory for the design of the application. In this paper it is investigated whether and how long a given task, activated by an external interrupt, is delayed until task completion. For that all latency times which can occur are discussed, specifically the worst cases. We are taking a closer look at realtime operating systems which encourage so-called kernel-level threads. The advantage of these kernel-level threads systems in contrast to traditional systems are discussed referring to performance. At the moment we are testing two systems, LynxOS and HP-RT. We want to measure the worst-case latency times and therefore illustrate how this is done.

Two Forms of Palilalia: A Clinicoanatomical Study

The clinical and neuroradiological findings of three patients with marked palilalia due to different neurological disorders are reported. These cases and others in the literature suggest the possibility of different variations. “Spasmodic, heterophonic palilalia” is typically observed in Parkinson's syndrome and pseudobulbar palsy: the content of palilalia is characteristically changed by interruption. “Atonic, homophonic, autoecholalic palilalia” is mainly seen in Pick's disease, and is not affected by external interruption.

Two forms of palilalia: a clinicoanatomical study.

The clinical and neuroradiological findings of three patients with marked palilalia due to different neurological disorders are reported. These cases and others in the literature suggest the possibility of different variations. "Spasmodic, heterophonic palilalia" is typically observed in Parkinson's syndrome and pseudobulbar palsy: the content of palilalia is characteristically changed by interruption. "Atonic, homophonic, autoecholalic palilalia" is mainly seen in Pick's disease, and is not affected by external interruption.

An enhanced realtime multitasking BASIC interpreter

This paper describes the implementation of an enhanced BASIC interpreter which provides the necessary features to support program execution in a realtime multitasking environment. The interpreter supports many of the features found in commercial realtime executives (RTXs) including process scheduling, message-based interprocess communication, interprocess synchronization and control, dynamic process creation/destruction, memory management, external event (interrupt) synchronization, and basic timing services. The kernel employs a preemptive scheduling policy based on process priority and allotted time-slice. To retain compatibility, the interpreter operates in a default single process mode if the multitasking extensions are not utilized. The interpreter is completely reentrant and may perform a context switch at any point during the execution of the current process. This allows a fast response to high priority processes made ready to execute by the occurrence of an external interrupt. The interpreter is mainly written in C and is portable to different microprocessor families. It is currently implemented for the i8088/86/186/286 family and has been ported to the IBM PC compatible systems.

Laryngeal spaces and lymphatics: current anatomic concepts.

This investigation evaluates the anatomic concepts of individual spaces or compartments within the larynx by isotope and dye diffusion. The authors identified continuity of spaces particularly within the submucosal planes and a relative isolation within the fixed structures resulting from the longitudinal pattern of fibroelastic tissues, muscle bands, and perichondrium. The historical data of anatomic resistance are refuted by the radioisotope patterns of dispersion and the histologic evidence of tissue permeability to the carbon particles. There is little clinical application of the compartment concept to the perimeter of growth and the configuration of extensive endolaryngeal cancers. The internal and extralaryngeal lymphatic network is presented and the regional associations are identified. The normal ipsilateral relationship is distorted by dispersion within the endolarynx supervening the anatomic midline. The effects of lymphatic obstruction caused by regional lymphadenectomy, tumor fixation, and irradiation-infection sequelae are illustrated; these result in widespread bilateral lymphatic nodal terminals. Finally, the evidence suggests that the internal network is modified by external interruption to accommodate an outflow system in continuity with the residual patent lymphatic channels.

Reference-Pulse Circular Interpolators for CNC Systems

Interpolation techniques for CNC manufacturing systems are either of the Reference-Pulse or Reference-Word type. Reference-Pulse interpolations emit a sequence of pulses as reference signals to the control loops, whereas Reference-Word interpolators provide binary words as references to Sampled-Data control loops. In the present paper, a number of Reference-Pulse interpolation methods are described, all of which function in an online iterative mode controlled by an external interrupt source. These methods are compared in terms of accuracy, maximum radius, uniformity of feedrate along the circular path, and maximum feedrate attainable. Selection of the appropriate interpolation method is found to depend on the specific application. Reference-Word interpolators will be covered in a subsequent paper.

Training mathematical psychology students in the use of a laboratory computer

FRANK M. GOODE University of Michigan, Ann Arbor, Michigan 48104 Training mathematical psychology students in the use of a laboratory computer PHYSICAL FACILITIES The primary equipment for the laboratory is a Xerox Data Systems Sigma 3 computer. This is a sophisticated process-control computer. The system architecture is defined around eight hardware registers with a sophisticated set of register-to-register, memory-to-register, and register-to-memory transfer instructions. The memory (16-bit words) is multiported to accommodate to the multiprocessor configuration of the basic system, involving independent (parallel) I/O processing and CPU processing. Current memory is composed of 40K words, arranged in three blocks of memory, each block ported both to the I/O processor and to the CPU. Memory is expandable to 65K, with a maximum of four blocks, each with four ports. Memory is functionally partitioned into foreground and background, with real-time processing in foreground protected by programmable hardware memory-protection registers. The real-time hardware priority-interrupt system includes up to 100 external interrupt levels. Four real-time clocks are installed on the computer. A wide range of peripheral equipment has been installed: 200-cpm card reader, 225-lpm line printer, 7-track 20-kc magnetic tape, 3 million character disk (fixed head, 17 msec average access, 170-kc transfer rate), 49 million character-disk pack drive (dual spindle, 87 msec average access, 312 kc transfer rate). Special systems equipment installed on the computer include 72 discrete input and output lines and eight communications lines operating at a variety of baud rates. Future expansion will fill out allowed memory, add a large number of discrete I/O lines, add two 9,600-baud lines, 28 additional slow-speed lines, and a 48,000-baud line linked to the University of Colorado CDC 6400. Terminal equipment now installed includes six Teletype machines (two Model 33KSRs, four Model 37KSRs), two UNIVAC Uniscope 100 keyboard/displays (character oriented), and an XDS character-oriented keyboard/display. Future expansion of terminals will be in the area of keyboard/display equipment and graphics displays. The laboratory is working with the Department of Electrical Engineering on campus to develop a graphics controller capability for the Minuteman I 0-17 computers the two departments own.