On the competitiveness of on-line real-time task scheduling

With respect to on-line scheduling algorithms that must direct the service of sporadic task requests we quantify the benefit of clairvoyancy, i.e., the power of possessing knowledge of various task parameters of future events. Specifically, we consider the problem of preemptively sheduling sporadic task requests in both uni- and multi-processor environments. If a task request is successfuly scheduled to completion, a value equal to the task's execution time is obtained; otherwise no value is obtained. We prove that no on-line scheduling algorithm can guarantee a cumulative value greater than 1/4th the value obtainable by a clairvoyant scheduler; i.e., we prove a 1/4th upper bound on the competitive factor of on-line real-time schedulers. We present an online uniprocessor scheduling algorithm TD ₁ that actually has a competitive factor of 1/4; this bound is thus shown to be tight. We further consider the effect of restricting the amount of overloading permitted (the loading factor), and quantify the relationship between the loading factor and the upper bound on the competitive factor. Other results of a similar nature deal with the effect of value densities (measuring the importance of type of a task). Generalizations to dual-processor on-line scheduling are also considered. For the dual-processor case, we prove an upper bound of 1/2 on the competitive factor. This bound is shown to be tight in the special case when all the tasks have the same density and zero laxity.     

A low energy dual-mode adder

VLSI designs are typically data-independent and as such, they must produce the correct result even for the worst-case inputs. Adders in particular assume that addition must be completed within prescribed number of clock cycles, independently of the operands. While the longest carry propagation of an n-bit adder is n bits, its expected length is only O(log₂ n) bits. We present a novel dual-mode adder architecture that reduces the average energy consumption in up to 50%. In normal mode the adder targets the O(log₂ n)-bit average worst-case carry propagation chains, while in extended mode it accommodates the less frequent O(n)-bit chain. We prove that minimum energy is achieved when the adder is designed for O(log₂ n) carry propagation, and present a circuit implementation. Dual-mode adders enable voltage scaling of the entire system, potentially supporting further overall energy reduction. The energy-time tradeoff obtained when incorporating such adders in ordinary microprocessor’s pipeline and other architectures is discussed.     

A system for increasing the effectiveness of electromechanical systems

An algorithm for determination and analysis of consumed power, power losses, and engineering and economical indices in ideal and real electromechanical complexes is developed. The choice of energy-efficient operative conditions is grounded.     

Comparison of Data-Driven Models for Cleaning eHealth Sensor Data: Use Case on ECG Signal

Wireless Personal Communications - Electronic Health Records (EHRs) enabled to store and process data recorded by sensors would mean standard-based personalization of medical services and would be...     

Zeolite membranes for hydrogen production from natural gas: state of the art

Journal of Porous Materials - Currently, hydrogen is produced industrially by processes requiring high energy consumption, especially by cracking fossil fuels and by splitting water. In recent...     

The effect of inertial force acceleration on the otolithic membrane

The purpose of this study was to examine the response of the otolithic membrane to vertical (Gz-axis) linear acceleration force. By collecting subjective sensation and objective data (vestibulo-spinal reflex response), our study investigated the consequence of exposing these sensory membranes to linear acceleration shear forces. We compared the pilot's response to saccular stimulation to response when shear forces were exerted on the sensing membrane of the utricle. We hypothesize saccular contribution to disorientation illusion and generation of the vestibulo-spinal reflex, with possible contribution to the “Giant Hand” phenomenon. Objective and subjective measures were used for comparison between the influence of +Gx on the utricle and +Gz stimulation on the saccule. We propose the belief that a better under standing of the vestibular function in acceleration conditions will lead to better understanding of flight illusions. Hopefully, this understanding will lead to better pilot education and, in turn, significantly aid in prevention of mishaps due to spatial disorientation     

The NavChair Assistive Wheelchair Navigation System.

The NavChair Assistive Wheelchair Navigation System [19] is being developed to reduce the cognitive and physical requirements of operating a power wheelchair for people with wide ranging impairments that limit their access to powered mobility. The NavChair is based on a commercial wheelchair system with the addition of a DOS-based computer system, ultrasonic sensors, and an interface module interposed between the joystick and power module of the wheelchair. The obstacle avoidance routines used by the NavChair in conjunction with the ultrasonic sensors are modifications of methods originally used in mobile robotics research. The NavChair currently employs three operating modes: general obstacle avoidance, door passage, and automatic wall following. Results from performance testing of these three operating modes demonstrate their functionality. In additional to advancing the technology of smart wheelchairs, the NavChair has application to the development and testing of "shared control" systems where a human and machine share control of a system and the machine can automatically adapt to human behaviors.     

Design Parameters for Sampled-Data Drives for CNC Machine Tools

A mathematical analysis of a typical sampled-data servo-drive for computer numerical control (CNC) machine tools is presented with the objective of providing the control engineer with useful design charts for the selection of system parameters. A mathematical model is first developed which facilitates the evaluation of the relation between servo-loop gain and computer sampling rate. The question of stability is reviewed, and a solution for the time response of the sampled-data system is presented. Different performance criteria are discussed including: selection of desired damping factor; maximum overshoot; integral of speed square-error; position steady-state error; and the absolute value of the error. The latter criterion has been chosen as the most useful approach. System performance evaluation is presented in the form of dimensionless charts. A final design procedure is recommended which utilizes a dimensionless chart to select sample rate and gain in order to achieve an optimal performance consistent with allowable contouring accuracy and closed-loop bandwidth.