Search results for "Duty"
showing 10 items of 116 documents
A cooperative lifetime extension MAC protocol in duty cycle enabled wireless sensor networks
2011
To reduce energy consumption in wireless sensor networks, the concept of duty cycle is used in many MAC protocols. Although these protocols provide efficient energy-conservation solutions, they cannot resolve the energy hole problem in a multi-hop network, where a few nodes near the sink must relay the packets from the rest of the network, and consequently exhaust their batteries earlier. The previously proposed REACT forwarding protocol triggers the cooperation of several nodes to extend transmission range and hop over the highly burdened node, thereby allowing it to save its energy and extend the lifetime of the network. However, the previous work lacked a MAC protocol with a duty cycle. …
Aggregated Packet Transmission in Duty-Cycled WSNs: Modeling and Performance Evaluation
2017
[EN] Duty cycling (DC) is a popular technique for energy conservation in wireless sensor networks (WSNs) that allows nodes to wake up and sleep periodically. Typically, a single-packet transmission (SPT) occurs per cycle, leading to possibly long delay. With aggregated packet transmission (APT), nodes transmit a batch of packets in a single cycle. The potential benefits brought by an APT scheme include shorter delay, higher throughput, and higher energy efficiency. In the literature, different analytical models have been proposed to evaluate the performance of SPT schemes. However, no analytical models for the APT mode on synchronous DC medium access control (MAC) mechanisms exist. In this …
Phase Margin Degradation of a Peak Current Controlled Converter at Reduced Duty Cycle
2010
An inner current loop is frequently used in many switching power supplies to achieve higher stability and a good current sharing. Nevertheless, some problems derived from its practical implementation can be encountered. One problem is related to the need of filtering of the sensed current and was discovered by the authors in the implementation of a 500 W converter, when peak current control was applied by sensing the switch current. This paper will demonstrate mathematically that an RC filter not only filters out the noise but also can cause a degradation of the phase margin, especially, if the needed duty cycle is close to zero. The main reason for it is the severe distortion of the curren…
Implementation and experimental validation of a real-time PWM algorithm based on B-Spline carriers for three phase voltage source inverters
2009
This paper presents the implementation and experimental results of an algebraic real-time sinusoidal pulse width modulation algorithm (SPWM) based on B-Spline carriers. B-spline functions are used as carrier signals with the aim to to reduce harmonic content of the three phase inverter output voltage. The presented algorithm eliminates the problem of B-spline recursive evaluation with convolution integrals or convolution sums in digital counterpart. The pulse pattern synthesis is made with the help pre-calculated duty cycle expressions. In this way there is no real need to synthesize the carrier signal so the hardware and the whole inverter control system becomes cheaper, more reliable and …
Identification and Experimental Validation of an Induction Motor Thermal Model for Improved Drivetrain Design
2017
The ability of an electric powertrain to perform according to mechanical specifications is equally important as assessing its thermal protection limits, which are affected by its electrical and thermal properties. Although rated parameters (such as power, torque, etc.) are easily accessible in catalogs of equipment producers, more specific properties like mass/length of copper winding, heat dissipation factor, etc., are not available to customers. Therefore, an effective selection of drivetrain components is limited due to the lack of sufficient data and the need to consult critical design decisions with suppliers. To overcome this limitation, we propose a method to estimate the temperature…
Guarding, guiding, gate opening: Prison officer work in a Norwegian welfare context
2017
Anne A is a prison officer, and for years, she has been working behind the walls—in low-security and high-security wings, with remand and sentenced prisoners. She says: We are there fifty per cent in order to keep an eye on them, to ensure that they stay here [in prison]. The other fifty per cent we are trying to help them. They may be drug users or have other problems, and it’s just as much our duty to help them as to watch them. And when we help, this contributes to security just as much as a locked door or an alarm.
Generalized PWM-VSI Control Algorithm Based on a Universal Duty-Cycle Expression: Theoretical Analysis, Simulation Results, and Experimental Validati…
2007
This paper presents a new approach in realizing various carrier-based pulsewidth-modulation techniques by a generalized control algorithm, which is referred to as the universal control algorithm and is obtained via unequal sharing of null states. The flexibility of such an approach allows one to easily and quickly control two-level inverters. Furthermore, this approach may be also extended with few changes to the control of multilevel inverters. The algorithm that is presented here for two-level voltage-source inverters (VSIs) also obtains efficient detection and management of both the linear and overmodulation ranges. In the overmodulation range, which is treated by using the alpha-beta co…
Control of solid-state fault current limiter for DG-integrated distribution systems
2017
Fault current limier (FCL) is a device that limits the system current under fault conditions without disconnecting the system and affecting the power system protection components such as circuit breakers. Many types of FCLs have been proposed to limit the magnitude of the fault current. Solid-state fault current limiters (SSFCLs) can limit the peak value of the fault current by applying several methods, such as controlling the system impedance or controlling the voltage that appears across the fault. In this paper, a new control scheme for the SSFCL circuit is presented. The control method is based on controlling the duty cycle of solid state switches to control the rms value of the system …
Análisis de los deberes del deporte en la universidad: ética cívica, derechos humanos, ética del deporte y fair play
2016
This article analyses the moral duties on the operation of the Sports Departments at Universities. Deontology, from the Greek Deon (duty) and logy (treated), refers to the sphere of duty. This ethical perspective, which is a key precursor from the German philosopher Immanuel Kant, raises the need to assume the duties that must be followed in interaction with others. In this sense the moral duties, as essential components of any code of ethics, guide the management model of Sports Departments at Universities. They have to undertake them in order to achieve its inner goal. Particularly, the article provides a panoramic analysis covering from the broadest to the most specific sources such as c…
Bioethical Aspects of Postmortem Imaging
2019
After a general overview of death in current medical-cultural context, this chapter examines the main moral aspects of postmortem imaging (PI). In the current debate the stressed ethical issues are fundamentally the following: (1) the noninvasive character of postmortem imaging that very likely makes the procedure less objectionable to relatives of the deceased; (2) the reliability of the methods that ought to be as effective as traditional autopsy, both when PI precedes and completes or substitutes traditional autopsy; and (3) the cost-benefit analysis, in individual and social terms. The chapter emphasizes the common prerequisite of these ethical aspects, that is, the corpse’s dignity and…