• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권10호
• /
• pp.4889-4902
• /
• 2018

It is a challenging issue to improve the energy efficiency of neighbor discovery in WSNs. This paper proposes an optimal discovery model (ODM) for the first time. Based on the model, we investigate the influence of the relative size of two unequal active slots on the energy efficiency. ODM provides the energy optimal value of the length of the larger active slot at a given duty cycle. Other than existing methods, the worst-case latency bound of ODM is only one period. This is a subversive conclusion, because almost all other related methods are based on a wake-up schedule that contains several periods. We theoretically deduce that ODM can reduce worst-case discovery latency by 43.89% compared to Searchlight-Trim when their duty cycles are the same. The simulations verify the advantage of ODM.

• Journal of Electrical Engineering and Technology
• /
• 제13권5호
• /
• pp.1935-1944
• /
• 2018

With the increase of the production of energy from renewable, it becomes important to look at techniques to store this energy. Therefore, a single winding bearingless flywheel motor (SWBFM) specially for flywheel energy storage system is introduced. For the control system of SWBFM, coupling between the torque and the suspension subsystems exists inevitably. It is necessary to build a reasonable radial force mathematical model to precisely control SWBFM. However, SWBFM has twelve independently controlled windings which leads to high-order matrix transformation and complex differential calculation in the process of mathematical modeling based on virtual displacement method. In this frame, a Maxwell tensor modeling method which is no need the detailed derivation and complex theoretical computation is present. Moreover, it possesses advantages of universality, accuracy, and directness. The fringing magnetic path is improved from straight and circular lines to elliptical line and the rationality of elliptical line is verified by virtual displacement theory according to electromagnetic torque characteristics. A correction function is taken to increase the model accuracy based on finite element analysis. Simulation and experimental results show that the control system of SWBFM with radial force mathematical model based on Maxwell tensor method is feasible and has high precision.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• 제41권10호
• /
• pp.1186-1189
• /
• 2016

A distributed uplink power control algorithm based on flocking model is proposed to improve the energy efficiency of mobiles station (MS) in cellular networks. As each bird in a flock matches its velocity with the average velocity of the adjacent birds, each MS in a cell matches its uplink rate with the average uplink rate of the co-channel MSs in adjacent cells by controlling its transmission power. Results show that the proposed algorithm effectively reduces the power consumption in the MS, while maintaining a low outage probability, which eventually improves the energy efficiency of the MS.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제16권6호
• /
• pp.1849-1876
• /
• 2022

Wireless Sensor Network (WSN) is considered as an integral part of the Internet of Things (IoT) for collecting real-time data from the site having many applications in industry 4.0 and smart cities. The task of nodes is to sense the environment and send the relevant information over the internet. Though this task seems very straightforward but it is vulnerable to certain issues like energy consumption, delay, throughput, etc. To efficiently address these issues, this work develops a cross-layer model for the optimization between MAC and the Network layer of the OSI model for WSN. A high value of duty cycle for nodes is selected to control the delay and further enhances data transmission reliability. A node measurement prediction system based on the Kalman filter has been introduced, which uses the constraint based on covariance value to decide the scheduling scheme of the nodes. The concept of duty cycle for node scheduling is employed with a greedy data forwarding scheme. The proposed Duty Cycle-based Greedy Routing (DCGR) scheme aims to minimize the hop count, thereby mitigating the energy consumption rate. The proposed algorithm is tested using a real-world wastewater treatment dataset. The proposed method marks an 87.5% increase in the energy efficiency and reduction in the network latency by 61% when validated with other similar pre-existing schemes.

• Journal of Electrical Engineering and information Science
• /
• 제1권1호
• /
• pp.58-69
• /
• 1996

This paper presents a new approach to derive an energy integral based on an Equivalent Mechanical Model(EMM), which is developed by introducing imaginary springs for line resistances. The proposed EMM shows that phasor currents and voltages are directly analogous to the two-dimensional force and displacement vectors, respectively. Through rigorous energy analysis of the proposed EMM, an exact energy integral expression is derived for multimachine systems, and several useful theorems are developed to derive an energy integral for power systems with detailed generator models the energy integral exactly reflects the internal resistance, saliency and flux-decaying effects of the generator. Finally, an illustrative example is given for a multimachine system adopting the Eq'-model for generators, which shows that the consideration of a detailed generator model does not aggravate the complicacy of the direct method of stability analysis in multimachine systems.

• Atmosphere
• /
• 제27권3호
• /
• pp.331-344
• /
• 2017

Solar energy is calculated using high-resolution digital elevation model (DEM). In focus on Seoul metropolitan area, correction coefficients of direct and diffuse solar energy with the topographic effect are calculated from DEM with 1720, 900, 450, 90 and 30 spatial resolutions ($m{\times}m$), respectively. The solar energy on the real surface with high-resolution is corrected using by the correction coefficients with topographic effect from the solar energy on horizontal surface with lower resolution. Consequently, the solar energy on the real surface is more detailed distribution than those of horizontal surface. In particular, the topographic effect in the winter is larger than summer because of larger solar zenith angle in winter. In Seoul metropolitan area, the monthly mean topographic effects are more than 200% in winter and within 40% in summer. And annual topographic effects are negative role with more than -60% and positive role with below 40%, respectively. As a result, topographic effect on real surface is not a negligible factor when calculating and analyzing solar energy using regional and global models.

• Journal of Communications and Networks
• /
• 제18권4호
• /
• pp.649-657
• /
• 2016

In this paper, we investigate energy efficiency (EE) of the traditional co-located and the distributed massive multiple-input multiple-output (MIMO) systems. First, we derive an approximate EE expression for both the idealistic and the realistic power consumption models. Then an optimal energy-efficient remote access unit (RAU) selection algorithm based on the distance between the mobile stations (MSs) and the RAUs are developed to maximize the EE for the downlink distributed massive MIMO systems under the realistic power consumption model. Numerical results show that the EE of the distributed massive MIMO systems is larger than the co-located massive MIMO systems under both the idealistic and realistic power consumption models, and the optimal EE can be obtained by the developed energy-efficient RAU selection algorithm.

• Journal of the Korea Society of Computer and Information
• /
• 제25권4호
• /
• pp.97-103
• /
• 2020

Wireless sensor networks collect and analyze sensing data in a variety of environments without human intervention. The sensor network changes its lifetime depending on routing protocols initially installed. In addition, it is difficult to modify the routing path during operating the network because sensors must consume a lot of energy resource. It is important to measure the network performance through simulation before building the sensor network into the real field. This paper proposes a WSN model for a low-energy adaptive clustering hierarchy protocol using DEVS kernel models. The proposed model is implemented with the sub models (i.e. broadcast model and controlled model) of the kernel model. Experimental results indicate that the broadcast model based WSN model showed lower CPU resource usage and higher message delivery than the broadcast model.

• International Journal of Aeronautical and Space Sciences
• /
• 제13권2호
• /
• pp.188-198
• /
• 2012

An improvement to the k-${\varepsilon}$ turbulence model is presented and is shown to lead to better agreement with data regarding supersonic base flows. The improvement was achieved by imposing a grid-independent realizability constraint in the Launder-Sharma k-${\varepsilon}$ model. The effects of compressibility were also examined. The numerical results show that the modified Launder-Sharma model leads to some improvement in the prediction of the velocity and turbulent kinetic energy profiles. Compressibility corrections also lead to better agreement in both the turbulent kinetic energy and the Reynolds stress profiles with the experimental data.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• 제16권8호
• /
• pp.5591-5599
• /
• 2015

For the effective energy management, this study proposed BIM(Building Information Modeling)-based Data Mining Model(B-DMM). To conduct this, BIM-based data mining researches were surveyed then the use-cases and scenarios related to the energy management were analyzed. By using this results, B-DMM for supporting the decision making related the energy management was proposed. The output will be used as a decision making tool for managing a building energy.