• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.2
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• pp.618-633
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• 2014

Relay technology is becoming more important for mobile communications and wireless internet of things (IoT) networking because of the extended access network coverage range and reliable quality of service (QoS) it can provide at low power consumption levels. Existing mobile multihop relay (MMR) technology uses fixed-point stationary relay stations (RSs) and a divided time-frame (or frequency-band) to support the relay operation. This approach has limitations when a local fixed-point stationary RS does not exist. In addition, since the time-frame (or frequency-band) channel resources are pre-divided for the relay operation, there is no way to achieve high channel utilization using intelligent opportunistic techniques. In this paper, a different approach is considered, where the use of mobile/IoT devices as RSs is considered. In applications that use mobile/IoT devices as relay systems, due to the very limited battery energy of a mobile/IoT device and unequal channel conditions to and from the RS, both minimum energy consumption and QoS support must be considered simultaneously in the selection and configuration of RSs. Therefore, in this paper, a mobile RS is selected and configured with the objective of minimizing power consumption while satisfying end-to-end data rate and bit error rate (BER) requirements. For the RS, both downlink (DL) to the destination system (DS) (i.e., IoT device or user equipment (UE)) and uplink (UL) to the base station (BS) need to be adaptively configured (using adaptive modulation and power control) to minimize power consumption while satisfying the end-to-end QoS constraints. This paper proposes a minimum transmission power consuming RS selection and configuration (MPRSC) scheme, where the RS uses cognitive radio (CR) sub-channels when communicating with the DS, and therefore the scheme is named MPRSC-CR. The proposed MPRSC-CR scheme is activated when a DS moves out of the BS's QoS supportive coverage range. In this case, data transmissions between the RS and BS use the assigned primary channel that the DS had been using, and data transmissions between the RS and DS use CR sub-channels. The simulation results demonstrate that the proposed MPRSC-CR scheme extends the coverage range of the BS and minimizes the power consumption of the RS through optimal selection and configuration of a RS.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.5
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• pp.1604-1617
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• 2014

This paper proposes RIX-MAC (Receiver-Initiated X-MAC), a new energy-efficient MAC protocol based on an asynchronous duty cycling. RIX-MAC improves energy efficiency through utilizing short preambles and adopting the receiver-initiated approach, where RIX-MAC minimizes sender nodes' energy consumption by enabling transmitters to predict receiver nodes' wake-up times. It also reduces receiver nodes' energy consumption by decreasing the number of control frames. We use the network simulator to evaluate RIX-MAC's performance. Compared to the prior asynchronous duty cycling approaches of X-MAC and PW-MAC, the proposed protocol shows a remarkable improvement in energy-efficiency and end-to-end delay.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.11
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• pp.557-560
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• 2005

This paper proposes the demand-side management(DSM) monitoring system of high efficient end-use equipments considering demand-side bidding (DSB). The effect on the market penetration of high efficient equipments by demand side bidding is analysed. Seasonal peak demand forecasting and penetration capacity of these equipments . are analysed.

• Journal of Navigation and Port Research
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• v.34 no.9
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• pp.705-709
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• 2010

Buildings nowadays are increasingly expected to need higher and more economic performance requirements. Energy consumption in buildings accounts for over 30% of total energy use. The Building Energy Management System (BEMS) and renewable energy (RE) technologies are considered as a potential measure to improve energy efficiency and reduce use of grid-power. It is, however, a challenge to utilise the intermittent energy supply of RE in building energy systems. This paper presents an experimental study on a RE-embedded BEMS. A control algorithm for the RE-embedded BEMS was designed to maximise the utilisation of RE and eventually to reduce electrical utility bill. The proposed system is tested at a laboratorial chamber with an air conditioner, fan and heater. The contribution of RE in building energy system is discussed to this end.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.1
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• pp.15-19
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• 2014

As the space of the wind power generator stator end is limited, it is difficult for us to place the inner evaporative cooling system in it. We use the non-overlapping concentrated windings scheme to solve the placing and cooling problem. The characteristic of a 5MW direct-driven permanent magnet generator with non-overlapping concentrated windings were analyzed under no-load, rating-load and short-circuit by (Finite Element Method) FEM for verification of design. We studied the connection methods of the stator windings and designed the end connection member. The heat dissipation of the stator end was simulated by FEM, the result showed that the end cooling could satisfy the wind generator operation needs. These results show that the direct-driven permanent magnet wind power generators with non-overlapping concentrated windings and inner evaporative cooling system can solve the cooling problem of wind power generator, and obtain good performance at the same time.

• Journal of Information Processing Systems
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• v.16 no.4
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• pp.845-858
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• 2020

This paper proposes a modified end-to-end secure low energy adaptive clustering hierarchy (ME-LEACH) algorithm for enhancing the lifetime of a wireless sensor network (WSN). Energy limitations are a major constraint in WSNs, hence every activity in a WSN must efficiently utilize energy. Several protocols have been introduced to modulate the way a WSN sends and receives information. The end-to-end secure low energy adaptive clustering hierarchy (E-LEACH) protocol is a hierarchical routing protocol algorithm proposed to solve high-energy dissipation problems. Other methods that explore the presence of the most powerful nodes on each cluster as cluster heads (CHs) are the sparsity-aware energy efficient clustering (SEEC) protocol and an energy efficient clustering-based routing protocol that uses an enhanced cluster formation technique accompanied by the fuzzy logic (EERRCUF) method. However, each CH in the E-LEACH method sends data directly to the base station causing high energy consumption. SEEC uses a lot of energy to identify the most powerful sensor nodes, while EERRCUF spends high amounts of energy to determine the super cluster head (SCH). In the proposed method, a CH will search for the nearest CH and use it as the next hop. The formation of CH chains serves as a path to the base station. Experiments were conducted to determine the performance of the ME-LEACH algorithm. The results show that ME-LEACH has a more stable and higher throughput than SEEC and EERRCUF and has a 35.2% better network lifetime than the E-LEACH algorithm.

• Korean Journal of Organic Agriculture
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• v.9 no.3
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• pp.23-44
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• 2001

To address complex solutions to tack1e the cost rise with the increasing of the prices of crude oil, and to lower warming gas discharge in agricultural sector in line with the framework Convention on Climate Change, we need to net only develop the methods of simply reducing energy use ratio, but also effectively energize resources discharged in the course of agricultural production aimed at enabling repealed farming, and develop systems to reinvest such energy into agricultural production and apply them to actual farming. To that end, specifically, we need to reduce the energy cost in agricultural production, and produce and harness bio gas that makes it possible to stabilize the continued supply of energy. Thus, in this research, we seek to discuss energy use volume and warming gas discharge, and the characteristics of bio gas and its use methods alike, in agricultural sector, and thus present methods for environment-friendly and continual development in agriculture.

• Journal of Korea Multimedia Society
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• v.22 no.6
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• pp.676-683
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• 2019

Wireless Sensor Networks (WSNs) consist of multiple tiny and power constrained sensors which use radio frequencies to carry out sensing in a designated sensor area. To effectively design and implement reliable WSN, it is critical to consider models, protocols, and algorithms that can optimize energy consumption of all the sensor nodes with optimal amount of packet delivery. It has been observed that deploying a single sink node comes with numerous challenges especially in a situation with high node density and congestion. Sensor nodes close to a single sink node receive more transmission traffic load compared to other sensors, thus causing quick depletion of energy which finally leads to an energy hole and sink hole problems. In this paper, we proposed the use of multiple energy efficient sink nodes with brute force technique under optimized parameters to improve on the number of packets delivered within a given time. Simulation results not only depict that, deploying N sink nodes in a sensor area has a maximum limit to offer a justifiable improvement in terms of packet delivery ratio but also offers a reduction in End to End delay and reliability in case of failure of a single sink node, and an improvement in the network lifetime rather than deploying a single static sink node.

• Architectural research
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• v.19 no.1
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• pp.7-11
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• 2017

Energy consumption in university building has steadily increased over the last decade, and a strong upward trend in recent years. This study was undertaken to analyze the relationship between energy consumption and their affecting factors, six academic buildings were considered. The factors limited to heating and cooling, which is the main end use (nearly 60 per cent of total energy consumption in university buildings), encompassing system and operating schedules (user activity) and area use. To understand how to building is used, operated and managed, walk-through assessment was conducted as well as interview with university staff. The results show that the energy consumption of the humanities building was somewhat smaller than the consumption of the science and engineering building, and its range was from $31.26kgoe/m^2$ to $23.52kgoe/m^2$, depending on heating and cooling system and area use. And the energy consumption of the science and engineering building was related to operating schedules (user activity) as well as laboratory equipment characteristics. More analysis on a larger number of buildings is required in the future, including building form and material performance level to generalize the significant factors influencing building energy consumption.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.223-228
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• 2003

In end milling processes, characterized by use of rotating tools, the underformed chip thickness varies periodically with the phase change of tool. In current study, as a new approach to analyse shear behaviors In the shear plane and chip-tool friction behavior chip-tool contact region during an end milling process. In this approach, an up-end milling process is transformed into an equivalent oblique cutting process. Experimental investigations for two sets of cutting tests i.e.. up-end milling and the equivalent oblique cutting test were performed to verify the presented model.