• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.3
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• pp.389-395
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• 2013

Ethernet is the most widely deployed access network protocol around the world. IEEE 802.3az WG released the EEE standard based on LPI mode to improve the energy efficiency of Ethernet. This paper proposes improved adaptive power control mechanism that can enhance energy-efficiency based on EEE from small Ethernet switch. The feature of this mechanism is that it predicts the traffic characteristic of next cycle by measuring the amount of traffic flowing in during certain period and adjusts the optimal threshold value to relevant traffic load. Performance evaluation results indicate that the proposed mechanism improves overall performance compared to traditional mechanism, since it significantly reduces energy consumption rate, even though average packet delay increases a little bit.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.6
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• pp.111-116
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• 2009

LEACH is a important hierarchical protocol in wireless sensor network. In LEACH, the head is randomly selected for balanced energy consume. In LEACH-C, the node that has more energy than the average value is selected for the network life cycle. However, the round continues, the improved protocol is needed because the energy and network are changed. In this paper, LEACH, LEACH-C is not considered the energy consumed in the round because of wasted energy and reduce the time for presenting a new round time was set. And proposed the new algorithm using the energy threshold for the cluster head selection and the round time. In simulation, we show the improved performance compared to existing protocols.

• International Journal of Highway Engineering
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• v.13 no.3
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• pp.65-73
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• 2011

Recently, researches to introduce the performance warranty contract are in progress for quality improvement of road pavements. The performance warranty contract is a type of contract in which contractors guarantee to maintain certain level of performance during a period from completion of construction. The contract use in Europe and the U.S is being increased because it has been known to contribute to improvement of structure quality, reduction of life cycle cost, development of construction techniques, and etc. The research on performance indicators, threshold values, and warranty durations is essential to effectively introduce the contract in Korea. In this study, literatures on the performance warranty contract for concrete pavements of the Minnesota, Indiana, and Florida of the U.S. were reviewed. Major distresses influencing the pavement performance were investigated and analyzed in the jointed concrete pavement sections of 21 Korean expressway routes to be compared to the performance indicators, threshold values, and warranty durations of the states. More accurate comparison is expected by investigation in planned sections for a long time.

• Journal of KIISE
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• v.42 no.12
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• pp.1495-1502
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• 2015

Data compression involves a trade-off between delay time and data size. Greater delay times require smaller data sizes and vice versa. There have been many studies performed in the field of wireless sensor networks on increasing network life cycle durations by reducing data size to minimize energy consumption; however, reductions in data size result in increases of delay time due to the added processing time required for data compression. Meanwhile, as energy generation occurs periodically in solar energy-based wireless sensor networks, redundant energy is often generated in amounts sufficient to run a node. In this study, this excess energy is used to reduce the delay time between nodes in a sensor network consisting of solar energy-based nodes. The energy threshold value is determined by a formula based on the residual energy and charging speed. Nodes with residual energy below the threshold transfer data compressed to reduce energy consumption, and nodes with residual energy above the threshold transfer data without compression to reduce the delay time between nodes. Simulation based performance verifications show that the technique proposed in this study exhibits optimal performance in terms of both energy and delay time compared with traditional methods.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.5
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• pp.153-161
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• 1998

The knock in a spark ignition engine has been investigated to avoid the damage to the engine and unpleasant feeling caused by the pressure waves propagating across the combustion chamber. Knock intensity and knock onset angle were used as physical parameters to quantify the knock characteristics. The knock intensity is defined as a peak to peak value of the bank pass filtered combustion pressure signal and the knock onset angle is determined as the crank angle at which this signal exceeded the threshold level on each cycle. The cyclic variation of knock in four valve single cylinder engine was investigated with these two parameters. The location of autoignition was also examined by ion probes in the cylinder head gasket and squish region in the combustion chamber. For this measurement, a single cylinder engine was modified to accept the pressure transducer, 18 ion probes in the squish region and 8 ion probes in the specially designed PCB (Printed \ulcornerCircuit Board) cylinder head gasket.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.14 no.4
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• pp.305-312
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• 2014

This paper discusses real-time peak shaving algorithms for a large-scale battery energy storage system (BESS). Although several transmission and distribution functions could be implemented for diverse purposes in BESS applications, this paper focuses on a real-time peak shaving algorithm for an energy time shift, considering wind power generation. In a high wind penetration environment, the effective load levels obtained by subtracting the wind generation from the load time series at each long-term cycle time unit are needed for efficient peak shaving. However, errors can exist in the forecast load and wind generation levels, and the real-time peak shaving operation might require a method for wind generation that includes comparatively large forecasting errors. To effectively deal with the errors of wind generation forecasting, this paper proposes a real-time peak shaving algorithm for threshold value-based peak shaving that considers fuzzy wind power generation.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.10
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• pp.821-829
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• 1991

In this paper, a BICMOS technology that has CMOS devices for digital application and bipolar devices for high voltage (80V) analog applications is presented. Basic concept to design BICMOS device is simple process technology without making too many performance trade-offs. The base line process is poly gate p-well CMOS process and three additional masking steps are added to improve bipolar characteristics. The key ingredients of bipolar integration are n+ buried layer process, up/down isolation process and p-well base process. The bipolar base region is formed simultaneously with the region of CMOS p-well area to reduce mask and heat cycle steps. As a result, hFE value of NPN bipolar transistor is 100-150(Ic=1mA). Collector resistance value is 138 ohm in case of bent type collector structure. Breakdown voltage of BVebo, BVcbo and BVceo are 21V, 115V and78V respectively. Threshold voltage is ${\pm}$1.0V for NMOS and PMOS transistor. Breakdown voltage of NMOS and PMOS transistor is obtained 22V and 19V respectively. 41 stage CMOS ring oscillator has 0.8ns delay time.

• Journal of the Korea Society for Simulation
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• v.27 no.3
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• pp.45-52
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• 2018

We consider the busy period of an M/G/1/K queueing system with queue-length-dependent overload control policy. A variant of an oscillating control strategy that was recently analyzed by Choi and Kim (2016) is considered: two threshold values, $L_1({\leq_-}L_2)$ and $L_2({\leq_-}K)$, are assumed, and service rate and arrival rate are adjusted depending on the queue length to alleviate congestion. We investigate the busy period of an M/G/1/K queue with two overload control policies, and present the formulae to obtain the expected length of a busy period for each control policy. Based on the numerical examples, we conclude that the variability and expected value of the service time distribution have the most influence on the length of a busy period.

• Journal of Welding and Joining
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• v.23 no.6
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• pp.49-54
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• 2005

Inner Structured and Bonded(ISB) panel, a kind of metallic sandwich panel, consists of two thin skin plates bonded to a micro-patterned inner structure. Its overall thickness is $1\~3mm$and it has attractive properties such as ultra-lightweight, high efficiency in stiffness-to-weight and strength-to-weight ratio. In many previous studies, resistance welding, brazing and adhesive bonding are studied for joining the panel. However these methods did not consider productivity, but focused on structural characteristics of joined panels, so that the joining process is very complicated and expensive. In this paper, a new joining process with resistance welding is developed. Curved surface electrodes are used to consider the productivity and the stopper is used between electrodes during welding time to maintain the shape of inner structure. Welding time, gap of electrodes and distance between welding points are selected as the process parameters. By measuring the tensile load with respect to the variation of welding time and gap of electrodes, proper welding conditions are studied. Welding time is proper between 1.5-2.5cycle. If welding time is too long, then inner structures are damaged by overheating. Gap of electrode should be shorter than threshold value fur joint strength, when total thickness of inner structure and skin plate is 3.3mm, the threshold distance is 3.0mm.

• Journal of Korea Water Resources Association
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• v.43 no.8
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• pp.733-745
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• 2010

Seasonality of hydrologic extreme variable is a significant element from a water resources managemental point of view. It is closely related with various fields such as dam operation, flood control, irrigation water management, and so on. Hydrological frequency analysis conjunction with partial duration series rather than block maxima, offers benefits that include data expansion, analysis of seasonality and occurrence. In this study, nonstationary frequency analysis based on the Bayesian model has been suggested which effectively linked with advantage of POT (peaks over threshold) analysis that contains seasonality information. A selected threshold that the value of upper 98% among the 24 hours duration rainfall was applied to extract POT series at Seoul station, and goodness-fit-test of selected GEV distribution has been examined through graphical representation. Seasonal variation of location and scale parameter ($\mu$ and $\sigma$) of GEV distribution were represented by Fourier series, and the posterior distributions were estimated by Bayesian Markov Chain Monte Carlo simulation. The design rainfall estimated by GEV quantile function and derived posterior distribution for the Fourier coefficients, were illustrated with a wide range of return periods. The nonstationary frequency analysis considering seasonality can reasonably reproduce underlying extreme distribution and simultaneously provide a full annual cycle of the design rainfall as well.