• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.2
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• pp.422-429
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• 2007

Location awareness is one of the key functionalities to build an U-city. Recently, many of works of the location-aware systems are emerging to commercially apply to on-going large-scale apartment complex based on U-city. As dwellers or cars being attached with active tags are moving in the U-city complex, the active tags periodically broadcast their own identifiers and receivers fixed along the street or in building use those information to calculate location of them. There are several issues to be considered for such an environment. The first is that the number of active tags operating in the same region are large as much as tens of thousands, and the second is that the active tags should be alive without change of batteries more than a year, hence low power consumption is very important. In this paper we propose i) a new architecture for location-aware system considering such issues, ii) technical issues to implement it using active tags, and iii) a mathematical analytic model to investigate overall performance and verify it by comparing with actual experimental results. Through the analysis we can show the theoretical boundary of the lowest packet loss rate and the maximum number of tags with acceptable performance for the systems based on active tags. The results can be applied to practical design of location-based systems of U-City projects.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.578-584
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• 2021

This study comparatively analyzed the properties of hydration reaction and strength development of four types of pond ash(PA) and fly ash(FA), aiming for the effective use of PA. The PA whose chlorine content was highest due to the seawater movement method had a faster setting time, higher cumulative heat, and greater initial strength development than those of FA due to the acceleration of the cement hydration reaction. However, the activity factor increase rate decreased after seven days of curing due to the rapid generation of early hydrates. The PA that contained impurities, such as a large amount of unburned carbon, had a delayed setting time due to the lower hydration reaction. Moreover, the strength was degraded in all curing ages. The PA whose chlorine content was lower due to the freshwater movement method and the amorphous content exhibited similar hydration reactivity and strength development characteristics compared to that of FA. The thermogravimetric analysis results verified that it had a similar level of Ca(OH)₂ consumption and pozzolanic reactivity with that of FA. Conclusively, it is necessary to expand the application of the freshwater movement method and manage the ignition loss to raise PA's usability.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.650-656
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• 2018

The TFT-LCD industry is a kind of large-scale industrial Giant Microelectronics device industry and has a similar semiconductor process technology. Wet etching forms a relatively large proportion of the entire TFT process, but the number of published research papers on this topic is limited. The main reason for this is that the components of the etchant, in which the reaction takes place, are confidential and rarely publicized. Aluminum (Al) and copper (Cu), which have been used in recent years for the manufacture of large area LCDs, are very difficult materials to process using wet etching. Cu, a low-resistance material, can only be used in the wet etching process, and is used as a substitute for Al due to its high speed etching, low failure rate, and low power consumption. Further, the abnormal reaction of hydrogen peroxide ($H_2O_2$), which is used as an etching solution, requires additional piping and electrical safety devices. This paper proposes a method of minimizing the damage to the plant in the case of adverse reactions, though it cannot limit the adverse reaction of hydrogen peroxide. In recent years, there have been many cases in which aluminum etching equipment has been changed to copper. This paper presents a countermeasure against abnormal reactions by implementing safety PLC with a high safety grade.

• Journal of Energy Engineering
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• v.28 no.4
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• pp.35-41
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• 2019

In order to overcome these disadvantages, the halogen light source, which was previously used as a vehicle fog light, has increased power consumption and a short lifetime, and thus, an automobile light source is gradually being replaced with an LED. However, when the vehicle LED fog light is turned on, there is a disadvantage in reducing the life of the fog lamp due to the high heat generated from the LED. The heat generated by the LED inside the fog lamp is mainly emitted by the heatsink, but most of the remaining heat is released to the outside through convection. When cooling efficiency decreases due to convection, thermal energy generates heat to lenses, reflectors, and bezels, which are the main parts of lamps, or generates high temperatures in LED, thereby shortening the life of LED fog lights. In this study, we tried to improve the heat dissipation performance by convection in addition to the heat dissipation method by heat sink, and to determine the installation location of vents that can discharge the internal air or intake the external air of LED fog lamp for vehicle. Thermal fluid analysis was performed to ensure that the optimal data were reflected in the design. The average velocity of air increased in the order of Case3 and Case2 compared to Case1, which is the existing prototype, and the increase rate of Case3 was relatively higher than that of other cases. This is because the vents installed above and below the fog lamps induce the convective phenomena generated according to the temperature difference, and the heat is efficiently discharged with the increase of the air speed.

• Journal of the Korean GEO-environmental Society
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• v.17 no.10
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• pp.45-53
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• 2016

At present, coffee consumption amount is annually on the rise in Korea, which results in about 0.27 million tons of coffee waste annually. They are mostly classified as food waste and deserted with moisture contained, being a serious environmental issue. Existing slope greening techniques, which are vegetation based soil-media hydroseeding measures, have problems such as lack of coherence, dryness or lack of organic matters. Therefore in order to assess usability of Spent Coffee Ground (SCG), medium-to long-term growth test was conducted under the indoor and outdoor conditions. According to the result of growth test, when SCG was mixed with existing base materials, moisturizing power increased and organic matter content was reinforced, promoting germination and growth in a medium term. Among others, under the condition when supply of water was discontinued, withering rate was lower than existing base materials and diverse phenomena resulting from lack of nutrition decreased. Therefore, SCG as a waste organic matter with abundant nitrogen has the characteristic of inhibiting early growth but was found to have a quality favorable to long-term growth resulting from water containing ability and the supply of organic mater and is judged to be a material to replace or complement existing base materials.

• Journal of Advanced Navigation Technology
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• v.21 no.6
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• pp.554-560
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• 2017

Accurate altimetry is required for the reliable flight control of drones or unmanned air vehicles (UAVs), and the radar altimeter is commonly used owing to its accuracy for the ground level. Due to the limitation for size, weight and power consumption, the frequency modulated continuous wave (FMCW) radar is appropriate for drone because it has lower complexity than that of pulse Doppler (PD) radar. Especially, fast-ramp FMCW radar, which transmits linear FM signal during very short period, is generally utilized, because it is robust for the ego-motion of drone. Therefore, we present the design and implementation results of the radar signal processor (RSP) for fast-ramp FMCW radar system. The proposed RSP was designed with Verilog-HDL and implemented with Altera Cyclone-IV FPGA device. Implementation results show that the proposed RSP includes 27,523 logic elements, 15,798 registers and memory of 138Kbits and can measure the altimeter at the rate of 100Hz with the operating frequency of 50MHz.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.7
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• pp.61-69
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• 2010

In this paper, an 1.2V 8b 800MSPS A/D Converter(ADC) with an odd number of folding block to overcome the asymmetrical boundary-condition error is described. The architecture of the proposed ADC is based on a cascaded folding architecture using resistive interpolation technique for low power consumption and high input frequency. The ADC employs a novel odd folding block to improve the distortion of signal linearity and to reduce the offset errors. In the digital block, furthermore, we use a ROM encoder to convert a none-$2^n$-period code into the binary code. The chip has been fabricated with an $0.13{\mu}m$ 1P6M CMOS technology. The effective chip area is $870{\mu}m\times980{\mu}m$. SNDR is 44.84dB (ENOB 7.15bit) and SFDR is 52.17dBc, when the input frequency is 10MHz at sampling frequency of 800MHz.

• Plant Journal
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• v.12 no.1
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• pp.29-36
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• 2016

It is becoming increasingly important to make use of alternative energy source. because It is not able to rely on only fossil fuel for the recent increasing demand of energy consumption. With this situation, lots of studies for utilizing low grade energy such as industrial waste heat, solar energy, and geothermal energy have been conducted. The aim of this study is to predict the operation characteristics of working fluid by using performance analysis program (ThermoFlex) through the system analysis which is not mixing district return water but using ORC(Organic Rankine Cycle, hereinafter ORC) as a downstream cycle when accumulating district heating (hereinafter DH). In this study, We conducted the performance analysis for the case which has the district heating water temperature($120^{\circ}C$) and Flow rate of $163m^3/h$ (including District Heating return water flow), and examined several working fluid which is proper to this temperature. The case using R245fa (which is the best-case) showed 269.2kW power output, 6.37% efficiency. Additionally, Cut down on fuel was expected because of the boiler inlet temperature increase by being Formed $57.3{\sim}85^{\circ}C$ in a temperature of district heating return water, depending on a pressure change of a condenser in ORC system.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.87-95
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• 2013

In this paper, 2.5 Gb/s burst-mode clock and data recovery(CDR) is presented. Digital frequency calibration scheme is adopted to eliminate mismatch between the input data rate and the output frequency of the gated voltage controlled oscillator(GVCO) in the clock recovery circuitry. A jitter rejection scheme is also used to reduce jitter caused by input data. The proposed burst-mode CDR is designed using 0.11 ${\mu}m$ CMOS technology. Post-layout simulations show that peak-to-peak jitter of the recovered data is 14 ps with 0.1 UI input referred jitter, and maximum tolerance of consecutive identical digit(CID) is 2976 bits without input data jitter. The active area occupies 0.125 $mm^2$ without loop filter and the total power consumption is 94.5 mW.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.3
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• pp.96-101
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• 2015

This paper describes a design and implementation of the NFC bridge chip which performs interface between kinds of devices and mobile phones including NFC controller through NFC communication. The NFC bridge chip consists of the digital part and the analog part which are based on NFC Forum standard. Therefore the chip treats RF signals and then transforms the signal to digital data, so it can interface kinds of devices with the digital data. Especially the chip is able to detect RF signals and then wake up the host processor of a device. The wakeup function dramatically decreases the power consumption of the device. The carrier frequency is 13.56MHz, and the data rate is up to 424kbps. The chip has been fabricated with SMIC 180nm mixed-mode technology. Additionally an NFC bridge chip application to the blood glucose measurement system is described for an application example.