• The KIPS Transactions:PartC
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• v.13C no.1 s.104
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• pp.95-102
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• 2006

Nowadays, GPS is used widely, especially in case which needs precise position information, such as car navigation systems and various kinds of position measuring instruments in an outdoor environment. According to their applications, there are many kinds of GPS receivers with different costs and error rates. The maximum error range of the general-purpose GPS receiver is within 30m, though the error rate depends on receiving rate of signal and weather condition. RTK(Real-Time Kinematic) and DGPS(Differential Global Positioning System) have more precise accuracy than the general-purpose GPS. However end users can't afford use them because of their high price and large size of equipments. In order for the end user to obtain precise position information, it is important that GPS receivers has portability and low price. In this study, we introduce a new system that offers precise position information using the DGPS mechanism satisfying low cost and portability.

• Journal of information and communication convergence engineering
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• v.7 no.1
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• pp.19-23
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• 2009

In this paper, we propose a general idea about an RFID system which provides lighted weight algorithm. We discuss how RFID could be applied for this kind of system, especially, compact protocol. We evaluate a few protocols that have been suggested for use in passive RFID tagged systems. We can reduce security computation without losing security features by message integration and pre-computation in this paper. And the proposed protocol can be used in low-cost RFID systems that require a small computational load for both the back-end database and the tags.

• Journal of Korea Multimedia Society
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• v.17 no.9
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• pp.1084-1091
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• 2014

When demand for transmitting multimedia data increases, network congestion is more likely to occur and users will suffer high loss rate as well as high delay. In order to enhance quality-of-service (QoS) of video multicasting, we need to raise transmission reliability and reduce end-to-end delay. This paper proposes a routing mechanism for a OpenFlow-based small-scale network in order to multicast video reliably with low delay. In our method, multipath routing will be applied to Multiple Description (MD) Coded video to exploit its multi-description property. Through performance evaluation, our method shows improvement on loss rate, delay and video distortion.

• BMB Reports
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• v.48 no.12
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• pp.677-684
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• 2015

Cardiovascular function is regulated by the rhythmicity of circadian, infradian and ultradian clocks. Specific time scales of different cell types drive their functions: circadian gene regulation at hours scale, activation-inactivation cycles of ion channels at millisecond scales, the heart's beating rate at hundreds of millisecond scales, and low frequency autonomic signaling at cycles of tens of seconds. Heart rate and rhythm are modulated by a hierarchical clock system: autonomic signaling from the brain releases neurotransmitters from the vagus and sympathetic nerves to the heart's pacemaker cells and activate receptors on the cell. These receptors activating ultradian clock functions embedded within pacemaker cells include sarcoplasmic reticulum rhythmic spontaneous Ca²⁺ cycling, rhythmic ion channel current activation and inactivation, and rhythmic oscillatory mitochondria ATP production. Here we summarize the evidence that intrinsic pacemaker cell mechanisms are the end effector of the hierarchical brain-heart circadian clock system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.7
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• pp.1235-1240
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• 2008

In this paper, we presented an active RFID system in 2.45GHz range including LNA, Mixer and gain block. And in this work, a link budget model for RFID applications are proposed. We describe the detailed design and implementation of our system. Our components in RFID system has features such as low Noise Figure, reliable energy budget, and standard compliance with ISO 18000-4. Our receiver is effective for development and evaluation of prototype applications because of the flexibility of the design hardware. So, our platform will be suitable for versatile item management applications.

• Journal of the Semiconductor & Display Technology
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• v.20 no.2
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• pp.77-81
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• 2021

In this paper, a low-csst ECG system using a digital filter was implemented. After amplifying the analog ECG signal, it is converted into a digital signal and filtered. The developed ECG module is miniaturized by removing the analog filter element that occupies the existing volume and replacing it with a digital filter using a 3-stage Butterworth filter which is one of IIR filters. It uses a serial monitoring program with C# to check and save the ECG waveform measured on a computer screen. The ECG system using a developed digital filter in this paper uses a low-cost processor instead of an expensive, high-end processor, and its size and price are reduced by converting the analog filter to a digital filter. In addition, since the waveform of the developed ECG system is similar to the actual ECG waveform of MIT-BIU, it is considered that the existing analog filter can be replaced with the developed digital filter.

• ETRI Journal
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• v.36 no.3
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• pp.367-373
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• 2014

With high bandwidth, low interference, and low power consumption, optical network-on-chip (ONoC) has emerged as a highly efficient interconnection for the future generation of multicore system on chips. In this paper, we propose a new path-setup method for ONoC to mitigate contentions, such as packets, by recycling the setup packet halfway to the destination. A new, strictly non-blocking $6{\times}6$ optical router is designed to support the new method. The simulation results show the new path-setup method increases the throughput by 52.03%, 41.94%, and 36.47% under uniform, hotspot-I, and hotspot-II traffic patterns, respectively. The end-to-end delay performance is also improved.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.38-39
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• 2017

This paper proposes a new control method for an AC-DC Buck converter which is utilized as a front-end converter of a 2-stage high power density adapter. In the conventional adapter applications, 2-stage configuration shows higher power transfer efficiency and higher power density than those of the single stage flyback converter. In the 2-stage AC-DC converter, the boost converter is widely used as a front-end converter. However, an efficiency variation between high AC line and low AC line is large. On the other hand, the proposed conduction band control method for a buck front-end converter has an advantage of small efficiency variation. In the proposed control method, switching operation is determined by a band control voltage which represents output load condition, and an AC line voltage. If the output load increasesin low AC line, the switching operation range is expanded in half of line cycle. On the contrary, in light load and high line condition, the switching operation is narrowed. Thus, the proposed control method reduces switching loss under high AC line and light load condition. A 60W prototype which is configured the buck and LLC converter with the proposed control method is experimented on to verify the validity of the proposed system. The prototype shows 92.16% of AC-DC overall efficiency and 20.19 W/in 3 of power density.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2243-2257
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• 2016

This paper presents a two stage three-phase proton exchange membrane fuel cell (PEMFC) generation system. When the system is connected to a three-phase load, it is very sensitive to the characteristics and type of the load. Especially unbalanced three-phase loads, which result in a pulsating power that is twice the output frequency at the inverter output, and cause the dc-link to generate low frequency ripples. This penetrates to the fuel cell side through the front-end dc-dc converter, which makes the fuel cell work in an unsafe condition and degrades its lifespan. In this paper, the generation and propagation mechanism of low frequency ripple is analyzed and its impact on fuel cells is presented based on the PEMFC output characteristics model. Then a novel method to evaluate low frequency current ripple control capability is investigated. Moreover, a control scheme with bandpass filter inserted into the current feed-forward path, and ripple duty ratio compensation based on current mode control with notch filter is also proposed to achieve low frequency ripple suppression and dynamic characteristics improvement during load transients. Finally, different control methods are verified and compared by simulation and experimental results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.5
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• pp.435-446
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• 2014

Even if it is important to transmit high rate multimedia information without any transmission errors for surveillance systems, it is difficult to achieve error-free transmission due to infra-less adhoc networks. In order to reduce the transmission errors furthermore, additional signal overheads or retransmission of signals should be required, but they may lead to transmission delay. This paper represents a study on low delay and adaptive video transmission for the unmanned surveillance systems by developing system protocols. In addition, we introduce an efficient and adaptive control algorithm using system parameters for exploiting unmanned surveillance system properly over multi-channels.