• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.3
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• pp.199-206
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• 2013

This paper proposes a modified tag collection algorithm that improves the drawback of the identified slot scan-based tag collection algorithm presented in a previous paper to improve the tag collection performance in active RFID systems. The previous identified slot scan-based tag collection algorithm is optimized in situations where all the tags store the fixed size of data, so it could not result in a good performance improvement with tags having the variable size of data. The improved tag collection algorithm proposed in this paper first collects the slot size information required for the data transmission from each tag via the identified slot scan phase, and then performs the tag collection phase using the information, which resolves the problem of the previous identified slot scan-based tag collection algorithm. The simulation results for performance evaluation showed that the proposed tag collection algorithm resulted in the almost same tag collection performance as the previous algorithm when all the tags have the same size of data and led a large improvement of the tag collection performance in ISO/IEC 18000-7 unlike the previous algorithm when each tag has a random size of data.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7582-7588
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• 2015

Noncoherent receivers are favored for block-code-modulated ultrawideband impulse radio (UWB-IR) systems because of their low implementation complexity compared with coherent rake receivers. However, existing noncoherent schemes, such as transmitted reference (TR) systems and averaged differential receivers (ADR), suffer from performance degradation and energy efficiency loss. Codeword matching and signal aggregation (CMSA) is a low complexity noncoherent receiver for UWB-IR. As the frame/symbol duration is shortened to boost data rate, interframe interference (IFI) or intersymbol interference (ISI) occurs and degrades the detection performance of CMSA. In this paper, block coded correlator which consists of the delay components and the reference signal is proposed to improve the performance of the receiver. Simulation results show that the proposed system leads to the better performance compared to the conventional CMSA receiver.

• Journal of the Korean Institute of Gas
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• v.25 no.6
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• pp.1-6
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• 2021

In this study, we developed AMI terminals of 1 (reader): N (small transmitter). Currently, the government is focusing on the Gas AMI demonstration project to advance the outdated metering system of the urban gas industry, led by the government-sponsored ministries. The supply of gas AMI meters has the advantage of resolving uncertainties in privacy violations and measurement information and preparing for consumer safety through gas leakage detection. In the case of existing AMI meters, readers and transmitters were 1:1 methods, while this technology can be extended to multiple generations with a 1:N method, and a technology that can extend battery life by implementing a low-power design is applied. We hope that this research will contribute to the gas AMI supply project in the future.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.5
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• pp.129-134
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• 2024

Radar signal processing boards have been widely used in embedded systems with architectures including DSPs and FPGAs. There is high-speed real-time communication between DSP and FPGA, high-speed real-time communication between DSP and DSP, and high-speed communication between FPGA and external radar components. This paper describes general communication interfaces such as memory and External Memory Interface (EMIF), HyperLink between DSP, SRIO (Serial Rapidio) between FPGA and DSP, PCIe (PCI Express), RS422 communication with FPGA and external components for DSP to boot, and describes how to implement high communication performance using these interfaces. In particular, high-speed communication between DSP and FPGA is explained by analyzing speed and performance. And previously, it describes how to receive a lot of information at high speed via RS422 communication, from the method of parallel processing individual signals through multiple signals in order to control the external radar components and receive information. The new method improves the communication speed and performance of the radar signal processing board.

• Journal of Aerospace System Engineering
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• v.18 no.1
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• pp.53-63
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• 2024

Adopting an engine igniter with high efficiency and ignition performance is essential for reliable operation of liquid rocket engines. In this study, we developed a spark torch igniter for a 450 N-scale methane-oxygen liquid rocket engine by conducting numerical analyses, igniter manufacturing and validation. Specifically, we conducted a parametric study for maximizing the enthalpy at the igniter exit, specifically by adjusting the mass flow rate, nozzle area ratio, fuel-oxidizer mixture ratio, and the igniter length-to-diameter. The heat transferred via the igniter nozzle exit was computed using 3-dimensional numerical simulations. We also manufactured and tested the igniter based on a deduced design to confirm ignition performance of the designed spark torch igniter. The igniter developed through this study could contribute to the development of practical propulsion systems such as upper-stage engines of small launch vehicles.

• Journal of Digital Convergence
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• v.12 no.9
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• pp.201-207
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• 2014

In the cloud environment, the company needs data integration and analysis to make decision and policy. If new system is added to this environment, a lot of time and cost is needed due to disparate properties among systems when data is integrated. Therefore, in this paper, we propose a DBaaS hub system for multi-database service. The DBaaS may require a different database and need data integration for relevant service. Using the ontology, we propose a metadata query to resolve the interoperability issues between data of DBaaS. The meta-query is not a query to access the real data, but the query for the upper level. This method provides data integration by accessing the data with the converted query through an ontology when we access the actual database.We also constructs a document-oriented database system using the metadata.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.5
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• pp.96-104
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• 2004

This paper proposes a dc power regenerating systems, which can generate the excessive dc power from dc bus line to ac supply in substations for traction system The proposed regeneration inverter system for dc traction can be used as both an inverter and an active power filter(APF). As an regeneration inverter mode, it can recycle regenerative energy caused by decelerating tractions and as an active power filter mode, it can compensate for harmonic distortion produced by the rectifier substation. From the viewpoint of both power capacity and switching losses, the system is designed on the basis of three phase PWM inverters and composed of parallel inverters, output transformers, and an LCL filter.

• Journal of Advanced Navigation Technology
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• v.6 no.2
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• pp.130-137
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• 2002

We present Space-Time Trellis Coded Code Division Multiple Access systems, which maintain the full diversity and coding gain of Space-Time Trellis Codes(STTC) and have the immunity to performance degradation caused by multipath fading. These STTC CDMA systems are constructed by adding the spreading and despreading processes of PN codes to STTC systems. In multipath fading channels, delay spreaded signals are detected and combined, then decoded. According to the combining and decoding methods, there are four decoding methods. There are optimum ML decoding without combining, adding multipath signals in each receive antenna before decoding, combining multi path signals in each antenna before decoding, and combining all received signals before decoding. Performance of these methods is proportional to complexity. Besides, all methods are shown to compensate the irreducible error rate which appears in multipath fading channels.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.6
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• pp.1229-1236
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• 2009

Puretone audiometer, which is a machine used for measuring the minimum hearing threshold, can be cost-effectively implemented using computer with sound card and software. In this paper, we describe a puretone audiometer which has been designed and implemented based on a general PC with sound card. It supports air conduction and bone conduction test taking with automatic masking. It also provides multiple modes consisted of self-test, auto-test and manual test mode. Such multiple modes makes it possible to use in various environments like as home and/or hospital. Through measure of waveform of output voltage and sound pressure, we verified that puretone audiometer of this paper properly operates.

• The Transactions of the Korea Information Processing Society
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• v.7 no.11
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• pp.3417-3426
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• 2000

Most of conventional mobile agent systems requre that the users or the programmer should give the mobile agenl its detail behavioral script for accomplishing the given task. And during its runtime, such mobile agents just behave acording to the fixed script given by its user. Therefore it is impossible that conventional mobile agents autonomously build their own plans and execute. There in considering their ultirnale goals and the dynamic world states. One way to overcome such limtations of conventional mobile agent systems is to develop an mielligent mobile agent system ombedding a reactive planner.In this paper, we design both a modelof agent inobility and a model of inter-agent commuication based upon the representative reactive planning agent architecture called JAM. An then we develop an intelligent mobile agent system with planing capability, IMAS, by implementing addtional basic actions for agent moves and inter-agent comunication within JAM according too the predevined models. Unlike conventional mobile agents, IMAS agents can be able to adapt, their behaviors to the dynamic changes of their anvironment as well as build their own plans autonomously. Thus IMAS aents can snow higher flexibility and robustness than the conventional ones.