• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.1
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• pp.70-77
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• 2005

The study was results obtained from the trial make of the hybrid GPS-electromagnetic(EM) compass which overcome shortcoming of GPS compass and EM compass. The results were summarized as follows: GPS compass detected the stable ship's heading at 0.1^{\circ}$ intervals with the turning angular velocity of less than 25^{\circ}$/sec in the experiment for the characteristics of turning angular velocity with stepmotor, but in case of over 25^{\circ}$/sec the compass did not detect it. On the contrary, the EM compass always indicated the ship's heading with no connection of the turning angular velocity, however the compass is low accuracy compared with GPS one owing to a compass error. The ship's headings by the hybrid GPS-EM compass were displayed at fixed point and moving by car; if the GPS compass work the headings were displayed by GPS compass, if not, the heading is provided stably by adding or subtracting of a compass error to the heading of EM compass. Also, each ship's heading was derived from not only the GPS compass but also the EM one by add or subtract of the compass errors, and then was worked covariance for the analogy. The results show that the ship's heading of two compasses has been verified the similarity to 95% confidence level.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.3
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• pp.6-12
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• 2011

The fast growing of the number of users requires the development of reliable communication systems able to provide higher data rates. In order to meet those requirements, techniques such as Multiple Input Multiple Out (MIMO) and Orthogonal Frequency Division multiplexing (OFDM) have been developed in the recent years. In order to combine the benefits of both techniques, the research activity is currently focused on MIMO-OFDM systems. In addition, for a fast wireless channel environment, the data rate and reliability can be optimized by setting the modulation and coding adaptively according to the channel conditions; and using sub-carrier frequency, and power allocation techniques. Depending on how accurate the feedback-based system obtain the channel state information (CSI) and feed it back to the transmitter without delay, the overall system performance would be poor or optimal. In this paper, we propose a Signal to Noise Ratio (SNR) estimation algorithm where the preamble is known for both sides of the transciever. Through simulations made over several channel environments, we prove that our proposed SNR estimation algorithm is more accurate compared with the traditional SNR estimation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.1
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• pp.68-78
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• 2013

In this paper, we propose an early spectrum sensing(ESS) as an advance preparation for radio-access trial, which enables multi-mode terminals to access the most appropriate radio-access system in a cloud-conceptual base station system where multiple radio access technologies(RATs) coexist. Prior to a random access to one of RATs, a multi-mode terminal conducts a spectrum sensing over entire frequency bands of whole RATs, then select the RAT with the lowest sensing power, that is likely to have the most available spectrum. Thus, an access failure caused by that the selected RAT has no available radio spectrum could be avoidable in advance. In computer simulation, we consider as various RATs as possible. First, circuit and packet systems are taken into consideration. In addition, the packet systems are classified according to the feasibility of carrier aggregation(CA). In case of terminal, three modes are considered with circuit-only, packet-only, and multi-mode. Subsequently, packet traffic is classified into real-time and non-real-time traffic with three different tolerable delay levels. The simulation includes a call process starting with a call generation and ending up with a resource allocation reflecting individual user's QoS requirements and evaluates the proposed scheme in terms of the successful access probability, system access time, system balancing factor and packet loss probability.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.450-453
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• 2003

본 논문에서는 그룹별 가변 길이 직교코드 다중화를 이용한 OFDM (orthogonal frequency division multiplexing) 전송방식의 제안하고, 그룹별로 동일한 부반송파 개수를 가정하여 코드 길이에 따른 시스템 성능과 복잡도를 분석함으로써 최적의 시스템 파라미터들을 결정한다. 제안된 방식에서는 상호 상관성이 낮은 부반송파들로 동일 반송파 그룹으로 구분함으로써 부반송파 전체를 다수의 부반송파 그룹으로 나누고, 그룹마다 부반송파 개수와 동일한 길이의 직교코드들을 사용하여 다중화하여 전송한다. 따라서, 제안된 시스템을 사용하면 적절한 시스템 파라미터의 선정을 통하여 부반송파 전체를 하나의 그룹으로 하는 기존의 직교코드 다중화 방식에[2] 비하여 다이버시티 이득은 유지하면서 시스템 복잡도를 크게 줄일 수 있다. 또한, 제안된 직교코드 다중화 전송방식에서는 수신기에서 직교코드들간의 직교성 복원이 필수적이며, 수신기에서 불완전한 채널등화는 인접한 직교코드들 간에 상호 간섭을 유발하는 요인이 된다. 따라서, 채널추정 오류의 정도가 증가함에 따라 직교코드들 간의 상호 간섭으로 인하여 증가하는 비트오류를 줄이기 위하여 채널추정 오류의 정도에 따라 블록길이와 블록 인터리버 구조를 조절하여 시스템을 최적화 한다. 가변 길이 직교코드로는 길이에 상관 없이 직교성을 유지하며 에너지의 균등 분배가 가능한 DFT (discrete Fourier transform) 코드를 사용한다. 최적 시스템 파라미터를 결정하기 위하여 모의실험을 통하여 코드 길이에 따른 시스템 성능을 분석한다. 또한, 채널추정 오류가 존재하는 경우에 시스템 성능을 분석한다. 마지막으로, 채널 부호화를 적용하는 경우에 시스템 파라미터들을 최적화함으로써 부호화 이득이 시스템 성능과 시스템 복잡도 감소, 채널추정 오류의 극복에 미치는 영향을 분석한다. nature, in contrast to physical theories that are of a geometrical nature. An application to the interpretation of intelligence is proposed, based on the "intelligence"of movement. Co layer from 1.4 to 1.6 nm was measured to be ranged from 0.004 to 0.021 ${\AA}$$\^$-1/.문에 기업간 관계를 연구하는 측면에서는 탐험적 연구성격이 강하다. 더 나아가 본 산업의 주된 연구가 질적이고 기업내부만을 연구했던 것에 비교하면 시초적이라고 할 수 있다. 또한 관계마케팅, CRM 등의 이론적 배경이 되고 있는 신뢰와 결속의 중요성이 재확인하는 결과도 의의라고 할 수 있다. 그리고 신뢰는 양사 간의 상호관계에서 조성될 수 있는 특성을 가진 반면, 결속은 계약관계 초기단계에서 성문화하고 규정화 할 수 있는 변수의 성격이 강하다고 할 수가 있다. 본 연구는 복잡한 기업간 관계를 지나치게 협력적 측면에서만 규명했기 때문에 많은 측면을 간과할 가능성이 있다. 또한 방법론적으로 일방향의 시각만을 고려했고, 횡단적 조사를 통하고 국내의 한 서비스제공업체와 관련이 있는 컨텐츠 공급파트너만의 시각을 검증했기 때문에 해석에서 유의할 필요가 있다. 또한 타당성확보 노력을 기하였지만 측정도구 면에서 엄격한 개발과정을 준수하지는 못했다. 향후에는 모바일 컨텐츠 파트너의 기업의 특성을 조사하여 관계성 변수와의 상호관련연구를 진행할 필요가 있다. 관계기간, 의존성, 거래처의 단/복수여부, 서비스 범주 등의 제반 변수를 고려하여 이러한 변수가 양사와의 관계성 변수에 어떤 영향이 있는가를 검증할 필요가 있다. 또한 신뢰,

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.4
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• pp.6-14
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• 2011

The fast growing of the number of users requires the development of reliable communication systems able to provide higher data rates. In order to meet those requirements, techniques such as Multiple Input Multiple Out (MIMO) and Orthogonal Frequency Division multiplexing (OFDM) have been developed in the recent years. In order to combine the benefits of both techniques, the research activity is currently focused on MIMO-OFDM systems. In addition, for a fast wireless channel environment, the data rate and reliability can be optimized by setting the modulation and coding adaptively according to the channel conditions; and using sub-carrier frequency, and power allocation techniques. Depending on how accurate the feedback-based system obtain the channel state information (CSI) and feed it back to the transmitter without delay, the overall system performance would be poor or optimal. In this paper, we propose a Signal to Noise Ratio (SNR) estimation algorithm where the preamble is known for both sides of the transciever. Through simulations made over several channel environments, we prove that our proposed SNR estimation algorithm is more accurate compared with the traditional SNR estimation. Also, We applied AMC on several channel environments using the parameters of IEEE 802.11n, and compared the Throughput performance when using each of the different SNR Estimation Algorithms. The results obtained in the simulation confirm that the proposed algorithm produces the highest Throughput performance.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.122-122
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• 2014

수중방전을 환경분야에 적용하기 위한 플라즈마 부상법이 개발되었다. 플라즈마 부상법은 물 속에서 발생시킨 플라즈마가 가지고 있는 주요특성 중 물리적 특징인 쇼크웨이브, UV조사, 버블생성 등과 화학적 특징인 OH라디칼 및 염소산화물 생성 등을 이용하여 물 속에 존재하는 용존성 및 입자성 물질을 부상분리 기법으로 제거하는 공법이다. 유기물을 제거하는 기작으로는 침전, 여과, 분해 등이 있고, 이를 구현하기 위한 공정으로 중력침강법, 부상분리법, 멤브레인법, 미생물법 등이 있다. 이 중에서 가압공기부상법은 침강법에 비해 부지면적을 적게 소모하고 처리시간이 50% 이상 감소되는 특징이 있다. 가압공기부상법은 물 속에 공기를 과포화시킨 후 노즐을 통해 재분사할 때 발생하는 압력차에 의해 미세기포가 발생함을 이용하여 유기물을 분리하는 공법이다. 그러나, 가압용 장비 및 반송수가 필요하고, 미생물분리는 불가능한 단점이 있다. 이에 본 연구에서는 미생물살균과 유기물 분리가 동시에 일어나는 플라즈마를 이용한 부상분리기법을 개발하였다. 본 연구에서는 난분해성 용존유기물인 휴믹산 100 mg/L의 플라즈마 공기부상법에 의한 제거능을 확인하였다. 용존성 휴믹산을 입자성 물질로 전환하여 플록을 형성시키고자 알루미늄설페이트(Al2(SO4) $3{\cdot}18H2O$)를 100 mg/L 주입하였고, 침출수와 같이 염도가 높은 물을 모사하고자 35 g/L의 염화나트륨을 첨가한 상태에서 방전을 실시하였다. 방전에 사용된 전원은 EESYS사에서 제작한 펄스형 고전압 전원장치를 사용하였고 최대 15 kW의 출력 중 6 kW의 전력을 인가하였다. 전극 한 개는 2 mm 텅스텐봉을 세라믹튜브로 감싼 구조로 총 사용전극은 28개이다. 전극 한 개당 대략 200 Watt의 전력이 소모되며 이 때 최대의 버블이 생성됨을 확인하였다. 전극 1개에서 생성되는 버블의 부피는 14 mL/min 로 측정되었다. 버블의 크기는 평균 70 um이고 가압공기부상법에서 최적공기크기로 제시하고 있는 40~80 um 의 버블은 약 80% 가량 생성된다. 본 연구에서 사용된 반응시스템에서의 물의 높이는 약 500 mm 이고 전체 40 L의 수조가 3개의 벽으로 분리되어 4개의 수조로 분리되었다. 각 수조는 하부에 7개의 전극을 포함하고 있다. 플라즈마 발생시 생성되는 기포는 약 1분 방전 후에 포화농도에 도달하며 방전종료 후 약 4분간 수체 내에 남아있게 된다. 이를 공정에 적용하여 1분 방전 및 4분 휴지의 순서로 플라즈마를 인가하였다. 휴믹산 용액의 유량을 2 lpm 으로 운전하였을 때 최종 처리율은 94% 이고 이때의 대장균 살균능은 99%이다.

• Membrane Journal
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• v.24 no.1
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• pp.63-68
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• 2014

Manufacturing facility for non-alcoholic drink, the parts of the food industry, disposes wastewater which includes high organic concentration and low nitrogen, phosphorus concentration. For this kind of wastewater, the treatment plant consists mainly of aerobic reactor and chemical coagulation process. And sand-filter or activated carbon process is normally installed further. However, aerobic reactor must have long HRT to treat high concentration of organic contaminant included in this wastewater, so the large site area is required. And settling tank which is normally applied for wastewater treatment facility has some problems such as water quality degradation caused by the sludge spill. To solve these problems, we applied MBR system for the wastewater. And the MBR pilot plant was installed nearby the wastewater treatment facility of W food factory and operated during long term to evaluate treatment efficiency. This plant was operated about 3 months and than the result was 97% of organic removal rate on conditions of flow rate $20m^3/day$, HRT 29 hr, recycle 4Q. However, contaminant removal ratio of bio-reactor decreased and TMP of membrane increased rapidly on more conditions.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.11
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• pp.12-20
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• 2013

Even though extensive research results have been applied to wireless cellular systems to improve their capacity and coverage, severe performance degradation experienced in cell boundary areas still remains as a major limiting factor to prohibit further improvement of user equipment (UE) throughput. In the Long Term Evolution-Advanced (LTE-A) standard of the Third Generation Partnership Project (3GPP), Some advanced techniques have been introduced to overcome this "cell-edge problem", including coordinated multipoint transmission and reception (CoMP) and inter-cell interference coordination (ICIC). In this paper, we propose yet another strategy to improve the performance of low-tier UEs by using the concept of multiple beam direction patterns (BDPs). Such multiple BDPs can be implemented using multi-layer antenna arrays stacked vertically at base station (BS) sites to transmit signals in different main beam directions. In comparison to conventional three-sector antennas with a fixed beam pattern, the proposed methods makes signal transmission in a rotational fashion to significantly enhance the reception quality of UEs located near sector (or cell) edge areas, preventing the situation where certain UEs are marginally covered by the BS for the whole transmission time. Performance evaluation results show that the proposed scheme outperforms the conventional three-sector transmission by 171% in low 5% UEs in terms of the UE throughput.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.430-439
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• 2004

This paper describes a design of 8192/2048-point FFT/IFFT processor (CFFT8k2k), which performs multi-carrier modulation/demodulation in OFDM-based DVB-T receiver. Since a large size FFT requires a large buffer memory, two design techniques are considered to achieve memory-efficient implementation of 8192-point FFT/IFFT. A hybrid structure, which is composed of radix-4 single-path delay feedback (R4SDF) and radix-4 single-path delay commutator (R4SDC), reduces its memory by 20% compared to R4SDC structure. In addition, a memory reduction of about 24% is achieved by a novel two-step convergent block floating-point scaling. As a result, it requires only 57% of memory used in conventional design, reducing chip area and power consumption. The CFFT8k2k core is designed in Verilog-HDL, and has about 102,000 Bates, RAM of 292k bits, and ROM of 39k bits. Using gate-level netlist with SDF which is synthesized using a $0.25-{\um}m$ CMOS library, timing simulation show that it can safely operate with 50-MHz clock at 2.5-V supply, resulting that a 8192-point FFT/IFFT can be computed every 164-${\mu}\textrm{s}$. The functionality of the core is fully verified by FPGA implementation, and the average SQNR of 60-㏈ is achieved.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.3
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• pp.463-469
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• 2009

We performed the experimental study on the control of suspended dust in a cement packaging process for various ventilation systems. To effectively remove the dust generated in the cement packaging process, three different kinds of ventilation system, such as local exhaust ventilation, electrostatic scrubber, and local air supply system, were adopted. Dust concentrations in the packaging process were measured with the variation of the airflow rate of the ventilation systems and then their ventilation performance were evaluated. From the results, we knew that the ventilation performance was the best when the local exhaust ventilation and the electrostatic scrubber were simultaneously operated in the packaging process. In the electrostatic scrubber system, the effect of the airflow rate on the indoor dust removal efficiency was negligible so hat he system ust be operated at $2,700m^3/h$ for saving power consumption.