• 설비공학논문집
• /
• 제18권11호
• /
• pp.874-880
• /
• 2006

The power density and heat dissipation rate per unit area of the telecommunication equipment have been increased with the technology development in the footprint of telecommunication hardware. A proper heat dissipation method from the PCB module is very important to allow reliable operation of its electronic component. In this study, a hybrid air-conditioner for the telecommunication equipment room was designed to save energy and obtain system reliability. For high outdoor temperatures, the hybrid system operates in the vapor compression cycle, while, for low outdoor temperatures, the hybrid system works in the secondary fluid cooling cycle with no operation of the compressor. The performance of the hybrid air-conditioner was measured by varying outdoor and indoor temperatures. The hybrid air-conditioner yielded 50% energy saving compared with the conventional refrigeration system when the mode switch temperature was $8.3^{\circ}C$.

• 한국컴퓨터정보학회논문지
• /
• 제24권8호
• /
• pp.59-66
• /
• 2019

As the monetary value of cryptocurrency increases, the security measures for cryptocurrency becomes more important. A limitation of the existing cryptocurrency exchanges is their vulnerability to threats of hacking due to their centralized manner of management. In order to overcome such limitation, blockchain technology is increasingly adopted. The blockchain technology enables decentralization and Peer-to-Peer(P2P) transactions, in which blocks of information are linked in chain topology, and each node participating in the blockchain shares a distributed ledger. In this paper, we propose and implement a mobile electronic wallet that can safely store, send and receive cryptocurrencies. The proposed mobile cryptocurrency wallet connects to the network only when the wallet actively is used. Wallet owner manages his or her private key offline, which is advantageous in terms of security. JavaScript based wallet apps were implemented to respectively run on Android and iOS mobile phones. I demonstrate the process of transferring Ethereum cryptocurrency from an account to another account through Ropsten, a test net for Ethereum. Hardware wallets, such as Ledger Nano S, provide a slightly higher level of security, yet have the disadvantages of added burden of carrying additional physical devices and high costs (about 80$).

• 드라이브 ㆍ 컨트롤
• /
• 제15권4호
• /
• pp.30-38
• /
• 2018

Electronic control units (ECUs) are currently popular, and have evolved further towards the high-end application of autonomous vehicles in the automotive industry. Such digital technologies have also become widespread, in agriculture and construction equipment. Likewise, transmission control of high-speed tracked vehicles is based on the transmission control unit (TCU), performing complex gear change control functions, and diagnostic algorithms (a TCU's self-diagnostic and reporting capability of malfunction data through CAN communication). Since all functions of TCU are implemented by embedded-software, it is hardly possible to analyze specifications by reverse engineering. In this paper a real-time transmission simulator adaptable to TCU is presented, for analysis of diagnosis algorithm and standards. Signal simulation circuits are deliberately designed considering electrical characteristics of TCU inputs and various analysis tools, such as analog input auto scan function, and global output enable switch, are implemented in software. Test results from hardware-in-the-loop simulator verify tolerance time for each error, as well as cause of fault, error reset conditions.

• 터널과지하공간
• /
• 제28권6호
• /
• pp.547-554
• /
• 2018

크라우드소싱을 활용한 센서 자료 수집은 기존의 방식으로 얻기 어려운 고밀도 지반 진동 정보의 수집이 가능하다. 본 연구에서는 스마트폰과 같은 소형 전자기기에 탑재된 MEMS 센서를 활용한 크라우드소싱 방식 지반 진동 수집 시스템을 개발하였으며, 이를 위한 기반 체계 설계 및 클라이언트와 서버에 대한 구현을 수행하였다. 해당 시스템은 Android 기반의 스마트폰이나 Android Things 기반의 고정식 장비를 통해 진동 데이터를 신속히 수집하면서 하드웨어의 전력 및 데이터 사용량을 최소화할 수 있도록 설계되었다.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2019년도 춘계학술대회
• /
• pp.426-428
• /
• 2019

디지털 영상은 카메라 센서의 오작동 및 하드웨어의 오류와 같은 다양한 이유로 잡음에 훼손된다. 특히 AWGN은 전자장비 대부분에서 발견할 수 있기 때문에 다양한 영상 처리 과정에서 AWGN 제거가 필수적으로 이루어진다. 본 논문은 AWGN 환경에서 화소특성을 고려하여 잡음을 제거하는 필터 알고리즘을 제안하였다. 기존 방법들은 고주파 성분이 많은 영상에서 비교적 미흡한 성능을 보였으며, 이를 보완하기 위해 마스크 내부 화소 분포를 고려하여 필터링 범위를 설정하였으며, 각 성분에 적합한 필터의 출력은 정규분포에 따라 가중치를 가감하여 최종 출력을 정한다. 그리고 제안한 알고리즘의 성능을 평가하기 위해 시뮬레이션을 이용하여 기존 방법과 비교하였다.

• 반도체디스플레이기술학회지
• /
• 제20권3호
• /
• pp.71-76
• /
• 2021

Digital decimation filters are used in various digital signal processing systems using ADCs, including digital communication systems and sensor network systems. When the sampling rate of digital data is reduced, aliasing occurs. So, an anti-aliasing filter is necessary to suppress aliasing before down-sampling the data. Since the anti-aliasing filter has to have a sharp transition band between the passband and the stopband, the order of the filter is very high. However, as the order of the filter increases, the complexity and area of the filter increase, and more power is consumed. Therefore, in this paper, we propose two types of decimation filters, focusing on reducing the area of the hardware. In both cases, the complexity of the circuit is reduced by applying the required down-sampling rate in two times instead of at once. In addition, CIC decimation filters without a multiplier are used as the decimation filter of the first stage. The second stage is implemented using a CIC filter and a down sampler with an anti-aliasing filter, respectively. It is designed with Verilog-HDL and its function and implementation are validated using ModelSim and Quartus, respectively.

• 자동차안전학회지
• /
• 제11권2호
• /
• pp.11-16
• /
• 2019

This paper suggests an algorithm for detecting fault of longitudinal controller in autonomous vehicles. Guaranteeing safety in fault situation is essential because electronic devices in vehicle are dependent each other. Several methods like alarm to driver, ceding control to driver, and emergency stop are considered to cope with fault. This research investigates the fault monitoring process in fail-safe system, for controller which is responsible for accelerating and decelerating control in vehicle. Residual is computed using desired acceleration control command and actual acceleration, and detection of its abnormal increase leads to the decision that system has fault. Before computing residual for controller, health monitoring process of acceleration signal is performed using hardware and analytic redundancy. In fault monitoring process for controller, a process model which is fitted using driving data is considered to improve the performance. This algorithm is simulated via MATLAB tool to verify performance.

• 전기전자학회논문지
• /
• 제25권2호
• /
• pp.330-336
• /
• 2021

하드웨어 이중화 구성 수를 줄이는 대표적인 방법은 마이크로컨트롤러로 고장을 검출, 식별 및 수용을 위한 해석적 기법으로 구현하는 것이다. 본 논문에서는 해석적 기법 중 하나인 고장 검출 필터를 항공기 터보팬 엔진 시스템에 적용하였다. 고장 검출 필터는 특수한 형태의 관측기로써 특정한 고장 발생시 잔차가 출력 공간에서 일정한 방향을 유지함으로써 고장의 위치 판별이 가능한 장점이 있다. 이에 본 논문에서는 터보팬 엔진 내 공기 터빈 시스템의 단일 입출력 동적 시스템 모델링, 고장 검출 필터 설계 및 이를 적용한 모의실험 결과를 나타내었다. 모의실험 결과를 통해 고장 검출 필터가 갖는 방향성에 대한 민감성 효과로 고장 검출이 유효하게 적용될 수 있음을 보였다.

• 해양환경안전학회지
• /
• 제27권3호
• /
• pp.429-438
• /
• 2021

The mandatory installation of the ECDIS (Electronic Chart Display and Information System) became an important navigational equipment for navigation officer. In addition, ECDIS is a key component of the ship's digitalization in conjunction with various navigational equipment. Meanwhile, cyber-attacks emerge as a new threat along with digitalization. Damage caused by cyber-attacks is also reported in the shipping sector, and IMO recommends that cybersecurity guidelines be developed and included in International Security Management (ISM). This study analyzed the cybersecurity hazards of ECDIS, where various navigational equipment are connected. To this end, Importance-Performance Analysis (IPA) was conducted on navigation officer using ECDIS. As a result, the development of technologies for cyber-attack detection and prevention should be priority. In addition, policies related to 'Hardware and Software upgrade', 'network access control', and 'data backup and recovery' were analyzed as contents to be maintained. This paper is significant in deriving risk factors from the perspective of ECDIS users and analyzing their priorities, and it is necessary to analyze various cyber-attacks that may occur on ships in the future.

• Journal of Positioning, Navigation, and Timing
• /
• 제11권3호
• /
• pp.181-189
• /
• 2022

The public open signals from Global Navigation Satellite System (GNSS) including Global positioning system (GPS) are used widely by many peoples in the world except for the public regulated restriction signals which are encrypted. Nowadays there are growing concerns about GNSS signal spoofing which can deceive the GNSS receivers by abusing these open services. To counter these spoofing threats, many researches have been studied including array antenna techniques which can detect the direction of arrival by means of Multiple Signal Classification (MUSIC) algorithm. Originally the array antenna techniques were developed to countermeasure the jamming signal in electronic warfare by using the nulling or beamforming algorithm toward a certain direction. In this paper, we study the anti-spoofing techniques using array antenna to overcome the jamming and spoofing issues simultaneously. First, we will present the theoretical analysis results of spoofing signal response of Minimum Variance Distortionless Response (MVDR) algorithm in array antenna. Then the eigenvector algorithm of covariance matrix is suggested and verified to work with the existing anti-jamming method. The modeling and simulation are used to verify the effectiveness of the anti-spoofing algorithm. Also, the field test results show that the array antenna system with the proposed algorithms can perform the anti-spoofing function. This anti-spoofing method using array antenna is very effective in the view point of solving both the jamming and spoofing problems using the same array antenna hardware.