• Smart Structures and Systems
• /
• 제28권6호
• /
• pp.791-798
• /
• 2021

Current investigation aims to analyze the characteristics of magnetohydrodynamic boundary layer flow of bioconvection Casson fluid in the presence of nano-size particles over a permeable and non-linear stretchable surface. Fluid passes through the Darcy-Forchheimer permeable medium. Effect of different parameter such as Darcy-Forchheimer, porosity parameter, magnetic parameter and Brownian factor are investigated. Increasing Brownian factor leads to the rapid random movement of nanosize particles in fluid flows which shows an expansion in thermal boundary layer and enhances the nanofluid temperature more rapidly. For large values of Darcy-Forchheimer, magnetic parameter and porosity factor the velocity profile decreases. Higher values of velocity slip parameter cause decreasing trend in momentum layer with velocity profile.

• 한국소음진동공학회논문집
• /
• 제14권3호
• /
• pp.193-200
• /
• 2004

The Active Constrained Layer Damping(ACLD) combines the simplicity and reliability of passive damping with the low weight and high efficiency of active control to attain high damping characteristics. The proposed ACLD treatment consists of a viscoelastic damping which is sandwiched between an active piezoelectric layer and a host structure. In this manner, the smart ACLD consists of a Passive Constrained Layer Damping(PCLD) which is augmented with an active control in response to the structural vibrations. The arc type shell model is introduced to describe the interactions between the vibrating host structure, piezoelectric actuator and viscoelastic damping. The system is modeled by applying ARMAX model and changing a state-space form through the system identification method. An optimum control law for the piezo actuator is obtain by LQR(Linear Quadratic Regulator) method. The performance of the ACLD system is determined and compared with PCLD in order to demonstrate the effectiveness of the ACLD treatment. Also, the actuation capability of a piezo actuator is examined experimentally by varying thickness of viscoelastic material(VEM).

• International journal of advanced smart convergence
• /
• 제6권1호
• /
• pp.50-56
• /
• 2017

Wireless sensor nodes have limited energy, so it is important to optimize energy consumption to preserve network lifetime. Various protocols have been proposed for this purpose. LEACH protocol and SEP are the representative protocols. These protocols become less effective as the Sensor Field becomes wider. To improve this, MR-SEP and L-SEP were proposed. These protocols increase the energy efficiency by dividing the Sensor Field into layers and reducing the transmission distance. However, when dividing a layer, there are cases where it is divided inefficiently, and a node within a certain range from a Base Station has a better transmission efficiency than a direct transmission method using a cluster method. In this paper, we propose a Single-hop layer for L-SEP to improve inefficient layer division and near node transmission efficiency. When the larger the Sensor Field, the better the performance of the proposed method by up to 87%. The larger the sensor field, the more efficient the proposed method is over the conventional method. That is, the proposed method is suitable for the wide Sensor Field.

• 한국전기전자재료학회논문지
• /
• 제14권7호
• /
• pp.546-550
• /
• 2001

A new Lateral Trench Insulated Gate Bipolar Transistor(LTIGBT) with p$^{+}$ diverter was proposed to improve the characteristics of the conventional LTIGBT. The forward blocking voltage of the proposed LTIGBT with p$^{+}$ diverter was about 140V. That of the conventional LTIGBT of the same size was 105V. Because the p$^{+}$ diverter region of the proposed device was enclosed trench oxide layer, he electric field moved toward trench-oxide layer, and punch through breakdown of LTIGBT with p$^{+}$ diverter was occurred, lately. Therefore, the p$^{+}$ diverter of the proposed LTIGBT didn't relate to breakdown voltage in a different way the conventional LTIGBT. The Latch-up current densities of the conventional LTIGBT and proposed LTIGBT were 540A/$\textrm{cm}^2$, and 1453A/$\textrm{cm}^2$, respectively. The enhanced latch-up capability of the proposed LTIGBT was obtained through holes in the current directly reaching the cathode via the p$^{+}$ divert region and p$^{+}$ cathode layer beneath n$^{+}$ cathode layer./ cathode layer.

• International Journal of Computer Science & Network Security
• /
• 제23권5호
• /
• pp.128-134
• /
• 2023

The widespread usage of blockchain technology in cryptocurrencies has led to the adoption of the blockchain concept in data storage management systems for secure and effective data storage and management. Several innovative studies have proposed solutions that integrate blockchain with distributed databases. In this article, we review current blockchain databases, then focus on two well-known blockchain databases-BigchainDB and FalconDB-to illustrate their architecture and design aspects in more detail. BigchainDB is a distributed database that integrates blockchain properties to enhance immutability and decentralization as well as a high transaction rate, low latency, and accurate queries. Its architecture consists of three layers: the transaction layer, consensus layer, and data model layer. FalconDB, on the other hand, is a shared database that allows multiple clients to collaborate on the database securely and efficiently, even if they have limited resources. It has two layers: the authentication layer and the consensus layer, which are used with client requests and results. Finally, a comparison is made between the two blockchain databases, revealing that they share some characteristics such as immutability, low latency, permission, horizontal scalability, decentralization, and the same consensus protocol. However, they vary in terms of database type, concurrency mechanism, replication model, cost, and the usage of smart contracts.

• 한국컴퓨터정보학회논문지
• /
• 제29권9호
• /
• pp.1-7
• /
• 2024

본 논문은 MNIST 데이터셋을 활용한 손글씨 숫자 인식에서 합성곱 신경망(CNN)과 배치정규화(BN)를 결합한 모델을 제안한다. LeCun et al.의 LeNet-5 모델의 성과를 뛰어넘는 것을 목표로 6계층 신경망 구조를 설계하였다. 제안된 모델은 28×28 픽셀 이미지를 입력으로 받아 합성곱, 맥스 풀링, 완전연결계층을 거쳐 처리하며, 특히 배치정규화계층을 도입하여 학습 안정성과 성능을 향상시켰다. 실험에서는 60,000개의 훈련 이미지와 10,000개의 테스트 이미지를 사용하였으며, Momentum 최적화 알고리즘을 적용하였다. 모델 구성에서는 30개의 필터, 필터 사이즈 5×5, 패딩 0, 스트라이드 1을 사용하였고, ReLU 활성화 함수를 채택하였다. 훈련 과정에서는 미니배치 사이즈 100, 총 20 에포크, 학습률 0.1로 설정하였다. 결과적으로 제안된 모델은 99.22%의 테스트 정확도를 달성하여 LeNet-5의 99.05%를 상회하였으며, F1-score 0.9919를 기록하여 모델의 성능을 입증하였다. 또한, 본 논문에서 제안한 6계층 모델은 LeCun et al.의 LeNet-5(7계층 모델)와 Ji, Chun and Kim(10계층 모델)이 제안한 모델보다 더 단순한 구조로 모델의 효율성을 강조하였다. 본 연구의 결과는 AI 비전 검사기 등 실제 산업 응용에서 활용 가능성을 보여주며, 특히 스마트팩토리에서 부품의 불량 상태를 판별하는 데 효과적으로 적용될 수 있을 것으로 기대된다.

• IEIE Transactions on Smart Processing and Computing
• /
• 제4권5호
• /
• pp.354-365
• /
• 2015

This work presents an Internet of Things (IoT) system for home energy management based on a custom-designed Impulse Radio Ultra-Wideband (IR-UWB) transceiver that targets a generic and multi-standard control system. This control system enables the interoperability of heterogeneous devices: it integrates various sensor nodes based on ZigBee, EnOcean and UWB in the same middleware by utilizing an ad-hoc layer as an interface between the hardware and software. The paper presents as a first the design of the IR-UWB transceiver for a portable sensor node integrated with the middleware layer, and also describes the receiver connected to the control system. The custom-designed low-power transmitter on the sensor node is fabricated with 130 nm CMOS technology. It generates a signal with a 1.1 ns pulse width while consuming $39{\mu}W$ at 1 Mbps. The UWB sensor node with a temperature measurement capability consumes 5.31 mW, which is lower than the power level of state-of-the-art solutions for smart-home applications. The UWB hardware and software layers necessary to interface with the control system are verified in over-the-air measurements in an actual office environment. With the implementation of the presented sensor node and its integration in the energy management system, we demonstrate achievement of the broad flexibility demanded for IoT.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제11권2호
• /
• pp.1005-1018
• /
• 2017

This paper proposes an App Visualization (AppV) based on IoT Self-diagnosis Micro Control Unit (ISMCU) for accident prevention. It collects a current status of a vehicle through a sensor, visualizes it on a smart phone and prevents vehicles from accident. The AppV consists of 5 components. First, a Sensor Layer (SL) judges noxious gas from a current vehicle and a driver's driving habit by collecting data from various sensors such as an Accelerator Position Sensor, an O2 sensor, an Oil Pressure Sensor, etc. and computing the concentration of the CO collected by a semiconductor gas sensor. Second, a Wireless Sensor Communication Layer (WSCL) supports Zigbee, Wi-Fi, and Bluetooth protocol so that it may transfer the sensor data collected in the SL to ISMCU and the data in the ISMCU to a Mobile. Third, an ISMCU integrates the transferred sensor information and transfers the integrated result to a Mobile. Fourth, a Mobile App Block Programming Tool (MABPT) is an independent App generation tool that changes to visual data just the vehicle information which drivers want from a smart phone. Fifth, an Embedded Module (EM) records the data collected through a Smart Phone real time in a Cloud Server. Therefore, because the AppV checks a vehicle' fault and bad driving habits that are not known from sensors and performs self-diagnosis through a mobile, it can reduce time and cost spending on accidents caused by a vehicle's fault and noxious gas emitted to the outside.

• 인터넷정보학회논문지
• /
• 제16권2호
• /
• pp.1-6
• /
• 2015

본 논문에서는 고품질 멀티미디어 데이터를 IEEE 802.1 Audio Video Bridging 기반의 네트워크를 통해 스마트 자동차와 스마트 홈 및 스마트 공연장에서 실시간으로 송수신할 수 있는 임베디드 플랫폼을 설계를 통해 정밀한 시간 동기화 표준인 IEEE 802.1AS와 QoS 보장을 위한 자원할당 표준인 IEEE 802.1Qat 프로토콜 분석을 통해 성능을 검증한다. 이를 위해 MRP(Multiple Registration Protocol), MMAP(Multicast Address Acquisition Protocol), IEEE 1722, 1722.1 등 AVB의 핵심 Layer-2 프로토콜을 리눅스 운영체제를 기반으로 구현한다. 아울러 상용 AVB 엔드포인트와 연동 실험을 통해 상호 호환성 및 멀티미디어 스트림의 실시간 송수신이 가능함을 보인다.

• 한국인터넷방송통신학회논문지
• /
• 제17권2호
• /
• pp.119-126
• /
• 2017

TCP/IP 표준을 개발하는 IETF의 상위 기구인 IAB는 작은 사물에도 TCP/IP protocol stack을 붙이기로 결정했다. 이는 하나의 작은 사물도 하나의 통신 노드로 인정하여, 이를 다섯 개의 전 계층이 올라간 스마트 오브젝트로 확장하겠다는 상징적인 의미를 가진다. 이러한 배경 아래서 등장한 것이 웹을 기반으로 사물 간 지능적으로 네트워크를 구성해 통신하는 IoT/WoT이다. CoAP는 제한된 환경 내에서 사용할 수 있는 프로토콜로 사물이 인터넷에 연결될 것을 예상하여 만든 표준 규약이다. 이에 따라 본 논문에서는 CoAP 네트워크가 구축된 환경에서 CoAP와 연결되어 관련 사물들의 데이터를 수집하며 관리할 수 있는 Middleware API를 제안하고자 한다.