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A Novel Guidance Algorithm for Underactuated Ship Path-Following Control Based on Marine Practice
Liu Junpo,Zhao Baigang,Liang Cailei,Niu Yuna,Zhang Chuang 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.3
Ship path-following is necessary for both manned and unmanned ships. During ship navigation, the planned route consists of several waypoints rather than being an arbitrary curve. This makes it essential that practical guidance algorithms be able to track waypoints-based routes. To address this problem, this paper presents a novel guidance law that divides waypoints-based routes into two parts: straight segments and waypoint segments. To follow straight segments, a dynamic virtual vessel can be used to reduce tracking errors. However, when dealing with waypoint segments, a planning idea is adopted because of lacking effective reference signal for traditional guidance law. Having established an effective guidance law, a closed-loop gain shaping algorithm is used for the course controller. To validate the effectiveness of the proposed algorithm, a comparative simulation was carried out, with further tests on a high-quality navigation simulator, with it obtaining generally satisfactory results.
Influence of Injection System Parameters on Combustion Noise of a Small Power Non-Road Diesel Engine
Zhou Xinfeng,Ma Zhihao,Liu Yuna,Li Ao 한국자동차공학회 2023 International journal of automotive technology Vol.24 No.5
Combustion noise accounts for a large proportion of diesel engine noise. On the premise of not increasing the cost of diesel engine, the injection system parameters such as dynamic fuel supply advance angle and needle valve opening pressure are optimized, and the influence of the above parameters on the in-cylinder pressure, rate of pressure rise, in-cylinder pressure level (CPL) spectrum and high frequency pressure oscillation is analyzed. The study shows that reducing the dynamic fuel supply advance angle can effectively reduce the combustion noise, and appropriately increasing the needle valve opening pressure can also reduce the combustion noise. After the optimization of injection parameters, the combustion noise of the diesel engine with an electronically controlled VE pump-tube-nozzle injection system is significantly reduced compared with the prototype engine, and can reach the same level of combustion noise as the diesel engine with the common rail system without deterioration of fuel economy and emission performance. The experimental study can provide technical reference for diesel engines in the selection of injection system parameters and the optimization of combustion noise in the improvement stage.
Epitaxial Brownmillerite Oxide Thin Films for Reliable Switching Memory
Acharya, Susant K.,Nallagatla, Raveendra Venkata,Togibasa, Octolia,Lee, Bo W.,Liu, Chunli,Jung, Chang U.,Park, Bae Ho,Park, Ji-Yong,Cho, Yunae,Kim, Dong-Wook,Jo, Janghyun,Kwon, Deok-Hwang,Kim, Miyoung American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.12
<P>Resistive switching memory, which is mostly based on polycrystalline thin films, suffers from wide distributions in switching parameters including set voltage, reset voltage, and resistance in their low- and high-resistance states. One of the most commonly used methods to overcome this limitation is to introduce inhomogeneity. By contrast, in this paper, we obtained uniform resistive switching parameters and sufficiently low forming voltage by maximizing the uniformity of an epitaxial thin film. To achieve this result, we deposited an SrFeOx/SrRuO3 heteroepitaxial structure onto an SrTiO3 (001) substrate by pulsed laser deposition, and then we deposited an Au top electrode by electron-beam evaporation. This device exhibited excellent bipolar resistance switching characteristics, including a high on/off ratio, narrow distribution of key switching parameters, and long data retention time. We interpret these phenomena in terms of a local, reversible phase transformation in the SrFeOx film between brownmillerite and perovskite structures. Using the brownmillerite structure and atomically uniform thickness of the heteroepitaxial SrFeOx thin film, we overcame two major hurdles in the development of resistive random-access memory devices: high forming voltage and broad distributions of switching parameters.</P>