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Natural Convection Melting in a Rectangular Heat Storage Tank of Carbon Nanotube Dispersed Latent Heat Storage Material

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Journal of Thermal Science 2024年第3期33卷 847-855页

作者： Shin-ichi MORITA Tomoya SAITO Kazunori TAKAI Yasutaka HAYAMIZU Naoto HARUKI Division of Mechanical and Electrical Engineering Kitami Institute of Technology165 Koen-choKitami-shiHokkaido090-8507Japan National institute of technology Yonago College4448 Hikona-cyoYonago-shiTottori683-8502Japan Okayama Prefectural University 111 KubokiSoja-shiOkayama719-1197Japan

A dispersion system fluid can convect even if the dispersoid is a solid phase.Therefore,heat exchange performance can be improved while maintaining fluidity using a material with high thermal conductivity as the dispersoid.This study presents the melting performance evaluation results of a latent heat storage material with a carbon nanotube(CNT)dispersion system with high thermal conductivity,which enhances the thermal conductivity of the latent heat storage material and does not limit free convection.Increasing the thermal conductivity and enhancing the melting convection of the heat storage material result in increased latent heat storage speed.In this study,the thermal conductivity of the latent heat storage material was successfully increased by dispersing CNTs in the material.When 0.1%(in mass)of multi-wall CNT(MWCNT)was dispersed in a paraffin-based latent heat storage material,the shear stress increased by 1.5 times at a shear rate of 500 s^(-1),while taking into account the potential effects of convective inhibition.Therefore,a latent heat storage experiment was conducted in a rectangular heat storage tank using the CNT dispersion composition ratio as a parameter.A rectangular vessel with a heated vertical surface was used for the latent heat storage experiment.The melting speed was determined by comparing the amount of latent heat stored in a CNT-dispersed latent heat storage material and a single-phase latent heat storage material sample.The experimental results show that the time required for the latent heat storage material to completely melt in the heat storage tank was the shortest for the single-phase latent heat storage material sample.However,the fastest melting progress was observed for the sample with 0.02%(in mass)MWCNT content in the melting rate range of up to approximately 40%in the tank.The results indicate that this phenomenon is caused by the difference in the melting rates in the upper part of the tank.The generated data are useful for determining the shape and heat transfer surface arr

关键词： latent heat storage phase change carbon nano tube free convection heat transfer

Development of a validation technique for road surface profile applicable to point cloud data

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Journal of Road Engineering 2022年第2期2卷 114-123页

作者： Kazuya Tomiyama Yuki Yamaguchi Kazushi Moriishi Yuki Kotani Division of Civil and Environmental Engineering Kitami Institute of TechnologyKitami 090-8507Japan Obayashi Road Corporation Tokyo 101-8228Japan Graduate School of Engineering Kitami Institute of TechnologyKitami 090-8507Japan

In recent years,various information and communication technology(ICT)devices measuring three-dimensional(3D)point cloud data have been developed and widely used for the application of pavement surface investigation.However,ICT devices have generally been developed not only for measuring road surface profiles but for various geo-reference point clouds.In this background,the validation of surface profiles acquired with ICT devices fulfils an important role in proving the reliability of measurement result composed by point clouds.This study proposes a wavelet transform agreement(WTA)which involves a normalization factor of profile amplitude for further improvement in the wavelet-based coherence technique.The WTA analysis allows evaluating similarity/dissimilarity of two profiles considering both the location and wavelength simultaneously.For this purpose,a terrestrial laser scanner(TLS),a mobile mapping system(MMS),and an unmanned aerial vehicle(UAV)are employed to prove the advantage of WTA in practical applications.As a result,the advantages of WTA analysis are clearly recognized in the optimization for the measurement interval of TLS,the multi-line measurement of MMS for ride quality improvement of a pavement,and the efficient operation of UAV in terms of the flight altitude.This paper also shows the identification of aging development for surface roughness over time in terms of locations and wavelengths.These findings help not only to guarantee the accuracy of profile measurements but to realize the sophisticated way of using 3D point clouds acquired with ICT devices.The outcomes of this study contribute to the increase of productivity for pavement works with improving the quality of surface profile measurement.

关键词： Surface profile Profile validation Point cloud Wavelet agreement Wavelet coherence

Effect of dissolved oxygen on methane production from bottom sediment in a eutrophic stratified lake

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Journal of Environmental Sciences 2023年第3期125卷 61-72页

作者： Yasuyuki Maruya Keisuke Nakayama Masafumi Sasaki Katsuaki Komai Graduate School of Engineering Kyushu University744 MotookaNishi-KuFukuoka 819-0395Japan Graduate School of Engineering Kobe UniversityRokkodai-Cho 1-1Nada-KuKobe 657-8501Japan Department of Engineering Kitami Institute of TechnologyKohen-Cho 165Kitami 090-8507Japan

Clarifying the role of sulfate and dissolved oxygen (DO) in methane production may allow for precise and accurate modeling of methane emissions in eutrophic lakes.We conducted field observations of sulfate,methane,and DO concentrations in Lake Abashiri,a typical brackish and eutrophic lake in a cold region,to develop a DO-based method for quantitively estimating methane production in a eutrophic lake and analyzed the results.We found that sulfate concentrations decreased rapidly from 900.0 mg/L in water overlying the sediments to nearly 0.0 mg/L in the bottom sediment.Methane production was almost uniform across sediment depths of 0.05 to 0.25 m,ranging from 1400 to 1800μmol/m^(2)/day.Also,methane production was found to be a function of DO concentrations in water overlying the bottom and could be modeled by a logistic function:constant production at 1,400μmol/m^(2)/day for DO concentrations of 0.0 to 3.0 mg/L,rapidly decreasing to 0μmol/m^(2)/day for DO concentrations of 3.0 to 6.0 mg/L.This methane model was verified using a simple one-dimensional numerical model that showed good agreement with field observations.Our results thus suggest that the proposed methane model reduces uncertainty in estimating methane production in a eutrophic lake.

关键词： Dissolved oxygen(DO) Stratification Methane Anoxia Numerical simulation

Antarctic Radiosonde Observations Reduce Uncertainties and Errors in Reanalyses and Forecasts over the Southern Ocean:An Extreme Cyclone Case

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Advances in Atmospheric Sciences 2020年第5期37卷 431-440页

作者： Kazutoshi SATO Jun INOUE Akira YAMAZAKI Naohiko HIRASAWA Konosuke SUGIURA Kyohei YAMADA Kitami Institute of Technology Kitami 090-8507Japan Application Laboratory Japan Agency for Marine-Earth Science and TechnologyYokohama 236-0001Japan National institute of Polar Research Tachikawa 190-8518Japan SOKENDAI(Graduate University for Advanced Studies) Hayama 240-0193Japan University of Toyama Toyama 930-8555Japan

Cyclones with strong winds can make the Southern Ocean and the Antarctic a dangerous environment.Accurate weather forecasts are essential for safe shipping in the Southern Ocean and observational and logistical operations at Antarctic research stations.This study investigated the impact of additional radiosonde observations from Research Vessel"Shirase"over the Southern Ocean and Dome Fuji Station in Antarctica on reanalysis data and forecast experiments using an ensemble data assimilation system comprising the Atmospheric General Circulation Model for the Earth Simulator and the Local Ensemble Transform Kalman Filter Experimental Ensemble Reanalysis,version 2.A 63-member ensemble forecast experiment was conducted focusing on an unusually strong Antarctic cyclonic event.Reanalysis data with(observing system experiment)and without(control)additional radiosonde data were used as initial values.The observing system experiment correctly captured the central pressure of the cyclone,which led to the reliable prediction of the strong winds and moisture transport near the coast.Conversely,the control experiment predicted lower wind speeds because it failed to forecast the central pressure of the cyclone adequately.Differences were found in cyclone predictions of operational forecast systems with and without assimilation of radiosonde observations from Dome Fuji Station.

关键词： radiosonde data assimilation TIGGE Antarctica weather forecast

Measuring and evaluating of road roughness conditions with a compact road profiler and ArcGIS

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Journal of Traffic and Transportation Engineering(English Edition) 2016年第5期3卷 398-411页

作者： Nueraihemaitijiang Abulizi Akira Kawamura Kazuya Tomiyama Shun Fujita Graduate School of Engineering Kitami Institute of TechnologyHokkaido 090-8507Japan Department of Civil and Environmental Engineering Kitami Institute of TechnologyHokkaido 090-8507Japan Hokkaido Regional Development Bureau Ministry of LandInfrastructureTransport and TourismHokkaido 090-8507Japan

With a wide range of requirements throughout the world, high-quality road management is subject to increasing demand from a perspective of customer-oriented levels of service. In recent years, road administrators are requested to create a visual map of a road network to monitor conditions. To fulfill these requirements, this study conducted as follows. Firstly, this paper introduces a new compact road profiler to collect the profile data at ease. Using the international roughness index （IRI） to assess public roads in local cities of Japan＇s Hokkaido prefecture, this study also provides real-time monitoring of pavement roughness conditions. Moreover, this study deals with an effective method for visualizing collected IRI data as an attribute in a geographic information system （GIS） and the database of Japan digital road map （DRM）. Secondly, the authors present the measurement results of IRI at two different cities during different seasons by using GIS to compare the road conditions. According to the results clarified on different statistical characteristics of road profiles, this study recommends that it is necessary to establish pavement management system （PMS） in consideration of road class, network of local city, and evaluation and management of road conditions in winter quantitatively. Finally, the authors measure and evaluate ride quality by assessing differences between the inner wheel path （IWP） and outer wheel path （OWP） of the vehicle into account, using the previously mentioned profilers and the driving simulator, which is called KITDS. Results show that information from both wheel paths contributes to improve current monitoring process regarding pavement surface, and expects to construct a high level of PMS for road administration in the future.

关键词： Road engineering Road roughness Mobile compact profiler ArcGIS Ride quality Wheel path

Enhancement of DC-Link Protection of PMSG Based Wind Turbine under Network Disturbance by Using New Buck Controller System

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Journal of Mechanics Engineering and Automation 2017年第4期7卷 171-179页

作者： Linda Sartika Atsushi Umemura Rion Takahashi Junji Tamura Department of Electrical and Electronic Engineering Kitami Institute of Technology (KIT) Hokkaido 090-8507 Japan

Future Event Prediction Based on Temporal Knowledge Graph Embedding

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Computer Systems Science & Engineering 2023年第3期44卷 2411-2423页

作者： Zhipeng Li Shanshan Feng Jun Shi Yang Zhou Yong Liao Yangzhao Yang Yangyang Li Nenghai Yu Xun Shao University of Science and technology of China Hefei230027China Shenzhen CyberAray Co. Ltd.Shenzhen518038China Harbin institute of technology Shenzhen518055China National Engineering Research Center for Risk Perception and Prevention(RPP) Beijing100041China School of Regional Innovation and Social Design Engineering Kitami Institute of TechnologyKitami090-8507Japan

Accurate prediction of future events brings great benefits and reduces losses for society in many domains,such as civil unrest,pandemics,and crimes.Knowledge graph is a general language for describing and modeling complex systems.Different types of events continually occur,which are often related to historical and concurrent events.In this paper,we formalize the future event prediction as a temporal knowledge graph reasoning problem.Most existing studies either conduct reasoning on static knowledge graphs or assume knowledges graphs of all timestamps are available during the training process.As a result,they cannot effectively reason over temporal knowledge graphs and predict events happening in the future.To address this problem,some recent works learn to infer future events based on historical eventbased temporal knowledge graphs.However,these methods do not comprehensively consider the latent patterns and influences behind historical events and concurrent events simultaneously.This paper proposes a new graph representation learning model,namely Recurrent Event Graph ATtention Network(RE-GAT),based on a novel historical and concurrent events attention-aware mechanism by modeling the event knowledge graph sequence recurrently.More specifically,our RE-GAT uses an attention-based historical events embedding module to encode past events,and employs an attention-based concurrent events embedding module to model the associations of events at the same timestamp.A translation-based decoder module and a learning objective are developed to optimize the embeddings of entities and relations.We evaluate our proposed method on four benchmark datasets.Extensive experimental results demonstrate the superiority of our RE-GAT model comparing to various base-lines,which proves that our method can more accurately predict what events are going to happen.

关键词： Event prediction temporal knowledge graph graph representation learning knowledge embedding

Transient Stability Assessment of Synchronous Generator in Power System with High-Penetration Photovoltaics

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Journal of Mechanics Engineering and Automation 2012年第12期2卷 762-768页

作者： Masaki Yagami Takahiko Hasegawa Junji Tamura Department of Electrical and Digital Systems Engineering Hokkaido Institute of Technology Sapporo 006-8585 Japan Department of Electrical and Electronic Engineering Kitami Institute of Technology Kitami 090-8507 Japan

As photovoltaic (PV) capacity in power system increases, the capacity of synchronous generator needs to be reduced relatively. This leads to the lower system inertia and the higher generator reactance, and hence the generator transient stability may negatively be affected. In particular, the impact on the transient stability may become more serious when the considerable amounts of PV systems are disconnected simultaneously during voltage sag. In this work, the generator transient stability in the power system with significant PV penetration is assessed by a numerical simulation. In order to assess the impact from various angles, simulation parameters such as levels of PV penetration, variety of power sources (inverter or rotational machine), and existence of LVRT capability are considered. The simulation is performed by using PSCAD/EMTDC software.

关键词：暂态稳定评估同步发电机光伏系统电力系统高渗透暂态稳定性数值模拟 PSCAD

Transient Stability Analysis of Synchronous Generator in Power System with Renewable Power Sources Installed

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Journal of Mechanics Engineering and Automation 2016年第8期6卷 400-407页

作者： Masaki Yagami Yoshihiro Ichinohe Yohichiro Kojima Kenji Misawa Junji Tamura Department of Electrical and Electronic Engineering Hokkaido University of Science Sapporo 006-8585 Japan Department of Electrical and Electronic Engineering Kitami Institute of Technology Kitami 090-8507 Japan