• Applied Chemistry for Engineering
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• v.28 no.1
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• pp.118-124
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• 2017

An air cooling, open cathode type polymer electrolyte membrane fuel cell (PEMFC) has the advantages of system simplification and cost effectiveness. Open cathode PEMFC could suffer from reduced performance due to the membrane dehydration in low humidity of air. Effects of the cathode air flow rate, anode purge interval and long term storage on PEMFC performance were investigated in this work. Fan voltage is an important factor on air cooling PEMFC performance because the cathode air flow rate and stack temperature were controlled by fan voltage. The dead ended anode (DEA) method was applied to increase hydrogen usage. Periodical purge was used to discharge accumulated water and gas. The influence of long term non-operating condition on PEMFC performance degradation due to the membrane dehydration was also studied and the quick recovery method was developed.

• Tunnel and Underground Space
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• v.32 no.2
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• pp.144-159
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• 2022

The present study developed a sequential approach-based numerical simulator for modeling coupled thermal-hydrological-mechanical (THM) processes in the ground and investigated the computational performance of the coupling analysis algorithm. The present sequential approach linked the two different solvers: an open-source numerical code, OpenGeoSys for solving the thermal and hydrological processes in porous media and a commercial code, FLAC3D for solving the geomechanical response of the ground. A benchmark test of the developed simulator was carried out using a THM problem where an analytical solution is given. The benchmark problem involves the coupled behavior (variations in temperature, pore pressure, stress, and deformation with time) of a fully saturated porous medium which is subject to a point heat source. The results of the analytical solution and numerical simulation were compared and the validity of the numerical simulator was investigated.

• KIISE Transactions on Computing Practices
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• v.22 no.3
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• pp.151-156
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• 2016

Cloud computing systems require a huge number of storage servers due to the growing implications of power bills, carbon emissions, and logistics of data centers. These considerations have motivated researchers to improve the energy efficiency of storage servers. Most servers use a lot of power irrespective of the amount of computing that they are doing, and one important goal is to redesign servers to be power-proportional. However, Research on large-scale storage systems is hampered by their cost. It is therefore desirable to develop a scalable test-bed for evaluating the power consumption of large-scale storage systems. We are building on open-source projects to construct a test-bed which will contribute to the assessment of power consumption in tiered storage systems. Integrating the cloud application platform can easily extend the proposed testbed laying a foundation for the design and evaluation of low-power storage servers.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.111-114
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• 2017

As digital contents are widely used and require increasingly high quality, the data storage services over Internet also become more and more important. One of popular services, web-hard, provides lots of users with web-based functions for data storage, management and sharing but such storage utilization requires quite high cost compared to using portable storage devices. Moreover, some users may avoid putting their important data into open Internet area. On the other hand, portable storage devices are cheaper but can be used only when they are physically connected to host devices such as PC. Also additional management and security functions should be equipped to support data sharing among users. In this paper, we propose a web-based data storage system combining those advantages of aforementioned two approaches. The proposed system immediately provides web-based services for data management and sharing when a portable device such as SDD is connected to the server.

• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.4
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• pp.141-152
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• 2013

The applications and concerned technologies of cloud computing services, one of major trends in the information communication technology, are widely progressing and advancing. OpenStack, one of open source cloud computing platforms, is comprised of several service components; using these, it can be possible to build public or private cloud computing service for a given target application. In this study, a remote sensing image analysis processing service on cloud computing environment has designed and implemented as an operational test application in the private cloud computing environment based on OpenStack. The implemented service is divided into instance server, web service, and mobile app. A instance server provides remote sensing image processing and database functions, and the web service works for storage and management of remote sensing image from user sides. The mobile app provides functions for remote sensing images visualization and some requests.

• Korean Journal of Computational Design and Engineering
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• v.5 no.4
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• pp.293-300
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• 2000

The non-manifold geometric modeling technique is to improve design process and to Integrate design, analysis, and manufacturing by handling mixture of wireframe model, surface model, and solid model in a single data structure. For the non-manifold geometric modeling, Euler operators and other high level modeling methods are necessary. Boolean operation is one of the representative modeling method for the non-manifold geometric modeling. This thesis studies Boolean operations of non-manifold model with the data structure of selective storage. The data structure of selective storage is improved non-manifold data structure in that existing non-manifold data structures using ordered topological representation method always store non-manifold information even if edges and vortices are in the manifold situation. To implement Boolean operations for non-manifold model, intersection algorithm for topological cells of three different dimensions, merging and selection algorithm for three dimensional model, and Open Inventor(tm), a 3D toolkit from SGI, are used.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.489-492
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• 2007

Understanding the thermohydraulic processes in the aquifer is necessary for a proper design of the aquifer thermal energy utilization system under given conditions. Experimental and numerical test were accomplished to evaluate the relationship between the geothermal heat exchanger operation and hydrogeological conditions in the open-loop geothermal system. Sand tank experiments were designed to investigate the open-loop geothermal system. Water injection and extract ion system as open-loop borehole heat exchanger was applied to observe the temperature changes in time at injection well, extraction well and ambient groundwater. The thermohydraulic transfer for heat storage was simulated using FEFLOW for two cases of extraction and injection phase operation in sand tank model. As one case, the movement of the thermal plume was simulated with variable locations of injection and extraction well. As another case, the simulation was performed with fixed location of injection and extraction well. The simulation and experimental results showed that the temperature distribution depends highly on the injected water temperature and the length of injection time and the groundwater flow and pumping rate sensitively affect the heat transfer.

• Journal of the Korean Institute of Rural Architecture
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• v.18 no.4
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• pp.17-24
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• 2016

Since the users have direct access to search and browse freely, the open access system has been employed to all the usual modern libraries. However, library space shortage problem created by the continuously increasing printed materials caused the degradation of usability and quality of the library space. Open Access system is superior in user convenience but is inferior in space efficiency. Keeping the open access system is considered as one of the reasons of the space shortage problem. Even though the closed access system does not provide free access or easy browsing for the uses, it's space efficiency is much higher than the open access system. The closed access system should be employed as a plan to relieve space shortage problem. Since the closed access system does not allow the public direct access to books, it is very economical. It also provides much better space efficiency with higher book shelving density. In this article, closed access library system models and their characteristics are examined as the reduction plans for the library space shortage problems.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.11
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• pp.5404-5424
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• 2018

This work is mainly focused on two major topics in cloud platforms by using OpenStack as a case study: management and provisioning of resources to meet the requirements of a service demanded by remote end-user and relocation of virtual machines (VMs) requests to offload the encumbered compute nodes. The general framework architecture contains two subsystems: 1) An orchestrator that allows to systematize provisioning and resource management in OpenStack, and 2) A resource utilization based subsystem for vibrant VM relocation in OpenStack. The suggested orchestrator provisions and manages resources by: 1) manipulating application program interfaces (APIs) delivered by the cloud supplier in order to allocate/control/manage storage and compute resources; 2) interrelating with software-defined networking (SDN) controller to acquire the details of the accessible resources, and training the variations/rules to manage the network based on the requirements of cloud service. For resource provisioning, an algorithm is suggested, which provisions resources on the basis of unused resources in a pool of VMs. A sub-system is suggested for VM relocation in a cloud computing platform. The framework decides the proposed overload recognition, VM allocation algorithms for VM relocation in clouds and VM selection.

• Journal of the military operations research society of Korea
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• v.26 no.1
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• pp.115-124
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• 2000

In this paper, we are introduced a certification system for open network environment. The Kerberos which was developed by MIT uses a secret key cryptosystem for authentication. It is secure and efficient for closed network users to authenticate each others. However, the kerberos has a disadvantage of managing a lot of secret keys for In this paper, we are introduced a certification system for open network environment. users in the open network environment. This paper suggests a method that uses X.509 to provide public keys with certification to Kerberos users for authentication in the X.500 directory standard. And we also suggest the smartcard as data storage device to enhance the security and availability.