• Progress in Superconductivity
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• v.3 no.1
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• pp.23-27
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• 2001

We have investigated the mixed-state magnetoresistance of high quality c-axis-oriented MgB2 thin film for magnetic field from 0.5 T to 5.0 T, applied normal to ab-plane. The temperature dependence of magnetoresistance was well described by vortex glass and fluctuation theories for different temperature regimes. We observed glassy exponent of v(z-1)~3 and upper critical field of $H_{c2}$(0)~35 T, which is consistent with previous data obtained from direct $H_{c2}$(0) measurements. Interestingly, the thermally activated flux flow region was observed to be very narrow, suggesting that the pinning strength of this compound is very strong. This finding is closely related to the recent reports that the bulk pinning is dominant in $MgB_2$and the critical current density of $MgB_2$ thin film is very high, comparable to that of cuprate superconductor. The present results further suggest that $MgB_2$is beneficial to technical applications.ons.

• International Journal of Computer Science & Network Security
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• v.24 no.8
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• pp.32-42
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• 2024

The Internet of Things (IoT) is set to transform patient care by enhancing data collection, analysis, and management through medical sensors and wearable devices. However, the convergence of IoT device vulnerabilities and the sensitivity of healthcare data raises significant data integrity and privacy concerns. In response, this research introduces the Smart-Coord system, a practical and affordable solution for securing healthcare IoT. Smart-Coord leverages blockchain technology and coordinate-based access management to fortify healthcare IoT. It employs IPFS for immutable data storage and intelligent Solidity Ethereum contracts for data integrity and confidentiality, creating a hierarchical, AES-CBC-secured data transmission protocol from IoT devices to blockchain repositories. Our technique uses a unique coordinate system to embed confidentiality and integrity regulations into a single access control model, dictating data access and transfer based on subject-object pairings in a coordinate plane. This dual enforcement technique governs and secures the flow of healthcare IoT information. With its implementation on the Matic network, the Smart-Coord system's computational efficiency and cost-effectiveness are unparalleled. Smart-Coord boasts significantly lower transaction costs and data operation processing times than other blockchain networks, making it a practical and affordable solution. Smart-Coord holds the promise of enhancing IoT-based healthcare system security by managing sensitive health data in a scalable, efficient, and secure manner. The Smart-Coord framework heralds a new era in healthcare IoT adoption, expertly managing data integrity, confidentiality, and accessibility to ensure a secure, reliable digital environment for patient data management.

• KSBB Journal
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• v.23 no.2
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• pp.135-141
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• 2008

SMB (simulated moving bed) chromatography is a very useful utility for the separation of binary system. We simulated the separation of L-arabinose and L-ribose from the mixture by using lab-scale 4(1-1-1-1)-zone SMB chromatography. Preliminary experiments of PIM (pulse input method) were performed to measure adsorption isotherms of L-ribose and L-arabinose in $NH_2$ HPLC column, and experimental and simulated results from ASPEN chromatography were compared. To find the most suitable separation condition in SMB, we carried out a simulation in $m_2-m_3$ plane base on the triangle theory and calculated operating parameters (flow rate of four zone, switching time and feed concentration and so on) using ASPEN chromatography under the conditions of linear isotherms obtained from PIM.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.11a
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• pp.150-152
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• 2019

In this study, the effects of the wave field changes due to the coastal structure on the hydrodynamic performance of the OWC wave energy, converter are analyzed using a three-dimensional numerical wave tank technique (NWT). The OWC device is simulated numerically by introducing a linear pressure drop model, considering the coupling effect between the turbine and the OWC chamber in the time domain. The flow distribution around the chamber is different due to the change of reflection characteristics depending on the consideration of the breakwater model. The wave energy captured from the breakwater is spatially distributed on the plane of the front of the breakwater, and the converted pneumatic power increased when concentrated in front of the chamber. The change of the standing wave distribution is repeated according to the relationship between the incident wavelength and the length of the breakwater, and the difference in energy conversion performance of the OWC was confirmed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.408-413
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• 2004

Numerical and experimental investigation were car-ried out to clarify the flow structure of underexpanded jet from a square nozzle. The square nozzle rep-resents one of the clustered combustors of a linear aerospike engine. From the numerical results, the three-dimensional shock wave of the underexpanded square jet was found to be composed of two shocks. One is the intercepting shock which corresponds to the shock observed in two-dimensional planar jet. The other is the recompression shock divided into two types. The expansion fans coming from the nozzle edges interact with each other at the comers of the nozzle exit, and overexpanded regions are generated. Therefore one of the two recompression shocks is formed at the comers of the nozzle exit behind the overexpanded regions. As the jet goes downstream, the overexpanded regions grow larger to coalesce at the symmetry planes. Then, the other type of the recompression shock is generated. The three-dimensional shock structure formed by the intercepting shock and the recompression shocks dominates the expansion of the jet boundary. The shock detection algorithm us-ing CFD results was developed to reveal the relation between the shock waves and the jet boundary, and it was found that the cross-sectional jet shape becomes cross-shape. The key features observed in the numerical investigation were verified by the experimental results. The shock structure at the diagonal plane was in good agreement with the experimental schlieren images. Moreover, the cross-sections visualized by the Mie scattering method confirmed that the cross-section of the jet becomes cross-shape.

• Plant Journal
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• v.18 no.2
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• pp.41-45
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• 2022

The conventional communication method using mud flow pressure waves has a speed of 1-2 bps, so it takes a long time to communicate, making real-time control impossible. Although the sound wave communication method for improving the communication speed by 10 times or more has been commercialized, its use is limited due to its high price and there are not many application cases. In this study, the simulator corresponding to the facility was developed to develop performance similar to the actual test results. For simulating sound wave communication through a drill pipe, we proposed a governing equation that can simulate friction damping by mud and developed a numerical analysis model. The attenuation factor was corrected by comparing it with the attenuation rate of sound wave energy at the drilling site. The developed numerical analysis model was applied to the QPSK modulation type communication algorithm to confirm the excellent performance of the communication error rate of 0.04% in the ground. This is the communication performance under the condition that noise has not been mixed yet, and in order to apply it, the technology of reproducing the actual noise signal for mixing by securing the field noise data was established.

• The Journal of Engineering Geology
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• v.24 no.1
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• pp.137-146
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• 2014

The geology of the study area which is located in Samkoe-dong, Dong-gu, Daejeon city comprises black slate, limestone, and pebble-bearing phyllitic rock as meta-sedimentary rocks; and biotite granite and quartz porphyry intrusions. Face mapping revealed sliding in three or four sites of contained coaly slate, where the dip of the foliation and other discontinuities is parallel to the surface slope. The cause of the slope sliding is this parallelism as well as the swelling of the coaly slate when wet. In contrast, the slop on the opposite side of the road is relatively stable because the dip of the foliation and other discontinuities are oblique or normal to the surface slope. To ensure slope stability, a cut-and-cover tunnel was designed and constructed for the new road.

• Plant Journal
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• v.8 no.3
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• pp.55-63
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• 2012

This study aims to suggest the improved business process by analyzing the current design process on work flow of the 3D design of power plant, drawing a problems and setting the improving direction through the integration method of the business process reengineering(BPR). In order to realize the improved business process, the integrated design performance system focused on the 3D design was established and accordingly the study analyzed cases of project performances through the integration system and drew the improved effects quantitatively. In the result of the project performance applied with the 3D design integration system, it showed 20.4% design cost saving effect for appropriate rated cost and the integration of design information from each design parts, sub contracters and vendors reduced overlapped works and improved the consistency of repeated design alteration.

• Plant Journal
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• v.13 no.2
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• pp.39-45
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• 2017

This paper is a study on FEED validation model that can be used in the bidding stage of small utility equipment in offshore plant industry using system engineering technique. Currently, domestic marine plant equipment industry companies are faced with the financial risk of project execution as they enter marine plant. The major cause was the insufficient ability to verify the FEED output from the contractor (Engineering or Procurement and Construction) of the equipment manufacturer (COMPANY or EPC). Therefore, we propose FEED design verification method that simplifies the system engineering method that sequentially applies requirements analysis, function, performance analysis and physical architecture building process. Also, we verified the suitability of the developed model by comparing the results of applying the developed FEED verification model and the verification method that depends on the existing experience for the small utility equipment (Air Compressor).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.9
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• pp.799-804
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• 2007

The behavior of spray emanating from an injector to be employed in a liquid-propellant thrust chamber is investigated by optical measurement techniques. The injector has eight holes, each of which has 30 cant angle from the center-axis with the diameter of 0.406 mm. In order to examine an atomization process according to the spray-generation conditions and the evolution along spray downstream, variational features in the velocity and size of droplets obtained through Dual-mode Phase Doppler An 799emometry (DPDA) are delineated and discussed together with instantaneous plane images captured by using Nd:Yag laser sheet beam. A categorization of spray-flow regime representing the atomization and turbulent nature is made through evaluating the non-dimensional parameters, i.e., Reynolds number and Weber number based upon the theoretical injection velocity. These qualitative and quantitative data of spray breakup will be a firm basis for the design of brand-new thruster