• Journal of Ocean Engineering and Technology
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• v.33 no.5
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• pp.470-478
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• 2019

Because the global positioning system (GPS) is not available in underwater environments, an inertial navigation system (INS)/doppler velocity log (DVL) integrated navigation system is generally implemented. In general, an INS/DVL integrated system adopts a loosely coupled method. However, in this loosely coupled method, although the measurement equation for the filter design is simple, the velocity of the body frame cannot be accurately measured if even one of the DVL transducer signals is not received. In contrast, even if only one or two velocities are measured by the DVL transducers, the tightly coupled method can utilize them as measurements and suppress the error increase of the INS. In this paper, a filter was designed to regenerate the measurements of failed transducers by taking advantage of the tightly coupled method. The regenerated measurements were the normal DVL transducer measurements and the estimated velocity in RPM. In order to effectively estimate the velocity in RPM, a filter was designed considering the effects of the tide. The proposed filter does not switch all of the measurements to RPM if the DVL transducer fails, but only switches information from the failed transducer. In this case, the filter has the advantage of being able to be used as a measurement while continuously estimating the RPM error state. A Monte Carlo simulation was used to determine the performance of the proposed filters, and the scope of the analysis was shown by the standard deviation ($1{\sigma}$, 68%). Finally, the performance of the proposed filter was verified by comparison with the conventional tightly coupled method.

• Journal of Advanced Navigation Technology
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• v.23 no.4
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• pp.302-308
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• 2019

Aircraft data network (ADN) is a data networking for signal transmission among avionic systems in aircraft, and it mostly has been applied MIL-STD-1553B that guarantees high reliability considering its application environments. However, commercial Ethernet has been widely applied for ADN recently, and its range of applications have increased. Ethernet provides high speed of data transmission, however, it could not guarantee quality of service (QoS) so high as MIL-STD-1553B. In this paper, we propose dynamic routing and priority based data transmission schemes in order to improve the QoS of legacy Ethernet. Our propose schemes can be applied to Ethernet switch, and it is able to manage network traffic efficiently, and reduce the time for data transmission. We analyze the packet transmission time for both legacy and proposed schemes in Ethernet environments using simulation, and we show that our proposed scheme can reduce the time for data transmission compare to legacy spanning tree protocol.

• Journal of the Society of Disaster Information
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• v.15 no.3
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• pp.450-458
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• 2019

Purpose: The purpose of this study is to develop a new sewage bay that has removed its previous problems and verify the excellence of the maintainability of the new sewage bay. Method: The fluid characteristics in the developed sewage bay was analysed with computer simulation tool(COMSOL MultiphysicsTM ver. 3.2 ; COMSOL) and clarified the problems of the existing sewage bay. In addition, the durability of the newly developed sewage bay was verified by the long-term usability testing. Results: As a result of the simulation of a blocked drainage trap, an whirlpool and blockage did not occurred at the flow rate of 0.6m/sec, and we verified that switch device of drain trap was in good condition durably with 6 months long-term usability test. Conclusion: In this study, a newly advanced sewage bay was developed that solved the problems of the existing sewage bay structure. With the fluid simulation and the long-term usability tests, the excellence of the maintenance ability of the newly developed sewage bay was proved.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.11
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• pp.5179-5202
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• 2018

Transmission Control Protocol (TCP) is the most widely used protocol in the cloud data centers today. However, cloud data centers using TCP experience many issues as TCP was designed based on the assumption that it would primarily be used in Wide Area Networks (WANs). One of the major issues with TCP in the cloud data centers is the Incast issue. This issue arises because of the many-to-one communication pattern that commonly exists in the modern cloud data centers. In many-to-one communication pattern, multiple senders simultaneously send data to a single receiver. This causes packet loss at the switch buffer which results in TCP throughput collapse that leads to high Flow Completion Time (FCT). Recently, Software-Defined Networking (SDN) has been used by many researchers to mitigate the Incast issue. In this paper, a detailed survey of various SDN based solutions to the Incast issue is carried out. In this survey, various SDN based solutions are classified into four categories i.e. TCP Receive Window based solutions, Tuning TCP Parameters based solutions, Quick Recovery based solutions and Application Layer based solutions. All the solutions are critically evaluated in terms of their principles, advantages, and shortcomings. Another important feature of this survey is to compare various SDN based solutions with respect to different performance metrics e.g. maximum number of concurrent senders supported, calculation of delay at the controller etc. These performance metrics are important for deployment of any SDN based solution in modern cloud data centers. In addition, future research directions are also discussed in this survey that can be explored to design and develop better SDN based solutions to the Incast issue.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2019.10a
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• pp.8-8
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• 2019

The stringent response (SR) is characterized as a bacterial defense mechanism in response to various growth-inhibiting stresses. It is activated by accumulation of a small nucleotide regulator, (p)ppGpp, and induces global changes in bacterial transcription and translation. Recent work from our group has shown that (p)ppGpp plays a critical role in virulence and survival in Vibrio cholerae. The genes, relA and relV, are involved in the production of (p)ppGpp, while the spoT gene encodes an enzyme that hydrolyzes it in V. cholerae. A mutant strain defective in (p)ppGpp production (i.e. ${\Delta}relA{\Delta}relV{\Delta}spoT$ mutant) lost the ability to produce cholera toxin (CT) and lost their viability due to uncontrolled production of organic acids, when grown with extra glucose. In contrast, the ${\Delta}relA{\Delta}spoT$ mutant, a (p)ppGpp overproducer strain, produced enhanced level of CT and exhibited better growth in glucose supplemented media via glucose metabolic switch from organic fermentation to acetoin, a neutral fermentation end product, fermentation. These findings indicates that (p)ppGpp, in addition to its well-known role as a SR mediator, positively regulates CT production and maintenance of growth fitness in V. cholerae. This implicates SR as a promising drug target, inhibition of which may possibly downregulate V. cholerae virulence and survival fitness. Therefore, we screened a chemical library and identified a compound that induces medium acidification (termed iMAC) and thereby loss of wild type V. cholerae viability under glucose-rich conditions. Further, we present a potential mechanism by which the compound inhibits (p)ppGpp accumulation. Together, these results indicate that iMAC treatment causes V. cholerae cells to produce significantly less (p)ppGpp, an important regulator of the bacterial virulence and survival response, and further suggesting that it has a therapeutic potential to be developed as a novel antibacterial agent against cholera.

• Analytical Science and Technology
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• v.32 no.5
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• pp.185-195
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• 2019

Over the past decades, chiral switch of the proton pump inhibitors (PPIs) has been received widespread attention in therapeutic advantages as well as pharmaceutical analysis. In present study, the influence of cyclodextrins (CDs) on the chiral separation of four common PPIs (lansoprazole, omeprazole, pantoprazole, and rabeprazole) was investigated. The results demonstrated that capillary electrophoresis (CE) with dual CDs as a chiral selector system is a possible and promising method for the enantioseparation of these PPIs. Rabeprazole, which is the most challenging and acid-labile candidate among four PPIs, was selected for further development of the technique. To optimize CE condition, the effects of capillary parameters and background electrolytes on the enantioseparation were investigated. Finally, the best chiral separation was acheived by using sulfobutyl ether-${\beta}$-CD, and ${\gamma}$-CD as dual chiral selectors. The developed CE method not only provided the effective chiral separation but also showed the good stability of rabeprazole. The proposed method was successfully validated according to the International Conference on Harmonization guideline and effectively applied to determine rabeprazole enantiomers in commercial rabeprazole tablets, with recoveries ranging from 97.17 % to 103.29 % of the label content.

• The Journal of Asian Finance, Economics and Business
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• v.9 no.10
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• pp.265-275
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• 2022

In the current fast-growing market economy, the accounting-outsourcing trend of small and medium-sized enterprises is on the increase. Studies from both foreign and domestic sources have shown that many factors influence this decision. However, each country has different economic and political characteristics, so these factors and their degree of impact on accounting outsourcing also vary. This study aimed to determine the factors affecting the decision to outsource accounting activities of small and medium transport enterprises in Vietnam. A survey of 384 transport SMEs was conducted using the convenience sampling method. A personal interview with owners/managers/CFOs in 3 major cities of Vietnam based on a research review was conducted. The model examines the influence of many independent variables on accounting outsourcing. The multilinear regression analysis shows that the higher the Assets Specificity, the lower the degree of accounting outsourcing. In addition, the degree of outsourcing is positively and significantly related to frequency and trust in accountants. Besides, when we include control variables such as gender, administrative level, firm size, company age, education, and experience into the model. The results show that small and medium enterprises with limited resources should switch from the traditional internal accounting method to a professional accountant with external knowledge. Based on this study, the author proposes several implications for the accounting outsourcing of small and medium-sized transport enterprises in Vietnam to be more effective. Finally, this study also contributes to the basic knowledge of accounting outsourcing.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.11
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• pp.1391-1396
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• 2019

With the recent increase in the importance of software, software education is required in elementary schools in Korea. At this point, coding education combining play and education using smart toys is widely used. One of the most widely used smart toys is a block type smart toy. In this study, usability evaluation was performed to improve user's usability for block type smart toy with smartphone application. In order to achieve the purpose of this study, a heuristic technique with experts, one of various usability evaluation techniques, was performed. As a result of the analysis, it was found that the buttons and the switch of the menu were not well distinguished, and the cause of the error was not provided to the user. The results of this study can be the basis for improving the usability of applications for smart toy in the future.

• Journal of IKEEE
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• v.24 no.4
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• pp.1058-1063
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• 2020

This paper proposes a 12-bit SAR A/D(Successive Approximation Register Analog-to-Digital) converter that operates at low power for bio-signal and sensor signal processing. The conventional SAR A/D converter utilized the reduction of the dynamic current, which resulted in reducing total power consumption. In order to solve the limitation of the sampling time due to charging/discharging of the capacitor for reducing dynamic current, the different sampling time on the C-DAC bit switch operation was applied to reduce the dynamic current. In addition, lowering the supply voltage of the digital block to 0.6V led to 70% reduction of the total power consumption of the proposed ADC. The proposed SAR A/D was implemented with CMOS 65nm process 1-poly 6-metal, operates with a supply voltage of 1.2V. The simulation results demonstrate that ENOB, DNL/INL, power consumption and FoM are 10.4 bits, ±0.5LSB./±1.2LSB, 31.2uW and 2.8fJ/step, respectively.

• Journal of the Korea Convergence Society
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• v.12 no.2
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• pp.201-213
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• 2021

Recently, personal mobility has been spreading and using increasing, but the pedestrian environment is getting worse and accidents are also rapidly increasing. Therefore, this study conducts a status survey related to the elements of pedestrian disturbances in personal mobility and identifies the problems. The following measures are presented to improve the pedestrian environment for the mobility handicapped through expert opinion surveys. The movement of individual mobility means in the walking space is prohibited, and the speed limit shall be stipulated to enable the mobility handicapped to walk safely and conveniently. Parking spaces will have to create obstacle zones in the parking area next to the roadway or at the border of sidewalks and roads, and regulations are needed to collect illegally parked vehicles. It is necessary to switch from the existing automobile-oriented road to the road structure considering the use of low and medium-speed vehicles.