• Membrane Journal
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• v.33 no.4
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• pp.158-167
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• 2023

The increasing concerns for environmental pollution and depletion of natural resources have prompted the development of environmentally sustainable technologies. Pervaporation has garnered attention in recent decades due to its low energy consumption, environmental impact, and performance efficiency. This method has been used to separate chemical species and dehydrate organic solvents, as the membranes can be fine-tuned to fulfill the desired selectivity. Several separation processes, such as reverse osmosis and distillation, are being utilized in both experimental settings and industrial applications. However, pervaporation has several advantages, such as low operating pressure and temperature and a higher rejection rate. Nonetheless, the current state of membrane technology alone can't suffice the demands of practical applications. Composite membranes, on the other hand, can leverage the benefits of both organic and inorganic materials. Many studies have effectively incorporated inorganic nanomaterials such as graphene oxide (GO) and MXene (MX) in polymeric membranes to tackle the current limitations. This review investigates the recent development of 2D composite membranes in pervaporation and evaluates performance enhancement.

• Journal of Advanced Navigation Technology
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• v.27 no.3
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• pp.314-322
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• 2023

The use of unmanned aerial vehicles is rapidly increasing in order to effectively utilize limited manpower and minimize casualties on the battlefield. The requirements for ground control equipment vary depending on the operating concept and environment of the unmanned aerial system, but there are still common requirements. However, the lack of standardized system configurations to meet these common requirements makes it difficult to reuse common functions, leading to continuous acquisition costs. To solve this problem, this paper develops a Korean version of the UCS model using the UCS architecture. Furthermore, after designing elements related to service development not specified in the architecture (such as framework, communication middleware, service structure, etc.), we develop a Boilerplate to enhance developers' work efficiency based on this. The results of this study will serve as a foundation for effectively and economically carrying out the development of ground control equipment for unmanned aerial systems.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2812-2822
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• 2023

The supercritical carbon dioxide (sCO₂) Brayton power cycle is more effective than the conventional power cycle and is more widely applicable to heat sources. The inlet working conditions of the compressor have a higher influence on their operating performance because the thermophysical properties of the CO₂ vary dramatically close to the critical point. The flow in the sCO₂ compressor is simulated and the compressor performance is analyzed. The results show that the sCO₂ centrifugal compressor operates outside of its intended parameters due to the change in inlet temperature. The sCO₂ compressor requires more power as the inlet temperature increases. The compressor power is 582 kW when the inlet temperature is at 304 K. But the power is doubled when the inlet temperature increases to 314 K, and the change in the isentropic efficiency is within 5%. The increase in the inlet temperature significantly reduces the risk of condensation in centrifugal compressors. When the heat load of the sCO₂ power system changes, the inlet pressure to the turbine can be kept constant by regulating the rotational speed of compressors. With the increase in rotational speed, the incidence loss and condensation risk increase.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.6
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• pp.723-732
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• 2022

Cracking ammonia inside solid oxide fuel cell (SOFC) stack is a compact and simple way. To prevent sharp temperature fluctuation and increase cell efficiency, the decomposition reaction should be spread on whole cell area. This leading to a question that, how does anode thickness affect the conversion rate of ammonia and the cell voltage? Since the 0D model of SOFC is useful for system level simulation, how accurate is it to use equilibrium solver for internal ammonia cracking reaction? The 1D model of ammonia fed SOFC was used to simulate the diffusion and reaction of ammonia inside the anode electrode, then the partial pressure of hydrogen and steam at triple phase boundary was used for cell voltage calculation. The result shows that, the ammonia conversion rate increases and reaches saturated value as anode thickness increase, and the saturated thickness is bigger for lower operating temperature. The similar cell voltage between 1D and 0D models can be reached with NH₃ conversion rate above 90%. The 0D model and 1D model of SOFC showed similar conversion rate at temperature over 750℃.

• Journal of the Korea Society of Computer and Information
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• v.14 no.12
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• pp.191-199
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• 2009

The integrated medical information system is an effective medical diagnosis assistance system which offers an environment in which medial images and diagnosis information can be shared. Because of the large-scale medical institutions and their cooperating organizations are operating the integrated medical information systems, they can share medical images and diagnosis information. However, this system can only stored and transmitted information without other functions. To resolve this problem and to enhance the efficiency of diagnostic activities, a medical image analysis system is necessary. In this paper, the proposed relationship method analyzes medical images for features generation. Under this method, the medical images have been segmented into several objects. The medical image features have been extracted from each segmented image. Then, extracted features were applied to the Relationship Method for medical image analysis. Several experimental results that show the effectiveness of the proposed method are also presented.

• International Journal of Computer Science & Network Security
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• v.23 no.4
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• pp.172-178
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• 2023

When the mobile device moves from the coverage of one access point to the radio coverage of another access point it needs to maintain its connection with the current access point before it successfully discovers the new access point, this process is known as handoff. During handoff the acceptable delay a voice over IP application can bear is of 50ms whereas the delay on medium access control layer is high enough that goes up to 350-500ms. This research provides a suitable methodology on medium access control layer of the IEEE 802.11 network. The medium access control layer comprises of three phases, namely discovery, reauthentication and re-association. The discovery phase on medium access control layer takes up to 90% of the total handoff latency. The objective is to effectively reduce the delay for discovery phase to ensure a seamless handoff. The research proposes a scheme that reduces the handoff latency effectively by scanning channels prior to the actual handoff process starts and scans only the neighboring access points. Further, the proposed scheme enables the mobile device to scan first the channel on which it is currently operating so that the mobile device has to perform minimum number of channel switches. The results show that the mobile device finds out the new potential access point prior to the handoff execution hence the delay during discovery of a new access point is minimized effectively.

• Smart Structures and Systems
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• v.29 no.5
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• pp.661-675
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• 2022

In this paper, an electric vehicle drives with efficient control and low cost hardware using four quadrant DC converter with Permanent Magnet Direct Current (PMDC) motor fed by DC boost converter is presented. The main idea of this work is to improve the energy efficiency of the conversion chain of an electric vehicle by inserting a boost converter between the battery and the four quadrant-DC motor chopper assembly. Consequently, this method makes it possible to maintain the amplification gain of the 4 quadrant chopper constant regardless of the battery voltage drop and even in the presence of a fault in the battery. One of the most important control problems is control under heavy uncertainty conditions. The higher order sliding mode control technique is introduced for the adjustment of DC bus voltage and mechanical motor speed. To implement the proposed approach in the automotive field, experimental tests were carried out. The performances obtained show the usefulness of this system for a better energy management of an electric vehicle and an ideal control under different operating conditions and constraints, mostly at nominal operation, in the presence of a load torque, when reversing the direction of rotation of the motor speed and even in case of battery chamber failure. The whole system has been tested experimentally and its performance has been analyzed.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.6 no.7
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• pp.389-397
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• 2016

Digital Humanities System is a method to effectively share and spread Humanities information and knowledge to users by using information technology. It Also comes into the spotlight as a new research methodology for researches of Humanities researchers. Digital Humanities System distinguishes itself from other existing information systems. Therefore, when the system is developed, it needs to supply with manpower related to development process which is specialized for Digital Humanities System, not for the several established construction methodology. Digital Humanities System studies recently is mostly constructed using the usual methodology of information system construction. Because of its falling efficiency and usability after constructing the system, however, examples of failure of operating system occur. In this paper, accordingly, effective and creative Digital Humanities System development methodology will be studied from the point of view of information technology through collaboration with various field of expertise. In detail, based on information system methodologies in software engineering perspective, we propose a methodology to build a specialized system in the digital humanities.

• Convergence Security Journal
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• v.22 no.2
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• pp.9-19
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• 2022

As the expansion of digital transformation, we are more exposed to the threat of cyber attacks, and many institution or company is operating a signature-based intrusion prevention system at the forefront of the network to prevent the inflow of attacks. However, in order to provide appropriate services to the related ICT system, strict blocking rules cannot be applied, causing many false events and lowering operational efficiency. Therefore, many research projects using artificial intelligence are being performed to improve attack detection accuracy. Most researches were performed using a specific research data set which cannot be seen in real network, so it was impossible to use in the actual system. In this paper, we propose a technique for classifying major attack keywords in the security event log collected from the actual system, assigning a weight to each key keyword, and then performing a similarity check using TF-IDF to determine whether an actual attack has occurred.

• Smart Structures and Systems
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• v.31 no.3
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• pp.283-299
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• 2023

Structural stability of floating platforms has long since been a crucial issue in the field of marine engineering. Excessive motions would not only deteriorate the operating conditions but also seriously impact the safety, service life, and production efficiency. In recent decades, several control devices have been proposed to reduce unwanted motions, and an attractive one is the tuned heave plate (THP). However, the THP system may reduce or even lose its effectiveness when it is mistuned due to the shift of dominant wave frequency. In the present study, a novel adaptive tuned heave plate (ATHP) is proposed based on inerter by adjusting its inertance, which allows to overcome the limitation of the conventional THP and realize adaptations to the dominant wave frequencies in real time. Specifically, the analytical model of a representative semisubmersible platform (SSP) equipped with an ATHP is created, and the equations of motion are formulated accordingly. Two optimization strategies (i.e., J₁ and J₂ optimizations) are developed to determine the optimum design parameters of ATHP. The control effectiveness of the optimized ATHP is then examined in the frequency domain by comparing to those without control and controlled by the conventional THP. Moreover, parametric analyses are systematically performed to evaluate the influences of the pre-specified frequency ratio, damping ratio, heave plate sizes, peak periods and wave heights on the performance of ATHP. Furthermore, a Simulink model is also developed to examine the control performance of ATHP in the time domain. It is demonstrated that the proposed ATHP could adaptively adjust the optimum inertance-to-mass ratio by tracking the dominant wave frequencies in real time, and the proposed system shows better control performance than the conventional THP.