• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.7
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• pp.851-856
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• 2013

Recently, as the tactical environment has changedto one of network-centric warfare, where all components are connected through a network, much emphasis has been placed on the use of an artificial satellite for achieving high communication speeds. To provide a high-quality artificial satellite link, stabilization is very important in a platform. Previous stabilization control techniques used PI control, which is commonly used for vessels. However, for ground terminals that require a higher communication speed, the antenna should move faster to track an artificial satellite within a short period of time. Moreover, the terminals must be equipped with proper sensors and algorithms so that they can detect and compensate for external disturbances while tracking the artificial satellite. In this study, through the analysis of the dynamic model of an antenna system, a stabilization algorithm for ground terminals was proposed;this algorithm shows high isolation performance in the low-frequency range and includes $PI^2$ control.

• Journal of Korean Academy of Nursing
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• v.29 no.2
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• pp.238-247
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• 1999

The purpose of this study was to describe the relationship between family stress and adaptation in families with a disabled child through literature review using McCubbin's Double ABCX family crisis framework. The literature review focused on (1) family stress and factors affecting family stress, (2) the critical individual, familial and social resources which families acquire and employ over time in managing crisis situation. (3) the changes in definition and meaning families develop in an effort to make sense out of their predicament. (4) the coping strategies families employ. and (5) the range of outcomes of these family efforts The results showed that families reported financial difficulties and the burden of care-giving demands as major family stressors. Siblings of disabled children manifested depressive symptoms and social isolation. but was not consistent study results. The parents' views of the cause of the disabling condition fundamentally affected their behavior toward their disabled child. Especially. the fathers' views of the child's characteristics made the greatest contribution to positive changes in the mothers' perceptions. The term perceived social support refers to the cognitive appraisal by individuals that they are cared for and valued, that significant others are available to them if needed, and that they are satisfied with their interpersonal relationships. The perceived social support was more protective than social support source. network size and network density. Parental adaptation was found to be related to the child's communication competence rather than family coping strategies proposed by Lazarus and Folkman. One study results showed that there was no difference in depressive symptoms and physical health between mothers with a disabled child and those without all though mothers with a disabled child had negative attitudes and perceived themselves as having significantly less social support and lower family functioning. But a longitudinal study revealed decreases in the negative impact of the child and increases in sibling and overall family adaptation.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.6
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• pp.440-448
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• 2009

Facility power-line electromagnetic interference (EMI) filters are used to provide radio frequency(RF) isolation between dedicated power distribution services and noise sensitive local power distribution systems. This type of EMI filters generally needs a high current capacity and, in some special applications, a high insertion loss of a minimum 100dB from 14kHz through 10GHz per MIL-STD 220 is required. This paper deals with an analysis and design of a wideband facility power-line EMI filter with the above requirements. The characteristics of the inductor and capacitor at high frequencies are investigated. The characteristics and design method of the facility EMI filter with a high order LC network are also presented. The prototype filter is finally implemented and its performance is verified from the experimental results.

• Journal of Broadcast Engineering
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• v.13 no.3
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• pp.365-379
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• 2008

In this paper we consider technological requirements of the on-channel repeater to broadcast the terrestrial digital multimedia broadcasting (T-DMB) signals using single frequency networks (SFN) and propose the configuration and implementation method of the equalization on-channel repeater (OCR) that meet such requirements. The proposed equalization OCR not only has short time delay, but shows high output power and good quality of output signal by removing a feedback signal due to incomplete antenna isolation and multipath signal existing between the main transmitter and the OCR. In addition, computer simulations and laboratory tests results are provided to figure out performance of the proposed equalization OCR.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.12
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• pp.5375-5400
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• 2016

IOMMU is a hardware unit that is indispensable for DMA. Besides address translation and remapping, it also provides I/O virtual address space isolation among devices and memory access control on DMA transactions. However, currently commodity virtualization platforms lack of IOMMU virtualization, so that the virtual machines are vulnerable to DMA security threats. Previous works focus only on DMA security problem of directly assigned devices. Moreover, these solutions either introduce significant overhead or require modifications on the guest OS to optimize performance, and none can achieve high I/O efficiency and good compatibility with the guest OS simultaneously, which are both necessary for production environments. However, for simulated virtual devices the DMA security problem also exists, and previous works cannot solve this problem. The reason behind that is IOMMU circuits on the host do not work for this kind of devices as DMA operations of which are simulated by memory copy of CPU. Motivated by the above observations, we propose an IOMMU para-virtualization solution called PVIOMMU, which provides general functionalities especially DMA security guarantees for both directly assigned devices and simulated devices. The prototype of PVIOMMU is implemented in Qemu/KVM based on the virtio framework and can be dynamically loaded into guest kernel as a module, As a result, modifying and rebuilding guest kernel are not required. In addition, the device model of Qemu is revised to implement DMA access control by separating the device simulator from the address space of the guest virtual machine. Experimental evaluations on three kinds of network devices including Intel I210 (1Gbps), simulated E1000 (1Gbps) and IB ConnectX-3 (40Gbps) show that, PVIOMMU introduces little overhead on DMA transactions, and in general the network I/O performance is close to that in the native KVM implementation without IOMMU virtualization.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.744-749
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• 2013

The protection switching technology is widely adopted in the fiber-optical transmission equipments based on TDM(Time Division Multiplexing), such as PDH, SDH/SONET. A variety of protection switching algorithms for Ethernet networks and the progress of standardization are summarized in the document. There are several kinds of protection switching algorithms for Ethernet networks, such as STP, RSTP, MSTP and etc. However, since Ethernet signal move through detour route, it causes much time to recover. Accordingly, it is difficult to secure a usability of Ethernet networks and QOS(Quality of Service). Also, if the protection switching protocol standardized by IEEE and ITU-T is used, it remains a inherent network switching time for protection. Therefore, a specific protection switching algorithm for Ethernet are needed for seamless and stable operation of Ethernet networks service for Distribution Automation System(DAS). A reliable protection algorithm with no switching delay time is very important to implement Self-healing service for DAS. This study of FPGA based protection switching algorithm for Ethernet networks shows that in case of faults occurrence on distribution power network, immediate fault isolation and restoration are conducted through interaction with distribution equipments using P2P(Peer to Peer) communication for protection coordination. It is concluded that FPGA based protection switching algorithm for Ethernet networks available 0ms switching time is crucial technology to secure reliability of DAS.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.2045-2049
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• 2018

An antenna arrays for a satellite navigation systems require more antenna elements to mitigate multiple jamming signals. In order to maintain the small array size while increasing the number of antenna elements, miniaturization technique is essential for antenna design. In this work, an electrically small circular microstrip patch antenna with a 3 dB hybrid coupler is designed as an element antenna, where the 3 dB hybrid coupler can yield the circularly polarized radiation characteristic. The miniaturized element antenna typically has too large capacitance in GPS L1 and GLONASS G1 bands, making it difficult to match with a single stand-alone non-Foster matching circuit (NFMC) in a stable state. Therefore, we propose a new matching technique, referred to as the hybrid matching method, which consists of a NFMC and a passive circuit. This passive tuning circuit manages reactance of antenna elements at an appropriate capacitance without a pole in the operating frequency range. The antenna array is fabricated, and the measured results show a reflection coefficient of less than -10 dB and an isolation of greater than 50 dB. In addition, peak gain of the proposed antenna is increased by 22.3 dB compared to the antenna without the hybrid matching network.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.4
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• pp.1502-1520
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• 2021

This paper attempts to investigate Korean youth Not in Education, Employment and Training (NEET) and how daily activities and community participation may influence their positive emotions and job search desire. First, we conducted a focus group interview with 16 NEETs who participated in the Kakao NEET Company project. The project allowed participants to experience employment by founding a virtual company in which each participant selected a daily activity to perform as part of the company's operations. Second, the interview responses were categorized and assigned emotional values using the card sorting technique and multi-dimensional analysis (MDS). A total of 11 emotional values were derived through this process. Finally, a social network analysis was conducted in order to measure the density of relations among the emotional values. Results suggest that immersion, confidence, belongingness were the three highest values evaluated by participants. Furthermore, network diagrams imply that the stronger participants perceived social support and belongingness with others, the stronger their responsibility grew, further leading them to establish steady goals. In particular, the high eigenvector score for "desire for job" suggests that emotional values are sequentially connected to the immersion-social support-responsibility-goal-job desire. This sequence suggests that digital services that are developed with the aim to enhance social values such as the Kakao NEET Project may engender motivation and confidence in youth NEETs. The overall results suggest that a systematic approach to policymaking should be considered in order to provide fundamental solutions and expand opportunities for social participation and emotional comfort, as social isolation due to low self-esteem has been reported as one of the reasons for NEETs' failure in the labor market.

• International Journal of Computer Science & Network Security
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• v.21 no.11
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• pp.81-88
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• 2021

The presented scientific research substantiates the principles of the mechanism of the investment resources involvement in order to introduce innovations at enterprises in the context of digitalization using a resource-functional approach. The importance of attracting investment resources, which contributes to the modernization of production systems, the creation of a stable economic field of development of economic entities, is justified. The expediency of application of the resource-functional approach on research of the mechanism of attraction of investment resources for introduction of innovations at the enterprises in the conditions of digitalization is proved. The investment process is presented in the form of a chain of interdependent processes which include: attraction of investment resources, investments, increase of investment value, profit. It is proved that the mechanism of attracting investment resources for the introduction of innovations in enterprises in the context of digitalization cannot be considered in isolation from the process, due to the fact that the mechanism is aimed at performing specific functions. The functions of the mechanism include management, complex, coordination, monitoring, performance and control functions. Functions of the mechanism of attraction of investment resources for introduction of innovations at the enterprises in the conditions of digitalization are caused by the purposes of attraction of investment resources for innovative development; the presence of an objective nature; relative independence and homogeneity; implementation of functions in the process of investing in innovative activities of the enterprise.

• International Journal of Computer Science & Network Security
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• v.24 no.1
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• pp.133-139
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• 2024

The educational situation, which resulted from the announced self-isolation regime, intensified the forced decisions on the organization of the distance educational process. The study is topical because of the provision of distance learning based on the experience of Kyiv National University of Culture and Arts. The study was conducted in three stages. Systemic, socio-communicative, competence approaches, sociological methods (questionnaires and interviews) were chosen as methodological tools of the research. The results of a survey of teachers and entrants to higher education institutions on the topic "Using social networks and digital platforms for online classes under the conditions of quarantine restrictions" allowed to scientifically substantiate the need for deeper knowledge of such tools as Google Meet (79%), Zoom (13.78%) and Google Classroom (11.62%), which are preferred by entrants. Almost a third of entrants (34.26%) noted the lack of scientific and methodological support for learning the subjects. The study showed high efficiency of messengers in distance education. The study found that in the process of organizing communication in the student-teacher system, it is necessary to take into account the priority of Telegram on the basis of which it is necessary to implement a chatbot for convenient and effective exchange of information about the educational process. Further research should focus on the effectiveness of the use of Telegram. The effectiveness of using chatbots should also be considered. Chatbots can be used to automate routine components of the learning process.