• International Journal of Internet, Broadcasting and Communication
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• 제14권3호
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• pp.8-16
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• 2022

In this paper, we propose a method of reconstructing the file system to obtain digital forensics information from the APFS file system when meta information that can know the structure of the file system is deleted due to partial damage to the disk. This method is to reconstruct the tree structure of the file system by only retrieving the B-tree node where file/directory information is stored. This method is not a method of constructing nodes based on structural information such as Container Superblock (NXSB) and Volume Checkpoint Superblock (APSB), and B-tree root and leaf node information. The entire disk cluster is traversed to find scattered B-tree leaf nodes and to gather all the information in the file system to build information. It is a method of reconstructing a tree structure of a file/directory based on refined essential data by removing duplicate data. We demonstrate that the proposed method is valid through the results of applying the proposed method by generating numbers of user files and directories.

• Current Optics and Photonics
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• 제8권1호
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• pp.56-64
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• 2024

In response to the current situation where general methods cannot effectively compensate for the phase delay of ordinary optical mixers, a multi-layer spatial beam-splitting optical mixer is designed using total reflection triangular prisms and polarization beam splittings. The phase delay is generated by the wave plate, and the mixer can use the existing parallel plates in the structure to individually compensate for the phase of the four output beams. A mixer model is established based on the structure, and the influence of the position and orientation of the optical components on the phase delay is analyzed. The feasibility of the phase compensation method is simulated and analyzed. The results show that the mixer can effectively compensate for the four outputs of the optical mixer over a wide range. The mixer has a compact structure, good performance, and significant advantages in phase error control, production, and tuning, making it suitable for free-space coherent optical communication systems.

• Journal of information and communication convergence engineering
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• 제9권2호
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• pp.150-154
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• 2011

In this paper a four-pole elliptic function bandpass filter is designed with two ground slots. A research of microstrip bandpass filters (BPF) using defected ground structures (DGS) is presented. DGS technique allows designs of tight couplings without the necessity of using very narrow coupling gaps. The simulator Sonnet is used to design the resonator and to calculate the coupling coefficient of the basic coupling structure. Compared to similar microstrip filters without defected ground structure, the simulated performances of these novel structures indicate some technological advantages.

• 한국시뮬레이션학회논문지
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• 제7권2호
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• pp.63-78
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• 1998

The hierarchical cell structure consists of the macrocell and microcells to increase the system capacity and to achieve broad coverage. The hierarchical cell structure provides services for users in different mobility. In this paper, an analytical queueing model in mobile networks is proposed for the performance evaluation of the hierarchical cell structure. The model for networks with the multiple levels can simplify multi-dimensional ones into one-dimensional queueing model. The computational advantage will be growing as the layers are constructed in multiple levels. The computer simulation is provided for validating the proposed analytical model.

• 한국산업융합학회 논문집
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• 제23권1호
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• pp.41-48
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• 2020

Currently, the industry uses MODBUS communication method using RS485 as a communication method used when constructing distributed equipment and networks. However, this method has a rather good transmission and reception distance, but has a disadvantage of being a half-duplex communication method. Therefore, there is a great need for a full-duplex communication method that can simultaneously transmit and receive two-wire communications. Therefore, in this paper, we propose a new communication hardware equipment that can implement full-duplex communication method by communication signal level to overcome the disadvantage of communication speed. The proposed communication hardware is a structure that can transmit and receive at the same time on the same communication line in two equipments communicating in a two-wire system. The characteristic of this communication hardware is that the transmitter generates two-level signal for data transmission, but the receiver generates three-level electric signal according to the status of the transmission data generated by the receiver. The data transmission signal information of the receiver is present at the same time. Therefore, the receiving side can analyze the received signal based on the information on the current transmission signal and can analyze the signal only in the two communicating devices, so it can be seen that the communication security is very excellent.

• 대한안전경영과학회지
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• 제11권3호
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• pp.63-71
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• 2009

Safety is totally established through not only legal regulations and system but the establishment of safety culture. As a foundation of safety culture, safety and health communication is the essential condition. Therefore, in the case of researching safety culture the communication network of a organization is a crucial factor. This study has analysed the structure of occupational safety and health communication between domestic and foreign corporations comparatively by the statistical analysis. The occupational safety and health communication is composed of four sub-dimensions: general communication in working site, using safety information communication, communication with the board of directors, and communication with labor union. The nationality of corporations influences the safety communication significantly except for communication with labor union. Consequently it is possible to infer that the nationality of corporations is a significant factor for safety communication network.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전력기술부문
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• pp.111-113
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• 2006

Substation automation is one of the key issues for the enhancement of the power industrial foundation. IEC 60850 is an international standard specifying communication network and systems in substation. It supports interchangeability and interoperability of equipments from different vendors. ACSI(Abstract communication service interface) specifies basic communication structure for substation and IEDs. It supports communication as well as various services without proper protocols. For actual communication, MMS(Manufacturing Message Specification : ISO 9506) is used to map ACSI services. Solutions for the development of communication driver based don IEC 61850 are proposed in this paper.

• 한국데이타베이스학회:학술대회논문집
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• 한국데이타베이스학회 2008년도 연합학회학술대회
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• pp.321-338
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• 2008

Information and communication industry, which shows rapid growth rate, is now leading the global economic growth, contributing a ripple effect on general business and economic structure. It is said that information and communication industry enables swift economic growth taking a role as a basic industry of information-oriented society. Especially, rapid technical innovation promotes mutual growth of other related industries and it is technology-intensive. The purpose of this research is to analyze the management efficiency of information and communication industry using DEA method, and finally suggest numerical value for inefficient organizations to improve their efficiency. CCR-I, BCC-I efficiency and RTS(Returns to scale) of 29 companies engaged in information and communication industry was evaluated. With the results, I suggested model companies for benchmarking in information and communication industry. To summarize, 7 companies were selected with CCR-I efficiency rate 1, and 12 companies with BCC-I efficiency rate 1. RTS was finalized with 8 IRS companies, 10 DRS companies, and 11 CRS companies.

• Current Optics and Photonics
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• 제2권4호
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• pp.308-314
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• 2018

Visible light communication (VLC) is considered a strong future candidate for indoor wireless communication. However, its performance seems to be relatively unsatisfactory when compared to wireless local area network (WLAN) communication using millimeter waves. To improve the performance of VLC, numerous technologies have been proposed so far, in both electrical and optical domains. Among the proposals, optical beamforming (OB) is an optical-domain technology that can concentrate light in a specific direction or on a target spot. It can significantly improve VLC performance and can be widely used, because it does not depend on electrical modulation schemes. Therefore, this review discusses the concept, principle, and types of OB, the structure of a VLC system using OB, performance results of OB, and the combination of OB with electrical signal modulation in VLC. OB is expected to be one of the key techniques in future VLC implementations, similar to radio-frequency beamforming in millimeter-wave communication.

• 국제학술발표논문집
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• The 1th International Conference on Construction Engineering and Project Management
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• pp.974-979
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• 2005

Effective communication flow is a fundamental for the success of any construction projects. The key role of communications among project parties is even more critical in the case of Design-Build (DB) projects. Previous research has shown that these projects have an environment where integration between different project team members and schedule constraints increase channels of communication, and require faster communication flows. This paper summarizes the findings from research analyzing organizational structures and communication flow of the Texas State Highway 130 (SH130) project. Awarded in 2002, the SH130 project, totaling $1.3 billion USD, constitutes the "pilot" application for the DB approach in the state of Texas. A set of observations pertaining to team organization and communication issues in the design-build environment is included.