• Journal of electromagnetic engineering and science
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• 제5권3호
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• pp.140-145
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• 2005

In this paper, an experimental investigation for return loss and a software-based prediction for interference level of single-packaged filtering antenna composed of dielectric waveguide filter and PCB(Printed Circuit Board) slot antenna in transceiver module have been carried out with several different feeding structures in millimeter-wave regime. The implementation and embedding method of the existing air-filled waveguide filters working at millimeter-wave frequency on general PCB substrate have been described. In a view of the implementation of each components, the dielectric waveguide embedded in PCB and LTCC(Low Temparature Co-fired Ceramic) substrates has employed the via fences as a replacement with side walls and common ground plane to prevent energy leakage. The characteristics of several prototypes of filtering antenna embedded in PCB substrate are considered by comparing the wideband and transmission characteristics as a function of bent angle of transmission line connecting two components. In addition, as an essential to the packaging of transceiver module working at millimeter-wave, miniaturization technology maintaining the performances of independent components and the important problems caused by integrating and connecting the different components in different layers are described in this paper.

• Journal of Information Processing Systems
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• 제12권1호
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• pp.73-82
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• 2016

In cognitive radio networks (CRNs), the performance of the transmission control protocol (TCP) at the secondary user (SU) severely drops due to the mistrigger of congestion control. A long disruption is caused by the transmission of primary user, leading to the mistrigger. In this paper, we propose a cross-layer approach, called a CR-aware scheme that enhances TCP performance at the SU. The scheme is a sender side addition to the standard TCP (i.e., TCP-NewReno), and utilizes an explicit cross-layer signal delivered from a physical (or link) layer and the signal gives an indication of detecting the primary transmission (i.e., transmission of the primary user). We evaluated our scheme by implementing it onto a software radio platform, the Universal Software Radio Peripheral (USRP), where many parts of lower layer operations (i.e., operations in a link or physical layer) run as user processes. In our implementation, we ran our CR-aware scheme over IEEE 802.15.4. Furthermore, for the purpose of comparison, we implemented a selective ACK-based local recovery scheme that helps TCP isolate congestive loss from a random loss in a wireless section.

• 한국통신학회논문지
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• 제27권10C호
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• pp.980-986
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• 2002

하나의 클럭원으로 동기 되는 고속의 데이터 통신 시스템에서, 데이터와 클럭 사이의 다른 라우팅 경로나, 부품들의 다른 전달지연시간 또는 외부 잡음에 의한 데이터나 클럭의 불안정한 위상과 같은 여러 이유들로 인해 데이터를 잃어버릴 수가 있다. 본 논문에서는 이렇게 잃어버린 데이터를 탐지하고 원래의 데이터로 복원하여 보상 출력하는 기능을 갖는 디지털 회로를 제안하고 구현을 기술한다. 특히, 이러한 보상회로는 광 분야등과 같이 고속의 데이터 전송을 위한 통신 시스템에서 강한 안정성을 가지며 BER개선에 상당히 크게 영향을 준다. 이 회로는 Verilog HDL로 구현이 되었으며 통신 및 데이터 전송관련 디지털 ASIC구현에 기본적으로 응용이 가능하다.

• The Journal of Asian Finance, Economics and Business
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• 제9권8호
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• pp.145-155
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• 2022

Since 2014, the IFRS 9 has been the focus of the attention of many scholars across disciplines. The futuristic prediction of bank loan provision via a flexible ECL model has been observed as a game changer from the prior models offered in IAS 39. This study has two objectives; the first is to examine the impact on loan loss provisions (LLP), nonperforming loans (NPL), and the impairment loan losses (ILL) after the IFRS 9 in gulf banks. The second is to capture any variation in LLP, NPL, and ILL before and after IFRS9. The study used the two-way fixed effect model (TWFE) estimation and the DiD approach to attain its objectives. 54 gulf banks were selected from the periods between 2012 and 2020. The results indicate that LLP has significantly increased after the transition to IFRS 9, while the NPL has significantly decreased. The results did not capture a significant change in ILL after IFRS9 implementation. The results also indicate more consistency in LLP and NPL reporting after implementing the ECL model adopted in IFRS9. The study concluded that ECL model outcomes are in tandem with prior observation worldwide and pointed out some improvement opportunities for the future.

• Spatial Information Research
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• 제19권6호
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• pp.111-121
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• 2011

본 논문은 GIS를 기반으로 도시 무선 통신환경에서 지형 공간 요소를 활용하고, 전파 손실에 영향을 미치는 대표 간섭 요인을 고려한 무선 센서노드 배치 알고리즘을 제안하였다. 먼저, 경기도 고양시 일산의 주요 도로에서 전파 손실 실험을 수행하고, 얻어진 실험 결과는 지리정보 시스템으로 부터 추출 가능한 주변 환경 정보와의 상관관계를 정의하였다. 다음으로, 이의 활용을 통해 무선 센서노드의 무선 커버리지 결정 및 배치 시스템 구현에 필요한 세부 동작에 대해 기술하였다. 그 결과, 전파에 영향을 많이 미치는 건물이나 도로의 선형 구조의 반영을 통해, 5dB 이하의 오류 수준으로 경로손실을 평가할 수 있었다. 그리고 이를 기반으로 센서노드 배치를 보정할 수 있는 방법을 제시하였다.

• 대한의용생체공학회:의공학회지
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• 제45권1호
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• pp.26-36
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• 2024

Functional brain imaging techniques have been used to diagnose psychiatric disorders such as dementia, depression, and autism. Recently, these techniques have also been actively used to study hearing loss. The present study reviewed the application of the functional brain imaging techniques in auditory research, especially those focusing on hearing loss, over the past decade. EEG, fMRI, fNIRS, MEG, and PET have been utilized in auditory research, and the number of research studies using these techniques has been increasing. In particular, fMRI and EEG were the most frequently used technique in auditory research. EEG studies mostly used event-related designs to analyze the direct relationship between stimulus and the related response, and in fMRI studies, resting-state functional connectivity and block designs were utilized to analyze alterations in brain functionality in hearing-related areas. In terms of age, while studies involving children mainly focused on congenital and pre- and post-lingual hearing loss to analyze developmental characteristics with and without hearing loss, those involving adults focused on age-related hearing loss to investigate changes in the characteristics of the brain based on the presence of hearing loss and the use of a hearing device. Overall, ranging from EEG to PET, various functional brain imaging techniques have been used in auditory research, but it is difficult to perform a comprehensive analysis due to the lack of consistency in experimental designs, analysis methods, and participant characteristics. Thus, it is necessary to develop standardized research protocols to obtain high-quality clinical and research evidence.

• Healthcare Informatics Research
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• 제24권4호
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• pp.263-275
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• 2018

Objectives: Automated audiometry provides an opportunity to do audiometry when there is no direct access to a clinical audiologist. This approach will help to use hearing services and resources efficiently. The purpose of this study was to review studies related to automated audiometry by focusing on the implementation of an audiometer, the use of transducers and evaluation methods. Methods: This review study was conducted in 2017. The papers related to the design and implementation of automated audiometry were searched in the following databases: Science Direct, Web of Science, PubMed, and Scopus. The time frame for the papers was between January 1, 2010 and August 31, 2017. Initially, 143 papers were found, and after screening, the number of papers was reduced to 16. Results: The findings showed that the implementation methods were categorized into the use of software (7 papers), hardware (3 papers) and smartphones/tablets (6 papers). The used transducers were a variety of earphones and bone vibrators. Different evaluation methods were used to evaluate the accuracy and the reliability of the diagnoses. However, in most studies, no significant difference was found between automated and traditional audiometry. Conclusions: It seems that automated audiometry produces the same results compared with traditional audiometry. However, the main advantages of this method; namely, saving costs and increased accessibility to hearing services, can lead to a faster diagnosis of hearing impairment, especially in poor areas.

• ETRI Journal
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• 제25권1호
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• pp.19-24
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• 2003

This paper describes the performance of a Ku-band 5-bit monolithic phase shifter with metal semiconductor field effect transistor (MESFET) switches and the implementation of a ceramic packaged phase shifter for phase array antennas. Using compensation resistors reduced the insertion loss variation of the phase shifter. Measurement of the 5-bit phase shifter with a monolithic microwave integrated circuit demonstrated a phase error of less than $7.5{\circ}$ root-mean-square (RMS) and an insertion loss variation of less than 0.9 dB RMS for 13 to 15 GHz. For all 32 states of the developed 5-bit phase shifter, the insertion losses were $8.2{\pm}1.4$dB, the input return losses were higher than 7.7 dB, and the output return losses were higher than 6.8 dB for 13 to 15 GHz. The chip size of the 5- bit monolithic phase shifter with a digital circuit for controlling all five bits was 2.35 mm ${\times}$1.65 mm. The packaged phase shifter demonstrated a phase error of less than $11.3{\circ}$ RMS, measured insertion losses of 12.2 ${\pm}$2.2 dB, and an insertion loss variation of 1.0 dB RMS for 13 to 15 GHz. For all 32 states, the input return losses were higher than 5.0 dB and the output return losses were higher than 6.2 dB for 13 to 15 GHz. The size of the packaged phase shifter was 7.20 mm${\times}$ 6.20 mm.

• 한국지진공학회논문집
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• 제11권4호
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• pp.13-23
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• 2007

This paper focuses on providing a practical approach for decision making in Performance-Based Design (PBD). Satisfactory performance is defined by several performance objectives that place limits on direct (monetary) loss and on a tolerable probability of collapse. No specific limits are placed on conventional engineering parameters such as forces or deformations, although it is assumed that sound capacity design principles are followed in the design process. The proposed design procedure incorporates different performance objectives up front, before the structural system is created, and assists engineers in making informed decisions on the choice of an effective structural system and its stiffness (period), base shear strength, and other important global structural parameters. The tools needed to implement this design process are (1) hazard curves for a specific ground motion intensity measure, (2) mean loss curves for structural and nonstructural subsystems, (3) structural response curves that relate, for different structural systems, a ground motion intensity measure to the engineering demand parameter (e.g., interstory drift or floor acceleration) on which the subsystem loss depends, and (4) collapse fragility curves. Since the proposed procedure facilitates decision making in the conceptual design process, it is referred to as a Design Decision Support System, DDSS. Implementation of the DDSS is illustrated in an example to demonstrate its practicality.

• 전기학회논문지P
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• 제56권2호
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• pp.74-82
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• 2007

Interior permanent magnet synchronous motor(IPMSM) has become a popular choice in electric vehicle applications, due to their excellent power to weight ratio. This paper proposes efficiency optimization control of IPMSM drive using adaptive fuzzy learning control fuzzy neural network (AFLC-FNN) controller. In order to maximize the efficiency in such applications, this paper proposes the optimal control method of the armature current. The controllable electrical loss which consists of the copper loss and the iron loss can be minimized by the optimal control of the armature current. The minimization of loss is possible to realize efficiency optimization control for the proposed IPMSM. The optimal current can be decided according to the operating speed and the load conditions. This paper considers the design and implementation of novel technique of high performance speed control for IPMSM using AFLC-FNN controller. Also, this paper proposes speed control of IPMSM using AFLC-FNN and estimation of speed using ANN controller. The back propagation neural network technique is used to provide a real time adaptive estimation of the motor speed. The proposed control algorithm is applied to IPMSM drive system controlled AFLC-FNN controller, the operating characteristics controlled by efficiency optimization control are examined in detail.