• Journal of Advanced Navigation Technology
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• v.17 no.6
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• pp.693-699
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• 2013

In this paper, ${\pi}/4$-DQPSK modem according to ITU-R M.1842-1 recommendation Annex1 is investigated and simulated. At first, standardization and technical trend of VHF maritime mobile communication are introduced. The ${\pi}/4$-DQPSK modem defined in the Annex1 should support 28.8Kbps bit transmission rate within 25KHz frequency bandwidth. We describe the system model and simulation process of ${\pi}/4$-DQPSK modem transmitter and receiver design with RRC(Root Raised Cosine) transmitter and receiver filter. Then we suggest various graphical simulation results(time domain signals, constellation, power spectral density according to roll-off factor, eye diagram), and show simulated BER performance of the modem. From the simulation results, it is shown that roll-off factor of RRC filter affects to BER performance according to SNR and the designed simulation model meets the spectrum mask requirement suggested in ITU-R M.1842-1 recommendation.

• Journal of KIBIM
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• v.9 no.3
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• pp.41-53
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• 2019

As a central part in smart construction, BIM has been rapidly spread in construction industry at large. However, the level of applying BIM in construction stage is still relatively lower than that in design stage due to unclear application method, inadequate design BIM model, technical faults of BIM itself, etc. Under these circumstances, public owners inevitably need to adjust the scope and pace in BIM application considering their internal support and capabilities of contractors. This study aims to suggest major BIM-applicable tasks during construction stage in the process of establishing gradual long-term and short-term introduction strategy for public apartment housing projects. Those major tasks were identified with the combination of the importance of tasks and the future benefits of BIM using IPA method. To do so, the degrees of contribution to achieving objectives in construction, current task execution, and communication requirement were investigated by internal site managers. On the other hand, the expected benefits and current level of using BIM were assessed by BIM experts. Among operational tasks by phases, design review, construction plan review, making as-built drawing, etc. were categorized as major tasks. In addition, progress control, regular meeting, master schedule development, work inspection, on-site quality check, etc. were also drawn as major tasks by management areas. The results of this study will provide the useful reference for owners concerned about the introduction of new technologies.

• Journal of the Korea Institute of Building Construction
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• v.19 no.2
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• pp.193-200
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• 2019

In the context of increasing threats of EMP by neighboring countries in the security situation on the Korean peninsula, EMP protection facilities are a very important means of ensuring military operational capability. These EMP protection facilities should be constructed by comprehensively judging various factors about operation units. However, Defense Military Facilities Criteria and National Technical Guideline for EMP protection require at least 80dB shielding effectiveness without considering other options. In this study, we use objective and statistical methods to refine the consideration of the required EMP protection level based on the opinions of the experts. To do this, the Delphi technique is used for this study, and the survey was conducted from 53 experts related to EMP protection standard in the military and civilian sectors. The first questionnaire investigated the appropriate level of EMP protection, and the second questionnaire analyzed the factors considered in establishing EMP protection level. As a result of the factor analysis on the opinions of the experts, it was concluded that the EMP protection requirement level should be determined by variables of METT + TC.

• Journal of Korean Neurosurgical Society
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• v.62 no.6
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• pp.712-722
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• 2019

Objective : Although magnetic resonance guided focused ultrasound (MRgFUS) has been used as minimally invasive and effective neurosurgical treatment, it exhibits some limitations, mainly related to acoustic properties of the skull barrier. This study was undertaken to identify skull characteristics that contribute to optimal ultrasonic energy transmission for MRgFUS procedures. Methods : For ex vivo skull experiments, various acoustic fields were measured under different conditions, using five non-embalmed cadaver skulls. For clinical skull analyses, brain computed tomography data of 46 patients who underwent MRgFUS ablations (18 unilateral thalamotomy, nine unilateral pallidotomy, and 19 bilateral capsulotomy) were retrospectively reviewed. Patients' skull factors and sonication parameters were comparatively analyzed with respect to the cadaveric skulls. Results : Skull experiments identified three important factors related skull penetration of ultrasound, including skull density ratio (SDR), skull volume, and incidence angle of the acoustic rays against the skull surface. In clinical results, SDR and skull volume correlated with maximal temperature (Tmax) and energy requirement to achieve Tmax (p<0.05). In addition, considering the incidence angle determined by brain target location, less energy was required to reach Tmax in the central, rather than lateral targets particularly when compared between thalamotomy and capsulotomy (p<0.05). Conclusion : This study reconfirmed previously identified skull factors, including SDR and skull volume, for successful MRgFUS; it identified an additional factor, incidence angle of acoustic rays against the skull surface. To guarantee successful transcranial MRgFUS treatment without suffering these various skull issues, further technical improvements are required.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.8
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• pp.1022-1029
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• 2020

We investigate the joint selection problem of the transmit power level and the best access point for multi-access points. We further reduce the transmit power by jointly optimizing the transmit power and the access point selection. Our aim is to minimize the total transmit power, while each terminal maintains minimum signal to interference ratio requirement. We observe that the optimum solution can be achieved through proposed iterative algorithm for both TA link and AT link. Simulation results show that proposed algorithm (joint optimization of transmit power level and access point) outperforms the algorithm which optimizes the transmit power only. We also observe that the duality between the TA link and AT link does not hold in multi-access points environment. Accordingly, the resulting power vectors and the access point vectors for TA link and AT link are different in general.

• Journal of Navigation and Port Research
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• v.46 no.6
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• pp.501-508
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• 2022

The flow of global digitalization is leading to the emergence of a decentralized system environment based on blockchain or distributed ledger technology in the fields of economy, identity authentication, and logistics. Accordingly, a requirement that public services be searchable from several decentralized maritime service registries (MSRs) has been derived in terms of the discoverability of e-navigation services. This study describes a decentralized MSR environment composed of the MSR ledger and multiple local MSRs, and it has implemented a service search system that can search global e-navigation services in the environment through a web browser. This system is a decentralized application that dynamically generates service attributes, geometry information, and free text queries, and that provides users with relevant MSR and service access information from search results that are registered in the MSR ledger. In this study, we tested the established decentralized MSR environment and the system that performs service search within that environment, and we discussed its advantages and limitations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.11
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• pp.4084-4104
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• 2021

Visual place recognition (VPR) is a fundamental yet challenging task of mobile robot navigation and localization. The existing VPR methods are usually based on some pairwise similarity of image descriptors, so they are sensitive to visual appearance change and also computationally expensive. This paper proposes a simple yet effective four-step method that achieves adaptive convolutional neural network (CNN) landmark matching for VPR. First, based on the features extracted from existing CNN models, the regions with higher significance scores are selected as landmarks. Then, according to the coordinate positions of potential landmarks, landmark matching is improved by removing mismatched landmark pairs. Finally, considering the significance scores obtained in the first step, robust image retrieval is performed based on adaptive landmark matching, and it gives more weight to the landmark matching pairs with higher significance scores. To verify the efficiency and robustness of the proposed method, evaluations are conducted on standard benchmark datasets. The experimental results indicate that the proposed method reduces the feature representation space of place images by more than 75% with negligible loss in recognition precision. Also, it achieves a fast matching speed in similarity calculation, satisfying the real-time requirement.

• Journal of the Korean Orthopaedic Association
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• v.54 no.2
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• pp.91-99
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• 2019

Most patients experience pain relief and functional improvement after arthroscopic rotator cuff repair. In some patients, however, symptoms still remain after surgery. Failed rotator cuff repair is a complex outcome of biological, technical, and traumatic factors. Moreover, re-tears might or might not be the main cause for patients with persistent pain after rotator cuff repair. Therefore, a thorough understanding of the patient's history, physical examination, and appropriate imaging studies will be needed to evaluate and manage these patients. The patient's age, functional requirement, quality of the rotator cuff, preoperative range of motion, quality of the deltoid, and glenohumeral arthritis are factors to consider before performing revisional rotator cuff repair. Preoperative patient education is as important as the surgical technique for successful revisional rotator cuff repair.

• Journal of the Korean Society for information Management
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• v.41 no.2
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• pp.155-183
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• 2024

The purpose of this study is to understand the information use experience of total blindness with OTT. To achieve the study purpose, in-depth interview with nine total blindness using a semi-structured checklist was conducted. The data were analyzed using Colaizzi's phenomenological method. This study has found 5 categories, 13 theme clusters, and 47 themes. The five categories are as follows: 1) the purpose of information use, 2) difficulties of information use, 3) handling of difficulty in information seeking, 4) perception and feeling, 5) improvement requirement The implications of this study are as follows; 1) There are no significant differences between total blindness and the general people of Information request topic in the use of OTT, 2) negative experience was connected with the accessibility with OTT, 3) there is a demand of better conditions with technical sides of OTT, 4) On the whole, they have a positive perception with OTT services.

• 대한공업교육학회지
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• v.33 no.1
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• pp.149-168
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• 2008

The purpose of this study is to verify the effect of PSpice instruction on academic achievement in 'Combination logic circuit' unit of 'Digital Logic Circuit' in industrial high school. Three kinds of null hypotheses were formulated. Two classes of the third grade of C technical high school in Gyeong-buk were divided into experimental group and control group in order to verify null hypotheses. In the experimental design, 'Non-equivalent control group pretest-posttest' model was utilized. This experiment was conducted for six classes, the experimental group was applied to PSpice instruction method before the circuit traning while the control group was applied to traditional lecture oriented method before the circuit traning. Window SPSS 10.0 korean language version program was used for the data analysis and independent sample t-test was used to identify the average of each group. Significance level was set to .05 level. The results obtained in this study were as follows; First, PSpice instruction had not an effect on academic achievement according to a group type. However, these instruction had an effect on the following sub-domains; the psychomotor domain. Second, PSpice instruction had not an effect on academic achievement according to a studies level. However, these instruction for middle and low level students had an effect on the cognitive and psychomotor domain, and for middle level students had an effect on the affective domain. Third, PSpice instruction had not an effect on shortening of a training requirement. However, this instruction for low level students had an effect on shortening of a training requirement. The study results of simulation instruction was chiefly efficient in the psychomotor domain. We could know that simulation instruction is efficient as went to a low level students than an upper level students. Thus, We may make the study effectiveness in various instruction method.