• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.1
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• pp.107-117
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• 2011

In this study, the effect of temperature-induced uncertainty to damage monitoring using acceleration-impedance response features is analyzed for presterssed concrete(PSC) girder bridges. Firstly, a damage monitoring algorithm using global and local vibration features is designed. As global and local features, acceleration and electro-mechanical impedance features are selected respectively. Secondly, the temperature effect on the acceleration and impedance features for a lab-scaled PSC girder is experimentally analyzed. From the experimental results, compensation models for temperature-acceleration features and temperature-impedance features are estimated. Finally, the feasibility of the acceleration-impedance-based damage monitoring technique using the compensation model is evaluated in the PSC girder for which a set of prestress-loss and flexural stiffness loss cases were dynamically tested.

• Journal of Korean Society for Atmospheric Environment
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• v.25 no.1
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• pp.15-25
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• 2009

Donghae city is one of the most representative cement industrial city in Korea. The area is faced with the East Sea to the East and with high montane region of Tae-Back mountain range to the West. Many pollutant sources of air pollution are located near the coast, but the largest point sources of the region are located at the bottom of the mountain area in Donghae city. The local wind is highly affected by local topography and plays an important role in transport and dispersion of contaminants from the pollution sources. This study was designed to evaluate enhancement of MM5 predictions by using Four Dimensional Data Assimilation (FDDA), the SONDE data and the national meteorological station, data only. The alternative meteorological fields predicted with and without FDDA were used to simulate spatial and temporal variations of NOx in combined with Atmospheric Dispersion Models (CALPUFF). For the modeling domain, the alternative meteorological fields with 1.1 km spatial resolution were interpolated to the CALMET with 0.5 km resolution. The vertical layers set to have 35 and 12 layers for MM5 and CALPUFF, respectively. MM5 with the FDDA did not resulted in significant improvement of meteorological field prediction in Donghae region, which is primarily because of complex geography and wind scheme. The result of CALPUFF, however, showed reduction of uncertainty errors by using the interpolation scheme of the actual measurement data.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.176-181
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• 2010

The evaluation of shear modulus (or shear wave velocity) profile of the site is very important in various fields of geotechnical engineering. In the field, there exist spatial variations of shear modulus that case uncertainty in the geotechnical analysis or design. So it is necessary to evaluate the spatial variation of shear wave velocities of the soil site. In this study, the HWAW method is applied to the determination of a 3-D Vs map of soil site. The HWAW method, which is based on harmonic wavelet transforms, has been developed to determine phase and group velocities of waves. The HWAW method uses only the signal portion of the maximum local signal/noise ratio to evaluate the phase velocity in order to minimize the effect of the noise. The field testing of this method is relatively simple and fast because only one experimental setup, which consists of one pair of receivers on the surface, is needed using a short receiver spacing setup (1~3m). These characteristics make it possible to determine detailed local Vs profile in the site with lateral Vs variation and to evaluate 3-D Vs map by performing a series of tests on the grid. To estimate the applicability of the proposed method, field tests were performed. Through field applications validity and applicability of the proposed method were verified.

• Journal of the Korean earth science society
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• v.36 no.7
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• pp.643-648
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• 2015

Equations that could estimate the local magnitude of historical earthquakes, being difficult to calculate, in Sino-Korea craton was obtained using instrumental earthquake data for 22 Korean and 46 northeastern Chinese events. The obtained equations from intensity $I_0$ is $M_L=1.7+0.57{\times}I_0$. The equation from felt area FA for the Korean Peninsula is $M_L=4.29-1.34{\times}log(FA)+0.28{\times}log^2(FA)$. When the information on earthquake damage, effects, and felt area is all recorded at the same time, the former equation of intensity is more feasible than that of felt area due to uncertainty in earthquake felt area.

• Journal of Korean Society on Water Environment
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• v.25 no.4
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• pp.481-493
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• 2009

This study was conducted to performance appraisal of Total Maximum Daily Loads (TMDLs), especially in terms of performance on development & reduction plan and water quality status of unit watershed. Because load allocations for pollution sources were predicted redundantly by uncertainty of prediction, TMDLs master plan has been frequently changed to acquire load allocation for local development. Therefore, It need to be developed more resonable prediction techniques of water pollution sources to preventing the frequent change. It is suggested that the reduction amount have to be distributed properly during the planning period. In other words, it has not to be concentrated on the specific year (especially final year of the planning period). The reason why, if the reduction amount concentrate on the final year of the planning period, allotment loading amount could not be achieved in some cases (e.g., insufficiency of budget, extension of construction duration). If the development plan was developed including uncertain developments, it is necessary to be developed reduction plan considered with them. However, some of the plans in the reduction plan could not be accomplished in some case. Because, it is not considered financial abilities of local governments. Consequently, development plan must be accomplished to avoid uncertain developments, and to consider financial assistance to support the implementation of effective plan. Water quality has been improved in many unit watersheds due to the TMDLs, especially in geum river and yeongsang/seomjin river.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.808-811
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• 2015

Cognitive radio has been proposed as a promising dynamic spectrum allocation paradigm. In cognitive radio, spectrum sensing is a fundamental procedure that enables secondary users (unlicensed) employing unused portion of spectrum of primary users (licensed) without causing harmful interference. However, the performance of single-user spectrum-sensing scheme was limited by fading, noise uncertainty shadowing and hidden node problem. Cooperative spectrum sensing was proposed to mitigate these problem. In this paper, we observe cooperative sensing scheme with energy detection using three adaptive thresholds for local decision, which can mitigate sensing failure problem and improve sensing performance at local node. In cooperative scheme we employed OR rules as decision combining at fusion center. We evaluate our scheme through computer simulation, and the results show that with OR combination rule our scheme can achieve best performance than other schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.9
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• pp.798-809
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• 2013

In this paper, we propose robust relay and destination filter design methods for the multi-user peer-to-peer amplify-and-forward relaying systems while taking imperfect channel knowledge into consideration. Specifically, the relay and destination filter sets are developed to minimize the sum mean-squared-error (MSE). We first present a robust joint optimum relay and destination filter calculation method with an iterative algorithm. Motivated by the need to reduce computational complexity of the iterative scheme, we then formulate a simplified sum MSE minimization problem using the relay filter decomposability, which lead to two robust sub-optimum non-iterative design methods. Finally, we propose robust modified destination filter design methods which require only local channel state information between relay node and a specific destination node. The analysis and simulation results verify that, compared with the optimum iterative method, the proposed non-iterative schemes suffer a marginal loss in performance while enjoying significantly improved implementation efficiencies. Also it is confirmed that the proposed robust filter design methods provide desired robustness in the presence of channel uncertainty.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.4
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• pp.417-428
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• 2021

Since future maintenance cost estimation of infrastructure involves uncertainty, it is important to make use of a failure prediction model. However, it is difficult for local governments to develop accurate failure prediction models applicable to infrastructure due to a lack of budget and expertise. Therefore, this study estimated the life expectancy of asphalt road pavement of national highways using the Bayesian Markov Mixture Hazard model. In addition, in order to accurately estimate life expectancy, environmental variables such as traffic volume, ESAL (Equivalent Single Axle Loads), SNP (Structural Number of Pavement), meteorological conditions, and de-icing material usage were applied to retain reliability of the estimation results. As a result, life expectancy was estimated from at least 13.09 to 19.61 years by region. By using this approach, it is expected that it will be possible to estimate future maintenance cost considering local failure characteristics.

• Journal of Korean society of Dental Hygiene
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• v.18 no.6
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• pp.1067-1077
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• 2018

Objectives: The purpose of the study is to investigate the opinions of some local clinical dental hygienists on medical personnel of dental hygienists. It will be for provide the Future dental hygienist basic data necessary for medical personnel. Methods: A self-reported questionnaire was completed by 171 dental hygienists in Busan and Gyeongnam from December 1, 2017 to January 31, 2018. Structured questionnaires were uesd for analysis. The questionnaire consisted of general characteristics of the subjects(7 items), medical personnel necessity and opinions of dental hygienist(2 items), the opinions of distinction of the task between dental hygienists and other personnel(2 items), many frequency task in the dental clinic. The collected data were analyzed using frequency, percentage, descriptive statistics and ANOVA using IBM SPSS VER 20.0. Results: 89.5% of the dental hygienists required medical personnel of dental hygienist, the opinions on the necessity were as follows: 'role and quality improvement as oral health professionals', 'lack of legislation and application of dental hygienists duties'. There was no difference reason between dental hygienists and other personnel on duties, the reason were investigated to uncertainty of dental hygienist system, lack of dental hygienist workforce, dentists lack awareness of dental hygienist expertise. There was surveyed by the current many frequency duties in the dental clinic, assist for dental treatment, Oral health education and counselling, Preventive dental treatment. Conclusions: Legal guarantees for clinical dental hygienists work are absolutely required. Therefore, relevant government agencies and related organizations should resolve the contradiction of the legal system of medical law and medical technicians. The clinical dental hygienists should be promoted to medical personnel through the amendment of the medical law so that the duties practiced by the dental hygienist can be matched with the legal practice.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.463-471
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• 2024

Average and local convective heat transfer coefficients of nitrogen are measured experimentally in an electrically heated circular tube for a range of Reynolds number from 1.08 × 10⁴ to 3.60 × 10⁴, and wall-to-bulk temperature ratio from 1.01 to 1.77. The exit Mach number is up to 0.17, and the heat flux is up to 46 kW·m^-2. The molybdenum test section has a 62 diameters heated section with an inside diameter of 5 mm and a 30 diameters entrance section to ensure the fully-developed flow. Uncertainty of Nusselt number is less than 1.6 % in this study. The results indicate that the average heat transfer correlations evaluated by both the bulk and the modified film Reynolds numbers agree well with the experimental data. The local heat transfer results based on bulk properties are compared with previous empirical correlations. New prediction correlations are recommended which are significantly affected by the property variation and heated length. The comparison between the proposed correlations and experimental points shows that 88 % of experimental data fall into an error of 10 %, and almost all data are within an error of 20 %.