• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.12
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• pp.51-57
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• 2004

A simple fiber length measurement technique has been demonstrated by using a self-seeding laser oscillation of a Fabry-Perot laser diode. We induced a self-seeding laser oscillation through a closed-loop by adjusting the modulation frequency of a Fabry-Peort laser diode when the output optical pulse of the laser reinjected into the laser after passing through the closed-loop. The length of a fiber-under-test was calculated from the difference between my two modulation frequencies at which self-seeding laser oscillation occurs at a specific mode. We have experimentally confirmed the technique for various fiber lengths from 0.1 km to 75 km. The relative error between the measurement result of the proposed technique and that of a commercial instrument was less than 0.24 %. The repeatability of the proposed technique was better than 0.1 %.

• Journal of Oriental Neuropsychiatry
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• v.31 no.2
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• pp.89-99
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• 2020

Objectives: The purpose of this study was to identify the needs of bio-signal devices for the diagnosis, assessment, and analysis of neurocognitive disorder in Korean medicine (KM) hospitals and clinics. Methods: A questionnaire was developed to survey the current status of medical device use, and diagnosis and interventions for patients with cognitive disorders in KM hospitals and clinics. November 11~December 2, 2019, 114 responses (71.9% completed) were collected by internet-based questionnaires from the members of the Korean society of Oriental Neuropsychiatry. Results: The clinical requests were in the descending order of hematology analyzer, ultrasound imaging system, and electroencephalography among the 15 most commonly used devices of which research would support for their clinical usability. The biosignal-based devices showed the highest research demands for patients with mild cognitive impairment rather than more severe stages of cognitive impairment. Prevention rather than diagnosis, or several treatment regimens was the strongest clinical area of the KM for patients with neurodegenerative cognitive impairment. Many responded that five to 10 minutes of test duration and 20,000 won to 30,000 won of cost would be appropriated for a new device to be developed. Conclusions: There were strong demands for the development of bio-signal devices for neurocognitive disorders among the KM doctors. Specifically, it showed high needs for the technology that can be used in the prevention area of cognitive disorders. Additionally, new medical devices to assess cognitive functions and to obtain KM pattern-related information were the high needs.

• Computers and Concrete
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• v.14 no.3
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• pp.299-313
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• 2014

Effects of polypropylene (PP) fibers, steel fibers (SF) and hybrid on the properties of highstrength fiber reinforced self-consolidating concrete (HSFR-SCC) under different volume contents are investigated in this study. Comprehensive laboratory tests were conducted in order to evaluate both fresh and hardened properties of HSFR-SCC. Test results indicated that the fiber types and fiber contents greatly influenced concrete workability but it is possible to achieve self consolidating properties while adding the fiber types in concrete mixtures. Compressive strength, dynamic modulus of elasticity, and rigidity of concrete were affected by the addition as well as volume fraction of PP fibers. However, the properties of concrete were improved by the incorporation of SF. Splitting tensile and flexural strengths of concrete became increasingly less influenced by the inclusion of PP fibers and increasingly more influenced by the addition of SF. Besides, the inclusion of PP fibers resulted in the better efficiency in the improvement of toughness than SF. Furthermore, the inclusion of fibers did not have significant effect on the durability of the concrete. Results of electrical resistivity, chloride ion penetration and ultrasonic pulse velocity tests confirmed that HSFR-SCC had enough endurance against deterioration, lower chloride ion penetrability and minimum reinforcement corrosion rate.

• Advances in concrete construction
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• v.9 no.2
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• pp.207-215
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• 2020

This paper describes the experimental studies carried out to determine the properties of fresh and hardened concrete with Recycled Plastic Waste (RPW) as a partial replacement material for fine aggregates. In the experimental study, RPW was used for replacing river sand and manufactured sand (M sand) aggregates in concrete. The replacement level of fine aggregates was ranging from 5% to 20% by volume with an increment of 5%. M40 grade of concrete with water cement ratio of 0.40 was used in this study. Two different types of RPW were used, and they are (i) un-activated RPW and (ii) activated RPW. The activated RPW was obtained by alkali activation of un-activated RPW using NaOH solution. The hardened properties of the concrete determined were dry density, compressive strength, split tensile strength, flexural strength and ultrasonic pulse velocity (UPV). The properties of the concrete with river sand, M sand, activated RPW and un-activated RPW were compared and inferences were drawn. The effect of activation using NaOH solution was investigated using FT-IR study. The micro structural examination of hardened concrete was carried out using Scanning Electron Microscopy (SEM). The test results show that the strength of concrete with activated RPW was more than that of un-activated RPW. From the results, it is evident that it is feasible to use 5% un-activated RPW and 15% activated RPW as fine aggregates for making concrete without affecting the strength properties.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.2
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• pp.133-140
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• 2020

We discuss the method of a high precision range trigger and generation for a high range resolution radar. To verify the designed range resolution performance, we use test-equipments which can absolutely make a precision range shorter than the desined range resolution. The accuracy of generated range is proportional to the system reference clock. However, the system main processor is limited to input reference clocks and a higher available one is expensive in the conventional method. To solve this problem, we proposed that the range trigger and generation method using multi-phase-shiftings and integration. Through a experiment, we verified that the proposed method made problems which can be ocurred in the conventional method clear.

• Korean Journal of Clinical Pharmacy
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• v.10 no.3
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• pp.107-110
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• 2000

Theophylline and $\beta$-adrenergic agonists are frequently used together in patients with respiratory diseases. However the clinical impact of $\beta_2$-adrenergic agonists on the blood concentration of theophylline is not fully evaluated. Formoterol, a newly available oral ${\beta}_2$-adrenergic agonist is frequently used in pediatric respiratory patients. The objective of this study was to investigate the effect of oral formoterol on theophylline's blood concentration. Randomized prospective study was conducted. Twenty-four children were enrolled on the study. Their age ranged 2 to 73 months (mean 35.8 months). Theophylline group (12 patients) received 10 mg/kg/day of for theophylline orally. Theophylline/formoterol group (12 patients) received 10 mg/kg/day of theophylline and $4\;{\mu}g/kg/day$ of formoterol orally. All medications were administered at least for 5 days starting on admission day. Theophylline's trough concentrations were obtained on days 3 and day 5. Pulse rates were recorded before the study medications were given on admission, and days 3 and day 5. Statistical significance was calculated by two-tailed Student's t-test. Theophylline's levels in children given theophylline and formoterol together were lower an those given theophylline alone ($6.38\pm0.90\;{\mu}g/ml\;vs\;7.43\pm0.77\;{\mu}g/ml$ on day 3(p<0.05), $5.62\pm0.56\;{\mu}g/ml\;vs.\;6.78\pm0.61\;{\mu}g/ml$ on day 5 (p<0.05)). In both groups, theophylline's trough concentration on day 5 were lower than day 3. There was no significant side effects in both groups. In conclusion, the new ${\beta}_2$ selective adrenergic agonist formoterol reduced serum theophylline levels in children with respiratory diseases. Further investigation is needed to clarify the long term effect of this drug interaction.

• Journal of IKEEE
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• v.19 no.1
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• pp.118-123
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• 2015

According to the recent report, solar street lamp connected to a non Maximum Power Point Tracking(MPPT) charger, can lead to a system-wide decline in power output with as much as 30%. This paper proposes the charge controller with direct duty ration control for 250W solar street lamp in order to improve the efficiency of photovoltaic from these output power reduction. This paper covers the Pulse Width Modulation(PWM) controller and power conversion topology and analyze the MPPT method for charge controller. The power conversion part consists of push pull converter based on PWM controller using 8bit MCU in order to have lower manufacturing cost. The PWM controller with direct duty ratio control algorithm is constantly tracking the maximum power point of photovoltaic module and increases energy output power. The test results shows 97.1~97.4% MPPT efficiency and the experimental hardware is implemented based on the solar simulator condition for 241W. Thus, the implemented charge controller shows its feasibility for the real application, especially under solar street lamp.

• Structural Engineering and Mechanics
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• v.64 no.2
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• pp.243-257
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• 2017

Investigating the properties and durability of high-strength concrete exposed to sulfuric acid attack for the purpose of its application in structures exposed to this acid is of outmost importance. In this research, the resistance and durability of high-strength concrete containing macro-polymeric or steel fibers together with the pozzolans of silica fume or nano-silica against sulfuric acid attack are explored. To accomplish this goal, in total, 108 high-strength concrete specimens were made with 9 different mix designs containing macro-polymeric and steel fibers at the volume fractions of 0.5, 0.75, and 1.0%, as well as the pozzolans of silica fume and nano-silica with the replacement levels of 10 and 2%, respectively. After placing the specimens inside a 5% sulfuric acid solution in the periods of 7, 21, and 63 days of immersion, the effect of adding the fibers and pozzolans on the compressive properties, ultrasonic pulse velocity (UPV), and weight loss of high-strength concrete was investigated and the respective results were compared with those of the reference specimens. The obtained results suggest the dependency of the resistance and durability loss of high-strength concrete against sulfuric acid attack to the properties of fibers as well as their fraction in concrete volume. Moreover, compared with using nano-silica, using silica fume in the fibrous concrete mix leads to more durable specimens against sulfuric acid attack. Finally, an optimum solution for the design parameters where the crushing load of high-strength fibrous concrete is maximized was found using response surface method (RSM).

• Earthquakes and Structures
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• v.18 no.1
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• pp.73-82
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• 2020

With the coal mining depth increasing, both stress and gas pressure rapidly enhance, causing coal and gas outburst risk to become more complex and severe. The conventional method for prediction of coal and gas outburst adopts one prediction index and corresponding critical value to forecast and cannot reflect all the factors impacting coal and gas outburst, thus it is characteristic of false and missing forecasts and poor accuracy. For the reason, based on analyses of both the prediction indicators and the factors impacting coal and gas outburst at the test site, this work carefully selected 6 prediction indicators such as the index of gas desorption from drill cuttings Δh₂, the amount of drill cuttings S, gas content W, the gas initial diffusion velocity index ΔP, the intensity of electromagnetic radiation E and its number of pulse N, constructed the Bayes discriminant analysis (BDA) index system, studied the BDA-based multi-index comprehensive model for forecast of coal and gas outburst risk, and used the established discriminant model to conduct coal and gas outburst prediction. Results showed that the BDA - based multi-index comprehensive model for prediction of coal and gas outburst has an 100% of prediction accuracy, without wrong and omitted predictions, can also accurately forecast the outburst risk even for the low indicators outburst. The prediction method set up by this study has a broad application prospect in the prediction of coal and gas outburst risk.

• Computers and Concrete
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• v.21 no.4
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• pp.407-417
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• 2018

Concrete which is a composite material is one of the most important construction materials. Compressive strength is a commonly used parameter for the assessment of concrete quality. Accurate prediction of concrete compressive strength is an important issue. In this study, we utilized an experimental procedure for the assessment of concrete quality. Firstly, the concrete mix was prepared according to C 20 type concrete, and slump of fresh concrete was about 20 cm. After the placement of fresh concrete to formworks, compaction was achieved using a vibrating screed. After 28 day period, a total of 100 core samples having 75 mm diameter were extracted. On the core samples pulse velocity determination tests and compressive strength tests were performed. Besides, Windsor probe penetration tests and Schmidt hammer tests were also performed. After setting up the data set, twelve artificial intelligence (AI) models compared for predicting the concrete compressive strength. These models can be divided into three categories (i) Functions (i.e., Linear Regression, Simple Linear Regression, Multilayer Perceptron, Support Vector Regression), (ii) Lazy-Learning Algorithms (i.e., IBk Linear NN Search, KStar, Locally Weighted Learning) (iii) Tree-Based Learning Algorithms (i.e., Decision Stump, Model Trees Regression, Random Forest, Random Tree, Reduced Error Pruning Tree). Four evaluation processes, four validation implements (i.e., 10-fold cross validation, 5-fold cross validation, 10% split sample validation & 20% split sample validation) are used to examine the performance of predictive models. This study shows that machine learning regression techniques are promising tools for predicting compressive strength of concrete.