• Wind and Structures
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• v.10 no.4
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• pp.301-314
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• 2007

The lever-type active multiple tuned mass dampers (LT-AMTMD), consisting of several lever-type active tuned mass dampers (LT-ATMD), is proposed in this paper to attenuate the vibrations of long-span bridges under the excitation directly acting on the structure, rather than through the base. With resorting to the derived analytical-expressions for the dynamic magnification factors of the LT-AMTMD structure system, the performance assessment then is conducted on the LT-AMTMD with the identical stiffness and damping coefficient but unequal mass. Numerical results indicate that the LT-AMTMD with the actuator set at the mass block can provide better effectiveness in reducing the vibrations of long-span bridges compared to the LT-AMTMD with the actuator set at other locations. An appealing feature of the LT-AMTMD with the actuator set at the mass block is that the static stretching of the spring may be freely adjusted in accordance with the practical requirements through changing the location of the support within the viable range while maintaining the same performance (including the same stroke displacement). Likewise, it is shown that the LT-AMTMD with the actuator set at the mass block can further ameliorate the performance of the lever-type multiple tuned mass dampers (LT-MTMD) and has higher effectiveness than a single lever-type active tuned mass damper (LT-ATMD). Therefore, the LT-AMTMD with the actuator set at the mass block may be a better means of suppressing the vibrations of long-span bridges with the consequence of not requiring the large static stretching of the spring and possessing a desirable robustness.

• Journal of Digital Contents Society
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• v.16 no.4
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• pp.513-522
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• 2015

Various types of digital displays from PC monitor up to smart watch have been developed in response to the dramatic technological progress of electronics. Accordingly, web content creators have the need to provide web contents respectively depending on the different display environments, which increases production time and costs. As a technique for overcoming this, the responsive web design method has been proposed, which means a web page with the size of the screen being adjusted depending on the types of display. Although the responsive web system is increasingly implemented in the region of contents search pages of domestic portals, there are still many cases that contents are implemented separately for PC and for mobile. In this paper, we investigate the responsive types of the web implementation of contents search pages of domestic portal, and propose an efficient new UI for responsive web to individual types of contents search pages which responsive design is not applied to.

• The Korean Journal of Pharmacology
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• v.17 no.1 s.28
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• pp.27-32
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• 1981

It has been known that ethanol stimulates the secretion of gastric acid regardless of its route of administration. Recently, however, some studies have challenged this view and claimed that ethanol inhibits the gastric acid secretion. This study was undertaken to investigate the effects of ethanol on the gastric acid secretion in anesthetized rat in respect to the route of administration and the concentration of alcohol. Normal saline (pH adjusted to 6.0) was used as standard perfusion solution and ethanol was mixed as 0.8, 1.7, 5, 10 and 20%. Four ml of perfusion fluid was given into stomach via gastric tube and drained from duodenal tube every 5 min. Acid secretion was measured by back titration to pH 6.0 with N/20 NaOH and expressed as ${\mu}Eq/5$ min. Low concentration of ethanol up to 1.7% in perfusion solution caused little changes in acid secretion, but moderate concentration such as perfusion of 5% or 10% ethanol solution inhibited both the basal and histamine-induced gastric secretion. Moreover, loss of perfused acid was seen by 20% ethanol, which means back diffusion of hydrogen ions into the gastric mucosa. However, intravenous administration of ethanol, maintained at the level of 0.1% alcohol in blood, caused significant stimulation of gastric acid. We, therefore, conclude that in anesthetized rat ethanol has dual effects on acid secretion, i.e., inhibiting and enhancing by oral and intravenous administration, respectively, but further investigation is necessary to clarify these effects.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.7
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• pp.339-349
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• 2001

This paper suggests an optimal identification method for complex and nonlinear system modeling that is based on Fuzzy-Neural Networks(FNN). The proposed Hybrid Identification Algorithm is based on Yamakawa's FNN and uses the simplified inference as fuzzy inference method and Error Back Propagation Algorithm as learning rule. In this paper, the FNN modeling implements parameter identification using HCM algorithm and hybrid structure combined with two types of optimization theories for nonlinear systems. We use a HCM(Hard C-Means) clustering algorithm to find initial apexes of membership function. The parameters such as apexes of membership functions, learning rates, and momentum coefficients are adjusted using hybrid algorithm. The proposed hybrid identification algorithm is carried out using both a genetic algorithm and the improved complex method. Also, an aggregated objective function(performance index) with weighting factor is introduced to achieve a sound balance between approximation and generalization abilities of the model. According to the selection and adjustment of a weighting factor of an aggregate objective function which depends on the number of data and a certain degree of nonlinearity(distribution of I/O data), we show that it is available and effective to design an optimal FNN model structure with mutual balance and dependency between approximation and generalization abilities. To evaluate the performance of the proposed model, we use the time series data for gas furnace, the data of sewage treatment process and traffic route choice process.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.1
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• pp.151-159
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• 1993

In conjunction with a vertical network. horizontal geodetic control points provide the basic framework for topographic mapping and legal survey. The design of such networks as well as the technical means for obtaining their coordinates have been changed in time, and therefore Korea National Geographic Institute has planned and observed the precise geodetic network since 1975. The aim of this study is to investigate the systematic distortions of the precise geodetic network in Korea implementing by the simultaneous adjustment. The results show that there are large discrepancies between adjusted and public coordinates in Chun-nam and Kyung-buk areas. The coordinate discrepancies are mainly due to the non-rigorous adjustment method and the disregard of the orientation unknown of the first direction for some blocks.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.93-101
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• 2006

This research makes a new attempt to apply the activated seawater by electrolysis in the development of two-stage wet scrubber system to control the exhaust gas of large marine diesel engines. First, with using only seawater that is naturally alkaline (pH typically around 8.1). the $SO_2\;and\;SO_3$ are absorbed by relatively high solubility compared to other components of exhaust pollutants, and PM (Particulate Matter) is removed through direct contact with sprayed seawater droplets. Besides, the electrolyzed alkaline seawater by electrolysis, which contains mainly NaOH together with alkali metal ions $(i.e.\;Na^+,\;Mg^{2+},\;Ca^{2+})$, is used as the absorption medium of NOx and $CO_2$. Especially, to increase NOx absorption rate into the alkaline seawater. nitric oxide (NO) is adequately oxidized to nitrogen dioxide $(NO_2)$ in the acidic seawater, which means both volume fractions are adjusted to identical proportion. The results found that the strong acidic seawater was a valid oxidizer from NO to $NO_2$ and the strong alkaline seawater was effective in $CO_2$ absorption In the scrubber test, the SOx reduction of nearly $100\%$ could be achieved and also led to a sufficientPM reduction. Hence, the author believes that applying seawater and its electrolyte would bring the marine air pollution control system to an economical measure. Additionally it is well known that NOx and SOx concentration has a considerable influence on the $N_2O$ emission of green house gas. Although the $N_2O$ concentration exhausted from diesel engines is not as high, the green house gas effect is around 300 times greater than an equivalent volume of $CO_2$. Therefore, we investigated the $N_2O$ removal efficiency with using the electrolyzed seawater too. Finally this research would also plan to treat the effluent by applying electro-dialysis and electro-flotation technique s in the future.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.7
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• pp.750-757
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• 2005

The objective of this study is an understanding of the effect of inlet flow angle on the output power performance of a Francis hydraulic turbine, An optimum induced angle at the inlet of the turbine is one of the most important design parameters to have the best performance of the turbine at a given operating condition, In general. rotating speed of the turbine is varied with the change of water mass flowrate in a volute, The induced angle of the inlet water should be properly adjusted to the operating condition to have maximum energy conversion efficiency of the turbine, In this study. a numerical simulation was conducted to have detail understanding of the flow phenomenon in the flow path and output power of the model Francis turbine. The indicated power produced by the model turbine at a given operating condition was found numerically and compared to the brake power of the turbine measured by experiment at KIER. From comparison of two results, turbine efficiency or energy conversion efficiency of the model turbine was estimated. From the study, it was found that the rotating power of the turbine linearly increased with the rotating speed. It means that the higher volume flow rate supplied. the bigger torque on the turbine shaft generated. The maximum brake efficiency of the turbine is around 46$\%$ at 35 degree of induced angle. The difference between numerical and experimental output of the model turbine is defined as mechanical efficiency. The maximum mechanical efficiency of the turbine is around 93$\%$ at 25$\∼$30 degree of induced angle.

• Korean Journal of Applied Biomechanics
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• v.22 no.3
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• pp.357-363
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• 2012

The purpose of this study was to investigate the effects of different saddle heights on lower-limb joint angle and muscle activity. Six elite cyclists(age: $32.2{\pm}5.2years$, height: $171.0{\pm}3.5cm$, weight: $79.7{\pm}5.6kg$, cycle career: $13{\pm}6.2years$) participated in three min. submaximal(90 rpm) pedaling tests with the same load and cadence based on saddle heights where subject's saddle height was determined by his knee flexion angle when the pedal crank was at the 6 o'clock position. Joint angles(hip, knee, ankle joints) and the activity of lower limb muscles(biceps femoris(BF), vastus lateralis(VL), tibialis anterior(TA) and gastrocnemius medial(GM)) were compared by measuring 3D motion and electromyography(EMG) data. Results showed that there were significant differences in minimum hip & knee joint angle and range of motion of hip and knee joint between saddle heights. Onset timing and integrated EMG of only BF among 4 muscles were significantly different between saddle heights. Especially there was a negative relationship between minimum hip joint angle and onset timing of BF in most subject, which means that onset timing of BF became fast as the degree of bending of the hip joint became larger by saddle height. Optimal pedaling will be possible through increased amount of muscle activation due to the appropriate burst onset timing by proper pedaling posture with adjusted saddle height.

• Health Policy and Management
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• v.5 no.2
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• pp.155-172
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• 1995

This study is an empirical analysis on the equity in the delivery of heatlh care under the Korean Medical Insurance Corporation System. The purposes of this study are to find out effects of income on the health care utiliztion and measure the income-related inequity in the distribution of health care. This study was carried out based on the fact that the health insurance program has been organized to achieve the equity objective, "equal treatment for equal needs". Of 41, 828 insured persons who had been diagnosed in the 1993 Health Screening Test and utilifzation data from 1, January 1993 through 31, December 1993 were derived from the Benefit Managment File. Inequity was measured by means of I) share approach, ii) standardization concentration curve approach, iii) inequity index, iv) test for inequity. The major findings were as follows : 1. The expenditure shares of the top two quintile groups exceeded their morbidity shares, whereas the opposite was true of the bottom three quintile groups, Which showed a positive HI$_{LG}$ inequity index, suggesting the presence of some inequity favoring the rich group. 2. Compared with other residential areas, the rural area showed the highest positive HI$_{LG}$ irrespective of need indicatior applied. 3. Standardized expenditure concentration indices adjusted by age, gender and need structure were also found to be positive, and therefore still indicated that there has been inequity favoring the rich after the standardization. 4. The Loglikelihood Ratio (LR) test for the statistical significance of income-related inequity of medical care utilization was carried out using the logistic regression model. The resulting loglikelihood ratio test statistic value was 176, which did exceed the 0.5 percent critical value of the chi-square distribution with 28 degrees of freedom, which is 50.993. Therefore, the null hypothesis of no income-related inequity of medical care utilization was rejected at the 99.5 percent confidence level. 5. The Regression based F-test has been carried out for analyzing the income-related inequity of medical expenditure in terms of age, gender, morbidity indicators as explanary variables. The hypothesis of the absence of income-relate inequity was rejected for all need indicators at the 95% confidence level.nce level.

• Korean Journal of Human Ecology
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• v.13 no.5
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• pp.659-672
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• 2004

This study examines different individual, family, and school environmental variables that affect victimization by peer aggression among adolescents. The sample consists of 868 seventh and eighth graders. Statistics and method for data analysis include Cronbach's alpha, percentage, means, standard deviation, Pearson correlation, multiple regression, and hierarchical regression. The major findings of this study are as follows: First, adolescents, both withdrawn and aggressive, have lower achievement in school work. Boys experience more direct victimization by peer aggression. Adolescents, especially boys, often experience indirect victimization by peer aggression, when they become withdrawn, own lower self-esteem, and have lower achievement in school work. Second, adolescents have more direct victimization by peer aggression when their parents are negligent of them. Also, adolescents seem exposed to indirect victimization by peer aggression when they receive more physical and emotional abuse and negligence from their parents. Third, adolescents experience more victimization by peer aggression-whether it's direct or indirect, when they cannot get adjusted to peer relations and get teachers' supervision. Fourth, as to direct victimization by peer aggression, withdrawal, one of the individual variables, is the most reliable prediction followed by gender, negligence, adaptability in peer relations, aggression, and teacher's supervision in sequence. For indirect victimization by peer aggression, withdrawal is the most reliable prediction followed by adaptability in peer relations, gender, physical and emotional abuse, and negligence in sequence.