• Earthquakes and Structures
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• v.7 no.2
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• pp.141-157
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• 2014

The Conditional Mean Spectrum represents a powerful link between the seismic hazard information and the selection of strong ground motion records at a particular site. The scope of the paper is to apply for the city of Bucharest for the first time the method to obtain the Conditional Mean Spectrum (CMS) presented by Baker (2011) and to select, on the basis of the CMS, a suite of strong ground motions for performing elastic and inelastic dynamic analyses of buildings and structures with fundamental periods of vibration in the vicinity of 1.0 s. The major seismic hazard for Bucharest and for most of Southern and Eastern Romania is dominated by the Vrancea subcrustal seismic source. The ground motion prediction equation developed for subduction-type earthquakes and soil conditions by Youngs et al. (1997) is used for the computation of the Uniform Hazard Spectrum (UHS) and the CMS. The disaggregation of seismic hazard is then performed in order to determine the mean causal values of magnitude and source-to-site distance for a particular spectral ordinate (for a spectral period T = 1.0 s in this study). The spectral period of 1.0 s is considered to be representative for the new stock of residential and office reinforced concrete (RC) buildings in Bucharest. The differences between the Uniform Hazard Spectrum (UHS) and the Conditional Mean Spectrum (CMS) are discussed taking into account the scarcity of ground motions recorded in the region of Bucharest and the frequency content characteristics of the recorded data. Moreover, a record selection based on the criteria proposed by Baker and Cornell (2006) and Baker (2011) is performed using a dataset consisting of strong ground motions recorded during seven Vrancea seismic events.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.4
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• pp.724-730
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• 2017

SpaceWire invented for spacecrafts has Time-Code defined for time synchronization over SpaceWire network. A Time-Code suffers transmission delay of 14[bit-period] and jitter up to 10[bit-period] whenever it passes through a SpaceWire link, which is the primary cause of time synchronization error. This work presents a simple method to improve the time synchronization which uses two extended Time-Codes. Nodes on a SpaceWire network can find how much delay and jitter a received Time-Code has suffered while it passes through the network, and they can correct time synchronization error with this information. The proposed method was validated in a simulation environment developed based on OMNeT++. The simulation result showed that time synchronization error less than a few bit-periods can be achieved. The proposed method is cost effective and suitable for small-scale SpaceWire network systems.

• Journal of Family Resource Management and Policy Review
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• v.15 no.3
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• pp.131-151
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• 2011

This study attempted to estimate the level of perceived lack of time in Korean society, to link it to time management and to identify the possible association that accounts for time shortage. I employed the gender perspective in order to reveal the dynamics and complexity of the perception of a lack of time in the population. The sample for the study was drawn from the 1999 and 2009 Korean time diary data collected by the Korean National Statistical Office. From the original data, I selected a sample of second shift families(men and women who are presently working and raising children) living in metropolitan areas(including Seoul and six major urban areas in Korea). The dependent variable was time pressure measured by a single-item question on a four-point likert scale. The results of the study showed that working mothers perceived a greater time shortage as compared to working fathers. The time use pattern showed change during the periods, indicating that people worked fewer hours in paid labor and enjoyed more leisure hours and personal care hours. However, on average, people seemed to have experienced a greater time lack in 2009 as compared to 1999. The results from the ordered logistic regression model revealed that even though there were similarities in the impact of relevant factors, men's perception of a lack of time was more closely linked with their work role and social status, while for women, this perception was influenced by work and family duties. This indicates that Korean working mothers and fathers are facing a double jeopardy of time shortage in terms of combining their work and family roles. As a result, the level of time pressure by gender is converging toward a "never enough" phase. These findings generated policy implications and detailed suggestions.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.295-303
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• 2004

In this Paper, we discuss an active TCP link of unsynchronized transmission mode network in two-way traffic and the Improvement of its traffic patron thorough the network pathway of protocol is shown. This is because the traffic pattern is performed on the basis of existing windows which are distributing information in several periods of time in the way of interfacing LTS control module, which is controlling by an information of exceeding the time limit of feedback loop determined by RTP, with TCP. The simulation to utilize this efficiently is performed with the circumstance of bench mark based on physical modeling of the self-similarity traffic in the performance of TCP. In this paper, we use a methodology to understand and evaluate the effect of change of transmitting protocol in sticks under the condition of the self-similar traffic in two-way network and it is shown that an improvement of congestion control by self-similarity under a heavy condition.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.6
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• pp.489-496
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• 2021

The X-band frequencies for transmitting the data from earth observation satellites are limited, so a number of satellites share the frequency bands. In order for multiple satellites to utilize same or adjacent frequency bands, International Telecommunication Union - Radiocommunication (ITU-R) limits power flux density (PFD), which overcomes the interferences among multiple satellites. However, even under the regulation, the interference effect needs to be analyzed when multiple satellites are connected to communicate with multiple ground stations (GSs) located close to each other. In this paper, the interference effect is analyzed based on signal to interference plus noise ratio (SINR) when two low earth orbit (LEO) satellites operating in different orbits are connected to communicate with randomly located two GSs in Korean peninsula. From the analysis results, it is confirmed that there can be interferences during 365 days operation even if the satellites meet PFD requirement, but the periods under interference effects are short and the interference can be foreseen.

• Journal of Korean Society of Transportation
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• v.30 no.1
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• pp.19-30
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• 2012

The majority of daily travel demands concentrate at particular time-periods, which causes the difficulties in the travel demand analysis and the corresponding benefit estimation. Thus, it is necessary to consider time-specific traffic characteristics to yield more reliable results. Traditionally, na$\ddot{i}$ve, heuristic, and statistical approaches have been applied to address the peak-hour ratio. In this study, a hybrid clustering model which is one of the statistical methods is applied to calculate the peak-hour ratio and its duration. The 2009 national 24-hour traffic data provided by the Korea institute of Construction Technology are used. The analysis is conducted dividing vehicle types into passenger cars and trucks. For the verification for the usefulness of the methodology, the toll collection system data by the Korea Express Corporation are collected. The result of the research shows lower errors during the off-peak hours and night times and increasing error ratios as the travel distance increases. Since the method proposed can reduce the arbitrariness of analysts and can accommodate the statistical significance test, the model could be considered as a more robust and stable methodology. It is hoped that the result of this paper could contribute to the enhancement of the reliability for the travel demand analysis.

• Development and Reproduction
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• v.9 no.1
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• pp.1-5
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• 2005

The hypothalamo-pituitary-gonadal hormone axis is centrally controlled by a complex regulatory network of excitatory and inhibitory signals, that is dormant during infantile and juvenile periods and activated at puberty. The kisspeptins are the peptide products of the KiSS-1 gene and the endogenous agonists for the G protein-coupled receptor 54(GPR54). Although KiSS-1 was initially discovered as a metastasis suppressor gene, a recent evidence suggests the KiSS-1/GPR54 system is a key regulator of the reproductive system. Yet the actual role of the KiSS-1/GPR54 system in the neuroendocrine control of gonadotropin secretion remains largely unexplored, the system could be the first missing link in the reproductive hormonal axis. Central or peripheral administration of kisspeptin stimulates the hypothalamic-pituitary-gonadal axis, increasing circulating gonadotropin levels in rodents, sheep, monkey and human models. These effects appear likely to be mediated via the hypothalamic GnRH neuron system, although kisspeptins may have direct effects on the anterior pituitary gland. The loss of function mutations of the GPR54(GPR54-/-) have been associated with lack of puberty onset and idiopathic hypogonadotropic hypogonadism(IHH). So kisspeptin infusion may provide a novel mechanism for HPG axis manipulation in disorders of the reproductive system.

• Journal of Ginseng Research
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• v.3 no.2
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• pp.168-186
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• 1979

Three hundred gram of Korean ginseng root was extracted with 95% ethanol on a boiling water bath for about 300 hr. Evaporation of alcohol yieled 50.2g of dark brown residue which was used by dissolving 4 mg of the residue in 1 ml of physiological saline. The ginseng group and the saline group received each day 0.5 ml per 100 g body weight of ginseng extract and physiological saline, respectively. Both the ginseng and saline group with stress were exposed to positive radial acceleration (1∼29g), cold (5$^{\circ}C$, 0$^{\circ}C$ &-10$^{\circ}C$) and heat (35$^{\circ}C$) environment, and surgical stress. After termination of the last stress, the tolerance, body weight, visceral organ weight, basal metabolism rate, rectal temperature, the number of erythrocyte and leucocyte, hemoglobin level, hematocrit ratio, total serum protein content and it's fraction and the content of adrenal ascorbic acid in the experimental animal exposed to stress were measured and at the corresponding periods, the same measurements were also carried out with the ginseng and the saline groups without stress exposure (serving as control). Results obtained were as follows. 1. Administration of ginseng does depressed the decrease of the tolerance, body weight, visceral organ weight, basal metabolism rate, the number of erythrocyte, hemoglobin value, hematocrit ratio and the A/G ratio in the mice and rats exposed to various stress. 2. The change of the rectal temperature, eosinophile counts, total serum protein content and the content of adrenal ascorbic acid of ginseng group that exposured to various stress facilitates the reaction to, and accelerates the recovery from the stress. 3. Even after hypophysectomy which served the link between the central and the peripheral portion of the stress mechanism, the adrenal ascorbic acid content of ginseng group decreased significantly more than that of the saline group 30 min. after administration of ACTH, while the value approached the normal level significantly closer in the ginseng group than in the saline group 1 and 2 hr after ACTH administration. Judging from the above results, it is concluded that administration of ginseng extract tolerated the experimental animals under the environment of stressfu1 stmuli, although the ginseng has no significant influence upon the stress mechanism in the absence of stressful stimuli. The site of action of the ginseng appears to be in the peripheral portion of the stress mechanism.

• Journal of The Korean Association For Science Education
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• v.22 no.4
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• pp.796-805
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• 2002

This study examined the knowledge structure constructed by children before formal instruction, and successive changes in the structural complexity of knowledge during and after the learning of 'Structure and Function of Plant' unit. It also investigated how those changes were affected by children's learning modes. The researchers made the 5th graders draw the first draft of their concept map to see the pre-existing knowledge structure concerned with the unit and four more concept maps after completing every fourth lesson. And to see how long their knowledge structures were preserved, the researchers made children draw additional concept maps in 3 days, 3 months, and 7 months after completing the unit. Children drew their current concept maps on the basis of the previous one while learning the unit and without the previous one after completing the unit. Each concept map drawn by children showed the degree of their current understanding on the structures and functions of plants. The results revealed that only two levels of hierarchy and five relationships among the components of the first concept map(relationship, hierarchy, cross link and example) were proven to be valid in terms of conceptual relevance. Growth in the structural complexity of knowledge took place progressively throughout the unit and the effects of learning mode on the growth were favorably reflected in concept map scores of meaningful learners over time(relationship, cross link, example: p<.01, hierarchy: p<.05). Although there were some differences on the concept map scores between two types of learners, they commonly showed that knowledge restructuring had occurred apparently in the early periods from the 1st to the 6th lesson and had not occurred at all in the last period of the unit. The frequency of tuning was higher in rote learners than in meaningful learners throughout the unit, but the frequency of accretion was reverse. Concept map scores of rote learners constructed in the course of learning of the unit decreased little by little gradually in all the categories after completing the unit. However, the average total map score of meaningful learners increased a little more in 7 months than in 3 months after completing the unit. Therefore it can be inferred that meaningful learners construct more stable and well-differentiated knowledge structures than the rote learners.

• Journal of Korean Society of Transportation
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• v.17 no.1
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• pp.29-39
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• 1999

An earlier study of the effect of rain found that the capacity of freeway systems was reduced, but did not address the effects of rain on the nature of traffic flows. Indeed, the substantial variation due to the intensity of adverse weather conditions is entirely rational so that its effects must be considered in freeway facility design. However, all of the data in Highway Capacity Manual(HCM) have come from ideal conditions. The primary objective of this study is to investigate the effect of rain on urban freeway traffic flows in Seoul. To do so, the relations between three key traffic variables(flow rates, speed, occupancy), their threshold values between congested and uncontested traffic flow regimes, and speed distribution were investigated. The traffic data from Olympic Expressway in Seoul were obtained from Imagine Detection System (Autoscope) with 30 seconds and 1 minute time periods. The slope of the regression line relating flow to occupancy in the uncongested regime decreases when it is raining. In essence, this result indicates that the average service flow rate (it may be interpreted as a capacity of freeway) is reduced as weather conditions deteriorate. The reduction is in the range between 10 and 20%, which agrees with the range proposed by 1994 US HCM. It is noteworthy that the service flow rates of inner lanes are relatively higher than those of other lanes. The average speed is also reduced in rainy day, but the flow-speed relationship and the threshold values of speed and occupancy (these are called critical speed and critical occupancy) are not very sensitive to the weather conditions.