• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.4
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• pp.290-298
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• 2018

Herein, an S-band internally-matched power amplifier that shows a power capability of 300 W in a Long Term Evolution(LTE) band 7 is designed and fabricated using a CGHV40320D GaN HEMT from Wolfspeed. Based on the nonlinear model, the optimum source and load impedance are extracted from the source-pull and load-pull simulations at the fundamental and harmonic frequencies, and the harmonic impedance tuning circuits are implemented inside a ceramic package. The internally matched power amplifier, which is fabricated using a thin-film substrate with a high relative permittivity of 40 and an RF35TC PCB substrate, is measured at the pulsed condition with a pulse period of 1 ms and a duty cycle of 10%. The measured results show a maximum output power of 257~323 W, a drain efficiency of 64~71%, and a power gain of 11.5~14.0 dB at 2.62~2.69 GHz. The LTE-based measurement shows a drain efficiency of 42~49% and an ACLR of less than -30 dBc(excluding 2.62 GHz) at an average power of 79 W.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.5
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• pp.1025-1037
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• 2015

Flexible base isolation bearings that separate superstructure from ground have been widely used in the construction field because they make a significant contribution to increasing the fundamental period of the structure, thereby decreasing response acceleration transmitted into the superstructure. However, the established bearing devices installed to uphold the whole building give rise to some problems involved with failure and collapse due to lack of the capacity as modern structures are getting more massive and higher. Therefore, this study suggests new isolation bearings assembled with additional restrainers enabled to reinforcing and recentering, and then evaluates their performance to withstand the seismic load. The superelastic shape memory alloy (SMA) bars are installed into the conventional lead-rubber bearing (LRB) devices in order to provide recentering forces. These new systems are modeled as component spring models for the purpose of conducting nonlinear dynamic analyses with near fault ground motion data. The LRB devices with steel bars are also designed and analyzed to compare their responses with those of new systems. After numerical analyses, ultimate strength, maximum displacement, permanent deformation, and recentering ratio are compared to each model with an aim to investigate which base isolation models are superior. It can be shown that LRB models with superelastic SMA bars are superior to other models compared to each other in terms of seismic resistance and recentering effect.

• Applied Microscopy
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• v.40 no.4
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• pp.211-218
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• 2010

The mammalian ovary is innervated by sympathetic and sensory neurons which contribute to regulating several aspects of ovarian function, including blood flow, steroidogenesis and follicular development. The existence of a neural connection between central neurons and the ovary has been rarely reported, but the mechanism underlying integration of ovarian activity to broader neuroendocrine responses has not been reported. We have now used a viral transneuronal tracing technique combined with a conventional retrograde labeling procedure of CT-HRP to demonstrate that oxytocin-producing neurons of the hypothalamus are synaptically connected to the ovary. Since ovarian activity is suppressed but the activity of oxytocin neurons is increased during breast feeding. Our finding that the oxytocinergic neural connection is likely to provide a direct transsynaptic mechanism by which the central nervous system maintains the state of infertility that accompanies lactation in mammals.

• Journal of Mushroom
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• v.18 no.1
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• pp.100-106
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• 2020

Eight morel mushroom species were collected from Korea and other countries. The culture characteristics, genetic relationships, and beta-glucan content of the strains were analyzed. The mycelia of Morchella species exhibited optimal growth when cultured in dark at 25 ℃ in media with pH 7. The mycelia had a distinctive mycelial scent and characteristically changed color, being white initially, and then turning dark yellow to dark brown as it grew. The mycelia were classified into five types based on morphology. The isolates were identified as Morchella conica, two M. sextelata, M. importuna, M. esculenta, and three M. crassipes, based on ITS-rDNA sequences. PCR polymorphisms were variably produced within Morchella spp. using Universal Fungal Fingerprinting Primers (UFPF) and classified into four groups at the intra and inter species level. The strains, KMCC04971 and KMCC04407, showed the same banding pattern as M. conica and M. sextelata, respectively; however, these results were different from those of ITS analysis. Glucan content analysis by strain showed that the KMCC 04973 strain of M. importuna had the highest alpha- and beta-glucan content, at 16.4 g and 33.1 g per 100 g, respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.5
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• pp.124-135
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• 2011

The capacity of bearings installed at abutments and piers for continuous bridges is usually determined by the magnitude of the maximum vertical reaction at each support and the capacity of bearings placed at piers is higher than that at abutments. In this study, the possibility of the improved seismic performance of base-isolated continuous skew bridges was investigated by analysing the variation of the seismic behavior of them according to three arrangements of bearings. Based on the conventional arrangement of bearings(Case A), three arrangements of bearings such as Case A, Case B and Case C were selected considering the variation of the horizontal stiffness of the lead rubber bearing(LRB) installed at the pier. The seismic behavior of the total 36 skew bridges was investigated by conducting the response spectrum analysis using the hybrid response spectrum considered the effect of LRB's damping. Results of analyses show that a more desirable seismic behavior of base-isolated continuous skew bridges can be obtained by reducing the magnitude of the horizontal stiffness of LRB placed at the pier to similar to or less than that of LRB installed at abutments. The variation of LRB's stiffness at the pier brings about period elongation and the change of mode shapes of base-isolated skew bridges and results in the reduction of the total base shear, the maximum base shear at the pier and the girder stresses. Although positive effects on the seismic behavior of base-isolated skew bridges caused by the change of arrangement of bearings decreased slighty with an increase in the flexibility of the substructure, the proposed arrangements of bearings bring about the improved seismic performance of base-isolated continuous skew plate girder bridges with less than 10m height of piers.

• PNF and Movement
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• v.4 no.1
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• pp.45-50
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• 2006

Purpose : This study shows the movements of the ankle and the foot in walking stages, and helps to diagnose and treat the problems of the ankle and the foot. The foot in human is a mean of the transportation, body support, and shock absorber. However, the slightest changes in the anatomical position can cause a significant increase of the stress and force in the ankle and the foot. The regular compressive force in the ankle of the normal person is generated by the contraction of the gastrocnemius and popliteus muscles, and transmitted to the achilles tendon. The plantar flexion about 10 degrees occurs immediately after the heel strike, getting ready for the weight acceptance. The shear force about 80 % of the body weight is generated immediately after the heel off of the mid stance phase. In those who have a problem in the ankle, the compression force at the ankle decreased to 1/3 of the body weight, and the shear force decreased, and the compressive force was reached at their maximum level earlier than the normal people. Conclusion : Analysis of the movements at the ankle and the foot in walking phase can make the effort to diagnose and treat the ankle and foot with the problems. However, the further study is necessary.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.4
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• pp.94-103
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• 2016

For elevated railway station on which track is connected with superstructure of station, structural vibration level and structure-borne-noise level has exceeded the reference level due to structural characteristics which transmits vibration directly. Therefore, existing elevated railway station is in need of economical and effective vibration reduction method which enable train service without interruption. In this study, structural vibration non-transmissible system which is applied to vibroisolating material for column member is developed to reduce vibration. That system is cut covering material of the column section using water-jet method and is installed with vibroisolating material on cut section. To verify vibration reduction effect and structural performance for structural vibration non-transmissible system, impact hammer test and cyclic lateral load test are performed for 1/4 scale test specimens. It is observed that natural period which means vibration response characteristics is shifted, and damping ratio is increased about 15~30% which means that system is effective to reduce structural vibration through vibration test. Also load-displacement relation and stiffness change rate of the columns are examined, and it is shown that ductility and energy dissipation capacity is increased. From test results, it is found that vibration non-transmissible system which is applied to column member enable to maintains structural function.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.6
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• pp.603-612
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• 2017

Accidents associated with hazardous materials, including oil and HNS, in maritime transportation show increasing trend. Therefore, preventive countermeasures for such accidents should be provided. The purpose of this study is to analyze level of risk on human loss and potential damage to environment, using data on domestic marine accidents carrying hazardous materials (2002~2014), and identify high-risk accident types for urgent risk management which needs findings of accident causes and proper mitigation measures. High-risks on human loss are explosion and suffocation, occurred in process of ship maintenance and tank cleaning. On the other hand, high-risk on environmental damage is spill caused by ship accidents (collision, grounding and etc.). Especially, spill occurs during loading operation of oil and HNS onboard a ship. Strict operation supervision/management and safety education/training on a regular basis could prevent accidents, because human factors such as not wearing safety gear and careless cargo handling cause most of the marine accidents.

• Journal of the Korean Society for Railway
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• v.16 no.3
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• pp.196-201
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• 2013

As there is no failure data for the entire lifecycle of a product, when analyzing reliability measures based on early failure data only, there may be a significant error between the estimated mean life and the real one, because it can be underestimated, or on the other hand, it can be overestimated when analyzing reliability measures based on a large amount of censored data with the failure data. To resolve the issue, this study proposes an optimal sampling estimation procedure that selects the proportion of censored data to estimate the optimal distribution with the idea that the estimated distribution could be approximated as closely as the real life distribution. This would work if we sampled the optimal proportion on the censored data, because failure data has real intrinsic distribution in any situation. We validate the proposed procedure using an actual example. If the proposed method is applied to the maintenance policy of TWC (Train to Wayside Communication) system, then we can establish the optimal maintenance policy. Thus, we expect that it will be effective for improvement of reliability and cost savings.

• Journal of the Korea Society of Computer and Information
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• v.17 no.2
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• pp.215-224
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• 2012

This study performs an exploratory investigation of the needs of the customers who use academic information service from a research institute, K, that provides information services for domestic academic institutions of natural science and technology. K institute is planning customized services in order to improve customer satisfaction on the academic information service And therefore, the institute begins the research on customer needs analysis and customer segmentation. The research is regarded as well-timed, because CRM implementation in public organizations has been activated recently. Data mining and data warehousing techniques were used for pilot analyses. For the purpose of customer segmentation, a mixed segmentation model, which adds product life cycle concept to the 'balanced customer segmentation' model, which in turn considers the value of customers from the organizational viewpoint and the value of organizations from the customer's viewpoint, simultaneously, was applied. The result of investigation indicated that, in the case of K, 'balanced customer segmentation' and 'contents reach approach' which uses data warehouse/OLAP, rather than those customer segmentation techniques that are often used within the industry, are the more potent ways of approach. This exploratory case study is expected to provide a useful guideline for 'deriving an organizationally unique CRM model' that recently is one of the hot topics in the CRM area.