• Journal of the Korean Society for Aviation and Aeronautics
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• v.14 no.3
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• pp.16-22
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• 2006

The friction and wear of tire determined by frictional behavior of tire tread that translate driving force, cornering force and braking force between automobile and road as a result of frictional behavior of each tread block. The tire tread block is representative case of rubber block doing frictional behavior. In this paper, frictional behavior of rubber block under compressive force and shear force was analytically obtained by using slip starting position parameter instead of friction coefficient which is uncertain to express exact value between rubber and other surfaces yet. And local coefficients of friction were calculated as a function of compressive force, shear force, shear modulus of rubber, shape factor and slip starting position.

• Journal of Environmental Science International
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• v.18 no.8
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• pp.885-897
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• 2009

In order to make sure the impact of spatial resolution of wind energy map on the estimation of wind power density in the Korean Peninsula, the comparison studies on the characteristics of wind energy map with three different spatial resolutions were carried out. Numerical model used in the establishment of wind map is MM5 (5th generation Mesoscale Model) with RBAPS (Regional Data Assimilation and Prediction System) as initial and boundary data. Analyzed Period are four months (March, August, October, and December), which are representative of four seasons. Since high spatial resolution of wind map make the undulation of topography be clear, wind pattern in high resolution wind map is correspond well with topography pattern and maximum value of wind speed is also increase. Indication of island and mountains in wind energy map depends on the its spatial resolution, so wind patterns in Heuksan island and Jiri mountains are clearly different in high and low resolutions. And area averaged power density can be changed by estimation method of wind speed for unit area in the numerical model and by treatment of air density. Therefore the studiable resolution for the topography should be evaluated and set before the estimation of wind resources in the Korean Peninsula.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.4
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• pp.291-297
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• 2015

The wave spectrum was generated from wave data measured at the Chagwi-do site in Jeju, where a 10MW class floating wave-offshore wind hybrid power generation system will be installed. The latching control technology (Sheng et al.[2015]) was applied in order to improve the extracted power from WEC (Wave Energy Converter), which is heaving in corresponding irregular waves. The peak period as a representative value of irregular waves was used when we determined the latching duration. From the numerical results in the time-domain analysis, the latching control technology can significantly improve the extracted power about 50%.

• Journal of Radiation Protection and Research
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• v.36 no.4
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• pp.209-215
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• 2011

In order to investigate the soil-to-plant transfer factor (TF) of $^{99}Tc$ for Korean major upland crops (soybean, radish and Chinese cabbage), pot experiments were performed in a greenhouse. Soils were collected from four upland fields (two for soybean and two for radish and Chinese cabbage) around Gyeongju radioactive-waste disposal site. Three to four weeks before sowing, dried soils were mixed with a $^{99}Tc$ solution and the mixtures were put into pots and irrigated. TF values were expressed as the ratios of the $^{99}Tc$ concentrations in plants (Bq $kg^{-1}$-dry or fresh) to those in soils (Bq $kg^{-1}$-dry). There was no great difference in the TF value between soils. The TF values for soybean seeds were extremely lower than those for the straws, indicating a very low mobility of $^{99}Tc$ to seeds. As representative TF values of $^{99}Tc$, $1.8{\times}10^{-1}$, $1.2{\times}10^1$, $3.2{\times}10^2$ and $1.3{\times}10^2$ (for dry plants), arithmetic means for two soils, were proposed for soybean seeds, radish roots, radish leaves and Chinese cabbage leaves, respectively. In the case of the vegetables, proposals for fresh plants were also made. The proposed values are not sufficiently representative so successive updates are needed.

• Journal of the Korea Society of Computer and Information
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• v.20 no.4
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• pp.77-85
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• 2015

Recently, wireless sensor network(WSN) have been used in various fields to implement ubiquitous computing environment. WSN uses small, low cost and low power sensors in order to collect information from the sensor field. This paper proposes a clustering algorithm for energy efficiency of sensor nodes. The proposed algorithm is based on conventional LEACH, the representative clustering protocol for WSN and it prolongs network and nodes life time using sleep technique and changable transmission mode. The nodes of the proposed algorithm first calculate their clustering participation value based on the distance to the neighbor nodes. The nodes located in high density area will have clustering participation value and it can turn to sleep mode. Besides, proposed algorithm can change transmission method from conventional single-hop transmission to multi-hop transmission according to the energy level of cluster head. Simulation results show that the proposed clustering algorithm outperforms conventional LEACH, especially non-uniformly deployed network.

• Journal of the Korean Wood Science and Technology
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• v.42 no.4
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• pp.439-449
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• 2014

RPS (Renewable Portfolio Standard) has increased wood pellet demand dramatically in recent years in Korea where self-supply rate of wood pellet is not more than 10%. However global production capacity of wood pellet is prospected to be unable to meet the global demand after 2020. Therefore it is urgently needed to develop new sustainable biomass energy resources which can replace wood pellet at lower cost. As a result of this study EFB (empty fruit bunch) and MF (mesocarp fiber), the representative solid palm biomass, are estimated to be generated at the rate of 20 and 28 million tons per year (based on 10% moisture content) in Malaysia and Indonesia, respectively in 2012. Total annual generation rate of EFB and MF is estimated as 48 million tons per year only in Malaysia and Indonesia in 2012. With calorific value of over 90% of wood pellet EFB is expected to be a excellent biomass energy resource which can replace wood pellet. EFB can be utilized as fuel for power generation or industrial purpose. However EFB may not be a proper fuel for domestic and greenhouse heating because of its high ash content.

• Journal of Korea Water Resources Association
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• v.51 no.11
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• pp.989-998
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• 2018

Connectivity between water source and demand node can be served as a critical system performance indicator of the degree of water distribution network (WDN)' failure severity under abnormal conditions. Graph theory-based approaches have been widely applied to quantify the connectivity due to WDN's graph-like topological feature. However, most previous studies used undirected-unweighted graph theory which is not proper to WDN. In this study, the directed-weighted graph theory was applied for WDN connectivity analyses. We also proposed novel connectivity indicators, Source-to-Node Shortest Pathway (SNSP) and SNSP-Degree (SNSP-D) which is an inverse of the SNSP value, that does not require complicate hydraulic simulation of a WDN of interest. The proposed SNSP-D index was demonstrated in total 42 networks in J City, South Korea in which Pearson Correlation Coefficient (PCC) between the proposed SNSP-D and four other system performance indicators was computed: three resilience indexes and an energy efficiency metric. It was confirmed that a system representative value of the SNSP-D has strong correlation with all resilience and energy efficiency indexes (PCC = 0.87 on average). Especially, PCC was higher than 0.93 with modified resilience index (MRI) and energy efficiency indicator. In addition, a multiple linear regression analysis was performed to identify the system hydraulic characteristic factors that affect the correlation between SNSP-D and other system performance indicators. The proposed SNSP is expected to be served as a useful surrogate measure of resilience and/or energy efficiency indexes in practice.

• Journal of the Korean Geotechnical Society
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• v.38 no.3
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• pp.35-42
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• 2022

The N-value from the Standard Penetration Test (SPT), which is one of the representative in-situ test, is an important index that provides basic geological information and the depth of the bearing layer for the design of geotechnical structures. In the aspect of time and cost-effectiveness, there is a need to carry out a representative sampling test. However, the various variability and uncertainty are existing in the soil layer, so it is difficult to grasp the characteristics of the entire field from the limited test results. Thus the spatial interpolation techniques such as Kriging and IDW (inverse distance weighted) have been used for predicting unknown point from existing data. Recently, in order to increase the accuracy of interpolation results, studies that combine the geotechnics and deep learning method have been conducted. In this study, based on the SPT results of about 22,000 holes of ground survey, a comparative study was conducted to predict the depth of the bearing layer using deep learning methods and IDW. The average error among the prediction results of the bearing layer of each analysis model was 3.01 m for IDW, 3.22 m and 2.46 m for fully connected network and PointNet, respectively. The standard deviation was 3.99 for IDW, 3.95 and 3.54 for fully connected network and PointNet. As a result, the point net deep learing algorithm showed improved results compared to IDW and other deep learning method.

• Analytical Science and Technology
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• v.14 no.4
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• pp.1075-1081
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• 2001

Instrumental Neutron Activation Analysis as a representative method of nuclear analytical technique, has advantages of non-destructive, simultaneous multi-element analysis with the characteristics of absolute measurement method. Up to date, $k_0$-quantitative method which is accurate, convenient and user-friendly, has been generalized world-widely. In this study, it is intented to introduce the general concept of $k_0$-method and to measure $k_0$-parameters for the future implementation to our NAA system. For this objectives, the definition of relevant factors for the quantitative analysis and the equation for the experimental determination of parameters such as $Q_0$(${\alpha}$) and f were summarized. Furthermore, a foundation for the $k_0$-standardization method was prepared through the measurement of ${\alpha}$ and f-value which depend on the specific character of irradiation hole at NAA#1-hole of HANARO research reactor.

• Journal of The Korean Astronomical Society
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• v.47 no.6
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• pp.303-309
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• 2014

We present results of our investigation of the radio intrinsic brightness temperatures of compact radio jets. The intrinsic brightness temperatures of about 100 compact radio jets at 2, 5, 8, 15, and 86 GHz are estimated based on large VLBI surveys conducted in 2001-2003 (or in 1996 for the 5 GHz sample). The multi-frequency intrinsic brightness temperatures of the sample of jets are determined by a statistical method relating the observed brightness temperatures with the maximal apparent jet speeds, assuming one representative intrinsic brightness temperature for a sample of jets at each observing frequency. By investigating the observed brightness temperatures at 15 GHz in multiple epochs, we find that the determination of the intrinsic brightness temperature for our sample is affected by the flux density variability of individual jets at time scales of a few years. This implies that it is important to use contemporaneous VLBI observations for the multi-frequency analysis of intrinsic brightness temperatures. Since our analysis is based on the VLBI observations conducted in 2001-2003, the results are not strongly affected by the flux density variability. We find that the intrinsic brightness temperature $T_0$ increases as $T_0{\propto}{\nu}^{\xi}_{obs}$ with ${\xi}=0.7$ below a critical frequency ${\nu}_c{\approx}9GHz$ where the energy loss begins to dominate the emission. Above ${\nu}_c$, $T_0$ decreases with ${\xi}=-1.2$, supporting the decelerating jet model or particle cascade model. We also find that the peak value of $T_0{\approx}3.4{\times}10^{10}$ K is close to the equipartition temperature, implying that the VLBI cores observable at 2-86 GHz may be representing jet regions where the magnetic field energy dominates the total energy in jets.