• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.19 no.3
• /
• pp.107-115
• /
• 2009

Particular interest in the role of convection in vapor crystal growth has arisen since some single crystals under high gravity acceleration of $10g_0$ appear considerably larger than those under normal gravity acceleration ($1g_0$). For both ${\Delta}T=60\;K$ and 90 K, the mass flux increases by a factor of 3 with increasing the gravity acceleration from $1g_0$ up to $10g_0$. On the other hand, for ${\Delta}T=30\;K$, the flux is increased by a factor of 1.36 for the range of $1g_0{\leq}g{\leq}10g_0$. The maximum growth rates for $1g_0$, $4g_0$, $10g_0$ appear approximately in the neighborhood of y = 0.5, and the growth rates shows asymmetrical patterns, which indicate the occurrence of either one single or more than one convective cell. The maximum growth rate for $10g_0$ is nearly greater than that for $1g_0$ by a factor of 2.0 at $P_B=20\;Torr$. For three different gravity levels of $1g_0$, $4g_0$ and $10g_0$, the maximum growth rates are greater than the minimum rates by a factor of nearly 3.0, based on $P_B=20\;Torr$. The mass flux increases with increasing the gravity acceleration, for $1g_0{\leq}g_y{\leq}10g_0$, and decreases with increasing the partial pressure of component B, xenon (Xe), $P_B$. The $|U|_{max}$ is directly proportional to the gravity acceleration for $20\;Torr{\leq}P_B{\leq}300\;Torr$. As the partial pressure of $P_B$ (Torr) decreases from 300 Torr to 20 Torr, the slopes of the $|U|_{max}s$ versus the gravity accelerations increase from 0.1 sec to 0.17 sec. The mass flux of $Hg_2Cl_2$ is exponentially decayed with increasing the partial pressure of component B, $P_B$ (Torr) from 20 Torr up to 300 Torr.

• Journal of Korean Society for Atmospheric Environment
• /
• v.13 no.2
• /
• pp.147-159
• /
• 1997

One of the most critical problems associated with filter-pack data comparisons from various field networks is the use of different sampling flow rates. In this field study, the effects of various filter-pack(FP) sampling conditions were examined. Experiments were conducted to evaluate the effects of varying sampling flow rates (1.5 to 10 sLpm) on measured concentrations of dry acid deposition species. Collocated FP samples were also collected to determine sampling and analysis data reproducibility. Ambient air samples were collected simultaneously for the seven day durations at varous flow rate. The chemical species measured were sulfur dioxide ($SO_2$), particulate sulfate(P-$SO_{4}^{2+}$), nitric acid ($HNO_3$), and particulate nitrate (P-$NO_{3}^{-}$). The results indicated that the collocated samples can be measured reproducibly and that sampling bias for the species measured is not significant. It was concluded that variations in the flow rates (1.5 to 10 sLpm) did not significantly affect the concentration of the species of interest. Although the results were not significantly different between different flow rates, artifacts were more likely to occur at high flow conditions (>5 sLpm) (e.g., via volatilization of particulate nitrates) than at low flow conditions(<5 sLpm).

• Journal of Korea Water Resources Association
• /
• v.55 no.8
• /
• pp.565-575
• /
• 2022

Recently, in the field of water resource engineering, interest in predicting time series water levels and flow rates using deep learning technology that has rapidly developed along with the Fourth Industrial Revolution is increasing. In addition, although water-level and flow-rate prediction have been performed using the Long Short-Term Memory (LSTM) model and Gated Recurrent Unit (GRU) model that can predict time-series data, the accuracy of flow-rate prediction in rivers with rapid temporal fluctuations was predicted to be very low compared to that of water-level prediction. In this study, the Paldang Bridge Station of the Han River, which has a large flow-rate fluctuation and little influence from tidal waves in the estuary, was selected. In addition, time-series data with large flow fluctuations were selected to collect water-level and flow-rate data for 2 years and 7 months, which are relatively short in data length, to be used as training and prediction data for the LSTM and GRU models. When learning time-series water levels with very high time fluctuation in two models, the predicted water-level results in both models secured appropriate accuracy compared to observation water levels, but when training rapidly temporal fluctuation flow rates directly in two models, the predicted flow rates deteriorated significantly. Therefore, in this study, in order to accurately predict the rapidly changing flow rate, the water-level data predicted by the two models could be used as input data for the rating curve to significantly improve the prediction accuracy of the flow rates. Finally, the results of this study are expected to be sufficiently used as the data of flood warning system in urban rivers where the observation length of hydrological data is not relatively long and the flow-rate changes rapidly.

• Journal of the Economic Geographical Society of Korea
• /
• v.18 no.3
• /
• pp.348-365
• /
• 2015

This study empirically analyzes the recent conversion trend of Jeonsei to monthly rental contracts in the APT rental market and its major characteristics for three Gangnam districts using the real transaction Jeonsei and monthly rent prices data over the period of 2010.12 to 2015.4. The results show that in terms of deposits and substitutability the conventional apartment is more efficient than those of the reconstruction apartment. Moreover, monthly rental contracts are closely related with the movement of short-term interest rates. Given the same type of apartment, the result drawn from the substitutability between Jeonsei and monthly rental contracts reveals that the monthly leasing contract with the lower rate of deposit tends to have the higher conversion rate of Jeonsei to monthly rent. Thus, an urgent measure should be taken that the burdens of tenants with monthly rent contracts could be alleviated according to the rate of deposits.

• The Journal of the Korea Contents Association
• /
• v.20 no.10
• /
• pp.702-714
• /
• 2020

Stock investment is a personal investment technique that has gathered tremendous interest since the reduction in interest rates and tax exemption. However, it is risky especially for those who do not have expert knowledge on stock volatility. Therefore, it is well understood that accurate stock trend prediction can greatly help stock investment, giving birth to a volume of research work in the field. In order to compare different research works and to optimize hyper-parameters for prediction models, it is required to have an evaluation standard that can accurately assess performances of prediction models. However, little research has been done in the area, and conventionally used methods have been employed repeatedly without being rigorously validated. For this reason, we first analyze performance evaluation of stock trend prediction with respect to performance metrics and data composition, and propose a fair evaluation method based on prediction disparity ratio.

• Journal of the Korea Society for Simulation
• /
• v.17 no.3
• /
• pp.19-26
• /
• 2008

In this paper, we propose a dynamic prediction algorithm to predict the bond price using actual data set of treasure note (T-Note). The proposed algorithm is based on term structure model of the interest rates, which takes place in various financial modelling, such as the standard Gaussian Wiener process. To obtain cumulative distribution functions (CDFs) of actual data for the interest rate measurement used, we use the natural cubic spline (NCS) method, which is generally used as numerical methods for interpolation. Then we also use the random number generation scheme (RNGS) to calculate the pricing of bond through the obtained CDF. In empirical computer simulations, we show that the lower values of precision in the proposed prediction algorithm corresponds to sharper estimates. It is very reasonable on prediction.

• Journal of Digital Convergence
• /
• v.13 no.2
• /
• pp.159-175
• /
• 2015

The two-dimensional QR code has advantages such as directional nature, enough data storage capacity, ability of error correction, and ability of data restoration. There are two major issues like speed and correctiveness of recognition in the two-dimensional QR code. Therefore, this paper proposes a morphology-based algorithm of detecting the interest region of a barcode. Our research contents can be summarized as follows. First, the interest region of a barcode image was detected by close operations in morphology. Second, after that, the boundary of the barcode are detected by intersecting four cross line outside in a code. Three, the projected image is then rectified into a two-dimensional barcode in a square shape by the reverse-perspective transform. In result, it shows that our detection and recognition rates for the barcode image is also 97.20% and 94.80%, respectively and that outperforms than previous methods in various illumination and distorted image environments.

• Physical Therapy Korea
• /
• v.27 no.1
• /
• pp.53-62
• /
• 2020

Background: Pregnancy-related low back pain (PLBP) has fewer systematic guidelines than pregnancy-related pelvic girdle pain, previous studies have not evaluated physical therapy for this ailment in Korea. Objects: We aimed to provide a detailed account of clinical decision making by Korean physiotherapists while treating PLBP. Methods: In total, 955 questionnaires were distributed mainly in places of continuing education held by the Korean Physical Therapy Association from April to July 2019. The same questionnaire was posted on a website used by physiotherapists. We collected subject information, a specific Vignette typically represent symptoms of PLBP, and responses to multiple questions about decision making, subjective recognition and interest level in the field of women's health physiotherapy (WHPT). Results: The overall response rate was 56% (n = 537); of these, responses to 520 questionnaires were analyzed. Most respondents chose various combinations of physical therapy methods. There were significant differences in subjective recognition levels of WHPT according to gender (p < 0.05), age (p < 0.01), education level (p < 0.01), and clinical experience (p < 0.05). There were significant differences in interest according to gender (p < 0.01) and education level (p < 0.01). With respect to the types of treatment, significant differences were noted in selective rates for "manual therapy", "pain control", and "supportive devices" based on gender. Manual therapy tended to be chosen more with increasing age and clinical experience. With increased education level, there were fewer choices for the use of pain control. Conclusion: This is the first data on how Korean physiotherapists manage PLBP patients using the vignette method. We were able to recognize the Korean physical therapist's decision on PLBP patients, and observed statistically significant correlations. This may aid in developing future research and education plans in the WHPT field.

• Journal of Fisheries and Marine Sciences Education
• /
• v.28 no.5
• /
• pp.1319-1328
• /
• 2016

Since Ballast Water Management Convention has been effected, BWTS, applied to new-building vessels and existing vessels, have been developed from many countries with various treatment methods. However, BWTS is mainly typed Electrolysis, Ozone and UV type. Approximately 70 products have been type approved by the Flag Administrations. For the new-building vessels, the vessels' design and construction have been considered for arrangements and installations for BWTS. However, existing vessels which already construction had finished have problem with selection of BWTS type for installation and arrangement. The selection of the most economized BWTS system is important though, CAPEX has not been made any significant differences. However, OPEX is more important factor. Consequently, detail analysis of OPEX is the key to the selection of the most economized BWTS system and also it can be the purpose of this study. The feasibility study on the main three type of BWTS (Electrolysis, Ozone and UV type) for 175K Bulk Carrier and 57K Cargo ship has been conducted for this study. Because, these three type of BWTS have been the most frequently installed and used and the two type of object vessels are consist of the 40% of the world merchant ship market. For this study, interest rate, project duration (operation time after installation), maintenance cost and fuel oil price are considered as major factor of feasibility study. In addition, expecting Interest rates to sensitivity analysis conducted for more accurate feasibility study. For 175K Bulk carrier, ozone treatment system is more economical than other types. For 57K cargo ship, UV type is considered more economical than other types. However, it is concluded that electrolysis type is more suitable compare to installation space, total weight and electrical power consumption.

• Journal of the Korean Home Economics Association
• /
• v.48 no.1
• /
• pp.137-161
• /
• 2010

The aim of this study was to identify the most effective methods with which to revitalize Korean high school culinary education. To achieve this aim, a culinary recognition questionnaire survey of 616 students from 9 culinary high schools was carried out. The 9 surveyed schools represented the following of 7 regions: Chungnam, Busan, Incheon, Daegue, Jeonbuk, Gyeongbuk, and Gwangju. Collected data were subjected to descriptive analysis, $x^2$-test, t-test, and one-way ANOVA using SPSS(version 14.0). The results of this study are as follows. Culinary practice interest and learning demand of most students were high. 6.8% of students indicated that initial theory learning, followed by video education, and finally live demonstration is an effective teaching methodology. They preferred practicing on actual ingredients as the primary teaching and learning method, nominating technician cooking as the most favorite. As for areas needing improvement in culinary practice education, difficulties with material preparation and insufficient learning hours were identified as prominent factors by 66.8% of respondents. There was unanimous agreement that culinary practice education can be enhanced by highly skilled teachers, while interest for the discipline itself can be fostered by initiating and encouraging cooking participation in the home. Freshmen and special high school students suggested that a cooking related website is necessary to expand the current information interface, which is currently limited to colleagues and employers. In relation to culinary education revitalization, consistent promotion of departments, or high schools that have proven student satisfaction rates and effective culinary curriculum are required. Furthermore, teachers can also aid this process by more effective student pastoral care in order to improve school life satisfaction. However, teacher job satisfaction is an important component of this process, and better employment conditions and remuneration packages reflecting extra work must be considered as part of an attractive teacher-incentive employment policy.