• Journal of the Korea Society for Simulation
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• v.18 no.3
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• pp.13-21
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• 2009

The sensor nodes that form a wireless sensor network must perform both routing and sensing roles, since each sensor node always has a regular energy drain. The majority of sensors being used in wireless sensor networks are either unmanned or operated in environments that make them difficult for humans to approach. Furthermore, since many wireless sensor networks contain large numbers of sensors, thus requiring the sensor nodes to be small in size and cheap in price, the amount of power that can be supplied to the nodes and their data processing capacity are both limited. In this paper, we proposes the WSN(Wireless Sensor Network) algorithm which is applied sensor node that has low power consumption and efficiency measurement. Moreover, the efficiency routing protocol is proposed in this paper. The proposed algorithm reduces power consumption of sensor node data communication. It has not researched in LEACH(Low-Energy Adaptive Clustering Hierarchy) routing protocol. As controlling the active/sleep mode based on the measured data by sensor node, the energy consumption is able to be managed. In the event, the data is transferred to the local cluster head already set. The other side, this algorithm send the data as dependent on the information such as initial and present energy, and the number of rounds that are transformed into cluster header and then transferred. In this situation, the assignment of each node to cluster head evenly is very important. We selected cluster head efficiently and uniformly distributed the energy to each cluster node through the proposed algorithm. Consequently, this caused the extension of the WSN life time.

• Journal of The Geomorphological Association of Korea
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• v.18 no.3
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• pp.65-81
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• 2011

The landforms based on granite and basalt in Gosung, Gangwon province were analysed. Some part of this area experienced volcanic activities while most of the area was experiencing erosion of weathered mantle(saprolites) of mesoic granites during cenozoic period. Two different lithologies affect the mode of landscape evolution. The basalt covers the mountain tops as a 'cap rock' with flat surfaces. It shows relatively fresh rock surface with cliff or steep slops at the boundary with weathered granite. The blocks detached from the cliff accumulated at the foot of the cliff(talus) or moved and filled the valley(block streams). These debris slopes cover the deeply weathered granites. In the case of Oeum Mt. and Duibaekjae, the number of point of origin of the basalt flow is not clear. The orientation of blocks from block stream coincides with slope aspects and it can be assumed that the bolcks were moved by solifluction. The landscape change of the block streams are dominated by removal of weathered material from beneath of the valley rather than removal of bedrock blocks themselves.

• Korean Journal of Ecology and Environment
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• v.56 no.4
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• pp.363-374
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• 2023

The limitation in deriving the species richness representing the entire country of South Korea lies in its relatively short history of species field observations and the scattered observation data, which has been collected by various organizations in different fields. In this study, a comprehensive compilation of the observation data for plants held by agencies under the Ministry of Environment was conducted, enabling the construction of a time series dataset spanning over 100 years. The data integration was carried out using minimal criteria such as species name, observed location, and time (year) followed by data verification and correction processes. Based on the integrated plant species data, the comprehensive collection of plant species in South Korea has occurred predominantly since 2000, and the number of plant species explored through these surveys appears to be converging recently. The collection of species survey data necessary for deriving national-level biodiversity information has recently begun to meet the necessary conditions. Applying the Chao 2 method, the species richness of indigenous plants estimated at 3,182.6 for the 70-year period since 1951. A minimum cumulative period of 7 years is required for this estimation. This plant species richness from this study can be a baseline to study future changes in species richness in South Korea. Moreover, the integrated data with the estimation method for species richness used in this study appears to be applicable to derive regional biodiversity indices such as for local government units as well.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.6
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• pp.454-464
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• 2023

This paper proposes a low-power 8-bit asynchronous SAR ADC with a sampling rate of 1 MS/s for sensor node applications. The ADC uses bootstrapped switches to improve linearity and applies a VCM-based CDAC switching technique to reduce the power consumption and area of the DAC. Conventional synchronous SAR ADCs that operate in synchronization with an external clock suffer from high power consumption due to the use of a clock faster than the sampling rate, which can be overcome by using an asynchronous SAR ADC structure that handles internal comparisons in an asynchronous manner. In addition, the SAR logic is designed using dynamic logic circuits to reduce the large digital power consumption that occurs in low resolution ADC designs. The proposed ADC was simulated in a 180-nm CMOS process, and at a 1.8 V supply voltage and a sampling rate of 1 MS/s, it consumed 46.06 𝜇W of power, achieved an SNDR of 49.76 dB and an ENOB of 7.9738 bits, and obtained a FoM of 183.2 fJ/conv-step. The simulated DNL and INL are +0.186/-0.157 LSB and +0.111/-0.169 LSB.

• Journal of Science Education
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• v.47 no.3
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• pp.251-262
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• 2023

In this study, we examine other factors that may contribute to the decline in students' academic performance and educational attainment. Many media reports, as well as previous studies, have suggested that virtual learning is the main reason for the decline in students' academic performance. However, the 2020 National Student Achievement Survey, which was conducted in conjunction with the COVID-19 Distance Learning Environment Student Survey, showed that students were highly satisfied with distance learning (70-80%), and the analysis of the National Assessment of Educational Achievement showed that students' academic performance had already been declining year by year since 2017, with a general downward curve. For further confirmation, we analyzed the performance of high school students on mock exams and found that their performance was not normally distributed, but rather a right-skewed U-shaped distribution with a shrinking number of medians and severe polarization. We found that this phenomenon is not simply because of the mode or quality of the virtual classroom, but to a variety of factors, including environmental influences such as care and management at home, changes in investment in private education, increased time spent on online devices while taking virtual classes at the bottom, and increased time spent watching online content, games, and videos that are not related to learning.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.1
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• pp.98-106
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• 2024

Due to advancements in construction technology and analytical tools, an increasing number of cable-stayed bridges have been designed and constructed in recent years. A cable is a structural element that primarily transmits the main load of a cable-stayed bridge and plays the most crucial role in reflecting the overall condition of the entire bridge system. In this study, a vision-based method was applied to estimate the tension of the stay cables located at a long distance. To measure the response of a cable using a vision-based method, it is necessary to install feature points or targets on the cable. However, depending on the location of the point to be measured, there may be no feature points in the cable, and there may also be limitations in installing the target on the cable. Hence, it is necessary to find a way to measure cable response that overcomes the limitations of existing vision-based methods. This study proposes a method for measuring cable responses by utilizing the characteristics of cable shape. The proposed method involved extracting the cable shape from the acquired image and determining the center of the extracted cable shape to measure the cable response. The extracted natural frequencies of the vibration mode were obtained using the measured responses, and the tension was estimated by applying them to the vibration method. To verify the reliability of the vision-based method, cable images were obtained from the Hwatae Bridge in service under ambient vibration conditions. The reliability of the method proposed in this study was confirmed by applying it to the vibration method using a vision-based approach, resulting in estimated tensions with an error of less than 1% compared to tensions estimated using an accelerometer.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.7
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• pp.1125-1132
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• 2013

In the kimchi manufacturing process, the starter is cultured on a large-scale and needs to be supplied at a low price to kimchi factories. However, current high costs associated with the culture of lactic acid bacteria for the starter, have led to rising kimchi prices. To solve this problem, the development of a new medium for culturing lactic acid bacteria was studied. The base materials of a this novel medium consisted of Chinese cabbage extract, a carbon source, a nitrogen source, and inorganic salts. The optimal composition of this medium was determined to be 30% Chinese cabbage extract, 2% maltose, 0.25% yeast extract, and $2{\times}$ salt stock (2% sodium acetate trihydrate, 0.8% disodium hydrogen phosphate, 0.8% sodium citrate, 0.8% ammonium sulfate, 0.04% magnesium sulfate, 0.02% manganese sulfate). The newly developed medium was named MFL (medium for lactic acid bacteria). After culture for 24 hr at $30^{\circ}C$, the CFU/mL of Leuconostoc (Leuc.) citreum GR1 in MRS and MFL was $3.41{\times}10^9$ and $7.49{\times}10^9$, respectively. The number of cells in the MFL medium was 2.2 times higher than their number in the MRS media. In a scale-up process using this optimized medium, the fermentation conditions for Leuc. citreum GR1 were tested in a 2 L working volume using a 5 L jar fermentor at $30^{\circ}C$. At an impeller speed of 50 rpm (without pH control), the viable cell count was $8.60{\times}10^9$ CFU/mL. From studies on pH-stat control fermentation, the optimal pH and regulating agent was determined to be 6.8 and NaOH, respectively. At an impeller speed of 50 rpm with pH control, the viable cell count was $11.42{\times}10^9(1.14{\times}10^{10})$ CFU/mL after cultivation for 20 hr - a value was 3.34 times higher than that obtained using the MRS media in biomass production. This MFL media is expected to have economic advantages for the cultivation of Leuc. citreum GR1 as a starter for kimchi production.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.2
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• pp.95-109
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• 1993

In this study, the optimal configuration of arch structure has been tested by a decomposition technique. The object of this study is to provide the method of optimizing the shapes of both two hinged and fixed arches. The problem of optimal configuration of arch structures includes the interaction formulas, the working stress, and the buckling stress constraints on the assumption that arch ribs can be approximated by a finite number of straight members. On the first level, buckling loads are calculated from the relation of the stiffness matrix and the geometric stiffness matrix by using Rayleigh-Ritz method, and the number of the structural analyses can be decreased by approximating member forces through sensitivity analysis using the design space approach. The objective function is formulated as the total weight of the structures, and the constraints are derived by including the working stress, the buckling stress, and the side limit. On the second level, the nodal point coordinates of the arch structures are used as design variables and the objective function has been taken as the weight function. By treating the nodal point coordinates as design variable, the problem of optimization can be reduced to unconstrained optimal design problem which is easy to solve. Numerical comparisons with results which are obtained from numerical tests for several arch structures with various shapes and constraints show that convergence rate is very fast regardless of constraint types and configuration of arch structures. And the optimal configuration or the arch structures obtained in this study is almost the identical one from other results. The total weight could be decreased by 17.7%-91.7% when an optimal configuration is accomplished.

• Radiation Oncology Journal
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• v.6 no.1
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• pp.1-11
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• 1988

Recovery from potentially lethal damage (PLDR) after irradiation was studied in plateau-phase culture of Vero cells in vitro. Unfed plateau-phase cells were irradiated with dose of 1 to 9Gy using Cs-137 irradiator. Cells then were incubated again and left in situ for 0, 1, 2, 3, 4, 5, 6, and 24 hours and then were trypsinized explanted, and subcultured in fresh RPMI-1640 media containing $0.33\%$ agar. Cell survival was measured by colony forming ability. An adequate number of heavily irradiated Vero cells were added as feeder cells to make the total cell number constant in every culture dish. As the postirradiation in situ incubation time increased, surviving fraction increased by PLDR. The rate of PLDR was so rapid that increased surviving fraction reached saturation level at 2 to 4 hours after in situ incubation. As the radiation dose increased, the rate of PLDR fastened and the magnitude of increased surviving fraction at saturation level by PLOR also increased. In analysis of cell survival curve fitted to the linear-quadratic model, the linear inactivation coefficient $(\alpha)$ decreased largely and reached nearly to zero but the quadratic inactivation coefficient $(\beta)$ increased minimally by increment of postirradiation in situ incubation time. So PLDR mainly affected the damage expressed as $\alpha$, In the multitarget model, significant change was not obtained in $D_0\;but\;in D_q$. Therefore, shoulder region in cell survival curve was mainly affected by PLDR and terminal slope was not influenced at all. And dose-modifying factor by PLDR was relatively higher in shoulder region, that is, in low dose area below 3 Gy.

• Journal of Korean Academy of Nursing
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• v.29 no.4
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• pp.929-939
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• 1999

The purpose of this study was to identify knowledge of universal precautions and its performance in practice. The research was conducted from November 2 to 30, 1998. A total 515 student nurses ; 249 from a baccalaureate nursing college and 266 from second and third year of a 3-year community nursing college were surveyed. The results are as following : 1. The average score for universal precautions knowledge was 270.41$\pm$19.43/300(range 150-300). The results showed that 99.2% of students avoid injury from used needles, 98.6% answered that they always wash their hands if they had contact with the patient's blood and they always dispose of used needles in special collectors (97.7%) for needles. But, 39.2% responsed that they dispose of used needles after recapping them. 2. The average score for universal precautions knowledge of the senior students in the 4-year college was the highest (277.65$\pm$13.99). 3. The average score for the performance of universal precautions knowledge was 53.18 $\pm$5.91(range 14-70). The items : ‘I cautiously avoid injury from the used needles’(4.92$\pm$0.33), ‘I always wash my hands if there has been contact with the patient's blood’(4.91$\pm$0.34), and ‘I always disposed of used needles in the appropriate collector’(4.89$\pm$0.42) showed the highest performance. However ‘I always dispose of used needles after recapping them’(2.19$\pm$1.39) and ‘I always use protection goggles when in danger of contamination’(2.19$\pm$1.20) showed low performance level. 4. The highest average score for universal precautions performance was shown among the second year students in 3-year nursing college (54.19$\pm$6.92) between the groups. It showed that the level of the universal precautions performance was higher for those who had education on university precautions prior to performance of the universal precautions than for those without any prior education. 5. The percentage of students who reported the experience of direct contact with patients' blood and/or body fluids was 42.30%. The experience of direct contact with blood and/or body fluids of the educational group was significantly higher than those were not educated. 6. The most frequent cause of the direct contact was ‘needle pricking and/or skin cut’(63.04%). The most frequent substance with which the students contact was ‘blood’(59.85%). The majority of the sample had answered that the mode of contamination was ‘unknown’(63.54%). The majority of the sample answered that strategies used after contamination included ‘washing with soap’(33.61%). Reviewing the chart of patients or asking other health professionals(28.85%). 7. The number of students who had the experience of a needle stick and/or skin cut was 145(28.16%). The clinical practice places where the incidents occurred were mainly in the internal medicine unit (45.07%) and the surgical unit (31.92%) followed by the intensive care unit and the emergency unit in order. The experience of a needle stick and/or skin cut happened during on intra-muscular injection 47.34% and intravenous injection 21.81%. The causes of the needle stick and/or skin cut were ‘putting the needle cap back on 77(35.81%)’. The number of students who took an appropriate post management blood test and/or vaccination was 27(18.62%). 8. The Pearson Correlation Coefficient between the knowledge of universal precautions and performance of universal precautions in practice showed a positive correlation.