• Resources Recycling
• /
• v.32 no.6
• /
• pp.34-44
• /
• 2023

In this work, column flotation using factorial design was performed for recovering high-grade molybdenite concentrate. First, the flotation concentrate from Samyang Mining Plant was regrinded to a mean size of 165, 116, 46.7, and 38.4 ㎛ for an increase of the liberation degree. Tests were carried out for various variables affecting column flotation, and then the concentrates with molybdenite grade and recovery of 98.3 % and 95.28 % were obtained, respectively. Also, regression was performed using the statistical analysis program (SPSS 25) with the factorial design and experimental data on particle size, flow wash-water velocity and depressant that affect high grade. From the results, a model equation was derived to predict the molybdenite grade (MG) and recovery (MR) with the relationship between column flotation variables. Factors such as depressant concentration + wash-water velocity and particle size + depressant concentration + wash-water velocity were smaller than the significance level (0.05) and had a significant effect on the dependent variable, grade, and in the recovery model, only particle size and wash-water velocity factors affected the dependent variable, recovery.

• Journal of The Korean Association For Science Education
• /
• v.28 no.6
• /
• pp.579-591
• /
• 2008

Recently, there have been studies about Typically- Perceived-Situations (TPSs) and about critical examples as a way to understand students' preconceptions with context. TPS is a situation arising immediately in one's mind when he or she thinks about the concept, while a critical example is an example that becomes the most helpful in learning the concept. We might explore how the context is involved in the process of students' conceptual understanding by examining TPSs and critical examples together. This study analyzed, through questionnaires and interviews, the characteristics of TPSs and those of critical examples that secondary students hold about 'force' and 'mechanical energy conversion.' Students' TPSs and critical examples showed different characteristics according to the concept. In a case of force that is related to everyday life, there were various situations as TPSs and critical examples. Unlike force, there were a few situations as TPSs and critical examples such as a falling ball in the case of mechanical energy conversion. Students tended to regard situations that are usually experienced and understood easily as TPSs or critical examples. On the basis of the results of this study, it is concluded that it would be a good strategy to teach science concepts for teachers to start with the TPS of a concept, to introduce the concept, and then to expose the attributes of the concept with critical examples.

• Smart Media Journal
• /
• v.13 no.3
• /
• pp.18-26
• /
• 2024

Road surface monitoring is essential for maintaining road environment safety through managing risk factors like rutting and crack detection. Using autonomous driving-based UGVs with high-performance 2D laser sensors enables more precise measurements. However, the increased energy consumption of these sensors is limited by constrained battery capacity. In this paper, we propose a fusion sensor system for efficient surface monitoring with UGVs. The proposed system combines color information from cameras and depth information from line laser sensors to accurately detect surface displacement. Furthermore, a dynamic sampling algorithm is applied to control the scanning frequency of line laser sensors based on the detection status of monitoring targets using camera sensors, reducing unnecessary energy consumption. A power consumption model of the fusion sensor system analyzes its energy efficiency considering various crack distributions and sensor characteristics in different mission environments. Performance analysis demonstrates that setting the power consumption of the line laser sensor to twice that of the saving state when in the active state increases power consumption efficiency by 13.3% compared to fixed sampling under the condition of λ=10, µ=10.

• Journal of Bio-Environment Control
• /
• v.25 no.2
• /
• pp.83-88
• /
• 2016

In this study, previously reported surplus solar energy-related study result and current status of fan coil unit (FCU) for cooling and heating installed in the current sites were briefly examined and then a method to determine the number of FCUs required to recover surplus solar energy was schematically proposed to provide basic data for researchers and technical engineers in this field. The maximum, mean, and minimum outside temperatures during the experiment period were about $28.2^{\circ}C$, $4.4^{\circ}C$, and $-11.5^{\circ}C$, respectively. The horizontal surface solar radiation level outside the greenhouse was in a range of $0.8-20.5MJ{\cdot}m^{-2}$ and mean and total solar radiation were $10.8MJ{\cdot}m^{-2}$ and $1,187.5MJ{\cdot}m^{-2}$. The mean temperature and relative humidity in the greenhouse during the daytime were in a range of 18.8-45.5 and 53.5-77.5%. The total surplus solar energy recovered from the greenhouse during the experiment period was approximately 6,613.4MJ, which could supplement about 6.7% of the total heating energy 98,600.2 MJ. In addition, the number of FCUs installed for heating varies case to case, although similar FCUs are used. Thus, it is necessary to study the installation height, orientation and installation distance as well as the appropriate number of FCUs from the efficient and economical viewpoints. The required numbers of FCUs for surplus solar energy recovery were 8.4-10.9units and 6.1-8.0units based on air mass and circular flow rate that passed through the FCUs. Considering calculation methods and the risks such as efficiency and use environments of FCUs, it was found that about nine units (one unit per $24m^3$ approximately) needed to be installed. The required number of FCUs for surplus solar energy recovery was around one unit per $24m^3$ approximately.

• The Korean Journal of Nuclear Medicine Technology
• /
• v.17 no.1
• /
• pp.25-29
• /
• 2013

Purpose: In this study, we evaluated the accuracy of CT-based attenuation correction (AC) under the conventional CT protocol (140 kVp, on average 50-60 keV) by comparing the SPECT image qualities of different energy of radioisotopes, $^{201}Tl,\;^{99m}Tc$ and $^{131}I$. Materials and Methods: Using a cylindrical phantom, three different SPECT scans of $^{201}Tl$ (70 keV, 55.5 MBq), $^{99m}Tc$ (140 keV, 281.2 MBq) and $^{131}I$ (364 keV, 96.2 MBq) were performed. The CT image was obtained with 140 kVp and 2.5 mA in GE Hawkeye 4. The OSEM reconstruction algorithm was performed with 2 iterations and 10 subsets. The experiments were performed in the 4 different conditions; non-AC and non-scatter correction (SC), only AC, only SC, AC and SC in terms of uniformity and center to peripheral ratio (CPR). Results: The uniformity was calculated from the uniform whole region in the reconstructed images. For $^{201}Tl$ and $^{99m}Tc$, the uniformities were improved by about 10-20% AC was applied, but these were decreased by about 2% as SC was applied. The uniformity of $^{131}I$ was slightly increased as both AC and SC were applied. The CPR of the reconstructed image was close to one, when AC was applied for $^{201}Tl$ and $^{99m}Tc$ scans and $^{131}I$ was distant from 1 and that is only AC. Conclusion: The image uniformity improved by AC on low energy likely to $^{201}Tl$ and $^{99m}Tc$. However, image uniformity of high energy such as $^{131}I$ was improved, when both AC and SC was applied.

• Journal of the East Asian Society of Dietary Life
• /
• v.25 no.1
• /
• pp.30-38
• /
• 2015

The purpose of this study was to compare energy intake according to expected body mass index (BMI) in adolescents. A total of 280 middle school students were divided into current or/and expected obesity groups (underweight group; UWG, normal weight group; NWG, and overweight group; OWG) by BMI to compare energy intake and perception on body shape and weight control. The average age of total subjects was 15 years, and the distributions of boys and girls were 52.5% and 47.5%, respectively. The distribution of boys and girls was not significantly different among current obesity groups but was among expected obesity groups (15% and 82% in UWG vs. 71.4% and 16.5% NWG vs. 13.6% and 1.5% in OWG; P<0.001), indicating that girls wanted to lose weight more than boys. For body shape, most subjects in current obesity groups responded "fitness" in UWG (38.7%), "fitness" and "slightly chubby" in NWG (45.5% and 39%), and "slightly chubby" in OWG (65.2%), showing a significant difference (P<0.001). For interest in weight control, most subjects responded "average" in current UWcinterested" in current OWG (52.2%), whereas they responded "very interested" in expected UWG (55.7%), "average" in expected NWG (51.2%), and "not interested" in expected OWG (45.5%), showing a significant difference (P<0.001). The percentage of subjects with experience with weight control was significantly high in current OWG (71.7%), NWG (51.2%) and UWG (34.2%) as well as in expected UWG (57.3%), NWG (40.2%) and OWG (36.4%) in descending order (P<0.001). The daily energy intake of total subjects was 2,057.1 kcal without any significant difference among current obesity groups. However, it was significantly lower in expected UWG than expected NWG and OWG (1,943.1 kcal vs. 2,165.0 kcal or/and 2,152.1 kcal; P<0.001). To sum up these results, girls wanted to lose weight more than boys. The more students wanted to lose weight, the greater their experience and interest in weight control and the lower their energy intake.

• Korean Journal of Breeding Science
• /
• v.42 no.6
• /
• pp.674-678
• /
• 2010

A new sweetpotato variety, 'Daeyumi', was developed by Bioenergy Crop Research Center, National Institute of Crop Science (NICS), RDA in 2008. This variety was obtained from the cross between 'Jinhongmi' and 'Xusju 18' in 2000. The seedling and line selections were performed from 2001 to 2003, preliminary and advanced yield trials were carried out from 2004 to 2005, and the regional yield trials were conducted at six locations from 2006 to 2008. 'Daeyumi' has cordate leaf, green vine and petiole, elliptic storage root, red skin and yellow flesh color of storage root. This variety is also resistant to Fusarium wilt and nematode. The starch value was 25.9%, ethanol yield was 418 L/Ton, which was 7% higher than that of 'Yulmi' variety, and the total sugar content was 2.47 g/100g, dry weight. 'Daeyumi's initial temperature of starch gelatinization was lower, 76.2$^{\circ}C$, and the retrogradation process was earlier than 'Yulmi'. The average yield of storage root was 27.8 ton/ha in the regional yield trials, which was 36% higher than that of 'Yulmi' variety. Number of storage roots over 50 gram per plant was 3.0, and the average weight of one storage root was 152 gram. This variety can be used for the production of bioethanol and starch processing.

• Korean Journal of Breeding Science
• /
• v.42 no.6
• /
• pp.679-683
• /
• 2010

'Yeonjami' is a new sweetpotato variety developed for table use by Bioenergy Crop Research Center, National Institute of Crop Science (NICS), RDA in 2008. This variety was selected from the cross between 'Ayamurasakki' and 'Poly Cross' in 2000, and seedling and line selections were practiced from 2001 to 2003. Preliminary and advanced yield trials were carried out from 2004 to 2005. The regional yield trials were conducted at six locations from 2006 to 2008. 'Yeonjami' has cordate leaf, green vine and petiole, long elliptic storage root, purple skin and light purple flesh color of storage root. The average yield of storage root was 25.9 ton/ha in the regional yield trials, which was 15% higher than that of 'Sinjami' variety. Number of storage roots over 50 gram per plant was 2.9, and the average weight of one storage root was 153 gram. This variety was partly-resistant to Fusarium wilt and nematode. In addition, steamed 'Yeonjami' has higher polyphenol contents as 139.6 mg/100 g and higher biological activities as, which may improve the bioactivity in human.

• Membrane Journal
• /
• v.28 no.1
• /
• pp.75-82
• /
• 2018

Forward osmosis (FO) desalination system has been highlighted to improve the energy efficiency and drive down the carbon footprint of current reverse osmosis (RO) desalination technology. To improve the trade-off between water flux and salt rejection of thin film composite (TFC) desalination membrane, thin film nanocomposite membranes (TFN), in which nanomaterials as a filler are embeded within a polymeric matrix, are being explored to tailor the separation performance and add new functionality to membranes for water purification applications. The objective of this article is to develop a graphene nanocomposite membrane with high performance of water selective permeability (high water flux, high salt rejection, and low reverse solute diffusion) as a next-generation FO desalination membrane. For advances in fabrication of graphene oxide (GO) membranes, layer-by-layer (LBL) technique was used to control the desirable structure, alignment, and chemical functionality that can lead to ultrahigh-permeability membranes due to highly selective transport of water molecules. In this study, the GO nanocomposite membrane fabricated by LBL dip coating method showed high water flux ($J_w/{\Delta}{\pi}=2.51LMH/bar$), water selectivity ($J_w/J_s=8.3L/g$), and salt rejection (99.5%) as well as high stability in aqueous solution and under FO operation condition.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.7
• /
• pp.688-698
• /
• 2017

This study was conducted to identify the conceptual definitions and attributes of fatigue in hemodialysis patients based on the Hybrid Model of concept development. The Hybrid Model was used to investigate the main attributes and indicators of the concept by applying three stages. After a literature review, data were collected through observation and interviews including qualitative research in the field work stage. The participants included 10 patients in hemodialysis center of two hospitals in Gwang-ju, Korea. The attributes of fatigue concept in the hemodialysis patients were divided into four dimensions, physical activity, affective mood, social role, and cognitive reflection. The definition of fatigue by hemodialysis patients was defined as 'subjective feeling usually experienced in four dimensions during the process to recognize and adjust energy deficiency and limited functions caused by uremia and repeated hemodialysis for chronic renal failure'. Considering the dimensions and attributes derived from this study, it may be possible to develop an effective intervention program for fatigue in hemodialysis patients.