• Journal of the Korean Society of Earth Science Education
• /
• v.16 no.3
• /
• pp.340-350
• /
• 2023

This study analyzed the difficulty level of class on the seasonal change unit for 84 students at a university of education. The conclusions of this study are as follows. First, if we first present the four topics that make up the seasonal changes in elementary science, the subjects that have the greatest difficulty in teaching for prospective elementary school teachers are 'Why do seasonal changes occur?' (Teaching difficulty level 4.05), 'The sun changes depending on the season' What is the difference between the southern altitude and the length of day and night?' (difficulty level of class, 3.12), 'What is the relationship between the altitude of the sun, length of shadow, and temperature during the day?' (difficulty level of class, 2.85), 'How does the temperature change depending on the season?' (class difficulty level 2.80). As a result, in the elementary science season change unit, the class on the four topics 'Why do seasons change?', which is classified as a class topic that requires the concept of spatial perception, showed a higher level of class difficulty than other units. Second, in the seasonal change unit, various factors of class difficulty appeared depending on the class topic. When pre-service elementary school teachers look at the factors that make class difficult when teaching a lesson on seasonal changes in order of frequency, 42 (50%) said 'Experimental instruction for comparing the altitude of solar masculine according to the tilt of the axis of rotation', followed by 'Solar masculine'. 38 people (45%) answered 'Difficulty in explaining mid-high altitude and the length of day and night', 27 people (32%) answered 'Difficulty in explaining the concept of mid-high altitude', and 24 people (32%) answered 'Difficulty in explaining seasonal changes in the sun's position.' 29%), 20 people (24%) said 'Explain the reasonable reason why the height of the light should be adjusted when measuring the solar altitude', and 16 people (19%) said 'It is difficult to explain the reason for the discrepancy between the solar altitude and the maximum temperature'. ), 'difficulties in measuring sand (ground) temperature' were mentioned by 12 people (14%). Third, when analyzing the factors of class difficulty, there were more curriculum factors than teacher factors. In this context, the exploratory activities on 'Why do seasonal changes occur?', the fourth topic of the seasonal change unit in which elementary school pre-service teachers showed the greatest difficulty in teaching, need improvement in terms of the curriculum.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.19 no.2
• /
• pp.137-143
• /
• 2016

The sedimentary environment and sediment were surveyed at the West-Northern site of Chagwi-do nearby Jeju Island for the design of the embedded suction anchor system of 10 MW-class floating wave-offshore wind hybrid power generation system. According to the classification scheme of Chough et al.[2002], the echo type of the seismic profiles using the chirp III was classified. As a results, the center and west-northern area of survey site were proved to be type I-3 where subbottom layer with thickness 5~15 m exists under the flat seafloor. On the other hands, the east-southern area were regarded to be type I-1, I-2 and III-1 where seafloor reflection is much stronger than type I-3. Also, the physical tests (unit weight, moisture content, grain size, liquid limit, specific gravity) were performed with samples taken from 8 fixed locations. It is found that the sand (SP), the sand blended with silt (SM) and the mixture of SP-SM are distributed uniformly on the survey area.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.17 no.1
• /
• pp.3627-3641
• /
• 1975

The Government is trying to increase total food grain yield to meet national self sufficiency by means of increasing unit yield as well as extending crop land, and this year he set the target of 321,000 hectare of forest to clear for cropping. This study was carried to investigate the most efficient method of clearing hillock by bulldozer, and successful method to develope yielding potential of newly cleared land in short term. Since the conventional land clearing method is just earth leveling and root removing neglecting top soil treatment, the growth of crop was poor and farmer tends not to care the land. The top-soil-furrowing method is applied through out this study, that is advantageous especially for the land having shallow top soil and low fertility like Korean forest. In this study, various operating method were tried to find out most efficient method separately in connection with the land slope less than 25 percent and over, and several fertilizing methods to develop yielding potential. The results are as follows; 1) For the natural land slope utilization method, applicable to the land having less than 25 percent slope, reverse operating was more efficient than using forward gear of bulldozer. The operating time was 3 hour 32 minutes and 36 seconds using forward gear was 2 hour 32 minutes and 30 seconds for reverse gear operation per 1,000 square meter. 2) Bulldozer having angle blade adjustment needed 7hr 15min. for constructing of terrace per 10a compaire with the one having angle & tilt adjustment needed 6hr 4min for same operations. Specially there is significant difference for operation time of first period (earth cutting) such as bulldozer having angle blade adjustment needed 3hr 56min compaired with the one having angle & tilt adjustment 3hr 59min. In construction of terrace, the bull-dozer having tilting and angle blade adjustment was most suitable and performed efficiently. 3) For the fertilizer application treatment, the grass (Ladino clover) yield in first year was almost same as ordinary field's in the plot applied(N.P.K+lime+manure) while none fertilizer plot showed one tenth of it, and (N.P.K.+lime) applied plot yielded on third. 4) The effect of different land clearing method to yield showed significant difference between each treatment especially in the first year, and the conventional method was the lowest. In the second year, still conventional terracing plot yielded only half of ordinary field while the other plots showed as same as ordinary field's. 5) The downward top soil treatment plot showed most rapid improvement in soil structure during one year physio chemically, it showed increase in pH rate and organic composition, and the soil changed gradually from loam to sand-loam and the moisture content increased against the pF rate, and it gives good condition to grow hay due to the increase of field water capacity with higher available water content. 6) Since the soil of tested area was granite, the rate of soil errosion was increased about 2 to 5 percent influencing in soil structure more sand reducing clay content, and an optimum contour farming method should be prepared as a counter measure of errosion.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.5
• /
• pp.461-467
• /
• 2005

Phthalate esters is recently considered as an environmental pollutant. This study investigated removal methods of phthalate esters in water environment. On tap water treatment condition with batch test, removal efficiency of coagulation precipitation of one oxidation were $26.6{\sim}33.8%$ and $10{\sim}15%$, respectively. Phthalate esters was effectively removed by the activated carbon adsorption process on tap water treatment condition. The operation of raw water with EBCT of 10 minutes on continuous process satisfied the standard of drinking water by the WHO and US EPA when the concentration of phthalate esters was $100\;{\mu}g/L$. On pilot plant test, coagulation precipitation process got $32{\sim}44%$ of removal efficiency, sand filtration process $6{\sim}10%$ and ozone oxidation process $8{\sim}10%$, respectively. DEP, DBP, BBP and DEHP were not detected after the raw water was processed with activated carbon. The actual survey of phthalate esters removal by advanced water treatment showed that $29{\sim}76%$, $3{\sim}29%$ and $17{\sim}22%$ of phthalate esters were removed on coagulation precipitation process, sand filtration and ozone oxidation process, respectively. DEP, DBP, BBP and DEHP were not detected after the raw water was processed with activated carbon.

• Journal of the Korea Concrete Institute
• /
• v.14 no.3
• /
• pp.420-429
• /
• 2002

The amount of $CO_2$-silicate bonded waste foundry sand(WFS) occurred in Korea is over 800,000 ton per year. WFS, as a by-product, is generated through manufacturing process of foundry may affect our environmental contamination, The reason is that WFS has been buried itself not less than 90％ out of total WFS. So, it can give damage on the ground of contamination in soil and underwater. Therefore, it is necessary to establish the method recycling WFS because of being intensified waste management law. In this study, we performed the research with respect to harmful component analysis, the qualities of WFS mortar and concrete mixed with WFS. As the results the specific gravity of WFS is the same as that of natural aggregate while unit weight and percentage of solids of WFS are smaller than those of it. But it is found that WFS can be used by substituting WFS for natural aggregate after control of poor grade of WFS. The flowability of mortar and concrete with WFS is inferior to those of natural aggregate, and the setting time of concrete with WFS is faster than that with only natural aggregate, On the contrary, the bleeding of concrete with WFS is shown good result, and compressive and tensile strength of concrete substituted WFS for 30％ are higher than those with only natural aggregate regardless of elapsed time.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.34 no.5 s.118
• /
• pp.76-83
• /
• 2006

The purpose of this study was to investigate the performance of porous grass block. For the investigation, Festuca arundinacea and Zoysia japonica 'Zenith' were planted, and the volume of evapotranspiration and remains were examined based on different materials in the water tank in the experiment of Festuca arundinacea, the volume of water storage of treatment with perlite ($10.84{\iota}/m^2$) was higher than that with drainage ($7l/m^2$). The difference between the two was $3.84/m^2$. The drainage treatment without water storage capacity showed the higher degree of dryness in turf grass. The volume of evapo-transpiration of treatment with perlite was the highest (21.57mm/week). The volume of evapotranspiration of treatment with sand was 19.57mm/week, and with treatment with drainage was 18.24mm/week. Based on the measured volume of daily evapotranspiration of $2.60{\sim}3.08mm\;d^{-1}$, it was determined that the unit with water storage capacity would store water of one to two days usage compared to unite without such storage capacity. In the experiment of Zoysia japonica 'Zenith', the volume of water storage of treatment with perlite was $10.77l/m^2$ which was similar to the former experiment. The volume of evapotranspiration of treatment with perlite and sand were 21.64mm/week and 20.64mm/week, respectively. In case of airtight water tank, the volume was measured as 22.06mm/week. Each treatment has no notable difference in the volume of evapotranspiration. In conclusion, from the investigation in this study, porous grass block with water tank was found to be effective in plant growth under low irrigation. As the ecological area ratio and vegetated porous pavement have became more emphasized, additional study of rain infiltration and reservoir effect are needed in the future.

• Korean Journal of Soil Science and Fertilizer
• /
• v.48 no.5
• /
• pp.428-435
• /
• 2015

Pedotransfer functions (PTFs) were developed for each soil horizon to estimate hydraulic characteristics of mountainous forest soils in South Korea. Twenty one dominant soil series from 8 soil catenae such as granite-originated catena and volcanic ash-originated catena were selected for the study; gravel contents of selected soils were 10% or lower. Saturated conductivity (Ks) was measured for each horizon in situ. Particle size distribution and organic matter content of each horizon were also determined. Based on correlation analysis with total data set, sand separate showed positive relationship with Ks ($r=0.24^*$) while clay separate had negative relationship with Ks ($r=-0.29^{**}$). The correlation coefficients of sand, clay, and organic matter content with Ks increased to $0.41^{**}$, $-0.67^{***}$, and $0.58^{***}$, respectively, using data from granite- or gneiss-originated catena with exception of volcanic ash-originated catena and sedimentary rock-originated catena. Determination coefficients of PTFs were 0.31 for A horizon, 0.25 for B, and 0.35 for C with all data set while those were 0.74 for A, 0.48 for B, and 0.54 for C. Organic matter was a dominant factor affecting Ks in A horizon but clay content was selected as the only factor influencing Ks in C horizon. It implies that PTFs should be developed with understanding characteristics of parent materials and horizons. Developed PTFs for granite- or gneiss-originated catena were following: A horizon: Log ($K_s{\times}10^7$) = -0.031C + 0.398OM + 3.49 B horizon: Log ($K_s{\times}10^7$) = -0.028C + 0.141OM + 4.05 C horizon: Log ($K_s{\times}10^7$) = -0.072C + 4.66 where C is clay separate (%) and OM is organic matter content ($g\;kg^{-1}$). The unit of Ks is cm $sec^{-1}$.

• Korean Journal of Remote Sensing
• /
• v.37 no.5_1
• /
• pp.975-987
• /
• 2021

Potential habitat mapping of Meretrix lyrata which is found in large parts of South East Asian tidal flat was carried out to find out causes of collective death. Frequency Ratio (FR) method, one of geospatialstatistical method, was employed with some benthic environmental factors; Digital elevation model (DEM) made from Landsat imagery, slope, tidal channel distance, tidal channel density, sedimentary facesfrom WorldView-02 image. Field survey was carried out to measure elevation of each station and to collect surface sediment and benthos samples. Potential habitat maps of the all clams and the juvenile clams were made and accuracy of each map showed a good performance, 76.82 % and 69.51 %. Both adult and juvenile clams prefer sand dominant tidal flat. But suitable elevation of adult clams is ranged from -0.2 to 0.2 m, and that of juvenile clams is ranged from 0 to 0.3 m. Tidal channel didn't affect the habitat of juvenile clams, but it affected the adult clams. In the furtherstudy, comparison with case of Korean tidal flat will be carried out to improve a performance of the potential habitat map. Change in the benthic echo-system caused by climate change will be predictable through potential habitat mapping of macro benthos.

• Journal of Korean Academy of Nursing
• /
• v.25 no.1
• /
• pp.124-140
• /
• 1995

Cardiac cathererization has become a routine diagnostic procedure indicated for evaluation of a wide varity of cardiac conditions. Patients are admitted to the coronary care unit after cardiac catheterization. These conscious patients report feeling uncomfortable in the CCU, but no studies have been done on the effects of bed rest, sand bags on the femoral puncture site and restricted mobility for 4 to 12 hours or longer postprocedure. The main objective of this thesis is to provide basic data to nursing on interventions which de-crease the uncomfortableness experienced by patients in the CCU following cardiac catheterization. In this phenomenological study, the various discomforts felt by the patients were collected and classified. The study subjects were a convenience sample of 29 patients who were admitted to the CCU of a general hospital in Inchon following cardiac catheterization. They were conscious, so they were able to communicate without difficulty. The data were collected over an U days period from July 21, to October 14, 1994. The subjects were interviewed using unstructured open questions and the interviews were tape recorded with the patient's permission The data were analyzed using the Van Kaams phenomenological method. Reliability and validity were exammed by two professor of nursing science, one head nurse, one staff nurse and one cardiologist. The results of the study are summarized as follows ; 1. The 129 descriptive statements by the postcardiac catheterization patients of discomfort were organized into 19 themes. 2. The 19 themes were divided into 3 categories ; physical, psychological, and environmental aspects. 3. The problems concerning the physical aspect were the discomfort of restriction of movement, dysuria, medical devices, pain in the puncture site, symptom is related to the procedure of cardiac catheterization, headache and dizziness, leg painand tingling sensation, and chest pain. The problems concerning the psychological aspect were regret resulting from dependency, economic burden, dissatisfaction with medical personnel, dissatisfaction with medical service system, anxiety about the result of the procedure, concern about the prognosis, loneliness, and concern over treatment procedure. The problems concerning the environmental aspect were influence from neighboring patients, noise, and maladaptation to environmental change. The necessity for holistic care which satisfies physical, psychological, and environmental need must be emphasized in order to solve these discomforts.

• The Journal of Engineering Geology
• /
• v.28 no.1
• /
• pp.25-34
• /
• 2018

The physical properties and unsaturated characteristics of acid sulfate soils were investigated and analyzed. As the results of measuring physical properties of the acid sulfate soils obtained around the Ilkwang mine area, the dry unit weight is $1.246t/m^3$ and this soil is classified into the silty sand (SM) by USCS. Soil Water Characteristics Curves (SWCC) of the drying and wetting paths were measured by the automated SWCC apparatus. Also, Hydraulic Conductivity Functions (HCF) of the drying and wetting paths were estimated by the van Geunchten (1980) model which is the most well-known parameter estimation method. The hydraulic conductivity of acid sulfate soils in the dry path was continuously decreased with increasing the matric suction. However, the hydraulic conductivity in the wetting path was decreased relatively small with increasing matric suction and decreased suddenly just before water entry value of matric suction. Meanwhile, the hysteresis phenomenon was occurred in SWCCs and HCFs during the drying and wetting paths.