• Food Science and Preservation
• /
• v.21 no.3
• /
• pp.334-340
• /
• 2014

The moisture sorption isotherms of corn powder prepared from corn kernels roasted for 20 min at 160, 180, 200, 220, and $240^{\circ}C$ were determined at $20^{\circ}C$ using the static gravimetric method over the range of water activities ($a_w$) of 0.11~0.90. The moisture sorption isotherms showed a typical sigmoid shape, and the equilibrium moisture content tended to increase with increasing $a_w$, and increased sharply at above 0.75 $a_w$. At above 0.53 $a_w$, the equilibrium moisture content of the roasted corn powder increased with the increase in the roasting temperature. Six mathematical models (Bradley, Caurie, Halsey, Henderson, Kuhn, and Oswin) were used to fit the experimental data. The Oswin, Caurie, Henderson, and Halsey models were found to have suitability for describing the sorption curves, and the Oswin model was the best fit model for all the roasting temperatures. Concerning the monolayer moisture content, the Guggenheim-Anderson-Boer (GAB) equation showed high significance. The monolayer moisture content increased as the roasting temperature was increased, to 0.043 and 0.053 kg $H_2O/kg$ solids in the corn powder roasted at $180^{\circ}C$ and $240^{\circ}C$, respectively. These results suggest that the roasting temperatures of the corn kernels affected the moisture sorption characteristics ($20^{\circ}C$) of the corn powder.

• Journal of Korean Society of Forest Science
• /
• v.76 no.3
• /
• pp.243-248
• /
• 1987

The U.S. Forest Service administers the world's largest forestry research organization. From its modest beginning in 1876, some 30 years before the United States national forest system was established, the research branch has devoted its effort to meet current and future information needs of the forestry community of the United States, not just for the U.S. Forest Service. The research branch is one of three major administrative units of the U.S. Forest Service. The others being the National Forest System and State and Private Forestry. Currently the National Forest System comprises 155 national forests, 19 national grasslands, and 18 utilization projects located in 44 states. Puerto Rico, and the Virgin Islands. The National Forest System manages these areas for a large array of uses and benefits including timber, water, forage, wildlife, recreation, minerals, and wilderness. It is through the State and Private Forestry branch that the U.S. Forest Service cooperates and coordinates forestry activities and programs with state and local governments, forest industries, and private landowners. These activities include financial and technical assistance in disease, insect, and fire protection ; plan forestry programs ; improve harvesting and marketing practices ; and transfer forestry research results to user groups. Forestry research is carried out through eight regional Forest Experiment Stations and the Forest Product Laboratory. Studies are maintained at 70 administrative sites, and at 115 experimental forest and grasslands. All of the current sciences that composed modern forestry are included in the research program. These range from forest biology (i. e. silviculture, ecology, physiology, and genetics) to the physical, mathematical, engineering, managerial, and social sciences. The levels of research range from application, developmental, and basic research. Research planning and priority identification is an ongoing process with elements of the research program changing to meet short-term critical information needs(i. e. protection research) to long-term opportunities(i. e. biotechnology). Research planning and priority setting is done in cooperation with National Forest Systems, forest industries, universities, and individual groups such as environmental, wilderness, or wildlife organizations. There is an ongoing review process of research administration, organization, and science content to maintain quality of research. In the U.S. Forest Service the research responsibility is not completed until the new information is being applied by the various user group : I. e. technology transfer program. Research planning and development in the U.S. Forest Service is a dynamic activity. Porgrams for the year 2000 and beyond are now in the planning stage.

• Education of Primary School Mathematics
• /
• v.13 no.2
• /
• pp.85-97
• /
• 2010

The purpose of this study is to develop a teaching program in consideration of the geometrical thinking levels of students to make a contribution to teaching figures effectively. To do this, we checked the geometrical thinking levels of fourth-graders, developed a teaching program based on van Hiele's theory, and investigated its effect on their geometrical thinking levels. The teaching program based on van Hiele's theory put emphasis on group member interaction and specific activities through offering various geometrical experiences. It contributed to actualizing activity-centered, student-oriented, inquiry-oriented and inductive instruction instead of sticking to expository, teacher-led and deductive instruction. And it consequently served to improving their geometrical thinking levels, even though some students didn't show any improvement and one student was rather degraded in that regard - but in the former case they made partial progress though there was little marked improvement, and in the latter case she needs to be considered in relation to her affective aspects above all. The findings of the study suggest that individual variances in thinking level should be recognized by teachers. Students who are at a lower level should be given easier tasks, and more challenging tasks should be assigned to those who are at an intermediate level in order for them to have a positive self-concept about mathematics learning and ultimately to foster their thinking levels.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.3
• /
• pp.10-16
• /
• 2020

Computational simulations of adsorption columns were carried out to investigate the removal characteristics of VOCs from a laundry shop. n-Decane was selected as the representative component among the VOCs emitted, and the activity of the adsorbents, such as activated carbon, was evaluated using commercial CFD code. The mathematical framework was composed of continuity and Navier-stokes equations, and the simulation was performed using the Matlab program. The adsorption isotherms of LDF, Freundlich, and Langmuir were evaluated, and the adsorption amount of the adsorption isotherms with the adsorption parameter was compared. The simulation was carried out using a particle porosity, dispersion coefficient, particle density, bed diameter, and bed length of 0.79, 42.4 ㎠/min, 485 g/L, 2.0 cm, and 2.5 cm, respectively. The effect of the gas velocity, dispersion coefficient, and voidage on the adsorption amount was compared in the Langmuir adsorption isotherm. The simulation was carried out in the velocity range of 50 to 200 cm/min, dispersion coefficient range of 100 to 400 ㎠/min, and particle porosity range of 0.66 to 0.79. The simulation results of activated carbon with benzene coincided with the Langmuir isotherm. Three types of adsorption isotherm were compared under similar conditions, and the simulation results showed the efficient adsorption condition for hydrocarbons.

• Journal of Elementary Mathematics Education in Korea
• /
• v.13 no.1
• /
• pp.115-140
• /
• 2009

Freudenthal has advocated the mathematisation theory. Mathematisation is an activity which endow the reality with order, through organizing phenomena. According to mathematisation theory, the departure of children's learning of mathematics is not ready-made formal mathematics, but reality which contains mathematical germination. In the first place, children mathematise reality through informal method, secondly this resulting reality is mathematised by new tool. Through survey, it turns out that area unit of Korea's seventh elementary mathematics textbook is not correspond to mathematisation theory. In that textbook, the area formular is hastily presented without sufficient real context, and the relational understanding of area concept is overwhelmed by the practice of the area formular. In this thesis, first of all, I will reconstruct area unit of seventh elementary textbook according to Freudenthal's mathematisation theory. Next, I will perform teaching experiment which is ruled by new lesson design. Lastly, I analysed the effects of teaching experiment. Through this study, I obtained the following results and suggestions. First, the mathematisation was effective on the understanding of area concept. Secondly, in both experimental and comparative class, rich-insight children more successfully achieved than poor-insight ones in the task which asked testee comparison of area from a view of number of unit square. This result show the importance of insight in mathematics education. Thirdly, in the task which asked testee computing area of figures given on lattice, experimental class handled more diverse informal strategy than comparative class. Fourthly, both experimental and comparative class showed low achievement in the task which asked testee computing area of figures by the use of Cavalieri's principle. Fifthly, Experiment class successfully achieved in the area computing task which resulting value was fraction or decimal fraction. Presently, Korea's seventh elementary mathematics textbook is excluding the area computing task which resulting value is fraction or decimal fraction. By the aid of this research, I suggest that we might progressively consider the introduction that case. Sixthly, both experimental and comparative class easily understood the relation between area and perimeter of plane figures. This result show that area and perimeter concept are integratively lessoned.

• Journal of the Korean School Mathematics Society
• /
• v.12 no.1
• /
• pp.47-70
• /
• 2009

The purpose of this research was to confirm one of constructivists' assumptions that even children 조o are with low reasoning ability can make reflective abstracting ability and cognitive structures by this ability can make generation ability of new knowledge by themselves. To investigate the assumption, learner-centered instruction were implemented to 2nd grade classroom located in Suseong Gu, DaeGu City and with lesson plans which initially were developed by Burns and corrected by the researchers. Recordings videoed using 2 video cameras, observations, instructions, children's activity worksheets, instruction journals were analyzed using multiple tests for qualitative analysis. Some conclusions are drawn from the results. First, even children with low reasoning ability can construct mathematical knowledge on multiplication in their own. ways, Thus, teachers should not compel them to learn a learning lesson's goals which is demanded in traditional instruction, with having belief they have reasoning ability. Second, teachers need to have the perspectives of respects out of each child in their classroom and provide some materials which can provoke children's cognitive conflict and promote thinking with the recognition of effectiveness of learner-centered instruction. Third, students try to develop their ability of reflective and therefore establish cognitive structures such as webs, not isolated and fragmental ones.

• Journal of the Korean School Mathematics Society
• /
• v.22 no.3
• /
• pp.329-350
• /
• 2019

Productive struggle is a student's persevering effort to understand mathematical concepts and solve challenging problems that are not easily solved, but the problem can lead to curiosity. Productive struggle is a key component of students' learning mathematics with a conceptual understanding, and supporting it in learning mathematics is one of the most effective mathematics teaching practices. In comparison to research on students' productive struggles, there is little research on preservice mathematics teachers' productive struggles. Thus, this study focused on the productive struggles that preservice mathematics teachers face in solving a non-routine mathematics problem. Polya's four-step problem-solving process was used to analyze the collected data. Examples of preservice teachers' productive struggles were analyzed in terms of each stage of the problem-solving process. The analysis showed that limited prior knowledge of the preservice teachers caused productive struggle in the stages of understanding, planning, and carrying out, and it had a significant influence on the problem-solving process overall. Moreover, preservice teachers' experiences of the pleasure of learning by going through productive struggle in solving problems encouraged them to support the use of productive struggle for effective mathematics learning for students, in the future. Therefore, the study's results are expected to help preservice teachers develop their professional expertise by taking the opportunity to engage in learning mathematics through productive struggle.

• The Korean Journal of Nuclear Medicine
• /
• v.29 no.1
• /
• pp.48-53
• /
• 1995

This study investigates a simple mathematical model for the quantitative estimation of regional myocardial blood flow in experimental canine coronary artery thrombosis using Rb-82 dynamic myocardial positron emission tomography. The coronary thrombosis was induced using the new catheter technique by narrowing the lumen of coronary vessel gradually, which finally led to partial obstruction of coronary artery. Ten Rb-82 dynamic myocardial PET scans were performed sequentially for each experiment using our 5, 10 and 20 second acquisition protocol, respectively, and three regions of interest were drawn on the transaxial slices, one on left ventricular chamber for input function and the other two on normal and decreased perfusion segments for the flow estimation in those regions. Single compartment model has been applied to the measured sets of regional PET data, and the rate constants of influx to myocardial tissue were calculated for regional myocardial flow estimates with the three parameter fits of raw data by the Levenberg-Marquardt method. The results showed that, (1) single compartment model suggested by Kety-Schmidt could be used for the simple estimation of regional myocardial blood flow, (2) the calculated regional myocardial blood flow estimates were dependent on the selection of input function, which reflected partial volume effect and left ventricular wall motion, and (3) mathematically fitted input and tissue time activity curves were more suitable than the direct application of the measured data in terms of convergence.

• Analytical Science and Technology
• /
• v.26 no.5
• /
• pp.307-314
• /
• 2013

Selenium exists in various forms of chemical species. The activity and bioavailability is strongly dependent on its chemical form and concentration. Consequently the information on each selenium species and its concentration must be exactly determined for the food we take in. In this study, selenium species in seafood were separated and quantified by RP (reversed phase) HPLC (high performance liquid chromatography) coupled with ICP-MS (inductively coupled plasma mass spectrometry) using post-column isotope dilution. $^{79}Br$, which interferes on $^{80}Se$, has mostly been removed by solid phase extraction and then mathematical correction has been applied for the more accurate correction. The experimental result for CRM (certified reference material) DOLT-4 agreed well with the certified value but each selenium species could not be compared. SeCys (selenocysteine) and SeMet (selenomethionine) were the major species detected in seafood such as belt fish, spanish mackerel, and squid that have been serving as Korean diet. The concentrations found in Korean sea food for SeCys and SeMet were in the range of 0-661.6 mg/kg and 137.3-462.7 mg/kg, respectively.

• Journal of Elementary Mathematics Education in Korea
• /
• v.7 no.1
• /
• pp.45-64
• /
• 2003

This study analyzes divisor and multiple in elementary school mathematics textbooks published according to the first to the 7th curriculum, in a view point of the didactic transposition theory. In the first and second textbooks, the divisor and the multiple are taught in the chapter whose subject is on the calculations of the fractions. In the third and fourth textbooks, divisor and multiple became an independent chapter but instructed with the concept of set theory. In the fifth, the sixth, and the seventh textbooks, not only divisor multiple was educated as an independent chapter but also began to be instructed without any conjunction with set theory or a fractions. Especially, in the seventh textbook, the understanding through activities of students itself are strongly emphasized. The analysis on the each curriculum periods shows that the divisor and the multiple and the reduction of a fractions to the lowest terms and to a common denominator are treated at the same period. Learning activity elements are increase steadily as the textbooks and the mathematical systems are revised. The following conclusion can be deduced based on the textbook analysis and discussion for each curriculum periods. First, loaming instruction method also developed systematically with time. Second, teaching method of the divisor and multiple has been sophisticated during the 1st to 7th curriculum textbooks. And the variation of the teaching sequences of the divisor and multiple is identified. Third, we must present concrete models in real life and construct textbooks for students to abstract the concepts by themselves. Fourth, it is necessary to develop some didactics for students' contextualization and personalization of the greatest common divisor and least common multiple. Fifth, the 7th curriculum textbooks emphasize inquiries in real life which teaming activities by the student himself or herself.