• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.13 no.5
• /
• pp.443-451
• /
• 2020

A futuristic locomotion system called Hyperloop is projected for driving at ulta-high speed, levitated in the tube. In hyperloop localization of pods on the linear synchronous motor is essential for pod driving. precision localization is required for acceleration and deceleration of pods driving at speed above 1,000km/h, and also required for adjusting the pod speed driving at this very-high speed to maintain inter-vehicle distance. In this work, a new scale of localization is challenged by modified laser surface velocimeter. In acceleration the speed of a virtual pod is calculated along its displacement measured by laser reflection. Under the requirement of precise localization of the pod driving at ultra-high speed, a displacement measurement device, which detects the difference in reflections from tiles passing by the pod, is developed and evaluated through performance test. Tests of pod speeds below 500km/h have showed exact localization results of the precision in centimeters, and tests of pod speeds above 500km/h have showed localization with very low error rates under 0.1%. For the measurement above 500km/h, future works would pursue the error rate converges to zero.

• Journal of The Geomorphological Association of Korea
• /
• v.19 no.3
• /
• pp.109-121
• /
• 2012

Rock-surface temperatures were observed at a trachytic lava dome, called as Baeknokdam Northwest Face, in the summit area of Mt. Halla, Jeju Island, to examine the frequency and occurrence season of freeze-thaw cycles and the rate of temperature changes during a freezing period. Long-term measurements were recorded over 18 months from November 2006 to April 2008, at a 1-hour logging interval and rock depth of 1.5 cm. Both diurnal freeze-thaw cycles and effective freeze-thaw cycles appear in larger numbers on a south-facing rock face than a north-facing rock face. The diurnal cycles were dominantly observed on February and March for the south face and on November and April for the north face, respectively. The annual freeze-thaw cycles were confirmed in terms of the presence of seasonal freezing periods lasting from mid-November to mid-April for the south face and from early-November to late-April for the north face, respectively. The rate of decreasing temperatures during the seasonal freezing periods is larger on the north face than the south face. Notwithstanding the lower numbers of freeze-thaw events, the north face experiences a higher frost intensity since the number of hours below $-3^{\circ}C$ is larger on the north face than the south face. The number of freeze-thaw events and the duration of days with continuous sub-zero rock temperatures largely depend on the solar radiation controlled by the aspect of the monitored rock surfaces, and thus the high-frequency short-term frost cycle dominantly appears on the south face and the annual frost cycle on the north face, respectively.

• Analytical Science and Technology
• /
• v.21 no.3
• /
• pp.237-243
• /
• 2008

Nano core shell structures of $TiO_2$ particles coated on surface of ZnO nanoparticles were prepared by the polymerized complex and sol-gel method. The average particle size of ZnO by the polymerized complex method showed 100 nm and the average particle size of $TiO_2$ by the sol-gel method showed below 10 nm. The average particle size of $ZnO@TiO_2$ nano core shell struture represented about 150 nm. The agglomeration between the ZnO particles using the polymerized complex method was highly controlled by the uniform absorption of $TiO_2$ colloid on the spherical ZnO surfaces. The driving force of heterogeneous bonding between ZnO and $TiO_2$ was induced by the Coulomb force. The ZnO and $TiO_2$ particles electrified with + and - charges, respectively, resulted in strong bonding by the difference of iso-electric point (IEP) when they laid neutrality pH area, depending on the heterogeneous surface electron electrified by the different zeta potential on the pH values.

• Journal of Life Science
• /
• v.25 no.5
• /
• pp.496-506
• /
• 2015

This study explored adequate water temperature ranges for maintaining stable water quality in a biofloc- based zero-water exchange culture system. Five experimental tanks with the following temperatures were set up: 10℃, 15℃, 20℃, 25℃, and 30℃. First, a biofloc-based culture system was developed in the experimental tanks; then, the tanks were stocked with goldfish and went without a water exchange for 60 days. Conditions for developing a biofloc-based culture system and stable water quality in low concentrations of inorganic nitrogen compounds at 10℃, 15℃, 20℃, 25℃, and 30℃ were maintained after 17, 26, 43, 68, and 78 days, respectively. Beginning from when the goldfish were stocked in the biofloc-based culture tanks, concentrations of $NH_4{^+}-N$ remained constant and at low levels at 10℃ and 15℃, but they showed a gradual increase at 20℃, 25℃, and 30℃. Concentrations of $NO_2{^-}-N$ and $NO_3{^-}-N$ at 10℃ and 15℃ did not remain at low levels and immediately increased. While $NO_2{^-}-N$ concentrations at above 20℃ remained constant and stable at relatively low levels, $NO_3{^-}-N$ concentrations showed a gradual increase. Conditions of 15℃ and below could not maintain low and stable concentrations of $NO_2{^-}-N$. In the pH range of 4.0 to 6.0, $NH_4{^+}-N$ concentration decreased as the pH rose. However, there was no correlation between pH and $NH_4{^+}-N$ concentration in the pH range of 6.0 to 8.0. These results indicate that pH levels should be kept at pH 6.0 and above to maintain a low and stable concentration of $NH_4{^+}-N$ at above 20℃.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.33 no.5
• /
• pp.448-454
• /
• 2000

This study was to examine the physicochemical characteristics of coagulation reaction between ignited oyster shell powder (IOSP) and red tide organisms (RTO), and its feasibility, in developing a technology for the removal of RTO bloom in coastal sea,IOSP was made from oyster shell and its physicochemical characteristics were examined for particle size distribution, surface characteristic by scanning electron microscope, zeta potential, and alkalinity and pH variations in sea water. Two kinds of RTO that were used in this study, Cylindrotheca closterium and Skeletonema costatum, were sampled in Masan bay and were cultured in laboratory. Coagulation experiments were conducted using various c(Incentrations of IOSP, RTO, and a jar tester. The supernatant and RTO culture solution were analyzed for pH, alkalinity, RTO cell number, IOSP showed positive zeta potentials of $11.1{\~}50.1\;mV\;at\;pH\;6.2{\~}12.7$, A positive zeta potential of IOSP slowly decreased with decreasing pNa 4,0 to 2,0. When pNa reached zero, the zeta potential approached zero, When a pMg value was decreased, the positive zeta potential of IOSP increased until pMg 3.0 and decreased below pMg 3.0. IOSP showed 4.8 mV of positive zeta potential while RTO showed -9.2 mV of negative zeta potential in sea water. A positive-negative EDL (electrical double-layer) interaction occurred between $Mg(OH)_2$ adsorption layer of IOSP and RTO in sea water so that EDL attractive force always worked between them. Hence, their coagulation reaction occurred at primary minimum on which an extreme attractive force acted because of charge neutralization by $Mg(OH)_2$ adsorption layer of IOSP. As a result, the coagulation reaction was rapidly processed and was irreversible according to DLVO (Deriaguin-Landau-Verwey-Overbeek) theory. Removal rates of RTO were exponentially increased with increasing both IOSP concentration and G-value. The removal rates were steeply increased until 50 mg/l of IOSP and reached $100{\%}\;at\;400\;mg/l$ of IOSP. Removal rates of RTO were $70.5,\;70.5,\;81.7,\;85.3{\%}$ for G-values of $1,\;6,\;29,\;139\;sec^(-1)$at IOSP 100 mg/l, respectively. This indicated that mixing (i.e., collision among particles) was very important for a coagulation reaction.

• Journal of Bio-Environment Control
• /
• v.20 no.2
• /
• pp.93-100
• /
• 2011

Maintenance of adequate soil water potential during the period of crop growth is necessary to support optimum plant growth and yields. A better understanding of soil water movement within and below the rooting zone can facilitate optimal irrigation scheduling aimed at minimizing the adverse effects of water stress on crop growth and development and the leaching of water below the root zone which can have adverse environmental effects. The objective of this study was to evaluate the feasibility of using a portable irrigation controller with an Watermark sensor for the cultivation of drip-irrigated vegetable crops in a greenhouse. The control capability of the irrigation controller for a soil water potential of -20 kPa was evaluated under summer conditions by cultivating 45-day-old tomato plants grown in three differently textured soils (sandy loam, loam, and loamy sands). Water contents through each soil profile were continuously monitored using three Sentek probes, each consisting of three capacitance sensors at 10, 20, and 30 cm depths. Even though a repeatable cycling of soil water potential occurred for the potential treatment, the lower limit of the Watermark (about 0 kPa) obtained in this study presented a limitation of using the Watermark sensor for optimal irrigation of tomato plants where -20 kPa was used as a point for triggering irrigations. This problem might be related to the slow response time and inadequate soil-sensor interface of the Watermark sensor as compared to a porous and ceramic cup-based tensiometer with a sensitive pressure transducer. In addition, the irrigation time of 50 to 60 min at each of the irrigation operation gave a rapid drop of the potential to zero, resulting in over irrigation of tomatoes. There were differences in water content among the three different soil types under the variable rate irrigation, showing a range of water contents of 16 to 24%, 17 to 28%, and 24 to 32% for loamy sand, sandy loam, and loam soils, respectively. The greatest rate increase in water content was observed in the top of 10 cm depth of sandy loam soil within almost 60 min from the start of irrigation.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.28 no.4
• /
• pp.29-43
• /
• 2000

This study is carried out to investigate the cahracteristics of green management practices and green speed(i.e., ball-roll distance) on 129 Golf Courses in Korea, and to explain the effects of managemet practices that affect green speed. Data collected from green-keepers were subjected to frequency, correlation analysis, and multi-regression analysis using SPSSWIN(Statistical Package for the Social Science). The results are as follows. 1. In spring mowing height, 3.5-4 mm appeared the highest frequency(44.4%) and 4-4.5mm mowing height appeared the high frequency(41.0%). In summer mowing height, 4.5-5mm appeared the highest frequency(51.3%). In fall mowing height, 4-4.5mm appeared the highest frequency(41.0%). 2. In N-fertilizing amount of February and November, 0(zero) g/$m^2$ appeared the highest frequency. In N-fertilizing amount, of June and July 0-2 g/$m^2$ appeared the highest frequency. In N-fertilizing amount, of March, May, August, and September 2-4 g/$m^2$ appeared the highest frequency. In N-fertilizing amount, of October 2-4 or 6-8 g/$m^2$ appeared the highest frequency. 3. In spring topdressing times, 3-6 times appeared the highest frequency(52.6%). In spring topdressing amount, more than 2mm appeared the highest frequency(35.9%). In summer topdressing tierms, 0-3times appeared the highest frequency(71.8%). In summer topdressing amount, 0.5-1mm appeared the highest frequency(46.2%). In fall topdressing times, 0-3times appeared the highest frequency(47.4%). In fall topdressing amount, more than 2mm appeared the highest frequency(35.9%). 4. In spring irrigation tiems, 3-4times/a week appeared the highest frequency (30.6%). In spring irrigation amount, the irrigation below 5mm/day under appeared the highest frequency(38.7%). In summer irrigation times, 4-7times/ a week appeared the highest frequency(38.9%). In summer irrigation amount, 5-10mm/a day appeared the highest frequency(45.2%). In fall irrigation times, 2-3times/a week appeared the highest frequency(36.1%). In fall irrigation amount, the irrigation below 5mm/a day under appeared the highest frequency(45.2%). 5. In spring aeration times, 2 times appeared the highest frequency(55.2%). In spring aeration depth, 5-10mm appeared the highest frequency(81.6%). In fall aeration times, 1 time appeared the highest frequency(82.5%). In fall aeration depth, 5-10mm appeared the highest frequency(86.8%). 6. In spring green speed, 1.98-2.28 or 2.59-2.89mm appeared the highest frequency(32.7%). In summer green speed, 1.98-2.28mm appeared the highest frequency (46.9%). In fall green speed, 1.98-2.28mm appeared the highest frequency(38.8%). 7. The factors which affect green speed were mowing height, N-fertilizing, season, topdressing, irrigation, and aeration. Vertical mowing did not affect green speed. The order of the relevant important factors was mowing height >: N-fertilizing > season > topdressing > irrigation > aeration. Mowing height and N-fertilizing were the most important factors in green speed. As mowing height decreased, green sped always increased. As total N-fertilizing amount decreased, green speed increased. In summer, green sped decreased remarkably. As topdressing times increased and the topdressing amount decreased, green sped increased. As irrigation times increased and irrigation amount decreased, green speed increased.

• Economic and Environmental Geology
• /
• v.54 no.6
• /
• pp.689-698
• /
• 2021

Since the mine reclamation scheme was implemented from 2007 in Korea, various remediation programs have been decontaminated the pollution associated with mining and 254 mines were managed to reclamation from 2011 to 2015. However, as the total amount of contaminated mine drainage has been increased due to the discovery of potential hazards and contaminated zone, more efficient and economical treatment technology is required. Therefore, in this study, the adsorption properties of arsenic was evaluated according to the adsorbents which were derived from water treatment sludge(Alum based adsorbent, ABA-500) and granular ferric hydroxide(GFH), already commercialized. The alum sludge and GFH adsorbents consisted of aluminum, silica materials and amorphous iron hydroxide, respectively. The point of zero charge of ABA-500 and GFH were 5.27 and 6.72, respectively. The result of the analysis of BET revealed that the specific surface area of GFH(257 m²·g^-1) was larger than ABA-500(126~136 m²·g^-1) and all the adsorbents were mesoporous materials inferred from N₂ adsorption-desorption isotherm. The adsorption capacity of adsorbents was compared with the batch experiments that were performed at different reaction times, pH, temperature and initial concentrations of arsenic. As a result of kinetic study, it was confirmed that arsenic was adsorbed rapidly in the order of GFH, ABA-500(granule) and ABA-500(3mm). The adsorption kinetics were fitted to the pseudo-second-order kinetic model for all three adsorbents. The amount of adsorbed arsenic was increased with low pH and high temperature regardless of adsorbents. When the adsorbents reacted at different initial concentrations of arsenic in an hour, ABA-500(granule) and GFH could remove the arsenic below the standard of drinking water if the concentration was below 0.2 mg·g^-1 and 1 mg·g^-1, respectively. The results suggested that the ABA-500(granule), a low-cost adsorbent, had the potential to field application at low contaminated mine drainage.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 1993.06a
• /
• pp.1041-1043
• /
• 1993

Fuzzy logic based Control Theory has gained much interest in the industrial world, thanks to its ability to formalize and solve in a very natural way many problems that are very difficult to quantify at an analytical level. This paper shows a solution for treating membership function inside hardware circuits. The proposed hardware structure optimizes the memoried size by using particular form of the vectorial representation. The process of memorizing fuzzy sets, i.e. their membership function, has always been one of the more problematic issues for the hardware implementation, due to the quite large memory space that is needed. To simplify such an implementation, it is commonly [1,2,8,9,10,11] used to limit the membership functions either to those having triangular or trapezoidal shape, or pre-definite shape. These kinds of functions are able to cover a large spectrum of applications with a limited usage of memory, since they can be memorized by specifying very few parameters ( ight, base, critical points, etc.). This however results in a loss of computational power due to computation on the medium points. A solution to this problem is obtained by discretizing the universe of discourse U, i.e. by fixing a finite number of points and memorizing the value of the membership functions on such points [3,10,14,15]. Such a solution provides a satisfying computational speed, a very high precision of definitions and gives the users the opportunity to choose membership functions of any shape. However, a significant memory waste can as well be registered. It is indeed possible that for each of the given fuzzy sets many elements of the universe of discourse have a membership value equal to zero. It has also been noticed that almost in all cases common points among fuzzy sets, i.e. points with non null membership values are very few. More specifically, in many applications, for each element u of U, there exists at most three fuzzy sets for which the membership value is ot null [3,5,6,7,12,13]. Our proposal is based on such hypotheses. Moreover, we use a technique that even though it does not restrict the shapes of membership functions, it reduces strongly the computational time for the membership values and optimizes the function memorization. In figure 1 it is represented a term set whose characteristics are common for fuzzy controllers and to which we will refer in the following. The above term set has a universe of discourse with 128 elements (so to have a good resolution), 8 fuzzy sets that describe the term set, 32 levels of discretization for the membership values. Clearly, the number of bits necessary for the given specifications are 5 for 32 truth levels, 3 for 8 membership functions and 7 for 128 levels of resolution. The memory depth is given by the dimension of the universe of the discourse (128 in our case) and it will be represented by the memory rows. The length of a world of memory is defined by: Length = nem (dm(m)＋dm(fm) Where: fm is the maximum number of non null values in every element of the universe of the discourse, dm(m) is the dimension of the values of the membership function m, dm(fm) is the dimension of the word to represent the index of the highest membership function. In our case then Length=24. The memory dimension is therefore 128*24 bits. If we had chosen to memorize all values of the membership functions we would have needed to memorize on each memory row the membership value of each element. Fuzzy sets word dimension is 8*5 bits. Therefore, the dimension of the memory would have been 128*40 bits. Coherently with our hypothesis, in fig. 1 each element of universe of the discourse has a non null membership value on at most three fuzzy sets. Focusing on the elements 32,64,96 of the universe of discourse, they will be memorized as follows: The computation of the rule weights is done by comparing those bits that represent the index of the membership function, with the word of the program memor . The output bus of the Program Memory (μCOD), is given as input a comparator (Combinatory Net). If the index is equal to the bus value then one of the non null weight derives from the rule and it is produced as output, otherwise the output is zero (fig. 2). It is clear, that the memory dimension of the antecedent is in this way reduced since only non null values are memorized. Moreover, the time performance of the system is equivalent to the performance of a system using vectorial memorization of all weights. The dimensioning of the word is influenced by some parameters of the input variable. The most important parameter is the maximum number membership functions (nfm) having a non null value in each element of the universe of discourse. From our study in the field of fuzzy system, we see that typically nfm 3 and there are at most 16 membership function. At any rate, such a value can be increased up to the physical dimensional limit of the antecedent memory. A less important role n the optimization process of the word dimension is played by the number of membership functions defined for each linguistic term. The table below shows the request word dimension as a function of such parameters and compares our proposed method with the method of vectorial memorization[10]. Summing up, the characteristics of our method are: Users are not restricted to membership functions with specific shapes. The number of the fuzzy sets and the resolution of the vertical axis have a very small influence in increasing memory space. Weight computations are done by combinatorial network and therefore the time performance of the system is equivalent to the one of the vectorial method. The number of non null membership values on any element of the universe of discourse is limited. Such a constraint is usually non very restrictive since many controllers obtain a good precision with only three non null weights. The method here briefly described has been adopted by our group in the design of an optimized version of the coprocessor described in [10].

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.5 no.1
• /
• pp.13-21
• /
• 1985

This experiment was carried out to study the effect of the autumnal cutting times on the regrowth, the accumulated carbohydrate and dry matter yield of Italian ryegrass The results were summarized as follows: 1. In dry matter yield, the plot of earlier cutting was shown the highest yield (p<0.05), and that of the last-cutting was shown lower yield of dry matter than that the none-cutting plot. 2. TSC (Total Water Soluble Carbohydrate) content slightly decreased after the first cutting and gradually increased according to the regrowth, and then decreased again to the second cutting time. And also the TSC content levels of stubble, stem and leaf at one week before falling to sub-zero temperature were all the highest in the eariler cutting plot (p<0.01), and there was significant correlation between the TSC content level and the second harvested dry matter yield (p<0.05). 3. CGR (Crop Growth Rate) was decreased below $8^{\circ}C$. RLGR (Relative Leaf area Growth Rate) and NAR (Net Assimilation Rate) were both high during 30 days after regrowth, and low after regrowth in all plots. LAI (Leaf Area Index) rapidly increased during 50 days after cutting, and then slowly increased in all the plots, and maximum LAI was 3.4-5.8. Also dry matter yield increased in the plots having a high LAI to 70 days after cutting. 4. It was recognized that there were significant correlation between TSC, LAI, CGR, NAR, LWR (Leaf Weight Ratio) and the second harvested dry matter yield during the low temperature periods, and the degree of contribution to dry matter yield was in order of LWR>LAI>TSC>NAR>CGR.