• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.6
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• pp.27-33
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• 2008

Given a polynomial ${\hbar}(x){\in}F_q[x]$ of degree h, it is an important problem to determine the size of multiplicative subgroup of $\(F_q[x]/({\hbar(x))\)*$ generated by $x-s_1,\;x-s_2,\;{\cdots},\;x-s_n$, where $\{s_1,\;s_2,\;{\cdots},\;s_n\}{\sebseteq}F_q$, and for all ${\hbar}(x){\neq}0$. So far the best known asymptotic lower bound is $(rh)^{O(1)}\(2er+O(\frac{1}{r})\)^h$, where $r=\frac{n}{h}$ and e(=2.718...) is the base of natural logarithm. In this paper, we exploit the coding theory connection of this problem and prove a better lower bound $(rh)^{O(1)}\(2er+{\frac{e}{2}}{\log}r-{\frac{e}{2}}{\log}{\frac{e}{2}}+O{(\frac{{\log}^2r}{r})}\)^h$, where log stands for natural logarithm We also discuss about the limitation of this approach.

• Journal of Periodontal and Implant Science
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• v.42 no.2
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• pp.50-58
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• 2012

Purpose: This study evaluated histologically the tissue responses to and the effects of a customized nano-hydroxyapatite (n-HA) block bone graft on periodontal regeneration in a one-wall periodontal-defect model. Methods: A customized block bone for filling in the standardized periodontal defect was fabricated from prefabricated n-HA powders and a polymeric sponge. Bilateral $4{\times}{\times}4{\times}5$ mm (buccolingual width${\times}$mesiodistal width${\times}$depth), one-wall, critical-size intrabony periodontal defects were surgically created at the mandibular second and fourth premolars of five Beagle dogs. In each dog, one defect was filled with block-type HA and the other served as a sham-surgery control. The animals were sacrificed following an 8-week healing interval for clinical and histological evaluations. Results: Although the sites that received an n-HA block showed minimal bone formation, the n-HA block was maintained within the defect with its original hexahedral shape. In addition, only a limited inflammatory reaction was observed at sites that received an n-HA block, which might have been due to the high stability of the customized block bone. Conclusions: In the limitation of this study, customized n-HA block could provide a space for periodontal tissue engineering, with minimal inflammation.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.6
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• pp.535-544
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• 2017

In this paper, to overcome the limitation of information transmission and reception according to the RF system of UAV, it is necessary to check the position of many UAVs in flight on the basis of mobile communication and to make the LTE modem lightweight and low power And UAVs that are in operation are received and controlled. Through this study, we proposed a method to control real-time location tracking by connecting high-resolution images to the network anytime and anywhere. For this purpose, we propose the requirements and requirements of LTE modem using real-time high-speed data communication technology (3G, 4G LTE, Bluetooth) by presenting the communication module system of LTE-based UAV. N:N control system concept and implementation technology(Control system structure, control data flow chart, flight planning and transmission, real-time location tracking).

• Korean Journal of Environmental Biology
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• v.31 no.4
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• pp.383-392
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• 2013

The objective of this study was to determine the effects of N:P ratio on primary productivity measured as chlorophyll-a (CHL) using the approach of In Situ Nutrient Enrichment Bioassays (NEBs) in Daechung Reservoir. The effects of NEBs on the N:P mass ratios were compared with the field data obtained from monthly-chemical monitoring during 2009~2012. The short-term NEBs showed that the response of primary productivity in the phosphorus spiked treatments (5, 15, 20 and 30 N:P ratios) were greater than the responses in the control (C) and nitrogen spiked treatment (N:P ratio=150, $T_{VI}$). The response in the nitrogen treatment (N:P ratio=150, $T_{VI}$) was less compared to control and all five treatments ($T_I{\sim}T_{VI}$). The outcomes of the NEBs suggest that phosphorus limited the phytoplankton growth and nitrogen addition inhibited the algal growth. In the analysis of nutrients and CHL from the ambient epilimnetic water in Daechung Reservoir, minimum N:P ratios resulted in maximum concentrations of CHL. Overall, our results suggest that the N:P ratio was the key factor in regulating the phytoplankton growth in NEB experiments.

• Korean Journal of Agricultural and Forest Meteorology
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• v.1 no.2
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• pp.160-164
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• 1999

Subsurface environments, including the intermediate vadose zone and aquifers, may be contributing to increased atmospheric concentrations of $N_2$O. Denitrification appears to be the major source of $N_2$O in the subsurface environment. In the intermediate vadose zone, the level of denitrifying activity is dependent on the soil morphology, particularly stratified layers within the soil profile, which impede water and solute movement and create conditions favorable for denitrification. Movement of organic C from the soil surface appears to support denitrifying activity by providing an energy source and increasing the consumption of $O_2$. Denitrirication and $N_2$O production have been observed in aquifers but appear to be of greatest significance in shallow unconfined aquifers. The lack of organic C, N $O_2$, or anaerobiosis is often a limiting factor for activity but seems to be site specific. The presence of denitrifying bacteria does not appear to be a major limitation, based on published results, but the ubiquity of denitrifiers in subsurface environments needs to be confirmed. The fate of the $N_2$O produced in subsurface environments is unknown. Transport of $N_2$O by up ward diffusion, by outgassing at contacts with surface waters, and by ground water use need to be quantified to determine the contribution to atmospheric $N_2$O. Contamination of subsurface environment with N $O_3$$^{ }$ and organics has the potential for increasing the contribution to atmospheric $N_2$O by enhancing denitrification .

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.637-647
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• 2010

The Universal Soil Loss Equation (USLE)-based modeling systems have been widely used to simulate soil erosion studies. However the GIS-based USLE modeling systems have limitation in gully erosion evaluation which is one of the most important factor in soil erosion estimation. In this study, the integrated soil erosion evaluation system using with Sediment Assessment Tool for Effective Erosion Control (SATEEC) system, nLS and Unit Stream Power-based Erosion/Deposition (USPED) model was developed to simulate gully erosion. Gully head location using nLS model, USPED for gully erosion, and the SATEEC estimated sheet and rill erosion were evaluated and combined together with the integrated soil erosion evaluation system. This system was applied to the Haean-myeon watershed, annual average sediment-yield considering sheet, rill and gully erosion was simulated as 101,933 ton/year at the study watershed. if the integrated soil erosion evaluation system is calibrated and validated with the measured data, this system could be efficiently used in developing site-specific soil erosion best management system to reduce soil erosion and muddy water inflow into the receiving waterbody.

• Transactions on Electrical and Electronic Materials
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• v.14 no.5
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• pp.250-253
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• 2013

In this paper, we fabricated 3D pillar type silicon-oxide-nitride-oxide-silicon (SONOS) devices for high density flash applications. To solve the limitation between erase speed and data retention of the conventional SONOS devices, bandgap-engineered (BE) tunneling oxide of oxide-nitride-oxide configuration is integrated with the 3D structure. In addition, the tunneling oxide is modulated by another method of $N_2$ ion implantation ($N_2$ I/I). The measured data shows that the BE-SONOS device has better electrical characteristics, such as a lower threshold voltage ($V_{\tau}$) of 0.13 V, and a higher $g_{m.max}$ of 18.6 ${\mu}A/V$ and mobility of 27.02 $cm^2/Vs$ than the conventional and $N_2$ I/I SONOS devices. Memory characteristics show that the modulated tunneling oxide devices have fast erase speed. Among the devices, the BE-SONOS device has faster program/erase (P/E) speed, and more stable endurance characteristics, than conventional and $N_2$ I/I devices. From the flicker noise analysis, however, the BE-SONOS device seems to have more interface traps between the tunneling oxide and silicon substrate, which should be considered in designing the process conditions. Finally, 3D structures, such as the pillar type BE-SONOS device, are more suitable for next generation memory devices than other modulated tunneling oxide devices.

• Journal of Powder Materials
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• v.11 no.4
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• pp.308-313
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• 2004

An experimental study on the combustion of superfine aluminum powders (average particle diameter, a$_{s}$: ∼0.1 ${\mu}{\textrm}{m}$) in air is reported. The formation of aluminum nitride during the combustion of aluminum in air and the influence of the combustion scenario on the structures and compositions of the final products are in the focus of this study. The experiments were conducted in an air (pressure: 1 atm). Superfine aluminum powders were produced by the wire electrical explosion method. Such superfine aluminum powder is stable in air but once ignited it can burn in a self-sustaining way due to its low bulk: density (∼0.1 g/㎤) and a low thermal conductivity. During combustion, the temperature and radiation were measured and the actual burning process was recorded by a video camera. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and chemical analysis were performed on the both initial powders and final products. It was found that the powders, ignited by local heating, burned in a two-stage self-propagating regime. The products of the first stage consisted of unreacted aluminum (-70 mass %) and amorphous oxides with traces of AlN. After the second stage the AlN content exceeded 50 mass % and the residual Al content decreased to ∼10 mass %. A qualitative discussion is given on the kinetic limitation for AlN oxidation due to rapid condensation and encapsulation of gaseous AlN.N.

• Korean Journal of Child Studies
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• v.6 no.1
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• pp.17-40
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• 1985

This study investigated Korean children's early acquisition of negatives and focused on four research questions: 1) processing of negative variations; 2) the nature of negatives when negatives are completely acquired in Korean (in which meaning and form are matched in one to one mapping); 3) the validity of Bellugi's negative acquisition model in Korean; and 4) the cause of child's erroneous sentence production: limited ability or regularity in children's cognition. The language data of the five subjects (age span; 1.1 - 3.11) were collected by their parents in the natural setting of the home. The results showed that 1) the pivot form, was processed in many ways from a simple to a complicated form, such as <(X+X')+N> <(x+x')+N,Y> <(x+x') N,(y+y')>. It appeared that the children used a simple negative format to reach a one-step advanced negative format. 2) Korean negatives are divided into range of negation in the negative sentence (part or whole), strength of negation (absolute or general), functions of meaning (negation, absences, refusal, prohibition, impossibility). All five children acquired negative sentences in all functions and the complete range after 3 years of age. 3) In spite of the differences in age level, Bellugi's four stage model was in evidence; that is, Korean children's negative acquisition was almost identical with Bellugi's tour stage model in deep structure. 4) Analyses of children's error sentences showed that the sentences with errors were made not because of the children's limitation in cognitive ability but because of the strict application of regularity of rules from the original grammars. Consequently, the children produced negative sentences using two rules: the rule of additive complexity (from simple to complex) and the rule of division (from one to several).

• Journal of Korean Society of Water and Wastewater
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• v.21 no.6
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• pp.679-687
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• 2007

Nanoscale zero valent ion (nZVI) technology is emerging as an innovative method to treat contaminated groundwater. The activity of nZVI is very high due to their high specific surface area, and supporting this material can help to preserve its chemical nature by inhibiting oxidation. In this study, nZVI particles were attached to granular ion-exchange resin through borohydride reduction of ferrous ions, and chemical reduction of nitrate by this material was investigated as a potential technology to remove nitrate from groundwater. The pore structure and physical characteristics were measured and the change by the adsorption of nZVI was discussed. Batch tests were conducted to characterize the activity of the supported nZVI and the results indicated that the degradation of nitrate appeared to be a pseudo first-order reaction with the observed reaction rate constant of $0.425h^{-1}$ without pH control. The reduction process continued but at a much lower rate with a rate constant of $0.044h^{-1}$, which is likely limited by mass transfer. To assess the effects of other ions commonly found in groundwater, the same experiments were conducted in simulated groundwater with the same level of nitrate. In simulated groundwater, the rate constant was $0.078h^{-1}$ and it also reduced to $0.0021h^{-1}$ in later phase. The major limitation in application of ZVI for nitrate reduction is ammonium production. By using a support material with ion exchange capacity, the problem of ammonium release can be solved. The ammonium was not detected in the batch test, even when other competitive ions such as calcium and potassium existed.