• Elastomers and Composites
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• v.48 no.1
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• pp.39-45
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• 2013

Melt grafting of citraconic acid (CCA) onto an ethylene-propylene-diene terpolymer (EPDM) with various peroxide initiators was performed using a Haake Rheocorder. Finding the optimum running condition and concentration is critical for effective grafting and performance of grafted material. Therefore, this study focused on the effects of mixing (reaction) condition and monomer/initiator dosages on the grafting degree, grafting efficiency and crosslinking degree (gel content), melt flow index and mechanical properties of CCA-g-EPDM. As the grafting degree/crosslinking degrees increased, the tensile strength increased significantly, but elongation at break and melt flow index decreased. The initiator 2,5-dimethyl-2,5-di(tert-butyl peroxy)-hexane (T-101) appeared to meet for the best grafting(2.31%). The grafting degree increased markedly with increasing monomer CCA/initiator T-101 contents. The grafting degree also increased with increasing mixing temperature/time, and then leveled off or decreased/increased a little. The optimum monomer/initiator dosages and reaction temperature/time were found to be about 5/0.05 wt% and $180^{\circ}C$/15min, respectively.

• Korean Journal of Soil Science and Fertilizer
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• v.50 no.5
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• pp.369-382
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• 2017

Accurate and optimal water supply to cereal crop is critical in growing stalks and producing maximum yields. Recently, upland crops are cultivated in paddy field soils to reduce overproduced rice in Korea. In order to increase productivity of cereal crops in paddy fields which have poor percolation and drainage properties, it is necessary to fully understand crop response to excessive soil water condition and management of soil drainage system in paddy field. The objectives of this study were to investigate effects of excessive soil water to sesame growth and to quantify stress response using groundwater levels. Two cultivars of sesame were selected to investigate; Gunbak and Areum. These sesames were planted in paddy fields located in Miryang, Gyeongnam with different soil drainage levels and drainage systems. The experiment site was divided into two plots by drainage class; very poorly and somewhat poorly drained. Two different drainage systems were applied to alleviate excessive soil water in each plot: open ditch and pipe drainage system. Soil water contents and groundwater levels were measured every hour during growing season. Pipe drainage system was significantly effective to alleviate wet injury for sesame in paddy fields. Pipe drainage system decreased average soil moisture content and groundwater level during sesame cultivation. This resulted in greater yield and lignan contetns in sesame seeds than ones from open ditch system. Comparison between two cultivars, Gunbak had greater decrease in growth and yield by excessive soil water and high groundwater level than Areum. Seed components (lignan) showed decrease in seeds as soil water increased. When soil moisture content was greater than 40%, lignan content tended to decrease than ones from less soil moisture content. Based on these results, pipe drainage system would be more effective to reduce wet injury to sesame and increase lignan component in paddy field cultivation.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.4
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• pp.19-26
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• 2012

For a seismic design or performance evaluation of a structure, an experimental investigation on a scale model of the structure or numerical analysis based on the finite element model is considered. Regarding the numerical analysis, a three-dimensional finite element analysis is performed if a high accuracy of the results is required, while a sensitivity or fragility analysis which uses huge seismic ground motions leads to the use of a lumped-mass stick model. The conventional modeling technique to build the lumped-mass stick model calculates the amount of the lumped mass by considering the geometric shape of the structure, like a tributary area. However, the eigenvalues of the conventional model obtained through such a calculation are normally not the same as those of the actual structure. In order to overcome such a deficiency, in this study, a new lumped mass stick model is proposed. The model is named the "frequency adaptive-lumped-mass stick model." It provides the same eigenvalues and similar dynamic responses as the actual structure. A non-prismatic column is considered as an example, and its natural frequencies as well as the dynamic performance of the new lumped model are compared to those of the full-finite element model. To investigate the damping effect on the new model, 1% to 5% of the critical damping ratio is applied to the model and the corresponding results are also compared to those of the finite element model.

• Journal of Periodontal and Implant Science
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• v.36 no.2
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• pp.531-554
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• 2006

Oral implants must fulfill certain criteria arising from special demands of function, which include biocompatibility, adequate mechanical strength, optimum soft and hard tissue integration, and transmission of functional forces to bone within physiological limits. And one of the critical elements influencing the long-term uncompromise functioning of oral implants is load distribution at the implant- bone interface, Factors that affect the load transfer at the bone-implant interface include the type of loading, material properties of the implant and prosthesis, implant geometry, surface structure, quality and quantity of the surrounding bone, and nature of the bone-implant interface. To understand the biomechanical behavior of dental implants, validation of stress and strain measurements is required. The finite element analysis (FEA) has been applied to the dental implant field to predict stress distribution patterns in the implant-bone interface by comparison of various implant designs. This method offers the advantage of solving complex structural problems by dividing them into smaller and simpler interrelated sections by using mathematical techniques. The purpose of this study was to evaluate the stresses induced around the implants in bone using FEA, A 3D FEA computer software (SOLIDWORKS 2004, DASSO SYSTEM, France) was used for the analysis of clinical simulations. Two types (external and internal) of implants of 4.1 mm diameter, 12.0 mm length were buried in 4 types of bone modeled. Vertical and oblique forces of lOON were applied on the center of the abutment, and the values of von Mises equivalent stress at the implant-bone interface were computed. The results showed that von Mises stresses at the marginal. bone were higher under oblique load than under vertical load, and the stresses were higher at the lingual marginal bone than at the buccal marginal bone under oblique load. Under vertical and oblique load, the stress in type I, II, III bone was found to be the highest at the marginal bone and the lowest at the bone around apical portions of implant. Higher stresses occurred at the top of the crestal region and lower stresses occurred near the tip of the implant with greater thickness of the cortical shell while high stresses surrounded the fixture apex for type N. The stresses in the crestal region were higher in Model 2 than in Model 1, the stresses near the tip of the implant were higher in Model 1 than Model 2, and Model 2 showed more effective stress distribution than Model.

• The Journal of the Acoustical Society of Korea
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• v.32 no.3
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• pp.262-268
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• 2013

The performances of speech compression schemes appeared to be dependent on the response profiles to compressed stimuli and the features of individual languages to some extent. Although these response profiles were critical in comparing various compression outcomes, the related data were limited in number for Korean monosyllabic words. From the previous study, data from PNT (Preserving No Trait) compression was selected as a base set for comparison. In this study, the outcomes from PPT (Preserving Pitch Trait) and PTT (Preserving Time Trait) were analyzed under the same condition. Then, the properties of these three widely used representative compression schemes were quantitatively compared in normal hearing adults (N=20) for controlled Korean quintet digit sets (0 through 9). Results showed that PPT compression scheme exhibited the best perceptual performances for the Korean quintet digit sets in the final outcomes (PPT>PTT>PNT). The compression ratios of 50% performances were estimated as about 20%, 42%, and 44% for PPT, PTT, and PNT, respectively. The data indicated the influences of the salient psychoacoustic features of the three representative compressions on perceiving Korean monosyllabic digit words. This controlled procedure with monosyllabic quintet sets can evaluate efficiency and effectiveness of other compression schemes and may also contribute to diagnosing auditory processing disorders and fitting special hearing aids with compression issues.

• Polymer(Korea)
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• v.36 no.2
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• pp.223-228
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• 2012

Temperature and pH sensitive graft copolymers [Pluronic-$g$-poly(NIPAAm-$co$-MMA), Polymer A] and [Pluronic-$g$-poly( NIPAAm-$co$-MAA), Polymer C] were synthesized by macro radical graft polymerization with $N$-isopropylacrylamide (NIPAAM)/$N,N$-diethylaminoethylmethacrylate (DEAEMA) and $N$-isopropylacrylamide (NIPAAm)/methacrylic acid (MAA) based on Pluronic, respectively. The chemical structure and molecular weight of the graft copolymers was characterized by $^1H$ NMR and gel permeation chromatography. The aqueous solution properties of graft copolymers were measured using a UV-visible spectrophotometer, contact angle and dynamic light scattering equipment with different temperature and pH conditions. The obtained graft copolymers showed a very sensitive phase transition in response to temperature and pH in aqueous media which suggested that the amine group of DEAEMA segment and carboxylic group of MAA had a great influence on the lower critical solution temperatures (LCST) in Polymer A and C, respectively. The graft copolymers can be utilized for drug delivery system and molecular switching applications where responses to temperature and pH changes are relevant.

• Polymer(Korea)
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• v.32 no.3
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• pp.263-269
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• 2008

To develop carriers of hydrophobic anticancer agents based on chitosan, chitosan oligosaccharide lactate (COS) was chemically modified with lithocholic acid (LA) which is one of the bile acids as a hydrophobic group. The physicochemical properties of the lithocholic acid conjugated chitosan nanoparticles (COS-LA) were investigated using $^1H$-NMR spectroscopy, dynamic light scattering (DLS) and spectrofluorophotometer. COS-LA-paclitaxel (CLs-Tx) nanoparticles loading paclitaxel as an anticancer agent were prepared by a dialysis method and its loading efficiency was measured through HPLC. On the basis of DLS results, the estimated particle sizes of CLs-Tx were around 300 nm. Also, the critical micelle concentration (CMC) was proven to be dependent on the degree of substitution of lithocholic acid. It showed that the CLs-Tx has the superior potential for the application as a paclitaxel carrier.

• Korean Journal of Medicinal Crop Science
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• v.17 no.6
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• pp.439-444
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• 2009

This study was to set the guidelines of soil chemical components in order to assure the safety and quality of the panax ginseng from physiological disorder. The disorder symptoms appeared on the leaf with yellow spot, atrophy, yellow-brown spot, also showed red skin and rough skin of the root. Occurrence type of physiological disorder in cultivated field divided into two types : type I 'such as, yellow spot' consist of single disorder symptom; type II 'such as, yellow spot and yellow-brown spot' consist of two or more different disorder symptoms. The individual contribution of soil properties to the occurrence type was as follows ; The yellow spot was affected by Na > $NO_3$-N > salinity (EC) in soil. The same results was observed in red skin. Atrophy was affected by $NO_3$-N > salinity (EC) > Ca > Mg. Rough skin was affected by $P_2O_5$>pH>Organic material > K. It showed positive associated to $P_2O_5$, pH and K, but negative associated to organic matter. Simultaneous occurrence of two different disorder, including cases which yellow spot and yellow-brown spot, those were affected by $NO_3$-N > salinity (EC) > Na > Mg. In the case of atrophy plus yellow-brown spot, those also were affected by in the order : $NO_3$-N > salinity (EC) > Ca > Mg > Na. Red-rough skin was affected in the order : salinity (EC) > $NO_3$-N > K > Na. Soil chemical components appear to be related to occurrence of physiological disorder, particularly in salinity (EC) and $NO_3$-N. The salinity (EC) and $NO_3$-N were negative related to plant growth. In addition, exchangeable cation capacity play critical roles in attributing to complex occurrence of physiological disorder.

• Korean Journal of Materials Research
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• v.8 no.8
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• pp.693-698
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• 1998

The effects of $AI_{2}$$O_{3}$ and the ratio of $Na_2O/B_2O_3$ on the phase separation and optical properties of sodium borosilicate glass film fabricated by AFD(Aerosol Flame Deposition) were investigated. When AI,O, of 6wt% was added to $66SiO_2-27B_2O_3-7Na_2O$ the clear glass film without any crystallization was produced under air-quenching condition after consolidation. As the amount of $AI_{2}$$O_{3}$ increased from 1.5 to 6.0 wt% the refractive index linearly increased from 1.4610 to 1.4701, and the difference of TE and TM mode causing by residual stress in film increased gradually. However, the difference of TE and TM mode to reveal birefringence could be minimized by annealing below the glass transition temperature after consolidation and air quenching. On the other hand. as the ratio of $Na_2O/B_2O_3$ increased the refractive index and birefringence of glass film tended to increase, but the measurement of their values were not available at over the critical ratio of $Na_2O/B_2O_3$, because of the cloudiness due to crystallization. The phase separation was greatly accelerated with increasing the ratio of $Na_2O/B_2O_3$.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.6
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• pp.1259-1270
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• 2019

The upper bound of differential characteristic probability is mainly used to determine the number of rounds when constructing a block cipher. As the number of rounds affects the performance of block cipher, it is critical to evaluate the tight upper bound in the constructing process. In order to calculate the upper bound of differential characteristic probability, the previous searching methods for minimum number of active S-boxes constructed constraint equations for non-linear operations and linear operations, independently. However, in the case of BOGI design strategy, where linear operation is dependent on non-linear operation, the previous methods may present the less tight upper bound. In this paper, we exploit the properties of BOGI strategy to propose a new method to evaluate a tighter upper bound of differential characteristic probability than previous ones. Additionally, we mathematically proved the validity of our method. Our proposed method was applied to GIFT-64 and GIFT-128, which are based on BOGI strategy, and the upper bounds of differential characteristic probability were derived until 9 round. Previously, the upper bounds of differential characteristic probability for 7-round GIFT-64 and 9-round GIFT-128 were 2^-18.395 and 2^-26.885, respectively, while we show that the upper bounds of differential characteristic probability are more tight as 2^-19.81 and 2^-28.3, respectively.