• Restorative Dentistry and Endodontics
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• v.40 no.2
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• pp.113-122
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• 2015

Objectives: The aim of this paper was evaluating the ratios of electrical impedance measurements reported in previous studies through a correlation analysis in order to explicit it as the contributing factor to the accuracy of electronic apex locator (EAL). Materials and Methods: The literature regarding electrical property measurements of EALs was screened using Medline and Embase. All data acquired were plotted to identify correlations between impedance and log-scaled frequency. The accuracy of the impedance ratio method used to detect the apical constriction (APC) in most EALs was evaluated using linear ramp function fitting. Changes of impedance ratios for various frequencies were evaluated for a variety of file positions. Results: Among the ten papers selected in the search process, the first-order equations between log-scaled frequency and impedance were in the negative direction. When the model for the ratios was assumed to be a linear ramp function, the ratio values decreased if the file went deeper and the average ratio values of the left and right horizontal zones were significantly different in 8 out of 9 studies. The APC was located within the interval of linear relation between the left and right horizontal zones of the linear ramp model. Conclusions: Using the ratio method, the APC was located within a linear interval. Therefore, using the impedance ratio between electrical impedance measurements at different frequencies was a robust method for detection of the APC.

• Journal of the Korean Institute of Gas
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• v.24 no.1
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• pp.49-55
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• 2020

Experimental investigations were conducted to understand the multi-staged combustion characteristics of a swirl-stabilized double cone premixed burner nozzle used for industrial gas turbines for power generation. Multi-staged combustion is implemented by injecting the fuel through the existing manifold of the side slots as well as through the apex of the cone with two fuel injection angles which are slanted or axial. NOx and CO emissions, and wall temperature distributions were measured for various fuel distributions and operating conditions. Results show that NOx emissions are decreased when the fuel distribution to the apex is 3% of the total amount of fuel, which is due to more uniform fuel distribution inside the nozzle, hence less hot spots at the flame. NOx emissions are rather increased when the fuel distribution to the apex is 8% of the total amount of fuel for axial fuel injection by occurrence of flash back in premixing zone of burner.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.3
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• pp.51-55
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• 2008

Purpose: To develop the program used in calculating and estimating anamorphic prisms used to construct an anamorphoser. Methods: If there is a program which can show the apex angle and the volume of prism which are decided by the refraction index of anamorphic prisms and the expanding ratio of incident beam, the production of anamorphic prisms can be done accurately. Moreover, it could become a convenient tool to the design and production of whole optical systems using anamorphic prisms. Developing this program, first, we had to induce formulas of prism that decide the apex angle and the arrangement angle of anamorphic prisms with the given refraction index of anamorphic prism and the given expanding ratio of incident beam. Then we programmed them by delphi 6.0 language so that they could be visualized on screen and easily confirmed. Results: We could develop the program used in calculating and estimating anamorphic prisms used to construct an anamorphoser. Conclusions: Judging from the results of applying this developed program to actual business, we could conclude that this program is useful in calculation and production of anamorphic prisms which are used as components of an anamorphoser because this program can offer a lot of accuracy and quickness to producers.

• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.391-400
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• 1998

The aim of this study was to determine the shaping ability of stainless-steel K file (S-S K file), nickel-titanium K file (Ni-Ti K file) and engine driven nickel-titanium file (Quantec file) in resin simulated root canal. Computed tomography was used to evaluate the change of the root canal morphology. Thirty nine resin simulated root canal were divided into four groups (A:12, B:12, C:12, D:3). Resin simulated canals were scanned by computed tomography before instrumentation (1st C-T scan). Canals were instrumented using step back preparation technique with S-S K file in group A and Ni-Ti K file in group B. Group C was prepared with engine driven Ni-Ti file. Group D was uninstrumented to compare the 1st C-T scan images with 2nd C-T scan images of root canal. Instrumented canals were again scanned using computed tomography (2nd C-T scan), and reformated images of the uninstrumented canals were compared with images of the instrumented canals. In the sections of 2mm and 6mm from the apex, Quantec file caused significantly less canal transportation than S-S K file and Ni-Ti K file (p<0.05). Quantec file produced more centered than S-S K file and Ni-Ti K file in the sections of 2mm and 4mm from the apex (p<0.05). There was no significant difference in the removed volume of canals among the each groups (p>0.05). However the removed canal volume from the apex to 5mm were significantly higher than them from 5mm to 1mm (p<0.05) in each groups. Under the conditions of this study, preparation with Quantec file was more effective and produce more appropriate canal shapes than S-S K file and Ni-Ti K file.

• Restorative Dentistry and Endodontics
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• v.40 no.1
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• pp.44-49
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• 2015

Objectives: This study compared the ability of several techniques to remove calcium hydroxide (CH) from the root canal and determined the influence of CH residues on the accuracy of the electronic apex locator. Materials and Methods: Root canals of 90 human maxillary lateral incisors with confirmed true working length (TWL) were prepared and filled with CH. The teeth were randomly assigned to one of the experimental groups according to the CH removal technique (n = 14): 0.9% saline; 0.9% saline + master apical file (MAF); 17% ethylenediamine tetraacetic acid (EDTA); 17% EDTA + MAF; 5.25% sodium hypochlorite (NaOCl); 5.25% NaOCl + MAF. Six teeth were used as negative control. After CH removal, the electronic working length was measured using Root-ZX (Morita Corp.) and compared with TWL to evaluate Root-ZX accuracy. All specimens were sectioned longitudinally, and the area of remaining CH (CH) and total canal area were measured using imaging software. Results: The EDTA + MAF and NaOCl + MAF groups showed better CH removal than other groups (p < 0.05). Root-ZX reliability to prevent overestimated working length to be > 85% within a tolerance of ${\pm}1.0mm$ (p < 0.05). There was strong negative correlation between amount of CH residues and EAL accuracy (r = -0.800 for ${\pm}0.5mm$; r = -0.940 for ${\pm}1.0mm$). Conclusions: The mechanical instrumentation improves the CH removal of irrigation solutions although none of the techniques removed the dressing completely. Residues of CH medication in root canals affected the accuracy of Root-ZX adversely.

• Journal of Climate Change Research
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• v.9 no.2
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• pp.143-156
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• 2018

Evapotranspiration is a key element in designing and operating agricultural hydraulic structures. The profound effect of climate change to local agro-hydrological systems makes it inevitable to study the potential variability in evapotranspiration rate in order to develop policies on future agricultural water management as well as to evaluate changes in agricultural environment. The APEX-Paddy model was used to simulate local evapotranspiration responses to climate change scenarios. Nine Global Climate Models(GCMs) downscaled using a non-parametric quantile mapping method and a Multi?Model Ensemble method(MME) were used for an uncertainty analysis in the climate scenarios. Results indicate that APEX-Paddy and the downscaled 9 GCMs reproduce evapotranspiration accurately for historical period(1976~2005). For future periods, simulated evapotranspiration rate under the RCP 4.5 scenario showed increasing trends by -1.31%, 2.21% and 4.32% for 2025s(2011~2040), 2055s(2041~2070) and 2085s(2071~2100), respectively, compared with historical(441.6 mm). Similar trends were found under the RCP 8.5 scenario with the rates of increase by 0.00%, 4.67%, and 7.41% for the near?term, mid?term, and long?term periods. Monthly evapotranspiration was predicted to be the highest in August, July was the month having a strong upward trend while. September and October were the months showing downward trends in evapotranspiration are mainly resulted from the shortening of the growth period of paddy rice due to temperature increase and stomatal closer as ambient $CO_2$ concentration increases in the future.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.3
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• pp.311-317
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• 2021

Growth differences in Caulerpa okamurae thallus parts and the effects of apex removal on growth were examined. Erect fronds, stolons, and erect fronds with stolons (erect+stolon) were grown for 14 days, whereas erect fronds without and with apex removal (-A and +A fronds, respectively), were grown for 25 days. The relative growth rates (RGR) of C. okamurae thallus parts ranged from 1.91% to 4.93% day^-1 with maximal and minimal RGR for the stolon and erect+stolon treatments, respectively. Over the 25 days in culture, the -A fronds showed a higher RGR (2.48% day^-1) than the +A fronds (1.96% day^-1). More new erect fronds and stolons were produced by -A fronds than those by +A fronds. In addition, basal cutting of erect C. okamurae fronds resulted in a greater plant length increase than that obtained from top cutting. These findings indicate that vegetative growth is common in C. okamurae, which has excellent wound healing ability, and cutting damage to erect fronds may stimulate enhanced vegetative growth. Thus, we suggest that stolons and erect fronds of C. okamurae could be used as seeding materials for large scale cultivation. Furthermore, this edible species could be a potential seaweed resource for rapid skin regeneration cosmetics.

• Journal of the Korea Society of Computer and Information
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• v.25 no.12
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• pp.127-134
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• 2020

Recently, Harmful sites, including pornographic videos, drugs, personal information and hacking tool distribution sites, have caused serious social problems. However, due to the nature of the Internet environment where anyone can use it freely, it is difficult to control the user effectively. And the site operator operates by changing the domain to bypass the blockage. Therefore, even once identified sites have low persistence. In this paper, we propose multi-channel domain tracking technology, a technique that can effectively track changes in the domain addresses of harmful sites, including the same or similar content, by tracking changes in these harmful sites. Proposed technology is a technology that can continuously track information in a domain using OSINT technology. We tested and verified that the proposed technology was effective for domain tracking with a 90.4% trace rate (sensing 66 changes out of 73 domains).

• The korean journal of orthodontics
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• v.52 no.1
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• pp.42-52
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• 2022

Objective: This study compared soft tissue changes after extraction of the four premolars followed by maximum retraction of the anterior teeth according to the type of anterior teeth movement: tipping and translation. Methods: Patients who had undergone orthodontic treatment involving the extraction of four premolars were retrospectively selected and divided into either the tipping (n = 27) or translation (n = 26) groups based on the retraction of the incisor root apex and the axis changes of the incisors during the treatment period. Lateral pre- and post-treatment cephalograms were analyzed. Results: There were no significant differences between the tipping and translation groups before treatment. The retraction amounts of the root apex of the upper and lower incisors in the tipping group were 0.33 and 0.26 mm, respectively, and 5.02 and 5.31 mm, respectively, in the translation group (p < 0.001). The posterior movements of soft tissue points A and B in the tipping group were 0.61 and 1.25 mm, respectively, and 1.10 and 3.25 mm, respectively, in the translation group (p < 0.01). The mentolabial sulcus angle increased by 5.89° in the tipping group, whereas it decreased by 8.13° in the translation group (p < 0.001). Conclusions: An increased amount of retraction of the incisor root apex led to the increased posterior movement of soft tissue points A and B, and this appeared more distinct in cases involving the lower incisor and lower lip.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.240-240
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• 2021

최근 기상 이변으로 인한 재해 피해에 따라 기후변화에 대한 경각심이 높아지고 있으며, 국내 농업분야에서는 식량안보와 물이용에 대한 기후변화 영향을 완화할 실질적인 대책이 필요하다. 기후변화 적응 전략으로 생육기간 조절(TDS, Transplanting date shift)이 평가되었으나 유출, 관개량, 쌀 생산량 등에 미치는 영향에 대한 연구는 아직 미흡한 실정이다. 본 연구는 기후 변화에 대한 실질적인 적응 전략으로서 TDS뿐만 아니라 대표적인 논 BMP(Best management practice)인물꼬높이 조절(DOR, Drainage outlet rasing)도 평가하고자 하였다. 기후변화 적응 전략 평가를 위한 시나리오는 10개의 GCM과 APEX-Paddy 모형을 사용하여 TDS와 DOR을 조합하여 총 12개 시나리오를 구성하고 기후변화가 유출, 관개량 및 용수생산성에 미치는 영향을 분석하였다. 유출은 각 미래기간 (2020s, 2030s, 2040s) 동안 다르게 나타났으나 현재기간보다 증가하는 추세를 나타냈다. 쌀 생산량은 CO2 상승으로 인해 온도가 상승하면서 지속적으로 감소하였으나, TDS로 인해 상당한 양의 관개량이 절약되는 것을 나타냈다. 또한, DOR에 따라 미래기간의 유출량, 관개 요구량은 크게 감소된 반면 쌀 생산량은 소폭 증가하는 것을 나타냈다. DOR과 40일이 지연된 TDS를 포함하는 RM5 시나리오는 유출 감소 및 용수생산성 증가에 대한 영향이 가장 높은 시나리오로서 본 연구에서 가장 효과적인 BMP(Best Management Practice)로 평가되었다. 본 연구의 결과는 기후 조건을 고려하여 TDS와 DOR의 적절한 조합이 기후 변화의 부정적인 영향을 완화할 수 있을 것으로 시사한다.