• Bulletin of the Korean Chemical Society
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• v.26 no.2
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• pp.253-259
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• 2005

[$(tacn)_4Fe_4O_2(OH)_4]_2{\cdot}8Br{\cdot}9H_2O$ (tacn = 1,4,7-triazacyclononane), a tetranuclear iron(III) complex was synthesized by the hydrolysis of (tacn)FeCl3 and crystallizes in the orthorhombic space group, Pca2(1), with cell parameters, a = 37.574(3) $\AA$, b = 16.9245(12) $\AA$, c = 14.2830(11) $\AA$, V = 9082.9(12) ${\AA}^3$. [$(tacn)_4Fe_4O_2(OH)_4]^{4+}$ cations approach S4 point symmetry containing an adamantane skeleton. Four Fe(III) atoms have distorted octahedral environments with two hydroxo and an oxo bridges. Two [$(tacn)_4Fe_4O_2(OH)_4]^{4+}$ clusters having different Fe…Fe distances are connected to each other by the networked hydrogen bonds. The electrochemical behavior reveals irreversible three cathodic and two anodic peaks. Magnetic properties are characterized by antiferromagnetic (AF) interactions between Fe(III) ion spins. However, the low-lying states are still magnetic and exhibit a blocking behavior and a magnetic hysteresis at low temperatures.

• Korean Journal of Materials Research
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• v.10 no.5
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• pp.360-363
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• 2000

Deformation in the hysteresis loop of $Pb(Zr,Ti)O_3$ (PZT) thin films with various Zr/Ti ratios has been studied by varying the top electrode preparation method and the annealing temperature. Pt/PZT/Pt capacitors was found to be positively poled due to dc plasma potential generated during reactive ion etch (RIE) of Rt. Internal field is formed by space charges trapped at domain boundaries. Aging phenomenon such as constriction in the middle of the hysteresis loop was observed in the PZT film with top electrode deposited by sputtering. Top electrode annealing restores the hysteresis loop by removing the space charges. As Zr/Ti ratio decrease, voltage shift increases and an-nealing temperature at which internal field disappears also increases.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.7
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• pp.482-491
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• 2010

In conventional air-handling units, when the circulated air from the air-conditioned space pass through the cooling coil, the air is over-cooled to eliminate the moisture as well as to decrease the temperature. The purpose of this study is to estimate the thermal performance and energy saving of the cooling/reheating system using heat exchanger which can save both cooling energy and reheating energy by exchanging heat between the cooled air and reheated air. The energy balance equations to estimate the state of the air for each components were provided and the heat transfer rates and the energy saving rates for the system were calculated from the equations. The results showed that the energy saving was up to 40% under present conditions, and saving rates were significantly affected by the air velocity, inlet conditions and the effectiveness of heat exchanger.

• Journal of Periodontal and Implant Science
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• v.53 no.3
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• pp.233-244
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• 2023

Purpose: An implant-supported prosthesis consists of an implant fixture, an abutment, an internal screw that connects the abutment to the implant fixture, and the upper prosthesis. Numerous studies have investigated the microorganisms present on the implant surface, surrounding tissues, and the subgingival microflora associated with peri-implantitis. However, there is limited information regarding the microbiome within the internal screw space. In this study, microbial samples were collected from the supragingival surfaces of natural teeth, the peri-implant sulcus, and the implant-abutment screw hole, in order to characterize the microbiome of the internal screw space in healthy subjects. Methods: Samples were obtained from the supragingival region of natural teeth, the peri-implant sulcus, and the implant screw hole in 20 healthy subjects. DNA was extracted, and the V3-V4 region of the 16S ribosomal RNA was sequenced for microbiome analysis. Alpha diversity, beta diversity, linear discriminant analysis effect size (LEfSe), and network analysis were employed to compare the characteristics of the microbiomes. Results: We observed significant differences in beta diversity among the samples. Upon analyzing the significant taxa using LEfSe, the microbial composition of the implant-abutment screw hole's microbiome was found to be similar to that of the other sampling sites' microbiomes. Moreover, the microbiome network analysis revealed a unique network complexity in samples obtained from the implant screw hole compared to those from the other sampling sites. Conclusions: The bacterial composition of the biofilm collected from the implant-abutment screw hole exhibited significant differences compared to the supra-structure of the implant. Therefore, long-term monitoring and management of not only the peri-implant tissue but also the implant screw are necessary.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.4
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• pp.658-665
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• 2007

Oligodontia is defined as the congenital absence of six or more teeth in dentition, excluding the third molars. The prevalence of congenital missing teeth is about 1.6 to 9.6% of population and the prevalence of oligidontia is about 0.08 to 1.1%. The mandibular second premolar is the most frequently absent after the third molar, followed by the maxillary lateral incisor and upper second premolar. Females seem to be affected slightly more than males. Oligodontia may occur either in isolation, or as a part of a syndrome such as ectodermal dysplasia. Different causes are possible for oligodontia: physical obstruction or distruction of the dental lamina, space limitation, functional abnormalities of the dental epithelium, failure of induction of the underlying mesenchyme, chemotherapy, radiotherapy or genetic factor. Because oligodontia would result in esthetic and functional problems, such as facial asymmetry or occlusal disharmony, early diagnosis from clinical and radiographic examination was necessary. And appropriate treatment plan should be followed. This case report was about oral conditions and treatment of the oligodontia patients who have no specific systemic disease.

• Journal of the Korean Vacuum Society
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• v.17 no.4
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• pp.270-277
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• 2008

Vacuum is any air or gas pressure less than a prevailing pressure in an environmental or, specifically, any pressure lower than the atmospheric pressure and is used by a wide variety of scientists and engineering - including clean environment, thermal insulation, very long mean free path, plasma, space simulation[1]. The space environment is characterized by such a severe condition as high vacuum, and very low and high temperature. Since a satellite will be exposed to such a space environment as soon as it goes into its orbit, space environmental test should be carried out to verify the performance of the satellite on the ground under the space environmental conditions. A general and widely used method to simulate the space environment is using a thermal vacuum chamber which consists of vacuum vessel and thermally controlled shroud. As indicated by name of vacuum chamber, the vacuum technology is applied to design and manufacture of the thermal vacuum chamber. This paper describe the vacuum technology which is applied to space business.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.4
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• pp.123-131
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• 2006

The majority of pedestrian fatalities and injuries are caused by vehicle-pedestrian accidents. Recently, it has been recognized as a serious problem. Injuries of occupants in a vehicle have been decreased considerably. However, efforts for protection of pedestrians are still insufficient. These days, many advanced industries are striving for a better protection of pedestrians by using an active hood lift system, rather than reforming the existing structure. In this research, the active hood lift system is designed to enhance the performance for protection. The active hood lift system is analyzed by using the nonlinear finite element method. An optimization problem is formulated by incorporation of the analysis results. Orthogonal arrays are utilized to solve the formulated problem. An iterative optimization algothrithm using orthogonal arrays is utilized for design in the discrete space. It is found that the method can remarkably decrease the number of function evaluations.

• Journal of ILASS-Korea
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• v.19 no.4
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• pp.174-181
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• 2014

This study investigates the effects of nanoparticle size and temperature on the thermal conductivity enhancement of water-based alumina ($Al_2O_3$) nanofluids, using the centrifuging method and relative centrifugal forces of differing magnitude to produce nanofluids of three different particles without involving any dispersants or surfactants. We determined the coupling dependency in thermal conductivity enhancement relative to nanoparticle size and temperature of the alumina nanofluids and also experimentally showed that the effect of temperature on thermal conductivity is strongly dependent on nanoparticle size. Also, our experimental data presented that the effective medium theory models such as the Maxwell model and Hasselman and Johnson model are not sufficient to explain the thermal conductivity of nanofluids since they cannot account for the temperature- and size-dependent nature of water-based alumina nanofluids.

• Imaging Science in Dentistry
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• v.38 no.2
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• pp.117-120
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• 2008

The odontogenic keratocyst (OKC) is a developmental odontogenic cyst typically occurring in the jaws. Since the first description of OKC was published in 1956, the lesion has been of particular interest because of its specific histopathologic features, high recurrence rate, and aggressive behavior. Recurrences most commonly arise within bone at the site of the original cyst. However, as lining cells may find their way into surrounding tissues either from implantation during surgery or from cortical perforation recurrences may arise at a distance from the original cyst. Here, we report a rare case of recurrent OKC which was first developed in mandible and recurred within the masticatory space.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10b
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• pp.265-267
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• 2004

경제 여건의 향상 및 생활양식의 변화로 최근 우리나라에서도 당뇨병 환자가 늘어남에 따라 당뇨병의 예측 및 치료가 중요한 관심사가 되고 있다. 본 논문은 1993년과 1995년 두 차례에 걸쳐 경기도 연천 지역 주민들의 여러 가지 신체 지수 등을 조사한 데이터를 대상으로, 1차 년도의 데이터로부터 동일한 환자가 2차 년도에 정상상태를 유지하는지 흑은 당뇨병으로 진행이 되는지를 예측하는 문제를 다룬다. 혈당량, 허리둘레 등의 수치가 당뇨병의 발병에 영향을 끼치는 것은 알려진 사실이므로, 현재의 데이터로부터 앞으로의 발병 가능성을 예측하는 것이 가능하며, 이는 환자에게 보다 정확한 정보를 알려줄 수 있으므로 의미가 있는 일이다. 예측을 위해 본 논문에서는 분류기를 사용하며, 예측율을 높이기 위해 여러 분류기를 BKS로 결합하였다. BKS (behavior knowledge space) 결합 방법은 분류기간의 독립 가정이 필요 없으며, 데이터 크기가 크고 전형적인 경우에 좋은 결과를 낼 수 있는 방법이다. BKS 결합 방법을 통해 실험을 해본 결과 단일 분류기로 실험을 한 결과보다 향상된 성능을 얻을 수 있었으며, 투표 결합 방법과 비교하여 더 좋은 성능을 보였다.