• 열처리공학회지
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• 제14권2호
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• pp.89-95
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• 2001

The 7175Al alloy is particularly interesting for its high strength and sufficient ductility, fracture toughness and corrosion resistance. Currently vigorous efforts have been made to develop large rockets usable for various purposes in the space. This has created the demand of big size of 7175Al billet which would be applied to heavy forgings. The aim of this study is to investigate the quality level of big billet and the effect of billet size on the mechanical properties of large 7175Al ring roll forgings. The billets range from 370 mm to 720 mm in diameter were homogenized and forged after direct chill casting. The size and volume fraction of second phase particles In ${\Phi}720$ mm billet are larger than those of ${\Phi}370$ mm billet, and its ductility is lower for the condition of homogenization and T6 treatment. The Cu-rich phases formed in interdendritic sites are considered to provide the preferential crack path during cold upsetting. The fracture toughness of ring roll forgings which are made by ${\Phi}370$ mm billet is higher than those of ${\Phi}720$ mm billet.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.2309-2318
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• 2010

It is a plan the government increases a railroad section SOC investment, and to activate railroad construction while a railroad wins the spotlight with green transportation. But an error of the demand forecast that is a base of a railroad investment evaluation follows in occurring big, there is it with an operation with an obstacle of a railroad investment. Case of the Incheon International Airport Railroad which went into operation recently, While a present transportation demand showed about 10% than a demand forecasted in a past conference, it was magnified in a social problem. A lot of research was gone on in road project about traffic demand forecast and error, a study to find out the error cause is an insufficient situation although errors of a railroad occurs big. So, this study looked for errors and causes about trip generation model and modes sharing model of railroad demand forecast but it was defined causes so that it can occur similar problems in the future. Especially it investigated causes after comparing rate of development plan for the realization and O/D size in trip generation model and after comparing rate of modes sharing of past and current and conducting a survey for airport users. In conclusion, it suggested method to reduce errors of railroad demand forecasting in the future.

• International Journal of Advanced Culture Technology
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• 제6권4호
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• pp.58-64
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• 2018

The Extraposition phenomenon in English has been analyzed mainly through two approaches: a derivational approach under the Principles & Parameters framework (P&P) and a representational approach under the early Minimalist framework (MP). The first one tries to understand the phenomenon as a result of the movement of a Big Subject first to the end of a sentence which is then followed by the insertion of an expletive 'it' to the empty Subject position. On the other hand, the second one tries to understand it by way of assuming a Big Subject originally base-generated at the end of a sentence which is followed by the insertion of an expletive 'it' to the empty Subject position. The two approaches, however, are not free from theoretical defects at all: the full derivational approach was under controversy in terms of (1) the failure of the Binding Theory and (2) its inability to suggest anything about the marginal reading issue. On the while, the representational approach has been argued (1) to violate the thematic hierarchy that should be kept in D-structure, and (2) to be also unable to suggest the slightest difference in marginal reading issue as the first one. In this paper I focus mainly on analyzing the 'It'-Extraposition phenomenon in the Optimality Theory. I will show that by way of (i) some newly developed constraints such as Subj., and AHSubj. and (ii) a constraint hierarchy of Subj.>>AHSubj., the controversies of 'It-Extraposition' such as (1) the analysis of construction and (2) the very closely related issue of 'marginal reading issue' can be explained properly.

• 정보과학회 논문지
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• 제43권5호
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• pp.524-530
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• 2016

기존보다 데이터를 빠르게 접근하기 위한 노력과 비-휘발성 메모리의 발전은 메모리 파일 시스템 연구에 큰 기여를 해왔다. 메모리 파일 시스템은 파일 입출력의 고성능을 위해서 기존에 사용하는 읽기-쓰기 입출력보다 오버헤드가 적은 메모리 맵 파일 입출력을 사용하도록 제안하고 있다. 하지만 메모리 맵 파일 입출력을 사용하게 되면서 페이지 테이블을 구축할 때 발생하는 오버헤드가 전체 입출력 성능의 큰 부분을 차지하게 되었다. 또한 같은 파일이 반복적으로 접근될 때마다 페이지 테이블을 매번 삭제하기 때문에, 오버헤드가 불필요하게 중복되어서 발생한다는 점을 발견했다. 본 논문이 제안하는 매핑 캐시는 이러한 중복되는 오버헤드를 제거하기 위해서, 매핑이 해제될 때 파일의 페이지 테이블을 제거하지 않고 저장하고 있다가 다시 접근될 때 이를 재활용할 수 있도록 고안한 기법이다. 매핑 캐시는 기존 파일 입출력 성능보다 2.8배, 그리고 웹서버 전체 성능보다 12% 향상을 보였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기물성,응용부문
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• pp.145-147
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• 2005

In present, most of metallic structures(gas pipeline, oil pipeline, water pipeline, etc) are running parallel with subway and power line in seoul. Moreover subway system and power line make a stray current due to electrical corrosion on metallic structures. The owner of metallic structures has a burden of responsibility for the protection of corrosion and the prevention against big accident such as gas explosion or soil pollution and so on. So, they have to measure and analyze the data about P/S(Pipe to Soil) potential due to stray current of subway system. So, we have developed the Real-time Wireless Remote Monitoring System for Stray Current of Subway System. In this system, the permanent buried type reference electrode is necessary. In this paper, results of development of buried type reference electrode using porous ceramic$({\alpha}-Al_{2}O_{3})$ are presented.

• 천문학회보
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• 제36권1호
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• pp.49.2-49.2
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• 2011

To investigate whether radio galaxies have systematically different accretion disk compared to radio-quiet AGN, we obtained high quality optical spectra for a sample of 22 young radio galaxies, using the KAST Double Spectrograph at the Lick 3-m telescope. Young radio galaxies are particularly useful since the age of the radio phenomena is comparable to that of accretion disk. Based on the optical emission-line diagnostics of narrow line region, which is thought to be photoionized by the nuclear radiation, we constrain the states of the accretion disk. In addition to strong emission lines, i.e., [O I], [O II], [O III], and [Ne III], we use the [Ar III] line to break the degeneracy between the ionization parameter and the SED shape. We find that young radio galaxies show systematically different emission line ratios compared to radio-quiet Type II AGN, suggesting that young radio galaxies probably have the power-law SED without a strong big blue bump. We will present the main results of the emission-line diagnostics.

• Advances in Computational Design
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• 제7권2호
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• pp.129-137
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• 2022

Compo-casting method is one of the popular technique to produce metal based matrix composites. But, one of the main challenges in this process is un-uniform spreading of reinforced subdivisions (particles) inside the metallic matrix and the lack of desirable mechanical properties of the final produced composites due to the low bonding strength among the metal matrix and reinforcement particles. To remove these difficulties and to promote the mechanical properties of these kind of composites, the WARM ARB technique was utilized as supplementary technique to heighten the mechanical and microstructural evolution of the casted Al/Al₂O₃ composite strips. The microstructure evolution and mechanical properties of these composites have been considered versus different WARM ARB cycles by tensile test, average Vickers micro hardness test, wear test and scanning electron microscopy (SEM). The SEM results revealed that during the higher warm- ARB cycles, big alumina clusters are broken and make a uniform distribution of alumina particles. It was shown that cumulating the forming cycles improved the mechanical properties of composites. In general, combined compo-casting and ARB process would consent making Al/Al₂O₃ composites with high consistency, good microstructural and mechanical properties.

• 한국환경보건학회지
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• 제20권1호
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• pp.62-67
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• 1994

ZnO-$Fe_2O_3$ 복합금속 산화물 흡착제가 황화수소 제거능이나 황화된 흡착제의 산화적 재생반응에 미치는 영향을 고찰하였다. Zinc ferrite 흡착제가 가장 높은 황화수소 제거능을 나타내었고 혼합한 $Fe_2O_3$ 흡착제는 황화반응 도중 H$_2$S의 생성을 촉진시킴을 알 수 있었다. 또한 황화반응의 결과로 생성되는 금속황화물들이 H$_2$S 열분해의 촉매로 작용하였으며 H$_2$는 $Fe_2O_3$의 함량이 증가할수록 더 많이 발생하였다. 산화적 재생반응의 결과로부터 ZnS를 제외하고 $Fe_2O_3$를 혼합한 흡착제는 모두 잘 재생됨을 알 수 있었다. 또한 산화적 재생반응 도중 생성될 수 있다고 보고된 zinc sulfate는 생성되지 않았다. 그리고 SO$_2$ 발생 곡선의 형태나 완전재생에 소요되는 시간을 기준으로 판단해 볼 때 $Fe_2O_3$의 혼합량의 변화는 산화적 재생반응에 별다른 영향을 미치지 않음을 알 수 있었다.

• Journal of Dental Anesthesia and Pain Medicine
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• 제23권2호
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• pp.101-110
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• 2023

Background: Dentists make various efforts to reduce patients' anxiety and fear associated with dental treatment. Dental sedation is an advanced method that dentists can perform to reduce patients' anxiety and fear and provide effective dental treatment. However, dental sedation is different from general dental treatment and requires separate learning, and if done incorrectly, can lead to serious complications. Therefore, sedation is performed by a limited number of dentists who have received specific training. This study aimed to investigate the proportion of dentists who practice sedation and the main sedatives they use in the context of the Republic of Korea. Methods: We used the customized health information data provided by the Korean National Health Insurance. We investigated the number of dental hospitals or clinics that claimed insurance for eight main sedatives commonly used in dental sedation from January, 2007 to September, 2019 at the Health Insurance Review and Assessment Service. We also identified the changes in the number of dental medical institutions by region and year and analyzed the number and proportion of dental medical institutions prescribing each sedative. Results: In 2007, 302 dental hospitals prescribed sedatives, and the number increased to 613 in 2019. In 2007, approximately 2.18% of the total 13,796 dental institutions prescribed sedatives, increasing to 3.31% in 2019. In 2007, 168 institutions (55.6%) prescribed N₂O alone, and in 2019, 510 institutions (83.1%) made claims for it. In 2007, 76 (25.1%) hospitals made claims for chloral hydrate, but the number gradually decreased, with only 29 hospitals (4.7%) prescribing it in 2019. Hospitals that prescribed a combination of N₂O, chloral hydrate, and hydroxyzine increased from 27 (8.9%) in 2007 to 51 (9%) in 2017 but decreased to 38 (6.1%) in 2019. The use of a combination of N₂O and midazolam increased from 20 hospitals (6.6%) in 2007 to 51 hospitals (8.3%) in 2019. Conclusion: While there is a critical limitation to the investigation of dental hospitals performing sedation using insurance claims data, namely exclusion of dental clinics providing non-insured treatments, we found that in 2019, approximately 3.31% of the dental clinics were practicing sedation and that N₂O was the most commonly prescribed sedative.

• 정보과학회 논문지
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• 제43권11호
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• pp.1216-1222
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• 2016

대규모 웹 서비스의 등장으로 데이터의 규모가 점차 증가하는 추세이다. 이러한 대규모 데이터를 효율적으로 관리하기 위해 MySQL과 MariaDB와 같은 DBMS가 주로 사용되고 있으며, 이들은 데이터 관리를 위한 스토리지 엔진으로 InnoDB를 주로 사용한다. InnoDB는 ACID를 보장할 뿐만 아니라 대규모 데이터 처리에 적합하다는 장점이 있기 때문이다. InnoDB의 경우, I/O 성능 향상을 위해 버퍼 풀을 통해 데이터와 인덱스를 캐싱하며 락 경쟁(lock contention)을 줄이기 위해 다중 버퍼 풀을 지원한다. 그러나 다중 버퍼 풀 기법은 데이터 일관성 오버헤드를 증가시킨다. 본 논문에서는 다중 버퍼 풀 기법의 오버헤드를 분석한다. 실험 결과, 다중 버퍼 풀 기법을 사용함에 따라 락 경쟁이 최대 46.3%까지 완화되었지만 디스크 I/O와 fsync 명령이 증가하면서 DBMS의 처리량이 50.6%까지 떨어지는 현상을 확인하였다.