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      • KCI등재

        콘크리트용 건식생산 바텀애시 골재의 물리적 특성 평가

        하정수,양근혁,안태호 한국콘크리트학회 2021 콘크리트학회논문집 Vol.33 No.2

        The objective of this study is to examine the physical properties of bottom ash aggregates dry produced for concrete, comparing them to those of artificial lightweight and natural aggregates wherever possible. The tested properties include particle distribution curve, density, absorption, unit weight, solid volume, and porosity. The confined compressive strength of aggregates was assessed with respect to their solid-porosity ratios. Bottom ash particles need to be sorted by size and adequately blended to achieve the standard particle distribution curves. The solid volume can be selected as a critical parameter to determine the ten percent fines value (TFV), which represents the crushing resistance of aggregates. From a regression analysis using test data as a function of solid-porosity ratios, the confined compressive strength of bottom ash aggregates was estimated at 22.87 MPa, indicating a slightly higher strength than that of artificial lightweight aggregates (17.66 MPa) but lower value than that of natural aggregates. 이 연구의 목적은 콘크리트에 활용하기 위해 건식으로 생산한 바텀애시 골재의 물리적 특성을 확인하고 인공 경량골재 및 천연골재와 비교 평가하는 것이다. 평가 대상으로 한 물리적 특성은 입도분포, 밀도, 흡수율, 단위용적질량, 실적률 및 공극분포이다. 골재의 구속 압축강도는 고형분률 관점에서 평가하였다. 바텀애시 골재는 크기별로 적절하게 혼합함으로써 표준입도를 맞추어 사용할 필요가 있다. 골재의 파쇄 저항성을 나타내는 10 % 파쇄하중은 실적률과 가장 높은 상관관계를 가지는 것으로 나타났다. 구속 압축강도 측정결과와 골재 고형분률에 대한 회귀분석으로부터 바텀애시 골재의 압축강도는 22.87 MPa로, 인공 경량골재(17.66 MPa)보다 약간 높고 천연골재보다 낮았다.

      • KCI등재

        Hydroxyapatite Coating on Al2O3 by Hydrothermal Process

        하정수 한국세라믹학회 2003 한국세라믹학회지 Vol.40 No.12

        Hydrothermal deposition of hydroxyapatite coatings on Al2O₃ substrates was studied using aqueous solutions of Ca(NO₃)2ㆍ4H₂O and (NH4)2HPO4 containing EDTA disodium salt as a chelating agent for Ca2+. For the precipitation of the coatings the EDTA-Ca2+ chelates were dissociated thermally at 200℃ or decomposed by oxidation with H₂O2 at 90℃. Scanning electron microscopy and X-ray diffraction were used to investigate the deposition behavior and the phase of the coatings. Hydroxyapatite coatings were not deposited with the thermal dissociation method, whereas uniform deposition of the coatings (about 0.7 μm thickness) was obtained with the oxidative decomposition method. The coatings consisted of fine rod-like hydroxyapatite crystals (hexagonal structure) with 60-80 nm diameters, having some preferred orientation with their length (i.e., the c axis) perpendicular to the substrate.ate.

      • KCI등재
      • KCI등재

        Gas Pressure Sintering, Mechanical Properties and Microstructure of Three Kinds of Si3N4 Ceramic

        하정수,정덕수,Chang-Sam 한국세라믹학회 2004 한국세라믹학회지 Vol.41 No.10

        Three kinds of Si3N4 powders (M-11, SN-ESP and SN-E10) were gas-pressure sintered at 1700-1900℃ for 2 h under 18 atm N2. Their densification behavior was investigated and compared as well as the mechanical properties and microstructure of the resulting ceramics. SN-ESP and SN-E10 started to reach nearly full densification at 1750℃ and showed almost no decomposition up to 1900℃. In contrast, M-11 was not fully densified until 1800℃ and showed about 3 % weigh loss at 1900℃ indicating poor thermal stability. SN-ESP and SN-E10 showed much higher strength both at room temperature and 1200℃ than M-11 when fully densified. Compared with SN-ESP, SN-E10 was not only a little better in strength (both at room temperature and 1200℃) and fracture toughness but also much higher in the Weibull modulus due to more interlocked microstructure by well elongated grains.

      • KCI등재
      • KCI등재

        <한국한자어사전>의 음독구결

        하정수 단국대학교 동양학연구원 2016 東洋學 Vol.63 No.-

        This paper is aims to discuss on how to utilize the results of research of the Eumdok-Gugyeol until now. For this purpose, First We analyze the information Gugyeol of the Dictionary of Korean-Chinese Characters. It said the data problems that authority is concentrated on 地藏菩薩本 願經(Ksitigarbha pranidhana Sutra) of the 15th century and 正俗諺解(Jeongsok-eonhae) of the 16th century. These documents became the authority of gugyeol data in the Dictionary of Korean-Chinese Characters. Gugyeol information of the Dictionary of Korean-Chinese Characters does not show enough with the overall look of the Gugyeol. Therefore, when compiling the enlarged the Dictionary of Korean-Chinese Characters. Primarily by reviewing the data of the early Joseon, such as 楞嚴經 (Śūraṅgama Sūtra), 南明集(Nammyeongjip), 直指心體要節(Jikjisimcheyojeol) and manuscripts 蒙山法語略錄(Mongsanbeobeoyaknok) and 佛說四十二章經(Bulseolsasibijanggyeong), 詳校正本慈 悲道場懺法(Sanggyojeongbonjabi doryangchambeob), 梵網經菩薩戒(Beommanggyeongbosalgye), 大方廣圓覺略疏注經(Daebanggwangwongakyaksojugyeong), 永嘉證道歌(Yeonggajeungdoga) etc it argued that there is a need to accommodate the performance. Depending on the previous proposal it showed a more specific way to the entry of Dictionary of Eumdok-Gugyeol by example of ‘伊’(i) and ‘是’(si). And we argue that to solve this imbalance to the point of entry hierarchy of the description of contents. We argued that it is necessary to change the layer structure of entry in Chaja·Idu·Gugyeol(借字·吏讀·口訣) by referring to present the meanings in the 漢韓大辭典(Great Chinese-Korean Dictionary). Lastly, We analyzed the emergence of patterns of Eumdok-gugyeol trailing from the Chinese characters in the Dictionary of Eumdok-Gugyeol. And We examined the actual examples in this reference and associated with which to determine the word of the Dictionary of Korean-Chinese Characters. 본고는 한국한자어사전의 증보편찬에 음독구결 영역에서 지금까지의 연구 성과를 활용하는 방법을 논의하는 데 목적이 있다. 이를 위해 우선 한국한자어사전의 구결 정보를 분석하여, 구결 정보의 근간이 되는전거 자료가 15세기의 地藏菩薩本願經과 16세기의 正俗諺解에 편중되어 있는 문제점을 밝혔다. 이는 한국한자어사전에서 다루고 있는 구결 정보가 구결의 전체적인 양상을 충분히 보여 주지 못한다는 점을 시사한다. 따라서 한국한자어사전의 증보편찬 시에는 조선 초기의 楞嚴經 구결 자료와 南明集, 直指心體要節, 필사본 蒙山法語略錄, 佛說四十二章經, 詳校正本慈悲道場懺法, 梵網經菩薩戒, 大方廣圓覺略疏注經, 永嘉證道歌 등의 자료를 우선적으로 검토하여 그 성과를 수용할 필요가 있음을 주장하였다. 그리고 앞의 제안에 따라 음독구결사전의 표제어를 수록하는 구체적 방안을 논의하기 위해 한국한자어사전의 ‘伊’와 ‘是’ 의 예를 정리하여 제시하였다. 여기에서 파악된 사전 기술의 항목위계의 불균형한 점을 음독구결사전의 내용을 활용하여 해결할 수 있음을 주장하였다. 이를 위해 漢韓大辭典의 뜻풀이 방식을 참조하여 이두·구결·차자어에 한정하여 사전항목의 위계구조를 변경하는 것이 필요함을 주장하였다. 즉 구결 용례로 사용된예들을 동일한 용법으로 파악하여 용법별로 묶어서 구결 항목에 모아 기술하는 것이 사용자의 편의에 부합한다는 점을 강조하였다. 마지막으로 음독구결에서 한자에 후행하는 음독구결의 출현 양상을 분석하여, 한국한자어사전의 단어 판별 기준과의 관련성이 있는 실제 예를 검토하였다. 그 결과의 일부로 구체적인 예문 자료가 포함된 음독구결사전의 정보를 활용하여 한국한자어사전에 수록될 한자어로 판별될 가능성이 있는 단어를 제시하였다.

      • SCOPUSKCI등재

        Hydroxyapatite와 Al<sub>2</sub>O<sub>3</sub> 혼합분말의 상압소결에 의한 TCP/Al<sub>2</sub>O<sub>3</sub> 및 Fluorapatite/Al<sub>2</sub>O<sub>3</sub> 복합재료의 In-Situ 제조

        하정수,한유정,Ha, Jung-Soo,Han, Yoo-Jeong 한국재료학회 2019 한국재료학회지 Vol.29 No.2

        A powder mixture of 70 wt% $Al_2O_3$ and 30 wt% hydroxyapatite (HA) is sintered at $1300^{\circ}C$ or $1350^{\circ}C$ for 2 h at normal pressure. An $MgF_2$-added composition to make HA into fluorapatite (FA) is also prepared for comparison. The samples without $MgF_2$ show ${\alpha}$ & ${\beta}$-tricalcium phosphates (TCPs) and $Al_2O_3$ phases with no HA at either of the sintering temperatures. In the case of $1,350^{\circ}C$, a $CaAl_4O_7$ phase is also found. Densification values are 69 and 78 %, and strengths are 156 and 104 MPa for 1,300 and $1,350^{\circ}C$, respectively. Because the decomposition of HA produces a $H_2O$ vapor, fewer large pores of $5-6{\mu}m$ form at $1,300^{\circ}C$. The $MgF_2$-added samples show FA and $Al_2O_3$ phases with no TCP. Densification values are 79 and 87 %, and strengths are 104 and 143 MPa for 1,300 and $1,350^{\circ}C$, respectively. No large pores are observed, and the grain size of FA ($1-2{\mu}m$) is bigger than that of TCP ($0.7{\mu}m{\geq}$) in the samples without $MgF_2$. The resulting $TCP/Al_2O_3$ and $FA/Al_2O_3$ composites fabricated in situ exhibit strengths 6-10 times higher than monolithic TCP and HA.

      • 지속적 외래 복막투석 중인 말기 신부전 환자들에서의 수근막 증후근

        하정수,이홍기,윤혁진,김양욱,김영훈,박인선 대한신장학회 2001 Kidney Research and Clinical Practice Vol.20 No.2

        Background: Carpal tunnel syndrome(CTS) is a long-term complication in dialysis patients which results from compression of the median nerve within the carpal tunnel. It has been reported to occur with increased frequency in the hemodialysis population, but, there are few reports concering long-term complications in CAPD because of the relatively shorter duration of dialysis in most CAPD patients. The aim of this study was to determine the incidence of CTS in patients undergoing CAPD. Methods: We analyzed 21 chronic renal failure (CRF) patients(males 14, females 7; age range 19-79 yr) undergoing CAPD. The patients were evaluated by questionnare, physical examination, and nerve conduction test(NCT). Age, gender, duration of CRF before CAPD, duration of CAPD, diabetic history were determined. Results: Among the total 21 patients undergoing CAPD, only 5 patients(24%) were CTS, diagnosed by NCT. Two of these patients were symptomatic CTS, three patients were non-symptomtic CTS. So, there were no relationship between the incidence of CTS and clinical symptoms. Among the diabetic dialysis patients, the incidence of CTS was 28.57%. Also there was no increase in the number of diatetic patients with CTS. Conclusion: It is concluded that the incidence of CTS in CAPD patients was similar with the previous reported incidence(2-31%) of hemodialysis patients. Since CTS is treatable, annual or even semiannual nerve conduction tests is indicated all CRF patients on chronic dialysis.

      • KCI등재

        修德寺 槿域聖寶館 所藏 妙法蓮華經卷第七의 角筆口訣

        하정수 구결학회 2016 口訣硏究 Vol.0 No.36

        본고는 修德寺 槿域聖寶館에 소장된 절첩본 妙法蓮華經卷第七에 각필로 기입된 부호를 살펴, 그 기입 양상을 파악하고 그 부호들의 일부를 판독하고자 한 것이다. 이 자료에는 단점, 쌍점, 직선, 곡선, 글자 등 다양한 형태의 부호가 각필로 기입되어 있다. 그 부호들 중에서 점토에 해당하는 11(‧)은 ‘’로, 21(‧)은 ‘’로, 31(‧)은 ‘’로, 45(‧)은 ‘’로, 51(‧)은 ‘’로 해독을 시도하였다. 이들은 형태와 위치가 분명하여 판독이 비교적 용이한 예이다. 해독의 방법은 구체적으로는 간경도감본 법화경언해의 언해 부분과 구결문을 참고하여 단점의 기능을 추정하였다. 이를 토대로 하여 法華經第七의 추정 단점 點圖를 제시하였다. 그러나 본고는 판독에 있어서는 기입된 각필 부호가 분명하지 않은 것이 많고 자료의 분량이 적다는 점에서, 해독에 있어서는 독법의 기준이 법화경언해에 편중되었다는 점에서 한계를 갖는다.

      • KCI등재

        Processing of Porous Ceramics with a Cellular Structure Using Polymer Beads

        하정수,김창삼 한국세라믹학회 2003 한국세라믹학회지 Vol.40 No.12

        Two processing routes (i.e., the gel casting and polymer preform routes) using polymer beads were studied to fabricate porous ceramics with a cellular structure. The gel casting route, comprising the gel casting of a ceramic slurry mixed with polymer beads, was found to be inadequate to produce porous ceramic bodies with a interconnected pore structure, due to complete coating of the slurry on the polymer beads, which left just isolated pores in the final sintered bodies. The polymer preform route, involving the infiltration of a polymer beads preform with the ceramic slurry, successfully produced porous ceramics with a highly interconnected network of spherical pores. The pore size of 250 -300 μm was demonstrated and the porosity ranged from 82 to 86%. This process is advantageous to control the pore size because it is determined by the sizes of polymer beads used. Another feature is the avoidance of hollow skeleton, giving a high strength. Two processing routes (i.e., the gel casting and polymer preform routes) using polymer beads were studied to fabricate porous ceramics with a cellular structure. The gel casting route, comprising the gel casting of a ceramic slurry mixed with polymer beads, was found to be inadequate to produce porous ceramic bodies with a interconnected pore structure, due to complete coating of the slurry on the polymer beads, which left just isolated pores in the final sintered bodies. The polymer preform route, involving the infiltration of a polymer beads preform with the ceramic slurry, successfully produced porous ceramics with a highly interconnected network of spherical pores. The pore size of 250 -300 μm was demonstrated and the porosity ranged from 82 to 86%. This process is advantageous to control the pore size because it is determined by the sizes of polymer beads used. Another feature is the avoidance of hollow skeleton, giving a high strength.

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