• Title/Summary/Keyword: $c_1$-construction

Search Result 1,667, Processing Time 0.024 seconds

The Influence of Atmostphere on High Temperature Crystal Growth

  • Klimm, D.;Schroder, W.
    • Proceedings of the Korea Association of Crystal Growth Conference
    • /
    • 1999.06a
    • /
    • pp.51-67
    • /
    • 1999
  • The growth of crystals with high melting points tfus$\geq$1$600^{\circ}C$ faces the researcher with experimental problems, as the choice of materials that withstand such high t is rather limited. Many metallic construction materials are in this high t range already molten or exhibit at least a drastically reduced mechanical strength. The very few materials with tfus》1$600^{\circ}C$ as e.g. W, Mo, and partially even Ir are more or less sensitive against oxygen upon heating. Whenever possible, high t crystal growth is performed under inert atmosphere (noble gases). Unfortunately, any oxides are not thermodynamically stable under such conditions, as reduction takes place within such atmosphere. A thoroughly search for suitable growth conditions has to be performed, that are on the one side "oxidative enough" to keep the oxides stable and on the other side "reductive enough" to avoid destruction of constructive parts of the crystal growth assembly. The relevant parameters are t and the oxygen partial pressure pO2. The paper discusses quantitatively relevant properties of interesting oxides and construction materials and ways to forecast their behavior under growth conditions.r growth conditions.

  • PDF

Comparison of National Standards for Blast Furnace Slag and Fly Ash between Korea and China (한국과 중국간의 고로슬래그 미분말 및 플라이 애시의 품질 규정 비교)

  • Hu, Yun-Yao;Lim, Gun-Su;kim, Jong;Han, Min-Cheol;Han, Cheon-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
    • /
    • 2022.11a
    • /
    • pp.63-64
    • /
    • 2022
  • In this study, the quality of mineral admixture, Comparison of blast-furnace slag(BS) and fly ash(FA)in Korea and China. In the case of BS, Korea is mainly classified into 1 type to 4 types according to the specific surface area, whereas China is classified into S105, 95, and 75 according to the activity index of 28 days of age. In the case of FA, Korea is like BS, is mainly classified into types 1 to 4 according to specific surface area, whereas China is classified into F, C (class F, class C) by ingredients and class I, II, and III according to powder and ignition loss.

  • PDF

Development of a new CVAP structural analysis methodology of APR1400 reactor internals using scaled model tests

  • Jongsung Moon;Inseong Jin;Doyoung Ko;Kyuhyung Kim
    • Nuclear Engineering and Technology
    • /
    • v.56 no.1
    • /
    • pp.309-316
    • /
    • 2024
  • The U.S. Nuclear Regulatory Commission (NRC) Regulatory Guide (RG) 1.20 provides guidance on the comprehensive vibration assessment program (CVAP) to be performed on reactor internals during preoperational and startup tests. The purpose of the program is to identify loads that could cause vibration in the reactor internals and to ensure that these vibrations do not affect their structural integrity. The structural vibrational analysis program involves creating finite element analysis models of the reactor internals and calculating their structural responses when subjected to vibration loads. The appropriateness of the structural analysis methodology must be demonstrated through benchmarks or any other reasonable means. Although existing structural analysis methodologies have been proven to be appropriate and are widely used, this paper presents the development of an improved new structural analysis methodology for APR1400 reactor internals using scaled model tests.

A Study on Risk Influence Factors of Ground Subsidence through Soil Investigation Analysis (지반조사 분석을 통한 지반함몰 위험영향인자 연구)

  • Joung, Ho Young;Lee, Gil Hwan
    • Journal of Korean Society of Disaster and Security
    • /
    • v.10 no.1
    • /
    • pp.43-46
    • /
    • 2017
  • Recently, the development of underground space is being actively carried out in the urban area by saturation, and the excavation works are mainly carried out by various excavation methods by the structures adjacent to the ground and underground excavation. During such excavation work, ground subsidence accidents are occurring due to inattention construction, lack of construction technology, and leakage of ground water. For the prevention of ground subsidence we studied the method of risk influence factors by soil investigation. Analysis of 75 sites soil investigation by U.S.C.S (Unified Soil Classification System), construction method, depth of excavation and we studied the risk influence factors with ground subsidence.

Performance Assessment of Hollow Precast Segmental Bridge Columns with Reinforcement Details for Material Quantity Reduction (조립식 물량저감 중공 철근콘크리트 교각의 성능평가)

  • Kim, Tae-Hoon;Park, Dong-Kyu;Lee, Jae-Hoon;Shin, Hyun-Mock
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.20 no.1
    • /
    • pp.33-43
    • /
    • 2016
  • This study investigates the performance of hollow precast segmental bridge columns with reinforcement details for material quantity reduction. The proposed triangular reinforcement details are economically feasible and rational, and facilitate shorter construction periods. The precast segmental bridge columns provides an alternative to current cast-in-place systems. We tested a model of hollow precast segmental bridge columns under a constant axial load and a quasi-static, cyclically reversed horizontal load. We used a computer program, Reinforced Concrete Analysis in Higher Evaluation System Technology (RCAHEST), for analysis of reinforced concrete structures. The used numerical method gives a realistic prediction of performance throughout the loading cycles for hollow precast segmental bridge column specimens investigated. As a result, proposed reinforcement details for material quantity reduction was equal to existing reinforcement details in terms of required performance.

Study on the Collector Efficiency of an Air Heater in a Solar Air Conditioning System (태양열 이용 냉난방 공조시스템 중 공기식 집열기의 집열효율에 관한 연구)

  • Kim, B.C.;Shin, H.J.;Choi, K.H.;Kum, J.S.
    • Solar Energy
    • /
    • v.20 no.4
    • /
    • pp.1-8
    • /
    • 2000
  • The suggested year round solar air conditioning system has been developed for cooling and heating. In particular, this system focused on cooling and dehumidification and it could reduce a peak time owing to the use of air conditioners in summer. This study was performed to find out how much heating loads could be saved and furthermore whether this suggested system would be possible to do heating without a switch of system in real situations. Through model house experiments, the following conclusions were obtained. 1) The collector efficiency was 36% at maximum, but more improved structure of suggested collector could increase its efficiency. 2) The temperature of outlet air was about $30^{\circ}C$ and it could reduce heating loads. 3) Measured temperature and calculated one agreed well within ${\pm}1.5^{\circ}C$.

  • PDF

Repaired concrete columns with fiber reinforced thixotropic mortar: experimental & FEA approach

  • Achillopoulou, Dimitra V.;Arvanitidou, Konstantinia C.;Karabinis, Athanasios I.
    • Computers and Concrete
    • /
    • v.15 no.1
    • /
    • pp.73-88
    • /
    • 2015
  • Following previous studies, the current paper describes the results of an experimental program concerning the repair of reinforced concrete columns by thixotropic pseudo plastic mortar, preformed to analyze and quantify the influence of initial construction damage to the behavior of the repaired element. Five columns (section scale 1:2) were designed according to the minimum requirements of reinforcement of ductility orientated codes' design with variables the percentages of initial construction damages. All were tested in axial compression with repeated cycles up to failure. For comparison reasons, another one of the same characteristics, yet healthy, was constructed and tested as a reference specimen. A numerical study (Finite Element Analysis) was conducted for further investigation of the behavior of the thixotropic mortar as repair material. The results indicate that: a) surpassing a specific amount of damage, columns even suitably repaired present lower strain capacity, b) finite element analysis present the same way of deboning of the repaired material taking into consideration the buckling of the reinforcement bars.

A Case Study of Hybrid Air Conditioning and Ventilation System (환기 병용형 냉난방 시스템 설계 및 현장 적용 사례 연구)

  • Lee, Hong-Cheol;Hwang, In-Ju;Shin, Hyun-Joon
    • Proceedings of the SAREK Conference
    • /
    • 2008.11a
    • /
    • pp.89-94
    • /
    • 2008
  • In this study it was evaluated that hybrid air conditioning and ventilation system to reduce energy consumption and keep on comfortable indoor environment in an underground shopping center. Room temperature by hybrid HAVC system was controled as $1.8{\sim}2.1^{\circ}C$ low and indoor humidity was controled as $4.1{\sim}5.0%RH$ low, and response was fast in $2.0{\sim}2.5$ times compared with conventional system. And also transportation efficiency of hybrid HVAC system was improved in about 27%, and total energy consumption rate of hybrid HVAC system is decreased in 16% compared with conventional system.

  • PDF

A Study on the Biogasification of Municipal and Industrial Wastewater Sludge (도시 하수 및 공장 폐수 슬러지의 바이오가스화에 관한 연구)

  • Kim, Jahyun;Kim, Seogku;Hwang, Injoo;Ahn, Jaehwan;Kang, Sungwon;Lee, Wontae;Lim, Junhyuk;Lee, Jeakun;Lee, Taeyoon
    • Journal of the Korean GEO-environmental Society
    • /
    • v.15 no.9
    • /
    • pp.5-12
    • /
    • 2014
  • Anaerobic digestion was investigated for the stabilization of sludge, decrease of volatile solids, production of biogas for wastewater sludge. In this study, total solids and volatile solids, elemental analysis were conducted to determine characteristics of various types of sludges and investigate the feasibility of biogas production of Municipal Wastewater Sludge (MWS), Industrial Wastewater Sludge (IWS), mixed sludge (Mix), and Municipal Wastewater Sludg Cake (MWSC). Total solids, volatile solids, and C/N ratio were determined in the range of 11.2~20.6 %, 62.1~83.1 % of TS and 4.96~8.33 %. Using the biochemical methane potential (BMP test), mixed sludge and wastewater sludge finished the methane production within approximately 20 day and 16~17 day. Sludge cake finished within 10 day. Mixed sludge produced 395.5 mL $CH_4$ per g of Volatile Solid (VS) and resulted in the highest methane production. For carbon dioxide production, five sludges had similar value of accumulated carbon dioxide production except for sludge cake.

A CONSTRUCTION OF HERGLOTZ SPACES

  • Lee, Byung-Kwon;Yang, Mee-Hyea
    • The Pure and Applied Mathematics
    • /
    • v.11 no.3
    • /
    • pp.207-215
    • /
    • 2004
  • Let W(z) be a power series with operator coefficients such that multiplication by W(z) is contractive in extC(z). The overlapping space $\varepsilon$(W) of D(W) in C(z) is a Herglotz space with Herglotz function $\varphi$(z) which satisfies $\varphi$(z) + ${\varphi}^*(z^{-1})$ = 2[1-W$^*(z^{-1})W(z)]$.

  • PDF