• International Journal of Concrete Structures and Materials
• /
• v.10 no.1
• /
• pp.47-60
• /
• 2016

The objective of this study was to evaluate the capability of different strength-maturity models to account for the effect of the hydration heat on the in-place strength development of high-strength concrete specifically developed for nuclear facility structures under various ambient curing temperatures. To simulate the primary containment-vessel of a nuclear reactor, three 1200-mm-thick wall specimens were prepared and stored under isothermal conditions of approximately $5^{\circ}C$ (cold temperature), $20^{\circ}C$ (reference temperature), and $35^{\circ}C$ (hot temperature). The in situ compressive strengths of the mock-up walls were measured using cores drilled from the walls and compared with strengths estimated from various strength-maturity models considering the internal temperature rise owing to the hydration heat. The test results showed the initial apparent activation energies at the hardening phase were approximately 2 times higher than the apparent activation energies until the final setting. The differences between core strengths and field-cured cylinder strengths became more notable at early ages and with the decrease in the ambient curing temperature. The strength-maturity model proposed by Yang provides better reliability in estimating in situ strength of concrete than that of Kim et al. and Pinto and Schindler.

• Elastomers and Composites
• /
• v.56 no.1
• /
• pp.6-11
• /
• 2021

In order to develop an ultra-high-density elastomeric material for substitution of steel dynamic dampers, a new curing system and technique for high-loading of the filler were examined in this study. Mechanochemical modification of chloroprene rubber (MAH-g-CR) using an internal mixer was carried out with maleic anhydride (MAH) as a reactive monomer. The optimum amount of MAH was 10 phr and the efficient grafting of MAH on CR could be achieved at a mixing temperature of 100℃. After preparing MAH-g-CR, 50 mol% epoxidized natural rubber (ENR 50) was blended with MAH-g-CR to develop a "self-curable rubber blend system" via reaction between the functional groups of the elastomeric matrices without the curing agent and additives. The content of ENR 50 was fixed at 30 wt.% throughout evaluation of the curing behavior of the MAH-g-CR/ENR blend. Tungsten powder was added to the MAH-g-CR/ENR matrix up to 60 vol.% to obtain ultra-high-density, and the maximum density obtained was 7.57 g/㎤. Stable ts2 (scorch time) and t90 (90% cure time) could be obtained even when tungsten powder was incorporated up to 60 vol.%. In addition, the tensile strength and damping properties of MAH-g-CR/ENR containing 60 vol.% of tungsten were better than those of CR containing 60 vol.% of tungsten.

• Journal of Technologic Dentistry
• /
• v.45 no.3
• /
• pp.74-80
• /
• 2023

Purpose: This study aimed to evaluate the fit of the anterior and posterior teeth printed using two light-curing three-dimensional (3D) printers. Methods: Anterior and posterior single crowns were designed using dental software and were printed using 2 types of 3D printers, liquid crystal display (LCD) and digital light processing (DLP) (n=40). After the printed crown was scanned again from inside and outside, the prepared teeth were evaluated using a 3D program. To compare the root mean square (RMS) results among groups (α=0.05), the one-way analysis of variance and Tukey's test were used. Results: No statistically significant difference was found between the mean RMS values of the anterior and posterior teeth (p>0.05). However, as a result of comparing the internal, external, and tooth shapes, the DLP group showed significantly low errors in the inner and outer surfaces than LCD group (p<0.05). Conclusion: In terms of clinical acceptance standard of 100 ㎛, the fit of the anterior and posterior teeth fabricated using LCD and DLP was clinically acceptable.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.11a
• /
• pp.727-730
• /
• 2005

The purpose of this study evaluates possibilities of waste phosphogypsum into concerts by steam curing admixture. The waste phosphogypsum is made use of 4 forms(Dehydrate, $\beta$-Hemihydrate, III-Anhydrite and II-Anhydrite) which were changed to in low temperature of calcination. The penetration depth and compressive strength of cement mortar are investigated to evaluate the chloride ion and carbonation resistance. As a result, chloride ion and carbonation resistance of cement mortar admixed with waste phosphogypsum are more excellent than cement mortar contained OPC alone. The internal pores of cement mortar are decreased by using waste phosphogypsum, because the hydrates of ettringite which is denesified in structure is much formed in early ages at steam curing. These densified effect is concluded with improving the resistance to attack of cement mortar including waste phospogypsum.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1988.05a
• /
• pp.67-69
• /
• 1988

In this study, after changing the curing condition of hardner(DDM) and filler($SiO_2$) contents dielectric and dynamic mechanical properties were studied according to the variation of temperature. As the result we obtained a correlative $\alpha$-peak at 125-150[$^{\circ}C$] from dielectric and mechanical properties. With increasing curing condition and filler contents both dielectric and internal friction loss were, decreased, peak temperature shifted to high temperature, but there was no variation on peak temperature with filler contents. As the above result we knew the correspondence between dielectric and mechanical characteristics.

• The Journal of Internal Korean Medicine
• /
• v.30 no.1
• /
• pp.228-232
• /
• 2009

Objective : To expend the oriental medicine-based strategies or therapeutics for anemia, including iron deficiency anemia. Methods : A 23 year-old man suffering from severe and chronic iron deficiency anemia was believed to have disorder of iron absorption. He had neither specific medical cause nor positive response to western treatments. Blood and biochemical parameters such as levels of hemoglobin, ferritin, transferrin and serum iron were serially chased during treatments. Result : Bojungicki-tang was given to the patient based on diagnosis as a deficiency of spleen qi. The hemoglobin level was normalized along with administration of Bojungicki-tang. Also, the distortions of biochemical indicators (ferritin, transferrin and serum iron) reached a normal range within three months. Conclusion : Bojungicki-tang could be a curing remedy for iron deficiency anemia caused by problems in iron absorption if symptom-differentiation has deficiency of spleen qi.

• Korean Journal of Oriental Medicine
• /
• v.15 no.2
• /
• pp.39-50
• /
• 2009

Objectives : Because of emphasizing a side of preventive medicine in the oriental medicine, an interest in Doinqigong(導引氣功: Physical and breathing exercise) has been elated recently. But, it has a limited sphere of application in the present south korea. Therefore we would like to bring out its sphere of application and detailed method in the oriental medicine classics. Method : We have researched theories and methods of Doinqigong in the Junghwaeujeon(中華醫典: Oriental medicine classic collections) DB according to below the procedure. (1) Making a related words list: We have used existing study of Doinqigong to make a list. It has been connected with Doinqigong. It includes not only technical terms, but also general terms. (2) Searching sentences: We have searched sentence that contain terms related with Doinqigong in the Junghwaeujeon DB. (3) Analysis of related sentences: We have searched and classified sentence by theory and method. Result : Results & Conclusion : (1) The total number of oriental medicine classics connected with Doinqigong is twelve. (2) The methods of Doinqigong have classified into three large groups: They are the Doinqigong for preservationing of good health, the Doinqigong for curing disease and the Doinqigong for internal organs and channels. (3) The number of Doinqigong for preservationing of good health in the seven oriental medicine classics is about ten. For example, the Okeumhi(五禽戱: Five animal's dance), the Paldangeum(八段錦: Eight motions of qigong) and so on. The number of oriental medicine classics connected with Doinqigong for curing disease is seven. They contain internal diseases, surgical diseases, diseases of five sensory organs and various diseases in the order of their frequency. The Doinqigong for internal organs and channels is only the Yookjageul(六字訣: Six sound's treatment).

• Polymer(Korea)
• /
• v.38 no.4
• /
• pp.417-424
• /
• 2014

Reactivity and rheological behavior of highly concentrated polymer bonded explosives (PBX) simulant was studied. As a binder, thermosetting hydroxyl terminated polybutadiene (HTPB) was used. By using bimodal $CaCO_3$ (size ratio 10:1) and sugar particles (size ratio 25:1) as fillers, maximum 75 v% filling was possible during melt mixing. The relative viscosities of bimodal suspension were much lower than those of unimodal one and showed minimum values at 0.25 of fine particle fraction. In curing experiment, as curing temperature increased, the time of initiation and completeness of curing reaction became shortened, the torque kept low, and the change of internal temperature decreased.

• Journal of the Korea Institute of Building Construction
• /
• v.16 no.4
• /
• pp.305-311
• /
• 2016

This study examined the long-term inelastic characteristics, including unrestrained shrinkage and creep, of low-heat cement concrete under different ambient curing temperatures. To achieve the designed compressive strength of 42MPa, water-to-binder ratios were selected to be 27.5, 30, and 32.5% for curing temperatures of 5, 20, and $40^{\circ}C$, respectively. Test results showed that the shrinkage strains of concrete mixtures tended to decrease with the decrease in curing temperature because of the delayed evaporation of internal capillary and gel waters. Meanwhile, creep strains were higher in concrete specimens under lower curing temperature due to the occurrence of the transition temperature creep. The design models of KCI provision gave better accuracy in comparison with test results than those of ACI 209, although a correction factor for low-heat cement needs to be established in the KCI provision.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.5
• /
• pp.489-494
• /
• 2004

Long Period Gratings (LPG) is currently receiving considerable attention because of their consistent measuring results fur pressure, temperature, strain and flow. LPG is easier to prepare and has a high sensitivity compared with Fiber Bragg Gratings (FBG). In addition, this kind of optical fiber sensors could be used for implementations in various structures. In this paper, LPG was used to monitor in situ the resin flow and the curing process in VARTM (Vacuum Assisted Resin Transfer. Molding). In order to demonstrate the effectiveness of the method, FBG is inserted into the glass mat to monitor the resin flow using optical spectrum analyzer (OSA). The curing reactions in VARTM are also observed using the same method. From the results, the attenuation wavelength shift and the loss change of attenuation band can be obtained from the status of the RTM (Resin Transfer Molding) sample owing to the internal variations of the .effective index, temperature, and pressure. It is shown that the proposed LPG is more effective in monitoring the curing reaction than FBG.