• Title/Summary/Keyword: $\beta$-expansion

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Chemo-Mechanical Analysis of Bifunctional Linear DGEBA/Linear Amine (DDM, DDS) Resin Casting Systems (DGEBA/방향족 아민(DDM, DDS) 경화제의 벤젠링 사이의 관능기 변화가 물성 변화에 미치는 영향에 대한 연구)

  • 명인호;정인재;이재락
    • Composites Research
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    • v.12 no.4
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    • pp.71-78
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    • 1999
  • To determine the effect of chemical structure of linear amine curing agents on thermal and mechanical properties, standard epoxy resin DGEBA was cured with diaminodiphenyl methane (DDM), diaminodiphenyl sulphone (DDS) in a stoichiometrically equivalent ratio. From this work, the effect of aromatic amine curing agents. In contrast, the results show that the DGEBA/DDS cure system having the sulfone structure between the benzene rings had higher values in the conversion of epoxide, density, shrinkage (%), glass transition temperature, tensile modulus and strength, flexural modulus and strength than the DGEBA/DDM cure system having methylene structure between the benzene rings, whereas the DGEBA/DDM cure system presented higher values in the maximum exothermic temperature, thermal expansion coefficient, and thermal stability. These results are caused by the relative effects of sulfone group having strong electronegativity and methylene group having (+) repulsive property and stem from the effect of the conversion ratio of epoxide group. The result of fractography shows that the each grain size of the DDM/DGEBA system with feather-like structure is larger than that of the DDS/DGEBA system.

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Electronic Word-of-Mouth in B2C Virtual Communities: An Empirical Study from CTrip.com (B2C허의사구중적전자구비(B2C虚拟社区中的电子口碑): 관우휴정려유망적실증연구(关于携程旅游网的实证研究))

  • Li, Guoxin;Elliot, Statia;Choi, Chris
    • Journal of Global Scholars of Marketing Science
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    • v.20 no.3
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    • pp.262-268
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    • 2010
  • Virtual communities (VCs) have developed rapidly, with more and more people participating in them to exchange information and opinions. A virtual community is a group of people who may or may not meet one another face to face, and who exchange words and ideas through the mediation of computer bulletin boards and networks. A business-to-consumer virtual community (B2CVC) is a commercial group that creates a trustworthy environment intended to motivate consumers to be more willing to buy from an online store. B2CVCs create a social atmosphere through information contribution such as recommendations, reviews, and ratings of buyers and sellers. Although the importance of B2CVCs has been recognized, few studies have been conducted to examine members' word-of-mouth behavior within these communities. This study proposes a model of involvement, statistics, trust, "stickiness," and word-of-mouth in a B2CVC and explores the relationships among these elements based on empirical data. The objectives are threefold: (i) to empirically test a B2CVC model that integrates measures of beliefs, attitudes, and behaviors; (ii) to better understand the nature of these relationships, specifically through word-of-mouth as a measure of revenue generation; and (iii) to better understand the role of stickiness of B2CVC in CRM marketing. The model incorporates three key elements concerning community members: (i) their beliefs, measured in terms of their involvement assessment; (ii) their attitudes, measured in terms of their satisfaction and trust; and, (iii) their behavior, measured in terms of site stickiness and their word-of-mouth. Involvement is considered the motivation for consumers to participate in a virtual community. For B2CVC members, information searching and posting have been proposed as the main purpose for their involvement. Satisfaction has been reviewed as an important indicator of a member's overall community evaluation, and conceptualized by different levels of member interactions with their VC. The formation and expansion of a VC depends on the willingness of members to share information and services. Researchers have found that trust is a core component facilitating the anonymous interaction in VCs and e-commerce, and therefore trust-building in VCs has been a common research topic. It is clear that the success of a B2CVC depends on the stickiness of its members to enhance purchasing potential. Opinions communicated and information exchanged between members may represent a type of written word-of-mouth. Therefore, word-of-mouth is one of the primary factors driving the diffusion of B2CVCs across the Internet. Figure 1 presents the research model and hypotheses. The model was tested through the implementation of an online survey of CTrip Travel VC members. A total of 243 collected questionnaires was reduced to 204 usable questionnaires through an empirical process of data cleaning. The study's hypotheses examined the extent to which involvement, satisfaction, and trust influence B2CVC stickiness and members' word-of-mouth. Structural Equation Modeling tested the hypotheses in the analysis, and the structural model fit indices were within accepted thresholds: ${\chi}^2^$/df was 2.76, NFI was .904, IFI was .931, CFI was .930, and RMSEA was .017. Results indicated that involvement has a significant influence on satisfaction (p<0.001, ${\beta}$=0.809). The proportion of variance in satisfaction explained by members' involvement was over half (adjusted $R^2$=0.654), reflecting a strong association. The effect of involvement on trust was also statistically significant (p<0.001, ${\beta}$=0.751), with 57 percent of the variance in trust explained by involvement (adjusted $R^2$=0.563). When the construct "stickiness" was treated as a dependent variable, the proportion of variance explained by the variables of trust and satisfaction was relatively low (adjusted $R^2$=0.331). Satisfaction did have a significant influence on stickiness, with ${\beta}$=0.514. However, unexpectedly, the influence of trust was not even significant (p=0.231, t=1.197), rejecting that proposed hypothesis. The importance of stickiness in the model was more significant because of its effect on e-WOM with ${\beta}$=0.920 (p<0.001). Here, the measures of Stickiness explain over eighty of the variance in e-WOM (Adjusted $R^2$=0.846). Overall, the results of the study supported the hypothesized relationships between members' involvement in a B2CVC and their satisfaction with and trust of it. However, trust, as a traditional measure in behavioral models, has no significant influence on stickiness in the B2CVC environment. This study contributes to the growing body of literature on B2CVCs, specifically addressing gaps in the academic research by integrating measures of beliefs, attitudes, and behaviors in one model. The results provide additional insights to behavioral factors in a B2CVC environment, helping to sort out relationships between traditional measures and relatively new measures. For practitioners, the identification of factors, such as member involvement, that strongly influence B2CVC member satisfaction can help focus technological resources in key areas. Global e-marketers can develop marketing strategies directly targeting B2CVC members. In the global tourism business, they can target Chinese members of a B2CVC by providing special discounts for active community members or developing early adopter programs to encourage stickiness in the community. Future studies are called for, and more sophisticated modeling, to expand the measurement of B2CVC member behavior and to conduct experiments across industries, communities, and cultures.

Antioxidant Protection of Alnus firma Sieb. et Zucc Leaves against Photoinhibition in Tailings (폐석지내(廢石地內) 광(光) 저해(沮害)에 대한 사방오리나무 잎의 항산화(抗酸化) 보호(保護))

  • Han, Sim-Hee;Lee, Jae-Cheon;Lee, Wi Young;Park, Youngki;Oh, Chang-Young;Kim, Jong-Kab
    • Journal of Korean Society of Forest Science
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    • v.95 no.1
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    • pp.124-130
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    • 2006
  • To explore the development of photoprotective mechanisms, chlorophyll a fluorescence, chlorophyll and carotenoid content and antioxidant enzyme activity in leaves were investigated at different vitality and leaf development stage of Alnus firma Sieb. et Zucc under tailing condition. The lowest maximum photochemical efficiency (Fv/Fm) in leaves of high- and low-vitality plants were observed at 12:00 pm and 2:00 pm, respectively, and the decrease of Fv/Fm in leaves of all plants were almost completely restored at 6:00 pm. Fv/Fm of full-expansion leaves was higher than that of emergence leaves at all measurement time. Chlorophyll, ${\beta}$-carotene and xanthophyll content in leaves of high-vitality plants and in full-expansion leaves were higher when compared to those of low-vitality plants and emergence leaves. Especially xanthophyll contents in both stage leaves of high-vitality plants were higher than 8.7 times and 18.8 times those of low-vitality plants. Only SOD activity was seen significant difference between leaf stage in leaves of high-vitality plants.

Differential Effect of MyD88 Signal in Donor T Cells on Graft-versus-Leukemia Effect and Graft-versus-Host Disease after Experimental Allogeneic Stem Cell Transplantation

  • Lim, Ji-Young;Ryu, Da-Bin;Lee, Sung-Eun;Park, Gyeongsin;Choi, Eun Young;Min, Chang-Ki
    • Molecules and Cells
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    • v.38 no.11
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    • pp.966-974
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    • 2015
  • Despite the presence of toll like receptor (TLR) expression in conventional $TCR{\alpha}{\beta}$ T cells, the direct role of TLR signaling via myeloid differentiation factor 88 (MyD88) within T lymphocytes on graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL) effect after allogeneic stem cell transplantation (allo-SCT) remains unknown. In the allo-SCT model of C57BL/6 ($H-2^b$) ${\rightarrow}$ B6D2F1 ($H-2^{b/d}$), recipients received transplants of wild type (WT) T-cell-depleted (TCD) bone marrow (BM) and splenic T cells from either WT or MyD88 deficient (MyD88KO) donors. Host-type ($H-2^d$) P815 mastocytoma or L1210 leukemia cells were injected either subcutaneously or intravenously to generate a GVHD/GVL model. Allogeneic recipients of MyD88KO T cells demonstrated a greater tumor growth without attenuation of GVHD severity. Moreover, GVHD-induced GVL effect, caused by increasing the conditioning intensity was also not observed in the recipients of MyD88KO T cells. In vitro, the absence of MyD88 in T cells resulted in defective cytolytic activity to tumor targets with reduced ability to produce IFN-${\gamma}$ or granzyme B, which are known to critical for the GVL effect. However, donor T cell expansion with effector and memory T-cell differentiation were more enhanced in GVHD hosts of MyD88KO T cells. Recipients of MyD88KO T cells experienced greater expansion of Foxp3- and IL4-expressing T cells with reduced INF-${\gamma}$ producing T cells in the spleen and tumor-draining lymph nodes early after transplantation. Taken together, these results highlight a differential role for MyD88 deficiency on donor T-cells, with decreased GVL effect without attenuation of the GVHD severity after experimental allo-SCT.

The Relation of Communication Types of Nurses, Satisfaction on Nursing Services and Intent to Revisit the Hospital Perceived by Patients Admitted to Comprehensive Nursing Care Service (간호·간병통합서비스를 이용한 입원환자가 인식한 간호사의 의사소통유형, 간호서비스 만족도 및 병원재이용 의도의 관계)

  • Kim, So-Yeong;Kim, Won-Dong;Lee, Sun-Mi
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.11
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    • pp.321-331
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    • 2017
  • This study was conducted to identify communication types of nurses, satisfaction with nursing services and intent to revisit the hospital by hospitalized patients, and to investigate factors influencing intent to revisit the hospital at a time of expansion of comprehensive nursing care service. The subjects consisted of 123 hospitalized patients in sixgeneral hospitals with more than 100 beds in Gyeongsangnam-do. Data were collected by a self-report questionnaire from July 1 to July 30, 2017. The collected data were analyzed by t-test, ANOVA, Pearson's correlation coefficients, and hierarchical regression. There were significant differences in intend to revisit the hospital depending on age(F=9.83, p<0.001), gender(t=-3.82, p<0.001), marital status(t=2.24, p=0.028), education(F=11.92, p<0.001) and days of hospitalization(F=7.81, p<0.001). Intent to revisit the hospital indicated a significantly positive correlation between informative(r=0.609, p<0.001) and affiliative(r=0.536, p<0.001) communication types and satisfaction with nursing services(r=7.97, p<0.001), as well as a significantly negative correlation with authoritative communication types(r=-0.356, p<0.001). Factors influencing intent to revisit the hospital were informational communication type(${\beta}=0.38$, p=0.003) and satisfaction with nursing services(${\beta}=0.84$, p<0.001). Based on these findings, it is necessary to develop various educational programs and conduct systematic education to facilitate effective communication between nurses and patients in order to improve the quality of nursing service and satisfaction of patients admitted to comprehensive nursing care services.

Development of Venturi System for Microbubble Generation (미세기포 생성을 위한 벤츄리 시스템 개발)

  • Yun, Jeong Eui;Kim, Joo Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.10
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    • pp.865-871
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    • 2014
  • This study was conducted with the aim of developing a venturi-type air supply system for a microbubble generator. In order to determine the influence of the varying geometry of the venturi tube on the flow characteristics, a computational fluid dynamics (CFD) simulation was performed using the commercial CFD software ANSYS CFX-15. Furthermore, in order to elucidate the effects of variation in major design dimensions such as the air supply hole size, position of holes, and number of holes on the air supply characteristics, two-phase multiflow CFD analysis was performed. The analysis results showed that the starting point of expansion on the venturi tube with 0.75 is the best hole position and that the air supply hole size and the number of holes are linearly proportional to the amount of air.

The Cell Survival and Differentiation after Transplantation, Which Harvest from Adult Rat Brain by High-speed Centrifugation Method

  • Kim, Jong-Tae;Yoo, Do-Sung;Woo, Ji-Hyun;Huh, Pil-Woo;Cho, Kyung-Sock;Kim, Dal-Soo
    • Journal of Korean Neurosurgical Society
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    • v.38 no.2
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    • pp.121-125
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    • 2005
  • Objective : Many recent reports have shown that the mature mammalian brain harbors multipotent stem cells, rendering the brain capable of generating new neurons and glia throughout life. Harvested stem cells from an adult rat are transplanted in order to evaluate the cell survival and differentiation. Methods : Using a percoll gradient with a high speed centrifugation method, we isolate neural stem/progenitor cells were isolated from the subventricular zone[SVZ] of a syngeneic adult Fisher 344 rats brain. For 14days expansion, the cultured cells comprised of a heterogeneous population with the majority of cells expressing nestin and/or GFAP. After expanding the SVZ cells in the presence of basic fibroblast growth factor-2, and transplanting then into the hippocampus of normal rats, the survival and differentiation of those cells were examined. For transplantation, the cultured cells were labeled with BrdU two days prior to use. In order to test their survival, the cells were transplanted into the dorsal hippocampus of normal adult Fisher 344 rats. Results : The preliminary data showed that at 7days after transplantation, BrdU+ transplanted cells were observed around the injection deposition sites. Immuno-fluorescent microscopy revealed that the cells co-expressed BrdU+ and neuronal marker ${\beta}$-tubulin III. Conclusion : The data demonstrate that the in vitro expanded SVZ cells can survive in a heterotypic environment and develop a neuronal phenotype in the neurogenic region. However more research will be needed to examine the longer survival time points and quantifying the differentiation in the transplanted cells in an injured brain environment.

Characteristics of Shear Strength for joined SiC-SiC Ceramics (SiC세라믹스 동종재 접합재의 전단강도 특성 평가)

  • Yoon, Han Ki;Jung, Hun Chea;Hinoki, T.;Kohyama, A.
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.5
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    • pp.483-487
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    • 2014
  • In this study, joining methods with SiC powder as the joining adhesives were studied in order to avoid the residual stresses coming from CTE (Coefficient of Thermal Expansion) mismatch between substrate and joining layer. The shear strength and microstructure of joined material between SiC substrates are investigated. The commercial Hexoloy-SA (Saint-Gobain Ceramics, USA) used in this work as substrate material. The fine ${\beta}$-SiC nano-powder which the average particle size is below 30 nm, $Al_2O_3$, $Y_2O_3$, and $SiO_2$ were used as joining adhesives. The specimens were joined with 20MPa and $1400-1900^{\circ}C$ by hot pressing in argon atmosphere. The shear test was performed to investigate the bonding strength. The cross-section of the joint was characterized by using an optical microscope and scanning electron microscopy (SEM).

Expression of Epstein-Barr Virus Gene and Clonality of Infiltrated T Lymphocytes in Epstein-Barr Virus-associated Gastric Carcinoma

  • Lee, Jae-Myun;Kim, Ho-Guen;Noh, Sung-Hoon;Lee, Won-Young;Kim, Se-Jong;Park, Jeon-Han
    • IMMUNE NETWORK
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    • v.11 no.1
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    • pp.50-58
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    • 2011
  • Background: Epstein-Barr virus associated gastric lymphoepithelioma-like carcinoma (LELC) is characterized by the intensive infiltration of lymphoid cells, the presence of EBV, and the better prognosis over typical adenocarcinoma. Thus, it was assumable that viral latent proteins may be responsible for the recruitment of a certain T cell repertoire to EBV-associated gastric carcinoma. Methods: To examine above possibility, EBV gene expression in gastric carcinoma tissues and usage of TCR among the tumor infiltrating lymphocytes were analyzed. Results: EBV specific DNA and EBERs RNA were detected in 4 out of 30 patients. RT-PCR analysis revealed that all 4 of EBV-positive tumor tissues expressed EBNA1 mRNA and BARTs and LMP2a was detected only one sample out of 4. However, the EBNA2 and LMP-1 transcripts were not detected in these tissues. $CD8^+$ T cells were the predominant population of infiltrating lymphocytes in the EBV-positive gastric carcinoma. According to spectra type analysis of infiltrating T cells, 10 predominant bands were detected by TCR $V{\beta}$ CDR3 specific RT-PCR from 4 EBV-positive tumor tissues. Sequence analysis of these bands revealed oligoclonal expansion of T cells. Conclusion: These findings suggest that clonally expanded T cells in vivo might be a population of cytotoxic T cells reactive to EBV-associated gastric carcinoma.

Influence of Sintering Additives and Temperature on Fabrication of LPS-SiC (액상소결법에 의한 탄화규소 제조시 소결조제와 온도의 영향)

  • JUNG HUN-CHAE;YOON HAN-KI
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2004.11a
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    • pp.266-270
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    • 2004
  • SiC materials have been extensively studied for high temperature components in advanced energy system and advanced gas turbine because it has excellent high temperature strength, low coefficient of thermal expansion, good resistance to oxidation and good thermal and chemical stability etc. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture still impose a severe limitation on practical applications of SiC materials. For these reasons, SiC/SiC composites can be considered as a promising for various structural materials, because of their good fracture toughness compared with monolithic SiC ceramics. But, high temperature and pressure lead to the degradation of the reinforcing jiber during the hot pressing. Therefore, reduction of sintering temperature and pressure is key requirements for the fabrication of SiC/SiC composites by hot pressing method. In the present work, monolithic Liquid Phase Sintered SiC (LPS-SiC) was fabricated by hot pressing method in Ar atmosphere at $1800^{\circ}C$ under 20MPa using $Al_2O_3,\;Y_2O_3\;and\;SiO_2$ as sintering additives in order to low sintering temperature and sintering pressure. The starting powder was high purity $\beta-SiC$ nano-powder with all average particle size of 30mm. The characterization of LPS-SiC was investigated by means of SEM and three point bending test. Base on the composition of sintering additives-, microstructure- and mechanical property correlation, tire compositions of sintering additives are discussed.

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