Effects of Carbonation on the Microstructure of Cement Materials

Son Tung Pham,William Prince 한국콘크리트학회 2014 International Journal of Concrete Structures and M Vol.8 No.4

The objective of this work was to examine the influence of carbonation on the microstructure of cement materials. Different materials, which were CEM I mortar and paste, CEM II mortar and paste, were carbonated at 20℃, 65 % relative humidity and 20 % of CO₂ concentration. The specific surface area and pore size distribution were determined from two methods: nitrogen adsorption and water adsorption. The results showed that: (1) nitrogen adsorption and water adsorption do not cover the same porous domains and thus, we observed conflicts in the results obtained by these two techniques; (2) the CEM II based materials seemed to be more sensible to a creation of mesoporosity after carbonation than the CEM I based materials. The results of this study also helped to explain why observations in the literature diverge greatly on the influence of carbonation on specific surface area.

Stock Market Reactions to the Comprehensive and Progressive Agreement for Trans-Pacific Partnership’s Approval: Evidence from Vietnam

Son Tung Ha,Thi Hong Hanh Pham,Thi Nguyet Anh Nguyen 세종대학교 경제통합연구소 2021 Journal of Economic Integration Vol.36 No.3

We examine the stock market performance of Vietnam’s listed firms in response to the country’s approval of the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP). Employing an event study methodology, we first calculate the abnormal returns of all listed Vietnamese firms around the CPTPP’s approval date. Then, we attempt to link these abnormal returns to firms’ characteristics. We find evidence that the announcement of the CPTPP’s approval is associated with positive abnormal returns for Vietnam’s listed firms. We also find considerable heterogeneity in the magnitude and pace of the impacts of the CPTPP’s approval on market returns across Vietnam’s two stock exchanges. However, we fail to reject the null hypothesis that the market did not react to the CPTPP’s approval at the sectoral level.

Factors Influencing Horizontal Cooperation Among Logistics Enterprises: An Empirical Study from Vietnam

Son Tung LE,Thi Yen PHAM,Van Thi DAO,Manh Trung PHUNG 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.12

Horizontal cooperation is seen as an effective way to raise a competitive advantage in logistics and transportation. However, there are many logistics enterprises still operating individually instead of cooperating. This research aims to investigate the factors influencing the decision of horizontal cooperation by surveying a large sample of Vietnamese logistics companies. This study employs 161 logistics companies to examine correlations between potential factors and horizontal collaboration. The structural equation model (SEM) was used to test the conceptual model and the relationships among variables. The findings revealed that information sharing was the most important predictor of 161 supply chain providers’ horizontal collaboration decisions, which resulted in increased profitability or service quality. Besides, trust in partners was found to be positively related to the degree of horizontal cooperation among logistics companies. Finally, the finding of this research is that reputation had a positive effect on the strategy of horizontal cooperation. Our findings suggest that SME managers should be concerened about their information sharing, their reputation as well as their trust in partners if they would be invited in cooperation with another firm to increase service quality, performance, and competitive advantage.

Formulation and in vivo imaging evaluation of colonic targeting tablets prepared by a simple dry powder coating technique

Tung Nguyen-Thach,Nguyen Canh-Hung,Nguyen Van-Duong,Nguyen Thi-Hong-Thuy,Nguyen Van-Lam,Tran Cao-Son,Pham Thi-Minh-Hue 한국약제학회 2020 Journal of Pharmaceutical Investigation Vol.50 No.4

Purpose The study aimed firstly to determine the release behavior of the model drug (berberine chloride) from the dry coated tablets. The second objective of this study was to evaluate the exact location of the dry coated tablets in in vivo. Methods The colon targeting tablets were developed by dry powder coating technique on pan coater. The drug release behavior was determined in the three continuous mediums: pH 1.2; 7.4 and 6.8 plus pectinase. The location of the dry coated tablets in the gastrointestinal tract of human volunteers was observed through the X-ray imaging of the dry coated tablets containing the optimized radiocontrast agents. Results The release kinetics of berberine chloride from the dry coated tablets was mainly controlled by erosion and enzyme sensitive mechanism. The optimum dry coated tablets having the coating powders of pectin 102:HPMC K4 M (2:1) with the coating level of 200%, and the tablet core with BaSO4 10% and iobitridol 30% as radiocontrast agents were observed in the caecum and ascending colon of human volunteers after 5–6 h of oral administration. Conclusion The successful development of these dosage forms is believed to have a high potential in precisely monitoring the release of highly potent drugs such as anti-inflammatory drugs in bowel diseases.

Adsorption of pharmaceuticals onto trimethylsilylated mesoporous SBA-15

Bui, Tung Xuan,Pham, Viet Hung,Le, Son Thanh,Choi, Heechul Elsevier 2013 Journal of hazardous materials Vol.254 No.-

<P><B>Abstract</B></P> <P>The adsorption of a complex mixture of 12 selected pharmaceuticals to trimethylsilylated mesoporous SBA-15 (TMS-SBA-15) has been investigated by batch adsorption experiments. The adsorption of pharmaceuticals to TMS-SBA-15 was highly dependent on the solution pH and pharmaceutical properties (i.e., hydrophobicity (log <I>K</I> <SUB>ow</SUB>) and acidity (p<I>K</I> <SUB>a</SUB>)). Good log–log linear relationships between the adsorption (<I>K</I> <SUB>d</SUB>) and pH-dependent octanol–water coefficients ( K ow pH ) were then established among the neutral, anionic, and cationic compounds, suggesting hydrophobic interaction as a primary driving force in the adsorption. In addition, the neutral species of each compound accounted for a major contribution to the overall compound adsorption onto TMS-SBA-15. The adsorption kinetics of pharmaceuticals was evaluated by the nonlinear first-order and pseudo-second-order models. The first-order model gave a better fit for five pharmaceuticals with lower adsorption capacity, whereas the pseudo-second-order model fitted better for seven pharmaceuticals having higher adsorption capacity. In the same group of properties, pharmaceuticals having higher adsorption capacity exhibited faster adsorption rates. The rate-limiting steps for adsorption of pharmaceuticals onto TMS-SBA-15 are boundary layer diffusion and intraparticle diffusion including diffusion in mesopores and micropores. In addition, the adsorption of pharmaceuticals to TMS-SBA-15 was not influenced by the change of initial pharmaceutical concentration (10–100μgL<SUP>−1</SUP>) and the presence of natural organic matter.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Trimethylsilylated SBA-15 for adsorptive removal of a mixture of 12 pharmaceuticals. </LI> <LI> Hydrophobic interaction as a primary driving force in the adsorption. </LI> <LI> The rate-limiting steps were diffusion through boundary layer, mesopores and micropores. </LI> <LI> Adsorption efficiency was not changed as pharmaceutical concentration varied. </LI> <LI> Adsorption efficiency was not influenced by the presence of natural organic matters. </LI> </UL> </P>

Dual-band isotropic metamaterial absorber based on near-field interaction in the Ku band

The Linh Pham,Hong Tiep Dinh,Dinh Hai Le,Xuan Khuyen Bui,Son Tung Bui,Hong Luu Dang,Anh Duc Phan,Dac Tuyen Le,Dinh-Lam Vu 한국물리학회 2020 Current Applied Physics Vol.20 No.2

We numerically and experimentally investigate single-band and dual-band isotropic metamaterial absorbers (IMAs) based on metallic disks. By optimizing the diameter of the metallic disks and the thickness of the dielectric substrate, the single-band IMA is observed at 16.2 GHz with absorptivity of 97%. When adding one diskpair to the structure, the dual-band IMA is obtained at 12.8 and 15.5 GHz due to the symmetry breaking. The physical mechanics is explained by near-field coupling effect and equivalent LC circuit model. The measurement results performed in the range 12–18 GHz show a good agreement with simulation and theoretical analysis. Our findings demonstrate a new approach to achieve dual-band and multi-band IMAs.

Impact of EVFTA on Trade Flows of Fruits between Vietnam and the EU

Duc Trong TRAN,Van Thu BUI,Ngoc Minh VU,Tung Son PHAM,Hue Minh TRUONG,Thuy Thu DANG,Tu Van TRINH 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.5

The European Union Vietnam Free Trade Agreement (EVFTA) took effect on August 1 paving the way for increased trade between the EU and Vietnam; this marked a huge turning point for the Vietnamese economy. Agriculture products, especially fruits, must be listed when it comes to Vietnam export industries that profit the most from EVFTA. After a period of study, with the desire to contribute to the improvement in the efficiency of Vietnam’s agricultural products to the EU, the researchers want to assess the impact of the EVFTA on the flows of Vietnamese fruits to the EU market. The study uses a quantitative analysis method via the WITS-SMART model with data on export turnover and tariff reductions in parallel with the analysis of changes in factors affecting the trade flows of fruits between the two markets when the EVFTA takes effect. As a result, Vietnam’s fruit importing from the EU is expected to escalate by 29.18% in 2021, while the flow of export will only inch up by 0.955%, which is rather low compare to the increase in import value. Hence, effective policies must be introduced in Vietnam to innovate production methods and increase product quality, so that the EVFTA can be used to boost Vietnam’s fruit exports to the EU.