Effect of Zn/Al Cation Ratio on Corrosion Inhibition Capabilities of Hydrotalcites Containing Benzoate Against Carbon Steel

Thuy Duong Nguyen,To Thi Xuan Hang,Thu Thuy Pham,Anh Son Nguyen,Thu Thuy Thai,Gia Vu Pham,Ngoc Bach Ta 한국부식방식학회 2022 Corrosion Science and Technology Vol.21 No.6

Corrosion inhibitors based on Zn-Al hydrotalcites containing benzoate (ZnAlHB) with different molar ratios of Zn/Al were prepared with a co-precipitation process. Compositions and structures of the resulting hydrotalcites were studied with suitable spectroscopic methods such as inductively coupled plasma mass spectrometry (ICP-MS), ultraviolet-visible spectrophotometry (UV-Vis), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and surface zeta potential measurements, respectively. Results of physico-chemical studies showed that crystallite sizes, compositions of products, and surface electrical properties were significantly changed when the molar ratio of Zn/Al was increased. The release of benzoate from hydrotalcites also differed slightly among samples. Anticorrosion abilities of hydrotalcites intercalated with benzoate at a concentration of 3 g/L on carbon steel were analyzed using electrochemical impedance spectroscopy (EIS), polarization curve, energy-dispersive X-ray spectroscopy (EDX), and SEM. Corrosion inhibition abilities of benzoate modified hydrotalcites in 0.1 M NaCl showed an upward trend with increasing Zn/Al ratio. The reason for the dependence of corrosion resistance on the Zn/Al ratio was discussed, including changes in the microstructure of hydrotalcites such as crystal size, density, uniformity, and formation of ZnO.

Biodiversity and Enzyme Activity of Marine Fungi with 28 New Records from the Tropical Coastal Ecosystems in Vietnam

Pham, Thu Thuy,Dinh, Khuong V.,Nguyen, Van Duy The Korean Society of Mycology 2021 韓國菌學會誌 Vol.49 No.6

The coastal marine ecosystems of Vietnam are one of the global biodiversity hotspots, but the biodiversity of marine fungi is not well known. To fill this major gap of knowledge, we assessed the genetic diversity (ITS sequence) of 75 fungal strains isolated from 11 surface coastal marine and deeper waters in Nha Trang Bay and Van Phong Bay using a culture-dependent approach and 5 OTUs (Operational Taxonomic Units) of fungi in three representative sampling sites using next-generation sequencing. The results from both approaches shared similar fungal taxonomy to the most abundant phylum (Ascomycota), genera (Candida and Aspergillus) and species (Candida blankii) but were different at less common taxa. Culturable fungal strains in this study belong to 3 phyla, 5 subdivisions, 7 classes, 12 orders, 17 families, 22 genera and at least 40 species, of which 29 species have been identified and several species are likely novel. Among identified species, 12 and 28 are new records in global and Vietnamese marine areas, respectively. The analysis of enzyme activity and the checklist of trophic mode and guild assignment provided valuable additional biological information and suggested the ecological function of planktonic fungi in the marine food web. This is the largest dataset of marine fungal biodiversity on morphology, phylogeny and enzyme activity in the tropical coastal ecosystems of Vietnam and Southeast Asia. Biogeographic aspects, ecological factors and human impact may structure mycoplankton communities in such aquatic habitats.

Global and Regional Right Ventricular Function Investigation by 2D Speckle Tracking Echocardiography in Congenital Heart Disease Patients With Pulmonary Arterial Hypertension

Pham Thuy Thu,Nguyen Hoai Thi Thu 아시아심장혈관영상의학회 2022 Cardiovascular Imaging Asia Vol.6 No.2

Objective: The aim of our study was to evaluate the global and regional free wall longitudinal strains of the right ventricle (RV) to detect RV dysfunction in congenital heart disease (CHD) patients with pulmonary arterial hypertension (PAH). Materials and Methods: Seventy CHD patients with PAH and 30 normal controls were enrolled in this study. Patients were placed into three subgroups including patients with pretricuspid shunt Eisenmenger syndrome (ES) (Group A), patients with post- tricuspid shunt ES (Group B), and patients with non-fixed PAH (Group C). The World Health Organization functional classification (WHO FC) was used to functionally classify the study population. RV free wall strain (FWS); regional RV strains of apical, mid, basal FWS; and RV global longitudinal strain (GLS) were measured by 2D speckle tracking echocardiography (STE), while other parameters were measured by conventional echocardiography. Results: Forty-three patients (61.4%) were classified as WHO FC III or greater. Mean RVFWS and RVGLS were -20.42%±5.9% and -17.62%±5.5%, respectively. All RV strains including regional FWS were lower in patients compared with healthy controls (p<0.001). RV strains exhibited a higher rate of RV dysfunction compared to the conventional parameters. Mean RVGLS and RVFWS in the two ES groups were lower compared to that in Group C (p<0.001). Within regional trains, basal FWS in Group C was higher than in Group A (p<0.001) but similar to that of Group B. RVFWS, RVGLS, and regional FWS significantly correlated with pulmonary arterial systolic pressure and WHO FC. Conclusion: In CHD with PAH, 2D-STE parameters are potentially more capable of early detection of RV dysfunction than are conventional echo indices.

Gallium Nitride PIN Avalanche Photodiode with Double-step Mesa Structure

Thu Thi Thuy Pham,Hyungsik Shin,Eugene Chong,Ho-Young Cha 대한전자공학회 2018 Journal of semiconductor technology and science Vol.18 No.5

Typical gallium nitride (GaN) PIN avalanche photodiodes (APDs) are fabricated using a beveled mesa structure due to the difficulty of the ion-implantation process for GaN. The bevel angle of mesa structure must be very small in order to suppress the localized electric field at the junction sidewall that limits the maximum APD gain. In this study, we proposed a double-step mesa structure that can suppress the high electric field at the junction sidewall while maximizing the electric field strength inside the active region under the avalanche bias condition.

Extracting OWL Ontology from XML instances via XML Schema

( Pham Thi Thu Thuy ),( Young-koo Lee ),( Sungyoung Lee ) 한국정보처리학회 2009 한국정보처리학회 학술대회논문집 Vol.16 No.2

Currently, XML and its schema language have become the standard for data representation and information exchange format on the current web. Unfortunately, problems happen when integrating different data sources since XML mainly supports the document structure but lack consideration on sharing knowledge of data. Meanwhile, Semantic Web technologies, such as Web Ontology Language (OWL), can include the structure as well as the semantics of the data. Therefore, finding a way to integrate XML data as OWL ontology receives a high interest nowadays. In this paper we present a mapping notation to convert XML Schema to OWL domain knowledge and an effective method to transform XML instances into OWL individuals. While keeping the XML original structure, our work also adds more semantics for the XML document. Moreover, whole of the transformation processes are done automatically without any user interference. Further, our transforming approach provides the solution for duplicate element names in XML document which has not mentioned in the previous work. Our results in existing OWL syntaxes can be loaded immediately by OWL editors and Semantic Web applications.

Inhibitory Effect of Benzoate-intercalated Hydrotalcite with Ce³⁺-loaded clay on Carbon Steel

( Thuy Duong Nguyen ),( Thu Thuy Pham ),( Anh Son Nguyen ),( Ke Oanh Vu ),( Gia Vu Pham ),( To Thi Xuan Hang ) 한국부식방식학회 2023 Corrosion Science and Technology Vol.22 No.1

This work studied the inhibitory effect of the combination of benzoate-intercalated hydrotalcite (HT-BZ) and Ce³⁺-loaded clay (Clay-Ce) on carbon steel (CS). HT-BZ was prepared by the co-precipitation method and Clay-Ce was fabricated by a cation exchange reaction. HT-BZ and Clay-Ce were assessed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) coupled with zeta potential measurement. Electrochemical measurements coupled with scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) were used for studying the inhibitory action of the mixture of HT-BZ and Clay-Ce on steel electrodes immersed in 0.1 M NaCl. For comparison, the inhibitory effect of HT-BZ or Clay-Ce alone was also evaluated. The results showed that HT-BZ combined with Clay-Ce provided synergistic inhibition of the CS substrate. The mixture of 0.5 g/L HT-BZ + 0.5 g/L Clay-Ce provided 93.5% inhibition efficiency. The protective mechanism of the HT-BZ + Clay-Ce mixture consisted of the reaction of released BZ and Ce³⁺ and the deposition of HT-BZ and Clay-Ce structures on the CS substrate.

A Semantic Approach for Transforming XML Data into RDF Ontology

Thuy, Pham Thi Thu,Lee, Young-Koo,Lee, Sungyoung Springer-Verlag 2013 Wireless personal communications Vol.73 No.4

Corrosion Protection Properties of Cobalt Salt for Water-Based Epoxy Coatings on 2024-T3 Aluminum Alloy

Thu Thuy Thai,Anh Truc Trinh,Gia Vu Pham,Thi Thanh Tam Pham,Hoan Nguyen Xuan 한국부식방식학회 2020 Corrosion Science and Technology Vol.19 No.1

In this paper, the efficiency and the inhibition mechanisms of cobalt salts (cobalt nitrate and cobalt-exchangesilica Co/Si) for the corrosion protection of AA2024 were investigated in a neutral aqueous solution byusing the electrochemical impedance spectroscopy (EIS) and polarization curves. The experimental measurementssuggest that cobalt cation plays a role as a cathodic inhibitor. The efficiency of cobalt cation was importantat the concentration range from 0.001 to 0.01 M. The formation of precipitates of oxides/hydroxides ofcobalt on the surface at low inhibitor concentration was confirmed by the Scanning Electron Microscopy/EnergyDispersive X-Ray Spectroscopy (SEM/EDS) analysis. EIS measurements were also conducted for the AA2024surface covered by water-based epoxy coating comprising Co/Si salt. The results obtained from exposurein the electrolyte demonstrated the improvement of the barrier and inhibition properties of the coating exposedin the electrolyte solution for a lengthy time. The SEM/EDS analysis in artificial scribes of the coatingafter salt spray testing revealed the release of cobalt cations in the coating defect to induce the barrierlayer on the exposed AA2024 substrate.

Filter-free AlGaN Photodiode with High Quantum Efficiency for Partial Discharge Detection

Thu Thi Thuy Pham,June-Heang Choi,Chun-Hyung Cho,Ho-Young Cha 대한전자공학회 2020 Journal of semiconductor technology and science Vol.20 No.2

In this study, we developed filter-free AlGaN based PIN photodiodes for partial discharge detection that can detect ultraviolet emission with a wavelength between 230 nm and 270 nm. The PIN epitaxial structure consisted of a p-Al0.6Ga0.4N/i- Al0.46Ga0.54N/n-Al0.6Ga0.4N heterostructure with p-GaN/p-AlGaN grading layers on top for improved ohmic contact formation. The fabricated photodiode exhibited highly selective photoresponse characteristics from 230 nm to 270 nm without an external filter. A peak photoresponsivity of 125 mA/W and quantum efficiency of 60% were achieved at 245 nm for a photodiode with a window diameter of 250 μm under zero bias condition where the dark current was only 1.3 × 10-8 A/cm². The proposed AlGaN PIN photodiode has the advantages of zero standby power and no need for an external filter.

Biodiversity and Enzyme Activity of Marine Fungi with 28 New Records from the Tropical Coastal Ecosystems in Vietnam

( Thu Thuy Pham ),( Khuong V. Dinh ),( Van Duy Nguyen ) 한국균학회 2021 Mycobiology Vol.49 No.6

The coastal marine ecosystems of Vietnam are one of the global biodiversity hotspots, but the biodiversity of marine fungi is not well known. To fill this major gap of knowledge, we assessed the genetic diversity (ITS sequence) of 75 fungal strains isolated from 11 surface coastal marine and deeper waters in Nha Trang Bay and Van Phong Bay using a culturedependent approach and 5 OTUs (Operational Taxonomic Units) of fungi in three representative sampling sites using next-generation sequencing. The results from both approaches shared similar fungal taxonomy to the most abundant phylum (Ascomycota), genera (Candida and Aspergillus) and species (Candida blankii) but were different at less common taxa. Culturable fungal strains in this study belong to 3 phyla, 5 subdivisions, 7 classes, 12 orders, 17 families, 22 genera and at least 40 species, of which 29 species have been identified and several species are likely novel. Among identified species, 12 and 28 are new records in global and Vietnamese marine areas, respectively. The analysis of enzyme activity and the checklist of trophic mode and guild assignment provided valuable additional biological information and suggested the ecological function of planktonic fungi in the marine food web. This is the largest dataset of marine fungal biodiversity on morphology, phylogeny and enzyme activity in the tropical coastal ecosystems of Vietnam and Southeast Asia. Biogeographic aspects, ecological factors and human impact may structure mycoplankton communities in such aquatic habitats.