Seasonal Dynamics of Tropical Forest Vegetation in Ngoc Linh Nature Reserve, Vietnam Based on UAV Data

Seasonal dynamics in tropical forests are closely related to the variation in forest canopy gaps. The canopy gaps change continuously in shape and size between the rainy and dry seasons, leading to the variation in the vegetative indicators. To monitor the variation of the canopy gaps, UAVs were used to collect datas in the mentioned tropical forests at an altitude of over 1,000m in Ngoc Linh Nature Reserve, Vietnam with a post-processing image resolution of about 8cm, which allows the detection of relatively small gaps. The analysis results at 10 squares of 1 ha showed a decrease in the area of ​​ canopy gaps from the rainy season in September 2019 to the dry season of May 2020. The mixed broad-leaved or broadleaf forest dominates with a greater variation, when the area of ​​the gaps decreases significantly. The variation in forest canopy gaps and vegetative indicators are closely related to the high differentiation of terrain, the seasonal and the dry season climatic characteristics. The fluctuation of the vegetation cover affects the habitats of the species under the forest canopy such as animals, birds and soil fauna. This is one of the scientific bases that contributes to the management and conservation of flora and fauna biodiversity, especially in mountainous tropical forests such as Ngoc Linh Nature Reserve

Evaluation of land cover changes and secondary ecological succession of typical agroforestry landscapes in Phu Yen Province

The study of land cover changes as well as landscape succession has theoretical and practical significance. Determining the characteristics, causes, and trends of the changes and succession of a landscape allows for assessing the natural and human characteristics of the territory. On this basis, appropriate solutions and policies in resource management, socioeconomic development, and environmental protection are available for each locality. Applying and integrating remote sensing data with field investigations and surveys improves the accuracy and reliability of research results. From the establishment of a land cover change map based on land cover map data collected in 2010, 2015, and 2020, variations in the land cover types of Phu Yen Province were observed. In the period 2010–2015, the area of natural forests and grasslands, shrubs, and bare lands decreased rapidly, whereas the covered areas of intentionally planted forests, industrial trees, and crops increased significantly. The secondary ecological succession of the agroforestry landscape of Phu Yen Province in the last 50–60 years occurred under the strong influence of human activities. Under the impact of chemical warfare and policies and farming practices of the local people, several evergreen broad-leaved tropical forest landscape units have undergone four to six stages of succession, with the interweaving of the economic development policy of Phu Yen Province and farming practices of the local people, making the structure and length of each period and succession very different

The Organizational Structure of the Securities Company Under the Law of Vietnam Current

Purpose: The article researches on the organizational structure of securities company under the Securities Law 2019 in order to point out some limitations and shortcomings and propose for recommendations to improve law about organizational structure on this form of company.   Theoretical framework: Recent literature points out that securities companies play very important role in the development of Vietnam's stock market. However, in the current stage of development, from the influence and impact of international integration and the increasingly fierce competitive pressure, the securities companies have encountered many difficulties to survive. In there, limits and problems in regulations about securities company organizational structures has caused many difficulties for these companies when organization and operation. On the other hand, in the context of judicial reform in Vietnam, the issue of complete law system and expanding the freedom to business has always been paid special attention by the Party and Vietnam State.   Design/methodology/approach: The authors have combined traditional research methods of legal science such as legal analysis method, legal efficiency assessment method and legal comparison method.   Findings: According to research, regulations on the organizational structure of a securities company are directly related to the efficiency of management and administration of this company. In there, Supervisory Board/Internal Audit Committee always ensuring to limit negative and fraudulent acts of the company’s leaders, to better ensure the legitimate rights and interests of the company's members and customers. Therefore, the authors have proposed several solutions such as the need to stipulate the mandatory requirement of a Supervisory Board for the securities trading company under the model of limited liability company, and expand and strengthen the powers of the Supervisory Board/Internal Audit Committee, independent members in securities companies doing business in the form of joint stock company. These are important bases to contribute to perfecting the Law on the organizational structure of securities companies in Vietnam and further enhancing the stability and safety of the Vietnamese stock market.   Research, Practical & Social implications: This research may support many develop future research in Vietnam. At the same time, the research to help foreign investors' activities in Vietnam's stock market.   Originality/value: The research of the freedom to business and organizational structure of securities companies become more and more urgent and very important in Vietnam

Environmental Issues in the South China Sea: Legal Obligation and Cooperation Drivers

Recently, we have been witnessing a critical level of a the degradation of the marine environment and depletion of fish stocks in the South China Sea. This has many adverse consequences on the politics, economics of the countries in the region as well as on the socio-economic life of the coastal population. One of the activities that has been causing serious damage to the marine environment and living resources of the South China Sea is the large-scale land reclamation and artificial island construction undertaken by China in the Spratly and Paracel islands recently. These activities have caused severe harm to the precious coral reef environment and thus, violated the obligation to preserve and protect fragile ecosystems and the habitat of depleted, threatened or endangered species under the international law of the seaThe paper explores the impact of China’s large-scale land reclamation and artificial island construction activities on the marine biodiversity of the South China Sea, explains what the legal obligation under the international law of States to protect and preserve the marine environment is and suggests a number of options in order to bring a halt to such activities and restore the damaged marine ecosystem. The paper puts particular emphasis on the cooperation drivers torwards a healthy, prosperous and peaceful South China Sea, which also contribute to the management and possibly, resolution of the current disputes in this region.Keywords: marine environmental issues, legal obligation, cooperation drivers, large-scale reclamation, artificial islands, blue solutions and fragile ecosystems

The context of school-based cyberbullying prevention in Vietnamese public schools: A cross-sectional study

Cyberbullying is a form of violence that has been present in schools for a long time and negatively impacts the mental health of students. Different countries have different strategies for avoiding cyberbullying. However, research on school-based cyberbullying prevention is limited in Southeast Asian developing countries.  This study aims to explore the current implementation of school-based cyberbullying prevention in public schools in a developing country. The framework of prevention programs is based on three aspects: (1) Developing curricula on how to behave when being a victim of cyberbullying.  (2) Strengthening the students' skills to deal with cyberbullying. (3) Promulgating specific provisions in the legal document on handling cyberbullying. School-based cyberbullying prevention among students in public schools is currently a research gap because of the limitations in the management of students using the internet and educational policies. This is a cross-sectional study that surveyed 400 participants who are Vietnamese teachers, administrators and school psychologists. The results show that the limitations of school-based cyberbullying prevention for Vietnamese students include professional knowledge, practical experience and personnel in charge of this work.  This constraint has resulted in an upsurge in incidents of cyberbullying in Vietnam. The findings add to the important evidence on cyberbullying prevention in a developing country that is working to research and develop an appropriate school-based cyberbullying prevention strategy

ZnO/CdS Bilayer used for Electrode in Photovoltaic Device

In this article we present the fabrication and characterization of the nanoporous ZnO and/or ZnO/CdS thin films onto indium doped-tin oxide (ITO) substrates, based on the thermal evaporation technique followed by thermal treatment. The preparation method was relatively simple and low-cost for large scale uniform coating to produce clean, dense and strong adhesion to substrate thin films. The nanostructured ZnO and ZnO/CdS thin films were characterized by X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). The nanostructured ZnO/CdS bilayer film was used in a photo-electrochemical (PEC) cell as a working electrode and a Pt net as a counter electrode. The results show that the photovoltaic cell with nanostructured ZnO/CdS bilayer film electrode has significantly improved photoelectric capability in comparison with that of ZnO electrode

Application of multispectral UAV to estimate mangrove biomass in Vietnam: A case study in Dong Rui commune, Quang Ninh Province

Mangroves play an important role in coastal estuarine areas with different ecological functions, such as reducing the impact of waves and currents, accumulating biomass and sequestering carbon. However, estimation of terrestrial biomass in mangrove areas, especially in Vietnam, has not been fully studied. The application of unmanned aerial vehicles (UAV), mounted with multispectral cameras combined with field verification is an effective method for estimating terrestrial biomass for mangroves, as it reduces field survey time and allows for greater spatial range research. In this study, ground biomass was estimated for the mangrove area in the Dong Rui commune, based on multispectral image data obtained from UAV and survey results in 16 standard cells measuring actual biomass according to four regression models: Log-Log, Log-Lin, Lin-Log and Lin-Lin. The results of comparing the data from these four models show that the log-log model has the highest accuracy with a high correlation coefficient (R2 = 0.831). Based on the results of the analysis and selection of ground-based biomass estimation models, a biomass map was established for the UAV flying area in the Dong Rui mangrove forest with biomass values ranging from 20 Mg/ha to 150 Mg/ha. In summary, we present a biomass estimation method through four basic linear regression models for mangrove areas, based on multispectral image data obtained from ultrahigh-resolution UAV. The resulting research results can serve as a basis for managers to calculate and synchronise the payment of carbon services, thus contributing to effectively promoting the livelihoods of local people

AN UPDATED CHECKLIST AND COMMENTS FOR SECTION PIQUETIA (CAMELLIA, THEACEAE)

New Camellia species in section Piquetia have recently been discovered. It is necessary to enumerate the number of species and update the specific characteristics of this section. Based on the study of more than 30 pieces of literature and a large number of specimens, a total of 15 species belonging to section Piquetia, including two new species, are identified. A taxonomic key to all species is provided, and typical characteristics of the section are also discussed. Information on the distribution, ecology, and conservation status of each species, as well as notes on the differences between closely related species, is also provided.

. In vitro propagation of the new orchid Dendrobium trankimianum T. Yukawa

Dendrobium trankimianum T. Yukawa is a beautiful, endemic orchid of Vietnam, a new species with a first - published description in 2004. It is very rare and expected to be added to the IUCN Red List status - CR. In vitro studies of orchid D. trankimianum T. Yukawa were conducted in order to conserve and increase the genetic pool of this precious wild orchid species. The results showed that full-strength MS medium supplemented with 2.0 mg/L BA and 0.5 mg/L NAA (10.24 PLBs/explant; 90.11% explants formed PLBs) or full-strength MS medium supplemented with 1.5 mg/L TDZ and 0.5 mg/L NAA (14.11 PLBs/explant; 92.06% explants formed PLBs) were the most suitable for protocorm formation. For subculture, suitable growth of shoots were obtained on full-strength MS medium supplemented 1.5 mg/L BA (22.35 shoots/explant; shoots length of 1.96 cm) and full-strength MS medium supplemented with 60 g ripe banana per liter (25.11 shoots/explant; shoots length of 2.12 cm). The shoots in vitro were transferred to half-strength MS supplemented with different concentrations of IAA, IBA and NAA to investigate root formation. The best rooting occurred at 0,5 mg/L NAA (7.91 roots/shoot; root length of 4.01 cm; 98.51% root formation). The plantlets with uniform growth were planted on different substrate: Eco clean soil, Coconut fiber, Fern fiber, 50% Rice husk in combination with 50% Eco clean soil for research the most suitable substrate. After 60 days of transplantion and acclimatization, the result showed that Fern fiber was suitable substrate for plantlet growth in a nursery garden (8.0 roots/ explant; root length of 5.5 cm; survival rate of 93.29%)

Nanocomposite Thin Film TiO2/CdS Electrodes Prepared by Thermal Evaporation Process for Photovoltaic Applications

The incorporation of cadmium sulfide (CdS) into TiO2 nanoparticle thin films was investigated. The nanoparticle TiO2 thin film onto an indium doped–tin oxide (ITO) substrate was deposited by Electron Beam Deposition (EBD) combined with thermal process. Then a CdS thin film was vacuum-deposited onto the pre-deposited TiO2 film by a thermal evaporation technique. The obtained TiO2/CdS was characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM). The TiO2/CdS nanocomposite film was used in a photo-electrochemical (PEC) cell as a working electrode and a platinum electrode as a counter electrode. The electrolyte solution contains 1 M KCl and 0.1M Na2S. The results show that the cell with TiO2/CdS composite film electrode has significantly improved photoelectric capability in comparison with that of the pure TiO2 thin films