Improvement of Step Tracking Algorithm Used for Mobile Receiver System via Satellite

In the mobile communication via satellite, received systems are mounted on the mobile device such as ship, train, car or airplane. In order to receive continuous signals, received antenna system must be steered in both the azimuthal and elevation angle to track a satellite. This paper proposes the improved step-tracking algorithm using for mobile receiver system via satellite Vinasat I. This paper also presents the results of study, design and manufacture of the discrete-time controller system for the fast tracking of a satellite by applying an improved step tracking algorithm with fuzzy proportional integral derivative proportional integral derivative controller. Simulated and experimental results indicate that the system performances obtain from applying the improved step tracking algorithm and the fuzzy controller was better than traditional control systems

CAMELLIA HOABINHENSIS (THEACEAE: SECT. CHRYSANTHA), A NEW YELLOW-FLOWERED SPECIES FROM NORTHERN VIETNAM

A new species, Camellia hoabinhensis (section Chrysantha, Theaceae), is described and illustrated based on specimens collected from a lowland forest on limestone hills in Hoa Binh Province, northern Vietnam. The species is characterized by its small habit to 4.5 m tall, large flowers 9.0–9.5 cm in diameter with 18–19 light yellow petals, and hairy filaments, ovaries, and styles. A comparison of the new species with similar species, C. euphlebia, C. impressinervis, C. phanii, and C. velutina, is provided. The IUCN conservation status of the proposed species is Data Deficient (DD)

Design of a Front-End for Satellite Receiver

This paper focuses on the design and implementation of a front-end for a Vinasat satellite receiver with auto-searching mechanism and auto-tracking satellite. The front-end consists of a C-band low-noise block down-converter and a L-band receiver. The receiver is designed to meet the requirements about wide-band, high sensitivity, large dynamic range, low noise figure. To reduce noise figure and increase bandwidth, the C-band low-noise amplifier is designed using T-type of matching network with negative feedback and the L-band LNA is designed using cascoded techniques. The local oscillator uses a voltage controlled oscillator combine phase locked loop to reduce the phase noise and select channels. The front-end has successfully been designed and fabricated with parameters: Input frequency is C-band; sensitivity is greater than -130 dBm for C-band receiver and is greater than -110dBm for L-band receiver; output signals are AM/FM demodulation, I/Q demodulation, baseband signals

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

RECOVERY OF POLY(3-HYDROXYBUTYRATE) FROM Yangia sp. ND199 BY SIMPLE DIGESTION WITH SODIUM HYPOCHLORITE

Polyhydroxyalkanoate (PHA) is a biodegradable polymer synthesized intracellularly by many microorganisms. After extraction from the cells, they possess the common features of non-toxic, biocompatible, biodegradable and recyclable. These features render them highly competitive with polypropylene or other petroleum-derived plastics, especially in medicine. The isolation and purification of PHA from bacterial cells are the key step of PHA production process. There are several methods have been used for OHA purification, these include solvent extraction, enzymatic hydrolysis, and chemical digestion. In this study we used chemical digestion method for purification of PHB from Yangia sp. ND199. Among various chemical tested (NaOH, HCl, KOH, NaOCl, and SDS), NaOCl was found as an efficient chemical for PHB recovery and PHB purity from Yangia sp. ND199. The optimal purity and recovery conditions were a ratio of 1:1 (v/v, solution containing 100 g/l bacterial cells and solution containing 6% NaOCl), a 30 oC temperature and a 1 h treatment time. Under such conditions, a purity of 99% and a recovery of 94% were obtained. This method is sumple and can be developed and used for industrial scale

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%)

TÍNH TOÁN CÁC ĐẶC TRƯNG SÓNG Ở KHU VỰC NINH THUẬN - BÌNH THUẬN BẰNG MÔ HÌNH SWAN TRÊN LƯỚI PHI CẤU TRÚC

The wave model SWAN (version 41.01A) with unstructured grid has been applied for Ninh Thuan - Binh Thuan waters. This model is SWAN Cycle III using a vertex-based, fully implicit finite difference method. It can accommodate unstructured meshes with a high variability in geographic resolution suitable for representing complicated bottom topography in shallow areas and irregular shoreline. In particular, the unstructured meshes (triangular meshes) can be used to calculate the flow by finite element method. This is very helpful in solving the problems of interactions between wave-current and wave-wave. The initial results indicate that the approach to SWAN model is reasonable, stable for any time step while permitting local mesh refinements in interested areas. A lot of applications are shown to verify the correctness and numerical accuracy of the unstructured version of SWAN.Mô hình sóng SWAN (phiên bản 41.01A) với lưới phi cấu trúc đã được áp dụng thử nghiệm vào tính sóng tại vùng biển Ninh Thuận - Bình Thuận. Đây là mô hình sóng thế hệ thứ ba, sử dụng phương pháp sai phân hữu hạn, ẩn hoàn toàn dựa trên các cạnh của điểm lưới phần tử phi cấu trúc với một sự khác nhau lớn về độ phân giải không gian nhằm phù hợp với một địa hình đáy phức tạp đại diện cho vùng nước nông và đường bờ khúc khuỷu. Đặc biệt, có thể sử dụng cùng mạng lưới tam giác phi cấu trúc trong tính toán dòng chảy bằng phương pháp phần tử hữu hạn. Điều này rất hữu ích trong giải quyết bài toán tương tác sóng - dòng và sóng - sóng. Những kết quả bước đầu cho thấy, cách tiếp cận ứng dụng mô hình tính sóng này là hợp lý, ổn định cho bước thời gian bất kỳ cho mạng lưới làm mịn, mang đặc trưng địa phương trong vùng nghiên cứu. Một số ứng dụng được chứng minh tính hợp lý của phiên bản lưới phi cấu trúc trong mô hình SWAN

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

Ownership, technology gap and technical efficiency of small and medium manufacturing firms in Vietnam: A stochastic meta frontier approach

The ownership - efficiency relationship in a firm has always been an important topic. In this paper, we focus on the state owned versus non-state-owned status of Vietnamese manufacturing firms, to shed light into the relationship between these two variables when using a more state-of-the-art method as a stochastic meta-frontier method. Applying the method for two periods: one during the global economic crisis and the other after the end of the crisis, the study determines that in both periods, there was a strong evidence that non-state-owned firms performed much better than state owned counterpart. We also found that the difference became even larger during the harsh time and sub-industries with non-state-owned firms could outperform the state-owned firms, significantly