Some Aspects of the Reproductive Biology and Behaviour of the Asiatic Giant Honeybee, Apis Dorsata Fabricius

Up to now, little is known about the reproductive biology of the Asiatic wild giant honeybee Apis dorsata. so a comprehensive study on its reproductive biology is needed to improve the beekeeping technique. This study was implemented in the U-Minh Melaleuca forest. Vietnam and the Campus of Universiti Putra Malaysia, Selangor between July 1 995 and January 1997. It was aimed to determine the following: i) The drone t1ight time, sperm number of a sexually-mature drones and age of sexual maturity of drones ii) The number of queen cells and mating nights of v irgin queens. The observation on four colonies of A. dorsata showed that drones started to t1y at 3.4 ± 2.4 (n = 16) minutes after sunsets and stopped after a duration of 24.7 ± 1.0 (n = 16) minutes. The sperm count o f drones during days after emergence indicated that A. dorsata drones became sexually-mature after eightdays- old and a sexually-mature drone had 1.24 ± 0.39 (n = 31) million spermatozoa

To the construction model of portal with open source software for schools in Vietnam

Секция 11. Цифровые медиатехнологииThe report examines aspects of creating a model of an information portal with open source software for use in schools. Creating modules-channels links between "school - teachers - parents - students". As the main base of the educational portal system chosen to the Moodle learning environment, to support teaching and training activities for teachers and students. Designed for integration module k-NN training «feedback» oriented to student work. The proposed model is successfully applied to the portal practice in secondary schools in Vietnam

Performance of an Inline RZ-DPSK Pulse Compression Using Raman Amplifier and Its Application in OTDM Tributary

We experimentally investigate the performance of a distributed Raman amplifier (DRA)-based pulse compressor for a phase modulated signal. A 10 Gb/s return-to-zero (RZ)-differential phase shift keying (DPSK) signal is compressed to picosecond range after transmission. Pulsewidth is continuously compressed in a wide range from 20 to 3.2 ps by changing the pump power of the DRA while the compressed waveforms are well-matched with sech2 function. Error-free operations at bit-error-rate (BER) of 10-9 are achieved for the compressed signals of various pulsewidths with low power penalties within 2.3 dB compared to the back-to-back. After the compression, the 10 Gb/s signal is used to generate a 40 Gb/s RZ-DPSK optical time division multiplexing (OTDM) signal. This 40 Gb/s OTDM signal is then successfully demultiplexed to 10 Gb/s DPSK signal by using an optical gate based on four-wave mixing (FWM) in a highly nonlinear fiber (HNLF)

Waveform Conversion and Wavelength Multicasting with Pulsewidth Tunability Using Raman Amplification Multiwavelength Pulse Compressor

A combination of nonreturn-to-zero (NRZ)-to-return-to-zero (RZ) waveform conversion and wavelength multicasting with pulsewidth tunability is experimentally demonstrated. A NRZ data signal is injected into a highly nonlinear fiber (HNLF)-based four-wave mixing (FWM) switch with four RZ clocks compressed by a Raman amplification-based multiwavelength pulse compressor (RA-MPC). The NRZ signal is multicast and converted to RZ signals in a continuously wide pulsewidth tuning range between around 12.17 and 4.68 ps by changing the Raman pump power of the RA-MPC. Error-free operations of the converted RZ signals with different pulsewidths are achieved with negative power penalties compared with the back-to-back NRZ signal and the small variation among received powers of RZ output channels at a bit-error-rate (BER) of 10-9. The NRZ-to-RZ waveform conversion and wavelength multicasting without using the RA-MPC are also successfully implemented

Characterization of carboxymethyl cellulase produced by Trichoderma asperellum

Background: The present study characterized extracellular carboxymethyl cellulase (CMCase), an enzyme catalyzes the hydrolysis of the cellulose, from Trichoderma asperellum PQ34 that was isolated from agricultural cultivation soil in Thua Thien Hue, Vietnam.Methods: CMCase was produced by culturing T. asperellum PQ34 on Czapek-Dox medium supplemented with carboxymethyl cellulose (CMC) at 28ºC for 96 h at a shaking speed of 150 rpm. Enzyme activity was spectrophotometerically determined with CMC used as a substrate and the absorbance was measured at 540 nm. The molecular weight of CMCase was determined by zymogram based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with 0.2% CMC.Results: CMCase achieved the highest activity after 4 days of culture with the optimal pH and temperature at 4 and 55°C. The enzyme maintains pH and thermal stability in the range of 4-5 and 10-40°C and the relative activity of both is more than 90%. The presence of metal ions at 5 mM such as Ca2+, Al3+, or Co2+ increased the enzyme activity up to 133%, 124%, and 217%, respectively. CMCase was stable with 1 mM ethylenediaminetetraacetic acid and 1 M urea, but inhibited by 5% sodium dodecyl sulfate (SDS) and 5% Triton-X100. Zymographic analysis showed that CMCase from T. asperellum PQ34 consists of two enzymes with a molecular weight of about 31 and 66 kDa.Conclusion: CMCases from T. asperellum PQ34 exhibited characteristics of an acidic and thermostable enzyme. The interaction of Co2+ and CMCase resulted in a significant increase in enzyme activity, however they were strongly inhibited by 5% SDS.Keywords: Carboxymethyl cellulase; Cellulase; Endo-β-1,4-glucanase, Trichoderma asperellu

Effect of the green-emitting CaF2:Ce3+,Tb3+ phosphor particles’ size on color rendering index and color quality scale of the in-cup packaging multichip white LEDs

In this paper, we investigate the effect of the green-emitting CaF2:Ce (3+), Tb (3+) phosphor particle's size on the color rendering index (CRI) and the color quality scale (CQS) of the in-cup packaging multichip white LEDs (MCW-LEDs). For this purpose, 7000K and 8500K in-cup packaging MCW-LEDs is simulated by the commercial software Light Tools. Moreover, scattering process in the phosphor layers is investigated by using Mie Theory with Mat Lab software. Finally, the research results show that the green-emitting CaF2: Ce (3+), Tb (3+) phosphor's size crucially influences on the CRI and CQS. From that point of view, CaF2: Ce (3+), Tb (3+) can be proposed as a potential practical direction for manufacturing the in-cup packaging phosphor WLEDs.Web of Science13235134

Energy harvesting over Rician fading channel: A performance analysis for half-duplex bidirectional sensor networks under hardware impairments

In this paper, a rigorous analysis of the performance of time-switching energy harvesting strategy that is applied for a half-duplex bidirectional wireless sensor network with intermediate relay over a Rician fading channel is presented to provide the exact-form expressions of the outage probability, achievable throughput and the symbol-error-rate (SER) of the system under the hardware impairment condition. Using the proposed probabilistic models for wireless channels between mobile nodes as well as for the hardware noises, we derive the outage probability of the system, and then the throughput and SER can be obtained as a result. Both exact analysis and asymptotic analysis at high signal-power-to-noise-ratio regime are provided. Monte Carlo simulation is also conducted to verify the analysis. This work confirms the effectiveness of energy harvesting applied in wireless sensor networks over a Rician fading channel, and can provide an insightful understanding about the effect of various parameters on the system performance.Web of Science186art. no. 1781

UNDERSTANDING THE STATUS AND CHALLENGES OF MANGROVE CONSERVATION IN CENTRAL VIETNAM: CASE STUDY IN DUY XUYEN DISTRICT, QUANG NAM PROVINCE

Abstract: While mangrove forests support large surrounding populations and diverse economic activities, mangrove areas in Central Vietnam are decreasing. This study, thereforce, aims to understand the current status and threats facing mangrove conservation and development. A survey of 52 respondents was conducted in Duy Xuyen district, the largest area of mangrove forests of Quang Nam province. The results show that 17 mangrove species belong to 11 families, in which 8 significant species and 9 minor species were found in this site. The distribution of species was uneven with dominated by Nipah palms (Nypafruticans Wurmb). Although the mangrove species had several useful functions including protection against wind, wave break and serving tourism development, mangrove areas have been decreasing from 26.39ha to 18.22ha during period of 1999-2018. In which, 67.3% of respondents argued that the conversion of mangroves to aquaculture is one of the main causes of mangrove loss. The study also provided some suggestions related to a long-term development strategy for both government and local community, especially who are directly involving in the mangrove for their livelihoods.Keywords: Central Vietnam, development strategy, mangrove forests, livelihood