Zooplankton Composition in Super-Intensive Whiteleg Shrimp, Litopenaeus vannamei (Boone, 1931) Culture Tanks

This study aimed to determine the zooplankton species composition in super-intensive whiteleg shrimp, Litopenaeus vannamei (Boone, 1931) tanks. The research was conducted from January to May 2021 in Bac Lieu City, Bac Lieu province, Vietnam. Eleven sampling times were divided into two periods, the nursery phase (six times) and the grow-out phase (five times) of shrimp culture. The results showed that water quality parameters fluctuated dramatically during the culture period, in which some nutrient concentrations tended to increase at the end of the shrimp culture period. Nine zooplankton species were recorded, of which five species belonged to Protozoa, three Rotifera species, and one Copepoda species. The number of zooplankton species did not differ significantly among the sampling periods. Protozoa had the highest species composition and density during most of the shrimp culture period. Copepoda was only identified in the nursery stage of shrimp culture. The species component of zooplankton had a close positive correlation with temperature, but their abundance did not have a significant relationship with water quality parameters because each species was affected by the different water quality parameters. Zoothamnium sp. had significantly positive correlations with total ammonia nitrogen (TAN), nitrate (NO3)-, total phosphorus (TP), and total nitrogen (TN) concentrations. The rotifer Brachionus plicatilis had a strong relationship with TP content, whereas Dartintinnus alderae had a strong relationship with alkalinity. Protozoa dominance in shrimp tanks could affect shrimp growth, decreasing the economic efficiency of shrimp farming. Therefore, the results of this study contribute to water quality and natural food management to improve shrimp productivity

Conservation of Natural and Cultural Heritage in the Huong Son Complex of Natural Beauty and Historical Monuments, Northern Vietnam

The Huong Son Complex has long been recognised as an important sacred landscape in Vietnam due to its spiritual and cultural values. The area also retains many aesthetic and biological values. Unfortunately, its cultural and natural treasures are currently at risk due to anthropogenic impacts, mainly associated with increased spiritual tourist activities. Some urgent solutions have been implemented, but they give priority to protecting cultural values and sometimes conflict with nature conservation efforts. This problem was encountered during our recent bat conservation research in Huong Son. Our preliminary findings revealed symbiotic relationships between natural and cultural heritage in Huong Son; thus, linking nature and culture in conservation planning and management is critical for the sustainable development of the site. However, the application of this approach in Huong Son, and other sacred places in Vietnam, is challenged by gaps in basic research and the inadequate attention of local stakeholders

CHARACTERIZATION OF CARBONATED STEELMAKING SLAG AND ITS POTENTIAL APPLICATION IN CONSTRUCTION

In the current context of Vietnam, the solid waste of steel slag occupy ground for dumping and lead to severe environmental issue due to their high content of heavy metal and fine dust. For the purpose of large-scale recycling steel slag, up to now one of the most relevant solutions is to use as aggregate for asphaltic and/or cement concrete. In this paper, we aim to analyze the influence of the accelerated carbonation condition in the laboratory on the physio-chemical properties of carbonated steel slag. Materials composition were characterized by using different analysis techniques of XRD, SEM, TG and others measurement of the physio-properties (density, L.O.I..) were also realized with regards to the requirement of the national standard for concrete aggregate. In conclusion, we will discuss the effect of reaction condition and on the feasibility of implementing this specific treatment method on a larger scale.Keywords: steelmaking slag, solid waste, CO2 sequestration, accelerated carbonation, concrete aggregate

Parameter Estimation and Predictive Speed Control of Chopper-Fed Brushed DC Motors

This paper presents an effective speed control method for brushed DC motors fed by a DC chopper using the concept of Finite Control Set-Model Predictive Control (FCS-MPC). As this control algorithm requires the parameters of the controlled object, the estimation of motor parameters is first performed by using two types of data. The first data includes the output speed response corresponding to the step input voltage to obtain the transfer function in the no-load regime. The second data consists of the motor speed and armature current when a load torque is applied to the motor shaft. The discrete-time equation of the motor armature circuit is used to obtain the future values of the armature circuit current and the motor speed. A cost function is defined based on the difference between the reference and predicted motor speed. The optimal switching states of the DC chopper are selected corresponding to the maximum value of the cost function. The performance of the proposed speed control algorithm is validated on an experimental system. The simulation and experimental results obtained show that the MPC controller can outperform the conventional proportional-integral (PI) controller

FATTY ACID COMPOSITION AND ANTIOXIDANT ACTIVITY OF CAMELLIA NINHII SEED OIL COLLECTED IN LAM DONG PROVINCE

The seed oil of Camellia ninhii was studied for the first time on its fatty acid composition by gas chromatography-mass spectrometry (GC-MS) and antioxidant activity by the DPPH method. The results show that unsaturated fatty acids account for the largest amount, especially oleic acid with 45.43% of the total sample analyzed. In addition, other fatty acids, palmitic, linoleic, pentadecanoic, and two aromatic acids, benzoic and cinnamic, were present. The sample of C. ninhii seed oil exhibited mild antioxidant activity against DPPH free radicals with IC50 = 0.94 mg/mL

Simplified extended Kalman filter phase noise estimation for CO-OFDM transmissions

We propose a flexible simplified extended Kalman filter (S-EKF) scheme that can be applied in both pilot-aided and blind modes for phase noise compensation in 16-QAM CO-OFDM transmission systems employing a small-to-moderate number of subcarriers. The performance of the proposed algorithm is evaluated and compared with conventional pilot-aided (PA) and blind phase search (BPS) methods via extensive an Monte Carlo simulation in a back-to-back configuration and with a dual polarization fiber transmission. For 64 subcarrier 32 Gbaud 16-QAM CO-OFDM systems with 200 kHz combined laser linewidths, an optical signal-to-noise ratio penalty as low as 1 dB can be achieved with the proposed S-EKF scheme using only 2 pilots in the pilot-aided mode and just 4 inputs in the blind mode, resulting in a spectrally efficient enhancement by a factor of 3 and a computational effort reduction by a factor of more than 50 in comparison with the conventional PA and the BPS methods, respectively

Chemical constituents from the leaves of Styrax argentifolius H.L. Li and their antioxidative activity

Searching for bioactive agents from medicinal plants, the phytochemical investigation on the EtOAc extract of the Vietnamese Styrax argentifolius leaves has resulted in the isolation and structural determination of five compounds, including one nor-neolignan egonoic acid (1), one lignan (+)-pinoresinol (2), one sterol (20R)-3β-hydroxysitgmasta-5,22-dien-7-one (3), and two triterpenoids lupeol (4), and 2α,3α,24-trihydroxy-urs-12-en-28-oic acid (5). The chemical structures of these secondary metabolites were elucidated by NMR and MS spectral data. All isolated compounds were first observed in S. argentifolius species. Sterol 3 and triterpenoid 5 were detected in genus Styrax for the first time. With the IC50 value of 19.10 µg/mL, compound 2 possessed the strong activity in DPPH radical scavenging assay

HYDROGEN-PLASMA-TREATED NANO TIO2 FOR PHOTOCATALYTIC OXIDATION OF VOCS IN AIR STREAM

Unlike water treatment processes, the photocatalytic oxidation of VOCs in air stream exhibits many challenges. This study will develop the hydrogen-plasma-treated TiO2 with improvement in photocatalytic activity. The hydrogen-plasma-treatment was carried out in the non-thermal atmospheric pressure reactor at room temperature or above. The catalysts were prepared and analyzed by advanced techniques such as X-ray diffraction (XRD), scanning electro-microscopy (SEM) and transmission electro-microscopy (TEM). The photocatalytic activity of the catalyst has been investigated under UV light with various reaction conditions such as different initial toluene/formaldehyde concentrations and water content. Significantly, the conversion of toluene by a plasma-treated sample was 1.5 times higher than the bare TiO2 in a similar reaction condition