Tạp chí Khoa học Đại học Đà Lạt

STUDY ON NEUTRON – GAMMA PULSE SHAPE DISCRIMINATION ALGORITHMS FOR SCINTILLATION DETECTOR

2017-01-03T08:44:41+07:00

The four neutron - gamma pulsed shape discrimination algorithms for the model NE213 scintillation detector by using digital signal processing were developed. In this study, a pulse generator, pulse digitizer and neutron - gamma pulsed shape discrimination algorithms are simulated in Matlab, Simulink software. The results obtained show that the method to rise-time discrimination has a quality factor (Figure-of-Merits: FOM=1.09), pulsed gradient analysis method (FOM = 0.66), charge comparison method (FOM = 2.21), and correlation pattern method (FOM = 1.97). This result is the basis for building systems for measurements of neutron using scintillation detectors

UNIVERSAL VOLTAGE-MODE BIQUADRATIC FILTER SYNTHESIS USING NODAL ADMITTANCE MATRIX EXPANSION

2017-01-03T08:44:41+07:00

This paper presents a systematic synthesis procedure for generating universal voltagemode biquadratic filters based on the nodal admittance matrix expansion. The obtained eight equivalent circuits can realize all five standard filter functions namely lowpass, bandpass, highpass, notch and allpass employing only two active elements. The obtained circuits offer the following advantages: five inputs and two outputs, simple circuit configuration, orthogonal controllability between pole frequency and quality factor, and low active and passive sensitivities. The workability of some synthesized filters is verified by HSPICE simulations to demonstrate the usefulness of the proposed method.

STUDY ON THE ACCUMULATION OF COPPER FROM SOIL TO BIOMASS OF SOME VEGETABLES

2017-01-03T08:59:52+07:00

In this study, the accumulation of copper from soil to biomass of spinach, lettuce, carrot and potato was investigated. The results of this work showed that the absorption of copper from soil to these plants depended on biological features of each plant and thus, might be usefully applicable in agricultural cultivation of the mentioned plants.

EFFECT OF DISINFECTION SOLUTION DIOX FORTE (CHLORINE DIOXIDE - CLO2) ON PROLONGING SHELFLIFE OF GRAPES AND TOMATOES

2017-01-03T08:44:42+07:00

This paper reports a study of the effect of disinfection solution Diox Forte (chlorine dioxide - ClO2) at 0, 10, 20, 40, 80 and 160 ppm on the shelflife of grapes and tomatoes at room temperature and cold store (5oC). The shelflives of grapes and tomatoes were significantly increased when treated with Diox Forte at 40 ppm for grapes and 10 – 20 ppm for tomatoes. The shelflife of grapes treated with Diox Forte at 40 ppm at room temperature and cold store (5oC) was increased for up to 17 days and 22 days, respectively. Meanwhile, the shelflife of tomato cultivars ‘Rista’ and ‘Triatlon’treated with Diox Forte at 40 ppm was significantly increased by 45 days and 29 days, respectively, compared to those of untreated tomatoes; the shelflife of cultivar ‘Octavio’ treated with Diox Forte at 10 ppm reached a maximum at 46 days, compared to untreated tomatoes; and cultivar ‘Olivade’ did not response to Diox Forte solutions. In the absence of Diox Forte, the shelflife of cultivar ‘Octavio’ was the highest with 40 days, followed by ‘Olivade’ (31 days) and ‘Triatlon’ (25 days) as compared to cultivar ‘Rista’ (24 days)

CAMELLIA THUONGIANA - A NEW YELLOW CAMELLIA SPECIES FROM VIETNAM

2017-01-03T08:44:42+07:00

Camellia thuongiana Luong, Anna Le & Lau (Theaceae), a new yellow Camellia species from Doanket commune, Dahuoai district, Lamdong province, is described and illustrated. Based on morphological data we affirm that this new species belong to section Chrysantha.

THE EXTENT TO WHICH DOWNSTREAM BUYERS ARE ABLE TO FULFIL FLOWER FARMERS NEEDS IN DALAT

2017-01-03T08:44:42+07:00

This study seeks to examine the gap between what farmers want and what they actually receive from their downstream buyers in Dalat – Vietnam. The sample consisted of 206 chrysanthemum and rose farmers in Dalat and reports on their exchange transactions with their most preferred and second most preferred buyer. Both social and economic criteria are identified as influencing the farmers’ choice of downstream buyer, reinforcing the importance of relational marketing in the transitional economies as a means of risk mitigation.

DIVERSITY OF ALGAE SPECIES IN XUANHUONG LAKE, DALAT

2017-01-03T08:44:42+07:00

Xuanhuong Lake is considered the heart of Dalat. In this study, algal abundance and diversity in Xuanhuong Lake were studied. Water samples were collected from four different sampling sites from September 2012 to January 2013. The identified species were 75 species belonging to 13 orders, 8 classes, 5 phyla (Cyanophyta, Chlorophyta, Bacillatoriophyta, Euglenophyta, Pyrrhophyta). Chlorophyta has the most species with 33 species (44%), the next was Bacillatoriophyta with 18 species (24%), Cyanophyta with 12 species (16%), Euglenophyta with 11 species (15%), and the least was Pyrrophyta: 1 species (1%). There has also been bioindicator species including Euglena viridis, Euglena acus, and Synedra ulna. Therefore, Xuanhuong Lake is considered mesosaprobic

THE FIRST REPORT OF PESTALOTIOPSIS SP. CAUSING CROWN ROT DISEASE ON STRAWBERRIES IN DALAT

2017-01-03T08:44:43+07:00

Study on the pathogens causing strawberries crown rot disease was complied with the methodology of Koch. Results from isolating 150 samples of infected plant parts collected from three strawberry cultivated areas in Dalat (Ward 7, Ward 8 and Ward 12) indicated that there were 327 isolates belonging to six fungal species. Most fungi isolated from infected parts were identified as Botrytis cinerea, Verticillium sp., Cylindrocarpon destructans, Fusarium oxysporum, Rhizoctonia sp. and Pestalotiopsis sp., in which the main fungi consistently isolated were Pestalotiopsis sp.. By fulfilling Koch’s postulates, the results of pathogenesis test indicated that Pestalotiopsis sp. was a pathogen causing the crown rot disease on strawberries in Dalat. This is the first report on the association of Pestalotiopsis sp. with crown rot disease of strawberries in Vietnam.

USING METHODS OF SOLARIZATION, BIO-FUMIGATION, BURNING AND KEEP DRYING SOIL CONTROL ROOT- KNOT NEMATODES ON LETTUCES, IN LAM DONG

2017-01-03T08:44:43+07:00

Root-knot nematodes (Meloidogyne sp.) are an important plant – parasitc group on green lollo lettuce. Experiments, included solarizion, bio-fumigation, burning and keep drying soil were carried out to control root-knot nematades on lettuces in Lamdong province. The results showed that burning method was the most effective (in soil) with only 28 juveniles/100g of soil and 96.75% after treating compared to the control with 1312 nematodes/100g of soil. The infection proportion of root-knot nematodes (1.433) and the number of juveniles of root-knot nematoses (201 juveniles/5g of root) in the burning were the lowest. Therefore, the height and the yield of crop treated with this method were the highest, proved by 25.99 cm and 30.25 tons/ha, respestively. In contrast, the root infection proportion in the control was the highest, acounting for 5.733 while the figures for the height (18.8 cm) and the yield of crop (15.93 tons/ha) were the lowest.

A STUDY OF WINE FERMENTATION FROM MUCILAGE OF COCOA BEANS (Theobroma cacao L.)

2017-01-03T08:44:43+07:00

Cocoa mucilage, a by-product of cocoa beans processing, constitutes 10% of total cocoa beans, with soluble solids up to 17.78oBx, pH of 3.43 – 3.5, rich in sugar, minerals, organic acids and phenolic compounds. The aim of this research is to ferment cocoa bean mucilage to produce a beverage with alcohol concentration of 11.2%. The fundamental microorganism for ethanolic fermentation is Saccharomyces cerevisiae with a density of 2x107cfu/ml in conjunction with 1% (w/v) of commercial fermentation powder product. The product of fermentation was assessed in terms of ethanol concentration, and optimum primary fermentation conditions were at the temperature of 28oC with the duration of 7 days. Secondary fermentation, which helped in stabilizing the quality of wine, occurred at 18oC for 30 days. The final product attribute is warm orange to bright rust in color, transparent, with a distinct aroma and sensory assessment according to TCVN 3215-79 and 3217 – 79 achiving a good score of 16.39. Therefore, it can be concluded that cocoa bean mucilage can be used for alcoholic beverage fermentation, contributing to diversifying processing products and increasing the application potentials for cocoa.