Tạp chí Phát triển Khoa học và Công nghệ Đại học Quốc gia Thành phố Hồ Chí Minh

The paper presented a method for calcul of maximum rate of waste that can be inject into a river. This method is based on the mathematic programing and the solution of transport equation. A calculation was perfomed for Sai gon - Dong nai river system.

The FT-Raman spectra of gasolines can provide vital information concerning aromatic ring/methylene ratios and by which the additives presenting in blended gasolines can be identified. In addition, we also use some frequencies as diagnoses for the blended gasolines. Then, the grade of gasolines (octane 83, octane 92, octane 95,...) will be determined by the mentioned ratios and the relative intensities of diagnostic bands.

Effect of initial sulfur dioxide content in must on the kinetics of wine rimary fermentation, using yeast immobilized in calcium alginate gel was examined. Initial sulfur dioxide content in must was adjusted from 12ppm to 312ppm. Our experimental results indicated that the maximum specific growth rate of the immobilized yeast was 1-2 times less han that of the free yeast. On the contrary, the sugar uptake rate and ethanol production rate of the immobilized yeast were 1.23-1.90 times and 1.22-1.81 times, respectively, more than those of the free yeast. The volatile acid content and pH value of the final wine fermented by immobilized yeast were lower. Thus, the organoleptic properties and biological stability of the wine were ameliorated. In general, the yeast immobilized in calcium alginate gel was more resistant to sulfur dioxide than the free yeast.

Soil erosion is a global environmental problem. The affecting main factors for soil erosion processes are different due to the specific areas. The calculated results of soil erosion, by Ha Quang Hai and Tran Tuan Tu, demonstrated that Song Be basin is eroded very huge, about 321 tons/ha/year. The article is based on factors proposed by R.P.C Morgan in 2005, using the analytic hierarchy process AHP (Thomas L. Saaty, 1970) to determine the weights for these factors. Since then, the article concluded main factors affecting soil erosion at Song Be basin. Research results showed that the Terrain factor has the largest weight (0.30), followed by two factors: Plant cover (0.29) and Rain (0.28). The article also identified four main factors impacting on the soil erosion at Song Be basin, including: slope, land cover ratio, intensity of rainfall and slope length. These results will be the basis for subsequent studies to adjust USLE model more applicably for erosion characteristics in the researched area.

This paper presents a method to compute the induced voltage on underground cable caused by lightning striking the ground in the vicinity, taking in consideration the earth resistivity as a complex function of the frequency, and the earth conductance values as well as its permittivity as functions of the frequency. Computation results for one-layer earth and two-layer earth are presented in diagrams.

Can Gio coastal zone is composed of funnel – shaped estuaries (Soai Rap, Dong Tranh, Long Tau) and coastal line from Dong Hoa headland to Can Gio headland. Dominant dynamic geomorphic process in study area is coastal erosion by tides and waves. In the study, the using associative methods: collection of data, analysis of satellite imageries, GIS and field work is to detect and identify levels of coastal erosion. Results of this research have indicated that erosion process in study area has been taking place during several decades with moderate rate 5 – 12m/year and even 22m/year in sensitive segments. Especially, the sand dune from Dong Hoa headland to Can Gio headland, Long Tau estuary and the Eastern shore of Thanh An Island are seriously eroded. Coastal erosion in Can Gio, Viet Nam as well as throughout the world is relative to sea level rise happening gradually. Anthropogenic activities such as: Buildings of hydroelectric dams, exploitation of sand are the other factors have accelerated erosion in the area.

In this paper, a software for calculating and simulating equidose lines of the cylindrical surface gamma sources such as Co60, Cs137, Tc99, I131, I_r^192 ... was designed based on MATLAB. From this software, we can estimate and simulate the equidose lines (2D), equidose surfaces (3D) of the above gamma sources. Especially, the equidose lines of the gamma sources with shielding iron, lead, ...) are also simulated .This software can be used to estimate the shielding thickness.

Accordance with the research project "Study on geodynamic hazards on Ho Chi Minh Highway (Tay Nguyen area) and suggestion of prevention and protection approaches " directed by Dr. Dau Van Ngo and two recent field trips of investigation in August and November 2004, the paper presents some typical slope landslides along this Highway.

This study investigated the effects of five initial tannin contents (1.8, 2.8, 3.8, 9.8 and 17.8g of acid tannic/L) on the kinetics of red wine fermentation, using yeast immobilized in calcium alginate gel. Our experimental results showed that in the medium with high tannin content (9.8 and 17.8g of acid tannic/L), maximum cell density and maximum specific growth rate of the immobilized cells were higher than those of the free cells. In all cases, the glucose utilization rate and ethanol production rate of the immobilized yeast were always higher than those of the free yeast. Moreover, using immobilized yeast in wine fermentation decreased pH value and volatile acidity of the culture. Thus the colloidal and biological stability and the organoleptic characteristics of the final product were ameliorated.

Vietnamese banks have recently boosted online services besides traditional ones. The parallel existence of these two service channels will have a positive impact on customers if both of them are well evaluated. However, if either is badly evaluated, the opposite is true. What types of services to invest in to receive customers’ highest overall satisfaction remains a question to companies. This study examined various impacts of the perceived quality of two types of services on customers’ overall satisfaction. The relationship between positive impact of perceived quality of online services and the perceived quality of traditional services is also tested. Using a survey of 435 customers of Vietcombank, we found that online service quality affects the overall satisfaction stronger than traditional service quality. In addition, online service quality also has a significant impact on customer evaluation of traditional services.