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

Recent changes in the electric utility infrastructure have created opportunities for many technological innovations, including the employment of distributed generation (DG) to achieve a variety of benefits. Both utility and customers benefit from DG. Among many benefits of distributed generation, there are many directions to solve problem of DG but all also want to accomplish to achieve the optimality of the power system development and operation. The benefits are classified into two groups - technical and economics, so the problem of DG also has two directions for solving. In this paper, an algorithm using the primal dual interior point (PDIP) method for solving nonlinear optimal power flow (OPF) problems is presented. The main purpose is to optimize location and sizing of DG on distributed systems for solving the problem of line loss reduction. The equality constraints and inequality constraints are solved in a nonlinear manner based on the Karush-Kuhn-Tucker (KKT) conditions. Two simplified models of a 10-bus and 42-bus radial distribution system have been simulated in MATLAB to illustrate the use of the line loss reduction index.

In this paper, we fabricated silver-coated polyurethane foams and used it as a bacterial filter for contaminated drinking water. Flexible PU foams were soaked in silver colloidal solutions for 10hrs, then washed and air-dried at room temperature. The prepared silver colloidal solutions and silver-coated PU materials were characterized by several techniques including TEM, FE-SEMEDS, UV-Vis, ICP-AAS, and Raman spectroscopy. The TEM images showed that the size of silver nanoparticles in colloidal solutions varies from 6 to 12nm, The Raman, FE-SEM/EDS and ICP-AAS data illustrated that silver nanoparticles were stable on the PU foam and were not washed away by water. Furthermore, the microbiological tests (tube tests and flow test) were carried out on silver-coated PU materials with the Coliforms, E. coli, and B. subtillis. The obtained results showed that the bacteria were killed completely with antibacterial efficiency of 100% being observed. Our research suggests that silver-coated polyurethane foams can be used as excellent good antibacterial water filters and would have several applications in other sectors.

This literature review focuses on meat tenderness and flavor, which are most important in determining meat quality, but difficultly predictable and maintained. Meat tenderness primarily relates to muscle tissues while meat flavor is mostly resulted from fatty tissues. Many studies have indicated that not only protein composition of muscle fibers but also handling and slaughtering conditions, genetic traits, and growth progress could affect meat tenderness. Surprisingly, there is somewhat connection between tenderness and flavor through marbling of meat cuts. The more marbling the meat cut has, the more flavorful and tender it is. Some clear understandings of those quality traits of meat are important to improve quality of meat and processed meat products.

Fresh tea shoots (one shoot and two or three young leaves) were extracted using microwave-assisted extraction method (MAE). Several factors such as ethanol concentrations (0-99.5° (volume percentage)), material: solvent ratio (1:4 to 1:12), extraction time, oven power were studied to optimise conditions at laboratory scale. MAE archived good yield (82.46 %) after 6 minutes microwave radiation, that was higher than that of extraction at room temperature in 24 hours, conventional heating extraction at reflux temperature in 60 minutes or ultrasound-assisted extraction in 60 minutes. Afterward, MAE method was employed to investigate five types (LD97, LDPI, PHI, TB14, HAT) of tea (Camellia sinensis (L.) O. Kuntze) from Bao Loc, Lam Dong. HAT (20.49 % dried weight of total catechins) was found as suitable material for polyphenols extraction.

This study aims at identifying components of retail service quality in Vietnamese Supermarkets. A survey of 440 shoppers in various supermarkets in HCMC has resulted that service quality of supermarket composes of 4 factors namely Service Personnel, Physical Aspects, Policy and Reliability. Among which, Service personnel has the strongest impact and Physical Aspects has the weakest one, while the role of Reliability is not confirmed by the data. From these findings, managerial as well as theoretical implications have been discussed.

Recently, the field of differential equations has been studying in a very abstract method. Instead of considering the behaviour of one solution of a differential equation, one studies its sheaf-solution (see[8]). Instead of studying a differential equation, one studies differential inclusion (see[10]). Specially, one studies set differential equation ( a differential equation whose variables and derivative are sets, ( see[1-7]), a fuzzy differential equation is generalized to be fuzzy control differential equation (FCDE), (see[13]). In this paper, a set differential equation is generalized to be set control differential equation (SCDE) and we present the existence and comparison of solutions of (SCDE).This paper is a continuation of our works in this direction (see [11-15]).

Recently, the field of differential equations has been studying in a very abstract method. Instead of considering the behaviour of one solution of a differential equation, one studies its sheaf-solution (see[10-11]). Instead of studying a differential equation, one studies differential inclusion (see[9]). Especially, one studies fuzzy differential equation (a differential equation whose variables and derivative are fuzzy sets, see[1-7]).In this paper, a fuzzy differential equation is generalized to be fuzzy control differential equation (FCDE) and we present the existence and comparison of solutions of (FCDE). This paper is a continuation of our works in this direction (see (10-13]).

The purpose of this study is to develop the education quality measurement scale of Master of Business Administration (MBA) program in Vietnam. Cronbach’s Alpha, Exploring Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) were used to test the model with the support of SPSS and AMOS. The result of this study on the sample of 307 MBA students of Public and Private Universities in Ho Chi Minh City and neighbouring provinces indicates that MBA program education quality measurement scale includes five components: (1) Perceived program quality, (2) Perceived quality of life, (3) Perceived quality of lecturing faculty, (4) Perceived quality of academic facilities, and (5) Perceived quality of outcome.

Silica nanoparticles (SiO2 NPs) were synthesized from rice husk ash (RHA) by chemical treatment and calcination. The size of SiO2 NPs evaluated by transmission electron microscope (TEM) was of 20 - 50 nm and the size distribution of SiO2 NPs measured by dynamic laser scattering (DLS) was of Gaussian mode. The X-ray diffraction (XRD) pattern with only one peak at 2θ ~ 220 confirmed the amorphous phase of SiO2 NPs. The Fourier transform infrared (FTIR) and energydispersive X-ray (EDX) spectra were also used to evaluate the functional groups and the purity of SiO2 NPs. The SiO2 NPs powder with high purity could be suitably produced by calcination of acid treated RHA at 7000C for 2h. The obtained SiO2 NPs product can be potentially used for numerous purposes of application, especially as filler in paints.

Thirty types of commercial Vietnamese-brand teas (21 green teas, 5 black teas, 4 oolong teas) in Ho Chi Minh city were investigated for total polyphenols content (TPC acid gallic equivalent), total catechins content (TCC-catechin equivalent) and DPPH (2,2 diphenyl-1-picrylhydrazyl) free radical scavenger activity (RSA - Vitamine C equivalent). It was found that green tea had the highest TPC (15.06 ± 0.53 ppm), TCC (7.33 ± 1.71 ppm) and RSA (288 ± 23 mg) in three grams dried tea, higher than those of oolong tea, whereas black tea had the lowest TPC, TCC, RSA. However, high inconsistency and high deviation from mean values were observed within green tea group. Unexpectedly, several green tea types had low TPC, TCC, and RAC, even as low as those of black tea. This evidence demonstrated the instability and unevenness of green tea quality in Vietnam market.