Trường Đại học Khoa học Tự nhiên, Đại học Quốc gia Thành phố Hồ Chí Minh

In Vietnam, the Cai river basin - Phan Rang in Ninh Thuan province is considered to tolerate the most serious drought, which has influenced seriously on the lives and economy of the people in the region. Using Multi-Criteria Analysis method - MCA integrated with GIS for eight factors: evaporation (ETo), rainfall, groundwater, surface water annual flow module, vegetable matter (NDVI), river density, humidity of land and slope to build a system of component maps identifying the level and the change of drought, namely meteorological one in the Cai river basin - Phan Rang, Ninh Thuan province each year. According to the average results of the study period (2000–2014), the drought at this region has 3 levels: medium drought with 0.05 %, severe drought with 80.90 %, very severe drought with 19.05 % of the studied area. At the same time, the value of factors: evaporation (ETo) is from 1417.02–1817.00 mm, rainfall is from 640.9– 910.8 mm, groundwater is from 0–11 (1/s/km2), surface water annual flow module is from 9 – 23 (1/s/km2), vegetable matter is (NDVI) from -0.4 – 0.6, river density is from 0–1.6 km/km2, humidity of land is from 3.65–55 % and slope is from 0o– 62.8o. This study focuses only on the meteorological drought, we need more detailed researchs to continue estimating the 3 types of drought (agricultural, hydrological, socio-economic) to be able to recognize drought in this region more fully, thereby giving effective measures against drought.

In this study, we have synthesized polyurethane based on monoglyceride and 4.4 '-diphenyl methanediisocyanate (MDI) – an environmentally friendly polymer. Graphene oxite (GO) was used to reinforce for polyurethane forming polyurethane/graphene oxide (PU/GO) nanocomposite. The synthesis of PU and PU/GO was performed directly on the twinscrew extruder. This is a simple, time saving, economical and environmentally friendly method. Nanocomposites were manufactured with GO phase changed from 0.5% to 1.5% by weight. Structural analysis results of PU/GO showed a good dispersion through TEM figure (transmission electron microscopy). In addition, the mechanical and thermal properties of the nanocomposite were improved as compared to the original polyurethane. This study is a new step for the synthesis of polyurethane and nanocomposite based on polyurethane by the melt intercalation method.

Weak anion exchange sorbent based on cross-linked polystyrene with primary secondary amine group was prepared by substitution nucleophilic reaction (SN2) between methylene chloride group and 1,2-ethylene diamine. The effect of factors, namely the weight ratio of amine over methylene chloride, reaction time and temperature on nitrogen percentage were studied using experimental design approach. The amination yield rose as all of factors increased but was reduced while both temperature and time increased simultaneously. Nitrogen percentage of the products were varied from 4.0% to 6.3%. Sorbents with predicted capacity of 4.5%, 5.0%, 6.3%, and 6.5% were synthesized. The results showed that the actual capacities of the products were close to the predictions, especially for those in the experimental domain, indicating a good model that can be used to prepare sorbents of any desired capacity. The sorbent application ability of multiresidue pesticides analysis in food were initially investigated through both aspects: interference elimination and analyte content conservation.

The transparent electrode films SnO2: Sb were prepared by reactive magnetron sputtering method on glass substrate with various substrate temperatures. The material of target is alloy of Sn (99,5% purity) doped Sb (5% Sb by weight). The deposition processes were carried out in mixture of Ar (99,99% purity) and 02 (99,999% purity) gas. The vacuum inside the deposition chamber can get to about 10-5 torr. The substrate temperatures during the depositing processes were kept at fixed values between the room temperature and 450ºC. The dependence of crystal size and conductivity of films on substrate temperature were also investigated.

The aim of this work is to describe the source rocks in Cuu long Basin mainly consisting Cenozoic sediments (lower Oligocene + upper Eocene, upper Oligocene and lower Miocene) that are poor to rich in organic matter. The organic carbon (TOC%) in lower Oligocene + upper Eocene source rocks contains mostly kerogen type II, sometimes type I, III is 1.19-2.87%; in upper Oligocene source rocks containing mostly kerogen type II, sometimes type I and III is 1.14-4.0%; and in lower Miocene source rocks contains mostly kerogen type III is 0.64-1.32%. The Oligocene sediments are mostly deposited in lagoonal, estuarial and mixed environment. The depostitional environment of the organic matter in the lower Miocene sediments is terrestry.

The granite of the Song Ma block mainly consists of two types of granite: biotite granite and hornblende-biotite granite. Biotite granites have the percent of plagioclase (35– 45%), K-feldspar (25–35%), quartz (~20%) and biotite (~10%). Biotite-hornblende granite with the content of plagioclase (40–50%), Kfeldspar (10–15%), hornblende (5–10%) and biotite (5%). Zircon crystals were selected from the granite of Song Ma block are V0741, V0856 and V1006 samples with the LA-ICPMS U-Pb analyses gave concordant ages concentrated at 257±4Ma, 262±3Ma and 241±6Ma (weighted mean). Those ages are older than the results of the previous research. The mineral assemblages and geochemical characteristics show the typical of I-type granites. The results of Hf isotope composition analysis give the value of εHf(t) from +7.3 to +13.9, which is proven the sources of the granite Song Ma block similar to the granite of Phan Si Pan zone, NW Viet Nam during the period from late Permian to early Triassic.

By finite difference method, the Schrödinger equation with different effective masses in different layers of some quantum well systems is solved. From this, the effect of number of wells, barrier width, well width, electric field on energies in quantum well systems are investigated.

This research was carried out to measure and evaluate the emission of particulate matters and the emission of carbonyl compounds from diesel engine KAMA - KDE3500T generator under 1.5 kW load for seven test fuels: B0 (pure diesel fuel) B10 (10 % palm biodiesel + 90 % pure diesel fuel), B20, B30, B50, B75, and B100, respectively. The results showed that the emission concentration of particulate matters reduced from B0 to B20, and increased from B30 to B100. The concrete data were that 348.65 mg/m3, 297.27 mg/m3, 168.59 mg/m3, 169.74 mg/m3, 259.98 mg/m3, 330.30 mg/m3 and 522.98 mg/m3 for B0, B10, B20, B30, B50, B75 and B100, respectively. The emission concentration of carbonyl compound raised form B0 to B30, and suddenly decreased at B50, and increased again from B75 to B100. The concrete data were that 67.99 mg/m3, 87.35 mg/m3, 99.10 mg/m3, 100.96 mg/m3, 65.79 mg/m3, 102.32 mg/m3, 102.38 mg/m3 for B0, B10, B20, B30, B50, B75 and B100, respectively. The highest concentration compounds were formaldehyde, acetaldehyde, and acetone.

This paper presents a 10-b ADC designed in a 0.18-μm CMOS technology. The ADC achieves 10-b resolution by using the cascaded folding technique in both the fine and coarse converters. Folding stages are pipelined to improve the settling time. As a result, this ADC can achieve the sampling rate up to 100MS/s. Moreover, instead of using a costly single track-and-hold circuit, a distributed track-and-hold circuit is used to reduce the chip area and the power consumption. This also allows utilizing the open-loop architecture of the folding technique, thus improving the performance of the system. The simulation results show that with a 49 MHz sine-wave input, the ADC consumes 66 mW and the effective number of bit (ENOB) is 9.28-b. Taking into account of process variations by using a Monte Carlo simulation, the DNL varies from ±0.45LSB to ±0.25LSB. The layout of the ADC occupies 1.2 mm2 die area.

The paper describes the approximation of Bayesian estimator for the location parameter, variance parameter and compound parameter in the 2 – dimensional nonlinear models.