Showing papers by "Southwest University of Science and Technology published in 2005"

Multi‐zone modeling of probable SARS virus transmission by airflow between flats in Block E, Amoy Gardens

Abstract: UNLABELLED More than 300 residents of a private high-rise housing estate were infected with severe acute respiratory syndrome within a short period during the 2003 epidemic in Hong Kong. The outbreak occurred after the identified index patient visited a flat on a middle floor in Block E of the Amoy Gardens estate on two nights. Approximately 45% of the subsequently infected people resided in Block E, while the other 55% of infected cases mainly resided in six other blocks close to Block E. The distribution of the infected flats in Block E conformed to a non-uniform spatial pattern. Probable environmental causes for airborne transmission associated with the air movements between flats in Block E are identified. The well-established multi-zone airflow modeling method was used to analyze the virus-laden bio-aerosol dispersion between flats through door and window leakage areas in Block E under six different scenarios. The distribution of infection risk in Block E matched with the virus concentrations in flats predicted with the use of multi-zone modeling. Our study shows the importance of ventilation design in high-rise residential apartments. PRACTICAL IMPLICATIONS The present study on the Amoy Gardens outbreak presented a scenario in which crowded living spaces might lead to infection disasters. There is a need to improve the current sanitary drainage design and maintenance standards to avoid any leakage of foul gas into the indoor environments. Our study revealed the need for a review of indoor air quality and ventilation design in buildings including offices, homes and hotels. The study has implications to public health in, for example, the control of other airborne respiratory infectious diseases such as influenza, and in bio-terror safety in buildings.

Transport and deposition of Bacillus subtilis through an intact soil column

Abstract: Bacterial transport in unsaturated soils is much less well understood than in saturated conditions, especially for intact soils. This paper aims to investigate the fate and transport of bacteria in intact soils with different water saturations, and particularly the effect of low suction (and hence removal of water flow in the largest macropores). An intact soil column (0.50 m diameter by 0.70 m depth) with a tension infiltrometer was used to investigate the transport and deposition of Bacillus subtilis endospores (i.e. dormant and persistent bacteria) during saturated and unsaturated flows. Soil porosity and pore size distribution were measured. Porosity decreased with depth and macropores were concentrated in the topsoil. Three tensiometers and a temperature sensor were installed along the soil column to monitor matric suction and temperature. Breakthrough curves for bacteria and chemical tracer Br − at 0 and 0.5 kPa suction were obtained during the 3-month leaching experiment. Bacterial breakthrough occurred earlier than the inert chemical tracer, which is consistent with effects of pore size exclusion. Also, saturated flow gave a significantly higher concentration and recovery ratio of leached bacteria, i.e. 51% v. 0.88%. Recovery of Br − in leachate at both suctions reached >85%. The column was destructively sampled for deposited endospores at the completion of leaching. Bacterial deposition was concentrated in the top 0.10 m, then decreased abruptly and was relatively constant with column depth, although showing some irregularity at the bottom of the column. Additional keywords: unsaturated intact soil, tension infiltrometer, pore size exclusion, air-water interface, film straining.

Rheological behavior comparison between PET/HDPE and PC/HDPE microfibrillar blends

Abstract: The rheological behaviors of in situ microfibrillar blends, including a typical semicrystalline/semicrystalline (polyethylene terephthalate (PET)/high-density polyethylene (HDPE)) and a typical amorphous/semicrystalline (polycarbonate (PC)/HDPE) polymer blend were investigated in this study. PET and PC microfibrils exhibit different influences on the rheological behaviors of microfibrillar blends. The viscosity of the microfibrillar blends increases with increased PET and PC concentrations. Surprisingly, the length/diameter ratio of the microfibrils as a result of the hot stretch ratio (HSR) has an opposite influence on the rheological behavior of the two microfibrillar blends. The stretched PET/HDPE blend exhibits higher viscosity than the unstretched counterpart, while the stretched PC/HDPE blend exhibits lower viscosity than the unstretched blend. The data obtained in this study will be helpful for constructing a technical foundation for the recycling and utilization of PET, PC, and HDPE waste mixtures by manufacturing microfibrillar blends in the future. POLYM. ENG. SCI., 45:1231–1238, 2005. © 2005 Society of Plastics Engineers

A hybrid classifier based on rough set theory and support vector machines

Abstract: Rough set theory (RST) can mine useful information from a large number of data and generate decision rules without prior knowledge. Support vector machines (SVMs) have good classification performances and good capabilities of fault-tolerance and generalization. To inherit the merits of both RST and SVMs, a hybrid classifier called rough set support vector machines (RS-SVMs) is proposed to recognize radar emitter signals in this paper. RST is used as preprocessing step to improve the performances of SVMs. A large number of experimental results show that RS-SVMs achieve lower recognition error rates than SVMs and RS-SVMs have stronger capabilities of classification and generalization than SVMs, especially when the number of training samples is small. RS-SVMs are superior to SVMs greatly.

Morphology and mechanical properties of poly (phenylene sulfide)/isotactic polypropylene in situ microfibrillar blends

Abstract: The morphology and mechanical properties of the in situ microfibrillar blend based on isotactic polypropylene (iPP) and poly (phenylene sulfide) (PPS) were examined. The microfibrillar PPS/iPP blend was prepared through a slit-die extrusion, hot stretching, and water quenching process. Morphological observation indicated that the well-defined PPS microfibrils were achieved by the method used in this study, which provided a promising method for both PPS and PP recycling. The morphology study showed that the minimum diameter of PPS phase was independent of PPS concentration. The diameter of most PPS fibrils in the microfibrillar blend was unexpectedly comparable to that of the PPS particles in the common blend at the same PPS content. The tensile strength of microfibrillar blend was higher than that of common blend, indicating the mechanical enhancement of microfibrillar processing to the PPS/iPP blend. The tensile strength of the microfibrillar blend also increased with stretching. POLYM. ENG. SCI., 45:1303–1311, 2005. © 2005 Society of Plastics Engineers

In‐Situ Microfibrillar PET/iPP Blend via a Slit Die Extrusion, Hot Stretching and Quenching Process: Influences of PET Concentration on Morphology and Crystallization of iPP at a Fixed Hot Stretching Ratio

Abstract: In‐situ microfibrillar poly(ethylene terephthalate) (PET)/isotactic polypropylene (iPP) was fabricated via a slit die extrusion, hot stretching, and quenching process. Morphological observation shows that well‐defined microfibrils were generated in‐situ. The microfibrils become larger with the increase of PET concentration. The presence of PET microfibrils shows significant nucleation ability for crystallization of iPP. Higher concentration of PET microfibril corresponds to faster crystallization of the iPP matrix, while the variation of PET concentration has little influence on the onset and maximum crystallization temperatures of iPP matrix during cooling from melt. Optical microscopy observation reveals that transcrystallites form in the microfibrillar blend, in which the PET microfibrils play as the center row nuclei. In the as‐stretched microfibrillar blends, small‐angle X‐ray scattering measurements show that the long period of lamellar crystals of iPP is not affected by the presence of PET micofibe...

Evaluation of Bioactivity and Cytocompatibility of Nano-Hydroxyapatite/Collagen Composite In Vitro

Abstract: A nano-hydroxyapatie/collagen composite was fabricated by an in situ synthesis technique. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) analyses for the composite indicated crystals on the collagen fibril matrix exhibited certain orientation. Bioactivity of the composite was investigated through in vitro tests in a sterile simulated body fluid (SBF) system. Scanning electron microscopy and energy-dispersive X-ray analysis of the composite showed that the composite had the ability to induce the formation of calcium phosphate crystals on the surface of the composite in SBF. The cytocompatibility of the composite was evaluated by in vitro cytotoxicity test. Both the results from MTT assay and scanning electron microscope (SEM) observations indicated that the composite had no adverse impact on cell proliferation and morphology. The results imply the composite is high bioactive and has good cytocompatibility.

Experimental study on vibration effects of ground due to shallow tunnel blasting

Abstract: Taking the project of Renhechang shallow tunnel for Chongqing—Huaihua railway as the background,the field experiments of vibration effects of the ground in tunneling blasting have been done. Based on the measurement of the waveforms of the vibration velocity in different distances away from the tunneling blasting sources on the ground,the vibration characteristic of the ground and its varying laws are studied. Four blasting experiments for the shallow tunnel were carried out and twenty-seven waveforms of measured point vibration were obtained. The results of the tests and analysis show that:(1) the seismic effect of cutting hole blasting is the most intensive and its vibration intensity is over two times greater than that of the other blast-holes blasting;(2) the vibration velocities of the ground resulting from relief,breast and trim holes blasting do not always become greater with the increase of their single period charges;(3) the excavation region of the shallow tunnel may cause the hollow effect of ground vibration in tunneling blasting;and (4) the blasting vibration effect along the tunneling direction can be forecasted by Sadov′s formula,but the formula is not suited to the forecast of the opposite direction. Moreover,for Renhechang shallow tunnel,the attenuation parameters of seismic waves along the tunneling direction are K = 232.8 and α = 1.90.

Preparation and Characterization of Collagen by Hydrogel Formation Method

Abstract: A kind of medical collagen was prepared by hydrogel formation method. Chemical and physical properties were investigated by FTIR, amino acid analysis, SDS-PAGE, carbohydrate content analysis, heavy metal content analysis. Degradation experiments in vivo and subsequent histological investigations were carried out to evaluate the biological performance. The results suggested that the collagen achieved is promising in tissue engineering scaffold materials for a long-term (more than 12 weeks) implantation application.

A real-time algorithm of dynamic background extraction in image sequence

Abstract: A fast and precise obtainment of static background in image sequence is key step in monitor control system. A real-time algorithm of dynamic extraction for static background is put forward by means of the characteristics in environment and moving objects with static background. Large amounts of experimental results demonstrate that the algorithm has the properties of rapidity, simplicity, applicability and a small dependence with weather.

Periodic Wave Solutions to Dispersive Long-Wave Equations in (2+1)-Dimensional Space

Abstract: Periodic wave solutions to the dispersive long-wave equations are obtained by using the F-expansion method, which can be thought of as a generalization of the Jacobi elliptic function method. In the limit case, solitary wave solutions are obtained as well.

Nonisothermal Crystallization Nucleation of In‐Situ Fibrillar and Spherical Inclusions in Poly (Phenylene Sulfide)/Isotactic Polypropylene Blends

Abstract: Nonisothermal crystallization nucleation and its kinetics of in‐situ fibrillar and spherical dispersed phases in poly (phenylene sulfide) (PPS)/isotactic polypropylene (iPP) blends are discussed. The PPS/iPP in‐situ microfibrillar reinforced blend (MRB) was obtained via a slit‐die extrusion, hot stretching, and quenching process, while PPS/iPP common blend with spherical PPS particles was prepared by extrusion without hot stretching. Morphological observation indicated that the well‐defined PPS microfibrils were in situ generated. The diameter of most microfibrils was surprisingly larger than or equal to the spherical particles in the common blend (15/85 PPS/iPP by weight). The nonisothermal crystallization kinetics of three samples (microfibrillar, common blends, and neat iPP) were investigated with differential scanning calorimetry (DSC). The PPS microfibrils and spherical particles could both act as heterogeneous nucleating agents during the nonisothermal crystallization, thus increasing the onset and ...

Experimental Study of the High Temperature Mechanical Behaviors of TLP Bonding of Two Ni-Base Single Crystals

Abstract: In this paper, the mechanical behavior of Ni-base single crystals joint created by TLP bonding is presented. Experimental study has been performed on the TLP single crystal under loading conditions of static uniaxial tension, creep and Three-points-bending (T-P-B) at temperature of 850 °C. Specimens made of the base material, Ni-base single crystal specimens without bonding, were also tested under the same loading conditions. The mechanical behaviors of TLP single crystal is compared to the behaviors of base material. It was found that the static strength of the TLP specimens with the boundary normal to the tensile direction was 63% of the strength of the base material. The creep strength and the fracture ductile strength was more than 57% and 55% of that of the single crystal base material, respectively. The macro and micro graphs of fracture surfaces of specimens indicated that the fracture modes of the samples were brittle fracture.

In Vitro and In Vivo Biocompatibility of Nano-Hydroxyapatite/Collagen Composites

Abstract: A nano-grade hydroxyapatite/collagen composite was prepared by an in situ synthesis technique from calcium nitrate, diammoniun hydrogen phosphate, and a cowhide collagen sol at low temperature. XRD and TEM analyses of the composite indicated that crystals formed in the collagen fibril matrix were nanohydroxyapatite with low crystallinity. Biocompatibility of the composite was evaluated by in vitro cytotoxicity test and in vivo genotoxicity and sensitization test. No mutagenic activity of the composite was observed in mouse micronucleus tests. No evidence of dermal sensitization of the composite was found in guinea pig maximization tests. The results from a filter diffusion test indicated that the composite did not induce a cytotoxic behavior. All these results suggest that the composite has excellent biocompatibility.

The study of AlN ceramics sintered at superhigh pressure with belt-type press technology

Abstract: The effects of Y2O3 content, sintering time, sintering temperature, sintering pressure on thermal conductivity of AlN ceramics had been studied. X-ray diffraction (XRD), scanning electron microscope (SEM), laser conductometer and laser granularity dimension analysis measurer were respectively used to measure the phases, microstructure, thermal conductivity and particle size distribution of the samples. These studies reveal that the Y2O3 is an effective sintering addtive, and the best conditions of sintering are that the pressure is 5.15× 109 Pa, the temperature is 1700∘C and the sintering time is 115 min. Under these conditions, the sintered body has reasonable structure and its thermal conductivity is 200 w/(m⋅k).

An example of solution multiplicity in a building with bi-directional flow openings

Abstract: We addressed the question of whether the assumption of unidirectional flow found in previous studies has led to the existence of two stable ventilation solutions in a two-opening building. The findings of multiple solutions in building ventilation raise the question of whether the macroscopic flow analysis and/or computational fluid dynamics simulations can provide sufficient accuracy to predict airflow patterns for guiding practical design of natural and hybrid ventilation. We extended previous analyses of a building with two unidirectional flow openings to one with two bi-directional flow openings. We considered natural ventilation driven by combined thermal buoyancy and opposing wind forces. A Newton–Rapson method was used to solve the non-linear governing equations for air-flows and a Runge–Kutta method was used for heat balance in the building. The airflow and heat balance calculations are fully coupled. We found that two stable solution sexisted under a certain combination of identical natural drivi...

Radar emitter signal recognition based on feature selection and support vector machines

Abstract: One of the intelligent aspects of human beings in pattern recognition is that man identifies an object in real world using Marked Characteristic Principle (MCP). This paper proposes a humanoid recognition method for radar emitter signals. The main points of the method include feature ordering and an improved one-versus-rest multiclass classification support vector machines. According to MCP, an approach for computing marked characteristic coefficients is presented to obtain the most marked feature of every radar emitter signal. Subsequently, a support vector network is designed using the improved one-versus-rest combination approach of several binary support vector machines. Experimental results show that the introduced method has faster recognition speed and better classification capability than conventional recognition approaches.

Preparation and antimicrobial ability of natural proous antibacterial materials

Abstract: The liquid ion exchange method, solid salt melt method and dry-wet circulation method were used to prepare natural porous antimicrobial materials with natural minerals, such as zeolite, spilite, palygorskite and montmorillonite, respectively. Atomic absorption spectrum and X-ray diffraction analysis were carried out to investigate the effects of Ag+, Cu2+ and Zn2+ on antimicrobial abilities of natural porous minerals, and the effect of preparation method on ion exchange capacity of antimicrobial material, respectively. The results show that for the ion exchange capacity, clay mineral is higher than fibrous mineral, i. e. both zeolite and montmorillonite are higher; the antimicrobial ability of material with Ag+ is the best; the exchange capacities of materials with Cu2+ or Zn2+ are all higher, but the antimicrobial ability of Cu2+ is better than that of Zn2+.

Three-dimensional fluorescence spectra of mineral oil and extraction method of characteristic parameters

Abstract: To realize the on-line fluorescence monitoring of mineral oil pollution in water, three-dimensional spectral characteristic of oil-water intermixtures must be studied and the characteristic must be extracted. Using excitation wavelength, fluorescence wavelength and fluorescence intensity as three-dimensional system of coordinate, through sampling and surface fitting, three-dimensional fluorogram is gotten, which can provide gist for oil discrimination when presented in contour chart (finger-print map of oils). But there is little difference between characteristics of three-dimensional fluorogram because of the similarity of constituent and structure of similar oils. Therefore this paper introduces quantitative analysis method-characteristic parameter method which starts with analyzing statistical characteristic of three-dimensional fluorogram. Using RFPC fluorescence spectrometer (Shimadzu, Japan), three-dimensional fluorescence spectra of diesel oil, machine oil, gasoline oil, crude oil are measured and parameterized. The result shows that as a quantitative classified discrimination method of three-dimensional fluorescence spectra, the parameter of characteristic parameter method possesses definiteness for three-dimensional fluorescence spectra, and it is applicable, available when used in oil discrimination.

Multiple Solutions in a Building with Four Openings Ventilated by Combined Forces

Abstract: Ever since the existence of two stable ventilation solutions in a two-opening building was identified, questions have been asked whether multiple solutions of natural ventilation exist in complex buildings and what are the physical mechanisms that can lead to the existence of multiple solutions in complex buildings. We examined a simple one-zone building with four openings using the simple macroscopic method of thermo-fluid modelling by assuming that the air temperature in the building was uniform. A conventional network modelling computer program was used to simulate the four-opening building ventilated by combined buoyancy and wind forces. The ventilation flow rate in the simple four-opening building was found to be a linear superimposition of that in two corresponding twoopening buildings with opposing and assisting winds respectively. We have shown that when the ventilation flow in the two-opening building with opposing wind is sufficiently strong, two stable solutions and one unstable solution can ex...

Three-dimensional world's simulation roaming system based on vega/multigen

Abstract: Virtual reality technology (virtual reality, which is abbreviated as VR) is known as the border technology of fairy again It is a latest hi-tech practical technique developed at the end of the 20th century involving numerous disciplines The three-dimensional simulation system under software platform multigen creator and vega mainly is developed The solution to a series of key techniques is discussed such as the modeling method based on creator, the effect generation of the sky based on modeling and vega software environment, bump check, the transfering of the sound, the development of visual simulation software and the implement of whole system

Effect of LDPE-g-MAH as compatibilizer on thermal properties, mechanical properties and morphology of LDPE/lignin blow film

Abstract: The blends low-density polyethylene(LDPE) and lignin were compatilized by the graft copolymer of maleic anhydride(MAH) onto low-density polyethyleneThe effects of LDPE-g-MAH contents on thermal properties,FTIR spectral analyses mechanical properties, rheological behavior and morphology of LDPE/lignin blends were investigatedThe results of TG-DSC indicated the addition of compatibilizer decreased melting temperature, improved thermal stabilityFTIR elucidated the existence of an intermolecular hydrogen-bonding interaction between lignin and LDPE-g-MAHRheological behavior analysis for the blends demonstrated that the blends were processableScanning electron microscopy (SEM) micrograph showed that the compatibilizer LDPE-g-MAH could improve the dispersity of lignin in LDPE and reduce the dispersed phase sizeThe introduction of LDPE-g-MAH effectively improved the mechanical properties of LDPE/lignin blow filmWhen mass ratios of lignin, LDPE and LDPE-g-MAH were 25/75/10, the blow film had excellent mechanical property