bluuebunny/crossref_metadata_2025 huggingface dataset:
The Research on the Strength of Cement Mortar with Different Particle Size of Waste Glass Powder
Authors: Ke Guo Jun , Wang Yan Chao , Zou Pin Yu , Zeng Dai Nian
Published: December 2014

To study the strength of cement mortar with different particle size of waste glass powder, grinding and screening the colorless waste glasses to 38-53,53-75,75-150,150-300,300-600μm, and as supplementary cement materials replacing the cement of cement mortar at 5,10,15,20,25,30%, respectively. Meanwhile divide the experiment into two parts:containing water reducer or not and add fly ash as comparison at the same time, measuring the flexural and compressive strength of cement mortar for 28 days. It is concluded that the flexural and compressive strength of cement mortar are decreased when mix with water reducer with maintaining the dosage of water;The optimum size and amount of waste glass powder in the cement mortar keep the same whether it is mixed water reducer or not; The flexural and compressive strength for 28days of the cement mortar reach the best value and differ with the baseline group very few whether it's mixed water reducer or not.
Development and Evaluation of Nanofluid Heavy-Duty Coolant
Authors: Chen Jin Mao , Leng Guan Jun , Yi Ru Juan , Gao Bo
Published: December 2014

In order to meet the demand of heat rejection requirement of heavy-duty engine, a novel nanofluid heavy-duty coolant was developed in this paper by taking advantage of nanofluid heat transfer technique and organic acid technique. Comparing with conventional heavy-duty coolant, the heat transfer capacity increased more than 10%, which solved the problems of limited thermal conductivity and convective heat transfer performance. The coolant possessed the characteristics of a qualified engine coolant should have and could be a promising engine coolant.
Structure Optimization of Open Turbine Type Agitator
Authors: Zhang Hui Min , Liao Hui Liang
Published: December 2014

Regarding open turbine type agitator, CFD method was used to simulate the mixing flow field with different number of blades, different blade angles and different ratio of blade lengths and diameters. In addition, according to the mixing effect, the parameters of agitator structure are optimized. Numerical simulations are verified by PIV experiments. The Multiple reference frame model conforms to the reality. Agitator structure is optimized when the ratio of blade length and diameter is 0.74, the blade angle is 45 °,blade number is 6, leading to the best the mixing effect with least stirring dead areas.
Experimental Investigation on Viscosities of Cu-H2O Nanofluids
Authors: Zheng Zhao Zhi
Published: December 2014

In this study, Cu-H2O nanofluids with different mass fraction and nanoparticle size were prepared by supersonic oscillator through appending hydrophilic dispersant into deionized water. The viscosities of Cu-H2O nanofluids and H2O were investigated experimentally under different temperature. The experimental results show that the viscosities of nanofluids increase apparently compared to the deionized water, and increases with increasing nanoparticle size, mass fraction. What’s more, the viscosity of nanofluids decreases with increasing temperature. The results also demonstrated that the Cu-H2O nanofluids are Newtonian fluids.
Experimental Investigation on Surface Tension of Water-Based Graphene Oxide Nanofluids
Authors: Zheng Zhao Zhi
Published: December 2014

The water-based graphene oxide nanofluids were prepared. The surface tension of nanofluids with different mass fraction, temperature and different nanoparticle size was researched. The surface tension value was measured through ringmethod. The experimental results show that the surface tension of nanofluids is increased with increasing the mass faction of nanoparticles. But the surface tension of nanofluids with maximum concentration (0.1 wt %) is only increased up to 2.9% compared with deionized water. The surface tension of nanofluids decreases with increasing temperature and decreasing nanoparticle size. The results of this paper may provide reference for the research of absorption liquid for absorption refrigeration cycle.
Enhance the Power Capability of TaN Thin Film Resistor by Improving Processes
Authors: Wang Bin , Cao Qian Tao , Song Zhen Guo
Published: December 2014

Technologies of TaN thin-film resistors were studied, the thin films were prepared by the D.C. sputtering system, and the trimming methods of the resistor were anodic oxidation and autoxidation. We laid emphasis on the study of power capability of TaN thin film resistor in this paper. We acquired the resistors with the average power capability of 13W/mm2.
Heat Slug Material Variation Analysis on Thermal Dissipation of High Power LED
Authors: Retnasamy Vithyacharan , Sauli Zaliman , Vairavan Rajendaran , Taniselass Steven , Kamarudin Hussin
Published: December 2014

Accession of power in high power LED light source has resulted in thermal issue which causes reliability malfunction due to deficient heat dissipation. However, the heat disspation of high power LED can be enhance by improving packaging material selection.Thus, in this work, the connotation of heat slug material on the thermal performance of high power LED package was analyzed through simulation method. The significance of two heat slug materials, copper (Cu) and copper diamond (CuDia) were evaluated in terms of junction temperature, von Mises stress and thermal resistance. The simulation was executed using Ansys version 11 at ambient temperature of 25 °C with natural convection condition.
Copper Based Heat Slug Structure Variation Analysis on Heat Dissipation of High Power LED
Authors: Retnasamy Vithyacharan , Sauli Zaliman , Vairavan Rajendaran , Kamarudin Hussin , Shahimin Mukhzeer Mohamad , Taniselass Steven , Menon P. Susthitha
Published: December 2014

Excess heat generated by the high power LED package significantly impacts the performance and reliability of the light source. Significance of heat dissipation are influenced by each packaging component of high power LED. This paper demonstrates simulation analysis on single chip high power LED where the significance of the copper based heat slug structure on the heat dissipation was analyzed. The simulation analysis was carried out by using Ansys version 11 and heat dissipation of two types of heat slug structure, rectangular and cylindrical were compared. The outcome exhibited that the structure of the heat slug significantly influences the heat dissipation of LED chip due to its surface area.
Reinforcement Possibilities of Round Timber Bolted Joints
Authors: Klajmonová Kristýna , Lokaj Antonín
Published: December 2014

In this article the results of round timber bolted joints with inserted steel plates tests are presented. First, unreinforced round timber specimens were tested. Mechanical reinforcement by using modified washers, steel bands, BOVA plates and boost with screws of round timber specimens based on test result was then proposed. Reinforced specimens of various densities were then tested and rate of improvement in tensile strength was established for each of five proposed reinforcement methods. Tests were carried out on EU100 pressure machine in Faculty of Civil Engineering of VŠB-TUO Ostrava.
Experimental Research on Strengthening and Fastening for Thick-Section Aluminium Alloy Bolted Joints
Authors: Zhao Qing Yun , Huang Hong , Xiao Qing Dong , Liu Feng Lei
Published: December 2014

For 7050-T7451 plate with the thickness of 16mm, ∅6 hi-bolts were installed with 0.11mm interference by electromagnetic riveting. Split-sleeve cold expansion was employed with 4% expansion. Combine joining of 4% expansion+0.11mm interference was carried out. The effect of strengthening was estimated from microstructure, stress and fatigue life. The results show that the microstructures are the same before and after strengthened. Along the installing direction, materials flow locate near the exit. Residual compressive stresses generate by strengthening process and gradually increase by the process of interference bolted joining, split-sleeve cold expansion and combine joining, within some diameter in the exit. The fatigue lives N50 also gradually increase by the process of interference bolted joining, split-sleeve cold expansion and combine joining.
The Fire Taking Cotton Flame Retardant Fabric Style Test and Analysis
Authors: Yang Liu , Yang Jian Zhong , Li Long
Published: December 2014

This study selected the six cotton flame retardant fabrics, respectively, as a fire taking waterproof moisture permeable layer and comfortable fabric with fabric KES - FB fabric style instrument test study of mechanical performance under low stress, Respectively for three kinds of laminating fabrics and three kinds of non-laminating fabric fabrics were analyzed, and the results indicate: As waterproof and moisture permeable layer in the fire service, the effect of flame retardant canvas fabric style for the three best; By contrast to the non-laminating fabric, cotton antistatic fabric can be seen the best taking performance. If follow-up studies, the outer layer and the insulating layer to select a better flame retardant properties of materials (e.g. PBO fabric as the outer layer, aramid 1313 as the insulating layer), can be considered as an anti-static fabric with a cotton inner layer to improve wearing comfort.
Thermal Decomposition Conditions of Emulsion Matrix in the Emulsifier
Authors: Zhou Hui Sheng , Xie Xing Hua , Xu Kang
Published: December 2014

The main background was the "3.11" accident in this paper. The starting point was based on the experts’ conclusions of investigation and analysis in the accident. Combining the decomposition mechanism of ammonium nitrate in the emulsion explosives and the lessons from the production of emulsion explosives explosion, the conditions of the emulsion explosives (matrix) thermal decomposition in the emulsifier are given that are the formation of hot spot and the accumulation of heat. Then the factors of hot spots generated in the production of emulsion explosives and the occurred conditions of the heat accumulation are analyzed and summarized.
Enlightment of “May 20” Explosion Accident
Authors: Xie Xing Hua , Wang Lei , Zhou Hui Sheng
Published: December 2014

This paper introduces the "5.20" of the emulsion explosive incident and analysis the cause of the accident. Based on the production of explosion accident summarizes the security problems of emulsion explosive production process, and relevant measures are put forward. Combining the decomposition mechanism of ammonium nitrate in the emulsion explosives and the lessons from the production of emulsion explosives explosion, the conditions of the emulsion explosives (matrix) thermal decomposition in the emulsifier are given that are the formation of hot spot and the accumulation of heat. Then the factors of hot spots generated in the production of emulsion explosives and the occurred conditions of the heat accumulation are analyzed and summarized.
Deflagration to Detonation Transition of Explosives without the Effects of Shock Waves
Authors: Xie Xing Hua , Xu Kang , Zhou Hui Sheng
Published: December 2014

Inthis paper, the deflagration to detonation transition in explosives without theeffects of detonators was studied by the analyzing the accident in theproduction and storage process of explosives. Combining the decompositionmechanism of ammonium nitrate in the emulsion explosives and the lessons fromthe production of emulsion explosives explosion, the conditions of the emulsionexplosives (matrix) thermal decomposition in the emulsifier are given that arethe formation of hot spot and the accumulation of heat. Then the factors of hotspots generated in the production of emulsion explosives and the occurredconditions of the heat accumulation are analyzed and summarized.
An Experimental Study on Anchor Performance of Bare CFRP Tendons with Bond Type Anchor
Authors: Jung Woo Tai , Keum Moon Seoung , Kang Jae Yoon , Park Jong Sup
Published: December 2014

Despite of their outstanding axial strength, CFRP tendons necessitate special anchorage due to their low lateral shear strength. In order to cope with such CFRP tendon, the conventional bond type anchor needs to be improved. The results of bond tests executed on 10-mm diameter CFRP tendons coated with sand and oxide revealed that, even if the average bond strength increases by 3 times compared to the non-coated bare tendon, the coated CFRP tendon still requires excessively long anchored length for bonding. Therefore, this study applies a method enabling to shorten the bonded length and improving further the bond performance compared to sand or oxide coating. The improvement of the bond characteristics is achieved by splitting the ends of the CFRP tendon so as to widen the bonded area by 3.5 times. The test results showed that the anchor performance of the CFRP tendon reaches 95% of its tensile strength making it applicable for the bond type anchor.
Research of Directional Stress Distribution on the Fully Plastic Bulged Pressure Hull
Authors: Lu Guo Chun , Chu Guan Nan
Published: December 2014

In order to improve the ultimate capacity of pressure hull, a new method to improve the external bearing limit is put forward and residual stress is used. Based on the lame formula, the bilinear hardening model is considered to deduce the residual stress formula. Two influence parameters are analyzed by theoretical and numerical methods. The accordance of results shows that the accuracy of theoretical derivation can be verified by FEM. The 3D models with residual stress or not are built in ABAQUS. According to a lot of data of simulation experiments, the result indicates that the directional residual stress is useful, especially compressive on the outer surface of the pipe and the hoop stress keeps tensile on the inside surface. This kind of stress distribution is helpful to the cylinder structure and can improve its ultimate capacity of external pressure. Thus, the formula considering hardening material can guide the full plastic bulging to produce the desired stress distribution.
Study of UV Irradiation on Behavior of NBR Rubber from Oil Seal
Authors: Zhang Hui , Chang Chao
Published: December 2014

Ultraviolet light has been considered a main factor of natural aging threats the oil sealing’s lifetime when using outdoor. In this work, we will compare the behavior of NBR (the mostly used material for sealing) during UV aging. To analyze the characteristics of UV irradiation behavior of NBR,their surface morphology and infrared spectroscopy were measured,after the irradiated at UV environment for period time. The results showed that the surface of rubber occur more white spots and the aging began occurred.
Study on Viscosity Evaluation of Foamed Epoxy Asphalt
Authors: Huang Ming , Wen Xue Jun , Jian Xu , Zheng Xiao Guang , Huang Wei Dong
Published: December 2014

Foamed epoxy asphalt, which is a kind of epoxy asphalt with a brand-new curing system, has excellent construction performance. Based on the change of viscosity-temperature curves, several mixing amounts of new anhydride curing agents used in B-component of epoxy asphalt have been proposed. Through adjusting the content variation of B component to make the viscosity meet curing conditions. Meanwhile, the curing system formula has been improved by monitoring the viscosity change in the curing process, which can effectively slow down the curing reaction, make the performance of foamed epoxy asphalt achieve the construction requirements, and also provide enough time to complete mixing, paving and rolling in the process of construction. Material A1, A2, N1, and American ChemCo epoxy asphalt was studied by viscosity tests.
Out-of-Plane Thermal Conductivity of Silicon Thin Film Doped with Germanium
Authors: Chen Hui , Chen Wei Yu , Chen Yun Fei , Bi Ke Dong
Published: December 2014

The out-of-plane thermal conductivity of silicon thin film doped with germanium is calculated by non-equilibrium molecular dynamics simulation using the Stillinger-Weber potential model. The silicon thin film is doped with germanium atoms in a random doping pattern with a doping density of 5% and 50% respectively. The effect of silicon thin film thickness on its thermal conductivity is investigated. The simulated thicknesses of silicon thin film doped with germanium range from 2.2 to 10.9 nm at an average temperature 300K. The simulation results indicate that the out-of-plane thermal conductivity of the silicon thin film doped with germanium decreases linearly with the decreasing film thickness. As for the film thickness of 9.8nm and the average temperature ranging from 250 to 1000 K, the investigation shows that the temperature dependence of the film thermal conductivity is not sensitive.
FPGA Based Low Power ROM Design Using Capacitance Scaling
Authors: Bansal Meenakshi , Bansal Neha , Saini Rishita , Kalra Lakshay , Mohan Singh Preet , Pandey Bishwajeet , Akbar Hussain D.M.
Published: December 2014

An ideal capacitor will not dissipate any power, but a real capacitor will have some power dissipation. In this work, we are going to design capacitance scaling based low power ROM design. In order to test the compatibility of this ROM design with latest i7 Processor, we are operating this ROM with frequencies (2.9GHz, 3.3GHz, 3.6GHz, 3.8GHz and 4.0GHz) supported by i7 processor.By using different capacitance there comes is reduction in I/O Power and Total power but not in other Powers like Clock, and Leakage (almost negligible). When capacitance goes from 30pF to 5pF, there is a saving of 28.12% occur in I/O Power, saving of 0.2% occur in Leakage Power, there will be a saving of 11.54% occur in Total Power. This design is implemented on Virtex-5 FPGA using Xilinx ISE and Verilog.
Research on Fabrication of TaN Thin Film Resistors by Using Light Field Mask Method for Microwave Circuits
Authors: Cao Qian Tao , Bin Wang , Song Zhen Guo , Long Jiang Hua
Published: December 2014

Photolithography and etching by using dark field mask method in the fabrication of TaN thin film resistors applied in microwave circuits exists a problem of narrow alignment window. It results in inconsistency and poor yield. The process of TaN thin film resistors fabricated with Al2O3/TaN/ TiW/Au multistructure by using light field mask method was mainly discussed in this paper. Overlay accuracy of multilayer microstructure and accuracy of line width and line space of TaN thin films were measured by using metallographic microscope. Nonuniformity of resistances of TaN thin film resistors was also analyzed. Research on fabrication of TaN thin film resistor using light field mask method could achieve the following technical specifications: Overlay errors of multilayer microstructure on the direction parallel to two terminal electrodes’ connectivity were zero; Overlay errors of multilayer microstructure on the direction perpendicular to two terminal electrodes’ connectivity floated within 5μm to-5μm; Line width error of TaN thin film was from-2μm to 1μm. Nonuniformity of resistances of TaN thin film resistors was also consistent with the thickness nonuniformity of TaN thin film. Compared with dark field mask method, experiments revealed that photolithography and etching by means of light field mask method had advantages of wide window of alignment, high alignment precision and good uniformity. It can be concluded that photolithography and etching by using light field mask method will be widely applied in the fabrication of TaN thin film resistors for microwave integrated circuits.
Recognition and Segmentation Method of Adhering Bars Based on Support Vector Machine
Authors: Liu Guo Hua , Liu Bing Le , Li Liang Yu
Published: December 2014

This paper proposes a new solution to recognize and segment adhering bars. A support vector machine (SVM) is constructed according to the feature vectors of training samples to recognize the adhesions type of bars. The geometric feature values and moment feature values based on Blob regions in the image are extracted, which are the input feature vectors of support vector machine. The trained classifier is used for identifying the adhesions type of bars in the image. Finally, classification and recognition are realized by support vector machine. The experimental result shows that the recognition accuracy based RBF kernel achieves 100%. The method is feasible and effective for the recognition and segmentation of the adhering bars.
The Preliminary Study on Wheel-and-Rail Dynamical Model of High-Speed Train
Authors: Du Jian Hua , Shen Hong Yun , Wang Yu Lin
Published: December 2014

the study on dynamical model of wheel and rail of high-speed train is a focus nowadays. In this paper, the dynamical model of wheel and rail of high-speed train is constructed according to the damping force and the dry friction between wheel and rail. The dynamics of the model was studied and the dynamical system of wheel and rail without collision was analyzed, which povides the theoretical basis for engineering.
Utilization of Waste Materials from Industrial Processes of a Brazilian Sugarcane Mill for Energy Production
Authors: Verdú Ramos Ricardo Alan , Scarpin Lucas Mendes , Macedo Maia Cassio Roberto , Dias Filho Newton Luiz , Alves Thiago Antonini , Passolongo Rodnei
Published: December 2014

This work presents the thermodynamic, thermoeconomic, and economic analyses of utilization of waste materials from industrial processes of a modern Brazilian sugarcane mill (bagasse, straw and vinasse) for energy production. The first case considers a conventional steam thermal power plant constituted, among other equipment, by a steam boiler of high-pressure and high-temperature and by an extraction-condensation steam turbine, being all mechanical driving electrified, and using just bagasse as fuel. The second case considers a modified steam thermal power plant in which is incorporated systems to be possible the utilization of straw and vinasse as complementary fuel to bagasse by means of a combined cycle, with the addition of a gas turbine and a heat recovery steam generator, among other equipment.
Active Control of Structural Sound Radiation in an Acoustic Enclosure Using Distributed Point Force Actuators
Authors: Chen Da Lin , Chen Nan
Published: December 2014

This paper demonstrates an investigation about the active control of sound radiation in the enclosure cavity consists of two flexible plates. One of the flexible plates is driven by a point force to generate the primary sound field in the cavity, and using some point forces which are located at different locations on the receiving plate to suppressing the panel vibration and then to minimum the cavity sound pressure level (SPL); meanwhile some actuators are located on the other panel surfaces to reduce the sound pressure level at some frequencies that can’t be well reduced by only effect on one panel. The better result shows the possibility of applying distributed cooperative control method to the structural-acoustic coupled system.
Non-Linear PID Controller Parameter Optimization of Vertical Take-Off and Landing Stage for Tilt Rotor Aircraft
Authors: Zhang Yuan Qi , Zhao Wei Ping , Xiang Song
Published: December 2014

Proportion, integration and differential gain of nonlinear PID Controller is nonlinear function of controlling error. This paper performed the non-linear PID controller parameter optimization of vertical take-off and landing stage for tilt rotor aircraft using the genetic algorithm. Dual loop control is used. Inner loop is angular velocity loop. Outer loop is angular position loop. According to the features of stability control of vertical take-off and landing stage of tilt rotor aircraft, system ascend time, steady error, and weighted overshoot are chosen as objective function of optimization. Simulation results show that controller designed by the present method can meet the requirement of control.
Carbon Nanotubes as a Nonlinear Buckled Beam for Nanoelectromechanical Systems
Authors: Chan Yue , Thamwattana Ngamta , Hill James M.
Published: December 2014

In this paper, we examine the nonlinear nanoelectromechanical effect on a doubly clamped suspended single-walled carbon nanotube which could be used for pressure sensor. Coulomb-blockade effects will be explored and investigated. We adopt the full expression of curvature term in the elastic energy and use a modified Euler’s method to determine the nanotube’s maximum displacement in all bending regimes. We find that while the approximate solution given by Sapmaz et al. [1] underestimates the maximum displacement of the buckled nanotube in the weak bending regime, the approximate solution fails to obtain the correct maximum displacement as given by our numerical solution. Accordingly, the effect of curvature must be properly addressed for this nanoelectromechanical system to be used as an accurate sensor.
Magnetic Property of Ni-Doped Bi5Ti3FeO15 Multiferroic Ceramics
Authors: Li Jian Qing , Yu Ling Feng , Chen Zi Peng , Ma Zheng Zheng
Published: December 2014

Multiferroic ceramics of Bi5Ti3Fe1-xNixO15(x=0.1,0.2,0.5,0.7) are synthesized b the conventional solid state reaction, and their microstructure, magnetic properties are investigated. X-ray diffraction patterns show that a four-layer Aurivillus phase is formed in each sample and the diffraction peaks change obviously with the temperature increasing. The Ni ion modification induces remarkable ferromagnetism (FM) at room temperature. And the x=0.2 sample has the greatest saturation magnetization Ms~0.26552 emμ/g, and the coercive field Hc~ 0.65478 kOe
The Modern Current Sensors of Synthetic Magnetic Resin Part 2 - AC Current Sensor up to 2 000 amps
Authors: Lokvenc Jaroslav , Drtina René , Šedivý Josef
Published: December 2014

The article presents previously unpublished results of the development of current sensors, designed on the basis of cold-cast possibilities of magnetic materials and their applications for measurement purposes in the field of electricity and power electronics. Listed are the fundamental characteristics of the magnetic alloy resin schematic draft sensor dI/dt of a core of magnetic material molded and the measurement results of the prototype produced industrially.
Effect of High Pressure Treatment and Synthesis on Multiferroic Properties of 0.9BiFeO3-0.1SrTiO3 Ceramics
Authors: Ma Zheng Zheng , Chen Zi Peng , Li Jian Qing , Huang Hai Jun
Published: December 2014

The solid solution ceramics of 0.9BiFeO3-0.1SrTiO3(BFST) were processed under cool-high pressure (BFST-H1, BFST-H2) and high temperature-high pressure (BFST-H3). And the high pressure synthesis with different temperature was used to prepare the sample BFST-H4 and BFST-H5. X-ray diffraction showed that these ceramics are almost of single phase. Among all the samples, the 3GPa,900°C high pressure synthesized one shows the optimal ferroelectricity at room temperature, with enhanced magnetic properties was observed.
Reinforcing Epoxy Resin with Polydopamine-Coated Al(OH)3: A Biomimetic Method to Constructing Organic-Inorganic Hybrid Materials
Authors: Li Jian , Wen Xue Mei , Zhang Wei , Chen Yu Ping , Xiao Ying , Xiong Chen Xue , Zhu Wei , Jiang Tao
Published: December 2014

A facile biomimetic method was developed to enhance the interfacial interaction in organic-inorganic hybrid materials. By mimicking mussel adhesive proteins, a monolayer of polydopamine (PD) was constructed on surface of Al (OH)3 particles through a controllable coating pathway. The modified Al (OH)3 (PD-Al (OH)3) was incorporated into an epoxy resin. It is found that the strong interfacial interactions brought by the polydopamine benefits the effective interfacial stress transfer, leading to greatly improved flexural properties of the organic-inorganic hybrid resin.
Effects of Cu/Ba Ratio in Precursor on MOCVD-Deposited YBa2Cu3O7-x Films on YYC Buffered Ni-W Alloy Tape
Authors: Zhang Fei , Xiong Jie , Zhao Rui Peng , Xue Yan , Tao Bo Wan
Published: December 2014

To study the effects of Cu/Ba ratio of precursor on YBa2Cu3O7-x (YBCO) film, we have employed the technique of metal-organic chemical vapor deposition to prepare 500 nm thick YBCO films on CeO2/YSZ/Y2O3 (YYC) buffered Ni-W alloy tapes at series of Cu/Ba ratios of precursor. The analysis obtained from X-ray diffraction and scanning electron microscope revealed that the YBCO films crystallized better and became more continuous and denser as Cu/Ba ratio increased from 0.81 to 1.00, yielding that the critical current density (Jc) of YBCO films at 77K and 0T rose from 1.0 MA/cm2 to 1.4 MA/cm2. Moreover, the energy dispersive spectroscopy indicated that the increase in Cu/Ba ratio of precursor made the Cu/Ba ratio of the YBCO film matrix closer to the theoretical value of 1.5. However, for the Cu/Ba ratio of precursor in the range of 1.00~1.21, the crystallization and texture deteriorated severely and many unexpected precipitates of Ba-Cu-O and Cu-O arose, resulting in the dramatic drop of Jc from 1.4 MA/cm2 to 0.1 MA/cm2.
Drying Kinetics Evaluation of Solid Red Bricks
Authors: Barreira E. , Delgado João M.P.Q. , de Freitas V.P.
Published: December 2014

Moisture is one of the most deteriorating factors of buildings. The moisture content depends on hygroscopic equilibrium between buildings materials and environment, which is determined by the drying and wetting rate of masonry. So, the moisture content is not only determined by the water that is absorbed by the material, but also by the amount of water that is evaporated under favourable conditions, which is described by the drying process.This work presents the results of an experimental evaluation of the drying kinetics of solid red brick, considering the bulk moisture transfer. The drying kinetics was assessed considering different environment conditions (air temperature and humidity). The experimental results showed that the drying flux is extremely dependent of temperature and relative humidity in the first stage of the drying process. The values obtained were between 0.025 kg/m2h (T=15oC and RH=80%) and 0.135 kg/m2h (T=30oC and RH=50%), for the worst and better drying ambient conditions.Different first-order kinetics models, available in the literature, were adjusted to describe the drying process and estimate the equilibrium moisture content of the samples. The results point that Midilli et al. model allows the best fit and that the drying time constant is strongly affected by the drying air conditions. It was also estimated the apparent molecular diffusion coefficient for solid red brick samples and its variation with temperature.
Key Mechanisms behind Pedestrian Dynamics: Individual and Collective Patterns of Motion
Authors: Miguel Antonio Ferreira
Published: December 2014

Locomotion consists of cyclic events controlled by the neuronal activity of networks called central pattern generators. For a correct management of pedestrian flows, under regular or safety-critical situations, a deep understanding of individual and crowd dynamics is crucial. Here, we examine the emergence of walking and running forms of human gait. Individual locomotion and its interaction with other pedestrians is studied. Another key aspect examined is the self-organization experienced by a group of individuals which is a key concept to understand crowd dynamics. Self-organization leads to emergent properties, meaning that the whole system has characteristics that differ qualitatively from those of the component parts. The mechanisms behind the emergence of self-organized pattern of motion are also studied.
Performance over Time of Adhesive Systems for Bonding Ceramic Tiles – A Detailed Case Study
Authors: de Freitas V.P. , Corvacho H. , Quintela M. , Delgado João M.P.Q.
Published: December 2014

An efficient adhesive bonding of exterior ceramic tiles applied on façades is an obvious important factor to ensure the safety and the durability of the façade. The failure of adhesive bonding is a common issue with relevant technical and economic consequences.The aim of this work is to present an evaluation of the performance overtime of adhesives systems in bonded ceramic tiles on façades, based on extensive experimental research works carried out at the Laboratory of Building Physics (LFC).A detailed case study is presented which evaluate the performance of adhesives systems to be used on the façades of a building located near the sea. For this purpose, accelerated ageing tests are performed following two different ageing procedures, allowing the comparison of the performance over time of the systems under analysis).
Flow Past a Sphere Buried in a Porous Media: Concentration Boundary Layer Thickness
Authors: Delgado João M.P.Q. , Vázquez da Silva M.
Published: December 2014

In this work, consideration is given to the problem of dissolution of a buried solid sphere in the liquid flowing uniformly through the packed bed around it. The differential equations describing fluid flow and mass transfer by advection and diffusion in the interstices of the bed are presented and the method for obtaining their numerical solution is indicated.From the surface concentration fields, given by the numerical solution, the concentration boundary layer thickness as a function of the relevant parameters were undertaken. Mathematical expressions that relate the dependence with the Peclet number and d/d1 ratio of an immersed active sphere are proposed to describe the approximate size of the concentration boundary layer thickness.
Modelling the Pore Level Heat Transfer in Porous Media Using the Immersed Boundary Method
Authors: Malico I. , Ferreira de Sousa P.J.S.A.
Published: December 2014

This work presents the extension of a compact finite difference immersed boundary method for the detailed calculation of fluid flow and heat transfer in porous media. The unsteady incompressible Navier-Stokes and energy conservation equations are solved with fourth-order Runge-Kutta temporal discretization and fourth-order compact schemes for spatial discretization, which allows achieving highly accurate calculations. Verification proves that the method is higher than third-order accurate. Three test cases were used for the validation of the method: (i) isothermal flow around a square cylinder in a plane parallel channel, (ii) isothermal flow through an infinite row of square cylinders and iii) flow and heat transfer around a square cylinder in a plane parallel channel. The validation tests establish confidence in the application of the method to porous media. As an example of such an application, direct numerical simulations are conducted for a staggered array of equal size square cylinders. Although the problem is rather complex from the geometrical point of view, a Cartesian grid is employed, with all its advantages. The potential of applying an immersed boundary method to the solution of a multiphase problem with complex internal boundaries is demonstrated.
Moisture Diffusion in Unsaturated Polyester Composites Reinforced with Macambira Natural Fiber: A Finite-Volume Approach
Authors: de Almeida Cruz V.C. , Delgado João M.P.Q. , de Lima Antonio Gilson Barbosa , Silva Nóbrega M.M. , de Carvalho L.H. , Cavalcanti W.S.
Published: December 2014

This paper presents a theoretical and experimental study about water absorption in unsaturated polyester polymer composites reinforced with vegetable fibers, with particular reference to macambira fiber. A mathematical modeling based on the liquid diffusion theory has been proposed and numerical procedures using the finite volume technique are presented and discussed. Results of the water absorption kinetic and moisture content distribution for the polymer composites are shown and analyzed. The knowledge of moisture distribution inside the composite is essential for determination of areas that may show delamination problems (moisture induced degradation) due to the weakness of the fiber-matrix interface and consequently reduction in the mechanical properties of the composites.
Research on Car-Following Model Considering Lateral Offset
Authors: Xu Lun Hui , Hu Sang En , Luo Qiang , Zhang Lai Yu
Published: December 2014

The conventional models of car-following are too idealistic since they did consider that vehicles travel in middle of the lane. In order to depict the real car-following behaviors better, in this paper we present a new car-following model by introducing the minimum safe distance and proposing the concepts of maximum escape speed (MES) after taking into account the leading vehicle position in the road and the impact of the centerline separation between the leading vehicle and the following vehicle on the car-following behavior, extending the car-following model into two-dimensional model. Finally, the numerical simulation analysis was made using the built model by the Matlab simulation platform. It is found that required minimum safety distance of the presented model is less than the previous models required. Meanwhile, the model can describe some macroscopic phenomena in the actual traffic flow and can improve effectively the road capacity and smooth.
Inorganic Pollutants in South Algeria Waters and Treatment Options by Adsorption onto Clay
Authors: Achour Samia , Bouchemal Fattoum , Youcef Leila
Published: December 2014

The chemical quality of several water samples comprised groundwater from various aquifers and water dam, in Biskra area of South Algeria was investigated. Water samples were collected to monitor water chemistry of major ions and minor ions comprising inorganic pollutants such as fluoride, phosphates, nitrates and trace element as cadmium. The results showed a high salinity associated with an excessive hardness. The concentrations of many inorganic compounds are above the permissible limits for standard drinking water in almost water sources. The pollution is mainly attributed to a geological origin and an extensive use of fertilizers. Some water need adequate treatment to overcome inorganic pollution problem for drinking purpose. The adsorption of fluoride, nitrate, phosphate and cadmium ions onto Algerian bentonitic clay was studied in batch system. The results showed that sulphuric acid activated bentonite was more efficient than raw clay for fluoride, nitrate and phosphate removal. The results also revealed that cadmium adsorption was better with raw bentonite. The equilibrium data were confirmed using Langmuir isotherm model.
Strategies for Sustainable Urban Transport: A Case Study of Cotonou, Benin
Authors: Gomina Mama Fousséni , Yang Zhong Zhen , Xia Dan Dong
Published: December 2014

The unrestrained growth in urbanization and motorization generally contributes to an urban land use and transport system that is socially, economically, and environmentally unsustainable. Urban mobility systems are much diversified in developing countries taking into account their components in terms of transport modes and the development path linked to the urban growth. This paper uses Cotonou as a case study, which is the largest urban and economic city of Benin. The paper first reviews literatures on sustainable transport systems to comprehend the concept of sustainable development and transport. Based on the municipal development plan (MDP) adopted by the local authorities, the paper then evaluates the existing transport policies, projects and infrastructure system, to determine if the current paradigm is moving toward or away from sustainable transport. Furthermore, the principles for sustainable urban transport are developed to see what significance municipal transport policies have given to urban transport from a sustainable transport point of view. Finally some strategies are suggested, adoption of which may lead to a sustainable urban development and transport system in the city of Cotonou.Key words: Sustainable development; urbanization; Bus Rapid Transit; socio-economic; land use and urban transport system.
Effect of Nickel: Zinc Ratio in Nickel-Zinc-Ferrite Nanoparticles as Surfactant on Recovery Efficiency in Enhanced Oil Recovery
Authors: Zaid Hasnah Mohd , Wan Azahar W.A. , Soleimani H. , Ahmad Latiff N.R. , Shafie Afza , Lee Kean Chuan , Beh H.G.
Published: December 2014

Integration of nanoparticles in enhanced oil recovery (EOR) has been intensively studied in recent years due to their unique properties owing to the nanoscale dimensions, rendering them to have different properties in comparison with its bulk material. Application of magnetic nanoparticles such as ferrites was able to exploit their rheological properties as a chain-like structure formed due to dipole-dipole alignment with the applied magnetic field. Ferromagnetic nanoparticles had shown an increment in the oil recovery under the irradiation of an EM wave. In this research, the influence of magnetic nanoparticles nickel-zinc-ferrite, Ni1-xZnxFe2O2 in the form of nanofluids on the recovery efficiency in EOR was studied. Nickel-zinc-ferrite magnetic nanoparticles with various values of x were synthesized to observe the effect of nickel to zinc ratio on recovery efficiency. The nanoparticles were characterized using X-ray Diffraction (XRD) and Vibrating Sample Magnetometer (VSM). Coreflooding experiments were conducted where the nanofluids were injected into the compacted sand saturated with crude oil under EM irradiation. The amount of oil recovered from the core was evaluated. VSM tests shows that the sample with x = 0.5 had the highest magnetization of 52.6 emu/g. The nanofluids prepared from the sample also achieved the highest crude oil recovery of 26.07% of the residual oil in place (ROIP).
Preparation of Nanocrystalline Ba-Cu-Si Clathrate Powders by Mechanical Milling Using a Process Control Agent
Authors: Zolriasatein A. , Yan Xin Lin , Rogl Peter , Shokuhfar A. , Paschen S.
Published: December 2014

Nanostructured Ba-Cu-Si clathrate powders were synthesized by mechanical milling using different amounts of process control agent (PCA). We investigated systematically the effects of PCA on the phase constitution and crystallite size of nanopowders using X-ray diffraction (XRD) as well as the particle size and morphology by scanning electron microscopy (SEM). The PCA increases the powder yield by reducing the powder agglomeration. No detectable reaction occurred between the PCA and the clathrate phase, and thus the composition of the clathrate phase is unchanged after milling. Compared to the powders milled without PCA, the crystalline size of powders with PCA is reduced from about 70 to about 50 nm.
Characteristics of Nanostructured Cr75Ni25 Alloy Powders Produced by High-Energy Ball Milling
Authors: Triaa S. , Faghi L. , Otmane F. , Kali-Ali F. , Azzaz M.
Published: December 2014

Nanomaterial Cr75Ni25 alloy with a mean crystallite size of 8.3 nm and microstrain of 1.23% after 48h of milling was synthesized by mechanical alloying using a high energy planetary ball milling. The morphological changes and particles size were investigated by scanning electron microscopy and laser diffraction. Magnetic results were measured by Foucault currants, coercive field and residual magnetisation. Structural change during ball milling was evaluated by X-ray diffraction. It was found that the paramagnetic Cr0.8Ni0.2 phase with bcc structure appears for 12 h of milling.
Pore Size Control of Macro Porous Carbonized Material by Pyrolysis of Resin/Carbon Composite: Synthesis of Na-A Zeolite Membrane
Authors: Aroua S. , Lounis A. , Condom S.
Published: December 2014

the porous carbon solid (mean pore size 0.1μm ; porosity 32%) was prepared by pyrolysis of composite paste of phenolic resin/AC with a mass ratio (1/1) and a mean grain size of AC of 2.28 μm. The porous agent (starch and PVB) is then added to the paste at 5% and 9% respectively to maintain a pore size of 0.1 microns and maximum porosity. A layer of pure zeolite Na-A is deposited on the carbon support after an oxidation by nitric acid and a seeding of the surface with pre-synthesized Na-A zeolite crystals.
Preparation of Samarium Iron Garnet Nanoparticles via Modified Conventional Mixing Oxides Method
Authors: Al Habashi Ramadan , Abbas Zulkifly
Published: December 2014

This work is concerned with the preparation of samarium iron garnet (Sm3Fe5O12) nanoparticles via an improved technique named: Modified Conventional Mixing Oxides (MCMO) method. This material was characterized by XRD, FESEM, EDX and TEM. Metal oxides and ethanol solution were used as raw materials to prepare Sm3Fe5O12 (SmIG) material. Single-phase SmIG nanoparticles with an average particle value of 25 nm and average crystallite size value of 44 nm have been synthesized at 1350 °C via the MCMO method. SmIG powders with grain sizes below 1 μm and high purity have been presented by FESEM and EDX results, respectively. Lattice constant value of 12.535 Å and density value of 6.221 g.cm-3, were calculated for the SmIG sample. The latter has reached around 99% of its theoretical density. The MCMO method appears to be an attractive route due to the enhancement of structural properties of the interested sample with high yield in the nanoscale product as compared to other preparation techniques.
Synthesis and Characterization of Polymer Nanocomposites Containing Fe- 40 at.% Si Powder Particles Prepared by High Energy Ball Mill
Authors: Siahmed F. , Faghi Lotfi
Published: December 2014

Fe‒Si alloys are widely used as transformer magnets and magnetic cores because of their excellent soft magnetic properties. Fe60Si40 powders were milled in a high energy planetary ball mill (Rctsch PM400) under argon atmosphere at different time of milling. The metal powders obtained have an average diameter d50 of 2.5 to 6 um. The introduction of Si into Fe can result in a decrease of magnetic anisotropy (therefore leading to a decrease of coercivity). The nanocomposite magnetic cores were made from the Fe60Si40 powder obtained by high energy ball milling for different milling time. The particles of powder were mixed with unsaturated polyester (UP) to obtain toroidal cores. The polymerization process was made under a magnetic field H-500 Am. and ensured a preferential orientation of powder particles. Influences of the metallic powder fraction on soft magnetic properties as well as thermal increase under isothermal conditions were investigated along with the possibility to control these properties with the size and amount of powder fraction. It was also found that the soft magnetic properties of the polymer composites can be controlled in a wide range and depends on the mass fraction of the metallic powder Fe60Si40 in the composite, on shape and size of the powder particles and their orientation in the composite.
On the Stiffness of Carbon Nanotubes with Spiral Distortion
Authors: Yengejeh Sadegh Imani , Öchsner Andreas
Published: December 2014

Perfect and spiral configurations of carbon nanotubes (CNTs) were modeled by a commercial finite element package and their tensile behavior was studied. Computational tests with cantilevered boundary conditions were performed to evaluate their Young’s modulus. It was concluded that the existence of any imperfection, spiral shape in particular, in the structure of perfect CNTs results in a remarkable reduction in the stiffness. It was also revealed that the Young’s modulus of perfect CNTs decreases by introducing spiral distortion.
A Numerical Evaluation of the Influence of Atomic Modifications on the Elastic and Shear Behavior of Connected Carbon Nanotubes with Parallel Longitudinal Axes
Authors: Yengejeh Sadegh Imani , Kazemi Seyedeh Alieh , Öchsner Andreas
Published: December 2014

This study deals with the investigation of the tensile and shear behavior of connected carbon nanotubes (CNTs) with parallel longitudinal axes by performing several computational tests. In particular, the effect of imperfections on the mechanical properties, i.e. Young’s modulus and shear modulus, of these nanoconfigurations was analyzed. For this purpose, straight hetero-junctions were simulated in their perfect form and different boundary conditions were considered. In the second phase the three most likely atomic defects, i.e. impurities (doping with Si atoms), vacant sites (carbon vacancy) and introduced perturbations of the ideal geometry in different amounts to the perfect models, were simulated. Finally, the mechanical properties of imperfect hetero-junctions were numerically evaluated and compared with the behavior of perfect ones. It was concluded that the existence of any type of imperfections in the structure of connected CNTs leads to a reduction in the Young’s modulus as well as the shear modulus, and as a result, lower stiffness of these straight nanostructures.