Academic Journals

Three-dimensional Si/hard-carbon/graphene network as high-performance anode material for lithium ion batteries

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

The Si/hard-carbon/graphene (Si/HC/G) composite material used as lithium ion battery (LIB) anode was synthesized by emulsion polymerization of the mixture of resorcinol and formaldehyde in the suspension of silicon nanoparticles, followed by loading on the graphene sheets and annealing treatment of 800 °C. The as-prepared three-dimensional Si/HC/G composite is composed of the Si/HC microspheres on the graphene network. In the portion about Si/HC, some of the Si nanoparticles are embedded into the hard carbon, which can provide the great strength alleviating the volume expansion and shrinkage of Si. The graphene portion can connect Si/HC microspheres preventing the electrode cracks and can provide the pathway to improve the transport of electrons and diffusion of lithium ions. Hence, the Si/HC/G composite could not only avoid the pulverization of the Si-based material but also enhance the electronic conductivity, displaying excellent electrochemical performances. Compared with the HC and Si/HC samples, the Si/HC/G composite possesses the specific charge capacity of 514.8 mA h g−1 at the high current density of 2 A g−1 and has the high charge capacity of 818 mA h g−1 at the current density of 100 mA g−1 after 100 charge and discharge cycles. Resultantly, the Si/HC/G composite shows great potential for the application of lithium ion battery anode material in the future.

Categories: Academic Journals

Effect of mechanical depoling on piezoelectric properties of Na 0.5 Bi 0.5 TiO 3 – x BaTiO 3 in the morphotropic phase boundary region

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

The effect of mechanical stress on the direct piezoelectric properties of pre-poled (1 − x)(Na0.5Bi0.5)TiO3–xBaTiO3 (NBT–xBT) in the range 4% ≤ x ≤ 13% was studied in situ using a mechanical load frame. Prior to mechanical loading, compositions near the morphotropic phase boundary (MPB, x = 6–7% BT) exhibited enhanced ferroelectric and piezoelectric properties compared to compositions further from the MPB. Specifically, the lowest ferroelectric coercive field and highest piezoelectric coefficient within this composition range occur at x = 7% BT. During mechanical compression, the MPB compositions exhibited the lowest depoling stress. The results demonstrate that, while favorable piezoelectric and ferroelectric properties can be obtained at compositions near the MPB, these compositions are also the most susceptible to the effects of mechanical depoling. Ferroelastic domain wall motion is suggested as the primary factor that may be responsible for these behaviors.

Categories: Academic Journals

Optimal sidewall functionalization for the growth of ultrathin TiO 2 nanotubes via atomic layer deposition

The Behavior Analyst - Thu, 02/01/2018 - 00:00
Abstract

One of the most suitable approaches for the production of inorganic nanotubes is by means of carbon nanotube (CNT) templates coated by atomic layer deposition (ALD). This approach is attractive because it has the potential of controlling the wall thickness down to the Angstroms level. However, it is a recognized fact that the chemistry of the substrate surface can delay the full coverage at the initial stages of the ALD coating process, mainly due to nucleation issues. This is an important issue that might restrict laying down homogeneous coatings within the ultrathin range, which is the foundation for producing self-supported inorganic nanotubes. Here, we explore the early stage of the TiO2 nucleation on CNT templates systematically functionalized with different chemical groups (COOH, OH) or N-doped. The effects of the functionalization on the nucleation process from tetrakis (dimethylamino) titanium and water were meticulously studied by means of transmission electron microscopy. Observations revealed grain-like growth of TiO2 over pristine, purified and –OH-functionalized CNTs. In contrast, COOH functionalization yielded good conformality, which was improved on N-doped CNTs. Results were confirmed by X-rays photoelectron spectroscopy analysis. We recommend either COOH or N-doped CNTs for the production of ultrathin TiO2 nanotubes.

Categories: Academic Journals

Helical gold nanotube film as stretchable micro/nanoscale strain sensor

The Behavior Analyst - Thu, 02/01/2018 - 00:00
Abstract

A micro/nanoscale strain sensor based on helical gold nanotube films (GNTFs) is proposed, which is prepared by magnetron sputtering using carbon nanocoils (CNCs) as templates. The gauge factor of the sensor reaches 5, while the stretch of it can achieve more than 10% owing to the helical geometries. The resistance increase of GNTFs with temperature decreasing from 300 to 4 K indicates a thermal activation tunneling model for electron transport. With thicknesses increasing from 16 to 32 nm, the GNTFs show a structural transition from discontinuous to quasi-continuous film. In this transition region, the conductive path of GNTFs increases rapidly, resulting in a rapid resistance decrease of CNC–GNTF composite structure. When a helical GNTF is stretched, the resistance is increased. The helical GNTFs in the transition region exhibit the highest response sensitivity, which owes to the special torsion-dominated strains of this helical structure to some extent. The unique helical morphology gives the sensor great stretchability and special electrical response. Choosing appropriate CNCs and GNTFs with suitable thickness, the helical GNTFs can be used as micro/nanostretchable strain sensors, stretchable electrodes or connects, resonators in micro/nanoelectromechanical system.

Categories: Academic Journals

A high-performance aromatic co-polyimide fiber: structure and property relationship during gradient thermal annealing

The Behavior Analyst - Thu, 02/01/2018 - 00:00
Abstract

A high-performance aromatic co-polyimide (co-PI) fiber was prepared by thermal treating the polyamic acid (PAA) precursor fiber produced through a wet spinning technique. A gradient thermal treatment protocol, which was selected based on the thermogravimetric analysis of PAA fibers, was employed for achieving the best structure and fiber performance. The structural and morphological variations of fibers at different thermal treatment stages were verified by Fourier transform infrared spectroscopy, sonic orientation detection, wide-angle X-ray diffraction and scanning electronic morphology. Thermal treatment cycloimidizes the PAA precursor into PI fibers with the concomitant development of a laminar orientation structure expanded from outer to inner layers of the fiber. The ordered chain repeat length is calculated to be 1.62 nm in the meridian direction. Mechanical measurements indicate that the synthesized co-PI fiber achieves optimum fracture strength and initial modulus up to 3.56 and 101 GPa, respectively. Thermal characterization results indicate a 5% weight loss temperature under nitrogen up to 591 °C and a glass transition temperature at 340 °C.

Categories: Academic Journals

Broad-spectrum antimicrobial activity of bacterial cellulose silver nanocomposites with sustained release

The Behavior Analyst - Thu, 02/01/2018 - 00:00
Abstract

Bacterial cellulose-based antifouling materials have been produced by incorporation of silver nanoparticles for broad-spectrum antimicrobial activity. Three variations of silver nitrate (AgNO3) to reducing agent concentrations have been tried to vary the silver nanoparticle dimension. The formation of silver nanoparticles was also evidenced by the X-ray diffraction, and the crystallite size was found to decrease with increase in NaBH4 concentration. AgBC composites having < 2% (W/W) of silver exhibited 99.9% antimicrobial activity which was sustained up to 72 h against spoiled food derived mixed microbial culture. On the other hand, only 90% activity was observed with colloidal AgNPs due to aggregate formation. Composites displayed superior antimicrobial activity than colloid with equivalent amount of silver. Food stuff was protected from microbial spoilage for 30 days when stored in AgBC nanocomposites, whereas spoilage was noticed within 15 days for food stuff stored in regular polythene bag. Therefore, the AgBC composite having < 2% silver can be used as a lining of regular food packaging material to extend shelf life till 30 days. Toxicity due to high amount of silver can be prevented with these composites and can be safely used in healthcare applications such as food packaging, wound dressing, hospital bed lining and surgical apparels.

Categories: Academic Journals

Synthesis of green phosphors from highly active amorphous silica derived from rice husks

The Behavior Analyst - Thu, 02/01/2018 - 00:00
Abstract

In this work, high purity amorphous silica derived from rice husk (RH) biomass was used to prepare green phosphor (Zn2SiO4:Mn2+). Based on the solid phase reaction under high temperature, the optimum doping concentration and reaction temperature were identified. The overall performance in terms of photoluminescence intensity and quantum yield of the RH-derived phosphor was superior to the one derived from commercial silica and close to the one made from silicic acid. The results showed that the phosphor derived from RH silica could serve as an alternative to commercial phosphor because of its decent properties and inexpensive green resource.

Categories: Academic Journals

Electric properties of MnZn ferrite/polyaniline composites: the implication of polyaniline morphology

The Behavior Analyst - Thu, 02/01/2018 - 00:00
Abstract

(Di)electric properties of MnZn ferrite particles coated by conductive (emeraldine salt) and non-conductive (emeraldine base) forms of PANi were measured and discussed in relation to properties of individual components of such composite. The electric response in a wide frequency (0.1 Hz–10 MHz) and temperature (−150 to 100 °C) range was determined. Recorded relaxation processes were identified as a result of hopping charge carriers, which either only polarize or give rise to DC conductivity. Temperature dependence of conductivity modelled by variable range hopping model indicated different system dimensionality: 3D in PANi bulk and 1D in PANi film, that is result of PANi morphology variation. AC conductivity frequency spectra were well approximated by power law model, and temperature evolution of its exponent was related to the type of charge involved in the charge transport. Altogether, the overlayer of conductive PANi increases by two orders of magnitude the electrical conductivity of ferrite/PANi composite compared to pristine ferrite, whereas non-conductive PANi reduced it by three orders of magnitude. Therefore, the electrical properties of ferrite/PANi composites are determined by electrical properties of PANi, which in turn depend upon mesoscale charge transport in PANi.

Categories: Academic Journals

Three-dimensional Si/hard-carbon/graphene network as high-performance anode material for lithium ion batteries

The Behavior Analyst - Thu, 02/01/2018 - 00:00
Abstract

The Si/hard-carbon/graphene (Si/HC/G) composite material used as lithium ion battery (LIB) anode was synthesized by emulsion polymerization of the mixture of resorcinol and formaldehyde in the suspension of silicon nanoparticles, followed by loading on the graphene sheets and annealing treatment of 800 °C. The as-prepared three-dimensional Si/HC/G composite is composed of the Si/HC microspheres on the graphene network. In the portion about Si/HC, some of the Si nanoparticles are embedded into the hard carbon, which can provide the great strength alleviating the volume expansion and shrinkage of Si. The graphene portion can connect Si/HC microspheres preventing the electrode cracks and can provide the pathway to improve the transport of electrons and diffusion of lithium ions. Hence, the Si/HC/G composite could not only avoid the pulverization of the Si-based material but also enhance the electronic conductivity, displaying excellent electrochemical performances. Compared with the HC and Si/HC samples, the Si/HC/G composite possesses the specific charge capacity of 514.8 mA h g−1 at the high current density of 2 A g−1 and has the high charge capacity of 818 mA h g−1 at the current density of 100 mA g−1 after 100 charge and discharge cycles. Resultantly, the Si/HC/G composite shows great potential for the application of lithium ion battery anode material in the future.

Categories: Academic Journals

Effect of mechanical depoling on piezoelectric properties of Na 0.5 Bi 0.5 TiO 3 – x BaTiO 3 in the morphotropic phase boundary region

The Behavior Analyst - Thu, 02/01/2018 - 00:00
Abstract

The effect of mechanical stress on the direct piezoelectric properties of pre-poled (1 − x)(Na0.5Bi0.5)TiO3–xBaTiO3 (NBT–xBT) in the range 4% ≤ x ≤ 13% was studied in situ using a mechanical load frame. Prior to mechanical loading, compositions near the morphotropic phase boundary (MPB, x = 6–7% BT) exhibited enhanced ferroelectric and piezoelectric properties compared to compositions further from the MPB. Specifically, the lowest ferroelectric coercive field and highest piezoelectric coefficient within this composition range occur at x = 7% BT. During mechanical compression, the MPB compositions exhibited the lowest depoling stress. The results demonstrate that, while favorable piezoelectric and ferroelectric properties can be obtained at compositions near the MPB, these compositions are also the most susceptible to the effects of mechanical depoling. Ferroelastic domain wall motion is suggested as the primary factor that may be responsible for these behaviors.

Categories: Academic Journals

Dynamics characteristics analysis and control of FWID EV

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

Compared with internal combustion engine (ICE) vehicles, four-wheel-independently-drive electric vehicles (FWID EV) have significant advantages, such as more controlled degree of freedom (DOF), higher energy efficiency and faster torque response of an electric motor. The influence of these advantages and other characteristics on vehicle dynamics control need to be evaluated in detail. This paper firstly analyzed the dynamics characteristics of FWID EV, including the feasible region of vehicle global force, the improvement of powertrain energy efficiency and the time-delays of electric motor torque in the direct yaw moment feedback control system. In this way, the influence of electric motor output power limit, road friction coefficient and the wheel torque response on the stability control, as well as the impact of motor idle loss on the torque distribution method were illustrated clearly. Then a vehicle dynamics control method based on the vehicle stability state was proposed. In normal driving condition, the powertrain energy efficiency can be improved by torque distribution between front and rear wheels. In extreme driving condition, the electric motors combined with the electro-hydraulic braking system were employed as actuators for direct yaw moment control. Simulation results show that dynamics control which take full advantages of the more controlled freedom and the motor torque response characteristics improve the vehicle stability better than the control based on the hydraulic braking system of conventional vehicle. Furthermore, some road tests in a real vehicle were conducted to evaluate the performance of proposed control method.

Categories: Academic Journals

Development of a self-driving car that can handle the adverse weather

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

Lane and road recognition are essential for self-driving where GPS solution is inaccurate due to the signal block or multipath in an urban environment. Vision based lane or road recognition algorithms have been studied extensively, but they are not robust to changes in weather or illumination due to the characteristic of the sensor. Lidar is a sensor for measuring distance, but it also contains intensity information. The road mark on the road is made to look good with headlight at night by using a special paint with good reflection on the light. With this feature, road marking can be detected with lidar even in the case of changes in illumination due to the rain or shadow. In this paper, we propose equipping autonomous cars with sensor fusion algorithms intended to operate in a different weather conditions. The proposed algorithm was applied to the self-driving car EureCar (KAIST) in order to test its feasibility for real-time use.

Categories: Academic Journals

Schlieren, Shadowgraph, Mie-scattering visualization of diesel and gasoline sprays in high pressure/high temperature chamber under GDCI engine low load condition

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

Three visualization methods, Schlieren, Shadowgraph, and Mie-scattering, were applied to compare diesel and gasoline spray structures in a constant volume chamber. Fuels were injected into a high pressure/high temperature chamber under the same in-cylinder pressure and temperature conditions of low load in a GDCI (gasoline direct injection compression ignition) engine. Two injection pressures (40 MPa and 80 MPa), two ambient pressures (4.2 MPa and 1.7 MPa), and two ambient temperatures (908 K and 677 K) were use. The images from the different methods were overlapped to show liquid and vapor phases more clearly. Vapor developments of the two fuels were similar; however, different liquid developments were seen. At the same injection pressure and ambient temperature, gasoline liquid propagated more quickly and disappeared more rapidly than diesel liquid phase. At the low ambient temperature and pressure condition, gasoline and diesel sprays with higher injection pressures showed longer liquid lengths due to higher spray momentum. At the higher ambient temperature condition, the gasoline liquid length was shorter for the higher injection pressure. Higher volatility of gasoline is the main reason for this shorter liquid length under higher injection pressure and higher ambient temperature conditions. For a design of GDCI engine, it is necessary to understand the higher volatility of gasoline.

Categories: Academic Journals

Influence of the geometric parameters of the vehicle frontal profile on the pedestrian’s head accelerations in case of accidents

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

The goal of this paper is to determine how the geometry of the vehicle’s frontal profile is influencing the pedestrian’s head accelerations (linear and angular) in car-to-pedestrian accidents. In order to achieve this goal, a virtual multibody dummy of the pedestrian was developed and multiple simulations of accidents were performed using vehicles with different frontal profile geometry, from different classes. The type of accidents considered is characteristic for urban areas and occur at relatively low speed (around 30 km/h) when an adult pedestrian is struck from the rear and the head acceleration variation are the measurement of the accident severity. In the accident simulation 3D meshes were applied on the geometry of the vehicles, in order to define the contact surface with the virtual dummy, similar with real vehicles. The validation of the virtual pedestrian dummy was made by performing two crash-tests with a real dummy, using the same conditions as in the simulations. The measured accelerations in the tests were the linear and angular accelerations of the head during the impact, and these were compared with the ones from the simulations. After validating the virtual model of the car-to-pedestrian accident, we were able to perform multiple simulations with different vehicle shapes. These simulations are revealing how the geometric parameters of the vehicle’s frontal profile are influencing the head acceleration. This paper highlights the main geometric parameters of the frontal profile design that influence the head injury severity and the way that the vehicles can be improved by modifying these parameters. The paper presents an approach to determine the “friendliness” of the vehicle’s frontal profile in the car-to-pedestrian collision.

Categories: Academic Journals

Belief and fuzzy theories for driving behavior assessment in case of accident scenarios

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

The estimation of the overspeed risk before the accident is among the main goals of this paper. The proposed method uses the Energy Equivalent Speed (EES) to assess the severity of an eventual accident. However, the driver behavior evaluation should take into account the parameters related to the Driver, the Vehicle and the Environment (DVE) system. For this purpose, this paper considers a two-level strategy to predict the global risk of an event using the Dempster-Shafer Theory (DST) and the Fuzzy Theory (FT). This paper presents two methods to develop the Expert Model-based Basic Probability Assignment (EM based BPA), which is the most important task in the DST. The first one is based on the accident statistics and the second method deals with the relationship between the Fuzzy and Belief measurements. The experimental data is collected by one driver using our test vehicle and a Micro-intelligent Black Box (Micro-iBB) to collect the driving data. The sensitivity of the developed models is analysed. Our main evaluation concerns the Usage Based Insurance (UBI) applications based on the driving behavior. So, the obtained masses over the defined referential subsets in the DST are used as a score to compute the driver’s insurance premium.

Categories: Academic Journals

Development of twin-chamber on-wheel resonator for tire cavity noise

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

Tire cavity noise is a noise which produces reverberations. Given the ringing in the ears that it causes vehicle occupants, it has long been one of the main road noise issues. For the countermeasure against tire cavity noise, since drastic solution is still more difficult for the downstream measure against a body system with the increase of big weight, its device in the tire cavity of the countermeasure against the origin is the most effective for a light weight and drastic solution. Some reduction devices of tire cavity noise have come to be commercialized in recent years. As a commercialization example, what equipped the tire inside surface with the noise absorbing material, and the thing which equipped roadwheel with the resonator are developed. However, application of these devices is limited to some of tires and high-class vehicle types from cost restrictions, and at present, it does not result in technical generalization and has not diffused through it so much. Since the new structure which reduces weight and cost by 50 % or more was suggested towards generalization of the Helmholtz resonator technology which is a flexible device which can equip roadwheel and does not limit a tire brand and commercial production was realized, this paper introduces that theoretical background and realization structure. And this device has been successfully applied to mass-production models on the market.

Categories: Academic Journals

Model-based automatic test case generation for automotive embedded software testing

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

We propose a method to automatically generate software and hardware test cases from a UML model developed through a model-based development process. Where languages such as source-code languages are used within the model, input and expected values for each test case are generated using a custom parser. As a next step, unit test cases are combined to generate integration test cases using a bottom-up approach. Then these cases are converted into hardware test cases for approval testing of embedded systems, using XQuery and hardware mapping tables. We demonstrate this process by applying it to the power window switch module of a Hyundai Santa Fe vehicle. Our approach provides an automatic testing procedure for embedded systems developed by model-based methods, and generates test cases efficiently using a recombination of signals. In conclusion, our proposed method could help reduce the resources needed for test case generation from software to hardware.

Categories: Academic Journals

Tire wear estimation based on nonlinear lateral dynamic of multi-axle steering vehicle

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

This paper presents a novel nonlinear dynamic model of a multi-axle steering vehicle to estimate the lateral wear amount of tires. Firstly, a 3DOF nonlinear vehicle dynamic model is developed, including dynamic models of the hydropneumatic suspension, tire, steering system and toe angle. The tire lateral wear model is then built and integrated into the developed vehicle model. Based on the comparison of experimental and simulation results, the nonlinear model is proved to be better than a linear model for the tire wear calculation. In addition, the effects of different initial toe angles on tire wear are analyzed. As simulation results shown, the impact of the dynamic toe angle on the tire wear is significant. The tire wear amount will be much larger than that caused by normal wear if the initial toe angle increases to 1° - 1.5°. The results also suggest that the proposed nonlinear model is of great importance in the design and optimazation of vehicle parameters in order to reduce the tire wear.

Categories: Academic Journals

Hydraulic control system design for a PHEV considering motor thermal management

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

In this paper, a design method for a PHEV hydraulic control system was proposed considering motor thermal management. Dynamic models of the target PHEV were developed including the hydraulic system, which consists of one mechanical and one electric oil pump. The required motor cooling flow was designed based on the motor temperature, which was obtained from a one-dimensional thermal equivalent circuit model including the heat source and oil spray cooling. Combining the PHEV powertrain model, hydraulic control system model, and the motor thermal model including the cooling system, an integrated simulator was developed for the target PHEV. Using the integrated simulator, the temperatures of MG1 and MG2 were investigated for various motor cooling flow rates when the PHEV underwent a highway driving cycle. The energy consumption of the hydraulic control system was also evaluated. It was found from the simulation results that a hydraulic control system of the target PHEV could be designed that satisfied the required flow for the motor cooling, lubrication and brake control using the design procedure proposed in this study.

Categories: Academic Journals

Flame propagation model for a rotary Atkinson cycle SI engine

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

The rotary Atkinson cycle engine includes two modes of combustion: combustion initiation and propagation in ignition chamber and then flame jet entrainment and propagation in expansion chamber. The turbulent flame propagation model is a predictive model for SI engines which could be developed for this type of combustion for the rotary Atkinson engine similar to the congenital engine with pre-chamber; in split combustion chamber SI engines, small amount of fuel is burned in pre-chamber while the fuel burned in ignition chamber of rotary Atkinson cycle is considerable. In this study a mathematical modeling of spherical flame propagation inside ignition chamber and new combined conical flame and spherical flame propagation model of a new two-stroke Atkinson cycle SI engine will be presented. The mathematical modeling is carried out using two-zone combustion analysis and the model also is validated against experimental tests and compared with previous study using non-predictive Weibe function model.

Categories: Academic Journals

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