Linear variable optical filter-based ultraviolet microspectrometer

An IC-compatible linear variable optical filter (LVOF) for application in the UV spectral range between 310 and 400 nm has been fabricated using resist reflow and an optimized dry-etching. The LVOF is mounted on the top of a commercially available CMOS camera to result in a UV microspectrometer. A special calibration technique has been employed that is based on an initial spectral measurement on a xenon lamp. The image recorded on the camera during calibration is used in a signal processing algorithm to reconstruct the spectrum of the mercury lamp and the calibration data is subsequently used in UV spectral measurements. Experiments on a fabricated LVOF-based microspectrometer with this calibration approach implemented reveal a spectral resolution of 0.5 nm.     

Parameter variations and the effects of hydrogen: An experimental investigation in a lean premixed low swirl combustor

With a global focus on the reduction of fossil fuel consumption and harmful pollutant emissions, new technologies have been raised offering reduced emissions with the combustion of alternative and renewable fuels. Low swirl combustion and the addition of highly reactive fuels into the fuel stream are two methods that have been shown to meet these challenges. In the present study, the thermo-acoustic behavior of a lean premixed low swirl combustor is examined by the variation of several parameters: the equivalence ratio, bulk velocity, chamber pressure, and the addition of hydrogen into the fuel mixture. It is reported that the natural modes of the chamber employed shift upwards for both fuel mixtures examined when increasing the equivalence ratio. As additional heat is dumped into the chamber, the increase in acoustic energy is being pumped through these natural modes. An increase in the bulk velocity is found to have opposite effects on these dominant acoustic modes for the two mixtures investigated. The methane mixture shows negative shifts in frequency when increasing the bulk velocity, whereas the hydrogen-methane mixture displays upward-shifting frequencies. Elevating the chamber pressure results in an increase in the acoustic modes for both mixtures, although the trend is more consistently linear for the hydrogen-methane flames.     

Mechanical Properties of Pumpkin

Mechanical properties of three common varieties of pumpkin were evaluated and statistically compared. Toughness, rupture force, shear strength, and cutting force were determined for Jarrahdale, Jap, and Butternut varieties. The investigation was carried out in three cases of flesh, skin and unpeeled product, ignoring the toughness and rupture force of flesh. Relative contribution of skin to unpeeled case of each property was estimated. Varieties were found statistically alike in rupture force, toughness, and maximum shear strength force of unpeeled cases. Also the skin of three varieties showed similar strength in shear (p>0.05). Jap and Butternut varieties for some other properties showed close values. Maximum shear strength force of flesh, shear strength of unpeeled case, and relative contribution of skin to shear strength of unpeeled case were close (p>0.05) for these varieties. Jarrahdale had no difference in shear strength of flesh with two other varieties. It was also similar (p>0.05) to Jap in relative contribution of skin to shear strength, rupture force, and toughness of unpeeled case.     

Estimative current mode control technique for DC-DC converters operating in discontinuous conduction mode

A new control technique for DC-DC converters is introduced and applied to a boost converter operating in discontinuous conduction mode (DCM). In contrast to conventional control methods, the principal idea of the proposed control scheme is to obtain samples of the required signals and estimate the required switch-on time. The proposed technique is applicable to any converter operating in DCM, including power factor correctors (PFC), however, this letter mainly focuses on boost topology. In this letter, the main mathematical concept of a new control algorithm is introduced, as well as the robustness investigation of the proposed method with simulation and experimental results.     

Novel Switched Reluctance Machine Configuration With Higher Number of Rotor Poles Than Stator Poles: Concept to Implementation

There is a great demand for efficient, quiet, reliable, and cost-effective motor drives for propulsion systems in hybrid and plug-in hybrid electric vehicles. Owing to a rigid structure and the absence of magnetic source on the rotor, a switched reluctance machine (SRM) is inherently robust and cost effective. In spite of these advantages, several challenges in the control of this machine remain an issue, including high levels of torque ripple, acoustic noise, and a relatively low torque density. This paper presents a new family of SRMs which have higher number of rotor poles than stator poles. Using a newly defined pole design formula, several novel combinations of the stator–rotor poles have been proposed. From the simulation and experimental analysis of a prototype 6/10 configuration, it has been observed that this machine produces higher torque per unit volume and comparable torque ripple when compared to a conventional 6/4 SRM with similar number of phases and constraints in volume. The results presented in this paper make this family of machines a strong contender for survivable high-performance applications for automotive propulsion systems. The simulation and experimental results for the prototype 6/10 configuration have been presented and compared to a conventional 6/4 design for verification.      

Application of neural networks and State-space averaging to DC/DC PWM converters in sliding-mode operation

A novel output feedback neural controller is presented in This work for the implementation of sliding-mode control of dc/dc converters. The controller, which consists of a multilayer perceptron, has been trained in order to be robust for large variations of system parameters and state variables. Fast dynamic behavior is the other main advantage of the proposed controller, which allows realization of all beneficial features of the sliding-mode control technique. Other advantages of the controller are simplicity and low cost. Computer simulations have been carried out to investigate the effectiveness of the controller in voltage regulation for a relatively complex dc/dc converter topology of the Cuk converter. Simulation results confirm the excellent performance of the control system in response to large signal variations. In order to verify the simulation results, a controller prototype has been designed and built using analog components. The controller is applied to regulate the output voltage of the Cuk converter. Experimental results confirm the analytical and simulation achievements.     

Modeling and Simulation of Various Hybrid-Electric Configurations of the High-Mobility Multipurpose Wheeled Vehicle (HMMWV)

Although hybrid-electric vehicles have been studied mainly with the aim of increasing fuel economy, little has been done in order to improve both fuel economy and performance. However, vehicular-dynamic-performance characteristics such as acceleration and climbing ability are of prime importance in military vehicles such as the high-mobility multipurpose wheeled vehicle (HMMWV). This paper concentrates on the models that describe hybridized HMMWV vehicles and the simulation results of those models. Parallel and series configurations have been modeled using the advanced-vehicle-simulator software developed by the National Renewable Energy Laboratory. Both a retrofit approach and a constant-power approach have been tested, and the results are compared to the conventional model results. In addition, the effects of using smaller engines than the existing ones in hybrid HMMWV drive trains have been studied, and the results are compared to the data collected from an actual implementation of such a vehicle. Moreover, the integrated-starter/alternator (ISA) configuration has been considered, and the results were encouraging     

Modeling and Simulation of Electric and Hybrid Vehicles

This paper discusses the need for modeling and simulation of electric and hybrid vehicles. Different modeling methods such as physics-based Resistive Companion Form technique and Bond Graph method are presented with powertrain component and system modeling examples. The modeling and simulation capabilities of existing tools such as Powertrain System Analysis Toolkit (PSAT), ADvanced VehIcle SimulatOR (ADVISOR), PSIM, and Virtual Test Bed are demonstrated through application examples. Since power electronics is indispensable in hybrid vehicles, the issue of numerical oscillations in dynamic simulations involving power electronics is briefly addressed     

Flame structure changes resulting from hydrogen-enrichment and pressurization for low-swirl premixed methane–air flames

With the current focus on alternate and renewable fuels, fuel flexibility has become a driving factor in the design of new turbines. Flame stability is heavily impacted by the presence of hydrogen in the fuel stream (as is common in many alternative fuels). This study examines how the flame dynamics change in response to the systematic addition of hydrogen in a low-swirl lean premixed methane–air burner. Stability maps for these test cases show that adding hydrogen broadens the blow-off limits, with 20% hydrogen resulting in a 7% change while 40% hydrogen results in a 35% larger stable region. The most dramatic manifestation of hydrogen addition is the greatly decreased radius of curvature of the local flame surface, which is visible from the increased wrinkling of the flame front. Increases in both pressure and hydrogen enrichment result in higher means and variances of flame front curvatures. The flame surface density is in agreement with the aforementioned flame front curvature PDFs in that increasing the pressure and hydrogen concentration leads to an increase in the maximum flame surface density.     

Influence of mechanical activation and thermal treatment time on nanoparticle forsterite formation mechanism

This paper reports the successful synthesis and formation of nanoparticle forsterite powder by mechanical activation and its subsequent annealing. Talc and magnesium carbonate were used as basic starting reactants. Simultaneous thermal analysis (STA), X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DLS), atomic absorption spectrometry (AAS) and Fourier transform infrared spectroscopy (FT-IR) techniques were utilized to characterize the as-milled and annealed samples. The results showed that forsterite was not produced directly and that the formation of enstatite was unavoidable during the synthesis of forsterite. The nanoparticle forsterite powder obtained had a crystallite size of 30 nm and mean particle size of 135 nm after 10 h milling and subsequent annealing at 1000 °C for 10 min.