Correlation between central receiver size and solar field using flat heliostats

In Central Receiver Systems (CRSs), thousands of heliostats track the sunrays and reflect beam radiation on to a receiver surface. The size of the reflected image and the extent of reflection from the heliostats are one of the important criteria that need to be taken into account while designing a receiver, since spillage losses may vary from 2 to 16% of the total losses. The present study aims to determine the size of an external cylindrical receiver, such that the rays reflected from all the heliostats in the field are intercepted. A dimensionless correlation with respect to tower height and receiver size (diameter and height) as a function of heliostat size and its position is discussed in the paper. This correlation could be used as a first-order approximation to estimate the receiver dimensions. When applied to the Ivanpah Solar Electricity Generating Station (ISEGS) plant, the correlation yields satisfactory estimation of receiver dimensions.     

Optimization of Lithium Content and Sintering Aid for Maximized Li+ Conductivity and Density in Ta‐Doped Li7La3Zr2O12

Ta‐doped cubic phase Li₇La₃Zr₂O₁₂ (LLZ) lithium garnet received considerable attention in recent times as prospective electrolyte for all‐solid‐state lithium battery. Although the conductivity has been improved by stabilizing the cubic phase with the Ta⁵⁺ doping for Zr⁴⁺ in LLZ, the density of the pellet was found to be relatively poor with large amount of pores. In addition to the high Li⁺ conductivity, density is also an essential parameter for the successful application of LLZ as solid electrolyte membrane in all‐solid‐state lithium battery. Systematic investigations carried out through this work indicated that the optimal Li concentration of 6.4 (i.e., Li_6.4La₃Zr_1.4Ta_0.6O₁₂) is required to obtain phase pure, relatively dense and high Li⁺ conductive cubic phase in Li_7?xLa₃Zr_2?xTa_xO₁₂ solid solutions. Effort has been also made in this work to enhance the density and Li⁺ conductivity of Li_6.4La₃Zr_1.4Ta_0.6O₁₂ further through the Li₄SiO₄ addition. A maximized room‐temperature (33°C) total (bulk + grain boundary) Li⁺ conductivity of 3.7 × 10^?4 S/cm and maximized relative density of 94% was observed for Li_6.4La₃Zr_1.4Ta_0.6O₁₂ added with 1 wt% of Li₄SiO₄.     

Quantitative Fourier transform infrared analysis for anisidine value and aldehydes in thermally stressed oils

A Fourier transform infrared (FTIR) transmission-based spectroscopic method was investigated for the simultaneous monitoring of aldehyde formation and the determination of anisidine value (AV) in thermally stressed oils. Synthetic calibration standards were prepared by adding known amounts of hexanal,t-2-hexenal andt,t-2,4-decadienal to canola oil (these compounds considered representative of aldehydic compounds formed during oxidation) plus random amounts of other compounds representative of oxidation by-products. The standards were analyzed for their chemical AV. With the partial least squares (PLS) technique, an FTIR spectrometer was calibrated to predict both the concentrations of individual aldehyde types and AV, with the individual aldehyde contributions being related to the chemical AV by multiple linear regression to derive “apparent” AV values. The predictive capability of the PLS calibrations was assessed by analyzing canola oils that were thermally stressed at 120, 155, and 200°C. The apparent AV, predicted for these samples, matched the chemical AV values within ±1.65 AV units. A PLS calibration also was derived by using thermally stressed samples as calibration standards. This approach provided similar predictive accuracy as the use of synthetic calibration standards. As such, quantitative determination of AV by FTIR spectroscopy was shown to be feasible, and the synthetic calibration approach provided additional information on the aldehyde types present in a sample and allowed the use of a simple gravimetric approach for calibrating an FTIR spectrometer. This study provides the basis for the development of a rapid, automated FTIR method for the direct analysis for AV of thermally stressed fats and oils in their neat form without the use of chemical reagents. The implementation of such a method as a quality control tool would eliminate the use and disposal of hazardous solvents and reagents, required by the conventional chemical method, and drastically reduce analysis time (∼2 min/sample). Possible applications include monitoring of the oxidative state of frying oils or evaluation of oxidative stability of biodegradable lubricants.     

Ohmic Tempering of Frozen Potato Puree

Frozen potato puree samples were tempered using an ohmic heating technique. Three salt concentrations (0.50, 0.75, and 1.00 %) and three frequency levels (10, 20, and 30 kHz) were used as experimental variables, and the effects of salt concentration and frequency on ohmic tempering were investigated. Temperature, electrical current, and voltage were measured during the ohmic tempering. Electrical conductivities were evaluated based on the sample geometry and the ohmic heating principle. Increasing the salt concentration and/or frequency increased the electrical conductivity and heating rate, and hence contributed to decreasing the tempering time for the frozen potato puree samples. The tempering time was lowest with the highest salt concentration employed, and longest for the lowest salt concentration and frequency. Temperature differences within the sample during ohmic heating were found to be lowest when employing 0.50 % salt concentration and 10 kHz frequency.     

OSMOTIC DRYING KINETICS OF CYLINDRICAL APPLE SLICES OF DIFFERENT SIZES

The objective of this study was to evaluate the osmotic drying kinetics of cylindrical slices of apples as influenced by particle size at different concentrations of sucrose solutions and different temperatures. Osmotic drying was carried out, with cut apple cylinders of three different sizes (12, 17 and 20mm diameter), all with a length to diameter ratio of 1:1, in a well agitated large tank containing the osmotic solution at the desired temperature. The solution to fruit volume ratio was kept greater than 60. A central composite rotatable design (CCRD) was used with dive levels of sucrose concentrations (34-63°Brix) and five temperatures (34-66°C). Kinetic parameters included weight loss, moisture loss, solids gain, rates of moisture loss and solids gain generally increased with increasing treatment time, temperature and concentration of osmotic solution, and decreased with an increase in sample size. The parameter “osmotic drying time to achieve a given moisture loss” obviously showed the opposite. Composite models were developed to describe the effect of process variables and particle size on the drying behavior of apple slices.     

Object-oriented methodology for intersection simulation model under heterogeneous traffic conditions

In developing countries like India, the traffic on roads is highly heterogeneous in nature, with vehicles of widely varying static and dynamic characteristics. In this type of traffic, vehicles do not follow lane discipline and they move freely over the entire width of roadway based on availability of space. To study this type of complex traffic flow and associated vehicular interactions, simulation is considered as an effective tool. An object-oriented methodology (OOM) for heterogeneous traffic simulation is proposed in this paper with focus on mid-block and intersection flow modeling. The paper presents the basics and advanced features of object-oriented programming (OOP) in detail in the context of traffic flow. The sample C++ code is discussed in detail to demonstrate the implementation of OOP features, such as encapsulation, inheritance and polymorphism. The contribution of this research work is the development of software objects for various components such as vehicle, traffic, link and node. This software can be adopted for heterogeneous traffic simulation programs, in general.     

Effects of fat,casein and lactose on high-pressure destruction of Escherichia coli K12 (ATCC-29055) in milk

High-pressure (HP) destruction of Escherichia coli K12 suspended in commercial pasteurized milk (0, 3.25 and 5% fat), peptone water (0.1%), and phosphate buffer (0.2 mol/l Na₂HPO₄ and 0.2 mol/l NaH₂PO₄) supplemented with different amounts of casein or lactose (1–4%) was investigated. HP treatment resulted in the highest level of E. coli destruction in the buffer (possibly because it contained no nutrients), followed by those in peptone water and least in milk. Therefore, milk and peptone provided some baro-protection to the destruction of E. coli during the HP treatment. Fat content in milk between 0, 3.25 and 5% had no significant (P > 0.05) influence on the HP destruction of E. coli. The supplement of either casein or lactose to milk did not influence the level of HP destruction of E. coli. However, the baro-protection became significant during HP treatment when casein or lactose was added the buffer. The buffer solution supplemented with 1–4% casein showed a baro-protective effect equivalent to that in milk. Lactose supplement to buffer also caused baro-protection, though the effect was relatively less pronounced. However, no significant difference in the baro-protection effect was observed among the buffer samples supplemented with different levels (1, 2 and 4%) of lactose or casein. Therefore the major contributors for baro-protection of E. coli in milk during HP treatment appear to be casein and lactose, rather than the fat content.     

A Vision for Supporting Autonomous Navigation in Urban Environments

The autonomous navigation systems (ANS), such as autonomous ground vehicles (AGVs), unmanned aerial vehicles (UAVs), and unmanned submersible vehicles (USVs), and modern vehicles with actuators, sensors, and computer control perform three basic functions: context gathering using sensors, processing, and action. Most researchers have put all three functions into the ANS or the robot itself to overcome occlusions and handle the environment's dynamics. However, this causes the ANS and robotic systems to be bulky and expensive. It also impedes the introduction of vehicles with ANS in urban environments, where they must coexist with existing cars and highways. The approach presented distributes the context-gathering and processing functions using sensor networks and wireless communications technologies to reduce costs and make ANS widespread. The system uses sensors mounted on moving vehicles and stationary objects such as lampposts, traffic lights, toll plazas, and buildings to gather information at different levels     

A sector element for thin plate flexure

This paper presents a sector shape of an element ideally suited for the analysis of sectorial and annular plates. A conforming function with twenty degrees of freedom is developed in polar co-ordinates to represent the deformation of the element in bending. The finite element method is applied to some plate bending problems to illustrate the power and efficiency of sector elements.