Analysis and design of broadband U-slot cut rectangular microstrip antennas

Broadband microstrip antenna using variations of U-slot has been widely reported. However, in most of the reported work, an in-depth explanation about the mode introduced by U-slot and procedure to design U-slot cut antennas at any given frequency is not explained. In this paper, first an extensive analysis to study the broadband response in symmetrical and a new configuration of asymmetrical U-slot cut rectangular microstrip antennas is presented. The U-slot tunes higher-order orthogonal mode resonance frequency of the patch with respect to fundamental mode to realise wider bandwidth. Further formulation in resonant length at modified patch modes in symmetrical U-slot cut antenna is proposed. Frequencies calculated using these formulations show closer agreement with simulated and measured results. Using proposed formulations, a procedure to design U-slot cut antenna at different frequencies over 800–4000 MHz range which shows broadband response is explained. Thus, the proposed work gives an insight into the functioning of widely used U-slot cut antennas and the formulations will be helpful for designing at any given frequency.     

Iodine potassium iodide improves the contrast‐to‐noise ratio of micro‐computed tomography images of the human middle ear

High‐resolution imaging of middle‐ear geometry is necessary for finite‐element modeling. Although micro‐computed tomography (microCT) is widely used because of its ability to image bony structures of the middle ear, it is difficult to visualize soft tissues – including the tympanic membrane and the suspensory ligaments/tendons – because of lack of contrast. The objective of this research is to quantitatively evaluate the efficacy of iodine potassium iodide (IKI) solution as a contrast agent. Six human temporal bones were used in this experiment, which were obtained in right‐left pairs, from three cadaveric heads. All bones were fixed using formaldehyde. Three bones (one from each pair) were stained in IKI solution for 2 days, whereas the other three were not stained. Samples were scanned using a microCT system at a resolution of 20 μm. Eight soft tissues in the middle ear were segmented: anterior mallear ligament, incudomallear joint, lateral mallear ligament, posterior incudal ligament, stapedial annular ligament, stapedius muscle, tympanic membrane and tensor tympani muscle. Contrast‐to‐noise ratios (CNRs) of each soft tissue were calculated for each temporal bone. Combined CNRs of the soft tissues in unstained samples were 6.1 ± 3.0, whereas they were 8.1 ± 2.7 in stained samples. Results from Welch's t‐test indicate significant difference between the two groups at a 95% confidence interval. Results for paired t‐tests for each of the individual soft tissues also indicated significant improvement of contrast in all tissues after staining. Relatively large soft tissues in the middle ear such as the tympanic membrane and the tensor tympani muscle were impacted by staining more than smaller tissues such as the stapedial annular ligament. The increase in contrast with IKI solution confirms its potential application in automatic segmentation of the middle‐ear soft tissues.     

SURFACE TENSION-DRIVEN CONVECTION IN A CYLINDRICAL GEOMETRY

Three aspects of surface tension-driven natural convection in a bounded cylindrical geometry are investigated. First, the linear stability of the steady subcritical and supercritical convective solutions near the critical point is examined using a perturbation analysis and the theory of differential operators. Second, the effect of small surface tension gradients on free surface flows in deep fluid layers is studied. It is shown that surface tension effects produce subcritical convective solutions for this buoyancy-dominated flow. Finally, solutions are obtained for finite amplitude surface tension-driven flows in a cylindrical container.     

CONSTRUCTION AND OPERATIONAL EXPERIENCE OF A 6000 m SOLAR POND AT KUTCH, INDIA

A 6000 m² solar pond was constructed at Bhuj in India in the premises of a milk processing dairy plant to supply process heat and demonstrate the technical and economic viability of solar pond technology in the Indian context. An inexpensive lining scheme, consisting of alternating layers of clay and LDPE (low density polyethylene) combination was used for lining the pond. The pond attained a maximum temperature of 99.8°C under stagnation in May 1991 but developed leakage soon after. A failure analysis that was carried out subsequently indicated that the leakage was caused by the combination of high stagnation temperature and large air pockets below the liner. The lining scheme was re-designed and the pond re-established in June 1993. Hot water supply to the dairy started in September 1993 and continued until April 1995. After an interruption of nearly one year, hot water was resumed in August 1996. The total cost of construction of the Bhuj Solar Pond was US$90 000 (1997 prices), including heat exchanger and piping etc., corresponding to a unit cost of US$15 m⁻².     

On postponement strategies for product families with multiple points of differentiation

Several researchers have studied the benefits of product and process design that calls for delaying the differentiation of products. Previous research has focused on products having only one point of differentiation. However, in reality most product families have several points of differentiation. In this paper, we develop two models to study products with more than one point of differentiation. In each model, we examine the benefits of delayed differentiation at each of these points, and derive the necessary conditions when one type of delayed differentiation is more beneficial than the other. Our analysis indicates that demand variabilities, correlations and the relative magnitudes of the lead times play an important role in determining which point of differentiation should be delayed.     

INVESTIGATION INTO THE THEORIES OF DESORPTION ISOTHERMS FOR ROUGH RICE AND PEANUTS

SUMMARY— Several existing mathematical models are investigated with respect to their range of applicability to biological materials. It is found that a logarithmic plot of vapor pressure of water in the material vs. vapor pressure of pure water can best describe the sorption phenomenon. The general form of the equation is: In P = f₁ (W) In P_s+ f₂ (W). The functions f₁ (W) and f₂ (W) may differ significantly from material to material. The method of determining these functional relationships is described in detail for rough rice and peanuts. The comparison of experimental and computed values for peanuts shows that this method can predict the required sorption isotherm data within 2% deviation from the experimental values.     

A method for unbalanced transportation problems in fuzzy environment

In this paper, we consider the fully fuzzy unbalanced transportation problem in which the total availability/production is more than the total demand and propose a method to solve it. Such problems are usually solved by adding a dummy destination. Since the dummy destination has no existence in reality, the excess availability is not transported at all and is held back at one or more origins. The method proposed in this paper gives the additional information that to which of the destination(s) the excess availability be transported for future demand at minimum cost. The advantage of the proposed method over the existing method is that the fuzzy optimal solution obtained does not involve the dummy destination. The method has been illustrated with the help of an example.     

Ultraviolet sensing properties of polyvinyl alcohol-coated aluminium-doped zinc oxide nanorods

Undoped and aluminium (Al)-doped zinc oxide (ZnO) nanorods have been synthesized by electrochemical route. The synthesized materials have been characterized by X-ray diffraction, UV–visible spectrometer and scanning electron microscope. The Al-doped ZnO nanorods have been coated with polyvinyl alcohol. Current–voltage characteristics have been investigated in dark and under UV-light illumination. Aluminium doping in ZnO increase its electrical conductivity and further polyvinyl alcohol coating on Al-doped ZnO increase UV sensitivity of the material. Response and recovery time of Al-doped ZnO and PVA-coated Al-doped ZnO nanorods have been recorded. PVA-coated Al-doped ZnO nanorods shows very fast response and recovery time of 10 s in comparison to uncoated ZnO (20 min) nanorods.     

Optimization of processing parameters in induction hardening using response surface methodology

In this paper, an effective procedure of response surface methodology (RSM) has been utilized for finding the optimal values of process parameters while induction hardening of AISI 1040 under two different conditions of the material i.e., rolled and normalized. Various process parameters, such as feed rate (speed at which the induction coil moves, which is measured in mm/sec), current, dwell time (time after which heat intensity starts to heat work piece in seconds) and gap between the work piece and induction coil have been explored by experiments. Hardness at two different conditions has been considered as performance characteristic. The experiment plan was based on rotatable, central composite design (CCD). The experimental results showed that the proposed mathematical models suggested could describe the performance indicators within the limits of the factors being investigated. The obtained optimal process parameters have been predicted and verified by confirmation experiments. Microstructure and SEM (scanning electron microscope) analyses were also done for justification of the work.     

A Study of Solvent Extraction of Lipids from Whole Peanut Kernels Using All-Purpose Automatic Solvent Extractor

Extraction of lipids from whole peanut kernels can be accomplished much faster in an automatic solvent extractor with a lower solvent: seed ratio than by immersion or in a Soxhlet extractor. A possible explanation of the function of moisture in the extraction of lipids from the whole peanut kernels has been put forward. This mode of extraction is expected to produce economically fat-lean kernels, while oil is obtained as a co-product.