HYDROSOL DEPOSITION IN GRANULAR BEDS—AN EXPERIMENTAL STUDY

Experiments were conducted to study the deposition of particles from suspensions flowing through packed beds. The experimental data obtained include both the initial and transient state particle collection. The initial collection efficiencies were compared with predictions based on existing theories. Agreement between experiments and predictions was generally good except for the case when significant repulsive force barrier exists between filter grains and particles. The transient state data obtained under the presence of unfavorable surface interactions show a steady decline in collection efficiency with time, which cannot be reconciled with any existing theories.     

Recurrent bilateral renal calculi in a tetraplegic patient

An 18-year-old male developed C-5 complete tetraplegia following a motor-cycle accident in May 1975. The neuropathic bladder was managed by an indwelling urethral catheter. He developed recurrent episodes of urinary infection with Proteus species. In September 1975, an X-ray of the abdomen revealed small calculi in both the kidneys. In July 1976, he underwent transurethral resection of the bladder neck and division of the external urethral sphincter; subsequently, he was put on a penile sheath drainage. He continued to suffer from repeated episodes of urinary tract infection with Proteus, Providencia, and Pseudomonas species, and he was treated with antibiotics. In 1980, intravenous urography (IVU) showed two large stones in the left kidney with marked caliectasis. The IVU performed in 1984 showed an increase in the size of the calculi in the left kidney which was grossly hydronephrotic. There were clusters of small calculi in the right kidney. The left renal calculi were treated by percutaneous lithotripsy in two sessions. In 1988, an X-ray of the abdomen revealed staghorn calculus in the right kidney and recurrence of stones in the left kidney. The staghorn calculus in the right kidney was treated by percutaneous nephrostolithotomy in two sessions. In 1991, he was admitted with acute urinary infection. IVU showed a stone in the pelviureteric junction with no excretion of contrast in the left kidney. Percutaneous nephrostomy drainage was established followed by left percutaneous nephrostolithotomy. In 1992, he was found to retain large amount of urine in the bladder; subsequently, his mother was taught to perform regular intermittent catheterisations. In 1995, he was admitted with acute urine infection. Abdominal X-ray revealed recurrence of large stones in both kidneys. With multiple sessions of Extracorporeal Shockwave Lithotripsy (ESWL), about 80% clearance was achieved on the left side. Right staghorn renal stone awaits treatment. This case shows that recurrent urinary infection in spinal cord injury patients is a predisposing factor for renal lithiasis. These patients require annual urological evaluation. Urinary tract calculi, if detected, should be dealt with promptly to prevent renal damage due to urinary obstruction and urosepsis. Renal calculi can be treated effectively and safely by ESWL in spinal cord injury patients, thus avoiding the need for an invasive procedure. It is essential to achieve low-pressure, adequate emptying of the urinary bladder in patients with spinal cord injury in order to prevent recurrent urinary infection and its sequelae. Social issues involved in the care of a tetraplegic patient play a vital role in the implementation of ideal medical treatment and need to be addressed promptly to avoid any compromise in the quality of medical care.     

Linear phase cosine modulated maximally decimated filter banks withperfect reconstruction

We propose a novel way to design maximally decimated FIR cosine modulated filter banks, in which each analysis and synthesis filter has a linear phase. The system can be designed to have either the approximate reconstruction property (pseudo-QMF system) or perfect reconstruction property (PR system). In the PR case, the system is a paraunitary filter bank. As in earlier work on cosine modulated systems, all the analysis filters come from an FIR prototype filter. However, unlike in any of the previous designs, all but two of the analysis filters have a total bandwidth of 2π/M rather than π/M (where 2M is the number of channels in our notation). A simple interpretation is possible in terms of the complex (hypothetical) analytic signal corresponding to each bandpass subband. The coding gain of the new system is comparable with that of a traditional M-channel system (rather than a 2M-channel system). This is primarily because there are typically two bandpass filters with the same passband support. Correspondingly, the cost of the system (in terms of complexity of implementation) is also comparable with that of an M-channel system. We also demonstrate that very good attenuation characteristics can be obtained with the new system     

The digital all-pass filter: a versatile signal processing buildingblock

The properties of digital all-pass filters are reviewed and a broad overview of the diversity of applications in digital filtering is provided. Starting with the definition and basic properties of a scalar all-pass function, a variety of structures satisfying the all-pass property are assembled, with emphasis placed on the concept of structural losslessness. Applications are then outlined in notch filtering, complementary filtering and filter banks, multirate filtering, spectrum and group-delay equalization, and Hilbert transformations. In all cases, the structural losslessness property induces very robust performance in the face of multiplier coefficient quantization. Finally, the state-space manifestations of the all-pass property are explored, and it is shown that many all-pass filter structures are devoid of limit cycle behavior and feature very low roundoff noise gain     

Orthonormal and biorthonormal filter banks as convolvers, andconvolutional coding gain

Convolution theorems for filter bank transformers are introduced. Both uniform and nonuniform decimation ratios are considered, and orthonormal as well as biorthonormal cases are addressed. All the theorems are such that the original convolution reduces to a sum of shorter, decoupled convolutions in the subbands. That is, there is no need to have cross convolution between subbands. For the orthonormal case, expressions for optimal bit allocation and the optimized coding gain are derived. The contribution to coding gain comes partly from the nonuniformity of the signal spectrum and partly from nonuniformity of the filter spectrum. With one of the convolved sequences taken to be the unit pulse function,,e coding gain expressions reduce to those for traditional subband and transform coding. The filter-bank convolver has about the same computational complexity as a traditional convolver, if the analysis bank has small complexity compared to the convolution itself     

Comparison of the optimum base width for ECL propagation delay andmaximum oscillation frequency

The condition for minimum ECL propagation delay time, as the device base width is varied, is obtained in terms of the transistor delay times. This condition is compared to that for optimum maximum oscillation frequency, and it is shown that minimum ECL delay occurs essentially when the base width is chosen to optimize a combination of the “average” and peak maximum oscillation frequencies     

Potentiodynamic polarization analysis of silver-palladium alloys in chloride solutions

A comprehensive anodic potentiodynamic polarization analysis of Ag-Pd binary alloys in chloride solutions has revealed composition dependent active-passive polarization profiles. The results are interpreted in terms of the transition metal properties of Pd and the electron donor acceptor theory of passivation.     

Continuous precipitation in Cu-rich Cu-Ti binary and Cu-Ti-Al ternary alloys

An investigation has been carried out to study precipitation in a Cu-4% Ti binary and a Cu-2.1% Ti-2.4% Al ternary alloys which develop modulated microstructures upon ageing. Precipitate-free zones near the grain boundaries were observed on ageing immediately below a critical temperature representing the transition from the coherent to the incoherent region of the coherent phase diagram. In addition, a pronounced tendency for elastic interaction between the precipitate particles was detected, giving rise to aligned groups of precipitates containing a maximum of eight or nine particles in each group. At least near this critical temperature, decomposition occurs in the metastable region of the coherent phase diagram rather than in the spinodal region. The formation of the modulated structures in these alloys is, therefore, considered to arise not necessarily through spinodal decomposition. Continuous precipitation in a Cu-2.1% Ti-5% Al alloy is shown to result in spherical particles with no alignment. The effect of Al addition on the coherent solvus temperature is discussed in terms of a vacancy solute interaction mechanism.     

Biopreservative technologies of food: an alternative to chemical preservation and recent developments

Food Science and Biotechnology - Despite centuries of developing strategies to prevent food-associated illnesses, food safety remains a significant concern, even with multiple technological...