Ionomers: The sodium salt of poly(ethylene-co-methacrylic acid)

A chemical method and an improved absorbance ratio method are presented to determine the degree of neutralization of poly(ethylene-co-methacrylic acid). Compared to the chemical method, the absorbance ratio method is simple and fast. It can be used also to determine the degree of neutralization when the chemical method is not suited to the system. By means of this absorbance ratio method, the influences of various reaction conditions on the rates of neutralization were observed. In the neutral system at the optimal water content a maximal rate of neutralization is obtained. The rate of neutralization is increased by increasing the temperature or the concentration of metal hydroxide or by decreasing the concentration of the copolymer.     

Correction to `surface snow properties effects on millimeter-wavebackscatter' (May 1988 300-306)

In the above mentioned paper (ibid., vol.26, no.3, May 1988) the exponential coefficients of percent liquid water content V_W in Table II are too large in magnitude by a factor of 10 (i.e. -0.990 should be -0.0990, etc.)     

On Administering Questionnaires in Organizational Settings

The administration of a questionnaire is much more difficult than implied in the phrase noted earlier, "The questionnaire was administered to all members of the system on system time." Every person who has used the technique more than once or twice is, or should be aware of many of the things mentioned above. Somehow their hard won inspirations are not passed on to others and the uninitiated wander in and come away bloodied if not bowed.     

Effects of cooling rate on the microstructure and tensile behavior of a Sn-3.5wt.%Ag solder

The tensile behavior and microstructure of bulk, Sn-3.5Ag solders as a function of cooling rate were studied. Cooling rate is an important processing parameter that affects the microstructure of the solder and, therefore, significantly influences mechanical behavior. Controlled cooling rates were obtained by cooling specimens in different media: water, air, and furnace. Cooling rate significantly affected secondary dendrite-arm size and spacing of the Sn-rich phase, as well as the aspect ratio of Ag₃Sn. The Sn-rich dendrite-arm size and spacing were smaller for water-cooled specimens than for air-cooled specimens. Furnace cooling yielded a nearly eutectic microstructure because the cooling rate approached equilibrium cooling. The morphology of Ag₃Sn also changed from spherical, at a fast cooling rate, to a needlelike morphology for slower cooling. The changes in the microstructure induced by the cooling rate significantly affected the mechanical behavior of the solder. Yield strength was found to increase with increasing cooling rate, although ultimate tensile strength and strain-to-failure seemed unaffected by cooling rate. Cooling rate did not seem to affect Young’s modulus, although a clear coorelation between modulus and porosity was obtained. The mechanical behavior was correlated with the observed microstructure, and fractographic analysis was employed to elucidate the underlying damage mechanisms.     

An optimal vector-network-analyzer calibration algorithm

We present an iterative algorithm for calibrating vector network analyzers based on orthogonal distance regression. The algorithm features a robust, yet efficient, search algorithm, an error analysis that includes both random and systematic errors, a full covariance matrix relating calibration and measurement errors, 95% coverage factors, and an easy-to-use user interface that supports a wide variety of calibration standards. We also discuss evidence that the algorithm outperforms the MultiCal software package in the presence of measurement errors and accurately estimates the uncertainty of its results.     

Repeatability of treadmill exercise ejection fraction and wall motion using technetium 99m-labeled sestamibi first-pass radionuclide ventriculography

Bacterial antibodies were studied in acute, intermediate and convalescent phase sera (mean duration from first to last sample 36 days) of 121 children hospitalized for acute lower respiratory tract infection. Antibody responses were observed in 45% of all cases and in 29% of the 21 children < 1 year old. A total of 15 responses to Streptococcus pneumoniae (pneumolysin), 20 to Haemophilus influenzae, 9 to Moraxella catarrhalis, 3 to chlamydiae and 8 to Mycoplasma pneumoniae were found. In 79 patients with 4 consecutive samples available, 52% of the 31 responses were measurable within 5 days from admission. Overall the responses were not associated with upper respiratory tract bacterial findings or acute otitis media. Significantly more responses were found in the 121 children with acute lower respiratory tract infection than in healthy controls (P < 0.007). We conclude that bacterial antibody assays provide a useful tool in the study of the etiology of acute lower respiratory tract infection in young children, even if the interval between paired serum samples is short.     

The machining of sintered bronze

Orthogonal machining experiments have been conducted on specimens of sintered bronze. At low porosities and low depths of cut, a continuous chip is formed as a result of compaction and shear local to the tip of the tool. At higher porosities, and larger depths of cut, discontinuous chips form due to alternate compaction of the chip and brittle fracture. The transition occurs when the depth of cut is about 0.6 times the size of the plastic zone size associated with brittle fracture.     

Cascaded frequency domain bandpass filters for multivernier spectra

Passive sonar processing generally consists of many concurrent verniers on each beam or channel which are very narrow bands centered at widely separated, independent frequencies sparsely placed across the total search band. Each is analyzed by a fast Fourier transform (FFT) with extremely narrow coefficients. A cascaded frequency domain filter structure that provides such verniers with fewer computations than other methods is described     

Microporosity of heat-treated manganese dioxide

A structural and micro-pore analysis of a series of heat treated electrolytic manganese dioxide (EMD) samples has been conducted. In terms of crystal structure, the original EMD with γ-MnO₂ structure (orthorhombic unit cell) was found to progressively convert to β-MnO₂ (tetragonal unit cell) at elevated temperatures. The structural transition was kinetically limited, with the higher temperatures leading to a greater degree of transformation. The orthorhombic γ-MnO₂ unit cell was found to contract along the a and b axes, while along the c axis an expansion was observed only at the highest heat treatment temperatures. These changes occur as a result of manganese ion diffusion leading to the formation of a denser, more defect free material. The porosity of these heat treated EMD samples was also examined by N₂ gas adsorption combined with various interpretive techniques such as the Kelvin equation, MP method, Dubinin–Radushkevich method, Dubinin–Astakhov method and a more modern density functional theory based approach. Despite shortcomings associated with certain techniques, all clearly indicated that the EMD micro-pore volume decreased and the meso- and macro-pore volume increased as the heat treatment temperature was increased. This was justified as a result of manganese ion movement during the structural rearrangement causing the small pores to be progressively sintered shut, while the larger pores were formed as a result of stress-induced cracking in the denser final product.