Information management systems for dairy factory laboratories

Dairy laboratories are responsible for measuring the quality of ingredients, intermediate products and finished products. A particular challenge in the food processing sector is that consistently high quality products must be made from raw material which varies widely in composition and to some extent in quality. Consequently, routine milk sampling and analysis form part of the quality control system in any dairy plant. Sampling and data collection begin at the milk collection point on the farm, and so the collection truck must be considered part of the informationlquality control management system. Computerized information management systems relieve the workload on the laboratory manager by assisting with tasks such as organizing the workload; tracking samples; monitoring instruments; acquiring, storing, reporting and analysing test data; and with additional functions such as Good Laboratory Practice and IS0 9000. Of particular significance to laboratories is that computer interfaces and computer technology inside analytical instruments have opened new ways of integrating on-line measurements in the process, and on-line laboratory data. With the increasing rationalization of the dairy industry there are fewer laboratories, and a laboratory often processes samples for several factories, which requires good integration. The number of samples which are submitted is increased and the cost of automation becomes justified ,     

Crystallization of Nuclear Waste Disposal Glass

The rate of bulk crystallization and shear viscosity η of a zinc borosilicate simulated nuclear waste disposal glass (SNWDG) were measured above the glass transition temperature T_g . Using recent theories and experimental data for the temperature dependence of η at < T_g , the crystallization rate below T_g was calculated; well below T_g the SNWDG (and, more generally, any high-silica glass) will not crystallize appreciably over any important time period for radioactive decay of fission products.     

Glass Formation in the Pseudobinary Metallic Selenide Systems MmSen-Ge1.5As0.5Se3

The glass-forming regions were investigated for pseudobinary systems of the composition X M _m Se _n -(1– X )Ge_1.5As_0.5Se₃ (M _m Se _n =PbSe, CdSe, BaSe, ZnSe, or La₂Se₃). Systems containing PbSe, CdSe, and BaSe contain substantial regions of glass formation, and differential scanning calorimetry, electron microscopy, and water corrosion tests were used to characterize these glasses. The glasses were generally phase-separated, and the available data suggest that for PbSe melts the region of liquid-liquid immiscibility spans almost the entire pseudobinary composition range. A few studies of glass formation were conducted for CdSe-M _m Se _n -Ge_1.5As_0.5Se₃ pseudoternary and M _m Se _n -GeSe₂ binary melts.     

Heat Capacity and Equilibrium Polymerization of Vitreous Se

The contribution to the heat capacity of liquid Se, _p,r, arising from the ring-polymer equilibrium was calculated from the equilibrium polymerization theory of Tobolsky and co-workers. Above the polymerization transition temperature (∼360°K), _p,r∼(1/8)(Θ H₃²/RT²)(M/M_o) , where Θ H ₃ is the enthalpy change for the polymerization propagation step and (M/M₀) is the monomer fraction of Se₈ rings. Below the transition temperature, _p,r is negligibly small. Heat capacities were measured for glassy and liquid Se from 180° to 280°K and from 320° to BOOK, respectively. Using available literature data and the equilibrium polymerization theory, the temperature dependence of the heat capacity of liquid Se was calculated; it agreed within experimental error with the measured temperature dependence.     

Heat Capacity and Structural Relaxation of Mixed-Alkali Glasses

Heat capacities of a series of mixed-alkali glasses of composition (in mol%) 24.4(Na₂O + K₂O)-75.6SiO₂ were measured in the transition region by differential scanning calorimetry. The glass heat capacities at 700 K and the equilibrium liquid heat capacities are the same for all glasses on a per-g atom basis and equal, respectively, to 5.6 ± 0.1 and 6.8 ± 0.1 cal/g atom K. The glass transition temperatures exhibited negative deviations from additivity, but the heat capacity curves in the transition region of all the glasses for identical heating rates and thermal histories could be superimposed on the same reduced plot. This behavior indicates that the shapes of the structural relaxation functions are the same for all the glasses. These results support Shelby's conclusion that there is no unique "mixed-alkali effect" on thermodynamic or structural relaxation properties and that the term should be reserved for properties relating to ionic transport.     

Weak-Electrolyte Models for the Mixed-Alkali Effect in Glass

A weak electrolyte model for the mixed-alkali effect on electrical conductivity and ionic mobility in glass was developed for the dilute foreign alkali region. The basic assumptions are (a) that alkali transport in single-alkali glasses is due to a small concentration of mobile species and (A) adding small amounts of foreign alkali suppresses, by mass action, the mobile species concentration. The model was developed explicitly for the case where the mobile species are interstitial cations or cation pairs and was applied to analysis of conductivity data for 0.242(K₂O +Na₂O)–0.758SiO₂ glasses in the dilute Na+ region. The analysis allows the fraction of mobile cations in the single-alkali glass to be calculated. This varies from 0.5% at 25° to 6% at 500°C for 0.242K₂O–0.758SiO₂ glass and is in good agreement with estimates of the extent of dissociation from internal friction data and an ionic jump model of conductivity.     

Electrical and Mechanical Relaxations in a Mixed-Alkali Silicate Glass

Electrical relaxation measurements from 0.04 Hz to 2.5 MHz between 80° and 283°C and mechanical relaxation measurements from 120 to 3600 Hz between -44° and 305°C were conducted for 0.5Na₂O·0.5K₂O·3SiO₂ glass. The average time constant for the electric-field relaxation, which is controlled by the diffusion of the more mobile Na⁺ ion, was smaller by a factor of ∼30 to 50 than that for the mechanical relaxation associated with the mixed-alkali internal friction peak. This result supports the theory of Day and co-workers that the time constant for mixed-alkali mechanical relaxation is controlled by the less mobile alkali ion (K⁺). The results indicate that a distinct mixed-alkali electrical relaxation analogous to mixed-alkali mechanical relaxation is not observed because the electric field in the glass decays rapidly to zero via diffusion of the more mobile cation, rather than because the mixed-alkali mechanical-relaxation mechanism is inherently electrically inactive.