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Agricultural commodities such as cereal grains, oilseeds, and nuts are dried before and during storage to minimize, if not prevent, degradation of quality. While drying, heat and mass transfer occur simultaneously resulting in the removal of moisture from the product over time. As the moisture is removed, mass and volume are reduced. Such losses produce shrinkage, and thus, density changes throughout the drying product for the duration of the drying process. Density is an important parameter because it is indicative of other quality parameters such as test weight. It is also critical for operators because it can be used to estimate grain mass in silos, determine resistance to airflow, and predict grain pressure in silos. Despite its usefulness, bulk density is difficult to measure at specific locations within a bed of grain or seed. It can be calculated for small quantities and estimated for large quantities by gravimetric means; however, it has been shown that bulk density varies throughout a bed of grain or seed. Such variances are caused by compaction from upper layers and differences in moisture content. Therefore, an eighth-scale grain drying system was used to observe the real-time change in bulk density within a 153,000-cm³ volume bed of wheat. Bulk density was determined empirically at the center of the volume from dielectric properties measured with a microwave sensor, and it was simulated at other locations by modeling heat and mass transfer. Comparison between the bulk density determined from simulation and that measured empirically at the center of the volume of wheat resulted in a root mean square error (RMSE) of 0.0054 g/cm3; thus, the accuracy of the models was confirmed. Real-time knowledge of bulk density at various locations can aid in monitoring the quality of the product being dried and provide essential information concerning the pressure and airflow throughout the entire volume. [ABSTRACT FROM AUTHOR]

Microwave moisture sensors represent a sound solution for real-time, nondestructive determination of moisture content in grains, seeds, nuts, and other agricultural products. One of the most critical phases in developing these sensors is their calibration against standard methods, in this instance, the oven-drying technique. In this study, dielectric properties of different varieties of wheat, and corn were measured at 10 GHz and an average room temperature of 25.2°C to investigate the influence of variety in calibrating microwave moisture sensors. Dielectric properties measured for all varieties tested for a given material were nearly superimposed, and the same was observed when plotting density-independent calibration function, ψ, as a function of moisture content. Performance of individual moisture calibration equations in predicting moisture content was compared to that from a single moisture calibration equation established for all varieties combined through computation of the standard error of calibration (SEC). In most instances, for both wheat and corn the SEC corresponding to individual varieties were nearly the same as that corresponding to all varieties combined. In addition, it was observed that a unified calibration can be established for both wheat and corn whereby moisture can be predicted from a single moisture calibration equation based on measurement of the dielectric properties at a single microwave frequency. Here, such an equation provided moisture content in wheat and corn with a SEC of 0.87%. [ABSTRACT FROM AUTHOR]

Institutional investors (active vs. passive) play various roles in the capital market and in assets prices, in particular. Institutional investors affect assets prices either because they play a monitoring role and mitigate the agency problem, or because they have information advantages, or finally, they can arbitrage away mispricing. This research note relates Hu, Ke, and Yu’s (forthcoming) article to both the traditional positive views that institutional investors are sophisticated and help correct stock mispricing and the complementary emerging literature that argues that institutions may contribute to stock return anomalies rather than eliminate them. My research note concludes that current research on the role of institutional investors has generated a number of useful insights. I identify many fundamental questions that remain unanswered, and changes in the economic environment that raise new questions for research. [ABSTRACT FROM AUTHOR]