Analysis of Spotty Deposits on Fine Paper and Investigation of Key Factors Affecting Alkyl Ketene Dimer Spot Formation.

Defect spots degrade paper quality and often cause sheet breaks and other problems in the subsequent coating process. We encountered sporadic surges of defect spots on paper from a paper machine producing printing and writing grades of paper. We found that white or light-colored filler spots and waxy, translucent, elliptical spots accounted for 27.3 and 34.4% of these defects, respectively, and that both types of defect contained unhydrolyzed AKD as a major component. Paper machine's wet-end deposits, however, did not contain unhydrolyzed AKD as a deposit component. We hypothesized that the colloidal stability of AKD was the main factor causing the increase in spot defects, and we verified this by deposit testing experiments. Among the papermaking additives tested, bentonite caused the most significant increase in AKD deposition during testing, which was attributed to its causing the electrostatic coagulation of cationically charged AKD emulsion particles. In contrast, anionically charged AKD emulsions showed improved stability and less deposit formation in the presence of bentonite.

UV/Vis Spectrometry-Based Analysis of Alkyl Ketene Dimer (AKD) Retention to Solve the Waxy Spot Problem in the Papermaking Process.

A sudden surge in the number of translucent and oval-shaped waxy spots caused a serious production loss of the papermaking process. The investigation of the spots revealed that the alkyl ketene dimer (AKD) sizing agent caused the waxy spot problem. A ultraviolet/visible (UV/vis) spectrometry method for the quantitative analysis of AKD was developed and used to reduce the waxy spot problem in paper products. The results showed that the method could be used to quantify AKD in both papermaking stock and white water. The major factors in the papermaking wet end that were associated with the waxy spot problem were evaluated, and practical approaches to solving the AKD retention problem and the waxy spot problem were proposed and implemented. The dosage of a retention aid was found to be the principal factor controlling AKD retention. However, varying the retention aid dosage resulted in the deterioration of the paper formation; therefore, this was not a suitable solution to the waxy spot problem. The type of fixing agent and AKD used was found to be the secondary factor affecting the AKD retention and papermaking system cleanliness. Mill trials were conducted on a paper machine to examine the effects of different fixing agents and AKD types on AKD retention and the waxy spot count at the reel. This approach identified a combination of fixing agent and AKD type that substantially improved AKD retention and reduced the formation of translucent waxy spots in the resulting paper products.

A data-driven modeling approach to stochastic computation for low-energy biomedical devices.

Low-power devices that can detect clinically relevant correlations in physiologically-complex patient signals can enable systems capable of closed-loop response (e.g., controlled actuation of therapeutic stimulators, continuous recording of disease states, etc.). In ultra-low-power platforms, however, hardware error sources are becoming increasingly limiting. In this paper, we present how data-driven methods, which allow us to accurately model physiological signals, also allow us to effectively model and overcome prominent hardware error sources with nearly no additional overhead. Two applications, EEG-based seizure detection and ECG-based arrhythmia-beat classification, are synthesized to a logic-gate implementation, and two prominent error sources are introduced: (1) SRAM bit-cell errors and (2) logic-gate switching errors ('stuck-at' faults). Using patient data from the CHB-MIT and MIT-BIH databases, performance similar to error-free hardware is achieved even for very high fault rates (up to 0.5 for SRAMs and 7 × 10(-2) for logic) that cause computational bit error rates as high as 50%.

The State of the Art and Practice in Digital Preservation.

The goal of digital preservation is to ensure long-term access to digitally stored information. In this paper, we present a survey of techniques used in digital preservation. We also introduce representative digital preservation projects and case studies that provide insight into the advantages and disadvantages of different preservation strategies. Finally, the pros and cons of current strategies, critical issues for digital preservation, and future directions are discussed.