Hydrogen limitation--a method for controlling the performance of membrane biofilm reactor for autotrophic denitrification of wastewater.

Hydrogen-driven denitrification using the fiber membrane biofilm reactor (MBfR) was evaluated for consistent operation in tertiary wastewater treatment. The possibility of controlling the process rates, as well as biofilm parameters by supplying limited amounts of electron donor (hydrogen), was tested. Limiting the hydrogen supply proved to be efficient in controlling the biofilm growth and performance of the MBfR. Denitrification rates remained unchanged for both synthetic wastewater (SWW) and real municipal wastewater (MWW) effluent as well through the fluctuations in the substrate (NO3-N) concentration. The average denitrification rates were 0.50 (+/- 0.02) g NO3-N per day per m2 for SWW and 0.59 (+/- 0.04) g NO3-N per day per m2 for MWW. Biofilm density rather than thickness was the determining factor in substrate diffusion and biofilm sloughing, ultimately determining operating stability. Limited hydrogen supply assured constant volatile solids (VS) concentration in the biofilm. It was determined that VS/TS ratio higher than 0.25 assured stable biofilm operation. Decrease of VS/TS ratio below 0.25 led to shearing of the nonbiological outer layers of the biofilm. The values of chemical oxygen demand (COD), volatile suspended solids (VSS) and total suspended solids (TSS) in the final effluent were stable and well below wastewater effluent guidelines. Substitutions of bicarbonate with gaseous carbon dioxide as the carbon source did not affect denitrification rates despite lower than optimum pH conditions.     

System Test Planning of Software: An Optimization Approach

This paper extends an exponential reliability growth model to determine the optimal number of test cases to be executed for various use case scenarios during the system testing of software. An example demonstrates a practical application of the optimization model for system test planning.     

A touch of the future: contact-expressive devices

Contact-expressive devices could improve our lives-from practical improvements that let us interact with devices when other modalities are impossible, inappropriate, or inadequate to devices that have important consequences for physical well-being. We can also imagine using contact expressions in devices that are pleasurable, playful, artistic, or otherwise important to a human's experience. This paper discusses the technical development of sensor-motor systems, tactile interfaces, and technologies that can embody and understand affect. Contact-expressive devices are technologies that understand and use touch in meaningful ways-that can distinguish between a press and a caress. Also discussed are the following issues: technical requirements and the nature of contact expressions. Although a fairly large body of research exists regarding nonverbal communication, the majority of this work is on visual expression (facial expressions, physical appearance, direction of gaze, physical posture, and other visible forms of body language) and paralinguistics (such as vocal inflection, pitch, volume, and speech rate). Work needs to begin on studies of human contact with the goal of leveraging those insights for the design of contact-expressive devices-and work needs to begin on the implementation of technologies that have rich contact-expressive range and appeal.     

Nanoscale Crystallization in the Amorphous Alloy Fe79P14.2Si4.4Mn2.2V0.2 upon Pulsed Photon Annealing

The effect of pulsed photon annealing with energy densities from 1.4 to 42 J/cm² for various lengths of time on the structure of the amorphous alloy Fe₇₉P_14.2Si_4.4Mn_2.2V_0.2 was studied by x-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The results demonstrate that short-term irradiation with low energy densities leads to surface relaxation of the amorphous alloy, increases the strength of the surface layer, and reduces the internal-friction peak. Longer term photon annealing leads to crystallization of the alloy throughout the sample thickness.     

An efficient TDMA start-up and restart synchronization approach for distributed embedded systems

A desired attribute in safety-critical embedded real-time systems is a system time and event synchronization capability on which predictable communication can be established. Focusing on bus-based communication protocols, we present a novel, efficient, and low-cost start-up and restart synchronization approach for TDMA environments. This approach utilizes information about a node's message length that forms a unique sequence to achieve synchronization such that communication overhead can be avoided. We present a fault-tolerant initial synchronization protocol with a bounded start-up time. The protocol avoids start-up collisions by deterministically postponing retries after a collision. We also present a resynchronization strategy that incorporates recovering nodes into synchronization.     

Reliability assessment of polysilicon MEMS structures under mechanical fatigue loading

This paper examines the current status and methodologies of study of material and system reliability in Microelectromechanical Systems (MEMS). This includes: a review of the current literature in the area of MEMS regarding failure analysis experimental investigations; testing methods and philosophies for material characterization and possible mechanistic analytical solutions for estimating material properties. The paper proposes a reliability framework that encompasses all the available information. This statistical platform will enable the MEMS design engineer to distill all the available information in the literature into a stand-alone semi-empirical material reliability model, and a holistic system-level model for a complete system.     

Thermodynamics of Chemical Interactions in the CdTe–ZnTe–O2–C System during Melt Growth of Cd1 – x Zn x Te Crystals

Thermodynamic analysis is used to identify the possible chemical reactions of CdTe and ZnTe with the container material and gaseous atmosphere during Bridgman growth. Thermodynamic parameters of carbide and oxycarbide formation in the growth system are evaluated. The calculation results are consistent with the well-known fact that oxygen-containing impurities can be removed from the growth charge by calcination in hydrogen. Moreover, as shown in experiment, the removal of oxygen from the charge ensures a substantial decrease in the carbon content of the crystals.