Equilibrium stability in decentralized design systems

The focus of this paper is on complex systems, and it presents a theoretical study of the design of complex engineering systems. More particularly, this paper studies the stability of equilibria in decentralized design environments. Indeed, the decentralization of decisions is often recommended in the design of complex systems, and the decomposition and coordination of decisions are a great challenge. The mechanisms behind this network of decentralized design decisions create difficult management and coordination issues. However, developing efficient design processes is paramount, especially with market pressures and customer expectations. Standard techniques to modelling and solving decentralized design problems typically fail to understand the underlying dynamics of the decentralized processes and therefore result in suboptimal solutions. This paper aims to model and understand the mechanisms and dynamics behind a decentralized set of decisions within a complex design process. Complex systems that are multidisciplinary and highly nonlinear in nature are the primary focus of this paper. Therefore, techniques such as response surface approximations and Game Theory are used to discuss and solve the issues related to multidisciplinary optimization. Nonlinear control theory is used in this paper as a new approach to study the stability of equilibrium points of the design space. Illustrations of the results are provided in the form of the study of the decentralized design of a pressure vessel.     

Effect of Auditory Waiting Cues on Time Estimation in Speech Recognition Telephony Applications

Previous empirical research in subjective time estimation and applied work in auditory interface design imply that designers can use auditory stimuli during system processing to manipulate users' perception of its duration. Two experiments investigate the effect of system response time (SRT) duration and rate of change of an auditory waiting cue on participants' subjective time estimates and perceived affect. The results showed that perceived SRT duration and ratings of perceived anxiety, stress, and impatience increased as ticking rate increased. However, with a slow rate (2-sec ticking), participants underestimated the duration of SRT, but indicated a significant increase in negative affect as compared with silent conditions. These results suggest that interface designers may reduce the subjective duration and negative affective states of SRT through carefully chosen, slow tempo system processing tones. The results of this research also stress the importance of thoughtful, informed interface design that makes contact with the empirical literature of the cognitive sciences.     

Assessing the efficacy of pre-harvest,chlorine-based sanitizers against human pathogen indicator microorganisms and Phytophthora capsici in non-recycled surface irrigation water

Many factors must be considered in order to develop and implement treatment systems to improve the microbial quality of surface water and prevent the accidental introduction of plant and human pathogens into vegetable crops. The efficacy of chlorine gas (Cl_2(g)) and chlorine dioxide (ClO₂) injection systems in combination with rapid sand filtration (RSF) was evaluated in killing fecal indicator microorganisms in irrigation water in a vegetable-intensive production area. The efficacy of ClO₂ and Cl_2(g) was variable throughout the distribution systems and coliform bacteria never dropped below levels required by the United States Environmental Protection Agency for recreational waters. Sampling date and sampling point had a significant effect on the abundance of coliforms in Cl_2(g)- and ClO₂-treated water. Sampling date and sampling point also had a significant effect on the abundance of generic Escherichia coli in Cl_2(g) treated water but only sampling point was significant in ClO₂ treated water. Although the waterborne plant pathogen Phytophthora capsici was detected in five different sources of surface irrigation water using baiting and P. capsici-specific PCR, in vitro studies indicated that ClO₂ at concentrations similar to those used to treat irrigation water did not reduce mycelial growth or direct germination of P. capsici sporangia and reduced zoospore populations by less than 50%. This study concludes that injection of ClO₂ and Cl_2(g) into surface water prior to rapid sand filtration is inadequate in reducing fecal indicator microorganism populations and ClO₂ ineffectively kills infectious propagules of P. capsici. Additional research is needed to design a system that effectively targets and significantly reduces both plant and human pathogens that are present in surface irrigation water. A model for a multiple barrier approach to treating surface water for irrigation is proposed.     

The Expanding Role of Traceability in Seafood: Tools and Key Initiatives

In the last decade, a range of drivers within the seafood sector have incentivized the application of traceability to issues beyond food safety and inventory management. Some of the issues motivating the expanded use of traceability within the global seafood sector include: increased media attention on the legal and social risks within some seafood supply chains, governmental traceability requirements, private‐sector sustainability commitments, and others. This article begins with an overview of these topics in the seafood industry, and why many nongovernment organizations (NGOs), companies, and government actors have turned to traceability as a tool to address them. We discuss how traceability connects to key requirements of environmental sustainability and social responsibility. Later, we review the range of traceability services, tools, software solutions, and the due diligence measures that are currently being leveraged within the seafood sector. The paper concludes with a discussion of several NGO‐ and industry‐led traceability initiatives that are examples of seafood traceability improvements.     

Study of Scale-Removal Methods in a Double-Pipe Heat Exchanger

The objective of the present study was to examine the effectiveness of four cleaning methods for the removal of tube-side fouling in a double-pipe heat exchanger. The four cleaning methods are (1) hydrolazing with 10,000-psi head pressure, (2) hydrolazing with 20,000-psi head pressure, (3) chemical cleaning, and (4) brush punching. Fouled tubes were prepared using water from a cooling tower. Each test started with a brand new tube. When the overall heat transfer coefficient dropped by 40% from the initial peak value, scales in the fouled tubes were removed using one of the above four methods. Both the overall heat transfer coefficient and inside diameter were measured before and after fouling, by which the effectiveness of a particular cleaning method was evaluated. The chemical cleaning method was found to be most effective, whereas the brush punching was least effective. When a fouled tube was kept dry, brush punching completely removed scales, indicating that surface wetness plays an important role in scale removal.     

Following Chemical Charge Trapping in Pentacene Thin Films by Selective Impurity Doping and Wavelength‐Resolved Electric Force Microscopy

Charge trapping is one of several factors that limit the performance of organic electronic materials, yet even in pentacene, a prototypical small‐molecule semiconductor, the precise chemical nature of charge trapping remains poorly understood. Here the effects of three chemical trap‐precursor candidates are examined by layering thin‐film pentacene transistors with different pentacene defect species. The resulting charge trapping is studied in each device via scanning‐probe electric force microscopy coupled with variable‐wavelength sample illumination. Firstly, it is found that layering with pentacen‐6(13H)‐one (PHO) readily produces uniform charge trapping everywhere in the transistor channel, as expected for an active blanket‐deposited trap‐precursor. However, layering with 6,13‐dihydropentacene (DHP) produces fewer, more‐isolated traps, closely resembling the surface potential distribution in pristine pentacene thin films. Secondly, the rates of trap‐clearing versus illuminating wavelength (trap‐clearing spectra) are measured, revealing enhanced trap‐clearing rates at wavelengths assigned to the absorption of either pentacene or the charged trap species. The trap‐clearing spectrum for the PHO‐layered sample closely resembles the spectrum obtained from pentacene aged in a working transistor, while the trap‐clearing spectrum for the DHP‐layered sample resembles the spectrum observed in pristine pentacene. We conclude that PHO competently creates traps in pentacene that match the expected trap‐clearing spectrum for degraded pentacene, while DHP does not, and that the chemical trap species in aged pentacene is very likely PHO⁺.