Compact modeling approach for microchannel cooling and its validation

Microsystem Technologies - This paper presents a new compact modeling technique to describe the convective heat transfer realized by laminar flow of coolant in integrated microchannels used for...     

Towards a generalized physicochemical framework

Process models used for activated sludge, anaerobic digestion and in general wastewater treatment plant process design and optimization have traditionally focused on important biokinetic conversions. There is a growing realization that abiotic processes occurring in the wastewater (i.e. 'solvent') have a fundamental effect on plant performance. These processes include weak acid-base reactions (ionization), spontaneous or chemical dose-induced precipitate formation and chemical redox conversions, which influence pH, gas transfer, and directly or indirectly the biokinetic processes themselves. There is a large amount of fundamental information available (from chemical and other disciplines), which, due to its complexity and its diverse sources (originating from many different water and process environments), cannot be readily used in wastewater process design as yet. This position paper outlines the need, the methods, available knowledge and the fundamental approaches that would help to focus the effort of research groups to develop a physicochemical framework specifically in support of whole-plant process modeling. The findings are that, in general, existing models such as produced by the International Water Association for biological processes are limited by omission of key corrections such as non-ideal acid-base behavior, as well as major processes (e.g., ion precipitation). While the underlying chemistry is well understood, its applicability to wastewater applications is less well known. This justifies important further research, with both experimental and model development activities to clarify an approach to modeling of physicochemical processes.     

Improved Adhesion of Waterborne Polyurethanes by Hybridizations

Aqueous polyurethane dispersions based on isophorone diisocyanate (IPDI), poly (tetramethylene adipate) glycol (PTAd), and dimethylolproprionic acid (DMPA) were synthesized by a prepolymer mixing process. Effects of the molecular weight of PTAd and types of hybridizations, viz. blending, semi-interpenetrating polymer network (IPN), and full IPNs with polybutylacrylate have been determined. It was found that thermal, mechanical, and adhesion properties of the polyurethane dispersions increased with increasing molecular weight of polyols.

Regarding the effects of hybridization, full IPNs gave the greatest tensile strength and elongation at break with a fast drying rate, whereas semi-IPNs gave the greatest initial as well as final adhesion, implying that a certain degree of chain mobility would augment the penetrations of adhesive molecules into the soft polyurethane foam substrates.     

Ring-opening copolymerization of 2,4-bisphenyl-1,3,2,4-dioxadiphosphetane-2,4-dioxide with oxetane via zwitterion intermediates

Summary Copolymerization of 2,4-bisphenyl-1,3,2,4-dioxadiphosphetane-2,4-dioxide (DPO) with oxetane, a cyclic ether, was found to take place at 90 and 120°C without initiator. Copolymers obtained have a structure of phosphonate-ether units (1), which was determined by ³¹P, ¹H and ¹³C NMR, IR and elemental analysis. Oxetane was incorporated into 1 in a slight excess in all runs(m value in 1=1.5–2.1). A small amount(<15%) of a by-product (2) was always formed. Other cyclic ethers such as ethylene oxide and propylene oxide did not afford copolymers but gave 11 addition products, 10 and 11, quantitatively. The copolymerization is reasonably explained by a mechanism in which DPO behaves as an electrophilic monomer and oxetane as a nuicleophilic one. A pyrophosphonate species is considered to be a key intermediate to lead to copolymer 1 and the whole reaction course is discussed in detail.     

Catastrophic Transitions of Construction Contracting Behavior

The ways to manage a construction project very much depend on the attitude of the people involved. Collectively this is identified as construction contracting behavior (CCB). The CCB of the construction industry is adversarial as pinpointed in many industry-wide reviews. A more cooperative project delivery approach has therefore been advocated. In fact, drive for efficiency provides the incentive for cooperation. Nevertheless, members of a project team, in representing their respective organizations, are often in conflict. The dichotomous pair of cooperation and aggression forces therefore coexist. It is not uncommon to note that CCB turns aggressive as the construction activities of a project intensify. This change is often sudden and thus matches well with the phenomenon of hysteresis described by the catastrophe theory (CT). It is hypothesized that the dynamics of CCB can be modeled by CT. The three-variable CT models include CCB (as dependent variable), cooperation forces (as normal factor) and aggression forces (as splitting factor). With data collected from a survey fitted by the Cuspfit program, it was found that trust intensity is an effective normal factor. Contract incompleteness and competitive inertia are splitting factors that trigger aggression.     

Spreadsheet quality assurance: a literature review

Spreadsheets are very common for information processing to support decision making by both professional developers and non-technical end users. Moreover, business intelligence and artificial intelligence are increasingly popular in the industry nowadays, where spreadsheets have been used as, or integrated into, intelligent or expert systems in various application domains. However, it has been repeatedly reported that faults often exist in operational spreadsheets, which could severely compromise the quality of conclusions and decisions based on the spreadsheets. With a view to systematically examining this problem via survey of existing work, we have conducted a comprehensive literature review on the quality issues and related techniques of spreadsheets over a 35.5-year period (from January 1987 to June 2022) for target journals and a 10.5-year period (from January 2012 to June 2022) for target conferences. Among other findings, two major ones are: (a) Spreadsheet quality is best addressed throughout the whole spreadsheet life cycle, rather than just focusing on a few specific stages of the life cycle. (b) Relatively more studies focus on spreadsheet testing and debugging (related to fault detection and removal) when compared with spreadsheet specification, modeling, and design (related to development). As prevention is better than cure, more research should be performed on the early stages of the spreadsheet life cycle. Enlightened by our comprehensive review, we have identified the major research gaps as well as highlighted key research directions for future work in the area.