Conjoint-analysis-based multiattribute optimization: application in acoustical design

The concept of customer preference, or product value, prevalent in economics and management science, is just beginning to be used in engineering design. This concept and the associated measurement approaches offer us a theoretically appealing way to aggregating customer preferences for multiple product attributes into a single objective function, representing total product value, which may then be maximized. Among these methods, conjoint analysis has emerged as the most popular approach in marketing to estimate the value that customers attach to different features of a product that can be at different levels. In this paper, we use conjoint analysis in a novel way to assess a product designer’s preferences for addressing a practical problem in acoustical design. We incorporate a designer’s preferences for reducing noise in a curved pressure vessel excited with broadband noise. The shell is part of a large industrial machine. The “product” here refers to a broadband vibration absorber(s) attached to the structure. Through direct interaction with the design engineer, we elicit his/her preferences for various alternative design configurations and specify an aggregate value function. We then apply optimization techniques, interfaced to simulation codes, to maximize the value function. We show that this method provides more economical designs compared to certain conventional formulations. We conclude by summarizing some limitations to this research, which point to several future research opportunities.     

Seepage behavior of soil mixed with randomly distributed recycled plastic materials

Seepage through embankment fill materials is crucial issue in the construction of embankments for irrigation and drainage projects. Proper ground improvement methods should be used to improve the strength and stability characteristics of soil used as fill material. Utilization of waste plastic materials to enhance the engineering properties of soil is a sustainable approach. Additionally, the use of raw products directly from plastic recycling units in the form of flakes and pellets as soil additives has the potential to further enhance the economic benefits of this method. This study randomly mixed plastic materials with soil for use in the construction of earth embankments, such as river levees, dykes, and canal diversion structures, and evaluated the effectiveness of these materials in reducing seepage failures in hydraulic structures. To achieve these goals, this study collected high-density polyethylene (HDPE) plastic from plastic recycling units and used soil mixed with HDPE plastic in the form of flakes and pellets in different contents as embankment fill materials, then evaluated how these materials affected the piping features. Laboratory experiments were conducted to determine the seepage velocity and critical hydraulic gradient of soil mixed with plastics in various contents and to compare the values with those of plain soil. The results showed that random distribution of waste plastics in the form of flakes and pellets in soil is an effective method for improving the piping resistance of soil.     

Novel thermo‐responsive semi‐interpenetrating network microspheres of gellan gum‐poly(N‐isopropylacrylamide) for controlled release of atenolol

Thermoresponsive microspheres of gellan gum‐poly(N‐isopropylacrylamide), i.e., GG‐P(NIPAAm) semi‐interpenetrating polymer networks (semi‐IPNs) have been prepared by ionic crosslinking and used to study the controlled release (CR) of atenolol (ATL), an antihypertensive drug. Interaction of the drug with polymers was studied by Fourier transform infrared (FTIR) spectroscopy. Differential scanning calorimetry (DSC) was used to confirm the polymorphism and molecular level dispersion of ATL. Scanning electron microscopy (SEM) indicated spherical nature and smooth surfaces of the microspheres with some debris attached on their surfaces. Mean particle size measured by laser light diffraction ranged between 34 and 76 μm. Equilibrium swelling performed at 25°C and 37°C in pH 7.4 phosphate buffer exhibited thermoresponsive nature of the polymers. In vitro drug release performed at 25°C and 37°C indicated temperature‐dependency of ATL release, which was extended up to 12 h. In vitro release profiles at both the temperatures confirmed thermoresponsive nature of the polymers giving pulsatile trends. The % cumulative release data have been fitted to an empirical equation to estimate transport parameters and to understand the nature of drug release. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Changes in carbohydrates and the activity of α-galactosidase,pentosanase and lipase during germination of groundnuts (Arachis hypogea)

The quantitative changes in carbohydrates of two varieties (i.e., red netal and HG-4) of groundnuts during germination have been investigated. On germination, raffinose, stachyose and verbascose decreased gradually up to 48 h and almost disappeared completely in later stages of germination (140 h). Glucose and fructose levels increased 4–6 fold; while sucrose content increased considerably throughout germination in both the varieties of groundnuts. The starch content increased about four fold during germination in both the varieties. The pentosan content was almost constant up to 36 h but decreased in later stages of germination. The oil content decreased significantly from 52 to 8.0%. The fairly high initial α-galactosidase and lipase activity in resting seeds, increased considerably during germination in both the varieties studied. On the other hand the pentosanase activity was not detected up to 36 h of germination but it appears to increase abruptly afterwards.     

Multi-mode interference-based photonic crystal logic gates with simple structure and improved contrast ratio

We present a MMI-based photonic crystal all-optical logic gate structure for logic functions such as XNOR, XOR, OR and NAND with square-type lattice of Si rods in air host. Phase-based logic inputs produce intensity-based logic outputs with high contrast ratio. The calculated ON to OFF contrast ratio for the logic functions XNOR/XOR and OR/NAND is 40.41 and 37.40 dB, respectively. Further, it is improved by 11.53 and 12.46% for XNOR/XOR and OR/NAND logic functions, respectively, by reducing the back reflection with the introduction of absorbing waveguides. The structure in both the forms has a fast response period that is less than or equal to 0.131 ps. The size of the structure is quite compact with dimension \(6.4\,\upmu \hbox {m} \times 8.8\,\upmu \hbox {m}\).     

Characterization of phospholipid reverse micelles in relation to membrane processing of vegetable oils

Studies were conducted to determine the critical micelle concentration (CMC) of phospholipids in vegetable oils and the size of reverse micelles to understand their rejection phenomenon in the membrane process. The CMC values of phosphatidylcholine (PC) in triolein and phospholipids in crude soybean oil were determined to be 440 and 1020 mg/kg, respectively, by using TCNQ (7,7,8,8‐tetracyano‐quinodimethane) solubilization technique. The surface tension measurements of these samples gave similar values of CMC. From small‐angle X‐ray scattering (SAXS) analysis, the size of the PC micelles was determined to be in the range of 3.56 to 4.70 nm. The characterization of reverse micelles formed in the oil system was found useful in enhancing the understanding of the possible rejection phenomenon of phospholipids by non‐porous polymeric composite membranes used in our earlier studies on vegetable oils and in suggesting suitable types of membranes for the same.     

Chemoenzymatic Buta-1,3-diene Synthesis from Syngas Using Biological Decarboxylative Claisen Condensation and Zeolite-Based Dehydration

A method for producing buta-1,3-diene (1,3-BD) by an amalgamation of chemical and biological approaches with syngas as the carbon source is proposed. Syngas is converted to the central intermediate, acetyl-CoA, by microorganisms through a tetrahydrofolate metabolism pathway. Acetyl-CoA is subsequently converted to malonyl-CoA using a carbonyl donor in the presence of a carboxylase enzyme. A decarboxylative Claisen condensation of malonyl-CoA and acetaldehyde ensues in the presence of acyltransferases to form 3-hydroxybutyryl-CoA, which is subsequently reduced by aldehyde reductase to give butane-1,3-diol (1,3-BDO). An ensuing dehydration step converts 1,3-BDO to 1,3-BD in the presence of a chemical dehydrating reagent.     

Techno-economic analysis of processes for Aspergillus carbonarius polygalacturonase production

A techno-economic analysis of submerged (SmF) and solid state fermentation (SSF) processes for Aspergillus carbonarius polygalacturonase production was performed to make an appropriate process selection. The downstream processing involved integrated membrane process (IMP) and alginate affinity precipitation (AAP). For a production scale of 30kL purified polygalacturonase concentrate per year, the total upstream cost of SmF was 14% lower than the SSF process. Downstream processing cost by IMP was 47% lower than AAP. The SmF-IMP process required a total capital investment that was 15-24% lower than the SmF-AAP and SSF-AAP processes. The corresponding unitary product cost was also lower by 24-36% in SmF-IMP process. Thus the SmF-IMP process proved to be very attractive from an economic point of view.