Modeling of a non-Newtonian flow between parallel plates in a flip chip encapsulation

The viscosity of the underfill encapsulant may be different under the conditions of different shear rate, filler content, and temperature. Most of the encapsulant is epoxy containing silica fillers. It exhibits non-Newtonian behavior in the underfill flow. The effect of the viscosity variations on the underfill filling flow was investigated in this study. An analytical model of the filling flow is proposed to accomplish the shear-rate depending viscosity. Due to the addition of fillers in the encapsulant, the viscosity may exhibit both shear thinning and thickening behaviors depending on the temperature and filler content. This study proposes a model of the viscosity considering both effects. In the situations demonstrated in the results, the shear thinning and thickening effects may have major influence on the velocity profile and the filling speed.     

Durable antimicrobial finish of cotton fabrics

Cotton fabrics were treated with Biopag, which does not have any functional groups that are reactive toward cellulose, using crosslinking agents or a binder, for the purpose of imparting a durable antimicrobial finish. In this respect, it was found that the crosslinking agents were more effective than the binder. It was confirmed by FT‐IR that the characteristic split peaks of Biopag were still seen even after repeated launderings. The crosslinking agents deteriorated the whiteness and tensile strength of the Biopag‐treated cotton fabrics, while the wrinkle recovery angles (WRAs) were significantly improved. The one‐step padding of Biopag and the crosslinking agent was found to be superior to the two‐step padding method in which Biopag padding was followed by padding of crosslinking agent in respect of WRA, whereas the whiteness and tensile strength were vice versa. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

A methodology for systemic‐structural analysis and design of manual‐based manufacturing operations

The main objective of this study was to develop a method for systemic‐structural analysis and design of manufacturing assembly operations based on the activity theory. The “activity” was defined as behavior distinctively specific to workers, associated with mobilizations and realization of conscious manufacturing goals. The fundamental units of analysis of activity are actions that are both motor and mental. Activity is considered as a complicated structure of actions that are logically ordered in space and time. Each action is comprised of different operations. The building blocks of motor actions are motions. The building blocks of cognitive actions are mental operations. Activity integrates not merely cognitive and behavioral components, but the energy components as well. The proposed methodology is illustrated using an example of two manufacturing assembly operations. © 2001 John Wiley and Sons, Inc.     

Direct Physical Imaging and Chemical Probing of LiFePO4 for Lithium‐Ion Batteries

The control of unexpectedly rapid Li intercalation reactions without structural instability in olivine‐type LiFePO₄ nanocrystals is one of the notable scientific advances and new findings attained in materials physics and chemistry during the past decade. A variety of scientific studies and technological investigations have been carried out with LiFePO₄ to elucidate the origins of many peculiar physical aspects as well as to develop more effective synthetic processing techniques for better electrochemical performances. Among the several features of LiFePO₄ that have attracted much interest, in this article we address four important issues—regarding doping of aliovalent cations, distribution of Fe‐rich secondary metallic phases, nanoparticle formation during crystallization, and antisite Li/Fe partitioning—by means of straightforward atomic‐scale imaging and chemical probing. The direct observations in the present study provide significant insight into alternative efficient approaches to obtain conductive LiFePO₄ nanocrystals with controlled defect structures.     

Sliding mode control of a shear-mode type ER engine mount

This paper presents feedback control characteristics of a shear-mode type electro-rheological (ER) engine mount. The field-dependent yield stress of an arabic gum-based ER fluid is obtained using a couette type electroviscometer, and it is incorporated into the governing equation of motion of the ER engine mount, which is derived from a bond graph model. A sliding mode controller which directly represents the field-dependent damping force is formulated by taking into account the stiffness and damping properties of the systems as parameter uncertainties. The controller is then experimentally realized by imposing a semi-active actuating condition. The effectiveness of the proposed ER engine mount is demonstrated showing capabilities of isolating the vibrations due to sinusoidal and random excitations.     

Seismic response prediction for cabinets of nuclear power plants by using impact hammer test

An effective method to predict the seismic response of electrical cabinets of nuclear power plants is developed. This method consists of three steps: (1) identification of the earthquake-equivalent force based on the idealized lumped-mass system of the cabinet, (2) identification of the state-space equation (SSE) model of the system using input-output measurements from impact hammer tests, and (3) seismic response prediction by calculating the output of the identified SSE model under the identified earthquake-equivalent force. A three-dimensional plate model of cabinet structures is presented for the numerical verification of the proposed method. Experimental validation of the proposed method is carried out on a three-story frame which represents the structure of a cabinet. The SSE model of the frame is accurately identified by impact hammer tests with high fitness values over 85% of the actual frame characteristics. Shaking table tests are performed using El Centro, Kobe, and Northridge earthquakes as input motions and the acceleration responses are measured. The responses of the model under the three earthquakes are predicted and then compared with the measured responses. The predicted and measured responses agree well with each other with fitness values of 65-75%. The proposed method is more advantageous over other methods that are based on finite element (FE) model updating since it is free from FE modeling errors. It will be especially effective for cabinet structures in nuclear power plants where conducting shaking table tests may not be feasible. Limitations of the proposed method are also discussed.     

Strain hardening behavior during manufacturing of tube shapes by hydroforming

Safe and robust process design relies on knowledge of the evolution of the mechanical properties in a tube during hydroforming. The manufacturing of tubular shapes generally consists of three main stages: bending, preforming, and expansion. The latter is usually called hydroforming. As a result of these three steps, the final product’s strain hardening history is nonlinear. In the present study, the strain hardening behavior during hydroforming was experimentally investigated. The variation of local flow stress and/or local hardness was used as an index of the strain hardening during the various steps and the local flow stress and/or local hardness were used with respective correlations to determine the effective strain. The strain hardening behavior during hydroforming after preforming has been successfully analyzed by using the relationships between hardness, flow stress, and effective strain for variable pre-strains prior to hydroforming. The comparison of predicted hardness with measured hardness confirms that the methodology used in this study is feasible, and that the strain hardening behavior can be quantitatively estimated with good accuracy.     

Esterification of Acrylic Acid with 1,4‐Butanediol in a Batch Distillation Column Reactor over Amberlyst 15 Catalyst

The esterification reaction of acrylic acid (AA) with 1,4‐butanediol (BD) to produce 4‐hydroxybutyl acrylate (HBA) was carried out in a batch reactive distillation mode over the Amberlyst 15 catalyst. The reactive distillation was highly desirable to increase the reaction rate of BD and eventually to obtain the high purity of HBA because the unreacted BD was not easily separable to the produced HBA after the reaction. The reaction pressure below 760 mm Hg was used to remove the by‐product water from the reaction zone. The air‐bubbling operation was successfully applied to prevent the polymerization of reactants and products under the vacuum condition (400 ～ 760 mm Hg). The reaction rates were strongly dependent on the reaction pressure, especially, the reaction rate of BD disappearance. The increased reaction rate of BD by the reactive distillation enabled to produce a high purity of HBA.     

The interface between designer and maintainer

The usual aim of computer-aided design is to bridge the interface between design and production. However, an interface also exists between design and maintenance. The author of this paper introduces some concepts, which are currently being considered, for improving design for maintainability with manual design processes and indicates their potential development for use with c-a.d. systems.