AN OVERVIEW OF TAGUCHI METHOD AND NEWLY DEVELOPED STATISTICAL METHODS FOR ROBUST DESIGN

Robust Design is an important method for improving product quality, manufacturability, and reliability at low cost. Taguchi's introduction of this method in 1980 to several major American industries resulted in significant quality improvement in product and manufacturing process design. While the robust design objective of making product performance insensitive to hard-to-control noise was recognized to be very important, many of the statistical methods proposed by Taguchi, such as the use of signal-to-noise ratios, orthogonal arrays, linear graphs, and accumulation analysis, have room for improvement. To popularize me use of robust design among engineers, it is essential to develop more effective, statistically efficient, and user-friendly tech niques and tools. This paper first summarizes the statistical methods for planning and analyzing robust design experiments originally proposed by Taguchi; then reviews newly developed statistical methods and identifies areas and problems where more research is needed. For planning experiments, we review a new experiment format, the combined array format, which can reduce the experiment size and allow greater flexibility for estimating effects which may be more important for physical reasons. We also discuss design strategies, alternative graphical tools and tables, and computer algorithms to help engineers plan more efficient experi ments. For analyzing experiments, we review a new modeling approach, die response model approach, which yields additional information about how control factor settings dampen the effects of individual noise factors; this helps engineers better under stand die physical mechanism of the product or process. We also discuss alternative variability measures for Taguchi's signal-to-noise ratios and develop methods for empirically determining the appropriate measure to use.     

Autonomy-oriented computing (AOC): formulating computational systems with autonomous components

Autonomous multientity systems are plentiful in natural and artificial worlds. Many systems have been studied in depth and some models of them have been built as computational systems for problem solving. Central to these computational systems is the notion of autonomy. This article surveys research work done along this direction and presents autonomy-oriented computing (AOC) as a paradigm to describe systems for solving hard computational problems and for characterizing the behaviors of a complex system. AOC differs from major complex-system-related studies such as artificial life, simulated evolution, and multiagent systems in that AOC is not just intended to replicate complex behavior, emulate evolution, or coordinate the functioning of many interacting agents. AOC emphasizes the modeling of autonomy in the entities of a complex system and the self-organization of them in achieving a specific goal. Through implemented applications, we describe three main approaches to AOC, as well as an AOC framework with formal definitions of essential constructs and their interrelationships, including the notions of emergent autonomy, self-organization, and the interactions among entities and environment.     

On the order reduction of linear function observers

This note analyzes a new algorithm presented in [1] for designing a linear function observer with a minimum number of arbitrary poles. It shows that the maximum order of the observer of [1] isnu + ... + nu_{p} - pforp leq qandn - qforp geq q, instead ofp(nu_{1} - 1)as suggested in [1], wherenu{i}, i = 1top, are the descending ordered observability indexes of system (A, C) andn,p, andqare the order of the system, the number of the functions, and the number of the system outputs, respectively. This note also shows the significance of this result. For presentational purposes, only a special case of [1] is considered here. However, the technical properties as proved in this note are general.     

Curcumin provides potential protection against the activation of hypoxia and prolyl 4-hydroxylase inhibitors on prostate-specific antigen expression in human prostate carcinoma cells

Scope: Prostate‐specific antigen (PSA) is a well‐known marker for diagnosing and monitoring prostate cancer. Curcumin, a yellow curry pigment, has been reported to enhance androgen receptor (AR) degradation. We examined the effects of curcumin on increasing PSA expression by hypoxia and prolyl hydroxylase inhibitors, L ‐mimosine and dimethyloxalylglycine (DMOG), in human prostate carcinoma LNCaP cells. Methods and results: The ³H‐thymidine incorporation assay revealed that either L ‐mimosine or DMOG treatments attenuated cell proliferation. Immunoblot and enzyme‐linked immunosorbent assays (ELISA) indicated that both L ‐mimosine and DMOG have an effect similar to hypoxia, which stabilized hypoxia‐inducible factor‐1α (HIF‐1α) and induced PSA gene expression. The results of the immunoblot and transient gene expression assays indicated that induction of the PSA expression by hypoxia is both HIF‐1α‐ and AR‐dependent. Immunoblot assays revealed that a curcumin treatment (10 μM) decreased the protein abundance of AR but did not significantly affect the protein levels of HIF‐1α and vascular endothelial growth factor, which were induced by hypoxia. ELISA and transient gene expression assays indicated that curcumin blocked the activation of L ‐mimosine or DMOG treatment on PSA expression. Conclusions: These results indicate that curcumin blocked the enhanced effect of PSA expression by L ‐mimosine and DMOG that induce hypoxia condition.     

A Versatile Iterative Framework for the Reconstruction of Bandlimited Signals from Their Nonuniform Samples

In this paper, we study a versatile iterative framework for the reconstruction of uniform samples from nonuniform samples of bandlimited signals. Assuming the input signal is slightly oversampled, we first show that its uniform and nonuniform samples in the frequency band of interest can be expressed as a system of linear equations using fractional delay digital filters. Then we develop an iterative framework, which enables the development and convergence analysis of efficient iterative reconstruction algorithms. In particular, we study the Richardson iteration in detail to illustrate how the reconstruction problem can be solved iteratively, and show that the iterative method can be efficiently implemented using Farrow-based variable digital filters with few general-purpose multipliers. Under the proposed framework, we also present a completed and systematic convergence analysis to determine the convergence conditions. Simulation results show that the iterative method converges more rapidly and closer to the true solution (i.e. the uniform samples) than conventional iterative methods using truncation of sinc series.     

A mux-based High-Performance Single-Cycle CMOS Comparator

In this brief, a new architecture for high-fan-in CMOS comparator is proposed. The architecture is based on a hierarchical two-stage comparator structure and a dynamic MUX is used instead of a comparator in the second stage of the structure. By doing so, the fast dynamic MUX significantly improves the overall delay of the high-fan-in comparators. At the same time, a novel high-performance static priority encoder is proposed to generate the control signal for the MUX. A 64-bit MUX-based comparator has been built and compared with the existing fastest single-cycle design in the study by Lam and Tsui (2006). From both the post-layout simulation and test-chip measurement results, it is shown that the performance is improved by around 28%.     

Influence of the unstable glow discharge plasma state on the CW CO2 laser output

An extension of the high nitrogen partial pressure CW Co₂ laser regime, which operates without auxiliary cooling, to the high-nitrogen high-helium partial pressure regime with an output power one order of magnitude greater is discussed. Both regimes rely on an unstable glow discharge plasma with extended electrodes that presents nonperiodic voltage spikes     

Plasma sprayed hydroxyapatite coatings on titanium substrates. Part 1: Mechanical properties and residual stress levels

Heat treatment and the introduction of a Ti bond coat have been applied to hydroxyapatite (HA) coatings sprayed using different plasma powers and gas mixtures. Attempts were made in this way to achieve optimal coating properties for orthopaedic implants. In particular, the effects on the degree of crystallinity, the adhesion, the OH ion content and the purity were evaluated. Heat treatment at 700 C for 1 h in air proved to be effective in increasing the crystallinity, regaining the OH- ion and removing other non-HA compounds, although it caused a significant decrease in the degree of adhesion (interfacial fracture toughness) for those specimens sprayed at high powers. This heat treatment was found to induce significant transformation of amorphous HA to the crystalline form, while not detrimentally changing the properties of the underlying Ti-6Al-4V substrates. Precoating with a 100 microm Ti layer increased the adhesion of the HA coatings on Ti-6Al-4V substrates, primarily by providing a rougher surface and promoting better mechanical interlocking. Changes in coating properties during immersion in biological fluids were also studied and were found to depend critically on the chemical composition of the fluids. Small precipitates formed on the coating surfaces when immersed in Ringers solution. These might account for the apparent drop in the degree of crystallinity when measured using X-ray diffraction. A significant drop in the interfacial adhesion was found for those coatings sprayed at high powers. This could be offset by prior precoating with a titanium bond coat and suitable heat treatment. In summary, the following processing sequence is suggested in order to achieve optimum coating properties: precoating the substrate with a layer of Ti (approximately 100 microm), spraying HA at a sufficiently high-power level (depending on particle size and gas mixture) and heat treatment at 700 degrees C for 1 h in air.