A variotherm mold for micro metal injection molding

In this paper, a variotherm mold was designed and fabricated for the production of 316L stainless steel microstructures by micro metal injection molding (MIM). The variotherm mold incorporated a rapid heating/cooling system, vacuum unit, hot sprue and cavity pressure transducer. The design of the variotherm mold and the process cycle of MIM using the variotherm mold were described. Experiments were conducted to evaluate the molded microstructures produced using variotherm mold and conventional mold. The experiments showed that microstructures of higher aspect ratio such as 60 m × height 191 m and 40 m × height 174 m microstructures could be injection molded with complete filling and demolded successfully using the variotherm mold. Molded microstructures with dimensions of 60 m × height 191 m were successfully debound and sintered without visual defects.     

Local determinacy of abstract local dynamical systems

O. Hájek proved in his book Dynamical Systems in the Plane (Chapter III) that there isat most one abstract local dynamical system which is locally equivalent to, or equivalently an extension of, a given elementary dynamical system, and suggested a question of finding reasonable conditions on the latter for the existence ofat least one such abstract local dynamical system. An elementary dynamical system is said to satisfy the No-Intersection Axiom and is called an abstract germ if(x ₁, t) = (x ₂,t) impliesx ₁ =x ₂. We show that is (uniquely) extendable to an abstract local dynamical system if and only if is an abstract germ, and hence the question is completely answered. After introducing various kinds of isomorphisms of abstract germs and abstract local dynamical systems corresponding to those of continuous germs and continuous local dynamical systems, we obtain some sufficient conditions for extendability of isomorphisms and possibility of restriction of them, and thus establish the local determinacy of abstract local dynamical systems up to isomorphisms in some wider categories.Dedicated to Professor Yusuke HAGIHARA in Commemoration of His Seventy-Seventh Anniversary     

Generating Boolean \mu-expressions

In this paper, we consider the class of Boolean -functions, which are the Boolean functions definable by -expressions (Boolean expressions in which no variable occurs more than once). We present an algorithm which transforms a Boolean formulaE into an equivalent -expression-if possible-in time linear in E times , where E is the size ofE andn _m is the number of variables that occur more than once inE. As an application, we obtain a polynomial time algorithm for Mundici's problem of recognizing -functions fromk-formulas [17]. Furthermore, we show that recognizing Boolean -functions is co-NP-complete for functions essentially dependent on all variables and we give a bound close to co-NP for the general case.     

Material characterization of composite laminates using dynamic response and real parameter-coded microgenetic algorithm

An efficient nondestructive evaluation procedure is proposed for inversely determining material constants of composite laminates using dynamic response at one point on the plate surface. Material constants of composite laminates are determined by minimizing the difference between the measured dynamic response of the actual plate and the computed response of the plate with assumed material properties. For robust and efficient function minimization, a real parameter-coded microgenetic algorithm (real-GA) is proposed on the basis of the existing binary coded uniform microgenetic algorithm (uniform GA). Four different crossover operators are constructed for the real-GA. Performances of the present real-GA and the existing uniform GA are studied using several typical benchmark test functions and an order-3 deceptive function. The present real-GA is then implemented as the inverse solver in the minimization process of material characterization. From hundreds of tests conducted on the benchmark functions, the order-3 deceptive function, and the material characterization problems, it is found that the real-GA is two to five times faster in converging to the global optimum compared with the uniform GA. Numerical examples for material characterization of composite laminates have demonstrated the robustness, efficiency, and accuracy of the proposed procedure.     

Conditions for the Light-Traffic Insensitivity to Loss Probability in a GI/G/m/0 Queueing System

A loss queueing system GI/G/m/0 is considered. Let a(x) be a p.d.f. of interarrival intervals. Assume that this function behaves like cx^-1 for small x. Further let B(x) be a d.f. of service time; (1/) be the mean service time. Conditions are derived for the light-traffic insensitivity of the loss probability to the form of B(x) as (/ ) 0. In particular, the condition = 1 is necessary. Estimates for the loss probability are obtained.     

Metallic microgripper with SU-8 adaptor as end-effectors for heterogeneous micro/nano assembly applications

This paper presents design, fabrication, and characterization of easy-to-handle electroplated nickel microgrippers with SU-8 adaptors for heterogeneous micro/nano assembly applications. Two distinctive designs of microgrippers as end-effectors of micro/nano assembly applications have been developed in this work. The first design is 200 m thick electroplated nickel microgripper with a plastic mechanical displacement amplifier that is driven by a piezoelectric actuator. The piezoelectric actuator is capable of creating 5 m displacement which is amplified to 10 m by the plastic mechanical amplifier and finally such displacement generates 50–139 m microgripper tip displacement. The second design is 20 m thick electroplated nickel microgripper embedded in SU-8 adaptor for easy-to-handle operation. The second design is electro-thermally actuated using a set of joule-heated bent beams. With applied actuation voltage in the range of 2–4 V, the microgripper generates tip displacement of 4–32 m. Extensive thermal and mechanical finite element modeling have been carried out and measurement results were compared with the simulation results. Such developed easy-to-handle microgrippers can be used for micro/nano pick-and-place assembly applications.This work was supported by the National Institute of Standards and Technology-Advanced Technology Program (NIST-ATP 70NANB1H3021). The authors would like to thank the members of Design Engineering Group at Zyvex Corporation, Mr. Yohannes Desta from the Center for Advanced Microstructures and Devices (CAMD) at Louisiana State University for the valuable technical discussions, and the members of Micro and Nano Device and Systems (MiNDS) Laboratory and Cleanroom staffs at the University of Texas at Dallas.     

Fabrication of a ZnO piezoelectric micro cantilever with a high-aspect-ratio nano tip

This paper reports on a ZnO piezoelectric micro cantilever with a high-aspect-ratio (HAR) nano tip, which is proposed for a ferroelectric material based nano storage system. The system uses the interaction between the nano tip and a storage medium, and the HAR nano tip is needed to suppress undesirable effects caused by the small gap between the cantilever and the storage medium. The fabrication process for the cantilever with the HAR nano tip consists of three parts: the HAR nano tip formation, the cantilever fabrication, and the bonding/releasing process. The HAR nano tip is formed by the Si deep reactive ion etching for a long shaft and the anisotropic wet etching for a nano tip end. The cantilever is made up of 1 m-thick LPCVD poly-Si layer and 0.2 m-thick Si nitride layer, and has 0.5 m-thick ZnO actuation layer. A final releasing process is followed by an anodic bonding process. The fabricated HAR nano tip has 6 m side length, over 18 m height, and less than 15 nm tip radius, which is built on the 85 m-wide, 300 m-long, and 1.2 m-thick cantilever. The experimental results show a linear behavior with respect to input voltage of 1 to 5 V and the first resonance frequency at 17.9 kHz.     

Mesh Selection for a Nearly Singular Boundary Value Problem

In this paper, we investigate the numerical solution of a model equation u _xx = exp(– ) (and several slightly more general problems) when 1 using the standard central difference scheme on nonuniform grids. In particular, we are interested in the error behaviour in two limiting cases: (i) the total mesh point number N is fixed when the regularization parameter 0, and (ii) is fixed when N. Using a formal analysis, we show that a generalized version of a special piecewise uniform mesh 12 and an adaptive grid based on the equidistribution principle share some common features. And the optimal meshes give rates of convergence bounded by |log()| as 0 and N is given, which are shown to be sharp by numerical tests.     

Deep sub micron high aspect ratio polymer structures produced by hard X-ray lithography

Microfabrication using X-ray lithography is a well established process in many laboratories worldwide. Radiation spectra, mask technology and process conditions are optimized for patterning resist thicknesses of several hundred micrometers with lateral dimensions of a few microns. This article provides first results as to how far these technologies can be extended to form structures with sub-micrometer lateral dimensions in resist layers of a few micrometers thickness. Available equipment and processes of the 2.5 GeV electron storage ring ANKA and the process technology of the Institut für Mikrostrukturtechnik (IMT) in Karlsruhe, Germany, have been applied. An X-ray mask with a 2.7 m Ti-membrane and 20 m thick Au-absorbers is used to expose 1.6 m PMMA resist on silicon wafers. As the smallest features on the mask are 2 m, a double exposure with an intermediate deliberate relative movement between mask and resist generated sub-micron resist test structures. Smallest feature sizes are between 300 and 400 nm. They are not yet limited by diffraction, but by different process conditions that lead to adhesion loss, resist cracking and surface rounding. It has been shown that an intermediate layer of 1.2 m thick polyimide between resist and substrate significantly enhances adhesion and reduces resist cracking. Reducing the beam power impinging onto the sample from typically 21 to 0.4 W leads to a 50% reduction of the surface rounding at the top of the microstructures. To demonstrate the capability to pattern thicker resist layers, first samples with an increased resist thickness of 4.1 m and an aspect ratio of up to 8 were processed. Finally, a metal mesh with 2 m thick Au-absorbers and 900 nm hexagonal holes was applied to pattern showpieces of sub micron features using a reduced electron energy of 1.3 GeV.The high resolution metal mesh was provided by R. Fettig of IMT.     

Context-free text grammars

A text is a triple=(, ₁, ₂) such that is a labeling function, and ₁ and ₂ are linear orders on the domain of ; hence may be seen as a word (, ₁) together with an additional linear order ₂ on the domain of . The order ₂ is used to give to the word (, ₁) itsindividual hierarchical representation (syntactic structure) which may be a tree but it may be also more general than a tree. In this paper we introducecontext-free grammars for texts and investigate their basic properties. Since each text has its own individual structure, the role of such a grammar should be that of a definition of a pattern common to all individual texts. This leads to the notion of ashapely context-free text grammar also investigated in this paper.     

A Genetic Algorithm Based Approach to Optimal Toll Level and Location Problems

The derivative based approach to solve the optimal toll problem is demonstrated in this paper for a medium scale network. It is shown that although the method works for most small problems with only a few links tolled, it fails to converge for larger scale problems. This failure led to the development of an alternative genetic algorithm (GA) based approach for finding optimal toll levels for a given set of chargeable links. A variation on the GA based approach is used to identify the best toll locations making use of location indices suggested by Verhoef (2002).     

Sound and Complete Qualitative Simulation Needs “Quantitative” Filtering

The AI methodology of qualitative reasoning furnishes useful tools to scientists and engineers who need to deal with incomplete system knowledge during design, analysis, or diagnosis tasks. Qualitative simulators have a theoretical soundness guarantee; they cannot overlook any concrete equation implied by their input. On the other hand, the basic qualitative simulation algorithms have been shown to suffer from the incompleteness problem; they may allow non-solutions of the input equation to appear in their output. The question of whether a simulator with purely qualitative input which never predicts spurious behaviors can ever be achieved by adding new filters to the existing algorithm has remained unanswered. In this paper, we show that, if such a sound and complete simulator exists, it will have to be able to handle numerical distinctions with such a high precision that it must contain a component that would better be called a quantitative, rather than qualitative reasoner. This is due to the ability of the pure qualitative format to allow the exact representation of the members of a rich set of numbers.     

A Delay-Averaged Logistic Model

For the equation x(t) = x(t) (1-(1/) _t-- ^t- x(u)du), > 0, > 0, > 0, conditions for the stability of a nonzero stationary solution under small perturbations are determined.     

Recognition of handwritten musical notes by a modified Neocognitron

A neural network for recognition of handwritten musical notes, based on the well-known Neocognitron model, is described. The Neocognitron has been used for the what pathway (symbol recognition), while contextual knowledge has been applied for the where (symbol placement). This way, we benefit from dividing the process for dealing with this complicated recognition task. Also, different degrees of intrusiveness in learning have been incorporated in the same network: More intrusive supervised learning has been implemented in the lower neuron layers and less intrusive in the upper one. This way, the network adapts itself to the handwriting of the user. The network consists of a 13×49 input layer and three pairs of simple and complex neuron layers. It has been trained to recognize 20 symbols of unconnected notes on a musical staff and was tested with a set of unlearned input notes. Its recognition rate for the individual unseen notes was up to 93%, averaging 80% for all categories. These preliminary results indicate that a modified Neocognitron could be a good candidate for identification of handwritten musical notes.     

The effects of a “distinct window” screen design on computer-mediated group decision making

An experiment was performed to test a distinct-window conferencing screen design as an electronic cue of social status differences in computer-mediated group decision-making. The screen design included one distinct window to symbolize high-status, and two nondistinct windows to symbolize low-status. The results indicated that the distinct-window screen design did produce status affects in groups of peers making decisions on judgmental problems. Randomly assigned occupants of the distinct window had greater influence on group decisions and member's attitudes than occupants of nondistinct windows.The authors would like to thank Shyam Kamadolli and Phaderm Nangsue, the programmers who developed the software used in this experiment. We would also like to thank the editor and our three anonymous reviewers for exceedingly helpful comments on an earlier draft of this article.     

Fabrication and preliminary testing of X-ray lenses in thick SU-8 resist layers

Deep X-ray lithography processing of SU-8 negative resist layers with thicknesses of up to 1 mm and physical-chemical properties of SU-8 polymer structures were investigated to find the optimum conditions for the fabrication of X-ray refractive lenses. The exposure was carried out at the ANKA storage ring in Karlsuhe, Germany. Experimental tests of the lenses were performed at the ESRF in Grenoble, France. First lenses showed a gain in the range of 20, a full width at half maximum of the focal spot intensity of approximately 2 m to 3 m and unique radiation stability of the optical characteristics.     

One problem of mathematical optimal control theory

The necessary conditions obtained by the author in a previous study for the extremum of a functional that depends on the control function on the compact set and on a -measurable subset in (where is the ordinary Lebesgue measure) subject to functional equality and inequality constraints are generalized here to an arbitrary continuous Radon measure.Translated from Kibernetika, No. 4, pp. 69–73, July–August, 1990.     

Minimization of norms and logarithmic norms by diagonal similarities

It is a commonly occurring problem to find good norms · or logarithmic norms (·) for a given matrix in the sense that they should be close to respectively the spectral radius (A) and the spectral abscissa (A). Examples may be the certification thatA is convergent, i.e. (A)A<1 or stable, i.e. (A)(A)<0. Often the ordinary norms do not suffice and one would like to try simple modifications of them such as using an ordinary norm for a diagonally transformed matrix. This paper treats this problem for some of the ordinary norms.

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Minimisierung von Normen und Logarithmischen Normen durch Diagonale Transformationen

Zusammenfassung Ein oft vorkommendes praktisches Problem ist die Konstruktion von guten Normen · und logarithmischen Normen (·) für eine gegebene MatrixA. Mit gut wird dann verstanden, daß A den Spektralradius (A)=max |₁| und (A) die Spektralabszisse (A)=max Re _i gut approximieren. Beispiele findet man für konvergente Matrizen wo (A)A<1 gewünscht ist, und für stabile Matrizen wo (A)(A)<0 zu zeigen ist. Wir untersuchen hier, wie weit man mit Diagonaltransformationen und dengewöhnlichsten Normen kommen kann.

     

The dynamic clusters method in nonhierarchical clustering

Given a finite setE R ⁿ, the problem is to find clusters (or subsets of similar points inE) and at the same time to find the most typical elements of this set. An original mathematical formulation is given to the problem. The proposed algorithm operates on groups of points, called samplings (samplings may be called multiple centers or cores); these samplings adapt and evolve into interesting clusters. Compared with other clustering algorithms, this algorithm requires less machine time and storage. We provide some propositions about nonprobabilistic convergence and a sufficient condition which ensures the decrease of the criterion. Some computational experiments are presented.     

Modelling default and likelihood reasoning as probabilistic reasoning

This paper presents a probabilistic analysis of plausible reasoning about defaults and about likelihood. Likely and by default are in fact treated as duals in the same sense as possibility and necessity. To model these four forms probabilistically, a logicQDP and its quantitative counterpartDP are derived that allow qualitative and corresponding quantitative reasoning. Consistency and consequence results for subsets of the logics are given that require at most a quadratic number of satisfiability tests in the underlying prepositional logic. The quantitative logic shows how to track the propagation error inherent in these reasoning forms. The methodology and sound framework of the system highlights their approximate nature, the dualities, and the need for complementary reasoning about relevance.Much of this research was done while at the University of Technology, Sydney, Broadway, NSW, Australia, and some at the Turing Institute, 36 Nth. Hanover Str., Glasgow, Scotland.