bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue and Fracture Behavior of a Steel Cord/Rubber Composite
Authors: Rao S. , Daniel I. M. , McFarlane D.
Published: August 2002

The objective of this study was to investigate the fatigue and fracture behavior of steel cord/rubber composites used in tire belts under constant cyclic strain loading. The material was a specially made tire belt layer in the form of rubber sheets reinforced with unidirectional cords consisting of two pairs of twisted steel wires. Failure mechanisms, damage development, and fatigue life were determined for single belt layers with different cord orientations. Tests were conducted at cord angles of 22°, 72°, and 90° degrees with a cyclic strain amplitude of 8.3% at a frequency of 10 Hz. Five different stages of damage development were observed: microcrack initiation, microcrack multiplication, macrocrack formation, slow macrocrack propagation, and fast macrocrack propagation leading to final failure. In the case of the 22° cord specimens, where the in-plane shear component was dominant, damage development consisted of microcrack initiation at the cord/rubber interface, the formation of more microcracks and macrocracks, and finally the formation of a major fatal macrocrack along the cord direction. In the case of 90° cord specimens, dominated by transverse tension, initial microcracks occurred within the cord, they propagated across the thickness of the specimen, and finally a major macrocrack propagated across the entire width of the specimen. The final crack propagated in part along the cord/rubber interface and in part within the cord. In the case of the 72° cord specimens, where both in-plane shear and transverse tension are critical, the initial microcracks occurred within the cord and the final macrocrack along the interface. For the same cyclic strain amplitude, the 90° specimens had the shortest fatigue life, and the 72° specimens had the longest. Additional tests were conducted at different strain amplitudes. The normalized modulus decreases slowly and nearly linearly with normalized fatigue lifetime up to a certain value of the latter, approximately 80% of the normalized logarithmic lifetime, and then it drops sharply. Cyclic strain amplitude also affects the failure mechanisms. High amplitudes produce localized damage, whereas low amplitudes produce dispersed damage. A residual life model was proposed based on stiffness degradation.
Analysis of Heat Transfer Mechanisms in Polyurethane Rigid Foam
Authors: Biedermann A. , Kudoke C. , Merten A. , Minogue E. , Rotermund U. , Ebert H. -P. , Heinemann U. , Fricke J. , Seifert H.
Published: August 2002

Polyurethane closed cell rigid foams have been widely used as insulants in the building and refrigeration industry and also for district heating pipes. It is the special combination of its excellent insulation performance and the mechanical stability due to the foaming process which makes this material very attractive for these applications. The replacement of CFCs, which have been banned as blowing agents since 1993, by hydrocarbons in Europe caused a decrease in the insulation capability of polyurethane (PU) rigid foams. The additional global requirement to reduce energy losses also adds an incentive to search for potentials which would improve the thermal performance of rigid foams. To overcome this problem, the heat transfer within PU rigid foams via
Pharmacotherapeutic Advances in Cardiac Resuscitation: A Review of the Advanced Cardiac Life Support (ACLS) 2000 Guidelines and Their Impact on Pharmacy Practice
Authors: DiGregorio Robert V.
Published: August 2002

The treatment of sudden cardiac death is a challenging area of pharmacotherapy. Despite decades of medication use, outcomes from the treatment of cardiac arrest remain poor. Recent advances in the treatment of cardiac arrest have been incorporated into the American Heart Association’s Advanced Cardiac Life Support 2000 guidelines. A summary and review of these guidelines are presented. Included in the changes to the cardiac arrest treatment guidelines are new medications (amiodarone and vasopressin), new approaches to using medications and the evidence to support these changes. The implications of instituting these new guidelines and strategies for the implementation of the new paradigm are discussed.
Smart Fluid Damping: Shaping the Force/Velocity Response through Feedback Control
Authors: Sims Neil D. , Stanway Roger , Johnson Andrew R. , Peel David J. , Bullough William A.
Published: August 2002

It is now well known that smart fluids [electrorheological (ER) and magnetorheological (MR)] can form the basis of controllable vibration damping devices. With both types of fluid, however, the force/velocity characteristic of the resulting damper is significantly non-linear, possessing the general form associated with a Bingham plastic. In a previous paper the authors showed that by using a linear feedback control strategy it is possible to produce the equivalent of a viscous damper with a continuously variable damping coefficient. In the present paper the authors illustrate an extension of the technique, by showing how the shape of the force/velocity characteristic can be controlled through feedback control. This is achieved by using a polynomial function to generate a set point based upon the damper velocity. The response is investigated for polynomial functions of zero, 1st and 2nd order. It is shown how the damper can accurately track higher order polynomial shaping functions, while the zero-order function is particularly useful in illustrating the dynamics of the closed-loop system.
Wave Propagation in Electromechanical Structures: Induced by Surface-Bonded Piezoelectric Actuators
Authors: Wang X. D. , Huang G. L.
Published: August 2002

Surface-bonded piezoelectric actuators can be used to generate Rayleigh wave for monitoring surface damages of structures. This paper provides an analytical and numerical study to simulate the wave propagation in an elastic half plane with surface-bonded piezoceramic actuators under high-frequency electric loads. Based on a one dimensional actuator model, the wave propagation induced by a single actuator is studied first by using integral transform method and solving the resulting integral equations. The single actuator solution is then implemented into a Pseudo-incident wave method to study the wave propagation induced by multiple actuators. Two aspects of the work are examined. The first is concerned with the determination of the effect of the geometry, the material mismatch and the loading frequency upon the resulting waveform, while the second is concerned with the effect of the interaction between actuators upon the induced wave propagation.
Three Dimensional Micro-Mechanical Modeling of Woven Fabric Composites
Authors: Sheng Shang Zhong , Van Hoa Suong
Published: August 2002

A three dimensional micro-mechanical model is developed by using a three dimensional geometric model and the variational principles for woven fabric composites. The unified modeling strategy starts with developing the three dimensional description of the general woven fabric geometry based on textile processing science, and then a variational potential energy method and a variational complementary energy method are presented respectively to obtain the three dimensional stiffness and compliance matrices associated with the geometric model. This method takes into account the continuity of the yarn without having to discretize it as previous methods. This study results in new closed form of continuous integration formulae to predict 3D elastic properties for woven fabric composites, which can provide a link between micro-structural design and macro-structural analysis. The model is validated by experiments available in the literature [35,36].
Elasto-Plastic Stress Analysis of Aluminum Metal Matrix Laminated Plates with a Circular Hole under Transverse Loading
Authors: Sayman Onur , Aykul Halil
Published: August 2002

Metal-matrix composites provide new materials with superior properties. They give high strength and stiffness and fatigue properties. In this study, a stainless steel fiber reinforced aluminum metal-matrix laminated simply supported plate with a circular hole is loaded transversely. Elastic, elasto-plastic and residual stresses are calculated in the symmetric and/or antisymmetric cross-ply and angle-ply laminated plate for small deformations by using finite elements method. Load steps are chosen 200, 400 and 600. Isoparametric quadrilateral element with nine node is developed for the elasto-plastic analysis. Metal-matrix composite laminated plate is manufactured by using moulds under the action of 30 MPa and heating up 600°C. The first-order shear deformation theory is used in the study.
Gellan Film as an Implant for Insulin Delivery
Authors: Li Jing , Kamath Kalpana , Dwivedi Chandradhar
Published: August 2002

Gellan gum is an anionic polysaccharide produced by the aerobic fermentation of Pseudomonas elodea in batch culture. Gellan undergoes calcium-induced cross-linking to form a three-dimensional network, and this property makes it particularly attractive for the incorporation of biological moieties such as proteins. In this study, a procedure for the preparation of gellan films was developed and optimized, and the characteristics of these films were investigated. In addition, the effects of the concentration of each ingredient in gellan films and in vitro release behavior of fluorescein isothiocyanate dextran from these films was examined.

This film device was implanted for insulin delivery in diabetic rats. The blood glucose levels of the diabetic rats implanted with insulin-loaded films were about half of those implanted with blank films, and this therapeutic effect of insulin could last for one week. Both in vitro and in vivo studies indicated that the gellan film could be an ideal candidate in the development of protein delivery systems.
Structural Integrity of Quasi-Isotropic Composite Laminates with Embedded Optical Fibers
Authors: Skontorp Arne
Published: August 2002

Embedded optical fibers are considered for use in structural monitoring of aircraft fiber-reinforced composite structures, such as wings and stabilizers. However, it is crucial that these optical fibers do not themselves significantly degrade the load-bearing ability of the composite. An embedded optical fiber, having a diameter an order of magnitude larger than the reinforcing fibers of a composite, alters the microstructure of the composite and gives rise to perturbations in the stress fields.

The present study is an experimental investigation into how the introduction of embedded optical fibers affects the failure modes of a composite laminate. Quasi-isotropic composites with two realistic embedded optical fiber configurations were investigated, i.e. closely spaced optical fibers and optical fiber loops. Closely spaced optical fibers may be necessary near connectors and in some sensing schemes making use of multiple sensors. Similarly, changing the direction of an optical fiber is necessary in some sensing schemes and in cases where a single optical fiber is to be used to monitor a larger area.

Static tensile and compressive experiments, as well as fatigue experiments, were conducted to study effects of the embedded optical fibers. Extensive post-failure fractographic examinations were carried out to identify if any failure modes were related to the presence of the optical fibers. Both room temperature dry, and high temperature (90'C) wet conditions were considered.

It was found that the embedded optical fibers did not initiate fiber-dominated failure in the composite, and therefore did not cause any significant deterioration of the composite strength, neither in tension nor in compression. However, the damage evolution process was affected by the optical fibers as they were preferred sites for matrix cracking, especially in the hot-and-wet condition. In fatigue, damage grew from the edges of the specimens, not from the optical fibers, and the fatigue life was not affected by the optical fibers.
Physical Properties and Blood Compatibility of Poly(Urethaneamideimide) and Poly(Urethaneureas) with Aliphatic Side Chains
Authors: Calusinski G. , Masiulanis B. , Jurkowski P.
Published: August 2002

The synthesis, tensile strength, thermostability and hydrophilicity of the poly(urethaneamideimide) and the poly(urethaneureas) with N-aliphatic side chains are presented. These elastomers were compared in blood compatibility with determination of the common indices and with immunologic tests of the P-thromboglobulin activity and the total activity of the complement.
Analysis and Parametric Study of Non-Circular Pressurized Sandwich Fuselage Cross Section Using a High-Order Sandwich Theory Formulation
Authors: Thomsen Ole Thybo , Vinson Jack R.
Published: August 2002

Results obtained as part of a design study regarding a non-circular pressurized sandwich fuselage cross section are presented. The originating problem is associated with preliminary studies for the “Global Range Transport” envisaged by the “New World Vistas” program of the United States Air Force. The modeling and analysis is conducted using a high-order sandwich theory formulation in which the elastic response of each face laminate is accounted for, including bending-stretching coupling, and including the transverse flexibility of the core material. The paper includes a presentation of the high-order sandwich theory approach adopted for the analysis of the fuselage section, including the formulations for flat and curved sandwich panels. The paper is concluded by presentation of the results of a parametric study, which includes the effects on the structural response of varying the sandwich panel mid-plane asymmetry, the core properties, and the radius of curvature of the fuselage cross section corners.
Influence of Moisture Absorption on Mechanical Properties of Wood Flour-Polypropylene Composites
Authors: Stark Nicole
Published: August 2002

Wood-plastic composites are being examined for a greater number of structural-type applications that may be exposed to different environments, some of them adverse. This paper discusses the influence of moisture absorption on the mechanical properties of wood flour-polypropylene composites. Composites filled with 20% or 40% wood flour (by weight) were placed in different environments, removed periodically, and tested for moisture content and mechanical properties. The composites filled with 20% wood flour (20%WF) absorbed moisture in all the environmental exposures, but no significant degradation of properties was observed. The 40%WF composites absorbed more moisture than did the 20%WF composites. The flexural properties of composites subjected to a water bath and to 90% relative humidity were lower than the flexural properties of the other composites. Tensile properties and notched impact strengths decreased only for composites placed in a water bath. Unnotched impact strengths did not change significantly with absorption of moisture.
The Inclusion of In-Plane Stresses in Delamination Criteria
Authors: Fenske Matthew T. , Vizzini Anthony J.
Published: August 2002

Delamination is characterized as the failure of the interply resin-rich region. The interply resin layers are modeled and the six component stress state is determined using a finite element analysis. The Modified von Mises Delamination Criterion using both the in-plane and interlaminar stresses is developed and applied to the average stress state within 1.75 ply thicknesses of the edge. The MVMDC shows good correlation to experimental data as well as to other criteria. TheMVMDCis not sensitive to the thickness of the interply resin layer. Instead it is merely the presence of such a layer and the stresses that result in the layer that can indicate delamination failure of a laminate. Thus consideration of the full stress state in the failure of the interply resin layer is valid and indicates the potential for interaction between the in-plane loading and delamination.
Thermosetting Cellular Elastomers Reinforced with Carbon Black and Silica Nanoparticles
Authors: Galezewski Alexander , Wilusz Eugene
Published: August 2002

Closed-cell materials were prepared from two types of thermo-setting elastomers: carboxyacrylonitrile-butadiene copolymer (nitrile) and iso-butylene-isoprene copolymer (butyl) filled with nanometer-size particles of carbon black and silica for the purpose of reinforcing. A chemical-blowing agent, p, p′-oxybis(benzene-sulfonyl hydrazide), which decomposes rapidly between 153° and 160°C with a release of nitrogen, and a low-pressure compression molding process were used in the fabrication. The resulting cellular materials had a density range of 0.7 to 0.8 g/cc. A balance between the cure and the blow rates is needed to provide satisfactory processing. The curing characteristics of the formulations were studied with an oscillating disk rheometer. Viscoelastic properties were gathered with a dynamic mechanical analyzer over a -90° to 80°C temperature interval. Glass transition temperatures were determined with a differential scanning calorimeter. Other properties, such as thermal stability, abrasion resistance, tensile strength, tear strength, and hardness, were also determined. The data indicate that the cellular nitrile materials should excel in applications where wear-durability is needed, with nitrile materials containing carbon black being more abrasion resistant than those reinforced with silica; butyl cellular materials, on the other hand, either with carbon black or silica, should excel in applications where good flexibility and energy dissipation at temperatures below -40°C are desired.
Modeling of Process Induced Residual Stresses in Resin Transfer Molded Composites with Woven Fiber Mats
Authors: Golestanian Hossein , El-Gizawy A. Sherif
Published: August 2002

Cure-dependent mechanical properties are used in finite element-based models to determine process-induced residual stresses and deformations in composite parts. The complete cure cycle in resin transfer molding process is modeled in a series of sub steps. The composite mechanical properties are specified in each step according to the composite cure history. The cool down stage after the composite cure is also analyzed. The effects of resin shrinkage on the development of residual stresses and deformations are investigated as well. Case studies involving composite parts with woven carbon and fiberglass mats and epoxy resin are presented to demonstrate the effectiveness of the developed models. Residual stresses were found to be compressive throughout the investigated composite parts. Resin shrinkage resulted in a decrease in residual stresses. The present study establishes the bases for quantifying the combined effects of thermomechanical and thermochemical responses of the material on the development of process induced residual stresses and deformations in resin transfer molded composites.
Active Cabin Noise and Vibration Control for Turboprop Aircraft Using Multiple Piezoelectric Actuators
Authors: Grewal A. , Zimcik D. G. , Hurtubise L. , Leigh B.
Published: August 2002

The Active Structural Acoustic Control (ASAC) technique was applied to reduce propeller-induced noise and vibration in the passenger cabin of the deHavilland Dash-8 turboprop aircraft. Piezoceramic elements were used for structural actuation while velocity feedback of the fuselage was achieved through the use of accelerometers. Three actuators comprised of segmented piezoelectric elements were designed with the objective of reducing the noise and vibration levels at the propeller Blade Passage Frequency (BPF). Twelve accelerometers were grouped to effectively form three sensors. Second order classical compensators were designed for each of the three dominant control loops in order to achieve high gain at the BPF, rendering the closed-loop system insensitive to disturbances at the control frequency. The propeller acoustic field on the port side of the aircraft was simulated in a laboratory using a speaker-ring consisting of four loudspeakers. The control system was tested using this acoustic field, producing noise attenuation as high as 28 dB in the interior, and fuselage vibration reduction as high as 16 dB.
Damping Property of Epoxy Matrix Composite Beams with Embedded Shape Memory Alloy Fibers
Authors: Ju Dong-Ying , Shimamoto Akira
Published: August 2002

In this present paper, an epoxy matrix composite beam with embedded SMA fibers of TiNi alloy are applied to improve the damping capacity of a beam in free vibration. In particular, an experimental method to measure the damping capacity of a beam structure using current control is proposed here. In addition, an analytical model of frequency vibration of a composite beam based on thermo-metallo-mechanical behavior due to electric heating in the SMA fiber is also proposed. The analytical results are compared with obtained experimental frequency data. Calculated and measured results illustrate the effects of current on the damping and frequency values.
Topographic Study of Shape Memory Alloy Wires Used as Actuators in Smart Materials
Authors: Gabry B. , Thiebaud F. , Lexcellent C.
Published: August 2002

The aim of this work is to characterize the interface between a shape memory alloy wire (SMA) and a resin epoxy matrix. More precisely, we want to associate the roughness of the wire with the adhesion between the fiber/matrix. The effect of various surface treatments applied to SMA NiTi wires on the quality of the fiber/matrix interface is presented and discussed. First, a profilometric study is carried out on the different wires. The parameters, which characterize the vertical distribution of the roughness and the wire morphology, are determined. The topographic study reveals that the surface treatments which are applied strongly modify the external surface of the wire. In the second part of this work the adhesion fiber/matrix is quantified by using a pull-out test. These experimental results are analyzed and compared with the roughness parameters. This comparative study enables us to determine the wire morphology which will guarantee the best adhesion fiber/matrix. The roughness parameters are sufficient for the choice of the wire which will be embedded into the resin.
Smooth Peas, Wrinkled Peas and Garbanzo Beans in Production of Sweetened Paste
Authors: Klamczynska B. , Czuchajowska Z. , Baik B. K.
Published: August 2002

Smooth peas, wrinkled peas and garbanzo beans were evaluated for production of sweetened paste with regard to yield and quality. Wrinkled peas required longer cooking times (6.5 h and 5.5 h) than smooth peas (2.5 h) and garbanzo beans (3.5 h). The yield of fine cotyledon particles which were used for production of sweetened paste was 65.8% for garbanzo bean cv. Sanford, 63.2% for smooth pea cv. Columbian, but only 33.7% for wrinkled pea cv. Alsweet and 30.1% for wrinkled pea cv. Bonito. Scanning electron microscope (SEM) pictures revealed that the fine fraction consisted of single, intact cells, while the coarse fraction, which was removed with hulls during paste preparation, was made of clusters of cells with extensive connective tissue. SEM results provided evidence that connective tissue prevented separation of cells during the process and is responsible for formation of coarse fraction, which did not pass through the screen during the paste production process. The fine fraction for all legumes had higher starch content than the coarse fraction, but lower protein, ash and free lipids content. The fine fraction contained 50.1% and 59.2% of particles smaller than 106 µ m for garbanzo bean cv. Sanford and smooth pea cv. Columbian, respectively, but only 25.5% for wrinkled pea cv. Bonito and 18.7% for wrinkled pea cv. Alsweet. Therefore, smoothness and melting rates were highest in smooth peas and lowest in both wrinkled pea cultivars. There were no significant differences in overall acceptance between pastes prepared from smooth peas, wrinkled peas and garbanzo beans and commercial azuki paste.
Penetration Failure Mechanisms of Armor-Grade Fiber Composites under Impact
Authors: Lee B. L. , Walsh T. F. , Won S. T. , Patts H. M. , Song J. W. , Mayer A. H.
Published: August 2002

The penetration failure mechanisms of“armor-grade” fiber-reinforced composites with very low resin content were assessed under transverse impact loading in comparison with those of dry reinforcing fabrics. Failure of dry fabrics consisted of the successive fracture of individual yarns along the periphery of the penetrating head as well as the movement of yarns slipping off from the penetrator. In contrast, the principal yarns in the composites, which faced the penetrating head, failed to carry the load mostly through fracture due to the constraint of the resin matrix and the reduced yarn mobility. As a result, the composites absorbed more energy than the fabrics. The ratio of the number of broken yarns in the fabrics to that of the composites correlated quite well with the corresponding ratio of energy absorbed, confirming that fiber straining is responsible for most of the energy absorption in penetration failure. Numerical modeling was utilized to show that yarn slippage in the fabrics results in a smaller effective penetrator radius leading to a decrease in energy absorption capacity with equal penetrator masses. Although the resin matrix itself did not absorb significant amounts of energy, it certainly had an indirect effect on the energy absorption capacity of composites by influencing the number of yarns broken. Stiffer resin matrix prevented the yarn movement to a greater degree and thereby forced the penetrator to engage and break more yarns. Up to the thickness of 3 mm, the dependence of the kinetic energy for full perforation of composites on the laminate thickness was close to the case of ductile monolithic materials such as polycarbonate or aluminum but in less linear fashion. The deviation from the linearity was attributed to a unique mode of tensile failure of armor-grade composites in which a critical level of kinetic energy for full perforation is lowered by the mobility of yarns.
Utilization of Polyurethane Foam Scrap as a Sole Binder for Recycling of Automotive Interior Trim Products
Authors: Gebreselassie Girma M. , Wolf Harold G. , Sendijarevic Vahid , Anjum Qavi , Klempner Daniel , Frisch Kurt C.
Published: August 2002

A number of rear-seat-to-back-window trim panels (CHMSL covers) were manufactured by thermoforming ground polyurethane-cored headliner (UROCOR) scrap with PMDI as a binder with and without water as a component of the composite mixture utilizing industrial equipment at a Lear plant in Holland, Michigan. Unexpectedly, it was found that UROCOR scrap which contains a significant amount of flexible and semi-rigid polyurethane foam can be thermoformed without addition of PMDI. In order to confirm that the polyurethane scrap can be used as a binder, the polyurethane seating foam scrap was successfully recycled as the sole scrap and in 75/25 and 50/50 mixtures with resinated fibers.
Blood-Compatible Materials: A Perspective
Authors: Sharma Chandra P.
Published: August 2002

The interrelation of physicochemical properties with biological interactions at the interface to understand blood compatibility of materials in contact with blood has been discussed. The bioethics for human experimentation and future research outlook has been projected.
TYPE INFERENCE FOR FIRST-CLASS MESSAGES WITH FEATURE CONSTRAINTS
Authors: MÜLLER MARTIN , NISHIMURA SUSUMU
Published: August 2002

We present a constraint system, OF, of feature trees that is appropriate to specify and implement type inference for first-class messages. OF extends traditional systems of feature constraints by a selection constraint x  z, "by first-class feature tree" y, which is in contrast to the standard selection constraint x[f]y, "by fixed feature" f. We investigate the satisfiability problem of OF and show that it can be solved in polynomial time, and even in quadratic time if the number of features is bounded. We compare OF with Treinen's system EF of feature constraints with first-class features, which has an NP-complete satisfiability problem. This comparison yields that the satisfiability problem for OF with negation is NP-hard. Further we obtain NP-completeness, for a specific subclass of OF with negation that is useful for a related type inference problem. Based on OF we give a simple account of type inference for first-class messages in the spirit of Nishimura's recent proposal, and we show that it has polynomial time complexity: We also highlight an immediate extension of this type system that appears to be desirable but makes type inference NP-complete.
LANGUAGES FOR REACTIVE SPECIFICATIONS: SYNCHRONY VS ASYNCHRONY
Authors: SHYAMASUNDAR R. K. , RAMESH S.
Published: August 2002

Asynchronous and Synchronous languages have been in use for the specification of reactive systems. One of the main distinguishing features of these two classes lies in the way nondeterminism is used for the specification of programs. From this viewpoint, we analyze CSP (a typical asynchronous language) and ESTEREL (a synchronous language). The synchronous language Esterel is based on the notions of determinism, input nondeterminacy and parallelism whereas CSP is built on the notions of nondeterminism, concurrency and distribution. The main objectives of the study are to assess:

• The role of nondeterminism in the specification of the behaviour and realization of programs: A clear distinction between local and global nondeterminism enables us to distinguish between implementational nondeterminism and environmental/input nondeterminism. The results in this direction would enable one to achieve observable determinism where the implementational choices can be hidden and thus, analyze the program behaviour with reference to the real environmental nondeterminism in the specification. This leads to a proper refinement of specifications and aids in deriving distributed implementations of finite state transition systems that are not necessarily deterministic.

• The implementability of asynchronous languages through synchronous languages. The implementability of asynchronous languages in synchronous languages not only provides a realistic implementation but also provides higher level abstractions (such as multi-process interactions) for reactive specifications using features such as broadcast, interrupts, exception handling mechanisms etc.
FINDING SMALL EQUIVALENT DECISION TREES IS HARD
Authors: ZANTEMA HANS , BODLAENDER HANS L.
Published: August 2002

Two decision trees are called decision equivalent if they represent the same function, i.e., they yield the same result for every possible input.

We prove that given a decision tree and a number, to decide if there is a decision equivalent decision tree of size at most that number is NP-complete. As a consequence, finding a decision tree of minimal size that is decision equivalent to a given decision tree is an NP-hard problem.

This result differs from the well-known result of NP-hardness of finding a decision tree of minimal size that is consistent with a given training set. Instead our result is a basic result for decision trees, apart from the setting of inductive inference.

On the other hand, this result differs from similar results for BDDs and OBDDs: since in decision trees no sharing is allowed, the notion of decision tree size is essentially different from BDD size.
Automatic Evaluation of the Links–Gould Invariant for all Prime Knots of up to 10 Crossings
Authors: De Wit David
Published: August 2002

This paper describes a method for the automatic evaluation of the Links–Gould two-variable polynomial link invariant (LG) for any link, given only a braid presentation. This method is currently feasible for the evaluation of LG for links for which we have a braid presentation of string index at most 5. Data are presented for the invariant, for all prime knots of up to 10 crossings and various other links. LG distinguishes between these links, and also detects the chirality of those that are chiral. In this sense, it is more sensitive than the well-known two-variable HOMFLY and Kauffman polynomials. When applied to examples which defeat the HOMFLY invariant, interestingly, LG 'almost' fails. The automatic method is in fact applicable to the evaluation of any such state sum invariant for which an appropriate R matrix and cap and cup matrices have been determined.
ON OPTIMAL SETTING OF CONTROL LIMITS FOR GEOMETRIC CHART
Authors: XIE M. , GOH T. N. , KURALMANI V.
Published: August 2002

Control charts based on geometric distribution have shown to be very useful in the monitoring of high yield manufacturing processes and other applications. It is well known that the traditional 3-sigma limits will give too many false alarms and the probability limits should be used. This paper shows that the average time to alarm may even increase at the beginning when the process is deteriorated. A new procedure is established for the setting of control limits so that the average run length is maximized when the process is at the normal level. Hence the chart sensitivity can be improved. For the derivation of the control limits in this new procedure, a simple adjustment factor is suggested so that the probability limits can be used after the adjustment.
AN ENUMERATION METHOD FOR THE MINIMAL PATHS OF NETWORK SYSTEMS
Authors: FARD NASSER S. , LEE HUNHEE
Published: August 2002

This paper presents a technique for the enumeration of minimal paths of two-terminal networks. The method is developed based on the multiway tree structure that has been used widely for sorting and searching. The new technique does not require any matrix multiplication; it only requires a connection matrix. Furthermore, this simple method has capability of evaluating the reliability of a network after a topological modification, without going through the entire evaluation process. The method is compared with the existing algorithms, and the application simplicity of this method is demonstrated through examples.
BILATERAL ASYMPTOMATIC PISIFORM AND HAMATE COALITION — A CASE REPORT
Authors: El-Morshidy A. F. , Rabia F. , Mukaimi A.
Published: August 2002

Abnormal anatomy of carpal bones is uncommon. We report on a multitrauma patient that, was initially misdiagnosed as scaphoid dislocation, which later was proven to be pisiform hamate coalition.
RECURRENT SYNOVIAL CHONDROMATOSIS OF THE INDEX FINGER CASE REPORT AND LITERATURE REVIEW
Authors: Kumar A. , Thomas A. P.
Published: August 2002

We report a case of synovial chondromatosis of the proximal interphalangeal joint of the dominant right index finger with a follow-up of four years. The lesion recurred within a year of complete excision of the fibrous sac containing cartilaginous nodules. Despite early recurrence and extensive calcification around the proximal phalanx, no malignant changes were noted on histological examination. The patient remains asymptomatic for two years after the second operation.
Conceptualising and Measuring Urban Competitiveness in Major English Cities: An Exploratory Approach
Authors: Deas Iain , Giordano Benito
Published: August 2002

Recent years have witnessed considerable academic debate with regard to the ways in which urban competitiveness can best be conceptualised and measured. In this paper we draw on these theoretical discussions in an attempt to interrogate the dynamics of competitiveness. We report on research to develop indicators to explore the relationship between sources (the initial stock of assets in a city) and outcomes of competitiveness (the result of attempts to exploit these assets by firms) across a sample of urban areas. We argue that urban asset bases provide a strong predictor of competitive performance in English cities, but that this general pattern is interrupted by some cities for which competitive outcomes are stronger or weaker than might be expected in light of underlying asset bases. The study findings provide some tentative methodological suggestions, augmenting the limited volume of empirically focused work regarding the means by which different aspects of the contested concept of competitiveness might best be measured. The findings also illustrate the differing competitive fortunes of major English cities and provide pointers with regard to priorities for policymakers in moulding and managing urban asset bases.
Ecological Modernisation as a Framework for Sustainable Development: A Case Study in Sweden
Authors: Fudge Colin , Rowe Janet
Published: August 2002

Sweden has long been an acknowledged leader in Europe in terms of its commitment to environmental protection linked with ecologically based technological innovation, and to social democratisation and high levels of welfare provision. Following the 1992 UN Conference on Environment and Development in Rio, Agenda 21 was received warmly as codifying an existing determination to pursue development which may be sustainable. However, over the last decade the economy has come under increasing pressure from globalisation and social change. Although the environmental agenda remains strong, a schism seems to be developing with key socioeconomic drivers. The Swedish government has responded with a policy framework of ecological modernisation, through which it hopes to regain the high ground economically, environmentally, and socially. We report on a study for the Swedish Research Councils in which we explore aspects of this national policy framework, and how it is being interpreted in selected projects in Sweden's three major cities and two case-study towns. We examine tensions in integration and implementation; and argue that Swedish norms may favour an unduly ‘expert’ and even ‘technocorporatist’ view of sustainable development which its current ecological modernisation programme does little to address. We discuss the cultural and institutional change which may be required if the current conception of ecological modernisation is to deliver development which is sustainable.
The Space of the Surface
Authors: La Marche Jean
Published: August 2002

In this paper I examine how notions of the surface are being reconstituted in architectural theory and practice. Specifically, I contrast how modernist-influenced theory treated surfaces with how some architectural theorists today are beginning to think about them. Whereas modernist theory saw surfaces as dedicated to the expression of interior volume, recent interactive technologies such as ‘smart walls’ mean that surfaces no longer are fixed but can, instead, be changed in ways that are beyond the control of the architects who designed the structures of which they are a part. This means that surfaces are much less predictable and much more subject to transformation by individual users than in the past. Such a technological revolution, I argue, is ‘de-authorizing’ architecture as it is understood in conventional, professional, and disciplinary terms, and is bringing about new conceptions of time and space in architectural practice.
Environmental Impacts of Urban Sprawl: A Survey of the Literature and Proposed Research Agenda
Authors: Johnson Michael P
Published: August 2002

‘Urban sprawl’ has recently become a subject of popular debate and policy initiatives from governmental bodies and nonprofit organizations. However, there is little agreement on many aspects of this phenomenon: its definition, its impacts—both nonmonetary and monetary—economic and policy models that predict the presence of sprawl, and decision-support models that could assist policymakers in evaluating alternative development schemes that may have characteristics of sprawl. In particular, there is relatively little research on urban sprawl that focuses specifically on measurement and modeling of environmental impacts. The purpose of this paper is twofold: to survey the literature on urban sprawl, with a focus on environmental aspects and to identify a research agenda that might result in a greater number of anaytical tools for academics and practitioners to characterize, monetize, model, and make planning decisions about sprawl.
Maps, Measurements, and Landmines: The Global Landmines Crisis and the Politics of Development
Authors: Mather Charles
Published: August 2002

The humanitarian impact of landmines was well publicised during the 1990s. The efforts by nongovernmental organisations during this decade led to an international treaty banning the production, stockpiling, and use of antipersonnel landmines. Since the late 1990s a series of important changes have occurred in the management and coordination of humanitarian demining, which are associated with the emergence of a new development discipline for those affected by landmines. I suggest that these changes have important implications for the exercise of power. I also argue, however, that this development discourse is being repoliticised through a process of ‘cadastral politics’.
A General Framework for Estimation and Inference of Geographically Weighted Regression Models: 1. Location-Specific Kernel Bandwidths and a Test for Locational Heterogeneity
Authors: Páez Antonio , Uchida Takashi , Miyamoto Kazuaki
Published: August 2002

Geographically weighted regression (GWR) has been proposed as a technique to explore spatial parametric nonstationarity. The method has been developed mainly along the lines of local regression and smoothing techniques, a strategy that has led to a number of difficult questions about the regularity conditions of the likelihood function, the effective number of degrees of freedom, and in general the relevance of extending the method to derive inference and model specification tests. In this paper we argue that placing GWR within a different statistical context, as a spatial model of error variance heterogeneity, or what might be termed locational heterogeneity, solves these difficulties. A maximum-likelihood-based framework for estimation and inference of a general geographically weighted regression model is presented that leads to a method to estimate location-specific kernel bandwidths. Moreover, a test for locational heterogeneity is derived and its use exemplified with a case study.
Location of Adult Children as an Attraction for Black and White Elderly Primary Migrants in the United States
Authors: Liaw Kao-Lee , Frey William H , Lin Ji-Ping
Published: August 2002

By using information on state of birth in the 1990 Census of the United States, the authors create a variable serving as a proxy for the distribution of adult children in 1985. This variable is then used in a two-level nested logit model to explain the 1985 – 90 interstate primary migration of elderly black people and elderly white people within the context of environmental amenities and other factors. The main findings are as follows. First, the location of adult children as well as environmental amenities are among the most important attractions for the primary migration of elderly black and white people. Their effects are stronger on white people than on black people. Because a relatively high proportion of out-migrated black adult children are located in the industrial states of the snowbelt and a relatively high proportion of their white counterparts are located in high-amenity states of the sunbelt, the attractions of adult children and environmental amenities are more prone to counter each other for elderly black people and to reinforce each other for elderly white people. Consequently, the net transfers of elderly primary migrants are small and somewhat oriented toward the snowbelt for black people, but they are voluminous and strongly oriented toward the sunbelt for white people. Second, the attraction of adult children is strong for not only the unmarried but also the married elderly, although it is somewhat stronger for the widowed aged 75 years and over. This finding can be taken as evidence for the viability of the ‘modified extended family’ system, which not only legitimizes the out-migration of adult children for career advancement but also encourages the migration of elderly parents to be close to their non-coresident children for services that require continual proximity. It also suggests that the elderly do not have a strong tendency to delay their migration toward non-coresident children until the loss of a spouse or becoming very old.
The Influence of Location and Distance on the Supply of Business Advice
Authors: Bennett Robert J , Smith Colin
Published: August 2002

The authors examine the geographical relations between small business clients and their external suppliers of business advice. The analysis is based on the stratified random sample survey carried out by the ESRC Centre for Business Research in 1999. The analysis demonstrates the importance of localisation in a simplistic sense: a large percentage of advisors are drawn from within 10 km of the client, and almost all from within 50 km for most types of advisor. There are important differences between types of advisors, with public sector advisors, chambers of commerce, and enterprise agencies being the most localised. However, the high degree of localisation is shown to be chiefly dependent on the agglomeration benefits of the accessibility and size of centres in which advisors are located. The general pattern of client – advisor relations is demonstrated to be modelled accurately by a standard spatial interaction model. A key finding is that the spatial pattern of the location of the supply of advisors, particularly the size of the business centres in which they are located, is a key determinant of choice and must be taken into account simultaneously with any role of distance which influences demand, in order to explain the pattern of choice of business advisors. This suggests that small business support policies should be focused chiefly towards small and medium-sized enterprises that have difficulty in accessing major supply sources by virtue of their locations; that is, they should be focused on rural and more peripheral areas.
Requiem for a National Ideal? Social Solidarity, the Crisis of French Social Security, and the Role of Global Financial Markets
Authors: Clark Gordon L
Published: August 2002

It is well appreciated that demographic trends threaten the integrity of continental European systems of social security. For France these trends imply a long-term financial crisis as well as a crisis of confidence in national economic and social institutions. The payment of social security entitlements is a recurrent and largely unresolved political issue; proposals for comprehensive reform are heavily contested, involving political interests willing to go to the streets. At the same time, governments' incremental changes in benefit formula and accounting have discounted the expected value of future retirement benefits. In this paper, I begin by sketching the logic of pay-as-you-go social security, identifying the basic economic principles and social institutions that sustain such systems. One goal of the paper is to articulate the economic and philosophical roots of social solidarity and the importance of the state as the custodian of the social contract between generations. In doing so, I sketch out the French ideal: a coherent social security system based upon self-reinforcing mutual obligations and institutions. A second goal of the paper is to show how and why the French social security system became unsustainable. Demographic trends have been exacerbated by the use of the retirement system as a form of labour-market compensation policy, thereby undercutting both its financial and its political legitimacy. The third goal of the paper is to indicate how and why global financial markets may play a significant role in resolving the crisis of social security. Basically, I dispute the argument that national systems of social security will persist into the future; internal inconsistencies and the possible defection of those not served by such institutions combined with external opportunities may overturn the past. By making this argument, I do not mean to suggest that the Anglo-American model is necessarily superior to social security systems based on social solidarity. Rather, my point is entirely argumentative: solemn incantations that defend the past, whatever their best intentions, may simply reinforce the nature and significance of the pending crisis.