The neural net of neural network research

In this paper we discuss the limits and potentials of bibliometric mapping based on a specific co-word analysis. The subject area is neural network research. Our approach is a simulation of expert assessment by offering the reader a narrative of the field which can be used as background information when reading the bibliometric maps. The central issue in the applicability of bibliometric maps is whether these maps may supply additional intelligence to users. In other words, whether such a bibliometric tool has an epistemological value, in the sense that it ecriches existing knowledge by supplying unexpected relations between specific pieces of knowledge (synthetic value) or by supplying unexpected problems (creative value). We argue that sophisticated bibliometric mapping techniques are indeed valuable for open new avenues to study science as a self-organizing system in the form of a neural network like structure of which the bibliometric map is a first-order aproximation. In that sense, this paper deals with the neural net of neural network research as our bibliometric techniques in fact mimic a connectionistic approach.     

On the equivalence of integral formulations for certain exterior and interior boundary value problems in mechanics

A procedure is given which relates various linear boundary value problems. It is shown that a relations exists between certain exterior and interior problems. For computational purposes an interior problem is more desirable. The method is restricted by the requirement that the Neumann function, or its equivalent, be known for the problem being considered.Dedicated to Professor Menahem M. Schiffer, with reverence and gratitude     

A bibliometric profile of top-scientists a case study in chemical engineering

We carefully selected a group of chemical engineering scientists internationally recognized as top-scientists in their field. A method has been developed to systematically compare bibliometric characteristics of these top-scientists with an average scientist in chemical engineering. This method also includes citation-analysis of books and proceedings. The results show a very clear bibliometric profile. First, top-scientists references are more numerous and, fourth, they concern more recent literature. Our fifth findings is that the journals used by top-scientists for their publications are representative for the field of chemical engineering as a whole. But they differ in specific aspects significantly from the average journal structure in chemical engineering: the published work of top-scientists is both general as well as more specialistic than the average work in chemical engineering.     

Systematic derivation of contour integration formulae for laplace and elastostatic gradient BIE's

A complete set of contour integrands is derived for the primary BIE's of elastostatics and potential flow. Because of surface-independent properties of vector potentials, these apply to nonplanar surfaces and can be differentiated at the fixed point, producing contour integrands for both the so-called hypersingular and Cauchy singular parts of the gradient BIE. The results are applicable to far field, near field and on surface cases. Numerical examples demonstrate exact agreement with surface quadrature, and contour plots are given showing variation of the hypersingular integrands in on surface cases.     

A note on the utility of international publication data

This note focuses on a possible limitation of international publication data as a measure of research activity. It is argued that differences in the pressure and/or capacity to publish may exist between countries which would necessitate the standardization of publication data on a country basis. The argument is supported by statistical tests performed on data recently utilized to measure agricultural scientific research activity.     

Measuring national output in physics: Delimitation problems

In a study of the Dutch publication output in physics we tested methods of delimitating fields by journal categories in theScience Citation Index (SCI) compared to the classification of individual publications into subfields in the subject specific databasePhysics Briefs (PHYS). Different methods of measuring national scientific output were compared as well. In this paper we report the main findings on these issues, based on a study of six selected subfields in physics. The main conclusion with respect to the use of different classification methods is that in most of the selected fields in physics the method which delimitates fields by journal categories yields an incomplete picture of the output of a country. Particularly because this method neglects a considerable number of articles published in general journals. With respect to different methods of counting publications it was corroborated by the Dutch data inPhysics Briefs that: 1. so-called integer counted world shares are very much influenced by the degree of internationalisation and 2. first author counting gives a satisfactory approximation of fractional counting. Citation indicators based on first author counting, however, may be distorted in fields with a large fraction of international co-authored publications.     

The structure and superconducting behavior of some V-Al binary alloys and of ternary ‘β-W’ alloys based on the V-Al system

Results are given for the structure and superconducting behavior of binary V-Al alloys and of -W ternary alloys based on V₃X-V₃Al where X=Si, Ge, Sn, Ga, and Sb. No -W phase was observed in the binary V-Al system at 25 at. % Al. Instead the alloys were bcc. However, some evidence was found for a martensitic transformation in alloys rapidly quenched from high temperatures. Solid solubility of Al in the -W phase V₃X was restricted as would be expected from the absence of a binary -W V₃Al phase. The superconducting transition temperatures varied systematically with composition in a manner consistent with the phase structure of the alloys.     

A frequency distribution function derived from a stochastic model considering human behaviors and its comparison with an empirical bibliometric distribution

Simon's stochastic model is extended to take both selective and random factors in human behaviors into consideration. The resulting distribution function is of non-steadystate type and approaches the Poisson distribution at the random limit while the Yule (or Zipf) distribution at the selective limit. A comparison of the theoretical distribution with an observed one for classification items indexed in a bibliorgraphic database is made. The results give some insights into statistical features of a class in which the total number of elements is fixed.     

Two Outfalls in an Estuary: Cooperative Pollution Minimization

Two outfalls, each with given tidally averaged discharge rates, are discharging into the same narrow (rapidly mixed) estuary. The lowest achievable concentration peak (in position and time) for the principal contaminant species is attained with an all or nothing discharging policy. The discharge rate is either all that is allowed by concentration peak or is nothing. The nothing regime corresponds to the water from the less vulnerable outfall with the relatively small discharge load, which would otherwise have had the greatest pollution impact at the more vulnerable outfall. Constructive (exact) algorithms are presented for the all or nothing partition and for the cooperative discharge rates at the two outfalls.     

Mapping co-word structures: A comparison of multidimensional scaling and leximappe

The LEXIMAPPE method and Multidimensional Scaling (MDS) are discussed as methods to visualize (map) characteristics of structures of word-occurrence (co-word) relations. Utilization of MDS is proposed as an alternative mapping method able to circumvent problematic features of LEXIMAPPE maps of the total co-word structure. A comparison of both methods on the same real-life co-word matrix demonstrates topological advantages of an extended MDS-mapping.     

Cutting, by ‘pressing and slicing,’ of thin floppy slices of materials illustrated by experiments on cheddar cheese and salami

Why it is easier to cut with even the sharpest knife when pressing down and sliding than when merely pressing down alone is explained. A variety of cases of cutting where the blade and workpiece have different relative motions is analysed and it is shown that the greater the slice/push ratio given by (blade speed parallel to the cutting edge/blade speed perpendicular to the cutting edge), the lower the cutting forces. However, friction limits the reductions attainable at the highest . The analysis is applied to the geometry of a wheel cutting device (delicatessan slicer) and experiments with a cheddar cheese and a salami using such an instrumented device confirm the general predictions.     

A bibliometric study of differential item functioning

Summary This study presents a bibliometric analysis of scientific output in the area of Differential Item Functioning (DIF), the aim being to offer an overview of research activity in this field and characterise its most important aspects and their evolution over the last quarter of the 20th century, thus providing data regarding the basis on which this activity is being developed at the beginning of the 21st century. The analysis makes use of the Web of Science database, the search being restricted to articles published between 1975 and 2000 and which contain the terms differential item functioning, DIF or item bias. The various analyses focus on the presentation of publication frequencies and percentages, as well as on the application of Bradfords law of scattering and Lotkas law.     

An incremental stress-based constitutive modeling on anisotropic damaged materials

An incremental form of anisotropic damage constitutive equation is proposed both for brittle and ductile materials. Based on the concept of irreversible thermodynamics that damage processes are history independent coupled with irreversible energy dissipation, two types of definition for damage representation are established, known as damage tensor D and damage strain tensor ^d, to describe constitutive responses of damaged materials. A state variable coupled with damage and other observable state variables, i.e. ^d, is formulated separately from other internal variables and defined as an equivalent damage variable. A constitutive relation due to damage is finally formulated by introducing damage flow potential function employing the theory of irreducible integrity bases. A clear physical representation based on theoretical foundations and rigorous mathematical arguments of the conventional damage models defined in terms of damage effect tensor M(D) is also elucidated. Validity of the proposed model is verified by comparing with the formulations of conventional damage effect tensor. A plastic potential function coupled with damage is also introduced by employing the anisotropic plastic flow theory, so that the proposed damage model can be applied to characterize a wide range of damage problems of practical engineering interest.     

Combining make to order and make to stock

In inventory control and production planning one is tempted to use one of two strategies: produce all demand to stock or produce all demand to order. The disadvantages are well-known. In the make everything to order case (MTO) the response times may become quite long if the load is high, in the make everything to stock case (MTS) one gets an enormous inventory if the number of different products is large.In this paper we study two simple models which combine MTO and MTS, and investigate the effect of combining MTO and MTS on the production lead times.     

Principal Rings and their Invariant Factors

In this article we put forward a new look at the theory of principal and Invariant-Factor rings, with a view toward facilitating the formalization, automation, and archiving of results and their proofs. We take an elementary and constructive approach: standard techniques such as prime ideals and factorization of elements are avoided, and determinant constructions are minimized. Using such computationally friendly methods, the main existence and uniqueness results on invariant factors for a f.g. torsion module are derived, and several new algebraic constructions and results are found. The lattice of principal integral ideals for any commutative Bézoutian ring is explicitly constructed based on a first-order proof overlooked in the literature, together with a proof that this lattice is distributive. A Lagrange quotient theorem for finitely generated modules over any principal ring is stated for the first time. A very constructive new proof is given that a principal ring has the Hermite property, so is also an Invariant-Factor ring. A calculus that is needed in the ideal lattice, naturally yields a number of formulas valid for a function lattice.     

Convolutional Codes of Goppa Type

A new kind of Convolutional Codes generalizing Goppa Codes is proposed. This provides a systematic method for constructing convolutional codes with prefixed properties. In particular, examples of Maximum-Distance Separable (MDS) convolutional codes are obtained.This research was partially supported by the Spanish DGI through research project BFM2003-00078 and by the Junta de Castilla y León through research projects SA071/04 and SA032/02.     

Effect of thickness on the fracture characteristics of fetal membranes

The mechanical characteristics of the chorioamniotic membrane were evaluated with a new burst test apparatus by rupturing 35 specimens that were taken from a sample of seven afterbirths. Strength, stiffness, toughness, and ductility were measured. Mechanical characteristics did not change significantly with variation in thickness. While ductility should not correlate with thickness, the lack of a significant increase in strength, stiffness and toughness with an increase in thickness is most unusual and requires an explanation. Subsequently, an additional experiment, which was designed to ascertain the mechanical stability of membrane specimens with prolonged exposure to air, showed a dramatic increase in stiffness as membranes were allowed to dry. The increase in stiffness indicates that strength and toughness also increase with drying, provided that ductility remains constant. Thus, the degree of hydration of the membrane, which is reflected in thickness, regulates mechanical characteristics. The increase in the water content of certain amniotic layers has a lubricating effect on the amnion-chorion interface. This lubrication increases as term approaches. Thus, hydration must increase as gestation progresses, and strength, stiffness, and toughness must decrease until the membrane is weak enough to rupture at the end of gestation. Thus, hydration must increase as gestation progresses, and strength, stiffness, and toughness must decrease until the membrane is weak enough to rupture at the end of gestation.     

Response to the discussion by I.V. Rokach of the paper entitled: “Analysis of the dynamic responses for a pre-cracked three-point bend specimen”

The following response to the discussion of the above mentioned paper is divided into two parts: (1) a response to the issue of our comparison of the apparent period of specimen oscillation, , and the natural vibration period of a cracked specimen, T, and (2) a verification of the applicability of our model to short time-to-fracture tests, which Rokach has questioned, due to a lack of knowledge of Hopkinson bar techniques.     

Cohesive crack models for semi-brittle materials derived from localization of damage coupled to plasticity

Based on discontinuous displacement approximation of the continuum and shear band kinematics, two cohesive crack models are derived within the constitutive framework of coupled damage and plasticity. The models employ the Rankine fracture criterion, and the model parameters are determined from a uniaxial tension test (mode I cracking). Bifurcation analysis is used in order to diagnose critical directions along which the crack will gradually develop and propagate. These directions depend on the actual stress state and are kept fixed after fracture has initiated, whereby a fixed crack model is obtained. A discrete crack strategy is employed at the finite element implementation in the sense that interfaces (that represent the cohesive crack) are introduced along inter-element boundaries. This implementation strategy calls for gradual realignment of the mesh as a key feature of the algorithm. Numerical results from the analysis of mixed mode fracture in a notched concrete plate are presented.     

On some new variational formulations and finite element models in classical elastoplasticity

Summary The paper deals with the systematic development of variational methods and associated finite element schemes for the approximate analysis of elastoplastic continua. The major difference between these novel models and existing ones consists in treating the yield condition as an a posteriori (natural) constraint and not as an a priori (essential) constraint. The advantages of this approach over existing ones are pointed out and discussed from a theoretical and a computational standpoint as well.With 1 Figure