Transverse and Longitudinal Bose-Einstein Correlations

We show how a difference in the correlation length longitudinally and transversely, with respect to the jet axis in e+e- annihilation, arises naturally in a model for Bose-Einstein correlations based on the Lund string model. In genuine three-particle correlations the difference is even more apparent and they provide therefore a good probe for the longitudinal stretching of the string field. The correlation length between pion pairs is found to be rather independent of the pion multiplicity and the kaon content of the final state.Comment: 8 page

The Diagonalisation of the Lund Fragmentation Model I

We will in this note show that it is possible to diagonalise the Lund Fragmentation Model. We show that the basic original result, the Lund Area law, can be factorised into a product of transition operators, each describing the production of a single particle and the two adjacent breakup points (vertex positions) of the string field. The transition operator has a discrete spectrum of (orthonormal) eigenfunctions, describing the vertex positions (which in a dual way corresponds to the momentum transfers between the produced particles) and discrete eigenvalues, which only depend upon the particle produced. The eigenfunctions turn out to be the well-known two- dimensional harmonic oscillator functions and the eigenvalues are the analytic continuations of these functions to time-like values (corresponding to the particle mass). In this way all observables in the model can be expressed in terms of analytical formulas. In this note only the 1+1-dimensional version of the model is treated but we end with remarks on the extensions to gluonic radiation, transverse momentum generation etc, to be performed in future papers.Comment: 15 pages, 7 figure

The Lund Fragmentation Process for a Multi-gluon String According to the Area Law

The Lund Area Law describes the probability for the production of a set of colourless hadrons from an initial set of partons, in the Lund string fragmentation model. In this paper we will present a general method to implement the Area Law for a multi-gluon string state. The partonic states are in general given by a perturbative QCD cascade and are consequently defined only down to a cutoff in the energy momentum fluctuations. We will show that our method defines the states down to the hadronic mass scale inside an analytically calculable scenario. We will then show that there is a differential version of our process which is closely related to the generalised rapidity range \lambda, which has been used as a measure on the partonic states. We identify \lambda as the area spanned between the directrix curve (the curve given by the parton energy momentum vectors laid out in colour order, which determines the string surface) and the average curve (to be called the P-curve) of the stochastic X-curves (curves obtained when the hadronic energy-momentum vectors are laid out in rank order). Finally we show that from the X-curve corresponding to a particular stochastic fragmentation situation it is possible to reproduce the directrix curve (up to one starting vector and a set of sign choices, one for each hadron).Comment: 1 title page + 36 pages, 20 figure

Corrosion of fasteners in furfurylated wood : final report after 9 years exposure outdoors

Corrosion of some common fastener materials – mild steel, stainless steel, zinc-coated steel, brass and Sanbond Z (nickel, zinc and chromate) coated steel – has been evaluated after nine years’ exposure outdoors in untreated Scots pine and furfurylated beech and Southern yellow pine (SYP). The furfurylation was carried out according to a process that resulted in approximately 40 % Weight Percent Gain (WPG). The results show that the corrosion of fasteners in furfurylated wood according to the particular specification is considerably more severe than in untreated wood and very similar to the corrosion caused by thermally modified wood. Mild steel and zinc coated steel have been most susceptible. Stainless steel has not been attacked at all and is therefore strongly recommended for furfurylated wood in outdoor applications

About Appropriation of Mobile Applications: The Applicability of Structural Features and Spirit

This paper presents early findings of a study on how users appropriate a computerised mobile system designed to administer service orders. The theoretical lens used was Adaptive Structuration Theory (AST) and focused on Structural Features, Spirit and Appropriation of Structure. In order to accomplish the purpose, two aspects were to be considered: the system’s structure and the user’s appropriation, because the structure of a system affects the appropriation of the system. The study was conducted at a large international company’s Swedish subsidiary operating in heavy industry, machines and transportation. The methods used were a blend of several instruments, such as analysing documents, observations and interviews. These qualitative empirical data were analysed from the perspective of AST. The initial results demonstrate that some of the tested constructs within AST are not applicable to computerised mobile information and therefore some adjustments must be made in AST to fit the mobile computing domain. In order to test these results further, at least two possible strategies lie ahead: either a closer study of the underlying assumptions of Structural Features and Spirit or a broader test of more of the propositions in the AST framework

ENHANCING THE ACCENTUATED FACTOR FRAMEWORK: DEPENDENCIES BETWEEN FACTORS

Handheld computing and mobile information systems are continuously breaking new ground, with an increased importance for business. However, there is evidence that we still have lessons to learn concerning the design of handheld information systems. Handheld information system poses challenges to the designer in the unique properties of handheld technologies and the conditions of use of handheld technologies. Hence, this paper is based on the assumption that handheld information systems has unique properties, and dependencies between properties, that should to be considered in the design of such a system in order to design appropriate information systems for the mobile workforce. The purpose in this paper is to further enhance the usefulness of the Accentuated Factor Framework by describing dependencies between factors in the framework and by this enhance the efficacy in the design process. The theoretical foundation for the paper is the Accentuated Factor Framework, illustrating the unique properties of handheld information systems whereas the expected use settings are the mobile workforce. The empirical data collection was performed via interviews with experienced practitioners, case studies, workshops and studies of software. The Accentuated Factor Framework enhanced with explanatory dependencies between factors provides the opportunity to enhance the design process by reducing the risk of reengineering in design

Revisiting the Role of Common Labeling in a Context of Asymmetric Information: Critique and Extensions

Households in the Western Hemisphere are no longer self sufficient in food production. Viewing the product from the shelves in the grocery store makes it difficult for the consumer to gain insight in the production practices and the quality attributes to the product. Formally, we can describe this as the food products purchased from a grocery store contain less search characteristic. Thus, the consumer cannot determine the quality of the product before the purchase. Instead the food products are characterized to be more of experience (quality is revealed after purchase) or credence characteristic (quality is not revealed even after purchase). Although it is not possible to determine the quality of the packaged food product on the shelves, the issues concerning food product quality are not trivial issues in society. The consumers may boycott not only food that can contain food-borne diseases, but also products that may be considered processed or produced in an unethical or hazardous method for the environment. For example, the linkage between the BSE (Bovin Spongiform Encephalopati) in beef and CJD (Creutzfeld-Jakobs Disease) in humans changed the consumption pattern rapidly in Europe, although not all countries reported occurrence of BSE. Consequently, these issues create incentives for the agribusiness firm to design programs for differentiating food products on basis of the perceived quality aspects. Producers supplying products that appeal to consumers? tastes have incitement to differentiate their products by other means than the pricing mechanism. The differentiation process is carried out through implementation of quality-, or certification programs. Certification programs and organizations like ISO, USDA, FAIRTRADE, CROP-WATCH, PDO, PGI, and Organic Europe, distinguish the product quality in terms of in production process, origin, and other tangible or intangible characteristics. When one or several stages in the food chain join to establish specific quality standards, both producers and consumers might reap economic gains through lowered uncertainty and increased efficiency. On the contrary, there is also a probability that the development of quality programs may further enhance market power, thus offset the potential social gains of the program. In essence, a certification program used by individual stages in the agribusiness chain may lead to vertical or horizontal cooperation (collusion), thus potentially moving away from perfect competition. Marette, Crespi, and Schiavina (1999) observe that agricultural markets are working imperfectly due to asymmetric information, where the consumers lack perfect information about the product quality. The suppliers, on the other hand, have incentives to produce both high and low quality products, although the consumers always prefer the higher quality products. The authors hypothesize that the societal welfare increases if consumers can distinguish between high quality and low quality products. Marette et al test this hypothesis by developing a partial equilibrium model under imperfect information in two elaborate scenarios. The model derived by Marette et al treats labeling in agricultural markets in a delicate way. With the certification scheme in place the consumer are able to distinguish between high and low quality products. However, the certification implies that the high quality producers gain market power. The low quality producers are no longer producing, and the high quality producers can exercise market power by either colluding on quantities, e.g. act as a joint monopolist, or play a quantity setting Nash-Cournot game. Essentially, they show that the societal welfare increases when high quality producers come together in a certification scheme and eliminate asymmetric information. Nevertheless, it is crucial to note that the assumptions build in the partial equilibrium framework drives the results. First, the authors choose to use a demand function, which strictly discriminates high quality from low quality products. Second, the authors? assumes that all firms have access to the same technology and have identical marginal cost of production. Third, the certification scheme does not alter the high quality firms? marginal cost. The objective of this study is to analyze certification programs and its impact on the market structure using a programmable mixed complementarity model. This study continues developing the model from Marette et al. Specifically, this study attempts to relief some of the rather restrictive assumptions on consumer and producer behavior that Marette et al have in their paper. First, the results are not stable for perturbations of the quality parameters, and the cost of certification. The results are not invariant to the cost of certification, and for high cost of certification, both producers and consumers are worse off. Second, constructing a utility function that permits demand for low quality products yield rather interesting results as both low quality and high quality producers can coexist under certification. The (aggregate) output level increases with certification. Nevertheless, the prices charged are vastly different between the certified and non-certified product: the high quality products are seven times expensive than the low quality (uncertified) product. Essentially, with certification the consumers? surplus and low quality producers profit decreases, whereas the high quality producers profit increases. The producer profit for high quality producers increases from .02 to .145 units since they produce more units of output to higher price. The low quality producers on the other hand serve the fringe market with relatively small prices, and their profit decreases to .006 units. When there are no high quality producers on the market, the low quality producers supply the whole market. As the high quality producers increase in number, the Nash-Cournot equilibrium approaches the competitive market outcome, i.e. the market price approaches the firm?s marginal cost. Hence, as the market price approaches zero, each producer supplies an infinite small unit of output, and the total welfare approaches unity. Nevertheless, with certification, there is a clear trend towards the low quality producers becoming fringe suppliers. The qualitative difference between varying the number of high and low quality firms is that the welfare is increasing in the number of high quality producer, whereas the total welfare impact is ambiguous when varying the number of low quality producer. Hence, there are two aggregate types of consumers: one inelastic and another elastic segment of consumers. The inelastic high quality type has a strictly higher willingness to pay for high quality products. The second type, on the other hand, also likes high quality, but is more sensitive to price changes than the high quality type. The study proposes by in large three major revisions to the model developed by Marette et al. First, instead of using a linear utility function that serves as a linear approximation to any utility function it is deemed appropriate to first a concrete representation of consumer behavior using a second order Taylor-series approximation to consumer demand where consumers? decision parameters include prices for both certified and uncertified products. Second, rather than assuming a zero unit of production, it is deemed appropriate to extend the framework by developing an underlying production technology with associate marginal cost. Third and lastly, the current model setup does not allow low quality producers to supply high quality goods. This is a rather abstract assumption, however, and should be extended to allow producers to interchangeably supply both high and low quality products, based on profit maximizing principles rather than subjectively chosen rules.