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Lubrication and friction are the core processes in cold strip rolling, which are the key links to realizing the stable production of high‐quality strips, reflecting country advanced level in rolling technology. This review investigates the crucial properties of lubrication and friction in cold strip rolling by analyzing the mechanism, characterization methods, and influencing factors. The lubricant forms an oil film on the surface of rolls and strips based on the lubrication dynamics and tribology theory, changing the asperity contact state in the loaded roll gap, leading to changes in friction characteristics. Oil film thickness and coefficient of friction (COF) are crucial parameters for characterizing and judging the characteristics of lubrication and friction, theoretical calculations have become the core analytical method, and the study of the measurement method is still a great challenge. Parameters like rolling speed and oil viscosity affect the lubricant distribution and asperity contact in the loaded roll gap, changing the lubrication and friction state. The influence of parameters is strongly linked to the experimental or rolling environment. Prospective research trends on lubrication and friction in cold strip rolling are presented based on the status of research on lubrication and friction characterization. [ABSTRACT FROM AUTHOR]

The glides of curling stones to the button on curling-sheet ice are composed of three segments: (i) an initial high-speed travel characterized by mild decelerations (and minor curls); (ii) a slower-speed segment with visibly greater rates of deceleration (and curl); and (iii) an abrupt end-of-travel. It is proposed here that these three travel segments correlate with the three well-known frictional regimes of tribology's Stribeck curve: (i) a hydrodynamic (wet) frictional regime in which, at high speeds, the generation of frictional heat from shearing stress within a lubricating water film is sufficient to melt ice and fully isolate the rock's running-band from the ice surface, i.e., from mutually abrasive contact; (ii) a mixed frictional regime where, with ever-more severe friction and ever-stronger deceleration and thus ever-lower speeds, the generation of frictional heat is progressively less and the lubricating water film becomes ever-thinner, allowing rock and ice asperities to cut ever-more abrasively into their opposing surfaces; and (iii) a totally dry, highly abrasive frictional regime in which, at very low speeds, lubrication ends because of the lack of sufficient frictional heat to maintain a water film and thus the rock's advance comes to an abrupt end. [ABSTRACT FROM AUTHOR]

The behavioral literature suggests that minor frictions can elicit desirable behavior without obvious coercion. Using closures of ATMs in a densely populated city as an instrument for small frictions to physical banking access, we find that customers affected by ATM closures increase their usage of the bank's digital platform. Other spillover effects of this adoption of financial technology include increases in point-of-sale transactions, electronic funds transfers, automatic bill payments and savings, and a reduction in cash usage. Our results show that minor frictions can help overcome the status quo bias and facilitate significant behavior change. This paper was accepted by David Sraer, finance. Supplemental Material: Data and the online appendix are available at https://doi.org/10.1287/mnsc.2023.4972. [ABSTRACT FROM AUTHOR]

Behavioral scientists have begun to research 'sludge,' excessive frictions that make it harder for people to do what they want to do. Friction is also an important concept in transaction-cost economics. Nevertheless, sludge has been discussed without explicit referral to transaction costs. Several questions arise from this observation. Is the analogy to friction used differently in both literatures? If so, what are the key differences? If not, should we develop the concept of sludge when the well-established literature on transaction costs already exists? This conceptual article shows that sludge and transaction costs are related, but distinct, concepts, and that the literature on sludge can benefit from incorporating elements from transaction-cost research. For example, we suggest defining sludge as aspects of the choice architecture that lead to the experience of costs, organize sludges using a typology inspired by the transaction-cost literature, highlight specificity, uncertainty, and frequency as important determinants of the 'sludginess' of choice architecture, and show that sludge audits can be conducted using methods developed in the transaction-cost literature. [ABSTRACT FROM AUTHOR]

This paper studies the implications of business cycle frictions for the diffusion of permanent changes in automation. Incorporating task‐based production in different versions of the New Keynesian model reveals considerable short‐run implications. Price‐distorting nominal rigidities amplify the labor displacement and attenuate the productivity and welfare gains of automation during the transition to the new equilibrium. They exacerbate the falls in the labor income share, the job finding probability, the value of long‐term contracts, and labor market tightness. The inflation response follows a J‐curve. Frictions in capital supply and wage rigidities amplify the labor displacement and attenuate the productivity gains too. [ABSTRACT FROM AUTHOR]

We develop a new housing search index (HSI) extracted from online search activity on a limited set of keywords related to the house-buying process. We show that HSI has strong predictive power over subsequent changes in house prices, both in-sample and out-of-sample and after controlling for the effect of commonly used predictors, and relate our findings to models of search-induced frictions. Our results imply that search data can be used as an early indicator of where the market is going. This paper was accepted by David Sraer, finance. Funding: We acknowledge support from the Danish Finance Institute and from the Independent Research Fund Denmark [Grants DFF 7024-00020B and DFF 7015-00017B]. Supplemental Material: The online appendix and data are available at https://doi.org/10.1287/mnsc.2023.4672. [ABSTRACT FROM AUTHOR]

Copyright of Hallazgos: Revista de Investigaciones is the property of Ediciones USTA and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In practice, firms face a number of scarce innovation projects. They choose one towards which to direct their effort, but do not coordinate these choices. This gives rise to coordination frictions. This paper develops an expanding-variety endogenous growth model to study the implications of these frictions for growth and welfare. We find that the coordination failure generates a number of foregone innovations and reduces the economy-wide research intensity. Both effects decrease the growth rate. This creates a general equilibrium effect that endogenously amplifies the fraction of wasteful simultaneous innovation. Furthermore, formalizing the coordination frictions uncovers a novel link between the "stepping on toes" and "standing on shoulders" externalities—their magnitudes are endogenously determined through the ratio of firms to innovation projects. We find that the "stepping on toes" externality is larger for all parameter values. [ABSTRACT FROM AUTHOR]

This paper combines an input–output model and a novel regional labour market matching model in order to identify potential bottlenecks in regional labour markets resulting from shocks in demand caused by the energy transition. Identifying these bottlenecks provides relevant information for policymakers to determine in which regions and industries policy intervention in labour markets may be needed to ensure a smooth transformation. We analyse the effects of a shock that is illustrative for the energy transition in the Netherlands. Our results indicate that the aim of the Dutch government to substantially reduce greenhouse gas emissions may, at least in the short run, be hampered by bottlenecks in labour markets. [ABSTRACT FROM AUTHOR]

Although leveraged exchange-traded funds (ETFs) are popular products for retail investors, how to hedge them poses a great challenge to financial institutions. We develop an optimal rebalancing (hedging) model for leveraged ETFs in a comprehensive setting, including overnight market closure and market frictions. The model allows for an analytical optimal rebalancing strategy. The result extends the principle of "aiming in front of target" introduced by Gârleanu and Pedersen (2013) from a constant weight between current and future positions to a time-varying weight because the rebalancing performance is monitored only at discrete time points, but the rebalancing takes place continuously. Empirical findings and implications for the weekend effect and the intraday trading volume are also presented. This paper was accepted by Agostino Capponi, finance. Funding: M. Dai acknowledges support from the National Natural Science Foundation of China [Grant 12071333], the Hong Kong Polytechnic University [Grant P0039114], and the Singapore Ministry of Education [Grants R-146-000-243/306/311-114 and R-703-000-032-112]. H. M. Soner acknowledges partial support from the National Science Foundation [Grant DMS 2106462]. C. Yang acknowledges support from the Chinese University of Hong Kong [Grant 4055132 and a University Startup Grant]. Supplemental Material: Data and the online supplement are available at https://doi.org/10.1287/mnsc.2022.4407. [ABSTRACT FROM AUTHOR]

It has been about three decades since Mozambique transitioned from a brutal civil war and one-party rule to peace and democracy. Although Mozambique has not relapsed into another large-scale civil war, sustainable peace and democracy in the country have become ever more elusive. In 2013, military clashes between Renamo and the Frelimo-led government resumed and prompted a new peace process, whilst poverty and inequalities are rampant, authoritarianism is on the rise, and an Islamic insurgency erupted in the northern region. Accordingly, while some scholars still praise Mozambique's post-war peacebuilding as successful, others have claimed that peacebuilding failed. This article evades the binary of successful or failed liberal peacebuilding in Mozambique. Instead, it applies the concepts of friction and hybridity to offer an alternative way of reading the 30 years of peace (building) in Mozambique. The article argues that frictions in values and interests between the international/liberal peacebuilders and local (non-liberal) elites have resulted in a negative and unstable hybrid peace, that is, a precarious peace in Mozambique. [ABSTRACT FROM AUTHOR]

Several structural results for the set of competitive equilibria in trading networks with frictions are established: The lattice theorem, the rural hospitals theorem, the existence of side‐optimal equilibria, and a group‐incentive‐compatibility result hold with imperfectly transferable utility and in the presence of frictions. While our results are developed in a trading network model, they also imply analogous (and new) results for exchange economies with combinatorial demand and for two‐sided matching markets with transfers. [ABSTRACT FROM AUTHOR]

This paper studies arbitrage-free financial markets with bid-ask spreads whose super-hedging prices are submodular. The submodular assumption on the super-hedging price, or the supermodularity usually assumed on utility functions, is the formal expression of perfect complementarity, which dates back to Fisher, Pareto, and Edgeworth, according to Samuelson (J Econ Lit 12:1255–1289, 1974). Our main contribution provides several characterizations of financial markets with frictions that are submodular as a consequence of a more general study of submodular pricing rules. First, a market is submodular if and only if its super-hedging price is a Choquet integral and if and only if its set of risk-neutral probabilities is representable as the core of a submodular non-additive probability that is uniquely defined, called risk-neutral capacity. Second, a market is representable by its risk neutral capacity if and only if it is equivalent to a market, only composed of bid-ask event securities. [ABSTRACT FROM AUTHOR]

This article explores how experiences related to daily mobility negatively impact and shape the way women in Accra engage with and perceive the city they live in and the opportunities it provides for them. In Accra, being mobile is crucial for women's ability to work and provide for their families and for their identity as modern and hardworking women. However, when traveling through the city women are faced with severe traffic congestion, a volatile public transport system and gendered confrontations, which create frictions in their daily mobility. These frictions make it difficult for women to plan their everyday lives and their immediate futures, they reduce their ability to move alone or after dark and challenge their conceptions of gender equality and rights to the city. Underscoring the socio-material structures that shape mobility, I argue that women's everyday mobility in Accra is circumscribed by these frictions, which impact their lives on multiple levels and ultimately construct a mistrust of, and disillusionment with, the city's ability to provide for its citizens. This perspective on mobility contributes to an improved understanding of urban life and urban identities as shaped through mobility and the circumstances created by the specific transport system. [ABSTRACT FROM AUTHOR]

With the closure of the border with then-Macedonia in early 2016, it was foreseeable that Greece would become the "last station" for a large number of refugees. Flanked by the agreement between Turkey and the European Union of March 2016, Greece underwent a profound transformation from a transit country to a recipient country. Through a new regulation, the Emergency Support Instrument, initially activated by the European Commission 2016–2019, international humanitarian aid operations were supported for the first time in the EU. The article analyzes the resulting frictions on the basis of empirical field research and a broad literature review. While frictions similar to those in other non-European humanitarian operations exist, specific peculiarities due to the operation taking place in an austerity-ridden member state of the EU must also be noted. [ABSTRACT FROM AUTHOR]

We construct experimental economies, populated with human subjects, with different institutional features that have a structure and incentives similar to a dynamic stochastic general equilibrium model. An experimental economy with monopolistic competition and no menu costs generates empirical patterns that are closer to the U.S. economy than simulations or the other experimental environments. We observe greater welfare and output in a setting where goods are perfect substitutes compared to treatments with monopolistic competition. Discretionary human central bankers produce lower output and welfare compared to an automated instrumental rule. Menu costs reduce inflation volatility. [ABSTRACT FROM AUTHOR]

We investigate the links between firm-level total factor productivity (TFP) growth and technical efficiency change, and their implications on firm-level stock returns. We estimate TFP growth of US firms between 1966 and 2015 and decompose TFP growth into returns to scale, technical progress, and technical efficiency change components. We show that most of the variation in TFP growth is explained by variation in technical efficiency change. Moreover, we examine the effects of important macro- and micro-level factors on inefficiency as well as its asset pricing implications. We find that low-efficiency firms are more vulnerable to a wide class of aggregate economic shocks, and the well-known five stock return anomalies (Fama and French in J Financ Econ 116(1):1–22, 2015) are more pronounced among those firms. Our results also emphasize the role of macroeconomic determinants of efficiency, and the stability effects of many useful policy targets on firm-level TFP. [ABSTRACT FROM AUTHOR]

Copyright of Revista Iberoamericana de Turismo is the property of Revista Iberoamericana de Turismo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We investigate the effects of banks' operating costs on allocations and welfare in a low interest rate environment. We introduce an explicit production function for banks in a microfounded model where banks employ labor resources, hired on a competitive market, to run their operations. In equilibrium, this generates a spread between interest rates on loans and deposits, which reflects the underlying monetary policy and the efficiency of financial intermediation. In a deflation or low‐inflation environment, equilibrium deposits yield zero returns. Hence, banks soak up labor resources to offer deposits that do not outperform idle balances, thus reducing aggregate efficiency. [ABSTRACT FROM AUTHOR]

Global political economists have highlighted how states and corporations enact environmentally destructive practices and create commodities that legitimate those same activities. Linking macroeconomic systems to situated micropractices, how a by-product of US ethanol production, distillers' grains, has been transformed into a global animal feed commodity is explored in this study. The effect of this transformation is to legitimate both biofuel production and intensive livestock operations, while delegitimating the resistant 'food vs. fuel' argument proposed by critics of biofuel production. Yet the process of creating an animal feed commodity from industrial waste is also problematic, characterized by the creation of multiple 'frictions of consumption', concerning the product's storability, flowability and digestibility. Bioscience experts work to overcome these frictions; yet these frictions may also offer opportunities for those seeking to resist these environmentally destructive industries. [ABSTRACT FROM AUTHOR]

The physical properties of the four samples of okra pods from Suez (S), Kafer Elsheigh (K), Mansoura (M), Dakahlia (D) were presented. However, there are no detailed studies concerning the physical dried okra fruit. Geometric properties, gravimetric properties and frictional properties were determined at 86.69% (S), 84.67% (K), 87.65% (M) and 85.83% (D) moisture content. For gravimetric properties, the values of mass, one thousand okra pods mass, true, bulk densities, porosity and density ratio of four okra pod varieties were established between 0.40-0.53 g, 294.72-502.94 g, 359.88-392.50 kg/m³, 266.76-301.90 kg/m³, 70.20-84.69% and 15.31-29.80%, respectively. For frictional properties, the values of coefficients of statistic and kinetic friction on 10 structural surfaces and angle of repose were established in between 29.18-44.88, 0.46-0.77 and 22.29-37.77 degree, respectively. These properties are necessary for the design of equipments for harvesting, processing, transportation, cleaning, sorting, sizing, separating and packing. [ABSTRACT FROM AUTHOR]

We show how frictions and continuous transfers jointly affect equilibria in a model of matching in trading networks. Our model incorporates distortionary frictions such as transaction taxes and commissions. When contracts are fully substitutable for firms, competitive equilibria exist and coincide with outcomes that satisfy a cooperative solution concept called trail stability. However, competitive equilibria are generally neither stable nor Pareto‐efficient. [ABSTRACT FROM AUTHOR]

We use a competitive search (price-posting) framework to experimentally examine how buyer information and fairness perceptions affect market behavior. We observe that moving from zero to one uninformed buyers leads to higher prices in both 2 (seller) x 2 (buyer) and 2 x 3 markets: the former as predicted under standard preferences, the latter the opposite of the theoretical prediction. Perceptions of fair prices--elicited in the experiment--are a powerful driver of behavior. For buyers, fair prices correlate with price responsiveness, which varies systematically across treatments and impacts sellers' pricing incentives. For sellers, fair prices correlate with underpricing, which also varies systematically across treatments. [ABSTRACT FROM AUTHOR]

Copyright of Social & Cultural Geography is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the canonical model of frictionless markets, arbitrage is usually taken to force all trades of homogeneous goods to occur at essentially the same price. In the real world, however, arbitrage possibilities are often severely restricted and this may lead to substantial price heterogeneity. Here we focus on frictions that can be modeled as the bargaining constraints induced by an incomplete trading network. In this context, the interplay among the architecture of the trading network, the buyers' valuations, and the sellers' costs shapes the effective arbitrage possibilities of the economy. We characterize the configurations that, at an intertemporal bargaining equilibrium, lead to a uniform price. Conceptually, this characterization involves studying how the network positions and valuations/costs of any given set of buyers and sellers affect their collective bargaining power relative to a notional or benchmark situation in which the connectivity is complete. Mathematically, the characterizing conditions can be understood as price-based counterparts of those identified by the celebrated Marriage Theorem in matching theory. [ABSTRACT FROM AUTHOR]

The paper proposes the analysis of the main drivers of the economic growth in Central and Eastern Europe, in three emerging countries: Czech Republic, Hungary and Poland, with a development stage similar with that of Romania. Given the vulnerabilities of the Central and Eastern Europe region at the beginning and during the recent global economic and financial crisis, there is an increased interest to identify the models that can describe the principalcharacteristics of the Central and Eastern Europe macroeconomic variables: gross domestic product, investment, wages and salaries, inflation, hours worked, consumption and themonetary variable- interest rate. Moreover, another scope is to analyze the frictions that describe the evolution of the seven data series, as the stochastic dynamic of the macroeconomic model is driven by orthogonal structural shocks. [ABSTRACT FROM AUTHOR]

The directed search model (Peters 52(5):1117-1127, ) is static; its dynamic extensions typically restrict strategies, often assuming price or match commitments. We lift such restrictions to study equilibrium when search can be directed over time, without constraints and at no cost. In equilibrium, trade frictions arise endogenously, and price commitments, if they do exist, are self-enforcing. In contrast to the typical model, there exists a continuum of equilibria that exhibit trade frictions. These equilibria support any price above the static price, including monopoly pricing in arbitrarily large markets. Dispersion in posted prices can naturally arise as temporary or permanent phenomenon despite the absence of preexisting heterogeneity. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper offers new insights into Beveridge curve analysis by modelling the unemployment-vacancy rate relationship within a Markov regime-switching environment in which the probabilities of curve-shifting are determined endogenously by shift factors. Shift factors include structural factors such as labour market participation and net migration, while cyclical variables include GDP growth, the real rate of interest, and labour productivity. This approach enables us to estimate regime-specific parameters and to assess the role played by these factors in influencing the transition probabilities of switching between regimes. Using New Zealand data, we show that increases in the participation rate have shifted the Beveridge curve inward, while increases in net migration have shifted the curve outward. [ABSTRACT FROM AUTHOR]

This paper is analyzing the impact of the construction element position of ship winch drum on the effects of torque transmission by friction in the mechanization welding process. The driving and driven wheels (construction elements) were examined for the general case of the load distribution. Based on this examination, the construction of the device that should provide the reliable torque transmission and the movement of the drum in the process of its welding are proposed. This construction is characterized by a high level of flexibility and ability to change the friction torque based on changing drum position in regard to the driving and driven wheels (construction elements). With this new construction, problems related to the movement synchronization are avoided, unlike the all previously known constructions of this type, which lead to the positive impact on the wear intensity of friction gears. [ABSTRACT FROM AUTHOR]

At beginning, the kinematic model and dynamic model of a differential mobile robot (DMR), and the dynamic model of left‐ and right‐wheel DC motors are combined to be the controlled system. The control inputs of the proposed controlled system are the input voltages for the left‐ and right‐wheel motors. The (indirect) outputs are the two‐dimensional (2D) position and orientation of a DMR. Owing to the under‐actuated characteristic, the direct reference input (i.e. two desired motor currents) using the first sliding surface is designed, so that the 2D position and orientation of the DMR are simultaneously controlled by two motor currents (i.e. the direct output). On the other hand, the second sliding surface is designed as the linear dynamics of tracking error of motor currents. Under completely (or partially) known frictions and uncertainties, the hierarchical sliding‐mode under‐actuated control with suitable conditions is designed, such that two motor currents asymptotically track two desired motor currents, respectively. Then the asymptotic tracking for the 2D position and orientation of a DMR is achieved. The simulations for various trajectories, completely and partially known frictions and uncertainties, and control parameters are presented to evaluate the effectiveness and robustness of the proposed method. [ABSTRACT FROM AUTHOR]

When creating competing models of economic fluctuations, researchers typically introduce frictions in their models aiming at replicating the observed movements in the data. This paper implements a business cycle accounting procedure for the Swedish economy. Both the 1990s and the 2008 recessions are given special focus. Evidence is provided for properties that structural extensions to the business cycle model need to have in order to replicate the movements in the data. Distortions to the labor market and movements in total factor productivity are the most determinant features to be modeled with respect to real variables as well as deviations from a Taylor rule for interest rate setting, though the latter plays little role for both the 1990s and the 2008 recessions. The distortions share a structural break during the 1990s crisis but not during the recent one. [ABSTRACT FROM AUTHOR]

This article explores how the Toba, an indigenous group in the North of Argentina, shape places and an urban subjectivity in the frictions of their mobility between villages, the urban barrio (neighborhood), and the periurban bush. I argue that the experience of Toba moving to the city is better understood as frictions between the Toba desire to progress in the city, the organization of difference in space, and their multiple movements “back” to the villages. In addition, I analyze their contemporary hunting trips, which take urban Toba to the nearby bush, as a mobility that shapes a form of indigeneity engaged with access to both the city center and the bush. This practice confronts them with ranch owners and police but reconnects the barrio and the bush by traversing them. If frictions emerge between forces that trigger movement and forces that slow that movement down, in the frictions of mobility the Toba have at once shaped their position in the city and overflowed its limits. [ABSTRACT FROM PUBLISHER]

In a Dutch self-study project, five teacher educators studied their own practices with three experienced researchers as the facilitators of the group. These facilitators also conducted a self-study of the whole project, particularly focusing on helping and hindering aspects of the facilitation process. In this article, we report two of the teacher educators' self-studies, one in the context of foreign language teaching and the other in the context of deepening student teacher reflection. In addition, we describe the design and outcomes of the self-study carried out by the facilitators. We discuss what we have learnt from each of the three studies, but we also emphasize going beyond the story, drawing conclusions that may be of interest to the broader community of teacher educators. We work to deepen the awareness of the people we work with, but an important outcome of the self-studies is also deepening our own awareness of certain phenomena in our practices, which are elaborated in this article. Another common thread in each of the studies is the impact a self-study can have on the professional identity of the individual researchers. [ABSTRACT FROM AUTHOR]

Joseph Alois Schumpeter’s approach to the phenomenon of unemployment differs strongly from the traditional classification with its strict distinctions between frictional, cyclical and structural unemployment. By relating these three categories to his theory of creative destruction, Schumpeter collapsed them all into one: technological unemployment. In our paper, we provide a systematic overview and discussion of Schumpeter’s varied writings on unemployment, from 1908 to 1954. We compare his view with the positions of some of his contemporaries, such as Wicksell, Hicks, Beveridge and Keynes. Finally, we discuss to what extent recent writers, such as Aghion, Howitt and Caballero, have integrated Schumpeter’s approach into modern macroeconomics. [ABSTRACT FROM AUTHOR]

We investigate the effects of disinflation policies on key macroeconomic variables. Using euro area data and structural vector autoregressions (SVARs), we identify disinflation shocks as the only shocks that drive nominal variables to a lower long-run level. We find that in the immediate aftermath of a disinflation shock, the euro area enters in a persistent recession. We use these dynamic responses to estimate a DSGE model with imperfect information about the disinflation shock. We find that both nominal and real frictions and monetary policy gradualism have played a prominent role in the recessionary effect of disinflation shocks. Conversely, allowing for imperfect credibility does not yield a better fit, except when we shut key model's frictions down. [ABSTRACT FROM AUTHOR]

Start-ups of new firms are important for economic growth. However, start-up rates differ significantly between countries and within regions of the same country. A large empirical literature studies the reasons for this and endeavours to identify the regional determinants of start-ups. By contrast, there is a much smaller theoretical literature attempting the formal modelling of the start-up process within a region. In this article, we seek to contribute to this small literature by introducing a general theoretical model of the entrepreneurial start-up process. The model links start-ups to economic growth and can be applied to understand growth in a regional context. We derive a number of propositions which fit the stylised facts from the empirical literature: (i) growth in the regional economy is driven by an expansion in the number of start-up firms supplying intermediate goods and services; (ii) improvements in human capital will improve the rate of start-ups; (iii) improvements in the relative rates of return to entrepreneurs and business conditions will raise start-up rates; (iv) an increase in regional financial concentration will reduce the start-up rate in a region; and (v) increased agglomeration/urbanisation in a region has an a priori ambiguous effect on start-up rates. [ABSTRACT FROM AUTHOR]

This work introduces a set-theoretic foundation of deterministic bilateral matching processes and studies their properties. In particular, it formalizes a link between matching and informational constraints by developing a notion of anonymity that is based on the agents’ matching histories. It also explains why and how various matching processes generate different degrees of “informational isolation” in the economy. We illustrate the usefulness of our approach to modeling matching frameworks by discussing the classical turnpike model of Townsend. [ABSTRACT FROM AUTHOR]

ABSTRACT The ability of prisms to effectively dissipate contact stress at the surface will influence wear rates in teeth. The aim of this investigation was to begin to quantify the effect of prism orientation on surface stresses. Seven finite element models of enamel micro- structure were created, each model differing in the angulation of prism orientation with regard to the wear sur- face. For validation purposes, the mechanical behavior of the model was compared with published experimental data. In order to test the enamel under lateral loads, a compressed food particle was dragged across the surface from the dentino-enamel junction (DEJ) towards the outer enamel surface (OES). Under these conditions, tensile stresses in the enamel model increased with increases in the coefficient of friction. More importantly, stresses were found to be lowest in models in which the prisms approach the surface at lower angles (i.e., more obliquely cut prisms), and highest when the prisms approached the surface at 600 (i.e., less obliquely cut). Finally, the direction of travel of the simulated food particle was reversed, allowing comparison of the difference in behavior between trailing and leading edge enamels (i.e., when the food particle was dragged either towards or away from the DEJ). Stresses at the trailing edge were usually lower than stresses at the leading edge. Taken together with what is known about prism orientation in primate teeth, such findings imply greater wear resistance at the inter- cuspal region and less wear resistance at the lateral enamel at midcrown. Such findings appear to be sup- ported by archeological evidence. [ABSTRACT FROM AUTHOR]

To assess the performance of small-cap stocks net of transaction costs, we analyze 165 actively managed small-cap oriented portfolios. Our analysis addresses three areas of interest: (i) performance net of transaction costs, (ii) the magnitude of trading costs incurred when rebalancing an actively managed portfolio, and (iii) the potential for momentum strategy profits when investing in small-cap stocks.Using conditional estimation, we find that small-cap funds have earned a significantly positive abnormal return of about 2% per year in the period January 1986 to December 2000. We also estimate the cost of January rebalancing to be 0.4% of portfolio value, a value that is significant for over 20% of the portfolios under study.Finally, after trading frictions are taken into account, we find evidence that small-cap portfolios exhibit significant return patterns, similar in nature to momentum patterns initially documented in a frictionless setting by [J. Finance 48 (1993) 65; J. Finance 56 (2001) 699]. Our findings support recent behavioral models, which attempt to explain these patterns. Consistent with the findings of Jegadeesh and Titman, we find that past “winners” continue to outperform in the next 12 months, followed by a performance reversal. [Copyright &y& Elsevier]

This paper studies the problem of pricing contingent claims in a market which has frictions in the form of costs, such as penalty functions corresponding to constraints. An arbitrage-free interval is identified, and a fair price based upon utility functions is proposed. It provides a framework to study incomplete markets that is simpler than the one related to constraints on portfolios introduced by Karatzas and Kou. [ABSTRACT FROM AUTHOR]

This paper is concerned with the dynamic analysis of flexible, nonlinear multi-body systems undergoing contact involving friction and rolling. A continuous friction law is used to model the friction forces between contacting bodies. This avoids the numerical problems associated with the discontinuity inherent to Coulomb's friction law and eliminates the need for different sets of equations modeling sliding and rolling as distinct phenomena. On the other hand, continuous friction laws eliminate specific physical phenomena implied by Coulomb's friction law. The condition of vanishing relative velocity between two contacting bodies is not possible: sticking or rolling are replaced by creeping with a small relative velocity. Discrete events such as transition from slipping to rolling or rolling to slipping are eliminated, together with the high frequency phenomena they are likely to cause. The computational issues associated with the continuous friction law and with the enforcement of the non-holonomic rolling constraint are addressed in this paper. This work is developed within the framework of energy preserving and decaying time integration schemes that provide unconditional stability for nonlinear, flexible multi-body systems undergoing contact involving friction and rolling. [ABSTRACT FROM AUTHOR]

This paper describes research being undertaken to develop a more realistic test for measuring the slip resistance of complete shoe soles and thus determine the effectiveness of sole patterns as well as sole materials and floor surfaces. The frictional forces between shoe and ground have been measured in normal walking using a force platform and photographic techniques used to record human slipping experiments. This has led to the development of an experimental test which reproduces slip conditions in walking as closely as possible. Using this test it has been found that slip severity depends on how friction changes as the shoe moves. Furthermore, it seems that a single measurement of friction may not be sufficient to completely predict the slip resistance of a shoe sole. Further work is necessary to understand the complex nature of slip resistance between shoe sole and ground. [ABSTRACT FROM PUBLISHER]

Urban cycling is a sustainable transport mode that many cities are promoting. However, few cities are taking advantage of geospatial technologies to represent and analyse cycling mobility based on the behavioural patterns and difficulties faced by cyclists. This study analyses a geospatial dataset crowdsourced by urban cyclists using an experimental, mobile geo-game. Fifty-seven participants recorded bicycle trips during one week periods in three cities. By aggregating them, we extracted not only the cyclists' preferred streets but also the frictions faced during cycling. We successfully identified 284 places potentially having frictions: 71 in Münster, Germany; 70 in Castelló, Spain; and 143 in Valletta, Malta. At such places, participants recorded bicycle segments at lower speeds indicating a deviation from an ideal cycling scenario. We describe the potential frictions inhibiting bicycle commuting with regard to the distance to bicycle paths, surrounding infrastructure, and location in the urban area. [ABSTRACT FROM AUTHOR]