Bilateral Contact Research Articles

Systemic Illiquidity in the Federal Funds Market

This paper shows how the intra-day allocation and pricing of overnight loans of federal funds reflect the decentralized inter-bank market in which these loans are traded. A wouldbe borrower or lender typically finds a counterparty institution by direct bilateral contact. Once in contact, say by telephone, the two counterparties to a potential trade negotiate terms that reflect their incentives for borrowing or lending, as well as the attractiveness of their respective options to forego a trade and to continue “shopping around.” This overthe-counter (OTC) pricing and allocation mechanism is quite distinct from that of most centralized markets, such as an electronic limit-order-book market in which every order is anonymously exposed to every other order with a centralized order-crossing algorithm. While there is a significant body of research on the micro-structure of specialist and limit-order-book markets, most OTC markets do not have comprehensive transactionslevel data available for analysis. The federal funds market is a rare exception. We go beyond a previous study by Craig Furfine (1999) of the microstructure of the federal funds market by modeling how the likelihood of matching a particular borrower with ∗Banking Studies, Federal Reserve Bank of New York, 33 Liberty Street, New York, NY 10045. We are grateful for support and data from The Federal Reserve Bank of New York and for comments from Guillaume Plantin, Jamie McAndrews, Craig Furfine, Michael Fleming, and anonymous federal funds traders. We have also benefited from comments by Andrew Metrick, Jeremy Stein, Ken French, Larry Harris, Owen Lamont, John Taylor, and Randy Westerfield. The views expressed here are not necessarily those of The Federal Reserve Bank of New York or the Federal Reserve System.

Existence and Uniqueness to a Dynamic Bilateral Frictional Contact Problem in Viscoelasticity

In this paper we examine an evolution problem which describes the dynamic bilateral contact of a viscoelastic body and a foundation. The contact is modeled by a friction multivalued subdifferential boundary condition which incorporates the Coulomb law of friction, the SJK model and the orthotropic friction law. The main result concerns the existence and uniqueness of weak solutions to the hyperbolic variational inequality when the friction coefficient is sufficiently small. The proof is based on a surjectivity result for multivalued operators and a fixed point argument.

Numerical analysis and simulations of a quasistatic frictional contact problem with damage in viscoelasticity

We consider a quasistatic problem which models the bilateral contact between a viscoelastic body and a foundation, taking into account the damage and the friction. The damage which results from tension or compression is then involved in the constitutive law and it is modelled using a nonlinear parabolic inclusion. The variational problem is formulated as a coupled system of evolutionary equations for which we state the existence of a unique solution. Then, we introduce a fully discrete scheme using the finite element method to approximate the spatial variable and the Euler scheme to discretize the time derivatives. Error estimates are derived and, under suitable regularity hypotheses, the convergence of the numerical scheme obtained. Finally, a numerical algorithm and results are presented for some two-dimensional examples.

Evaluation of Electric Power Procurement Strategies by Stochastic Dynamic Programming

In deregulated electricity markets, the role of a distribution company is to purchase electricity from the wholesale electricity market at randomly fluctuating prices and to provide it to its customers at a given fixed price. Therefore the company has to take risk stemming from the uncertainties of electricity prices and/or demand fluctuation instead of the customers. The way to avoid the risk is to make a bilateral contact with generating companies or install its own power generation facility. This entails the necessity to develop a certain method to make an optimal strategy for electric power procurement.In such a circumstance, this research has the purpose for proposing a mathematical method based on stochastic dynamic programming and additionally considering the characteristics of the start-up cost of electric power generation facility to evaluate strategies of combination of the bilateral contract and power auto-generation with its own facility for procuring electric power in deregulated electricity market. In the beginning we proposed two approaches to solve the stochastic dynamic programming, and they are a Monte Carlo simulation method and a finite difference method to derive the solution of a partial differential equation of the total procurement cost of electric power. Finally we discussed the influences of the price uncertainty on optimal strategies of power procurement.

Aeromonas caviae keratitis associated with contact lens wear

Objective We report the first case of bilateral contact lens–related Aeromonas caviae keratitis associated with A. caviae contamination of the contact lens case. The presence of virulence factors produced by Aeromonas species was also investigated. Design Case report. Intervention and testing Conjunctival swabs and corneal scrapings from both eyes were inoculated for culture. The contact lens case was also cultured. The isolate was analyzed for the presence of virulence properties, such as gelatinase and protease production. The presence of virulence genes, such as the cytolytic enterotoxin (AHCYTOEN) and type IV Aeromonas pilus ( tap) genes, was investigated using polymerase chain reaction. The susceptibility of A. caviae to 6 commercial contact lens disinfecting solutions was tested. Main outcome measures Culture results, protease activity, and gelatinase production were analyzed. Polymerase chain reaction amplification products were visualized in ethidium bromide–stained agarose gel. Bacterial growth after exposure to contact lens disinfecting solutions was assessed. Results Aeromonas caviae was grown bilaterally from the conjunctiva, cornea, and contact lens case. The organism showed protease and gelatinase production. Polymerase chain reaction amplification revealed that the A. caviae strain contained the AHCYTOEN and tap virulence genes. Incubation for the minimum recommended time with all tested disinfecting solutions was effective in killing A. caviae. Conclusions Aeromonas caviae should be considered a possible etiologic agent of contact lens–associated keratitis. The presence of virulence factors may be important in determining corneal infection. Commercial contact lens disinfecting solutions, along with proper lens case hygiene, may be effective in preventing A. caviae keratitis in soft contact lens wearers.

Tube Methods for BV Regularization

In this paper tube methods for reconstructing discontinuous data from noisy and blurred observation data are considered. It is shown that discrete bounded variation (BV)-regularization (commonly used in inverse problems and image processing) and the taut-string algorithm (commonly used in statistics) select reconstructions in a tube. A version of the taut-string algorithm applicable for higher dimensional data is proposed. This formulation results in a bilateral contact problem which can be solved very efficiently using an active set strategy. As a by-product it is shown that the Lagrange multiplier of the active set strategy is an efficient parameter for edge detection.

DD-type Domain Decomposition Method for Frictional Contact Problem

The bilateral or unilateral contact problem with Coulomb friction between two elastic bodies is considered [1]. An algorithm is introduced to solve the resulting finite element system by a non-overlapping domain decomposition method. The global problem is transformed to a smaller problem on the contact surface. The solution is obtained by using a successive approximation method, in each step of this algorithm we solve two intermediate problems the first with prescribed tangential pressure and the second with prescribed normal pressure.

Characteristics and functional outcomes of 130 patients with keratoconus attending a specialist contact lens clinic.

To evaluate the demographic profile, management and functional outcomes of patients with keratoconus attending the contact lens clinic of a tertiary ophthalmic referral centre over a one year period. A retrospective cohort analysis was conducted by reviewing the computerised hospital records of 130 patients attending The Western Eye Hospital contact lens department over the period 1st Jan 1999 to 31st Dec 1999. Data on age, gender, referral pattern, visual acuity, contact lens fitting, degree of visual success, and some information on penetrating keratoplasty were obtained. 16.4% of all patients attending the Contact Lens clinic had keratoconus. The mean age at referral was 28.6 years and the mean age of keratoconus during the study period was 34.9 years. There was a predominance of male patients. Optometrists formed 72.2% of the referrals, and had prescribed some form of refractive correction in 70% of patients (two-thirds contact lenses) prior to hospital assessment. Of the 130 patients seen in the department during the study period, the post-referral management included bilateral contact lens fitting for 102 patients (78.5%), monocular contact lens fitting for 24 patients (18.5%) and no intervention in four patients (3%). The types of contact lenses used included PMMA lenses (2.7%), rigid gas permeable lenses (96.1%) of the spherical, elliptical and special cone lens designs, Keratosoft or Softperm lenses (0.8%) and scleral lenses (0.4%). Eleven eyes of eight patients had received penetrating keratoplasty (PK) prior to hospital assessment, of whom seven eyes needed post-surgical contact lens fitting. The main reasons for PK were contact lens intolerance (83%), frequent contact lens displacement (8.5%) and unsatisfactory visual acuity despite good contact lens fit (8.5%). Sixty-five per cent of patients were able to wear their contact lenses for more than 12 hours a day. With contact lens wear, 87% of patients had a visual acuity of 6/9 or better and 59% of eyes had improved visual acuity of 0.6 logMAR or more. Optometrists were the main source of referral for keratoconus patients to the Hospital Eye Service (HES). The mean age at referral was 28.6 years, with a predominance of male patients. Blurred vision formed the main presenting visual symptom on initial hospital assessment; subsequently, more than two-thirds of patients required bilateral contact lenses. Rigid gas permeable contact lenses remain the mainstay treatment for advanced keratoconus, with various designs enabling a large proportion of patients to attain improved visual acuity.

A viscoelastic frictionless contact problem with adhesion

We consider a model for the quasistatic, bilateral, adhesive and frictionless contact between a viscoelastic body and a rigid foundation. The adhesion process on the contact surface is modeled by a surface internal variable, the bonding field, and the tangential shear due to the bonding field is included. The problem is formulated as a coupled system of a variational equality for the displacements and an integro-differential equation for the bonding field. The existence of a unique weak solution for the problem is established by construction of an appropriate mapping which is shown to be a contraction on a Hilbert space. We also consider the problem describing the bilateral contact between two viscoelastic bodies, and establish similar results.

Dual formulation of a quasistatic viscoelastic contact problem with tresca's friction law

We consider quasistatic evolution of a viscoelastic boby which is in bilateral frictional contact with a rigid foundation. We derive two variational formulations for the problem:the primal formulation in terms of the displacements and the dual formulation in terms of the stress field. We prove the existence of a unique solution to each one and establish the equivalence between the two variational formulations. We also prove the continuous dependence of the solution on the friction yield limit.

Dynamic bilateral contact with discontinuous friction coefficient

Dynamic bilateral contact with discontinuous friction coefficient

Loneliness, Sex, Romantic Jealousy, and Powerlessness

The revised UCLA Loneliness Scale, items from a revision of an interpersonal jealousy personality scale varying in partner-rival contact, and vignettes depicting partner-rival contact were administered to 194 female and 97 male college students in Study 1. Those measures and a measure of powerlessness, comprising the learned helplessness attribution style, were administered to 44 female and 28 male college students in Study 2. Results showed that the relation between jealousy and both loneliness and powerlessness varied as a function of the type of contact between romantic partner and rival. Loneliness and powerlessness were: (i) positively associated with jealousy for unilateral contact (e.g., a partner admiring an opposite-sex person), (ii) not associated with jealousy for bilateral contact (e.g., a partner having an opposite-sex person as a friend), and (iii) negatively associated with jealousy for mutual contact (e.g., a partner kissing an opposite-sex person). Regression analyses indicated that powerlessness mediated, in part, the relation between loneliness and jealousy. Although some sex differences were found in jealousy, those differences did not conform to the pattern expected on the basis of sex differences in powerlessness. It was proposed that lonely individuals tended to display situationally inappropriate jealousy because of their powerlessness and that tendency posed a problem for their romantic relationships.

Existence and uniqueness for a quasistatic frictional bilateral contact problem in thermoviscoelasticity

We prove the existence and uniqueness of the weak solution for a quasistatic thermoviscoelastic problem which describes bilateral frictional contact between a deformable body and a moving rigid foundation. The model consists of the heat equation for the temperature, the elliptic viscoelasticity system for the displacements, the SJK-Coulomb law of friction and frictional heat generation condition. The proof is accomplished in two steps. First, the existence of solutions for a regularized problem is established and a priori estimates obtained. Then the limit function, which is the weak solution of the original problem, is shown to be the unique fixed point of the solution operator when the friction coefficient is small.

Evolutionary variational inequalities arising in quasistatic frictional contact problems for elastic materials

We consider a class of evolutionary variational inequalities arising in quasistatic frictional contact problems for linear elastic materials. We indicate sufficient conditions in order to have the existence, the uniqueness and the Lipschitz continuous dependence of the solution with respect to the data, respectively. The existence of the solution is obtained using a time‐discretization method, compactness and lower semicontinuity arguments. In the study of the discrete problems we use a recent result obtained by the authors (2000). Further, we apply the abstract results in the study of a number of mechanical problems modeling the frictional contact between a deformable body and a foundation. The material is assumed to have linear elastic behavior and the processes are quasistatic. The first problem concerns a model with normal compliance and a version of Coulomb′s law of dry friction, for which we prove the existence of a weak solution. We then consider a problem of bilateral contact with Tresca′s friction law and a problem involving a simplified version of Coulomb′s friction law. For these two problems we prove the existence, the uniqueness and the Lipschitz continuous dependence of the weak solution with respect to the data.

The mortar finite element method for contact problems

The purpose of this paper is to describe a domain decomposition technique: the mortar finite element method applied to contact problems between two elastic bodies. This approach allows the use of no-matching grids and to glue different discretizations across the contact zone in an optimal way, at least for bilateral contact. We present also an adaptation of this method to unilateral contact problems.

Referral patterns, treatment management and visual outcome in keratoconus.

To determine the patterns of referral, the hospital-based management and the subjective degree of visual success achieved by keratoconics attending the Corneal Service at Sunderland Eye Infirmary, England, a specifically designed anonymous questionnaire was mailed to 160 keratoconus subjects. The following responses were obtained from 97 (61%) respondents: mean age of first referral (22.88 +/- 8.36 years); gender (male:female ratio 3:1); source of initial referral (optometrists 90%); visual symptoms experienced before referral (46% complained of blurred/distorted vision); and the type of visual correction before referral (70% wore a refractive correction: 72% spectacles, 28% contact lenses). Initial post-referral treatment included bilateral contact lens fitting (65%), monocular contact lens correction (26%), penetrating keratoplasty (8%) and no intervention (1%). Two-thirds of subjects were presently wearing contact lenses (67%), with the mean period of successful lens wear being 8.26 +/- 7.92 years, and 31% had undergone penetrating keratoplasty (PK) since initial referral. A subjective evaluation of visual acuity with contact lenses was made by respondents using a visual analogue scale. The mean value was 86.86 +/- 15.25 (range 50-100 mm), with 50 mm representing moderate visual acuity. Of those who underwent PK the mean subjective evaluation of the change in post-operative vision compared with pre-operatively was 82.41 +/- 26.57 (range 1-100 mm), with 50 mm representing no visual change. The majority of subjects therefore noted a moderate to marked visual improvement following PK. In this fairly young group of patients, predominantly male, the majority wore a refractive correction for approximately 10 years before referral to the Hospital Eye Service (HES). Most referrals were initiated by optometrists. On initial HES assessment the treatment for two-thirds was bilateral contact lens fitting; only a quarter were fitted monocularly. However, by the time of this study only a tenth retained monocular contact lens correction, with the mean length of time from diagnosis to bilateral contact lens wearing being approximately 5 1/2 years. The progressive nature of this disease is further evidenced by the large number of contact lens sets required by patients (approximately 5) and by the number of patients (n = 22) requiring PK, the mean length of time from diagnosis to corneal graft being approximately 8 1/2 years.

Analysis of a quasistatic viscoplastic problem involving tresca friction law

The quasistatic evolution of an elastic-viscoplastic body in bilateral contact with a rigid foundation is considered. The contact involves viscous friction of Tresca type. Two variational formulations of the problem are proposed, followed by existence and uniqueness results. Some properties involving the equivalence between the previous variational formulations, the continuous dependence of the solution with respect to the data as well as a convergence result with respect to the friction yield limit are also obtained.

A hyperbolic—parabolic system modelling the thermoelastic impact of two rods

The dynamic thermoelastic impact of two rods is modelled by a coupled system of two quasivariational inequalities and two equalities that reflect a bilateral contact condition and a radiation condition for the temperatures. The existence of a weak solution is established using a penalization method that employs Galerkin approximations and a priori estimates.

Openness to Dyadic Ethnic Contact and Student Outcomes

Relations between readiness to engage in more intimate bilateral or unilateral dyadic ethnic contact and student outcomes were investigated in 28 desegregated sixth, seventh, and eighth grades in Israel. Desired level of intimacy was determined by students' ratings of their readiness to maintain more or less intimate social contact with each of their classmates. Unilateral and bilateral openness to social interaction were defined by comparing respondents' desired intimacy with target's readiness to reciprocate these expectations. As hypothesized, academic and social outcomes of higher-status Western students as well as lower-status Middle Eastern classmates were primarily related to bilateral, reciprocated contact with members of the dominant group. These outcomes were generally unrelated to unilateral, unreciprocated contact with higher-status members or to unilateral or bilateral contact with members of the lower-status group. Results are discussed by converging reference group theory and elicited reciprocal intimacy.

Harmonic Response of Smoothly Embedded Rigid Sphere

The category of problems that examines the dynamic behavior of inclusions embedded in elastic media is of particular interest to the study of dynamic soil‐structure interaction. In a majority of investigations, the interface between the inclusion and the surrounding elastic medium is assumed to be perfectly bonded. This paper examines the elastodynamic problem pertaining to the steady rectilinear oscillations of a spherical rigid inclusion that is embedded in smooth bilateral contact with an isotropic elastic medium of infinite extent. The bilateral contact is maintained by the application of a uniform radial stress field at infinity. The inclusion is subjected to a harmonic oscillation. The analytical solution for the resulting elastodynamic problem is developed in exact closed form. The numerical results presented in the paper illustrate the manner in which the dynamic compliance of the embedded rigid spherical inclusion is influenced by the frictionless boundary conditions at the inclusion‐elastic medium interface.