Finite element analysis of moving contact in mechanically fastened joints

The Finite Element Method (FEM) has made a number of otherwise intractable problems solvable. An important aspect for achieving an economical and accurate solution through FEM is matching the formulation and the computational organisation to the problem. This was realised forcefully in the present case of the solution of a class of moving contact boundary value problems of fastener joints. This paper deals with the problem of changing contact at the pin-hole interface of a fastener joint. Due to moving contact, the stresses and displacements are nonlinear with load. This would, in general, need an interactive-incremental approach for solution. However, by posing the problem in an inverse way, a solution is sought for obtaining loads to suit given contact configuration. Numerical results are given for typical isotropic and composite plates with rigid pins. Two cases of loading are considered: (i) load applied only at the edges of the plate and (ii) load applied at the pin and reacted at a part of the edge of the plate. Load-contact relationships, compliance and stress-patterns are investigated. This paper clearly demonstrates the simplification achieved by a suitable formulation of the problem. The results are of significance to the design and analysis of fastener joints.

Reducing age bias and turnover intentions by enhancing intergenerational contact quality in the workplace: The role of opportunities for generativity and development

Based on socio-emotional selectivity and self-categorization theories, we developed and tested a model on how the interplay between employee age and opportunities for generativity and development predicts age bias and turnover intentions via intergenerational contact quality in the workplace. We hypothesized indirect effects of opportunities for generativity on outcomes through intergenerational contact quality among older workers only, whereas we expected that the indirect effects of opportunities for development are stronger for young compared with older workers. Data came from 321 employees in Belgium who responded to an online questionnaire. Results showed that age moderated the relationships of opportunities for generativity and development with intergenerational contact quality consistent with the expected patterns. Furthermore, age moderated the indirect effects of opportunities for generativity and development on age bias through intergenerational contact quality, but not on turnover intentions. Implications for future research and practical suggestions for managing intergenerational contact at work are discussed.

Morphological changes in the conjunctiva, episclera and sclera following short-term miniscleral contact lens wear in rigid lens neophytes

PURPOSE To quantify the influence of short-term wear of miniscleral contact lenses on the morphology of the corneo-scleral limbus, the conjunctiva, episclera and sclera. METHODS OCT images of the anterior eye were captured before, immediately following 3h of wear and then 3h after removal of a miniscleral contact lens for 10 young (27±5 years) healthy participants (neophyte rigid lens wearers). The region of analysis encompassed 1mm anterior, to 3.5mm posterior to the scleral spur. Natural diurnal variations in thickness were measured on a separate day and compensated for in subsequent analyses. RESULTS Following 3h of lens wear, statistically significant tissue thinning was observed across all quadrants, with a mean decrease in thickness of -24.1±3.6μm (p<0.001), which diminished, but did not return to baseline 3h after lens removal (-16.9±1.9μm, p<0.001). The largest tissue compression was observed in the superior quadrant (-49.9±8.5μm, p<0.01) and in the annular zone 1.5mm from the scleral spur (-48.2±5.7μm), corresponding to the approximate edge of the lens landing zone. Compression of the conjunctiva/episclera accounted for about 70% of the changes. CONCLUSIONS Optimal fitting miniscleral contact lenses worn for three hours resulted in significant tissue compression in young healthy eyes, with the greatest thinning observed superiorly, potentially due to the additional force of the eyelid, with a partial recovery of compression 3h after lens removal. Most of the morphological changes occur in the conjunctiva/episclera layers.

The real area of contact and compliance of rough cylinders in compression

Bearing area analysis has been used to study the real area of contact and compliance of rough turned steel cylinders in compression. Calculations show that the elastic real area of contact is very small compared to the plastic real area of contact, and that local compliance due to flattening of asperity tips is a small proportion of the total compliance obtained from experiments. The fact that increased load brings more and more new asperities under load rather than enlarging the contact spots leads to a rather simple load-compliance relation for a rough cylinder, viz., W' = Nh · K1δn, where W0 = K1δn defines the load-compliance relation of the individual asperities, and Nh represents the number of asperities bearing the load.

In response: UV–vis light transmittance through tinted contact lenses and the effect of color on values

In the study, we used the Agilent 8453 spectrophotometer (which is equipped with a limiting aperture that restricts the light beam to the central 5 mm of the contact lens), to measure the transmittance of various coloured contact lenses including the one Day Acuvue define manufactured by Johnson and Johnson which the authors represent. We measured the instrument baseline before the transmittance spectra of lenses were tested. The values of lens transmittances were thus the difference between baseline and lens measurement at each time. The transmittance measurements were obtained at 0.5 nm intervals, from 200 to 700 nm after a soak in saline to remove the influence of any surface active agents within the packaging products. The technique used in our study was not very different from how other research studies [2], [3], [4], [5] and [6] have measured the spectra transmittances of contact lenses...

Drag reduction by a forward facing aerospike for a large angle blunt cone in high enthalpy flows

Drag reduction studies are conducted using a flat disc tipped aerospike for a 120-degree apex angle blunt cone model in high enthalpy flows. Accelerometer based force balance is used for the drag force measurement in the newly established free piston driven shock tunnel, HST3. Drag reduction upto about 58 percent has been achieved for Mach 8 flow of 5 MJ/kg specific enthalpy at zero degree angle of attack.

Three-dimensional corner reflector of arbitrary apex angle

A method of analysing a 3-dimensional corner reflector antenna of arbitrary apex angle is given. Expressions have been obtained for the far field of the 3-dimensional corner reflector fed by a dipole. The radiation resistance and the directive gain of the antenna have been calculated. The method described is applicable even when the feed dipole is arbitrarily oriented. It is found that the radiation along a prescribed direction can be circularly polarised (right or left) by suitably orienting the feed dipole.

real area of contact and compliance of rough cylinders in compression

Bearing area analysis has been used to study the real area of contact and compliance of rough turned steel cylinders in compression. Calculations show that the elastic real area of contact is very small compared to the plastic real area of contact, and that local compliance due to flattening of asperity tips is a small proportion of the total compliance obtained from experiments. The fact that increased load brings more and more new asperities under load rather than enlarging the contact spots leads to a rather simple load-compliance relation for a rough cylinder, viz., W' = Nh · K1δn, where W0 = K1δn defines the load-compliance relation of the individual asperities, and Nh represents the number of asperities bearing the load.

Tissue compression following short-term miniscleral contact lens wear

To quantify regional (nasal, superior, temporal and inferior) and location specific (corneal and scleral) tissue compression following short-term miniscleral contact lens wear.

Metal-insulator transition of naxwo3 studied by angle-resolved photoemission spectroscopy

The electronic structure of sodium tungsten bronzes NaxWO3 is investigated by high-resolution angle-resolved photoemission spectroscopy (ARPES). The ARPES spectra measured in both insulating and metallic phases of NaxWO3 reveals the origin of metal-insulator transition (MIT) in sodium tungsten bronze system. It is found that in insulating NaxWO3 the states near the Fermi level (E-F) are localized due to the strong disorder caused by the random distribution of Na+ ions in WO3 lattice. Due to the presence of disorder and long-range Coulomb interaction of conduction electrons, a soft Coulomb gap arises, where the density of states vanishes exactly at E-F. In the metallic regime the states near E-F are populated and the Fermi level shifts upward rigidly with increasing electron doping (x). Volume of electron-like Fermi surface (FS) at the Gamma(X) point of the Brillouin zone gradually increases with increasing Na concentration due to W 5d t(2g) band filling. A rigid shift of the Fermi energy is found to give a qualitatively good description of the Fermi surface evolution. As we move from bulk-sensitive to more surface sensitive photon energy, we found the emergence of Fermi surfaces at X(M) and M(R) point similar to the one at the Gamma(X) point in the metallic regime, suggesting that the reconstruction of surface was due to rotation/deformation of WO6 octahedra.

A New Type of Dihedral Angle for the Description of Bimolecular Structures

Abstract is not available.

In vivo assessment of inflammatory cells in contact lens wearers

Dissatisfaction with, and discontinuation from, contact lens wear is a source of major frustration and inconvenience to users, and a problem that is thought to cost the contact lens industry hundreds of millions of dollars each year. By directly and non-invasively monitoring inflammatory cells in the tissues at the front of the eye in symptomatic and asymptomatic lens wearers, the candidate has been able to demonstrate an inflammatory basis for contact lens discomfort. This finding may pave the way towards the development of strategies to make contact lenses more safe and afford greater levels of comfort.

Calculating the bound spectrum by path summation in action-angle variables

The density of states n(E) is calculated for a bound system whose classical motion is integrable, starting from an expression in terms of the trace of the time-dependent Green function. The novel feature is the use of action-angle variables. This has the advantages that the trace operation reduces to a trivial multiplication and the dependence of n(E) on all classical closed orbits with different topologies appears naturally. The method is contrasted with another, not applicable to integrable systems except in special cases, in which quantization arises from a single closed orbit which is assumed isolated and the trace taken by the method of stationary phase.

Chromosomal rearrangements, phenotypic variation and modularity: A case study from a contact zone between house mouse Robertsonian races in Central Italy

The Western European house mouse, Mus musculus domesticus, is well-known for the high frequency of Robertsonian fusions that have rapidly produced more than 50 karyotipic races, making it an ideal model for studying the mechanisms of chromosomal speciation. The mouse mandible is one of the traits studied most intensively to investigate the effect of Robertsonian fusions on phenotypic variation within and between populations. This complex bone structure has also been widely used to study the level of integration between different morphogenetic units. Here, with the aim of testing the effect of different karyotypic assets on the morphology of the mouse mandible and on its level of modularity, we performed morphometric analyses of mice from a contact area between two highly metacentric races in Central Italy. We found no difference in size, while the mandible shape was found to be different between the two Robertsonian races, even after accounting for the genetic relationships among individuals and geographic proximity. Our results support the existence of two modules that indicate a certain degree of evolutionary independence, but no difference in the strength of modularity between chromosomal races. Moreover, the ascending ramus showed more pronounced interpopulation/race phenotypic differences than the alveolar region, an effect that could be associated to their different polygenic architecture. This study suggests that chromosomal rearrangements play a role in the house mouse phenotypic divergence, and that the two modules of the mouse mandible are differentially affected by environmental factors and genetic makeup.

Risk factors for open angle glaucoma; a clinical and molecular genetic study

Glaucoma, optic neuropathy with excavation in the optic nerve head and corresponding visual field defect, is one of the leading causes for blindness worldwide. However, visual disability can often be avoided or delayed if the disease is diagnosed at an early stage. Therefore, recognising the risk factors for development and progression of glaucoma may prevent further damage. The purpose of the present study was to evaluate factors associated with visual disability caused by glaucoma and the genetic features of two risk factors, exfoliation syndrome (ES) and a positive family history of glaucoma. The present study material consisted of three study groups 1) deceased glaucoma patients from the Ekenäs practice 2) glaucoma families from the Ekenäs region and 3) population based families with and without exfoliation syndrome from Kökar Island. For the retrospective study, 106 patients with open angle glaucoma (OAG) were identified. At the last visit, 17 patients were visually impaired. Blindness induced by glaucoma was found in one or both eyes in 16 patients and in both eyes in six patients. The cumulative incidence of glaucoma caused blindness for one eye was 6% at 5 years, 9% at 10 years, and 15% at 15 years from initialising the treatment. The factors associated with blindness caused by glaucoma were an advanced stage of glaucoma at diagnosis, fluctuation in intraocular pressure during treatment, the presence of exfoliation syndrome, and poor patient compliance. A cross-sectional population based study performed in 1960-1962 on Kökar Island and the same population was followed until 2002. In total 965 subjects (530 over 50 years) have been examined at least once. The prevalence of exfoliation syndrome (ES) was 18% among subjects older than 50 years. Seventy-five of all 78 ES-positives belonged to the same extended pedigree. According to the segregation and family analysis, exfoliation syndrome seemed to be inherited as an autosomal dominant trait with reduced penetrance. The penetrance was more reduced for males, but the risk for glaucoma was higher in males than in females. To find the gene or genes associated with exfoliation syndrome, a genome wide scan was performed for 64 members (28 ES affected and 36 controls) of the Kökar pedigree. A promising result was found: the highest two-point LOD score of 3.45 (θ=0.04) in chromosome18q12.1-21.33. The presence of mutations in glaucoma genes TIGR/MYOC (myocilin) and OPTN (optineurin) was analysed in eight glaucoma families from the Ekenäs region. An inheritance pattern resembling autosomal dominant mode was detected in all these families. Primary open angle glaucoma or exfoliation glaucoma was found in 35% of 136 family members and 28% were suspected to have glaucoma. No mutations were detected in these families.