Search results

This is a chapter from Mr. Clark's forthcoming book on “Marine Lubrication”, which we shall publish early next year. This book will be the most comprehensive work on this subject ever published and will deal with all aspects of lubrication of marine machinery.

The growth of research on the cognitive origins of market performance has focused on the impact of categories as a primary cognitive mechanism by which exchange occurs. In this research, performance outcomes are typically reduced when firms and products fail to meet audiences’ expectations about membership into categories. The ensuing literature has focused on spanning categories as evidence of not meeting audience expectations while largely ignoring the specific study of expectations themselves. This chapter argues that expectations for market behavior are important in their own right, and can impact market outcomes even when categorical boundaries are respected. Using the market for engagement rings as a setting, I show how lack of adherence to expectations can both increase and decrease market value even as the engagement rings adhere to categorical boundaries. Rather than simply focusing on category spanning as evidence that audience expectations have not been met, the findings suggest that expectations should be considered explicitly, with implications for competitive strategy.

A DSIR Sponsored Research Programme on the Development and Application of the Matrix Force Method and the Digital Computer. This work presents a rational method for the structural analysis of stressed skin fuselages for application in conjunction with the digital computer. The theory is a development of the matrix force method which permits a close integration of the analysis and the programming for a computer operating with a matrix interpretive scheme. The structural geometry covered by the analysis is sufficiently arbitrary to include most cases encountered in practice, and allows for non‐conical taper, double‐cell cross‐sections and doubly connected rings. An attempt has been made to produce a highly standardized procedure requiring as input information only the simplest geometrical and elastic data. An essential feature is the use of the elimination and modification technique subsequent to the main analysis of the regularized structure in which all cutouts have been filled in. Current Summary A critical historical appraisal of previous work in the Western World on fuselage analysis is given in the present issue together with an outline of the ideas underlying the new theory.

Presents the numerical investigations of interaction of several coaxial vortex rings in inviscid fluid. For the solution of non‐linear system of ordinary differential equations chooses the method of extrapolation with variable step and order. Controls the accuracy of calculations by the conditions of conservation of the first integrals and also by the comparison of numerical results with the known analytical solutions. Discusses the problems of order and chaos, and presents examples of mixing of fluid particles by interaction of two and three vortex rings.

This paper aims to investigate the suitability of additive manufacturing to produce O-ring seals.

The O-rings were made by the PolyJet-Matrix technology using four different digital materials and then tested for relaxation properties under static and dynamic (sliding) conditions. The approximation of the relaxation curves involved modelling with a Prony series.

The PolyJet-Matrix technology offers new opportunities to model elastomeric elements, with examples being the O-rings produced and tested for their relaxation properties. Describing the behaviour of the particular materials fabricated with this technology by using relaxation functions will extend the knowledge base on digital materials.

The four types of photopolymers used in the experiment differed in viscoelastic properties. The analysis of the stress relaxation of the O-ring models was performed at four different step displacements of the loading element.

The test results may be useful for the design of O-ring seals made of new elastomeric materials. The relaxation properties of the O-rings made of such materials can be applied to analyse the dynamics of seals, for instance, face seals.

The originality of the work lies in the use of digital materials to design and produce elastomeric elements with different relaxation properties, which was confirmed by the test results. This paper presents results of a relaxation analysis for a ring model and the material that the ring is made of. It also discusses how 3D printing and digital materials can be applied in practice.

This paper aims to describe a novel type of attitude control system (ACS) in different configurations. This servomechanism is compared with control moment gyro (CMG) in significant parameters of performance for ACS of rigid satellite.

This new actuator is the fluid containing one or more rings and fluid flow is supplied by pump. The required torque control is obtained by managing fluid angular velocity. The cube-shaped satellite with three rings of fluid in the principle axes is considered for modeling. The satellite is considered rigid and nonlinear dynamics equation is used for it. In addition, the failure of the pyramid-shaped satellite with an additional ring fluid is discussed.

The controller model for four fluid rings has more complexity than for three fluid rings. The simulation results illustrated that four fluid rings need less energy for stabilization than three fluid rings. The performance of this type of actuator is compared with CMG. At last, it is demonstrated that performance parameters are improved with fluid ring actuator.

Fluid ring actuator can be affected by environmental pressure and temperature. Therefore, freezing and boiling temperature of the fluid should be considered in system designation.

Fluid ring servomechanism can be used as ACS in rigid satellites. This actuator is compared by CMG, the prevalent actuator. It has less displacement attitude maneuver.

The results provide the feasibility and advantages of using fluid rings as satellite ACS. The quaternion error controller is used for this model to enhance its performance.

Ferric and ferrous oxides are used for coating of piston rings in order to obtain the layer, facilitating their wearing‐in at the beginning of work. This paper aims to present study and the implementation of the anti‐wear technology of piston rings production with the application of ferrous oxides. Those rings are intended for two‐stroke self‐ignited diesel engines used for driving the diesel locomotives.

It was decided to use magnetite, Fe₃O₄, together with a binding agent, sodium metasilicate. Working out the adequate technology of filling the grooves of piston rings required performing a broad research range. It is possible to apply three different technologies. In order to find out which of the three methods of filling grooves gives the best results, the series of experiments were planned.

Experimental results cover the variability intervals of input factors enabling the selection of their best combination by the analysis of the regression function. The paper describes the experimental plan for the wet technology with water‐glass, since it occurred to be the best considering the equipment of the factory in which it was implemented. In order to cover the variability field of input factors, the multifactor Hartley's plan was applied. On the basis of the performed investigations, it was found that all input factors are significantly influencing the filling quality of ring grooves on piston rings.

This technology in one of the Polish factories in piston rings production was implemented. The implemented technology allows the production of approximately 500,000 rings annually.

The paper presented a new anti‐wear technology of the sealing piston rings for diesel.

In this paper, we study the different kinds of the primeness on the class of near-rings and we give new characterizations for them. For that purpose, we introduce new concepts called set-divisors, ideal-divisors, etc. and we give equivalent statements for 3-primeness which make 3-primeness looks like the forms of the other kinds of primeness. Also, we introduce a new different kind of primeness in near-rings called K-primeness which lies between 3-primeness and e-primeness. After that, we study different kinds of prime ideals in near-rings and find a connection between them and new concepts called set-attractors, ideal-attractors, etc. to make new characterizations for them. Also, we introduce a new different kind of prime ideals in near-rings called K-prime ideals.

The paper aims to investigate the friction and wear properties of three surface-modified piston rings matched with a chromium-plated cylinder liner.

Samples were taken from the chromium-plated cylinder liner, Cr-Al2O3 ring, CrN ring and Mo ring. Tribo-tests were conducted on a reciprocating sliding tribometer under fully formulated engine oils. Friction coefficients and wear depths of three friction pairs were tested. Surface morphologies of cylinder liners and piston rings before and after test were analyzed.

Experimental results show that in the Cr-Al2O3 piston ring, scuffing occurred easily when matched with the chromium-plated cylinder liner; compared with the Mo ring, the CrN ring could decrease the wear depth of the piston ring from 2.7 to 0.2 μm, and the wear depth of cylinder liner remained; however, the friction coefficient increased from 0.113 to 0.123. The tribological performances of three surface-modified piston rings were significantly different when they matched with chromium-plated cylinder liner.

Chromium-plated cylinder liner and the three kinds of surface-modified piston rings have excellent friction and wear properties, respectively. However, according to the systematic characteristics of internal combustion (IC) engine tribology, only the appropriate cylinder liner–piston ring can improve the tribological performance of the IC engine. This paper reports the tribological performance of three surface-modified piston rings matched with a chromium-plated cylinder liner. The results can be used as reference for the design of high-power-density diesel engine.

GRAPHITE, either alone or in combination with other materials, has long been used as a lubri‐cant for specific purposes, and in recent years the self‐lubricating property of carbon has been applied to the use of engineering components—such as carbon bearings and piston rings for compressors—constructed entirely of carbon.