Tribological characteristics of nitrogen (N+) implanted iron

The effect of implantation of nitrogen ions (1.5 MeV) on the friction and wear characteristics of pure ion sliding against M-50 steel (unimplanted) was studied in a pin-on-disk sliding friction apparatus. Test conditions included room temperature (25 C), a dry air atmosphere, a load of 1/2 kg (4.9 N), sliding velocities of 0.043 to 0.078 m/sec (15 to 25 rpm), a pure hydrocarbon lubricant (n-hexadecane), or a U.S.P. mineral oil and nitrogen ion implantation doses of 5x10 to the 15th power and 5x10 to the 17th power ions/sq cm. No differences in wear rates were observed in the low dose experiments. In the high dose experiments, small reductions in initial (40 percent) and steady state (20 percent) wear rates were observed for nitrogen implanted iron riders as compared with unimplanted controls. No differences in average friction coefficients were noted for either dose. Auger electron spectroscopy combined with argon ion bombardment revealed a subsurface Gaussian nitrogen distribution with a maximum concentration of 6 atomic percent at a depth of 0.8 microns. Similar analysis within the wear scar of an implanted rider after 20 microns of wear yielded only background nitrogen concentration. No inward migration of nitrogen ions was observed

Universal binding energy relations in metallic adhesion

Rose, Smith, and Ferrante have discovered scaling relations which map the adhesive binding energy calculated by Ferrante and Smith onto a single universal binding energy curve. These binding energies are calculated for all combinations of Al(111), Zn(0001), Mg(0001), and Na(110) in contact. The scaling involves normalizing the energy by the maximum binding energy and normalizing distances by a suitable combination of Thomas-Fermi screening lengths. Rose et al. have also found that the calculated cohesive energies of K, Ba, Cu, Mo, and Sm scale by similar simple relations, suggesting the universal relation may be more general than for the simple free electron metals for which it was derived. In addition, the scaling length was defined more generally in order to relate it to measurable physical properties. Further this universality can be extended to chemisorption. A simple and yet quite accurate prediction of a zero temperature equation of state (volume as a function of pressure for metals and alloys) is presented. Thermal expansion coefficients and melting temperatures are predicted by simple, analytic expressions, and results compare favorably with experiment for a broad range of metals

Universal binding energy relations in metallic adhesion

Scaling relations which map metallic adhesive binding energy onto a single universal binding energy curve are discussed in relation to adhesion, friction, and wear in metals. The scaling involved normalizing the energy to the maximum binding energy and normalizing distances by a suitable combination of Thomas-Fermi screening lengths. The universal curve was found to be accurately represented by E*(A*)= -(1+beta A) exp (-Beta A*) where E* is the normalized binding energy, A* is the normalized separation, and beta is the normalized decay constant. The calculated cohesive energies of potassium, barium, copper, molybdenum, and samarium were also found to scale by similar relations, suggesting that the universal relation may be more general than for the simple free electron metals

Friction wear and auger analysis of iron implanted with 1.5-MeV nitrogen ions

The effect of implantation of 1.5-MeV nitrogen ions on the friction and wear characteristics of pure iron sliding against steel was studied in a pin-on disk apparatus. An implantation dose of 5 x 10 to the 17th power ions/sq cm was used. Small reductions in initial and steady-state wear rates were observed for nitrogen-implanted iron riders as compared with unimplanted controls. Auger electron spectroscopy revealed a subsurface Gaussian nitrogen distribution with a maximum concentration of 15 at. % at a depth of 8 x 10 to the -7th m. A similar analysis within the wear scar of an implanted rider after 20 microns of wear yielded only background nitrogen concentration, thus giving no evidence for diffusion of nitrogen beyond the implanted range

Analysis of plasma-nitrided steels

The analysis of plasma nitrided steels can be divided to two main categories - structural and chemical. Structural analysis can provide information not only on the hardening mechanisms but also on the fundamental processes involved. Chemical analysis can be used to study the kinetics for the nitriding process and its mechanisms. In this paper preliminary results obtained by several techniques of both categories are presented and the applicability of those techniques to the analysis of plasma-nitrided steels is discussed

Temperature effects on the universal equation of state of solids

Recently it has been argued based on theoretical calculations and experimental data that there is a universal form for the equation of state of solids. This observation was restricted to the range of temperatures and pressures such that there are no phase transitions. The use of this universal relation to estimate pressure-volume relations (i.e., isotherms) required three input parameters at each fixed temperature. It is shown that for many solids the input data needed to predict high temperature thermodynamical properties can be dramatically reduced. In particular, only four numbers are needed: (1) the zero pressure (P=0) isothermal bulk modulus; (2)it P=0 pressure derivative; (3) the P=0 volume; and (4) the P=0 thermal expansion; all evaluated at a single (reference) temperature. Explicit predictions are made for the high temperature isotherms, the thermal expansion as a function of temperature, and the temperature variation of the isothermal bulk modulus and its pressure derivative. These predictions are tested using experimental data for three representative solids: gold, sodium chloride, and xenon. Good agreement between theory and experiment is found

Universality in the compressive behavior of solids

It was discovered that the isothermal equation of state for solids in compression is a simple, universal form. This single form accurately describes the pressure and bulk modulus as a function of volume for tonic, metallic, covalent, and rare gas solids

A possible hazard of splenectomy

The first case of splenectomy in St. Luke`s Hospital of a four months old infant is described. The infant died from a fulminating septicemia just over six weeks after splenectomy. Similar case studies indicated that fulminating infection occurs after splenectomy, particularly in infancy which could result fatal. In this regard, this study recommends that splenectomy should not be performed in the preschool child. Furthermore a careful follow-up of all splenectomised patients is advisable, by also treating any infection no matter how minor it may appear to be.peer-reviewe

Globally Monotonic Tracking Control of Multivariable Systems

© 1963-2012 IEEE. In this technical note we present a method for designing a linear time invariant (LTI) state-feedback controller to monotonically track a step reference at any desired rate of convergence for any initial condition. This method is developed for multi-input multi-output (MIMO) systems, and can be applied to strictly/nonstrictly proper systems, and also minimum/nonminimum-phase systems. This framework shows that for MIMO systems the objectives of achieving a rapid settling time, while at the same time avoiding overshoot/undershoot, are not always competing objectives

Age estimation in children by measurement of open apices in teeth: an Indian formula.

The aim of this paper is twofold: first, to evaluate an Indian sample by Cameriere\u2019s European formula; and second, if this formula turns out to be unsuitable, to study a specific formula for Indian children. Orthopantomographs taken from 480 Indian children (227 girls and 253 boys) aged between 3 and 15 years were analyzed. Following the pilot study, subjects\u2019 age was modeled as a function of gender (g), region of country (C), and morphological variables (predictors: x5, the distance between the inner sides of the open apex of the second premolar divided by the tooth length; s \ubc x1 \ufe x2 \ufe x3 \ufe x4 \ufe x5 \ufe x6 \ufe x7, sum of normalized open apices; N0, the number of teeth with root development complete. Results showed that all these variables except gender and second premolar contributed significantly to the fit so that all were included in the regression model, yielding the following linear regression formula: Age \ubc 9:402 0:879 C \ufe 0:663 N0 0:711 s 0:106s N0 where C is a dummy variable equal to 0 for the center or north of India and 1 for the south. The above equation, with the variables considered, explained 89.7% (R2=0.897) of total deviance. The median of the residuals (observed age minus predicted age) was \u20130.063 years, with an interquartile range of 1.10 years