Present study provides a simple analytical formula, the “Klingel-like formula” or “Pascal’s Formula” that can be used as a reference to test some results of existing railway codes and specifically those using rigid contact. It develops properly the 3D Newton-Euler equations governing the 6 degrees of freedom（Do F） of unsuspended loaded wheelsets in case of zero wheel-rail friction and constant conicity. Thus, by solving numerically these equations, we got pendulum like harmonic oscillations of which the calculated angular frequency is used for assessing the accuracy of the proposed formula so that it can in turn be used as a fast practical target for testing multi-body system（MBS） railway codes. Due to the harmonic property of these pendulum-like oscillations, the square ω~2 of their angular frequency can be made in the form of a ratio K/M where K depends on the wheelset geometry and load and M on its inertia. Information on K and M are useful to understand wheelsets behavior. The analytical formula is derived from the first order writing of full trigonometric Newton-Euler equations by setting zero elastic wheel-rail penetration and by assuming small displacements. Full trigonometric equations are numerically solved to assess that the formula provides ω~2 inside a 1% accuracy for usual wheelsets dimensions. By decreasing the conicity down to 1 × 10 -4 rad, the relative formula accuracy is under 3 × 10-5. In order to test the formula reliability for rigid contact formulations, the stiffness of elastic contacts can be increased up to practical rigidity（Hertz stiffness × 1000）.

In multi-body dynamics, we model a non-conformal wheel/rail contact at one centre point since this contact is flat and Hertzian. However, the quasi-conformal contact requires more points since the contact is curved and non-Hertzian. The methodology in solving these points during dynamic simulations is the basis of this development. In this online effort, first, we present a general contact joint and the gutter search method of Pascal and Jourdan [The rigid-multi-Hertzian method as applied to conformal contacts. USA: ASME; 2007] in the context of a multi-body approach. Next, by adopting the non-iterative approach, a subset of these points with positive profile interpenetrations is selected to idealise one curved contact by a set of multi-Hertzian patches for which the Hertz normal contact solution is available. Finally, the feasibility of this multibody approach together with its implementation in two different codes is evaluated by simulating the motion of an isolated wheelset with realistic inertia. On tangent tracks, the wheelset with non-conformal pairing displays self-excited unstable oscillations while it displays a stable behaviour below a critical speed with conformal profiles. A further study reveals the net friction losses at multiple patches within the curved contact being the reason for the stable behavior.

Recently, publications aiming at wheel-rail contact surveys let readers think that multi-Hertzian methods present severe drawbacks with respect to 'virtual penetration' methods. These surveys criticise multi-Hertzian solutions mainly because presenting 'larger contacts overlaps' and 'frequent secondary contacts near the border of the first contact', both obvious geometric possibilities of which the practical occurrence and eventual inconvenience would remain purely theoretical unless established over definite methods demonstrating poor practical results. Recent surveys all quote Piotrowski-Chollet 2005 survey of wheel-rail contact models that attempted to illustrate defective multi-Hertzian techniques by concentrating on the method initiated by Sauvage in the 1990s and further developed by Pascal. The 2005 paper not only gives no evidence of practical inconveniences of Sauvage's method but also confuses static geometric contact overlaps with the dynamical overlapping of forces. In reality it mixes Sauvage method up with a quite different technique. Thus a clarification is now necessary by reminding what the proper Sauvage technique really is and by showing some of its practical successful applications. The present paper, focusing on determination of normal contact forces in conformal situations, intends to explain clearly the advantages of the unequivocal localisation of secondary ellipses in that multi-Hertzian method which has been developed in INRETS VOCOcodes in the 1990s and successfully used by SNCF and ALSTOM in the INRETS-SNCF code, VOCODYM, and later in Pascal's online calculation of railway elastic contacts code. It proved its effectiveness for studying freight wagons derailments as well as rail wear and headcheck, unrounded wheels wear, high-speed lines' deformations or TGV comfort. While simulating American ACELA trainsets' behaviour on the US North-East Corridor tracks, prior to actual tests, as part of the commercial contract. It has been also a major tool for bringing back together French and American Safety Standards.

The Euler equation is a correct way for writing rotational moments of solids. But it is simple only if written in rotating frames. Applying it to railway wheelsets is difficult because it necessitates using the Euler angles, or Euler parameters, combined to rotation matrices or, numerically more stable, quaternions. Euler angles can be avoided in railway specific codes, by writing dynamical equations in track frames. However, academic literature [Landau LD, Lifshitz EM. Mechanics (Institute of Physical Problems, USSR Academy of Sciences, Moscow), Vol. 1, Course of theoretical physics. 21st English ed. Oxford (UK): Elsevier; 1960; Shabana AA, Zaazaa KE, Sugiyama H. Railroad vehicle dynamics. CRC Press; 2008.] does not provide simple solutions as to how properly writing equations of gyroscopic moments in no rotating frames. This paper describes how it is possible, owing to an approximation validated for railway applications, to avoid Euler angles and rotation matrices, while correctly taking into account gyroscopic effects. Using a most severe example, emphasising gyroscopic effects, it is demonstrated that a fast specific code using the approximation provides results equivalent to those of an multi body system generalised code with no approximation.

This paper presents the Online Calculation of Railway Elastic Contacts (OCREC), a dynamic railway calculation tool based on an advanced contact kernel, and its coupling with the MSC ADAMS multi-body commercial software. The OCREC contact kernel is used as a subroutine of multi-body codes in order to calculate contact forces between wheelsets and rails. The OCREC method is "online" as it not only redefines new contact parameters at each time step but also determines all simultaneous contacts on each wheel as allowed by Hertz Elasticity theory. From the normal forces and relative velocities given by the Hertz theory, Tangential Forces are calculated using Kalker's FASTSIM (modified for elliptical pressure distribution).After a description of the OCREC theory, the paper presents the linkage between OCREC and MSC ADAMS software. OCREC calculates contact forces within a Frenet frame (oxyz) following the track layout where ox is tangent to the track; oy is horizontal and oz normal to oxy. As ADAMS calculates inside a different frame, and as it has no built-in track system, it was necessary to develop a program capable of connecting 3 different frames: the 'dummy' track frame, the Frenet frame and the fixed ADAMS frame. Note that the 'dummy' frame is directly calculated from railway track curvature measurements recorded in so-called 'space curves'.The OCREC ADAMS link is first validated by a bogie rolling on a dummy track. With the equations of the OCRECYM code established directly within the "dummy" frame, the OCREC-ADAMS results are compared to a specific OCRECYM validation code. Then, the results from an actual railway case are presented: behavior of one coach is calculated on a real measured track including curves and defaults. During the following step, the OCREC-ADAMS results are compared to OCRECYM results. After some model updating for adjustment to physical properties of elastic joints (helicoidal springs), a good correlation is obtained between the codes.The analysis of the different force and displacement components proves this kind of numerical tool's capabilities of assessing the railway vehicle's dynamic behavior. Especially, the Y/Q safety ratio is well calculated. Thus, the OCREC contact kernel, which is powerful for complex contact topologies such as conformal contacts, and necessary for high speed safety calculation, can be used as a subroutine of standard multi-body software, giving it high capabilities for dynamic railway calculation.

The new benchmark, which is the focus of this report, uses a single unsuspended wheelset loaded with a constant vertical force, running on an idealized frictionless and rigid perfect track (the call for simulations and full problem description were announced at the Long Beach Railway Symposium in September 2005). The elimination of wheelset suspension avoids the need for calculating sprung mass response and its corresponding contribution to wheel rail contact. Similarly, the idealization of track as frictionless and rigid eliminates the compounding effects of factors such as tangential forces and track response on wheel rail contact. While in principle it could have been possible to isolate treatment of wheel rail contact using quasi-static calculations, the proposed benchmark was deemed more beneficial to allow for the inclusion of simulation codes that exclusively utilized rigid contact and to gage the influence of dynamic variations. It was expected to find different force results due to differences in coding assumptions. In addition, differences in wheel/rail impact forces that otherwise could seem negligible are expected to produce displacement bifurcations. Results suggest that codes using elastic contact appear to be more consistent at predicting derailment resulting from the conditions in this benchmark. This may further suggest that these conditions may be more challenging to predict using rigid contact.

Multi-Hertzian Methods are used in Railway codes to calculate elastically normal forces of Wheel/Rail Contacts. Such methods may be properly applied to calculate forces of several elliptical simultaneous contacts. They may also be applied as a sum of Hertzian contacts to approximate normal forces of non elliptical patches such as presented in the 3D drawing. Solving such cases necessitates to choose the location, the ellipticity and the maximum indentation of elementary ellipses. In order to solve this problem it is usual to consider the maxima of the function of un-deformed profiles indentation in the symmetry plane YOZ. However these methods cannot solve cases when this function has only one maximum and has no symmetry. The “Rigid-Multi-Hertzian Method” solves these difficult cases on a topology basis: at first by searching the locations of all potential contacts in the rigid situation during a pure lateral translation (OY) of the wheel across the rail. During this translation, contact locations can be discontinuous and forbidden areas are identified as “Gutters” of which the Edges are stored. The second phase uses the indentation function to calculate indentations at gutter edges where secondary ellipses are assumed to be located; the main ellipse is located as usual. This method allows to solve conformal cases and develops smooth continuous contact forces during dynamical simulations. This paper presents the method in more details using the example of a quasi-conformal pair of profiles (S1002 and UIC60). Taking advantage of the analytical definition of these profiles, it is proposed as a benchmark to calculate the resultant normal force (amplitude and direction in upper figure) for one case of which all the surface details are disclosed: numerical data of both surfaces can be re-produced using the attached software. Contact Forces could be compared either using this method (results are given) or using numerical data as inputs to FEM calculations of commercial codes available to researchers who would like to assess the accuracy of this Rigid-Multi-Hertzian Method with respect to more sophisticated tools. One FEM calculation, using ANSYS, is presented and results are in good agreement with this method. Note: This method was first mentioned in 1991 & 1993 in papers [3], [4] but it could not be applied by third parties because implementation details were not disclosed. However it has been used since by the author to produce lookup tables of equivalent mono-patches as input data of Vocodym successful “rigid” software. It has now been developed to be used on line in the dynamical elastic software Ocrec.

For the wheel/rail contact problem, the Hertz theory for two elastic bodies in contact is commonly used to determine the shape and dimensions of the contact area and the local deformation of the wheel and rail surfaces at the contact region. The shape of the contact area is assumed to be elliptical. The ratio of the contact ellipse semi-axes is equal to the ratio of two non-dimensional contact area coefficients, known as m and n coefficients. Hertz presented a table of these two coefficients, determined as a function of an angular parameter, theta. Most railroad vehicle dynamic codes use this table with online interpolation to determine the contact ellipse semi-axes.Recently, it was found that this original table may be too coarse, and that more data points are needed within the table for solving the wheel/rail contact accurately. This paper discusses the effect of the accuracy of the m and n coefficients in solving for wheel/rail contact, and demonstrates this effect with two numerical examples that show the resulting differences in the dynamic behavior of railroad vehicles dependent on this accuracy. A new table with more data points is presented that is recommended for use in railroad vehicle dynamic codes that employ the Hertzian contact for solving the wheel/rail contact interaction. This modified table was originally derived by Jean-Pierre Pascal as a part of collaborative research between the Federal Railroad Administration (FRA) and the French Ministry of Transportation.

A crucial step in understanding the origin and maintenance of biological diversity is the assessment of its distribution over space and time and across environmental gradients. At the regional scale, two important attributes of species can be assessed that provide insight into speciation processes: species geographical and environmental ranges. The endemic tree flora of the Western Ghats is an interesting case for analyzing broad‐scale biodiversity patterns because of the steep environmental gradients that characterize this tropical region of India. We analysed species geographical and environmental ranges by Canonical Correlation Analysis of point data from herbarium collections. We performed partial analyses to discriminate spatial and environmental correlates of species distribution, and evaluate the contribution of higher taxonomic ranks to these ranges. We identified different levels of organization in the distribution of endemism: 1) general features, such as the concentration of endemic species in the southern part of the Western Ghats, and the decrease in endemic species richness along the altitudinal and the dry season length gradients, and 2) patterns specific to genera or families, such as species niche separation along the environmental gradients. Our analyses enabled us to formulate hypotheses about the diversification of the endemic tree flora of the Western Ghats. They also confirm the value of Canonical Correlation Analysis as the suitable method for collection data analysis.

The forests in Cat Tien National Park, appear as a mosaic of different communities, distinct from each other with respect to their floristic and structural parameters. The objectives of this study are (1) to characterize the different formations occurring in the lowland part and (2) to identify the main successional trends in the area. Understanding forest succession is important for silviculture and restoration of forests and land rehabilitation, as adequate information on the ecological role of local species in the functioning of the forests is not available in Vietnam. Five plots (1 ha each) were established in the lowland part of Cat Tien National Park, where all the trees ≥ 10 cm d.b.h. (diameter at breast height) were located, measured and identified. A systematic sampling was made to assess the regeneration. Three plots (A, C and D) can be considered as secondary forests on the basis of their structural parameters. Plots A and C are dominated by Lagerstrmia calyculata and plot D by Dipterocarpus alatus. The other two plots can be regarded as mature forests. Plot B corresponds to a semideciduous formation dominated by Lagerstrmia calyculata and Fabaceae species, and plot E to an evergreen one dominated by dipterocarp species. The floristic composition of plots A and C will change in the future because dominant canopy species are rare or absent in regeneration. A correspondence analysis performed on the number of trees per species shows two kinds of successional trends: one from A to B on shallow and drier soils, and another from C to E on deeper and wetter soils.

In this prospective controlled study, the pharmacokinetic profiles of alpha-interferon 2b (alphaIFN-2b) were determined by the enzyme-linked immunosorbent assay method in hepatitis C virus-positive (HCV+) dialysis and nonuremic patients, after a single subcutaneous injection of 3 million units. Ten HCV+/RNA+ patients (group A) with a normal renal function (mean serum creatinine: 1.03 +/- 0.26 [SD] mg/dl) and 10 HCV+/RNA+ patients undergoing chronic hemodialysis (group B) were included. The pharmacokinetic profiles of alphaIFN were determined after the very first subcutaneous injection of the drug. Plasma alphaIFN concentrations were determined before the injection and then 1, 2, 3, 4, 6, 8, 12, 16, 20, 24, 28, 32, and 36 h after the injection. They were assessed by means of an enzyme-linked immunosorbent assay test. Patients from both groups had a similar body surface area. It was found that in group B: (1) the mean maximum (SD) serum alphaIFN concentration (Cmax) was significantly higher (52 +/- 12 pg/ml) than in group A (39 +/- 12 pg/ml; P = 0.03); (2) the time at which Cmax occurred (Tmax) was significantly higher (10 +/- 3 h) than in group A (7.5 +/- 2 h; P = 0.05); (3) the observed area under the plasma alphaIFN concentration-time curve was about twice as much, i.e., 936 +/- 212 pg x h/ml, as that for group A (485 +/- 184 pg x h/ml; P < 0.0001); and (4) the alphaIFN half-life was significantly longer (9.6 +/- 2.9 h) than in group A (5.3 +/- 1.3 h). As early as 24 h after the alphaIFN injection was given, the drug was no longer detectable in nonuremic patients' sera, whereas it could be detected up to the next injection in all of the dialysis patients' sera. When trough levels of alphaIFN were measured just before the 10th injection, they were always below the threshold level in the 10 patients from group A, i.e., 4.1 pg/ml, whereas in group B they were measurable for four of nine patients (P = 0.05) and ranged between 5.8 and 36.1 pg/ml. Severe neurologic side effects were observed only in group B, i.e., in three patients. Hemoglobin levels did significantly decrease but only in group B patients, and this was significantly correlated with the Cmax (r = 0.67; P = 0.03). This is the first controlled study to demonstrate that the clearance of alphaIFN is about twice as low in dialysis patients as in nonuremic patients. These results might be of relevance when deciding the optimal alphaIFN therapy scheme for HCV+ patients, either with normal renal function or undergoing chronic hemodialysis.

model and the other cytokines should be scrutinized.

We studied the efficacy of three interferon alfa-2b (IFN-alpha 2b) regimens for the retreatment of patients with chronic hepatitis C (CHC) with prior complete response followed by relapse. Consecutive patients with CHC who had a complete biochemical response but relapse after a first course of 6 months of IFN with 3 million units (MU) given subcutaneously three times per week were enrolled in the study. Six to 24 months after the end of the first treatment, the patients were randomly assigned to receive IFN with either the same regimen (group 1), a regimen of 12 months with 3 MU (group 2), or a regimen of 6 months with 10 MU (group 3). Sustained biochemical response was defined as normal serum alanine transaminase (ALT) values during the follow-up and sustained virological response as a clearance of hepatitis C virus (HCV) RNA from the serum at the end of follow-up (6 months' posttreatment). Histological improvement was defined as a decrease of 1 point in Metavir score between the first liver biopsy and a biopsy performed at 6 months' postretreatment. Two hundred forty-seven patients were randomized: 75 to group 1, 91 to group 2, and 81 to group 3. In an intent-to-treat analysis, 12%, 36.3%, and 18.5% of patients had a sustained biochemical response after retreatment in groups i, 2, and 3, respectively (P <.001); 13.8%, 32.4%, and 17.2% of patients had a sustained virological response after retreatment in groups i, 2, and 3, respectively (P <.05). A low viral load and patients in group 2 were independently associated with a sustained biochemical response. A low Knodell score index before treatment, patients with a high level of ALT before retreatment, genotype 3, low viral load, and patients in group 2 were independently associated with sustained virological response. Younger age, a high level of ALT, a low level of gamma-glutamyl transferase before retreatment, low viral load, and patients in group 2 were independently associated with sustained biochemical and virological response. Among the 80 patients with repeated liver biopsies, 47.6% had improved histological activity scores; this improvement was associated with a sustained biochemical and virological response. In patients with CHC initially treated with 3 MU of IFN given subcutaneously three times per week over a 6-month period, and who subsequently developed a relapse after a biochemical response, retreatment with a regimen of 3 MU of IFN given three times per week for 12 months produced better biochemical and virological sustained response rates than regimens involving a higher dose or a shorter duration of retreatment. The biochemical and virological sustained response was associated with histological improvement.

Observations of circular structures in a permanent plot in a natural dense tropical forest of the Western Ghats (India) led to formulation of new hypotheses on the spatial organization resulting from interactions between trees. Here we propose a canopy regeneration process that does not involve treefall gaps. The peculiar spatial circular structure is composed of a central dominant tree with less than two trees under its crown and five or more other trees forming a ring at the limit of its crown. Such a structure is supposed to occur under certain conditions and, in particular, under strong competition for light. We describe a regeneration mechanism based on replacement of the central tree by a shift to one of the trees in its peripheral ring so that progressive recovery of the canopy occurs without large gap dynamics. We built a spatial simulator of forest dynamics in order to investigate the occurrence of such spatial structures and to examine their role in canopy regeneration. The model is an individual-based spatial model for mixed uneven-aged forest stands and accounts for annual evolution of the trees in the simulated stand, incorporating mortality, recruitment, growth and competition processes. The main originality of this model lies in the description of crown growth in eight cardinal directions, and in the use of neighbor position and size to express competitive interactions. The model demonstrates the development of the circular spatial structures in simulated stands as those observed in the permanent plot and shows that the proposed canopy regeneration mechanism can occur in the absence of perturbation. (C) 1997 Elsevier Science B.V.

A marked change in vegetation of the Western Ghats at ca. 3500 yr BP (uncalibrated14C yr) has been observed from a study of two marine cores taken from the inner shelf off Karwar (Karataka, western India), near the mouth of the Kalinadi River. This change is indicated by decrease in tree pollen, particularly those of evergreen forests, reduction of mangrove derived pollen, and by corresponding increase of savanna grass pollen. At the same time, the stable carbon isotopic ratios of organic matter increased abruptly, indicating a higher contribution of organic matter of marine origin and consequently reduced input of terrestrial organic matter due to reduced flow of the Kalinadi River. All these changes point to a less humid climate and shorter rainy season in the region, and are unlikely to result from human activity. The pattern of drier climate associated with forest reduction, increase of savanna elements, decrease of the mangrove vegetation, lower fresh water runoff of the Kalinadi River, continued up to ca. 2200 yr BP. Since then, the pollen assemblages have remained uniform up to the present day. We conclude that the climate similar to the present one was established in the studied area about 2200 yr ago.