The Efficiency of Gears in Consideration of Gear Size and Skewness of Gear Axes

1978 ◽  
Vol 100 (1) ◽  
pp. 85-91
Author(s):  
Y. Fujii ◽  
S. Shimachi
Keyword(s):  
High Efficiency ◽  
Contact Point ◽  
Gear Ratio ◽  
Gear Transmission ◽  
The Other ◽  
Gear Teeth ◽  
Contact Points ◽  
Transmission Mechanisms ◽  
The Mean ◽  
Instantaneous Axis

From the investigation about the dimensions of skew-axes gears now in common use, the ratio of the pitch radius of pinion to that of gear is found to depend almost only upon the gear ratio. On the other hand, the offset of the gear axes is desired to be as large as possible in usual cases of gear transmission mechanisms. Under these situations, the position of the mean contact point where a pair of gear teeth is expected to transmit power in high efficiency is investigated. The results are as follows: 1) The mean contact point which corresponds to high efficiency is in the neighborhood of the ruled surface swept by the instantaneous axis as the gear ratio continuously varies. 2) The majority of the mean contact points of gears now in use nearly coincide with the point mentioned in 1.

GEOMETRY OF CONTACT BETWEEN SELF-AFFINE SURFACES

Fractals ◽  
1995 ◽  
Vol 03 (01) ◽  
pp. 113-122 ◽  
Author(s):  
FRANCK PLOURABOUÉ ◽  
STÉPHANE ROUX ◽  
JEAN SCHMITTBUHL ◽  
JEAN-PIERRE VILOTTE
Keyword(s):  
Probability Distribution ◽  
Contact Point ◽  
Relative Shift ◽  
Lévy Walk ◽  
Contact Points ◽  
Roughness Exponent ◽  
Mean Shape ◽  
Before And After ◽  
Levy Walk ◽  
The Mean

We study the geometry of the contact between two rigid self-affine surfaces. We investigate the mean shape of the surface in the vicinity of the contact point as well as the probability distribution of apertures a as a function of the distance to the contact point. The latter reveals two distinct scaling regimes which are characterized. We show that as the two surfaces are shifted with respect to each other, the contact point on one surface undergoes a “Levy walk”. If u is the relative shift of the surfaces, the distance d between the two contact points (before and after the shift), scales as d ∝ uα where the exponent α is shown to be equal to the roughness exponent of the surfaces.

Mechanism of Lubrication by Surrounding Gas Molecules in Adhesive Wear

1978 ◽  
Vol 100 (4) ◽  
pp. 492-499 ◽  
Author(s):  
Norimune Soda ◽  
Tadashi Sasada
Keyword(s):  
Transition Point ◽  
Adhesive Wear ◽  
Contact Point ◽  
Free Time ◽  
Fundamental Relation ◽  
Clean Surface ◽  
Critical Transition ◽  
Contact Points ◽  
The Mean ◽  
Gas Molecules

To explain quantitatively the lubricating effect of gas molecules on adhesive wear, the authors have introduced a new concept of mean free time of a small contact point. When a bridge formed between two contact points is sheared off and a small clean surface is exposed to surrounding gases, it must have a free time t until it forms the next bridge when sliding. During this time t, the gas molecules attack the clean spot and can easily form a chemisorbed monolayer when the contact pressure p is low or when the sliding speed v is low. The authors have verified the fundamental relation between the mean free time t and the value pv, and have found that the critical transition point from the mild to severe wear corresponds to the condition where the mean free time of a sheared junction is just enough to be covered by the chemisorbed monolayer of surrounding gas molecules.

scholarly journals Design of Geometrical Parameters and Kinematical Characteristics of a Non-circular Gear Transmission for Given Parameters

2021 ◽  
Vol 11 (3) ◽  
pp. 1000
Author(s):  
Silvia Maláková ◽  
Matej Urbanský ◽  
Gabriel Fedorko ◽  
Vieroslav Molnár ◽  
Samuel Sivak
Keyword(s):  
Design Procedure ◽  
Gear Ratio ◽  
Gear Transmission ◽  
Gear Train ◽  
Final Part ◽  
Geometrical Parameters ◽  
Practical Application ◽  
Center Of Rotation ◽  
Gear Teeth ◽  
Pitch Curve

In this paper, the authors present the design of a suitable gear transmission with the continuously changing gear ratio in the range from 0.5 through 1.0 to 2.0 and back during one revolution of intermeshing gears, according to demands specified for a practical application. The gear train was designed as a pair of identical elliptical gears and the design procedure of the suitable pitch curve (ellipse) is described. The center of rotation of each of the gears is coincident with one of the pitch ellipse foci, so the gears are placed eccentrically. The gear teeth have involute profiles, but the involutes for the active and for the passive tooth sides are different. These are gears with an asymmetrical tooth profile. In the final part, the paper deals with kinematical characteristics of the designed non-circular gear transmission, which differ from the kinematical characteristics of standard circular gear transmissions with a constant gear ratio.

The Relationship between the Distribution Characteristics of Cutting Speed at the Contact-Point and the Surface Quality of Gear Teeth

2010 ◽  
Vol 135 ◽  
pp. 128-133 ◽  
Author(s):  
Guo Xing Liang ◽  
Ming Lv ◽  
Xiao Xu Gao
Keyword(s):  
Surface Roughness ◽  
Contact Line ◽  
Surface Texture ◽  
Contact Point ◽  
Cutting Speed ◽  
Distribution Characteristics ◽  
Gear Teeth ◽  
Contact Points ◽  
The Relationship

In the paper, the vector expression of cutting speed on the contact-points has been obtained by the coordinate transformation. The cutting speed is the contact-point position function which is correlated with contact-line in the process of honing gear. It is diverse along the direction of the tooth depth, so the surface texture of workpiece gear has a visible difference from the top to the root of the tooth. It is showed in the results that the surface roughness value of same tooth has further increscent differences with the increasing honing speed, and the surface of tooth is in the same quality.

scholarly journals Analysis of interjaw ratios in relation to permanent tooth size in subjects with class I malocclusion

2010 ◽  
Vol 63 (5-6) ◽  
pp. 343-348
Author(s):  
Gordana Filipovic ◽  
Mirjana Janosevic ◽  
Maja Stosic
Keyword(s):  
Contact Point ◽  
Permanent Dentition ◽  
The Other ◽  
Class I ◽  
Tooth Size ◽  
Mean Values ◽  
Lower Jaw ◽  
Tooth Width ◽  
The Mean ◽  
Anterior Ratio

Introduction. A certain ratio of maxillary to mandibular tooth size is very important for the proper occlusion formation. In regular occlusion, the teeth must be proportional to size. A discrepancy in tooth size between the mandibular and maxillary arch is usually the cause of disharmonious occlusion ratios. One of the most widespread methods in determining of discrepancy in tooth size between the upper and lower jaw is the Bolton analysis of mesiodistal width of permanent teeth. Material and methods. The subjects of both sexes with the permanent dentition and occlusive ratio of Angle Class I classification had had the precise impressions taken on the basis of which the study models were obtained. 60 patients were selected for this investigation (30 males and 30 females) according to the following criteria: the presence of completely erupted teeth of permanent dentition from the first molar on one side to the first molar on the other side of the dental string; good quality of the study models; the absence of mesiodistal and occlusive abrasion, caries lesions, Class II fillings; the absence of prosthetic or composite restoration; the absence of anomalies in regard to shapes, structures and tooth development. We measured the mesiodistal width of each tooth from the first molar on one side to the first molar on the other side, from the mesial contact point to the distal contact point with the greatest interproximal distance. Results. The obtained results for mesiodistal tooth width of the right and left side do not show statistically significant differences. The mean values of the Bolton anterior ratio showed neither the sexual dimorphism nor did the mean values of the Bolton total ratio show any differences in sexes. The mean values of the Bolton anterior ratio in our examinees of both sexes are significantly higher compared to the values of Bolton norms. The mean values of the Bolton total ratios in our examinees of both sexes were not statistically different compared to the values of Bolton norms. Conclusion. Determining of intermaxillary ratios is an important diagnostic and prognostic value in orthodoncy since it offers a possibility to predict the outcome of orthodontic therapy applied on persons with tooth size discrepancy related to the upper and lower jaw.

Multi-Center Study of Thromboplastin Calibration Precision – Influence of Reagent Species, Composition, and International Sensitivity Index (ISI)

1993 ◽  
Vol 69 (01) ◽  
pp. 035-040 ◽  
Author(s):  
A M H P van den Besselaar ◽  
R M Bertina
Keyword(s):  
Oral Anticoagulants ◽  
International Normalized Ratio ◽  
The Other ◽  
World Health ◽  
Rabbit Brain ◽  
Sensitivity Index ◽  
Bovine Plasma ◽  
Significant Difference ◽  
The Mean ◽  
International Sensitivity Index

SummaryFour thromboplastin reagents were tested by 18 laboratories in Europe, North-America, and Australasia, according to a detailed protocol. One thromboplastin was the International Reference Preparation for ox brain thromboplastin combined with adsorbed bovine plasma (coded OBT/79), and the second was a certified reference material for rabbit brain thromboplastin, plain (coded CRM 149R). The other two thromboplastin reagents were another rabbit plain brain thromboplastin (RP) with a lower ISI than CRM 149R and a rabbit brain thromboplastin combined with adsorbed bovine plasma (RC). Calibration of the latter two reagents was performed according to methods recommended by the World Health Organization (W. H. O.).The purpose of this study was to answer the following questions: 1) Is the calibration of the RC reagent more precise against the bovine/combined (OBT/79) than against the rabbit/plain reagent (CRM 149R)? 2) Is the precision of calibration influenced by the magnitude of the International Sensitivity Index (ISI)?The lowest inter-laboratory variation of ISI was observed in the calibration of the rabbit/plain reagent (RP) against the other rabbit/plain reagent (CRM 149R) (CV 1.6%). The highest interlaboratory variation was obtained in the calibration of rabbit/plain (RP) against bovine/combined (OBT/79) (CV 5.1%). In the calibration of the rabbit/combined (RC) reagent, there was no difference in precision between OBT/79 (CV 4.3%) and CRM 149R (CV 4.2%). Furthermore, there was no significant difference in the precision of the ISI of RC obtained with CRM 149R (ISI = 1.343) and the rabbit/plain (RP) reagent with ISI = 1.14. In conclusion, the calibration of RC could be performed with similar precision with either OBT/79 or CRM 149R, or RP.The mean ISI values calculated with OBT/79 and CRM 149R were practically identical, indicating that there is no bias in the ISI of these reference preparations and that these reference preparations have been stable since their original calibration studies in 1979 and 1987, respectively.International Normalized Ratio (INR) equivalents were calculated for a lyophilized control plasma derived from patients treated with oral anticoagulants. There were small but significant differences in the mean INR equivalents between the bovine and rabbit thromboplastins. There were no differences in the interlaboratory variation of the INR equivalents, when the four thromboplastins were compared.

Prothrombin Time Standardization: Report of the Expert Panel on Oral Anticoagulant Control

1979 ◽  
Vol 42 (04) ◽  
pp. 1073-1114 ◽  
Keyword(s):  
Prothrombin Time ◽  
Expert Panel ◽  
The Other ◽  
Rabbit Brain ◽  
Calibration Constant ◽  
Freeze Dried ◽  
The Mean ◽  
Point Of Intersection ◽  
And Control ◽  
Standardization Report

SummaryIn collaborative experiments in 199 laboratories, nine commercial thromboplastins, four thromboplastins held by the National Institute for Biological Standards and Control (NIBS & C), London and the British Comparative Thromboplastin were tested on fresh normal and coumarin plasmas, and on three series of freeze-dried plasmas. One of these was made from coumarin plasmas and the other two were prepared from normal plasmas; in each series, one plasma was normal and the other two represented different degrees of coumarin defect.Each thromboplastin was calibrated against NIBS&C rabbit brain 70/178, from the slope of the line joining the origin to the point of intersection of the mean ratios of coumarin/normal prothrombin times when the ratios obtained with the two thromboplastins on the same fresh plasmas were plotted against each other. From previous evidence, the slopes were calculated which would have been obtained against the NIBS&C “research standard” thromboplastin 67/40, and termed the “calibration constant” of each thromboplastin. Values obtained from the freeze-dried coumarin plasmas gave generally similar results to those from fresh plasmas for all thromboplastins, whereas values from the artificial plasmas agreed with those from fresh plasmas only when similar thromboplastins were being compared.Taking into account the slopes of the calibration lines and the variation between laboratories, precision in obtaining a patient’s prothrombin time was similar for all thromboplastins.

Platelet Suruival and Function in Rats with Enhanced Thrombotic Tendency

1985 ◽  
Vol 54 (04) ◽  
pp. 739-743 ◽  
Author(s):  
Federica Delaini ◽  
Elisabetta Dejana ◽  
Ine Reyers ◽  
Elisa Vicenzi ◽  
Germana De Bellis Vitti ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Nephrotic Syndrome ◽  
Platelet Function ◽  
Laboratory Tests ◽  
Thrombus Formation ◽  
The Other ◽  
Mean Survival Time ◽  
The Mean ◽  
And Function ◽  
Thrombotic Tendency

SummaryWe have investigated the relevance of some laboratory tests of platelet function in predicting conditions of thrombotic tendency. For this purpose, we studied platelet survival, platelet aggregation in response to different stimuli, TxB2 and 6-keto-PGFlα production in serum of rats bearing a nephrotic syndrome induced by adriamycin. These animals show a heavy predisposition to the development of both arterial and venous thrombosis. The mean survival time was normal in nephrotic rats in comparison to controls. As to aggregation tests, a lower aggregating response was found in ADR-treated rats using ADP or collagen as stimulating agents. With arachidonic acid (AA) we observed similar aggregating responses at lower A A concentrations, whereas at higher AA concentrations a significantly lower response was found in nephrotic rats, despite their higher TxB2 production. Also TxB2 and 6-keto-PGFlα levels in serum of nephrotic rats were significantly higher than in controls. No consistent differences were found in PGI2-activity generated by vessels of control or nephrotic rats.These data show that platelet function may appear normal or even impaired in rats with a markedly increased thrombotic tendency. On the other hand, the significance of high TxB2 levels in connection with mechanisms leading to thrombus formation remains a controversial issue.

Voronoi Analysis of a Soccer Game

2004 ◽  
Vol 9 (3) ◽  
pp. 233-240 ◽  
Author(s):  
S. Kim
Keyword(s):  
Collective Behavior ◽  
Quantitative Assessment ◽  
The Other ◽  
Analysis Method ◽  
Random System ◽  
Soccer Game ◽  
Voronoi Polygons ◽  
The Mean

This paper describes a Voronoi analysis method to analyze a soccer game. It is important for us to know the quantitative assessment of contribution done by a player or a team in the game as an individual or collective behavior. The mean numbers of vertices are reported to be 5–6, which is a little less than those of a perfect random system. Voronoi polygons areas can be used in evaluating the dominance of a team over the other. By introducing an excess Voronoi area, we can draw some fruitful results to appraise a player or a team rather quantitatively.

Solid, slightly soluble phosphorus compounds as nutrient source in activated sludge treatment of forest industry wastewaters

1997 ◽  
Vol 35 (2-3) ◽  
pp. 131-138 ◽  
Author(s):  
Pirjo-Riitta Rantala ◽  
Hannu Wirola
Keyword(s):  
Activated Sludge ◽  
The Other ◽  
Phosphorus Compounds ◽  
Forest Industry ◽  
Phosphorus Concentration ◽  
Nutrient Source ◽  
Sludge Treatment ◽  
Grain Sizes ◽  
Soluble Phosphorus ◽  
The Mean

The aim of the study was to determine if solid, slightly soluble compounds can be used as nutrient source in activated sludge treatment plants instead of liquid phosphoric acid. Four different solid materials were tested in lab-scale solubility tests to find compounds which are least soluble. Two materials were chosen for further studies: apatite and raw phosphate. The use of apatite and raw phosphate as nutrient source was studied in lab-scale activated sludge reactors along with a control reactor where phosphorus was added in liquid form. The phosphorus dosage, measured as elementary phosphorus, was the same for all three reactors. The reactors were fed with pre-clarified chemi-thermomechanical pulp mill (CTMP) wastewater. There were no significant differences in the reductions of organic matter between the three reactors. The mean effluent concentration of total phosphorus was 3 mg P/l in the control reactor and less than 1 mg P/1 in the other two reactors. The soluble phosphorus concentration was more than 2 mg P/l in the control reactor and less than 0.5 mg P/l in the other two. Apatite was an even better nutrient source than raw phosphate. Further lab-scale tests were conducted using two different grain sizes of apatite. No significant differences were found between the studied grain sizes (<0.074 mm and 0.074 mm-0.125 mm). Apatite was then used in full-scale at a CTMP-mill two different times. The experiments showed that the mean concentrations of phosphorus can be reduced radically by using apatite as a nutrient source instead of liquid phosphorus. Solid phosphorus compounds are a viable alternative to reduce the phosphorus load from forest industry wastewater treatment plants.

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