scholarly journals The properties of torsional vibrations reciprocating engine shafts.— Part I

1926 ◽  
Vol 113 (764) ◽  
pp. 259-271 ◽  
Keyword(s):  
Quantitative Agreement ◽  
Engineering Practice ◽  
Torsional Vibrations ◽  
Reciprocating Motion ◽  
Numerical Accuracy ◽  
Reciprocating Engine ◽  
Refined Method ◽  
Analytical Results ◽  
The Subject ◽  
Set Up

In a previous paper by the writer an examination was made of the torsional vibrations occurring in a reciprocating engine shaft. The case studied was that of a shaft driven by a six-cylinder engine, all parts except the shaft being considered rigid. Certain interesting results, arising from the action of the reciprocating parts, appeared. On account of the importance of the subject of torsional vibrations in engineering practice, and on account of the unexpected nature of the analytical results, it was considered of some interest to examine in greater detail the effect of the reciprocating parts in producing or modifying the vibrations. For this purpose a model is proposed which, it is considered, is as simple as can be conceived, and which, at the same time, involves the characteristics of reciprocating motion. The model is described and the analytical results obtained in Part I of this paper. To verify the analysis, the model was set up in the laboratory and the vibrations observed. Further, to simplify the experimental work, it was thought sufficient for the purposes of verification to arrange it in the first place so as to give only a qualitative agreement with theory, and therefore a precise quantitative agreement was not aimed at, and should not be looked for. An experiment on a much more refined method is being proceeded with to examine minutely into the numerical accuracy of the theory. The details of the present experiment and the numerical results are given in Part II.

Torsional Vibrations in Reciprocating Engines

1976 ◽  
Vol 20 (01) ◽  
pp. 32-39
Author(s):  
M. S. Pasricha ◽  
W. D. Carnegie
Keyword(s):  
Torsional Vibration ◽  
Mean Value ◽  
Engineering Practice ◽  
Torsional Vibrations ◽  
Secondary Resonance ◽  
Reciprocating Engines ◽  
Marine Engines ◽  
The Subject ◽  
Theoretical Results ◽  
Crank Mechanism

In the case of reciprocating engines, there are certain critical speeds of running at which the torsional vibrations in the shaft become large in amplitude and introduce an element of danger into the system. Fairly simple methods have been devised for the practical calculations to predict the torsional vibration characteristics from the constants of the machinery. The torsional vibration phenomenon in the running gear of reciprocating machinery is usually dealt with by considering a series of constant inertias connected by sections of massless shafting. In recent years several cases of fractures in the crankshafts of large marine engines have been attributed to the phenomenon of secondary resonance, which is explained from the fact that the effective inertia of each slider-crank mechanism varies about a mean value in relation to the position of the crank. Simplified theories predicted these designs of diesel engines as safe in practice. In view of the importance of the subject of torsional vibrations in engineering practice, the effects of variation in inertia on the torsional vibration of the system are examined in detail in the present paper. A comparison of theoretical results with Goldsbrough's experimental results is included.

M. V. Nadkarni. Farmer's Movements in India. New Delhi: Allied Publishers Pvt. Ltd., 1987.237 pp.,Price: (hardbound edition) Rupees (Indian) 100.00.

1988 ◽  
Vol 27 (3) ◽  
pp. 333-335
Author(s):  
Khwaja Sarmad
Keyword(s):  
Tamil Nadu ◽  
Rural Poverty ◽  
Price Policy ◽  
New Delhi ◽  
Root Cause ◽  
The Subject ◽  
The Rich ◽  
Land Holdings ◽  
Set Up ◽  
Agricultural Price

This book is a comprehensive analysis of farmers' movements in India with a focus on the movements in Tamil Nadu, Maharashtra, Punjab and Karnatka. It examines the economic, social and political aspects of the farmers' struggle for a better deal within regional and national perspectives and evaluates the potential impact of these struggles on economic development in general, and on rural development, in particular. In a most competent way the author has presented the current state of the debate on the subject. He deals exhaustively with the subject of agricultural price policy and argues against the proposition that favourable price-setting for farm products is adequate to alleviate rural poverty. A better way to tackle this problem is to improve the per capita output in the rural sector, since the root cause of the problem is not unfavourable terms of trade but the increasing proportion of land holdings, which are economically not viable. Agricultural price policy is analyzed within the context of class relations, which enables to establish a link between the economic and political demands of the farmers. This analysis leads the author to conclude, that in contrast with the peasants' movements in India, which helped to break up the feudal agrarian set-up, the recent farmers' movements, with a few exceptions, have little revolutionary content. Their leadership has been appropriated by the rich landowners, who have transformed the movements into a lobby for advancing their own interests, within the existing power structure, to the neglect of the poorer peasantry.

HUBUNGAN ANTARA JIWA WIRAUSAHA MAHASISWA DENGAN MOTIVASI, LINGKUNGAN KELUARGA DAN PENDIDIKAN PADA POLITEKNIK LP3I JAKARTA KAMPUS BEKASI

2018 ◽  
Vol 6 (2) ◽  
pp. 14
Author(s):  
Darmawan Darmawan ◽  
Jajang Setiawan
Keyword(s):  
Key Words ◽  
Family Background ◽  
Research Result ◽  
Education Institution ◽  
Education Level ◽  
Study Program ◽  
Economic Level ◽  
The Subject ◽  
Set Up

<p align="center"><strong>ABSTRACT</strong><strong></strong></p><p align="center"><strong> </strong></p><p align="justify"><em>Today, the growth of economic level begins to rise again that is generated by the increase of   different kind of product and different kind of businesses that are offered by both individual businesses that are done easly independently. To deal with all of business trends, the education institution has to prepare the students to be able to set up a business idenpendedntly through the subject of entrepeuneurship.  As it is regulated in Vision and Mision of study program and is also regulated in the curriculum of lectures. </em><em></em></p><p align="justify"><em>This research is aimed at to find out the correlation between the spirit of entrepeunership and motivation , Family background, and education level. Based on the research result, the finding showed that the spirit of entrepeneurship correlated with the motivation and family background. Based on the finding, it was also found that education level did not correlate with that the spirit of entrepeneurship. In regard with the findings, it is important to develop more the motivation of students to touch up the sperit of entrepenuership. </em><em></em></p><p align="justify"> </p><p><em>Key words: Entrepenuer, Students, Entrepeuneurship. </em></p>

scholarly journals On Kaufmann's theory of the impact of the pianoforte hammer

1920 ◽  
Vol 97 (682) ◽  
pp. 99-110 ◽  
Keyword(s):  
Initial Conditions ◽  
Practical Importance ◽  
Prima Facie ◽  
Point Of View ◽  
Infinite Length ◽  
Modes Of Vibration ◽  
Rigorous Treatment ◽  
The Subject ◽  
Set Up ◽  
The Impact

The theory of the vibrations of the pianoforte string put forward by Kaufmann in a well-known paper has figured prominently in recent discussions on the acoustics of this instrument. It proceeds on lines radically different from those adopted by Helmholtz in his classical treatment of the subject. While recognising that the elasticity of the pianoforte hammer is not a negligible factor, Kaufmann set out to simplify the mathematical analysis by ignoring its effect altogether, and treating the hammer as a particle possessing only inertia without spring. The motion of the string following the impact of the hammer is found from the initial conditions and from the functional solutions of the equation of wave-propagation on the string. On this basis he gave a rigorous treatment of two cases: (1) a particle impinging on a stretched string of infinite length, and (2) a particle impinging on the centre of a finite string, neither of which cases is of much interest from an acoustical point of view. The case of practical importance treated by him is that in which a particle impinges on the string near one end. For this case, he gave only an approximate theory from which the duration of contact, the motion of the point struck, and the form of the vibration-curves for various points of the string could be found. There can be no doubt of the importance of Kaufmann’s work, and it naturally becomes necessary to extend and revise his theory in various directions. In several respects, the theory awaits fuller development, especially as regards the harmonic analysis of the modes of vibration set up by impact, and the detailed discussion of the influence of the elasticity of the hammer and of varying velocities of impact. Apart from these points, the question arises whether the approximate method used by Kaufmann is sufficiently accurate for practical purposes, and whether it may be regarded as applicable when, as in the pianoforte, the point struck is distant one-eighth or one-ninth of the length of the string from one end. Kaufmann’s treatment is practically based on the assumption that the part of the string between the end and the point struck remains straight as long as the hammer and string remain in contact. Primâ facie , it is clear that this assumption would introduce error when the part of the string under reference is an appreciable fraction of the whole. For the effect of the impact would obviously be to excite the vibrations of this portion of the string, which continue so long as the hammer is in contact, and would also influence the mode of vibration of the string as a whole when the hammer loses contact. A mathematical theory which is not subject to this error, and which is applicable for any position of the striking point, thus seems called for.

scholarly journals Theorizing Teacher Responsibility in an Age of Neoliberal Accountability

2019 ◽  
Vol 1 (1) ◽  
pp. 179-195 ◽  
Author(s):  
Tina Besley
Keyword(s):  
Homo Economicus ◽  
Teacher Responsibility ◽  
Keynesian Economics ◽  
The Great Depression ◽  
Market Rationality ◽  
The Subject ◽  
Neoliberal Policies ◽  
Set Up ◽  
The Individual ◽  
The Welfare State

This article explores concepts of teacher responsibility, accountability, being in loco parentis, and responsibilization as many advanced capitalist societies have dropped policies and practices that were set up in the mid 19th century after the Great Depression in the welfare state under Keynesian economics. Since the early 1980s most of these states have adopted neoliberal policies and market rationality for all aspects of social policy including education. Under neoliberalism, the subject theorised by Homo economicus, is one that is theorised as a rational autonomous individual, with its responsibilized behavior underpinning much of how not only teachers but students now are compleed to behace and perform. These have resulted in major shifts in attitudes to professionalism of teachers, in responsibilising individuals and so have impacted on subjectivity as the state has pulled back from all manner of social provision and has responsibilized the individual to be a consumer-citizen, a prudential and entrepreneurial self even in terms of education. The upshot is increasing use of audits, checklists and accountability regimes for teachers who are becoming increasingly a de-professionalised in a low-trust managerialist environment with students as consumers.

Computer Simulation of a Press Feed Mechanism and Experimental Confirmation

1994 ◽  
Vol 116 (1) ◽  
pp. 248-256 ◽  
Author(s):  
C. Chassapis ◽  
G. G. Lowen
Keyword(s):  
Computer Simulation ◽  
Data Acquisition System ◽  
Quantitative Agreement ◽  
Drive Shaft ◽  
Strain Gages ◽  
Motion Equations ◽  
Qualitative And Quantitative ◽  
Bending Strain ◽  
Out Of Plane ◽  
Set Up

An experimentally verified simulation of the elastic-dynamic behavior of a lever-type feed mechanism is presented. Based on a combination of experimental and analytical findings, simplified motion equations could be introduced. In the experimental set-up, the motion of the mechanism is monitored by three angular encoders, which are attached to the drive shaft, the rocker-link shaft, and the feed roller shaft, respectively. Their output, which is stored in a specially designed data acquisition system, allows the correlation of the instantaneous rotations of the feed roller and the rocker shafts to that of the drive shaft. Strain gages provide in and out-of-plane bending-strain histories of the bent coupler. Experiment and theory, for different loading conditions, are correlated by way of the coupler strain, the clutch windup angle and the total feed length. Good qualitative and quantitative agreement between computed and experimental results was found.

Variations in Skin Resistance and Their Relationship to G.S.R. Conditioning

1960 ◽  
Vol 106 (442) ◽  
pp. 281-287 ◽  
Author(s):  
Irene Martin
Keyword(s):  
Action Potentials ◽  
Background Activity ◽  
Skin Resistance ◽  
Muscle Action ◽  
Muscle Tonus ◽  
Experimental Procedure ◽  
Discontinuous Nature ◽  
The Subject ◽  
Neural Excitation ◽  
Set Up

Any particular system which is being conditioned is likely to maintain a certain level of background activity throughout the experimental procedure; either of a discontinuous nature, as, for example, with eyeblink, heart rate and respiratory cycle, or continuously, as in the case of basal skin resistance and muscle tonus. This background activity or level of arousal does not remain constant but usually varies in time, presumably as a result of underlying neural excitation or inhibition. It may increase throughout an experiment if the subject becomes highly motivated, as with the gradients of muscle action potentials observed by Bartoshuk (1955), or decrease, if the subject becomes more relaxed and familiar with the set-up, as Duffy and Lacey (1946) found with level of skin conductance.

External work in level and grade walking on a motor-driven treadmill

1960 ◽  
Vol 15 (5) ◽  
pp. 759-763 ◽  
Author(s):  
J. W. Snellen
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Total Energy Expenditure ◽  
The Body ◽  
External Work ◽  
Thermal Exchange ◽  
Level Walking ◽  
The Subject ◽  
Set Up ◽  
Physical Laws

When studying a walking subject's thermal exchange with the environment, it is essential to know whether in level walking any part of the total energy expenditure is converted into external mechanical work and whether in grade walking the amount of the external work is predictable from physical laws. For this purpose an experiment was set up in which a subject walked on a motor-driven treadmill in a climatic room. In each series of measurements a subject walked uphill for 3 hours and on the level for another hour. Metabolism was kept equal in both situations. Air and wall temperatures were adjusted to the observed weighted skin temperature in order to avoid any heat exchange by radiation and convection. Heat loss by evaporation was derived from the weight loss of the subject. All measurements were carried out in a state of thermal equilibrium. In grade walking there was a difference between heat production and heat loss by evaporation. This difference equaled the caloric equivalent of the product of body weight and gained height. In level walking the heat production equaled heat loss. Hence it was concluded that in level walking all the energy is converted into heat inside the body. Submitted on April 26, 1960

scholarly journals Coriolis effects on the elliptical instability in cylindrical and spherical rotating containers

2007 ◽  
Vol 585 ◽  
pp. 323-342 ◽  
Author(s):  
M. LE BARS ◽  
S. LE DIZÈS ◽  
P. LE GAL
Keyword(s):  
Growth Rates ◽  
Close Agreement ◽  
Unstable Mode ◽  
Quantitative Agreement ◽  
Fixed Rate ◽  
Elliptical Instability ◽  
Normal Mode Theory ◽  
Set Up ◽  
First Time ◽  
Selection Of

The effects of the Coriolis force on the elliptical instability are studied experimentally in cylindrical and spherical rotating containers placed on a table rotating at a fixed rate $\tilde{\Omega}^G$. For a given set-up, changing the ratio ΩG of global rotation $\tilde{\Omega}^G$ to flow rotation $\tilde{\Omega}^F$ leads to the selection of various unstable modes due to the presence of resonance bands, in close agreement with the normal-mode theory. No instability occurs when ΩG varies between −3/2 and −1/2 typically. On decreasing ΩG toward −1/2, resonance bands are first discretized for ΩG<0 and progressively overlap for −1/2 ≪ ΩG < 0. Simultaneously, the growth rates and wavenumbers of the prevalent stationary unstable mode significantly increase, in quantitative agreement with the viscous short-wavelength analysis. New complex resonances have been observed for the first time for the sphere, in addition to the standard spin-over. We argue that these results have significant implications in geo- and astrophysical contexts.

Finite Element Simulation and Experimental Study on Blow Forming of Plastic Cups

2011 ◽  
Vol 148-149 ◽  
pp. 1319-1322
Author(s):  
Xiao Hu ◽  
Yi Sheng Zhang ◽  
Hong Qing Li ◽  
De Qun Li
Keyword(s):  
Finite Element ◽  
Thickness Distribution ◽  
Viscoelastic Model ◽  
Engineering Practice ◽  
Fe Model ◽  
Thin Wall ◽  
Forming Process ◽  
Element Simulation ◽  
Physically Based ◽  
Set Up

Blow forming process of plastic sheets is simple and easy to realize, thus, it is widely used for plastic thin-wall parts. In the practical production, an effective method is needed for the preliminary set-up of process parameters in order to achieve accurate control of thickness distribution. Thus, a finite element method (FEM) code is used to simulate blow forming process. For better description of complex material theological characteristics, a physically based viscoelastic model (VUMAT forms Buckley model) to model the complex constitutive behavior is used. Nonlinear FE analyses using ABAQUS were carried out to simulate the blow forming process of plastic cups. The actual values at different locations show a satisfactory agreement with the simulation results: as a matter of fact the error along the cell mid-section did not exceed 0.02 mm on average, corresponding to 5% of the initial thickness, thus the FE model this paper can meet the requirements of the engineering practice.

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