1,008 research outputs found
On the strength of columns
The main object of these experiments was to
determine how columns behave before collapse under
axial loading. The original title of the research
was "An investigation into the factors determining
the strength of built-up steel struts". The title
had to be amended as the testing machines necessitated
the use of "model" sections.In mathematical investigations the columns
considered are taken as ideal, and therefore materially
different from actual columns. To some
extent this difference could be attributed to the
difference between theoretical assumed conditions
of elasticity and those found in actual metals as
manufactured. A more important cause of the
difference is the varying nature of the end conditions
employed. The results of the accurate researches
of such men as Tetmajer, Hodgkinson,
Christie and Howard, who brought with them not only
ripe experience but careful and clear methods of experimenting
are a testimony to the difficulty of reconciling
theory and experiment.In the enthusiasm generated more than 150
years ago by the work of Euler, mathematical formulae
were established with the purpose of making
allowance for the imperfections existing in a practical
column. So far a 3 the author is aware the
subject has been treated only mathematically and
no one has approached it experimentally, except to
determine the effects of the direct eccentricity
of loading. Despite the many minute mathematical
investigations made, the comparative accuracy and
even the validity of them is still doubtful. The
a uthor’s discussions on the "Imperfection tests"
show that the only variant of noteworthy consequence
is the eccentricity of loading: the other
imperfections, unless of a critical magnitude,
having practically negligible effects on the ultimate
strength of a column.Among the most notable features of the au t h o r ’s
work could be considered the collective view of
the stress-strain diagrams, thejintroduction of the
virtual coefficients of elasticity, the definite
divisions of the column graph, quantitative data
about "permanent set", "imperfection tests" and
the method for the adequate allowance in area due
to rivet holes in a built-up piece.The bending formulae determined for long
columns represent more accurately most of the experimental
results. The yield range,- represented
by a straight line law,- has not been definitely
formulated. This is due to the fact that the exact
values of the critical compressive and the tensile
stress determining the range were not known with
sufficient accuracy for the materials used by the
earlier experimenters. No one, except Robertson,
has carried out crushing tests with a view to
determine the exact compressive stress-strain relations.
It can be stated that the yield range
will be represented by an equation of the formp = A + B - Cx2/k , where
A - a constant depending on the material.
B = a constant depending on the end conditions,
C =a reducing factor depending on the end
conditions.The behaviour of built-up columns has been the
subject of world-wide discussion. The author’s
views regarding the "non-homogeneous" action of the
columns and the reduction in area for rivet holes
are fully described in this Thesis.Though the present investigations embrace
only a’”limited part of the vast field of experimental
columns, the author feels that similar methods
applied to full-sized sections will give results of
value to the practical designer. A programme of
column tests should include not only tension tests
but also crushing tests with a view to determine
the primary stress-strain relations. More "rivetreduction"
experiments are needed to test the conclusions
arrived at for the adequate allowance in
area due to rivet holes
Numerical Modeling of a Wave Turbine and Estimation of Shaft Work
Wave rotors are periodic-flow devices that provide dynamic pressure exchange and efficient energy transfer through internal pressure waves generated due to fast opening and closing of ports. Wave turbines are wave rotors with curved channels that can produce shaft work through change of angular momentum from inlet to exit. In the present work, conservation equations with averaging in the transverse directions are derived for wave turbines, and quasi-one-dimensional model for axial-channel non-steady flow is extended to account for blade curvature effects. The importance of inlet incidence is explained and the duct angle is optimized to minimize incidence loss for a particular boundary condition. Two different techniques are presented for estimating the work transfer between the gas and rotor due to flow turning, based on conservation of angular momentum and of energy. The use of two different methods to estimate the shaft work provides confidence in reporting of work output and confirms internal consistency of the model while it awaits experimental data for validation. The extended wave turbine model is used to simulate the flow in a three-port wave rotor. The work output is calculated for blades with varying curvature, including the straight axial channel as a reference case. The dimensional shaft work is reported for the idealized situation where all loss-generating mechanisms except flow incidence are absent, thus excluding leakage, heat transfer, friction, port opening time, and windage losses. The model developed in the current work can be used to determine the optimal wave turbine designs for experimental investment
Foreseeing India-China relations : the 'compromised context' of rapprochement
For more about the East-West Center, see http://www.eastwestcenter.org/</a
Automatic semantic segmentation and classification of remote sensing data for agriculture
Automatic semantic segmentation has expected increasing interest for researchers in recent years on multispectral remote sensing (RS) system. The agriculture supports 58 % of the population, in which 51 % of geographical area is under cultivation. Furthermore, the RS in agriculture can be used for identification, area estimation and monitoring, crop detection, soil mapping, crop yield modelling and production modelling etc. The RS images are high resolution images which can be used for agricultural and land cover classifications. Due to its high dimensional feature space, the conventional feature extraction techniques represent a progress of issues when handling huge size information e.g., computational cost, processing capacity and storage load. In order to overcome the existing drawback, we propose an automatic semantic segmentation without losing the significant data. In this paper, we use SOMs for segmentation purpose. Moreover, we proposed the particle swarm optimization technique (PSO) algorithm for finding cluster boundaries directly from the SOMs. On the other hand, we propose the deep residual network to achieve faster training process. Deep Residual Networks have been proved to be a very successful model on RS image classification. The main aim of this work is to achieve the overall accuracy greater than 85 % (OA > 85 %). So, we use a convolutional neural network (CNN), which outperforms better classification of certain crop types and yielding the target accuracies more than 85 % for all major crops. Furthermore, the proposed methods achieve good segmentation and classification accuracy than existing methods. The simulation results are further presented to show the performance of the proposed method applied to synthetic and real-world datasets
Volumetric Plasma Discharge in a Coaxial Electrode Configuration Using Repetitively Pulsed Nanosecond Discharges
Transient plasma discharges can be created in di erent electrode geometries and the
use of a coaxial electrodes can assist in initiating ignition at multiple points at the same
time to create volumetric ignition. The current study investigates discharge formation in a
coaxial electrode in quiescent, atmoshpheric and non-reacting conditions. This is the rst
systematic study to understand the behavior of such a discharge as a function of di erent
pulse parameters like pulse width (40-110 ns), repetition frequency (1-50 kHz) and input
voltage (14-20 kV). Additionally, the polarity of the central electrode was changed between
positive and negative. An intensi ed ccd camera was used to visualize the discharge for-
mation. The exposure of the camera is set to capture 500 discharges in a single frame. The
discharges were found to behave di erently for positive and negative polarity discharges.
The positive polarity discharge tends to form a strong arc and spins around the outer
cylinder which is con rmed using a high speed camera. The negative polarity discharges
form a uniform streamer discharge for most of the pulse parameters. The current study
has provided an initial understanding of the dynamics of plasma discharges in a coaxial
electrode
A REVIEW ON PHARMACO KINETIC DRUG INTERACTIONS OF STATINS
The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are generally well tolerated as monotherapy. Statins are associated with two important adverse effects, asymptomatic elevation in liver enzymes and myopathy. Myopathy is most likely to occur when statins are administered with other drugs. Statins are substrates of multiple drug transporters (including OAT- -P1B1, BCRP and MDR1) and several cytochrome P450 (CYP) enzymes (including CYP3A4, CYP2C8, CYP2C19, and CYP2C9). Possible adverse effects of statins can occur due to interactions in concomitant use of drugs that substantially inhibit or induce their methabolic pathway. This review aim is to summarize the most important interactions of statins
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