Theoretical Analyses and Experimental Studies of Reliability and Stability of the Gland Packing

Author(s):  
Hao Mu-Ming ◽  
Gu Yong-Quan
Author(s):  
Jerzy Wojewoda ◽  
Andrzej Stefański ◽  
Marian Wiercigroch ◽  
Tomasz Kapitaniak

In this paper, the phenomena of hysteretic behaviour of friction force observed during experiments are discussed. On the basis of experimental and theoretical analyses, we argue that such behaviour can be considered as a representation of the system dynamics. According to this approach, a classification of friction models, with respect to their sensitivity on the system motion characteristic, is introduced. General friction modelling of the phenomena accompanying dry friction and a simple yet effective approach to capture the hysteretic effect are proposed. Finally, the experimental results are compared with the numerical simulations for the proposed friction model.


2018 ◽  
Vol 45 (10) ◽  
pp. 4519-4528 ◽  
Author(s):  
Ran Zhang ◽  
Juan P. Cruz-Bastida ◽  
Daniel Gomez-Cardona ◽  
John W. Hayes ◽  
Ke Li ◽  
...  

Author(s):  
Edgar Onea

This chapter provides an overview of the most important theoretical positions on the exhaustivity inference often associated with it-clefts in English and comparable structures in other languages alongside with a brief review of the results of a number of experimental studies. There is a surprising discrepancy between the predictions of the theoretical analyses and the empirical findings. While theoretical approaches tend to derive exhaustivity as a necessary semantic inference, most experimental studies suggest that the exhaustivity of it-clefts might be a pragmatic inference. The chapter discusses this discrepancy in some detail and suggests some potential solutions.


2015 ◽  
Vol 15 (2) ◽  
pp. 187-234 ◽  
Author(s):  
Anthi Revithiadou ◽  
Kalomoira Nikolou ◽  
Despina Papadopoulou

Greek is a morphology-dependent stress system, where stress is lexically specified for a number of individual morphemes (e.g., roots and suffixes). In the absence of lexically encoded stress, a default stress emerges. Most theoretical analyses of Greek stress that assume antepenultimate stress to represent the default (e.g., Malikouti-Drachman & Drachman 1989; Ralli & Touratzidis 1992; Revithiadou 1999) are not independently confirmed by experimental studies (e.g., Protopapas et al. 2006; Apostolouda 2012; Topintzi & Kainada 2012; Revithiadou & Lengeris in press). Here, we explore the nature of the default stress in Greek with regard to acronyms, given their lack of overt morphology and fixed stress pattern, with a goal of exploring how stress patterns are shaped when morphological information (encapsulated in the inflectional ending) is suppressed. For this purpose, we conducted two production (reading aloud) experiments, which revealed, for our consultants, first, an almost complete lack of antepenultimate stress and, second, a split between penultimate and final stress dependent on acronym length, the type of the final segment and the syllable type of the penultimate syllable. We found two predominant correspondences: (a) consonant-final acronyms and end stress and (b) vowel-final acronyms and the inflected word the vowel represents, the effect being that stress patterns for acronyms are linked to the inflected words they represent only if enough morphonological information about the acronym’s segments is available to create familiarity effects. Otherwise, we find a tendency for speakers to prefer stress at stem edges.


2019 ◽  
Vol 33 (31) ◽  
pp. 1950371
Author(s):  
Tianlong Liu ◽  
Shiliang Wang ◽  
Lizhen Hou ◽  
Han Huang

Pentagonal noble metal crystals, with a five-fold-twinned (FFT) structure that exhibits prominent noncrystallographic symmetry, have been the focus of research in the past several decades due to their promising applications in various fields such as chemical and biological sensors, electronics and optoelectronics. A great deal of previous experimental studies and theoretical analyses suggested that such an FFT structure could only exist in the nanoscale crystals, because of the lateral restriction in growth, or in microscale crystals with re-entrant grooves that can effectively release the internal strain. In this study, we synthesized the microscale single-crystalline and multi-twinned Ag crystals with various morphologies, using physical vapor deposition (PVD). FFT Ag microwhiskers with diameters up to 10 [Formula: see text]m were produced, but without re-entrant grooves on their side surfaces. Our findings suggest that FFT whiskers can be formed without the use of any surface-capping agents or without necessitating restriction in lateral growth. This further suggests that the current understanding of the surface passivation or the strain-restriction formation of five-fold-twined micro- and nanowhiskers needs improvement.


CORROSION ◽  
1968 ◽  
Vol 24 (8) ◽  
pp. 247-251 ◽  
Author(s):  
W. D. FRANCE ◽  
N. D. GREENE

Abstract The protection of crevices poses an important problem in industrial applications of anodic protection. Experimental studies with a special crevice assembly have shown that the interiors of crevices often remain active and corrode at a rapid rate. These experiments, together with theoretical analyses, demonstrate that the ability to passivate crevices during anodic protection is controlled by electrolyte characteristics, crevice geometry, and the electrochemical behavior of the protected metal. Of these, critical anodic current density, ic, is the most important parameter.


2007 ◽  
Vol 21 (18n19) ◽  
pp. 3320-3323
Author(s):  
DE-HUA LIN ◽  
DA-JIAN CUI ◽  
BO LI

On the basis of Fan and Malozovsky theory, which had discussed the non-phonon mechanism of the layered Fermi liquid superconductivity, and of the experimental studies and theoretical analyses obtained by Zhang et al. as well as other scientists, we have analyzed and discussed the extrinsic and intrinsic factors of affecting the transition temperature Tc of cuprate superconductors. We also will present some possible approaches to explore new high Tc superconductive materials, and pay more attention to the non-traditional phonon mechanism, low dimensional or quasi two-dimensional system, and hexagonal structure materials, etc.


2019 ◽  
Vol 863 ◽  
pp. 893-903 ◽  
Author(s):  
Sergio Maldonado ◽  
Gustavo A. M. de Almeida

The problem of determining the threshold of motion of a sediment particle resting on the bed of an open channel has historically been dominated by an approach based on the time–space-averaged bed shear stress (i.e. Shields criterion). Recently, experimental studies have promoted an alternative approach to predict the dislodgement threshold, which is based on the impulse of the flow-induced force. Nonetheless, theoretical analyses accompanying these studies result in complex expressions that fail to provide a direct estimate of said impulse threshold. We employ the work–energy principle to derive a prediction of the fundamental impulse threshold that the destabilising hydrodynamic force must overcome in order to achieve full particle dislodgement. For the bed configuration studied, which is composed of spheres, the proposed expression depends on the mobile particle’s size and mass, and shows excellent agreement with experimental observations previously published. The derivation presented in this paper may thus represent a robust theoretical framework that aids in the reinterpretation of existing data, as well as in the design of future experiments aimed at analysing the importance of hydrodynamic impulse as a criterion for prediction of particle dislodgement.


1975 ◽  
Vol 229 (1) ◽  
pp. 215-221 ◽  
Author(s):  
WW Eckman ◽  
RD Phair ◽  
JD Fenstermacher ◽  
CS Patlak ◽  
C Kennedy ◽  
...  

Influence of capillary permeability on local cerebral blood flow (LCBF) estimated by the autoradiograhpic diffusible-indicator method was analyzed by computer simulation. Its influence increases with increasing flow. With normal perfusion rates in gray matter, capillary permeability coefficient x surface area (PS value) must exceed 0.12 cm3-s(-1)-g(-1) for estimated LCBF to attain 95% of true values in all structures. In white matter, with its lower perfusion rates, the PS value must exceed 0.035 cm3-s(-1)-g(-1) for equivalent accuracy. [14C]antipyrine, widely used in the LCBF technique, has a PS value below these values and leads to undersestimation of LCBF. Experimental studies in cats in which LCBF was measured with either [14C]antipyrine or the freely diffusible, radioactive gas, [131I]trifluoroiodomethane, demonstrated consistently lower estimates of LCBF with [14C]antipyrine than with the gas; the deviations in the various cerebral structures approximated those predicted by the theoretical analyses. These results suggest that the uptake of [14C]antipyrine by cerebral tissues is diffusion limited as well as flow limited, and it therefore is not an ideal tracer for the autoradiographic LCBF technique.


1994 ◽  
Vol 116 (1) ◽  
pp. 38-46 ◽  
Author(s):  
Y. G. Long ◽  
K. Nagaya ◽  
H. Niwa

The problem of inserting a long optical fiber into a long helical steel tube by means of vibration is modelled as a block repeatedly sliding and jumping inside a vibrating long tube which is in a spatial curved-line shape. Analytical models and equations are established by considering three kinds of motion states involved: relative sliding motion, flying motion, and bumping. Thorough investigations are carried out for the inclined friction with component velocities and for the oblique impact. The detailed motion of the whole response, called the “subperiodic motion,” is revealed through numerical solutions. Fundamental influences of some basic parameters on the motion of the system are discussed. Appropriate ranges for both the frequency and the amplitudes of vibration are discovered to be very narrow. Conveying materials inside vibrating tubes is quite different from, or opposite to, conveying materials on vibrating plates in ordinary use. Experimental studies confirm the theoretical analyses presented.


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