Common Test Conditions Research Articles

The temporal response of the friction coefficient of articular cartilage depends on the contact area

The hypothesis of this study is that the time constant for the transient increase in friction coefficient of articular cartilage under a constant load is proportional to the size of the contact area, as predicated by the dependence of the frictional response on interstitial fluid pressurization. This hypothesis is verified experimentally from measurements of the frictional response of bovine articular cartilage disks of three different diameters (4, 6 and 8 mm) against glass. At two different applied stresses (0.127 and 0.254 MPa), the coefficient of determination of a linear regression of the time constant versus the contact area yielded R 2=0.892 and R 2=0.979 ( p<0.001). The results of this study provide a cogent explanation for the expectation that the friction coefficient in situ will not achieve the elevated equilibrium values observed under common testing conditions.

Transient Soil Vapor Extraction from a Pressure‐Controlled Well

AbstractNew semianalytical solutions for transient soil vapor extraction are developed for P (pressure) or P2 linearizations of the governing air flow equation. Our method treats flow rate and wellhead pressure as two distinct variables instead of customarily coupling them together. An extraction well can be either pressure or flow rate controlled with uniform applied pressure along the screen and nonuniform radial flux. The two linearizations yield different solutions for subsurface pressures; the difference increases with applied wellhead pressure. This increasing difference serves as a constraint on the magnitude of the wellhead pressure used in a test. The P equation is preferred for simulating the vadose zone pressure because it allows for more flexible implementation of boundary conditions. The solutions cover the common field test condition of unrestricted flow of atmospheric air into the vadose zone and can be readily modified for a leaky confining layer or time‐varying pressure at the ground surface. Analysis of field test data showed that the new model can closely simulate transient subsurface pressure distribution and revealed mutual dependence of porosity θ, and permeability krand kzfor the problem analyzed. The estimated kz/krwas greater than 1, higher than would be expected for natural soil in the absence of secondary effects on permeability, such as vertical cracks.

H.264/AVC error resilience tools suitable for 3G mobile video services *

The emergence of third generation mobile system (3G) makes video transmission in wireless environment possible, and the latest 3GPP/3GPP2 standards require 3G terminals support H.264/AVC. Due to high packet loss rate in wireless envi- ronment, error resilience for 3G terminals is necessary. Moreover, because of the hardware restrictions, 3G mobile terminals support only part of H.264/AVC error resilience tool. This paper analyzes various error resilience tools and their functions, and presents 2 error resilience strategies for 3G mobile streaming video services and mobile conversational services. Performances of the proposed error resilience strategies were tested using off-line common test conditions. Experiments showed that the proposed error resilience strategies can yield reasonably satisfactory results.

Building equipment from products with known EMC performance

In order for system integrators to use EMC data derived from testing components and subsystems two areas must be addressed: common installation rules and common test conditions. Provided the above issues are addressed the modular method to compliance based on the arguments and methods described in this paper can be used within a technical construction file to show compliance with the EMC Directive (89/336/EEC). (10 pages)

Moniliformis moniliformis Infection Has No Effect on Some Behaviors of the Cockroach Diploptera punctata

The behavior of the cockroach Diploptera punctata parasitized with the acanthocephalan Moniliformis moniliformis was examined for parasite-induced alterations. No significant difference in behavior was found between parasitized and unparasitized animals in the following behavioral tests: (1) choice of white/black, horizontal/vertical substrate under light and dark conditions; (2) temporal and directional response to a bright light source; (3) choice between light and dark (photophilia); and (4) activity (time spent moving, distance, and velocity). A comparison of uninfected animals under 2 light conditions showed that light affected the activity of uninfected animals and their response to substrate. Diploptera punctata is the first nondomestic cockroach to be examined for behavioral responses to Moniliformis infection. This is the first report of an arthropod in which acanthocephalan infection has failed to alter behavior under at least some common test conditions.

Improvement of structural models using covariance analysis and nonlinear generalized least squares

The next generation of large, flexible space structures will be too light to support their own weight, requiring a system of structural supports for ground testing. The authors have proposed multiple boundary-condition testing (MBCT), using more than one support condition to reduce uncertainties associated with the supports. MBCT would revise the mass and stiffness matrix, analytically qualifying the structure for operation in space. The same procedure is applicable to other common test conditions, such as empty/loaded tanks and subsystem/system level tests. This paper examines three techniques for constructing the covariance matrix required by nonlinear generalized least squares (NGLS) to update structural models based on modal test data. The methods range from a complicated approach used to generate the simulation data (i.e., the correct answer) to a diagonal matrix based on only two constants. The results show that NGLS is very insensitive to assumptions about the covariance matrix, suggesting that a workable NGLS procedure is possible. The examples also indicate that the multiple boundary condition procedure more accurately reduces errors than individual boundary condition tests alone.