Weak Seams Research Articles

Influence of technological parameters on the upholstery seams in furniture

Influence of technological parameters of the upholstery seams in furniture. Based on the real problem of weak seams in covers of wooden furniture, a multifaceted analysis of the issue was performed. As a result, it was decided to carry out comparative laboratory strength tests of seams made with the use of various technological parameters. For the production of test samples, we used different yarn threads to find the best and sufficiently strong seams for used fabrics. The test results show that not only the thread and fabric used, but also the sewing technology parameters have a significant influence on the seam strength. Overall, these results indicate that to increase the seam strength, it is necessary to choose thread type B with very high strength and low elongation at break. This solution will minimize the risk of broken threads in case of deviation of material features and technological parameters, which can be variable in the long duration of large-scale production.

Physical simulation and compatibility evaluation of multi-seam CBM co-production: Implications for the development of stacked CBM systems

Multi-layer co-production is a mainstream method for efficient development of coalbed methane (CBM) and coal series gas under multi-seam conditions. However, interlayer interferences during CBM co-production caused by differences in reservoir properties (especially permeability and pressure) between stacked CBM systems severely restrict the output of CBM from the production layers. The identification of interlayer interferences and optimization of production layer combinations are important scientific issues that need to be explored to achieve high CBM production. Physical simulation is an effective means of accomplishing this research objective. Physical simulations of CBM co-production were performed under designed permeability and pressure combinations based on self-developed experimental equipment, which is mainly composed of an injection subsystem, a vacuum subsystem, the model body subsystem, and a separation and metering subsystem. Coal samples were collected from three CBM basins in China to form a series of five permeability levels, specifically 0.2, 2, 10, 50, and 100 mD. We focused our analysis on the contribution of gas production from each production layer using the gas flow data obtained from the physical simulation experiments. The co-mining compatibility of the production layers is divided into four types based on the grading evaluation of gas contribution: Grade I, II, and III compatible, and incompatible, which represent gas production contribution of the weak seam ≥37.5%, 25%–37.5%, 12.5%–25%, and ≤12.5%, respectively. On this basis, a template for discriminating CBM co-production compatibility is constructed using the permeability ratio and pressure difference as basic parameters. The gas and water production data of representative CBM wells in the Bide-Santang basin were used to verify the reliability of the template, and the compatibility discrimination results show consistency with the production data. The average daily gas production per unit of coal thickness presents a decreasing trend with deteriorating compatibility of co-producing seams. Finally, an integrated technical process for the development of stacked CBM systems is proposed, including the hierarchical optimization of production layer combinations, identification of interlayer interferences and sources of produced water, and selection of suitable development methods and technology. We divided the production layer combinations into four types representing different development potentials based on the hierarchical method: most favorable, favorable, sub-favorable, and unfavorable. Suggestions are made for the key geological constraints (weak water-bearing reservoir, compatibility of CBM systems, shallow groundwater interference, and deep CBM condition) and specific development strategies for different types of production layer combinations. This study will enrich the geological understanding of CBM co-production and provide theoretical and technical support for the efficient development of stacked CBM systems.

Failure Mechanism and Factor of Safety for Spatially Variable Undrained Soil Slope

This paper aims to investigate the differences in factor of safety (FS) and failure mechanism (FM) for spatially variable undrained soil slope between using finite element method (FEM) , finite difference method (FDM), and limit equilibrium method (LEM). The undrained shear strength of cohesive soil slope is modeled by a one‐dimensional random field in the vertical direction. The FS and FM for a specific realization of random field are determined by SRT embedded in FEM‐ and FDM‐based software (e.g., Phase2 6.0 and FLAC) and LEM, respectively. The comparative study has demonstrated that the bishop method (with circular failure surface) exhibits performance as fairly good as that of SRT both in FS and FM for the undrained slope cases where no preferable controlling surfaces such as hydraulic tension crack and inclined weak seams dominate the failure mechanism. It is, however, worthwhile to point out that unconservative FM is provided by the Bishop method from the aspect of failure consequence (i.e., the failure consequence indicated by the FM from the Bishop method is smaller than that from SRT). The rigorous LEM (e.g., M‐P and Spencer method with noncircular failure surface) is not recommended in the stability analysis of spatially variable soil slopes before the local minima and failure to converge issues are fully addressed. The SRT in combination with FEM and/or FDM provides a rigorous and powerful tool and is highly preferable for slope reliability of spatially variable undrained slope.

Drilled Shaft Design and Load Testing in Florida Intermediate Geomaterial and Weak Limestone

This case study summarizes the design, construction, load testing, and integrity testing of nonredundant drilled shafts for a bridge project in northwest Florida. The subsurface profile consisted mainly of calcareous sandy and silty clay (marl and marlstone) interfingered with limestone and cemented sand layers. The results of unconfined compression tests revealed significant variability in strength, with strata within the depth of interest holding strength properties that fall within the generally accepted range of cohesive intermediate geomaterial. This paper discusses local geology, geotechnical investigation, design, construction, load testing, and site-specific correlations. Important aspects of the project, including the use of the shaft inspection device to examine the cleanliness of the bottom of the shafts, Osterberg cell load testing, and the site-specific correlations developed from the results, as well as integrity testing with cross-hole sonic logging and a thermal integrity profiler, are presented. The inability of the standard penetration test (SPT) to delineate boundaries adequately between strong and (relatively) weaker layers is presented, as well as nonlinear site-specific relationships between anticipated skin friction resistance and SPT blow count. The nonlinear SPT-based relationships attempt to address the strain incompatibility between strong and weak seams that may exist within a given stratum. Proposed correlations for skin friction and end bearing that are based on laboratory strength testing are presented in terms of revised unconfined compressive strength to address variability in strength characteristics across the site.

Observations on Limit Equilibrium–Based Slope Reliability Problems with Inclined Weak Seams

This study addresses the complexity of slope reliability problems based on limit equilibrium methods (LEMs). The main focus is on the existence of multiple failure modes that poses difficulty to many LEM-based slope reliability methods. In particular, when weak seams are present, the failure modes associated with those seams may be difficult to detect. A systematic way of searching the failure modes is proposed, and its robustness over slopes with or without weak seams is demonstrated. It is found that in the presence of weak seams, assuming circular slip surfaces may cause underestimation of slope failure probability. The conclusion of the study promotes the use of finite elements as the stability method for reliability evaluation because it is not necessary to search for failure surfaces in finite-element stability analysis.

Weak seams: Controversy over welding theory and practice in american shipyards, 1938-1946

At the height of World War II, America's record-setting shipyards were stunned when several merchant ships literally cracked in half. Worried that endemic manufacturing defects might endanger the entire wartime merchant marine, engineers argued that poor workmanship by shipyard welders had contributed to the accidents, that their own technical expertise should be more highly valued, and that they should be granted greater authority over the shipyard workforces. However, administrators in US Maritime Commission rejected these arguments. Instead, federal officials and shipyard managers assumed that many factors had contributed to the fractures and chose to implement a few modest, practical measures which soon stopped the fracture epidemic: improved worker training, the elimination through redesign of certain structural flaws in the endangered ships' hulls, and especially the installation of reinforcing devices at weak points in the ships. This episode not only draws attention to the way warfare heightens the stakes of technical controversies, but demonstrates the utility and resilience, even and especially at highly-charged moments, of practical knowledge and straightforward craftsmanship.

Weak Seam Seal Prompts Recall of Medical Vac Pac

Weak Seam Seal Prompts Recall of Medical Vac Pac

Simplified moment tensor analysis and unified decomposition of acoustic emission source: Application to in situ hydrofracturing test

An application of a moment tensor analysis to acoustic emission (AE) is studied to elucidate crack types and orientations of AE sources. In the analysis, simplified treatment is desirable, because hundreds of AE records are obtained from just one experiment and thus sophisticated treatment is realistically cumbersome. Consequently, a moment tensor inversion based on P wave amplitude is employed to determine six independent tensor components. Selecting only P wave portion from the full‐space Green's function of homogeneous and isotropic material, a computer code named SiGMA (simplified Green's functions for the moment tensor analysis) is developed for the AE inversion analysis. To classify crack type and to determine crack orientation from moment tensor components, a unified decomposition of eigenvalues into a double‐couple (DC) part, a compensated linear vector dipole (CLVD) part, and an isotropic part is proposed. The aim of the decomposition is to determine the proportion of shear contribution (DC) and tensile contribution (CLVD + isotropic) on AE sources and to classify cracks into a crack type of the dominant motion. Crack orientations determined from eigenvectors are presented as crack‐opening vectors for tensile cracks and fault motion vectors for shear cracks, instead of stereonets. The SiGMA inversion and the unified decomposition are applied to synthetic data and AE waveforms detected during an in situ hydrofracturing test. To check the accuracy of the procedure, numerical experiments are performed on the synthetic waveforms, including cases with 10% random noise added. Results show reasonable agreement with assumed crack configurations. Although the maximum error is approximately 10% with respect to the ratios, the differences on crack orientations are less than 7°. AE waveforms detected by eight accelerometers deployed during the hydrofracturing test are analyzed. Crack types and orientations determined are in reasonable agreement with a predicted failure plane from borehole TV observation. The results suggest that tensile cracks are generated first at weak seams and then shear cracks follow on the opened joints.

Engineering Geophysics — A Geophysicist’s View

Thirty years ago some engineering organizations expected geophysics, applied virtually in isolation, to provide cheap answers to engineering questions. After some expensive lessons it is recognized today that geophysical methods are fully effective only when used with sufficient geological understanding and calibration. Common applications most useful in engineering are in two categories. First, is the location of features with anomalous physical properties. Such features include dykes, deeply weathered zones, major fault zones, buried channels, cavities and landslipped masses, all of which are potential hazards during the construction of tunnels and dams. Basic dykes have been located by airborne magnetometer, and where forming ridges on the sea bed, by side-scan sonar. During the planning of Sugarloaf Inlet Tunnel a deeply weathered unit was located by airphoto interpretation and refraction seismic traverses. Early recognition of this unit enabled the tunnel to be located so as to pass beneath the weathered zone. Seismic refraction and magnetic methods have also been successful in locating faults and buried channels. Concealed cavities have proven more difficult to locate, despite the use of micro-gravity, seismic, resistivity, shallow EM, Sirotem and ground-radar techniques. Landslipped masses can usually be recognized by their distinctive geomorphological features, but where such features are absent, a landslipped mass might be detected by its anomalously low seismic wave velocity. The second application category is the delineation of boundaries between features with contrasting physical properties, for example between 'overburden' and 'bedrock'. Where the overburden is geologically young transported material overlying unweathered rock, the boundary is readily determined by the seismic refraction method. Where the overburden comprises weathered rock in-situ, its boundary with the fresh rock is often highly irregular and gradational, and weathered profile reversals can occur. Caution is suggested in the interpretation of travel-time plots obtained from such variable masses. The author questions the value of geophysical methods for assessing the strength and compressibility of rock masses, and the effectiveness of grouting. He proposes seven other civil and mining engineering applications as more worthy of research, viz: location of hazardous features offshore, location of thin weak seams in rock masses, delineation of fresh rock 'boulders' within residual soils, location of cavities, development of remote-reading instruments for monitoring rock subsidence during and after mining, assessment of thicknesses of mechanically loosened rock, and detection of leakage areas in reservoir floors.

Interaction of chlorpromazine with the human erythrocyte membrane.

The interaction of the amphipath chlorpromazine (CPZ) with the human erythrocyte membrane was evaluated. The partition coefficient of CPZ between the membrane bilayer and the aqueous compartment, measured spectrophotometrically, ranged between 1 and 3 X 10(3). An independent estimate, 4.6 X 10(3), was obtained by a novel method which avoided the measurement of binding and determined instead the variation of the hemolytic potency of the amphipath with the ratio of buffer volume to membrane volume. The maximal uptake of CPZ exceeded 2 X 10(9) molecules/red cell, corresponding to a volume greater than that of the bilayer itself. Such heavily loaded membranes were increased in thickness more than 2-fold, suggesting the formation of a CPZ-rich zone at the center of the bilayer. Ghosts loaded with massive levels of CPZ condensed approximately 20-fold in surface area and increased proportionately in thickness, suggesting the formation of a novel CPZ-lipid solution. CPZ caused hemolysis by a colloid-osmotic mechanism. By measuring the simultaneous uptake of mannitol and sucrose, we determined that CPZ induced holes of constant size but variable number. If circular, the holes would have had a diameter of approximately 14 A. The time-averaged number of holes ranged from 0.09 per cell (signifying intermittency) to 16. Freeze-fracture electron microscopy of CPZ-treated red cells revealed multiple round patches of nearly particle-free bilayer up to 0.3 micron in diameter with crowding of the intramembrane particles into the surrounding membrane. We interpret these images to signify lateral phase separation within the CPZ-treated bilayer. Hemolysis could, therefore, result from the intermittent opening of weak seams at phase boundaries; these could then be fluctuating slits approximately 14 A in width and of variable length, rather than simple circular holes.