Signs Of Impending Failure Research Articles

Seismic behavior of geosynthetic-reinforced retaining walls backfilled with cohesive soil

This study investigates the seismic performance of geosynthetic-reinforced modular block retaining walls backfilled with cohesive, fine grained clay-sand soil mixture. Shaking table tests were performed for three ½ scaled (wall height 190 cm) and ¼ scaled model walls to investigate the effects of backfill type, the influence of reinforcement length and reinforcement stiffness effects. The El Centro and Kobe earthquake records of varying amplitudes were used as base acceleration. Displacement of the front wall, accelerations at different locations, strains on the reinforcements, and the visual observations of the facing and the backfill surface were used to evaluate the seismic performance of model walls. The model walls were subjected to rigorous shaking and the walls did not exhibit any stability problems or signs of impending failure. The maximum deformations observed on the models with cohesive backfill was less than half of the deformation of the sand model. The load transfers between the geogrid and cohesive soil was comparable to that of sand and hence the needed reinforcement length was similar as well. As a result; the model walls with cohesive backfills performed within acceptable limits under seismic loading conditions when compared with granular backfilled counterparts.

Deep Learning to Detect Road Distress from Unmanned Aerial System Imagery

Surface distress is an indication of poor or unfavorable pavement performance or signs of impending failure that can be classified into a fracture, distortion, or disintegration. To mitigate the risk of failing roadways, effective methods to detect road distress are needed. Recent studies associated with the detection of road distress using object detection algorithms are encouraging. Although current methodologies are favorable, some of them seem to be inefficient, time-consuming, and costly. For these reasons, the present study presents a methodology based on the mask regions with convolutional neural network model, which is coupled with the new object detection framework Detectron2 to train the model that utilizes roadway imagery acquired from an unmanned aerial system (UAS). For a comprehensive understanding of the performance of the proposed model, different settings are tested in the study. First, the deep learning models are trained based on both high- and low-resolution datasets. Second, three different backbone models are explored. Finally, a set of threshold values are tested. The corresponding experimental results suggest that the proposed methodology and UAS imagery can be used as efficient tools to detect road distress with an average precision score up to 95%.

Long-term outcome of low contact stress total knee arthroplasty with different mobile bearing designs.

to evaluate the differences in clinical outcome and survivorship of three different mobile bearings for total knee arthroplasty. a retrospective study was conducted in 60 patients (53 females, 7 males, mean age: 68 years and 5 months) each submitted to total knee replacement using one of the three different mobile bearings of the LCS system (Depuy Johnson & Johnson, Warsaw, IN). The diagnosis was knee osteoarthritis in 57 cases and rheumatoid arthritis in three cases. Three different groups of 20 cases each were identified: total knee arthroplasties with mobile menisci (group 1); total knee arthroplasties with the rotating platform (group 2); and total knee arthroplasties with the anteroposterior glide platform (group 3). As regards the component fixation, 33 implants were cementless, three were cemented, and in 24 only the tibial component was cemented. The patella was not replaced. although the duration of follow-up differed between the three groups, the clinical and radiological results at final follow-up showed no revision of femoral and/or tibial components for mechanical or septic reasons, and no signs of impending failure. One meniscal bearing, showing polyethylene wear after 17 years, was successfully replaced. the present retrospective study confirmed the long-term effectiveness of knee implants with mobile bearings, in which the congruity of the surfaces makes it possible to overcome the problem of high contact stresses that may result in polyethylene wear and osteolysis; at the same time, these implants eliminate constraint forces thereby reducing the risk of mechanical loosening. Level III, retrospective comparative study.

Concerns about Landsat 5 failure

An electronic component on board the Landsat 5 Earth observation satellite has indicated signs of impending failure, and the U.S. Geological Survey (USGS) has stopped acquiring images from the satellite, the agency announced on 18 November. USGS engineers have suspended imaging activities for 90 days to explore options for restoring image transmissions from the satellite, which was launched in 1984 and has operated long beyond the 3 years it was designed to last. “This anticipated decline of Landsat 5 provides confirmation of the importance of the timely launch of the next Landsat mission and the need for an operational and reliable National Land Imaging System,” said Anne Castle, assistant secretary for water and science at the U.S. Department of the Interior. USGS is part of the Interior department. Landsat 7, launched in 1999 with a 5‐year design life, remains in orbit. Landsat 8, the Landsat Data Continuity Mission, has a January 2013 scheduled launch.

Successful Salvage of a Recurrently Dislocating Oxford Medial Unicompartmental Bearing

Dislocation of the bearing of the Oxford medial unicompartmental arthroplasty is a rare but serious complication. We report the case of a 48-year–old woman with a classic anteromedial arthritis who had 2 bearing dislocations within the first 3 months after index surgery. These were attributable to posterior bony impingement of the bearing against a small retained osteophyte. After arthroscopic resection of the osteophyte, she has retained her original components with no further dislocations or signs of impending failure 7 years later. This case report emphasizes the importance of osteophyte removal from the back of the femoral condyle during an Oxford unicompartmental arthroplasty.

Comparison among total knee arthroplasties with a mobile bearing: menisci versus rotating platform versus AP glide platform

A retrospective study was conducted on 60 patients (53 females, seven males with a mean age of 68 years and 5 months) who underwent a total knee replacement using a mobile bearing. The diagnosis was primary osteoarthritis in 57 cases and rheumatoid arthritis in three cases. None of the patients underwent a bilateral procedure, thus 60 implants (33 all cementless, three all cemented, 24 with only the tibial component cemented) were considered. Three different groups were identified: Group 1: first 20 total knee arthroplasties with menisci. Group 2: first 20 total knee arthroplasties with rotating platform. Group 3: first 20 total knee arthroplasties with AP glide platform. Clinical and radiological results at the final follow up, although different in time among the three groups, have shown no revision due to mechanical or septic reasons, and no signs of impending failure.

The results at nine to twelve years of the use of a hydroxyapatite-coated femoral stem.

We describe the clinical and radiological outcome of 100 consecutive total hip replacements in 86 patients using the JRI Furlong hydroxyapatite-coated femoral component. The follow-up was 100% at a mean of ten years (9.0 to 12.0). All 54 living patients (62 hips) were examined annually. Their mean Merle d'Aubigné score was 5.8/5.6/4.6. A total of 32 patients had died. Their notes at the last annual assessment recorded a similar outcome to that of the living patients. Radiographs showed no radiolucent lines around any femoral component and there were no signs of impending failure. One patient required excision arthroplasty, but the femoral component had been bonded satisfactorily. There have been no other revisions of femoral components. Our findings suggest that the hydroxyapatite coating gives a satisfactory prosthesis-bone interface which is preferable to any other system.

The results at nine to twelve years of the use of a hydroxyapatite-coated femoral stem

We describe the clinical and radiological outcome of 100 consecutive total hip replacements in 86 patients using the JRI Furlong hydroxyapatite-coated femoral component. The follow-up was 100% at a mean of ten years (9.0 to 12.0). All 54 living patients (62 hips) were examined annually. Their mean Merle d’Aubigné score was 5.8/5.6/4.6. A total of 32 patients had died. Their notes at the last annual assessment recorded a similar outcome to that of the living patients. Radiographs showed no radiolucent lines around any femoral component and there were no signs of impending failure. One patient required excision arthroplasty, but the femoral component had been bonded satisfactorily. There have been no other revisions of femoral components. Our findings suggest that the hydroxyapatite coating gives a satisfactory prosthesis-bone interface which is preferable to any other system.

The Furlong hydroxyapatite-coated femoral prosthesis. A 4- to 7-year follow-up study.

We report the clinical and radiograph outcome of 77 Furlong hydroxyapatite fully coated femoral prosthesis in 71 patients undergoing primary total hip replacement, with mean follow-up of 65 months (range 48-82 months). The patients' average age at surgery was 55 years. The clinical results, as determined by Harris hip score, were excellent or good for 84% of the hips. Thigh pain which was not disturbing was present in 9% of the hips. No femoral component had been revised for aseptic loosening, and none were considered loose radiographically at the time of final follow-up evaluation. Serial radiographs revealed an excellent quality of bone around the prostheses, with positive evidence of bone ingrowth and no signs of impending failure.

Review of Aerothermally Induced Vibrations in Gas Turbine Engines

High or changing vibration amplitude patterns in turbomachines are signs of impending failure or a machines deterioration. If properly diagnosed, this information can help improve performance, reliability; reduce maintenance cost; and avoid serious outages. Vibrations could be caused by structural or aerodynamic excitations, in addition to combustion pulsations. Methods of decreasing vibrations are mentioned, where selection of proper materials plays an important role. These areas are reviewed briefly in this work.

Recognition and Use of Sentinel Markers in Preventing Industrial Disasters

AbstractWorkers, managers, occupational health and safety inspectors, and the general community can be trained to detect and promote action by the use of sentinel markers for detecting industrial disasters. A sentinel marker is a pre-disaster warning sign of impending failure in prevention. Administration sentinel markers are: weak occupational health and safety programs; lack of spontaneous access to top management; failure to accept responsibility for sub-contractors; absence of written disaster plans and drills for emergency response in the factory and in the adjacent community; non-investigation of prodromal leaks, exposures, spills, or injuries; punishment of “trouble-some” individuals (“whistleblowers”) reporting prodromal events; non-use or misuse of data on illness, injury, and absenteeism; and sub-optimal work conditions and supervision of shift workers. Information sentinel markers are: absence of worker and community right-to-know programs; non-use of data on earlier mishaps from similar technologies; and failure to provide toxicologic data to hospitals in the pre-disaster phase. Technological sentinel markers include the absence of fail-safe controls, interlocks, and automated alarm systems driven by real-time monitoring. Transportation sentinel markers include sub-optimal vehicle standards, alcohol and drug abuse, and fatigue in drivers. Preventive programs based on identification of all sentinel markers by workers and others outside a narrow spectrum of specialists are suggested to be more effective than are selective actions based on risk assessment analysis.

Effect of Fuel-Air Mixture Heterogeneity on Vibrations in Continuous Combustion Systems

High vibration amplitudes can be a sign of impending failure or deterioration of equipment. In this work, a rarely researched phenomena, namely the effect of fuel heterogeneity in continuous combustion systems on the induced vibration and noise, is studied. The vibration pattern is obtained via a real-time spectrum analyzer. The use of spectrum analyzer with proper filtering made it possible to distinguish between the induced aerodynamic and combustion vibration. This could be done by comparing the vibration characteristic of reacting and nonreacting cases. Noise measurements are also obtained using a sensitive sound level meter. The results show a remarkable effect of the fuel heterogeneity ratio on the vibration and noise pattern. For liquified petroleum gas (LPG) and kerosine the vibration amplitudes at all frequencies were found to decrease with the increase of the air mass flow rate and henceforth increase after they attain certain minimum. The minimum amplitudes were in the range of 80 to 100 kg/h depending on the heterogeneity ratio. For intermediate values of LPG percentage an opposite trend was noticed i.e. the vibration level is first increased as the air mass flow rate increases until it attains a maximum then it decreases with any further increase in the air mass flow rate. Concerning the noise, slight effect of heterogeneity was observed in the high frequency noise pattern, however the low frequency noise (combustion roar) was found to be increasing with the increase of heterogeneity ratio.

A clinical and radiographic assessment of a porous-surfaced, titanium alloy dental implant system in dogs.

A new endosseous dental implant system incorporating a porous-surface geometry with a tapered, truncated-cone shape was placed bilaterally in edentulous areas of dog mandibles in a two-stage procedure. All implants had been stabilized by bone ingrowth by the time of the second procedure (insertion of a transgingival collar and implant-supported bridge). The transgingival collar had a porous-surface geometry on its apical one-third, and was meant to encourage gingival connective tissue ingrowth and attachment, but in fact provided an excellent milieu for bacterial contamination. As a consequence, many of the implants showed clinical and radiographic signs of impending failure by eight months. Only those implants for which the porous coat, including that of the transgingival collar, was completely submerged in bone were observed to be successful. This study reports on the radiographic and clinical assessment of this implant system in dogs during the period of function.

Stability charts for simple earth slopes allowing for tension cracks : Cousins, B F Proc 3rd Australia-New Zealand Conference on geomechanics, Wellington, 12–16 May 1980, V2, P101–105. Publ Wellington: New Zealand institution of Engineers, 1980

In a previous paper by the author (Cousins, 1978) stability charts were presented for simple earth slopes ignoring tension cracks. Tension cracks are usually the first sign of impending failure in cohesive soils and therefore should be taken into account. In this paper the effect of tension cracks both dry and filled with water is investigated. Stability charts are presented for toe circles with no water in the tension crack and for a homogeneous pore pressure ratio r = 0, 0.25 and 0.5. A chart is also given for pore pressure ratio r = 0 with the tension crack filled with water. The charts have been constructed assuming the worst possible location and depth of the tension crack. As such they represent a lower bound for the safety factor. The maximum reduction in safety factor of 40% was found for slope angle a = 60degrees and dimensionless parameter lambda = 20 with the tension crack filled with water. For most cases the reduction was much less than this.

Pyrolytic Graphite in the Design of a Compact Inert Heater of a Lanthanum Hexaboride Cathode

Pyrolytic graphite serves two functions in a new type of LaB6 cathode; it supports and heats the LaB6 emitter. The high anisotropic resistivity of pyrolytic graphite allows a compact heater-emitter design a few millimeters in size, and the chemical compatibility of graphite with LaB6 at the operating temperature of about 1500°C prevents any lifetime reducing chemical reactions between the two materials. Typical heating power inputs have been measured to be 15 W at a heating current of about 3 A. One of these LaB6 cathodes has been tested in a demountable vacuum system at an average emission current density of 1.6 A/2cm for over 900 h without signs of impending failure.