Comparison of microleakage between different restorative materials to restore marginal gap at crown margin

Background An occurrence of secondary caries around the indirect restoration margin is reported to remain a leading cause of failures. Objective This study aimed to test the interfacial microleakage of conventional glass-ionomer (CGI), resin-modified glass ionomer (RMGI) and Nano-hybrid composite (CR) restorations at a full veneer margin crown. Methods Ninety human extracted molar teeth were divided into three groups (n = 30). Each group was subdivided into three subgroups (n = 10) according to the extent of the structural defects; The structural defect in G1 had a depth of 1.5 mm, width and length at 2 mm and 1 mm intrusion within the crown cervical margin. The corresponding structural defect dimension values for G2 were 2, 5, 4 and 2 mm with defects extending onto the root structure. Meanwhile, G3: structural deficiency of 2 mm depth, 3 mm width and 3 mm length and with 1.5 mm extension into the prepared teeth. These structural defects in each subgroup were restored with CGI, RMGI and CR. Artificial carious lesion formation was induced at the cervical finish line with a demineralizing solution. The artificial carious lesions were restored as per the group distribution. Subsequently, teeth samples were prepared and cemented with Nickel-chromium full coverage restorations utilizing glass-ionomer luting cement. Teeth samples were thermocycled, isolated with nail varnish, and immersed in 0.1% methylene blue for 24 h. The teeth samples were sectioned longitudinally, dye penetration was evaluated with a stereomicroscope. The data were analyzed with Kruskal–Wallis and Mann–Whitney U tests. Results CGI-G1 recorded the highest micro-leakage score at 1.450; while CR-G3 recorded the least score (0.350). At a cementum-restoration interface, CR-G1 (0.850) documented the lowest micro-leakage; RMGI-G3 had a greater value at 1.700. Conclusions The hybrid CR could be effectively used to restore the restoration of a marginal gap around crown margins.

Improvement and determination of the influencing factors of coiled tubing fatigue life prediction

The fatigue life prediction model cannot accurately predict the service life of coiled tubing operations, resulting in waste and accidental fracture of coiled tubing. This article introduces the fatigue life prediction model of coiled tubing and a detection system developed using weak magnetic detection method and eddy current detection method. The detection device is used to detect accurate defect dimension, wall thickness reduction, and diameter deformation to improve the accuracy of fatigue life prediction. Furthermore, the actual defect dimension is included in the fatigue life assessment calculation to eliminate the influence of the existing model on the immobilization of defects and corrosion influence factors. By analyzing field operation cases and measured values, the effects of defects, wall thickness reduction, and diameter growth on fatigue life are studied to improve the accuracy of parameters and the integrity of basic data in the calculation process. The influence of reverse bending and weld on fatigue life is discussed. The residual life can be predicted more accurately by combining field testing technology and fatigue life evaluation method. Field measurement input of fatigue life prediction model is the main means to improve its accuracy and practicability.

Development of a Novel Method To Evaluate Well Integrity During CO2 Underground Storage

Summary A safe and ecologic underground storage of carbon dioxide (CO2) requires long-term integrity of the wells affected by the injected CO2, including both active wells and abandoned wells. In line with other investigators, technical integrity is assumed if there is no significant leak in the subsurface system from the storage reservoir. The evaluation of integrity of abandoned wells over a long time frame during CO2 underground storage can only be performed indirectly and requires a comprehensive understanding of relevant thermal/hydraulic/mechanical/chemical processes affecting well integrity. This paper presents an integrated approach coupling qualitative features, events, and processes (FEPs) and scenario analysis with quantitative-model development and consequence analysis. The qualitative analysis provides a solid and comprehensive study on all the FEPs that affect well integrity. The mechanical model presents the stress distribution of the casing/cement/rock composite system and provides a quantification of the defect dimension caused by different load conditions. The defect dimension can be used to compute equivalent permeability of the cement sheath by use of empirical correlations, which is an important input parameter for the following CO2-leakage simulation, provided it is considered that CO2 can only migrate through the defects instead of the cement matrix. When integrity is compromised, the storage reservoir will leak CO2. For this leakage, a numerical model is presented to simulate the flow of CO2 along abandoned wellbores during the storage period, such as 1,000 years. It is found from the FEP analysis that the most-critical system components are caprock, casing/cement/rock composite system, and abandonment elements. By building a geomechanical model and a leakage model, it is also found that in the simulated scenarios the CO2-leakage rate is very small except for when using cement sheaths of very poor quality, which can lead to a leakage rate exceeding the maximum-allowable value. The sensitivity analysis shows that the vertical permeability of the cement sheath plays the most critical role. In comparison with previous studies, this method is comprehensive and easy to implement.

Comparison of Cable Insulation Control in Weak and Strong Electric Fields

In this paper the modern methods of cable products insulation control are referred. A comparison of efficiency of the cable insulation defects control by changing in cable area capacitance is carried out in the strong and weak electric fields. The electric cable can be represented as a cylindrical capacitor, but to simplify the issue the insulation area is represented as a plate capacitor with anisotropic dielectric. The cable insulation model is created in the software Comsol Multyphysic. The effect of the defect dimension on the cable area electric capacitance in a strong and weak electric field is described. Also, the control sensitivity of both methods was assessed and compared with each other. The control sensitivity in a weak electric field is slightly higher for the defects with small size (less than 70% from insulation thickness). The control sensitivity in a strong electric field is considerably higher for the defects with big size (more than 70% from insulation thickness).

Analysis of Influence Factors in Step Heating Thermography to Composite Materials

In process of Thermal Wave NDT, as a result of influence from kinds of factors, such as noise, intensity of heating signal, defect dimension, it is very difficult to get good testing data. In order to resolve it, the method of numerical computing was taken to simulate the process of heat conduction in sample. At the simulating process, some valuable phenomenon were found, and as follows: When time of heating time was enough, temperature changing at surface would be steady, and rate of changes could be approximately considered as a constant; the biggest contrast would delay, as depth and diameter increased; the greater intensity of heating signal was, the quicker change of contrast was; and it was more important to ascertain the best testing time when the biggest contrast occurred. And these were valuable to acquire more precise testing result.

Quantitative Analysis of the Defect Dimension for Fracture Surface of Fracture Splitting Connecting Rod

The fracture surface of con-rod is difficult to be quantitatively described due to its indented macro morphology. Thus, the range of fracture surface defect dimension has no uniform standard. In order to solve this question, 3D software about the digital fracture surface reconstruction was developed by combining the fracture splitting technology of con-rod with reverse engineering, which realized the reproduction of its morphology and completed the real area calculation of the surface. The results show that the fracture surface area processed by fracture splitting is 13.1% larger than that of the plane processed by machining. It represents that the defect dimension range of fracture surface is improved compared to empirical value without reducing the bearing capacity and usability.

Research of Ultrasonic Image Evaluation Based on Defect Dimension

Objective method of image quality evaluating is necessary for the research of ultrasonic imaging quality of different ultrasonic testing method, and deterministic calculation method is essential for the defect analyzing of ultrasonic image. Defect analyzing method of ultrasonic image is researched by threshold segmentation, noise point rejecting and area filling. Experiment results indicated that the defect position and size can be adjudged by the ultrasonic image.