This paper developed a piezoelectric-transducer-based damage detection of concrete materials after blasting. Two specimens (with or without an energy-relieving structure) were subjected to a 40 m ...deep-underwater blasting load in an underwater-explosion vessel, and their damage was detected by a multifunctional piezoelectric-signal-monitoring and -analysis system before and after the explosion. Statistical-data analysis of the piezoelectric signals revealed four zones: crushing, fracture, damage, and safe zones. The signal energy was analyzed and calculated by wavelet-packet analysis, and the blasting-damage index was obtained after the concrete specimen was subjected to the impact load of the underwater explosion. The damage of the two specimens gradually decreased from the blast hole to the bottom of the specimen. The damage index of the specimen with the energy-relieving structure differed for the fracture area and the damage area, and the damage protection of the energy-relieving structure was prominent at the bottom of the specimen. The piezoelectric-transducer-based damage monitoring of concrete materials is sensitive to underwater blasting, and with wavelet-packet-energy analysis, it can be used for postblasting damage detection and the evaluation of concrete materials.
Key Points
A decision making framework considering the epistemic uncertainty is proposed.
The effects of sample size on potential risk of alternatives and ranking result.
The ranking of project ...alternatives can be changed by adjusting the sample size.
Epistemic uncertainty is a result of knowledge deficiency about the system. Sampling error exists when limited amounts of hydrologic data are used to estimate a T year event quantile. Both the natural randomness of hydrologic data and the sampling error in design quantile estimation contribute to the uncertainty in flood damage estimation. This paper presents a framework for evaluating a flood‐damage‐mitigation project in which both the hydrologic randomness and epistemic uncertainty due to sampling error are considered in flood damage estimation. Different risk‐based decision‐making criteria are used to evaluate project merits based on the mean, standard deviation, and probability distribution of the project net benefits. The results show that the uncertainty of the project net benefits is quite significant. Ignoring the data sampling error will underestimate the potential risk of each project. It can be clearly shown that adding data to existing sample observations leads to improved quality of information, enhanced reliability of the estimators, and reduced sampling error and uncertainty in the project net benefits. Through the proposed framework, the proper length of the extended record for risk reduction can be determined to achieve the required level of acceptable risk.
Grain boundaries (GBs) are believed as potent defect sinks that contribute to the radiation damage reduction of materials. The defect-GB interaction has been extensively studied in pure metals, but ...only a few works shed light on the influence of material component such as alloying elements. In this study, the GB-mediated reduction of radiation defects in four W-based alloys (W–Re, W–Ta, W–Mo and W–V) is systematically investigated by atomistic simulations. Quantitative results show that the defect reduction in W-based alloys is significantly decreased comparing with elementary W. The principal reason for this decrease is the presence of various micro configurations where the solute-defect binding interactions are strong. Solutes with high local stress for each atom have a positive effect on the absorption of interstitials by GB. The ability of GB to absorb interstitials is enhanced with the increasing temperature, and also the accumulation of vacancies is increased when the temperature is as high as 1200 K. The findings in this work provide useful information on the design of radiation tolerance materials.
Graphic Abstract
There are several algorithms for determining control forces of active devices in civil engineering structures. Uniform distribution of deformations theory is a structural concept which mainly focuses ...on equalizing deformations in order to promote the utilization of ductility capacity of structural elements thereby mitigating damages to a structure. In common active control algorithms, deformation uniformity and reducing damages are barely noted. In this research, a new active control algorithm regarding uniform deformation theory will be proposed. Uniform distribution of Deformation Control (UDC) algorithm consists of a massless optimized Virtual Added linear structure with Pinned connections (VAP) which is added to a desired original structure. This VAP can be treated as an added stiffness matrix. Once the parameters of the VAP were optimized in a manner that the desired responses were obtained from the new integrated structure, then, the new integrated structure is developed and analyzed in each time step. Finally, the VAP beams axial forces are extracted and applied to the original structure as control forces via active control devices such as active tendons.
This proposed control algorithm is simple and effective in reducing responses especially drifts, making more uniform thereby reducing structural damages as well as decreasing the required capacity of actuators and the power consumption eventually. High potential and promising performance of the proposed UDC algorithm will be represented through numerical investigation in an office building example. The results are compared with Nonlinear Instantaneous Optimal Control (NIOC) algorithm as a very common active control algorithm for linear and nonlinear structures.
Diabetes is a chronic disease where millions of sufferers invasively prick their skin over the course of a day to take blood samples. Non-invasive glucose monitoring would bring relief to diabetics ...because it offers reduced skin damage. Microwave sensors are becoming a good choice for non-invasive glucose monitoring. This Letter presents two designs based on microwave sensors. The sensors have elliptical shapes and consist of a patch reflector and dielectric resonator (DR) that resemble a human thumb. A four-layer thumb model is presented, with a focus on the permittivity of the blood layer. The thumb was moved to various positions on the two microwave sensors to observe the effect it had on the frequency shift with various blood permittivity values. Observations showed that the elliptical DR sensor was less sensitive to errors and thumb positioning when taking glucose measurements than the elliptical patch sensor. The elliptical DR had an error of 55 MHz from the centre frequency, whereas that of the elliptical patch was 140 MHz. The effects of thumbs with various blood permittivity values were explored and explained.
Commercial polypropylene fibers are incorporated as reinforcement of cement-based materials to improve their mechanical and damage performances related to properties such as tensile and flexural ...strength, toughness, spalling and impact resistance, delay formation of cracks and reducing crack widths. Yet, the production of these polypropylene fibers generates economic costs and environmental impacts and, therefore, the use of alternative and more sustainable fibers has become more popular in the research materials community. This paper addresses the characterization of recycled polypropylene fibers (RPFs) obtained from discarded domestic plastic sweeps, whose morphological, physical and mechanical properties are provided in order to assess their implementation as fiber-reinforcement in cement-based mortars. An experimental program addressing the incorporation of RPFs on the mechanical-damage performance of mortars, including a sensitivity analysis on the volumes and lengths of fiber, is developed. Using analysis of variance, this paper shows that RPFs statistically enhance flexural toughness and impact strength for high dosages and long fiber lengths. On the contrary, the latter properties are not statistically modified by the incorporation of low dosages and short lengths of RPFs, but still in these cases the incorporation of RPFs in mortars have the positive environmental impact of waste encapsulation. In the case of average compressive and flexural strength of mortars, these properties are not statistically modified when adding RPFs.
This paper focuses on finding a suitable drill bit for drilling Carbon Fiber Reinforced Plastic (CFRP). The drilling characteristics of the dagger drill, the double point angle drill, and the candle ...stick drill are studied. The results show that the side edge has poor ability to remove burrs, and the tip structure of the outer corner of the candle stick drill can greatly reduce the entry damage. However, the outer corner small tip structure of the candle stick drill cannot effectively remove the uncut fiber around θ = 0° of hole exit. The long secondary cutting edge of the dagger drill makes a small thrust force at the drilling exit stage and reduces the dropping speed of the thrust force, leading a lower impact on the laminate bottom. Then, a new tool is developed for drilling CFRP based on the advantages of the three kinds of drill bits. The drill has a long secondary cutting edge, a small tip diameter and a small tip structure of the outer corner. And its drilling characteristics are analyzed. The result shows that the new compound drill bit can effectively remove fibers and reduce thrust force at the drilling exit stage, form burr-free and small delamination hole. The drill reduces the waste of CFRP in manufacturing process since the exit damage is reduced substantially, which is in line with the concept of green manufacturing.
The focus of this work is on fatigue estimation and data-based controller design for wind turbines. The main purpose is to include a model of the fatigue damage of the wind turbine components in the ...controller design and synthesis process. This study addresses an online fatigue estimation method based on hysteresis operators, which can be used in control loops. The authors propose a data-based model predictive control (MPC) strategy that incorporates an online fatigue estimation method through the objective function, where the ultimate goal in mind is to reduce the fatigue damage of the wind turbine components. The outcome is an adaptive or self-tuning MPC strategy for wind turbine fatigue damage reduction, which relies on parameter identification on previous measurement data. The results of the proposed strategy are compared with a baseline model predictive controller.
Risk‐based decision making of flood‐damage‐reduction (FDR) projects evaluates different design alternatives that have uncertain inundation–reduction benefits and costs. Uncertainties in FDR projects ...arise from, but are not limited to, the natural randomness of hydrological events, knowledge deficiency in hydrologic models, and the parameters, among others. This study investigates how the flood damage estimation is affected by the epistemic uncertainty resulting from using finite flood data in defining the flood‐frequency relationship and its effects on risk‐based decision making. A Monte Carlo simulation is applied in the study to simulate the epistemic uncertainty associated with the sampling error of the flood magnitude. The model parameter uncertainty is explicitly considered in the estimation of statistical features of flood damage. A recently developed decision rule on the basis of expected opportunity loss (EOL) is applied to the risk‐based evaluation of the relative merits of several competing flood mitigation projects. EOL‐based decision rule has the advantages of considering a decision maker's risk‐aversion attitude and incorporating more complete statistical features of project outcomes, including their correlations. The influence of the model parameter uncertainty on the project evaluation results is examined through an example FDR project with five design alternatives in which flood magnitude follows a Gumbel distribution.
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