Effects of mistuning on dynamic behavior of nonlinear cyclic systems with lump masses and cubic nonlinearity

Mistuning in cyclic symmetric systems increases severely the forced response of system and splits the modes. This paper concerns with nonlinear behavior of mistuned cyclic systems. A nonlinear, mistuned model based on the method of multiple scales is proposed and formulated in which nonlinearity and mistuning parameter is assumed to be in of low order. Next, two mistuned systems were considered and solved by the multiple scale technique. Numerical results demonstrate that mistuning can lead to repeating and scattering of jump phenomena during the excitation frequency whereas in tuned cyclic system it occurs simultaneously (synchronously).Peer ReviewedPostprint (published version

Effect of compaction pressure on consolidation behaviour of unsaturated silty soil

The effect of compaction pressure on subsequent soil behaviour during isotropic consolidation has been investigated by conducting controlled-suction triaxial tests on samples of an unsaturated compacted silty soil. A comprehensive set of laboratory experiments was carried out in a double-walled triaxial apparatus on samples of unsaturated soil that were prepared using two different compaction pressures. The axis translation technique was used for creating the desired suctions in the samples. In the experiments, the soil samples were subjected to isotropic consolidation under constant suctions. The results show that different compaction pressures produce different fabrics in a soil and therefore affect the behaviour of the soil. The results also show that the value of yield stress and the location of the loading¿collapse (LC) yield curve are functions of soil fabric. Furthermore, it is shown that the slopes of normal consolidation lines for densely and loosely compacted samples differ in unsaturated conditions but are the same in saturated soils. A comparison is made between the behaviour of the dense and loose samples, and the difference in the behaviour is explained

REPEATABILITY OF CARDIAC MAGNETIC RESONANCE RADIOMICS: A MULTICENTRE MULTI-VENDOR TEST-RETEST STUDY

Aims: To evaluate the repeatability of cardiac magnetic resonance (CMR) radiomics features on test-retest scanning using a multi-centre multi-vendor dataset with a varied case-mix. Methods and Results: The sample included 54 test-retest studies from the VOLUMES resource (thevolumesresource.com). Images were segmented according to a pre-defined protocol to select three regions of interest (ROI) in end-diastole and end-systole: right ventricle, left ventricle (LV), and LV myocardium. We extracted radiomics shape features from all three ROIs and, additionally, first-order and texture features from the LV myocardium. Overall, 280 features were derived per study. For each feature, we calculated intra-class correlation coefficient (ICC), within-subject coefficient of variation, and mean relative difference. We ranked robustness of features according to mean ICC stratified by feature category, ROI, and cardiac phase, demonstrating a wide range of repeatability. There were features with good and excellent repeatability (ICC ≥ 0.75) within all feature categories and ROIs. A high proportion of first-order and texture features had excellent repeatability (ICC ≥ 0.90), however, these categories also contained features with the poorest repeatability (ICC < 0.50). Conclusion: CMR radiomic features have a wide range of repeatability. This paper is intended as a reference for future researchers to guide selection of the most robust features for clinical CMR radiomics models. Further work in larger and richer datasets is needed to further define the technical performance and clinical utility of CMR radiomic

Effect of cement on treatment of a clay soil contaminated with glycerol

This is the author accepted manuscript. The final version is available from American Society of Civil Engineers via the DOI in this record.An investigation into the behavior of a contaminated clay soil and its treatment was carried out through a program of experimental tests. The contaminated soil samples were prepared with different percentages (3, 6, and 9%) of a glycerol solution with 40% concentration. The samples were prepared as mixtures of clean or glycerol-contaminated soil with different cement contents (3, 6, and 9%). Atterberg limits and unconfined compressive strength (UCS) tests were conducted on the samples. The results showed that Atterberg limits are reduced by adding glycerol or cement or adding glycerol to soil-cement. Both the strength and stiffness of the contaminated soil are reduced by increasing the degree of contamination. The results of treated soil showed that adding cement to contaminated soil increases the strength and the amount of increase in strength is dependent on the percent of cement, curing time and degree of contamination. Based on scanning electron microscopy analysis, it was found that the presence of glycerol prevents the interaction between soil and cement

Effect of thermal history on the properties of bentonite

PublishedJournal ArticleThis is the author accepted manuscript. The final version is available from Springer Verlag via the DOI in this record.© 2016, Springer-Verlag Berlin Heidelberg.The effect of thermal history on the properties of bentonite was studied through a number of experimental tests. The desired thermal history was created on samples of bentonite by keeping them at a fixed temperature (50, 100, 150, 200 and 250 °C) for a specific duration (3, 7, 14 and 30 days). Standard compaction, Atterberg limits, free swelling and swelling pressure tests were carried out on the samples on the dry side of optimum, optimum and wet side of optimum of the compaction curve with desired thermal history. In addition chemical tests were carried out on the flooding water at the end of the swelling test. The results showed that the changes in compaction characteristics were not considerable but the Atterberg limits, free swelling and swelling pressure of the soil were changed due to the thermal history in comparison with the soil without any thermal history. The magnitudes of free swelling and swelling pressure were dependent on the location of prepared sample on the compaction curve. In addition, the changes in Atteberg limits and swelling parameters (amount of free swelling and swelling pressure) were functions of magnitude of temperature and duration of time that the sample experienced the temperature in its temperature history. The effects of temperature and also duration of exposure of the soil to temperature was discussed with the aid of the Diffuse Double Layer (DDL) theory. It was found that the temperature may change the gradation of soil due to cementation of particles as a result of formation of some salts and oxides that help to paste the particles together and change the properties of the soil

Effect of Mono Ethylene Glycol Solution on Mechanical Behavior of a Clay Soil

This is the author accepted manuscript. The final version is available from ASTM International via the DOI in this record This article presents the results of an investigation into the behavior of a clay soil contaminated with mono ethylene glycol (MEG) through a program of experimental tests. Soil specimens were prepared with water or different concentrations (10, 25 and 40 %) of MEG by the slurry method. One-dimensional consolidation and consolidated undrained (CU) triaxial tests were performed on the specimens. The results of the consolidation tests showed that the preconsolidation pressure is increased and the value of λ (slope of normal consolidation line) is decreased with an increase in the concentration of MEG. In addition, the results of the CU triaxial tests indicated that the friction angles (in term of total and effective stresses) are greater for the MEG solution than for water as pore fluid, and their values are increased with an increase in the concentration of the MEG solution. It was also shown that Roscoe surface exists for contaminated soil in q, p′, v space, and its position in this space is dependent on the concentration of pore fluid

Models for predicting the seepage velocity and seepage force in a fiber reinforced silty soil

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Randomly reinforced soil is used in hydraulic projects such as temporary canals, earth dams, stream restoration and so on for controlling seepage. This paper presents an investigation into the effect of random reinforcement on the seepage velocity and seepage force in a silty soil. Experimental tests were carried out on randomly reinforced samples with two types of fiber at different lengths and percentages. The results show that the random reinforcement of soils with fiber is an effective technique in controlling the seepage velocity and seepage force. Regression models were developed based on the experimental data for determination the seepage velocity and seepage force. The proposed models include the length of fiber, fiber content of soil and hydraulic gradient. Comparison between the model predictions and the experimental results shows that the proposed models can satisfactorily predict the seepage velocity and seepage force for a randomly reinforced silty soil. Analysis of the results of the proposed models shows that the seepage velocity increases with increasing the hydraulic gradient but decreases with increasing fiber length and fiber content. In addition the seepage force increases with increasing the fiber length and fiber content of the soil

Treatment of a clay soil deposited in saline water by cement

This is the author accepted manuscript. The final version is available from Taylor & Francis (Routledge) via the DOI in this record.The behavior and treatment of a clay soil deposited in natural and saline (sodium chloride) water is studied through experimental tests. A clay soil was deposited in natural water and water with different concentrations of sodium chloride (40, 80 and 150 g/L) in a reservoir at lab. The samples were taken from dry deposited soil and they were treated with 5, 8 and 10% cement. Atterberg limits, compaction and unconfined compression tests were carried out on the deposited soil and treated soil samples. The results show that the physical and mechanical behaviors of soil deposited in natural water and salinity water are not the same and they are function of salt concentration. The results also indicate that cement can improve the strength of the deposited soil in saline water but this improvement is not a direct function of salt concentration. In addition, for a constant salt concentration the strength of treated soil is function of percent of cement and curing time. Based on SEM (Scanning Electron Microscopy) analysis, it was found that salt concentrations of 80 and 150 g/L may have prevented the interaction between soil and cement in the deposited soil

Properties of Clay Soil and Soil Cement Reinforced with Polypropylene Fibers

This is the author accepted manuscript. The final version is available from American Concrete Institute via the DOI in this recordRandomly reinforced cohesive soils can be used as construction material in many civil engineering projects. These materials may be subjected to compressive, tensile or flexural stresses in their life. The presence of stabilizing agents or fibers may affect their resistance against various loads. In this work a clay soil was reinforced randomly at four different lengths of fiber ((10, 15, 20 and 25 mm) [0.394, 0.591, 0.788 and 0.985 in]) with fiber inclusions of 0.5 and 1%. Reinforced soil-cement samples were also prepared with 8 and 10% cement and reinforced similar to the soil. Unconfined compressive and tensile strength tests were carried out on the prepared samples. The results show that the compressive strength is increased with fiber length up to about 10 mm (0.394 in). When length of fiber is larger than 10 mm (0.394 in), the compressive strength is still increased but with a slow rate. The results for the reinforced soil-cement samples indicate that for a given fiber and cement content increasing the length of fiber has no significant effect on the strength of the sample. The tensile strength of reinforced soil is increased by increasing the fiber inclusion and length of fiber. For the reinforced soil-cement samples the tensile strength is increased with increasing fiber content, length of fiber, percent of cement and curing time