• Structural Monitoring and Maintenance
• /
• v.7 no.1
• /
• pp.13-25
• /
• 2020

One of the most important aspects in structural health monitoring is the detection of fatigue damage. Structural components such as heavy-duty bolts work under high dynamic loads, and thus are prone to accumulate fatigue damage and cracks may originate. Those heavy-duty bolts are used, for example, in wind power generation and mining equipment. Therefore, the investigation of new and more effective monitoring technologies attracts a great interest. In this study the acoustic emission (AE) technology was employed to detect incipient damage during fatigue testing of a M36 bolt. Initial results showed that the AE signals have a high level of background noise due to how the load is applied by the fatigue testing machine. Thus, an advanced signal processing method in the time-frequency domain, the Hilbert-Huang Spectrum (HHS), was applied to reveal AE components buried in background noise in form of high-frequency peaks that can be associated with damage progression. Accordingly, the main contribution of the present study is providing insights regarding the detection of incipient damage during fatigue testing using AE signals and providing recommendations for further research.

• Geomechanics and Engineering
• /
• v.7 no.6
• /
• pp.665-678
• /
• 2014

In discrete element modeling, 2D software has been widely used in order to gain further insights into the fundamental mechanisms with less computational time. The porosities used in 2D DEM studies should be determined with appropriate approaches based on 3D laboratory porosities. This paper summarizes the main approaches for converting porosities from 3D to 2D for DEM studies and theoretical evaluations show that none of the current approaches can be widely used in dealing with soil mechanical problems. Therefore, a parabolic equation and a criterion have been suggested for the determination of 2D porosities in this paper. Moreover, a case study has been used to validate that the 2D porosity obtained from the above suggestion to be rational with both the realistic contact force distribution in the specimen and the good agreement of the DEM simulation results of direct shear tests with the corresponding experimental data. Therefore, the parabolic equation and the criterion are suggested for the determination of 2D porosities in a wide range of polydisperse particle systems, especially in dealing with soil mechanical problems.

• Structural Engineering and Mechanics
• /
• v.46 no.5
• /
• pp.673-693
• /
• 2013

This paper presents a systematic design and training procedure for the feed-forward back-propagation neural network (NN) modeling of both forward and inverse behavior of a rotary magnetorheological (MR) damper based on experimental data. For the forward damper model, with damper force as output, an optimization procedure demonstrates accurate training of the NN architecture with only current and velocity as input states. For the inverse damper model, with current as output, the absolute value of velocity and force are used as input states to avoid negative current spikes when tracking a desired damper force. The forward and inverse damper models are trained and validated experimentally, combining a limited number of harmonic displacement records, and constant and half-sinusoidal current records. In general the validation shows accurate results for both forward and inverse damper models, where the observed modeling errors for the inverse model can be related to knocking effects in the measured force due to the bearing plays between hydraulic piston and MR damper rod. Finally, the validated models are used to emulate pure viscous damping. Comparison of numerical and experimental results demonstrates good agreement in the post-yield region of the MR damper, while the main error of the inverse NN occurs in the pre-yield region where the inverse NN overestimates the current to track the desired viscous force.

• International Journal of Fluid Machinery and Systems
• /
• v.2 no.4
• /
• pp.315-323
• /
• 2009

Pressure oscillations triggered by the unstable interaction of dynamic flow features of the hydraulic turbine with the hydraulic plant system - including the electrical design - can at times reach significant levels and could lead to damage of plant components or could reduce component lifetime significantly. Such a problem can arise for overload as well as for part load operation of the turbine. This paper discusses an approach to analyze the overload high pressure oscillation problem using computational fluid dynamic (CFD) modeling of the hydraulic machine combined with a network modeling technique of the hydraulic system. The key factor in this analysis is the determination of the overload vortex rope volume occurring within the turbine under the runner which is acting as an active element in the system. Two different modeling techniques to compute the flow field downstream of the runner will be presented in this paper. As a first approach, single phase flow simulations are used to evaluate the vortex rope volume before moving to more sophisticated modeling which incorporates two phase flow calculations employing cavitation modeling. The influence of these different modeling strategies on the simulated plant behavior will be discussed.

• Korean Journal of Veterinary Research
• /
• v.56 no.3
• /
• pp.161-166
• /
• 2016

Hyperadrenocorticism (HAC) is a common endocrinopathy among dogs that causes multisystemic signs. This study was conducted to evaluate cardiocirculatory, biochemical, and hemostatic parameters in dogs with HAC at diagnosis, in addition to verifying whether abnormal parameters could be controlled by initial treatment with trilostane. Fifteen dogs with HAC were assessed by systolic blood pressure measurement, electrocardiography, Doppler echocardiography, serum concentration of troponin I, and biochemical and hemostatic profile at diagnosis and after trilostane therapy. Unlike biochemical parameters, hemostatic and cardiocirculatory parameters were not significantly influenced by the onset of treatment. The authors believe that clinical treatment with trilostane for 3 to 4 months might not be sufficient for the stabilization of cardiocirculatory abnormalities such as hypertension. Therefore, dogs with HAC must receive cardiocirculatory monitoring at diagnosis and during drug treatment.

• Journal of Magnetics
• /
• v.19 no.2
• /
• pp.155-160
• /
• 2014

The heating produced by the absorption of radiofrequency (RF) has been considered a secondary undesirable effect during MRI procedures. In this work, we have measured the power absorbed by distilled water, glycerol and egg-albumin during NMR and non-NMR experiments. The samples are dielectric and examples of different biological materials. The samples were irradiated using the same RF pulse sequence, whilst the magnetic field strength was the variable to be changed in the experiments. The measurements show a smooth increase of the thermal power as the magnetic field grows due to the magnetoresistive effect in the copper antenna, a coil around the probe, which is directly heating the sample. However, in the cases when the magnetic field was the adequate for the NMR to take place, some anomalies in the expected thermal powers were observed: the thermal power was higher in the cases of water and glycerol, and lower in the case of albumin. An ANOVA test demonstrated that the observed differences between the measured power and the expected power are significant.

• Geotechnical Engineering
• /
• v.3 no.4
• /
• pp.31-40
• /
• 1987

A helical probe test (HPT) suitable for in.situ soil exploration to a shallow depth and compaction control were developed and tested in different soils alongside traditional in-situ tests, including Standard Penetration Test (SPT), Cone Penetration Test (CPT) and in-situ density test. The helical probe test is economical and can be performed by a single person. The torque necessary to insert the probe Is used as a measure of soil characteristics. It was found that: the HPT test correlates well with the SPT test and the correlation is not sensitive to the soil type; the HPT test correlates well with the CPT test, but the correlation is sensitive to the soil type; the HPT torque provides a sensitive measure of relative compaction rind in-situ dry density of compacted soils; the reverse torque ratio decreases with increasing average grain sloe.

• KIEE International Transactions on Power Engineering
• /
• v.5A no.1
• /
• pp.79-84
• /
• 2005

In many countries, the electric power industry is undergoing significant changes known as deregulation and restructuring. These alterations introduce competition in generation and retail and require open access to the transmission network. The competition of the electric power industry causes many issues to surface. Among them, unbundling of the transmission service is probably the most complicated as it is a single and integrated sector and the transmission revenue requirement must be allocated to market participants in a fair way. In these situations, it is valuable to research the methodologies to allocate transmission usage. The power tracing method offers useful information such as which generators supply a particular load or how much each generator (load) uses a particular transmission line. With this information, we can allocate required transmission revenue to market participants. Recently, several algorithms were proposed for tracing power flow but there is no dominant power tracing method. This paper proposes a power tracing method based on graph theory and complex-current distribution. For practicability, the proposed method for transmission usage allocation is applied to IEEE 30 buses and compared with the method proposed by Felix F.Wu.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.31 no.7
• /
• pp.1052-1063
• /
• 2007

This study focuses on the analysis of body images appearing in the fashion illustrations since the 1990's and thereby attempts to determine relationship between their expressional features and aesthetic values in reference to theory of post-structuralism. Especially among numerous post-structuralist, Michel Foucault, Gilles Deleuze/Felix Guattari, and Julia Kristeva set unique arguments on body, which provide valuable leads to decipher the image of body. For that reason, body images shown in the fashion illustration are categorized into grotesque body, fragmented body, humanoid body, and post-gendered body, and reviewed their characteristics and aesthetic values based on critics of above three scholars. Findings are summarized as follows: First, image of body entails meaning of an resistance of traditional social concepts and order, and second it serves the purpose of creating a new and unique sense. Finally, it is not an object of representation of physical facts, but rather a representation of the real itself, apart from presenting the original material. Given arguments enhance understanding of images of body in fashion illustration in a broader sense.

• Journal of Crop Science and Biotechnology
• /
• v.10 no.2
• /
• pp.106-111
• /
• 2007

Increasing genetic variability with mutagenic agents has been broadly employed in plant breeding because it has the potential to alter one or more desirable traits. In this study, a molecular analysis assessed by Amplified Fragment Length Polymorphisms(AFLPs) and a morphological analysis based on seedlings subjected to aluminum stress were compared. Also, an analysis of allelic frequencies was performed to observe unique alleles present in the pool. Genetic distances ranging from 0.448 to 0.953 were observed, suggesting that mutation inducing was effective in generating variability. The genetic distances based on morphological data ranged from 0(genotypes 22 and 23) to 30.38(genotypes 15 and 29). In the analysis of allelic frequency, 13 genotypes presented unique alleles, suggesting that mutation inducing was also targeting unique sites. Mutants with good performance under aluminum stress(9, 15, 18 and 27) did not form the same clusters when morphological and molecular analyses were compared, suggesting that different genomic regions may be responsible for their better performance.