Proposed Analysis Procedure Research Articles

A high-static-low-dynamic-stiffness delayed resonator vibration absorber

Delayed resonator (DR), which enables complete vibration suppression through loop delay tuning, has been extensively investigated as a linear active dynamic vibration absorber since its invention. Besides, the nonlinear high-static-low-dynamic stiffness (HSLDS) has been widely used in vibration isolators for broadband (yet incomplete) vibration reduction. This work combines the benefits of DR and the nonlinear HSLDS characteristics, thus creating a nonlinear DR (NDR). Three unexplored topics are considered: (1). To address the nonlinear dynamics that are made complicated by the introduction of delay and the nonlinearity coupled between the NDR and the primary structure; (2). To tune the control parameters to seek possible complete vibration suppression in the nonlinear case, and accordingly, to determine the operable frequency band; (3). To evaluate how the HSLDS characteristics can enhance the performance of the linear DR (LDR) and how to design an NDR to maximize its benefits. Without loss of generality, a classic nonlinear HSLDS structure with three springs and two links is considered, and mathematical tools and computational algorithms are introduced or proposed to efficiently address theoretical analysis. Using the parameters of an experimental setup, we show that a properly tuned NDR suppresses the vibrations on the primary structure to a sufficiently low level. Besides, the HSLDS characteristics extend the operable frequency band compared with the LDR, while strong nonlinearity limits such extension. The proposed analysis procedures for delay-coupled nonlinear dynamics, alongside the control parameter tuning, determination of operable frequency bands, and structural design rules, establish a basic theoretical framework for the NDR design.

A suitable procedure of dose reduction factor measurements of X-ray shields during computed tomography examination - The importance of considering positional changes of an X-ray tube

During computed tomography (CT) examinations, radio-sensitive organs located outside the field of view (FOV) are usually exposed to radiation caused by both direct and scattered X-rays. Traditionally, the use of radiation protection products has been an option for reducing exposure doses. The catalog value of the dose reduction factor (DRF) for a commercial X-ray shield is generally determined by the manufacturer using a plain X-ray irradiation system to measure the difference in dose with and without the shield. In contrast, actual shielding ability measurements during clinical CT examinations are usually evaluated using a similar equation, but it is not guaranteed that the incident directions of X-rays will be the same between the measurement data with and without a shield. The purposes of this study are to introduce a novel method for evaluating DRF by accounting for the influence of the X-ray incident direction in helical scanning and to obtain knowledge about the correctness of previously reported DRF values. Experiments pertaining to chest CT examinations were performed using a human body phantom and small-type dosimeters which consist of an optically stimulated luminescence element using Al2O3:C. A total of 100 examinations were iteratively performed, both with and without a shield. The corresponding DRF was then calculated. The novelty of the proposed analysis procedure lies in a paired analysis method, where the DRF is calculated by reorganizing numerous acquired data sets with and without the shield to pair similar incident angles of X-rays. As a result, the DRF values were estimated to be 48.5 ± 4.3%, 48.7 ± 2.7%, and 48.9 ± 1.5% based on the data results within the 10–40 data sets, 40–70 data sets, and 70–100 data sets, respectively. When the DRF values were obtained by the conventional method without applying our sorting procedure, the results were 48.4 ± 8.1%, even when the 70–100 data sets were used. This result indicates that the proposed method can analyze DRF with higher accuracy. In the example of thyroid X-ray shield, while there was no significant difference in the most probable values of DRF between the conventional and proposed methods coincidentally, we believe it is important to evaluate DRF based on a scientifically correct approach because the mathematical formulas for calculating these two values differ. In conclusion, when calculating the DRF of shielding materials during CT examination, it is imperative that data analysis considers the significant impact of differences in incident X-ray directions on the measured exposure dose data.

Numerical investigation of subcooled two-phase flow and heat transfer characteristics in a liquefied natural gas cargo containment system

The increase demand in liquefied natural gas (LNG) leads to an increase in the import and export of LNG cargo using LNG carriers with composite insulation and double-hull structures for membrane-type storage tanks. Therefore, the transient characteristics of cryogenic heat transfer in LNG cargo containment systems have become important for understanding the physics when LNG vaporizes into the gas phase to minimize the cargo loss of boil-off gas (BOG). However, public papers on fundamental research on long-term computational fluid dynamics (CFD) simulations are still lacking. In the present study, the transient flow behaviors of LNG fluids and the heat transfer characteristics were numerically studied by applying the simplified single-layer insulation in an LNG cargo containment system, based on an initial temperature of TLNG,0 = 110.5 K and saturation temperature of TLNG,sat = 111.5 K in the boundary condition of IGC code. The proposed analysis procedure can serve as a reference for relative comparison of predicted BOG difference in LNG cargo holds.Consequently, the heat transfer mode between the two-phase methane and the solid insulation could be typically classified into two different regimes: (1) a subcooled regime before reaching the saturation temperature from the initial temperature, and (2) a boiling regime after reaching the saturation temperature. In the subcooled regime, the subcooled liquid exhibited bulk flow motion induced by natural convection. The loss rate of LNG mass per time interval was extracted from the best-fit correlations as −0.0448 kg/s at 1 d (105 s) to cool down the insulation system and −0.0072 kg/s at 5 d (5 × 105 s) to reach the LNG saturation temperature. When the predicted value of the loss rate of LNG mass by the CFD simulation was regarded as the generation rate of boil-off gas, it was smaller than the designed value of the boil-off gas of 0.464 kg/s corresponded to boil-off rate (BOR) about 0.2 %/day. In the boiling regime and under sufficiently cooled conditions, the loss rate of LNG mass per time interval did not consistently exceed the BOR value. The liquid flow exhibited a turbulent-like motion despite the relatively low velocity at 10 d (106 s). Especially, the increase in the effective thermal conductivity was a good indicator for distinguishing between the boiling and subcooled regimes.

A change point-based analysis procedure for improving the success rate of decision-making in clinical trials with delayed treatment effects.

A delayed treatment effect is a commonly observed phenomenon in tumor immunotherapy clinical trials. It can cause a loss of statistical power and complicate the interpretation of the analytical findings. This phenomenon also poses challenges for interim analysis in the context of phase II/III seamless design or group sequential design. It shows potential to lead researchers to make incorrect go/no-go decisions. Despite its significance, rare research has explored the impact of delayed treatment effects on the decision success rate of the interim analysis and the methods to compensate for this loss. In this study, we propose an analysis procedure based on change points for improving the decision success rate at the interim analysis in the presence of delayed treatment effects. This procedure primarily involves three steps: I. detecting and testing the number and locations of change points; II. estimating treatment efficacy; and III. making go/no-go decisions. Simulation results demonstrate that when there is a delayed treatment effect with a single change point, using the proposed analysis procedure significantly improves the decision success rate while controlling the type I error rate. Moreover, the proposed method exhibits very little disparity compared to the unadjusted method when the proportional hazards assumption holds. Therefore, the proposed analysis procedure provides a feasible approach for decision-making at the interim analysis when delayed treatment effects are present.

Systematic review of construction project delays in Kuwait

Over the past two decades, numerous global studies, including those conducted in Kuwait, have focused on examining and understanding delays in construction projects. These investigations aimed to identify causes of delays and rank them based on their impact on project objectives. In pursuit of this research goal, the present study adopts a systematic approach to analyze construction delays, building on related previous research efforts. The primary objective of this analytical approach was to determine the most significant and influential causes of delays and investigate changes in these causes over the span of two decades, during which measures were taken to address delays. Through comprehensive analyses, the critical delay causes within the Kuwaiti construction industry were identified as: contractor site management incompetence, subcontractor-related challenges, design quality deficiencies, problems arising from the used contract, and supply chain disruptions affecting labor availability and construction materials. Additionally, the body of research on the subject was divided into two distinct groups: studies conducted before and after the year 2010. A comparative examination of the outcomes from these two groups revealed notable enhancement for internal site management delay sources, which involve direct management teams including contractors, supervisors, and owners, whereas the influence of external delay causes increased, primarily attributed to the impact of governmental regulations. To assess the dissimilarities between the results of these two groups, an ANOVA analysis was applied, affirming the presence of statistically significant differences. The study concludes by emphasizing key areas requiring further attention to effectively mitigate the causes of delays in construction projects. Moreover, the proposed analysis procedure holds potential applicability to other countries, serving as a valuable tool to augment the understanding of delay analysis within the construction domain on a broader scale.

Robustness analysis of gain‐scheduled Model Predictive Control for Linear Parameter Varying systems: An Integral Quadratic Constraints approach

AbstractIn this paper, we evaluate the robustness qualities of Model Predictive Control (MPC) algorithms applied for Linear Parameter Varying (LPV) systems. Specifically, we analyze gain‐scheduled LPV MPC schemes, that is, those that use model predictions based on the LPV scheduling variables available at each sampling instant. Accordingly, we extend previous results on finite‐horizon robustness analysis of linear time‐variant (LTV) systems, employing Integral Quadratic Constraints (IQCs) to describe the input‐output behavior of prediction uncertainties. We provide two main novelties in our formulation: (i) we propose a parameter‐dependent Karush–Kuhn–Tucker (KKT) inequality to describe the existence and feasibility of the LPV MPC control inputs; and (ii) we model the uncertainties that arise due to the unavailability of the scheduling trajectory along the prediction horizon as a bounded interconnection in the form of a Linear Fractional Transformation (LFT). Accordingly, we use dissipativity arguments (‐hard IQCs) in order to compute robust induced gains of the closed‐loop system (specifically, the and ‐to‐Euclidean metrics), taking into account the MPC prediction uncertainties. We also generate the set of reachable states from a given initial condition. A benchmark example is used to illustrate the proposed analysis procedure.

Experimental and MCFT-Based Study on Steel Fiber-Reinforced Concrete Subjected to In-Plane Shear Forces

Testing of concrete panels subjected to pure in-plane shear loading is necessary to elucidate the shear behavior of concrete. However, available data for predicting the shear capacity and behavior of steel fiber-reinforced concrete are rather limited. This study aims to evaluate the shear capacity and behavior of fiber-reinforced concrete made of highly flowable strain hardening fiber-reinforced concrete (HF-SHFRC) experimentally and analytically, respectively, using a panel tester loaded under pure shear and modified compression field theory (MCFT). The test was conducted using a panel test machine at the University of Toronto. The test results of the HF-SHFRC demonstrated strain hardening behavior at tension after the first crack, as indicated by the increase in the shear stress after the first crack in the HF-SHFRC panel. An analysis procedure is proposed for predicting the shear strength of steel fiber-reinforced concrete (SFRC) based on experimental data of the SFRC panels to obtain reliable results. A comparison of results obtained from the proposed analysis procedure and experiments show that it accurately predicted the response of the HF-SHFRC. The proposed MCFT-based analysis procedure can provide valuable insight for understanding the behavior of the SFRC panels under shear loading.

Reliable Integrity Preservation Analysis of Video Contents with Support of Blockchain Systems

In this article, we propose an integrity preservation analysis scheme of video contents working on the blockchain systems. The proposed scheme stores the core points of video contents analysis in the blockchain system permanently so that any user can easily verify the results of the proposed analysis procedure and their reliability. The scheme first examines the codec software characteristics of digital camera devices and video editing tools in advance, and stores them in the blockchain systems. Next, the scheme extracts the codec software characteristic from the target video file and compares it with the prepared characteristics in the blockchain system. With a matched characteristic, the scheme finds out the source camera device or the source video editing tool that generates the target video file. We also propose an integrity preservation trace scheme to record the transformation history of video contents into the blockchain systems. This scheme compares the original video and its transformed video frame by frame, and stores the comparison result with a hash value of the transformed video in the blockchain system. Then, the integrity analysis and transformation history of the target file can be easily searched in the blockchain system, where the hash value of the video file is used as the index of searching operation. We implement the proposed scheme into a practical tool upon a commercial blockchain system, Klaytn. Experimental results show that the proposed scheme carries out the integrity analysis of video contents with 100% accuracy, and provides the transformation history of non-original video contents with 100% accuracy when a proper parameter is given. It is also shown that the proposed scheme completes the integrity analysis within at most one second, and the search operation for transformation history within at most four seconds.

Structural Analysis and Design of Sustainable Cross-Laminated Timber Foundation Walls

There is widespread enthusiasm toward utilizing mass timber panels (MTP), mainly cross-laminated timber (CLT), in construction, including for the basements of low-rise buildings. CLT is deemed a sustainable alternative to the widely used concrete foundation walls due to significant advantages such as less vulnerability to cracking due to uneven load distribution and presence of concentrated loads, higher thermal resistance, less construction time due to whole-wall prefabrication and installation, and less detrimental environmental effects. This study is part of an extensive research program aimed at developing the structural analysis and design concepts and methodology for constructing house foundation walls using MTPs, focusing on the usage of CLT. After comparison of CLT basements with their equivalent concrete ones from the sustainability point of view, and a brief discussion on geotechnical and hygrothermal considerations, the main theme of the article includes the structural analysis and design methodology, requirements, and the procedure to achieve a reliable and efficient design of a CLT basement. A simplified analysis procedure to design the laminate thicknesses and the number of layers in CLT foundation walls for different scenarios considering various variables such as soil type and backfill height is discussed, and results in the form of pre-engineered design tables are provided. The findings of this study demonstrate that, depending on the soil type and backfill height, 3–7-ply CLT panels would be needed for net wall heights of up to 3 m. Additionally, advanced finite element analyses are performed on sample architypes to validate the simplified analysis procedure used for design. It is shown that the proposed analysis procedure and the pre-engineered tables produce conservative and efficient results.

Contribution of cornea to the peripheral ocular refraction in the two-dimensional visual field

The evaluation of the contact lenses for myopia control is often focused on the change in corneal refractive power, which is applied to indicate the contribution of the cornea to the peripheral ocular refractions (POR). However, this concept lacks a direct relationship to the POR for a realistic human eye with structural and optical irregularities. In this study, we propose a mathematically rigorous and highly efficient procedure for specifying the contribution of the cornea to the POR based on the wavefronts propagating along the chief rays from the iris center to the entrance pupil center. Using generalized ray tracing, the complexity in the impacts of the geometry of both corneal surfaces and their orientation within the human eye are fully explained with analytical equations. As a case study, the proposed procedure is performed on a realistic corneal model constructed from the measurement data on children. An approximately linear relationship has been found between the POR and the vergence of the wavefronts at the iris center for all the visual field locations. Based on this finding, we find that the contribution of the cornea to the POR can be summarized by the slope and intercept parameters derived from the linear fits in the two-dimensional visual field. The proposed analysis procedure provides a powerful tool for evaluating the peripheral optical effects of the contact lens design.

Application of two-dimensional warped discrete Fourier transform to nonlinear two-dimensional amplitude demodulation

This study introduces a novel nonlinear two-dimensional (2D) warped discrete Fourier transform (WDFT) amplitude demodulation method that allows higher-resolution measurements on specific two-dimensional regions of interest. The specific application in this study addresses the need for the nonlinear 2D amplitude demodulation of fringe-wave fields acquired by a deformed Mach–Zehnder interferometer. The proposed method exploits the properties based on which the WDFT can obtain frequency spectra sampled at non-equidistant intervals and the symmetry of the Fourier transform. As a result, this 2D-WDFT-based method can be used to nonlinearly demodulate the amplitude of the 2D interference fringe wave field to obtain a high-resolution localized fringe envelope. This study describes the proposed analysis procedure and its application using this 2D WDFT-based demodulation scheme. Experimental verification of the proposed approach was conducted with the use of deformed Mach–Zehnder interferometry. The successful experimental validation proves the efficiency of the proposed algorithm for amplitude demodulation with dense sampling points located in the central part of the envelope. To the best of the authors’ knowledge, this is the first investigational report on a 2D nonlinear envelope demodulator.

Constraint-corrected fracture mechanics analysis of nozzle crotch corners in pressurized water reactors

This paper presents fracture mechanics analysis results for various cracks located at pressurized water reactor pressure vessel nozzle crotch corners taking into consideration constraint effect. Technical documents such as the ASME B&PV Code, Sec.XI were reviewed and then a fracture mechanics analysis procedure was proposed for structural integrity assessment of various nozzle crotch corner cracks under normal operation conditions considering the constraint effect. Linear elastic fracture mechanics analysis was performed by conducting finite element analysis with the proposed analysis procedure. Based on the evaluation results, elastic-plastic fracture mechanics analysis taking into account the constraint effect was performed only for the axial surface crack of the reactor pressure vessel outlet nozzle with cladding. The fracture mechanics analysis result shows that only the axial surface crack in the reactor pressure vessel outlet nozzle has the stress intensity factor exceeding the low bound of upper-shelf fracture toughness irrespectively of considering the constraint effect. It is confirmed that the J-integral for the axial crack of the outlet nozzle does not exceed the ductile crack initiation toughness. Hence, it can be ensured that the structural integrity of all the cracks is maintained during the normal operation.

Standardised quantification of structural efficiency of hybrid reinforcement systems for developing concrete composites

Various types of materials and technologies have been developed either for reinforcing or strengthening concrete structures. However, there is no uniform methodology to quantify and compare the mechanical characteristics of different reinforcement systems. Residual stiffness of flexural elements is the suggested measure of the reinforcement’s structural effectiveness, involving concrete into composite action. This manuscript proposes a new testing layout designed to form multiple cracks in a small laboratory specimen and a simplified analytical approach to quantifying the flexural stiffness of the standardised test samples. The achieved analytical solution to the stiffness problem requires neither iterative calculations nor the loading history description. That makes it acceptable for quantifying and comparing the residual stiffness of elements with various combinations of reinforcement materials. The proposed analysis procedure also enables determining the mechanical performance decay under repeated and long-term loading conditions without a loss of the calculation adequacy. Flexural tests illustrate the application of the proposed technique—the 38 specimens were mechanically loaded until failure. Several composite reinforcement schemes, including steel and glass fibre reinforced polymer (GFRP) bars, externally bonded carbon fibre (CF) sheets, and near-surface mounted (NSM) carbon fibre reinforced polymer (CFRP) strips in various combinations, are considered. The analysis reveals an exceptional efficiency of hybrid reinforcement systems, combining steel and CFRP components.

Shock Absorption Characteristics and Optimal Design of Corrugated Fiberboard Using Drop Testing

The application of corrugated paper to buffer packaging has increased with the rise of the circular economy. The dynamic buffer curve is the key to designing the buffer packaging structure but requires multiple testing by small- and medium-sized enterprises (SMEs) without resources. In this study, we propose drop testing to perform a fractional factorial experiment and establish a regression model of impact strength through experimental data. The analysis results show that static stress, falling height, and buffer material thickness are the key variables of impact strength, and an impact strength prediction model (R2 = 94.1%) was obtained. Model verification using the buffer package design of a personal computer showed that the measured values of impact strength fell within the estimated 95% confidence interval. These results indicate that SMEs can use the proposed analysis procedure to improve the design of corrugated paper using minimal resources.

An efficient simplified elastic–plastic analysis procedure using engineering formulae for strain-based fatigue assessment of nuclear safety class 1 piping system subjected to severe seismic loads

This paper proposes an efficient simplified elastic–plastic analysis procedure using engineering formulas to perform strain-based fatigue design considering the plasticity that occurs in nuclear safety class 1 piping systems during severe seismic loads, and then presents the application results of the procedure to a pressurizer surge line system. The total strain amplitudes, fatigue assessment results, and total calculation time were compared between the proposed procedure and the detailed dynamic finite element elastic-plastic analysis. The comparison confirmed that the proposed analysis procedure can efficiently derive reasonable and conservative results for nuclear safety class 1 piping systems under severe seismic loads.

Detection of fraudulent transactions using SAS Viya machine learning algorithms

The article presents the results of applying machine learning techniques to detect fraudulent banking transactions. The market of antifraud systems was studied. Ensemble methods for solving classification problem as well as dimensionality reduction techniques were examined. The proposed analysis procedure is based on the selection of the best machine learning model and the identification of the most significant features for detecting fraud. Results-based recommendations can be used in financial institutions as well as in other organizations, where it is required to identify and prevent entities’ fraudulent actions that pose a threat to the functioning of business processes and electronic systems. The proposed fraud detection methodology was implemented on the cloud-based analytical platform Statistical Analysis System (SAS) Viya.

Cluster analysis based fringe-activity range detector

A novel clustering-analysis approach is proposed in this work. This approach addresses the fringe-activity range-detection issue often encountered in vertical-scanning wideband interferometry. The proposed approach exploits the fact that the fringe signal formed by a wideband light source, which is composed of deterministic signals and a random noise signal. As a result, the number of clusters in the proposed clustering method can be easily specified as 2, in advance. The proposed analysis procedure and its development using a k-means method-based clustering scheme are described in this paper. To the best of the authors’ knowledge, this is the first investigation report regarding fringe-activity range detection. The details of the proposed approach are introduced within the framework of femtosecond optical frequency comb-based interferometry. Experimental results demonstrate the efficiency of the proposed algorithm with respect to the fringe-activity range detection.

Detection of Acinetobacter baumannii in fresh produce using modified magnetic nanoparticles and PCR

Foodborne pathogens represent a major public health concern. In this respect, Acinetobacter baumannii is emerging as multi-drug resistant food pathogen. Screening of A. baumannii in food is a lengthy process. The aim of this study is to develop a fast and efficient protocol for detecting A. baumannii as well as other potential pathogens in fresh food.A. baumannii was collected from strawberry samples (n = 93) and were identified by DNA sequencing and polymerase chain reaction (PCR; recA). Hydrophobic magnetic nanoparticles (OA-MNP) were synthesized and tested for capturing A. baumannii and other bacteria from broth medium. Their ability to immobilize bacteria was assessed and the accuracy of PCR performed on immobilized bacteria was compared against control.A. baumannii (n = 14) was isolated form fresh produce as confirmed by sequencing and PCR. OA-MNPs were able to capture A. baumannii as well as other bacteria from broth medium. Intact DNA was extracted from immobilized bacteria and was successfully recruited for subsequent PCR.In conclusion, OA-MNP can be used for immobilizing food pathogens from broth medium. PCR can be performed using DNA extracted from immobilized bacteria for identification. The proposed analysis procedure may shorten the time required for detection of bacterial contamination in food.

Simplified elastic-plastic analysis procedure for strain-based fatigue assessment of nuclear safety class 1 components under severe seismic loads

This paper proposes a simplified elastic-plastic analysis procedure using the penalty factors presented in the Code Case N-779 for strain-based fatigue assessment of nuclear safety class 1 components under severe seismic loads such as safety shutdown earthquake and beyond design-basis earthquake. First, a simplified elastic-plastic analysis procedure for strain-based fatigue assessment of nuclear safety class 1 components under the severe seismic loads was proposed based on the analysis result for the simplified elastic-plastic analysis procedure in the Code Case N-779 and the stress categories corresponding to normal operation and seismic loads. Second, total strain amplitude was calculated directly by performing finite element cyclic elastic-plastic seismic analysis for a hot leg nozzle in pressurizer surge line subject to combined loading including deadweight, pressure, seismic inertia load, and seismic anchor motion, as well as was derived indirectly by applying the proposed analysis procedure to the finite element elastic stress analysis result for each load. Third, strain-based fatigue assessment was implemented by applying the strain-based fatigue acceptance criteria in the ASME B&PV Code, Sec. III, Subsec. NB, Article NB-3200 and by using the total strain amplitude values calculated. Last, the total strain amplitude and the fatigue assessment result corresponding to the simplified elastic-plastic analysis were compared with those using the finite element elastic-plastic seismic analysis results. As a result of the comparison, it was identified that the proposed analysis procedure can derive reasonable and conservative results.

Random decrement technique for detection and characterization of nonlinear behavior

When performing operational modal analysis, the mechanical system being investigated is assumed to be linear. If this assumption is not true, errors could be made when estimating the modal parameters of the system. There are no generally accepted robust analysis procedures available that can verify or validate the assumption of linearity in an output-only setting. In the present study, a method of detecting nonlinear behavior from a random response signal is proposed. The method is based on the random decrement (RD) technique, which involves identifying triggering points (TPs) in a measured response signal. The proposed procedure is to identify a set of TPs, where each member of the set represents a unique initial condition. A RD signature is then calculated for each set member of TPs. For the response of a linear system, all RD signatures are equal regardless of the initial conditions. For a nonlinear system, not all RD signatures will be equal for different initial conditions. Detection of nonlinear behavior is then possible by using principal component analysis and a parameterization of RD signatures to analyze the sameness of all the RD signatures in the set. The proposed analysis procedure is investigated with numerical and experimental test cases of a single-degree-of-freedom stick-slip system. Results show that it is possible to distinguish between linear and nonlinear behavior using this method. It is also possible to characterize which aspect of the system the nonlinear behavior relates to.