Articoli di riviste: "Vcact"

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Zhou, Li Ming, Guang Wei Meng, Feng Li e Hui Wang. "Cell-Based Smoothed Finite Element Method-Virtual Crack Closure Technique for a Piezoelectric Material of Crack". Mathematical Problems in Engineering 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/371083.

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In order to improve the accuracy and efficiency of solving fracture parameters of piezoelectric materials, a piezoelectric element, tailored for the virtual crack closure technique (VCCT), was used to study piezoelectric materials containing a crack. Recently, the cell-based smoothed finite element method (CSFEM) and VCCT have been used to simulate the fracture mechanics of piezoelectric materials. A center cracked piezoelectric materials with different material properties, crack length, mesh, and smoothing subcells at various strain energy release rates are discussed and compared with finite element method-virtual crack closure technique (FEM-VCCT). Numerical examples show that CSFEM-VCCT gives an improved simulation compared to FEM-VCCT, which generally simulates materials as too stiff with lower accuracy and efficiency. Due to its simplicity, the VCCT piezoelectric element demonstrated in this study could be a potential tool for engineers to practice piezoelectric fracture analysis. CSFEM-VCCT is an efficient numerical method for fracture analysis of piezoelectric materials.

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Noor, Shazia, Hadeed Ashraf, Muhammad Sultan e Zahid Mahmood Khan. "Evaporative Cooling Options for Building Air-Conditioning: A Comprehensive Study for Climatic Conditions of Multan (Pakistan)". Energies 13, n. 12 (12 giugno 2020): 3061. http://dx.doi.org/10.3390/en13123061.

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This study provides comprehensive details of evaporative cooling options for building air-conditioning (AC) in Multan (Pakistan). Standalone evaporative cooling and standalone vapor compression AC (VCAC) systems are commonly used in Pakistan. Therefore, seven AC system configurations comprising of direct evaporative cooling (DEC), indirect evaporative cooling (IEC), VCAC, and their possible combinations, are explored for the climatic conditions of Multan. The study aims to explore the optimum AC system configuration for the building AC from the viewpoints of cooling capacity, system performance, energy consumption, and CO2 emissions. A simulation model was designed in DesignBuilder and simulated using EnergyPlus in order to optimize the applicability of the proposed systems. The standalone VCAC and hybrid IEC-VCAC & IEC-DEC-VCAC system configurations could achieve the desired human thermal comfort. The standalone DEC resulted in a maximum COP of 4.5, whereas, it was 2.1 in case of the hybrid IEC-DEC-VCAC system. The hybrid IEC-DEC-VCAC system achieved maximum temperature gradient (21 °C) and relatively less CO2 emissions as compared to standalone VCAC. In addition, it provided maximum cooling capacity (184 kW for work input of 100 kW), which is 85% higher than the standalone DEC system. Furthermore, it achieved neutral to slightly cool human thermal comfort i.e., 0 to −1 predicted mean vote and 30% of predicted percentage dissatisfied. Thus, the study concludes the hybrid IEC-DEC-VCAC as an optimum configuration for building AC in Multan.

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Low, Audrey, Levinia Lim, Linda Lim, Benjamin Wong, Eveline Silva, Kok Pin Ng e Nagaendran Kandiah. "Construct validity of the Visual Cognitive Assessment Test (VCAT)—a cross-cultural language-neutral cognitive screening tool". International Psychogeriatrics 32, n. 1 (21 maggio 2019): 141–49. http://dx.doi.org/10.1017/s1041610219000504.

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ABSTRACTBackground:The Visual Cognitive Assessment Test (VCAT) is a language-neutral cognitive screening tool designed for use in culturally diverse populations without the need for translations or adaptations. While it has been established to be language-neutral, the VCAT’s construct validity has not been investigated.Methods:471 participants were recruited, comprising 233 healthy comparisons, 117 mild cognitive impairment (MCI), and 121 mild Alzheimer’s disease (AD) patients. VCAT and domain-specific neuropsychological tests were administered in the same sitting. Construct validity was assessed by analyzing domain-specific associations between the VCAT and well-established cognitive assessments. Reliability (internal consistency) was measured by Cronbach’s alpha. Diagnostic ability (area under the curve) and recommended cutoffs were determined by receiver operating characteristic (ROC) analysis.Results:The VCAT and its subdomains demonstrated good construct validity in terms of both convergent and divergent validity and good internal consistency (α = .74). ROC analysis found that the VCAT was on par with the Mini Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) at distinguishing between healthy comparisons, MCI, and mild AD. Consistent with previous studies, VCAT scores were not affected by language of administration or ethnicity in our cohort. Findings suggest the following cutoffs: Dementia 0–19, MCI 20–24, Normal 25–30.Conclusion:This study established the construct validity of the VCAT, which is vital to ensure its subdomains effectively measure the cognitive processes they were designed to. The VCAT is capable of detecting early cognitive impairments and allows for meaningful cross-cultural comparisons, especially useful for international collaborations and clinical trials, and for clinical use in diverse multiethnic populations.

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Ng, Li Yun, Chen Joo Chin, Monica Danial, Stephenie Ann Albart, Purnima Devi Suppiah, Kurubaran Ganasegeran, Wei Theng Tan et al. "Validation of the Visual Cognitive Assessment Test (VCAT) for the Early Diagnosis of Cognitive Impairment in Multilingual Population in Malaysia". Psych 4, n. 1 (1 gennaio 2022): 38–48. http://dx.doi.org/10.3390/psych4010003.

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As Malaysia undergoes a demographic transformation of population aging, the prevalence of dementia is expected to rise, posing a major public health threat issue. Early screening to detect cognitive impairment is important to implement appropriate clinical interventions. The Visual Cognitive Assessment Test (VCAT) is a language-neutral cognitive assessment screening tool suitable for multilingual populations. This study was aimed to validate the VCAT screening tool for the detection of cognitive impairment amongst the population of Malaysia. A total of 184 participants were recruited, comprising 79 cognitively healthy participants (CHP), 46 mild cognitive impairment (MCI) patients, and 59 mild dementia (Alzheimer’s disease and Vascular Dementia) patients from five hospitals between May 2018 and December 2019 to determine the usefulness of VCAT. Diagnostic performance was assessed using area under the curve (AUC), and receiver operating characteristic (ROC) analysies was performed to determine the recommended cutoff scores. ROC analyses for the VCAT was comparable with that of MoCA (Montreal Cognitive Assessment) in differentiating between CHP, MCI, and mild dementia (AD and VaD) participants. The findings of this study suggest the following optimal cutoff score for VCAT: Dementia 0–19, MCI 20–23, Normal 24–30. The mean ± SD time to complete the VCAT was 10.0 ± 2.75 min in the CHP group and 15.4 ± 4.52 min in the CI group. Results showed that 76.0% of subjects thought that the instructions in VCAT were similar or easier to understand compared with MoCA. This study showed that the VCAT is a valid and useful screening tool for patients with cognitive impairment in Malaysia and is feasible to be used in the clinical settings.

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Yozgat, Can Yilmaz, Yanki Celik Yilmazer e Yilmaz Yozgat. "Pulmonary Atresia with Intact Ventricular Septum associated with Ventriculo-Coronary Arterial Communication in a Fetus at 21 Weeks of Gestation". Case Reports in Obstetrics and Gynecology 2020 (15 luglio 2020): 1–3. http://dx.doi.org/10.1155/2020/7581483.

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Pulmonary atresia with the intact ventricular septum (PA-IVS) is a rare anomaly that has an absent communication between the right ventricle and pulmonary arterial circulation. PA-IVS has a hypoplastic and hypokinetic and thickened right ventricle with the intact ventricular septum. It can be diagnosed with PA-IVS in routine obstetric ultrasound examination because the four-chamber view of PA-IVS is generally abnormal. The size of the right ventricular cavity is proportional to the Z value of the diameter of the tricuspid valve. The essential associated cardiac finding of PA-IVS is ventricular-coronary arterial communications (VCAC). The hypertensive RV forces blood through the intramyocardial sinusoids with continuous fistulous contact with the epicardial branches of RCA. It is called the VCAC. A color Doppler can detect VCAC due to its location in the pericardium along the coronary artery. If patients have VCAC and tricuspid Z score below -4, all of these conditions are infallible signs of high mortality rates in their fetal or postnatal lives. Our aim in presenting this case is to remind perinatologists if they detect an abnormal four-chamber view of the fetus’s heart, they should also carefully examine whether VCAC exists. Herein, we report a case of PA-IVS and VCAC at 21 weeks’ gestation with fetal echocardiographic images.

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Yulisa, Arma, Joonyeob Lee, Sang Hyeok Park e Seokhwan Hwang. "Simultaneous effect of cathode potentials and magnetite concentrations on methanogenesis of acetic acid under different ammonia conditions". Environmental Engineering Research 27, n. 6 (29 novembre 2021): 210317–0. http://dx.doi.org/10.4491/eer.2021.317.

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Electromethanogenesis (EM) is a system that facilitates direct interspecies electron transfer (DIET) in anaerobic digestion (AD) by providing an external power supply to favor desired reactions. Substrates of AD commonly contain ammonia (NH3) as biodegradation product of nitrogen-rich compounds that can deteriorate the stability of AD process. Optimized cathode potential (VCAT) and magnetite (Mag) concentration ([Mag]) are expected to improve AD efficiency in the presence of NH3. Response surface analysis with central composite face-centered design was used in this study to investigate the effect of VCAT and [Mag] under different total ammonia nitrogen concentration ([TAN]). Highest cumulative methane production was achieved at VCAT = -737.4 mV, [Mag] = 18.2 mM, and [TAN] = 1.5 g/L; highest acetate degradation rate was achieved at VCAT = 757.6 mV, [Mag] = 21.4 mM, and [TAN] = 1.5 g/L. The study demonstrated that VCAT promotes either microbial growth or electrochemical NH3 removal. A Shift from acetoclastic to hydrogenotrophic pathway was also observed by the increase of hydrogenotrophic methanogen populations at the end of experiment. This study is beneficial for process control of AD under different NH3 conditions.

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Manke, Sunanda, Kavita Khare e S. D. Sapre. "VCAT synchroniser-reduction of buffer size in VCAT enabled next generation SDH networks". European Transactions on Telecommunications 22, n. 8 (1 settembre 2011): 500–514. http://dx.doi.org/10.1002/ett.1500.

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Liu, Bing, Jie Meng, Zhen Yang, Ying Wang, Hua Zhi Xie, Wen Chao Zhang, Cheng Ming He e Xiang Yang Deng. "Exploration of the Relationship of the Voltage Critical Clearing Time and the Voltage Transient Transmission Capacity". Applied Mechanics and Materials 488-489 (gennaio 2014): 905–9. http://dx.doi.org/10.4028/www.scientific.net/amm.488-489.905.

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Both the voltage critical clearing time (VCCT) and the voltage transient transmission capacity (VTTC) are always used to evaluate the stability of the system transient voltage, and their relationships are studied and clarified in the paper. The stability of the transient voltage is mainly depended on the dynamic reactive characteristics of load and the transmission characteristics of voltage and power. Based on the analysis on the dynamic reactive characteristics of load and the transmission characteristics of a power transmission network, the characteristics of the VCCT and the VTTC are studied in this paper. Finally, a conclusion, i.e. the margin of the VCCT and the VTTC has a nonlinear characteristic, is obtained by simulations on the actual power grid. According to the conclusion, the voltage stability cannot be exactly reflected by the VCCT margin.

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Krscanski, Sanjin, e Josip Brnic. "Prediction of Fatigue Crack Growth in Metallic Specimens under Constant Amplitude Loading Using Virtual Crack Closure and Forman Model". Metals 10, n. 7 (20 luglio 2020): 977. http://dx.doi.org/10.3390/met10070977.

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This paper considers the applicability of virtual crack closure technique (VCCT) for calculation of stress intensity factor range for crack propagation in standard metal specimen geometries with sharp through thickness cracks. To determine crack propagation rate and fatigue lifetime of a dynamically loaded metallic specimen, in addition to VCCT, standard Forman model was used. Values of stress intensity factor (SIF) ranges ΔK for various crack lengths were calculated by VCCT and used in conjunction with material parameters available from several research papers. VCCT was chosen as a method of choice for the calculation of stress intensity factor of a crack as it is simple and relatively straightforward to implement. It is relatively easy for implementation on top of any finite element (FE) code and it does not require the use of any special finite elements. It is usually utilized for fracture analysis of brittle materials when plastic dissipation is negligible, i.e., plastic dissipation belongs to small-scale yielding due to low load on a structural element. Obtained results showed that the application of VCCT yields good results. Results for crack propagation rate and total lifetime for three test cases were compared to available experimental data and showed satisfactory correlation.

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Bernstein, G., D. Caviglia, R. Rabbat e H. Van Helvoort. "VCAT-LCAS in a clamshell". IEEE Communications Magazine 44, n. 5 (maggio 2006): 34–36. http://dx.doi.org/10.1109/mcom.2006.1637944.

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Jong, Sun Zek, Norizzati Saedon, Sarah Kiyu, Pey June Tan e Maw Pin Tan. "46 The Relationship between Cognitive Function and Physical Performance among Older Adults Attending a Falls and Syncope Service in Kuala Lumpur". Age and Ageing 48, Supplement_4 (dicembre 2019): iv9—iv12. http://dx.doi.org/10.1093/ageing/afz164.46.

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Abstract Introduction Recent studies identified a relationship between gait difficulties and risk of developing dementia, a condition now termed motoric cognitive risk. We interrogated a clinical dataset to determine the relationship between cognitive assessment scores and physical performance scores to identify the strength of association between these two types of measures. Methods Consecutive patients referred to the falls and syncope service and the University of Malaya Medical Centre were recruited. The cognitive function of consenting individuals was assessed using the Montreal Cognitive Assessment (MoCA) and Visual Cognitive Assessment Tool (VCAT). Physical performance was assessed using hand grip strength (HGS), timed-up-and-go (TUG) and functional reach (FR). Results One hundred and forty-seven individuals, mean age (standard deviation,SD)=76.1 (7.8) years, 85 (58%) women were included. The mean (SD) for right and left HGS, FR and TUG scores for the overall population were 19.1 (7.0)kg, 19.0 (12.1)kg, 28.9 (39.7)cm, TUG 19.2 (11.0)s respectively. The mean MoCA and VCAT scores were 21.1 (7.1) and 20.3 (6.3) respectively. Right HGS correlated moderately with MoCA (r=0.367) and VCAT scores (r=0.397). Left HGS had a weak to moderate correlation with MoCA (r=0.281) and VCAT (0.271). FR, however, was not correlated with either MoCA (r=0.073) and VCAT (0.020). TUG scores were moderately negatively correlated with MoCA (-0.3206) but weakly correlated with VCAT (-0.175) Conclusion Our evaluation of the relationship between cognitive scores and physical performance in a falls and syncope clinic setting found that a relationship exists between muscle strength measured with grip strength and composite assessment of gait and balance using the TUG. Dynamic balance measured with functional reach, however, was not associated with cognitive function. Future studies will need to identify the possible mechanisms linking cognitive function with strength and gait in order to establish cognitive function as a modifiable risk factor for falls in older adults.

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Gurney, Karen, e Eithne Mills. "VCAT, Hanover and the Transgender Conundrum". Alternative Law Journal 32, n. 4 (dicembre 2007): 203–7. http://dx.doi.org/10.1177/1037969x0703200403.

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Guzman Barragan, Blanca Lisseth. "Contextos locales de la vigilancia de la calidad del agua para consumo humano en de los países de América Latina: Brasil y Colombia". Revista de Salud Pública 17, n. 6 (19 febbraio 2016): 961–72. http://dx.doi.org/10.15446/rsap.v17n6.40977.

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Analizar comparativamente los sistemas nacionales de vigilancia de la calidad del agua para consumo humano (VCACH) de Brasil y Colombia, con el fin de comprender como están organizadas las prácticas en estos países, sus límites y posibilidades.Métodos: Se utilizó la metodología Cross Nacional, mediante el análisis documental de fuentes secundarias, las cuales fueron obtenidas a través de las instituciones responsables y páginas oficiales. Con el propósito de discutir las convergencias y divergencias entre los dos sistemas, considerando las directrices de la Organización Mundial da Salud. Resultados: Los marcos legales de la VCACH en Brasil y Colombia comienzan a definirse en la década 70-80, coincidiendo con la visibilidad internacional de esta temática. Las prácticas de VCACH en el Brasil estuvieron definidas y organizadas en un programa nacional, lo que solamente se está dando en Colombia recientemente. Las actuales legislaciones avanzan en los componentes que orientan las prácticas de vigilancia, por ejemplo, incorporación de metodologías de evaluación de riesgo. La legislación colombiana establece la regulación de la prestación de los servicios de abastecimiento de agua, aspecto no contemplado en la legislación brasilera. Elementos como descentralización, intersectorialidad, universalidad y el derecho a información son contemplados en las legislaciones de ambos países, aunque las acciones de VCACH necesiten avanzar para la efectiva operatividad de los mismos. Conclusiones: Brasil y Colombia presentan semejanzas en los procesos de definición de la VCACH, estando en momentos distintos de implementación de las acciones de VCACH. Estas son necesarias para garantizar los derechos humanos relacionados con la preservación de ambiente, así como la universalidad del acceso a agua potable en cantidades y en calidad adecuadas, contribuyendo en la promoción de la salud.

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Zhou, Li Ming, Guang Wei Meng, Xiao Lin Li e Feng Li. "Analysis of Dynamic Fracture Parameters in Functionally Graded Material Plates with Cracks by Graded Finite Element Method and Virtual Crack Closure Technique". Advances in Materials Science and Engineering 2016 (2016): 1–14. http://dx.doi.org/10.1155/2016/8085107.

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Based on the finite element software ABAQUS and graded element method, we developed a dummy node fracture element, wrote the user subroutines UMAT and UEL, and solved the energy release rate component of functionally graded material (FGM) plates with cracks. An interface element tailored for the virtual crack closure technique (VCCT) was applied. Fixed cracks and moving cracks under dynamic loads were simulated. The results were compared to other VCCT-based analyses. With the implementation of a crack speed function within the element, it can be easily expanded to the cases of varying crack velocities, without convergence difficulty for all cases. Neither singular element nor collapsed element was required. Therefore, due to its simplicity, the VCCT interface element is a potential tool for engineers to conduct dynamic fracture analysis in conjunction with commercial finite element analysis codes.

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Jain, Sfoorti. "Credit Pit Detection in Subordinate Securities: A French Perspective". Ushus - Journal of Business Management 18, n. 3 (1 luglio 2019): 65–85. http://dx.doi.org/10.12725/ujbm.48.6.

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The purpose of this research is to prepare a predictive model for identifying credit crisis using an artificial neural network. The paper also aims to find out the driver and driven relationship between various financial instruments like CDS, FRA, IRS, and the Volatility index (VCAC) and government securities for France. The model, thus, is directed towards finding a threshold for credit pit events and linking various events corresponding to that dates where the threshold is breached to validate the accuracy and usefulness of the model. From the research, it is found that for France, the CDS-FRA-VCAC model derives the threshold for VCAC to indicate the probability of credit crisis or financial market crash. It is also found that sovereign bonds have a huge impact on France economy including various derivatives. This is probably why the Eurozone debt crisis impacted France much more than the 2008 financial crash.

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Zhou, Hong Liang. "Implementation of Crack Problem of Functionally Graded Materials with ABAQUS^TM". Advanced Materials Research 284-286 (luglio 2011): 297–300. http://dx.doi.org/10.4028/www.scientific.net/amr.284-286.297.

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An implementation method of the virtual crack closure technique (VCCT) for fracture problems of non-homogeneous materials such as functionally graded materials (FGMs) with commercial finite element software ABAQUSTMis introduced in this paper. In order to avoid the complex post proceeding to extract fracture parameters, the interface crack element based on the VCCT is developed. The heterogeneity of FGMs is characterized though user subroutine UMAT and the interface crack element is implemented by user subroutine UEL. Several examples are analyzed to demonstrate the accuracy of the present method.

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YOKOTA, Hideo, Masaomi NISHIMURA, Sakiko NAKAMURA, Kazuaki FUKASAKU, Akitake MAKINOUCHI e Ryutaro HIMENO. "1202 Individual modeling using a VCAT system". Proceedings of the JSME annual meeting 2005.5 (2005): 145–46. http://dx.doi.org/10.1299/jsmemecjo.2005.5.0_145.

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Chuang, Yung-Cheng, Cong-Sheng Su e Yu-Jui Liang. "Influence of Failure-Load Prediction in Composite Single-Lap Joints with Brittle and Ductile Adhesives Using Different Progressive-Damage Techniques". Polymers 16, n. 7 (2 aprile 2024): 964. http://dx.doi.org/10.3390/polym16070964.

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The usage of adhesively bonded joints, such as single-lap and double-lap joints, is increasing rapidly in aerospace composite structures as a popular alternative to bolts and rivets. Compared to the conventional joining methods such as fastening and riveting, adhesive-bonding technology better prevents damage to composite structures due to the smooth configuration and the mitigation of stress concentration around holes. In this work, the built-in progressive-damage-modeling techniques in Abaqus, including the cohesive zone model (CZM) and the virtual crack closure technique (VCCT), are used to predict the strength and progressive failure of composite single-lap joints subjected to tensile loading. Modeling of an adhesive layer by using a zero/non-zero-thickness cohesive element, cohesive surface, and VCCT is investigated, as is the effect of brittle and ductile adhesives. Two-dimensional finite-element models with different damage-modeling strategies are performed in this study. The failure-load predictions are compared with the experimental results obtained from the literature. For the ductile adhesive, the predicted failure loads using a zero/non-zero-thickness cohesive elements and a cohesive surface are all shown to be in good agreement with the experiments. However, the VCCT technique predicts higher failure loads. For a brittle adhesive, on the other hand, the predictions by zero/non-zero-thickness cohesive elements and cohesive surfaces reveal notable deviations compared to the experimental results. In contrast to the ductile adhesive, the VCCT technique is revealed to be accurate in predicting the brittle adhesive.

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Xi, Liang, Xiu Li Zhao, Chong Wei Shang, Guang Ming Kong e Xu Liu. "Fatigue Crack Propagation Life Prediction of 2A12 Aluminum Alloy Based on VCCT". Advanced Materials Research 1081 (dicembre 2014): 196–99. http://dx.doi.org/10.4028/www.scientific.net/amr.1081.196.

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The fatigue crack propagation behavior of the prior corrosion 2A12 aluminum alloy fastener involving a central hole was investigated. The virtual crack closure technique (VCCT), is straightforward and not sensitive to the FEA mesh size, was carried out to calculate strain energy release rate and SIFs of AA 2A12 under different stress levels and corrosion years. Based on the VCCT, the simulation carried out to analyze the corrosion fatigue crack growth behavior. It was proved to be convenient to simulate the crack propagation life and the predicted crack growth curve was in good agreement with the experimental results.

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Goyal, Ravi, Rupinder Kaur Sodhi e Anuj Gupta. "DEVELOPMENT AND VALIDATION OF A NOVEL METHOD FOR CAUSALITY ASSESSMENT USING SUSPECTED ADVERSE DRUG REACTIONS TO ANGIOTENSIN-CONVERTING ENZYME INHIBITORS". Asian Journal of Pharmaceutical and Clinical Research 11, n. 11 (7 novembre 2018): 307. http://dx.doi.org/10.22159/ajpcr.2018.v11i11.27749.

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Objectives: The study has been designed to develop, test reliability, and construct validity of a novel versatile causality assessment tool (VCAT) method.Methods: The study included 427 literature case reports of angiotensin-converting enzyme inhibitors with suspected adverse drug reactions from 1990 to February 25, 2016. The causality of these cases was assessed independently by 3 raters in 3 phases of the study. Kappa (k) and intra-class correlation Intraclass Correlation Coefficient (ICC) were used to test reliability and validity of the VCAT method.Results: Intra-rater reliability was high between Phase I and Phase III (k=0.84–0.93; % agreement: 92.3–96.3%). Inter-rater agreement was good in Phase I (k=0.87–0.89, % agreement: 93.7–94.1%, ICC: 0.975) and Phase III (k=0.85–0.89, % agreement: 93–94.4%, ICC: 0.973). Validity was proved by the high agreement observed between Phase I and Phase II (k=0.78–0.94; % agreement: 89.7–97.2%; p<0.001); and between Phase II and Phase III (k=0.8–0.9; % agreement: 90.2–94.8%; p<0.001).Conclusion: VCAT method is a standardized causal assessment tool that gives valid and reproducible results. It has shown good agreement with the expert judgment method. This method may overcome the limitations enthralled with existing methods of causality assessment.

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Zhong, Zhi Peng, Shui Wan e Lin Yun Zhou. "A new Interface Element Method on Computation of the Interface Crack Propagation Energy Release Rate". Applied Mechanics and Materials 204-208 (ottobre 2012): 4573–77. http://dx.doi.org/10.4028/www.scientific.net/amm.204-208.4573.

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A new interface element method was proposed to calculate the strain energy release rates(SERR) based on the virtual crack closure technique (VCCT). A Lagrange multiplier was introduced between the node pair at crack tip to obtain the internal forces. Then from the VCCT, the SERR was solved by using the forces and displacements near the crack tip. Examples for stationary cracks under the two typical cases are given. Meanwhile, the relationship curves between crack energy release rate and the length of crack, plate depths were plotted respectively.The example shows that the interface element used to calculate the SERR is simple, efficient, and highly accurate in analysis of 2D crack growth problems, and without requiring the special singularity element or collapsed element at crack tip.

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Kulathumani, V., R. A. Moparthi e Y. P. Fallah. "VCAST: Scalable Dissemination of Vehicular Information with Distance-Sensitive Precision". International Journal of Distributed Sensor Networks 9, n. 11 (gennaio 2013): 586193. http://dx.doi.org/10.1155/2013/586193.

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Gliszczynski, A., S. Samborski, N. Wiacek e J. Rzeczkowski. "Mode I Interlaminar Fracture of Glass/Epoxy Unidirectional Laminates. Part II: Numerical Analysis". Materials 12, n. 10 (16 maggio 2019): 1604. http://dx.doi.org/10.3390/ma12101604.

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The paper deals with numerical analysis of double cantilever beam (DCB) predefined to Mode I Interlaminar Fracture Tests of GRFP unidirectional laminates. The numerical analyses were performed in the ANSYS® program based on the finite element. In geometrically nonlinear analysis, two algorithms, responsible for initiation and propagation of delamination front, were applied: Virtual Crack Closure Technique (VCCT) and Cohesive zone method (CZM). Due to the unidirectional arrangement of layers of the laminate, the problem of DCB test was solved with the use of one- and three-dimensional models with the implementation of linear interface element and contact element. The present study highlights the limitations of existing formulae used to reliably reflect the behavior of DCB. The use of three-dimensional models allowed confirming the curved shape of the delamination front observed in experimental studies. The application of the VCCT in the three-dimensional model led to an underestimation of the global response (force–opening displacement curve) recorded during numerical DCB test.

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Volkov, V. V., I. L. Simakova e I. A. Tikhonovskaya. "Evaluation of the New Compression-Perimeter Test Effectiveness in the Early Diagnosis of Glaucoma". Ophthalmology in Russia 17, n. 2 (23 giugno 2020): 229–37. http://dx.doi.org/10.18008/1816-5095-2020-2-229-237.

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Purpose: To evaluate the effectiveness of a new modification of the vacuum-perimeter test (VPT) by V.V. Volkov in the early diagnosis of glaucoma in comparison with the results of the original test and its known modification — vacuum-compression automated test (VCAT) in an open comparative clinical research. Patients and Methods. The study involved 26 patients (47 eyes) (average age 52.9 ± 8.5 years) with suspected open-angle glaucoma (OAG). Patients were divided into three groups: 1-st — 19 eyes with preglaucoma, 2-nd — 18 eyes with the early stage of OAG, 3-rd — 10 eyes of five patients with unconfirmed glaucoma. The control group (4-th) included 20 eyes of 10 healthy people (average age 56.4 ± 4.4 years). Along with the standard ophthalmological examination, all patients underwent perimetry on Humphrey Visual Field Analyzer II 745i (Germany-USA), our modification of Frequency Doubling Technology (FDT) perimetry, evaluation of the optic nerve head (ONH) on Heidelberg Retina Tomograph (HRT 3, Germany) and three stress tests: VPT, VCAT and our modification — vacuum-contrast-frequency test (VCFT). VCFT was created on the base of FDT perimetry with the aim of increasing the sensitivity of the original test (VPT) for detection of preglaucoma through the use of non-standard stimulus and increasing the number of investigated points of central visual field. Results. According to the National classification (1975) the diagnosis of preglaucoma was determined on the basis of a positive result of at least one of three stress tests, taking into account the risk factors for the development of glaucoma in patients. The early stage of OAG was established on the base of International standards for structural and functional assessment of the ONH (2003). The specificity of all three compared stress tests was 100 %, which confirmed their negative results in all patients (10 eyes) from the 3-rd group. However, the sensitivity of VCFT (75 %) was significantly higher than VPT (21.05 %) and VCAT (21.05 %), which is due, we believe, to the specific nature of VCFT stimulus. Conclusion. According to the obtained data, the developed new modification of VPT — VCFT on the specificity of the results was not worse, and the sensitivity was better than the original VPT and VCAT in the diagnosis of preglaucoma. VCFT is quickly performed and comfortable for patients.

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25

Hasani Najafabadi, S. H., Stefano Zucca, D. S. Paolino, G. Chiandussi e Massimo Rossetto. "Numerical Computation of Stress Intensity Factors in Ultrasonic Very-High-Cycle Fatigue Tests". Key Engineering Materials 754 (settembre 2017): 218–21. http://dx.doi.org/10.4028/www.scientific.net/kem.754.218.

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The correct computation of the Stress Intensity Factor (SIF) in ultrasonic Very-High-Cycle Fatigue (VHCF) loading conditions is a key issue when investigating the crack growth rate curve with pre-cracked specimens or when evaluating critical SIF values from fracture surfaces of failed specimens. Dynamic conditions related to the resonance of the vibrating specimen, contact nonlinearity between crack faces and stress singularity at the crack tip make the SIF computation difficult and cumbersome. Generally, numerical computation through Finite Element Models (FEMs) under non-linear dynamic conditions makes use of direct integration methods (implicit or explicit). However, in the high frequency regime of ultrasonic VHCF tests, the procedure may lead to an unacceptable computational time. In order to reduce the computational time, a hybrid procedure based on the Harmonic Balance Method (HBM) and on the Virtual Crack Closure Technique (VCCT) is originally presented and applied in this paper. The dynamic field parameters calculated with the HBM are used as input data for the computation of the SIF through the VCCT.

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Wu, Mengjie, Yuyan Zhang, Xin Dai e Ling Jiang. "Studies on the Mechanical Models and Behaviors for the Stamp/Film Interface in Microtransfer Printing". Materials 15, n. 17 (26 agosto 2022): 5915. http://dx.doi.org/10.3390/ma15175915.

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Abstract (sommario):

The adhesion/delamination characteristics at the stamp/film interface are critical for the efficiency of film microtransfer printing technology. To predict and regulate the interface mechanical behaviors, finite element models based on the J-integral, Virtual Crack Closure Technology (VCCT), and the cohesive zone method (CZM) were established and compared. Then, the effects of pulling speed and interface parameters on the pull-off force, which is used to characterize the interface adhesion strength, were investigated. Comparisons between the simulation results and previous experimental results demonstrated that the model based on the CZM was more applicable than the models based on the J-integral and VCCT in analyzing the adhesion/delamination behaviors of the stamp/film interface. Furthermore, the increase in pulling speed could enlarge the pull-off force for the viscoelastic stamp/film interface, while it had no influence on the pull-off force for the elastic stamp/film interface. In addition, a larger normal strength and normal fracture energy resulted in a larger pull-off force, which was beneficial to the realization of the picking-up process in microtransfer printing.

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Cibulka, Radek, Lenka Baxová, Hana Dvořáková, František Hampl, Petra Ménová, Viktor Mojr, Baptiste Plancq e Serkan Sayin. "Catalytic effect of alloxazinium and isoalloxazinium salts on oxidation of sulfides with hydrogen peroxide in micellar media". Collection of Czechoslovak Chemical Communications 74, n. 6 (2009): 973–93. http://dx.doi.org/10.1135/cccc2009030.

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Three novel amphiphilic alloxazinium salts were prepared: 3-dodecyl-5-ethyl-7,8,10-trimethylisoalloxazinium perchlorate (1c), 1-dodecyl-5-ethyl-3-methylalloxazinium perchlorate (2b), and 3-dodecyl-5-ethyl-1-methylalloxazinium perchlorate (2c). Their catalytic activity in thioanisole (3) oxidation with hydrogen peroxide was investigated in micelles of sodium dodecylsulfate (SDS), hexadecyltrimethylammonium nitrate (CTANO3) and Brij 35. Reaction rates were strongly dependent on the catalyst structure, on the type of micelles, and on pH value. Alloxazinium salts 2 were more effective catalysts than isoalloxazinium salts 1. Due to the contribution of micellar catalysis, the vcat/v0 ratio of the catalyzed and non-catalyzed reaction rates was almost 80 with salt 2b solubilized in CTANO3 micelles. Nevertheless, the highest acceleration was observed with non-amphiphilic 5-ethyl-1,3-dimethylalloxazinium perchlorate (2a) in CTANO3 micelles (vcat/v0 = 134). In this case, salt 2a presumably acts as a phase-transfer catalyst bringing hydrogen peroxide from the aqueous phase into the micelle interior. Synthetic applicability of the investigated catalytic systems was verified on semi-preparative scale.

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28

Miravete, Antonio, e Miguel A. Jime´nez. "Application of the finite element method to prediction of onset of delamination growth". Applied Mechanics Reviews 55, n. 2 (1 marzo 2002): 89–106. http://dx.doi.org/10.1115/1.1450763.

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The present article is concerned with the application of the finite element method to the analysis of the onset of delamination growth in composites by means of the virtual crack closure technique (VCCT). The article reviews first the application of linear elastic fracture mechanics (LEFM) to the analysis of delamination, as well as the reasons why the VCC technique is the standard method of combining LEFM and the finite element method to predict onset of delamination growth. The article also reviews the different solutions proposed in the literature to deal with the oscillatory singularity associated with a crack between two dissimilar materials (as is the case for a delamination) and the practical details of the VCCT application in a general 3D analysis. Finally, the results of a numerical study of the mixed mode bending (MMB) interlaminar fracture test are shown. The study applies the concepts reviewed along the rest of this article and presents some practical recommendations for the analysis of a delamination front using finite elements. This review article includes 77 references.

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Bacarreza, Omar, e M. H. Aliabadi. "A Novel Methodology for Fatigue Delamination Growth Analysis of Composites". Key Engineering Materials 488-489 (settembre 2011): 763–66. http://dx.doi.org/10.4028/www.scientific.net/kem.488-489.763.

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Abstract (sommario):

A novel methodology for analysis of fatigue delamination growth, capable of dealing with complex delamination shapes and mixed-modes in a computationally efficient way, is proposed. It combines the VCCT to find the energy release rates and the XFEM to update the geometry during the progressive failure, thus making it very robust and computationally efficient. The methodology is demonstrated at coupon level.

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Pirondi, A., G. Giuliese e F. Moroni. "Development of a cohesive zone model for three-dimensional simulation of joint de-bonding/delamination under mixed-mode I/II fatigue loading". International Journal of Structural Integrity 5, n. 3 (12 agosto 2014): 171–86. http://dx.doi.org/10.1108/ijsi-02-2014-0008.

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Abstract (sommario):

Purpose – In this work, the cohesive zone model (CZM) developed by some of the authors to simulate the propagation of fatigue defects in two dimensions is extended in order to simulate the propagation of defects in 3D. The paper aims to discuss this issue. Design/methodology/approach – The procedure has been implemented in the finite element (FE) solver (Abaqus) by programming the appropriate software-embedded subroutines. Part of the procedure is devoted to the calculation of the rate of energy release per unit, G, necessary to know the growth of the defect. Findings – The model was tested on different joint geometries, with different load conditions (pure mode I, mode II pure, mixed mode I/II) and the results of the analysis were compared with analytical solutions or virtual crack closure technique (VCCT). Originality/value – The possibility to simulate the growth of a crack without any re-meshing requirements and the relatively easy possibility to manipulate the constitutive law of the cohesive elements makes the CZM attractive also for the fatigue crack growth simulation. However, differently from VCCT, three-dimensional fatigue de-bonding/delamination with CZM is not yet state-of-art in FE softwares.

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Hao, Rui, Zongyi Wen, Haohui Xin e Weiwei Lin. "Fatigue Life Prediction of Notched Details Using SWT Model and LEFM-Based Approach". Materials 16, n. 5 (26 febbraio 2023): 1942. http://dx.doi.org/10.3390/ma16051942.

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Abstract (sommario):

The fatigue crack initiation life of unwelded steel components accounts for the majority of the total fatigue life, and the accurate prediction of it is of vital importance. In this study, a numerical model utilizing the extended finite element method (XFEM) and Smith–Watson–Topper (SWT) model is established to predict the fatigue crack initiation life of notched details extensively used in orthotropic steel deck bridges. Using the user subroutine UDMGINI in Abaqus, a new algorithm was proposed to calculate the damage parameter of SWT under high-cycle fatigue loads. The virtual crack-closure technique (VCCT) was introduced to monitor crack propagation. Nineteen tests were performed, and the results were used to validate the proposed algorithm and XFEM model. The simulation results show that the proposed XFEM model with UDMGINI and VCCT can reasonably predict the fatigue lives of the notched specimens within the regime of high-cycle fatigue with a load ratio of 0.1. The error for the prediction of fatigue initiation life ranges from −27.5% to 41.1%, and the prediction of total fatigue life has a good agreement with the experimental results with a scatter factor of around 2.

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Rzeczkowski, Jakub, e Sylwester Samborski. "Experimental and Numerical Research of Delamination Process in CFRP Laminates with Bending-Twisting Elastic Couplings". Materials 15, n. 21 (3 novembre 2022): 7745. http://dx.doi.org/10.3390/ma15217745.

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Abstract (sommario):

This paper aims at experimental and numerical research of delamination process in carbon/epoxy composite laminates with different fiber orientation angles in stacking sequence exhibiting the bending–twisting elastic couplings. Experimental specimens were subjected to the double cantilever beam (DCB) tests according to the ASTM D5528 regulations. Values of the mode I strain energy release rates were calculated by using three different data reduction schemes: the modified beam theory, the compliance calibration method and the modified compliance calibration. Determination of delamination initiation point was conducted in twofold way: by visual observation of crack tip using high resolution camera and by utilization of the acoustic emission technique. Numerical analyss were prepared in Abaqus/CAE Software environment by using the virtual crack closure technique (VCCT). The numerical beam model consisted of SC8R continuum shell elements. Obtained outcomes revealed that extensive fiber bridging phenomenon occurring during delamination process pronouncedly affected propagation values of strain energy release rate (GIprop) and numerically obtained load–displacement curves. Nevertheless, in initial stage of delamination, results obtained by using the VCCT were in agreement with experimental data. The greatest value of the mode I fracture toughness equal 0.56 N/mm was obtained for the BT45 laminate.

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Chithiramohan, Tamara, Smrithi Santhosh, Grace Threlfall, Louise Hull, Elizabeta B. Mukaetova-Ladinska, Hari Subramaniam e Lucy Beishon. "Culture-Fair Cognitive Screening Tools for Assessment of Cognitive Impairment: A Systematic Review". Journal of Alzheimer's Disease Reports 8, n. 1 (16 febbraio 2024): 289–306. http://dx.doi.org/10.3233/adr-230194.

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Abstract (sommario):

Background: Cognitive screening tools are important in the detection of dementia, including Alzheimer’s disease; however, they may contain cultural biases. Objective: This review examines culture-fair cognitive screening tools and evaluates their screening accuracy, strengths, and limitations. Methods: Medline, Embase, PsychINFO and CINAHL were searched. The protocol was registered on PROSPERO (CRD42021288776). Included studies used a culture-fair tool to assess cognition in older adults from varying ethnicities. Narrative synthesis was conducted. Results: 28 studies were included assessing eleven different tools. The Rowland Universal Dementia Assessment Scale (RUDAS) was as accurate as the Mini-Mental State Examination (MMSE) (AUC 0.62-0.93), with a similar sensitivity (52–94%) and better specificity (70–98%), and the Multicultural Cognitive Examination (MCE) had improved screening accuracy (AUC 0.99) compared to RUDAS (AUC 0.92). The Visual Cognitive Assessment Test (VCAT) was equivalent to MMSE (AUC 0.84–0.91). The Kimberley Indigenous Cognitive Assessment tool (KICA) had AUC of 0.93–0.95; sensitivity of 90.6%, specificity 92.6%. Conclusions: The RUDAS, KICA and VCAT were superior to MMSE for screening dementia in ethnic minorities. Other tools also showed good screening accuracy. Further research should be done to validate tools in different populations.

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Kim, T. W., H. Y. Jeong, J. H. Choe e Y. H. Kim. "Prediction of the Fatigue Life of Tires Using CED and VCCT". Key Engineering Materials 297-300 (novembre 2005): 102–7. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.102.

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Abstract (sommario):

A new simulation methodology using the finite element method (FEM) was proposed to predict the fatigue life of tires. In the FEM simulation the cracking energy density (CED) was calculated, and the virtual crack closure technique (VCCT) was used to calculate the strain energy release rate (SERR) for a crack. First, a plane in an element on which CED had its maximum was determined, and a crack was created on the plane. Once a crack was introduced, another plane on which CED had its maximum was again determined, and the crack was further elongated along the plane. In addition, SERR was calculated for every crack increment by using VCCT, and it was represented as a function of the crack length. Then, the fatigue life of a tire was determined using Paris law. For Paris law, the initial crack length and the final crack length as well as the material constants should be known. In this paper, the initial crack length was set in a way that the fatigue life predicted by using Paris law became the same as the test data for a tire model (Tire A), and the final crack length was determined from the cross-section views of failed tires which showed cracks grown about halfway toward the carcass from the carcass turn-up edge. Finally, the fatigue life for another tire model (Tire B) was predicted by using Paris law, and the predicted fatigue life was compared with the test data.

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Schmidt, Jakob, Marcus Klingenhöfer, Jörg Kaufmann, Holger Cebulla e Lothar Kroll. "Characterization of the interlaminar fracture toughness of unidirectional thermoplastic composites". Technologies for Lightweight Structures (TLS) 5, n. 1 (24 marzo 2022): 77–85. http://dx.doi.org/10.21935/tls.v5i1.157.

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Abstract (sommario):

In this study, the critical energy release rate in mode I (G1c) for thermoplastic composites made of carbon fiber (CF) and glass fiber (GF) with a polyamide 6 (PA6) matrix is investigated. Double cantilever beam (DCB) was used as the specimen for the mode I test, and the ASTM D 5528-13 was chosen as standard. Moreover, different methodological approaches were applied by comparing different data reduction schemes from the ASTM D 5528-13 and further analytic approaches from the literature. In addition to the conducted experiments, a numerical model of the DCB test is developed and the virtual crack closure technique (VCCT) is performed on the numerical model to determine G1c for PA6-CF and PA6-GF. For the interlaminar fracture toughness G1c a value of 2.87 mJ/mm2 was determined for PA6-GF and a value of 2.16 mJ/mm2 for PA6-CF, which indicate that the use of PA6 as matrix in a composite structure leads to good resistance to damage. A comparison of the different methodological approaches showed a good agreement between the analytical approaches from the literature and the ASTM D 5528-13. In contrast, the values generated for G1c by the VCCT method were significantly higher than those of the other methods.

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Katajisto, Harri, Petri Kere e Mikko Lyly. "A model for fast delamination analysis of laminated composite structures". Rakenteiden Mekaniikka 53, n. 2 (30 marzo 2020): 67–84. http://dx.doi.org/10.23998/rm.82730.

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Abstract (sommario):

Delamination is one of the major failure mechanisms for composites and traditionally the simulation requires high expertise in fracture mechanics and dedicated knowledge of the Finite Element Analysis (FEA) tool. Yet, the simulation cycle times are high. Geometrically nonlinear analysis approach, which is based on the Reissner-Mindlin-Von K´arm´an type shell facet model, has been implemented into the Elmer FE solver. Altair ESAComp software runs the Elmer Solver in the background. A post-processing capability, which enables the prediction of the delamination onset from the FEA output, has been implemented into the AltairESAComp software. A Virtual Crack Closure Technique (VCCT) speciﬁcally developed for shell elements deﬁning the Strain Energy Release Rate (SERR) related to the diﬀerent delamination modes at the crack front is used. The onset of delamination is predicted using the relevant delamination criteria that utilize the SERR data and material allowables in the form of fracture toughness. The modeling methodology is presented for laminates including initial through-the-width delamination. Examples include delamination in the solid laminate and debonding of the skin laminate in the sandwich structure. Rather coarse FE mesh has proved to yield good results when compared to typical approaches that utilize the standard VCCT or Cohesive Zone Elements.

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Vishwanath, K. S. "Computational Investigation of Square Embedded Delamination of a Composite Laminate using VCCT". International Journal for Research in Applied Science and Engineering Technology 9, n. VI (10 giugno 2021): 381–84. http://dx.doi.org/10.22214/ijraset.2021.34923.

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Abstract (sommario):

The fiber reinforced polymer laminates are widely implemented in aviation industry due to its advantages and applications other materials in terms of strength to weight ratio, dsign features and many more. The strength of the interface compared to longitudinal and lateral directions of the plies are comparatively less and give rise too poor transverse direction strength. Hence a failure mechanism called delamination will occur in case when tools are dropped or due to poor manufacturing which would give rise to interface delamination. In this paper, VCCT is employed at the interface between base and sub laminate to investigate for a square shape delamination geometry of 20mm buckling driven delamination growth. The computational prediction of delamination growth initiation is obtained by solving a T300/976 specimen for geometric non linearity using SC8R continuum shell elements of Abaqus CAE and by plotting the required energy release rate at the delamination geometry.

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Yao, Anlin, Wenbo He, Taolong Xu, Hongye Jiang e Dongfang Gu. "3D-VCCT based fracture analysis method for gas pipelines with multiple cracks". Natural Gas Industry B 6, n. 5 (ottobre 2019): 488–96. http://dx.doi.org/10.1016/j.ngib.2019.03.005.

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Karmakov, S., F. Cepero-Mejías e J. L. Curiel-Sosa. "Numerical analysis of the delamination in CFRP laminates: VCCT and XFEM assessment". Composites Part C: Open Access 2 (ottobre 2020): 100014. http://dx.doi.org/10.1016/j.jcomc.2020.100014.

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40

Wang, Qing Yuan, Yong Jie Liu, Xiang Guo Zeng e Hua Yan Chen. "Study on Calculation Method of Fracture Parameters of the Tubular Based on 3D VCCT". Key Engineering Materials 385-387 (luglio 2008): 713–16. http://dx.doi.org/10.4028/www.scientific.net/kem.385-387.713.

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Abstract (sommario):

The stress intensity factor (SIF) for tubular specimens were calculated based on virtual crack closure technique （VCCT）. The effects of geomet rical factors (inner radius, wall thickness and relative crack length) and external loads on the SIF were analyzed, respectively, by use of the single-variable approach. Finally, an approximate formula for SIF of compact-tensile tubular specimens was obtained as all factors mentioned were considered, which was presented as a reference for the tubular engineering design.

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Tawfik, Ahmed Bahgat, Sameh Youssef Mahfouz e Salah El-Din Fahmy Taher. "Nonlinear ABAQUS Simulations for Notched Concrete Beams". Materials 14, n. 23 (30 novembre 2021): 7349. http://dx.doi.org/10.3390/ma14237349.

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Abstract (sommario):

The numerical simulation of concrete fracture is difficult because of the brittle, inelastic-nonlinear nature of concrete. In this study, notched plain and reinforced concrete beams were investigated numerically to study their flexural response using different crack simulation techniques in ABAQUS. The flexural response was expressed by hardening and softening regime, flexural capacity, failure ductility, damage initiation and propagation, fracture energy, crack path, and crack mouth opening displacement. The employed techniques were the contour integral technique (CIT), the extended finite element method (XFEM), and the virtual crack closure technique (VCCT). A parametric study regarding the initial notch-to-depth ratio (ao/D), the shear span-to-depth ratio (S.S/D), and external post-tensioning (EPT) were investigated. It was found that both XFEM and VCCT produced better results, but XFEM had better flexural simulation. Contrarily, the CIT models failed to express the softening behavior and to capture the crack path. Furthermore, the flexural capacity was increased after reducing the (ao/D) and after decreasing the S.S/D. Additionally, using EPT increased the flexural capacity, showed the ductile flexural response, and reduced the flexural softening. Moreover, using reinforcement led to more ductile behavior, controlled damage propagation, and a dramatic increase in the flexural capacity. Furthermore, CIT showed reliable results for reinforced concrete beams, unlike plain concrete beams.

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Jahanshahi, M., J. Rowe, T. Saleem, R. G. Brown, P. Limousin-Dowsey, J. C. Rothwell, D. G. T. Thomas e N. P. Quinn. "Striatal Contribution to Cognition: Working Memory and Executive Function in Parkinson's Disease before and after Unilateral Posteroventral Pallidotomy". Journal of Cognitive Neuroscience 14, n. 2 (1 febbraio 2002): 298–310. http://dx.doi.org/10.1162/089892902317236911.

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Abstract (sommario):

The basal ganglia are intimately connected to the frontal cortex via five fronto-striatal circuits. While the role of the frontal cortex in cognition has been extensively studied, the contribution of the basal ganglia to cognition has remained less clear. In Parkinson's disease, posteroventral pallidotomy (PVP) involves surgical lesioning of the internal section of the globus pallidus (GPi, the final output pathway from the basal ganglia) to relieve the motor symptoms of the disorder. PVP in Parkinson's disease provides a unique opportunity to investigate the impact of disruption of striatal outflow to the frontal cortex on cognition. We assessed executive function and working memory after withdrawal of medication in 13 patients with Parkinson's disease before and 3 months after unilateral PVP compared to 12 age-and IQ-matched normals assessed twice with an interval of 3 months. The tests used were: Wisconsin Card Sorting (WCST), Self-Ordered Random Number Sequences, Missing Digit Test, Paced Visual Serial Addition Test (PVSAT), and Visual Conditional Associative Learning Test (VCALT). After PVP, the patients performed significantly better on the Self-Ordered Random Number Sequences and the WCST, an improvement that was also observed in the normals across the two assessment and is therefore likely to reflect practice effects. Relative to the normals, the patients showed significant differential change following PVP on the Missing Digit Test and PVSAT, on which they performed worse after compared to before surgery, while the controls performed better on the second assessment. For the patients, performance on the VCALT also indicated deterioration after PVP, but the changes approached significance. The side of PVP had no effect on the results. The pattern of change observed 3 months after PVP was maintained at 15-month follow-up. The results suggest that striatal outflow to the frontal cortex may be essential for those aspects of executive function that showed deterioration after PVP. &

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Raso, Vagner, e Júlia Maria D'Andrea Greve. "Exercício aeróbico ou com pesos melhora o desempenho nas atividades da vida diária de mulheres idosas". Revista Brasileira de Medicina do Esporte 18, n. 2 (aprile 2012): 87–90. http://dx.doi.org/10.1590/s1517-86922012000200004.

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Abstract (sommario):

Este estudo aleatorizado não controlado teve como objetivo determinar o efeito de um protocolo de exercício com pesos ou aeróbico no desempenho das atividades da vida diária em mulheres idosas. Para tanto, a amostra foi constituída por 41 mulheres idosas aparentemente saudáveis na faixa etária de 60 a 85 anos de idade (x: 65,1 ± 7,9 anos) divididas aleatoriamente em grupo exercício com pesos (n: 22) ou aeróbico (n: 19). O grupo exercício com pesos consistiu na execução de três séries de oito a 12 repetições a 60% de uma repetição máxima no exercício leg press 45º. O grupo exercício aeróbico consistiu em pedalar em cicloergômetro durante 40 minutos a 60% da frequência cardíaca de reserva. Os dois protocolos foram realizados três vezes por semana durante cinco semanas. As atividades da vida diária selecionadas foram velocidade para se levantar de uma posição sentada (VLPS), velocidade para se levantar de uma posição deitada (VLPD), velocidade para subir escada (VSE) e velocidade para calçar e amarrar o tênis (VCAT). O grupo exercício aeróbico melhorou significativamente o desempenho em VCAT (19,1%), enquanto o exercício com pesos incrementou significativamente o desempenho em VSE (4,3%) e VLPS (8,9%). Os resultados deste estudo permitem concluir que tanto o exercício com pesos como o aeróbico induziram efeito positivo nas atividades da vida diária, sugerindo que ambas as modalidades de exercício devem ser associadas a um programa adequado de exercícios para a melhora da capacidade funcional de pessoas idosas.

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Vishwanath, K. S. "Computational Investigation of through the Width Delamination of a Composite Laminate using VCCT". International Journal for Research in Applied Science and Engineering Technology 9, n. VI (10 giugno 2021): 128–31. http://dx.doi.org/10.22214/ijraset.2021.34890.

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Abstract (sommario):

The fiber reinforced polymer laminates have found extensive applications because of its advantages over other materials in terms of strength, stiffness, stability, weight saving features, resistance to corrosion and erosion and many more. But due to poor transverse direction strength, a failure mechanism called delamination will occur in case of poor manufacturing or when tools are dropped which would make an impact. In this paper, VCCT is implemented at the interface between base and sub laminate to investigate for 20mm through the width buckling driven delamination growth. The computational prediction of delamination growth initiation is obtained by solving a T300/976 specimen for geometric non linearity using SC8R continuum shell elements of Abaqus CAE and by plotting the required energy release rate at the edge of delamination geometry.

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Zhang, Angeline, Pryseley Assam, Dianne Bautista, Audrey Low, Simon Kang Seng Ting e Nagaendran Kandiah. "P3-249: VISUAL COGNITIVE ASSESSMENT TOOL (VCAT): A SCREENING TOOL FOR MULTILINGUAL SOCIETIES". Alzheimer's & Dementia 10 (luglio 2014): P722—P723. http://dx.doi.org/10.1016/j.jalz.2014.05.1340.

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Wang, Dong Xu, e Liang Wu. "Virtual Crack Closure Technique in the Analysis of Concrete Arch Dam Cracks". Applied Mechanics and Materials 444-445 (ottobre 2013): 1466–70. http://dx.doi.org/10.4028/www.scientific.net/amm.444-445.1466.

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Abstract (sommario):

In this paper, a 3-dimension finite element with dummy nodes for calculating and outputting the stress energy release (SERR) at the crack tip was built up based on virtual crack closure technique (VCCT), it is presented to demonstrate the virtual crack closure technique has high accuracy and good feasibility. The calculation results curve and the analytical solution curve are in good agreement. The results show that the proposed interface elements can be used to calculate to get accurate results by finite element analysis. It can give us some new ideas for Hydraulic structure crack research.

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47

Kong, Guang Ming, Xu Dong Li e Zhi Tao Mu. "Corrosion Fatigue Crack Propagation of 6151-T6 Aluminum Alloy Based on Virtual Crack Closure Technique". Advanced Materials Research 998-999 (luglio 2014): 31–34. http://dx.doi.org/10.4028/www.scientific.net/amr.998-999.31.

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Using the virtual crack closure technique (VCCT), an interface element that can calculate stress intensity factors (SIFs) directly and simulate the crack propagation conveniently has been developed. Based on an accelerated corrosion experiment, the fatigue crack propagation behavior of the 6151-T6 aluminum alloys under different corrosion years and stress levels were simulated, and it was proved to be convenient to calculate strain energy release rate and SIFs of AA 6151-T6 under different stress levels and corrosion years. The proposed method is characterized by higher accuracy and less calculation elements, provides a new way for engineering fracture analysis of the structure.

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48

Ahn, Jae S., e Kwang S. Woo. "Delamination of laminated composite plates by p-convergent partial discrete-layer elements with VCCT". Mechanics Research Communications 66 (giugno 2015): 60–69. http://dx.doi.org/10.1016/j.mechrescom.2015.02.009.

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49

Saffari, Seyed Ehsan, See Ann Soo, Raziyeh Mohammadi, Kok Pin Ng, William Greene e Negaenderan Kandiah. "Modelling the Distribution of Cognitive Outcomes for Early-Stage Neurocognitive Disorders: A Model Comparison Approach". Biomedicines 12, n. 2 (8 febbraio 2024): 393. http://dx.doi.org/10.3390/biomedicines12020393.

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Background: Cognitive assessments for patients with neurocognitive disorders are mostly measured by the Montreal Cognitive Assessment (MoCA) and Visual Cognitive Assessment Test (VCAT) as screening tools. These cognitive scores are usually left-skewed and the results of the association analysis might not be robust. This study aims to study the distribution of the cognitive outcomes and to discuss potential solutions. Materials and Methods: In this retrospective cohort study of individuals with subjective cognitive decline or mild cognitive impairment, the inverse-transformed cognitive outcomes are modelled using different statistical distributions. The robustness of the proposed models are checked under different scenarios: with intercept-only, models with covariates, and with and without bootstrapping. Results: The main results were based on the VCAT score and validated via the MoCA score. The findings suggested that the inverse transformation method improved the modelling the cognitive scores compared to the conventional methods using the original cognitive scores. The association of the baseline characteristics (age, gender, and years of education) and the cognitive outcomes were reported as estimates and 95% confidence intervals. Bootstrap methods improved the estimate precision and the bootstrapped standard errors of the estimates were more robust. Cognitive outcomes were widely analysed using linear regression models with the default normal distribution as a conventional method. We compared the results of our suggested models with the normal distribution under various scenarios. Goodness-of-fit measurements were compared between the proposed models and conventional methods. Conclusions: The findings support the use of the inverse transformation method to model the cognitive outcomes instead of the original cognitive scores for early-stage neurocognitive disorders where the cognitive outcomes are left-skewed.

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Zaghouani Chakroun, Amal, e Dorra Mezzez Hmaied. "Evidence on aggregate volatility risk premium for the French stock market". Managerial Finance 46, n. 1 (31 ottobre 2019): 72–91. http://dx.doi.org/10.1108/mf-11-2018-0535.

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Purpose The purpose of this paper is to examine alternative six- and seven-factor equity pricing models directed at capturing a new factor, aggregate volatility, in addition to market, size, book to market, profitability, investment premiums of the Fama and French (2015) and Fama and French’s (2018) aggregate volatility augmented model. Design/methodology/approach The models are tested using a time series regression and Fama and Macbeth’s (1973) methodology. Findings The authors show that both six- and seven-factor models best explain average excess returns on the French stock market. In fact, the authors outperform Fama and French’s (2018) model. The authors use sensitivity of aggregate volatility of a stock VCAC as a proxy to construct the aggregate volatility risk factor. The spanning tests suggest that Fama and French’s (1993, 2015, 2018) and Carhart’s (1997) models do not explain the aggregate volatility risk factor FVCAC. The results show that the FVCAC factor earns significant αs across the different multifactor models and even after controlling for the exposure to all the other in Fama and French’s (2018) model. The asset pricing tests show that it is systematically priced. In fact, the authors find a significant and negative (positive) relation between the aggregate volatility risk factor and the excess returns in the French stock market when it is rising (falling), in addition, periods with downward market movements tend to coincide with high volatility. Originality/value The authors contribute to the related literature in several ways. First, the authors test two new empirical six- and seven-factor model and the authors compare them to Fama and French’s (2018) model. Second, the authors give new evidence about the VCAC, using it for the first time to the authors’ knowledge, to construct a volatility risk premium.

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