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Following encouraging findings on the potential of helicoidal laminates under transverse loads to significantly outperform cross-ply laminates, a more extensive study was undertaken to include thicker helicoidal laminates with the greater range of variation in inter-ply angles. Previous research has shown that thin helicoidal laminates outperform cross-ply laminates when the inter-ply angle is less than 10°. It was reported that the small inter-ply angles in helicoidal laminates make them more resistant to delamination. Consequently, less delamination occurs and they are deeper inside the laminates. This delays catastrophic failure, which occurs when transverse cracks propagating from the surface of the laminates merges with the delamination. The current study shows that thick helicoidal laminates with small inter-ply angles promote a different damage mechanism not apparent in thin laminates. Hence reducing inter-ply angles does not always lead to higher transverse load bearing capability. Observations from CT scan images of thick helicoidal laminates suggest that higher delamination resistance offered by small inter-ply angles is offset by the ease with which cracks between fibers propagates transversely when the angle is too small. Hence, helicoidal laminates comprising 73 plies of unidirectional carbon fiber reinforced laminas with 2.5° inter-ply angle could not achieve the peak loads of 73-ply laminates with 10° inter-ply angle. The optimal inter-ply angle to achieve high peak load appears to be between 5° to 10°. This study shows that the peak transverse load for helicoidal laminates can be up to 73% higher than that of cross-ply laminates when they are optimized. [ABSTRACT FROM AUTHOR]

Previous research has shown that stacking unidirectional laminates helicoidally with small interply angles resulted in improvements in transverse load resistance. Guided by computational simulations, damage evolution within helicoidal and cross-ply laminates was tracked with further experiments to offer an insight into key differences responsible for their distinct load bearing characteristics. Under transverse loads, the first form of damage is delamination. Unlike cross-plys, which suffer multiple delamination of about the same size throughout the thickness, delamination is harder to initiate in helicoidal laminates due to the small angle between each ply. A large delamination eventually formed at the mid-plane. Transverse cracks then appear on the tensile surface of both types of specimens and propagate upwards with increasing loads. Load drops occur whenever the transverse cracks propagate to the delamination immediately above them. In the case of cross-plys, where there are multiple delamination, multiple load drops occur. Load drops in helicoidal laminates are delayed until the cracks reach the large delamination in the mid-plane. Helicoidal specimens do not experience multiple loads drops and can attain high peak load before catastrophic failure. It is shown that even higher peak load is achieved by selectively seeding delamination in helicoidal laminates to further delay the merging of transverse cracks with the dominant delamination. [ABSTRACT FROM AUTHOR]

This study reports on the shock wave protective performance of woven Twaron fabric impregnated with shear thickening fluid (STF). The STF was prepared from a combination of mechanical and ultrasonic mixing of fumed silica nanoparticles dispersed in liquid polyethylene glycol (PEG) polymer. The shear thickening characteristics were determined from rheological tests. Two shock wave parameters governing blast related injuries are used to evaluate the performance of the STF treated fabrics – peak pressure and rate of pressure rise. The results of our shock tube tests demonstrate that the STF treated fabric composites offer superior shock wave protection as compared to untreated (neat) fabric and fabric impregnated with PEG only. After STF treatment, the normalised average peak pressure amplification is significantly reduced from 2.46 to 1.49 while the attenuation in normalised maximum rate of pressure rise is even more pronounced – from 2.3 to 0.76. Apparent material density is found to correlate with the average peak pressure and maximum rate of pressure rise. This implies that the density increases enough to increase the equilibrium sound speed in the fabric, and therefore preclude the formation of shock wave in the fabric. Ballistic tests using steel projectiles were also conducted to check that the STF treated fabrics continued to enhance ballistic protection as reported by other researchers. Overall, the results show that the STF treated fabrics have potential applications not only for ballistic protection but also for shock wave mitigation. [ABSTRACT FROM AUTHOR]

Abstract: Background: The impact of intraoperative rupture on prognosis is controversial in early-stage epithelial ovarian cancer (EOC). Thus, we performed a meta-analysis to determine its impact and to evaluate factors to increase its risk. Methods: We searched PubMed, Embase, and the Cochrane Library till May 2011, and 9 eligible studies including 2382 patients were evaluated. All patients were classified into three groups: no rupture; intraoperative rupture; preoperative involvement. Results: Preoperative involvement decreased progression-free survival when compared with intraoperative rupture (PFS; HR, 1.47; 95% CI, 1.01–2.14), which also showed poorer PFS than no rupture (HR, 2.41; 95% CI, 1.74–3.33). Although preoperative involvement reduced PFS when compared with intraoperative rupture (HR, 2.63; 95% CI, 1.11–6.20), there was no difference in it between intraoperative rupture and no rupture in patients who underwent complete surgical staging operation and adjuvant platinum-based chemotherapy if needed (HR, 1.49; 95% CI, 0.45–4.95). Furthermore, adhesion to adjacent tissues, grade 2 or 3 disease were more common (ORs, 2.01 and 2.47; 95% CIs, 1.20–3.37 and 1.12–5.46), whereas mucinous tumor was less frequent (OR, 0.51; 95% CI, 0.37–0.72) in intraoperative rupture than in no rupture. Conclusions: Intraoperative rupture may not decrease PFS when compared with no rupture in patients with early-stage EOC who underwent complete surgical staging operation and adjuvant platinum-based chemotherapy. Furthermore, more adhesion to adjacent tissues and grade 2 or 3 disease, and less mucinous tumor are expected to increase the risk of intraoperative rupture. [Copyright &y& Elsevier]

Abstract: Doppel protein (Dpl) is a paralog of the cellular form of prion protein (PrPC). Its ectopic expression in the CNS elicits significant cerebellar Purkinje cell degeneration in some lines of PrP knockout mice. However, little is known about the Dpl-mediated neurodegenerative mechanism. To understand the molecular and intracellular pathways underlying Purkinje cell degeneration, here, we investigated the regulation of calcium-release channel protein, type 1 inositol 1,4,5-trisphosphate receptor (IP3R1) gene in Ngsk mice. These knockout mice express high levels of Dpl and eventually develop cerebellar degeneration. We observed that the expression level of IP3R1 gene is reduced in the cerebella of Ngsk mice as early as 3 months of age compared with age-matched controls along with the reduction in DNA binding activity of nuclear factor of activated-T cells (NFAT) which is transcription factor of IP3R1. Notably, expression of PrP restored the reduced DNA binding activity of NFATc4 by Dpl. Reduced expressions of brain-derived neurotrophic factor (BDNF) and ionotropic glutamate receptor subtype 2 or B (GluR2), which are regulated by NFATc4, were also restored by PrP expression. In light of these findings, we suggest a mechanism for Dpl-mediated Purkinje cell degeneration linked to reduced gene expression of proteins related to neuronal activity. Decrease in IP3R1 gene expression may lead to functional deficits and ultimately death of Purkinje cells in Ngsk mice. [Copyright &y& Elsevier]

Abstract: In this brief communication, a treatment is reported to study the instability behaviors of fluid-conveying pipes. With the help of the properties of the defined parabolic functions in dispersion relations, the various instability conditions and ranges of the systems with respect to structural and fluid parameters can be determined and classified in a more direct manner, which can help to better understand the dynamical properties of long pipes conveying fluid. The treatment method suggested in this paper can also be extended for the instability analysis of other dynamic systems. [Copyright &y& Elsevier]

Abstract: This paper deals with the human head response to a sudden motion without direct contact with another solid object, i.e. to non-contact impact. A computational simulation approach is presented for this study, which is accomplished by the integration of a coated articulated total body (ATB) model with a finite element (FE) head model. The present approach includes two major aspects: one is to simulate the sudden motion of the human head with the whole body by means of the ATB model; and the other is to predict the head deformation and stress induced by the sudden motion through using the FE head model. The agreement between the simulation results and the published experimental data [Wismans J, Hermans J. MADYMO 3D simulations of hybrid III dummy sled tests. In: Backailis SH, Mertz HJ, editors. Hybrid III: the first human-like crash test dummy, SAE PT-44; 1994. p. 735–49; Nahum AM, Smith R, War CC. Intracranial pressure dynamic during head injury. In: 21st Stapp car crash conference proceedings, SAE 770922; 1977] is obtained. The intracranial pressure response and the head stress response are then predicted using the present approach. The correlation between the head motion and the brain stresses are also explored. In addition, the head injury induced by the non-contact impact is evaluated. [Copyright &y& Elsevier]

Abstract: Thermoelastic vibration and damping of cylindrical shell structures is studied in this paper. The general thermoelastic coupled equations for cylindrical thin shells are presented first. Since the general governing equations are quite complicated, they are then simplified with Donnell–Mushtari–Vlasov approaches for the cylindrical shells under transverse deflection-dominated vibrations. By solving the simplified thermoelastic equations with Galerkin method, the approximate solutions for thermoelastic damping in a cylindrical shell structure are obtained. The solutions are suitable for the predictions of thermoelastic damping of tubular oscillator structures. Some numerical examples for micro- or nano-tube resonators are provided to illustrate the results. [Copyright &y& Elsevier]

Abstract: This study aims at building an efficient agent-based dynamic scheduling for real-world manufacturing systems with various products, processes, and disturbances. Ant colony intelligence (ACI) is proposed to be combined with local agent coordination so as to make autonomous agents adaptive to changing circumstances and to give rise to efficient global performance. The work here differs from other dynamic scheduling research in two areas: (1) a more generic and realistic manufacturing model with multiple product types, multiple/parallel multi-purpose machines with sequence-dependent setup constraints, and various dynamic disturbances is used, (2) ACI integrated with both machine agents and job agents to solve not only the task allocation problem, but also the task sequencing problem. The implementation of the aforementioned issues in a multi-agent system (MAS) is discussed. Simulation results show that, for most of the performance measures, a MAS integrated with well-designed ant-inspired coordination performs well compared to a MAS using dispatching rules. [Copyright &y& Elsevier]

Abstract: Investigations of wave and vibration properties of single- or multi-walled carbon nanotubes based on nonlocal beam models have been reported recently. However, there are numerous inconsistencies in the handling of the governing equations, applied forces, and boundary conditions based on some of the reported nonlocal beam models. In this paper, the consistent equations of motion for the nonlocal Euler and Timoshenko beam models are provided, and some issues on the nonlocal beam theories are discussed. The models are then applied to the studies of wave properties of single- and double-walled nanotubes. The wave and vibration properties of the nanotubes based on the presented nonlocal beam equations are studied, and scale effects are discussed. [Copyright &y& Elsevier]

Abstract: This paper studies the thermally induced vibration and its control for thin isotropic and laminated composite plates. The structural intensity (SI) pattern of the plates which have different material orientations and boundary conditions was analyzed. The thermoelasticity simulation is performed using the finite element method. It shows that the structural energy flows are dependent on the material structures as well as the boundary conditions for a prescribed thermal source. The position to attach a damper for controlling the thermally induced vibration is investigated based on the virtual sources and sinks of the SI patterns. [Copyright &y& Elsevier]

Abstract: The effectiveness of the cupping technique, a treatment modality in Traditional Chinese Medicine, in stimulating acupuncture points for pain relief was examined in this paper from a biomechanical perspective. Parametric studies including the effects of vacuum pressure, loading rate, friction coefficient at the cup–skin interface, and size and shape of the cup were carried out using a model based on the finite-element method. The anatomical structures of skin, fat, and muscle were modelled. All the soft-tissue layers were assumed to be nonlinearly elastic and viscoelastic. The rim of the cup was also modelled to study the interaction between cup and skin; the cup rim was assumed to be rigid. The simulation results showed that the stresses in the soft tissue were increased for increasing applied vacuum pressures and that the effects of cupping were mostly limited to the region enclosed by the cup. The simulations also indicated that the magnitude of the applied vacuum may have had direct implications for the severity of bruising of the skin following cupping treatment. Most significantly, the simulation results contradicted the established practice of cup size selection according to the depth of the disorder. Experimental verification of the proposed multi-layered finite-element model is presented. The nature of the bruising inherent to the cupping treatment is also explained by the proposed model. [Copyright &y& Elsevier]

Abstract: This paper aims to employ the finite element analysis method (FEA) to derive equivalent stiffness properties of sandwich structures with various types of cores. The core may be composed of continuous or discrete structural components, different from conventional continuum cores and honeycomb core. For efficient analysis of its structural behaviour, the 3-D sandwich construction can be idealised as an equivalent 2-D orthotropic thick plate continuum. The proposed approach provides a rapid but accurate tool to assess the equivalent stiffness properties for the 2-D continuum. The present method is validated by comparing computational results with reported theoretical derivations. Finally the method is applied to a composite laminated circular-core sandwich panel, in order to demonstrate the versatility of this approach for complicated sandwich structures. [Copyright &y& Elsevier]

Abstract: A method is proposed for determining the level of 224Ra in plant samples by measuring its descendant nuclide 212Pb at 239keV by gamma-ray spectrometry. Variations of 224Ra and 212Pb over time during sample preparation and counting were delineated prior to gamma-ray measurement. The 224Ra concentrations in plant samples were measured by their direct uptake from soil, which could be determined and distinguished from that resulting from decay of 228Th inside the plants. We propose that a field-growing Dicranopteris linearis, which actively accumulates radium, can be used as an indicator of the nutritional transportation and metabolic rate of radium and other alkaline earth elements. We investigated the influence of rainfall on 224Ra concentrations in fronds of D. linearis and the corresponding uptake rates. 224Ra could serve as a natural tracer of growth in plants over a several days. Its presence and content in plants implies a temporal mineral metabolic rate, which can provide useful information for plant physiological and environmental investigations. [Copyright &y& Elsevier]

Abstract: This paper presents an alternative method for the derivation of exact solutions of a simply supported rectangular functionally graded piezoelectric plate or laminate. In the approach, the related equations and formulas are developed in terms of an elegant formalism similar to the Stroh formalism, which can be expressed in more concise and easier handling forms comparing to the approach used in literature for the problems [Zhong Z, Shang ET. Three-dimensional exact analysis of a simply supported functionally gradient piezoelectric plate. Int J Solids Struct 2003;40:5335–52]. Numerical examples for a single plate with functionally graded piezoelectric material (FGPM) and a two-layer FGPM laminated plate are presented. Based on the results, the validity range of 2-D thin plate theories, and the influences of material gradient index and layer thickness on interfacial and surface properties of a FGPM laminate under mechanical and/or electrical forces are discussed. [Copyright &y& Elsevier]

Abstract: This paper presents passive and active vibro-acoustic noise control methods for attenuating the interior noise level in box structures which can be an analogy of cabins of vehicle and aircraft. The structural intensity (SI) approach is adopted to identify the predominant vibration panels and interior noise sources for box structures. In the study, the finite element method is used to determine the structural vibration and structural intensity in the box surfaces. According to structural intensity vectors plot and structural intensity stream lines presentation, the possible effective control positions where the dampers may be attached and the active control forces may act to reduce vibration and interior noise, are identified. From the study, it can be demonstrated that the structural intensity approach and stream line presentation are possible methods for identifying the vibro-acoustic interior noise source and predominant panels which may be modified to reduce the interior noise level. The structural intensity methodology, passive and active noise control results can be extended to the further study of the vibration and interior noise control of actual cabins of vehicles and aircraft. [Copyright &y& Elsevier]

Abstract: The transmissions of transient energy flow and dynamic transient response of plate structures under low-velocity impact are presented. The structural intensity approach is used to study the transient dynamic characteristics of plate structures under low-velocity impact. In the dynamic impact response analysis, nine-node degenerated shell elements with assumed shear and membrane strain fields are adopted to model the target and impactor. The dynamic contact-impact algorithm and the governing equations for both the target and impactor are derived based on the updated Lagrangian approach. Explicit integration algorithm has been adopted in the time integration process. The novel structural intensity streamline representation is introduced to interpret energy flow paths for transient dynamic response of plates under low-velocity impact. The effects of plates with and without structural damping on the energy flow and energy path are discussed. Numerical results, including contact force, deflection histories and transient energy flow vectors as well as structural intensity streamlines, show that the present method and representation are an efficient approach for exploring dynamic response for plate structures subjected to low-velocity impact. [Copyright &y& Elsevier]

Abstract: The present study introduces the concept of structural intensity, which can be interpreted as power flux, into fracture mechanics. It is derived theoretically that the normal component of the structural intensity along crack edge equals J-integral. SI is the power flux or vector representation of the J-integral at the crack tip. Using the finite element method, the structural intensity can be easily calculated. The numerically calculated structural intensity is adopted to visualize the J-integral of a crack tip. Directional power flow path and magnitude at the crack tip is demonstrated schematically with the structural intensity, which facilitates convenient evaluation of the crack propagation status. [Copyright &y& Elsevier]

Abstract: In the present paper, the exact solutions of a simply supported functionally graded piezoelectric plate/laminate under cylindrical bending are derived. With similar derivation procedure as that used for Stroh formalism, the eigenrelation and general solutions for the problems can be expressed in very concise forms, which are convenient for further treatments of both analytic and numerical studies. The exact solutions can be served as benchmarks to verify and improve various approximate theories and numerical methods. To show the influence of material gradients, numerical examples based on the exact solutions are given, and some properties of the mechanical and electric responses of the plates under mechanical and electrical forces are discussed. [Copyright &y& Elsevier]

The structural intensities in isotropic and orthotropic laminae and composite laminated plates with and without a hole of different rim conditions are studied using the finite element method. Patterns of superposition among structural stress fields, intensity vectors, mode shapes and streamlines of energy flow are obtained for the various cases. It is found that the hole completely changes the distributions of the stress and energy flow path in plates. Despite its nature of mode dependent the pattern of energy flow may be different from each other despite having similar structural mode shapes, moreover the position of maximum stress is not corresponding to the position of maximum structural intensity. [Copyright &y& Elsevier]

The transmission of vibrational energy flow in stiffened plates is analyzed by the structural intensity method. Three typical cases for ship and marine structures are selected as examples: a plate with one longitudinal stiffener under lateral area pressure excitation, a longitudinally stiffened plate under point force excitation, and a cross-stiffened plate under in-plane pressure excitation. The relationships between structural intensity and structural mode shapes and the effects of stiffeners on the changes of energy flow in plate are discussed. Finally, the potential application of structural intensity technique towards the design for stiffened plates of marine structures is explored and presented. [Copyright &y& Elsevier]

The main purpose of this paper is to apply structural intensity technique to indicate the magnitude and direction of vibration energy flow for a rotating system, so as to modify and control the energy flow path to reduce the vibrational problems. Numerical simulations are carried out for a rotating flexible disk-spindle system supported by ball bearing and flexible shaft by the finite element method, and the vibrational energy transmission caused by an eccentric mass is analyzed by using structural intensity technique. The structural intensities in hybrid 1D, 2D and 3D elements, which are used to model different components of HDD, are obtained. Three different damping effects on the diversion and dissipation of energy flow are investigated. The calculated results show that different types of damping or dampers have different effect on energy flow path in HDD. Through numerical simulation, a more reasonable design scheme may be explored by scientifically arranging damping components for HDD to further suppress its vibration and noise problems. [Copyright &y& Elsevier]

Three-dimensional finite element analysis of head and disk contact effects induced by impact in magnetic head disk interface (HDI) are presented. Elastic–plastic contact simulations are performed using abaqus. The entire contact–impact procedures during head disk collision under the dynamic loading of half-sine pulse acceleration with profiles of 300 and 500 g amplitude and 1.0 ms in duration are described in detail. Simulation results for the contact pressure distribution at HDI, von Mises equivalent stress, and equivalent plastic strain fields are examined and interpreted in terms of impact history. A comprehensive history of head disk relative displacement and von Mises equivalent stresses within contact region are provided and the evolution of plasticity are discussed. It is shown that finite element method can provide the simulation of the contact behavior resulting from the dynamic loading. [Copyright &y& Elsevier]

In the past decade, meta-materials have drawn increasing attention from researchers due to their unique properties, including wave attenuation with potential applications in acoustic engineering. A number of meta-material designs have been proposed for wave attenuation at different frequencies. In this work, a new configuration of chiral honeycomb composites is proposed for the attenuation of mid to low frequency elastic waves in structural applications. The dispersion characteristics of the proposed structure were investigated numerically. The results show that the proposed structure is able to create multiple bandgaps at mid frequency range. Interestingly, two extra bandgaps induced by local resonance effect can be created with slight reduction of the chiral angle of the structural unit cell, and one bandgap is located in the low frequency range. The wave attenuation performance of the proposed composite structure was also simulated using sound transmission loss finite element analysis, demonstrating its potential in real applications. [ABSTRACT FROM AUTHOR]

Natural and synthetic fibers are increasingly being used as reinforcements in various applications. While the latter is popular for its generally superior mechanical properties, natural fibers are eco-friendly, cheap and have good vibro-acoustic properties. As more businesses are investing in green and sustainable technologies, natural fibers have been gaining attention in recent years and are already being used in various applications such as car interior, sporting equipment, etc. To date, their applications have been limited to those not requiring very demanding mechanical performance. In this paper, mechanical performance enhancement of natural fiber composites through hybridization with carbon fibers was benchmarked against one of the strongest and stiffest natural fibres, flax, through various interlayer flax-carbon hybrids at low carbon fibre volume fractions. Besides strength and stiffness characterization of hybrid laminates, this work investigates the effects of interlaminar hybrid fiber dispersion on tensile performance. The results suggested that morphology of mating hybrid plies might affect stiffness in woven fabrics. Hybrid laminates with single carbon plies interspersed with flax plies displayed lower tensile stiffness due to absence of nesting of the stiffer woven carbon plies and architectural crimp mismatch between flax and carbon woven fabrics. Comparisons with rule of hybrid mixture predictions showed reasonably good agreement in hybrid laminates exhibiting linear behavior, but significant over-predictions in highly dispersed laminates due to large deviations from linearity. [ABSTRACT FROM AUTHOR]

In this paper, an adaptive multi-fidelity (AMF) approach is applied to model progressive damage in composite laminates subjected to bending. The AMF approach has previously been proposed to efficiently model progressive damage where only the required fidelity is activated and demonstrated for the analysis of open hole tensile (OHT) problems. This paper extends the application of AMF to include the prediction of delamination migration in composite laminates. Fidelity refinement is performed to convert low-fidelity shell elements into enriched brick elements when matrix cracks or interface failure initiates. The accuracy of the method in modelling delamination migration is examined for different loading offset ratios and element transition parameters. The results are benchmarked against experimental data for cross-ply and angle-ply laminates from the literature. It is demonstrated that the AMF method may improve computational efficiency up to 60% without loss of accuracy for progressive failure analysis of composites under bending load. [ABSTRACT FROM AUTHOR]