bluuebunny/crossref_metadata_2025 huggingface dataset:
Intricate Interrelation Between Robustness and Probability in the Context of Structural Optimization
Authors: Amir Oded , Elishakoff Isaac
Published: May 2015

In this study, we deal with the problem of structural optimization under uncertainty. In previous studies, either of three philosophies were adopted: (a) probabilistic methodology, (b) fuzzy-sets-based design, or (c) nonprobabilistic approach in the form of given bounds of variation of uncertain quantities. In these works, authors are postulating knowledge of either involved probability densities, membership functions, or bounds in the form of boxes or ellipsoids, where the uncertainty is assumed to vary. Here, we consider the problem in its apparently pristine setting, when the initial raw data are available and the uncertainty model in the form of bounds must be constructed. We treat the often-encountered case when scarce data are available and the unknown-but-bounded uncertainty is dealt with. We show that the probability concepts ought to be invoked for predicting the worst- and best-possible designs. The Chebyshev inequality, applied to the raw data, is superimposed with the study of the robustness of the associated deterministic optimal design. We demonstrate that there is an intricate relationship between robustness and probability.
Combustion Characteristics of Lean Burn and Stoichiometric With Exhaust Gas Recirculation Spark-Ignited Natural Gas Engines
Authors: Xu Hui , LaPointe Leon A.
Published: May 2015

Natural gas (NG) has been widely used in reciprocating engines for various applications such as automobile, electricity generation, and gas compression. It is in the public interest to burn fuels more efficiently and at lower exhaust emissions. NG is very suitable to serve this purpose due to its clean combustion, small carbon footprint, and, with recent breakthroughs in drilling technologies, increased availability and low cost. NG can be used in lean burn spark-ignited (LBSI) or stoichiometric EGR spark-ignited (SESI) engines. Selection of either LBSI or SESI requires accommodation of requirements such as power output/density, engine efficiency, emissions, knock margin, and cost. The work described in this paper investigated the feasibility of operating an engine originally built as an LBSI under SESI conditions. Analytical tools and workflow developed by Cummins, Inc., are used in this study. The tools require fundamental combustion properties as inputs, including laminar flame speed (LFS), adiabatic flame temperature (AFT), and auto-ignition interval (AI). These parameters provide critical information about combustion duration, engine out NOx, and relative knock propensity. An existing LBSI engine operating at its as released lambda was selected as baseline. The amount of exhaust gas recirculation (EGR) for the SESI configuration was selected so that it would have the same combustion duration as that of the LBSI at its reference lambda. One-dimensional (1D) cycle simulations were conducted under both SESI and LBSI conditions assuming constant output power, compression ratio, volumetric efficiency, heat release centroid, and brake mean effective pressure (BMEP). The 1D cycle simulations provide peak cylinder pressure (PCP) and peak unburned zone temperature (PUZT) under LBSI and SESI conditions. The results show that the SESI configuration has lower PCP but higher PUZT than that of the LBSI for the same output power. Also, for the same combustion duration, SESI has higher AFT than that of LBSI, resulting in higher engine out NOx emissions. The SESI configuration has shorter AI than that of LBSI engine, or smaller relative knock margin. Reduction of output power and emissions aftertreatment in the form of a three-way catalyst (TWC) is required to operate under SESI engine conditions.
An Analytical Molecular Mechanics Model for Elastic Properties of Graphyne-n
Authors: Hou Juan , Yin Zhengnan , Zhang Yingyan , Chang Tienchong
Published: May 2015

Graphynes, a new family of carbon allotropes, exhibit superior mechanical properties depending on their atomic structures and have been proposed as a promising building materials for nanodevices. Accurate modeling and clearer understanding of their mechanical properties are essential to the future applications of graphynes. In this paper, an analytical molecular mechanics model is proposed for relating the elastic properties of graphynes to their atomic structures directly. The closed-form expressions for the in-plane stiffness and Poisson's ratio of graphyne-n are obtained for small strains. It is shown that the in-plane stiffness is a decreasing function whereas Poisson's ratio is an increasing function of the number of acetylenic linkages between two adjacent hexagons in graphyne-n. The present analytical results enable direct linkages between mechanical properties and lattice structures of graphynes; thereby, providing useful guidelines in designing graphyne configurations to suit their potential applications. Based on an effective bond density analysis, a scaling law is also established for the in-plane stiffness of graphyne-n which may have implications for their other mechanical properties.
Ground Mobile Schatz Mechanism
Authors: Liu Chao , Yao Shun , Wang Hao , Yao Yan-An
Published: May 2015

We put forward a novel proposition that a mechanism can move in a constant direction and change its moving directions only by one actuator and construct a single-DOF (degree of freedom) ground mobile mechanism based on the well-known Schatz mechanism. This ground mobile Schatz mechanism has six links, one of which is designed as a spoke octahedron and an other one as a tail link. When the actuator rotates in one direction, the spoke octahedron can roll on the ground to let the ground mobile Schatz mechanism to move in a straight line pushed by the tail link. When the actuator rotates in the opposite direction, the tail link can be lifted to change its landing point and the relative position between it and the spoke octahedron, then the spoke octahedron can roll in another direction pushed by the tail link. In addition, it is also an untraditional application of the Schatz mechanism that it is used as a novel ground mobile mechanism. Locomotion analysis, gait planning and stability analysis are performed, respectively, and a prototype is developed and tested.
Evaluation of a Prototype Hybrid Vacuum Pump to Provide Vacuum-Assisted Suspension for Above-Knee Prostheses
Authors: Major Matthew J. , Caldwell Ryan , Fatone Stefania
Published: May 2015

Vacuum-assisted suspension (VAS) of prosthetic sockets utilizes a pump to evacuate air from between the prosthetic liner and socket, and are available as mechanical or electric systems. This technical note describes a hybrid pump that benefits from the advantages of mechanical and electric systems, and evaluates a prototype as proof-of-concept. Cyclical bench testing of the hybrid pump mechanical system was performed using a materials testing system to assess the relationship between compression cycles and vacuum pressure. Phase 1 in vivo testing of the hybrid pump was performed by an able-bodied individual using prosthesis simulator boots walking on a treadmill, and phase 2 involved an above-knee prosthesis user walking with the hybrid pump and a commercial electric pump for comparison. Bench testing of 300 compression cycles produced a maximum vacuum of 24 in-Hg. In vivo testing demonstrated that the hybrid pump continued to pull vacuum during walking, and as opposed to the commercial electric pump, did not require reactivation of the electric system during phase 2 testing. The novelty of the hybrid pump is that while the electric system provides rapid, initial vacuum suspension, the mechanical system provides continuous air evacuation while walking to maintain suspension without reactivation of the electric system, thereby allowing battery power to be reserved for monitoring vacuum levels.
Experimental and Numerical Investigation of Laser Forming of Closed-Cell Aluminum Foam
Authors: Zhang Min , Jun Chen Chang , Brandal Grant , Bian Dakai , Lawrence Yao Y.
Published: May 2015

Aluminum foams are generally very attractive because of their ability of combining different properties such as strength, light weight, thermal, and acoustic insulation. These materials, however, are typically brittle under mechanical forming, and this severely limits their use. Recent studies have shown that laser forming is an effective way for foam panel forming. In this paper, the laser formability of Al–Si closed-cell foam through experiments and numerical simulations was investigated. The bending angle as a function of the number of passes at different laser power and scan velocity values was investigated for large- and small-pore foams. In the finite element analysis, both effective-property and cellular models were considered for the closed-cell foam. Multiscan laser forming was also carried out and simulated to study the accumulative effect on the final bending angle and stress states. The maximum von Mises stress in the scanning section was on the order of 0.8 MPa, which was lower than the yield strength of the closed-cell foam material. This paper further discussed the reasonableness and applicability of the two models.
Channel Dimensional Error Effect of Stamped Bipolar Plates on the Characteristics of Gas Diffusion Layer Contact Pressure for Proton Exchange Membrane Fuel Cell Stacks
Authors: Qiu Diankai , Yi Peiyun , Peng Linfa , Lai Xinmin
Published: May 2015

Thin metallic bipolar plates (BPPs) fabricated by stamping technology are regarded as promising alternatives to traditional graphite BPPs in proton exchange membrane (PEM) fuel cell. However, during the stamping process, dimensional error in terms of the variation in channel height is inevitable, which results in performance loss for PEM fuel cell stack. The objective of this study is to investigate the effect of dimensional error on gas diffusion layer (GDL) pressure characteristics in the multicell stacks. At first, parameterized finite element (FE) model of metallic BPP/GDL assembly is established, and the height of channels is considered as varying parameters of linear distribution according to measurements of actual BPPs. Evaluation methods of GDL contact pressure are developed by considering the pressure distribution in the in-plane and through-plane directions. Then, simulation of the assembly process for a series of multicell stacks is performed to explore the relation between dimensional error and contact pressure based on the evaluation methods. Influences of channel number, cell number, and clamping force on the constitutive relation are discussed. At last, experiments are conducted and pressure sensitive films are used to obtain the actual GDL contact pressure. The numerical results show the same trend as experimental results. This study illustrates that contact pressure of each cell layer is in severely uneven distribution for the in-plane direction, and pressure change is unavoidable for the through-plane direction in the multicell stack, especially for the first several cells close to the endplate. The methodology developed is beneficial to the understanding of the dimensional error effect, and it can also be applied to guide the assembling of PEM fuel cell stack.
Reconciling Compressor Performance Differences for Varying Ambient Inlet Conditions
Authors: Smith Natalie R. , Berdanier Reid A. , Fabian John C. , Key Nicole L.
Published: May 2015

Careful experimental measurements can capture small changes in compressor total pressure ratio (TPR), which arise with subtle changes in an experiment's configuration. Research facilities that use unconditioned atmospheric air must account for changes in ambient compressor inlet conditions to establish repeatable performance maps. A unique dataset from a three-stage axial compressor has been acquired over the duration of 12 months in the Midwest U.S., where ambient conditions change significantly. The trends show a difference in compressor TPR measured on a cold day versus a warm day despite correcting inlet conditions to sea level standard day. To reconcile these differences, this paper explores correcting the compressor exit thermodynamic state, Reynolds number effects, and variations in rotor tip clearance (TC) as a result of differences in thermal growth.
Propensity of Soot Deposition in a Rectangular Exhaust Gas Recirculation Cooler Using Kalman Filter
Authors: Mirsadraee Alireza , Reza Malayeri M.
Published: May 2015

The detection of fouling in exhaust gas recirculation (EGR) coolers of diesel engines should be fast and accurate. This would facilitate deciding an effective strategy to combat fouling and to prolong the lifetime of EGR coolers. In the present study, the propensity of soot deposition in a rectangular EGR cooler is modeled using Kalman filters. Noises, coherent feature of many deposition processes which can be resulted from measurement sensors such as thermocouples or incidental deposit flake-off, are also considered in the model. The Kalman filter minimizes the estimation error covariance by considering the measurement and process noise covariance matrices while it can simultaneously handle the noisy data. The results are characterized with measurement process noise covariance. The relation between these two defines the smoothness and shape of the estimated trend of fouling resistance. Comparisons of the experimental data and the resultant model confirmed the usefulness of the applied method for various operating conditions of an EGR cooler prone to particulate deposition of soot particles. The paper proceeds with the impact of such models in monitoring fouling and taking an appropriate mitigation approach in diesel engines.
Minimization of Heat Load Due to Secondary Reactions in Fuel Rich Environments
Authors: Shewhart Andrew T. , Polanka Marc D. , Robertson Jacob J. , Greiner Nathan J. , Rutledge James L.
Published: May 2015

The demand for increased thrust, higher engine efficiency, and reduced fuel consumption has increased the turbine inlet temperature and pressure in modern gas turbine engines. The outcome of these higher temperatures and pressures is the potential for unconsumed radical species to enter the turbine. Because modern cooling schemes for turbine blades involve injecting cool, oxygen-rich air adjacent to the surface, the potential for reaction with radicals in the mainstream flow, and augmented heat transfer to the blade arises. This result is contrary to the purpose of film cooling. In this environment, there is a competing desire to consume any free radicals prior to the flow entering the rotor stage while still maintaining surface temperatures below the metal melting temperature. This study evaluated various configurations of multiple cylindrical rows of cooling holes in terms of both heat release and effective downstream cooling. Results were evaluated based on net heat flux reduction (NHFR) and a new wall absorption (WA) parameter which combined the additional heat available from these secondary reactions with the length of the resulting flame to determine which schemes protected the wall more efficiently. Two particular schemes showed promise. The two row upstream configuration reduced the overall augmentation of heat by creating a short, concentrated reaction area. Conversely, the roll forward configuration minimized the local heat flux enhancement by spreading the reaction area over the surface being cooled.
A Study of Combustion Inefficiency in Diesel Low Temperature Combustion and Gasoline–Diesel RCCI Via Detailed Emission Measurement
Authors: Dev Shouvik , Divekar Prasad , Xie Kelvin , Han Xiaoye , Chen Xiang , Zheng Ming
Published: May 2015

Reduction of engine-out NOx emissions to ultra-low levels is facilitated by enabling low temperature combustion (LTC) strategies. However, there is a significant energy penalty in terms of combustion efficiency as evidenced by the high levels of hydrocarbon (HC), carbon monoxide (CO), and hydrogen emissions. In this work, the net fuel energy lost as a result of incomplete combustion in two different LTC regimes is studied—partially premixed compression ignition (PPCI) using in-cylinder injection of diesel fuel and reactivity controlled compression ignition (RCCI) of port injected gasoline and direct injected diesel. A detailed analysis of the incomplete combustion products was conducted. Test results indicated that carbon monoxide (CO), hydrogen, and light hydrocarbon (HC) made up for most of the combustion in-efficiency in the PPCI mode, while heavier HC and aromatics were significantly higher in the RCCI mode.
Structure and interfacial analysis of nanoscale TiNi thin film prepared by biased target ion beam deposition
Authors: Hou Huilong , Hamilton Reginald F. , Horn Mark W.
Published: May 2015

Ultrathin, 65 nm thick, TiNi alloy films were fabricated by cosputtering Ti and Ni targets using the recently developed biased target ion beam deposition technique. Preheating the substrate by exposure to a low energy ion source resulted in as-deposited films with a pure B2 atomic crystal structure containing no secondary crystal structures or precipitates. Continuous films were produced with a smooth surface and minimal substrate/film interfacial diffusion. The diffusion layer was a small ratio of film thickness, which is a prerequisite for the B2 phase to undergo the martensitic transformation in ultrathin films.
Depleted iron stores and iron deficiency anemia associated with reduced ferritin and hepcidin and elevated soluble transferrin receptors in a multiethnic group of preschool-age children
Authors: Weiler Hope A. , Jean-Philippe Sonia , Cohen Tamara R. , Vanstone Catherine A. , Agellon Sherry
Published: May 2015

Iron deficiency anemia is prevalent in subgroups of the Canadian population. The objective of this study was to examine iron status and anemia in preschool-age children. Healthy children (n = 430, 2–5 years old, Montreal, Quebec, Canada) were sampled from randomly selected daycares. Anthropometry, demographics, and diet were assessed. Biochemistry included hemoglobin, ferritin, soluble transferrin receptors (sTfR), ferritin index, markers of inflammation (C-reactive protein, interleukin 6 (IL-6), and tumour necrosis factor alpha (TNFα)), and hepcidin. Iron deficiency and anemia cutoffs conformed to the World Health Organization criteria. Differences among categories were tested using mixed-model ANOVA or χ2tests. Children were 3.8 ± 1.0 years of age, with a body mass index z score of 0.48 ± 0.97, and 51% were white. Adjusted intakes of iron indicated <1% were at risk for deficiency. Hemoglobin was higher in white children, whereas ferritin was higher with greater age and female sex. Inflammatory markers and hepcidin did not vary with any demographic variable. The prevalence of iron deficiency was 16.5% (95% confidence interval (CI), 13.0–20.0). Three percent (95% CI, 1.4–4.6) of children had iron deficiency anemia and 12.8% (95% CI, 9.6–16.0) had unexplained anemia. Children with iron deficiency, with and without anemia, had lower plasma ferritin and hepcidin but higher sTfR, ferritin index, and IL-6, whereas those with unexplained anemia had elevated TNFα. We conclude that iron deficiency anemia is not very common in young children in Montreal. While iron deficiency without anemia is more common than iron deficiency with anemia, the correspondingly reduced circulating hepcidin would have enabled heightened absorption of dietary iron in support of erythropoiesis.
Structural and ultrastructural evaluation of the aortic wall after transplantation of bone marrow-derived cells (BMCs) in a model for atherosclerosis
Authors: Felix Alyne Souza , Monteiro Nemesis , Rocha Vinícius Novaes , Oliveira Genilza , Nascimento Ana Lucia , de Carvalho Laís , Thole Alessandra , Carvalho Jorge
Published: May 2015

Stem cells are characterized by their ability to differentiate into multiple cell lineages and display the paracrine effect. The aim of this work was to evaluate the effect of therapy with bone marrow-derived cells (BMCs) on glucose, lipid metabolism, and aortic wall remodeling in mice through the administration of a high-fat diet and subsequent BMCs transplantation. C57BL/6 mice were fed a control diet (CO group) or an atherogenic diet (AT group). After 16 weeks, the AT group was divided into 4 subgroups: an AT 14 days group and AT 21 days group that were given an injection of vehicle and sacrificed after 14 and 21 days, respectively, and an AT-BMC 14 days group and AT-BMC 21 days group that were given an injection of BMCs and sacrificed after 14 and 21 days, respectively. The BMCs transplant had reduced blood glucose, triglycerides, and total cholesterol. There was no significant difference in relation to body mass between the transplanted groups and non-transplanted groups, and all were different than CO. There was no significant difference in the glycemic curve among AT 14 days, AT-BMC 14 days, and AT 21 days, and these were different than the CO and the AT-BMC 21 days groups. The increased thickness of the aortic wall was observed in all atherogenic groups, but was significantly smaller in group AT-BMC 21 days compared to AT 14 days and AT 21 days. Vacuoles in the media tunic, delamination and the thinning of the elastic lamellae were observed in AT 14 days and AT 21 days. The smallest number of these was displayed on the AT-BMC 14 days and AT-BMC 21 days. Marking to CD105, CD133, and CD68 were observed in AT 14 days and AT 21 days. These markings were not observed in AT-BMC 14 days or in AT-BMC 21 days. Electron micrographs show the beneficial remodeling in AT-BMC 14 days and AT-BMC 21 days, and the structural organization was similar to the CO group. Vesicles of pinocytosis, projection of smooth muscle cells, and delamination of the internal elastic lamina are seen in groups AT 14 days and AT 21 days. Endothelial cells were preserved, and regular and continuous contour in internal elastic lamelae were observed in the CO, the AT-BMC 14 days, and AT-BMC 21 days groups. In conclusion, in an atherosclerotic model using mice and atherogenic diet, the injection of BMCs improves glucose, lipid metabolism, and causes a beneficial remodeling of the aortic wall.
Historical (1860) forest structure in ponderosa pine forests of the northern Front Range, Colorado
Authors: Brown Peter M. , Battaglia Michael A. , Fornwalt Paula J. , Gannon Benjamin , Huckaby Laurie S. , Julian Chad , Cheng Antony S.
Published: May 2015

Management of many dry conifer forests in western North America is focused on promoting resilience to future wildfires, climate change, and land use impacts through restoration of historical patterns of forest structure and disturbance processes. Historical structural data provide models for past resilient conditions that inform the design of silvicultural treatments and help to assess the success of treatments at achieving desired conditions. We used dendrochronological data to reconstruct nonspatial and spatial forest structure at 1860 in fourteen 0.5 ha plots in lower elevation (∼1900–2100 m) ponderosa pine (Pinus ponderosa Douglas ex P. Lawson & C. Lawson) forests across two study areas in northern Colorado. Fires recorded by trees in two or more plots from 1667 to 1859 occurred, on average, every 8–15 years depending on scale of analysis. The last fire recorded in two or more plots occurred in 1859. Reconstructed 1860 stand structures were very diverse, with tree densities ranging from 0 to 320 trees·ha−1, basal areas ranging from 0.0 to 17.1 m2·ha−1, and quadratic mean diameters ranging from 0.0 to 57.5 cm. All trees in 1860 were ponderosa pine. Trees were significantly aggregated in 62% of plots in which spatial patterns could be estimated, with 10% to 90% of trees mainly occurring in groups of two to eight (maximum, 26). Current stands based on living trees with a diameter at breast height of ≥4 cm are more dense (range, 175–1010 trees·ha−1) with generally increased basal areas (4.4 to 23.1 m2·ha−1) and smaller trees (quadratic mean diameters ranging from 15.7 to 28.2 cm) and contain greater proportions of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and Rocky Mountain juniper (Juniperus scopulorum Sarg.). This is the first study to provide detailed quantitative metrics to guide restoration prescription development, implementation, and evaluation in these and similar ponderosa pine forests in northern Colorado.
The importance of coarse woody debris for vascular plants in temperate mixed deciduous forests
Authors: Chećko Ewa , Jaroszewicz Bogdan , Olejniczak Katarzyna , Kwiatkowska-Falińska Anna J.
Published: May 2015

Deadwood in various stages of decomposition and diverse spatial arrangements provides habitat for numerous organisms. However, knowledge on the colonization of deadwood by vascular plants in mixed deciduous forests is insufficient. We carried out our study in an oak–lime–hornbeam forest in northeastern Poland. Downed logs were colonized by 49 vascular plant species, a number higher than reported from any other type of forest. Species richness and abundance of plants increased with log diameter and decomposition. The former was higher on broadleaf deadwood than on coniferous deadwood (46 vs. 38 species). The frequency and abundance on logs were higher for small-seeded plants (<1 mg) than for bigger, heavier seeded plants. Deadwood surface served as an ecological filter, keeping small seeds in cracks, but allowing bigger seeds to roll down. Tree seedling density increased with wood decomposition. However, for eight of nine species, it was higher on the ground than on deadwood. Only spruce seedlings were recorded almost exclusively on deadwood, constituting a crucial substrate for spruce regeneration in meso-eutrophic forests. Therefore, we stress the importance of constant deadwood supply, on the scale of decades, to ensure the diversity of this substrate and to allow the natural dynamics of deadwood-dependent species populations.
Wildfire as a key determinant of peatland microtopography
Authors: Benscoter Brian W. , Greenacre Dan , Turetsky Merritt R.
Published: May 2015

Microtopography is a common attribute of wetlands, particularly boreal bog and fen peatlands. This self-organized patterning is primarily an autogenic process; however, the role of allogenic forces such as disturbance in the maintenance of microtopography is poorly understood. In this study, we quantify the effect of fire on the distribution of the microtopographic gradient in boreal bogs using a before–after wildfire natural experiment. We also quantify the change in spatial abundance of microforms in boreal treed peatlands over a 100-year successional chronosequence. Wildfire nearly doubled the range of the microtopographic gradient, increasing the relative abundance of low-elevation microforms (hollows), although the distribution of elevations was influenced by peatland ontogeny at the time of wildfire. Through succession, raised microforms (hummocks) became more abundant, presumably due to autogenic surface drying facilitating hummock species expansion into adjacent hollows. Although autogenic processes may be responsible for the development of self-organized spatial patterning in wetlands, disturbances such as wildfire are necessary for maintaining boreal peatland microtopography over extended time scales. Because of the tight linkage between microtopography, species diversity, and ecosystem function, these feedbacks between wildfire and microtopography are critical for understanding peatland dynamics and the potential impact of a changing environment.
k-essence cosmologies in Kantowski–Sachs and Bianchi space–times
Authors: Singh T. , Chaubey R. , Singh Ashutosh
Published: May 2015

We investigate Kantowski–Sachs, locally rotationally symmetric Bianchi-I and Bianchi-III cosmology with k-essence and found a set of models that dissipate the initial anisotropy. We obtain the conditions leading to a regular bounce of the average geometry. We show that the linear k-field and polynomial kinetic function models evolve asymptotically to Friedmann–Robertson–Walker cosmologies. For linear k-essence we find the general solution in these cosmologies, when the k-field is driven by an inverse scalar potential.
The Pioneer anomaly in covariant theory of gravitation
Authors: Fedosin Sergey G.
Published: May 2015

The difference of equations of motion in the covariant theory of gravitation and in the general theory of relativity is used to explain the Pioneer anomaly. Calculation shows that the velocities of a spacecraft in both theories at equal distances can differ by several centimetres per second. This leads also to a possible explanation of the flyby anomaly and comet disturbances, which are not taken into account by the general theory of relativity.
Microcrystalline Preparation of Akebia Saponin D for its Bioavailability Enhancement in Rats
Authors: Wang Qiao-Han , Yang Xiao-Lin , Xiao Wei , Wang Zhen-Zhong , Ding Gang , Huang Wen-Ze , Yang Zhong-Lin , Zhang Chun-Feng
Published: May 2015

Akebia Saponin D (ASD) or asperosaponin VI is the most abundant constituent of the rhizome of Dipsacus asper, which has been used for the treatment of lower back pain, traumatic hematoma and bone fractures. In recent years, it was reported that ASD was a potential treatment strategy for Alzheimer's disease (AD). However, the low bioavailability of ASD limited its clinical utility. Microcrystalline preparation is one of the effective methods to improve drug absorption. The drugs prepared by different methods can present different solid forms (polymorphs), and different polymorphs have significantly different bioavailabilities. The objective of this study was to prepare ASD polymorphs using the different preparation processes and to evaluate their physicochemical properties and oral absorption. ASD-2 obtained by the antisolvent process was simpler and had higher recovery (78.5%) than that of ASD-1 by a two-step macroporous resin column separation (56.5%). The ASD polymorphs were characterized using differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM). The results revealed that ASD-2 existed in microcrystalline form, while ASD-1 was amorphous. Furthermore, the equilibrium solubility, dissolution in aqueous solution and pharmacokinetic parameters of the samples were determined. ASD-2 showed lower aqueous solubility than that of ASD-1 (p < 0.01). In addition, ASD-2 showed lower dissolution with only 65% of the drug released while ASD-1 had a higher dissolution with 99% of drug released at the end of the 180 min testing period. Although ASD-1 significantly increased solubility and dissolution, the AUC0-20hof ASD-2 was 4.3 times that of the amorphous ASD-1 in vivo. Data suggest that the microcrystalline preparation of ASD-2 is not only reasonable in economy and suitable for large-scale preparation, but also a promising method to enhance bioavailability of ASD.
Interactions of the Julia Set with Critical and (Un)Stable Sets in an Angle-Doubling Map on ℂ\{0}
Authors: Hittmeyer Stefanie , Krauskopf Bernd , Osinga Hinke M.
Published: May 2015

We study a nonanalytic perturbation of the complex quadratic family z ↦ z2 + c in the form of a two-dimensional noninvertible map that has been introduced by Bamón et al. [2006]. The map acts on the plane by opening up the critical point to a disk and wrapping the plane twice around it; points inside the disk have no preimages. The bounding critical circle and its images, together with the critical point and its preimages, form the so-called critical set. For parameters away from the complex quadratic family we define a generalized notion of the Julia set as the basin boundary of infinity. We are interested in how the Julia set changes when saddle points along with their stable and unstable sets appear as the perturbation is switched on. Advanced numerical techniques enable us to study the interactions of the Julia set with the critical set and the (un)stable sets of saddle points. We find the appearance and disappearance of chaotic attractors and dramatic changes in the topology of the Julia set; these bifurcations lead to three complicated types of Julia sets that are given by the closure of stable sets of saddle points of the map, namely, a Cantor bouquet and what we call a Cantor tangle and a Cantor cheese. We are able to illustrate how bifurcations of the nonanalytic map connect to those of the complex quadratic family by computing two-parameter bifurcation diagrams that reveal a self-similar bifurcation structure near the period-doubling route to chaos in the complex quadratic family.
Adaptive Control for Buck Power Converter Using Fixed Point Inducting Control and Zero Average Dynamics Strategies
Authors: Hoyos Velasco Fredy Edimer , García Nicolás Toro , Garcés Gómez Yeison Alberto
Published: May 2015

In this paper, the output voltage of a buck power converter is controlled by means of a quasi-sliding scheme. The Fixed Point Inducting Control (FPIC) technique is used for the control design, based on the Zero Average Dynamics (ZAD) strategy, including load estimation by means of the Least Mean Squares (LMS) method. The control scheme is tested in a Rapid Control Prototyping (RCP) system based on Digital Signal Processing (DSP) for dSPACE platform. The closed loop system shows adequate performance. The experimental and simulation results match. The main contribution of this paper is to introduce the load estimator by means of LMS, to make ZAD and FPIC control feasible in load variation conditions. In addition, comparison results for controlled buck converter with SMC, PID and ZAD–FPIC control techniques are shown.
Chua's Circuit: Control and Synchronization
Authors: Irimiciuc Stefan-Andrei , Vasilovici Ovidiu , Dimitriu Dan-Gheorghe
Published: May 2015

Chaos-based data encryption is one of the most reliable methods used in secure communications. This implies a good control of a chaotic system and a good synchronization between the involved systems. Here, experimental results are shown on the control and synchronization of Chua's circuits. The control of the chaotic circuit was achieved by using the switching method. The influence of the control signal characteristics (amplitude, frequency and shape) on the system's states was also investigated. The synchronization of two similar chaotic circuits was studied, emphasizing the importance of the chaotic state characteristics of the Master system in respect to those of Slave system. It was shown that the synchronization does not depend on the chaotic state type, neither on the dimension (x, y or z) used for synchronization.
Coexistence of Chaos with Hyperchaos, Period-3 Doubling Bifurcation, and Transient Chaos in the Hyperchaotic Oscillator with Gyrators
Authors: Kengne J.
Published: May 2015

In this paper, the dynamics of the paradigmatic hyperchaotic oscillator with gyrators introduced by Tamasevicius and co-workers (referred to as the TCMNL oscillator hereafter) is considered. This well known hyperchaotic oscillator with active RC realization of inductors is suitable for integrated circuit implementation. Unlike previous literature based on piecewise-linear approximation methods, I derive a new (smooth) mathematical model based on the Shockley diode equation to explore the dynamics of the oscillator. Various tools for detecting chaos including bifurcation diagrams, Lyapunov exponents, frequency spectra, phase portraits and Poincaré sections are exploited to establish the connection between the system parameters and various complex dynamic regimes (e.g. hyperchaos, period-3 doubling bifurcation, coexistence of attractors, transient chaos) of the hyperchaotic oscillator. One of the most interesting and striking features of this oscillator discovered/revealed in this work is the coexistence of a hyperchaotic attractor with a chaotic one over a broad range of system parameters. This phenomenon was not reported previously and therefore represents a meaningful contribution to the understanding of the behavior of nonlinear dynamical systems in general. A close agreement is observed between theoretical and experimental analyses.
Analysis of a Car-Following Model with Driver Memory Effect
Authors: Xin Zhi , Xu Jian
Published: May 2015

A nonlinear car-following model considering memory effect of human drivers is studied by means of theoretical analysis and numerical simulation. We model the memory effect of the response of drivers to the traffic situation for a car-following model by introducing a system variable related to velocity. The memory effect of the drivers is a kind of state-dependent delay. The stability of the car-following model with two kinds of time delay is studied. The hysteresis loop of traffic flow from different initial states is compared. The effect of the maximum time delay on the stability is discussed.
On the Limit Cycles for a Class of Continuous Piecewise Linear Differential Systems with Three Zones
Authors: Lima Maurício Firmino Silva , Pessoa Claudio , Pereira Weber F.
Published: May 2015

Lima and Llibre [2012] have studied a class of planar continuous piecewise linear vector fields with three zones. Using the Poincaré map, they proved that this class admits always a unique limit cycle, which is hyperbolic. The class studied in [Lima & Llibre, 2012] belongs to a larger set of planar continuous piecewise linear vector fields with three zones that can be separated into four other classes. Here, we consider some of these classes and we prove that some of them always admit a unique limit cycle, which is hyperbolic. However we find a class that does not have limit cycles.
Bifurcations and Exact Solutions in a Model of Hydrogen-Bonded-Chains
Authors: Li Jibin , Chen Fengjuan , Tchakoutio-Nguetcho A. S.
Published: May 2015

A model of dynamics of protons in hydrogen-bonded quasi-one-dimensional networks was derived, which is a singular system of the second kind with three parameters and two singular straight lines. In this paper, we use the method of dynamical systems to discuss the bifurcations of phase portraits of the vector fields defined by the singular system. Corresponding to the phase orbits of the system in different parameter conditions, we compute all possible exact parametric representations of solutions. It is shown that in given parameter conditions, there exist solitary wave solutions, kink wave solutions and periodic wave solutions. The mentioned system has no peakon solution.
Effect of Wind Turbine Noise on Workers' Sleep Disorder: A Case Study of Manjil Wind Farm in Northern Iran
Authors: Abbasi Milad , Monnazzam Mohammad Reza , Zakerian SayedAbbolfazl , Yousefzadeh Arsalan
Published: May 2015

Noise from wind turbines is one of the most important factors affecting the health, welfare, and human sleep. This research was carried out to study the effect of wind turbine noise on workers' sleep disorder. For this, Manjil Wind Farm, because of the greater number of staff and turbines than other wind farms in Iran, was chosen as case study. A total number of 53 participants took part in this survey. They were classified into three groups of mechanics, security, and official. In this study, daytime sleepiness data of workers were gathered using Epworth Sleepiness Scales (ESS) was used to determine the level of daytime sleepiness among the workers. The 8-h equivalent sound level (LAeq,8h) was measured to determine the individuals' exposure at each occupational group. Finally, the effect of sound, age, and workers' experience on individuals' sleep disorder was analyzed through multiple regression analysis in the R software. The results showed that there was a positive and significant relationship between age, workers' experience, equivalent sound level, and the level of sleep disorder. When age is constant, sleep disorder will increase by 26% as per each 1 dB increase in equivalent sound level. In situations where equivalent sound level is constant, an increase of 17% in sleep disorder is occurred as per each year of work experience. Because of the difference in sound exposure in different occupational groups. The effect of noise in repairing group was about 6.5 times of official group and also 3.4 times of the security group. Sleep disorder effect caused by wind turbine noise in the security group is almost two times more than the official group. Unlike most studies on wind turbine noise that address the sleep disorder among inhabitants nearby wind farms, this study, for the first time in the world, examines the impact of wind turbine noise on sleep disorder of workers who are more closer to wind turbines and exposed to higher levels of noise. So despite all the good benefits of wind turbines, it can be stated that this technology has health risks for all those exposed to its sound. However, further research is needed to confirm the results of this study.
Quantum chemical investigation of spectroscopic studies and hydrogen bonding interactions between water and methoxybenzeylidene-based humidity sensor
Authors: Muhammad Shabbir , Irfan Ahmad , Al-Sehemi Abdullah G. , Al-Assiri M. S. , Kalam Abul , Chaudhry Aijaz R.
Published: May 2015

A quantum chemical investigation has been performed to spotlight the structure–property relationship among methoxybenzeylidene-based humidity sensor and water molecules. The chemical interactions among (E)-2-(4-(2-(3,4-dimethoxybenzeylidene)hydrazinyl)phenyl) ethane-1,1,2-tricarbonitrile (DMBHPET) sensor and water molecules have been studied using density functional theory (DFT) methods. The molecular structural parameters, binding energies and Infrared (IR) spectroscopic analyses have been performed to assess the nature of intermolecular interactions. Three different positions have been identified for possible attachments of H2O molecules through hydrogen bonding interactions. These positions include NH (complex 1a), p- OCH3(complex 1b) and N=N (complex 1c) group in sensor molecule (1) for the chemical adsorption of water molecules. While, the complex 1abc includes all three sites with simultaneously three H2O molecules attached to it through hydrogen bonding. The binding energies calculated for complex 1a( NH … H2O ), complex 1b( CH3O … H2O ), complex 1c( N=N … H2O ) and complex 1abc are -30.97, -18.41, -13.80 and -65.36 kcal/mol, respectively. The counterpoise (CP) scheme has been used to correct the basis set superposition error (BSSE) in calculation of binding energies of sensor and H2O complexes. The higher binding energy of -65.36 kcal/mol for complex 1abc represents that the present methoxybenzeylidene-based sensor has significant potential through hydrogen bonding formation for sensing humidity as indicated in our previous experimental investigation. The evidence of hydrogen bonding interactions between sensor 1 and H2O molecules has been traced through structural parameters, red shift in IR spectra as well as molecular electrostatic maps. Thus the present investigation highlights the first computational framework for a molecular level structure-binding activity of a methoxybenzeylidene-based sensor and water molecules.
A Two-Step Taylor Galerkin Smoothed Finite Element Method for Lagrangian Dynamic Problem
Authors: Cui Xiang Yang , Chang Shu , Li Guang Yao
Published: May 2015

In this paper, a two-step Taylor Galerkin smoothed finite element method (TG-SFEM) is presented to deal with the two-dimensional Lagrangian dynamic problems. In this method, the smoothed Galerkin weak form is employed to create discretized system equations, and the cell-based smoothing domains are used to perform the smoothing operation and the numerical integration. The stability and the adaptation of elements aberrations presented in the two-step TG-SFEM are studied through detailed analyses of numerical examples. In the analysis of wave propagation, the proposed method can provide smoother displacement and stress than the common SFEM does, and energy fluctuations are found to be minimal. In the large deformation problems, the TG-SFEM can acclimatize itself to the mesh distortion effectively and stay bounded for long durations because the isoparametric elements are replaced, and area integration over each smoothing cells is recast into line integration along edges and no mapping is needed. Therefore, the stability, flexibility of elements distortion and the property of energy conservation of the TG-SFEM applied on two-dimensional solid problems are well represented and clarified.
A Smoothed Finite Element Method (S-FEM) for Large-Deformation Elastoplastic Analysis
Authors: Liu Jun , Zhang Zhi-Qian , Zhang Guiyong
Published: May 2015

An edge-based smoothed finite element method (ES-FEM) using 3-node triangular element was recently proposed to improve the accuracy and convergence rate of the standard finite element method (FEM) for 2D elastic solid mechanics problems. In this research, ES-FEM is extended to large-deformation plasticity analysis, and a selective edge-based/node-based smoothed finite element (selective ES/NS-FEM) method using 3-node triangular elements is adopted to address volumetric locking problem. Validity of ES-FEM for large-deformation plasticity problem is proved by benchmarks, and numerical examples demonstrate that, the proposed ES-FEM and selective ES/NS-FEM method possess (1) superior accuracy and convergence properties for strain energy solutions comparing to the standard FEM using 3-node triangular element (FEM-T3), (2) better computational efficiency than FEM-T3 and similar computational efficiency as FEM using 4-node quadrilateral element and 6-node quadratic triangular element, (3) a selective ES/NS-FEM method can successfully simulate problems with severe element distortion, and address volumetric locking problem in large-deformation plasticity analysis.
Numerical Integration Approach Based on Radial Integration Method for General 3D Polyhedral Finite Elements
Authors: Lv Jun , Sheng Guoyu , Gao Xiaowei , Zhang Hongwu
Published: May 2015

We construct an efficient quadrature method for the integration of the Galerkin weak form over general 3D polyhedral elements based on the radial integration method (RIM). The basic idea of the proposed method is to convert the polyhedral domain integrals to contour plane integrals of the element by utilizing the RIM which can be used for accurate evaluation of various complicated domain integrals. The quadrature construction scheme for irregular polyhedral elements involves the treatment of the nonpolynomial shape functions as well as the arbitrary geometry shape of the elements. In this approach, the volume integrals for polyhedral elements with triangular or quadrilateral faces are evaluated by transforming them into face integrals using RIM. For those polyhedral elements with irregular polygons, RIM is again used to convert the face integrals into line integrals. As a result, the volume integration of Galerkin weak form over the polyhedral elements can be easily carried out by a number of line integrals along the edges of the polyhedron. Some benchmark numerical examples including the patch tests are utilized to demonstrate the accuracy and convenience of the proposed method.
Localization of quantum topology in the presence of matter and gauge fields
Authors: Atyabi Farzaneh
Published: May 2015

In this paper a toy model of quantum topology is reviewed to study effects of matter and gauge fields on the topology fluctuations. In the model a collection of N one-dimensional manifolds is considered where a set of boundary conditions on states of Hilbert space specifies a set of all topologies perceived by quantum particle and probability of having a specific topology is determined by a partition function over all the topologies in the context of noncommutative spectral geometry. In general the topologies will be fuzzy with the exception of a particular case which is localized by imposing a specific boundary condition. Here fermions and bosons are added to the model. It is shown that in the presence of matter, the fuzziness of topology will be dependent on N, however for large N the dependence is removed similar to the case without matter. Also turning on a particular background gauge field can overcome the fuzziness of topology to reach a localized topology with classical interpretation. It can be seen that for large N more opportunities can be provided for choosing the background gauge field to localize the fuzzy topology.