The concept of concurrent material and structure optimization aims at alleviating the computational discovery of optimum microstructure configurations in multiphase hierarchical systems, whose ...macroscale behavior is governed by their microstructure composition that can evolve over multiple length scales from a few micrometers to centimeters. It is based on the split of the multiscale optimization problem into two nested sub-problems, one at the macroscale (structure) and the other at the microscales (material). In this paper, we establish a novel formulation of concurrent material and structure optimization for multiphase hierarchical systems with elastoplastic constituents at the material scales. Exploiting the thermomechanical foundations of elastoplasticity, we reformulate the material optimization problem based on the maximum plastic dissipation principle such that it assumes the format of an elastoplastic constitutive law and can be efficiently solved via modified return mapping algorithms. We integrate continuum micromechanics based estimates of the stiffness and the yield criterion into the formulation, which opens the door to a computationally feasible treatment of the material optimization problem. To demonstrate the accuracy and robustness of our framework, we define new benchmark tests with several material scales that, for the first time, become computationally feasible. We argue that our formulation naturally extends to multiscale optimization under further path-dependent effects such as viscoplasticity or multiscale fracture and damage.
Computational simulations have the potential to assist in liver resection surgeries by facilitating surgical planning, optimizing resection strategies, and predicting postoperative outcomes. The ...modeling of liver tissue across multiple length scales constitutes a significant challenge, primarily due to the multiphysics coupling of mechanical response and perfusion within the complex multiscale vascularization of the organ. In this paper, we present a modeling framework that connects continuum poroelasticity and discrete vascular tree structures to model liver tissue across disparate levels of the perfusion hierarchy. The connection is achieved through a series of modeling decisions, which include source terms in the pressure equation to model inflow from the supplying tree, pressure boundary conditions to model outflow into the draining tree, and contact conditions to model surrounding tissue. We investigate the numerical behaviour of our framework and apply it to a patient-specific full-scale liver problem that demonstrates its potential to help assess surgical liver resection procedures
This paper presents a new pattern‐reconfigurable antenna. This antenna has been designed, fabricated, and measured for 2.45 GHz band application. It provides six different radiation patterns in the ...azimuth plane at the same angle interval. First, a new single‐pole three‐throw switching network with one input and three outputs has been built on the circuit simulator and afterward validated by structural simulation. This reconfigurable switching network provides six switching conditions by the combination of turning ‘ON’ and ‘OFF’ states of the used four radio frequency p‐i‐n diode switches. Second, three curved printed dipole antennas are designed with an equal interval of 120° in the azimuth plane. Finally, switching network and curved printed dipole antennas are simultaneously simulated for 2.45 GHz band applications followed by fabrication. Maximum half‐power beamwidth and average gain are obtained as 110° and 4 dBi, respectively, and the radiation efficiency is always better than 90.2%.
This study describes an array antenna that allows for reconfiguration of the three significant antenna properties, that is, radiation pattern, half‐power beamwidth (HPBW), and single and ...bi‐directional beam. A reconfigurable reflecting surface (RRS) has been designed and incorporated with the array antenna on the top and bottom. The RRS works to reflect or pass the incident electromagnetic wave. It enables us to reconfigure from single to multibeam radiation in the ±z direction. It also provides two levels of HPBW, that is, 49.6° and 95°. Eventually, the same three sets of antennae have been stacked and rotated with a 60° angle to achieve the radiation pattern reconfiguration in the entire azimuth plane. It conforms to reconfigure all three antenna properties in six directions at an equal interval of 60° angle. The achieved maximum gain in a narrow beam is 9.56 dBi. The proposed reconfigurable antenna array can be used in modern wireless communication applications.
There is a global concern about adverse health effects of particulate matter (PM) originating from diesel engine exhaust. In the current study, parametric investigations were carried out using a CRDI ...(Common Rail Direct Injection) diesel engine operated at different loads at two different engine speeds (1800 and 2400 rpm), employing diesel and 20% biodiesel blends (B20) produced from Karanja oil. A partial flow dilution tunnel was employed to collect and measure the mass of the primary particulates from diesel and biodiesel blend collected on a 47 mm quartz substrate. The collected PM (particulate matter) was subjected to chemical analyses in order to assess the amount of Benzene Soluble Organic Fraction (BSOF) and trace metals using Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES). For both diesel and biodiesel, BSOF results showed decreasing levels with increasing engine load. B20 showed higher BSOF as compared to those measured with diesel. The concentration of different trace metals analyzed also showed decreasing trends with increasing engine loads. In addition, real-time measurements for Organic Carbon (OC), Elemental Carbon (EC) and total particle-bound Polycyclic Aromatic Hydrocarbons (PAHs) were carried out on the primary engine exhaust coming out of the partial flow dilution tunnel. Analysis of OC/EC data suggested that the ratio of OC to EC decreases with corresponding increase in engine load for both fuels. A peak in PAH concentration was observed at 60% engine load at 1800 rpm and 20% engine load at 2400 rpm engine speeds almost identical for both kinds of fuels. Comparison of chemical components of PM emitted from this CRDI engine provides new insight in terms of PM toxicity for B20
vis-a-vis diesel.
► PM of B20 & diesel were analysed for BSOF, trace metals, real-time OC, EC & PAHs. ► B20 showed lower particulate mass emission at all engine operating conditions. ► BSOF was higher for B20 PM, indicating higher toxic potential of biodiesel. ► OC was higher for B20. With increasing engine load, (i) OC/EC & (ii) PAHs decreased. ► Metals in the PM showed a decreasing trend with increasing engine load.
This paper discusses a proposed antenna that can simultaneously reconfigure three different antenna properties. Those properties are radiation pattern, Half-Power Beamwidth (HPBW), and multibeam ...reconfiguration in the azimuth plane. To make all this feasible, a new unconventional Single Pole Six Throw (SP6T) switching network has been designed and analyzed. To introduce the reconfigurability, five switchable open stub lines are inserted into the switching network. It makes it feasible to drive the input power to the desired number of output ports by providing the impedance matching at power splitting points. At last, six curved printed dipole (CPD) antennas have been designed with the switching network. This antenna can be switched in 13 different cases. Among all, it produces six narrow beams, three wide beams, three dual beams, and one triple beam in the azimuth plane with an equal interval of angles. The measured result agrees with the simulation outcomes. The average gain in single wide and single narrow beams is 3.8 dBi and 4.8 dBi, respectively.
In this paper, a hybrid plasmonic waveguide (HPW) that has a low optical loss with variable nonlinearity (γ) and ultralow dispersion (D) has been proposed. We analyzed and compared four different ...light confinement regions in the proposed HPW structure, namely air, SiO
2
, Si
3
N
4
, and Al
2
O
3
based on Si
3
N
4
and SiO
2
platforms. The optimized HPW gives the largest propagation length (L
p
) of 6.5 mm, which is 60% longer than that of the SiO
2
platform, with a low propagation loss (L
m
) of 0.8 dB/mm, as well as a high figure of merit (FoM) of 419,850 (> 10
5
) with the Si
3
N
4
platform at 1550 nm wavelengths. Moreover, the HPW shows better results for nonlinear coefficient and dispersion with the Si
3
N
4
platform which have been obtained as 4.49 × 10
6
/(kmW) and 6.1 × 10
–5
ps
2
/m. The simulation also shows that the proposed HPW has excellent fabrication tolerance. This device may serve as a fundamental building block of photonic integrated circuits (PICs) for wide applications in LiDAR, nanofocusing, nanolasing, sensing, and nonlinear optics.
The research toward high-performing pressure sensors has been going on for more than two decades, with the goal of improving key parameters, namely the high gauge factor (GF) and device stability for ...future applications. In the present work, the piezoresistivity of the polycrystalline molybdenum disulfide (MoS2) is harnessed for pressure sensing applications with very low noise levels. The fabricated microelectromechanical systems (MEMS) pressure sensor exhibits a high GF of ~92 with pressure sensitivity of ~<inline-formula> <tex-math notation="LaTeX">0.46 \mu \text{A} </tex-math></inline-formula>/Pa and a low nonlinearity of ~12% in the applied pressure range 0-20 kPa. This exceptional performance is explained based on fluctuation-induced tunneling in the polycrystalline MoS2-based pressure sensor. The tunneling barrier between two grains gets modified with the application of external pressure. Furthermore, the noise analysis of the fabricated MEMS pressure sensor shows that the noise level gets altered with the applied stress due to the modified barrier potential.
The diesel tailpipe emissions typically undergo substantial physical and chemical transformations while traveling through the tailpipe, which tend to modify the original characteristics of the diesel ...exhaust. Most of the health-related attention for diesel exhaust has focused on the carcinogenic potential of inhaled exhaust components, particularly the highly respirable diesel particulate matter (DPM). In the current study, parametric investigations were made using a modern automotive common rail direct injection (CRDI) sports utility vehicle (SUV) diesel engine operated at different loads at constant engine speed (2400 rpm), employing diesel and 20% biodiesel blends (B20) produced from karanja oil. A partial flow dilution tunnel was employed to measure the mass of the primary particulates from diesel and biodiesel blend on a 47-mm quartz substrate. This was followed by chemical analysis of the particulates collected on the substrate for benzene-soluble organic fraction (BSOF) (marker of toxicity). BSOF results showed decrease in its level with increasing engine load for both diesel and biodiesel. In addition, real-time measurements for organic carbon/elemental carbon (OC/EC), and polycyclic aromatic hydrocarbons (PAHs) (marker of toxicity) were carried out on the diluted primary exhaust coming out of the partial flow dilution tunnel. PAH concentrations were found to be the maximum at 20% rated engine load for both the fuels. The collected particulates from diesel and biodiesel-blend exhaust were also analyzed for concentration of trace metals (marker of toxicity), which revealed some interesting results.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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