Parametric Study Research Articles

Simplified excavation-induced lateral displacement assessment in Sydney area

Excavations change the stress state of the in-situ ground. The altered stress state causes lateral and vertical displacement in the buildings and structures adjacent to the excavation. In areas like the Sydney region, tectonic locked-in horizontal stresses at shallow depth exceed the vertical stress and the high in-situ horizontal stresses cause possibility of excavation-induced displacement in good quality rocks (e.g., Hawkesbury Sandstone Class I, II, and III). This paper estimates the magnitude and shape of the excavation-induced displacement trough along the excavation edge in Hawkesbury Sandstone. A parametric study was undertaken using three-dimensional finite element analysis to estimate the maximum lateral excavation-induced displacement as well as the lateral displacement trough as a function of the ground type, excavation depth and width, and principal in-situ stress orientation. The results were verified by comparing with monitoring results published for Sydney Sandstone.

Energy-Efficient Passive Cooling Design for Residential Buildings in Hot and Arid Climates: A Parametric Study

Energy-Efficient Passive Cooling Design for Residential Buildings in Hot and Arid Climates: A Parametric Study

Investigation on the band narrowing and shifting effects of micro-perforated panel absorbers.

Micro-perforated panel (MPP) absorbers exhibit multiple resonance bands with increased bandwidth narrowing and shifting in higher frequencies, limiting their effectiveness. This study investigates the effects of narrowing and shifting in higher-order resonance bands of MPP absorbers. First, an acoustic impedance model for MPP absorbers is introduced, and the narrowing and shifting coefficients are defined and modeled to quantify these effects. It is observed that a larger ratio of acoustic resistance to acoustic mass is favorable for reducing the narrowing and shifting effects. Subsequently, the theoretical model is validated using a numerical model, and a parametric study is conducted to explore the influence of geometric parameters on the narrowing and shifting effects. The study reveals that decreasing aperture and panel thickness, while increasing perforation ratio and cavity depth, reduces the narrowing and shifting coefficients. Remarkably, ultra-micro-perforated panels (UMPPs) with an aperture below 0.1 mm and perforation constant below 0.0046, having relatively larger acoustic resistance and smaller acoustic mass, demonstrate near-zero band narrowing and shifting. Finally, UMPPs are fabricated using micro-electro-mechanical systems (MEMS) technology, and their normal absorption coefficients are measured. Results align with theoretical predictions, confirming UMPPs' ability to achieve zero narrowing and shifting compared to ordinary MPPs and verifying the study's findings.

A parametric study regarding structural design of a bioprosthetic aortic valve by 3D fluid-structure interaction simulations

Since the introduction of transcatheter aortic valve (AV) implantation as a viable option, surgical bioprosthetic AVs have recently started incorporating shorter struts considering future valve-in-valve procedures. However, the effect of leaflet coaptation geometry on the longevity of these valves remains unexplored. To address this gap, we performed a finite element analysis on bioprosthetic AVs with varying strut heights using a two-way fluid-structure interaction method. To establish a baseline, we used a standard height based on a rendered platform image of the CE PERIMOUNT Magna Ease valve from Edward Lifesciences in Irvine, CA. Bovine pericardium properties were assigned to the leaflets, while normal saline properties were used as the recirculating fluid in hemodynamic simulations. The physiological pressure profile of the cardiac cycle was applied between the aorta and left ventricle. We calculated blood flow velocity, effective orifice area (EOA), and mechanical stress on the leaflets. The results reveal that as the strut height increases, the stroke volume increases, leakage volume decreases, and EOA improves. Additionally, the maximum mechanical stress experienced by the leaflet decreases by 62% as the strut height increases to 1.2 times the standard height. This research highlights that a low-strut design in bioprosthetic AVs may negatively affect their durability, which can be useful in design of next-generation bioprosthetic AVs.

Crashworthiness design of novel CFRP functionally-graded conical square structures with variable circumscribed diameters

Crashworthiness design of novel CFRP functionally-graded conical square structures with variable circumscribed diameters

Analysis of a friction-induced vibration piezoelectric energy generator under linear, bi-linear, and impact conditions

The mismatch in natural frequencies between the piezoelectric energy generator and the energy source affects its energy generation performance. In this research, a novel piezoelectric energy generator with linear, bi-linear, and impact design configurations is proposed. The energy generator utilizes friction as excitation to achieve self-exciting friction-induced vibration (FIV) close to the systems’ resonant frequencies for piezoelectric energy generation. The dynamic response under FIV is described by a mathematical model incorporating the piezoelectric coupling effect. The energy generation from piezoelectric material is evaluated by simulating the charging process of a capacitor using an iterative method. The reliability of the model and the stable high-frequency FIV phenomenon with linear, bi-linear, and impact design configurations are validated by experiment. Furthermore, parameter studies are conducted to investigate their effect on the efficiency and effectiveness of energy generation. With a normal load FN = 30 N and an initial sliding velocity v0 = 0.542 m/s, the linear, bi-linear, and impact design configurations yield peak-to-peak voltages of approximately 2.9 V, 3.8 V, and 20.6 V, respectively. Higher voltages can be generated under optimal operating conditions. The proposed energy generator can be integrated into rotating or sliding equipment to harness the energy derived from FIV. Enhanced energy generation performance can be achieved by modifying structural design and incorporating materials with better properties. The current study paves the way for piezoelectric energy generation using FIV and explores the potential of utilizing dynamic frictional signals in sensing and structural health monitoring scenarios.

Aerodynamics and aeroacoustics of ducted propellers: A study on the design and geometry effects

Ducted propellers present broad applicability in urban air mobility vehicles due to their enhanced operational safety, improved aerodynamic performance, and potential to mitigate noise emissions. This study proposes a numerical approach for designing adequate duct geometries, focusing on the duct's lip profile, expansion ratio, and tip clearance, aiming to provide valuable design guidance for ducted propellers. The simulations are validated through experimental data, showing reasonable agreement in terms of thrust generation and far-field noise. The mean flow and generated thrust are characterized with a parametric study using steady simulations, while delayed detached eddy simulations are employed to capture transient flow characteristics and investigate noise generation. The noise levels were computed using the integral solution of the Ffowcs-Williams and Hawkings equation. The lip geometry impacts the flow distribution and generated thrust, modifying the tonal noise. Furthermore, slightly divergent ducts can increase the total thrust by minimizing flow separation on the duct wall while increasing the suction on the duct lip. The primary noise sources are identified at the propeller's leading edge and tip. The results reveal that divergent ducts effectively reduce tonal noise at all observer angles but increase broadband noise, attributed to the noise sources at the leading edge of the propeller and the interaction with the duct lip. Additionally, reducing the tip clearance from 2 to 1 mm enhances the total thrust by more than 20% without causing extra noise generation.

Performance Evaluation of R1224yd as Alternative to R123 and R245fa for Vapor Compression Heat Pump System

The search for environmentally friendly refrigerants for vapor compression systems has been a significant focus recently due to environmental concerns such as ozone depletion and global warming. In this study, the potential of R1224yd as an alternative refrigerant is investigated. A thermodynamic analysis of a 4-kW air conditioning system is conducted to assess the performance of R1224yd. The system is analyzed from a thermodynamic perspective, and key performance indicators such as the Coefficient of Performance and exergy efficiency. The results are then compared to R245fa and R123. Furthermore, a parametric study is performed to examine the impact of key parameters, such as evaporating and condensing temperatures, on the system's performance. This analysis provides insights into the sensitivity of the system's performance to variations in these parameters. The results indicate that R1224yd is a promising candidate as an environmentally friendly alternative refrigerant compared to R123 and R245fa. Because R1224yd has the lowest environmental impact. It has about 700 kg CO2 indirect emission, but about zero kgCO2 for direct emission. While, based on the thermodynamic results, R1224yd offers better performance compared to R245fa which has 1-3% higher in performance value and exergy efficiency, and has comparable performance to R123. This suggests that R1224yd can be a viable option for the systems, providing improved energy efficiency and lower environmental impact.

Parametric study of soft pneumatic robot grippers through finite element analysis

This paper investigates the gripping stress and deformation of pneumatically-actuated fluidic elastomer actuation (FEA)-based soft robotic gripper through ansys finite element analysis software. By varying gripper parameters, i.e. Input pressures and clearance to the object, simulations on the deformation of the soft fingers are performed to achieve gripping of the object. The motivation of this parametric study is to facilitate the design optimization of soft robotic grippers. Results demonstrate that grippers with lesser clearance to the object require lesser input pressure to achieve similar gripping stress on the object although it is evident that grippers with higher clearance are able to cater for wider range of object sizes.

A hybrid solar-driven vacuum thermionic generator and looped multi-stage thermoacoustically driven cryocooler system: Exergy- and emergy-based analysis and optimization

Significant high-quality heat is wasted in the vacuum thermionic generator (VTIG), which can be efficiently utilized as a prime mover of a bottoming system for cogeneration applications. For this purpose, a new environmental-friendly hybrid system composed of a heliostat solar field, VTIG, and looped multi-stage thermoacoustically driven cryocooler (LMTC) is established, in which the high-temperature heat source of the solar receiver runs the VTIG to generate power, and the LMTC recovers the waste heat of the VTIG to produce a cooling load. Thermodynamic, economic, and environmental analyses of the system are carried out based on exergy and emergy concepts. Moreover, a parametric study is performed to assess the effect of design parameters on the system's thermodynamic, economic, and environmental criteria. Finally, the multi-criteria salp swarm optimization algorithm and decision-making procedures are conducted to improve the exergetic performance and decrease the system's cost and monetary emergy rates along with the environmental impact and ecological emergy rate. Findings depict that at the reliable, optimal operation of the system, the exergetic efficiency can reach 29.36% with a maximum power of 17.2 MW and cooling load of 0.260 MW. The system's cost and monetary emergy rate can be reduced to 0.059 $/s and 5.94 × 1010 seJ/s, with 10.6% and 10% reductions, respectively. Moreover, the environmental impact and ecological emergy rates decline by 6% and 7.4%, respectively. The theoretical findings may offer guidance for the optimum designing and practical running of such a solar solid-state cogeneration system.

Flow dynamics of a liquid–liquid bi-swirl injector

This work presents detailed two-phase flow simulations of liquid–liquid bi-swirl injectors for engineering applications. Liquid oxygen and kerosene are delivered into the injector, which is initially filled with air. A parametric study is conducted on the recess length of the inner tube to investigate its effect on the flow dynamics and spray pattern. The simulations are performed using an improved multiphase flow solver in OpenFOAM, which employs the volume-of-fluid approach for interface tracking and the large-eddy simulation technique for turbulence modeling. Detailed flow dynamics of both fuel and oxidizer, along with their spray patterns, are examined systematically. A comprehensive account is provided on the impact of the recess length on flow evolution, including the film thickness, air core diameter, and spray cone angle. Spectral and dynamic mode decomposition analyses are performed to further examine the flow structures and dynamics. Results from this study can be effectively used to facilitate the design optimization of injectors for liquid-fueled propulsion systems.

Biosafety and toxicity assessment of transgenic cotton-harboring insecticide and herbicide tolerant genes on albino mice.

Genetic engineering has revolutionized agriculture by transforming biotic and abiotic stress-resistance genes in plants. The biosafety of GM crops is a major concern for consumers and regulatory authorities. A 14-week biosafety and toxicity analysis of transgenic cotton, containing 5 transgenes ((Cry1Ac, Cry2A, CP4 EPSPS, VIP3Aa, and ASAL)), was conducted on albino mice. Thirty mice were divided into three groups (Conventional, Non-transgenic, without Bt, and transgenic, containing targeted crop) according to the feed given, with 10 mice in each group, with 5 male and 5 female mice in each group. During the study, no biologically significant changes were observed in the non-transgenic and transgenic groups compared to the control group in any of the study's parameters i.e. increase in weight of mice, physiological, pathological, and molecular analysis, irrespective of the gender of the mice. However, a statistically significant change was observed in the hematological parameters of the male mice, while no such change was observed in the female study group mice. The expression analysis, however, of the TNF gene increases many folds in the transgenic group as compared to the non-transgenic and conventional groups. Overall, no physiological, pathological, or molecular toxicity was observed in the mice fed with transgenic feed. Therefore, it can be speculated that the targeted transgenic crop is biologically safe. However, more study is required to confirm the biosafety of the product on the animal by expression profiling.

A computed tomography (CT)-based morphometric study of various skull base parameters and their anatomical relationships relevant to endoscopic endonasal skull base surgery.

Endoscopic skull base surgery requires a thorough understanding of skull base anatomy. Orientation to regional anatomy to avoid complications like internal carotid artery injury can be assisted by knowledge of certain bony landmarks. These landmarks are themselves highly variable structures. This study focuses on the radiological morphometric characterization of these landmarks, which can be of great assistance to surgeons for better planning of endoscopic skull base approaches. Computed tomography scans of patients without skull base pathologies were analyzed retrospectively for the following parameters - Vidian canal (VC) length, VC and foramen rotundum (FR) distance from midline, the angle between the axis of VC and petrous internal carotid artery (pICA) and between VC and palatovaginal canal, the horizontal, vertical and direct distances between VC and FR and the patterns of sphenoid sinus (SS) pneumatization. The VC-pICA angle was more obtuse and VC and FR were placed farther off the midline on the left as compared to the right side. Similarly, the distances between VC and FR were more on the left side. The VC length and distance of VC and FR from the midline were longer in males than in females. The VC-pICA angle was more obtuse in females. The post-sellar variant was the predominant pneumatization pattern seen (57.9%), and the incidence of lateral recess pneumatization was 15%. The results of our study can be utilized for a better understanding of the anatomy of the skull base. In skull base pathologies with distorted anatomical landmarks, a basic understanding of their interrelations can be used to have a better anatomical orientation. All these measures can help in avoiding complications and make extended endoscopic approaches safe.

УЛЬТРАЗВУКОВОЕ ИССЛЕДОВАНИЕ ДИАФРАГМЫ КАК ПРЕДИКТОР УСПЕШНОГО ОТЛУЧЕНИЯ ПАЦИЕНТОВ ОТ АППАРАТА ИСКУССТВЕННОЙ ВЕНТИЛЯЦИИ ЛЕГКИХ

The relevance of the survey is linked with the persistent problem of weaning patients who have been on mechanical ventilation for a long time. The objective. To conduct a literature analysis in order to summarize the results of modern researches devoted to the study of sonographic parameters that allow estimation of diaphragmatic functions for predicting successful weaning of patients from artificial lung ventilation. Material and methods. In total 33 Russian-language and English-language sources were analyzed. Results. The following ultrasound parameters of the diaphragm were analyzed in detail: diaphragm excursion, diaphragm thickening fraction, diaphragmatic rapid shallow breathing index, and the time to peak inspiratory amplitude of the diaphragm. Conclusions. The ability to timely diagnose diaphragm dysfunction using ultrasound minimizes the risk of respiratory and cardiac failure. Currently there are methods of the diaphragm muscle stimulation to improve the recovery of lost functions.

Экспериментальное исследование гидравлических характеристик сферических насадок для массообменных аппаратов

A critical analysis of the trends in the development of nozzles for mass transfer devices is given, some designs are described in which the transfer of heat and mass is organized from the standpoint of today technically the most perfect. It is shown that the specific surface, the free specific volume of the nozzle and the hydraulic resistance of the layer are determined as the main characteristics of irregular type packing bodies. The scheme and description of an experimental setup for determining the hydrodynamic characteristics of nozzles in laboratory conditions are given. The results of studies of the hydrodynamic parameters of a layer consisting of a spherical hollow irregular nozzle for a dry and irrigated column are presented. The singular velocities of the gas flow corresponding to the transition points (points of deceleration, suspension, inversion or choking) to different hydrodynamic modes of operation of the filling mass transfer columns (film, intermediate, turbulent) and corresponding pressure drops have been experimentally determined. The dependences of the hydraulic resistance of the nozzle layer on the gas velocity in the column for dry and irrigated nozzles with a 1 m high layer are determined. The main reasons for the decrease in gas pressure in the layer of the irrigated nozzle are indicated. The singular gas flow velocities and their corresponding pressure drops are calculated using known empirical dependencies for dry and irrigated nozzles. The results of experimental studies and engineering calculations were compared, thereby proving the possibility of using computational equations with satisfactory accuracy (up to 15%). The study of the hydrodynamics of the layer and its hydraulic characteristics has shown that the spherical, hollow nozzle design with evenly spaced holes on the surface provides an effective redistribution of working phases in the mass transfer apparatus.

Mid-infrared dual-comb spectroscopy with quantum cascade lasers

Since its invention in 1994, the quantum cascade laser (QCL) has emerged as a versatile light source of wavelength 4–12 µm, covering most of the mid- and long-wavelength infrared spectral ranges. Its application range has widened even further since frequency comb operation and its use as a light source for dual-comb spectroscopy (DCS) was demonstrated. In this tutorial, we introduce the unique properties of QCL frequency combs, such as high optical power, multi-GHz repetition rate, and narrow optical linewidths. Implemented in a dual-comb spectroscopy setup, this allows for broadband, low-noise measurements of strongly absorbing samples with sub-microsecond time resolution, and spectral resolution better than 10−3 cm−1/30 MHz. The advantages of QCL DCS will be discussed in the context of its broad range of applications. The high optical power (both total and per comb tooth) is leveraged for measurements in aqueous solution or at large stand-off distances. Microsecond temporal resolution measurements address the demand for probing rapid protein dynamics and combustion diagnostics. MHz-level spectral resolution, in turn, facilitates accurate line parameter studies in low pressure and cold molecular gases. Future development directions of the technology are discussed, including sub-microsecond response DCS, instrument miniaturization, or its expansion toward THz frequencies. Overall, the tutorial aims at giving a broad introduction to QCL DCS and its applications.

Structural performance of detachable precast concrete column-column joint

A novel type of detachable precast concrete column-column joint (DPC) is proposed in this study to solve the problems in current column-column dry connections including complex load path, uncertainty of structural stiffness of beam-column joints and inconvenience for disassembly. The dry connection technology is applied by composing of steel plate and concrete. Finite element models of DPC were created to study its structural performance including hysteresis curve, skeleton curve, ductility, and energy dissipation capacity. The benchmark models are firstly established and validated against the test data and after that a small-scale parametric study is prepared. The effect of axial pressure ratio and eccentricity distance size on the seismic performance of DPC was studied. Results indict that the optimal value of axial pressure ratio ranges from 0.5 to 0.7. With increase of the axial pressure ratio, the ductility coefficient shows a decreasing trend in general. The eccentricity has little effect on the energy dissipation capacity of the joint.

A comparative study of resistivity models for simulations of magnetic reconnection in the solar atmosphere

Context. Plasmoid-mediated reconnection plays a fundamental role in different solar atmospheric phenomena. Numerical reproduction of this process is therefore essential for developing robust solar models. Aims. Our goal is to assess plasmoid-mediated reconnection across various numerical resistivity models in order to investigate how plasmoid numbers and reconnection rates depend on the Lundquist number. Methods. We used the Bifrost code to drive magnetic reconnection in a 2D coronal fan-spine topology, carrying out a parametric study of several experiments with different numerical resolution and resistivity models. We employed three anomalous resistivity models: (1) the original hyper-diffusion from Bifrost, (2) a resistivity proportional to current density, and (3) a resistivity quadratically proportional to electron drift velocity. For comparisons, experiments with uniform resistivity were also run. Results. Plasmoid-mediated reconnection is obtained in most of the experiments. With uniform resistivity, increasing the resolution reveals higher plasmoid frequency with weaker scaling to the Lundquist number, obtaining 7.9–12 plasmoids per minute for SL ∈ [1.8 × 104, 2.6 × 105] with a scaling of SL0.210 in the highest-resolution resistivity cases, transcending into Petschek reconnection in the high-SL limit (where the diffusive effects of the resistivity become small compared to the non-uniform viscosity) and Sweet-Parker reconnection in the low-SL limit. Anomalous resistivity leads to similar results even with lower resolution. The drift-velocity-dependent resistivity excellently reproduces Petschek reconnection for any Lundquist number, and similar results are seen with resistivity proportional to current-density though with slightly lower reconnection rates and plasmoid numbers. Among the different resistivity models applied on the given numerical resolution, the hyper-diffusion model reproduced plasmoid characteristics in closest resemblance to those obtained with uniform resistivity at a significantly higher resolution.

Parametric study of WEDM of titanium grade 12 using RSM and desirability approach

The present experimental study aims to scrutinize the effect of different process parameters on the material removal rate (MRR) and surface roughness (SR) of titanium grade 12 alloy during wire electro-discharge machining (WEDM) using response surface methodology. Four parameters (pulse-on time, pulse-off time, wire feed and gap voltage) and three levels of each selected variable are considered to conduct the experimental work. Depending on experimental results, a mathematical model is generated for both MRR and SR. An analysis of variance (Anova) study is performed to find significant process parameters. The Anova results show that the developed models for both MRR and SR are significant, and pulse-on time is found to be the most significant parameter. Additionally, the desirability approach is used to scrutinize the single-objective and multi-objective criteria of response variables. The desirability functions for all of the cases are found to be 1. The maximum MRR is observed to be 12.4845 mm3/s, while the minimum value of SR is found to be 1.4911 μm. For multi-objective optimization, the maximum value of MRR and the minimum value of SR are obtained as 12.0942 mm3/min and 1.7167 μm, respectively. Finally, the surface morphology of the machined surfaces is examined using scanning electron microscopy micrographs.

Parametric study of passive flow enhancement on a magnus VAWT blade using response surface methodology and direct-forcing immersed boundary method

The Magnus vertical axis wind turbine harnesses the principle of the Magnus effect in conjunction with a vertical axis orientation. This mechanism is based on the lift and drag produced by rotating cylinders to propel the rotor and generate power. The proposed method involved installing a flat plate near each rotating cylinder to generate a higher unidirectional torque. As the configuration of the plate affects both the flow pattern and the forces exerted on the blade, the current study aims to identify an optimal blade configuration consisting of a rotating cylinder and a flat plate. A numerical model of the direct-forcing immersed boundary method was used to simulate the flow past a single blade using the static rotor simulation approach, and the Box–Behnken design for the response surface methodology (RSM) was applied to find an optimized flat plate arrangement that would produce the highest mean torque coefficient (CT¯). Three design parameters were examined, specifically the length of the plate (L/D), the gap between the plate and the cylinder (g/D), and the plate's shift angle with respect to the cylinder axis (β). The Reynolds number was 5000, and the cylinder spin ratio (α) was 3. The optimum configuration to achieve a maximum CT¯ was identified at L/D=0.53, g/D=0.1, and β=0°. Validating this optimal CT¯ yielded a value of 0.290, indicating an increase in torque of almost 70% compared to the central design. Furthermore, this value corresponds closely to the predicted result obtained through the RSM optimization method. Considering the flow analysis at various positions, it is crucial to emphasize a critical scenario where the potential for countertorque emerges due to excessive drag at ψ=0° and ψ=315°.