Design Parameters Research Articles

Simulation Based Analysis and Design of Passive Back Exoskeleton for Squat Lifting

Abstract Back pain is the most common musculoskeletal disorder that manual material handling laborers face as they lift heavy objects. To overcome the back pain problem, an assistive device (Exoskeleton) can be worn during lifting. Through musculoskeletal simulation, this work investigates how the passive back exoskeleton affects the spinal muscle forces and spinal joint reaction loads. Such simulation findings can provide insights to improve the back exoskeleton design further. For this purpose, the passive exoskeleton is modeled as a set of elastic elements (springs), and dynamic analysis for a lifting cycle is done during a squat lifting task. Musculoskeletal simulations were carried out in OpenSim software utilizing the open-source OpenSim lifting full body model. The model is modified by adding an external spring that provides assistive forces like a passive exoskeleton. During the whole lifting cycle, the erector spine muscle is strained, so unloading the erector spine muscle is the primary goal of most back support exoskeletons. This work aims to identify optimal spring configurations and design parameters for a passive back exoskeleton to aid in squat lifting by varying spring parameters and through a formulation of a multi-objective optimization problem. The optimized back exoskeleton is expected to reduce compressive and shear forces on the L5S1 joint during lifting.

Lessons learned from Mn/ROAD (1992 – 2007): Low-Volume Road Concrete Pavement Design and Performance

This paper examines the design and general performance of the five original MnROAD low-volume road (LVR) concrete pavement test sections, which were constructed in 1993 and have been subjected to more than 300,000 80-kN (18-kip) equivalent single-axle loads (ESALs) by a controlled stream of heavy trucks. The test sections include pavements with varying panel lengths, joint designs, foundation designs and drainage systems. Ride quality histories and current distress summaries are presented, along with maintenance records and deflection data. Performance life projections are made on the basis of IRI records, and these projections are compared with predictions that result from using as-built data in selected common design procedures. The effectiveness of various design and construction parameters is evaluated in the context of the performance measures and predictions. Initial ride quality appears to be one of the most important parameters affecting performance life. The accuracy of various design procedures is evaluated in terms of the test section performances. The new AASHTO Mechanistic-Empirical Pavement Design Guide provided pavement performance estimates that most closely matched observed IRI trends, but even this procedure underpredicted project performance by about 23 percent.

PROPOSED SPECIFICATION FOR CONSTRUCTION OF AIRFIELD CONCRETE PAVEMENT

The Standards for Specifying Construction of Airports, FAA Advisory Circular: AC 150/5370- 10B incorporates Item P-501 – Portland Cement Concrete Pavement. Airfield concrete pavement project funded under the Federal Airport Improvement Program (AIP) are typically developed in accordance with the requirements contained in Item P-501 and sometimes in conjunction with specific project requirements and local practices related to material availability and regional concerns, and as approved by the FAA. Item P-501 provides guidance on the following: 1. Concrete materials (including composition and materials requirements) 2. Construction methods (including equipment, concrete placement, finishing, jointing, curing, and sealing) 3. Method of acceptance (including sampling and testing) 4. Contractor quality control 5. Basis for payment As part of a recent study, a proposed specification for construction of concrete airfield pavements has been developed for possible adoption by the FAA. The proposed specification places emphasis on the need to produce a durable end product, vis-à-vis, a durable concrete pavement. The product requirements that are specified are a combination of prescriptive requirements for certain materials as well as end product requirements for the as-delivered concrete and for the as-placed concrete. There is less emphasis on the means and methods to produce the end product. This should allow the contractor reasonable flexibility to use innovative construction methods and equipment that will result in cost savings to owner agencies without sacrificing the quality of the product. Specifically, the proposed specification will allow constructors to identify sources of variability in the airfield concrete pavement construction process and to minimize the variability; thus delivering an end product that is consistent and durable. The proposed specification intent is to: 1. Inspire creativity and maintain a standard for the evaluation of the construction 2. Incorporate a system of measurement consistent with acceptance criteria that will validate the design parameters 3. Encourage innovation and be "results-oriented" 4. Result in a product of the highest quality and consistent with the available local materials. This paper presents highlights of the proposed specification.

A Pilot Study of Instrumented Unbonded Concrete Overlay in Toronto

Unbonded concrete overlays provide structural rehabilitation and can be cost effective when the existing pavements are highly distressed and/or removal of existing pavement layers is not desirable. This paper describes a pilot study, which involves a three way partnership between the University of Waterloo, the Cement Association of Canada and the City of Toronto, to evaluate and document the performance of the first instrumented unbonded concrete overlay in Canada. The rehabilitation area is located at a heavily-trafficked intersection on Bloor Street and Aukland Road in the City of Toronto. The large volumes of bus traffic from the nearby subway station caused significant damage to the pavement structure. The rehabilitation design was composed of placing an unbonded concrete overlay on Bloor Street and replacing the section on Aukland Road with full depth exposed concrete. Twelve strain gauges are embedded in the concrete layer and they are strategically located along the wheel paths of the buses. The sensors are being monitored to assess long-term performance of the concrete overlay and the full depth concrete subjected to traffic and climatic loads. This paper outlines the design parameters, site conditions, and material properties of the overlay. The construction and full-scale instrumentation of this project are described, followed by preliminary analyses of up-to-date performance records.

Observation of broadband super-absorption of electromagnetic waves through space-time symmetry breaking.

Using time as an additional design parameter in electromagnetism, photonics, and wave physics is attracting considerable research interest, motivated by the possibility to explore physical phenomena and engineering opportunities beyond the limits of time-invariant systems. Here, we report the experimental demonstration of enhanced broadband absorption of electromagnetic waves in a continuously modulated time-varying system, exceeding one of the key theoretical limits of linear time-invariant absorbers. This is achieved by harnessing the frequency-wave vector transitions and enhanced interference effects enabled by breaking both continuous space- and time-translation symmetries in a periodically time-modulated absorbing structure operating at radio frequencies. Furthermore, we demonstrate broadband coherent wave absorption using a secondary control wave, observing a nearly perfect, reconfigurable, antireflection effect over a broad continuous bandwidth. Our findings provide insights into enhanced wave absorption in time-varying scenarios and may enable the development of devices operating in a regime fundamentally beyond the reach of linear time-invariant systems.

A model-based investigation of the dynamic and control characteristics of an electric power-assisted bicycle with the varied design parameters

A model-based investigation of the dynamic and control characteristics of an electric power-assisted bicycle with the varied design parameters

Joint design and joint performance of Plain Concrete Pavements (JPCP) - Investigations and experiences in Germany -

Unreinforced concrete pavements have to be equipped with longitudinal and transversal kerbs to guarantee controlled cracking (JPCP). The designs of such joints depending on the technical requirements are given in respective specifications. Main features for the design are aiming first for the controlled cracking at the foreseen position during young age of the concrete as well as avoidance of wild cracking during service life, second for sufficient load transfer at the joint to reduce edge load effects and third for a good long time performance, which requires joint sealing. This paper focus on research works performed in the field of joint efficiency (dowelling) of transversal joints, which is especially related to the design parameters and the positioning of dowels. New developments and alternative solutions concerning the today’s usage of coated steel bars must be done within the area of conflicts of following headings: Load transfer efficiency, longitudinal resistance, long-time behaviour (corrosion). FEM models and laboratory tests offer evaluation criteria for modified parameters. Especially the coating-material foreseen to cover the steel bar must be evaluated within the area of conflicts shown above. Additionally the actual dowel position and alignment is of importance. Non-destructive inspection tools are under development. The outputs of these investigations are strengthening the background for the updating work concerning the respective specifications.

Dimension Reduction of MUSIC Database for Tailored Clustering Using Lasso

The tailored clustering enabled regionalization (TCER) framework has shown that the prediction error of design parameters at a target site can be reduced by constructing a transformation model from a cluster that only contains sites with geotechnical properties similar to the target site. These sites are retrieved from a global/regional database. However, the similarity between any two sites will reduce when the number of properties increases. TCER will be ineffective if too many properties are included in the database (e.g., structural health monitoring and remote sensing databases). The current study presents a least absolute shrinkage and selection operator for databases with incomplete records (denoted by HMLasso; a dimension reduction method) to improve the performance of TCER in high dimensional databases. HMLasso is utilized to construct a dimensionally reduced database, which includes only the properties relevant to the design parameters, from a high-dimensional database. TCER is then adopted to retrieve a cluster from the dimensionally reduced database for inferring the design parameters at a target site. The capability of HMLasso to enhance the performance of TCER in terms of identifying clusters similar to the target site and reducing the prediction error of design parameters are demonstrated using real-world geotechnical databases.

A Litz Wire-Based Inductor Model for a DC-DC Converter-Fed Single-Phase Inverter

Inductors play a major role in the power electronics domain, particularly in DC-DC converter design. The objective of this paper is to reach inductance value by means of fewer turns, using Litz wire wound on a ferrite core. In the manufacture of inductors, the key aspects of the design criteria include the choice of the core material, the type of copper coil and insulation materials, and their overall size. Taking into consideration the design parameters with no compromises on performance, Litz wire with the least turns is introduced into an inductor in certain DC-DC converters. Once the DC settled voltage is reached, it is given to a single-phase inverter for loading and application measures. This approach provides a small-level inductor design for maximized efficiency with improved thermal behavior. The hardware model for the proposed method has been developed using a DC-DC converter fed with a single-phase inverter model. The proposed DC-DC converter has been tested, performance-wise, by applying different load levels. It is observed, from the results, that the Litz wire-based approach achieves maximum efficiency with improved thermal behavior.

The investigation of optimization parameters of sodium borate solution treated with different surfactants

In this study, the Taguchi method was applied to determine the optimal conditions in the process of changing the antimicrobial activities of sodium borate solution through the addition of commercial surfactants such as cosmocol, NP7, loradac, and tianol 40. The type and ratio of surfactants were used as parameters in an orthogonal array design to reduce the number of experiments during the optimization process. Antimicrobial test results were employed to validate the impact of surfactants on the sodium solution.

Development of CPAP Overlay Interfaces for Efficient Administration of Aerosol Surfactant Therapy to Preterm Infants

The administration of surfactant aerosol therapy to preterm infants receiving continuous positive airway pressure (CPAP) respiratory support is highly challenging due to small flow passages, relatively high ventilation flow rates, rapid breathing and small inhalation volumes. To overcome these challenges, the objective of this study was to implement a validated computational fluid dynamics (CFD) model and develop an overlay nasal prong interface design for use with CPAP respiratory support that enables high efficiency powder aerosol delivery to the lungs of preterm infants when needed (i.e., on-demand) and can remain in place without increasing the work of breathing compared with a baseline CPAP interface. Realistic in vitro experiments were first conducted to generate baseline validation data, and then the CFD model, once validated, was used to explore key design parameters across a range of preterm infant nose-throat geometries and aerosol delivery conditions. The most important factors for efficient aerosol delivery were shown to be (i) maintaining the aerosol delivery flow rate below the tracheal flow rate (to minimize CPAP line loss) and (ii) concentrating the aerosol within the first portion of the inhalation waveform. An optimized design was shown to deliver approximately 37–60% of the nominal dose through the system and to the lungs with low intersubject variability (1050–2200 g infants) across two modes of device actuation (automated and manual) with room for further improvement. Ergonomic curvatures and streamlining of the prong geometries were also found to reduce work of breathing and flow resistance compared with a commercial alternative.Graphical

Guided Waves in Composite Overwrapped Pressure Vessels and Considerations for Sensor Placement Towards Structural Health Monitoring – An Experimental Study

Abstract The utilization of composite overwrapped pressure vessels (COPVs) to store hydrogen, especially at high pressures, is gaining more popularity due to their lightweight design and high storage density, offering significant economic advantages. However, the presence of material defects or fatigue can lead to critical failures, requiring an innovative and robust approach to ensure safe operation and system integrity. Developing a continuous structural health monitoring (SHM) system for COPVs can provide comprehensive real-time information about their condition, facilitating a shift away from periodic inspections. This study scrutinizes the behavior of guided waves (GWs) within COPVs to design a sensor network for damage detection and localization. First, the dispersive and multimodal propagation behavior of GWs is experimentally investigated. Subsequently, important parameters for the network design are derived and finally a sensor network consisting of fifteen piezoelectric transducers is designed to cover the entire cylindrical area. The effectiveness is then evaluated experimentally by placing artificial defects on the surface of the COPV. The multi-layered dataset of GW signals was analyzed using both commonly used ultrasonic features (e.g., amplitude, frequency, time of flight) as well as statistical features (kurtosis, skewness, variance, etc.). These features were utilized to compute a damage index, and the effectiveness of the detection performance was assessed using receiver operating characteristic curves. It can be seen that some features are more sensitive and robust under varying experimental conditions. The results show that ultrasonic GW SHM system is a promising solution for damage detection and localization in COPVs.

Compact High-Zoom-Ratio Mid-Wavelength Infrared Zoom Lens Design Based on Particle Swarm Optimization

This paper presents an automated method for solving the initial structure of compact, high-zoom-ratio mid-wave infrared (MWIR) zoom lenses. Using differential analysis, the focal length variation process of zoom lenses under paraxial conditions is investigated, and a model for the focal power distribution and relative motion of three movable lens groups is established. The particle swarm optimization (PSO) algorithm is introduced into the zooming process analysis, and a program is developed in MATLAB to solve for the initial structure. This algorithm integrates physical constraints from lens analysis and evaluates candidate solutions based on key design parameters, such as total lens length, zoom ratio, Petzval field curvature, and focal length at tele end. The results demonstrate that the proposed method can efficiently and accurately determine the initial structure of compact MWIR zoom lenses. Using this method, a mid-wave infrared zoom lens with a zoom ratio of 50×, a total length of less than 530 mm, and the ratio of focal length to total length approximately 2:1 was successfully designed. The design validates the effectiveness and practicality of this method in solving the initial structure of zoom lenses that meet complex design requirements.

A Radiation-Based Analytical Model for the Computation of Temperature in the Arc Column of Submerged Arc Additive Manufacturing (SAAM) Process

Abstract Submerged Arc Additive Manufacturing (SAAM) is an advanced Wire Arc-based Additive Manufacturing (WAAM) technique known for its uniform deposition structure, high deposition rate, and superior surface finish. However, it is difficult and expensive to experimentally investigate the arc column in SAAM due to its submerged nature under flux. This paper presents an effective alternative: developing a radiation-based analytical model to predict the complex temperature distribution within the SAAM arc column. It focuses on the radiation heat transfer phenomenon since the temperatures attained inside the arc column are beyond the melting temperature of the material involved, and the presence of granular flux and slag intensifies the effect of the same. The model incorporates key input process parameters like wire diameter, stick-out length, current, voltage, and travel speed alongside design parameters like bead width, penetration depth, and material reinforcement. The double ellipsoidal heat source model is the foundation for generating the temperature profile. The predicted temperature profile resembles the double ellipsoid in other arc welding-based additive manufacturing techniques. The model's predictions showed a deviation of approximately 14% from experimental results, validating its effectiveness. Extensive parametric studies were carried out using the developed model. It was observed that longer stick-out lengths dampened temperature variations, while higher currents confined the affected zone further. Increased travel speed reduces the heating and cooling rate, while voltage behaves the opposite way. This analytical approach offers a cost-effective alternative for optimizing process parameters to achieve desired dimensions and deposition quality.

Tailoring Design of Microneedles for Drug Delivery and Biosensing.

Microneedles (MNs) are emerging as versatile tools for both therapeutic drug delivery and diagnostic monitoring. Unlike hypodermic needles, MNs achieve these applications with minimal or no pain and customizable designs, making them suitable for personalized medicine. Understanding the key design parameters and the challenges during contact with biofluids is crucial to optimizing their use across applications. This review summarizes the current fabrication techniques and design considerations tailored to meet the distinct requirements for drug delivery and biosensing applications. We further underscore the current state of theranostic MNs that integrate drug delivery and biosensing and propose future directions for advancing MNs toward clinical use.

Anchoring of Radially Expandable Microcapsule Robots in Blood Vessels Based on the Anchoring Method in Fan-Shaped Peristaltic Tubes

Radially expandable capsule robots are essential in alleviating thrombosis due to their unique anchoring and expansion capabilities within blood vessels. Despite their potential, research in this area remains limited, highlighting the need for further exploration. This study draws inspiration from the stable anchoring mechanisms observed in fan-shaped peristaltic tubes to establish a robust anchoring resistance model specifically for capsule robots in vascular environments. The research investigates the biomechanical characteristics of blood vessels under expansion conditions, deriving the longitudinal profile equation to better understand these interactions. Based on the established model, various optimization methods are proposed to enhance the anchoring performance of the capsule robots. To validate the model's accuracy, anchoring resistance is tested using a phantom vessel on an experimental platform. By integrating kinematic and mechanical analyses, an inchworm-type expansion force model is developed to evaluate anchoring performance quantitatively, allowing for an in-depth analysis of how design parameters influence anchoring resistance. This provides vital theoretical support for the design and optimization of capsule robots aimed at improving clinical outcomes in thrombotic conditions

Exploring the Design of Low Cd BEV by Comparing the Characteristic Parameters and Curves of the Li Auto Mega and ZEEKR 009

As the Battery Electric Vehicle (BEV) market expands, consumer expectations for BEV performance are rising rapidly, with range anxiety becoming a major concern. Merely increasing battery size isnt a long-term solution. Instead, optimizing key design parameters to enhance aerodynamic efficiency is crucial. This paper examines the evolution of Multi-Purpose Vehicles (MPVs) by comparing the traditional MPV designs with newer, low drag models. in terms of appearance parameters and explore the future development of MPVs appearance. Specifically, the Li Auto Mega and ZEEKR 009 are analyzed, highlighting the stark differences in their designs. The study finds that the more aggressive and innovative design elements of the Mega effectively reduce the drag coefficient (Cd), offering valuable insights for future MPV designs

An Individual Participant Data Meta-Analysis to Support Power Analyses for Randomized Intervention Studies in Preschool: Cognitive and Socio-Emotional Learning Outcomes

There is a need for robust evidence about which educational interventions work in preschool to foster children’s cognitive and socio-emotional learning (SEL) outcomes. Lab-based individually randomized experiments can develop and refine such interventions, and field-based randomized experiments (e.g., cluster randomized trials) evaluate their effectiveness in real-world daycare center settings. Applying reliable estimates of design parameters in the context of a priori power analyses is essential to ensure that the sample size of these studies is adequate to support strong statistical conclusions regarding the strength of the intervention effect. However, there is little knowledge on relevant design parameters with preschool children. We therefore utilized a systematic collection of individual participant data from four German probability samples (554 ≤ N ≤ 2928) with preschool children (aged two to six years) to estimate and meta-analyze design parameters. These parameters are relevant for planning single-level (e.g., in non-clustered lab-based settings), two-level (children nested in daycare centers), and three-level (children nested in groups, with groups nested in daycare centers) randomized intervention studies targeting cognitive and SEL outcomes assessed with three methods (standardized tests, parent ratings, and educator ratings). The design parameters depict between-group and -center differences as well as the proportion of variance in the outcomes explained by different covariate sets (socio-demographic characteristics, baseline measures, and their combination) at the child, group, and center level. In conclusion, this paper provides a rich source of design parameters, recommendations, and illustrations to support a priori power analyses for randomized intervention studies in early childhood education research.

Finite Element Analysis of Stress Distribution in Cancellous Bone During Dental Implant Pilot Drilling

Background/Objectives: This study investigates stress distribution in cancellous bone during pilot drilling for dental implants using the Cowper–Symonds model. Understanding the biomechanical effects of drilling parameters on bone health is essential for optimizing implant stability and longevity. Methods: A finite element analysis (FEA) approach was employed to simulate the pilot drilling process in cancellous bone. A three-dimensional jawbone model was developed from CT scan data, processed using 3D Slicer, and refined with CAD tools. The drilling simulation incorporated a rigid pilot drill and flexible cancellous bone, utilizing explicit dynamic methods. Stress distribution was evaluated for drilling depths ranging from 6 mm to 16 mm, with mesh density and strain rate effects considered to ensure accuracy. Results: The results showed an increase in stress levels with drilling depth, with maximum stress recorded at 16 mm. Initial contact stress was 17.3 MPa, rising to 228.9 MPa at deeper penetration due to increased interaction between the drill and bone. Stress distribution patterns emphasized the critical role of drilling depth and design parameters in mitigating bone damage. Conclusions: This study highlights the importance of optimized drilling protocols and pilot drill design to reduce stress and preserve bone integrity. The findings provide valuable insights into improving implant procedures and demonstrate the utility of FEA as a robust tool for evaluating biomechanical impacts during implant placement. Future research should incorporate cortical bone and thermal effects for a comprehensive analysis.

Numerical analysis on heat transfer enhancement of Al2O3 and CuO-water nanofluids in annular curved tubes

The present investigation presents numerically the thermo-hydraulic performance of annular curved tubes in the turbulent flow region. The three-dimensional (3D) computational fluid dynamic (CFD) model was developed by using a commercial ANSYS 14.5 package to get additional insights on the thermo-hydraulic performance on a level of detail that is not always available in experiment results. The turbulent k-ε realize model was employed to examine the effect of Al2O3-water and CuO-water nanofluids on the heat transfer and fluid flow characteristics at different key design parameters. Three coil geometry shapes (including helical, spiral, and conical), five annular cross-section shapes (including circular, elliptical, square, rectangular, and triangular), and three cross-section areas were also investigated in this study. The numerical simulations were carried out at Reynolds numbers of 4700 to 26,700 and nanofluid volume concentrations, φ of 1%, 3%, and 5%, with constant wall temperature (CWT) heat transfer boundary conditions. The result showed that the addition of Al2O3 (45 nm) and CuO (29 nm) nanoparticles to water improves the heat transfer coefficient by 48.8%, 25.7%, and 8.4% and 37.1%, 20%, and 8.7%, respectively, at φ of 5%, 3%, and 1%, while the penalty of pressure drop is approximately negligible. The heat transfer rate per unit pumping power for helical design achieved 21.6% and 5.34% higher than conical and spiral designs, respectively, for the same curvature ratio, cross-section area, and coil length. Also, the circular shape achieved a higher heat transfer enhancement than elliptical, square, rectangular, and triangular shapes by 4%, 14.6%, 17.8%, and 30.1%, respectively. The maximum thermo-hydraulic performance index reached 1.68 and 1.58 for both Al2O3-water and CuO-water nanofluids, respectively, at φ of 5%.