Load In Design Research Articles

Effect of knock on piston thermal load of a high compression ratio natural gas engine based on stepwise decoupling calculation

High compression ratio natural gas engine (NGE) is prone to knock at high load, which aggravates the thermal load of piston. Therefore, accurately evaluating the piston thermal load in the practical design is essential to enhance engine reliability and improve performance. The typical piston thermal load simulation adopts uniform wall boundary conditions, making it difficult to reveal the influence of turbulent flame and knock on the piston thermal load. In this paper, a stepwise decoupling method is applied to calculate the piston thermal load. The advancement of this method lies in its integration of chemical reaction mechanism with computational fluid dynamics (CFD) to calculate the spatial variations in heat transfer coefficient (HTC) and near-wall gas temperature at the piston top. Moreover, the conjugate heat transfer (CHT) method is adopted to solve the piston thermal load by coupling the thermal boundary conditions (TBC) obtained in the first step with the cooling oil boundary conditions. Based on this method, the effect of knock on piston thermal load of a high compression ratio NGE under different knock intensities is explored in this paper. It is found that turbulent combustion causes uneven distribution of thermal load at piston top. The decrease in knock intensity significantly reduces the gas temperature, heat flux and thermal load at piston top. Particularly under severe knock, the average temperature of piston is 22.9 K and 32.4 K higher than that of light knock and normal combustion, respectively. Furthermore, the main factor affecting the piston temperature field distribution is the gas temperature rather than the HTC. The gas temperature at piston top is overall the highest on the side near the inlet valve pit, which leads to a higher temperature on this side. Compared to light knock and normal combustion, when severe knock occurs, the thermal load on the exhaust valve pit increases significantly. This study provides an effective method for analyzing the heat transfer of the piston under knocking combustion, which is of guiding significance for controlling the thermal load of the high-temperature components in the combustion chamber.

Effects of incident solar radiation on evaporative heat loss through firefighter turnout composites incorporating microporous and bi-component type moisture barrier components

Solar radiation is a significant source of firefighter heat stress. In this study, the influence of solar radiation on heat transfer through firefighter fabric composites was evaluated using a modified sweating guarded hotplate exposed to simulated solar radiation. It demonstrated that the heat transfer depended on the intensity of the incident radiation, the color of the outer shell materials, and the type of moisture barrier incorporated in the composite. For ensembles with microporous moisture barrier, evaporative resistance decreased steadily with radiation. In contrast, the evaporative resistance of firefighter ensembles with bi-component moisture barriers initially increased in lower-level radiation intensity and then dropped as the exposure became more intense. To the best of our knowledge, these have never been reported before. The new findings from this study demonstrate the need to address the property change in bi-component moisture barriers under radiant heat load in material design, testing, and mathematical modeling.

Optimal Design and Operation of Hybrid Renewable Energy Systems for Oakland University

This research paper presents a comprehensive study on the optimal planning and design of hybrid renewable energy systems for microgrid (MG) applications at Oakland University. The HOMER Pro platform analyzes the technical, economic, and environmental aspects of integrating renewable energy technologies. The research also focuses on the importance of addressing unmet load in the MG system design to ensure the university’s electricity demand is always met. By optimizing the integration of various renewable energy technologies, such as solar photovoltaic (PV), energy storage system (ESS), combined heat and power (CHP), and wind turbine energy (WT), the study aims to fulfill the energy requirements while reducing reliance on traditional grid sources and achieving significant reductions in greenhouse gas emissions. The proposed MG configurations are designed to be scalable and flexible, accommodating future expansions, load demands changes, and technological advancements without costly modifications or disruptions. By conducting a comprehensive analysis of technical, economic, and environmental factors and addressing unmet load, this research contributes to advancing renewable energy integration within MG systems. It offers a complete guide for Oakland University and other institutions to effectively plan, design, and implement hybrid renewable energy solutions, fostering a greener and more resilient campus environment. The findings demonstrate the potential for cost-effective and sustainable energy solutions, providing valuable guidance for Oakland University’s search for energy resilience and environmental surveillance, which has a total peak load of 9.958 MW. The HOMER simulation results indicate that utilizing all renewable resources, the estimated net present cost (NPC) is a minimum of USD 30 M, with a levelized energy cost (LCOE) of 0.00274 USD/kWh. In addition, the minimum desired load will be unmetered on some days in September.

LOOKING BEYOND SELF-REPORTED COGNITIVE LOAD: INVESTIGATING THE USE OF EYE TRACKING IN THE STUDY OF DESIGN REPRESENTATIONS IN ENGINEERING DESIGN

AbstractDesigners are experiencing greater mental demands given the complexity of design tools, necessitating the study of cognitive load in design. Researchers have identified task- and designer-related factors that affect cognitive load; however, these studies primarily use self-reported measures that could be inaccurate and incomplete. Little research has tested the accuracy and completeness of self-reported measures and we aim to explore this gap. Towards this aim, we seek to answer the question: How does cognitive load vary based on the different design representations used, and do these differences depend on the measure of cognitive load? From our results, we see that the design representations vary in the range of cognitive load experienced by designers when using them. Moreover, this role of the range of cognitive load variance was observed given our use of pupil diameter. These findings call for the use of a multi-modal approach for measuring cognitive load with the combined use of subjective (e.g., self-report) and objective measures (e.g., physiological measures), as well as the use of both retrospective (e.g., self-report) and concurrent measures (e.g., physiological measures).

EEG-BASED COGNITIVE LOAD INDICATORS IN CAD MODELLING TASKS OF VARYING COMPLEXITY

AbstractAs an initial step towards a better understanding of cognitive load in computer-aided design (CAD), the herein presented study investigated cognitive load imposed on 24 mechanical engineers during two CAD modelling tasks of intentionally different complexity levels. The cognitive load has been rarely studied in the CAD context, which resulted in the lack of understanding if and how the EEG-based indicators available from the literature reflect the changes in cognitive load imposed on engineering designers in CAD activities. Therefore, cognitive load was measured and analysed using three EEG-based indicators to explore insights that might be obtained from them. The initial analysis revealed different cognitive load results from the employed indicators for the same EEG data. In addition, the study implies that the cognitive load results obtained through the used indicators are only partially coherent with the CAD modelling task complexity. Hence, the results imply that the chosen EEG-based indicator matters when measuring and analysing cognitive load in CAD modelling tasks and that its adjustment for CAD context might be needed.

Perancangan Single Girder Gantry Crane 2 Ton di PT Spindo Unit VI

In carrying out the design process, the main factor that must be considered is the lifting strength of the crane against the maximum load borne. Because the inaccuracy of the design process can result in malfunctions, even causing work accidents. Therefore, it is necessary to do the right design so that it can be used safely. In this design, the design of a lifting aircraft with a single girder gantry crane is designed with a lifting capacity of up to 2 tons, a lifting height of 4 meters, and a transfer width of 5 meters.. The design method used is by substituting the values ​​and other factors needed into the known equations to obtain the final result. To determine the maximum tensile strength of the load in this crane design, the equation for the maximum tensile force is used to obtain a result of 633.12 kg. Then for the steel rope chosen in this design is the 222 wire construction with parallel positions. By using the equation for resistance of the motor to movement, the power needed to move the crane is also 23,215 HP

Method of constructing stochastic near-extreme daily weather data for efficient calculation of probabilistic load in air-conditioning system design

To solve the oversizing problem of the air-conditioning systems caused by the deterministic method of calculating design load, the probabilistic method has been proposed, in which the design load is selected based on the load probability distribution. In the probabilistic method, obtaining the probabilistic load based on the annual weather scenarios is time-consuming. Thus, it seems more efficient to determine the design load by obtaining the probabilistic near-extreme load directly through stochastic simulation. Therefore, a refined stochastic near-extreme daily weather (SNDW) model, in which the coupling of weather parameters was considered, was proposed to quantify the uncertainty of weather parameters in the stochastic simulation of near-extreme load. Taking Tianjin in China as an example, the SNDW model was established, and the probabilistic design loads of three types of buildings were calculated on this basis. The results showed that compared to the benchmark method, the application of the SNDW model could ensure about 1.5% of the relative error of the design load selected, and the average simulation time was reduced to 1/23 of the benchmark. Finally, the adaptability of the SNDW model to different climatic zones was verified.

Imperfection sensitivity of FGM cylindrical shells under compression

The behavior of FGM cylindrical shells with imperfections under compression was analyzed. Two cases of the ceramics-metal phase arrangement regarding the shell thickness, as well as a case where the coupling matrix determined according to the classical laminate plate theory equaled zero, owing to which the shell was homogenous transversely, was assumed in the analytical–numerical calculations. Cylindrical shell edges were simply supported. Thermal loads were neglected in this study. Within the first-order approximation of the non-linear Byskov-Hutchinson theory, a value of the ultimate load-carrying capacity corresponding to the critical load of the actual structure with imperfections was determined. This approach allows one to determine the imperfection sensitivity surface as well. It was assumed in the numerical calculations that the material of cylindrical shell gradients complied with Hooke’s law. The critical load of real shells (i.e., with imperfections) is treated as the failure load in standard provisions, design and verifications calculations. An analytical–numerical method (ANM) developed by the authors was applied in the calculations. In this approach, Lagrange’s description, precise strains for thin-walled panels and the second Piola-Kirchhoff’s stress tensor, the exact transition matrix method and the numerical method of the transition matrix using Godunov’s orthogonalization are used. All results were validated with the finite element method.

Efficient approach for calibration of load and resistance factors in the limit state design of a breakwater foundation

This study proposes a facile procedure to overcome extensive computational burdens in Monte Carlo simulation (MCS)-based load and resistance factors (LRFs) calibration. Accordingly, a reliability analysis (RA) was conducted on a surrogate set of the constructed response surface functions (RSFs) rather than direct application to the actual implicit problems. Owing to the simplicity of the RA approach, the LRFs were then calibrated using an optimization framework. An adaptive boundaries algorithm was proposed to effectively reduce the number of iterations in the optimization. To elucidate the proposed procedure, four examples: two on slopes and two on foundation stability of breakwaters under earthquake loading were investigated. The results revealed that the surrogate RSFs set that was constructed for numerous failure surfaces not only accurately evaluated the system RA of the actual problems but also allowed for a relatively easier calibration of the LRFs within the optimization framework. In addition, it was found that in the calibration of the LRFs, the RSFs need to be reconstructed to properly account for the variation in the sampling points. The successful convergence of the proposed optimization model took only tens of minutes instead of dozens of days required using the basic. This validates the efficiency and accuracy of the proposed procedure.

Signaling in virtual reality influences learning outcome and cognitive load

Virtual reality (VR) learning environments are highly visual and need instructional aid to help the learner. Presenting too much visual information can impair selection and organization processes by overloading the learner's cognitive capacity. Signaling could support these processes by highlighting relevant information. In this study we used signals in form of textual annotations. Research on multimedia design principles provides evidence that such signals can foster learning, but we address the question whether the signaling principle is also applicable in a virtual reality learning environment. Particularly, we investigate the effects on learning by measuring different learning outcomes as well as different types of cognitive load, i.e., extraneous, and germane load in a between-subjects design. Participants (n = 107) were randomly assigned to a group with or without annotations in a VR learning environment. We assumed that learning material with integrated annotations lead to higher learning outcome, lower extraneous cognitive load (ECL), and higher germane cognitive load (GCL) than the control group. Results show that annotations improved learners' recall performance and GCL compared to a control group but had no effects on deeper levels of processing and on ECL. This indicates that annotations in VR can help learners to process the information on a recall level, but not due to a relief in ECL. When VR learning environments should support learners in recall and at the same time foster GCL, then adding annotations can be an appropriate approach.

Memory Load Alters Perception-Related Neural Oscillations during Multisensory Integration.

Integrating information across different senses is a central feature of human perception. Previous research suggests that multisensory integration is shaped by a context-dependent and largely adaptive interplay between stimulus-driven bottom-up and top-down endogenous influences. One critical question concerns the extent to which this interplay is sensitive to the amount of available cognitive resources. In the present study, we investigated the influence of limited cognitive resources on audiovisual integration by measuring high-density electroencephalography (EEG) in healthy participants performing the sound-induced flash illusion (SIFI) and a verbal n-back task (0-back, low load and 2-back, high load) in a dual-task design. In the SIFI, the integration of a flash with two rapid beeps can induce the illusory perception of two flashes. We found that high compared with low load increased illusion susceptibility and modulated neural oscillations underlying illusion-related crossmodal interactions. Illusion perception under high load was associated with reduced early β power (18-26 Hz, ∼70 ms) in auditory and motor areas, presumably reflecting an early mismatch signal and subsequent top-down influences including increased frontal θ power (7-9 Hz, ∼120 ms) in mid-anterior cingulate cortex (ACC) and a later β power suppression (13-22 Hz, ∼350 ms) in prefrontal and auditory cortex. Our study demonstrates that integrative crossmodal interactions underlying the SIFI are sensitive to the amount of available cognitive resources and that multisensory integration engages top-down θ and β oscillations when cognitive resources are scarce.SIGNIFICANCE STATEMENT The integration of information across multiple senses, a remarkable ability of our perceptual system, is influenced by multiple context-related factors, the role of which is highly debated. It is, for instance, poorly understood how available cognitive resources influence crossmodal interactions during multisensory integration. We addressed this question using the sound-induced flash illusion (SIFI), a phenomenon in which the integration of two rapid beeps together with a flash induces the illusion of a second flash. Replicating our previous work, we demonstrate that depletion of cognitive resources through a working memory (WM) task increases the perception of the illusion. With respect to the underlying neural processes, we show that when available resources are limited, multisensory integration engages top-down θ and β oscillations.

A method for p-y curve based on Vesic expansion theory

In the recent years, the construction of urban infrastructure projects has developed rapidly. When the structure systems of these major infrastructures are subjected to various horizontal loads during operation, it may cause permanent lateral deformation of the pile and instability and damage of the foundation soil. Therefore, it is important to study the interaction of pile-soil system under horizontal load in the pile foundation design, which can provide reference for the design of pile foundation and guide for engineering practice. Based on Vesic expansion theory and according to the actual stress state of the surrounding soil during the horizontal displacement of the pile foundation, the formula of the soil resistance force on the pile side of compression zone are derived, the p-y curve model based on stress increment is established, and the applicability of the calculation method through examples verification are demonstrated in this paper. It is concluded through analysis that when the theoretical method proposed in this paper is applied to the calculation of mechanical response of the pile side soil under horizontal loads; the results of this method are in good agreement with the field measured data in model test, especially when a larger horizontal displacement the pile foundation has come up.

Nonlinear solutions of lateral response for single pile under the combined action of axial and lateral loads

For the study of the laterally loaded pile under axial load, most of the past research always confined the surrounding soil of pile in the linear elastic and elastic-plastic. In order to consider the nonlinear property of soil around the pile more realistically and improve the design of single piles under combined vertical and lateral loads, a nonlinear analysis method based on the hyperbola p-y curve model is applied to calculate the lateral response of pile. The relevant computer program is developed by MATLAB language, and the relevant solving algorithm is presented. The reliability of this approach was verified through comparisons with the measured data from model tests. The calculation results indicate that the approach was more convenient and accurate than the existing methods. The proposed method is applicable for laterally loaded pile under axial load in preliminary engineering design.

Applicability analysis of solar heating system in China based on a reliability-based optimization method for auxiliary heater capacity

Solar heating system (SHS) is affected by weather uncertainty. In order to ensure the system reliability, the auxiliary heater is required and the capacity is determined by the maximum heating load in conventional design. But solar energy not only contains energy value but also capacity value, which provides a chance for reducing auxiliary heater capacity. If ignored, it will lead to over-design and over-invest of the system. Furthermore, this value varies in different regions, so applicability analysis is needed. This paper proposes a reliability-based optimization method for auxiliary heater capacity. Based on the weather data of 16 capital cities in China, hourly heating load of a reference building and energy supply are simulated by EnergyPlus and TRNSYS. The optimal capacity is obtained by dichotomy optimization considering the temporal match of energy supply and demand. Compared with the conventional design results, the auxiliary heater capacity, cost and CO2 emissions can be reduced by 7.10 %–21.53 %, 1.97 %–4.33% and 1.68 %–5.83 %. The comprehensive benefit is higher in low latitude regions, especially in Tibet with abundant solar energy resources and lower heating load. Such distribution characteristics are helpful to guide the application of SHS in different regions and optimize the existing energy design scheme.

Disclosure Spontaneity and Managers’ Explanations for Performance

There is considerable variation across firms and disclosure settings in the level of advance preparation for disclosures. Further, disclosures that involve less preparation are more spontaneous and can affect market outcomes. Despite this, little is known about how spontaneity affects disclosure characteristics. Using an experiment and a survey, we investigate how managers’ explanations for performance differ when issued more spontaneously. Our experiment varies cognitive load and task performance in a 2x2 between-participants design, and asks participants to report the reasons for their performance on an abstract task. We find that participants provide more internal reasons for performance when they respond more spontaneously following both good and poor performance. A follow-up survey of IROs documents reasons for different amounts of disclosure preparation, as well as potential consequences. Our results shed light on why managers invest in different levels of disclosure preparation, and provide evidence on how disclosure spontaneity affects disclosure characteristics.

Increased Working Memory Load in a Dual-Task Design Impairs Nonverbal Social Encoding in Children with High and Low Attention-Deficit/Hyperactivity Disorder Symptoms.

Children with attention-deficit/hyperactivity disorder (ADHD) are known to have difficulty with peer relations, though the mechanisms by which these children struggle with interpersonal relationships are not well known. The current study examined the relation between working memory (WM) and the encoding of nonverbal social cues using a dual-task paradigm tested in children with High and Low ADHD symptoms. A total of 40 children were recruited (20 High ADHD; 20 Low ADHD) and completed computerized tasks of social encoding and WM in both single- and dual-task conditions. A series of repeated measures mixed-model ANOVAs revealed that both children with High ADHD and Low ADHD performed significantly worse during the dual-task condition compared to the single task conditions. Also, children with High ADHD had significantly lower performance than Low ADHD children on task-based social encoding and WM. This study supports the role of WM in nonverbal social encoding in children.

Study on buffering performance of thin-walled metal tube with different angles

Abstracts High frequency shock load is often generated during pyrotechnic device working, which is detrimental to spacecraft structures and electric devices. Therefore, it is valuable to reduce the shock load in pyrotechnic device design. Actually, there are several ways to decrease pyroshock loads, such as reduction of powder, installation of buffering structure, insulation of damageable devices, and so on. Considered assuring the function of pyrotechnic device and minimum of structure modification, shock absorbing structure is more propitious to be introduced in pyrotechnic device. In this paper, based on the method of thin-walled metal tube diameter-expanding, a thin-walled tube shock buffering structure was designed on a separate bolt. Built on the simplified structure of a separate bolt, the model of cone piston impacting thin-walled tube absorber was established, and the thin-walled tube shock absorbing characteristics and the relation between cone angles and absorber performance were analyzed. The results showed that the change of buffering force of thin-walled tube could be divided into four phases, and each phase was correspondent to the cone piston structure. In addition, as the cone angle increases, the max shock acceleration changes in the style of decrease-increase-decrease-increase, which is the result of coupled effects of cone piston max enter depth, buffering force and energy loss. In short, these results could establish the relationships between thin-walled tube absorbing performance and its structure, which is of significance to develop low-shock pyrotechnic device.

Nepal Earthquake 25 April 2015: Hydro projects damaged, risks and lessons learned for design considerations

The 25 April 2015 Nepal earthquake of magnitude 7.8 epicentre at Gorkha and magnitude 7.3 aftershocks on 12 May epicentre at Dolakha had devastating impacts on 14 districts including Kathmandu, capital city of Nepal. Death toll was nearly 9,000 and hundreds of thousands of inhabitants became homeless. The earthquake severely damaged mainly surface structures of hydro projects, access roads, clay mortar stone masonry houses and structurally weak concrete houses. Landslides, rock falls, debris flow, liquefaction, river damming, Landslides Dammed Outburst Flood (LDOF) and Glacial Lake Outburst Flood (GLOF) are expected earthquake-induced hazards. However, landslides and grounds shaking were responsible for major damaged. A total of 15 hydro projects in operations and under construction were affected by the earthquake. In hydro projects damages were recorded in surface structures such as power house, settling basin, penstock pipes, and diversion weir constructed at base of steep terrains. For instance, surface penstock pipe, lying at base of rock cliff, of running 40 MW Upper Bhote Koshi Project was ruptured by rock falls and as a result flooded surface powerhouse located downstream by water from penstock and headrace tunnel. Similarly, diversion weir, surface settling basin and headrace penstock pipe of running 5 MW Mialung Project were also severely damaged by slides and rock falls. On the other hand, only minor cracking of sprayed concrete at corners and protruded edges in underground structures were observed. In hydro projects, there is a practice of considering seismic load in design of structures but the effects of earthquake induced hazards were not foreseen. This devastating earthquake gave good lessons for design considerations of hydro projects in future. This article summarises earthquake damage, risks and lessons learned for Hydro projects in Nepal.

An approach to simplify the vehicle load in excavation-supporting structures design

In the design of underground excavation supporting structures, vehicle loads are generally considered as a constant distributed load of 20 kPa in the practical design method, and the equivalent soil layer method is also used. However, these methods do not take into account the dynamic properties of vehicle loads, and are relatively conservative in considering the influence of vehicle loads. Aiming at this problem, an improved method is presented to better solve this issue. Following the vehicle dynamics theory, vehicle loads are composed of static and dynamic loads; the quarter-truck model with two-degrees of freedom is introduced to simplify vehicle loads. According to motion differential equations of the two degrees of freedom vibration system, the dynamic vehicle load is deduced and expressed as a simple harmonic load. In an underground subway station, this simple harmonic load conversion method was introduced to convert the vehicle load, and was compared to the equivalent soil layer method and practical design method through numerical simulations. Some lateral displacement curves of supporting structures and settlements of road surfaces were obtained. The results revealed that the simple harmonic load conversion method can effectively reflect the influence of vehicle loads in the design of underground excavation-supporting structures..

Experimental and analytical behavior of a new type of concrete‐filled steel tube tied‐arch bridge with trough girder

AbstractTrough girders are widely accepted in engineering on account of lowing construction depth and protection against traffic noise pollution, but most of them are used for simple‐supported girder bridges with a span of generally less than 30 m. On the railway line of Nanjing–Qidong in China a new railway bridge will be built which has a span of over 64 m but a construction depth of less than 2.4 m on which Shanghai–Nantong railway line is also passed, so the type of concrete‐filled steel tube tied‐arch bridge with trough girder was chosen. For such a new structure hardly used in engineering, there are no research results yet available about mechanical properties of the structure. This paper therefore makes for the bridge an experimental model of 1:4 geometric scale in order to test mechanical properties under operation load, cracking load, and ultimate load such as cracking diagram, load‐carrying capacity, stress distribution, and failure mechanism. According to the experimental results, when the model is subjected to longitudinal bending moment, the failure mode is similar to that of pure bending of a girder, and when the model is subjected to transverse bending moment failure mode behaves like the flexural failure mode of the traditional reinforced concrete structure. A non‐linear element analysis is also made on the model with the results in good agreement with that of the experiment. The same modeling method is applied to the finite element analysis of the real bridge, considering various load in design. In the analysis, it is finally verified that this new type of bridge meets specification requirements in strength, rigidity, and resistance to cracking.