共查询到14条相似文献，搜索用时 15 毫秒
2.
Itiswellknownthatthereexistsanindoortempera turedistribution[1] inbuildingrooms.Asthedistancetotheexternalwallvaries ,thetemperatureisdifferent .However,whenwedesignaheating ,ventilationandairconditioning (HVAC)system ,theindoorairvolumeisstillmodeledas“onepoint”or“perfectlymixed”untilre cently.Thisnegligenceofindoortemperaturedistribu tionsisoneofthemainreasonsofthemalfunctionoftheair conditioningcontrolsystem ,whichinturncausesthecomplaintsoftheroomoccupantsaboutindoorthermalcomfort.Th… 相似文献
3.
Marine pipeline damage subjected to dropped objects from platforms or supply vessels is analyzed to introduce an easy and applicable approach to investigating the damage induced by impact load from drop weight. A practical engineering example was presented and analyzed using the commercial program "ANSYS/LS-DYNA", which is a powerful tool with an explicit dynamic solver. And rational agreement of the results with previous works was obtained. The suggested procedure might be taken as a checking analysis of the protection measures of pipelines in addition to the general risk assessment method. 相似文献
4.
The current situation and difficulties of the structural system reliability analysis are mentioned. Then on the basis of Monte Carlo method and computer simulation, a new analysis method reduced expanding load method (RELM) is presented, which can be used to solve structural reliability problems effectively and conveniently. In this method, the uncertainties of loads, structural material properties and dimensions can be fully considered. If the statistic parameters of stochastic variables are known, by using this method, the probability of failure can be estimated rather accurately. In contrast with traditional approaebes,RELM method gives a much better understanding of structural failure frequency and its reliability index β is more meaningful. To illustrate this new idea, a specific example is given. 相似文献
5.
Simulation of Airblast Load and Its Effect on RC Structures 总被引：1，自引：0，他引：1
In the analysis of a structure subjected to an explosion event, the determination of the blast load constitutes a crucial step. The effect of the blast load on the structure depends not only on the peak shock overpressure, but also the impulse (hence the duration). For structures with a regular geometry, the blast load may be fairly well estimated using appropriate empirical formulae; however, for more complex situations, a direct simulation using appropriate computational techniques is necessary. This paper presents a numerical simulation study on the prediction of the blast load in free air using a hydrocode, with focus on the sensitivity of the simulated blast load to the mesh grid size. The simulation results are compared with empirical predictions. It is found that the simulated blast load is sensitive to the mesh size, especially in the close-in range, and with a practically affordable mesh grid density, the blast load tends to be systematically underestimated. The study is extended to internal blast cases. An example concrete slab under internal explosion is analyzed using a coupled analysis scheme. The internal blast load from the simulation is examined and the response of the RC slab is commented. 相似文献
6.
In order to study the seismic behavior of frame with specially shaped columns,the hysteretic curve was analyzed based on a quasi-static test of a two-span,three-story frame with specially shaped columns.The top layer framework curve and the corresponding resilience model were obtained from the hysteretic curve.And the stiffness and strength degeneration were also investigated.The results indicated that the stiffness degeneration is not obvious,thus the frame with specially shaped columns has high earthquake-resistant behavior.The resilience model calculated from the test can provide reference for design and nonlinear finite element analysis. 相似文献
7.
With the terms of the exact series solution taken as trial functions, the method of point collocation was used to calculate the large deflection of a circular plate. The axisymmetrical bending formulae were developed for the calculation of a circular plate subjected to polynomial distributed loads, a concentrated load at the center, uniform radial forces and moments along the edge or their combinations. The support may be elastic. The buckling load was calculated. Under action of uniformly distributed load, central load or their compound load, solutions were compared with those obtained by other methods, Buckling beyond critical thrust was compared with that calculated by the power series method. The method presented in this paper has advantages of wide convergent range, high precision and short computing time. Moreover, the computing time is nearly independent of the complexity of the loads. 相似文献
8.
A Review of Current Researches on Blast Load Effects on Building Structures in China 总被引：2，自引：0，他引：2
LI Zhongxian DU Hao BAO Chunxiao 《天津大学学报(英文版)》2006,12(B09):35-41
The damages of building structures subjected to multifarious explosions cause huge losses of lives and property. It is the reason why the blast resistance and explosion protection of building structures become an important research topic in the civil engineering field all over the world. This paper provides an overview of the research work in China on blast loads effect on building structures. It includes modeling blast shock wave propagation and their effects, the dynamic responses of various building structures under blast loads and the measures to strengthen the building structures against blast loads. The paper also discusses the achievements and further work that needs be done for a better understanding of the blast loads＇ effects on building structures, and for deriving effective and economic techniques to design new or to strengthen existing structures. 相似文献
9.
Effects of exhaust gas recirculation （ EGR） on homogeneous charge combustion of n-heptane was studied through simulation and experiment. Experiments were carried out in a single cylinder, four-stroke, air cooled engine and a single cylinder, two-stroke, water cooled engine. In the four-stroke engine, experiments of the effects of EGR were examined using heated N2 addition as a surrogate for external EGR and modifying engine to increase internal EGR. The ignition timing was sensitive to EGR due to thermal and chemical effects. EGR or extra air is a key factor in eliminating knock during mid-load conditions. For higher load operation the only way to avoid knock is to control reaction timing through the use of spark ignition. Experimental and modeling results from the twostroke engine show that auto-ignition can be avoided by increasing the engine speed. The twostroke engine experiments indicate that high levels of internal EGR can enable spark ignition at lean conditions. At higher load conditions, increasing the engine speed is an effective method to control transition from homogeneous charge compression ignition （ HCCI） operation to non-HCCI operation and successful spark ignition of a highly dilute mixture can avoid serious knock. 相似文献
10.
Hochberg Katrin Becker Sebastian Louis Malte Klein Pascal Kuhn Jochen 《Journal of Science Education and Technology》2020,29(2):303-317
Journal of Science Education and Technology - Mobile devices (smartphones or tablets) as experimental tools (METs) offer inspiring possibilities for science education, but until now, there has been... 相似文献
11.
The current study investigated how a guidance method that segments a complex task into simpler subtasks affects adults’ inquiry-based learning in a science simulation environment. In a multivariate inquiry task, participants were asked to investigate the effects of all variables in one round of inquiry. In another group, participants were guided to investigate the effect of one variable at a time. The results indicate that the guided participants conducted more systematic and comprehensive investigations and reported a lower level of cognitive load compared with the unguided participants. The current findings provide implications for designing simulation-based learning environments to facilitate learning. (Keywords: scientific reasoning, inquiry learning, guidance, science education, cognitive load) 相似文献
12.
The purpose of this study is to examine the moderating role of cognitive load experience between students’ scientific epistemic beliefs and information commitments, which refer to online evaluative standards and online searching strategies. A total of 344 science-related major students participated in this study. Three questionnaires were used to ascertain the students’ scientific epistemic beliefs, information commitments, and cognitive load experience. Structural equation modeling was then used to analyze the moderating effect of cognitive load, with the results revealing its significant moderating effect. The relationships between sophisticated scientific epistemic beliefs and the advanced evaluative standards used by the students were significantly stronger for low than for high cognitive load students. Moreover, considering the searching strategies that the students used, the relationships between sophisticated scientific epistemic beliefs and advanced searching strategies were also stronger for low than for high cognitive load students. However, for the high cognitive load students, only one of the sophisticated scientific epistemic belief dimensions was found to positively associate with advanced evaluative standard dimensions. 相似文献
13.
Jon-Chao Hong Ming-Yueh Hwang Kai-Hsin Tai Chi-Ruei Tsai 《Research in Science Education》2017,47(6):1193-1212
Based on the cognitive-affective theory, the present study designed a science inquiry learning model, predict-observe-explain (POE), and implemented it in an app called “WhyWhy” to examine the effectiveness of students’ science inquiry learning practice. To understand how POE can affect the cognitive-affective learning process, as well as the learning progress, a pretest and a posttest were given to 152 grade 5 elementary school students. The students practiced WhyWhy during six sessions over 6 weeks, and data related to interest in learning science (ILS), cognitive anxiety (CA), and extraneous cognitive load (ECL) were collected and analyzed through confirmatory factor analysis with structure equation modeling. The results showed that students with high ILS have low CA and ECL. In addition, the results also indicated that students with a high level of self-confidence enhancement showed significant improvement in the posttest. The implications of this study suggest that by using technology-enhanced science learning, the POE model is a practical approach to motivate students to learn. 相似文献
14.
This study classified students into different cognitive load (CL) groups by means of cluster analysis based on their experienced CL in a gene technology outreach lab which has instructionally been designed with regard to CL theory. The relationships of the identified student CL clusters to learner characteristics, laboratory variables, and cognitive achievement were examined using a pre-post-follow-up design. Participants of our day-long module Genetic Fingerprinting were 409 twelfth-graders. During the module instructional phases (pre-lab, theoretical, experimental, and interpretation phases), we measured the students’ mental effort (ME) as an index of CL. By clustering the students’ module-phase-specific ME pattern, we found three student CL clusters which were independent of the module instructional phases, labeled as low-level, average-level, and high-level loaded clusters. Additionally, we found two student CL clusters that were each particular to a specific module phase. Their members reported especially high ME invested in one phase each: within the pre-lab phase and within the interpretation phase. Differentiating the clusters, we identified uncertainty tolerance, prior experience in experimentation, epistemic interest, and prior knowledge as relevant learner characteristics. We found relationships to cognitive achievement, but no relationships to the examined laboratory variables. Our results underscore the importance of pre-lab and interpretation phases in hands-on teaching in science education and the need for teachers to pay attention to these phases, both inside and outside of outreach laboratory learning settings. 相似文献