203 publications from this institution
ABSTRACT To explore the potential application of CFRTP in primary aircraft load‐bearing structures, this study proposes a novel hybrid welded/bolted joining method for heterogeneous CFRTP/titanium alloy structures. Various characterization techniques were employed to investigate the low‐velocity impact response and residual tensile properties of single welded joint (SWJ), single bolted joint (SBJ), and hybrid welded/bolted joint (HWBJ). The results indicate that, compared with SBJ and SWJ, HWBJ exhibits significant advantages in improving stress distribution and controlling local deformation. Specifically, HWBJ demonstrates the lowest peak force (2.45 kN), prolonged load duration (10.23 ms), maximum elastic recovery rate (56.33%), and minimal energy absorption rate (72.76%), highlighting its superior impact damage control capability. This mechanistic advantage directly translates into a smaller delamination damage projection area (245 mm 2 ) and a higher post‐impact interfacial failure load (6.60 kN). The synergistic consolidation effect—where welding provides local rigidity while bolting suppresses crack propagation—is considered the key mechanism underlying the superior performance of HWBJ. Overall, this study conclusively underscores the considerable potential of HWBJ as a reliable joining solution, providing both theoretical support and experimental paradigms for innovations in heterogeneous material joining technology, thereby facilitating the advancement of aerospace manufacturing toward high performance and sustainability.
Based on Johansen yield theory (European yield model) and experimental observations, mechanical models and capacity equations for nail connectors used in wood-frame shear walls with cross-prefabricated ply-bamboo sheathing panels were studied. Embedment strength of ply-bamboo panel was obtained in accordance with a British Standards Institution (BSI) standard. Monotonic and cyclic tests of nails applied in timber-bamboo shear walls were performed to validate the capacity equations. The adopted capacity equation based on European yield model meets the test results well, in the average and with a reduced scatter. The theoretical and experimental results obtained from the research suggested a capacity model and equations to predict the bearing capacity of timber-bamboo nail connections, indicating that ply-bamboo panels can be used as sheathings for light-weight timber structures, as well as included in existing timber design code.
Software problems – problems whose solution is software-intensive – come in many forms. Given that software and computers are deeply embedded in society, one general characteristic of software problems is that their early requirements are expressed “deep into the world”, i.e., in terms that end-users and other stake-holders would recognise and understand. The developer is left with the difficult task of interpreting such requirements closer to the software solution. In this paper, we introduce problem reduction, a systematic transformation from requirements to specifications by which a software problem with requirements deep in the world becomes a simpler software problem with the same solution. Problem reduction helps the developer because the simpler problem has requirements that are ‘closer to the machine’, i.e., closer to specification. Indeed, repeated application of problem reduction can lead directly to a software specification in certain cases. We reflect on how problem reduction captures certain requirements engineering practices, and provide a set of rules for its application.
Recently, air quality has become a hot topic due to its profound impact on the quality of the human living environment. This paper selects the tourist city of Dalian as the research object. The concentration and spatial distribution of PM10 and NO2 in the main urban area were analyzed during the peak tourist seasons in summer and winter. Simulations were used to explore the spatial and temporal variation patterns of PM10 and NO2, combining building and road density at different scales to reveal the coupling relationship between individual pollutant components and urban parameters. The results show that the PM10 concentration is high in the center and NO2 is concentrated in the northern district of Dalian City. In an area with a radius of 100 m, the dilution ratio of building density and road density to the concentration of the PM10 pollutants is at least 43%. Still, the concentration of NO2 is only coupled with road density. This study reveals the spatial and temporal variation patterns of PM10 and NO2 in Dalian, and finds the coupling relationship between the two pollutants and building density and road density. This study provides a reference for preventing and controlling air pollution in urban planning.
One or two stories lightweight glubam structures based on industrialized ply-bamboo panels, along with corresponding mechanical researches have been introduced in this paper. The main structural elements, especially the lightweight frame shear wall with its metal connections, and its mechanical performance have been studied in recent 10 years. The modelling and design of such structure can be based on connection system information. The performance of a prototype house from 2009 to 2019 were also reported at the end of this paper. Existing researches indicated that the lightweight glubam structures has large potential to be widely used as residential or small commercial structures in city or rural regions.
Distribution network reconfiguration is a complex and discrete nonlinear combinatory optimization problem. In this paper, an adaptive harmony search algorithm based on positive feedback (PFAHSA) is proposed to solve the problem for reducing power loss in distribution systems. The PFAHSA incorporates a local optimal method based on positive feedback mechanism into traditional harmony improvising criteria for better utilization of harmony memory (HM) and higher convergence speed. The algorithm parameters are updated adaptively by modified entropy, which measures the diversity of HM, to avoid prematurity and improve search success rate. The proposed method is testified on the IEEE 33- and 69-bus systems and is compared with other conventional approaches. Simulation results show that the proposed method features faster optimization speed and better global convergence performance.
Fracture failure occurred in the control arm of the rear axle suspension of a certain vehicle model. To determine the root cause of the failure, comprehensive analyses were conducted, including macroscopic fracture examination, microscopic fracture analysis, microstructural characterization, and hardness testing. The results indicate that the failure was caused by the combined effects of material defects, improper manufacturing processes, and service loading conditions. The fundamental cause of the fracture lies in the initiation of microcracks at the interface between coarse Al-Fe-Si-Mn inclusions and the matrix under cyclic loading. The presence of a strength gradient induced by local segregation of Si further accelerated crack propagation along the inclusion/matrix interface. Under cyclic stress, the cracks propagated progressively through a fatigue striation mechanism and exhibited intergranular fracture in the precipitation-enriched zones along grain boundaries. Ultimately, these factors led to premature fatigue failure of the control arm.
In order to discuss the physiological characteristics of salt tolerance in peppermint and provide the theoretical basis for its development and utilization in saline areas, the effects of different concentrations of NaCl(0, 100,150, 200, 250 mmol/L) on the growth and antioxidant system of peppermint were studied. The results showed that peppermint could keep normal growth under 100 and 150 mmol/L NaCl stress by up-regulating the activities of antioxidant enzymes(SOD, POD, CAT, APX) and the contents of non-enzymatic antioxidant(AsA, GSH, carotenoid) to alleviate NaCl-induced oxidative stress. With the increase of concentrations of NaCl treatment(200 and 250 mmol/L), the activities of antioxidant enzymes and the contents of non-enzymatic antioxidant initially increased but then decreased within the duration of NaCl treatment, which resulted in the growth inhibition of peppermint. The higher the concentrations of NaCl, the more the enzyme activities and antioxidant contents reduced. In all, the results demonstrated that peppermint could tolerate 150 mmol/L NaCl stress. Under this concentration of NaCl stress, peppermint had stronger antioxidant capacity and could maintain normal growth. However, peppermint plants would be damaged under higher concentrations of NaCl stress.
In order to investigate the evolution regularity of pore water pressure in loess slope under the influence of rainfall,the tests on spot artificial rainfall simulation and pore water pressure on a typical part of loess slope in Niujiaogou of Huxian County are carried out. The experimental result indicates that( 1) the pore water pressure is affected by rainfall intensity,rainfall duration and slope soil thickness under the condition of artificial rainfall simulation;( 2) when daily rainfall is 274 mm and continuous rainfall lasts more than 4 d,the pore water pressure of shallow slope within 2. 0 m is in turn reduces from the outside to the inside,the increasing degree of pore water pressure successively gets smaller, there is a hysteresis phenomenon for pore water pressure during the process of rainfall,the lag period is 10 h at the depth of0. 4 m,and the soil lag period is extended below 0. 4 m;( 3) the pore water pressure of soil below 2. 0 m depth is not affected;( 4) the pore water pressure is successively decreases from the inside to the outside after the rain stops,the pore water pressure reduce most rapidly during 24 h,and it gradually slows down after 2- 3 d,afterwards it gradually become stable.
Abstract Engineered bamboo products have been increasingly used in construction. However, there are few studies on its shear performance. Thus, the shear properties of bamboo lamina strips were investigated by the Iosipescu shear test. This study aimed to obtain the shear stress-strain curves and the lamina’s corresponding strength and modulus values, which can be used to design and model bamboo structural components. With this goal, 120 specimens were tested, considering the effect of loading directions on bamboo fiber, the existence of bamboo nodes, standard thickness, and fiber volume fraction. The characteristic shear strength values were also estimated based on the test data. Results show that the bamboo nodes and standard thickness have a negligible effect on the shear modulus and strength values. In contrast, the shear properties were determined by the loading directions and fiber volume fraction. The specimens’ measured shear strength and modulus loaded parallel/perpendicular to the bamboo fiber direction were about 10 MPa/15 MPa and 550 MPa/1000 MPa. The fiber and matrix-dominate failure modes were noticed for the specimens, and the unidirectional bio-fiber reinforced composite theoretical model could be used to predict the modulus values of fiber-dominate samples based on the measured volume fraction of the fiber.
