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Experimental Study on Influence Factors and Empirical Formula of K0 for Coarse Grained Soil
Mingjie Jiang,Jungao Zhu,Shengshui Chen,Xiaodong Wang,Wanli Guo 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.8
The earth pressure coefficient at rest K0 is a key mechanical parameter of soil, so studying K0 of coarse grained soil has important theoretical value and practical significance in geotechnical engineering works. To investigate the influence factors of K0 for coarse grained soil, a series of K0 compression tests for a sandy gravel and a rockfill were conducted by utilizing a newly-developed largescale K0 device. The test data show that there is a negative linear correlation between K0 and initial relative density Dr0. The data also show that the increasing vertical effective stress will decrease the K0 value, and the effect of low on the K0 is more obvious. Large-scale consolidated drained (CD) triaxial tests for soils used for K0 compression test were carried out, and according to the data of CD triaxial tests and K0 compression tests the correlation between K0 and effective internal friction angle φ′ is established. Based on the result, an empirical equation is presented. This equation can be used to predict the K0 value of the coarse grained soil under a random consolidation condition and stress condition according to the value of φ′. Furthermore, this empirical formula is verified by K0 compression tested data.
Visual Tracking Algorithm Based on Probabilistic Graphical Model
Mingjie Zhang,Baosheng Kang 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.9
In complicated scene, in order to solve the temporal occlusion problem of target tracking, a novel particle filter tracking algorithm based on graphical model is proposed. Graphical model is applied to particle filtering in this method. Firstly, dividing the target into several key regions, and extracting the characteristic value of each region. Then, these regions are applied to construct graphical model. In the process of target tracking by using particle filter method, graphical models can compensate for the lacking information of the occluded region. The state of the occluded part can be inferred by the graphical model. Finally, experimental results have demonstrated that the proposed tracking algorithm is effective, and it can reliably track moving target.
Mingjie Shao,Wenke Liu,Lingyan Zha,Chengbo Zhou,Yubin Zhang,Baoshi Li 한국원예학회 2020 Horticulture, Environment, and Biotechnology Vol.61 No.6
This study investigated the eff ects of constant light and alternating relatively high-intensity (500 μmol m −2 s −1 ) and lowintensity(150 μmol m −2 s −1 ) red–blue LEDs (4R:1B) on the biomass production and quality of hydroponic purple-leaf lettuce( Lactuca sativa L. cv. ‘Zishan’) in an environmentally controlled plant factory. Four treatments were set up to separate1 h of high light into four diff erent alternating frequencies in a 24-h light−dark cycle (16/8 h): one time (A1), three times(A3), six times (A6), and twelve times (A12). In addition, one constant light treatment with the same daily light integral(DLI, 9.8 mol m −2 per day) as other treatments was set as the control (CK, 170 μmol m −2 s −1 ). The results indicated thatA6 signifi cantly reduced shoot fresh weight and increased the root–shoot ratio of lettuce compared with CK, but there wasno signifi cant diff erence among other treatments. Alternating light treatments did not promote the accumulation of solublesugar, soluble protein, and phenolic substances compared with CK. Meanwhile, A12 signifi cantly promoted the accumulationof total ascorbate (TA) in lettuce leaves compared with other treatments but decreased ascorbate/TA ratio. Above all, underthe same DLI condition, alternating high and low light did not have obvious positive eff ects on biomass production and theaccumulation of nutrient substance in lettuce under constant light was better than that under alternating light. Therefore,compared with the fl uctuating radiation with the same DLI, constant radiation is a better choice for lettuce production.
Mingjie Zhang,Jian Gang Yang,Wanfu Zhang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.3
Rotordynamic instability problem caused by seal force widely exists in turbomachines. The fluid-induced force in the seal is determined by the pressure distribution associated with the flow field structure, particularly with the circumferential flow characteristics. In the previous study, the authors found that the helix-comb seal can effectively change the circumferential flow field. The specially designed helical deflectors can reverse the circumferential flow direction of the fluid inside the seal. A considerable static stability enhancement is obtained. However, the transient rotordynamic characteristics of the helix-comb seal are not reported. In the present study, the transient rotordynamic characteristics of the helix-comb seal are investigated further. The rotordynamic coefficients, effective damping, and aerodynamic work of the helix-comb seal are calculated and compared with those of the labyrinth seal. Results reveal that compared with the labyrinth seal, the helix-comb seal considerably improves rotordynamic stability, particularly at a high preswirl ratio. The desirable rotordynamic stability can be obtained with flow field control.
Nonlinear vibration of FG-CNTRC curved pipes with temperature-dependent properties
Mingjie Liu,Shaoping Bi,Sicheng Shao,Hadi Babaei 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.46 No.4
In the current research, the nonlinear free vibrations of curved pipes made of functionally graded (FG) carbon nanotube reinforced composite (CNTRC) materials are investigated. It is assumed that the FG-CNTRC curved pipe is supported on a three-parameter nonlinear elastic foundation and is subjected to a uniform temperature rise. Properties of the curved nanocomposite pipe are distributed across the radius of the pipe and are given by means of a refined rule of mixtures approach. It is also assumed that all thermomechanical properties of the nanocomposite pipe are temperature-dependent. The governing equations of the curved pipe are obtained using a higher order shear deformation theory, where the traction free boundary conditions are satisfied on the top and bottom surfaces of the pipe. The von Kármán type of geometrical non-linearity is included into the formulation to consider the large deflection in the curved nanocomposite pipe. For the case of nanocomposite curved pipes which are simply supported in flexure and axially immovable, the motion equations are solved using the two-step perturbation technique. The closed-form expressions are provided to obtain the small- and large-amplitude frequencies of FGCNTRC curved pipes rested on a nonlinear elastic foundation in thermal environment. Numerical results are given to explore the effects of CNT distribution pattern, the CNT volume fraction, thermal environment, nonlinear foundation stiffness, and geometrical parameters on the fundamental linear and nonlinear frequencies of the curved nanocomposite pipe.
Mingjie Zhang,Jian Gang Yang,Wanjun Xu,Yalei Xia 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.5
Minimizing unwanted leakage between stationary and rotating parts is the main function of annular seals. A Mixed labyrinth seal (MLS) with two specially designed lateral teeth installed on a Staggered labyrinth seal (SLS) is proposed to improve seal performance. A 3D computational fluid dynamics calculation model of MLS is set up. The twin vortex structure that appears in the seal cavity and flow path is more complicated in MLS than in SLS. MLS reduces leakage by about 30 % compared with SLS. Rotordynamic analysis of MLS is also conducted by calculating cross-coupled stiffness. The cross-coupled stiffness of MLS is about 75 % to 85 % that of SLS. The dependence of seal performance on the parameters of the lateral teeth is investigated through a simulation test. The lateral teeth should be set in the middle of the seal cavity, and the gap between the two lateral teeth should be similar to the tip clearance.