DEVELOPMENT OF AN ENGINE CALIBRATION MODEL USING GAUSSIAN PROCESS REGRESSION

Tianhong Pan,Yang Cai,Shan Chen 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.2

To enhance the calibration efficiency, reduce the fuel consumption and improve the emission performance of the engine, a calibration method using Gaussian Process Regression (GPR) is proposed in this work. First, the design of experiment (DoE) is constructed by using the Space-filling method, and the engine bench sampling test is implemented according to results of DoE. Then, the square exponential covariance function is selected through the comparison of four covariance functions, and the corresponding hyper-parameters are optimized by using Newton gradient algorithm. Finally, the GPR model of the engine is established and its calibration performance is validated by the experimental data. The comparison shows that the performance of the developed GPR model is superior to the Polynomial model and Neural Network model, whose coefficient of determination (R2) of Fuel Consumption (FC), NOx emission (NOx) and Soot emission (Soot) are up to 0.9980, 0.9326 and 0.9247. The case study demonstrates that the virtual calibration optimization based on GPR model improves the fuel consumption performance greatly, while taking NOx and Soot emission indicators into account.

Numerical analysis on scale effect of elasticity, strength and failure patterns of jointed rock masses

Peitao Wang,Tianhong Yang,Tao Xu,Meifeng Cai,Changhong Li 한국지질과학협의회 2016 Geosciences Journal Vol.20 No.4

It is of great importance to study the failure process and scale effect of jointed rock mass in the field of rock mechanics and mining engineering. In the present paper, initially the uniaxial compression test on granite was performed and acoustic emission (AE) sequence was acquired during the compression process in laboratory. Results from numerical simulations using the particle flow code in two dimensions (PFC2D) were presented, and compared with experimental measurements. It was observed that the approach was reasonably good in predicting the real response of granite rock samples. The mechanical parameter of joint model was then calibrated based on PFC2D model with experimental results. Finally the mechanical properties of complex rocks with discrete fracture network (DFN) were studied and scale effects on the elasticity and strength were then investigated. The result showed that the failure pattern was similar when the ratio of joint contact bond strength (both shear and normal) to rock contact bond strength was in the range of 3~9%. The elastic modulus and strength parameters were changed with the sizes of rock sample for DFN models. Moreover, the variation of rock failure pattern under different sizes was also studied and finally the representative elementary volume (REV) size of the considered rock mass was estimated to be 9 × 9 m. It is suggested that the failure pattern analysis should be considered in the REV study of jointed rock mass.

Life Cycle of Dermacentor everestianus Hirst, 1926 (Acari: Ixodidae) under Laboratory Conditions

Shang Jin,Tianhong Wang,Tuo Li,Ming Liu,Qingying Jia,Xiaolong Yang,Hui Wang,Zhijun Yu,Jingze Liu 대한기생충학열대의학회 2017 The Korean Journal of Parasitology Vol.55 No.2

IMPROVED HYBRID A-STAR ALGORITHM FOR PATH PLANNING IN AUTONOMOUS PARKING SYSTEM BASED ON MULTI-STAGE DYNAMIC OPTIMIZATION

Meng Tianchuang,Yang Tianhong,Huang Jin,Jin Wenrui,Zhang Wei,Jia Yifan,Wan Keqian,Xiao Gang,Yang Diange,Zhong Zhihua 한국자동차공학회 2023 International journal of automotive technology Vol.24 No.2

The recent proliferation of intelligent technologies has promoted autonomous driving. The autonomous parking system has become a popular feature in autonomous driving. Hybrid A-star algorithm is a commonly used path planning algorithm for its simplicity to deploy and the good characteristics of the generated paths in the practical engineering. To further enhance the path safety and efficiency of path planning in the autonomous parking system, this paper proposes an improved hybrid A-star algorithm through the safety-enhanced design and the efficiency-enhanced design. The safety-enhanced design integrates the Voronoi field potential into the path searching stage to take more account of path safety. The efficiency-enhanced design proposes a multi-stage dynamic optimization strategy which divides the path planning into multiple stages and performs dynamic optimization in each stage. Through simulation experiments, it is verified that the proposed improved algorithm not only generates a much safer path which stays farther from the obstacles but also significantly improves the searching efficiency in terms of time and space, merely at a finite cost of pre-processing work which can also be repeatedly utilized. We hope this paper will promote relative research on path planning in autonomous parking and serve as a reference for the practical engineering.

A comparative study of hydraulic fracturing with various boreholes in coal seam

Honglei Liu,Tianhong Yang,Tao Xu,Qinglei Yu 한국지질과학협의회 2015 Geosciences Journal Vol.19 No.3

Comparative numerical study on hydraulic fracturing with various boreholes in coal seam combined with in situ experiments was carried out to investigate the fracturing mechanism and loosening effect of hydraulic fracturing in coal seam. Hydraulic fracturing models with single-borehole, three-borehole and fiveborehole were built based on in situ tests in Chengshan coalmine, Jixi city, Heilongjiang province, China and the changes of water pressure and shear stress around boreholes during hydraulic fracturing were analyzed. The influence of hydraulic fracturing with controlling borehole on crack initiation and propagation was discussed. According to the in situ testing results, it is found that controlling boreholes in hydraulic fracturing not only can control the direction of crack propagation, but also can judge the effect of crack initiation and breakdown. The work in this paper is of great importance for the design of hydraulic fracturing technology and the alternative of the parameters in theory and practice.

Impact of rock microstructures on failure processes - Numerical study based on DIP technique

Yu, Qinglei,Zhu, Wancheng,Tang, Chun'an,Yang, Tianhong Techno-Press 2014 Geomechanics & engineering Vol.7 No.4

It is generally accepted that material heterogeneity has a great influence on the deformation, strength, damage and failure modes of rock. This paper presents numerical simulation on rock failure process based on the characterization of rock heterogeneity by using a digital image processing (DIP) technique. The actual heterogeneity of rock at mesoscopic scale (characterized as minerals) is retrieved by using a vectorization transformation method based on the digital image of rock surface, and it is imported into a well-established numerical code Rock Failure Process Analysis (RFPA), in order to examine the effect of rock heterogeneity on the rock failure process. In this regard, the numerical model of rock could be built based on the actual characterization of the heterogeneity of rock at the meso-scale. Then, the images of granite are taken as an example to illustrate the implementation of DIP technique in simulating the rock failure process. Three numerical examples are presented to demonstrate the impact of actual rock heterogeneity due to spatial distribution of constituent mineral grains (e.g., feldspar, quartz and mica) on the macro-scale mechanical response, and the associated rock failure mechanism at the meso-scale level is clarified. The numerical results indicate that the shape and distribution of constituent mineral grains have a pronounced impact on stress distribution and concentration, which may further control the failure process of granite. The proposed method provides an efficient tool for studying the mechanical behaviors of heterogeneous rock and rock-like materials whose failure processes are strongly influenced by material heterogeneity.

Theoretical investigation of deformation characteristics of stratified rocks considering geometric and mechanical variability

Peitao Wang,Meifeng Cai,Fenhua Ren,Changhong Li,Tianhong Yang 한국지질과학협의회 2017 Geosciences Journal Vol.21 No.2

Anisotropy is one of the most distinct features of stratified rock mass and it must be considered in engineering design and stability analysis. On the basis of linear elastic theory and displacements equivalence, a computational model considering elastic anisotropy was established. The equivalent elastic modulus and equivalent Poisson’s ratio of the stratified rock perpendicular and parallel to the loading direction were discussed. The relations of material properties and geometry parameters with the equivalent elastic modulus and equivalent Poisson’s ratio in two directions were studied. Uniaxial compressive test was conducted and the elastic modulus and Poisson’s ratio in the proposed model agreed well with experimental results. The comparison between a comprehensive set of experimental data and theoretical analysis data proves that the proposed constitutive model can effectively characteristic the mechanical behavior of stratified rocks. The proposed model can consider the effects of material parameters and geometry parameters of rock and joints on the mechanical behavior of stratified rock mass. Moreover, the elastic anisotropy was considered in the model. Thus, the model can supply some valuable reference in studying deformation of stratified rock mass and engineering design.

KETCH1 imports HYL1 to nucleus for miRNA biogenesis in <i>Arabidopsis</i>

Zhang, Zhonghui,Guo, Xinwei,Ge, Chunxiao,Ma, Zeyang,Jiang, Mengqiu,Li, Tianhong,Koiwa, Hisashi,Yang, Seong Wook,Zhang, Xiuren National Academy of Sciences 2017 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.114 No.15

<P>MicroRNA (miRNA) is processed from primary transcripts with hairpin structures (pri-miRNAs) by microprocessors in the nucleus. How cytoplasmic-borne microprocessor components are transported into the nucleus to fulfill their functions remains poorly understood. Here, we report KETCH1 (karyopherin enabling the transport of the cytoplasmic HYL1) as a partner of hyponastic leaves 1 (HYL1) protein, a core component of microprocessor in Arabidopsis and functional counterpart of DGCR8/Pasha in animals. Null mutation of ketch1 is embryonic-lethal, whereas knockdown mutation of ketch1 caused morphological defects, reminiscent of mutants in the miRNA pathway. ketch1 knockdown mutation also substantially reduced miRNA accumulation, but did not alter nuclear-cytoplasmic shuttling of miRNAs. Rather, the mutation significantly reduced nuclear portion of HYL1 protein and correspondingly compromised the pri-miRNA processing in the nucleus. We propose that KETCH1 transports HYL1 from the cytoplasm to the nucleus to constitute functional microprocessor in Arabidopsis. This study provides insight into the largely unknown nuclear-cytoplasmic trafficking process of miRNA biogenesis components through eukaryotes.</P>