Mechanical Behavior in Perfobond Rib Shear Connector with UHPC-Steel Composite Structure with Coarse Aggregate

Maojun Duan,Shiyu Zhang,Xu Wang,Fenghui Dong 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.4

Using experimental and numerical analysis, this paper aims at investigating the mechanical behavior in Perfobond rib (PBL) shear connectors with ultrahigh-performance concrete (UHPC)-steel composite structures. Twelve push-out specimens fabricated according to the design used for the connectors in the UHPC-steel composite structures in bridges have been investigated. The main objective of this paper was to discuss the mechanism of failure and the influence of different parameters on PBL shear connectors mechanical properties, including the diameter of transverse rebar, hole spacing and number of holes. The results showed that the failure mode of this type is different from that of conventional concrete specimens. During the failure of specimens, there are few cracks and the overall stiffness still maintain a high level, and reveal that a balance between the size of transverse rebar and the diameter of the hole. In addition, the basic form of the ultimate bearing capacity of existing PBL shearing bonds is summarized, and a new concept of steel fiber shearing in UHPC is proposed. Finally, based on the elastic foundation beam model, the full curve calculation formula of UHPC single-hole PBL shear bond is derived by using Timoshenko beam element. The formula calculation results are in good agreement with the experimental values.

Chatter Detection and Identification in High-Efficient Robotic Milling CFRP Composites Using Acoustic Emission Technique

Maojun Li,Dingxiao Huang,Haobo Han,Xujing Yang 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.5

Industrial robots are preferred to be applied for machining lightweight, thin-walled and large aerospace composite components due to less energy consumption and flood coolant pollution, easier setup and portability compared to heavy machining centers. However, chatter is the main concern as robots present considerably lower stiffness than machine tools. This paper reported the first demonstration of applying acoustic emission (AE) technique to analyze chatter using short-time Fourier transform, fast Fourier transform and wavelet packet decomposition methods during high-speed robotic milling of CFRP composites for aerospace applications. The stability lobe diagram and surface topography were further investigated to verify chatter phenomenon. It was interesting to find that the energy distribution of decomposition components of acoustic emission signals and the maximum amplitude of AE data gradually concentrated from the tooth passing frequency to the rotation frequency of milling cutter when increasing spindle speed. The significant changes in maximum amplitude in frequency domain after 2500 low-pass filtered and surface topography clearly characterized the incidence of chatter. The stable operating zone indicated in the stability lobe diagram was validated by experimental results.

Ontology-Based Exchange of Product Data Semantics between CAD and CAE

Qinyi Ma,Yajun Wang,Yan Lv,Xin Jin,Maojun Zhou 보안공학연구지원센터 2014 International Journal of Multimedia and Ubiquitous Vol.9 No.12

The interoperation of various applications will need a representation that goes beyond the traditional geometry-based one, which is inadequate for capturing semantic information. This paper proposes an approach to annotate the CAD models based on ontology with the aim of making the design intent understood by computer and applied in engineering analysis, such as FEA. The paper presents the design domain ontology and FEA domain ontology, and applies feature technologies and the semantic Web to complete annotation. Semantic markup can embed the engineering semantic information such as product function, and design principle into the CAD geometry data through annotating, it makes the analyzers reuse design ideas quickly and conveniently to increase efficiency. The semantic file is proposed to support an exchange of product data semantics between CAD and CAE. The main idea of the approach is presented and key technologies are elaborated, including the creation of the FEA solution template, and the matching algorithm between semantic markup file and FEA template file. Finally, the feasibility and effectiveness of the approach is empirically validated by a case study.

Research on a new method to optimize the thermal characteristics of an engine nacelle cooling module

Lei Guo,Maojun Zhou,Jing Hu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.5

Heat reflow in the fan rotation center of a forced convection cooling system has a great influence on heat dissipation. In this research, a calculation model of the external flow field of an engine compartment’s cooling module was established. Computational fluid dynamics method was used to calculate and analyze the heat flow characteristics of the existing radiator. By comparing the calculations with the experimental results, the regions and the reasons for the heat reflow were found. The existing heat dissipation scheme was recalculated by using the secondary heat dissipation model, and an optimized and improved scheme was proposed to introduce a deflector cone structure to eliminate heat reflow. This structure was connected to the fan hood by four blades. The front end of the structure acted as a diversion for the conical structure, and the back end was a hollow cylinder structure, making it easier for the fluid to transition to the conical structure. Both ends and the distance between the vertebrae were set to range from 2-5 mm. The research results showed that the secondary heat dissipation model could more accurately describe the heat reflow problem of the engine compartment, the heat flow organization of the improved structure was more reasonable, and the temperature distribution was more uniform. Moreover, the theoretical heat dissipation effect of the improved structure was more than 10 % higher than that of the existing structure.

Experimental Study on Surface Integrity and Kerf Characteristics During Abrasive Waterjet and Hybrid Machining of CFRP Laminates

Xujing Yang,Xiangchen Lin,Maojun Li,Xiaogeng Jiang 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.12

The use of abrasive waterjet to cut CFRP laminates has been proved to be feasible with several advantages compared with traditional machining methods, while relatively poor surface quality and kerf taper impede its application in automotive industry. In this work, the influence of various process parameters including hydraulic pressure, cutting speed and stand-off distance on surface integrity and kerf characteristics was comprehensively studied. A statistical model was further developed using response surface method involving 17 trials. Statistical analysis found that higher level of cutting speed led to the decrease of kerf width and the increase of surface roughness. Based on optimizing the expected function of responses, the minimum taper error of 0.058 mm and superior surface roughness (Ra) of 3.58 μm were obtained. Furthermore, hybrid machining strategy integrating AWJ and CNC milling processes was proposed to cut CFRP laminate in order to obtain both high efficiency and superior surface quality. The depth of cut for post-milling process was set down to 0.1 mm. It was found that kerf taper was completely removed with relatively flat surface, and surface roughness (Ra ~ 1.20 μm) was reduced by up to 5.61 μm with an overall decrease of about 80%.

Dark Septate Endophyte (DSE) Fungi Isolated from Metal Polluted Soils: Their Taxonomic Position, Tolerance, and Accumulation of Heavy Metals In Vitro

Yujie Zhang,Yan Zhang,Maojun Liu,Xiaodong Shi,Zhiwei Zhao 한국미생물학회 2008 The journal of microbiology Vol.46 No.6

To understand the possible role of the plant root associated fungi on metal tolerance, their role in the uptake of heavy metals and the potential transfer of these metal ions to the plant, three strains of dark septate endophytic (DSE) fungi were isolated from a waste smelter site in southwest China, and one strain was isolated from a non-contaminated site. According to molecular phylogenetic analysis of the ITS 1-5.8S rDNA-ITS 2 gene regions and morphological characteristics, one is identified as Exophiala pisciphila, and the other three are non-sporulating fungi under the experiment condition with the nearest phylogenetic affinities to the Thysanorea papuana strain EU041814. Tolerance and accumulation abilities of the three DSE strains for metals were investigated in liquid culture. Minimum inhibitory concentrations (MIC) of Pb, Zn, and Cd were determined. It was demonstrated that the tolerance of the DSE strains varied between metal species and strains. The E. pisciphila strain is able to accumulate lead and cadmium over 20% and 5% of dry weight of biomass, respectively. Partial of the sequestrated metals can be washed with CaCl2. Morphological and enzyme activity changes taking place in the presence of excessive Pb, Cd, and/or Zn also indicate that the mechanism of heavy metal tolerance and accumulation of the DSE strains would be a complex process. The findings indicated promising tolerance and accumulation of the DSE strains with potential values in metal cycling and restoration of soil and water system.

Single Pixel Compressive Camera for Fast Video Acquisition using Spatial Cluster Regularization

( Yang Peng ),( Yu Liu ),( Kuiyan Lu ),( Maojun Zhang ) 한국인터넷정보학회 2018 KSII Transactions on Internet and Information Syst Vol.12 No.11

Single pixel imaging technology has developed for years, however the video acquisition on the single pixel camera is not a well-studied problem in computer vision. This work proposes a new scheme for single pixel camera to acquire video data and a new regularization for robust signal recovery algorithm. The method establishes a single pixel video compressive sensing scheme to reconstruct the video clips in spatial domain by recovering the difference of the consecutive frames. Different from traditional data acquisition method works in transform domain, the proposed scheme reconstructs the video frames directly in spatial domain. At the same time, a new regularization called spatial cluster is introduced to improve the performance of signal reconstruction. The regularization derives from the observation that the nonzero coefficients often tend to be clustered in the difference of the consecutive video frames. We implement an experiment platform to illustrate the effectiveness of the proposed algorithm. Numerous experiments show the well performance of video acquisition and frame reconstruction on single pixel camera.

High-frame-rate Video Denoising for Ultra-low Illumination

( Xin Tan ),( Yu Liu ),( Zheng Zhang ),( Maojun Zhang ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.11

In this study, we present a denoising algorithm for high-frame-rate videos in an ultra-low illumination environment on the basis of Kalman filtering model and a new motion segmentation scheme. The Kalman filter removes temporal noise from signals by propagating error covariance statistics. Regarded as the process noise for imaging, motion is important in Kalman filtering. We propose a new motion estimation scheme that is suitable for serious noise. This scheme employs the small motion vector characteristic of high-frame-rate videos. Small changing patches are intentionally neglected because distinguishing details from large-scale noise is difficult and unimportant. Finally, a spatial bilateral filter is used to improve denoising capability in the motion area. Experiments are performed on videos with both synthetic and real noises. Results show that the proposed algorithm outperforms other state-of-the-art methods in both peak signal-to-noise ratio objective evaluation and visual quality.

A putative pathogen-resistant regulatory pathway between MicroRNAs and candidate target genes in maize

Jian Gao,Mao Luo,Chun Zhang,Hua Peng,Haijian Lin,Yaou shen,Maojun Zhao,Guangtang Pan,Zhiming Zhang 한국식물학회 2015 Journal of Plant Biology Vol.58 No.4

MicroRNAs (miRNAs) are a family of small non-coding RNAs that, in most cases, negatively regulate gene expression at the post-transcriptional level. Plant miRNAs have been implicated in developmental processes and adaptation to environmental stress including biotic and abiotic stresses. Here, we report a comprehensive analysis of miRNAs and associated target genes under banded leaf and sheath blight (BLSB) stress caused by R. solani in maize. Eight differentially expressed miRNAs were randomly selected from deep sequencing results and validated by qRT-PCR together with their putative target genes, most of which are transcription factors as well as metabolic genes involved in auxin signaling. The results revealed that majorities of the analyzed miRNAs show an inverse correlation with their corresponding predicted target genes. In addition, a putative regulatory network of miRNAs-mRNAs responsive to R. solani was constructed. This study provides insight into the regulatory functions of miRNAs, thereby expanding our knowledge of the molecular mechanisms of pathogen resistance.

A Novel Video Stitching Method for Multi-Camera Surveillance Systems

( Xiaoqing Yin ),( Weili Li ),( Bin Wang ),( Yu Liu ),( Maojun Zhang ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.10

This paper proposes a novel video stitching method that improves real-time performance and visual quality of a multi-camera video surveillance system. A two-stage seam searching algorithm based on enhanced dynamic programming is proposed. It can obtain satisfactory result and achieve better real-time performance than traditional seam-searching methods. The experiments show that the computing time is reduced by 66.4% using the proposed algorithm compared with enhanced dynamic programming, while the seam-searching accuracy is maintained. A real-time local update scheme reduces the deformation effect caused by moving objects passing through the seam, and a seam-based local color transfer model is constructed and applied to achieve smooth transition in the overlapped area, and overcome the traditional pixel blending methods. The effectiveness of the proposed method is proved in the experiements.