Numerical Simulation of the Thermal Stress Field during Vertical Bridgman CdZnTe Single Crystal Growth

Juncheng Liu,Guodong Zhang 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5

The thermal stress field of CdZnTe single crystals grown with the vertical Bridgman method was simulated with the thermal elastic finite-element model. The effects of the growth parameters, the furnace temperature gradient, the crucible descending velocity, and the thickness of the graphite lm plating on the quartz crucible inner wall, on the thermal stress field were investigated. The stress at the crystal's edge is much larger than that at the crystal's center, and the stress at the crystal's bottom is larger than that at the crystal's top. Them aximum stress 'σmax'appearsat the location where the crystal adhere to the crucible's inner wall. When the furnace's temperature gradient was increased from 5 K/cm to 20 K/cm, the stress in the crystal increased a great deal. If no graphite lm was plated on the crucible's inner wall, the stress at the crystal's l edge increased several times while the stress at the crystal's center increased only a little. On the contrary, when the thickness of the graphite film was increased from 250 μm to 500 μm, up to a pure graphite crucible, the stress at the crystal's edge decreased a little, while the stress at the crystal's center decreased a lot. In the range of the 0.5 ∽ 3 mm/h, the crucible's descending velocity had little effect on the stress.

Cyclic behaviour and modelling of stainless-clad bimetallic steels with various clad ratios

Xinpei Liu,Huiyong Ban,Juncheng Zhu,Brian Uy 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.34 No.2

Stainless-clad (SC) bimetallic steels that are manufactured by metallurgically bonding stainless steels as cladding metal and conventional mild steels as substrate metal, are kind of advanced steel plate products. Such advanced composite steels are gaining increasingly widespread usage in a range of engineering structures and have great potential to be used extensively for large civil and building infrastructures. Unfortunately, research work on the SC bimetallic steels from material level to structural design level for the applications in structural engineering field is very limited. Therefore, the aim of this paper is to investigate the material behaviour of the SC bimetallic steels under the cyclic loading which structural steels usually could encounter in seismic scenario. A number of SC bimetallic steel coupon specimens are tested under monotonic and cyclic loadings. The experimental monotonic and cyclic stress-strain curves of the SC bimetallic steels are obtained and analysed. The effects of the clad ratio that is defined as the ratio of the thickness of cladding layer to the total thickness of SC bimetallic steel plate on the monotonic and cyclic behaviour of the SC bimetallic steels are studied. Based on the experimental observations, a cyclic constitutive model with combined hardening criterion is recommended for numerical simulation of the cyclic behaviour of the SC bimetallic steels. The parameters of the constitutive model for the SC bimetallic steels with various clad ratios are calibrated. The research outcome presented in this paper may provide essential reference for further seismic analysis of structures fabricated from the SC bimetallic steels.

Mussel-Inspired Multifunctional Coating for Enhancing the UV-Resistant Property of Polypropylene Fibers

Zhengyi Liu,Juncheng Hu,Qi Sun,Li Chen,Xia Feng,Yiping Zhao 한국고분자학회 2017 Macromolecular Research Vol.25 No.5

In this paper, UV-resistant polypropylene (PP) fibers were prepared with a simple and versatile strategy. The PP fiber was firstly coated a polydopamine (PDA) layer by simply dipping the fiber into an alkaline dopamine solution. Then, the titania (TiO2) nanoparticles were chemically bound to the PDA layer through the reduction capacity of catechol groups in PDA, endowing the fibers with excellent UVresistant properties. The surface chemical composition of modified fibers was confirmed by attenuated total reflectance fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The surface morphology and the crystalline structure of the modified fibers were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively. Thermo stability was characterized by thermogravimetry analysis. Besides, the mechanical and UV protection properties were further investigated through monofilament tensile and the UV transmittance test. The results showed that the PDA and TiO2 were successfully coated on fiber surface. Comprared to the pristine fiber, the modified fiber exhibited better thermal stability. Particularly, the as-prepared PP-PDA-TiO2 fibers could strongly resist the UV rays with no change in mechanical properties.

A Windowed-Total-Variation Regularization Constraint Model for Blind Image Restoration

Ganghua Liu,Wei Tian,Yushun Luo,Juncheng Zou,Shu Tang 한국정보처리학회 2022 Journal of information processing systems Vol.18 No.1

Blind restoration for motion-blurred images is always the research hotspot, and the key for the blind restorationis the accurate blur kernel (BK) estimation. Therefore, to achieve high-quality blind image restoration, thisthesis presents a novel windowed-total-variation method. The proposed method is based on the spatial scale ofedges but not amplitude, and the proposed method thus can extract useful image edges for accurate BKestimation, and then recover high-quality clear images. A large number of experiments prove the superiority.

An Improved Eclat Algorithm for Mining Association Rules Based on Increased Search Strategy

Zhiyong Ma,Juncheng Yang,Taixia Zhang,Fan Liu 보안공학연구지원센터 2016 International Journal of Database Theory and Appli Vol.9 No.5

Although Eclat algorithm is an efficient algorithm for mining association rules, there are some disadvantages which limit the efficient of Eclat. In this paper, we proposed an improved Eclat algorithm called Eclat_growth which is based on the increased search strategy. There are three main steps in the Eclat_growth algorithm. First, it scans the database and stores it into a table using vertical data format. Then, it builds an increased two-dimensional pattern tree and the TID_sets of itemsets in the vertical data format table are added into the pattern tree row by row. New frequent itemsets are generated by combining the new added item data with the existing frequent itemsets in the pattern tree. Finally, all frequent itemsets can be found by picking up all nodes of the pattern tree. In the process of generating new frequent itemsets, the prior knowledge is used to fully clip the candidate itemsets. In the process of generating an intersection of two itemsets and calculating the support degree, we proposed a new method called BSRI (Boolean array setting and retrieval by indexes of transactions) to reduce the run time. By comparing Eclat_growth with Eclat, Eclat-diffsets, Eclat-opt and hEclat, it is indicated that Eclat_growth has the highest performance in mining associating rules from various databases.

Effects of Sb doping on the structure and properties of SnO2 films

Mingyue Sun,Juncheng Liu,Beiping Dong 한국물리학회 2020 Current Applied Physics Vol.20 No.3

Transparent heat-insulating SnO2 films were prepared on the glass substrate with sol-gel. The effects of Sb doping on the structure and photoelectric properties of the films were investigated. The films were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), Ultraviolet–Visible-Near Infrared Spectrometer (UV-VIS-NIR) and Hall Effect tester. The results show that the doping of Sb did not change the basic crystal structure of the SnO2 film, but reduced the crystallinity of the film. With the increase of Sb doping, the grain size decreases first and then maintains basically invariable. The sheet resistance of the film decreases first and then increases. The transmittance of the substrate glass coated with this film (hereinafter referred to as the film's transmittance) in the near-infrared region (780–2500 nm) decreases from 92.55% to 60.48%, and increases a little when the doping amount exceeded 11 mol%. And its transmittance of visible light (380–780 nm) fluctuated slightly between about 81% and 86%.

A Simulation Study on the Impact of Abandoned Trolley Cases on Pedestrian Evacuation

Dongyue Xu,Jinghong Wang,Juan Liu,Yan Wang,Juncheng Jiang 대한토목학회 2023 KSCE JOURNAL OF CIVIL ENGINEERING Vol.27 No.3

Many pedestrians empirically think that discarding luggage can improve evacuation efficiency, but it is unclear whether discarding luggage is an effective evacuation strategy. Previous models also oversimplified the interference of abandoned luggage on pedestrians. Hence, an extended social force model integrates pedestrian interaction with abandoned luggage like trolley cases was firstly proposed. A simulation based on a real metro station was carried out to examine the effectiveness of evacuation strategy like abandoning trolley cases at the bottleneck such as gate machine and metro carriage door, and the influence mechanism of abandoned trolley cases on pedestrians was investigated. The results show that discarding the trolley cases at the gate machine and at the metro carriage door cannot improve evacuation efficiency but increase the evacuation time by 78.7% and 14.9% at these two positions when the carrying ratio is 50%, respectively. When the occupancy rate of trolley case at the gate machine and metro carriage door is below 19% and 11%, pedestrians tend to detour the abandoned trolley cases and this behavior significantly increased the collisions between pedestrians at bottlenecks, and when the occupancy rate exceeds, they tend to push aside the trolley cases and the evacuation efficiency is further reduced.

Effects of SiC content on microstructure and properties of carbon/ceramic conductive composites

Xiao Gao,Xin Zheng,Jie Gao,Juncheng Liu,Jiahai BAI,Guoliang Yuan 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.12

The effects of SiC content on the phase composition, microstructure, sintering performance, mechanical and electricalproperties of the carbon/ceramic conductive composites were investigated. The results show that when SiC content increasesfrom 1 wt% to 3 wt%, lamellar graphite structure can be seen in the microstructure of the composites, and the porosity andwater absorption increases gradually. With further increase of SiC content to 6 wt% and 9 wt%, lamellar graphite disappears,and granular SiC crystals fill in the ceramic phase, thus increasing the densification degree of the composites. When SiCcontent is in the range of 1 wt% to 3 wt%, the shrinkage rate decreases sharply while the weight loss decreases a little. As SiCcontent increases from 3 wt% to 9 wt%, both the shrinkage rate and weight loss basically keep unchanged. With the increaseof SiC content, the bending strength of the composites first decreases and then increases, and finally reaches the peak value at9 wt% SiC. However, the resistivity presents an opposite variation trend, and the conductivity is best as SiC content is 9 wt%.

Transcriptome profile of one-month-old lambs' granulosa cells after superstimulation

Wu, Yangsheng,Lin, Jiapeng,Li, Xiaolin,Han, Bing,Wang, Liqin,Liu, Mingjun,Huang, Juncheng Asian Australasian Association of Animal Productio 2017 Animal Bioscience Vol.30 No.1

Objective: Superstimulatory treatment of one-month-old lambs can achieve synchronous development of numerous growing follicles. However, these growing follicles cannot complete maturation and ovulation. Oocyte maturation and competence are acquired during follicular development, in which granulosa cells play an essential role. Methods: In this study, we applied RNA sequencing to analyze and compare gene expression between prepubertal and adult superstimulated follicle granulosa cells in sheep. Results: There were more than 300 genes that significantly differed in expression. Among these differently expressed genes, many extracellular matrix genes (EGF containing Fibulin Like Extracellular Matrix Protein 1, pentraxin 3, adrenomedullin, and osteopontin) were significantly down-regulated in the superstimulated follicles. Ingenuity pathway and gene ontology analyses revealed that processes of axonal guidance, cell proliferation and DNA replication were expressed at higher levels in the prepubertal follicles. Epidermal growth factor, T-Box protein 2 and beta-estradiol upstream regulator were predicted to be active in prepubertal follicles. By comparison, tumor protein P53 and let-7 were most active in adult follicles. Conclusion: These results may contribute to a better understanding of the mechanisms governing the development of granulosa cells in the growing follicle in prepubertal sheep.

Influence of raw material grain composition on the properties of fused silica ceramics

Qingtao Wang,Sen Li,Huaqin Yu,Fengzhi Li,Huijun Xu,Haibo Qiao,Juncheng Liu,Qingyang Du 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.8

Fused silica ceramics were prepared by slip casting method with various particle sizes (d50 ≈ 2.31 μm, 19.79 μm, and 71.46 μm)from three types of fused silica powder. The influence of raw material grain composition on the viscosity of slurry, bulk density,porosity, water absorption, and flexural strength of the fused silica ceramics was investigated. The slurry viscosity wasmeasured by an XND-1 viscometer. The bulk density, porosity, and water absorption of the sintered samples were obtainedby the Archimedes method. The flexural strength was measured by a three-point bending test. The phase composition andmicrostructure of the samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Theresults show that when the grain composition was 5 : 3 : 2, slurry viscosity was 150.79 mPa·s with solid content of 75%, thefused silica ceramic particles were packed most tightly and demonstrate bulk density of 2.02 g/cm3, porosity of 6.99%, waterabsorption of 3.47%, and flexural strength of 51.27 MPa.