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RISS 인기검색어
- 검색키워드
- 저자 : Jiancheng Dong (검색결과 3 건)
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Hao Jiancheng,Li Zhaoyu,Li Xiangyu,Xie Fubao,He Dong,Tang Kai 한국CDE학회 2022 Journal of computational design and engineering Vol.9 No.5
When machining a complex freeform part, using a non-spherical tool could significantly improve the machining efficiency, as one can adaptively adjust the tool posture to maximize its contact area with the part surface. However, since adjusting the tool posture requires changing the tool orientation, a five-axis machine tool is needed, which is extremely expensive as compared to a conventional three-axis machine tool. Moreover, for a complex freeform surface with high curvature variation, to match its curvature change, the tool axis has to drastically change accordingly, thus inducing high velocity and acceleration on the machine tool’s rotary axes. To address these issues, in this paper we propose a partition-based 3 + 2-axis strategy for machining a general complex freeform surface with a non-spherical tool. As only a finite small number of distinct tool orientations are needed for 3 + 2-axis machining, an indexed three-axis machine tool suffices, thus relieving the need of an expensive five-axis machine tool. In addition, the much-increased rigidity of the three linear axes of the machine tool will greatly improve the kinematics and dynamics of the machine tool and thus enhance the machining accuracy. Experiments in both computer simulation and physical machining are carried out, whose results confirm that, when compared to using a conventional spherical cutter, by using a non-spherical cutter and adaptively adjusting the contacting tool posture and the feed direction, significant improvement in machining efficiency could be achieved, e.g., more than 50% achieved in our experiments.
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Chonghui Fan,Kelong Ao,Pengfei Lv,Jiancheng Dong,Di Wang,Yibing Cai,Qufu Wei,Yang Xu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.08
Fluorescent nitrogen-doped carbon dots (N-CDs) with excellent stability were prepared via single-step hydrothermal carbonization of citric acid (CA) and ethylenediamine (EDA). The as-prepared N-CDs emit blue fluorescence under the excitation of 365 nm and have a size distribution of 2.80 ffi 0.47 nm with benign size effect. The structure and morphology were further characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. It was found that the surface of the N-CDs was successfully functionalized, which presented water solubility and chelation with Fe3+. XRD results display a diffraction peak at 23.9 ℃, which corresponds to the (002) interlayer spacing of a graphitic structure revealing an amorphous carbon phase. Furthermore, due to good sensitivity, N-CDs were used as probes for Fe3+ detection. The low limit of detection of 0.6 μM as a fluorescence probe was successfully obtained based on the linear relationship between (F0 - F) / F0 and concentration of Fe3+ ions. Besides the satisfactory fluorescence, PVA/N-CDs membranes and fluorescent inks demonstrate potential for anti-counterfeiting applications due to its characteristic flexibility, transparency, removability and invisibility under ambient lighting.
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Huiqun Wu,Chendong Wang,Cong Chen,Xiaotao Xu,Yi Zhu,Aimin Sang,Kui Jiang,Jiancheng Dong 대한신경과학회 2020 Journal of Clinical Neurology Vol.16 No.1
Background and Purpose Previous studies have explored the association between retinal vascular changes and cognitive impairment. The retinal vasculature shares some characteristics with the cerebral vasculature, and quantitative changes in it could indicate cognitive impairment. Hence, a comprehensive meta-analysis was performed to clarify the potential relationship between retinal vascular geometric changes and cognitive impairment. Methods Relevant databases were scrupulously and systematically searched for retinal vascular geometric changes including caliber, tortuosity, and fractal dimension (FD), and for cognitive impairment. The Newcastle-Ottawa Scale was used to evaluate the methodological quality of included studies. RevMan was used to perform the meta-analysis and detect publication bias. Sensitivity analyses were also performed. Results Five studies that involved 2,343 subjects were finally included in the meta-analysis. The results showed that there was no significant association between central retinal artery equivalents (Z=1.17) or central retinal venular equivalents (Z=1.74) and cognitive impairment (both p>0.05). Similarly, no significant difference was detected in retinal arteriolar tortuosity (Z=0.91) and venular tortuosity (Z=1.31) (both p>0.05). However, the retinal arteriolar FD (mean difference: -0.03, 95% CI: -0.05, -0.01) and venular FD (mean difference: -0.03, 95% CI: -0.05, -0.02) were associated with cognitive impairment. Conclusions A smaller retinal microvascular FD might be associated with cognitive impairment. Further large-sample and well-controlled original studies are required to confirm the present findings.
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