FORMATION OF NANOLITER BUBBLES IN MICROFLUIDIC T-JUNCTIONS

JING FAN,YUXIANG ZHANG,LIQIU WANG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2010 NANO Vol.5 No.3

A numerical study on nanoliter bubble formation process in microfluidic T-junctions is conducted. The simulated bubble sequence agrees well with experiments. The pressure and velocity distribution in liquid phase, and streamlines of relative velocity of liquid to bubbles are obtained. We also studied pressure variation at the junction and gas flow rate for the first several bubbles, and illustrated the special impact of channel width ratio on bubble formation process. Finally, we derived the critical nondimensional gas pressure above which bubbles can be generated.

MICROSTRUCTURAL EFFECTS ON MACROSCALE THERMAL PROPERTIES IN NANOFLUIDS

JING FAN,LIQIU WANG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2010 NANO Vol.5 No.2

The recent first-principle model shows that heat conduction in nanofluids can be diffusion-dominant or thermal-wave-dominant depending on their microscale physics (structures, properties and activities). As the first attempt of quantifying when and to what extent thermal waves become important, we numerically examine effects of particle–fluid conductivity ratio, particle shape, volume fraction and nondimensional particle–fluid interfacial area in the unit-cell on macroscale thermal properties for nanofluids consisting of in-line arrays of perfectly dispersed two-dimensional circular, square and hollow particles, respectively. In simple and perfectly dispersed nanofluids, the heat conduction is diffusion-dominant so the effective thermal conductivity can be predicted adequately by the mixture rule with the effect of particle shape and particle–fluid conductivity ratio incorporated into its empirical parameter. Thermal waves appear more likely at smaller particle–fluid conductivity ratio (< 1) and lower particle-volume-fraction, which agrees with the experimentally observed significant conductivity enhancement in the oil-in-water emulsion. The computed thermal conductivity predicts some experimental data in the literature very well and shows the sensitivity to the nondimensional particle–fluid interfacial area in the unit-cell.

A Robust Approach for Overlay Text Localization and Extraction in Complex Video Scene

Jingfan Tang,Zhitao Li,Xingqi Wang,Ming Jiang,Ziyang Li 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.10

Overlay text in video carries important semantic clues for video information retrieval and summarization. In this paper, we propose a robust method that is able to accurately locate text lines and extract text even in complex video scene. In the text localization stage, this paper adopts the method based on corner point. First, corner detection is used to extract corners as text features from video frames. Then multi-layer filtering mechanism (MLFM) is used to locate the text lines, which consists of corners clustering, corners horizontal projection, background filtering and heuristic rules. This MLFM can effectively remove the isolated corners, locate the text lines accurately and remove the background or pseudo text lines automatically. In the text extraction stage, this paper proposed a twice binarization method that combines with polarity judgment on image. The polarity judgment was used as a guide to adjust the first binarization threshold when we perform the first binarization. After the first binarization, a main proportion of the image has been processed, and the rest will be processed by the second binarization. Experimental results show that this approach can fast and robustly locate text lines and extract text in video even under complex background.

The Vision-Based Target Recognition, Localization, and Control for Harvesting Robots: A Review

Jingfan Liu,Zhaobing Liu 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.25 No.2

In recent years, the elderly population has increased, leading to a labor shortage and the increasing cost of training experienced labor. Owing to the continuous optimization of machine vision, multi-sensor technologies, control methods, and end-effector structures, harvesting robots have experienced rapid development. However, most harvesting robots still require intelligent solutions, and the lack of integration with artificial intelligence limits them to small-scale applications without mass production. This paper reviews key technologies for vision-based sensing and control of harvesting robots, focusing on potential applications of vision for target recognition and localization in complex agricultural environments, describing improved solutions for different target detection and localization algorithms, and comparing their detection results. The challenges and future trends of applying these key vision sensing and control techniques in harvesting robots are also described and discussed in this review.

A Modified Quantum Dot-Based Dot Blot Assay for Rapid Detection of Fish Pathogen Vibrio anguillarum

( Yang Zhang ),( Jingfan Xiao ),( Qiyao Wang ),( Yuanxing Zhang ) 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.8

Vibrio anguillarum, a devastating pathogen causing vibriosis among marine fish, is prevailing in worldwide fishery industries and accounts for grievous economic losses. Therefore, a rapid on-site detection and diagnostic technique for this pathogen is in urgent need. In this study, two mouse monoclonal antibodies (MAbs) against V. anguillarum, 6B3-C5 and 8G3-B5, were generated by using hybridoma technology and their isotypes were characterized. MAb 6B3-C5 was chosen as the detector antibody and conjugated with quantum dots. Based on MAb 6B3- C5 labeled with quantum dots, a modified dot blot assay was developed for the on-site determination of V. anguillarum. It was found that the method had no cross-reactivity with other than V. anguillarum bacteria. The detection limit (LOD) for V. anguillarum was 1 × 10³ CFU/ml in cultured bacterial suspension samples, which was a 100-fold higher sensitivity than the reported colloidal gold immunochromatographic test strip. When V. anguillarum was mixed with turbot tissue homogenates, the LOD was 1 × 10³ CFU/ml, suggesting that tissue homogenates did not influence the detection capabilities. Preenrichment with the tissue homogenates for 12 h could raise the LOD up to 1 × 10² CFU/ml, confirming the reliability of the method.

Family of Dual-Input Dual-Buck Inverters Based on Dual-Input Switching Cells

Fan Yang,Hongjuan Ge,Jingfan Yang,Runyun Dang,Hongfei Wu 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.4

A family of dual-DC-input (DI) dual-buck inverters (DBIs) is proposed by employing a DI switching cell as the input of traditional DBIs. Three power ports, i.e. a low voltage DC input port, a high voltage DC input port and an AC output port, are provided by the proposed DI-DBIs. A low voltage DC source, whose voltage is lower than the peak amplitude of the AC side voltage, can be directly connected to the DI-DBI. This supplies power to the AC side in single-stage power conversion. When compared with traditional DBI-based two-stage DC/AC power systems, the conversion stages are reduced, and the power rating and power losses of the front-end Boost converter of the DI-DBI are reduced. In addition, five voltage-levels are generated with the help of the two DC input ports, which is a benefit in terms of reducing the voltage stresses and switching losses of switches. The topology derivation method, operation principles, modulation strategy and characteristics of the proposed inverter are analyzed in-depth. Experimental results are provided to verify the effectiveness and feasibility of the proposed DI-DBIs.

Family of Dual-Input Dual-Buck Inverters Based on Dual-Input Switching Cells

Yang, Fan,Ge, Hongjuan,Yang, Jingfan,Dang, Runyun,Wu, Hongfei The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.4

A family of dual-DC-input (DI) dual-buck inverters (DBIs) is proposed by employing a DI switching cell as the input of traditional DBIs. Three power ports, i.e. a low voltage DC input port, a high voltage DC input port and an AC output port, are provided by the proposed DI-DBIs. A low voltage DC source, whose voltage is lower than the peak amplitude of the AC side voltage, can be directly connected to the DI-DBI. This supplies power to the AC side in single-stage power conversion. When compared with traditional DBI-based two-stage DC/AC power systems, the conversion stages are reduced, and the power rating and power losses of the front-end Boost converter of the DI-DBI are reduced. In addition, five voltage-levels are generated with the help of the two DC input ports, which is a benefit in terms of reducing the voltage stresses and switching losses of switches. The topology derivation method, operation principles, modulation strategy and characteristics of the proposed inverter are analyzed in-depth. Experimental results are provided to verify the effectiveness and feasibility of the proposed DI-DBIs.

Exploring precise deposition and influence mechanism for micro-scale serpentine structure fiber

Wang, Han,Ou, Weicheng,Zhong, Huiyu,He, Jingfan,Wang, Zuyong,Cai, Nian,Chen, XinDu,Xue, Zengxi,Liao, Jianxiang,Zhan, Daohua,Yao, Jingsong,Wu, Peixuan Techno-Press 2022 Advances in nano research Vol.12 No.2

Micro-scale serpentine structure fibers are widely used as flexible sensor in the manufacturing of micro-nano flexible electronic devices because of their outstanding non-linear mechanical properties and organizational flexibility. The use of melt electrowriting (MEW) technology, combined with the axial bending effect of the Taylor cone jet in the process, can achieve the micro-scale serpentine structure fibers. Due to the interference of the process parameters, it is still challenging to achieve the precise deposition of micro-scale and high-consistency serpentine structure fibers. In this paper, the micro-scale serpentine structure fiber is produced by MEW combined with axial bending effect. Based on the controlled deposition of MEW, applied voltage, collector speed, nozzle height and nozzle diameter are adjusted to achieve the precise deposition of micro-scale serpentine structure fibers with different morphologies in a single motion dimension. Finally, the influence mechanism of the above four parameters on the precise deposition of micro-scale serpentine fibers is explored.

Effect of TiC Nanoparticles Supported by Ti Powders on the Solidification Behavior and Microstructure of Pure Aluminum

Bingyi Zhao,Qizhou Cai,Bing Li,Jingfan Cheng 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.5

A novel grain refi ner consisting of TiC nanoparticles (NPs) supported by Ti powders (abbr. TiC/Ti refi ner) was preparedby high-energy milling. The addition of 0.5 wt% TiC/Ti refi ner converted the structure of pure Al from coarse dendrites tofi ne equiaxed grains with the average grain size of 114.7 μm, and it also increased the nucleation temperature of α(Al) from656.7 to 664.4 °C. When TiC/Ti refi ner was introduced into Al melt, the heat released from the Al–Ti reaction promoted theuniform dispersion of TiC NPs. The dissolution of the reaction product TiAl 3 released Ti atoms into the melt and thus formeda “Ti-rich transition region” around TiC NPs. The dispersive TiC NPs could act as the heterogeneous nuclei for α(Al) andthe “Ti-rich transition region” further improved the lattice orientation relationship between Al ( ̄11̄ 1 ) and TiC ( 11̄1 ) planes,which eventually resulted in the refi ning of α(Al).

Reentry Risk and Safety Assessment of Spacecraft Debris Based on Machine Learning

Hu Gao,Zhihui Li,Depeng Dang,Jingfan Yang,Ning Wang 한국항공우주학회 2024 International Journal of Aeronautical and Space Sc Vol.25 No.1

Uncontrolled spacecraft will disintegrate and generate a large amount of debris in the reentry process. Ablative debris may cause potential risks to the safety of human life and property on the ground. Therefore, predicting the landing points of spacecraft debris and forecasting the degree of risk of waste to human life and property is very important. In view that it is difficult to predict the reentry process and the reentry point in advance, the debris generated from reentry disintegration may cause ground damage for the uncontrolled space vehicle on the expiration of service. In this paper, we adopt the object-oriented approach to consider the spacecraft and its disintegrated components as consisting of simple basic geometric models and introduce three machine learning models: the support vector regression (SVR), decision tree regression (DTR), and multilayer perceptron (MLP) to predict the velocity, longitude, and latitude of spacecraft debris landing points for the first time. Then, we compare the prediction accuracy of the three models. Furthermore, we define the reentry risk and the degree of danger, and we calculate the risk level for each spacecraft debris and make warnings accordingly. The experimental results show that the proposed method can obtain high-accuracy prediction results in at least 10 s and make safety-level warning more real-time.