NEW METHODOLOGY FOR DETERMINATION OF LOAD SPECTRA FOR THE VEHICLE ACCELERATED DURABILITY TESTING ASSOCIATED WITH THE TIME CORRELATED FATIGUE DAMAGE ANALYSIS METHOD

Jiawei Yu,Songlin Zheng,Jinzhi Feng,Lihui Zhao 한국자동차공학회 2017 International journal of automotive technology Vol.18 No.3

The generation of valid and effective test spectra from proving ground recorded load spectra is critical for automotive durability testing. Traditional methods mostly based on spectrum damage were used to select load spectra. Statistical characteristics of load spectra were taken into account, and a new load spectra determination method based on a concatenation of a multi-section minimum standard deviation spectrum (CMSD) was proposed. The CMSD spectra were created and based on proving ground recorded load spectra. Fatigue damage analyses showed that the CMSD spectra approximated the mean damage spectra and were representative of proving ground load spectra. Subsequently, the CMSD spectra were edited by applying the time correlated fatigue damage (TCFD) analysis method to generate accelerated loading spectra. The spectra editing process of the TCFD was discussed in detail. Validation of the accelerated spectra was conducted from amplitude and frequency domains. The same fatigue damage and identical spectrum properties were retained in the accelerated spectra. A vehicle 4-post testing was finally conducted where the accelerated loading spectra were applied as the target spectra. Several fatigue fracture phenomena occurred during our test, which showed good agreement with the field test. Therefore, the load spectra determination method CMSD associated with the load spectra editing method TCFD were demonstrated reasonable and practical.

Long spin coherence length and bulk-like spin-orbit torque in ferrimagnetic multilayers

Yu, Jiawei,Bang, Do,Mishra, Rahul,Ramaswamy, Rajagopalan,Oh, Jung Hyun,Park, Hyeon-Jong,Jeong, Yunboo,Van Thach, Pham,Lee, Dong-Kyu,Go, Gyungchoon,Lee, Seo-Won,Wang, Yi,Shi, Shuyuan,Qiu, Xuepeng,Awano Springer Science and Business Media LLC 2019 Nature materials Vol.18 No.1

The length of guide RNA and target DNA heteroduplex effects on CRISPR/Cas9 mediated genome editing efficiency in porcine cells

Jiawei Lv,Shuang Wu,Renyue Wei,Yan Li,Junxue Jin,Yanshuang Mu,Yu Zhang,Qingran Kong,Xiaogang Weng,Zhonghua Liu 대한수의학회 2019 Journal of Veterinary Science Vol.20 No.3

The clustered regularly interspaced short palindrome repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system is a versatile genome editing tool with high efficiency. A guide sequence of 20 nucleotides (nt) is commonly used in application of CRISPR/Cas9; however, the relationship between the length of the guide sequence and the efficiency of CRISPR/ Cas9 in porcine cells is still not clear. To illustrate this issue, guide RNAs of different lengths targeting the EGFP gene were designed. Specifically, guide RNAs of 17 nt or longer were sufficient to direct the Cas9 protein to cleave target DNA sequences, while 15 nt or shorter guide RNAs had loss-of-function. Full-length guide RNAs complemented with mismatches also showed loss-of-function. When the shortened guide RNA and target DNA heteroduplex (gRNA:DNA heteroduplex) was blocked by mismatch, the CRISPR/Cas9 would be interfered with. These results suggested the length of the gRNA:DNA heteroduplex was a key factor for maintaining high efficiency of the CRISPR/Cas9 system rather than weak bonding between shortened guide RNA and Cas9 in porcine cells.

Optimization Design of the Decentralized Multi-Vehicle Cooperative Controller for Freeway Ramp Entrance

Wang Jiawei,Ma Fangwu,Yu Yang,Zhu Sheng,Gelbal Sukru Yaren,Aksun-Guvenc Bilin,Guvenc Levent 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.3

This research presents a multi-vehicle control strategy combining the merging control and platoon control to deal with the merging scenario in the freeway ramp entrance. In the merging controller, a selection algorithm is presented firstly to determine the merging sequence based on the initial states of the vehicles in the cooperative area. Subsequently, the optimized longitudinal trajectory of the facilitating vehicle and on-ramp vehicle is addressed by solving the Hamiltonian function. As for the platoon controller, string stability is analyzed to attenuate the impact of merging on the mainline traffic, considering the influence of communication time delay. Smooth mode switching is achieved by introducing the tracking policy of platoon controller to determine the terminal states of the facilitating vehicle. The proposed strategy is simulated at two typical merging scenarios, where two on-ramp vehicles attempt to cut into a six-vehicular platoon, to validate its feasibility and advantage.

Derivation of endothelial cells from porcine induced pluripotent stem cells by optimized single layer culture system

Renyue Wei,Jiawei Lv,Xuechun Li,Yan Li,Qianqian Xu,Junxue Jin,Yu Zhang,Zhonghua Liu 대한수의학회 2020 Journal of Veterinary Science Vol.21 No.1

Regenerative therapy holds great promise in the development of cures of some untreatable diseases such as cardiovascular diseases, and pluripotent stem cells (PSCs) including induced PSCs (iPSCs) are the most important regenerative seed cells. Recently, differentiation of human PSCs into functional tissues and cells in vitro has been widely reported. However, although porcine reports are rare they are quite essential, as the pig is an important animal model for the in vitro generation of human organs. In this study, we reprogramed porcine embryonic fibroblasts into porcine iPSCs (piPSCs), and differentiated them into cluster of differentiation 31 (CD31)-positive endothelial cells (ECs) (piPSC-derived ECs, piPS-ECs) using an optimized single-layer culture method. During differentiation, we observed that a combination of GSK3β inhibitor (CHIR99021) and bone morphogenetic protein 4 (BMP4) promoted mesodermal differentiation, resulting in higher proportions of CD31-positive cells than those from separate CHIR99021 or BMP4 treatment. Importantly, the piPS-ECs showed comparable morphological and functional properties to immortalized porcine aortic ECs, which are capable of taking up low-density lipoprotein and forming network structures on Matrigel. Our study, which is the first trial on a species other than human and mouse, has provided an optimized single-layer culture method for obtaining ECs from porcine PSCs. Our approach can be beneficial when evaluating autologous EC transplantation in pig models.

Identification method of nonlinear maneuver model for unmanned surface vehicle from sea trial data based on support vector machine

Gongxing Wu,Jiawei Zhang,Guofu Li,Linling Wang,Qiang Yu,Jiamin Guo 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8

In order to solve the difficulty of modeling the unmanned surface vehicle (USV) nonlinear maneuver model, a combination identification method of linear hydrodynamic coefficients and nonlinear hydrodynamic coefficients based on support vector machine (SVM) is proposed. The identification principle of USV hydrodynamic coefficients is briefly introduced and a regression algorithm of the SVM is derived for the USV maneuver model. Then, the linear hydrodynamic coefficients of the hull are identified by using a series of USV turning test data at small water-jet angles. And the large water-jet angle turning motion test data and the identified linear hydrodynamic coefficients are used to identify the nonlinear hydrodynamic coefficients for USV. The fourth-order Runge-Kutta method is used to design the USV maneuver simulation program, and a series of USV turning motion simulation experiments are carried out. The simulation data is compared with the corresponding USV sea trial data. Through comparative analysis, it is shown that the USV maneuver mathematical model established in this paper can describe the maneuverability of the USV. It is feasible to use the combination method of SVM to identify the hydrodynamic coefficient of USV.

Clamping Error Calibration Algorithm of Aero-Engine Blade Surface Polishing

Dongbo Wu,Zesheng Wang,Jiawei Liang,Hui Wang,Kung Zhang,Jie Yu 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.7

Polishing is an effective process method to improve the surface quality of aero-engine blade. The clamping error between fixture and blade leads to position error of blade surface and reduces processing quality. In this paper, a laser calibration system and a calibration algorithm are proposed to compensate clamping error. Firstly, theoretical point data of blade surface is obtained from CAD model, and the measurement point data of blade surface is obtained through laser sensor. A modified ICP algorithm is designed to calculate the coordinate transformation between the theoretical points and the measurement points. Secondly, Bezier surface is introduced to evaluate the calibration accuracy based on the distance between fitting surfaces rather than points. Finally, the point cloud registration is optimized by particle swarm optimization (PSO) algorithm based on the Bezier surface evaluation. The calibration algorithm combined ICP algorithm, Bezier surface evaluation and PSO algorithm to realize clamping error compensation. The quality of polished blade surface is consequently improved.

Long supplementary light duration under same daily light integral provided by white plus blue light-emitting diodes improves quality of greenhouse-grown tomato seedlings

Li Xin,Wang Chunling,Liu Jiawei,Guo Yu,Cheng Fei,Yang Yanjie,Yan Zhengnan 한국원예학회 2023 Horticulture, Environment, and Biotechnology Vol.64 No.6

Optimizing light conditions is critical for plant growth and seedling production in greenhouse, especially in seasons when the sunlight is insuffi cient. In the present study, tomato ( Solanum Lycopersicum cv. Fenbeibei) seedlings were grown at two levels of supplementary light duration of 6 h·d − 1 (short) (07:00–10:00 and 15:00–18:00) or 12 h·d − 1 (long) (04:00–10:00 and 15:00–21:00) provided by white light-emitting diodes (LEDs, white long and white short, WL and WS) or combinations of white and blue LEDs (white & blue long and white & blue short, WBL and WBS) with same supplementary daily light integral (at 5.5 mol m − 2 d − 1 ) after sowing, and tomato seedlings grown under sunlight only were set as the control. The per centages of light intensity provided by white and blue LEDs under the WB treatments were 85% and 15%, respectively. The results indicated that tomato seedlings grown under WBL treatment exhibited the lowest plant height and shortest hypocotyl length, which was decreased by 34.6% and 41.8%, respectively, compared with the control. The chlorophyll a, chlorophyll b, and total chlorophyll contents of tomato seedlings grown under WBL were signifi cant higher than those under other treat ments. The root fresh weight, root dry weight, and the stem fi rmness of the greenhouse-grown tomato seedlings under WBL were increased by 21.5%, 41.2%, and 38.6%, compared with those grown under WBS, respectively. The sucrose content of tomato seedlings under WBL was increased by 60.4%, compared with that under WL. In conclusion, 12 h·d − 1 supplementary light provided by combinations of white and blue LEDs led to compact morphological characteristics, superior mechanical properties, and satisfactory growth performance. Our fi ndings provide an available lighting strategy to obtain the desired morphological and quality properties of tomato seedlings grown in the seasons with insuffi cient light.

Comparative Study of Two Common In Vitro Models for the Pancreatic Islet with MIN6

Chao Xinxin,Zhao Furong,Hu Jiawei,Yu Yanrong,Xie Renjian,Zhong Jianing,Huang Miao,Zeng Tai,Yang Hui,Luo Dan,Peng Weijie 한국조직공학과 재생의학회 2023 조직공학과 재생의학 Vol.20 No.1

BACKGROUND: Islet transplantation is currently considered the most promising method for treating insulin-dependent diabetes. The two most-studied artificial islets are alginate-encapsulated b cells or b cell spheroids. As three-dimensional (3D) models, both artificial islets have better insulin secretory functions and transplantation efficiencies than cells in twodimensional (2D) monolayer culture. However, the effects of these two methods have not been compared yet. Therefore, in this study, cells from the mouse islet b cell line Min6 were constructed as scaffold-free spheroids or alginate-encapsulated dispersed cells. METHODS: MIN6 cell spheroids were prepared by using Agarose-base microwell arrays. The insulin secretion level was determined by mouse insulin ELISA kit, and the gene and protein expression status of the MIN6 were performed by Quantitative polymerase chain reaction and immunoblot, respectively. RESULTS: Both 3D cultures effectively promoted the proliferation and glucose-stimulated insulin release (GSIS) of MIN6 cells compared to 2D adherent cells. Furthermore, 1% alginate-encapsulated MIN6 cells demonstrated more significant effects than the spheroids. In general, three pancreatic genes were expressed at higher levels in response to the 3D culture than to the 2D culture, and pancreatic/duodenal homeobox-1 (PDX1) expression was higher in the cells encapsulated in 1% alginate than that in the spheroids. A western blot analysis showed that 1% alginate-encapsulated MIN6 cells activated the phosphoinositide 3-kinase (PI3K)/serine/threonine protein kinase (AKT)/forkhead transcription factor FKHR (FoxO1) pathway more than the spheroids, 0.5% alginate-, or 2% alginate-encapsulated cells did. The 3D MIN6 culture, therefore, showed improved effects compared to the 2D culture, and the 1% alginate-encapsulated MIN6 cells exhibited better effects than the spheroids. The upregulation of PDX1 expression through the activation of the PI3K/AKT/FoxO1 pathway may mediate the improved cell proliferation and GSIS in 1% alginate-encapsulated MIN6 cells. CONCLUSION: This study may contribute to the construction of in vitro culture systems for pancreatic islets to meet clinical requirements.

A Generative Adversarial Network to Denoise Depth Maps for Quality Improvement of DIBR-Synthesized Stereoscopic Images

Zhang Chuang,Sun Xian-wen,Xu Jiawei,Huang Xiao-yu,Yu Gui-yue,Park Seop Hyeong 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.4

Depth map quality is an important factor that aff ects the quality of synthesized stereoscopic images in stereoscopic visual communication systems using the depth image-based rendering (DIBR) technique. This paper proposes a method using a generative adversarial network (GAN) to denoise depth maps corrupted by several types of distortion. The generative network of the proposed GAN builds on convolutional layers, residual layers, and transposed convolutional layers with symmetric skip connections. The discriminative network of the proposed GAN is designed as a convolutional neural network. The generative network for denoising depth maps is trained with cropped depth maps where distortion is applied. Objective and subjective assessment of denoised depth maps and DIBR-synthesized stereoscopic images demonstrate that the proposed GAN eff ectively reduces the distortion in the depth maps and improves the quality of DIBR-synthesized stereoscopic images.