Development Issues of An ISG PM Machine and Control System

Xiaojiang Chen,Murray Edington,Roger Thornton,Yunzhou Fang,Qingfeng Peng 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-

This paper focuses on addressing some practical considerations in developing an ISG PM system for hybrid electric-vehicle (HEV) applications. Extensive practical test results and theoretical analyses are presented and analyzed. Firstly, the ISG PM machine design is discussed in term of the machine size, pole-pair number, permanent magnet flux, inductance, etc. A cost-effective machine design example, which was successfully demonstrated in a mild ISG HEV application, is analyzed. Its performance test results are evaluated. Subsequently, the impacts of the position sensors on the ISG performance are investigated exclusively. Three prominent position sensor candidates are studied in detail to examine their limitation and feasibility for ISG applications. Furthermore, the control related issues are discussed. The torque control of the ISG machine is implemented through vector control algorithm. Flux-weakening control is employed to achieve a wide speed range of constant-power operation. The impact of the inverter DC-link voltage variation is explored. In addition the digital control delay influence and its effective compensation strategy are addressed.

Biochemical Characterization of Exoribonuclease Encoded by SARS Coronavirus

Chen, Ping,Jiang, Miao,Hu, Tao,Liu, Qingzhen,Chen, Xiaojiang S.,Guo, Deyin Korean Society for Biochemistry and Molecular Biol 2007 Journal of biochemistry and molecular biology Vol.40 No.5

The nsp14 protein is an exoribonuclease that is encoded by severe acute respiratory syndrome coronavirus (SARS-CoV). We have cloned and expressed the nsp14 protein in Escherichia coli, and characterized the nature and the role(s) of the metal ions in the reaction chemistry. The purified recombinant nsp14 protein digested a 5'-labeled RNA molecule, but failed to digest the RNA substrate that is modified with fluorescein group at the 3'-hydroxyl group, suggesting a 3'-to-5' exoribonuclease activity. The exoribonuclease activity requires $Mg^{2+}$ as a cofactor. Isothermal titration calorimetry (ITC) analysis indicated a two-metal binding mode for divalent cations by nsp14. Endogenous tryptophan fluorescence and circular dichroism (CD) spectra measurements showed that there was a structural change of nsp14 when binding with metal ions. We propose that the conformational change induced by metal ions may be a prerequisite for catalytic activity by correctly positioning the side chains of the residues located in the active site of the enzyme.

Drilling Machinability Evaluation on New Developed High-strength T800S/250F CFRP Laminates

Jinyang Xu,Ming Chen,Qinglong An,Xiaojiang Cai 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.

The new developed high-strength CFRP laminates are widely employed in varieties of applications and are mainly used in main loadbearing structural components of large commercial aircrafts. Drilling is one of the important operations in manufacturing composite structure, often a final operation during assembly. Defects such as burrs and delamination in drilling of CFRP are always serious problems and lead to rejection and impose heavy loss. In the present research, the machinability of a new developed high-strength T800S/250F CFRP laminate is evaluated by using CVD coated twist drill and CVD coated dagger drill. The machinability was investigated in terms of drilling forces, burr defect, hole wall surface morphology and delamination damage. The results indicate that feed rate is the most significant factor affecting the machined surface finish followed by the spindle speed. The dagger drill showed excellent drilling performance than the twist drill and was more suitable for drilling of T800S/250F CFRP laminate. The results also highlight the importance of employing the high speed drilling to minimize the drilling-induced defects.

An Unreliable Opportunistic Spectrum Sharing System with Sensitive Secondary Users

Shensheng Tang,Rong Yu,Xiaojiang Chen,Chenghua Tang,Yi Xie 보안공학연구지원센터 2016 International Journal of u- and e- Service, Scienc Vol.9 No.3

The focus of this paper is on the modeling and performance analysis of an unreliable opportunistic spectrum sharing (OSS) system at the call level with sensitive secondary users. Unreliable spectrum sensing is modeled by type I and type II false alarm events and class-A and class-B misdetection events, which brings more flexibility for the purpose of performance evaluation. Spectrum sensing errors negatively impact the performance of primary users and secondary users, particularly when a call collision happens. To maximize the protection of primary users under call collisions, it is required in the system design that secondary users be sensitive to the call collisions, to protect primary users. We model the unreliable OSS system through a two-dimensional Markov process and develop the steady-state probabilities of the system as well as several performance metrics of interest.

Drilling Temperature and Hole Quality in Drilling of CFRP/Aluminum Stacks Using Diamond Coated Drill

Chang-Ying Wang,Yu-Han Chen,Qinglong An,Xiaojiang Cai,Wei-Wei Ming,Ming Chen 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

Composite/metal stack materials, most often consisting of carbon fiber reinforced polymer (CFRP) composites and aluminum or titanium alloy (Al or Ti), have been widely used in the aviation industry. It is still a challenge to make holes on the composite/metal stack materials with high quality. This paper aims to investigate the influence of drilling parameters on the drilling of stack materials consisting of T800/X850 CFRP and 7075-T651 Al with regard to drilling force, drilling temperature, hole diameter and hole surface quality. Diamond coated drill bits with double point angles were employed in the drilling tests. The drilling temperature was measured utilizing a rotational motion temperature measuring system. It is indicated that maximum drilling temperature increases with the increase of spindle speed, while, it decreases with increasing feed rate. The thrust force and drilling temperature increase abnormally during drilling of the Al layer, which can be attributed to the evacuation difficulty of the long and flexible Al chips. It is found that sudden drops in the surface profile of CFRP are caused by the cavities owning to the resin degradation effects. The influences of different stack sequences on the drilling temperature and hole surface quality have also been discussed.

Upregulated Long Noncoding RNA LINC01234 Predicts Unfavorable Prognosis for Colorectal Cancer and Negatively Correlates With KLF6 Expression

Xiao Jiang,Qiaoying Zhu,Pengxi Wu,Fengsheng Zhou,Jun Chen 대한진단검사의학회 2020 Annals of Laboratory Medicine Vol.40 No.2

Background: LINC01234, a long noncoding RNA (lncRNA), is overexpressed in several cancers, including colorectal cancer (CRC). We investigated the role of LINC01234 in CRC development and confirmed its correlation with Krüppel-like factor 6 (KLF6), a tumor suppressor gene that is dysregulated in CRC. Methods: We tested mRNA levels using quantitative reverse transcription PCR (qRT-PCR). Tissue samples from patients with CRC, inflammatory bowel disease (IBD), hyperplastic polyp, and adenoma were included. Correlations between clinicopathological parameters, overall survival (OS) rate, and LINC01234 were analyzed using Kruskal-Wallis H test. Additionally, cell proliferation, apoptosis, and tumor formation in nude mice were tested to investigate the mechanism of LINC01234. Western blotting was used to determine protein levels. Results: LINC01234 expression was significantly upregulated in CRC tissues and CRC cell lines than in non-tumor tissues and normal epithelial cells, respectively. LINC01234 was associated with high tumor stage, larger tumor size, and metastasis. Patients with higher LINC01234 expression showed reduced OS. Cell proliferation was inhibited by LINC01234 knockdown, whereas apoptosis was enhanced. Mice injected with SW480 cells with LINC01234 knockdown displayed decreased tumor volume, weight, and Ki-67 levels compared with those injected with control cells. KLF6 was negatively regulated by LINC01234. Overexpression of KLF6 showed effects similar to those observed following LINC01234 knockdown on cell proliferation and apoptosis. Conclusions: LINC01234 could be a prognostic biomarker in CRC patients. Upregulation of LINC01234 in CRC promotes tumor development through negative regulation of KLF6.