For spark-ignition (SI) engines, downsizing, exhaust gas recirculation and lean burn are promising methods for meeting more stringent emission regulations and lower fuel consumption requirements. With these technologies, high density and high flow velocity around the spark plug at spark timing bring severe challenges for stable ignition. The ignition processes could be affected by breakdown phases and restrikes under high-density conditions. A quantitative evaluation for the breakdown phase is of great significance especially for high power density engines. In this study, the experiments with pressure up to 40 bar and temperature up to 450 K are established to evaluate the breakdown voltage and current, with different spark plug gaps. The breakdown voltage is related to the ambient density, spark plug gap distance and gas composition. The coil parameters have little effects on the breakdown voltage. The breakdown current shows positive correlation with the breakdown voltage, and is also affected by the coil characteristics. The breakdown voltage and current show the nonlinear correlations with the pressure and gap distance. With the increase of pressure or gap distance, the increase rates of the breakdown voltage and current decrease. The fuel concentration and species have little effects on the breakdown voltage when the fuel concentration is applicable for engine operations. Finally, a novel expression of the breakdown voltage is constructed as a function of ambient pressure, temperature and spark plug gap distance. The newly developed expression is valuable for simulating spark ignition processes for a wide range of ambient density for SI engines.
Download This Paper Open PDF in Browser Add Paper to My Library Share: Permalink Using these links will ensure access to this page indefinitely Copy URL Dynamics of Ring Dark Solitons in a Two-Dimensional Dipolar Bose-Einstein Condensate 7 Pages Posted: 1 Oct 2022 See all articles by Suying ZhangSuying ZhangShanxi UniversityGuoquan YangJinzhong UniversitySiyu XieJinzhong UniversityYan ZhaoJinzhong University Abstract We study the dynamics of ring dark solitons in a two-dimensional dipolar Bose-Einstein condensate, which exhibits complicated dynamical behaviors quite different from those in a scalar condensate. We explore the effects of dipolar interaction on the dynamics of ring dark solitons. In the case the polarization direction of dipolar atoms is vertical to the condensate, the dipolar interaction shows isotropy, it is found that there exists a critical value of relative strength between the dipolar and contact interactions for the collapse of shallow ring dark soliton. We also find that the bigger dipolar interaction can induce more vortex-antivortex pairs accompanied by the collapse of ring dark solitons. When the orientation of dipolar atoms is not vertical to the condensate, the dipolar interaction shows anisotropy, the ring dark solitons first shrink to an elliptical configuration and then decay to lump solitons or vortex-antivortex pairs. And we find the vortex recombination, annihilation, oblique collisions, and catching up during the collapse of ring dark solitons. Keywords: Bose-Einstein condensate, dipole-dipole interaction, vortex Suggested Citation: Suggested Citation Zhang, Suying and Yang, Guoquan and Xie, Siyu and Zhao, Yan, Dynamics of Ring Dark Solitons in a Two-Dimensional Dipolar Bose-Einstein Condensate. Available at SSRN: https://ssrn.com/abstract=4234923 Suying Zhang (Contact Author) Shanxi University ( email ) No.92 Wucheng RdTaiyuan, 030006China Guoquan Yang Jinzhong University ( email ) Jinzhong,China Siyu Xie Jinzhong University ( email ) Jinzhong,China Yan Zhao Jinzhong University ( email ) Jinzhong,China Download This Paper Open PDF in Browser Do you have a job opening that you would like to promote on SSRN? Place Job Opening Paper statistics Downloads 0 Abstract Views 0 PlumX Metrics Feedback Feedback to SSRN Feedback (required) Email (required) Submit If you need immediate assistance, call 877-SSRNHelp (877 777 6435) in the United States, or +1 212 448 2500 outside of the United States, 8:30AM to 6:00PM U.S. Eastern, Monday - Friday. Submit a Paper Section 508 Text Only Pages SSRN Quick Links SSRN Solutions Research Paper Series Conference Papers Partners in Publishing Jobs & Announcements Newsletter Sign Up SSRN Rankings Top Papers Top Authors Top Organizations About SSRN SSRN Objectives Network Directors Presidential Letter Announcements Contact us FAQs Copyright Terms and Conditions Privacy Policy We use cookies to help provide and enhance our service and tailor content. To learn more, visit Cookie Settings. This page was processed by aws-apollo-4dc in 0.219 seconds
To construct a cell line of oral mucosa epithelial cells that stably express human telomerase reverse transcriptase (hTERT) by lentiviral vectors, approaches for the establishment of stable and efficient immortalized oral mucosa epithelial cell lines were explored.Whole RNA was extracted from 293T cells. The hTERT gene was amplified by polymerase chain reaction (PCR) and cloned into the lentiviral vector as pLVX-puro-hTERT. The lentivirus particles were successfully packaged and used to infect primary oral epithelial cells. The positive cell clones were selected by puromycin. Finally, the expression of hTERT was examined by real-time fluorescent quantitative PCR (qRT-PCR) and Western blot analysis.The sequencing results confirmed the construction of the recombinant lentivirus pLVX-puro-hTERT. The morphology of infected cells was similar to that of normal oral mucosal epithelial cells, with a cobble stone-like appearance. The qRT-PCR and Western blot results showed that hTERT was overexpressed in infected cells compared with the normal group (P<0.05).The oral epithelial cell line with stable expression of hTERT was successfully established by the lentivirus, which provides an experimental basis for the establishment of a highly efficient and stable oral epithelial immortalized cell line.目的 通过慢病毒法建立稳定表达外源性人端粒酶逆转录酶（hTERT）基因的口腔黏膜上皮细胞（OMECs），探索构建高效、稳定的永生化OMECs细胞系的方法。方法 提取293T细胞总RNA，应用聚合酶链反应（PCR）法扩增hTERT基因全长，构建重组慢病毒载体pLVX-puro-hTERT。包装慢病毒颗粒后感染人正常OMECs，经嘌呤霉素抗性筛选获得阳性克隆，采用实时荧光定量PCR法和Western blot法检测hTERT基因mRNA和蛋白的表达水平。结果 成功构建了pLVX-puro-hTERT过表达慢病毒载体并感染到OMECs中；感染细胞与正常OMECs形态相似，呈铺路石样生长；实时荧光定量PCR和Western blot结果均显示，hTERT在感染细胞中高表达，与正常细胞相比差异有统计学意义（P<0.05）。结论 通过慢病毒法成功建立了过表达hTERT的OMECs稳定细胞系，为构建高效、稳定增殖的人永生化OMECs细胞系奠定了实验基础。.
Porous chitosan/saccharomycetes adsorption microspheres were successfully prepared by using silica gel as porogen. The morphology of porous chitosan/saccharomycetes microspheres was characterized by scanning electron microscopy, the interaction between molecules was characterized by Fourier transform infrared spectroscopy, and the crystallization property of the microspheres was characterized by X-ray diffraction. The results showed that the adsorption sites of amino and hydroxyl groups had been provided by the porous chitosan/saccharomycetes microspheres for the removal of preservatives, pigments, and other additives in food. The surface roughness of microspheres could be improved by increasing the mass ratio of saccharomycetes. The increase in silica gels could make the microsphere structure more compact. The porous chitosan/saccharomycetes microspheres could be used as adsorbents to adsorb doxycycline in wastewater.
This paper considers a novel factor structure -- Partially Observable Factor Model -- where both observable factors and latent factors exist in the model simultaneously. Such factor structure can make sure both interpretability and goodness-of-fit at the same time. Necessary estimation methodologies for this partially observable factor model are developed in this paper for the high frequency data. The proposed estimation methodology is robust to jumps, microstructure noise and asynchronous observation times simultaneously. In the case of finite dimensionality, we provide the estimation theory for the integrated eigenvalues of the residual covariance matrix, which including the bias-corrected estimator, central limit theorem and asymptotic variance estimator. As a result, the asymptotic normality of the bias-corrected estimator can be applied to test the existence of the latent factors. In the case of high dimensionality, we proposed the estimation method for the high dimensional covariance and precision matrices. In contrast to the existing literature, which assuming the residual covariance matrix generated from regression to be weakly correlated or sparse, this paper relaxed such assumptions and designed a new estimator for this task. The theoretical development of this new estimator is non-trivial and the convergence rates are established accordingly. Monte Carlo simulation demonstrates the validity of our estimation methodologies. Empirical study demonstrates that the latent factors significantly exist in the residual process of the high frequency regression.
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