65 research outputs found

    Research of NiMH Battery Modeling and Simulation Based on Linear Regression Analysis Method

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     The battery state-of-charge estimation was one of core issues in the development of electric vehicles battery management system, and higher accurate model was needed in state-of-charge estimation correctly. Therefore, accurate battery modeling and simulation was researched here. The Thevenin equivalent circuit model of NiMH battery was established for the poor accuracy of traditional model. Based on the data which were brought from the 6V 6Ah NiMH battery hybrid pulse cycling test experiments, Thevenin model parameters were identified by means of the linear regression analysis method. Then, the battery equivalent circuit simulating model was built in the MATLAB/Simulink environment. The simulation and experimental results showed that the model has better accuracy and can be used to guide the battery state-of-charge estimation

    Determination of band alignment in the single layer MoS2/WSe2 heterojunction

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    The emergence of transition metal dichalcogenides (TMDs) as 2D electronic materials has stimulated proposals of novel electronic and photonic devices based on TMD heterostructures. Here we report the determination of band offsets in TMD heterostructures by using microbeam X-ray photoelectron spectroscopy ({\mu}-XPS) and scanning tunneling microscopy/spectroscopy (STM/S). We determine a type-II alignment between MoS2\textrm{MoS}_2 and WSe2\textrm{WSe}_2 with a valence band offset (VBO) value of 0.83 eV and a conduction band offset (CBO) of 0.76 eV. First-principles calculations show that in this heterostructure with dissimilar chalcogen atoms, the electronic structures of WSe2\textrm{WSe}_2 and MoS2\textrm{MoS}_2 are well retained in their respective layers due to a weak interlayer coupling. Moreover, a VBO of 0.94 eV is obtained from density functional theory (DFT), consistent with the experimental determination.Comment: ^ These authors contributed equally. *Corresponding author E-mail: [email protected], [email protected] 20 pages, 4 figures in main tex

    Furan-containing double tetraoxa[7]helicene and its radical cation

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    An unprecedented furan-based double oxa[7]helicene 1 was achieved, featuring a stable twisted conformation with π-overlap at both helical ends. The excellent conformational stability allowed for optical resolution of 1, which provided a pair of enantiomers exhibiting pronounced mirror-imaged circular dichroism and circularly polarized luminescence activity. The radical cation of 1 was obtained by chemical oxidation as evidenced by UV-Vis-NIR absorption, electron paramagnetic resonance spectroscopy and in situ spectroelectrochemistry. The present work is the starting point for the investigation of open-shell oxahelicenes

    Rational synthesis of an atomically precise carboncone under mild conditions

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    在已知的碳的存在形态中,还有一种锥型的碳结构,早在50年前人们在热解碳时发现了这类结构,此前也常被人们称为碳纳米锥,虽然这类碳纳米锥有望作为扫描隧道显微镜的探针、场发射头等替代材料,但始终未能找到合适方法精准地合成它们。因此,这类锥型碳材料尚未得到人们足够重视和开发。功能团簇材料创新研究群体的谢素原、张前炎课题组与美国波士顿学院的Lawrence Scott教授合作,首次通过有机合成途径,在温和的条件下合成得到了首例结构明确的碳锥单元(碳锥子)C70H20及其可溶衍生物。他们通过实验、理论计算、结构分析,最终在他们合成的碳锥子结构中,仅有1个五元环在锥顶,而在锥顶和锥缘之间(围绕着中心五元环)有2圈由六元环组成的完整的稠圈层,谢素原等将这一碳锥子命名为carboncone[1,2]。通过这一典型的碳锥子(carboncone[1,2]),有望借助气相沉积等技术不断增加稠圈层数(m)来制备具有确定锥角的系列单壁纳米碳锥(carboncone[1,m>2])。随着研究的深入,不久的将来人类有望合成出其它四种不同锥角的碳锥子(carboncone[n=2-5,m]),完整地研究探索和开发利用这类锥型结构的碳材料。 化学化工学院2015级硕士生朱正钟(主要负责合成)和2017级博士生陈佐长(主要负责理论计算)为该论文的共同第一作者。Carboncones, a special family of all-carbon allotropes, are predicted to have unique properties that distinguish them from fullerenes, carbon nanotubes, and graphenes. Owing to the absence of methods to synthesize atomically well-defined carboncones, however, experimental insight into the nature of pure carboncones has been inaccessible. Herein, we describe a facile synthesis of an atomically well-defined carboncone[1,2] (C70H20) and its soluble penta-mesityl derivative. Identified by x-ray crystallography, the carbon skeleton is a carboncone with the largest possible apex angle. Much of the structural strain is overcome in the final step of converting the bowl-shaped precursor into the rigid carboncone under mild reaction conditions. This work provides a research opportunity for investigations of atomically precise single-layered carboncones having even higher cone walls and/or smaller apex angles.This research was supported by the National Natural Science Foundation of China (21771152, 21721001, 21390390, 21827801, 51572231, 21571151, and 21701134), the 973 Program of China (2015CB932301), the Major Science and Technology Project between University-Industry Cooperation in Fujian Province (2016H6023), and the Fundamental Research Funds for the Central Universities (20720170028 and 20720160084). This research was also supported financially by the U.S. National Science Foundation (CHE-0809494 and CHE-1149096). 研究工作得到国家自然科学基金(21771152等)、科技部重大科学研究计划项目(2015CB932301)和福建省高校产学合作项目、中央高校基本科研业务费、美国国家科学基金等的资助

    Statefinder Diagnostic for Dilaton Dark Energy

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    Statefinder diagnostic is a useful method which can differ one dark energy model from the others. The Statefinder pair {r,s}\{r, s\} is algebraically related to the equation of state of dark energy and its first time derivative. We apply in this paper this method to the dilaton dark energy model based on Weyl-Scaled induced gravitational theory. We investigate the effect of the coupling between matter and dilaton when the potential of dilaton field is taken as the Mexican hat form. We find that the evolving trajectory of our model in the rsr-s diagram is quite different from those of other dark energy models.Comment: 6 pages, 4 figures, type errors corrected, reference no. changed, accepted by Astrophysics and Space Scienc

    Dual Antiplatelet Therapy vs Alteplase for Patients With Minor Nondisabling Acute Ischemic Stroke

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    Importance Intravenous thrombolysis is increasingly used in patients with minor stroke, but its benefit in patients with minor nondisabling stroke is unknown. Objective To investigate whether dual antiplatelet therapy (DAPT) is noninferior to intravenous thrombolysis among patients with minor nondisabling acute ischemic stroke. Design, Setting, and Participants This multicenter, open-label, blinded end point, noninferiority randomized clinical trial included 760 patients with acute minor nondisabling stroke (National Institutes of Health Stroke Scale [NIHSS] score ≤5, with ≤1 point on the NIHSS in several key single-item scores; scale range, 0-42). The trial was conducted at 38 hospitals in China from October 2018 through April 2022. The final follow-up was on July 18, 2022. Interventions Eligible patients were randomized within 4.5 hours of symptom onset to the DAPT group (n = 393), who received 300 mg of clopidogrel on the first day followed by 75 mg daily for 12 (±2) days, 100 mg of aspirin on the first day followed by 100 mg daily for 12 (±2) days, and guideline-based antiplatelet treatment until 90 days, or the alteplase group (n = 367), who received intravenous alteplase (0.9 mg/kg; maximum dose, 90 mg) followed by guideline-based antiplatelet treatment beginning 24 hours after receipt of alteplase. Main Outcomes and Measures The primary end point was excellent functional outcome, defined as a modified Rankin Scale score of 0 or 1 (range, 0-6), at 90 days. The noninferiority of DAPT to alteplase was defined on the basis of a lower boundary of the 1-sided 97.5% CI of the risk difference greater than or equal to −4.5% (noninferiority margin) based on a full analysis set, which included all randomized participants with at least 1 efficacy evaluation, regardless of treatment group. The 90-day end points were assessed in a blinded manner. A safety end point was symptomatic intracerebral hemorrhage up to 90 days. Results Among 760 eligible randomized patients (median [IQR] age, 64 [57-71] years; 223 [31.0%] women; median [IQR] NIHSS score, 2 [1-3]), 719 (94.6%) completed the trial. At 90 days, 93.8% of patients (346/369) in the DAPT group and 91.4% (320/350) in the alteplase group had an excellent functional outcome (risk difference, 2.3% [95% CI, −1.5% to 6.2%]; crude relative risk, 1.38 [95% CI, 0.81-2.32]). The unadjusted lower limit of the 1-sided 97.5% CI was −1.5%, which is larger than the −4.5% noninferiority margin (P for noninferiority <.001). Symptomatic intracerebral hemorrhage at 90 days occurred in 1 of 371 participants (0.3%) in the DAPT group and 3 of 351 (0.9%) in the alteplase group. Conclusions and Relevance Among patients with minor nondisabling acute ischemic stroke presenting within 4.5 hours of symptom onset, DAPT was noninferior to intravenous alteplase with regard to excellent functional outcome at 90 days. Trial Registration ClinicalTrials.gov Identifier: NCT0366141

    Online Parameter Estimation of the Ni-MH Batteries Based on Statistical Methods

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    Based on the application of the power batteries, this paper uses a statistical method to estimate the internal resistance and open-circuit voltage of Ni-MH battery. Battery status is monitored and simulated by battery pack test bench. Through using ideal battery model and fitting the data of measured voltage and current, the battery internal resistance and open-circuit voltage are estimated. The average relative error between battery statistic internal resistance and pulse internal resistance is less than 15% in different state of charge. Relative error is influenced by dispersion and symmetry of charge or discharge current. Average of absolute error in open-circuit voltage is about 5% respectively. The results show that it is feasible and accurate to estimate the parameters of Ni-MH battery by using statistical method

    Development of Service Quality Scale for Surgical Hospitalization

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    Background/purposeFindings from literature showed inconsistent results for applying service quality scale in hospitals. Moreover, hospitalization services are provided by diversified departments and a scale designed to measure the overall hospitalization quality is difficult and capturing special characteristics of different departments is also not an easy task. This study attempted to develop a service quality scale for surgical hospitalization (SQSH).MethodsForty-two items were designed via literature review, interviews with patients, health professionals and experienced care givers. A cross-sectional survey was conducted in one hospital. A total of 271 patients in surgical wards were chosen using stratified random sampling; 57.7% of the sampled patients were aged below 55, and 52.2% were male.ResultsThe response rate was 93.4%. Twenty-nine items were retained through the scale development process and six factors were formed: needs management, assurance, sanitation, customization, convenience and quiet, and attention. Six factors explained 57.3% of total variance. Five experts assessed the content validity; content validity index was 0.964. Furthermore, all Cronbach's a exceeded 0.642 and all factor loadings exceeded 0.5. The concurrent validity correlation was 0.583, which had a p value below 0.01.ConclusionThe SQSH has sufficient usefulness, reliability and validity. Future research on service quality can apply the SQSH scale to link with utilization intention and patient loyalty and attempt to develop a hospitalization quality scale for other departments
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