On a class of locally projectively flat general (α, β)-metrics

Xiaohuan Mo,Hongmei Zhu 대한수학회 2017 대한수학회보 Vol.54 No.4

General $(\alpha,\beta)$-metrics form a rich class of Finsler metrics. They include many important Finsler metrics, such as Randers metrics, square metrics and spherically symmetric metrics. In this paper, we find equations which are necessary and sufficient conditions for such Finsler metric to be locally projectively flat. By solving these equations, we obtain all of locally projectively flat general $(\alpha,\beta)$-metrics under certain condition. Finally, we manufacture explicitly new locally projectively flat Finsler metrics.

Non-devastating Islanding Detection for Micro-grid Based on Mathematical Statistics

Xiaohuan Wang,Chunjiang Zhang,Wenchao Zhao,Xiao Mu 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

Conventional passive islanding detection methods have disadvantages of non-detection zone (NDZ). Active ones can reduce or eliminate NDZ, but their operation mechanism is forcing the voltage or frequency into the fault range, which is a devastating islanding detection approach. However, the non-devastating islanding method without NDZ is desirable for micro-grid applications. A novel active islanding detection method based on mathematical statistics for three-phase inverter is proposed. In this paper, 0-1 sequence is used to modulate the PWM modulation wave by amplitude adjustment. Then the voltage of point of common coupling (PCC) is sampled and the variance based on mathematics features is calculated in real-time. According to the value of variance, the islanding can be determined. The proposed method not only conquers the disadvantage of the destroy that conventional active islanding detection methods result in to the utility grid, but also detects the islanding effectively when the DG power production match to the load power requirement. And it is quick and effective under the ideal and non-ideal utility grid and the false islanding also can be prevented. Simulation and experiment results verify the correctness and feasibility of the proposed method. This method is suitable for the grid-connected /stand-alone dual-mode micro-grid system.

Suppression and stability analysis of frequency coupling effect in grid‑connected inverters

Xiaohuan Wang,Aihua Yang,Yang Liu,Xiaojun Zhao 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.6

With the proposal of the “dual carbon target” in China, the rapid development of renewable energy, mainly photovoltaic and wind power, has been promoted. However, a large amount of renewable energy connected to a grid results in its proportion in the power system going from a low state to a high state. Under a high proportion, the asymmetry of the control structure or parameters in the three-phase grid-connected inverter controller lead to a strong coupling relationship between the sub/super synchronous frequency components, or frequency coupling effect (FCE). This phenomenon can deteriorate the power quality of the inverter system, amplify the harm of frequency oscillation, and even cause system disassembly. To solve the above problems, a unified impedance model considering the FCE induced by the phase-locked loop (PLL), the current loop (CL), and the power outer loop (POL) is established. Based on the established output impedance model, a parameter optimization theoretical analysis method is designed considering the critical stability of the PLL bandwidth and the CL asymmetry degree. Meanwhile, an improved control strategy for the PLL and the POL is proposed. Experimental results show that the proposed parameter optimization and structure improvement strategies can effectively suppress the infl uence of frequency coupling and enhance system stability. Finally, simulation and experimental results verify the correctness of the theoretical analysis and the eff ectiveness of the proposed strategy.

Psychological Resilience of Second-Pregnancy Women in China: A Cross-sectional Study of Influencing Factors

Xiaohuan Jin,Xinyuan Xu,Junyan Qiu,Zexun Xu,Lixue Sun,Zhilin Wang,Ling Shan 한국간호과학회 2021 Asian Nursing Research Vol.15 No.2

Purpose The aim of the study was to evaluate the status of psychological resilience among women in their second pregnancy and to investigate the possible influencing factors. Methods A total of 275 women in their second pregnancy and who met the criteria were surveyed from two public hospitals in China from July 2018 to January 2019. The instruments included the General Self-designed Questionnaire, Connor–Davidson Resilience Scale, Social Support Rate Scale, and 36-item Pregnancy Stress Rating Scale. Results The total psychological resilience score of second-pregnancy women was relatively low. Multivariate regression analysis identified five factors associated with psychological resilience: intimacy with husbands, social support utilization, gender of the first child, high-risk pregnancy of the first child, and the stress caused by worrying about the health and safety of the mother and fetus. Conclusion Women in their second pregnancy represent a unique population, and their low psychological resilience score deserves attention. Identification of factors contributing to decreased psychological resilience may enable us to design prevention and intervention strategies and to deliver specific psychological supports to pregnant women at high risk of developing negative psychology.

The mechanism of mesna in protection from cisplatin-induced ovarian damage in female rats

Xiaohuan Li,Shu Yang,Xiangyang Lv,Haimei Sun,Jing Weng,Yuanjing Liang,Deshan Zhou 대한부인종양학회 2013 Journal of Gynecologic Oncology Vol.24 No.2

Objective: Cisplatin is a widely used chemotherapeutic agent in the treatment of cancers in clinic; but it often induces adverse effects on ovarian functions such as reduced fertility and premature menopause. Mesna could attenuate the cisplatin-induced ovarian damages; however, the underlying mechanism is still unknown. This study aimed to figure out the underlying mechanism of the protection of mesna for ovaries against cisplatin therapy in cancers. Methods: We performed female adult Sprague-Dawley rats into normal saline control (NS), low-dose cisplatin (CL), high-dose cisplatin (CH), CL plus mesna (CL+M), and CH plus mesna (CH+M) groups and detected anti-Müllerian hormone (AMH)-positive follicle, oxidative stress status and anti-oxidative capability in ovaries. Results: AMH-positive follicles were significantly decreased after cisplatin administration, which was significantly reversed when mesna was co-administered with cisplatin. The end product of lipid peroxidation, malondialdehyde (MDA), was significantly increased, but the anti-oxidative enzymatic activity of superoxide dismutase (SOD) and glutathione (GSH) were significantly decreased in cisplatin groups when compared with NS group. In contrast, after co-administration of cisplatin with mesna, MDA was significantly decreased whereas the activity of SOD and the concentration of GSH were increased. Moreover, mesna did not decrease the anti-tumor property of cisplatin in HePG2 cell lines. Conclusion: Cisplatin damages the granulosa cells by oxidative stress to deplete the ovarian reserve and mesna could protect ovarian reserve through anti-oxidation. These results might highlight the mechanism of the protection of mesna for ovarian reserve and open an avenue for the application of mesna as a protective additive in cisplatin chemotherapy in clinical practise.

Organic-rich source rock characterization and evaluation of the Cretaceous Qingshankou Formation: results from geophysical logs of the second scientific drilling borehole in the Songliao Basin, NE China

Xiaohuan Zhang,Changchun Zou,Jinhuan Zhao,Ning Li,Shuxia Zhang,Kouamelan Serge Kouamelan,Liang Xiao,Huolin Ma,Yixiong Niu 한국지질과학협의회 2019 Geosciences Journal Vol.23 No.1

The second continental scientific drilling (SKII east) borehole in the Songliao Basin has been planned to be the deepest borehole to drill through the Cretaceous continental strata under the framework of the International Continental Scientific Drilling Program (ICDP) up to date. This borehole was designed not only to explore the potential relationships between dinosaur extinction and climate environment during the Cretaceous but also to achieve new breakthroughs in oil and gas exploration. The high hydrocarbon (oil and gas) potential of a source rock is highly dependent on its organic content. We used geophysical log data of Borehole SKII east to evaluate the organic content of organic-rich source rock. In the period of the first member in the Qingshankou Formation (K2qn1) from the study area, high accommodation space and anoxic environment could promote organic matter deposition. Firstly, based on geological information and abundant geophysical log data, the basic geophysical characteristics (including petrophysical, lithological, mineralogical, and sedimentary properties) of the Qingshankou Formation in Borehole SKII east were studied. Secondly, geophysical log response characteristics (including resistivity, porosity, radioactivity, mineral and element) of organic-rich source rocks were analyzed. Thirdly, we tried to obtain suitable methods to predict total organic carbon (TOC) content of the target formation with geophysical log data. The laboratorymeasured TOC values of core samples from Borehole SKI south were used to make calibrations with calculated TOC values from geophysical logs. Results from improved ΔlogR technique and Dual_Vsh method are consistent, and indicate that these two methods are effective in this formation. The calculated TOC values from these two methods are relatively desirable, and show that the organic-rich source rocks with high TOC content occurred in the K2qn1 (1646.00~1669.00 m). The highest TOC content can reach 9.15%. The bed thicknesses of organic-rich source rocks are totally up to 7.88 m. These organic-rich source rocks can be considered as excellent. This study demonstrated that improve ΔlogR technique can be applied to evaluate source rocks in the formations without maturity data, and the new method Dual_Vsh is also valid in the Qingshankou Formation. The organic-rich source rock evaluation results could promote further exploration and development of oil and gas resources in the upper Cretaceous formations, Songliao Basin.

On Finsler metrics of constant S-curvature

Xiaohuan Mo,Xiaoyang Wang 대한수학회 2013 대한수학회보 Vol.50 No.2

In this paper, we study Finsler metrics of constant S-curva- ture. First we produce infinitely many Randers metrics with non-zero (constant) S-curvature which have vanishing H-curvature. They are counterexamples to Theorem 1.2 in [20]. Then we show that the existence of (α, β)-metrics with arbitrary constant S-curvature in each dimension which is not Randers type by extending Li-Shen’ construction.

Computer simulation of the nonlinear static behavior of axially functionally graded microtube with porosity

Li, Xiaohuan,Wang, Tian,Liu, Fang,Zhu, Zhiwen Techno-Press 2021 Advances in nano research Vol.11 No.4

Static analysis of microstructures, including bending and buckling, is widely practiced in the fabrication and creation of applications such as actuation, sensing, and energy recovery. This article aims to inquire about the static behavior of non-uniform and imperfect microtubes through a numerical solution. Based on the modified couple stress theory, the first-order shear deformation theory and Von-Karman nonlinear theory, and employing the energy conservation method, the linear and nonlinear governing equations are derived. The porosity-dependent material in both ceramic and metal phases makes the functionally graded materials which are varied along tube length, moreover, cross-sections are also considered uniform and nonuniform via three valuable functions. Finally, the linear and nonlinear equations are solved utilizing the generalized differential quadrature method (GDQM) coupled with the numerical iteration method.

ON A CLASS OF LOCALLY PROJECTIVELY FLAT GENERAL (α, β)-METRICS

Mo, Xiaohuan,Zhu, Hongmei Korean Mathematical Society 2017 대한수학회보 Vol.54 No.4

General (${\alpha},{\beta}$)-metrics form a rich class of Finsler metrics. They include many important Finsler metrics, such as Randers metrics, square metrics and spherically symmetric metrics. In this paper, we find equations which are necessary and sufficient conditions for such Finsler metric to be locally projectively flat. By solving these equations, we obtain all of locally projectively flat general (${\alpha},{\beta}$)-metrics under certain condition. Finally, we manufacture explicitly new locally projectively flat Finsler metrics.

ON FINSLER METRICS OF CONSTANT S-CURVATURE

Mo, Xiaohuan,Wang, Xiaoyang Korean Mathematical Society 2013 대한수학회보 Vol.50 No.2

In this paper, we study Finsler metrics of constant S-curvature. First we produce infinitely many Randers metrics with non-zero (constant) S-curvature which have vanishing H-curvature. They are counterexamples to Theorem 1.2 in [20]. Then we show that the existence of (${\alpha}$, ${\beta}$)-metrics with arbitrary constant S-curvature in each dimension which is not Randers type by extending Li-Shen' construction.