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Irregular frequency effects in the calculations of the drift forces
Liu, Yujie,Falzarano, Jeffrey M. Techno-Press 2019 Ocean systems engineering Vol.9 No.1
Accurate calculation of the mean drift forces and moments is necessary when studying the higher order excitations on the floater in waves. When taking the time average of the second order forces and moments, the second order potential and motion diminish with only the first order terms remained. However, in the results of the first order forces or motions, the irregular frequency effects are often observed in higher frequencies, which will affect the accuracy of the calculation of the second order forces and moments. Therefore, we need to pay close attention to the irregular frequency effects in the mean drift forces. This paper will discuss about the irregular frequency effects in the calculations of the mean drift forces and validate our in-house program MDL Multi DYN using some examples which are known to have irregular frequency effects. Finally, we prove that it is necessary to remove the effects and demonstrate that the effectiveness of the formula and methods adopted in the development of our program.
Liu, Yuji,Shi, Haiping,Liu, Xingyuan Department of Mathematics 2013 Kyungpook mathematical journal Vol.53 No.2
In this article, we establish the existence of at least three unbounded positive solutions to a boundary-value problem of the nonlinear singular fractional differential equation. Our analysis relies on the well known fixed point theorems in the cones.
Liu, Yuji,Liu, Xingyuan Korean Mathematical Society 2009 대한수학회논문집 Vol.24 No.1
Motivated by [Linear Algebra and its Appl. 420(2007), 218-227] and [Linear Algebra and its Appl. 425(2007), 171-183], we, in this paper, study the solvability of periodic boundary value problems of higher order nonlinear functional difference equations with p-Laplacian. Sufficient conditions for the existence of at least one solution of this problem are established.
Yujie Liu,Shen Wang,Jiebin Qi,Xuewei Wang,Xiaoqiang Yan 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.25 No.8
The cold rolling mills are complex electro-hydro-mechanical systems in which vibrations are usually detected as issues during production process. In the present work, the vibrations with frequencies of 80Hz were found at top of the rolling mill and the pressure behind servo valve during the production process. In order to understand the vibration mechanism and to explore the measurements for vibration suppression, the dynamic models were proposed to describe valve spool, 8-DOF cold rolling mill, and hydraulic system based on the dynamic characteristics of servo-valve. The analytical solutions and numerical solutions were obtained for the vibration rules for the valve spool displacement and the output flow rate under different working conditions. Moreover, the influence of dynamic characteristics of servo-valve on the vibrations and optimization of the servo-valve were discussed. The results suggest that the dynamic characteristics of servo-valve have a significant influence on the hydro-mechanical coupled vibration of rolling mill and the vibrations can be dampened by improving the dynamic characteristics of rolling mill. This work is expected to provide a new perspective to suppress the hydro-mechanical coupled vibrations.
Yuji Liu,Xingyuan Liu 충청수학회 2012 충청수학회지 Vol.25 No.3
Su±cient conditions for the existence of at least one solution of a class of multi-point boundary value problems of the fractional di??erential equations at resonance are established. The main theorem generalizes and improves those ones in [Liu, B., Solv-ability of multi-point boundary value problems at resonance(II), Appl. Math. Comput., 136(2003)353-377], see Remark 2.3. An example is presented to illustrate the main results.
Yujie Yang,Xiansong Liu,Shuangjiu Feng,Xucai Kan,Qingrong Lv,Feng Hu,Jiangli Ni,Chaocheng Liu,Wei Wang 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.4
The microstructural, spectral, magnetic and electric properties of hexaferrites Ba0.40Sr0.60-xNdxFe12.00-xZnxO19 (0.00 ≤ x ≤ 0.30)synthesized by the solid-state reaction route have been studied. XRD results confirmed that the hexaferrites with Nd-Zncontent (x) of 0.00 ≤ x ≤ 0.24 were single M-type phase, and the hexaferrite with x = 0.30 exhibited the M-type phase andimpurity phase. The remanence (Br) increased with x from 0.00 to 0.06, and then decreased when x ≥ 0.06. The intrinsiccoercivity (Hcj) and magnetic induction coercivity (Hcb) decreased with x from 0.00 to 0.30. Br indicated a linear decreasingbehavior with increasing temperature from 20 oC to 140 oC. Hcj raised linearly with increasing temperature from 20 oC to 140oC. The value of aBr basically remained constant with Nd-Zn content (x). The value of aHcj increased with x from 0.00 to 0.12,and began to decrease when x ≥ 0.12. The electrical resitivity (ρ) presented a decreasing trend with x from 0.00 to 0.30.
Formation and failure characteristics of a landslide induced by excavation in western Henan, China
Haining Liu,Suzhen Duan,Han Dong Liu,Weiguo Wang,Yujie Jia 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.7
Engineering construction in mountainous areas is a key factor inducing slope failure, whichposes severe threats to life and property safety during construction and operation. Thus, clearunderstanding of slope structure and potential failure mechanisms is of great importance forslope reinforcement. The Shangge landslide, located in a mountainous area of WesternHenan, China, was triggered by excavation along a toll station. The slope was still unstableafter a row of anti-sliding piles were constructed. To clarify the deformation characteristics andfailure mechanism of this landslide and provide reinforcement guidance for slopes with similargeological conditions, a combined method of field investigation, displacement monitoring,and numerical simulation was employed. The results indicate that the natural slope comprisesa dual structure of soil and rock, and that the soil, with poor permeability and high watermoisture, was prone to form a potential sliding surface. Secondly, slope excavation was thedirect triggering factor. Lastly, but most importantly, the preliminary investigation work failed toaccurately expose the potential position of the sliding surface, and the existing anti-slide pilesfailed to cross the potential sliding surface, which made them unable to effectively improveslope stability. The numerical simulation verified that the recommended piles installed on theplatform of level 2 could significantly improve slope stability. Therefore, when carrying outengineering slope design in similar geological environments, the slope structure and materialcomposition should be fully identified, and the influence of groundwater on the slope stabilitystate should be emphasized. These results can provide a reference for similar slopereinforcement designs.