Computational mathematical modeling of the nonlinear vibration characteristics of AFG truncated conical nano pipe based on the nonlocal strain gradient theory

Ruihua Zhang,Yiqing Cao 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.42 No.5

In the present paper, the numerical dynamic analysis of a functionally graded nano-scale nonuniform tube was investigated according to the high-order beam theory coupled with the nonlocal gradient strain theory. The supposed crosssection is changed along the pipe length, and the material distribution, which combines both metal and ceramics, is smoothly changed in the pipe length direction, which is called axially functionally graded (AFG) pipe. Moreover, the porosity voids are dispersed in the cross-section and the radial pattern that the existence of both material distribution along the tube length and porosity voids make a two-dimensional functionally graded (2D-FG) truncated conical pipe. On the basis of the Hamilton principle, the governing equations and the associated boundary conditions equations are derived, and then a numerical approach is applied to solve the obtained equations.

Image Variational Decomposition Based on Dual Method

Ruihua Liu,Ruizhi Jia 보안공학연구지원센터(IJSIP) 2013 International Journal of Signal Processing, Image Vol.6 No.1

Image Restoration Based on L1 + L1 Model

Ruihua Liu 보안공학연구지원센터 2014 International Journal of Signal Processing, Image Vol.7 No.5

In this paper, we firstly propose a new image restoration model including non-smooth l1-norm data-fidelity term and non-smooth l1-norm regularization term based on the bilateral total variation regularization. Secondly, we prove the existence of minimal solutions of our proposed energy functional model. Thirdly, we consider the convergence of the discrete numerical algorithm, and obtain that the limit point of the solution sequence is the minimal point of our proposed energy functional. Finally, we give some experimental simulation results in the case of the single noisy image without blurring, multiple different noisy images without blurring, single noisy image with blurring, and multiple different noisy images with different blurring, respectively. The restoration results show our model works effectively.

Risk Factors and Characteristics of the Recurrence of Juvenile Nasopharyngeal Angiofibroma: A 22-Year Experience With 123 Cases at a Tertiary Center

Ruihua Fang,Jian Li,Weiping Wen,Wei Sun,Rui Xu,Jianbo Shi,Liang Peng,Yinyan Lai,Fenghong Chen,Yihui Wen 대한이비인후과학회 2022 Clinical and Experimental Otorhinolaryngology Vol.15 No.4

Objectives. Despite the efficacy of surgical treatments, the high rate of recurrence in juvenile nasopharyngeal angiofibroma (JNA) after surgery remains an unresolved problem. The present study comprehensively analyzed the risk factors and characteristics of JNA recurrence, providing clinical guidance for reducing recurrence. Methods. A total of 123 patients who underwent surgery for JNA between 1997 and 2019 at a single hospital were analyzed retrospectively. Univariate and multivariate analyses were used to assess the clinical risk factors for the recurrence of JNA. The relapse-free survival and annual cumulative recurrence rates were analyzed for subgroups defined according to clinical parameters. Results. After screening, 78 of the 123 patients were included in the present study. The main risk factors associated with JNA recurrence included the year of diagnosis, tumor size, sphenoid bone invasion, Radkowski stage, surgical approach, and intraoperative bleeding. Importantly, the surgical approach and sphenoid bone invasion were independent prognostic factors affecting recurrence. Patients who underwent endoscopic surgery without sphenoid bone invasion exhibited longer relapse-free survival. In the present study, the overall cumulative recurrence rate of JNA was 38.7%, and recurrence occurred mainly in the first year after the initial surgery. Conclusion. Endoscopic surgery achieved better relapse-free survival in JNA patients, and patients with sphenoid bone invasion should be carefully explored to avoid residual JNA. The recurrence rate of JNA differed among subgroups defined based on clinical parameters and was highest in the first year after surgery. Computed tomography or magnetic resonance imaging, along with close follow-up, should be performed strictly within 1 year after the primary operation.

Fabrication and Mechanical Properties of Completely Biodegradable Hemp Fiber Reinforced PLA Composites

Ruihua Hu,Jun Hee Song,Jun Yong Choi,Phan Quoc Thai,Jae Kyoo Lim 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.3

A fabrication method of a kind of completely biodegradable PLA composites reinforced by short hemp fiber is developed in this paper. The fibers were treated in 6% NaOH aqueous solution and untreated respectively. In these two cases, the composites with 30%, 40% and 50% fiber volume fraction were prepared. The tensile strength, tensile modulus and flexural strength were tested. The results showed that the mechanical properties of this composite with 40% alkali treated fiber volume fraction have the highest values. They are 54.6㎫, 8.5㎬ and 112.7 ㎫ respectively. These values are competitive to those of glass fiber reinforced polypropylene. The density of this composite is 1.23g/㎝3, which is much lower than glass fiber reinforced composites with similar fiber volume fraction. The specific strength was also calculated. Fracture surfaces of the composites were observed by SEM. The results showed that there is still a potential enhancement in the properties by optimizing the fabrication condition.

Research on Calculation Method of Fuel Temperature According to Airworthiness Regulations

Ruihua Zhang,Weihua Liu 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.6

How to establish a general fuel tank thermodynamic model that meets the requirements of airworthiness certification and how to obtain the equilibrium temperature difference △T and time constant τ in the Monte Carlo evaluation model after obtaining the fuel temperature change law within specific flight envelope are the bottleneck issues need to be solved urgently in the airworthiness certification process of fuel tank flammability. This paper builds the fuel temperature simulation calculation model on the MATLAB/Simulink software platform to obtain the fuel temperature change law and obtains the high-order functional expression of the fuel temperature change law in each stage by means of MATLAB polynomial piecewise fitting function. The exponential attenuation equation stipulated in the Monte Carlo evaluation model is used to characterize the change law of fuel temperature. Among which the total ambient temperature (TAT) is obtained by the method specified in the evaluation model, and the equilibrium temperature difference and time constant are obtained by the improved genetic algorithm. The equilibrium temperature difference and time constant obtained by the inversion are input into Monte Carlo model for calculation, the calculated temperature data and the actual measured flight data are compared to verify the reliability of the method.

Computational Studies on Mesh Stiffness of Paralleled Helical Beveloid Gear Pair

Ruihua Sun,Chaosheng Song,Caichao Zhu,Yawen Wang,Xingyu Yang 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.1

Considering the asymmetrical left and right tooth profiles including the transient curve at the tooth root region and the varying thickness along the axial direction due to the cone angle, we build the accurate profile curve model including the transient curve at the tooth root of helical beveloid gear with machining parameters to solve the problem of non-applicability of real digital model. According to the feature of gear shape varying along tooth width direction, we introduced the slicing method and derived its grouping formula. Finally, the efficient and accurate slicing-based mesh stiff ness calculation model of paralleled helical beveloid gears was proposed using potential energy theory. Then, mesh stiff ness was calculated using finite element contact model for comparison and verification. Finally, the impacts of macro geometry parameters including cone angle, normal pressure angle, helix angle, tooth width and addendum coefficient on single and total mesh stiff ness were analyzed. The calculated mesh stiff ness correlates well with the results from FEM with the maximum peak error is 4.8%. Results show that the tooth width shows an obvious incremental impact on average total mesh stiff ness. When the pressure angle, helix angle, cone angle and addendum coefficient increase, the average total mesh stiff ness increases first and then decreases. For the fluctuating value, it increases as the tooth width, helix angle and cone angle increase. However, the pressure angle and addendum coefficient show an opposite impact on the fluctuating value.

Friele Color Matching Model of Digital Rotor Spinning Viscose Mélange Fabric

Ruihua Yang,Kanglei Zhang,Zhuo Wang 한국섬유공학회 2022 Fibers and polymers Vol.23 No.4

Digital rotor spinning involves spinning fibers that have been dope-dyed together with one of several differenthues in a manner that enables the color tuning of the resultant yarn. A small inventory of colored fibers provides access to awide gamut of shades and production of textiles in a variety of colorways. To overcome the issues with the current intelligentcolor matching system for digital rotor spinning viscose melange yarn, in this study, a digital rotor spinning frame was used tospin selected red, yellow, and blue dope-dyed viscose staple fibers into 66 types of melange yarns at a ratio gradient of 10 %. The corresponding yarns were knitted as fabric samples, and then a Datacolor650 spectrophotometer was used to performcolor testing and record the experimental data. The parameter σ of the Friele model was assigned within [0,1]. The optimalvalue of σ was 0.134 when the average color difference of the bi-component melange sample was minimal, which was usedfor the construction of a color matching system based on the Friele model. In addition, this study verifies the obtained optimalvalue of σ using the full-spectrum color matching method. The average error between the predicted ratio and actual ratio ofthe three-component melange sample was 10.21 %, while the predicted average color difference was 0.4561. This indicatesthat the empirical parameters of the Friele model obtained in this study yield a good prediction accuracy of digital rotorspinning viscose melange products.

A Graph-Based Matching Algorithm on Sub-Sequence of Near Duplicated Video

Liao Ruihua,Zhao Kai 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.11

As to solving the effectiveness and efficiency problem in the process of detecting the near duplicated video, we the thesis proposes a graph-based matching algorithm on sub-sequence of near duplicated video. The method will built similarity researching results based on the features of key frames feature into the query matching diagram, and then the near duplicated video detection is converted into a problem of searching the longest path in the matching results graph. As for its main advantage, firstly, it can find the best matching sequence in many cluttered matching results, which can effectively exclude a lot of noises brought by certain false “high similarity” matching, thus to some extent it can compensate the deficiencies of the underlying characterization force. Secondly, because it fully understands and uses the timing characteristics of the video sequences, the positioning accuracy of near duplicated video is with a high degree. Finally, multiple discrete paths existing in the matching results graphs are automatically detected, thus the situation where two video segments may exist several near duplicated videos can be detected once time. Experimental results show that the graph-based matching algorithm on video sub sequence improve the detection accuracy, at the same time improve the detection efficiency, which achieved good practice effect.

Finite-time Issue of Discrete-time Linear Switched Systems With Partial Finite-time Unstable Modes Based on an Inverse Weighted Switching Scheme

Yunpeng Zhan,Ruihua Wang,Shumin Fei 제어·로봇·시스템학회 2024 International Journal of Control, Automation, and Vol.22 No.2

The work proposes a multiple convex Lyapunov function and an inverse weighted switching scheme to investigate the finite-time stability and finite-time boundedness for a class of discrete-time switched linear systems with partial finite-time unstable modes. A multiple convex Lyapunov function is put forth by constructing a convex combination of positive definite matrices, which can relax the restricted conditions of the Lyapunov function and make it carry more decision variables than traditional Lyapunov function methods. Besides, the inverse weighted switching scheme is devised by summing the reciprocal of each dwell time with weighting coefficients, by which tighter dwell time bounds are ensured. On the basis of the new Lyapunov function and switching scheme, the finitetime control for a class of switched linear systems with partial finite-time unstable modes is addressed. Different from other researches that require all subsystems to be controllable, we only require the existence of one controllable subsystem. In the end, two numerical examples and a tunnel diode circuit example are provided to verify the effectiveness of the developed results.