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Two-stage layoutesize optimization method for prow stiffeners
Zhijun Liu,Shingo Cho,Akihiro Takezawa,Xiaopeng Zhang,Mitsuru Kitamura 대한조선학회 2019 International Journal of Naval Architecture and Oc Vol.11 No.1
Designing sophisticate ship structures that satisfy several design criteria simultaneously with minimum weight and cost is an important engineering issue. For a ship structure composed of a shell and stiffeners, this issue is more serious because their mutual effect has to be addressed. In this study, a two-stage optimization method is proposed for the conceptual design of stiffeners in a ship's prow. In the first stage, a topology optimization method is used to determine a potential stiffener distribution based on the optimal results, whereupon stiffeners are constructed according to stiffener generative theory and the material distribution. In the second stage, size optimization is conducted to optimize the plate and stiffener sections simultaneously based on a parametric model. A final analysis model of the ship-prow structure is presented to assess the validity of this method. The analysis results show that the two-stage optimization method is effective for stiffener conceptual design, which provides a reference for designing actual stiffeners for ship hulls.
Two-stage layout-size optimization method for prow stiffeners
Liu, Zhijun,Cho, Shingo,Takezawa, Akihiro,Zhang, Xiaopeng,Kitamura, Mitsuru The Society of Naval Architects of Korea 2019 International Journal of Naval Architecture and Oc Vol.11 No.1
Designing sophisticate ship structures that satisfy several design criteria simultaneously with minimum weight and cost is an important engineering issue. For a ship structure composed of a shell and stiffeners, this issue is more serious because their mutual effect has to be addressed. In this study, a two-stage optimization method is proposed for the conceptual design of stiffeners in a ship's prow. In the first stage, a topology optimization method is used to determine a potential stiffener distribution based on the optimal results, whereupon stiffeners are constructed according to stiffener generative theory and the material distribution. In the second stage, size optimization is conducted to optimize the plate and stiffener sections simultaneously based on a parametric model. A final analysis model of the ship-prow structure is presented to assess the validity of this method. The analysis results show that the two-stage optimization method is effective for stiffener conceptual design, which provides a reference for designing actual stiffeners for ship hulls.
EXISTENCE OF PERIODIC SOLUTION OF SOME ECO-EPIDEMIOLOGICAL SYSTEMS
Zhijun Liu,Sahabuddin Sarwardi 한국전산응용수학회 2010 Journal of applied mathematics & informatics Vol.28 No.5
The effect of impulse in the ecological models makes them more realistic. Recently, the eco-epidemiological models have become an important field of study from the both mathematical and ecological view points. In this article, we consider some eco-epidemiological systems under the influence of impulsive force. A set of sufficient conditions for the permanence of the system are derived. Stability of the trivial solution and at least one strictly positive periodic solution are obtained. Numerical examples are given in support to our analytical findings. Finally, a short discussion concludes the paper.
EXISTENCE OF PERIODIC SOLUTION OF SOME ECO-EPIDEMIOLOGICAL SYSTEMS
Liu, Zhijun,Sarwardi, Sahabuddin The Korean Society for Computational and Applied M 2010 Journal of applied mathematics & informatics Vol.28 No.5
The effect of impulse in the ecological models makes them more realistic. Recently, the eco-epidemiological models have become an important field of study from the both mathematical and ecological view points. In this article, we consider some eco-epidemiological systems under the influence of impulsive force. A set of sufficient conditions for the permanence of the system are derived. Stability of the trivial solution and at least one strictly positive periodic solution are obtained. Numerical examples are given in support to our analytical findings. Finally, a short discussion concludes the paper.
( Guangyao Liu ),( Shan Li ),( Nan Chen ),( Ziyang Zhao ),( Man Guo ),( Hong Liu ),( Jie Feng ),( Dekui Zhang ),( Zhijun Yao ),( Bin Hu ) 대한소화기기능성질환·운동학회(구 대한소화관운동학회) 2021 Journal of Neurogastroenterology and Motility (JNM Vol.27 No.3
Background/Aims Irritable bowel syndrome (IBS) is a prevalent functional gastrointestinal disease characterized by recurrent abdominal pain and bowel dysfunction. However, the majority of previous neuroimaging studies focus on brain structure and connections but seldom on the inter-hemispheric connectivity or structural asymmetry. This study uses multi-modal imaging to investigate the abnormal changes across the 2 cerebral hemispheres in patients with IBS. Methods Structural MRI, resting-state functional MRI, and diffusion tensor imaging were acquired from 34 patients with IBS and 33 healthy controls. The voxel-mirrored homotopic connectivity, fractional anisotropy, fiber length, fiber number, and asymmetry index were calculated and assessed for group differences. In addition, we assessed their relevance for the severity of IBS. Results Compared with healthy controls, the inter-hemispheric functional connectivity of patients with IBS showed higher levels in bilateral superior occipital gyrus, middle occipital gyrus, precuneus, posterior cingulate gyrus, and angular gyrus, but lower in supplementary motor area. The statistical results showed no significant difference in inter-hemispheric anatomical connections and structural asymmetry, however negative correlations between inter-hemispheric connectivity and the severity of IBS were found in some regions with significant difference. Conclusions The functional connections between cerebral hemispheres were more susceptible to IBS than anatomical connections, and brain structure is relatively stable. Besides, the brain areas affected by IBS were concentrated in default mode network and sensorimotor network. (J Neurogastroenterol Motil 2021;27:426-435)
Energy spread minimization in a cascaded laser wakefield accelerator via velocity bunching
Zhang, Zhijun,Li, Wentao,Liu, Jiansheng,Wang, Wentao,Yu, Changhai,Tian, Ye,Nakajima, Kazuhisa,Deng, Aihua,Qi, Rong,Wang, Cheng,Qin, Zhiyong,Fang, Ming,Liu, Jiaqi,Xia, Changquan,Li, Ruxin,Xu, Zhizhan American Institute of Physics 2016 Physics of plasmas Vol.23 No.5
Landing Dynamic and Key Parameter Estimations of a Landing Mechanism to Asteroid with Soft Surface
Zhijun Zhao,JingDong Zhao,Hong Liu 한국항공우주학회 2013 International Journal of Aeronautical and Space Sc Vol.14 No.3
It is of great significance to utilize a landing mechanism to explore an asteroid. A landing mechanism named ALISE (Asteroid Landing and In Situ Exploring) for asteroid with soft surface is presented. The landing dynamic in the first turning stage, which represents the landing performance of the landing mechanism, is built by a Lagrange equation. Three key parameters can be found influencing the landing performance: the retro-rocket thrust T, damping element damping c₁, and cardan element damping c₂. In this paper, the retro-rocket thrust T is solved with considering that the landing mechanism has no overturning in extreme landing conditions. The damping element damping c₁ is solved by a simplified dynamic model. After solving the parameters T and c₁, the cardan element damping c₂ is calculated using the landing dynamic model, which is built by Lagrange equation. The validities of these three key parameters are tested by simulation. The results show a stable landing, when landing with the three estimated parameters T, c₁, and c₂. Therefore, the landing dynamic model and methods to estimate key parameters are reasonable, and are useful for guiding the design of the landing mechanism.
Single nucleotide polymorphism-based analysis of the genetic structure of Liangshan pig population
Liu, Bin,Shen, Linyuan,Guo, Zhixian,Gan, Mailing,Chen, Ying,Yang, Runling,Niu, Lili,Jiang, Dongmei,Zhong, Zhijun,Li, Xuewei,Zhang, Shunhua,Zhu, Li Asian Australasian Association of Animal Productio 2021 Animal Bioscience Vol.34 No.7
Objective: To conserve and utilize the genetic resources of a traditional Chinese indigenous pig breed, Liangshan pig, we assessed the genetic diversity, genetic structure, and genetic distance in this study. Methods: We used 50K single nucleotide polymorphism (SNP) chip for SNP detection of 139 individuals in the Liangshan Pig Conservation Farm. Results: The genetically closed conserved population consisted of five overlapping generations, and the total effective content of the population (Ne) was 15. The whole population was divided into five boar families and one non-boar family. Among them, the effective size of each generation subpopulation continuously decreased. However, the proportion of polymorphic markers (P<sub>N</sub>) first decreased and then increased. The average genetic distance of these 139 Liangshan pigs was 0.2823±0.0259, and the average genetic distance of the 14 boars was 0.2723±0.0384. Thus, it can be deduced that the genetic distance changed from generation to generation. In the conserved population, 983 runs of homozygosity (ROH) were detected, and the majority of ROH (80%) were within 100 Mb. The inbreeding coefficient calculated based on ROH showed an average value of 0.026 for the whole population. In addition, the inbreeding coefficient of each generation subpopulation initially increased and then decreased. In the pedigree of the whole conserved population, the error rate of paternal information was more than 11.35% while the maternal information was more than 2.13%. Conclusion: This molecular study of the population genetic structure of Liangshan pig showed loss of genetic diversity during the closed cross-generation reproduction process. It is necessary to improve the mating plan or introduce new outside blood to ensure long-term preservation of Liangshan pig.