A topological optimization method for flexible multi-body dynamic system using epsilon algorithm

Zhi-Jun Yang,Xin Chen,Robert Kelly 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.37 No.5

In a flexible multi-body dynamic system the typical topological optimization method for structures cannot be directly applied, as the stiffness varies with position. In this paper, the topological optimization of the flexible multi-body dynamic system is converted into structural optimization using the equivalent static load method. First, the actual boundary conditions of the control system and the approximate stiffness curve of the mechanism are obtained from a flexible multi-body dynamical simulation. Second, the finite element models are built using the absolute nodal coordination for different positions according to the stiffness curve. For efficiency, the static reanalysis method is utilized to solve these finite element equilibrium equations. Specifically, the finite element equilibrium equations of key points in the stiffness curve are fully solved as the initia solution, and the following equilibrium equations are solved using a reanalysis method with an error controlled epsilon algorithm. In order to identify the efficiency of the elements, a non-dimensional measurement is introduced. Finally, an improved evolutional structural optimization (ESO) method is used to solve the optimization problem. The presented method is applied to the optimal design of a die bonder. The numerical results show that the presented method is practical and efficient when optimizing the design of the mechanism.

INVESTIGATION OF HOMOLOGOUS SERIES AS PRECURSORY HYDROCARBONS FOR ALIGNED CARBON NANOTUBE FORMATION BY THE SPRAY PYROLYSIS METHOD

ZHI YANG,HUAGUI NIE,XUEMEI ZHOU,ZHEN YAO,SHAOMING HUANG,XIAOHUA CHEN 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2011 NANO Vol.6 No.3

The precursory carbon source is one of the key parameters which govern the formation of carbon nanotubes (CNTs). In this work, by selecting four homologous series, namely n-pentane, n-hexane, n-heptane and n-octane, as investigated targets, we comparatively study the relationship between thermodynamic properties of the precursory carbon source and formation of aligned CNTs. We find that all of these alkanes are favored for the growth of aligned CNTs in a suitable growth environment. But only n-heptane can yield the aligned CNTs with relatively high quality, high yield and narrow diameter distribution. Furthermore, after considering the link between thermodynamic properties of the precursory carbon source and the morphology characteristic of the nanotube samples, we find that the Gibbs free energy and formation enthalpy of precursory carbon sources play critical roles in the nanotube formation. In additions some possible explanations are proposed to better understand these phenomena. These rules will be very helpful in making clearer the formation mechanism from the precursory carbon sources to the CNTs, and preparing large-scale aligned CNTs with diameter control at low cost.

SYNTHESIZING A WELL-ALIGNED CARBON NANOTUBE FOREST WITH HIGH QUALITY VIA THE NEBULIZED SPRAY PYROLYSIS METHOD BY OPTIMIZING ULTRASONIC FREQUENCY

ZHI YANG,HUAGUI NIE,XUEMEI ZHOU,ZHEN YAO,SHAOMING HUANG,XIAOHUA CHEN 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2011 NANO Vol.6 No.4

Nebulized spray pyrolysis (NSP) offers ease of scaling into an industrial scale process method for large-scale CNT synthesis. In the method, ultrasonic frequency plays an important role in the formation of well-aligned carbon nanotubes (CNTs). In this work, we obtain well-aligned CNTs with high quality by optimizing ultrasonic frequency via the NSP method. SEM, TEM and HRTEM results show that the aligned CNTs obtained under an ultrasonic frequency of 1.8 MHz have good alignment, uniform nanotube length (~200 μm), high density and no trace of other carbon nanoparticles. The Raman spectra result further confirms that the aligned CNTs have a high graphitization degree. Furthermore, we find that ultrasonic frequency is an important factor in determining the nanotube diameter. The higher the ultrasonic frequency, the smaller the nanotube diameter. This rule may be very helpful in the preparation of large-scale well-aligned CNTs with high quality and diameter-controlled at low cost.

Synchronous Ectopic Pancreatoblastoma in a Child: A Case Report

Zhi-Hao Yang,Jian-Bo Gao,Song-Wei Yue,Xue-Hua Yang,Hua Guo 대한의학회 2011 Journal of Korean medical science Vol.26 No.6

Pancreatoblastoma is a rare primary pancreatic neoplasm of children that may arise in any portion of the pancreas. We report a case of a 3-yr-old boy who presented to with abdominal pain our hospital and a progressive bulge in his right abdomen. Biochemical evaluation and serum levels of tumoral markers were within reference limits. On the computed tomography, two tumors were found. One located in the head of the pancreas;however, a laparotomy revealed that the head of pancreas was compressed but normal. The other was in the left abdomen near the spleen and the tail of the pancreas. The diagnosis of two synchronous pancreatoblastoma originating from the omentum was confirmed by pathology. Therefore, a pancreatoblastoma should be considered when a large well-defined, lobulated, and heterogeneous mass is identified in the pancreas of children. In addition, an ectopic pancreatoblastoma should be considered when identified within or near the ectopic pancreatic tissue.

Distinctive Endophytic Fungal Assemblage in Stems of Wild Rice (Oryza granulata) in China with Special Reference to Two Species of Muscodor (Xylariaceae)

Zhi-lin Yuan,Zhen-zhu Su,Li-juan Mao,Yang-qing Peng,Guan-mei Yang,Fu-cheng Lin,Chu-long Zhang 한국미생물학회 2011 The journal of microbiology Vol.49 No.1

Ecological niches in the rhizosphere and phyllosphere of grasses capable of sustaining endophytes have been extensively studied. In contrast, little information regarding the identity and functions of endophytic fungi in stems is available. In this study, we investigated the taxonomic affinities, diversity, and host specificities of culturable endophytes in stems of wild rice (Oryza granulata) in China. Seventy-four isolates were recovered. Low recovery rate (11.7%) indicated that there were relatively few sites for fungal infection. Identification using morphology, morphospecies sorting, and molecular techniques resulted in classification into 50 taxa, 36 of which were recovered only once. Nucleotide sequence similarity analysis indicated that 30% of the total taxa recovered were highly divergent from known species and thus may represent lineages new to science. Most of the taxa were classified as members of the classes Sordariomycetes or Dothideomycetes (mainly in Pleosporales). The presence of Arthrinium and Magnaporthaceae species, most often associated with poaceous plants, suggested a degree of host specificity. A polyphasic approach was employed to identify two Muscodor taxa based on (i) ITS and RPB2 phylogenies, (ii) volatile compounds produced, and (iii)an in vitro bioassay of antifungal activity. This to our knowledge is only the second report regarding the isolation of Muscodor spp. in China. Therefore, we hypothesize that wild plants represent a huge reservoir of unknown fungi. The prevalence, novelty, and species-specificity of unique isolates necessitate a reevaluation of their contribution to ecosystem function and fungal biodiversity.

Biomechanical Evaluation of 2 Endoscopic Spine Surgery Methods for Treating Lumbar Disc Herniation: A Finite Element Study

Yang Zou,Shuo Ji,Hui Wen Yang,Tao Ma,Yue Kun Fang,Zhi Cheng Wang,Miao Miao Liu,Ping Hui Zhou,Zheng Qi Bao,Chang Chun Zhang,Yu Chen Ye 대한척추신경외과학회 2024 Neurospine Vol.21 No.1

Objective: This study aimed to evaluate the effects of 2 endoscopic spine surgeries on the biomechanical properties of normal and osteoporotic spines. Methods: Based on computed tomography images of a healthy adult volunteer, 6 finite element models were created. After validating the normal intact model, a concentrated force of 400 N and a moment of 7.5 Nm were exerted on the upper surface of L3 to simulate 6 physiological activities of the spine. Five types of indices were used to assess the biomechanical properties of the 6 models, range of motion (ROM), maximum displacement value, intervertebral disc stress, maximum stress value, and articular protrusion stress, and by combining them with finite element stress cloud. Results: In normal and osteoporotic spines, there was no meaningful change in ROM or disc stress in the 2 surgical models for the 6 motion states. Model N1 (osteoporotic percutaneous transforaminal endoscopic discectomy model) showed a decrease in maximum displacement value of 20.28% in right lateral bending. Model M2 (unilateral biportal endoscopic model) increased maximum displacement values of 16.88% and 17.82% during left and right lateral bending, respectively. The maximum stress value of L4–5 increased by 11.72% for model M2 during left rotation. In addition, using the same surgical approach, ROM, maximum displacement values, disc stress, and maximum stress values were more significant in the osteoporotic model than in the normal model. Conclusion: In both normal and osteoporotic spines, both surgical approaches were less disruptive to the physiologic structure of the spine. Furthermore, using the same endoscopic spine surgery, normal spine biomechanical properties are superior to osteoporotic spines.

Damage identification in beam-like pipeline based on modal information

Yang, Zhi-Rong,Li, Hong-Sheng,Guo, Xing-Lin,Li, Hong-Yan Techno-Press 2007 Structural Engineering and Mechanics, An Int'l Jou Vol.26 No.2

Damage detection based on measured vibration data has received intensive studies recently. Frequently, the damage to a structure may be reflected by a change of some system parameters, such as a degradation of the stiffness. In this paper, we apply a method to nondestructively locate and estimate the severity of damage in corrosion pipeline for which a few natural frequencies or mode shapes are available. The method is based on the strain modal sensitivity ratio (SMSR) and the orthogonality conditions sensitivities (OCS) applied to vibration features identified during the monitoring of the pipeline. The advantage of these methods is that it only requires measuring few modal parameters. The SMSR-based and OCS-based damage detection methods are illustrated using computer-simulated and laboratory testing data. The results show that the current method provides a precise indication of both the location and the extent of corrosion pipeline.

Soft Tissue Reconstruction of Complete Circumferential Defects of the Upper Extremity

Zhi Yang Ng,Shaun Shi Yan Tan,Alexandre Gaston Lellouch,Curtis Lisante Cetrulo Jr,Harvey Wei Ming Chim 대한성형외과학회 2017 Archives of Plastic Surgery Vol.44 No.2

Background Upper extremity soft tissue defects with complete circumferential involvement are not common. Coupled with the unique anatomy of the upper extremity, the underlying etiology of such circumferential soft tissue defects represent additional reconstructive challenges that require treatment to be tailored to both the patient and the wound. The aim of this study is to review the various options for soft tissue reconstruction of complete circumferential defects in the upper extremity. Methods A literature review of PubMed and MEDLINE up to December 2016 was performed. The current study focuses on forearm and arm defects from the level at or proximal to the wrist and were assessed based on Tajima’s classification (J Trauma 1974). Data reviewed for analysis included patient demographics, causality, defect size, reconstructive technique(s) employed, and postoperative follow-up and functional outcomes (when available). Results In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, 14 unique articles were identified for a total of 50 patients (mean=28.1 years). Underlying etiologies varied from extensive thermal or electrical burns to high impact trauma leading to degloving or avulsion, crush injuries, or even occur iatrogenically after tumor extirpation or extensive debridement. Treatment options ranged from the application of negative pressure wound dressings to the opposite end of the spectrum in hand transplantation. Conclusions With the evolution of reconstructive techniques over time, the extent of functional and aesthetic rehabilitation of these complex upper extremity injuries has also improved. The proposed management algorithm comprehensively addresses the inherent challenges associated with these complex cases.

Quinoxaline-Based Wide Band Gap Polymers for Efficient Nonfullerene Organic Solar Cells with Large Open-Circuit Voltages

Yang, Jie,Uddin, Mohammad Afsar,Tang, Yumin,Wang, Yulun,Wang, Yang,Su, Huimin,Gao, Rutian,Chen, Zhi-Kuan,Dai, Junfeng,Woo, Han Young,Guo, Xugang American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.27

<P>We present here a series of wide-band-gap (<I>E</I><SUB>g</SUB>: >1.8 eV) polymer donors by incorporating thiophene-flanked phenylene as an electron-donating unit and quinoxaline as an electron-accepting co-unit to attain large open-circuit voltages (<I>V</I><SUB>oc</SUB>s) and short-circuit currents (<I>J</I><SUB>sc</SUB>s) in nonfullerene organic solar cells (OSCs). Fluorination was utilized to fine-tailor the energetics of polymer frontier molecular orbitals (FMOs) by replacing a variable number of H atoms on the phenylene moiety with F. It was found that fluorination can effectively modulate the polymer backbone planarity through intramolecular noncovalent S···F and/or H···F interactions. Polymers (P2-P4) show an improved molecular packing with a favorable face-on orientation compared to their nonfluorinated analogue (P1), which is critical to charge carrier transport and collection. When mixed with IDIC, a nonfullerene acceptor, P3 with two F atoms, achieves a remarkable <I>V</I><SUB>oc</SUB> of 1.00 V and a large <I>J</I><SUB>sc</SUB> of 15.99 mA/cm<SUP>2</SUP>, simultaneously, yielding a power-conversion efficiency (PCE) of 9.7%. Notably, the 1.00 V <I>V</I><SUB>oc</SUB> is among the largest values in the IDIC-based OSCs, leading to a small energy loss (<I>E</I><SUB>loss</SUB>: 0.62 eV) while maintaining a large PCE. The P3:IDIC blend shows an efficient exciton dissociation through hole transfer even under a small energy offset of 0.16 eV. Further fluorination leads to the polymer P4 with increased chain-twisting and mismatched FMO levels with IDIC, showing the lowest PCE of 2.93%. The results demonstrate that quinoxaline-based copolymers are promising donors for efficient OSCs and the fluorination needs to be fine-adjusted to optimize the interchain packing and physicochemical properties of polymers. Additionally, the structure-property correlations from this work provide useful insights for developing wide-band-gap polymers with low-lying highest occupied molecular orbitals to minimize <I>E</I><SUB>loss</SUB> and maximize <I>V</I><SUB>oc</SUB> in nonfullerene OSCs for efficient power conversion.</P> [FIG OMISSION]</BR>

Diffusion of Polystyrene Latex Particle in Poly(vinyl alcohol)/DMSO Gel Matrix

Zhi Yang Xu,Jae Ha Park,Il Hyun Park 한국고분자학회 2006 한국고분자학회 학술대회 연구논문 초록집 Vol.2006 No.10