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Finite elements analysis

Takamasa Ogawa, Yuji Sato, Noboru Kitagawa, Momoe Nakatsu
STATEMENT OF PROBLEM: Although the retention force of maxillary complete dentures has been measured in numerous studies with different devices, the biomechanical mechanism associated with the generation of this retention force cannot be determined. PURPOSE: The purpose of this clinical study was to investigate whether 3-dimensional finite-element analysis can be used to estimate the retention force of maxillary complete dentures. MATERIAL AND METHODS: The study included 12 participants (6 men and 6 women, mean 77...
October 17, 2016: Journal of Prosthetic Dentistry
Ryo Suzuki, Kohta Ito, Taeyong Lee, Naomichi Ogihara
Accurate identification of the material properties of the plantar soft tissue is important for computer-aided analysis of foot pathologies and design of therapeutic footwear interventions based on subject-specific models of the foot. However, parameter identification of the hyperelastic material properties of plantar soft tissues usually requires an inverse finite element analysis due to the lack of a practical contact model of the indentation test. In the present study, we derive an analytical contact model of a spherical indentation test in order to directly estimate the material properties of the plantar soft tissue...
September 22, 2016: Journal of the Mechanical Behavior of Biomedical Materials
Xuemin Cheng, Yikang Yang, Qun Hao
The thermal environment is an important factor in the design of optical systems. This study investigated the thermal analysis technology of optical systems for navigation guidance and control in supersonic aircraft by developing empirical equations for the front temperature gradient and rear thermal diffusion distance, and for basic factors such as flying parameters and the structure of the optical system. Finite element analysis (FEA) was used to study the relationship between flying and front dome parameters and the system temperature field...
October 17, 2016: Sensors
Jiang Zhu, Li Qi, Yusi Miao, Teng Ma, Cuixia Dai, Yueqiao Qu, Youmin He, Yiwei Gao, Qifa Zhou, Zhongping Chen
Elastography provides a powerful tool for histopathological identification and clinical diagnosis based on information from tissue stiffness. Benefiting from high resolution, three-dimensional (3D), and noninvasive optical coherence tomography (OCT), optical micro-elastography has the ability to determine elastic properties with a resolution of ~10 μm in a 3D specimen. The shear wave velocity measurement can be used to quantify the elastic modulus. However, in current methods, shear waves are measured near the surface with an interference of surface waves...
October 20, 2016: Scientific Reports
Xing Zhou Qu, Ming Yi Wang, Hui Shan Ong, Chen Ping Zhang
OBJECTIVES: This study aimed to evaluate the stability of prostheses supported by zygoma implants and remaining teeth for subjects who had undergone hemi-maxillectomy. METHODS: Ten patients were included in the study. Oral rehabilitation was performed using a temporary prosthesis that was supported by remaining teeth for the first three months. Then, a zygoma implant was placed to provide support for a final prosthesis in addition to the remaining teeth. Each prosthesis was tailor-made according to biomechanical three-dimensional finite element analysis results...
October 1, 2016: Clinics
Ian Swyer, Ronald Soong, Michael D M Dryden, Michael Fey, Werner E Maas, André Simpson, Aaron R Wheeler
Nuclear magnetic resonance (NMR) spectroscopy is extremely powerful for chemical analysis but it suffers from lower mass sensitivity compared to many other analytical detection methods. NMR microcoils have been developed in response to this limitation, but interfacing these coils with small sample volumes is a challenge. We introduce here the first digital microfluidic system capable of interfacing droplets of analyte with microcoils in a high-field NMR spectrometer. A finite element simulation was performed to assist in determining appropriate system parameters...
October 19, 2016: Lab on a Chip
Giordano Tasca, Matteo Selmi, Emiliano Votta, Paola Redaelli, Francesco Sturla, Alberto Redaelli, Amando Gamba
BACKGROUND: Aortic root aneurysm can be treated with valve-sparing procedures. The David and Yacoub techniques have shown excellent long-term results but are technically demanding. Recently, a new and simpler procedure, the Sleeve technique, was proposed with encouraging results. We aimed to quantify the biomechanics of the initially aneurysmal aortic root (AR) after the Sleeve procedure to assess whether it induces abnormal stresses, potentially undermining its durability. METHODS: Two finite element (FE) models of the physiologic and aneurysmal AR were built, accounting for the anatomical asymmetry and the nonlinear and anisotropic mechanical properties of human AR tissues...
October 15, 2016: Annals of Thoracic Surgery
Ling He, Deli Li, Jiwu Zhang, Xiucheng Li, Songhe Lu, Zhihui Tang
OBJECTIVE: The aim of this study was to evaluate cross-sectional area of the abutments, strain distribution in the periimplant bone, stress in the abutments and dental root-analog implant by different abutment design under different loading conditions, through three-dimensional finite element analysis. METHODS: Two three-dimensional finite element models were established. Two types of abutments, oval cross section abutment (OCSA) and circular cross section abutment (CCSA) were designed, keeping the size of the thinnest implant wall 0...
October 13, 2016: Implant Dentistry
Lin Li, Mary Cazzell, Olajide Babawale, Hanli Liu
Atlas-guided diffuse optical tomography (atlas-DOT) is a computational means to image changes in cortical hemodynamic signals during human brain activities. Graph theory analysis (GTA) is a network analysis tool commonly used in functional neuroimaging to study brain networks. Atlas-DOT has not been analyzed with GTA to derive large-scale brain connectivity/networks based on near-infrared spectroscopy (NIRS) measurements. We introduced an automated voxel classification (AVC) method that facilitated the use of GTA with atlas-DOT images by grouping unequal-sized finite element voxels into anatomically meaningful regions of interest within the human brain...
October 2016: Neurophotonics
Jiansong Zhang, Hui Guo, Hongfei Fu, Yanzhen Chang
Combining subspace correction method with least-squares finite element procedure, we construct a new overlapping domain decomposition parallel algorithm for solving the first-order time-dependent convection-diffusion system. This algorithm is fully parallel. We analyze the convergence of approximate solution, and study the dependence of the convergent rate on the spacial mesh size, time increment, iteration number and sub-domains overlapping degree. Both theoretical analysis and numerical results suggest that only one or two iterations are needed to reach to given accuracy at each time step...
2016: SpringerPlus
Diogo F Almeida, Rui B Ruben, João Folgado, Paulo R Fernandes, Emmanuel Audenaert, Benedict Verhegghe, Matthieu De Beule
Femur segmentation can be an important tool in orthopedic surgical planning. However, in order to overcome the need of an experienced user with extensive knowledge on the techniques, segmentation should be fully automatic. In this paper a new fully automatic femur segmentation method for CT images is presented. This method is also able to define automatically the medullary canal and performs well even in low resolution CT scans. Fully automatic femoral segmentation was performed adapting a template mesh of the femoral volume to medical images...
October 14, 2016: Medical Engineering & Physics
Leo Fradet, Xiaoyu Wang, Lawrence G Lenke, Carl-Eric Aubin
BACKGROUND: Proximal junctional failure is a severe proximal junctional complication following adult spinal instrumentation and involving acute proximal junctional kyphotic deformity, mechanical failure at the upper instrumented vertebra or just above, and/or proximal junctional osseoligamentous disruption. Clinical studies have identified potential risk factors, but knowledge on their biomechanics is still lacking for addressing the proximal junctional failure issues. The objective of this study was to develop comprehensive computational modeling and simulation techniques to investigate proximal junctional failure...
October 11, 2016: Clinical Biomechanics
Wenhao Song, Dongsheng Zhou, Yu He
BACKGROUND: The aim of this study was to compare the biomechanical characteristics between bilateral and unilateral lumbo-iliac fixation in unilateral comminuted sacral fractures (USF) by finite element analysis. METHODS: A 3-dimensional finite element model of unilateral sacral fractures was simulated. Three kinds of implants were instrumented into the model, including the unilateral lumbopelvic fixation (ULF), bilateral lumbopelvic fixation (BLF), and unilateral iliac fixation with bilateral lumbar pedicle screws (UBF)...
October 2016: Medicine (Baltimore)
Yuta Shimura, Yuji Sato, Noboru Kitagawa, Miyuki Omori
BACKGROUND: Proper implant placement is very important for long-term implant stability. Recently, numerous biomechanical studies have been conducted to clarify the relationship between implant placement and peri-implant stress. The placement of multiple implants in the edentulous posterior mandible has been studied by geometric analysis, three-dimensional finite element analysis (FEA), model experimentation, etc. Offset placement is a technique that reduces peri-implant load. However, few studies have used multiple analyses to clarify the value of the offset placement under identical conditions...
December 2016: Int J Implant Dent
Sho Kayumi, Yoshiyuki Takayama, Atsuro Yokoyama, Nana Ueda
BACKGROUND: The purpose of this study was to investigate the influence of occlusal forces (the contractile force of masticatory muscles) exerted during occlusal adjustment on the distribution of the forces among teeth, implants, and temporomandibular joints (TMJs) in intercuspal clenching in cases with bilateral missing molars and premolars by using finite element analysis. METHODS: A three-dimensional finite element model of the mandible with eight implants in the premolar and molar regions was constructed...
December 2015: Int J Implant Dent
Miyuki Omori, Yuji Sato, Noboru Kitagawa, Yuta Shimura, Manabu Ito
BACKGROUND: Three-dimensional finite element analysis (FEA) is effective in analyzing stress distributions around dental implants. However, FEA of living tissue involves many conditions, and the structures and behaviors are complex; thus, it is difficult to ensure the validity of the results. To verify reproducibility and validity, we embedded implants in experimental models and constructed FEA models; implant displacements were compared under various loading conditions. METHODS: Implants were embedded in the molar regions of artificial mandibles to fabricate three experimental models...
December 2015: Int J Implant Dent
Mansi Manish Oswal, Ulhas N Amasi, Manish S Oswal, Ashish S Bhagat
PURPOSE: Clinical success of implant prosthodontics is dependent in part upon the type of implant thread design. The selection of implant thread design plays an important role in the outcome of the treatment. This study was undertaken to evaluate the pattern of stress distribution using a finite element analysis; hence, the area which would be bearing maximum load for a given design would be arrived. MATERIALS AND METHODS: Three implants with different thread designs, namely V-thread, buttress, and reverse buttress thread designs were considered and dimensions were standardized...
October 2016: Journal of Indian Prosthodontic Society
Chunguang Piao, Jin Oh Kim
This paper considers the influence of the different thickness of the piezoelectric discs used in assembly of an ultrasonic sandwich transducer. The transducer consists of two piezoelectric discs with different thickness between 0 and 2.0mm and with same diameter 28mm. Its vibration characteristics of the radial and axial motions were investigated theoretically and experimentally in axisymmetric vibration modes. Theoretically, the differential equations of piezoelectric motions were solved to produce characteristic equations that provided natural frequencies and mode shapes...
September 28, 2016: Ultrasonics
Wei Xu, Jianquan Yao, Xianchao Yang, Jia Shi, Junfa Zhao, Cheng Zhang
A hollow fiber temperature sensor filled with graphene-Ag composite nanowire and liquid is presented and numerically characterized. The coupling properties and sensing performances are analyzed by finite element method (FEM) using both wavelength and amplitude interrogations. Due to the asymmetrical surface plasmon resonance sensing (SPR) region, the designed sensor exhibits strong birefringence, supporting two separate resonance peaks in orthogonal polarizations. Results show that x-polarized resonance peak can provide much better signal to noise ratio (SNR), wavelength and amplitude sensitivities than y-polarized, which is more suitable for tempertature detecting...
October 8, 2016: Sensors
Chao Tang, Haibo Huang, Peng Gao, Xi-Yun Lu
The self-propulsion of a three-dimensional flapping flexible plate near the ground is studied using an immersed boundary-lattice Boltzmann method for fluid flow and a finite-element method for plate motion. When the leading edge of the flexible plate is forced into a vertical oscillation near the ground, the entire plate moves freely due to the fluid-structure interaction. The mechanisms underlying the dynamics of the plate near the ground are elucidated. Based on the propulsive behaviors of the flapping plate, three distinct regimes due to the ground effect can be qualitatively identified...
September 2016: Physical Review. E
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