The simple expansion chamber muffler is a base control device whose use is to attenuate sound power, and has been known for a long time. Some of the most compelling research has focused on the mufflers with a straight inlet and outlet. To date, a muffler with a right angle inlet has never been studied. Therefore, the purpose of this work is to analyze the simple expansion chamber muffler with a right angle inlet. The numerical results show a comparable agreement between the experiment and other numerical approaches. A discussion is also presented in this work on the muffler with a different radius to that of the inlet/outlet pipe, a different inlet part, etc. The result clearly shows that the attenuation of the muffler with a right angle inlet is better than that with a straight inlet at particular frequencies. In addition, the mufflers do not have any absorbent linings attached to the inside of them, unlike the right angle-inlets which do. However, the propagation of sound in the muffler with a right angle inlet can lead its sound power to be attenuated about 10 ∼ 40dB at those particular frequencies.

In this study, the failure response of two serial bolted joints in composite laminates was investigated. The composite material was consisted of epoxy matrix and glass fibers. To find out the effects of joint geometry and stacking sequences on the failure response, parametric studies were performed experimentally. Three different geometrical parameters that were the edge distance-to-hole diameter ratio (E/D), plate width-to-hole diameter ratio (W/D) and the distance between two serial holes-to-hole diameter ratio (K/D) were investigated. Hence, E/D, W/D and K/D ratios were considered from 1 to 5, 2 to 5 and 3 to 5, respectively. In addition, the failure tests were carried out for a range of preload moments as 2, 3, 4, 5 Nm and without any preload moments as 0Nm. Tested composite laminates were oriented two different stacking sequences as [0°]8 and [0°/0°/90°/90°]s. Experimental results point out that failure response of two serial bolted composite joints are firmly effected from material parameters, geometrical parameters and the magnitudes of applied preload moments.

Anterior Lumbar Interbody Fusion (ALIF) has been widely used to treat internal disc degeneration. However, different cage positions and their orientations may affect the initial stability leading to different fusion results. The purpose of the present study is to investigate the optimum cage position and orientation for aiding an ALIF having a transfacet pedicle screw fixation (TFPS). A three-dimensional finite element model (ALIF with TFPS) has been developed to simulate the stability of the L4/L5 fusion segment under five different loading conditions. The Taguchi method was used to evaluate the optimized placement of the cages. Three control factors and two noise factors were included in the parameter design. The control factors included the anterior-posterior position, the medio-lateral position, and the convergent-divergent angle between the two cages. The compressive preload and the strengths of the cancellous bone were set as noise factors. From the results of the FEA and the Taguchi method, we suggest that the optimal cage positioning has a wide anterior placement, and a diverging angle between the two cages. The results show that the optimum cage position simultaneously contributes to a stronger support of the anterior column and lowers the risk of TFPS loosening.

Research on new techniques of side-inlet/outlet mufflers equipped with internal non-perforated intruding tubes has been discussed in recent literature; however, the research work of multi-chamber sideinlet/outlet mufflers in conjunction with cross-flow tubes and open-ended perforated intruding tubes which may efficiently increase the acoustical performance is rare. Therefore, the main purpose of this paper is not only to analyze the sound transmission loss (STL) of three kinds of side-inlet/outlet mufflers (a three-chamber muffler with cross-flow tubes, a five-chamber muffler with cross-flow tubes and a nonperforated tube, and a five-chamber muffler with cross-flow tubes and a perforated tube) but also to optimize their best design shape within a limited space.

In this paper, both the generalized decoupling technique and plane wave theory in solving the coupled acoustical problem are used. A four-pole system matrix in evaluating the acoustic performance is also deduced in conjunction with a simulated algorithm (SA). A numerical case in finding the optimal STL of mufflers, which is constrained within a basement with a side-inlet/outlet, at targeted tones has been introduced. Before the optimization is carried out, an accuracy check of the mathematical model is performed. Results reveal that the maximal STL is precisely located at the desired target tone. Moreover, it has been seen that mufflers with more chambers will increase the acoustic performance for both pure tone and broadband noise. Additionally, the acoustical performance of mufflers conjugated with perforated intruding tubes is superior to those equipped with non-perforated tubes.

Consequently, the approach used for seeking the optimal design of the STL proposed in this study is indeed easy and quite effective.

This paper characterizes the mass transfer and replenishment of glucose and oxygen in tissue engineered cartilage constructs by a numerical approach. Cell population growth modulated by glucose and oxygen is incorporated in the mathematic model. The distribution of synthesized type II collagen and its influence on mediating the chondrocyte growth over scaffold are also investigated. Results from simulation are compared with the experiments in literature to verify the formulation and predictions. It is found that, under static culture, the oftentimes observed phenomenon that the overall cell number densities in thick scaffolds are smaller than in thin scaffolds is mainly due to depletion of glucose rather than oxygen. Cell growth is found to be more sensitive to the change in glucose concentration for thick scaffolds, whereas to be more sensitive to the change in oxygen concentration for thin scaffolds. Results also demonstrate the modulation of chondrocyte growth by type II collagen, presenting the biphasic impact of type II collagen which promotes chondrocyte growth in the initial phase of cultivation, while inhibits cell growth in the long term. The numerical model provides a useful reference for developing cartilaginous constructs in tissue engineering.

The pressure distributions around a square cylinder in a crossflow were experimentally studied in a wind tunnel. The subject of study was conventional, but the results presented new findings. The experiments were performed by using a home-made linear pressure scanner. The ranges of Reynolds number and incidence angle were 2 × 104 - 9.4 × 104 and 0° - 45°, respectively. According to the topological flow patterns, the flows around the square cylinder at incidence showed three characteristic regimes: The subcritical, supercritical, and wedge flows. A critical incidence angle αcri = 15° separated the regimes of subcritical and supercritical modes. The results of current study provided information regarding the effects of the topological flow patterns on surface pressure distribution, drag, and lift characteristics. The pressure distributions, drag, and lift presented different characteristics in different characteristic flow regimes and had close correlations with the flows. At the critical incidence angle 15° which separated the subcritical and supercritical regimes, the surface-averaged pressure coefficient on each face displayed local extreme value—The drag coefficient attained a minimum of 1.6, the lateral force coefficient reached a maximum of 0.9. The appearance of the minimum drag at the critical incidence angle was attributed to the reduction of wake width which was induced by two surface flow phenomena: (1) reattachment of the separated boundary layer on the lateral surface facing windward at the critical incidence angle and (2) flow pattern change on the lateral surface facing leeward.

In this paper, the development of a portable polymerase chain reaction (PCR) device is presented. Integrating electromagnetic mini-actuators for bi-directional fluid transport, the proposed device, whose dimension is 67mm × 66mm × 25mm, can be fully operated with a 5V DC voltage. The device consists of four major parts: A disposable channel chip in which PCR mixture is manipulated and reacted, a heater chip which generates different temperature zones for PCR reaction, a linear actuator array for pumping PCR mixture, and a circuit module for controlling and driving the system. The advantages of the device include the rapid temperature responses associated with continuous-flow-type PCR devices, as well as the programmable thermal cycling associated with chamber-type PCR devices. The thermal characteristics are measured and discussed. PCR amplification is successfully performed for the 122 bp segment of MCF-7/adr cell line. Due to its small footprint, this self-contained system potentially can be employed for point-of-care (POC) applications.

A multi-cross-correlation method (MCCM) was developed in a particle image velocimetry (PIV) auto-processing system to reduce spurious vectors and improve accuracy of measurements. This technique is an improvement based on conventional cross-correlation method (CCM). Four typical neighboring interrogation windows were specified to be overlapped and calculated by MCCM. A high cross-correlation value is obtained in which many particle images match up with their corresponding spatially shifted partners, and small cross-correlation peaks due to interference of noises during experiments are reduced. Several parameters such as out-of-plane motions, particle size, and seeding density are considered for checking both MCCM and conventional PIV algorithms. The examination gives authenticity to the merits of MCCM for avoiding particles loss or mistaken velocity vectors.

This study predicts the failure behavior of an IM7/977-2 carbon epoxy composite material through a unified constitutive model. The traction-separation response and damage initiation and evolution behavior were studied by modeling a composite double cantilever beam subjected to a Mode I delamination. Damage within the composite panels was also taken into consideration through the use of the disturbed state concept (DSC). The finite element modeling software Abaqus was used to model the failure behavior of the composite using a unified constitutive modeling approach. The finite element model was validated by comparing the model results to referenced laboratory testing performed on IM7/977-2 carbon epoxy composite. The results of the finite element modeling performed in this study are in good agreement with the referenced laboratory testing. The damaged states associated with various stages of loading are presented in this study.

This paper has developed an accurate method for calculating the first and second derivatives of dynamic responses with respect to the design variables of structures subjected to dynamic loads. An efficient algorithm to calculate the dynamic responses, their first and second derivatives with respect to the design variables is formulated based on the Newmark-β method. The algorithm is achieved by direct differentiation and only a single dynamics analysis is required. An example is demonstrated with the new method proposed in this paper and the analytical method. The comparative numerical results show the new method is highly accurate compared to the analytical method.

Analysis of deformation and stress field in a circular elastic cylinder under the extension is presented, with emphasis on the end effect. The problem is formulated on the basis of the state space formalism for axisymmetric deformation of transversely isotropic materials. A rigorous solution that satisfies the prescribed end conditions is determined by using symplectic eigenfunction expansion, thereby, the applicability of the Saint-Venant solution is examined. The results show that the end effect is significant but confined to a local region near the base of the cylinder where the end plane is perfectly bonded or subjected to a concentrated load. As the axial stiffness increases, the end effect on the stress state increases at the loaded end but decreases at the bonded end. The displacement and stress distributions across the section are uniform throughout the length of the cylinder except near the ends.

Considering the SD (strength differential) effect on compressive strength and tensile strength in zirconia ceramic material, a yield criterion with a special parameter is introduced. In addition, by analogy with associated flow rule, the constitutive model of phase transformation ceramic material has been established. Under generalized plane strain condition, the theoretical toughening expressions of mixed-mode I-III stationary cracks and steady-state growing cracks have been developed with the constitutive model. The crack toughening effect has been discussed in detail with the Poisson ratio, parameters k / α (the ratio of nominal yield strength and SD effect factor) and ω (the scale factor of mode I crack and mode III). The integral calculation shows that phase transformation toughening of stationary cracks is negative shielding effect and the toughening effect of the steady-state growing cracks change obviously with the increase of parameter k / α. Comparison between experimental data and theoretical data indicates that the yield criterion is in accord with the actual characteristics of the zirconia ceramic, when the expression of mixed-mode I-III crack is reduced to mode I crack. The results obtained in present paper can provide the useful theoretical reference for the research of phase transformation toughening in ceramic materials.

This paper adopts the finite-volume multi-stage (FMUSTA) scheme to the two-dimensional coupled system combining the shallow water equations and the advection-diffusion equation. For the convection part, the numerical flux is estimated by adopting the FMUSTA scheme, where high order accuracy is achieved by the data reconstruction using the monotonic upstream schemes for conservation laws method. For the diffusion part, the evaluations of first-order derivatives are solved via the method of Jacobian transformation. The hydrostatic reconstruction method is employed for treatment of source terms. The overall accuracy of resulting scheme is second-order both in time and space. In addition, the scheme is non-oscillatory and conserves the pollutant mass during the transport process. For scheme validation, six advection and diffusion transport tests are simulated. The influences of the grid spacing and limiters on the numerical performance are also discussed. Furthermore, the scheme is employed in the simulation of suspended sediment transport in natural-irregular river topography. From the satisfactory agreements between the simulated results and the field measured data, it is demonstrated that the proposed FMUSTA scheme is practically suitable for hydraulic engineering applications.

This study assessed the optimal process for the surface smoothing of 3D image models of in vivo human ossicles. A 3D image model of the ossicles was reconstructed from high resolution computed tomography imaging data. Three smoothing methods including constrained smoothing, unconstrained smoothing and smoothsurface will be discussed. The volume of the 3D image model produced by unconstrained smoothing differed substantially from the original model volume prior to smoothing. Constrained smoothing had an uneven effect on the surface of the 3D image models. Using the smoothsurface module, we were able to obtain an optimal surface of the 3D image model of the human ossicles including the malleus, incus and stapes, using 20 iterations and a λ value of 0.6.

Stair locomotion is an important but challenging functional activity for people with lower limb pathology. This study aimed to investigate the bilateral changes in force-bearing on lower limbs during stair locomotion in patients with unilateral ACL deficiency. The ground reaction forces (GRF) were collected from three force platforms: One at ground level in front of a 5-step stair and two on the first two steps respectively. Parameters in vertical and anterior-posterior GRF were extracted and compared between the ACL-deficient (ACLD) and control groups. The ACLD group showed significantly slower stepping cadences in both stair ascent and stepping down to the ground (p < 0.05). The vertical GRF in the ACLD group demonstrated smaller peak forces but larger minimum forces between the two peaks than those in the control group during both stair ascent and descent. Significantly reduced anterior propulsive forces and push-off rates in the late stance were also found in both limbs of the ACLD group (p < 0.05). The slower cadences and reduced force-bearing on the affected limb suggested a protective strategy was adopted. However, the anterior loading parameters in the early stance on the unaffected limb demonstrated different adaptations with significantly larger magnitudes during stair ascent but reduced magnitudes during stair descent (p < 0.05). Similar results were also found in the weight- transferring strategies between legs in consecutive steps with a significantly larger percentage of lift-up forces but a smaller percentage of impact forces on the leading unaffected limb. The results of this study indicated a cautious force-bearing strategy and bilateral adaptation were apparent in the patients with unilateral ACL deficiency. This information may provide a safety guideline for the patients and be helpful for a better use of the stair tasks as part of a rehabilitation program.

The aortic pulse wave velocity (PWV) is a useful clinical index to assess the aortic compliance and cardiovascular risk in a noninvasive manner. In this research, our previously developed axial velocity profile method (Yu et al., [11]) was modified to be more user-friendly and applied to the study of PWV of diabetic patients for the first time, using phase-contrast magnetic resonance imaging (PC-MRI) technique to analyze the spatial and temporal profiles of the axial velocity along the descending aorta for measurement of the aortic PWV. The PWV results from healthy volunteers and diabetic patients were studied and compared. It is shown that the PWV of diabetic patients is much higher than that of health volunteers, the aortic compliance of diabetic patients is substantially worse than that of health volunteers. These results are in good agreement with early studies using different measurement techniques of PWV. The axial velocity profile method is again validated and proven to be a useful tool of long-term prognosis for patients with diabetes mellitus or hypertension.

The goal of the combustion research is to achieve optimum combustion mode. Reaction Front velocity is one of the most important parameter that is studied in this field. Most biomass consumed at the present time is burned in fixed or moving beds. Fixed-bed combustion systems are characterized by the slow combustion of large particles subjected to an oxidizing ambient. In this paper a model for propagation of a reaction front of wood particles in a fixed Bed is presented. Once the bed is ignited, an apparent flame zone is formed at the bed's top surface and the flame front moves downwards into the bed of fuel at a speed depending on fuel type and operating parameters. Effect of different parameters such as air flow rate through the bed, primary air temperature, moisture content, particle size and number density of fuel particles on the reaction front velocity has been studied. In order to compare the results of this model with the associated experimental data three species of wood fuels are studied and the agreement is found to be satisfactory.