A new quality appearance evaluation technique for automotive bodies including effect of flexible parts tolerances

Part tolerances have a crucial effect on the quality of products. In vehicle design, tolerance analysis is of central importance in quality appearance evaluation of automotive bodies and significantly taken into consideration by manufacturers in recent decades. This paper evaluates the surface quality of a car’s roof as one of the key quality characteristics in vehicle design. Compared to previous research in the area of quality appearance evaluation of automotive bodies, which are based on the assumption of part rigidity, the current research proposes to include part flexibilities in the analysis. The results of this study shows that input tolerances have a considerable effect on the surface quality of the final assembled product.     

Diffusion of dimethyl sulfoxide in tissue engineered collagen scaffolds visualized by computer tomography

Cryopreservation is a convenient method for long-term preservation of natural and engineered tissues in regenerative medicine. Homogeneous loading of tissues with CPAs, however, forms one of the major hurdles in tissue cryopreservation. In this study, computer tomography (CT) as a non-invasive imaging method was used to determine the effective diffusion of Me2SO in tissue-engineered collagen scaffolds. The dimensions of the scaffolds were 30 x 30 x 10 mm3 with a homogeneous pore size of 100 microm and a porosity of 98%. CT images were acquired after equilibrating the scaffolds in phosphate buffered saline (PBS) and transferring them directly in 10% (v/v)Me2SO. The Me2SO loading process of the scaffold could thus be measured and visualized in real time. The experimental data were fitted using a diffusion equation. The calculated effective diffusion constant for Me2SO in the PBS loaded scaffold was determined from experimental diffusion studies to be 2.4 x 10(-6) cm2/s at 20 degrees C.     

A model for quantitative changes in the magnetic resonance parameters of muscle in children after therapeutic irradiation

Purpose/ObjectiveThis study aimed to develop objective models of radiation effects on musculature in children with soft tissue sarcoma using treatment dosimetry and clinical and quantitative magnetic resonance imaging (MRI) parameters that may be used to guide treatment planning or predict side effects.MethodsIn the initial 13 patients undergoing external beam radiation therapy (RT) on a Phase II study of conformal or intensity-modulated RT for the treatment of soft tissue sarcoma approved by an Institutional Review Board, we evaluated quantitative MRI changes in the musculature to assess radiation-related treatment effects. Patients with soft tissue sarcoma, including Ewing's sarcoma, had quantitative T₁, T₂ and dynamic enhanced MRI (DEMRI) performed before, during (Week 4) and after RT (Week 12). Regions of interest were selected in consistent locations within and outside the high-dose regions (on ipsilateral and contralateral sides when available). Mean RT dose, T₁, T₂ and DEMRI parameters were calculated and modeled using a mixed random coefficient dose model.ResultsThe mean doses to the high- and low-dose regions were 56.4 Gy (41.8–75.3 Gy) and 13.0 Gy (0.1–37.5 Gy), respectively. Compared with tissues distant from the tumor bed, maximal enhancement was significantly increased in tissues adjacent to the tumor/tumor bed prior to RT (60.6 vs. 44.2, P=.045) and remained elevated after 12 weeks. T₁ was significantly elevated in tissues adjacent to the tumor bed prior to RT (942.4 vs. 759.0, P=.0078). The slope of longitudinal change in T₁ was greater for tissues that received low-dose irradiation than those that received high-dose irradiation (P=.0488). The effect of dose on the slope of T₂ was different (P=.0333) when younger and older patients are compared.ConclusionsAcute affects of irradiation in muscle are quantifiable via MRI. These models provide evidence that quantifiable MRI parameters may be correlated with patient parameters of radiation dose and clinical factors including patient age. Long-term follow-up will be required to determine if acute changes correlate with clinically significant late effects.     

Irreversibility of nanomaterial due to MHD via numerical approach

Journal of Thermal Analysis and Calorimetry - In current research, MAPLE software was utilized to scrutinize the heat transfer of copper–H2O nanomaterial migration over a sheet. Entropy...     

Use of Biochar Prepared from the Açaí Seed as Adsorbent for the Uptake of Catechol from Synthetic Effluents

This work proposes a facile methodology for producing porous biochar material (ABC) from açaí kernel residue, produced by chemical impregnation with ZnCl₂ (1:1) and pyrolysis at 650.0 °C. The characterization was achieved using several techniques, and the biochar material was employed as an adsorbent to remove catechol. The results show that ABC carbon has hydrophilic properties. The specific surface area and total pore volume are 1315 m²·g⁻¹ and 0.7038 cm³·g⁻¹, respectively. FTIR revealed the presence of oxygenated groups, which can influence catechol adsorption. The TGA/DTG indicated that the sample is thermally stable even at 580 °C. Adsorption studies showed that equilibrium was achieved in <50 min and the Avrami kinetic model best fits the experimental data, while Freundlich was observed to be the best-fitted isotherm model. Catechol adsorption on ABC biochar is governed by van der Waals forces and microporous and mesoporous filling mechanisms. The Q_max is 339.5 mg·g⁻¹ (40 °C) with 98.36% removal of simulated effluent, showing that açaí kernel is excellent biomass to prepare good biochar that can be efficiently used to treat real industrial effluents.     

Observer-based model reference adaptive control for unknown time-delay chaotic systems with input nonlinearity

Existence of unknown time-delay in the systems is a drastic restriction that it can menace the stability criteria and even deteriorate the performance system. This undesired case would be more intensified if that the uncertain input nonlinearity effects are also considered. To handle the input nonlinearities effects (results in dead-zone and/or hysteresis phenomena) and also unknown time-delay in the chaotic systems, this paper presents an observer-based Model Reference Adaptive Control (MRAC) scheme for a class of unknown time-delay chaotic systems with disturbances. This new method is a delay-independent variable-structure control method which is integrated with an observer system. The main task of the proposed approach is to accomplish a perfect tracking procedure such that unknown parameters are adapted via output estimation error. Furthermore, stability of the closed-loop system is achieved by means of the Lyapunov stability theory. Finally, the proposed methods are applied to some famous chaotic systems to verify the effectiveness of the proposed methods.     

Vibration time series analysis of bubbling and turbulent fluidization

A non-intrusive vibration monitoring technique was used to study the hydrodynamics of a gas–solid fluidized bed. Experiments were carried out in a 15 cm diameter fluidized bed using 226, 470 and 700 μm sand particles at various gas velocities, covering both bubbling and turbulent regimes. Auto correlation function, mutual information function, Hurst exponent analysis and power spectral density function were used to analyze the fluidized bed hydrodynamics near the transition point from bubbling to turbulent fluidization regimes. The first pass of the autocorrelation function from one half and the time delay at which it becomes zero, and also the first minimum of the mutual information, occur at a higher time delay in comparison to stochastic systems, and the values of time delays were maximum at the bubbling to turbulent transition gas velocity. The maximum value of Hurst exponent of macro structure occurred at the onset of regime transition from bubbling to turbulent. Further increase in gas velocity after that regime transition velocity causes a decrease in the Hurst exponent of macro structure because of breakage of large bubbles to small ones. The results showed these methods are capable of detecting the regime transition from bubbling to turbulent fluidization conditions using vibration signals.     

Ruthenium(0)-catalyzed sp3 C-H bond arylation of benzylic amines using arylboronates

A Ru-catalyzed direct arylation of benzylic sp(3) carbons of acyclic amines with arylboronates is reported. This highly regioselective and efficient transformation can be performed with various combinations of N-(2-pyridyl) substituted benzylamines and arylboronates. Substitution of the pyridine directing group in the 3-position proved to be crucial in order to achieve high arylation yields. Furthermore, the pyridine directing group can be removed in high yields via a two-step protocol.     

Computational approaches to aspect-ratio-dependent upper bounds and heat flux in porous medium convection

Direct numerical simulation (DNS) has shown that Rayleigh–Bénard convection in a fluid-saturated porous medium self-organizes into narrowly spaced plumes at (ostensibly) asymptotically high values of the Rayleigh number Ra. In this Letter a combination of DNS and upper bound theory is used to investigate the dependence of the Nusselt number Nu on the domain aspect ratio L at large Ra  . A novel algorithm is introduced to solve the optimization problems arising from the upper bound analysis, allowing for the best available bounds to be extended up to Ra≈2.65×10⁴$\mathit{Ra}\approx 2.65\times {10}^4$. The dependence of the bounds on L(Ra)$L(\mathit{Ra})$ is explored and a “minimal flow unit” is identified.