Materials Science

Introduction: Stress shielding is a common complication following endoprosthetic reconstruction surgery. The resulting periprosthetic osteopenia often manifests as catastrophic fractures and can significantly limit future treatment options. It has been long known that bone plates with lower elastic moduli are key to reducing the risk of stress shielding in orthopedics. Inclusion of open space lattices in metal endoprostheses is believed to reduce the prosthesis modulus potentially improving stress shielding. However, no in vivo data is currently available to support this assumption in long bone reconstruction. This manuscript aims to address this hypothesis using a sheep model of extraarticular bone defect. Methods: Initially, CT was used to create a virtual resection plan of the distal femoral metaphyses and to custom design endoprostheses specific to each femur. The endoprostheses comprised additively manufactured Ti6Al4V-ELI modules that either had a solid core with a modulus of ~120 GPa (solid implant group) or an open space lattice core with unit cells that had a modulus of 3-6 GPa (lattice implant group). Osteotomies were performed using computer-assisted navigation followed by implantations. The periprosthetic, interfacial and interstitial regions of interest were evaluated by a combination of micro-CT, back-scattered scanning electron microscopy (BSEM), as well as epifluorescence and brightfield microscopy. Results: In the periprosthetic region, mean pixel intensity (a proxy for tissue mineral density in BSEM) in the caudal cortex was found to be higher in the lattice implant group. This was complemented by BSEM derived porosity being lower in the lattice implant group in both caudal and cranial cortices. In the interfacial and interstitial regions, most pronounced differences were observed in the axial interfacial perimeter where the solid implant group had greater bone coverage. In contrast, the lattice group had a greater coverage in the cranial interfacial region. Our findings suggest that reducing the prosthesis modulus by inclusion of an open-space lattice in its design has a positive effect on bone

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A materials plays an important role in their photophysical properties. Here, the authors select the asymmetric acceptor pyridal[2,1,3]thiadiazole (PT) to construct two D-A isomers (p-TPA-PT and d-TPA-PT) with different twist angle and rotation freedom due to the donor triphenylamine (TPA) proximal or distal to N-atom (pyridyl), as well as a symmetric bis-triphenylaminesubstituted compound DTPA-PT for their investigation. On the basis of experimental and theoretical analysis, the authors have explained how the difference in twist-angle and freedom of rotation affects the photophysical properties of these materials. The p-TPA-PT has small twist angles with a relative large k r , however, the more freedom of rotation of the D-A bond causes larger k nr , which is comparable to the k r , and thus a lower photoluminescence (PL) efficiency is obtained in the doped film. Although the d-TPA-PT has relative large twist angles with low k r , the suppressed rotation of the DA bond significantly reduces k nr , resulting in more competitive k r when compared with the p-TPA-PT, consequently relatively higher PL efficiency is observed. The DTPA-PT, combination of p-TPA-PT and d-TPA-PT, shows highest k r , much larger than its k nr , therefore shows highest PL efficiency. As a result, the DTPA-PT based organic light emitting diode (OLED) shows beautiful deep-red emission, maximum external quantum efficiency of 3.87%, L max = 12 000 cd m -2 , which is among the best deep-red OLED devices.

The polyaniline (PANI)-based pseudo-supercapacitor has been extensively studied due to its good conductivity, ease of synthesis, low-cost monomer, tunable properties and remarkable specific capacitance. In this work, a three-dimensional cross-linked carbon network (3D-CCN) was used as a contact-resistance-free substrate for PANI-based pseudo-supercapacitors. The ordered PANI nanowires (PaNWs) were grown on the 3D-CCN to form PaNWs/3D-CCN composites by in-situ polymerization, which occurred when a reaction solution containing aniline penetrated the hierarchical, microporous structure of the 3D-CCN.

A cationic water‐soluble polyfluorene (P2) containing a high density of tetraalkylammonium side chains in polymer backbone was synthesized and characterized. The polymer shows excellent water solubility up to 100 mg · mL−1 as well as high photoluminescence (PL) quantum yield of 44% in water. The relatively high cationic density and appropriate side chain length of the polymer are the key factors to achieve such high water solubility. The reduction potential of P2 is decreased as compared with its neutral polymer, reflecting the enhanced electron injection abilities. The standard NPB/Alq3 device using such a polymer as the electron injection layer shows nearly three‐fold enhancement in the electroluminescence (EL) efficiency.magnified image

A soluble all-aromatic poly(2,5-diphenyl-1,4-phenylenevinylene) (2,5-DP-PPV) is synthesized by utilizing aromatic phosphonium and aldehyde monomers through Wittig reaction. The H 1 NMR and FTIR measurements indicate that over 50% content of cis-vinylene units exist in polymer backbone. The diphenyl-substituted benzaldehyde monomer plays an important role to enhance cis-products (Z-selectivity) in Wittig reactions. The twisted cis-segments in polymer backbone reduce the interchain interactions and enhance the solubility of such all-aromatic PPV derivative in common organic solvents. 2,5-DP-PPV exhibits good solubility in common organic solvents, such as tetrahydrofuran and chloroform. The polymer film exhibits a blue light emission (k max ¼ 485 nm) and a very high photoluminescence efficiency of 78%. The cis-trans photo isomerization of this polymer in solution and the impact on the optical properties are also investigated. V

ABSTRACTPolyimides (PIs) are highly desirable materials due to their excellent physical, chemical properties, and widespread applications. In this article, a new PI containing bipyrimidine units was prepared from a newly synthesized 5,5′‐bis[(4‐amino) phenoxy]‐2,2′‐bipyrimidine and 3‚3′‚4‚4′‐biphenyltetracarboxylic dianhydride via a two‐step method. The as‐synthesized PI not only showed high thermal stability and excellent mechanical properties, but also possessed high dielectric constant (7.1, 100 Hz) and low dielectric loss (below 0.04) in a wide frequency range from 100 Hz to 105 Hz. The obtained PI promises potential applications in electronic products. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40828.

The luminescence at the absorption maximum of c-Si solar cells (1002 nm) of Ytterbium (3+) ions (Yb 3+ ) make them a suitable candidate for solar spectrum converting material for c-Si solar cell. In this work oleic acid functionalized lanthanum fluoride (OA-LaF 3 ) nanoparticles doped with Nd 3+ , Yb 3+ (2-5 nm) were synthesized by coprecipitation method in which Nd 3+ (Neodymium (3+) ions) acts as the sensitizer for Yb 3+ . The oleic acid chemisorption on LaF 3 nanoparticles was confirmed by FTIR and TGA analysis. OA-LaF 3 : Nd 3+ Yb 3+ nanoparticles (Nd 3+ -10 mol%, Yb 3+ -0 to 20 mol% ) luminescent at 880 nm, 1053 nm, 1325 nm (Nd 3+ ions) and 1002 nm (Yb 3+ ions) was observed for excitation at 575 nm. The excitation spectra for the Yb 3+ emission from OA-LaF 3 : Nd 3+ Yb 3+ showed all the excitation peaks of Nd 3+ in the visible region. This confirmed the energy transfer from Nd 3+ to Yb 3+ ions. The increase in the Yb 3+ emission intensity at 1002 nm was observed as Yb 3+ dopant concentration increased from 0 to 5%. Above 5% of Yb 3+ doping concentration, Yb 3+ luminescence was observed to be decreasing, which was attributed to the concentration quenching.

The luminescence at the absorption maximum of c-Si solar cells (1002 nm) of Ytterbium (3+) ions (Yb 3+ ) make them a suitable candidate for solar spectrum converting material for c-Si solar cell. In this work oleic acid functionalized lanthanum fluoride (OA-LaF3) nanoparticles doped with Nd 3+ , Yb 3+ (2-5 nm) were synthesized by coprecipitation method in which Nd 3+ (Neodymium (3+) ions) acts as the sensitizer for Yb 3+ . The oleic acid chemisorption on LaF3 nanoparticles was confirmed by FTIR and TGA analysis. OA-LaF3: Nd 3+ Yb 3+ nanoparticles (Nd 3+ -10 mol%, Yb 3+ -0 to 20 mol% ) luminescent at 880 nm, 1053 nm, 1325 nm (Nd 3+ ions) and 1002 nm (Yb 3+ ions) was observed for excitation at 575 nm. The excitation spectra for the Yb 3+ emission from OA-LaF3: Nd 3+ Yb 3+ showed all the excitation peaks of Nd 3+ in the visible region. This confirmed the energy transfer from Nd 3+ to Yb 3+ ions. The increase in the Yb 3+ emission intensity at 1002 nm was observed as Yb 3+ dopant concentration increased from 0 to 5%. Above 5% of Yb 3+ doping concentration, Yb 3+ luminescence was observed to be decreasing, which was attributed to the concentration quenching.

h i g h l i g h t s g r a p h i c a l a b s t r a c t Thermal degradation of PMMA nanocomposites having oleic acid functionalized LaF 3 : Nd 3þ nanoparticles as filler is studied. Nanocomposites were transparent and NIR luminescent. The improvement in the thermal stability was attributed to the low mobile polymer interface region around nanoparticles.

Ilmenite is the prime mineral used for the production of titania-rich slag and ferrotitanium alloy throughout the globe. In the current research, a 30 kW DC extended arc plasma reactor is employed for the aluminothermic reduction of ilmenite into ferrotitanium. For low-temperature operation, flux is added targeting low melting slag where CaO/Al 2 O 3 ratio is varied from 0.8 to 1.6. Further, to lower down the Al consumption, carboaluminothermic reduction tests are carried out in stages without interruption. The effect of stage-wise reductant addition and CaO/Al 2 O 3 ratio on ferrotitanium yield and titanium recovery is studied, corroborated to the slag chemistry. FeTi26 alloy is obtained through the carboaluminothermic smelting route with 25% excess stoichiometric Al in charge composition. The formation of calcium titanate and calcium aluminates governs slag chemistry and reduction kinetics.

Different metallurgical wastes are generated during pyro processing of iron ore, which is used for making sponge iron or hot metal and for producing steel. Apart from these wastes, coke fines are generated during the coke making, and iron ore fines are generated during mining of iron ore. Although iron ore fines are used for making pellet after beneficiation still, it generates a huge quantity of iron ore waste during beneficiation with comparatively lower iron content. In the present study, briquettes are made by a stiff extrusion process from metallurgical waste like iron ore fines and coke fines with the addition of Portland cement as a binder and clay as a rheology modifier. Physical properties of the briquettes are evaluated, and reducibility of the briquettes is studied in comparison to lumpy iron ore. Phase analysis and microstructural analysis of the briquettes and lumpy iron ore are carried out after firing at different temperatures in the simulated blast furnace condition. Physical and mineralogical properties are correlated with the reducibility of the briquettes and lumpy iron ore. Briquettes made by a stiff extrusion process show a better mechanical strength fired at a different temperature to take the load of burden and better reducibility than lumpy iron ore. The briquettes after self-curing are charged to a 23 mt3 blast furnace which shows encouraging results.

An approach was developed to upgrade the bauxite ore by molecular hydrogen and hydrogen plasma. A gibbsite-type bauxite sample was obtained from National Aluminium Company (NALCO), Odisha, India. The obtained sample was crushed and sieved (to 100 μm) prior to the chemical analysis and grain-size distribution study. The bauxite sample was calcined in the temperature range from 500 to 700°C for different time intervals to optimize the conditions for maximum moisture removal. This process was followed by the reduction of the calcined ore by molecular hydrogen and hydrogen plasma. Extraction of alumina from the reduced ore was carried out via acid leaching in chloride media for 2 h at 60°C. X-ray diffraction, scanning electron microscopy, thermogravimetry in conjunction with differential scanning calorimetry, and Fourier transform infrared spectroscopy were used to determine the physicochemical characteristics of the material before and after extraction. Alumina extracted from the reduced ore at the optimum calcination temperature of 700°C and the optimum calcination time of 4 h is found to be 90% pure.

Mucoadhesive polymeric (carbopol 934) suspension of ciprofloxacin was prepared by ultrasonication and optimized with the aim of developing an oral controlled release gastro-retentive dosage form. The qualitative analysis of the formulation was performed by fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray powder diffraction (XRD), and scanning electron microscopy (SEM) analyses. FTIR (400 cm -1 to 4000 cm -1 region) and Raman (140 to 2400 cm -1 region) Spectroscopic studies were carried out and the spectra were used for interpretation. XRD data of pure drug, polymer and the formulation were obtained using a powder diffractometer scanned from a Bragg's angle (2q) of 10° to 70°. The dispersion of the particle was observed using SEM techniques. The particle size distribution and aspect ratio of particles in the polymeric suspension were obtained from SEM image analysis. The results from FTIR and Raman spectroscopic analyses suggested that, in formulation, the carboxylic groups of ciprofloxacin and hydroxyl groups of C934 undergo a chemical interaction leading to esterification and hydrogen bonding. The XRD data suggested that the retention of crystalline nature of ciprofloxacin in the formulation would lead to increase in stability and drug loading; decrease in solubility; and delay in release of the drug from polymeric suspension with better bioavailability and penetration capacity. The SEM image analysis indicated that, in the formulation maximum particles were having aspect ratio from 2 to 4 and standard deviation was very less which provided supporting evidences for homogeneous, uniformly dispersed, stable controlled release ciprofloxacin suspension which would be pharmaceutically acceptable.

This paper explains the sliding wear performance of red mud, fly ash, and carbon composite coating on mild steel. The complex mixture of red mud, fly ash, and carbon is plasma sprayed at 9 kW operating power level. The coatings are examined to study the coating morphology, XRD phase transformation, wear rate, and wear morphology. Wear rate (in terms of cumulative mass loss) with sliding time has been demonstrated in the study. At first pure red mud is plasma coated to observe the coating characteristics and then compounded with 20% carbon, 30% carbon, and 20% carbon + 30% fly ash, separately by weight and sliding wear test conducted using pin on disc wear tester. The trial was performed at fixed track diameter of 100 mm and at sliding speed of 100 rpm (0.523 m/s) at a load of 30 N. The results are compared. Declined cumulative mass loss by inclusion of fly ash and carbon is seen. This might be due to augmented interfacial tension and dense film build-up at boundary layer.

This work aims to assess the effects of flame-wall impingement on the combustion and soot processes of diesel flames. For this work, experimental measurements were performed in a constant-volume combustion chamber (CVCC) at ambient conditions that are representative of compression-ignition engines. The characteristics of impinging and free flames were compared at two identical ambient and injector conditions (20.8 kg/m 3 ambient density, 6 MPa ambient pressure, 1000 K bulk temperature, 15 and 10 vol% ambient O 2 concentration, and 100 MPa injection pressure). To simulate flame-wall impingement, a flat plane steel wall, normal to the injector axis, was initially placed at 53 mm from nozzle, but was varied from 53 to 35 mm during the experiments. Under the test conditions of this work, it was found that wall impingement resulted in lower soot temperature and soot content, in addition to a loss of momentum for the wall jet. The results also revealed that decreasing impingement distance from the nozzle resulted in reduced soot temperature and soot level for the wall jet. The reduced soot content observed for the wall jet appeared to be mainly driven by enhanced mixing. Flame transparency modeling was also performed to assess the uncertainties of two-color measurements for flameplane wall impingement. The analysis indicated that the derived soot temperature and concentration values would be affected by the actual temperature profiles, rendering the technique useful to reveal trends, but not reliable for absolute soot concentration measurements.

The use of color-ratio pyrometry (CRP) methods, with variable or prescribed soot content (KL) to image flameewall interactions was examined, with results compared with that obtained using the more mature two-color pyrometry (TCP) technique. The CRP and TCP methods were applied to flameewall impingement images recorded in a optically-accessible constant volume combustion chamber (CVCC) under compression-ignition (CI) engine conditions. Good correlation in the result trends were observed for the CRP method with fixed KL output and that generated using TCP. Slight discrepancies in the predicted absolute temperature values were observed, which were linked to the difference in the KL value prescribed to the CRP method, and the KL value predicted using TCP. No useful output was obtained with CRP method with variable soot output because of channel noise. A simplified flame transparency modeling was performed to assess the inherent errors associated with the pyrometry methods. The results indicated that the uncertainties arising from the fixing of the KL output appeared acceptable.

The aim of this study is to investigate the impact of walls on soot processes of a post-injection strategy with different dwell times. The experiments were performed in an optically-accessible constant-volume combustion chamber (CVCC) simulating compression ignition engine conditions with moderate exhaust gas recirculation (EGR). The experiments with various injection strategies were performed at ambient conditions with gas density, pressure and temperature of 20.8 kg/m 3 , 6 MPa and 1000 K respectively, and 15 vol.% O 2 concentration. The main and post injections had a quantity ratio of 8:2 (main:post) totaling 10 mg, and a flat wall was placed 35 mm axially from the injector. The dwell time between the main and post injections was also varied to induce different levels of interaction between the injections. High-speed flame 1 Page 1 of 38 Energy & Fuels natural luminosity imaging and two-color pyrometry technique were applied to observe flame characteristics and to obtain soot temperature and KL factor information, respectively. By comparing the wall jet and free jet cases with no direct jet interaction, it was found that the wall affected the post jet flame structure similarly to a single jet or the main jet. However, the post jet with greater extent of interaction with the main jet induced by shorter dwell time can achieve better mixing for the wall jet case. Increased interaction between the main and post jets, also appeared to induce a soot oxidation phase, which was otherwise not observed when the injections were more temporally separated.

AlN thin films are an attractive material that have some excellent characteristics, such as high surface acoustic wave (SAW) velocity (nearly twice that of quartz and LiNbO3), piezoelectricity, high-temperature stability, and stable chemical properties. AlN and ZnO are the primary materials of piezoelectric films, and they have the same crystal structure, the hexagonal wurtzite structure. The Y-rotated, X-propagating quartz (ST-quartz)

This work investigates the viscoelastic properties of the fluoropolyol (FPOL) polymer on the surface acoustic wave (SAW) organophosphorous vapor sensors. A complex shear modulus is used to express different polymer types (glassy, glassy-rubbery, and rubbery). The different polymer types leads to different propagating properties of SAW, such as attenuation change and velocity shift. Calculation results indicate that the glassy-rubbery film exhibits the highest sensitivity for detecting organophosphorous vapor. The thicker the glassy and glassy-rubbery film implies a higher sensitivity. Moreover, the SAW vapor sensor based on the rubbery film represents the response of acoustically thick layers which has a peak in attenuation with an increasing vapor adsorption. The selectivity factor between DMMP (10 ppm) and H2O (40%RH) is so low that the selectivity of FPOL film towards water is ineffecient. However, the selectivity factor between ethanol (10 ppm) and DMMP (10 ppm) is as high as 25...

DC electric field effects on the real part of the relative dielectric constant and the loss factor of barium strontium titanate for application in phased array antennas have been studied. The real part of the relative dielectric constant of the specimens decreases with increasing applied DC field. The loss factor under bias DC electric field is slighter than the real

Flexible electronics sensors are designed and fabricated for tactile multiscanning and large area applications. The algorithm matrix is derived for multiscanning switch of tactile sensing. The thixotropy materials, bump, and resistance material are printed on the polyimide substrate. A gap between the top electrode and the resistance layers provides a buffer distance to increase the radius of curvature for large bending. Experiment results show that a flexible electronics sensor with a printed a resistance layer and an algorithm matrix performed the multiscanning functions. The membrane without a bump had a delay time of about 0.2 s at the transient response and took a longer time to reach the stable state after a force is applied. For printing thick structures on the flexible substrates, diffusion effects, and dimensional shrinkages can be reduced by using a thixotropy material with a high viscosity. The probability distribution density of the printed resistance values, a thickness...

Waveguides provide several advantages such as acoustic and optical beam confinement, prolongation of delay time, and high acoustic intensity for the acoustic devices. Using proton exchange (PE) with benzoic acid, we have investigated the surface acoustic wave (SAW) properties of a PE waveguide using Z-cut LiNbO 3 . With this tight energy confinement, the acoustic waveguide structure enables the guided SAW to be in a suitable mode for dilute electrolyte sensing. Furthermore, it is noteworthy that the dielectric constant of a PE layer can be deduced from the critical conductivity.

By choosing appropriate microemulsion systems, hexagonal cobalt (Co) and cobalt-nickel (1:1) alloy nanoparticles have been obtained with cetyltrimethylammonium bromide as a cationic surfactant at 500 °C. This method thus stabilizes the hcp cobalt even at sizes (<10 nm) at which normally fcc cobalt is predicted to be stable. On annealing the hcp cobalt nanoparticles in H 2 at 700 °C we could transform them to fcc cobalt nanoparticles. Microscopy studies show the formation of spherical nanoparticles of hexagonal and cubic forms of cobalt and Co-Ni (1:1) alloy nanoparticles with the average size of 4, 8 and 20 nm, respectively. Electrochemical studies show that the catalytic property towards oxygen evolution is dependent on the applied voltage. At low voltage (less than 0.65 V) the Co (hexagonal) nanoparticles are superior to the alloy (Co-Ni) nanoparticles while above this voltage the alloy nanoparticles are more efficient catalysts. The nanoparticles of cobalt (hcp and fcc) and alloy (Co-Ni) nanoparticles show ferromagnetism. The saturation magnetization of Co-Ni nanoparticles is reduced compared to the bulk possibly due to surface oxidation.

Let R be a real closed field. The Pierce-Birkhoff conjecture says that any piecewise polynomial function f on R n can be obtained from the polynomial ring R[x 1 , . . . , x n ] by iterating the operations of maximum and minimum. The purpose of this paper is threefold. First, we state a new conjecture, called the Connectedness conjecture, which asserts, for every pair of points α, β ∈ Sper R[x 1 , . . . , x n ], the existence of connected sets in the real spectrum of R[x 1 , . . . , x n ], satisfying certain conditions. We prove that the Connectedness conjecture implies the Pierce-Birkhoff conjecture. Secondly, we construct a class of connected sets in the real spectrum which, though not in itself enough for the proof of the Pierce-Birkhoff conjecture, is the first and simplest example of the sort of connected sets we really need, and which constitutes the first step in our program for a proof of the Pierce-Birkhoff conjecture in dimension greater than 2. Thirdly, we apply these ideas to give two proofs of the Connectedness conjecture (and hence also of the Pierce-Birkhoff conjecture in the abstract formulation) in the special case when one of the two points α, β ∈ Sper R[x 1 , . . . , x n ] is monomial. One of the proofs is elementary while the other consists in deducing the (monomial) Connectedness conjecture as an immediate corollary of the main connectedness theorem of this paper.

— The Lyapunov’s second method for the stability analysis of nonlinear dynamic systems requires finding Lyapunov functions. Unfortunately, finding a suitable Lyapunov function is a tedious process for a given complex nonlinear system if it is not impossible. On the other hand there are several algebraic approaches like the eigenvalue method for analyzing or designing linear time invariant systems. In this paper, we develop the eigenvalue method for the stability analysis of extended homogeneous nonlinear systems. In the case of polynomial homogeneous systems of zero degree it is shown that the zero equilibrium state of system is globally asymptotically stable if and only if all the homogeneous eigenvalues have negative real parts. Ultimately, an example is presented to describe the approach. Index Terms-- homogeneous nonlinear system, asymptotical stability, nonlinear eigenvalue.

A large number of wind pressure measurements were performed to investigate the influence of upstream surrounding buildings on the wind pressures and forces on a cubical low-rise building. The primary purpose of the present study was to understand the effects of proximity buildings by introducing the two different normalization methods for the wind pressures and to examine the methodology of design application. The considered parameters were the area densities and long upstream distance under the turbulent boundary layer representing a suburban area. Results show that wind pressures decrease with increasing area density, but the variations of mean and fluctuating components within one area density are relatively small. And most of the increases in the local wind pressure coefficients originate from the rapid decrease in local velocity pressures at the model position. And by using the interference factor which is an exponential function of area density only, it was found that the wind loads on structural frames and component/cladding element of the target low-rise building in group can be easily evaluated.

The primary purpose of the present work was to understand the characteristics of wind force correlations and quasi-static wind load combinations of a target model in a large group. Fluctuating pressures were integrated over the surfaces, and along-wind force, across-wind force, uplift force, along-wind overturning moment, across-wind overturning moment and torsional moment were obtained and used in the analyses. Firstly, the characteristics of wind force correlations, including the ratio of force coefficients, phase-plane expression and cross-correlation coefficients, were investigated for an isolated model and for a target model in a large group. Then, peak normal stresses in columns of a simple frame model were examined to check the wind load combination effects. Lastly, a shielding factor of a combination factor was proposed in the form of an exponential function.

The concrete-filled tubular (CFT) structure consists of high strength, favourable ductility, fire resistance and huge energy absorption. The cost and time of construction can be reduced as there is no shuttering required for CFT columns. The confinement outcome of CFT column possesses higher stiffness as compared to hollow steel tube columns. In this article, testing is administered on twelve specimens of natural and artificial sand M25 grade CFT columns with a ratio of diameter to variable tube thickness (D/t of 27.72, 22.18 and 18.48). The twelve CFT columns have been tested under axial compression. The behaviour of CFT columns has been studied in terms of axial load-carrying capacity, deflection and buckling effects and compared the behaviour with numerical results determined using Eurocode 4 and AISC 360-10. The performance of CFT columns increased, as the thickness of tube increased with the effective confinement. The experimental and the numerical results of CFT columns have been validated by using ANSYS 14.5. The axial load-carrying capacity of an artificial sand CFT specimen has been improved significantly. Therefore, the natural sand could be replaced with artificial sand for CFT columns.

This paper presents characterization studies of flash point, kinematic viscosity and refractive index for several biodiesel/ diesel blends. Biodiesel is produced from soybean, corn, olive, canola, almond, grape and peanut oils. Regression equations are presented to estimate the kinematic viscosity, refractive index and flash point of the studied biodiesel and their blends with diesel fossil fuel as a function of the blend composition. Moreover, as viscosity and refractive index measurements are simple, fast and require very small volume of samples, a correlation study for the blends is conducted to estimate the flash point from these two properties. It is shown that when kinematic viscosity and refractive index are both used for the estimation of the blends flash point, the R 2 values are higher than those found using simple correlations.

Hydroxyapatite/polycaprolactone (HA/PCL) composites have been extensively explored in laser powder bed fusion (L-PBF) for bone tissue engineering. However, conventional mechanical mixing methods for preparing composite powders often yield inhomogeneous compositions and suboptimal flowability. In this study, HA/PCL powders were prepared and optimized for L-PBF using the modified emulsion solvent evaporation method. The morphology, flowability and thermal and rheological properties of the powders were systematically investigated, along with the mechanical and biological properties of the fabricated specimens. The HA/PCL powders exhibited spherical morphologies with a homogeneous distribution of HA within the particles. The addition of small amounts of HA (5 wt% and 10 wt%) enhanced the processability and increased the maximum values of the elastic modulus and yield strength of the specimens from 129.8 MPa to 166.2 MPa and 20.2 MPa to 25.1 MPa, respectively, while also improving their biocompatibility. However, excessive addition resulted in compromised sinterability, thereby affecting both mechanical and biological properties.

During corneal wound healing, corneal keratocytes are exposed to both biophysical and soluble cues that cause them to transform from a quiescent state to a repair phenotype. How keratocytes integrate these multiple cues simultaneously is not well understood. To investigate this process, primary rabbit corneal keratocytes were cultured on substrates patterned with aligned collagen fibrils and coated with adsorbed fibronectin. After 2 or 5 days of culture, keratocytes were fixed and stained to assess changes in cell morphology and markers of myofibroblastic activation by fluorescence microscopy. Initially, adsorbed fibronectin had an activating effect on the keratocytes as evidenced by changes in cell shape, stress fiber formation, and expression of alpha-smooth muscle actin (α-SMA). The magnitude of these effects depended upon substrate topography (i.e., flat substrate vs aligned collagen fibrils) and decreased with culture time. When keratocytes were simultaneously exposed to adsorbed fibronectin and soluble platelet-derived growth factor-BB (PDGF-BB), the cells elongated and had reduced expression of stress fibers and α-SMA. In the presence of PDGF-BB, keratocytes plated on the aligned collagen fibrils elongated in the direction of the fibrils. These results provide new information on how keratocytes respond to multiple simultaneous cues and how the anisotropic topography of aligned collagen fibrils influences keratocyte behavior.

In this study, Er 3+ doped ZnO semiconductor quantum dots (QDs) were synthesized using a wet chemical method. The successful doping of Er 3+ ions into the ZnO host lattice and the elemental composition was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The ZnO and Er 3+ doped ZnO QDs with a hexagonal structure, spherical shape, and particle size of approximately 5 nm were revealed by XRD and transmission electron microscopy (TEM). The absorption, luminescence properties, and fluorescence lifetimes of the samples were studied as the concentration of Er 3+ ions varied. The intensity parameters, emission transition probabilities, branching ratios, and emission lifetimes of the excited levels of Er 3+ ions in the ZnO host were determined using the Judd-Ofelt theory, which provided insight into the covalent relationship between the ions and ligands as well as the nature of the ZnO host lattice. Moreover, the energy transfer process from the ZnO host to Er 3+ ions and the yield of this process are explained in detail along with specific calculations. The Er 3+ doped ZnO QDs displayed a significantly longer lifetime than undoped ZnO, which opens up many potential applications in fields such as photocatalysis, optoelectronics, photovoltaics, and biosensing.

A significant amount of research has been conducted on FRP-confined circular columns, but much less is known about rectangular/square columns in which the effectiveness of confinement is much reduced. This paper presents the results of experimental investigations on low strength square concrete columns confined with FRP. Axial compression tests were performed on ten intermediate size columns. The tests results indicate that FRP composites can significantly improve the bearing capacity and ductility of square section reinforced concrete columns with rounded corners. The strength enhancement ratio is greater the lower the concrete strength and also increases with the stiffness of the jacket. The confined concrete behaviour was predicted according to the more accepted theoretical models and compared with experimental results. There are two key parameters which critically influence the fitting of the models: the strain efficiency factor and the effect of confinement in non-circular sections.

Bacterial adhesion to the surface of materials is the first step in biofilm formation, which will lead to conditions that may compromise the health status of patients. Recently, polydopamine (PDA) has been proposed as an antibacterial material. Therefore, the objective of the current work was to assess and compare the adhesion of Streptococcus mutans to the surface of poly(methyl methacrylate) (PMMA) discs that were modified using PDA following a biomimetic approach versus smooth PDA-coated PMMA surfaces. In addition, an assessment of the growth inhibition by PDA was performed. PMMA discs were manufactured and polished; soft lithography, using the topography from the Crocosmia aurea leaf, was used to modify their surface. PDA was used to smooth-coat PMMA discs by dip-coating. The growth inhibition was measured using an inhibition halo. The surfaces were characterized by means of atomic force microscopy (AFM), the contact angle (CA), and Fourier-transform infrared spectroscopy (FTIR). Polydopamine exhibited a significant antibacterial effect when used directly on the S. mutans planktonic cells, but such an effect was not as strong when modifying the PMMA surfaces. These results open the possibility of using polydopamine to reduce the adhesion and growth of S. mutans, which might have important consequences in the dental field.

Tungsten carbide exhibits platinum‐like behavior, which makes it an interesting potential substitute for noble metals in catalytic applications. Tungsten carbide nanocrystals (≈5 nm) are directly synthesized through the reaction of tungsten precursors with mesoporous graphitic C3N4 (mpg‐C3N4) as the reactive template in a flow of inert gas at high temperatures. Systematic experiments that vary the precursor compositions and temperatures used in the synthesis selectively generate different compositions and structures for the final nanocarbide (W2C or WC) products. Electrochemical measurements demonstrate that the WC phase with a high surface area exhibits both high activity and stability in hydrogen evolution over a wide pH range. The WC sample also shows excellent hydrogen oxidation activity, whereas its activity in oxygen reduction is poor. These tungsten carbides are successful cocatalysts for overall water splitting and give H2 and O2 in a stoichiometric ratio from H2O decomposit...

The polymerized complex (PC) method was used to synthesize highly dispersed iron-based catalysts for the oxygen reduction reaction (ORR). The catalysts were prepared with an addition of 1,10-phenanthroline (Phen) and transition metals (M), such as Ta, Ti, and W, in an attempt to enhance the ORR activity and durability of the catalysts. The composition and properties of the catalysts were characterized by thermogravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. The catalyst components, after extensive dissolution in a strong acid solution, were characterized by inductively coupled plasma mass spectroscopy and ultraviolet-visible spectroscopy. It was found that the Ti-Fe catalyst showed improved ORR performance, and the Ta-Fe catalyst showed enhanced stability towards ORR in acidic solution. The catalytic activity and stability for ORR was observed by adding Ti or Ta into the catalyst formulation, suggesting that the interaction between added hetero-ions (Ti and Ta) and ionic Fe active sites was beneficial for the ORR. A single-cell test with the synthesized catalyst in the cathode initially generated a high power density, but the low stability remains an issue to be solved.

This paper summarizes the effect of activator ratio on the processing of cement powder. Geopolymer slurry was produced via alkaline activation of calcined kaolin. Once the geopolymer slurry solidified, it was crushed and ground to obtain cement powder. Ultilizing the concept of "just adding water", hardened cement paste could be produced from cement powder. This paper concluded that solids-to-liquid and sodium silicate-to-sodium hydroxide ratios have a significant effect on compressive strength of hardened cement paste. The optimum solids-to-liquid and sodium silicate-to-sodium hydroxide ratios were 0.80 and 0.20, respectively. SEM micrographs showed that a processing route to produce cement powder by "just adding water" was possible, and the structure became denser and fewer unreacted particles were observed.

Kaolin geopolymers were produced by the alkali-activation of kaolin with an activator solution (a mixture of NaOH and sodium silicate solutions). The NaOH solution was prepared at a concentration of 6-14 mol/L and was mixed with the sodium silicate solution at a Na2SiO3/NaOH mass ratio of 0.24 to prepare an activator solution. The kaolin-to-activator solution mass ratio used was 0.80. This paper aimed to analyze the effect of NaOH concentration on the compressive strength of kaolin geopolymers at 80 • C for 1, 2, and 3 d. Kaolin geopolymers were stable in water, and strength results showed that the kaolin binder had adequate compressive strength with 12 mol/L of NaOH concentration. When the NaOH concentration increased, the SiO2/Na2O decreased. The increased Na2O content enhanced the dissolution of kaolin as shown in X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses. However, excess in this content was not beneficial for the strength development of kaolin geopolymers. In addition, there was the formation of more geopolymeric gel in 12 mol/L samples. The XRD pattern of the samples showed a higher amorphous content and a more geopolymer bonding existed as proved by FTIR analysis.

High density polyethylene (HDPE) and polybenzimidazole fiber (PBI) composites were prepared by melt blending in a twin screw extruder. The thermomechanical properties of PBI fiber reinforced HDPE composite samples (1%, 4%, and 8%) of fiber lengths 3 mm and 6 mm were investigated using differential scanning calorimeter (DSC), universal testing machine, rheometer, and scanning electron microscopy (SEM). The effects of fiber content and fiber lengths on the thermomechanical properties of the HDPE‐PBI composites were studied. The DSC analysis showed a decrease in crystallinity of HDPE‐PBI composites with an increase of fiber loading. SEM images revealed homogeneous distribution of the fibers in the polymer matrix. The thermal behavior of the composites was evaluated from thermogravimetric analysis and the thermal stability was found to increase with the addition of fibers. The evidence of homogeneous distribution was verified by the considerably high values of tensile strength and flexu...

This paper reports a high-performance impedance-type inclinometer fabricated in a glass-SU-8-glass sandwich structure for wide angle and rapid angle response measurement. The output signal of the proposed inclinometer is reading from a movable metal pendulum based on the electrical potential measurement scheme. Two kinds of metal of Ga-In-Sn alloy and mercury are used as the pendulum mass of the inclinometer. The friction force between the liquid metal and substrate surfaces is dramatically reduced by applying the organicbased surfactant of SDS. Results show the proposed inclinometer has a very wide linear range of 320 o and a high angle resolution of 0.3 o (S/N=3). The measured results indicate that there is no time lag for the sensor output under the rotation speed of 1/8 RPS and also no damping effect for an instant stop from a rotation speed of 45 o /s. The proposed inclinometer provides a simple yet high performance solution for tile angle measurement.

the sensitivity of the sensor. The nanometer scale grain size of the sputtered oxide thin film is conducive to improving the sensitivity of the gas sensor. The experimental results indicate that the developed device has a sensitivity of 10 ohm ppm -1 at 300 o C and a detection capability of less than 1.0 ppm.

The optical transmission properties of photonic crystal fibers (PCFs) can be manipulated by modifying the pattern arrangement of the air channels within them. This paper presents a novel MEMS-based technique for modifying the optical transmission properties of commercial photoniccrystal fiber (PCF) by selectively filling the voids within the fiber structure with liquid crystals. In the proposed approach, an un-cured SU-8 ring pattern with a thickness of 5 µm is fabricated using a novel stamping method. The PCF is then brought into contact with the SU-8 pattern and an infra-red (IR) laser beam is passed through the fiber in order to soften the SU-8 surface; thereby selectively sealing some of the air channels with molten SU-8. Liquid crystals (LCs) are then infiltrated into the un-sealed holes in the PCF via capillary effects in order to modify the transmission properties of the PCF. Two selectively-filled PCFs are fabricated, namely an inner-ring LC-PCF and a single-line LC-PCF, respectively. It is shown that the two LC-PCFs exhibit significantly different optical behaviors. The practical applicability of the proposed selective-filling approach is demonstrated by fabricating an electric field sensor. The experimental results show that the sensor has the ability to measure electric fields with an intensity of up to 40 kV/cm.

This paper presents a novel process for fabricating integrated microfluidic devices with embedded electrodes which utilizes low-cost UV curable resins. Commercial UV glue is sandwiched between two substrates and is used for both the structural material and the bonding adhesive. During the exposure procedure, the pattern of micro-fluidic channels is defined using a standard lithography process while the two substrates are bonded. The un-cured UV glue is then removed by vacuum suction to form the sealed microfluidic channel. With this simple approach, conventional high-temperature bonding processes can be excluded in the fabrication of sealed microfluidic structures such that the developed method is highly advantageous for fabricating microchip devices with embedded electrodes. The overall time required to fabricate the sealed microchip device is less than 10 min since no time-consuming etching and bonding process is necessary. An innovative micro-reactor integrated with an in-channel micro-plasma generator for real-time chemical reaction analysis is fabricated using the developed process. On-line mass-spectrum (MS) detection of an esterification reaction is successfully demonstrated, which results in a fast, labelfree, preparation-free analysis of chemical samples. The developed process can thus show its potential for rapid and low-cost microdevice manufacturing.

This paper reports a high-performance impedance-type inclinometer fabricated in a glass-SU-8-glass sandwich structure for wide-angle measurements with rapid sensing response. The output signal of the proposed-inclinometer is read from a moving-metal pendulum based on the electrical potential measurement scheme. Two types of pendulum mass made by Ga-In-Sn alloy and mercury are used for the inclinometer. The friction between the liquid metal and substrate surfaces is dramatically reduced by applying an organic-based surfactant of SDS. Experimental results show the developed inclinometer has a wide linear range (320 • ) and a high angle resolution (0.3 • ). Performance test shows no time lag for the sensor output under a rotation speed of 1/8 rps, and no damping effect for an instant stop from a rotation speed of 45 • /s. The developed inclinometer provides a simple yet high-performance solution for tile angle measurement.

This paper presents a new method for CE-EC determination of Mercaptopurine (MP), one of the most important medicines for inflammatory bowel disease (IBD) and acute lymphoblastic leukemia (ALL) treatment, in a PMMA-based microfluidic chip. A simple and reliable process for preparing the template of gold nanoelectrode ensemble (GNEE) and fabricating the integrated microfluidic chip is reported in the present study. The use of GNEE electrodes for both electric current decoupling and signal sensing in the proposed CE-EC chip not only enhances the signal response but also decreases the background noise during detection. Results show that a good detection limit of 100 nM for detecting mercaptopurine is achieved with the proposed method. In addition, the measured results also shows a good linear response between the detected CE-EC signals and the concentration of MP within the range of 100 nM-10 mM (R 2 = 0 989). The proposed microchip device provides a novel and fast detection method for mercaptopurine analysis.

This paper proposes a novel three-dimensional (3D) vortex micromixer for micro-total-analysis-systems (µTAS) applications which utilizes self-rotation effects to mix fluids in a circular chamber at low Reynolds numbers (Re). The microfluidic mixer is fabricated in a three-layer glass structure for delivering fluid samples in parallel. The fluids are driven into the circular mixing chamber by means of hydrodynamic pumps from two fluid inlet ports. The two inlet channels divide into eight individual channels tangent to a 3D circular chamber for the purpose of mixing. Numerical simulation of the microfluidic dynamics is employed to predict the self-rotation phenomenon and to estimate the mixing performance under various Reynolds number conditions. Experimental flow visualization by mixing dye samples is performed in order to verify the numerical simulation results. A good agreement is found to exist between the two sets of results. The numerical results indicate that the mixing performance can be as high as 90% within a mixing chamber of 1 mm diameter when the Reynolds number is Re = 4. Additionally, the results confirm that self-rotation in the circular mixer enhances the mixing performance significantly, even at low Reynolds numbers. The novel micromixing method presented in this study provides a simple solution to mixing problems in the lab-chip system.

This paper presents a parametric experimental investigation into the electrokinetic instability (EKI) phenomenon within three different types of microfluidic device, namely T‐type, cross‐shaped, and cross‐form with an expansion configuration. The critical electric field strength at which the EKI phenomenon is induced is examined as a function of the conductivity ratio, the microchannel width, the expansion ratio, and the surface treatment of the microchannel walls. It is found that the critical electric field strength associated with the onset of EKI is strongly dependent on the conductivity ratio of the two samples within the microfluidic device and reduces as the channel width increases. The surfaces of the microchannel walls are coated with hydrophilic or hydrophobic organic‐based spin‐on‐glass (SOG) nanofilms for glass‐based microchips. The experimental results indicate that no significant difference exists in the critical electric field strengths in the hydrophilic or hydrophob...