Structural Analyses and Assessment of Historical Kamanl? Mosque in Izmir, Turkey

Historical structures are one of the most precious pieces of cultural accumulation. In this study, an interdisciplinary work was conducted to assess the structural condition of a historical masonry structure, Urla Kamanl? Mosque in ?zmir, Turkey. The structure is a member of group of structures, Yah?i Bey Complex, which includes a Turkish bath, a tomb, two fountains, and a primary school. The structure dates back to early 14th century to mid-15th century. History investigation, measurement survey, long-term settlement, and moisture observations were conducted. Nondestructive and destructive material tests were performed on stone, brick, and mortar. 3D finite-element model of the structure was used to investigate the critical locations of the structure under its self-weight, seismic load, and settlement load. Linear elastic and nonlinear settlement analyses were conducted to investigate the reason for massive cracks challenging the structural integrity.     

Vortex Pinning by an Inhomogeneous Magnetic Field

We discuss the transport properties of a superconducting film under the influence of a tesla range spatially alternating magnetic field created by magnetic nanostructures placed outside a superconducting film with an insulating barrier between both so that they interact only via the magnetic field. A simple model for pinning by the spatially periodic magnetic field from the magnetic nanostructure qualitatively describes the data.     

Dynamic and geometric error assessment of an XYC axis subset on five-axis high-speed machine tools using programmed end point constraint measurements

This paper presents a technique for assessing the volumetric errors on a five-axis machine tool for motion involving two linear axes and one rotary axis at selected feed rates using data from two sources. The first source of data is obtained through a programmed end point constraint procedure with measurement of the 3D volumetric positioning errors between a point on the tool holder and another fixed to the machine table reference frame. The tests involve maintaining the nominal coincidence of these two points whilst exercising the three axes. The second source of data is the position feedback signal from the encoder provided by the machine controller. Tests were carried out at low and high feed rates to evaluate the effect of geometric and dynamic errors. Polynomial functions are used to represent and then predict the geometric errors. The predicted geometric errors are then added to the dynamic errors provided by the servo errors from position feedback signals and propagated to the tool centre point and are compared with the measured volumetric errors. It shows that the influence of the geometric errors are dominant at low feed, whereas the effects of the servo errors of the linear axes become dominant as the feed increases, reaching 80% of the total error at a feed of 10,000 mm/min.     

Interaction of cell culture with composition effects on the mechanical properties of polycaprolactone-hydroxyapatite scaffolds fabricated via selective laser sintering (SLS)

In the current study PCL/HA composites were fabricated using SLS as two- and three-dimensional lattice structures and exposed to a cellular component (MC 3T3 osteoblast-like cells). The main aims were to determine the mechanical differences due to powder composition and to observe the physical and mechanical changes pertaining to cell presence. These structures were characterized by compressive mechanical testing, and the effects of cell culturing and degradation on mechanical properties of the scaffolds with different PCL/HA compositions were determined. Moreover, changes in the scaffold morphology due to the cell culture conditions were determined by μ-CT analysis.Cells steadily grew on the scaffolds for 21 days with preferential distribution around the macropores and initially PCL/HA(15%) composites had higher cell numbers. Removal of loosely sintered parts was observable during the culturing period. Cell culture conditions did not change the compressive moduli significantly but had a distinct effect on compressive strength. For PCL/HA(15%) composites, an initial loss in strength caused by cell culture was reversed by longer cell exposure, with compressive strength of the structures restored to the initial properties (p ≤ 0.05). μ-CT measurements showed widespread morphological changes in the scaffolds, such as a decrease in the roughness of the struts. In general, in the initial period composites with lower HA content (15 wt.%) showed better metabolic activity compared to the higher HA content, however by day 14 the performance of the two compositions was equal. These results suggest that changes in sintering due to the differences in powder composition can have profound effects on the short and long term mechanical properties of the scaffold particularly under cell culture conditions, and this should be closely considered for SLS processing of scaffolds.     

Attenuated total reflection-infrared nanofluidic chip with 71 nL detection volume for in situ spectroscopic analysis of chemical reaction intermediates

We present a micromachined silicon attenuated total reflection-infrared (ATR-IR) crystal with integrated nanofluidic glass channels which enables infrared spectroscopic studies with only 71 nL sample volume. Because of the short path length through silicon, the system allows IR spectroscopy down to 1200 cm(-1), which covers the typical fingerprint region of most organic compounds. To demonstrate proof-of-principle, the chip was used to study a Knoevenagel condensation reaction between malononitrile and p-anisaldehyde catalyzed by different concentrations of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in solvent acetonitrile. By in situ measurement, it was demonstrated for the first time that at certain concentrations of DBU, reaction intermediates become stabilized, an effect that slows down or even stops the reaction. This is thought to be caused by increased ionic character of the solvent, in which protonated DBU stabilizes the intermediates. This clearly demonstrates that infrared mechanistic studies of chemical reactions are feasible in volumes as little as 71 nL.     

Experimental and Numerical Failure Analysis of Vertical Rods Used in Paper Molding Machine

A failure investigation has been conducted on the vertical rods which used in paper molding machines. The vertical rods are important elements for paper molding machines to support press forces. Each of the vertical rods that are analyzed was broken into two parts in service. The two failed vertical rod specimens were exposed to various tests such as visual inspection, chemical analysis, hardness measurement, metallographic examination with optical and scanning electron microscopes. A stress analysis was also carried out by the finite element technique for the determination of highly stressed regions on the vertical rods. The results indicated that due to high stress concentrations, the vertical rods failed by fatigue with cracks initiated at the surface close to the shoulder region which has sharp corner.     

CVD Grown Tungsten Oxide for Low Temperature Hydrogen Sensing: Tuning Surface Characteristics via Materials Processing for Sensing Applications

The intrinsic properties of semiconducting oxides having nanostructured morphology are highly appealing for gas sensing. In this study, the fabrication of nanostructured WO₃ thin films with promising surface characteristics for hydrogen (H₂) gas sensing applications is accomplished. This is enabled by developing a chemical vapor deposition (CVD) process employing a new and volatile tungsten precursor bis(diisopropylamido)-bis(tert-butylimido)-tungsten(VI), [W(N^tBu)₂(NⁱPr₂)₂]. The as-grown nanostructured WO₃ layers are thoroughly analyzed. Particular attention is paid to stoichiometry, surface characteristics, and morphology, all of which strongly influence the gas-sensing potential of WO₃. Synchrotron-based ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), X-ray photoelectron emission microscopy (XPEEM), low-energy electron microscopy (LEEM) and 4-point van der Pauw (vdP) technique made it possible to analyze the surface chemistry and structural uniformity with a spatially resolved insight into the chemical, electronic and electrical properties. The WO₃ layer is employed as a hydrogen (H₂) sensor within interdigitated mini-mobile sensor architecture capable of working using a standard computer's 5 V 1-wirebus connection. The sensor shows remarkable sensitivity toward H₂. The high, robust, and repeatable sensor response (S) is attributed to the homogenous distribution of the W⁵⁺ oxidation state and associated oxygen vacancies, as shown by synchrotron-based UPS, XPS, and XPEEM analysis.