Dynamic performance of squeeze-film bearings

Earlier work has shown that oil-film forces can be modelled by linear coefficients. Identification techniques were used to generate numerical values for these coefficients. This paper has shown the invalidity of applying the perturbation techniques normally used in bearing studies to derive expressions for linearized coefficients to represent a cavitated oil-film. An alternative approach was developed based upon energy techniques to obtain estimates for linearized coefficients. Some current work being undertaken suggests that an alternative analytical approach is possible. These results will be reported in due course

Failure of the Standard Coupled-Channels Method in Describing the Inelastic Reaction Data: On the Use of a New Shape for the Coupling Potential

We present the failure of the standard coupled-channels method in explaining the inelastic scattering together with other observables such as elastic scattering, excitation function and fusion data. We use both microscopic double-folding and phenomenological deep potentials with shallow imaginary components. We argue that the solution of the problems for the inelastic scattering data is not related to the central nuclear potential, but to the coupling potential between excited states. We present that these problems can be addressed in a systematic way by using a different shape for the coupling potential instead of the usual one based on Taylor expansion.Comment: 10 pages, 4 figures, 1 table, Latex:RevTex4 published in J. Phys. G: Nucl. Part. Phy

MODELIRANJE GORIVA I POTENCIJALNO PONAŠANJE POŽARA U TURSKOJ

Description of fuel characteristics is an essential input to fire behavior models that can provide decision-support for fire management. Fuel models describe fuel characteristics for fire modeling systems based on Rothermel’s fire spread model. In this study, fire behavior data collected in field experiments in different fuel complexes in Turkey is used in the process of fuel model development. Nine fuel models were built for low and tall maquis, Anatolian black pine (P. nigra J.F. Arnold subsp. nigra var. caramanica (Loudon) Rehder), litter, and slash variable in age and load. BehavePlus simulations of fire rate of spread, flame length and fireline intensity for typical summer weather conditions highlight the quite different fire potential between the studied fuel types. The difficulty in dealing with fuel complexes dominated by live fuels was evident from the simulations. On the contrary, the model correctly predicted the observed temporal decrease of fire behavior in slash. This study shows the crucial importance of experimental fire data to parameterize fuel models.Opis karakteristika goriva je nužan podatak za modele ponašanja požara koji mogu dati podršku odlukama za požarno upravljanje. Modeli goriva opisuju karakteristike goriva za sustave modeliranja požara koji se temelje na Rothermelovom modelu širenja požara. U ovoj studiji, podaci o ponašanju požara prikupljeni u terenskim eksperimentima u različitim kompleksima goriva u Turskoj korišteni su u procesu razvoja modela goriva. Napravljeno je devet modela goriva za nisku i visoku makiju, anatolski crni bor (P. nigra J.F. Arnold subsp. nigra var. caramanica (Loudon) Rehder), stelju te otpad, varijable u starosti i težini. BehavePlus simulacije stope širenja požara, duljine plamena i intenziteta požarne fronte za tipične ljetne vremenske uvjete naglašavaju potpuno drukčiji potencijal požara između izučavanih tipova goriva. Iz simulacija su očite teškoće u bavljenju kompleksom goriva kojima dominira živo gorivo. Nasuprot tomu, model je točno predvidio privremeno smanjenje ponašanja požara u otpadu. Ova studija pokazuje ključnu važnost eksperimentalnih podataka o požaru, kako bi se izvršila parametrizacija modela goriva

Exchange Rate Pass-Through in Turkey : Has it Changed and to What Extent?

This study analyses the impact of exchange rates on domestic prices in Turkey. We seek to demonstrate the variations (if any) in the exchange rate pass-through across different exchange rate regimes, identify the determinants of this change, and characterize the degree and extent of pass-through across different sub-sectors. Our empirical results reveal that the pass-through of exchange rates to domestic prices has declined in the post-2001 period in comparison with the earlier episodes –thanks to a decline in the “indexation” behavior. These findings suggest that switching to floating exchange rate regime and implementing an ambitious disinflation policy have contributed, to a large extent, to the reduction in the pass-through. Nevertheless, the impact of exchange rate on inflation, especially in the traded good is still notable, pointing out that the effect of nominal exchange rate movement on relative prices have increased in the float period.Exchange rate pass-through, Time-varying parameters, Seemingly unrelated regressions, Disinflation, Floating exchange rate regime

Microfluidic preparation of polymer nanospheres

In this work, solid polymer nanospheres with their surface tailored for drug adhesion were prepared using a V-shaped microfluidic junction. The biocompatible polymer solutions were infused using two channels of the microfluidic junction which was also simultaneously fed with a volatile liquid, perfluorohexane using the other channel. The mechanism by which the nanospheres are generated is explained using high speed camera imaging. The polymer concentration (5-50 wt%) and flow rates of the feeds (50-300 µl min(-1)) were important parameters in controlling the nanosphere diameter. The diameter of the polymer nanospheres was found to be in the range of 80-920 nm with a polydispersity index of 11-19 %. The interior structure and surfaces of the nanospheres prepared were studied using advanced microscopy and showed the presence of fine pores and cracks on surface which can be used as drug entrapment locations

Expressed Willingness of STEM Teachers to Teach Engineering

Teaching engineering at the middle and high school levels has been a topic of discussion among scholars regarding the challenges it creates. One of the most critical challenges at the school level is identifying qualified teaching staff to lead engineering courses. The present study explored teachers’ willingness to lead an engineering course and the reasons behind their willingness or unwillingness to do so. The study involved 434 participants, who were enrolled in a STEM professional development program and were diverse regarding their teaching subjects, the grade levels they taught, and the locations of their schools in Turkey. In this mixed-methods study, researchers collected data at the beginning of an online professional development program. Quantitative data were analyzed descriptively, while qualitative data were analyzed with a data-driven codebook. Almost two-thirds of the participants were keen to teach an engineering course, yet differences were observed according to the subjects they taught and their professional backgrounds. Most of the mathematics teachers, the group with the highest percentage of willingness, seemed to have a holistic approach towards engineering, with half emphasizing collaboration between teachers and engineers. The study provided further insights into how initial teacher training and continuous professional development programs can be structured based on teacher expectations and needs

Astronomical Site Selection for Turkey Using GIS Techniques

A site selection of potential observatory locations in Turkey have been carried out by using Multi-Criteria Decision Analysis (MCDA) coupled with Geographical Information Systems (GIS) and satellite imagery which in turn reduced cost and time and increased the accuracy of the final outcome. The layers of cloud cover, digital elevation model, artificial lights, precipitable water vapor, aerosol optical thickness and wind speed were studied in the GIS system. In conclusion of MCDA, the most suitable regions were found to be located in a strip crossing from southwest to northeast including also a diverted region in southeast of Turkey. These regions are thus our prime candidate locations for future on-site testing. In addition to this major outcome, this study has also been applied to locations of major observatories sites. Since no goal is set for \textit{the best}, the results of this study is limited with a list of positions. Therefore, the list has to be further confirmed with on-site tests. A national funding has been awarded to produce a prototype of an on-site test unit (to measure both astronomical and meteorological parameters) which might be used in this list of locations.Comment: 17 pages, 10 figures, accepted by Experimental Astronom

T-shaped microfluidic junction processing of porous alginate-based films and their characteristics

In this work, highly monodisperse porous alginate films from bubble bursting were formed on a glass substrate at ambient temperature, by a T-shaped microfluidic junction device method using polyethylene glycol (PEG) stearate and phospholipid as precursors in some cases. Various polymer solution concentrations and feeding liquid flow rates were applied for the generation of monodisperse microbubbles, followed by the conversion of the bubbles to porous film structures on glass substrates. In order to compare the physical properties of polymeric solutions, the effects of alginate, PEG stearate (surfactant), and phospholipid concentrations on the flowability of the liquid in a T-shaped microfluidic junction device were studied. To tailor microbubble diameter and size distribution, a method for controlling the thinning process of the bubbles’ shell was also explored. In order to control pore size, shape, and surface as well as internal structure morphologies in the scalable forming of alginate polymeric films, the effect of the feeding liquid’s flow rate and concentrations of PEG-stearate and phospholipid was also studied. Digital microscopy images revealed that the as-formed alginate films at the flow rate of 100 µL·min−1 and the N2 gas pressure of 0.8 bar have highly monodisperse microbubbles with a polydispersity index (PDI) of approximately 6.5%. SEM captures also revealed that the as-formed alginate films with high PDI value have similar monodisperse porous surface and internal structure morphologies, with the exception that the as-formed alginate films with the help of phospholipids were mainly formed under our experimental environment. From the Fourier-transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurements, we concluded that no chemical composition changes, thermal influence, and crystal structural modifications were observed due to the T-shaped microfluidic junction device technique. The method used in this work could expand and enhance the use of alginate porous films in a wide range of bioengineering applications, especially in tissue engineering and drug delivery, such as studying release behaviors to different internal and surface morphologies

Utilization of microfluidic V-junction device to prepare surface itraconazole adsorbed nanospheres.

Itraconazole is widely used as an anti-fungal drug to treat infections. However its poor aqueous solubility results in low bioavailability. The aim of the present study was to improve the drug release profile by preparing surface itraconazole adsorbed polymethylsilsesquioxane (PMSQ) nanospheres using a V-junction microfluidic (VJM) device. In order to generate nanospheres with rough surface, the process flow rate of Perfluorohexane (PFH) was set between 50 and 300 μl min(-1) while the flow rate of PMSQ and itraconazole solution were constant at 300 μl min(-1). Variations in the PFH flow rate enable the controlled size generation of nanospheres. PMSQ nanospheres adsorbing itraconazole were characterized by SEM, FTIR and Zetasizer. The release of itraconazole from PMSQ nanosphere surface was measured using UV spectroscopy. Nanosphere formulations with a range of sphere size (120, 320 and 800nm diameter) were generated and drug release was studied. 120nm itraconazole coated PMSQ nanospheres were found to present highest drug encapsulation efficiency and 13% drug loading in a more reproducible manner compared to 320nm and 800nm sized nanosphere formulations. Moreover 120nm itraconazole coated PMSQ nanospheres (encapsulation efficiency: 88%) showed higher encapsulation efficiency compared to 320nm (encapsulation efficiency: 74%) and 800nm (encapsulation efficiency: 62%) sized nanosphere formulations. The itraconazole coated PMSQ nanospheres were prepared continuously at rate of 2.6×10(6) per minute via VJM device. Overall the VJM device enabled the preparation of monodisperse surface itraconazole adsorbed nanospheres with controlled in vitro drug release profile