Film Speed Research Articles

Modeling of a Grooved Parallel Bearing with a Mass-Conserving Cavitation Algorithm

Several load-supporting mechanisms have been studied to deal with the cavitation problem in parallel bearings. The formation of cavities and their disposition affect the pressure generated in a continuous thin film and hence the load capacity of bearings. In solving the Reynolds equation, proper cavitation boundary conditions must be applied. In this article, the mass-conserving Vijayaraghavan-Keith cavitation algorithm is utilized to analyze the hydrodynamic lubrication performance of parallel bearings with one or more grooves. Using the finite difference method, a one-dimensional Reynolds equation is discretized. Gauss-Seidel iteration is used to solve the obtained set of linear algebraic equations. For a given lubricant, sliding speed, and minimum film thickness, several comparative studies are made between the Vijayaraghavan-Keith cavitation algorithm and a published analytic solution. Several factors affecting the hydrodynamic lubrication performance are considered, such as cavitation pressure, inlet length, groove number, and textured pattern. The analysis results validate the Vijayaraghavan-Keith cavitation algorithm. It is found that the Vijayaraghavan-Keith algorithm is not sensitive to the textured groove depth. In addition, inlet roughness, inlet suction, and quasi-antisymmetric integration are identified to be the essential features that generate hydrodynamic pressure in parallel bearings.

Highly porous metal oxide polycrystalline nanowire films with superior performance in gas sensors

In this work, we report for the first time a simple two-step route to fabricate a novel porous metal oxide film composed of polycrystalline nanowires with ultra-small nanoparticles, good interconnectivity between nanoparticles, and a high density of ultra-fine nanopores. The as-prepared metal oxide films combine the advantages of small crystal size, high surface-to-volume ratio, and one-dimensional-nanowire-induced unique charge transport paths (with correspondingly high interconnectivity). Taking In2O3 as an example, porous In2O3 films, composed of polycrystalline In2O3 nanowires with ultra-small nanocrystals (less than 10 nm) and a high density of ultra-fine nanopores (1.6–3.1 nm), have shown very high sensitivity and good reproducibility towards ethanol gas, which are 10–20 times higher than for In2O3 octahedra and commercial SnO2 thick films. The response/recovery speeds of the as-prepared porous In2O3 films are also 5–6 times higher than for In2O3 octahedra, SnO2 nanobelts, and commercial SnO2 thick films. We believe that such metal oxide flexible films made from highly porous nanowires will replace their traditional thick film counterparts, not only in gas sensors but also in other functional devices, such as batteries, supercapacitors, solar cells, etc.

A measure for quantifying the radiopacity of restorative resins

To evaluate the utility of the X-ray attenuation coefficient as a measure for quantifying the radiopacity of restorative resins at different exposure times and film speeds. Five restorative resins were made into disks, measuring 10 mm in diameter with thicknesses of 0.5, 1.0, 1.5, 2.0, and 2.5 mm. These resin disks, an aluminum step wedge, and a lead disk were placed on size 4 Ultraspeed® D and Insight® E/F films. X-ray parameters were 65 kVp, 10 mA, and 30-cm focus-to-film distance. Exposure times were 0.3, 0.15, and 0.10 s for the D-speed films and 0.15, 0.10, and 0.05 s for the E/F-speed films. At each exposure setting, three D- and E/F-speed films were exposed and processed immediately with an automatic processor. The optical density was measured with a transmission densitometer. The net optical density (D) was used to calculate the linear attenuation coefficients (μ) using lnD = −μ x + lnD 0, where D and D 0 denote the optical density of the specimen and background, respectively. The linear attenuation coefficients (mm−1) of the five restorative resins were 0.24–0.27 for Sorare®, 0.30–0.34 for Estelite®, 0.36–0.39 for Gradia®, 0.51–0.54 for Clearfil AP-X®, and 0.52–0.56 for Beautifil®. These were all higher than that of dentin (0.15–0.19). There was no significant difference in the attenuation coefficients at different exposure times or film speeds. Attenuation coefficients can be used instead of aluminum wedges of equivalent thickness to quantify the radiopacity of restorative resins.

Do we observe Gerstner waves in wave tank experiments?

We investigate theoretically the effects of viscosity and surface films on small-amplitude Gerstner waves in deep water. The analysis is performed by using a Lagrangian formulation of fluid motion. For inviscid fluids with a free surface Gerstner waves of arbitrary amplitude are exact solutions of the nonlinear Lagrangian equations. These waves have a trochoidal surface shape. They possess vorticity, but have no mean wave momentum, i.e. induce no net drift in the fluid. By expanding the wave motion after the wave steepness as a small parameter, we demonstrate how Gerstner waves to second order in wave steepness change due to viscosity, leading to a mean drift near the surface and a backward drift beneath the surface layer, so that they conserve total (zero) mean wave momentum. In addition, if the surface is covered by a freely floating inextensible film, the mean drift at the surface (the film speed) increases dramatically. A comparison with experimental data for the drift of thin plastic sheets in wave tanks is made, showing that the presence of viscosity-modified Gerstner waves cannot be ruled out on the basis of these observations.

Magnetic Field Dependent Characteristics of Al-doped ZnO by High Power Impulse Magnetron Sputtering (HIPIMS)

In this study characteristics of Al-doped ZnO thin film by HIPIMS (High power impulse sputtering) are discussed. Deposition speed of HIPIMS with conventional balanced magnetic field is measured at about 3 nm/min, which is 30% of that of conventional RF sputtering process with the same working pressure. To generate additional magnetic flux and increase sputtering speed, electromagnetic coil is mounted at the back side of target. Under unbalanced magnetic flux from electromagnet with 1.5A coil current, deposition speed of AZO thin film is increased from 3 nm/min to 4.4 nm/min. This new value originates from the decline of particles near target surface due to the local magnetic flux going toward substrate from electromagnet. AZO film sputtered by HIPIMS process shows very smooth and dense film surface for which surface roughness is measured from 0.4 nm to 1 nm. There are no voids or defects in morphology of AZO films with varying of magnetic field. When coil current is increased from 0A to 1A, transmittance of AZO thin film decreases from 80% to 77%. Specific resistance is measured at about <TEX>$2.9{\times}10-2\Omega{\cdot}cm$</TEX>. AZO film shows C-axis oriented structure and its grain size is calculated at about 5.3 nm, which is lower than grain size in conventional sputtering.

Optimisation of patient protection and image quality in diagnostic radiology

To determine the examination frequencies, quality of radiographic images and the entrance surface dose (ESD) in patients undergoing general radiographic examinations. Prospective study on the device performance, film reject rate, patient dose, and image quality during the use of standard and fast speed film screen combination. Radiology Department of Kenyatta National Hospital, a referral, teaching and research hospital in Kenya. A total of 837 adult and 229 paediatric patients undergoing diagnostic examinations were assessed for patient dose and image quality. The X-ray tube output measurements and X-ray exposure parameters were determined. The patients ESD on standard 200 and fast 400 speed film screen combination was determined. The radiographic image quality was assessed. The findings were compared with the international diagnostic reference levels (DRL's) for determination of dose optimisation in diagnostic radiography. The relative frequency of examination was 80% and 20% for adults and paediatric patients respectively. The image quality improvement by 13% was achieved and patient dose reduction range of 31% to 77%. The patient dose reduction and image quality was achieved through a quantitative quality control (QC) assessment of processes involved in producing radiographs. The study leads to the introduction of the concept of plan- do-check-act on QC results and optimise with a view of patient dose reduction. The department appreciated the value of a quality assurance (QA) programme and continues to collect data for establishment of DRL's.

Dynamics of expanding foam films under additionally applied pressure

Abstract A new drainage model was applied to expanding and draining foam films, which were exposed to an additional pressure, generated by a special nano-pump, except the capillary one. The foam films, prepared from 10 −4 M aqueous solution of tetraethylene glycol octyl ether C 8 E 4 + 10 −5 M NaCl, were formed in Scheludko cell. A double-concaved drop in the film holder of the Scheludko cell was positioned. The tips of the drop were approached toward each other by sucking out liquid from the side of the meniscus with a given volumetric flow rate by nano-pump controlled by PC. After formation of the foam film the nano-pump was left to continue working. The latter made the film expand with a certain rate until reaching a critical size, where it stopped expanding. The experiment was performed with different volumetric flow rates of the nano-pump in the range of 100 nL/s–10,000 nL/s. A fitting procedure with only one matching parameter – the additional pressure, was performed giving good agreement with the experimental data. A correlation curve speed of nano-pump – additional pressure was determined. The speed of film expanding at each particular case was measured and an empiric equation: expanding rate vs. additional pressure was suggested. In addition, the dependence critical film radius vs. additional pressure was obtained as well. The current experiment aimed at imitating the process of collision between bubbles at foam agitation. It indicated that the shear stresses generated by agitation make the bubbles collide with different speeds forming variety of bubble contact areas.

Electroless deposition of CoPtWP magnetic thin films

CoPtWP magnetic thin films were prepared by electroless deposition. The influence of bath pH, deposition temperature and bath composition on the deposition speed, alloy content, microstructure, and magnetic properties of CoPtWP thin films were investigated. It was found that deposition speed increased gradually with the bath pH and deposition temperature. The cobalt content in the CoPtWP thin films varied from 77 at.% to 85 at.% by controlling the bath pH. The microstructure of CoPtWP thin films was dependent on bath pH and deposition temperature: two mixed structures, face centered cubic (fcc) and hexagonal close packed (hcp), were observed at low pH values and low deposition temperature. With the increase of pH values and deposition temperature, the intensity of fcc (111) peak suppressed gradually. The surface morphology was markedly influenced by bath pH, deposition temperature and bath composition. VSM and MFM measurements revealed that perpendicular coercivity had been increased with the bath pH. Unique hard magnetic properties of CoPtWP thin films with large perpendicular magnetic anisotropy were obtained at 90 °C and bath pH 13.0.

Crystallization behavior of amorphous Alx(Ge2Sb2Te5)1−x thin films

Crystallization properties of thermally deposited amorphous Alx(Ge2Sb2Te5)1−x (x=0.06 and 0.10) films were investigated. The crystallization was performed by both macroscopic thermal annealing and nanopulse laser illumination (λ=658 nm and beam diameter &amp;lt;2 μm). The Al0.10(Ge2Sb2Te5)0.90 film exhibited a very stable one-step phase transition from amorphous→face-centered cubic (fcc) in the annealing temperature range of 100–300 °C. The Al0.10(Ge2Sb2Te5)0.90 film had a higher sheet resistances (RS) in both the amorphous and crystalline phases compared to the Ge2Sb2Te5 film, resulting in lower set and reset programming currents in the phase-change random-access memory. The crystallization speed (v) of the amorphous films was quantitatively and qualitatively evaluated through the analysis of the surface images and the nanopulse reflection-response curves. Conclusively, the Al atom added into Ge2Sb2Te5 serves as a center for suppression of the fcc-to-hexagonal phase transition and the v-value was largely improved by the proper addition of Al, e.g., v[Al0.10(Ge2Sb2Te5)0.90]&amp;gt;v[Ge2Sb2Te5]. Additionally, the improved v was believed to result from improvements in both the nucleation and growth processes.

Low cost digital radiography system for weld joints and castings testing

A low cost digital radiography system (DRS) for testing weld joints and castings in laboratory was assembled. The DRS is composed from X-ray source, scintillator, first surface mirror with Aluminum coating, charged coupled device (CCD) camera and lens. The DRS was used to test flawed carbon steel welded plates with thicknesses up to 12 mm. The comparison between the digital radiographs of the plates weldments and the radiographs of the same plates weldments using medium speed film type had shown that, the detection capability of the weld flaws are nearly identical for the two radiography techniques, while the sensitivity achieved in digital radiography of the plates weldments was one Image Qualits Indicator (IQI) wire less than the sensitivity achieved by conventional radiography of the same plates weldments according to EN 462-1. Further, the DRS was also successfully used to test (100x100x100) mm3 Aluminum casting with artificial flaws of varied dimensions and orientations. The resulted digital radiographs of the casting show that, all the flaws had been detected and their dimensions can be measured accurately, this confirm that, The proposed DRS can be used to detect and measure the flaws in the Aluminum and others light metals castings accurately.

Nonlinear Dynamic Behavior of Turbocharger Rotor-Bearing Systems With Hydrodynamic Oil Film and Squeeze Film Damper in Series: Prediction and Experiment

Current trends for advanced automotive engines focusing on downsizing, better fuel efficiency, and lower emissions have led to several changes in turbocharger bearing system design and technology. Automotive turbochargers run faster and use engine oils with very low viscosity under high oil inlet temperature and low feed pressure. The development of high performing bearing systems, marrying innovation with reliability, is a persistent challenge. This paper shows progress on the nonlinear dynamic behavior modeling of the rotor-radial bearing system (RBS) incorporating two oil films in series: a hydrodynamic one with a squeeze film damper commonly used in turbochargers. The developed fluid bearing code predicts bearing rotational speed (in the case of fully floating design), operating inner and outer bearing film clearances, effective oil viscosity, taking into account its shear effect, and hydrostatic load. A rotordynamics code uses this input to predict the nonlinear lateral dynamic response of the rotor-bearing system. The model predictions are validated with test data acquired on a high speed turbocharger RBS of a 6.0 mm journal diameter running up to 250,000 rpm (maximum speed), 5W30 oil type, 150°C oil inlet temperature, and 4 bar oil feed pressure. The tests are conducted at a rotordynamics technology laboratory using a high performance data acquisition system. Turbochargers with four combinations of inner and outer RBS clearances are tested. Prediction and measured synchronous response and total motion are in good agreement. Both demonstrate the nonlinear character of the RBS behavior, including several subsynchronous frequency components across the operating speed range. The nonlinear predictive model aids the development of high performance and optimized turbocharger RBS with faster development cycle times and increased reliability.

PRAM을 위한 Si-doped Ge2Sb2Te5박막의 상변화 특성 연구

In this paper, we report the changes of electrical, structural and optical characteristics in <TEX>$Ge_2Sb_2Te_5$</TEX> thin films according to an increase of Si content. The Si-doped <TEX>$Ge_2Sb_2Te_5$</TEX> thin films were prepared by rf-magnetron co-sputtering method. Isothermal annealing was carried out at <TEX>$N_2$</TEX> atmosphere. The crystallization speed (v) of amorphous thin films was evaluated by detecting the reflection response signals using a nano-pulse scanner (wavelength = 658 nm) with illumination power of 1~17 mW and pulse duration of 10~460 ns. Structural phase changes were evaluated by XRD, and the optical transmittance was measured in the wavelength range of 300~3000 nm using UV-vis-NIR spectrophotometer. The sheet resistance (RS) of the thin films was measured using 4 point probe. Conclusivlely, the v-value decreased with an increase of Si content, while the RS-values of both crystalline and amorphous phases were increased. In particular, fcc-to-hexagonal transition was suppressed by the added Si atoms.

Investigation of TiO2 Thin Film Growth by Layer-by-Layer Self-Assembly for Application to Optical Devices

Recently, optical thin films fabricated using a water-based process have been strongly demanded. We fabricated TiO2 thin films consisting of poly(diallyl dimethyl ammonium chloride) (PDDA) and titanium(IV) bis(ammonium lactate) dihydroxide (TALH) for optical devices fabricated using layer-by-layer self-assembly. We report the effects of the pH and concentration of a solution, immersion time, and the amount of NaCl added to a solution on the thickness, morphology, surface roughness, and transmittance of fabricated thin films. The thickness, surface morphology, and transparency of (PDDA/TALH) thin films were determined by ellipsometry, field-emission scanning microscopy (FE-SEM), atomic force microscopy (AFM), and ultraviolet–visible (UV–vis) spectrometry. It was found that the thickness and surface morphology of (PDDA/TALH) multilayer films can be controlled by adjusting the TiO2 particle size of TALH solution. TiO2 particle size was controlled by adjusting the pH of TALH solution and the concentration of PDDA solution, and by adding NaCl to PDDA solution. It was found that we can increase deposition speed while maintaining optical quality by suppressing the surface roughness within 10 nm. These experimental results showed that the fabrication speed of thin films can be markedly increased, by approximately 6-fold.

Improved Coating Window for Slot Coating

Slot die is a premetered coating operation in which the coating solution is extruded from a feed slot onto the surface of a substrate passing through. The defect-free region of operation is known as the “coating window”, and the wider it is, the more versatile the operation will be. The slot-coating experiments reported here were carried out with two types of coating solutions, a hard coating solution with low viscosity and a polysilica solution with high viscosity. The coating windows were measured as flow rates q versus minimum and maximum coating speeds, Vmin and Vmax, respectively. Therefore, at a given flow rate of the coating solution, there exists a minimum speed and a maximum speed that border the corresponding coating window, outside which coating defects occur. Also, in our experiments, the coating windows shifted to higher coating speed and obtained thinner coating film thicknesses through different settings of the die angle to the substrate and different geometries of die lips. The data showed that the coating windows shifted to higher speed and thinner film thicknesses when the die angle and the geometry of the die lips were varied appropriately. These results have important practical implications. The fundamental principles involved here are also applicable to other premetered coating processes.

Nano-scale effects on Young's modulus of nanoimprint polymers measured by photoacoustic metrology

The ultrashort laser pulse photoacoustic method has been used to characterise the physical properties of spin-coated PMMA layers onto Si wafers with thicknesses from 586 to 13 nm, . Acoustic speeds of polymer films were derived from the measured time of flight of acoustic waves in polymers and from their calculated visco-elastic properties. A 12% increase, in comparison to the PMMA bulk value, of the acoustic speeds was measured for polymer films with thicknesses below 80 nm, which corresponds to an increase in Young's modulus of 26%. In addition, we found that adding a hexamethyldisilazane primer monolayer between the polymer film and the Si substrate lessen the increase in Young's modulus, suggesting that the nanoscale changes are due to interface effects.

UHV-ERDA investigation of NEG coatings

Abstract Non-evaporable getter (NEG) coatings are widely used in large vacuum systems such as particle accelerators. Since NEG coatings produced at the GSI Helmholtzzentrum fur Schwerionenforschung have a finite thickness of typically 1 μm, ion beam analysis techniques such as ERDA and RBS are the methods of choice to study element and depth-resolved evolution of the getter film during gas pumping. The film thickness and stoichiometry can be determined by RBS while ERDA is sensitive to lighter elements such as carbon, nitrogen and oxygen, the main residual gas components of a vacuum environment. In this work we first present exsitu and insitu measurements of NEG thin films using ERDA. For the investigation of the pumping speed and capability of the getter films, we have used a vacuum test chamber where getter coated samples can be activated and saturated in a very controlled way. Afterwards, depth distributions of the pumped gas components have been measured using ERDA. To study the gas components in NEG coatings online, i.e., during activation or pumping, we have set up an ERDA system working at vacuum pressures down to 10 - 11 mbar . A special target heater system allows to activate the getter coatings insitu at typical temperatures between 180 and 300 °C in a UHV environment with tolerable influence to the total and partial gas pressure. With this UHV-ERDA setup, a temperature dependent diffusion process of gas components into the getter material could be analyzed for the first time.

A study in Europe of patient dosimetry in diagnostic radiology: protocol development and findings

In a multi-centre study more than 600 patient measurements of patients receiving thorax radiography were performed in five European cities. Participating centres were Fulda, Liverpool, Nicosia, Passau and Sofia. The dose quantities measured were the air kerma-area product (AKAP), incident air kerma and entrance surface air kerma (ESAK). In addition, for each patient sex, age, weight, height, focus-to-film distance, focus-to-skin distance, patient thickness, kV, mAs, field size and the nominal film speed were registered. Different X-ray machines were used in the participating centres--Thoravision, flat panel detector and film screen combinations in two centres (analogue system). The tube voltages employed varied between 60 and 150 kV and the nominal film speed between 200 and 400/800. All mean dose values (ESAK and AKAP) for the different centres showed a different value for female and male populations. The differences were up to 100 % and always higher for the mean AKAP. For a thorax posteroanterior examination, the mean ESAK varied between 0.06 and 0.46 mGy and the mean AKAP varied between 60 and 690 mGy cm(2). The differences in the results obtained as well as the methodologies for multi-national, multi-centre studies will be discussed. Future perspectives for this type of study within the framework of radiation protection and quality assurance in Europe will also be discussed as well as the role and function of multi-national radiological data sets including patient dose values.

Evaluation of surface radiation dose to the thyroid gland and the gonads during routine full-mouth intraoral periapical and maxillary occlusal radiography.

Aim:The quantitative aspects of radiation doses to critical organs can help the dental professionals to take the necessary radiation protective measures as deemed necessary and can help the general public to allay radiation exposure fear in dental radiography, if any. Our study determines the surface radiation dose to thyroid and gonads in full-mouth intraoral periapical (IOPA) and maxillary occlusal radiography.Materials and Methods:A total number of 120 subjects participated in the study. The surface radiation dose was estimated to the thyroid gland and the gonads in full-mouth IOPA radiography using 10 IOPA (E speed films) and in maxillary occlusal radiography. The measurements were calculated using a digital pocket dosimeter (PD-4507).Results:The average dose at the thyroid gland level during full-mouth intraoral and maxillary occlusal radiography was estimated to be 10.93 mRads (1.093 × 10-2 mGy) and 0.4 mRads (4.0 × 10-2 mGy), respectively. The average surface radiation dose at the gonadal region during a full mouth intraoral and maxillary occlusal radiography was estimated to be 1.5 mRads (1.5 × 10-2 mGy) and 0.15 mRads (1.5 × 10-3 mGy), respectively.Conclusion:Our results suggest that although the radiation exposure doses to critical organs namely thyroid and gonads is within the safe limits still precautionary measures for these organs are advocated.

Newest Trend of Particle Counter Technologies, and the Adaptability to the Particle Measurement in Manufacturing Processes

The importance of the contamination particle control in state of the art electron device production, such as a semiconductor, is increasing more than ever. Particle counter has been widely used as the technique of measuring particles suspended in the liquid phase and the gaseous phase. ITRS has been showing concretely the number concentration of particles, which should be controlled, in air, gas and liquid in contact with wafers. First, the leading-edge technology of the liquid-borne particle counter is shown, since the request about particle control in liquid of ITRS is considered as the typical information on a market trend. Meanwhile, the level of the particle contamination in process, such as a vacuum process does not have the shared roadmap. However, since TFT-LCD and PV which industrial scale has expanded rapidly, needs a high speed film deposition at a large substrate, the particle contamination control in vacuum process has been attracting attention. So the technique of the particle measurement in PECVD reactor is shown as an example of the particle measurement in vacuum processes which are expected as new application of a particle counter technology. Finally, a subject common to the measurement technique which uses a light scattering phenomenon as a principle, and the directivity of its improvement is shown.

Appropriate Film Speed for Ionospheric Fading Records from Winds Equipment

Appropriate Film Speed for Ionospheric Fading Records from Winds Equipment