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1
Gartshore, I., M. Salcudean y P. Matys. "FILM COOLING EFFECTIVENESS". Transactions of the Canadian Society for Mechanical Engineering 15, n.º 1 (marzo de 1991): 43–56. http://dx.doi.org/10.1139/tcsme-1991-0002.
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Rahman, Nor Dawirah, Anna Lynn Abu Bakar, Wan Hurani Osman y Mohammad Aqmal Hafidz Musa. "THE EFFECTIVENESS OF FILM REVIEW IN ENHANCING STUDENTS’ ENGLISH SPEAKING SKILLS". International Journal of Education, Psychology and Counseling 6, n.º 41 (31 de julio de 2021): 23–37. http://dx.doi.org/10.35631//ijepc.641003.
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This study highlighted the effectiveness of film review in enhancing English speaking skills among students at the tertiary level. The population involved was 30 students from an Essential Communication Skills class at Universiti Malaysia Sabah. There were two parts of film review carried out for this study, namely, Part 1: Individual Film Review Presentation and Part 2: Group Discussion and 2 weeks prior, the teacher-researcher provided materials such as examples of vocabularies, grammars, phrases and sentences students could use to describe film genres, characters, themes, recommendations and criticisms in their film review. For Part 1 of the film review, in groups of 5, individual students orally presented the review of their chosen film whilst showing their power point slides whereas for Part 2, they gave ideas and opinions on the best film of those presented by their group members. The objective of this study was to identify students’ perceptions on the effectiveness of film review in enhancing their English-speaking skills. To accomplish that objective, this study employed a survey research design and the instrument utilised in the data collection was an online questionnaire comprising 10 questions on students’ perceptions on English film watching and review which was administered to 30 respondents. The data was then analysed using a google form spreadsheet and presented in pie charts and bar graphs. The findings depicted that students perceived that film review enhanced their English-speaking skills in the aspects of motivation and confidence in speaking simple English and applying appropriate English grammars, vocabularies, pronunciation, intonation, and conversational phrases in expressing ideas and opinions. They also opined that English subtitles in films and guidance from educators in reviewing films contributed positively to the development of their English-speaking acquisition as well as deduced that film review was an effective English learning tool. These positive findings hence signalled that the teaching and learning of English through films should be sustained in the future. It is recommended that future studies include larger numbers of respondents and interviews of students and teachers to obtain more holistic findings on the film review effectiveness towards students’ English-speaking competency. Other interesting topics to be studied are the challenges encountered by both learners and educators in the teaching and learning of English through films and ways to overcome them.
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Kim, Do Hyoung, Han Ki Yoon, Do Hoon Shin y Riichi Murakami. "Electromagnetic Wave Shielding Properties of ITO/PET Thin Film by Film Thickness". Key Engineering Materials 345-346 (agosto de 2007): 1585–88. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.1585.
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The thin films of indium tin oxide (ITO) are used for a variety of electronic devices such as solar cells, touch panels, liquid crystal displays (LCDs). However, these electronic devices are not strong enough against heavy impact since their ITO thin films are deposited on glass substrates. Therefore, ITO thin films were prepared by the inclination opposite target type DC magnetron sputtering equipment onto the Polyethylene Terephthalate (PET) substrate at room temperature using oxidized ITO with In2O3 and SnO2 in a weight ratio of 9:1. In this study, the transmittance, resistivity and electromagnetic wave shielding effectiveness of the ITO thin films prepared at various sputtering time (20~80min namely film thickness; 130~500nm) are measured. The results show that transmittance of the ITO thin films could show about 70% in the range of a visible ray by the variation of film thickness. It also can be seen that a minimum exists in the resistivity of ITO thin films for the variation of film thickness. Electromagnetic wave shielding effectiveness was increased as film thickness increased.
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Mathison, R. M., M. G. Dunn, M. M. Weaver y A. Dushko. "Measurement of Air Film Damping Effectiveness". Journal of Turbomachinery 127, n.º 3 (1 de marzo de 2004): 557–63. http://dx.doi.org/10.1115/1.1928288.
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Air film damping systems have attracted considerable interest within the gas turbine industry because of their effectiveness at controlling modes of vibration without environmental limitations. Though still in the early stages of development, air film dampers have promise for improving the high cycle fatigue characteristics of solid gas turbine airfoils. This study used experimental methods to compare the vibrational response of a solid flat plate with the response of an identically sized plate that incorporated an air film damper. It also investigated the influence of elevated pressures on air film damping effectiveness, the impact of the damper on the various vibration modes, and the relative strain levels of the air film cover plate to the solid backing. The results show that the air film damper is very effective in controlling the two-stripe mode for which it was designed. Increasing the surrounding air pressure makes the damper more effective and shifts the resonant frequencies lower.
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Courtis, Matthew, Alexander Murray, Ben Coulton, Peter Ireland y Ignacio Mayo. "Influence of Spanwise and Streamwise Film Hole Spacing on Adiabatic Film Effectiveness for Effusion-Cooled Gas Turbine Blades". International Journal of Turbomachinery, Propulsion and Power 6, n.º 3 (31 de agosto de 2021): 37. http://dx.doi.org/10.3390/ijtpp6030037.
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To meet the challenges of increased thermal loads and performance demands on aero-engine turbine blades, more advanced cooling techniques are required. This study used a modification of the well-known Goldstein equation to predict film effectiveness for an individual film cooling hole and applied the Sellers’ superposition method to apply these films across effusion-cooled configurations. In doing so, it tackles a relatively unchallenged problem of film holes in close spanwise proximity. An experimental set-up utilised infrared cameras to assess the film effectiveness of nine geometries of varying spanwise and streamwise spacings. Higher porosity led to increased thermal protection, and the spanwise spacing had the most profound impact, with film effectiveness approaching 0.9. Additionally, greater uniformity in the spanwise direction was observed. The modified Goldstein-Sellers method showed good agreement with experimental results although lateral mixing was underestimated. This method represents a tool that could be easily implemented in the industry for rapid assessment of novel cooling geometries.
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Mizoguchi, Makoto, Naoko Iwata, Kentaro Hayashi, Shigeru Aso y Yasuhiro Tani. "Film Cooling Effectiveness in High Enthalpy Flows". JOURNAL OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES 55, n.º 641 (2007): 259–65. http://dx.doi.org/10.2322/jjsass.55.259.
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Sturgess, G. J. "Design of Combustor Cooling Slots for High Film Effectiveness: Part I—Film General Development". Journal of Engineering for Gas Turbines and Power 108, n.º 2 (1 de abril de 1986): 354–60. http://dx.doi.org/10.1115/1.3239911.
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The metal liners of gas turbine engine combustors usually have to be provided with some form of thermal protection from the high temperatures of the reacting mixture of gases contained therein. For aircraft gas turbines, where weight is a factor, the protective medium is air. The air is most usually introduced by tangential injection as a discrete film at a number of axial stations along the combustor liner so that as the cooling potential of one film is depleted it is periodically renewed by another. Although invariably referred to as film cooling, the most important function of the film air is to act as a relatively cool barrier between the vulnerable liner and the reacting gases. The design margin for error is very small. Failure to design a cooling slot that provides a high film effectiveness can result in thermal damage to the liner. Manufacturing considerations almost always determine how a real slot design is reduced to practice. The resulting liners (inner and outer in the case of an annular combustor) contain no two slots that are exactly alike in aerodynamic behavior and, therefore, in film effectiveness performance. Phenomenological models of the film cooling process are invariably based on considerations of two-dimensional shear mixing. Empirical factors may be introduced to account for the differences in performance existing between two-dimensional film slots and real slots. However, such methods are not of much help in designing a slot configuration that will deliver good performance, for making comparative evaluations of competing designs, or in establishing the performance penalties associated with compromises made for manufacturing reasons. Heuristic arguments are used to derive a dimensionless grouping of internal geometric parameters that describe the lateral aerodynamic uniformity of the films produced by practical slots. It is assumed that the average film effectiveness is uniquely related to the film lateral uniformity. Experimental data from a number of different practical slot designs are examined in terms of this geometric mixing parameter, and film effectiveness is shown to depend on it over a wide range of axial distances and film blowing ratios. It is concluded that the geometric mixing parameter provides a means to differentiate good film cooling slot designs from poor ones.
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Jumper, G. W., W. C. Elrod y R. B. Rivir. "Film Cooling Effectiveness in High-Turbulence Flow". Journal of Turbomachinery 113, n.º 3 (1 de julio de 1991): 479–83. http://dx.doi.org/10.1115/1.2927899.
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The mechanisms influencing film cooling effectiveness on a flat plate in high free-stream turbulence using a single row of 30 deg slant-hole injectors are examined. The primary area of focus is the area within 40 diameters downstream of injection. Of interest are blowing ratios for optimum film cooling effectiveness within 10 diameters downstream of injection, and the decay of film cooling effectiveness down the plate. Film cooling flow Reynolds numbers. Re, from 24,700 to 86,600 and free-stream turbulence intensities from 14 to 17 percent were examined. Changes in Reynolds number or free-stream turbulence broadened and increased the blowing ratios for optimum film cooling effectiveness. In comparison with tests conducted at 0.5 percent free-stream turbulence, higher free-stream turbulence causes a faster decay in film cooling effectiveness, or a reduction in the effective cooling length, and a reduction of the level of cooling effectiveness at the higher Reynolds numbers.
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Cheng, Hung-Chuan, Chong-Rong Chen, Shan-hui Hsu y Kuo-Bing Cheng. "Electromagnetic Shielding Effectiveness and Conductivity of PTFE/Ag/MWCNT Conductive Fabrics Using the Screen Printing Method". Sustainability 12, n.º 15 (22 de julio de 2020): 5899. http://dx.doi.org/10.3390/su12155899.
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The management of the electromagnetic interference (EMI) of thin, light, and inexpensive materials is important for consumer electronics and human health. This paper describes the development of conductive films that contain a silver (Ag) flake powder and multiwall carbon nanotube (MWCNT) hybrid grid on a polytetrafluoroethylene (PTFE) film for applications that require electromagnetic shielding (EMS) and a conductive film. The Ag and MWCNT hybrid grid was constructed with a wire diameter and spacing of 0.5 mm. The results indicated that the proposed conductive films with 0.4 wt% MWCNTs had higher electromagnetic shielding effectiveness (EMSE) and electrical conductivity than those with other MWCNT loading amounts. The results also showed that the film with 0.4 wt% MWCNT loading had a high 62.4 dB EMSE in the 1800 MHz frequency and 1.81 × 104 S/cm electrical conductivity. This combination improved stretchability, with 10% elongation at a 29% resistivity change rate. Conductive films with Ag/MWCNT electronic printing or lamination technologies could be used for EMI shielding and electrically conductive applications.
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Okita, Yoji y Masakazu Nishiura. "Film Effectiveness Performance of an Arrowhead-Shaped Film-Cooling Hole Geometry". Journal of Turbomachinery 129, n.º 2 (21 de junio de 2006): 331–39. http://dx.doi.org/10.1115/1.2437781.
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This paper presents the first experimental and numerical work of film effectiveness performance for a novel film-cooling method with an arrowhead-shaped hole geometry. Experimental results demonstrate that the proposed hole geometry improves the film effectiveness on both suction and pressure surface of a generic turbine airfoil. Film effectiveness data for a row of the holes are compared to that of fan-shaped holes at the same inclination angle of 35 deg to the surface on a large-scale airfoil model at engine representative Reynolds number and Mach number in a high-speed tunnel with moderately elevated temperature mainstream flow. The film effectiveness data are collected using pressure-sensitive paint. Numerical results show that the coolant film with the proposed hole geometry remains well attached to the surface and diffuses in the lateral direction in comparison with the conventional laidback fan-shaped holes for coolant to mainstream blowing ratios of 0.6–3.5.
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Wilfert, Gu¨nter y Stefan Wolff. "Influence of Internal Flow on Film Cooling Effectiveness". Journal of Turbomachinery 122, n.º 2 (1 de febrero de 1999): 327–33. http://dx.doi.org/10.1115/1.555449.
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Film cooling experiments were conducted to investigate the effects of internal flow conditions and plenum geometry on the film cooling effectiveness. The film cooling measurements show a strong influence of the coolant inlet conditions on film cooling performance. The present experiments were carried out on a flat plate with a row of cylindrical holes oriented at 30 deg with respect to a constant-velocity external flow, systematically varying the plenum geometry and blowing rates 0.5⩽M⩽1.25. Adiabatic film cooling measurements using the multiple narrow-banded thermochromic liquid crystal technique (TLC) were carried out, simulating a flow parallel to the mainstream flow with and without crossflow at the coolant hole entry compared with a standard plenum configuration. An impingement in front of the cooling hole entry with and without crossflow was also investigated. For all parallel flow configurations, ribs were installed at the top and bottom coolant channel wall. As the hole length-to-diameter ratio has an influence on the film cooling effectiveness, the wall thickness has also been varied. In order to optimize the benefit of the geometry effects with ribs, a vortex generator was designed and tested. Results from these experiments show in a region 5⩽X/D⩽80 downstream of the coolant injection location differences in adiabatic film cooling effectiveness between +5 percent and +65 percent compared with a standard plenum configuration. [S0889-504X(00)01102-8]
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Zhang, Xiao Ning y Qing Wang. "Shielding Effectiveness Simulation of Brass-Iron Sandwich Films". Solid State Phenomena 124-126 (junio de 2007): 1613–16. http://dx.doi.org/10.4028/www.scientific.net/ssp.124-126.1613.
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This paper presents a simulation method on shielding effectiveness(SE). The method is completely general and able to optimize shielding materials. We found a sandwich structure that it can efficiently shield plane wave, using this simulation method. The relationship of film thickness and its skin depth was investigated in this study. Two-dimensional curves and three-dimensional graphs were calculated by tri-layer SE formulas. A sandwich structure, which is 3μm iron-brass-iron films, is capable of excellent shielding properties: the SE is between -73dB and -100dB in the frequency range of 1MHz~10MHz. Another sandwich structure with 12μm thickness of brass-iron-brass films can offer -680dB shielding attenuation. Simulation experiments indicate that sandwich films with diamagnetic and ferromagnetic layers have outstanding contribution on SE.
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Zhang, Bo, Libing Lin, Naru Zhang, Shuangsong Xue y Honghu Ji. "Experimental investigation of geometrical effect on flow and heat transfer performance of lamilloy cooling structure". Thermal Science 24, n.º 3 Part A (2020): 1835–43. http://dx.doi.org/10.2298/tsci190528071z.
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Effect of film hole diameter to discharge coefficients and film cooling effectiveness of the lamilloy were experimentally investigated at the blowing ratios ranging from 0.6 to 2.5. Generally, the cooling effectiveness on the test surface is increased with the film hole diameters and blowing ratios increasing, and the variation tendency along the streamwise through the centerline of film holes also keeps consistent. In the upstream, all configurations have a relatively lower cooling effectiveness, however, with the flows to the downstream, cooling effectiveness grows gradually, and the peak values of effectiveness appeared periodically, the position matches the film hole positions. Besides, between the film holes, fluctuation exists simultaneously. By comparison, the cooling effectiveness and discharge coefficients are both increased with the blowing ratio with same film hole diameters, Moreover, under the same blowing ratios, the cooling effectiveness and discharge coefficients are getting higher when hole diameters increase.
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Jałoweicki, Marcin y Izabela Betlej. "Effect of the essential oils addition on the rate of bacterial cellulose surface overgrowth by mold fungi". Annals of WULS, Forestry and Wood Technology 114 (28 de junio de 2021): 43–51. http://dx.doi.org/10.5604/01.3001.0015.2372.
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Effect of the essential oils addition on the rate of bacterial cellulose surface overgrowth by mold fungi. The aim of this study was to determine the effectiveness of protecting films made of bacterial cellulose with essential oils against overgrowth by mold fungi. The cellulose film produced by microorganisms forming a pellicle called SCOBY was modified by introducing into the cellulose pulp essential oils: cinnamon and manuka. Samples of the protected film were treated with mold fungi: Chaetomium globosum, Aspergillus niger and Trichoderma viride. On the basis of the tests conducted, the rate of film overgrowth by mold fungi and the effectiveness criteria of cellulose film protection with essential oils were determined. The addition of cinnamon oil protected the film against the growth of Aspergillus niger and Chaetomium globosum fungi. Manuka oil slowed down the growth of Chaetomium globosum microorganisms on the surface of the bacterial cellulose film sample, but did not protect the samples from overgrowth. The essential oils tested were ineffective against the fungus Trichoderma viride.
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Méndez, Ignasi, Juan José Rovira-Escutia y Bozidar Casar. "A protocol for accurate radiochromic film dosimetry using Radiochromic.com". Radiology and Oncology 55, n.º 3 (10 de agosto de 2021): 369–78. http://dx.doi.org/10.2478/raon-2021-0034.
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Abstract Background Radiochromic films have many applications in radiology and radiation therapy. Generally, the dosimetry system for radiochromic film dosimetry is composed of radiochromic films, flatbed scanner, and film analysis software. The purpose of this work is to present the effectiveness of a protocol for accurate radiochromic film dosimetry using Radiochromic.com as software for film analysis. Materials and methods Procedures for image acquisition, lot calibration, and dose calculation are explained and analyzed. Radiochromic.com enables state-of-the-art models and corrections for radiochromic film dosimetry, such as the Multigaussian model for multichannel film dosimetry, and lateral, inter-scan, and re-calibration corrections of the response. Results The protocol presented here provides accurate dose results by mitigating the sources of uncertainty that affect radiochromic film dosimetry. Conclusions Appropriate procedures for film and scanner handling in combination with Radiochromic.com as software for film analysis make easy and accurate radiochromic film dosimetry feasible.
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Ekkad, S. V., D. Zapata y J. C. Han. "Film Effectiveness Over a Flat Surface With Air and CO2 Injection Through Compound Angle Holes Using a Transient Liquid Crystal Image Method". Journal of Turbomachinery 119, n.º 3 (1 de julio de 1997): 587–93. http://dx.doi.org/10.1115/1.2841162.
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This paper presents detailed film effectiveness distributions over a flat surface with one row of injection holes inclined streamwise at 35 deg for three blowing ratios (M = 0.5, 1.0, 2.0). Three compound angles of 0, 45, and 90 deg with air (D.R. = 0.98) and CO2 (D. R. = 1.46) as coolants are tested at an elevated free-stream turbulence condition (Tu ≈ 8.5 percent). A transient liquid crystal technique is used to measure local heat transfer coefficients and film effectiveness. Detailed film effectiveness results are presented near and around film injection holes. Compound angle injection provides higher film effectiveness than simple angle injection for both coolants. Higher density injectant produces higher effectiveness for simple injection. However, lower density coolant produces higher effectiveness for a large compound angle of 90 deg. The detailed film effectiveness obtained using the transient liquid crystal technique, particularly in the near-hole region, provided a better understanding of the film cooling process in gas turbine components.
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He, Wei, Qing Hong Fang, Wei Lin, A. S. Luyt y Tie Jun Ge. "Study on Anti-Fog Films of Polyethylene Modified with Inorganic Micrometer Diatomite". Applied Mechanics and Materials 200 (octubre de 2012): 347–50. http://dx.doi.org/10.4028/www.scientific.net/amm.200.347.
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Anti-fog films of low density polyethylene (LDPE) modified with micrometer diatomite were prepared by a process of blow molding. Through examination of antifogging property of the film added the anti-fog agents, the modification effectiveness of inorganic micrometer diatomite and the influence of different treating agents were studied with Fourier transform infrared spectrometer (FTIR), mechanical properties, and antifogging performances. The results indicate that the anti-fog property of the film can be improved by premixing inorganic micrometer diatomite with the anti-fog agents; the film modified by inorganic micrometer diatomite added surface treatment agent has obviously effectiveness anti-fog properties than that the films modified only by the anti-fog agents. Addition of polyacrylamide can make the anti-fog durability of the films modified by inorganic micrometer diatomite be further prolonged. It was observed that the tensile strength does not show any decrease, however, elongation at break show a massive decreased.
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Yang, Fan y Mohammad E. Taslim. "Effects of Diffusion Film Hole Exit Area on the Film Cooling Effectiveness". International Journal of Rotating Machinery 2022 (17 de septiembre de 2022): 1–13. http://dx.doi.org/10.1155/2022/5994933.
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One popular method for the protection of gas turbines’ hot sections from high-temperature combustor gases is film cooling. Substantial amounts of research have been conducted to accomplish this task with the minimum cooling flow, maximum surface coverage, and minimal aerodynamic inefficiencies or structural penalties. In this study, a combined experimental and numerical investigation was conducted on three selected film-cooling hole geometries. These geometries were designed with the same initial metering (feed) section, a cylindrical hole of 30° inclination angle, followed by three different forward expansion section geometries. The expansion sections had a 7° laid-back angle and a 17° expansion angle in each lateral direction. However, different interior corner radii were used to blend the metering hole to the exit area, creating three different expansion geometries with almost the same exit areas. In practice, this variation in expansion geometry could represent manufacturing faults or tolerances in laser drilling of the film holes. This study shows that the variations in film-cooling effectiveness are not significant even though the expansion geometries are significantly different. The Pressure Sensitive Paint (PSP) technique was used to obtain the detailed distribution of film-cooling effectiveness on the surface area downstream of these film holes. Adiabatic film cooling effectiveness was measured at blowing ratios of 0.5, 1.0, and 2.0. CFD models of these film holes were also run, and the results were compared with the test data. The major conclusions of this study were that these proposed new geometries produced higher film effectiveness than the conventional 7°-7°-7° diffusion film holes, for the same exit area, the expansion section geometry of the film holes did not have a significant effect on the film coverage, and the numerical results were in good agreement with the test data.
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Zhuang, S. Y., B. Yin y Z. L. Zhu. "Simulating the effectiveness of surface film on water evaporation and ammonia volatilisation". Soil Research 40, n.º 7 (2002): 1243. http://dx.doi.org/10.1071/sr01027.
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The application of surface films to flooded rice fields is one of the most effective measures of controlling ammonia volatilisation for improving nitrogen use efficiency. The feasibility of using a surface film is determined to some extent by the longevity of the effectiveness and this has never been estimated accurately in the field. The concept of half-life was introduced to estimate the effective life of a surface film by calculation from its effect on water evaporation. A simple laboratory experiment was carried out to validate the usefulness of the half-life concept. The results showed that effects on ammonia volatilisation could be quantified using a logistic equation based on the half-life concept.
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Sun, Jie, Fuxing Zhang, Jin Wang, Jakov Baleta, Gongnan Xie y Bengt Sunden. "Effect of dielectric barrier discharge plasma on film cooling performance". Thermal Science 26, n.º 5 Part B (2022): 4157–68. http://dx.doi.org/10.2298/tsci2205157s.
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To improve film cooling effectiveness of a gas turbine blade, a kind of plasma actuator is introduced on the blade surface. The effect of three arrangements of plasma actuators on flow characteristics and film cooling performance is numerically investigated by a verified turbulence model. Results show that the coolant air under plasma is pulled down to the wall, and the near-wall air is sped up to promote the film cooling effectiveness downstream the wall. It is discovered that the plasma actuators near the film hole show weaker aerodynamic actuation than that downstream the wall. Compared with the plasma actuators off case, the maximum improvement in the wall-averaged film cooling effectiveness of the case with up plasma actuators is 11.7% under low blowing ratios. The wall-averaged film cooling effectivenesses of the cases with down plasma actuators and up-down plasma actuators increase by 138.3% and 122.9% under the blowing ratio of 1.5.. Vortex structures are broken up, and vortex is separated by two jets induced by aerodynamic actuation. The maximum wall pressure difference reaches 1.89% when plasma actuator is arranged downstream the wall.
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Taslim and, M. E. y A. Khanicheh. "Film Effectiveness Downstream of a Row of Compound Angle Film Holes". Journal of Heat Transfer 127, n.º 4 (30 de marzo de 2005): 434–40. http://dx.doi.org/10.1115/1.1865222.
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Effects that two different compound-angle film-hole configurations have on film cooling effectiveness are investigated. Effectiveness measurements have been made downstream of a single row of compound-angle cylindrical holes with a diameter of 7.5 mm, and a single row of compound-angle, diffuser-shaped holes with an inlet diameter of 7.5 mm. Both geometries were inclined with respect to the coverage surface at an angle α of 25 deg. The cylindrical holes, however, were oriented perpendicular to the high-temperature airflow direction while the diffuser-shaped holes had a compound angle of 45 deg with respect to the high temperature air flow direction. Both geometries were tested over a blowing ratio range of 0.7 to 4.0 Surface temperatures were measured along four longitudinal rows of thermocouples covering the downstream area between two adjacent holes. The results showed that the best overall protection over the widest range of blowing ratios was provided by the diffuser-shaped film cooling holes, particularly at high blowing ratios. The increased cross-sectional area at the shaped hole exit lead to a reduction of the momentum flux of the jet exiting the hole. Therefore, the penetration of the jet into the main flow was reduced, resulting in an increased cooling effectiveness. CFD analyses were also performed to study the film cooling effectiveness downstream of the row of holes. Comparisons between the test and numerical results showed a reasonable agreement between the two, thus CFD can be considered a viable tool to predict the cooling performance of different film cooling configurations in a parametric study.
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Zhang, Wei, Rui Zeng, Song Liu y Guangchao Li. "Effect of Blockage Inside Holes on Film Cooling Performance on the Suction Side of a Turbine Guide Vane". Energies 15, n.º 8 (16 de abril de 2022): 2935. http://dx.doi.org/10.3390/en15082935.
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In order to study the effect of thermal barrier coating deposition inside the film holes of turbine guide vanes on film cooling performance, film effectiveness on the suction side is measured by infrared thermal imaging technology. Film effectiveness is obtained at blockage ratios of 0, 0.2, 0.5, and 0.8, and blowing ratios of 0.7, 1.05, and 1.4. Film effectiveness decreases and the spanwise inhomogeneity becomes evident with an increase of the blockage ratio. When blowing ratios increase from 0.7 to 1.4, the surface averaged film effectiveness decreases by 55–60% at a large blockage ratio of 0.8, 21–27% at the middle blockage ratio of 0.5 and by no more than 11% at a small blockage ratio of 0.2. The rounded corners formed by blockage enhance the adhesion of the film at the small blockage ratio of 0.2, thereby improving the film cooling performance near the hole exit. There is a maximum increase of 0.2 in film effectiveness within four hole diameters.
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Chen, Ji, Xiao Chen, Jin Guo, Runyun Zhu, Mengran Liu, Xixi Kuang, Wenqing He y Yao Lu. "Agricultural, Ecological, and Social Insights: Residual Mulch Film Management Capacity and Policy Recommendations Based on Evidence in Yunnan Province, China". Sustainability 13, n.º 4 (3 de febrero de 2021): 1603. http://dx.doi.org/10.3390/su13041603.
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Mulch film contaminates the environment while increasing agricultural yield. As such, the factors that impact the residual film management capacity of farmers must be identified, which would also be helpful for the sustainable development and security of agriculture. We investigated 10 counties across nine cities (states) by surveying 1284 households. The improved entropy-weighted composite index and the grey correlation analysis model were employed to measure the residual film management capacity from five dimensions: human capital, use behavior, management skills, public policy, and willingness. The entropy-weighted composite index results showed that residual film being harmful to the environment had the highest overall rate of 0.0745, followed by the effectiveness of mulch film, which was 0.0715. The results of the grey correlation analysis model showed that willingness to use biodegradable mulch film had the highest correlation of 0.8960, followed by educational level of the laborers, which was 0.8824. We found that residual film being harmful to the environment, effectiveness of mulch film, willingness to use biodegradable mulch film, and educational level of the laborers were the major factors influencing the residual mulch film pollution knowledge of households. Based on this finding, the government should increase subsidies for promoting biodegradable mulch film and publicize the hazards of residual films using diversified means in multiple channels.
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Chang, Ho, Yun Min Yeh, Ching Song Jwo y Sih Li Chen. "Measurement of Electromagnetic Shielding Effectiveness of the Composite Carbon Fibers/Nickel Thin Film". Key Engineering Materials 437 (mayo de 2010): 580–83. http://dx.doi.org/10.4028/www.scientific.net/kem.437.580.
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This paper presents the development of a conductive composite film and the measurement of electromagnetic (EM) shielding effectiveness (SE) of the prepared film. A coaxial transmission-line technique based on ASTM D4935-99 Standard was used to measure the electromagnetic shielding effectiveness. A nickel nanofluid with an average particle size of 50 nm was prepared with a self-developed nanofluid synthesis system. By using a polymer blending method, carbon fiber and carbon fiber/nickel nanoparticles were blended with waterborne polyurethane (WPU) to prepare conductive composite films of 0.25 mm thick. Experimental results have shown that the electromagnetic shielding effectiveness value of the prepared conductive composite material can reach 26 dB within the range of 50 MHz ~ 1.5GHz.
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Gau, C. y W. B. Hwang. "Effect of Weak Swirling Flow on Film Cooling Performance". Journal of Turbomachinery 112, n.º 4 (1 de octubre de 1990): 786–91. http://dx.doi.org/10.1115/1.2927722.
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Experiments have been performed in a large circular pipe to study and obtain the film cooling effectivenesses with the presence of weak swirling flow in the mainstream. The swirling flow is generated by a flat vane swirler situated upstream. Cooling film is injected from an annular slot formed by the pipe wall and the circular cover plate. The radial temperature distribution measurements at several axial locations were used to infer the rate of mixing of film jet with swirling flow. The swirl number, which increases with turbulence intensity and swirl velocity in the mainstream, can significantly increase the mixing rate of film jet with swirl flow and decrease the film cooling effectiveness. During the course of the experiments, the blowing ratio ranged from 0.5 to 1.75 and the swirl number ranged from 0 to 0.6. Correlation equations for the film cooling effectiveness, which account for the effect of swirling flow, are obtained.
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Heidmann, James D., Barbara L. Lucci y Eli Reshotko. "An Experimental Study of the Effect of Wake Passing on Turbine Blade Film Cooling". Journal of Turbomachinery 123, n.º 2 (1 de febrero de 1997): 214–21. http://dx.doi.org/10.1115/1.1354621.
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The effect of wake passing on the showerhead film cooling performance of a turbine blade has been investigated experimentally. The experiments were performed in an annular turbine cascade with an upstream rotating row of cylindrical rods. Nickel thin-film gauges were used to determine local film effectiveness and Nusselt number values for various injectants, blowing ratios, and Strouhal numbers. Results indicated a reduction in film effectiveness with increasing Strouhal number, as well as the expected increase in film effectiveness with blowing ratio. An equation was developed to correlate the span-average film effectiveness data. The primary effect of wake unsteadiness was found to be correlated by a streamwise-constant decrement of 0.094St. Steady computations were found to be in excellent agreement with experimental Nusselt numbers, but to overpredict experimental film effectiveness values. This is likely due to the inability to match actual hole exit velocity profiles and the absence of a credible turbulence model for film cooling.
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Jiang, H. Wanda y J. C. Han. "Effect of Film Hole Row Location on Film Effectiveness on a Gas Turbine Blade". Journal of Heat Transfer 118, n.º 2 (1 de mayo de 1996): 327–33. http://dx.doi.org/10.1115/1.2825848.
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Experiments were performed to study the effect of film hole row location on local film effectiveness distribution of a turbine blade model with air or CO2 film injection. Tests were performed on a five-blade linear cascade at the chord Reynolds number of 3.0 × 105 at the cascade inlet. A combination of turbulence grid and unsteady wake was used to create a higher free-stream turbulence level. The test blade had three rows of film holes in the leading edge region and two rows each on the pressure and suction surfaces. Film hole row locations were set by leaving the film holes at that row location open and covering the remaining rows. In addition, the additive nature of film cooling on the turbine blade model was examined by comparing the measured film effectiveness with the predicted effectiveness from the superposition method. Results show that injection from a different film hole row location provides a different effectiveness distribution on pressure and suction surfaces depending on local mainstream velocity and blade curvature. In most cases, the superposition method holds downstream of the last film hole row.
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KITAMURA, Tsuyoshi, Ken-ichiro TAKEISHI, Masaaki MATSUURA y Ryoma NOGAMI. "Film Cooling Effectiveness on Transonic Turbine airfoils". Proceedings of the Thermal Engineering Conference 2004 (2004): 281–82. http://dx.doi.org/10.1299/jsmeted.2004.281.
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Jindal, Prakhar, Shubham Agarwal y R. P. Sharma. "A Brief Review on Numerical Studies on Film Cooling Effectiveness". Applied Mechanics and Materials 852 (septiembre de 2016): 699–706. http://dx.doi.org/10.4028/www.scientific.net/amm.852.699.
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Film cooling is employed for effective cooling in nozzles and combustion chambers using a spray of coolant fluid in the mainstream flow to cool the body. Experimental analysis was performed elaborately in the past years to get an exact analysis of film cooling effectiveness with different parameters. This approach was however discouraged due to its high cost and time consumption. Recently, researchers switched to the use of numerical platforms for investigation of complex film cooling systems. The paper discusses in detail the numerical analysis of the film cooling systems done so far and the numerical models employed for such a complex analysis along with the advantages and trade-offs of such a numerical approach. This study was carried out to extend database knowledge about the numerical film cooling for its various applications. Therefore, an appropriate cooling technique should be designed to protect these parts. Film cooling is one of the most effective external cooling methods. Various numerical film cooling techniques presented in the literature have been investigated. Moreover, challenges and future directions of numerical film cooling techniques have been reviewed and presented in this paper. The aim of this review is to summarize recent development in research on film cooling techniques and attempt to identify some challenging issues that need to be solved for future research.
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Butt, Muhammad A. "Thin-Film Coating Methods: A Successful Marriage of High-Quality and Cost-Effectiveness—A Brief Exploration". Coatings 12, n.º 8 (4 de agosto de 2022): 1115. http://dx.doi.org/10.3390/coatings12081115.
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In this review, several cost-effective thin-film coating methods, which include dip-coating, spin-coating, spray-coating, blade-coating, and roll-coating, are presented. Each method has its own set of advantages and disadvantages depending on the proposed application. Not all of them are appropriate for large-scale production due to their certain limitations. That is why the coating method should be selected based on the type and size of the substrate, including the thickness and surface roughness of the required thin films. The sol–gel method offers several benefits, such as simplicity in fabrication, excellent film uniformity, the capacity to cover surfaces of any size and over vast areas, and a low processing temperature. Nevertheless, these coating methods are somewhat economical and well managed in low-budget laboratories. Moreover, these methods offer thin films with good homogeneity and low-surface roughness. Furthermore, some other thin-film deposition methods, for instance, physical vapor deposition (PVD) and chemical vapor deposition (CVD), are also discussed. Since CVD is not restricted to line-of-sight deposition, a characteristic shared by sputtering, evaporation, and other PVD methods, many manufacturing methods favor it. However, these techniques require sophisticated equipment and cleanroom facilities. We aim to provide the pros and cons of thin-film coating methods and let the readers decide the suitable coating technique for their specific application.
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Narang, Upvan, Lawrence Mainwaring, Gina Spath y Joe Barefoot. "In-vitro Analysis for Microbial Barrier Properties of 2-Octyl Cyanoacrylate-Derived Wound Treatment Films". Journal of Cutaneous Medicine and Surgery 7, n.º 1 (enero de 2003): 13–19. http://dx.doi.org/10.1177/120347540300700103.
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Background: In recent years, 2-octyl cyanoacrylate monomer has been formulated for various wound care products that have been approved by the Food and Drug Administration (FDA). Purpose: To evaluate the in vitro effectiveness of 2-octyl cyanoacrylate formulation-based films as barriers to various pathogens, including bacteria, fungi, and yeast. Methods: The barrier properties of the cyanoacrylate films prepared by the following two methods were tested: (1) prepolymerized film and (2) in situ polymerized film. The upper surface of films was inoculated such that the microorganisms would have to penetrate the film to colonize the media beneath. Nine different organisms were used. Plates were observed for growth at two, four, and seven days after inoculation. Results: No growth was observed in any test, with the exception of prepolymerized film challenged with Pseudomonas aeruginosa. The pattern of growth observed suggests that the bacteria colonized the medium by traveling around and not through the film. Conclusions: 2-Octyl cyanoacrylate-based films are excellent microbial barriers.
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Abuaf, N., R. Bunker y C. P. Lee. "Heat Transfer and Film Cooling Effectiveness in a Linear Airfoil Cascade". Journal of Turbomachinery 119, n.º 2 (1 de abril de 1997): 302–9. http://dx.doi.org/10.1115/1.2841113.
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A warm (315°C) wind tunnel test facility equipped with a linear cascade of film cooled vane airfoils was used in the simultaneous determination of the local gas side heat transfer coefficients and the adiabatic film cooling effectiveness. The test rig can be operated in either a steady-state or a transient mode. The steady-state operation provides adiabatic film cooling effectiveness values while the transient mode generates data for the determination of the local heat transfer coefficients from the temperature–time variations and of the film effectiveness from the steady wall temperatures within the same aerothermal environment. The linear cascade consists of five airfoils. The 14 percent cascade inlet free-stream turbulence intensity is generated by a perforated plate, positioned upstream of the airfoil leading edge. For the first transient tests, five cylinders having roughly the same blockage as the initial 20 percent axial chord of the airfoils were used. The cylinder stagnation point heat transfer coefficients compare well with values calculated from correlations. Static pressure distributions measured over an instrumented airfoil agree with inviscid predictions. Heat transfer coefficients and adiabatic film cooling effectiveness results were obtained with a smooth airfoil having three separate film injection locations, two along the suction side, and the third one covering the leading edge showerhead region. Near the film injection locations, the heat transfer coefficients increase with the blowing film. At the termination of the film cooled airfoil tests, the film holes were plugged and heat transfer tests were conducted with non-film cooled airfoils. These results agree with boundary layer code predictions.
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NEETOO, HUDAA, MU YE y HAIQIANG CHEN. "Effectiveness and Stability of Plastic Films Coated with Nisin for Inhibition of Listeria monocytogenes". Journal of Food Protection 70, n.º 5 (1 de mayo de 2007): 1267–71. http://dx.doi.org/10.4315/0362-028x-70.5.1267.
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Plastic films were coated with a cellulose-based carrier solution containing nisin, a natural antimicrobial peptide with the potential to inhibit growth of food spoilage and pathogenic microorganisms such as Listeria monocytogenes. Five commercial plastic films with different chemical compositions and surface properties were compared in this study: low-density polyethylene, ethylene–vinyl acetate copolymer, and three types of ethylene–methacrylic acid copolymers: Surlyn 1601, Nucrel 0403, and Nucrel 0903. The films were coated with nisin at a concentration of 1,000 IU/cm2. Nisin-coated films were stored at room temperature (21°C) and at 4°C and analyzed weekly for 12 weeks. Antimicrobial activity of the different nisin-coated films against a nisin indicator strain, Lactococcus lactis subsp. cremoris ATCC 14365, and against L. monocytogenes ATCC 19115 was assessed using an inhibition zone assay. Nisin incorporated into the films was recovered by a boiling and extraction procedure, and its activity was quantified using an agar well diffusion assay. Film type did not have any significant effect on the antimicrobial activity of the nisin-coated films (P < 0.05); all five film types had comparable inhibition zones on both assays. The films maintained stable activity for the duration of the study, both at room temperature and refrigeration. The results of this study demonstrate that commercially available packaging films can be coated with nisin and the resulting antimicrobial films can be conveniently stored at room temperature with no adverse effect on nisin activity.
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Prapamonthon, Prasert, Hua Zhao Xu y Jian Hua Wang. "Film Cooling Performances at Different Turbulence Intensities Using Conjugate Heat Transfer Analysis". Applied Mechanics and Materials 872 (octubre de 2017): 271–78. http://dx.doi.org/10.4028/www.scientific.net/amm.872.271.
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This study presents a numerical investigation of cooling performances of a modified vane of the film-cooled vane reported by Timko (NASA CR-168289) at different mainstream turbulence intensities (Tus). A 3D conjugate heat transfer (CHT) analysis with SST k-ω turbulence model in FLUENT V.15 is used. Three different mechanisms in CHT analysis, i.e. fluid flow, heat convection between solid surfaces and flowing fluid in an external mainstream and internal cooling passages, and heat conduction within the vane structure, are simultaneously considered. Numerical results are conducted in terms of overall cooling effectiveness at Tu=3.3, 10, and 20%. Comparison between overall cooling effectiveness and film effectiveness under adiabatic assumption is discussed at the three Tus, also. The findings of this research indicate the following phenomena: 1) overall cooling effectiveness decreases with Tu, and this effect on the pressure side (PS) is stronger than that on the suction side (SS) in general. 2) By comparison with adiabatic film effectiveness, the level of overall cooling effectiveness in most regions is higher and more uniform than that of adiabatic film effectiveness for all three Tus. 3) In the leading edge (LE), when Tu increases, near the exits of film holes overall cooling effectiveness deteriorates, but adiabatic film effectiveness improves. Furthermore, a large area with relatively low overall cooling effectiveness is able to move with Tu in the LE region.
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Zhang, Jian, Qun Zheng, Guoqiang Yue y Yuting Jiang. "Investigation on flow field and heat transfer characteristics of film cooling with different swirling directions for coolant flow". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 235, n.º 6 (2 de marzo de 2021): 1394–405. http://dx.doi.org/10.1177/0957650921997633.
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In this paper, a hexagonal prism inlet chamber is used to form a swirling flow for the film cooling, and three kinds of compound angle of film hole ( γ = 10°, 20°, 30°) with clockwise swirling or counterclockwise swirling are used for numerical simulation studies. The influence of different compound angles of film hole and the swirling directions for the film cooling effectiveness are obtained. The results show that the film cooling effectiveness and spanwise cooling coverage range of the clockwise swirling or counterclockwise swirling flow both are low when the compound angle of film hole is 10°. With the increasing compound angle of film hole, the kidney shaped vortex of film hole exit gradually weakens until it disappears, which reduces the entrainment effect by the coolant jet. So that the spanwise coverage range of two swirling modes is obviously improved. When the compound angle of film hole is 30° compared to 10°, the average spanwise film cooling effectiveness of clockwise swirling and counterclockwise swirling are increased by about 133.75 and 212.6%, respectively. The average spanwise film cooling effectiveness on the downstream of film hole for counterclockwise swirling is increased by about 140% compared with clockwise swirling.
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Guang-Chao, Li, Zhou Shuai, Zhang Wei, Kou Zhi-hai y Xu Rang-shu. "Investigation of Film Cooling Effectiveness of Dual-fanned Hole with Various Exit Widths". International Journal of Turbo & Jet-Engines 37, n.º 4 (18 de noviembre de 2020): 353–61. http://dx.doi.org/10.1515/tjj-2017-0030.
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AbstractFilm cooling effectiveness downstream of one row of holes of 30 degree inclination angle was measured by using a steady-state thermochromic liquid crystal technique at blowing ratios of 0.5, 1.0, 1.5 and 2.0, respectively. Three kinds of dual-fanned holes which have the same expanded entrance width and the different expanded exit widths were tested. The configuration of only expanded entrance, but cylindrical exit hole, was tested to examine the effect of the expanded entrance on film cooling performance. The numerical simulation for the three expanded exit configurations was carried out explaining the mechanism of film cooling by the flow and thermal field. The only expanded entrance has a weak influence on film cooling effectiveness. The ${W_o} = 1.5d$ configuration provides a lift of film cooling effectiveness compared to ${W_o} = 1.0d$ configuration. Film cooling effectiveness is not sensitive to the change of configurations from ${W_o} = 1.5d$ to ${W_o} = 2.0d$. Film cooling effectiveness for ${W_o} = 2.5d$ performs significantly better than the other configurations due to the presence of the anti-vortex. The effect of dual-fanned exit width on film cooling effectiveness is strongly dependent on the blowing ratios.
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Kim, S. M., K. D. Lee y K. Y. Kim. "NUMERICAL STUDY ON FILM-COOLING EFFECTIVENESS FOR VARIOUS FILM-COOLING HOLE SCHEMES". Journal of computational fluids engineering 16, n.º 4 (31 de diciembre de 2011): 92–99. http://dx.doi.org/10.6112/kscfe.2011.16.4.092.
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Ligrani, P. M., R. Gong, J. M. Cuthrell y J. S. Lee. "Bulk flow pulsations and film cooling—II. Flow structure and film effectiveness". International Journal of Heat and Mass Transfer 39, n.º 11 (julio de 1996): 2283–92. http://dx.doi.org/10.1016/0017-9310(95)00287-1.
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CHENG, Fengna, Haiping CHANG, Jingyang ZHANG y Xingjiang TIAN. "Effect of film-hole configuration on film-cooling effectiveness of squealer tips". Journal of Thermal Science and Technology 12, n.º 1 (2017): JTST0004. http://dx.doi.org/10.1299/jtst.2017jtst0004.
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Bakker, Gerben. "Selling French Films on Foreign Markets: The International Strategy of a Medium-Sized Film Company". Enterprise & Society 5, n.º 1 (marzo de 2004): 45–76. http://dx.doi.org/10.1017/s1467222700013185.
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Foreign markets largely shaped the business strategy of Les Films Albatros, a medium-sized, internationally networked specialty producer of films in interwar France. Depending more on foreign revenues than did the Hollywood studios, Albatros also realized higher gross returns. Because films were capital goods providing a perishable product (seats at a specific time), their price depended on both expected performance and the threshold ticket-selling capacity necessary to recoup cinema fixed costs; some films could not be sold at any price. Given the small potential market for its films, Albatros had to find an intricate balance between producing at low cost and delivering films with at least threshold ticket-selling capacity. It did so by differentiating its films, entering film distribution in France, coproducing internationally, and cooperating with Pathé and Gaumont, the two largest French film companies. While its larger European rivals were obsessed with operational effectiveness vis-à-vis Hollywood, Albatros, by adopting a distinct strategic position, hardly had to pay attention to operational effectiveness at all. It was making a differentiated product for needs unserved by Hollywood.
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Benzaoui, Karim, Achour Ales, Ahmed Mekki, Abdelhalim Zaoui, Boudjemaa Bouaouina, Ajay Singh, Oussama Mehelli y Mehdi Derradji. "Electromagnetic interference shielding effectiveness of polypyrrole-silver nanocomposite films on silane-modified flexible sheet". High Performance Polymers 34, n.º 3 (27 de diciembre de 2021): 310–20. http://dx.doi.org/10.1177/09540083211064535.
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The conventional electromagnetic interference (EMI) shielding materials are being gradually replaced by a new generation of supported conducting polymer composites (CPC) films due to their many advantages. This work presents a contribution on the effects of silane surface–modified flexible polypyrrole-silver nanocomposite films on the electromagnetic interference shielding effectiveness (EMI-SE). Thus, the UV-polymerization was used to in-situ deposit the PPy-Ag on the biaxial oriented polyethylene terephthalate (BOPET) flexible substrates whose surfaces were treated by 3-aminopropyltrimethoxysilane (APTMS). X-ray Photoelectron Spectroscopy (XPS) analyzes confirmed the APTMS grafting procedure. Structural, morphological, thermal, and electrical characteristics of the prepared films were correlated to the effect of substrate surface treatment. Thereafter, EMI-SE measurements of the elaborated films were carried out as per ASTM D4935 standard for a wide frequency band extending from 50 MHz to 18 GHz. The obtained results confirmed that the APTMS-treated BOPET film exhibit higher EMI shielding performance and better electrical characteristics compared to the untreated film. In fact, a 32% enhancement of EMI-SE was noted for the treated films compared to the untreated ones. Overall, these results put forward the role played by the surface treatment in strengthening the position of flexible PPy-Ag supported films as high-performance materials in electronic devices and electromagnetic interference shielding applications.
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Wambersie, Augustin, Holt Wong, Peter Ireland y Ignacio Mayo. "Experiments of Transpiration Cooling Inspired Panel Cooling on a Turbine Blade Yielding Film Effectiveness Levels over 95%". International Journal of Turbomachinery, Propulsion and Power 6, n.º 2 (4 de junio de 2021): 16. http://dx.doi.org/10.3390/ijtpp6020016.
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Panels were tested at different locations around the turbine blade, on both suction and pressure surfaces. Three different surface porosities were also tested. Results demonstrated that the approach can be very successful with high levels of film cooling effectiveness, exceeding 95%, achieved using low coolant mass flow rates. Increasing the surface porosity also proved to be an important parameter in the panel’s performance. Additionally, staggering the film holes lead to significant positive interactions between individual films, resulting in much improved panel performance.
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Takeishi, K., S. Aoki, T. Sato y K. Tsukagoshi. "Film Cooling on a Gas Turbine Rotor Blade". Journal of Turbomachinery 114, n.º 4 (1 de octubre de 1992): 828–34. http://dx.doi.org/10.1115/1.2928036.
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The film cooling effectiveness on a low-speed stationary cascade and the rotating blade has been measured by using a heat-mass transfer analogy. The film cooling effectiveness on the suction surface of the rotating blade fits well with that on the stationary blade, but a low level of effectiveness appears on the pressure surface of the rotating blade. In this paper, typical film cooling data will be presented and film cooling on a rotating blade is discussed.
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Dai, Ping y Nai Yun Yu. "Numerical Study on the Influence of Hole Shape on Film Cooling Effectiveness". Advanced Materials Research 716 (julio de 2013): 699–704. http://dx.doi.org/10.4028/www.scientific.net/amr.716.699.
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Effects of hole shapes on film cooling effectiveness downstream of one row of film holes at the blade were investigated using a three-dimensional finite volume method and multi-block technique. The present study also received velocity vectors about different hole shapes. The hole geometries studied include standard cylindrical hole and forward diffused shaped hole and converging slot-hole. It was found that the film cooling effectiveness of cylindrical holes obviously declined along with increasing the blowing ratio. Results of the shaped holes configuration present a marked improvement, with a high effectiveness at the lateral area between adjacent holes and effectiveness of the converging slot-hole was superior to other holes in various blowing ratios. The film cooling effectiveness realized by the slot-holes compared to the cylindrical and forward diffused shaped holes was more excelled at downstream of the intersection of the two slot-holes. The converging slot-hole and forward diffused shaped hole can reduce the vortex intensity, and then enhance the film cooling effectiveness.
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Du, H., J. C. Han y S. V. Ekkad. "Effect of Unsteady Wake on Detailed Heat Transfer Coefficient and Film Effectiveness Distributions for a Gas Turbine Blade". Journal of Turbomachinery 120, n.º 4 (1 de octubre de 1998): 808–17. http://dx.doi.org/10.1115/1.2841793.
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Unsteady wake effects on detailed heat transfer coefficient and film cooling effectiveness distributions from a gas turbine blade with film cooling are obtained using a transient liquid crystal technique. Tests were performed on a five-blade linear cascade at a axial chord Reynolds number of 5.3 × 105 at cascade exit. Upstream unsteady wakes are simulated using a spoke-wheel type wake generator. The test blade has three rows of film holes on the leading edge and two rows each on the pressure and suction surfaces. Air and CO2 were used as coolants to simulate different coolant-to-mainstream density ratio effect. Coolant blowing ratio for air injection is varied from 0.8 to 1.2 and is varied from 0.4 to 1.2 for CO2. Results show that Nusselt numbers for a film-cooled blade are much higher compared to a blade without film injection. Particularly, film injection causes earlier boundary layer transition on the suction surface. Unsteady wakes slightly enhance Nusselt numbers but significantly reduce film cooling effectiveness on a film-cooled blade compared with a film-cooled blade without wakes. Nusselt numbers increase slightly but film cooling effectiveness increase significantly with an increase in blowing ratio for CO2 injection. Higher density coolant (CO2) provides higher effectiveness at higher blowing ratios (M = 1.2) whereas lower density coolant (Air) provides higher effectiveness at lower blowing ratios (M = 0.8).
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Cheng-xiong, Pan, Zhang Jing-zhou y Huang Ke-nan. "Numerical Investigation of Partial Blockage Effect on Film Cooling Effectiveness". Mathematical Problems in Engineering 2014 (2014): 1–13. http://dx.doi.org/10.1155/2014/167193.
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Three-dimensional numerical calculation was performed to investigate the effects of partial blockage inside cylindrical film holes on the film cooling effectiveness over a flat plate. Five blockage ratios ranged from 0.1 to 0.5 and a series of blockage positions were considered under the blowing ratios of 0.3–1.5. It is found that the blockage position has a significant influence on mainstream-coolant jet interaction. The partial blockage located at the leading edge of coolant-hole exit mitigates the primary vortices due to mainstream-coolant jet interaction. The coolant jet penetration along vertical direction is suppressed and the peak velocity along streamwise direction is augmented under the action of partial blockage at the upstream side of film holes, providing an increment of film cooling effectiveness, especially under high blowing ratio. While the partial blockages located at the trailing or lateral edges of coolant-hole exit weaken the film cooling effectiveness. In relation to the partial blockage located in the vicinity of coolant-hole exit, the partial blockage located in the vicinity of coolant-hole inlet or middle has less impaction on the film cooling effectiveness under low blowing ratio.
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Rajendran, Diana y Martin Andrew. "Using Film to Elucidate Leadership Effectiveness Models: Reflection on Authentic Learning Experiences". Journal of University Teaching and Learning Practice 11, n.º 1 (1 de enero de 2014): 92–108. http://dx.doi.org/10.53761/1.11.1.8.
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Abstract This paper examines how students in a third year management unit at a university of technology in Australia evaluate the usefulness of film as a tool for developing a deeper understanding of the theoretical leadership effectiveness model developed by Robbins (1997). The study reviews the range of studies describing the use of films in teaching leadership, playing into a perceivable gap in empirical studies demonstrating how students engage in applying the concepts of leadership. This study specifically considers whether films are effective interventions for achieving engagement in an assessment task aimed at identifying applications of theory to cases of leadership in action. As part of an action research cycle, thirty students (30) participated in three different focus groups. Transcriptions subsequently produced thick descriptions on which thematic analysis was conducted to extract key themes (Ryan & Bernard, 2003). The results suggest that films can communicate, embody and articulate the effectiveness of behaviours of leadership Robbins conveyed. The results also indicate that students value films as a medium for contextualising actions that demonstrate different leadership styles. It is perceived as a way of catering to diverse learning styles and as a way of building autonomy. We conclude that while films can be motivating and lend authenticity to assessment tasks, students need clear direction in making links between theoretical concepts and narrative filmic constructions of leaders and leadership behaviour. This leads to the next stage of our action research cycle.
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Zhang, Bo, Quan Hong, Yun Bai, Jiquan Li y Honghu Ji. "Numerical investigation of heat transfer in film layer under supersonic condition of convergent-divergent transition". Thermal Science 24, n.º 3 Part B (2020): 2279–88. http://dx.doi.org/10.2298/tsci190401310z.
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The distribution of film cooling effectiveness in supersonic mainstream of circle-rectangular Convergent-Divergent transition has been numerically investigated under different pressure ratios. The shock wave exerted superior influence on film cooling. In supersonic main flow, extra compression waves formed in upstream of the film holes, resulted by the obstruction of the multiple cooling jets. This exerted extra pressure to the boundary-layer, induced adverse pressure gradient, and led to weakening of the film flow attachment ability and decreasing of local cooling effectiveness. Bow oblique shock wave occurred in front of holes, the two oblique bow shaped low pressure zones formed on both sides of the hole, and low cooling effectiveness zones appeared accordingly. The inefficient region at the leading edge of the hole destroyed the film developing between holes, decreased the cooling effectiveness accumulation in the rear part. The decrease of hole incline angle caused an increase of cooling effectiveness, which reduced reverse velocity gradient caused by shock wave in the boundary-layer and improved film attachment. The influence of main flow pressure ratio to film cooling was also investigated, and found with increasing of the ratio, the influence will became even significant.
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Zhang, Luzeng J. y Ruchira Sharma Jaiswal. "Turbine Nozzle Endwall Film Cooling Study Using Pressure-Sensitive Paint". Journal of Turbomachinery 123, n.º 4 (1 de febrero de 2001): 730–38. http://dx.doi.org/10.1115/1.1400113.
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Endwall surface film cooling effectiveness was measured on a turbine vane endwall surface using the pressure-sensitive paint (PSP) technique. A double staggered row of holes and a single row of discrete slots were used to supply film cooling in front of the nozzle cascade leading edges. Nitrogen gas was used to simulate film cooling flow as well as a tracer gas to indicate oxygen concentration such that film effectiveness by the mass transfer analogy could be obtained. Cooling mass flow was controlled to be 0.5 to 3.0 percent of the mainstream mass flow. The free-stream Reynolds number was about 283,000 and Mach number was about 0.11. The free-stream turbulence intensity was kept at 6.0 percent for all the tests, measured by a thermal anemometer. The PSP was calibrated at various temperatures and pressures to obtain better accuracy before being applied to the endwall surface. Film effectiveness distributions were measured on a flat endwall surface for five different mass flow rates. The film effectiveness increased nonlinearly with mass flow rate, indicating a strong interference between the cooling jets and the endwall secondary flows. At lower mass flow ratios, the secondary flow dominated the near wall flow field, resulting in a low film effectiveness. At higher mass flow ratios, the cooling jet momentum dominated the near wall flow field, resulting in a higher film effectiveness. The comparison between hole injection and slot injection was also made.
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Hale, C. A., M. W. Plesniak y S. Ramadhyani. "Film Cooling Effectiveness for Short Film Cooling Holes Fed by a Narrow Plenum". Journal of Turbomachinery 122, n.º 3 (1 de febrero de 1999): 553–57. http://dx.doi.org/10.1115/1.1303705.
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The adiabatic, steady-state liquid crystal technique was used to measure surface adiabatic film cooling effectiveness values in the near-hole region X/D<10. A parametric study was conducted for a single row of short holes L/D⩽3 fed by a narrow plenum H/D=1. Film cooling effectiveness values are presented and compared for various L/D ratios (0.66 to 3.0), three different blowing ratios (0.5, 1.0, and 1.5), two different plenum feed configurations (co-flow and counterflow), and two different injection angles (35 and 90 deg). Injection hole geometry and plenum feed direction were found to affect short hole film cooling performance significantly. Under certain conditions, similar or improved coverage was achieved with 90 deg holes compared with 35 deg holes. This result has important implications for manufacturing of thin-walled film-cooled blades or vanes. [S0889-504X(00)00603-6]