Journal articles on the topic 'Labyrinths Models'
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Otsuka, K., M. Suzuki, M. Negishi, S. Shimizu, T. Inagaki, U. Konomi, T. Kondo, and Y. Ogawa. "Efficacy of physical therapy for intractable cupulolithiasis in an experimental model." Journal of Laryngology & Otology 127, no. 5 (April 10, 2013): 463–67. http://dx.doi.org/10.1017/s0022215113000698.
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AbstractObjective:To investigate what kinds of stimuli are effective in detaching otoconia from the cupula in three experimental models of cupulolithiasis.Methods:Three experimental models of cupulolithiasis were prepared using bullfrog labyrinths. Three kinds of stimuli were applied to the experimental models. In experiment one (gravity), the labyrinth preparation was placed so that the cupula-to-crista axis was in the horizontal plane with the canal side in the downward position. In experiment two (sinusoidal oscillation), the labyrinth preparation was placed 3 cm from the rotational centre of a turntable, which was sinusoidally rotated with a rotational cycle of 1 Hz and a rotational angle of 30°. In experiment three (vibration), mechanical vibration was applied to the surface of the bony capsule around the labyrinth using a surgical drill.Results:In experiments one, two and three, the otoconial mass was respectively detached in 2 out of 10 labyrinth preparations, none of the labyrinth preparations, and all of the labyrinth preparations.Conclusion:Vibration was the most effective stimulus for detaching the otoconia from the cupula in these experimental models of cupulolithiasis.
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Paranina, Galina N. "Northern Labyrinths – Gnomons and models of geographical Space." Procedia - Social and Behavioral Sciences 19 (2011): 593–601. http://dx.doi.org/10.1016/j.sbspro.2011.05.174.
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Shtengel, Kirill, and L. P. Chayes. "Vertex models and random labyrinths: phase diagrams for ice-type vertex models." Journal of Statistical Mechanics: Theory and Experiment 2005, no. 07 (July 27, 2005): P07006. http://dx.doi.org/10.1088/1742-5468/2005/07/p07006.
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Moore, J. Jeffrey. "Three-Dimensional CFD Rotordynamic Analysis of Gas Labyrinth Seals." Journal of Vibration and Acoustics 125, no. 4 (October 1, 2003): 427–33. http://dx.doi.org/10.1115/1.1615248.
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Labyrinth seals are utilized inside turbomachinery to provide noncontacting control of internal leakage. These seals can also play an important role in determining the rotordynamic stability of the machine. Traditional labyrinth seal models are based on bulk-flow assumptions where the fluid is assumed to behave as a rigid body affected by shear stress at the interfaces. To model the labyrinth seal cavity, a single, driven vortex is assumed and relationships for the shear stress and divergence angle of the through flow jet are developed. These models, while efficient to compute, typically show poor prediction for seals with small clearances, high running speed, and high pressure.* In an effort to improve the prediction of these components, this work utilizes three-dimensional computational fluid dynamics (CFD) to model the labyrinth seal flow path by solving the Reynolds Averaged Navier Stokes equations. Unlike bulk-flow techniques, CFD makes no fundamental assumptions on geometry, shear stress at the walls, as well as internal flow structure. The method allows modeling of any arbitrarily shaped domain including stepped and interlocking labyrinths with straight or angled teeth. When only leakage prediction is required, an axisymmetric model is created. To calculate rotordynamic forces, a full 3D, eccentric model is solved. The results demonstrate improved leakage and rotordynamic prediction over bulk-flow approaches compared to experimental measurements.
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Melo, Verônica G. M. L., Ana C. S. Araújo, Antonio P. Camargo, Leonardo L. Melo, José A. Frizzone, and Wagner W. A. Bombardelli. "Head Loss in Thin-Walled Drip Tapes with Continuous Labyrinth." Scientific World Journal 2019 (December 10, 2019): 1–11. http://dx.doi.org/10.1155/2019/8640893.
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Thin-walled drip tapes with continuous labyrinth have been used for irrigation of vegetables and other short-cycle crops, especially due to their low cost. The continuous labyrinths welded into the pipe inner wall affect the head loss along such emitting pipes. In addition, the flow cross section of thin-walled pipes may change due to the effects of the operating pressure, which also has consequences for the head loss. The objective of this work was to investigate experimentally the friction factor and the head loss on thin-walled drip tapes with continuous labyrinths operated under various pressures. Two models of commercial thin-walled drip tapes with continuous labyrinths were evaluated. Nonperforated samples were used to determine the head-loss equations. The equations were adjusted as a function of flow rate and pressure head at the pipe inlet. Alternatively, the diameter in the Darcy–Weisbach equation was adjusted as a function of the pressure head by a power-law model. The possibility of using a mean diameter in the Darcy–Weisbach equation was also analyzed. Experimental investigation indicated that the friction factor in the Darcy–Weisbach equation can be accurately described using a power-law model, like the Blasius equation, but characterized by a coefficient a=0.3442 for the Turbo Tape and a=0.3225 for the Silver Tape. The obtained values of a are larger than those generally used and available in the literature. The influence of the operating pressure on the pipe diameter can be neglected for the purpose of calculating the head loss. The two approaches, considering the variation of the diameter with the pressure head and considering an optimum average diameter for the calculation of head loss by the Darcy–Weisbach equation, produce similar results, allowing accurate prediction of head loss. Evaluating the proposed mathematical models, 95% of predictions presented relative errors of head loss smaller than 5%. For the Turbo Tape, the optimum diameter for the purpose of calculating the head loss is 16.01 mm, which is very close to the value indicated by its manufacturer (15.9 mm). For the Silver Drip, the optimum diameter is 15.71 mm, while the manufacturer gives a value of 16.22 mm, which produces considerable error in the calculation of head loss.
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Rhode, D. L., J. A. Demko, U. K. Traegner, G. L. Morrison, and S. R. Sobolik. "Prediction of Incompressible Flow in Labyrinth Seals." Journal of Fluids Engineering 108, no. 1 (March 1, 1986): 19–25. http://dx.doi.org/10.1115/1.3242535.
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A new approach was developed and tested for alleviating the substantial convergence difficulty which results from implementation of the QUICK differencing scheme into a TEACH-type computer code. It is relatively simple, and the resulting CPU time and number of numerical iterations required to obtain a solution compare favorably with a previously recommended method. This approach has been employed in developing a computer code for calculating the pressure drop for a specified incompressible flow leakage rate in a labyrinth seal. The numerical model is widely applicable and does not require an estimate of the kinetic energy carry-over coefficient for example, whose value is often uncertain. Good agreement with measurements is demonstrated for both straight-through and stepped labyrinths. These new detailed results are examined, and several suggestions are offered for the advancement of simple analytical leakage as well as rotordynamic stability models.
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Garrison, Thomas G., Dustin Richmond, Perry Naughton, Eric Lo, Sabrina Trinh, Zachary Barnes, Albert Lin, Curt Schurgers, Ryan Kastner, and Sarah E. Newman. "Tunnel Vision." Advances in Archaeological Practice 4, no. 2 (May 2016): 192–204. http://dx.doi.org/10.7183/2326-3768.4.2.192.
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AbstractArchaeological tunneling is a standard excavation strategy in Mesoamerica. The ancient Maya built new structures atop older ones that were no longer deemed usable, whether for logistical or ideological reasons. This means that as archaeologists excavate horizontal tunnels into ancient Maya structures, they are essentially moving back in time. As earlier constructions are encountered, these tunnels may deviate in many directions in order to document architectural remains. The resultant excavations often become intricate labyrinths, extending dozens of meters. Traditional forms of archaeological documentation, such as photographs, plan views, and profile drawings, are limited in their ability to convey the complexity of tunnel excavations. Terrestrial Lidar (light detection and ranging) instruments are able to generate precise 3D models of tunnel excavations. This article presents the results of a model created with a Faro™ Focus 3D 120 Scanner of tunneling excavations at the site of El Zotz, Guatemala. The lidar data document the excavations inside a large mortuary pyramid, including intricately decorated architecture from an Early Classic (A.D. 300–600) platform buried within the present form of the structure. Increased collaboration between archaeologists and scholars with technical expertise maximizes the effectiveness of 3D models, as does presenting digital results in tandem with traditional forms of documentation.
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Kalish, John M., Reidar Nydal, Kjell H. Nedreaas, George S. Burr, and Gro L. Eine. "A Time History of Pre- and Post-Bomb Radiocarbon in the Barents Sea Derived from Arcto-Norwegian Cod Otoliths." Radiocarbon 43, no. 2B (2001): 843–55. http://dx.doi.org/10.1017/s0033822200041515.
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Radiocarbon measured in seawater dissolved inorganic carbon (DIC) can be used to investigate ocean circulation, atmosphere/ocean carbon flux, and provide powerful constraints for the fine-tuning of general circulation models (GCMs). Time series of 14C in seawater are derived most frequently from annual bands of hermatypic corals. However, this proxy is unavailable in temperate and polar oceans. Fish otoliths, calcium carbonate auditory, and gravity receptors in the membranous labyrinths of teleost fishes, can act as proxies for 14C in most oceans and at most depths. Arcto-Norwegian cod otoliths are suited to this application due to the well-defined distribution of this species in the Barents Sea, the ability to determine ages of individual Arcto-Norwegian cod with a high level of accuracy, and the availability of archived otoliths collected for fisheries research over the past 60 years. Using measurements of 14C derived from Arcto-Norwegian cod otoliths, we present the first pre- and post-bomb time series (1919–1992) of 14C from polar seas and consider the significance of these data in relation to ocean circulation and atmosphere/ocean flux of 14C. The data provide evidence for a minor Suess effect of only 0.2‰ per year between 1919 and 1950. Bomb 14C was evident in the Barents Sea as early as 1957 and the highest 14C value was measured in an otolith core from a cod with a birth date of 1967. The otolith 14C data display key features common to records of 14C obtained from a Georges Bank mollusc and corals from the tropical and subtropical North Atlantic.
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Roushangar, Kiyoumars, Mohammad Taghi Alami, Jalal Shiri, and Mahdi Majedi Asl. "Determining discharge coefficient of labyrinth and arced labyrinth weirs using support vector machine." Hydrology Research 49, no. 3 (March 3, 2017): 924–38. http://dx.doi.org/10.2166/nh.2017.214.
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Abstract A labyrinth weir is a linear weir folded in plan-view which increases the crest length and the flow rate for a given channel width and an upstream flow depth. The present study aimed at determining discharge coefficients of labyrinth and arced labyrinth weirs using support vector machine (SVM)-based models. A total of 527 laboratory test data of four types of weirs, namely, Normal and Inverted orientation Labyrinth Weirs in flume (NLW, ILW) and Arced Labyrinth Weirs with and without nappe Breakers in reservoir (ALW, ALWB), were captured from the published literature and utilized to feed the SVM-based models. The obtained results revealed the capability of the SVM-based models in determining discharge coefficients. The results showed that the SVM-based model of arced labyrinth weir (ALW) produced the most accurate results when three dimensionless parameters, e.g. (HT/P) head water ratio, (α/θ) angle ratio and (Lc/W) magnification ratio, were introduced as input parameters (Root mean square error [RMSE]= 0.013 and R2 = 0.970 for the test stage). Nonetheless, sensitivity analysis showed that Froude number and head water ratio are the most influential parameters on discharge coefficients of the labyrinth and arced labyrinth weirs, respectively.
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Ahmadi, Zobeideh, Seyed Asadollah Mohseni Movahed, and Javad Mozaffari. "The effects of dentate crest and a row of consecutive orifices along and below the crest edge on labyrinth weir efficiency." Canadian Journal of Civil Engineering 46, no. 6 (June 2019): 552–55. http://dx.doi.org/10.1139/cjce-2018-0008.
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A labyrinth weir is one of the most effective ways of increasing weir discharge efficiency compared with a linear overflow structure. In this study, two proposed models of labyrinth weir, one with a dentate crest and another with a row of orifices along and below the crest edge were compared with a simple labyrinth weir, measuring their effects on the discharge coefficient. Experiments on nine labyrinth weir models were conducted in the hydraulic laboratory flume. These experiments indicated that creation of both dentate crest edge and row of consecutive orifices led to an increased discharge coefficient of between 11 to 25.3% and 31.6 to 52.9%, respectively, relative to simple labyrinth weir. By increasing the upstream head water, the discharge coefficient for the labyrinth weir model with dentate crest and the model with a row of consecutive orifices are closer together and eventually will converge.
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Aradhana, Aradhana, B. Singh, and P. Sihag. "Predictive models for estimation of labyrinth weir aeration efficiency." Journal of Achievements in Materials and Manufacturing Engineering 1, no. 105 (March 1, 2021): 18–32. http://dx.doi.org/10.5604/01.3001.0014.8742.
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Purpose: The purpose of the study is to estimate the aeration efficiency (E20) of Labyrinth weir using artificial intelligent (AI)-based models. Design/methodology/approach: The aeration efficiency (E20) was collected by using the nine models of Labyrinth weir with different shapes and dimensions. A total of 180 observations were used out of which 126 used to train the AI-based models and the remaining used to test the model. This observation consists of input variables such as Fraud number (Fr), Reynolds number (Re), numbers of keys (N), the ratio of head to the width of the channel (H/W), the ratio of crest length to width of the channel (L/W), the ratio of drop height to width of the channel (D/W) and shape factor (SF) and E20 as the output variables. The AI-based models used were Fuzzy Logic, multi-linear regression (MLR), adaptive neurofuzzy interface system (ANFIS), and artificial neural network (ANN). Findings: The main findings of this investigation are that ANN is the best AI-based model that can estimate the E20 accurately than MLR, ANFIS, and Fuzzy Logic. Sensitivity analysis depicts that drop height at labyrinth weir is the essential factors for the estimation of E20; further, parametric studies have also been performed. Research limitations/implications: The proposed AI-based models can be used in the estimation of E20 with different shapes of labyrinth weir but still it needs improvement for the different dimensions. Practical implications: The best AI-based model can be used to calculate the E20 with the different values of input variables. Originality/value: There are no such AI-based models such as ANN, ANFIS, and Fuzzy Logic, available in the literature which can estimate the values of E20 accurately.
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Hussain, Ruqiya Abed, Sawsan Abdullah Hassan, and Asmaa Abdul Jabbar Jamel. "Experimental Study on Flow over Triangular Labyrinth Weirs." International Journal of Design & Nature and Ecodynamics 17, no. 2 (April 27, 2022): 249–55. http://dx.doi.org/10.18280/ijdne.170211.
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Recently, many research studies have focused on labyrinth weirs' hydraulic performance, especially as dependent on engineering features. In the current study, the hydraulic properties of flow over labyrinth triangular weirs models (from the upper perspective) with sharp crest have been experimentally studied and compare their efficiency with suppressed rectangular weirs (conventional weirs). Twelve fiberglass models are developed for this reason and tested in a 6m in length, 30cm in width, and 40cm height in laboratory flume, nine models were constructed for triangular labyrinth weirs and three models were constructed for suppressed rectangular weirs, Three alternative heights (p=15, 20, and 25cm) were employed in this research, for each height, the vertex angle (θ) changed three times (60օ, 90օ, 120օ), and for each one of these weirs was used, seven different discharge were approved. The overall tests in this study were 84. The dimensionless parameters on which the discharge coefficient (Cd) is dependent were obtained using dimensional analysis. parameters were plotted. According to this experimental present study, as compared to linear weirs, labyrinth triangular weirs shown to be more hydraulically efficient. Also, the height of the weir (P) has effects on the discharge coefficient, where (Cd) increased with decreasing (P). Also, the vertex angle of triangular labyrinth weirs(θ) has a major influence on discharge coefficient and on weir performance, where the discharge coefficient raises when decreases the value of angle(θ), in another means, when the angle decreases gave an increase in the path of the flow, where it gave the triangular labyrinth weir with an angle of 60o the discharge coefficient reached its greatest value (2.55), followed by the weir with an angle of 90o and 120o respectively. In other words (a small vertex angle gives more length effective (Le) to the weir) and this leads to an increase in flow capacity or performance for the weir.
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Yousif, Omed S. Q., and Moses Karakouzian. "Effect of Corner Shape on Hydraulic Performance of One-Cycle Rectangular Labyrinth Weirs." Fluids 5, no. 3 (July 20, 2020): 117. http://dx.doi.org/10.3390/fluids5030117.
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The hydraulic performance of rectangular labyrinth weirs has been investigated by many researchers, however, the effects of the corner shape on the hydraulic performance of rectangular labyrinth weirs have not been addressed in the current literature. Accordingly, this experimental study aims to explore the effect of the corner shape of on discharge efficiency of rectangular labyrinth weirs. Five flat-crested rectangular labyrinth weirs, with five different corner shapes, were made of High-Density Polyethylene Plastic (HDPE) and tested in a rectangular flume. Under different overflow discharges, the discharge coefficients for the rectangular labyrinth weirs were determined. The results showed that the shape of corners for rectangular labyrinth weirs was an effective factor. For example, rounding or beveling the corners can significantly increase the discharge capacity of the rectangular labyrinth weirs. However, the rounded corner shape was slightly better than the beveled corner shape. Among all labyrinth weir models tested in this study, the rectangular labyrinth weir with a semi-circular apex showed the highest hydraulic efficiency, while the one with an acute-angle corner shape showed the lowest hydraulic efficiency. For the rectangular labyrinth weir having a semi-circular shape, although the original effective length reduced by about 14%, the discharge coefficient, CL, increased by 16.7% on average. For the rectangular labyrinth weir that has an acute-angle corner shape, although the effective length (LC) of the weir increased by 23%, its discharge capacity decreased by 35.2% on average. Accordingly, improper folding of the side-walls of the rectangular labyrinth weir led to a significant reduction in the weir’s hydraulic performance.
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Wang, Zhiguo, Bo Zhang, Yuanxiang Chen, Sheng Yang, Hongmei Liu, and Honghu Ji. "Investigation of Leakage and Heat Transfer Properties of the Labyrinth Seal on Various Rotation Speed and Geometric Parameters." Coatings 12, no. 5 (April 25, 2022): 586. http://dx.doi.org/10.3390/coatings12050586.
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To investigate the influence of the variation of geometric parameters on the leakage and heat transfer characteristics of labyrinth seals at various rotational speeds, the labyrinth seal models with different geometric parameters were numerically simulated based on the control variable methods. Results show the aerodynamic mechanism of leakage characteristics changing with rotational speed, as well as the leakage characteristics of labyrinth seals under the coupling action of geometric parameters and rotating speeds. When the characteristic scale changes along the direction of centrifugal force, the variation trend of labyrinth seal leakage characteristics is consistent at different rotational speeds. However, the leakage characteristics of labyrinth seals show the difference of rotational speed when the feature scale changes along the axis. At the same time, the laws of convective heat transfer on the surface of the rotor and stator are shown by the results of the studies, which provides reference for the thermodynamic analysis of labyrinth seals.
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Wang, Zhiguo, Bo Zhang, Yuanxiang Chen, Sheng Yang, Hongmei Liu, and Honghu Ji. "Investigation of Leakage and Heat Transfer Properties of the Labyrinth Seal on Various Rotation Speed and Geometric Parameters." Coatings 12, no. 5 (April 25, 2022): 586. http://dx.doi.org/10.3390/coatings12050586.
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To investigate the influence of the variation of geometric parameters on the leakage and heat transfer characteristics of labyrinth seals at various rotational speeds, the labyrinth seal models with different geometric parameters were numerically simulated based on the control variable methods. Results show the aerodynamic mechanism of leakage characteristics changing with rotational speed, as well as the leakage characteristics of labyrinth seals under the coupling action of geometric parameters and rotating speeds. When the characteristic scale changes along the direction of centrifugal force, the variation trend of labyrinth seal leakage characteristics is consistent at different rotational speeds. However, the leakage characteristics of labyrinth seals show the difference of rotational speed when the feature scale changes along the axis. At the same time, the laws of convective heat transfer on the surface of the rotor and stator are shown by the results of the studies, which provides reference for the thermodynamic analysis of labyrinth seals.
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Lorencin, Ivan, Nikola Anđelić, Vedran Mrzljak, and Zlatan Car. "Exergy analysis of marine steam turbine labyrinth (gland) seals." Pomorstvo 33, no. 1 (June 28, 2019): 76–83. http://dx.doi.org/10.31217/p.33.1.8.
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The paper presents an exergy analysis of marine steam turbine labyrinth (gland) seals - an inevitable component of any marine steam turbine cylinder, in three different operating regimes. Throughout labyrinth seals, steam specific enthalpy can be considered as a constant because the results obtained by this assumption do not deviate significantly from the results of complex numerical models. Changes in labyrinth seals exergy efficiency and specific exergy destruction are reverse proportional. The analyzed labyrinth seals have high exergy efficiencies in each observed operating regime at the ambient temperature of 298 K (above 92%), what indicates seals proper operation. An increase in the ambient temperature resulted with a decrease in labyrinth seals exergy efficiency, but even at the highest observed ambient temperature of 318 K, seals exergy efficiency did not fall below 90.5% in each observed operating regime.
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Mohammed, Rangeen Shihab, and Shaker Abdulatif Jalil. "Hydraulic Performance of Sharp-Crested Labyrinth Weir." Academic Journal of Nawroz University 11, no. 1 (February 7, 2022): 47–56. http://dx.doi.org/10.25007/ajnu.v11n1a1025.
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Weirs are used as a control structure in the waterways. Among the influencing geometrical parameters on the weir performance is the total crest length. Experimental work on 27 geometric models of two-cycle Labyrinth shape crest weir is tested. The tested physical models consist of three weir heights, three apex widths and the sidewall angle is between (4.67°≤ α ≤ 19°), with three models of rectangular labyrinth weirs. The weirs of the wider apex and the same total length perform better and its coefficient of discharge is higher. Labyrinth weirs of longer sidewall length and contents same apex width performance batter. The larger value of sidewall angle and for a constant apex width reduces the value of discharge coefficient. The value of Cd range from (0.34-0.83) for the ratio of upstream head to the weir height (h/P) is ranged (0.08-0.48). The equations to predict the value of the discharge coefficient are suggested within the limitations of the present study.
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Aurahman, Tara H., Jehan M. Fattah Sheikh Suleimany, and Taban K. Hamad. "Determination of Discharge Coefficient for both Semicircular and Triangular Labyrinth Weirs." Polytechnic Journal 11, no. 2 (December 30, 2021): 56–64. http://dx.doi.org/10.25156/ptj.v11n2y2021.pp56-64.
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A Labyrinth weir is a type of nonlinear weir folded in plan-view, with the ability to pass a large flow at low heads due to an increase in the effective length of the weir crest for a given channel width. The discharge coefficients (Cd) were experimentally determined for both semicircular and triangular labyrinth weirs of varying sidewall angles (α) under free-flow conditions using eight physical models. Dimensional analyses are conducted using the Buckingham π theorem to find the dependent and non-dependent variables. A nonlinear empirical equation was developed using (Statistical Package for the Social Sciences 22) software. The findings show that the discharge coefficient decreases with the increase of headwater to (Ht/P) for both types of labyrinth weir with different plan forms. It is found that the efficiency of the semicircular and triangular labyrinth is higher than linear weir for (Ht/P ≤ 0.45) and decreases with increasing the value of (Ht/P) due to interference of flow between the layers in downstream. The obtained results revealed that the discharge coefficient (Cd) values obtained empirically using multivariable power regression and 5th degree polynomial equations considerably agree with the experimental data, for both of the semicircular and triangular labyrinth weirs. Furthermore, the correlation coefficient R2was (0.9951) and (0.9637) using 5th degree polynomial equation, and their values were (0.9643) and (0.9274) using multivariable power regression equation for both semicircular and triangular labyrinth weir models, respectively. The results in the present study compared quite well with the predicted results of the proposed equations obtained by other investigators.
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Sun, Tao, Yi Zhang, Zhong Yi Wang, and Hai Ou Sun. "Numerical Study on Flow Characteristics in Stepped Labyrinth Seal." Advanced Materials Research 230-232 (May 2011): 582–86. http://dx.doi.org/10.4028/www.scientific.net/amr.230-232.582.
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Vapor seal is an indispensable component in steam turbine for economic and safe operation. The flow characteristics in vapor seal have a significant effect on the performance of vapor seal. Considering the flow field characteristics and engineering applications, the following work has been done: First, the models of the labyrinth glands with stepped teeth have been established through Computational Fluid Dynamics software Fluent. The full-flow simulation result is acquired. Second, based on the numerical results, the characteristics of the flow field in stepped labyrinth seal have been studied. At last, the best structure for stepped labyrinth seal is achieved.
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Kim, N., S. Y. Park, and D. L. Rhode. "Predicted Effects of Shunt Injection on the Rotordynamics of Gas Labyrinth Seals." Journal of Engineering for Gas Turbines and Power 125, no. 1 (December 27, 2002): 167–74. http://dx.doi.org/10.1115/1.1520539.
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A recent CFD perturbation model for turbomachinery seal rotordynamics was extended for labyrinth shunt injection with an arbitrarily high pressure gas. A large number of measured cases with labyrinth injection pressure at approximately 13.8 bars (200 psi) were computed and compared with measurements. The drastically reduced (negative) cross-coupled stiffness, which is the primary advantage from the use of shunt injection in gas labyrinth seal applications, was well predicted. The agreement with measurements for k, C, and Ceff was within about 40%, 60% and 10%, respectively. In addition, it was found that moving the injection toward the high pressure end of the seal gives k, C, and Ceff values that are rotordynamically only slightly more stabilizing. Further, the radial distributions of the flow perturbation quantities give support to the two-control volume approach for developing bulk-flow models for labyrinth seal rotordynamics.
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Kiselev, Vladimir Vyacheslavovich, and Dmitriy Valerievich Pomukhin. "Experimental hydrops of labyrinth." Terapevt (General Physician), no. 12 (December 6, 2021): 37–43. http://dx.doi.org/10.33920/med-12-2112-04.
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Difficulties in approbation of drugs for the treatment of vestibular dysfunction are associated with a lack of knowledge of the mechanisms of its development. In particular, it is necessary to take into account the initial state of the vestibular analyzer, which significantly affects the research results. Therefore, the modeling of pathological processes that manifest in vestibular dysfunction is the optimal method for studying both its mechanisms and the effectiveness of medications for its relief. Endolymphatic hydrops is found in most diseases manifested by peripheral vestibular syndrome. We have proposed several models of endolymphatic hydrops in rats to study various aspects of its pathogenesis and approbate means of treating vestibular dysfunction.
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Subramanian, Sivakumar, A. S. Sekhar, and B. V. S. S. S. Prasad. "Assessment of Analytical Predictions for Radial Growth of Rotating Labyrinth Seals." International Journal of Turbo & Jet-Engines 35, no. 3 (July 26, 2018): 265–79. http://dx.doi.org/10.1515/tjj-2016-0041.
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Abstract Radial growth predictions of rotating labyrinth seals are conventionally obtained from one-dimensional analytical models. However, these predictions quantitatively differ within themselves by about 5-500 %. Simulations using three-dimensional finite element method (FEM) are carried out in this paper for a typical labyrinth seal, subjected to high rotational speed and temperature, for a range of radius-to-length ratio of the rotor. Taking the predicted values by FEM as reference, four analytical models are assessed and their errors are quantified. These errors are found to be independent of rotational speed and temperature but significantly vary with the radius-to-length ratio of the rotor. Based on this finding, simple analytical models, together with correction factor charts, are suggested.
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Liu, Chunrui, Lidong He, Xingyun Jia, Haozhe Zhu, Tao Chen, and Wenhao Wang. "Effect of Installation Error on Rotary Seal of Aero Engine." Aerospace 9, no. 12 (December 14, 2022): 820. http://dx.doi.org/10.3390/aerospace9120820.
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The rotary seal is a key component of the aero engine. Under actual working conditions, most rotary seals always operate in an eccentric state (caused by installation errors), and when a large eccentricity occurs, it may lead to a large amount of gas leakage, resulting in a decrease in aero engine efficiency, which ultimately affects the reliability and life of the aero engine. Therefore, the effect of installation error on the rotary seal of the aero engine was studied in this research. The flow field numerical models of the honeycomb seal, labyrinth seal, and hybrid labyrinth–honeycomb seal were established, the effects of the honeycomb seal, labyrinth seal, and hybrid labyrinth–honeycomb seal on leakage were numerically analyzed, the sealing mechanisms of three types of seals were revealed, and the effect of radial eccentricity on the leakage of three types of seals was also studied. Additionally, the high-pressure and high-speed rotary seal experiment bench was improved, the effect of eccentricity on the leakage characteristics of the honeycomb seal, labyrinth seal, and hybrid labyrinth–honeycomb seal was studied using the improved experiment bench, and the leakage characteristics of the three types of seals were compared under the same condition. The experimental results are consistent with the numerical simulation results; the honeycomb seal is the least sensitive to eccentricity, and its sealing performance is the best. The research results in this paper reveal the seal mechanisms of the honeycomb seal, labyrinth seal, and hybrid labyrinth–honeycomb seal and demonstrate the effect law of eccentricity regarding the leakage characteristics of these three types of seals. The results of this research can provide theoretical support for aero engine efficiency improvement.
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Mammar, Lahouari, Yahiaoui Tayeb, Omar Ladjedel, and Ondřej Šikula. "Fluid Thermal Effect on Non-contacting Labyrinth Seal of 20 MW Steam Turbine." Periodica Polytechnica Mechanical Engineering 64, no. 1 (December 17, 2019): 31–42. http://dx.doi.org/10.3311/ppme.14176.
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This paper is divided into two parts; the first describes a CFD analysis of a gland packing labyrinth seals in 20 MW steam turbine in LNG plant using ANSYS CFX code as an isothermal simulation in fluid domain. The results of two turbulence models k-ε and k-ω SST are compared and validated against experimental data. It is shown that the labyrinth seal leakage is proportional to the clearance cube so any variation in clearance can have a significant impact on the steam leakage. This clearance between the shaft and the labyrinth seal vary as a function of operating temperature due to the different rates of thermal expansion of the materials for these two components. Likewise the fluid temperature has a direct effect on fluid dynamic behavior. For that; the second part of the paper investigates the effect of fluid thermal conditions of the labyrinth seal via the heat transfer and Nusselt number variation in the stator and the rotor, for different cases of inlet temperature (400 °C, 200 °C, 100 °C, 50 °C) and pressure ratio (2.5, 4.5, 6.5) for an ideal gas. Also it is important to know the temperature distribution across tooth and cavities of the labyrinth seal, and finally the Influence of Inlet total temperature on fluid pressure drop in the labyrinth seal will be treated for improving and readjusting the steam turbine sealing system.
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Wasilczuk, Filip, Pawel Flaszynski, Piotr Kaczynski, Ryszard Szwaba, Piotr Doerffer, and Krzysztof Marugi. "Leakage flow analysis in the gas turbine shroud gap." Aircraft Engineering and Aerospace Technology 91, no. 8 (September 2, 2019): 1077–85. http://dx.doi.org/10.1108/aeat-01-2018-0038.
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Purpose The purpose of the study is to measure the mass flow in the flow through the labyrinth seal of the gas turbine and compare it to the results of numerical simulation. Moreover the capability of two turbulence models to reflect the phenomenon will be assessed. The studied case will later be used as a reference case for the new, original design of flow control method to limit the leakage flow through the labyrinth seal. Design/methodology/approach Experimental measurements were conducted, measuring the mass flow and the pressure in the model of the labyrinth seal. It was compared to the results of numerical simulation performed in ANSYS/Fluent commercial code for the same geometry. Findings The precise machining of parts was identified as crucial for obtaining correct results in the experiment. The model characteristics were documented, allowing for its future use as the reference case for testing the new labyrinth seal geometry. Experimentally validated numerical model of the flow in the labyrinth seal was developed. Research limitations/implications The research studies the basic case, future research on the case with a new labyrinth seal geometry is planned. Research is conducted on simplified case without rotation and the impact of the turbine main channel. Practical implications Importance of machining accuracy up to 0.01 mm was found to be important for measuring leakage in small gaps and decision making on the optimal configuration selection. Originality/value The research is an important step in the development of original modification of the labyrinth seal, resulting in leakage reduction, by serving as a reference case.
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Frączek, D., and W. Wróblewski. "Validation of numerical models for flow simulation in labyrinth seals." Journal of Physics: Conference Series 760 (October 2016): 012004. http://dx.doi.org/10.1088/1742-6596/760/1/012004.
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Picardo, Arthur, and Dara W. Childs. "Rotordynamic Coefficients for a Tooth-on-Stator Labyrinth Seal at 70 Bar Supply Pressures: Measurements Versus Theory and Comparisons to a Hole-Pattern Stator Seal." Journal of Engineering for Gas Turbines and Power 127, no. 4 (March 1, 2004): 843–55. http://dx.doi.org/10.1115/1.1924634.
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Rotor dynamic and leakage coefficients are presented for a labyrinth seal that was tested at a supply pressure of 70 bar-a and speeds up to 20,200 rpm. Tests were conducted at clearances of 0.1 mm and 0.2 mm, pressure ratios of 0.10, 0.31, and 0.52, and three preswirls ratios. Comparisons are made between test data and predictions from one-control-volume and two-control-volume bulk-flow models. Generally, theoretical predictions agree poorly with the test results, with the one-control volume model giving better predictions. The one-control-volume model provides a conservative prediction for effective damping; i.e., this parameter is underestimated. Both models under predict leakage rates. Comparisons are also made between rotordynamic coefficients of labyrinth and hole-pattern seals.
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Choi, Dong-Chun, and David L. Rhode. "Development of a Two-Dimensional Computational Fluid Dynamics Approach for Computing Three-Dimensional Honeycomb Labyrinth Leakage." Journal of Engineering for Gas Turbines and Power 126, no. 4 (October 1, 2004): 794–802. http://dx.doi.org/10.1115/1.1772405.
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A new approach for employing a two-dimensional computational fluid dynamics (CFD) model to approximately compute a three-dimensional flow field such as that in a honeycomb labyrinth seal was developed. The advantage of this approach is that it greatly reduces the computer resource requirement needed to obtain a solution of the leakage for the three-dimensional flow through a honeycomb labyrinth. After the leakage through the stepped labyrinth seal was measured, it was used in numerically determining the value of one dimension (DTF1) of the simplified geometry two-dimensional approximate CFD model. Then the capability of the two-dimensional model approach was demonstrated by using it to compute the three-dimensional flow that had been measured at different operating conditions, and in some cases different distance to contact values. It was found that very close agreement with measurements was obtained in all cases, except for that of intermediate clearance and distance to contact for two sets of upstream and downstream pressure. The two-dimensional approach developed here offers interesting benefits relative to conventional algebraic-equation models, particularly for evaluating labyrinth geometries/operating conditions that are different from that of the data employed in developing the algebraic model.
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Gligorijević, Živorad, and Enes Ćorović. "Development trends of the Textile industry of the Republic of Serbia in labyrinths neoliberal growth model." Ekonomika 68, no. 1 (2022): 1–14. http://dx.doi.org/10.5937/ekonomika2201001g.
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The textile industry of the Republic of Serbia, for a long time, has been one of the key drivers of economic growth, the mainstay of exports, demographic change and the bearers of social policy. However, in the period from 2000 to 2008, that is, in the period of application of the neoliberal model of growth, it was treated by the creators of economic policy as a relic of the past and the socialist model of growth and continuously recorded negative production results. In accordance with the above, the main goal of the research in this paper is to analyze the key macroeconomic indicators to consider the development trends of this industry in this period. The analysis used the method of induction, while the analysis of competitiveness of the textile industry of Serbia used the following indicators: market share analysis and RCA index (revealed competitive advantage index). The results of the research clearly indicate the disastrous consequences of the application: first, shock therapy in the liberalization of trade flows, second, the wrong model of privatization and third, inadequate economic policy measures, but also the fact that the textile industry has maintained a significant share in exports Republic of Serbia.
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Rhode, D. L., J. S. Younger, and M. D. Wernig. "Flow Visualization and Leakage Measurements of Stepped Labyrinth Seals: Part 2—Sloping Surfaces." Journal of Turbomachinery 119, no. 4 (October 1, 1997): 844–48. http://dx.doi.org/10.1115/1.2841196.
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An experimental investigation was conducted to determine the geometry–leakage relationship for advanced, stepped labyrinth seals. A unique, variable-geometry water test facility was constructed and used to acquire leakage resistance measurements for two-dimensional, planar models. Flow visualization techniques were also used to assist in identifying and understanding the turbulence generating flow patterns. It was found that contoured surfaces and restrictor tooth leading-edge shapes of proper dimensions can be incorporated into the cavity geometry to reduce seal leakage. Specifically, the combination of a sloping surface and a curved surface on the rotor within the labyrinth cavity gave significant improvement.
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Baek, Seung Il, and Joon Ahn. "Optimizing the Geometric Parameters of a Straight-Through Labyrinth Seal to Minimize the Leakage Flow Rate and the Discharge Coefficient." Energies 14, no. 3 (January 29, 2021): 705. http://dx.doi.org/10.3390/en14030705.
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A straight-through labyrinth seal is one of the most popular non-contacting annular seals through which energy dissipation by turbulence viscosity interaction is achieved with a series of teeth and cavities. The geometric parameters of the straight-through labyrinth seal, such as clearance, tooth width, tooth height, cavity width, and tooth inclination angle, affect its performance. The space for installing a labyrinth seal in turbomachinery is limited, and so it is important to optimize its geometry for a fixed axial length in order to minimize the leakage flow rate and the discharge coefficient. The objective of the current study is to understand the effects of changing the geometric parameters of the seal on the leakage flow rate and the discharge coefficient, and to determine the optimized geometry for a fixed axial length. When the whole axial length is fixed, the most effective way to decrease the discharge coefficient is to reduce the cavity width by increasing the number of cavities. However, if the number of cavities is too high, the beneficial effect of more cavities can be reversed. The results of this study will help turbomachinery manufacturers to design a more efficient labyrinth seal. Numerical simulations of leakage flow for the straight-through labyrinth seal were carried out using Reynolds-Averaged Navier–Stokes (RANS) models, and the results for their discharge coefficients and pressure distributions were compared to previously published experimental data.
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Maatooq, Jaafar S. "Predicting the Flow Velocity at the Toe of a Labyrinth Stepped Spillway." Journal of Engineering Research [TJER] 18, no. 1 (October 6, 2021): 20–25. http://dx.doi.org/10.53540/tjer.vol18iss1pp20-25.
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The velocity at the toe of a spillway is a major variable when designing a stilling basin. Reducing this velocity leads to reduce the size of the basin as well as the required appurtenances which needs for dissipating the surplus kinetic energy of the flow. If the spillway chute is able to dissipate more kinetic energy, then the resulting flow velocity at the toe of spillway will be reduced. Typically, stepped spillway is able to dissipate more kinetic energy than that of a smooth surface. In the present study, the typical uniform shape of the steps has been modified to a labyrinth shape. It is postulated that a labyrinth shape can increase the dissipation of kinetic energy through increasing the overlap between the forests of nappe will circulating the flow that in turns leading to further turbulence. This action can reduce the jet velocities near the surfaces, thus minimizing cavitation. At the same time the increasing of circulation regions will maximize the opportunity for air entrainment which also helps to dissipate more kinetic energy. The undertaken physical models were consisted of three labyrinth stepped spillways with magnification ratios (width of labyrinth to width of conventional step) WL/W are 1.1, 1.2, and 1.3 as well as testing a conventional stepped spillway (WL/W=1). It is concluded that the spillway chute coefficient is directly proportional to the labyrinth ratio and its value decreases as this ratio increases.
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BAAKE, M., U. GRIMM, and R. J. BAXTER. "A CRITICAL ISING MODEL ON THE LABYRINTH." International Journal of Modern Physics B 08, no. 25n26 (November 1994): 3579–600. http://dx.doi.org/10.1142/s0217979294001512.
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A zero-field Ising model with ferromagnetic coupling constants on the so-called Labyrinth tiling is investigated. Alternatively, this can be regarded as an Ising model on a square lattice with a quasi-periodic distribution of up to eight different coupling constants. The duality transformation on this tiling is considered and the self-dual couplings are determined. Furthermore, we analyze the subclass of exactly solvable models in detail parametrizing the coupling constants in terms of four rapidity parameters. For those, the self-dual couplings correspond to the critical points which, as expected, belong to the Onsager universality class.
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Benhamou, Simon, and Valérie Séguinot. "How to find one's way in the labyrinth of path integration models." Journal of Theoretical Biology 174, no. 4 (June 1995): 463–66. http://dx.doi.org/10.1006/jtbi.1995.0112.
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Colombo, A., and B. W. Karney. "Pipe breaks and the role of leaks from an economic perspective." Water Supply 3, no. 1-2 (March 1, 2003): 163–69. http://dx.doi.org/10.2166/ws.2003.0099.
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A map depicting the major elements, interactions, and life cycle analysis issues of a typical water distribution system is presented as a network labyrinth. From this, focus is placed on the influence of leaks on energy and water consumption as well as the dissipation of hydraulic transients. Straightforward analytical expressions are derived in order to relate the energy efficiency of a leaky pipe to leak location and orifice properties. The ability of leaks to relieve pressure during hydraulic transients is briefly discussed with several challenges and issues surrounding the quantification of this attenuation effect being put forward. Considered from the broader perspective of the network labyrinth, a better understanding of leak related effects has implications for pipe rehabilitation models, system economics and environmental sustainability.
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Courtney, Jennifer A., Rebecca L. Wilson, James Cnota, and Helen N. Jones. "Conditional Mutation of Hand1 in the Mouse Placenta Disrupts Placental Vascular Development Resulting in Fetal Loss in Both Early and Late Pregnancy." International Journal of Molecular Sciences 22, no. 17 (September 2, 2021): 9532. http://dx.doi.org/10.3390/ijms22179532.
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Congenital heart defects (CHD) affect approximately 1% of all live births, and often require complex surgeries at birth. We have previously demonstrated abnormal placental vascularization in human placentas from fetuses diagnosed with CHD. Hand1 has roles in both heart and placental development and is implicated in CHD development. We utilized two conditionally activated Hand1A126fs/+ murine mutant models to investigate the importance of cell-specific Hand1 on placental development in early (Nkx2-5Cre) and late (Cdh5Cre) pregnancy. Embryonic lethality occurred in Nkx2-5Cre/Hand1A126fs/+ embryos with marked fetal demise occurring after E10.5 due to a failure in placental labyrinth formation and therefore the inability to switch to hemotrophic nutrition or maintain sufficient oxygen transfer to the fetus. Labyrinthine vessels failed to develop appropriately and vessel density was significantly lower by day E12.5. In late pregnancy, the occurrence of Cdh5Cre+;Hand1A126fs/+ fetuses was reduced from 29% at E12.5 to 20% at E18.5 and remaining fetuses exhibited reduced fetal and placental weights, labyrinth vessel density and placenta angiogenic factor mRNA expression. Our results demonstrate for the first time the necessity of Hand1 in both establishment and remodeling of the exchange area beyond early pregnancy and in patterning vascularization of the placental labyrinth crucial for maintaining pregnancy and successful fetal growth.
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Talebinejad, Mohammad Reza, and Mohammad Shahi. "The labyrinth of ethics in journalistic translated discourse." Babel. Revue internationale de la traduction / International Journal of Translation 63, no. 1 (June 29, 2017): 89–108. http://dx.doi.org/10.1075/babel.63.1.06tal.
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Abstract Given that both translation ethics and journalistic translation are still two under-explored areas in translation research, this study sets out to discover the ethical model of Iranian translators’ performance in a climate of conflict. To achieve the objective, the researchers monitored and collected the translated journalistic texts concerning the Iranian nuclear negotiations published by a state-run news agency from three days before the Almaty I nuclear talks to three days after the Almaty II negotiations. The monitoring phase resulted in 20 pairs of STs and TTs. The comparative textual analysis indicated patterned and motivated ideological interference in translations which could be accounted for by resorting to teleological models of ethics. Theoretical analysis revealed conceptual overlap between ethics and ideology that could explain the reduction of ethics into ideology in the news agency.
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Zdebik, Anselm A., Philine Wangemann, and Thomas J. Jentsch. "Potassium Ion Movement in the Inner Ear: Insights from Genetic Disease and Mouse Models." Physiology 24, no. 5 (October 2009): 307–16. http://dx.doi.org/10.1152/physiol.00018.2009.
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Sensory transduction in the cochlea and vestibular labyrinth depends on fluid movements that deflect the hair bundles of mechanosensitive hair cells. Mechanosensitive transducer channels at the tip of the hair cell stereocilia allow K+ to flow into cells. This unusual process relies on ionic gradients unique to the inner ear. Linking genes to deafness in humans and mice has been instrumental in identifying the ion transport machinery important for hearing and balance. Morphological analysis is difficult in patients, but mouse models have helped to investigate phenotypes at different developmental time points. This review focuses on cellular ion transport mechanisms in the stria vascularis that generate the major electrochemical gradients for sensory transduction.
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Zeinali, Mina, Maggie Lee, Arthi Nadhan, Anvya Mathur, Casey Hedman, Eric Lin, Ramdane Harouaka, et al. "High-Throughput Label-Free Isolation of Heterogeneous Circulating Tumor Cells and CTC Clusters from Non-Small-Cell Lung Cancer Patients." Cancers 12, no. 1 (January 3, 2020): 127. http://dx.doi.org/10.3390/cancers12010127.
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(1) Background: Circulating tumor cell (CTC) clusters are emerging as clinically significant harbingers of metastases in solid organ cancers. Prior to engaging these CTC clusters in animal models of metastases, it is imperative for technology to identify them with high sensitivity. These clusters often present heterogeneous surface markers and current methods for isolation of clusters may fall short. (2) Methods: We applied an inertial microfluidic Labyrinth device for high-throughput, biomarker-independent, size-based isolation of CTCs/CTC clusters from patients with metastatic non-small-cell lung cancer (NSCLC). (3) Results: Using Labyrinth, CTCs (PanCK+/DAPI+/CD45−) were isolated from patients (n = 25). Heterogeneous CTC populations, including CTCs expressing epithelial (EpCAM), mesenchymal (Vimentin) or both markers were detected. CTCs were isolated from 100% of patients (417 ± 1023 CTCs/mL). EpCAM− CTCs were significantly greater than EpCAM+ CTCs. Cell clusters of ≥2 CTCs were observed in 96% of patients—of which, 75% were EpCAM−. CTCs revealed identical genetic aberrations as the primary tumor for RET, ROS1, and ALK genes using fluorescence in situ hybridization (FISH) analysis. (4) Conclusions: The Labyrinth device recovered heterogeneous CTCs in 100% and CTC clusters in 96% of patients with metastatic NSCLC. The majority of recovered CTCs/clusters were EpCAM−, suggesting that these would have been missed using traditional antibody-based capture methods.
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Chen, Xueli, Zhengying Wei, Caixiang Wei, and Kun He. "Machine Learning Approaches to Estimate Flow Rate of Drip Irrigation Emitter Based on Structure Parameters and Pressure." Journal of Physics: Conference Series 2203, no. 1 (February 1, 2022): 012017. http://dx.doi.org/10.1088/1742-6596/2203/1/012017.
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Abstract The agricultural water-saving irrigation systems need to be adapted to local conditions, and irrigation emitters with different flow rates need to be designed to meet actual needs. In this study, machine learning approaches were used to predict the flow rate of the labyrinth emitters. The structural parameters of the emitter [number of channel units (N), channel unit length (L), channel width (W), tooth height (H) and channel depth (D)] and working pressure (P) were considered as independent variables. The applied machine learning models included k-nearest neighbor (KNN), multi-layer perceptron (MLP), support vector machine (SVM) and radial basis function artificial neural network (RBF-ANN). The accuracy of the machine learning model was evaluated by the mean square error (MSE) and coefficient of determination (R 2). The results show that the MSE and R2 of the RBF-ANN model were higher than the corresponding parameters of the other three models, indicating the RBF-ANN model can predict the flow rate of the labyrinth emitter more accurately. The research provides a reference for the rapid design of emitters with different flow rate. It is helpful to realize the automation of agricultural irrigation, and then realize the construction of a smart agricultural irrigation system.
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Song, Bum Ho, and Seung Jin Song. "Lateral Forces From Single Gland Rotor Labyrinth Seals in Turbines." Journal of Engineering for Gas Turbines and Power 126, no. 3 (July 1, 2004): 626–34. http://dx.doi.org/10.1115/1.1690771.
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Even though interest in labyrinth seal flows has increased recently, an analytical model capable of predicting turbine flow response to labyrinth seals is still lacking. Therefore, this paper presents a new model to predict flow response in an axial turbine stage with a shrouded rotor. A concentric model is first developed, and this model is used to develop an eccentric model. Basic conservation laws are used in each model, and a nonaxisymmetric sealing gap is prescribed for the eccentric model. Thus, the two models can predict the evolution of a uniform upstream flow into a nonuniform downstream flow. In turbines with concentric shrouded rotors, the seal flow is retarded in the axial direction and tangentially underturned. In turbines with eccentric shrouded rotors, flow azimuthally migrates away from and pressure reaches its peak near the maximum sealing gap region. Finally, the rotordynamic implications of such flow nonuniformities are discussed and compared against eccentric unshrouded turbine predictions.
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Cangioli, Filippo, Paolo Pennacchi, Leonardo Nettis, and Lorenzo Ciuchicchi. "Design and Analysis of CFD Experiments for the Development of Bulk-Flow Model for Staggered Labyrinth Seal." International Journal of Rotating Machinery 2018 (2018): 1–16. http://dx.doi.org/10.1155/2018/9357249.
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Nowadays, bulk-flow models are the most time-efficient approaches to estimate the rotor dynamic coefficients of labyrinth seals. Dealing with the one-control volume bulk-flow model developed by Iwatsubo and improved by Childs, the “leakage correlation” allows the leakage mass-flow rate to be estimated, which directly affects the calculation of the rotor dynamic coefficients. This paper aims at filling the lack of the numerical modelling for staggered labyrinth seals: a one-control volume bulk-flow model has been developed and, furthermore, a new leakage correlation has been defined using CFD analysis. Design and analysis of computer experiments have been performed to investigate the leakage mass-flow rate, static pressure, circumferential velocity, and temperature distribution along the seal cavities. Four design factors have been chosen, which are the geometry, pressure drop, inlet preswirl, and rotor peripheral speed. Finally, dynamic forces, estimated by the bulk-flow model, are compared with experimental measurements available in the literature.
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Otsuka, K., M. Negishi, M. Suzuki, T. Inagaki, M. Yatomi, U. Konomi, T. Kondo, and Y. Ogawa. "Experimental study on the aetiology of benign paroxysmal positional vertigo due to canalolithiasis: comparison between normal and vestibular dysfunction models." Journal of Laryngology & Otology 128, no. 1 (January 2014): 68–72. http://dx.doi.org/10.1017/s0022215113003381.
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AbstractObjectives:Using American bullfrog models under normal conditions and under vestibular dysfunction, we investigated whether mechanical vibration applied to the ear could induce otoconial dislodgement.Methods:Vibration was applied to the labyrinth of the bullfrog using a surgical drill. The time required for the otoconia to dislodge from the utricular macula was measured. Vestibular dysfunction models were created and the dislodgement time was compared with the normal models. The morphology of the utricular macula was also investigated.Results:In the normal models, the average time for otoconial dislodgement to occur was 7 min and 36 s; in the vestibular dysfunction models, it was 2 min and 11 s. Pathological investigation revealed that the sensory hairs of the utricle were reduced in number and that the sensory cells became atrophic in the vestibular dysfunction models.Conclusion:The otoconia of the utricle were dislodged into the semicircular canal after applying vibration. The time to dislodgement was significantly shorter in the vestibular dysfunction models than in the normal models; the utricular macula sustained significant morphological damage.
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Willenborg, K., S. Kim, and S. Wittig. "Effects of Reynolds Number and Pressure Ratio on Leakage Loss and Heat Transfer in a Stepped Labyrinth Seal." Journal of Turbomachinery 123, no. 4 (February 1, 2001): 815–22. http://dx.doi.org/10.1115/1.1397304.
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The influence of Reynolds number and pressure ratio on the operating characteristics of a stepped labyrinth seal was experimentally determined. The geometries investigated represent designs of a stepped labyrinth seal typical for modern jet engines. Heat transfer and discharge measurements were obtained for two plane models with various seal clearances. The experiments covered a range of Reynolds numbers and pressure ratios. Independent variation of Reynolds number and pressure ratio was obtained by adjusting the back pressure at the seal exit for a given pressure ratio. Dimensionless discharge coefficients, describing the sealing performance, were derived from the measured leakage rates. Pressure ratio, Reynolds number, tip geometry, and seal clearance all affected the sealing performance. Finite element calculations were employed to calculate the local heat transfer coefficients from the measured wall and gas temperatures. Averaging of the local values yielded mean heat transfer coefficients and mean Nusselt numbers. The heat transfer was mainly determined by the Reynolds number. Compressibility effects on the heat transfer were observed to be very small.
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Neenan, James, M., Tobias Reich, Serjoscha Evers, Patrick Druckenmiller, Dennis Voeten, Jonah Choiniere, Paul Barrett, Stephanie Pierce, and Roger Benson. "3D models related to the publication: Evolution of the sauropterygian labyrinth with increasingly pelagic lifestyles." MorphoMuseuM 4, no. 1 (December 7, 2017): 62. http://dx.doi.org/10.18563/journal.m3.62.
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曾, 成天. "Evaluation of Existing Models Based on Experiments of Supercritical Carbon Dioxide Flows through Labyrinth Seal." Nuclear Science and Technology 08, no. 04 (2020): 193–202. http://dx.doi.org/10.12677/nst.2020.84023.
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Brownell, J. B., J. A. Millward, and R. J. Parker. "Nonintrusive Investigations Into Life-Size Labyrinth Seal Flow Fields." Journal of Engineering for Gas Turbines and Power 111, no. 2 (April 1, 1989): 335–42. http://dx.doi.org/10.1115/1.3240258.
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Investigations into the thermodynamic processes in labyrinth seal flow fields have been carried out using the nonintrusive optical technique of holographic interferometry. Labyrinth seals in the form of two-dimensional actual size models were used. The types of seal geometry tested reflected those in current use in aerogas turbines, their sizes being typically 10 mm × 20 mm in section with sealing constrictions as small as 0.25 mm. The tests provided a great deal of information that had not previously been available and confirmed several experimental and theoretical results that were not fully understood. The data were obtained in the form of isodensity contour maps. These full field density measurements of the test section flow were analyzed in several ways to provide an insight into the processes occurring within the labyrinth seal. The effects of kinetic energy carry-over upon seal stage performance were dramatically demonstrated in both straight-through and stepped seals. Useful qualitative, as well as quantitative, information regarding the flow field structure could be obtained from the isodensity maps. An indication of particular flow features was obtained at a glance. The optical technique was found to be ideally suited to the investigations and the expected difficulties associated with working in the very small test sections did not arise. The configuration of the optical system ensured that image aberrations were minimized and temporal flow instabilities did not adversely affect the isodensity contour maps. The paper reviews the optical technique and presents a selection of the holographic results along with their interpretation.
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Sheikh Suleimany, Jehan M. Fattah, Tara H. Aurahman, and Bruska S. Mamand. "Flow simulation over semicircular labyrinth weir using ANSYS -fluent." Tikrit Journal of Engineering Sciences 29, no. 1 (April 5, 2022): 83–98. http://dx.doi.org/10.25130/tjes.29.1.7.
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This study investigates the flow of a semicircular labyrinth weir in an open channel by experimental and numerical methods. The experiments were carried out in a channel with a length of 3.5m and width of 0.25m and 0.3m height under five different flow rates. Five different discharge values over the weir were used. In each experiment, flow rate and flow depth were measured. Numerical processes solved using mathematical equations of fluid flow through the computational fluid dynamics using ANSYS FLUENT code. The Volume of Fluid (VOF) model is designed for the case of water and air-immiscible faces. Standard k-epsilon turbulence models were tested. A mass balance result indicates that the maximum error between the inlet and outlet discharges of the main channel does not exceed 12% for discharge values of 4.31 L/sec. The results indicate that by increasing the discharge flow rate, the percentage of error decreased to 0.4% for discharge, 14.6 L/sec. The findings show that the free water surface profile obtained from the numerical model compared to experimental values complies well with the experimental results.
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Sheikh Suleimany, Jehan M. Fattah, Tara H. Aurahman, and Bruska S. Mamand. "Flow simulation over semicircular labyrinth weir using ANSYS -fluent." Tikrit Journal of Engineering Sciences 29, no. 1 (April 23, 2022): 59–74. http://dx.doi.org/10.25130/tjes.29.1.6.
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This study investigates the flow of a semicircular labyrinth weir in an open channel by experimental and numerical methods. The experiments were carried out in a channel with a length of 3.5m and width of 0.25m and 0.3m height under five different flow rates. Five different discharge values over the weir were used. In each experiment, flow rate and flow depth were measured. Numerical processes solved using mathematical equations of fluid flow through the computational fluid dynamics using ANSYS FLUENT code. The Volume of Fluid (VOF) model is designed for the case of water and air-immiscible faces. Standard k-epsilon turbulence models were tested. A mass balance result indicates that the maximum error between the inlet and outlet discharges of the main channel does not exceed 12% for discharge values of 4.31 L/sec. The results indicate that by increasing the discharge flow rate, the percentage of error decreased to 0.4% for discharge, 14.6 L/sec. The findings show that the free water surface profile obtained from the numerical model compared to experimental values complies well with the experimental results.
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Forte, Paola, and Fabio Latini. "Theoretical Rotordynamic Coefficients of Labyrinth Gas Seals: a Parametric Study on a Bulk Model." International Journal of Rotating Machinery 5, no. 1 (1999): 67–76. http://dx.doi.org/10.1155/s1023621x99000068.
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To date, available mathematical bulk models for the determination of linearized rotordynamic coefficients of labyrinth gas seals yield results which are not always in good agreement with the experimental ones. The object of this work is to discuss the limits of these models and to point out possible improvements and aspects that need further investigation.After a study of the steady flow characteristics with an FEM code, a parametric computer program, based on a known two-volume model, has been developed. A perturbation approach has been applied to the governing equations of the bulk model to calculate the stiffness and damping coefficients. Predicted coefficients are compared to the results of an earlier one-volume model.The model has also been tested with different expressions of the axial velocities in the two volumes and different laws for leakage and shear stress. The theoretical results are compared to the published experimental ones, pointing out the small effect of the various parameters in improving the correlation and the need of more complex models.