Academic literature on the topic 'Head size ratio'
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Journal articles on the topic "Head size ratio"
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Taura, Tomoyuki, Masao Noguchi, Seiji Tsuji, Hirofumi Dokawa, Ai Mori, and Narihiro Okazaki. "Review of Enlargement Ratio of the Femoral Head: Using a Ring to Decide Femoral Head Size." Orthopedics & Traumatology 57, no. 4 (2008): 548–52. http://dx.doi.org/10.5035/nishiseisai.57.548.
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Baker, Robert L., and Blair W. Feltmate. "Development of Ischnura verticalis (Coenagrionidae: Odonata): Effects of Temperature and Prey Abundance." Canadian Journal of Fisheries and Aquatic Sciences 44, no. 9 (September 1, 1987): 1658–61. http://dx.doi.org/10.1139/f87-202.
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Increased food availability increased rate of development within an instar, head width ratio (ratio of headwidth of later instar over head width in previous instar), and weight per unit head width of newly molted larval Ischnura verticalis (Say) (Coenagrionidae: Odonata) reared in the laboratory. Temperature affected rate of development but not weight per unit head width or head width ratio. Mortality was not affected by any treatment. Rate of development was negatively correlated with both weight per unit head width and head width ratio. Results suggest that the developmental process has evolved to reduce risks associated with small size at the expense of a more rapid development.
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Waddell, Bradford S., Chelsea Koch, Myra Trivellas, Jayme C. Burket, Timothy Wright, and Douglas Padgett. "Have large femoral heads reduced prosthetic impingement in total hip arthroplasty?" HIP International 29, no. 1 (May 7, 2018): 83–88. http://dx.doi.org/10.1177/1120700018761153.
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Background: Prosthetic impingement is implicated in dislocation after total hip arthroplasty (THA). While use of larger diameter femoral heads reduces the incidence of dislocation, the effect of larger heads upon impingement rate is unknown. We assessed retrieved THA components for evidence of impingement to determine if large femoral heads reduced the rate of impingement in primary THA and what factors might influence impingement. Methods: Liners from 97 primary THAs retrieved at revision arthroplasty were scored for evidence of impingement, defined as wear or deformation on the rim of the component. Component inclination and version were measured from anteroposterior and cross-table lateral radiographs. Results: Independent of revision diagnosis, 77% of liners demonstrated evidence of impingement. Impingement was less prevalent and less severe as head size increased. Severe impingement was observed in 50% of the liners with 28-mm heads, 15% of liners with 32-mm heads, and 21% of liners with 36-mm heads. Regardless of head size, 76% of liners revised for instability demonstrated impingement. Decreased head-neck ratio, use of an elevated liner, increased length of implantation, and increased version were associated with increased severity of impingement. Discussion: We showed that larger head sizes are associated with decreased incidence of impingement on retrieved acetabular liners when compared to smaller head sizes. Larger heads have reduced but not eliminated impingement, which remains a potential source of instability.
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Jia, Xiang, Jian Sheng Liu, Hong Ping An, and Min Qin. "Forming Technology and Simulation of Large Head Forgings." Key Engineering Materials 831 (February 2020): 64–70. http://dx.doi.org/10.4028/www.scientific.net/kem.831.64.
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Head forging is an indispensable part of major technical equipment, which is required to produce high quality products because of its large volume and complex structure and long service under high temperature and high pressure. By means of DEFORM-3D numerical simulation and scaling experiment, the dynamic recrystallization dynamics model of SA508-3CL steel is established. Meanwhile, the head forming scheme is designed. The effects of different blank height-diameter ratio size, punch shape size and upper and lower die matching relationship on forging forming are emphatically analyzed. Finally, the reasonable head forming scheme is determined, and the 1:8 head forming scale test is carried out. The results show that the size of the head forging basically coincides with the design size and meets the load of the hydraulic press, which proves the rationality of the forming process of the head. The study provides a theoretical basis for the manufacture of the same type of large variable wall thickness head forgings.
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Suzuki, Hidenori, Shintaro Beppu, Daisuke Nishikawa, Hoshino Terada, Michi Sawabe, and Nobuhiro Hanai. "Lymph Node Ratio in Head and Neck Cancer with Submental Flap Reconstruction." Biomedicines 10, no. 11 (November 14, 2022): 2923. http://dx.doi.org/10.3390/biomedicines10112923.
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This study aimed to investigate the relationship between the lymph node ratio (LNR) and survival results of patients with head and neck squamous cell carcinoma (HNSCC) reconstructed by a submental artery flap (SMAF) to limit tumor size. This study retrospectively recruited 49 patients with HNSCC who underwent both primary resection and neck dissection with SMAF reconstruction. The LNR was the ratio of the number of metastatic lymph nodes to the sum number of examined lymph nodes. A LNR of 0.04 was the best cut-off value for HNSCC-specific death on receiver operating curve analysis. Patients with LNRs > 0.04 were univariately related to cancer-specific, disease-free, distant metastasis-free, and locoregional recurrence-free survival than those with LNRs ≤ 0.04 by log-rank test. In a Cox’s proportional hazards model with hazard ratio (HR) and 95% confidence interval (CI) adjusting for pathological stage, extranodal extension and or surgical margins, the LNR (>0.04/≤0.04) predicted multivariate shorter cancer-specific (HR = 9.24, 95% CI = 1.49–176), disease-free (HR = 3.44, 95% CI = 1.23–10.3), and distant metastasis-free (HR = 9.76, 95% CI = 1.57–187) survival. In conclusion, LNR for patients of HNSCC with SMAF reconstruction for limited tumor size was a prognostic factor for survival outcomes.
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Ai, Heng Yu, Ming Ming Wang, Lu Han, Burigude, Bo Wei, and Yan Qiu Jia. "Features on Head Loss of Flocculation Tank Installed with Small Mesh Grid." Advanced Materials Research 777 (September 2013): 424–29. http://dx.doi.org/10.4028/www.scientific.net/amr.777.424.
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Small mesh grid is mostly used as flocculation equipment in present water plant, and its head loss is closely related to flocculation effect. Flocculation tank installed with several grid groups in different mesh sizes were tested with a view to evaluating its head loss characteristics, including the frictional and local head losses. The tests were carried out at pilot scale, using a steel tank as flocculation basin. The grids are made of plastic material and the cross section size of the grid trips is 7 mm in width and 2 mm in height. The results indicate that relative roughness is most associated with frictional resistance coefficient (FRC), whereas Reynolds number was unrelated to that. The ratio of frictional head loss to total head loss of the basin does not vary with the variation of channel velocity, and the ratio is always less than 6% in this case. Local resistance coefficient (LRC) decreases with the increase of mesh size. In order to improve the utilization rate of head loss, the preferred mesh size of the grid should be 30-40 mm. The optimal space between the neighboring grid layers can maximize the utilization of turbulent kinetic energy loss generated by grids.
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VERDADE, L. M. "Regression equations between body and head measurements in the broad-snouted caiman (Caiman latirostris)." Revista Brasileira de Biologia 60, no. 3 (August 2000): 469–82. http://dx.doi.org/10.1590/s0034-71082000000300012.
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In the present study, regression equations between body and head length measurements for the broad-snouted caiman (Caiman latirostris) are presented. Age and sex are discussed as sources of variation for allometric models. Four body-length, fourteen head-length, and ten ratio variables were taken from wild and captive animals. With the exception of body mass, log-transformation did not improve the regression equations. Besides helping to estimate body-size from head dimensions, the regression equations stressed skull shape changes during the ontogenetic process. All age-dependent variables are also size-dependent (and consequently dependent on growth rate), which is possibly related to the difficulty in predicting age of crocodilians based on single variable growth curves. Sexual dimorphism was detected in the allometric growth of cranium but not in the mandible, which may be evolutionarily related to the visual recognition of gender when individuals exhibit only the top of their heads above the surface of the water, a usual crocodilian behavior.
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Rumrich, Isabell Katharina, Otto Hänninen, Matti Viluksela, and Kirsi Vähäkangas. "Effect of Grandmaternal Smoking on Body Size and Proportions at Birth." International Journal of Environmental Research and Public Health 18, no. 9 (May 7, 2021): 4985. http://dx.doi.org/10.3390/ijerph18094985.
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Many long-term adverse effects of smoking during pregnancy are known. Increasingly, adverse effects in the grandchild after grandmaternal smoking during pregnancy are reported. We explored this in a birth cohort of 24,000 grandmother–mother–child triads identified from the Finnish Medical Birth Register in 1991–2016. Multiple logistic regression was used to analyze the association between any smoking during pregnancy by both grandmother and mother, or only grandmother or mother on adverse birth outcomes. No smoking by neither grandmother nor mother was used as the reference. As endpoints, preterm birth, low birth weight, small for gestational age (birth weight, birth length, head circumference), and body proportionality (low ponderal index, high brain-to-body ratio, high head-to-length ratio) were included. Smoking by both grandmother and mother was consistently associated with higher risks than smoking only by the mother. Birth length and weight were especially sensitive to (grand)maternal smoking. In conclusion, the combined effect of grandmaternal and maternal smoking is associated with higher risks than only maternal smoking.
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Willigenburg, NW, RA Bouma, VAB Scholtes, VPM van der Hulst, DFP van Deurzen, and MPJ van den Bekerom. "Does the innate relative size of the humeral head and glenoid affect the risk of anterior shoulder instability?" Shoulder & Elbow 11, no. 6 (October 23, 2018): 424–29. http://dx.doi.org/10.1177/1758573218805099.
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Background Bony lesions after shoulder dislocation reduce the joint contact area and increase the risk of recurrent instability. It is unknown whether the innate relative sizes of the humeral head and glenoid may predispose patients to shoulder instability. This study evaluated whether anterior shoulder instability is associated with a larger innate humeral head/glenoid ratio (IHGR). Methods We evaluated CT scans of 40 shoulders with anterior shoulder instability and 48 controls. We measured axial humeral head diameter and glenoid diameter following native contours, discarding any bony lesions, and calculated IHGR by dividing both diameters. Multivariate logistic regression determined whether the IHGR, corrected for age and gender as potential confounders, was associated with anterior shoulder instability. Results Mean IHGR was 1.48 ± 0.23 in the group with anterior shoulder instability and 1.42 ± 0.20 in the group without anterior shoulder instability. Measurements for axial humeral head and axial glenoid diameters demonstrated excellent intra-rater reliability (ICC range: 0.94–0.95). IHGR was not significantly associated with anterior shoulder instability (OR = 1.105, 95%CI = 0.118–10.339, p = 0.930). Discussion The innate ratio of humeral head and glenoid diameters was not significantly associated with anterior shoulder instability in this retrospective sample of 88 shoulder CT scans.
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Moskalenko, Valentyna A., and Valeriy P. Kolosha. "Some aspects of evaluating the cost efficiency level in dairy farming." Socio-Economic Problems of the Modern Period of Ukraine, no. 6(146) (2020): 114–19. http://dx.doi.org/10.36818/2071-4653-2020-6-18.
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The problems related to the level of economic efficiency of dairy farming depending on the level of production intensity are analyzed. The paper emphasizes that the theory of costs is one of the basic in economics and the object of constant attention of scientists. The objective of the study is to assess the impact of the level of costs per cow on the efficiency of milk production and test the relative cost efficiency ratio on the example of a set of enterprises. The agricultural enterprises of Harkivska oblast selling milk as part of their marketable products are the object of the study. The set of studied enterprises is divided into five groups with a cost level from UAH 30,000 per cow to more than UAH 60,000 per cow. A clear relationship between the level of costs and the size of enterprises is found. The dependence shows that enterprises with higher production intensities have more livestock and agricultural land. In the group with a cost level of up to UAH 30,000 per head, one enterprise has on average 157 heads and 1,805 hectares of agricultural land, in the group with a cost level of more than UAH 60,000/head – 559 heads and 4,266 hectares of agricultural land. The paper also establishes that the level of costs per cow very closely determines the level of its productivity. In the group with a cost level of up to UAH 30,000 per head, the average productivity of animals was 4,257 kg/head, in the group with a cost level of UAH 40,000 to UAH 50,000 per head – 6,787 kg/head, and with a cost level of over UAH 60,000 per head – 10,178 kg/head. Approbation of the proposed relative cost efficiency ratio made it possible to establish that this parameter allows assessing both economic and technological efficiency of milk production. The value of the relative cost efficiency ratio in terms of income was over 1 in 38 enterprises and, accordingly, less than 1 – in 39 enterprises. The value of the relative cost efficiency ratio in terms of productivity was over 1 in 23 enterprises and lower in 54 enterprises.
Dissertations / Theses on the topic "Head size ratio"
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Biju, Dona. "A parametric study of oil-jet lubrication in gear wheels." Thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-150786.
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A parametric study of oil-jet lubrication in gear wheels is conducted using Computational Fluid Dynamics (CFD) to study the effect of the different design parameters on the cooling performance in a gearbox. Flow in oil jet lubrication is found to be complex with the formation of oil ligaments and droplets. Various hole radii of 1.5, 2 and 2.5 mm along with five oil velocities is analyzed and it is found that at lower volumetric rates, velocity has more effect on the cooling and at higher volumetric rates, hole size has more effect on the cooling. At higher velocities, the heat transfer is much greater than the actual heat production in the gear wheel, hence these velocity ratios are considered less suitable for jet lubrication. At low velocity ratios of below 2, the oil doesn’t fully impinge the gear bottom land and the sides leading to low cooling. Based on the cooling, impingement length and amount of oil lost to the casing surface, 2 mm hole with a velocity ratio of 2.225 is selected for a successful oil jet lubrication. Varying the inlet position in X, Y and Z directions (horizontal, vertical and lateral respectively) is found to have no improvement on the cooling. Making the oil jet hit the gear wheel surface at an angle is found to increase the cooling. Analysis with the use of a pipe to supply oil was conducted with circular and square inlet and it was found that the heat transfer decreases in both cases due to the splitting of oil jet caused by the combination of the effects of high pressure from the pipe and vorticity in the air field. A method has been developed for two gear analysis using overset meshes which can be used for further studies of jet lubrication in multi-gear systems. Single inlet is found to be better for cooling two gear wheels as it would require a reduced volumetric flow rate compared to double inlets. Oil system requirements for jet lubrication was studied and it was concluded that larger pumps have to be used to provide the high volumetric rates and highly pressurized oil required. On comparing the experimental losses from dip lubrication and the analytical losses for jet lubrication, dip lubrication is found to have lesser loses and more suitable for this case. Good quality lubrication would reduce the fuel consumption and also increase the longevity of gearboxes and hence more research into analyzing alternate lubrication systems can be carried out using the results from this thesis.
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Lam, Pang Kit Jerry. "Three-dimensional Investigations of Different Sulfides in Steels by Using Electrolytic Extraction." Thesis, KTH, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-195349.
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The emphasis of this study is focusing on three-dimensional (3D) investigations of the manganese sulfide (MnS) inclusions characteristics in steels by using electrolytic extraction (EE). Two steel grades, 42CrMo4 and 157C, heat treated (HT) at 900 oC were investigated. 42CrMo4 steel samples were heat treated for 5, 10, 15 and 30 minutes while 157C steel samples were heat treated for 5 minutes. Samples of 42CrMo4 were taken from middle zone of an as-cast steel bar while that for grade 157C were taken from 3 different zones (centre, middle and surface). Inclusions were collected on film filters and analyzed by SEM for classification and determination of their characteristics including the size, number density (Nv), morphology and composition. The aspect ratio (AR) as well as particle size distribution (PSD) were also compared for steel samples conducted at various HT times. The result showed that EE is a reliable method of investigation inclusion characteristics. The inclusions were classified into 3 types according to their morphology and composition. Type I was elongated rod-like MnS, type II was coarsened sheet-like MnS and type III was spherical MnS inclusions. In addition, HT significantly reduced the Nv and fairly reduced AR but no significant reduction in size observed. The peak of PSD decreased with an increased HT time. The change of Nv, length, AR and PSD could be altered because of uneven inclusion distribution in filter and different sampling positions.
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Parkes, Anthony Richard. "The impact of size and location of pool fires on compartment fire behaviour." Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2009. http://hdl.handle.net/10092/3444.
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An understanding of compartment fire behaviour is important for fire protection
engineers. For design purposes, whether to use a prescriptive code or performance
based design, life safety and property protection issues are required to be assessed. The
use of design fires in computer modelling is the general method to determine fire safety.
However these computer models are generally limited to the input of one design fire,
with consideration of the complex interaction between fuel packages and the
compartment environment being simplified. Of particular interest is the Heat Release
Rate, HRR, as this is the commonly prescribed design parameter for fire modelling. If
the HRR is not accurate then it can be subsequently argued that the design scenario may
be flawed. Therefore the selection of the most appropriate fire design scenario is
critical, and an increased level of understanding of compartment behaviour is an
invaluable aid to fire engineering assumptions.
This thesis details an experimental study to enhance the understanding of the impact and
interaction that the size and location of pool fires within an enclosure have upon the
compartment fire behaviour. Thirty four experiments were conducted in a reduced scale
compartment (½ height) with dimensions of 3.6m long by 2.4m wide by 1.2m high
using five typical ventilation geometries (fully open, soffit, door, window and small
window). Heptane pool fires were used, located in permutations of three evenly
distributed locations within the compartment (rear, centre and front) as well as larger
equivalent area pans located only in the centre. This thesis describes the experimental
development, setup and results of the experimental study. To assist in the classification
of compartment fire behaviour during the experiments, a ‘phi’ meter was developed to
measure the time dependent equivalence ratio. The phi meter was developed and
configured to measure O₂, CO₂ and CO. The background development, calibration, and
experimental results are reported. A review of compartment fire modelling using Fire
Dynamics Simulator, has also been completed and the results discussed.
The results of this experimental study were found to have significant implications for
Fire Safety Engineering in that the size of the fire is not as significant as the location of
the fire. The effect of a fire near the vent opening was found to have a significant impact
on compartment fire behaviour with the vent located fuel source increasing the total
compartment heat release rate by a factor of 1.7 to that of a centrally placed pool fire of
the same total fuel area. The assumption that a fire located in the centre of the room
provides for the highest heat release rate is not valid for post-flashover compartment
fires. The phi meter was found to provide good agreement with the equivalence ratio
calculated from total compartment mass loss rates, and the results of FDS modelling
indicate that the use of the model in its current form can not be applied to complex pool
fire geometries.
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Payne, Stephanie. "Phenotypic variation and thermoregulation of the human hand." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/285561.
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The hand has the highest surface area-to-volume ratio of any body part. This property offers the potential for the hand to serve an important function in thermoregulation through radiative heat loss. Theoretically, the capacity for heat loss may be influenced by hand and digit proportions, but the extent to which these proportions influence the hand's radiative properties remains under-investigated. Although hand morphology is highly constrained by both integration and functional dexterity, phenotypic variation in hand and digit proportions across human populations shows broad ecogeographic patterns. These patterns have been associated with climate adaptation. However, the theory linking climate adaptation to such ecogeographic patterns is based on underlying assumptions relating to thermodynamic principles, which have not been tested in vivo. This study sought to determine the influence of hand and digit proportions on heat loss from the hands directly, the additional anthropometric factors that may affect this relationship, and the impact of variation in hand proportions on dexterity in the cold. The relationship between hand proportions and thermoregulation was tested through both laboratory-based investigation and a field study. The laboratory investigation assessed the relationship between hand proportions and heat loss, the influence of body size and composition on this relationship, and the effect of morphological variation on manual dexterity. Participants (N=114; 18-50 years of age), underwent a 3-minute ice-water hand-immersion. Thermal imaging analysis was used to quantify heat loss. Hand and digit proportions were quantified using 2D and 3D scanning techniques; body size and composition were measured using established anthropometric methods and bio-impedance analysis. After accounting for body size, hand width, digit-to-palm length ratio, and skeletal muscle mass were significant predictors of heat loss from the hand, whilsthand length and fat mass were not. A separate set of participants (N=40) performed a Purdue pegboard dexterity test before and after the immersion test, which demonstrated that digit width alone negatively correlated with dexterity. The field study tested whether phenotypic variation in upper limb proportions could be attributed to cold adaptation or selection for dexterity in living populations exposed to significant energetic stress. Upper limb segment lengths were obtained from participants (N=254; 18-59 years of age), from highland and lowland regions of the Nepalese Himalayas using established anthropometric methods, and relative hand proportions were assessed in relation to severe energetic stress associated with life at high altitude. Relative to height, hand length and hand width were not reduced with altitude stress, whilst ulna length was. This indicates that cold adaptation is not shaping hand proportions in this case, although phenotypic variation in other limb segments may be attributed to cold adaptation or a thrifty phenotype mechanism. The current study provides empirical evidence to support the link between surface area-to-volume ratio, thermodynamic principles and ecogeographical patterns in human hand morphology. However, this research also demonstrates the complexity of the hand's role in thermoregulation; not only do other factors such as muscularity affect heat loss from the hand, but hand morphology is also highly constrained by integration and dexterity.
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Wang, Ju-Li, and 王茹立. "Effects of Heat Treatment and Ba/Ti Ratio on Particle Size, Crystalline Phase, Curie Temperature and Dielectric Constant of BaTiO3 Powder." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/73470570956534520144.
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碩士國立成功大學
資源工程學系碩博士班
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Barium titanate is a dielectric and ferroelectric material that used widely in electrical applications, including multilayer ceramics capacitors (MLCCs), PTCR thermistors, etc. Moreover, the microstructure, crystalline phase, Curie temperature and dielectric constant of barium titanate are affected easily by Ba/Ti ratio and particle size. In order to realize the effects of Ba/Ti ratio on BaTiO3 powder, high purity BaCO3 and TiO2 were used to synthesize non-stoichiometric BaTiO3 via solid state reaction, and tried different heating parameters to control the BaTiO3 powder with similar particle size in this study. After analyzing the powder with similar particle size, the tetragonality decreases and the Curie temperature shifts to lower temperature when Ba/Ti ratio strays from 1. The dielectric constant of BaTiO3 powder is also measured in this study. The dielectric constant shows higher when Ba/Ti ratio is closed to stoichiometry. The dielectric constant of bulk is measured. The dielectric constant of bulk with Ba/Ti ratio = 0.9837 is higher than each other just because that with grain size about 0.7 ~1 �慆, moreover, the distribution of grain size is quit homogeneous.
Books on the topic "Head size ratio"
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Burns, Jack O. A Lunar Far-side Very Low Frequency Array: Proceedings of a workshop sponsored by the National Aeronautics and Space Administration, Washington, D.C., the University of New Mexico, Albuquerque, New Mexico, and the BDM Corporation, Albuquerque, New Mexico, and held at the BDM Corporation, Albuquerque, New Mexico, February 18-19, 1988. Washington: NASA, 1989.
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Jean, Vernin, Benkhaldoun Zouhair, Muñoz-Tuñón Casiana, and International Astronomical Union, eds. Astronomical site evaluation in the visible and radio range: IAU technical workshop : proceedings of a workshop held at Cadi Ayyad University, Marrakech, Morocco, 13-17 November 2000. San Francisco, Calif: Astronomical Society of the Pacific, 2002.
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Halle, H. Tube vibration in industrial size test heat exchanger (pitch-to-diameter ratio 1.42). Argonne National Laboratory, 1986.
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Rez, Peter. Buildings. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198802297.003.0003.
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Most of the energy used by buildings goes into heating and cooling. For small buildings, such as houses, heat transfer by conduction through the sides is as much as, if not greater than, the heat transfer from air exchanges with the outside. For large buildings, such as offices and factories, the greater volume-to-surface ratio means that air exchanges are more significant. Lights, people and equipment can make significant contributions. Since the energy used depends on the difference in temperature between the inside and the outside, local climate is the most important factor that determines energy use. If heating is required, it is usually more efficient to use a heat pump than to directly burn a fossil fuel. Using diffuse daylight is always more energy efficient than lighting up a room with artificial lights, although this will set a limit on the size of buildings.
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Williams, Sonja D. Epilogue. University of Illinois Press, 2017. http://dx.doi.org/10.5406/illinois/9780252039874.003.0013.
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This epilogue discusses Richard Durham's legacy. Throughout his life Durham fought for freedom, justice, and equality for African Americans and other oppressed people, whether through poetry or print reporting, broadcast drama or political speechmaking. In the years following her husband's death, Clarice Durham mounted a campaign to keep his legacy alive. Today, via online archives, Internet users may listen to forty-two original broadcasts of Durham's Destination Freedom episodes. Web users may also hear his CBS Radio Workshop dramas and view the only two programs known to have survived from Bird of the Iron Feather. In addition, Destination Freedom episodes are available for on-site listening in the Chicago Public Library's Vivian G. Harsh Research Collection. On November 3, 2007, Durham was inducted into the Museum of Broadcast Communications' National Radio Hall of Fame.
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Noises, Smelly. All We Hear Is Radio Dada : 100 Pages Blank Journal, College Ruled Line Paper, Pocket Size: 6 X 9. Independently Published, 2021.
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(Editor), Jean Vernin, Zouhair Benkhaldoun (Editor), and Casiana Muanoz-Tuanon (Editor), eds. Astronomical Site Evaluation in the Visible and Radio Range: Iau Technical Workshop: Proceedings of a Workshop Held at Cadi Ayyad University, Marrakech, ... the Pacific Conference Series, Volume 266). Astronomical Society of the Pacific, 2002.
Find full textBook chapters on the topic "Head size ratio"
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Liu, Wanli, and Weiyan Xin. "Study on Flow Distribution on Diversion Surface at the Head of Sandbar in Bifurcated Reach." In Lecture Notes in Civil Engineering, 210–18. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-6138-0_19.
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AbstractThe rule of flow distribution in the diversion region at the head of sandbar of bifurcated reach is studied. The results show that there are diversion points and stagnation points in the diversion area at the head of sandbar in straight-bifurcated reach, and there exists diversion surface due to the difference between flow directions of surface and bottom in the diversion area at the head of sandbar in meandering-bifurcated reach. The concept of diversion surface is put forward through the study. It refers to the curved surface along vertical direction calculated according to the diversion ratio of two branches in the local reach of the head of sandbar in diversion area. Natural flow characteristics at the head of typical bifurcated reach in the middle reaches of the Yangtze River are studied based on the concept of diversion surface, and the layout principle of regulation project at the head of sandbar in bifurcated reach is put forward, that is, the project at the head of sandbar should be set near the relatively stable diversion surface if the diversion ratio of two branches is not planned to be changed, while the purpose can be achieved by deflecting the starting point of the project to one side if it is made to play the role of changing the diversion ratio of two branches. The proposal of the concept and calculation method of diversion surface provides a theoretical basis for the design and construction of location of regulation works in bifurcated reach.
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Hötte, Felix, Oliver Günther, Christoph von Sethe, Matthias Haupt, Peter Scholz, and Michael Rohdenburg. "Lifetime Experiments of Regeneratively Cooled Rocket Combustion Chambers and PIV Measurements in a High Aspect Ratio Cooling Duct." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 279–93. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-53847-7_18.
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Abstract This paper aims at experimental investigations of the life limiting mechanisms of regeneratively cooled rocket combustion chambers, especially the so called doghouse effect. In this paper the set up of a cyclic thermo-mechanical fatigue experiment and its results are shown. This experiment has an actively cooled fatigue specimen that is mounted downstream of a subscale GOX-GCH$$_{\text {4}}$$ combustion chamber with rectangular cross section. The specimen is loaded cyclically and inspected after each cycle. The effects of roughness, the use of thermal barrier coatings, the length of the hot gas phase, the oxygen/fuel ratio and the hot gas pressure are shown. In a second experiment the flow in a generic high aspect ratio cooling duct is measured with the Particle Image Velocimetry (PIV) to characterize the basic flow. The main focus of the analysis is on the different recording and processing parameters of the PIV method. Based on this analysis a laser pulse interval and the window size for auto correlation is chosen. Also the repeatability of the measurements is demonstrated. These results are the starting point for future measurements on the roughness effect on heat transfer and pressure loss in a high aspect ratio cooling duct.
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Brockmeyer, Douglas. "Traumatic Atlanto-Axial Dislocation." In Pediatric Neurosurgery, 101–7. Oxford University Press, 2019. http://dx.doi.org/10.1093/med/9780190617073.003.0012.
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The presence of atlanto-axial dislocation (AOD) must be ruled out in pediatric patients with high-energy traumatic injuries. Young children are particularly prone to AOD given the high ratio of head to body size and mass. Dynamic x-rays and distracting cervical collars should not be used if a suspicion of AOD is present, as these can lead to neurologic compromise. A condylar-C1 interval (CCI) of greater than 4 mm on cervical spine CT with coronal and sagittal reconstructions is consistent with AOD. MRI will confirm the diagnosis and extent of ligamentous injury. Careful immobilization and elevation of blood pressure should be initiated and surgical stabilization with an occiput to C2 fusion planned. Instrumentation of the craniocervical spine may be challenging based on age and anatomy. Careful intraoperative technique will result in high rates of fusion.
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Zafer Alibaba, Halil. "Adaptive Thermal Comfort of an Office for Energy Consumption-Famagusta Case." In Zero-Energy Buildings [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.101077.
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The aim of this study was to determine how much thermal comfort can be obtained through heat/energy transfers between the office/external air and the transparent/opaque surfaces of an office by combining different transparent and opaque wall surface ratios with different window opening percentages using dynamic thermal simulations. It found that the optimum window-to-wall ratio (WWR) for energy conservation is 40%, with a 20% window opening ratio. The 80% and 90% thermal comfort ranges of the adaptive thermal comfort methodology are found in May, October, September, and the yearly average, while June and August are only in the range of 80% acceptability. The office constantly loses heat through air flow with any glass size on its external facade and any window opening ratio. Moreover, all sizes of opaque and transparent internal surfaces transferred heat from outside by conduction, while the opaque wall similarly always transferred energy to heat up the office air internally and outside air externally through convection. The external glass also heats the office air by convection, except in the months of January, November, and December.
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Quiros, Peter A., and Alfredo A. Sadun. "Inherited or Congenital Optic Nerve Diseases." In Visual Fields. Oxford University Press, 2010. http://dx.doi.org/10.1093/oso/9780195389685.003.0010.
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In this chapter, we discuss inherited/congenital optic nerve diseases and their related visual fields defects. It is important for the ophthalmologist to establish, on the basis of the visual fields defect whether the optic nerve is involved and, if so, whether this is at the level of the optic disc or further back. In addition, the visual fields defect can help establish whether the etiology is acquired or congenital. If the former is the case, then the visual fields defect may reveal an insult that is rapidly progressive and hence requires immediate and aggressive management. The diseases are divided into the categories of congenital optic disc anomalies and heredodegenerative optic atrophies. Congenital optic disc anomalies include aplasias, dysplasias (hyperplasia and hypoplasia), optic nerve colobomas and pits, anomalous disc elevations: pseudopapilledema with or without hyaline bodies (drusen), and tilted disc and crescents. Absence of the optic disc (aplasia) is extremely rare and only a few case reports have been published in the literature. Optic disc size varies and may be larger (hyperplasia) or smaller (hypoplasia) than normal. Hyperplasia is much less common than hypoplasia and is usually related to ametropias. Optic nerve hypoplasia (ONH) may be unilateral or bilateral and isolated or associated with different syndromes. It may be associated with good or poor visual prognosis. It is the most common congenital optic disc anomaly encountered in pediatric ophthalmic practice. When the nerve head is slightly or segmentally reduced, especially in the presence of normal visual acuity, the diagnosis is based on comparison of disc photographs or calculation of the ratio of the disc center-to-fovea distance to disc diameter. Usually this ratio is increased in hypoplasia and, if higher than 3.0, is almost diagnostic. Sometimes the hypoplastic disc is surrounded by a ring of sclera and a ring of hyperpigmentation, described as “double-ring sign”. Maternal diabetes and use of teratogenic agents such as phenytoin, alcohol, quinine, and cocaine may be associated with ONH.
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Wang, Fang, Lixian Xiao, Jianqiu Wang, and Yongtai He. "Study on the Properties of Lauric Acid Paraffin Wax Volcanic Rock Shape-Stabilized Phase Change Materials." In Advances in Energy Research and Development. IOS Press, 2022. http://dx.doi.org/10.3233/aerd220015.
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Taking lauric acid-paraffin wax (LA-PW) volcanic rock (VR) shape-stabilized phase change materials with particle sizes of 1–3mm and 4–6mm as the research objects, analysis was made on the enthalpy, infrared spectrum, leakage characteristics, heat storage, heat release of shape-stabilized phase change materials. The results show that shape-stabilized phase change material has lower enthalpy with the increase in mass fraction of volcanic rock, but the material melting point and freezing point remain basically unchanged, and the shape-stabilized phase change material does not produce new substances, displaying stable composition. It can be seen from the leakage characteristics that, under the same ratio, shape-stabilized phase change material with a volcanic rock particle size of 1–3 mm has greater thermal stability than that with a volcanic rock particle size of 4–6 mm.
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Matthews, Michael D. "Leading Others in the Digital Age." In Head Strong, 199–215. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190870478.003.0011.
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The dominance of digital and social media in our lives presents opportunities both to enhance positive social influence and to interfere with it. Traditional military chain of command is rigid and evolved in the era before radio communication was possible. The ability to issue orders and plans in near real-time enables the speed of decision-making to be greatly increased, increasing the lethality of contemporary military operations. On the negative side, misuse of social media by individual solders can have devastating negative impacts at the strategic level. In this context topics of soft power and external manipulation of social media to disrupt morale are discussed. Psychologists may help the military better understand the positive use of information technology to achieve mission success and also develop training and other methods to mitigate against the social use of these technologies.
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Goyal, Bhupesh, Akash Pandey, and Mayur Katariya. "Effect of Porosity and Size of Pores on Structural Performance of Porous Aluminium Materials." In Advances in Transdisciplinary Engineering. IOS Press, 2022. http://dx.doi.org/10.3233/atde220756.
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Porous materials are the combination of composites of the solid phases and the pore formed within the solid phase. Material contains voids or pores are known as porous materials. Porosity, size of pores and distribution of pores in the material are important property of porous materials. Due to the significant contribution of pores and percentage porosity available inside the material provides better effect on the thermomechanical, physical and chemical properties. Porosity is considered as the most important of these parameters. Pores increases the surface area of any materials which improves the heat transfer rate in thermal use. Taking the advantage of this parameter, precautionary steps are need to be implemented to improve the utilization of waste heat which are the advantages towards the energy scenario. There are such evidences available which shows that the low grade energy can be extracted by using efficient thermal energy storage devices which directly utilized in the domestic as well as commercial purpose. Pores with varied same size, porosity and different orientation of pores inside the material also give different output in terms of thermomechanical as well as structural performance under the same input parameters. The use of porosity for the enhancement of different thermomechanical properties like thermal conductivity, heat transfer rate has attracted the current researchers. This intend to give high strength to weight ratio with better heat transfer capability and thermal conductivity. The Effect of the different orientations of pores and pore size is important for improving the heat transfer rate in porous materials. Using transient thermal analysis, comparison of solid cylindrical part and porous cylindrical part with different orientation of pore and pore size in analysis software helps to decide the best combination of parameters which improves thermal efficiency. Simulation models are prepared for same size and external dimensions for solid as well as porous material. The porous material geometry is again modelled with different pore diameters to evaluate their contribution towards the thermal properties. The connectivity of pores and the effect of pore size is analyzed for the same boundary conditions. The results are presented in terms of the effect of pore size on the thermal properties of the porous material as well as the effect of percentage porosity on these properties against the solid material are also analysed.
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Wang, Yun. "EFFICIENCIES IN POWER PLANT." In Practical Handbook of Thermal Fluid Science, 102–20. BENTHAM SCIENCE PUBLISHERS, 2023. http://dx.doi.org/10.2174/9781681089195123010009.
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INTRODUCTION In thermodynamics, several major devices related to energy conversion are introduced, including the internal combustion engines (ICE), steam turbine, boiler, heat exchanger, and heat pump. Thermal efficiency is a dimensionless performance measure of these devices. In general, thermal efficiency is the fraction of energy addition in the form of heat or thermal energy converted to useful output, as shown in Fig. (6.1), given as a percentage value. The nominally Otto-cycle ICE in automobiles can reach about 30% efficiency at the flywheel. Rankine-cycle steam turbine thermal efficiency can be as high as 41%. In heat pump cycles where heat rejection in the high-temperature side is the useful output, the efficiency is usually defined as the ratio of the rejected heat to the compressor work input, commonly called the coefficient of performance (COP). Refrigeration moves heat from a confined space and dissipates it in the atmosphere. Heat pumps move heat from one spot (often from the atmosphere or underground) to a home of business. Residential refrigerators and air conditioners are based on a vapor-compression mechanical refrigeration cycle. The former generally has a COP over 1 in practice, while the latter may have a COP over 3 to 5. The COP of heat pumps is generally higher than that of their refrigerator counterparts.
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Kosti, Siddhartha. "Numerical Study of Nanocomposites for Energy Applications." In Research Anthology on Synthesis, Characterization, and Applications of Nanomaterials, 656–84. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-8591-7.ch029.
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Nanocomposites are defined as a combination of nanoparticles reinforced into the base material. They are of very small sizes (1nm = 10-9m) and possesses higher thermal properties. They are widely utilized in different applications, like in energy, construction, biomedical, chemical, electronics, agriculture, cosmetics, etc. This chapter deals with the application of nanocomposites (SiC/Al2O3/B4C/TiO2/ZnO/SiO2) in the field of energy applications by analyzing their properties (thermal-conductivity/density/specific-heat) using numerical models. The effect of nanoparticles reinforced wt. % concentration into a base material (Al6061/Al7075/H2O) is also analyzed. Results show that nanocomposites have higher effective thermal conductivity and are suitable for high heat-releasing energy devices. It is found that the addition of nanoparticles increases the surface area to volume ratio, which further increases the energy transfer rate. Results show that nanocomposites with lower effective density are suitable when there is a requirement of reduction in weight for the same heat release application.
Conference papers on the topic "Head size ratio"
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Kirkham, Anthony J. "Optical Design of Dual-combiner Head-up Displays." In International Lens Design. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/ild.1990.ltud3.
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A head-up display ('HUD') projects collimated flight information "head up" to the pilot, being superimposed upon the outside world scene by means of a partially reflective 'combiner' glass. The lens design form is invariably a field-flattened Petzval type, working at an aperture ratio between F/0.9 and F/1.4. Fields of view are typically 25 degrees (total), with an instantaneous field of view ('IFOV') around 16° azimuth by 10° elevation. The IFOV is limited by the finite size of the optics.
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Hinnant, Chris. "Fatigue Testing and Life Estimates of Welded Flat Head Pressure Vessel Joints." In ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/pvp2006-icpvt-11-93967.
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Experimental results for the cyclic pressure fatigue of several pressure vessels with flat heads are reported and compared against various fatigue design methods. The geometry is based on a welded joint presented in a recent paper by Kalnins, Bergsten, and Rana (2005). Weld designs between the head and shell include full penetration welds completed from a single side and both sides of the shell. Unique characteristics of this test include thin plate design, a large D/t ratio, and a low membrane-to-bending ratio. These are aspects of flat head geometries which have not been widely reported in the literature. Allowable fatigue cycles for ASME Section VIII, Division 2, IIW, PD 5500, EN 13445, API 579, and the Master S-N method (proposed for the ASME Section VIII, Division 2 rewrite project) are presented. Results show that several of these design method produce non-conservative fatigue life predictions. In addition, the fatigue results demonstrate that size effects and plate thickness effects have diminishing influence for thin plates failing at less than 100,000 cycles. Finally, the fatigue strength of stainless steel is compared to carbon steel and the lack of a unified approach to stainless steel fatigue design is discussed.
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Zangeneh Kazemi, Pouya, Ponnambalam Ravi Selvaganapathy, and Chan Y. Ching. "Microfabricated EHD Pumps With High Aspect Ratio Electrodes." In ASME 2007 5th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2007. http://dx.doi.org/10.1115/icnmm2007-30140.
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This work presents the design, fabrication and testing of electrohydrodynamic (EHD) micropumps with three dimensional (3-D) electrodes. It is known that the body force on the fluid due to an electric field is increased by increased injection of charges. In this design, 3-D micro pillars are used electrodes to provide high electrode-fluid contact area and to improve charge injection. Three different electrode designs were used to investigate the effect of different parameters, such as electrode spacing and pillars size, on the pump performance. The electrodes were fabricated using nickel, and were integrated into a microchannel of dimensions 22mm × 5mm × 100μm. The micropumps were tested under a no-flow condition with ethanol as the working fluid. The preliminary results suggest that the new 3-D electrodes improve pump performance over pumps with 2-D planar electrodes. A maximum pressure head of 780 Pa was achieved at an applied voltage of 150 V with the 3-D electrodes.
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Iwanaga, Toshiaki, Satoshi Sugaya, Hiroshi Inada, and Tadashi Nomura. "Magneto-optical Recording Readout Performance Evaluation." In Optical Data Storage. Washington, D.C.: Optica Publishing Group, 1987. http://dx.doi.org/10.1364/ods.1987.wa2.
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Important factors in read and write processes for magnetooptical disk are that readout carrier to noise ratio (C/N) is high, readout signal envelope is smooth,optical efficiency is high, head size is compact and head weight is light. This paper summarizes results from many studies on optical retardation influence in magneto-optical head and disk substrate. Improvements in a magneto-optical head and disk drive system are presented.
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Colbrunn, R. W., J. J. Bottros, C. B. Greeson, A. van den Bogert, and W. K. Barsoum. "A Robotic Model of Hip Dislocation Potential: Total Hip Arthroplasty Versus Femoral Head Resurfacing." In ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53799.
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Hip dislocation often results from neck impingement and subsequent subluxation. Having a model to study impingent-free range of motion (ROM) and dislocation potential at the impingement postures can elucidate the contribution to joint stability of prosthetic design, component position, anatomical variables, and biomechanical factors. Much controversy surrounds the resurgence of femoral head resurfacing (FHR) and its biomechanical implications of retaining the femoral neck, particularly its head-neck ratio. We have developed a dynamic cadaveric robotics model that functions in real time under load-control parameters to recreate in vivo hip mechanics. This study specifically identifies and compares the impingent-free ROM and a stability index value that quantifies the dislocation potential in the native hip, femoral head resurfacing and total hip replacement (size 28, 36mm femoral heads).
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guoqiang, Sun, and Xu wu. "Ergonomics Experiment Research on Visual Characteristics of Head-Up-Display Failure Warning." In Intelligent Human Systems Integration (IHSI 2023) Integrating People and Intelligent Systems. AHFE International, 2023. http://dx.doi.org/10.54941/ahfe1002839.
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With the gradual adaptation of HUD (Head-Up-Display) in civil transportation, it was normal for civil pilots or even drivers to use it. Howev-er, any failure warning of airplane HUD was so fatal that required pilot to search for it immediately and make correct response to recover. As the pri-mary indicator of HUD warning, failure flag was well-designed especially in visual coding, which directly affected pilot’s recognition and acquisition of warning information. This research developed ergonomics experiment of HUD simulation interface and designed character size of failure flag as ex-periment variable. The participants were required to perform signal detection task and response to signal (warning occurred) or noise (no warning) accord-ingly. Therefore, both sensitivity and response bias were measured to analyze visual characteristics of failure flag and its influence on HUD warning.The mechanical failures of airplane were mainly caused by unreasonable mecha-nism structures or improper system operations, which was excluded from conse-quence of any manually operation or other outside factors . And the failure flag was shown on HUD when the sensor status was unavailable and the same parameter from different sources did not match . The representative mechanical failure flags were included with indicated airspeed warning, barometrical altitude warning, head-ing warning and ground proximity warning. Moreover, HUD failure warning could be displayed in various channels of visual, auditory and tactile manners, and the first two were most widely used channels . The visual channel of HUD failure warning was normally designed in visual coding technology, which was involved with size, position, salient of blink or textbox frame. And the auditory channel focused on volume and tone of warning voice. Specifically, the minimum character size of failure flag was 1/200 of the visual field distance, i.e., at least 0.18-inch character was required to be shown on HUD at distance of 36-inch away. In addition, the aspect ratio for English letter was required as 3:5 , and its typeface was selected as Arial . To analyze the effect of visual coding on failure flag on HUD, this research firstly developed HUD interface simu-lation, and then carried out ergonomics experiment to validate the influence of char-acter size.3.2Experiment InterfaceAs shown in Fig.3, the experiment interface was displayed on 17-inch computer screen with visual distance of 60cm. The screen resolution was 1440×900 and aver-age luminance was 120cd/m2. The participants were required to interact with exper-iment computer through normal mouse and keyboard. The HUD interface was simu-lated on GL Studio platform, and the experiment was realized using C++ and net communication technology on Visual Studio 2012. Each interaction with experiment computer was recorded and output when the experiment task was completed.3.4Experimental TaskThe participants were required to perform signal detection task during the experi-ment block, followed by the order of Latin Square fashion. And each block lasted for ten minutes with interval of five minutes. Moreover, the failure flag was designed to occur at possibility of 75%, with noise-signal ratio as 1:3. To response each failure flag, they need to press corresponding button of W/A/S/D/E on keyboard according to the specific warning. And SPACE button was expected to be pressed when no warning was shown.ResultsBoth statistics analysis and signal detection method were used to process the exper-iment results. First, descriptive statistics was used to illustrate central tendency and dispersion degree of detection performance. Then, repeated measured ANOVA was used to examine the effect of character size. In addition, sensitivity d’ and response bias were processed to evaluate the influence of failure warning based on signal detection theory.
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He, Shuquan, Baoyun Qiu, Shiji Chu, and Xiaoli Feng. "Numerical Simulation of Flow Fields and Head Losses of Trash-Barriering in Pumping Station Based on VOF Model." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-36617.
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In order to calculate flow fields behind the trash rack and the head loss caused by trash-barriering, the waterweed lump congregated in front of the trash rack was simplified as watertight entity that has the same shape and the same size of the waterweed lump. We adopted ANSYS CFX software and VOF method in numerical simulation of the flow fields of trash-barriering, calculated several schemes, and analyzed the influences of blockage. The results show that: the water level difference and the head loss of numerical simulation are consistent with results of experiment. Because of tiny water permeability of the waterweed lump in front of the trash rack, there are nuances between the flow fields behind the trash rack of numerical simulation and experiment. The specific gravity of the waterweeds is less than that of water and the waterweeds block the up part of the trash rack, which makes the flow velocity through the down unblocked part of the trash rack increase rapidly. As a result, the velocity behind the trash rack increases in the lower area, and decreases, even the backflow appears in the upper area. With the increase of the blockage ratio, the turbulence scale behind the trash rack increases. When the blockage ratio increases to 0.7, the velocity uniformity already decreases to −1.57. The head loss of trash-barriering increases when the blockage ratio and the velocity in front of the trash rack increase. For certain velocity in front of the trash rack, when the blockage ratio reaches 0.6∼0.7, the head loss would increase rapidly.
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Howard, Jonathon, and Abraham Engeda. "Analysis and Design of Centrifugal Blowers for the Pressure Ratio Range 1.2 - 1.8." In ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-59821.
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Abstract Centrifugal/centrifugal compressor designs within pressure ratio range of 2.0–4.0 have well-established guidelines for most common gases, and it is possible to determine optimum compressor geometry for numerous applications as characterized by specific speed or flow coefficient. Specific speed can be correlated to various combinations of inlet tip-exit diameter ratio, inlet hub-tip diameter ratio, blade exit back-sweep, and inlet-tip absolute tangential velocity for solid body pre-whirl. For centrifugal compressors in the pressure ratio range of 1.2–1.8, commonly known as blowers, there lacks organized and systematic optimum design procedures. Blowers, among many others uses, are widely used in HVAC, and provide air for ventilation and industrial process requirements. Due to broad applications in industry, blowers comprise an important sub-group of turbomachinery. This paper provides analysis and design data for blowers in the pressure ratio range of 1.2–1.8. Specific speed is determined from the data provided, and accurate correlations to possible achievable maximum efficiencies are established within a good operational range. Furthermore, plots of impeller exit flow angle, inlet tip-exit diameter ratio, inlet hub-tip diameter ratio, head coefficient, and blade exit back-sweep are provided over a range of specific speeds for various tip speeds to permit rapid selection of optimum blower size and shape for a variety of applications. The design procedure follows a method that enables efficient blade passage sizing. When the blower inlet and outlet velocities, diameters, blade widths, and blade angles are determined and fixed, the blade passage and profile will be sized by applying an energy, momentum, and continuity balance analysis. The application of these equations equates the proper pressure and velocity distribution throughout the blower impeller. Generally, the passage is designed to accommodate an optimum prescribed diffusion rate.
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Saczalski, Kenneth J., Mark C. Pozzi, and Joseph Lawson Burton. "Comparison of High and Low Speed Rear-Impact Head and Neck Injury Risk Measures Related to Occupant Size and Vehicle Seat Strength Characteristics." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-68492.
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This study demonstrates the use of efficient inferred statistical “factorial methods” for scientifically evaluating, with a relatively few tests, the rear-impact occupant “head and neck injury risk” performance of 2 different types of vehicle front seats, with adjustable headrests, when various size occupants are subjected to high and low impact severities. The 2 seat types studied included the stronger “belt-integrated seat” (BIS) designs, with restraints attached and having strength levels beyond 14 kN, and the more common but weaker single recliner (SR) seats, without attached restraints and having only about 3.2 kN strength. Sled-body-buck systems and full vehicle to barrier tests were run with “matched pairs” of surrogates in the 2 seat types at speed changes of 12.5 to 50 kph. Three sizes of Hybrid-III adult surrogates (i.e. 52 kg small female, 80 kg average male, and an average male surrogate ballasted to about 110 kg) were used in the evaluations. Also, some tests were run with 6 year-old Hybrid-III child surrogates located behind the front seats due to interest in potential child injury from collapsing front seats. The 2-level factorial method, combined with a biomechanical ratio comparison and a “student-t” test evaluation, were used to compare safety performance of the 2 seat designs. The resulting data analysis indicates that, in the mid to high range of rear impact severity (i.e. 20 to 50 kph), the stronger BIS seat systems tend to provide greatly improved “head-neck” protection over the weaker SR type seats for both the front seated adult occupants and rear seated children. At the low range of impact severity (i.e. 12.5 to 19 kph) there was no significant statistical difference between either seat types, except that the headrests of both could be improved.
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Shu, Xue-Dao, Tai-Zhu Chen, Ying Chang, Ying Zhu, and Wen-Wei Gong. "Forming Technology and Microstructure Distribution of Automobile Oil Pump Shaft by Extruded Cross Wedge Rolling." In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-10341.
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Abstract In order to improve the material utilization ratio of automobile oil pump shaft, the extrusion wedge cross rolling process was developed to form automobile oil pump shaft, the results show that the volume of the blank head produced by extrusion cross wedge rolling is reduced by about 75% compared with that produced by traditional cross wedge rolling, and the material utilization ratio can be increased to about 95%. The microstructure distribution of automobile oil pump shaft formed by this process was studied systematically by fem simulation and experiment, get the forming process can make the grain size of oil pump shaft rolling parts refine continuously, and finally obtain fine and uniform grain structure. The average grain size measured by the experiment is in good agreement with the simulation results. The research results lay a theoretical foundation for reducing oil pump cost and improving life.
Reports on the topic "Head size ratio"
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Willits, Daniel H., Meir Teitel, Josef Tanny, Mary M. Peet, Shabtai Cohen, and Eli Matan. Comparing the performance of naturally ventilated and fan-ventilated greenhouses. United States Department of Agriculture, March 2006. http://dx.doi.org/10.32747/2006.7586542.bard.
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The objectives of this project were to predict the performance of naturally and fan-ventilated greenhouses as a function of climate, type of crop, evaporative cooling and greenhouse size, and to estimate the effects of the two cooling systems on yield, quality and disease development in the different crops under study. Background In the competitive field of greenhouse cultivation, growers and designers in both the US and Israel are repeatedly forced to choose between naturally ventilated (NV) and fan ventilated (FV) cooling systems as they expand their ranges in an effort to remain profitable. The known advantages and disadvantages of each system do not presently allow a clear decision. Whether essentially zero operating costs can offset the less dependable cooling of natural ventilation systems is question this report hopes to answer. Major Conclusions US It was concluded very early on that FV greenhouses without evaporative pad cooling are not competitive with NV greenhouses during hot weather. During the first year, the US team found that average air temperatures were always higher in the FV houses, compared to the NV houses, when evaporative pad cooling was not used, regardless of ventilation rate in the FV houses or the vent configuration in the NV houses. Canopy temperatures were also higher in the FV ventilated houses when three vents were used in the NV houses. A second major conclusion was that the US team found that low pressure fogging (4 atm) in NV houses does not completely offset the advantage of evaporative pad cooling in FV houses. High pressure fog (65 atm) is more effective, but considerably more expensive. Israel Experiments were done with roses in the years 2003-2005 and with tomatoes in 2005. Three modes of natural ventilation (roof, side and side + roof openings) were compared with a fan-ventilated (with evaporative cooling) house. It was shown that under common practice of fan ventilation, during summer, the ventilation rate is usually lower with NV than with FV. The microclimate under both NV and FV was not homogeneous. In both treatments there were strong gradients in temperature and humidity in the vertical direction. In addition, there were gradients that developed in horizontal planes in a direction parallel to the direction of the prevailing air velocity within the greenhouse. The gradients in the horizontal direction appear to be larger with FV than with NV. The ratio between sensible and latent heat fluxes (Bowen ratio) was found to be dependent considerably on whether NV or FV is applied. This ratio was generally negative in the naturally ventilated house (about -0.14) and positive in the fan ventilated one (about 0.19). Theoretical models based on Penman-Monteith equation were used to predict the interior air and crop temperatures and the transpiration rate with NV. Good agreement between the model and experimental results was obtained with regard to the air temperature and transpiration with side and side + roof ventilation. However, the agreement was poor with only roof ventilation. The yield (number of rose stems longer than 40 cm) was higher with FV
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Seginer, Ido, Daniel H. Willits, Michael Raviv, and Mary M. Peet. Transpirational Cooling of Greenhouse Crops. United States Department of Agriculture, March 2000. http://dx.doi.org/10.32747/2000.7573072.bard.
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Background Transplanting vegetable seedlings to final spacing in the greenhouse is common practice. At the time of transplanting, the transpiring leaf area is a small fraction of the ground area and its cooling effect is rather limited. A preliminary modeling study suggested that if water supply from root to canopy is not limiting, a sparse crop could maintain about the same canopy temperature as a mature crop, at the expense of a considerably higher transpiration flux per leaf (and root) area. The objectives of this project were (1) to test the predictions of the model, (2) to select suitable cooling methods, and (3) to compare the drought resistance of differently prepared seedlings. Procedure Plants were grown in several configurations in high heat load environments, which were moderated by various environmental control methods. The difference between the three experimental locations was mainly in terms of scale, age of plants, and environmental control. Young potted plants were tested for a few days in small growth chambers at Technion and Newe Ya'ar. At NCSU, tomato plants of different ages and planting densities were compared over a whole growing season under conditions similar to commercial greenhouses. Results Effect of spacing: Densely spaced plants transpired less per plant and more per unit ground area than sparsely spaced plants. The canopy temperature of the densely spaced plants was lower. Air temperature was lower and humidity higher in the compartments with the densely spaced plants. The difference between species is mainly in the canopy-to-air Bowen ratio, which is positive for pepper and negative for tomato. Effect of cooling methods: Ventilation and evaporative pad cooling were found to be effective and synergitic. Air mixing turned out to be very ineffective, indicating that the canopy-to-air transfer coefficient is not the limiting factor in the ventilation process. Shading and misting, both affecting the leaf temperature directly, proved to be very effective canopy cooling methods. However, in view of their side effects, they should only be considered as emergency measures. On-line measures of stress: Chlorophyll fluorescence was shown to accurately predict photosynthesis. This is potentially useful as a rapid, non-contact way of assessing canopy heat stress. Normalized canopy temperature and transpiration rate were shown to correlate with water stress. Drought resistance of seedlings: Comparison between normal seedlings and partially defoliated ones, all subjected to prolonged drought, indicated that removing about half of the lowermost leaves prior to transplanting, may facilitate adjustment to the more stressful conditions in the greenhouse. Implications The results of this experimental study may lead to: (1) An improved model for a sparse canopy in a greenhouse. (2) A better ventilation design procedure utilizing improved estimates of the evaporation coefficient for different species and plant configurations. (3) A test for the stress resistance of transplants.
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FINITE ELEMENT SIMULATION FOR ULTRA-HIGH-PERFORMANCE CONCRETE-FILLED DOUBLE-SKIN TUBES EXPOSED TO FIRE. The Hong Kong Institute of Steel Construction, August 2022. http://dx.doi.org/10.18057/icass2020.p.263.
Full textAbstract:
Ultra-high-performance concrete (UHPC) or ultra-high-strength concrete (UHSC) are alternatively used to reduce construction materials, thereby achieving more sustainable constructions. Moreover, engaging the advantages of concrete cores and outer steel tubes in concrete-filled steel tubes (CFST) or ductile concrete-filled double-skin tubes (CFDST) is of great interest for the better performance of such members under fire. Nevertheless, current design provisions do not provide design models for UHPC-filled double-skin tubes under fire, and existing finite-element (FE) methodologies available in the literature may not accurately simulate the behaviour of CFDST exposed to fire. Therefore, this paper develops a comprehensive FE protocol implementing the scripting technique to model CFDST members for heat transfer and coupled (simultaneously or sequentially) thermal-stress analyses. Various modelling parameters incorporated in the proposed FE routine include the cross-sectional geometry (circular, elliptical, hexagonal, octagonal, and rectangular), the size (width, diameter, and wall thickness), interactions, meshing, thermal- and mechanical-material properties, and boundary conditions. The detailed algorithm for heat transfer analysis is presented and elaborated via a flow chart. Validations, verifications, and robustness of the developed FE models are established based on extensive comparison studies with existing fire tests available in the literature. As a result, and to recognize the value of the current FE methodology, an extensive parametric study is conducted for different affecting parameters (e.g., nominal steel ratio, hollowness ratio, concrete cylindrical strength, yield strength of metal tubes, and width-to-thickness ratio). Extensive FE results are used for optimizing the fire design of such members. Consequently, a simplified and accurate analytical model that can provide the axial load capacity of CFDST columns under different fire ratings is presented
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Analysis of Recompression-Regeneration sCO 2 Combined Cycle Utilizing Marine Gas Turbine Exhaust Heat: Effect of Operating Parameters. SAE International, July 2022. http://dx.doi.org/10.4271/2022-01-5059.
Full textAbstract:
Gas turbines are fast being explored to replace the existing steam or diesel-based power packs to propel marine transportation. Marine gas turbines have already come to power high-speed marine vessels transporting perishable goods as well as high-speed naval fleets. This article investigates the potential of gas turbine to be made hybrid with supercritical recompression-regeneration carbon dioxide (CO2) cycle drawing thermal energy from the exhaust of marine gas turbines. The recompression unit acts as the topping cycle and the regeneration unit acts as the bottoming cycle of the proposed combined supercritical CO2 (sCO2) cycle. The cycle has a maximum temperature of 530°C and supercritical pressure of 20 MPa. The proposed sCO2 powerplant is compact because of the smaller size of the turbomachinery, owing to the low specific volume of working fluid in the supercritical range. The proposed combined cycle is analyzed for different operating conditions including maximum temperature, minimum temperature, and cycle pressure ratio. The thermal efficiency of the proposed sCO2 cycle is 30.77% and efficiency of the hybrid cycle (including marine GT) is 58.17%, i.e., enhancement in thermal efficiency of the marine vessel power pack by 18.6%. Further the power output of the gas turbine-sCO2 hybrid cycle is enhanced by nearly 23.5% to 45.7 megawatts (MW). The second law of thermodynamic efficiency of the proposed combined cycle is close to 52.5%. The proposed hybrid gas turbine-sCO2 cycle has immense potential to replace the aging propulsion systems of existing marine vessels as the proposed power cycle is greener and more compact.