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1
Wu, Qing, Colin Cole, Maksym Spiryagin, and Weihua Ma. "Preload on draft gear in freight trains." Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 232, no. 6 (October 31, 2017): 1615–24. http://dx.doi.org/10.1177/0954409717738849.
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Adjusting draft gear preloads requires minimum or no structural changes to the existing coupler systems. Better or optimal preloads are more promising to be implemented than modifying other parameters such as wedge angles and spring stiffness. This paper presents a method to model draft gear preloads and investigates the numerical step-size requirements for the simulations of draft gear preloads. The implications of preloads on the draft gear impact performance, longitudinal train dynamics performance and coupler fatigue damage were also investigated. The results show that step sizes of less than 2.5 and 0.2 ms (with the fourth Runge–Kutta solver) are recommended to simulate preloads during the simulations of longitudinal train dynamics and wagon impacts, respectively. Wagon impact simulations indicate that the increase of draft gear preloads can noticeably decrease the maximum draft gear deflection during wagon impacts. Longitudinal train dynamics simulations for a distributed power train with 214 vehicles on a 320 km long track were conducted. The longitudinal train dynamics simulations indicate that, when the preload is increased from 0 to 100 kN, the difference of maximum vehicle accelerations is insignificant. When the draft gear preload is further increased to 200 or 300 kN, maximum vehicle accelerations are evidently increased. Draft gear preloads do not noticeably influence the maximum tensile coupler forces. However, preloads have evident implications for maximum compressive coupler forces, especially for the second half of the train. Coupler fatigue damage calculations show that the sum of coupler fatigue damage evidently decreases with the increase of draft gear preload. The damage for the zero preload case is 8.7 times than that of the 300 kN preload case.
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Astbury, Nerys M., Emma J. Stevenson, Penelope Morris, Moira A. Taylor, and Ian A. Macdonald. "Dose–response effect of a whey protein preload on within-day energy intake in lean subjects." British Journal of Nutrition 104, no. 12 (September 28, 2010): 1858–67. http://dx.doi.org/10.1017/s000711451000293x.
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The effect of consuming different amounts of whey protein on appetite and energy intake was investigated in two separate studies using randomised, crossover designs. Healthy-weight men and women (range: BMI 19·0–25·0 kg/m2, age 19·4–40·4 years) consumed one of four 400 ml liquid preloads, followed by an ad libitum test meal 90 min later. In study 1, preloads were 1675 kJ with 12·5, 25 or 50 % of energy from protein, and in study 2, preloads were 1047 kJ with 10, 20 or 40 % energy from protein. Flavoured water was used as the control in both the studies. Appetite ratings were collected immediately before 30, 60 and 90 min after consuming the preloads; and immediately, 30 and 60 min after consuming the test meal. In study 1, energy intake following the control preload (4136 (sem 337) kJ) was significantly higher than each of the 12·5 % (3520 (sem 296) kJ), 25 % (3384 (sem 265) kJ) and 50 % (2853 (sem 244) kJ) protein preloads (P < 0·05). Intake after the 12·5 % preload was significantly higher than following 25 and 50 % preloads (P < 0·05). In study 2, energy intake following the control preload (4801 (sem 325) kJ) was higher than following the 10 % (4205 (sem 310) kJ), 20 % (3988 (sem 250) kJ) and 40 % (3801 (sem 245) kJ) protein preloads (P < 0·05). There were no differences in subjective appetite ratings between preloads in either study. These findings indicate a dose–response effect of protein content of the preload on energy intake at a subsequent meal.
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Szlosarek, Robert, and Matthias Kröger. "Fatigue behavior of bolted boreholes under various preloads." Materials Testing 64, no. 2 (February 1, 2022): 195–201. http://dx.doi.org/10.1515/mt-2021-2032.
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Abstract Bolted joints are one of the most used joining technologies in engineering. It is possible to join different kind of materials and to transmit heavy loads. Nevertheless, they are vulnerable to fatigue cracks. The present research investigates the dependency between the preload of the bolt and the initiation of a fatigue crack in the bolted sheet. Therefore, a representative bolt connection with a bolt of size M22 was selected in combination with a 5 mm thick sheet made of steel S355MC (1.0976). The bolted sheet was loaded by a fluctuating tension load and a load ratio of 0.1. The test results show a strong correlation of the preload and the number of load cycles to crack for preloads from 0 kN to 30 kN. The load cycles to crack are increased by about factor 20 by using a preload in contrast to the sheet without any preload. For higher preloads, the load cycles to crack does not change considerably. However, the crack initiation location changes by increasing the preload. For small preloads, the crack starts at the bolt hole, and for high preloads, the crack starts at the fretting zone.
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Hulshof, Toine, Cees De Graaf, and Jan A. Weststrate. "Short-term satiating effect of the fat replacer sucrose polyester (SPE) in man." British Journal of Nutrition 74, no. 4 (October 1995): 569–85. http://dx.doi.org/10.1079/bjn19950159.
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The effects of different amounts of the non-absorbable fat replacer sucrose polyester (SPE), water, and fat added to six warm preload lunches on feelings of appetite and food intake were investigated in two studies that were replicates of each other. In the first study thirty-nine subjects consumed rice preloads; in the second study thirty-five subjects consumed macaroni preloads. The six preloads were fixed on three energy levels: 1·8, 2·7, or 3·7MJ. At 2 h after preload consumption a test-meal buffet of thirty-one products was presented. Food intake was recorded on the study day, and the day after the study day. For women no energy compensation occurred in either study. Men showed a tendency to compensate for the energy differences between the preloads. However, when the fat of the preloads was replaced by SPE, energy compensation was less than 50% and non-significant. Statistically significant energy-compensation (66 %) was found when fat was replaced by water. No macronutrient-specific compensation occurred in men or women in either study. Lower total fat and energy intakes were found with the preloads where fat was replaced by SPE compared with the preloads containing fat. The appetite ratings were in line with the energy intake values, with no differences in women, and higher appetite ratings after the lower energy preloads in men. This short-term study indicates that SPE may be a useful aid to reduce fat and energy intakes.
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Wang, Zhi Gang, Ze Yu Weng, Qi Peng Cao, Jin Hu Mei, and Fu Hong Zhu. "Study on the Relation of Wheel Hub Bearing Preload and Natural Frequency by Dynamic Test." Key Engineering Materials 693 (May 2016): 1453–57. http://dx.doi.org/10.4028/www.scientific.net/kem.693.1453.
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Preloads have an important influence on working performance and service life of wheel hub bearing. In order to study the action mechanism, carrying out the study on the effect of wheel hub bearing preload on the natural frequency is particularly important. Aiming at a certain type of car wheel hub bearing, the wheel hub bearing swept-sine vibration test system is built, and the conclusion is got after testing on wheel hub bearings with different preloads. The conclusion is that the natural frequency of wheel hub bearing increases with preload increasing, but increasing trend tends to slow.
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PATEL, VIPULKUMAR ISHVARBHAI, QING QUAN LIANG, and MUHAMMAD N. S. HADI. "NUMERICAL ANALYSIS OF CIRCULAR CONCRETE-FILLED STEEL TUBULAR SLENDER BEAM-COLUMNS WITH PRELOAD EFFECTS." International Journal of Structural Stability and Dynamics 13, no. 03 (April 2013): 1250065. http://dx.doi.org/10.1142/s0219455412500654.
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This paper presents a new numerical model for the nonlinear analysis of circular concrete-filled steel tubular (CFST) slender beam-columns with preload effects, in which the initial geometric imperfections, deflections caused by preloads, concrete confinement and second order effects are incorporated. Computational algorithms are developed to solve the nonlinear equilibrium equations. Comparative studies are undertaken to validate the accuracy of computational algorithms developed. Also included is a parametric study for examining the effects of the preloads, column slenderness, diameter-to-thickness ratio, loading eccentricity, steel yield stress and concrete confinement on the behavior of circular CFST slender beam-columns under eccentric loadings. The numerical model is demonstrated to be capable of predicting accurately the behavior of circular CFST slender beam-columns with preloads. The preloads on the steel tubes can affect significantly the behavior of CFST slender beam-columns and must be taken into account in the design.
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Koller, Heiko, Michael Mayer, Juliane Zenner, Herbert Resch, Alfred Niederberger, Johann Fierlbeck, Wolfgang Hitzl, and Frank L. Acosta. "Implications of the center of rotation concept for the reconstruction of anterior column lordosis and axial preloads in spinal deformity surgery." Journal of Neurosurgery: Spine 17, no. 1 (July 2012): 43–56. http://dx.doi.org/10.3171/2012.4.spine11198.
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Object In thoracolumbar deformity surgery, anterior-only approaches are used for reconstruction of anterior column failures. It is generally advised that vertebral body replacements (VBRs) should be preloaded by compression. However, little is known regarding the impact of different techniques for generation of preloads and which surgical principle is best for restoration of lordosis. Therefore, the authors analyzed the effect of different surgical techniques to restore spinal alignment and lordosis as well as the ability to generate axial preloads on VBRs in anterior column reconstructions. Methods The authors performed a laboratory study using 7 fresh-frozen specimens (from T-3 to S-1) to assess the ability for lordosis reconstruction of 5 techniques and their potential for increasing preloads on a modified distractable VBR in a 1-level thoracolumbar corpectomy. The testing protocol was as follows: 1) Radiographs of specimens were obtained. 2) A 1-level corpectomy was performed. 3) In alternating order, lordosis was applied using 1 of the 5 techniques. Then, preloads during insertion and after relaxation using the modified distractable VBR were assessed using a miniature load-cell incorporated in the modified distractable VBR. The modified distractable VBR was inserted into the corpectomy defect after lordosis was applied using 1) a lamina spreader; 2) the modified distractable VBR only; 3) the ArcoFix System (an angular stable plate system enabling in situ reduction); 4) a lordosizer (a customized instrument enabling reduction while replicating the intervertebral center of rotation [COR] according to the COR method); and 5) a lordosizer and top-loading screws ([LZ+TLS], distraction with the lordosizer applied on a 5.5-mm rod linked to 2 top-loading pedicle screws inserted laterally into the vertebra). Changes in the regional kyphosis angle were assessed radiographically using the Cobb method. Results The bone mineral density of specimens was 0.72 ± 22.6 g/cm2. The maximum regional kyphosis angle reconstructed among the 5 techniques averaged 9.7°−16.1°, and maximum axial preloads averaged 123.7–179.7 N. Concerning correction, in decreasing order the LZ+TLS, lordosizer, and ArcoFix System outperformed the lamina spreader and modified distractable VBR. The order of median values for insertion peak load, from highest to lowest, were lordosizer, LZ+TLS, and ArcoFix, which outperformed the lamina spreader and modified distractable VBR. In decreasing order, the axial preload was highest with the lordosizer and LZ+TLS, which both outperformed the lamina spreader and the modified distractable VBR. The technique enabling the greatest lordosis achieved the highest preloads. With the ArcoFix System and LZ+TLS, compression loads could be applied and were 247.8 and 190.6 N, respectively, which is significantly higher than the insertion peak load and axial preload (p < 0.05). Conclusions Including the ability for replication of the COR in instruments designed for anterior column reconstructions, the ability for lordosis restoration of the anterior column and axial preloads can increase, which in turn might foster fusion.
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Paretkar, Dadhichi, Marleen Kamperman, David Martina, Jiahua Zhao, Costantino Creton, Anke Lindner, Anand Jagota, Robert McMeeking, and Eduard Arzt. "Preload-responsive adhesion: effects of aspect ratio, tip shape and alignment." Journal of The Royal Society Interface 10, no. 83 (June 6, 2013): 20130171. http://dx.doi.org/10.1098/rsif.2013.0171.
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We tested the adhesive response of polymer surfaces structured with arrays of cylindrical fibrils having diameters of 10–20 µm and aspect ratios 1–2.4. Fibrils had two different tip shapes of end-flaps and round edges. A preload-induced mechanical buckling instability of the fibrils was used to switch between the states of adhesion and non-adhesion. Non-adhesion in fibrils with round edges was reached at preloads that caused fibril buckling, whereas fibrils with end-flaps showed adhesion loss only at very high preloads. The round edge acted as a circumferential flaw prohibiting smooth tip contact recovery leading to an adhesion loss. In situ observations showed that, after reversal of buckling, the end-flaps unfold and re-form contact under prevailing compressive stress, retaining adhesion in spite of buckling. At very high preloads, however, end-flaps are unable to re-form contact resulting in adhesion loss. Additionally, the end-flaps showed varying contact adaptability as a function of the fibril–probe alignment, which further affects the preload for adhesion loss. The combined influence of preload, tip shape and alignment on adhesion can be used to switch adhesion in bioinspired fibrillar arrays.
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Melanson, Kathleen J., Margriet S. Westerterp-Plantenga, Wim H. M. Saris, Françoise J. Smith, and L. Arthur Campfield. "Blood glucose patterns and appetite in time-blinded humans: carbohydrate versus fat." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 277, no. 2 (August 1, 1999): R337—R345. http://dx.doi.org/10.1152/ajpregu.1999.277.2.r337.
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We assessed the extent to which a possible synchronization between transient blood glucose declines and spontaneous meal initiation would lend support to the interpretation of a preload study with isoenergetic (1 MJ) isovolumetric high-fat or simple carbohydrate (CHO) preload drinks. Ten men (18–30 yr) fasted overnight and then were time blinded and made aware that they could request meals anytime. At first meal requests, volunteers consumed a preload; ad libitum meals were offered at subsequent requests. Postabsorptively, transient declines in blood glucose were associated with meal requests (χ2 = 8.29). Subsequent meal requests occurred during “dynamic declines” in blood glucose after the peak induced by drink consumption (100%). These meal requests took twice as long to occur after high-fat than after CHO preloads (fat = 126 ± 21, CHO = 65 ± 15 min), consistent with differences in interpolated 65-min satiety scores (fat = 38 ± 8.2, CHO = 16 ± 4). Postprandially, transient blood glucose declines were associated with meal requests (χ2 = 4.30). Spontaneous meal initiations were synchronized with transient and dynamic blood glucose declines. Synchronization of intermeal interval and dynamic declines related to higher satiating efficiency from high-fat preloads than from simple CHO preloads.
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Fukuoka, Toshimichi, and Tomohiro Takaki. "Finite Element Simulation of Bolt-Up Process of Pipe Flange Connections." Journal of Pressure Vessel Technology 123, no. 3 (December 19, 2000): 282–87. http://dx.doi.org/10.1115/1.1358842.
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Achieving uniform bolt preload is difficult when tightening a pipe flange with a number of bolts. Several bolt-tightening strategies have been proposed so far for achieving uniform bolt preloads. It seems, however, that effective guidelines for tightening pipe flange connections have not been established. In this study, a numerical approach is presented for estimating the scatter in bolt preloads and achieving the uniform bolt preloads when tightening each bolt one by one in an arbitrary order. Numerical analyses are conducted using three-dimensional FEM as an elastic contact problem. The analytical objects are pipe flanges specified in JIS B 2238 with an aluminum gasket inserted. The validity of the numerical procedures proposed here is ascertained by experiment.
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Rolls, B. J., S. Kim, A. L. McNelis, M. W. Fischman, R. W. Foltin, and T. H. Moran. "Time course of effects of preloads high in fat or carbohydrate on food intake and hunger ratings in humans." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 260, no. 4 (April 1, 1991): R756—R763. http://dx.doi.org/10.1152/ajpregu.1991.260.4.r756.
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A high-carbohydrate (CHO) yogurt (81% CHO) and a high-fat yogurt (65% fat), containing similar levels of protein, were given in equal volumes as preloads to 14 normal-weight, nondieting males and 14 normal-weight, nondieting females. The yogurts were formulated to have similar energy densities and sensory properties, so that differences in responses to the preloads would depend on postingestive physiological effects. Three intervals (30, 90, and 180 min) between the preloads and a self-selection meal consisting of a variety of foods were utilized. The self-selection meal was served at the subject's normal lunchtime under all conditions. In the 30-min-delay condition, subjects accurately compensated for the calories in the preloads compared with a no-preload condition, but as the interval increased, compensation was less precise. No significant differences in subsequent food intake were found between the high-CHO and high-fat yogurts at any time interval. Also, there were no differences in ratings of hunger and fullness between the yogurts. The macronutrient composition of the preloads did not affect the types of foods, or macronutrients, consumed at lunch.
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Muurahainen, N. E., H. R. Kissileff, J. Lachaussee, and F. X. Pi-Sunyer. "Effect of a soup preload on reduction of food intake by cholecystokinin in humans." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 260, no. 4 (April 1, 1991): R672—R680. http://dx.doi.org/10.1152/ajpregu.1991.260.4.r672.
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Cholecystokinin octapeptide (CCK-8) or saline was intravenously infused for 5 min before and 5 min during a meal of macaroni and beef, served 20 min after a preload of either 100 or 500 g of soup to 12 nonobese men. Intake of the test meal was significantly lower when CCK-8 was given, following the larger preload, than after any of the other treatments. There were no significant differences among the other three treatment conditions. These results are consistent with the hypothesis that gastric, but not merely pregastric, stimulation interacts with CCK-8 to reduce food intake in humans. Although gastric filling seems to be the most likely stimulus for the interactive effect with CCK-8, other factors such as activation of nutrient-sensitive sites cannot be eliminated. In addition, hunger ratings were significantly lower immediately after the larger soup preloads than after the smaller. Hunger ratings after the soup also correlated better with test-meal intake after the large soup preloads with and without CCK-8 than after the smaller preloads. Hunger did not correlate significantly with test meal intake after the small soup preload with CCK-8. These results suggest that hunger ratings are more sensitive predictors of intake when the stomach is relatively full (i.e., after a large preload) than when it is relatively empty (i.e., after a small preload) at the time the hunger rating is taken.
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Reid, Marie, and Richard Hammersley. "The effects of sucrose and maize oil on subsequent food intake and mood." British Journal of Nutrition 82, no. 6 (December 1999): 447–55. http://dx.doi.org/10.1017/s0007114599001701.
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The effects of sucrose and oil preloads were explicitly compared in a single-blind controlled trial using a between-subjects design. Eighty adult subjects (forty-three male, thirty-seven female) aged 18–50 years received at 11.00 hours one of four yoghurt preloads. All were 80 g low-fat, unsweetened yoghurt (188 kJ), containing additionally (1) saccharin (control, 23 kJ), or (2) 40 g sucrose (859 kJ), (3) 40 g maize oil (1569 kJ), (4) 20 g sucrose, 20 g maize oil (1213 kJ). Subjects were normal eaters and of normal weight (male mean weight: 68·8 (sd 3·2) kg, BMI 21·8 (sd 1·6) kg/m2; female mean weight: 53·7 (sd 5·1) kg, BMI 20·4 (sd 1·2) kg/m2). Food intake was measured with a food diary and mood with ten single Likert scales. ANOVA was conducted using preload type (saccharin, sucrose, oil, sucrose + oil), sex (male, female) and early v. late breakfast times as factors. Mood was analysed using the same design, with time of rating (immediate, 60 min, 120 min) as an additional factor. Men ate more after the saccharin preload than after the other preloads, but did not vary the time of their next solid food. Women increased the intermeal interval only after the oil preload, which also had the highest energy content value, but did not vary the energy content of their next solid food. The saccharin preload decreased rated tiredness at 2 h compared with the sucrose preload, possibly due to its lower energy content. The preloads containing sucrose or sucrose + oil increased calmness between 1 and 2 h afterwards, compared with the saccharin preload. It is concluded that both sucrose and oil increase the intermeal interval in men, but that women are less sensitive to preloading. The mood effects suggest that tiredness after carbohydrate at 2 h may in part be a decrease in rated energy compared with the increased rated energy found after a preload with low energy content. Carbohydrate may genuinely increase calmness. These effects apply to non-restrained eaters of normal weight.
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Michael, Welch. "Bolted Joint Preload Distribution from Torque Tightening." Strojnícky časopis - Journal of Mechanical Engineering 71, no. 2 (November 1, 2021): 329–42. http://dx.doi.org/10.2478/scjme-2021-0039.
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Abstract The purpose of this paper is to develop an understanding of how bolt preloads are distributed within a joint as each bolt is tightened in turn by the use of a calibrated torque wrench. It discusses how the order that the joints nuts/bolts are tightened can affect the final bolt preload. It also investigates the effect on incrementally increasing the bolt preload through a series of applications of the controlled torque tightening sequence. Classical analysis methods are used to develop a method of analysis that can be applied to most preloaded bolted joints. It is assumed that the static friction coefficient is approximately 15% less than the dynamic friction. It is found that the bolt preload distribution across the joint can range from slightly above the target preload to significantly less than the target preload. The bolts with a preload greater than the target preload are found to be those tightened towards the end of the tightening sequence, usually located close to the outer edges of the joint’s bolt array. The bolts with a preload less than the target preload are those tightened early in the tightening sequence, located centrally within the joints bolt array. The methods presented can be used to optimise bolted joint design and assembly procedures. Optimising the design of preloaded bolted joints leads to more efficient use of the joints.
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Shih, Wei-Cheng, Furqan Furqanuddin, Po-Lin Lee, and Jui-Pin Hung. "Monitoring of Preload Variation of Linear Guide Positioning Stage Using Artificial Neural Network." Applied Sciences 11, no. 17 (August 27, 2021): 7902. http://dx.doi.org/10.3390/app11177902.
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In this paper, we propose an artificial neural network (ANN) predictive model to identify the linear guide preload based on the measured vibration features of the feeding stage. In this study, the relationship between the contact stiffness and preload level of a linear guide was investigated by an experimental analysis. Furthermore, the stage was assembled with different linear guide preloads for the motion test to assess the vibrations. Vibration levels with changes in preload values and feeding rates were examined. The predictive models were established and verified based on a dataset collected from tests using an ANN approach. The ANN models were shown to have an excellent accuracy of 96.5% in the training datasets, which were collected from stages with sliding blocks rated at consistent preloads. The average percentage prediction error in the verification dataset was approximately 8.54–11.23%. This is probably because the stage with an unevenly distributed preload in the sliding blocks induces vibration with more fluctuation, which eventually affects the prediction accuracy. The results verify the feasibility of online preload identification for the condition monitoring of the feeding system.
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Millithaler, Pierre, Émeline Sadoulet-Reboul, Morvan Ouisse, Jean-Baptiste Dupont, and Noureddine Bouhaddi. "Identification of representative anisotropic material properties accounting for friction and preloading effects: A contribution for the modeling of structural dynamics of electric motor stators." Journal of Vibration and Control 24, no. 2 (August 8, 2016): 237–59. http://dx.doi.org/10.1177/1077546316637941.
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Simulating the dynamic behavior and determining equivalent material properties for anisotropic models, superelements or structures subjected to preloads or friction remains a challenging issue. Amongst other practical applications, modeling interactions between the steel sheets in industrial magnetic cores of electric motor stators is a complex task, as it requires anticipating behavioral heterogeneities in the structure, and possibly represents significantly costly operations for performing modal or dynamic response simulations. In this article, a method for identifying equivalent material properties to anisotropic structures is developed, which is able to take into account the influence of preloads and friction on the material properties, later used in structural dynamics simulations. The proposed approach can be used with superelements, converting stiffness matrices into elasticity matrices. The method is first applied to a triclinic model, and recreates its elasticity matrix with little derivation. Then, an equivalent linear material is computed for a continuous structure under preloading. Compared at low frequencies, the vibration behavior of the preloaded structure and its equivalent effective media are in good agreement. The operation is repeated with a laminated stack under preloading. Again, the dynamic behavior of the equivalent structure shows good accuracy compared to the initial preloaded stack. Finally, the magnetic core of an electric machine stator is modeled with equivalent anisotropic material properties, accounting for friction and preload in the yoke's and the teeth's steel sheets. The simulation of the structure's low-frequency radial vibration modes is satisfying, and shows improvement compared to orthotropic properties.
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Long, S. J., K. Hart, and L. M. Morgan. "The ability of habitual exercise to influence appetite and food intake in response to high- and low-energy preloads in man." British Journal of Nutrition 87, no. 5 (May 2002): 517–23. http://dx.doi.org/10.1079/bjn2002560.
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The present study tested the hypothesis that habitual exercisers demonstrate an increased accuracy of regulation of food intake in compensation for previous dietary energy intake. Twenty-three lean healthy male subjects were divided into two groups on the basis of their habitual exercise levels: non-exercisers (no exercise sessions/week, n 9), and exercisers (>two exercise sessions of 40 min or more/week, n 14). The appetite response to covert liquid preloads of high (2513 kJ) energy (HE) and low (1008 kJ) energy (LE) was investigated Sixty minutes after the preload subjects were offered an ab libitum buffet-style meal and energy intake (EI) was calculated. Subjective hunger and satiety were assessed throughout using self-rated visual-analogue scales. Buffet EI in non-exercisers was not significantly different following the LE or HE preloads (mean compensation 7 %), but the exercise group significantly reduced their energy intake following the HE, compared with the LE, preload (mean compensation 90 %; P=0·0035). A broadly similar pattern of response was observed for both moderate (two to three sessions/week, n 7) and high exercisers (>four sessions/week, n 7). There were no significant differences between hunger or satiety ratings following HE or LE preloads for either group. However non-exercisers scored significantly higher on their self-ratings of hunger at the start of the study, before preload consumption, compared with the exercisers (P<0·01). These findings demonstrate that habitual exercisers have an increased accuracy of short-term regulation of food intake in compensation for preload manipulation, and provide additional support for advocating regular exercise in the prevention of overweight and obesity.
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Li, Tiemin, Fuhua Li, Yao Jiang, Haitong Wang, and Yunsong Du. "Modeling of axial contact stiffness of a double-nut with preloads." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 232, no. 4 (December 6, 2016): 629–38. http://dx.doi.org/10.1177/0954406216682768.
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Ball screw drives are commonly used to provide linear motion in machine tools. And stiffness is one of the most important performance indexes. However, stiffness of nuts with different preloads is difficult to be calculated precisely because of complex structures. In order to improve the calculating accuracy, a new model is proposed with the consideration of geometry errors of grooves and balls based on the existing theoretical model. The influence of geometry errors on axial deformation of double-nut is analyzed and modeled. Meanwhile, a preload-adjustable ball screw drive is constructed on the basis of a modified double-nut mechanism. A novel loading mechanism is designed to apply axial load on the working table and test the force in real time. Two laser displacement sensors are adopted to test axial deformation of the double-nut. The axial stiffness of the double-nut is analyzed based on the axial load and the axial deformation. Stiffness simulations of the new improved model, the theoretical model, and the empirical model are also analyzed. The contrastive analysis shows that the experimental results agree much better with the axial stiffness calculated by the new improved model. This study provides a more accurate model to calculate the stiffness of the double-nut with preloads for preloaded ball screw drives.
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Miguéns-Gómez, Alba, Marta Sierra-Cruz, Esther Rodríguez-Gallego, Raúl Beltrán-Debón, M. Teresa Blay, Ximena Terra, Montserrat Pinent, and Anna Ardévol. "Effect of an Acute Insect Preload vs. an Almond Preload on Energy Intake, Subjective Food Consumption and Intestinal Health in Healthy Young Adults." Nutrients 14, no. 7 (March 31, 2022): 1463. http://dx.doi.org/10.3390/nu14071463.
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Protein is considered the most satiating macronutrient, and its effect on satiety and food intake is source-dependent. For the first time, we compared the effect of the administration of an insect or almond preload, both containing 20 g of protein, on appetite and food intake in human subjects. Participants consumed both foods and a vehicle as a liquid preload on three separate days. They were then offered a breakfast and lunch buffet meal at which food intake was measured. Visual analogue scale (VAS) questionnaires were completed following the three preloads to assess appetite and other sensations. At breakfast, reduced energy intake was observed for both preloads compared with vehicle. At lunch, food intake only differed in the insect group, which consumed more than the vehicle. Insect preload increased the total amount of protein ingested with a slight increase in total energy consumed, differently than almond, which significantly increased total protein and energy consumed. There was no correlation between indigestion-sensation ratings and food intake. Moreover, the insect preload resulted in lower sleepiness and tiredness ratings compared with the almond preload. Thus, insect-derived protein may be suitable as a safe ingredient for snacks intended for elderly or infirm patients who require increased protein intake.
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Potier, Mylène, Gilles Fromentin, Aurélie Lesdema, Robert Benamouzig, Daniel Tomé, and Agnès Marsset-Baglieri. "The satiety effect of disguised liquid preloads administered acutely and differing only in their nutrient content tended to be weaker for lipids but did not differ between proteins and carbohydrates in human subjects." British Journal of Nutrition 104, no. 9 (June 17, 2010): 1406–14. http://dx.doi.org/10.1017/s0007114510002126.
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Whether protein is the macronutrient with the strongest satiety effect remains a matter of debate because of the diversity of study designs employed. The aim of the present study was to compare the effect of different liquid preloads made up of proteins, fats or carbohydrates only, under stringently controlled conditions, on satiety. Fifty-six subjects participated in the present study which consisted of four randomised test days, i.e. 1 d per macronutrient and one control day. During each test day, the subjects were required to consume the preload in full, and then their subsequent food intake was measured. The volunteers were divided into two groups: the first (T0) group, which consumed the preload immediately before lunch, and the second (T1) group, which consumed it 1 h beforehand. The main results showed that the participants consumed significantly less at lunch following the consumption of all three preloads than on the no-preload day, and consumed less after the consumption of the carbohydrate preload than after the consumption of the lipid preload. When energy from the preload was included, overall energy intake was significantly greater in all the three preload conditions than in the situation involving no preload, with only partial compensation for preload energy in all conditions. Total daily energy intake was highest after the lipid preload ingestion, but this could be a chance finding since it was not significantly higher than that observed after protein or carbohydrate preload ingestion. No significant effects of the interval between the preload and test meal ingestion were found. These results do not confirm the greater satiety effect of proteins than of carbohydrates, but partially confirm the weaker effect of fats.
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Lin, Shen Yung, C. T. Chung, R. W. Chang, and C. K. Chang. "Effect of the Bearing Preload on the Characteristics of the Spindle Stiffness." Key Engineering Materials 419-420 (October 2009): 9–12. http://dx.doi.org/10.4028/www.scientific.net/kem.419-420.9.
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The main objective of this study is to investigate the effect of bearing preloads on the characteristics of spindle stiffness. Finite element model for spindle-bearing system is established enabling the variation of spindle stiffness calculations under different bearing preloads. On the other hand, the spindle stiffness may also be obtained from the experiment and its result may be utilized to validate the numerical calculations. The front-end section of spindle is acted by poise weights at different directions, and their corresponding deformations are measured through dial indicator. Three bearing preload conditions, i.e. light, medium and heavy preloads are selected, which are imposed on the bearing to investigate the spindle stiffness variation, respectively. In addition, the effects of the geometrical parallelism error at the end surfaces of spacer due to the manufacturing tolerance or some imperfection on the spindle stiffness are studied. Finally, the impact test on the spindle-bearing body is performed by hammer and the corresponding vibration signal on the spindle surfaces is acquired by accelerometer. The spindle stiffness may be reflected in the other manner through the signals processing by spectrum analysis.
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Yu, Wei Xiong, and Sheng Chun Yang. "Study on Dynamic Properties of Semi-Active Seism Isolator for Building." Advanced Materials Research 598 (November 2012): 299–302. http://dx.doi.org/10.4028/www.scientific.net/amr.598.299.
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The dynamic properties of semi-active seism isolator for building made of magnetorheological elastomers (MRE) were studied. Semi-active seism isolators were designed with MRE, and their dynamic properties at different amplitudes, frequencies, preloads or currents were tested. The results show that the dynamic stiffness decreases with the increase of amplitude or preload, but increases with the rise of frequency or current; the damping ratio ascends with the increase of amplitude, but declines with the rise of preload.
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Warwick, Z. S., and H. P. Weingarten. "Dynamics of intake suppression after a preload: role of calories, volume, and macronutrients." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 266, no. 4 (April 1, 1994): R1314—R1318. http://dx.doi.org/10.1152/ajpregu.1994.266.4.r1314.
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Twenty-four-hour cumulative food intake is the summation of repeated bouts of feeding, separated by intermeal intervals. Intake in a given meal influences subsequent feeding by modulating the duration of the intermeal interval, meal size, or both. Analysis of the time course of the effect of an individual meal on subsequent feeding may therefore clarify the controls of meal patterning and 24-h intake. In the present experiments, rats consumed a preload and then ate a test meal ad libitum. With the length of the preload-to-test meal interval varied from 10 to 180 min, the time course of the impact of various preloads on meal size was revealed. The main findings were the following: 1) caloric content, rather than volume, was the primary determinant of the intake-reducing effect of a glucose preload; 2) no differences in the time course of intake reduction were found after isocaloric preloads of fructose, glucose, and sucrose; 3) a fat preload attenuated subsequent intake less than an isocaloric sucrose preload; and 4) a short-lived (< 20 min) effect of sensory-specific satiety was evident. These findings are consistent with what is known about long-term effects of dietary manipulations on 24-h intake. Because daily intake reflects multiple iterations of feeding followed by an intermeal interval, a focused study of the duration of the impact of meals on subsequent ingestion may clarify the relationship between controls of individual meals and 24-h food intake.
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Ludwig, Melanie, Alexander Asteroth, Christian Rasche, and Mark Pfeiffer. "Including the Past: Performance Modeling Using a Preload Concept by Means of the Fitness-Fatigue Model." International Journal of Computer Science in Sport 18, no. 1 (July 1, 2019): 115–34. http://dx.doi.org/10.2478/ijcss-2019-0007.
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Abstract In mathematical modeling by means of performance models, the Fitness-Fatigue Model (FF-Model) is a common approach in sport and exercise science to study the training performance relationship. The FF-Model uses an initial basic level of performance and two antagonistic terms (for fitness and fatigue). By model calibration, parameters are adapted to the subject’s individual physical response to training load. Although the simulation of the recorded training data in most cases shows useful results when the model is calibrated and all parameters are adjusted, this method has two major difficulties. First, a fitted value as basic performance will usually be too high. Second, without modification, the model cannot be simply used for prediction. By rewriting the FF-Model such that effects of former training history can be analyzed separately – we call those terms preload – it is possible to close the gap between a more realistic initial performance level and an athlete's actual performance level without distorting other model parameters and increase model accuracy substantially. Fitting error of the preload-extended FF-Model is less than 32% compared to the error of the FF-Model without preloads. Prediction error of the preload-extended FF-Model is around 54% of the error of the FF-Model without preloads.
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Griffith, Charlotte, Kamille Piacquadio, Morgan Braden, and Heather Leidy. "Effects of Protein Source and Quantity on Appetite Control, Satiety and Subsequent Food Intake in Healthy Adults." Current Developments in Nutrition 5, Supplement_2 (June 2021): 409. http://dx.doi.org/10.1093/cdn/nzab038_021.
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Abstract Objectives To examine whether consumption of breakfast preloads varying in protein source and quantity affect measures of appetite, satiety and subsequent energy intake in healthy adults. Methods Thirty-seven healthy adults (Age: 26 ± 4; BMI: 23 ± 2) participated in this randomized crossover design study. On 3 consecutive days, participants consumed 325 kcal preload breakfast yogurts, varying in protein quality (Whey vs. Pea) and quantity (20, 30, 40 g) vs. an isocaloric carbohydrate preload (Control). On day 4, participants completed a 5-hr in clinic testing day. At baseline time -15 min, questionnaires assessing hunger, fullness, desire to eat, prospective food consumption, and eating initiation, were completed. At time 0 min, the respective preload was provided, and palatability assessed. At time 15 min, after consumption, similar questionnaires were completed every 30 min during the 4-h postprandial period followed by an ad libitum pizza lunch. There was a 3–7 day washout period between testing days. To assess main effects of protein source, paired sample t-tests of incremental area under the curve (iAUC) were computed for 20g Pea vs. 20g Whey preloads on 4-h hunger, fullness, desire to eat, prospective food consumption, eating initiation and lunch energy intake. To assess main effects of protein quantity, repeated measures ANOVA was computed between control and pea protein preloads of 20g, 30g, and 40g on 4-h hunger, fullness, desire to eat, and prospective food consumption niAUC, eating initiation, and lunch energy intake. P < 0.05 was considered statistically significant. Statistical analyses were performed using The R Foundation (R; version 4.0.3). Results No main effects of protein source or quantities were detected for 4-h postprandial hunger, fullness, desire to eat, and prospective food consumption niAUC. On average, participants requested to eat again 2-h after breakfast (134 ± 12 min) and consumed on average 830 ± 10 kcals at lunch with no differences between protein sources or quantities. Conclusions In the context of an acute feeding study, no differences in postprandial appetite, satiety, and subsequent food intake were detected when comparing protein preloads varying in source and quantity. These data suggest that 20 g pea protein is sufficient to elicit satiety effects and can be used as a plant-based alternative for whey protein. Funding Sources Roquette.
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Gheller, Brandon J. F., Julia O. Totosy de Zepetnek, Jo M. Welch, Melissa D. Rossiter, Bohdan Luhovyy, Neil R. Brett, and Nick Bellissimo. "Effect of video game playing and a glucose preload on subjective appetite, subjective emotions, and food intake in overweight and obese boys." Applied Physiology, Nutrition, and Metabolism 44, no. 3 (March 2019): 248–54. http://dx.doi.org/10.1139/apnm-2018-0281.
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Video game playing (VGP) is associated with overweight/obesity (OW/OB). VGP and caloric preloads in the pre-meal environment influence short-term food intake (FI) in healthy-weight children. Therefore, the purpose of the present study was to examine the effect of pre-meal VGP and a glucose preload on subjective emotions, subjective appetite, and FI in boys with OW/OB. On 4 separate mornings, boys with OW/OB (n = 22; mean ± SD: age = 11.9 ± 1.6 years; body mass index percentile = 94.3 ± 3.9) participated in 4 test conditions. Two hours after a standardized breakfast, boys consumed equally sweetened preloads (250 mL) of sucralose (0 kcal) or glucose (200 kcal), with or without 30 min of subsequent VGP. Immediately after each test condition, FI was evaluated during an ad libitum pizza meal. Subjective appetite was measured at 0 (baseline), 15, and 30 min. Subjective emotions (aggression, anger, excitement, disappointment, happiness, upset, and frustration) were measured at 0 and 30 min. VGP did not affect FI, but the glucose preload decreased FI compared with the sucralose control (Δ = −103 ± 48 kcal, p < 0.01). However, cumulative FI (preload kcal + meal kcal) was 9% higher after the glucose preload (p < 0.01). Subjective appetite increased with time (p < 0.05) but was not influenced by preload or VGP. Frustration was the only subjective emotion that increased following VGP (p < 0.01). A glucose preload, but not VGP, suppressed FI in boys with OW/OB, suggesting a primary role of physiological factors in short-term FI regulation.
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Astbury, Nerys M., Moira A. Taylor, and Ian A. Macdonald. "Polydextrose results in a dose-dependent reduction in ad libitum energy intake at a subsequent test meal." British Journal of Nutrition 110, no. 5 (January 23, 2013): 934–42. http://dx.doi.org/10.1017/s0007114512005776.
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Previous studies have reported that polydextrose can reduce food intake; however, the optimal dose required to achieve this effect is currently unknown. The present study investigated the effects of consuming a range of doses of polydextrose on appetite and energy intake (EI) using a randomised within-subject, cross-over design. For this purpose, twenty-one participants (n 12 men, n 9 women) consumed an 837 kJ liquid preload containing 0 g (control), 6·3, 12·5 or 25 g polydextrose. Subjective appetite ratings were collected using visual analogue scales and an ad libitum test meal was served 90 min later. Participants recorded EI for the remainder of the day in a food diary. Test meal EI following the control preload (5756 (sem 423) kJ) was significantly higher than following the 6·3 g (5048 (sem 384) kJ), 12·5 g (4722 (sem 384) kJ) and 25 g (4362 (sem 316) kJ) preloads (P< 0·05), and EI following the 6·3 g preload was significantly higher than following the 25 g preload (P< 0·01). There were no differences in self-reported EI during the remainder of the day between the preloads containing the varying doses of polydextrose. Total EI (breakfast+preload+ad libitum test meal+remainder of the day) was significantly higher when the control preload was consumed (12 051 (sem 805) kJ) compared with either the 12·5 g (10 854 (sem 589) kJ) or 25 g (10 658 (sem 506) kJ) preload (P< 0·05). These differences in EI were not accompanied by corresponding differences in subjective appetite ratings. In summary, polydextrose effectively reduces subsequent EI in a dose-dependent manner.
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Griffioen-Roose, Sanne, Monica Mars, Graham Finlayson, John E. Blundell, and Cees de Graaf. "The effect of within-meal protein content and taste on subsequent food choice and satiety." British Journal of Nutrition 106, no. 5 (May 9, 2011): 779–88. http://dx.doi.org/10.1017/s0007114511001012.
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It is posed that protein intake is tightly regulated by the human body. The role of sensory qualities in the satiating effects of protein, however, requires further clarification. Our objective was to determine the effect of within-meal protein content and taste on subsequent food choice and satiety. We used a cross-over design whereby sixty healthy, unrestrained subjects (twenty-three males and thirty-seven females) with a mean age of 20·8 (sd 2·1) years and a mean BMI of 21·5 (sd 1·6) kg/m2 were offered one of four isoenergetic preloads (rice meal) for lunch: two low in protein (about 7 % energy derived from protein) and two high in protein (about 25 % energy from protein). Both had a sweet and savoury version. At 30 min after preload consumption, subjects were offered an ad libitum buffet, consisting of food products differing in protein content (low/high) and taste (sweet/savoury). In addition, the computerised Leeds Food Preference Questionnaire (LFPQ) was run to assess several components of food reward. The results showed no effect of protein content of the preloads on subsequent food choice. There was an effect of taste; after eating the savoury preloads, choice and intake of sweet products were higher than of savoury products. No such preference was seen after the sweet preloads. No differences in satiety were observed. To conclude, within one eating episode, within-meal protein content in these quantities seems not to have an effect on subsequent food choice. This appears to be mostly determined by taste, whereby savoury taste exerts the strongest modulating effect. The results of the LFPQ provided insight into underlying processes.
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Li, Minghang, Meng Ma, Weining Liu, and Bolong Jiang. "Influence of static preload on vibration reduction effect of floating slab tracks." Journal of Vibration and Control 25, no. 6 (November 28, 2018): 1148–63. http://dx.doi.org/10.1177/1077546318813403.
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To effectively reduce the railway vibration and its environmental impact, vibration mitigation measures are increasingly used. The vibration reduction effect of railway tracks is described quantitatively by insertion loss (IL). ILs obtained from in situ measurements under moving train loads and laboratory tests under artificial excitation differ significantly due to the different track loading state between these two methods. The differences of track loading state are induced by the moving effect of train passages and the preloads effect of vehicle masses, the latter of which is a significant factor to discuss in this paper. In order to study the static preload by vehicle masses influence on the vibration reduction effect in isolated tracks, the steel spring floating slab track and regular slab track, as a reference case, were compared. First, a theoretical simplified model was constructed, following which a finite–infinite element coupled model was built, which was calibrated by experimental test results. Impact loads were applied to both tracks with preloads using unsprung wheelsets or sprung vehicle-body masses, with the total mass varying from 0 t to 30 t. The results demonstrate that the increase in preload of unsprung mass makes the natural frequencies further reduced, and the peak IL value increased from 39 dB to 48 dB. The increase in preload has a significant effect on vibration responses below 5 Hz, and the application of the preload has different effects on the reduction effect in different frequency ranges.
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Fenander, Å. "Frequency dependent stiffness and damping of railpads." Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 211, no. 1 (January 1, 1997): 51–62. http://dx.doi.org/10.1243/0954409971530897.
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The vertical stiffness and damping of studded rubber railpads have been measured, both in a complete track and in a test rig, as functions of frequency under different static preloads. Also, for more compact polymer-based railpads, track measurements were performed. The stiffness of the studded railpads was found to increase strongly with preload, but only weakly with frequency. The loss factor of the studded railpads was found to be nearly independent of preload and to increase only slightly with frequency. A fractional derivative model of the dynamic behaviour of the railpad is proposed.
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Chapman, Ian, John Newnham, and Paul Wallace. "The Tightening of Bolts to Yield and Their Performance Under Load." Journal of Vibration and Acoustics 108, no. 2 (April 1, 1986): 213–21. http://dx.doi.org/10.1115/1.3269326.
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The mechanism of tightening bolted joints and the stress distribution in the bolt are analyzed. Measurements were made of static and dynamic strength of joints. It is shown that all bolts behave elastically when external loads are applied to the joint even when the fastener was tightened to its torque-tension yield point. It is shown that joints generally fail when the external loads are sufficient to overcome the bolt preload. Fatigue reesults show that joint fatigue strength increases with preload, and that high fatigue bolts gave an improvement over standard fasteners at all preloads.
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Zhu, Pei Hao, Lian Hong Zhang, Bing Yu, and Qi Zhi Xie. "Tie Rod Preload Analysis of a 100MN Hydraulic Press." Applied Mechanics and Materials 121-126 (October 2011): 3632–36. http://dx.doi.org/10.4028/www.scientific.net/amm.121-126.3632.
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The classical preload design method of prestressed frame of hydraulic presses is based on the assumption that the beams of the frame are rigid, which is not agree with practice. In order to eliminate the unbalance load of the frame of a 100MN hydraulic press due to improper prestressing, tie rod preload distribution in prestressing of the frame is researched with respectively mechanics of materials and the finite element methods. According to mechanics of materials and finite element analysis results, reasonable tie rod preloads and sequence of preloading are obtained and the unbalance load of the frame of the hydraulic press is solved. It also provides references for the preload design of prestressed frame of hydraulic presses.
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Li, Fei, QiLin Zhao, Haosen Chen, and Sheng Luo. "Research on preload relaxation for composite pre-tightened tooth connections." Science and Engineering of Composite Materials 26, no. 1 (January 28, 2019): 197–208. http://dx.doi.org/10.1515/secm-2019-0002.
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AbstractPreload is the primary reason why pre-tightened tooth connections (PTTC) can transfer relatively large loads. However, creep of the composite would cause the preload relaxation, resulting in reducing bearing capacity of the connection. To study the preload relaxation of PTTC caused by the creep of composites, a prediction formula is deduced by converting the viscoelastic problem to an elastic problem using Laplace transform. Meanwhile, long-term experimental research on the preload relaxation of composite pre-tightened tooth connection with different initial preloads and different geometry sizes was made. The theoretical results are compared with experimental data obtained by long-term experiment, and the results indicate that the calculation formula can predict the preload relaxation well in linear viscoelastic state. The preload relaxation mainly occurs at the beginning of loading and it tends to be steady in the middle and later periods.
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Farhat, Grace, Victoria Berset, and Lauren Moore. "Effects of Stevia Extract on Postprandial Glucose Response, Satiety and Energy Intake: A Three-Arm Crossover Trial." Nutrients 11, no. 12 (December 12, 2019): 3036. http://dx.doi.org/10.3390/nu11123036.
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Non-nutritive sweeteners (NNS) are suggested to lower energy intake in the diet, but they have been paradoxically involved in the epidemic of obesity and Type 2 diabetes. Stevia is the least studied sweetener. This study aims to investigate the effect of stevia on postprandial glucose levels, appetite and food intake. Methods: 30 participants (20 females/10 males; 26.1 (10.56) years; body mass index (BMI) 23.44 (3.42) Kg/m2) took part in a three-arm crossover trial where they received preloads of water, sugar (60 g) and stevia (1 g) on three different days, followed by an ad libitum pizza lunch. Breakfast was standardised. A one-day diet diary was collected on each test day. Visual analogue scales (VAS) were used to assess subjective feelings of appetite. Blood glucose samples were collected at 30-min intervals until 120 min post lunch. Results: Energy intake did not significantly differ between preloads for ad libitum meals (p = 0.78) and overall day (p = 0.33). VAS scores for hunger and desire to eat (DTE) were lower following stevia preload compared to water (p < 0.05). After adjusting for the sugar preload and calorie content, postprandial glucose levels did not significantly differ between interventions. Conclusion: Stevia lowers appetite sensation and does not further increase food intake and postprandial glucose levels. It could be a useful strategy in obesity and diabetes prevention and management.
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Weller, Aron, Ludmila Tsitolovskya, Iris H. Gispan, and Gerard P. Smith. "Ontogeny of hypertonic preabsorptive inhibitory control of intake in neonatal rats." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 278, no. 1 (January 1, 2000): R44—R49. http://dx.doi.org/10.1152/ajpregu.2000.278.1.r44.
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The ontogenetic development of postingestive inhibitory control of ingestion by the osmotic load of a preload was examined in rats. On postnatal days 6 (P6) and 12 (P12), pups were deprived for either 6 or 24 h. Gastric preloads (5% body wt) of water, mannitol (a sugar alcohol that is not absorbed) in six concentrations [from 0.125 M (hypotonic) to 1.0 M (hypertonic)], or sham preloads were administered 5 min before a 30-min intake test. Compared with sham treatment, isotonic mannitol (0.25 M), a probe of volumetric control, significantly reduced intake on P12, but not on P6. Compared with isotonic mannitol, the three highest hypertonic concentrations (0.5, 0.66, and 1.0 M) significantly decreased intake on P12, at both levels of deprivation. On P6, 0.66 and 1.0 M mannitol reduced intake after 24 h, but not after 6 h, of deprivation. Thus, on P6, the hypertonic control was detectable only after prolonged deprivation and the volumetric control was not present. On P12, both controls were observed and the hypertonic control was more potent than on P6.
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Kari, L. "An analytical temperature-dependent collocation model for preloaded rubber cylinders." Journal of Strain Analysis for Engineering Design 37, no. 4 (May 1, 2002): 289–99. http://dx.doi.org/10.1243/030932402760074517.
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The non-linear temperature-dependent stiffness of an axially preloaded rubber cylinder is examined by an analytical collocation model, where influences of temperature, cylinder diameter and length, material parameters and prestrain are investigated. The rubber is assumed to be incompressible with the deviatoric response determined by an extended neo-Hookean free energy function, embodying a temperature shift function, being directly proportional to the temperature and to the temperature-dependent rubber density. The model is based on a semi-inverse method where the motion is split into two deformations: the first, a homogeneous temperature expansion, while the second, a preload deformation where material planes parallel to the bonded metal plate in the rubber cylinder are assumed to remain parallel, with the boundary conditions on the free rubber surface satisfied by collocation. The stiffness depends strongly on the preload—particularly for larger diameter-length ratios—and on the temperature covering —60 to + 60° C, where the shift function factor directly proportional to the temperature is found to play the greatest role. Contrary to other semi-inverse models, this model coincides at vanishing preloads with a well-known linear formula while extending the applicable shape factor range to cover shape factors typically found for vibration isolators.
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Xia, Zhongxian, Yuhou Wu, Hua Wei, Kexuan Ren, Longfei Gao, Jian Sun, and Songhua Li. "Experimental Research on the Influence of Working Conditions on Vibration and Temperature Rise of Si3N4 Full-Ceramic Bearing Motors." Shock and Vibration 2021 (November 8, 2021): 1–16. http://dx.doi.org/10.1155/2021/1176566.
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Working conditions such as lubrication, preload, and rotational speed have important influence on vibration and temperature rise of the spindle motor. In this study, controlled variable experiments are carried out on the silicon nitride (Si3N4) full-ceramic ball bearing and steel bearing of the same type, and the vibration signal characteristics and temperature rise of the spindle motor are tested and analysed, by changing the lubrication conditions, preloads, and rotational speeds of the spindle motor. Through the research, it is found that as the rotational speed increases, the vibration velocity of the Si3N4 full-ceramic bearing spindle motor under different preloads and lubrication conditions shows an overall increasing trend; kurtosis generally presents a downward trend and gradually flattens, indicating that although the vibration velocity increases at high speeds, the vibration signal shows a relatively stable state. As the rotational speed increases, the difference of vibration velocity under the condition of applying preload and no preload decreases, indicating that the influence of preload on the vibration of full-ceramic bearing spindle motor decreases with the increase in rotational speeds. At the same time, it is found that fr and 5fr have greater impact on the vibration of full-ceramic bearing spindle motor, where fr is the frequency of the bearing in normal operation, and 5fr is 5 times of the normal operating frequency. Lubrication conditions have little effect on the temperature rise of full-ceramic bearing spindle motor, and the temperature rise under nonlubricated conditions is even slightly lower than that under grease lubrication conditions. The research results show that the vibration velocity and temperature rise of Si3N4 full-ceramic bearing spindle motor are less than those of steel bearing with the same type, indicating that full-ceramic bearing has better performance than steel bearing under the same working conditions.
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Yin, Dong Mei, and Zhen Xiao Li. "Foreign Objects Damage on the Leading Edge of the Blade with Centrifugal Preload." Applied Mechanics and Materials 148-149 (December 2011): 958–62. http://dx.doi.org/10.4028/www.scientific.net/amm.148-149.958.
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The influence of centrifugal prestress on the foreign object damage of engine blades was analyzed by numerical simulation. A nonlinear dynamic model for foreign object damage of blade with centrifugal prestress was established. And the dynamic relaxation method was used to obtain the initial stress and displacement field of blade in the beginning of the dynamic analysis of impact. Numerical simulations of foreign objects impacting on the leading edges of the blades under different centrifugal preloads were carried out. The results indicate that the local plastic deformation on the impact location of blade with centrifugal preload, which is produced at the moment of impact, is decreasing with the increase of the preload. The growth of crack produced on the lead edge of blade is accelerated with the preload increasing.
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Samarakoon, S. M. Samindi M. K., Bartosz Piatek, and G. H. M. J. Subashi De Silva. "Investigation of the Flexural Behavior of Preloaded and Pre-Cracked Reinforced Concrete Beams Strengthened with CFRP Plates." Materials 16, no. 1 (December 20, 2022): 22. http://dx.doi.org/10.3390/ma16010022.
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This paper investigates the flexural behavior of preloaded reinforced concrete (RC) beams, strengthened with Carbon Fiber Reinforced Polymer (CFRP) plates using an experimental program, analytical procedure, and Finite Element Method (FEM) simulation. The RC beams were subjected to preloads of 30%, 50% and 70% of the yielding load, prior to installation of the strengthening system. The eight RC-strengthened beams with a reinforcement configuration of 3Ø12 and two CarboDur S512 plates have been evaluated using bending tests. The failure modes of all the RC-strengthened beams were governed by the widening of flexural cracks within a constant bending zone, followed by debonding of the CFRP plates. The plates were debonding simultaneously or one plate prior to the other plate. The ultimate moment capacity is not significantly reduced while increasing preload levels from 0% to 70%. The moment capacity is increased by 70% to 80% in the CFRP strengthened beams, compared with un-strengthened beams indicating the potential of capacity enhancement that can be attained by externally bonded CFRP.
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Lu, Xuejiao, Jiacan Lu, Zhihong Fan, Anshu Liu, Wenqi Zhao, Yixue Wu, and Ruixin Zhu. "Both Isocarbohydrate and Hypercarbohydrate Fruit Preloads Curbed Postprandial Glycemic Excursion in Healthy Subjects." Nutrients 13, no. 7 (July 19, 2021): 2470. http://dx.doi.org/10.3390/nu13072470.
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This study aimed to investigate the impact of fruit preloads on the acute postprandial glycemic response (PGR) and satiety response of a rice meal in healthy female subjects based on iso-carbohydrate (IC) and hyper-carbohydrate (HC) contents, respectively. The IC test meals including (1) rice preload (R + 35R), (2) orange preload (O + 35R), (3) apple preload (A + 35R) and (4) pear preload (P + 35R), contained 50.0 g available carbohydrates (AC) where the preload contributed 15.0 g and rice provided 35.0 g. The HC meals included (1) orange preload (O + 50R), (2) apple preload (A+50R) and (3) pear preload (P + 50R), each containing 65.0 g AC, where the fruits contributed 15.0 g and rice provided 50.0 g. Drinking water 30 min before the rice meal was taken as reference (W + 50R). All the preload treatments, irrespective of IC or HC meals, resulted in remarkable reduction (p < 0.001) in terms of incremental peak glucose (IPG) and the maximum amplitude of glycemic excursion in 180 min (MAGE0–180), also a significant decrease (p < 0.05) in the area of PGR contributed by per gram of AC (AAC), compared with the W + 50R. Apple elicited the lowest PGR among all test meals, as the A + 35R halved the IPG and slashed the incremental area under the curve in 180 min (iAUC0–180) by 45.7%, while the A + 50R reduced the IPG by 29.7%, compared with the W + 50R. All the preload meals and the reference meal showed comparable self-reported satiety in spite of the difference in AC. In conclusion, pre-meal consumption of three fruits effectively curbed post-meal glycemia even in the case of a 30% extra carbohydrate load.
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Wang, Pengpeng, Lan Zhang, and Liquan Wang. "Influence of Temperature on the Bolt Loads and Variation in a Bolted Flange for Subsea Pipeline Connection." Mathematical Problems in Engineering 2021 (May 5, 2021): 1–9. http://dx.doi.org/10.1155/2021/5636941.
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This article proposed an analytic and finite element-combined modelling method for the investigation of temperature effects on bolt loads and variation in a bolted flange for subsea pipeline connection. With this method, the preloads of bolt in the bolted flange assembly were investigated under different medium liquid temperatures in the pipeline. The simulation results illustrate that the deviation of bolt loads can be increased due to the medium liquid temperature increasing. The final bolt load deviation increases along with the increasing of the initial deviation of bolt preloads in a constant medium liquid temperature. The final distribution of bolt loads can be affected by the initial condition of the bolts. When bolt preloads are staggered, the variance of the final bolt loads is minimized; when the bolt preloads are axisymmetric, the final bolt load variance is the maximum.
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Schwartz, Gary J., Cynthia F. Salorio, Chris Skoglund, and Timothy H. Moran. "Gut vagal afferent lesions increase meal size but do not block gastric preload-induced feeding suppression." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 276, no. 6 (June 1, 1999): R1623—R1629. http://dx.doi.org/10.1152/ajpregu.1999.276.6.r1623.
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Subdiaphragmatic vagal afferent (SVA) signals arising from gut sites may provide critical feedback for the control of food intake within a meal. To evaluate the role of SVAs in both spontaneous and scheduled meals, food intake was assessed in two paradigms in male Sprague-Dawley rats. In the first study, control (Con) rats ( n = 6) and rats with subdiaphragmatic vagal deafferentation (SDA) ( n = 7) had 12-h nightly access to Ensure liquid diet (1 kcal/ml). SDA rats had larger and fewer meals and maintained initial rapid rates of licking, yet total numbers of licks were unaffected. In the second study, Con ( n = 8) and SDA ( n = 7) rats had scheduled access to 12.5% liquid glucose after overnight food deprivation. Glucose intake was assessed after 5-ml gastric preloads of 0.9% saline or glucose, peptone, and Intralipid solutions at three concentrations (0.5, 1, and 2 kcal/ml). Glucose and peptone preloads suppressed intake similarly in Con and SDA rats, whereas Intralipid was ineffective. These results suggest that meal-related SVA signals 1) are not critical in determining preload-induced feeding suppression after deprivation, yet 2) contribute to satiety during spontaneous meals.
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Berti, Cristiana, Patrizia Riso, Antonella Brusamolino, and Marisa Porrini. "Effect on appetite control of minor cereal and pseudocereal products." British Journal of Nutrition 94, no. 5 (November 2005): 850–58. http://dx.doi.org/10.1079/bjn20051563.
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Recent findings suggest that Western diets based on highly palatable foods are likely to be much less satiating than more traditional diets or those typical of less developed countries. In particular, some alternative crops (for example, buckwheat, oat, barley, spelt, rye, quinoa, amaranth) seem to be of great nutritional interest and to represent important recipes for healthier and typical regional foods. The objective of the present study was to investigate the effect on subsequent food intake and feelings of satiety of alternative oat bread, oat and buckwheat pasta and of quinoa as compared with their wheat counterparts and rice, respectively. Three different experiments (one specific for each alternative crop food) were conducted, all with a within-subjects design. The preloading paradigm strategy was used. Results showed that preload energy level influenced total energy intake (preload plus ad libitum test meal intake), larger preloads inducing more eating than smaller preloads. No effect of formulation was observed on energy intake, as the consumption of alternative crop formulations did not decrease the total energy intake as compared with that of the counterparts. Satiating efficiency indices (SEI) for alternative crop foods were higher with respect to traditional cereal foods. In particular, white bread was the least satisfying food (SEI =0·2) and the different time of consumption (for lunch or as a snack) did not affect energy intake. In conclusion, oat or buckwheat formulations, and also quinoa, may be exploited for their potential impact on eating behaviour, particularly considering they are good sources of functional substances.
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Hwang, Pyung, and Polina V. Khan. "Bifurcation Analysis of the Load/Unload Systems With Multiple Flying Height States." Journal of Tribology 128, no. 3 (March 22, 2006): 665–69. http://dx.doi.org/10.1115/1.2197852.
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The load/unload behavior of the hard disk drive slider is studied in terms of the air bearing static characteristics. The application of numerical continuation methods to calculate spacing diagrams is proposed. The algorithm that detects multiple flying height states and fold points is developed. The relationship between suspension force x-offset and critical preload is found for femto size sliders. The second fold corresponding to the critical preload for unloading is found in the negative air bearing force area. The range of x-offsets and preloads where bi-stable phenomenon exists is depicted on the stability diagram. The perturbation method is used to check the dynamic system characteristic values near the fold points and to determine the stability of the solution branches. The present procedure can be employed to study the multiple flying height states in the terms of any other pair of parameters besides the preload and x-offset.
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Yan, Shao Ze, Kai Zheng, and Jian Xun. "Mechanical Properties of Piezoelectric Stack Actuators under Electro-Mechanical Loading." Key Engineering Materials 336-338 (April 2007): 331–34. http://dx.doi.org/10.4028/www.scientific.net/kem.336-338.331.
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The responses of the piezoelectric stack actuator under electro-mechanical loading are investigated. Two types of tests are performed: influences of the preload on characteristics of the stack and dynamic test. Experimental results indicate strong dependence of the stack properties on the electro-mechanical loading conditions. The displacement output is initially enhanced with an increase of the mechanical preload, and the maximum value is obtained at the preload of about 0.4 kN. But much higher preload will cause the decrease of the displacement output. The effective piezoelectric coefficient and the hysteresis degree are employed to describe the variations of the stack’s performances caused by the mechanical preload. The effective piezoelectric coefficient under different preloads can be calculated by using experimental results of the displacement output and input voltage. Within low frequency band of about 400 Hz, the displacement magnitude of the stack is nearly constant, and the phase lag increases with the increase of the driving frequency at the applied sine sweep voltage with the amplitude of 150V.
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Sun, Haoyu, Hao Yin, Jiang Liu, and Xilong Zhang. "Efficiency Model for Traveling Wave-Type Ultrasonic Motors Based on Contact Variables and Preload." Actuators 10, no. 7 (July 12, 2021): 158. http://dx.doi.org/10.3390/act10070158.
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The contact interface variables are difficult to measure for an ultrasonic motor. When the ultrasonic motor works under different preloads, the error between the traditional efficiency model and the real output is quite large. In order to solve these two problems, we propose a novel efficiency model. It takes measured preload and the feedback voltage data as the input, which may offer better accuracy and on-line ability. Firstly, the effect of the preload on the drive characteristics is investigated, and the relationship between preload and the change in motor energy input is analyzed. Secondly, a contact model based on measured preload and feedback voltage is built, providing a more accurate description of the contact variables. Finally, an efficiency model was developed with a new composite stator structure. A preload test rig for a 60 mm ultrasonic motor is built and real operating conditions are measured. The results show that the correlation coefficient of the present model is 0.991, larger than 0.925 of the conventional model. The proposed model is more consistent with the real working conditions for the motor.
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Zhang, Z., Y. Xiao, YQ Liu, and ZQ Su. "A quantitative investigation on vibration durability of viscoelastic relaxation in bolted composite joints." Journal of Composite Materials 50, no. 29 (July 28, 2016): 4041–56. http://dx.doi.org/10.1177/0021998316631810.
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Time-dependent behavior and factors affecting preload relaxation in a carbon/epoxy composite bolted joint under resonance were studied. The effect of viscoelasticity of composite material on bolt relaxation was studied quantitatively through modal analysis from the perspective of energy dissipation and stiffness degradation. Damping ratio and resonance frequency were utilized to characterize the effects of preload relaxation on structural dynamic response. The loss of preload was found to decrease with increasing initial preloads over a 10 h vibration fatigue. However, an increase in preload loss occurred as exciting frequency increases. Vibration fatigue damage was found to result in decaying stiffness and amplitude responses of the bolted joints, along with an increase in damping ratio. As a proof-of-concept study, a beam-like specimens with and without bolted joints were comparatively excited to ascertain their respective dynamic responses; results revealed that relaxation in bolted joints could be attributed to the conjunct mechanisms between viscoelastic behavior of polymer matrix composites and interface friction for different contact surfaces, where such relaxation behavior was mainly due to viscoelasticity of the joint materials.
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He, Ping, Yong Li, Shoulong Chen, Hoghua Xu, Lei Zhu, and Lingyan Wang. "Core looseness fault identification model based on Mel spectrogram-CNN." Journal of Physics: Conference Series 2137, no. 1 (December 1, 2021): 012060. http://dx.doi.org/10.1088/1742-6596/2137/1/012060.
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Abstract In order to realize transformer voiceprint recognition, a transformer voiceprint recognition model based on Mel spectrum convolution neural network is proposed. Firstly, the transformer core looseness fault is simulated by setting different preloads, and the sound signals under different preloads are collected; Secondly, the sound signal is converted into a spectrogram that can be trained by convolutional neural network, and then the dimension is reduced by Mel filter bank to draw Mel spectrogram, which can generate spectrogram data sets under different preloads in batch; Finally, the data set is introduced into convolutional neural network for training, and the transformer voiceprint fault recognition model is obtained. The results show that the training accuracy of the proposed Mel spectrum convolution neural network transformer identification model is 99.91%, which can well identify the core loosening faults.
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Zhang, Yue, Cheng Wei, Jiang Zhang, and Yang Zhao. "Modeling and Analysis of Wire Rope in the Drilling Device Using ANCF Method." Advanced Materials Research 1006-1007 (August 2014): 30–33. http://dx.doi.org/10.4028/www.scientific.net/amr.1006-1007.30.
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The wire rope of drilling device is modeled by using absolute nodal coordinate formulation (ANCF) which is presented for the analysis of three dimensional flexible cable in this paper. This formulation is suited for the analysis of large rotation and deformation problem. Only axial and bending deformations are taken into account in this paper, which increases the computational efficiency without affecting the precision. Vibrations of the drilling mechanism and the wire rope under different preloads are simulated. It can be seen from the emulational results that resonance will occur when the preload increases to a certain value and the amplitude is the largest in this case.
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Fukuoka, Toshimichi, and Tomohiro Takaki. "Finite Element Simulation of Bolt-Up Process of Pipe Flange Connections With Spiral Wound Gasket." Journal of Pressure Vessel Technology 125, no. 4 (November 1, 2003): 371–78. http://dx.doi.org/10.1115/1.1613304.
Full textAbstract:
It is well known that a large amount of scatter in bolt preloads is observed when bolting up a pipe flange connection, especially in the case of using a spiral wound gasket. In this study, a numerical approach is proposed, which can simulate the bolt-up process of a pipe flange connection with a spiral wound gasket inserted. The numerical approach is designed so as to predict the scatter in bolt preloads and achieve uniform bolt preloads at the completion of pipe flange assembly. To attain the foregoing purposes, the stress-strain relationship of a spiral wound gasket, which shows highly nonlinear behavior, is identified with a sixth-degree polynomial during loading and with an exponential equation during unloading and reloading. Numerical analyses are conducted by three-dimensional FEM, in which a gasket is modeled as groups of nonlinear one-dimensional elements.