Difference In Vertical Displacement Research Articles

Numerical Investigation of the Temperature Field Effect on the Mechanical Responses of Conventional and Cool Pavements.

Conventional asphalt pavement has a deep surface color and large thermal inertia, which leads to the continuous absorption of solar thermal radiation and the sharp rise of surface temperature. This can easily lead to the permanent deformation of pavement, as well as aggravate the urban heat island (UHI) effect. Cool pavement with a reflective coating plays an important role in reducing pavement temperature and alleviating the UHI effect. It is of great significance to study the influence of temperature on the mechanical response of different types of pavement under vehicle loading. Therefore, this study examined the heat exchange theory between pavement and the external environment and utilized the representative climate data of a 24 h period in the summer. Two kinds of three-dimensional finite element models were established for the analysis of temperature distribution and the mechanical responses of conventional pavement and cool pavement. The results show that in this environmental condition, conventional pavement temperatures can exceed 50 °C under high temperatures in summer, which allows for the permanent deformation of pavement and further affects the service life of asphalt pavement. The temperature difference in a conventional pavement surface between 6 h (24.7 °C) and 22 h (30.2 °C) is much less than that between 22 h (30.2 °C) and 13 h (50.1 °C) in the summer. However, the difference in the vertical displacements of the pavement surface between 6 h and 22 h is much larger than that between 22 h and 13 h. One reason is that the difference in temperature distribution between the morning and night leads to changes in pavement structure stiffness, resulting in significant differences in vertical displacement. Cool pavement has a significant cooling effect, which can reduce the surface temperature of a road by more than 15 °C and reduce the vertical displacement of the pavement by approximately 11.3%, which improves the rutting resistance of the pavement. However, the use of cool pavement will not change the horizontal strain at the bottom of the asphalt base and will not improve the fatigue resistance of asphalt pavement. This research will lay the foundation for further clarifying the difference in the mechanical properties between the two types of pavements in the management and maintenance stage.

Finite Element Modeling of the Dynamic Response of Critical Zones in a Ballasted Railway Track

The critical zones are the discontinuities along a railway line that are highly susceptible to differential settlement, due to an abrupt variation in the support conditions over a short span. Consequently, these zones require frequent maintenance to ensure adequate levels of passenger safety and comfort. A proper understanding of the behavior of railway tracks at critical zones is imperative to enhance their performance and reduce the frequency of costly maintenance operations. This paper investigates the dynamic behavior of the critical zone along a bridge-open track transition under moving train loads using two-dimensional finite element approach. The influence of different subgrade types on the track behavior is studied. The effectiveness of using geogrids, wedge-shaped engineered backfill and zone with reduced sleeper spacing in improving the performance of the critical zone is evaluated. The numerical model is successfully validated against the field data reported in the literature. The results indicate that the subgrade soil significantly influences the track response on the softer side of the critical zone. The difference in vertical displacement between the stiffer and the softer side of a track transition decreases significantly with an increase in the strength and stiffness of the subgrade soil. The subgrade layer also influences the contribution of the granular layers (ballast and subballast) to the overall track response. As the subgrade becomes stiffer and stronger, the contribution of the granular layers to the overall track displacement increases. The mitigation techniques that improve the stiffness or strength of granular layers may prove more effective for critical zones with stiff subgrade than critical zones with soft subgrade. Among all the mitigation techniques investigated, the wedge-shaped engineered backfill significantly improved the performance of the critical zone by gradually increasing the track stiffness.

Analysis of loess fracture on slope stability based on centrifugal model tests

Natural slopes are very common for the complicated topography in the loess area; meanwhile, many artificial slopes were produced by large-scale engineering construction and excavation in recent years. The fractures are widely distributed in the slope, which have a great impact on the slope stability. It is difficult to find out a reasonable method of evaluating the stability of fractured slopes. So, the influence of loess fracture on slope stability was studied by using geotechnical centrifugal testing machine to simulate the process of stress-strain change of slope and systematically studied the influence factors of loess fissure on slope displacement and stress field change, deformation, and failure process. The results show that the displacement of the fractured loess slope is generally larger than that of the integrated loess slope. The difference in vertical displacement of slope edge between the two models is the largest, up to 2 cm. The horizontal displacements of the two models in the slope have a large difference before 1200 s, and the maximum displacement is 1.25 cm. After 1200 s, the difference gradually decreases. There is a great difference in the stress change trend between the two models. The stress in the slope foot, slope top, and slope edge of the fractured slope model has obviously reduced abruptly during the test, and the stress in the integrated loess slope model has little change during the test. It reflects the influence of fractures on the stress distribution of slopes, and the sudden change of stress is a response to the local failure of slopes. The results can provide reference for stability evaluation of fractured loess slopes and the prediction of the risk of loess landslide.

Influence of rigidity of retainers on dynamic behavior of implant-supported removable partial dentures

BackgroundImplant-supported removable partial dentures (ISRPDs) are an effective treatment for partially edentulous patients. ISRPDs improve patients’ satisfaction and oral function to a greater extent than RPDs by improving denture stability and enhancing support. However, the effect of a type of direct retainer on displacement of the abutment teeth and dentures in ISRPDs remains unclear. Therefore, we made a resin mandibular model of unilateral mandibular distal-extension partial edentulism for mechanical simulation and compared the dynamic behavior of the abutment teeth and the denture base among different tooth-borne retainers with various rigidities for RPDs and ISRPDs.MethodsA resin mandibular model for mechanical simulation that had unilateral mandibular distal-extension edentulism and was missing the first molar, second molar, first premolar, and second premolar, and a denture fabricated from the patient’s computed tomography images were used. Three types of direct retainers with different connecting rigidities were evaluated. The vertical displacement of the denture base and buccal and lingual sides and the mesial displacement of the abutment teeth were measured.ResultsRegardless of the rigidity of the direct retainers and loading positions, the displacement of the denture bases in the ISRPDs was significantly smaller than that in the RPDs (P < 0.001). There was no significant difference in vertical displacement of the denture bases among direct retainers with various connecting rigidities in the ISRPDs. Conversely, horizontal displacement of the abutment teeth in both the RPDs and ISRPDs tended to be larger with the cone crown telescope, which has high rigidity, than with the cast cingulum rest and wire clasp, which have much lower rigidities.ConclusionOur results suggested that cast cingulum rest and wire clasps as direct retainers are appropriate ISRPDs to minimize denture movement and suppress displacement of the remaining teeth in patients with unilateral mandibular distal-extension partial edentulism.

A novel way to dynamize a spatial frame and optimize fracture healing

BackgroundFracture site motion creates mechanical strains on the healing tissues which influences bone formation. Axial micro-motion maximizes dilatational strains, whereas shearing motions maximize deviatoric strains on the healing tissues. Dilatational strains optimize bone healing, deviatoric strains retard bone healing. Dynamization of external fixation using either an Ilizarov or Spatial Frame platform is used to increase loading on the limb which increases the mechanical stress and strain on the tissues to improve healing. The scientific literature does not address how dynamization of the spatial frame effects fracture site motion. The purpose of this study is to assess the effect of modified shoulder bolts incorporated into a spatial frame during dynamic loading. MethodsFive identical two-ring spatial frame constructed were mounted on Sawbones tibias with an osteotomy performed distal to the tibial tubercle. Sinusoidal load was applied at a rate of 0.25 Hz. Axial force and displacement, in addition to motion of the proximal and distal tibia segments were recorded. Eight constructs were tested: 1) All struts of the Spatial Frame rigid, 2) Strut #1 loose, 3) Struts #1 and #3 loose, 4) Struts #1, #3 and #5 loose, 5) All struts loose, 6) All struts rigid with dynamization bolts on the proximal end, 7) All struts rigid with dynamization bolts on alternating sides, 8) Threaded rods between the rings with two millimeters of dynamization. ResultsNo difference in vertical displacement was observed between the Ilizarov and all struts locked. No significant difference in shear values between all struts locked and modified shoulder bolt struts was observed. Increase in vertical movement with the modified shoulder bolts was an average of 1.83 mm. Significant shear forces at the fracture site were observed with unlocking single or multiple struts of the spatial frame. ConclusionModified shoulder bolts can be used for spatial frame dynamization without increasing shear motion.

Effects of topography on dynamic responses of single piles under vertical cyclic loading

This paper describes model tests of single piles subjected to vertical cyclic compressive loading for three kinds of topography: sloping ground, level ground, and inclined bedrock. Comprehensive dynamic responses involving cyclic effects and vibration behaviours are studied under various load combinations of dynamic amplitude, mean load, frequency and number of cycles. Test results show that permanent settlement can generally be predicted with a quadratic function or power function of cycles. Sloping ground topography produces more pronounced settlement than level ground under the same load condition. For vibration behaviour, displacement amplitude is weakly affected by the number of cycles, while load amplitude significantly influences dynamic responses. Test results also reveal that increasing load amplitude intensifies nonlinearity and topography effects. The strain distribution in a pile and soil stress at the pile tip are displayed to investigate the vibration mechanism accounting for sloping ground effects. Furthermore, the dynamic characteristics among three kinds of topography in the elastic stage are studied using a three-dimensional finite method. Numerical results are validated by comparing with experimental results for base inclination topography. An inclined soil profile boundary causes non-axisymmetric resultant deformation, though a small difference in vertical displacement is observed.

The influence of pole lengths on O2-cost, kinematics, and performance in double poling at high speeds before and after a training period with long poles

PurposePrevious studies have found an acute performance improvement with longer pole lengths in double poling (DP) at low-to-moderate speeds. We investigated the influence of pole lengths (PL) on O2-cost, 3D kinematics, and performance in DP at moderate-to-high speeds before (Pre) and after (Post) eight training sessions with long poles on a rollerski treadmill.MethodsSeven male and four female skiers completed tests with two different PLs (84 and 90% of body height). Submaximal O2-cost (1º; 4.5 [females] or 6 m s−1 [males]) and a peak velocity test (1º; ∼ 7.3 m s−1) were assessed before and after a six week training period. The training sessions consisted of 50 min of low-moderate intensity training and 4 × 10 s maximal sprints with PL90%.ResultsOn average for all tests, PL84% induced 1.0 ± 1.0% higher peak velocity compared to PL90% (mean ± CI) with no difference in vertical displacement of center of mass (COMz). From Pre to Post, peak velocity and cycle time were increased and the displacement of COMz were reduced similarly for both PLs. At moderate speed, PL90% induced less displacement of COMz with subsequent 1.1 ± 0.7% lower O2-cost compared to PL84%. From Pre to Post, the O2-cost and COMz were reduced similarly for both PLs.ConclusionsLonger PL than skiers self-selected lengths reduce O2-cost at moderate speeds, but induced lower peak velocity. Eight sessions of training with PL90% did not influence the difference between PL84% and PL90% on O2-cost, kinematics or peak velocity.

Validity of a Commercially Available Inertial Measurement Unit for Vertical Jump Height Measurement

3D motion capture (3D) systems are the gold standard for assessing displacement during movements such as a drop vertical jump (DVJ) and a countermovement jump (CMJ). However, it is not feasible to use 3D in the field during game or practice situations. URPOSE: To examine validity of vertical jump height measured by inertial measurement units (IMU). METHODS: Eleven male (15.4±0.9yrs, 178.0±6.5cm, 80.5±13.04kg) high school football players participated. A small IMU placed in an elastic belt was worn around the waist of each subject during 3 CMJ and DVJ trials. Maximum vertical jump height was recorded as the vertical displacement of the pelvis using standard 3D techniques. A 2X2 repeated measures ANOVA (p<0.05) was used to determine differences in vertical displacement between measurement methods and movement type. 95% limits of agreement (LOA) and Bland Altman plots were utilized to determine the level of agreement between IMU and 3D during each task. RESULTS: A significant interaction between measurement and movement was found in vertical displacement (p<0.05). During the CMJ, the displacement measurement was not different (3D: 46.9±5.4cm, IMU: 45.9±3.8cm p=0.36). However, during the DVJ, the IMU measurement was statistically underestimated (45.0±3.7cm p=0.001) compared to 3D (48.7±5.7cm). Bland Altman plots and 95% LOA (Figure) illustrate a systematic error between the IMU and 3D during the DVJ where jump height was underestimated by the IMU. Interestingly, during both tasks, agreement between measurement methods seem to increase at higher jump heights. CONCLUSIONS: IMU technology is advancing with potential utility for on-field and in-game use. However, the algorithms which calculate vertical jump height may need to be adapted for varying types of complex movements.Figure

Body position and technique effects on displacement in the dyno maneuver in rock climbing

AbstractThis study compared vertical displacement of rock climbers performing a dyno maneuver using a squat jump (SJ) and a counter-movement (CM) technique. These techniques were tested at three different starting positions, varying in distance between hand and foot holds. Thirteen recreational rock climbers performed two SJ and two CM dynos at each starting position. Vertical displacement was measured through video analysis. Results showed that there were no significant differences in vertical displacement of the hand (VDH) between jump techniques (p > 0.05). There was, however, a significant improvement in VDH as the subjects moved from the low-to-medium and medium-to-high starting positions (p < 0.05). Therefore, a climber should base their technique on preference or experience while leaving a sufficient amount of space between the hands and feet if possible.

Displacements of tower foundations in permafrost regions along the Qinghai–Tibet Power Transmission Line

In permafrost regions along the Qinghai–Tibet Power Transmission Line (QTPTL) from Golmud, Qinghai Province to Lhasa, Tibet Autonomous Region, China, 130 tower foundations were selected for foundation displacement observations. Based on observations, displacement characteristics and mechanisms of tower foundations in plateau permafrost soils were analyzed. The results showed that vertical displacement of the footings (VDF) was the dominant displacement type of tower foundations, while changes in footing span (horizontal distance between two tower footings) (CFS) and differences in vertical displacement (DVD) between two adjacent footings of each tower were relatively small. The VDF of most tower foundations (about a quarter of the 130 observed foundations) performed as settlement rather than frost jacking. Due to the effective cooling of thermosyphons, frost jacking of tower foundations mainly occurred in cold seasons (from October to the next May); and because of the hysteresis of heat transfer process in foundation soils, settlement happened in cold seasons, too. Combining with the analysis of the thermal regimes of foundation soils, it was found that the ground temperature under the foundation was the most important factor influencing the VDF of tower foundations. In addition, the creep of the underlying warm and high ice-content permafrost was inferred as the main cause for the foundation settlement. The relatively slight frost jacking of tower foundations mainly resulted from frost heaving in situ of foundation soils and heaving possibly due to considerable water migration within the foundation pit. On slope terrains, the downslope movement (creep) of active layer soils resulted in considerable CFS of tower foundations. DVD between two adjacent tower footings might be derived from jacking of tower foundations with thermosyphons and the artesian sub-permafrost water migration. The effect of the latter was stronger, especially when the artesian water resulted in the development of ground icing. These results and conclusions may provide valuable references for the design and maintain of similar structures in permafrost regions.

Late Quaternary activity of faults and recurrence interval of earthquakes in the eastern Hokuriku region, northern central Japan, on the basis of precise cryptotephra analysis of fluvial terrace sequences

About 2000 active faults are known to exist within the land area of Japan. Most of these active faults have deformed the topographic surfaces which were formed in the late Quaternary, including fluvial terraces; and the formative ages of these terraces are estimated mainly by tephrochronology. Fluvial terraces in the eastern Hokuriku region, comprising the Toyama, Tonami, and Kanazawa Plains, northern central Japan, are widely distributed and have been deformed by reverse active faults. The formative age of terraces in this area has not been reported, as volcanic ash deposits are rarely visible within terrace deposits and the overlying loamy soil, and outcrops of fluvial terraces are quite scarce in this area. In the present study, we carried out a drilling survey on these terraces to obtain samples of the overlying loamy soil and upper part of terrace deposits. From these samples, we extracted some well-known widespread volcanic ash, from which we were able to estimate the approximate age of the terraces and the vertical slip rate of the active faults. Late Quaternary fluvial terraces in eastern Hokuriku are divided into 12 levels: Terraces 1 to 12 in descending order. Widespread tephras such as the Kikai-Tozurahara Tephra (K-Tz: 95 ka) are contained in the lowest part of the loamy soil in Terrace 4 and the Daisen-Kurayoshi Pumice (DKP: 55 ka) is present in the lowest part of the loamy soil in Terrace 6. From the ages and the vertical displacements of the fluvial terraces, the late Quaternary average vertical slip rates of active faults in eastern Hokuriku are estimated to be 0.2–0.9 mm/year (Uozu fault), 0.1–0.4 mm/year (Kurehayama fault), 0.1–0.3 mm/year (Takashozu fault), 0.1–0.4 mm/year (Hohrinji fault), and 0.5–0.8 mm/year (Morimoto-Togashi fault). We also estimated the recurrence interval of earthquakes related to active faults from displacement per event and ages of terraces and no significant difference in vertical displacement per single earthquake for different active faults, and recurrence intervals tend to be inversely proportional to vertical displacement rates. This study demonstrates that a combination of drilling of loamy soil and precise cryptotephra analysis of fluvial terraces can be used to estimate the formative age of the terraces and the average slip rate of active faults in areas where volcanic ash deposits are rare.

SEGMENTAL MOTION OF THE SPINE DURING VARIED RUNNING SPEEDS OF MIDDLE DISTANCE RUNNERS

Previous studies have not examined motions of the spine during running. PURPOSE The purpose of this study was to measure the vertical and lateral displacements of cervical and thoracic vertebra during running on a treadmill at various speeds. METHODS Four competitive collegiate middle distance runners (21.4 ±1.9 yrs) ran on a treadmill under four speed conditions: 10.8; 12.1; 13.8; and 16.1 km/hr. Reflective markers were attached over the skin of C7 and even numbered thoracic vertebra from T2 to T12. Each condition was videotaped and digitized using an Ariel Performance Analysis System. Vertical and lateral displacements were calculated during a single stride for each condition. Displacement comparisons between conditions in each direction were made using a one-way ANOVA with repeated measures. RESULTS Amounts of vertebral displacement within each speed remained relatively constant. Significantly greater lateral movement of lower vertebra (T4 thru T12) was observed at faster speeds. Vertical vertebral displacement decreased from upper to lower vertebra within each speed. There were no significant differences in vertical displacement across speeds for the upper vertebra (C7 thru T4), but significantly less vertical displacement was observed for the lower vertebra (T6 thru T12) at the two fastest speeds compared with the two slower speeds. CONCLUSION At faster rates of running speed lateral spine movement increases and vertical movement decreases for lower thoracic vertebra. The latter result suggests a more stable vertical center of gravity, possibly resulting in more efficient motion.

Effect of Aging on Swelling and Swell-Shrink Behavior of a Compacted Expansive Soil

Abstract Effect of aging on swelling and swell-shrink behavior of a compacted expansive soil is investigated in this paper. An expansive soil having a liquid limit of 100% is used for this purpose. Compacted specimens were prepared and aged for a predetermined number of days (7, 15, 30, and 90 days) to study their swelling and swell-shrink behavior. It has been shown that aging improves the resistance to compression of compacted specimens. The swelling potentials of specimens also decreased with aging. The dominant factors that influence the aging effects are the water content and degree of saturation at the beginning of the aging process. The changed behavior of aged specimens is attributed to particle rear-rangements and formation of bonds, which affect the surface area absorbing water during swelling. The cyclic swell-shrink tests on aged specimens indicated that the differences in vertical displacement during the first swelling were eliminated in the subsequent cycles when specimens were shrunk more, but the aging effect was found to persist with cycles for specimens subjected to lower shrinkage magnitudes.

Surface Correlations and Exchange at a Spherical Liquid Interface

The paper gives a new derivation of the rms displacement and slope of the surface of a spherical drop in the presence of thermally excited capillary waves. Calculations for a spherical surface have the advantage, over similar calculations for a plane surface, that they avoid the difficulty of having to choose an arbitrary upper limit for the wavelength. Expressions are obtained for time and distance correlation functions of the vertical displacement, of the difference in vertical displacement between different times or locations, of vertical velocity, and of the difference of vertical velocity between separate times or locations on the surface. The correlation function for the difference in vertical velocity between two points on the surface rapidly attains a constant, nonzero value as the separation of the points increases. The limiting value of the velocity difference is related to the speed of motion along the reaction coordinate when the process of accommodation into the bulk liquid is treated by transition-state theory. This leads to an estimate of the physical length of the critical region of the reaction coordinate that must be traversed if accommodation is to occur.

ＣＦＲＰ積層材の静的横せん断特性

The first experiment for obtaining the static transverse shear modulus and failure strain of CFRP Laminates is presented in this paper. In order to obtain these values, the difference in vertical displacement of two points on the neutral axis of a short beam specimen is measured by a newly devised electro-optical extensometer. The transverse isotropy is first confirmed by our proposed method. Furthermore, the experimental results of transverse shear modulus and failure strain are compared with those based on a classical lamination theory and a three dimensional FEM code, respectively.

Maxillary superimposition: A comparison of three methods for cephalometric evaluation of growth and treatment change

Two anatomic methods are statistically compared with the implant method for superimposing serial head films in 18 subjects with metallic implants. Findings showed that the “best fit” method—that is, superimposition along the palatal plane registered at ANS—traditionally used by orthodontists, significantly underestimates the eruption of the teeth by 30% to 50%. The “structural method,” which is based on the use of stable structures in the maxilla, showed no significant differences in vertical displacement of selected landmarks in comparison with the implant method.