Line Displacement Research Articles

ANALYSIS OF LANDSLIDES BASED ON DISPLACEMENTS OF LINES

Abstract. Nowadays, the development of UAS has allowed the obtaining of high resolution and accurate cartographic products, such as DSMs and orthoimages. These products can be used in studies of the evolution of landslides. The stability of slopes is a main issue because, among others, it can suppose a serious risk to infrastructures. Until this moment, some studies for analysing slope movements have been carried out using the comparison of positions of well-defined points or comparing two surfaces obtained from two DSMs. In this paper we present a methodology for analysing landslides based on some linear elements located on the terrain. More specifically, we analyse some lines of road sections which are located on an unstable slope, checking the movements of the landslide and their effect on the infrastructure. The methodology includes the obtaining of high resolution orthoimages and DSMs which correspond to two or more epochs of the same landslide, the 3D digitizing of common linear elements, and the computing of the displacements of matched lines (from two epochs) using positional control methods based on lines. The proposed methodology has been tested using two DSMs and two orthoimages (corresponding to two epochs) obtained from two photogrammetric projects developed with an UAS. This real case was applied to an unstable slope with landslides which affected several sections of a road. The results have demonstrated the viability of the proposed methodology in analysing the behaviour of the landslide and more specifically, the effects on these infrastructures.

EFFECT OF LOADING RATE ON FRACTURE BEHAVIOUR OF Mg-Al-Zn ALLOYS

In recent years, magnesium alloys are widely used for automotive applications as structural components due to its lightweight property and high specific strength. In this regards, magnesium alloys are subjected to high velocity and impact loads during accident. Hence, understanding the impact and dynamic behaviours of magnesium alloys are essential. In this study, the effect of loading rates on the fracture behaviour of Mg-Al-Zn alloys was investigated using pre-cracked single-edge notched bending (SENB) specimens. Three-point bending tests were conducted at different loading rates of 5, 50 and 500 mm/min. The Mg-Al-Zn alloys that used in the present study were extruded AZ31 and AZ61 magnesium alloys. From the load-load line displacement results, both alloys exhibited nonlinear fracture behaviour. The maximum load (Pmax) of these two alloys increased with increasing loading rate. Comparing both alloys, AZ61 exhibited higher Pmax than that of AZ31 due to the higher volume of b-phase and smaller grain size in AZ61. Fracture surface observation revealed that both alloys fractured in ductile manner with large scale yielding and high shear lips ratio at all loading rates.

Assessment of diffusion tensor image quality across sites and vendors using the American College of Radiology head phantom

The purpose of this study was to explore the feasibility of assessing quality of diffusion tensor imaging (DTI) from multiple sites and vendors using American College of Radiology (ACR) phantom. Participating sites (Siemens (n=2), GE (n=2), and Philips (n=4)) reached consensus on parameters for DTI and used the widely available ACR phantom. Tensor data were processed at one site. B0 and eddy current distortions were assessed using grid line displacement on phantom Slice 5; signal‐to‐noise ratio (SNR) was measured at the center and periphery of the b=0 image; fractional anisotropy (FA) and mean diffusivity (MD) were assessed using phantom Slice 7. Variations of acquisition parameters and deviations from specified sequence parameters were recorded. Nonlinear grid line distortion was higher with linear shimming and could be corrected using the 2nd order shimming. Following image registration, eddy current distortion was consistently smaller than acquisition voxel size. SNR was consistently higher in the image periphery than center by a factor of 1.3–2.0. ROI‐based FA ranged from 0.007 to 0.024. ROI‐based MD ranged from 1.90×10−3 to 2.33×10−3mm2/s(median=2.04×10−3mm2/s). Two sites had image void artifacts. The ACR phantom can be used to compare key quality measures of diffusion images acquired from multiple vendors at multiple sites.PACS number(s): 87.57.‐s, 87.19.lf

Ductile tearing simulation of Battelle pipe test using simplified stress‐modified fracture strain concept

AbstractIn this paper, numerical ductile tearing simulation results are compared with six circumferential through‐wall and surface cracked pipes made of two materials (SA‐333 Gr. 6 and A106 Gr. B carbon steels), performed at Battelle. For simulation, a model using a simplified fracture strain model is employed, by analysing tensile data of the material. By comparing experimental J‐R data with FE simulation results, the damage model dependent on the element size is determined based on the ductility exhaustion concept. The model is used to simulate ductile tearing behaviour of six circumferential through‐wall and surface cracked pipes. In all cases, simulated results agree well with experimental load, crack length and crack mouth opening displacement versus load line displacement data.

Intrinsic Sacral Deformity in L5 Istmic Lythic Spondylolysthesis

Introduction A deformity in the sacrum has been reported in patients with spondylolysthesis (Antoniades, Spine 2000) Hypothesis Besides sagittal profile, the sacrum in itself is deformed, probably due to a fixed point in the sacoiliac joints acting as fulcrum and deforming force from ventral displacement of gravity line. Matherial and Methods A control group (group C), matchable for age and gender, was compared with a series of 83 patients with L5 istmic lythis spondylolysthesis (group A), which was later subdivided in low grade (Meyerding types I and II, group A1, n = 67) and high grade (Meyerding III or IV, group A2, n = 16) Variable Proximal sacral kyphosis measured by the angle formed by the S1 posterior wall and the S2 posterior wall, if S1 was kyphotic on S2 then it was considered a positive angle, other wise being negative. Statistics SPSS 21.0, working with means or medians and appropriate tests after studying whether the variable showed a normal distribution. Results Group C lordosis -2° (minimum -8°; maximum +7°). Group A kyphosis +10° (minimum -11°; maximum +30°). And then: Group A1 kyphosis +10° (minimum -11°; maximum +30°). Group A2 kyphosis +15° (minimum +5°; maximum +26°). There were statistically relevant differences between group C and group A and also between groups A1 and A2. Conclusion Besides spinopelvic balance issues, there is an intrinsic deformity in the sacrum of patients with L5 istmic lythic spondylolysthesis, even more in high grade lysthesis.

The temperature monitoring during the reactor core material irradiation by analyzing the structure of graphite-like boron nitride

Possibility has been shown for determining the temperature of in-core irradiation using a single structural analysis of irradiated boron-nitride ceramics without a time-consuming research stage, including post-irradiation annealing. This is explained by the fact that steady structural states, depending on temperature and not depending on exposure dose, may develop in nanocrystalline graphite-like ceramic boron nitride in high-dose environments. A temperature dependence of the position of the X-ray line (002) has been obtained for the radiation-induced steady structure of ceramics. This dependence can be used for determination of temperature in a fast reactor in a range of 690 to 1870K.It has been found using X-ray structural analysis that reaction-sintered boron-nitride ceramics in the initial and irradiated states comprises two structural components. The first one corresponds to defect-free hexagonal and rhombohedral structures. The X-ray line displacements relate to the second component the nanocrystallites of which contain a great deal of microdeformations stabilized by clusters of vacancy discs.

Enhancement of contact line mobility by means of infrared laser illumination. II. Numerical simulations

A droplet that moves on a solid substrate with a velocity higher than a certain critical velocity disintegrates, i.e., leaves behind residual droplets. Infrared laser illumination can be used to increase the droplet mobility and suppress the shedding of droplets. By means of two-dimensional numerical simulations, we studied the effect of a non-uniform temperature distribution on the dynamics of straight receding contact lines. A streamfunction-vorticity model is used to describe the liquid flow in the vicinity of the receding contact line. The model takes into account the thermocapillary shear stress and the temperature-dependent liquid viscosity and density. A second, coupled model describes the laser-induced displacement of the contact line. Our results show that the reduction of the liquid viscosity with increasing temperature is the dominant mechanism for the increase of the critical velocity. Thermocapillary shear stresses are important primarily for low substrate speeds.

Non-linearly Restoring Performance of SFT's Catenary Mooring-lines under Consideration of its Dynamic Behaviors

Submerged floating tunnel (SFT) needs to be fixed or controlled in expected position by its supporting system which can be classified into two types: tension tendon or catenary mooring-line. The later one, catenary mooring-line, is often used for floating body due to its lower cost and easier installment. In this paper, the dynamic behaviors including inertia and hydrodynamic damping of the mooring-line are considered compared with the quasi-static method where only the static restore force is involved, and the nonlinear dynamic response model of the mooring system is developed based on finite element simulations. The influences of the amplitude and frequency of SFT motion, along with mooring-line's structural parameters, on mooring line's displacement and dynamic tension are studied. Also, the taut-slack phenomenon caused by inertial force and hydrodynamic damping is analyzed. Our results shows that when the motion of the SFT is smaller, the dynamic response of the mooring-line is a stable stand wave, and the value of dynamic tension due to dynamic characteristics is about 20% of the quasi-static method, and the tension amplitude difference is around three times larger than the quasi-static method. As SFT movement get larger, the dynamic tension corresponding is about 30% higher than the quasi-static tension. When the mooring-line becomes slack, the response is characterized as travelling wave. The magnification factor of top tension caused by mooring-line's dynamic behavior drops with increase of mooring-line mass density but rises with the increase of the initial tension ratio.

Hot stamping of AA6082 tailor welded blanks: experiment and FE simulation

An advanced forming technology, solution Heat treatment, Forming and in-die Quenching (HFQ ® ), has been employed to form AA6082 tailor welded blanks (TWBs). In comparison with conventional stamping of TWBs, the mechanical properties and formability of AA6082 laser TWBs could be improved under the HFQ ® forming condition. The TWB was divided into three physical zones, i.e. base metal, heat affected zone (HAZ) and weld zone, based on the hardness distribution. It was found that the degraded hardness of the weldment can be restored after HFQ ® forming. TWBs of AA6082 with different thickness ratios of 2 (2–1 mm), 1.3 (2–1.5 mm) and 1 (1.5–1.5 mm) were used to study the TWB thickness ratio effects on the forming behaviour. Hemispherical punch dome tests on the TWBs with varying thickness ratios demonstrated different formabilities, and indicated increased displacement of the weld line with increasing thickness ratio. Finite element (FE) modelling was adopted to analyse the weld line movement and strain distributions during HFQ ® forming.

Assessment of fracture line in maxillofacial region using panoramic digital radiographs and panoramic inverted digital radiographs: A comparative study

Introduction: Many times fractures go undetected, if not examined properly. For initial diagnosis and proper treatment plan of facial injuries, diagnostic images play a crucial role in providing necessary information. Aims and Objectives: To compare the diagnostic accuracy of conventional digital radiography and inverted digital panoramic imaging in detecting maxillofacial fractures. Materials and Methods: A total of 50 orthopantomographs were collected from the archives of dental and maxillofacial radiology. High quality radiographs with maximum sharpness, ideal contrast, and density were only included which were made using a digital OPG machine. The digital data were saved as jpeg files. Both conventional radiographs as well as inverted digitized images were evaluated by 3 expert radiologists twice with an interval of 10 days. The presence of a radiolucent line in conventional digital radiographs and radiopaque line in inverted digital image which depicted the fracture line was classified according to a 3 point confidence scale. Statistical Analysis Used: Intra observer variation was calculated using Student t test. Inter examiner agreement was calculated by kappa statistics by point (κ). Results: All the examiners showed poor to fair agreement for mandibular fractures and displacement of fracture line in both direct digital and inverted panoramic radiograph. Conclusions: Both the imaging modalities were reliable and there was no significant difference in the diagnostic accuracy.

A Fault Diagnosis Method of High Voltage Circuit Breaker Based on Moving Contact Motion Trajectory and ELM

In order to avoid the deficiencies of conventional high voltage circuit breaker mechanical properties detection methods, a new algorithm based on image block matching with diamond search strategy is presented in this paper. The motion of auxiliary mark on the pull rod or shaft is firstly recorded by a high-speed and high-definition digital camera when the circuit breaker is open or close. Then the motion trajectory is acquired through diamond image block matching method. The mechanical parameters, such as travel and open and close velocity, are calculated according to the travel-time curve of the circuit breaker. Finally, evaluation model is constructed taking mechanical parameters characteristic values as inputs of ELM. Comparing to the existing techniques, our method is a noncontact measurement based on computer vision. It is easy and convenient for practical application since it need not any electrical and mechanical connection to the breaker. Another advantage of our method is that it can obtain the line and angle displacement simultaneously. The experiment results on the circuit breaker of 220 kv show that our method is effective for breaker mechanical properties detection.

Study on a Ship with 6 Degrees of Freedom Inertial Measurement System and Related Technologies

We research ship 6 DOF inertial measurement method and displacement reconstruction form acceleration signal to establish the strap-down inertial navigation measurement system through sensors configuration technology. The inertial measurement system consists of three groups of vertically mounted angular rate and acceleration sensors. Through designing an FIR integration filter and studying the ship displacement signal reconstruction from the acceleration, the filter parameters design method and implementation way were determined. By means of the beam vibration to analog ship heave motion reconstructs linear displacement form acceleration signals. The root mean square error of the reconstructed line displacement is 0.004 mm, and the mean value of the displacement peak value is 5.92%, which is close to the design precision of the filter. The test shows that the measurement system and the FIR filter to achieve the predetermined precision with noise suppression.

Surface normal interpolation for five axis CNC milling

This paper presents an algorithm for five-axis CNC interpolation. The algorithm generates cutter location points by interpolating the surface normals along a desired path. The surface normals are represented by line coordinates which tie a orientation vector with a specific point in space. The algorithm uses line displacements to generate an approximation of the surface normals along a path. The main advantage of this method is that it relates the angular velocity of the tool to the feed rate requirement of the interpolation. An example is shown of the interpolation technique on a Bezier surface.

Role of diffusion on molecular tagging velocimetry technique for rarefied gas flow analysis

The molecular tagging velocimetry (MTV) is a well-suited technique for velocity field measurement in gas flows. Typically, a line is tagged by a laser beam within the gas flow seeded with light emitting acetone molecules. Positions of the luminescent molecules are then observed at successive times and the velocity field is deduced from the analysis of the tagged line displacement and deformation. However, the displacement evolution is expected to be affected by molecular diffusion, when the gas is rarefied. Therefore, there is no direct and simple relationship between the velocity field and the measured displacement of the initial tagged line. This paper addresses the study of tracer molecules diffusion through a background gas flowing in a channel delimited by planar walls. Tracer and background species are supposed to be governed by a system of coupled Boltzmann equations, numerically solved by the direct simulation Monte Carlo (DSMC) method. Simulations confirm that the diffusion of tracer species becomes significant as the degree of rarefaction of the gas flow increases. It is shown that a simple advection–diffusion equation provides an accurate description of tracer molecules behavior, in spite of the non-equilibrium state of the background gas. A simple reconstruction algorithm based on the advection–diffusion equation has been developed to obtain the velocity profile from the displacement field. This reconstruction algorithm has been numerically tested on DSMC generated data. Results help estimating an upper bound on the flow rarefaction degree, above which MTV measurements might become problematic.

Producing and imaging a thin line of He2∗ molecular tracers in helium-4

Cryogenic helium-4 has long been recognized as a useful material in fluids research. The unique properties of helium-4 in the gaseous phase and the normal liquid phase allow for the generation of turbulent flows with exceptionally high Reynolds and Rayleigh numbers. In the superfluid phase, helium-4 exhibits two-fluid hydrodynamics and possesses fascinating properties due to its quantum nature. However, studying the flows in helium-4 has been very challenging largely due to the lack of effective visualization and velocimetry techniques. In this article, we discuss the development of novel instrumentation for flow-visualization in helium based on the generation and imaging of thin lines of metastable He*₂ tracer molecules. These molecular tracers are created via femtosecond-laser field-ionization of helium atoms and can be imaged using a laser-induced fluorescence technique. By observing the displacement and distortion of the tracer lines in helium, quantitative information about the flow field can be extracted. We present experimental results in the study of thermal counterflow in superfluid helium that validate the concept of this technique. We also discuss anticipated future developments of this powerful visualization technique.

A Hybrid Haptic Sensation for Teleoperation of Hydraulic Manipulators

In this paper, a control scheme is designed for stable haptic teleoperation of hydraulic manipulators. The controller results in a stable position tracking for the hydraulic actuator (slave) in both unconstrained and constrained motions. The force feedback at the haptic (master) side is a combination of two different sensations. For free motion, the haptic device provides a haptic force based on the position error between the displacements of the master and the slave. The force also serves to alert the operator when the slave is ahead or behind in position tracking of the master. Once the slave comes in contact with the environment, the haptic force is augmented by the interaction force. The uniqueness, continuation, and existence of the Filippov solution to this system with the discontinuity surfaces are proven first. The extension of Lyapunov's stability theory to nonsmooth systems is then employed to prove the stability by constructing a Lyapunov function. The effectiveness of the controller is validated via experimental studies. It is shown that while stable, the system performs well in terms of position tracking of the hydraulic actuator and providing a haptic feel to the operator. The measurements required by the controller are supply pressure, actuator's line pressures, interaction force, and displacements of the master and slave.

Gap-balancing technique combined with patient-specific instrumentation in TKA.

Combining patient-specific instrumentation (PSI) with a balancer device in total knee arthroplasty (TKA) to achieve functional femoral rotational alignment is a novel technique. The primary goal of this study was to introduce a new method to combine PSI with a gap-balancing technique and to determine the impact of the technique on rotation of the femoral component. Twenty-five primary TKAs (15 women, 10 men) were prospectively studied. All TKAs involved PSI with an associated gap-balancing device. Front plane alignment was performed intraoperatively with the PSI, followed by rectangular, symmetrical extension and creation of a flexion gap using the balancer device to set the femoral rotation. Femoral component rotation was between 3° internal and 6° external rotation versus the transepicondylar axis. There were no postoperative signs of patellofemoral dysfunction. In no cases was the resulting joint line displacement >3 mm. The mean elevation was 1.2 ± 0.9 mm (range 0-3). The leg axis was straight in all cases (±3°), at a mean of 1.6° ± 1.0° varus (range 0°-3° varus). PSI was with the gap-balancing technique was successfully used without affecting anatomical alignment. With the balancer device, PSI can be used more widely than techniques based solely on landmarks, as the soft-tissue tension can be taken into account, thus virtually eliminating flexion instabilities.

Comparison among estimation methods of C* parameter for axially oriented external surface crack in cylinders

C* is usually used to describe the creep crack growth. ASTM E1457 allows C* to be calculated from creep load line displacement rate. However in components it is difficult or impossible to measure load line displacement rate. Therefore for the components C* must be determined by finite element methods or reference stress concepts. Estimates of C* obtained by reference stress methods will depend on the collapse mechanism adopted and therefore several estimations are proposed. This paper presents a numerical study of non-linear fracture mechanics parameter predictions under elevated temperature for axially oriented external surface crack in cylinder. Comparison of C* calculated from FE analysis and different reference methods is conducted. The values of C* obtained from the API579 net section solution are also found to be slightly conservative and give the closest agreement to the F.E. contour integral C*. In addition, the comparison between C* of homogeneous material and TYPE IV cracking is conducted. The difference between homogeneous material and TYPE IV cracking is almost negligible and therefore the reference stress solutions for homogenous material could be applied to estimate C* for TYPE IV cracking.

Numerical study of the applicability of the η-factor method to J-resistance curve determination of steam generator tubes using non-standard specimens

The suitability of the η-factor method for the determination of J-resistance curves of thin walled steam generator tubes was evaluated using elastoplastic finite element analysis. Different candidate non-standard specimens’ geometries were considered. It was shown how high constraint conditions associated with deep cracks geometries and prevailing bending loads favor the η-factor validity while low constraint configurations resulted in a η-factors exhibiting a higher dependence on the applied load. It was also verified that η-factors based on the crack mouth opening displacement (CMOD) showed much less dependency on the loading level than η-factors derived from load line displacement (LLD).

A statistical study of fundamental toroidal mode standing Alfvén waves using THEMIS ion bulk velocity data

AbstractWe have studied the statistical properties of toroidal mode standing Alfvén waves with a fundamental eigenmode structure along the field line, denoted T1 waves, in the L range 7–12, using THEMIS‐D data for 2008–2013. T1 wave events were identified in hourly data segments using an automated procedure that detects narrowband oscillations in the azimuthal component of the ion bulk velocity. For each event we determined the frequency, amplitude, ellipticity, and the orientation angle of the polarization ellipse, and we examined the L and magnetic local time dependence of the detection rate and physical properties of the T1 waves. Confirming previous observations in space and on the ground, we found a pronounced dawn‐dusk asymmetry in the wave detection rate and amplitude. The detection rate in the dawn sector is approximately twice as high as that in the dusk sector, and the amplitude in the dawn sector is larger by ∼50%. The same asymmetry is also evident in the velocity amplitude averaged in the fixed Pc5 band (1.7–6.7 mHz) and in the amplitude of the electric field and field line displacement that are derived from the velocity amplitude. The ellipticity and the orientation angle of the polarization ellipse are organized by local time, in accordance with the theoretical prediction of toroidal mode waves excited by field line resonance with tailward propagating waves in the magnetosphere, which are in turn driven by external sources. Although infrequently, T1 waves are also detected in the midnight sector, suggesting magnetotail sources for this subset of events.