Motion Of Point Research Articles

Acceptable migration of a fully cemented rotating hinge-type knee revision system measured in 20 patients with model-based RSA with a 2-year follow-up

Rotating hinged knee implants are highly constrained prostheses used in cases in which adequate stability is mandatory. Due to their constraint nature, multidirectional stresses are directed through the bone-cement-implant interface, which might affect fixation and survival. The goal of this study was to assess micromotion of a fully cemented rotating hinged implant using radiostereometric analysis (RSA). 20 patients requiring a fully cemented rotating hinge-type implant were included. RSA images were taken at baseline, 6 weeks, and 3, 6, 12, and 24 months postoperatively. Micromotion of femoral and tibial components referenced to markers in the bone was assessed with model-based RSA software, using implant CAD models. Total translation (TT), total rotation (TR), and maximal total point motion (MTPM) were calculated (median and range). At 2 years, TTfemurwas 0.38 mm (0.15-1.5), TRfemurwas 0.71° (0.37-2.2), TTtibiawas 0.40 mm (0.08-0.66), TRtibiawas 0.53° (0.30-2.4), MTPMfemurwas 0.87 mm (0.54-2.8), and MTPMtibiawas 0.66 mm (0.29-1.6). Femoral components showed more outliers (> 1 mm, > 1°) compared with tibial components. Fixation of this fully cemented rotating hinge-type revision implant seems adequate in the first 2 years after surgery. Femoral components showed more outliers, in contrast to previous RSA studies on condylar revision total knee implants.

QUANTIFYING SLIDING DISTANCE DURING CAM-TYPE HIP IMPINGEMENT FOR A SET OF ACTIVITIES

Cam-type femoroacetabular impingement is caused by bone excess on the femoral neck abutting the acetabular rim. This can cause cartilage and labral damage due to increased contact pressure as the cam moves into the acetabulum. However, the damage mechanism and the influence of individual mechanical factors (such as sliding distance) are poorly understood. The aim of this study was to identify the cam sliding distance during impingement for different activities in the hip joint.Motion data for 12 different motion activities from 18 subjects, were applied to a hip shape model (selected as most likely to cause damage, anteriorly positioned with a maximum alpha angle of 80°). The model comprised of a pointwise representation of the acetabular rim and points on the femoral head and neck where the shape deviated from a sphere (software:Matlab).The movement of each femoral point was tracked in 3D while an activity motion was applied, and impingement recorded when overlap between a cam point and the acetabular rim occurred. Sliding distance was recorded during impingement for each relevant femoral point.Angular sliding distances varied for different activities. The highest mean (±SD) sliding distance was for leg-crossing (42.62±17.96mm) and lowest the trailing hip in golf swing (2.17±1.11mm). The high standard deviation in the leg crossing sliding distances, indicates subjects may perform this activity in a different manner.This study quantified sliding distance during cam impingement for different activities. This is an important parameter for determining how much the hip moves during activities that may cause damage and will provide information for future experimental studies.

INTERNAL TIME OF A MECHANICAL SYSTEM

One of the most urgent unsolved problems of modern science is the extension of the second law of thermodynamics to conservative mechanical systems that are in a state far from thermodynamic equilibrium. How does the collective motion of the material points of the system, each of which is described by time-reversible equations, become irreversible? Thus, the increase in entropy of an ideal gas in a state close to equilibrium indicates the irreversible nature of the evolution of a conservative mechanical system, which is definitely an ideal gas. That is, entropy acts as internal time and sets the direction to the future or the "arrow of time". The paper deals with obtaining a characteristic of a conservative mechanical system that would have the properties of entropy. The goal is to extend the second law of thermodynamics to conservative mechanical systems that are in a state far from equilibrium. Analytical methods were used to analyze the differential equations of motion of a phase liquid particle as an image of a mechanical system in a multidimensional space. The evolution of the distribution of the probability of a particle of a phase fluid staying on a hypersurface of equal energy is considered. For a conservative mechanical system, a value is introduced whose properties allow us to apply the term "internal time" to it. Its growth determines the difference between future events and past events, which is an inherent property of subjective time. When approaching the state of equilibrium, internal time slows down, and physical time, accordingly, accelerates relative to internal time. Internal time is as universal as physical time, in the sense that it is determined for each system by a universal formula. The proposed approach made it possible to solve the fundamental problem of replacing the averaging of the probability density in the phase space by averaging in time along the trajectory of the point in the phase space. We used the fact that the equation of motion of a conservative system can be obtained as the equation of motion of a particle of a phase liquid, using the law of conservation of matter. The equations of motion of a particle were transferred to the motion of a point. In contrast, when using the traditional approach, the equation of motion of a point in phase space was taken as the basic law of nature. An understanding of internal time allows us understand the emergence of dissipative structures in the future.

IN VIVO PILOT STUDY OF TIBIOFEMORAL KINEMATICS DURING LOADED DYNAMIC ACTIVITIES

Biplane video X-ray (BVX) – with models segmented from magnetic resonance imaging (MRI) – is used to directly track bones during dynamic activities. Investigating tibiofemoral kinematics helps to understand effects of disease, injury, and possible interventions.Develop a protocol and compare in-vivo kinematics during loaded dynamic activities using BVX and MRI.BVX (60 FPS) was captured whilst three healthy volunteers performed three repeats of lunge, stair ascent and gait. MRI scans were performed (Magnetom 3T Prisma, Siemens). 3D bone models of the tibia and femur were segmented (Simpleware Scan IP, Synopsis). Bone poses were obtained by manually matching bone models to X-rays (DSX Suite, C-Motion Inc.). Mean range of motion (ROM) of the contact points on the medial and lateral tibial plateau were calculated using custom MATLAB code (MathWorks). Results were filtered using an adaptive low pass Butterworth filter (Frequency range: 5-29Hz).Gait and Stair ascent activities from one participant's data showed increased ROM for medial-lateral (ML) translation in the medial compartment but decreased ROM in anterior-posterior (AP) translation when comparing against the same translations on the lateral compartment of the tibial plateau. Lunge activity showed increased ROM for both ML and AP translation in the medial compartment when compared with the lateral compartment.These results highlight the variability in condylar translations between different activities. Understanding healthy in-vivo kinematics across different activities allows the determination of suitable activities to best investigate the kinematic changes due to disease or injury and assess the efficacy of different interventions.Acknowledgements: This research was supported by the Engineering and Physical Sciences Research Council (EPSRC) doctoral training grant (EP/T517951/1).

Synthesizing Audio from Tongue Motion During Speech Using Tagged MRI Via Transformer.

Investigating the relationship between internal tissue point motion of the tongue and oropharyngeal muscle deformation measured from tagged MRI and intelligible speech can aid in advancing speech motor control theories and developing novel treatment methods for speech related-disorders. However, elucidating the relationship between these two sources of information is challenging, due in part to the disparity in data structure between spatiotemporal motion fields (i.e., 4D motion fields) and one-dimensional audio waveforms. In this work, we present an efficient encoder-decoder translation network for exploring the predictive information inherent in 4D motion fields via 2D spectrograms as a surrogate of the audio data. Specifically, our encoder is based on 3D convolutional spatial modeling and transformer-based temporal modeling. The extracted features are processed by an asymmetric 2D convolution decoder to generate spectrograms that correspond to 4D motion fields. Furthermore, we incorporate a generative adversarial training approach into our framework to further improve synthesis quality on our generated spectrograms. We experiment on 63 paired motion field sequences and speech waveforms, demonstrating that our framework enables the generation of clear audio waveforms from a sequence of motion fields. Thus, our framework has the potential to improve our understanding of the relationship between these two modalities and inform the development of treatments for speech disorders.

Adaptive Visual Servoing Shape Control of a Soft Robot Manipulator Using Bézier Curve Features

Soft continuum robot outperforms its rigid counterpart when executing in complicated environments thanks to its high dexterity of the redundant configuration. Shape control is regarded as a prerequisite to applications in unstructured environments. In this article, we develop an adaptive image-based visual servoing (IBVS) algorithm using an uncalibrated camera to realize visual shape control of the cable-driven soft manipulator. A Bézier curve is selected to be the feature providing shape information of the soft robot. An adaptive law is proposed to simultaneously solve the uncalibrated problem and to analytically model the motion of curve control points. The control algorithm is then designed with third-order Bézier curve being the image features, and theoretically proves its stability. The algorithm has been experimentally validated in the cable-driven soft continuum robot. The experiment results demonstrate rapid converging performance to C-type and S-type reference shapes.

Variational problem of adaptive optimal control. Theoretical and applied computer analysis

The problem of adaptive optimal control of a dynamical system, which belongs to the class of conditional variational problems with moving boundaries, is considered. A variational and computer study of the controlled adaptive motion of a material point is carried out for the problem of the energy quality functional minimizing with a moving, not predetermined right transboundary and in the case when the mass of the point changes depending on the unfixed final time. The problem is solved using the schemes and procedures of the classical calculus of variations, as well as adaptive estimation techniques, including the derivation of the variation of the auxiliary quality functional, the corresponding Euler equations, and the adaptive estimation algorithm. When solving a general conditional variational problem, the obtained closed system of differential equations was studied for the formation of an adaptive optimal control system for a dynamic plant with a given performance functional. The results of the unconditional formulation of the problem are generalized to the case of additional differential (nonholonomic) and holonomic constraints. In a variational adaptive optimal control problem, the transversality condition is formulated in terms of the local programming condition. The developed variational scheme of adaptive optimal synthesis can be used in the calculation and design of controlled dynamic systems. This optimization scheme is also promising for use in systems where operating time is non-fixed in advance. The results achieved in this paper concern obtaining specific equations, expressions, and formulas relative to the model example under study and finding graphs of the main time functions that determine the nature of the movement of the control object and the quality of the corresponding transients. The proposed adaptive optimal control algorithms for purposeful movement of the studied material point were tested in digital mode and showed their effectiveness which makes them promising for further use in more complex nonlinear adaptive systems of dynamic optimal control.

Volumetric measurement of a Newtonian fluid flow through three-dimensional porous media using Lagrangian particle tracking (Shake-the-Box) technique

This work experimentally investigates the pressure-driven flow of a pure Newtonian fluid through three-dimensional (3D) porous media models. The porous media model consists of square arrays of rods that also could be interpreted as a periodic tandem rod arrangement. We employed a time-resolved three-dimensional particle tracking velocimetry (3D Shake-the-Box) technique for a range of Reynolds numbers 111 ≤ R e ≤ 890 to observe flow structures and vortex formation between the rods in porous media structures with different porosities of ε = 0.7 , 0.8 , and 0.9 , which corresponds to the spacing ratio of L D = 1.75 , 2 , and 3, where L is the distance between the centers of the rods, and D is the diameter of the rods. For all the examined cases, we further analyzed the effect of the Reynolds number and the spacing ratio on the instantaneous and averaged patterns of velocity, vorticity, and the other flow parameters after obtaining the two-dimensional velocity fields using the bin-averaging method. We observed both symmetrical and asymmetrical patterns of structure and recirculation regions between the rods depending on the Reynolds number and spacing ratio. Increasing the Reynolds number reduced the symmetrical patterns of flow structures with respect to the centerline of the gap region, while the spacing ratio was randomly affecting the symmetry degree. Vortex shedding was considerable for the two examined high Reynolds numbers of Re = 444 and Re = 890 behind the upstream rod as the porosity increased. The backward movement of the reattachment point has been observed by increasing the Reynolds number.

Natural Grasp Intention Recognition Based on Gaze in Human-Robot Interaction.

While neuroscience research has established a link between vision and intention, studies on gaze data features for intention recognition are absent. The majority of existing gaze-based intention recognition approaches are based on deliberate long-term fixation and suffer from insufficient accuracy. In order to address the lack of features and insufficient accuracy in previous studies, the primary objective of this study is to suppress noise from human gaze data and extract useful features for recognizing grasp intention. We conduct gaze movement evaluation experiments to investigate the characteristics of gaze motion. The target-attracted gaze movement model (TAGMM) is proposed as a quantitative description of gaze movement based on the findings. A Kalman filter (KF) is used to reduce the noise in the gaze data based on TAGMM. We conduct gaze-based natural grasp intention recognition evaluation experiments to collect the subject's gaze data. Four types of features describing gaze point dispersion ( fvar), gaze point movement ( fgm), head movement ( fhm), and distance from the gaze points to objects ( fdj) are then proposed to recognize the subject's grasp intentions. With the proposed features, we perform intention recognition experiments, employing various classifiers, and the results are compared with different methods. The statistical analysis reveals that the proposed features differ significantly across intentions, offering the possibility of employing these features to recognize grasp intentions. We demonstrated the intention recognition performance utilizing the TAGMM and the proposed features in within-subject and cross-subject experiments. The results indicate that the proposed method can recognize the intention with accuracy improvements of 44.26% (within-subject) and 30.67% (cross-subject) over the fixation-based method. The proposed method also consumes less time (34.87 ms) to recognize the intention than the fixation-based method (about 1 s). This work introduces a novel TAGMM for modeling gaze movement and a variety of practical features for recognizing grasp intentions. Experiments confirm the effectiveness of our approach. The proposed TAGMM is capable of modeling gaze movements and can be utilized to process gaze data, and the proposed features can reveal the user's intentions. These results contribute to the development of gaze-based human-robot interaction.

The Use of Disk-Shaped Diaphragm of Vehicles in Double-Circuit Diaphragm Pumps

Introduction. The article concentrates on improving the efficiency of double-circuit diaphragm pumps, which can be successfully used in heat and water supply systems of industrial and agricultural facilities where there is excess head. It is advisable to equip double-circuit diaphragm pumps with disc-shaped diaphragms interconnected by a rod, for example, from motor vehicles, and to drive them from the available head of the hydraulic network. In order to increase the efficiency of their work and further use, it is necessary to predict the hydraulic characteristics according to the geometric parameters of the membranes and the cycle of their operation in dynamics. Aim of the Article. The article aims at obtaining adequate calculated dependencies of pumped liquid flow rate on speed of double-circuit diaphragm pumps. Materials and Methods. There were used the idealization method from differential geometry, physical experiment, and mathematical statistics to solve the tasks for identifying the relationship between the rod motion and the liquid flow rate for a poppet diaphragm with different geometric surfaces in dynamics. There have been obtained the dependences of pumped liquid volume on the movement of the point of attachment by the poppet diaphragm and the volume flow rate on the movement speed of the point of attachment by the poppet diaphragm with specific geometric parameters for the parabolic and chain line. An experimental testing of the dependence of displaced pumped liquid flow rate on the movement of the attachment point to the stem for the diaphragm type 30 was carried out. Results. Based on the obtained dependences of the volume flow rate on the speed of movement of the point of attachment by a poppet diaphragm with specific geometric parameters for a parabolic and chain line, there were constructed the graphs of dependences of the volume flow rate on the frequency of the working cycle. For practical implementation, there are proposed the dependencies for constructing the hydraulic characteristics of a two-circuit membrane (the dependence of the volume flow rate on the frequency of the working cycle) obtained on the basis of a parabolic interpretation. Discussion and Conclusion. The hydraulic characteristics of a two-circuit membrane pump are close to the equation of a straight line and are consistent with experimental dependencies within 4%.

Passability and Internode Mechanics Analysis of a Multisection Micro Pipeline Robot

In submarine oil and gas pipelines, the movement of a differential pressure multisection pipeline robot mainly relies on the front and rear driving pressure difference of the fluid and the friction between the cup and the pipe wall. The passability of the pipeline is a key point to guarantee success in scanning and detecting the inner wall of a pipeline by robot. When the multisection pipeline robot moves, the force of the internode connection points changes the degree of freedom of the robot. The existence of the connection points causes speed fluctuations in the robot during the movement process which, in turn, affects the detection accuracy of the pipeline. Consequently, a systematic analysis of the connection point movement is of great importance. In this paper, a rigid–flexible, coupled, multibody, dynamic motion system is established, where a multisection micro pipeline robot is built. The cup of the robot is set as a flexible body. The motion law of the differential pressure multisection pipeline robot is analyzed through simulation, and the robot’s motion speed and internode stress of the different cabin sections are explored jointly in practice. Taking the transportation of an oil and gas pipeline into full consideration, the motion law and force of the multisection pipeline robot are analyzed by changing the bulge and turning the radius of the inner wall of the pipeline. A corresponding experimental bench is built to explore the effects of different numbers of cups and lengths of the cabin sections on the turning characteristics of the robot. Simulations and experiments results are highly similar and within the error range. To this end, the presented work provides significant information for the model selection of multisection micro pipeline robots in the fields of submarine oil and gas pipelines.

Promising results of an non-invasive measurement of knee implant loosening using a loading device, CT-scans and 3D image analysis

BackgroundAfter total knee arthroplasty up to 13% requires revision surgery to address loosening. No current diagnostic modalities have a sensitivity or specificity higher than 70–80% to detect loosening, leading to 20–30% of patients undergoing unnecessary, risky and expensive revision surgery. A reliable imaging modality is required to diagnose loosening. This study presents a new and non-invasive method and evaluates its reproducibility and reliability in a cadaveric study. MethodsTen cadaveric specimens were implanted with a loosely fitted tibial components and CT scanned under load towards valgus and varus using a loading device. Advanced three-dimensional imaging software was used to quantify displacement. Subsequently, the implants were fixed to the bone and scanned to determine the differences between the fixed and the loose state. Reproducibility errors were quantified using a frozen specimen in which displacement was absent. FindingsReproducibility errors, expressed as mean target registration error, screw-axis rotation and maximum total point motion were 0.073 mm (SD 0.033), 0.129 degrees (SD 0.039) and 0.116 mm (SD 0.031), respectively. In the loose condition, all displacements and rotation changes were larger than the reported reproducibility errors. Comparing the mean target registration error, screw axis rotation and maximum total point motion in the loose condition to the fixed condition resulted in mean differences of 0.463 mm (SD 0.279; p = 0.001), 1.769 degrees (SD 0.868; p < 0.001) and 1.339 mm (SD 0.712; p < 0.001), respectively. InterpretationThe results of this cadaveric study show that this non-invasive method is reproducible and reliable for detection of displacement differences between fixed and loose tibial components.

Controlled movement of lower strike points by applying a divertor coil on the EAST tokamak

A new in-vessel water-cooled coil has been placed below the lower tungsten-covered divertor in EAST, aiming at moving the strike points in the divertor and spreading the heat flow on the targets. To achieve controlled movement of the strike points by the plasma control system (PCS) when applying the in-vessel coil, the plasma equilibrium configurations are predicted by the tokamak equilibrium (TEQ) code. The divertor coil current is involved in these calculations. The shape control parameters in the PCS are adjusted according to the predesigned equilibria from the TEQ code. The strike point movement over a wide range has been achieved in the experiment while keeping the main plasma stable. Thus, this method for divertor strike point movement with the assistance of the divertor coil is feasible.

Articulation differences of /s/ observed using inverse tongue atlas modeling

Depending on the vowel context, the consonant /s/ can be articulated by engaging different functional units of the tongue. An inverse finite element (FE) tongue model comprising hexahedral elements generated from a 4D statistical MRI atlas of 22 speakers performing the speech tasks “a geese” (tongue moving forwards) and “a souk” (tongue moving backwards) is used to study this articulatory behavior. The model uses a state-of-the-art inverse tracking controller to simulate the motion of internal tissue points of the different speakers deformed into the atlas space. Motion tracking is successfully carried out by minimizing the L2-norm of velocity error of FEM nodes using the Cottle–Dantzig algorithm. The results show that for “a-geese,” the utterance of /s/ in context of vowel /i/ showed increase in activation of tongue protruder muscles such as genioglossus posterior, floor muscle geniohyoid by ∼5% more than in the case of “a-souk.” In “a-souk” relative activity increased in the tongue retractor muscles mid- and anterior-genioglossus, and superior longitudinal by ∼4%. Our findings are consistent with subject-specific state-of-the-art models and with articulatory expectations. The inverse atlas tongue model can be further used to estimate such articulation behavior on extended datasets of subjects performing more variations of speech tasks.

WiCRF: Weighted Bimodal Constrained LiDAR Odometry and Mapping With Robust Features

Accurate localization is a fundamental capability of autonomous driving systems, and LiDAR has been widely used for localization systems in recent years due to its high reliability and accuracy. In this paper, we propose a robust and accurate LiDAR SLAM, which innovates feature point extraction and motion constraint construction. For feature extraction, the proposed adaptive point roughness evaluation based on geometric scaling effectively improves the stability and accuracy of feature points (plane, line). Then, outliers are removed with a dynamic threshold filter, which improves the accuracy of outlier recognition. For motion constraint construction, the proposed weighted bimodal least squares is employed to optimize the relative pose between current frame and point map. The map stores both 3D coordinates and vectors (principal or normal vectors). Using vectors in current frame and point map, bimodal reprojection constraints are constructed. And all constraints are weighted according to the neighboring vector distribution in the map, which effectively reduces the negative impact of vector errors on registration. Our solution is tested in multiple datasets and achieve better performance in terms of accuracy and robustness.

Uncemented Tibial Fixation Has Comparable Prognostic Outcomes and Safety Versus Cemented Fixation in Cruciate-Retaining Total Knee Arthroplasty: A Meta-Analysis of Randomized Controlled Trials

Cemented and uncemented fixation are the primary methods of tibial prosthesis fixation in total knee arthroplasty. However, the optimal fixation method remains controversial. This article explored whether uncemented tibial fixation has better clinical and radiological outcomes, fewer complications, and revision rates compared to cemented tibial fixation. We searched the PubMed, Embase, Cochrane Library, and Web of Science databases up to September 2022 to identify randomized controlled trials (RCTs) that compared uncemented total knee arthroplasty (TKA) and cemented TKA. The outcome assessment consisted of clinical and radiological outcomes, complications (aseptic loosening, infection, and thrombosis), and revision rate. Subgroup analysis was used to explore the effects of different fixation methods on knee scores in younger patients. Nine RCTs were finally analyzed with 686 uncemented knees and 678 cemented knees. The mean follow-up time was 12.6 years. The pooled data revealed significant advantages of uncemented fixations over cemented fixations in terms of the Knee Society Knee Score (KSKS) (p = 0.01) and the Knee Society Score-Pain (KSS-Pain) (p = 0.02). Cemented fixations showed significant advantages in maximum total point motion (MTPM) (p < 0.0001). There was no significant difference between uncemented fixation and cemented fixation regarding functional outcomes, range of motion, complications, and revision rates. When comparing among young people (<65 years), the differences in KSKS became statistically insignificant. No significant difference was shown in aseptic loosening and the revision rate among young patients. The current evidence shows better knee score, less pain, comparable complications and revision rates for uncemented tibial prosthesis fixation, compared to cemented, in cruciate-retaining total knee arthroplasty.

In Vivo Postoperative Motion of Fixed and Mobile Medial Pivot Knees Under Weight-Bearing Conditions after Cruciate-Sacrificing Total Knee Arthroplasty.

In vivo three-dimensional (3D) motion under weight-bearing conditions was analyzed postoperatively in medial pivot cruciate-substituting (CS) knee systems with fixed and mobile inserts. Tibiofemoral knee kinematics during squatting were captured with X-ray fluoroscopy for 4 patients in each cohort. The 3D motion of implants was analyzed with KneeMotion motion analysis software (LEXI Corporation; Tokyo, Japan). In addition, anterior-posterior (AP) movement of the distal-most points and the angle of axial rotation of the femoral component on the tibial component were assessed in both cohorts. Mean AP movement of the femoral component on the tibial component was 3.8±0.5 mm on the medial side and 9.5±0.5 mm on the lateral side in the cohort with fixed prostheses and 5.9±2.1 mm on the medial side and 10.0±2.5 mm on the lateral side in the cohort with mobile prostheses. The mean angle of axial rotation of the femoral component on the tibial component was 14.4±1.1 degrees and 8.2±2.7 degrees of external rotation for fixed knees and mobile knees, respectively. Postoperative motion analysis confirmed that fixed and mobile CS implants, which have a similar design, guided medial pivot motion under weight-bearing conditions. However, motion differed between these implant types after mid-flexion: bicondylar rollback after medial pivot motion was noted in the mobile cohort.

Numerical Study of Wall Heat Transfer Effects on Flow Separation in a Supersonic Overexpanded Nozzle

In this study, numerical simulations have been carried out to analyze the effect of convective heat transfer on flow separation occurring in a DLP-PAR nozzle. Heat transfer coefficient (0, 200 and 1000 w/m2K) was applied to the nozzle wall to incorporate the cooling effect for different gas inlet temperatures ranging from 1000 to 1500 K. The impact of the cooling effect was analyzed based on nozzle wall temperature and wall static pressure. The wall static pressure distribution also characterizes movement of the separation point. For an inlet temperature of 1000 K, a detailed heat transfer study was carried out for four different nozzle pressure ratios (14, 22, 30 and 40). Significant amount of heat transfer was observed for pressure ratio 14, which in turn had an impact on flow separation. The wall cooling resulted in a shift of the point of separation towards the nozzle exit. For the nozzle pressure ratio of 14, this shift was by about 8.8%, indicating that the flow separation can be delayed by way of cooling for the considered inlet temperature. For higher inlet temperatures, the effect of heat transfer on flow separation seems to be negligible. The current study concludes that the separation point can be controlled by convective cooling for inlet gas temperatures below 1500 K so that the optimal performance of the nozzle can be achieved.

Gridded cemented riprap for scour protection around monopile in the marine environment

A novel gridded cemented riprap (GCRP) composed of loose riprap stones and cemented stone clusters is proposed, which combines high stability of large stones and excellent flexibility to follow ground deformation. A series of physical experiments were performed in a large-scale flume, and two extreme wave-current conditions of an offshore wind farm with a return period of 50 and 100 years, respectively, were selected. The anti-scouring performance of riprap and GCRP is studied in detail. It is found that the magnitude of wave leads to downstream movement of the maximum scour point. The armor stones around monopile cannot maintain their stability under the extreme wave-current condition, and riprap layer gradually disintegrates during scour process. The stability of riprap layer is significantly improved by fully or gridded grouting. Fully cemented riprap (FCRP) and GCRP remain intact even under the combined wave-current condition of return period of 100 years. For FCRP, scour occurs at the downstream edge and the erosion of underlying sand bed takes place. The anti-scouring performance of GCRP is better than riprap and FCRP, the maximum depth of scour hole around GCRP is reduced 80% than unprotected monopile.

An Efficient Methodology for Detecting the Vertical Movement of Structures

Details regarding the public safety of engineering structures can be gleaned from measurements and monitoring. The development of a methodology for monitoring and analyzing structures' vertical displacement is explained in this paper. The developed methodology aims to add a new dimension to geometric leveling, and leveling routing, by applying a least squares solution for level network adjustment and performing statistical analysis to assess the change in vertical displacement. To monitor and analyze the vertical deformation of a building in Cairo, Egypt, the proposed methodology was utilized. Twenty monitoring points, five auxiliary points, and three local reference stations were utilized. All the measurements were taken with a geodetic invar staff and an automatic level with an attachment of a parallel plate micrometer. The observations were made for an interval of 81 months. The least squares adjustment technique was applied to obtain the adjusted levels and observations and to generate the required statistical data. The results of the subsequent epochs were compared to the results of the first epoch to determine the vertical movement of the monitoring points for each epoch. In addition, the significance of the present displacement was ascertained by comparing the values of vertical displacement to the determined 95% corresponding confidence intervals. The findings demonstrated that the building remained stable throughout the monitoring period. The case study demonstrates how effectively geometric leveling with least square adjustment can be used to monitor the vertical displacement of structures.