Magnitude Angle Research Articles

Role of conservative management in the reduction of Cobb angle among adolescent idiopathic scoliosis. A systematic review

IntroductionPhysiotherapy Scoliosis Specific Exercises (PSSE) is a conservative approach for the management of adolescent idiopathic scoliosis (AIS) designed according to the guidelines of the International Society on Scoliosis Orthopaedic and Rehabilitation Treatment (SOSORT). Hence the aim of the study is to evaluate the effectiveness of PSSE and conservative management strategies for patients with AIS.MethodsA systematic review was conducted and searches were carried out on a virtual database. The primary outcome measure analysed in this paper was Cobb angle and angle of trunk rotation, while the secondary outcome included functional capacity. A total of twelve studies were included in the review, which was analysed to determine the effects of conservative management of spinal scoliosis among adolescent aged children.ResultsThe study was conducted on patients who had developed idiopathic scoliosis and had a Cobb angle of greater than 10°. The significance of the conservative management protocol was estimated based on the reduction of Cobb angle by > 5° post-intervention.ConclusionsThis review concluded that therapeutic exercises alone have added to the noninvasive standard of care in reducing magnitude of Cobb angle among AIS patients. The studies reviewed in this paper provide significant evidence that a minimum of sixteen weeks of the exercise-based protocol has been able to produce a statistically and clinically significant result in Cobb angle reduction by almost 5° to 8°.

Pore-scale Analysis of CO2-brine Displacement in Berea Sandstone and Its Implications to CO2 Injectivity

For storage in deep saline formations, where CO2 is injected into the pore spaces of rocks previously occupied by saline groundwater (brine), relative permeability is a key input parameter for predictive models. CO2 injectivity is considered to reach the maximum value at the CO2 endpoint relative permeability when brine saturation becomes irreducible. The objective of this study is to investigate the effect of viscosity ratio, interfacial tension and wettability on relative permeability during CO2-brine drainage. A multiphase lattice Boltzmann model (LBM) is employed to numerically measure pore-scale dynamics in CO2-brine flow in the sample of Berea sandstone. CO2/brine with interfacial tension from 30 to 45 mN/m and viscosity ratio from 0.05 to 0.17 (the range of values expected for typical storage reservoirs conditions) are carried out to systematically assess the influence on the relative permeability curves. Although CO2 storage in sandstone saline aquifers is predominantly water wet, there are contradictory results as to the magnitude of the contact angle and its variation with fluid conditions. Therefore, the range of wetting conditions is studied to gain a better insight into the effect of wettability on supercritical CO2 displacement. In this study, it is observed that interfacial tension variations play a trivial impact while both of viscosity ratio and wettability are likely to have a significant effect on relative permeability curves under representative condition of storage reservoirs. We also perform a near-wellbore scale geomechanics analysis to investigate the impact of relative permeability on CO2 injectivity. The result shows that water-wet condition facilitates the CO2 injection when there is no fracture induced.

Distributed hierarchal control strategy for multi-bus AC microgrid to achieve seamless synchronization

• Pinning consensus-based controller is designed for seamless synchronization. • A natural conflict between the frequency and phase regulation has been resolved. • BP based PI controller is used to update the fixed gain parameters of SC. • FPI and SB based FLC are designed to generate the correction signals for SC. In this research work, a distributed hierarchal control scheme is proposed that ensures a smooth synchronization of islanded microgrid with the utility grid. In this method, a pinning consensus-based distributed controller is designed where all Distributed Generation Units (DGs) are allowed to regulate their frequencies and output power in proportion to their capacities while only regulating DGs are responsible for eliminating the phase angle and voltage magnitude mismatch. Hence, the magnitude, phase angle, and frequency are controlled explicitly while ensuring proportionate power sharing. To enhance the performance of the system, the fixed gain parameters of the secondary controller are made adaptive by using a back propagation based proportional integral controller. Moreover, a fuzzy proportional integral controller and steepest descent based fuzzy logic controller are designed that use an adjustable parameter to generate the compensation correction signals for the secondary controller to eliminate the voltage magnitude and phase angle mismatch. Furthermore, to ensure a seamless reconnection, a control strategy based on the synchronization criteria is designed that control the operation of the static switch. Finally, the effectiveness of the method under different scenarios is validated through simulation results.

IMPROVING THE PROCESS OF PROCESSING HOLES WITH DRILLS

"One of the urgent problems of mechanical engineering is the processing of holes, which are subject to high requirements for the accuracy of size, shape and location. Most often, hole processing is carried out with the help of rod measuring tools. This is due to their following advantages: relatively high productivity, low costs for pre-production. The quality of the machined holes is determined mainly by the accuracy of the cutting tools, machines and accessories used. The drilling process with existing drills takes place under severe cutting conditions. The magnitude of the front angle on the transverse edge is very unfavorable. For standard spiral drills, the front angle γ on the transverse edge is up to minus 57–60. In view of this, on the transverse edge, instead of cutting, there is a crumpling, squeezing and scraping of metal. When drilling holes with existing drills, the transverse edge of the drill perceives up to 80 % of the axial force, i.e. the resistance to axial feed is created by the contact area of the transverse edge with the workpiece. The specified working conditions of the transverse edge significantly worsen the processing conditions and the quality of the treated hole. To eliminate the transverse edge, a new design of a spiral drill is proposed – a two-vertex spiral drill without a transverse edge, preliminary patent of the Republic of Kazakhstan № 19559. The elimination of the transverse edge on the drill allows you to dramatically reduce the heating and wear of the drill during the cutting process, increase the durability of the drills. The analysis of the results shows that the accuracy of the diametrical dimensions of the holes after processing with two-vertex spiral drills increased by 1, 2 quality compared with spiral drills; roughness decreased by 1, 2 classes. Keywords: spiral drill, jumper, sharpening, durability, accuracy, productivity "

Robust Damping Controller for Synchronous Generators under Operational Uncertainties

Power system stabilizers have been widely used to create sufficient damping against low-frequency oscillations. Due to appearing new uncertainties in operational conditions of power systems, robust design of stabilizers and damping controllers is a crucial requirement for small signal stability. In this paper, a robust local damping controller is developed considering the possible uncertainties in operational conditions. The developed damping controller is optimized based on the H-infinity method in presence of uncertainties in electrical variables of the synchronous machine including rotor angle, rotor speed, and terminal voltage magnitude. In the proposed robust damping controller, only the practically available control signals such as the deviation of the rotor speed of the synchronous generators are used. To fulfill the robust and internal stabilities of the damping controller under a given horizon of operational uncertainties, a novel design based on the combination of the developed robust damping controller and the conventional power system stabilizer is introduced. Simultaneous damping of local oscillatory modes and the internal stability of the proposed robust controller is achieved via a multi-objective function. The efficacy of the proposed local damping controller is compared with the conventional stabilizer and a damping controller that is designed using the pole placement approach.

Novel method of residual stress reduction for AlSi10Mg manufactured using selective laser melting without compromise of mechanical strength

ABSTRACT AlSi10Mg is often used to fabricate functional parts by Laser Beam Powder Bed (LBPB) fusion but is limited by the residual stresses formed during the process. Conventional methods of stress relief of AlSi10Mg often compromise the mechanical properties due to the high-temperature used. This paper solves the dilemma by using a novel method of residual stress relief without compromising its mechanical properties. This process uses a lower temperature for treatment followed by uneven cooling, inducing thermal stress during the cooling process such that it cancels out the existing residual stress that remains. The compressive strength of the part was not compromised after this treatment, verified by microstructure images. From electron backscatter diffraction (EBSD) analysis, the change in density of low angle grain boundaries (LAGB) and magnitude of residual stress relieved via this method followed the same trend, indicating the induction of dislocations from the stress-induced during uneven cooling.

Numerical Investigation of Hydraulic Fracture Network Formation of Jointed Shale with Oriented Perforation

This paper aims at exploring the fracture evolution as well as capturing the fracture network formation of jointed shale during hydraulic fracturing process by numerical simulation using the Rock Failure Process Analysis System of Flow (RFPA—Flow). The simulations were successfully completed following two stages. In the first stage, a series of simulations are performed to investigate the influence of different angle-oriented perforations on fracture initiation and propagation. The simulation results agreed well with the experimental results confirming the validity of the RFPA-Flow code in the application. In the second stage, extensive hydraulic fracturing simulations on jointed shale with different angled-joint planes and different angle-oriented perforations were performed. The simulation results demonstrated that the fracture evolution changes significantly as the magnitude of α (the angle between perforation and the joint plane) increased. It was found that a large α value could lead to a larger the tensile stress region around the fracture tip resulting in more joint planes pulled apart. It could also induce more secondary fractures and hence a more complex fracture could be formed. As a result, the α value of 60° to 90° were found to aid in the fracture network generation. On the other hand, the angle β being the angle between the parallel joints and the maximum stress direction was another important factor in fracture evolution. Its influence on fracturing performance was similar to angle α. It was found that the initiation and breakdown pressure of jointed shale were in proportional to the magnitude of angle β. Therefore, this paper introduced an efficient approach to promote the formation of a complex fracture network in jointed shale with the presence of oriented perforation, which could offer valuable guidance for the design of unconventional reservoir reconstruction.

Density functional theory studies on molecular geometry, spectroscopy, HOMO-LUMO and reactivity descriptors of titanium(IV) and oxidozirconium(IV) complexes of phenylacetohydroxamic acid.

The molecular geometry of new titanium(IV) and oxidozirconium(IV) phenylacetohydroxamate complexes [TiCl2 (L1)2 ] (I) and [ZrO(L1)2 ] (II) (where L1=Potassium phenylacetohydroxamate=C6 H5 CH2 CONHOK) computed by B3LYP/6-311++G(d,p) method has shown these to be distorted octahedral and square pyramidal, respectively. A comparison of computed characteristic bond lengths (CO, CN, and NO) of complexes with that of free ligand has shown chelation through carbonyl and hydroxamic oxygen atoms (O, O coordination). The TiO/ZrO bond lengths in complexes are suggestive of weak coordination through (carbonyl CO) and strong covalent (hydroxamic NO) bonding of the ligand. The magnitude of ClTiCl bond angle involving two chloride atoms is suggestive of cis-conformation at titanium metal in (I). The thermodynamic parameters Gibbs free energy, enthalpy, entropy, nuclear internal energy, constant volume heat capacity, and internal energy of ligand and complexes have been computed. From the energies of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), the global reactivity descriptors such as ionization potential (IP), electron affinity (EA), chemical potential (μ), hardness (η), softness (S), electronegativity (χ), electrophilicity index (ω), and dipole moment have been calculated. The computed vibrational frequencies, 1 H and 13 C NMR spectra have substantiated the molecular structure of complexes. The thermal behavior of complexes has been studied by thermogravimetric techniques (TGA, DTG, and DTA) in N2 atmosphere has shown complexes are thermally stable.

Impaired supporting function of the feet in adolescents with congenital cleft lip and palate with a mesial ratio of dentition

BACKGROUND: Impaired occlusal relationships of dental rows can cause adaptive changes in the entire musculoskeletal system, including the feet. Thus, studying the biomechanics of the feet with the possibility of changing the medical rehabilitation program of patients with dentomaxillofacial anomalies of various geneses is important.
 AIM: To investigate the plantographic characteristics of the feet in adolescents with congenital cleft lip and palate and combined dentomaxillofacial anomaly with a mesial ratio of dental rows and analyze patterns of distribution of plantar pressure before and after reconstructive operations on the jaws and restoration of facial harmony.
 MATERIALS AND METHODS: The study included 31 patients of both sexes aged 1517 years, who were divided into two groups. The first group consisted of 15 patients with congenital cleft lip and palate after the early stages of reconstructive surgery (cheilorhinoplasty and uranoplasty) and developed a combined dentomaxillofacial anomaly. The second group, with milder lesion, included 16 patients with combined dentomaxillofacial anomaly and do not have congenital cleft lip and palate. Patients had skeletal forms of mesial ratios of dental rows. To correct the bite and restore the aesthetics of the face, all patients underwent simultaneous bone reconstructive (orthognathic) surgery on the upper and lower jaws, including genioplasty in some of them, to restore the normal relationship of the jaw bones and harmonize the face. The plantographic characteristics of the feet were studied in patients before surgery and 16 months after surgery. The results of these two groups were compared with a pantographic examination of 18 healthy children (control group) without these pathologies in the maxillofacial region and without impairment of the supporting function of the foot.
 RESULTS: The first and second groups had a significant decrease in the indices of support on both feet before surgery: t, up to 85 (normal, 96); m, up to 16 (normal, 23); and s, up to 20 (normal, 24), which indicate a decrease in the spring function of the transverse and longitudinal arches and impairment of the supporting function of the feet. It was most pronounced in patients with congenital cleft lip and palate. Deviations in the magnitude of the Clark angle were multidirectional on the left and right feet, which indicated an abnormally high asymmetry of the load distribution between the feet. Functional relationships between the foot arches were pathologically enhanced to values of rs = 0.83 (normal, rs = 0.14), which indicated a formed pathological support strategy of the feet. After reconstructive operations on the jaws, the biomechanics of the feet in patients with combined dentomaxillofacial anomaly (without congenital cleft lip and palate) tended to normalize.
 CONCLUSIONS: It is necessary to consider the possible aggravating effect of the feet with a modified support strategy on the condition of the dentofacial area. Moreover, the comprehensive diagnosis plan of adolescents with congenital cleft lip and palate and combined dentomaxillofacial anomaly and combined dentomaxillofacial anomaly (without congenital cleft lip and palate) should include a study of the supporting function of the feet, considering rehabilitation measures to correct the distribution of plantar pressure.

Assessment of distance-near control disparity in basic and divergence excess paediatric intermittent exotropia

ABSTRACT Clinical Relevance In intermittent exotropia (IXT), deviation is better controlled at near fixation. Understanding of the mechanism responsible for this common observation may improve clinical management of IXT. Background The physiological basis for the distance-near difference in control of deviation in IXT is vastly undetermined. A new parameter, ‘control score disparity (CSD)’, defined as the difference between distance and near control scores, is introduced. Association of CSD with positive fusional amplitude (PFA), accommodative convergence to accommodation (AC/A) ratio and distance angle of deviation was investigated to further understand the mechanisms. Method Patients aged between four and fifteen years with basic and divergence excess IXT were included. Subjects with previous strabismus surgery, amblyopia and inability to perform clinical tests were excluded. A standardized office-based scoring system was used to assess IXT controls. Subjects were sub-divided into group 1 (CSD <2) and group 2 (CSD ≥2). Pearson’s univariate and regression analysis were used to determine relationships between CSD and other independent variables. Results Mean age of the total 141 subjects (57.6% female) was 6.8 ± 2.5 years. Basic IXT was more common (60%) and 60% had CSD ≥2. The mean±SD distance angle of deviation, AC/A ratio, PFA and CSD were 22.1 ± 6.6 prism dioptres, 5.0 ± 1.0, 28.6 ± 6.3 prism dioptre and 2.0 ± 0.5, respectively. CSD was significantly correlated to PFA (r = 0.64, p < 0.001) and AC/A ratio (r = 0.27, p < 0.001) in overall samples and Group 2 subjects (r = 0.41, p = 0.001). Conclusions PFA is a major factor associated with the distance/near difference of IXT control. Individuals with a higher PFA demonstrated greater CSD. While AC/A ratio was associated in better control at near in divergence excess IXT, magnitude of angle appears irrelevant.

Decompression Alone in the Setting of Adult Degenerative Lumbar Scoliosis and Stenosis: A Systematic Review and Meta-Analysis.

Systematic review and meta-analysis.OBJECTIVESSurgical decompression alone for patients with neurogenic leg pain in the setting of degenerative lumbar scoliosis (DLS) and stenosis is commonly performed, however, there is no summary of evidence for outcomes. A systematic search of English language medical literature databases was performed for studies describing outcomes of decompression alone in DLS, defined as Cobb angle >10˚, and 2-year minimum follow-up. Three outcomes were examined: 1) Cobb angle progression, 2) reoperation rate, and 3) ODI and overall satisfaction. Data were pooled and weighted averages were calculated to summarize available evidence. Across 15 studies included in the final analysis, 586 patients were examined. Average preoperative and postoperative Cobb angles were 17.6˚ (Range: 12.7 - 25˚) and 18.0 (range 14.1 - 25˚), respectively. Average change in Cobb angle was an increase of 1.8˚. Overall rate of reoperation ranged from 3 to 33% with an average of 9.7%. Average ODI before surgery, after surgery, and change in scores were 56.4%, 27.2%, and an improvement of 29% respectively. Average from 8 studies that reported patient satisfaction was 71.2%. Current literature on decompression alone in the setting of DLS is sparse and is not high quality, limited to patients with small magnitude of lumbar coronal Cobb angle, and heterogenous in the type of procedure performed. Based on available evidence, select patients with DLS who undergo decompression alone had minimal progression of Cobb angle, relatively low reoperation rate, and favorable patient-reported outcomes.

Time-coordination entry guidance using a range-determined strategy

A time-coordination entry guidance method based on a range-determined strategy is developed for hypersonic glide vehicles. This method is composed of two components: a time-constrained entry guidance algorithm and a coordinated flight time generation approach. Different from the previous work, the proposed strategy provides a novel scheme to solve the coordinated entry guidance problem, significantly reducing the computational load and the coupling between flight time control and the motion form. Firstly, the longitudinal guidance algorithm generates the flight profile based on the flight time constraint while considering adaptability to external disturbance. The magnitude of the bank angle and the range-to-go command can be derived from the profile. The command is used to plan the lateral trajectory represented by the Bézier curve in lateral guidance. Then, the heading error corridor can be established according to the line-of-sight between the vehicle and the reference point on the lateral trajectory, which controls the bank angle reversal time. The profile and the lateral trajectory are updated to guide the vehicle to the terminal point while meeting terminal and path constraints. This paper discusses how to estimate the adjustable range of a single vehicle's flight time and illustrates an approach for multi-vehicle coordinated flight time generation. Numerical simulations are conducted in nominal and dispersed conditions, and the results demonstrate the method's efficiency and robustness.

Neuronavigation maximizes accuracy and precision in TMS positioning: Evidence from 11,230 distance, angle, and electric field modeling measurements

BackgroundResearchers and clinicians have traditionally relied on elastic caps with markings to reposition the transcranial magnetic stimulation (TMS) coil between trains and sessions. Newer neuronavigation technology co-registers the patient's head and structural magnetic resonance imaging (MRI) scan, providing the researcher with real-time feedback about how to adjust the coil to be on-target. However, there has been no head to head comparison of accuracy and precision across treatment sessions. Objective/Hypothesis: In this two-part study, we compared elastic cap and neuronavigation targeting methodologies on distance, angle, and electric field (E-field) magnitude values. MethodsIn 42 participants receiving up to 50 total accelerated rTMS sessions in 5 days, we compared cap and neuronavigation targeting approaches in 3408 distance and 6816 angle measurements. In Experiment 1, TMS administrators saved an on-target neuronavigation location at Beam F3, which served as the landmark for all other measurements. Next, the operators placed the TMS coil based on cap markings or neuronavigation software to measure the distance and angle differences from the on-target sample. In Experiment 2, we saved each XYZ coordinate of the TMS coil from cap and neuronavigation targeting in 12 participants to compare the E-field magnitude differences at the cortical prefrontal target in 1106 cap and neuronavigation models. ResultsCap targeting was significantly off-target for distance, placing the coil an average of 10.66 mm off-target (Standard error of the mean; SEM = 0.19 mm) compared to 0.3 mm (SEM = 0.03 mm) for neuronavigation (p < 0.0001). Cap targeting also significantly deviated for angles off-target, averaging 7.79 roll/pitch degrees (SEM = 1.07°) off-target and 5.99 yaw degrees (SEM = 0.12°) off-target; in comparison, neuronavigation targeting positioned the coil 0.34 roll/pitch degrees (SEM = 0.01°) and 0.22 yaw (SEM = 0.004°) off-target (both p < 0.0001). Further analyses revealed that there were significant inter-operator differences on distance and angle positioning for F3 (all p < 0.05), but not neuronavigation. Lastly, cap targeting resulted in significantly lower E-fields at the intended prefrontal cortical target, with equivalent E-fields as 110.7% motor threshold (MT; range = 58.3–127.4%) stimulation vs. 119.9% MT (range = 115–123.3%) from neuronavigated targeting with 120% MT stimulation applied (p < 0.001). ConclusionsCap-based targeting is an inherent source of target variability compared to neuronavigation. Additionally, cap-based coil placement is more prone to differences across operators. Off-target coil placement secondary to cap-based measurements results in significantly lower amounts of stimulation reaching the cortical target, with some individuals receiving only 48.6% of the intended on-target E-field. Neuronavigation technology enables more precise and accurate TMS positioning, resulting in the intended stimulation intensities at the targeted cortical level.

Study on Caster Angle and Steering Stability of Racing Car

The topic in this article is the influence of the caster angle of the automobile. High speed and large steering is a working condition that a racing car must experience, this paper is eager to find the law of the influence of caster angle of kingpin on steering instability under high speed and large steering condition.The caster angle of the Kingpin is of great significance to the steering of a vehicle. On the one hand, it determines the stability of a vehicle when it is running in a straight line, and on the other hand, it determines the return force of the steering wheel when it is turning. In contrast, a smaller caster angle makes steering easier, but less stable at high speeds, while a larger caster angle means a slower steering with a more pronounced return to normal but better stability at high speeds, the determination of the magnitude of the caster angle is very important for the ride comfort of the vehicle.

Flow decorrelation in heavy-ion collisions at $\sqrt{s_{_{\rm NN}}}$=27 and 200 GeV with 3D event-by-event viscous hydrodynamics

We present the first calculation of longitudinal decorrelation of anisotropic flow at RHIC Beam Energy Scan (BES) energies using event-by-event viscous hydrodynamic model (vHLLE), with two different initial states (GLISSANDO2 and UrQMD) and hadronic cascade. We investigate the origin of the observed decorrelation by checking separately flow angle and flow magnitude decorrelation and by calculating decorrelation in the initial state eccentricity.

Bearing Capacity Factors of Flat Base Footing by Finite Elements

This paper presents the computations of vertical bearing capacity factors Nc, Nq, and Nγ, of the smooth and rough strip, circular and ring footings resting on soil with a friction angle (ϕ) ranging from 5° to 45° using a finite element viscoplastic strain method obeying the Mohr-Coulomb yield criterion. The numerical difficulty could be improved to some extent by using the proper magnitude of soil dilation angle (ψ) in the analysis of high non-associative flow. The effects of domain and mesh size are presented thoroughly. The factors are calculated individually and found to be in close agreement with the existing solutions. However, differences are also reported and discussed. The magnitude of bearing capacity factors increases with increasing ϕ. Moreover, the factors with a rough base are significantly greater than the smooth base at high values of ϕ. Moreover, this work also indicates that the shape factors may depend on ϕ.

Vector Trajectory Method for Obstacle Avoidance Constrained Planetary Landing Trajectory Optimization

Considering the requirement of avoiding obstacles in different planetary landing missions, this article presents a generalized method dealing with the obstacle avoidance constrained landing trajectory optimization problem with vectorized strategy, i.e., vector trajectory method (VTM). By introducing a trajectory direction constraint with vectorized description, the character of the obstacle avoidance trajectory can be more specifically depicted. Moreover, by satisfying proper trajectory direction constraint, the lander’s particular performances, such as the observation to the target or probability of a safe flight, can be improved. To this end, the VTM and relevant theorem are first developed, revealing the relationship between the two aspects of obstacle avoidance constraint (i.e., distance constraint and trajectory direction constraint). Then, both aspects of constraints are uniformly transformed as the auxiliary angle magnitude constraint with the vectorized strategy, which significantly simplifies the solving procedure of obstacle avoidance constrained trajectory optimization problem. Finally, the proposed VTM is illustrated in detail through the examples with the planetary landing background of atmospheric entry and powered descent landing.

Numerical simulation of creep fracture evolution in fractured rock masses

The initiation, expansion, and penetration of microscopic cracks in rock is the macroscopic manifestation of creep. This paper investigates mechanical creep characteristics and fracture evolution processes in rock masses with different fracture angles, lengths, and rock bridge dip angles. Single fractures, dual parallel fractures, and fracture groups are considered. The approach comprises discrete element simulation based on continuum mechanics, utilizing the continuous and discontinuous software, GDEM. Single-fracture rock masses are characterized by a progressive fracture development mode dominated by tensile shear failure. The rate of creep and fracture magnitude both increase according to fracture length. With increasing fracture inclination angle, creep rate and fracture magnitude increase and decrease. The creep rate and degree of rupture are highest for fractures inclined at 30°. The dual-fracture rock mass exhibits both tensile crack failure and compressional shear failure. Creep rates are highest, and rupture effects are most apparent at rock bridge inclination angles of 90°. If the rock bridge is too long or too short, the stable creep stage is prolonged, but the creep acceleration stage intensifies due to interaction between fracture-bounded rock masses. The failure mode, in this case, involves collective failure by tension fractures and compressional shear. Creep rate and fracture magnitude increase with the number of fractures, which accelerates rock mass deformation to a certain extent. However, when the number of fractures reaches a certain threshold, a relatively stable structure may become established, slowing down the creep rate, especially during the creep acceleration stage. This study can provide a theoretical basis and reference for investigating the creep rupture law of rock mass engineering and the prevention and control of fractured rock mass geological disasters.

Analysis of image-to-image registration performance of multitemporal KOMPSAT-3∙3A imagery with respect to convergence angle

ABSTRACT Unlike numerous studies on the impact of a convergence angle between two stereo images, its effects on image-to-image registration have not been extensively investigated. In this study, we analysed the impact of the magnitude of the convergence angles of very-high-resolution (VHR) satellite image pairs on registration accuracy with respect to the two-dimensional (2D) geometric alignment. To perform image-to-image registration, we used an iterative process to extract a large number of well-distributed conjugate points (CPs) by combining area- and feature-based matching approaches. To evaluate the proposed method’s ability to extract CPs and demonstrate the relationship between the registration performance and the magnitude of the convergence angles, we conducted experiments using KOMPSAT-3 and KOMPSAT-3A satellite images acquired over Daejeon, South Korea. A total of 18 satellite images were used to generate 153 image pairs with different convergence angles. Two transformation models, affine and piecewise linear transformations, were used independently to warp a target image to a reference image, and their performances were compared. An analysis of the affine transformation with respect to the size of the convergence angles revealed that a larger convergence angle between images resulted in lower accuracy of the registration performance. This result differs from the convergence angle condition required in stereo images to extract accurate 3D information. However, the piecewise linear transformation achieved a reliable registration performance regardless of the magnitude of the convergence angles.

Multispiral computed tomography upper-level arteriovenous conflicts (abdominal cavity and retroperitoneal space)

Introduction. Continuous improvement and increased availability of high-tech research methods, such as computed X-ray tomography (CT) and magnetic resonance imaging (MRI) with contrast enhancement, qualitatively change the diagnostic search for combined vascular pathology, including when conducting studies of other organs and systems, even in the absence of any clinical manifestations.The purpose of the study: to evaluate the possibilities and determine the indications for CT diagnosis of arteriovenous conflicts of the abdominal cavity, retroperitoneal space.Research objectives: to determine CT parameters and the algorithm of CT analysis of upper-level arteriovenous conflicts in modern radiation and urological aspects.Materials and methods. The study included 34 patients with arteriovenous conflicts of the abdominal cavity and retroperitoneal space detected by computer X-ray tomography. The average age of patients is 39±11.0 years; the number of male patients is 19 (55.9%), female — 15 (44.1%). Children’s patients accounted for 23.5% (8 people; average age 11±7 years). The preoperative diagnostic algorithm included a clinical examination, ultrasound diagnostics, a comprehensive study of laboratory parameters, CT-arterio/venography.The results of the study. Among the upper—level arteriovenous conflicts, superior mesenteric artery syndrome prevailed — it was observed in 23 patients (67.6%), of which aortomesenteric duodenal compression (Wilkie syndrome) was detected in 12 patients (52.2%); aortomesenteric venous compression (Nutcracker syndrome) — in 11 patients (47.8%). Among children’s patients, aortomesenteric tweezers prevailed (5 patients — 62.5%). A combination of upper-level syndromes was detected in 6 patients (17.6%). Compression syndrome of the left renal vein (aortovertebral venous compression, posterior nutcracker syndrome), or Nutcracker syndrome was detected in 11 patients (32.4%), which in all cases (100%) was a «random finding» of CT diagnostics.Conclusions. It is recommended to perform CT-, MR-studies with contrast enhancement (in angiography mode) in patients with a suspected diagnosis of arteriovenous conflict with the expansion of the scanning zone to the level of the abdominal cavity, retroperitoneal space and pelvis in order to exclude combined multi-level vascular pathology. Mandatory for radiation analysis are the magnitude of the aortomesenteric angle, the magnitude of the aortomesenteric distance for the left renal artery, the magnitude of the aortovertebral distance for the left renal artery, the magnitude of the aortomesenteric distance for the duodenum; analysis of concomitant variant vascular pathology at the levels studied.