Extensive Load Research Articles

Anomaly detection framework to prevent DDoS attack in fog empowered IoT networks

Internet of things or in short IoT is a network of interconnected entities such as computing devices, mechanical machines, digital gadgets etc. Cloud based IoT infrastructures are susceptible to Distributed Denial of Service (DDoS) attacks. A DDoS attack may render the server useless for a long period of time causing the services to crash due to extensive load. In this project we will try to introduce the concept of fog computing and try to explain its importance in a 3-tier architecture. We have proposed an anomaly detection architecture for IoT networks where the detection actually happens on the fog layer. The algorithm is based on the CRPS metric which is a single variable algorithm which is the case in most statistical algorithms. Therefore, we have proposed a way to use multiple variables and shown why it is required in a heterogeneous network like IoT. For detection purposes(testing data) we have used Week 5 Day 1 data of DARPA 99 as it contains a TCP SYN attack initiated once for a duration of 6 min 51 s and for ICMP Week 4 Day 1 data of DARPA 99 is used it has 2 attacks for 1s each. The algorithm is able to identify these attacks correctly.

Simulation of a Stand-alone Hybrid PV-Diesel Systems for Critical Island Loads

Micro-grid is an effective solution to increase the power distribution reliability by using renewable energy sources or hybrid with a diesel generator. In this research, a hybrid energy system using a solar power system designed for extraction of 100 kW at peak power, at standard condition 1000 W/m2 and 25 ˚C with a diesel generator designed 500 KVA at peak power is simulated for a standalone microgrid utilities. For extraction maximum power, the duty ratio of a converter is adjusting based on the specific value of maximum power point (MPP) voltage of the PV array. Thus, the DC voltage of the inverter side is kept constant to meet the grid specifications, e.g. 400 V and 50 Hz. The PV array is modelling by nonlinear equations which describe the effect of real irradiance levels for the Western Desert in Egypt on DC voltage. The solar power system is designed in an actual location with a diesel generator, supplying a three-phase load of about 300 KW contain 60 KW of critical police loads and 240 KW of normal police loads. Due to the fluctuations in solar irradiance, load sharing between the PV system and the diesel generator is controlled. The load sharing is verified numerically by the Newton-Raphson method for a three-bus ring distribution system. Numerical and simulation results show the capability of the designed PV system to share the load with the diesel generator over the year.The proposed system helps to achieve security and stability, especially in border and remote places due to the high cost of connecting these places with the public network, as well as the difficulty of maintaining diesel generators and delivering fuel. Due to the sunny climate of the Western Desert in Egypt, so the hybrid energy system with any renewable sources helping in increase generation capacity for any future extension loads power requirements without increase the storage units of diesel generator, reduce maintenance of diesel generator, increase the lifetime of diesel generator, helping to keep the environment clean, maintains reliable electricity to the consumer and can be portable from place to another without any additional cost.
 The proposed system helps to achieve security and stability, especially in border and remote places due to the high cost of connecting these places with the public network, as well as the difficulty of maintaining diesel generators and delivering fuel. Due to the sunny climate of the Western Desert in Egypt, so the hybrid energy system with any renewable sources helping in increase generation capacity for any future extension loads power requirements without increase the storage units of diesel generator, reduce maintenance of diesel generator, increase the lifetime of diesel generator, helping to keep the environment clean, maintains reliable electricity to the consumer and can be portable from place to another without any additional cost.

Modeling of Tunneling Total Loads Based on Symbolic Regression Algorithm

The tunneling total load is one of the core control parameters for safe and efficient construction using tunneling machines. However, because the tunneling process involves complex coupling relationships between the equipment and the local geology, theoretical derivation is difficult. The development of tunneling data detection and acquisition technology has led to extensive load modeling based on data analysis and machine learning. However, it is difficult to obtain an explicit interpretable model that satisfies certain physical rules. In this paper, a modeling method based on symbolic regression is proposed. The method mainly includes three modules: construction of π quantities, feature selection, and model training. Through dimensional analysis, the π quantities are constructed so as to impose physical constraints on the training process. Feature selection based on a nonlinear random forest model is used to improve the modeling efficiency. Finally, an explicit nonlinear load model is obtained using symbolic regression, which satisfies the basic equilibrium theory of mechanics and the dimensional rules of physics. The proposed approach is compared with general linear regression and an artificial neural network. The results show that the proposed method produces a load model that is interpretable and accurate, providing an excellent reference for construction excavation.

Development of a constitutive model for fibre reinforced cemented Toyoura sand

In this study, the modified Severn-Trent constitutive model is used to simulate the mechanical behaviour of unreinforced, cemented, fibre, and fibre reinforced cemented Toyoura sand consolidated under drained and undrained triaxial compression and extension loading conditions. The model parameters are derived based on the experimental results in the current study, parametric study, trial and error, and by comparison with previous research studies. The comparisons covered ranges of material from 0–3% fibre, 0–3% cement, and 20–60% relative densities. The experimental results and model simulations were compared in terms of deviatoric stress versus axial strain, volumetric strain versus axial strain, and stress path behaviour. Two additional parameters () obtained from the laboratory tests are added to the standard Severn-Trent model to simulate the stress–strain behaviour of cement and fibre reinforced Toyoura sand. Calibration exercises based on studies in the literature and comparisons with the experimental studies herein are conducted with the modified version of the Severn-Trent model. A close agreement of model simulations with the experimental results is observed for many of the tests performed on pure Toyoura sand, cemented, fibre, and fibre reinforced cemented Toyoura sand. The modified model successfully captured the main features of the behaviour (e.g., increase in strength and stiffness with cement additive, increase in volumetric dilatancy due to fibre and cement additives, and general stress path behaviour for drained and undrained conditions) for different types of composite materials with reasonable accuracy. Hence, the current study might serve and should be considered as a step towards modelling of the behaviour of composite materials.

DDoS prevention architecture using anomaly detection in fog-empowered networks

The world of computation has shown wide variety of wonders in the past decade with Internet of Things (IoT) being one of the most promising technology. Emergence of IoT brings a lot of good to the technology pool with its capability to provide intelligent services to the users. With ease to use, IoT is backed by a strong Cloud based infrastructure which allows the sensory IoT devices to perform specific functions. Important features of cloud are its reliability and security where the latter must be dealt with proper care. Cloud centric systems are susceptible to Denial of Service (DoS) attacks wherein the cloud server is subjected to an overwhelming number of incoming requests by a malicious device. If the same attack is carried out by a network of devices such as IoT devices then it becomes a Distributed DoS (DDoS) attack. A DDoS attack may render the server useless for a long period of time causing the services to crash due to extensive load. This paper proposes a lightweight, efficient and robust method for DDoS attack by detecting the compromised node connected to the Fog node or edge devices before it reaches the cloud by taking advantage of the Fog layer and prevent it from harming any information recorded or from increasing the unnecessary traffic in a network. The chosen technology stack consists of languages and frameworks which allow proposed approach to works in real time complexity for faster execution and is flexible enough to work on low level systems such as the Fog nodes. The proposed approach uses mathematical models for forecasting data points and therefore does not rely on a computationally heavy approach such as neural networks for predicting the expected values. This approach can be easily modelled into the firmware of the system and can help make cloud services more reliable by cutting off rogue nodes that try to attack the cloud at any given point of time.

Kinematics of a Novel Canine Cervical Fusion System.

The aim of this study was to determine the biomechanical behaviour of a novel distraction-fusion system, consisting of an intervertebral distraction screw, pedicle locking screws and connecting rods, in the canine caudal cervical spine. Biomechanical study in cadaveric canine cervicothoracic (C3-T3) spines (n = 6). Cadaveric spines were harvested, stripped of musculature, mounted on a four-point bending jig, and tested using non-destructive four-point bending loads in extension (0-100 N), flexion (0-60 N) and lateral bending (0-40 N). Angular displacement was recorded from reflective optical trackers rigidly secured to C5, C6 and C7. Data for primary and coupled motions were collected from intact spines and following surgical stabilization (after ventral annulotomy and nucleotomy) with the new implant system. As compared with the intact spine, instrumentation significantly reduced motion at the operated level (C5-C6) with a concomitant non-significant increase at the adjacent level (C6-C7). The combination of a locking pedicle screw-rod system and intervertebral spacer provides an alternative solution for surgical distraction-stabilization in the canine caudal cervical spine and supports the feasibility of using this new implant system in the management of disc-associated cervical spondylomyelopathy in dogs. The increase in motion at C6-C7 may suggest the potential for adjacent level effects and clinical trials should be designed to address this.

Biomechanical Analysis of Sagittal Plane Pin Placement Configurations for Pediatric Supracondylar Humerus Fractures

Anterior to posterior (AP) pinning is the recommended sagittal pin configuration in divergent lateral entry coronal pinning of pediatrics supracondylar fractures. However, there was still a lack of evidence regarding alternative sagittal pins configurations. We aimed to compare the construct stiffness of alternative sagittal pin configurations by using synthetic bone models. Sixty synthetic pediatric humeri were osteotomized to create a supracondylar fracture. After the fracture reduction, all specimens were fixed in the coronal plane with divergent lateral entry pin configurations in four different patterns in the sagittal plane: AP, crossed, divergent and parallel sagittal pin configuration. Each configuration was tested with five loading patterns. The AP sagittal pin had significantly lower construct stiffness than the divergent (p = 0.003) and the parallel sagittal pin configuration (p = 0.005) in external rotation loading tests. The divergent sagittal pin had the highest construct stiffness in extension, valgus, and external rotation loads, but the parallel sagittal pin had lower construct stiffness under extension load than the divergent and crossed sagittal pin configurations. The divergent sagittal pin configuration provides greater construct stiffness than other sagittal pin configurations due to the maximal pin spreading distance at the fracture site and the pin angle lock mechanism.

Improved Compartment Balancing Using a Robot-Assisted Total Knee Arthroplasty.

BackgroundRobot-assisted surgery was developed to improve accuracy and outcomes in total knee arthroplasty (TKA). One important determinant of TKA success is a well-balanced knee throughout the range of motion. The purpose of this study is to determine if robot-assisted TKA (RA-TKA) results in improved intracompartmental ligament balance compared with conventional jig-based instrumentation (CM-TKA).MethodsThis retrospective cohort study included 2 cohorts—a CM-TKA (n = 49) vs RA-TKA (n = 37) cohort. Demographic and intraoperative data, including intraoperative compartment loads, were measured after final implant implantation in extension (10°), mid-flexion (45°), and full flexion (90°), using an intraoperative compartment pressure sensor. An a priori power analysis revealed our study exhibited >80% power in detecting a 5-pound (lb) difference in compartment loads in the 2 cohorts.ResultsThere was no difference between medial and lateral compartment loads in extension, mid-flexion, and full flexion for the conventional (15.1 lbs, 15.9 lbs, and 13.4 lbs, respectively) vs RA-TKA (14.2 lbs, 15.1 lbs, and 10.3 lbs, respectively). The percentage of patients with high load compartment pressure in flexion (>40 lbs) by the conclusion of the surgery was significantly greater for the conventional (18%) vs the robotic TKA cohort (3%, P = .025). The percentage of patients with unbalanced knees (>20 lbs differential between medial and lateral compartments) in flexion was significantly greater in the conventional (24%) vs robotic TKA cohort (5%, P = .018).ConclusionsIn this series, RA-TKA resulted in improved intraoperative compartment balancing in flexion with no observed difference in mid-flexion and extension compared with CM-TKA.

Клинические примеры эффективности коррекции астигматизма слабой степени в нормализации зрительных функций

In today’s world, the extensive visual load increases the demands on the quality of optical correction. Inadequate optical correction results in additional load on the accommodation system of the eye, increased fatigue, and complaints of asthenopia. Full optical correction is an essential requirement for the correct functioning of a visual analyzer. However, if baseline impairments of accommodation response (fusion) are not considered, full optical correction (eyeglasses or contact lenses) provokes visual discomfort. Daily disposable contact lenses (CL) with power change for each additional month is helpful in these cases, thereby allowing for a stepwise transition to the complete correction of ametropias and recovery of physiological accommodation, convergence, and better central and binocular vision quality. Prescription of spherical (not toric) CL, whose optical power was calculated by the spherical equivalent of sphero-cylindrical correction, is a typical error when correcting low astigmatism. This error negatively affects accommodative response and visual working capacity. A complete correction of astigmatism (even a low one) is required for visual recovery to reduce visual fatigue and improve working capacity and academic performance. When prescribing optical correction, binocular vision patterns and a dominant eye should be considered. Keywords: astigmatism, accommodation, binocular vision, visual discomfort, asthenopia, toric soft contact lenses. For citation: Lobanova I.V., Rybakova E.G., Romanova T.B. Clinical examples of the effective correction of low astigmatism for improving vision. Russian Journal of Clinical Ophthalmology. 2021;21(4):249–252 (in Russ.). DOI: 10.32364/2311-7729-2021-21-4-249-252.

Impact of Screw Diameter and Length on Pedicle Screw Fixation Strength in Osteoporotic Vertebrae: A Finite Element Analysis.

Study DesignBiomechanical study.PurposeTo quantitatively investigate the effect of screw size on screw fixation in osteoporotic vertebrae with finite element analysis (FEA)Overview of LiteratureOsteoporosis poses a challenge in spinal instrumentation; however, the selection of screw size is directly related to fixation and is closely dependent on each surgeon’s experience and preference.MethodsTotal 1,200 nonlinear FEA with various screw diameters (4.5–7.5 mm) and lengths (30–50 mm) were performed on 25 patients (seven men and 18 women; mean age, 75.2±10.8 years) with osteoporosis. The axial pullout strength, and the vertebral fixation strength of a paired-screw construct against flexion, extension, lateral bending, and axial rotation were examined. Thereafter, we calculated the equivalent stress of the bone-screw interface during nondestructive loading. Then, using diameter parameters (screw diameter or screw fitness in the pedicle [%fill]), and length parameters (screw length or screw depth in the vertebral body [%length]), multiple regression analyses were performed in order to evaluate the factors affecting various fixations.ResultsLarger diameter and longer screws significantly increased the pullout strength and vertebral fixation strength; further, they decreased the equivalent stress around the screws. Multiple regression analyses showed that the actual screw diameter and %length were factors that had a stronger effect on the fixation strength than %fill and the actual screw length. Screw diameter had a greater effect on the resistance to screw pullout and flexion and extension loading (β=0.38–0.43, p<0.01); while the %length had a greater effect on resistance to lateral bending and axial rotation loading (β=0.25–0.36, p<0.01) as well as mechanical stress of the bone-screw interface (β=−0.42, p<0.01).ConclusionsThe screw size should be determined based on the biomechanical behavior of the screws, type of mechanical force applied on the corresponding vertebra, and anatomical limitations.

Secondary ossification center induces and protects growth plate structure.

Growth plate and articular cartilage constitute a single anatomical entity early in development but later separate into two distinct structures by the secondary ossification center (SOC). The reason for such separation remains unknown. We found that evolutionarily SOC appears in animals conquering the land - amniotes. Analysis of the ossification pattern in mammals with specialized extremities (whales, bats, jerboa) revealed that SOC development correlates with the extent of mechanical loads. Mathematical modeling revealed that SOC reduces mechanical stress within the growth plate. Functional experiments revealed the high vulnerability of hypertrophic chondrocytes to mechanical stress and showed that SOC protects these cells from apoptosis caused by extensive loading. Atomic force microscopy showed that hypertrophic chondrocytes are the least mechanically stiff cells within the growth plate. Altogether, these findings suggest that SOC has evolved to protect the hypertrophic chondrocytes from the high mechanical stress encountered in the terrestrial environment.

Behaviour of Uniform Drava River Sand in Drained Condition—A Critical State Approach

Numerous triaxial tests on sand and sand-like materials have been performed worldwide during the past several decades. Their results provided a development of the advanced soil constitutive models and laboratory testing devices, as well as the establishment of a worldwide database of different types of uniform sandy materials. From such research, the critical state and steady state theory has emerged as one of the most useful tool for the modelling of a soil behaviour. This paper presents the results of static drained tests performed on the uniform Drava River sand from the Osijek region in Croatia. The main aim was to determine the shear behaviour and critical state, given that these characteristics are mostly unknown for the tested sand material. A series of detail triaxial tests were performed in drained conditions for three different initial relative densities, DR, and two different loading directions; e.g., axial compression and axial extension. In total, 18 drained tests were performed. The study indicated that the value of 33.75∘ is the critical friction angle for the tested sand. The relative density of 57% is determined as the critical relative density. Additionally, the study confirmed the difference in critical state for compression and extension loading. In addition, the results indicate that the sample preparation procedure has an important impact on the critical state of loosely prepared sandy samples. These results give the first insights into the behaviour of the Drava River sand, which can generally contribute to the worldwide sand behaviour knowledge base.

DAMAGING AND DESTRUCTION OF REDUCTION TRAINS OF MI-8 HELICPTER AND ITS MODIFICATIONS

The results of quantitative factographic study of the Mi-8 helicopter (its modifications) reduction trains with different types of gear coupling, the destruction of which occurred while in flight due to the presence of preliminary material damage at the stage of production of the gear wheels and during their operational employment are presented in a generalized form. Contact teeth destruction as the main cause of failures of high-speed gear wheels in well-lubricated enclosed gears are considered. The causes of the wearing and sticking of the teeth along their lateral surfaces as well as scoring and destruction depending on the origin of the cracks are revealed.&#x0D; The main causes of damaging and destruction of helicopter reduction trains, locations and origination of fatigue cracks spots are identified. Different types of contact and fatigue destructions due to various reasons are considered.&#x0D; Dynamic loading of gear wheels disks as a result of their rotation damages the material of the wheels in the area of multi-cycle fatigue due to the repeatability of flight load cycles.&#x0D; Lamination or deep contact destruction of the material, which sometimes take place in gears with surface hardened (cemented, tempered, nitrided, etc.) teeth, are much more dangerous than surface destruction of the material since sufficiently large fractions of the hardened material layer are split away from the teeth that can quickly break down an entire gear train.&#x0D; The main causes of contact teeth destruction are load concentration along the length and profile of the teeth, the presence of residual tensile stresses on the working surfaces of the teeth, adverse operational damage to the tooth profiles and negative effect of lubricating fluid on the teeth.&#x0D; For a repaired gear train the cause of the uneven load distribution along the length of the teeth may be the poor assembly of the gear wheels and other transmission parts which leads to unsatisfactory contact of the gear teeth in the assembled unit.&#x0D; The revealed peculiarities of the destruction process indicate regular crack proliferation from flight to flight. According to the operation conditions of the gear weel, its regular extensive loading refers only to the full cycle of starting and stopping the reducer train or unloading the helicopter in flight, which in this case corresponds to the cycle of helicopter operation in one flight. Therefore, the number of detected fatigue lines corresponds to the number of helicopter flights.&#x0D; To increase the smoothness of gear train running which affects positioning accuracy, reduce wear during running-in, decrease noise, eliminate early jamming, and ultimately, to increase the resource, it is necessary to eliminate the edge interaction of the teeth, which causes their excessive wear.

3D constitutive modeling of electro-magneto-visco-hyperelastic elastomers: a semi-analytical solution for cylinders under large torsion–extension deformation

The rise of a new class of smart materials known as electro-magnetorheological elastomers (EMREs) requires comprehensive understanding of their electro-magneto-visco-hyperelastic behaviors. The aim of this paper is to develop a generalized three-dimensional (3D) continuum-based framework of the electro-magneto-visco-hyperelastic behaviors of EMREs. The finite strain model is established based on the linear viscoelasticity theory and non-linear electro-magneto-elastic framework. As EMRE devices can be used in a cylindrical shape undergoing shear and normal stresses in many engineering applications like artificial muscles, a boundary-value problem simulating torsion–extension deformations of EMRE cylinders is developed in the finite strain regime and solved semi-analytically. The behaviors of EMRE cylinders under different loading conditions such as purely mechanical loading, purely electric loading as well as full coupling between mechanical, electric and magnetic loading are studied in detail. Influence of different parameters such as electric field, magnetic field, applied strain (-rate) and their coupling on the induced moment and axial force of the EMRE cylinder as well as its relaxation and creep under torsion–extension loading is also examined. It is shown that EMREs have adaptive capability and great potential in applications where the stiffness needs to be controllable. Due to simplicity and accuracy, the model is expected to be used in the future studies dealing with the analysis of EMREs in particular cylinders under torsion–extension developments like 4D printing of artificial EMRE-based cylindrical muscles.

Immediate and Short-Term Effects of Short- and Long-Duration Isometric Contractions in Patellar Tendinopathy.

Isometric muscle contractions are used in the management of patellar tendinopathy to manage pain and improve function. Little is known about whether long- or short-duration contractions are optimal to improve pain. This study examined the immediate and short-term (4 weeks) effects of long- and short-duration isometric contraction on patellar tendon pain, and tendon adaptation. Repeated measures within groups. Clinical primary care. Participants (n = 16, males) with patellar tendinopathy. Short-duration (24 sets of 10 seconds) or long-duration (6 sets of 40 seconds) isometric knee extension loading (85% maximal voluntary contraction), for 4 weeks. Immediate change in pain with single-leg decline squat (SLDS) and hop, as well as change in pain and tendon adaptation [within-session anterior-posterior (AP) strain] were assessed over 4 weeks. Pain was significantly reduced after isometric loading on both SLDS (P < 0.01) and hop tests (P < 0.01). Pain and quadriceps function improved over the 4 weeks (P < 0.05). There was significant AP strain at each measurement occasion (P < 0.01). Although transverse strain increased across the training period from ∼14% to 22%, this was not significant (P = 0.08). This is the first study to show that short-duration isometric contractions are as effective as longer duration contractions for relieving patellar tendon pain when total time under tension is equalized. This finding provides clinicians with greater options in prescription of isometric loading and may be particularly useful among patients who do not tolerate longer duration contractions. The trend for tendon adaptation over the short 4-week study period warrants further investigation.

Extension Mechanism of the Proximal Interphalangeal Joint of the Human Phalanx: A Cadaveric Biomechanical Study.

Our purpose was to compare the contributions of these two systems to assess PIP joint extension in fresh cadaver models. Nine middle fingers of fresh cadavers were used. The PIP joint angle was measured while an extension load was applied on the extensor tendons. Specimens on which extension load was applied on the extrinsic extensors were classified as the extrinsic group, and those on which extension load was applied on the intrinsic extensors were classified as the intrinsic group. Linear regression analyses were performed to obtain regression equation and the extension load-PIP joint angle curve. The mean of slope of the curve was compared between the two groups using paired t-test. The same experiments were done for the metacarpophalangeal (MP) joint in 0° and 60° flexion to evaluate the effect of MP joint flexion on PIP joint extension. The mean slope of the extension load-PIP joint angle curve of the extrinsic group was significantly greater than that of the intrinsic group. With the MP joint in 0° flexion, the mean slope of the extrinsic and intrinsic groups was -0.148 and -0.117, respectively (greater absolute value means greater slope, p = 0.01). With the MP joint in 60° flexion, the mean slopes were -0.147 and -0.104, respectively (p = 0.015). The contribution of the intrinsic extensor for PIP joint extension shows decreasing trends with MP joint flexion. The extrinsic extensors have greater contribution for PIP joint extension compared with the intrinsic extensors.

DAMAGING AND DESTRUCTION OF REDUCTION TRAINS OF MI-8 HELICPTER AND ITS MODIFICATIONS

The results of quantitative factographic study of the Mi-8 helicopter (its modifications) reduction trains with different types of gear coupling, the destruction of which occurred while in flight due to the presence of preliminary material damage at the stage of production of the gear wheels and during their operational employment are presented in a generalized form. Contact teeth destruction as the main cause of failures of high-speed gear wheels in well-lubricated enclosed gears are considered. The causes of the wearing and sticking of the teeth along their lateral surfaces as well as scoring and destruction depending on the origin of the cracks are revealed.&#x0D; The main causes of damaging and destruction of helicopter reduction trains, locations and origination of fatigue cracks spots are identified. Different types of contact and fatigue destructions due to various reasons are considered.&#x0D; Dynamic loading of gear wheels disks as a result of their rotation damages the material of the wheels in the area of multi-cycle fatigue due to the repeatability of flight load cycles.&#x0D; Lamination or deep contact destruction of the material, which sometimes take place in gears with surface hardened (cemented, tempered, nitrided, etc.) teeth, are much more dangerous than surface destruction of the material since sufficiently large fractions of the hardened material layer are split away from the teeth that can quickly break down an entire gear train.&#x0D; The main causes of contact teeth destruction are load concentration along the length and profile of the teeth, the presence of residual tensile stresses on the working surfaces of the teeth, adverse operational damage to the tooth profiles and negative effect of lubricating fluid on the teeth.&#x0D; For a repaired gear train the cause of the uneven load distribution along the length of the teeth may be the poor assembly of the gear wheels and other transmission parts which leads to unsatisfactory contact of the gear teeth in the assembled unit.&#x0D; The revealed peculiarities of the destruction process indicate regular crack proliferation from flight to flight. According to the operation conditions of the gear wheel, its regular extensive loading refers only to the full cycle of starting and stopping the reducer train or unloading the helicopter in flight, which in this case corresponds to the cycle of helicopter operation in one flight. Therefore, the number of detected fatigue lines corresponds to the number of helicopter flights.&#x0D; To increase the smoothness of gear train running which affects positioning accuracy, reduce wear during running-in, decrease noise, eliminate early jamming, and ultimately, to increase the resource, it is necessary to eliminate the edge interaction of the teeth, which causes their excessive wear.

Percutaneous posterior full-endoscopic cervical foraminotomy and discectomy: a finite element analysis and radiological assessment

Percutaneous posterior full-endoscopic cervical foraminotomy and discectomy (PECFD) is recognized as a safe, effective, and minimally invasive treatment for cervical spondylotic radiculopathy (CSR). However, the potential mechanisms of the degenerative changes and postoperative recurrence after PECFD are unclear. In this study, a finite element (FE) analysis and radiological assessment were performed to evaluate the biomechanical effects after PECFD. The FE model indicated that the ROM and IDP of C5–C6 increased significantly after PECFD in the extension loading. The radiological evaluation revealed that the extension ROM of C2–C7 and the operative level increased significantly at the one-year follow-up compared with that obtained preoperatively. Combining the FE results and radiological changes, we conclude that the increase in the ROM and IDP at the operative level in the extension loading is the potential cause of the degenerative changes and recurrences after PECFD surgery.

Pain and load progression following an early maximal strength training program in total hip- and knee arthroplasty patients.

Total hip arthroplasty (THA) and total knee arthroplasty (TKA) patients significantly increase muscle strength after maximal strength training (MST) initiated soon after surgery. Owing to severe postoperative pain, knee patients are anticipated to be more limited in performing heavy load exercises than hip patients. The aim of the present study was to describe pain and load progression during early MST in THA and TKA patients. Explorative study based on secondary analyses from two randomized controlled trials: 26 THA and 16 TKA patients had their training sessions logged. They trained at 85-90% of their maximal capacity in leg press, and abduction/knee-extension of the operated leg (4 × 5 repetitions) for 8-10 weeks, initiated early postoperatively. Knee patients experienced significantly more pain than hip patients during the training sessions (p < 0.03), however, pain before and after training was not different (p > 0.09). All patients significantly increased leg press training load until the last intervention week (p < 0.01). This study demonstrates that TKA patients experience more pain than THA patients during training following a MST program but not more than moderate levels during or after training. Pain before and after training is not different. Both groups significantly increased load progression during the intervention. These findings indicate that both THA and TKA patients might perform MST with extensive load progression early after surgery without compromising pain. The studies were registered at ClinicalTrials.gov .

Numerical simulation of lateral and transforaminal lumbar interbody fusion, two minimally invasive surgical approaches

The present study aims to compare spinal stability after two different minimally invasive techniques, the lateral lumbar interbody fusion (LLIF) and the transforaminal lumbar interbody fusion (TLIF) approaches. Two nonlinear three-dimensional finite element (FE) models of the L4–L5 functional spinal unit (FSU) were subjected to the loads that usually act on the lumbar spine. Findings show that the LLIF approach yields better results for torsion load case, due to the larger surface area of the implant. For extension, flexion and lateral bending loads, the TLIF approach presents smaller displacements probably due to the anterior placement of the cage and to the smaller damaged area of the annulus fibrosus.