Real Joint Research Articles

Tribological Behavior of Nanocomposites Based on UHMWPE Aged in Simulated Synovial Fluid.

Ultra High molecular weight polyethylene (UHMWPE) suffers wear degradation in total joint replacements and it needs to be improved. Thus, we enhanced wear resistance of UHMWPE with carbon nanofiller and paraffin oil and studied its tribological behavior in Simulated Synovial Fluid (SSF) for 60 days at 37 °C to reproduce the conditions of a real joint. Ageing in biological fluid accelerates the wear action but nanocomposite exhibited a higher wear resistance compared to UHMWPE because of its higher structural homogeneity. Carbon nanofiller closes the porosity of UHMWPE hindering SSF to penetrate inside. Wear resistance of the nanocomposite with 1.0 wt.% of CNF improved of 65% (before ageing) and of 70% (after 60 days in SSF) with respect to pure UHMWPE.

Reaching a milestone in pharmaceutical patenting in Brazil.

Reaching a milestone in pharmaceutical patenting in Brazil.

Research progress of knee-salvage treatment for knee osteoarthritis

To review the progress of knee-salvage treatment based on the step therapy idea for knee osteoarthritis (KOA). The domestic and foreign literature in recent years was searched, and the treatments of KOA at different stages were summarized and analyzed. The treatment of KOA is aimed at alleviating symptoms, delaying structural changes of joints, maintaining joint function, and improving quality of life. So the conservative treatment is still the first choice for KOA at early stage. Arthroscopic surgery can assist in the diagnosis and classification, simultaneously remove the intra-articular irritants, and limitedly repair the cartilage. Osteotomy is suitable for the KOA with abnormal lower extremity weight bearing line and articular line. And it can effectively balance the weight bearing stress of knee joint, improve the clinical symptom, and alleviate the progression of disease. Joint distraction can improve the mechanical environment of knee joint and repair the defect cartilage partly. With the technical development, unicompartmental knee arthroplasty (UKA) is back in fashion in recent years. It is a kind of real joint surface replacement, which is an important means of knee preservation method in patients with anterior medial KOA. At present, there are many knee-salvage treatments based on the severity of the disease. Osteotomy and UKA are the most widely used and successful surgical techniques for knee preservation. However, the indications should be properly selected, and the surgeon should accumulate enough clinical experience. Otherwise, it is difficult to achieve good results.

An Optimized Trajectory Planning for Welding Robot

In order to improve the welding efficiency and quality, this paper studies the combined planning between welding parameters and space trajectory for welding robot and proposes a trajectory planning method with high real-time performance, strong controllability and small welding error. By adding the virtual joint at the end-effector, the appropriate virtual joint model is established and the welding process parameters are represented by the virtual joint variables. The trajectory planning is carried out in the robot joint space, which makes the control of the welding process parameters more intuitive and convenient. By using the virtual joint model combined with the B-spline curve affine invariant, the welding process parameters are indirectly controlled by controlling the motion curve of the real joint. To solve the optimal time solution as the goal, the welding process parameters and joint space trajectory joint planning are optimized.

Discontinuous deformation analysis of super section tunnel surrounding rock stability based on joint distribution simulation

Based on binocular stereo photography measurement technology, the actual distribution information of joints and fractures in the tunnel face were obtained via image processing and feature extraction, and the preliminary evaluation of surrounding rock stability of Laohushan tunnel was conducted according to surrounding rock classification method. Since all available surrounding rock classification approaches didn’t consider the influences of the size effect of tunnel excavation span and unfavorable geologic bodies such as weak-fracture zones, an improved discontinuous deformation analysis (DDARF) method was adopted to conduct a numerical simulation of the deformation and fracture processes of the surrounding rock. Using the traveling wave method, triangle DDA blocks were automatically generated in the calculation zone, and the block boundaries were divided into real joints and virtual joints. Based on the real joint information obtained via aforementioned photographic measurement, the real joints in the tunnel face were dynamically modified, in order to achieve the simulation of joint distribution. The results revealed that the fracture evolution regularity, deformation failure mechanism, and block dropping phenomenon that the DDARF joint simulation model calculated are in good agreement with actual conditions, while those obtained based on conventional models present differences from field situation. Additionally, focusing on the localised rockfall phenomenon of Laohushan tunnel, the crack extension rate was introduced to conduct a quantitative comparison of the rock crack evolution process with or without anchor supporting. The research results offer practical guidance for field construction and anchorage support scheme optimization.

Kinematic models of lower limb joints for musculo-skeletal modelling and optimization in gait analysis.

Kinematic models of lower limb joints have several potential applications in musculoskeletal modelling of the locomotion apparatus, including the reproduction of the natural joint motion. These models have recently revealed their value also for in vivo motion analysis experiments, where the soft-tissue artefact is a critical known problem. This arises at the interface between the skin markers and the underlying bone, and can be reduced by defining multibody kinematic models of the lower limb and by running optimization processes aimed at obtaining estimates of position and orientation of relevant bones. With respect to standard methods based on the separate optimization of each single body segment, this technique makes it also possible to respect joint kinematic constraints. Whereas the hip joint is traditionally assumed as a 3 degrees of freedom ball and socket articulation, many previous studies have proposed a number of different kinematic models for the knee and ankle joints. Some of these are rigid, while others have compliant elements. Some models have clear anatomical correspondences and include real joint constraints; other models are more kinematically oriented, these being mainly aimed at reproducing joint kinematics. This paper provides a critical review of the kinematic models reported in literature for the major lower limb joints and used for the reduction of soft-tissue artefact. Advantages and disadvantages of these models are discussed, considering their anatomical significance, accuracy of predictions, computational costs, feasibility of personalization, and other features. Their use in the optimization process is also addressed, both in normal and pathological subjects.

A Unified Approach for Second-Order Control of the Manipulator With Joint Physical Constraints

Kinematic control of manipulators with joint physical constraints, such as joint limits and joint velocity limits, has received extensive studies. Many studies resolved this problem at the second-order kinematic level, which may suffer from the self-motion instability in the presence of persistent self-motion or unboundedness of joint velocity. In this paper, a unified approach is proposed to control a manipulator with both joint limits and joint velocity limits at the second-order kinematic level. By combining the weighted least-norm (WLN) solution in the revised joint space and the clamping weighted least-norm (CWLN) solution in the real joint space, the unified approach ensures the joint limits and joint velocity limits at the same time. A time-variant clamping factor is incorporated into the unified approach to suppress the self-motion when the joint velocity diverges, or the end-effector stops, which improves the stability of self-motion. The simulations in contrast to the traditional dynamic feedback control scheme and the new minimum-acceleration-norm (MAN) scheme have been made to demonstrate the advantages of the unified approach.

Adhesion and Cohesion Testing of Joint Sealants after Artificial Weathering – New Test Method

The use of construction sealants is an important area not just of the building construction. Each building requires a careful processing of all details and façades are no exception. From today's point of view we may note that sealing of façade joints and different types of cracks, fissures or gaps is nothing unusual and, therefore, it is astonishing that there still occur defects that often cause a significant decrease of the durability of the structures and sealed structures. This paper deals with testing of a selected group of construction sealants at a so-called ‘real joint’. The real joint is a term defining a set of testing samples when the testing body contains a sealant applied in a manner corresponding to its real application. Cement bonded particleboard board was representing the façade cladding in this research since during the sealing there often occur complications with adhesion of sealants. For the presented experiment the existing testing methods that are used for verification of adhesion of cladding materials were studied and modified. According to the opinion of the authors those modified methods simulate well the parameters of the external environment and thus also the negative influences that may have a significant impact on the sealed joint in practice. The measured results prove that in the application of the sealants it is very important to follow the technology discipline and namely it is necessary upfront to verify whether the chosen materials are compatible. In most tested cases, diversion from the above-given steps resulted in failure of the sealed joint.

A real options and joint ventures perspective for strategic decision-making process in the case of dynamic industrial environments

Strategic decision – making process represents a challenge in a dynamic industrial environment. Nowadays, many instruments and techniques are used in the process of decision-making. The perspective regarding real options analysis (ROA), joint ventures (JVs) and strategic decision-making process (SDMP) is very important to be analyzed because it represents a key source to obtain competitive advantage in a turbulent environment characterized by competitiveness, dynamism and a proactive thinking. The aim of the paper is to offer an interesting framework that emphasizes the relationship between real options (ROs), JVs, transaction cost (TC), bargaining models (BM), agency theory (AT) and SDMP. Also, the paper analyzes a real case study and it suggests a business model that includes elements that conduce to an innovative management. The findings are very useful for decision-makers from organizations, researchers and students.

Longitudinal bonded joints of timber beams using plywood and LVL plates

The content of this article is to analyze destructive testing results of longitudinal solid wood joints of structural size beams with external glued wood-based panels (plywood, laminated veneer lumber – LVL) stressed in bending.The aim of this article is to compare the carrying capacity and the real joint behaviour under load with values obtained using numerical modelling and calculation according to valid standards.

GLOBAL OPTIMIZATION METHOD APPLIED TO THE KINEMATICS OF GAIT IN PREGNANT WOMEN

Morphological changes are associated to pregnancy, such as weight gain and increased volume of the trunk. The soft tissue artifact can also increase with these characteristics and affect the real joint kinematics. The main objective of this study was to understand the effect of using three different constraining sets in the lower limb joints, in the amount of soft tissue artifact (STA) of pregnant women, in order to obtain the most appropriated joint set to be used in gait and in this population. The ankle, knee and hip joints were modeled respectively with the following characteristics: (1) Universal–revolute–spherical (URS), (2) spherical–revolute–spherical (SRS) and (3) spherical–spherical–spherical (SSS). The six degrees of freedom (6DOF) model was used as the basis for comparison and considered the one with the highest error associated to the STA. In pregnant women, the URS model seems to affect more the kinematic variables when compared with the 6DOF model. Assuming that the kinematic error associated with pregnant women is increased due to the STA, the URS model may be affecting more the angular kinematics of the knee joint. SSS model seems to be more appropriated to analyze gait in second trimester pregnant women.

A new protocol for wear testing of total knee prostheses from real joint kinematic data: Towards a scenario of realistic simulations of daily living activities

A new tendency in the field of wear testing of total knee replacements is represented by realistic simulations of various motor tasks of daily living (chair sitting and rising, squat, stair ascent, etc.). Various studies have shown in fact the limits of the ISO 14243 standards, in particular the concern about the ability of the level walking simulations to recreate the main wear mechanisms which occur on the knee implant during its in vivo lifespan. The recently proposed protocols for the simulation of these motor tasks still lack accuracy and consistency between the various degrees of freedom, which are necessary for a good replication of the mechanical behavior in a replaced knee.In the present study a realistic scenario for simulation of various motor tasks using a displacement controlled wear testing machine is presented. Stair climbing, chair sit/stand cycle, and squat cycle were analyzed through video-fluoroscopy in a population of knee replacement patients to extract flexion/extension and intra/extra rotation angles, together with anterior/posterior translation. Corresponding axial load data were arranged by gait analysis from a control population. The proposed protocol was tested on a displacement controlled wear simulator.Kinematic and load data revealed good consistency across subjects. The knee simulator showed an accurate reproduction of the various motion and load patterns, with average error lower than 5%. The obtained dataset for wear simulator, containing all the displacement and loading parameters for stair climbing, chair sit/stand and squat activities, is fully reported.

Electronic ‘Knowledge Factories’ versus Micro-environment of Innovation: Who Will Win?

The end of the 20th century was marked by several studies that revealed the collective mechanisms of the development of knowledge as a joint activity in working teams. Thus, the idea that acquiring knowledge was an unproblematic transfer of what is already available and can be unilaterally transferred and assimilated was rejected [Lave, Wenger, 1991]. The aim of this paper is to study the possibilities of electronic network platforms to use the collective nature of knowledge in the interests of further developing knowledge and innovation through online communication of professionals.Based on a literature review on the development of knowledge, the paper compares the basic principles of knowledge application in formulating new decisions during real joint activity and during online communication within specialized platforms for ‘knowledge exchange’. The author argues that electronic networking platforms contribute to the fragmentation of knowledge representation of participants, eluding a common sense and purpose. Thus, such platforms blur the boundary between knowledge and information. The article indicates that the desire to increase the effectiveness of collective creativity via online communication risks not developing competencies, discretion, and exploration of others’ experiences. Instead, this desire leads to strengthening external control and separation of functions into primary routine operations when an individual participant is valued not for his/ her knowledge and previous experience, but for his/ her communicative capabilities. The produced effect is akin to the industrial revolution of the machine era; when this effect is widespread, there are risks that knowledge workers will be turned into easily replaceable, piecemeal workers. To avoid this, electronic platforms should either learn to recreate the conditions of offline micro-environments of innovation, or not claim to fulfil the role of knowledge production.

Synthesized multi-station tribo-test system for bio-tribological evaluation in vitro

Tribological tests play an important role on the evaluation of long-term bio-tribological performances of prosthetic materials for commercial fabrication. Those tests focus on the motion simulation of a real joint in vitro with only normal loads and constant velocities, which are far from the real friction behavior of human joints characterized with variable loads and multiple directions. In order to accurately obtain the bio-tribological performances of artificial joint materials, a tribological tester with a miniature four-station tribological system is proposed with four distinctive features. Firstly, comparability and repeatability of a test are ensured by four equal stations of the tester. Secondly, cross-linked scratch between tribo-pairs of human joints can be simulated by using a gear-rack meshing mechanism to produce composite motions. With this mechanism, the friction tracks can be designed by varying reciprocating and rotating speeds. Thirdly, variable loading system is realized by using a ball-screw mechanism driven by a stepper motor, by which loads under different gaits during walking are simulated. Fourthly, dynamic friction force and normal load can be measured simultaneously. The verifications of the performances of the developed tester show that the variable frictional tracks can produce different wear debris compared with one-directional tracks, and the accuracy of loading and friction force is within ±5%. Thus the high consistency among different stations can be obtained. Practically, the proposed tester system could provide more comprehensive and accurate bio-tribological evaluations for prosthetic materials.

Development of an embedded control system by means of dsPIC applied in a 4 DOF robot

In this paper the design and implementation of an embedded control system, using DSCs (Digital Signal Controller) devices of dsPIC type, applied on a four DOF (Degrees Of Freedom) robotic manipulator OWI-535 model is presented. The mathematical model of manipulator is elaborated obtaining joint trajectories to achieve the tracking of a test Cartesian trajectory. A control structure based on a Master/Slave configuration, between two dsPIC30F4013 through SPI (Serial Peripheral Interface) protocol is developed. In such a system, algorithms are implemented: PID (Proportional Integral Derivative) with anti-windup and, generation PWM (Pulse-Width Modulation) and data acquisition, in the DSCs master and slave, respectively. The results are exposed by comparative curves between the desired and real joint trajectories and joint error graphs, generated from real data of the implementation.

Learning to balance an NAO robot using reinforcement learning with symbolic inverse kinematic

An autonomous humanoid robot (HR) with learning and control algorithms is able to balance itself during sitting down, standing up, walking and running operations, as humans do. In this study, reinforcement learning (RL) with a complete symbolic inverse kinematic (IK) solution is developed to balance the full lower body of a three-dimensional (3D) NAO HR which has 12 degrees of freedom. The IK solution converts the lower body trajectories, which are learned by RL, into reference positions for the joints of the NAO robot. This reduces the dimensionality of the learning and control problems since the IK integrated with the RL eliminates the need to use whole HR states. The IK solution in 3D space takes into account not only the legs but also the full lower body; hence, it is possible to incorporate the effect of the foot and hip lengths on the IK solution. The accuracy and capability of following real joint states are evaluated in the simulation environment. MapleSim is used to model the full lower body, and the developed RL is combined with this model by utilizing Modelica and Maple software properties. The results of the simulation show that the value function is maximized, temporal difference error is reduced to zero, the lower body is stabilized at the upright, and the convergence speed of the RL is improved with use of the symbolic IK solution.

指の正確な関節構造に基づく筋骨格モデルによる日常動作での筋長変化の評価

Essential understanding of human hand dexterity is very important to make a dexterous robot hand like human hand. In this paper, we focus on the human thumb which can make the movement of opposition. The widely known musculoskeletal model of human thumb uses moment arms which were estimated from the measurements of a specimen. However, the moment arms were derived with an assumption that its joint structure can be approximated by the universal-joint model. However, universal-joint is not appropriate for modeling the real joint structure. In this paper, we evaluate a musculoskeletal model of human thumb in in daily performance which we constructed based on its real joint structure so that we can annualize muscle-skeletal activities more accurately. It is shown that the estimated muscle length with the conventional thumb model has larger error than than the one with the proposed model.

Principal–Agent Issues in Real Estate Funds and Joint Ventures

Principal–Agent Issues in Real Estate Funds and Joint Ventures

Considering human resource constraints for real joint production and maintenance schedules

This study deals with the problem of scheduling jobs and preventive maintenance (PM) activities in production workshops jointly in order to reduce failure occurrence. PM activities can be planned at fixed periods (time-based PM) or in response to a signal provided from a machine’s captor after anomaly detection (condition-based PM). Maintenance activities’ planning depends on different constraints like human resources, spare parts availability and past operating duration of the machine.Proposed related works evaluate possible arrangements of both production and maintenance activities according to different criteria (makespan (Cmax: completion date of the last operation on the last machine), machine’s failure risk, jobs’ lateness, etc.). However, maintenance activities are frequently considered as production jobs. In fact, maintenance activities present different constraints and cannot be planned in the same manner as production ones. In addition to that, most of current works deal with the time-based maintenance planning even so condition-based maintenance is qualified as more realistic and more economic than the former.This work discusses a new approach to integrate the scheduling of production and maintenance operations. Proposed approach takes explicitly into account human resources availability and skills when updating integrated production and maintenance schedules. It is based on multi-agent systems for modeling the production workshop.

Evaluation of Secondary Hardening and Microstructure in the Real T24 Steel Weld Joint

Development of new steels with higher creep resistance must be based on detailed knowledge of strengthening and degradation processes, structural stability at high temperature exposure and their welding. This paper is concerned with the real weld joint hardness and microstructure of progressive low alloy creep resistance T24 steel. These steel is widely used in many power-plant constructions all over the Europe. Welding the T24 steels components is one of the most important technological procedures. The aim of the performed investigation is to evaluate the hardness and microstructure in the heat affected zone (HAZ) and the weld metal. Results of the secondary hardening in the real weld joints after low temperature post weld heat treatment (460°C/48h) and without post weld heat treatment at service temperature are described in this paper. Obtained results are compared to the hardness values of the weld joint post weld heat treated at recommended temperature (740°C). The microstructure of the real weld joints was analysed by transmission electron microscopy (TEM) in order to identify minority phases - MX nanoparticles and/or coarse (M23C6) particles. Secondary hardening of the not heat treated and low temperature heat treated T24 weld joint was proved.