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Centrifugal dampers are used to reduce the vibrations and irregularities of motion of rotating parts subjected to torque perturbations. Compliant mechanisms can be used for building compact and simple embodiments of such devices. On the other hand, the elasto-kinematic behaviour of compliant structures requires a more accurate design with respect to standard solutions. The study discusses a methodology for designing compliant centrifugal dampers based on the arrangement of a collection of leaf flexure hinges connecting peripheral masses. The design is based on the equations of motion written under the approximation of an equivalent pseudo-rigid assembly. To preserve accuracy, the pseudo-rigid surrogate model is deduced taking into account second-order kinematic invariants and Euler–Savary equations, thus providing second-order approximation of the relative motion. This strategy combines accuracy and simplicity. The design can benefit from design equations for choosing the dimensions of the flexible links and the weight of the peripheral masses. An example of application is also discussed and a comparison with a flexible multibody model is also presented to demonstrate the accuracy of the proposed methodology.

In Industry 4.0 era, rapid changes to the global landscape of manufacturing are transforming industrial plants in increasingly more complex digital systems. One of the most impactful innovations generated in this context is the “Digital Twin”, a digital copy of a physical asset, which is used to perform simulations, health predictions and life cycle management through the use of a synchronized data flow in the manufacturing plant. In this paper, an innovative approach is proposed in order to contribute to the current collection of applications of Digital Twin in manufacturing: a Digital Shadow cloud-based application to enhance quality control in the manufacturing process. In particular, the proposal comprises a Digital Shadow updated on high performance computing cloud infrastructure in order to recompute the performance prediction adopting a variation of the computer-aided engineering model shaped like the actual manufactured part. Thus, this methodology could make possible the qualification of even not compliant parts, and so shift the focus from the compliance to tolerance requirements to the compliance to usage requirements. The process is demonstrated adopting two examples: the structural assessment of the geometry of a shaft and the one of a simplified turbine blade. Moreover, the paper presents a discussion about the implications of the use of such a technology in the manufacturing context in terms of real-time implementation in a manufacturing line and lifecycle management.

Plant protection strategies in organic viticulture are based on the application of copper products, which is well known to generate a consistent environmental impact due to the accumulation of copper in soils and its negative effects on edaphic biodiversity. Life Green Grapes is a demonstrative project aiming to improve the sustainability of viticulture throughout the supply chain: from vine nursery to the table. In this paper, we report the main results obtained over three growing seasons (2018-2020) in response to the adoption of a strategy based on a reduced use of copper products in an organic vineyard. Plant protection treatments have been strictly planned according to forecasting models for disease development and fungicides have been partially substituted with products improving plant resistance. Green manure, known for contributing to the health of the vineyard, was also adopted. Results suggest the effectiveness of the “Green Grapes” strategy under low downy mildew pressure. Furthermore, no declines in grape quality have been observed; on the contrary, the synergic effect of green manure and substances beneficial to plants improved yield. An overall positive influence on the edaphic biodiversity was also observed.

The pin-in-the-slot joint is a common element in machines, and the dynamics of joints with clearances is an actively investigated topic. Important applications of such a joint can be found in Geneva mechanisms, robotized gear selectors, centrifugal vibration absorbers (CPVA) and other important mechanical devices. The paper will review the main analytical steps required to obtain the equations characterizing the different force contact models. Furthermore, a numerical test bench where such models are introduced for modeling the clearances between the pin and slot is proposed. In this regard, the present study will offer a comparison and discussion of the numerical results obtained with the different force contact models herein reviewed.

The protection of grapevine biodiversity and the safeguarding of genetic variability are certainly primary and topical objectives for wine research, especially in territories historically devoted to viticulture. To assess the autochthonous germplasm of three different districts of Southern Umbria (Central Italy), the plant material of 70 grapevines retrieved from reforested land plots or old vineyards was collected, and their genetic identity was investigated using 13 microsatellite markers (SSR). The results revealed the presence of 39 unique genotypes, divided into 24 already-known cultivars and 15 never-reported SSR profiles. Most of the grapevine accessions were then vegetatively propagated and cultivated in a vineyard collection both to be protected from extinction and to be evaluated at the ampelographic level. Overall, this work emphasizes the need for recovering the threatened genetic variability that characterizes minor neglected grapevine cultivars or biotypes of Southern Umbria germplasm, and the requirement to revalue and exploit the more valuable genetic resources to enhance the local agri-food economy.

Despite phenotypic plasticity that allows the adaptation to harsh environments, when vines experience severe abiotic stresses, they can suffer from metabolic damages affecting grape production and quality. Grafting is an affordable strategy to mitigate these negative consequences since the rootstock can increase the drought tolerance in the scion. This work explored the effects of pre-veraison water deficit on vines grafted on different rootstocks (Mgt 101-14 and 1103 Paulsen) to obtain physiological, biochemical, and molecular information about the influence on grape quality. Repeated measurements were carried out to assess vine physiology, production, technological maturity, and berry phenolic composition. qRT-PCRs were executed on berry skins at maturity to assess the expression levels of ten genes and five miRNAs involved in the phenylpropanoid pathway. Water stress caused significant alterations in grape technological maturity. The rootstock effect was not detected in primary metabolism while it was well defined in the accumulation of phenolic compounds in berries (such as anthocyanins). Finally, significant differences were identified in gene and miRNA expression between water-stressed and well-watered vines. In conclusion, the response to water stress can be modulated by rootstocks, which mainly act by regulating secondary metabolism, especially in grapes.

Esca disease is an increasingly widespread grapevine syndrome that currently has no valid remedies; it causes countless symptoms and almost always leads to plant death. The aim of this work was to develop a method for the early diagnosis of the presence of the fungal complex responsible for esca disease on leaves, through the identification of fluorimetric parameters of Photosystem II (PSII) efficiency, which can signal not yet evident physiological dysfunctions.

This paper summarizes research performed over the past decade on the direct molecular simulation of dilute gas flows. Similar to the molecular dynamics method, a potential energy surface is the sol...

Comparisons are made between potential energy surfaces (PESs) for N2+N and N2+N2 collisions and between rate coefficients for N2 dissociation that were computed using the quasi-classical trajectory...

Comparisons are made between potential energy surfaces (PES) for N(2) + N and N(2) + N(2) collisions and between rate coefficients for N(2) dissociation that were computed using the quasiclassical trajectory method (QCT) on these PESs. For N(2) + N we compare the Laganà’s empirical LEPS surface with one from NASA Ames Research Center based on ab initio quantum chemistry calculations. For N(2) + N(2) we compare two ab initio PESs (from NASA Ames and from the University of Minnesota). These use different methods for computing the ground state electronic energy for N(4), but give similar results. Thermal N(2) dissociation rate coefficients, for the 10,000K-30,000K temperature range, have been computed using each PES and the results are in excellent agreement. Quasi-stationary state (QSS) rate coefficients using both PESs have been computed at these temperatures using the Direct Molecular Simulation of Schwartzentruber and coworkers. The QSS rate coefficients are up to a factor of 5 lower than the thermal ones and the thermal and QSS values bracket the results of shock-tube experiments. We conclude that the combination of ab initio quantum chemistry PESs and QCT calculations provides an attractive approach for the determination of accurate high-temperature rate coefficients for use in aerothermodynamics modeling.

The research work carried out aimed at verifying the efficacy of Trichoderma-based products on the fertility maintenance in vineyard soils, in case of replanting. The presence of a hypofertile horizon, in fact, can cause problems in the engrafting of rooted cuttings and a slowing down in their vegetative development. The trial was carried out at the experimental farm of CREA − Research Center for Viticulture and Enology of Arezzo, during the setting up of a new Sangiovese vineyard. Rooted grafts treated with three different formulations containing some Trichoderma spp. strains were planted, considering an untreated negative control. In addition, treatments with the same formulations were repeated in the 2014-2016 three-year period, by spraying the soil, with an injector pole. Every year the shoot length and the pruning wood weight were evaluated, as well as the presence/absence of Trichoderma spp. on the root systems. Moreover, in 2016 the photosynthetic efficiency of the vines was verified. The presence of Trichoderma spp. within the rhizosphere of the vines treated was stable over time; the differences found between treated and untreated thesis were considerable, while only minor differences emerged among the plants subjected to the three different treatments. According to the results obtained, the application of Trichoderma-based products can be considered a valid practice to be used during vineyard implantation in case of difficult edaphic conditions.

For the first time in the literature, we present 2D simulations of hypersonic flows around a cylinder obtained from accurate ab initio potential energy surfaces (PESs). We compare results obtained from a low fidelity (empirical) and a high fidelity (ab initio) PES, thus demonstrating the impact of PES accuracy on the entire aerothermodynamic field around the body. We observe that the empirical PES is not adequate to accurately reproduce rotational and vibrational relaxation in the hypersonic flow, both in the compression and expansion regions of the flow field. This approach, enabled by advancements in large-scale computing, paves the way to the direct simulation of hypersonic flows where the only modeling input is the PES that describes molecular interactions between the various air constituents. Such flow field simulations provide benchmark solutions for the validation of reduced-order models.

This paper aims to evaluate the effectiveness of the centrifugal pendulum applied to an internal combustion engine as vibration damper. In particular, a specific design strategy, based on an energy equivalence, is analysed using a series of multibody simulations. A simplified model is initially discussed and different solution morphologies simulated. The present solution is based on the roller-in-slot centrifugal pendulum, designed to have the same kinematic behaviour of lumped mass models. The reasons why the centrifugal pendulum has had in recent years numerous applications are evidenced, together with a discussion of some design strategies. The main characteristics and requirements of this vibration damper are presented. Simulation strategy is subsequently showed, with a description of all bodies, forces and parameters used in the different systems analysed. To assess the effectiveness of the design strategy, a comparison among the simulation results of the different solutions is offered.

Cardan joint is a key component in many mechanical applications. Due to the redundancy of kinematic constraints, the accurate determination of reaction forces and the assessment of dynamic effects caused by joint tolerances are very challenging tasks. This paper presents a computer-aided multibody modelling approach for the simulation of a Cardan joint with manufacturing errors. During the modelling phase, the elasticity of flexible bodies is lumped and the joint compliance is taken into account using concentrated non-linear spring elements. Numerical examples have been developed and discussed in order to test the feasibility of the proposed methodology.

The paper deals with the description, development and validation of an equivalent FEM element assembly suitable for the simulation of very compliant knitted meshes, like those used in elastic coatings, deployable antennas, medical applications and similar. The assembly is based on a network of lumped springs able to reproduce the orthotropic behaviour of the mesh when stretched along two directions. The parameters of the model have been identified by experimental tests using a dedicated biaxial testing device. The effectiveness of the modelling technique has been validated under two test settings, providing in-plane or out-of-plane displacements. For deformations up to 50%, the differences observed between experiments and numerical results are bounded below 6%. Copyright © 2015 John Wiley & Sons, Ltd.

Introduction: Complications and challenges arising from the intraoperative double-stapling technique are seldom reported in colorectal surgery literature. Partial or full-thickness rectal injuries can occur during the introduction and the advancement of the circular stapler along the upper rectum. The aim of this study is to address some of these issues by designing and optimizing a "phantom" anvil manufactured to overcome difficulties throughout the rectal introduction and advancement of the circular stapler for the treatment of benign and malignant colon disease. Methods: The design of the "phantom" anvil has been performed using computer-aided modeling techniques, finite element investigations, and 2 essential keynotes in mind. The first one is the internal shape of the anvil, which is used for the connection to the gun. The second is the shape of the cap, which makes possible the insertion of the gun through the rectum. The "phantom" anvil has 2 functional requirements, which have been taken into account. The design has been optimized to avoid colorectal injuries, neoplastic dissemination (ie, mechanical seeding) and to reduce the fecal contamination. Results: Numerical simulations show that a right combination of both top and bottom fillet radii of the shape of the anvil can reduce the stress for the considered anatomic configuration of >90%. Both the fillet radii at the top and the bottom of the device influence the local stress of the colon rectum. Conclusions: A dismountable device, which is used only for the insertion and advancement of the stapler, allows a dedicated design of its shape, keeping the remainder of the stapler unmodified. Computer-aided simulations are useful to perform numerical investigations to optimize the design of this auxiliary part for both the safety of the patient and the ease of the stapler advancement through the rectum.

A new rotational energy exchange model for direct simulation Monte Carlo and multi-temperature Navier–Stokes methods is presented. The direct simulation Monte Carlo model is based only on collision quantities and reduces to a rotational collision number in the continuum limit, applicable for use with the Jeans relaxation equation. The model is formulated based on recent molecular dynamics simulations of rotational relaxation in nitrogen (Valentini et al., Physics of Fluids, Vol. 24, No. 10, 2012, p. 106101) and accounts for the dependence of the relaxation rate on the direction to the equilibrium state. This enables a single parameterization of the model to accurately simulate rotational relaxation in both compressing and expanding flows, unlike the widely used Parker model. The direct simulation Monte Carlo model is simple to implement, numerically efficient, and accurately reproduces a range of pure molecular dynamics solutions, including isothermal relaxations, normal shock waves, and expansions. A gen...

The early defoliation of the fruiting area is a technique that offers considerable advantages both in relation to the quality of grapes and to pest control; on the other hand, when a very warm summer occurs, the risk of grape sunburn may increase. This paper reports the results of a pre-flowering defoliation trial carried out in the province of Arezzo (Italy) in 2017, an exceptionally hot and dry year. The results confirmed the validity of this technique in limiting yield while achieving a concurrent higher concentration of phenolic compounds without increasing the risk of burns and radiative damages of grapes.

In this paper, a comparison between two different formulations of elastic splines is made. The two methods under investigation are based on the Bezier and Hermite interpolants. The strategies have been implemented and compared using two simulation cases involving medium and large deflections of a slender element. The investigation has been carried out considering the same number of degrees of freedom, and the two approaches have been compared in terms of complexity, accuracy and robustness. Both methods have also been compared with nonlinear finite element models.

In this paper the influences of some relevant dimensional and geometrical errors on both the kinematic performance and the dynamic performance of an automotive Rzeppa ball joint were investigated. The study focused on the development of a dedicated and improved multi-body three-dimensional model of the joint and the corresponding numerical simulations of different configurations. The model is able to manage the presence of the redundant constraints which are present in the joint architecture because of the use of spring connections between parts which replace most of the kinematic constraints or geometrical contact conditions. Three types of error were investigated, and both kinematic irregularities and dynamic irregularities are reported in graphs and discussed. The effects of different articulation angles between the inner ring and the outer ring were also investigated.

This paper discusses an application of dual algebra to the analysis of human knee joint stiffness matrix. According to the proposed methodology, the general stiffness matrix characterizing the elasticity properties of the knee ligaments is reduced to a dual diagonal stiffness matrix. For this purpose, the similarity transform was extended to the field of dual numbers. The theoretical framework proposed seems particularly useful when comparing stiffness matrices obtained from different experimental setup and within different Cartesian coordinate systems.

Nitrogen dissociation is studied using direct molecular simulation with a new potential-energy surface. Both ${N}_{2}$ - ${N}_{2}$ and $N$ - ${N}_{2}$ processes are simulated as they concurrently take place in an evolving nonequilibrium gas system. The coupling between vibrational excitation and dissociation is quantified leading to several new insights.

Several approaches have been used to devise a model of the human tibiofemoral joint for embedment in lower limb musculoskeletal models. However, no study has considered the use of cadaveric 6 × 6 compliance (or stiffness) matrices to model the tibiofemoral joint under normal or pathological conditions. The aim of this paper is to present a method to determine the compliance matrix of an ex vivo tibiofemoral joint for any given equilibrium pose. Experiments were carried out on a single ex vivo knee, first intact and, then, with the anterior cruciate ligament (ACL) transected. Controlled linear and angular displacements were imposed in single degree-of-freedom (DoF) tests to the specimen, and the resulting forces and moments were measured using an instrumented robotic arm. This was done starting from seven equilibrium poses characterized by the following flexion angles: 0 deg, 15 deg, 30 deg, 45 deg, 60 deg, 75 deg, and 90 deg. A compliance matrix for each of the selected equilibrium poses and for both the intact and ACL-deficient specimen was calculated. The matrix, embedding the experimental load–displacement relationship of the examined DoFs, was calculated using a linear least squares inversion based on a QR decomposition, assuming symmetric and positive-defined matrices. Single compliance matrix terms were in agreement with the literature. Results showed an overall increase of the compliance matrix terms due to the ACL transection (2.6 ratio for rotational terms at full extension) confirming its role in the joint stabilization. Validation experiments were carried out by performing a Lachman test (the tibia is pulled forward) under load control on both the intact and ACL-deficient knee and assessing the difference (error) between measured linear and angular displacements and those estimated using the appropriate compliance matrix. This error increased nonlinearly with respect to the values of the load. In particular, when an incremental posterior–anterior force up to 6 N was applied to the tibia of the intact specimen, the errors on the estimated linear and angular displacements were up to 0.6 mm and 1.5 deg, while for a force up to 18 N, the errors were 1.5 mm and 10.5 deg, respectively. In conclusion, the method used in this study may be a viable alternative to characterize the tibiofemoral load-dependent behavior in several applications.

This paper deals with the description of a novel methodology in order to achieve realistic interactive simulations in an augmented reality environment. The challenge for achieving robust, real-time and accurate simulations is one of the most promising research areas in augmented reality. The key point is to increase the level of interaction between the user and the scene changing the user's role from spectator to actor. In the specific implementation, the interaction between the scene and the user is achieved with the use of an invasively-low device. The methodology is based on the use of a depth infra-red camera in addition to a standard image sensor in order to acquire the three-dimensional geometry of the scene and perform an efficient user tracking. Following this approach, it is also possible to manage occlusions between real objects and virtual ones. All these features have been integrated to a real-time dynamic solver in order to produce accurate manipulation of objects and dynamic simulations. The...

In the last decades, several different formalisms have been proposed in the literature in order to simulate the dynamics of multibody systems. First, the choice of the coordinates leads to very different formalisms. The set of constraint equations appears very different in complexity or in size depending on whether either relative, natural or reference point Cartesian coordinates are adopted. Second, once such a choice has been made, different solution strategies can be followed. It seems that formalisms based on redundant coordinates are often used in commercial software, whereas those based on a minimum number of coordinates are usually preferred in real-time computations. In this paper, with reference to models with redundant absolute coordinates, the problem of coordinate reduction will be discussed and a group of 11 different methods will be compared on the basis of their computational efficiency. In particular, methods based on constraint orthogonalization and on the use of pseudoinverse matrices have been selected, together with other methods based on least-squares block solution. The methods have been implemented on three different test cases. The main purpose is to provide hints and guidelines on the choice and availability of solution strategies during simulation of moderate size multibody systems. Copyright © 2011 John Wiley & Sons, Ltd.

We present a microscopic description for the impacting process of silicon nanospheres onto a silicon substrate. In spite of the relatively low energy regime considered (up to 1 eV/atom), the impacting process exhibits a rich behavior: A rigid Hertzian model is valid for speeds below 500 m/s, while a quasi-ellipsoidal deformation regime emerges at larger speeds. Furthermore, for speeds up to 1000 m/s the particle undergoes a soft landing and creates a long-lived coherent surface phonon. Higher speeds lead to a rapid attenuation of the coherent phonon due to a partial diamond cubic to-tin phase transformation occurring in the particle.

Accurate modeling of high-temperature hypersonic flows in the atmosphere requires consideration of collision-induced dissociation of molecular species and energy transfer between the translational and internal modes of the gas molecules. Here, we describe a study of the N2 + N2⟶N2 + 2N and N2 + N2⟶4N nitrogen dissociation reactions using the quasiclassical trajectory (QCT) method. The simulations used a new potential energy surface for the N4 system; the surface is an improved version of one that was presented previously. In the QCT calculations, initial conditions were determined based on a two-temperature model that approximately separates the translational-rotational temperature from the vibrational temperature of the N2 diatoms. Five values from 8000 K to 30,000 K were considered for each of the two temperatures. Over 2.4 × 10(9) trajectories were calculated. We present results for ensemble-averaged dissociation rate constants as functions of the translational-rotational temperature T and the vibrational temperature T(v). The rate constant depends more strongly on T when T(v) is low, and it depends more strongly on T(v) when T is low. Quasibound reactant states contribute significantly to the rate constants, as do exchange processes at higher temperatures. We discuss two sets of runs in detail: an equilibrium test set in which T = T(v) and a nonequilibrium test set in which T(v) < T. In the equilibrium test set, high-v and moderately-low-j molecules contribute most significantly to the overall dissociation rate, and this state specificity becomes stronger as the temperature decreases. Dissociating trajectories tend to result in a major loss of vibrational energy and a minor loss of rotational energy. In the nonequilibrium test set, as T(v) decreases while T is fixed, higher-j molecules contribute more significantly to the dissociation rate, dissociating trajectories tend to result in a greater rotational energy loss, and the dissociation probability's dependence on v weakens. In this way, as T(v) decreases, rotational energy appears to compensate for the decline in average vibrational energy in promoting dissociation. In both the equilibrium and nonequilibrium test sets, in every case, the average total internal energy loss in the dissociating trajectories is between 10.2 and 11.0 eV, slightly larger than the equilibrium potential energy change of N2 dissociation.

In this paper the authors present a control strategy for tendon driven mechanisms. The aim of the control system is to find the correct torques which the motors have to exert to make the end effector describe a specific trajectory. In robotic assemblies this problem is often solved with closed loop algorithm, but here a simpler method, based on a open loop strategy, is developed. The difficulties in the actuation are in keeping the belt tight during all working conditions. So an innovative solution of this problem is presented here. This methodology can be easily applied in real time monitoring or very fast operations. For this reason several virtual reality simulations, developed using codes written in Virtual Reality Markup Language, are also presented. This approach is very efficient because it requires a very low cpu computation time, small size files, and the manipulator can be easily put into different simulated scenarios.

Mechanical and aerospace applications often require that mechanisms deploy in a quick stable and reliable way. The objective of this study is to implement a general optimization procedure to perform a first stage conceptual design of HSD mechanisms, focusing on both kinematics and dynamics. In particular, the authors will focus on the development of design charts. In the very first part of the work, a parametric lumped-mass system will be modeled in order to reduce the number of parameters for the synthesis phase. A correlation will be established between geometry, inertia and initial position to guarantee the maximum value of acceleration during deployment of the deployable arm by means of the principle of virtual work. In the second part of this work, the influence of important factors such as friction and joint clearance on the overall dynamics of the system will be investigated. Finally, a coupled dynamic and structural analysis of the helical spring, that actuates the mechanism, will be carried out in order to achieve optimal performance. The developed charts will also take into account the space limitation requirement, that are often needed for both aerospace and mechanical applications. A final example will summarize all the points covered by this research effort. Results will be validated using the commercial software ABAQUS.

In this chapter, an enhanced methodology for interactive, accurate, fast and robust multibody simulations using Augmented Reality is presented and discussed. This methodology is based on the integration of a mechanical tracker and a dedicated impulse based solver. The use of the mechanical tracker for the interaction between the user and the simulation allows to separate the processing of the data coming from the position tracking from those coming from the image collimation processing. By this way simulation results and visualization remain separated and the precision is enhanced. The use of a dedicated sequential impulse solver allows a quick and stable simulation also for a large number of bodies and overabundant constraints. The final result of this work is a software tool able to manage real time dynamic simulations and update the augmented scene accordingly. The robustness and the reliability of the system will be checked over two test cases: a ten pendula dynamic system and of a cross-lift mechanism simulation.

OBJECTIVE--To determine whether the increasing use of percutaneous transluminal angioplasty in patients with unstable angina has reduced the need for bypass surgery and whether this change in the choice of treatment affected the outcome at one year in patients with unstable angina who were admitted to hospital in two different periods of time. DESIGN--Retrospective analysis of consecutive patients with unstable angina (angina at rest with ST-T changes during pain) who underwent coronary arteriography in two different periods of time. PATIENTS--158 patients were admitted to hospital between January 1988 and June 1989 (group 1) and 140 patients admitted between January 1992 and June 1993 (group 2). RESULTS--Coronary angioplasty procedures nearly doubled from 29% in group 1 to 56% in group 2 whereas bypass surgery decreased from 36% in group 1 to 23% in group 2 (P < 0.01). Coronary angioplasty increased and bypass surgery decreased in patients with one vessel disease (P < 0.01), two vessel disease (P < 0.05), and three vessel disease (P < 0.01). Coronary angioplasty also increased and bypass surgery decreased in refractory angina and in patients with ejection fraction < 0.50 (both P < 0.05). At 1-year follow up, 14 patients in group 1 (9%) and 10 in group 2 (7%) either died or had myocardial infarction (P = NS). Revascularisation procedures were needed in 16 group 1 patients (10%) and 27 group 2 patients (19%, P < 0.05). CONCLUSIONS--Coronary angioplasty became more widely used in patients with unstable angina. This reduced the need for bypass surgery in patients with multivessel disease, refractory angina, and depressed left ventricular function. This change in treatment did not affect 1-year mortality or the myocardial infarction rate. More patients in the more recent group in which angioplasty was the preferred treatment required a further revascularisation procedure than in the earlier group in which bypass grafting was more often used as the initial treatment.

Recent hardware and software improvements fuelled the developing of innovative methodologies for achieving interactive simulations in augmented reality environments. These new approaches have changed the role of the user which is not more a simple spectator of the scene, but he is an active protagonist, altering the contents and taking part into simulation. All these enhancements have deeply modified the concept of augmented reality and have opened new scenarios for future applications in different technical and entertainment fields. The purpose of the chapter is to present recent methodologies for implementing high-interactive augmented reality simulations. In a first part, the chapter describes the most important approaches underling architectures, tangible interfaces, system-related and user-related aspects. Then, the chapter focuses on the emerging natural interface concept which allows to interpret the intent of the user without the use of additional tracking devices. This methodology is suitable for didactical, entertainment and technical applications and experimental tests are presented in order to evaluate the relating human factor as usability, accuracy, robustness, training difficulties, realism in comparison with standard methodologies.

Although no study has definitively shown that unfocused screening of skin cancer is effective, many campaigns have been organized with the aim of increasing awareness on melanoma risk factors. The objective of this study was to analyse the results of the Skin Cancer Screening Day in Italy during the period 2005-2007, to determine the priorities for melanoma control plans in a Mediterranean country. A total of 5002 patients were screened by dermatologists in 31 cities. Individuals who considered themselves to have many naevi and those with a family history of melanoma showed a higher number of common and atypical naevi. Ten melanomas, 20 basal cell carcinomas and two squamous cell carcinomas were histopathologically confirmed. Our observations provide the following suggestions for melanoma prevention strategies: (a) an unfocused campaign is suitable to inform the public about the importance of self-examination of the skin, but is not useful to identify a larger number of melanomas; and (b) melanoma screening campaigns should focus on a selected population, which meets rigorous risk criteria to maintain higher cost-effectiveness. The financial support to effective melanoma screening programmes could be increased, especially in southern populations where lower levels of self-surveillance and socioeconomic conditions represent risk factors for late identification of melanoma.

Dynamic squat is one of the most executed fitness exercise. Its use is widespread both for rehabilitation and training purposes. Several typologies of the squat exercise can be performed. The most important are the front squat and the back squat. In the front squat the barbell is held in front of the body across the clavicles and deltoids, while in the back squat exercise the bar is held on the back of the body at the base of the neck. In this paper we will refer to dynamic back squat. The squat exercise can be performed with or without the help of a machine that has the scope of guiding the person during the movement and ensuring his stability and safety. The use of this type of machine is often necessary when the workout is heavy and the risk of incorrect exercise and injuries is high. On the other hand, the rigid structure of this device often overconstrains the lifting movement. From all these observations, the purpose of the paper is to discuss an alternative design of a mechanism able to maintain the advantage to allow a free-body execution and to preserve the safety of the athletes as well. The proposed mechanism has been designed starting from an anthropometric study on the squat movement. This has been performed by using a motion capture system and applying computer-aided engineering techniques. The design activity started from the experimental investigation of the trajectory of the barbell during the natural execution of the unrestricted back squat exercise. The tests have been performed on several subjects with different mass, anthropometry and gender. In a second phase, the data have been processed and analyzed and a specific mechanism, able to reproduce the natural trajectories, has been synthetized. Finally, the design and optimization of the entire structure has been performed through the use of virtual prototyping techniques.

Dual quaternions and dual quaternion interpolation are pow erful mathematical tools for the spatial analysis of rigid body motions. In thispaper, after a review of some basic results and formulas, it will be presented an attempt to use t hese tools for the the kinematic modeling of human joints. In particular, the kinematic para meters extracted from experimen- tally acquired data are compared with those theoretically c from dual quaternions rigid body motion interpolation.

In this paper a complex prosthesis of dental implants, inserted in a mandible bone, has been analyzed using a virtual model. The study has been performed by means of a three-dimensional finite element model including the implants, the bridging structure and the bone. The interaction between implant screws and bone has been simulated in detail. Four different load conditions has been implemented to mimic the masticatory phase. The stress distribution in the implants and in the bone has been evaluated. Effects of possible temperature variation and assembling errors have been also taken into account. Moreover, the stiffening effect of the stabilizing bar that connect the implants has been also discussed. Starting from the results of the numerical investigations an optimization of the shape of the implants has been proposed in order to optimize the assembling procedure.

Tolerance allocation influences production costs in a big way. For this reason it is very important to have an accurate study about the effects of manufacturing errors on the functioning and performances of linkages. In this paper, the authors present a computer-aided methodology based on a 3D geometrical approach using the dual-algebra fundamentals. The purpose is to give ail useful tool which can be integrated into CAD software in order to evaluate the performances of spatial mechanisms with mechanical errors. The proposed methodology has been validated by means of experimental tests on a Cardan joint mechanism with clearances, misalignments and dimensional errors. Copyright (c) 2005 John Wiley & Sons, Ltd.

The comfort assessment for car occupants is not an easy task to achieve. It is a matter of personal perceiving, thus a solution which may seem comfortable to one could be not to another. Moreover it is a field which requires knowledge both from science and medicine. The vibrational comfort analysis is the topic of this paper. There are different international standards to define the vibrational comfort through computed indices. In particular the British Standard BS 6841 [1] introduces the Vibration Dose Value (VDV). The main idea which lies behind the VDV is to estimate the whole body vibration. In fact the standard suggests the main locations for acceleration measurement (feet, seat and back) and their direction axes. The overall number of acquisitions is twelve. A numerical code for the vibrational comfort analysis of car occupants, estimating the VDV for each of them, has been developed. The code, named DAViD, is based on a multibody approach [2]. It has been validated by means of experimental tests [3,4]. In this paper the influence of the anthropometric features (height and weight) and the inclination of the backrest on the VDV has been investigated. The code is an useful tool for predicting at the seat design level the vibrational discomfort.