Internal Spring Research Articles

Comparison of three quick methods to estimate crab size in the land crabs <i>Cardisoma guanhumi</i> Latreille, 1825 and <i>Ucides cordatus</i> (Crustacea: Brachyura: Gecarcinidae and Ucididae)

<span>Para la estimación de la estructura de tamaños en cangrejos terrestres comerciales y la obtención de información relevante para su manejo, es necesario utilizar métodos rápidos, confiables y no destructivos. Cardisoma guanhumi y Ucides cordatus son dos cangrejos terrestres que son explotados comercialmente en el Caribe y en Brasil. El propósito de este trabajo es suministrar métodos indirectos para la estimación del tamaño del caparazón de los cangrejos y por consiguiente, de la estructura de tallas. Los muestreos se llevaron a cabo en Carenero <em>(C. guanhumi</em>) y en Cumaná (<em>U. cordatus</em>) (Venezuela). Se utilizaron tres métodos para estimar el diámetro de sus madrigueras: Vernier, compás y fotografía. Estos se correlacionaron con el tamaño real del cangrejo. Se aplicó el análisis de regresión Ordinary Least Squares Model II y la capacidad de predicción se probó utilizando el modelo II Mayor Axis para las regresiones. <em>Cardisoma guanhumi</em> mostró una fuerte dispersión de sus datos en los métodos de Vernier y fotografía. Menos dispersión se obtuvo con el método del compás y fue el más preciso (r2= 0.61). Para <em>U. cordatus</em> las medidas con Vernier fueron la más adecuadas (r2= 0.71). Sin embargo los tres métodos fueron confiables. Los diferentes métodos mostraron ventajas y desventajas y dependerá del que aplique los métodos, decidir cuál será el más adecuado para sus propósitos</span>

Correction of craniosynostosis using modified spring-assisted surgery.

The use of springs in craniofacial surgery was originated at Sahlgrenska University Hospital in 1997 as a way of remodeling the cranial vault postoperatively. After a decade of development, spring technology has been improved to a greater extent. However, there still exist some problems, such as the poor consistency of steel wire stretches, the wrong position of steel wire, the problem of increasing the elasticity of springs, and so on. We have designed a spring device for external uses. This device is composed of 3 parts. The first part is the outside of the spring ring. This ring is the same as the internal spring, only a little bigger. The second part is a small U-shaped hook, which is made of titanium plates and linked to the skull portion. The U-shaped hook is approximately 1 cm long and 1 cm wide. The hang is approximately 1 cm long and 0.6 cm wide. The U-shaped level length is 1 cm, but the level width should be equal to or bigger than the thickness of the skull. The third part is a steel wire, which is placed at 1 end of hook. We first conduct a strip craniotomy, then put 2 hooks at the bone ends and, after that, fix hooks on the skull. Finally, we pull the steel wire of the hook end out of the scalp, connect it with the external spring, and draw out the external spring. We performed 24 craniofacial spring placement procedures for 12 patients with craniosynostosis. We used 6 springs for 3 patients who had anterior plagiocephaly, 12 springs for 6 patients who had scaphocephaly, and 3 springs for another patient who had metopic synostosis and holoprosencephaly. We also used 3 springs for 2 patients who had metopic synostosis. The 12 patients have not required further surgeries so far, and there were no major complications. Spring dislodgement had not caused any complication in early cases. We could easily change the position of the spring rings from outside the scalp, regularly correct the elasticity of the spring rings, and replace spring rings to increase the traction. The head shapes of the 12 children have been improved significantly to use external spring rings. This therapeutic modality in craniofacial surgery has allowed minimization of the extent of surgery without compromising clinical outcomes. The authors have shown that the use of external spring techniques is safe and, in selected situations, offer significant advantages over other methods of treatment. It makes up for a number of shortcomings of internal springs.

Endoscopic craniosynostosis repair.

Craniosynostosis is a rare condition that affects approximately one child in every 2,000 live births, and involves pathological fusion of two or more skull bones. Consequences of craniosynostosis include possible limitation of brain growth and cosmetic effects on the appearance of the child. Traditional repairs for these conditions over the past 3-4 decades have involved an open operation with a large skin incision and major manipulations of the skull bones. More recently, minimally invasive endoscopic techniques have been developed to release the skull bones, followed by postoperative treatment with either an external orthosis or internal springs and distractors to achieve the desired correction. In this review minimally invasive endoscopic repair will be reviewed. A general overview of the condition and techniques for correction will be discussed, followed by specific application of these surgeries for different craniosynostosis diagnoses. Attention to the subtleties of each specific condition will be highlighted. Over the past two decades clinical experience and a large number of publications have substantiated the benefits of minimally invasive endoscopic techniques for the treatment of craniosynostosis. These techniques have clear benefits for selected patients, and should be part of the standard of care for this condition at craniofacial centers.

Multi-Objective Optimization of Internal Combustion Engine Valve Springs Based on NSGA-II

The design of engine valve spring generally belongs to multi-objective optimum design. The traditional trying means and the graphical methods are difficult to solve the multi-objective optimization problem, and the traditional multi-objective algorithms have certain defects. The elitist non-dominated sorting genetic algorithm (NSGA-II) is an excellent multi-objective algorithm, which is widely used to solve problems of multi-objective optimization. This method can improve the design quality and efficiency, and it has much more engineering practical value.

Contractile Hydrostatically Coupled Dielectric Elastomer Actuators

The so-called hydrostatically coupled dielectric elastomer actuators (HC-DEAs) have recently been described as a means to improve versatility and safety of electroactive polymer actuators made of DEs. HC-DEAs use an incompressible fluid that mechanically couples a DE-based active part to a passive part interfaced to the load. In this paper, we present the ongoing development of linear contractile HC-DEAs. The actuator is made of two rigid disks (circular frames) that support an active membrane, consisting of a DE film coated with compliant electrodes. The frames and the membrane delimit a closed chamber, filled with the fluid. The pressure of the fluid is used to provide the actuator with a barrel-like shape, while keeping the length of the structure limited by a counteracting element (such as an internal spring or the external load itself); combining this element with the internal pressure allows the structure to be axially precompressed. As a result of an electrical activation of the membrane, outward radial buckling and related axial contraction of the device are achieved. This paper presents preliminary assessment of static electromechanical performance of prototypes made of silicone and water, studying combined effects of precompression, voltage, and stress relaxation.

A novel precision bender system for focusing mirrors

A novel mirror bender system utilizing cam-shaft mover (CSM) with 100 µm eccentricity was designed and successfully tested. The system was initially tested and characterized in the laboratory, and then later the performance was verified using the Advanced Photon Source synchrotron radiation source. The force from the two separate CSMs is translated to both ends of a mirror through a small-diameter bellows feed-through. The system uses an internal spring assembly to compensate for atmospheric pressure. A compact gear box with 10:1 ratio between the stepper motor and cam shaft is used to increase the precision of the bender system. This bender system is equipped with a precise rotary potentiometer and load cell for feedback. A system resolution better than 0.2 µm per step was achieved. This bender system was designed as a separate unit, is very compact and can be used to bend a mirror in both the vertical and horizontal planes. Details of the system design, changes made from the prototype system to the production unit and test results are presented here.

Energy Efficient Control of Robots with Variable Stiffness Actuators

Variable stiffness actuators realize a particular class of actuators characterized by the property that the apparent output stiffness can be changed independently of the output position. This is feasible due to the presence of internal springs and internal actuated degrees of freedom. In this work, we establish a port-based model of variable stiffness actuators and we derive an energy efficient control strategy. In particular, when the variable stiffness actuator acts on a mechanical system, the internal degrees of freedom are used to achieve the desired nominal behavior and the internal springs are used as a potential energy buffer. The release of energy from the springs, as well as the apparent output stiffness, are regulated by control of the internal degrees of freedom. Simulation results on a robotic joint illustrate the effectiveness of the control strategy during the tracking of a periodic motion in presence of disturbances.

Exact nonequilibrium work generating function for a small classical system

We obtain the exact nonequilibrium work generating function (NEWGF) for a small system consisting of a massive Brownian particle connected to internal and external springs. The external work is provided to the system for a finite-time interval. The Jarzynski equality, obtained in this case directly from the NEWGF, is shown to be valid for the present model, in an exact way regardless of the rate of external work.

Closed-form solutions for Euler–Bernoulli arbitrary discontinuous beams

Euler–Bernoulli arbitrary discontinuous beams acted upon by static loads are addressed. Based on appropriate Green’s functions here derived in a closed form, the response variables are obtained: (a) for stepped beams with internal springs, as closed-form functions of the beam discontinuity parameters, without enforcing neither internal nor boundary conditions; (b) for stepped beams with internal springs and along-axis supports, as closed-form functions of the unknown reactions of the along-axis supports only, to be computed by enforcing pertinent conditions. A remarkable reduction in computational effort is achieved, in this manner, compared to competing methods in the literature.

FastSize™ Medical Extender for the treatment of Peyronie’s disease

This paper reports on the scientific principles, treatment protocol and initial trial results of the FastSize™ Medical Extender, a new medical device developed for the treatment of Peyronie’s disease and phalloplasty utilizing controlled periodic stretching of the penis; other uses of the device are also mentioned. Initial Institutional Review Boards monitored clinical trials of the device indicate that significant (10–45°) improvement in curvatures are achievable and that larger scale trials are therefore justified. The device appears to meet a previously unmet need within the population of Peyronie’s disease sufferers for a noninvasive, nonsurgical first-option treatment modality. The device works by holding the penis in a cradle and subjecting it to gentle stretching, the tension being provided by small metal extensions that are added to the cradle frame to provide traction against internal springs. Patient education is minimal for the device, but patient compliance with the extended daily treatment procedure is critical for significant curvature change. While a review of appropriate reimbursement codes has not been conducted, the pricing of the device makes it easily affordable. Although it has not yet been formally studied, the device also appears to have applications beyond Peyronie’s disease; such as offering potential for offsetting penile shortening prior to implant surgery, preventing shortening following PD penile reconstruction and after radical prostatectomy where loss of penile length is commonly reported. The recent trial noted that, over a 6-month period, patients reported increases in penile length of 1–2.0 cm, with an accompanying increase in girth. There are no alternative devices available that have proven efficacy as a result of a clinical trial and, given reproducible results, the device will begin to play an important role in treatments that require penile tissue remodeling. Future developments should include larger scale, multicenter trials aimed at reproducing the results of the initial study on Peyronie’s disease, also trials in conjunction with pharmacological treatment involving plaque remodeling agents such as verapamil and interferon, and trials that will investigate the possible benefits of the device for penile enlargement that may help pre- and postsurgical candidates for penile implants and penile reconstruction following prostatectomy.

A solution method for Euler–Bernoulli vibrating discontinuous beams

The eigenvalue problem of Euler–Bernoulli discontinuous beams is addressed. Specifically, for stepped beams with internal translational and rotational springs, it is shown that a formulation of well-established lumped-mass methods employing exact influence coefficients is readily feasible, based on appropriate Green’s functions yielding the response of the discontinuous beam to a static unit force. The latter are not available in the literature; here they are derived, in a closed form, for arbitrary boundary conditions. Advantages of the proposed eigensolution are pointed out and future developments are also discussed.

A Pilot Study to Compare the Episure™ Autodetect™ Syringe with the Glass Syringe for Identification of the Epidural Space in Parturients

The Episure AutoDetect syringe, a spring-loaded syringe, is a new loss-of-resistance syringe with an internal compression spring that applies constant pressure on the plunger. In this pilot study, we compared the spring-loaded syringe with the standard glass syringe for identification of the epidural space during initiation of epidural analgesia in parturients. The primary outcome was the incidence of failed epidural analgesia. Three-hundred and twenty-five women were enrolled. Eight residents performed 291 procedures (90%) and two attendings performed 34 procedures (10%). Epidural analgesia failed in five subjects in the glass syringe group and in no subject in the spring-loaded syringe group (P = 0.025).

Design of a piecewise linear vibration isolator for jump avoidance

Piecewise linear isolators are smart passive vibration isolators that provide effective isolation for high frequency/low amplitude excitation. This can be done by introducing a soft primary suspension and a relatively damped secondary suspension. Such a piecewise isolator prevents the system from a high relative displacement in low frequency/high amplitude excitation. By employed an averaging method it is possible to obtain an implicit function for frequency response of a symmetric bilinear vibration isolator system under steady-state harmonic excitation. This function is examined for jump avoidance. A condition is derived which when met ensures that the undesirable phenomenon of ‘jump’ does not occur and the system response is functional. The jump avoidance and sensitivity of the condition are examined and investigated as the dynamic parameters vary. The results of this investigation can be directly employed in design of effective piecewise linear vibration isolators. A linear vibration system is defined as one in which the quantities of mass (or inertia), stiffness, and damping are linear in behaviour and do not vary with time [1]. Although mathematical models employing a linear ordinary differential equation with constant coefficients portray a simple and manageable system for analytical study, in most cases they are an incomplete representation simplified for the sake of analysis. Most real physical vibration systems are more accurately depicted by non-linear governing equations, in which the non-linearity may stem from structural constraints causing a change in stiffness and damping characteristics, or from inherent non-linear behaviour of internal springs and dampers. This paper focuses on a general form of such a non-linear system. This study of piecewise-linear systems will allow hazardous system behaviour over operating frequency ranges to be gauged and controlled in order to avoid premature fatigue damage, and prolong the life of the system.

Transport Distraction Osteogenesis Using Nitinol Spring

Some experiments in rabbits have presented the potential feasibility of using shape memory alloy spring for continuous distraction osteogenesis. To confirm the effectiveness of such method, we established canine models for the exploratory experiments of transport distraction osteogenesis using nitinol springs. Simple devices, including an internal 60-mm long sinusoid-shaped nitinol springs were used in the study. All dogs needed only one operation. In the operation, osteotomy was performed to create a 40-mm unilateral segmental mandibular body defect and a tooth-bearing transport bone disc. After reconstructive fixation of the remnant mandible, the spring was constricted and anchored across the distraction gap to activate transport distraction immediately. At the second experimental stage, an ePTFE sheet was further fixed to protect the defect and distraction gap before closing the incision. Control dogs underwent the same operation except for anchoring of the spring to examine the spontaneous bone regeneration. Automatic bone transportation, as a gradual slowdown process, was observed under the effect of the spring. The transport disc could get to the opposite side of the defect, or stopped halfway when ePTFE sheet intervened. Mandibular reconstruction was achieved in all these dogs and better in dogs with sheet protection. No integrated bone mass was found in the defect of control dogs. The study further proves that continuous distraction osteogenesis using nitinol springs is a practical technique, although the devices need more improvement for better control of the process of distraction and the quality of regenerated bone.

Effect of Internal Moment Release on the Eigenfrequencies of Combined Linear Systems

A method for analyzing the free vibration of complex structural systems, consisting of a simple oscillator attached to a beam with an internal hinge, is presented. A mathematical model possessing important features of singularity functions with their higher order derivatives is proposed to account for the effect of internal hinge and spring force interacting between the oscillator and supporting structure. The particular integral approach together with Laplace transformation is proved to be an efficient alternative to solve the generalized differential equation for the normal modes of dynamically combined systems. Exact vibration frequencies for clamped–pinned and pinned–pinned boundaries are determined. The results are extended to the cases in which the oscillator or internal hinge is removed from the structure. It is shown that the presence of internal hinge does not alter the generalized orthogonality relation for the combined system. The search for the optimal location of the internal hinge, which maximizes the desired natural frequency, is discussed. It is concluded that a combined system with an optimally positioned hinge vibrates with the same natural frequency as an equivalent system without a hinge.

Modelling and Dynamic Response of a Damper with Relief Valve

This paper outlines several possible methods of modelling a passive hydraulic damper with a bypass tube that is opened by a precompressed relief valve. Initially a simple algebraic model is derived which is developed into a more computationally complex model incorporating the dynamics of the internal spring valve and fluid compressibility. Numerical simulations indicate realistic dynamical phenomena and suggest key design parameters.

Fast and Accurate Pressure Control using On-Off Valves

Pneumatic cylinders and pneumatic muscles are lightweight, clean and multifunctional actuators, requiring pressureregulating valves for positioning. To use them in mobile applications commercial pressure-regulating valves are quite heavy and rather slow. Therefore an intelligent controlled array of fast switching on-off valves is presented as an alternative. The speed of the on-off valves determines the performance of the pressure-regulating valve. To reduce the opening time of the valves, a higher voltage is applied on the coil for a short time. The influence of this method on the heating of the valve will be discussed. A diode, which drains away the electromagnetic power from the coil, reduces the closing time. When working with pneumatic muscles, it is in some cases justified to remove the internal spring to enhance the opening time. A modified bang-bang controller, with more than one level and a dead zone is presented. Experimental results on a fixed volume are discussed. A special designed collector combines 6 on-off valves into a lightweight pressure control valve island, which is perfectly suited for walking robots such as the pneumatic actuated biped Lucy.

Rapid lengthening of rabbit mandibular ramus by using nitinol spring: a preliminary study.

Nitinol is well known for its shape memory and superelasticity, which means it can return to its original shape from large deflections and produce moderate forces in the process. Based on these characteristics, the authors attempted to use an internal Nitinol spring for automatic lengthening of mandibular ramus. Twenty adult white rabbits underwent transverse osteotomy in unilateral mandibular ramus to remove a 15.0 mm condylar segment and L-osteotomy in remnant ramus to create a vascularized transport disc. The S-shaped Nitinol spring, with two ends bent as perpendicular underprops, was constricted and secured across the transverse gap of L osteotomy by the underprops. Six animals were killed 6 days after operation for observation of bone transport rate. Other surviving rabbits were killed 8 weeks later for morphologic and histologic examination. Mechanical testing revealed moderate output of tensile elasticity by constricted spring on shape recovery in 37 degrees C. Rapid lengthening of mandibular ramus, more than 9.0 mm in 5 to 6 days, and new bone formation in 8 weeks were found. The radiograph and histologic appearance of regenerated bone was similar to those seen with traditional distraction osteogenesis. This preliminary study demonstrates the possibility of spring-mediated rapid mandibular lengthening across an osteotomy. However, the method needs additional scientific investigation for its clinical feasibility.

Modeling the dynamics of piano keys

The models of piano keys available in the literature are crude: two degrees of freedom and a very few dynamical or geometrical parameters. Experiments on different piano mechanisms (upright, grand, one type of numerical keyboard) exhibit strong differences in the two successive phases of the key motion which are controlled by the finger. Understanding the controllability of the escapement velocity (typically a few percents for professional pianists), the differences between upright and grand pianos, the rationale for the numerous independent adjustments by technicians, and the feel by the pianist require sophisticated modeling. In addition to the inertia of the six independently moving parts of a grand piano mechanism, a careful modeling of friction at pivots and between the jack and the roll, of damping and nonlinearities in felts, and of internal springs will be presented. Simulations will be confronted to the measurements of the motions of the different parts. Currently, the first phase of the motion and the transition to the second phase are well understood while some progress must still be made in order to describe correctly this short but important phase before the escapement of the hammer. [Work done in part at the Laboratory for Musical Acoustics, Paris.]

Effects of linking up of discontinuities on fracture growth and groundwater transport

It is proposed that the growth of fractures is the basic process for generating and maintaining permeability in solid rock (bedrock). Many extension fractures grow as hydrofractures, whereas many shear (and extension) fractures grow through the formation of transverse fractures that connect the adjacent tips of existing fractures. In a boundary-element analysis, the hydrofractures are modeled as being driven open by a fluid overpressure that varies linearly from 10 MPa at the fracture centre to 0 MPa at the fracture tip. The host rock has a uniform Young's modulus of 10 GPa, a Poisson's ratio of 0.25, and is dissected by vertical joints and horizontal contacts, each of which is modeled as an internal spring of stiffness 6 MPa m−1. The number of joints and contacts, and their location with respect to the hydrofracture tip are varied in different model runs. The results of the analyses indicate that the tensile stresses generated by overpressured hydrofractures open up joints and contacts out to considerable distances from the fracture tip, so that they tend to link up to form a hydraulic pathway. Using the same Young's modulus, Poisson's ratio, and internal spring constant for joints as in the hydrofracture models, boundary-element models were made to study the interaction stresses that cause neighbouring joints to become interconnected through the growth of linking transverse fractures that, ultimately, may evolve into shear fractures. The models were subjected to tensile stress of 6 MPa acting normal to the joint planes as the only loading. The offset (horizontal distance) and underlap (vertical distance) between the adjacent tips of the joints were varied between model runs. The results show a concentration of tensile and shear stresses in the regions between the neighbouring tips of the joints, but these regions become smaller when the underlap of the joints decreases and changes to overlap. These stress-concentration regions favour the development of transverse (mostly shear) fractures that link up the nearby tips of the joints, so as to form a segmented shear or extension fracture. Analytical results on aperture variation of a hydrofracture in a homogeneous, isotropic rock are compared with boundary-element results for a hydrofracture dissecting layered rocks. The aperture is larger where the hydrofracture dissects soft (low Young's modulus) layers than where it dissects stiff layers. Aperture variation may encourage subsequent groundwater-flow channeling along a pathway generated by a hydrofracture in layered rocks.