Stair Step Research Articles

The spiral staircase: tonotopic microstructure and cochlear tuning.

Although usually assumed to be smooth and continuous, mammalian cochlear frequency-position maps are predicted to manifest a staircase-like structure comprising plateaus of nearly constant characteristic frequency separated by abrupt discontinuities. The height and width of the stair steps are determined by parameters of cochlear frequency tuning and vary with location in the cochlea. The step height is approximately equal to the bandwidth of the auditory filter (critical band), and the step width matches that of the spatial excitation pattern produced by a low-level pure tone. Stepwise tonotopy is an emergent property arising from wave reflection and interference within the cochlea, the same mechanisms responsible for the microstructure of the hearing threshold. Possible relationships between the microstructure of the cochlear map and the tiered tonotopy observed in the inferior colliculus are explored.

Differences in onset time between the vastus medialis and lateralis during stair stepping in individuals with genu varum or valgum.

[Purpose] We investigated the difference in onset time between the vastus medialis and lateralis according to knee alignment during stair ascent and descent to examine the effects of knee alignment on the quadriceps during stair stepping. [Subjects] Fifty-two adults (20 with genu varum, 12 with genu valgum, and 20 controls) were enrolled. Subjects with > 4 cm between the medial epicondyles of the knees were placed in the genu varum group, whereas subjects with > 4 cm between the medial malleolus of the ankle were placed in the genu valgum group. [Methods] Surface electromyography was used to measure the onset times of the vastus medialis and vastus lateralis during stair ascent and descent. [Results] The vastus lateralis showed more delayed firing than the vastus medialis in the genu varum group, whereas vastus medialis firing was more delayed than vastus lateralis firing in the genu valgum group. Significant differences in onset time were detected between stair ascent and descent in the genu varum and valgum groups. [Conclusion] Genu varum and valgum affect quadriceps firing during stair stepping. Therefore, selective rehabilitation training of the quadriceps femoris should be considered to prevent pain or knee malalignment deformities.

Transport characteristics of thermal plume driven by turbulent mixing in stairwell

A set of experiments was conducted to study the transport characteristics of thermal plume driven by turbulent mixing in a 1/3 scale stairwell with single opening. The opening location was varied at the stairwell height direction to obtain different air supply conditions. When the thermal plume moves upwardly in the vertical stairwell, the interface between the upper cold layer and the lower hot layer is unstable. The gravitational instability leads to the turbulent mixing in the two layers. The location of the thermal plume front is determined using the temperature increases at different measuring points. Based on the dimensional analysis, the plume front location can be expressed as a function of time and effective gravitational acceleration. The velocity of thermal plume in stairwell is lower than those in hollow shafts, resulting from the block and cooling effects of stair steps. The comparison of the experimental and calculated plume front locations shows good agreement with the maximum error less than 20%. The results could improve the understanding of thermal plume movement driven by turbulent mixing in stairwells.

Adjustable Cross Wheel Design and Experimental Study

Fixed distance triangular wheel is often mounted on a tool car and achieve up and down stairs function, but because of the different standards in the height and width of the stair steps, it is used with large vibration, and easy to lock, so difficult to promote it’s use. With studies, the paper put forward the adjustable cross wheel structure; the wheel can adjust the steps of stairs by changing the distance, and have better stability in using. Furthermore through the experiment, the paper proves the rationality of the design and finds the problem, proposes the solution method.

The Changes of Muscle Strength and Functional Activities During Aging in Male and Female Populations

Aging is associated with the loss of muscle strength and difficulties in functional activities. The aim of this study was to investigate the changes of muscle strength and functional activities during aging in male and female individuals. This study was a cross-sectional study recruiting healthy individuals aged 40–89 years. The muscle strength of bilateral hip flexors, knee extensors, and ankle plantar flexors were measured. Activities including functional reach test, timed up and go test, and alternating stair stepping were also measured. A total of 373 male and 371 female individuals participated in this study. The muscle strength of hip flexors and knee extensors were all significantly decreased after age 80 years as compared with the age group of 40–49 years in both male and female groups. The abilities of functional reach and timed up and go task were significantly decreased after age 70 years in the male group and decreased after age 60 years in the female group as compared with the age group of 40–49 years. We noted that the muscle strength and functional activities were decreased earlier in female than male individuals. The decrease of functional activities during the aging process seems to be earlier than the decrease of muscle strength. It is important to implement functional activities training in addition to strengthening exercise to maintain functional levels of the geriatric population.

Footprint-Driven Locomotion Composition

One of the most efficient ways of generating goal-directed walking motions is synthesising the final motion based on footprints. Nevertheless, current implementations have not examined the generation of continuous motion based on footprints, where different behaviours can be generated automatically. Therefore, in this paper a flexible approach for footprint-driven locomotion composition is presented. The presented solution is based on the ability to generate footprint-driven locomotion, with flexible features like jumping, running, and stair stepping. In addition, the presented system examines the ability of generating the desired motion of the character based on predefined footprint patterns that determine which behaviour should be performed. Finally, it is examined the generation of transition patterns based on the velocity of the root and the number of footsteps required to achieve the target behaviour smoothly and naturally.

Slip flow 해석을 위한 격자볼츠만 방법의 곡면처리기법

The lattice Boltzmann (LB) method has been used to simulate rarefied gas flows in a micro-system as an alternative tool. However, previous results were mainly focused on a simple geometry with flat walls because the LB method is modeled on uniform Cartesian lattices. When previous boundary conditions for the microflows are applied to curved walls, the use of them requires approximation of the curved boundary by a series of stair steps, and introduces additional errors. For macroflows, no-slip curved wall boundary treatments have been developed remarkably in order to overcome these limits. However, the investigations for the slip curved wall boundary have rarely been performed for microflows. In this work, a curved boundary treatment of the LB method for a slip flow has been introduced. The results of the LB method for 2D microchannel and 3D microtube flows are in excellent agreement with the analytical solutions.

The talk test: a useful tool for prescribing and monitoring exercise intensity.

This review focuses on recent literature examining the validity and reliability of the talk test for prescribing and monitoring exercise intensity. The utility of the talk test for high-intensity interval training and recently proposed exercise training guidelines for patients with atrial fibrillation is also examined. In healthy adults and patients with cardiovascular disease, comfortable speech is likely possible (equivocal or last positive talk test stage) when exercise intensity is below the ventilatory or lactate threshold, and not likely possible (negative talk test stage) when exercise intensity exceeds the ventilatory or lactate threshold. The talk test can be used to produce exercise intensities (moderate-to-vigorous intensity, 40-80% (Equation is included in full-text article.)) within accepted Canadian Association of Cardiovascular Prevention and Rehabilitation and American College of Sports Medicine guidelines for exercise training, to monitor exercise training for patients with atrial fibrillation, and help avoid exertional ischemia. The talk test has been shown to be consistent across various modes of exercise (i.e., walking, jogging, cycling, elliptical trainer and stair stepper). It may not be practical for high-intensity interval training. The talk test is a valid, reliable, practical and inexpensive tool for prescribing and monitoring exercise intensity in competitive athletes, healthy active adults and patients with cardiovascular disease. Healthcare professionals should feel comfortable in advocating its use in a variety of clinical and health-promotion settings.

A task oriented haptic gait rehabilitation robot

This paper presents the concept, design process, and the prototype of a novel haptics-based lower-extremity rehabilitation robot for bed-ridden stroke patients. This system, named Virtual Gait Rehabilitation Robot (ViGRR), is required to provide the average gait motion training as well as other targeted exercises such as leg press, stair stepping and motivational gaming, in order to facilitate motor learning and enable the training of daily activities such as walking and maintaining balance. The system requirements are laid out and linked to the design of a redundant planar 4DOF robot concept prototype. An iterative design optimization loop was setup to obtain the robot kinematic and dynamic parameters as well as the actuators. The robot’s mechanical design, model, safety features, admittance controllers, and the architecture of the haptic controller are presented. Preliminary experiments were planned and performed to evaluate the capability of the system in delivering task-based virtual-reality exercises and trajectory following scenarios.

Implementation of method of lines to predict water levels due to a storm along the coastal region of Bangladesh

In this study, the method of lines (MOL) has been applied to solve two-dimensional vertically integrated shallow water equations in Cartesian coordinates for the prediction of water levels due to a storm surge along the coast of Bangladesh. In doing so, the partial derivatives with respect to the space variables were discretized by the finite difference (central) method to obtain a system of ordinary differential equations (ODEs) with time as independent variable. The classical fourth-order Runge–Kutta method was used to solve the obtained system of the ODEs. We used a nested finite difference scheme, where a high resolution fine grid model (FGM) capable of incorporating all major islands along the coastal region of Bangladesh was nested into a coarse grid model (CGM) covering up to 15°N latitude of the Bay of Bengal. The boundaries of the coast and islands were approximated through proper stair step. Appropriate tidal condition over the model domain was generated by forcing the sea level to be oscillatory with the constituent M 2 along the southern open boundary of the CGM omitting wind stress. Along the northeast corner of the FGM, the Meghna River discharge was taken into account. The developed model was applied to estimate water levels along the coast of Bangladesh due to the interaction of tide and surge associated with the April 1991 storm. We also computed our results employing the standard finite difference method (FDM). Simulated results show the MOL performs well in comparison with the FDM with regard to CPU time and stability, and ensures conformity with observations.

Mechanical and Dynamic Characteristics of Laminated Glass Sheets Used for Staircases

In case of laminated glass strips, the mechanical characteristics of the composite element are different from the values that are obtained for the same element from a homogeneous and isotropic material. The experimental tests presented in the paper aims to determine the mechanical characteristics of laminated glass strips used to make a staircase. For the experiment, quasi-static and dynamic tests were conducted on different glass stair steps, made from normal and tempered glass, with different number and thicknesses glass sheets. The paper presents the carrying out conditions for the experiments, the synthesis of data processing and comments on the experimental results. Experimental test results led to the constructive solution of the glass staircase steps. For staircase building up, tempered glass was chosen and the values obtained for the mechanical properties, strength and deformation capacity of the system were used in its design. Whole set of experimental tests led to a successful design and build-up of the glass staircase.

Alternative curved-boundary treatment for the lattice Boltzmann method and its application in simulation of flow and potential fields

Since the lattice Boltzmann method originally carries out the simulations on the regular Cartesian lattices, curved boundaries are often approximated as a series of stair steps. The most commonly employed technique for resolving curved-boundary problems is extrapolating or interpolating macroscopic properties of boundary nodes. Previous investigations have indicated that using more than one equation for extrapolation or interpolation in boundary conditions potentially causes abrupt changes in particle distributions. Therefore, a curved-boundary treatment is introduced to improve computational accuracy of the conventional stair-shaped approximation used in lattice Boltzmann simulations by using a unified equation for extrapolation of macroscopic variables. This boundary condition is not limited to fluid flow and can be extended to potential fields. The proposed treatment is tested against several well-established problems and the solutions order of accuracy is evaluated. Numerical results show that the present treatment is of second-order accuracy and has reliable stability characteristics.

Analysis of Dynamic Stability for Articulated-tracked Robot Climbing Stairs

Dynamic stability problem for articulated-tracked robot climbing stairs, when articulated-tracked robot contacts with stair steps in one point, two or more points, an identification method of dynamic stability criterion is proposed. Through the analysis of the robot to climb stairs obstacle process, action plan of the robot, inertia force of the center of mass, moment of inertia of driving wheels and arm wheels and influence of the tracked edge contacting the stairs are considered, obstacle dynamic equation of the critical attitude is built. Based on necessary and sufficient conditions of non slippage on the robot climbing the stairs, combined with the relationship of the ratio of equivalent traction force and equivalent support force with the static friction coefficient of track and stairs in the robot coordinate system, dynamic stability criterions of the robot contacting stair steps in one point, two and three points are obtained in the process of climbing stairs. The results indicate that the robot contacts stair steps in two and three points with an unstable state easily in the process of climbing stairs, numerical simulation results demonstrate the effectiveness of the method, a theoretical basis for the dynamic stability judgment of articulated-tracked robot is provided.

Conforming Delaunay Triangulation of Stochastically Generated Three Dimensional Discrete Fracture Networks: A Feature Rejection Algorithm for Meshing Strategy

We introduce the feature rejection algorithm for meshing (FRAM) to generate a high quality conforming Delaunay triangulation of a three-dimensional discrete fracture network (DFN). The geometric features (fractures, fracture intersections, spaces between fracture intersections, etc.) that must be resolved in a stochastically generated DFN typically span a wide range of spatial scales and make the efficient automated generation of high-quality meshes a challenge. To deal with these challenges, many previous approaches often deformed the DFN to align its features with a mesh through various techniques including redefining lines of intersection as stair step functions and distorting the fracture edges. In contrast, FRAM generates networks on which high-quality meshes occur automatically by constraining the generation of the network. The cornerstone of FRAM is prescribing a minimum length scale and then restricting the generation of the network to only create features of that size and larger. The process is fully automated, meaning no adjustments of the mesh are performed, and the meshing of the individual fractures has been parallelized. Reported mesh statistics show that the computational meshes generated using FRAM are of high quality. Furthermore, the method does not require solving additional systems of linear equations which is needed if a nonconforming mesh is used. Details of the FRAM approach are provided, including its mathematical underpinnings and an algorithm for its implementation. We demonstrate the method's applicability by generating a DFN with similar statistics as the fractured granite at the Forsmark site in Sweden containing 6 700 fractures, and also solve the fully saturated Darcy flow equations to show the quality of the flow solutions which result from computation on the mesh.

Comparative Studies on Generation of Stair Step Radiation Patterns

Antenna array synthesis is usually done by controlling amplitude and phase levels or element spacing functions of the array to get the desired characteristics of the radiation pattern. In this paper, design of equispaced linear array of dipoles is presented. A new amplitude distribution is proposed for generation of stair step patterns with zero phase. These patterns are produced from dipole elements using Fourier transform method. The goal of the work is to compensate mutual coupling effects of a linear dipole array. The computed patterns are compared with those of the isotropic elements for different number of elements. The deviation in the patterns of array of isotropic radiators and the array of practical element is found to be minimum. These patterns are used to identify multiple targets moving in different altitudes and different angular regions.

Evaluation of Vibration and Structural Performance of an Innovative Sliding Step Steel Stair Using Full-Scale Mock-up Test

본 연구에서는 주거용 및 사무용 계단시공의 작업공정의 단순화 및 시공품질 향상을 목적으로 개발된 혁신적인 계단 시스템인 슬라이딩스텝 철골계단의 진동 및 구조성능 평가를 수행하였다. 슬라이딩스텝 철골계단은 각형 강재 스트링거와 시공오차를 흡수할 수 있도록 설계된 스트링거 연결재 및 계단벽체 시공이 용이하도록 벽체 반대방향으로 이동이 가능한 슬라이딩 스텝으로 구성되어 있다. 하지만 철골계단의 경우 철골 접합부의 구조적 안전성 확보와 더불어, 비교적 경량에 저감쇠인 철골재 사용으로 인한 낮은 진동성능이 발현될 수 있기 때문에 진동성능에 대한 확보를 파악하는 것이 필수적으로 요구된다. 이에 본 연구에서는 진동성능 및 구조적 안전성 확보여부를 파악하기 위해 실물대 목업실험을 실시하였다. 진동성능 및 중량으로 인한 경제성 등을 종합적으로 판단하기 위해 콘크리트를 채운 스트링거와 콘크리트를 채우지 않은 스트링거를 교체해가며 각 경우에 대한 주거용 및 사무용 계단의 진동성능을 평가하였다. 또한 각 용도별로 한 개의 계단을 선정한 후, 재하실험을 통해 철골 접합부의 구조적 안전성과 스트링거 중앙부의 잔류 처짐 및 사용성 검토를 수행하였다. 실물대목업실험 결과 접합부 시스템의 경우 사용하중의 160%인 극한하중에 대해서도 탄성상태를 유지하며 재하실험 후에도 어떠한 균열이나 이상이 발견되지 않는 등 충분한 강성과 강도를 확보하고 있음을 확인하였다. 또한 스트링거 중앙부 처짐은 주거용/사무용 계단 모두 역시 동일한 하중조건 하에서 사용성에 문제가 없을 정도의 미미한 수준의 최대처짐과 잔류처짐이 발생하였으며, 최대하중이 가해질 때까지 스트링거가 탄성상태를 유지하는 등 설계하중을 지지할 수 있는 충분한 내력을 보유한 것으로 평가되었다. 진동성능 검토 결과 총 일곱 개의 스트링거 타입 중 다섯 개의 타입이 북미기준와 유럽기준에서 제시하는 기준의 허용치를 만족함을 확인하였다. In this study, an innovative steel stair system is presented which enables rapid erection and high quality control in both residential and office building construction. This system features two lightweight steel stringers of box shape, bolted connections easy to absorb construction tolerance, and stair steps movable transversely (or sliding steps) such that the work space needed for concrete stairway wall could be easily provided. In this type of stairway system, other than providing robust connecting details, ensuring vibration performance is especially important since this system may be vibration-sensitive due to lightweight nature and/or probable low damping. To tackle these issues, a series of full-scale mock-up tests were conducted by using box-shape stringer members with or without concrete-fill. The connection system was shown to be sufficiently stiff and strong, or it remained elastic even under the 160% of service load level. Among the seven stringer alternatives, five exhibited satisfactory vibration performance according to the related North American and European acceptance criteria.

Dispersion engineering of surface plasmons

In this work, it is shown how the shapes of surface plasmon dispersion curves can be engineered by manipulating the distribution of the electromagnetic fields in multilayer structures, which themselves are controlled by the free electron density in metal-like materials, such as doped semiconductors in the THz spectral range. By having a nonuniform free electron density profile, reduced relative to that in typical bulk metals, the electromagnetic fields of surface plasmons are distributed in different metallic materials that have different complex dielectric permittivities. As the in-plane component of surface plasmon's wave-vector increases, they become more confined to a particular layer of the multilayer structure and have energies that are predictable by considering the permittivity of the layer in which the fields are most concentrated. Unusual and arbitrary shapes of surface plasmon dispersion curves can be designed, including stair steps and dovetails shapes.

Unicondylar knee arthroplasty: what’s new?

Unicondylar knee arthroplasty (UKA) has gained increasing interest over the last decade. Unicondylar knee arthroplasty implantation is extremely demanding due to the fact that the prosthesis needs to be integrated in the natural anatomy of the knee in order to preserve the integrity of the other two compartments and all related ligaments. This ensures the integrity of the natural knee kinematic. Biomechanical studies using robotic technology have shown that knee kinematic does not change significantly after medial UKA as reported in the issue [5]. Similar findings have been published by others using fluoroscopy [1, 3]. Normal AP translation but with less knee rotation has been observed in patients during deep flexion after medial UKA in comparison with the natural knee. Other tasks such as treadmill gait and stair stepping have also been studied. The preservation of both cruciate ligaments contributes to a significant functional advantage. This could explain why patients, following UKA, demonstrate higher positive postoperative clinical outcomes than after total knee arthroplasty [15]. However, the achievement of a perfect component placement, allowing knee kinematics as close as possible to normal, remains a huge challenge. There is an ongoing discussion about the ideal choice of patient for UKA. Isolated medial or lateral osteoarthritis, a good range of motion, stability of the collateral and cruciate ligaments, and no significant deformity used to be the primary requirements for UKA. Long-standing weight-bearing X-rays will provide the information about leg alignment and degree of OA. Stress X-rays might be helpful for the assessment of the contralateral compartment. Two papers of the current issue deal with clinical aspects that might be relevant for patient selection for UKA [6, 14]. One focuses on the impact of patients’ pain location on the clinical and functional outcome, whilst the other evaluates the impact of anterior instability on the survival rate following UKA. A retrospective analysis showed that patellofemoral osteoarthritis does not appear to be a contraindication for UKA [4]. The same group has published a paper in the current issue about the preoperative pain location as a poor predictor of outcome following UKA. Pure medial or anterior knee pain was compared with generalized knee pain. No difference after one and 5 years was observed between the groups [14]. The finding may cause confusion in terms of patient selection for UKA. Unfortunately, the question about the more appropriate indications and predictors for UKA remains unanswered. This study is very interesting because it shows the difficulty of interpretation of pain in osteoarthritis. The suprapatellar pouch, the Hoffa fat pad, the medial and lateral retinacular, and the cruciate ligaments are the most sensitive structures in the knee [8]. No pain sensation was found during palpation of the femoral condyle and the tibia plateau, the area of cartilage degeneration. This might partially explain why it is sometimes difficult to localize the pain in an osteoarthritic knee. Pain in osteoarthritis also involves numerous interactive pathways including biological, psychological and social factors [13]. R. Becker (&) Department of Orthopaedics and Traumatology, City Hospital Brandenburg, Hochstrasse 26, 14770 Brandenburg, Havel, Germany e-mail: roland_becker@yahoo.de

The recent decline in employment dynamics

Abstract We document and attempt to explain the recent decline in employment dynamics in the U.S. We have four major empirical findings. First, each measure exhibits a “stair step” pattern, with the declines concentrated in recessions and little increase during subsequent expansions. Second, changes in the composition of workers and businesses can explain only a small amount of the decline. Third, any explanation for the decline in job creation and job destruction will account for no more than one-third of the decline in hires and separations. Fourth, the decline in hires and separations is driven by the disappearance of short-duration jobs. JEL Codes E24, J63

Comparison of steps and energy expenditure assessment in adults of Fitbit Tracker and Ultra to the Actical and indirect calorimetry

Epidemic levels of inactivity are associated with chronic diseases and rising healthcare costs. To address this, accelerometers have been used to track levels of activity. The Fitbit and Fitbit Ultra are some of the newest commercially available accelerometers. The purpose of this study was to determine the reliability and validity of the Fitbit and Fitbit Ultra. Twenty-three subjects were fitted with two Fitbit and Fitbit Ultra accelerometers, two industry-standard accelerometers and an indirect calorimetry device. Subjects participated in 6-min bouts of treadmill walking, jogging and stair stepping. Results indicate the Fitbit and Fitbit Ultra are reliable and valid for activity monitoring (step counts) and determining energy expenditure while walking and jogging without an incline. The Fitbit and standard accelerometers under-estimated energy expenditure compared to indirect calorimetry for inclined activities. These data suggest the Fitbit and Fitbit Ultra are reliable and valid for monitoring over-ground energy expenditure.