Pivot Phase Research Articles

Traffic Light Control Systems: Requirements Engineering

Requirements Engineering (RE) is the most important activity and pivot phase in the software development life cycle. It consists mainly of requirements analysis, design, and specification. The application of RE in a business domain aims to generalize its different specific approaches by meta-models under which each specific approach is an instance or specialization. RE is being applied more and more in different business domains, and its application benefits are found to be valuable. Despite these active RE applications and their added values in different domains, the Traffic Light Control (TLC) domain has not yet been approached, regardless of its everyday interest. The work presented in this paper is part of a TLC enhancement project that explores RE's potential contributions to leveraging TLC quality. Thus, in this work, different recent specific approaches to TLC are analyzed, and a large part of this business domain's functional/ non-functional requirements are elicited and specified. Moreover, the traffic context-aware traffic light control systems (CTLC) are also considered. They are deeply analyzed and compared to the typical TLC systems. As a primary result, the tangling of different concerns was stated, and a separate concerns paradigm was applied. This leads to requirements specification through separated agents. This should lead to TLC and CTLC systems development and maintenance cost reduction. An important agent dealing with security aspects and their evolving technologies is introduced. The impact evaluations of the RE on some TLC and CTLC current approaches are also presented.

Inbound tourism in Latvia during three decades of independence: development phases, key drivers and challenges

This article reviews the development of inbound tourism in Latvia over the three decades following the restoration of its independence following occupation by the USSR. The analysis uses the tourist area life cycle framework, which describes tourism development and factors during different development stages. The first stage can be described as the post 1991–2000 “economic pivot and transition phase”, where the orientation of the tourism economy shifted from east to west. Secondly, a “tourism boom phase” occurred between 2001–2009, bookended by the commencement of the EU transition process and concluding with the global financial crisis in Europe. Thirdly, a “managed growth phase” was characterised by a period of steady growth of the tourism economy. This phase included the demand surge associated with Riga becoming the European Union’s “capital of culture” and greater integration with external industry trends, concluding with the COVID-19 crisis of 2020. The article describes the crucial developmental factors and challenges in each development phase of post-independence inbound tourism.

Methodological review and detailed guidance for the life cycle interpretation phase.

Life cycle interpretation is the fourth and last phase of life cycle assessment (LCA). Being a “pivot” phase linking all other phases and the conclusions and recommendations from an LCA study, it represents a challenging task for practitioners, who miss harmonized guidelines that are sufficiently complete, detailed, and practical to conduct its different steps effectively. Here, we aim to bridge this gap. We review available literature describing the life cycle interpretation phase, including standards, LCA books, technical reports, and relevant scientific literature. On this basis, we evaluate and clarify the definition and purposes of the interpretation phase and propose an array of methods supporting its conduct in LCA practice. The five steps of interpretation defined in ISO 14040–44 are proposed to be reorganized around a framework that offers a more pragmatic approach to interpretation. It orders the steps as follows: (i) completeness check, (ii) consistency check, (iii) sensitivity check, (iv) identification of significant issues, and (v) conclusions, limitations, and recommendations. We provide toolboxes, consisting of methods and procedures supporting the analyses, computations, points to evaluate or check, and reflective processes for each of these steps. All methods are succinctly discussed with relevant referencing for further details of their applications. This proposed framework, substantiated with the large variety of methods, is envisioned to help LCA practitioners increase the relevance of their interpretation and the soundness of their conclusions and recommendations. It is a first step toward a more comprehensive and harmonized LCA practice to improve the reliability and credibility of LCA studies.

Particle Filter-Based Inter-System Positioning Model for Non-Overlapping Frequency Code Division Multiple Access Systems

In the process of composing a double-differenced positioning model, it is difficult to separate different frequency signals between code division multiple access (CDMA) systems, the single-difference ambiguity of the pivot satellite and phase differential inter-system biases (PDISBs). Hence it is difficult to calibrate in advance the bias between systems in order to build an inter-system model which only needs one pivot satellite. Based on analysis of the stability of PDISB parameters for non-overlapping frequency CDMA systems, this study adopts a particle filter to estimate the fractional part of the PDISBs (F-PDISBs) between the systems and proposes a particle filter-based inter-system positioning model. Results show that the F-PDISBs and code DISBs for the baselines with the same receiver types and some with different receiver types are rather stable over time and for these baselines it is feasible to use a particle filter to estimate the F-PDISB parameters in the initial stage. Having attained the F-PDISBs, the inter-system model can be constructed to improve positioning accuracy in complex operational environments.

Electrical Stimulation to Reduce the Overload in Upper Limbs During Sitting Pivot Transfer in Paraplegic: A Preliminary Study.

Transfer is a key ability and allows greater interact with the environment and social participation. Conversely, paraplegics have great risk of pain and injury in the upper limbs due to joint overloads during activities of daily living, like transfer. The main goal of this study is to verify if the use of functional electrical stimulation (FES) in the lower limbs of paraplegic individuals can assist the sitting pivot transfer (SPT). The secondary objective is to verify if there is a greater participation of the lower limbs during lift pivot phase. A preliminary study was done with one complete paraplegic individual. Temporal parameters were calculated and a kinetic assessment was done during the SPT. The preliminary results showed the feasibility of FES for assisting the SPT.

Effect of Shoulder Pain on Shoulder Kinematics During Weight-Bearing Tasks in Persons With Spinal Cord Injury

Nawoczenski DA, Riek LM, Greco L, Staiti K, Ludewig PM. Effect of shoulder pain on shoulder kinematics during weight-bearing tasks in persons with spinal cord injury. ObjectiveTo assess 3-dimensional scapulothoracic and glenohumeral kinematics between subjects with spinal cord injury and disease (SCI/D) with and without shoulder pain during a weight-relief raise and transfer task. DesignCase-control, repeated-measures analysis of variance. SettingMovement analysis laboratory. ParticipantsSubjects (N=43; 23 with clinical signs of impingement and 20 without) between 21 and 65 years of age, at least 1 year after SCI/D (range, 1–43y) resulting in American Spinal Injury Association Impairment Scale T2 motor neurologic level or below, and requiring the full-time use of a manual wheelchair. InterventionsWeight-relief raises and transfer tasks. Main Outcome MeasuresAn electromagnetic tracking system acquired 3-dimensional position and orientation of the thorax, scapula, and humerus. Dependent variables included angular values for scapular upward and downward rotation, posterior and anterior tilt, and internal and external rotation relative to the thorax, and glenohumeral internal and external rotation relative to the scapula. The mean of 3 trials was collected, and angular values were compared at 3 distinct phases of the weight-relief raise and transfer activity. Comparisons were also made between transfer direction (lead vs trail arm) and across groups. ResultsKey findings include significantly increased scapular upward rotation for the pain group during transfer (P=.03). Significant group differences were found for the trailing arm at the lift pivot (phase 2) of the transfer, with the pain group having greater anterior tilt (mean difference ± SE, 5.7°±2.8°). The direction of transfer also influenced kinematics at the different phases of the activity. ConclusionsPotentially detrimental magnitude and direction of scapular and glenohumeral kinematics during weight-bearing tasks may pose increased risk for shoulder pain or injury in persons with SCI/D. Consideration should be given to rehabilitation strategies that promote favorable scapular kinematics and glenohumeral external rotation.

Investigation of Apnea Turn at butterfly and breast stroke race

The purpose of this study was to clarify a characteristic of “Apnea Turn” which is a new turning method under water and to compare with a conventional turning method, “Open Turn”. The subjects were elite competitive swimmers (n=10), whose specialties were butterfly and breast stroke. The turn phase was defined as a section from 5m front the wall and 5m after the wall. As results, the time of turn phase revealed that Apnea Turn tends to be shorter than Open Turn (5.55± 0.27s and 5.62±0.33s respectively). The time of turn -in- phase and turn -out- phase of turn phase in Apnea Turn was shorter than Open Turn, but pivot phase was significantly longer than Open Turn. The push-off velocity of Apnea Turn was higher than Open Turn significantly (p<0.01). These results suggest that Apnea Turn will be able to contribute to improve the swimming performance and then it may become prospective a new turning method. Therefore, this Apnea Turn will be a new turning method. For future studies, it is important to investigate the motion of pivot and to reduction in pivot phase.

Kinematic modifications after surgical correction of equinovarus foot deformity in chronic hemiplegic adults

nertia during the pivot phase. The actual pivot phase required hree specific power phases in the transverse plane (A2T, 2T, H2T), which provided rotational power to displace the oG toward the new direction. The rotational power at the nkle appears to have been a result of a counter movement uring the deceleration phase, which resulted in an absorption 1T phase prior to the generation A2T phase. The timings of he transverse power peaks suggest that rotation was coming own the kinetic chain initiated from the hip. However, it is robable that the upper body segments lead the pivot [1]. The ipsilateral crossover turn did not require increased uscular demand during the turn phase, as there was no pivot hase suggesting the turn was a result of a fall rather than by ny active means. Because there was no pivot and the foot as rooted to the ground, to complete the crossover, an H3T eneration phase externally rotated the hip/pelvis toward the ew direction.

Strategies Used for Unconstrained Direction Change during Walking

Full functional mobility requires adaptations, such as turning, to the basic straight locomotor pattern. The aim was to assess the mechanics of completing a complex turning manoeuvre. A full 3-dimensional kinematic and kinetic analysis of the ipsilateral limb was carried out during both straight gait and unconstrained turning through 90 degrees. 10 healthy university students participated. Analysis indicated that two distinctive substrategies of the spin turn-ipsilateral pivot and ipsilateral crossover-were employed. The ipsilateral pivot was the more dynamic turn and required two additional power phases at the ankle and hip to facilitate the pivot phase. The ipsilateral crossover uses a fall into the new direction. The spin turn is a more complex action than previously indicated.

Physiological coxa varus?genu valgus influences internal knee and ankle joint moments in females during crossover cutting

This study evaluated the ankle and knee electromyographic, kinematic, and kinetic differences of 20 nonimpaired females with either neutral (group 1) or coxa varus-genu valgus (group 2) alignment during crossover cutting stance phase. Two-way mixed model ANOVA (group, session) assessed mean differences ( p<0.05) and correlation analysis further delineated relationships. During impact absorption, group 2 displayed earlier peak horizontal braking (anterior-posterior) ground reaction force timing, decreased and earlier peak internal knee extension moments (eccentric function), and earlier peak internal ankle dorsiflexion moment timing (eccentric function). During the pivot phase, group 2 displayed later and eccentrically-biased peak ankle plantar flexion moments, increased peak internal knee flexion moments (eccentric function), and later peak knee internal rotation timing. Correlation analysis revealed that during impact absorption, subjects with coxa varus-genu valgus alignment (group 2) displayed a stronger relationship between knee internal rotation velocity and peak internal ankle dorsiflexion moment onset timing ( r= -0.64 vs r = -0.26) and between peak horizontal braking ground reaction forces and peak internal ankle dorsiflexion moment onset timing ( r= 0.61 vs r= 0.24). During the pivot phase these subjects displayed a stronger relationship between peak horizontal braking ground reaction forces and peak internal ankle plantar flexion moment onset timing ( r= -0.63 vs r= -0.09) and between peak horizontal braking forces and peak internal ankle plantar flexion moments ( r= -0.72 vs r= -0.26). Group differences suggest that subjects with coxa varus-genu valgus frontal-plane alignment have an increased dependence on both ankle dorsiflexor and plantar flexor muscle group function during crossover cutting. Greater dependence on ankle muscle group function during the performance of a task that requires considerable 3D dynamic knee joint control suggests a greater need for frontal and transverse plane weight bearing tasks that facilitate eccentric ankle muscle group function to optimize injury prevention conditioning and post-surgical rehabilitation programs.

Design space optimization using a numerical design continuation method

AbstractA generalized optimization problem in which design space is also a design to be found is defined and a numerical implementation method is proposed. In conventional optimization, only a portion of structural parameters is designated as design variables while the remaining set of other parameters related to the design space are often taken for granted. A design space is specified by the number of design variables, and the layout or configuration. To solve this type of design space problems, a simple initial design space is selected and gradually improved while the usual design variables are being optimized. To make the design space evolve into a better one, one may increase the number of design variables, but, in this transition, there are discontinuities in the objective and constraint functions. Accordingly, the sensitivity analysis methods based on continuity will not apply to this discontinuous stage. To overcome the difficulties, a numerical continuation scheme is proposed based on a new concept of a pivot phase design space. Two new categories of structural optimization problems are formulated and concrete examples shown. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Implanted functional neuromuscular stimulation systems for individuals with cervical spinal cord injuries: Clinical case reports

Objective: To determine the feasibility of providing the ability to stand and to facilitate the performance of standing transfers to individuals with cervical-level spinal cord injuries via functional neuromuscular stimulation (FNS). The applicability of implantable technology to this population was investigated, and the characteristics of the potential system users were explored. The effects of FNS on the effort and assistance required to stand and complete standing transfers were examined. Setting: Institutional rehabilitation practice. Design: Nonrandomized controlled trial. Patients: Twenty-four individuals with low cervical spinal cord injuries were evaluated for inclusion in a program of lower extremity FNS, four of whom received the intervention. Intervention: Chronically indwelling percutaneous intramuscular electrodes were used to exercise the hip, knee, and trunk extensors and develop activation patterns to produce standing function. These temporary systems were then replaced with silicone-enclosed helical wire electrodes suitable for eventual use with an eight-channel implantable receiver/stimulator. Main Outcome Measures: Full sensory and motor evaluations were performed and physical contraindications to stimulation were catalogued. For active subjects, American Spinal Injury Association Total Motor Scores with and without FNS were recorded, along with quadriceps strength and ability to complete exercise, standing, controlled sitting, and standing transfer maneuvers. Performances of implanted electrodes were determined by the stability of recruitment properties, impedances or surface potentials, and serial radiographs. Results: Motor scores increased an average of nine points with stimulation over baseline volitional values. With FNS, all four volunteers were able to exercise, stand, and sit independently or with minimal assistance. Although they required varying degrees of assistance with the pivot phase of the transfer maneuver, all were able to raise and lower their body weight independently with stimulation and to use the system to facilitate standing transfers. One participant received the implantable receiver/stimulator, which remains operational at follow-up more than 3 years later. Conclusion: FNS can provide the ability to exercise, stand, and transfer to individuals with tetraplegia, even in the presence of medical complications and upper extremity impairment. FNS facilitates standing transfers by eliminating the heavy lifting usually required by a caregiver, thus decreasing the effort and assistance necessary to gain access to places impossible to approach with conventional sliding transfers.

Solution of large dense transportation problems using a parallel primal algorithm

We implemented a version of primal transportation algorithm on a 14 processor BBN Butterfly computer and solved a variety of large, fully dense, randomly generated transportation and assignment problems ranging in size up to m = n = 3000. The algorithm alternates between a search and pivot phase. Processors independently locate possible pivots by concurrently searching the reduced cost matrix. Pivots are then performed sequentially by all processors. This parallelization strategy is justified since we have found that the search phase of the algorithm becomes the dominant activity with increasing problem size. The parallel algorithm has the added advantage of being easy to implement. A speedup of approximately 7 was obtained on large problems. The empirical difficulty of solving an n × n transportation problem was proportional to n a where a varied between 2.0 and 2.2 with increasing shipping amounts.