Dual Leg Research Articles

A Photovoltaic-based Novel Transformerless High Gain Converter for DC Microgrid Applications

Aim: A typical microgrid network sourced by renewable energy encounters a technical setback owing to the voltage imbalance across the source integration and load power dissemination. Transformers employed to stabilize the potential may deteriorate the network efficiency and increases the cost and size of the system as well. Introduction: Photovoltaic based transformerless high gain DC-DC converter (THG-DC) is proposed here to aid the microgrid infrastructure. Microgrid fuelled by renewable energy sources demands the high gain converter interface to boost low voltage generation. The proposed THG-DC is employed with four switched inductors and three active power switches (IGBT) which are brought together under dual leg configurations. Methods: The proposed topology offers dual-duty cycle modes of regulating the active switches to realize the desired output voltage. Moreover, it is reliable to drive the proposed THG-DC with lower values of duty cycles to achieve a higher gain. The voltage stress across the switches is minimized and the magnitude of inductor current ripples is quashed to an extent. The proposed THGDC is simple in architecture and easy to control in all three operating modes. Results: The operating characteristics and performance investigation of the novel converter during the continuous and discontinuous modes are elucidated briefly and the comparative analysis on switching stress, gain, and efficiency are executed to justify the standards of the proposed THGDC. Conclusions: Finally, the miniature prototype model is experimented with in the laboratory (0.3 kW) and the obtained results are in agreement with the theory. It is evident from the investigations that the proposed THG-DC shows its dominance over other converters on the voltage gain, switching stress, number of components, and overall efficiency.

Newly designed single‐stage dual leg DC‐DC/AC buck‐boost converter for grid connected solar system

SummaryThis paper proposes a novel single‐stage buck‐boost inverter based on dual leg. Modulation techniques, working principle, guidelines for components design, and guidelines are discussed and presented. A theoretical concept is initially tested in Simulink platform and practically verified with a test bench model. A practical model is developed to verify the simulation model and tested different modes of operation are analyzed. The main advantages of the proposed work are as follows: The number of passive components is less, switching frequency components are not high so leakage current is very less, and voltage control in a wide range is achieved without using a DC link capacitor. High efficiency can be achieved due to multi‐stage operation. This proposed work is suitable for high/low voltage PV‐based energy conversion. Electromagnetic interference is also reduced due to continuous input current.

Design and implementation of dual‐leg generic converter for DC/AC grid integration

SummaryA newly designed generic photo‐voltaic (PV) DC‐DC/DC‐AC converter is for direct current (DC) grid or single‐phase alternating current (AC) grid integration. Main concept of the proposed converter is universal power conversion, and the same converter is used for DC‐DC/DC‐AC applications which also aiming for minimum redundancy because the proposed converter can be able to produce DC and AC output from the fixed/variable DC source. The proposed converter is designed with single‐stage dual leg topology, with a designed filter, and protection circuits are connected in output/grid side. The proposed circuit is compared with existing topologies, and comparative analyses are made in both chopper (DC‐DC) and inverter (DC‐AC) modes for universal or generic operation. Real‐time implementation of the proposed model is prepared for the power rating of 3.5 KW during inverter mode and 4 KW when same circuit working in chopper mode. Hardware results are obtained from the model from both chopper and inverter modes. Finally, correct applications, advantages, and future work are concluded in the last section.

The effect of expertise upon perceived reach- and grasp-ability in rock climbers

ABSTRACT Affordance perception is a forward-looking act of the opportunities of action offered by the environment and relative to individual capacities. This is exemplified by experienced rock climbers who must determine the task goal (use hold for support or facilitate movement) when balancing on one or both of their feet. The present study examined how the base of support (single and dual leg balance) and hold size affect an individual’s ability to determine their maximum boundary of reach- and grasp-ability. The maximal boundary of reach-ability and grasp-ability was determined using a sliding assessment hold. Twenty participants (10 climbers and 10 non-climbers) provided verbal estimates of maximal reach to a big and a small hold while balancing on one or two feet. Perceptual accuracy differed depending on whether the objective was reach-ability or grasp-ability (p < 0.001). Neither standing on one or two feet, nor climbing expertise affected perceptual accuracy. The results suggest that the task goal (e.g., grasp-ability or reach-ability) affects the accuracy of perception of action boundaries.

Effect of Weight Bearing Variations &amp; Heel Height on Forefoot Width for Orthopaedic Imaging

Category:Basic Sciences/Biologics; Midfoot/ForefootIntroduction/Purpose:The biomechanics of a foot when weight bearing change significantly due to the changes in the function through the gait cycle. Variations in heel height are known to influence load distribution in weightbearing, thus affecting change in forefoot widths. Weight bearing in radiographs are commonly used to identify these changes, which may have clinical relevance. However, there are limited studies that accurately quantify the extent of these differences in the forefoot to be analysed effectively. Hence, there is a need to investigate different weight bearing conditions and its influence on forefoot width changes required for accurate analysis of imaging. This study's aim is to evaluate the significance and degree of foot splaying with different modes of weight-bearing and heel height to achieve optimum increase in forefoot width.Methods:32 volunteers with no clinical issues with their feet were selected for this study. Weight bearing photographs of their feet were reviewed by 2 foot and ankle surgeons (under blinded conditions) to ensure they were normal morphologically. The forefoot width is measured using sliding callipers between the medial margin of the first metatarsal head and lateral margin of the fifth metatarsal head when non weight bearing - NWB, partial weight bearing - PWB (dual leg stance) and full weight bearing - FWB (single leg stance). Single leg stance measurement is also taken at increasing heel heights of 2cm (FWB1), 4cm (FWB2) and 6cm (FWB3) using polyurethrane blocks. Each individual foot non weight-bearing width will act as its own control for the changes in the differing positions measured.Results:Statistical analysis of data demonstrated the results with the use of student t-test analysis via SPSS which showed statistically significant differences in forefoot width in both genders(p<0.05). There is an increasing trend of forefoot width as weightbearing conditions increase up to 2cm of elevated heel height. However, forefoot width decreases as heel height increases beyond 2cm in both genders. Female subjects have a higher trend of percentage of increase in mean forefoot width compared to males in all weightbearing conditions except for full weightbearing with 6cm heel height elevation.Conclusion:In conclusion, there is a linear trend of increase in forefoot width with increase from non-weightbearing up to 2cm heel height inclination. Full weightbearing with 2cm heel height inclination produces the widest foot splaying in this study. Larger future studies will need to be conducted to validate these findings.

A comparison between two different immobilization devices for radiation therapy treatment of pelvic cancer using VMAT

ObjectivesTo assess setup reproducibility of low kneefix with feetfix (LKF-FF) system and its operator-reported convenience by reference to low dual leg positioner (LDLP), among patients treated with pelvic radiotherapy. MethodsA retrospective controlled trial was carried out at the radiotherapy unit. It included patients who underwent radical radiotherapy to the pelvis using VMAT, and who benefitted from LDLP (N = 30) or LKF-FF (N = 30) immobilization system. Average absolute shifts (AAS) and total vector errors (TVE) were computed and compared between the two systems, using translational (lateral, longitudinal and vertical) and rotational (X, Y and Z planes) directions. Accuracy rates were computed on pooled data including 1529 VMAT images, 819 in LDLP and 710 in LKF-FF groups, using different cutoffs. Radiotherapists' subjective assessment of the device's ease of setup, handling, cleaning, and storage, and patient comfort was carried out comparatively between the two devices. ResultsNo statistically significant difference was observed between the two systems in systematic settings, while LKF-FF outperformed LDLP in random settings; notably in vertical translation and X and Z rotational shifts. Analysis of TVEs showed significant decrease in rotational TVE in LKF-FF group (mean=1.38° versus 2.38, p = 0.003) by reference to LDLP, respectively; however, both systems had comparable translational TVE (p = 0.590). In pooled analysis, LKF-FF enabled an overall increase in setup accuracy rates in rotational directions by up to 15% and 19% at ±1° and ±2° accuracy levels, respectively (p<0.05). Subjective assessments showed that the two immobilization systems were comparable regarding all investigated dimensions; however, the overall radiotherapists’ preference leaned toward LDLP. ConclusionThe newly implemented LKF-FF system outperformed LDLP in terms of setup reproducibility, notably in rotational directions, where it enhanced setup accuracy rates by up to 19%. Long-term use of LKF-FF may improve the users’ satisfaction.

Analysis of the s2 alar-iliac screw as compared with the traditional iliac screw: does it increase stability with sacroiliac fixation of the spine?

Background ContextArthrodesis of the lumbosacral junction continues to be a challenge in pediatric and adult spinal deformity surgery. PurposeTo evaluate the biomechanical rigidity of two types of lumbosacral fixation. Our hypothesis was that the use of S2 alar-iliac (S2AI) fixation will result in statistically similar biomechanical fixation as compared with use of an iliac screw with a 95% confidence interval. Study SettingControlled biomechanical laboratory MethodsTen human cadaveric lumbosacral specimens were separated into two test groups: (1) S2AI (n=5) and (2) iliac screw (n=5). S2AI and iliac screws were placed according to current clinical practice techniques. Specimens were mounted in an unconstrained dual leg stance configuration for testing in flexion, extension, lateral bending, and axial rotation. These loads were induced by moving the offset loading arm 10 mm in the respective direction from the point of neutral motion with displacement control up to a 10 N-m moment, except axial rotation which used a 4 N-m moment. Optical tracking was used to monitor motion of the vertebra, pelvis, and fixation instrumentation during testing. Specimens were tested in intact and instrumented states. The stiffness values between S2AI and iliac screw configurations were compared. DisclosureThe present study received external research support (>$50,000 –<$75,000) from Stryker Spine (Allendale, NJ, USA). ResultsThere was a consistent trend of increased construct stiffness for all S2AI samples compared with the iliac screw group. However, none of the groups tested reached statistical significance for a 95% confidence interval. ConclusionsS2AI screws are just as stable as iliac screws with biomechanical testing in flexion, extension, rotation, lateral bending, and axial rotation. Given the similarities of biomechanical testing to human movements, these findings support S2AI screws as a viable option for lumbosacral fixation.

Transversal Oxide-Metal Thermoelectric Device for Low-Power Energy Harvesting

Abstract The concepts of dual leg, unileg and transversal oxide thermoelectric harvesting devices were compared with regard to the dimensionless figure of merit calculated from published data on common dual leg oxide thermoelectric generators. The analysis shows that the application of the transversal thermoelectric effect does not significantly reduce the expected electrical output power density of thermoelectric devices utilizing thermoelectric oxides. At the same time, the transversal device layout is simple in comparison to the common dual leg device. A transversal thermoelectric harvester consisting of a tilted multilayer stack La1.97Sr0.03CuO4/Ag was prepared and analyzed in detail. Simulations using the finite elements method were performed to verify the results. Based on this data, the electrical power density of the transversal oxide-metal device is estimated to be in the range of currently published data on oxide dual leg devices, thus allowing energy harvesting for low power applications.

Modifying the Classical One-Dimensional Catalyst Model to Include Axial Conduction and Diffusion

Lean NOx trap (LNT) catalytic aftertreatment devices are one potential option for the reduction of oxides of nitrogen (NOx) in the exhaust of compression ignition engines. They work through a controlled modulation between a storage phase that captures NOx over an alkali earth metal and a regeneration phase that reduces the stored nitrates on the surface using a rich pulse of injected fuel or via stoichiometric engine operation. This rich phase has an associated fuel penalty while being relatively difficult to control through temperature and chemical species. In order to improve system efficiency, a number of researchers have proposed dual leg LNT systems using two LNTs, one of which is always storing while the other is undergoing regeneration. The majority of the exhaust flows through the storage LNT while only a small fraction (low space velocity) advects across the regeneration LNT. This increases the regeneration residence time, improving effectiveness and decreasing the amount of fuel used. From an LNT simulation standpoint, most researchers utilize the classical one-dimensional (1D) aftertreatment model constructed from the Euler equations of motion that neglect axial conduction and diffusion. This paper explores the applicability of this model under low flow situations prevalent in a dual leg LNT system through a carbon monoxide light-off experiment. The authors chose this type of experiment in order to focus purely on fluid mechanics and not the choice of LNT reaction mechanism. The results suggest that a Navier–Stokes (N–S) version of the 1D aftertreatment model is preferred for the regeneration leg of a dual LNT system. Moreover, the authors provide the solution of such a model within this paper.

Patient-Specific and Generic Immobilization Devices for Prostate Radiotherapy

The purpose of our study was to compare interfractional bony setup variations in pelvic anatomy with two immobilization devices, the patient-specific Vac-Lok and the generic Dual Leg Positioner system (both Civco Medical Solutions, Kalona, IA), for bilateral proton radiotherapy of the prostate. Two groups of 10 patients were studied. Computed tomography (CT) was performed three times a week, yielding 233 CT image sets for the vacuum system group and 252 for the other group. The translational shifts of the pelvic bone and prostate and rotation of the upper femurs of the femoral heads with respect to the simulation CT images were analyzed. Along the anterior-posterior and lateral axes, mean and systematic translational variations of the pelvic bone and prostate, relative to skin fiducials, were significantly lower in the Vac-Lok group (all p 0.01) than in the Dual Leg Positioner group. Abduction of the upper femur, the dominant rotation, had random rotational variations of 1.9° and 2.0° and systematic rotations of 3.1&#176 and 2.9&#176 for the vacuum and generic system groups, respectively. Femoral abduction was highly correlated with anterior prostate displacement for both femurs in both groups (p tion introduced during simulation CT, particularly with the generic immobilization system. High degrees of femoral rotation may introduce prostate translation and distal misalignment of lateral proton beams with the prostate.

Locomotion skills for simulated quadrupeds

We develop an integrated set of gaits and skills for a physics-based simulation of a quadruped. The motion repertoire for our simulated dog includes walk, trot, pace, canter, transverse gallop, rotary gallop, leaps capable of jumping on-and-off platforms and over obstacles, sitting, lying down, standing up, and getting up from a fall. The controllers use a representation based on gait graphs, a dual leg frame model, a flexible spine model, and the extensive use of internal virtual forces applied via the Jacobian transpose. Optimizations are applied to these control abstractions in order to achieve robust gaits and leaps with desired motion styles. The resulting gaits are evaluated for robustness with respect to push disturbances and the traversal of variable terrain. The simulated motions are also compared to motion data captured from a filmed dog.

Research on hydraulic-powered roof supports test problems

The load-bearing characters of hydraulic-powered roof support with dual telescopic legs were analyzed. With a specific type hydraulic-powered roof support with dual telescopic legs for research object, the inside load test problems in factories was analyzed, and the correct test methods were given, which can enhance the test efficiency and make the factories away from the error design of hydraulic-powered roof supports and legs.

SU-FF-J-72: Evaluation and Comparison of Inter-Fractional Femoral Head Variations for Two Pelvic Immobilization Devices

Purpose: To compare and evaluate the inter-fractional femoral head (FH) translation and rotation of prostate cancer patients receiving conventional lateral proton radiotherapy using two commercially available pelvic immobilization devices, the Vac-Lok™ and Dual Leg Positioner (Civco Medical Solutions). Methods and Materials: This study enrolled two groups of ten patients to investigate inter-fractional FH variations. Each patient received serial in-room CT scans during his or her routine radiotherapy treatment. The FH and upper femurs were contoured on each set and exported to in-house CT registration software. Daily translation and rotation of the FH were assessed with a rigid registration of the FH from the reference CT to the daily CT, followed by a rotational registration of the upper femur. Results: The average daily translational variation of the FH relative to external skin fiducials was almost identical between both groups along all three directions (AP: 0.24 cm vs. 0.20 cm, SI: 0.11 cm vs. 0.11 cm, RL: 0.26 cm vs. 0.29 cm, Vac-Lok and Dual Leg Positioner group respectively). The dominant rotation was found in the axial plane. The average daily rotational variation was 1.94 degrees for the Vac-Lok group and 2.04 degrees for the Dual Leg Positioner group. The standard deviation of patients' systematic FH rotation was 3.13 degrees for the Vac-Lok group and 3.05 degrees for the Dual Leg Positioner group. Conclusion: Both pelvic immobilization devices appeared to give identical FH immobilization. A 2-degree (1SD) random FH rotation may not have significant dosimetry impact to proton therapy; however, a larger than expected 3-degree systematic rotation (1SD) may be a concern. Additional effort should be made to reduce the uncertainty at the initial treatment simulation. When considering the convenience of use, the Dual Leg Positioner system is ideal because it does not require additional storage space for patient-specific immobilization devices.

The AIDA toolset for design and implementation analysis of distributed real-time control systems

This article introduces a toolset that integrates the design and performance analysis of control systems with embedded real-time system design. The toolset enables specification and analysis of real-time implementations of control applications. Control system designs are imported to a real-time system-modelling domain in which the functionality is distributed on a target computer system. The control functionality is partitioned into operating system processes, inter-process communications are defined and the triggering of processes is specified. Once the real-time design is complete, the response times and release jitter of the processes and their contained functions can be analysed and the system information exported back to the control domain. This enables analysis of the resulting control performance with account taken to implementation effects such as delays and release jitter due to resource sharing and scheduling. The usage of the toolset is demonstrated on a dual leg controller for a walking robot. The case study shows how the toolset is used to describe a system, from the control system specification to the design of its implementation on a distributed network of processors. Different implementation solutions are suggested and evaluated based on simulated control system performance.

The dual leg and sole flap in the replacement of skin defects of the heel

The dual leg and sole flap in the replacement of skin defects of the heel