2D Shape Transformation Using 3D Blending

Abstract Computer animation is one of the key components of a multimedia document or presentation. Shape transformation between objects of different topology and positions is an open modeling problem in computer animation. We propose a new approach to solving this problem for two given 2D shapes. The key steps of the proposed algorithm are: dimension increase by converting input 2D shapes into halfcylinders in 3D space, bounded blending with added material between the half-cylinders, and making cross-sections for getting frames of the animation. We use the bounded blending set operations defined using R-functions and displacement functions with the localized area of influence applied to the functionally defined 3D half-cylinders. The proposed approach is general enough to handle input shapes with arbitrary topology defined as polygons with holes and disjoint components, set-theoretic objects, or analytical implicit curves. The obtained unusual amoeba-like behavior of the 2D shape combines metamorphosis with the non-linear movement on the plane

Comparative analysis of forest lands cadastral appraisal estimated with regards to wood and food resources

Cadastral appraisal of forest fund is one of the topical challenges of modern natural resource management. The paper delivers comparison of different approaches to cadastral appraisal of forest lands. The authors suggest a uniformed model to compare objectively and choose the most effective use of parcels

Salvage of Failed Femoral Neck Fracture Fixation with Conversion Total Hip Arthroplasty Using the Direct Anterior Approach.

Purpose: Failed femoral neck fracture (FNF) fixation with Materials and Methods: Medical records for 42 patients with a prior history of FNF fixation who underwent conversion THA with hardware removal between 2009 and 2019 were retrospectively reviewed. Surgery was performed by a single surgeon at a single institution. All patients underwent hardware removal followed by direct anterior approach (DAA) THA using two separate incisions. Clinical outcomes, radiographic findings, and perioperative morbidity and mortality are reported. Results: Clinically, there were no postoperative dislocations, periprosthetic fractures, or infections at follow-up. After a mean follow-up of 4 years, the mean hip disability and osteoarthritis outcome score, junior (HOOS, Jr) was 91. Radiographically, the mean postoperative cup abduction was 44 degrees and the mean cup anteversion was 21 degrees with an improvement in preoperative leg length discrepancy. Perioperative complications included one case of immediate foot drop and two readmissions for medical issues. One patient died one month after conversion THA. Conclusion: Salvage of failed FNF treatment may be managed with conversion THA and DAA with a separate incision for hardware removal. Preservation of posterior soft tissues using a DAA and intraoperative fluoroscopy may mitigate well-known complications related to fracture and dislocation. While favorable clinical outcomes are possible, salvage surgery is still not without substantial surgical and medical risks

Modified Two-Stage Exchange for Periprosthetic Joint Infection in UKA.

Periprosthetic joint infection (PJI) is a rare complication following unicompartmental knee arthroplasty (UKA), and current management guidelines are still evolving. This report presents a novel surgical technique of resection arthroplasty with an articulated hemispacer as part of a 2-stage exchange protocol. A 66-year-old man developed a culture-negative PJI four months after a medial UKA. Rather than conventional full resection arthroplasty, the patient underwent partial resection with preservation of the lateral and patellofemoral compartments to maintain vascularized bone stock. An articulating hemispacer fashioned from the old implants after sterilization was reimplanted medially to preserve function during the course of antibiotic treatment. After successful eradication of infection, the patient underwent an uncomplicated conversion total knee replacement facilitated by prior preservation of bone stock. No stems or augments were needed. Therefore, a partial resection arthroplasty with an articulating hemispacer used in a 2-stage exchange protocol may be a reasonable option to eradicate infection and maintain function. In future cases of infected UKA, this technique warrants further consideration and investigation

Modeling and Visualization of Multi-material Volumes

The terminology of multi-material volumes is discussed. The classification of the multi-material volumes is given from the spatial partitions, spatial domain for material distribution, types of involved scalar fields and types of models for material distribution and composition of several materials points of view. In addition to the technical challenges of multi-material volume representations, a range of key challenges are considered before such representations can be adopted as mainstream practice

Management of failed UKA to TKA: conventional versus robotic-assisted conversion technique.

BACKGROUND: Failure of unicompartmental knee arthroplasty (UKA) is a distressing and technically challenging complication. Conventional conversion techniques (CCT) with rods and jigs have produced varying results. A robotic-assisted conversion technique (RCT) is an unexplored, though possibly advantageous, alternative. We compare our reconstructive outcomes between conventional and robotic methods in the management of failed UKA. METHODS: Thirty-four patients with a failed UKA were retrospectively reviewed. Patients underwent conversion total knee arthroplasty (TKA) with either a CCT or RCT. Seventeen patients were included in each group. All procedures were done by a single surgeon at a single institution, with a mean time to follow-up of 3.6 years (range, 1 to 12). The primary outcome measures were the need for augments and polyethylene thickness. Secondary outcome measures were complications, need for revision, estimated blood loss (EBL), length of stay, and operative time. RESULTS: The mean polyethylene thickness was 12 mm (range, 9 to 15) in the CCT group and 10 mm (range, 9 to 14) in the RCT groups, with no statistical difference between the two groups (P = 0.07). A statistically significant difference, however, was present in the use of augments. In the CCT group, five out of 17 knees required augments, whereas none of the 17 knees in the RCT group required augments (P = 0.04). Procedurally, robotic-assisted surgery progressed uneventfully, even with metal artifact noted on the preoperative computerized tomography (CT) scans. Computer mapping of the residual bone surface after implant removal was a helpful guide in minimizing resection depth. No further revisions or reoperations were performed in either group. CONCLUSIONS: Robotic-assisted conversion TKA is technically feasible and potentially advantageous. In the absence of normal anatomic landmarks to guide conventional methods, the preoperative CT scans were unexpectedly helpful in establishing mechanical alignment and resection depth. In this limited series, RCT does not seem to be inferior to CCT. Further investigation of outcomes is warranted

MATHEMATICAL MODELLING OF TRANSIENTS IN THE ELECTRIC DRIVE OF THE SWITCH – THE MAIN EXECUTIVE ELEMENT OF RAILWAY AUTOMATION

Goal. To develop a mathematical and imitation model of the electric drive of the railroad switch as a two- and three-mass electromechanical system based on DC and AC motors as the main executive element of railway automation. The modelling is based on the parameters of the SP-6m switches as the main modification of the executive element of the Ukrainian domestic railways automation system. Methodology. The authors have presented the mechanical part of the railroad switch as a three-mass construction scheme with serial connection of elastic masses. Special attention is paid to the character of the movement of the switch point tongues, when describing them in the form of two- and three- mass kinematic schemes, as well as to the mechanical state of the traction and connections as nodes, which are most sensitive to the negative effects of some modes of the railroad switch. Results. A simulation mathematical model of SP-6m switch for AC and DC motors, which allows to study the influence of various factors, has been developed and tested at the stand of the Automation Laboratory of the Ukrainian State University of Railway Transport, Kharkiv. The deviation in the basic parameters of the switch translation process is less than 5 %. Originality. For the first time a mathematical model of an electric drive of the railroad switch is developed, which takes into account elastic relations and load characteristics as an object of controlling the speed of movement of switch point tongues. Practical significance. We have created a mathematical model of the electric drive of the railroad switch which allows to examine the influence of various factors, including the influence of the environment on the operation of the switch

Nitrogenation and sintering of (Nd-Zr)Fe10Si2 tetragonal compounds for permanent magnets applications

International audienceNd(1-x)Zr(x)Fe10Si2 alloys have been prepared in the tetragonal ThMn12-type structure by arc-melting and melt-spinning and then nitrogenated to improve their magnetic properties. For x = 0.4 and 0.6 the Curie temperature and magnetic anisotropy fields increase from 280-300 ºC to about 390 ºC and from 2.8-3 T to 4.5-5 T respectively. The saturation magnetization remains almost unchanged. The nitrogenated powders were processed by spark plasma sintering (SPS) leading to compact pellets, which retain the full nitrogen content and magnetic properties up to 600 ºC, but segregated Fe-Si at elevated temperatures. Nitrogenation and SPS processing are, therefore, appropriate for sintering metastable materials such as (Nd,Zr)Fe10Si2 into compact material without loosing functional properties. This opens a way towards a new family of permanent magnets, lean of critical raw materials

Probing photo-ionization: simulations of positive streamers in varying N2:O2 mixtures

Photo-ionization is the accepted mechanism for the propagation of positive streamers in air though the parameters are not very well known; the efficiency of this mechanism largely depends on the presence of both nitrogen and oxygen. But experiments show that streamer propagation is amazingly robust against changes of the gas composition; even for pure nitrogen with impurity levels below 1 ppm streamers propagate essentially with the same velocity as in air, but their minimal diameter is smaller, and they branch more frequently. Additionally, they move more in a zigzag fashion and sometimes exhibit a feathery structure. In our simulations, we test the relative importance of photo-ionization and of the background ionization from pulsed repetitive discharges, in air as well as in nitrogen with 1 ppm O2 . We also test reasonable parameter changes of the photo-ionization model. We find that photo- ionization dominates streamer propagation in air for repetition frequencies of at least 1 kHz, while in nitrogen with 1 ppm O2 the effect of the repetition frequency has to be included above 1 Hz. Finally, we explain the feather-like structures around streamer channels that are observed in experiments in nitrogen with high purity, but not in air.Comment: 12 figure