A method for solving the problem of bend sequencing in sheet metal manufacturing is presented. The algorithm developed divides the part into basic shapes (channels and spirals) and determines the ...partial sequences associated with them. The complete bending sequences associated with the complete part were obtained from the combination of these partial sequences. To make this combination possible, several strategies were defined to reduce the number of solutions and, therefore, the searching time. All sequences (partial and complete) were checked considering possible part-tool collisions and tolerance constraints. The last stage was to order the sequences by taking into account the total process time. To attain the required process time accuracy, a robot was used for the handling operations. Finally, the sequence associated with the lower process time was selected as the optimal solution.
Spontaneous breaking of Lorentz symmetry at energies on the order of the Planck energy or lower is predicted by many quantum gravity theories, implying non-trivial dispersion relations for the photon ...in vacuum. Consequently, gamma-rays of different energies, emitted simultaneously from astrophysical sources, could accumulate measurable differences in their time of flight until they reach the Earth. Such tests have been carried out in the past using fast variations of gamma-ray flux from pulsars, and more recently from active galactic nuclei and gamma-ray bursts. We present new constraints studying the gamma-ray emission of the galactic Crab Pulsar, recently observed up to TeV energies by the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) collaboration. A profile likelihood analysis of pulsar events reconstructed for energies above 400 GeV finds no significant variation in arrival time as their energy increases. Ninety-five percent CL limits are obtained on the effective Lorentz invariance violating energy scale at the level of ( ) for a linear, and ( ) for a quadratic scenario, for the subluminal and the superluminal cases, respectively. A substantial part of this study is dedicated to calibration of the test statistic, with respect to bias and coverage properties. Moreover, the limits take into account systematic uncertainties, which are found to worsen the statistical limits by about 36%-42%. Our constraints would have been much more stringent if the intrinsic pulse shape of the pulsar between 200 GeV and 400 GeV was understood in sufficient detail and allowed inclusion of events well below 400 GeV.
Context.
The BL Lac object 1ES 0647+250 is one of the few distant
γ
-ray emitting blazars detected at very high energies (VHEs; ≳100 GeV) during a non-flaring state. It was detected with the MAGIC ...telescopes during a period of low activity in the years 2009−2011 as well as during three flaring activities in the years 2014, 2019, and 2020, with the highest VHE flux in the last epoch. An extensive multi-instrument data set was collected as part of several coordinated observing campaigns over these years.
Aims.
We aim to characterise the long-term multi-band flux variability of 1ES 0647+250, as well as its broadband spectral energy distribution (SED) during four distinct activity states selected in four different epochs, in order to constrain the physical parameters of the blazar emission region under certain assumptions.
Methods.
We evaluated the variability and correlation of the emission in the different energy bands with the fractional variability and the Z-transformed discrete correlation function, as well as its spectral evolution in X-rays and
γ
rays. Owing to the controversy in the redshift measurements of 1ES 0647+250 reported in the literature, we also estimated its distance in an indirect manner through a comparison of the GeV and TeV spectra from simultaneous observations with
Fermi
-LAT and MAGIC during the strongest flaring activity detected to date. Moreover, we interpret the SEDs from the four distinct activity states within the framework of one-component and two-component leptonic models, proposing specific scenarios that are able to reproduce the available multi-instrument data.
Results.
We find significant long-term variability, especially in X-rays and VHE
γ
rays. Furthermore, significant (3−4
σ
) correlations were found between the radio, optical, and high-energy (HE)
γ
-ray fluxes, with the radio emission delayed by about ∼400 days with respect to the optical and
γ
-ray bands. The spectral analysis reveals a harder-when-brighter trend during the non-flaring state in the X-ray domain. However, no clear patterns were observed for either the enhanced states or the HE (30 MeV <
E
< 100 GeV) and VHE
γ
-ray emission of the source. The indirect estimation of the redshift yielded a value of
z
= 0.45 ± 0.05, which is compatible with some of the values reported in the literature. The SEDs related to the low-activity state and the three flaring states of 1ES 0647+250 can be described reasonably well with the both one-component and two-component leptonic scenarios. However, the long-term correlations indicate the need for an additional radio-producing region located about 3.6 pc downstream from the gamma-ray producing region.
A novel Cu catalyst film was prepared by oblique angle physical vapour deposition (OAD) on a K-βAl 2 O 3 solid electrolyte (alkaline ionic conductor) for catalytic/electrocatalytic purposes. This ...technique allowed us to obtain a highly porous and electrically conductive Cu catalyst electrode which was tested in the partial oxidation of methanol (POM) reaction for H 2 production and its catalytic activity was in situ enhanced via electrochemical promotion of catalysis (EPOC). The electropromotional effect was reversible and reproducible, and allowed us to increase both hydrogen and methyl formate production rates by almost three times under optimal promotion conditions (320 °C, 2.2 × 10 −7 mol of K + transferred). The observed promotional effect was attributed to a decrease in the Cu catalyst work function as a consequence of the controlled migration of electropositive K + ions which favoured the chemisorption of electron acceptor molecules (O 2 ) at the expense of the electron donor ones (CH 3 OH). Under the reaction conditions these ions formed some kinds of potassium surface compounds as demonstrated by SEM, EDX and XPS post-reaction characterization analyses. The obtained results demonstrate the interest of the used catalyst-electrode preparation technique for the electrochemical activation of non-noble metal catalyst films.
•Extrinsic calibration procedure for a conoscopic holography (CH) sensor in a CMM.•CMM errors map included in the calibration model.•Two different test spheres used as calibration artefacts.•Method ...evaluated by measurement of a ball-plate and a tailor-made test part.•Calibration method valid for CH sensors integrated in CMMs and CNC machine tools.
In the present work, a procedure for extrinsic calibration of a 1D conoscopic holography sensor integrated in a CMM was developed, whereby it is possible to relate the coordinates of points captured by the sensor with the coordinate system of the machine. The procedure uses the information of the CMM error map to compensate the influence of these errors when associating the sensor measurements with the machine coordinate system. The calibration method was based on digitizing a test sphere and minimizing the error between the diameter of a least-squares fit of the digitized points and the value of its certified diameter. Results were compared for two test spheres of different diameter and material. To evaluate the efficacy of the calibration method, 3D distances between the spheres of a ball-plate were measured as well as several 3D geometrical features on a tailor-made test part. The tests carried out showed that the calibration method is independent of the type of test sphere used and that it is able to suitably compensate the positioning errors of the machine. Therefore, the calibration method proposed is applicable to integrate these type of sensors in CMMs and CNC machine tools with several controlled axes.
Las luxaciones periastragalinas son una entidad poco frecuente (<1%) de las lesiones traumáticas del pie. Se produce una pérdida de relación anatómica entre astrágalo, calcáneo y escafoides. Solo hay ...pequeñas series publicadas.
Presentamos los casos de una serie de pacientes (N=13) con luxaciones periastragalinas en los que se realizó un análisis descriptivo de las principales variables epidemiológicas, clínicas y radiológicas, a partir de las cuales se propone un algoritmo de tratamiento urgente. Se excluyeron los casos con fracturas del cuello del astrágalo, cuerpo del calcáneo o fracturas-luxación de Chopart aisladas.
La mediana de edad fue de 48,5 años con predominio del sexo masculino (69,23%). Cinco pacientes sufrieron caídas-entorsis sobre el tobillo y los 8 restantes mecanismos de alta energía. Las luxaciones mediales (9) predominaron sobre las laterales (4). Además, 4 pacientes presentaron luxaciones abiertas, 2 de ellas tipo IIIC que precisaron amputación. Se solicitó TC en un 76,93% de pacientes y 10 presentaron lesiones óseas asociadas del pie. Se realizó cirugía mediante reducción abierta en todas las lesiones abiertas y en un caso en el que fracasó la reducción cerrada. Cinco pacientes precisaron fijador externo tipo delta. Se objetivó esclerosis subcondral articular en un 77,77% de los casos; si bien solo uno precisó artrodesis subtalar.
Las luxaciones periastragalinas son una urgencia traumatológica y precisan una reducción precoz e inmovilización posterior. La fijación externa temporal transarticular es una buena opción de inmovilización en luxaciones abiertas. Son lesiones graves con alta probabilidad de artrosis precoz.
Subtalar dislocations are a rare entity (<1%) in traumatic foot injuries. There is a loss of anatomical relationship between the talus, calcaneus and scaphoid. There are only small-published series.
We present a series of patients (N=13) with subtalar dislocations in which a descriptive analysis of the main epidemiological, clinical and radiological variables was carried out, from which an urgent treatment algorithm is proposed. Cases with fractures of the neck of the talus, body of the calcaneus, or isolated Chopart fracture-dislocations were excluded.
The median age was 48.5 years with a predominance of males (69.23%). Five patients suffered falls or sprained ankles and the other eight suffered high-energy mechanisms. The medial dislocations (nine) predominated over the lateral ones (four). In addition, four patients presented open dislocations, two of them type IIIC that required amputation. CT scans were requested in 76.93% of patients and 10 presented associated bone lesions of the foot. Open reduction surgery was performed in all open lesions and in one case in which closed reduction failed. Five patients required a delta-type external fixator. Subchondral articular sclerosis was observed in 77.77% of cases; although only one required subtalar arthrodesis.
Subtalar dislocations are a traumatic emergency that require early reduction and subsequent immobilization. Transarticular temporary external fixation is a good immobilization option in open dislocations. They are serious lesions with a high probability of early osteoarthritis.
This work analyses the directional effect shown by the high-density point clouds digitized with a conoscopic holography (CH) sensor. The asymmetric shape of the laser spot for this sensor yields ...directionality to appear along the largest spot dimension and to occur repeatedly under different working conditions. To study this effect, several digitizing tests were performed under different conditions on a surface machined by EDM with a uniform and isotropic finish, so that the directional effect should not appear. Nevertheless, the use of the 2D Fourier transform (2DFT) confirmed the existence of directionality in the point clouds along the largest spot direction and that it appeared repetitively under different working conditions. Thus, this effect could be considered as a systematic error associated to the CH sensor and then, feasible to be reduced. The use of an anisotropic 2D Gaussian filter is suggested for this purpose. The results found before and after applying the filter were compared to those obtained by a confocal microscope, which was used as reference due to the absence of directionality in the captured images. Results show that the filtered point clouds suitably fit the actual surface topography.
•Digitizing of high density point clouds by a conoscopic holography sensor.•Directionality appears and it can be quantified by 2D Fourier Transform.•Gaussian filtering reduces point cloud directionality.•The filter may be adjusted to different lenses.•The filter may be adjusted to different positions of digitized surface within DOF.
Abstract
We report on a long-lasting, elevated gamma-ray flux state from VER J0521+211 observed by VERITAS, MAGIC, and Fermi-LAT in 2013 and 2014. The peak integral flux above 200 GeV measured with ...the nightly binned light curve is (8.8 ± 0.4) × 10
−7
photons m
−2
s
−1
, or ∼37% of the Crab Nebula flux. Multiwavelength observations from X-ray, UV, and optical instruments are also presented. A moderate correlation between the X-ray and TeV gamma-ray fluxes was observed, and the X-ray spectrum appeared harder when the flux was higher. Using the gamma-ray spectrum and four models of the extragalactic background light (EBL), a conservative 95% confidence upper limit on the redshift of the source was found to be
z
≤ 0.31. Unlike the gamma-ray and X-ray bands, the optical flux did not increase significantly during the studied period compared to the archival low-state flux. The spectral variability from optical to X-ray bands suggests that the synchrotron peak of the spectral energy distribution (SED) may become broader during flaring states, which can be adequately described with a one-zone synchrotron self-Compton model varying the high-energy end of the underlying particle spectrum. The synchrotron peak frequency of the SED and the radio morphology of the jet from the MOJAVE program are consistent with the source being an intermediate-frequency-peaked BL Lac object.
Polymethylmethacrylate (PMMA) bone cement is a biomaterial used to anchor prostheses during joint replacement surgery. Residual methylmethacrylate monomer (MMA) may be related with the cytotoxic ...effect of PMMA. The aim of the present paper was to investigate the effect of two different cement mixing methods: hand stirring at atmospheric pressure and under partial vacuum (0.330 and 0.154 bar) on residual monomer liberation in phosphate buffer saline solution from acrylic cement powder. Residual MMA content was determined by high-performance liquid chromatography. Mathematical models were applied to experimental dissolution data revealing that monomer release was significantly reduced in bone cement powder obtained at 0.154 bar vacuum pressure compared to the other mixing conditions. The kinetic models applied are consistent with a simple diffusion mechanism of the monomer from the polymer matrix.
The first metatarsophalangeal joint arthrodesis is indicated for the treatment of various pathologies as a technique to reduce pain and improve the support of the first radius. Numerous surgical ...techniques and fixation methods have been described, with the combination of a dorsal plate and an interfragmentary screw being the one that has shown to be the most stable construct in biomechanical studies. Our aim is to analyze the radiological results after metatarsophalangeal arthrodesis of the hallux using a dorsal plate associated or not with an interfragmentary screw. The differences in terms of consolidation rates and complications in patients diagnosed with hallux rigidus, hallux valgus, hallux varus and failure of previous surgeries were evaluated.BACKGROUND AND AIMSThe first metatarsophalangeal joint arthrodesis is indicated for the treatment of various pathologies as a technique to reduce pain and improve the support of the first radius. Numerous surgical techniques and fixation methods have been described, with the combination of a dorsal plate and an interfragmentary screw being the one that has shown to be the most stable construct in biomechanical studies. Our aim is to analyze the radiological results after metatarsophalangeal arthrodesis of the hallux using a dorsal plate associated or not with an interfragmentary screw. The differences in terms of consolidation rates and complications in patients diagnosed with hallux rigidus, hallux valgus, hallux varus and failure of previous surgeries were evaluated.A retrospective cohort study of 55 patients with a mean age of 65.10 years in whom a dorsal plate was used was performed. Patients were divided into two groups depending on whether or not an interfragmentary screw was used. The minimum follow-up was 6 months after surgery. The assessment of the pre and postoperative radiological results was based on the variation of the hallux angle, the intermetatarsal angle and the dorsal metatarsophalangeal angle of the hallux, as well as the cases of nonunion identified in each study group.MATERIALS AND METHODSA retrospective cohort study of 55 patients with a mean age of 65.10 years in whom a dorsal plate was used was performed. Patients were divided into two groups depending on whether or not an interfragmentary screw was used. The minimum follow-up was 6 months after surgery. The assessment of the pre and postoperative radiological results was based on the variation of the hallux angle, the intermetatarsal angle and the dorsal metatarsophalangeal angle of the hallux, as well as the cases of nonunion identified in each study group.The radiological results, statistically significant differences (p<0.05) were only found in the dorsal metatarsophalangeal angle between both study groups. No statistically significant differences were found regarding the radiological evaluation of the pre and postoperative hallux angle and intermetatarsal angle. An equal decrease of each angles was observed in both study groups. Regarding the consolidation rate, statistically significant differences (p<0.05) were found between group A, which associated an interfragmentary screw, presenting a consolidation rate of 92%, and group B, which did not associate an interfragmentary screw, and that presented a union rate of 63%.RESULTSThe radiological results, statistically significant differences (p<0.05) were only found in the dorsal metatarsophalangeal angle between both study groups. No statistically significant differences were found regarding the radiological evaluation of the pre and postoperative hallux angle and intermetatarsal angle. An equal decrease of each angles was observed in both study groups. Regarding the consolidation rate, statistically significant differences (p<0.05) were found between group A, which associated an interfragmentary screw, presenting a consolidation rate of 92%, and group B, which did not associate an interfragmentary screw, and that presented a union rate of 63%.Hallux metatarsophalangeal arthrodesis of the hallux with a dorsal plate and interfragmentary screw show best results regarding consolidation rate and complications compared to those cases in which an interfragmentary screw was not used.CONCLUSIONHallux metatarsophalangeal arthrodesis of the hallux with a dorsal plate and interfragmentary screw show best results regarding consolidation rate and complications compared to those cases in which an interfragmentary screw was not used.
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