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\"Un matin, une fillette attrape un arc-en-ciel et l'enferme dans un bocal en verre. Au début, l'arc-en-ciel paraît hésitant dans son nouvel environnement. Pourtant, l'enfant en prend bien soin. Elle lui donne des friandises, le montre à ses amis et l'emmène partout avec elle. Tous deux deviennent inséparables! Mais, un jour, l'arc-en-ciel commence à dépérir. Malgré les blagues et les grimaces de la fillette, rien ne semble lui redonner le sourire.\"--leslibraires.ca.
Book
Intensity modulated radiation therapy
Intensity modulated radiation therapy (IMRT) has become standard of care for most cancer sites that are managed by radiation therapy. This book documents the evolution of this technology over 35 years to the current level of volumetric arc modulated therapy (VMAT). It covers every aspect of this radiation treatment technology, including the fundamentals of IMRT/VMAT, basic principles and advanced processes for implementation. The physics of IMRT is followed by the clinical application in major disease sites such as central nervous system, head and neck, breast, lung, prostate and cervix. It also provides updated references on each component of IMRT/VMAT. This book is written by leading experts in the field with extensive clinical experience in the practice and implementation of this technology. Part of IPEM-IOP Series in Physics and Engineering in Medicine and Biology.
eBook
Study on arc behavior and droplet transfer in twin-electrode TIG-MIG indirect arc welding
A twin-electrode TIG-MIG (T-TIG-MIG) indirect arc welding method was proposed in this paper. The arc behavior and droplet transfer process were preliminarily investigated; moreover, the process stability was assessed, and bead-on-plate welding was conducted. Results showed T-TIG-MIG indirect arc burnt between a wire and two tungsten electrodes and was essentially formed by the coupling of two single-electrode TIG-MIG indirect arcs. The wire feeding speed (WFS) determined the equilibrium position of the wire end, and the vicinity of the tungsten tips was an ideal position for arc shape and droplet detachment, where the arc was more concentrated with a higher coupling degree. With the increase of the welding current, the arc length and stiffness increased gradually; so did the process stability and the spreadability of the weld bead. When the current exceeded the critical current, the droplet transfer mode changed into streaming spray transfer, since the electromagnetic force and the arc pressure increased considerably. Compared to conventional cold-wire T-TIG welding under the same current, the wire deposition rate of T-TIG-MIG indirect arc welding increased by about 186%, while the range of the heat-affected zone reduced by about 41%.
Journal Article
Research on single-phase grounding fault of power system based on new small current grounding system
China’s vast power grid, with its intricate line configuration, occasionally experiences unpredictable malfunctions. The neutral grounding method holds a pivotal role in addressing these failures and maintaining the distribution network’s operation. This article delves into an innovative low-current grounding system that incorporates arc suppression coils and parallel resistance grounding technology. This grounding technique not only mitigates arcs but also facilitates rapid line selection and tripping. Even in high-resistance conditions, it can precisely detect fault points in overhead distribution lines and promptly isolate the faulty segment. Its characteristics have been validated through simulation
Journal Article
Arc shape and dynamic behavior of the Tri-Arc twin-wire GMAW process
Abstract The triple-arc (Tri-Arc) twin-wire gas metal arc welding (GMAW) is a novel twin-wire welding method, compared with the conventional twin-wire GMAW process; it decouples heat input and deposition rate by creating an inter-electrode arc between the two wire ends, called the middle-arc (M-arc). To determine the arc shape and dynamic behavior of this special welding process and to clarify the decoupling characteristics of it, in this paper, a high-speed camera and a synchronized data acquisition system captured dynamic arc shapes and welding current signals. The analysis of the experimental results indicates that the Tri-Arc twin-wire welding has three operating modes: single-wire single-arc, twin-wire dynamic double-arc, and twin-wire dynamic three-arc. At least two arcs exist in the twin-wire dynamic three-arc welding process, dynamically forming two different arc shapes and their respective mirror image shapes: a “μ” shape and a “Γ” shape. In addition, the process for forming the “Γ”-shaped arc is clarified. The mechanism of deposition rate improvement and heat input reduction of the Tri-Arc twin-wire welding process is that the M-arc increases the current to melt one welding wire while preheating the other wire without passing through the workpiece.
Journal Article
Enhancement of Additive Manufacturing Processes for Thin-Walled Part Production Using Gas Metal Arc Welding (GMAW) with Wavelet Transform
Additive manufacturing encompasses technologies that produce three-dimensional computer-aided design (CAD) models through a layer-by-layer production process. Compared to traditional manufacturing methods, additive manufacturing technologies offer significant advantages in producing intricate components with minimal energy consumption, reduced raw material waste, and shortened production timelines. AM methods based on shielded gas welding have recently piqued the interest of researchers due to their high efficiency and cost-effectiveness in manufacturing critical components. However, one of the most formidable challenges in additive manufacturing methods based on shielded gas welding lies in the irregularity of weld bead height at different points, compromising the precision of components produced using these techniques. In this current research, we aimed to achieve uniform weld heights along the welding path by considering the most influential parameters on weld bead geometry and conducting experimental tests. Input parameters of the process, including nozzle angle, welding speed, wire speed, and voltage, were considered. Simultaneously, image processing and wavelet transform were employed to assess the uniformity of weld bead height. These parameters were applied to produce intricate parts after identifying optimal parameters that yielded the smoothest weld lines. According to the results, the appropriate bead for manufacturing the part was extracted. The results show that the smoothest bead line is achieved in 27 V as the highest level of voltage, at a 90° nozzle position and the maximum wire feed rate. Parts manufactured using this method across different layers exhibited no distortions, and the repeatability of production substantiated the high reliability of this approach for component manufacturing.
Journal Article
Motivic Euler Products and Motivic Height Zeta Functions
A motivic height zeta function associated to a family of varieties parametrised by a curve is the generating series of the classes,
in the Grothendieck ring of varieties, of moduli spaces of sections of this family with varying degrees. This text is devoted to the
study of the motivic height zeta function associated to a family of varieties with generic fiber having the structure of an equivariant
compactification of a vector group. Our main theorem describes the convergence of this motivic height zeta function with respect to a
topology on the Grothendieck ring of varieties coming from the theory of weights in cohomology. We deduce from it the asymptotic
behaviour, as the degree goes to infinity, of a positive proportion of the coefficients of the Hodge-Deligne polynomial of the above
moduli spaces: in particular, we get an estimate for their dimension and the number of components of maximal dimension. The main tools
for this are a notion of motivic Euler product for series with coefficients in the Grothendieck ring of varieties, an extension of
Hrushovski and Kazhdan’s motivic Poisson summation formula, and a motivic measure on the Grothendieck ring of varieties with
exponentials constructed using Denef and Loeser’s motivic vanishing cycles.
eBook
Applying Mobile Augmented Reality (AR) to Teach Interior Design Students in Layout Plans: Evaluation of Learning Effectiveness Based on the ARCS Model of Learning Motivation Theory
In this paper we present a mobile augmented reality (MAR) application supporting teaching activities in interior design. The application supports students in learning interior layout design, interior design symbols, and the effects of different design layout decisions. Utilizing the latest AR technology, users can place 3D models of virtual objects as e.g., chairs or tables on top of a design layout plan and interact with these on their mobile devices. Students can experience alternative design decision in real-time and increases the special perception of interior designs. Our system fully supports the import of interior deployment layouts and the generation of 3D models based on design artefacts based on typical design layout plan design symbols and allows the user to investigate different design alternatives. We applied John Keller’s Attention, Relevance, Confidence, and Satisfaction (ARCS) learning motivation model to validate our solution to examine the students’ willingness and verify the ability of students to improve learning through MAR technology. We compared a sample experimental group of N = 52 test-subjects with a sample of N = 48 candidates in a control group. Learning indicators as learning interest, confidence, satisfaction and effective have been utilized to assess the students’ learning motivation through the use of MAR technology. The learning results have been determined by the independent sample t testing. The significance of the post-test had a p-value < 0.05 difference. The result of the study clearly shows that the reference group utilizing MAR technology as a learning aid show a higher learning effectiveness as the control group. Thus, we conclude that MAR technology does enhance students’ learning ability for interior design and making appropriate design decisions.
Journal Article
Interhemispheric Conjugacy of Multiple Transpolar Arcs
Multiple transpolar arcs appearing simultaneously in the polar cap have gained much interest in recent years. By analyzing Defense Meteorological Satellite Program Special Sensor Ultraviolet Spectrographic Imagers data, we report for the first time, that less than half of the multiple arc events occur simultaneously in both hemispheres. In 60% of the cases, multiple arcs appear in only one hemisphere. There is a clear difference in interplanetary magnetic field (IMF) conditions for those two groups. Conjugate multiple arcs appear on average during stronger northward IMF and smaller IMF clock angles than non‐conjugate multiple arcs. Only non‐conjugate multiple arcs show a dependence on IMF BX. They form in the northern (southern) hemisphere during negative (positive) BX. An IMF BX induced interhemispheric asymmetry in the magnetospheric field line topology might explain why multiple arcs appear sometimes in only one hemisphere. Plain Language Summary Occasionally, multiple auroral arcs form far poleward of the main auroral oval. These multiple transpolar arcs were so far believed to almost always be conjugate (appearing in both hemispheres simultaneously). We show for the first time that more than half of them appear in only one hemisphere. Conjugate multiple arcs appear when the magnetic field in the solar wind (IMF) is strongly northward. Non‐conjugate multiple arcs show a less strong dependency on northward IMF. Interestingly, we found a clear correlation between non‐conjugate multiple arc events and IMF BX. This is unexpected, as in general, polar auroral arcs do not show any clear dependence on BX. Non‐conjugate multiple arcs appear mainly in the southern hemisphere when the IMF points sunward, and in the northern hemisphere when it points tailward. As IMF BX is known to introduce an interhemispheric asymmetry in the field‐line topology close to the reconnection sites, this may affect the formation of multiple arcs differently in the two hemispheres, and thus might explain the non‐conjugacy of those events. Key Points Multiple transpolar arcs (TPAs) appear during stronger northward interplanetary magnetic field (IMF) than isolated TPAs Hemisphere‐conjugate multiple TPAs appear for smaller IMF clock angles than non‐conjugate multiple arcs Non‐conjugate multiple arcs show an IMF BX dependence with northern (southern) hemisphere arcs appearing for negative (positive) BX
Journal Article
Study of the hardfacing process using self-shielding flux-cored wire with an exothermic addition with a combined oxidizer of the Al-(CuO/Fe2O3) system
Analysis of publications has shown that the use of the exothermic addition with a combined oxidizer (
x
CuO + (
x
-1)Fe
2
O
3
-Al) as components of filler materials will reduce energy consumption and increase the efficiency of the welding/hardfacing process. However, in the literature, there are no studies of exothermic addition with combined oxidizers, which allow to vary the chemical composition of the deposited metal within a wide range. In this paper, the use of exothermic addition with combined oxidizer (
x
CuO + (
x
-1)Fe
2
O
3
-Al) was considered. To study the characteristics, standard methods were used to determine the arc stability, melting characteristics, weld bead morphology, melting-energy characteristics, and efficiency parameters, and mechanical properties were made. The structural characteristics were analyzed by optical microscope (OM), X-ray diffractometer (XRD). Microhardness values of the hardfaced samples were obtained using a Vickers hardness tester. The greater stability of arc voltage was shown by the processes performed with flux-cored wires in which oxidizing agents of exothermic addition Al-CuO-Fe
2
O
3
in the core filler were taken with an equal content of oxidizing agents or with a slight excess of oxidizing agent CuO/(CuO + Fe
2
O
3
) = 0.5–0.6, whereas the greater stability of the welding current was shown by the processes carried out with the use of flux-cored wire with the exothermic addition with an equal or greater proportion of Fe
2
O
3
oxidizer in the combined oxidizer CuO/(CuO + Fe
2
O
3
) ≤ 0.5. Further studies of melting characteristics (deposition rate, spattering factor, etc.), melting-energy characteristics (melt-off coefficient
C
M
and deposition rate coefficient
C
d
), and efficiency showed the efficiency of using exothermic addition with combined oxidizer of Al-CuO-Fe
2
O
3
system. The study showed high arc stability of the hardfacing process, an increase in deposition efficiency (De), and a decrease in spattering loss, which increased deposition rate from 4.73 kg·h
−1
to 6.42 kg·h
−1
compared to exothermic addition with simple Al-Fe
2
O
3
system. Analysis of weld bead morphology showed improvement in weld bead parameters. The results showed high energy efficiency and productivity of the welding/hardfacing process with the introduction of exothermic addition with combined oxidizer of CuO-Fe
2
O
3
-Al system at the following share of copper oxide in combined oxidizer CuO/(CuO + Fe
2
O
3
) = 0.5–0.6.
Journal Article