Articles de revues sur le sujet « BoxcarSoA »

A 40-nm broad pulse centred at 320nm is produced from an amplified Yb-doped fiber laser operated at 50kHz, and used in a BOXCARS geometry setup for 2DES, with shot-to-shot monitoring of the relative optical phase stability.

The BOXCARS technique has been used to study the collisional vibrational energy transfer from 1, 2-trans-dichloroethene excited into a quasicontinuum by a pulsed CO2 laser. The temporal evolution behaviour for vibrational energies in different modes was obtained. It has been shown that both the rate and maximum energy transferral to the ν4 mode are slightly larger than rates and energy transferral to the ν1 and ν2 modes and that this specificity declines with increase in excitation energy. The mechanism for this specificity is discussed.

Simultaneous measurements of temperature and relative concentrations of fuel, oxygen, and nitrogen using combined vibrational coherent anti-Stokes Raman Spectroscopy (CARS) and dual-broad-band rotational CARS have been demonstrated with the use of a Nd:YAG laser and a single dye laser. With the use of a double-folded BOXCARS phase-matching scheme, both the vibrational and the rotational CARS signals were generated in such a way that the signals were superimposed at the spectrograph. With an additional mirror arrangement inside the spectrograph, both signals were recorded simultaneously on a single diode-array detector. The accuracy of single-shot fuel concentration measurements has been investigated, and measurements in a methane/air diffusion flame have been demonstrated. The influence of systematic errors on measured concentrations is discussed.

The BOXCARS technique has been used to investigate the vibrational energy transfer between highly excited SF6 and N2O. It was found that the apparent rate and the amount of energy transferred to the ν1 (1285.0 cm−1) and ν3 (2223.5 cm−1) modes of N2O strongly depend on the excitation energy. The amount of energy transferred to the ν1 mode is slightly larger than that transferred to the ν3 mode, while the rate of energy transfer to the ν1 mode is slightly less than that to the ν3 mode. The rates and the amounts of energy transferred to both the ν1 and ν3 modes show greater dependence on the partial pressure of SF6 than on the partial pressure of N2O. A model has been proposed to explain the observed results.

The BOXCARS technique was used to investigate the V–V energy transfer between highly excited SF6 and CH4. The rates and the amounts of energy transferred to both the ν1 and ν3 modes depend strongly on excitation intensity and partial pressure of SF6 and CH4, and within experimental error, the variation of these quantities in both modes is identical, which is contrary to the situation in other polyatomic molecules. The results indicate that V–T energy transfer in CH4 plays an important role in the relaxation of the excess vibrational energy transferred from SF6 to CH4, and that the intermode V–V energy transfer between the ν1 and ν3 modes of CH4 is much faster than the interspecies V–V energy transfer between highly excited SF6 and CH4.

The BOXCARS technique was used to investigate the vibrational energy transfer between highly excited SF6 and CS2, and for the sensitized photodissociation of CS2. The analysis of data, as reported in our previous studies, to extract vibrational temperature from the CARS signal has been revised in the present work to adjust for the fact that the ground-state population may not be constant. The current investigation suggests that IR laser excitation of SF6 and the energy exchange between excited SF6 and CS2 create a high-lying vibrational energy reservoir in the CS2 vibrational manifold. The rate of energy transfer depends on the partial pressures of SF6 and CS2, and the excitation intensity. The transfer rate shows greater dependence on the partial pressure of SF6 than on the partial pressure of CS2. At higher excitation energies, the energy reservoir leads to photofragmentation products.

The BOXCARS technique was used to investigate the V–V energy transfer between highly excited SF6 and N2. It was found that a Boltzmann population distribution among vibrational levels of N2 is present by 1 μs after laser excitation of SF6 and is maintained during the energy-transfer processes. The maximum energy transferred to N2 increases linearly with the increase of the average number of photons absorbed [Formula: see text] by SF6 in the range [Formula: see text]. The maximum energy transferred to the N2 vibrational levels increases with the partial pressure of SF6 and decreases with the partial pressure of N2. The apparent rate of energy increase in the N2 vibrational levels increases with both partial pressures of SF6 and N2. However, both the rate and the amount of energy transferred to N2 vibrational levels depend more strongly on the partial pressure of SF6 than on the partial pressure of N2. A model calculation produces a reasonable fit to the experimental data.

Phase-match in degenerate four-wave mixing (DFWM) is not automatically achieved in the forward folded boxcars geometry. In this paper, we first design a simple image aligning system composed of an optical system, CCD camera and the related software. We can feasibly obtain well overlapped spot in the sample cell without moving the sample cell under this system. Also, we have proven the three pumping light beams are well overlapped in the sample cell when the three pumping light beams are on the same spot on CCD camera. This method minimizes the deviation by our eyes aligning. We can easily and timely know the effect of the pointing stability on the optical path by monitoring facula changing with the laser beam pointing and disturbs of the environment. So, this is a good choice for fast adjusting the light path and finding the overlapped spot. Finally, Steady DFWM signals have been obtained in the iodine vapor. This system makes it feasible that the potential application of FG-DFWM is used as a diagnostic tool in combustion research and environment monitoring.

We present a novel learning framework for vehicle recognition from a single RGB image. Unlike existing methods which only use attention mechanisms to locate 2D discriminative information, our work learns a novel 3D perspective feature representation of a vehicle, which is then fused with 2D appearance feature to predict the category. The framework is composed of a global network (GN), a 3D perspective network (3DPN), and a fusion network. The GN is used to locate the region of interest (RoI) and generate the 2D global feature. With the assistance of the RoI, the 3DPN estimates the 3D bounding box under the guidance of the proposed vanishing point loss, which provides a perspective geometry constraint. Then the proposed 3D representation is generated by eliminating the viewpoint variance of the 3D bounding box using perspective transformation. Finally, the 3D and 2D feature are fused to predict the category of the vehicle. We present qualitative and quantitative results on the vehicle classification and verification tasks in the BoxCars dataset. The results demonstrate that, by learning such a concise 3D representation, we can achieve superior performance to methods that only use 2D information while retain 3D meaningful information without the challenge of requiring a 3D CAD model.

A coherent anti-Stokes Raman scattering (CARS) setup has been developed to detect contamination of atmospheric nitrogen by nitric oxide (NO). To allow spatially resolved measurements and the possibility of utilizing windows close by the test volume, we chose the folded BOXCARS setup with a CARS lens of focal length 0.5 m and a diameter of 80 mm. A frequency-doubled Nd:YAG laser (= 532 nm; EL = 50 mJ; L = 10 ns; repetition rate, 10 s−1; bandwidth, 0.05 cm−1) serves as pump for a dye laser ( Ep = 25 mJ; EL = 2 mJ; bandwidth, 0.03 cm−1), which is tunable between 585 and 615 nm. Nitric oxide CARS spectra including the first hot band have been measured with high spectral resolution in a temperature range from 300 to 800 K. The detection limit of NO is on the order of 0.25% in nitrogen under atmospheric pressure. With suppression of the nonresonant background in the application of polarization CARS, the detection limit could not be scaled down in a desirable manner. The comparison between measured and calculated CARS spectra of NO in an N2 surrounding confirms the reliability of the energy matrix elements and the Lorentzian width of the type ( p, T = 0.06(298 K/T)0.6 p/ p0 cm−1.

After creating a substantial corpus of art that was political in the sense that the female body and social justice are political, but which had not dealt with national politics, the Colombian painter Débora Arango (1907–2005) embarked on an extended series of works that chronicled and critiqued politics and politicians during the undeclared civil war known as la Violencia (c. 1946 to 1965). This essay examines Arango’s first five paintings about the national politics of Colombia and, by extension, the role of the artist as witness. Arango’s earliest political paintings represent the Liberal politician Jorge Eliécer Gaitán, the rioting that erupted after his assassination in Bogotá on April 9, 1948, and the government’s suppression of Liberal rebels in Antioquia. This essay documents her personal connection to Gaitán, considers the cultural politics of the era, places the paintings in historical context, and analyzes the stylistic changes and international sources Arango employed to visualize the abuse of power. The undated watercolor Gaitán (by 1948), which portrays the politician speaking to a vast, enthusiastic crowd, is the only political painting she ever created that does not criticize its subject. After Gaitán’s murder she switched to a more expressionistic visual language to condemn the violence that followed, first in Masacre del 9 de abril, then in three paintings that depict the transport of rebels in railroad boxcars in ways that evoke the Holocaust. The five images are the matrix from which her incisive political satire of the 1950s evolved.

Abstract The Gratitude Train was sent from France to America in 1949. Conceived as a ‘thank you’ for American help during and after the world wars, it contained 52,000 personal objects chosen and donated by French people who wanted to express their gratitude to Americans. The objects were divided between forty-nine boxcars, and each state received one of these boxcars containing approximately 1000 objects. What where these objects? Who sent them? Why have they been forgotten? Why do they matter? This article is interested not only in the story of the Gratitude Train, but in the stories within the objects themselves. By closely analysing a porcelain dog, a silver spoon and a painting, it traces the longer life biographies and trajectories of these objects and uncovers a range of both intended and unintended emotions as well as meanings, be they collective or individual. The unique and almost completely unknown Gratitude Train collection offers valuable inroads into our understanding of the relationship between objects, emotions and international relations, as well as into the materiality of gratitude at the heart of the age of extremes.

Two-dimensional electronic spectroscopy (2DES) can be implemented with different geometries, e.g., BOXCARS, collinear, and pump–probe geometries. The pump–probe geometry has the advantage of overlapping only two beams and reducing phase cycling steps. However, its applications are typically limited to observing the dynamics with single-quantum coherence and population, leaving the challenge to measure the dynamics of the double-quantum (2Q) coherence, which reflects the many-body interactions. We demonstrate an experimental technique in 2DES under pump–probe geometry with a designed pulse sequence and the signal processing method to extract 2Q coherence. In the designed pulse sequence, with the probe pulse arriving earlier than the pump pulses, our measured signal includes the 2Q signal as well as the zero-quantum signal. With phase cycling and data processing using causality enforcement, we extract the 2Q signal. The proposal is demonstrated with rubidium atoms. We observe the collective resonances of two-body dipole–dipole interactions in both the D1 and D2 lines.

Installations of artificial structures in coastal oceans create de facto habitat for marine life. These structures encompass wide varieties of physical characteristics, reflecting their multiple, diverse purposes and creating a need to understand which characteristics maximize fish habitat. Here, we test how physical characteristics – horizontal area, vertical relief, and spatial isolation – relate to fish density from echosounder surveys over artificial structures like concrete pipes, train boxcars, and ships purposely sunk to function as reefs. Echosounder mapping of 31 artificial reef structures and associated fish across a 200 km linear length of the continental shelf of North Carolina, USA, revealed that structures with greater horizontal area and vertical relief host higher fish densities than smaller, shorter structures. Artificial structure spatial arrangement also relates to fish density, as isolated structures are generally associated with greater localized fish densities than structures closer to one another. Patterns in the relationships between fish density and reef characteristics differed for schooling fish, as there was some evidence that reefs of intermediate area exhibited higher schooling fish density. These results suggest that intentional design and spatial arrangement of marine built structures like artificial reefs relates to and can be deliberately incorporated into siting and deployment decisions to enhance their role as fish habitat.

Landing in the Midwest after a lifetime in Los Angeles, I was shocked to learn how “famous” that great city really is. It used to seem perfectly reasonable that the freeways on CHiPs looked just like the ones I rode to school. When I was five, I remember being secretly bummed that my mom never took us to the disco-classical mural from Xanadu, which I was convinced had to be hidden somewhere in Venice Beach. In high school, it never seemed strange that the Peach Pit on Beverly Hills 90210 was the same as the Rose City Diner. From the L.A. River to the Griffith Park Observatory, from the Hollywood Sign to Venice Beach, the places I had been in, through, and around were inscribed with meanings in ways that I could never fully grasp. Even marginalized localities like Inglewood, Compton, and East L.A., which especially during the 1980s and early 1990s were being ravaged by urban warfare, got to be the stars of movies, songs, and many music videos. And on April 29, 1992, the corner of Florence and Normandie “blew up” into a full blown riot, sparked by the acquittal of the four white officers who beat black motorist, Rodney King. I could watch the city burn on T.V. or from the hill behind my house. All my life, I lived with a foot in each L.A., the one that’s outside my living room and the one that’s inside my living room, oblivious to the fact that I lived in a famous city. It was only after I moved away from L.A. that I realized my homesickness could often be softened by a click of the remote. I could look for a familiar stretch of road, a bit of the skyline, or a clean but otherwise familiar segment of sidewalk, and it didn’t even matter who, what, where, or why was taking place in the story on screen. It was as though fragments of my life had been archived for me in media space. Some memories were real and some just recollections of other representations – like seeing the observatory in Bowfinger and wondering if I was remembering Rebel Without a Cause or a second grade field trip. But when I arrived here, the question that greeted me most often at parties was, “Why are you in Bowling Green!?!” And the second was, “Did you meet any famous people?” And so I tell them about how I went to driver’s education class with Mayim Byalik, the star of Blossom. Or that I met Annette Funicello one New Year’s Eve at my Uncle Phil’s house. Aside from the occasional queer chuckle about my brush with Blossom, this record is unimpressive. People are hoping for something a little bit more like, “I spent the night in jail with Poison,” “I was an extra on Baywatch,” or “I was at the Viper Room the night River Phoenix passed away.” In spite of my lackluster record of interactions with the rich and the famous, I would still get introduced as being “from California.” I had become the recipient of a second-rate, secondhand fame, noted for being from a place where, if I were more ambitious, I could have really rubbed shoulders with famous people. To young people, many of whom were itching to travel to a place like LA or New York, I was a special kind of failure. But if you aren’t famous, if you are a loser like me, life in L.A. isn’t about the a-list at all. It is about living in a city that captures the imagination, even as you walk down the street. So earning notoriety in a city that speaks in spectacle is an exercise in creativity. It seems like everybody, even the most down-to-earth people, are invested in developing a character, an image, a persona that can bubble up and be noticed in spite of the overwhelming glow of Hollywood. Even at my suburban high school, during the late 1980s and early 1990s, I knew upper-middleclass boys who got nose jobs and manicures. I knew girls who would go trolling for rich men to buy them pretty things that their parents couldn’t afford. There were kids whose parents helped them cheat their way into college. There were wannabe junkies who drove their moms’ minivans into the ghetto to score. I saw people panic, pout, and scream over cars and allowances and shoes. I know that consumer culture is growing stronger just about everywhere, but back home it happened a lot sooner and a lot stronger. Because of our proximity to Hollywood, the crest of the cultural tidal wave looks much higher and its force is much stronger. And I guess I was just too fat to be in California, so I left. However, every once in a while, somebody does manage to make a scene in L.A. A little loser, or whatever you want to call one of the peasants who tend to the vast fiefdoms of L.A.’s elites, rises from banality to achieve celebrity, even if it is a minor celebrity, in the City of Angels. One such figure is the notorious Daniel Ramos, who in 1991 became a central figure in the city’s struggle over its own image. Daniel Ramos was not a star, a politician, or a leader of industry – but before he even appeared in the news, he had trafficked illegally in making a name for himself. A teenager from the projects, Ramos was more widely known as “Chaka,” a graffiti writer credited with over 10,000 tags from San Diego to San Francisco. I had seen Chaka’s tags just about everywhere, and had determined that he might be superhuman. His name, taken after a hairy little missing link from the popular fantasy show, The Land of the Lost, made me smirk as it conjured up images of a sub-humanoid with broken dialect creeping out from the darkness with cans of paint, marking the walls with his sign, calling out to the rest of us half-humans stranded in the land of the lost. Meanwhile, L.A.’s rich and famous whizzed by, casting resentful glances at Chaka’s do-it-yourself media blitz. I knew that Chaka was “bad,” but my imagination loved him. And when he allegedly left his mark in the courthouse elevator on the day of his release from a five-month stretch in prison (Costello), I couldn’t help but feel glad to know that Chaka was still alive, that legends don’t die (his name even made it, through the hand of Dave Grohl, into Nirvana’s “Smells Like Teen Spirit Video” in 1991). For me, and I imagine for many others, it was the beginning of a political awakening. I wondered what was so bad about graffiti, even though I had been taught all my life that it was wrong. More than ten years later, as I sit by the railroad tracks in my small, Midwestern town, eagerly waiting for messages from California painted on the sides of boxcars, I find myself asking a related question – what is good about advertising? I’m not the first to make the welcomed association between graffiti and advertising. In an interview with the vastly capable scholar, Joe Austin, New York graffiti legend IZ THE WIZ explained it thusly: OK, now you’re on a poorer economic level and what do you have? Years ago, and even today, a boxer makes a name for himself in the boxing ring. So when this art form starts developing, why would it be any different? It’s all in the name. When you’re poor, that’s all you got. (40) Austin elaborates on this insight, explaining: The proliferation of posters, advertisements, and signs bearing the images and names of products and proprietors in twentieth-century cities is one obvious place to begin. These are the directly visible extensions of individual/corporate identities into the new shared urban public spaces of the streets, a quantitatively and qualitatively new site in human history where hundreds of thousands of often spectacularly displayed names abound, each catching the eyes of potential consumers and imprinting itself on their memories. (39) So, on one level, the story of Chaka is the story of a poor man who went toe to toe with big media, in a town run by big media, and held his own. It is the story of someone who has managed to say in no insignificant way, “I am here.” Or has Ramos himself yelled as he was being shackled by police, “I am the famous ‘Chaka’” (Walker A4). In spite of everything else, Ramos had a name that was widely recognized, respected by some, reviled by others. Nancy Macdonald, in her important study the culture of writing, shifts the focus away from the more solidly class-based argument employed by Austin in his study of the origins of New York graffiti art to one which lends itself more readily to understanding the culture of writing in the 1990s, after hip hop had become more accessible to middleclass enthusiasts. Macdonald explains, “Writers use the respect and recognition of their peers to validate their masculine identities” (124). While I am reluctant to downplay the class struggle that certainly seems to have implicitly informed Chaka’s quest for recognition, his outlaw appeal lends itself such an interpretation. In a city like Los Angeles, where middle class agency and upward mobility for the service class are not simply functions of wealth, but also of scrupulously maintained images, feelings of powerlessness associated with the lack of a compelling image are to be expected. It is the engine that drives the exuberant extravagance of consumer culture, lifestyle choices, and ultimately biopolitics. In a society where culture and capital are the dual poles which determine one’s social standing, the pursuit of notoriety is not simply a measure of masculinity – hijacking images is a way to assert one’s agency in spite of the diminished value of unskilled labor and the collective fear of underclass masculinities. In her book Wallbangin’: Graffiti and Gangs in L.A., Susan A. Philips provides discussion of Chaka’s contribution to L.A. graffiti. Notably, Chaka was seen by those in the graffiti community as an everyman, who was responsible for two significant cultural achievements: he “open[ed] up the style of the New York-based tags and creat[ed] the phenomenon of the individual tagger” (Phillips 320). He also, as Phillips notes, “wrote tags that you could read…in blockish gang-type lettering” (320). Unlike his New York graffiti-writing peers, which are best known for their beautiful “wildstyle,” Chaka did not typically traffic in multicolor murals and displays of painterly virtuosity. His chief accomplishment was his cunning pervasiveness and daring criminality. As such, his body of work should be seen as incompatible with High Art attempts to bring collectible graffiti into gallery spaces through the 1980s and ‘90s. Chaka’s medium, in a sense, has less to do with paint, than it has to do with the city and its rules. For the majority of the public, Chaka was seen as an individual face for the graffiti pandemic that was strategically linked in the public mind with specter of gang violence. However, to those familiar with the writing scene in L.A., Chaka is more than a lone individual: THE OG’Z OF THE LEGION OF DOOM WERE THE ONE RESPONSIBLE FOR BRINGING THE EARLY LOS ANGELES GRAFFITI SCENE TO IT’S KNEES! AND GAVE US MOST OF THE LEGENDS WE KNOW TODAY! I REMEMBER I TIME WHEN EVERY LOS ANGELES INTERSTATE HEAVEN ROCKED BY EITHER LEST-CAB-STANS-SUB OR THE CHAKA!!! (god i miss those days!) remember the CAB undercover story on the news where he did those loks on dope throwies on the 110 pasadena? I think it was chuck henry channel 7 ??? does anyone still have that on vhs? i had it on vhs along with the CHAKA PUBLIC SERVICE ANOUNCEMENT (that was great!). (Poncho1DEcrew) Instead of being an individual tagger, Chaka is recognized as a member of a crew (LOD), who managed to get up in legendary ways. In reclaiming freeway overpasses (the “Heavens”), walls, trains, road signs, and just about everything else for his crew, vicariously for the many other people who respect his name, and also for himself, Chaka is more than simply selfish, as is often suggested by his detractors. In the heavens is the right place to begin. High up in the sky, over the freeways, for all to see, the writing in the heavens is visible, mysterious, and ultimately risky. The problem of climbing along the girders underneath the bridges, escaping detection, but leaving something bold points to what distinguishes writing from an ad-campaign. Sure, some of what the tagger does is about simply being a recognized image all over the place. But the other part is about finding the place, working within environmental constraints, battling against time, stretching one’s limits, and doing it with style. While the image may be everywhere, the act of writing itself is a singularity, shrouded by secrecy, and defined by the moment of its doing. The aftereffect is a puzzle. And in the case of Chaka, the question is, “How the hell did this guy get up over 10,000 times?” While I can’t see how he did it and I don’t know where, exactly, he got all that paint, I do know one thing: Chaka went everywhere. He mapped the city out as a series of landmarks, he put his name to the space, and he claimed Los Angeles for people other than the ones who claim to own the rights to beam their generalized and monolithic messages into our living rooms. Instead of archiving the city in the banalities of mass media, he has created an archive of an alternative L.A., filled with singularities, and famous in the way that only one’s hometown can be. Instead of being a celebrity, renowned by virtue of a moderately unique character, his ability to generate money, and an elite image, Chaka represents an alternative fame. As a modern day “everyman” and folk hero, he brings a message that the city belongs to all people. Far from the naïve and mean-spirited equations between graffiti writing and canine scent-marking as a primitive drive to mark territorial boundaries with undesirable substances (writers:paint::dogs:piss), Chaka’s all-city message is not so much a practice of creating exclusionary spaces as it is an assertion of one’s identity in a particular space. A postmodern pilgrim, Chaka has marked his progress through the city leaving a perceptible record of his everyday experience, and opening up that possibility for others. This is not to say that it is necessary for all people to paint in order to break loose from the semiotic order of the city, it is only to say that is hopeful to realize that this order is not fixed and that is not even necessarily our own. Reflecting back on my own experience as one who has grown up very much in love in the produced spaces of the scripted and archived fame of Los Angeles, the realization that such an overwhelming place is open even to my own inscriptions is an important one. This realization, which has been many years in the making, was set into place by the curious fame of Chaka. For a writer and scholar disturbed by the “death of the author,” it comes as a relief to see writing resurrected in the anti-authoritarian practice of a teenage boy from the projects. References Austin, Joe. Taking the Train: How Graffiti Art Became an Urban Crisis in New York City. New York: Columbia UP, 2001. Costello, D. “Writing Was on the Wall.” Courier-Mail 9 May 1991. Macdonald, Nancy. The Graffiti Subculture: Youth, Masculinity and Identity in London and New York. Hampshire: Palgrave, 2001. Phillips, Susan A. Wallbangin’: Graffiti and Gangs in L.A. Chicago: U of Chicago P, 1999. Poncho1DEcrew. 50mm Los Angeles Forum. 18 June 2004. 11 July 2004 http://www.50mmlosangeles.com/>. Walker, Jill. “Letter from the Streets; Handwriting on the Wall: 10,000 Chakas.” Washington Post 4 May 1991: A4. Citation reference for this article MLA Style Heckman, Davin. "Being in the Shadow of Hollywood: Celebrity, Banality, and the Infamous Chaka." M/C Journal 7.5 (2004). echo date('d M. Y'); ?> <http://journal.media-culture.org.au/0411/12-heckman.php>. APA Style Heckman, D. (Nov. 2004) "Being in the Shadow of Hollywood: Celebrity, Banality, and the Infamous Chaka," M/C Journal, 7(5). Retrieved echo date('d M. Y'); ?> from <http://journal.media-culture.org.au/0411/12-heckman.php>.