A review of progressive collapse research and regulations

History has demonstrated that buildings designed to conventional design codes can lack the robustness necessary to withstand localised damage, partial or even complete collapse. This variable performance has led governmental organisations to seek ways of ensuring all buildings of significant size possess a minimum level of robustness. The research community has responded by advancing understanding of how structures behave when subjected to localised damage. Regulations and design recommendations have been developed to help ensure more consistent resilience in all framed buildings of significant size, and rigorous design approaches have been specified for buildings deemed potentially vulnerable to extreme loading events. This paper summarises some of the more important progressive collapse events, to identify key attributes that lead to vulnerability to collapse. Current procedures and guidelines for ensuring a minimum level of performance are reviewed and modelling methods for structures subjected to localised damage are described. These include increasingly sophisticated progressive collapse analysis procedures, including linear static and non-linear static analysis, as well as non-linear static pushover and linear dynamic methods. Finally, fully non-linear dynamic methods are considered. Building connections potentially represent the most vulnerable structural elements in steel-framed buildings; their failure can lead to progressive collapses. Steel connections also present difficulties with respect to frame modelling and this paper highlights benefits and drawbacks of some modelling procedures with respect to their treatment of connections

Ideology, Hegemony, Discourse: A Critical Review of Theories of Knowledge and Power

For over a century, social theorists have attempted to explain why those who lack economic power consent to hierarchies of social and political power. They have used ideology, hegemony and discourse as key concepts to explain the intersections between the social production of knowledge and the perpetuation of power relations. The Marxist concept of ideology describes how the dominant ideas within a given society reflect the interests of a ruling economic class. In this paper, I trace the movement from this concept of ideology to models of hegemony and discourse. I then trace a second set of ruptures in theories of ideology, hegemony and discourse. Marx and others link ideology to a vision of society dominated by economic class as a field of social power. However, theorists of gender and race have questioned the place of class as the locus of power. I conclude by arguing that key theorists of gender and race Hall, Smith, hooks and Haraway offer a more complex understanding of how our consent to networks of power is produced within contemporary capitalist societies. This argument has important implications for theory and practice directed at destabilizing our consent to power

Method to Automatically Register Scattered Point Clouds Based on Principal Pose Estimation

Three dimensional (3-D) modeling is important in applications ranging from manufacturing to entertainment. Multiview registration is one of the crucial steps in 3-D model construction. The automatic establishment of correspondences between overlapping views, without any known initial information, is the main challenge in point clouds registration. An automatic registration algorithm is proposed to solve the registration problem of rigid, unordered, scattered point clouds. This approach is especially suitable for registering datasets that are lacking in features or texture. In general, the existing techniques exhibit significant limitations in the registration of these types of point cloud data. The presented method automatically determines the best coarse registration results by exploiting the statistical technique principal component analysis and outputs translation matrices as the initial estimation for fine registration. Then, the translation matrices obtained from coarse registration algorithms are used to update the original point cloud and the optimal translation matrices are solved using an iterative algorithm. Experimental results show that the proposed algorithm is time efficient and accurate, even if the point clouds are partially overlapped and containing large missing regions

Bulletin No. 364 - The Halogeton Problem in Utah

Halogeton (Halogeton glomeratus) although introduced into Utah only 20 years ago, has spread widely on the west desert and into extensive areas on the east desert. This plant has become the most feared poisonous plant in the state because people have been lead to believe that it would limit livestock production to areas kept free of the weed

Public Engagement in Climate Communication on China’s Weibo: Network Structure and Information Flows

This article provides an empirical study of public engagement with climate change discourse in China by analysing how Chinese publics participate in the public discussion around two Intergovernmental Panel on Climate Change reports and how individual users interact with state and elite actors on the pre-eminent Chinese microblogging platform Weibo. Using social network analysis methods and a temporal comparison, we examine the structure of climate communication networks, the direction of information flows among multiple types of Weibo users, and the changes in information diffusion patterns between the pre- and post-Paris periods. Our results show there is an increasing yet constrained form of public engagement in climate communication on Weibo alongside China’s pro-environmental transition in recent years. We find an expansion of public engagement as shown by individual users’ increasing influence in communication networks and the diversification of frames associated with climate change discourse. However, we also find three restrictive interaction tendencies that limit Weibo’s potential to facilitate multi-directional communication and open public deliberation of climate change, including the decline of mutually balanced dialogic interactions, the lack of bottom-up information flows, and the reinforcement of homophily tendencies amongst eco-insiders and governmental users. These findings highlight the coexistence of both opportunities and constraints of Weibo being a venue for public engagement with climate communication and as a forum for a new climate politics and citizen participation in China

Design and Synthesis of Nonequilibrium Systems

The active transport of ions and molecules across cell membranes is essential to creating the concentration gradients that sustain life in all living organisms, be they bacteria, fungi, plants, animals or Homo sapiens. Nature uses active transport everywhere for everything. Molecular biologists have long been attracted to the study of active transport and continue to this day to investigate and elucidate the tertiary structures of the complex motor proteins that sustain it, while physicists, interested in nonequilibrium statistical mechanics, have developed theoretical models to describe the driven ratcheting motions that are crucial to its function. The increasingly detailed understanding that contemporary science has acquired relating to active transport, however, has yet to lead to the design and construction of artificial molecular motors capable of employing ratchet-driven motions that can also perform work against concentration gradients. Mechanically interlocked molecules (MIMs) in the form of pseudo- and semirotaxanes are showing some encouraging signs in meeting these goals. This review summarizes recent progress in making artificial molecular motors that can perform work by “pumping” tetracationic rings into high-energy states. The launching pad is a bistable [2]rotaxane whose dumbbell component contains two electron-donating recognition sites, one, a tetrathiafulvalene (TTF) unit, which interacts more strongly with the ring component, cyclobis(paraquat-p-phenylene) (CBPQT4+), containing two electron-accepting bipyridinium units, than does the other 1,5-dioxynaphthalene (DNP) unit. Switching can be induced electrochemically by oxidizing the TTF unit to a TTF•+ radical cation, whereupon Coulombic repulsion takes care of moving the ring to the DNP unit. Reduction of the radical cation resets the switch. Molecular switches operate at, or close to, equilibrium. Any work done during one switching event is undone during the reset. Molecular motors, on the other hand, rely on a flux of energy, and a ratchet mechanism to make periodic changes to the potential energy surface of a system in order to move molecules uphill to higher energy states. Forging a path from molecular switches to motors involved designing a molecular pump prototype. An asymmetric dumbbell with a 2-isopropylphenyl (neutral) end and a 3,5-dimethylpyridinium (charged) end with a DNP recognition site to entice CBPQT4+ rings out of solution exhibits relative unidirectional movement of the rings with respect to the dumbbell. Redox chemistry does the trick. During the oxidative cycle, the rings enter the dumbbell by passing over the neutral end onto the recognition site; in the reduction cycle, much of the recognition is lost and the rings find their way back into solution by leaving the dumbbell from the charged end. This on-one-end, off-the-other process can be repeated over and over again using light as the energy source in the presence of a photosensitizer and a compound that shuttles electrons back and forth. Although this prototype demonstrates ratchet-driven translational motion, no work is done. A ring enters the dumbbell from one end and leaves from the other end. Another deficiency of the prototype is the fact that, although the recognition site is muted on reduction, it retains some attraction for the ring. What if the recognition site was attractive initially and then became repulsive? This question was answered by turning to radical chemistry and employing the known stabilization behavior of a bipyridinium radical cation and the bisradical dication, generated on reduction of the CBPQT4+ ring, to pluck rings out of solution and thread them over the charged end of the pump portion of a semidumbbell. On subsequent oxidation, the pump is primed and the rings pass through a one-way door, given a little thermal energy, onto a collecting-chain where they find themselves accumulating where they would rather not be present. In this manner, an artificial molecular pump mimics the pumping machinery commonplace in biological systems. Looking beyond this state-of-the-art artificial molecular pump, we discuss, from a theoretical standpoint, the measures that would need to be taken in order to render its operation autonomous

Media Coverage and Perceived Policy Influence of Environmental Actors: Good Strategy or Pyrrhic Victory?

In this article we analyze how media coverage for environmental actors (individual environmental activists and environmental movement organizations) is associated with their perceived policy influence in Canadian climate change policy networks. We conceptualize media coverage as the total number of media mentions an actor received in Canada’s two main national newspapers—the Globe and Mail and National Post. We conceptualize perceived policy influence as the total number of times an actor was nominated by other actors in a policy network as being perceived to be influential in domestic climate change policy making in Canada. Literature from the field of social movements, agenda setting, and policy networks suggests that environmental actors who garner more media coverage should be perceived as more influential in policy networks than actors who garner less coverage. We assess support for this main hypothesis in two ways. First, we analyze how actor attributes (such as the type of actor) are associated with the amount of media coverage an actor receives. Second, we evaluate whether being an environmental actor shapes the association between media coverage and perceived policy influence. We find a negative association between media coverage and perceived policy influence for individual activists, but not for environmental movement organizations. This case raises fundamental theoretical questions about the nature of relations between media and policy spheres, and the efficacy of media for signaling and mobilizing policy influence

Do neighbourhood environmental perceptions affect practices?

In this paper, we examine how environmental practices related to public transit and urban green space use are influenced by perceptions of local level environmental change, neighbourhood inhabitation, and socio-demographic factors. The analysis shows that perceptions of change and neighbourhood inhabitation offer better explanations for changing local environmental practices than socio-demographic orientations. We contribute to social practice theory by drawing attention to the interplay of environmental perceptions and neighbourhood inhabitation as factors that facilitate changing environmental practices. By gaining insight into the relationship between perceptions of change and environmental practices, we thereby learn how sustainability goals, such as those embodied by SDG11, can be translated into social practices at the community level.Dans cet article, nous examinons comment les pratiques environnementales liées au transport en commun et à l’utilisation des espaces verts urbains sont influencées par les perceptions du changement environnemental au niveau local, l’habitation des quartiers et les facteurs sociodémographiques. L’analyse montre que les perceptions du changement et de l’habitat du quartier offrent de meilleures explications pour l’évolution des pratiques environnementales locales que les orientations sociodémographiques. Nous contribuons è la théorie de la pratique sociale en attirant l’attention sur l’interaction des perceptions environnementales et de l’habitation du quartier en tant que facteurs qui facilitent l’évolution des pratiques environnementales. En acquérant un aperçu de la relation entre les perceptions du changement et les pratiques environnementales, nous apprenons ainsi comment les objectifs de durabilité, tels que ceux incarnées par ODD (Agenda 2030 du développement durable), peuvent être traduits en pratiques sociales au niveau communautaire

Bulletin No. 385 - Comparitive Nutritive Value and Palatability of Some Introduced and Native Forage Plants for Spring and Summer Grazing

From 1952 to 1954 studies were conducted on foothill ranges of central Utah to determine the forage production, palatability, and nutritive value of some of the more important native and introduced species used for spring and summer grazing. Plants studied were four introduced wheatgrasses (crested, tall, pubescent, and intermediate) , four native grasses (western wheatgrass, beardless wheatgrass, squirreltail grass, and Indian ricegrass), and two introduced annual forbs (Russian-thistle, and smother weed). Field digestibility trials were conducted to determine the nutrient content by the lignin-ratio technique. In addition, both sheep and cattle preferences were studied on areas where both introduced and native species were planted