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The paper aims to introduce the fabrication of a medium steel aircraft part by hybrid deposition and micro-rolling technology (HDMR) and illustrate its advantages, microstructure features and mechanical properties of the part.

The HDMR technology contains two procedures happening almost at the same time: the welding deposition procedure and then the micro-rolling procedure. It takes the gas metal arc welding as the heat source to melt a metal wire and deposit metal in the welding deposition procedure. The metal just deposited is rolled synchronously by a micro roller following the welding torch in micro-rolling procedure almost at the same time layer by layer. The paper presents a contrast of the grain morphology of metal parts produced respectively by HDMR and freedom arc deposition (FAD) and the mechanical properties of metal parts of the same metal from HDMR casting, forging and FAD methods.

HDMR breaks the dendrite grain of welding beads into the fine crisscross grains. The mechanical properties of metal parts are improved distinctly by the micro-rolling procedure compared to casting, forging and FAD.

In addition, the application of HDMR technology has succeeded in the fabrication of an eligible aircraft metal part, which is quite difficult to achieve using other additive manufacturing (AM) or casting technologies.

HDMR has the advantage of equiponderance manufacturing by micro-rolling compared to other AM technologies. The metal part fabricated by HDMR technology obtains the fine crisscross grains and brings hope for AM metal components with excellent mechanical properties for aircraft applications.

This paper aims to study the effect of laser energy on the formability, microstructure and mechanical properties of AZ61D alloy to assist systematic study of laser additive manufacturing of magnesium alloys.

In this study, porous magnesium alloy samples were prepared by using different laser parameters. The changes of the formability and microstructure were observed by SEM, and the mechanical properties were tested. The above results were analyzed to obtain optimized laser parameters.

When the laser power is between 85 and 95 W (pulse width 3.0 ms, frequency 40 Hz), the surface morphology of the selective laser-melted (SLMed) porous samples are smooth and even. At 80 W, SLMed porous samples have a maximum relative density of 99.2 per cent. Because of the “solute capture” effect and the evaporization of magnesium, the fraction of ß-Mg17Al12 increases from 42.1 to 52.1 per cent when power rises from 80 to 105 W. The ultimate compressive strength of SLMed porous magnesium alloys is strengthened with the increase of laser power.

The effect of laser parameters on microstructure and mechanical properties of porous magnesium alloys prepared by SLM has not been reported.

This paper aims to analyze the different between matrix and overhanging structure and indicate the laws and mechanism of overhanging structure formed by selective laser melting (SLM).

This paper includes processing the matrix and overhanging structure with optimized parameters and analyzing the microstructure and properties of matrix and overhanging with OM, SEM, XRD etc. so as to analyze and reveal the laws and mechanism of overhanging structure formed by SLM.

The solidification of overhanging structure begins from the structure’s edge and extends to its center; the distribution of the Cr with a diameter of 250 nm in the Fe matrix is uniform; the grain in the overhanging structure is growing faster than the grain in the matrix. The overhanging structure mainly composed by austenite has no apparent layer. Moreover, the microhardness of the overhanging structure is 258.6-294.0 Hv0.3, smaller than the microhardness of the matrix which is 236.4-300.9 Hv0.3.

This paper clarifies how to manufacture overhanging structure and non-overhanging structure matrix with optimized parameters, analyzes the microstructures and compares the properties of both overhanging structure and non-overhanging structure “matrix”, so as to analyze the reasons for the forming of the overhanging structure, which in turn lauds basic data foundation for the theoretical studies in the future.

This paper aims to systematically investigate the effect of the heat treatment process parameters on the microstructure and mechanical properties of the selective laser melting (SLM) AlSi10Mg alloy.

The samples with very low porosity were fabricated with optimized processing parameters on a self-developed SLM system. The heat treatment of using the temperature of 170°C∼400°C and the holding time of 0.5∼12 h was studied, and the evolution of the microstructure and mechanical properties of AlSi10Mg alloy under direct aging and annealing was investigated and obtained.

After annealing above 300°C for 1 h, the dendrite Si in the sample occurs spheroidization, and the molten pool contour becomes blurred or even disappeared completely, but low-temperature heat treatment does not change the morphology and size of grains significantly. Except for holding at 200°C for 1 h, all other heat treatment processes cause the tensile and yield strengths of SLM AlSi10Mg alloys to decrease and the elongation to increase. When the annealing temperature is higher than 200°C, the higher the temperature and the longer the holding time, the more obvious this effect is.

The correlation between the mechanical properties and microstructure of SLM AlSi10Mg alloy under different conditions was obtained. According to the characteristics of SLM forming, the direct aging and annealing process are mainly studied, which provided new information for the heat treatment of SLM AlSi10Mg alloy and promoted the engineering application of SLM AlSi10Mg alloy.

Using visual materials to understand a social object requires the researcher to know that object's purpose, and this is true whether the object is an artifact, a restricted event, a small social world, or something as massive as the modern city. I argue that the purpose of the city as a settlement is driven by the need to safely sleep in peace at night while satisfying other basic biophysical needs during the day as conveniently as possible. An examination of these needs identifies 10 functional prerequisites for human settlement, entangling its inhabitants in involuntary community with entities and events other than themselves, whether they like it or not. In addition, the rise of the modern city exacerbates the challenge of living in a reluctant community and pressures its inhabitants to come to terms with the consequences for how these relationships affect daily life. I highlight nine challenges posed as questions that have been particularly salient in American urban history since the mid-nineteenth century. How these challenges have been addressed indicates not only what it takes to make a modern city a settlement suitable for satisfying human needs, but also just how deeply invested its residents are in making the city work. Finally, the 10 functional prerequisites and nine moral challenges not only provide a framework for researching the city, but also suggest a coherent outline for imagining a “shooting script” or guide for conducting visual research.

An on-line professional development environment, Knowledge Networks On the Web (KNOW), is described as an example of how on-line video can be employed in support of teacher learning in systemic reform contexts. The design of KNOW is founded on the notion that teacher learning is most effective when it can be linked directly to the classroom enactment of curriculum, and when it can leverage the knowledge of a community of teachers. A conceptual model of teacher learning and a model for conducting research based on that model are described to explain how teacher learning from the use of KNOW can be linked to student learning to improve overall system design.

The study is carried out to analytically reconnoiter geotechnical index properties of subgrade soils as key variables that shape the cost profile of road infrastructure projects in a tropical geographic setting with starkly heterogenous ground conditions.

Using the Niger Delta region, as a point of reference, data on geotechnical index properties of subgrade soils at spatially dispersed locations for 61 completed highway projects are collated. Exploratory statistical tests were carried out to infer significant associations with final project costs before regression analysis. Regression analysis is principally deployed as an explanatory analytical tool, relevant to quantify the sensitivity of highway project costs to the individual and collective impact of geotechnical variables.

Several parameters of expansivity and compressibility exhibited significantly strong associations with the final costs recorded on the highway projects. The statistical analysis further established a cause-effect relationship, whereby small changes in the geotechnical properties of sub-grade soils at project locations, would result in disproportionately large changes in the cost of road construction.

The study findings provide insight into the sensitivity of road construction costs to geotechnical variables, which can serve as a useful input in financial risk analysis for development appraisal and the generation of location adjustment factors.

The study statistically demonstrates location-induced construction cost profiles, triggered in response to the spatial geotechnical variability and occurrence of problem subgrade soils in the humid tropics, which may be different from those traditionally established in studies of cold and temperate climate soils.

This research makes a fresh contribution by exploring an understudied aspect of the Tropicália movement: visual performance. After offering a historical overview, we examine the movement’s communicative legacy. We contend that, in addition to song’s lyrics and musical symbols, it is vital to consider a third dimension: visual performance.

The addition of the visual allows for a more fundamental understanding of the many complex meanings that the Tropicalistas constructed in their resistance to political oppression, as well as broader cultural mores and expectations.

Our examination of archival performance videos reveals that Tropicalistas employed modes of dress and a specific, intentional orientation toward their listeners as particularly powerful tools of expression. Revealing these two dimensions of Tropicália performance allows us to better understand the importance of performance as a key element of resistance. The Tropicália movement’s performative reconfigurations of self and other became a vital channel through which the Tropicalistas manage to speak truth to power to challenge the oppressive military regime and question assumptions about Brazilian national identity.

Exploring the role of performance as part of the overall meaning of musical expression opens up new vistas of understanding. While relevant to Tropicália as a pivotal and wholly Brazilian artistic movement, the contributions of this study have implications beyond this particular setting. The analytical approach reveals how artistic movements can serve as both the substance and the expression of national being.

Current news on environmental problems frequently emphasizes the totally unprecedented nature of the ecological crises that beset us in this nation and the Western world as a whole. We are told, for example, that the summer of 1988 constituted “the hottest summer on record” in North America. Similarly we hear mat Boston Harbor has never in its history been so polluted, and in European waters seal populations died of an epidemic in 1988 on a scale never before witnessed by man. By stressing this “never before” aspect of events, it is sometimes argued mat the experience of the past is largely irrelevant for policy planners. Since our circumstances are new, so the argument runs, past experience leaves us with little or no instruction for the formulation of a practical public policy for the environment.