Packings of 3D stars: stability and structure

© 2016, Springer-Verlag Berlin Heidelberg.We describe a series of experiments involving the creation of cylindrical packings of star-shaped particles, and an exploration of the stability of these packings. The stars cover a broad range of arm sizes and frictional properties. We carried out three different kinds of experiments, all of which involve columns that are prepared by raining star particles one-by-one into hollow cylinders. As an additional part of the protocol, we sometimes vibrated the column before removing the confining cylinder. We rate stability in terms of r, the ratio of the mass of particles that fall off a pile when it collapsed, to the total particle mass. The first experiment involved the intrinsic stability of the column when the confining cylinder was removed. The second kind of experiment involved adding a uniform load to the top of the column, and then determining the collapse properties. A third experiment involved testing stability to tipping of the piles. We find a stability diagram relating the pile height, h, versus pile diameter, (Formula presented.) , where the stable and unstable regimes are separated by a boundary that is roughly a power-law in h versus (Formula presented.) with an exponent that is less than unity. Increasing vibration and friction, particularly the latter, both tend to stabilize piles, while increasing particle size can destabilize the system under certain conditions

A low noise 410-495 heterodyne two tuner mixer, using submicron Nb/Al2O3/Nb tunneljunctions

A 410-495 GHz heterodyne receiver, with an array of two Nb/Al2O3/Nb tunneljunctions as mixing element is described. The noise temperature of this receiver is below 230 K (DSB) over the whole frequency range, and has lowest values of 160 K in the 435-460 GHz range. The calculated DSB mixergain over the whole frequency range varies from -11.9 plus or minus 0.6 dB to -12.6 plus or minus 0.6 dB and the mixer noise is 90 plus or minus 30 K

Comparison of measured and predicted performance of a SIS waveguide mixer at 345 GHz

The measured gain and noise of a SIS waveguide mixer at 345 GHz have been compared with theoretical values, calculated from the quantum mixer theory using a three port model. As a mixing element, we use a series array of two Nb-Al2O3-Nb SIS junctions. The area of each junction is 0.8 sq microns and the normal state resistance is 52 omega. The embedding impedance of the mixer has been determined from the pumped DC-IV curves of the junction and is compared to results from scale model measurements (105 x). Good agreement was obtained. The measured mixer gain, however, is a factor of 0.45 plus or minus 0.5 lower than the theoretical predicted gain. The measured mixer noise temperature is a factor of 4-5 higher than the calculated one. These discrepancies are independent on pump power and are valid for a broad range of tuning conditions

Functionally Graded Aggregate Structures: Digital Additive Manufacturing with Designed Granulates

In recent years, loose granulates have come to be investigated as architectural systems in their own right. They are defined as large numbers of elements in loose contact, which continuously reconfigure into variant stable states. In nature they are observed in systems like sand or snow. In architecture, however, they were previously known only from rare vernacular examples and geoengineering projects, and are only now being researched for their innate material potentials. Their relevance for architecture lies in being entirely reconfigurable and in allowing for structures that are functionally graded on a macro level. Hence they are a very relevant yet unexplored field within architectural design. The research presented here is focused on the potential of working with designed granulates, which are aggregates where the individual particles are designed to accomplish a specific architectural effect. Combining these with the use of a computer-controlled emitter-head, the process of pouring these aggregate structures can function as an alternative form of 3D printing or digital additive manufacturing, which allows both for instant solidification, consequent reconfiguration, and graded material properties. In its first part, the paper introduces the field of research into aggregate architectures. In its second part, the focus is laid on designed aggregates, and an analytical design tool for the individual grains is discussed. The third part presents research conducted into the process of additive manufacturing with designed granulates. To conclude, further areas of investigation are outlined especially with regard to the development of the additive manufacturing of functionally graded architectural structures. The potentials of the methodologies developed in this process are shown through the fabrication of a full-scale installation. By integrating material, fabrication, and design constraints into a streamlined computational methodology, the process also serves as a model for a more intuitive production workflow, expanding the understanding of glass as a material with wide-ranging possibilities for a more performative architecture

Material Computation in Architectural Aggregate Systems

Aggregates are defined as large amounts of elements being in loose contact. In architecture they are mainly known as an additive in concrete construction. Relatively few examples use aggregates in their unbound form as an architectural material system in their own right. The investigation of potential architectural applications however is both a very relevant and unexplored branch of design research. Loose granular systems are inherently different from other architectural construction systems. One of the most decisive distinctions lies in the way information on those granular architectural systems is being generated, processed, and integrated into the design process. Several mathematical methods have been developed to numerically model granular behaviour. However, the need and also the potential of using so-called,materiali computation is specifically relevant with aggregates, as much of their behaviour is still not being described in these mathematical models. This paper will present the current outcome of a doctorate research on aggregate architectures with a focus on information processing in machine and material computation. In the first part, it will introduce definitions of material and machine computation. In the second part, the way machine computation is employed in modelling granulates will be introduced. The third part will review material computation in granular systems. In the last part, a concrete example of an architectural aggregate model will be explained with regard to the given definition of material computation. Conclusively a comparative overview between material and machine computation in aggregate architectures will be given and further areas of development will be outlined.

Performative Architectural Morphology: Robotically manufactured biomimetic finger-joined plate structures

Performative Architectural Morphology is a notion derived from the term Functional Morphology in biology and describes the capacity of an architectural material system to adapt morphologically to specific internal constraints and external influences and forces. The paper presents a research project that investigates the possibilities and limitations of informing a robotically manufactured finger-joint system with principles derived from biological plate structures, such as sea urchins and sand dollars. Initially, the material system and robotic manufacturing advances are being introduced. Consequently, a performative catalogue is presented, that analyses both the biological system's basic principles, the respective translation into a more informed manufacturing logic and the consequent architectural implications. The paper concludes to show how this biologically informed material system serves to more specifically respond to a given building environment

Hygroscapes: Innovative Shape Shifting Façades

This chapter focuses on the testing and design of shape shifting façade prototypes that are programmed to passively sense stimuli and respond in a controlled setting based on the hygroscopic properties of wood. Wood is introduced in this context as a low-tech smart material with a naturally soft responsive mechanism that offers a substitute for mechanical actuators. First, a set of physical experiments were conducted to deduce the design parameters that affect wood morphology, behavior and response time upon changes in humidity levels and moisture content, including dimensional ratio, grain orientation, material thickness, type of wood, and lamination. We then report on the process and outcome of a workshop held at the American University in Cairo, with the main challenge of regulating the morphology and hygroscopic behavior of wood to work as an actuator with specifically desired motion for adaptive building façade prototypes. Based on the observations and analysis of concepts and mechanisms, we discuss shape shifting grammars as a framework for devising adaptive façade prototypes from a generative design perspective, where specific combinations of motion parameters are used to induce semantic rules and customized commands for the overall behavior of shape shifting mechanisms