Integrated Hardware Garbage Collection

Garbage collected programming languages, such as Python and C#, have accelerated software development. These modern languages increase productivity and software reliability as they provide high-level data representation and control structures. Modern languages are widely used in software development for mobile, desktop, and server devices, but their adoption is limited in real-time embedded systems. There is clear interest in supporting modern languages in embedded devices as emerging markets, like the Internet of Things, demand ever smarter and more reliable products. Multiple commercial and open-source projects, such as Zerynth and MicroPython, are attempting to provide support. But these projects rely on software garbage collectors that impose high overheads and introduce unpredictable pauses, preventing their use in many embedded applications. These limitations arise from the unsuitability of conventional processors for performing efficient, predictable garbage collection. We propose the Integrated Hardware Garbage Collector (IHGC); a garbage collector tightly coupled with the processor that runs continuously in the background. Further, we introduce a static analysis technique to guarantee that real-time programs are never paused by the collector. Our design allocates a memory cycle to the collector when the processor is not using the memory. The IHGC achieves this by careful division of collection work into single-memory-access steps that are interleaved with the processor’s memory accesses. As a result, our collector eliminates run-time overheads and enables real-time program analysis. The principles behind the IHGC can be used in conjunction with existing architectures. For example, we simulated the IHGC alongside the ARMv6-M architecture. Compared to a conventional processor, our experiments indicate that the IHGC offers 1.5–7 times better performance for programs that rely on garbage collection. The IHGC delivers the benefits of garbage-collected languages with real-time performance but without the complexity and overheads inherent in software collectors.

AM-FFF of Objects Using Commercial PLA Based Shape Memory Polymer Printed by an Open-Source 3D Printer

The 4D additive manufacturing processes are considered today as the "next big thing" in R&D. The aim of this research is to provide two examples of commercial PLA based shape memory polymer (SMP) objects printed on an open-source 3D printer in order to proof the feasibility of such novel 4D printing process. To that purpose, a PLA based filament of eSUN (4D filament e4D-1white, SMP) was chosen, and two applications, a spring and a vase, were designed by 3D-printing with additive manufacturing (AM) fused filament fabrication (FFF) technique. The 4D-printed objects were successfully produced, the shape memory effect and their functionality were demonstrated by achieving the shape-memory cycle of programming, storage and recovery.

Ciclo Escena y Memoria: una rebeldía amorosa

En el presente trabajo se abordan dos eventos teatrales: la representación de la obra Villa, del dramaturgo chileno Guillermo Calderón, y el Ciclo Escena y Memoria, coordinado por Jorge Villegas. Ambos eventos tuvieron lugar en el campo teatral independiente de la ciudad de Córdoba, Argentina, durante el año 2019. Desde una perspectiva sociohistórica abordamos la relación de dichos eventos con el ejercicio de la memoria en la ciudad. De Villa retomamos las actuales inquietudes respecto al uso político de los sitios de la memoria, para formular la pregunta: ¿es posible representar el horror del terrorismo de Estado? Del Ciclo nos interesan las redefiniciones respecto al cruce entre teatro y militancia política, y la habilitación de nuevos espacios de comunidad social a partir del dolor de los cuerpos.AbstractThis article addresses two theatrical events: the play Villa, by Chilean playwright Guillermo Calderón, and the Performing Arts and Memory Cycle, coordinated by Jorge Villegas. Both were produced in 2019 as part of the independent theater scene in the city of Córdoba, Argentina. These events are discussed from a socio-historical perspective, in order to understand the how they are related to the city’s collective memory. In Villa it’s possible to identify the political use of the memory sites and how Calderón works with a fundamental question: is it possible to represent the horror of State terrorism? In the Performing Arts and Memory Cycle, the author discusses the intersection between theatre and political militancy, and the enabling of new spaces for social community where bodies have been subjected to pain. Recibido: 27 de marzo 2020Aceptado: 16 de julio de 2020

Design and characterization of 3D multilayer woven reinforcements shape memory polymer composites

Shape memory polymer (SMP) composites are attractive and excellent smart materials due to their outstanding properties and rich functionality as they combine typical mechanical and functional properties of composites with shape memory properties. In particular, 3D reinforced preforms have tremendous potential for the development of functional composites by using the capabilities of 3D woven fabric preform design, and polymer shape memory behavior. Within that scope, this work aims to investigate the shape memory behavior and shape recovery properties of a specific type of 3D multilayer woven SMP composite in response to external stimuli. For this purpose, nine different multilayer stitched fabrics are produced with different weave structures, and different fabric thread densities using polyimide filaments. Then, a series of tests is carried out on these fabrics to evaluate their mechanical and physical properties. The layered fabric design that delivers high mechanical performance is next involved to manufacture the SMP composite samples, for which shape recovery capability is investigated. Fold-deploy and other shape memory cycle tests are performed to evaluate the shape memory characteristics. An optical 3D scanner based on fringe projection is further proposed to precisely acquire the geometry data and perform deformation analysis to quantitatively evaluate the shape fixity and shape recovery behaviors. The results from this study are very promising, demonstrating that these multilayer SMP structures can successfully be recovered following the desired design constraints without noticeable damage.

Simulation of shape memory cycle of a polymeric beam undergoing large deflection using a simple incremental approach

Shape memory polymers are a group of polymers which can store a temporary shape at a relatively cold temperature and recover when heated above its glass transition temperature. Various constitutive models exist in literature to simulate the uniaxial shape memory cycle. One such popular model is based on the concept of multiple natural configurations. In the present work, the stress-strain-based model is adapted for bending application by converting it into a scalar moment-curvature-based relationship. The adapted model is used in a numerical framework for large deflection of beams to simulate the shape memory cycle. The employed numerical framework is based on linearising the non-linear governing differential equation and subsequently solving it in steps by numerical integration. The results are presented in suitable non-dimensional form for generality. Since coefficient of thermal expansion plays a minimal role in bending, it is found that the bending results are considerably different from their uniaxial counterpart. The approach may be claimed to be computationally economic as compared to finite element method because here large matrix inversion is avoided.

A lamination model for shape memory polymer/woven fabric composites

Based on continuum mechanics and finite element method, a lamination model was developed for shape memory polymer composites (SMPCs) reinforced by woven fabrics. SMPCs were modeled as a laminated structure with woven fabric reinforcements embedded in shape memory polymers (SMPs). Thermo-responsive SMPs were defined by a 3D phenomenological model based on the phase transition approach, while woven fabric reinforcements were characterized by an anisotropic hyperelastic model. The proposed model was validated by comparing numerical results of a SMPC in the shape memory cycle of bending deformation with experimental data. Applications of the lamination model were demonstrated on numerical simulations of a tube made of SMPC in three shape memory cycles with different deformation modes. The proposed model is simple and applicable in the simulations of various shape memory cycles related to SMPCs. It also provides a theoretical foundation for the analysis and design optimization of woven fabric reinforced SMPC structures.