3D interactive topology optimization on hand-held devices

This educational paper describes the implementation aspects, user interface design considerations and workflow potential of the recently published TopOpt 3D App. The app solves the standard minimum compliance problem in 3D and allows the user to change design settings interactively at any point in time during the optimization. Apart from its educational nature, the app may point towards future ways of performing industrial design. Instead of the usual geometrize, then model and optimize approach, the geometry now automatically adapts to the varying boundary and loading conditions. The app is freely available for iOS at Apple’s App Store and at http://www.topopt.dtu.dk/TopOpt3D for Windows and OSX.     

Improving topology optimization intuition through games

This paper describes the educational game, TopOpt Game, which invites the player to solve various optimization challenges. The main purpose of gamifying topology optimization is to create a supplemental educational tool which can be used to introduce concepts of topology optimization to newcomers as well as to train human intuition of topology optimization. The players are challenged to solve the standard minimum compliance problem in 2D by distributing material in a design domain given a number of loads and supports with a material constraint. A statistical analysis of the gameplay data shows that players achieve higher scores the more they play the game. The game is freely available for the iOS platform at Apple’s App Store and at http://www.topopt.dtu.dk/?q=node/909 for Windows and OSX.     

Topology optimization using PETSc: An easy-to-use,fully parallel,open source topology optimization framework

This paper presents a flexible framework for parallel and easy-to-implement topology optimization using the Portable and Extendable Toolkit for Scientific Computing (PETSc). The presented framework is based on a standardized, and freely available library and in the published form it solves the minimum compliance problem on structured grids, using standard FEM and filtering techniques. For completeness a parallel implementation of the Method of Moving Asymptotes is included as well. The capabilities are exemplified by minimum compliance and homogenization problems. In both cases the unprecedented fine discretization reveals new design features, providing novel insight. The code can be downloaded from www.topopt.dtu.dk/PETSc.     

A web-based topology optimization program

The paper presents a web-based interface for a topology optimization program. The program is accessible over the World Wide Web at the address http://www.topopt.dtu.dk. The paper discusses implementation issues and educational aspects as well as statistics and experience with the program. Received September 29, 2000     

A 99 line topology optimization code written in Matlab

The paper presents a compact Matlab implementation of a topology optimization code for compliance minimization of statically loaded structures. The total number of Matlab input lines is 99 including optimizer and Finite Element subroutine. The 99 lines are divided into 36 lines for the main program, 12 lines for the Optimality Criteria based optimizer, 16 lines for a mesh-independency filter and 35 lines for the finite element code. In fact, excluding comment lines and lines associated with output and finite element analysis, it is shown that only 49 Matlab input lines are required for solving a well-posed topology optimization problem. By adding three additional lines, the program can solve problems with multiple load cases. The code is intended for educational purposes. The complete Matlab code is given in the Appendix and can be down-loaded from the web-site http://www.topopt.dtu.dk. Received October 22, 1999     

Detecting privacy leaks in the RATP App: how we proceeded and what we found

We analyzed the RATP App, both Android and iOS versions, using our instrumented versions of these mobile OSs. Our analysis reveals that both versions of this App leak private data to third-party servers, which is in total contradiction to the In-App privacy policy. The iOS version of this App doesn’t even respect Apple guidelines on cross-App user tracking for advertising purposes and employs various other cross-App tracking mechanisms that are not supposed to be used by Apps. Even if this work is illustrated with a single App, we describe an approach that is generic and can be used to detect privacy leaks from other Apps. In addition, our findings are representative of a trend in Advertising and Analytics (A&A) libraries that try to collect as much information as possible regarding the smartphone and its user to have a better profile of the user’s interests and behaviors. In fact, in case of iOS, these libraries even generate their own persistent identifiers and share it with other Apps through covert channels to better track the user, and this happens even if the user has opted-out of device tracking for advertising purposes. Above all, this happens without the user knowledge, and sometimes even without the App developer’s knowledge who might have naively included these libraries during the App development. Therefore this article raises many questions concerning both the bad practices employed in the world of smartphones and the limitations of the privacy control features proposed by Android/iOS Mobile OSs.     

QR Panopticism: User Behavior Triangulation and Barcode-Scanning Applications

ABSTRACT

The increasingly ubiquitous two-dimensional barcodes designed by the Denso Wave company, known as the QR code, were originally intended to track millions of parts as they moved about on high-speed assembly lines. Since then, these increasingly ubiquitous black and white squares have been applied to an ever-broader range of nonindustrial uses. In order to make use of these codes, the vast majority of consumers use smart phone technologies in order to convert the codes into usable information. However, neither Apple’s iOS nor Google’s Android operating systems include a robust native capability to decode printed barcodes. As a result, users of these devices must download and install third-party applications that will do this work for them. Our research question is straightforward: are there privacy and security risks associated with this emerging QR app ecosystem? We installed and analyzed over twenty of the most popular QR code applications. Our findings suggest that a majority of the most popular QR code readers found in the Apple App and Google Play marketplaces are not passive systems, but instead capture and transmit additional data about the device back to the application developer. The paper then considers the privacy and security implications of the QR code app ecosystem.     

TelePatch: a middle layer for screening device fragmentation

Solutions in the domain of mobile computing face a typical problem of fragmentation due to permissible customization to android framework. Fragmentation is a problem at the device side where the expected behavior of an application is not exhibited identically over all other devices. Presently, cross-layer design is becoming essential aspect of the app development, targeted to deliver an energy-efficient and productive solution. Fragmentation is posing an enormous challenge for development community, and solutions are designed per case basis. There are solutions developed in the domain of graphics and Web access, but as far as the fragmentation with core framework is considered, the solution is still missing. In this paper, we are proposing an intermediate background app residing between the application and the core framework. The proposed app TelePatch generates a map between the intended calls with actually supported calls. The map so obtained can be used by the interested application to obtain the services from the core framework. In our case, we have deployed TelePatch with NeSen, used for capturing the network-state parameters using telephony API of the Android.     

A simple and compact Python code for complex 3D topology optimization

This paper presents a 100-line Python code for general 3D topology optimization. The code adopts the Abaqus Scripting Interface that provides convenient access to advanced finite element analysis (FEA). It is developed for the compliance minimization with a volume constraint using the Bi-directional Evolutionary Structural Optimization (BESO) method. The source code is composed of a main program controlling the iterative procedure and five independent functions realizing input model preparation, FEA, mesh-independent filter and BESO algorithm. The code reads the initial design from a model database (.cae file) that can be of arbitrary 3D geometries generated in Abaqus/CAE or converted from various widely used CAD modelling packages. This well-structured code can be conveniently extended to various other topology optimization problems. As examples of easy modifications to the code, extensions to multiple load cases and nonlinearities are presented. This code is useful for researchers in the topology optimization field and for practicing engineers seeking automated conceptual design tools. With further extensions, the code could solve sophisticated 3D conceptual design problems in structural engineering, mechanical engineering and architecture practice. The complete code is given in the appendix section and can also be downloaded from the website: www.rmit.edu.au/research/cism/.     

Multi-material topology optimization for practical lightweight design

Topology optimization is one of the most effective tools for conducting lightweight design and has been implemented across multiple industries to enhance product development. The typical topology optimization problem statement is to minimize system compliance while constraining the design space to an assumed volume fraction. The traditional single-material compliance problem has been extended to include multiple materials, which allows increased design freedom for potentially better solutions. However, compliance minimization has the limitations for practical lightweight design because compliance lacks useful physical meanings and has never been a design criterion in industry. Additionally, the traditional compliance minimization problem statement requires volume fraction constraints to be selected a priori; however, designers do not know the optimized balance among materials. In this paper, a more practical method of multi-material topology optimization is presented to overcome the limitations. This method seeks the optimized balance among materials by minimizing the total weight while satisfying performance constraints. This paper also compares the weight minimization approach to compliance minimization. Several numerical examples prove the success of weight minimization and demonstrate its benefit over compliance minimization.     

Multi-objective concurrent topology optimization of thermoelastic structures composed of homogeneous porous material

The present paper studies multi-objective design of lightweight thermoelastic structure composed of homogeneous porous material. The concurrent optimization model is applied to design the topologies of light weight structures and of the material microstructure. The multi-objective optimization formulation attempts to find minimum structural compliance under only mechanical loads and minimum thermal expansion of the surfaces we are interested in under only thermo loads. The proposed optimization model is applied to a sandwich elliptically curved shell structure, an axisymmetric structure and a 3D structure. The advantage of the concurrent optimization model to single scale topology optimization model in improving the multi-objective performances of the thermoelastic structures is investigated. The influences of available material volume fraction and weighting coefficients are also discussed. Numerical examples demonstrate that the porous material is conducive to enhance the multi-objective performance of the thermoelastic structures in some cases, especially when lightweight structure is emphasized. An “optimal” material volume fraction is observed in some numerical examples.     

Growth method for size,topology, and geometry optimization of truss structures

The problem of optimally designing the topology of plane trusses has, in most cases, been dealt with as a size problem in which members are eliminated when their size tends to zero. This article presents a novel growth method for the optimal design in a sequential manner of size, geometry, and topology of plane trusses without the need of a ground structure. The method has been applied to single load case problems with stress and size constraints. It works sequentially by adding new joints and members optimally, requiring five basic steps: (1) domain specification, (2) topology and size optimization, (3) geometry optimization, (4) optimality verification, and (5) topology growth. To demonstrate the proposed growth method, three examples were carried out: Michell cantilever, Messerschmidt–Bölkow–Blohm beam, and Michell cantilever with fixed circular boundary. The results obtained with the proposed growth method agree perfectly with the analytical solutions. A Windows XP program, which demonstrates the method, can be downloaded from http://www.upct.es/~deyc/software/tto/.     

Combined shape and topology optimization for minimization of maximal von Mises stress

This work shows that a combined shape and topology optimization method can produce optimal 2D designs with minimal stress subject to a volume constraint. The method represents the surface explicitly and discretizes the domain into a simplicial complex which adapts both structural shape and topology. By performing repeated topology and shape optimizations and adaptive mesh updates, we can minimize the maximum von Mises stress using the p-norm stress measure with p-values as high as 30, provided that the stress is calculated with sufficient accuracy.     

Extended optimality in topology design

Most existing studies of 2D problems in structural topology optimization are based on a given (limit on the) volume fraction or some equivalent formulation. The present note looks at simultaneous optimization with respect to both topology and volume fraction, termed here “extended optimality”. It is shown that the optimal volume fraction in such problems — in extreme cases — may be unity or may also tend to zero. The proposed concept is used for explaining certain “quasi-2D” solutions and an extension to 3D systems is also suggested. Finally, the relevance of Voigt’s bound to extended optimality is discussed.     

An artificial pancreas system in android phones: A dual app architecture

An Artificial Pancreas (AP) system centered around an Android Smartphone is proposed in this paper. This unique architecture involves two separate but interacting modular Android applications (Apps) that are designed for unique functionalities. Even though an artificial pancreas system is a safety-critical system that demands a complex architecture and careful coding process, owing to their modular nature, these apps could be designed and developed through rapid prototyping processes. The first app (App-A), which runs in the front-end, serves as the user interface and acts as a connection hub for the hardware devices, was developed on the Android studio platform. Necessary communication protocols to enable communication with the hardware devices are incorporated into this app. The second app (App-B), which runs in the back-end, is developed using Simulink’s Android support package. It contains a safety-critical model predictive control algorithm with appropriate constraints to compute the required insulin rate, augmented with a Kalman Filter for estimating the states. There is an additional safety logic as well to prevent insulin over-dosage, thereby augmenting to the cause of a safety-critical control algorithm. The contribution of this work is a modular software framework and prototyping methodology that can be used for rapid development, testing and deployment of Android based AP-systems.     

Nonlinear diffusions in topology optimization

Filtering has been a major technique used in homogenization-based methods for topology optimization of structures. It plays a key role in regularizing the basic problem into a well-behaved setting, but it has the drawback of a smoothing effect around the boundary of the material domain. In this paper, a diffusion technique is presented as a variational approach to the regularization of the topology optimization problem. A nonlinear or anisotropic diffusion process not only leads to a suitable problem regularization but also exhibits strong edge-preserving characteristics. Thus, we show that the use of nonlinear diffusions brings the desirable effects of boundary preservation and even enhancement of lower-dimensional features such as flow-like structures. The proposed diffusion techniques have a close relationship with the diffusion methods and the phase-field methods from the fields of materials and digital image processing. The proposed method is described and illustrated with 2D examples of minimum compliance that have been extensively studied in recent literature of topology optimization.     

Status and trends of mobile-health applications for iOS devices: A developer's perspective

Modern smart mobile devices offer media-rich and context-aware features that are highly useful for electronic-health (e-health) applications. It is therefore not surprising that these devices have gained acceptance as target devices for e-health applications, turning them into m-health (mobile-health) apps. In particular, many e-health application developers have chosen Apple's iOS mobile devices such as iPad, iPhone, or iPod Touch as the target device to provide more convenient and richer user experience, as evidenced by the rapidly increasing number of m-health apps in Apple's App Store. In this paper, the top two hundred of such apps from the App Store were examined from a developer's perspective to provide a focused overview of the status and trends of iOS m-health apps and an analysis of related technology, architecture, and user interface design issues. The top 200 apps were classified into different groups according to their purposes, functions, and user satisfaction. It was shown that although the biggest group of apps was medical information reference apps that were delivered from or related to medical articles, websites, or journals, mobile users disproportionally favored tracking tools. It was clear that m-health apps still had plenty of room to grow to take full advantage of unique mobile platform features and truly fulfill their potential. In particular, introduction of two- or three-dimensional visualization and context-awareness could further enhance m-health app's usability and utility. This paper aims to serve as a reference point and guide for developers and practitioners interested in using iOS as a platform for m-health applications, particular from the technical point of view.     

虚拟实验App服务端架构设计与实现

随着互联网科技的迅速发展,Android 系统智能手机的普及,移动App 有着开发迅速、用户使用增长量快等特点,但支撑起App网络服务的后台服务器的开发是个难题。本文从接口设计、架构环境选择、对象存储服务、用户验证方案等方面介绍虚拟实验服务端技术的设计与实现。     

基于轻量级加密算法的手机短信加密软件

针对Android智能手机的恶意软件正在迅速增长并危害手机用户的个人隐私和系统安全,为了实现手机短信的隐私保护和秘密通信,设计并开发了一款利用轻量级对称加密算法对短信进行加密发送的手机隐私保护软件.该软件面向Android手机而开发,具有软件开启密码保护、联系人导入、会话密钥设置、短信导入与加解密功能.该软件为智能手机隐私泄露提供了一个可行的解决方案.     

Topology optimization applied to the design of 2D swirl flow devices

The design of fluid devices, such as flow machines, mixers, separators, and valves, with the aim to improve performance is of high interest. One way to achieve it is by designing them through the topology optimization method. However, there is a specific large class of fluid flow problems called 2D swirl flow problems which presents an axisymmetric flow with (or without) flow rotation around the axisymmetric axis. Some devices which allow such simplification are hydrocyclones, some pumps and turbines, fluid separators, etc. Once solving a topology optimization problem for this class of problems using a 3D domain results in a quite high computational cost, the development and use of 2D swirl models is of high interest. Thus, the main objective of this work is to propose a topology optimization formulation for 2D swirl flow fluid problem to design these kinds of fluid devices. The objective is to minimize the relative energy dissipation considering the viscous and porous effects. The 2D swirl laminar fluid flow modelling is solved by using the finite element method. A traditional material model is adopted by considering nodal design variables. An interior point optimization (IPOPT) algorithm is applied to solve the optimization problem. Numerical examples are presented to illustrate the application of this model for various 2D swirl flow cases.