Total Optimal Synthesis Method for Truss Structures Subject to Static and Frequency Constraints

Abstract: In a previous study, we presented an efficient optimal structural synthesis method for truss structures in which the design variables are coordinates of the panel points, cross-sectional areas, and discrete material kinds subjected to stress and displacement constraints. In this paper, the synthesis method is extended to solve design problems subject to stress, displacement, and fundamental natural-frequency constraints. The design problem is formulated in terms of discrete material kinds and continuous shape and sizing variables and which are approximated by a convex and separable subproblem. The approximate subproblem is expressed in direct and/or reciprocal design variables and shape, material, and sizing sensitivities. Each subproblem is solved by a two-stage minimization process. In the first stage, the continuous shape and sizing variables are optimized by a dual method. Second, the discrete material and continuous sizing variables are improved by a discrete sensitivity analysis. Using the proposed two-stage minimization procedure, both the discrete material kinds and the continuous shape and sizing variables can be systematically improved to obtain an optimal solution. The rigorousness, reliability, and efficiency of the method are illustrated by applying it to the minimum cost design of truss structures subject to stress, displacement, and fundamental natural-frequency constraints.     

Knowledge spillovers, location of industry, and endogenous growth

A Grossman–Helpman–Romer-type (Grossman and Helpman in Innovation and growth in the world economy, 1991; Romer in J Polit Econ 98:71–102, 1990) endogenous-growth model is developed in this study. This model has two countries in which there are knowledge spillovers that are partially local. Owing to these spillovers, the innovation costs in a particular country decrease as the number of firms locating in both that country and the other country increases. If international knowledge spillovers are symmetric, the innovation sector is in the country with the larger market. However, if international knowledge spillovers are asymmetric, the innovation costs may be in the small-market country. When innovation costs are lower in the country with a large market, the growth rate increases with a reduction of transportation costs. However, when innovation costs are lower in the country with the smaller market, the growth rate decreases with a reduction in transportation costs. We are grateful to Marcus Berliant, Masahisa Fujita, Koichi Futagami, Tatsuo Kinugasa, Takuo Imagawa, Tomoya Mori, Se-il Mun, Hisahiro Naito, Ryoji Ohdoi, Tatsuyoshi Saijyo, and Akihisa Shibata for their helpful comments and suggestions. Any remaining errors are the responsibility of the authors.     

Selection of Suitable Maximum-heart-rate Formulas for Use with Karvonen Formula to Calculate Exercise Intensity

 The Karvonen formula, which is widely used to estimate exercise intensity, contains maximum heart rate, HR_max, as a variable. This study employed pedaling experiments to assess which of the proposed formulas for calculating HR_max was the most suitable for use with the Karvonen formula. First, two kinds of experiments involving an ergometer were performed: an all-in-one-day experiment that tested eight pedaling loads in one day, and a one-load-per-day experiment that tested one load per day for eight days. A comparison of the data on 7 subjects showed that the all-in-one-day type of experiment was better for assessing HR_max formulas, at least for the load levels tested in our experiments. A statistical analysis of the experimental data on 47 subjects showed two of the HR_max formulas to be suitable for use in the Karvonen formula to estimate exercise intensity for males in their 20 s. In addition, the physical characteristics of a person having the greatest impact on exercise intensity were determined.     

Initial deflection of silicon-on-insulator thin membrane micro-mirror and fabrication of varifocal mirror

Thin membranes fabricated from silicon-on-insulator (SOI) wafer are valuable for deformable mirrors. The mirror is controlled to generate a specific wave-front with precision smaller than a wavelength. Here, we investigate quantitatively the initial deflection of the thin membrane mirrors fabricated from SOI wafer, which are often used in micro-electro-mechanical systems. A 1-μm-thick and 450-μm-diameter mirror fabricated from SOI wafer deflects upward around the circumference at an angle of 0.12°. The maximum deflection of the mirror is 320 nm at the center. The stress conditions of the mirrors are analyzed on the basis of material strength theory. The deflection is explained by the residual stress of the buried oxide layer of SOI wafer. The in-plane stresses of the micro-mirrors of diameters from 450 μm to 860 μm range from compressive stress of 1.2 MPa to tensile stress of 2.1 MPa. Furthermore, based on the above experimental and theoretical analyses, a 1-μm-thick varifocal micro-mirror of the diameter of 400 μm is fabricated. The focus of the mirror is varied from −28 mm to 21 mm with the deviation smaller than 4 nm from parabola in the mirror central region.     

Pareto frontier exploration in multiobjective topology optimization using adaptive weighting and point selection schemes

Topology optimization has been used in many industries and applied to a variety of design problems. In real-world engineering design problems, topology optimization problems often include a number of conflicting objective functions, such to achieve maximum stiffness and minimum mass of a design target. The existence of conflicting objective functions causes the results of the topology optimization problem to appear as a set of non-dominated solutions, called a Pareto-optimal solution set. Within such a solution set, a design engineer can easily choose the particular solution that best meets the needs of the design problem at hand. Pareto-optimal solution sets can provide useful insights that enable the structural features corresponding to a certain objective function to be isolated and explored. This paper proposes a new Pareto frontier exploration methodology for multiobjective topology optimization problems. In our methodology, a level set-based topology optimization method for a single-objective function is extended for use in multiobjective problems, using a population-based approach in which multiple points in the objective space are updated and moved to the Pareto frontier. The following two schemes are introduced so that Pareto-optimal solution sets can be efficiently obtained. First, weighting coefficients are adaptively determined considering the relative position of each point. Second, points in sparsely populated areas are selected and their neighborhoods are explored. Several numerical examples are provided to illustrate the effectiveness of the proposed method.     

Level set-based topology optimization for the design of a peltier effect thermoelectric actuator

Thermoelectric actuators are a type of thermal actuator that generates motion through the input of thermal energy by thermoelectric devices. Thermoelectric actuators utilize thermal expansion and contraction effects, achieved by heating and cooling appropriate parts of the mechanism, which enables specified motions to be carried out and can provide quicker response times than those of typical thermal compliant mechanisms that rely on thermal expansion effects alone. However, the need to consider both thermal expansion and contraction effects makes the design process more complex. This paper proposes a topology optimization method, especially appropriate for the conceptual design of thermoelectric actuators, that uses a level set function to represent structural shape profiles so that optimized configurations have clear structural boundaries. Several numerical examples of thermoelectric actuator design problems are presented to confirm the effectiveness and utility of the proposed method.     

Development of a color‐tunable polychromatic organic‐light‐emitting‐diode device for roll‐to‐roll manufacturing

A flexible vertically stacked flexible polychromatic color‐tunable OLED has been developed by means of low resistive intermediate electrode technology. The polychromatic OLED has a capability to show 16 million colors with 105% National Television Committee Standard (NTSC) color reproduction. The device can produce arbitrary shape with arbitrary colors, suitable for artistic expressions, just as many as those used in information displays. Independently controlled red, green, and blue light‐emitting layers are stacked vertically. With conventional indium tin oxide technology, because of the temperature restriction, it was quite difficult to achieve low resistance on plastic substrate. The reported numbers were all more than 80 Ω/□. According to the surface mobility control using Fick's law analysis, low sheet resistance 7.34 Ω/□ on plastic film was developed. At first, flexible 7.17 cm² transparent OLED was fabricated for the performance confirmation of transparent electrode. And then polychromatic color‐tunable OLED with the same size were successfully fabricated on plastic. With optical length optimization for each color stack of polychromatic OLED, more than 100% color reproduction in National Television Committee Standard was achieved by stack design. The polychromatic device can be used for colored illumination, as well as for organic‐light‐emitting display pixels for three times emission than conventional pixel design. The device is fabricated on plastic substrate so that the polychromatic organic‐light‐emitting‐diode device is manufacturable with roll‐to‐roll production line.     

Studying just-in-time defect prediction using cross-project models

Unlike traditional defect prediction models that identify defect-prone modules, Just-In-Time (JIT) defect prediction models identify defect-inducing changes. As such, JIT defect models can provide earlier feedback for developers, while design decisions are still fresh in their minds. Unfortunately, similar to traditional defect models, JIT models require a large amount of training data, which is not available when projects are in initial development phases. To address this limitation in traditional defect prediction, prior work has proposed cross-project models, i.e., models learned from other projects with sufficient history. However, cross-project models have not yet been explored in the context of JIT prediction. Therefore, in this study, we empirically evaluate the performance of JIT models in a cross-project context. Through an empirical study on 11 open source projects, we find that while JIT models rarely perform well in a cross-project context, their performance tends to improve when using approaches that: (1) select models trained using other projects that are similar to the testing project, (2) combine the data of several other projects to produce a larger pool of training data, and (3) combine the models of several other projects to produce an ensemble model. Our findings empirically confirm that JIT models learned using other projects are a viable solution for projects with limited historical data. However, JIT models tend to perform best in a cross-project context when the data used to learn them are carefully selected.     

Multimodal Scene Understanding Framework and Its Application to Cooking Recognition

We propose a multimodal “scene understanding” framework using sensory and text information. Scene understanding is defined by extracting information such as What, When, Where, Who, Why, and How on the surrounding environment. Although scene understanding has been studied, information on why and how was not considered. We constructed a framework for extracting how information, in addition to the conventional information based on multimodality and background knowledge. This framework was applied to a cooking scene, in which how information was defined as a cooking procedure. This framework was evaluated by constructing an audio-visual multimodal cooking recognition system, utilizing recipes as background knowledge. A Convolutional Neural Network (CNN) and a Hierarchical Hidden Markov Model (HHMM) were adopted in this system. Our experiments showed the robustness of the proposed framework in noisy and/or occluded situations. An interactive cooking support system based on the proposed framework might suggest the next step for cooking procedures via human–robot communications.     

The technologies of in‐cell optical touch panel with novel input functions

Abstract— The technologies behind an in‐cell optical touch‐panel LCD with novel input functions will be described. By improving both the optical and electrical signal‐to‐noise ratio (SNR), a touch‐panel operation robust to ambient conditions can be achieved with a low‐power consumption suitable for integration into mobile products. The high SNR also enables a range of novel input functions making the in‐cell optical touch panel a promising platform for the next‐generation of user interface.