Cell Layout Research Articles

The properties of optimal two-dimensional phononic crystals with different material contrasts

By modifying the spatial distribution of constituent material phases, phononic crystals (PnCs) can be designed to exhibit band gaps within which sound and vibration cannot propagate. In this paper, the developed topology optimization method (TOM), based on genetic algorithms (GAs) and the finite element method (FEM), is proposed to design two-dimensional (2D) solid PnC structures composed of two contrasting elastic materials. The PnCs have the lowest order band gap that is the third band gap for the coupled mode, the first band gap for the shear mode or the XY34Z band gap for the mixed mode. Moreover, the effects of the ratios of contrasting material properties on the optimal layout of unit cells and the corresponding phononic band gaps (PBGs) are investigated. The results indicate that the topology of the optimal PnCs and corresponding band gaps varies with the change of material contrasts. The law can be used for the rapid design of desired PnC structures.

A Low-Voltage Radiation-Hardened 13T SRAM Bitcell for Ultralow Power Space Applications

Continuous transistor scaling, coupled with the growing demand for low-voltage, low-power applications, increases the susceptibility of VLSI circuits to soft-errors, especially when exposed to extreme environmental conditions, such as those encountered by space applications. The most vulnerable of these circuits are memory arrays that cover large areas of the silicon die and often store critical data. Radiation hardening of embedded memory blocks is commonly achieved by implementing extremely large bitcells or redundant arrays and maintaining a relatively high operating voltage; however, in addition to the resulting area overhead, this often limits the minimum operating voltage of the entire system leading to significant power consumption. In this paper, we propose the first radiation-hardened static random access memory (SRAM) bitcell targeted at low-voltage functionality, while maintaining high soft-error robustness. The proposed 13T employs a novel dual-driven separated-feedback mechanism to tolerate upsets with charge deposits as high as 500 fC at a scaled 500-mV supply voltage. A $32\times 32$ bit memory macro was designed and fabricated in a standard 0.18- $\mu \text{m}$ CMOS process, showing full read and write functionality down to the subthreshold voltage of 300 mV. This is achieved with a cell layout that is only $2\times $ larger than a reference 6T SRAM cell drawn with standard design rules.

Designing cellular manufacturing systems considering S-shaped layout

In this paper, we present a new layout framework, called S-shaped layout, for the layout of cellular manufacturing systems. Based on the proposed S-shaped layout, we formulate an integrated bi-objective cell formation and layout problem, considering parameters such as part demands, operation sequences, machine dimensions and aisle widths. The first objective is to minimize the total inter- and intra-cell material handling costs. Also, the second objective is to maximize the total similarity between machines. A normalized weighted sum method is suggested to unify these objectives. As the problem is NP-hard, an efficient hybrid solution method combining simulated annealing and dynamic programming is developed to solve large-sized problems in a reasonable computational time. Finally, by solving numerical examples from the literature the suggested approach is compared with two recently developed approaches.

Challenges and key technologies in robotic cell layout design and optimization

Automatic operation system with industrial robots has become more and more popular, especially with the urgent requirement from 3C (Communication, computer and consumer electronics) manufactory. A robot cell, which often involves one or more robots and accessory equipment, can be regarded as part of the larger theme of cellular manufacturing. The objective that most interests manufacturers is the investment return rate. It is largely determined by the productivity of robotic cell, and the leading time of robotic production system. Therefore, a fast and efficient method to design a robotic cell layout with the maximum throughput for a given task is undeniably a worthy research topic. This paper attempts to discuss the challenges and key technologies in the robotic cell layout optimal design. The proper selection of configuration for task, manual operation skill learning and translation, collaborative design tool-chain, optimization in cell layout and operation scheduling, optimal end-of-arm tooling design, and human–robot collaboration are included in this discussion with existing or on-going problem-solving key technologies.

A stochastic second‐order and two‐scale thermo‐mechanical model for strength prediction of concrete materials

SummaryA stochastic thermo‐mechanical model for strength prediction of concrete is developed, based on the two‐scale asymptotic expressions, which involves both the macroscale and the mesoscale of concrete materials. The mesoscale of concrete is characterized by a periodic layout of unit cells of matrix‐aggregate composite materials, consisting of randomly distributed aggregate grains and cement matrix. The stochastic second‐order and two‐scale computational formulae are proposed in detail, and the maximum normal stress is assumed as the strength criterion for the aggregates, and the cement paste, in view of their brittle characteristics. Numerical results for the strength of concrete obtained from the proposed model are compared with those from known experiments. The comparison shows that the proposed method is validated for strength prediction of concrete. The proposed thermo‐mechanical model is also employed to investigate the influence of different volume fraction of the aggregates on the strength of concrete. Copyright © 2016 John Wiley & Sons, Ltd.

Triple Patterning Lithography Aware Optimization and Detailed Placement Algorithms for Standard Cell-Based Designs

Triple patterning lithography (TPL) is regarded as a promising technique to handle the manufacturing challenges in the 14nm technology node and beyond. It is necessary to consider TPL in early design stages to make the layout more TPL friendly and reduce the manufacturing cost. In this paper, we propose a flow to co-optimize cell layout decomposition and detailed placement. Our cell decomposition approach can enumerate all coloring solutions with the minimum number of stitches. The experimental results show that our approach can outperform the existing work in all aspects of stitch number, half-perimeter wirelength (HPWL), and running time. We further extend our placer to consider the displacement of cells as a constraint and as an objective, respectively, which can help to preserve the quality of the input placement. Effectiveness of the extensions is verified by the experiments.

Vibration Modeling of PEM Fuel Cell for Prediction of Cell Number Effects by Experimental Data

AbstractOne of the most important challenges in increasing the performance, reliability and lifetime of fuel cells is the mechanical load effects that occur on real applications. Therefore, the vibration model of fuel cell that predicts the behavior of various fuel cell layouts is very useful. The fuel cell is made up of different adjacent layers that may have semi opposite mechanical properties. This special structure leads to occurrence of non‐linear behavior of fuel cell under dynamic mechanical vibrations and so, a black box method is selected for modeling of its vibration behavior. In this study, the mechanical load experiments in various shape and axes were applied on five layouts of proposed fuel cell and the vibration of its body measure by some accelerometers. The NNARXM neural network is created and trained with the experimental data of three layouts of the fuel cell. Then, the prediction error of this neural network, validated with the two other experimental data of fuel cell layouts, by correlation coefficients and histogram of prediction errors. Neural network validation shows the well prediction of both untrained layout and suitable estimation for any desired layout.

Long-term soiling of silicon PV modules in a moderate subtropical climate

The results of 28 silicon-based PV modules which were installed from 1981 to 1985 in a free rack configuration in the outdoor test facility of the European Solar Test Installation (ESTI) and dismantled at the end of 2014 without cleaning were analysed. The system was composed of modules with two series-connected laminates mounted in a single frame produced by the same manufacturer but using different cell layouts and cover glasses (plain glass or textured glass). The effects of long-term soiling on the PV module performance for more than 30years of outdoor exposure in a moderate subtropical climate and the influence of different cleaning methods from manual cleaning to the use of high pressure water washing were investigated. The influence of the cover glasses and the mismatch due to the particular manufacturing design were also analysed. It was observed that a manual cleaning was effective at improving the output of all the module types. However, additional high pressure water spraying on plain glass modules showed no further improvement, but showed small improvements on the textured glass modules. Overall improvements in Pmax after cleaning ranged from 3.5% to 19.4%, with an average value of 9.8% and an average improvement in Isc of 6.7% were obtained.

An integrated mathematical model for solving dynamic cell formation problem considering operator assignment and inter/intra cell layouts

The aim of this paper is to present an integrated mathematical model to solve the dynamic cell formation problem considering operator assignment and inter/intra cell layouts problems with machine duplication, simultaneously. The proposed model includes three objectives which the first objective seeks to minimize inter/intra cell part movements and machine relocation, the second objective minimizes machine and operator related costs and the third objective maximizes consecutive forward flows ratio. In order to validate the proposed model, a numerical example is presented and solved by the sum weighted method. Due to NP-hardness of the model, two meta-heuristics namely multi-objective simulated annealing (MOSA) and multi-objective vibration damping optimization (MOVDO) present to solve the proposed model. Finally, two algorithms have been compared using multi-objective criteria.

Basic memory elements using DICE cells for fault-tolerant 28 nm CMOS RAM

A CMOS DICE (Dual Interlocked Storage Cell) cell consists of two transistor groups whose layout on the crystal increases the cell’s stability against the impact of single nuclear particles. A fault of the cell’s state does not take place if the particle impacts transistors of one group only. The topological layouts of basic memory elements with a different relative position of two transistor groups of 28 nm CMOS DICE cells were designed and analyzed. Different cell layouts with a distance between the sensitive pairs of transistors of two groups of 1, 2, and 3 µm and a set of basic memory elements for designing memory arrays of static RAM with increased stability with respect to state faults due to the particle track charge separation between two transistor groups of the cell were proposed. The area of the DICE cells is larger by a factor of 2.1–2.5 than that of sixtransistor cells with transistors of the same size.

A Low Frequency Broadband Flextensional Ultrasonic Transducer Array.

In this paper, we propose the design and the fabrication of a multicell, piezoelectrically actuated, flextensional transducer array structure, characterized by a low mechanical impedance, thus allowing wideband and high-sensitivity immersion operation in the low ultrasonic frequency range. The transducer structure, consisting of a plurality of circular elementary cells orderly arranged according to a periodic hexagonal tiling, features a high flexibility in the definition of the active area shape and size. We investigate, by finite element modeling (FEM), the influence of different piezoelectric and elastic materials for the flexural plate, for the plate support and for the backing, on the transducer electroacoustic behavior. We carry out the dimensioning of the transducer components and cell layout, in terms of materials and geometry, respectively, by aiming at a circular active area of 80-mm diameter and broadband operation in the 30-100-kHz frequency range in immersion. PZT-5H ceramic disks and a calibrated thickness stainless steel plate are chosen for the vibrating structure, and FR-4 laminates and a brass plate, respectively, for the plate support and the backing. The diameter of the individual cells is set to 6 mm resulting in 121 cells describing a quasi-circular area, and the total thickness of the transducer is less than 10 mm. We report on the fabrication process flow for the accurate assembly of the transducer, based, respectively, on epoxy resin and wire bonding for the mechanical and electrical interconnection of the individual parts. The results of the electrical impedance and transmit pressure field characterization are finally reported and discussed.

A real options model of phased migration to cellular manufacturing

The literature is replete with models that examine various aspects of cellular manufacturing (CM), such as optimisation of cell layouts. However, many firms may realise zero to marginal returns from CM. Given this uncertainty, the manager should first determine the value of CM to the firm before deploying it. Although traditional valuation models employing discounted cash flow analysis allow for uncertainty, they treat future investments as fixed when computing the investment’s present value. The real options (RO) logic of valuation allows the manager to exercise the option to invest in or abandon a project based on expected outcomes. Future investments are thus options. This paper presents an RO model for CM migration that addresses whether a firm should migrate to CM; and it prescribes the sequence of cell deployment, which has not been addressed in the literature. Our model is also much more transparent and accessible to practitioners, with an accompanying software tool for prospective users. Finally, we use simulation extensively to discover the drivers of the optimal cell deployment sequence. Our results show that there is a complex interplay between net present value, speed of cellularisation, inter-cell learning and volatility in terms of their influence on the cell sequence.

Two base station location techniques with adjusted measurements in circular scattering environments

SummaryIn circular scattering environments, novel location techniques with only two base stations (BSs) are proposed in this paper. The proposed techniques estimate the true or line‐of‐sight ranges and angle based on non‐line‐of‐sight range and angle measurements. Three new variables are introduced when range measurements and angle measurement are available from two BSs and the serving BS, respectively. Bounds and relationships between the three variables are extracted from the geometry of the cell layout with the unknown and known scattering radius conditions, respectively. Our aim is to obtain the estimation of three new variables and then the hybrid line of position technique with the adjusted ranges, and angle is utilized to obtain the position estimation of a mobile station. In order to obtain the estimation of three new variables, a new nonlinear objective function is built to form the constrained nonlinear optimization and solved by the existing optimization algorithms. However, because of the nonconvex objective function, the optimization algorithm may converge to the local optimum and lead to bad performance. Thus, a heuristic search algorithm is proposed by averaging all the potential point. Simulation results show that the proposed techniques outperform conventional hybrid techniques. Copyright © 2015 John Wiley & Sons, Ltd.

Environmental Effect on the Leaf Morphology and Anatomy of Berberis microphylla G. Forst

Berberis microphylla G. Forst is a fruit shrub native from Patagonia, considered as a non-timber forest product. In recent years, there has been an increased demand for its fruits, both for fresh and industrialized consumption, being the establishment of commercial orchards in different sites a need to meet this demand. B. microphylla cloned plants have been introduced from Ushuaia, Tierra del Fuego to Buenos Aires province in order to evaluate its phenotypic plasticity and the possibility of fruit production. At the same time, a comparative study on the morphology and anatomy of the mature leaves of B. microphylla grown in two different environmental conditions was carried out. Moreno leaves were significantly larger than Ushuaia leaves in all the morphological parameters registered, while Ushuaia leaves were more circular than Moreno leaves with the highest roundness and elongation indexes. Nevertheless, histological sections showed that Ushuaia leaves have one more layer of palisade cells respect to Moreno leaves. Ushuaia leaves showed higher palisade cells, larger abaxial epidermal cells and thicker cuticles than Moreno leaves. The stomatal density was superior on Moreno leaves. Scanning Electron Microscope of abaxial epidermis showed a surface with numerous ridges of different forms that prevent the layout of epidermal cells on Moreno leaves. Appearance of this surface is glossy and oily. On the contrary, epidermal cells are well recognized on Ushuaia leaves. Stomata of anomocytic type were observed and surface looks waxy. Auto-fluorescence on leaf cross sections were observed on the vascular bundles and partially on the epidermis cells. B. microphylla leaves showed a high phenotypic plasticity between the two sites of cultivation. The changes in the leaf morphology and structure observed in Moreno leaves could indicate that the plants are trying to adjust its morphology to the new culture conditions i.e. higher temperatures and lower irradiance.

Simple and rapid fabrication of disposable carbon-based electrochemical cells using an electronic craft cutter for sensor and biosensor applications

This work describes the construction of an all-plastic disposable carbon-based electrochemical cell (DCell) using a simple procedure based on the use of a home cutter printer for prototyping and laminating. The cutter printer and adhesive vinyl films were used to produce three electrodes in an electrochemical cell layout, and a laminating process was then used to define the geometric area and insulate the electrodes. The DCell showed excellent performance in several applications including the determination of toxic metals in water samples, the immobilization of DNA and the detection of Salmonella. An unmodified DCell was applied for Pb and Cd detection in the range of 100–300ngmL−1 with a limit of detection of 50 and 39ngmL−1 for Cd and Pb, respectively. DNA was successfully immobilized on a DCell and used for studies of interaction between bisphenol A and DNA. The square wave voltammetry of a DNA modified DCell presented a guanine oxidation current 2.5 times greater after exposure of the electrode to bisphenol A and no current variation for the adenine moiety indicating that bisphenol A showed a preference for DNA interaction sites. A magneto-immunoassay was developed using a DCell for Salmonella detection in milk samples. The system presented a linear range from 100 to 700 cellsmL−1 with a limit of detection of 100 cellsmL−1 and good recovery values between 93% and 101% in milk samples, with no interference from Escherichia coli. Using the proposed method, hundreds of DCells can be assembled in less than two hours, at a material cost of less than US $0.02 per cell. The all-plastic disposable electrochemical cell developed was successfully applied as an electrochemical sensor and biosensor. The feasibility of the developed all-plastic disposable electrochemical cell was demonstrated in applications as both sensor and biosensor.

Conceptual layout design of CFETR Hot Cell Facility

CFETR (China Fusion Engineering Test Reactor) is new generation of Tokomak device beyond EAST in China. An overview of hot cell layout design for CFETR has been proposed by ASIPP&USTC. Hot Cell, as major auxiliary facility, not only plays a pivotal role in supporting maintenance to meet the requirements of high duty time 0.3–0.5 but also supports installation and decommissioning.Almost all of the Tokomak devices are lateral handling internal components like ITER and JET, but CFETR maintain the blanket module from 4 vertical ports, which is quite a big challenge for the hot cell layout design. The activated in-vessel components and several diagnosis instruments will be repaired and refurbished in the Hot Cell Facility, so the appropriate layout is very important to the Hot Cell Facility to ensure the high duty time, it is divided into different parts equipped with a variety of RH equipment and diagnosis devices based on the functional requirements. The layout of the Hot Cell Facility should make maintenance process more efficient and reliable, and easy to service and rescue when a sudden events taking place, that is the capital importance issue considered in design.

Conceptual Model of Management in Automotive Projects

In automotive industry the development of new products, involve complex engineering processes subject to time pressures and fierce competition on the automotive market. An important role in the development of such projects it is the process planner. The position of process planner involves the interface between the department of design and development and production department, managing the projects in terms of technic side till implement them in series production. This paper develops in teach mode a conceptual model to scroll the successive phases of the project, designed to position the process planner, in order to transfer the knowledge to the students, in the field of project management of new product development in the automotive industry. Through a case study it will be creates a conceptual model in methodological way, namely that exemplifies the main phases of automotive projects: the quote, concept, release of design, testing and qualification of product and final phase of preparing and launching in series production. Preliminary phase namely quotation phase includes defining the project team and submitting the offer. Process steps are established for each operation and the estimated cost for devices and equipment, project time planning, and can generate the first effective phase of the project, namely the concept phase, called the foundation project also. Next phase of concept phase is the release of design, thereupon the design is frozen, as well as the product bill of materials. PP sets: final steps of the process; production line (cell layout design); material flow; Process Failure Mode and Effects Analysis (P-FMEA) and highlighting the top 5 risks assumed; In testing phase and product qualification, the PP manages and harmonizes in the smallest detail in order to achieve this target, to complete the preparation and launch in series production.

Rapid Co-Optimization of Processing and Circuit Design to Overcome Carbon Nanotube Variations

Carbon nanotube field-effect transistors (CNFETs) are promising candidates for building energy-efficient digital systems at highly-scaled technology nodes. However, carbon nanotubes (CNTs) are inherently subject to variations that reduce circuit yield, increase susceptibility to noise, and severely degrade their anticipated energy and speed benefits. Joint exploration and optimization of CNT processing options and CNFET circuit design are required to overcome this outstanding challenge. Unfortunately, existing approaches for such exploration and optimization are computationally expensive, and mostly rely on trial-and-error-based ad hoc techniques. In this paper, we present a framework that quickly evaluates the impact of CNT variations on circuit delay and noise margin, and systematically explores the large space of CNT processing options to derive optimized CNT processing and CNFET circuit design guidelines. We demonstrate that our framework: 1) runs over 100x faster than existing approaches, and 2) accurately identifies the most important CNT processing parameters, together with CNFET circuit design parameters (e.g., for CNFET sizing and standard cell layouts), to minimize the impact of CNT variations on CNFET circuit speed with less than 5% energy cost, while simultaneously meeting circuit-level noise margin and yield constraints.

EPlace-MS: Electrostatics-Based Placement for Mixed-Size Circuits

We propose an electrostatics-based placement algorithm for large-scale mixed-size circuits (ePlace-MS). ePlace-MS is generalized, flat, analytic and nonlinear. The density modeling method eDensity is extended to handle the mixed-size placement. We conduct detailed analysis on the correctness of the gradient formulation and the numerical solution, as well as the rationale of dc removal and the advantages over prior density functions. Nesterov’s method is used as the nonlinear solver, which shows high yet stable performance over mixed-size circuits. The steplength is set as the inverse of Lipschitz constant of the gradient function, while we develop a backtracking method to prevent overestimation. An approximated nonlinear preconditioner is developed to minimize the topological and physical differences between large macros and standard cells. Besides, we devise a simulated annealer to legalize the layout of macros and use a second-phase global placement to reoptimize the standard cell layout. All the above innovations are integrated into our mixed-size placement prototype ePlace-MS, which outperforms all the related works in literature with better quality and efficiency. Compared to the leading-edge mixed-size placer NTUplace3, ePlace-MS produces up to 22.98% and on average 8.22% shorter wirelength over all the 16 modern mixed-size benchmark circuits with the same runtime.

Self-Aligned Double Patterning Aware Pin Access and Standard Cell Layout Co-Optimization

Self-aligned double patterning (SADP) is being considered for use at the 10-nm technology node and below for routing layers with pitches down to $\boldsymbol {\sim }50$ nm because it has better line edge roughness and overlay control compared to other multiple patterning candidates. To date, most of the SADP-related literature has focused on enabling SADP-legal routing in physical design tools while few attempts have been made to address the impact SADP routing has on local, standard cell (SC) I/O pin access. At the same time, via layers are used to connect the local SADP routing layers to the I/O pins on lower metal layers. Due to the high via density on the Via-1 layer, the litho-etch-litho-etch (LELE)-aware Via-1 design becomes a necessity to achieve legal pin access at the SC level. In this paper, we present the first study on SADP-aware pin access and layout optimization at the SC level. Accounting for SADP-specific and Via-1 design rules, we propose a coherent framework that uses depth first search, mixed integer linear programming, and backtracking method to enable LELE friendly Via-1 design and simultaneously optimize SADP-based local pin access and within-cell connections. Our experimental results show that, compared with the conventional approach, our framework effectively improves pin access of the SCs and maximizes the pin access flexibility for routing.