Topological photonics: fundamental concepts, recent developments, and future directions

Topological photonics is emerging as a new paradigm for the development of both classical and quantum photonic architectures. What makes topological photonics remarkably intriguing is the built-in protection as well as intrinsic unidirectionality of light propagation, which originates from the robustness of global topological invariants. In this Perspective, we present an intuitive and concise pedagogical overview of fundamental concepts in topological photonics. Then, we review the recent developments of the main activity areas of this field, categorized into linear, nonlinear, and quantum regimes. For each section, we discuss both current and potential future directions, as well as remaining challenges and elusive questions regarding the implementation of topological ideas in photonics systems

Developing a Trade-off between Upgrade Action Time and Warranty Length for Second-hand Electrical Components

One way of improving the reliability and reducing the warranty servicing cost for second-hand items is through actions such as overhaul and upgrade which are carried out by the dealer or a third party. For second-hand electrical components, the improvement involves testing of items for a short time, called upgrade action time, before their release to the market. The items that fail during the test are scrapped or repaired; only items that survive the test are considered to be of good quality and released to the market. In this paper, a cost model is developed to achieve a trade-off between reducing the warranty servicing cost and increasing the upgrade action cost for a second-hand electrical component sold under various warranty policies

An Investigation of High Performance Heterojunction Silicon Solar Cell Based on n-type Si Substrate

In this study, high efficient heterojunction crystalline silicon solar cells without using an intrinsic layer were systematically investigated. The effect of various parameters such as work function of transparent conductive oxide (ϕTCO), density of interface defects, emitter and crystalline silicon thickness on heterojunction silicon solar cell performance was studied. In addition, the effect of band bending and internal electric field on solar cell performance together with the dependency of cell performance on work function and reflectance of the back contact were investigated in full details. The optimum values of the solar cell properties for the highest efficiency are presented based on the results of the current study. The results represent a complete set of optimum values for a heterojunction solar cell with high efficiency up to the 24.1 % with VOC = 0.87 V and JSC =32.69 mA⋅cm – 2

Modeling and Analysis of Resource Sharing Approach in Common Platform Strategy Using Petri Net Theory

The most competitive advantages in business and manufacturing is resource-sharing.We must share common resources to produce a group of product family with using common platform strategy. This strategy helps us to increase profit and value in business. It is necessary to apply this strategy to model and analyze resource achievability in different situations. In this paper we try to develop a practical model for analyzing common resource behavioral in platform area with using Petri net theory. Petri Nets have been successfully used for modeling and control the dynamics of flexible manufacturing systems.This paper presents some important concepts about common platform and petri net theory and then presents numerical examples to show how to use Petri net for modeling and analysis in common platform. This model is very useful for common platform strategy and can be used to determine reliability of common platform systems in an effective way

An Investigation of High Performance Heterojunction Silicon Solar Cell Based on n-type Si Substrate

In this study, high efficient heterojunction crystalline silicon solar cells without using an intrinsic layer were systematically investigated. The effect of various parameters such as work function of transparent conductive oxide (ϕTCO), density of interface defects, emitter and crystalline silicon thickness on heterojunction silicon solar cell performance was studied. In addition, the effect of band bending and internal electric field on solar cell performance together with the dependency of cell performance on work function and reflectance of the back contact were investigated in full details. The optimum values of the solar cell properties for the highest efficiency are presented based on the results of the current study. The results represent a complete set of optimum values for a heterojunction solar cell with high efficiency up to the 24.1 % with VOC = 0.87 V and JSC =32.69 mA⋅cm – 2

Warranty and Sustainable Improvement of Used Products through Remanufacturing

Currently, a large number of used/second-hand products are being sold with remanufacturing. Remanufacturing is a process of bringing used products to a better functional state and can be applied as a way for (1) controlling the deterioration process, (2) reducing the likelihood of a failure over the warranty period and (3) making the used item effectively younger. Remanufacturing is relatively a new concept and has received very limited attention. In this paper, we develop an important sustainable improvement approach for used items sold with failure free warranty to determine the optimal improvement level. Our model makes a useful contribution to the reliability growth literature, as it captures the uncertainty and suggests improvement in the remanufacturing process. By using this model, the dealers can decide whether and how much to invest in remanufacturing projects

Monte Carlo Simulation to Compare Markovian and Neural Network Models for Reliability Assessment in Multiple AGV Manufacturing System

We compare two approaches for a Markovian model in flexible manufacturing systems (FMSs) using Monte Carlo simulation. The model which is a development of Fazlollahtabar and Saidi-Mehrabad (2013), considers two features of automated flexible manufacturing systems equipped with automated guided vehicle (AGV) namely, the reliability of machines and the reliability of AGVs in a multiple AGV jobshop manufacturing system. The current methods for modeling reliability of a system involve determination of system state probabilities and transition states. Since, the failure of the machines and AGVs could be considered in different states, therefore a Markovian model is proposed for reliability assessment. The traditional Markovian computation is compared with a neural network methodology. Monte Carlo simulation has verified the neural network method having better performance for Markovian computations.We compare two approaches for a Markovian model in flexible manufacturing systems (FMSs) using Monte Carlo simulation. The model which is a development of Fazlollahtabar and Saidi-Mehrabad (2013), considers two features of automated flexible manufacturing systems equipped with automated guided vehicle (AGV) namely, the reliability of machines and the reliability of AGVs in a multiple AGV jobshop manufacturing system. The current methods for modeling reliability of a system involve determination of system state probabilities and transition states. Since, the failure of the machines and AGVs could be considered in different states, therefore a Markovian model is proposed for reliability assessment

Two-dimensional Warranty Cost Analysis for Second-hand Products

In spite of the recent steady increase of the volume of the second-hand markets, often customers remain in doubt regarding the quality and durability of the secondhand products. Aiming to reduce and share this uncertainty, dealers offer warranty on their products. Offering warranty for second-hand products is a relatively new marketing strategy employed by dealers of used electronic equipment, furniture, automobiles, etc. Usually, for used products, the dealer’s expected warranty cost is a function of product reliability, past age and usage, servicing strategy and conditions and terms of the warranty policy/contract. Sometimes the offered policy is limited by two parameters, typically the product age and usage after the sale. This type of policies is referred to as two-dimensional warranty policies. In this article, we develop statistical models for estimating the dealer’s expected warranty cost for second-hand products sold with two-dimensional free repair/replacement warranty

Design of a Hybrid Genetic Algorithm for Parallel Machines Scheduling to Minimize Job Tardiness and Machine Deteriorating Costs with Deteriorating Jobs in a Batched Delivery System

This paper studies the parallel machine scheduling problem subject to machine and job deterioration in a batched delivery system. By the machine deterioration effect, we mean that each machine deteriorates over time, at a different rate. Moreover, job processing times are increasing functions of their starting times and follow a simple linear deterioration. The objective functions are minimizing total tardiness, delivery, holding and machine deteriorating costs. The problem of total tardiness on identical parallel machines is NP-hard, thus the under investigation problem, which is more complicated, is NP-hard too. In this study, a mixed-integer programming (MILP) model is presented and an efficient hybrid genetic algorithm (HGA) is proposed to solve the concerned problem. A new crossover and mutation operator and a heuristic algorithm have also been proposed depending on the type of problem. In order to evaluate the performance of the proposed model and solution procedure, a set of small to large test problems are generated and results are discussed. The related results show the effectiveness of the proposed model and GA for test problems

Exact Mixed Integer Programming for Integrated Scheduling and Process Planning in Flexible Environment

This paper presented a mixed integer programming for integrated scheduling and process planning. The presented process plan included some orders with precedence relations similar to Multiple Traveling Salesman Problem (MTSP), which was categorized as an NP-hard problem. These types of problems are also called advanced planning because of simultaneously determining the appropriate sequence and minimizing makespan in the process of scheduling. There are alternative machines for each operation and different sequences for each order, which create a flexible environment for production planning. In process planning ansd integrated scheduling, most mathematical models have two sets of ordered pairs with precedence or non-precedence relations between operations; therefore, these models cannot be solved using optimization software. Therefore, in this paper, this problem was modeled by a new approach and solved by GAMS software. The model was validated by the existing data in the literature