Decision Supporting Methodology and System Based on Theory of Constraints for Making an Optimal Product Portfolio Strategy in Shipbuilding Industry

Shipbuilding is a typical ‘build to order’ industry. It has a business model that generates revenues from building various ships and offshore products in accordance with owner’s requirements at each production stage. Under uncertainty in shipping market, it is very essential for the shipbuilder to prepare the fast and competitive decision for product portfolio strategy in order to maximize contribution margin by exploiting production facilities and constraints. TOC(theory of constrains) proposed by Dr. goldratt in 1979 has been evolved into a management philosophy with practices and principles spanning a multitude of operations management sub-disciplines.[1] In this study, we introduce the unique decision supporting methodology for the optimal product portfolio sets based on TOC. This methodology is established by adopting the concept of Drum Buffer Rope (DBR)[2] in constraints planning and Throughput Account (TA)[3][4][5] in management accounting of TOC. In addition, Decision Supporting System (DSS)[6] is implemented by applying this methodology. This DSS system provides a throughput estimator with reflecting the cost structure of shipbuilding industry and a resource simulator built on heuristic algorithms to operate major constraint-resources in shipyard such as dock, quay and pre-erection area etc. Several examples are presented to show that the proposed methodology and system can effectively support the strategic decision-making process of a global shipbuilding company

On The Stability Problem of Quadratic Functional Equations in 2-Banach Spaces

In this paper, we investigate the stability problem in the spirit of Hyers-Ulam, Rassias and Gavruta for the quadratic functional equation: f(2x + y) + f(2x - y) = 2f(x + y) + 2f(x - y) + 4f(x) - 2f(y) in 2-Banach spaces. These results extend the generalized Hyers-Ulam stability results by the quadratic functional equation in normed spaces to 2-Banach spaces

Homomorphisms and derivations on C*-ternary algebras assocoated with a generalized Cauchy-Jensen type additive functional equation

In this paper, we prove the generalized Hyers-Ulam stability of C∗-ternary homomorphisms and C∗-ternary derivations on C∗-ternary algebras associated with the generalized Cauchy-Jensen type additive functional equation for all xi; xj ∈ X where n ∈ Z+ is a fixed integer with n ≥ 3. &nbsp

The impact of Arctic sea ice loss on mid-Holocene climate.

Mid-Holocene climate was characterized by strong summer solar heating that decreased Arctic sea ice cover. Motivated by recent studies identifying Arctic sea ice loss as a key driver of future climate change, we separate the influences of Arctic sea ice loss on mid-Holocene climate. By performing idealized climate model perturbation experiments, we show that Arctic sea ice loss causes zonally asymmetric surface temperature responses especially in winter: sea ice loss warms North America and the North Pacific, which would otherwise be much colder due to weaker winter insolation. In contrast, over East Asia, sea ice loss slightly decreases the temperature in early winter. These temperature responses are associated with the weakening of mid-high latitude westerlies and polar stratospheric warming. Sea ice loss also weakens the Atlantic meridional overturning circulation, although this weakening signal diminishes after 150-200 years of model integration. These results suggest that mid-Holocene climate changes should be interpreted in terms of both Arctic sea ice cover and insolation forcing

Mid-Holocene Northern Hemisphere warming driven by Arctic amplification.

The Holocene thermal maximum was characterized by strong summer solar heating that substantially increased the summertime temperature relative to preindustrial climate. However, the summer warming was compensated by weaker winter insolation, and the annual mean temperature of the Holocene thermal maximum remains ambiguous. Using multimodel mid-Holocene simulations, we show that the annual mean Northern Hemisphere temperature is strongly correlated with the degree of Arctic amplification and sea ice loss. Additional model experiments show that the summer Arctic sea ice loss persists into winter and increases the mid- and high-latitude temperatures. These results are evaluated against four proxy datasets to verify that the annual mean northern high-latitude temperature during the mid-Holocene was warmer than the preindustrial climate, because of the seasonally rectified temperature increase driven by the Arctic amplification. This study offers a resolution to the "Holocene temperature conundrum", a well-known discrepancy between paleo-proxies and climate model simulations of Holocene thermal maximum

Optimizing Transportation Sequence in Warehouse with Genetic Algorithms

International audienceOptimizing transportation sequence is crucial to reduce material handling costs in warehouse operations and thus in total logistics costs. Transportation sequence is the ordering of storage and retrieval jobs that a material handling device has to perform to finish an order list. In many studies, the optimization of transportation sequence has been simplified as an order-picking problem, and accordingly solved as a classical traveling salesman problem. However, transportation sequence is a double-cycle storage and retrieval problem (DCSRP) in itself, meaning that the combination of storage and retrieval jobs into double cycles has to be considered simultaneously. In this paper, we propose formulating the DCSRP as a permutation problem and applying several genetic algorithms to solve the formulated problem. Extensive computational experiments were performed to demonstrate the capability of the approach. The experimental analysis confirms that our approach could solve the problem efficiently on the one hand, and addresses the question of which genetic operators are best applied to the formulated DCSRP on the other hand