Order release in a workload controlled flow-shop with sequence-dependent set-up times

In this paper, we report a simulation study on the role of sequence-dependent set-up times in decision making at the order release level of a workload controlled make-to-order flow-shop. The study evaluates the potential for set-ups savings, dependent on the level of workload in the shop, for two alternative strategies, namely considering set-up times centrally, within the release decision or locally, within the dispatching decision. These strategies are compared and assessed on the basis of two main performance measures namely time in system and standard deviation of the job lateness. Results indicate that the local strategy, which has been traditionally adopted in practice and in most of the studies dealing with sequence-dependent set-up times, does not always give the best results. The release frequency and the shop workload appear critical to the selection of the strategy to adopt, strongly influencing system performance.Fundação para a Ciência e a Tecnologia (FCT)Universidade do Minh

Hydroxide catalysis bonding for astronomical instruments

Hydroxide catalysis bonding (HCB) as a jointing technique has been under development for astronomical applications since ∼1998 (patented by D.-H. Gwo). It uses an aqueous hydroxide solution to form a chemical bond between oxide or oxidisable materials (e.g., SiO2, sapphire, silicon and SiC). It forms strong, extremely thin bonds, and is suitable for room temperature bonding, precision alignment, operation in ultra-low vacuum and down to temperatures of 2.5 K. It has been applied in the NASA satellite mission Gravity Probe B and in the ground-based gravitational wave (GW) detector GEO600. It will soon fly again on the ESA LISA Pathfinder mission and is currently being implemented in the Advanced LIGO and Virgo ground-based GW detectors. This technique is also of considerable interest for use in other astronomical fields and indeed more broadly, due to its desirable, and adjustable, combination of properties. This paper gives an overview of how HCB has been and can be applied in astronomical instruments, including an overview of the current literature on the properties of hydroxide catalysis bonds

TFDD: A trust-based framework for reliable data delivery and DoS defense in VANETs

[EN] A trust establishment scheme for enhancing inter-vehicular communication and preventing DoS attacks `TFDD¿ is proposed in this paper. Based on a developed intrusion detection module (IDM) and data centric verification, our framework allows preventing DDoS attacks and eliminating misbehaving nodes in a distributed, collaborative and instantaneous manner. In addition, a trusted routing protocol is proposed that, using context-based information such as link stability and trust information, delivers data through the most reliable way. In this study, the simulation results obtained demonstrate the effectiveness of our trust framework at detecting dishonest nodes, as well as malicious messages that are sent by honest or dishonest nodes, after a very low number of message exchanges. Furthermore, colluding attacks are detected in a small period of time, which results in network resources being released immediately after an overload period. We also show that, in a worst-case scenario, our trust-based framework is able to sustain performance levels, and outperforming existing solutions such as T-CLAIDS and AECFV.Kerrache, CA.; Lagraa, N.; Tavares De Araujo Cesariny Calafate, CM.; Lakas, A. (2017). TFDD: A trust-based framework for reliable data delivery and DoS defense in VANETs. Vehicular Communications. 9:254-267. doi:10.1016/j.vehcom.2016.11.010S254267

The structuring of production control systems

Co-ordination of the activities of production units is necessary to realise the required delivery performance in the market. These should not conflict with reaching the production economics objectives of each of the units. Production structure is needed to reduce the complexity and should minimise the loss of potential flexibility. Any structure will have some elements in common — the definition of basic elements (e.g. capacities) as a first step in production control structure design; the introduction of product units and the decomposition of the total production control to Goods Flow Control and Production Unit Control; the relationship of sales and manufacturing and the interference of products and capacities as two main determining factors of the Goods Flow Control structure. The generality of these elements means it is possible to develop a small but relatively complete set of reference structures. A reference structure for Goods Flow Control in a repetitive manufacturing situation is discussed. Its main elements are master planning, material co-ordination, workload control and work order release

Orlicky's Material Requirements Planning

xxi, 308 p. : Ill.; 21 c

Production and inventory control : Principles and techniques

443 p.; 21 cm