Catálogo de publicaciones - libros

The flow simulating ink transfer process of gravure printing applications was investigated numerically using a finite difference approach. The flow was assumed to be described by the Reynolds equation and the Oldroyd B model. In this simple situation, it turns out that the velocity and pressure fields are the same as in the Newtonian case. However, two non-zero components of non-Newtonian stress tensor survive and they are likely to change the characteristics of ink transfer mechanism compared with that of the Newtonian case. In this preliminary study, the behavior of the non-Newtonian stress tensor was investigated at several representative streamwise locations.

Winding is an integral operation in almost every web handling process and center-wound rolls are suitable and general scheme in winding system. However, the internal stresses within center-wound rolls can cause damage such as buckling, spoking, cinching, etc. Wound roll quality and performance are known to be related to distribution of in-roll stresses. It is therefore necessary to analyze the relationship between taper tension in winding section and internal stress distribution within center-wound roll to prevent winding failure. In this study, a new taper tension control method for producing high quality wound roll was developed. The new method was induced from analyzing the winding mechanism by using the stress model in center-wound rolls, nip induced tension model, taper tension profile-telescoping relationship, and taper tension type-internal stresses relationship, etc. Auto taper tension profile making method for avoiding the damage (telescoping, buckling, cinching, etc.) is presented. Simulation results show that the proposed method is very useful.

Roll to roll (R2R) manufacturing, also known as ’web processing’, is the process of creating electronic devices on a roll of flexible plastic or metal foil. With the need for increased performance and productivity in the R2R industry, effective control and on-line supervision for web quality is essential. In this paper, we presents a system for on-line measurement of wrinkles, a defect inccurring due to compressive stresses developed in the web . This machine vision system, based on structured light ranging and multi-threaded processing is able to measure wrinkle height on a transparent web.

The terminology burr defines undesirable result of plastic deformation formed in machining process causing degradation of the accuracy and functionality of the product and its assemblies. To supervise the quality of the machined part, effective edge measurement and analysis are necessary. In this paper, we presented a laser-based measurement system including softwares for control and characterisation of burr parameters. Experiments were carried out showing that micro burr around 10 m and burr formed on a curved surface was successfully measured and analyzed.

This study is intended to analyze the effect of thin ink-film thickness around rotating printing roll on the printing quality in the gravure printing process which is used for making electronics circuit like a RFID tag with a conductive ink. The present work numerically estimates the film thickness around rotating roller partially immersed in ink, in which the volume of fluid (VOF) method was adopted to figure out the film formation process around rotating roller. Parameter studies were performed to compare the effect of ink viscosity, surface tension, roller rotating speed and immersed angle on the film thickness. The result indicates that the film thickness has a strong dependency on the fluid viscosity, while the surface tension effect becomes negligible.

Standard components usage in a press die is recognized as a way for a cost reduction and a short lead time. It also provides a way for a quick maintenance of a dieunder repair. It is expected to contribute to integration of CAD/CAM system for manufacturing dies in the future. This paper presents a 3D CAD library which is constructed using the standard components and is used for designing a press die. This 3D CAD library is generated by a database system made of Microsoft Access for standard components and by CATIA V5 R10 API for geometric features. The library is implemented using Visual Basic 6.0 utility of CATIA API function in the Windows NT environment. It creates a 3D model of the standard components of press die easily when a die designer inputs numerical values of geometric features and the BOM of the completely assembled parts. It also generates automatically the assembly drawing of die set by using variables for standard values of die parts. Therefore users can save the cost of time to design the press die components, and even a beginner can use this program with ease. The test results of the 3D CAD library for designing shearing and bending dies verify its usefulness and feasibility.

In this paper, we present security analysis on Temporally-Ordered Routing Algorithm (TORA) routing protocol. We first identify three attack goals, namely route disruption, route invasion and resource consumption. Then, we study on how to achieve these attack goals through misuses of routing messages. The analysis shows that three misuse actions on the routing messages, including drop, modify and forward, and active forge, enable the malicious attacker to conduct real time attacks on TORA protocol. We demonstrate the attacks using NS-2 software and then analyze the simulation results. The simulation results verify our analysis and we observe that through certain misuses, an inside attacker can degrade the network performance, disrupting the route creation process and consume scarce network resource.

In UMTS (Universal Mobile Telecommunication System), a protocol called UMTS AKA (Authentication and Key Agreement) is used to securely authenticate an MS (Mobile Station). However, the UMTS AKA has several drawbacks such as network bandwidth consumption and synchronization problem. In this paper, we propose a new authentication protocol for UMTS that overcomes these problems. Moreover, our protocol enhances the security of the protocol by providing better privacy and also provides perfect forward secrecy. Furthermore, our protocol also provides mutual authentication between an MS and its HN (Home Network) and between an MS and the SN (Serving Network).

Recently, the bilinear pairings such as the Weil and the Tate pairings defined on algebraic curves over a finite field have found applications in the design of cryptographic protocols. One useful application in mobile environments is for secure group communication over a public network. The members in the group need to establish a common group key that will be used to encrypt messages to be broadcast to the group. Furthermore, it is important to update the group key with low computational costs when the members join and leave the group. In this paper, we propose a pairing-based key exchange protocol for dynamic groups. The proposed protocol achieves low communication complexity and provides some computational savings by the batch verification of signatures. We show that the security of our scheme is guaranteed against an active adversary in the random oracle model under the bilinear Diffie-Hellman (BDH) assumption.

Deniability is defined as a privacy property which enables protocol principals to deny their involvement after they had taken part in a particular protocol run. Lately, Chou et al. had proposed their ID-based deniable authentication protocol after proving the vulnerability to Key-Compromise Impersonation (KCI) attack in Cao et al.’s protocol. In addition, they claimed that their protocol is not only secure, but also able to achieve both authenticity and deniability properties. However, in this paper, we demonstrate that Chou et al.’s protocol is not flawless as it remains insecure due to its susceptibility to the KCI attack. Based on this, we propose an enhanced scheme which will in fact preserves the authenticity, the deniability and the resistance against the KCI attack.