Transcoding of MPEG Bitstreams

This paper discusses the problem of transcoding as it may occur in, for instance, the following situation. Suppose a satellite transmits an MPEG-compressed video signal at say 9 Mbit/s. This signal must be relayed at a cable head end. However, since the cable capacity is only limited, the cable head end will want to relay this incoming signal at a lower bit-rate of, say, 5 Mbit/s. The problem is how to convert a compressed video signal of a given bit-rate into a compressed video signal of a lower bit-rate. The specific transcoding problem discussed in this paper is referred to as bit-rate conversion. Basically, a transcoder used for such a purpose will consist of a cascaded decoder and encoder. It is shown in the paper that the complexity of this combination can be significantly reduced. The paper also investigates the loss of picture quality that may be expected when a transcoder is in the transmission chain. The loss of quality as compared to that resulting in the case of transmission without a transcoder is studied by means of computations using simplified models of the transmission chains and by means of using computer simulations of the complete transmission chain. It will be shown that the presence of two quantizers, i.e. cascaded quantization, in the transmission chain is the main cause of extra losses, and it will be shown that the losses in terms of SNR will be some 0.5 ¿ 1.0 dB greater than in the case of a transmission chain without a transcoder

Generalization and performance improvement of a coherence multiplexing system

Usually a coherence multiplexing system uses delay-filters at the transmitter and receiver to perform the code. An extension to other filter types is described. Using a continuous source the signal-to-beat noise ratio is proportional to the square of the inverse of the number of simultaneous users. A further extension is made by using a pulsed source and by replacing the filters by banks of filters. Each element of each filter bank also comprizes a unique delay. In that case the SNR can be made proportional to the inverse of the number of users, so that more users can be handled simultaneously

Coherence Multiplex System Topologies

Coherence multiplexing is a potentially inexpensive form of optical code-division multiple access, which is particularly suitable for short-range applications with moderate bandwidth requirements, such as access networks, LANs, or interconnects. Various topologies are known for constructing an optical transmission system in which several channels are coherence-multiplexed in one optical fiber. In this paper, the parallel array, the intrinsic reference ladder (IRL), and the discontinuous series system topologies will be further considered and compared with respect to code orthogonality requirements, theoretical performance, and some practical implementation aspects. A modification to the IRL system is proposed, resulting in a significant improvement in the theoretical performance

Reduced zinc oxide levels in sulphur vulcanisation of rubber compounds : mechanistic aspects of the role of activators and multifunctional additives

This thesis has been devoted to a great many different possibilities to reduce the level of ZnO in rubber compounds, with emphasis on the development of a new type of activator. It must be realised that vulcanisation is a complex process, whereby many ingredients and parameters play an important role. ZnO and zinc-containing species are considered indispensable for the vulcanisation process and certainly difficult to substitute. Long-term solutions for the reduction of emissions of zinc into the environment should be focused on the development of new and effective concepts for completely new zinc-free vulcanisation systems. Short-term strategies will be mainly concentrated on reduced dosages of zinc and a higher chemical activity, combined with an increased solubilisation. In this respect progress has been made by the development of the ZnClay. In summary, the research described in this thesis combines a pragmatic in-rubber investigation and a fundamental study of the chemistry all through the vulcanisation reactions cascade. It has contributed to a better understanding of the role of the activator in the sulphur vulcanisation process

Sustainable Laser Sintering with PA12 : Applications for re-use of aged powder

Selective Laser Sintering (SLS) with Polyamide 12 is increasingly used for production of functional components for prototyping and end-use. Common grades of PA12 powders age and cause a stock of unsintered powder material that cannot be re-used within the SLS process. This research explores and validates processes and applications that could drive sustainable re-use of the materia

AMBITION Deel 1: Business Case : hoe Nederlandse bedrijven gebruik maken van 3D-metaalprinten

Onderdeel van het project AMbition. Deze publicatie is tot stand gekomen door een onderzoek naar 3D-metaalprinten van 2019 tot 2021. Dit onderzoek is uitgevoerd door onderzoekers, docenten en studenten van hogeschool Windesheim in samenwerking met bedrijven. Binnen dit project is ook onderzoek gedaan vanuit een bedrijfskundig perspectief waarbij de volgende drie onderwerpen zijn onderzocht: - Verandermanagement binnen bedrijven om 3D-metaalprinten mogelijk te maken. - De toegevoegde waarde van de verschillende 3D-metaalprinttechnieken. - Kostprijsberekeningen van 3D-metaalprinten