A Method about Embedding Watermark in PDF Document

Abstract

Foreword Those of us who have worked on fracture for a long time often suspect that the subject has far-reaching implications in fields other than our own. Most come to the subject via various aspects of structural integrity or material development but we observe cracks in rocks and see mowers cutting grass, for example, and perceive that these could be described within a general framework of fracture mechanics. Putting this framework in place and explaining the arguments with supporting evidence is a huge task and it is this that Brian Cotterell has achieved. We are given a historical review of the subject and intriguing explorations of the influence of fracture in making stone tools and designing classical buildings, for example. The whole area of the influence of fracture in biology is described via its effect on evolution. One is given a whole new perspective on the properties and design of teeth by this section. Biology is probably the next growth area in the subject and this book is a wonderful primer for anyone entering this new field. When this is followed by a review of the importance of fracture in the development of electronic materials one gains some perspective of the enormous range of the book. I have, I hope, given some idea of the scope of Fracture and Life. It is an intellectual achievement of the highest order and required extraordinary diligence by the author to read, let alone review and summarise, the vast literature covered. The book is timely since the subject is changing and moving into new fields. The next generation now have a perfect starting point for this quest. Preface Fracture affects everything. On a grand scale fracture has played a part in the evolution of the world as we know it. The evolution of life has seen constant interplay between plants and animals avoiding being torn or eaten, and the need of other animals to eat. Human evolution has been greatly affected by the fact that stones were easily flaked to produce sharp tools. Without stone tools human evolution might have been radically different. Civilization has required the development of means to cut and fracture to fashion artefacts and structures as well as the development of the technology to avoid fracture. As civilizations became more sophisticated, so the need to control fracture grew. New technologies and materials brought new fracture problems. Fortunately, scientists and engineers are now largely very successful at controlling fracture so that most people do not even think about its possibility apart from breaking their own bones. Man's understanding of fracture has developed with time. Even before we became human our hominid ancestors knew how to flake sharp stone tools. The very attribute that made stone tools easy to flake also made them easily broken and more durable metal tools finally replaced them. The ancient civilizations produced enduring stone buildings that required the development of the means to quarry and fashion stone. Building techniques had also to be developed to ensure that the buildings did ...

Research on a watermarking recognition method for PDF documents based on natural language processing

“…This method mainly focuses on the frequency, position, and other attributes of words, and have problems with low recognition accuracy and robustness. The watermark embedding method based on image processing is suitable for many non-text watermark scenarios, such as embedding watermark images into PDF document images through matrix singular value decomposition 9 . This method requires high permissions for the files being read and the recognition rate is too slow.…”