A dual watermark-fingerprint system

This article proposes a multimedia content protection system in which all copies of a protected object are identically watermarked, but each user has a distinct secret detection key that differs from the secret embedding key. An attacker with access to one detection key can fool the corresponding watermark detector but not other watermark detectors. Surprisingly, analogous to a criminal action, during this attack the attacker necessarily inserts his or her fingerprint into the modified content. Even a collusion clique of relatively large size cannot entirely remove the secret marks from the protected content by colluding their detection keys. More importantly, if the clique is not large enough, traces of the detection keys of all colluders can be detected with relatively high accuracy in the attacked clip. Our proposed watermark-fingerprint system achieves a minimum collusion size K that grows linearly with the size N of the marked object. In addition, we can augment our watermark-fingerprint system with a segmentation layer. The media content is partitioned into 5 segments, in which media players as well as forensic analyzers can reliably detect a watermark or fingerprint. Only detection keys that belong to the same segment can participate in the collusion clique. With segmentation, the minimum collusion size K grows as 0(N log N). Therefore, with or without segmentation, our watermark-fingerprint system significantly improves on the best-known asymptotic resistance to (fingerprint) collusion attacks of about O(N/sup 1/4/). Because we use a new protection protocol, comparing our system to classic fingerprint systems might seem unfair. However, such a comparison is important because the two technologies share a common goal: multimedia copyright enforcement. Our aim in this article is to characterize the collusion attacks against this system under the assumption that watermark detection is robust against signal-processing attacks on the protected object.     

Fast computation of discrete cosine transform through fast Hartley transform

A relationship between the discrete cosine transform (DCT) and the discrete Hartley transform (DHT) is derived. It leads to a new fast and numerically stable algorithm for the DCT.     

A plasticity concrete material model for DYNA3D

Lagrangian finite element codes with explicit time integration are extensively used for the analysis of structures subjected to explosive loading. Within these codes, numerous material models have been implemented. However, the development of a realistic but efficient concrete material model has proven complex and challenging.

The plasticity concrete material model in the Lagrangian finite element code DYNA3D was assessed and enhanced. The main modifications include the implementation of a third, independent yield failure surface; removal of the tensile cutoff and extension of the plasticity model in tension; shift of the pressure cutoff; implementation of a three invariant formulation for the failure surfaces; determination of the triaxial extension to triaxial compression ratio as a function of pressure; shear modulus correction; and implementation of a radial path strain rate enhancement. These modifications insure that the response follows experimental observations for standard uniaxial, biaxial and triaxial tests in both tension and compression, as shown via single element analyses. The radial path strain rate enhancement insures constant enhancement for all those tests. As a full scale example, a standard dividing wall subjected to a blast load is analyzed and the effects of the modifications assessed.     

Improved spread spectrum: a new modulation technique for robust watermarking

This paper introduces a new watermarking modulation technique, which we call improved spread spectrum (ISS). When compared with traditional spread spectrum (SS), the signal does not act as a noise source, leading to significant gains. In some examples, performance improvements over SS are 20 dB in signal-to-noise ratio (SNR) or ten or more orders of magnitude in the error probability. The proposed method achieves roughly the same noise robustness gain as quantization index modulation (QIM) but without the amplitude scale sensitivity of QIM. Our proposed ISS is as robust in practice as traditional SS.     

Yield and fruit quality of four sweet corn hybrids (Zea mays) under conventional and integrated fertilization with vermicompost

BACKGROUND: Vermicompost has been proposed as a valuable fertilizer for sustainable agriculture. The effects of vermicompost on yield and quality of sweet corn were evaluated in this study. In two field trials, sweet corn plants were grown under (i) a conventional fertilization regime with inorganic fertilizer, and integrated fertilization regimes in which 75% of the nutrients were supplied by the inorganic fertilizer and 25% of the nutrients were supplied by either (ii) rabbit manure, or (iii) vermicompost. All three types of fertilization regime were supplied at two doses. Two pairs of nearly isogenic sweet corn hybrids homozygous for sugary1 and shrunken2 mutants were included in the trials to explore fertilizer × genotype interactions. Growth, yield and ear quality of the plants were evaluated in relation to the three fertilization regimes. RESULTS: In general, the integrated regimes yielded the same productivity levels as the conventional treatment. Moreover, both vermicompost and manure produced significant increases in plant growth and marketable yield, and also affected the chemical composition and quality of the marketable ear. Nevertheless, most of the observed effects of the organic fertilizers were genotype‐dependent. CONCLUSION: The results confirm that the use of organic fertilizers such as vermicompost has a positive effect on crop yield and quality. Nevertheless, these effects were not general, indicating the complexity of the organic amendment–plant interactions and the importance of controlling genetic variation when studying the effects of vermicompost on plant growth. Copyright © 2011 Society of Chemical Industry     

Extended lapped transforms: properties, applications, and fastalgorithms

The family of lapped orthogonal transforms is extended to include basis functions of arbitrary length. Within this new family, the extended lapped transform (ELT) is introduced, as a generalization of the previously reported modulated lapped transform (MLT). Design techniques and fast algorithms for the ELT are presented, as well as examples that demonstrate the good performance of the ELT in signal coding applications. Therefore, the ELT is a promising substitute for traditional block transforms in transform coding systems, and also a good substitute for less efficient filter banks in subband coding systems     

Bond between Carbon Fiber Reinforced Polymer Bars and Concrete. I: Experimental Study

The bond characteristics of four different types of carbon fiber reinforced polymer (CFRP) rebars (or tendons) with different surface deformations embedded in lightweight concrete were analyzed experimentally. In a first series of tests, local bond stress-slip data, as well as bond stress-radial deformation data, needed for interface modeling of the bond mechanics, were obtained for varying levels of confining pressure. In addition to bond stress and slip, radial stress and radial deformation were considered fundamental variables needed to provide for configuration-independent relationships. Each test specimen consisted of a CFRP rebar embedded in a 76-mm-(3 in.)-diam, 102-mm-(4 in.)-long, precracked lightweight concrete cylinder subjected to a constant level of pressure on the outer surface. Only 76 mm (3 in.) of contact were allowed between the rebar and the concrete. For each rebar type, bond stress-slip and bond stress-radial deformation relationships were obtained for four levels of confining axisymmetric radial pressure. It was found that small surface indentations were sufficient to yield bond strengths comparable to that of steel bars. It was also shown that radial pressure is an important parameter that can increase the bond strength almost threefold for the range studied. In a second series of tests, the rebars were pulled out from 152-mm-(6 in.)-diam, 610-mm-(24 in.)-long lightweight concrete specimens. These tests were conduced to provide preliminary data for development length assessment and model validation (Part II).     

Fracture energy for three point bend tests on single edge notched beams: Proposed evaluation

The research in fracture mechanics of concrete is reviewed in an attempt to reconcile the different, and sometimes contradictory, approaches for evaluation of the fracture energy, G_f. An improved method to measure G_f for beams in three point bending is presented. This method is expected to provide a more reliable characterization of the fracture toughness of concrete.     

Effective communication: tips on technical writing

The impact of a technical article may have as much to do with how well it is presented as with the engineering or scientific significance of the work. A well-written article is easier to understand and easier to remember; the more readers that remember your work, the higher the likelihood it will get cited. This article reviews some basic principles and discusses a few tips (dos and don'ts) about writing technical papers.