Humans can often estimate tactile properties of objects from vision alone. For example, during online shopping, we can often infer material properties of clothing from images and judge how the material would feel against our skin. What visual information is important for tactile perception? Previous studies in material perception have focused on measuring surface appearance, such as gloss and roughness, and using verbal reports of material attributes and categories. However, in real life, predicting tactile properties of an object might not require accurate verbal descriptions of its surface attributes or categories. In this paper, we use tactile perception as ground truth to measure visual material perception. Using fabrics as our stimuli, we measure how observers match what they see (photographs of fabric samples) with what they feel (physical fabric samples). The data shows that color has a significant main effect in that removing color significantly reduces accuracy, especially when the images contain 3-D folds. We also find that images of draped fabrics, which revealed 3-D shape information, achieved better matching accuracy than images with flattened fabrics. The data shows a strong interaction between color and folding conditions on matching accuracy, suggesting that, in 3-D folding conditions, the visual system takes advantage of chromatic gradients to infer tactile properties but not in flattened conditions. Together, using a visual-tactile matching task, we show that humans use folding and color information in matching the visual and tactile properties of fabrics.

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We propose a novel security enhancement technique for a physical layer secure orthogonal frequency division multiplexed passive optical network (OFDM-PON) based on three-dimensional Brownian motion and chaos in cell (3DBCC). This method confuses an OFDM symbol via transforming it into a 3D symbol matrix and a 3D cell matrix with different size lengths. Different dividing-confusion rules then generate different complementary cumulative distribution functions (CCDFs) of peak-to-average power ratio (PAPR). And we can pre-estimate bit error rate (BER) performance by calculating the CCDF values. We also find that the processing time decreases with the matrix's side length decreasing simultaneously. A new weighted comprehensive value (Q) is further used to evaluate the overall performance between the processing time and the BER. Finally, an experiment successfully demonstrates a physical layer secure OFDM signal transmission with 22.06-Gb/s data rate over a 25.4-km standard single mode fiber (SSMF). These results indicate that cell (5) has the weighted optimum overall performance, which verifies that the proposed encryption technique is promising for building a physical layer security enhanced OFDM-PON system with a low processing time delay and a good BER for future access network systems.

In the paper, a deoxyribonucleic acid (DNA) extension code with 3-bit binary streams is proposed to encrypt the downlink data for orthogonal frequency division multiplexing passive optical network (OFDM-PON). It has 8 bases to make up 4 pairs of complementary codes. And it can obtain 384 matching rules, which greatly improves the randomness of matching. Here, two DNA addition operation rules are also proposed to encrypt the data. DNA extension rules can reduce half coding operations. Three 1-dimensional (1-D) chaotic systems are used to encrypt the code and control the rules. The encryption method based on the uplink streams from optical network units (ONUs) makes the security of downlink signals not just depending on the security of chaotic systems. Finally, a 22.06 Gb/s DNA extension code encryption signal is transmitted through a back-to-back (BTB) system and a 25-km standard single-mode fiber (SSMF). The proposed method not only improves the security but also reduces the computational complexity. The experimental results show that the proposed method has the ability to resist optical channel response and fiber nonlinearity, which is a promising candidate for solving the security enhancement in access networks.INDEX TERMS DNA extension code, OFDM-PON, uplink stream, 1-D chaotic system, security enhancement.