We present the design and fabrication of a phenanthrenequinone-doped poly(methyl methacrylate) photopolymer material. Large blocks of samples were made, and the material showed negligible shrinkage after optical exposures. We recorded and reconstructed 250 holograms at a single spot, using a 1-cm(3) block.
This paper presents a design and development of a low power consumption, and low cost, human identification system using a pyroelectric infrared (PIR) sensor whose visibility is modulated by a Fresnel lens array. The optimal element number of the lens array for the identification system was investigated and the experimental results suggest that the lens array with more elements can yield a better performance in terms of identification and false alarm rates. The other parameters of the system configuration such as the height of sensor location and sensor-to-object distance were also studied to improve spectral distinctions among sensory data of human objects. The identification process consists of two parts: training and testing. For the data training, we employed a principal components regression (PCR) method to cluster data with respect to different registered objects at different speed levels. The feature data of different objects walking along the same path in training yet at random speeds are then tested against the pre-trained clusters to decide whether the target is registered, and which member of the registered group it is.
This study investigated the structural and mechanical properties of Klebsiella pneumoniae type 3 fimbriae, which constitute a known virulence factor for the bacterium. Transmission electron microscopy and optical tweezers were used to understand the ability of the bacterium to survive flushes. An individual K. pneumoniae type 3 fimbria exhibited a helix-like structure with a pitch of 4.1 nm and a three-phase force-extension curve. The fimbria was first nonlinearly stretched with increasing force. Then, it started to uncoil and extended several micrometers at a fixed force of 66 ؎ 4 pN (n ؍ 22). Finally, the extension of the fimbria shifted to the third phase, with a characteristic force of 102 ؎ 9 pN (n ؍ 14) at the inflection point. Compared with the P fimbriae and type 1 fimbriae of uropathogenic Escherichia coli, K. pneumoniae type 3 fimbriae have a larger pitch in the helix-like structure and stronger uncoiling and characteristic forces.
A comparative analysis of phenanthrenequinone-doped poly(methyl methacrylate) materials fabricated at California Institute of Technology and National Chiao Tung University is performed in order to understand the dierences exhibited in their recording and baking dynamics. Ó 2001 Published by Elsevier Science B.V.Keywords: Holography; Photopolymer material; PQ-PMMA; Grating dynamics; Temperature eect Phenanthrenequinone-(PQ-) doped poly(methyl methacrylate) (PMMA) [1,2] has been used as a recording material in optical memories and other holographic systems [3±6]. This material consists of a polymeric basis doped with chromophores, the PQ molecules. This material is lightweight and durable, and does not suer from shrinkage. High optical quality samples of dierent shapes and thicknesses can be obtained. These properties make it an excellent candidate for holographic memory modules. In this paper, we compare the PQ±PMMA samples that we use at California Institute of Technology (Caltech) with those fabricated at National Chiao Tung University (NCTU) and try to understand the dierences in behavior they exhibit.Sample preparation consists of dissolving PQ molecules ( 6 0.7%) in liquid methyl methacrylate (MMA) together with azo-bis-isobutyrolnitrile, a polymerization thermal initiator. This solution is poured into molds and allowed to polymerize in a pressure chamber. The preparation process followed at Caltech diers from the one followed at NCTU in the temperature at which the pressure chamber is set during polymerization. For the Caltech material, the temperature of the chamber is set to 80°C. On the other hand, at NCTU the polymerization process is split into two steps [4,7]. First, the solution is let to rest at room temperature for approximately 120 h until the solution turns homogeneously viscid. At this point, the
This paper proposes a real-time human identification system using a pyroelectric infrared (PIR) detector array and hidden Markov models (HMMs). A PIR detector array with masked Fresnel lens arrays is used to generate digital sequential data that can represent a human motion feature. HMMs are trained to statistically model the motion features of individuals through an expectation-maximization (EM) learning process. Human subjects are recognized by evaluating a set of new feature data against the trained HMMs using the maximum-likelihood (ML) criterion. We have developed a prototype system to verify the proposed method. Sensor modules with different numbers of detectors and different sampling masks were tested to maximize the identification capability of the sensor system.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.