Decorative near-infrared transmission filters featuring high-efficiency and angular-insensitivity employing 1D photonic crystals

We present a new scheme for visibly-opaque but near-infrared-transmitting filters involving 7 layers based on one-dimensional ternary photonic crystals, with capabilities in reaching nearly 100% transmission efficiency in the near-infrared region. Different decorative reflection colors can be created by adding additional three layers while maintaining the near-infrared transmission performance. In addition, our proposed structural colors show great angular insensitivity up to ±60° for both transverse electric and transverse magnetic polarizations, which are highly desired in various fields. The facile strategy described here involves a simple deposition method for the fabrication, thereby having great potential in diverse applications such as image sensors, anti-counterfeit tag, and optical measurement systems.

     

Frequency Insertion Strategy for Channel Assignment Problem

This paper presents a new heuristic method for quickly finding a good feasible solution to the channel assignment problem (CAP). Like many other greedy-type heuristics for CAP, the proposed method also assigns a frequency to a call, one at a time. Hence, the method requires computational time that increases only linear to the number of calls. However, what distinguishes the method from others is that it starts with a narrow enough frequency band so as to provoke violations of constraints that we need to comply with in order to avoid radio interference. Each violation is then resolved by inserting frequencies at the most appropriate positions so that the band of frequencies expands minimally. An extensive computational experiment using a set of randomly generated problems as well as the Philadelphia benchmark instances shows that the proposed method perform statistically better than existing methods of its kind and even yields optimum solutions to most of Philadelphia benchmark instances among which two cases are reported for the first time ever, in this paper. Won-Young Shin was born in Busan, Korea in 1978. He received B.S. in industrial engineering from Pohang University of Science and Technology (POSTECH) in 2001 and M.S in operation research and applied statistics from POSTECH in 2003. Since 2003 he has been a researcher of Agency for Defense Development (ADD) in Korea. He is interested in optimization of communication system and applied statistics. Soo Y. Chang is an associate professor in the Department of Industrial Engineering at Pohang University of Science and Technology (POSTECH), Pohang, Korea. He teaches linear programming, discrete optimization, network flows and operations research courses. His research interests include mathematical programming and scheduling. He has published in several journals including Discrete Applied Mathematics, Computers and Mathematics with Application, IIE Transactions, International Journal of Production Research, and so on. He is a member of Korean IIE, and ORMSS. Jaewook Lee is an assistant professor in the Department of Industrial Engineering at Pohang University of Science and Technology (POSTECH), Pohang, Korea. He received the B.S. degree in mathematics with honors from Seoul National University, and the Ph.D. degree from Cornell University in applied mathematics in 1993 and 1999, respectively. He is currently an assistant professor in the department of industrial engineering at the Pohang University of Science and Technology (POSTECH). His research interests include nonlinear systems, neural networks, nonlinear optimization, and their applications to data mining and financial engineering. Chi-Hyuck Jun was born in Seoul, Korea in 1954. He received B.S. in mineral and petroleum engineering from Seoul National University in 1977, M.S. in industrial engineering from Korea Advanced Institute of Science and Technology in 1979 and Ph.D. in operations research from University of California, Berkeley, in 1986. Since 1987 he has been with the department of industrial engineering, Pohang University of Science and Technology (POSTECH) and he is now a professor and the department head. He is interested in performance analysis of communication and production systems. He has published in several journals including IIE Transactions, IEEE Transactions, Queueing Systems and Chemometrics and Intelligent Laboratory Systems. He is a member of IEEE, INFORMS and ASQ.     

Identification of the adverse effect of nitrate on the phosphate release rate and improvement of EBPR process models.

The adverse effect of nitrate on the phosphate release rate in the anaerobic phase was observed and was hardly explainable with conventional EBPR process models. Four possible mechanisms were proposed including substrate competition, reduced fermentation, parallel reaction and sequential reaction. Batch experiments were designed and conducted to identify the dominant mechanism. Results showed that the sequential reaction was the only possible mechanism where only denitrification occurred if any nitrate existed in the anaerobic phase. Then the phosphate release following after the nitrate was completely removed. Nitrate inhibition effect was added into the PHA storage rate to incorporate the sequential reaction in the conventional ASM3 plus EAWAG bio-P module (ASM3 + P). Nitrate inhibition coefficient, K(I,NO,PAO) was found to be as low as 0.05 mg/L. This correlated well with experimental observation where no also meant that the anaerobic compartment of a continuous flow reactor could be seriously affected by the residual nitrate contained in the sludge recycle flow. This phenomenon caused overestimation of the phosphate uptake rate and consequently underestimation of PO4(3-) -P concentration. This problem was resolved by incorporation of a nitrate inhibition term in the ASM3 + P for more accurate simulation of the EBPR process.     

Inhibition of microbial growth in ready‐to‐eat food stored at ambient temperature by modified atmosphere packaging

This study was undertaken to develop a modified atmosphere package to control microbial growth in ready‐to‐eat (RTE) products stored at ambient temperature. Ethanol and/or limonene associated with modified atmosphere (CO₂ : O₂ : N₂ = 30% : 5% : 65%) was used to inhibit the growth of total air‐borne microorganisms and Escherichia coli in RTE products stored at 25°C. The results indicated that 0.05% ethanol vapour in the headspace was effective to inhibit the growth of air‐borne microorganisms and E. coli at 25°C for 72 h in a model study, and the effectiveness was related to ethanol content. Both 73 ppm limonene and 0.05% ethanol vapour enhanced the bacteriostatic effect of modified atmosphere in RTE sushi roll products, and no off‐flavour was detected using this formulated gas; however, no significant inhibitory effect was observed for RTE cold noodle products. This study concludes that combinations of carbon dioxide, ethanol or limonene vapours are effective to inhibit microbial growth in RTE food at ambient temperature, and the outcome may be due to the hurdle effect. Copyright © 2003 John Wiley & Sons, Ltd.     

Fast handoff with reducing waste rate approach for wireless resources management in UMTS mobile networks

3G Wideband CDMA systems adopt the Orthogonal Variable Spreading Factor code tree as the channelization codes management for achieving high data rate transmission in personal multimedia communications. It assigns a single channelization code for each accepted connection. Nevertheless, it wastes the system capacity when the required rate is not powers of two of the basic rate. One good solution is to assign multiple codes for each accepted connection but it causes two inevitable drawbacks: long handoff delay and new call setup delay due to high complexity of processing with multiple channelization codes, and high cost of using more number of rake combiners. Especially, long handoff delay may result in more call dropping probability and higher Grade of Service, which will degrade significantly the utilization and revenue of the 3G cellular systems. Therefore, we propose herein an adaptive efficient codes determination algorithm based on the Markov Decision Process analysis approach to reduce the waste rate and reassignments significantly while providing fast handoff. Numerical results demonstrate that the proposed approach yields several advantages, including the lowest GOS, the least waste rate, and the least number of reassignments. Meanwhile, the optimal number of rake combiners is also analyzed in this paper. This research was supported in part by the National Science Council of Taiwan, ROC, under contract NSC-93-2213-E-324-018.     

Synthesis of amphiphilic magnetic microspheres by dispersion copolymerization of styrene and poly(ethylene oxide) macromonomer

Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe₃O₄ magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g^?1. © 2003 Society of Chemical Industry     

Effect of modified atmosphere packaging on the shelf-life of coated, whole and sliced mushrooms

Whole and sliced fresh mushrooms (Agaricus bisporus) were packaged with PVC wrap or two polyolefins (PD-941 and PD-961) films after coating with CaCl₂ and chitosan. Package gas composition, color, weight loss and maturity were measured during storage at 12 °C and 80%RH. For PD-961, the highest in-package concentration occurred during the first day of storage regardless of treatments, while wrap and PD-941 showed varying degrees in-package concentration with different processes and coatings. The whiteness of whole mushrooms varied significantly with the type of coating, but not with the type of films. The extent of darkening was greater in coated whole mushrooms than in sliced ones. Weight loss occurred in all packages and varied from 3 (g/100 g) to about 7 (g/100 g) after 6 days of storage. Due to a lower permeability, PD-961 packages had the lowest weight loss. The type of packaging films significantly affected the maturity index, where PD-961 most effectively lowered maturity index for both whole and sliced mushrooms, thus extending the shelf-life. The type of coating did not appear to affect maturity index except for the wrap package where chitosan coating markedly lowered the maturity index of sliced mushrooms.     

Effects of genotype and treatment on the antioxidant activity of sweet potato in Taiwan

Six genotypes of sweet potato commercially available in Taiwan, including TNG57, TNG66, TNG68, TYY1, RP and WP, were used as samples in this study of the effects of steaming and kneading with pre-steaming treatments on the antioxidant components and antioxidant properties of methanolic extracts. Steam treatment increased the total phenols contents of all genotypes (2–13 times), flavonoids content of RP (1.3 times) and anthocyanins contents of RP and WP (5–6 times). Steam treatment also increased the reducing power and scavenging DPPH radical effect of sweet potato flours. For the methanolic extracts of steamed and kneaded flours, reducing powers were 0.02–1.70 at 5.0 mg ml⁻¹ and the scavenging effects on DPPH radicals were 19–92% at 2.5 mg ml⁻¹. Both showed the order of RP > WP > TYY1 and TNG66 > TNG57 and TNG68. However, the chelating effect of the six genotypes at 1.0 mg ml⁻¹ ranged from 50% to 73%. Contents of total phenols, flavonoids, and anthocyanins of sweet potato flours were significantly positively correlated with the reducing power and scavenging DPPH radical effects. After steaming and kneading treatments, RP showed the highest increase in the contents of total phenols, flavonoids and anthocyanins among the six genotypes studied.     

Optically preamplified receiver performance due to VSB filtering for 40-Gb/s optical signals modulated with various formats

Optically preamplified receiver performance according to the vestigial sideband (VSB) filtering has been numerically investigated for 40-Gb/s optical signals modulated with nonreturn-to-zero, duobinary nonreturn-to-zero (NRZ), return-to-zero (RZ), carrier-suppressed RZ, and duobinary carrier-suppressed RZ formats. The VSB filtering enables the spectral widths of NRZ, duobinary NRZ, and RZ signals to be reduced without severe power penalties at the receiver. On the other hand, carrier-suppressed RZ and duobinary carrier-suppressed RZ signals have no large advantages over VSB filtering because of the characteristics of their signals. Our results suggest that RZ signals are the most suitable modulation format for VSB filtering, without considering the filter loss, because of the tolerance of the intersymbol interference and a large spectral width. However, duobinary NRZ signals are the most suitable modulation format for VSB filtering, considering the filter loss, because of their narrow spectral width.     

Spectral shape tunable band-rejection filter using a long-period fiber grating with divided coil heaters

We have developed a new type of tunable band rejection filter, which provides high spectral-shaping flexibility in a wide tuning range. The filter consists of a long-period fiber grating (LPFG) with divided coil heaters. Each of the divided coil heaters is controlled individually to adjust a temperature distribution along the LPFG and to modify the spectral shape of the LPFG filter. The tunable band rejection filter is demonstrated to function properly when applied as an erbium-doped fiber amplifier gain-flattening filter.