A two-user approximation-based transmit beamforming for physical-layer multicasting in mobile cellular downlink systems

Multicast has been known as an efficient transmission technique for group-oriented applications such as multi-party video conferencing, video streaming for paid users, online gaming, and social networking. In this paper, we investigate physical-layer multicasting in mobile cellular downlink systems, where the antennas at base station are employed to transmit common signals to multiple users simultaneously. A central design problem of downlink physical-layer multicasting is the search for the optimal beamforming vector that maximizes the multicast rate. Traditionally, the problem has been formulated as a quadratically constrained quadratic programming problem and shown to be NP-hard in general. In this paper, starting from examining the Karush–Kuhn–Tucker stationary conditions, a new method based on two-user approximation is proposed for the search for the optimal beamforming vector. The method is able to achieve a much higher multicast rate than the existing methods and provides an attractive trade-off between performance and complexity, especially for the case of using a large number of antennas. Using a large number of antennas at base station, also known as the large-scale multiple-input and multiple-output technique, has been regarded widely as one of the most promising technologies to increase system capacity, coverage, and user throughput for future generations of mobile cellular systems.     

Kinetics of thermal destruction of Salmonella in ground chicken containing trans-cinnamaldehyde and carvacrol

We investigated the heat resistance of an eight-strain cocktail of Salmonella serovars in chicken supplemented with trans cinnamaldehyde (0 to 1.0%, wt/wt) and carvacrol (0 to 1.0%, wt/wt). Inoculated meat was packaged in bags that were completely immersed in a circulating water bath and held at 55 to 71°C for predetermined lengths of time. The recovery medium was tryptic soy agar supplemented with 0.6% yeast extract and 1% sodium pyruvate. D-values in chicken, determined by linear regression, were 17.45, 2.89, 0.75, and 0.29 min at 55, 60, 65, and 71°C, respectively (z = 9.02°C). Using a survival model for nonlinear survival curves, D-values in chicken ranged from 13.52 min (D(1), major population) and 51.99 min (D(2), heat-resistant subpopulation) at 55°C to 0.15 min (D(1)) and 1.49 min (D(2)) at 71°C. When the Salmonella cocktail was in chicken supplemented with 0.1 to 1.0% trans-cinnamaldehyde or carvacrol, D-values calculated by both approaches were consistently less at all temperatures. This observation suggests that the addition of natural antimicrobials to chicken renders Salmonella serovars more sensitive to the lethal effect of heat. Thermal death times from this study will be beneficial to the food industry in designing hazard analysis and critical control point plans to effectively eliminate Salmonella contamination in chicken products used in this study.     

Hepatoprotection of silymarin against thioacetamide-induced chronic liver fibrosis

BACKGROUND: Liver fibrosis is chronic liver damage usually caused by alcohol, viruses or other toxins and is characterised by an excessive accumulation of extracellular matrix proteins such as collagen. The aim of this study was to establish an animal model of chronic liver damage and investigate molecular mechanisms of silymarin hepatoprotective effects. RESULTS: Thioacetamide (TAA; 100 mg kg^?1 intraperitoneal (i.p.) injection three times weekly) effectively induced chronic liver fibrosis in male ICR mice. Then 24 ICR mice were randomly divided into four groups: (1) saline (i.p.) + water (gavage); (2) saline (i.p.) + 150 mg kg^?1 silymarin (gavage); (3) 100 mg kg^?1 TAA (i.p.) + water (gavage); (4) 100 mg kg^?1 TAA (i.p.) + 150 mg kg^?1 silymarin (gavage). Eight weeks of TAA treatment resulted in lower body weight, serum cholesterol and triglycerides as well as increased liver size, ALT, AST and LDH values (P < 0.05). These TAA‐induced effects were attenuated by silymarin (P < 0.05); therefore silymarin also ameliorated TAA‐induced liver lesions. Effects of silymarin on TAA‐induced chronic liver damage may be attributed to down‐regulation of hepatic MMP‐2, MMP‐13, TIMP‐1, TIMP‐2, AP‐1, KLF6, TGF‐β1, α‐SMA and COL‐α1. CONCLUSION: A mouse model of chronic liver fibrosis was successfully established by injecting 100 mg kg^?1 TAA three times weekly in male ICR mice. Meanwhile, silymarin showed hepatoprotection against TAA‐induced damage. Copyright © 2011 Society of Chemical Industry     

Antimicrobial Effects of Allyl Isothiocyanate and Modified Atmosphere on Pseduomonas Aeruginosa in Fresh Catfish Fillet under Abuse Temperatures

The effects of allyl isothiocyanate (AIT; 18 and 36 μg/L) in vapor phase, modified atmosphere (MA; 49% CO₂, 0.5% O₂, and 50.5% N₂), and their combinations on the growth behavior of Pseduomonas aeruginosa in fresh catfish fillet at different abuse temperatures (8, 15, and 20 °C) were evaluated in this study. Lag phase, maximum growth rate, and shelf life were used as parameters to analyze the antimicrobial effects. Both gaseous AIT and MA alone inhibited the growth potential of P. aeruginosa effectively, prolonging the shelf life by 1.5 to 3.4 times compared to the control at abuse temperatures between 8 and 20 °C. The synergistic effect was observed at 8 °C, extending the shelf life of fresh catfish by more than 6.5 times (≥ 550 h). In addition, the maximum growth rate decreased with decreasing storage temperature, but it was not significantly influenced by the addition of AIT or MA. Hence, the combination of AIT and MA may be used as an effective antimicrobial system to reduce the microbial risks due to temperature abuse and to improve the shelf life of fresh catfish fillet. The proper combination of AIT and MA may be further optimized for industrial applications.     

The wear of ultrafine WC–Co hard metals

The wear performance of ultrafine-grained tungsten carbide–cobalt (WC–Co) hard metals during three-body abrasion and particle erosion has been evaluated and compared to that of similar conventional coarser grained hard metals. The tungsten carbide grain size varied between 0.5 and 3 μm with cobalt contents ranging from 6 to 15%. Silica particles were used in both forms of testing. Erosion was carried out at 60 ms⁻¹ at an impact angle of 75° and abrasion at a velocity of 0.5 ms⁻¹ and a load of 50 N.

The wear resistance of the ultrafine grades was found to be at least double that of the closest conventional fine grained hard metals. These increases in wear performance are considerably higher than any corresponding increase in hardness which is, at most, 25% and is not achieved at the expense of fracture toughness which is maintained at a similar level to that of conventional fine grained hard metals. The increase in wear resistance coincides with a change in the mechanism of material removal. Sub-micron materials experience ductile deformation and bulk removal of material whilst coarser grades display more localised response with extensive fragmentation of the WC grains.     

Three-dimensional millimeter-wave imaging for concealed weapondetection

Millimeter-wave imaging techniques and systems have been developed at the Pacific Northwest National Laboratory (PNNL), Richland, WA, for the detection of concealed weapons and contraband at airports and other secure locations. These techniques were derived from microwave holography techniques that utilize phase and amplitude information recorded over a two-dimensional aperture to reconstruct a focused image of the target. Millimeter-wave imaging is well suited for the detection of concealed weapons or other contraband carried on personnel since millimeter-waves are nonionizing, readily penetrate common clothing material, and are reflected from the human body and any concealed items. In this paper, a wide-bandwidth three-dimensional holographic microwave imaging technique is described. Practical weapon detection systems for airport or other high-throughput applications require high-speed scanning on the order of 3 to 10 s. To achieve this goal, a prototype imaging system utilizing a 27-33 GHz linear sequentially switched array and a high-speed linear scanner has been developed and tested. This system is described in detail along with numerous imaging results     

Multiple-dwell and sequential code acquisition with diversity forFFH/MFSK spread-spectrum systems under band multitone jamming

Pseudonoise code acquisition is investigated for constant hopping rate fast frequency-hopped (FFH)/M-ary frequency-shift keying systems under the effects of white Gaussian noise and band multitone jamming. In particular, serial search acquisition systems based on the traditional multiple-dwell test (up to three dwells) and three novel sequential tests are analyzed and compared. Analytical results show the following in a heavily jammed environment: (1) the inherent time diversity in an FFH system can significantly improve the acquisition performance of the multiple-dwell test and (2) the novel sequential tests can significantly outperform the multiple-dwell test. Our analytical results are verified by computer simulations     

Variable dwell-time code acquisition for direct-sequencespread-spectrum systems on time-variant Rayleigh fading channels

Variable dwell-time code acquisition based on multiple-dwell or sequential linear tests is investigated for direct-sequence spread-spectrum systems on time-variant Rayleigh fading channels. Unlike in the conventional additive white Gaussian noise channels, the channel memory incurred by fading renders the exact analysis of the acquisition systems extremely difficult, if not impossible. In this paper, a novel method is developed to evaluate the mean acquisition time of the acquisition systems very accurately. The effects of Rayleigh fading are evaluated, and comparisons are made between double-dwell and sequential linear tests. Numerical results show that Rayleigh fading may result in 1-4-dB loss in performance, and the sequential linear test can outperform double-dwell test by a margin of 1-2 dB. The analytical results are verified by computer simulations     

Parameter extraction of resistive thermal microsensors by ACelectrical method

Obtaining device parameters of thermal microsensors is essential for evaluating their performances and simulation modeling. We report an AC electrical method for extracting these parameters experimentally with relatively simple instrumentation. The basic parameters of resistive microsensors, the resistance, temperature coefficient of resistance, thermal capacitance, and conductance, are derivable from the second harmonic signal of the output voltage induced by a sinusoidal driving current. The results are compared with other methods     

A low-power ASIC design for cell search in the W-CDMA system

This paper presents a low-power ASIC design for cell search in the wideband code-division multiple-access (W-CDMA) system. A low-complexity algorithm that is able to work satisfactorily under the effect of large frequency and clock errors is designed first. Then, a set of low-power measures are employed in the design of hardware architecture and circuits. Finally, through power analysis, critical blocks are identified and redesigned so as to further reduce the power consumption. The final design shows that the power is reduced by 51% from the original design of 133.6 mW to 65.49 mW, and its core area is also reduced by 31.9% from 3.4/spl times/3.4 mm/sup 2/ to 2.8/spl times/2.8 mm/sup 2/. The design is implemented and verified in a 3.3-V 0.35-/spl mu/m CMOS technology with clock rate 15.36 MHz.