Improvement of low-speed operation performance of DTC forthree-level inverter-fed induction motors

A direct torque control algorithm for three-level inverter-fed induction motors is presented. Basic voltage selection methods similar to a two-level inverter provoke some problems such as stator-flux drooping phenomenon and undesirable torque control deterioration appeared, especially at low-speed operation. To overcome these problems, an algorithm with the basic switching sectors subdivided and intermediate voltage vectors applied is proposed in this paper. This algorithm basically considers applications in which direct torque-controlled induction motors are fed by three-level inverters with maximum switching frequency lowered around 1 kHz. An adaptive observer is also employed to bring better responses at the low-speed operation, by estimating some state variables and motor parameters which take a deep effect on the performance of the low-speed operation. Simulation and experiment results verify effectiveness of the proposed algorithm     

Simulation and design methodology for a 50-Gb/s multiplexer/demultiplexer package

A 50 Gb/s package for SiGe BiCMOS 4:1 multiplexer and 1:4 demultiplexer targeting SONET OC-768 serial communication systems is introduced in this work. The package was designed to facilitate bit-error-rate tests and constructed with high-speed coaxial connectors, transmission lines on ceramic substrate, ribbon bonds for chip-to-package interconnects, and a metal composite housing. Numerical simulations were conducted to guide the package design, and both small signal measurements and operational tests were performed thereafter to verify the design and modeling concepts. To keep the model structure under the existing computing capability, the simulation was segmented into three sections - coaxial connector to transmission line, transmission line alone, and transmission line to ribbon bond, and then the results were assembled to predict the performance of the entire package. The package was operated up to 50 Gb/s with low degradation to input digital waveforms and free of error.     

Monitoring of roasting-induced changes in ginsenoside composition of ginseng (Panax ginseng C.A. Meyer)

This study was intended to roast freeze-dried ginseng in order to determine the effect of roasting conditions on major ginsenosides by monitoring their changes using response surface methodology. As the roasting temperature and time increased, the contents of ginsenoside Re, Rg₁, Rf, Rb₁, Rc, Rb₂, and Rd tended to decrease but that of ginsenoside Rg₃ increased, reaching the maximum content (0.96 mg/g) at 189.99°C and 20.29 min as compared to the initial value (0.01 mg/g). The total ginsenoside content was estimated to be increased from 4.30 to 5.19 mg/g at 140.17°C and 27.51 min. It was found that the roasted ginseng has different ginsenoside compositions from raw ginseng. Therefore, further studies are needed to investigate the functional and biological properties of roasted ginseng as compared to the conventional white and red ginseng.     

Robust trade-off portfolio selection

Robust portfolio selection explicitly incorporates a model of parameter uncertainty in the problem formulation, and optimizes for the worst-case scenario. We consider robust mean–variance portfolio selection involving a trade-off between the worst-case utility and the worst-case regret, or the largest difference between the best utility achievable under the model and that achieved by a given portfolio. While optimizing for the worst-case utility may yield an overly pessimistic portfolio, optimizing for the worst-case regret may result in a complete loss of robustness; we theoretically demonstrate this point. Robust trade-off portfolio compromises these two extremes, enabling more informative selections. We show that, under a widely used ellipsoidal uncertainty model, the entire optimal trade-off curve can be found via solving a series of semidefinite programs (SDPs). We then extend the model to handle the union of finitely many ellipsoids, and show that trade-off analysis under this quite general uncertainty model also reduces to a series of SDPs. For more general uncertainties, we propose an iterative algorithm based on the cutting-set method. Under the finite-union-of-ellipsoids model, this algorithm offers an alternative to the SDP in exploring the optimal trade-off curve. We illustrate the promises of the trade-off portfolios by using historical stock returns data.

     

Effect of Drying Treatment on Physical Identification Characteristics of Irradiated Seasonings

The effect of different drying treatments such as spray drying and vacuum drying on the sensitivity of physical detection methods (photostimulated luminescence (PSL), electron spin resonance (ESR), and thermoluminescence (TL)) was investigated for four types of irradiated seasonings. The slurry feed of each seasoning was exposed to γ-ray irradiation at doses of 0, 5, 10 kGy before being subjected to drying process. Spray drying was applied to beef and soybean seasoning while garlic and broth seasoning were exposed to vacuum drying according to routine protocols adopted in the industry. The samples were analyzed by PSL as a rapid screening method followed by validated methods including ESR spectroscopy and TL analysis. The PSL photon counts drastically dropped in all irradiated samples after both drying processes. No ESR signal was obtained from any of the irradiated seasonings before or after the drying applications. All the irradiated seasoning samples produced typical TL glow curves between the specific temperature range of 150–250 °C. However, the shape, peak, and intensity of TL glow curves were greatly affected particularly after the spray drying treatment. In conclusion, the dry treatment can significantly affect the irradiation detection characteristics in seasoning samples.     

Integrated on-chip 0.35 μm BiCMOS current-mode DC–DC buck converter

A current-mode DC–DC buck converter with a fully integrated power module is presented in this article. The converter is implemented using BiCMOS technology in amplifier and power MOSFET in a current sensor. The current sensor is realised by the power lateral double-diffused MOSFET with the aspect ratio much larger than that of a matched p-MOSFET. In addition, BiCMOS technology is applied in the error amplifier for an accurate current sensing and a fast transient response. The DC–DC converter is fabricated with 0.35?µm BiCMOS process. Experimental results show that the fully integrated converter operates at 1.3?MHz switching frequency with a supply voltage of 5?V. The output DC voltage is obtained as expected and the output ripple is controlled to be within 2% with a 30?µH off-chip inductor and 100?µF off-chip capacitor.     

Effect of cooking on radiation-induced chemical markers in beef and pork during storage

Raw and cooked beef and pork loins were irradiated at 0 or 5 kGy. The radiation-induced marker compounds, such as hydrocarbons, 2-alkylcyclobutanones (2-ACBs), and sulfur volatiles, were determined after 0 and 6 mo of frozen storage. Two hydrocarbons (8-heptadecene [C(17:1)] and 6,9-heptadecadiene [C(17:2)]) and two 2-ACBs (2-dodecylcyclobutanone [2-DCB] and 2-tetradecylcyclobutanone [2-TCB]) were detected only in irradiated raw and cooked meats. Although precooked irradiated meats produced more hydrocarbons and 2-ACBs than the irradiated cooked ones, the amounts of individual hydrocarbons and 2-ACBs, such as 8-heptadecene, 6,9-heptadecadiene, 2-DCB, and 2-TCB, were sufficient enough to detect whether the meat was irradiated or not. Dimethyl disulfide and dimethyl trisulfide were also determined only in irradiated meats but dimethyl trisulfide disappeared after 6 mo of frozen storage under oxygen-permeable packaging conditions. The results indicated that 8-heptadecene, 6,9-heptadecadiene, 2-DCB, 2-TCB, and dimethyl disulfide, even though they were decreased with storage, could be used as marker compounds for the detection of irradiated beef and pork regardless of cooking under the frozen conditions for 6 mo. PRACTICAL APPLICATION: Radiation-induced chemical changes such as specific hydrocarbons, 2-ACBs, and sulfur volatiles may be used as potential identification markers by regulatory authorities to confirm irradiation history of frozen stored raw or cooked beef and pork.     

Identification of a gamma-irradiated ingredient (garlic powder) in Korean barbeque sauce by thermoluminescence analysis

Thermoluminescence (TL) analysis was applied to identify gamma-irradiated garlic powder in Korean barbeque sauce before and after pasteurization (85 °C, 30 min), when blended in different ratios (1%, 3%, and 5%). The sauce sample with nonirradiated garlic powder gave a background glow curve. However, the sample blended with irradiated ingredient (1 and 10 kGy) showed typical TL glow curves at temperatures of 150 to 200 °C. The identification properties of sauce samples were more influenced by blending ratios than by irradiation doses, showing that 3% and 5% added samples produced glow curves at 150 to 250 °C. After pasteurization of the samples containing the irradiated ingredient, TL glow intensity decreased but did not change its shape or temperature range. As a result, the pasteurization of Barbeque sauces containing irradiated ingredients had reduced TL glow intensity, but the shape and temperature range of glow curve were still able to provide information required for confirming irradiation treatment. PRACTICAL APPLICATION: To monitor the irradiated food in international market, thermoluminescence (TL) analysis is considered most promising identification technique because of its sensitivity and long-term stability. In this study the applicability of TL analysis to detect an irradiated ingredient (garlic powder) added in low quantity to a food matrix (sauce) was investigated. The effect of processing (pasteurization) on TL results was also evaluated.     

Microbial assessment of medicinal herbs (Cnidii Rhizoma and Alismatis Rhizoma), effects of electron beam irradiation and detection characteristics

Food Science and Biotechnology - Medicinal herbs comprise of heavy microbial contaminations. This study aimed to assess microbial hazards including foodborne pathogens in 20 commercial medicinal...     

Effects of approved dose of e-beam irradiation on microbiological and physicochemical qualities of dried laver products and detection of their irradiation status

Food Science and Biotechnology - Most commercial dried laver products show higher microbial contamination. This work evaluated effects of approved dose (7 kGy)—recommended in the...