A novel method for elimination of line-current harmonics insingle-stage PFC switching regulators

This paper studies a particular single-stage power-factor-correction (PFC) switching regulator employing a discontinuous-conduction-mode (DCM) boost-input cell and a continuous-current-mode (CCM) forward output cell. Although this single-stage PFC regulator can provide a reasonably high power factor when its PFC stage is operating in discontinuous mode, substantial reduction in line-current harmonics is possible by applying a suitable frequency-modulation scheme. This paper derives a frequency-modulation scheme and proposes a practical implementation using a simple translinear analog circuit. A quantitative analysis on the total harmonic distortion (THD) of the line current when the circuit is subject to a limited range of frequency variations is presented along with some considerations for practical design. Experimental data obtained from a prototype confirms the effectiveness of the proposed frequency-modulation scheme. The proposed analog translinear circuit allows custom integrated circuit implementation, making it a viable low-cost solution to the elimination of line-current harmonics in switching regulators     

Micromachined piezoelectric force sensors based on PZT thin films

A micromachined lead zirconate titanate (PZT) force sensor for scanning force microscope (SFM) is conceptualized by its piezoelectricity. The fabrication procedure is interpreted, and mechanical characteristics of the micromachined PZT force sensors with various lengths are studied in this paper. A compact SFM is constructed by using the piezoelectric PZT sensor. A very clear image is taken by this SFM. The current study of the micromachined PZT force sensor can be considered as a breakthrough of design of SFM as well as a good example of integrated piezoelectric microdevices     

Modified atmosphere packaging of a mixed prepared vegetable salad dish

The aim of this study was to design a modified atmosphere package for a mixed vegetable salad consisting of 75 g of cut carrot, 55 g of cut cucumber, 20 g of sliced garlic and 50 g of whole green pepper. Respiration data of all the components were combined with film permeability data to predict package atmospheres and design optimal packages for experimental testing for improved shelf-life of the produce. The optimal package avoided minimum O₂ and maximum CO₂ tolerance limits, and chilling injury temperatures for any component. A pouch form package made of 27 mm low density polyethylene developed a modified atmosphere of 2.0–2.1% O₂ and 5.5–5.7% CO₂, which was beneficial for all components and provided better quality retention than other test packages.     

A neural network-based power system stabilizer using power flowcharacteristics

A neural network-based power system stabilizer (neuro-PSS) is designed for a generator connected to a multi-machine power system utilizing the nonlinear power flow dynamics. The use of power flow dynamics provides a PSS for a wide range of operation with reduced size neural networks. The neuro-PSS consists of two neural networks: neuro-identifier and neuro-controller. The low-frequency oscillation is modeled by the neuro-identifier using the power flow dynamics, then a generalized backpropagation-through-time (GBTT) algorithm is developed to train the neuro-controller. The simulation results show that the neuro-PSS designed in this paper performs well with good damping in a wide operation range compared with the conventional PSS     

Laser scanning path generation considering photopolymer solidification in micro-stereolithography

It is essential to automate the scanning path generation process to effectively implement the micro-stereolithography. However, a scanning path that is generated based only on a 3D CAD model introduces dimensional inaccuracies. In micro-stereolithography, the photopolymer solidification is affected by fabrication conditions, such as the optical properties (laser power, laser scanning speed, laser scanning pitch focusing condition, etc.) and material properties of the photopolymer. Thus, the photopolymer solidification phenomena must be considered when generating a laser scanning path. In this paper, a scanning path generation algorithm that uses 3D CAD data and considers the photopolymer solidification phenomena is proposed to improve the dimensional accuracy in micro-stereolithography. Multi-line photopolymer solidification experiments were performed for various laser scanning conditions to examine the photopolymer solidification phenomena. From these experiments, linear relations between the solidification length (width) and scanning length (width) were acquired and stored in a database. Subsequently, these data were utilized to compensate the scanning path of the laser beam. In addition, experiments for determining the layer thickness in the z-direction were performed and these results were also used in the scanning path generation algorithm.This research was supported by the Highly Advanced National Project (http://www.most.go.kr), which performs some of the National R&D Program, and sponsored by the Korean Ministry of Science and Technology under the contract project code M10214000116-02B1500-02010.     

Characterization of ultrashort optical pulses with third-harmonic-generation based triple autocorrelation

We present a method to obtain complete information of femtosecond pulses. By measuring triple-optical autocorrelation directly with third-harmonic generation, without spectral information, a temporal pulse shape can be obtained by analytical calculation without direction-of-time ambiguity. Combining the resulting optical pulse shape with its corresponding optical spectrum, the exact phase and color variations in time can all be recovered with a Gerchberg-Saxton algorithm through an iterative calculation with an O(n) complexity.     

Rapid and comprehensive indicator for evaluation of performance of treatment processes and of river waters.

Naturally occurring UV active compounds, commonly present in almost all source waters, can be rapidly monitored by their ultraviolet absorbance at 260 nm (E260). Herein, the extent of correlation between the E260 and the removal efficiency of the hazardous contaminants, endocrine disrupters and dioxins, were investigated using various treatment and river source waters. The detection of various types of hazardous contaminants using sophisticated analytical methods, such as high resolution gas chromatography (HRGC)/high resolution mass spectrometry (HRMS) and high performance liquid chromatography (HPLC)/inductively coupled plasma (ICP)/mass spectrometry (MS), as well as various short-term bioassays, can require hours or even days for results to be obtained. The removal of the E260 correlated well with those of individual contaminants, such as endocrine disruptor chemicals and dioxins, with the various treatment processes employed. In the plots of the endocrine disrupters against the DOC/E260, a correlation was found with the endocrine activity of the Korean/Japanese river waters employed in this study.     

Formation of C4 species in the deactivation of a Pd/SiO2 catalyst during the selective hydrogenation of acetylene

The deactivation characteristics of Pd/SiO₂ in the selective hydrogenation of acetylene were correlated with changes in the amount of the C4 species produced. The amounts of butenes produced changed in parallel with the catalyst activity, indicating that the rate limiting step for butene production was the same as that for acetylene hydrogenation. On the other hand, the amount of 1,3-butadiene produced changed, showing a maximum with catalyst deactivation because 1,3-butadiene is an intermediate in the sequential reaction process which involves both the production and consumption of 1,3-butadiene. This was verified by a simultaneous TG/reaction experiment showing that 1,3-butadiene was a precursor of green oil. The catalyst showed a self-regenerative behavior in its activity and the amounts of C4 species produced during the early stage of deactivation because two opposite factors, which contributed to either the lowering or the promotion of activity, were involved in the process. A specific type of polymer species, produced during the initial period of deactivation, is proposed to be responsible for the promotion of catalyst activity.     

BioFET sensor for detection of albumin in urine

Characterisation of a BioFET for detection of albumin in a mixture of human urine is presented. To avoid electrolyte effect of the urine, it was measured in PBS (phosphate buffer saline) at a fixed pH after albumin binding. The drain current was modulated by the albumin bound to the anti-albumin immobilised on the gate surface of the BioFET. The current variation ratio was likely to be proportional to the concentration of the albumin in the range 50-250 mg/1. The results show the feasibility of the BioFET as a urinary albumin sensor.     

Foveation-Based Error Resilience and Unequal Error Protection over Mobile Networks

By exploiting new human-machine interface techniques, such as visual eyetrackers, it should be possible to develop more efficient visual multimedia services associated with low bandwidth, dynamic channel adaptation and robust visual data transmission. In this paper, we introduce foveation-based error resilience and unequal error protection techniques over highly error-prone mobile networks. Each frame is spatially divided into foveated and background layers according to perceptual importance. Perceptual importance is determined either through an eye tracker or by manually selecting a region of interest. We attempt to improve reconstructed visual quality by maintaining the high visual source throughput of the foveated layer using foveation-based error resilience and error correction using a combination of turbo codes and ARQ (automatic reQuest). In order to alleviate the degradation of visual quality, a foveation based bitstream partitioning is developed. In an effort to increase the source throughput of the foveated layer, we develop unequal delay-constrained ARQ (automatic reQuest) and rate compatible punctured turbo codes where the punctual pattern of RCPC (rate compatible punctured convolutional) codes in H.223 Annex C is used. In the simulation, the visual quality is significantly increased in the area of interest using foveation-based error resilience and unequal error protection; (as much as 3 dB FPSNR (foveal peak signal to noise ratio) improvement) at 40% packet error rate. Over real-fading statistics measured in the downtown area of Austin, Texas, the visual quality is increased up to 1.5 dB in PSNR and 1.8 dB in FPSNR at a channel SNR of 5 dB.