Hyeon-Jin Jeon

Analysis of Frequency Mismatch in Narrowband Active Noise Control

This paper analyzes the effects of frequency mismatch between the actual frequency of the primary noise and the frequency of the synthesized reference signal in narrowband active noise control (ANC) systems using the filtered-X least-mean-square (FXLMS) algorithm. Two stability conditions are derived in terms of the frequency mismatch and the phase error of the estimated secondary-path model. Conditions to guarantee that ANC systems can achieve noise reduction are also developed by considering the overall effect of frequency mismatch and phase error. The optimum step-size to reach the minimum excess mean-square error is obtained and analyzed. Theoretical analysis shows that the noise reduction and convergence rate are functions of frequency mismatch, step size, and phase error in the secondary-path model for the FXLMS algorithm. Computer simulations are conducted to verify the analysis results presented in the paper.

A Narrowband Active Noise Control System With Frequency Corrector

The performance of narrowband active noise control (ANC) systems degenerates significantly under the frequency mismatch between the synthesized reference signal and the primary noise. This paper proposes a new narrowband ANC system that incorporates a frequency corrector for the internal reference signal generator to mitigate the ill-effects caused by the frequency mismatch. The proposed frequency estimator uses the iterative frequency estimation algorithm based on the minimum variance distortionless response spectrum that has advantages of accuracy and fast convergence. The performance of the new narrowband ANC system is analyzed under the conditions of frequency mismatch and the secondary-path phase estimation error. The frequency and amplitude of the primary noise are modeled as time-varying variables in the theoretical analysis. Computer simulations are conducted to demonstrate the performance of the new ANC system and to verify the analysis results.

Iterative Frequency Estimation Based on MVDR Spectrum

Frequency estimation is an important task in a power system since the frequency deviation is a yardstick for the power system abnormal operating conditions. This paper presents a new frequency-estimation algorithm based on the minimum variance distortionless response spectrum that has advantages of accuracy, fast convergence, and modest complexity. To reduce complexity without a trade off of accuracy, an iterative searching method is introduced. An adaptive step-size method is also introduced to reduce gradient noise. Complexity of the proposed algorithm is O(K) or O(K 2) depending on environments where K is the dimension of correlation matrix. When compared with other conventional adaptive algorithms, simulation results show that the proposed algorithm improves convergence speed, and has lower frequency estimation error in cases of high signal-to-noise ratio.

Optimization of Maillard reaction with ribose for enhancing anti-allergy effect of fish protein hydrolysates using response surface methodology

Halibut is served on sushi and as sliced raw fish fillets. We investigated the optimal conditions of the Maillard reaction (MR) with ribose using response surface methodology to reduce the allergenicity of its protein. A 3-factored and 5-leveled central composite design was used, where the independent variables were substrate (ribose) concentration (X1, %), reaction time (X2, min), and pH (X3), while the dependent variables were browning index (Y1, absorbance at 420nm), DPPH scavenging (Y2, EC50 mg/mL), FRAP (Y3, mM FeSO4/mg extract) and β-hexosaminidase release (Y4, %). The optimal conditions were obtained as follows: X1, 28.36%; X2, 38.09min; X3, 8.26. Maillard reaction products of fish protein hydrolysate (MFPH) reduced the amount of nitric oxide synthesis compared to the untreated FPH, and had a significant anti-allergy effect on β-hexosaminidase and histamine release, compared with that of the FPH control. We concluded that MFPH, which had better antioxidant and anti-allergy activities than untreated FPH, can be used as an improved dietary source.

IEEE 802.15.4 BPSK Receiver Architecture Based on a New Efficient Detection Scheme

This paper proposes a new differential-detection scheme for IEEE 802.15.4 BPSK receivers. The proposed detection scheme derives not only the decision variables for data detection but also a timing signal ready for synchronization by a simple technique. A receiver architecture based on the new detection scheme is then proposed. Based on simulation results on the receiver performance, it is shown that with a conventional radio-frequency front end the receiver could meet at a big margin the sensitivity requirement of the IEEE 802.15.4 standard.

A triple-isotope approach for discriminating the geographic origin of Asian sesame oils.

The aim of this study was to investigate the effects of the geographic location and climatic characteristics of the sesame-producing sites on the carbon, hydrogen, and oxygen stable isotope ratios of Korean sesame oil. In addition, the study aimed to differentiate Korean sesame oil from Chinese and Indian sesame oils using isotopic data in combination with canonical discriminant analysis. The isotopic data were obtained from 84 roasted oil samples that were prepared from 51 Korean, 19 Chinese, and 14 Indian sesame seeds harvested during 2010-2011 and distributed in Korea during the same period. The δ(13)C, δD, and δ(18)O values of Korean sesame oil were negatively correlated with latitude, distance from the sea, and precipitation (May-September), respectively. By applying two canonical discriminant functions, 89.3% of the sesame oil samples were correctly classified by their geographic origin, indicating that the triple-isotope approach is a useful tool for the traceability of the oils.

Cocoa Butter Equivalents Prepared by Blending Fractionated Palm Stearin and Shea Stearin

The aim of this study was to assess the possibility of commercial use as a cocoa butter equivalent (CBE). The CBE was prepared by blending fractionated palm stearin and shea stearin in a weight ratio of 40:60 and contained 81.9% total symmetric monounsaturated triacyl-glycerols. The CBE was blended with cocoa butter in weight ratios (CBE:cocoa butter) of 5:95, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20, and 90:10. The blends were evaluated for their fatty acid and triacylglycerol compositions, thermal melting/crystallization behaviors, and solid fat content. The 5:95, 10:90, 20:80, and 30:70 blends showed similar melting/crystallization temperature ranges and enthalpies to those of cocoa butter. Furthermore, they showed similar changes in solid fat content to those of cocoa butter as a function of temperature. These results indicate that the CBE can be blended with cocoa butter at 30% for the manufacture of chocolate products without significantly altering their physical properties.

Improved physicochemical properties and hepatic protection of Maillard reaction products derived from fish protein hydrolysates and ribose

High amounts of waste products generated from fish-processing need to be disposed of despite their potential nutritional value. A variety of methods, such as enzymatic hydrolysis, have been developed for these byproducts. In the current study, we investigated the physicochemical, biological and antioxidative properties of fish protein hydrolysates (FPH) conjugated with ribose through the Maillard reaction. These glycated conjugates of FPH (GFPH) had more viscous rheological properties than FPH and exhibited higher heat, emulsification and foaming stability. They also protected liver HepG2 cells against t-BHP-induced oxidative stress with enhanced glutathione synthesis in vitro. Furthermore, it was shown that GFPH induced upregulation of phase II enzyme expression, such as that of HO-1 and γ-GCL, via nuclear translocation of Nrf2 and phosphorylation of ERK. Taken together, these results demonstrate the potential of GFPH for use as a functional food ingredient with improved rheological and antioxidative properties.

Narrowband active noise control earmuffs system for hearing protection

This paper proposes a new narrowband active noise control earmuffs system. The proposed system can be regarded as an adequate hearing protection solution for workers who work near rotating machines.

Frequency mismatch in narrowband active noise control

This paper analyzes the effects of frequency error in internal signal generator for narrowband active noise control systems. Two stability conditions and the optimum step-size to achieve the minimum excess mean-square error are analyzed in the paper. The noise reduction is formulated as a function of frequency mismatch, step size, and phase error in the estimation of the secondary path. The theoretical analysis presented in the paper is verified by computer simulations.