• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.12C
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• pp.1142-1148
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• 2007

In this paper, we propose ASLM (Adaptive Selective Mapping; ASLM) scheme based on peak observation for PAPR (Peak-to-Average Power Ratio) reduction of OFDM (Orthogonal Frequency Division Multiplexing) signals. The proposed scheme is composed of three steps: peak scaling, sequence selection, and SLM procedures. In the first step, the peak signal samples in the IFFT (Inverse Fast Fourier Transform) outputs of the original input sequence are scaled down. In the second step, the sub-carrier positions where the power difference between the original input sequence and the FFT output of the scaled signal is large, are identified. Then, the phase sequences having the maximum number of phase-reversed sequence words only for these positions are selected. Finally, the generic SLM procedure is performed by using only the selected phase sequences for the original input sequence. Simulation results show that the proposed scheme significantly reduces the complexity in terms of IFFT and PAPR calculation than the conventional SLM, while maintaining the PAPR reduction performance.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.230-233
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• 2003

Simulation model of induction type fixed speed wind power generator is developed. It is shown that the peak value of inrush current during start up changes according to the firing angle control strategy of soft starter. New proposed firing angle control scheme showed $25\%$ of reduction of peak current which results in smaller drop of gird voltage at the point of common coupling during start up.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1909-1912
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• 2002

We propose in this paper a companding scheme or peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems. By exploiting statistical distribution of OFDM transmit signals, the proposed scheme effectively reduces the PAPR by compressing the peak signals, while maintaining the average power unchanged. Simulation results are provided to show good performance of the proposed scheme.

• Proceedings of the IEEK Conference
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• 2002.06a
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• pp.17-20
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• 2002

We propose in this paper a companding scheme for PAPR (Peak-to-Average Power Ratio) reduction in OFBM (Orthogonal Frequency Division Multiplexing) systems. By exploiting statical distribution of OFDM transmit signals, the proposed scheme effectively reduces the PAPR by compressing the peak signals, while maintaining the average power unchanged. Simulation results are provided to show good performance of the proposed scheme.

• Archives of Pharmacal Research
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• v.22 no.4
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• pp.335-339
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• 1999

The oxidation-reduction potentials of cosmetic raw materials, showing tyrosinase inhibitory action, and phenolic compounds structurally similar to L-tyrosine were determined by cylcic voltammetry. The voltammograms obtained could be classified ito 4 patterns (patterns 1-4). Patterns 1, characterized by oxidation and reduction peaks as a pair, was observed with catechol, hydroquinone or phenol, and pattern 2 exhibiting another oxidation peak in addition to oxidation and reduction peaks as a pair was found with arbutin, kojic acid, resorcinol, methyl p-hydroxybenzoate and L-tyrosine as the substrate of tyrosinase. Pattern 3 with an independent oxidation peak only was expressed by L-ascorbic acid, and pattern 4 with a reduction peak only at high potentials, by hinokitiol. The tyrosinase inhibitory activity of these compounds was also evaluated using the 50% inhibitory concentration ($IC_{50}$) and the inhibition constant (Ki) as parameters. Hinokitiol, classified as patterns 4, showed the highest inhibitory activity (lowest $IC_{50}$ and Ki). Hydroquinone showing the second highest activity belonged to pattern 1, which also included compounds exhibiting pattern 2 was relatively low with Ki values being in the order of 10-4 M. Although there was no consistent relationship between oxidation-reduction potentials and tyrosinase inhibitory action, the voltammetry data can be used as an additional index to establish the relationship between the structure and the tyrosine inhibitory activity.

• Bulletin of the Korean Chemical Society
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• v.15 no.12
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• pp.1050-1054
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• 1994

Eu(Ⅲ) exhibits one electron-transfer reduction at E$_{1/2}$ =-0.617 V vs. Ag/AgCl and the hypersensitive peak at 618 nm corresponding to $^5D_0$ ${\leftrightarro}$ $^7F_2$ transition in 0.10 M LiClO$_4$ aqueous solutions. Upon the addition of carboxylate or sulfonate anions to the Eu(Ⅲ) aqueous solutions, the reduction potential shifts negatively and the reduction current decreases because of the complex formation between Eu(Ⅲ) ions and the anions. However, for the case of carboxylate anion (acetate or propionate) the shift of reduction peak potential and the emission intensity at 618 nm are greater. The results are interpreted in terms of the differences in the formation constants and the hypersensitivity.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.2
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• pp.67-74
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• 2008

This paper proposes two peak-windowing algorithms for peak-to-average power reduction(PAPR) of orthogonal frequency division multiple access(OFDMA) downlink systems. The Proposed algorithms mitigate the effect of excessive suppression due to successive peaks or relatively high peaks of the signal. First, multi-stage peak windowing algorithm is proposed, which exploits multiple threshold of target PAPR in order to step down the peaks gradually. Secondary, variable-length peak windowing algorithm is proposed, which adapts the window length with respect to the existence of successive peaks within a half of window length. Therefore, the proposed method reduces the distortion of signal amplitude caused by window overlapping. The proposed algorithms outperform the conventional peak windowing with the aid of window-length adaptation or sequential peak power reduction. Simulation results show the efficiency of the proposed algorithms over OFDMA downlink systems, especially WiBro systems.

• Journal of Drive and Control
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• v.16 no.3
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• pp.59-66
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• 2019

Hydraulic systems are essential for most of the construction equipments due to their various advantages, such as very powerful, quick response speed, precision control and remote control. Moreover, they are necessary to apply the electro hydraulic systems for precise and remote controls. Operating the small electronic joystick of the remote controller for the control of a multipurpose work machine with remote control technology increases the possibility of a sudden operation compared to the use of a conventional hydraulic joystick. When a joystick is suddenly operated, the peak pressure is generated in the system due to the quick response of the system. Then a vibration is generated due to the peak pressure, which causes instability to the operation of the construction equipment. Therefore, in this study, we confirmed the level of reduction of peak pressure occurring in the electro hydraulic system by using AMESim, when the output signal of the step shape generated by the sudden operation of the electronic joystick was changed by using the convolution operation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4C
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• pp.230-238
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• 2005

An orthogonal frequency division multiplexing (OFDM) system consists of a number of independently modulated subcarriers and, thus, a high peak-to-average power ratio (PAR) can occur when the subcarriers are added coherently. The high PAR brings such disadvantages as an increased complexity of the analog-to-digital (ADC) and digital-to-analog (DAC) converters and a reduced efficiency of the radio frequency (RF) power amplifier. In this paper, we propose a novel PAR reduction scheme called selective mapping of partial tones (SMOPT). The SMOPT scheme has a reduced complexity, lower sensitivity to peak reduction tones (PRT) positions, and a shorter processing time as compared with the conventional tone reservation (TR) scheme. The performance of the SMOPT scheme is analyzed based on the IEEE 802.1la wireless local area network(WLAM) physical layer model. Numerical results show that the SMOPT scheme outperforms the TR scheme under various scenarios.

• Journal of Broadcast Engineering
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• v.8 no.3
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• pp.238-249
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• 2003

Eureka 147 DAB system based on the orthogonal frequency division multiplexing (OFDM) was adopted as the transmission scheme for terrestrial digital multimedia broadcasting (DMB) system in Korea. The OFDM has several advantages comparing to the single carrier modulation. However, its high Peak-to-average power ratio (PAPR) increases the complexity of the D/A and A/D converters and reduces the efficiency of the high power amplifier To reduce the high PAPR of OFDM, various techniques such as clipping, peak windowing, companding, selected mapping (SLM), Partial transmit sequences (PTS), etc. have been proposed. In this paper, we propose modified configurations of SLM and PTS for effective implementation and evaluate the performance on the PAPR reduction of DMB system. The simulation results show that the modified SLM (MSLM) has merits in reducing the amount of computation and hardware complexity due to the reduction of the number of vector $P^{(U)}$, while satisfying the same performance and maintaining the same required bits (RB) for side information. With the same amount of computation and the same RB, the modified PTS (MPTS) is also shown to be better than PTS in the performance of PAPR reduction.