Lg Chem, Ltd

Daewoo Electronics Co., Ltd.

Jeong-Kyu Kim

Sang-Soon Choi

Chul-Hwan Choi

Yeong-Dae Kim

Sang-Yun Jung

The present invention relates to a method for preparing cerium carbonate that can improve yield and productivity of cerium carbonate, cerium carbonate powder, and a method for preparing cerium oxide using the same. The method for preparing cerium carbonate comprises the steps of mixing a cerium precursor and urea; and, elevating the temperature of the mixture to 50&#x2dc;250&#xb0; C. under solvent free condition to react the cerium precursor and urea.

Method for preparing cerium carbonate and method for preparing cerium oxide powder

This invention provides a method for preparing 2-(2-hydroxyphenyl)-2H-benzotriatzole of formula (I) below, consisting of steps of: a) performing a first reduction in which hydrazine hydrate is added to a compound of formula (II) below with or without a phase transition catalyst in the presence of solvents which include a nonpolar solvent, water, and an alkaline compound, thereby preparing a compound of formula (III) below; and b) performing a second reduction in which water is added to the compound of formula (III) prepared in step a), and then zinc powder and sulfuric acid are added thereto with or without the phase transition catalyst, wherein, X is halogen or hydrogen; R is hydrogen, C -C alkyl, C -C cycloalkyl, phenyl, or phelyl-C -C alkyl; and R&prime; is C -C alkyl, C -C cycloalkyl, phenyl, or phenyl-C1-C4 alkyl.

Method for preparing 2-(2-hydroxyphenyl)-2H-benzotriazole

An audio data playback clock signal generating apparatus of a digital VCR synchronizes an audio frame playback synchronization signal with a video frame synchronization signal when an audio data recorded in a magnetic tape is played back based on a phase error of an audio data frame size AF-SIZE and an audio data playback clock signal of the previous video frame. The audio data playback clock signal generating apparatus comprises an audio data frame size decoder, a low pass filter, a voltage-controlled oscillator, and phase error generating block and can be implemented by a large scale integration(LSI) to thereby provide a non-complex circuit and an accurate synchronization between the audio frame playback synchronization signal and the video frame synchronization signal.

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Seoul, South Korea

Jeong-Kyu Kim