• Korean Journal of Materials Research
• /
• v.21 no.7
• /
• pp.403-409
• /
• 2011

Micro speakers are used to reproduce sound in small electric and information and communications devices, such as cellular phones, PMPs, and MP3 players. The acoustical properties and sound quality, which are changed due to the decreased size of the speaker, are often adjusted varying the type and thickness of the diaphragm. The most widely used diaphragm material is thin polymer. It was previously reported by the author of this paper that the resonance frequency of a micro speaker is changed by the type and thickness of a polymer diaphragm. In this paper, the frequency response near the resonance frequency of a micro speaker was studied as functions of the type and thickness of the polymer diaphragm. While $R_{max}$ and $R_{DC}$ were affected by the type and thickness, an analysis of the electrical impedance curve revealed that $R_o(= R_{max}/R_{DC})$ and ${\Delta}f$ were not changed. Thus, $Q_{TS}$ which was function of $R_o$, ${\Delta}f$, and the resonance frequency, is only related to the resonance frequency. The increase of the resonance frequency led to a proportional rise of $Q_{TS}$. The change of the frequency response near the resonance frequency was not dependent on the type or thickness of the polymer diaphragm, but was affected by the resonance frequency.

• Tuberculosis and Respiratory Diseases
• /
• v.46 no.2
• /
• pp.204-214
• /
• 1999

Background: Resting pulmonary function tests(PFTs) are routinely used in the evaluation of pulmonary impairment/disability. But the significance of the cardiopulmonary exercise test(CPX) in the evaluation of pulmonary impairment is controvertible. Many experts believe that dyspnea, though a necessary part of the assessment, is not a reliable predictor of impairment. Nevertheless, oxygen requirements of an organism at rest are different from at activity or exercising, and a clear relationship between resting PFTs and exercise tolerance has not been established in patients with chronic pulmonary disease. As well, the relationship between resting PFTs and dyspnea is complex. To investigate the relationship of dyspnea, resting PFTs, and CPX, we evaluated the patients of stabilized chronic pulmonary disease with clinical dyspnea rating(baseline dyspnea index, BDI), resting PFTs, and CPX. Method: The 50 patients were divided into two groups: non-severe and severe group on basis of results of resting PFTs(by criteria of ATS), CPX(by criteria of ATS or Ortega), and dyspnea rating(by focal score of BDI). Groups were compared with respect to pulmonary function, indices of CPX, and dyspnea rating. Results: 1. According to the criteria of pulmonary impairment with resting PFTs, $VO_2$max, and focal score of BDI were significantly low in the severe group(p<0.01). According to the criteria of $VO_2$max(ml/kg/min) and $VO_2$max(%), the parameters of resting PFTs, except $FEV_1$ were not significantly different between non-severe and severe(p>0.05). According to focal score($FEV_1$(%), FVC(%), MW(%), $FEV_1/FVC$, and $VO_2$max were significantly lower in the severe group(p<0.01). However, in the more severe dyspneic group(focal score<5), only $VO_2$max(ml/kg/min) and $VO_2$max(%) were low(p<0.01). $FEV_1$(%) was correlated with $VO_2$max(%)(r=0.52;p<0.01), but not predictive of exercise performance. The focal score had the correlation with max WR(%) (r=0.55;p<0.01). Sensitivity and specificity analysis were utilized to compare the different criteria used to evaluate the severity of pulmonary impairment, revealed that the classification would be different according to the criteria used. And focal score for dyspnea showed similar sensitivity and specificity. Conclusion : According to these result, resting PFTs were not superior to rating of dyspnea in prediction of exercise performance in patients with chronic pulmonary diseases and less correlative with focal score for dyspnea than $VO_2$max and max WR. Therefore, if not contraindicated, CPX would be considered to evaluate the severity of pulmonary impairment in patients with chronic pulmonary diseases, including with severe resting PFTs. Current criteria used to evaluate the severity of impairment were insufficient in considering the degree of dyspnea, so new criteria, including the severity of dyspnea, may be necessary.

• Journal of Pharmaceutical Investigation
• /
• v.18 no.2
• /
• pp.61-67
• /
• 1988

The influence of different suppository bases on the dissolution, and the bioavailability of aspirin suppositories in rabbits and humans was investigated using Witepsol H15 (WIT), WIT-Tween 80 (TWE), WIT-sodium lauryl sulfate (SLS), polyethylene glycol (PEG), hollow WIT (WIT-HOLL) and capsule incorporated into WIT (WIT-CAP). The results obtained were as follows: 1) Dissolution rates of aspirin suppositories with different bases in distilled water were faster in the order of WIT-TWE >WIT-SLS >PEG >WIT-HOLL >WIT >WIT-CAP. 2) The maximum blood levels $(C_{max})$ of aspirin in rabbits and humans were highest in WIT-TWE and WIT-SLS bases, but $C_{max}$ from WIT base was lower than that in oral administration of aspirin suspension. 3) The times reaching the maximum blood levels $(T_{max})$ in rabbits were 1 hr for oral administration, 1.5-2.5 hr for WIT-TWE, WIT-SLS, PEG, and WIT bases, and 2.5-4.0 hr for WIT-HOLL and WIT-CAP bases, but $T_{max}$ in humans were 1 hr for oral administration and WIT-TWE base, and 2-4 hr for WIT and WIT-HOLL bases. 4) Relative bioavailability (RBA) of aspirin suppositories in rabbits was higher in WIT-SLS, WIT-TWE and PEG bases than that in oral administration, and RBA of aspirin suppositories in humans was higher in the order of WIT-TWE >PEG >WIT-HOLL >oral >WIT bases tested. 5) Good correlation between dissolution rates and $C_{max}$ was obtained: y = 0.60x+32.23 (r = 0.96) for rabbits, and y = 0.60x+35.74 (r = 0.97) for humans.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.10 no.2
• /
• pp.97-102
• /
• 2010

In this paper, an area-efficient FFT processor is proposed for IEEE 802.16e mobile WiMax systems. The proposed scalable FFT processor can support the variable length of 128, 512, 1024 and 2048. By reducing the required number of non-trivial multipliers with mixed-radix (MR) and multi-path delay commutator (MDC) architecture, the complexity of the proposed FFT processor is dramatically decreased without sacrificing system throughput. The proposed FFT processor was designed in hardware description language (HDL) and synthesized to gate-level circuits using 0.18um CMOS standard cell library. With the proposed architecture, the gate count for the processor is 46K and the size of memory is 64Kbits, which are reduced by 16% and 27%, respectively, compared with those of the 4-channel radix-2 MDC (R2MDC) FFT processor.

• Journal of the Korean Mathematical Society
• /
• v.42 no.5
• /
• pp.933-948
• /
• 2005

Let R be a commutative ring with identity and let M be an R-module. Then M is called a multiplication module if for every submodule N of M there exists an ideal I of R such that N = 1M. Let M be a non-zero multiplication R-module. Then we prove the following: (1) there exists a bijection: N(M)$\bigcap$V(ann$\_{R}$(M))$\rightarrow$Spec$\_{R}$(M) and in particular, there exists a bijection: N(M)$\bigcap$Max(R)$\rightarrow$Max$\_{R}$(M), (2) N(M) $\bigcap$ V(ann$\_{R}$(M)) = Supp(M) $\bigcap$ V(ann$\_{R}$(M)), and (3) for every ideal I of R, The ideal $\theta$(M) = $\sum$$\_{m(Rm :R M) of R has proved useful in studying multiplication modules. We generalize this ideal to prove the following result: Let R be a commutative ring with identity, P $\in$ Spec(R), and M a non-zero R-module satisfying (1) M is a finitely generated multiplication module, (2) PM is a multiplication module, and (3) P$^{n}$M$\neq$P$^{n+1}$ for every positive integer n, then $\bigcap$$^{$\_{n=1}$(P$^{n}$ + ann$\_{R}$(M)) $\in$ V(ann$\_{R}$(M)) = Supp(M) $\subseteq$ N(M).

• Korean Journal of Environmental Biology
• /
• v.40 no.3
• /
• pp.352-362
• /
• 2022

Photosynthesis and respiration of seagrasses are mainly controlled by water temperature. In this study, the photosynthetic physiology and respiratory changes of the Asian surfgrass Phyllospadix japonicus, which is mainly distributed on the eastern and southern coasts of Korea, were investigated in response to changing water temperature (5, 10, 15, 20, 25, and 30℃) by conducting mesocosm experiments. Photosynthetic parameters (maximum photosynthetic rate, P_max; compensation irradiance, I_c; and saturation irradiance, I_k) and respiration rate of surfgrass increased with rising water temperature, whereas photosynthetic efficiency (α) was fairly constant among the water temperature conditions. The P_max and I_k dramatically decreased under the highest water temperature condition (30℃), whereas the I_c and respiration rate increased continuously with the increasing water temperature. Ratios of maximum photosynthetic rates to respiration rates (P_max : R) were highest at 5℃ and declined markedly at higher temperatures with the lowest ratio at 30℃. The minimum requirement of H_sat (the daily period of irradiance-saturated photosynthesis) of P. japonicus was 2.5 hours at 5℃ and 10.6 hours at 30℃ for the positive carbon balance. Because longer H_sat was required for the positive carbon balance of P. japonicus under the increased water temperature, the rising water temperature should have negatively affected the growth, distribution, and survival of P. japonicus on the coast of Korea. Since the temperature in the temperate coastal waters is rising gradually due to global warming, the results of this study could provide insights into surfgrass responses to future severe sea warming and light attenuation.

• Journal of Pharmaceutical Investigation
• /
• v.37 no.3
• /
• pp.197-203
• /
• 2007

A bioequivalence study of $Dilast^{TM}$ Capsule (Chong Kun Dang Pharma. Co., Ltd.) to $Ketas^{(R)}$ Capsule (Han Dok Pharma. Co., Ltd.) was conducted according to the guidelines of Korea Food and Drug Administration (KFDA). Twenty eight healthy male Korean volunteers received each medicine at the ibudilast dose of 20 mg in a $2{\times}2$ crossover study. There was one week wash-out period between the doses. Plasma concentrations of ibudilast were monitored by a liquid chromatography-tandem mass spectrometry (LC-MS/MS) for over a period of 36 hours after drug administration. $AUC_t$ (the area under the plasma concentration-time curve from time zero to 36 hr) was calculated by the linear trapezoidal rule method. $C_{max}$ (maximum plasma drug concentration) and $T_{max}$ (time to reach $C_{max}$) were compiled from the plasma concentration-time data. Analysis of variance was carried out using logarithmically transformed $AUC_t\;and\;C_{max}$. No significant sequence effect was found for all of the bioavailability parameters indicating that the crossover design was properly performed. The 90% confidence intervals of the $AUC_t$ ratio and the $C_{max}$ ratio for $Dilast^{TM}$ $Capsule/Ketas^{(R)}$ Capsule were $log0.93{\sim}log1.06$ and $log0.93{\sim}log1.11$, respectively. These values were within the acceptable bioequivalence intervals of $log0.80{\sim}log1.25$. Thus, our study demonstrated the bioequivalence of $Dilast^{TM}$ Capsule and $Ketas^{(R)}$ Capsule with respect to the rate and extent of absorption.

• Journal of Pharmaceutical Investigation
• /
• v.37 no.4
• /
• pp.255-261
• /
• 2007

A bioequivalence study of $Nimegen^{TM}$ soft capsule (Medica Korea Pharma. Co., Ltd.) to $RoAccutane^{(R)}$ soft capsule (Roche Korea Ind. Co., Ltd.) was conducted according to the guidelines of Korea Food and Drug Administration (KFDA). Thirty healthy male Korean volunteers received each medicine at the isotretinoin dose of 60 mg in a $2{\times}2$ crossover study. There was one week wash-out period between the doses. Plasma concentrations of isotretinoin were monitored by a high performance liquid chromatography (HPLC) for over a period of 48 hours after drug administration. $AUC_t$ (the area under the plasma concentration-time curve from time zero to 48 hr) was calculated by the linear trapezoidal rule method. $C_{MAX}$ (maximum plasma drug concentration) and $T_{MAX}$ (time to reach $C_{MAX}$) were compiled from the plasma concentration-time data. Analysis of variance was carried out using logarithmically transformed $AUC_t\;and\;C_{MAX}$. No significant sequence effect was found for all of the bioavailability parameters indicating that the crossover design was properly performed. The 90% confidence intervals of the $AUC_t$ ratio and the $C_{MAX}$ ratio for $Nimegen^{TM}/RoAccutane^{(R)}$ were $log0.860{\sim}log0.98\;and\;log0.85{\sim}log1.00$, respectively. These values were within the acceptable bioequivalence intervals of $log0.80{\sim}log1.25$. Thus, our study demonstrated the bioequivalence of $Nimegen^{TM}\;and\;RoAccutane^{(R)}$ with respect to the rate and extent of absorption.

• Journal of Life Science
• /
• v.17 no.9 s.89
• /
• pp.1255-1259
• /
• 2007

The purpose of this study was to elucidate incidence of $VO_2$ plateau by comparing data derived from different time averaging intervals during incremental cycling exercise to $VO_2max$. Seventeen subjects (age: $23.5{\pm}3.3$ years and $VO_2max$: $3.65{\pm}0.73$ L/min, respectively) completed $VO_2max$ tests on cycle ergometer which breath by breath gas ex-change data were obtained. These data were time-averaged into 11-breath, 15, 30 and 60 s sampling intervals. The incidence of plateau were 100, 35, 24 and 6% for the 11 breath, 15 s, 30 s and 60 s averaging, respectively. No correlation was between ${\Delta}$ $VO-2$ at $VO_2max$ and $VO_2max$ (r=0.008). 53% (maximal HR within 10 b/min) and 100% $(RER{\geq}1.15)$ of subjects met the criteria for attainment of $VO_2max$. This data indicate that shorter sampling intervals (11 breath) is the most suitable for de-tection of the $VO_2$ plateau and RER can be used for the criteria for attainment of $VO_2max$ but not maximal HR. Also, the incidence of a plateau is not related to training status or physical fitness of subjects.

• Applied Biological Chemistry
• /
• v.36 no.2
• /
• pp.134-137
• /
• 1993

Yongia sonchifolia Max. has been used as raw materials of traditional Kimchi and medicinal herb in Korea. This study was performed to investigate biologically active components in the plant. First, the writer carried out the experiment of antitumor screening test against Sarcoma-180A and the cytotoxic activity against Chinese hamster V-79 cells with methanol extract of the plant. And the aqueous solution of the extract from roots of Youngia sonchifolia Max. was partitioned into n-hexane. The concentrated extract of n-hexane layer was chromatographed on silica gel column and developed with n-hexane and ethylacetate. Two yellow elutes, on concentration, were recrystallized from ethylacetate, and the $R_f$ value of TLC of the crystal was 0.43. After analysis by $^{1}H-NMR$, $^{13}C-NMR$ and MS to confirm the structure, the author could identify the compound as bauerenyl acetate, a naturally occurring pentacyclic triterpene. The crystal was colorless plate and m.p. was $280{\sim}282^{\circ}C$.