• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.8
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• pp.629-637
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• 2013

Chaos communication systems have the characteristics such as non-periodic, wide-band, non-predictability of signals and easy implementation. There have been many studies about chaos communication systems because of these advantages. But, chaos communication systems have low BER(Bit Error Rate) compare to general digital communication system. Existing researches on chaos communication systems only analyze BER performance according to various chaos maps. There are no studies on analysis of BER performance according to PDF(Probability Density Function) of chaos maps. In this paper, we analyze the BER performance according to changing parameter, equation, and initial values of chaos map's PDF. In addition, we propose new chaos map to improve BER performance. Simulation results show that BER performance of CDSK(Correlation Delay Shift Keying) is changed when PDF of chaos map changed. And the proposed chaos map has a better BER performance compare to previous chaos maps such as Tent map, Logistic map, and Henon map.

• The Korean Journal of Ecology
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• v.26 no.4
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• pp.155-163
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• 2003

In order to analyze the succession process from a pine forest to an oak forest, the tree growth of Pinus densiflora and Quercus mongolica ssp. crispula was monitored in a permanent quadrat for 23 years. The measurements were carried out for the stem diameter (DBH) of Pinus densiflora between 1977 and 1999 and for the height of Quercus mongolica ssp. crispula saplings between 1998 and 2000. The floristic composition and the locations of the individual P. densiflora and Q. mongolica ssp. crispula trees and saplings in the quadrat were recorded. P densiflora and Q. mongolica ssp. crispula individuals were randomly distributed within the quadrat. The relative growth rates (RGR) of DBH in P. densiflora were 0.085 $yr^{-1}$ for large trees and 0.056 $yr^{-1}$ for small trees in 1977. The RGR of height for Q. mongolica ssp. crispula was 0.122 $yr^{-1}$. The growth curve for DBH of P. densiflora was approximated by the logistic equation: $$DBH(t) = 30 {[1+1.16exp(-0.13 t)]}^{-1}$$ where DBH (t) the DBH (cm) in year t and t is the number of years since 1977. The growth in height of P. densiflora and Q. mongolica ssp. crispula was described by following equations: $$H (t) = 20.2 {[1+0.407exp(-0.137 t)]}^{-1} (P. densiflora)$$ $$H (t) = 30 {[1+20.7exp(-0.122 t)}^{-1} (Q. mongolica ssp. crispula)$$ Where H (t) is the tree height (m) in year t and t is the number of years since 1977 in P. densiflora and 1998 in Q. mongolica ssp. crispula. With these equations we predicted that the height of Q. mongolica ssp. crispula increases from 2 m in 1999 to 20 m in 2029. Therefore, Q. mongolica ssp. crispula and P. densiflora will be approximately the same height in 2029. The years required for succession from a pine forest to an oak forest are expected 33 with the range between 23 and 44 years.

• Speech Sciences
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• v.10 no.4
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• pp.201-219
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• 2003

Background: The perceptual assessment is generally performed by the voice specialist. The objective evaluation is performed in a voice laboratory. Research in voice laboratories has generated a variety of different objective tests and parameters. The perceptual evaluation is one of the most controversial topics in voice research. Review of literature reveals a wide variety of rating scales and reliability data fluctuating from study to study. Unfortunately, there is no widely accepted valid method for classifying voice disorders and assessing outcome after voice treatment. Objectives: The goals of this research were to identify important objective acoustic parameters of vocal quality, and to establish an objective and quantitative correlate of the perceived vocal quality. Materials and Methods : We evaluated the voice analyzed data from 122 dysphonic patients and 20 normal volunteers. A computerized speech lab. 4300B(CSL) was used to carry out the analysis of each voice sample. Results: Three dysphonia severity indices(DSI) were created using discriminant analysis. DSI is based on the weighted combination of the following selected set of acoustic parameters: absolute jitter(Jita in us), smoothed pitch period perturbation (sPPQ in %), amplitude perturbation quotient(APQ in %), soft phonation index(SPI), average fundamental frequency(Fo in Hz), lowest fundamental frequency(Flo in Hz), and smoothed amplitude perturbation quotient(sAPQ in %). The DSI, being the discriminating rule calculated by the logistic regression, consists of three equation based on statistically significant acoustic parameters. Three DSI were created to reflects best the degree of hoarseness as expressed by G from the GRBAS scale. The more positive this DSI is for a patient, the worse the vocal quality. The more it is negative, the better it is. The effect of sex is included implicitly in the DSI-1 and DSI-2, so that a separate DSI-1 and DSI-2 for males and females need not be used. The DSI is objective because no perceptual input is required for its calculation. Conculsion : This research demonstrates that the voice function values calculated from three different multivariate objective dysphonia severity indices are significantly associated with subjective voice assessments. These multivariate objective dysphonia severity indices may be appropriate for use in clinical trials and outcomes research on treatment effectiveness for voice disorders.

• Korea journal of population studies
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• v.8 no.2
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• pp.79-92
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• 1985

Fertility has been declined since 1966 (see Table 1). This fertility reduction was duely caused by age at first marriage, induced abortion and contraceptive practice which has been largely increased in recent years. Although tbe proximate determinant such as induced abortion, age at marriage and breastfeeding can and do have an effect on fertility, the principal cause of the reduction in fertility in Korea during the fertility transition can be supported by correlation between level of fertility and contraceptive prevalence (See Fig. 4). Taking a regression equation between fertility (TER. Y) and prevalence level (X), the total fertility rate in 1984 was estimated as 1.9 and 2.1 based on lenear and expotential function shown as follow; $Y_1$=5.709-0.0549 X and $Y_2$_______80________ 1+e2.433+0.017X ($R^2$=O. 93) ($R^2$=0. 96) Where $Y_1$ and $Y_2$ denote total fertility rates obtained through two equations respectivelly. The peak of contraceptive prevalence was assumdd as 80 percent which is almost upper limit in human society. On the other hand, an observed value of 1984 fertility level obtained from five month period shows 2.1 which is coincident with logistic fitting after the adjustment of response error assumed around 10 to 20 percent, At any rate, fertility of Korean women will have been reached replacement level (2.1) by 1985.Thus policy for family planning program must be reviewed toward the direction of integrated approach particularly with MCH program inasmuch as fertility in Korea has already shown population replacement level that require more good quality of service in family planning and their There must be an advanced level of fertility in Korea because wide use of contraception and induced life abortion and age at marriage will effect modern fertility which shows up and down trend between 2.1 and 1.5 in general.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.6
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• pp.1000-1006
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• 2021

The maturity and spawning of the common octopus Octopus vulgaris were studied using 317 samples collected monthly from January to December of 2020 from the coastal waters of Yeosu, Korea. The mantle length (ML) of O. vulgaris ranged from 5.1 to 19.7 cm and body weight (BW) ranged from 117.6 to 3,645.4 g. We analyzed monthly changes in sex ratio, gonadosomatic index (GSI), histological maturity stage, and body weight at 50%, 75% and 97.5% group maturity. The sex ratio was 1:1.02, which was not significantly different from the value that expected. Based on histological observation of the gonad development and gonadosomatic index, the spawning periods lasted throughout the year, with peak spawning periods estimated from March to April and July to August. The percentages of sexually mature females estimated using a logistic equation were over 50% at 554.46 g BW, 75% at 1,134.38 g BW and 97.5% at 2,474.22 g BW respectively.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.58 no.1
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• pp.1-9
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• 2022

In this study, the selection action on the mesh in the net pot for whelk (Buccinum opisthoplectum) is experimentally considered, and the selectivity was compared by the SELECT model and the Nashimoto's method with the probability model according to the contact shape of the mesh and the whelk. The experiments of the mesh size selectivity was conducted for two mesh sizes: 70 mm (inner stretched size 65.4 mm) and 44 mm (inner stretched size 39.5 mm). Selectivity experiments were conducted three times in total for each mesh size used 264 whelks. In addition, Nashimoto's method analyzed the retention probability using probability model for whether the mesh passed or not based on the carapace width of the whelk. As a result of the selectivity analysis, the 50% selection carapace width for the mesh size of 70 mm was similar to 43.62 mm in the SELECT model and 42.64 mm in the Nashimoto's method. However, the 44 mm mesh with relatively small mesh size showed differences of 40.01 mm and 26.80 mm, respectively. As for the mesh size selectivity of whelk, it was found that the smaller the mesh size, the lower the selectivity. In addition, in the selectivity study on the mesh size of whelk, an evaluation method that closely considers the contact shape between the mesh and the target species is required.

• Microbiology and Biotechnology Letters
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• v.9 no.4
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• pp.225-230
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• 1981

The kinetic study of rifamycin B production in batch culture of Nocardia mediterranei was undertaken in part of our endeavor to optimize the fermentation condition. The growth parameters such as $\mu$$_{m}$ and Ks values for nitrogen source were evaluated by employing Monod equation. From the experiments, $\mu$$_{m}$ and Ks were 0.15hr$^{-1}$ and 8.35g/1, respectively. The growth kinetics in batch culture was found successfully interpreted by logistic law, i.e., the initial specific growth rate and the maximum cell mass concentration were determined as function of pH and both found to have maxima. For the production of rifamycin B, a non-growth associated production kinetics was employed and the specific productivity as a function of pH was found to have two maximum points. The yield coefficient and the specific productivity were calculated as mean values in production phase. Utilizing these experimental data as a function of pH, the optimal condition for the rifamycin B production was discussed with regad to the pH effect on the cell growth and production of the antibiotic. As a result, growth phase at pH 6.5 and production phase at pH 7.0 were found to be recommended.ded.

• Journal of Yeungnam Medical Science
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• v.40 no.4
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• pp.402-411
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• 2023

Background: We hypothesized that fatty liver disease (FLD) is associated with a high prevalence of hearing loss (HL) owing to metabolic disturbances. This study aimed to evaluate the association between FLD and HL in a large sample of the Korean population. Methods: We used a dataset of adults who underwent routine voluntary health checkups (n=21,316). Fatty liver index (FLI) was calculated using Bedogni's equation. The patients were divided into two groups: the non-FLD (NFLD) group (n=18,518, FLI <60) and the FLD group (n=2,798, FLI ≥60). Hearing thresholds were measured using an automatic audiometer. The average hearing threshold (AHT) was calculated as the pure-tone average at four frequencies (0.5, 1, 2, and 3 kHz). HL was defined as an AHT of >40 dB. Results: HL was observed in 1,370 (7.4%) and 238 patients (8.5%) in the NFLD and FLD groups, respectively (p=0.041). Compared with the NFLD group, the odds ratio for HL in the FLD group was 1.16 (p=0.040) and 1.46 (p<0.001) in univariate and multivariate logistic regression analyses, respectively. Linear regression analyses revealed that FLI was positively associated with AHT in both univariate and multivariate analyses. Analyses using a propensity score-matched cohort showed trends similar to those using the total cohort. Conclusion: FLD and FLI were associated with poor hearing thresholds and HL. Therefore, active monitoring of hearing impairment in patients with FLD may be helpful for early diagnosis and treatment of HL in the general population.

• Annals of Occupational and Environmental Medicine
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• v.35
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• pp.14.1-14.10
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• 2023

Background: Shift work is known to cause changes in the circadian rhythm of the human body and adversely affect not only physical health but also mental health. Some studies have demonstrated the correlation between shift work and thyroid stimulating hormone (TSH), a hormone that changes according to the diurnal rhythm, but few studies have reported the different TSH levels according to the shift work type. This study aimed to investigate changes in TSH according to the shift work type. Methods: This study included 1,318 female workers who had a medical checkup at a university hospital in Changwon from 2015 to 2019. Shift work types were classified as non-shift work, regular 2 shifts, and irregular three shifts, and a TSH ≥ 4.2 mIU/L was defined as abnormal. A general linear model (GLM) was used to compare the TSH levels and the risk of subclinical hypothyroidism in each year, and a binary logistic analysis was performed using a generalized estimation equation (GEE) to compare the risk of subclinical hypothyroidism over the 5-year period. Results: Of the 1,318 participants included in this study, 363, 711, and 244 were non-shift, two-shift, and irregular three-shift workers, respectively. In the GEE analysis, after adjusting for age, body mass index, smoking, and alcohol consumption, the odds ratios (ORs) were 1.81 (95% confidence interval [CI]: 1.15-2.86; p = 0.011) in 2 shifts and 2.02 (95% CI: 1.23-3.32; p = 0.006) in irregular three shifts, compared to non-shift. Conclusions: Our results showed that shift work had a higher risk of subclinical hypothyroidism than non-shift work and that there was a significant difference in the risk of subclinical hypothyroidism according to the shift work type. These findings suggest that the shift work type can be considered in future thyroid function tests and evaluations.

• The Korean journal of internal medicine
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• v.39 no.4
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• pp.668-679
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• 2024

Background/Aims: This cross-sectional study aimed to investigate biologics treatment disparities in rheumatoid arthritis (RA) patients based on socioeconomic status (SES). Methods: Data from the KOrean Observational Study Network for Arthritis (KORONA) database were analyzed to assess various factors associated with SES, health behaviors, and biologics use. Logistic regression and structured equation modeling (SEM) were utilized for data analysis. Results: Among 5,077 RA patients included, 393 (7.7%) patients were identified as biologics users. Within the entire cohort, 31.8% of the participants were in the low-income and low-education groups, and 39.3% of the participants were in the high-income and high-education groups. Despite the patients with low income or low education experienced higher disease activity at diagnosis, had more comorbidities, exhibited higher medication compliance, underwent more check-ups, and had more hospital admissions than their counterparts, the odds of patients with low-income receiving biologics were 34% lower (adjusted odds ratio = 0.76, 95% confidence interval: 0.60-0.96, p = 0.021) after adjustment for demographics and comorbidities. SEM and pathway analyses confirmed the negative impact of low SES on biologics use. Conclusions: The findings suggest that SES plays a significant role in biologics use among RA patients, indicating potential healthcare inefficiencies for low SES patients. Moreover, adverse healthcare habits negatively affect biologics use in RA patients. The study highlights the importance of considering socioeconomic factors while discussing biologics use and promoting equitable access to biologics for optimal RA management.