• Journal of Korean Society of Environmental Engineers
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• v.28 no.5
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• pp.501-510
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• 2006

To investigate the effects of MLSS concentration and influent C/N ratio on the nitrogen removal efficiency of alternately intermittently aerated nonwoven fabric filter bioreactors, the MLSS concentrations of the reactors were maintained at approximately 5,500 mg/L, 10,000 mg/L and 15,000 mg/L, and the influent TCOD/TKN ratio was decreased gradually from 5 to 2 by adding $NH_4Cl$. The influent was prepared by diluting a food waste leachate to a TCOD concentration of about 300 mg/L. The results of the experiment showed F/M ratios less than 0.112 g TCOD/g MLSS-day, average TCOD removal efficiencies of above 95%, and an average observed microbial yield coefficient of 0.283 g MLSS/g COD removed. The nitrification efficiencies were computed to be always better than 96% except one case where the nitrification efficiency was 90.5% when the MLSS concentration and the influent TCOD/TKN ratio was 5,500 mg/L and 2, respectively. The denitrification efficiency deteriorated as the influent TCOD/TKN ratio decreased. The average denitrification efficiency at the MLSS concentration of 10,000 mg/L was 10.7% better than that at the MLSS concentration of 5,500 mg/L, and the denitrification rate improved at a rate of 2.66 mg NL as the MLSS concentration increased by 1,000 mg/L. When the MLSS concentration was 15,000 mg/L, however, the average denitrification efficiency was merely 4.6% higher compared to when the MLSS concentration was 5,500 mg/L, and the denitrification rate increased at a rate of 0.75 mg N/L per 1,000 mg/L MLSS increase. Therefore, no strict proportional relationship was found between MLSS concentration and endogenous denitrification rate. The average alkalinity consumption rate was 3.36 mg alkalinity/mg T-N removed, which is similar to the theoretical value of 3.57 mg alkalinity/mg T-N removed, but the rate increased as the influent TCOD/TKN ratio decreased.

• Korea journal of population studies
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• v.19 no.1
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• pp.139-159
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• 1996

This study comparatively examines a causal model of employee attatchment which focuses on employee's organizational commitment and intent to stay with an organization. This study is based on two separate studies of employee attachment among teachers : the U.S. case of the Chicago Public Schools (CPS) and the South Korean case of the Seoul Educational District (SED). The main purpose of this study is to replicate in Korea the CPS study. A revised model based on the unique characteristics of Korean teachers is also developed and estimated. The Price Mueller model of employee attachment provides the basic theoretical framework for this study. It includes five general classes of variables : 1) employee responses to work variables : job satisfaction, commitment, and intent to stay; 2) psychological stress variables: role ambiguity, role conflict, work overload, and quality of students; 3) social structural variables: autonomy, routinization, distributive justice, and legitimacy; 4) economic structural variables: pay, job security, promotional opportunities, and job opportunities; and 5) work orientation variables : career commitment, normative commitment, work motivation, affectivity, work values, and met expectations. The data was collected through questionnaire survey and a sample of 649 secondary school teachers in Seoul, South Korea, was included in the final analysis. Covariance structure analysis (LISREL) was used to estimate the causal model. The results indicate that the endogenous variables of job satisfaction and commitment play a considerably less important role than in the U.S. model in mediating the effects of the exogenous variables on intent to stay, and the model fails to explain the majority of the variance in intent to stay. In addition, the new variables added to the revised Korean model do not bave significant effects on intent to stay. The structural characteristics of the employment relationship and labor markets associated with Korean teachers forced mobility and closed external markets - are largely accountable for the major differences between the Korean and the U.S. cases. The study suggests that conceptual and empirical work on what produces employee attachment under these structural constraints needs to receive more attention in future studies.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.14
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• pp.79-86
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• 1973

In order to investigate the heading responses of naked barleys and their grain yields under the different sowing times in spring sowing at 9 levels and to select the promising variety, present work was carried out with 11 recommended naked barley varieties and 2 newly developed lines for the period of 3 years from 1971 to 1973 at Iri, these results being summarized as follows: 1. Under spring sowing cultures, 'Wanju naked barley' being spring habit showed the highest yields among them. However, Sedohadaka and Bangju being winter habit were also considered as the promising varieties. 2. In the case of sowing the spring type naked barleys in spring the optimum sowing time of barleys at Iri was estimated in the late of February or the early of March. 3. The number of main culm leaves and tillering per hill of 'Wanju naked barley' were not influenced at sowing times. But winter type barleys being sown in spring, they were outstandingly increased in accordance with the sowing time being late, especially after the critical sowing time. 4. In comparison with average days from germinating to heading date under different seasonal sowing at the same variety, 'Wanju naked barley' took 64.4 days to get heading and Kikaihadaka and Hyangchoen gwa, the low spring growing habit varieties, 72-73 days. 5. Young spikelet differentiation stage (length of young spikelet: 0.3-0.5mm) arrived at about 30 days before heading date in comfortable sowing time without regarding spring or winter type. But number of main culms disclosed great differences among them; barleys being high spring type were 4 leaves and low about 6. 6. In the view of morphology, culm length under the different seasonal sowing could not be found out differences in the high spring type barleys, but in the low, it was grately shortened by postponing the sowing time. The barley height of rosette form had no difference at any sowing time.difference at any sowing time.

• Tuberculosis and Respiratory Diseases
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• v.51 no.5
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• pp.416-425
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• 2001

Background : The incidence of drug-resistant tuberculosis has recently decreased in Korea. However, it is still one of the major obstacles in treating pulmonary tuberculosis. This study was performed to determine the prevalence and clinical characteristics associated with drug-resistance in pulmonary tuberculosis at the tertiary referral hospital in Pusan, Korea. Methods : The medical records of 138 patients, who had been diagnosed as active pulmonary tuberculosis were retrospectively reviewed, and results of drug susceptibility from May 1997 to June 2000. The relationships among those with a history of previous tuberculosis treatment, the extent of lung involvement, the presence of cavities on the initial chest X-ray films and patterns of drug resistance were analyzed. Results : The total number of patients who had drug resistance to at least one drug was 55(39.9%). Among them 34(24.6%) had resistance to isoniazid(INH) and rifampin(RFP). There was drug resistance in 20(22%) of 91 patients without previous tuberculosis therapy, and among them 9(9.9%) were multi-drug resistant. Thirty-two(74.5%) out of 47 patients with previous therapy were drug-resistant and 25(53.2%) were multidrug resistant. For all 138 patients, resistance to INH was the most common(34.1%), followed by RFP(26.1%) and ethambutol(EMB)(14.5%). Drug resistance to INH, RFP, PZA and streptomycin(SM) were independently associated with a history of previous treatment(odds ratio; 9.43, 9.09, 8.93 and 21.6 respectively, p<0.01). The extent of lung involvement on the chest films was significantly associated with the drug resistance to INH and RFP(odds ratio; 2.12 and 2.40 respectively, p<0.01). The prevalence of drug resistance to RFP, INH and RFP was significantly more common in patients with a cavitary lesion on the chest films by multivariate analysis(odds ratio; 4.17 and 4.81 respectively, p<0.05). Conclusion : This study revealed that patients with a prior treatment history for pulmonary tuberculosis, and the presence of a cavitary lesion on chest films had a higher prevalence of anti-tuberculosis drug resistance. A very careful clinical and microbiological examination is needed for patients with such characteristics.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.5 no.1
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• pp.69-86
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• 1969

On the growing of the interspecific hybrid ginseng plant, the phenomena of hybrid vigoures are observed in the root, stem, and leaf, but it can not produce seeds favorably since the ovary is abortive in most cases in interspecific hybrid plants. The present investigation was undertaken in an attempt to elucidate the embryological dses of the seed failure in the interspecific hybrid of ginseng (Panax Ginseng ${\times}$ P. Quinque folium). And the results obtained may be summarized as follows. 1). The vegetative growth of the interspecific hybrid ginseng plant is normal or rather vigorous, but the generative growth is extremely obstructed. 2). Even though the generative growth is interrupted the normal development of ovary tissue of flower can be shown until the stage prior to meiosis. 3). The division of the male gameto-genetic cell and the female gameto-genetic cell are exceedingly irregular and some of them are constricted prior to meiosis. 4). At meiosis in the microspore mother cell of the interspecific hybrid, abnormal division is observed in that the univalent chromosome and chromosome bridge occure. And in most cases, metaphasic configuration is principally presented as 23 II+2I, though rarely 22II+4I is also found. 5). Through the process of microspore and pollen formation of F1, the various developmental phases occur even in an anther loclus. 6). Macro, micro and empty pollen grains occur and the functional pollen is very rare. 7). After the megaspore mother cell stage, the rate of ovule development is, on the whole, delayed but the ovary wall enlargement is nearly normal. 8). Degenerating phenomena of ovules occur from the megaspore mother cell stage to 8-nucleate embryo sac stage, and their beginning time of constricting shape is variously different. 9). The megaspore arrangement in the parent is principally of the linear type, though rarely the intermediate type is also observed, whereas various types, viz, linear, intermediate, Tshape, and I shape can be observed in hybrid. 10). After meiosis, three or five megaspore are some times counted. 11). Charazal end megaspore is generally functional in the parents, whereas, in F1, very rarely one of the center megaspores (the second of the third megaspore) grows as an embryo sac mother cell. 12). In accordance with the extent of irregularity or abnormality in meiosis, division of embryo sac nuclei and embryo sac formation cause more nucellus tissue to remain within th, embryo sac. 13). Even if one reached the stage of embryo sac formation, the embryo sac nuclei are always precarious and they can not be disposed to theil proper, respective position. 14). Within the embryo sac, which is lacking the endospermcell, the 4-celled proembryo, linear arrangement, is observed. 15). Through the above respects, the cause of sterile or seed failure of interspecific hybrid would be presumably as follows, By interspecific crossing gene reassortments takes place and the gene system influences the metabolism by the interference of certain enzyme as media. In the F1 plant, the quantity and quality of chemicals produced by the enzyme system and reaction system are entirely different from the case of the parents. Generally, in order to grow, form, and develop naw parts it is necessary to change the materials and energy with reasonable balance, whereas in the F1 plant the metabolic process becomes abnormal or irregular because of the breakdown of the balancing. Thus the changing of the gene-reaction system causes the alteration of the environmental condition of the gameto-genetic cells in the anther and ovule; the produced chemicals cause changes of oxidatio-reduction potential, PH value, protein denaturation and the polarity, etc. Then, the abnormal tissue growing in the ovule and emdryo sac, inhibition of normal development and storage of some chemicals, especially inhibitor, finally lead to sterility or seed failure. Inconclusion, we may presume that the first cause of sterile or seed abortion in interspecific hybrids is the gene reassortment, and the second is the irregularity of the metabolic system, storage of chemicals, especially inhibitor, the growth of abnormal tissue and the change of the polarity etc, and they finally lead to sexual defect, sterility and seed failure.