• Journal of Astronomy and Space Sciences
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• v.26 no.4
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• pp.499-510
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• 2009

In this paper, relative orbit of Low Earth Orbit satellites is determined using only GPS measurements and the effects of Equatorial Spread-F (ESF), that is one of biggest ionospheric irregularities, are investigated. First, relative orbit determiation process is constructed based on doubly differenced GPS observations. In order to see orbit determination performance, relative orbit of two GRACE satellites is estimated for one month in 2004 when no ESF is observed. The root mean square of the achieved baselines compared with that from K-Band Ranger sensor is about 2~3 mm and average of 95% of ambiguities are resolved. Based on this performance, the relative orbit is estimated for two weeks of two difference years, 2003 when there are lots of ESF occurred, and 2004 when only few ESF occurred. For 2003, the averaged baseline error over two weeks is about 15 mm. That is about 4 times larger than the case of 2004 (3.6 mm). Ionospheric status achieved from K-Band Ranging sensor also shows that more Equatorial Spread-F occurred at 2003 than 2004. Investigation on raw observations and screening process revealed that the ionospheric irregualarities caused by Equatorial Spread-F gave significant effects on GPS signal like signal loss or enhancement ionospheric error, From this study, relative orbit determination using GPS observations should consider the effect of Equatorial Spread-F and adjust orbit determination strategy, especially at the time of solar maximum.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.27 no.1
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• pp.46-53
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• 2001

The prevalence of supernumerary teeth is between $1{\sim}3%$. Of these, $90{\sim}98%$ occur in the maxilla with particular predilection for the premaxilla, preceded by mandibular third premolars, mandibular forth molars and maxillary paramolars. The most common ones occur in the maxillary anterior region, they may occur singly between the central incisors(mesiodens), or they may be double(mesiodentes). Maxillary anterior supernumeraries may erupt into the oral cavity or remain unerupted. It is found that approximately 25% are erupted, while the rest are unerupted. They are usually a small tooth with a cone-shaped crown and a short root. They may cause delayed eruption, median diastema, bodily displacement or rotation of the adjacent permanent teeth. Occasionally they may lead to the developement of dentigerous cyst or primordial cyst, or eruption into nasal cavity. In this study, 109 supernumeraries surgically extracted from premaxilla in 84 patients are analysed. The results are as follows : 1. Sex distribution of male and female is 2.2 : 1. 2. Almost cases are in pediatric age from 5 to 12 years old (87%). 3. Problems with supernumeraries are tooth malpositon, diastema, delayed eruption, eruption to nasal cavity and cyst formation. 4. Of 109 supernumeraries, 16(15%) are erupted into oral cavity, 92(84%) are impacted, and 1(1%) is erupted into nasal cavity. 5. Of 84 patients, 59(70%) have one supernumeray while 25(30%) have two supernumeraries. 6. Of 109 supernumeraries, 96(88%) are found within the region of the central incisors. 7. Of 109 supernumeraries, 94(86%) are vertically impacted, 11(10%) are horizontally impacted, 3(3%) are labiopalatally impacted and 1(1%) is impacted in nasal cavity. 8. Of 84 patients, we used palatal flap in 67(80%), labial flap in 6(7%), both flaps in 4(5%) and no flap in 7(8%). And incisive nerve was cut in 33(49%) of 67 palatal flaps. 9. Extration with ostectomy was done in 72 supernumeraries(66%), without ostectomy in 37 teeth(34%). 10. Extraction with tooth sectioning was done in 21 supernumeraries(19%), without tooth sectioning was done in 88 teeth(81%). 11. We used local anesthesia in 70 patients(83%) and general anesthesia in 14 ones(17%).

• Archives of Reconstructive Microsurgery
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• v.19 no.1
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• pp.1-6
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• 2010

Schwannoma of the brachial plexus region is very rare. There has not been general agreement in terms of surgical outcome from limited number of studies. We analyzed surgical outcomes from 11 cases of schwannomas which occurred in the brachial plexus. From February 2000 to August 2009, 11 patients with schwannomas of the brachial plexus region were surgically treated by a single surgeon. We retrospectively reviewed the medical records and MRI of our cases, and evaluated the neurologic deficit and the recurrence of tumors after surgery. All the cases were proven histologically as schwannomas. The mean age of the patients was 52.6(36~67) years old, 4 of them were male and 7 were female. The tumor was located in the left side in 9 patients, and right in 2. The mean postoperative follow-up was 24.7(6~78) months. Initial presentation was usually painless, palpable mass. The mass was located in various level of the brachial plexus such as root, trunk, cord, or terminal branch level. The size of mass was from $1.5{\times}1.5{\times}0.5$ cm to $11.0{\times}10.0{\times}6.0$ cm. Eight of 11 patients showed no neurologic deficit. Three patients showed postoperative neurologic deficit; two of them had transient sensory deficit, and one of them had weakness of flexor pollicis longus and 2nd flexor digitorum profundus. There were no recurrences. The schwannoma of the brachial plexus region should be considered as a curable lesion with an acceptable surgical risk of injury to neurovascular structures. With precise surgical techniques, these tumors can be removed to improve patient's symptoms with minimal morbidity.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.4
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• pp.607-612
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• 2009

The malignant tumor in childhood is one of the main causes of children s death due to disease. The traditional treatment for the malignancy is known for the radiation therapy and the chemical therapy or both. However, the treatments tend to induce intraoral complications. Different from adults, almost all children on cancer therapy are expected to have dental complications, because their permanent teeth are on the developmental stage. The degree of dental complication depends on the patient's age, type of chemical and other factors-radiation dose and frequency. In this report, 3 children who had experienced the anti-cancer therapy on their age between 1 and 4 years were selected and dental complications were examined. The children have chance for the various oral complications including the developmental problems such as agenesis, microdontia and hypoplasia of the teeth. Therefore, it's important to understand the side-effects of anticancer therapy during the permanent teeth had been developmental stage in young patients. Also, oral health care specialists, including pediatric and hospital dentist can support the oncology team by providing basic oral care, implementing oral care protocols, delivering emergency dental treatment undergoing anticancer treatment.

• Journal of the korean academy of Pediatric Dentistry
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• v.41 no.4
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• pp.306-313
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• 2014

Impacted teeth are teeth with a delayed eruption time or that are expected to erupt incompletely. Those teeth can cause a series of potential problems such as root displacement and resorption, periodontal problems in adjacent teeth, referred pain and the formation of cysts and odontogenic tumors. The purpose of this study was to investigate characteristics and treatment of child and adolescent patients younger than 15 years of age that were diagnosed with an impacted tooth who visited the Chosun University Dental Hospital. The impacted tooth, its etiology, treatment and traction period were surveyed through electric medical records, radiographs in 335 patients. We excluded the impacted third molar, supernumerary and deciduous teeth from this study. The most frequently impacted teeth are upper canine, followed by the upper incisor. The most common etiologies of impaction were an abnormal eruption pathway and localized pathologic lesions. The treatment of an impacted tooth was mostly orthodontic traction. The traction period was relatively short in cases with distinct obstacles, with an impacted upper incisor and if patients were younger. An orthodontic traction is considered to be more unfavorable if the patient gets older. Therefore, an early diagnosis and a precise treatment plan through a regular check-ups are mandatory.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.10 no.4
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• pp.27-37
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• 2015

Start up a company is critical to the regional economy and job creation and so get support from government and other organizations, but there are still exist of high rate of failure and CEO's stressful fear of failure. New firms are of utmost importance for the vitality of national economic driving forces but for those failed firms, they caused social and economic problems directly and indirectly, and brought frustration to the founders. The many education and research programs about entrepreneurship and venture creation were undertaken by the country and organizations, but the education and research about the vigilance of failed to start up company were almost ignored. If the attention can be put into the research about failed companies and the research can make the founders and pre-CEOs aware the failure of establishing a company, that would be very valuable as scenarios to see the company risks. This case study shows the finding the reasons which caused the failure of small venture companies and it's implications in the filed of establishing companies. The technology based venture company which had run 10 years in Daedeok's IT field was selected as the research object. The results show that the important factors such as entrepreneur characteristics(lack of communication and management knowledge), business management(lack of business expertise) and technology(loss of unique feature of product and lack of product extension) were the root cause of failures.

• Journal of Korean Society of Forest Science
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• v.95 no.1
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• pp.50-54
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• 2006

Biomass expansion factors and stem density values were commonly used in converting stand volumes into total carbon stocks for the purpose of national inventories of greenhouse gas emissions and carbon sequestration. The objective of this study was to examine the influence of stand age classes on aboveground and total biomass expansion factors, and stem density values in Chamaecyparis obtusa species. A total of 25 representative sample trees based on the three different stand age classes were destructively sampled to measure green weights and dry weights of the major four(root, stem, branch and foliage) portions of C. obtusa species grown in Jangseung-gun of southern Korea. According to the results of this study, as stand age classes increase, total biomass expansion factors tended to be decreased with the ranges from 3.64 to 1.44, while the stem density values tended to be slightly increased with the ranges from $0.35(g/cm^3)$ to $0.44(g/cm^3)$. There were statistically significant differences in biomass expansion factors and stem density values between stand age classes, but became nearly constant after 30 years old for C. obtusa species. This information could be very useful to improve a national-scaled inventory of greenhouse gas emissions and carbon sequestration for the C. obtusa species by applying different biomass expansion factors and stem density values.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.34 no.1
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• pp.81-85
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• 1989

One of the most important cultural techniques of pearl millet (Pennisetum americanum (L.) Leeke) is to encourage rapid and uniform emergence of seedlings to establish good stand and to let them grow well. Thus the objectives of the study were to investigate the effects of pre-sowing seed soaking and planting depth on dormancy breaking, germination and emergence of the seedlings, and to estimate the optimum planting season of pearl millet in Suwon, Korea. The seeds with dormancy germinated 99 to 100 percent when soaked in the H$_2$O$_2$ 1％ solution for 24 hours and rinsed with pure water, but germinated only 38％ and 83％ when soaked in pure water for 24 hours just after harvest and drying, and one month later from the harvest time, respectively. The seeds of Australia inbred line did not germinate at the constant 10$^{\circ}C$, but germinated at the constant 11$^{\circ}C$. It also was possible to estimate the optimum planting season by applying minimum temperature 11$^{\circ}C$ for germination. The minimum air temperature reached from late April in Suwon, Korea in regular years but fluctuated from late April to early May in 1986 and 1987. Thus, the safe planting season was mid-May for rapid and uniform germination of pearl millet seed. The optimum depth of planting was 2∼4cm under the optimum soil moisture condition, and 4 to 6 cm under the drier soil moisture condition. Subcoleoptile internode(mesocotyle) length increased according to increased depth of planting. Seedling crown placement also became deeper due to deeper planting of the seeds. The subcoleoptile internode length and seedling crown depth were positively correlated with actual planting depth, indicating that deeper planting would be not good for appropriate adventitious root and tiller development.

• Journal of Ginseng Research
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• v.28 no.1
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• pp.52-59
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• 2004

The ginsengs showing different ages(1, 2 and 3 years) are collected from the granite, phyllite and shale area. Keumsan and are analysed for the incompatible elements with the soils. In the soils, granite areas are high in the most of element and shale areas show high correlations among the element pairs. In the comparisons for differences of ginseng ages within the same area, granite and phyllite areas are high in the 2 year ginsengs while the shale ares are high in the 3 year ginsengs in the most of the elements. Positive correlations are dominant regardless area differences and high correlations are shown in the 3 year ginsengs, indicating the absorptions of the eligible element content with increasing ages. In the comparisons of area for the ginsengs of the same age, Rb, Cs and Ga, in the case of the granite area, are low in the 2 year ginsengs while most of elements are low in the 3 year ginsengs. High element contents are shown in the shale area, which are compared with granite and phyllite areas, indicating differences of dominant minerals. In the comparisons of the parts, upper parts are mainly high. High correlations are shown in the 3 year ginsengs, suggesting the similarities of absorption degrees within root as well as upper parts with the age. In the comparisons between soils and ginsengs, elements except Ba and Sr, are mainly high in the soils.

• Journal of Pharmaceutical Investigation
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• v.30 no.3
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• pp.173-178
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• 2000

The purpose of this work is to develop a transurethral suppository containing prostaglandin $E_1\;(PGE_1)$, which stabilizes the drug, gives no irritation to physiological body and enhances the erectile response of $PGE_1.\;PGE_1$ transurethral suppositories were prepared with various amounts of compositions such as saturated polyglycolysed glyceride $(Suppocire^{\circledR}\;AP,\;SAP)$, polyoxyethylene hydrogenated castor oil (HCO-50) and ethanol. The melting points, viscosities and $PGE_1$ release of the suppositories were investigated. Ocular irritation test was carried out after application of $PGE_1$ suppository to rabbit's eye. The intracavernous pressure (ICP), penile length and duration of erectile response were determined after transurethral administration of $PGE_1$ suppository and compared with those after intracavernosal injection of $PGE_1$ solution to cats. HCO-50 hardly affected the melting points and viscosities of $PGE_1$ suppositories. Additionally, $PGE_1$ transurethral suppositories, whose melting point ranges was $34-35^{\circ}C$, was speedily melted in physiological body. HCO-50 significantly decreased the dissolution rates of $PGE_1$ from the suppositories. Dissolution mechanism analysis showed the release of $PGE_1$ was proportional to the square root of time, indicating that $PGE_1$ might be released from the suppositories by Fickian diffusion. The release rate of $PGE_1$ from $PGE_1$ suppository [PGE1/SAP/HCO-50/ethanol (1/94.5/2.5/2%)] was about 80% within 2 h. This $PGE_1$ suppository gave no significant irritation to the ocular tissue, expecting that it gave no irritation to the urethral tissue less sensive than ocular tissue. Furthermore, $PGE_1$ in this suppository was stable at $4^{\circ}C$ for 2 years. This suppository increased the ICP and penile erection similar to those of injectable $PGE_1$ solution. However, it gave 2.5-fold increased duration of erectile response than injectable $PGE_1$ solution. Our results suggested that it gave more effective erectile response than injectable $PGE_1$ solution in cats. It is concluded that this $PGE_1$ suppository with good safety, excellent stability and enhanced erectile response, could be a more effective and convenient transurethal delivery system of $PGE_1$.