• International Journal of Aeronautical and Space Sciences
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• v.6 no.1
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• pp.44-51
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• 2005

To provide more accurate and reliable positioning and timing services to Korean nationwide users, the Ministry of Maritime Affairs and Fisheries of Korea is implementing Korean NDGPS (Nationwide DGPS), which is operational partly. And it also has a plan to construct WADGPS (Wide Area Differential GPS) system using sites and equipments of the NDGPS reference stations. For that, Seoul National University GNSS Laboratory is implementing and testing prototypes of WRS (Wide-area Reference Station) and WMS (Wide-area Master Station). Until now, because there are not enough installed WRSs to be used for computing wide area correction information, we cannot test algorithms of WMS with the data processed actually in WRSs. Therefore to evaluate the performance of the algorithms, we made a MATLAB program which can process RINEX (Receiver INdependent Exchange) format data with WADGPS algorithm. Using that program which consists of WRS, WMS and USER modules, we processed the data collected at NDGPS reference stations, which are saved in RINEX format. In WRS module, we eliminate the atmospheric delay error from the pseudorange measurement, smooth the measurement by hatch filter and calculate pseudorange corrections for each satellite. WMS module collects the processed data from each reference stations to generate the wide area correction information including estimated satellite ephemeris errors, ionospheric delays at each grid point, UDRE (User Differential Range Error), GIVE (Grid Ionosphere Vertical Error) and so on. In USER part, we use the measurements of reference stations as those of users and estimate the corrected users' positions and protection levels (HPL, VPL). With the results of estimation, we analyzed the performance of the algorithms. We assured the estimated UDRE /GIVE values and the protection levels bound the corresponding errors effectively. In this research, we can expect the possible performance of WADGPS in Korea, and the developed modules will be useful to implementation and improvement of the algorithms.

• Korean Journal of Poultry Science
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• v.34 no.4
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• pp.301-318
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• 2007

Marek's disease (MD) is a highly contagious lymphoproliferative disease of poultry caused by the oncogenic herpesvirus designated Marek's disease virus (MDV). MD has a worldwide distribution and is thought to cause an annual loss over US$ one billion to the poultry industry. Originally described as a paralytic disease, today MD is mostly manifested as an acute disease with tumors in multiple visceral organs. MD is controlled essentially by the widespread use of live vaccines administered either in ovo into 18-day-old embryos or into chicks immediately after they hatch. In spite of the success of the vaccines in reducing the losses from the disease in the last 30 years, MDV strains have shown continuous evolution in virulence acquiring the ability to overcome the immune responses induced by the vaccines. During this period, different generations of MD vaccines have been introduced to protect birds from the increasingly virulent MDV strains. However, the virus will be countered each new vaccine strategy with ever more virulent strains. In spite of this concern, currently field problem from MD is likely to be controled by strategy of using bivalent vaccine. But, potential risk factors for outbreak of MD are still remained in this condition. The major factors can be thought that improper handling and incorrect administration of the vaccine, infection prior to establishment of immunity, suppression of immune system by environmental stress and outbreaks of more virulent MDV strain by using vaccine and genetic resistance of host.

• The Korean Journal of Zoology
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• v.32 no.4
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• pp.314-321
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• 1989

배의 발생과 분화에 따른 혈청 alpha-fetoprotein (AFP)의 생리적 기능 규명을 위한 기초실험의 일환으로, 모체와는 완전히 독립된 상태에서 발생과 분화가 이루어지는 계배의 혈청을 재료로 하여 CM-Sephadex C-50, hydroxyapatite 및 DEAE-Sepharose A-25등의 크로마토그라피 방법에 의해 닭 혈청 AFP를 분리하였다. 계 AFP는 분자량이 약 60 Kd로 사람 및 다른 포유동물 AFP의 분자량 (64-74 Kd)보다 작았다. 닭 AFP, 계배혈청 및 닭 혈청 등을 토끼에 면역하여 항체를 제조하였고, 이를 이용하여 닭의 배발생 단계에 따른 혈청 AFP 함량의 변화를 전기영동 및 면역학적 방법으로 정성 및 정량 분석을 실시하였다. 혈청 AFP 함량은 발생 7일-배 (AFP 농도 : 0.81 mg/ml)부터 점차 증가하여 13일-배에서 최고치인 2.46 mgfml로 나타났으며 그 이후 급격히 감소되어 부화 직후에는 매우 낮은 농도 (0.22mg/ml)였고 부화 4일에 거의 없어 졌으며, 이와 같은 AFP 함량의 변화는 혈청 알부민 함량의 변화와 거의 반비례 함을 알았다. For the preliminary step to investigate the site of AFP synthesis, the ontogenic characteristics and the physiological function of AFP, alpha-fetoprotein was isolated from chick embryo serum through the procedures of CM-Sephadex C-50, hvdroxvapatite and DEAE-Sephadex A-50 chro-matography. The isolated AFP was proved to be pure and its molecular weight was found to be about 60 Kd. With this purified AFP, rabbit anti-chick hor was produced. The serum AFP level in chick embryo has been investagated by using polyacrylamide gel electrophoresis, immunoelec-trophoresis and single radial immunodiffusion from 7 days of incubation until 4 days after hatch-ing. It was found that the AFP level is increased from 0.81 mg/ml at daw-7 embryo to maximum value of 2.46 mg/ml at day-13 embryo, followed by rapid decreases until hatching.

• Environmental Analysis Health and Toxicology
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• v.24 no.1
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• pp.17-23
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• 2009

Nanotechnology, one of the technologies that forms the core of the recent scientific innovation, is used much in our real lives. Especially products that use nano silver are being sold, with its positive characteristics resulting from the antibacterial effects of both nano materials and silver. But critiques have pointed out that nano silver diffused into everyday life too quickly as we do not have done any comprehensive research about the material, and worry that nano silver will affect the ecology adversely. Therefore, this research focuses on investigating the toxicity of silver nanoparticles first. To compare the effects of exposure to silver nanoparticles at pre-somite stage and somite stage(10 hours after fertilization), we exposed zebrafish embryos to silver nanoparticles(15, 30 ppt) during embryogenesis, and then checked the details of catalase enzyme activity. The hatch rate decreased in the silver nanoparticles exposed groups(15 and 30 ppt); furthermore, the hatched fishes had an abnormal notochord, damaged eyes and curved tail. The catalase activities of the 15 ppt exposed group at somite stage increased relative to those in the control group. Therefore, the silver nanoparticles could seriously damage the development of zebrafish embryos. Especially, exposure to silver nanoparticles at somite stage did severer damage than exposure since pre-somite stage did.

• Korean journal of applied entomology
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• v.31 no.4
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• pp.480-485
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• 1992

Laboratory studies were done to evaluate the effects of diflubenzuron on embryonic and postembryonic development of Riptortus clavatus Thunberg. Diflubenzuron prevented egg hatch; younger eggs(O-12 h old) were 2 times as susceptible as older(48-60 h old) eggs, but embryos of both younger and older eggs developed normally. Susceptibility of nymphs to diflubenzuron decreased with each successive molt. Compared with the first instar, relative tolerance to diflubenzuron was 1.5 times for the second instar, 18.2 times for the third instar, 39. 4 times for the fourth ins tar and 42.4 times for the fifth instar. Even as low concentrations, diflubenzuron prevented significant numbers of third instar nymphs from developing to fourth and fifth instar nymphs or adults. Weight, longevity and fecundity of adults surviving treatment in the final (fifth) instar were also adversely affected.

• Korean journal of applied entomology
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• v.35 no.2
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• pp.164-172
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• 1996

The comparative toxicity of abamectin to the predatory mite, Amblyseius womersleyi Schicha and the spider mites, Tetranychus urticae Koch and T. kanzawai Kishida was evaluated by leaf disc method. Abamectin was much less toxic to A. womersleyi than to the spider mites. Although survival rate of adult females of A. womersleyi tended to decrease with increasing abamectin concentration, 8-78% of predators remained alive at concentrations of 0.38-6 ppm. Likewise, reproduction was significantly reduced with increasing abamectin concentration. Abamectin neither affect the hatch of A. womersleyi eggs nor the development of surviving immature predators. Survival of immature predators decreased with increasing abamectin concentration. However, 42-90% of immature predators reached adulthood at 0.38-3 ppm. Adult female predators survived on a diet of spider mites intoxicated with abamectin, although their fecundity and the sex-ratio of the progeny were significantly affected. Abamectin at selective sublethal concentrations (0.38-0.75 ppm) could he of value in adjusting predatorlprey ratios in integrated management of T. urticae and T. kanzawai.

• Clinical and Experimental Reproductive Medicine
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• v.26 no.3
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• pp.345-353
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• 1999

In the studies on the hatching mechanisms in mammals, many investigators focused on the embryonic intrinsic factor(s) in in vitro culture, but the uterine environment as the extrinsic factor(s) is thought to play an important role in hatching mechanism. Therefore, to evaluate the effect of uterine environment on the hatching event in vivo, the immature(GV) and ovulated(MII) oocytes, and the late 2-cell embryos of mouse were transferred to pseudopregnant foster mother's uterus during peri-implantation period. So it was verified whether there would happen hatching by only uterine environment independently on embryonic stage. The ultrastructural changes of the zona surface of transferred group were compared with those 01 in vivo and vitro group by SEM. 36 hrs after transfer, the immature and ovulated oocytes almost degenerated, and the late 2-cell embryos developed to various embryonic stages. However, the embryos which didn't develop to blastula stage did not hatch. The ultrastructural network of ZP in transferred group seemed to be smoothed uniformly, which was different from in vitro group. In conclusion, it is suggested that the uterine environment during peri-implantation period enhances the embryo hatching by provoking the structural change of ZP.

• Korean journal of applied entomology
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• v.44 no.3 s.140
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• pp.231-235
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• 2005

This study was conducted to obtain the optimal spray time for Pseudaulacaspis prunicota (Maskell) (Homoptera: Diaspididae) in early seaon in Jeju. Oviposition time of overwintered females and activity of hatched nymphs of P. prunicola were monitored, and the phenology data were compared with the outputs estimated by a degree-days model of P. pentagona (Targioni-Tozzetti)). Overwintered females of P. prunicola began to lay eggs from mid to late April, and the eggs started to hatch from early May followed by the active migration of the hatched nymphs during mid May. The phenological events of P. prunicola in early season were likely comparable with those of P. pentagona reported in southern Korea and in central Japan. A degree-day model, which predicts the proportion of >50% hatched egg batches of P. pentagona (y=1[exp(-(-a+bx))]; y, proportion; x, degree-days based on $10.5^{\circ}C$ from 1 January; a=-18.80 and b=0.073), accurately described the migration time of P. prunicola hatched nymphs. Thus, it is considered that the degree-day model can be used for predicting the optimal spray time for P. prunicola in early season.

• Korean Journal of Ichthyology
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• v.23 no.2
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• pp.150-157
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• 2011

In this study we described reproduction study of Korean endemic species, Acheilognathus koreensis and three other acheilognathinae species A. signifer, Rhodeus pseudosericeus, and R. uyekii. Morphology of egg shape and larvae just hatched is unique by the species respectively. There is no interrelation factor between size of female and number of spawned eggs per one time. Minium water temperature for spawning of A. koreensis was observed in $13.0^{\circ}C$ having low hatching rate with 43.5 percent. The egg of A. koreensis began to hatch approximately 79 hours after insemination. As higher as water temperature until $22.0^{\circ}C$ hatching elapsed time for developing eggs of A. koreensis and three species in this study was shortened. A. koreensis was grew up to be a adult enough which can be join to new production for three hundred days after hatching with 52.4 mm in total length. This reproduction study will be applied to preservation of Korean endemic fresh water fishes basically.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.6
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• pp.821-830
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• 2010

Deck plates and hatch coming of large container carrier and offshore structures are joined by ultra-thick plates whose thickness is more than 60mm. Traditionally FCAW has been used to join the thick plates in butt joint. However, FCAW has been replaced with EGW since the welding efficiency of EGW is higher than that of FCAW. Tandem EGW using two electrodes has been applied to vertical position welding by several shipyards. EGW requires one or two layers of bead whereas FCAW requires more than 20 layers of weld bead in thick welding. However, high welding residual stresses are generated by EGW since it uses higher heat input than FCAW. In the present study, a finite element model is suggested to predict the residual stresses induced by the tandem EGW. Butt specimen of EH40 TMCP shipbuilding steel plates vertical welding was modeled by a three-dimensional model. Residual stresses were measured by X-ray diffraction method and to verify the numerical result. The results show a good agreement with experimental result.