• Applied Microscopy
• /
• v.45 no.3
• /
• pp.144-149
• /
• 2015

Nothobranchius guentheri and Nothobranchius patrizii have special life cycle to sustain the dry season. So, we investigated the fertilized eggs morphology, and compared ultrastructures of surface structures and the cross section of fertilized egg envelopes using light and electron microscopes to determine whether these fertilized eggs and egg envelopes show the species specificity or have special structure to sustain the dry season. These fertilized eggs were spherical, yellowish, demersal and adhesive, and had a one-sided large oil droplet. The whip-like structures, adhesive filament were distributed throughout egg envelope in both species. But, that of N. guentheri was covered with fibrous structures, and that of N. patrizii was smooth. The egg envelope consisted of two distinct layers: an outer, electron-dense layer containing adhesive filaments and an inner layer of 16 to 17 horizontal electron-dense lamellae alternating with 15 to 16 interlamellae of lower electron density in both species. The external shapes of fertilized egg and section of fertilized egg envelope were same, but ultrastructure of adhesive filaments on the outer surface was concluded to show species specificity. Our data indicate that the ultrastructural differences of adhesive filament and outer surface of fertilized egg envelope show species specificity although these species belong to same genus.

• Transactions of Materials Processing
• /
• v.24 no.3
• /
• pp.176-180
• /
• 2015

The current study is concerned with the prediction of fracture strains for DP980 steel sheets over a wide range of loading paths. The use of DP980 steel is increasing significantly in automotive industries for enhanced safety and higher fuel efficiency. The material behavior of advanced high-strength steels (AHSSs) sheets sometimes show unpredictable and sudden fracture during sheet metal forming. A modified Lou-Huh ductile fracture criterion is utilized to predict the formability of AHSSs because the conventional forming limit diagram (FLD) constructed based on necking is unable to evaluate the formability of AHSSs sheets. Fracture loci were extracted from three dimensional fracture envelopes by assuming the plane-stress condition to evaluate equivalent plastic strains at the onset of fracture for a wide range of loading paths. Three different types of specimens -- pure shear, dog-bone and plane strain grooved -- were utilized for tensile testing to calibrate the fracture model of DP980 steel sheets. Fracture strains of each loading path were evaluated such that there shows little deviation between fracture strains predicted from the fracture model and the experimental measurements. From the comparison, it is clearly shown that the three dimensional fracture envelopes can accurately predict the onset of the fracture of DP980 steel sheets for complicated loading conditions from compressive loading to shear loading and to equibiaxial tensile loading.

• Communications of the Korean Mathematical Society
• /
• v.8 no.2
• /
• pp.169-180
• /
• 1993

• The Bulletin of The Korean Astronomical Society
• /
• v.25 no.2
• /
• pp.95-95
• /
• 2000

• Bulletin of the Korean Space Science Society
• /
• 2008.04a
• /
• pp.17.5-18
• /
• 2008

• Bulletin of the Korean Space Science Society
• /
• 2002.05b
• /
• pp.19.2-19
• /
• 2002

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2002.03a
• /
• pp.51-58
• /
• 2002

The relative site amplification factors in southern Korea were determined from coda waves using coda normalization method. The seismograms of 15 events at 79 stations were used in this study. Seismogram envelopes were obtained by the Hilbert transform of bandpass-filtered velocity seismograms with frequency bands at 1-2Hz, 2-4Hz, 4-8Hz, 8-l6Hz and 16-32Hz. The envelopes were stabilized by application of moving-average scheme with time window of 1 second. The relative amplitudes of seismogram envelope were computed by dividing the amplitude of seismogram envelope at one site by the amplitude of seismogram envelope at reference site. The relative site amplification factors were obtained by taking averages of the relative amplitude. Values of relative site amplification factors in southern Korea are generally low in western area and high in eastern area.

• Applied Microscopy
• /
• v.20 no.2
• /
• pp.117-126
• /
• 1990

Structural changes of the vitelline envelopes during oogenesis of a polychaete, Nectoneanthes oxypoda, were examined with a scanning electron micrscope. Oocytes grow in the same coelomic fluid to the final stage, but the surface appears to change in the structure during oogenesis. Projections, which were identified to be microvilli, change in shape, number and size. Short microvilli, which cover the surface of oocyte of $33{\mu}m$ diameter densely, grow in length, reaching a maximum at the stage of $73{\mu}m$. The number of microvilli increases with the stages of oogenesis, reaching a plateau at the stage of $82{\mu}m$. The observations suggest that control of material transport including yolk precursor proteins may be correlated with the structural changes in the microvilli.

• Journal of Astronomy and Space Sciences
• /
• v.12 no.2
• /
• pp.168-178
• /
• 1995

We have modeled the dust envelopes around carbon stars with close attention to the evolution of the structure of the dust shells. We use various dust density distributions to take account the effect of the superwind due to the helium shell flash by adding a density increased region. Depending on the position and quality of the density increased region, the model results are different from the results with conventional density distribution. The new results fit the observations of some carbon stars better. The IR two-color diagrams comparing the results of the super wind models and IRAS observation of 252 carbon stars have been made. The new results can explain much wider regions on the IR two-color diagrams.

• Journal of Astronomy and Space Sciences
• /
• v.12 no.2
• /
• pp.157-167
• /
• 1995

OH/IR stars are the most massive and youngest subclass in asymptotic giant branch stars which pass through sporadic superwind phases. We have modeled the dust envelopes around OH/IR stars with close attention to the evolution of the structure of the dust shells. We use various dust density distributions to take account the effect of the superwind due to the helium shell flash by adding a density increased region. Depending on the position and quality of the density increased region, the model results are different from the results with conventional density distribution. The new results fit the observations of some OH/IR stars better. Especially, the OH/IR stars with excessive 30-100$\mu$m emission can be better explained by the new results. The IR two-color diagrams comparing the results of the superwind models and IRAS observation of 95 OH/IR stars have been made. The new results can explain much wider regions on the IR two-color diagrams.