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Isofemale lines of Drosophila melanogaster were established from Daejon in Korea and were examined in order to investigate the changes of cytotype or strain type by P-M system through 1∼15 generations. The results are as follows: 1. Using π_2 (strong P) strains and bw;st (true M) strains as standard strains, the mean sterility frequencies from Cross A were 20.8%∼34.6% for each generations and the mean sterility frequencies from Cross B were 0.0%∼0.3%. 2. Frequency of strain with P cytotype for each generation was analyzed to be 44.8%(G₁), 59.2%(G₂), 43.7%(G₄), 36.7%(G_7), 29.2%(G_10) and 36.7%(G_15). Therefore it was tend to be low as increased with generation number, but the differencies in percentage of GD sterility between each generation are non-significant statistically. 3. Among the isofemale lines, type conversions were observed. Q→M', M'→Q and M'→M changes have occured with frequency of 18.4%, 8.2% and 4.1%, respectively. The remaining lines (69.3%) were unchanged through several generations. 4. The results suggest that Drosophila melanogaster are appeared temporally as a certain strain type in natural population, but the type conversions were represented by interactions between P elements in each genome and cytoplasm for each generation.
Determination of the stress intensity factors was studied by many scientists. There are several methods in this. Up to now, what is the most useful method is Irwin's two parameter method by measuring the maximum distance, direction and the order of a fringe loop. But, in this paper, the stress intensity factors were determined by new method measuring the initial direction. in which the maximum shearing stress is minimum and distance and number of fringe loop in arbitarary direction. In this result, we have several concuiusions. 1) Determination of the stress intensity factor by this new method than conventional method is easy and has small error. 2) When the finite width strip with a oneside crack and a pair of symmetrical near hole is under the uniaxial tension, there is only the stress intensity factor of opening mode and stresses near the crack are increasing as the hole is closed to the crack tip. In particular, when the hole is in the direction of 60°, stresses near the crack are very large 3) In case of unsymmetrical hole, the initial direction in which the maximum shearing stress is minimum is not zero degree but turned. 4) When the distance between hole and crack tip is larger than 3 times of the hole diameter, stresses in the vicinity of crack is not effected by the hole.
간질발작을 포함한 전형적인 삼징후가 동반된 결절성경화증 환자를 대상으로 뇌파검사, 뇌전산화단층촬영술 및 단일광자방출단층촬영술을 시행하였다. 뇌전산화단층촬영술에서는 상의하석회화병소와 조영제증강이 뚜렷하지 않은 피질에 연한 저음영 소견이 관찰되었으며 이어서 시행한 단일광자방출단층촬영술에서는 뇌전산화단층촬영술 소견보다 더 광범위한 부위에 관류결손이 관찰되었다. 단일광자방출단층촬영술은 결절성경화증 환자에서 간질발현 병소인 피질결절을 발견하는데 있어서 전산화단층촬영술 및 뇌파검사보다 더 유용한 방법이며 치료방침 결정이나 예후판정에 있어서도 큰 도움을 줄 것으로 기대된다. Two patients with a well-established diagnosis of tuberous sclerosis and epilepsies as their principal clinical symptom were examined by conventional surface electroencephalography(EEG), computed tomography, and single photon emission computed tomography(SPECT) using the 99mTc hexamethyl prophyleneamine oxime(99mTc-HMPAO). The interictal EEG showed various abnormalities of poor localizing value. Brain computed tomography surely demonstrated subependymal calcifications, although the cortical lesions were not so conspicuous. However, the SPECT images of each patient clearly demonstrated decreased cerebral perfusion in cortical areas. It may be assumed that such perfusion defect areas represent the epileptic cortical tubers or those of altered myelination, which are characteristics of the disease.
The term hydraulic fracturing has been used in the geotechnical engineering literature to describe situations in earth embankment dams where the reservoir water pressure initiates and propagates a cracks. The term has also been used in situations where an existing crack is further widened by the reservoir water pressure. The mechanisms of hydraulic fracturing in the core of rockfill dams that have been proposed to date are quite qualitative and have been postulated in the course of investigations to find the causes of leakage or failures as a results of internal erosion. In this study, the various mechanisms of hydraulic fracturing are outlined and the finite element analyses of 5 representative rockfill dams in Korea were conducted to examine the assumption that hydraulic fracturing occurs in embankment cores when the reservoir water pressure exceeds the total normal stresses. This numerical analyses use the hyperbolic model and its parameters from the conventional triaxial tests. As the results of the analyses, the total normal stresses by FEM exceed the water pressures in most cases which is contray to the fact that the water pressures exceed the total normal stresses by the pressure meters in the case of Soyanggang dam.
The results both non-destructive test and compressive strength test, by rebound hammer testing method, to highly heated concrete are the inferential formula of compressive strength, as follows : (1) Air circuit leave for 24 hours after heating Fc= 7.53R-70.69 (2) Air circuit leave for one month after heating Fc= 7.62R-78.07
It was known by photoelastic and fracture experiments that the theory of fracture path of crack problems, fracture grows to the direction which the maximum shearing stresses arc minimum at the vicinity of crack tip, could be applied to the general stress concentration problems. That is the theory is like this, fracture initiation occurs at the maximum stress concentrated point and frature grows to the direction which the maxi-mum shearing stresses are minimum at the stress concentrated field.
It is very important for geotechnical engineers to understand properties of coefficient of permeability. The Kozeny-Carman equation is generally used at the present for estimating the coefficient of permeability. Even though the equation proposed by Kozeny-Carman gives fairly good results in estimating of sandy soils. But it is not appropriate for fine-grained soils such as clay. In the case of clayey soils, structure and distribution of particles play and important role in the coefficient of permeability. These structure and distribution are also closely related to specific surface. Large specific surface means that the grain size is very small. Soils possessing large amount of fine grains have a long flow of water. The study comes to the conclusion that the mostly related factor between specific surface and permeability appears to be #200 passing percentage in the case of compacted clays and clay content for marine clay. So new equation is proposed with the two factor in this study. But the developed equation can be used for estimating rough values in the field. That is, it is skeptical to calculate an accurate coefficient of permeability of soils. The other equations proposed until now were considered. But the results of the equations developed by plasticity index or effective grain size are far from the actual value.
Samples of clay minerals were analyzed using an X-ray diffraction test. Also, the geotechnical properties of the distribution of clay minerals were evaluated after collecting physical and mechanical soil data from Korea Land Corporation, Korea Highway Corporation and the Rural Development Corporation. The results of the X-ray diffraction analysis showed that Korean soft marine clay exists in mixed caly mineral conditions, predominantly illite and muscovite (muscovite causing the formation of illite) existed in all investigated areas. Kaolinite is prevalent in the estuary of the Han River, the estuary of the Kum River, as well as the Asan Bay area. Illite is prevalent in Noksan and Yangsan·Mulkum along the estuary of the Nakdong River. In the estuary of the Han River, montmorillonite is prevalent. These montmorillonites are carried to those areas from the Yellow Sea or they were formed and carried down from China. In order to find out the engineering characteristics based in clay mineral distribution, soil indexes were compared to one another. As a result, the condition of particle size distribution affects the physical and mechanical properties rather than the type of the clay minerals found, because of the small amount of clay minerals detected within Korean marine clay.
Various modes of load transfer may exist in rockfill dams. If the core is softer than the shells, load is transferred from the core onto the shells as a result of greater downward displacement of the core with respect to the shells. But if the core is stiffer than the shells, load transfer occurs from the shells onto the core. In this study, the mechanisms of load transfer in rockfill dams have been outlined and load transfer of Juam main and regulation dam with central core are evaluated by load transfer ratio. The load transfer ratio is defined as the ratio of computed values of major principal stresses in the core to the core overburden stresses. The vertical stresses are determined by the FEM, which use hyperbolic model and incremental method to simulate placement of successive layers of fill. The hyperbolic paramaters for the core was estimated from a series of conventional triaxial tests carried out during construction. From the results of this analyses and its comparison with the values measured by soil pressure meters, it has been shown that significant load transfer from the core to the shells was observed in two dams and that the load transfer ratios predicted are higher than the values measured.