• Korean Journal of Materials Research
• /
• v.11 no.8
• /
• pp.708-712
• /
• 2001

Microwave dielectric properties of $(Pb_{0.2}Ca_{0.8})[(Ca_{1/3}Nb{2/3})_{1-x}Ti_x]O_3$ ceramics were investigated as a function of $Ti^{4+}$ content (0.05$\leq$x$\leq$0.35). A single perovskite phase was obtained from x=0.05 to x=0.15, and $TiO_2$ and $CaNb_2O^6$ were detected as a secondary phase beyond x=0.2. The structure was changed from orthorhombic at x=0.05 to cubic at x=0.35. Dielectric constant(K) was increased with increase of $Ti^{4+}$ content due to increase of rattling effect, and was inversely proportional to the cube of the average radius of B-site cation, however, Qf value was decreased, which was due to the decrease of grain size and the secondary phase. With the increase of $Ti^{4+}$ content, the temperature coefficient of resonant frequency(TCF) was controlled from -27.36 ppm/$^{\circ}C$ value to +18.4 ppm/$^{\circ}C$ value, which was caused by the influence of tolerance factor(t) and the bond valence of B-site. Typically, K of 51.67, Qf of 7268(GHz), TCF of 0 ppm/$^{\circ}C$ were obtained in the $(Pb_{0.2}Ca_{0.8})[(Ca_{1/3}Nb_{2/3})_{0.8}Ti_0.2]O_3$ sintered at 13$50^{\circ}C$ for 3h.

• Journal of the Korean earth science society
• /
• v.21 no.2
• /
• pp.174-187
• /
• 2000

The Quaternary coarse-grained sandy sediments are distributed along the channels of Seomjin River. The fluvial sediments were sedimentologically studied in horizontal and vertical distributions. To analyze depositional environments and facies changes in the sediments, sediment sampling from river mouth to upper stream and desctriptive approaches to the sediment profiles outcropped near Kurye were carried out. The sediments along the stream lines of the river are assigned to very coarse to coarse sand in grain size. The sediment grains are widely scattered in sorting and moderately sorted in average. For skewness and kurtosis, the sediments ranges from very fine to very coarse skewed and from very lepto-kurtic to extremelyl epto-kurtic states, respectively. The sediments are divided into slightly gravelly sand, gravelly sand and sandy gravel in sediment type. The pain shape in the sandy sediments are dominant in equant and tabular forms showing wide varieties. The sandy sediments are mostly poorly sorted and are highly variable in surface texture with SEM. Some smaller grains in the sediments ordinarily show polished surfaces. Of those grains, quartz ones are commonly angular to surounded. On the basis of facies changes and sedimentary structures, outcropped fluvial sediment profiles in Kurye are classified into xGyS, mGyS, gGyS, xSM, xS, mS, mGyM, IgM in facies. These eight facies are reformed as facies assemblage I and ll. The facies assemblage I and II are interpreted as the products of the channel deposits in braided stream and flood plain ones besides channels, respectively. The change facies assemblage I with facies assemblage ll imply that depositional environments hadbeen migrated from braied sream to flood plain ones.

• Korean Journal of Agricultural Science
• /
• v.10 no.2
• /
• pp.334-344
• /
• 1983

This study was conducted to investigate the variables affecting the performance of hammer mills by the theoretical and dimensional analysis, and evaluate the power requirements of hammer mills for farm use in Korea. From the theoretical analysis, 16 variables affecting the performance of hammer mills were defined. In order to develop the mathematical relationships among the variables, the dimensional analysis was made for power requirements and $12{\pi}$ parameters were obtained. For the evaluation of the power requirements of hammer mills, approximate rates of grinding for 1HP, 3HP, 5HP, 6HP, 8HP, and 10HP were analyzed. Then, the fineness of grinding recommendation and average feeding rate of grain for livestock which is native cattle, dairy cattle, beef cattle, swine, broilers, and layers, were estimated. Finally number of livestock feeding shelled corn and barley were estimated from the above for one hour's hammer mill operation having the various power requirements. From this study it is known that 5HP is considered as an enough power for feed grinding of any kinds of livestock of Korean farm, as far as the grinding capacity is concerned.

• 한국해양학회지
• /
• v.30 no.5
• /
• pp.480-492
• /
• 1995

Petrographic investigation has been carried out to determine the composition of the beach sediments and the affecting factors which have controlled their compositional variations from Hyupjae, Aeweol, Iho, Samyang, Hamdeok, Sehwa, Pyoseon, Jungmun, and Hwasun areas along the coast of the Cheju Island. Average mean sizes of the beach sediments are Hyupjae 2.2ø, Aeweol 0.8ø, Iho 1.4ø, Samyang 2.4ø, Hamdeok 1.6ø, Sehwa 1.5ø, Pyoseon 2.1ø, Jungmun 0.4ø, and Hwasun 0.9ø, thus, aries from 0.4 to 2.4ø. The beach sediments from Pyoseon and Hwasun areas are poorly sorted, those from Aeweol and Jungmun areas are moderately sorted and those from the rest of the areas are moderately well sorted. While-colored beach sediments in Hyupjae, Aeweol, Hamdeok, Sehwa, and Pyoseon areas are mostly composed of calcareous shells (more than 85%) such as mollusk, red algae, benthic foraminiferas, etc., whereas volcanic rock fragment is the dominant component of the black-colored beach sediments in Iho, Samyang, and Hwasun areas. Especially, the relatively white-colored beach sediment in Jungmun area, which is on e of the carbonate-dominant areas, shows a higher content of rock fragments than the other carbonate-dominant areas. The beach sediments in Pyoseon area show a high content of carbonate intercalates. Considering the contributions by organisms according to grain size, grains with the size range of 1∼2ø are mostly composed of calcareous red algae fragments, and grains with the size range of 2∼3ø consist of mollusk fragments. It is also notable that bryozoan fragments comprise about 48% of the sediment in Samyang area with the size range of 0∼1ø. The composition of the beach sediments in Cheju Island appears o be controlled by the riverine supply rate of volcanic rock fragments, the lithology of the rocks distributed ear the beaches, the direction of alongshore currents, and the direction of storms, etc.. It is suggested that the beach sediments in Iho and Samyang areas show black color because of the higher supply rate of the volcanic rock fragments from the nearby rivers, whereas those in the rest of the areas show white color due to the relatively lower content of volcanic rock fragments and higher content of carbonate components transported from shallow marine environment. In Hwasun area, the content of volcanic rock fragments is high, and they are directly from the tuffaceous rocks distributed nearby. Also, the volcanic rock fragments in Jungmun area are transported not only from the rivers nearby but also from the nearby tuffs by storm activities. The beach sediment in Pyoseon area contains a high content of carbonate intercalates, which formed in the nearby shallow marine environment through marine cementation. This indicates that active marine cementation occurs in shallow marine environment near Pyoseon area.

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

• Applied Biological Chemistry
• /
• v.8
• /
• pp.101-111
• /
• 1967

Daily doses of phenylmercuric acetate arranged in $30{\gamma}\;(group\;I)$, 3{\gamma}\;(group\;II)$ and $0.3{\gamma}\;(group\;III)$ were administered respectively to rabbits for 90 days. The chief histopathological changes in the organs and the analytical data on mercury residues in the excretion and liver were as follows. 1. Kidney: In group I, severe degrees of vacuolization and cloudy swelling were occurred in the epithelial cells of proximal convoluted tubules and severe cloudy swelling and coagulative necrosis were observed in the proximal straight tubules. There were many hyaline casts in the collecting tubules. In group II, moderate degrees of vacuolization and cloudy swelling were observed in the epithelial cells of proximal convoluted tubules and moderate cloudy swelling and coagulative necrosis were encountered in the proximal straight tubules. A little numbers of hyaline casts were located in the lumen of collecting tubules. In group III, slight degree of cloudy swelling were observed in the epithelial cells of proximal convoluted and straight tubules. 2. Liver: In group I, cloudy swelling, fatty changes and coagulative necrosis were observed in the central zone of hepatic lobules. Dissociation of hepatic cell cords was encountered. Hyperplsia of hepatic cells were remarkable in group II. No Pathological changes were observed in group III. 3. Spleen: Deposition of hemosiderin pigment was prominant in group I and small amount of the pigment was observed in group II. There were no pathological changes in group III. 4. Adrenal, colon and heart: No pathological changes were detected in all 3 groups. 5. In an average about 76.5% of mercury was excreted from group I, 85.4% from group II and 79.8% from group III. 6. Mercury content in the liver was 0.0348 g in group I, 0.00378 g and 0.00066 g in group II and group III respectively. 7. In general, as to increased mercury doses the concentration of mercury accumulation in the liver became higher, how·ever, the accumulation quantity against a total amount of mercury doses showed an adverse trend. In other word, the quantity of mercury accumulation was not increased proportionately by higher dose of mercury.

• Journal of Soil and Groundwater Environment
• /
• v.11 no.6
• /
• pp.28-34
• /
• 2006

Laboratory column tests using $Cl^-$ tracer were conducted to study the correlation of soil particle distribution and hydrodynamic dispersion mechanism with three kinds of ununiformed soil samples, in which the ratio of gravel and sand versus silt and clay is 24.5 for S-1 soil, 4.48 for S-2 soil, and 0.4 for S-3 soil. Chloride breakthrough curves with time were fitted with gaussian functions. The relative concentrations of chloride were converged to 1.0 after 0.7 hours for S-1, 6.3 hours for S-2, and 389 hours for S-3. Average linear velocity, longitudinal dispersion coefficient, and longitudinal dispersivity were calculated by chloride breakthrough curves. Longitudinal dispersion coefficients were $1.20{\times}10^{-4}\;m^2/sec$ for S-1, $8.87{\times}10^{-7}\;m^2/sec$ for S-2, and $1.94{\times}10^{-9}\;m^2/sec$ for S-3. Peclet numbers calculated by the molecular diffusion coefficient of chloride and the mean grain diameters of soils were $2.59{\times}10^2$ for S-1, $6.27{\times}10^0$ for S-2, and $1.35{\times}10^{-4}$ for S-3. Mechanical dispersion was dominant for the hydrodynamic dispersion mechanism of S-1. Both mechanical dispersion and molecular diffusion were dominant for the hydrodynamic dispersion mechanism of S-2, but mechanical dispersion was ascendant over molecular diffusion. Hydrodynamic dispersion in S-3 was occurred mainly by molecular diffusion. When plotting three soils on the graph of $D_L/D_m$ versus Peclet number produced by Bijeljic and Blunt (2006), the values of $D_L/D_m$ for S-1 and S-2 were more than 2.0 order compared to their graph. S-3 was not plotted on their graph because the Peclet number was as small as $1.35{\times}10^{-4}$.

• Journal of the Korean Wood Science and Technology
• /
• v.34 no.1
• /
• pp.52-60
• /
• 2006

This study investigated how wood properties (i.e., annual rings, sapwood, heartwood, and cracks) might affect preservative treatment in Japanese larch (Larix leptolepis) round-wood product. We specially focused on small-diameter (~10 cm diameter) wood that is commercially sold in market. Among 100 wood samples, the groups of sample with 13~16, 17~20 annual rings represented 33 and 27 in each frequency, while 2~3 and 4~5 mm annual ring width accounted for 72 and 68 in frequency. More than a half (54%) of wood samples contained a mix of heartwood and sapwood in its surface. The rest (46%) had only heartwood exposed in the wood surface. A wide range of checks were showed in the wood samples, but the highest frequency was observed in samples with 1~6 surface (1~14 mm in size) checks and 1~4 end-grain (8~14 mm in size) checks in each round-wood sample. Pressure treatment resulted in a wide range of penetration of ACQ (Alkaline Copper Quat) into the wood, showing $4.3{\pm}4.19mm$ penetration in the wood samples contained a mix of heartwood and sapwood in its surface. However preservative treatment was much less effective for the heartwood only wood samples, ranging average 1.3 mm with ACQ and 1.1 mm with CCA (Chromated Copper Arsenate). These penetration results shown in heartwood samples did not meet the penetration standard that is required for H3 by the Korean Forest Service in relation to wood preservation treatment. These low penetration results were not significantly improved even if we incised wood samples to improve treatment effect, showing only small increase of 0.7 mm with ACQ and 0.6 mm with CCA. When preservative treatment was tested with heartwood, penetration of preservatives decrease with increase of annual rings per a cross-section area (r=0.5345). We also found that the length and number of check had no effect on preservative treatment, showing r=0.1301 and r=0.1802, respectively.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.4 no.2
• /
• pp.117-126
• /
• 1999

Hampyong Bay is a semienclosed and macrotidal bay which opens to the eastern Yellow Sea through a narrow inlet in the southwestern coast of Korea. In order to understand the tidal-flat sedimentation in the semienclosed setting, morphology, sediments, accumulation rate and sea cliff erosion were investigated in the tidal flat of Hampyong Bay. The tidal flat of Hampyong Bay lacks intertidal drainage systems, and generally shows the concave-upward profile whose relief is designated by marked morphological features such as high-tide beaches, intertidal sand shoals and tidal creeks. Surfacial sediments of the tidal flat mainly consist of mud, sandy mud, gravelly mud, gravelly sand and muddy gravel, thus showing the textural characteristics of multimodal grain-size distribution, poorly sorting and positive skewness. The sediments generally coarsen landward due to the increase in coarse fraction content. Sedimentary structures are deeply bioturbated, but parallel lamination and lenticular bedding are locally found in the mudflat near mean low water line. Annual accumulation rates across the tidal flat (along Line SM) average -5.2 cm/yr with a range of -45.8~+4.2 cm/yr, indicating that the tidal flat is erosional. In general, erosion rates of upper and lower tidal flat are higher than those of middle tidal flat. Seasonally, the erosion rates are much higher during spring and winter when dominant wind direction corresponds to the long axis of Hampyong Bay. Sea cliffs are eroded at a rate of 1.4 m/yr. The biggest sea cliff erosion generally occurs 1~2 months later after tidal flats were extensively eroded. Such erosions of tidal Oats and sea cliffs in the semienclosed bay setting are interpreted to be due to wind waves coupled with local sea-level rise.

• Journal of Plant Biology
• /
• v.38 no.1
• /
• pp.95-105
• /
• 1995

Complete microsporogenesis of Hibiscus syriacus L. were carried out employing LM, TEM, and SEM to investigate the pollen ontogeny that undergoes considerable structural differentiation. The process first began with several cell diYisions in the anther primordium that produces 3 different tissues of epidennal, archesporial, and connective tissues. Only archesporial tissue involved further differentiation into the tapetum and formation of reproductive cells, pollen mother cells (PMC). The tapetum and PMC were closely associated with each other structurally and metabolically by exhibiting numerous plasmodesmata, mitochondria, and many small vacuoles in their dense cytoplasm. A callosic wall began to surround the PMC while meiosis took place in the PMC to produce 4 microspores. When thick callose encircled each microspore as a frame, the sporodenn development initiated from the plasma membrane of a pollen grain in a tetrad. The first fonned sporoderm layer was bacules and tectum of sexine that originated from the plasma membrane. After the dissolution of a callose, further development Qf sporoderm continued in the order of nexine 1, nexine 2, and intine layer. The nexine layer was thicker (ca. $2-3.5\;\mu\textrm{m}$) than the intine layer whose thickness was about $0.9-1.5\;\mu\textrm{m}$. Upon completion of the sporoderm development, that is after intine formation, spines and apertures of pollen surface ornamentation initiated from the tectum. Spines were dimorphic, about $4-9\;\mu\textrm{m}\;an;15-20\;\mu\textrm{m}$ in length, and no basal cushion was detected. The mature pollen grains ranged $100-200\;\mu\textrm{m}$ in diameter, but their average was about $170\;\mu\textrm{m}$. About 120 spines were observed over the spheroidal pollen surface. Apertures were simple punctures of $2-3\;\mu\textrm{m}$ in diameter and about 50 apertures were arranged somewhat helically over the surface. Comparing such features of form and size of the pollen, sporodenn sculpture and structure, and aperture and spine conditions with known evolutionary trends in the genus Hibiscus, Hibiscus syriacus seemed to possess many advanced features in the sporodenn differentiation.iation.