• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.221-221
• /
• 2014

The present work proposes an improved numerical simulator for design and modification of large area capacitively coupled plasma (CCP) processing chamber. CCP, as notoriously well-known, demands the tremendously huge computational cost for carrying out transient analyses in realistic multi-dimensional models, because electron dissociations take place in a much smaller time scale (${\Delta}t{\approx}10-8{\sim}10-10$) than time scale of those happened between neutrals (${\Delta}t{\approx}10-1{\sim}10-3$), due to the rf drive frequencies of external electric field. And also, for spatial discretization of electron flux (Je), exponential scheme such as Scharfetter-Gummel method needs to be used in order to alleviate the numerical stiffness and resolve exponential change of spatial distribution of electron temperature (Te) and electron number density (Ne) in the vicinity of electrodes. Due to such computational intractability, it is prohibited to simulate CCP deposition in a three-dimension within acceptable calculation runtimes (<24 h). Under the situation where process conditions require thickness non-uniformity below 5%, however, detailed flow features of reactive gases induced from three-dimensional geometric effects such as gas distribution through the perforated plates (showerhead) should be considered. Without considering plasma chemistry, we therefore simulated flow, temperature and species fields in three-dimensional geometry first, and then, based on that data, boundary conditions of two-dimensional plasma discharge model are set. In the particular case of SiH4-NH3-N2-He CCP discharge to produce deposition of SiNxHy thin film, a cylindrical showerhead electrode reactor was studied by numerical modeling of mass, momentum and energy transports for charged particles in an axi-symmetric geometry. By solving transport equations of electron and radicals simultaneously, we observed that the way how source gases are consumed in the non-isothermal flow field and such consequences on active species production were outlined as playing the leading parts in the processes. As an example of application of the model for the prediction of the deposited thickness uniformity in a 300 mm wafer plasma processing chamber, the results were compared with the experimentally measured deposition profiles along the radius of the wafer varying inter-electrode gap. The simulation results were in good agreement with experimental data.

• Journal of KIISE:Information Networking
• /
• v.29 no.3
• /
• pp.299-313
• /
• 2002

Recently, the demand for mobile communications and multimedia services has rapidly increased so that conventional cellular system cannot fulfill the requirement of users (capacity and QoS) any more. Therefore, the hierarchical cellular system has been suggested in order to guarantee the QoS and to admit large population of users. IMT-2000 adopts the hierarchical cellular structure, which requires a call control algorithm capable of manipulating and utilizing the complicated structure of hierarchical cellular structure with handiness and efficiency. In this thesis, as an improvement of conventional combined algorithm, a new call control algorithm considering the moving speed of terminal and bandwidth is suggested. This algorithm employs buffers and guard channels to reduce the failure rate. Also, this algorithm considers the moving speed of terminal and bandwidth to elevate the efficiency. Furthermore, calls are handled separately according to the moving speeds of terminal and bandwidths to improve the QoS and reduce the handover rate. As an evaluation of the suggested algorithm, a model hierarchical cellular system is constructed and simulations are conducted with various types of traffic. As the result of the simulations, such indices as block rate, drop rate, channel utilization, and the number of inter layer handovers are examined to demonstrate the excellency fo the suggested algorithm.

• Journal of KIISE:Information Networking
• /
• v.29 no.1
• /
• pp.24-30
• /
• 2002

Label switching technology is currently emerging as a solution for the rapidly growing of Internet traffic demand. Multiprotocol label switching(MPLS) is one of the standards made by the Internet Engineering Task Force(IETE) intended to enhance speed, scalability, and inter-opearability between label switching technologies. In MPLS, utilization of label space is a very important factor of network performance because labels are basic unit in packet switching. We propose a algorithm to effectively use label space by a multiple disconnect timer at the label switching router. Our algorithm is based on multiple utilization of the connection release timer over the MPLS network with multiple domains. In our algorithm, a relatively linger timeout interval is assigned to the traffic with higher class by the aid of the packet classifier. This reduces delay for making a new connection and also reduces the amount of packets which will be routed to the layer 3. Simulation results shows that reduction of required label number in MPLS network and this indicate our algorithm offers better performance than the existing ones in term of utilization of label space.

• Smart Media Journal
• /
• v.8 no.2
• /
• pp.29-38
• /
• 2019

With the advancement of information and communication technology, tactical networks are continuously being converted to All-IP future tactical networks that integrate all application services based on Internet protocol. Futuristic tactical mesh network is built with tactical WAN (wide area network) nodes that are inter-connected by a mesh structure. In order to guarantee QoS (quality of service) of application services, tactical service mesh (TSM) is suggested as an intermediate layer between infrastructure and application layers for futuristic tactical mesh network. The tactical service mesh requires dynamic QoS monitoring and control for intelligent QoS coordination. However, legacy networking nodes used for existing tactical networks are difficult to support these functionality due to inflexible monitoring support. In order to resolve such matter, we propose a tactical mesh WAN node as a hardware/software co-designed networking node in this paper. The tactical mesh WAN node is conceptually designed to have multi-access networking interfaces and virtualized networking switches by leveraging the DANOS whitebox server/switch. In addition, we explain how to apply eBPF-based traffic monitoring to the tactical mesh WAN node and verify the traffic monitoring feasibility for supporting QoS coordination of tactical-mesh traffic.

• Economic and Environmental Geology
• /
• v.45 no.2
• /
• pp.71-78
• /
• 2012

Illite-smectite mixed layers (I-S) occurring authigenically in diagenetic and hydrothermal environments reacts toward more illite-rich phases as temperature and potassium ion concentration increase. For that reason, I-S is often used as geothermometry and/or geochronometry at the field of hydrocarbons or ore minerals exploration. Generally, I-S shows X-ray powder diffraction (XRD) patterns of ultra-thin lamellar structures, which consist of restricted numbers of sillicate layers (normally, 5 ~ 15 layers) stacked in parallel to a-b planes. This ultra-thinness is known to decrease I-S expandability (%S) rather than theoretically expected one (short-stacking effect). We attempt here to quantify the short stacking effect of I-S using the difference of two types of expandability: one type is a maximum expandability ($%S_{Max}$) of infinite stacks of fundamental particles (physically inseparable smallest units), and the other type is an expandability of finite particle stacks normally measured using X-ray powder diffraction (XRD) ($%S_{XRD}$). Eleven I-S samples from the Geumseongsan volcanic complex, Uiseong, Gyeongbuk, have been analyzed for measuring $%S_{XRD}$ and average coherent scattering thickness (CST) after size separation under 1 ${\mu}m$. Average fundamental particle thickness ($N_f$) and $%S_{Max}$ have been determined from $%S_{XRD}$ and CST using inter-parameter relationships of I-S layer structures. The discrepancy between $%S_{Max}$ and $%S_{XRD}$ (${\Delta}%S$) suggests that the maximum short-stacking effect happens approximately at 20 $%S_{XRD}$, of which point represents I-S layer structures consisting of ca. average 3-layered fundamental particles ($N_f{\approx}3$). As a result of inferring the $%S_{XRD}$ range of each Reichweite using the $%S_{XRD}$ vs. $N_f$ diagram of Kang et al. (2002), we can confirms that the fundamental particle thickness is a determinant factor for I-S Reichweite, and also that the short-stacking effect shifts the $%S_{XRD}$ range of each Reichweite toward smaller $%S_{XRD}$ values than those that can be theoretically prospected using junction probability.

• Korean Journal of Environment and Ecology
• /
• v.36 no.3
• /
• pp.338-349
• /
• 2022

This study aims to investigate whether modular community planting, which entailed planting a variety of species of seedlings at high density, was more effective in restoring natural forests than the existing mature tree planting. We also investigated whether the planting density of the modular community planting facilitates growth or improves the tree layer coverage. We conducted outdoor experiments in which the samples were divided into a mature tree planting plot (control plot), where mature trees were planted at wide intervals, and a modular community planting (MCP) plot (treatment plot), where multiple seedlings were planted in high density. The MCP plot was further divided into the plot in which 3 seedlings were planted per m² and the plot of 1 seedling per m². We measured the specimens' survival rate, growth rate (tree height, crown width, and root collar diameter), and cover rate for 26 months from May 2019 and the predicted future tree height growth using the measured tree height. The survival rate and relative growth rate of the MCP were higher than those of the mature tree planting plot. The vertical coverage rate of the tree crown in the MCP exhibited complete coverage of the ground before 23 months, while the coverage rate of the mature tree planting decreased due to transplantation stress. The seedlings in the MCP, which were planted at high density, grew well and were predicted to grow higher than the mature trees in the large tree planting plot within 5 to 6.5 years after planting. It was due to multiple species, seedlings, high-density planting, and planting foundation improvements, such as soil enhancement and mulching. In other words, the seedlings planted in the MCP had a higher survival rate as their environmental adaptation after planting was better, and their early growth was also larger than the trees in the mature planting plot. The high-density mixed planting of various native species not only mitigated the inter-complementary environmental pressures but also facilitated growth by inducing competition between species. Moreover, the planting foundation improvement effectively increased the seedlings' viability and growth rate. A reduction in follow-up management costs is expected as the tree layer coverage sharply increases due to the higher planting density. In the MCP (3 seedlings per m² and 1 seedling per m²), the tree height growth was promoted with the higher planting density, and the crown width and root collar diameter tended to be larger with the lower planting density, but these differences were not statistically significant.

• Korean Journal of Weed Science
• /
• v.17 no.3
• /
• pp.269-280
• /
• 1997

Collated data from the 1995-1996 field surveys of weed seeds buried in the plough layer of peat soil in Selangor district were analysed to assess species-dominance and spatial pattern of distribution of weed seeds based on selected quantitative indices and index of dispersion. Forty five species within 14 families were recorded of which 24 were broadleaves, 12 grasses and 9 sedges. They comprised ca. 53.2, 31.2 and 15.6%, respectively based on total population counts. Total seed population was ca. $8.14{\times}10^7$ seeds/ha within the fast 25cm soil depth. Wide variabilities in population counts were registered among species ranging from < $7.0{\times}10^4$ seeds/ha for Amaranthus gracilis to ca. $5.64{\times}10^6$ seeds/ha for Heteropogon contortus. Seeds of Cleome rutidesperma was the most abundant(ca. $2.347{\times}10^7$ seeds/ha). Difference in seed population counts may be attributed to inherent variation in fecundity, population fluxes, their spatial distribution patterns and the agronomic practices prevailing in the areas of survey. The profile distribution of soil seed banks was skewed within the first 0 - 10cm depth, comprising ca. 69% of the total seed counts. Seed counts in the 10 - 15, 15 - 20 and 20 - 25cm soil profiles were in the order of 17.9, 8.6 and 4.0% of the total populations, respectively. Weed seeds of all species displayed different degree of aggregated pattern of distribution with variance-to-mean ratios of > 1 and Lloyd's mean crowding($m^*$) values from 1.244 for Cyperus iria, Phyllanthus debilis, Phyllanthus urinaria, Scirpus grosses and urinaria lagopodiodes to 9607.7 for Cleome rutidosperma. Lloyd's patch indices(Ip) ranging from 5.1 for Aeschynomene indica to 188.5 for Bracharia reptans were registered. Differences in the VMR, $m^*$ and Ip values among species suggested inter-alia inherent variabilities in their disposal capacity from seed source and different agronomic practices prevailing in the areas surveyed.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.14
• /
• pp.165-172
• /
• 1973

The sterile phenomenon is frequently found in the inter-species hybrids of ginseng as in other plants. It is known that among the hybrids between Panax Ginseng (PG) and Panax Quinquefolium (PQ), and between Panax Ginseng and Paxax Japonicus (PI), PG${\times}$PI is fertile only very rarely, while PG ${\times}$ PQ is always sterile. Therefore, in order to clarify the relationship between this sterility phenomenon and the metabolism of free amino acids, the changes of free amino acids through the formation of the flower organs and seeds of two hybrids, PG ${\times}$ PQ and PG ${\times}$ PI were investigated by thin layer chromatography. The results are summarized as follows: 1. Distinct differences in the quantity and number of free amino acids were recognized between PG ${\times}$ PQ, PG ${\times}$ PI and their parent plants. From the hybrid PG ${\times}$ PQ, 19 kinds of ninhyrin sensitive substances were detected in all. They were (1) 17 amino acids: alanine, valine, leucine, phenylalanine, proline, hydroxy-proline, serine, threonine, tyrosine, aspartic acid, glutamic acid, lysine, arginine, ${\gamma}$-amino butyric acid, ${\beta}$-alanine, cysteic acid and tryptophan, and (2) two amides: asparagine and glutamine. From the hybrid PG ${\times}$ PI, in addition to the above 19 substances, methionine and one unknown substance were detected. 2. Generally, alanine, as partie acid, glutamic acid, cysteic acid and asparagine were detected in large amounts in the two hybrids as in PG, PG and PJ but it was a noticeable fact concerning these two hybrids that the largest quantity of asparagine was found at microspore satge and pollen mature stage. 3. The decrease of cysteic acid in the two hybrids at the red ripened stage was the same as in PQ and PJ but opposite to the change in PG. The detection of methionine in PG ${\times}$ PJ was worthy of notice. 4. The change of proline was conspicuously different from that in their parent plants. It was detected as a trace of color at the micros pore stage while asparagine was detected in the greatest amount at that time. It is well known that the quantity of proline is closely related to the sterility of plant. This fact was also found true in the formation of ginseng seeds. It was reported as well that asparagine accumulated when proline decreased. 5. The deficiency of proline seemed to be closely related with the sterility of hybrids and with the degradation of pollen in anther. 6. The difference in the changes of free amino acids between the selfed lines of PG, PQ and PJ, and their hybrids seemed to be caused by the transformation of gene-action system by hybridization. On these phenomena along with proline metabolim and its physiological role in seed formation further studies are required.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.12 no.4
• /
• pp.380-389
• /
• 2007

Stable carbon and nitrogen isotopes were analyzed in suspended particulate organic matter, macroalgae and macrobenthic invertebrates in order to determine the importance of primary organic matter sources in supporting food webs of rocky subtidal and intertidal macroalgal beds in the Korean coasts. Investigations were conducted at the inter tidal sites within Gwangyang bay, a semi-enclosed and eutrophicated bay, and the subtidal sites of the east coast, a relatively oligotrophic and open environment, in May and June 2005. Water-column suspension feeders showed more negative $\delta^{13}C$ values than those of the other feeding guilds, indicating trophic linkage with phytoplankton and thereby association with pelagic food chains. In contrast, animals of the other feeding guilds, including interface suspension feeders, herbivores, deposit feeders, omnivores and predators, displayed relatively less negative $\delta^{13}C$ values than those of the water-column suspension feeders and similar with that of macroalgae, indicating exclusive use of macroalgae-derived organic matter and association with benthic food chains. Most the macrobenthic species were considered to form strong trophic links with benthic food chains. In addition, the distribution of higher $\delta^{15}N$ values in macrobenthic consumers and macroalgae at the intertidal sites of Gwangyang Bay than those at the subtidal sites of the east coast suggests that anthropogenic nutrients may enhance the macroalgal production at the intertidal sites and in turn be incorporated into the particular littoral food web in Gwangyag Bay. These results confirm the dominant role of macroalgae in supporting rocky subtidal and intertidal food webs in the Korean coasts.

• Journal of the Korean Vacuum Society
• /
• v.17 no.3
• /
• pp.226-233
• /
• 2008

The nucleation and evolution process of Ge nano-islands on Si(001) surfaces grown by chemical vapor deposition have been explored using atomic force microscopy (AFM). The Ge nano-islands are grown by exposing the substrates to a mixture of gasses GeH4 and H2 at pressure of 0.1-0.5Torr and temperatures of $600-650^{\circ}C$. The effect of growth conditions such as temperature, Ge thickness, annealing time on the shape, size, number density, and surface distribution was investigated. For Ge deposition greater than ${\sim}5$ monolayer (ML) with a growth rate of ${\sim}0.1ML/sec$ at $600^{\circ}C$, we observed island nucleation on the surface indicating the transition from strained layer to island structure. Further deposition of Ge led to shape transition from initial pyramid and hut to dome and superdome structure. The lateral average size of the islands increased from ${\sim}20nm$ to ${\sim}310nm$ while the number density decreased from $4{\times}10^{18}$ to $5{\times}10^8cm^{-2}$ during the shape transition process. In contrast, for the samples grown at a relatively higher temperature of $650^{\circ}C$ the morphology of the islands showed that the dome shape is dominant over the pyramid shape. The further deposition of Ge led to transition from the dome to the superdome shape. The evolution of shape, size, and surface distribution is related to energy minimization of the islands and surface diffusion of Ge adatoms. In particular, we found that the initially nucleated islands did not grow through long-range interaction between whole islands on the surface but via local interaction between the neighbor islands by investigation of the inter-islands distance.