• Journal of Astronomy and Space Sciences
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• v.26 no.4
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• pp.425-438
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• 2009

We reevaluate the Burton equation (Burton et al. 1975) of predicting Dst index using high quality hourly solar wind data supplied by the ACE satellite for the period from 1998 to 2006. Sixty magnetic storms with monotonously decreasing main phase are selected. In order to determine the injection term (Q) and the decay time ($\tau$) of the equation, we examine the relationships between $Dst^*$ and $VS_s$, ${\Delta}Dst^*$ and $VS_s$, and ${\Delta}Dst^*$ and $Dst^*$ during the magnetic storms. For this analysis, we take into account one hour of the propagation time from the ACE satellite to the magnetopause, and a half hour of the response time of the magnetosphere/ring current to he solar wind forcing. The injection term is found to be $Q(nT/h)\;=\;-3.56VS_s$ for $VS_s$ > 0.5mV/m and Q(nT=h) = 0 for $VB_s\;{\leq}\;0.5mV/m$. The $\tau$ (hour) is estimated as $0.060Dst^*\;+\;16.65$ for $Dst^*$ > -175nT and 6.15 hours for $Dst^*\;{\leq}\;-175nT$. Based on these empirical relationships, we predict the 60 magnetic storms and find that the correlation coefficient between the observed and predicted $Dst^*$ is 0.88. To evaluate the performance of our prediction scheme, the 60 magnetic storms are predicted again using the models by Burton et al. (1975) and O'Brien & McPherron (2000a). The correlation coefficients thus obtained are 0.85, the same value for both of the two models. In this respect, our model is slightly improved over the other two models as far as the correlation coefficients is concerned. Particularly our model does a better job than the other two models in predicting intense magnetic storms ($Dst^*\;{< \atop \sim}\;-200nT$).

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.6
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• pp.449-469
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• 2011

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering during 2010. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) Research trends of thermal and fluid engineering have been surveyed as groups of general thermal and fluid flow, fluid machinery, and new and renewable energy. Various topics were presented in the field of general thermal and fluid flow. Research issues mainly focused on the thermal reliability of axial fan and compressor in the field of fluid machinery. Studies on the design of ground source heat pump systems and solar chemical reactors were executed in the field of new and renewable energy. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer in thermoelectric cooling/power generation systems, combined heat and power systems, carbon nano fluid with PVP, channel filled with metal foam and smoke ventilation in a rescue station of a railroad tunnel. Also the studies on flow boiling of R123/oil mixture in a plain tube bundle and R410A charge amount in an air cooled mini-channel condenser were reported. In the area of industrial heat exchangers, researches on plate heat exchanger, shell and tube heat exchanger, enthalpy exchanger, micro channel PCHE were performed. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer in thermoelectric cooling/power generation systems, combined heat and power systems, carbon nano fluid with PVP, channel filled with metal foam and smoke ventilation in a rescue station of a railroad tunnel. Also the studies on flow boiling of R123/oil mixture in a plain tube bundle and R410A charge amount in an air cooled mini-channel condenser were reported. In the area of industrial heat exchangers, researches on plate heat exchanger, shell and tube heat exchanger, enthalpy exchanger, micro channel PCHE were performed. (3) Refrigeration systems with alternative refrigerants such as hydrocarbons, mixed refrigerants, and CO2 were studied. Performance improvement of refrigeration systems are tried applying various ideas of refrigerant subcooling, dual evaporator with hot gas bypass control and feedforward control. The hybrid solar systems combining the solar collection devices with absorption chillers or compression heat pumps are simulated and studied experimentally as well to improve the understanding and the feasibility for actual applications. (4) Research trend in the field of mechanical building facilities has been found to be mainly focused on field applications rather than performance improvements. Various studies on heating and cooling systems, HVAC facilities, indoor air environments and energy resources were carried to improve the maintenance and management of building service equipments. In the field of heating and cooling systems, papers on a transformer cooling system, a combined heat and power, a slab thermal storage and a heat pump were reported. In the field of HVAC facilities, papers on a cooling load, an ondol and a drying were presented. Also, studies on HVAC systems using unutilized indoor air environments and energy resources such as air curtains, bioviolence, cleanrooms, ventilation, district heating, landfill gas were studied. (5) In the field of architectural environment and energy, studies of various purposes were conducted such as indoor environment, building energy, renewable energy and green building. In particular, renewable energy and building energy-related researches have mainly been studied reflecting the global interest. In addition, many researches which related the domestic green building certification of school building were performed to improve the indoor environment of school.

• Korean Journal of Plant Resources
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• v.24 no.5
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• pp.642-649
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• 2011

Ginseng growth is largely affected by characteristics of soil in Ginseng field. In this study, we determined the critical ranges of physico-chemical properties of soil for optimization of ginseng growth by analyzing the soils from Anseong and Pocheon regions in Gyeonggi province. Fresh weight of ginseng was 2 to 5 fold higher in good growth field compared to poor growth field within Anseong region. In the case of Pocheon region, 1.5 to 2 fold differences of fresh weight of ginseng was observed between good and poor growth field. These results indicate the difference of ginseng growth even in the same region. Based on these results, critical ranges of physico-chemical properties of soils were determined by comparing the good and poor growth field of each regions, which are follows; more than 50% of soil porosity, 2.0~2.8 g/kg of total nitrogen, 500~900 mg/kg for Av. $P_2O_5$, 2.3~3.5 $cmol_c\;kg^{-1}$ for Exch. Ca in Anseong; less than 13% of liquid phase, 400~650 mg/kg for Av. $P_2O_5$, 4.0~4.7 $cmol_c\;kg^{-1}$ for Exch. Ca, less than 0.8 and 0.5 $cmol_c\;kg^{-1}$ for Exch. Mg and K, respectively, in Pocheon. Interestingly, we found that ginseng growth was affected by exchangeable base ratio (Ca:Mg:K) especially in Anseong region, which were 6:2:1 in good growth field while 4:2:1 in poor growth field. Critical ranges for nutrient contents of ginseng leaves were also characterized, which are less than 0.2% and 0.22% of each P and Mg, respectively, in Anseong, while less than 1.8% and 0.18% of each N and P, respecively, and 1.5~3.0% of K in Pocheon. In addition, we determined critical ranges for inorganic nutrient contents in the current study.

• Journal of the Korean earth science society
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• v.29 no.6
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• pp.454-465
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• 2008

Benthic foraminiferal assemblage and AMS radiocarbon dating of core sediments from the northern shelf of the East China Sea were analyzed in order to understand the paleoenvironment and sedimentary environmental changes around the Korean marginal seas since the last glacial maximum (LGM). The core sediments, containing continuous records of the last 16,000 years, reveal a series of well-defined vertical changes in number of species (S), P/T ratio and species diversity (H) as well as foraminiferal assemblage. Such down-core variations display a sharp change at a core depth of approximately 240 cm, which corresponds to ca. 10,000 year B.P. The sediments of the lower part of the core (240${\sim}$560 cm, Zone I), including the well-developed tide-influenced sedimentary structures, are characterized by high abundances of Ammonia beccarii and Elphidium clavatum (s.l.) and low values in number of species, P/T ratio and diversity. These tide-influenced signatures and foraminiferal assemblage characters suggest that the sediments of Zone I were deposited in a coastal environment (water depths of 20${\sim}$30 m) such as tidal estuary with an influence of the paleo-rivers (e.g., old-Huanghe and Yangtze rivers) during the early phase of the sea-level rise (ca. 16,000 to 10,000 years) since the LGM. In contrast, the upper core sediments (0${\sim}$240 cm, Zone II) are characterized by abundant Eilohedra nipponica and Bolivina robusta with a minor contribution of A. ketienziensis angulata and B. marginata. and high values in number of species, P/T ratio and diversity. Based on relative abundance of these assemblage, Zone II can be divided into two subzones (IIa and IIb). Zone IIa is interpreted to be deposited under the inner-to-middle shelf environment during the marine transgression in the early Holocene (after ca. 9,000 yr B.P.) when sea level rapidly increased. The sediments of zone IIb most likely deposited after 6,000 yr B.P. under the outer shelf environment (80${\sim}$100 m water depth), which is similar to modem depositional environments. The muddy sediments of zone IIb were probably transported from the old-Huanghe and Yangtze Rivers during the late Holocene. We suggest that the present-day oceanographic conditions over the Yellow and the East China Seas have been established after ca. 7,000${\sim}$6,000 yr B.P. when the Kuroshio Current began to influence this area.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.11 s.353
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• pp.58-68
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• 2006

This work proposes a 10b 250MS/s $1.8mm^2$ 85mW 0.13um CMOS A/D Converter (ADC) for high-performance integrated systems such as next-generation DTV and WLAN simultaneously requiring low voltage, low power, and small area at high speed. The proposed 3-stage pipeline ADC minimizes chip area and power dissipation at the target resolution and sampling rate. The input SHA maintains 10b resolution with either gate-bootstrapped sampling switches or nominal CMOS sampling switches. The SHA and two MDACs based on a conventional 2-stage amplifier employ optimized trans-conductance ratios of two amplifier stages to achieve the required DC gain, bandwidth, and phase margin. The proposed signal insensitive 3-D fully symmetric capacitor layout reduces the device mismatch of two MDACs. The low-noise on-chip current and voltage references can choose optional off-chip voltage references. The prototype ADC is implemented in a 0.13um 1P8M CMOS process. The measured DNL and INL are within 0.24LSB and 0.35LSB while the ADC shows a maximum SNDR of 54dB and 48dB and a maximum SFDR of 67dB and 61dB at 200MS/s and 250MS/s, respectively. The ADC with an active die area of $1.8mm^2$ consumes 85mW at 250MS/s at a 1.2V supply.

• Journal of Periodontal and Implant Science
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• v.26 no.4
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• pp.949-965
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• 1996

The main goal of periodontal therapy is to restore the lost periodontal tissue and establish the attachment appratus. Current acceptable therapeutic techniques are included : removal of diseased soft tissue, demineralization of exposed root surface, using the barrier membrane for preventing the downgrowth of gingival epithelial cell, insertion of graft materials as a scaffolding action, and biological mediators for promoting the cell activity. The latest concept one among them has been studied which based on the knowledge of cellular biology of destructed tissue. Platelet-derived growth factor(PDGF) is one of the polypeptide growth factor which have been reported as a biological mediator to regulate activities of wound healing progress including cell proliferation, migration, and metabolism. The purposes of this study is to evaluate the influences of the PDGF as biological mediator to periodontal ligament and bone marrow cell. Both right and left maxillary first molar were extracted from rat which had treated with 0.4% ${\beta}-Aminopropionitril$ for 5 days, and feeded until designed date to sacrifice under anesthesisa. Periodontal ligament were removed from the extracted socket of the rat, and cultured with Dulbecco's Modified Essential Medium(DMEM) contained with 10% Fetal Bovine Serum, 100U/ml penicillin, $100{\mu}g/ml$ streptomycin, $0.5{\mu}g/ml$ amphotericin-B. Bone marrow cell were culture from bone marrow suspension with which washed out from femur with same medium. The study was performed to evaluate the effect of PDGF to periodontal ligament and bone cell, cell proliferation rate, total protein synthesis, and alkaline phosphatase activity of rat periodontal ligament(PDL) cell and bone stromal(RBS) cell in vitro. The effects of growth factors on both cells were measured at 3, 5th day after cell culture with (control group) or without growth factors(experimental group). The results were as follows: 1. The tendency of cell proliferation under the influence of PDGF showed more rapid proliferation pattern than control at 3 and 5 days after inoculation. 2. The activity of Alkaline phosphatase revealed 14, 80% increased respectively at 3, 5 days culture than control group. Measurements of ALPase levels indicated that PDL cells had significantly higher activity when compared with that of co-culture groups and GF only(P<0.05). And, ALPase activity in 10 days was higher than that of 7 days(P<0.05). 3. The tendency of formation of the mineralized nodule were observed dose-depend pattern of PDL cells. There was statistically significant difference among group l(PDL 100%), 2(PDL 70%:GF 30%), and 3(PDL 50%:GF 50%)(P<0.01). But, there was no difference among group 3, 4(PDL 30%:GF 70%), and 5(GF 100%). 4. Also, the number of nodule was greater in co-culture of PDL 70% and GF 30% than in culture of PDL 70%(P<0.05). From the above results, it is assumed that the PDGF on PDL cells and RMB cell culture. GF stimulates the cell growth, which is not that of PDL cells but GF. And, the activity of ALPase depends on the ratio of PDL cells, and ALPase may relate to the initial phase of nodule formation. Also, it is thought that the calcified nodule formation principally depends on PDL cells, is inhibited by GF, and affected by cell density. In conclusion, platelet-derived growth factor can promote rapid osteogenesis during early stage of periodontal tissue regeneration.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.3
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• pp.75-85
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• 2009

This work proposes a 13b 100MS/s 0.13um CMOS ADC for 3G communication systems such as two-carrier W-CDMA applications simultaneously requiring high resolution, low power, and small size at high speed. The proposed ADC employs a four-step pipeline architecture to optimize power consumption and chip area at the target resolution and sampling rate. Area-efficient high-speed high-resolution gate-bootstrapping circuits are implemented at the sampling switches of the input SHA to maintain signal linearity over the Nyquist rate even at a 1.0V supply operation. The cascode compensation technique on a low-impedance path implemented in the two-stage amplifiers of the SHA and MDAC simultaneously achieves the required operation speed and phase margin with more reduced power consumption than the Miller compensation technique. Low-glitch dynamic latches in sub-ranging flash ADCs reduce kickback-noise referred to the differential input stage of the comparator by isolating the input stage from output nodes to improve system accuracy. The proposed low-noise current and voltage references based on triple negative T.C. circuits are employed on chip with optional off-chip reference voltages. The prototype ADC in a 0.13um 1P8M CMOS technology demonstrates the measured DNL and INL within 0.70LSB and 1.79LSB, respectively. The ADC shows a maximum SNDR of 64.5dB and a maximum SFDR of 78.0dB at 100MS/s, respectively. The ABC with an active die area of $1.22mm^2$ consumes 42.0mW at 100MS/s and a 1.2V supply, corresponding to a FOM of 0.31pJ/conv-step.

• Journal of Chest Surgery
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• v.39 no.6 s.263
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• pp.427-433
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• 2006

Background: Current vascular prostheses are considered still inadequate for reconstruction of small-diameter vessels. To evaluate the potential use of xenograft vessels as small diameter arterial grafts, we implanted porcine vessels in goats. The grafts were treated with two different processes, freezing and acellularization, before implantation, and gross inspection as well as microscopic examination followed after a predetermined period. Material and Method: Bilateral porcine carotid arteries were harvested and immediately stored at $-70^{\circ}C$ within tissue preservation solution. One of them was designated as frozen xenograft vessel. The other one was put on acellularization process using NaCl-SDS solution and stored frozen until further use. Grafts were implanted in the place of carotid arteries of the same goat. The grafts have remained implanted for 1, 3, and 6 months in three animals, respectively. Periodic ultrasonographic examinations were performed during the observation period. After explantation, the grafts were analyzed grossly and histologically under light microscope. Result: All animals survived the experimental procedure without problems. Ultrasonographic examinations showed excellent patency of all the grafts during the observation period. Gross examination revealed nonthrombotic, patent lumens with smooth surfaces. Microscopic examinations of the explanted grafts showed cellular reconstruction at the 6-month stage in both grafts. Although more inflammatory responses were observed in the early phase of frozen xenografts, there was no evidence of significant rejection. Conclusion: These findings suggest that porcine xenograft vessels, regardless of pre-implantation processes of acelluarization or freezing, can be acceptably implanted in goats, although short duration of observation in a small number of animals may limit this study.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.5
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• pp.87-97
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• 2016

This work proposes a time-shared 10b DAC based on a two-step resistor string to minimize the effective area of a DAC channel for driving each AMOLED display column. The proposed DAC shows a lower effective DAC area per unit column driver and a faster conversion speed than the conventional DACs by employing a time-shared DEMUX and a ROM-based two-step decoder of 6b and 4b in the first and second resistor string. In the second-stage 4b floating resistor string, a simple current source rather than a unity-gain buffer decreases the loading effect and chip area of a DAC channel and eliminates offset mismatch between channels caused by buffer amplifiers. The proposed 1-to-24 DEMUX enables a single DAC channel to drive 24 columns sequentially with a single-phase clock and a 5b binary counter. A 0.9pF sampling capacitor and a small-sized source follower in the input stage of each column-driving buffer amplifier decrease the effect due to channel charge injection and improve the output settling accuracy of the buffer amplifier while using the top-plate sampling scheme in the proposed DAC. The proposed DAC in a $0.18{\mu}m$ CMOS shows a signal settling time of 62.5ns during code transitions from '$000_{16}$' to '$3FF_{16}$'. The prototype DAC occupies a unit channel area of $0.058mm^2$ and an effective unit channel area of $0.002mm^2$ while consuming 6.08mW with analog and digital power supplies of 3.3V and 1.8V, respectively.

• Journal of Animal Science and Technology
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• v.49 no.6
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• pp.783-800
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• 2007

The current study was conducted to investigate the effect of high quality hay on the performance and carcass characteristics of Hanwoo steers. Twenty(20) Hanwoo(7 months old) were allocated into either Control(rice straw fed) or Treatment(timothy hay and rice straw fed) group(10 animals per group) and fed for 710 days until the animals reached at 30 months old. Concentrates were fed according to the feeding program composed with three(3) phases; growing, fattening, and finishing period. For the overall feeding period, final body weights were 761.3 and 799.6kg for the Control and Treatment groups, respectively, showing 38.3kg heavier body weight in Treatment group. ADG were 0.79 and 0.84kg for Control Treatment groups, respectively. These results might be because of the intake of high quality hay during growing phase and the effects persisted until the end of the experiment. Feed intake tended to be higher in Treatment group whereas feed conversion did not show significant difference between groups. Cold carcass weights were 451.0 and 475.3kg for Control and Treatment, There were no significant difference between groups in both yield and quality grade. There were no remarkable differences in physico-chemical characteristics fatty acid composition of carcasses between groups. In conclusion, it would be beneficial to feed high quality hay such as timothy during growing period of Hanwoo steers to produce high quality beef with heavier live and carcass weight.