• Journal of the Korean Society of Industry Convergence
• /
• v.25 no.5
• /
• pp.843-851
• /
• 2022

This paper was conducted to study the conditions for the manufacture and operation of artificial snow removal and ice-making test facilities so that the test equipment can be tested in a low-temperature environment using the polar environment performance test facility. The polar environment performance test Facility is designed to artificially simulate extreme environments up to -65 ℃, and is a mid-to-large low-temperature environment test facility that can perform performance tests on offshore plant equipment, ships, leisure, and offshore structures. To verify the safety of deck work of ships operating in polar environments, artificial snow removal and artificial ice making devices were manufactured, and we conducted research on various operating environments using these facilities. For the efficient operation of artificial snow and ice making facilities, it is important to continuously supply dry air, and it has been found that installing an additional heater at the tip of the nozzle is effective in preventing freezing.

• ETRI Journal
• /
• v.46 no.3
• /
• pp.485-500
• /
• 2024

A hardware architecture is presented to decode (N, K) polar codes based on a low-density parity-check code-like decoding method. By applying suitable pruning techniques to the dense graph of the polar code, the decoder architectures are optimized using fewer check nodes (CN) and variable nodes (VN). Pipelining is introduced in the CN and VN architectures, reducing the critical path delay. Latency is reduced further by a fully parallelized, single-stage architecture compared with the log N stages in the conventional belief propagation (BP) decoder. The designed decoder for short-to-intermediate code lengths was implemented using the Virtex-7 field-programmable gate array (FPGA). It achieved a throughput of 2.44 Gbps, which is four times and 1.4 times higher than those of the fast-simplified successive cancellation and combinational decoders, respectively. The proposed decoder for the (1024, 512) polar code yielded a negligible bit error rate of 10^-4 at 2.7 E_b/N_o (dB). It converged faster than the BP decoding scheme on a dense parity-check matrix. Moreover, the proposed decoder is also implemented using the Xilinx ultra-scale FPGA and verified with the fifth generation new radio physical downlink control channel specification. The superior error-correcting performance and better hardware efficiency makes our decoder a suitable alternative to the successive cancellation list decoders used in 5G wireless communication.

• Journal of the Korean earth science society
• /
• v.34 no.7
• /
• pp.645-661
• /
• 2013

The synoptic, thermodynamic, and dynamic characteristics of a heavy snowfall event that occurred in Seoul metropolitan area on 27 to 28 December 2010 was investigated. During this period there was a distinctive case that was identified as a polar low. We analyzed surface and upper level weather charts, snowfall amount, sea surface temperature, satellite imagery, sounding, and the National Center for Environmental Prediction global $1^{\circ}{\times}1^{\circ}$ reanalysis data. The polar low developed in an area where there was strong baroclinicity in the lower level aided by strong conditional instability due to 925 hPa warm air advection and 700 hPa cold air advection. The development mechanism of polar low is due, in part, to the tropopause folding, which advected stratospheric air increasing potential vorticity in mid-level and inducing cyclonic vorticity and convergence in low-level. Eventually clouds developed and there were snowfall total of 10 cm in Seoul metropolitan area and as much as 20 cm in southern parts of Korea. During the snowfall development, there was a $-45^{\circ}C$ cold core at 500 hPa and shortwave maintained $3-5^{\circ}$ separation with surface trough, which favored the development of polar low located in the warm sector and cyclonic advection area. The height of the dynamical tropopause lowered to 700 hPa during the peak development and increase in potential vorticity allowed strong vertical motion to occur. Overall, there was a close relationship between the development of snowfall and tropopause undulation. The heaviest snowfall occurred east of the tropopause folding where strong cyclonic vorticity, vertical motion, and moisture advection all coincided while the polar low was passing through the Korean peninsula.

• Ocean and Polar Research
• /
• v.27 no.2
• /
• pp.215-219
• /
• 2005

We isolated and identified three protease-producing bacteria that had inhabited the region around the Korean Arctic Research Station Dasan located at Ny-Alesund, Svalbard, Norway $(79^{\circ}N,\;12^{\circ}E)$. Biofilms were collected from the surface of a floating pier and from dead brown algae in a tide pool near the seashore. The biofilm samples were transported to the Korea Polar Research Institute (KOPRI) under frozen conditions, diluted in sterilized seawater, and cultured on Zobell agar plates with 1% skim milk at $10^{\circ}C$. Three clear zone forming colonies were selected as protease-producing bacteria. Phylogenetic analysis based on 16S rDNA sequences showed that these three stains shared high sequence similarities with Pseudoalteromonas elyakovii, Exiguobacterium oxidotofewm Pseudomonas jessenii, respectively. We expect these Arctic bacteria may be used to develop new varieties of protease that are active at low temperatures.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.5 no.1
• /
• pp.104-118
• /
• 1995

This study was performed to evaluate factors affecting desorption of organic solvents collected on charcoal tube and to find out the optimum condition. Desorption efficiency for polar analytes was improved when several polar desorption solvents such as methanol, dimethylformamide(DMF), 2-(2-butoxyethoxy)ethanol were added to carbon disulfide($CS_2$). The best improvement was achieved when 10% dimethylformamide(DMF) in $CS_2$ was used as desorption solvent. During storage of polar analytes, recovery was greatly reduced. Especially, the recovery of cyclohexanone was decreased to 18.1 % after a month storage at $34^{\circ}C$. After two weeks storage, recovery of polar analytes was sharply decreased. Water adsorbed on charcoal interfered the recovery of polar analytes but didn't interfere that one of nonpolar solvent, toluene. When 10% DMF in $CS_2$ was used as desorption solvent, the effect of water on recovery was decreased, comparing with Desorption efficiency increased when analyte loading increased, and usage of 10% DMF in $CS_2$ decreased the loading effect. Increasing volume of desorption solvent was not effective to improve desorption efficiency of analytes when 10% DMF was used. Continuous shaking and sonication is not helpful to increase the desorption efficiency of analytes except cyclohexanone using 10% DMF. When silica gel used as adsorbent, methanol was better desorbent than dimethylsulfoxide. Analytes adsorbed on silica gel showed high recovery in low concentration and less affected by humidity. On the basis of this study, the following conclusions have been drawn. To improve the recovery of polar organic materials in air samples, it is necessary to analyze samples as soon as possible after they were collected. Otherwise, samples must be stored at low temperature. Using two components of desorption solvents, such as 10% DMF in $CS_2$, the effects of loading and humidity decreased for polar analytes such as methyl ethyl ketone and methyl isobutyl ketone. When work place has high humidity with low concentration of polar organic solvents, silica gel can be used as adsorbent, because it produces quantitative recovery for polar analytes at this condition. But it should be noted that high humidity makes breakthrough easy in silica gel samples.

• Ocean and Polar Research
• /
• v.23 no.2
• /
• pp.77-95
• /
• 2001

Temperature, salinity, nutrients, chlorophyll-a, and primary production were measured within the upper 200 m water column in the area around the South Shetland Islands in January, 2000. Surface temperature was relatively high in the Drake Passage north of the South Shetland Islands and low in the northeastern area of the Antarctic Peninsula. In contrast, surface salinity was low in the Drake Passage and increased toward the Antarctic Peninsula, reaching the maximum value in the northeastern area of the Antarctic Peninsula. Surface nutrients were low in the Drake Passage and high in the area near the South Shetland Islands. Surface chlorophyll-a was also low in the Drake Passage and near the Antarctic Peninsula and high in the area of the northern King George Island. The study area could be classified as four geographical zones based on the characteristic shape of the T/S diagrams;the Drake Passage, the Bransfield Strait, the mixed zone, and the Weddell Sea. Each geographical zone showed apparently different physical, chemical, and biological characteristics. Phytoplankton biomass was relatively low in the Drake Passage and the Weddell Sea and high in the Bransfield Strait and the mixed zone. The low phytoplankton biomass in the Weddell Sea could be explained by the low water temperature and deep surface mixing down to 200 m. The high grazing pressure and low availability of iron could be responsible for the low phytoplankton biomass in the Drake Passage.

• Journal of Microbiology
• /
• v.45 no.4
• /
• pp.281-285
• /
• 2007

Cold environments, including polar and alpine regions, are colonized by a wide diversity of micro-organisms able to thrive at low temperatures. There is evidence of a wide range of metabolic activities in alpine cold ecosystems. Like polar microorganisms, alpine microorganisms playa key ecological role in their natural habitats for nutrient cycling, litter degradation, and many other processes. A number of studies have demonstrated the capacity of alpine microorganisms to degrade efficiently a wide range of hydrocarbons, including phenol, phenol-related compounds and petroleum hydrocarbons, and the feasibility of low-temperature bioremediation of European alpine soils by stimulating the degradation capacity of indigenous microorganisms has also been shown.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.14 no.3
• /
• pp.313-321
• /
• 2014

A low-power low-cost polar transmitter for EDGE is designed in $0.18{\mu}m$ CMOS. A differential delta-sigma modulator (DSM) tunes a three-terminal voltage-controlled oscillator (VCO) to perform RF phase modulation, where the VCO tuning curve is digitally pre-compensated for high linearity and the carrier frequency is calibrated by a dual-mode low-power frequency-locked loop (FLL). A digital intermediate-frequency (IF) pulse-width5 modulator (PWM) drives a complementary power-switch followed by an LC filter to achieve envelope modulation with high efficiency. The proposed transmitter with 9mW power dissipation relaxes the time alignment between the phase and envelope modulations, and achieves an error vector magnitude (EVM) of 4% and phase noise of -123dBc/Hz at 400kHz offset frequency.

• Journal of Microbiology
• /
• v.44 no.6
• /
• pp.694-698
• /
• 2006

Several marine bacterial strains were isolated from Undaria pinnatifida (Miyok in Korean). Sixty-six strains were isolated on R2A agar media at $10^{\circ}C$ and identified by a phylogenetic analysis of the 16S rRNA gene sequences. They were grouped into 10 different sequence types based on the initial sequence analysis of the 5' domain of the gene (approximately 500 bp). Full sequences of 16S rRNA gene, were obtained from one strain in each sequence type and the species-affiliation was determined using phylogenetic and sequence similarity analyses. The results of the analyses indicated that they were closely related to Psychrobacter aquimaris, P. celer, P. nivimaris, P. pulmonis, Psychromonas arctica or Bacillus psychrodurans. These bacteria are marine or psychrotrophic bacteria. Because the sporophytes of U. pinnatifida are cultured on the costal area during winter, the U. pinnatifida-associated bacteria appeared to grow at low temperatures. U. pinnatifida sporophytes can be a good source for the isolation of psychrotrophic bacteria.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.1076-1079
• /
• 2003

The vector field histogram(VFH) uses a two-dimensional Cartesian histogram grid as a world model. The VFH method subsequently employs a two-stage data-reduction process in order to compute the desired control commands for the vehicle. In the first stage the histogram grid is reduced to a one dimensional polar histogram that is constructed around the robot's momentary location. Each sector in the polar histogram contains a value representing the polar obstacle density in that direction. In the second stage, the algorithm selects the most suitable sector from among all polar histogram sectors with a low polar obstacle density, and the steering of the robot is aligned with that direction. We applied this algorithm to our simulation program and tested..