• Journal of the Korean earth science society
• /
• v.30 no.4
• /
• pp.454-463
• /
• 2009

In this study, from January 2006 to February 2009, we observed 107 ice spikes formed in a natural state, and analyzed their environment. We developed an experimental device to reproduce ice spikes in laboratory and successfully made 531 ice spikes. We analyzed the process of the formation and the principle of how those ice spikes grow through videotaped data of the formation in the experiment. In the natural world, when the surface of water and the lower part of a vessel begin to freeze, a vent (breathing hole) develops at the surface where an ice is not frozen; this vent serves as the seed of an ice spike. It is assumed that the volume expansion of ice in the vessel which occurs when water freezes makes the supercooled water go upward through the vent and becomes an ice bar called an ice spike. In the laboratory, however, when distilled water is poured into an ice tray cube and kept in the experimental device for about one and a half hours at a temperature of -12- $-13^{\circ}C$, a thin layer of ice then begins to develop on the surface of the water, the vent is formed, and ice spikes form for about 10-30 minutes. These spikes stop growing when the end becomes clogged. Ice spikes can be described as falling into seven categories of shape, with the apex type topping the list followed by the slant type in the natural state and the vertical type predominating in the laboratory.

• Korean Chemical Engineering Research
• /
• v.48 no.2
• /
• pp.268-274
• /
• 2010

Emission of heavy metals as hazardous air pollutants has been focused with tightening regulatory limits due to their hazardousness. Measurements and characteristic investigations of heavy metals emitted from a commercial power plant burning anthracite coal have been carried out. The plant consists of a circulating fluidized bed combustor, a cyclone, a boiler and an electrostatic precipitator(ESP) in series. Dust and gaseous samples were collected to measure main heavy metals including gaseous mercury before ESP and at stack. Dust emissions as total particulate matter (TPM), PM-10 and PM-2.5 at inlet of ESP were very high with 23,274, 9,555 and $7,790mg/Sm^3$, respectively, as expected, which is much higher than those from pulverized coal power plants. However TPM at stack was less than $0.16mg/Sm^3$, due to high dust removal efficiency by ESP. Similarly heavy metals emission showed high collection efficiency across ESP. From particle size distribution and metal enrichment in sizes, several metal concentrations could be correlated with particle size showing more enrichment in smaller particles. Mercury unlike other solid metals behaved differently by emitting as gaseous state due to high volatility. Removal of mercury was quite less than other metals due to it's volatility, which was 68% only. Across ESP, speciation change of mercury from elemental to oxidized was clearly shown so that elemental mercury was half of total mercury at stack unlike other coal power plants which equipped wet a scrubber.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.3A
• /
• pp.368-376
• /
• 2006

This paper describes a Fcore_GenSim(Parameterized FFT Core Generation & Simulation Program), which can be used as an essential If(Intellectual Property) in various OFDM modem designs. The Fcore_Gensim is composed of two parts, a parameterized core generator(PFFT_CoreGen) that generates Verilog-HDL models of FFT cores, and a fixed-point FFT simulator(FXP_FFTSim) which can be used to estimate the SQNR performance of the generated cores. The parameters that can be specified for core generation are FFT length in the range of 64 ~2048-point and word-lengths of input/output/internal/twiddle data in the range of 8-b "24-b with 2-b step. Total 43,659 FFT cores can be generated by Fcore_Gensim. In addition, CBFP(Convergent Block Floating Point) scaling can be optionally specified. To achieve an optimized hardware and SQNR performance of the generated core, a hybrid structure of R2SDF and R2SDC stages and a hybrid algorithm of radix-2, radix-2/4, radix-2/4/8 are adopted according to FFT length and CBFP scaling.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.3A
• /
• pp.232-239
• /
• 2011

IEEE 802.11n standard provides a framework for new link adaptation. A station can request that another station provide a Modulation and Coding Scheme (MCS) feedback, to fully exploit channel variations on a link. However, if the time elapsed between MCS feedback request and the data frame transmission using the MCS feedback becomes bigger, the previously received feedback information may be obsolete. In that case, the effectiveness of the feedback-based link adaptation is compromised. If a station can estimate how fast the channel quality to the target station changes, it can improve accuracy of the link adaptation. The contribution of this paper is twofold. First, through a thorough NS-2 simulation, we show how the coherence time affects the performance of the MCS feedback based link adaptation of 802.11n networks. Second, this paper proposes an effective algorithm for coherence time estimation. Using Allan variance information statistic, a station estimates the coherence time of the receiving link. A proposed link adaptation scheme considering the coherence time can provide better performance.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.5C
• /
• pp.413-421
• /
• 2008

The paper derives asymptotic formulas for the MSE distortion and the signal-to-noise ratio of a mismatched fixed-rate minimum MSE Laplacian quantizer. These closed-form formulas are expressed in terms of the number N of quantization points, the mean displacement $\mu$, and the ratio $\rho$ of the standard deviation of the source to that for which the quantizer is optimally designed. Numerical results show that the principal formula is accurate in that, for rate R=$log_2N{\geq}6$, it predicts signal-to-noise ratios within 1% of the true values for a wide range of $\mu$, and $\rho$. The new findings herein include the fact that, for heavy variance mismatch of ${\rho}>3/2$, the signal-to-noise ratio increases at the rate of $9/\rho$ dB/bit, which is slower than the usual 6 dB/bit, and the fact that an optimal uniform quantizer, though optimally designed, is slightly more than critically mismatched to the source. It is also found that signal-to-noise ratio loss due to $\mu$ is moderate. The derived formulas can be useful in quantization of speech or music signals, which are modeled well as Laplacian sources and have changing short-term variances.

• Journal of the Korean Electrochemical Society
• /
• v.7 no.1
• /
• pp.21-25
• /
• 2004

The electrochemical behaviors of dissolved hydrogen and hydrogen peroxide at a platinum disk electrode were investigated in boric acid solution by potentiostatic polarization method at the temperature of 25 and $200^{\circ}C$. The oxidation of dissolved hydrogen at $25^{\circ}C$ was kinetically controlled reaction, the rate of which depends upon the electron transfer on the electrode surface. As temperature was raised, however, the electrochemical characteristics of dissolved hydrogen were changed from a kinetically controlled reaction to a diffusion controlled one. One notable feature, with dissolved hydrogen at high temperature, is that an abnormal potential range was observed, where the oxidation rate of dissolved hydrogen rapidly decreased just before starting potential of water oxidation. We think it is caused by the deactivation of the electrode that results from the adsorption of hydroxyl ion on the surface of the platinum disk. On the contrary, a definite change with temperature was not identified in the case of the hydrogen peroxide except for the increase in current density that was due to the increasing diffusion coefcient with an increase of temperature.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.4 s.95
• /
• pp.427-437
• /
• 2005

In this paper, the perceived audio level metering algorithm of digital audio sound to be able to operate in real-time is proposed. Through analyzing a conventional recommendation ITU-RBS1387-I for objective audio quality analysis, FFT-based loudness metering algorithm is implemented and the real-time method of that algorithm was advised and proved. The proposed method is based on look-up table. In order to prove the proved method, using 23 pure tones and 30 preselected digital audio samples, its performance and operation time is evaluated. Its performance, compared with an original algorithm's, have a good figure of less than $2\;\%$ error even if look-up table related with spectral spreading have large level resolution of $10\;\cal{dB}$. The proposed algorithm take only 1/21 of original algorithm's measuring time. Also, in the proposed algorithm auditory pitch group energy calculation take 1/450 of original algorithm's and excitation calculation take 1/3.57. In conclusion, the proposed algorithm is expected to be implemented into DSP-based real-time loudness meter.

• Journal of Environmental Health Sciences
• /
• v.44 no.1
• /
• pp.98-105
• /
• 2018

Objectives: In Mongolian housing, they use coal as a fuel for indoor heating and cooking. The combustion of coal releases particulate matter, which can affect indoor air quality. The purpose of this study was to analyze the concentrations of indoor $PM_{2.5}$ in winter time dwellings in ger town. Methods: In this study, indoor $PM_{2.5}$ concentrations, temperature and humidity in houses were measured by a real-time PM monitor, while the time activity patterns of the residents were also observed. Results: The correlation between factors that may affect the indoor air quality was analyzed.The indoor $PM_{2.5}$ concentrations were $178.4{\pm}152.7{\mu}g/m^3$ (n=37). Five types of indoor $PM_{2.5}$ concentrations have been classified, which were associated with indoor activity. The stove type, fuel types and indoor activities such as cleaning, cooking and opening the stoves were not significantly associated with indoor $PM_{2.5}$ levels. Conclusions: Further study is needed to determine the effect of stove type through 24hours of indoor air quality monitoring.

• Journal of Gastric Cancer
• /
• v.8 no.4
• /
• pp.198-203
• /
• 2008

Purpose: Multiple early gastric cancer (MEGC) accounts for between 4.5% and 11.7% of all early gastric cancers (EGC). We investigated the treatment of MEGC from the viewpoint of the clinicopathologic features of the disease. Materials and Methods: 2,281 patients with EGC underwent gastric resection at the Department of Surgery, Severance Hospital during the 11 years between January 1994 and December 2004 and we carried out a retrospective analysis of these patients. Results: There were 91 cases of synchronous MEGC (4.0%) according to the diagnostic criteria of Moertel: there were 81 double, 9 triple and 1 quadruple lesions. Of the 102 accessory lesions, 64 (62.7%) were less than 10 mm in diameter and 83 (81.4%) were located in the same region as the main lesion. The most frequent histologic type of main lesion was a well differentiated adenocarcinoma, which was found in 52 cases (57.1%). There were 49 mucosal main lesions and 42 submucosal main lesions. Lymph node metastasis was detected in 6 cases (6.6%): 1 in mucosal lesions and 5 in submucosal main lesions Conclusion: Solitary EGC and MEGC had very similar clinopathological features and a similar prognosis. Therefore, we believe that the general EGC treatment guidelines can be applied for multiple EGC. It is important to evaluate the whole stomach before and during the operation and then after examining the resected specimen.

• Journal of the Korean Data and Information Science Society
• /
• v.25 no.3
• /
• pp.601-609
• /
• 2014

The most widely used data mining technique for big data analysis is to generate meaningful association rules. This method has been used to find the relationship between set of items based on the association criteria such as support, confidence, lift, etc. Among them, confidence is the most frequently used, but it has the drawback that we can not know the direction of association by it. The attributably pure confidence was developed to compensate for this drawback, but the value was changed by the position of two item sets. In this paper, we propose four symmetrically and attributably pure confidence measures to compensate the shortcomings of confidence and the attributably pure confidence. And then we prove three conditions of interestingness measure by Piatetsky-Shapiro, and comparative studies with confidence, attributably pure confidence, and four symmetrically and attributably pure confidence measures are shown by numerical examples. The results show that the symmetrically and attributably pure confidence measures are better than confidence and the attributably pure confidence. Also the measure NSAPis found to be the best among these four symmetrically and attributably pure confidence measures.