• Convergence Security Journal
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• v.22 no.5
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• pp.145-154
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• 2022

Recently, the widespread proliferation and high sophistication of botnets are having serious consequences not only for enterprises and users, but also for cyber warfare between countries. Therefore, research to detect botnets is steadily progressing. However, the DGA-based botnet has a high detection rate with the existing signature and statistics-based technology, but also has a high limit in the false positive rate. Therefore, in this paper, we propose a detection model using text-based n-gram to detect DGA-based botnets. Through the proposed model, the detection rate, which is the limit of the existing detection technology, can be increased and the false positive rate can also be minimized. Through experiments on large-scale domain datasets and normal domains used in various DGA botnets, it was confirmed that the performance was superior to that of the existing model. It was confirmed that the false positive rate of the proposed model is less than 2 to 4%, and the overall detection accuracy and F1 score are both 97.5%. As such, it is expected that the detection and response capabilities of DGA-based botnets will be improved through the model proposed in this paper.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.E1
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• pp.29-33
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• 2004

In environmental studies, decisions are often made on the analytical data indicating certain contaminants as being 'detected' or 'non-detectible.' Since detection limits are analytical method specific, one has to first review the concepts and definitions associated with analytical method systems and specifications. In this study, the experimental analytical values for a series of low level standards (for an ionic species) were used as an example to estimate two different method detection limits (MDL). The scores of EPA's MDL and Pallesen's MDL determined by real analytical scores are 0.0575 and 0.0561 mg/L, respectively for our nitrate data. These scores determined by two different MDL models are roughly similar, while there are apparent differences between two methods with respect to statistical and systematical procedure. However, determination of MDL for one's laboratory provides some practical applications which helps to assure one's regulating authorities that one's measured scores are accurate.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.1975-1979
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• 2011

The modification of a gas diffusion layer (GDL), a vital component in polymer electrolyte fuel cells, is described here for use in the electrochemical detection of antibody-antigen biosensors. Compared to other substrates (gold foil and graphite), mouse anti-rHBsAg monoclonal antibody immobilized on gold-coated GDL (G-GDL) detected analytes of goat anti-mouse IgG antibody-ALP using a relatively low potential (-0.0021 V vs. Ag/AgCl 3 M NaCl), indicating that undesired by-reactions during electrochemical sensing should be avoided with G-GDL. The dependency of the signal against the concentration of analytes was observed, demonstrating the possibility of quantitative electrochemical biosensors based on G-GDL substrates. When a sandwich method was employed, target antigens of rHBsAg with a concentration as low as 500 ng/mL were clearly measured. The detection limit of rHBsAg was significantly improved to 10 ng/mL when higher concentrations of the 4-aminophenylphosphate monosodium salt (APP) acting on substrates were used for generating a redox-active product. Additionally, it was shown that a BSA blocking layer was essential in improving the detection limit in the G-GDL biosensor.

• Journal of Radiation Protection and Research
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• v.24 no.3
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• pp.171-184
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• 1999

In this paper, using statistical theory the basic concepts and the formulars of lower limit of detection were deasribed. Assuming that risks of 5% are acceptable (95% confidence level), lower limits of detection were calculated on the measuring apparatus for alpha, beta and gamma nuclides. Also, on the basis concepts of lower limit of detection, the MDA values were calculated for the radionuclides detected easily in the environment. These results make it possible to evaluate confidence limits on the radioanalytical results in the environmental sample.

• Archives of Pharmacal Research
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• v.16 no.3
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• pp.227-230
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• 1993

A new device to detect methamphetamine (MA), amphetamine(A) and its metabolites in urine was developed using the paper strip method and the test tube method of dry chemical reagents. The reagent containing tetrabromophenolphthalein ethyl ester (TBPE) and borax. For the TBPE paper strip method, a device was prepared with a window at each end of the reagent paper strip ; one window is for the sample application, and the other window is for the methylene chloride. The diffused sample from one window reacts with reagent in the paper and produces color at the point where it meets with methylene chloride which has diffused form the other side. A positive smaple produces as red-purple color and the negative sample a greenish color, with a detection limit of 5-10 ppm. The result can be obtained within one minute. For the TBPE test tube method which contains dry reagents, the detection limit is 5 ppm and the result can be obtaineed within 30 seconds, however the carry-on is not as convenient as the paper strip method. The performance of both methods were evlauated by comparing with the results of gas chromatography (GC) and fluorescence polarizaiton immunoassay (FPIA). The results were proven that both methods were useful as primary screening reagents to detect MA in urine and in dry powder.

• Bulletin of the Korean Chemical Society
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• v.25 no.6
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• pp.833-837
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• 2004

DeniLite$^{TM}$ laccase immobilized platinum electrode was used for amperometric detection of hydroquinone (HQ) and homogentisic acid (HGA) by means of substrate recycling. In case of HQ, the obtained sensitivity is 280 nA/ ${\mu}$M with linear range of 0.2-35 ${\mu}$M ($r^2$ = 0.998) and detection limit (S/N = 3) of 50 nM. This high sensitivity can be attributed to chemical amplification due to the cycling of the substrate caused by enzymatic oxidation and following electrochemical regeneration. In case of HGA, the obtained sensitivity is 53 nA/ ${\mu}$M with linear range of 1-50 $[\mu}M\;(r^2$ = 0.999) and detection limit of 0.3 ${\mu}$M. The response times ($t_{90%}$) are about 2 seconds for the two substrates and the long-term stability is 60 days for HQ and around 40-50 days for HGA with retaining 80% of initial activities. The very fast response and the durable long-term stability are the principal advantages of this sensor. pH studies show that optimal pH of the sensor for HQ is 6.0 and that for HGA is 4.5-5.0. This shift of optimal pH towards acidic range for HGA can be attributed to the balance between enzyme activity and accessibility of the substrate to the active site of the enzyme.

• ETRI Journal
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• v.45 no.3
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• pp.418-432
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• 2023

In this work, we proposed a low-complexity hybrid layered tabu-likelihood ascent search (LTLAS) algorithm for large multiple-input multiple-output (MIMO) system. The conventional layered tabu search (LTS) approach involves many partial reactive tabu searches (RTSs), and each RTS requires an initialization and searching phase. In the proposed algorithm, we restricted the upper limit of the number of RTS operations. Once RTS operations exceed the limit, RTS will be replaced by low-complexity likelihood ascent search (LAS) operations. The block-based detection approach is considered to maintain a higher signal-to-noise ratio (SNR) detection performance. An efficient precomputation technique is derived, which can suppress redundant computations. The simulation results show that the bit error rate (BER) performance of the proposed detection method is close to the conventional LTS method. The complexity analysis shows that the proposed method has significantly lower computational complexity than conventional methods. Also, the proposed method can reduce almost 50% of real operations to achieve a BER of 10^-3.

• Journal of Electrochemical Science and Technology
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• v.10 no.4
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• pp.361-372
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• 2019

The silver nanoparticles/polyaniline/reduced graphene oxide nanocomposite modified glassy carbon electrode (Ag/PANI/RGO/GCE) was prepared by the electrochemical method. The Ag/PANI/RGO nanocomposite was characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, X-ray diffraction (XRD), and electrochemical impedance spectroscopy (ESI). Two electrochemical techniques namely differential pulse voltammetry (DPV) and cyclic voltammetry (CV) were used to the electrochemical behaviors investigation of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The Ag/PANI/RGO/GCE exhibited remarkable electrocatalytic activity towards the oxidation reaction of AA, DA, and UA in Britton-Robinson (BR) solution (pH=4.0). Under the optimal conditions, the determinations of AA, DA, and UA were accomplished using DPV. AA-DA and DA-UA peak potential separations were 130 and 180 mV, respectively. For simultaneous detection, the linear response ranges were in the two concentration ranges of 0.05-0.8 mM and 2.0-16.0 mM with detection limit 0.412 μM (S/N = 3) for AA, 0.7-90.0 μM and 90.0-1000.0 μM with detection limit 0.023 μM (S/N = 3) for DA, and 0.8-70.0 μM and 70.0-1000.0 μM with detection limit 0.050 μM (S/N = 3) for UA. This modified electrode showed good sensitivity, selectivity, and stability with applied to determine AA, DA, and UA in human urine and drug.

• Journal of the Korean Society of Radiology
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• v.5 no.1
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• pp.5-10
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• 2011

Based on basic concept of detection limit, sample measurement time & background measurement time was considered, and MDA values according to background measurement time and sample measurement time in land samples(river soil, surface soil, drinking water, underground water, surface water, pine leaf, mugwort) analysis among environmental samples were compared. Seeing the water sample analysis result, it was shown that most of the samples were not detected, and most of the samples in land specimen analysis showed to be below the detection limit of "Ministry of Education, Science and Technology Announcement Je-2008-28-ho", but $^{137}Cs$ which is one of artificial radioactive nuclide was detected in some samples. It can be traced back to 1950s and 1960s when nuclear tests were carried out in atmosphere and catastrophic Chernobyl atomic power station accident that caused fallouts in the sky, and this is common level of detection that can be observed worldwide. Seeing the result that the $^{134}Cs$(which is a isotope of $^{137}Cs$, and it has relatively short half life) was not detected in all samples, it can be considered it doesn't affect to the operation of atomic power station.

• Bulletin of the Korean Chemical Society
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• v.26 no.2
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• pp.268-272
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• 2005

Different detection characteristics of fluorescence immunochromatography method and high performance liquid chromatography (HPLC) method for the analysis of cyanobacterial toxins were studied. In particular, low and high limits of detection, detection time and reproducibility and detectable microcystin species were compared when fluorescence immunochromatography method and high performance liquid chromatography method were applied for the detection of microcystin (MC), a cyclic peptide toxin of the freshwater cyanobacterium Microcystis aeruginosa. A Fluorescence immunochromatography assay system has the unique advantages of short detection time and low detection limit, and high performance liquid chromatography detection method has the strong advantage of individual quantifications of several species of microcystins.