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A Study on Network Intrusion Detection using Autoencoder
Seongchul Park,Sanghyun Seo,Juntae Kim 한국정보기술학회 2017 Proceedings of The International Workshop on Futur Vol.2017 No.5
Network packet data used in network intrusion detection are mixed with noise and outliers. When trying to classify network attacks, these noise and outliers cause performance degradation. Therefore, in order to improve the detection performance of the intrusion detection system, it is necessary to remove the noise and the outliers included in the network packet. In this paper, we use autoencoder, one of the unsupervised learning models, to remove noise and outliers in data. In conclusion, this paper shows that we can expect the improvement of intrusion detection system through noise removal and dimension reduction by using autoencorder to existing classification algorithm for KDD Cup 1999 dataset.
Complete photodissociation dynamics of CF<sub>2</sub>I<sub>2</sub> in solution
Park, Seongchul,Shin, Juhyang,Yoon, Hojeong,Pak, Youngshang,Lim, Manho The Royal Society of Chemistry 2019 Physical chemistry chemical physics Vol.21 No.13
<P>Photodissociation dynamics of CF2I2 in cyclohexane were evaluated by probing the C-F stretching mode over a wide time range after ultraviolet excitation using femtosecond infrared spectroscopy. After the ultrafast (<0.2 ps) state-selective photodissociation of CF2I2 as in the gas phase (267 nm excitation led to exclusive three-body dissociation (CF2 + I + I), 350 nm to exclusive two-body dissociation (CF2I + I), and 310 nm to a mixture of three- and two-body dissociations), various secondary reactions were observed. Once produced, some nascent CF2 radicals immediately formed a complex with the departing I atom (I⋯CF2), which produced either CF2I or CF2 radicals. The produced CF2I geminately recombined with the I atom, whereas the CF2 radical reacted bimolecularly to produce C2F4 with a diffusion-limited rate constant of 8.1 × 10<SUP>9</SUP> M<SUP>−1</SUP> s<SUP>−1</SUP>. Some nascent CF2I radicals were produced with sufficient excess energy to further dissociate into CF2 and I, or immediately reacted with the dissociated I atom to form the I2-CF2 isomer that rapidly dissociated into CF2 and I2. Other nascent CF2I radicals geminately recombined with the I atom with various time constants. Thus, the nascent photoproducts, CF2 and CF2I take various reaction paths: complex formation, secondary dissociation, isomer formation, and fast and slow germinate rebindings. The ensuing reaction path of the nascent photoproduct is dictated by its internal energy as well as solvent environment, which leads to different interactions between the photoproduct and solvent. Measurement over a broad time range with a structure-sensitive probe could reveal the fate of all the reaction intermediates, which allows evaluation of the complete reaction dynamics in solution.</P>
Park, Seongchul,Park, Jaeheung,Lin, Han-Wei,Lim, Manho Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.3
Femtosecond vibrational spectroscopy was used to measure the vibrational population relaxation time ($T_1$) of different anions bound to ferric myoglobin ($Mb^{III}$) and hemoglobin ($Hb_{III}$) in $D_2O$ at 293 K. The $T_1$ values of the anti-symmetric stretching (${\nu}_1$) mode of NCS in the $NCS^-$ bound to $Mb^{III}$ ($Mb^{III}$NCS) and $Hb_{III}$ ($Hb_{III}$NCS) in $D_2O$ are $7.2{\pm}0.2$ and $6.6{\pm}0.2$ ps, respectively, which are smaller than that of free NCS. in $D_2O$ (18.3 ps). The $T_1$ values of the ${\nu}_1$ mode of NCO in the $NCO^-$ bound to $Mb^{III}$ ($Mb^{III}$NCO) and $Hb_{III}$ ($Hb_{III}$NCO) in $D_2O$ are $2.4{\pm}0.2$ and $2.6{\pm}0.2$ ps, respectively, which are larger than that of free $NCO^-$ in $D_2O$ ($1.9{\pm}0.2$ ps). The smaller $T_1$ values of the ${\nu}_1$ mode of the heme-bound NCS suggest that intramolecular vibrational relaxation (VR) is the dominant relaxation pathway for the excess vibrational energy. On the other hand, the longer $T_1$ values of the ${\nu}_1$ mode of the heme-bound NCO suggest that intermolecular VR is the dominant relaxation pathway for the excess vibrational energy in the ${\nu}_1$ mode of $NCO^-$ in $D_2O$, and that intramolecular VR becomes more important in the vibrational energy dissipation of the ${\nu}_1$ mode of NCO in $Mb^{III}$NCO and $Hb_{III}$NCO.
Seongchul Park,Jaeheung Park,Han-Wei Lin,임만호 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.3
Femtosecond vibrational spectroscopy was used to measure the vibrational population relaxation time (T1) of different anions bound to ferric myoglobin (MbIII) and hemoglobin (HbIII) in D2O at 293 K. The T1 values of the anti-symmetric stretching (ν1) mode of NCS in the NCS− bound to MbIII (MbIIINCS) and HbIII (HbIIINCS) in D2O are 7.2 ± 0.2 and 6.6 ± 0.2 ps, respectively, which are smaller than that of free NCS− in D2O (18.3 ps). The T1 values of the ν1 mode of NCO in the NCO− bound to MbIII (MbIIINCO) and HbIII (HbIIINCO) in D2O are 2.4 ± 0.2 and 2.6 ± 0.2 ps, respectively, which are larger than that of free NCO− in D2O (1.9 ± 0.2 ps). The smaller T1 values of the ν1 mode of the heme-bound NCS suggest that intramolecular vibrational relaxation (VR) is the dominant relaxation pathway for the excess vibrational energy. On the other hand, the longer T1 values of the ν1 mode of the heme-bound NCO suggest that intermolecular VR is the dominant relaxation pathway for the excess vibrational energy in the ν1 mode of NCO− in D2O, and that intramolecular VR becomes more important in the vibrational energy dissipation of the ν1 mode of NCO in MbIIINCO and HbIIINCO.
Park Yejin,Park Seongchul,Shin Juhyang,임만호 대한화학회 2022 Bulletin of the Korean Chemical Society Vol.43 No.4
The dynamics of photoexcited chlorobenzene (PhCl) and 4-fluoroiodobenzne (4- FPhI) in CCl4 were investigated using time-resolved infrared spectroscopy. When excited at 267 nm, 50% (70%) of the excited PhCl (4-FPhI) dissociates the Cl (I) atom immediately, and the remaining molecules relax into the T1 state via intersystem crossing (ISC) with a time constant of 70–80 ps. About half of the dissociated halogen atoms geminately recombine with the nascent radical with a time constant of 100–150 ps, reducing the number of generated radicals that are available to react with other reaction partners. The remaining radicals also recombine with the dissociated halogen atom on a timescale of tens of nanoseconds. Interestingly, the ISC of the light Cl-atom-involved PhCl was as efficient as that of the heavy I-atom-involved 4-FPhI. Detailed photoexcitation dynamic studies of PhCl and 4-FPhI can be utilized to understand the reaction dynamics of Ph and its derivatives.