Jae-Seo Lee

Detecting P2P Botnets Using a Multi-phased Flow Model

In this paper, we propose a useful method for modeling multi-phased flows of P2P botnet traffic. Botnets are becoming more sophisticated and more dangerous each day and attackers use the P2P protocol to avoid centralized botnet topologies. We focus on the feature that a peer bot generates multiple traffic to communicate with large number of remote peers. In this case, phased botnet flows have similar patterns, which occur at irregular intervals. We compress duplicated flows via flow grouping and construct a transition model of the clustered flows using a probability-based matrix. A flow state is decided by features consisting of; protocol, port, and traffic. Our model involves transition information about the state values. Finally, we use the likelihood ratio for detection. In the experimental evaluation, we show the efficiency of our proposed system with the SpamThru, Storm, and Nugache botnets.

Developmental toxic potential of 1,3-dichloro-2-propanol in Sprague-Dawley rats.

This study investigated the potential adverse effects of 1,3-dichloro-2-propanol (1,3-DCP) on pregnant dams and the embryo-fetal development after maternal exposure on gestational days (GD) 6 through 19 in Sprague-Dawley rats. The test chemical was administered to pregnant rats by gavage at dose levels of 0, 10, 30, and 90mg/kg per day (n=10 for each group). All dams underwent Caesarean sections on GD 20, and their fetuses were examined for morphological abnormalities. Maternal toxicity was noted at 90mg/kg/day. Manifestations of toxicity included clinical signs of illness, lower body weight gain, decreased food intake, and increases in the weight of the adrenal glands and the liver. Developmental toxic effects including decreases in fetal body weight and increases in visceral and skeletal variations also occurred at the highest dose. At 30mg/kg, only a minimal maternal toxicity, including a decrease in maternal food intake and an increase in the liver weight, was observed. No adverse maternal or developmental effects were observed at 10mg/kg/day. These results revealed that a 14-day repeated oral dose of 1,3-DCP was minimally embryotoxic but not teratogenic at a maternal toxic dose (90mg/kg/day), and was not embryotoxic at a minimally maternal toxic dose (30mg/kg/day) in rats. Because the developmental toxicity of 1,3-DCP was observed only in the presence of maternal toxicity, it is concluded that the developmental findings observed in the present study are secondary effects to maternal toxicity. Under these experimental conditions, the no-observed-adverse-effect level of 1,3-DCP is considered to be 10mg/kg/day for dams and 30mg/kg/day for embryo-fetal development.

The correlation of carotid artery calcification on panoramic radiographs and determination of carotid artery atherosclerosis with ultrasonography

OBJECTIVES To investigate the association of carotid artery calcification (CAC) on panoramic radiographs and determine carotid artery atherosclerosis with ultrasonography. STUDY DESIGN The study included 4050 subjects aged 50 years and older. Panoramic radiographs for the presence of CAC were interpreted. Common carotid artery intima-media thickness (CCA-IMT), carotid bulb IMT (CB-IMT), carotid plaques, and the diameter of the common carotid artery (CCA-diameter) were measured by using ultrasonography. RESULTS CB-IMT was significantly greater in male subjects with CAC than in those without CAC. CCA-diameter was significantly greater in subjects with CAC than in those without CAC in both genders. However, there was no significant difference in CCA-IMT. CAC was associated with carotid plaque (for men, odds ratio [OR] 2.14; 95% confidence interval [CI] 1.01-3.36; for women, OR 1.19; 95% CI 0.84-1.67). CONCLUSION CAC on panoramic radiographs was positively associated with IMT and plaque in men and positively associated with carotid diameter in both sexes. CAC on panoramic radiographs was positively associated with carotid atherosclerosis.

Deviation of landmarks in accordance with methods of establishing reference planes in three-dimensional facial CT evaluation.

Purpose This study aimed to investigate the deviation of landmarks from horizontal or midsagittal reference planes according to the methods of establishing reference planes. Materials and Methods Computed tomography (CT) scans of 18 patients who received orthodontic and orthognathic surgical treatment were reviewed. Each CT scan was reconstructed by three methods for establishing three orthogonal reference planes (namely, the horizontal, midsagittal, and coronal reference planes). The horizontal (bilateral porions and bilateral orbitales) and midsagittal (crista galli, nasion, prechiasmatic point, opisthion, and anterior nasal spine) landmarks were identified on each CT scan. Vertical deviation of the horizontal landmarks and horizontal deviation of the midsagittal landmarks were measured. Results The porion and orbitale, which were not involved in establishing the horizontal reference plane, were found to deviate vertically from the horizontal reference plane in the three methods. The midsagittal landmarks, which were not used for the midsagittal reference plane, deviated horizontally from the midsagittal reference plane in the three methods. Conclusion In a three-dimensional facial analysis, the vertical and horizontal deviations of the landmarks from the horizontal and midsagittal reference planes could vary depending on the methods of establishing reference planes.

Diagnostic reference levels in intraoral dental radiography in Korea

Purpose The objectives of this study were to survey the radiographic exposure parameters, to measure the patient doses for intraoral dental radiography nationwide, and thus to establish the diagnostic reference levels (DRLs) in intraoral dental X-ray examination in Korea. Materials and Methods One hundred two intraoral dental radiographic machines from all regions of South Korea were selected for this study. Radiographic exposure parameters, size of hospital, type of image receptor system, installation duration of machine, and type of dental X-ray machine were documented. Patient entrance doses (PED) and dose-area products (DAP) were measured three times at the end of the exit cone of the X-ray unit with a DAP meter (DIAMENTOR M4-KDK, PTW, Freiburg, Germany) for adult mandibular molar intraoral dental radiography, and corrections were made for room temperature and pressure. Measured PED and DAP were averaged and compared according to the size of hospital, type of image receptor system, installation duration, and type of dental X-ray machine. Results The mean exposure parameters were 62.6 kVp, 7.9 mA, and 0.5 second for adult mandibular molar intraoral dental radiography. The mean patient dose was 2.11 mGy (PED) and 59.4 mGycm2 (DAP) and the third quartile one 3.07 mGy (PED) and 87.4 mGycm2 (DAP). Doses at university dental hospitals were lower than those at dental clinics (p<0.05). Doses of digital radiography (DR) type were lower than those of film-based type (p<0.05). Conclusion We recommend 3.1 mGy (PED), 87.4 mGycm2 (DAP) as the DRLs in adult mandibular molar intraoral dental radiography in Korea.

Application of spherical coordinate system to facial asymmetry analysis in mandibular prognathism patients

Purpose The purpose of this study was to compare asymmetric mandibular prognathism individuals with symmetric mandibular prognathism individuals using a new alternate spherical coordinate system. Materials and Methods This study consisted of 47 computed tomographic images of patients with mandibular prognathism. The patients were classified into symmetric and asymmetric groups. Mandibular and ramal lines were analyzed using an alternate spherical coordinate system. The length as well as midsagittal and coronal inclination angle of the lines was obtained. The bilateral differences of the spherical coordinates of the facial lines were statistically analyzed in the groups. Results There were significant differences between the groups in bilateral difference of the length and midsagittal inclination angle of the lines (p<0.05). The bilateral difference of the length and midsagittal inclination angle of the lines has significant correlation with chin deviation (p<0.05). Conclusion The new alternate spherical coordinate system was able to effectively evaluate facial lines. The bilateral difference of lengths and midsagittal inclination of the facial lines might contribute to the facial asymmetry in mandibular prognathism individuals.

Reference dose levels for dental panoramic radiography in Gwangju, South Korea

This study assessed the reference dose levels for dental panoramic radiography in Gwangju city, South Korea based on the dose width product (DWP) and compared them with those already established elsewhere. A total of 44 panoramic dental radiographic sets (36 digital and 8 analogue panoramic sets) in 41 dental clinics in Gwangju city were chosen. The third quartile DWP was determined from 429 surface dose measurements of the adult surface dose in panoramic dental radiography. The third quartile DWP for panoramic radiography was 60.1 mGy mm. The proposed DWP reference levels of 60.1 mGy mm were less than or equal to those previously reported in other countries, such as Italy and UK, and acceptable for panoramic radiography in Gwangju, South Korea.

Diagnostic reference levels for panoramic and lateral cephalometric radiography of Korean children.

AbstractPediatric patients are considered to be more radiosensitive than adults; thus, radiation dose evaluations based on radiologic examinations are particularly important in this population. However, no national diagnostic reference levels (DRLs) are available for pediatric patients in the Republic of Korea. Therefore, the aim of this study was to determine the usage of panoramic and cephalometric radiography under the National Health Insurance (NHI) scheme and to investigate the current DRLs for child panoramic and lateral cephalometric radiography using dose area product (DAP). DAP values were obtained for standard child exposure settings used routinely by dentists. Analysis was performed on data obtained from 28 panoramic and 20 cephalometric x-ray units for the DAP investigation. DRLs for child panoramic and cephalometric radiography were found to be 95.9 mGy cm2 and 121.3 mGy cm2, respectively. These DRLs are higher than those recommended in the UK and Germany, which indicates that further effort is required to reduce pediatric doses in the Republic of Korea.

The location of midfacial landmarks according to the method of establishing the midsagittal reference plane in three-dimensional computed tomography analysis of facial asymmetry

Purpose The purpose of this study was to evaluate the influence of methods of establishing the midsagittal reference plane (MRP) on the locations of midfacial landmarks in the three-dimensional computed tomography (CT) analysis of facial asymmetry. Materials and Methods A total of 24 patients (12 male and 12 female; mean age, 22.5 years; age range, 18.2-29.7 years) with facial asymmetry were included in this study. The MRP was established using two different methods on each patients CT image. The x-coordinates of four midfacial landmarks (the menton, nasion, upper incisor, and lower incisor) were obtained by measuring the distance and direction of the landmarks from the MRP, and the two methods were compared statistically. The direction of deviation and the severity of asymmetry found using each method were also compared. Results The x-coordinates of the four anatomic landmarks all showed a statistically significant difference between the two methods of establishing the MRP. For the nasion and lower incisor, six patients (25.0%) showed a change in the direction of deviation. The severity of asymmetry also changed in 16 patients (66.7%). Conclusion The results of this study suggest that the locations of midfacial landmarks change significantly according to the method used to establish the MRP.

Interobserver agreement on the diagnosis of carotid artery calcifications on panoramic radiographs.

Purpose This study was performed to investigate the interobserver agreement on the detection of carotid artery calcifications on panoramic radiographs. Materials and Methods This study consisted of panoramic radiographs acquired from 634 male patients of the age of 50 years or older. Having excluded carotids of no diagnostic quality, 1008 carotids from the panoramic radiographs of the patients were interpreted by two oral and maxillofacial radiologists independently for the presence of carotid artery calcifications. Statistical analysis was used to calculate the interobserver agreement. Results Interobserver agreement was obtained for 932 carotids (92.4%). Inconsistent interpretation of 76 carotids (7.5%) between the two observers was found. Cohens kappa value was 0.688 (p<0.001). Conclusion The probability of a match between the two observers was substantially high.