• Journal of Biomedical Engineering Research
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• v.23 no.1
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• pp.61-72
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• 2002

In this parer, a new harmonic imaging technique is Proposed and evaluated experimentally. In the Proposed method. a weighted chirp signal with a hanning window is transmitted. The RF samples obtained on each array element are individually compressed by correlating with the reference signal defined as the 2nd harmonic component($2f_0$) of a transmitted chirp signal generated in a square-law system. The correlator output will then consist of the compressed version of the $2f_0$ component generated in tissue and the crosscorrelation sequence of the fundamental($f_0$) and 2f$_{0}$components. The Proposed method uses the compressed $2f_0$ component to form an image. for which the crosscorrelation term should be suppressed below at least -50dB. The Proposed method has two process, 2f$_{0}$-correlation and $2f_0$-correlation(PI) . $2f_0$-correlation can successfully eliminate the $f_0$ component with a single transmit-receive events and therefore is more efficient than the conventional Pulse inversion method in terms of the frame rate. 2i)-correlation(Pl) Performs pulse compression after applying pulse inversion method for the 2nd harmonic image with high resolution and SNR. Another advantage of the proposed method is that the SNR of 2nd harmonic imaging can be improved without limitation by increasing the duration of the chirp signal. The proposed method was verified through both the computer simulations and actual experiments .ts .

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.185-195
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• 2017

In recent years, unexpected bridge fire accidents have increased because of augmenting the number of traffic volumes and hazardous materials by the increment in traffics and distribution business. Furthermore, in accordance with the effort of using the under space of bridges, the ratio of occupied by combustible materials like oil tanker or lorry has been increased. As a result, the occurrence of bridge fire has been growing drastically. In order to mitigate the accident of bridge fire, risk assessment of bridge fire has been studied, however, practical risk models considering safety from users' viewpoints were scarce. This study represented quantitative risk assessment model applicable to national road bridges in Korea. The primary factors with significant impacts on bridge fire accidents was chosen such as clearance height, materials of bridges, arrival time of fire truck and fire intensity. The selected factors were used for Fire Dynamics Simulation (FDS) and the peak temperature calculated by FDS in accordance with the fire duration and fire intensity. The risk assessment model in bridge fire reflected the FDS analysis results, the fire damage criteria, and the grade of fire truck arrival time was established. Response plans for bridge fire accidents according to the risk assessment output has been discussed. Lastly, distances between bridges and fire stations were calculated by GIS network analysis. Based on the suggested assessment model and methodology, sample bridges were selected and graded for the risk assessment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1330-1338
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• 2015

In wireless communication network, the amount of packet data for the video streaming in the playout buffer of the receiver is changed with time according to network condition. If the amount of packet data is less than a specific buffer amount, the buffer underflow problem is generated. On the contrary, if the amount of packet data is more than a given buffer amount, the buffer overflow problem is occurred. When the playout of the video streaming is processed, these buffer underflow and overflow problems cause stop and skip phenomenons and then provide the discontinuity of playout. Therefore, to solve the buffer underflow and overflow problems of the video streaming in wireless communication network, This paper analyzes the combined effect of Token Bucket scheme, which controls the bursty traffic, and AMP(Adaptive Media Playout) scheme, which adaptively changes the playout speed of receiver. Through simulation, we found that the combination of Token Bucket and AMP schemes provides the superiority in terms of the occurrence number of buffer underflow and overflow, the stop duration time and the number of removed frames generated by underflow and overflow, and PSNR.

• Korean Journal of Bronchoesophagology
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• v.4 no.2
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• pp.211-218
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• 1998

There have been few large scale surveys of salivary gland tumors, because the salivary gland tumors comprised less than 3 percent of all neoplasms of the head and neck. Also there is a problem that the incidences of specific types of tumors have the variation according to the geographic regions. ]'nother Korean reports about salivary gland tumor, they only treated about 100 cases only. Objectives : The purpose of this study is to identify the frequency and clinical characteristics of salivary gland tumors and to compare with other Korean reports. Materials and Methods : We had performed to analyze 387 cases of salivary gland tumors from 1983 to June 1997, were reviewed in histopathological and clinical aspects. The diagnoses of individual tumors were based on the World Health Organization classification. Tumors were analyzed according to the histologic type site, age and sex. Results : The majority (79.1%) of cases occurred in the major salivary glands and 20.9% in the minor. The parotid gland was the most frequent site with 52.4％ and submandibular glands with 26.3%. Benign tumors were 79.3% of the tumors and malignant tmon were 20.7%. The most frequent tumor was pleomorphic adenoma occupied 63.8% of the total and frequency percent of histologic type of 98 malignant tumors showed 35.7% of mucoepidermoid carcinomas, 24.5% of adenoid cystic carcinomas. Overall gender with female predominance with 1 : 1.4 of male to female ratio. The average age of patients was 42.8 years. The most frequent chief complaint was a palpable mass. The duration of the symptom was shorter in the malignant salivary gland tumors (26.7 months) than in the benign salivary gland tumors (38.2 months). Conclusion : Comparing to the previous Korean reports, the present study confirms that the incidence of salivary gland tumor was lower in the parotid gland, and was higher in the submandibular and minor salivary glands.

• Journal of the Korean earth science society
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• v.24 no.4
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• pp.315-324
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• 2003

The characteristics of particles were evaluated through the measurement data of PM$_{2.5}$, PM$_{10}$ and TSP instruments located in air quality monitoring stations installed and operated by Seoul Metropolitan city. The data of particulate mass on the filter was collected bv a high volume air sampler during the sand storm period. The number of days of sand storm in Seoul showed a different pattern from 1990 to November 2002, We can see a trend of increased occurrence and duration of sand storms. The ratio of PM$_{10}$ to TSP was shown as 52.9% and 59.4% during the sand storm period in 2000 and 2001. respectively. It was indicated that the particles larger than 10${\mu}$m increased by approximately 10% in sand storm periods compared to no sand storm period. While PM$_{10}$ size fraction reached 71.4% in 2002, the contribution of sand storm to total particulate concentration was estimated to be 11.9% for PM$_{2.5}$, 23.1% for PM$_{10}$, 19% for TSP in 2002, respectively and sand storms highly correlated with annual total particulate concentration.

• Journal of Korean Foot and Ankle Society
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• v.23 no.4
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• pp.159-165
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• 2019

Purpose: This study investigated the recurrence rate after performing hallux valgus correction using scarf and Akin osteotomy, and also identified the correlation and cut-off values of both the preoperative and postoperative radiographic parameters as risk factors for the recurrence of hallux valgus. Materials and Methods: We reviewed 87 hallux valgus patients (122 feet) who received scarf and Akin osteotomy from January 2007 to August 2015. The clinical outcomes were evaluated using the visual analogue scale (VAS) and American Orthopaedic Foot and Ankle Society (AOFAS) scores. The radiological outcome measures included the hallux valgus angle (HVA), intermetatarsal angle (IMA), and distal metatarsal articular angle (DMAA) as determined on the serial weight bearing radiographs. Recurrence was defined as more than 20 degrees of HVA noted on the final follow-up radiograph. Those radiological factors associated with recurrence were evaluated and analyzed. Results: The mean follow-up duration was 20.6 months (12.0~46.5 months) and the mean age was 44 years (13~80 years). The VAS and AOFAS scores were significantly improved at the time of the final follow-up (7.0 to 2.0, p<0.001; 78.0 to 92.0, p<0.001; respectively). Significant corrections in the HVA, IMA, and DMAA were obtained (p<0.001). Eleven (9.0%: 11/122) cases experienced recurrent hallux valgus deformity. The postoperative IMA, DMAA and HVA showed significant moderate to strong correlation with HVA at the final follow-up (Pearson correlation coefficient: 0.44, 0.70, and 0.88, respectively; p<0.001). Postoperative HVA>16.7 degrees, postoperative DMAA>13.9 degrees, and postoperative IMA>8.2 degrees showed statistically significant correlation with radiological recurrence at the last follow-up, and the odds ratio of each variable was high in order. Conclusion: Our radiographic results indicated that postoperative HVA>16.7 degrees, postoperative DMAA>13.9 degrees, and postoperative IMA>8.2 degrees can be risk factors for hallux valgus recurrence. These risk factors may be helpful for modifying surgical procedures and preventing the recurrence of hallux valgus.

• Journal of Oral Medicine and Pain
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• v.32 no.3
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• pp.263-272
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• 2007

The purpose of this study was to analyze the nerve damage after tooth extraction and implant surgery, and to establish a predictive model for assessment and management of dysesthesia. In this questionnaire study, the subjects chosen for this study were 276 dentists who answered the questionnaire about dysesthesia after tooth extraction and implant surgery. The analysis of the results consist of the sex and age distribution, affected site, associated symptoms, rate and duration of the recovery. The results are summarized as follows. : 1. There were no significant difference between the sex and the dysesthesia. 2. The most common affected site was the mandibular region. In the group of the implant surgery, 100% affected the mandibular site. The tooth extraction group was 93.2% affected. 3. Pain was one of the most associated symptom with dysesthesia-46.5% of the tooth extraction and 44.8% of the implant surgery. 4. The recovery ratio was 72.3% in the tooth extraction, 71.8% in the implant surgery. Most of them, they recovered in $1{\sim}6$ months. In conclusion, most of dysesthesia may be recovered within 1 year. However, the possibility of persistent dysesthesia should not be neglected. Therefore, practitioners must discuss the possibility of nerve injury with their patients, and include this possibility in the consent forms. Various methods of monitoring recovery of sensation should be considered for objective assessment of prognosis. In addition, immediate referral to orofacial pain specialists can offer the patients an opportunity for more effective and noninvasive treatments.

• Journal of Oral Medicine and Pain
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• v.43 no.2
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• pp.27-33
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• 2018

Purpose: Many researchers have established a connection between sleep disturbances and the symptoms of temporomandibular disorder (TMD) in adults, but there are a few studies targeted at adolescents with TMD. The aim of this study was to analyze the sleep pattern of adolescents with TMD and to determine the effect of poor sleep quality on their clinical symptoms. Methods: The subjects were composed of 47 adolescents with TMD. The sleep pattern and preliminary information of patients were measured by self-reported questionnaires; Pittsburgh Sleep Quality Index (PSQI) and Questionnaire for TMD analysis. TMD pain was scored using the Numerical Rating Scale. The Kruskal-Wallis test, Mann-Whitney U test, Fisher's exact test and logistic regression were used for statistical analysis. Results: The poor sleeping group had statistically more females (25.00% males, 75.00% females) than the good sleeping group. As compared with that of good sleepers, sleep quality of poor sleepers was significantly worse in the items of subjective sleep quality, sleep latency, sleep duration, sleep disturbances, daytime dysfunction and global PSQI score. The sleep time of adolescents was much longer during vacation ($7.20{\pm}1.38hours$) than during school days ($6.10{\pm}1.26hours$). Poor sleep of patients was associated with the pain in the ear or in front of the ear, in the face, jaw, throat or temple and in neck or back. Adolescents with pain in those areas had significantly higher proportion of poor sleepers than adolescents with no pain in those areas. Conclusions: The high ratio of girls in poor sleeping group could reflect the greater prevalence of TMD in women than in men. Pain in peri-temporomandibular joint areas, neck or back could negatively influence sleep quality of adolescents with TMD.

• Journal of Radiation Protection and Research
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• v.42 no.3
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• pp.158-165
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• 2017

Background: Nuclear facilities in South Korea have generally adopted pressurized ion chambers to measure ambient gamma ray exposure rates for monitoring the impact of radiation on the surrounding environment. The rates assessed with pressurized ion chambers do not distinguish between natural and man-made radiation, so a further step is needed to identify the cause of abnormal variation. In contrast, using NaI(Tl) scintillation detectors to detect gamma energy rates can allow an immediate assessment of the cause of variation through an analysis of the energy spectra. Against this backdrop, this study was conducted to propose a more effective way to monitor ambient gamma exposure rates. Materials and Methods: The following methods were used to analyze gamma energy spectra measured from January to November 2016 with NaI detectors installed at the Korea Atomic Energy Research Institute (KAERI) dormitory and Hanbat University. 1) Correlations of the variation of rates measured at the two locations were determined. 2) The dates, intervals, duration, and weather conditions were identified when rates increased by $5nSv{\cdot}h^{-1}$ or more. 3) Differences in the NaI spectra on normal days and days where rates spiked by $5nSv{\cdot}h^{-1}$ or more were studied. 4) An algorithm was derived for automatically calculating the net variation of the rates. Results and Discussion: The rates measured at KAERI and Hanbat University, located 12 kilometers apart, did not show a strong correlation (coefficient of determination = 0.577). Time gaps between spikes in the rates and rainfall were factors that affected the correlation. The weather conditions on days where rates went up by $5nSv{\cdot}h^{-1}$ or more featured rainfall, snowfall, or overcast, as well as an increase in peaks of the gamma rays emitted from the radon decay products of $^{214}Pb$ and $^{214}Bi$ in the spectrum. This study assumed that $^{214}Pb$ and $^{214}Bi$ exist at a radioactive equilibrium, since both have relatively short half-lives of under 30 minutes. Provided that this assumption is true and that the gamma peaks of the 352 keV and 1,764 keV gamma rays emitted from the radionuclides have proportional count rates, no man-made radiation should be present between the two energy levels. This study proved that this assumption was true by demonstrating a linear correlation between the count rates of these two gamma peaks. In conclusion, if the count rates of these two peaks detected in the gamma energy spectrum at a certain time maintain the ratio measured at a normal time, such variation can be confirmed to be caused by natural radiation. Conclusion: This study confirmed that both $^{214}Pb$ and $^{214}Bi$ have relatively short half-lives of under 30 minutes, thereby existing in a radioactive equilibrium in the atmosphere. If the gamma peaks of the 352 keV and 1,764 keV gamma rays emitted from these radionuclides have proportional count rates, no man-made radiation should exist between the two energy levels.

• Tuberculosis and Respiratory Diseases
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• v.78 no.4
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• pp.349-355
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• 2015

Background: The tuberculin skin test (TST) is the standard tool to diagnose latent tuberculosis infection (LTBI) in mass screening. The aim of this study is to find an optimal cut-off point of the TST+ rate within tuberculosis (TB) contacts to predict the active TB development among adolescents in school TB outbreaks. Methods: The Korean National Health Insurance Review and Assessment database was used to identify active TB development in relation to the initial TST (cut-off, 10 mm). The 7,475 contacts in 89 schools were divided into two groups: Incident TB group (43 schools) and no incident TB group (46 schools). LTBI treatment was initiated in 607 of the 1,761 TST+ contacts. The association with active TB progression was examined at different cut-off points of the TST+ rate. Results: The mean duration of follow-up was $3.9{\pm}0.9years$. Thirty-three contacts developed active TB during the 4,504 person-years among the TST+ contacts without LTBI treatment (n=1,154). The average TST+ rate for the incident TB group (n=43) and no incident TB group (n=46) were 31.0% and 15.5%, respectively. The TST+ rate per group was related with TB progression (odds ratio [OR], 1.025; 95% confidence interval [CI], 1.001-1.050; p=0.037). Based on the TST+ rate per group, active TB was best predicted at TST+ ${\geq}$ 16% (OR, 3.11; 95% CI, 1.29-7.51; area under curve, 0.64). Conclusion: Sixteen percent of the TST+ rate per group within the same grade students can be suggested as an optimal cut-off to predict active TB development in middle and high schools TB outbreaks.