• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.05a
• /
• pp.996-1000
• /
• 2002

A porous tube, comprised of a resin-coated woven fabric has recently been used as an effective component for use in intake systems of internal combustion engines to reduce the intake roaring. For the prediction of the acoustic performance of an engine intake system with a porous woven hose, the acoustic wall impedance of the hose must be known. Because of its peculiar acoustical and structural characteristics, the accurate measurement of the wall impedance ofa porous woven hose is not easy. A new measurement technique is proposed herein, that is valid over the low to mid frequency ranges. The acoustics impedance is inversely estimated from an overdetermined set of measured pressure transmission coefficients for specimens of different lengths and the reflection coefficient of end termination. The method involves only one measurement, and, as a result, it is very simple. The measured TL for samples with arbitrary conditions, arbitrary porous frequency, arbitrary length, and arbitrary mean flow condition, are in reasonably good agreement with values predicted from curve-fitted impedance data.

• Journal of Chest Surgery
• /
• v.26 no.1
• /
• pp.36-43
• /
• 1993

Sixty four children [aged 2 days to 9 years] , 58 with complete transposition of the great arteries, 5 with Taussig-Bing double outlet right ventricle, and 1 with double outlet left ventricle plus left ventricular type single ventricle, have undergone anatomic correction from November 1987 to August 1992. Eleven underwent previous operations: pulmonary artery banding[7], modified Blalock-Taussig shunt[2], coarctoplasty[2], aortic arch reconstruction[1] . Of 58 patients with TGA, Type A coronary arteries of Yacoub were seen in 50[86%]. U-shaped coroanry arterial flaps were transfered to the neoaorta using trap door technique, and neopulmonary arterial tract was constructed using glutaraldehyde fixed autopericardium with Lecompte maneuver. There were 18 hospital deaths [28.1%] with no late mortality. Mean follow-up of 20.4\ulcorner11.9 months were achieved in all survivors. Postoperative cardiac catheterizations were done in 14 cases. Mean pressure gradients of pulmonary and aortic outflow tract were 15.0 $\pm$2.6 and 4.2$\pm$1.4mmHg, mild aortic valve insufficiencies were found in 2, and mean cardiac index was 5.18$\pm$0.19 L/min/M2. We conclude that we should continue anatomic correction for the complex congenital heart anomalies with the malposition of the great arteries because myocardial function seems to be well preserved, though we are still on the learning curve.

• International Journal of Precision Engineering and Manufacturing
• /
• v.9 no.4
• /
• pp.57-62
• /
• 2008

The aim of this investigation was to extract the fatigue properties at the designated fatigue life of copper foil and observe the mean stress and stress amplitude effects on both the fatigue life and the corresponding surface morphology. Tensile tests were performed to determine the baseline monotonic material properties of the proportional limit and ultimate tensile strength. Constant amplitude fatigue tests were carried out using a feedback-controlled fatigue testing machine. The mean stress and the stress amplitude were changed to obtain the complete nominal stress-life curves. An atomic force microscope was utilized to observe the relationship between the fatigue damage and the corresponding changes in surface morphology. A Basquin's exponent of-0.071 was obtained through the fatigue tests. An endurance limit of 122 MPa was inferred from a Haigh diagram. The specimen surface became rougher as the number of fatigue cycles increased, and there was a close relationship between the fatigue damage and the surface roughness evolution.

• Pediatric Gastroenterology, Hepatology & Nutrition
• /
• v.27 no.2
• /
• pp.88-94
• /
• 2024

Purpose: Infantile hypertrophic pyloric stenosis (IHPS) is a common gastrointestinal disease in neonates and hypochloremia metabolic alkalosis is a typical laboratory finding in affected patients. This study aimed to analyze the clinical characteristics of infants with IHPS and evaluate the association of clinical and laboratory parameters with ultrasonographic findings. Methods: Infants diagnosed with IHPS between January 2017 and July 2022 were retrospectively evaluated. Results: A total of 67 patients were included in the study. The mean age at diagnosis was 40.5±19.59 days, and the mean symptom duration was 11.97±9.91 days. The mean pyloric muscle thickness and pyloric canal length were 4.87±1.05 mm and 19.6±3.46 mm, respectively. Hyponatremia and metabolic alkalosis were observed in five (7.5%) and 36 (53.7%) patients, respectively. Serum sodium (p=0.011), potassium (p=0.023), and chloride levels (p=0.015) were significantly lower in patients with high bicarbonate levels (≥30 mmol/L). Furthermore, pyloric canal length was significantly higher in patients with high bicarbonate levels (p=0.015). To assess metabolic alkalosis in IHPS patients, the area under the receiver operating characteristic curve of pyloric canal length was 0.910 and the optimal cutoff value of the pyloric canal length was 23.5 mm. Conclusion: We found a close association between laboratory and ultrasonographic findings of IHPS. Clinicians should give special consideration to patients with pyloric lengths exceeding 23.5 mm and appropriate fluid rehydration should be given to these patients.

• The Journal of the Korea Contents Association
• /
• v.13 no.12
• /
• pp.829-839
• /
• 2013

This study is a descriptive research study with the purpose of predicting and comparing factors of depression affecting residents in a metropolitan city by using logistic regression analysis and decision-making tree analysis. The subjects for the study were 462 residents ($20{\leq}aged{\angle}65$) in a metropolitan city. This study collected data between October 7, 2011 and October 21, 2011 and analyzed them with frequency analysis, percentage, the mean and standard deviation, ${\chi}^2$-test, t-test, logistic regression analysis, roc curve, and a decision-making tree by using SPSS 18.0 program. The common predicting variables of depression in community residents were social dysfunction, perceived physical symptom, and family support. The specialty and sensitivity of logistic regression explained 93.8% and 42.5%. The receiver operating characteristic (roc) curve was used to determine an optimal model. The AUC (area under the curve) was .84. Roc curve was found to be statistically significant (p=<.001). The specialty and sensitivity of decision-making tree analysis were 98.3% and 20.8% respectively. As for the whole classification accuracy, the logistic regression explained 82.0% and the decision making tree analysis explained 80.5%. From the results of this study, it is believed that the sensitivity, the classification accuracy, and the logistics regression analysis as shown in a higher degree may be useful materials to establish a depression prediction model for the community residents.

• Journal of Korean Society of Transportation
• /
• v.22 no.3 s.74
• /
• pp.109-125
• /
• 2004

In recent decades, microscopic simulation models have become powerful tools to analyze traffic flow on highways and to assist the investigation of level of service. The existing microscopic simulation models simulate an individual vehicle's speed based on a constant free-flow speed dominantly specified by users and driver's behavior models reflecting vehicle interactions, such as car following and lane changing. They set a single free-flow speed for a single vehicle on a given link and neglect to consider the effects of highway design elements to it in their internal simulation. Due to this, the existing models are limitted to provide with identical simulation results on both curved and tangent sections of highways. This paper presents a model developed to estimate the change of free-flow speeds based on highway design elements. Nine neural network models were trained based on the field data collected from seven different freeway curve sections and three different locations at each section to capture the percent changes of free-flow speeds: 100 m upstream of the point of curve (PC) and the middle of the curve. The model employing seven highway design elements as its input variables was selected as the best : radius of curve, length of curve, superelevation, the number of lanes, grade variations, and the approaching free-flow speed on 100 m upstream of PC. Tests showed that the free-flow speeds estimated by the proposed model were statistically identical to the ones from the field at 95% confidence level at each three different locations described above. The root mean square errors at the starting and the middle of curve section were 6.68 and 10.06, and the R-squares at these points were 0.77 and 0.65, respectively. It was concluded from the study that the proposed model would be one of the potential tools introducing the effects of highway design elements to free-flow speeds in simulation.

• Journal of Gastric Cancer
• /
• v.18 no.1
• /
• pp.90-98
• /
• 2018

Purpose: We evaluated the learning curve and short-term surgical outcomes of robot-assisted distal gastrectomy (RADG) performed by a single surgeon experienced in open, but not laparoscopic, gastrectomy. We aimed to verify the feasibility of performing RADG without extensive laparoscopic experience. Materials and Methods: Between July 2012 and December 2016, 60 RADG procedures were performed by a single surgeon using the da $Vinci^{(R)}$ Surgical System (Intuitive Surgical). Patient characteristics, the length of the learning curve, surgical parameters, and short-term postoperative outcomes were analyzed and compared before and after the learning curve had been overcome. Results: The duration of surgery rapidly decreased from the first to the fourth case; after 25 procedures, the duration of surgery was stabilized, suggesting that the learning curve had been overcome. Cases were divided into 2 groups: 25 cases before the learning curve had been overcome (early cases) and 35 later cases. The mean duration of surgery was 420.8 minutes for the initial cases and 281.7 minutes for the later cases (P<0.001). The console time was significantly shorter during the later cases (168.6 minutes) than during the early cases (247.1 minutes) (P<0.001). Although the volume of blood loss during surgery declined over time, there was no significant difference between the early and later cases. No other postoperative outcomes differed between the 2 groups. Pathology reports revealed the presence of mucosal invasion in 58 patients and submucosal invasion in 2 patients. Conclusions: RADG can be performed safely with acceptable surgical outcomes by experts in open gastrectomy.

• Journal of Korean Neurosurgical Society
• /
• v.67 no.1
• /
• pp.60-72
• /
• 2024

Objective : Recently, robotic-assisted spine surgery (RASS) has been considered a minimally invasive and relatively accurate method. In total, 495 robotic-assisted pedicle screw fixation (RAPSF) procedures were attempted on 100 patients during a 14-month period. The current study aimed to analyze the accuracy, potential risk factors, and learning curve of RAPSF. Methods : This retrospective study evaluated the position of RAPSF using the Gertzbein and Robbins scale (GRS). The accuracy was analyzed using the ratio of the clinically acceptable group (GRS grades A and B), the dissatisfying group (GRS grades C, D, and E), and the Surgical Evaluation Assistant program. The RAPSF was divided into the no-breached group (GRS grade A) and breached group (GRS grades B, C, D, and E), and the potential risk factors of RAPSF were evaluated. The learning curve was analyzed by changes in robot-used time per screw and the occurrence tendency of breached and failed screws according to case accumulation. Results : The clinically acceptable group in RAPSF was 98.12%. In the analysis using the Surgical Evaluation Assistant program, the tip offset was 2.37±1.89 mm, the tail offset was 3.09±1.90 mm, and the angular offset was 3.72°±2.72°. In the analysis of potential risk factors, the difference in screw fixation level (p=0.009) and segmental distance between the tracker and the instrumented level (p=0.001) between the no-breached and breached group were statistically significant, but not for the other factors. The mean difference between the no-breach and breach groups was statistically significant in terms of pedicle width (p<0.001) and tail offset (p=0.042). In the learning curve analysis, the occurrence of breached and failed screws and the robot-used time per screw screws showed a significant decreasing trend. Conclusion : In the current study, RAPSF was highly accurate and the specific potential risk factors were not identified. However, pedicle width was presumed to be related to breached screw. Meanwhile, the robot-used time per screw and the incidence of breached and failed screws decreased with the learning curve.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.9
• /
• pp.2760-2764
• /
• 2013

Geniposide is a biologically active ingredient of gardenia fruit. A liquid chromatography-tandem mass spectrometric method was developed and validated for the determination of geniposide in rat plasma. The plasma samples were pretreated by solid-phase extraction and introduced into a BDS Hypersil $C_{18}$ column ($50{\times}2.1mm$, $5{\mu}m$) for chromatographic separation. The mobile phase consisted of 0.1% formic acid and 0.1% formic acid in acetonitrile, and gradient elution was performed at a flow rate of 0.25 mL/min. For mass spectrometric detection, multiple reaction monitoring was performed via an electrospray ionization source in positive mode. The calibration curve for geniposide was linear ($r^2=0.997$) in the concentration range of $0.005-1{\mu}g/mL$. The intra- and inter-day accuracies and precisions fulfilled the required criteria (${\pm}15%$). The developed method was subsequently used for pharmacokinetic analysis of geniposide after oral administration to rats at a dose of 50 mg/kg. The mean maximum plasma concentration of geniposide was $0.68{\pm}0.29{\mu}g/mL$ at $0.44{\pm}0.13h$, and the mean area under the plasma concentration versus time curve was $1.46{\mu}g{\cdot}h/mL$.

• Asian Pacific Journal of Cancer Prevention
• /
• v.13 no.9
• /
• pp.4587-4592
• /
• 2012

Purpose: This study used receiver operating characteristic curve to analyze Surveillance, Epidemiology and End Results (SEER) neuroblastoma (NB) and other peripheral nerve cell tumors (PNCT) outcome data. This study found under usage of radiotherapy in these patients. Materials and methods: This study analyzed socio-economic, staging and treatment factors available in the SEER database for NB and other PNCT. For the risk modeling, each factor was fitted by a generalized linear model to predict the outcome (soft tissue specific death, yes/no). The area under the receiver operating characteristic curve (ROC) was computed. Similar strata were combined to construct the most parsimonious models. A random sampling algorithm was used to estimate the modeling errors. Risk of neuroendocrine (other endocrine including thymus as coded in SEER) death was computed for the predictors. Results: There were 5261 patients diagnosed from 1973 to 2009 were included in this study. The mean follow up time (S.D.) was 83.8 (97.6) months. The mean (SD) age was 18 (25) years. About 30.45% of patients were un-staged. The SEER staging has high ROC (SD) area of 0.58 (0.01) among the factors tested. We simplified the 4-layered risk levels (local, regional, distant, un-staged/others) to a simpler 3-tiered model with comparable ROC area of 0.59 (0.01). Less than 50% of PNCT patients received radiotherapy (RT) including the ones with localized disease. This avoidance of RT use occurred in adults and children. Conclusion: The high under-staging rate may have precented patients from selecting definitive radiotherapy (RT) after surgery. Using RT for, especially, adult PNCT patients is a potential way to improve outcome.