Showing papers by "Yonsei University published in 1997"

A new approach to fuzzy modeling

Abstract: This paper proposes a new approach to fuzzy modeling. The suggested fuzzy model can express a given unknown system with a few fuzzy rules as well as Takagi and Sugeno's model (1985), because it has the same structure as that of Takagi and Sugeno's model. It is also as easy to implement as Sugeno and Yasukawa's model (1993) because its identification mimics the simple identification procedure of Sugeno and Yasukawa's model. The suggested algorithm is composed of two steps: coarse tuning and fine tuning. In coarse tuning, fuzzy C-regression model (FCRM) clustering is used, which is a modified version of fuzzy C-means (FCM). In fine tuning, gradient descent algorithm is used to precisely adjust parameters of the fuzzy model instead of nonlinear optimization methods used in other models. Finally, some examples are given to demonstrate the validity of this algorithm.

Effect of obesity on total and free insulin-like growth factor (IGF)-1, and their relationship to IGF-binding protein (BP)-1, IGFBP-2, IGFBP-3, insulin, and growth hormone

Abstract: OBJECTIVES: We investigated the effect of obesity on the serum levels of total and free IGF-1 and their relationship to the circulating levels of insulin and IGF binding proteins (IGFBPs) in age and sex-matched groups. SUBJECTS: The study included 43 obese subjects (ideal body weight; IBW>120%) and 45 controls (IBW<100%). All of the subjects were male. MEASUREMENT: Total IGF-1, free IGF-1, IGFBP-1, IGFBP-2, IGFBP-3, and insulin were measured in obese subjects and normal control subjects. RESULTS: No significant differences in the circulating levels of total and IGFBP-3 were observed between the obese and control groups. In contrast to total IGF-1, free IGF-1 in obese subjects was significantly increased compared to normal controls (P<0.05). Serum total and free IGF-1 were inversely correlated with age (r=−0.42, P=0.001, and −0.44, P=0.001). Fasting serum insulin concentrations were elevated in all the obese subjects (P<0.05) and positively correlated with IBW (r=0.57, P=0.001). The levels of serum GH and IGFBP-1 were suppressed in all the obese subjects (P<0.05). IGFBP-1 was inversely correlated with IBW (r=−0.51, P=0.001) and serum insulin concentrations (r=minus;0.48, P=0.001). The IGFBP-2 concentrations were also suppressed in obese subjects and inversely related to free IGF-1 (r=−0.48, P=0.001). Using multiple linear regression analysis, total IGF-1 and insulin concentrations were positively correlated (r=0.58, P=0.001) and free IGF-1 and IGFBP-1 concentrations were negatively correlated (r=−0.57, P=0.001). CONCLUSION: We confirmed that total IGF-1 and IGFBP-3 concentrations were not significantly different between the obese and control groups, despite GH hyposecretion in obesity. We also found that free IGF-1 concentrations were higher in obese subjects than in normal controls. It seems likely that overnutrition and chronic hyperinsulinaemia in obesity may alter this regulated growth response by insulin stimulation of IGF-1 production and suppression of hepatic IGFBP-1 and IGFBP-2 production, which may inhibit IGF-1 bioactivity.

The dissected aorta: part III. Anatomy and radiologic diagnosis of branch-vessel compromise.

Abstract: PURPOSE: To determine the anatomic, hemodynamic, and radiologic characteristics of branch-vessel compromise in patients with aortic dissection. MATERIALS AND METHODS: Sixty-two patients with aortic dissection were evaluated with aortography (n = 62), intravascular ultrasound (US) (n = 35), and manometry (n = 56). Branch-vessel compromise with ischemia was suspected in 40 of these patients. Radiologic and manometric findings were correlated with clinical findings of ischemia. Femoral artery pulse strength was correlated with access from the respective femoral artery to the true and false lumina of the dissected aorta. RESULTS: Twenty-six of 40 patients suspected of having ischemia had angiographic evidence of branch-vessel compromise, and intravascular US helped identify two types of branch-vessel compromise in them: static (dissection intersected and narrowed the vessel origin) and dynamic (dissection spared the vessel origin, but the dissection flap appeared to compress the true lumen at or above the ori...

Consumer evaluations of fast‐food services: a cross‐national comparison

Abstract: A growing number of US fast‐food franchises are expanding operations to overseas markets. Critical to the success of these service firms is an understanding of the way consumers in foreign markets evaluate their services. Reports the findings of a study that examined and compared the expectations and perceptions of US customers with those of South Korean clients about an international fast‐food chain. Reveals several important differences between the two groups of customers. Discusses the implications of the results for US fast‐food companies in international markets.

Neural-network classifiers for recognizing totally unconstrained handwritten numerals

Abstract: Artificial neural networks have been recognized as a powerful tool for pattern classification problems, but a number of researchers have also suggested that straightforward neural-network approaches to pattern recognition are largely inadequate for difficult problems such as handwritten numeral recognition. In this paper, we present three sophisticated neural-network classifiers to solve complex pattern recognition problems: multiple multilayer perceptron (MLP) classifier, hidden Markov model (HMM)/MLP hybrid classifier, and structure-adaptive self-organizing map (SOM) classifier. In order to verify the superiority of the proposed classifiers, experiments were performed with the unconstrained handwritten numeral database of Concordia University, Montreal, Canada. The three methods have produced 97.35%, 96.55%, and 96.05% of the recognition rates, respectively, which are better than those of several previous methods reported in the literature on the same database.

Retrospective analysis of factors related to clinical outcome of guided tissue regeneration procedures in intrabony defects

Abstract: The purpose of this retrospective study was to determine factors affecting clinical outcome of guided tissue regeneration (GTR) in the treatment of intrabony periodontal defects. 38 patients each contributing 1 isolated intrabony defect treated with GTR were included in this analysis. Patient and defect characteristics, and defect-specific recordings relative to clinical outcome 6 months postsurgery were assessed. GTR treatment resulted in clinically and statistically significant improved probing depths (PD), clinical attachment levels (CAL), and probing bone levels (PBL). Presurgery PD and PBL were of predictive value for CAL gain and PBL gain, respectively. CAL and PBL gain did not correlate to defect depth or configuration. Cigarette smoking exhibited a highly significant negative correlation to parameters of clinical outcome.

Nodular hepatocellular carcinomas: detection with arterial-, portal-, and delayed-phase images at spiral CT

Abstract: PURPOSE: To evaluate the effectiveness of three-phase spiral computed tomography (CT) for the evaluation of nodular hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Images obtained at three-phase spiral CT in 45 patients with 81 nodular HCCs were reviewed. Images were obtained with 10-mm collimation and 10 mm/sec table speed during intravenous administration of 2 mL/kg 68% nonionic contrast material at a rate of 3 mL/sec. Hepatic arterial-phase (AP), portal-phase (PP), and delayed-phase (DP) images were obtained 25-30 seconds, 60-70 seconds, and 300 seconds, respectively, after injection of the contrast material. Lesion detectability and conspicuity were compared among these three protocols by two readers. RESULTS: The AP images depicted a statistically significantly larger number of lesions (n = 67), although the differences in the number of lesions depicted between the PP and DP images were not statistically significant. Twenty-one lesions were detected only with the AP images, three with the PP i...

Aucnet: Electronic Intermediary for Used-Car Transactions

Abstract: Introduction As the advent of nearly ubiquitous information infrastructures promotes the development of electronic commerce applications, new electronic market intermediaries are emerging which bring significant changes in the economics of marketing and distribution channels by interposing themselves between suppliers and consumers in electronic marketplaces (Rayport and Sviokla 1994). On the one hand, these electronic intermediary services can increase efficiency for search, contract formation and trade settlement involved with market transactions (Lee and Clark 1996a). On the other hand, the electronic intermediary services create new transaction risks (Lee 1997a).

Separation of Hydrogen Mixtures by a Two-Bed Pressure Swing Adsorption Process Using Zeolite 5A

Abstract: A study on a two-bed six-step pressure swing adsorption (PSA) process using zeolite 5A was performed experimentally and theoretically for bulk separation of H2/CO and H2/CH4 systems (70/30 vol %) as major components in coke oven gas. When the pressure is cycled between 1 and 11 atm at ambient temperatures, 70% H2 in the feed could be concentrated to 99.99% in the product with a recovery of 75.87% in the H2/CO mixture and 80.38% in the H2/CH4 mixture. The effects of adsorption pressure, P/F ratio, adsorption/purge step time, and pressure equalization step time were investigated experimentally. If the product end of an adsorption bed was not contaminated during the adsorption and depressurizing pressure equalization steps, elongation of both the adsorption and purge steps gave good adsorbent productivity and recovery without any decrease in purity. Certain elongations of step time in the pressure equalization step resulted in a better performance of a PSA process. When the H2 mole fraction of effluent strea...

Relationship between loss of heterozygosity of tumor suppressor genes and histologic differentiation in hepatocellular carcinoma.

Abstract: BACKGROUND Hepatocellular carcinoma (HCC) is one of the most common human tumors in Asia and Africa. The molecular genetic changes involving both protooncogenes and tumor suppressor genes are known to be involved in hepatocarcinogenesis, but the roles of the known tumor suppressor genes in hepatocarcinogenesis are not fully elucidated. In this study, the authors analyzed the loss of heterozygosity (LOH) of known tumor suppressor genes in HCC and evaluated the relationship between LOH of tumor suppressor genes and clinicopathologic features. METHODS The authors assessed the LOH of the 10 known tumor suppressor genes (VHL, APC, EXT1, WT1, Rb1, p53, BRCA1, nm23, DPC4, and DCC) with microsatellite markers in 29 consecutively resected HCC specimens. RESULTS The authors found frequent LOH of tumor suppressor genes in HCC. Twenty five of 29 cases (86%) had LOH of tumor suppressor genes and 17 cases (59%) had LOHs involving 2-4 tumor suppressor genes. Among the tumor suppressor genes, frequent LOH was noted in the p53 (66%), Rb1 (33%), EXT1 (33%), and APC (20%) genes. LOH of the p53 gene and multiple LOH of the tumor suppressor genes were more frequent in poorly differentiated HCCs (P = 0.02). CONCLUSIONS The LOH of tumor suppressor genes is frequent in HCCs and LOH of the p53 gene and accumulated LOHs are related to poorly differentiated HCC. Abnormalities of the p53 gene or the accumulated abnormalities of the tumor suppressor genes may play a role in the aggressive progression of HCC. Cancer 1997; 80:865-72. © 1997 American Cancer Society.

Small arterial-portal venous shunts: a cause of pseudolesions at hepatic imaging.

Abstract: PURPOSE: To compare hepatic angiographic findings of small arterial-portal venous shunts with those of other imaging modalities, and to determine whether these shunts are related to hepatocellular carcinoma. MATERIALS AND METHODS: At hepatic angiography in 223 patients, small arterial-portal venous shunts not directly related to hepatocellular carcinoma and focal areas of parenchymal contrast material enhancement more than 1 cm in diameter were found in 28 patients. These 28 patients were prospectively evaluated with computed tomography (CT) during arterial portography (CTAP) (n = 12), CT after iodized oil administration (n = 23), intraoperative ultrasonography (n = 5), or follow-up hepatic angiography (n = 13). Magnetic resonance (MR) images (n = 10) and dynamic CT scans (n = 4) in these patients were retrospectively reviewed. RESULTS: Arterial-portal venous shunts noted at angiography manifested as perfusion defects at CTAP in 10 patients and as an area of arterial contrast enhancement at dynamic CT in ...

Epitaxial growth of Y2O3 films on Si(100) without an interfacial oxide layer

Abstract: Heteroepitaxial Y2O3 films were grown on Si(100) substrates by the technique of reactive ionized cluster beam deposition. The crystallinity of the films was investigated with reflection high energy electron diffraction (RHEED), glancing angle x-ray diffraction (GXRD), and the interface was examined by high resolution transmission electron microscopy (HRTEM). Under the condition of 5 kV acceleration voltage at the substrate temperature of 800 °C, the Y2O3 film grows epitaxially on the Si(100) substrate. RHEED and GXRD results revealed that the epitaxial relationship between Y2O3 and Si(100) is Y2O3(110)//Si(100), and HRTEM observation showed a sharp interface without an amorphous layer.

Sonographic findings in tuberculous epididymitis and epididymo-orchitis

Abstract: Purpose This paper presents the sonographic findings in scrotums of patients affected with tuberculous epididymitis or epididymo-orchitis. Methods Eighteen patients with a total of 22 abnormal hemiscrotums (4 patients had bilateral lesions) underwent scrotal sonography. Pathologic confirmation was obtained via epididymectomy in 10 cases, epididymo-orchiectomy in 7 cases, and scrotal exploration and biopsy in 3 cases. The histopathologic diagnosis was tuberculous epididymitis in 12 cases and epididymo-orchitis in 8 cases. Results Lesions involved the head of the epididymis in 8 cases, the tail in 5 cases, and the entire epididymis in 9 cases. The enlarged epididymis was hypoechoic in 13 cases, hyperechoic in 2 cases, and of mixed echogenicity in 7 cases. The echotexture was heterogeneous in 17 cases and homogeneous in 5 cases. Testicular involvement in 7 cases appeared as a diffusely enlarged hypoechoic testis in 2 cases, an ill-defined hypoechoic lesion in 1 case, a well-demarcated hypoechoic lesion in 2 cases, and multiple small hypoechoic nodules in an enlarged testis in 2 cases. Hydrocele, sinus tract, and extratesticular calcifications were seen in 12, 4, and 2 cases, respectively. Conclusions The heterogeneous and hypoechoic swelling of the epididymis or the concomitant hypoechoic lesion of the testis with associated sinus tract or extratesticular calcifications may be helpful in the diagnosis of tuberculous epididymitis or epididymo-orchitis, especially in patients with known genitourinary tuberculosis. © 1997 John Wiley & Sons, Inc. J Clin Ultrasound25: 390–394, 1997.

A Study of the Electrochemical Redox Behavior of Electrochemically Precipitated Nickel Hydroxides Using Electrochemical Quartz Crystal Microbalance

Abstract: Nickel hydroxides are an important material with applications in nickel-based batteries, fuel cells, electrolyzers, and electrosynthesis and electrochromic devices. The electrochemical behavior of nickel hydroxides has been studied extensively because of their application in nickel-cadmium and nickel-metal hydride batteries. Electrochemical redox reactions of electrochemically precipitated thin films of nickel hydroxide have been studied by an electrogravimetric method with the aid of electrochemical quartz crystal microbalance. Cyclic voltamassograms show that in alkaline solutions {alpha}-Ni(OH){sub 2} gains mass during its oxidation and loses moss during reduction. The mass change of {alpha}-Ni(OH){sub 2} film is explained by the process of intercalation and deintercalation involving K{sup +} and H{sup +} ions. {beta}-Ni(OH){sub 2} film, on the other hand, shows a mass change behavior completely opposite to that of {alpha}-Ni(OH){sub 2}, losing mass during oxidation and gaining mass during reduction. Its mass change is explained by the intercalation and deintercalation of H{sup +} ions. Phase transformation from {alpha}-Ni(OH){sub 2} to {beta}-Ni(OH){sub 2} is found to proceed with a formation of intermediate phases. The cyclic voltammograms taken during the phase transformation show that the intermediate phases behave as single phases. Cyclic voltamassograms taken simultaneously, however, show that the intermediate phases behave as a microscopic mixture ofmore » {alpha}-Ni(OH){sub 2} and {beta}-Ni(OH){sub 2}.« less

Hypopigmentation in the Prader-Willi syndrome correlates with P gene deletion but not with haplotype of the hemizygous P allele.

Abstract: The Prader-Willi syndrome (PWS) usually results from a paternal deletion of 15q11-q13 or maternal disomy for chromosome 15. Reduced pigmentation of skin, hair, and eyes is common in PWS and was suggested previously to be associated with the 15q11-q13 deletion. The P gene, located in this same region, is associated with OCA2, an autosomal recessive disorder that is the most frequent form of tyrosinase-positive oculocutaneous albinism. We studied 28 individuals with PWS and found that hemizygosity for the P gene was significantly correlated with the occurrence of hypopigmentation among PWS patients. However, we found little or no relationship between the occurrence of hypopigmentation and the polymorphism haplotype of the intact P allele. Thus, our results indicate that hypopigmentation is likely the result of deletion of the P gene in the context of PWS but do not support the linked hypothesis that hypopigmentation results from hemizygosity for variant P alleles with reduced function. Am. J. Med. Genet. 71:57–62, 1997. © 1997 Wiley-Liss, Inc.

High-resolution computed tomography in patients with bronchial asthma: correlation with clinical features, pulmonary functions and bronchial hyperresponsiveness.

Abstract: The high-resolution computed tomography (HRCT) studies for bronchial asthma (BA) have revealed abnormal radiologic findings such as bronchial wall thickening, bronchiectasis, emphysema and mosaic pattern of lung attenuation. But the clinical significance of these findings are not yet clarified. In this study, we quantified the bronchial wall thickness and evaluated HRCT features in 57 BA subjects (338 bronchi) who had precipitating factors of irreversible airway remodeling, 19 COPD subjects (70 bronchi) and 10 healthy subjects (23 bronchi). Then we correlated HRCT findings with the clinical features, pulmonary functions and methacholine PC20 (PC20M) and studied their clinical significance. The bronchial wall for BA was about 1.48 mm thicker than that for COPD and about 2.34 mm thicker than for healthy controls (p < 0.0001, respectively). But the individual mean ratio of bronchial wall thickness to luminal diameter (BWT/LD) in asthmatics did not correlate with the clinical features, lung functions and PC20M. Abnormal HRCT findings, such as bronchiectasis (17.5%), emphysema (5.3%) and mosaic pattern of lung attenuation (17.5%) were found in BA. These findings were more common in BA with moderate to severe airflow limitation (FEV1 < 80%, p < 0.05) and patients with these changes had a more prolonged history of asthma (p < 0.05). PC20M was higher in BA with these abnormal changes (p < 0.001) but these patients' FEV1 (p < 0.05), FEF25-75 (p < 0.05) and specific airway conductance (p < 0.05) were lower than those having BA without such findings. In this study we showed that the bronchial wall was more significantly thickened in BA but that it did not correlate well with the clinical features, lung functions and PC20M. Additionally, patients having BA with abnormal airway and air space HRCT findings had a prolonged history of asthmatic symptoms, loss of lung functions and decreased bronchial hyperresponsiveness. These results suggested the possibility that HRCT can be used for the differentiation of BA from COPD or healthy controls. Furthermore, patients having BA with abnormal HRCT changes demonstrate poor lung function and less hyperreactive bronchi than those without. We concluded that HRCT may be useful for the prognosis and treatment of bronchial asthma cases who have the precipitating factors of irreversible airway remodelling.