DETERMINATION OF LINEAR AND NONLINEAR ROLL DAMPING COEFFICIENTS OF A SHIP SECTION USING CFD

The most prevalently used method to obtain the nonlinear roll damping coefficient is the free roll decay test. However, this method can only be conducted at the resonance frequency and thus cannot consider the effect of the frequency. This is a certain limitation as the resonance frequency can be changed at any time by the ship’s loading conditions. Therefore, it is worth investigating the frequency dependency of the nonlinear roll damping coefficients. In this study, a numerical method was proposed to derive the linear and nonlinear roll damping coefficients of ships at different frequencies. Fully nonlinear CFD simulations of forced harmonic roll motion were conducted and the roll damping coefficients were calculated. Then, the damping coefficients were decomposed into the linear and nonlinear components using the linear regression analysis. The linear roll damping coefficients were compared with potential coefficients and showed a good agreement, while the nonlinear roll damping coefficients were compared with the coefficients calculated using a semi-empirical method. The nonlinear roll damping coefficients calculated from the proposed method showed a strong frequency dependency. Finally, possible rationales for the frequency dependence of the nonlinear roll damping coefficient were investigated

A NUMERICAL STUDY ON THE OPEN WATER PERFORMANCE OF A PROPELLER WITH SINUSOIDAL PITCH MOTION

When a ship operates in waves, the ship moves with 6 degrees-of-freedom, and a propeller at the stern of the ship cannot avoid moving due to the ship motion. Therefore, it is important to analyse the propulsion performance while considering the ship motion in waves for efficient ship operation. The pitch motion of the ship has a dominant effect on the variation of the propeller performance and results in sinusoidal pitch motion of the propeller. In this study, a numerical analysis was done using a KP458 model propeller with a diameter of 10 cm, which was designed for the KLVCC2 body plan. The propeller performance was calculated using computational fluid dynamics (CFD) at several constant tilt angles. Numerical simulations were then conducted with sinusoidal pitch motion in several conditions of varying pitch angle. The variations of the thrust and torque of the propeller in sinusoidal pitch motion were compared with the results obtained in constant tilt angles

A STUDY ON THE SENSITIVITY ANALYSIS OF THE HYDRODYNAMIC DERIVATIVES ON THE MANEUVERABILITY OF KVLCC2 IN SHALLOW WATER

To assess the manoeuvrability of ships in shallow water at the early design stage, reliable simulation models which present shallow water effect are required. However, studies on the manoeuvrability of ship at low speeds in shallow water have been performed less than manoeuvrability in deep water. Also, the limitation of model that the effects of the keel clearance on manoeuvrability are applied to has been validated through previous studies. In this study, the manoeuvrability characteristics of the ship sailing in shallow water at low speed are evaluated by applying the mathematical model considering the shallow water effect. And the sensitivity analysis on shallow water manoeuvring simulation is performed in order to determine hydrodynamic derivatives which are necessary to be derived exactly due to the limitation of the shallow water model used in previous studies. Through this study, it could be confirmed that great importance of estimation of manoeuvrability could be found through the sensitivity index factor of hydrodynamic derivatives changing in the situation operating the shallow water at low speed

Treatment of Keratoacanthoma with 5% Imiquimod Cream and Review of the Previous Report

Keratoacanthoma (KA) is a benign epidermal tumor, characterized by rapid and abundant growth, a tendency toward spontaneous regression and histopathologic similarity to squamous cell carcinoma (SCC). Because KA can be easily misdiagnosed as SCC, surgery is considered the treatment of choice. Recently, regression of KAs following application of 5% imiquimod cream (Aldara®) has been reported. We present 4 cases of KA treated with topical imiquimod, applied 3 to 4 times a week. Obvious improvement was observed after 4 to 6 weeks of application and the lesions were almost cleared leaving scars after 9 to 11 weeks. These results show that topical imiquimod can be an effective option for the conservative management of KA as previously reported. We also suggest that lesions treated with imiquimod cream should be considered for biopsy to judge histopathological remission after 5 to 8 weeks of application to shorten the duration of the treatment

Clinical significance and predictive factors of early massive recurrence after radiofrequency ablation in patients with a single small hepatocellular carcinoma

Background/Aims Radiofrequency ablation (RFA) is one of the most frequently applied curative treatments in patients with a single small hepatocellular carcinoma (HCC). However, the clinical significance of and risk factors for early massive recurrence after RFA—a dreadful event limiting further curative treatment—have not been fully evaluated. Methods In total, 438 patients with a single HCC of size ≤3 cm who underwent percutaneous RFA as an initial treatment between 2006 and 2009 were included. Baseline patient characteristics, overall survival, predictive factors, and recurrence after RFA were evaluated. In addition, the incidence, impact on survival, and predictive factors of early massive recurrence, and initial recurrence beyond the Milan criteria within 2 years were also investigated. Results During the median follow-up of 68.4 months, recurrent HCC was confirmed in 302 (68.9%) patients, with early massive recurrence in 27 patients (6.2%). The 1-, 3-, and 5-year overall survival rates were 95.4%, 84.7%, and 81.8%, respectively, in patients with no recurrence, 99.6%, 86.4%, and 70.1% in patients with recurrence within the Milan criteria or late recurrence, and 92.6%, 46.5%, and 0.05% in patients with early massive recurrence. Multivariable analysis identified older age, Child-Pugh score B or C, and early massive recurrence as predictive of poor overall survival. A tumor size of ≥2 cm and tumor location adjacent to the colon were independent risk factors predictive of early massive recurrence. Conclusions Early massive recurrence is independently predictive of poor overall survival after RFA in patients with a single small HCC. Tumors sized ≥2 cm and located adjacent to the colon appear to be independent risk factors for early massive recurrence

Association between glycemic status and the risk of acute pancreatitis: a nationwide population-based study

Background Although diabetes is reportedly associated with the occurrence of acute pancreatitis (AP), the risk of AP according to the duration and severity of diabetes is not yet clear. We aimed to investigate the risk of AP based on glycemic status and the presence of comorbidities using a nationwide population-based study. Methods We enrolled 3,912,496 adults who underwent health examinations under the National Health Insurance Service in 2009. All participants were categorized by glycemic status as normoglycemic, impaired fasting glucose (IFG), or diabetes. Baseline characteristics and the presence of comorbidities at the time of health check-up were investigated, and the occurrence of AP was followed up until 31 December 2018. We estimated the adjusted hazard ratios (aHRs) for AP occurrence according to the glycemic status, duration of diabetes (new-onset, duration < 5 years, or ≥ 5 years), type and number of anti-diabetic medications, and presence of comorbidities. Results During the observation period of 32,116,716.93 person-years, 8,933 cases of AP occurred. Compared with normoglycemia, the aHRs (95% confidence interval) were 1.153 (1.097–1.212) in IFG, 1.389 (1.260–1.531) in new-onset diabetes, 1.634 (1.496–1.785) in known diabetes < 5 years, and 1.656 (1.513–1.813) in patients with known diabetes aged ≥ 5 years. The presence of comorbidities associated with diabetes severity had a synergistic effect on the relationship between diabetes and AP occurrence. Conclusion As glycemic status worsens, the risk of AP increases, and there is a synergistic effect when comorbidities coexist. To reduce the risk of AP, active control of factors that can cause AP should be considered in patients with long-standing diabetes and comorbidities

Transarterial chemoembolization versus resection for intermediate-stage (BCLC B) hepatocellular carcinoma

Background/Aims: Several studies have suggested that surgical resection (SR) can provide a survival benefit over transarterial chemoembolization (TACE) for hepatocellular carcinoma (HCC) at the intermediate stage according to the Barcelona Clinic Liver Cancer (BCLC) staging system. However, the criteria for SR remain to be determined. This study compared the long-term outcome of intermediate-stage HCC patients treated by either TACE or SR as a primary treatment modality, with the aim of identifying the patient subgroup that gained a survival benefit by either modality. Methods: In total, 277 BCLC intermediate-stage HCC patients treated by either TACE (N=225) or SR (N=52) were analyzed. Results: The overall median survival time was significantly better for SR than TACE (61 vs. 30 months, P=0.002). Decision-tree analysis divided patients into seven nodes based on tumor size and number, serum alpha-fetoprotein (AFP) level, and Child-Pugh score, and these were then simplified into four subgroups (B1–B4) based on similarities in the overall hazard rate. SR provided a significant survival benefit in subgroup B2, characterized by ‘oligo’ (2–4) nodules of intermediate size (5–10 cm) when the AFP levels was <400 ng/ml, or ‘oligo’ (2–4) nodules of small to intermediate size (<10 cm) plus a Child-Pugh score of 5 when the AFP level was ≥400 ng/mL (median survival 73 vs. 28 months for SR vs. TACE respectively; P=0.014). The survival rate did not differ significantly between SR and TACE in the other subgroups (B1 and B3). Conclusion: SR provided a survival benefit over TACE in intermediate-stage HCC, especially for patients meeting certain criteria. Re-establishing the criteria for optimal treatment modalities in this stage of HCC is needed to improve survival rates

Assessment of the Efficacy of Reducing Peginterferon Alfa-2a and Ribavirin Dose on Virologic Response in Koreans with Chronic Hepatitis C

BACKGROUND/AIMS: The virologic response of Koreans to combination therapy for chronic hepatitis C is similar to westerns; however, dose modification occurs more frequently in Koreans. We evaluated the rates of peginterferon alpha-2a and ribavirin dose modifications and their effect on the virologic response in Koreans. METHODS: Patients with detectable HCV RNA and enrolled from multicenters were treated with peginterferon alpha-2a (180 microgram/week) and ribavirin (800 mg/day) for 24 weeks (genotype non-1, n=37) or peginterferon alpha-2a (180 microgram/week) and ribavirin (1,000-1,200 mg/day) for 48 weeks (genotype 1, n=55). RESULTS: Early virologic response (EVR) and sustained virologic response (SVR) were 77.2% (genotype 1, 75%; non-1, 81%) and 66.3% (genotype 1, 56%; non-1, 81%), respectively. The frequency of dose modification was 32.6% within the first 12 weeks and 52.2% during the entire treatment period. No difference was found in SVR regardless of dose modification. However, the SVR for patients using > or =80% of the peginterferon dose was significantly higher than for those using <80% (81.3 vs. 50.0%, p=0.007), despite varying ribavirin doses. No difference was found in SVR regardless of whether the ribavirin dose was <80% or not. These results did not change based on genotype. CONCLUSIONS: We suggest that using at least 80% of the peginterferon alpha-2a dose in Koreans not only maintains SVR but also reduces drug side effects during the entire treatment period. A lower dose of ribavirin may be as efficacious as a standard doseope

Static and dynamic prognostic factors for hepatitis-B-related acute-on-chronic liver failure

Background/AimsHepatitis-B-related acute-on-chronic liver failure has a poor prognosis. However, the advent of potent oral antiviral agents means that some patients can now recover with medical treatment. We aimed to identify the prognostic factors for hepatitis-B-related acute-on-chronic liver failure including the initial as well as the dynamically changing clinical parameters during admission.MethodsSixty-seven patients were retrospectively enrolled from 2003 to 2012 at Samsung Medical Center. The patients were classified into three categories: Recovery group (n=23), Liver transplantation group (n=28), and Death group (n=16). The Liver transplantation and Death groups were combined into an Unfavorable prognosis group. We analyzed the prognostic factors including the Model for End-Stage Liver Disease (MELD) scores determined at 3-day intervals.ResultsA multivariable analysis showed that the unfavorable prognostic factors were a high initial MELD score (≥28) (odds ratio [OR] =6.64, p=0.015), moderate-to-severe ascites at admission (OR=6.71, P=0.012), and the aggravation of hepatic encephalopathy during hospitalization (≥grade III) (OR=15.41, P=0.013). Compared with the baseline level, significant reductions in the MELD scores were observed on the 7th day after admission in the Recovery group (P=0.016).ConclusionsDynamic changes in clinical parameters during admission are useful prognostic factors for hepatitis-B-related acute-on-chronic liver failure

Prognostic Value of Immunohistochemical Staining of p53, bcl-2, and Ki-67 in Small Cell Lung Cancer

Small cell lung cancer (SCLC) is one of the most fatal cancers in humans and many factors are known to be related to its poor prognosis. Immunohistochemical (IHC) stainings were done on SCLC specimens in order to investigate the prognostic value of the apoptosis-related gene expression and the tumor proliferative maker, and the relationships among these IHC results and patients clinical characteristics, chemoresponsiveness, and survival were analyzed. The medical records of 107 patients were reviewed retrospectively. IHC stainings for p53, bcl-2 and Ki-67 expressions were performed in the 66 paraffin-embedded biopsy samples. Sixty-six out of the 107 patients were evaluable for response rate and survival. The overall response rate was 75% (95% Confidence Interval=74-76%) and the median survival time was 14 months. The median survival time of limited stage was 16 months and that of extensive stage was 10 months. The prevalence of p53, bcl-2 and Ki-67 expression was 62%, 70%, and 49%, respectively. There were no correlations among the immunoreactivities of p53, bcl-2 and Ki-67 with clinical stage, chemoresponsiveness or overall survival. The clinical stage was the only prognostic factor influencing survival. The expression rates of p53, bcl-2, and Ki-67 were relatively high in SCLC without any prognostic significance. The exact clinical role of these markers should be defined through further investigations