Multiphase pumps are core equipment for offshore plant industry. They are utilized in diverse areas. According to a report about the tendency of multiphase pumps for offshore plant, a helico-axial pump is the most preferred. A helico-axial pump with advanced technologies is widely known to have large handling capacity and operability even at high GVF ranges. However, its disadvantage is that its mechanical efficiency is lower than other multiphase pumps. Because of this, a numerical optimization was performed in this study to enhance the hydraulic performance of multiphase pumps. Before numerical optimization, reliability verification of numerical analysis for single-phase and multiphase flow was carried out. To perform a single objective optimization for high efficiency, design variables and ranges were selected. The single objective optimization was conducted for both impeller and diffuser. The objective function was evaluated at design points using Latin-hypercube sampling, one experiment technique, in design ranges. The performance of the experiment sets was evaluated using advanced computational fluid dynamics. After that, the response surface of a second-order polynomial function which was produced based on the performance evaluation results was used to find the optimal point. The results showed remarkable increases in a higher performance level than the base model. The reason for performance improvement was analyzed through comparison of the internal flow field. Additionally, numerical results were compared to results of performance evaluation through experiment.
This research aimed to systematically maximize hydraulic efficiency and suction specific speed for mixed-flow pump using a commercial CFD packages and optimization tool. First, mixed-flow pump was initially designed according to the traditional design method, and then the blade shape was redesigned by focusing on the hydraulic efficiency. Second, the efficiency-oriented optimum design was selected as the reference model. The objective was to improve the suction specific speed under the specific condition of the mixed-flow pump through the multi-objective optimization technique. The incidence angles and meridional plane were optimized through a systematic optimization process, namely, central composite method and response surface approximation. The optimization results indicated that the suction specific speed values of the reference and optimum model were 88.13 and 289.65, respectively. Furthermore, the hydraulic efficiency was kept within ± 1% compared to the reference model as the constraint condition. The hydraulic efficiency of the reference and optimum model were 91.44% and 90.40%, respectively. The reasons for the improved efficiency and suction performance were investigated through internal flow field analysis. Finally, the reliability of the optimization was demonstrated by comparing the numerical and experimental results. ARTICLE HISTORY
A 58-year-old female presented with ocular pain and decreased visual acuity in both eye. She had received periocular acupuncture therapy 4 days earlier. Dilated fundoscopy revealed vitreous hemorrhage. B-scan ultrasonography revealed vitreous opacity. Thus, at the request of the patient, vitrectomy was performed in only the right eye, and did not performed in the left eye. Intraoperatively, we identified retinal laceration in the temporal and inferior retina. In the left eye, the sites of retinal hemorrhage were observed in the temporal and inferior retina in the fundus examination, and a barrier laser photocoagulation was performed around the lesion. At the three-month postoperative follow-up, the patient's visual acuity was 0.5 in the right eye without macular edema. In the left eye, visual acuity was 0.01 with macular edema observed on optical coherence tomography. Conclusions: Authors present a case of a patient with vitreous hemorrhage and ocular perforations caused by periocular acupuncture therapy in both eye, able to compare the results of eyes that performed vitrectomy and that did not performed vitrectomy in a same patient. The recovery of visual acuity in eye that performed vitrectomy was better than eye that did not performed vitrectomy. Therefore, we consider performing vitrectomy in patients with eye perforation.
ObjectiveCytomegaloviruses (CMV) can have a significant impact on the prognosis of immunocompromised patients. Unlike in the transplantation and AIDS fields, only a few studies on CMV infections have been published in the field of autoimmunity. In this study, we examined the clinical outcomes of CMV infections in patients with autoimmune diseases at a single tertiary medical institution.MethodsA retrospective study was performed to identify the mortality risk factors associated with CMV infections in patients with autoimmune diseases. We reviewed the medical records of patients with autoimmune diseases who were diagnosed with CMV infections using real-time quantitative polymerase chain reaction between December 2005 and March 2016. Clinical and laboratory parameters as well as treatment outcomes were analyzed.ResultsSeventy-three CMV infected patients were separated into survivors and non-survivors. Non-survivors had significantly higher median CMV-DNA copy numbers than survivors (95,500 vs 6,700 copies/mL, p = 0.005) and demonstrated significantly more frequent incidents of CMV pneumonitis (69.2 vs 36.2%, p = 0.007). After adjusting for multiple confounding covariates, the log CMV-DNA copies/mL (hazard ratio, 1.48; 95% confidence interval, 1.14–1.92; p = 0.003) and the presence of concurrent infections (hazard ratio, 22.00; 95% confidence interval, 2.75–175.97, p = 0.004) were identified as independent mortality risk factors. Furthermore, patients with high CMV copy numbers (> 60,000 copies/mL) had higher in-hospital mortality than those with low CMV copy numbers (p < 0.05).ConclusionsCMV-DNA copy numbers and concurrent infections are predictors of in-hospital mortality in CMV-infected patients with autoimmune diseases. Therefore, serial measurements of CMV-DNA copy numbers and close observation for signs of other infections are recommended for patients with autoimmune diseases who have concurrent CMV infection.
ObjectivesNew methods for obtaining appropriate information for users have been attempted with the development of information technology and the Internet. Among such methods, the demand for systems and services that can improve patient satisfaction has increased in hospital care environments.MethodsIn this paper, we proposed the Hospital Exam Reservation System (HERS), which uses the data mining method. First, we focused on carrying clinical exam data and finding the optimal schedule for generating rules using the multi-examination pattern-mining algorithm. Then, HERS was applied by a rule master and recommending system with an exam log. Finally, HERS was designed as a user-friendly interface.ResultsHERS has been applied at the National Cancer Center in Korea since June 2014. As the number of scheduled exams increased, the time required to schedule more than a single condition decreased (from 398.67% to 168.67% and from 448.49% to 188.49%; p < 0.0001). As the number of tests increased, the difference between HERS and non-HERS increased (from 0.18 days to 0.81 days).ConclusionsIt was possible to expand the efficiency of HERS studies using mining technology in not only exam reservations, but also the medical environment. The proposed system based on doctor prescription removes exams that were not executed in order to improve recommendation accuracy. In addition, we expect HERS to become an effective system in various medical environments.
Owing to the exhaustion of onshore resources, the development of resources has been expanded to the deep subsea. As the necessity of offshore plants is steadily increasing, there is an increasing interest in studying multiphase transportation technology. Multiphase pumps differ from single phase pumps in many ways, including performance evaluation, internal flow characteristics, and complex design methods. The primary issue of multiphase flow transport technology is that the characteristics of the internal flow change according to the gas volume fraction (GVF). Many theoretical and experimental analyses have been conducted to understand the mechanism of the internal flow field in multiphase pumps. As advanced computational fluid dynamics (CFD) based on the three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations have become reliable tools, numerical analyses accompanied by experimental research have been applied to investigate the hydraulic performance and internal flow field of multiphase pumps. A number of studies have been conducted to investigate these phenomena. However, the understanding of the detailed mechanisms of phase separation and the forces that occur in the internal flow is not completely clear. This study aimed to establish a multiphase flow analysis method with high reliability when the internal flow of the multiphase pump is bubbly flow. To ensure the reliability of the numerical analysis, the numerical results were compared with the experimental data. Additionally, to analyze the detailed dynamic flow phenomena in the multiphase pump, the effects of various interphase forces acting between the liquid and gas phase and the particle diameter of the gas phase on the hydraulic performance were investigated.
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