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161 result(s) for "Cheng, Po-Wen"
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A passively self‐adjusting floating wind farm layout to increase the annual energy production
Wake losses inside a wind farm occur due to the aerodynamic interactions when a downwind turbine is in the wake of upwind turbines. The ability of floating offshore wind turbines (FOWTs) to relocate their positions in the horizontal plane introduces an opportunity to decrease the wake losses in a floating wind farm (FWF). Our goal is to use this ability to passively move the downwind FOWT out of the wake of upwind ones. Since the mooring system (MS) attached to a FOWT is responsible for its station keeping, the horizontal motions of the FOWT depend on the MS design. Hence, if we can design the MS to passively move the FOWT out of the wake, we can increase the FWF annual energy production (AEP). In this paper, we investigate if we can benefit from relocating FOWTs in a FWF and increase its AEP. In addition, we present a novel approach that considers the ability of a FOWT to relocate its position as a new degree of freedom (DoF) in the FWF layout design. This means we will have a self‐adjusting wind farm layout where the FOWTs passively re‐arrange themselves depending on the wind direction and the wind speed. Consequently, we will have a slightly different wind farm layout for every wind direction and every wind speed. To achieve this layout, we include the MS design as part of the FWF's layout design. In a self‐adjusting FWF layout, each FOWT is attached to a customized MS design allowing it to relocate its position in the best way possible according to the wind direction, to increase the overall AEP of the wind farm. The results of one case study show that the novel approach can increase the FWF's AEP by 1.6% when compared with a current state of the art optimized floating wind farm layout. Finally, we implemented our method as an open‐source python tool to be used and enhanced further within the wind energy community.
Health-related quality of life and utility in head and neck cancer survivors
Background This study seeks to assess quality of life (QOL) and utility scores of head and neck cancer survivors. Methods We compared QOL as indicated by EORTC QLQ-C30, QLQ-H&N35, utility scores by time trade off (TTO) with previous published reference values and tested series characteristics related to global QOL and utility. Results A total of 127 patients were recruited. Of the patients, 102 (80%) completed the utility assessment. Cancer survivors had lower scores compared with norm values. Patients without a spouse had a lower utility than those with a spouse. Patients with a low annual family income also had lower global QOL and utility scores ( p  < 0.05). Other factors were not significantly related to QOL and utility scores. Conclusion Disease and treatment of head and neck cancer lead to disability and poor health-related QOL and utility. Economic status may contribute to health-related QOL and utility, while marital status is related to utility for head and neck cancer patients.
Control design methods for floating wind turbines for optimal disturbance rejection
An analysis of the floating wind turbine as a multi-input-multi-output system investigating the effect of the control inputs on the system outputs is shown. These effects are compared to the ones of the disturbances from wind and waves in order to give insights for the selection of the control layout. The frequencies with the largest impact on the outputs due to limited effect of the controlled variables are identified. Finally, an optimal controller is designed as a benchmark and compared to a conventional PI-controller using only the rotor speed as input. Here, the previously found system properties, especially the difficulties to damp responses to wave excitation, are confirmed and verified through a spectral analysis with realistic environmental conditions. This comparison also assesses the quality of the employed simplified linear simulation model compared to the nonlinear model and shows that such an efficient frequency-domain evaluation for control design is feasible.
A study to quantify surgical plume and survey the efficiency of different local exhaust ventilations
This study aimed to compare the concentration of surgical smoke produced by different tissues and electric diathermy modes and to measure the effectiveness of various local exhaust ventilations. We compared the surgical plume concentration from different tissues and settings with a porcine tissue model. We also compared the efficiency of three local exhaust ventilations: (1) a desktop unit (Medtronic Rapid Vac), (2) a central evacuation system with ENT suction, and (3) a central evacuation system with a urethral catheter (PAHSCO Urethral Catheter). In the cutting setting, the skin tissue had a higher concentration of total suspended particulates (TPS), which were 1990 ± 2000 (mean ± SD, μg/m 3 ), 6440 ± 3000 and 9800 ± 2300 at 15, 30 and 45 s, respectively (p < 0.05). In the coagulation setting, the adipose tissue had a higher concentration of TPS, which were 3330 ± 2600, 11,200 ± 5500 and 15,800 ± 7300, respectively (p < 0.05). We found that all three smoke extractors had more than 96% efficiency in clearing surgical smoke. With electric diathermy, skin tissue in the cutting model and adipose tissue in the coagulation mode will produce higher concentration of particles within surgical plumes. An electric surgical scalpel adapted with a urethral catheter is a simple and effective way to exhaust smoke in surgical operations.
The outcomes and decision-making process for neck lymph nodes with indeterminate fine-needle aspiration cytology
This study aims to propose a cytological classification, to evaluate predictive factors of the final malignancy, and to suggest a proper management strategy for neck lymph nodes (LNs) with indeterminate cytology. Patients who had neck lymphadenopathy with indeterminate cytology between 2007 and 2017 were analyzed retrospectively in a tertiary medical center. Cytological classification was conducted according to the cytological descriptions. We examined the clinical characteristics according to the final diagnosis of the neck lymphadenopathy. According to the final diagnoses, there were 142 malignant and 95 benign neck LNs among 237 patients. Multivariate analyses using a stepwise logistic regression model showed that cytological classification [p < 0.001, OR = 5.67 (3.48-9.23)], prior history of malignancy [p = 0.01, OR = 2.97 (1.26-6.99)], long axis [p = 0.01, OR = 3.06 (1.33-7.06)], short-to-long axis (S/L) ratio [p = 0.047, OR = 2.15 (1.01-4.57)] and internal echogenicity [p = 0.01, OR = 2.72 (1.26-5.86)] were independent predictors of malignancy. In patients who have neck LNs with indeterminate cytology, a cytological classification and four other predictors (prior history of malignancy, long axis ≥ 1.93 cm, S/L ratio ≥ 0.64 and heterogeneity of internal echogenicity) are statistically associated with the risk of malignancy and helpful in guiding further management.
Evaluation of control methods for floating offshore wind turbines
The challenge of controlling floating offshore wind turbines arises due to the soft support structures and complex environmental excitations. Reducing the generator speed and power fluctuation, damping the motions of the floating platform and alleviating the fatigue loads at the tower base have been investigated in recent projects. This paper reviews and summarizes a selection of methodologies that have been discussed over the past years. These methods are then evaluated on the TELWIND-5MW-FOWT. First, linear analysis of the closed-loop with different control approaches is performed. Next, coupled aero-hydro-servo-elastic simulations with Bladed are carried out and evaluated. The motions and loads with different control approaches will be compared, advantages and limitations of each method will also be discussed.
Incorporation of shear wave elastography into a prediction model in the assessment of cervical lymph nodes
To assess the performance of shear wave elastography (SWE) and an extended model in predicting malignant cervical lymph nodes (LNs). 109 patients who underwent ultrasound (US) and SWE before needle biopsy were enrolled. The optimal cutoff value of elasticity indices (EIs) was determined by receiver operating characteristic (ROC) curves. The c-statistic, net reclassification improvement (NRI) and integrated discrimination improvement (IDI) were used to compare extended model and traditional one. Malignant LNs had higher EIs than benign nodes (p < 0.001). The optimal cutoff point was 42 kilopascal, corresponding to 83.3% sensitivity, 64.7% specificity, and 68.8% overall accuracy. A multivariable logistic regression analysis confirmed that EI was an independent predictor for malignancy. The new extended prediction model had a positive NRI (0.96) and IDI (0.10) for predicting malignant neck LNs. Nevertheless, the c-statistic was not significantly different between the two models. The parameter of SWE theoretically improve the model performance. However, its real clinical impact is minor, as the parameters of US-based model is already very robust. SWE can be considered as an adjunctive quantitative tool beyond conventional US examination.
A predictive model for advanced oropharyngeal cancer patients treated with chemoradiation
Background To analyze clinical characteristics in the prediction of death within 1 year in advanced oropharyngeal cancer patients treated with chemoradiation. Methods One hundred forty-seven advanced oropharyngeal cancer patients who underwent curative-intent chemoradiation treatment were retrospectively enrolled. The pre-treatment clinical parameters including inflammatory markers were reviewed. Results The 1-year death rate for all patients was 29% [95% confidence interval (CI): 23–37%]. In multivariate logistic regression analysis, hemoglobulin (Hb) < 13.5 g/dl was an independent indicator of death within 1-year [Odds ratio (OR) 5.85, 95% CI 2.17–15.75, p  < 0.001]. Systemic immune inflammation (SII) ≥ 1820 was also a significant factor for prediction of death within 1 year (OR 4.78, 95% CI 1.44–15.85, p  = 0.011). We further used gander, age, Hb and SII to develop a nomogram to predict death within 1 year. The c-index of the model was 0.75 (95%CI 0.66–0.83). For patients with low nomogram score (< 14) versus high nomogram score (≥ 14), the 1-year and 2-year OS rates were 91 and 71% versus 53 and 29%, respectively. ( p  < 0.001). A difference in the disease persistence or recurrence rate between patients with high and low nomogram score was significant (73 and 28%, respectively; p  < 0.001). Conclusions The pre-treatment Hb < 13.5 g/dl and SII ≥ 1820 are associated with higher risks of death within 1-year in patients with advanced oropharyngeal cancers. Nomogram can aid in patient counseling and treatment modality adjustment. The development of a more effective treatment protocol for patients with high nomogram score will be essential.
ANDroMeDA - A Novel Flying Wind Measurement System
A noval multirotor aircraft was developed at the University of Stuttgart, designed especially for wind speed measurements. Currently the aircraft is equipped with a combined Prandtl / triple hot wire probe but in general the design is modular. The measurement performance of the overall system is validated and compared to conventional measurement techniques. Methods of validation are a free flight in calm air, wind tunnel tests and a hovering flight next to a met mast. It could be shown that the measurements show a good agreement between 4 m/s and 13 m/s. The maximum wind speed that can be measured could be determined to 25 m/s by extrapolation of the flight envelope but has to be confirmed in the future.
Voice Therapy for Benign Voice Disorders in the Elderly: A Randomized Controlled Trial Comparing Telepractice and Conventional Face-to-Face Therapy
Purpose: Previous studies have reported that voice therapy via telepractice is useful for patients with nodules and muscle tension dysphonia. Nevertheless, telepractice for elderly patients with voice disorders has not yet been investigated. We conducted this study to examine the hypothesis that voice therapy via telepractice is not inferior to conventional voice therapy. Method: Eighty patients with dysphonia aged more than 55 years participated in this study from September 2016 to June 2018. After screening the inclusion and the exclusion criteria, 69 patients were randomized into telepractice (33 patients) and conventional (36 patients) groups. The outcome measurements included Voice Handicap Index-10, videolaryngostroboscopy, maximum phonation time, auditory-perceptual evaluation, and acoustic analysis. Paired \"t\" test, Wilcoxon signed-ranks test, and repeated measures analysis of variance were used to examine treatment outcomes. Results: The diagnoses of voice disorders included atrophy (n = 33), unilateral vocal paralysis (n = 13), muscle tension dysphonia (n = 7), nodules (n = 6), and polyps (n = 10). No significant differences were observed in age, sex, and baseline measurements between the two groups. Twenty-five patients in the telepractice group and 24 patients in the control group completed at least four weekly sessions. Significant improvements were observed for all the outcome measures (p < 0.05) in both groups. Improvements in Voice Handicap Index-10 in the telepractice group (24.84 ± 5.49 to 16.80 ± 8.94) were comparable to those in the conventional group (22.17 ± 7.29 to 13.46 ± 9.95, p = 0.764). Other parameters also showed comparable improvements between the two groups without statistically significant differences. Conclusions: This is the first randomized controlled trial comparing telepractice and conventional voice therapy in elderly patients with voice disorders. The results showed that the effectiveness of voice therapy via telepractice was not inferior to that of conventional voice therapy, indicating that telepractice can be used as an alternative to provide voice care for elderly patients with vocal disorders.