The role of renewable energy sources in the Polish power system is growing. The highest share of installed capacity goes to wind and solar energy. Both sources are characterized by high variability ...of their power output and very low dispatchability. Taking into account the nature of the power system, it is, therefore, imperative to predict their future energy generation to economically schedule the use of conventional generators. Considering the above, this paper examines the possibility to predict day-ahead wind power based on different machine learning methods not for a specific wind farm but at national level. A numerical weather prediction model used operationally in the Institute of Meteorology and Water Management–National Research Institute in Poland and hourly data of recorded wind power generation in Poland were used for forecasting models creation and testing. With the best method, the Extreme Gradient Boosting, and two years of training (2018–2019), the day-ahead, hourly wind power generation in Poland in 2020 was predicted with 26.7% mean absolute percentage error and 4.5% root mean square error accuracy. Seasonal and daily differences in predicted error were found, showing high mean absolute percentage error in summer and during daytime.
Elementem meteorologicznym bardzo istotnym z punktu widzenia mieszkańców miast jest wiatr, wpływający m.in. na temperaturę odczuwalną, zasięg miejskiej wyspy ciepła czy stężenie zanieczyszczeń w ...atmosferze. Na podstawie badań przeprowadzonych w Toruniu w 2012 roku stwierdzono duże deformacje kierunku oraz zmniejszenie prędkości wiatru w stosunku do terenów podmiejskich. Najmniejsze średnie prędkości wiatru odnotowano na terenach leśnych (0,2 m·s–1 ) oraz parkowych (0,6 m·s–1 ), a największe wystąpiły na obszarze o zabudowie wielorodzinnej (1,1 m·s–1 ). Analizie poddano również modyfi kacje kierunków wiatru. Największe wystąpiły na obszarze leśnym, a najmniejsze na obszarze o zabudowie zróżnicowanej.
To evaluate fetal heart anatomy in the late first and in the early second trimester.
The study included 75 fetuses between 11 and 19 weeks' gestation. Exams were performed using transabdominal or ...transvaginal probes.
The proportion of cases successfully visualized to all cases in particular week of pregnancy was following: 11 week--0/1 (0%), 12--1/1 (100%), 13 week--1/1 (100%), 14--18/23 (79%), 15--6/9 (67%), 16--23/27 (86%), 17--4/5 (80%), 18--6/6 (100%), 19--2/2 (100%). In 11 weeks' gestation two ventricles and two atrias could be imaged. Anatomy was seen from 12 weeks' gestation with transvaginal and from 13 weeks' gestation with transabdominal transducers. Two tricuspid regurgitations were detected. The interventricular septum was the most difficult structure to visualize in all cases. The grey scale alone was not sufficient for accurate examination of the heart and it was necessary to use colour Doppler to confirm normal forward flow to both ventricles and to identify outflow tracts.
1. Successful visualization of the heart in early pregnancy is possible from 12 weeks' gestation with transvaginal and from 13 weeks' gestation with transabdominal probe. 2. Fetal echocardiography between first and second trimester should lead to better understanding of fetal hemodynamics in normal and abnormal fetuses and help to introduce new therapeutic treatment in some cases.
Total knee arthroplasty (TKA) is widely accepted method for treatment of severe osteoarthritis. The aim of this paper was to retrospectively review patients operated in our institution with total ...condylar knee arthroplasty due to osteoarthritis and assess clinical and radiological results of this procedure. All patients treated with TKA between 1998 and 2001 were reviewed, those with diagnosis of rheumatoid arthritis were excluded from the study. One hundred and one TKA in 68 patients were studied. WOMAC protocol and KSS (Knee Society Score) were used to evaluate patients clinically, and KSS alone for radiological analysis. Bone-implant interface has been studied, position of the implants and mechanical axis of the limb both pre- and postoperatively. Excellent and good results were achieved in 89% of TKA. Subjective self-assessment was usually worse than objective one. Radiolucency was found in 16 cases (more often around tibial component than the femoral one), usually without clinical symptoms of the loosening. An accurate alignment within the range of 3 to 9 degrees valgus has been found in 68% of the knees. Subjective scores were worse than objective clinical assessment. The clinical score was higher than radiological one. The tendency to varus tibial implant fixation was observed. Suboptimal implantation has not led to implant loosening in mid-term results.
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