Wyniki wyszukiwania - Biblioteka Nauki

1

Analysis of parameters for determining power output of rail traction vehicles

100%

Sikory J.

Logistyka

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2007

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tom nr 3

CD-CD

EN

This contribution focuses on the characteristics of common patterns of demand specifications for rail traction vehicles operating at industrial locations; followed by the analysis of track conditions on routes given by the operator and the analysis of trains travelling at low speed. In conclusion, the paper gives a graphical representation of the parameters that have been designed for determining the power demand from the diesel engine in the rail traction vehicle.

2

Differences in Force-Velocity Characteristics of Upper and Lower Limbs of Male Kickboxers

100%

Nikolaïdis P. , Fragkiadiakis G. , Papadopoulos V. , Karydis N.

Baltic Journal of Health and Physical Activity

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2011

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tom 3

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nr 3

147-153

EN

Background: Despite the increasing popularity of kickboxing, few studies have been conducted with regard to the physiology or the biomechanics of this sport. The aim of the present study is to examine the ratios of mechanical characteristics between upper and lower limbs of male kickboxers.Material/Methods: Fourteen male Caucasians, all members of recreational sport clubs, aged 21.77 (5.19) yr [mean (standard deviation)], body height 1.78 (0.067) m, body mass 75.4 (8.9) kg, body fat 14 (5) % and somatotype 3.5-4.9-2.3, performed the Force-velocity (F-v) test for both upper and lower extremities. The F-v test included five supramaximal pedal sprints, each lasting 7 sec, against incremental braking force (20-60 N for upper limbs and 30-70 N for lower limbs), on modified arm-cranking and on a cycle ergometer (Ergomedics 874, Monark, Sweden).Results: Maximal anaerobic power, Pmax, of upper limbs was associated with Pmax of lower limbs (r = 0.81, P < 0.001) and their ratio was 0.464 (0.079). The respective values of correlation coefficients of the theoretical maximal force, F0, were r = 0.63 (P < 0.05) and 0.57 (0.133), and of velocity, v0, r = 0.44 (P = 0.12) and 0.829 (0.095).Conclusions: In spite of moderate correlations between upper and lower limbs' F0 and v0, a stronger relationship was found with regard to Pmax. Separate upper and lower extremities' power output measures would be useful in evaluating training programs and in understanding the importance of power output for kickboxing performance.

3

Mechanical, Hormonal and Psychological Effects of a Non-Failure Short-Term Strength Training Program in Young Tennis Players

88%

Sarabia J. M. , Fernandez-Fernandez J. , Juan-Recio C. , Hernández-Davó H. , Urbán T. , Moya M.

Journal of Human Kinetics

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2015

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tom 45

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nr 1

81-91

EN

This study examined the effects of a 6-week non-failure strength training program in youth tennis players. Twenty tennis players (age: 15.0 ± 1 years, body height: 170.9 ± 5.1 cm, body mass: 63.3 ± 9.1 kg) were divided into experimental and control groups. Pre and post-tests included half squats, bench press, squat jumps, countermovementjumps and side-ball throws. Salivary cortisol samples were collected, and the Profile of Mood States questionnaire was used weekly during an anatomical adaptation period, a main training period and after a tapering week. The results showed that, after the main training period, the experimental group significantly improved (p<0.05) in mean and peak power output and in the total number of repetitions during the half-squat endurance test; mean force, power and velocity in the half-squat power output test; Profile of Mood States (in total mood disturbance between the last week of the mean training period and the tapering week); and in squat-jump and countermovement-jump height. Moreover, significant differences were found between the groups at the post-tests in the total number of repetitions, mean and peak power during the half-squat endurance test, mean velocity in the half-squat power output test, salivary cortisol concentration (baselines, first and third week of the mean training period) and in the Profile of Mood States (in fatigue subscale: first and third week of the mean training period). In conclusion, a non-failure strength training protocol improved lower-limb performance levels and produced a moderate psychophysiological impact in youth elite tennis players, suggesting that it is a suitable program to improve strength. Such training protocols do not increase the total training load of tennis players and may be recommended to improve strength.

4

Jumping Abilities and Power-Velocity Relationship in Judo Athletes: Comparative Analysis Among Age Categories

88%

Buśko K.

Human Movement

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2015

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tom 16

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nr 2

78-82

EN

Purpose. The aim of the study was to examine age differences in the maximal power and height of rise of the body mass centre measured in spike jump (SPJ) and counter-movement jump (CMJ), and power-velocity relationship of lower extremities between cadet and U23 age class judo athletes. Methods. Seven cadets (age 16.6 ± 0.7 years) and eight U23 age class (21.3 ± 1.4 years) Polish judoists took part in the study. The maximal power and height of jump were measured at SPJ and CMJ jumps. Power- velocity relations (P-v) were determined from 5 maximal cycle ergometer exercise bouts at increasing external loads equal to 2.5, 5.0, 7.5, 10.0 and 12.5% of body weight (BW). Results. Cadet judoists had a significantly smaller maximal power output (11.56 ± 1.21 W ・ kg-1) than U23 athletes (12.69 ± 0.67 W ・ kg-1). The optimal velocity was similar in both group (119.3 ± 16.0 rpm and 119.6 ± 15.5 rpm, respectively). Significant age differences were founded between the cadet and U23 athletes for power output at external load equal 12.5% BW. Cadet judoists generated insignificantly lower maximal power in CMJ and SPJ than U23 judo athletes with except of the absolute maximal power in SPJ. The age difference was observed in height of CMJ. Conclusions. Based on the characteristics of F-v curve we can see in which direction follow the effects of training. Application of CMJ and SPJ in jumping test allows to assess changes in neuromuscular coordination. The use of the both methods give better information to optimal training control.

5

88%

Nikolaidis P.

Journal of Human Kinetics

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2012

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tom 32

87-95

EN

While there is a direct relationship between maximal anaerobic power (Pmax) and swimming performance, the relationship between upper and lower limbs with regard to Pmax and force-velocity (F-v) characteristics is not clear. The aim of the present study was to examine the effect of age and sex on the ratios of mechanical characteristics between upper and lower extremities of adolescent swimmers. Seventeen girls (aged 14.7±1.8 yr) (mean±standard deviation) and 28 boys (14.6±1.4 yr), all members of competitive swimming clubs, performed a F-v test for both legs and arms. In legs, boys had higher values of Pmax (t43=2.4, p<0.05), Pmax expressed in relative to body mass values (rPmax, t43=3.4, p<0.01) and v0 (t43=4.3, p<0.001), while no differences were found for F0 (t43=1.0, p=0.31) and v0/F0 (t43=0.55, p=0.59). In arms, boys had higher values of Pmax (t43=3.2, p<0.01), rPmax (t43=3.9, p<0.001) and v0 (t43=3.4, p<0.01), while no differences were found for F0 (t43=1.9, p=0.06) and v0/F0 (t43=0.16, p=0.87). However, no sex difference was found with regard to the ratios of Pmax (t43=1.9, p=0.06), F0 (t43=1.2, p=0.23) and v0 (t43=1.3, p=0.20) between upper and lower extremities. There was direct relationship between age and Pmax of legs (r=0.64, p<0.01 in girls; r=0.43, p<0.05 in boys) and arms (r=0.56, p<0.05; r=0.57, p<0.01 respectively), while there was not any significant association between age and the ratios of mechanical characteristics of upper and lower limbs. These findings emphasize the need for separate evaluation of arms' and legs' force-velocity characteristics on a regular basis and the consideration of these measures in training design.

6

The Effect of Sonication Parameters on the Thickness of the Produced MoS2 Nano-Flakes

88%

Taghavi N. S. , Afzalzadeh R.

Archives of Acoustics

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2021

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tom Vol. 46, No. 1

31--40

EN

Liquid Phase Exfoliation (LPE) is a common route to produce two-dimensional MoS2 nanosheets. In this research, MoS2 powder is exfoliated by an ultrasonic probe (sonicator) in a water-ethanol solution. It is reported that MoS2 as a prototype 2D Transition Metal Dichalcogenide, has a band gap that increases with a decreasing number of layers. There are some factors that affect the average band gap energy value and the thickness of the exfoliated flakes. We varied different parameters of the ultrasonic probe like power, pulse percentage and time duration of sonication to investigate the effects on the number of MoS2 layers. Our findings from the UV-Visible spectra, SEM, FESEM and TEM images indicate that the minimum thickness for these samples was acquired at 50% of the input power of the sonicator we used (∼65 W) and the optimum pulse percentage is 50%. The current study also found that the average amount of band gap increased with an increase in sonication time, and then remained unchanged after 60 minutes.

7

Changes of Maximal Muscle Torque and Maximal Power Output of Lower Extremities in Male Judoists During Training

75%

Buśko K. , Nowak A.

Human Movement

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2008

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tom 9

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nr 2

111-115

EN

Purpose. The aim of the study was to follow changes of the maximal muscle torque and maximal power output of lower extremities in male judoists during pre-competition training (PCT). The original hypothesis assumed that different training loads would cause changes of the maximal muscle torque and maximal power output of legs in male judoists during pre-competition training, but not changes of the topography of the maximal muscle torque in all muscle groups. Basic procedures. The study sample consisted of five male judoists from the Polish National Team. Muscle torque measurements in static conditions were performed shortly before PCT (I), after the strength training mesocycle (II) and immediately after PCT (III). Ten muscle groups were examined: flexors and extensors of the trunk, shoulder, elbow, hip and knee. The maximal power output of legs was measured on a dynamometric platform during counter-movement jumps (CMJ) and bounce counter-movement jumps (BCMJ). Main findings. The sums of the muscle torque of both arms and the trunk were changed insignificantly during pre-competition training (PCT). The sum of muscle torque of the right and left lower extremities increased significantly between the measurements I and III. The muscle percent topography of muscle groups also showed significant changes. Maximal power output of lower extremities measured during CMJ decreased significantly, but increased during BCMJ. Conclusion. PCT caused changes of the maximal muscle torque of lower extremities, but the muscle topography of the muscle groups revealed significant changes, too. The maximal power output of lower extremities measured during CMJ decreased.

8

The Effect of Sonication Parameters on the Thickness of the Produced MoS2 Nano-Flakes

75%

Taghavi N. S. , Afzalzadeh R. , Taghavi N. S. , Afzalzadeh R.

|

9

Wpływ parametrów geometrycznych obudowy rurowej na moc siłowni wiatrowej

75%

Romański L. , Charkiewicz M.

Inżynieria Rolnicza

|

2008

|

tom R. 12, nr 5(103)

213-219

PL

W pracy przedstawiono wyniki badań efektów pracy siłowni wiatrowej umieszczonej w obudowie rurowej. W porównaniu do siłowni wolnostojącej generuje ona około 50% większą moc prądu elektrycznego. Obudowy rurowe instalowane przed jak i za wirnikiem powinny być jak najkrótsze. Wartość szczeliny obwodowej nie może przekraczać 1 mm.

EN

The paper presents results of the research on operation effects of wind power plant built-in in a tubular housing. Compared to a free-standing wind power plant, it generates approximately 50% higher power output of electric current. Tubular housings installed before and past the windwheel shall be as short as possible. Circumferential gap size shall not exceed 1 mm.

10

Thermodynamic analysis and analytical simulation of the Rallis modified Stirling cycle

75%

Ranjan R. K. , Verma S. K.

Archives of Thermodynamics

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2019

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tom Vol. 40, no 2

35--67

EN

A Stirling cycle was developed by Rallis considering the adiabatic behaviour instead of isothermal behaviour of working fluid inside the expansion/compression volume, since the isothermal processes are very difficult to be realised in actual practice due to irreversibilities. In order to increase the performance of Rallis Stirling cycle engine, two modified versions of Rallis Stirling cycle engine model have been proposed and developed, called as Rallis modified Stirling cycle engine (RMSE). In this paper, the thermodynamic analysis of the developed models have been carried out and the simulated results are compared with the Rallis ideal model of Stirling cycle engine, as this model describes more accurately the thermodynamic cycle of practical Stirling machines. The results reveal the fact that the thermal efficiency of RMSE I model is enhanced by 38.06% and that of RMSE II model by 48.42%, whereas the power output is increased by 58.05% and 78.19% in case of RMSE I and RMSE II model respectively, when compared with the Rallis ideal adiabatic model of Stirling engine.

11

A Physiological and Kinematic Comparison of two Different Lean Back Positions During Stationary Rowing on a Concept II Machine

75%

Bell G. , Bennett J. , Reynolds W. , Syrotuik D. , Gervais P.

Journal of Human Kinetics

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2013

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tom 37

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nr 1

99-108

EN

This study compared two different body positions at the finish of a stroke during stationary rowing exercise on physiological and kinematic measurements. Nine male and five female rowers volunteered for the study: mean age (± SD), body height and body mass were 27 ±9 yrs, 180.5 ±12.3 cm and 81.2 ±14.2 kg. The two body positions at the finish were controlled at an upright posture or a novel greater lean back position. All subjects completed 3 different experimental trials on a Concept IID rowing machine at 3 different exercise intensities and comparisons were made between the lean back position at the same stroke rate and the same power output as the upright trial. Power output, heart rate, oxygen uptake, energy expenditure and % efficiency were higher (p<0.05) with the greater lean back position at the same stroke rate compared to all other conditions. Range of motion at the hip, ankle, and elbow and the handle velocity and distance moved were greater (p<0.05) with the lean back position. In conclusion, a greater lean back posture at the finish during stationary rowing produces a higher power output and improved efficiency at the same stroke rate but at an elevated physiological cost compared to a more upright position. Despite the higher energy expenditure, the relative gain in power output and efficiency with no negative kinematic changes suggests that a greater lean back position at the finish will enhance performance during stationary rowing exercise.

12

Stability Performance Analysis for Variable-Speed Variable-Pitch WECS Based on Dynamic Feedforward Neural Network Control

75%

Li T. , Ji Z.

Przegląd Elektrotechniczny

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2012

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tom R. 88, nr 7b

243--247

EN

Wind energy conversion system (WECS) is a complex nonlinear system, when the wind speed is above the rated value. For a smooth integration of wind generators into the utility grids, two subsystems are built for the WESC based on two-time-scale. NNPID compensator is designed to compensate slow dynamics blade pitch angle, in order to reduce fluctuations of the power output. Compensator for the slow dynamics blade pitch angle is designed based on dynamic feedforward neural network (DFNN), its approximation capabilities are verified by the SCADA (supervisory control and data acquisition) wind farm data collected. Control performances of the DFNN with different structure are compared and analysed, results show that the method can effectively reduce the interference caused by disturbed parameters of the WECS. Safety of the system is improved, and a better idea is provided for application of the DFNN in wind power systems field.

PL

System konwersji energii wiatrowej jest szczególnie złożony gdy prędkość wiatru przekracza założone wartości. Zaproponowano dynamiczny układ sterowania z siecią neuronową DFNN. Osiągnięto lepsze bezpieczeństwo pracy systemu i zmniejszenie zakłóceń.

13

Power output of a wind turbine in tubular housing equipped with a diffuser

63%

Romański L.

Technical Sciences / University of Warmia and Mazury in Olsztyn

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2008

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tom nr 11

277-282

EN

This paper presents the results of a study conducted on a model wind turbine in tubular housing equipped with a diffuser. The impact of the diffuser's diameter and length on the wind turbine's power output was tested. The highest output was reported when the ratio of the diffuser's inlet and outlet diameter was 1.7 and relative diffuser length reached approximately 0.6.

PL

W artykule przedstawiono wyniki badań modelu siłowni wiatrowej pracującej w obudowie rurowej z zainstalowanym dyfuzorem. Testowano wpływ średnicy i długości dyfuzora na generowaną przez tę siłownię moc. Najwyższe wartości mocy uzyskano wówczas, gdy stosunek średnicy wlotowej do wylotowej dyfuzora wynosił 1,7, a względna długość dyfuzora około 0,6.

14

Nowe bloki energetyczne oparte na paliwie węglowym i gazie o mocy powyżej 400 MW, ich rola w krajowym systemie elektroenergetycznym

63%

Lacroix L.

Prace Naukowe Politechniki Śląskiej. Elektryka

|

2014

|

tom z. 2-3

7--20

PL

Niniejszy artykuł opisuje aktualnie budowane i planowane do budowy bloki energetyczne oparte na paliwie węglowym - węglu kamiennym i węglu brunatnym oraz na paliwie gazowym. Głównym celem tych inwestycji jest zastąpienie wycofywanych bloków, by móc utrzymać zbilansowanie systemu elektroenergetycznego z odpowiednią nadwyżką zainstalowanej mocy. Powody wycofania pewnej ilości istniejących bloków podane są w dalszej części artykułu. W artykule opisano skrótowo nową technologię wytwarzania pary w kotłach o tzw. parametrach nadkrytycznych, podwyższających znacznie sprawność bloków węglowych w stosunku do technologii obecnie stosowanej. Artykuł ukazuje też pewne zagrożenia dla pracy bloków o poziomie mocy powyżej 850 MW w okresie występowania tzw. dolin obciążenia dobowego systemu elektroenergetycznego. W artykule wspomniano też o Dyrektywie unijnej IED, która nakazuje ograniczenia emisji szkodliwych substancji (gazów) do atmosfery, głównie chodzi tu o szkodliwe gazy, jak: dwutlenek siarki czy wielotlenki azotu oraz dwutlenek węgla.

EN

This article describes the construction and the plans for the construction of power units based on carbon fuel - coal and lignite and the gaseous fuel. The main objective of these investments is to replace the withdrawn blocks to be able to maintain a balance of power system with adequate surplus installed capacity. The reasons for the withdrawal of a certain amount of existing units are described later in the article. The article briefly describes the new technology of steam generation in boilers of the socalled. supercritical parameters, which increase significantly the efficiency of coal-fired units in relation to the technology currently used. The article presents a certain threat to the operation units on the level of power above 850MW at the time of the so-called (off peak ). valleys of daily load of the power system The article also mentioned about the IED European Directive, which requires the limitation of emissions of harmful substances (gases) into the atmosphere, mainly it is a harmful gases: as sulfur dioxide or nitrogen multioxides and carbon dioxide.

15

Selected aspects of the choice of live steam pressure in PWR nuclear power plant

63%

Laskowski R. , Smyk A. , Jurkowski R. , Ancé J. , Wołowicz M. , Uzunow N.

Archives of Thermodynamics

|

2022

|

tom Vol. 43, no 3

85--109

EN

In commercially available generation III and III+ PWR (pressurized water reactor) reactors, pressure of steam produced in steam generators varies in a relatively wide range from 5.7 to 7.8 MPa. Therefore, it is important to ask which value of steam pressure should be used for a specific unit, taking into account different location conditions, the size of the power system and conditions of operation with other sources of electricity generation. The paper analyzes the effect of steam pressure at the outlet of a steam generator on the performance of a PWR nuclear power plant by presenting changes in gross and net power and efficiency of the unit for steam pressures in the range of 6.8 to 7.8 MPa. In order to determine losses in the thermal system of the PWR power plant, in particular those caused by flow resistance and live steam throttling between the steam generator and the turbine inlet, results concerning entropy generation in the thermal system of the power plant have been presented. A model of a nuclear power plant was developed using the Ebsilon software and validated based on data concerning the Olkiluoto Unit 3 EPR (evolutionary power reactor) power plant. The calculations in the model were done for design conditions and for a constant thermal power of the steam generator. Under nominal conditions of the Olkiluoto Unit 3 EPR power unit, steam pressure is about 7.8 MPa and the steam dryness fraction is 0.997. The analysis indicates that in the assumed range of live steam pressure the gross power output and efficiency increase by 32 MW and 0.735 percentage point, respectively, and the net power output and efficiency increase by 27.8 MW and 0.638 percentage point, respectively. In the case of all types of commercially available PWR reactors, water pressure in the primary circuit is in the range of 15.5−16.0 MPa. For such pressure, reducing the live steam pressure leads to a reduction in the efficiency of the unit. Although a higher steam pressure increases the efficiency of the system, it is necessary to take into account the limitations resulting from technical and economic criteria as well as operating conditions of the primary circuit, including the necessary DNBR (departure from nucleate boiling ratio) margin. For the above reasons, increasing the live steam pressure above 7.8 MPa (the value used in EPR units that have already been completed) is unjustified, as it is associated with higher costs of the steam generator and the high-pressure part of the turbine.

16

Ocena względnej mocy użytecznej silnika o zapłonie iskrowym na podstawie wartości parametrów termodynamicznych spalin i prędkości obrotowej wału korbowego

63%

Markowski J. , Pielecha J. , Merkisz J. , Nowak M.

Combustion Engines

|

2015

|

tom R. 54, nr 3

469--474

PL

Podczas badań emisji związków szkodliwych spalin w warunkach eksploatacji środków transportu przydatne są informacje dotyczące parametrów pracy silnika. Informacje te wykorzystywane są do zdefiniowania m.in. wartości obciążenia silnika podczas eksploatacji środka transportu. W większości pojazdów produkowanych obecnie wykorzystuje się do tych celów informacje z systemów diagnostycznych. Natomiast w badaniach emisji związków szkodliwych z silników tłokowych stosowanych w małych samolotach jest to utrudnione, ponieważ nie wszystkie samoloty są wyposażone w pokładowe rejestratory parametrów lotu. Dlatego w przeprowadzonych badaniach emisji zanieczyszczeń z tłokowych napędów samolotów poszukiwano narzędzia, umożliwiającego dokonanie oceny obciążenia silnika podczas prowadzonych pomiarów w warunkach eksploatacji. W artykule przedstawiono propozycję algorytmu dotyczącego oceny wartości obciążenia tłokowego silnika lotniczego o zapłonie iskrowym na podstawie wartości temperatury spalin i prędkości obrotowej wału korbowego.

EN

During the research of exhaust emission under operating conditions of means of transport the engine's parameters are highly useful information. That information is used to define values of the engine load during the operation of the means of transport. In most vehicles produced nowadays the information from diagnostic systems is used for this purpose. The other hand, emissions testing of harmful compounds from piston engines used in small aircrafts is difficult because not all aircraft are equipped in on-board flight data recorders. Therefore, in the area of emissions from aircraft piston engines appeared the necessity of creation tool allowing evaluation engine load during the measurements under operating conditions. The article includes an algorithm for the assessment of the load values of aircraft's spark-ignition engines based on exhaust gas temperature and rotation speed of the crankshaft.

17

Changeability of heat output of heat pump with scroll type compressor

63%

Knaga J.

Teka Komisji Motoryzacji i Energetyki Rolnictwa

|

2007

|

tom 07A

18

Metoda monitorowania plonu roślin przez pomiar mocy na WOM ciągnika podczas zbioru kukurydzy sieczkarnią polową

51%

Lisowski A. , Klonowski J. , Sypuła M. , Nowakowski T. , Chlebowski J.

Problemy Inżynierii Rolniczej

|

2004

|

tom R. 12, nr 3

13--20

PL

Podczas badań stwierdzono, że uwzględnienie stanu technicznego maszyny wymaga pomiaru mocy dla dwu stanów: pod obciążeniem i na biegu jałowym. Uzasadniono, że podczas pomiaru mocy potrzebny jest również ciągły pomiar prędkości ruchu agregatu ciągnik-sieczkarnia i wilgotności roślin. Wymagana jest także informacja o przełożeniu między prędkością obrotową wału napędzającego i napędzanego, liczbie noży na tarczy zespołu rozdrabniającego oraz szerokości i liczbie zbieranych rzędów roślin kukurydzy.

EN

Paper presented the method of monitoring the yield of green maize harvested with a tractor driven forage harvester. The method is based on measuring the tractor PTO power output. It was stated that to recognize the technical condition of the machine, power measurements have to be taken at two states - under loading and at idle running. The power output measurements should be accompanied by continuous monitoring of the tractor-forage harvester speed and testing moisture content of plants harvested. The technical parameters such as rotational speed ratio of driving and driven shafts, the number of knives on chopper flywheel, spacing and number of harvested plant rows, are also necessary to be known.