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1

Generalized plane waves in a rotating thermoelastic double porous solid

Pathania Vijayata, Kumar Rajesh, Gupta Vipin, Barak M. S.

International Journal of Applied Mechanics and Engineering

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2022

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Vol. 27, no. 4

138--154

EN

The propagation of plane waves in a rotating homogeneous, isotropic, thermoelastic solid with double porosity following Lord-Shulman’s theory of thermoelasticity has been investigated. It is assumed that the medium rotates about an axis normal to the surface with a uniform angular velocity. There may exist five coupled waves that evolved due to the longitudinal, transverse disturbance, voids of type-I and type-II, and temperature change in the medium. The secular equation for the model under consideration has been derived with the help of formal solutions and boundary conditions. The amplitude of displacements, temperature change and volume fraction fields for voids of type-I and type-II have also been computed analytically. Finally, numerical computations have been carried out for magnesium crystal material to understand the behavior of amplitude of phase velocity, penetration depth, specific loss, displacement components, temperature change, and volume fraction field due to type-I and type-II voids corresponding to the different rotation rates. Various graphs have been plotted to support the analytical findings. The study may be used in the development of rotation sensors, material design and thermal efficiency.

2

Effects of rotation on Jeffrey nanofluid flow saturated by a porous medium

Rana Gian C.

Journal of Applied Mathematics and Computational Mechanics

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2021

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Vol. 20, nr 3

17--29

EN

In this paper, the effects of rotation on a Jeffery nanofluid flow in a porous medium which is heated from below is studied. Darcy model is employed for porous medium and the Jeffrey fluid model is used as a base fluid. The Navier-Stokes equations of motion of fluid are modified under the influence of the Jeffrey parameter, naoparticles and rotation. The basic perturbation technique based on normal modes is applied to derive the dispersion relation for a Rayleigh number. The effects of the Taylor number, Jeffrey parameter, Lewis number, modified diffusivity ratio, nanoparticles Rayleigh number and medium porosity on the stationary convection of the physical system have been analyzed analytically and graphically. It is observed that the rotation parameter has a stabilising influence for both bottom/top-heavy configurations.

3

Effect of magnetic field dependent viscosity on the unsteady ferrofluid flow due to a rotating disk

Bhandari A.

International Journal of Applied Mechanics and Engineering

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2020

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Vol. 25, no. 2

22--39

EN

The effect of magnetic field dependent viscosity on ferrofluid flow due to a rotating disk is studied in the presence of a stationary magnetic field. The results for velocity profiles for various values of MFD viscosity parameter are shown graphically. These results are compared with the ordinary case when the applied magnetic field is absent. Besides, the shear stress on the wall of the disk and its surface is calculated numerically.

4

Algorytmy do analizy składowych wektora prędkości

Gawor Marek, Sobczyk Jacek, Wodziak Waldemar

Prace Instytutu Mechaniki Górotworu PAN

|

2019

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T. 21, nr 1-4

39--47

PL

W artykule przedstawiono algorytmy komputerowe zaprojektowane w celu analizy składowych płaskiego pola prędkości. Informacje o składowych wektora prędkości pochodzą z programu Dantec Dynamic Studio lub programu powstałego w Instytucie. Analizowane są wszystkie pliki z wybranego katalogu. Programy te generują płaskie pola prędkości wyznaczane przy pomocy anemometrii cyfrowej (Particle Image Velocimetry – PIV). W programie możemy analizować składowe wektora prędkości wzdłuż linie poziomej i pionowej. Możemy zapisać pliki w celu narysowania trójwymiarowego pola wybranej składowej wektora prędkości lub zmiany składowych w czasie. Istnieje możliwość wyznaczenia sumy, wartości średniej, odchylenia standardowego, czy rotacji wektora prędkości.

EN

Algorithms used to analyze velocity of vector components are presented in the paper. Information about velocity components come from Dantec Dynamic Studio Program or program designed by the authors. All of the files from the selected catalogue are analyzed. As a result 2D velocity fields are generated from the PIV data. The authored computer program allows to analyze velocity vector components along horizontal and vertical lines. Files saved are used to draw a three dimensional velocity fields or to visualize variations of the components of velocity vectors in time. Statistical parameters such as: sum, mean, standard deviation or rotation of the velocity vector are routinely computed.

5

An insight into the evolution of rotation operator to quaternion’s. Computer graphics perspective

Sami Saad Bin, Tariq Humera

Journal of Applied Mathematics and Computational Mechanics

|

2019

|

Vol. 18, nr 1

77--87

EN

Rotations are an integral part of various computational techniques and mechanics. The objective in this paper is twofold: first to have a classical insight into the history of quaternions, a problem that Hamilton faced for over a decade and secondly to look at into its applications from computer graphics perspective. Thorough revision of quaternion algebra and its use case as a rotation operator has been presented. A quaternion simulation algorithm has been written and practiced to generate simulation results. Results show that though quaternions supersede Euler angles technically but are tricky to use and control for e.g. when same quaternion is applied on a different vector axis, the particle is not able to reach its initial position and an incomplete rotation effect has been recorded and observed.

6

Rotation, initial stress, gravity and electromagnetic field effect on P wave reflection from stress-free surface elastic half-space with voids under three thermoelastic models

Abo-Dahab S. M., Rida S. Z., Mohamed R. A., Kilany A. A.

Mechanics and Mechanical Engineering

|

2018

|

Vol. 22, nr 1

313--328

EN

The present paper is devoted to investigate the influence of the rotation, thermal field, initial stress, gravity field, electromagnetic and voids on the reflection of P wave under three models of generalized thermoelasticity: Classical and Dynamical coupled model (CD), Lord-Shulman model (LS), Green-Lindsay model (GL), The boundary conditions at stress-free thermally insulated surface are satisfied to obtain Algebraic system of four equations in the reflection coefficients of various reflected waves. It is shown that there exist four plane waves; P1, P2, P3 and P4. In addition, the reflection coefficients from insulated and isothermal stress-free surface for the incident P wave are obtained. Finally, numerical values of the complex modulus of the reflection coefficients are visualized graphically to display the effects of the rotation, initial stress, gravity field magnetic field, thermal relaxation times and voids parameters.

7

Compressible analysis of Bénard convection of magneto rotatory couple-stress fluid

Mehta C. B., Singh M.

International Journal of Applied Mechanics and Engineering

|

2018

|

Vol. 23, no. 1

91--105

EN

Thermal Instability (Benard’s Convection) in the presence of uniform rotation and uniform magnetic field (separately) is studied. Using the linearized stability theory and normal mode analyses the dispersion relation is obtained in each case. In the case of rotatory Benard’s stationary convection compressibility and rotation postpone the onset of convection whereas the couple-stress have duel character onset of convection depending on rotation parameter. While in the absence of rotation couple-stress always postpones the onset of convection. On the other hand, magnetic field on thermal instability problem on couple-stress fluid for stationary convection couple-stress parameter and magnetic field postpones the onset of convection. The effect of compressibility also postpones the onset of convection in both cases as rotation and magnetic field. Graphs have been plotted by giving numerical values to the parameters to depict the stationary characteristics. Further, the magnetic field and rotation are found to introduce oscillatory modes which were non-existent in their absence and then the principle of exchange of stability is valid. The sufficient conditions for non-existence of overstability are also obtained.

8

The effect of rotation on the onset of electrohydrodynamic instability of an elastico-viscous dielectric fluid layer

Rana G. C., Chand R., Sharma V.

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2016

|

Vol. 64, nr 1

143--149

EN

In this paper the combined effect of uniform rotation and AC electric field on the onset of instability in a horizontal layer of an elastico-viscous fluid stimulated by the dielectrophoretic force due to the variation of dielectric constant with temperature is studied. Walters’ (model B’) fluid model is used to describe rheological behaviour of an elastico-viscous fluid. The onset criterions for stationary and oscillatory convection are derived for the case of free-free boundaries. It is observed that Walters’ (model B’) fluid behaves like an ordinary Newtonian fluid and rotation has stabilizing influence whereas AC electric field has destabilizing influence on the stability of the system. The necessary condition for the occurrence of oscillatory convection is also obtained. The present results are in good agreement with the earlier published results.

9

Ocena efektów unieruchomienia kręgosłupa u zdrowych ochotników podczas pionizacji i rotacji noszy typu deska w zależności od rozmieszczenia, liczby i siły zaciśnięcia pasów mocujących

Wołoszyn P., Baumberg I., Kamiński M.

Logistyka

|

2015

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nr 6

1562--1569, CD

PL

Negatywne konsekwencje unieruchomienia w noszach typu deska zostały opisane w wielu publikacjach. Odnoszą się one jednak wyłącznie do osoby leżącej na wznak w poziomej pozycji noszy. W praktyce ratowniczej występują okoliczności zmuszające do zmiany położenia noszy: ich rotacji i pionizacji. Uwidacznia to kolejny obszar potencjalnie negatywnych konsekwencji związany z przemieszczaniem się ciała. W eksperymencie przetestowano 4 układy pasów zaciśniętych z siłą 80 N wskazując, że I i II układ równolegle do siebie ułożonych 4 par pasów powodował najmniejszy zakres równomiernego przemieszczenia podczas zmiany położenia noszy.

EN

The negative consequences of an immobilization the patients on the long backboard were described in numerous publications but only with relation to transportation in the horizontal position of the stretchers. Our experiment was designed to identify the range of displacement of the body immobilized on a LBB after tilting to vertical position or rotation along long axis, depending on the location, number and force of tension applied to fixing straps. According to our findings we suggest to use 4 pairs of fixing straps placed parallel to each other (like in II pattern) and tightened with use of 80 N force when the tilting to vertical position is anticipated and to use I pattern in all other circumstances.

10

Podwodne tamy poprzeczne jako konstrukcje aktywujące przepływ masy w ciekach rzecznych

Shchodro A. E., Mykola-Moklyak M.

Zeszyty Naukowe. Inżynieria Lądowa i Wodna w Kształtowaniu Środowiska

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2014

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Nr 11

18--29

PL

Niniejsza praca dotyczy działania podwodnych tam poprzecznych usytuowanych pod ostrym kątem w stosunku do nurtu rzeki. Za taką konstrukcją powstaje spiralny nurt ze spiralną strukturą, co z powodu wysokich wartości prędkości chwilowej wzdłuż konstrukcji i rotacji przyczynia się do znaczącego wzrostu przepływu masy w cieku, podmywania strefy brze-gowej, przypuszczalnie dodatkowego przyciągania tlenu atmosferycznego do cieku oraz prawie całkowitego mieszania ścieków zrzucanych za tamą z nurtem rzeki.

EN

This paper considers the operation of low submerged (flooded) groins oriented by the sharp angle relatively to the incoming flow. Helical flow with a spiral structure arise behind such construction which, due to high values of transitional velocity directed along the construction and rotating, providing a significant enhancement of mass transfer in the stream, washing of the riverside zone, and supposing additional attraction of atmospheric oxygen into the stream and also almost complete initial mixing of wastewater discharged behind the groin with the river flow.

11

Zarządzanie zasobami magazynowymi – stanem magazynu

Kurek K.

Nowoczesne Hale

|

2014

|

Nr 2

58--60

PL

Sztuka zarządzania magazynem to z jednej strony dążenie do maksymalizacji wykorzystania fizycznej struktury magazynu, a z drugiej – optymalizacja składowanego tam zapasu. W artykule opublikowanym w numerze 3/2013 czasopisma TWiM nasza uwaga skupiała się na tym, jak do danego nam magazynu „wcisnąć” jak najwięcej towaru, tak by najefektywniej wykorzystać jego fizyczną wielkość/strukturę.

12

Effect of magnetic field on thermal instability of Oldroydian viscoelastic rotating fluid in porous medium

Thakur R. C., Rana G. C.

International Journal of Applied Mechanics and Engineering

|

2013

|

Vol. 18, no. 2

555--569

EN

In this paper, we investigate the effect of a vertical magnetic field on thermal instability of an Oldroydian visco-elastic rotating fluid in a porous medium. By applying the normal mode analysis method, the dispersion relation governing the effects of rotation, magnetic field and medium permeability is derived and solved analytically and numerically. For the case of stationary convection, the Oldroydian viscoelastic fluid behaves like an ordinary Newtonian fluid and it is observed that rotation has a stabilizing effect while the magnetic field and medium permeability have a stabilizing/destabilizing effect under certain conditions on thermal instability of the Oldroydian viscoelastic fluid in a porous medium. The oscillatory modes are introduced due to the presence of rotation, the magnetic field and gravity field. It is also observed that the ‘principle of exchange of stability’ is invalid in the presence of rotation and the magnetic field.

13

Eksploatacja w rowie II-rzędu złoża węgla brunatnego Bełchatów - dobór technologii prowadzenia robót górniczych dla zabezpieczenia eksploatacji do rzędnej - 110 m n.p.m.

Czarnecki L., Jurczuk M.

Górnictwo Odkrywkowe

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2013

|

R. 54, nr 1

62--68

PL

W artykule przedstawiono problemy związane z zabezpieczeniem eksploatacji w zachodniej części rowu II-rzędu, gdzie stwierdzono występowanie struktury geologicznej, w granicach której wydzielono dwa rejony zagrożeń, rejon X/S (w zakresie rzędnych +90/ -25 m n.p.m.) oraz rejon XV/S (20/ -110 m n.p.m.) W trakcie prowadzenia eksploatacji w piętrach VII i VIII, dochodziło do rozwoju niewielkich osuwisk oraz obserwowano reakcje reperów powierzchniowej sieci obserwacyjnej. W marcu 2011 roku, w czasie realizacji zabierki w piętrze VIII (eksploatacja do rzędnej +20 m n.p.m.), doszło do rozwoju osuwiska i strefowego wyparcia poziomu na wysokość ok. 3-4 m . Obserwacje wskazywały na możliwość rozwoju wieloskarpowego osuwiska, które utrudni eksploatację w strefie do rzędnej -110 m n.p.m. Podczas eksploatacji w VIII i IX piętrze górniczym, poprzez zestramianie zbocza oraz kontrolowane prowokowanie pełzania osuwającego się fragmentu zbocza, wyeksploatowano znaczny fragment osuniętych gruntów. Pozwoliło to na ograniczenie zagrożeń dla eksploatacji w zakresie rzędnych -20/-110 m n.p.m.

EN

Problems connected with securing exploitation in the western part of II-order graben were presented in paper. Occurrence of geological structure was noted in that area, in which two hazardous areas were distinguished. Area X/S (ordinate +90/-25 m a.s.l) and area XV/S (20/-110 m a.s.l). During exploitation in levels VII and VIII, expansion of small landslides and reaction of superficial observation network bench marks occurred. In march 2011, during exploitation in level VIII (exploitation to ordinate +20 m a.s.l), expansion of landslide and zonal displacement of level, up to 3-4 m occurred. Observations showed possibility of multiscarp landslide, that will make exploitation difficult in zone, up to ordinate -110 m a.s.l. During level VIII and IX exploitation, sloping of slide and controlled provoking of crawling of sliding bevel was performed. During that, part of slided part was exploited. That allowed to limit the hazards for exploitation in ordinates -20/-110 m a.s.l.

14

A Characterization of the Rivlin-Ericksen Viscoelastic Fluid in the Presence of a Magnetic Field and Rotation

Banyal A. S.

Engineering Transactions

|

2012

|

Vol. 60, iss. 4

355-355

EN

A layer of Rivlin-Ericksen viscoelastic fluid heated from below is considered in the presence of an uniform vertical magnetic field and rotation. Following the linearized stability theory and normal mode analysis, this paper mathematically establishes the condition for characterizing oscillatory motion, which may be neutral or unstable, for rigid boundaries at the top and bottom of the fluid. It is established that all non-decaying slow motions starting from rest, in the configurations, are necessarily non-oscillatory in the regime TAF 2 + TA 4 + Qp2 2 1; where TA is the Taylor number, Q is the Chandrasekhar number, p2 is the magnetic Prandtl number, and F is the viscoelasticity parameter. This result is important, since it holds for all wave numbers for rigid boundaries of infinite horizontal extension at the top and bottom of the fluid, and the exact solutions of the problem investigated in closed form are not obtainable.

15

Zagrożenia osuwiskowe w Zakładzie Górniczym KWB Bełchatów w trakcie prowadzenia eksploatacji w najgłębszej części złoża, w rowie II rzędu

Sędor A., Czarnecki L.

Górnictwo i Geoinżynieria

|

2011

|

R. 35, z. 2

519-526

PL

W artykule przedstawiono zagrożenia osuwiskowe występujące w trakcie prowadzenia eksploatacji w rowie II rzędu, tj. w najgłębszej części złoża Bełchatów. Omówiono główne tektoniczne granice struktury oraz ich wpływ na bezpieczeństwo robót górniczych. Artykuł zawiera dokładną charakterystykę strefy uskokowej tzw. uskoku północnego brzeżnego (UNB nr 2), udokumentowaną w trakcie prowadzenia eksploatacji. Zrzut uskoku notowany w podłożu mezozoicznym wynosi od 60 do 200 m. Charakter strefy ulega zmianie od rozległej fleksury do szeregu powierzchni uskokowych o zróżnicowanym kącie i kierunku upadu. Ciekawym elementem tej strefy są pojawiające się coraz częściej powierzchnie nasunięć zlokalizowane po północnej stronie uskoku. Drugim istotnym elementem scharakteryzowanym w artykule jest blok skał mezozoicznych budujących południowy brzeg rowu Kleszczowa. Strefa ta zwana blokiem paleoosuwiskowym (BP) zlokalizowana jest na południowym uskoku brzeżnym Rowu Kleszczowa tzw. USB nr 1. Blok paleoosuwiskowy ma długość około 1700 metrów i jest prawdopodobnie szeregiem bloków przesuniętych ku północy poza górną krawędź uskoku USB nr 1 na odległość około 140 metrów w efekcie starych osuwisk. Szacunkowa objętość BP wynosi około 118 mln m3 przy udokumentowanej miąższości 260 metrów. W granicach BP wykartowano do tej pory 11 mniejszych bloków zalegających w obrębie osadów trzeciorzędowych. Przedstawiono wyniki dotychczasowych prac terenowych zmierzających do rozpoznania deformacji wewnętrznych BP. Zwrócono uwagę na praktyczny aspekt rozpoznania struktur powodujących wewnętrzną anizotropię bloku, jako elementu niezbędnego dla prawidłowego planowania i bezpiecznego prowadzenia robót górniczych.

EN

In this article described landslide hazards occur while mine technology for extraction in II order graben, the deepest part of the brown coal deposit Bełchatów. Discussed major tectonic structure have influence to safe mine extraction. The article contains precise characteristic fault line called "North border fault line" (UNB no. 2) documented while mine extractions. Drop has been recorded in the Mesozoic substratum and amount 60 to 200 meters. The style of zone is varied from expansive flexure to series fault lines varied angle and dip direction. Interest aspect of this zone is appearing more often imply surfaces in the north side of fault line. The second important aspect described in this article is block of Mesozoic rock which is building south border Kleszczow graben. The zone called paleolandslide block (BP) is locating in the south border fault line Kleszczow graben called USB no. 1. Paleolandslide block is 1700 meters long and it is probably blocks group move to the north board fault line USB no. 1 about 140 meters bring about old landslide. Estimate volume BP is 118 mln m3 with documented depth 260 meters. In the board BP charted 11 lower block group deposit in the Tertiary sediments. Described results previous field work driving to better knowledge deformations inside BP. It was taken note of practical aspect recognition structure cause steady inside block as necessary element to right planning and safe mining extraction.

16

Torque of the shank rotating muscles in patients with knee joint injuries

Hrycyna M., Zieliński J.

Acta of Bioengineering and Biomechanics

|

2011

|

Vol. 13, no. 4

77-83

EN

The aim of the study was to evaluate the torque of the shank rotating muscles in patients with reconstructed anterior cruciate ligament (ACL) and rehabilitation accomplished in comparison with a control group. The study was carried out on the group of 187 males. For the purpose of the study a prototype testing device for the shank rotating muscles' torque under static conditions was used. The study was based on the measurement of maximal torque at selected angles (-30 degree, 0 degree, 45 degree) of the shank rotation as well as on the angle (30 degree, 60 degree, 90 degree) of flexion of the knee joint. The results obtained in the group with reconstructed anterior cruciate ligament (ACL) and rehabilitation accomplished were comparable to those the control group and mostly of no statistical significance. Lack of significant differences between the values of shank rotating muscles' torque achieved in an injured limb compared to an uninjured one may testify to an effective rehabilitation process. The results of the research can serve as a diagnostic tool for the rehabilitation process development.

17

The tectonic evolution of Lake Eğirdir, West Turkey

Karaman M. Erkan

Geologos

|

2010

|

Vol. 16, No. 4

223--234

EN

Lake Eğirdir is one of the most important fresh-water lakes of Turkey. It has a tectonics-related origin. The area formed under a roughly N-S compressional tectonic regime during the Middle Miocene. The stresses caused slip faults west and east of Isparta Angle, and the lake formed at the junction of these faults. The area subsided between normal faults, thus creating the topographic condition required for a lake. The lacustrine sediments have fundamentally different lithologies. After the Late Miocene, central Anatolia started to move westwards, but western Anatolia moved in a SW direction along the South-western Anatolian Fault , which we suggest to have a left lateral slip, which caused that the Hoyran Basin moved t7 km towards the SW and rotated 40º counterclockwise relative to Lake Eğirdir.

18

Effect of Rotation in Case of 2-D Problem of the Generalized Thermo-viscoelasticity with Two Relaxation Times

Othman M. I. A.

Mechanics and Mechanical Engineering

|

2009

|

Vol. 13, nr 2

105-127

EN

In this paper, a two-dimensional problem of thermoviscoelasticity with two relaxation times when the entire medium rotates with a uniform angular velocity is studied. The normal mode analysis is used to obtain the exact expressions for the temperature, displacement and thermal stress components. The resulting formulation is applied to the case of a thick plate subjected to a time-dependent heat source on each face. Numerical results are given and illustrated graphically. Comparisons are made with the results predicted by the coupled theory and with the theory of generalized thermoelasticity with two relaxation times in the absence of rotation and for different values of time.

19

Deformation in a Generalized Thermoelastic Medium with Hydrostatic Initial Stress Subjected to Different Sources

Ailawalia P., Kumar S., Khurana G.

Mechanics and Mechanical Engineering

|

2009

|

Vol. 13, nr 1

5-24

EN

In the present problem we study the deformation of a rotating generalized thermoelastic medium with hydrostatic initial stress subjected to three different type of sources. The components of displacement, force stress and temperature distribution are obtained in Laplace and Fourier domain by applying integral transforms. The general solution obtained is applied to a specific problem of a half-space subjected to concentrated force, distributed force and a moving source. These components are then obtained in the physical domain by applying a numerical inversion method. Some particular cases are also discussed in context of the problem. The results are also presented graphically to show the effect of rotation and hydrostatic initial stress.

20

Wpływ rotacji herbicydów na liczebność chwastów odpornych w monokulturze kukurydzy

Kucharski M., Sekutowski T.

Inżynieria Rolnicza

|

2007

|

R. 11, nr 3 (91)

129-133

PL

Celem prowadzonych badań było określenie wpływu rotacji herbicydów na liczebność chwastów odpornych w monokulturze kukurydzy. W latach 2000-2004 prowadzono doświadczenie na plantacji kukurydzy, uprawianej od 1992 roku w monokulturze, którą corocznie odchwaszczano herbicydami triazynowymi. Na polu tym zidentyfikowano odporne na atrazynę Amaranthus retroflexus, Chenopodium album i Echinochloa crus-galli. W roku 2000 plantację podzielono na dwie części. Na jednej części nadal, corocznie stosowano herbicydy triazynowe, na drugiej zaś zmieniono dotychczas stosowane herbicydy na środki z grupy sulfonylomocznika. W roku 2004 obie części plantacji poddano ocenie stanu zachwaszczenia, z oznaczonych powierzchni pobrano próbki chwastów i metodą pomiaru fluorescencji określono liczebność osobników odpornych w poszczególnych zbiorowiskach. Uprawa kukurydzy w monokulturze oraz brak zmianowania herbicydów przyczyniły się do wystąpienia i rozwoju odporności biotypów Amaranthus retroflexus, Chenopodium album i Echinochloa crus-galli. Wprowadzenie rotacji herbicydów o różnym mechanizmie działania umożliwiło wzrost skuteczności zwalczania chwastów i ograniczyło liczebność osobników odpornych w populacji o około 8-15% w porównaniu do stanu z roku 2000.

EN

The aim of investigations was evaluation of herbicides rotation effect on variation of the number of resistant weed biotypes found in maize monoculture. Investigations were conducted on a maize field cultivated since 1992 as monoculture, where triazine herbicides were applied annually. In 2000 this field was divided into two blocks. On the first block application of triazine herbicides continued. On second block triazine herbicides were replaced by sulfonylurea herbicides. Using the fluorescence method on these fields the number of resistant weed biotypes was determined (Amaranthus retroflexus, Chenopodium album and Echinochloa crus-galli). After the four years the number of resistant biotypes was checked again. On the field, where triazine herbicides were applied, the increase of the number of resistant weeds was observed. Rotation of herbicides caused the decrease of the number of resistant weeds by 8-15% in comparison with the situation in 2000.