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1

Peridynamics compatible with boundary conditions and its verification in plane elastic problems

Yu M., Zhou Z., Huang Z.

Archives of Mechanics

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2024

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Vol. 76, nr 1-2

3--38

EN

In the peridynamic (PD) theory established by Silling and his collaborates, the equation of motion is incompatible with the traction boundary conditions. In order to impose boundary conditions, a technique used is to set a fictitious boundary layer and transforming traction into a body force. This technique is easy to operate, but it is difficult to adapt to complex boundary constraints. To solve this problem, the new peridynamic governing equations with boundary conditions (PDBC) are introduced and simplified. In PDBC, the influence of the boundary conditions is confined to a boundary layer with finite thickness, by which, the surface correction can be shunned. A nonlinear implicit solver for PDBC is implemented. This solver is used to simulate the plane stress problems. The elastic deformations of a rectangular plate under three different boundary conditions, i.e., traction, displacement and mixed boundary conditions, are solved based on the bond-based and ordinary state-based constitutive models. Comparison of computational results between PDBC, the classical elastic theory and the original PD verifies the applicability and accuracy of PDBC and the implicit algorithm.

2

Modeling and experimental investigation of a controllable rotary fluid damper

Cao X., Zhou J., Yu M., Wang Y.

Archives of Mechanics

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2023

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Vol. 75, nr 4

493--516

EN

Controllable rotary fluid damper (CRFD) is an efficient and cheap energy dissipation device, which is used to reduce the impact of vibration in mechanical systems. In this paper, the CRFD controlled by a servo motor is developed to reduce the effects of vibrations in the helicopter flight control system. The dynamic mechanical characteristic of the CRFD is experimentally investigated by the MTS machine. Due to the complex factors such as high shear thinning rate and compressibility of the damping medium, inertia of moving parts and internal friction, the CRFD studied has highly nonlinear hysteresis characteristics. The accuracy of the damper modeling is of great significance for designing effective vibration reduction methods. Therefore, a new generalized viscous–nonlinear elastic model is proposed to track the mechanical characteristics of CRFD. On the basis of parameter sensitivity analysis, the proposed generalized viscous–nonlinear elastic model is modified. According to the identification results of the modified model, the main parameters are fitted as polynomial functions of motor rotation angle. Through error analysis between analytical torques and experimental torques, it is concluded that the modified generalized viscous–nonlinear elastic model has the smallest error compared with Kwok and Maxwell models, which indicates that the proposed modified model can accurately describe the mechanical characteristics of the CRFD under different working conditions.

3

Peridynamic analysis of 2-dimensional deformation and fracture based on an improved technique of exerting traction on boundary surface

Zhou Z., Yu M., Wang X., Huang Z.

Archives of Mechanics

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2022

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Vol. 74, nr 6

441--461

EN

For 2-dimensional problems in peridynamics, the transfer functions of boundary traction are constructed. The peridynamic motion equation introducing the boundary traction is improved and used to solve some typical 2-dimensional deformation and fracture problems, including the uniaxial tension and pure bending of plate, and fracture of a plate with the small circular hole or central crack. The acquired numerical solutions are close to the analytical solutions of elasticity and numerical solutions given by the finite element method. The results show that the improved technique of exerting traction on a boundary surface is valid for calculating the deformation and failure of solid. It provides a new method and path for the analysis of traction boundary value problems in peridynamics.

4

Leaching kinetic study of Y and Eu from waste phosphors using hydrochloric acid solution containing hydrogen peroxide

Yu M., Jiang Z., Mei G., Chen X.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 2

238--248

EN

The leaching kinetics of Y and Eu from waste phosphors using a hydrochloric acid (HCl) solution containing hydrogen peroxide (H2O2) were investigated. Characterization of the waste phosphors was performed using XRD to ascertain the phases as (Y0.95Eu0.05)2O3 (red phosphors), (Ce0.67Tb0.33)MgAl11O19 (green phosphors), (Ba0.9Eu0.1)Mg2Al16O27 (blue phosphors), and SiO2 (quartz). The influence of factors such as HCl concentration, addition amount of H2O2, temperature, and reaction time on the leaching performance of Y and Eu was investigated. The maximum leaching recoveries of Y (99.87%) and Eu (88.72%) were obtained at 4 M HCl, 0.2 cm3/g H2O2, 60 ℃ temperature, and 180 min of reaction time at a liquid-to-solid ratio of 7.5 cm3/g. Leaching kinetic results showed the best fit with the shrinking sphere model (1-(1-x)1/3)=kct), ensuring that the overall leaching process was governed by a chemical control mechanism. Activation energies of 42.35 and 33.28 kJ/mol were acquired for leaching of Y and Eu, respectively, at 40-70 ℃, which further supports the proposed chemical control leaching process.

5

Moving-aperture-based three-dimensional micro-measurement system

Fan S., Yu M., Jiang G., Wang Y., Wang W., Li W.

Optica Applicata

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2018

|

Vol. 48, nr 4

533--547

EN

To overcome the depth-of-field limitation of an optical microscope image, a three-dimensional measurement method with a superior depth-of-field is proposed. In the proposed method, light-field information of different angles is obtained by moving the aperture and the three-dimensional scene is reconstructed by using a computational reconstruction technology. First, stereo matching of different aperture position images is performed to obtain the multi-aperture imaging deviation. The focal plane moving distance is thereby estimated. Then, the relational expression between the image coordinates and the focal plane moving distance is determined according to the image coordinates. Two dimensional coordinates of the space point are obtained by the expression coefficients. Finally, the depth coordinates are computed, and three-dimensional reconstruction of the spatial points is completed. Experiments of three-dimensional measurements of the calibration board with different angles and circuit boards are conducted. The results show that the maximum error of the distance measurement is controlled into 0.84%, and the maximum angle measurement error is controlled into 4.56%.

6

Research on a square Cassegrain-type solar concentrating reflector with a double pyramid

Zhang Y., Yang H., Jiang P., Mao S., Yu M.

Optica Applicata

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2016

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Vol. 46, nr 3

461--471

EN

A structure of a solar concentrating reflector is designed in this paper to improve the usage of solar energy. For the dark image which is the result of the secondary mirror in the new type of the Cassegrain solar concentrating system, a double pyramid system is used to improve this phenomenon. By eliminating the dark image, the system enhanced the concentration ratio and the working efficiency. Meanwhile, both the primary and secondary mirrors are shaped into a square section in order to get a better match with a square photovoltaic receiver. While the length of the primary mirror is 89m and the block ratio is 20%, the concentration ratio is equal to 118.86.

7

Disparity servoing based fast autofocusing method for stereomicroscope

Liu Y., Yu M., Cui L., Jiang G., Wang G., Fan S.

Optica Applicata

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2016

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Vol. 46, nr 4

651--663

EN

A disparity servoing based fast autofocusing method is proposed for stereomicroscopes according to linear relationship between the disparity change in stereomicroscopic images and the move distance of a motorized translation stage. For a certain stereomicroscope, the calibration of a disparity range of clear images at each magnification is implemented offline. After that, the disparity of the stereomicroscopic image is used as an index to represent the sharpness of an arbitrary image. If the disparity does not satisfy the requirement, move steps and direction of a step motor are calculated by utilizing the linear relationship between the disparity change and the move distance of the stage. The iteration will be continued until the disparity of the captured stereomicroscopic image approximates to the clearest disparity. The experimental results show that the proposed method only requires a few iterations and less time to reach the focus position, and the disparity error is less than 0.5 pixel.

8

A super depth of field height measurement based on local disparity

Cui L., Liu Y., Yu M., Jiang G., Fan S., Wang Y.

Optica Applicata

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2015

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Vol. 45, nr 2

205--214

EN

A super depth of field height measurement method is proposed to measure the object height with the optical stereoscopic microscope. The quasi-Euclidean epipolar rectification algorithm is utilized on the original stereoimage to obtain rectified stereoimages and calibrate two camera parameters. Then, feature points are obtained by the SURF (speed up robust feature) algorithm and their corresponding disparities are calculated. The disparity-depth of field curve is fitted by combining the step height values of a stepper motor. Moreover, through local disparity value got from feature points on the object, the relative shift height is calculated through regression analysis. Finally, according to binocular vision geometry, the thickness of the object can be calculated. Experimental results show that the measurement error in Z direction is from 1.51% to 7.71%, which indicates that the proposed method is able to measure the height of a microobject beyond depth of field within a tolerant error.

9

Indoor positioning based on foot-mounted IMU

Guo H., Uradziński M., Yin H., Yu M.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2015

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Vol. 63, nr 3

629--634

EN

The paper presents the results of the project which examines the level of accuracy that can be achieved in precision indoor positioning by using a pedestrian dead reckoning (PDR) method. This project is focused on estimating the position using step detection technique based on foot-mounted IMU. The approach is sensor-fusion by using accelerometers, gyroscopes and magnetometers after initial alignment is completed. By estimating and compensating the drift errors in each step, the proposed method can reduce errors during the footsteps. There is an advantage of the step detection combined with ZUPT and ZARU for calculating the actual position, distance travelled and estimating the IMU sensors’ inherent accumulated error by EKF. Based on the above discussion, all algorithms are derived in detail in the paper. Several tests with an Xsens IMU device have been performed in order to evaluate the performance of the proposed method. The final results show that the dead reckoning positioning average position error did not exceed 0.88 m (0.2% to 1.73% of the total traveled distance – normally ranges from 0.3% to 10%), what is very promising for future handheld indoor navigation systems that can be used in large office buildings, malls, museums, hospitals, etc.

10

A new design of a photonic crystal fiber with a beam shaping effect and flexible management of dispersion and confinement loss

Huang Y., Jiang P, Yang H., Yu M.

Optica Applicata

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2014

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Vol. 44, nr 3

375--387

EN

A new design of a guiding-index photonic crystal fiber which possesses a beam shaping effect and flexible control of dispersion has been proposed in this paper. It can shape a Gaussian beam into a circular hollow beam with certain dimension, which can be used in optical communication systems with a Cassegrain antenna to improve transmission efficiency by avoiding the loss of energy caused by the subreflector center reflection. In addition, its dispersion and confinement loss can be changed in a broad range by slightly adjusting structural parameters under condition that the hollow beam dimension remains about the same. Fairly practical properties, zero dispersion or flattened dispersion, can be obtained when structural parameters are set appropriately. A series of models with different parameters are analyzed and compared. Results of numerical simulation show that the ultra-low dispersion of 1.802 ps/km/nm can be obtained when λ = 1.31 μm. Several modest design parameters are given as well.

11

Experimental Study of Clothing Tactile Comfort Based on Electro-neurophysiology

Wang Y., Wang Y., Zhao M. M., Yu M., Li J.

Fibres & Textiles in Eastern Europe

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2014

|

Vol. 22, no. 4 (106)

102--106

EN

Electromyography (EMG) and electroencephalography (EEG) methods were used to evaluate the reaction of human skin to tactile stimuli evoked by textiles. The peak value of the EMG and energy percentage of the weave of the EEG when the subjects came into contact with 9 kinds of fabrics were selected for tests and next clothing was made on their basis. They were utilized as two important evaluating indexes. Statistical analysis was carried out to verify the correlation between the data obtained from objective measurements and the subjective measurements. The results showed that when the subjects came into contact with thicker, heavier and stiffer fabrics, the peak values of the myoelectric potential induced were higher. When clothing with a higher mass density was worn, energy percentages of the weave at both the left and right occipitalia were higher.

PL

Dla oceny reakcji ludzkiej skóry na dotykowe stymulacje materiałami włóknistymi stosowano elektromiografię (EMG) i elektroencefalografie (EEG). Wartość szczytowa przebiegu EMG oraz procent energii fali EEG w czasie kiedy badane osoby znajdowały się w kontakcie z 9 rodzajami materiałów włókienniczych posłużyła do ich selekcji dla stosowanych testów. Na tej podstawie wykonano odzież przeznaczona dla osób testowanych. Przeprowadzono analizę statystyczna dla zweryfikowania korelacji pomiędzy wynikami uzyskanymi z obiektywnych pomiarów oraz subiektywnych testów. Wyniki wykazały, że kiedy osoby badane znajdowały się w kontakcie z grubszymi i cięższymi i sztywniejszymi materiałami to wartość piku EMG była wyższa. Kiedy ubranie wykonane było z udziałem przędz o wyższej masie liniowej procent energii fali lewej i prawej połówki potylicy był wyższy.

12

An all-fibre multi-parameter sensor for composite structures based on a chirped fibre Bragg grating

Zhan Y., Yang F., Gu K., Wu H., Yu M., Li L.

Opto-Electronics Review

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2013

|

Vol. 21, No. 3

283-287

EN

An all-fibre multi-parameter sensor for composite structures based on a chirped optical fibre Bragg grating (CFBG) has been studied theoretically and experimentally. The principle of multi-parameters sensing with a single CFBG is based on that the centre wavelength and the FWHM (full width at half maximum) in the reflection spectrum of a CFBG vary linearly with the temperature and/or the axial stress. A wavelength matched optical fibre long period grating (LPG) and another wavelength matched reference CFBG (CFBGR) have been used to interrogate the signal of the sensor CFBG (CFBGS). The temperature and strain of the composite structure have been monitored real-time with one CFBG as a single sensor head. The temperature resolution of 0.12ºC and the strain resolution of 1.1με for a composite structure have been realized in experiments. The experiment results agree well with the theoretical analyses.

13

Cuttings transport with foam in highly inclined wells at simulated downhole conditions

Xu J., Ozbayoglu E., Miska S., Yu M., Takach N.

Archives of Mining Sciences

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2013

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Vol. 58, no. 2

481--494

EN

Along with the rapidly growing demand and development activities in unconventional resources, is the growth of environmental awareness and concerns among the public. Foam, as an alternative to traditional drilling fluid, is gaining more and more momentum in the drilling industry. Drilling with foam can minimize formation damage, water usage, and drag and torque. Foam also costs less and leaves a much smaller environmental footprint than other commonly used drilling fluids, such as synthetic oil-based fluids, when developing vulnerable formations such as shale gas. As drilling in horizontal and near horizontal sections has become very common, and the need for such sections is increasing, it is very important to understand cuttings transport and hole cleaning issues when drilling with foam in such sections. A team from University of Tulsa Drilling Research Projects (TUDRP) conducted a series of experiments focused on studying the effects of change in hole inclination angle from 90 degrees to 70 degrees on cuttings transport with foam under Elevated Pressure and Elevated Temperature (EPET) conditions. This experimental and theoretical study also includes other influential parameters such as foam quality, foam flow rate, polymer concentration and drill pipe rotary speed. We have observed that there is no significant difference in cuttings concentration and frictional pressure losses as inclination changes from 70 to 90 degrees. Also, an increase in superficial foam velocity reduces cuttings concentration within the annulus. Pipe rotation influences cuttings concentration and frictional pressure losses for low quality foams, but does not have a significant effect on high quality foams. A correlation for the cuttings bed area and a computer simulator are developed for practical design and field applications. The predicted results are compared with experimental results from this study and previous studies. The comparison shows good agreement. We believe that the findings of this paper will help designers with the choice of optimal drilling fluid for drilling horizontal wells in unconventional (shale) gas/oil reservoirs.

PL

Równolegle ze stale rosnącym zapotrzebowaniem na prowadzenia prac udostępniających w złożach niekonwencjonalnych notuje się wzrost świadomości społecznej odnośnie zagadnień ochrony środowiska. Piana jako alternatywa dla tradycyjnej płuczki wiertniczej nabiera coraz większego znaczenia w górnictwie otworowym. Wiercenie przy użyciu piany pomogą ograniczać zniszczenia formacji geologicznych, redukuje zużycie wody, pozwala na zminimalizowanie oporów ruchu i momentów obrotowych silników. Ponadto, koszty piany są niższe a jej oddziaływanie na środowisko naturalne jest mniej znaczne niż w przypadku typowych płuczek opartych na olejach syntetycznych używanych w trakcie udostępniania trudnych w eksploatacji złóż, np. gazu łupkowego. Wiercenia odcinków poziomych lub prawie poziomych są już szeroko stosowane a zapotrzebowanie na takie odcinki wrasta, ważnym jest właściwe rozpoznanie problemów związanych z transportem urobku wiertniczego i czyszczeniem otworu w trakcie prowadzenia prac wiertniczych na tych odcinkach przy użyciu piany. Zespól badaczy z uniwersytetu w Tulsa zaangażowanych w projekt badawczy w dziedzinie wiertnictwa (TUDRP) przeprowadził serię eksperymentów mających na celu zbadanie wpływu zmiany kąta nachylenia otworu z 90 na 70 stopni na przebieg transportu urobku wiertniczego z wykorzystanie piany w warunkach podwyższonego ciśnienia i podwyższonych temperatur. Badania eksperymentalne i teoretyczne obejmowały także analizę pozostałych parametrów procesu: jakość piany, natężenie przepływu piany, stężenie polimerów, prędkość obrotowa przewodu wiertniczego. Nie stwierdzono znacznych różnic w stężeniu zwiercin ani utraty ciśnienia wskutek tarcia w trakcie zmiany kąta nachylenia z 90 na 70 stopni. Ponadto, dodatkowy wzrost prędkości ruchu piany prowadzi do zmniejszenia stężenia zwiercin w pierścieniu. Prędkość obrotowa przewodu wpływa na stężenie zwiercin i straty ciśnienia wskutek tarcia w przypadku stosowania pian niskiej jakości, efektu tego nie notuje się gdy wykorzystywane są wysokiej jakości piany. Dane z obszaru wiercenia skorelowane zostały z wynikami symulacji komputerowych do wspomagania projektowania i do wykorzystania w terenie. Prognozowane wyniki porównano z wynikami eksperymentów uzyskanymi w tym oraz w poprzednim programie badawczym. Porównanie to wykazuje dużą zgodność wyników. Mamy nadzieję, że wyniki obecnej pracy pomogą inżynierom projektantom w wyborze optymalnej płuczki wiertniczej do wierceń poziomych odcinków otworów przy eksploatacji niekonwencjonalnych złóż ropy i gazu (np. gazu łupkowego).

14

Effect of tripping velocity profiles on wellbore pressures and dynamic loading of drillstring

Wang Z., Miska S., Yu M., Takach N.

AGH Drilling, Oil, Gas

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2013

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Vol. 30, no. 1

269--286

EN

Tripping events are expensive and time-consuming. Thus, minimizing tripping time through choosing optimized tripping velocity becomes urgent. Surge or swab pressures in the wellbore and dynamic loading of drillstring will be generated during tripping. Also, dynamic velocity, which is the velocity at the bottom of drillstring, is different from the input velocity at surface. The effect of tripping velocity profile, i.e., tripping velocity changes with time, on the hook load, downhole pressure changes and drillstring dynamic velocity should be fully studied to achieve the optimization. In this study, the effects of tripping velocity profile on loading of drillstring, dynamic velocity and downhole pressure is investigated using numerical simulation. Bergeron's graphical method and Lubinski's approach are utilized to perform the simulations. Components of drillstring, wellbore depth, drillstring length and mud properties are also included in the simulations. Through the current work, a driller's typical way of changing tripping velocity may not be the best one. Selection of tripping velocity profiles should be adapted to depth: higher velocity, triangular/parabolic profiles in shallow wells and lower velocity, trapezoidal profiles in deep wells. Also, based on simulations, the oscillation magnitude of dynamic velocity can be as high as twice that of velocity at surface.

15

Research on the Key Technology of Image Guided Surgery

Weili S., Yanfang L., Yu M., Yinlong H.

Przegląd Elektrotechniczny

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2012

|

R. 88, nr 3b

29-33

EN

It research on the key technology on IGS (image-guided surgery). It proposes medical image segmentation based on PCNN and the virtual endoscopic scenes real-time rendering method based on GPU parallel computing technology, which improves the display quality of IGS’s virtual scene and real-time rendering speed. These methods are very important for IGS’s applications.

PL

Przedstawiono technologię operacji bazującej na prowadzonym systemie obrazu IGS. Zaproponowano segmentację obrazu I możliwość otrzymywania obrazu endoskopowego w trybie czasu rzeczywistego.

16

Experimental study of hydraulic sweeps in horizontal wells

Nguyen T. N., Miska S. Z., Yu M., Takach N. E., Ahmed R.

Wiertnictwo, Nafta, Gaz

|

2010

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T. 27, z. 1--2

307-331

EN

Drilling fluid sweeps are commonly run in the field to help clean the borehole of cuttings that have not been removed with normal drilling fluid circulation, especially in high angle or extended reach wells where efficient hole cleaning is more difficult to maintain. This study focuses on the use of "conventional" and "enhanced" sweeps in horizontal well bores. Not much information pertaining to the use of drilling fluid sweeps is available in the literature. Furthermore, there has been a lack of agreement as to which types of sweep fluids are most effective. Conventional sweeps most often include high viscosity fluids, high density fluids or a combination of both. In addition to conventional sweep fluids, an attempt was made to use enhanced sweep fluids, in which surfactants are used to attach cuttings to oil droplets that are intentionally introduced to the drilling fluid system. Because of their low density, oil droplets can have the ability to keep cuttings particles in suspension. The use of oil droplets is a new concept in cleaning horizontal and deviated wellbores. This work focuses on experimental analysis of sweep fluids with the goal of quantifying the sweep "efficiency". A small-scale sweep loop (SSL) was mainly used to conduct sweep experiments. Moreover, some experiments were carried out in a field-scale flow loop that operates at low-pressure ambient temperature (LPAT) conditions. Results show that pipe rotation plays a very important role in improving hole cleaning. Particularly, the improvement is substantial with high-viscosity fluids. The rotation of pipe has agitation effect that forces the cuttings particles into the main flow and facilitates the removal process. As anticipated, increasing the flow rate enhances the sweep efficiency or cuttings removal regardless of the drillpipe rotation. Furthermore, the study suggests that with a more rigorous evaluation of sweep efficiency, one can objectively determine the type and frequency of drilling sweep. The results of this study are useful for selection of the optimal sweep fluid.

PL

Płuczki czyszczące są powszechnie stosowane do oczyszczania otworów z pozostałości zwiercin, których nie udało się wynieść na powierzchnię za pomocą tradycyjnych płynów płuczkowych, głównie w przypadku otworów kierunkowych i rozgałęzionych, gdzie możliwość oczyszczenia jest ograniczona. Badania skoncentrowały się na wykorzystaniu konwencjonalnych i ulepszonych systemów czyszczących w otworach kierunkowych. W literaturze niezbyt wiele można znaleźć informacji na ten temat. Co więcej, brak jest zgody co do tego, która płuczka czyszcząca jest najskuteczniejsza. Tradycyjne płuczki czyszczące często zawierają płyny o wysokiej lepkości i/lub gęstości. Ponadto podjęto próbę stworzenia ulepszonych płuczek czyszczących, w których zastosowane surfaktanty mają powodować przyklejanie się zwiercin do drobin oleju, który celowo wprowadzono do systemu płuczkowego. Ze względu na niską gęstość, krople oleju utrzymują zwierciny w zawieszeniu. Zastosowanie kropli oleju to nowa koncepcja oczyszczania otworów horyzontalnych. W artykule skoncentrowano się na przeanalizowaniu płuczek czyszczących mających na celu zwiększenie skuteczności oczyszczania. Do badań z reguły stosowano mały obieg czyszczący SSL (small-scale sweep loop). Niektóre eksperymenty prowadzono na złożu w warunkach niskiego ciśnienia i temperatury otoczenia. Wyniki pokazują, że ruch rur odgrywa istotną rolę w zwiększeniu skuteczności oczyszczania otworu. Służy temu również zastosowanie wysoko lepkich płuczek. Rotacja rur podrywa zwierciny doprowadzając je do głównego strumienia, wspomagając proces oczyszczania. Jak przewidywano, ruch w otworze wzmaga wydajność oczyszczania lub wynoszenia zwiercin, niezależnie od rotacji rur. Z badań wynika, że szacując bardziej rygorystycznie zdolności czyszczące, można obiektywnie określić rodzaj i częstotliwość oczyszczania. Wyniki badań pozwalają na stosowny wybór optymalnego środka czyszczącego.

17

Ergonomics Hazards Analysis of Linemen’s Power Line Fixing Work in China

Yu M., Sun L., Du J., Wu F.

International Journal of Occupational Safety and Ergonomics

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2009

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Vol. 15, No. 3

309--317

EN

This study used qualitative and quantitative methods, such as OWAS (Ovako working posture analysis system) and behavior observation, to analyze musculoskeletal disorder (MSD) risk factors of power line fixing work in China. Video-based sampling was used to record and analyze the frequency and posture of on-pole activities. Those key subtasks showed ergonomics characteristics of on-pole fixing tasks. Insulator-fixing was the longest subtask (33% of total working time). Bar-installing was the second longest (26% of total working time). It was evident that bar-installing and insulator-fixing were full of hazardous risks. The action categories of the 2 subtasks were higher than of the other ones. The 2 subtasks were also time-consuming, difficult and induced MSDs. Assistant linemen faced more hazardous factors than chief linemen.

18

Effect of Ni addition on the microstructures of melt-spun CuCr ribbons

Yu M., Wang Y., Wang Y., Sun Z.

Materials Science Poland

|

2008

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Vol. 26, No. 3

675--680

EN

The microstructures and resistivities of melt-spun Cu75Cr25 and Cu(75.x)Cr25Nix (x = 1 or 3 wt. %) ribbons were studied. The size of the Cr-rich phase from liquid phase separation in the Cu75Cr25 microstructure can be decreased from the micrometer-scale to about 250 nm by using melt spinning. After annealing at 600 ° C for 3 h, the resistivity of Cu75Cr25 ribbon can meet the needs of contact. On the melt-spun base, alloying by Ni could further decrease the size of the Cr-rich phase from 250 nm to about 150 nm. However, when the Ni content is higher than or equal to 3%, the resistivity of annealed Cu75. xCr25Nix (x ≥ 3) ribbons is too high to be used by the medium-voltage vacuum interrupters. For nanograined CuCr alloys, its lower arc chopping current is advantageous to the use of contact and the circuitry protect, its long arc trace route and high velocity of spot direction motion could mitigate the partial ablate of cathode surface and the lifetime of contact could be prolonged.

19

Compensated ionization chamber for (n,α) reaction measurements at a spallation neutron source

Andrzejewski J., Yu M., Gledenov M., Korejwo A., Sobczak K., Szałański P.

Nukleonika

|

2007

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Vol. 52, nr 2

51-57

EN

The new spallation neutron facility n_TOF (neutron time-of-flight) at CERN opens wide possibilities in measurements of neutron induced reaction cross sections. The facility with its excellent energy resolution of neutrons, low repetition rate and most important – with a very high instantaneous luminosity, makes up an extra challenge for experimenters faced by doing measurements at a high peak intensity spallation source. Our proposition is directed to the use of a compensated ionization chamber for the (n, alpha) reaction cross section measurements we plan to carry out in a wide range of neutron energy. First experience gained with using such a kind of detector at ORELA (the Oak Ridge Electron Linear Accelerator) neutron source (ORNL) was very optimistic.

20

Modeling of ECD in casing drilling operations and comparison with experimentaland field data

Diaz H., Yu M., Miska S., Takach N.

Archives of Mining Sciences

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2007

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Vol. 52, no 4

457-481

EN

Three modeling approaches to the determination of equivalent circulating density (ECD) in Casing Drilling operations are considered in this study; viz., hook-load measurements, pump-pressure measurements and conventional hydraulic models. The bottom-hole pressure is obtained by adding the calculated annular pressure losses to the hydrostatic pressure. Since the annular clearance is very small in casing drilling, a narrow-slot flow approximation model is adopted that takes into account the effect of pipe rotation. A Yield-Power-Law (YPL) drilling fluid is considered in this study. Results from each of the three approaches are compared with experimental and field data. The differences between the calculated and measured bottom-hole pressures (hence ECD) are within a range of about [...]. In terms of the frictional pressure losses in the annulus, this range increases to about [...] in some instances. It is shown that pipe rotation plays an important role in determining ECD. The experimental data indicate an increase in the annular pressure losses with increasing pipe rotary speed. The hook-load measurements correlate well with flowing bottom-hole pressures.

PL

W artykule rozważono trzy podejścia do modelowań wykonywanych w celu określenia ekwiwalentnej gęstości cyrkulacyjnej (ECD) w operacjach wiercenia z równoczesnym rurowaniem); poprzez pomiary obciążenia haka, pomiary ciśnienia pomp oraz zastosowanie konwencjonalnych modeli hydraulicznych. Ciśnienie na dnie otworu otrzymywane jest przez dodanie obliczonych strat ciśnienia w przestrzeni pierścieniowej do ciśnienia hydrostatycznego. W przypadku rur okładzinowych wielkość przestrzeni pierścieniowej jest bardzo niewielka, dlatego zaadaptowano model wąskiej szczeliny, uwzględniający efekt rotacji rur. W artykule rozważano płuczkę opisywaną modelem reologicznym Herschela Bulkleya (YPL). Wyniki zastosowania wymienionych trzech podejść zostały porównane z danymi doświadczalnymi i terenowymi. Różnice pomiędzy wartościami ciśnienia obliczonego i zmierzonego na dnie otworu (a więc i ekwiwalentnej gęstości cyrkulacyjnej) pozostają na poziomie ok. [...]. W przypadku strat ciśnienia w przestrzeni pierścieniowej w niektórych przypadkach wartość ta ulega zwiększeniu do ok. [...]. Zwrócono uwagę, że rotacja rur odgrywa dużą rolę w określaniu ekwiwalentnej gęstości cyrkulacji. Dane doświadczalne wskazują na wzrost strat ciśnienia w przestrzeni pierścieniowej wraz z rosnącą prędkością obrotową rur. Uzyskano dobrą korelację między pomiarami obciążenia haka i ciśnienia przepływu na dnie otworu.