Fliuktuojanti asimetrija (FA) - tai asimetrijos forma, susijusi su atsitiktiniais nukrypimais nuo tikslios kūno simetrijos. Nustatyta, jog gyvūnų populiacijose FA lygis koreliuoja su tam tikrų aplinkos stresų, kuriuos individai patiria savo ontogenetiniame vystymesi, lygiu (Zakharov, 1989; Palmer, 1994). Tokiu būdu, FA gali būti aplinkos kokybės indikatoriumi: kuo mažiau asimetriškų individų populiacijoje, tuo optimalesnė aplinka. Dabartinė bebrų populiacija Lietuvoje yra susiformavusi iš keleto genetiškai skirtingų plitimo židinių. Galima daryti prielaidą, jog skirtingos genetinės struktūros populiacijos gali nevienodai reaguoti į aplinkos stresus. FA lygis buvo tiriamas dešimtyje upių baseinų lokaliose bebrų populiacijose. FA lygis buvo vertinamas pagal 5 metrinius ir 46 nemetrinius bebrų kaukolės požymius. Pirmuoju atveju FA lygis vertintas pagal skirtumų tarp kairės ir dešinės kaukolės pusių dispersiją, antruoju – pagal asimetriškų individų procentą populiacijoje. Tirtų individų imtis – 562. Tyrimų metu buvo nustatyta, kad mažiausiai FA lygis priklauso nuo bebrų lyties pagal nemetrinius kaukolės požymius. Daugiausiai – nuo individų amžinės struktūros. Mažiausiai asimetriški yra jaunikliai (FA lygis siekė 34%), dižiausias FA lygis nustatytas lytiškai subrendusių individų imtyje (46%). Taip pat nustatyta, kad juodą kailį turintys individai yra asimetriškesni už rudą kailį turinčius individus, o individai su dantų vystymosi anomalijomis yra asimetriškesni už dantų anomalijų... [toliau žr. visą tekstą] / Fluctuating asymmetry (FA) it is a form of asymmetry which is related with random deviations off accurate body symmetry. It has been stated, that in animal populations a level of FA correlates with a level of environmental stresses which occure during animals ontogenetic development (Zakharov, 1989; Palmer, 1994). Therefore FA could be an indicator of environmental quality: the less asymmetric individuals in population, the better environment. Present beaver population is formed from several genetically different places in Lithuania. So it could be that genetically different local populations can react to environmental stresses differently. Level of FA in ten river watersheds in local beaver populations has been investigated. Level of FA in skulls of beavers according to 5 metric and 46 non metric traits has been assessed. Level of FA has been assessed according to differences between left and right skull side dispersion in first case, in second case – according to percentage of asymmetric individuals in population. Number of investigated individuals is 562. It has been stated, that level of FA depends on beaver sex at least according to non metric skull traits. Mostly it depends on age structure of individuals. At least asymmetric there are juveniles (level of FA was 34%), great level of FA has been stated in adults (46%). Also it has been stated, that beavers who have black skin are more asymmetric than brown skin ones and individuals who have tooth anomalies are more... [to full text]

No description available.

The study of mixing processes in supersonic flow has a great interest for a number of applications including scramjet developments. However, the usual tools employed are very limited. Sampling probes generally have a poor frequency response, and that makes measurements of fluctuating concentration problematic. The goal of this study is to design, build and test a probe capable of measuring concentration fluctuations of at least 1 kHz. This study shows the design of such a probe and how a high frequency response was achieved. A prototype was built and tested. The tests consist of a calibration phase and experiments inside a hypersonic wind tunnel. These last tests served two purposes. The first one was to verify that the measurements made with the probe gave the correct value of the concentration. The second purpose was to assess the frequency response of the probe by putting it through a concentration step change. Tests were conducted with various known mixtures of Helium and air from 0% to 100% flowing at Mach 2.0 with T_t=300 °K and P_t=4.4 atm. The probe proved capable of measuring concentration fluctuations up to approximately 2.5 kHz while also giving the adequate accuracy for values of mean concentration. / Master of Science

Fluid mixing that is induced by hydrodynamic instability is ubiquitous in nature; the material interface between two fluids when perturbed even slightly, changes shape under the influence of hydrodynamic forces, and an additional zone called the mixing layer where the two fluids mix, develops and grows in size. This dissertation reports a study on the role of thermal fluctuations in fluid mixing at the interface separating two perfectly miscible fluids of different densities. Mixing under the influence of two types of instabilities is studied; the Rayleigh-Taylor (RTI) and Richtmyer-Meshkov (RMI) instabilities. The study was conducted using numerical simulations after verification of the simulation methodology. Specifically, fluctuating hydrodynamic simulations were used; the fluctuating compressible Navier-Stokes equations were the physical model of the system, and they were solved using numerical methods that were developed and implemented in-house. Our results indicate that thermal fluctuations can trigger the onset of RTI at an initially unperturbed fluid-fluid interface, which subsequently leads to mixing of multi-mode character. In addition we find that for both RMI and RTI, whether or not thermal fluctuations quantitatively affect the mixing behavior, depends on the magnitude of the dimensionless Boltzmann number of the hydrodynamic system in question, and not solely on its size. When the Boltzmann number is much smaller than unity, the quantitative effect of thermal fluctuations on the mixing behavior is negligible. Under this circumstance, we show that mixing behavior is the average of the outcome from several stochastic instances, with the ensemble of stochastic instances providing the bounds on mixing-related metrics such as the mixing width. Most macroscopic hydrodynamic systems fall in this category. However, when the system is such that the Boltzmann number is of order unity, we show that thermal fluctuations can significantly affect the mixing behavior; the ensemble-averaged solution shows a departure from the deterministic solution. We conclude that for such systems, it is important to account for thermal fluctuations in order to correctly capture their physical behavior.

No description available.

A study of the fluctuating wall pressure and unsteady velocity field in a flat plate turbulent boundary layer flow was conducted over a moderate range of Reynolds numbers to better understand the mechanisms by which the two fields are coupled. Individual and coincident measurements of the fluctuating pressure and velocity fields were acquired using a 20 element hydrophone array and a two-component Laser Doppler Anemometer, respectively. Estimates of the velocity power spectral density (PSD) revealed two primary trends predicted by turbulence theory, k⁻¹ in the region of (ky) = 10⁰ due to anisotropy of the large scales, and k⁻⁵/³ for larger values of (ky) where structures appear more isotropic. The mean velocity profiles, having been collapsed using outer scaling variables, exhibited the presence of a slightly adverse pressure gradient with a n = 6 power law shape. As for the fluctuating wall pressure, increased Reynolds numbers produced increases in the amplitude and frequency of the characteristic signatures from which the pressure spectral densities were also found to collapse reasonably well using outer scaling variables. The results suggest the location in the flow where the mechanisms responsible for driving the fluctuating wall pressure signatures reside. Space-time correlations and frequency-wavenumber analysis reveal a convective ridge in the fluctuating wall pressure corresponding to the passage of several organized structures at 75% of the free stream velocity for all Reynolds numbers tested. / text

No description available.

Livestock odour has been an obstacle for the development of livestock industry. Air dispersion models have been applied to predict odour concentrations downwind from the livestock operations. However, most of the air dispersion models were designed for industry pollutants and can only predict hourly average concentrations of pollutants. Currently, a livestock odour dispersion model that can consider the difference between livestock odour and traditional air pollutants and can account for the short time fluctuations is not available. Therefore, the objective of this research was to develop a dispersion model that is designed specifically for livestock odour and is able to consider the short time odour concentration fluctuations. A livestock odour dispersion model (LODM) was developed based on Gaussian fluctuating plume theory to account for odour instantaneous fluctuations. The model has the capability to predict mean odour concentration, instantaneous odour concentration, peak odour concentration and the frequency of odour concentration that is equal to or above a certain level with the input of hourly routine meteorological data.<p> LODM predicts odour frequency by a weighted odour exceeding half width method. A simple and effective method is created to estimate the odour frequency from multiple sources. Both Pasquill-Gifford and Hogstr¨¯m dispersion coefficients are applied in this model. The atmospheric condition is characterized by some derived parameters including friction velocity, sensible heat flux, M-O length, and mixing height. An advanced method adapted from AERMOD model is applied to derive these parameters. An easy to use procedure is generated and utilized to deal with the typical meteorological data input as ISC met file. LODM accepts and only requires routine meteorological data. It has the ability to process individual or multiple sources which could be elevated point sources, ground level sources, livestock buildings, manure storages, and manure land applications. It can also deal with constant and varied emission rates. Moreover, the model considers the relationships between odour intensity and odour concentrations in the model. Finally, the model is very easy to use with a friendly interface.<p> Model evaluations and validations against field plume measurement data and ISCST3 and CALPUFF models indicate that LODM can achieve fairly good odour concentration and odour frequency predictions. The sensitivity analyses demonstrate a medium sensitivity of LODM to the controllable odour source parameters, such as stack height, diameter, exit velocity, exit temperature, and emission rate. This shows that the model has a great potential for application on resolving odour issues from livestock operations. From that perspective, the most effective way to reduce odour problems from livestock buildings is to lessen the odour emission rate (e.g. biofiltration of exhaust air, diet changes).

Livestock odour has been an obstacle for the development of livestock industry. Air dispersion models have been applied to predict odour concentrations downwind from the livestock operations. However, most of the air dispersion models were designed for industry pollutants and can only predict hourly average concentrations of pollutants. Currently, a livestock odour dispersion model that can consider the difference between livestock odour and traditional air pollutants and can account for the short time fluctuations is not available. Therefore, the objective of this research was to develop a dispersion model that is designed specifically for livestock odour and is able to consider the short time odour concentration fluctuations. A livestock odour dispersion model (LODM) was developed based on Gaussian fluctuating plume theory to account for odour instantaneous fluctuations. The model has the capability to predict mean odour concentration, instantaneous odour concentration, peak odour concentration and the frequency of odour concentration that is equal to or above a certain level with the input of hourly routine meteorological data.<p> LODM predicts odour frequency by a weighted odour exceeding half width method. A simple and effective method is created to estimate the odour frequency from multiple sources. Both Pasquill-Gifford and Hogstr¨¯m dispersion coefficients are applied in this model. The atmospheric condition is characterized by some derived parameters including friction velocity, sensible heat flux, M-O length, and mixing height. An advanced method adapted from AERMOD model is applied to derive these parameters. An easy to use procedure is generated and utilized to deal with the typical meteorological data input as ISC met file. LODM accepts and only requires routine meteorological data. It has the ability to process individual or multiple sources which could be elevated point sources, ground level sources, livestock buildings, manure storages, and manure land applications. It can also deal with constant and varied emission rates. Moreover, the model considers the relationships between odour intensity and odour concentrations in the model. Finally, the model is very easy to use with a friendly interface.<p> Model evaluations and validations against field plume measurement data and ISCST3 and CALPUFF models indicate that LODM can achieve fairly good odour concentration and odour frequency predictions. The sensitivity analyses demonstrate a medium sensitivity of LODM to the controllable odour source parameters, such as stack height, diameter, exit velocity, exit temperature, and emission rate. This shows that the model has a great potential for application on resolving odour issues from livestock operations. From that perspective, the most effective way to reduce odour problems from livestock buildings is to lessen the odour emission rate (e.g. biofiltration of exhaust air, diet changes).

Tyrimo problema Mūsų visuomenėje neskiriama pakankamai dėmesio kairiarankiams, jų problemos yra ignoruojamos, apie ką kalbama ir užsienio autorių darbuose, tačiau iki šiol nėra pakankamai aiškios skirtingo abiejų žmonių rankų veiksnumo priežastys, sąsajos ir padariniai. Tyrimo tikslas. Ištirti, kaip priklauso dešiniarankiškumo/kairiarankiškumo laipsnis nuo fizinio aktyvumo lygio ir pobūdžio (t.y. ištirti dešiniarankiškumo ir kairiarankiškumo paplitimą tarp skirtingų sporto šakų atletų) ir nustatyti dešiniarankiškumo/kairiarankiškumo laipsnio sąsajas su rankų funkciniai ir anatominiais rodikliais. Darbo uždaviniai. 1. Anketavimo metodu nustatyti ir palyginti skirtingų sporto šakų atletų dešiniarankiškumo/kairiarankiškumo laipsnį. 2. Palyginti skirtingų sporto šakų atletų skirtingų rankų matmenų ir funkcinę asimetriją bei palyginti skirtingų sporto šakų ir grupių sportininkų rankų matmenų ir funkcinę asimetriją tarpusavyje. 3. Ištirti koreliacinę dešiniaranki���kumo/kairiarankiškumo laipsnio priklausomybę su rankų funkciniu ir matmenų asimetriškumu. Rezultatai. Iš visų tirtų 126 vyrų kairiarankių buvo 6,3 procento. Iš tirtų 33 kontrolinės grupės (nesportuojančiųjų) asmenų nė vieno pagal Bryden klausimyną nenustatėme esančio kairiarankiu. Tiek jėgos, tiek ištvermės sporto šakose buvo daugiau vyrų, kuriems dešinė ranka yra patogi rečiau/mažiau nei kairė (p<0,05). Tarp žaidėjų ir nesportuojančiųjų reikšmingas dešiniarankiškumo/kairiarankiškumo skirtumas nenustatytas (p>0,05)... [toliau žr. visą tekstą] / In the our days society, still not enough attention is paid at left-handed persons‘ problems, and we still lack the knowledge on the reasons and outcomes of the so-called hand preference, or handedness. Thus the aim of our study was to evaluate how the degree of handedness is dependent on the level and type of physical activity, and we studied three groups of athletes from different sports as well as sedentaries by standard questionnaire on hand preference as well as standard physical tests and anthropometry in order to determine the predilection of left/right-handedness among athletes from various different sports, and to obtain some better knowledge on the relationship of hand-preference with the functional and anthropometrical (a)symmetry of the hands. The results obtained revealed that among 126 of studied males 6.3 percent were clearly left-handed, but no one of the 33 control sedentaries was. Clear tendency was evident that among athletes of strength and endurance activities left-handedness was more expressed. This was not the case in ball-game athletes’ group. All groups when studies separately as well as one big group did not showed any signs of hand-size asymmetry, though some of the results of the tests for hand function were distinct between hands, the same in overall group and in four groups studied separately. These were handgrip strength, juggling with two baseballs, and maximal rate of hand and arm movements. The correlation between handedness score and... [to full text]