Supplementary Mass Research Articles

Nonlinear interaction of parametric excitation and self-excited vibration in a 4 DoF discontinuous system

Interaction between parametric excitation and self-excited vibration has been subjected to numerous investigations in continuous systems. The ability of parametric excitation to quench self-excited vibrations in such systems has also been well documented. But such effects in discontinuous systems do not seem to have received comparable attention. In this article, we investigate the interaction between parametric excitation and self-excited vibration in a four degree of freedom discontinuous mechanical system. Unlike majority of studies in which oscillatory nature of stiffness accounts for parametric excitation, we consider a much more practical case in which parametric excitation is provided by a massless rotor of rectangular cross section with a cylinder-like mass concentrated at the center. The rotor arrangement is placed on a friction-induced self-excited support in the form of a frame placed on a belt moving with constant velocity. This frame is connected to a supplementary mass. A Stribeck friction model is considered for the mass in contact with the belt. The frictional force between the mass and the belt is oscillatory in nature because of the variation of normal force due to parametric excitation from the rotor. Our investigations reveal mutual synchronization of parametric excitation and self-excited vibration in the system for specific parameter values. The existence of a stable limit cycle with constant synchronized fundamental frequency, for a range of parametric excitation frequencies, is established numerically. Investigation based on frequency spectra and Lissajous curves reveals complex synchronization patterns owing to the presence of higher harmonics. The system is also shown to exhibit Neimark–Sacker bifurcations under the variation of belt velocity. Furthermore, variation in belt velocity and coupling stiffness is seen to cause a breakup of quasi-periodic torus with small-amplitude oscillations to form large amplitude chaotic orbits. This points toward the possibility of vibration suppression in the system by tuning the parameters for stabilizing the small-amplitude quasi-periodic response. An example of co-existence of different attractors in the system is also presented.

Design and experiment of a direct-drive wave energy converter using a variable stiffness mechanism

This paper proposes a new method to achieve the resonant behavior of a point absorber floating buoy type of Wave Energy Converter using direct drive power take-off system. The system has four main components: a frame; a buoy with a guiding shaft; a supplementary mass coupled with a linear generator and a variable stiffness structure. Firstly, the motion in the vertical direction of the buoy in the sea is converted to an oscillating motion of the supplementary mass. Next, the mass is coupled with a copper coil. The coil motion inside a magnetic wall induces an electrical current in the coil as a linear generator. Besides, a pair of pre-tension springs creates a negative stiffness phenomenon that acts on the motion of the mass and increases the performance of the system. Finally, a variable stiffness structure is installed to control the trajectory of the mass, it can increase the velocity of the mass motion thus the performance of the system is improved. Configuration and working principles of WEC were introduced, studied and analyzed. The mathematical model was presented to explain system behavior. The numerical simulation had been carried out to evaluate the operation of the system. The experimental test rig had been set up and implemented to verify the effectiveness of the proposed structure.

Performance analysis of a tuned point absorber using SPH calm water and wave tank simulations

In this paper, two smoothed particle hydrodynamics (SPH) models, namely SPH-W and SPH-C were used to evaluate the motion response of a point absorber wave energy converter (WEC). In the SPH-W model, a long wave flume was constructed and a long simulation was performed to obtain the motion response of the WEC. In the SPH-C model, the SPH method is only used to find the hydrodynamic coefficients of the device by analysing a few seconds of free-decaying motion of WEC in calm water in a much smaller numerical flume. Then, these coefficients were inserted in the equation of motion of a heaving WEC that was solved using a 4th order Runge-Kutta (ODE45) solver in MATLAB. First, the energy conservation property of the WCSPH model was examined through a standing wave benchmark test. Then, the wave-point absorber interaction was simulated. While the simulation time for SPH-C model is much smaller than that of SPH-W, it gave almost similar results for the motion response of WEC. These two models were used to evaluate the effects of the control force and the draft of a cone-cylinder point absorber on its hydrodynamic responses. The results showed that compared to the effect of the supplementary inertia, changes in the draft of the WEC have a small influence on its hydrodynamic responses. The buoy draft has an inverse relationship with both added mass and damping coefficients. However, increasing the supplementary mass increases the added mass and decreases the hydrodynamic damping coefficients.

Modelling SARS-CoV-2 transmission in a UK university setting

Around 40% of school leavers in the UK attend university and individual universities generally host thousands of students each academic year. Bringing together these student communities during the COVID-19 pandemic may require strong interventions to control transmission. Prior modelling analyses of SARS-CoV-2 transmission within universities using compartmental modelling approaches suggest that outbreaks are almost inevitable.We constructed a network-based model to capture the interactions of a student population in different settings (housing, social and study). For a single academic term of a representative campus-based university, we ran a susceptible–latent–infectious–recovered type epidemic process, parameterised according to available estimates for SARS-CoV-2. We investigated the impact of: adherence to (or effectiveness of) isolation and test and trace measures; room isolation of symptomatic students; and supplementary mass testing.With all adhering to test, trace and isolation measures, we found that 22% (7%–41%) of the student population could be infected during the autumn term, compared to 69% (56%–76%) when assuming zero adherence to such measures. Irrespective of the adherence to isolation measures, on average a higher proportion of students resident on-campus became infected compared to students resident off-campus. Room isolation generated minimal benefits. Regular mass testing, together with high adherence to isolation and test and trace measures, could substantially reduce the proportion infected during the term compared to having no testing.Our findings suggest SARS-CoV-2 may readily transmit in a university setting if there is limited adherence to nonpharmaceutical interventions and/or there are delays in receiving test results. Following isolation guidance and effective contact tracing curbed transmission and reduced the expected time an adhering student would spend in isolation.

Multi-Disciplinary and Multi-Scale Assessment of Marine Renewable Energy Structure in a Tidal System

The French coast of the Atlantic and English Channel (EC) is promising for the development of Marine Renewable Energy (MRE), including wind, wave, and tidal stream, due to the high velocity of currents in some parts of the area. This paper, focusing on wind and tidal energy, discusses how the implementation of MRE converters influences biodiversity, and vice versa, through biofouling and reef effects. The understanding of these interactions requires the knowledge of the hydro-sedimentary conditions and the macrofauna. The research on these topics, performed at the Continental and Coastal Morphodynamic laboratory (M2C) (UNICAEN, France), is presented through a multi-disciplinary approach by i) studying the hydrodynamic conditions and the macrofauna in Alderney Race, ii) studying the biofouling effects on tidal turbines and their influence on the turbulent wake, iii) assessing the hydro-sedimentary impacts induced by the offshore wind farm, like scouring, and iv) taking an ecosystem approach on MRE, such as the reef effect. From an ecological perspective, the reef effect can be responsible for changes in the structure and function of the ecosystem. Although several studies have analyzed this effect at the species-or community-scale, the propagation of the reef effect at the ecosystem-scale remains unclear. Thus, understanding these ecosystem-scale effects is urgent for future research. From an engineering perspective, biofouling changes the structural characteristics (i.e., supplementary mass) of the converters and thus, affects their performance.

Business Continuity of Polio Eradication in the Context of COVID-19 Pandemic in Pakistan - A Success Story

Background: Pakistan is fighting with wild polio virus and Covid -19. Immunization gap could halt the achievements of Polio program and bridging the gap of immunity was only possible by supplemental immunization. This descriptive observational study on implementation of Supplementary Mass immunization Campaign with Oral Polio Vaccines during Covid -19 pandemic describes the process of strategic shift from conducting small scale target to full scale Pakistan National Immunization day. National Emergency Operational Cell (NEOC) Data was used for accessing the strategic shift & SIA indicator set by Global Polio Eradication Initiative.Methods: We analyzed the changes in process of SIA implementation and comprehended the strategic shift of campaign modalities, provision of personal protective equipment and measurement of the Covid-19 infection incidence amongst frontline health care workers. We analyzed the vaccine refusals numbers to rule out the fear of increase in refusal during Pandemic.Findings: Three SIA rounds were conducted with gradual increase from small-scale test campaign in six districts with children under five targets of seven hundred ninety thousand five hundred twenty-nine to a Sub National Immunization Days (SNIDs) August 2020 campaign conducted targeting thirty-four million under 5 children in one hundred thirty districts and National Immunization Days (NIDs) September 2020 country wide targeting forty million under 5 children in one-hundred sixty-three districts.Interpretation: National Emergency Action Plan(NEAP) of Pakistan has key program indicators. All three campaigns achieved target indicators. Number of vaccine refusal did not increase during Covid -19. Frontline vaccinators were provided with Sufficient number of Mask & Sanitizers and were trained on Standard operating procedures of WHO guideline for Polio SIA implementation. Infectivity with covid-19 did not increase in frontline workers.Funding Statement: No funding is taken for this research.Declaration of Interests: The authors whose names are listed as authors certify that they have No affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patentlicensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.Ethics Approval Statement: Approval was taken from National emergency operational cell, Polio eradication initiative Pakistan.

Explaining the Nature of the Mass m of Submicroparticles and the Phenomenon of Mass Variation with Velocity V in Ether

A brief history of mass nature is presented, including formulas for mass variation with velocity V. A new mass hypothesis (MH), on the nature of mass m is presented. Accordingly, the mass m0 of submicroparticle (SMP), is given by the kinetic energy accumulated inside the SMP, by the vortices/vibrations of groups of ether (ETH) cells, constituting the submicroparticles (SSMP). These SSMPs will also create the inertial force (FI) of the SMP, due to the opposition manifested by ETH, toward any accelerated movement of SMP. A new explanation of mass m increase, with V is proposed, admitting the existence of ether in the form of our model, HM16. The entrainment of the surrounding ETH of SMP, takes place, with speed VETH, which stores the EETH energy. The spatial variation of VETH around the SMP, was analysed using the method of potential motions, for a cylinder, moving in water-like fluid, or in ETH, resulting a spectrum of the lines of current ψ, indicating the size of VETH, rapidly decreasing with distance r. So resulted the kinetic energy EETH stored by the movement of the outer ETH, which provides the supplementary mass ms. The case of SMP which acquires velocity V, approaching c, was analysed. Then, a phase change (PC) will take place, through which the SMP, transforms into photons (PHs), when movements of the ETH from the outside including energy EETH is transferred into PH photons, having velocity c, representing ETH’s property.

Development of a Wave Energy Converter with Mechanical Power Take-Off via Supplementary Inertia Control

To reduce environmental pollution, alternative renewable energy resources have been explored for decades. Wave energy has a high energy density, high utilization time and no fuel costs, so it is considered as the most promising alternative to the fossil fuel resources. The number of studies of wave energy converters (WECs) has rapidly increased. This paper proposes a new method to achieve the resonant behavior of a point absorber floating buoy type of WEC using a mechanical power take-off system. By using the inertia characteristics of a hydraulic flywheel accumulator-based electro-hydraulic actuator to change the corresponding supplementary mass of the floating buoy, the total mass of the buoy was close to a match with the relatively low frequency of the wave, so that the buoy was in resonance with the wave. The specifications of the hydraulic flywheel accumulator system were proposed and studied. The working principle was analyzed, and a mathematical model was then derived to investigate the system operation. An experimental set-up was implemented to validate the mathematical model. Numerical simulation using MATLAB/Simulink was done to evaluate the operation of the system.

Thermodynamic performance and cost optimization of a novel hybrid thermal-compressed air energy storage system design

Abstract Compressed Air Energy Storage (CAES) can potentially allow renewable energy sources to meet electricity demands as reliably as coal-fired power plants. However, conventional CAES systems rely on the combustion of natural gas, require large storage volumes, and operate at high pressures, which possess inherent problems such as high costs, strict geological locations, and the production of greenhouse gas emissions. A novel and patented hybrid thermal-compressed air energy storage (HT-CAES) design is presented which allows a portion of the available energy, from the grid or renewable sources, to operate a compressor and the remainder to be converted and stored in the form of heat, through joule heating in a sensible thermal storage medium. The HT-CAES design incudes a turbocharger unit that provides supplementary mass flow rate alongside the air storage. The hybrid design and the addition of a turbocharger have the beneficial effect of mitigating the shortcomings of conventional CAES systems and its derivatives by eliminating combustion emissions and reducing storage volumes, operating pressures, and costs. Storage efficiency and cost are the two key factors, which upon integration with renewable energies would allow the sources to operate as independent forms of sustainable energy. The potential of the HT-CAES design is illustrated through a thermodynamic optimization study, which outlines key variables that have a major impact on the performance and economics of the storage system. The optimization analysis quantifies the required distribution of energy between thermal and compressed air energy storage, for maximum efficiency, and for minimum cost. This study provides a roundtrip energy and exergy efficiency map of the storage system and illustrates a trade off that exists between its capital cost and performance.

Manipulating cavitation by a wall jet: Experiments on a 2D hydrofoil

We report on the experimental investigation of cavitating flow control over a 2D model of guide vanes of a Francis turbine by means of a continuous tangential injection of liquid along the foil surface. The generated wall jet, providing supplementary mass and momentum, issues from a nozzle chamber inside the hydrofoil through a spanwise slot channel on its upper surface. High-speed imaging was used to distinguish cavity flow regimes, study the spatial patterns and time dynamics of partial cavities, as well as to evaluate the characteristic integral parameters of cavitation. Time-resolved LIF visualization of the jet discharging from the nozzle was employed to check if the generated wall jet is stable and spanwise uniform. Hydroacoustic measurements were performed by a hydrophone to estimate how the amplitudes and frequencies of pressure pulsations associated with cavity oscillations change with the injection rate. A PIV technique was utilized to measure the mean velocity, its fluctuations and the dominant turbulent shear stress component, which were all compared for different flow conditions and with the results for the unmodified (standard) foil. The effect of injection rate on cavitation and flow dynamics was examined for three attack angles, 0, 3 and 9°, and a range of cavitation numbers corresponding to different regimes. The low-speed injection was shown to lead to an intensification of turbulent fluctuations in the boundary layer and shrinking of the attached cavity length by up to 25% compared to the case without injection. The injection with a high velocity, in turn, causes a rise of the local flow velocity and a reduction of turbulent fluctuations near the wall, which, consequently, increases the foil hydrodynamic quality at a relatively low energy consumption for generation of the wall jet. However, in this case the vapor cavity becomes longer. Thus, the low-speed injection turns out to be effective to mitigate cavitation but the injection at a high velocity is more preferable from the standpoint of the flow hydrodynamics. In the whole, the implemented control method showed to be quite an efficient tool to manipulate cavitation and hydrodynamic structure of the flow and, thereby, under certain conditions, to suppress the cavitation-caused instabilities.

Structure and transport properties of proton-conducting BaSn0.5In0.5O2.75 and A-site substituted Ba0.9Ln0.1Sn0.5In0.5O2.8 (Ln = La, Gd) oxides

In this work, characterization of BaSn0.5In0.5O2.75, Ba0.9La0.1Sn0.5In0.5O2.8 and Ba0.9Gd0.1Sn0.5In0.5O2.8 perovskite-type oxides is reported concerning crystal structure, presence of protons in hydrated samples and transport properties of dense pellets in dry and wet atmospheres at elevated temperatures. Compounds possess cubic structure at room temperature, which is in accordance with Goldschmidt's tolerance factor t being close to 1. Introduction of smaller Ln partially substituting Ba results in a decreased unit cell volume. Upon hydration in wet air unit cell of the materials enlarge, with magnitude of the effect correlated with chemical composition. High temperature X-ray measurements in synthetic air revealed release of water from hydrated materials occurring above 200°C, and associated non-monotonous dependence of the respective unit cell parameter. No significant influence of dopants is found concerning thermal expansion of the studied oxides. Performed thermogravimetric measurements on hydrated and dried samples with supplementary mass spectroscopy analysis are in agreement with structural results, confirming presence of water in the hydrated compounds, but also show CO2 release during heating. Electrochemical impedance measurements, conducted for densified pellets in dry, H2O- and D2O-containing synthetic air, indicate an appearance of proton conductivity, with different dependence of bulk and grain boundary components on chemical composition. Supplementary electrical conductivity relaxation experiments, which allowed calculating diffusion and surface coefficients are also provided.

Hydrodynamic performance of concentric arrays of point absorbers

The behaviour of arrays of 12 heaving point absorbers in concentric arrangements is numerically assessed in a frequency domain model. The floaters are attached to a central cylindrical bottom-mounted structure. Each point absorber is restricted to the heave mode and is assumed to have its own linear power take-off system consisting of an external damping coefficient enabling power extraction and a supplementary mass coefficient tuning the point absorber to the incoming waves. The external damping and supplementary mass coefficients are optimized to maximize the power absorption by each floater in the array, with a restriction on the total control force that can be applied on the floaters. Various concentric arrangements with different radii and number of concentric circles are analysed to determine the most efficient among them. Moreover, the influence of the presence of a central bottom-mounted pillar and the effect of change in its dimension and shape on the power absorption are also studied.

Performance of optimally tuned arrays of heaving point absorbers

Arrays of heaving point absorbers in various arrangements are analysed to study their performance in terms of the amount of power absorption and the power uniformity among floaters. The numerical simulations for the determination of hydrodynamic coefficients and forces are obtained using a Boundary Element Method (BEM) code. A linear external damping coefficient is applied to enable power extraction and a supplementary mass is introduced to tune the floater to the incoming wave conditions. Each floater is assumed to have its own identical power take-off system. The external damping coefficient and the supplementary mass are individually optimized for each floater to maximize the total power absorption by the array. This optimization is implemented with slamming, stroke and force restrictions imposed on the floater motion by SQP method. Attention is also paid to the performance of each floater in various arrangements. Furthermore, the effect of incoming wave headings is taken into account. To quantify the performance, q-factor and coefficient of variation are compared for each array for a range of sea states. This present study will be helpful in the understanding and design of the best possible configuration of arrays of heaving point absorber WEC systems to extract more wave power and achieve better power recovery uniformity.

Determination of hydrocarbon levels in water via laser-induced acoustics wave

Hydrocarbon contamination in water is a major environmental concern in terms of foreseen collapse of the natural ecosystem. Hydrocarbon level in water was determined by generating acoustic wave via an innovative laser-induced breakdown in conjunction with high-speed photographic coupling with piezoelectric transducer to trace acoustic wave propagation. A Q-switched Nd:YAG (40mJ) was focused in cuvette-filled hydrocarbon solution at various concentrations (0–2000ppm) to induce optical breakdown, shock wave generation and later acoustic wave propagation. A nitro-dye (ND) laser (10mJ) was used as a flash to illuminate and frozen the acoustic wave propagation. Lasers were synchronised using a digital delay generator. The image of acoustic waves was grabbed and recorded via charged couple device (CCD) video camera at the speed of 30 frames/second with the aid of Matrox software version 9. The optical delay (0.8–10.0μs) between the acoustic wave formation and its frozen time is recorded through photodetectors. A piezo-electric transducer (PZT) was used to trace the acoustic wave (sound signal), which cascades to a digital oscilloscope. The acoustic speed is calculated from the ratio of acoustic wave radius (1–8mm) and optical time delay. Acoustic wave speed is found to linearly increase with hydrocarbon concentrations. The acoustic signal generation at higher hydrocarbon levels in water is attributed to supplementary mass transfer and impact on the probe. Integrated high-speed photography with transducer detection system authenticated that the signals indeed emerged from the laser-induced acoustic wave instead of photothermal processes. It is established that the acoustic wave speed in water is used as a fingerprint to detect the hydrocarbon levels.

Challenges and opportunities in the Israeli 2009 Pandemic Influenza Vaccination Program

Vaccines are a cornerstone in any pandemic influenza preparedness plan. Successful supplementary mass vaccination programs require proper advance planning. We aimed to identify general, and Israeli specific, challenges and opportunities before initiating the Israeli pandemic influenza vaccination program in order to better plan implementation of the program. Following the vaccination campaign the analysis was retrospectively examined in order to determine whether the challenges were properly identified and whether the opportunities were indeed realized. The major challenges identified were prioritization; ongoing communication with the public; balancing between central management and accessibility; and preventing vaccination errors. The major opportunity was expected to be the chance to enhance cooperation and communication between different organizations both within and outside of the health system at local, national and international levels. The vaccination program was planned based on this analysis. In retrospect, the analysis identified the key challenges and opportunities and appropriate measures were taken. However, the criticalness of acceptance of the vaccine among health care practitioners was not given sufficient attention and should be addressed in future vaccination programs. Analysis of global and local challenges and opportunities served as a useful tool for planning a pandemic influenza vaccination program. Lessons learned from this analysis could serve to foster cooperation and communication between various agencies in the event of planning rapid mass vaccination programs as well as for more routine public health vaccination campaigns.

Primary processes of charge separation in reaction centers of YM210L/FM197Y and YM210L mutants of Rhodobacter sphaeroides

Difference femtosecond absorption spectroscopy with 20-fsec temporal resolution was applied to study a primary stage of charge separation and transfer processes in reaction centers of YM210L and YM210L/FM197Y site-directed mutants of the purple bacterium Rhodobacter sphaeroides at 90 K. Photoexcitation was tuned to the absorption band of the primary electron donor P at 880 nm. Coherent oscillations in the kinetics of stimulated emission of P* excited state at 940 nm and of anion absorption of monomeric bacteriochlorophyll B(A)(-) at 1020 nm were monitored. The absence of tyrosine YM210 in RCs of both mutants leads to strong slowing of the primary reaction P* --> P(+)B(A)(-) and to the absence of stabilization of separated charges in the state P(+)B(A)(-). Mutation FM197Y increases effective mass of an acetyl group of pyrrole ring I in the bacteriochlorophyll molecule P(B) of the double mutant YM210L/FM197Y by a hydrogen bond with OH-TyrM197 group that leads to a decrease in the frequency of coherent nuclear motions from 150 cm(-1) in the single mutant YM210L to ~100 cm(-1) in the double mutant. Oscillations with 100-150 cm(-1) frequencies in the dynamics of the P* stimulated emission and in the kinetics of the reversible formation of P(+)B(A)(-) state of both mutants reflect a motion of the P(B) molecule relatively to P(A) in the area of mutual overlapping of their pyrrole rings I. In the double mutant YM210L/FM197Y the oscillations in the P* emission band and the B(A)(-) absorption band are conserved within a shorter time ~0.5 psec (1.5 psec in the YM210L mutant), which may be a consequence of an increase in the number of nuclei forming a wave packet by adding a supplementary mass to the dimer P.

SOUND ABSORPTION QUALITIES OF A CYLINDER-SHAPED ISOLATED ACOUSTIC RESONATOR/CILINDRINĖS FORMOS VIENETINIO AKUSTINIO REZONATORIAUS GARSO ABSORBCINĖS SAVYBĖS

In the article, an isolated acoustic resonator consisting of a cylinder-shaped hole of variable volume and with large and variable diameter is theoretically analyzed. Theoretical formulaes by which sound absorption of such resonator is computed are presented. The computations incorporate the influence exerted by overtones, i.e. odd harmonics, and supplementary resonator mass upon sound absorption. A change in the sound absorbtion depending on the resonator hole diameter, the angle of sound wave incidence and its volume, i.e. the distance to the rigid surface, has been established. Sound absorption reaches its maximum at low frequencies and it depends strongly on the hole diameter. Under constant hole diameter, sound absorption does not depend on the resonator volume, i.e. the distance to the rigid surface. Absorption notably depends on the angle of sound wave incidence. When this angle increases, absorption also increases at resonant frequency, while the frequency itself moves towards higher frequencies. When the sound wave incidence is 90 degrees with respect to resonator, maximum absorption is already observed at high frequencies. Real and imaginary parts of the radiation impedance of cylindric hole and of the impedance of the hole itself, as well as their dependency on frequency are computed. In this case, hole impedance consists of the impedances of the hole and air resiliency. The influence exerted by the real and imaginary parts upon sound absorption has been established. The resonance takes place when the imaginary parts of radiation and hole impedances intersect.

SOUND ABSORPTION QUALITIES OF A CYLINDER-SHAPED ISOLATED ACOUSTIC RESONATOR

Summary In the article, an isolated acoustic resonator consisting of a cylinder-shaped hole of variable volume and with large and variable diameter is theoretically analyzed. Theoretical formulaes by which sound absorption of such resonator is computed are presented. The computations incorporate the influence exerted by overtones, i.e. odd harmonics, and supplementary resonator mass upon sound absorption. A change in the sound absorbtion depending on the resonator hole diameter, the angle of sound wave incidence and its volume, i.e. the distance to the rigid surface, has been established. Sound absorption reaches its maximum at low frequencies and it depends strongly on the hole diameter. Under constant hole diameter, sound absorption does not depend on the resonator volume, i.e. the distance to the rigid surface. Absorption notably depends on the angle of sound wave incidence. When this angle increases, absorption also increases at resonant frequency, while the frequency itself moves towards higher frequ...

Effect of supplementary feeding and herbage mass on the intake and performance of grazing ewes in early lactation

ABSTRACT1. Two experiments were conducted to examine the effects of a cereal-based supplement and herbage mass on the intake and performance by Border Leicester × Scottish Blackface ewes nursing twin lambs in early lactation.2. In one experiment 16 ewes, individually penned, were given one of four amounts of supplement (0, 320, 640 and 960 g organic matter per ewe per day) and offered ad libitum freshly-cut perennial ryegrass herbage (organic-matter digestibility 82%). Intake of herbage and total organic matter digestibility declined linearly with increasing intake of supplement (0·84 g organic matter of herbage per g organic matter of supplement and 0·50 percentage units per 100 g organic matter of supplement respectively).3. In the second experiment three amounts of supplement (0, 480 and 960 g organic matter per ewe per day) were offered individually to groups of seven ewes grazing a perennial ryegrass sward of high digestibility, maintained at herbage masses of either 500 or 750 kg organic matter per ha. A further group of seven unsupplemented ewes were grazed on the same sward maintained at 1500 kg organic matter per ha. Intakes of herbage and digestible organic matter by ewes, and lamb live-weight gain, were all significantly greater and ewe live-weight loss significantly less at herbage masses of 750 and 1500 tha n at 500 kg organic matter per ha (P <0·05). The mean decline in herbage intake was 0·93g organic matter per g organic matter supplement consumed. Amount of supplement had no significant effect on lamb live-weight gain at either weight of herbage nor on ewe live-weight loss at the 750 kg organic matter per ha herbage mass. At 500 kg organic matter per ha herbage mass, intake of digestible organic matter was significantly greater and ewe live-weight loss was significantly less for 960 than for 0 and 480 g organic matter per day amounts of supplement (P <0·05).

Longitudinal impact by a supplementary mass along a cable with an end load

Longitudinal impact by a supplementary mass along a cable with an end load