Rear Lobe Research Articles

METHOD OF REDUCING THE LEVEL OF BACK RADIATION OF ELECTROMAGNETIC WAVES OF APERTURE ANTENNAS

A method has been proposed and developed that allows you to significantly reduce the level of back radiation of electromagnetic waves of aperture-type antennas of any design. The essence of the method is the excitation of slowed surface waves on the outer side of the edge of the antenna aperture, which are in antiphase with electromagnetic waves of back radiation. Slowed surface waves are formed by an impedance metal comb, which performs the function of a retarding system, placed on the outer side of the opening edge of the antenna. The dependence of the formed characteristics of the electromagnetic field on the design parameters of the impedance comb is shown. The method was tested on the horn-slot ship antenna of the “Mius” type navigation radar station. The results of modeling and calculation of the directional pattern (DP) of the antenna confirm that the proposed method allows to reduce the level of the rear lobe of the directional pattern of the horn-slit antenna with an impedance comb by approximately 1.4 times.

ЛИНЕЙНЫЙ ПРОФИЛЬ БЫКОВ ГОЛШТИНСКОЙ ПОРОДЫ ИМПОРТНОЙ СЕЛЕКЦИИ В ЗАВИСИМОСТИ ОТ ВЕЛИЧИНЫ ИНДЕКСА ГЕНОМНОЙ ПЛЕМЕННОЙ ЦЕННОСТИ

Much attention is paid to the study of the use of linear assessment of dairy cattle in cattle breeding practice. The purpose of the work is to analyze the linear profile data of imported bulls, depending on the value of the genomic breeding value index GTPI. The object of the study is Holstein bulls of the imported selection of JSC GPP Elita, which are used in selection and breeding work in the Republic of Tatarstan. To study the animals' exterior, a linear genomic profile was compiled. When studying the linear genomic profile of imported bulls, it was found that they are generally characterized by average height, not a deep body, insufficient body strength, the sacrum is in the correct position, but the width of the pelvis is well developed, while the legs are developed towards elephantiasis, and the hoof has a high heel. The characteristics of the udder are generally positive, the front lobes are tightly attached, as well as the rear lobes, the lobes are wide at the back and separated by a groove, according to the assessment, the ligament is not strong, the bottom of the udder is located high, and the teats are of medium setness and are slightly close together, and the hind legs also have good staging. When studying the linear profile of bulls with different indexes of genomic breeding value, data was obtained that allows us to talk about an improvement in exterior indicators in animals in the group with a GTPI index from 2401 to 2600, while they are tall, have a wide body, strong physique, and have good milk shape and developed udder. But animals have only one negative indicator based on the placement of their hind legs. As a result of the research, it can be recommended to better use imported bulls with GTPI from 2401 to 2600 to improve the exterior of animals.

Параметры изменчивости показателей телосложения и продуктивности голштинских коров в зависимости от уровня удоя

Abstract. The purpose of research - to explore the genetic variability parameters of features the physique and productivity of Holstein cows, depending on the level of their milk yield. Research methods. The SELEX database was used. Animals (1610 heads) were divided into 3 groups according to milk yield per 1 lactation: 1 – milk yield no more 7500 kg, 2 – 7501–9000 kg, group 3 9001 kg of milk and more. Correlograms are based on R scripts in R-Studio. Results. Cows of the 3rd group are taller (p ≤ 0,001), with a deeper body (p ≤ 0,001), a wide rear and a greater udder depth (p ≤ 0,001). In group 3, milk yield and protein are higher (p ≤ 0,01). Animals of group 2 are taller (p ≤ 0,001), with high hind lobes, longer teats (p ≤ 0,001), and deep udders (p ≤ 0,01). In group 2, r according to the ratio: height in the sacrum / depth of the udder (0,58). Animals of the 3rd group - height in the sacrum / milky type (0,77), strength / depth of the body (0,63), height, width of the buttocks / height of the posterior lobes (0,62…0,60). In group 1, r between signs: height of the rear lobes / position of the hindquarters and depth of the udder (0,72...0,79), length of the front lobes / height of the hind lobes, udder depth / central ligament (0,60). According to the milk protein h² in animals of groups 2 and 3 0,52...0,74. Animals of the 3rd group have a high h² in terms of height, body depth, heel and udder height, body strength and udder depth. In group 2, high h² in terms of the depth of the body, the position of the rear, the angle of the hind legs from the side, the location of the front nipples, the length of the nipples, and the strength of the physique. Scientific novelty. The use of digital technologies in the evaluation of animals makes it possible to more accurately establish the relationship between the characteristics of the productivity of dairy animals and the physique and contributes to an increase in milk yield, the qualitative composition of milk and the longevity of cows.

Study of the radiation pattern of a rectangular horn antenna in the operation of multimode propagation of electromagnetic waves

The object of research in the work is the process of radiation of electromagnetic waves and the directional properties of a rectangular horn antenna in a multimode operation. The existing problem is that in practice when developing and researching horn antennas, only the single-mode mode of their operation is taken into account. The fundamental mode of the rectangular waveguide that feeds this horn antenna is chosen as the base mode of the emitted electromagnetic wave. Radiation of higher types of electromagnetic waves is not taken into account. To take into account the impact of higher types of electromagnetic waves on the directional properties of a rectangular horn antenna, it is proposed to investigate a multimode mode consisting of three types of magnetic waves H10, H20, and H30. Horn antennas have high-quality wide-range properties and make it possible to obtain a maximum frequency coverage ratio of 1.5–1.8. In this paper, the directional properties of a rectangular horn antenna are determined by the example of calculating and modeling normalized radiation patterns of a standard horn-type for a wide frequency range with an average frequency of 12 GHz and a frequency overlap factor of 1.67. It has been established that when emitting three higher types of waves, it is possible to simultaneously improve the characteristics and directional properties of a horn antenna by changing the amplitude of each component of the constituent waves of electromagnetic radiation. The work aimed to study the normalized radiation patterns of a rectangular horn antenna to improve its directional properties. It was found that with increasing frequency, starting from the middle frequency of the operating frequency range, the radiation pattern of a rectangular horn antenna expanded. That is, the opening angle increased in the direction of the main radiation, with a decrease in the radiation amplitude, the level of the side and rear lobes increased, which leads to a deterioration in the characteristics of the horn antenna. For the selected geometric dimensions of the horn antenna in the frequency range of 12–12.5 GHz in the multimode mode, it was possible to provide almost the same beam width in the horizontal and vertical planes at the level of 13.2–13.6°.

The cyclopropylcarbinyl route to γ-silyl carbocations.

The mesylate derivative of cis-1-hydroxymethyl-2-trimethylsilylcyclopropane has been prepared, along with a number of related mesylates and triflates with substituents on the 1-position. These substrates all solvolyze in CD3CO2D to give products derived from cyclopropylcarbinyl cations that undergo further rearrangement to give 3-trimethylsilylcyclobutyl cations. These 3-trimethylsilylcyclobutyl cations are stabilized by a long-range rear lobe interaction with the γ-trimethylsilyl group. When the substituent is electron-withdrawing (CF3, CN, or CO2CH3), significant amounts of bicyclobutane products are formed. The bicyclobutanes are a result of γ-trimethylsilyl elimination from the cationic intermediate that has an unusually long calculated Si–C bond. The solvolysis chemistry of mesylate and triflate derivatives of trans-1-hydroxymethyl-2-trimethylsilylcyclopropane and 1-substituted analogs can be quite different since these substrates do not generally lead to 3-trimethylsilylcyclobutyl cations.

Modern technologies of robotized cowing milk

The studies were conducted in the conditions of LLC “Milk Group” of Sukhinichsky district of Kaluga region. The object of research is robotic milking machines, Swedish breed cows and Danish red breeds. Equality of development of the front and rear lobes, the udder index, the average milk flow rate and the frequency of delivery can be achieved only with long-term selection by type, good severity of signs of milkiness. Based on the selection of cows for milking on a robotized milking plant, the following requirements were put forward: high milk productivity and milk yield, tightly attached udder, nipples of the same size, the lower point of which should not be below 33 cm from the floor level, the minimum distance between the rear nipples in 3 cm, between the front nipples - 12.5 - 30 cm, the thickness of the nipples in the range of 1.5-3.5 cm, the rear nipples should be located 3 cm lower than the lower part of the udder, the minimum distance between the front and rear These udder teats - 7 cm, an angle of deviation from vertical teats should not exceed 30 °. The main reasons for the insignificant loss of milk during robotic milking are the milking of cows that do not have a full-fledged milk-giving reflex or the reflex was inhibited at the beginning of the milking of milk with a delay in putting the teat on the teats of the udder. The size of one-time milk yield, with the exception of the program indicators of this restriction on the milk yield, is determined by the frequency of effective visits to the robot (i.e., the multiplicity of milking during the day). In robotic milking, the frequency of milkings varies by day periods relatively little and drops to a minimum only in the second half of the night, in our opinion, due to the relatively late distribution of feed mixtures. It is also noted that cows of all ages have the same number of milkings on a robotized unit within 2 times.

Solar Influences on the Return Direction of High‐Frequency Radar Backscatter

AbstractCoherent‐scatter, high‐frequency, phased‐array radars create narrow beams through the use of constructive and destructive interference patterns. This formation method leads to the creation of a secondary beam, or lobe, that is sent out behind the radar. This study investigates the relative importance of the beams in front of and behind the high‐frequency radar located in Hankasalmi, Finland, using observations taken over a solar cycle, as well as coincident observations from Hankasalmi and the Enhanced Polar Outflow Probe Radio Receiver Instrument. These observations show that the relative strength of the front and rear beams is frequency dependent, with the relative amount of power sent to the front lobe increasing with increasing frequency. At the range of frequencies used by Hankasalmi, both front and rear beams are always present, though the main beam is always stronger than the rear lobe. Because signals are always transmitted to the front and rear of the radar, it is always possible to receive backscatter from both return directions. Examining the return direction as a function of local time, season, and solar cycle shows that the dominant return direction depends primarily on the local ionospheric structure. Diurnal changes in plasma density typically cause an increase in the amount of groundscatter returning from the rear lobe at night, though the strength of this variation has a seasonal dependence. Solar cycle variations are also seen in the groundscatter return direction, modifying the existing local time and seasonal variations.

3-Trimethylsilylcycloalkylidenes. γ-Silyl vs γ-Hydrogen Migration to Carbene Centers.

A series of γ-trimethylsilyl-substituted carbenes have been studied experimentally and by computational methods. In an acyclic system, 1,3-trimethylsilyl migration successfully competes with 1,3-hydrogen migration to the carbene center. The behavior of cyclic 3-trimethylsilyl-substituted carbenes contrasts with that of the acyclic system. Only 1,2-hydrogen migration processes are observed in the five-membered ring due to the high barrier to 1,3-hydrogen migration. In the cyclohexyl system, a small amount of a cyclopropane derived from 1,3-hydrogen migration occurs, as shown by a labeling study. In the cycloheptyl carbene system, a labeling study again showed that 1,3-hydrogen migration to the carbene center leads to the major product. Computational studies suggest that the cyclic carbenes all have lower energy conformations where the trimethylsilyl group is in a pseudo equatorial conformation where it cannot migrate to the carbene center. Computational studies also suggest that cyclohexyl and cycloheptyl carbene systems are slightly stabilized by a rear lobe interaction of the Si-C bond with the carbene center.

γ-Trimethylsilylcyclobutyl Carbocation Stabilization

A series of isomeric 3-trimethylsilyl-1-arylcyclobutyl carbocations, 10 and 11, where the cross-ring 3-trimethylsilyl group has the potential to interact with the cationic center, have been generated under solvolytic conditions. When the cationic center can interact with the rear lobe of the carbon-silicon bond, rate enhancements become progressively larger as the substituent on the aryl group becomes more electron-withdrawing. When the potential interaction with the trimethylsilyl group is via a front lobe interaction, there is minimal rate enhancement over the range of substituents. Computational studies have also been carried out on these cations 10 and 11. Calculated trimethylsilyl stabilization energies progressively increase with electron-withdrawing character of the aryl groups when the trimethylsilyl interaction is via the rear lobe. By way of contrast, there are minimal changes in stabilization energies when the potential trimethylsilyl interaction is via the front lobe of the carbon-silicon bond. These computational studies, along with the solvolytic studies, point to a significant rear lobe 3-trimethylsilyl stabilization of arylcyclobutyl cations. They also argue against any front lobe stabilization of the isomeric arylcyclobutyl cations.

3-Trimethylsilylcyclobutylidene. The γ-Effect of Silicon on Carbenes

3-Trimethylsilylcyclobutylidene was generated by pyrolysis of the sodium salt of the tosylhydrazone derivative of 3-trimethylsilylcyclobutanone. This carbene converts to 1-trimethylsilylbicyclobutane as the major product. A labeling study shows that this intramolecular rearrangement product comes from 1,3-hydrogen migration to the carbenic center and not 1,3-silyl migration. Computational studies show two carbene minimum energy conformations, with the lower energy conformation displaying a large stabilizing interaction of the carbene center with the rear lobe of the C3-Si bond. In this conformation, the trimethylsilyl group cannot migrate to the carbene center, and the most favorable process is 1,3-hydrogen migration. When the carbene is generated photochemically in methanol, it reacts by a protonation mechanism giving the highly stabilized 3-trimethylsilylcyclobutyl carbocation as an intermediate. When generated in dimethylamine as solvent, the carbene undergoes preferred attack of this nucleophilic solvent from the back of this C-Si rear lobe stabilized carbene.

Stereochemical Dependence of 3JCH Coupling Constants in 2-Substituted 4-t-Butyl-cyclohexanone and Their Alcohol Derivatives

Theoretical and experimental studies on (3)J(C2H6eq) NMR spin-spin coupling constants in both the 2-X-4-t-butyl-cyclohexanone (X = H, CH(3), F, Cl, and Br) and in their alcohol derivatives series are reported. Results thus found are rationalized in terms of the transmission of the Fermi contact contribution to such couplings. To this end, dependencies of (3)J(C2H6eq) couplings versus the C(2)-C(1)-C(6) angle are compared in both series for equatorial and axial X orientations. The main trend is described in terms of the rear lobes interaction. Besides, for X = halogen atom in equatorial orientation a rather strong interaction between oxygen and halogen lone pairs is observed, and its influence on (3)J(C2H6eq) couplings is discussed and rationalized in terms of different Fermi contact transmission pathways.

γ-Silyl Cyclobutyl Carbocations

A series of 3-trimethylsilyl-1-substituted cyclobutyl trifluoroacetates have been prepared and reacted in CD(3)CO(2)D. Rate data indicate that the substrates with the trimethylsilyl group cis to the leaving group react with assistance due to gamma-silyl participation. Rate enhancements range from a factor of 209 for alpha-phenyl-substituted cations to 4.6 x 10(4) for alpha-methyl-substituted cations to >10(10) for the unsubstituted gamma-trimethylsilylcyclobutyl cation. Acetate substitution products are formed with net retention of stereochemistry. These experimental studies, as well as B3LYP/6-31G* computational studies, are consistent with the involvement of carbocations where the rear lobe of the gamma-Si-C bond interacts strongly with the developing cationic center. Solvolytic rate studies, as well as computational studies, suggest that the secondary gamma-trimethylsilylcyclobutyl cation is even more stable than the beta-trimethylsilylcyclobutyl cation, i.e., the gamma-silyl effect actually outweighs the potent beta-silyl effect. Although computational studies suggest the existence of certain isomeric cations, where the front lobe of the Si-C bond interacts with the cationic center, solvolytic evidence for the involvement of these front lobe stabilized cations is less compelling.

Design of a multipolar weighting for acoustic antennae

This work describes the development of an acoustic antenna for which several kinds of weightings have been studied to obtain a narrow directivity with attenuated rear lobes. Later, this antenna will be used in a new device to measure the sound absorption coefficient of flat panels in industrial sites. It is often necessary, although quite difficult, to measure acoustic absorption coefficients in partially diffuse conditions, because predicting the sound pressure level at, for instance, a workplace requires in situ characterization of the facings. This antenna has been optimized so that the major part of the received acoustic energy would come from one portion only of an investigated facing present in an industrial room. The multipolar weighting is quite efficient because the associated directivity can be carried out with a limited number of microphones. The calculation technique is improved to achieve a constant sensitivity antenna within the desired frequency range with most of the secondary lobes rejected. The designed receiving system is composed of four antennae, each equipped with five sensors. The directivity, at 150–5000 Hz range, has been verified in an anechoic room.

The impact of the supporting structure on the antenna array parameters

The paper describes results of study of the effect of the surface impedance parameters of an antenna frame (a circular metal cylinder with radio-absorbing coating) on the parameters of an antenna array made as a set of longitudinal electric dipoles: radiation pattern, level of side and rear lobes, and input impedance.

Anodic oxidation of methyl alpha-dimethylsilyldihydrocinnamate. A novel silicon gamma-aryl effect.

The anodic oxidation of methyl 3-phenyl-2-dimethylsilylpropionate occurs at a potential almost 1 V positive of that required to oxidize other alpha-silyl esters. Semiempirical and ab initio calculations on the model compound 1-phenyl-2-trimethylsilylethane indicate that electron removal from these two compounds is highly stereoelectronically dependent. Both molecules exist almost exclusively in a conformation in which the phenyl group and silicon atom are anti and the side chain is perpendicular to the aromatic ring. This conformation has a higher energy HOMO orbital and lower computed ionization potential than the only other significantly populated conformation of 1-phenyl-2-trimethylsilylethane. Finally, the ab initio calculations show that in the cation radical of this model compound the ipso carbon of the aromatic ring and the side chain carbon bound to silicon draw significantly closer together than in the neutral species; an electrostatic potential map of the cation radical shows that the ipso carbon bears the highest degree of positive charge of any of the benzenoid carbons. We interpret these data, taken together, as an indication that this cation radical is stabilized by overlap of the rear lobe of the carbon-silicon bond with the p-orbital of the ipso carbon.

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 4: Bicycloalkanes

AbstractA systematic study of the one‐bond and long‐range J(C,C), J(C,H) and J(H,H) in the series of nine bicycloalkanes was performed at the SOPPA level with special emphasis on the coupling transmission mechanisms at bridgeheads. Many unknown couplings were predicted with high reliability. Further refinement of SOPPA computational scheme adjusted for better performance was carried out using bicyclo[1.1.1]pentane as a benchmark to investigate the influence of geometry, basis set and electronic correlation. The calculations performed demonstrated that classical ab initio SOPPA applied with the locally dense Dunning's sets augmented with inner core s‐functions used for coupled carbons and Sauer's sets augmented with tight s‐functions used for coupled hydrogens performs perfectly well in reproducing experimental values of different types of coupling constants (the estimated reliability is ca 1–2 Hz) in relatively large organic molecules of up to 11 carbon atoms. Additive coupling increments were derived for J(C,C), J(C,H) and J(H,H) based on the calculated values of coupling constants within SOPPA in the model bicycloalkanes, in reasonably good agreement with the known values obtained earlier on pure empirical grounds. Most of the bridgehead couplings in all but one bicycloalkane appeared to be essentially additive within ca 2–3 Hz while bicyclo[1.1.1]pentane demonstrated dramatic non‐additivity of −14.5 Hz for J(C,C), +16.6 Hz for J(H,H) and −5.5 Hz for J(C,H), in line with previous findings. Non‐additivity effects in the latter compound established at the SOPPA level should be attributed to the through‐space non‐bonded interactions at bridgeheads due to the essential overlapping of the bridgehead rear lobes which provides an additional and effective non‐bonding coupling path for the bridgehead carbons and their protons in the bicyclopentane framework. Copyright © 2003 John Wiley & Sons, Ltd.

Calibration error of L‐band sky‐looking ground‐based radiometers

A method is presented for estimating the calibration error affecting L‐band ground‐based radiometers, using the sky as a cold source. In a first step, the optimum conditions to perform this calibration are limited by removing sky areas where large radiation contributors (Sun and Moon) are present. In the region thus selected, an accurate computation of the brightness temperature measured by the antenna is performed using available sky background temperature survey charts (radio continuum and hydrogen HI line) and integrating the sky temperature over the directional gain pattern of a representative radiometer L‐band antenna. Contributions from rear lobe are not considered. After adding the atmospheric contribution, maps of the noise temperature and its error are produced for the region of interest. The best calibration orientation for a sky‐looking radiometer at medium northern latitude would be 0° in azimuth (northward) and an elevation equal to the radiometer's latitude. It is found that the computed total sky noise contribution is 6.6 K, with 24 hour variations of ±0.2 K and a maximum bias of ±0.6 K. The results are valid for the whole year, assuming low to moderate solar activity and no rain.

Unfolding cylindrical sonar

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Ab initio and experimental study of NMR coupling constants in bicyclo[1.1.1]pentane

The different dependences of NMR spin–spin coupling constants of a medium-sized molecule on the quality of the ground-state wavefunction is studied using three different basis sets of increasing size, namely, 6-31G, 6-31G* and 6-31G**. Calculations of the Fermi contact terms were also carried out using partially uncontracted s and p atomic orbitals with the same exponents as those of the 6-31G basis set. Bicyclo[1.1.1]pentane was chosen as a model compound; it was synthesized for the measurement of several couplings as part of this work in order to compare theoretical results with experimental values. The through-space transmission of couplings via the interaction of rear lobes of orbitals inside the bicyclic cage were studied with the IPPP approach using the above basis sets.

Analysis of the phosphorus lone-pair orientational effect on 31P 13C couplings in 7-(phosphamethyl)norbornene

An IPPP-INDO analysis of PC couplings is carried out in 7-(phosphamethyl) norbornene for the anti and syn conformations. A strong orientational effect of the P lone pair is expected to be responsible for the differences in the coupling values between conformations. Total couplings are decomposed into through-space and through-bond components. Further analysis of the through-space Fermi contact term is carried out by resolving it into contributions given by different “through-space coupling pathways”, each pathway being defined by excitations which are amenable to direct analysis using the inner-projected polarization propagator technique. The experimental trends of PC couplings in both conformations are closely reproduced. The differences between both conformations are found to be ruled by: (i) the orientation of the P lone pair, which is shown to be an efficient means of transmitting the spin information; (ii) the transmission through the CH rear lobe; and (iii) the orientational effect of the PC antibonding molecular orbital. From (iii) the important role played by vacant molecular orbitals is also brought to attention.