Level Width Research Articles

An optimal compact time-modulated circular antenna array synthesis using krill herd optimization

In this paper, an optimal far-field radiation pattern synthesis by using time modulation technique is carried out for a compact circular antenna array (CAA) design using a stochastic optimization method called krill herd (KH) optimization. A compact antenna array is achieved by reducing the inter-element spacing between the array elements, which leads to the miniaturization of the size of the array. On the other hand, an improved far-field radiation characteristic is achieved with a low side lobe level (SLL) and narrow first null beam width (FNBW). A low SLL is an essential requirement to reduce the interference with the other systems operating in the same frequency band. A narrow FNBW is necessary to obtain a high directivity. In time modulation technique, ‘time’ has the most significant role. It is considered the fourth-dimensional parameter, which plays the role of an additional degree of freedom to achieve an improved radiation pattern. The time-modulated antenna array (TMAA) radiates at various harmonic frequencies for the periodic switching time sequence. In this paper, the generation of the radiation pattern at the fundamental/central frequency only is considered. The KH algorithm is a flexible and robust search algorithm. It is applied here to find out the optimum sets of switching on-time duration for each array element and to determine the optimum inter-element separation between two array elements of the 20- and 36-element time-modulated circular antenna array (TMCAA). Particle swarm optimization (PSO) and differential evolution (DE) optimization techniques are also individually applied for the same design purpose to prove the superiority of the KH algorithm–based design. Finally, statistical analysis is performed to ensure the significance of the numerical results.

Study on the influence of sleeve height and implant length on accuracy of static computer-assisted implant surgery

Objective: To evaluate the influence of the sleeve lengths and implant lengths on accuracy of static computer-assisted implant surgery (sCAIS). Methods: Twenty-eight models of bilateral mandibular single tooth loss were included. Fifty-five implants were placed under the guidance of sCAIS (Straumann Bone Level 4.1 mm×10 mm). According to the height of metal sleeve of static guide plate, 55 implants were divided into 11 groups (free hand group, 1 mm group, 2 mm group, 3 mm group, 4 mm group, 5 mm group, 6 mm group, 7 mm group, 8 mm group, 9 mm group, 10 mm group), with 5 implants in each group. Eight research models were included. Group with 5 mm sleeve guides were used to place implants of different length, (Straumann Bone Level width 4.1 mm, height was 8 mm, 10 mm and 14 mm), 5 implants in each group. Eighteen patients with mandibular single tooth loss were included in the Department of Oral Implantology, Tianjin Stomatological Hospital from October 2018 to June 2019. There were 10 males and 8 females, 18-46(33.7±7.9) years old. A total of 18 implants were implanted and divided into 3 groups (free hand group, 3 mm group and 5 mm group) with 6 implants in each group. Digital software was used to compare the implant positions before and after implantation. Non-parametric Kruskal-Wallis test or one-way ANOVA were used to analyze the results. Results: There was no significant difference in implant vertical deviation between different sleeve height groups (1-10 mm) and free hand group, but the neck deviation in free hand group[(1.04±0.13) mm] was significantly higher than that in different sleeve height groups (1-10 mm) (P<0.05). The tip deviations of free hand group, 1 mm group and 2 mm group [(1.32±0.43), (0.83±0.10) and (0.78±0.11) mm, respectively] was significantly higher than that of 10 mm group [(0.31±0.14) mm](P<0.05). The angle deviation of free hand group and 1 mm group (3.99°±0.85° and 2.59°±0.69°), respectively] was significantly higher than that of 10 mm group (0.61°±0.03°) (P<0.05). The tip deviations of implants in the 14 mm group [(0.83±0.22) mm] was significantly higher than that in the 8 mm and 10 mm groups [(0.44±0.07) and (0.49±0.06) mm, respectively]. Clinical studies showed that there was no significant difference in neck deviation, tip deviation and angle deviation between 3 mm group and 5 mm group (P>0.05), but deviations were significantly lower than those in free hand group (P<0.05). Conclusions: The length of the sleeves has significant influence on the accuracy of the surgical guide. There was no significant difference in accuracy of the implant guide with 3 mm or 5 mm metal sleeves. The vitro study has some limitations and needs further systematic research.

Circular Antenna Array Synthesis Using Salp Swarm Optimization

Salp Swarm Algorithm (SSA) is used to design an optimal non uniform circular antenna arrays. Salp Swarm Algorithm which mimics the swarming behavior of salps in oceans is a nature-inspired optimization method. As it is simple and easy to apply, it has been applied to many different problems in the literature. SSA method optimally determined the positions and amplitudes of the circular antenna array elements to obtain radiation patterns with a low maximum sidelobe level (MSL) and narrow half power beam width (HPBW). Different sizes of antennas with 8, 10 and 12 elements are discussed to demonstrate the capability of the SSA algorithm. The results of MSL and HPBW obtained by SSA for the synthesis of circular antenna arrays are better than other compared optimization methods.

Modern Methods of Determining the Sizes of Neutron-Excess Nuclei

Results are presented from an experiment on the inelastic scattering of 11Li with an energy of 66 MeV off protons using the coupled-channel approach with a three-particle model of cluster excitation and the FRESCO code. The model of dipole excitation describes the experiment well. The proposed approach allows determination of the isotope’s excited level, the size of its dineutron periphery, and the potential width of the resonance level.

Source level measurements of killer whale (Orcinus orca) echolocation clicks

Biosonar is vital to odontocetes (toothed whales, dolphins, and porpoises) for navigation and finding food. Consequently, numerous details of their echolocation click parameters, such as source level and beam width, are known for many species; however, there is a data gap for killer whales (Orcinus orca). This information is essential for examining masking potential which could have an impact on their foraging abilities. The Southern Resident killer whales are an endangered population of orcas living along the Pacific coast of North America and underwater noise has been identified as a major threat towards their survival. This study used a 3D 24-element hydrophone array deployed in close proximity to wild killer whales to estimate source levels (SLs) and spectra of echolocation clicks. Future work will use these SLs to investigate masking potential from current and other noise scenarios.

Extraction of baryonia from the lightest antiprotonic atoms

Anti-protonic hydrogen and helium atoms are analyzed. Level shifts and width are expressed in terms of $\bar{p}$-nucleon sub-threshold scattering lengths and volumes. Experimental data are compared to results obtained from the 2009 version of the Paris $N\bar{N}$ interaction potential. Comparison with 1999 version is also made. Effects of $N\bar{N}$ quasi-bound states are discussed. Atomic 2P hyperfine structure is calculated for antiprotonic deuterium and the significance of new measurements is indicated.

Two-photon atomic level widths at finite temperatures

The thermal two-photon level broadening of the excited energy levels in the hydrogen and H-like helium is evaluated via the imaginary part of thermal two-loop self-energy correction for bound electron. All the derivations are presented in the framework of rigorous quantum electrodynamic theory at finite temperatures and are applicable for the H-like ions. On this basis, we found a contribution to the level broadening induced by the blackbody radiation which is fundamentally different from the usual line broadening caused by the stimulated two-photon decay and the Raman scattering of thermal photons. Numerical calculations of the two-loop thermal correction to the two-photon width for the $2s$ state in hydrogen and singly ionized helium atoms show that the effect could significantly exceed the higher-order relativistic and radiative QED corrections commonly included in the calculations. In addition, the thermal two-loop self-energy correction significantly exceeds the "ordinary" stimulated one-photon depopulation rate at the relevant laboratory temperatures. In this work, detailed analysis and the corresponding comparison of the effect with the existing laboratory measurements in H-like ions are carried out.

Kaonic hydrogen and deuterium in Hamiltonian effective field theory

The anti-kaon nucleon scattering lengths resulting from a Hamiltonian effective field theory analysis of experimental data and lattice QCD studies are presented. The same Hamiltonian is then used to compute the scattering length for the K−d system, taking careful account of the effects of recoil on the energy at which the K¯N T-matrices are evaluated. These results are then used to estimate the shift and width of the 1S levels of anti-kaonic hydrogen and deuterium. The K−p result is in excellent agreement with the SIDDHARTA measurement. In the K−d case the imaginary part of the scattering length and consequently the width of the 1S state are considerably larger than found in earlier work. This is a consequence of the effect of recoil on the energy of the K¯N energy, which enhances the role of the Λ(1405) resonance.

Thiocyanate-capped CdSe@Zn1-XCdXS gradient alloyed quantum dots for efficient photocatalytic hydrogen evolution

CdSe@Zn1-XCdXS QDs possessing a gradient alloy composition structure with an energy level width continuous increasing along the radial direction from the center to the surface were prepared and employed as a photocatalyst in a hydrogen generation system. Thiocyanate or mercaptopropionic acid capped QDs was adopted for assembling CdSe@Zn1-XCdXS QDs onto TiO2 film. Using as photocatalysts for hydrogen generation, it’s found that these gradient alloyed QDs/TiO2 photocatalysts exhibit excellent hydrogen production rates of 94 mmol/gh for MPA capped QDs and 951 mmol/gh for SCN capped QDs at 100 mW/cm2 AM 1.5 illumination without co-catalysts. Moreover, the SCN capped QDs demonstrate remarkably higher hydrogen evolution rate than that of the reference MPA capped QDs due to a higher ligand induced hole trap level, resulting in a much faster electron-hole separation and charge transfer rate compared with those of MPA capped QDs.

Distinguishing between topological and quasi Majorana zero modes with a dissipative resonant level

Distinguishing between topological Majorana zero modes and quasi Majorana modes -- trivial low energy Andreev bound states -- is an important step towards realizing topological hybrid nanowire devices. We propose that this distinction can be made by connecting a hybrid nanowire to a dissipative resonant level realized by a quantum dot weakly coupled to high resistance leads. We show that the qualitative temperature scaling of the width of the resonant level zero bias conductance peak provides a signature unique to true Majorana zero modes. The degeneracy induced by a true Majorana zero mode is further shown to stabilize this conductance peak against particle-hole asymmetry.

Synthesis of Linear Antenna Array with Optimal SLL and Beam Width

In many areas of wireless communications, there is a need for high directive radiating beams. To generate such a high directive beams, a linear array of antennas is preferred to that of using a single antenna. Generally a narrow beam width tends to have high directivity but specific to the applications there is also a need for wider beam widths. In case of a radar application it requires a narrow beam width when it is operating in target mode and on the other hand it requires wider beam width when it works under search mode. These optimal beam width variations can be obtained by using Optimization techniques. In this paper Biogeography based Optimization algorithm is used to generate narrow and wide beam widths for a Linear array antenna. While we try to optimize the beam widths of a linear array it will lead to an increase in the side lobe level which make it unavailable for practical applications. As a sensible antenna should always posses a very low side lobe levels a tradeoff should be made for both side lobe level and beam width. This tradeoff which has an optimal side lobe level along with directivity can be achieved by proposed fitness function optimization. The results obtained by using Genetic algorithm and Biogeography based optimization algorithm are compared.

A quantitative trait locus GW6 controls rice grain size and yield through the gibberellin pathway.

Grain size is one of the essential components determining rice yield and is a target for both domestication and artificial breeding. Gibberellins (GAs) are diterpenoid phytohormones that influence diverse aspects of plant growth and development. Several quantitative trait loci (QTLs) have been identified that control grain size through phytohormone regulation. However, little is known about the role of GAs in the control of grain size. Here we report the cloning and characterization of a QTL, GW6 (GRAIN WIDTH 6), which encodes a GA-regulated GAST family protein and positively regulates grain width and weight. GW6 is highly expressed in the young panicle and increases grain width by promoting cell expansion in the spikelet hull. Knockout of GW6 exhibits reduced grain size and weight, whereas overexpression of GW6 results in increased grain size and weight. GW6 is induced by GA and its knockout downregulates the expression of GA biosynthesis genes and decreases GA content in the young panicle. We found that a natural variation in the cis element CAAT-box in the promoter of GW6 is associated with its expression level and grain width and weight. Furthermore, introduction of GW6 to Oryza indica variety HJX74 can lead to a 10.44% increase in rice grain yield, indicating that GW6 has great potential to improve grain yield in rice.

History and Some Aspects of the Lamb Shift

Radiation is a process common to classical and quantum systems with very different effects in each regime. In a quantum system, the interaction of a bound electron with its own radiation field leads to complex shifts in the energy levels of the electron, with the real part of the shift corresponding to a shift in the energy level and the imaginary part to the width of the energy level. The most celebrated radiative shift is the Lamb shift between the 2 s 1 / 2 and the 2 p 1 / 2 levels of the hydrogen atom. The measurement of this shift in 1947 by Willis Lamb Jr. proved that the prediction by Dirac theory that the energy levels were degenerate was incorrect. Hans Bethe’s calculation of the shift showed how to deal with the divergences plaguing the existing theories and led to the understanding that interactions with the zero-point vacuum field, the lowest energy state of the quantized electromagnetic field, have measurable effects, not just resetting the zero of energy. This understanding led to the development of modern quantum electrodynamics (QED). This historical pedagogic paper explores the history of Bethe’s calculation and its significance. It explores radiative effects in classical and quantum systems from different perspectives, with the emphasis on understanding the fundamental physical phenomena. Illustrations are drawn from systems with central forces, the H atom, and the three-dimensional harmonic oscillator. A first-order QED calculation of the complex radiative shift for a spinless electron is explored using the equations of motion and the m a s s 2 operator, describing the fundamental phenomena involved, and relating the results to Feynman diagrams.

Analyzing Cascade Gamma-Decays of Nuclei at Energies of Excitation Below That of Neutron Bonding

Data obtained with the γ-calorimeter of the DANCE spectrometer at the Los Alamos National Laboratory (LANL) are reanalyzed using the empirical model developed at the Joint Institute for Nuclear Research (JINR, Dubna), in which the density and partial radiative widths of nuclear levels are simultaneously derived from the measured intensity of gamma two-stage cascade transitions as a function of primary transition energy E$_{1}$.

Free gingival grafts for implants exhibiting a lack of keratinized mucosa: Extended follow-up of a randomized controlled trial.

This study is an extended follow-up of a randomized controlled trial that evaluated 18-month outcomes following free gingival grafts (FGGs) around implants with <2mm keratinized mucosa (KM) compared to implants without KM augmentation. Follow-up data were obtained over 48months from 18 implants in the FGG group (11 subjects) and 8 implants in the no-surgery group (7 subjects) within the control group. FGGs were performed after 18months for 8 implants in the control group; these 8 implants constituted a delayed FGG group (5 subjects). The width of KM, mucosal recession (MR) and crestal bone level (CBL) were obtained. The increased width of KM and the reduced MR following FGGs were maintained for 48months in the FGG group, which exhibited less MR than the no-surgery group. The amount of crestal bone loss (0.4±0.4mm) in the no-surgery group was significantly greater than that in the FGG group (0±0.4mm) at 48months. In the delayed FGG group, reduced MR and no significant differences in CBL were observed compared with the pre-graft measurements. FGGs can be a practical treatment option to maintain CBL around implants with limited KM.

Relation between the localization length and level repulsion in 2D Anderson localization.

We report on the relation between the localization length and level-spacing characteristics of two-dimensional (2D) optical localizing systems. Using the tight-binding model over a wide range of disorder, we compute spectro-spatial features of Anderson localized modes. The spectra allow us to estimate the level-spacing statistics while the localization length $ \xi $ξ is computed from the eigenvectors. We use a hybrid interpolating function to fit the level-spacing distribution, whose repulsion exponent $ \beta $β varies continuously between 0 and 1, with the former representing Poissonian statistics and the latter approximating the Wigner-Dyson distribution. We find that the $ (\xi ,\beta ) $(ξ,β) scatter points occupy a well-defined nonlinear locus that is well fit by a sigmoidal function, implying that the localization length of a 2D disordered medium can be estimated by spectral means using the level-spacing statistics. This technique is also immune to dissipation since the repulsion exponent is insensitive to level widths, in the limit of weak dissipation.

Implementation of MOIDS Algorithm for Optimal Parameter Selection of SFPT for Modern Radars

Modern radars require signals of the large frequency range to attain relatively greater range resolution. Frequency stepping is the technique to convert the narrowband signal, i.e., a train of pulses into a wideband signal to achieve high accuracy in range resolution measurements. Due to the cause of constant step in frequency of successive pulses, grating lobes appeared when the period of pulse multiplied by step in frequency exceeds unity as is needed in modern radars. Hence to achieve the best resolution, grating lobes height, sidelobes level, and mainlobe width have to be minimum. In this paper an attempt has been made to diminish grating lobes, minimize sidelobes and reduce mainlobe width using MOIDSA to find the parameters of Stepped Frequency Pulse Train (SFPT) mechanism. The compromise between various lobes is obtained by using three dimensional Pareto fronts for different ranges of SFPT parameters.

Classification of instream ecological water demand and crucial values in a semi-arid river basin

Analyzing the instream environmental flow demand by coupling the hydrological cycle and the hydrodynamic process with aquatic ecological processes at watershed scale remains one of the most important yet most difficult issues. One or two of the above processes have been the focus in the evaluation of intra-annual ecological water demand in recent studies. In this study, a hydrology–hydrodynamic–habitat model was developed and applied to the Huangshui River basin. A new classification method for instream ecological water demand (IEWD), which considered sensitive species was proposed. The suitable level of IEWD and crucial values with different flow frequencies were analysed, including runoff, water level, water surface width and weighted usable areas (WUA). The results of the study indicated that monthly IEWD had an increasing trend during the flood season and a decreasing trend during the non-flood season in three sections at different suitable levels. With the increase of suitable levels, the range of IEWD in three sections also increased. The IEWD and crucial values were the lowest in March with the smallest range and were the highest from July to October because the amount of precipitation during that period accounted for nearly 84.3% of that of the entire year. Furthermore, the lower the flow frequency in three sections, the higher the suitable levels of IEWD, as well as water level and water surface width every month. When the flow frequency of 90% decreased to 75%, the value of IEWD increased by at least 55% during the wet season and doubled during the dry season. The WUA with the lowest or highest flow frequencies were relatively poor, especially reproduction period. The IEWD and crucial values at different suitable levels agreed with the actual situations. Thus, this study provided a new method for implementing river ecosystem restoration and aquatic ecosystem management.

Resonance Parameters, Autoionisation of &amp;lt;sup&amp;gt;2S+1&amp;lt;/sup&amp;gt;L&amp;lt;sup&amp;gt;o&amp;lt;/sup&amp;gt; Doubly Excited N&amp;lt;sup&amp;gt;5+&amp;lt;/sup&amp;gt; Ion States Associated with n=3 and 4, N&amp;lt;sup&amp;gt;6+&amp;lt;/sup&amp;gt; Threshold

The motivation of the diagonalization method is to take into consideration the coupling between closed and opened channels in term of perturbation theory and to neglect the indirect coupling as well but also the autoionisation states through the opened channels. This procedure leads to a relatively simple mathematical problem consisting of solving a system of linear algebraic equations instead of a system of coupled differential equations or integro-differential equations. Diagonalization method under LS coupling scheme for the states ^1,3P^o; ^1,3D^o; ^1,3F^o; ^1,3G^o; ^1,3H^o was performed. The partial widths for multi-channel autoionizing levels to sublevels of N⁶⁺ were carried out by neglecting the direct coupling between opened channels. The calculations of total and partial widths of the (nln'l') ^1,3L^o (L=1, 2, 3, 4 and 5) multiple-decay-channel system N⁵⁺ were performed. From L=1 to 2, the (4l4l') ^1,3Lo states located under n=3 and the (3lnl') ^1,3Lo</sup> states follow the same rules. All the (4l4l') ^1,3Go and (4l4l') ^1,3H^o states located under n=3 observe the rule 1.

An array pairing method for localizing distributed sources by acoustic beamforming.

An acoustic beamforming concept is presented that alleviates some misrepresentation caused by deconvolution algorithms that can oversimplify distributed sources as a series of point sources. In the Array Pairing Method (APM) an initial array beamforms the acoustic source, then an iterative randomized array is calculated whereby the square-rooted product of the beamformer output possesses a minimum product of Maximum Sidelobe Level (MSL) and Main Lobe Width (MLW). A single and distributed source simulation and a single and dual speaker experiment using the APM reveal significant improvements in MSL and MLW and resolution in the distributed source region.