Narrow Results

The spectral distribution of positron created by photon and the spectral distribution of photons radiated from electron in an oriented single crystal of intermediate thickness is calculated at intermediate energies. The energy loss of charged particles as well as photon absorption are taken into account. The used basic probabilities of processes include the action of field of axis as well as the multiple scattering of radiating electron or particles of the created pair (the Landau-Pomeranchuk-Migdal (LPM) effect).

We present a systematic study of transverse momentum $(p_T)$ spectra of charged particles in $p+p$ and Xe$+$Xe collisions at $\sqrt{s_{NN}}=5.44$ TeV. The published data of invariant yields of charged particles as a function of $p_T$ is taken from ALICE at LHC in the mid-pseudorapidity region $\left|\eta \right|<0.8$. The modified form of Tsallis distribution is used here to analyze the $p_T$ spectra of charged particles. The power law of Tsallis/Hagedorn form gives very good description of the charged particle spectra in $p+p$ collisions within a $p_T$ range of 0.15 GeV/$c$ to 50 GeV/$c$. When we go from $p+p$ collisions to heavy-ion (Xe$+$Xe) collisions, the original form of Tsallis/Hagedorn distribution is not able to describe the $p_T$ spectra of charged particles properly. This may be occurred due to the medium effects or the final state effects. Here we discuss two types of medium effects of charged particles in Xe$+$Xe collisions, one is the transverse flow in the low to intermediate $p_T$ region ($p_T\le 7$ GeV/$c$) and the other is the energy loss in the high $p_T$ region ($p_T>7$ GeV/$c$), using the modified Tsallis distribution.

In highly charged ion Xe^q+ (q=8, 15, 20, 25, 30) on C₆₀ collisions (v = 0.19 a.u.), the energy loss of projectiles in frontal collisions has been measured by analyzing the kinetic energy of scattered ions. Using singly charged projectiles He⁺, the measurement of the ejected electron number provides information on the electronic energy deposition during the fontal collision on the C₆₀ target.

A three-part tape-enhanced tube was used in the current hypothetical solar unit to save the most radiation possible. The three parts were joined at different angles ($\beta$). The parameters of the carrier base fluid after mixing with CuO nanopowder were calculated using a homogeneous model. By adjusting the range of Y${}^{+}$, multiple layers were used to precisely depict the behavior of flow close to the wall. The results show the components of irreversibility as bar charts, velocity contours, and exergy drop contours. The tape angle ($\beta$) and inlet velocity were thought to be the main driving forces. An evaluation of the accommodation’s validity using numerical data shows that it is sufficient. The wall temperature decreases by about 0.0257% as the nanofluid angle rises and more collisions with the wall take place. Xd falls off roughly 5.19% from 0^∘ to 45^∘ and 5.87% from 0^∘ to 90^∘ as the angle $\beta$ rises. As $\beta$ rises, the entropy of friction increases by 9.88%. The outer wall cools by about 0.87% and Xd falls by about 92.3% when $\beta =45^{\circ }$ and Re rises.

The energy gradient method is used to analyze the turbulent generation in the transition boundary layer flow. It is found that the maximum of the energy gradient function occurs at the wall for the Blasius boundary layer flow. At this location under a sufficiently high Reynolds number, even a low level of free-stream disturbance can cause the turbulent transition and sustain the flow to be in a state of turbulence. This is an excellent explanation of the physics of self-sustenance of wall turbulence. The mechanism of receptivity for boundary layer flow can also be understood from the energy gradient criterion. That is, the free-stream disturbance can propagate towards the wall by the "energy gradient" process to cause turbulent transition, and the transition point in boundary layer can be moved forward towards the leading edge when the level of external disturbance increases.

The contributions of radiative and collisional mechanisms for parton energy loss when it propagates inside a dense medium are calculated. The critical energy E_c, which characterizes the energy where both mechanisms contribute equally is estimated, and the quenching factor is calculated including collisional and radiative energy loss. Our results demonstrate the importance of collisional energy loss mechanism and suggest that it cannot be disregarded in the RHIC data analysis. However, the magnitude of the quenching factor is reduced by a factor smaller than two when the collisional energy loss contribution is included.

Interaction of intense ion radiation with matter has numerous applications in different fields of science, ranging from basic research of plasma properties to application in energy science. Energy loss processes of heavy ions in plasma and cold matter are important to understand the generation of high energy density states in matter. The hot dense plasma of an inertial fusion target is just one example. Of special interest are phase transitions, when irradiated matter passes through the parameter regime of warm dense matter, which is located in the phase diagram at high density but relatively low temperature. Typical parameters are in the pressure range of kbar to Mbar and temperatures ranging into the few eV regime. We present an overview on recent results and developments of beam plasma, and beam matter interaction processes studied with heavy ion beams from the GSI accelerator facilities, which consist of an rf-accelerator (UNILAC: Universal Linear Accelerator), a heavy ion synchrotron (SIS 18) and an experimental storage ring (ESR). The synchrotron SIS18 currently delivers an intense uranium beam that deposits about 1 kJ/g specific energy in solid matter. Using this beam, high energy density states close to the critical point of lead, have been reached and solid lead foils have been heated to a measured brightness temperature on the order of 5000 K.

The EMC and Cronin effects are explained by a unitarized evolution equation, in which the shadowing and antishadowing corrections are dynamically produced due to gluon fusions. For this sake, an alternative form of the GLR–MQ–ZRS equation is derived. The resulting gluon distributions, integrated and unintegrated, in protons and nuclei are used for analysis of the contributions of the initial parton distributions to the nuclear suppression factor in heavy-ion collisions. A simulation of the fractional energy loss is extracted from the data of RHIC and LHC, where the contributions of both nuclear shadowing and nuclear antishadowing effects are considered. We find a rapid crossover from weak energy loss to strong energy loss with the gluon jet at a universal critical energy, E_c ~ 10 GeV.

The emergent axion excitations in the quark–gluon plasma are generated by the sphaleron transitions. Their interactions with the photon and gluon fields are governed by the axion electro- and chromodynamics, respectively. We discuss the effect of the emergent axion on the photon production and energy loss in the quark–gluon plasma. In particular, we review the Chiral Cherenkov effect, and the impact of the chiral anomaly on bremsstrahlung.

Roughness measurement of knee implant surfaces is investigated. The study of roughness measurement show that the topography of knee implant surface is multi-scale and surface spectra follows a power law behavior. A magnification of rough surface topography implies that there is no difference between original and magnified profile of implant surface. For implant surface, statistical parameters such as variance of height, curvature, and slope are found to be scale-dependent. Fractal representation of implant surface shows that the size-distribution of the multi-scale contacts spots follows a power law and is characterized by the fractal dimension of implant surface.

Fractal surface description of the rough surfaces of knee implant is used to obtain force–displacement relationship of the contact force. Using an approximate function through the fusion of two piecewise functions, energy absorption of a knee implant in a single cycle of load–unload is obtained.

The Green's function method in the Dyson's formulation has been employed for the ab initio numerical study of structural effects on the device performances in terms of the minimum group velocity, energy loss and energy confinement in a quasi two-dimensional grated waveguide device model. The structure parameters to be varied in this work consist of the number of the grating teeth (N) and the grating groove depth (g). It is found that those parameters exhibit roughly linear and mostly monotonous variations at the lower resonance. The reduction of the group velocity and enhancement of energy confinement are also shown to be effectively attained by increasing N, while leaving the loss parameter relatively unaffected. On the other hand, the calculated results for the upper resonance wavelength are shown to exhibit consistently non-monotonous responses to increasing g. Similarly distinct behaviors are also found in the relationship between the minimum group velocity (v_{g, min}) and the energy loss (L) as well as that between v_{g, min} and the confined energy (W) for various N and g at the upper resonances. This peculiarly different behaviors are shown to be related to the variations of the associated local density of states with respect to N and g calculated for the upper resonance.

Rough surface height distribution can be nonsymmetric, depending on the process of surface preparation. The prevalent processes for implant surface involve turning and milling, both resulting in surface height distributions of nonsymmetric nature. Asymmetry in a surface height distribution is manifested through a parameter known as skewness. Unlike Gaussian distribution, Weibull distribution permits characteristics such as skewness and kurtosis in data to be included in the mathematical description of a height distribution. This paper develops hip implant contact model based on Weibull distribution of surface heights. The elastic–plastic interaction of implant surfaces are considered as macroscopically spherical surfaces containing micron-scale roughness. Symmetric and asymmetric roughness height distribution are compared. The total contact force is related to the minimum mean surface separation of the contacting rough surfaces. The force is obtained using statistical integral function of the asperity heights over the possible region of interaction of the roughness of surfaces. Approximate equations are obtained that relate the contact force to the minimum mean surface separation explicitly. The approximate equations are used to derive hysteretic energy loss per load–unload sequence, contact frequency, and damping. It is shown that energy loss per cycle, contact frequency, and damping are lower for asymmetric surface roughness distribution.

In this paper, the interaction of oblique water waves by two non-uniform submerged horizontal porous plates in the presence of a pair of trenches is analyzed towards the study of effective breakwater. The problem is modeled based on Darcy’s law for flow past a porous structure. The series solutions through matching conditions establish an over-determined system of equations, which is solved using the least-square method, giving rise to results for essential quantities such as dissipation coefficient, transmission and reflection coefficients, elevation and force whose graphs are oscillatory as a function of gap length. The study reveals that the submergence depth $D=0.2$ is the best value for many values of gap length, producing more dissipation and less force on the barriers. It is also found that after the critical angle, the force for all submergence depths is almost same. The porosity plays an important role in avoiding zero reflection and full transmission which will oscillate periodically with maxima and minima occurring. Hence, two submerged horizontal porous plates over uneven bottom topography will play a vital role in constructing an effective submerged breakwater reducing high wave impact.

The effectiveness of coastal vegetation as a barrier to mitigate a tsunami greatly depends on the magnitude of tsunami and vegetation structure. This paper summarizes a series of laboratory experiments that investigated the upstream flow structure and energy loss due to a hydraulic jump in a steady super-critical flow. The characteristics of the jump were determined against vegetation of variable density ($G∕d$, where $G=\mathrm{\text{spacing}}$ of each cylinder in cross-stream direction, $d=\mathrm{\text{diameter}}$ of cylinder), thickness (dn, where $d=\mathrm{\text{diameter}}$ of cylinder, $n=\mathrm{\text{number}}$ of cylinders in the stream-wise direction per unit of cross-stream width), and initial Froude number (Fr_o, where Froude number is obtained from a model without vegetation in the flume). In super-critical flow ($F{r}_o\text{-}1.67$–1.83), a weak hydraulic jump formed on upstream side of vegetation. The height of the jump, its location, and the resulting energy loss were increased by increasing both the vegetation density and thickness. Due to reduced reflection at vegetation front, the drag force against sparse vegetation ($G$/$d=2.13$) was higher compared to intermediate ($G$/$d=1.09$) and dense ($G$/$d=0.25$) vegetation. Under these conditions, the maximum energy reduction due to a weak hydraulic jump reached 9.4% for dense vegetation while it was 8.1% and 7.8% for intermediate and sparse vegetation, respectively.

We study the jet quenching effect in heavy ion collisions, based on medium-induced splitting functions calculated from Soft Collinear Effective Theory with Glauber Gluons. Our method is formulated in the language of DGLAP evolution equations with medium-induced splitting functions. In the small-x soft gluon approximation we analytically solve the evolution equations and find an intuitive connection to the energy loss approach. For central Pb+Pb collisions at the LHC we quantify the effect of finite-x corrections for the nuclear modification factor and compare to data.

We present the spectra of negative charged particle production in Au $+$ Au collisions from STAR for the first phase of the RHIC Beam Energy Scan Program measured over a wide range of collision energy $\sqrt{s_{NN}}=7.7-200GeV$, and transverse momentum of produced particle in different centralities at $\left|\eta \right|<0.5$. The spectra demonstrate strong dependence on collision energy which enhances with $p_T$. An indication of self-similarity of negative charged particle production in Au $+$ Au collisions is found. The constituent energy loss as a function of energy and centrality of collisions and transverse momentum of inclusive particle was estimated in the $z$-scaling approach. The energy dependence of the model parameters - the fractal and fragmentation dimensions and “specific heat”, was studied.

The origin of many power system issues are typically based on the electrical distribution systems as they are the tail ends of electric power systems. Whatever is embedded in distribution systems, its impact percolates in the whole power system. Different key technologies are available for distribution system performance improvement such as optimal distributed resources (DRs) allocation and network reconfiguration. The amount of actual benefit of these technologies depends on the modelling of load profile of the distribution system. The system load profile should be modelled by considering ground realities of distribution system such as allocation of dedicated feeders to different types of customers and load profile pattern of different category of customers. In this chapter, the DR allocation problem in radial distribution systems is modelled by considering a more realistic load profile of the system. Also, the consequences of ignoring load diversity among distribution buses on performance of distribution system are presented.

We discuss different physical processes which may be responsible for biological damage induced by an ion beam propogating through living tissue. The creation of free radicals and an electron plasma, dissociative attachment of low-energy electrons, and local heating mechanisms are considered. Numerical estimates are performed for the case of carbon ion beams. We conclude that all three mechanisms are capable of inflicting single and double strand breaks in DNA molecules and thus can be responsible for the observed enhanced biological effectiveness of ion beams in cancer therapy.

The spectral distribution of positron created by photon and the spectral distribution of photons radiated from electron in an oriented single crystal of intermediate thickness is calculated at intermediate energies. The energy loss of charged particles as well as photon absorption are taken into account. The used basic probabilities of processes include the action of field of axis as well as the multiple scattering of radiating electron or particles of the created pair (the Landau-Pomeranchuk-Migdal (LPM) effect).