Multistep Compound Research Articles

Problem with gradual absorption in MSD/MSC calculations

Replacing classical exciton model with the better founded Multistep Direct (MSD) and Multistep Compound (MSC) mechanisms has been impeded by incapability of the latter models to describe central part of the neutron emission spectra at incident neutron energies of about 14 MeV and above. We have ascribed this deficiency to the decrease of absorption to the MSC mechanism resulting from the concept of gradual absorption. We were able to obtain very good reproduction of experimentally measured neutron spectra using MSD/MSC calculations when this option was turned off. Such treatment is, however, at odds with the fundamental distinction between MSD and MSC mechanisms that should proceed through the chain of open (P-space) and closed (Q-space) configurations respectively. By blocking gradual absorption we allow the first stage of MSC to be fully populated from the incident channel that at higher incident energies is impossible. We discuss various attempts of addressing the problem that, so far, remains open. In addition, we present an evidence for much tighter spin distribution of particle-hole states than normally assumed.

Designed Synthesis of PDI/BiOCl-BiPO4 Composited Material for Boosted Photocatalytic Contaminant Degradation

Enhancing the photocatalytic performance for contaminant degradation to accelerate the large-scale application of photocatalysis still is an enduring challenge. Herein, ternary PDI/BiOCl-BiPO4 composited materials with the different contents of PDI were designed and constructed by the multi-step compound method. The tetracycline hydrochloride and rhodamine B were chosen as targeted pollutants to investigate the photocatalytic performance of PDI/BiOCl-BiPO4 composited materials. The structure and component of BiOCl-BiPO4 and PDI/BiOCl-BiPO4 samples were detailedly characterized by a sequence of physical and chemical characterizations. The optimized PDI/BiOCl-BiPO4 sample, namely PDI(5%)/BiOCl-BiPO4, exhibited the excellent photocatalytic activity for tetracycline hydrochloride and rhodamine B degradation. The major active species that were holes (h+) and superoxide radicals (•O2−) also can be determined in the photocatalytic degradation process by active species trapping experiments. Furthermore, the photoelectrochemical and fluorescence measurements manifest the crucial role of PDI material. It can reduce the recombination of photo-excited charge carrier and improve the separation and transfer of photo-generated electron-hole pairs, which is beneficial to the photocatalytic reaction process. It is anticipated that our work would provide a counterpart to prepare the high-efficiency composited material in heterogeneous photocatalysis.

Preequilibrium models for 58Ni (n, xp) reaction in Neutrons at 8, 9, 9.4, 11 and 14.8 MeV using the EMPIRE and TALYS codes

In this study, the calculations of proton emission spectra produced by 58Ni (n, xp) reaction are used in the framework of preequilibrium models with the EMPIRE and TALYS codes. Exciton Model predictions combined with the Kalbach angular distributions systematics and statistical Multi-step Direct (MSD) with Multi-step Compound (MSC) processes preequilibrium models were used. Also, some necessary parameters as optical model, level density, level density a-parameter and single-particle level density parameter have been investigated for our calculations. The comparison with experimental data shows clear improvement over the Exciton and MSD with MSC models calculations.

Comprehensive-perception dynamic reasoning for visual question answering

The goal of Visual Question Answering (VQA) is to answer questions based on an image. In the VQA task, reasoning plays an important role in dealing with relations because this task has a high requirement for modeling complex features. In most existing models, the features are only extracted and integrated between adjacent layers. This pattern arguably affects the integrity of information interaction during reasoning. In this paper, we propose a comprehensive-perception dynamic reasoning (CPDR) model to utilize the cross-layer object features for multi-step compound reasoning. It calculates the interactions among the object features from all previous layers and integrates these interactions to generate new object features, iteratively. Finally, the object features of all layers will be used for the final prediction. Empirical results show that our model achieves superior performance among VQA models which are not VLP-based, and incorporating the CPDR module into the VLP models brings considerable performance improvements.

Secondary emission in pre-equilibrium reaction effects on differential cross-section

The differential cross-sections of the pre-equilibrium reactions were calculated within the exciton model (EM) and Feshbach–Kerman–Konin (FKK) theory for some selected reactions targets ([Formula: see text] and [Formula: see text] with [Formula: see text] and [Formula: see text] reactions at low and high energies 10, 14, 16, 25 and 57 MeV using PRECO-2006 to investigate the importance of secondary emission in the pre-equilibrium reactions. The results showed that the emission of secondary nucleons showed a behavior in the resulting spectra, the most prominent of which is its significant contribution to adding to the spectra obtained through practical experiments. As multistep direct (MSD) and multistep compound (MSC) are the main two components in the pre-equilibrium reaction, it was shown that the MSD dominated above 5[Formula: see text]MeV emission energy rather than MSC reaction.

System Level Real-Time Simulation and Hardware-in-the-Loop Testing of MMCs

In this paper we present an approach for real-time simulation and Hardware-in-the-Loop (HIL) testing of Modular Multilevel Converters (MMCs) that rely on switching models while supporting system level analysis. Using the Latency Based Linear Multistep Compound (LB-LMC) approach, we achieved a 50 ns simulation time step for systems composed of several MMC converters and for converters of various complexity. To facilitate system level testing, we introduce the use of a serial communication-based (Aurora) interface for HIL testing of MMC converters and we analyzed the effect that communication latency has on the accuracy of the HIL test. The simulation and HIL results are validated against an MMC laboratory prototype.

Estimation Pre-Equilibrium Particle and Angular Distribution Spectra for the Neutrons Induce Nuclear Reactions on 90Zr Nuclei by using (FKK) Model

Particles pre - equilibrium spectra and angular distribution are calculated by usingFeshbach-Kerman- Koonin (FKK) model with PRECO-2006 code. The angular distribution of the nuclei of nuclear reactions between the nucleus of a target (90Zr) and the tapline of light particles wascalculated by using reactions of the multistep compound (MSC) and of multistep direct (MSD).Isospin, the finite well depth, and shell effects are considered. Byusing [(_40^90)〖Zr〗_50 ] as target material the cross section of [90Zr(n,n)90Zr], [90Zr(n,p)90Y], [90Zr(n,D)89Y], [90Zr(n,T)88Y], [90Zr(n,3He)88Sr] and [90Zr(n,4He)87Sr] reactions were estimated. Values of cross sections estimated are 550, 371, 16.3, 4.55, 0.271 and 2.35 mb/MeV respectively. Also the angular distribution of same nuclear reactions were estimated, and the values of angular distribution are 850, 392, 4.55, 4.55,0.27 and 2.35mb/sr.MeV respectively.

A Hardware-in-the-Loop Platform for DC Protection

Real-time (RT) simulation of power and energy conversion systems allows engineers to interface both simulation- and hardware-based controls using controller hardware-in-the-loop (CHiL) simulation of networks of power electronic converters (PECs) to de-risk highly developmental systems, such as next generation electrified transportation systems and dc microgrids. CHiL exploration and performance verification moves a design from technology readiness level (TRL) 3 to TRL 4 without incurring significant cost investments in developmental hardware platforms, which otherwise discourages such endeavors. An RT CHiL simulation platform suitable for explorations of protective equipment, protection schemes, and networked PEC dc and mixed dc-ac power distribution architectures must be capable of simulating common-mode behavior, various grounding schemes, and fault transients at sufficiently high resolution. This article demonstrates this capability using a latency-based linear multistep compound (LB-LMC) simulation method implemented in a commercially sustainable, adaptable, and expandable FPGA-based test and instrumentation platform. The proposed CHiL platform achieves RT power system simulations, including detailed switching commutations of networked PECs, with 50-ns resolution, and faithfully produces resonant and transient behaviors associated with line-to-ground (LG) and line-to-line (LL) faults and fault recovery in ungrounded PEC-based dc systems. This resolution in RT cannot be achieved with today's commercial off-the-shelf CHiL platforms. This article demonstrates the need for high-resolution RT simulation of LG and LL faults within dc systems, and demonstrates a CHiL approach that enables dc protection design explorations and protective control hardware testing while taking into account the realistic aspects that affect fault characteristics in PEC-based dc systems, such as cable current rating and length, cable and PEC parasitic LG capacitance, and PEC internal response to fault scenarios.

Collective Reactions in the Continuum

We show that pre-equlibrium inelastic scattering reactions to the continuum contain substantial collective components in addition to the multistep direct and multistep compound reactions. These collective reactions are investigated for the vibrational nuclei 56Fe, 58Ni, 90Zr, 93Nb, 208Pb and 209Bi , and the strongly-deformed, rotational W nucleus. The collective cross-sections are calculated using the experimental data for low-lying collective excitations supplemented where necessary by the giant multipole resonances evaluated using the energy-weight ed sum rule. The MSC and MSD cross-sections are evaluated by the Feshbach-Kerman-Koonin theory using a consistent set of parameters determined by analyses of (p, xn) reactions, that have practically no collective components. The results are compared with high-resolution neutron inelastic scattering data and prove able to account for the absolute magnitude of the cross-sections and also their detailed structure.

Real-Time Multi-FPGA Simulation of Energy Conversion Systems

In this paper we present a solution for real-time multi-FPGA simulation of energy conversion systems based on the Latency-Based Linear Multistep Compound (LB-LMC) simulation approach. The approach relies on a nodal decomposition approach derived from multiport network analysis, and fast parallel communication between Field Programmable Gate Array (FPGA) devices. The results presented in this paper –using a microgrid example– demonstrate how the developed real-time platform overcame the resource scalability limit of single FPGA solvers while achieving a time step size of 100 nanoseconds.

The pre-equilibrium and equilibrium double differential cross sections for the nucleons and light nuclei induce nuclear reactions on 27Al nuclei

The pre - equilibrium and equilibrium double differential crosssections are calculated at different energies using Kalbach Systematicapproach in terms of Exciton model with Feshbach, Kerman andKoonin (FKK) statistical theory. The angular distribution of nucleonsand light nuclei on 27Al target nuclei, at emission energy in the centerof mass system, are considered, using the Multistep Compound(MSC) and Multistep Direct (MSD) reactions. The two-componentexciton model with different corrections have been implemented incalculating the particle-hole state density towards calculating thetransition rates of the possible reactions and follow up the calculationthe differential cross-sections, that include MSC and MSD models.The finite well depth, isospin, shell effects, Pauli effect, chargeeffect, pairing, surface, angular and linear momentum distributionscorrections are considered in this work. The nucleons (n and p) andlight nuclei (2D and 3T) have been employed as projectiles at thetarget 27Al nuclei and at different incident energies (4MeV, 14 MeVand 14.8MeV). The results have been compared with the availableexperimental and theoretical published work. The comparisons showan acceptable agreement with the TALAYS code (Tendel 2014) forthe reactions: 27Al (n, n) 27Al, 27Al (p, n) 63Zn, 27Al (p, D) 62Cu, 27Al(p, p) 63Cu and 27Al (p, 4He)60Ni and at different emission energiesand angles.

Evaluation of the fine blanking tool for the precise clutch cam of automobile seat lifter pumping device

In this paper, the multi-step forming process was studied with the fine blanking (FB) tool and the FB experiments for the precise clutch cam of automobile seat lifer pumping device (PCC). In order to form the PCC, the multi-step compound FB tooling system was taken; the three forces were directly gained from the rams of the FB press and the other force was gained from the auxiliary hydraulic device in the FB press. The FB tool was optimally designed through the FB simulation and fabricated. From the FB experiments with the FB press (Mori Iron Co., Ltd, FB400), the 5 samples of the PCC were taken and measured. All samples fulfilled the tolerance conditions.

Response of multi-step compound pre-equilibrium reaction cross sections for the (p, n) reactions to forms of optical model parameters

In furtherance to improving agreement between calculated and experimental nuclear data, the nuclear reaction code GAMME was used to calculate the multi-step compound (MSC) nucleus double differential cross sections (DDCs) for proton-induced neutron emission reactions using the Feshbach-Kerman-Koonin (FKK) formalism. The cross sections were obtained for reactor structural materials involving 52Cr(p, n)52Mn, 56Fe(p, n)56Co, and 60Ni(p, n)60Cu reactions at 22.2 MeV incident energy using the zero-range reaction mechanism. Effective residual interaction strength was 28 MeV, and different optical potential parameters were used for the entrance and exit channels of the proton-neutron interactions. The calculated DDCs were fitted to experimental data at the same backward angle of 150°, where the MSC processes dominate. The calculated and experimental data agree well in the region of pre-equilibrium (MSC) reaction dominance against a weaker fit at the lower emission energies. We attribute underestimations to contributions from the other reaction channels and disagreement at higher outgoing energies to reactions to collectively excited states. Contrary to the FKK multi-step direct calculations, contributions from the higher stages to the DDCs are significant. Different sets of parameters resulted in varying levels of agreement of calculated and experimental data for the considered nuclei.

System-Level, FPGA-Based, Real-Time Simulation of Ship Power Systems

In this paper, we present a scalable approach for real-time simulation of ship power systems with high-frequency power electronics converters (100–200 kHz). The proposed approach is based on the latency-based linear multistep compound method and relies on field-programmable gate array (FPGA) execution. Several examples of increasing dimension and complexity are used to evaluate the scalability—both of in terms of computational delay and of resources usage—of the proposed approach. Real-time execution with a 50 ns time step is achieved for all the examples considered.

Evaluations of Reactions Cross Section of Radionuclide by Particles Induced Nuclear Reactions using Exifon Code

In this work the reaction cross section for the production radionuclide of and isotopesfrom bismuth-208 were calculated using EXIFON code in the energy range from 0 MeV to 30 MeV. The code is based on an analytical model for statistical multistep direct and multistep compound reactions (SMD/SMC model).The results obtained shows that production ofTlis not observed at this energy range because the interaction cross section is zero, and also the excitation functions for the production of Tl-205 and Tl-204 were obtained.

Calculation of Reactions Cross Section for Neutron-Induced Reactions on <sup>127</sup>I Isotope

In this work, the reaction cross-section for neutron-induced reactions on 127I isotope was calculated using EXIFON code in the energy range of incident particle from 0 MeV to 30 MeV. The code is based on an analytical model for statistical multistep direct and multistep compound reactions (SMD/SMC model). In order to see the effect of nuclear structure on cross sections, the calculation was done using nuclear shell structure effect and without considering shell structure effect. Obtained results and statistical analysis showed that shell structure effect does not give significant changes to the cross-section at considered energy ranges. This shows that EXIFON code is a good tool for investigation of nuclear reaction cross section and is useful in the production of the radioisotopes of Iodine, Antimony and tellurium of high purity and in an efficient manner using cyclotron or nuclear reactors, these isotopes have potential application for field of medical science especially for diagnostics and therapeutic purposes.

Investigation of the Shell Effect on Neutron Induced Cross Section of Actinides

Investigations has been made concerning the development of the effect of shell structure on neutron induced cross section, evaluations for Actinides elements in the energy range of 0-30 MeV. The EXIFON code, which is based on the analytical model for statistical multistep direct and multistep compound reactions, was used for the calculation of the cross section for (n-2n), (n-p) and (n-α) reaction channels. Results are compared with data from the experimental database, EXFOR from the IAEA nuclear data bank to deduce the shell effect. An empirical relation for the reaction cross section has been established for magic numbers nucleus in the (n-2n) reaction channel in the energy range. Results shows that the odd-even effect has also been observed as the cross section for odd-even nuclei are higher than their neighbouring even-even nuclei and with comparison in term of Shell correction, the cross section is higher when the Shell correction is not considered.

Double differential cross sections of proton emission in neutron induced reaction on27Al

Double differential sections for proton emission on aluminium are presented for 40 MeV incident neutron energies. Angular distributions, energy differential and total production cross sections are obtained. The results are compared to existing data and to nuclear model calculations which include preequilibrium and compound decay mechanisms. The EMPIRE code treats these mechanisms in the framework of TUL model for multistep direct and NVWY model for multistep compound. The Hauser Feshbach theory is used to calculate emission from the compound nucleus, with a full conservation of spin and parity.

Equilibrium and pre-equilibrium processes in theMn55(Li6,xp) andFe57(α,xp) reactions

Spectra of outgoing neutrons and protons from the 6Li+55Mn reaction and protons from the a+57Fe reaction have been measured with beams of 15 MeV 6Li ions and 30 MeV alpha-particles. These reactions proceed through the same 61Ni nucleus at the same excitation energy, thus allowing the difference in reaction mechanism to be studied. It is shown that spectra from the first reaction measured at backward angles are due to emission from a traditional compound nucleus reaction, in which the intermediate nucleus has reached statistical equilibrium; the spectra from the second reaction contain a significant fraction of pre-equilibrium emission at all angles. Level density pa- rameters of the residual nucleus 60Co have been obtained from the first reaction. Both emission spectra and angular distributions have been measured for the second reaction. It was found that the pre-equilibrium component exhibits a forward-peaked angular distribution, as expected, but with a steeper slope than predicted and with an unusual slight rise at angles above 120\deg. The backward- angle rise is explained qualitatively by the dominance of the multi-step compound mechanism at backward angles.

Deformation-dependent Tamura-Udagawa-Lenske multistep direct model

The multistep direct TUL model has been extended in order to account for nuclear deformation. The new formalism was tested in calculations of neutron emission spectra from the $^{232}\mathrm{Th}$($n$, $\mathit{xn}$) reaction. These calculations include vibration-rotational coupled channels for the inelastic scattering to low-lying collective levels, ``deformed'' multistep direct (MSD) for inelastic scattering to the continuum, multistep compound, and Hauser-Feshbach with advanced treatment of the fission channel. Prompt fission neutrons were also calculated. The comparison with experimental data shows clear improvement over the ``spherical'' MSD calculations and JEFF-3.1 and JENDL-3.3 evaluations. Similar calculational results have been obtained of neutron emission spectra from the stable deformed nuclei $^{181}\mathrm{Ta}$ and $^{184}\mathrm{W}$.