Exchange Contributions Research Articles

The Fourth-Order KN potential Matrix-Element in 3D basis

The aim of this study is to derive the fourth-order KN potential matrix-element. The matrix element is derived in 3D basis. Previous study about the-second order KN interaction shows that the result need to be improved, so we continue the study to the fourth-order. Potential matrix-element is derived from KN Interaction potential which is developed by Büttgen (Nucl. Phys. A506) dan Müller (Nucl. Phys. A513). The meson being exchanged in the fourth-order KN interaction is pion with intermediate state are NK* and ΔK*. Potential matrix-element is formulated from potential on 3D basis. We apply 3D technique in this study as a good alternative to Partial wave technique. That technique does not expand the free state in partial wave so it is useful in high energy scattering. Potential matrix-element derived from this study can be used to calculate differential cross section which can be used to calculate the contribution of pion exchange in KN scattering.

Ab-initio investigation of the fundamental properties of metals (X = Be, Mg, and Ca) encapsulated CsXO3 tin-based perovskite materials

Perovskite material are widely used in Solar cell device due to it promising properties and power conversion efficiencies (PCE). Most importantly, properties of the absorber layer such as the band gap, electronic, optical, chemical composition and the grain size of the perovskite absorbed layer are very sacrosanct when determining efficacy of the material for such application. Thus, in this work, the optical, structural stability, electronic, and mechanical properties of non-halide cubic perovskite CsXO3 (X = Mg, Be and Ca) was extensively studied using the first principles Density functional theory (DFT) approach. The structural, electronic and optoelectronic properties was evaluated using Quantum Espresso Simulation Package (QESP) with the plane wave self-consistent field (PWscf) code. The structural computation reveals that the Lattice constant as well as total energy of CsXO3 (X = Be, Mg and Ca) increases as the size of cation X (X = Be, Mg and Ca) increases such that CsCaO3 possess the highest energy. Contrary, the fermi energy decreases with increase in cationic size, however, CsCaO3 has the highest lattice constant value 4.3743 eV. Electronic properties investigation shows that the studied perovskite has a metallic property with no forbidden band. zero band gap materials can adsorb photon across the entire solar spectrum, including lower-energy photons which is an advantage over a non-zero band gap which can only absorb photon with energies higher than the band gap energy can be absorbed and converted into electricity. This enables more efficient utilization of sunlight and increased overall energy conversion. To ascertain the effect of atomic exchange and orbital contribution in the formation of electronic properties, partial density of state (PDOS) was calculated and the result reveal that electron transition occurs mostly from p-orbital oxygen atom having major contribution on the valence band to the d-orbital of Caesium atom having major contribution on the conduction band and X-cation having minor contribution. CsXO3 (X = Be, Mg and Ca) also shows fascinating optical properties and thus can be used to improve solar cell device.

Structural, dynamical and thermodynamical stability of Cd1-xZnxS ternary systems

Cd1-xZnxS alloys are currently explored as one class of the most promising for producing hydrogen energy under visible-light irradiation. Here, using an ab intio evolutionary algorithm, we reveal that CdS–ZnS systems can form nearly thermodynamically stable crystal phases of Cd3ZnS4 (P-43m), CdZnS2 (P-4m2), and CdZn3S4 (P-43m), with low miscibility temperatures of 130 °C. By decomposing the formation enthalpy of the alloys into multiple contributions, it is found that electronic charge exchange plays a key role in controlling the weak thermodynamic instability of Cd1-xZnxS alloys. Phonon dispersion and elastic constants calculations were carried out to demonstrate the dynamical and mechanical stabilities of these structures. The bandgap in CdZnS alloys is tunable from wide direct bandgaps of 2.54eV (CdS) → 2.70eV (Cd3ZnS4) →2.93eV (CdZnS2) → 3.33eV (CdZn3S4) → 3.86eV (ZnS), with a nonlinear dependence on the composition. We found a medium-sized optical bandgap bowing of ∼1eV and ∼0.7eV; while considering respectively the wurtzite (WZ) and zinc-blend (ZB) crystal phases as reference of the compounds parents CdS and ZnS. The bowing has a remarkable contribution due to the structural volume-deformation effect; whereas charge exchange contribution is found relatively weak.

Ligneous amendments increase soil organic carbon content in fine-textured boreal soils and modulate N2O emissions.

Organic soil amendments are used to improve soil quality and mitigate climate change. However, their effects on soil structure, nutrient and water retention as well as greenhouse gas (GHG) emissions are still poorly understood. The purpose of this study was to determine the residual effects of a single field application of four ligneous soil amendments on soil structure and GHG emissions. We conducted a laboratory incubation experiment using soil samples collected from an ongoing soil-amendment field experiment at Qvidja Farm in south-west Finland, two years after a single application of four ligneous biomasses. Specifically, two biochars (willow and spruce) produced via slow pyrolysis, and two mixed pulp sludges from paper industry side-streams were applied at a rate of 9-22 Mg ha-1 mixed in the top 0.1 m soil layer. An unamended fertilized soil was used as a control. The laboratory incubation lasted for 33 days, during which the samples were kept at room temperature (21°C) and at 20%, 40%, 70% or 100% water holding capacity. Carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) fluxes were measured periodically after 1, 5, 12, 20 and 33 days of incubation. The application of ligneous soil amendments increased the pH of the sampled soils by 0.4-0.8 units, whereas the effects on soil organic carbon content and soil structure varied between treatments. The GHG exchange was dominated by CO2 emissions, which were mainly unaffected by the soil amendment treatments. The contribution of soil CH4 exchange was negligible (nearly no emissions) compared to soil CO2 and N2O emissions. The soil N2O emissions exhibited a positive exponential relationship with soil moisture. Overall, the soil amendments reduced N2O emissions on average by 13%, 64%, 28%, and 37%, at the four soil moisture levels, respectively. Furthermore, the variation in N2O emissions between the amendments correlated positively with their liming effect. More specifically, the potential for the pulp sludge treatments to modulate N2O emissions was evident only in response to high water contents. This tendency to modulate N2O emissions was attributed to their capacity to increase soil pH and influence soil processes by persisting in the soil long after their application.

Phosphate adsorption on LDHs-biochar composite: Double-layer model for quantifying the contribution of ion exchange and ligand exchange.

The adsorption performance of layered double hydroxides (LDHs) is limited owing to self-aggregation. To avoid this and effectively control the eutrophication of water bodies, biochar (BC) was synthesized, herein, by pyrolyzing waste sheep manure at 500°C, and Ca-Al-LDHs were loaded on the surface via a coprecipitation method to obtain Ca-Al-LDHs-BC(CA) composites with varying LDH contents. The fitted maximum adsorption capacities of the CA-5%, CA-10%, CA-15%, and CA-20% samples (corresponding to samples with 5%, 10%, 15%, and 20% LDHs, respectively) were 10.21, 16.14, 22.40, and 28.47 mg g-1, which were (when converted into metal proportions) 1.48, 1.23, 1.15, and 1.13 times of that of single hydrotalcite, respectively. The double-layer model was fitted using the Levenberg-Marquardt iterative algorithm, which when combined with the characterization results, confirmed that the adsorption of phosphate ions by CA-BC occurred via the double-layer adsorption mechanism. Two types of direct adsorption were observed: ion exchange, which resulted in first-layer adsorption, and ligand exchange, which resulted in second-layer adsorption, with first-layer adsorption accounting for a higher proportion. This double-layer adsorption mechanism showed that LDHs-BC could achieve higher ligand exchange performance compared to that achieved using only LDHs.

Investigation on Pb2+ adsorption characteristics by AAEMs-rich biochar in aqueous solution: Performance and mechanism

Biochar derived from soybean straw with AAEMs (alkali and alkaline earth metals) enrichment could efficiently remove heavy metals from contaminated water. In this study, the influences of pyrolysis temperature on the physicochemical property and adsorption performance of soybean straw biochar were investigated. The contributions of different adsorption mechanisms were analyzed quantitatively. The results show that the soybean straw biochar exhibits excellent Pb2+ adsorption performance (157.2–227.2 mg g−1), with an order of BC800 > BC400 > BC600 > BC700 > BC500. The mechanisms of metal ion exchange (37.49%–72.58%) and precipitation with minerals (22.38%–58.03%) mainly control the Pb2+ adsorption, whereas complexation with organic functional groups (OFGs) and cation-Cπ interaction make the less contribution. The order of cation exchange capacity (CEC) is BC400 > BC800 > BC700 > BC600 > BC500, showing a high correlation (0.965) with the contribution of metal ion exchange with AAEMs. Moreover, Ca exhibits the strongest exchange capacity. The contribution of precipitation is consistent with the variation of soluble CO32− content in biochar. These results suggest that soybean straw biochar rich in AAEMs is a prospective adsorbent for Pb2+ elimination.

Parameterized model to approximate theoretical collision-induced absorption band shapes for O2-O2 and O2-N2

Collision-induced absorption from vibronic transitions of O2-O2 and O2-N2 collision complexes is an important contributor to light-matter interaction in the atmosphere with relevance to radiative heat transfer and remote sensing. Despite in-depth studies involving quantum calculations of this effect, comparisons between experiment and theory would benefit from less computationally burdensome calculations that closely approximate the temperature dependence of the theoretical band shape and intensity. Accordingly, we present a parameterized representation of recent quantum calculations for collision-induced absorption by O2-O2 and O2-N2 about the 1.27 μm monomer band of O2. This approach leverages the theoretical decomposition of the spectra into exchange and spin-orbit contributions, with each component having a distinct temperature-dependent band shape. Composite spectra are approximated as a linear combination of the theoretical profiles with seven adjustable parameters that scale the component intensities and their dependences on temperature. We demonstrate that this empirical representation can accurately simulate the theoretical calculations, and we present a global fit of the model to previously reported collision-induced absorption spectra (O2-O2, O2-N2, and O2-air) measured by cavity ring-down spectroscopy over the temperature range 271 K–332 K.

Adsorption performance and mechanisms of MgO-modified palygorskite/biochar composite for aqueous Cd (II): Experiments and theoretical calculation

The treatment of Cd2+ pollution in water has been a hot topic of research, while the studies for the preparation and application of biochar composites to treat Cd2+ and the corresponding micro-mechanisms were still lacking. In this study, a novel MgO-modified palygorskite/biochar derived from rice straw composite (MPBC) was synthesized to remove Cd2+ in the aqueous solution. Batch experiments were conducted to evaluate the adsorption ability for Cd2+ on MPBC. The results showed that the maximum adsorption capacity of MPBC was 441.1 mg/g, which was 4.6 times higher than that of the original biochar (BC). Adsorption mechanisms were clarified combine systematic characterization and density functional theory (DFT) calculations. Precipitation, complexation, ion exchange, and Cd-π interaction were the main adsorption mechanisms, and the contribution of the ion exchange, compared with 12.08% of BC, increased to 37.82%. The O atom of the MgO group performed negative electrostatic potentials as an electrophilic active site. The nucleophilic Cd tends to transfer electrons to the electrophilic O atom of the MgO group. Furthermore, the density of state (PDOS) identified that hybrid overlap occurred between MgO and Cd, and a new chemical bond was formed in the adsorption process. Overall, this work offers a new approach to removing aqueous Cd2+ and uses biowaste to create a sustainable environment.

A jeff = 1/2 Kitaev material on the triangular lattice: the case of NaRuO2

Motivated by recent reports of a quantum-disordered ground state in the triangular lattice compound NaRuO2, we derive a jeff = 1/2 magnetic model for this system by means of first-principles calculations. The pseudospin Hamiltonian is dominated by bond-dependent off-diagonal Γ interactions, complemented by a ferromagnetic Heisenberg exchange and a notably antiferromagnetic Kitaev term. In addition to bilinear interactions, we find a sizable four-spin ring exchange contribution with a strongly anisotropic character, which has been so far overlooked when modeling Kitaev materials. The analysis of the magnetic model, based on the minimization of the classical energy and exact diagonalization of the quantum Hamiltonian, points toward the existence of a rather robust easy-plane ferromagnetic order, which cannot be easily destabilized by physically relevant perturbations.

Dissecting the ingredients of optimally tuned range-separated hybrid models for reliable description of non-adiabatic couplings.

Perusing the non-radiative processes requires a reliable prediction of non-adiabatic couplings (NACs) describing the interaction of two Born-Oppenheimer surfaces. In this regard, the development of appropriate and affordable theoretical methods that accurately account for the NAC terms between different excited-states is desirable. In this work, we develop and validate several variants of the optimally tuned range-separated hybrid functionals (OT-RSHs) for investigating NACs and related properties, such as excited states energy gaps and NAC forces, within the time-dependent density functional theory framework. Particular attention is paid to the influence of the underlying density functional approximations (DFAs), the short- and long-range Hartree-Fock (HF) exchange contributions, and the range-separation parameter. Considering several radical cations and sodium-doped ammonia clusters with the available reference data for the NACs and related quantities as the working models, we have evaluated the applicability and accountability of the proposed OT-RSHs. The obtained results unveil that any combination of the ingredients in the proposed models is not proper for describing the NACs, but a particular compromise among the involved parameters is needed to achieve reliable accuracy. Scrutinizing the results of our developed methods, the OT-RSHs based on the PBEPW91, BPW91, and PBE exchange and correlation DFAs, including about 30% HF exchange at the short-range regime, appeared to be the best performers. We also find that the newly developed OT-RSHs with correct asymptotic exchange-correlation potential have superior performances as compared to their standard counterparts with the default parameters and many earlier hybrids with both fixed and interelectronic distance-dependent HF exchange. The recommended OT-RSHs in this study can hopefully be applicable as computationally efficient alternatives to the expensive wave function-based methods for the systems prone to non-adiabatic properties as well as to screen out the novel candidates prior to their challenging synthesis.

Kajian Keberhasilan Implementasi Kebijakan Online Single Submission Risk Based Approach (OSS-RBA) di DPMPTSP Kabupaten Ketapang pada Perusahaan Perkebunan

Online Single Submission Risk Based Approach (OSS-RBA) is a risk-based business licensing service system that is carried out online. It is important to know about the application of the OSS-RBA Policy because it relates to the country's national achievements in simplifying the business licensing process and attracting foreign investors. The plantation business sector, especially oil palm, is important to pay attention to. The high contribution of the country's foreign exchange originating from this industry is one of the reasons the government has made the business licensing process smooth. For this reason, this research aims to measure the level of success in implementing the OSS-RBA Policy in the Investment and One-Stop Integrated Services Service (DPMPTSP) Ketapang Regency, especially in plantation companies. This research uses a mixed method with purposive sampling. In this study, respondents were divided into two groups, specifically 4 respondents from the policy implementer and 35 respondents from the oil palm plantation company. The George Edward III Policy Implementation Model used theory, which determined four indicators that influence implementation: communication, resources, disposition, and bureaucratic structure. The research on communication indicators showed that there had been a clear and consistent transmission of information from policymakers to policy implementers and business actors. Meanwhile, equipment and authority resources have been fulfilled in the resource indicators. For disposition, licensing services have been provided optimally. Finally, regarding bureaucratic structure indicators, DPMPTSP Ketapang Regency has done SOPs for services and licensing activities.

Measuring the Potential Integration of Indonesian Sharia Capital Market with the OIC Member Countries

The Indonesian Composite Index (ICI) experienced a critical session, the data showed the ICI fell by 6.58% which was the biggest decline in the last 9 years. The prevailing notion was that this pressure stemmed from the prevalence of the Covid-19 concern and is anticipated to be alleviated once Covid-19 disseminates further. The purpose of this study is to determine the causality and long-term cointegration relationship between sharia stock in Indonesia and the Organization of Islamic Cooperation (OIC) member countries, as well as to determine the contribution of shares of OIC member countries, such as Egypt, Oman, Saudi Arabia, Kuwait, Turkey, Bahrain, and Malaysia in the collapse of the Islamic capital market in Indonesia. The method used in this research is quantitative by using secondary data in the form of daily prices of the Sharia index sourced from the website www.investing.com. The population of the countries related to this research is 56 members of the OIC that are active until 2021. For data analysis, several tests were conducted, such as; Testing Time Series Data, Vector Autoregressive (VAR), Granger Causality Test, Johansen Model Cointegration Test, and Contagion Effect Test. The study found that; has not been able to prove the existence of cointegration between the Indonesian Islamic stock exchange and the stock exchanges of OIC member countries other than the Malaysian stock exchange. However, this study proves the interdependence between the Malaysian and Indonesian Islamic stock exchanges, but in the long term, the contribution of the Indonesian stock exchange is greater than the Malaysian Islamic stock index. In addition, another finding was that during the Covid-19 shock, the Malaysian stock position index showed more independence, whereas the decline that occurred at the beginning of the pandemic was caused without the JII or ISSI intervention index.

{{rho }} exchange contribution to neutrinoless double beta decay

We consider rho meson contributions to neutrinoless double beta decay amplitude stemming from the hadronization of the short distance quark-electron currents. These contributions are evaluated within vacuum dominance approximation. The one and two rho exchange contributions affect the Fermi transition nuclear matrix element in a way that lead to near cancellations in the same chirality, left–left and right–right, short range amplitudes when these new contributions are combined with the conventional short range amplitudes, while the left–right amplitude almost triples. A rough estimate comparing this contribution to the long range pion exchange contribution indicates that rho exchange contribution can easily be mathcal {O}(10%) of the pion contribution. When considering precision predictions, rho exchange amplitudes should be included in any phenomenological study, like in left–right theories.

Comparison of the adsorption capacity and mechanisms of mixed heavy metals in wastewater by sheep manure biochar and Robinia pseudoacacia biochar.

Under various pyrolysis temperatures, the characteristics and heavy metal adsorption capabilities of biochar obtained from sheep manure (SMB) and Robinia pseudoacacia (RPB) were studied. The results indicated that SMB had higher yields, pH values, and ash contents than RPB. SMB3 and RPB3 have more oxygen-containing functional groups, whereas SMB8 and RPB8 have higher aromaticity and polarity. The maximum adsorption capacities of SMB for Pb2+ (20.2 mg·g-1), Cu2+ (13.9 mg·g-1), Cd2+ (3.2 mg·g-1), and total heavy metals (37.3 mg·g-1) were obtained by SMB3. However, the maximum adsorption capacities of RPB for Pb2+ (7.4 mg·g-1) and Cu2+ (10.5 mg·g-1) were obtained by RPB8. Furthermore, SMB and RPB had relatively higher adsorption capacities for Pb2+ and Cu2+ than for Cd2+. The pseudo-second-order model and the Freundlich Langmuir model provided a good fit to the adsorption kinetics and isotherms, indicating that chemical adsorption was dominant in the heavy metal adsorption by SMB and RPB. According to the contribution of various mechanisms, ion exchange and mineral precipitation were the primary mechanisms responsible for RPB8, while functional group complexation was the dominant mechanism for SMB3. This study provided important information on the comprehensive recycling utilization of SMB and RPB and promoted sustainable development.

Abundance and temperature of the outer hot circumgalactic medium

Context. Despite their vital importance to understanding galaxy evolution and our own Galactic ecosystem, our knowledge of the physical properties of the hot X-ray emitting phase of the Milky Way is still inadequate. However, sensitive SRG/eROSITA large area surveys are now providing us with the long-sought data needed to mend this state of affairs. Aims. Our aim is to constrain the properties of the Milky Way hot halo emission toward intermediate Galactic latitudes close to the Galactic anti-center. Methods. We analyzed the spectral properties of the integrated soft X-ray emission observed by eROSITA in the relatively deep eFEDS field. Results. We observe a flux of 12.6 and 5.1 × 10−12 erg cm−2 s−1 deg−2 in the total (0.3–2) and soft (0.3–0.6 keV) band. We measure the temperature and metal (oxygen) abundance of the hot circumgalactic medium (CGM) to be within kTCGM = 0.153–0.178 keV and ZCGM = 0.052–0.072 Z⊙, depending on the contribution of solar wind charge exchange (SWCX). Slightly higher CGM abundances ZCGM = 0.05–0.10 Z⊙ are possible, considering the uncertain extrapolation of the extragalactic cosmic X-ray background (CXB) emission below ~1 keV. To recover CGM abundances as high as ZCGM = 0.3 Z⊙, the presence of an additional component must be postulated, likely associated with the warm-hot intergalactic medium, providing ~15–20% of the flux in the soft X-ray band. We observe line widths of the CGM plasma smaller than Δυ ≤ 500 km s−1. The emission in the soft band is dominated (~47%) by the circumgalactic medium (CGM), whose contribution reduces to ~30% if heliospheric SWCX contributes at the level of ~15% also during solar minimum. The remaining flux is provided by the CXB (~33%) and the local hot bubble (~18%). Moreover, the eROSITA data require the presence of an additional component associated with the elusive Galactic corona plus a possible contribution from unresolved M dwarf stars. This component has a temperature of kT ~ 0.4– 0.7 keV, a considerable (~ kiloparsec) scale height, and might be out of thermal equilibrium. It contributes ~9% to the total emission in the 0.6—2 keV band, and is therefore a likely candidate to produce part of the unresolved CXB flux observed in X-ray ultra-deep fields. We also observe a significant contribution to the soft X-ray flux due to SWCX, during periods characterized by stronger solar wind activity, and causing the largest uncertainty on the determination of the CGM temperature. Conclusions. We constrain temperature, emission measure, abundances, thermal state, and spectral shape of the outer hot CGM of the Milky Way.

Calcium-doped magnetic humic acid nano particles for the efficient removal of heavy metals from wastewater: the role of Ca

ABSTRACT Ca doping is an effective method for improving the adsorption capacity of HA–Fe aggregates and regulating their structures. Understanding the structural characteristics of Ca–HA–Fe aggregates can help explore their microscopic adsorption effect on heavy metals. However, the heterogeneity of HA results in an incomplete understanding of the structural characteristics of the ternary system of Ca–HA–Fe aggregates and adsorption of the quaternary system of Ca–HA–Fe–Pb/Cu/Cd. In this study, interactions between Ca–HA–Fe ternary and Ca–HA–Fe–Pb/Cu/Cd quaternary systems were discussed from a molecular perspective. The structures of the basic structural units of HA were identified. Density functional theory (DFT) was employed to calculate the stable states of basic structural units of HA and Ca2+. The results showed that hydroxyl and carboxyl groups exhibited the highest capacity to bind with Ca2+. The interactions among Ca, HA, and Fe led to the formation of network aggregates. The binding energies of functional groups for heavy metals and the feasibility of ion exchange were calculated by the method of experiment and DFT. According to the contribution of functional group complexation and ion exchange, the ion exchange values for Pb2+, Cu2+, and Cd2+ were 66.71%, 62.87%, and 60.79%, respectively, which indicated that Ca2+ ion exchange showed considerable potential in enhancing the adsorption capacity of heavy metals.

Neutrinoless double beta decay in a left-right symmetric model with a double seesaw mechanism

We discuss a left-right (L-R) symmetric model with the double seesaw mechanism at the TeV scale generating Majorana masses for the active left-handed (LH) flavour neutrinos $\nu_{\alpha L}$ and the heavy right-handed (RH) neutrinos $N_{\beta R}$, $\alpha,\beta = e,\mu,\tau$, which in turn mediate lepton number violating processes, including neutrinoless double beta decay. The Higgs sector is composed of two Higgs doublets $H_L$, $H_R$, and a bi-doublet $\Phi$. The fermion sector has the usual for the L-R symmetric models quarks and leptons, along with three $SU(2)$ singlet fermion $S_{\gamma L}$. The choice of bare Majorana mass term for these sterile fermions induces large Majorana masses for the heavy RH neutrinos leading to two sets of heavy Majorana particles $N_j$ and $S_k$, $j,k=1,2,3$, with masses $m_{N_j} \ll m_{S_k}$. Working with a specific version of the model in which the $\nu_{\alpha L} - N_{\beta R}$ and the $N_{\beta R} - S_{\gamma L}$ Dirac mass terms are diagonal, and assuming that $m_{N_j} \sim (1 - 1000)$ GeV and ${\rm max}(m_{S_k}) \sim (1 - 10)$ TeV, $m_{N_j} \ll m_{S_k}$, we study in detail the new ``non-standard'' contributions to the $0\nu\beta\beta$ decay amplitude and half-life arising due to the exchange of virtual $N_j$ and $S_k$. We find that in both cases of NO and IO light neutrino mass spectra, these contributions are strongly enhanced and are dominant at relatively small values of the lightest neutrino mass $m_{1(3)} \sim (10^{-4} - 10^{-2})$ eV over the light Majorana neutrino exchange contribution. In large part of the parameter space, the predictions of the model for the $0\nu\beta\beta$ decay generalised effective Majorana mass and half-life are within the sensitivity range of the planned next generation of neutrinoless double beta decay experiments LEGEND-200 (LEGEND-1000), nEXO, KamlAND-Zen-II, CUPID, NEXT-HD.

Tourism Demand Prediction after COVID-19 with Deep Learning Hybrid CNN–LSTM—Case Study of Vietnam and Provinces

The tourism industry experienced a positive increase after COVID-19 and is the largest segment in the foreign exchange contribution in developing countries, especially in Vietnam, where China has begun reopening its borders and lifted the pandemic limitation on foreign travel. This research proposes a hybrid algorithm, combined convolution neural network (CNN) and long short-term memory (LSTM), to accurately predict the tourism demand in Vietnam and some provinces. The number of new COVID-19 cases worldwide and in Vietnam is considered a promising feature in predicting algorithms, which is novel in this research. The Pearson matrix, which evaluates the correlation between selected features and target variables, is computed to select the most appropriate input parameters. The architecture of the hybrid CNN–LSTM is optimized by utilizing hyperparameter fine-tuning, which improves the prediction accuracy and efficiency of the proposed algorithm. Moreover, the proposed CNN–LSTM outperformed other traditional approaches, including the backpropagation neural network (BPNN), CNN, recurrent neural network (RNN), gated recurrent unit (GRU), and LSTM algorithms, by deploying the K-fold cross-validation methodology. The developed algorithm could be utilized as the baseline strategy for resource planning, which could efficiently maximize and deeply utilize the available resource in Vietnam.

Constrained density functional theory calculations for estimation of forward and backward intermolecular charge transfer energy

AbstractCharge transfer (CT) in donor–acceptor complexes can occur in two directions: from donor to acceptor (forward CT, CTF) and from acceptor to donor (backward CT, CTB). For an ethylene and tetrafluoroethylene model system, coupled cluster calculations predict that CTF is more stable than CTB. Meanwhile, density functional theory (DFT) and time‐dependent DFT (TDDFT) employing B3LYP functional show a different CT state order depending on the Hartree–Fock exchange (HFX) contribution. The impact of basis sets as a possible cause to induce such unreasonable CT state reverse along with the increase of HFX was investigated. The physical origin of CT state reversal is examined in terms of molecular orbital energy. We analyzed two additional molecular pairs that feature CT state reversal along with the amount of HFX in B3LYP functional. Despite the reduced gap, we suggest constrained DFT using M06‐HF functional as an effective approach to estimate two CT state energies on equal footing.

Separation of Rare-Earth and Transition-Metal Contributions to the Interfacial Dzyaloshinskii-Moriya Interaction in Ferrimagnetic Co - Gd Alloys

Ferrimagnetic materials composed of rare earth (RE) and transition metals (TM) are of great interest for spintronic devices due to their tunable net moments and magnetic transport behaviors. Here we experimentally study the Dzyaloshinskii-Moriya interaction (DMI) in $\mathrm{Co}\text{\ensuremath{-}}\mathrm{Gd}$ ferrimagnets and find that the DMI strength increases substantially as the temperature approaches its moment compensation point. By subtracting the contribution of Heisenberg exchange coupled $\mathrm{Co}$-$\mathrm{Co}$ moments mediated by $\mathrm{Pt}$ from the total DMI strength, we observe a relationship ${D}_{\text{Co - Gd}}\ensuremath{\sim}{M}_{s}^{0.2\ifmmode\pm\else\textpm\fi{}0.06}$. The lower order indicates the weaker Heisenberg exchange compared with $\mathrm{Co}$-$\mathrm{Co}$ moments in $\mathrm{Co}\text{\ensuremath{-}}\mathrm{Gd}$ alloys. Our results reveal the intrinsic physics of DMI in RE-TM alloys by separating the different contributions of TM-TM and RE-TM sublattice moments from the total DMI and show the promising prospect for the fabrication of skyrmions in RE-TM ferrimagnets near the compensation point.