arXiv subjects

M. Anwar Hossain

Publications and source records attributed to M. Anwar Hossain.

18 recordsLinked to original sources

arXiv2026

mind_call: A Dataset for Mental Health Function Calling with Large Language Models

Large Language Model (LLM)-based systems increasingly rely on function calling to enable structured and controllable interaction with external data sources, yet existing datasets do not address mental health-oriented access to wearable sensor data. This paper presents a synthetic function-calling dataset designed for mental health assistance grounded in wearable health signals such as sleep, physical activity, cardiovascular measures, stress indicators, and metabolic data. The dataset maps diverse natural language queries to standardized API calls derived from a widely adopted health data schema. Each sample includes a user query, a query category, an explicit reasoning step, a normalized temporal parameter, and a target function. The dataset covers explicit, implicit, behavioral, symptom-based, and metaphorical expressions, which reflect realistic mental health-related user interactions. This resource supports research on intent grounding, temporal reasoning, and reliable function invocation in LLM-based mental health agents and is publicly released to promote reproducibility and future work.

cs.AI↗

arXiv2024

TextureMeDefect: LLM-based Defect Texture Generation for Railway Components on Mobile Devices

Texture image generation has been studied for various applications, including gaming and entertainment. However, context-specific realistic texture generation for industrial applications, such as generating defect textures on railway components, remains unexplored. A mobile-friendly, LLM-based tool that generates fine-grained defect characteristics offers a solution to the challenge of understanding the impact of defects from actual occurrences. We introduce TextureMeDefect, an innovative tool leveraging an LLM-based AI-Inferencing engine. The tool allows users to create realistic defect textures interactively on images of railway components taken with smartphones or tablets. We conducted a multifaceted evaluation to assess the relevance of the generated texture, time, and cost in using this tool on iOS and Android platforms. We also analyzed the software usability score (SUS) across three scenarios. TextureMeDefect outperformed traditional image generation tools by generating meaningful textures faster, showcasing the potential of AI-driven mobile applications on consumer-grade devices.

cs.CV↗

arXiv2024

DefectTwin: When LLM Meets Digital Twin for Railway Defect Inspection

A Digital Twin (DT) replicates objects, processes, or systems for real-time monitoring, simulation, and predictive maintenance. Recent advancements like Large Language Models (LLMs) have revolutionized traditional AI systems and offer immense potential when combined with DT in industrial applications such as railway defect inspection. Traditionally, this inspection requires extensive defect samples to identify patterns, but limited samples can lead to overfitting and poor performance on unseen defects. Integrating pre-trained LLMs into DT addresses this challenge by reducing the need for vast sample data. We introduce DefectTwin, which employs a multimodal and multi-model (M^2) LLM-based AI pipeline to analyze both seen and unseen visual defects in railways. This application enables a railway agent to perform expert-level defect analysis using consumer electronics (e.g., tablets). A multimodal processor ensures responses are in a consumable format, while an instant user feedback mechanism (instaUF) enhances Quality-of-Experience (QoE). The proposed M^2 LLM outperforms existing models, achieving high precision (0.76-0.93) across multimodal inputs including text, images, and videos of pre-trained defects, and demonstrates superior zero-shot generalizability for unseen defects. We also evaluate the latency, token count, and usefulness of responses generated by DefectTwin on consumer devices. To our knowledge, DefectTwin is the first LLM-integrated DT designed for railway defect inspection.

cs.CE↗

arXiv2023

Generative Model-Driven Synthetic Training Image Generation: An Approach to Cognition in Rail Defect Detection

Recent advancements in cognitive computing, with the integration of deep learning techniques, have facilitated the development of intelligent cognitive systems (ICS). This is particularly beneficial in the context of rail defect detection, where the ICS would emulate human-like analysis of image data for defect patterns. Despite the success of Convolutional Neural Networks (CNN) in visual defect classification, the scarcity of large datasets for rail defect detection remains a challenge due to infrequent accident events that would result in defective parts and images. Contemporary researchers have addressed this data scarcity challenge by exploring rule-based and generative data augmentation models. Among these, Variational Autoencoder (VAE) models can generate realistic data without extensive baseline datasets for noise modeling. This study proposes a VAE-based synthetic image generation technique for rail defects, incorporating weight decay regularization and image reconstruction loss to prevent overfitting. The proposed method is applied to create a synthetic dataset for the Canadian Pacific Railway (CPR) with just 50 real samples across five classes. Remarkably, 500 synthetic samples are generated with a minimal reconstruction loss of 0.021. A Visual Transformer (ViT) model underwent fine-tuning using this synthetic CPR dataset, achieving high accuracy rates (98%-99%) in classifying the five defect classes. This research offers a promising solution to the data scarcity challenge in rail defect detection, showcasing the potential for robust ICS development in this domain.

cs.CV↗

arXiv2020

Improving the Optical and Thermoelectric Properties of Cs2InAgCl6 with Substitutional Doping: A DFT Insight

New generation Indium based lead-free Cs2InAgCl6 is a promising halide material in photovoltaic applications due to its good air stability and non-toxic behavior. But its wide band gap (>3 eV) is not suitable for solar spectrum and hence reducing the photoelectronic efficiency for device applications. Here we report a significant band gap reduction from 3.3 eV to 0.6 eV by substitutional doping and its effect on opto-electronic and opto-thermoelectric properties from first-principles study. The results predict that Sn/Pb and Ga & Cu co-doping enhance the density of states significantly near the valence band maximum (VBM) and thus reduce the band gap by shifting the VBM upward while the alkali-metals (K/Rb) slightly increase the band gap. A strong absorption peak near Shockley-Queisser limit is observed in co-doped case while in Sn/Pb-doped case, we notice a peak in the middle of the visible region of solar spectrum. The nature of band gap is indirect with Cu-Ga/Pb/Sn doping with a significant reduction in the band gap. We observe a significant increase in the power factor (PF) (2.03 mW/mK2) for n-type carrier in Pb-dpoing, which is ~3.5 times higher than the pristine case (0.6 mW/mK2) at 500 K.

cond-mat.mtrl-sci↗

arXiv2019

First-principles prediction of extraordinary thermoelectric efficiency in superionic Li2SnX3(X=S,Se)

Thermoelectric materials create an electric potential when subject to a temperature gradient and vice versa hence they can be used to harvest waste heat into electricity and in thermal management applications. However, finding highly efficient thermoelectrics with high figures of merit, zT$\geq$1, is very challenging because the combination of high power factor and low thermal conductivity is rare in materials. Here, we use first-principles methods to analyze the thermoelectric properties of Li$_2$Sn$X_3$ ($X$=S,Se), a recently synthesized class of lithium fast-ion conductors presenting high thermal stability. In p-type Li$_2$Sn$X_3$, we estimate highly flat electronic valence bands that render high Seebeck coefficients exceeding 400 $μ$VK$^{-1}$ at 700K. In n-type Li$_2$Sn$X_3$, the electronic conduction bands are slightly dispersive however the accompanying weak electron-acoustic phonon scattering induces high electrical conductivity. The combination of high Seebeck coefficient and electrical conductivity gives rise to high power factors, reaching a maximum of 4 mWm$^{-1}$K$^{-2}$ in p-type Li$_2$SnS$_3$ and 8 mWm$^{-1}$K$^{-2}$ in n-type Li$_2$SnSe$_3$ at 300 K. Likewise, the thermal conductivity in Li$_2$Sn$X_3$ is low as compared to conventional thermoelectric materials, 2-5 Wm$^{-1}$K$^{-1}$ at room temperature. As a result, we estimate a maximum zT = 1.05 in p-type Li$_2$SnS$_3$ at 700 K and an extraordinary 3.07 (1.5) in n-type Li$_2$SnSe$_3$ at the same temperature (300 K). Our findings of huge zT in Li$_2$Sn$X_3$ suggest that lithium fast-ion conductors, typically employed as electrolytes in solid-state batteries, hold exceptional promise as thermoelectric materials.

cond-mat.mtrl-sci↗

arXiv2019

Optoelectronic and transport properties of Fe2TiGe with the Tran-Blaha modified Becke-Johnson potential

In this paper, we have performed first principles calculations to study optoelectronic, thermodynamic and transport properties of Fe2TiGe using density functional theory (DFT). The semi-classical Boltzmann transport theory is used to investigate transport properties. The calculated energy bands indicate that Fe2TiGe is an indirect band gap semiconductor with band gap 0.734 eV for TB-mBJ functional. Fe-3d and Ti-3d orbitals have the dominant contributions to the density of states due to strong hybridization between them. The maximum value of absorption coefficient is found to be 224x10^4 cm-1 in the ultraviolet region. It is found that the static refractive index of Fe2TiGe is 5.18 which is very close to that of Ge and much higher than that of GaAs. The obtained refractive index implies that Fe2TiGe is a potential optical material that can be used in optical devices such as photonic crystal, wave guides and solar cells. The Debye temperature at ambient condition is 570 K and decreases slowly with temperature. The Gruneisen parameter at ambient pressure and 300 K is 2.1 and slightly higher than that of PbTe (1.5). The calculated Seebeck coefficient and power factor at 300 K using TB-mBJ functional are 271x10^-6 VK^-1 and 5.9x10^10 Wcm^-1K^-2, respectively. Therefore, the calculated optoelectronic properties implies that Fe2TiGe is a potential candidate for photovoltaic device applications.

cond-mat.mtrl-sci↗

arXiv2019

An ab-initio study on physical properties of Pd2+ incorporated double perovskites CaPd3B4O12 (B = Ti, V)

Numerous physical properties of CaPd3Ti4O12 (CPTO) and CaPd3V4O12 (CPVO) double perovskites have been explored based on density functional theory (DFT). The calculated structural parameters fairly agree with the experimental data to confirm their stability. The mechanical stability of these two compounds was clearly observed by the Born stability criteria. To rationalize the mechanical behavior, we investigate elastic constants, bulk, shear and Young's modulus, Pugh's ratio, Poisson's ratio and elastic anisotropy index. The ductility index confirms that both materials are ductile in nature. The electronic band structure of CPTO and CPVO reveals the direct band gap semiconducting in nature and metallic characteristics, respectively. The calculated partial density of states indicates the strong hybridization between Pd 4d and O 2p orbital electrons for CPTO and Pd 4d and V 3d O 2p for CPVO. The study of electronic charge density map confirms the coexistence of covalent, ionic and metallic bonding for both compounds. Fermi surface calculation of CPVO ensures both electron and hole like surfaces indicating the multiple band nature. In the midst of optical properties, photoconductivity and absorption coefficient of both compounds reveal well qualitative compliance with consequences of band structure computations. Among the thermodynamic properties, the Debye temperature has been calculated to correlate its topical features including thermoelectric behavior. The studied thermoelectric transport properties of CPTO yielded the Seebeck coefficient (186 microVK-1), power factor (11.9 microWcm-1K-2) and figure of merit (ZT) value of about 0.8 at 800 K indicate that this material could be a promising candidate for thermoelectric device application.

cond-mat.mtrl-sci↗

arXiv2019

Prediction of fundamental properties of Be-B-Ta based novel ternary compounds from first-principles calculations

Be-B/B-Ta based compounds are very attractive to researchers because of their high density and ultra-hardness. But ternary Be-B-Ta compounds are neither synthesized nor predicted. In this paper, variable composition evolutionary crystal structure prediction calculations based on first-principles method have been performed to find the stable crystal structure containing Be-B-Ta at ambient condition. The predicted five compounds BeB$_2$Ta, BeB$_3$Ta$_2$ (high-pressure phase), BeBTa, BeBTa$_2$, and Be$_2$B$_2$Ta have been found to be highly dense and very hard materials. All these compounds are metallic and spin-orbit coupling (SOC) effect is significant in them. Only two of them (BeB$_2$Ta and Be$_2$B$_2$Ta) have been found to be superconductors within Migdal-Eliashberg theory. The calculated critical temperature including SOC effect is 8 and 9 K for BeB$_2$Ta and Be$_2$B$_2$Ta, respectively. Because of their energetic and dynamic stability, these compounds might be favorable to synthesize in the laboratory.

cond-mat.supr-con↗

arXiv2018

Optoelectronic and thermoelectric properties of Ba3DN (D = Sb, Bi): A DFT investigation

We have investigated the optoelectronic and thermoelectric properties of hexagonal antiperovskites Ba$_3$DN (D = Sb, Bi) using DFT calculations. The calculated equilibrium lattice parameters of both compounds are in good agreement with the available data. The calculated electronic structures indicate that they are direct bandgap semiconductors and the values of bandgaps are 1.35 and 1.33 eV for Ba3SbN and Ba3BiN, respectively. The inclusion of the spin-orbit effect split the conduction bands and the band gap of Ba$_3$BiN is much reduced. These two compounds have a high absorption coefficient, notably higher than that for GaAs and close to that for silicon. The obtained static refractive index is ~2.8 and 3.26, for Ba$_3$SbN and Ba$_3$BiN, respectively. We predict that both materials are suitable for a high-efficiency solar cell. Both compounds exhibit a high Seebeck coefficient and high power factor. Our analysis predicts that the studied materials are potential candidates in thermoelectric device applications.

cond-mat.mtrl-sci↗

arXiv2018

DFT based study on structural stability and transport properties of Sr3AsN: A potential thermoelectric material

Antiperovskite materials are well known for their high thermoelectric performance and gained huge research interest. Here, we report the structural stability and transport properties of Sr$_3$AsN from a precise first-principles study. The calculated equilibrium lattice parameters are in a good agreement with the available data. We find that Sr$_3$AsN is a mechanically, energetically and dynamically stable at ambient condition. Our calculated electronic structure indicates that it is a direct bandgap semiconductor, with a value ~1.2 eV. Sr-4d and N-2p orbitals mainly formulate the direct bandgap. This antiperovskite possesses a high Seebeck coefficient. Although its lattice thermal conductivity is comparatively low, electronic thermal conductivity is very high. The calculated maximum TE figure of merit is 0.75 at 700 K, indicating that it is a potential material for thermoelectric applications.

cond-mat.mtrl-sci↗

arXiv2018

First-principles prediction of phonon-mediated superconductivity in XBC (X= Mg, Ca, Sr, Ba)

From first-principles calculations, we predict four new intercalated hexagonal $X$BC ($X$=Mg, Ca, Sr, Ba) compounds to be dynamically stable and phonon-mediated superconductors. These compounds form a LiBC like structure but are metallic. The calculated superconducting critical temperature, $T{_c}$, of MgBC is 51 K. The strong attractive interaction between $σ$-bonding electrons and the B${_{1g}}$ phonon mode gives rise to a larger electron-phonon coupling constant (1.135) and hence high $T_c$; notably, higher than that of MgB$_2$. The other compounds have a low superconducting critical temperature (4-17 K) due to the interaction between $σ$-bonding electrons and low energy phonons (E${_{2u}}$ modes). Due to their energetic and dynamic stability, we envisage that these compounds can be synthesized experimentally.

cond-mat.supr-con↗

arXiv2018

High Seebeck coefficient and ultra-low lattice thermal conductivity in Cs2InAgCl6

The elastic, electronic and thermoelectric properties of indium-based double-perovskite halide, Cs2InAgCl6 have been studied by first principles study. The Cs2InAgCl6 is found to be elastically stable, ductile, anisotropic and relatively low hard material. The calculated direct bandgap 3.67 eV by TB-mBJ functional fairly agrees with the experimentally measured value 3.3 eV but PBE functional underestimates the bandgap by 1.483 eV. The relaxation time and lattice thermal conductivity have been calculated by using relaxation time approximation (RTA) within the supercell approach. The lattice thermal conductivity (\k{appa}l) is quite low (0.2 Wm-1K-1). The quite low phonon group velocity in the large weighted phase space, and high anharmonicity (large phonon scattering) are responsible for small \k{appa}l. The room temperature Seebeck coefficient is 199 μVK-1. Such high Seebeck coefficient arises from the combination of the flat conduction band and large bandgap. We obtain power factors at 300K by using PBE and TB-mBJ potentials are ~29 and ~31 mWm-1K-2, respectively and the corresponding thermoelectric figure of merit of Cs2BiAgCl6 are 0.71 and 0.72. However, the maximum ZT value obtained at 700K is ~0.74 by TB-mBJ potential. The obtained results implies that Cs2InAgCl6 is a promising material for thermoelectric device applications.

cond-mat.mtrl-sci↗

arXiv2018

Structural, elastic, optoelectronic and transport properties of Sr3SnO under pressure

We have presented the structural, elastic, optoelectronic and transport properties of Sr3SnO under pressure by using first principles method. The application of hydrostatic pressure causes charge transfer from Sr(5s) orbital to Sn(5p) and O(2p) orbitals. The increasing trend of Pughs ratio under pressure implies that the material tends to be ductile at high pressure. The semiconductor-metal transition occurs at 14 GPa and the density of states at the Fermi level is significantly increased at this pressure. The refractive index, optical conductivity, and absorption of Sr3SnO have been found to be high and comparable to that for typical materials used in photovoltaic. The material becomes n-type from 12 GPa and Hall coefficient also confirm it. Large Seebeck coefficient obtained at 12 GPa. Thus, Sr3SnO is a potential thermoelectric material possessing both p- and n-type nature. The detail physics of these changes under pressure has been explained within the available theory.

cond-mat.mtrl-sci↗

arXiv2018

Enhanced thermoelectric performance in Ca substituted Sr3SnO

We report 45% enhancement in the thermoelectric figure of merit, ZT of Sr3SnO via Ca substitution. First-principles calculations have been performed to study the electronic and thermoelectric transport properties of Ca substituted Sr3SnO (Sr3-xCaxSnO). The effects of Ca subtitution on bandgap are studied and detailed mechanisms are proposed to explain the obtained results. We have found that effective mass and thermopower of Sr3SnO redueces with the increase of hole concentration. The optimum hole concentration has been obtained for Sr2CaSnO and the corresponding Seebeck coefficient is 219 μV/K. The electrical conductivity of Sr3SnO and its alloys exhibits semiconducting nature which contradicts with experimental results in Ca3SnO. We have found that due to the Ca-deficiency, the Ca3SnO shows the metallic conductivity and removes this contradiction with our results. The lattice thermal conductivities (\kl) of Sr3SnO and Ca3SnO have been calculated by using both PBE and GW functionals. The lattice thermal conductivity obtained by PBE functional largely underestimates the experimental value for Ca3SnO. The total thermal conductivity (with kl obtained by GW) at 300K is 2.33 and 1.897 W/mK for Sr3SnO and Ca3SnO, respectively, with excellent agreement with experimental value 1.707 W/mK for Ca3SnO. The dimensionless figure of merit (ZT) for Sr2CaSnO at 500 K is 0.6 and making it promising for thermoelectric applications.

cond-mat.mtrl-sci↗

arXiv2018

Ultra-low lattice thermal conductivity in Cs2BiAgX6 (X=Cl, Br): Potential thermoelectric materials

We have explored electronic and thermoelectric properties of bismuth-based double-perovskite halides Cs2BiAgX6 by using first principles calculations. The calculated indirect bandgaps 2.85 eV and 1.99 eV for Cs2BiAgCl6 and Cs2BiAgBr6, respectively well agree with the measured value (2.77 eV of Cs2BiAgCl6 and 2.19 eV of Cs2BiAgBr6). We have calculated the relaxation time and lattice thermal conductivity by using relaxation time approximation (RTA) within supercell approach. The lattice thermal conductivities for both compounds are remarkably low and the obtained values at 300K for Cs2BiAgCl6 and Cs2BiAgBr6 are 0.078 and 0.065 Wm-1K-1, respectively. Such quite low lattice thermal conductivity arises due to low phonon group velocity in the large weighted phase space and large phonon scattering. The large Seebeck coefficient obtained for both halides at 400K. We have obtained the maximum power factors at 700K and the corresponding thermoelectric figure of merit for Cs2BiAgCl6 and Cs2BiAgBr6 are 0.775 and 0.774, respectively. The calculated results reveal that both halides are potential thermoelectric materials.

cond-mat.mtrl-sci↗

arXiv2018

Structural, elastic, electronic, magnetic and thermoelectric properties of new quaternary Heusler compounds CoZrMnX (X=Al, Ga, Ge, In)

We have performed a comprehensive set of first principles calculations to study the structural, elastic, electronic, magnetic and transport properties of new quaternary Heusler compounds CoZrMnX (X =Al, Ga, Ge, In). The results showed that all the quaternary Heusler compounds were stable in Type(I) structure. CoZrMnX are elastically stable and relatively hard materials. CoZrMnAl, CoZrMnGa, and CoZrMnIn are found to be ductile and CoZrMnGe is brittle in nature. The calculated Debye temperatures of all compounds are relatively high. The electronic structure calculations reveal that CoZrMnAl is nearly half metallic, CoZrMnGa and CoZrMnIn are metallic, and CoZrMnGe is a narrow indirect bandgap semiconductor. The calculated magnetic properties implies that CoZrMnAl, CoZrMnGa, and CoZrMnIn are ferromagnetic while CoZrMnGe is non-magnetic material. The CoZrMnAl is highly spin-polarized (96%) and CoZrMnGe is non-spin-polarized. Seebeck coefficent (S) in CoZrMnGe is relatively high (-106 μV/K at 650K) due to its semiconducting nature. The calculated thermoelectric figure of merit CoZrMnGe is 0.1 at 600K and for CoZrMnIn it is also 0.1 at 900 K. We hope our interesting results will inspire experimentalist to synthesis the new quaternary Heusler compounds CoZrMnX (X =Al, Ga, Ge, In).

cond-mat.mtrl-sci↗

arXiv2017

Elastic, electronic, thermodynamic and transport properties of XOsSi (X=Nb, Ta) superconductors: A first-principles exploration

A first-principles calculation has been performed to study elastic, electronic, thermodynamic, transport and superconducting properties of recently reported osmium based two superconductors, XOsSi (X=Nb, Ta). We have calculated elastic constants and elastic moduli of XOsSi for the first time. The calculated values of bulk, Youngs, shear moduli are reasonably larger than the average value obtained from the rule of mixtures of the constituents. NbOsSi and TaOsSi both compounds are found to be relatively hard material, elastically stable and ductile in nature. The obtained directional bulk modulus and shear anisotropic factors indicate that both compounds have high elastic anisotropy. The shear anisotropic factors show higher elastic anisotropy than the percentage anisotropy in these compounds. The Debye temperature and bulk modulus increases with pressure but decreases with temperature as usual for metals. The magnetic susceptibility of TaOsSi follow the Curie law but NaOsSi do not follow due to its delocalized magnetic moment and electronic specific heat slightly deviates from the linear relationship with temperature. The calculated band structures of XOsSi compounds show metallic nature. In both cases d-orbitals have the dominating contribution to the total density of states. The smaller electron-phonon coupling constant implies that XOsSi (X=Nb, Ta) are weakly coupled superconductors.

cond-mat.mtrl-sci↗