This study explores the thin-layer convective solar drying of Marrubium vulgare L.leaves under conditions typical of sun-rich semi-arid climates.Drying experiments were conducted at three inlet-air temperatures(40℃,5...This study explores the thin-layer convective solar drying of Marrubium vulgare L.leaves under conditions typical of sun-rich semi-arid climates.Drying experiments were conducted at three inlet-air temperatures(40℃,50℃,60℃)and two air velocities(1.5 and 2.5 m·s^(-1))using an indirect solar dryer with auxiliary temperature control.Moisture-ratio data were fitted with eight widely used thin-layer models and evaluated using correlation coefficient(r),root-mean-square error(RMSE),and Akaike information criterion(AIC).A complementary heattransfer analysis based on Reynolds and Prandtl numbers with appropriate Nusselt correlations was used to relate flow regime to drying performance,and an energy balance quantified the relative contributions of solar and auxiliary heat.The logarithmic model consistently achieved the lowest RMSE/AIC with r>0.99 across all conditions.Higher temperature and air velocity significantly reduced drying time during the decreasing-rate period,with no constantrate stage observed.On average,solar input supplied the large majority of the thermal demand,while the auxiliary heater compensated short irradiance drops to maintain setpoints.These findings provide a reproducible dataset and a modelling benchmark for M.vulgare leaves,and they support energy-aware design of hybrid solar dryers formedicinal plants in sun-rich regions.展开更多
Based on the characteristics of laser-induced surface ignition,energetic photosensitive films show promising potential to meet the ignition requirements of various energetic materials(EMs).In this study,DATNBI/ferric ...Based on the characteristics of laser-induced surface ignition,energetic photosensitive films show promising potential to meet the ignition requirements of various energetic materials(EMs).In this study,DATNBI/ferric alginate(DI/FeA),DI/cobalt alginate(DI/CoA),and DI/nickel alginate(DI/Ni A)films are fabricated by employing sodium alginate(SA)with a three-dimensional network structure as the film matrix,via ionic cross-linking of SA with Fe^(3+),Co^(2+),and Ni^(2+)ions.The study demonstrates that the ionic cross-linking enhances the hydrophobic performance of the films,with the water contact angle increasing from 82.1° to 123.5°.Concurrently,the films'near-infrared(NIR)light absorption improved.Furthermore,transition metal ions facilitate accelerated electron transfer,thereby catalyzing the thermal decomposition of DATNBI.Under 1064 nm laser irradiation,the DI/Fe A film exhibits exceptional combustion performance,with an ignition delay time as low as 76 ms.It successfully acts as an NIR laser ignition medium to initiate the self-sustained combustion of CL-20.This study demonstrates the synergistic realization of enhanced hydrophobicity,improved photosensitivity,and promoted catalytic decomposition through microstructural design of the material,providing new insights for the design of additive-free EMs in laser ignition applications.展开更多
Electrically controlled solid propellant(ECSP)offers multiple ignition and adjustable burning rate,serving as fuel for next-generation intelligent propulsion systems.To further enhance the combustion performance of EC...Electrically controlled solid propellant(ECSP)offers multiple ignition and adjustable burning rate,serving as fuel for next-generation intelligent propulsion systems.To further enhance the combustion performance of ECSP,a method utilizing electrochemical and thermal decomposition catalysts has been proposed.In this work,we investigated the combustion characteristics of hydroxylamine nitrate(HAN)-based ECSP incorporating cerium oxide(CeO_(2))and graphene oxide(GO)by using an electrically controlled combustion test system.Electrochemical impedance spectroscopy(EIS)and linear sweep voltammetry(LSV)were used to measure the electrical conductibility and overpotential of ECSP with various additives,and Tafel curves were calculated.Thermogravimetric analysis coupled with differential scanning calorimetry(TG-DSC)was employed to investigate the thermal decomposition behavior of ECSP.While the addition of CeO_(2) and GO reduced the conductivity of ECSP,both catalysts exhibited strong electrocatalytic properties and facilitated the thermal decomposition of ECSP.Between two catalysts,GO demonstrated superior electrochemical catalytic performance but weaker thermal decomposition catalytic ability than CeO_(2).The addition of catalysts significantly enhanced the combustion performance of HAN-based ECSP.Specifically,the ignition delay time was shortened by 10%~20%.CeO_(2) raised the burning rate by approximately 20%but GO exhibited a remarkable boost of 40%in burning rate at high voltage.The combination of GO and PVA produced a flame-retardant substance that negatively impacted the ignition delay of ECSP and resulted in a smaller increase in the burning rate of ECSP at low ignition voltages.展开更多
An energetic binder based on hydroxyl-terminated polybutadiene(HTPB),doped with different ratios of nitrocellulose(NC)(10%,20%,30%,and 50%),was developed to study the effect of NC doping on the thermal decomposition b...An energetic binder based on hydroxyl-terminated polybutadiene(HTPB),doped with different ratios of nitrocellulose(NC)(10%,20%,30%,and 50%),was developed to study the effect of NC doping on the thermal decomposition behavior of a composite propellant(CP)comprising ammonium nitrate(AN)as an oxidizer and magnesium(Mg)as a fuel.Optimization of the propellant formulation was conducted using Chemical Equilibrium with Applications-National Aeronautics and Space Administration(CEA-NASA)software,which demonstrated an increase in specific impulse by 12.09 s when the binder contained 50%NC.Fourier-transform infrared spectroscopy(FTIR)analysis confirmed the excellent compatibility between the components,and density measurements revealed an increase of 6.4%with a higher NC content.Morphological analysis using optical microscopy showed that NC doping improved the uniformity and compactness of the surface,reduced cavities,and achieved a more homogeneous particle distribution.Differential scanning calorimetry(DSC)analysis indicated a decrease in the decomposition temperature of the propellant as the NC content increased,while kinetic studies revealed a 48.68%reduction in the activation energy when 50%NC was incorporated into the binder.These findings suggest that the addition of NC enhances combustion efficiency and improves overall propellant performance.This study highlights the potential of the new HTPB-NC energetic binder as a promising approach for advancing solid propellant technology.展开更多
The present work aims to stabilize the room temperature allotropic transition of ammonium nitrate(AN)particles utilizing a microencapsulation technique,which involves solvent/non-solvent in which nitrocellulose(NC)has...The present work aims to stabilize the room temperature allotropic transition of ammonium nitrate(AN)particles utilizing a microencapsulation technique,which involves solvent/non-solvent in which nitrocellulose(NC)has been employed as a coating agent.The SEM micrographs revealed distinct features of both pure AN and NC,contrasting with the irregular granular surface topography of the coated AN particles,demonstrating the adherence of NC on the AN surface.Structural analysis via infrared spectroscopy(IR)demonstrated a successful association of AN and NC,with slight shifts observed in IR bands indicating interfacial interactions.Powder X-ray Diffraction(PXRD)analysis further elucidated the structural changes induced by the coating process,revealing that the NC coating altered the crystallization pattern of its pure form.Thermal analysis demonstrates distinct profiles for pure and coated AN,for which the coated sample exhibits a temperature increase and an enthalpy decrease of the room temperature allotropic transition by 6℃,and 36%,respectively.Furthermore,the presence of NC coating alters the intermolecular forces within the composite system,leading to a reduction in melting enthalpy of coated AN by~39%compared to pure AN.The thermal decomposition analysis shows a two-step thermolysis process for coated AN,with a significant increase in the released heat by about 78%accompanied by an increase in the activation barrier of NC and AN thermolysis,demonstrating a stabilized reactivity of the AN-NC particles.These findings highlight the synergistic effect of NC coating on AN particles,which contributed to a structural and reactive stabilization of both AN and NC,proving the potential application of NC-coated AN as a strategically advantageous oxidizer in composite solid propellant formulations.展开更多
To study the influence of silicon(Si)on 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(CL-20),NC/CL-20 composite explosives and Si/NC/CL-20 composite explosives were prepared by the electrostatic spraying ...To study the influence of silicon(Si)on 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(CL-20),NC/CL-20 composite explosives and Si/NC/CL-20 composite explosives were prepared by the electrostatic spraying method.The morphology,structure and thermal decomposition properties of the samples were analyzed using scanning electron microscopy(SEM),X-ray energy spectroscopy(EDS),infrared spectroscopy(FT-IR),and simultaneous thermal analyzer(TG-DSC).Additionally,the combustion process of the samples was tested using a high-speed camera.The results show that the addition of nano-Si contributes to the formation of composite explosives with regular morphology and smaller particle size.The Si/NC/CL-20 composite explosive has better and more uniform sphericity,with an average particle size of 73.4 nm,compared to the NC/CL-20 composite explosive.The Si/NC/CL-20 composite explosive which produced by the electrostatic spraying method,achieves physically uniform distribution of the components including NC,CL-20,Si.The addition of Si promotes the thermal decomposition of CL-20.In comparison to the NC/CL-20 composite explosive,the activation energy of the Si/NC/CL-20 composite explosive decreases by 16.78 kJ/mol,and the self-accelerated decomposition temperature and the critical temperature of thermal explosion decreases by 3.12 K and 2.61 K,respectively.Furthermore,Si/NC/CL-20 composite explosive has shorter ignition delay time and faster combustion rate compared to the NC/CL-20 composite explosive,which shows that Si can improve the combustion performance of CL-20.展开更多
A clean environment with low carbon emissions is the goal of research on the development of green and sustainable buildings that use bio-sourced materials in conjunction with solar energy to create more sustainable ci...A clean environment with low carbon emissions is the goal of research on the development of green and sustainable buildings that use bio-sourced materials in conjunction with solar energy to create more sustainable cities.This is particularly true in Africa,where there aren’t many studies on the topic.The current study suggests a 90 m^(2) model of a sustainable building in a dry climate that is movable to address the issue of housing in remote areas,ensures comfort in harsh weather conditions,uses solar renewable resources—which are plentiful in Africa—uses biosourced materials,and examines how these materials relate to temperature and humidity control while emitting minimal carbon emissions.In order to solve the topic under consideration,the work is split into two sections:numerical and experimental approaches.Using TRNSYS and Revit,the suggested prototype building is examined numerically to examine the impact of orientation,envelope composition made of bio-sourced materials,and carbon emissions.Through a hygrothermal investigation,experiments are conducted to evaluate this prototype’s effectiveness.Furthermore,an examination of the photovoltaic system’s production,consumption,and several scenarios used tomaximize battery life is included in the paper.Because the biosourcedmaterial achieves a thermal transmittance of 0.15(W.m^(-2).K^(-1)),the results demonstrate an intriguing finding in terms of comfort.This value satisfies the requirements of passive building,energy autonomy of the dwelling,and injection in-network with an annual value of 15,757 kWh.Additionally,compared to the literature,the heating needs ratio is 6.38(kWh/m^(2).an)and the cooling needs ratio is 49(kWh/m^(2).an),both of which are good values.According to international norms,the inside temperature doesn’t go above 26℃,and the humidity level is within a comfortable range.展开更多
Inverted perovskite solar cells(PSCs)have stood out in recent years for their great potential in offering low-temperature compatibility,long-term stability and tandem cell suitability.However,challenges persist,partic...Inverted perovskite solar cells(PSCs)have stood out in recent years for their great potential in offering low-temperature compatibility,long-term stability and tandem cell suitability.However,challenges persist,particularly concerning the use of nickel oxide nanoparticles(NiO_(x)NPs)as the hole transport material,where issues such as low conductivity,impurity-induced aggregation and interface redox reactions significantly hinder device performance.In response,this study presents a novel synthesis method for NiO_(x)NPs,leveraging the introduction of ammonium salt dopants(NH_(4)Cl and NH_(4)SCN),and the solar cell utilizing the doped NiO_(x)substrate exhibits much enhanced device performance.Furthermore,doped solar cells reach 23.27%power conversion efficiency(PCE)when a self-assembled monolayer(SAM)is further employed.This study provides critical insights into the synthesis and growth pathways of NiO_(x)NPs,propelling the development of efficient hole transport materials for high-performance PSCs.展开更多
The global drive for sustainable energy solutions intensified interest in anion exchange membrane water electrolysis(AEMWE),as a promising hydrogen production pathway,leveraging renewable energy sources.However,widesp...The global drive for sustainable energy solutions intensified interest in anion exchange membrane water electrolysis(AEMWE),as a promising hydrogen production pathway,leveraging renewable energy sources.However,widespread adoption is hindered by the high cost and non-optimised design of crucial components,such as porous transport layers(PTL)and flow fields.This study comprehensively investigates the interplay between structure,mechanics,and electrochemical performance of a low-cost knitted wire mesh PTL,focusing on its potential to enhance cell assembly and operation.Electrochemical characterisation was performed on a single 4 cm^(2)cell,using 1M KOH at 60℃.Knitted wire mesh PTL,characterised by approximately 70%porosity,2mm thickness,and 1.098 tortuosity,delivered a 33%improvement in current density compared to the standard cell configuration.Introducing a knitted PTL interlayer reduced cell voltage by 74 mV at 2 A cm^(−2)by improving compression force distribution across the active area,enhancing gas transport and maintaining optimal electrical and thermal conductivity.These findings highlight the significant potential of innovative PTL designs in AEMWE to improve mechanical and operational efficiency without increasing the cost.展开更多
Expansive soils, prone to being influenced by the environmental conditions, undergo expansion when water is introduced and shrinkage upon drying. This persistent volumetric fluctuation can induce differential movement...Expansive soils, prone to being influenced by the environmental conditions, undergo expansion when water is introduced and shrinkage upon drying. This persistent volumetric fluctuation can induce differential movements and result in cracking of structures erected upon them. The present research focuses on characterizing the behavior of pavements erected on expansive clays subjected to swelling and shrinkage cycles. Direct shear tests and oedometer tests were conducted in the laboratory on samples of expansive soils undergoing swelling-shrinkage cycles. The experimental data reveal a significant decrease in shear strength, evidenced by a reduction in shear parameters (internal friction angle, cohesion) and a decrease in the modulus of elasticity as the number of cycles increases. A numerical model based on the finite element method was developed to simulate the behavior of a pavement on an expansive clay substrate. The model results indicate an increase in total displacements with the increase in the number of shrinkage-swelling cycles, demonstrating a progressive degradation of the soil’s mechanical behavior. This study contributes to a better understanding of the complex phenomena governing the behavior of expansive soils and serves as a foundation for developing effective management and mitigation strategies for road infrastructures.展开更多
Composite microcrystals of the nitramines(NAs)viz.,RDX,HMX,BCHMX,and CL-20 with electrically conductive polyaniline(PANi)are a charge transfer complexes in coagglomerated composite crystals(CACs).The activation energi...Composite microcrystals of the nitramines(NAs)viz.,RDX,HMX,BCHMX,and CL-20 with electrically conductive polyaniline(PANi)are a charge transfer complexes in coagglomerated composite crystals(CACs).The activation energies of thermolysis,E_(a),of the pure NAs and their PANi-CACs were determined using the Kissinger method,and decomposition processes are discussed.Except for the RDX/PANi CACs,all the other CACs show higher E_(a) values for decomposition compared to their pure NA counterparts.For all CACs,relationships are specified between the E_(a) values,on the one hand,and the squares of the detonation velocities,enthalpies of formation,spark energy and impact sensitivities,on the other.The relationships between their low-temperature heats of decomposition,ΔH,from DSC,and their enthalpy of formation,logarithm of impact sensitivity,electric spark energy,as well as detonation energy,are described.The PANi favorably influences the density of the corresponding CACs;surprisingly close linear correlations were found,and explained,between these densities and the E_(a) values.This presence of PANi strongly increased the electrical spark sensitivity of the CACs in comparison to the base NAs.Based on the results obtained,it can be noted in particular the exceptional desensitization of HMX to impact and the increased sensitivity to electrical spark by coating its crystals with polyaniline.展开更多
The development of magnesium batteries strongly relies on the use of a Mg metal anode and its benefits of high volumetric capacity,reduction potential,low cost and improved safety,however,to date,it still lacks suffic...The development of magnesium batteries strongly relies on the use of a Mg metal anode and its benefits of high volumetric capacity,reduction potential,low cost and improved safety,however,to date,it still lacks sufficient cycling stability and reversibility.Along with the electrolyte selection,the interfacial processes can be affected by the anode itself applying electrode engineering strategies.In this study,six different Mg anode approaches–namely bare Mg metal,Mg foil with an organic and inorganic artificial solid electrolyte interphase,Mg alloy,Mg pellet and a tape-casted Mg slurry–are selected to be investigated by means of electrochemical impedance spectroscopy in Mg|Mg and Mg|S cells.While a plating/stripping overpotential asymmetry was observed and assigned to the desolvation during Mg plating,the impedance spectra of stripping and plating hardly differ for all applied anodes.In contrast,the sulfur species significantly influence the impedance response by altering the surface layer composition.By systematic process assignment of the gained spectra in Mg|Mg and Mg|S cells,specific equivalent circuit models for different anodes and cell conditions are derived.Overall,the study aims to give valuable insights into the interfacial processes of Mg anodes to support their further development toward long-lasting Mg batteries.展开更多
Concentrating Solar Power(CSP)is one of the most promising solar technologies for sustainable power generation in countrieswith high solar potential,likeChad.Identifying suitable sites is of great importance for deplo...Concentrating Solar Power(CSP)is one of the most promising solar technologies for sustainable power generation in countrieswith high solar potential,likeChad.Identifying suitable sites is of great importance for deploying solar power plants.This work focuses on the identification of potential sites for the installation of solar power plants in Chad as well as a comparative analysis using the Analytical Hierarchy Process(AHP),Fuzzy Analytical Hierarchy Process(FAHP),and Full Consistency Method(FUCOM).The results show that 35%of the Chadian territory,i.e.,an area of 449,400 km2,is compatible with the implementation of Concentrating Solar Power.The North,North,East,Southeast,and East zones are the most suitable.The main criteria for influence are direct normal irradiation,the soil slope,and the water resource.FUCOM gave a weight of 41.9%for Direct Normal Irradiation(DNI)compared to 32.71%and 31.81%for AHP and FAHP.This method can be applied to other renewable energy technologies such as photovoltaics,wind power,and biomass.Combining its different analyses will be a valuable tool for planning any renewable energy project in Chad.This work should also facilitate the techno-economic analysis of future CSP plants in Chad.展开更多
In order to analyze the influences of storage aging on the safety of typical elemental explosives,the aged cyclotrimethylene trinitramine(RDX)and cyclotetramethylene tetranitramine(HMX)were prepared by isothermal agin...In order to analyze the influences of storage aging on the safety of typical elemental explosives,the aged cyclotrimethylene trinitramine(RDX)and cyclotetramethylene tetranitramine(HMX)were prepared by isothermal aging tests.The reaction thresholds of aged RDX and HMX under any ignition probability were studied by Langlie-Optimal D method.The thermal decomposition characteristics of RDX and HMX after aging were analyzed by DSC and ARC.Experimental results showed that compared with unaged RDX and HMX,on the one hand,the critical impact energy and critical friction of RDX and HMX aged for 14,28,and 56 days are significantly reduced at an explosion probability of 50%,0.01%,and 0.0001%,respectively.With the increase of aging time,the mechanical sensitivity of RDX and HMX increases obviously.On the other hand,the initial decomposition temperature of RDX and HMX after 56 days of aging decreases,the decomposition heat decreases,the activation energy increases,and the reaction difficulty increases.展开更多
Gas channeling in fractures during CO_(2) injection into the deep coal seam seriously reduces the CO_(2) storage efficiency after the development of coalbed methane.The generation and migration of coal fines causes bl...Gas channeling in fractures during CO_(2) injection into the deep coal seam seriously reduces the CO_(2) storage efficiency after the development of coalbed methane.The generation and migration of coal fines causes blockages in the fractures in the stage of drainage and gas production,reducing the gas channeling effect of injected CO_(2) caused by the heterogeneity of the coal seam.To explore the impact of coal fines within coal seam fractures on the efficacy of CO_(2) storage,experiments on the production stage and CO_(2) injection for storage were conducted on coal combinations containing propped fractures,fractures,and matrix.The CO_(2) storage characteristics of coal at the constraint of coal fines,as well as the influence of multiple rounds of intermittent CO_(2) injection and different injection parameters on the CO_(2) storage effect,were analyzed.The research results show that blockage by coal fines increases the resistance to fluid flow in the fractures by 71.2%.The CO_(2) storage capacity and storage potential of coal with coal fines are 6.5 cm^(3)/g and 8.8%higher than those of coal without coal fines,while the CO_(2) storage capacity of fractured coal under the influence of coal fines has the largest increase of 9.4 cm^(3)/g.The CO_(2) storage of coal containing coal fines is significantly higher(6.6%)than that of the coal without coal fines.The CO_(2) storage effect of the coal with coal fines is improved with the increase in injection rate,whereas the CO_(2) storage effect of the coal without coal fines decreases significantly(by 7.8%).Multiple rounds of intermittent injection increases the CO_(2) storage volume of coal by 20.4%(with coal fines)and 17.1%(without coal fines).The presence of coal fines in fractures also slows down the downward trend of CO_(2) storage fraction after multiple rounds of CO_(2) injection.The blockage in fractures significantly increases the CO_(2) injection time and difficulty,but can increase the CO_(2) storage fraction by 4.7%-17.1%,and the storage volume by 1.9%-14%,increasing the feasibility of CO_(2) storage in fractured coal seams that have previously been exploited for methane production.The multiple rounds of intermittent CO_(2) injection and shut-in periods has shown potential for greater CO_(2) storage and injection efficiency.展开更多
Two-dimensional energetic materials(2DEMs),characterized by their exceptional interlayer sliding properties,are recognized as exemplar of low-sensitivity energetic materials.However,the diversity of available 2DEMs is...Two-dimensional energetic materials(2DEMs),characterized by their exceptional interlayer sliding properties,are recognized as exemplar of low-sensitivity energetic materials.However,the diversity of available 2DEMs is severely constrained by the absence of efficient methods for rapidly predicting crystal packing modes from molecular structures,impeding the high-throughput rational design of such materials.In this study,we employed quantified indicators,such as hydrogen bond dimension and maximum planar separation,to quickly screen 172DEM and 16 non-2DEM crystal structures from a crystal database.They were subsequently compared and analyzed,focusing on hydrogen bond donor-acceptor combinations,skeleton features,and intermolecular interactions.Our findings suggest that theπ-πpacking interaction energy is a key determinant in the formation of layered packing modes by planar energetic molecules,with its magnitude primarily influenced by the strongest dimericπ-πinteraction(π-π2max).Consequently,we have delineated a critical threshold forπ-π2max to discern layered packing modes and formulated a theoretical model for predictingπ-π2max,grounded in molecular electrostatic potential and dipole moment analysis.The predictive efficacy of this model was substantiated through external validation on a test set comprising 31 planar energetic molecular crystals,achieving an accuracy of 84%and a recall of 75%.Furthermore,the proposed model shows superior classification predictive performance compared to typical machine learning methods,such as random forest,on the external validation samples.This contribution introduces a novel methodology for the identification of crystal packing modes in 2DEMs,potentially accelerating the design and synthesis of high-energy,low-sensitivity 2DEMs.展开更多
In an environment where demand for housing is growing and the supply from public authorities is virtually non-existent,several mechanisms for housing production are emerging in the formal,semi-informal and informal co...In an environment where demand for housing is growing and the supply from public authorities is virtually non-existent,several mechanisms for housing production are emerging in the formal,semi-informal and informal construction sectors.The project owner wonders how much it costs to construct a building to an acceptable standard.Cost forecasting in general faces a number of difficulties,including a lack of available information during the preliminary phase of the project.As such,estimation becomes a crucial task involving great responsibility,which can lead to either more convincing results or chaotic situations.This study proposes a quick and effective method for estimating the cost of a single-storey F4 residential building.The modelling is done using multiple linear regression based on a statistical approach applied to twenty(20)projects that have already been completed.The project data are collected from design offices in the city of Brazzaville.The method expresses the cost of an F4 construction by certain project tasks,representing five(5)variables,three(3)of which are related to structural work and two(2)to finishing work,which are easy to determine.This approach,known as MECSO(Cost Estimation Model by Sub-structure),gives good results in all statistical tests carried out with reasonable confidence intervals.This method is very practical for engineering professionals working on the evaluation and control of construction costs.展开更多
Flat electronic bands in condensed matter provide a rich avenue for exploring novel quantum phenomena. Here, we report an optical spectroscopy study of a topological hourglass semimetal Nb_(3)SiTe_(6) with the electri...Flat electronic bands in condensed matter provide a rich avenue for exploring novel quantum phenomena. Here, we report an optical spectroscopy study of a topological hourglass semimetal Nb_(3)SiTe_(6) with the electric field of the incident light parallel to its crystalline ab-plane. The ab-plane optical conductivity spectra of Nb_(3)SiTe_(6) single crystals exhibit a remarkable peak-like feature around 1.20 eV, which is mainly contributed by the direct optical transitions between the two ab-initio-calculation-derived flat bands along the momentum direction Z–U. Our results pave the way for investigating exotic quantum phenomena based on the flat bands in topological hourglass semimetals.展开更多
Enhancing the output capacity of semiconductor bridge(SCB) through the application of composite nano-energetic films is a subject of wide concern. Furthermore, improving the safety, reliability, and production efficie...Enhancing the output capacity of semiconductor bridge(SCB) through the application of composite nano-energetic films is a subject of wide concern. Furthermore, improving the safety, reliability, and production efficiency of energetic semiconductor bridge(ESCB) is the primary focus for large-scale engineering applications in the future. Here, the Al/CuO nano-film ESCB was efficiently fabricated using 3D direct writing. The electrostatic safety of the film is enhanced by precisely adjusting the particle size of Al, while ensuring that the SCB can initiate the film with small energy. The burst characteristics of SCB/ESCB were thoroughly investigated by employing a 100 μF tantalum capacitor to induce SCB and ESCB under an intense voltage gradient. The solid-state heating process of both SCB and ESCB was analyzed with multi physical simulation(MPS). The experimental results demonstrate that the critical burst time of both SCB and ESCB decreases with increasing voltage. Under the same voltage, the critical burst time of ESCB is longer than that of SCB, primarily due to differences in the melting to vaporization stage. The MPS results indicate that the highest temperature is observed at the V-shaped corner of SCB. Due to the thermal contact resistance between SCB and the film, heat conduction becomes more concentrated in the central region of the bridge, resulting in a faster solid-state heating process for ESCB compared to SCB.The results of the gap ignition experiments indicate that at a 19 mm gap, an ESCB with a film mass of 10 mg can ignite nickel hydrazine nitrate(NHN) and cyclotrimethylenetrinitramine(RDX). This suggests that thermite ESCB can serve as a novel, safe, and reliable energy exchange element and initiator in largescale engineering applications.展开更多
Hydroelectric power production from Garafiri dam and rainfall are essential elements with the observation of hydroelectric power production in West African power system,particularly in Guinea.This article focuses on t...Hydroelectric power production from Garafiri dam and rainfall are essential elements with the observation of hydroelectric power production in West African power system,particularly in Guinea.This article focuses on the study and the influence of climate variability on hydroelectric power production at Garafiri dam over 16-year period(2008-2023).The aim of this work is to show the correlation between rainfall anomalies and hydroelectric power production at Garafiri dam.The method used consists of calculating precipitation anomalies at Garafiri site and those for the production of hydroelectric power from Garafiri dam over the study period.This approach led us to calculate the anomalies,leading to the study on climatic variability,in order to establish correlation between rainfall and hydroelectric power dam’s production.The trend with the correlation found made it possible to carry out a significance test between these two variables.These results clearly show that rainfall in Garafiri site increases hydroelectric power production and vice versa,which explains the interdependence between these two parameters,i.e.climatic variability and hydroelectric power production.展开更多
文摘This study explores the thin-layer convective solar drying of Marrubium vulgare L.leaves under conditions typical of sun-rich semi-arid climates.Drying experiments were conducted at three inlet-air temperatures(40℃,50℃,60℃)and two air velocities(1.5 and 2.5 m·s^(-1))using an indirect solar dryer with auxiliary temperature control.Moisture-ratio data were fitted with eight widely used thin-layer models and evaluated using correlation coefficient(r),root-mean-square error(RMSE),and Akaike information criterion(AIC).A complementary heattransfer analysis based on Reynolds and Prandtl numbers with appropriate Nusselt correlations was used to relate flow regime to drying performance,and an energy balance quantified the relative contributions of solar and auxiliary heat.The logarithmic model consistently achieved the lowest RMSE/AIC with r>0.99 across all conditions.Higher temperature and air velocity significantly reduced drying time during the decreasing-rate period,with no constantrate stage observed.On average,solar input supplied the large majority of the thermal demand,while the auxiliary heater compensated short irradiance drops to maintain setpoints.These findings provide a reproducible dataset and a modelling benchmark for M.vulgare leaves,and they support energy-aware design of hybrid solar dryers formedicinal plants in sun-rich regions.
基金supported by Research Fund of SWUST for PhD(Grant No.22zx7175)Sichuan Science and Technology Program(Grant No.2024NSFSC1097)。
文摘Based on the characteristics of laser-induced surface ignition,energetic photosensitive films show promising potential to meet the ignition requirements of various energetic materials(EMs).In this study,DATNBI/ferric alginate(DI/FeA),DI/cobalt alginate(DI/CoA),and DI/nickel alginate(DI/Ni A)films are fabricated by employing sodium alginate(SA)with a three-dimensional network structure as the film matrix,via ionic cross-linking of SA with Fe^(3+),Co^(2+),and Ni^(2+)ions.The study demonstrates that the ionic cross-linking enhances the hydrophobic performance of the films,with the water contact angle increasing from 82.1° to 123.5°.Concurrently,the films'near-infrared(NIR)light absorption improved.Furthermore,transition metal ions facilitate accelerated electron transfer,thereby catalyzing the thermal decomposition of DATNBI.Under 1064 nm laser irradiation,the DI/Fe A film exhibits exceptional combustion performance,with an ignition delay time as low as 76 ms.It successfully acts as an NIR laser ignition medium to initiate the self-sustained combustion of CL-20.This study demonstrates the synergistic realization of enhanced hydrophobicity,improved photosensitivity,and promoted catalytic decomposition through microstructural design of the material,providing new insights for the design of additive-free EMs in laser ignition applications.
基金supported by the National Natural Science Foundation of China(Grant No.12074187).
文摘Electrically controlled solid propellant(ECSP)offers multiple ignition and adjustable burning rate,serving as fuel for next-generation intelligent propulsion systems.To further enhance the combustion performance of ECSP,a method utilizing electrochemical and thermal decomposition catalysts has been proposed.In this work,we investigated the combustion characteristics of hydroxylamine nitrate(HAN)-based ECSP incorporating cerium oxide(CeO_(2))and graphene oxide(GO)by using an electrically controlled combustion test system.Electrochemical impedance spectroscopy(EIS)and linear sweep voltammetry(LSV)were used to measure the electrical conductibility and overpotential of ECSP with various additives,and Tafel curves were calculated.Thermogravimetric analysis coupled with differential scanning calorimetry(TG-DSC)was employed to investigate the thermal decomposition behavior of ECSP.While the addition of CeO_(2) and GO reduced the conductivity of ECSP,both catalysts exhibited strong electrocatalytic properties and facilitated the thermal decomposition of ECSP.Between two catalysts,GO demonstrated superior electrochemical catalytic performance but weaker thermal decomposition catalytic ability than CeO_(2).The addition of catalysts significantly enhanced the combustion performance of HAN-based ECSP.Specifically,the ignition delay time was shortened by 10%~20%.CeO_(2) raised the burning rate by approximately 20%but GO exhibited a remarkable boost of 40%in burning rate at high voltage.The combination of GO and PVA produced a flame-retardant substance that negatively impacted the ignition delay of ECSP and resulted in a smaller increase in the burning rate of ECSP at low ignition voltages.
文摘An energetic binder based on hydroxyl-terminated polybutadiene(HTPB),doped with different ratios of nitrocellulose(NC)(10%,20%,30%,and 50%),was developed to study the effect of NC doping on the thermal decomposition behavior of a composite propellant(CP)comprising ammonium nitrate(AN)as an oxidizer and magnesium(Mg)as a fuel.Optimization of the propellant formulation was conducted using Chemical Equilibrium with Applications-National Aeronautics and Space Administration(CEA-NASA)software,which demonstrated an increase in specific impulse by 12.09 s when the binder contained 50%NC.Fourier-transform infrared spectroscopy(FTIR)analysis confirmed the excellent compatibility between the components,and density measurements revealed an increase of 6.4%with a higher NC content.Morphological analysis using optical microscopy showed that NC doping improved the uniformity and compactness of the surface,reduced cavities,and achieved a more homogeneous particle distribution.Differential scanning calorimetry(DSC)analysis indicated a decrease in the decomposition temperature of the propellant as the NC content increased,while kinetic studies revealed a 48.68%reduction in the activation energy when 50%NC was incorporated into the binder.These findings suggest that the addition of NC enhances combustion efficiency and improves overall propellant performance.This study highlights the potential of the new HTPB-NC energetic binder as a promising approach for advancing solid propellant technology.
文摘The present work aims to stabilize the room temperature allotropic transition of ammonium nitrate(AN)particles utilizing a microencapsulation technique,which involves solvent/non-solvent in which nitrocellulose(NC)has been employed as a coating agent.The SEM micrographs revealed distinct features of both pure AN and NC,contrasting with the irregular granular surface topography of the coated AN particles,demonstrating the adherence of NC on the AN surface.Structural analysis via infrared spectroscopy(IR)demonstrated a successful association of AN and NC,with slight shifts observed in IR bands indicating interfacial interactions.Powder X-ray Diffraction(PXRD)analysis further elucidated the structural changes induced by the coating process,revealing that the NC coating altered the crystallization pattern of its pure form.Thermal analysis demonstrates distinct profiles for pure and coated AN,for which the coated sample exhibits a temperature increase and an enthalpy decrease of the room temperature allotropic transition by 6℃,and 36%,respectively.Furthermore,the presence of NC coating alters the intermolecular forces within the composite system,leading to a reduction in melting enthalpy of coated AN by~39%compared to pure AN.The thermal decomposition analysis shows a two-step thermolysis process for coated AN,with a significant increase in the released heat by about 78%accompanied by an increase in the activation barrier of NC and AN thermolysis,demonstrating a stabilized reactivity of the AN-NC particles.These findings highlight the synergistic effect of NC coating on AN particles,which contributed to a structural and reactive stabilization of both AN and NC,proving the potential application of NC-coated AN as a strategically advantageous oxidizer in composite solid propellant formulations.
基金National Natural Science Foundation of China(No.22275150)。
文摘To study the influence of silicon(Si)on 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(CL-20),NC/CL-20 composite explosives and Si/NC/CL-20 composite explosives were prepared by the electrostatic spraying method.The morphology,structure and thermal decomposition properties of the samples were analyzed using scanning electron microscopy(SEM),X-ray energy spectroscopy(EDS),infrared spectroscopy(FT-IR),and simultaneous thermal analyzer(TG-DSC).Additionally,the combustion process of the samples was tested using a high-speed camera.The results show that the addition of nano-Si contributes to the formation of composite explosives with regular morphology and smaller particle size.The Si/NC/CL-20 composite explosive has better and more uniform sphericity,with an average particle size of 73.4 nm,compared to the NC/CL-20 composite explosive.The Si/NC/CL-20 composite explosive which produced by the electrostatic spraying method,achieves physically uniform distribution of the components including NC,CL-20,Si.The addition of Si promotes the thermal decomposition of CL-20.In comparison to the NC/CL-20 composite explosive,the activation energy of the Si/NC/CL-20 composite explosive decreases by 16.78 kJ/mol,and the self-accelerated decomposition temperature and the critical temperature of thermal explosion decreases by 3.12 K and 2.61 K,respectively.Furthermore,Si/NC/CL-20 composite explosive has shorter ignition delay time and faster combustion rate compared to the NC/CL-20 composite explosive,which shows that Si can improve the combustion performance of CL-20.
文摘A clean environment with low carbon emissions is the goal of research on the development of green and sustainable buildings that use bio-sourced materials in conjunction with solar energy to create more sustainable cities.This is particularly true in Africa,where there aren’t many studies on the topic.The current study suggests a 90 m^(2) model of a sustainable building in a dry climate that is movable to address the issue of housing in remote areas,ensures comfort in harsh weather conditions,uses solar renewable resources—which are plentiful in Africa—uses biosourced materials,and examines how these materials relate to temperature and humidity control while emitting minimal carbon emissions.In order to solve the topic under consideration,the work is split into two sections:numerical and experimental approaches.Using TRNSYS and Revit,the suggested prototype building is examined numerically to examine the impact of orientation,envelope composition made of bio-sourced materials,and carbon emissions.Through a hygrothermal investigation,experiments are conducted to evaluate this prototype’s effectiveness.Furthermore,an examination of the photovoltaic system’s production,consumption,and several scenarios used tomaximize battery life is included in the paper.Because the biosourcedmaterial achieves a thermal transmittance of 0.15(W.m^(-2).K^(-1)),the results demonstrate an intriguing finding in terms of comfort.This value satisfies the requirements of passive building,energy autonomy of the dwelling,and injection in-network with an annual value of 15,757 kWh.Additionally,compared to the literature,the heating needs ratio is 6.38(kWh/m^(2).an)and the cooling needs ratio is 49(kWh/m^(2).an),both of which are good values.According to international norms,the inside temperature doesn’t go above 26℃,and the humidity level is within a comfortable range.
基金supported by the Open Research Fund of Songshan Lake Materials Laboratory(No.2021SLABFK09)the National Natural Science Foundation of China(No.22109093)+1 种基金the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning and the Shanghai Rising-Star Program(No.19QA1403800)the Project of Innovative Development Agency of Republic of Uzbekistan(No.FZ-20200929177)and Shanghai Technical Service Computing Center of Science and Engineering,Shanghai University.
文摘Inverted perovskite solar cells(PSCs)have stood out in recent years for their great potential in offering low-temperature compatibility,long-term stability and tandem cell suitability.However,challenges persist,particularly concerning the use of nickel oxide nanoparticles(NiO_(x)NPs)as the hole transport material,where issues such as low conductivity,impurity-induced aggregation and interface redox reactions significantly hinder device performance.In response,this study presents a novel synthesis method for NiO_(x)NPs,leveraging the introduction of ammonium salt dopants(NH_(4)Cl and NH_(4)SCN),and the solar cell utilizing the doped NiO_(x)substrate exhibits much enhanced device performance.Furthermore,doped solar cells reach 23.27%power conversion efficiency(PCE)when a self-assembled monolayer(SAM)is further employed.This study provides critical insights into the synthesis and growth pathways of NiO_(x)NPs,propelling the development of efficient hole transport materials for high-performance PSCs.
基金supported by the European Union and the Clean Hydrogen Joint Undertaking(Grant no.101112055).
文摘The global drive for sustainable energy solutions intensified interest in anion exchange membrane water electrolysis(AEMWE),as a promising hydrogen production pathway,leveraging renewable energy sources.However,widespread adoption is hindered by the high cost and non-optimised design of crucial components,such as porous transport layers(PTL)and flow fields.This study comprehensively investigates the interplay between structure,mechanics,and electrochemical performance of a low-cost knitted wire mesh PTL,focusing on its potential to enhance cell assembly and operation.Electrochemical characterisation was performed on a single 4 cm^(2)cell,using 1M KOH at 60℃.Knitted wire mesh PTL,characterised by approximately 70%porosity,2mm thickness,and 1.098 tortuosity,delivered a 33%improvement in current density compared to the standard cell configuration.Introducing a knitted PTL interlayer reduced cell voltage by 74 mV at 2 A cm^(−2)by improving compression force distribution across the active area,enhancing gas transport and maintaining optimal electrical and thermal conductivity.These findings highlight the significant potential of innovative PTL designs in AEMWE to improve mechanical and operational efficiency without increasing the cost.
文摘Expansive soils, prone to being influenced by the environmental conditions, undergo expansion when water is introduced and shrinkage upon drying. This persistent volumetric fluctuation can induce differential movements and result in cracking of structures erected upon them. The present research focuses on characterizing the behavior of pavements erected on expansive clays subjected to swelling and shrinkage cycles. Direct shear tests and oedometer tests were conducted in the laboratory on samples of expansive soils undergoing swelling-shrinkage cycles. The experimental data reveal a significant decrease in shear strength, evidenced by a reduction in shear parameters (internal friction angle, cohesion) and a decrease in the modulus of elasticity as the number of cycles increases. A numerical model based on the finite element method was developed to simulate the behavior of a pavement on an expansive clay substrate. The model results indicate an increase in total displacements with the increase in the number of shrinkage-swelling cycles, demonstrating a progressive degradation of the soil’s mechanical behavior. This study contributes to a better understanding of the complex phenomena governing the behavior of expansive soils and serves as a foundation for developing effective management and mitigation strategies for road infrastructures.
基金funding from the Student Grant Project no.SGS_2022_003 of the Faculty of Chemical Technology at the University of Pardubice Czechia.
文摘Composite microcrystals of the nitramines(NAs)viz.,RDX,HMX,BCHMX,and CL-20 with electrically conductive polyaniline(PANi)are a charge transfer complexes in coagglomerated composite crystals(CACs).The activation energies of thermolysis,E_(a),of the pure NAs and their PANi-CACs were determined using the Kissinger method,and decomposition processes are discussed.Except for the RDX/PANi CACs,all the other CACs show higher E_(a) values for decomposition compared to their pure NA counterparts.For all CACs,relationships are specified between the E_(a) values,on the one hand,and the squares of the detonation velocities,enthalpies of formation,spark energy and impact sensitivities,on the other.The relationships between their low-temperature heats of decomposition,ΔH,from DSC,and their enthalpy of formation,logarithm of impact sensitivity,electric spark energy,as well as detonation energy,are described.The PANi favorably influences the density of the corresponding CACs;surprisingly close linear correlations were found,and explained,between these densities and the E_(a) values.This presence of PANi strongly increased the electrical spark sensitivity of the CACs in comparison to the base NAs.Based on the results obtained,it can be noted in particular the exceptional desensitization of HMX to impact and the increased sensitivity to electrical spark by coating its crystals with polyaniline.
基金financially supported by the Federal Ministry for Education and Research of Germany(Bundesminis-terium für Bildung und Forschung,BMBF)and the European Commission within the projects“MagSiMal”(03XP0208)“E-MAGIC”(824066),respectively。
文摘The development of magnesium batteries strongly relies on the use of a Mg metal anode and its benefits of high volumetric capacity,reduction potential,low cost and improved safety,however,to date,it still lacks sufficient cycling stability and reversibility.Along with the electrolyte selection,the interfacial processes can be affected by the anode itself applying electrode engineering strategies.In this study,six different Mg anode approaches–namely bare Mg metal,Mg foil with an organic and inorganic artificial solid electrolyte interphase,Mg alloy,Mg pellet and a tape-casted Mg slurry–are selected to be investigated by means of electrochemical impedance spectroscopy in Mg|Mg and Mg|S cells.While a plating/stripping overpotential asymmetry was observed and assigned to the desolvation during Mg plating,the impedance spectra of stripping and plating hardly differ for all applied anodes.In contrast,the sulfur species significantly influence the impedance response by altering the surface layer composition.By systematic process assignment of the gained spectra in Mg|Mg and Mg|S cells,specific equivalent circuit models for different anodes and cell conditions are derived.Overall,the study aims to give valuable insights into the interfacial processes of Mg anodes to support their further development toward long-lasting Mg batteries.
文摘Concentrating Solar Power(CSP)is one of the most promising solar technologies for sustainable power generation in countrieswith high solar potential,likeChad.Identifying suitable sites is of great importance for deploying solar power plants.This work focuses on the identification of potential sites for the installation of solar power plants in Chad as well as a comparative analysis using the Analytical Hierarchy Process(AHP),Fuzzy Analytical Hierarchy Process(FAHP),and Full Consistency Method(FUCOM).The results show that 35%of the Chadian territory,i.e.,an area of 449,400 km2,is compatible with the implementation of Concentrating Solar Power.The North,North,East,Southeast,and East zones are the most suitable.The main criteria for influence are direct normal irradiation,the soil slope,and the water resource.FUCOM gave a weight of 41.9%for Direct Normal Irradiation(DNI)compared to 32.71%and 31.81%for AHP and FAHP.This method can be applied to other renewable energy technologies such as photovoltaics,wind power,and biomass.Combining its different analyses will be a valuable tool for planning any renewable energy project in Chad.This work should also facilitate the techno-economic analysis of future CSP plants in Chad.
基金supported by the National Key Laboratory of Energetic Materials, China (Grant No. 2023-LB-036-09).
文摘In order to analyze the influences of storage aging on the safety of typical elemental explosives,the aged cyclotrimethylene trinitramine(RDX)and cyclotetramethylene tetranitramine(HMX)were prepared by isothermal aging tests.The reaction thresholds of aged RDX and HMX under any ignition probability were studied by Langlie-Optimal D method.The thermal decomposition characteristics of RDX and HMX after aging were analyzed by DSC and ARC.Experimental results showed that compared with unaged RDX and HMX,on the one hand,the critical impact energy and critical friction of RDX and HMX aged for 14,28,and 56 days are significantly reduced at an explosion probability of 50%,0.01%,and 0.0001%,respectively.With the increase of aging time,the mechanical sensitivity of RDX and HMX increases obviously.On the other hand,the initial decomposition temperature of RDX and HMX after 56 days of aging decreases,the decomposition heat decreases,the activation energy increases,and the reaction difficulty increases.
基金supported by National Natural Science Foundation of China(52104048,42272198)。
文摘Gas channeling in fractures during CO_(2) injection into the deep coal seam seriously reduces the CO_(2) storage efficiency after the development of coalbed methane.The generation and migration of coal fines causes blockages in the fractures in the stage of drainage and gas production,reducing the gas channeling effect of injected CO_(2) caused by the heterogeneity of the coal seam.To explore the impact of coal fines within coal seam fractures on the efficacy of CO_(2) storage,experiments on the production stage and CO_(2) injection for storage were conducted on coal combinations containing propped fractures,fractures,and matrix.The CO_(2) storage characteristics of coal at the constraint of coal fines,as well as the influence of multiple rounds of intermittent CO_(2) injection and different injection parameters on the CO_(2) storage effect,were analyzed.The research results show that blockage by coal fines increases the resistance to fluid flow in the fractures by 71.2%.The CO_(2) storage capacity and storage potential of coal with coal fines are 6.5 cm^(3)/g and 8.8%higher than those of coal without coal fines,while the CO_(2) storage capacity of fractured coal under the influence of coal fines has the largest increase of 9.4 cm^(3)/g.The CO_(2) storage of coal containing coal fines is significantly higher(6.6%)than that of the coal without coal fines.The CO_(2) storage effect of the coal with coal fines is improved with the increase in injection rate,whereas the CO_(2) storage effect of the coal without coal fines decreases significantly(by 7.8%).Multiple rounds of intermittent injection increases the CO_(2) storage volume of coal by 20.4%(with coal fines)and 17.1%(without coal fines).The presence of coal fines in fractures also slows down the downward trend of CO_(2) storage fraction after multiple rounds of CO_(2) injection.The blockage in fractures significantly increases the CO_(2) injection time and difficulty,but can increase the CO_(2) storage fraction by 4.7%-17.1%,and the storage volume by 1.9%-14%,increasing the feasibility of CO_(2) storage in fractured coal seams that have previously been exploited for methane production.The multiple rounds of intermittent CO_(2) injection and shut-in periods has shown potential for greater CO_(2) storage and injection efficiency.
基金support from National Natural Science Foundation of China(Grant Nos.22275145,22305189and 21875184)Natural Science Foundation of Shaanxi Province(Grant Nos.2022JC-10 and 2024JC-YBQN-0112).
文摘Two-dimensional energetic materials(2DEMs),characterized by their exceptional interlayer sliding properties,are recognized as exemplar of low-sensitivity energetic materials.However,the diversity of available 2DEMs is severely constrained by the absence of efficient methods for rapidly predicting crystal packing modes from molecular structures,impeding the high-throughput rational design of such materials.In this study,we employed quantified indicators,such as hydrogen bond dimension and maximum planar separation,to quickly screen 172DEM and 16 non-2DEM crystal structures from a crystal database.They were subsequently compared and analyzed,focusing on hydrogen bond donor-acceptor combinations,skeleton features,and intermolecular interactions.Our findings suggest that theπ-πpacking interaction energy is a key determinant in the formation of layered packing modes by planar energetic molecules,with its magnitude primarily influenced by the strongest dimericπ-πinteraction(π-π2max).Consequently,we have delineated a critical threshold forπ-π2max to discern layered packing modes and formulated a theoretical model for predictingπ-π2max,grounded in molecular electrostatic potential and dipole moment analysis.The predictive efficacy of this model was substantiated through external validation on a test set comprising 31 planar energetic molecular crystals,achieving an accuracy of 84%and a recall of 75%.Furthermore,the proposed model shows superior classification predictive performance compared to typical machine learning methods,such as random forest,on the external validation samples.This contribution introduces a novel methodology for the identification of crystal packing modes in 2DEMs,potentially accelerating the design and synthesis of high-energy,low-sensitivity 2DEMs.
文摘In an environment where demand for housing is growing and the supply from public authorities is virtually non-existent,several mechanisms for housing production are emerging in the formal,semi-informal and informal construction sectors.The project owner wonders how much it costs to construct a building to an acceptable standard.Cost forecasting in general faces a number of difficulties,including a lack of available information during the preliminary phase of the project.As such,estimation becomes a crucial task involving great responsibility,which can lead to either more convincing results or chaotic situations.This study proposes a quick and effective method for estimating the cost of a single-storey F4 residential building.The modelling is done using multiple linear regression based on a statistical approach applied to twenty(20)projects that have already been completed.The project data are collected from design offices in the city of Brazzaville.The method expresses the cost of an F4 construction by certain project tasks,representing five(5)variables,three(3)of which are related to structural work and two(2)to finishing work,which are easy to determine.This approach,known as MECSO(Cost Estimation Model by Sub-structure),gives good results in all statistical tests carried out with reasonable confidence intervals.This method is very practical for engineering professionals working on the evaluation and control of construction costs.
基金Project supported by the Guangdong Basic and Applied Basic Research Foundation (Grant No. 2021B1515130007)the National Natural Science Foundation of China (Grant Nos. U21A20432 and 52273077)+1 种基金the National Key Research and Development Program of China (Grant No. 2022YFA1403800)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB33000000)。
文摘Flat electronic bands in condensed matter provide a rich avenue for exploring novel quantum phenomena. Here, we report an optical spectroscopy study of a topological hourglass semimetal Nb_(3)SiTe_(6) with the electric field of the incident light parallel to its crystalline ab-plane. The ab-plane optical conductivity spectra of Nb_(3)SiTe_(6) single crystals exhibit a remarkable peak-like feature around 1.20 eV, which is mainly contributed by the direct optical transitions between the two ab-initio-calculation-derived flat bands along the momentum direction Z–U. Our results pave the way for investigating exotic quantum phenomena based on the flat bands in topological hourglass semimetals.
基金supported by the National Natural Science Foundation of China(Grant Nos.22275092 and 52372084)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX24_0709)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.30923010920)the State Key Laboratory of Transient Chemical Effects and Control,China,(Grant No.6142602230201).
文摘Enhancing the output capacity of semiconductor bridge(SCB) through the application of composite nano-energetic films is a subject of wide concern. Furthermore, improving the safety, reliability, and production efficiency of energetic semiconductor bridge(ESCB) is the primary focus for large-scale engineering applications in the future. Here, the Al/CuO nano-film ESCB was efficiently fabricated using 3D direct writing. The electrostatic safety of the film is enhanced by precisely adjusting the particle size of Al, while ensuring that the SCB can initiate the film with small energy. The burst characteristics of SCB/ESCB were thoroughly investigated by employing a 100 μF tantalum capacitor to induce SCB and ESCB under an intense voltage gradient. The solid-state heating process of both SCB and ESCB was analyzed with multi physical simulation(MPS). The experimental results demonstrate that the critical burst time of both SCB and ESCB decreases with increasing voltage. Under the same voltage, the critical burst time of ESCB is longer than that of SCB, primarily due to differences in the melting to vaporization stage. The MPS results indicate that the highest temperature is observed at the V-shaped corner of SCB. Due to the thermal contact resistance between SCB and the film, heat conduction becomes more concentrated in the central region of the bridge, resulting in a faster solid-state heating process for ESCB compared to SCB.The results of the gap ignition experiments indicate that at a 19 mm gap, an ESCB with a film mass of 10 mg can ignite nickel hydrazine nitrate(NHN) and cyclotrimethylenetrinitramine(RDX). This suggests that thermite ESCB can serve as a novel, safe, and reliable energy exchange element and initiator in largescale engineering applications.
文摘Hydroelectric power production from Garafiri dam and rainfall are essential elements with the observation of hydroelectric power production in West African power system,particularly in Guinea.This article focuses on the study and the influence of climate variability on hydroelectric power production at Garafiri dam over 16-year period(2008-2023).The aim of this work is to show the correlation between rainfall anomalies and hydroelectric power production at Garafiri dam.The method used consists of calculating precipitation anomalies at Garafiri site and those for the production of hydroelectric power from Garafiri dam over the study period.This approach led us to calculate the anomalies,leading to the study on climatic variability,in order to establish correlation between rainfall and hydroelectric power dam’s production.The trend with the correlation found made it possible to carry out a significance test between these two variables.These results clearly show that rainfall in Garafiri site increases hydroelectric power production and vice versa,which explains the interdependence between these two parameters,i.e.climatic variability and hydroelectric power production.
