High Emission Research Articles

Optimization of Material Utilization by Developing a Reliable Design Criterion for Tool Construction in Cross-Wedge Rolling

The massive forming industry in Germany produces around 1.4 million parts every year, which are mainly used in safety-relevant areas such as the automotive industry. The production of these parts requires a considerable amount of energy, much of which remains unused and causes high CO2 emissions. An efficient approach to reduce these emissions and improve material utilization is cross-wedge rolling, which enables efficient material utilization but is limited by the so-called Mannesmann effect, which leads to unwanted material defects. This paper describes the development and validation of a safe design criterion for cross-wedge rolling tools in order to avoid material damage caused by the Mannesmann effect and thus increase resource efficiency in forging. Based on simulation-supported investigations and experimental tests, process maps are created for various materials. The validation is carried out both in an experimental test facility with real tools and in an industrial production facility, which leads to a significant reduction in excess material and CO2 emissions. The results show that the full resource potential of cross-wedge rolling can be exploited by optimizing process parameters and tool geometries.

Comparing Different Methodologies to Quantify Particulate Matter Accumulation on Plant Leaves

Urban air pollution poses a significant threat to human health, with metropolitan areas particularly affected due to high emissions from human activities. Particulate matter (PMx) is among the most harmful pollutants to human health, being composed of a complex mixture of substances related to severe pulmonary conditions. Urban green spaces play a vital role in mitigating air pollution by capturing PMx, and it is essential to select plant species with a high capacity for PMx accumulation to effectively enhance air quality. This study aimed to evaluate and compare the accuracy of two PMx quantification methods—light microscopy and filtration—which demonstrated a high correlation (R2 = 0.72), suggesting that both methods are reliable for assessing PMx accumulation on leaves. Light microscopy allowed for the visualization of PMx deposition, revealing the species warranting further analysis using the filtration method. Among the species analyzed, Euonymus japonicus, Ligustrum lucidum, Alnus glutinosa, Rubus ulmifolius, and Laurus nobilis demonstrated the highest total PMx accumulation, exceeding 50 µg cm−2, making them particularly valuable for air pollution mitigation. This study examined the correlation between leaf traits such as specific leaf area (SLA), leaf area (LA), leaf dissection index (LDI), and leaf roundness and PMx accumulation across the 30 different plant species. A multiple linear regression analysis indicated that these leaf traits significantly influenced PMx accumulation, with SLA and LA showing negative correlations and leaf roundness exhibiting a positive correlation with PMx deposition. In conclusion, this study highlights the importance of selecting plant species with specific leaf traits for effective air quality improvement in urban environments particularly in highly polluted areas, to enhance air quality and public health.

Optimizing carbon emission reduction strategies in power batteries: Ensuring compliance with the EU battery regulation's carbon labeling initiatives

Reducing carbon emissions from power batteries is essential for the low-carbon development of electric vehicles (EVs). In response to the carbon labeling requirements of the EU battery regulation, this study developed a three-tiered supply chain model incorporating the battery material supplier, the power battery manufacturer, and the EV company. Using Stackelberg game theory, the research evaluated four carbon emission reduction strategies and analyzed the impact of consumer environmental awareness on carbon emissions. The results reveal that for batteries with lower initial carbon footprints, increased consumer environmental awareness is associated with a reduction in carbon emissions. For batteries with higher initial carbon footprints, the relationship between consumer environmental awareness and carbon emissions is more complex. Below a certain threshold, higher environmental awareness leads to carbon emission reduction; however, beyond this threshold, increased environmental awareness can elevate carbon emissions. Moreover, under low consumer environmental awareness, a strategy of comprehensive collaboration among all supply chain tiers yields the highest economic benefits, albeit with higher emissions. As environmental awareness rises, the strategy where the material supplier independently reduces emissions and the battery manufacturer and EV company collaborate on emission reductions emerges as the most effective, striking an optimal balance between economic and environmental interests.

Optimisation of Parameters and Application of Green Recyclable Precast Hollow Steel Pipe Concrete Supports

Underground space development is a crucial approach to addressing traffic congestion in China’s cities, especially through underground construction. However, the traditional pit internal support system, particularly the concrete internal support system, has significant drawbacks. These include high energy consumption and carbon emissions, which are increasingly prominent issues. In this paper, a hollow precast concrete-filled steel tube (H-CFST) internal support system is proposed and a node connection scheme is designed. Through numerical simulation, the load-bearing characteristics of H-CFST with different aspect ratios, hollow ratios, hoop thicknesses, and hoop lengths are investigated, and the optimal design parameters are obtained. Finally, following a field application, monitoring data reveal that the precast H-CFST internal support demonstrates superior load-bearing capacity compared to the concrete internal support, successfully meeting the criteria for replacement of the concrete support.

Correlation between beverage consumption and droplet production during respiratory activity using interferometric Mie imaging experiment

This study investigates the effects of beverage consumption on droplet production during coughing and speaking. Interferometric Mie imaging (IMI) measures particle size using the diffraction characteristics of light and was used to examine the particle size distribution and particle count concentration of exhaled droplets without water (WW), with still water (SW), and with carbonated water (CW). The parameters of the IMI technique were calibrated using glass beads and respiratory droplets were measured for 16 subjects, which showed that drinking beverages had a significant impact on the particle size distribution during coughing and speaking. Another important aspect of this study was the variability in particle emissions among individuals. The results showed that the consumption of SW and CW led to a significant increase in total particle count concentrations in the coughing condition when compared with WW, with no significant difference among beverage type. Individuals with relatively high particle emissions WW showed more particle generation when consuming SW and CW. When speaking, SW ingestion significantly increased the total particle count concentrations when compared with the WW condition, whereas CW consumption did not increase the total particle count concentrations to the same extent as that in the SW condition. These results emphasize that the consumption of beverages such as SW and CW have the potential to significantly increase particle production during respiratory activities, amplifying the potential risks associated with infection transmission.

Industrial equipment optimization for combustion performance enhancement: a real-world case study

To address the issue of high NOx emission from the combustion chamber, this work optimized the industrial machine structure to enhance the combustion performance. The analysis results indicated that the flue gas recirculation (FGR) could effectively reduce the combustion temperature and the distribution of high-temperature regions in the machine chamber, thereby suppressing NOx formation without affecting the gas velocity inside the chamber. Based on the simulation analysis, the FGR technology was applied to modifying the machine structure and evaluated the modification effect in real-world application. It is found that after adding FGR, the oxygen content at the furnace outlet decreased from 13.8% to 10.5%, the NOx emission from the furnace decreased from 80 mg/m3 to 18 mg/m3, and the natural gas consumption decreased by more than 17%. These results demonstrate a significant impact on energy saving and emission reduction after optimizing the machine structure, which can provide a reference basis for subsequent researchers in this field.

Comprehensive analysis of laminar burning velocity in DEK/NH3-air premixed flames under varied pressure conditions

3-pentanone (DEK) is a biomass oxygenated fuel with high energy density and low emissions. It shows promising potential in increasing the combustion of NH3. This study examines the laminar burning velocity (LBV) of a fuel mixture composed of DEK/NH3-air. The LBV of DEK/NH3-air was determined with a constant-volume combustion bomb under the following conditions: initial temperature (T) of 448 K, pressure (P) of 1 to 3 atm, equivalence ratio (ϕ) between 0.7 and 1.3, and NH3 mole fraction (XNH3) varying from 0 % to 90 %. A combustion kinetic model for DEK/NH3 mixed fuel was developed and verified using experimental results. Overall, the model can capture the trend of LBV well. Subsequently, a comprehensive kinetic analysis was conducted utilizing this mechanism to elucidate the effect of NH3 mixing on DEK/NH3-air mixed fuel. The results indicate that LBV of DEK/NH3-air mixture declines as XNH3 increases, primarily attributed to the reduction in radical pool concentration. Conversely, the effect of the decrease in flame temperature is relatively minor. Furthermore, as XNH3 mole fraction decrease, there is a slight alteration in the consumption pathway of NH3. The elevation in DEK mole fraction leads to an increased production of radicals, thereby amplifying the oxidation process of NH3. The proportion of the oxidation of NHi pathway also increases. Finally, the change of NO content in DEK/NH3-air flame was observed. The rise in XNH3 leads to a gradual increase in the content of NO until it reaches a peak, after which it starts to decline. This phenomenon is dependent on the presence of O, OH, and NHi radicals. In addition, it has been discovered that augmenting ϕ can significantly reduce the concentration of NO in DEK/NH3-air mixture.

Sustainable Stabilization of Cadmium (Cd)-Contaminated Soil with Biochar-Cement: Evaluation of Strength, Leachability, Microstructural Characteristics, and Stabilization Mechanism

ABSTRACT To facilitate the solid waste reuse of cadmium (Cd)-contaminated soil and biochar and reduce the high emission of cement materials, we employed biochar-cement composite stabilizer to remedy Cd-contaminated soil. We assessed the effects of the biochar-cement composite stabilizer dosage and curing time on stabilized soil strength by using unconfined compressive strength (UCS) tests, leaching concentration and stabilization rate in Cd-contaminated soil stabilized by biochar-cement by using toxicity characteristic leaching procedure, and mechanism of change in strength and leaching characteristics by using scanning electron microscopy and X-ray diffraction. The research results demonstrate that biochar addition to cement-stabilized soil promoted cement hydration reaction and increased particle agglomeration. A low dosage of biochar improved stabilization effects. The optimal biochar dosage was 5%, which enhanced the early growth speed of the UCS. More cement improved the stabilized soil’s UCS. At a 5% cement dosage, adding biochar significantly reduced Cd leaching concentration, and improved the stabilization rate. At a 10% cement dosage, the biochar-cement composite stabilized soil’s stabilization rate was >99.8%. Calcium silicate hydrate, calcium aluminate hydrate, and ettringite were the main products of biochar-cement stabilized soil that filled soil and biochar pores; these substances encapsulated, adsorbed, or exchanged ions of Cd2+, achieving stabilization effects.

High emission of black carbon in heavy-duty diesel vehicles: Insights from microscopic operating conditions

The in-depth investigation of the high black carbon (BC) emission scenarios of heavy-duty diesel vehicles (HDDVs) is a crucial step toward developing effective control strategies. Chassis dynamometer tests were conducted for three in-use HDDVs, namely, vehicle #1, #2, and #3, focusing on the instantaneous BC characterizations during multiple driving conditions, i.e., speed phases and acceleration intervals. BC emission was found to increase with positive acceleration, and high acceleration could result in instantaneous BC spikes. The total BC emissions during velocity-acceleration interval 15–60 km h−1 and 0.1–0.9 m s−2 contributed to 43.4 ± 10.2 % of the whole-cycle emissions, while the proportions of time spent in the velocity-acceleration interval to the whole cycle were 23.1 ± 7.6 %. The cold-start microscopic operating condition was assessed by the cold-start extra emissions (CSEEs). Under various pre-defined cold-start durations, the proportions of CSEEs in the total cycle emissions were 9.4–21.0 %, 0–9.1 %, and 6.8–39.4 % for vehicles #1, #2, and #3, respectively. The CSEEs exhibited an initial rise, followed by a plateau as the assumed cold-start durations extended. A uniform cold-start duration of 600 s was established based on the criterion that the relative standard deviation (RSD) of CSEEs during the plateau period was <10 %. We proposed that the updated cold-start duration can enhance the accuracy and consistency of cold-start corrections in emission inventory models.

A quantitative comparison of economic viability, volatile organic compounds, and particle-bound carbon emissions from a diesel engine fueled with biodiesel blends

Despite the environmental advantages of biofuel blends, detailed studies on emissions of polycyclic aromatic hydrocarbons (PAHs), n-alkanes, and particle-bound carbon from diesel engines, particularly when fueled with biodiesel, remain limited. This study addresses these gaps by analyzing biodiesel blends from neem, linseed, and jatropha oils produced via mechanical extraction and assessing their impact on volatile organic compounds and particle-bound carbon emissions in diesel engine. Economic evaluations of production costs, engine modifications, and payback periods are also conducted. The result shows that jatropha biodiesel exhibits a calorific value of 35.7 MJ/kg, while neem biodiesel shows superior oxidative stability due to its low iodine value. Additionally, linseed biodiesel displays favorable cold flow properties due to its high density and cetane value. Compared to D100, the N10 and N30 blend notably reduced high molecular weight PAH emissions by 10.7 % and 38.4 %, respectively, with the N30 blend achieving a remarkable 76 % reduction in formaldehyde emissions. Conversely, the J10 blend increased specific PAHs, while the J30 blend reduced PAHs by 21.3 %. Both L10 and L30 blends showed reduced naphthalene emissions, with the J30 blend notably reducing elemental carbon (EC) by 31.4 %, although organic carbon (OC) slightly increased. In contrast, the N30 blend decreased both EC and OC emissions, demonstrating a dose-dependent relationship between biodiesel concentration and emissions reduction. Overall, Jatropha biodiesel blends offer the best balance of economic efficiency and emission reductions, resulting in shorter payback periods and lower carcinogenic risks. Neem and linseed blends also provide environmental benefits but with varying economic implications, highlighting the trade-offs between production costs and long-term sustainability.

Modeling the spatiotemporal dynamics of electric power consumption in China from 2000 to 2020 based on multisource remote sensing data and machine learning

China's rising electricity power consumption (EPC) is strongly correlated with carbon emissions. Timely and accurate analysis of the spatiotemporal dynamics of EPC is important to the realization of carbon peaking and carbon neutrality goals in China. However, due to data quality problems and limitations of modeling methods, the estimation accuracy warrants further improvement. In this study, the EPC in China from 2000 to 2020 was estimated based on multisource remote sensing data using the Random Forest (RF) model. Compared with previous studies, the accuracy of this study was improved by 39%–47%. The reasons were combining multisource remote sensing data can mitigate the quality issues of nighttime light (NTL) data, and the RF can capture the nonlinear relations between remote sensing data and EPC. In addition, the spatial pattern of the average EPC in China was dominated by the low-level EPC, as well as showing an obvious increasing trend. We also found that in the middle reaches of the Yellow River and northern coastal China, the low-speed increase in EPC led to high carbon emissions and emission intensity. We suggest optimizing the fuel fix of energy and adjusting the industrial structure, combining them with scientific and rational spatial planning.

Impact of different CO2 price paths on the development of the European electricity system

In energy system transformation studies, the assumption of linearly rising CO2 prices is common and based on the decreasing issued European allowances (EUA). The actual auction price for allowances is influenced by market dynamics, resulting in non-linear variations in CO2 prices due to the possibility of banking allowances. This study explores the impact of non-linear CO2 price trajectories on the European electricity market. Various scenarios, such as increasing prices with the market interest rate, early price peaks, collapse, or fluctuations, are examined until 2030. The study quantifies the effects on power plant investments, profitability, consumer costs, and government revenues. The findings reveal that early and high price signals lead to an earlier transition with 7 % more wind power plants but at 4 % higher costs. Conversely, lower initial prices delay power plant investments in wind power plants by 6 % and result in 21 % higher emissions. Compensation for climate impact costs can yield a positive cost-benefit analysis in scenarios with early and high price signals when emissions are avoided through mechanisms like the Market Stability Reserve (MSR).

Strategy to optimize the broadband near-infrared emission based on Eu2+-doped sulfureted garnet phosphors toward emerging spectroscopy applications

Eu2+-doped near-infrared (NIR) emitting phosphors, known for their high efficiency, broadband emission and spectral tunability, have gained much attention. However, achieving efficient NIR emission based on Eu2+ remains a challenge due to the co-existence of Eu3+, especially in materials (i.e. garnets and apatites) containing trivalent lanthanide cations. In this study, a Eu2+ doped sulfureted NIR-emitting garnet phosphor Ca3(Sc, Eu)2Si3(O, S)12: Eu2+ is successfully designed and synthesized. Notably, a strategy for regulating the initial valence state of dopants is proposed by using prepared EuS instead of the conventional Eu2O3 as raw material, enhancing the NIR emission by 135 %. Moreover, a sulfuration strategy is further introduced to enhance the NIR-emitting intensity and internal quantum efficiency by 192 % and 167.8 %, and to improve thermal stability by 154 % at 120 °C. The luminescence origin of the unusual broadband NIR emission is re-examined through chemical unit co-substitution strategy by introducing [Al3+Hf4+] to replace [Sc3+Si4+] ion pairs. Meanwhile, the spectral regulation and the performance optimization mechanism are systematically discussed. Finally, a green light pumped NIR LED device with a photoelectric efficiency of 9.43 %@100 mA and output power of 22.74 mW@100 mA is fabricated, showing remarkable potential in nondestructive testing and biomedical imaging applications.

Multispectral Hierarchical Metamaterials with Broadband Microwave Absorption, Gradient Infrared Emissivity, and High Visible Transparency

AbstractThe rapid progression of multispectral detectors poses a serious threat to weapon systems and personnel. The efficiency of stealth camouflage materials, however, has strong wavelength dependence, which limits their functionality to a specific spectral range. Here, a multispectral hierarchical metamaterial (MHM) with broadband microwave absorption, gradient infrared (IR) emissivity, and high visible transparency is proposed. The MHM design entails the integration of two distinct functional layers: the infrared camouflage layer (IRCL) and the radar absorbing layer (RAL). Specifically, leveraging the low‐pass and high‐impedance properties of capacitive frequency selective surfaces and adjustable filling ratio of low IR radiation materials, the IRCL achieves simultaneous high microwave transmission and gradient IR emissivity designs (emissivity gradients &gt; 0.15 at 3–5 and 8–14 µm). The RAL achieves broadband microwave absorption across radar C, X, Ku, and Ka bands through a circuit‐analog absorber designed with lossy materials. Furthermore, prioritizing materials with high transparency enhances the average optical transmittance (&gt;61.8%) of MHM in 380–760 nm. These distinctive features underscore the potential of the proposed MHM for advanced applications in camouflage and stealth technologies.

Analysis of Carbon Emission Reduction Potential of Different Star Green Science and Technology Museums in Cold Regions of China

Low-carbon development in the field of buildings is an important means to achieve the goal of “carbon peaking and carbon neutrality”. In public buildings, the operation of science and technology museum buildings (TMB) has high carbon emissions, and the application of green building technology for energy saving and carbon reduction has great potential. In this paper, typical TMB in cold areas are selected and built, and energy consumption is simulated by Designbuilder. The calculation boundaries and carbon emission factors of carbon emissions are set according to current standards, and the carbon reduction potential of green science and technology museum buildings (GTMB) under different levels is compared. The results show that compared with the benchmark building based on GB 55015-2021, the carbon emission of the GTMB is significantly reduced, and the carbon emission reduction rates of silver, gold, and platinum TMB are 7.9%, 13.4%, and 29.6%, respectively. Based on the existing optimization design of passive measures such as natural ventilation and natural lighting, the GTMB should pay more attention to the realization of its optimal control strategy and automatic control.

Electrified methane upgrading via non-thermal plasma: Intensified single-pass ethylene yield through structured bimetallic catalyst

Chemical valorization of methane (CH4) via modular electrified reactors could represent a profitable avenue for biogas producers. Ethylene (C2H4) is the most valuable product due to its large demand that results in high energy cost and carbon emissions. However, alternative electrified processes proposed so far cannot compete with the state-of-the-art fossil route in terms of energy efficiency. The catalytic plasma reactor presented in this work achieves 34.4 % C2H4 yield from non-oxidative CH4 coupling, by integrating a bimetallic Pd-Ag catalyst on the surface of a 3D-printed structured electrode in a nanosecond-pulsed-discharge plasma reactor. This performance sets a new benchmark for alternative C2H4 production, potentially relying purely on renewable energy. Onsite energy generation via the excess hydrogen produced in the process could allow recovery of 16 % of the input energy. Moreover, the process produces solid carbon deposit that can be collected on the surfaces in proximity of the plasma discharge. This residue shows amorphous features and significant incorporation of metal particles coming from the electrodes surface. Hence, its low surface area hampers its application as carbon black analogue.

Carbon metabolism mechanisms and evolution characteristics analysis of the food-water-energy nexus system under blue-green infrastructure changes

Food, water, and energy comprise a complex system (FWE nexus) that generates much carbon emissions during operation. At the same time, urban blue-green infrastructure (BGI) has a critical carbon sequestration function. This paper combines the functions of the FWE nexus and BGI and uses ecological network analysis (ENA) and the Markov model to measure the carbon metabolism (CM) mechanisms and evolutionary characteristics of BGI and FWE nexus (BGI-FWE nexus) complex systems. The results show that Guangzhou has high carbon emissions, and Zhaoqing and Huizhou have high carbon sequestration. Resident land and industrial and transportation land transfers to different land uses are more likely to produce positive carbon flows, while BGI transfers to other types are more likely to produce negative carbon flows. The study of CM mechanisms reveals a high proportion of competition relationships and a low proportion of mutualism relationships. The ecological utility index (EUI) tends to fall initially and then increase, peaking at 0.84 in 2015–2020, the highest value for the study period. The CM network has less system robustness (SR) and is in an unsustainable state of high redundancy and low efficiency. The mechanism evolution characterization study’s findings show a decreased likelihood of remaining original and less stability in the spatial transfer probability matrices of EUI and SR. In this study, we constructed a BGI-FWE nexus research framework based on the different CM functions of BGI and FWE nexus. The research framework contributes to the realization of carbon reduction in the FWE nexus system and is essential for the planning and management of urban BGI.

Impact of fiscal regulation on regional carbon intensity: assessing the carbon emission reduction effect of transparent government revenue and expenditure

ABSTRACT Fiscal regulations enhance fiscal compliance and reduce undue government intervention in economic performance, which may have important implications for low-carbon development. However, few empirical studies have investigated the impact of fiscal regulations on carbon intensity. Based on data from 278 cities in China from 2005 to 2020, this study constructed a difference-in-differences model using the release of the new Budget Law to investigate the impact of fiscal revenue and expenditure regulation on regional carbon emission intensity. The empirical results indicated that fiscal regulations can significantly reduce the intensity of carbon emissions. The mechanism tests indicate that fiscal regulation can optimize the allocation of local governments’ fiscal revenues and expenditures and improve infrastructure and innovation. Heterogeneity analyses indicate that the effect of fiscal regulation on reducing carbon emission intensity is more obvious in regions with high historical emissions and a high proportion of polluting industries. Based on the empirical results, the government should continuously improve fiscal transparency and the efficiency of fiscal fund use to reduce the impact of unreasonable fiscal revenue and expenditure on carbon emissions intensity.

Observed flash drought to persist in future over southern Africa

Southern Africa has experienced multiple occurrences of drought episodes, which is projected to persist in the future, considering all climate scenarios. Despite the documented change in a meteorological, agricultural, and hydrological drought situation in the region, few studies are yet to explore the changes in flash drought (hereafter; FD), which is characterized by a rapid reduction in root-zone soil moisture and more substantial intensification in few days to weeks. Here, we analyze the observed FD and related underlying drivers during the past 34 years. Also, we estimate the future changes in FD using the severity-duration magnitude matrix under the middle of the road (SSP2-4.5) and business as usual (SSP5-8.5), scenario. Lastly, the study investigates the role of anthropogenic warming using the fraction of attributable risk (FAR) approach and possible bivariate return periods of FD events. Our results demonstrate that the region has experienced multiple occurrences up to 72 pentads from 1980 to 2014. Underlying mechanisms revealed the compounding influence of Vapor Pressure Deficit (VPD), Potential Evapotranspiration (PET), and precipitation deficit that have a significant impact on the abrupt onset and rapid intensification of FD events and other hot extremes over the SAF region. Under a high emission scenario, the region will experience FD duration lasting for 30 days with >40 % severity projected to impact the region. Anthropogenic climate change and land use and land cover changes remain the most dominant drivers altering the FD events over the SAF region. The return period of FD events under the SSP5-8.5 scenario shows that the SAF region will witness multiple FD events of up to 80 pentads in the far future. These findings reinforce the need to limit the emission of greenhouse gases. Sustained warming of the climate will exacerbate the extreme events and other compounding factors, thus affecting the livelihoods of humans and life-supporting strata.

Impact of material-dependent radiation – longitudinal optical phonon interaction on thermal electric-dipole radiation from surface metal − semiconductor grating structures

Infrared thermal radiation emission in the 8.5 – 28 THz frequency region is obtained using surface metal–semiconductor grating structures on undoped (u-) GaAs, u-GaP, u-ZnO, u-GaN, and n-type SiC in a temperature range of 430 – 630 K. These emissions resonate with longitudinal optical (LO) phonon or LO-like lattice vibration energies determined by the zero points of the real parts of the dielectric functions in the surface structures. The emissions of materials with Reststrahlen bandwidths of a few tens of cm−1 show the emissions resonating with their LO phonon modes, while materials with bandwidth of more than 170 cm−1 show peak energies significantly lower than the LO phonon: LO-like phonon resonance. The emission intensity is found to be dominated by the balance of radiative and nonradiative LO or LO-like phonon annihilation rates. The radiative rate is dominated by the LO-phonon–radiation interaction Hamiltonian and the Bose-Einstein factor. High emission intensity is obtained for the structure on u-ZnO with intense LO-like phonon–radiation interaction. The dependence of the emission intensity on temperature and emission window width for various materials shows the effect of material-dependent metal/semiconductor interface conditions on the emission efficiency.