Minimum Density Research Articles

Carbon Sequestration Through Forestry: A Differential Equation Approach

Carbon sequestration through forestry represents a promising approach to partially counteract anthropogenic greenhouse gas emissions driving climate change. Tree growth naturally removes carbon dioxide from the atmosphere, storing it as biomass. Sustainably managed forests can effectively function as carbon sinks. However, determining optimal forestry policies involves balancing complex ecological dynamics with economic constraints. This study develops differential equation models quantitatively capturing forest growth, timber harvesting, and carbon sequestration dynamics. Logistic models are first adapted to simulate biomass accumulation of representative tree species. Lifecycle growth patterns spanning juvenile to mature phases are incorporated, along with climate effects. Biomass levels are proportionally related to carbon dioxide removal rates from the atmosphere. Deforestation impacts are analyzed by incorporating harvesting-induced biomass reductions. Sustainability constraints are implemented to ensure minimum viable tree densities across harvest rotations. Optimization techniques then identify management guidelines maximizing economic returns given ecological stability considerations. The goal is providing quantitative insights into rotation lengths, planting densities, and allowable cuts upholding both climate change mitigation and commercial demands. Findings can inform science-based forestry policies to leverage forests as sustainable natural carbon sinks.

Electret Modulation Strategy to Enhance the Photosensitivity Performance of Two-Dimensional Molybdenum Sulfide.

Due to the limited light absorption efficiency of atomic thickness layers and the existence of quenching effects, photodetectors solely made of transition metal dichalcogenides (TMDs) have exhibited an unsatisfactory detection performance. In this article, electret/TMD hybridized devices were proposed by vertically coupling a MoS2 channel and the PTFE film, which reveals an optimized photodetection behavior. Negative charges were generated in the PTFE layer through the corona charging method, akin to applying a negative bias on the MoS2 channel in lieu of a traditional voltage-driven back gate. Under a charging voltage of -6 kV, PTFE/MoS2 devices reveal improved photodetection performance (Rhybrid = 67.95A/W versus Ronly = 3.37 A/W, at 470 nm, 1.20 mW cm-2) and faster recovery speed (τd(hybrid) = 2000 ms versus τd(only) = 2900 ms) compared to those bare MoS2 counterparts. The optimal detection performance (2 orders of magnitude) was obtained when the charging voltage was -2 kV, limited by the minimum of the carrier density in MoS2 channels. This study provides an alternative strategy to optimize optoelectronic devices based on the 2D components through non-voltage-driven gating.

Dimensionless Number Group Analysis of Surface-Treated Powders

Modeling powder properties remains a complex and difficult area of study because particulate materials can behave differently under variable conditions based on their bulk and surface-level properties. The research presented in this manuscript was designed to support the fundamental understanding of powder systems by joining experimental and theoretical calculations of dimensionless numbers groups for design purposes. In order to do so, this work focused on two critical variables to better understand fluidization design: physical and chemical surface properties. To better resolve the influence of surface properties, surface-treated powders were used. Five different powder samples of varying particle size distribution were characterized using physical property measurements, including pressure drop profiles to obtain the minimum fluidization velocity, density measurements, and particle sizing. Using theoretical equations, the minimum fluidization velocity was also calculated to compare with those obtained experimentally and determine typical dimensionless number groups used in bulk handling system design. The results showed that the theoretically determined values were lower than those calculated using the experimentally umf. In the case of the Reynolds number, the experimental values were 3–20% higher than the theoretical values, which is an important distinction for designing conveying systems and pipeline flow. Similar results were observed for the theoretical and experimental Froude numbers, indicating an important dependence on the cohesive properties of the particle interactions. Additional dimensionless number groups were considered, including the granular bond number and flow factors. To investigate the influence of surface forces, Hamaker constants were utilized for alumina and polydimethylsiloxane in the calculation of the granular bond number. A lower granular bond was observed with a decrease in the Hamaker constant for PDMS, suggesting that the surface forces would be lower for our surface-treated powders.

Observation of a temperature dependent anomaly in the UV translucency of milk useful for UV-C preservation techniques

Milk fat globules and casein micelles are the dispersed particles of milk that are responsible for its typical white turbid appearance and usually make it difficult to treat with modern ultraviolet light (UV) preservation techniques. The translucency of milk depends largely on the refractive indices of the dispersed particles, which are directly affected by temperature changes, as incorporated triglycerides can crystallize, melt or transition into other polymorphs. These structural changes have a significant effect on the scattering properties and thus on the UV light propagation in milk, especially by milk fat globules. In this study, a temporary minimum in the optical density of milk was observed within UV wavelength at 14 °C when heating the milk from 6 to 40 °C. This anomaly is consistent with structural changes detected by a distinct endothermic peak at 14 °C using differential scanning calorimetry. Apparently, the optical density anomaly between 10 and 20 °C disappears when the polymorphic transition already has proceeded through previous isothermal equilibration. Thus, melting of equilibrated triglycerides may not affect the RI of milk fat globules at ca. 14 °C as much as melt-mediated polymorphic transitioning. An increased efficiency of UV-C preservation (254 nm) at the translucency optimum was demonstrated by temperature-dependent microbial inactivation experiments.

Evaluating the Effect of Vegetation Index Based on Multiple Tree-Ring Parameters in the Central Tianshan Mountains

Combining tree ring data with remote sensing data can help to gain a deeper understanding of the driving factors that influence vegetation change, identify climate events that lead to vegetation change, and improve the parameters of global vegetation index reconstruction models. However, it is currently not well understood how climate change at different elevations in the central Tianshan Mountains affects radial tree growth and the dynamics of forest canopy growth. We selected Schrenk spruce (Picea schrenkiana) tree core samples from different elevations in the central Tianshan Mountains. We analyzed the relationships of various tree-ring parameters, including tree-ring width, maximum latewood density (MXD), and minimum earlywood density (MID) chronologies, with 1982–2012 GIMMS (Global Inventory Modelling and Mapping Studies) NDVI (Normalized Difference Vegetation Index), 2001–2012 MODIS (moderate resolution imaging spectroradiometer) NDVI, and meteorological data. (1) There were strong correlations between tree-ring width chronologies and the lowest temperatures, especially in July. Tree-ring width chronologies at higher altitudes were positively correlated with temperature; the opposite pattern was observed at lower altitudes. MID chronologies were positively correlated with July temperature in high-altitude areas and mean temperature and highest temperature from May to September in low-altitude areas, and negatively correlated with precipitation during this period. MXD chronologies were mainly negatively correlated with precipitation. MXD chronologies were mainly positively correlated with temperature in April and May. (2) The correlations between MXD chronologies at each sampling point and NDVI in each month of the growing season were strong. Both MID and MXD chronologies were negatively correlated with GIMMS NDVI in July. The overall correlations between tree-ring parameters and MODIS NDVI were stronger than the correlations between tree-ring parameters and GIMMS NDVI in high-altitude areas; the opposite pattern was observed in low-altitude areas. Drought stress may be the main factor affecting tree ring parameters and NDVI. In the future, we should combine tree ring parameters with vegetation index to investigate a larger scale of forests.

Preparation and corrosion resistance mechanism of chromium-free Zn–Al+CeO2 composite coatings

This study aims to fabricate chromium-free Zn–Al + CeO2 composite coatings by integrating CeO2 nanoparticles into the chromium-free Zn–Al coating solution as a strengthening agent and subsequently applying a wet coating method. The corrosion resistance of the coatings was evaluated through NaCl immersion corrosion tests. The microscopic morphology, composition and electrochemical properties of the composite coatings before and after corrosion were analyzed using SEM and an electrochemical workstation. The corrosion resistance mechanism of the coatings was investigated as well. The results revealed that the CeO2 nanoparticles were uniformly distributed on the surface of the composite coating and in the gaps between Zn and Al powders, forming micron-sized particles due to the surface energy effect. The composite coating exhibited a minimum corrosion current density of 0.63 μA cm−2 and a maximum corrosion electrochemical reaction resistance of 35321 Ω cm2. Additionally, a complex precipitate formed by the reaction of certain Ce elements in the composite coating enhanced the cathodic protection of the coating. Moreover, Ce3+ reacted with the OH− generated by microelectrochemical corrosion, resulting in the formation of a precipitate that filled in the gaps between Zn and Al powders. Consequently, this process contributed to the formation of a microporous and flocculent coating structure. In conclusion, the incorporation of CeO2 nanoparticles had a favorable impact on the production of environmentally friendly and corrosion-resistant chromium-free Zn–Al coatings.

An energy-efficient irregular hexagonal tessellation-based approach for connected k-coverage in planar wireless sensor networks

In the design of planar wireless sensor networks (PWSNs), the preliminary tasks are to achieve both coverage and connectivity, which are essential for the correct operation of this type of network. A PWSN is said to be in perfect operational condition only when it is capable of guaranteeing both coverage of the field and connectivity among all the active sensor nodes. In order to achieve both coverage and connectivity in PWSNs, we intend to solve the problem of connected k-coverage in PWSNs, where each point in a field of interest is covered (or sensed) by at least k sensor nodes (k > 1) simultaneously and all the participating sensor nodes in the k-coverage process are connected to each other. In our study, we found an irregular hexagon, denoted by IrHx(rs/n), as the best polygon for tessellating a field of interest and allowing to deploy sensor nodes, where n > 1 is a natural number and rs is the radius of the sensing range of the sensor nodes. First, we construct our proposed irregular hexagon, IrHx(rs/n), which forms a tile, using the regular hexagon. Second, we compute the minimum sensor density required to k-cover a planar field of interest using our proposed IrHx(rs/n) tile. Third, we establish a relationship between the sensing and communication radii of the sensor nodes to ensure network connectivity in k-covered PWSNs. Finally, we substantiate our theory with various simulation results.

Application of modified fracture criteria incorporating T-stress for various cracked specimens under mixed mode I-II loading

Accurate assessment of fracture behavior and life prediction of cracked materials based on the mixed mode fracture criteria is of utmost importance in fracture mechanics. In this study, the modified fracture criteria incorporating T-stress for mixed mode I-II cracks were comprehensively reviewed. Additionally, a comparative analysis was conducted between the experimental results obtained from five different cracked configurations and the theoretical predictions according to these modified criteria. Moreover, a brief discussion was held regarding the effect of T-stress on both crack initiation angle and fracture toughness, accompanied by providing some suggestions. The results revealed that the predictive accuracy of modified criteria exhibited noticeable variations across different cracked configurations due to the significant disparities in both the sign and magnitude of T-stress around the crack tip. However, it was observed that the predicted curves based on the modified fracture criteria for the semi-circular bend and edge-crack triangular specimens had remarkable similarities owing to their similar biaxial stress ratio B. When the mode II loading dominated, the generalized maximum tangential stress, generalized minimum strain energy density and generalized averaged strain energy density criteria were suitable for the semi-circular bend, edge-crack triangular, central crack rectangular and short bend beam specimens with positive T-stresses, whereas the maximum tangential strain, generalized maximum tangential stress and generalized maximum tangential strain energy density criteria could provide better theoretical predictions for central cracked Brazilian disk specimens having a negative T-stress.

Robust small area estimation for unit level model with density power divergence.

Unit level model is one of the classical models in small area estimation, which plays an important role with unit information data. Empirical Bayesian(EB) estimation, as the optimal estimation under normal assumption, is the most commonly used parameter estimation method in unit level model. However, this kind of method is sensitive to outliers, and EB estimation will lead to considerable inflation of the mean square error(MSE) when there are outliers in the responses yij. In this study, we propose a robust estimation method for the unit-level model with outliers based on the minimum density power divergence. Firstly, by introducing the minimum density power divergence function, we give the estimation equation of the parameters of the unit level model, and obtain the asymptotic distribution of the robust parameters. Considering the existence of tuning parameters in the robust estimator, an optimal parameter selection algorithm is proposed. Secondly, empirical Bayesian predictors of unit and area mean in finite populations are given, and the MSE of the proposed robust estimators of small area means is given by bootstrap method. Finally, we verify the superior performance of our proposed method through simulation data and real data. Through comparison, our proposed method can can solve the outlier situation better.

Effect of adding cement kiln dust on the effective geotechnical properties of sand dunes in Najran–Sharourah, Kingdom of Saudi Arabia: a laboratory study

Sand dunes are one of the most common soil types all over the world, particularly in North Africa and the Arabian Peninsula. These dunes, with their regional extensions, are considered the main natural resource for fine aggregates being used in construction purposes. To use dune sands as a road construction material, suitable treatment is necessary. Sand dunes have typically been stabilized using a cement material, however, though extremely costly and consuming a substantial amount of energy, it is not particularly effective. Therefore, this study has investigated the potentiality of adding cement kiln dust (CKD) for enhancing the strength and durability of dune sands in Najran–Sharourah, SW Saudi Arabia. Twenty-seven specimens have been mixed with 0%, 10%, 20%, and 30% CKD plus 2% cement and then examined and assessed using macro-characterization techniques. Results indicated that the strength of the sand dune samples, treated with an enhanced mixture of 30% CKD and 2% cement, improved the minimum dry density from 1.652 at 0% to 1.854 g/cm3. The soil became more qualified as a construction material. This enhanced mixture can serve as a high-quality sub-base for both flexible and rigid pavements. Besides, micro-characterization techniques, including X-ray diffraction (XRD), back-scattered electron imaging (BEI), and scanning electron microscopy (SEM) supported by energy-dispersive X-ray (EDX), were applied to identify the various phases of the treated dune sands. Finally, the implementation of adding the CKD to the dune sands geomechanical parameters has been modeled, and a series of highly reliable mathematical equations have been introduced (0.938 ≤ R2 ≤ 1.0).

Sterilization of oil palm fruit utilizing continuous microwave sterilizer

This study evaluates the performance of a continuous microwave device in the sterilization of oil palm fruits spikelet. The device comprises four microwave generators (magnetron), a tunnel cavity driven by a belt conveyor, and a tray as a container for palm fruit. This study aims to evaluate the distribution and penetration of microwave energy into palm fruit and to examine the quality of palm oil concerning power density and residence time adjusted in this study. Continuous microwave sterilizer was operated at various masses of oil palm fruit (0.5, 1, 1.5 kg), residence time (6, 8, 10, 12, 14 min), and microwave power (180, 300, 450, 600, 800 W). The resulting temperature in this study ranged from 39 to 97 °C. Observation of the temperature gradient inside-out of a single fruit indicates the interior temperature at the kernel nut is always higher as compared to exterior temperature (abscission layer), with temperature differences ranging from 3 to 23 °C. A minimum power density of 300 W/kg, a residence time of 6 min, and a temperature of 50 °C were required to produce palm oil with FFA less than 5%. Performance indicators of the prototype used in this study are a number of moisture loss dan oil quality. The moisture loss during the sterilization process was around 0.5 to 10.6% which indicates some water content in the fruit, while the content of water, FFA, β-carotene and vitamin E ranging between 1.9 and 17.6%, 0.32-1.74%, 186.14-608.59 ppm and 165.47-610.17 ppm, respectively. © 2001 Elsevier Science. All rights reserved.

A highly antifouling and eco-friendly hydrogel coating based on capsaicin derivative -functionalized polymer

Antifouling hydrogels have received extensive attention in the field of marine antifouling due to their excellent hydrophilicity and environmental friendliness. However, the antifouling applications of traditional hydrogels are limited by their poor antibacterial properties, and capsaicin derivatives, as nontoxic and environmentally friendly antifoulants, can be used to improve the antibacterial properties of hydrogels. From the perspective of practical application, hydrogels were obtained by crosslinking the copolymer of the capsaicin derivative N,N'-((4,5,6-trihydroxy-1,3-phenylene) bis (methylene)) diacrylamide (TPA), lipophilic monomers and hydrophilic monomers. This hydrogel exhibited anti-protein performance due to its hydrophilicity, and the capsaicin derivative caused the hydrogel coating to exhibit excellent algae inhibition performance (the minimum adhesion density of diatoms on the surface of the hydrogel coating was less than 440 cells/mm2), better algae anti-adhesion abilities than hydrogel reported in the other paper, and antibacterial effects (the antibacterial rate was more than 95%). After 73 d of panel testing in a real marine environment, there was still a good antifouling effect in the hydrogel coating. Hence, the antifouling performance was improved significantly by capsaicin derivative (TPA)-functionalized hydrogel coating. A new strategy is provided in this study for the preparation of hydrogels with superior marine antifouling properties.

Estimation of solid-liquid coexistence curve for coarse-grained water models through reliable free energy method

The anomalies properties of water have been interpreted theoretically using several all-atom and coarse-grained water models. Here we use a robust and traditional free energy approach to develop the solid-liquid coexistence curve for water using coarse-grained monatomic mW and machine-learned bond order potential (ML-BOP) water models. We employ the pseudo-supercritical thermodynamic path in combining multiple histogram reweighting (MHR) and Gibbs-Duhem integration. The ML-BOP model has a broad density-temperature hysteresis loop and shows lower maximum and minimum densities as compared to the mW model. The computed excess Helmholtz free energy and the Gibbs free energy at the approximate melting temperature are higher for the ML-BOP model in comparison with the mW model. The pressure dependence fusion curve for both water models aligns with the literature. This analysis indicates that the free energy method accurately captures the solid-liquid transformation and the thermodynamic melting point of water.

Evaluating a new aphid biocontrol agent: The role of aphid density in modulating oviposition behaviour in the American hoverfly, Eupeodes americanus, and the aphid midge, Aphidoletes aphidimyza

AbstractHoverfly larvae are voracious predators of aphids but have limited dispersal capacity, so their survival depends critically on female selection of oviposition sites. For aphid control purposes, the ability of females to find small aphid colonies is especially valuable. In this study, the oviposition strategy and minimum aphid density triggering the oviposition of the American hoverfly, Eupeodes americanus (Wiedemann, 1830) (Diptera: Syrphidae), was compared with that of the aphid midge, Aphidoletes aphidimyza (Rondani, 1847) (Diptera: Cecidomyiidae), a predator commercially available in Canada as a reference. Oviposition behaviour was evaluated at densities of 0, 2, 5, 10, and 50 aphids per plant. This was tested on two economically significant plant/aphid systems: pepper plants infested by the green peach aphid, Myzus persicae (Sulzer 1776) (Hemiptera: Aphididae), and cucumber plants infested with the melon aphid, Aphis gossypii Glover 1877. Results showed that both predators lay their eggs in proportion to the size of the colony of aphids. Oviposition by E. americanus required a minimum density of 5 aphids on cucumber but only 2 on pepper, whereas for A. aphidimyza, it was also 5 aphids on cucumber, but 10 on pepper. The hoverfly laid more than twice as many eggs as A. aphidimyza on pepper. It also laid more eggs on pepper than on cucumber and the pattern is the opposite for A. aphidimyza. Therefore, the identity of the aphid‐host plant complex appears to modulate the oviposition of these predators. This study demonstrates the ability of E. americanus to respond to lower densities of aphids than A. aphidimyza early in the infestation on sweet pepper plants and shows that its oviposition rate is at least as effective as A. aphidimyza on cucumber. Consequently, these attributes of its oviposition behaviour indicate that E. americanus has great potential for use as an aphid biocontrol agent in these crops.

Environmental controls on macrozooplankton and fish distributions over diurnal to seasonal time scales in the northern Barents Sea

We present acoustic observations obtained by bottom mounted echosounders at two locations in the northern Barents Sea and a third on the northern continental slope of the Barents Sea. Data collected over a period of approximately two years reveal significant variability in the density and depth distribution of pelagic macrozooplankton and fish. Variability over diurnal to seasonal timescales is related to light conditions, prevailing currents, water column characteristics (temperature, stability, and pycnocline depth) and to sea ice conditions. Of particular importance is the relative volume of Polar Water and Atlantic influenced water present at the mooring sites. On the northern continental shelf, above average concentrations of macrozooplankton and fish were observed during late summer and early autumn following ice melt, and during winter. Minimum densities of macrozooplankton and fish were observed during spring and early summer. These data demonstrate the persistent presence of a macrozooplankton community throughout the winter months in the northern Barents Sea. On the Great Bank full depth diel vertical migrations were observed throughout the Polar Night and under sea ice. At the two more northerly stations the density of the sound scattering layers performing diel vertical migrations and the vertical range of the migrations was greatest during the transition period between the polar night and mid-night sun periods. Superimposed on the seasonal variability in density distribution was significant shorter-term variability driven by hydrographic processes occurring over synoptic time scales. Significant mixing events, or changes in the prevailing current direction that lead to a change in water mass characteristics, forced changes in the concentration and depth distribution of macrozooplankton over periods of hours that were on occasion of similar magnitude to the seasonal variability. On the northern continental slope, a mesopelagic sound scattering layer more than 300 m thick at its seasonal maximum, was located for most of the year within the warm core of the Atlantic Water Boundary Current, ascending into the epipelagic zone for 5–6 weeks during summer. The density and thickness of this sound scattering layer were greatest during the late summer/early autumn and lowest during early spring. Fish-like scatterers were present, concentrated within the deeper regions of the sound scattering layer, during the winter months and during July.

Microstructural Evolution and Magnetic and Corrosion Properties of FeCoNiAl0.2Yx High-Entropy Alloys

FeCoNiAl0.2Yx (x = 0, 0.05, 0.1, 0.2, 0.3) high-entropy alloys (HEAs) with different Y contents were prepared by a vacuum arc melting method, and experimental methods such as X-ray diffraction (XRD), scanning electron microscope (SEM), vibration sample magnetometer (VSM), hardness tester, and electrochemical workstation were used. The effects of rare Earth Y content on the microstructure, magnetic properties, and electrochemical corrosion properties of the alloy were investigated. The results showed that all FeCoNiAl0.2Yx alloys had a dendrite structure. When x = 0, the alloy consists of the FCC phase, after adding Y element, the HCP2 phase appeared in the alloy, and when x = 0.3, only the HCP1 phase existed in the alloy. The hardness of the alloy increased with the increase of Y content. The FeCoNiAl0.2Y0.1 alloy had the best magnetic properties, reaching a maximum saturation magnetization strength (Ms) of 139.25 emu g−1. The hysteresis area of FeCoNiAl0.2Yx alloys was very small, basically zero, and the hysteresis curves showed a very small lag. The corrosion potential of FeCoNiAl0.2Y0.1 alloy was −1.010 V, and the minimum corrosion current density of FeCoNiAl0.2Y0.1 alloy was 1.181 × 10−5 A cm−2. FeCoNiAl0.2Y0.1 alloy had relatively high corrosion potential and minimum corrosion current density and had excellent corrosion resistance.

Enhanced Tunneling Performance of Magnetic Helical Robots Utilizing Pecking Motion Generated by Alternating Rotating Magnetic Field

Magnetic helical robots (MHRs) actuated by an external magnetic field have been regarded as a possible application to treat occlusive vascular disease. We propose a pecking motion of an MHR to effectively tunnel an occlusive vascular lesion. The pecking motion is composed of a rotational driving motion and a linear impulsive motion of the MHR actuated by alternating rotating magnetic field (ARMF). The minimum magnetic flux density to synchronize the MHR to ARMF was mathematically determined from the equation of motion of the MHR and was experimentally verified. Finally, enhanced tunneling performance of the MHR with the pecking motion was verified by <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vitro</i> tunneling experiments with a pseudo-thrombus.

Microorganism inspired hydrogels: Optimization by response surface methodology and genetic algorithm based on artificial neural network

To optimize the synthetic process of microorganism inspired multistage porous hydrogel, the mathematical analysis strategies was applied to select the optimal experimental parameters. One-factor-at-a-time (OFAT) design was used to optimize the preparation process of yeast fermentation multistage porous hydrogels. The analysis of variance (ANOVA) was applied to determine the significant influencing factors, and the results revealed that the mass ratio of yeast to glucose (Ryeast/glucose), gelation temperature of yeast fermentation (Tgelation) and reaction time (treaction) had a significant influence on responses. Box-Behnken design (BBD) based response surface methodology (RSM) was used to design experiments and build the relationship between the input parameters and output responses. Ideal point method was used to transform a multi-objective optimization problem into a single-objective optimization problem. Artificial neural network (ANN) coupled genetic algorithm (GA) were employed to further optimize and predict the optimal preparation conditions of yeast fermentation multistage porous hydrogels. The results showed ANN coupled GA was a more effective tool in the modelling and optimization of the preparation of yeast fermentation multistage porous hydrogels. The optimized preparation conditions are Ryeast/glucose 1.84, Tgelation 25.00 °C, treaction 239.97 min. These values are expected to give us the minimum density, the maximum swelling degree and compressive strength. The research content of this paper provides theoretical support and factual basis for process optimization with complex influencing factors.

Improving Performance of Organic Photodetectors by Using TCNQ Doped Copper Thiocyanate as the Anode Interfacial Layer

AbstractThe responsivity and specific detectivity are critical figures of merits for organic photodetectors; however, it remains challenging to simultaneously enhance two such parameters, since enhancing external quantum efficiency corresponding to responsivities will inevitably increase leakage current and noises, resulting in decreased specific detectivity. To address such a trade‐off, an effective anode interfacial layer of 7,7,8,8‐tetracyanoquinodimethane (TCNQ) doped copper thiocyanate (CuSCN) is developed herein, which can enhance shunt resistance, increase depletion width, enhance hole extraction efficiency, as well as reduce trap density of states of organic photodetectors. The organic photodetectors based on doped CuSCN present a very low dark current density of 4.4 × 10−11 A cm−2 and an impressively high specific detectivity of 1.1 × 1014 Jones. As evidenced by X‐ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy measurements, the energy levels of the doped CuSCN:TCNQ film are deepened, associated with the occurrence of dopant bonding and charge transfer. In addition, it is found that increasing the delay time can suppress the hysteresis effects of current density–voltage characteristics of organic photodetectors and make the minimum dark current density obtainable at 0 V. These findings demonstrate the great potential of using molecular doping to adjust the anode interfacial layer for developing high‐performance organic photodetectors.

Analysis of one-shot device testing data under logistic-exponential lifetime distribution with an application to SEER gallbladder cancer data

In the literature, the reliability analysis of one-shot devices is found under accelerated life testing in the presence of various stress factors. The application of one-shot devices can be extended to the bio-medical field, where we often evidence that inflicted with a certain disease, survival time would be under different stress factors like environmental stress, co-morbidity, the severity of disease etc. This work is concerned with a one-shot device data analysis and applies it to SEER gallbladder cancer data. The two-parameter logistic-exponential distribution is applied as a lifetime distribution. For robust parameter estimation, weighted minimum density power divergence estimators (WMDPDE) is obtained along with the conventional maximum likelihood estimators (MLE). The asymptotic behaviour of the WMDPDE and the robust test statistic based on the density power divergence measure are also studied. The performances of estimators are evaluated through extensive simulation experiments. Later those developments are applied to SEER gallbladder cancer data. Citing the importance of knowing exactly when to inspect the one-shot devices put to the test, a search for optimum inspection times is performed. This optimization is designed to minimize a defined cost function which strikes a trade-off between the precision of the estimation and experimental cost. The search is accomplished through the population-based heuristic optimization method genetic algorithm.