| 1. |
- Niemi, MEK, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 2. |
- Hussain, Ijaz, et al.
(författare)
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Study of the Distribution of Radiative Defects and Reabsorption of the UV in ZnO Nanorods-Organic Hybrid White Light Emitting Diodes (LEDs)
- 2011
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Ingår i: Materials. - Basel, Switzerland : MDPI. - 1996-1944. ; 4:7, s. 1260-1270
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the low temperature aqueous chemical growth (ACG) method was employed to synthesized ZnO nanorods to process-organic hybrid white light emitting diodes (LEDs) on glass substrate. Electroluminescence spectra of the hybrid white LEDs demonstrate the combination of emission bands arising from radiative recombination of the organic and ZnO nanorods (NRs). Depth resolved luminescence was used for probing the nature and spatial distribution of radiative defects, especially to study the re-absorption of ultraviolet (UV) in this hybrid white LEDs structure. At room temperature the cathodoluminescence (CL) spectra intensity of the deep band emission (DBE) is increased with the increase of the electron beam penetration depth due to the increase of defect concentration at the ZnO NRs/Polyfluorene (PFO) interface and probably due to internal absorption of the UV. A strong dependency between the intensity ratio of the UV to the DBE bands and the spatial distribution of the radiative defects in ZnO NRs has been found. The comparison of the CL spectra from the PFO and the ZnO NRs demonstrate that PFO has a very weak violet-blue emission band, which confirms that most of the white emission components originate from the ZnO NRs.
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| 3. |
- Niaz, Rizwan, et al.
(författare)
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A new spatiotemporal two-stage standardized weighted procedure for regional drought analysis
- 2022
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Ingår i: PeerJ. - : PeerJ. - 2167-8359. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Drought is a complex phenomenon that occurs due to insufficient precipitation. It does not have immediate effects, but sustained drought can affect the hydrological, agriculture, economic sectors of the country. Therefore, there is a need for efficient methods and techniques that properly determine drought and its effects. Considering the significance and importance of drought monitoring methodologies, a new drought assessment procedure is proposed in the current study, known as the Maximum Spatio-Temporal Two-Stage Standardized Weighted Index (MSTTSSWI). The proposed MSTTSSWI is based on the weighting scheme, known as the Spatio-Temporal Two-Stage Standardized Weighting Scheme (STTSSWS). The potential of the weighting scheme is based on the Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), and the steady-state probabilities. Further, the STTSSWS computes spatiotemporal weights in two stages for various drought categories and stations. In the first stage of the STTSSWS, the SPI, SPEI, and the steady-state probabilities are calculated for each station at a 1-month time scale to assign weights for varying drought categories. However, in the second stage, these weights are further propagated based on spatiotemporal characteristics to obtain new weights for the various drought categories in the selected region. The STTSSWS is applied to the six meteorological stations of the Northern area, Pakistan. Moreover, the spatiotemporal weights obtained from STTSSWS are used to calculate MSTTSSWI for regional drought characterization. The MSTTSSWI may accurately provide regional spatiotemporal characteristics for the drought in the selected region and motivates researchers and policymakers to use the more comprehensive and accurate spatiotemporal characterization of drought in the selected region.
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| 4. |
- Yousuf Soomro, Muhammad, et al.
(författare)
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Hybrid organic zinc oxide white-light-emitting diodes on disposable paper substrate
- 2013
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley-VCH Verlag. - 1862-6300 .- 1862-6319. ; 210:8, s. 1600-1605
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Tidskriftsartikel (refereegranskat)abstract
- ZnO-organic hybrid white-light-emitting diodes (WLEDs) were demonstrated on a paper substrate. The configuration used for ZnO-organic hybrid WLEDs consists a layer of poly (9,9)-(dioctylfluorene) (PFO) on poly (3,4-ethylenedioxythiophene) poly (styrenesulfonate) (PEDOT: PSS) on n-type ZnO nanorods grown by a low-temperature chemical aqueous method on paper substrate. Room temperature photoluminescence, electroluminescence, and cathodoluminescence (CL) spectra reveal a broad visible region covering the range from 420 to 800nm. By using room temperature-CL, we got luminescence information, especially to verify the origin of specific emissions, the internal absorption of the ultraviolet and the spatial distribution of radiative defects. It was observed that the visible wavelength range depends on the penetration depth of the excitation. This suggests that the concentration of deep levels responsible for the visible luminescence is at the sample surface to a depth of 1-2 mu m when using an accelerating voltage up to 20-30kV. The results indicate that demonstration of WLEDs on paper substrate with reasonable electrical performance greatly influences the reduction of substrate cost, furthermore, this may open way to fabricate optoelectronics devices on disposable substrates for large-area applications.
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| 5. |
- Ashraf, Zeeshan, et al.
(författare)
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Statistical Downscaling Modeling for Temperature Prediction
- 2024. - 1
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Ingår i: Decision Making and Security Risk Management for IoT Environments. - Cham : Springer. - 9783031475894 - 9783031475924 - 9783031475900 ; , s. 147-169
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Bokkapitel (refereegranskat)abstract
- The application compares the Statistical Downscaling Model (SDSM) and partial least square (PLS) to bridge the gap between (minimum and maximum) daily temperatures of 11 sites in Punjab between 1961 and 2013 with atmospheric variables. The data set was utilized for the first time using the proposed framework, which uses PLS and SDSM in conjunction with several regression models to predict future conditions up to the year 2099 under various scenarios. HadCM3 (Hadley Centre Coupled Model 3) data for 26 variables are applied for calibration and validation. After calibration, a Q-Q plot of observed and modeled data was used to validate the model. HadCM3 daily data for A2 and B2 stories were used to generate future scenarios for the years 2014 to 2099. We generated the prediction after using explained variance and partial correlation to select predictors. Using partial least squares (PLS), we select predictive factors and construct future scenarios through 2099. Finally, we conduct a comparative analysis of models developed utilizing the SDSM and PLS approaches for selecting features. The root mean square error was used to pick meaningful anticipated results from many models. After the data is downscaled, it is evaluated and a substantial correlation with the observed data is discovered. After applying R-square and root mean square error (RMSE), we conclude that the PLS (partial least square) variable selection method is preferable to the SDSM method. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.
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| 6. |
- Habeeb, Rimsha, et al.
(författare)
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A Proposed Comparative Algorithm for Regional Crop Yield Assessment: An Application of Characteristic Objects Method
- 2022
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Ingår i: Mathematical problems in engineering (Print). - : Hindawi Publishing Corporation. - 1024-123X .- 1563-5147. ; 2022
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Tidskriftsartikel (refereegranskat)abstract
- The agriculture sector plays a vibrant role in the economic prosperity of advanced and developing countries. It is a crucial source of revenue for the majority of the population. Nevertheless, unfortunately, in Pakistan, the share of the agricultural sector in Gross Domestic Product (GDP) is gradually declining. Therefore, comprehensive strategies and actions need to be developed and implement to enhance the agricultural productivity of Pakistan. In this study, an attempt has been made to examine the crop yield revenue of Punjab, Pakistan, by ranking the districts according to their contribution to the agricultural GDP of Pakistan's economy. A Multi-Criteria Decision Making (MCDM) technique, namely, characteristic objects method (COMET), which is entirely free of the rank reversal paradox, is used for this purpose. However, to make a fair comparison, in this research, a comprehensive framework is proposed to normalize the crop yield revenue of Punjab under probabilistic nature. The proposed framework is applied to various districts of Punjab, Pakistan, from 1992 to 2019. It is concluded that Jhang, Faisalabad, and Rahim Yar Khan (RYK) are the highest-ranked districts, while Nankana Sahib, Rawalpindi, and Islamabad are the lowest-ranked districts of Punjab, Pakistan, according to their contribution to the agricultural GDP of Pakistan's economy. Outcomes associated with this research would be helpful to build precise and accurate budget allocation policies.
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| 7. |
- Habeeb, Rimsha, et al.
(författare)
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Modified Standardized Precipitation Evapotranspiration Index: spatiotemporal analysis of drought
- 2023
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Ingår i: Geomatics, Natural Hazards and Risk. - : Taylor & Francis. - 1947-5705 .- 1947-5713. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Drought monitoring is a complicated issue as it requires multiple meteorological variables to monitor and anticipate drought accurately. Therefore, developing a method that enables researchers, data scientists, and planners to comprehend drought mitigation policies more accurately is essential. In this research, based on the concepts behind the calculation of the Standardized Precipitation Evapotranspiration Index (SPEI), a new drought index is proposed for regional drought monitoring: the Modified Standardized Precipitation Evapotranspiration Index (MSPEI). The potential of the proposed index is based on the estimation of Reference Evapotranspiration (ETo). Therefore, the Modified Hargreaves-Samani (MHS) equation based on fuzzy logic calibration is used to estimate ETo. The proposed index is validated on ten meteorological stations in Pakistan at a one-month time scale. Afterward, based on the Pearson correlation, the performance of the proposed index is compared with the commonly used drought index (SPEI). Results showed a significant correlation (r > 0.7) between the quantitative values of MSPEI and SPEI for all ten stations. Moreover, a modified Tjostheims coefficient is used to estimate and test the spatial correlation between SPEI and MSPEI for different drought classes. According to our findings, the association between the SW, ND, ED, EW, MW, and SD patterns of MSPEI and SPI is 0.74, 0.834, 0.673, 0.592, 0.393, and 0.434, respectively. Meanwhile, considering the significance of future drought trend detection, this research is further extended to detect the future trend of MSPEI by using the Hurst index. In accordance with the results, Bahawalnagar, Sialkot, Lahore, Kotli, and Gilgit all have HI values greater than 0.5 (0.63, 0.58, 0.56, 0.55, and 0.53, respectively). In contrast, Muzaffarabad, Skardu, and Jhelum have HI values 0.47, 0.45 and 0.38, respectively; however, HI values of 0.5 are observed at Dera Ismail Khan (DIK) and Islamabad. Therefore, this research provides a basis for developing and enhancing drought hazard characterization, encouraging researchers and policymakers to monitor and forecast regional droughts using a more accurate drought index.
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| 8. |
- Niaz, Rizwan, et al.
(författare)
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Assessing the Probability of Drought Severity in a Homogeneous Region
- 2022
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Ingår i: Complexity. - UK : Hindawi Publishing Corporation. - 1076-2787 .- 1099-0526. ; 2022
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Tidskriftsartikel (refereegranskat)abstract
- The standardized precipitation index (SPI) is one of the most widely used indices for characterizing and monitoring drought in various regions. SPI's applicability has regional and time-scale constraints when it observes in several homogeneous climatic regions with similar characteristics. It also does not provide sufficient knowledge about precipitation deficits and the spatiotemporal evolution of drought. Therefore, a new method, the regional spatially agglomerative continuous drought probability monitoring system (RSACDPMS), is proposed to obtain spatiotemporal information and monitor drought characteristics more expeditiously. The proposed framework uses spatially agglomerative precipitation (SAP) and copulas’ functions to continuously monitor the drought probability in the homogenous region. The RSACDPMS is validated in the region of the Northern area of Pakistan. The outcomes of the current study provide a better quantitative way to obtain appropriate information about precipitation deficits and the spatiotemporal evolution of drought.
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| 9. |
- Omer, Talha, et al.
(författare)
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Optimization of Monitoring Network to the Rainfall Distribution by Using Stochastic Search Algorithms : Lesson from Pakistan
- 2022
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Ingår i: Tellus. Series A, Dynamic meteorology and oceanography. - : Stockholm University Press. - 0280-6495 .- 1600-0870. ; 74:1, s. 333-345
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Tidskriftsartikel (refereegranskat)abstract
- Agricultural production is greatly influenced by environmental parameters such as temperature, rainfall, humidity, and wind speed. The accurate information about environmental parameters plays a vital and useful role when making policies for the agriculture sector as well as for other sectors. Pakistan meteorological department observed these environmental parameters at more than 90 stations. The allocation of these monitoring stations is not made systematically correct. This leads to inaccurate predictions for unobserved locations. The study aims to propose a monitoring network by which these prediction errors of the environmental parameters can be minimized. The well-known prediction techniques named, model-based ordinary kriging and model-based universal kriging (UK) with the known Matheron variogram model are used for prediction purposes. We investigate the monitoring network of Pakistan for rainfall and focus on both the optimal deletion/addition of monitoring stations from/to this network. The two stochastic search algorithms, spatial simulated annealing, and genetic algorithm are used for optimization purposes. Furthermore, the minimization of the Average Kriging Variance (AKV) is taken as the interpolation accuracy measure. The spatial simulated annealing exhibits a lower AKV as compared to the Genetic algorithm when adding/removing the optimal/redundant locations from the monitoring network.
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| 10. |
- Raza, Muhammad Ahmad, et al.
(författare)
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A New Bayesian Network-Based Generalized Weighting Scheme for the Amalgamation of Multiple Drought Indices
- 2023
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Ingår i: Complexity. - : Hindawi Publishing Corporation. - 1076-2787 .- 1099-0526.
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Tidskriftsartikel (refereegranskat)abstract
- Drought is one of the most multifaceted hydrologic phenomena, affecting several factors such as soil moisture, surface runoff, and significant water shortages. Therefore, monitoring and assessing drought occurrences based on a single drought index are inadequate. The current study develops a multiscalar weighted amalgamated drought index (MWADI) to amalgamate multiple drought indices. The MWADI is mainly based on the normalized average dependence posterior probabilities (ADPPs). These ADPPs are obtained from Bayesian networks (BNs)-based Markov Chain Monte Carlo (MCMC) simulations. Results have shown that the MWADI correlates more with the standardized precipitation index (SPI) and the standardized precipitation temperature index (SPTI). As proposed, the MWADI synthesizes drought characteristics of different multiscalar drought indices to reduce the uncertainty of individual drought indices and provide a comprehensive drought assessment.
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