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Tax compliance can be affected by many factors such as magnitude of compliance cost, the extent of penalty, perceived fairness of the tax system, awareness level of taxpayers and perceptions of government spending. The purpose of the study is identifying factors that affect compliance of individual income taxpayers in Bangladesh. The target population of the study is individual income taxpayers of the fifteen zones of Dhaka. The sample size is determined to 385 self-assessment assesse and 376 general procedure return submitted income taxpayers to which the questionnaire was distributed during the period of 1st December 2019 to 15th February, 2020. The results of the ordered logistic regression model reveal that the fairness, tax penalty and relationship with regard to taxpayer’s perception of government spending have positive and significant relationships with compliance. It also examines the effects of compliance decisions of referrals on others compliance decisions. The findings show a negative but insignificant relationship between them which implies that individual income taxpayer’s make their compliance decisions independent of others' decisions. Finally, the study having evaluated the effect of cost of complying with the tax law on tax compliance and concluded that there is a negative relationship between them implying that higher cost of compliance will lead to lower levels of compliance. Therefore, this paper suggests that maintaining tax fairness, optimum levels of penalty, spending the tax revenue on public development projects, keeping tax rates to the minimum as much as possible and keeping compliance costs to the minimum can enhance the compliance of taxpayers.

The aerosol direct feedback effects (ADFEs) are neglected in traditional air quality modeling studies (where meteorology is used as input and not affected by the chemistry and aerosol microphysics) for estimating the impacts of aircraft emissions on air quality. In this study, aircraft landing and take-off (LTO) attributable change of O3 and PM2.5 concentrations through ADFEs for the year 2005 within the contiguous United States (CONUS) are quantified by a coupled meteorology-chemistry modeling system: Weather Research and Forecasting – Community Multi-scale Air Quality (WRF-CMAQ) model. We first quantified the effects of ADFEs of all aerosols within the CONUS (not the effects of aircraft LTO emissions) on surface meteorology and air quality and found that ADFEs changed on average the downward short-wave radiation (SWR), 2-m temperature (T2), planetary boundary layer (PBL) height, O3 and PM2.5 by −7.38 W/m2, −0.47 K, −20.72 m, −0.41 ppb and +0.28 μg/m3 in 2005. We also found a seasonal influence where ADFE-influenced change (decrease) of SWR, T2, PBL, O3 and change (increase) of PM2.5 were higher in summer than in winter. We found that the aircraft LTO emissions’ contribution to domain average surface concentration of O3 and PM2.5 were +0.0065 ppb and +0.0022 μg/m3 respectively when ADFEs are accounted for. The ADFEs decrease aircraft LTO attributable surface O3 and PM2.5 change by 21% and 23% respectively comparing with that without ADFE in 2005. We also found that in both without-and-with ADFE cases, the aircraft LTO emissions increases domain average of O3 from April to October and decreases from November to March showing a strong seasonal pattern. Our modeling study revealed that use of a coupled model with ADFE shows localized changes in air quality by aircraft LTO emissions across the domain which were masked when looking at domain averages for both O3 and PM2.5, and which may be important for accurately quantifying health risk due to air pollution exposures in densely populated areas.

Aviation emission of gas phase pollutants and particulate matter contribute to global radiative forcing and regional air quality degradation near airports. It is important to understand the formation and time evolution of these pollutants inside aircraft engines to design strategies for emission reduction. A physics and chemistry based zero-dimensional (0D) gas parcel model with detailed jet fuel chemistry and soot microphysics has been developed to predict the time evolution, formation history, and emission index (EI) of key combustion gases and size-resolved soot particles of an aircraft engine. The model was applied to a CFM56-2-C1 aircraft engine for idle operating condition, for which comprehensive measured data from the Aircraft Particle Emissions eXperiment (APEX) campaign are available. The measured EI data of four major pollutants, including CO, NOx (NO + NO 2 ), total hydrocarbon (HC) mass, and soot mass, were used to optimize the model parameters. The model predicts the time evolution of concentration of CO, NOx, HC, soot size distribution, CO 2 , H 2 O, SO 2 , NO, NO 2 , HONO, HNO 3 , SO 3 , H 2 SO 4 , O 2 , H, H 2 , O, OH, HO 2 , H 2 O 2 , and some HC species in the combustor and turbine. Reasonable agreement was found between the simulations and the measurements. It was found for idle operating condition that, for most of the combustion products, concentrations did not change significantly in the turbine and nozzle, however, HONO, H 2 SO 4 , and HO 2 concentrations did change by more than a factor of 10, while NOx, NO, NO 2 , O, OH, soot particle mass and soot particle number by less than a factor of 2. The developed model is computationally efficient and can be used to, study detailed chemical and microphysical processes during combustion, investigate the effects of different fuel compositions and operating conditions on aircraft emissions, and assist air quality study near aircraft emission sources.