The execution of mobile application using computational cloud resources is the latest augmentation strategy for resources constraint Smart Mobile Devices (SMDs). Computational offloading requires mobile application to be partitioned during the execution of the application on SMDs. Since an optimal partitioning approach promises optimization of energy savings and performance on SMDs, partitioning of mobile application at runtime is a challenging research perspective. This paper reviews existing Application Partitioning Approaches (APAs) from different domains including Mobile Cloud Computing (MCC). This work is driven by the objective to highlight the issues and challenges associated with the existing APAs in dealing with different context, utilizing the local and cloud resource during partitioning, and augmenting the execution of computation intensive mobile application. We proposes thematic taxonomy of current APAs, reviews current partitioning approaches by using thematic taxonomy, and investigates the implications and critical aspects of current partitioning approaches. The commonalities and deviations in such approaches are analysed based on significant parameters such as context-awareness, granularity level, annotation, and partitioning model. Finally, we put forward the open research issues in application partitioning approaches for MCC that remain to be investigated. I.

Abstract. The effects of aerosols on visibility through scattering and absorption of light and on climate through altering cloud droplet concentration are closely associated with their hygroscopic properties. Here, based on field campaigns in winter and summer in Beijing, we compare the size-resolved hygroscopic parameter (κgf) of ambient fine particles derived by an HTDMA (hygroscopic tandem differential mobility analyzer) to that (denoted as κchem) calculated by an HR-ToF-AMS (high-resolution time-of-flight aerosol mass spectrometer) measurements using a simple rule with the hypothesis of uniform internal mixing of aerosol particles. We mainly focus on contrasting the disparity of κgf and κchem between summer and winter to reveal the impact of atmospheric processes/emission sources on aerosol hygroscopicity and to evaluate the uncertainty in estimating particle hygroscopicity with the hypothesis. We show that, in summer, the κchem for 110, 150, and 200 nm particles was on average ∼10 %–12 % lower than κgf, with the greatest difference between the values observed around noontime when aerosols experience rapid photochemical aging. In winter, no apparent disparity between κchem and κgf is observed for those >100 nm particles around noontime, but the κchem is much higher than κgf in the late afternoon when ambient aerosols are greatly influenced by local traffic and cooking sources. By comparing with the observation from the other two sites (Xingtai, Hebei and Xinzhou, Shanxi) of north China, we verify that atmospheric photochemical aging of aerosols enhances their hygroscopicity and leads to 10 %–20 % underestimation in κchem if using the uniform internal mixing assumption. The effect is found more significant for these >100 nm particles observed in remote or clean regions. The lower κchem likely resulted from multiple impacts of inappropriate application of the density and hygroscopic parameter of organic aerosols in the calculation, as well as influences from chemical interaction between organic and inorganic compounds on the overall hygroscopicity of mixed particles. We also find that local/regional primary emissions, which result in a large number of externally mixed BC (black carbon) and POA (primary organic aerosol) in urban Beijing during traffic rush hour time, cause a 20 %–40 % overestimation of the hygroscopic parameter. This is largely due to an inappropriate use of density of the BC particles that is closely associated with its morphology or the degree of its aging. The results show that the calculation can be improved by applying an effective density of fresh BC (0.25–0.45 g cm−3) in the mixing rule assumption. Our study suggests that it is critical to measure the effective density and morphology of ambient BC, in particular in those regions with influences of rapid secondary conversion/aging processes and local sources, so as to accurately parameterize the effect of BC aging on particle hygroscopicity.

Organic aerosols (OAs) account for a large fraction of tropospheric fine particulate matter, but the hygroscopicity of OA is poorly understood. Here, we show remarkably‐enhanced water uptake capacity of OA due to formation of highly‐oxidized oxygenated OA on new particle formation (NPF) events in Beijing. While non‐nucleation processes also produce oxidized OA, their hygroscopicity exhibits little enhancement. As a result, a correlation between the hygroscopicity and oxidation state is absent for OA on non‐NPF days. Further analysis reveals that the highly‐oxidized oxygenated OA is 2.5 and 5‐fold as hygroscopic as the oxidized primary OA and less‐oxidized oxygenated OA, respectively. Our results suggest that nucleation‐initiated photooxidation of volatile organic compounds to produce water‐soluble organic acids may dominate on NPF days, and the aqueous oligomerization to yield less water‐soluble products might occur on non‐NPF days.

The evolution of haze, involving multiple processes such as nucleation, coagulation, and condensation, may exert complex effects on aerosols' cloud condensation nuclei (CCN) activity and number concentration (NCCN). Based on field campaigns carried out in the winters of 2014 and 2016 in Beijing, we show that NCCN was significantly enhanced by the evolution of haze, substantially driven by the nucleation process (or new particle formation). The enhancement factor of NCCN by such nucleation‐initiated haze episodes, E_NCCN, defined as the ratio of NCCN after haze events to NCCN prior to haze events, ranged from 2.2 to 6.5 at a supersaturation (S) = 0.76% and from 4.2 to 17.3 at S = 0.23%, the magnitude of which partially depends on the severity of the haze event. The enhancements are much greater than those previously observed and those from model simulations of contribution from new particle formation. This suggests that CCN sources from new particle formation may be underestimated, needing reevaluation in polluted environments where the subsequent growth of newly formed particles can last 2–3 days, yielding more CCN‐sized particles. We further quantified that the changes in particle size and composition during the nucleation‐initiated evolution of haze are responsible for > 80% and 12–20%, respectively, of the enhancement in CCN activity. The changes in particle composition had a limited impact because most of the ambient particles were already hydrophilic, with hygroscopic parameters of 0.2–0.65.

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