Partial Aggregation Research Articles

Feasibility study of compressed bricks utilizing rubber glove manufacturing residue

The demand of the rubber glove had increased significantly since early of the year 2020 due to the COVID-19 virus breakout especially in the medical and healthcare sector. Rubber Glove Manufacturing Residue (RGMR) is the by-product from the effluent treatment by coagulation process in the manufacturing procedure. Non-recyclable RGMR are disposed to landfill after treated. This research is aimed to reuse the RGMR in cemented interlocking bricks to address the natural resources depletion issues and greenhouse gases released from the burnt brick production. The comparison in terms of physical and mechanical properties was conducted in between RGMR and crumb rubber interlocking bricks (RIB). RGMR and crumb rubber were used as partial fine aggregate replacement by 10% while fly ash was used as a cement replacement material by 56%. Four mixes were tested, and the interlocking bricks were categorized as medium weight bricks. However, only control mix and RGMR-2 mix fulfilled the loadbearing masonry requirement of a minimum of 13.8 MPa. RGMR-2 utilizing 10% fine aggregate replacement using RGMR without cement replacement. As for the mixes utilizing fly ash and fine aggregate replacement, RGMR-1 mix and RIB mix show compressive strength of 12.15 MPa and 11.64 MPa respectively. Besides that, the use of RGMR reduced the water absorption compared to RIB mix due to the larger particle size of crumb rubber. The water absorption rate for RIB mix has exceeded the limit of water absorption for the medium weight bricks of 240 kg/m3. The finding indicates that the RGMR exhibited a better performance as compared to the crumb rubber.

Contrasting ground- and excited-state intramolecular aggregation in choline chloride-based deep eutectic solvents versus a liquid polymer.

Although the pyrenyl (Py) groups in several dipyrenyl (or bispyrenyl) compounds do not dimerize in the ground-state, they are known to intramolecularly aggregate exclusively in the excited-state to form excimers in common organic solvents. We present contrasting intramolecular aggregation behaviour of such a prototypical compound, 1,3-bis(1-pyrenyl)propane [1Py(3)1Py], dissolved in judiciously selected liquids having relatively high dynamic viscosities (η). Specifically, the intramolecular aggregation of 1Py(3)1Py is investigated in a liquid polymer polydimethylsiloxane with number average MW 2000, PDMS2000 (η293.15K = 21.4 mPa s), and is compared with aggregation of 1Py(3)1Py in deep eutectic solvents (DESs) constituted of the H-bond acceptor (HBA) choline chloride (ChCl) and H-bond donors (HBDs) urea and glycerol in a 1 : 2 mole ratio of ChCl : urea (η293.15K = 1372.0 mPa s) and ChCl : Gly (η293.15K = 473.0 mPa s), respectively, in 293.15 to 363.15 K temperature range. The HBD constituent of ChCl : Gly, glycerol (Gly) (η293.15K = 1412.0 mPa s) is also investigated for comparison purposes. It is found that while in PDMS2000, 1Py(3)1Py intramolecularly aggregates exclusively in the excited-state, thus forming a classical excimer, ground-state heterogeneity is clearly evident in both the DESs and Gly. High viscosity, a consequence of the extensive H-bonding in DESs/Gly, appears to induce the two Py units, both in the ground-state, to exist partly in a configuration where the interaction, albeit a weak one, takes place between the two. This ground-state interaction is not present in relatively low viscosity media PDMS2000 as observed in the common organic solvents. The role of viscosity/H-bonding of the solubilizing milieu on differential intramolecular aggregation in ground- and excited-states is highlighted.

Cyclic behaviour of beam-column joints made of crumb rubberised concrete (CRC) and traditional concrete (TC)

Crumb rubberised concrete (CRC) is a sustainable material that recycles rubber particles from end-of-life tyres as partial fine aggregates in concrete. To promote the applications of CRC in building structures, this paper presents an experimental study on the cyclic behaviour of beam-column joints from both CRC and traditional concrete (TC) frame structures. CRC with 15% rubber content by sand volume was employed. Three full scale CRC joint samples and one full scale TC sample were tested. Varying axial loads were applied on the top of columns and anti-symmetrical low-frequency cyclic loads were applied at the two beam ends. The failure modes, hysteretic behaviour, stiffness degradation, bearing capacity degradation, shearing capacity, displacement ductility and strain response of CRC and TC joints were investigated and compared. Both CRC and TC joint samples reached their ultimate loads due to shear failure. When CRC and TC were with similar strengths, the first crack loads, yielding loads, ultimate loads and ultimate displacements for TC and CRC joints at the same axial compression ratios were comparable with slight differences within 5%. However, CRC joints exhibited an improved energy dissipation ability by up to 10.4% over TC samples.

The effect of waste electronic plastics and waste marble dust as a partial aggregate replacement on concrete

Concrete is the most abundant material used in construction on present scenario where aggregates comprise of about three-fourth volume of concrete. On 2019, 28 Mt of E-waste generation was recorded in Nepal and its management has created a burden to the landfill sites. Also, marble dust is a waste obtained during processing and installation of marble which can be used as filler or fine aggregate in concrete for strength enhancement. Utilization of crushed E–waste plastics and waste marble dust in concrete will introduce a green and environment friendly method of construction without any compromise in the utility parameter and would represent positive effect to minimize the environmental degradation and replace naturally available aggregates which are continuously been used. The strength effects of waste electronic plastics and waste marble dust as aggregate replacement in concrete was studied in this research. For this study, 12 sets of concrete mixes were prepared with constant water cement ratio of 0.55. Marble dust was used as a sand replacement at 2.5%,5%,7.5% and 10% by volume of sand. Further 2 sets of 4% and 6% replacement of sand by marble dust was prepared to find out the optimum value as 5% replacement showed greater compressive strength. E-wastes plastics were then used as replacement to coarse aggregate at 1%, 2%, 3%, 4% and 5% along with 5% replacement of sand by waste marble dust. The workability test, compressive strength and flexural test of the mixes were determined. Based on the study, result showed that the compressive strength at 5% replacement of sand by marble dust was maximum while E-waste plastics replaced up to 4% had compressive strength greater than that of nominal mix concrete of grade M20. Flexural strength also increased of concrete containing E-plastic than that of normal concrete.

Permeable Reactive Concrete Using Recycled Waste Materials for Nutrient Contamination Removal in Urban Surface Runoff

In recent years, stormwater control measures (SCMs) such as permeable concrete pavement have been experimentally investigated and used to manage hydrologic and water quality impacts of stormwater runoff. Research revealed the potential of permeable pavement in reducing and delaying peak flow rate, reducing runoff volume, and capturing heavy metals and other particulate-bound pollutants from stormwater runoff. However, few studies have evaluated the effects of permeable pavement on nutrients in stormwater runoff. This research aims to produce permeable reactive concrete (PRC) from waste fly ash, waste gypsum board and waste coco peat and to investigate its effectiveness in removing nutrient contamination present in stormwater or urban surface runoff. The raw materials underwent through granulation process to produce granulated filtering media (GFM). Cylindrical samples of PRC were then made and subjected to various physical and water quality tests. The use of GFM as partial coarse aggregates of PRC for urban surface runoff management and nutrient contamination removal has been tested and evaluated. After performing all the tests, the researchers concluded that GFM as partial coarse aggregates of PRC is effective due to the significant increase in infiltration rate of the entire sample compared to the traditional permeable concrete that has an average infiltration rate of 2-6 mm/s. The results in the water quality test revealed that PRC with GFM as partial coarse aggregates lessen the nitrate, phosphate, and ammonia that are present on urban surface runoff.

New query optimization techniques in the Spark engine of Azure synapse

The cost of big-data query execution is dominated by stateful operators. These include sort and hash-aggregate that typically materialize intermediate data in memory, and exchange that materializes data to disk and transfers data over the network. In this paper we focus on several query optimization techniques that reduce the cost of these operators. First, we introduce a novel exchange placement algorithm that improves the state-of-the-art and significantly reduces the amount of data exchanged. The algorithm simultaneously minimizes the number of exchanges required and maximizes computation reuse via multi-consumer exchanges. Second, we introduce three partial push-down optimizations that push down partial computation derived from existing operators ( group-bys , intersections and joins ) below these stateful operators. While these optimizations are generically applicable we find that two of these optimizations ( partial aggregate and partial semi-join push-down ) are only beneficial in the scale-out setting where exchanges are a bottleneck. We propose novel extensions to existing literature to perform more aggressive partial push-downs than the state-of-the-art and also specialize them to the big-data setting. Finally we propose peephole optimizations that specialize the implementation of stateful operators to their input parameters. All our optimizations are implemented in the spark engine that powers azure synapse. We evaluate their impact on TPCDS and demonstrate that they make our engine 1.8X faster than Apache Spark 3.0.1.

Evaluation of spectroscopic, microscopic and hydrophobic properties of cetrimide and polyethylene glycol-400 plasticized ethyl cellulose films

The Cetrimide (CI) and Polyethylene glycol-400 (PEG-400) plasticized Ethyl cellulose (E) films were developed by solvent evaporation technique and evaluated their multifunctional properties systematically. The FTIR study affirmed the existence of secondary interactions in the composite films. FTIR-microscopy depicted the partial aggregation of CI and PEG-400 in the matrix. The UV–vis spectral analysis showed the composite films were a moderate barrier to UV light. As the result shows that the insertion of CI has resulted in more transparency. Water Contact Angle analyses demonstrated the insertion of CI & PEG-400 has decreased the hydrophobicity of E. Moisture content results revealed the films were moisture resistant and water solubility test exhibited that the plasticization effect of PEG-400 on E has resulted in a significant increase in solubility. The study of the swelling ratio assured the composite films were resistant to swell in water. Considering the results, composite films could be considered in the packaging field.

Principles governing control of aggregation and dispersion of aqueous graphene oxide

Controlling the structure of graphene oxide (GO) phases and their smaller analogues, graphene (oxide) quantum dots (GOQDs), is vitally important for any of their widespread intended applications: highly ordered arrangements of nanoparticles for thin-film or membrane applications of GO, dispersed nanoparticles for composite materials and three-dimensional porous arrangements for hydrogels. In aqueous environments, it is not only the chemical composition of the GO flakes that determines their morphologies; external factors such as pH and the coexisting cations also influence the structures formed. By using accurate models of GO that capture the heterogeneity of surface oxidation and very large-scale coarse-grained molecular dynamics that can simulate the behaviour of GO at realistic sizes of GOQDs, the driving forces that lead to the various morphologies in aqueous solution are resolved. We find the morphologies are determined by a complex interplay between electrostatic, {pi }–{pi } and hydrogen bonding interactions. Assembled morphologies can be controlled by changing the degree of oxidation and the pH. In acidic aqueous solution, the GO flakes vary from fully aggregated over graphitic domains to partial aggregation via hydrogen bonding between hydroxylated domains, leading to the formation of planar extended flakes at high oxidation ratios and stacks at low oxidation ratios. At high pH, where the edge carboxylic acid groups are deprotonated, electrostatic repulsion leads to more dispersion, but a variety of aggregation behaviour is surprisingly still observed: over graphitic regions, via hydrogen bonding and “face-edge” interactions. Calcium ions cause additional aggregation, with a greater number of “face-face” and “edge-edge” aggregation mechanisms, leading to irregular aggregated structures. “Face-face” aggregation mechanisms are enhanced by the GO flakes possessing distinct domains of hydroxylated and graphitic regions, with {pi }–{pi } and hydrogen bonding interactions prevalent between these regions on aggregated flakes respectively. These findings furnish explanations for the aggregation characteristics of GO and GOQDs, and provide computational methods to design directed synthesis routes for self-assembled and associated applications.

Promising self-emulsifying drug delivery system loaded with lycopene from red guava (Psidium guajava L.): in vivo toxicity, biodistribution and cytotoxicity on DU-145 prostate cancer cells

BackgroundSelf-emulsifying drug delivery systems (SEDDSs) have attracted attention because of their effects on solubility and bioavailability of lipophilic compounds. Herein, a SEDDS loaded with lycopene purified from red guava (nanoLPG) was produced. The nanoemulsion was characterized using dynamic light scattering (DLS), zeta potential measurement, nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), lycopene content quantification, radical scavenging activity and colloidal stability in cell culture medium. Then, in vivo toxicity and tissue distribution in orally treated mice and cytotoxicity on human prostate carcinoma cells (DU-145) and human peripheral blood mononuclear cells (PBMC) were evaluated.ResultsNanoLPG exhibited physicochemical properties with a size around 200 nm, negative zeta-potential, and spherical morphology. The size, polydispersity index, and zeta potential parameters suffered insignificant alterations during the 12 month storage at 5 °C, which were associated with lycopene stability at 5 °C for 10 months. The nanoemulsion showed partial aggregation in cell culture medium at 37 °C after 24 h. NanoLPG at 0.10 mg/mL exhibited radical scavenging activity equivalent to 0.043 ± 0.002 mg Trolox/mL. The in vivo studies did not reveal any significant changes in clinical, behavioral, hematological, biochemical, and histopathological parameters in mice orally treated with nanoLPG at 10 mg/kg for 28 days. In addition, nanoLPG successfully delivered lycopene to the liver, kidney and prostate in mice, improved its cytotoxicity against DU-145 prostate cancer cells—probably by pathway independent on classical necrosis and apoptosis—and did not affect PBMC viability.ConclusionsThus, nanoLPG stands as a promising and biosafe lycopene delivery system for further development of nanotechnology-based health products.Graphical

Influence of the Replacement of Ungraded-PKS Aggregate on Properties of Lightweight Pervious Concrete

Pervious concrete is not environmentally friendly due to presences of non-renewable material in its production. Pervious concrete has made a comeback as a green infrastructure and researchers came up with a proposal to use waste materials that potentially to work well as material in pervious concrete. The used of palm kernel shell (PKS) in pervious concrete is consider brilliant because Malaysia is of the larger oil palm producer in the world. In this study, natural aggregate was partially replaced by 0, 10, 15, and 20% by weight of PKS aggregate to produce lightweight pervious concrete based PKS. The testing conducted comprise of density, void content, compressive strength, and flexural strength. Inclusion of PKS aggregate reduces the mechanical properties of pervious concrete but significantly higher than recommended in the standard, utilizing some PKS aggregate as partial aggregate at up to 20% substitution level can produce lightweight PKS-pervious concrete. The pervious concrete containing 10% of PKS aggregate presented the most optimum mixture. Besides, the use of PKS as aggregate replacement in pervious concrete mixture indicates a good potential towards sourcing alternative sustainable materials for concrete.

Study of Using of Recycled Brick Waste (RBW) to produce Environmental Friendly Concrete: A Review

Several million tons of solid waste are produced each year as a result of construction and demolition activities around the world, and brick waste is one of the most widely wastes. Recently, there has been growing number in studies that conducted on using of recycling brick waste (RBW) to produce environmentally friendly concrete. The use of brick waste (BW) as potential partial cement or aggregate replacement materials is summarized in this review where the performance is discussed in the form of the mechanical strength and properties that related to durability of concrete. It was found that, because the pozzolanic activity of clay brick powder, it can be utilized as substitute for cement in replacement level up to 10%. Whereas, for natural coarse aggregate, recycled aggregate can be used instead of it, but in limited replacement level. Concrete manufacturing from recycled aggregate can give adequate strength and can be suitable for the producing medium or low strength concrete. On the other side, the utilization of fine recycled brick waste as aggregate in the concrete manufacturing provide development of the properties of concrete and it develops the durability of concrete in some cases when used with replacement level up to 10% by the weight of fine aggregate.

Performance of Concrete Mixes Containing TBM Muck as Partial Coarse Aggregate Replacements.

This study investigated the potential utilization of the TBM muck obtained from the Gold Line of the Doha Metro Project as a partial replacement of coarse aggregates in concrete mixes. First, the TBM muck particles were screened to coarse aggregate standard sizes. Then, concrete mixes were prepared using 0%, 25%, 50%, and 75% TBM muck replacement of coarse aggregates. The compressive and flexural strengths were determined for all mixes at 28 and 56 days. Moreover, the results obtained were validated using EDX analysis and SEM images. A t-statistical analysis did not show a significant impact of TBM muck usage on the compressive strength results of the concrete mixes. However, another t-statistical analysis showed that TBM muck replacement of coarse aggregates had adversely affected the flexural strength results. The EDX analysis indicated the presence of Na+ ions, which can replace the Ca2+ ions in the C-S-H gel, cause discontinuities of it, and hence reduce the strength at later ages. Finally, the SEM images showed that the ettringite and carbon hydroxide (C-H) contents in the mixes with TBM muck were higher than that of the control mix, while the C-S-H gel was less in such mixes.

Palm Kernel Shell as Partial Coarse Aggregate Replacement in Asphalt Mixture: Optimum Binder Content and Volumetric Properties Investigation

Pavement failures such as fatigue, rutting, cracking, bleeding, and stripping are typical pavement deterioration. Researchers have been experimenting with pavement modification to overcome these problems. This study determines the optimum binder content (OBC) for modifying an asphalt mixture with a partial replacement of coarse aggregate (5mm-14mm sieve size) with palm kernel shell (PKS). A 60/70 penetration grade bitumen was mixed with 10, 20 and 30% PKS at selected aggregate gradation following the Public Work Department of Malaysia (JKR/SPJ/2008-S4) specification. The preparation of 60 samples of unmodified and modified asphalt mixture employed the Marshall Method compacted with 75 blows. The OBC was determined based on five volumetric properties of asphalt mixture namely stability, flow, bulk density, void filled with asphalt, and void in total mix. The OBC and volumetric properties of the modified PKS asphalt mixture samples were compared with unmodified asphalt mixture samples in accordance to the specification. Results showed that the OBC sample with 30% aggregate replacement produced the highest OBC value of 5.53% relative to the control sample with 5.40% OBC. The trend for OBC with PKS replacement begins with 10% PKS with 5.30% OBC, 20% PKS with 5.32% OBC and 30% PKS. All volumetric properties of the PKS samples are within the specification limit. Thus, PKS has a promising potential as a coarse aggregate replacement in asphalt mixture.

Development of Functional Rubber-Based Impact-Absorbing Pavements for Cyclist and Pedestrian Injury Reduction

Cyclists, pedestrians and elderly people’s specific needs in urban road infrastructures are often neglected. They rarely benefit from safety measures or innovations. Inspired by playgrounds and aiming to reduce vulnerable road users (VRUs) injuries, the development of the rubber-based impact-absorbing pavements (IAP) offers a possibility to rethink the design of urban pavements and address safety on roads, which constitutes a major challenge in terms of attaining more sustainable, resilient, and safe cities. Therefore, bituminous mixtures with four different crumb rubber contents, 0%, 14%, 28%, and 33% (in total weight), were produced by partial aggregates substitution using the dry process. After the assessment of the geometrical and volumetric properties, the mechanical performances were evaluated. Finally, the samples were tested to measure the abrasion and impact attenuation with the well-known head injury criterion (HIC), at different temperatures from −10 to 40 °C, to obtain a wide range of values referring to possible weather conditions. A significant effect of the rubber percentage and layer thickness on impact attenuation was observed. All observations and results confirm the feasibility of the IAP concept and its positive effect on future injury-prevention applications.

Composite Films of HDPE with SiO2 and ZrO2 Nanoparticles: The Structure and Interfacial Effects.

Herein, we investigated the influence of two types of nanoparticle fillers, i.e., amorphous SiO2 and crystalline ZrO2, on the structural properties of their nanocomposites with high-density polyethylene (HDPE). The composite films were prepared by melt-blending with a filler content that varied from 1% to 20% v/v. The composites were characterized by small- and wide-angle x-ray scattering (SAXS and WAXS), small-angle neutron scattering (SANS), Raman spectroscopy, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). For both fillers, the nanoaggregates were evenly distributed in the polymer matrix and their initial state in the powders determined their surface roughness and fractal character. In the case of the nano-ZrO2 filler, the lamellar thickness and crystallinity degree remain unchanged over a broad range of filler concentrations. SANS and SEM investigation showed poor interfacial adhesion and the presence of voids in the interfacial region. Temperature-programmed SANS investigations showed that at elevated temperatures, these voids become filled due to the flipping motions of polymer chains. The effect was accompanied by a partial aggregation of the filler. For nano-SiO2 filler, the lamellar thickness and the degree of crystallinity increased with increasing the filler loading. SAXS measurements show that the ordering of the lamellae is disrupted even at a filler content of only a few percent. SEM images confirmed good interfacial adhesion and integrity of the SiO2/HDPE composite. This markedly different impact of both fillers on the composite structure is discussed in terms of nanoparticle surface properties and their affinity to the HDPE matrix.

Cockle Shell as Mixing Ingredient in Concrete: A Review

The demand for the population is boosting the production of edible and non-edible products that produce by-products that result in emissions being thrown as waste. The successful cockle trade also creates vestiges of cockle shell that are thrown away as waste. Despite the effects of climate change, industrial activity including calcareous and granite mining to satisfy the need for cement and concrete production, respectively, cannot be prevented as more structures are developed worldwide. The mechanical properties of concrete containing crushed cockle shell as partial fine aggregate, coarse aggregate and cement replacement were examined and reported in this paper. Cockle shell powder was used as cement replacement up to 75%. To sum up, the use of cockle shell is an appealing option for the construction industry and sustainable green climate.

The Utilisation of Recycled Concrete Aggregate as Partial Sand Replacement in Wall Panel Production

Recently, extensive research within the concrete industry has been devoted to a sustainable approach by using concrete waste as a natural aggregate replacement. The reason is that the volumes of building-related waste generated nowadays are becoming a significant threat to the environment but they may be used as a useful material in the construction industry. Hence, this study aims to investigate the effects of using recycled concrete aggregates as a partial fine aggregate replacement in mortar cubes and wall panels. Mortar cubes and wall panels sized 70.7 mm x 70.7 mm x 70.7 mm and 1000 mm x 300 mm x 100 mm, respectively, were prepared. The recycled concrete aggregate was mixed into the mortar at percentages of 0%, 50% and 100% of the total mortar volume and designated as 0RCA, 50RCA and 100RCA, respectively. The samples of both the mortar cubes and wall panels were assessed under a compressive strength test. The cubes samples were tested at the ages of 3 days, 14 days and 28 days. Meanwhile, the wall panels were compressively loaded for more than 28 days. It was found that the 0RCA mortar cubes represented the highest compressive strength compared to the other 50RCA and 100RCA samples by 46.6% and 38.8%, respectively. The 50RCA wall panels represented the highest ultimate load of 203.26 kN with strength effectiveness of 179.75% compared to 0RCA and 50RCA wall panels. This indicates that recycled concrete aggregates can be a useful material in the production of wall panels.

Experimental Investigations on Lightweight selfcompacting concrete produced with Sintered fly ash aggregate

The present research work explores the use of sintered fly ash aggregate (SFA) as a partial replacement to natural coarse aggregate (NCA) for the development of sustainable structural lightweight concrete (LWC). In this regard, the natural aggregates are partially replaced by the sintered fly ash aggregates, i.e.,0%, 10%, 15%, 20%,25% and 30% of its volume. To find out its performance, In the present research work, 40MPa concrete has been prepared and performed the Mechanical properties (such as Compressive strength and split tensile strengths) and Durability properties (like water absorption test and permeability) Based on the obtained results, The 20% of sintered fly ash aggregates based LWSCC has got higher strength (i.e., 56.88MPa) than others mixes, which was considered as optimum mix in the present research work. However, 20% sintered fly ash aggregates replaced mix has high strengths and durability performance.

Effect of crushed cockle shell as partial fine aggregate replacement on workability and strength of lightweight concrete

Dumping of cockle shell waste by cockle trade emits stinking smell and pollutes the environment. This study investigates the workability and compressive strength of lightweight concrete containing crushed cockle shell as fine aggregate substitution. Four concrete mixes were prepared by integrating diverse content of crushed cockle shell as partial fine aggregate substitution by weight of sand. Workability and compressive strength of concrete were determined via slump test and compressive strength test. Concrete mix become less workable as larger content of crushed cockle shell is integrated. Utilization of crushed cockle shell up to 10% enhances the concrete’s compressive strength.

FedPA: An adaptively partial model aggregation strategy in Federated Learning

Federated Learning has sparked increasing interest as a promising approach to utilize large amounts of data stored on network edge devices. Federated Averaging is the most widely accepted Federated Learning framework. In Federated Averaging, the server keeps waiting for client models to compute the global model in each round unless all client models are received or a pre-configured timer expires, therefore it suffers seriously from participant devices with weak computation and/or communication capability, which is a kind of straggler problem. In this paper we design FedPA, a framework based on partial model aggregation strategy, in which the server waits for only an appropriate number of device models (referred to as aggregation number) in each round. Our experiment shows that the accuracy loss of the aggregated global model in a single round is not significant if the aggregation number is decided carefully. We propose a waiting strategy to determine the aggregation number for each round dynamically and the aggregation number is adaptive to achieve a tradeoff between single-round training time and the expected number of rounds to reach the target accuracy. Stale models are also included during aggregation when they arrive, and their positive value and negative effect are carefully evaluated and reflected in the aggregation strategy. Experiments show that FedPA outperforms the baseline strategy FedAvg and other three algorithms named FedAsync, FLANP and AD-SG. It can work well in all scenarios with different distributions of data samples (characterized by non-IID ratio) and computation/communication capability (characterized by level of heterogeneity) among devices. Experiments also show that FedPA is robust when a certain amount of noise is added into the input from clients for privacy concerns.