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In order to understand the soot formation in Diesel engine, a turbulent jet flame is used to simulate the combustion in the cylinder. The experimental study is performed to investigate the evolution of soot morphology for the maturation of nascent particle in a turbulent lifted jet flame fueled by n-heptane/toluene mixtures. An ultrasonic atomizer is used to evenly spread the fuel droplets to acquire single primary particles. Transmission electron microscopy is used to study the morphology of the particle sampled from the flame at different heights. Small soot aggregates are acquired from all the samples. Particle maturation such as agglomeration is accelerated under a high temperature by comparing the particle morphology sampled on the centerline and the wings of the flame. The precursors of nascent particles are depicted as dark nucleation dispersed to semitransparent polycyclic aromatic hydrocarbons. The nanostructure of nascent particles transforms from an amorphous state to an onion structure with the maturation of particles. Surface growth initially dominates the maturation of nascent particles in the direction of outside to inside for single particles. Agglomeration begins to emerge with the increased probability of collision at the end of maturation. Surface growth and agglomeration increase the mean particle diameter as the flame height increases. The oxidability of particles that undergo surface growth and agglomeration notably increases. The structure of nascent particles is inclined to be ordered and the mean particle diameter decreases with oxidation dominating the combustion reaction.

In the course of recommending locations for establishing new facilities on urban planning or commercial programming, the location prediction offers the optimal candidates, which maximizes the number of served customers or minimize customer inconvenience, therefore brings the maximum profits. In most existing studies, only the spatial-temporal features are recognized to evaluate the location popularity, where social relationships of customers, which are significant factors for popularity assessing, have been ignored. Additionally, current researches also fail to take capacities and categories of the facilities into consideration. To overcome the drawbacks, we introduce a novel model of Multi-characteristic Information based Top-k Location Prediction (MITLP), it captures the spatio-temporal behaviors of customers based on historical trajectories, exploits the social relevancy from their friend relationships, as well as examines the category competitiveness of specific facilities thoroughly. Subsequently, by drawing on the feature evaluation and popularity quantization, MITLP will be implemented within a hybrid B-tree-liked recommending framework, Constrained Location and Social-Trajectory Clustered forest (CLSTC-forest), which can not only produce better performance in practice but also address the facility service constraints. Finally, extensive experiments conducted on real-world datasets demonstrate the higher efficiency and effectiveness of the proposed model.

Entity linking is a new technique in recommender systems to link users’ interaction behaviors in different domains, for the purpose of improving the performance of the recommendation task. Linking-based cross-domain recommendation aims to alleviate the data sparse problem by utilizing the domain-sharable knowledge from auxiliary domains. However, existing methods fail to prevent domain-specific features to be transferred, resulting in suboptimal results. In this paper, we aim to address this issue by proposing an adversarial transfer learning based model ATLRec, which effectively captures domain-sharable features for cross-domain recommendation. In ATLRec, we leverage adversarial learning to generate representations of user-item interactions in both the source and the target domains, such that the discriminator cannot identify which domain they belong to, for the purpose of obtaining domain-sharable features. Meanwhile each domain learns its domain-specific features by a private feature extractor. The recommendation of each domain considers both domain-specific and domain-sharable features. We further adopt an attention mechanism to learn item latent factors of both domains by utilizing the shared users with interaction history, so that the representations of all items can be learned sufficiently in a shared space, even when few or even no items are shared by different domains. By this method, we can represent all items from the source and the target domains in a shared space, for the purpose of better linking items in different domains and capturing cross-domain item-item relatedness to facilitate the learning of domain-sharable knowledge. The proposed model is evaluated on various real-world datasets and demonstrated to outperform several state-of-the-art single-domain and cross-domain recommendation methods in terms of recommendation accuracy.

Linking user accounts belonging to the same user across different platforms with location data has received significant attention, due to the popularization of GPS-enabled devices and the wide range of applications benefiting from user account linkage (e.g., cross-platform user profiling and recommendation). Different from most existing studies which only focus on user account linkage across two platforms, we propose a novel model ULMP (i.e., user account linkage across multiple platforms), with the goal of effectively and efficiently linking user accounts across multiple platforms with location data. Despite of the practical significance brought by successful user linkage across multiple platforms, this task is very challenging compared with the ones across two platforms. The major challenge lies in the fact that the number of user combinations shows an explosive growth with the increase of the number of platforms. To tackle the problem, a novel method GTkNN is first proposed to prune the search space by efficiently retrieving top-k candidate user accounts indexed with well-designed spatial and temporal index structures. Then, in the pruned space, a match score based on kernel density estimation combining both spatial and temporal information is designed to retrieve the linked user accounts. The extensive experiments conducted on four real-world datasets demonstrate the superiority of the proposed model ULMP in terms of both effectiveness and efficiency compared with the state-of-art methods.

Trip planning is one of the most important techniques in supporting digital map services. It aims to find a set of location based services (LBSs) that can cover all user intended activities specified in query, such that the services have reasonable spatial distribution. In the temporal domain, the planned trip is supposed to satisfy all the workflow temporal dependencies among intended activities required by users. However, existing service composition solutions do not consider the complex spatio-temporal characteristics. To address this problem, this paper studies the problem of workflow aware location based service composition, which targets to return a rational trip formed by a set of location-based services that not only are rationally distributed in spatial, but also ensure all intended activities and their temporal workflow constraints to be met. Particularly, we propose a collective spatial keyword search based method to speed up the query processing. Experimental study on two real datasets demonstrates the effectiveness and efficiency of our proposed algorithms.

European standards have set stringent particulate number (PN) regulations for gasoline direct injection (GDI) engine, proposing a great challenge for the particulate emission control. The dual-injection mode, which incorporates direct-injection with port-fuel-injection, is considered to be an effective approach to reduce PN emissions. In this study the combustion, gaseous and particulate emission characteristics under different direct-injection ratios in a dual-injection gasoline engine were investigated. The results show that dual-injection increases the peak of in-cylinder pressure curves and makes the heat release curves shift towards an earlier region. The dual-injection mode yields a notable CO reduction while there is a slight increase in NOx emission. Dual-injection can significantly reduce the PN emission compared with GDI engines. As the direct-injection ratio decreases, the PN concentration continuously declines. The peak of size distributions curves for dual-injection tends to shift towards the smaller diameter region, showing the ability to generate particles in smaller size. The soot particles from dual-injection have lower oxidation activation energy than those from direct-injection. According to the results above, it can be inferred that dual-injection can promote the combustion process and has remarkably positive effects on particle emission control owing to its reduced PN emissions and improved particle oxidation reactivity.

Key-based workload partitioning is now commonly used in parallel stream processing, enabling effective key-value tuple distribution over worker threads in a logical operator. While randomized hashing on the keys is capable of balancing the workload for key-based partitioning when the keys generally follow a static distribution, it is likely to generate poor balancing performance when workload variance occurs on the incoming data stream. This paper presents a new key-based workload partitioning framework, with practical algorithms to support dynamic workload assignment for stateful operators. The framework combines hash-based and explicit key-based routing strategies for workload distribution, which specifies the destination worker threads for a handful of keys and assigns the other keys with the hashing function. We formulate the rebalance operation as an optimization problem, with multiple objectives on minimizing state migration costs, controlling the size of the routing table and breaking workload imbalance among the worker threads. Despite of the NP-hardness nature behind the optimization formulation, we carefully investigate and justify the heuristics behind key (re)routing and state migration, to facilitate fast response to workload variance with ignorable cost to the normal processing in the distributed system. Empirical studies on synthetic data and real-world stream applications validate the usefulness of our proposals and prove the huge advantage of our approaches over state-of-the-art solutions in the literature.

This experimental study demonstrates the potential to apply the thermochemical fuel reforming (TFR) concept to simultaneously reduce emissions and improve brake specific fuel consumption in a spark-ignition natural gas engine. CH 4 , H 2 and CO are the major components of TFR exhaust gas over a range of rich equivalence ratios. A numerical analysis is conducted to illustrate the chemical reaction pathways for H 2 and CO formation, which occurs in the cylinder during the TFR process. The main reaction pathways for H 2 and CO formation under 3 modeling conditions (20%, 50% and 80% fuel consumed) are different from each other. According to the experimental analysis, thermochemical fuel reforming gas improves combustion performance and accelerates the burn rate in every phase of the natural gas engine. Combustion stability, brake thermal efficiency, brake specific fuel consumption (BSFC), brake specific hydrocarbon (BSHC) and brake specific carbon monoxide (BSCO) emissions can also be improved by TFR. The brake specific oxides of nitrogen (BSNO x ) emissions for natural gas engines, combined with a TFR system, are still lower than those of an original natural gas engine in the same operation mode. Thermochemical fuel reforming has been shown to be effective in simultaneously reducing emissions and improving thermal efficiency for a spark-ignition natural gas engine. Furthermore, a 1.2 equivalence ratio for cylinder 4 (TFR cylinder) can be recommended in future research on TFR optimization, based on BSFC and combustion stability.

Considering the characteristics of frequent occurrence and serious losses, a technology for the standpipe in flat roof of green building community was designed to alleviate the urban waterlogging, and a test was carried out to find out the influence of the concrete height, underlying surface and return period on reduction rate of peak discharge and rainwater pipe diameter. Results showed that the reduction rate of peak discharge increased with the increase of concrete height, and the reduction rate kept constant as 36.98% when the concrete height was 5 cm or more. The reduction rate of peak discharge increased with the increase of roof area proportion, while the reduction rate of peak discharge decreased with the increase of return period. At the same time, these results can be used to guide practical engineering.

Homogenous charge compression ignition (HCCI) engines feature high thermal efficiency and ultralow emissions compared to gasoline engines. However, unlike SI engines, HCCI combustion does not have a direct way to trigger the in-cylinder combustion. Therefore, gasoline HCCI combustion is facing challenges in the control of ignition and, combustion, and operational range extension. In this paper, an active fuel design concept was proposed to explore a potential pathway to optimize the HCCI engine combustion and broaden its operational range. The active fuel design concept was realized by real time control of dual-fuel (gasoline and n-heptane) port injection, with exhaust gas recirculation (EGR) rate and intake temperature adjusted. It was found that the cylinderto- cylinder variation in HCCI combustion could be effectively reduced by the optimization in fuel injection proportion, and that the rapid transition process from SI to HCCI could be realized. The active fuel design technology could significantly increase the adaptability of HCCI combustion to increased EGR rate and reduced intake temperature. Active fuel design was shown to broaden the operational HCCI load to 9.3 bar indicated mean effective pressure (IMEP). HCCI operation was used by up to 70% of the SI mode load while reducing fuel consumption and nitrogen oxides emissions. Therefore, the active fuel design technology could manage the right fuel for clean engine combustion, and provide a potential pathway for engine fuel diversification and future engine concept.

Ethanol-gasoline blended fuels have been widely applied in markets recently, as ethanol reduces life-cycle greenhouse gas emissions and improves anti-knock performance. However, its effects on particulate matter (PM) emissions from gasoline direct injection (GDI) engine still need further investigation. In this study, the effects of ethanol-gasoline blended fuels on particle size distributions, number concentrations, chemical composition and soot oxidation activity of GDI engine were investigated. It was found that ethanol-gasoline blended fuels increased the particle number concentration in low-load operating conditions. In higher load conditions, the ethanol-gasoline was effective for reducing the particle number concentration, indicating that the chemical benefits of ethanol become dominant, which could reduce soot precursors such as large n-alkanes and aromatics in gasoline. The volatile organic mass fraction in ethanol-gasoline particulates matter was higher than that in gasoline particulate matter because ethanol reduced the amount of soot precursors during combustion and thereby reduced the elemental carbon proportions in PM. Ethanol addition also increased the proportion of small particles, which confirmed the effects of ethanol on organic composition. Ethanol-gasoline reduced the concentrations of most PAH species, except those with small aromatic rings, e.g., naphthalene. Soot from ethanol-gasoline has lower activation energy of oxidation than that from gasoline. The results in this study indicate that ethanol-gasoline has positive effects on PM emissions control, as the soot oxidation activity is improved and the particle number concentrations are reduced at moderate and high engine loads.

This work is to investigate the internal flow pattern and macroscopic spray characteristics of R134a discharged through twin-orifice atomizers. Two inlet orifices with the diameters of 0.6 mm and 3.0 mm were subsequently implemented and connected to the supply line of R134a to find the influence of the inlet orifice geometry on flow and spray characteristics. Transparent atomizers were manufactured to study the effects of different diameters of discharge nozzles on the internal flow and atomization. An injection pressure of 6.0 MPa was operated to produce “stable” flash-boiling sprays vertically, and the ambient condition was atmospheric. Internal flow in the expansion chamber and external liquid atomization were observed simultaneously during the actuation. The relationship between the internal boiling flow in the expansion chamber and external flash-boiling spray were analyzed. A “sudden” gas–liquid transition was observed when the inlet/discharge orifice ratio is one. This work provides a guide and reference for the volatile or liquefied material discharged through a twin-orifice atomizer.

The Lower Silurian Longmaxi Formation (the Palaeozoic) is organic-rich (black) shale in the southern Sichuan Basin (the Yangtze Plate) of China. This study analyses the lateral extent and thickness, burial depth, total organic carbon content and thermal maturity of the Longmaxi Formation black shale as the key features of the shale gas reservoir. The thickness of the black shale ranges from 10 to 170 m. The thickest reservoir is located in Changning-Naxi-Yongchuan region. The TOC of the shale at the bottom of the formation (50-m thickness) is above 2.0%. The lateral distribution of TOC varies with the lateral distribution of thickness, with the maximum TOC in the Gongxian-Luzhou-Yongchuan region. The burial depth ranges from 2000 to 4500 m. The shale is thermally over mature. The evaluation of reservoir characteristics indicates that the Longmaxi Formation has conditions appropriate for shale gas accumulation and thus resource potential in the southern Sichuan Basin of China. The objective of this preliminary evaluation of the reservoir characteristics is to locate potential areas favourable for exploration. The most favourable areas are defined here as those where the thickness of black shale is more than 100 m and the burial depth is less than 3000 m; these cover approximately 12,600 km 2 . The most favourable areas, which cover an area of approximately 5100 km 2 , are located in the northeast Luzhou region.

Experiments were conducted on a diesel engine operating on Euro V diesel fuel, pure biodiesel and biodiesel blended with ethanol (BE blends) to assess the particulate and unregulated emissions with and without diesel oxidation catalyst (DOC). The results indicate an increase of particle number concentration, formaldehyde emission and acetaldehyde emission while a decrease of particulate mass concentration, when the diesel engine is operated with biodiesel, compared with the diesel fuel. Adding ethanol in biodiesel can help to control particulate emissions, especially particle number concentration. However, the unregulated emissions, such as formaldehyde, acetaldehyde and unburned ethanol are worsened with BE blended fuels. The diesel oxidation catalyst (DOC) can effectively reduce particulate mass concentration, particle number concentration and unregulated emissions for all different fuels, while the conversion efficiency of DOC is different for each fuel. The oxidation catalyst is not equally active for different hydrocarbon species. The oxidation catalyst is most active for unburned ethanol, then formaldehyde and benzene emissions. The effects of DOC on particulate and unregulated emissions are more obvious for BE blends than those for Euro V diesel fuel and biodiesel, indicating that application of biodiesel–ethanol blends together with DOC has the potential to reduce particulate emission and unregulated emissions of diesel engine.

In this study, the effect of ethanol on combustion and emissions in premixed low temperature combustion (LTC) was investigated in a four cylinders heavy-duty diesel engine. The biodiesel was used as an additive to prevent the stratification of ethanol and diesel blends. The premixed LTC is achieved by the medium level of EGR and the prolonged ignition delay. Compared with diesel fuel, ethanol–diesel–biodiesel blends have lower NO x emissions due to lower combustion temperature, resulting from the higher latent heat of vaporization. Unfortunately, the lower combustion temperature also leads to the higher HC and CO emissions. Smoke emissions for ethanol blends decrease obviously because of higher oxygen content and longer ignition delay. The oxygen in ethanol also has a favorable impact on the reduction of smoke emissions, which is obvious in high loads. Thus, the upper load limit of LTC mode is extended. Compared with diesel fuel, 20 vol.% ethanol in diesel and biodiesel blends (BDE20) has lower NO x and smoke emissions and higher brake thermal efficiency in LTC.

The HCCI-DI combustion mode was achieved in a heavy-duty diesel engine using the early pilot injection in the intake stroke and the main injection around compression top dead center (TDC). The effects of pilot injection quantity and EGR rate on HCCI-DI combustion and emissions were investigated. NOx emission has a dramatically decrease as the pilot injection quantity increases, but it is still in a high level that needs to be reduced. The smoke emission has a slight increase with the rise of pilot quantity, but it is always in a low level. The increasing HC and CO emissions can be easily removed by the diesel oxidation catalyst (DOC). The HCCI-DI combustion with low level of EGR is an effective method to reduce NOx emission further, and smoke emission increases as EGR rate increases, but it is in an acceptable level. The HCCI-DI combustion mode operating range is limited by the peak of cylinder pressure, the pressure rise rate and the cycle-to-cycle variations. There are optimal EGR rates and pilot quantities to achieve low NOx and low smoke emissions.

The Lower Silurian Longmaxi Formation is an organic-rich (black) mudrock that is widely considered to be a potential shale gas reservoir in the southern Sichuan Basin (the Yangtze plate) in Southwest China. A case study is presented to characterise the shale gas reservoir using a workflow to evaluate its characteristics. A typical characterisation of a gas shale reservoir was determined using basset sample analysis (geochemical, petrographical, mineralogical, and petrophysical) through a series of tests. The results show that the Lower Silurian Longmaxi Formation shale reservoir is characterised by organic geochemistry and mineralogical, petrophysical and gas adsorption. Analysis of the data demonstrates that the reservoir properties of the rock in this region are rich and that the bottom group of the Longmaxi Formation has the greatest potential for gas production due to higher thermal maturity, total organic carbon (TOC) enrichment, better porosity and improved fracture potential. These results will provide a basis for further evaluation of the hydrocarbon potential of the Longmaxi Formation shale in the Sichuan Basin and for identifying areas with exploration potential.

The Dongpu (东濮) depression is a Mesozoic subsidence and Cenozoic fault basin developed within the North China craton. Since the deposition of Permo-Carboniferous hydrocarbon source rock, the depression has undergone many tectonic disturbances and uplifts. The source rocks have undergone nonuniform uplift, deformation, deep burying, and magmatism, and those led to an interrupted or stepwise evolution of the hydrocarbon source rocks in Qinggu (庆古)-2 well. We have investigated the history of burying, heating, and hydrocarbon generation of the Permo-Carboniferous hydrocarbon source rocks not just on the basis of tectonic disturbance and deep burying, but also with new studies in apatite fission track analysis, fluid inclusion measurements, and the application of the numerical simulation of EASY%R o. The heating temperature of the source rocks pulsated upward from Indosinian to Himalayan stages and reached a maximum during early Himalayan. This led to the stepwise increases of organic maturation and multiple stages of hydrocarbon generation. This study delineated the tectonic stages, maturity evolved ranges, and the intensity of hydrocarbon generation of Permo-Carboniferous source rocks in Qinggu-2 well. The hydrocarbon generation mainly occurred during Indosinian and early Himalayan. The early Himalayan stage hydrocarbon generation is the larger one, but the Dongying (东营) movement, which happened at the end of early Himalayan, may destroy the trapped oil and gas. Thereby, future exploration will need to pay more attention to the Dongying movement effect in Qinggu-2 well area, and it may get new breakthrough in Permo-Carboniferous oil and gas.

Though, as a renewable energy resource, alcohol fuel has many advantages in China, it is difficult for diesel engines to operate on alcohol due to its low cetane number and high latent heat of vaporization. This paper proposes an approach to its ignition problem by combining internal exhaust gas recirculation (EGR) with injection of small diesel fuel. Based on this approach, a two-stroke single-cylinder diesel engine was developed. Preliminary studies demonstrated that the engine can run on alcohol with almost zero level of smoke and low exhaust gas temperature, and that the engine operating on alcohol has lower nitrogen oxide (NOx) emissions and 2–3% higher effective thermal efficiency than that operating on diesel fuel in moderate and high load zones.

A combustion control strategy is proposed for diesel engine to reduce PM and NOx emissions significantly, which adopts some technologies including internal exhaust gas recirculation (EGR), split spray, adjustable fuel delivery advance angle and the application of alternative fuels. Based on this strategy, a flexible fuel engine has been developed. The experimental results show that this engine can be fueled with diesel fuel, alcohol, dimethyl carbonate (DMC), etc. It works with extremely low levels of particulate matter (PM) and NOx, 2–3% higher effective thermal efficiency on moderate and high loads when alternative fuels are used. This engine not only has lower exhaust emissions, but also can be fueled with those alternative fuels, which are difficult to be ignited by compression.

A new concept of the controllable premixed combustion (CPC) system was proposed for dimethyl ether (DME) to explore a new approach to achieving ultra-low NOX emissions with the zero level of particulate matter exhaust emissions. The DME fuel was injected into the premix chamber by means of the electronically controlled low pressure injection system, then the mixture formation and combustion process were controlled with a control-valve set between the main chamber and the premix chamber. The test bench was constructed based on a single diesel engine. Preliminary studies demonstrated that ultra-low NOX emissions had been realized with zero particulate matter emissions under the optimum specifications of the DME engine, NOX emissions were less than 65 × 10−6. According to the engine combustion analysis, it was found that the control-valve played an important role in the pre-mixture formation and ignition timing.