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Many ensemble-based data assimilation (DA) methods use observation space localization to mitigate the sampling errors due to the insufficient ensemble members. Observation space localization is simpler and more timesaving than model space localization in implementation, but more difficult to directly assimilate satellite radiance observations, a kind of non-local observations. The vertical locations of radiance observations are undetermined and the transmission of observational information is thereby obstructed. To determine the vertical coordinates of radiance observations, a weighted average hypsometry is proposed. Using this hypsometry, AMSU-A radiance observations are directly assimilated with an ensemble four-dimensional variational (En4DVar) DA system. It consists of a four-dimensional ensemble-variational (4DEnVar) system providing ensemble covariance and a 4DVar system. Observing system simulation experiments show that the hypsometry alleviates the degradations in the late period of medium-range forecast in the Northern Extratropics that occur in the traditional peak-based hypsometry. It obviously improves the analysis qualities and forecast skills of the En4DVar system and its two components, especially in the Southern Extratropics, when incorporating AMSU-A radiance observations. The improvement in the En4DVar-initialized forecast is comparable to that in the 4DVar-initialized forecast in the Southern Extratropics and Tropics. It indicates that a proper hypsometry enables efficient extraction of useful information from AMSU-A radiance observations by 4DEnVar with observation space localization. Therefore, the 4DEnVar provides high-quality ensemble covariances for En4DVar.

Yankuang coal with the high coking property is difficult to use through direct combustion. The main purpose of this paper is to study the combustion characteristics and NOx emissions of this type of coal using preheating combustion technology. The experimental results show that after the pulverized coal is preheated, the char residue characteristic is significantly reduced from 5 to 1. During the preheating process, the preheating temperature is stable at about 910°C, and the particle size of char after preheating is reduced, and the pore structure and specific surface areas are increased. The combustion temperature of preheated fuel is stable at around 1100°C, and the combustion efficiency can reach more than 99% under different conditions. Changing the structure of the secondary air nozzles during the preheating combustion process can influence the characteristics of emissions. The NOx emission of the central nozzle is about 112 mg/Nm3 lower than that of the annular nozzle. Changing the tertiary air distribution modes can reduce the final NOx emissions to 215 mg/Nm3 (@6%O2), and the corresponding conversion ratio of fuel N to the final NOx is 4.2%. The results of this experiment prove that the Yankuang coal can achieve stable combustion by preheating combustion technology, and this proposed a new way for the utilization of Yankuang coal.

The experiments with λ p (ratio of the primary air flow to the theoretical combustion air) were launched on a bench-scale coal preheating combustion test rig. The effect of λ p on operating charact...

As a novel technology, coal preheating technology has been proved to be effective on NOx reduction by previous experiments. However, the role of some components of the fuel is still not clear in the preheating process and combustion process. To clarify the effects of volatile and carbon on NOx formation and reduction, three fuels with different volatile contents were used, and the experiments were launched in a bench-scale coal preheating combustion test apparatus. Results showed that the self-preheating burner was widely adaptable to the fuels and the fuels could be stably preheated to be above 860 °C. The coal gas mainly containing the combustible components of CO, H2, and CH4 was generated in the self-preheating burner, accompanying with the high-temperature coal char. Due to the high contents of carbon and volatiles, more combustible components in coal gas could be yielded by the bituminous coal after being preheated. Most of the volatile matters and carbon were released into the coal gas, and the vol...

The char combustion characteristics and NO emission characteristics of O2/CO2/H2O preheated by a circulating fluidized bed were studied; such analysis can simulate the actual wet flue gas recirculation process in the preheating combustion process. The study was divided into two parts: the preheating characteristics and the combustion characteristics. During preheating, the preheating temperature decreased as the steam concentration increased. In addition, both CO2 and H2O reacted with char in the gasification reactions, and the steam shift reaction occurred, so the CO concentration decreased and the H2 concentration increased. As the steam concentration increased, the reduction ratio of fuel-nitrogen to N2 decreased, indicating that steam hindered the nitrogen reduction process during preheating. During combustion, as the steam concentration increased, the combustion temperature variation in the region near the down-fired combustion chamber (DFC) inlet decreased, while the combustion temperature variation in the region away from the DFC inlet increased. The steam shift reaction was weakened along the path of the DFC. The NO emissions gradually increased as the steam concentration increased because the content of unstable nitrogenous compounds from the pre-circulating fluidized bed (PCFB) participating in the chemical reactions in the DFC increased. Under these conditions, the combustion efficiencies were all above 99.0%.

Pulverized coal combustion technology with preheating solid fuel in a circulating fluidized bed was used for the combustion test of ultra-low volatile carbon-based fuel. This paper first validated the feasibility and advantages of applying the combustion technology to this kind of fuel. The carbon-based fuel could achieve a stable preheating process in this test system. After the preheating, the apparent sensible heat of the fuel was significantly increased. This provided a necessary condition for the stable ignition and efficient combustion of the carbon-based fuel in the post-combustion chamber. The relative proportions of CO, H2, and CH4 in preheated coal gas were very low, and the effect of high-temperature coal gas at the entrance of the post-combustion chamber was greatly impaired, indicating that the combustion process in post-combustion chamber was mainly the combustion of preheated char. At the same time, the strong reducing atmosphere in the circulating fluidized bed also facilitated the reduction of fuel-nitrogen into N2, which resulted in low NOx emissions. On this basis, with the combination of preheating combustion technology and air-staging combustion technology, the NOx emissions had drastically decreased when the burnout air distribution position moved down or varied from a single-layer distribution to a multi-layer distribution system. The lowest original NOx emissions were 90.6 mg/m3 (at 6% O2), and the combustion efficiency exceeded 97%, which ultimately achieved efficient and clean combustion of ultra-low volatile carbon-based fuel.

This study investigated nitrogen oxide (NOx) emissions of pulverized coal combustion preheated by a circulating fluidized bed (CFB). During the test process, high-temperature fuel preheated in a CFB was burned in a down-fired combustor (DFC). The effect of air distribution on NOx emissions was studied in the DFC, including three types of secondary air nozzle structures, five secondary air ratios, and three tertiary air position arrangements. Under stable conditions, the conversion ratio of fuel-nitrogen to N2 in the CFB was 41.4%, which resulted in lower NOx emissions in the platform. In this study, secondary air could be injected into the combustor at the top (annular) or through the side wall (circular) of the DFC, both with high combustion efficiency. This means that the secondary air is completely separated from the burner, and burner structure is greatly simplified. NOx emissions from secondary air nozzle structures of center, annular, and circular ports were 565.66, 345.45, and 220.38 mg/Nm3 (@6% O2) respectively. NOx emissions initially decreased then increased with increases in secondary air ratio with the annular nozzle structure. NOx emissions could be further inhibited by rationally arranging tertiary air positions.

MILD (moderate or intense low-oxygen dilution) combustion of pulverized char in O2/CO2 was achieved by preheating fuel in a circulating fluidized bed (CFB). The purpose of this research was to study effects of oxygen-staging gas distribution on NO emissions under MILD combustion of pulverized char. First, the preheating characteristics were evaluated, including the conversion ratios of each fuel component and the composition of the coal gas. To calculate the nitrogen balance in the preheating process, the gas in the loop seal was changed to O2/N2. The results indicate that the conversion ratios of each component increased with the increasing oxygen concentration in the primary gas, and the conversion ratio of nitrogen was above 0.40. In addition, the reduced proportion of nitrogen increased with the increase of oxygen concentrations in the primary gas, surpassing 30.0%. The heating value of high-temperature coal gas also increased. Next, the effects of oxygen-staging gas distribution on NO emissions were investigated. Increasing oxygen concentrations in the primary gas and in the secondary gas as well as decreasing oxygen concentration in the tertiary gas all reduced NO emissions. The lowest NO emission was 26.8 mg/MJ, and the combustion efficiency was above 99.0%. These results demonstrate that the oxy-fuel preheating combustion technology with effective oxygen-staging gas distribution could achieve clean, efficient combustion of pulverized char.

Proanthocyanidins are the major active compounds extracted from Iris lactea Pall. var. Chinensis (Fisch.) Koidz (I. lactea). Proanthocyanidins exhibit a variety of pharmacological activities such as anti-oxidation, anti-inflammation, anti-tumor, and lowering blood lipids. However, the underlying mechanism of its regulating effect on lipid metabolism in diabetic conditions remains unclear. The present study investigated the effects of I. lactea-derived proanthocyanidins on lipid metabolism in mice of type 2 diabetes mellitus (T2DM). Results demonstrated a beneficial effect of total proanthocyanidins on dysregulated lipid metabolism and hepatic steatosis in high-fat-diet/streptozocin (STZ)-induced T2DM. To identify the mechanisms, six flavan-3-ols were isolated from proanthocyanidins of I. lacteal and their effects on adipogenesis and dexamethasone (Dex)-induced mitochondrial dysfunctions in 3T3-L1 adipocytes were determined. In vitro studies showed flavan-3-ols inhibited adipogenesis and restored mitochondrial function after Dex-induced insulin resistance, being suggested by increased mitochondrial membrane potential, intracellular ATP contents, mitochondrial mass and mitochondrial biogenesis, and reduced reactive oxygen species. Among the six flavan-3-ols, procyanidin B3 and procyanidin B1 exhibited the strongest effects. Our study suggests potential of proanthocyanidins as therapeutic target for diabetes.

The zebrafish model organism has been of exceptional utility for the study of vertebrate development and disease through the application of tissue-specific labelling and overexpression of genes carrying patient-derived mutations. However, there remains a need for a binary expression system that is both non-toxic and not silenced over animal generations by DNA methylation. The Q binary expression system derived from the fungus Neurospora crassa is ideal, because the consensus binding site for the QF transcription factor lacks CpG dinucleotides, precluding silencing by CpG-meditated methylation. To optimize this system for zebrafish, we systematically tested several variants of the QF transcription factor: QF full length; QF2, which lacks the middle domain; QF2w, which is an attenuated version of QF2; and chimeric QFGal4. We found that full length QF and QF2 were strongly toxic to zebrafish embryos, QF2w was mildly toxic, and QFGal4 was well tolerated, when injected as RNA or expressed ubiquitously from stable transgenes. In addition, QFGal4 robustly activated a Tg(QUAS:GFPNLS) reporter transgene. To increase the utility of this system, we also modified the QF effector sequence termed QUAS, which consists of five copies of the QF binding site. Specifically, we decreased both the CpG dinucleotide content, as well as the repetitiveness of QUAS, to reduce the risk of transgene silencing via CpG methylation. Moreover, these modifications to QUAS removed leaky QF-independent neural expression that we detected in the original QUAS sequence. To demonstrate the utility of our QF optimizations, we show how the Q-system can be used for lineage tracing using a Cre-dependent Tg(ubi:QFGal4-switch) transgene. We also demonstrate that QFGal4 can be used in transient injections to tag and label endogenous genes by knocking in QFGal4 into sox2 and ubiquitin C genes.

NO is one of the major pollutants generated in the process of coal thermal conversion, and shall be controlled in order to fulfil the requirements of industrial production and environmental protection. The ratio of oxygen concentration to carbon dioxide concentration (O2/CO2 ratio) is one of the key factors that affect the thermal coal-N transformation and nitrogen oxide generation. However, there are few related research in this field at present and the conclusion needs to be refined. This study adopted the coal self-preheating combustion technology to obtain the high-temperature coal char on a bench-sale test rig, and combustion and gasification experiments of this modified fuel were carried out on TG-MS combined analyzer. The sum of the percentage content of O2 and CO2 was always 21% and Ar percentage content was 79% to simulate actual combustion. With the advanced equivalent characteristic spectrum analysis (ECSA) method, a quantitative analysis was conducted on the release rate and generative rules of gas products with temperature change during combustion and gasification of graphite and high-temperature coal char under different O2/CO2 ratios. As per the results, O2/CO2 ratio was the main factor affecting combustion characteristics of fuel and NO emission. In the atmosphere of 11% CO2 + 10% O2 + 79% Ar, NO emission reached the highest level. NO, HCN and N2 release time of the high-temperature char of Shenmu bituminous coal was earlier than that of the high-temperature coal char of Shenmu semi-coke, with wider temperature range corresponding to the period of evolved gas. Reaction (NO + CO → 1/2N2 + CO2) was the most cardinal reaction that affected the release of NO during coal thermal conversion progress.

This work reports a newly preheated system with pulverized coal oxy-fuel moderate or intense low-oxygen dilution (MILD) combustion for low NOx emissions. During the experiment, high-temperature fue...

This study examined the combustion of pulverized char under an O2/CO2 atmosphere to (1) attempt to achieve a moderate or intense low-oxygen dilution (MILD) combustion process and (2) investigate the effects of gas distribution modes on NO emissions. First, fuel was preheated in a circulating fluidized bed (CFB) and then high-temperature preheated fuel from the CFB was burned in a down-fired combustor (DFC). The study was conducted with two secondary gas nozzle positions, three tertiary gas position arrangements, and four secondary oxygen ratios in the DFC. During the test process, the combustion temperature was uniform in the CFB and the CO2 concentration in the flue gas reached approximately 90%. MILD combustion was achieved when the secondary gas nozzle position was center and the char combustion reaction dispersed into the upper low-oxygen space in the DFC. The obvious flame front disappeared and the temperature profile in the DFC was more uniform which is also one of the important features of MILD combustion. This reduced NO emissions by around half while maintaining high combustion efficiency. NO emissions were further reduced by a particular arrangement of tertiary gas positions, but at the cost of reducing combustion efficiency.

This study reports an experimental investigation on the nitrogen oxide (NOx) emissions in pulverized fuel (coal and char) combustion through preheating with a circulating fluidized bed. The high-te...

This paper considers multiple resolvable group target estimation under clutter environment. The proposed algorithm involves two aspects: target estimation and group state (group size, shape, etc.) estimation. First, we propose dynamic models and observation function for the group targets. Second, we derive the connection relation of individual targets through the predicted target states. In the following step, we combine the graph theory with the group targets and build the adjacency matrix of the estimated state set. The connection information is used to correct the collaboration noise and estimate the target states. For group estimation, we focus on the number of subgroups, the group states and the group sizes. Finally, several examples are given to verify the proposed algorithm, respectively.

The experiments of the effect of particle size on flameless combustion characteristics and NOx emissions of Shenmu semi-coke were launched on a bench-scale coal preheating combustion test rig. The results revealed that the difference of fuel particle size greatly influenced the yield of each component in high-temperature coal gas and the reactive activity of coal char, thus subsequently affecting the final combustion process and NOx emissions. The specific surface area and pore volume of Shenmu semi-coke were both significantly increased after preheated, leading to a better reactivity and the improved combustion performance, especially when d50 (the mean particle size) = 163.84 μm, where the temperature of the down-fired combustor reached the highest. The different particle size of Shenmu semi-coke resulted in different preheating temperature, which further affected the content of each component in the high-temperature coal gas. During the self-preheating process, most volatile matter and fuel bound N were separated out and the released N was mainly converted to N2 and NH3, besides the conversion rate of each component (C, H, N and V) was the highest when d50 = 100.17 µm. Additionally, all experimental conditions achieved flameless combustion, with a transparent combustion area, but no flame front visible to the naked eye, and the highest combustion efficiency was 98.23% when d50 = 163.84 µm with the brightest flame image. It was discovered in this experimental that there was a critical value (d50 = 198.54 μm) of Shenmu semi-coke particles. When the particle size was lower than or higher than the critical value, NOx generated by combustion would decrease. The lowest NOx emission was 89.46 mg/m3 (@6% O2) when d50 was 35.34 μm.

In this study, we sought to achieve a stable high-efficiency and low-NOx combustion of weakly caking coal by preheating fuel in a pre-circulating fluidized bed (PCFB). When the operating temperature of the PCFB increased from 954 °C to 1048 °C and the fluidizing gas velocity increased from 2.02 m/s to 3.27 m/s, the stable operating time of the caking coal increased significantly from 290 min to 550 min. Moreover, the caking trend of the preheated char completely disappeared (RI = 0, GR.I = 0). The preheated char particles were obviously bonded together at 954 °C, while the char particles were still clearly separated at 1048 °C. These results indicate that the high preheating temperature and the high fluidizing gas velocity are beneficial to alleviate or even resolve the preheating instability of weakly caking coal. Based on the stable preheating operation, the temperature field and reaction field in the main combustion zone were relatively uniform. Gas-phase nitrogen-containing compounds in the post-combustion chamber existed mainly in the form of NO, and the NO concentration in the reducing zone was zero. With the gradual injection of the burnout air, the NO concentration first increased and then decreased to a stable level. By arranging the burnout air position separating the reducing zone and the oxidizing zone to broaden the reducing zone, NO emissions were further reduced without affecting the combustion effect. And the preheating combustion technology is verified to more flexibly arrange the number of air distribution layers in multilevel air distribution settings.

Higher effective combustion with fundamental pollution ultra-low NOx emissions for pulverized coal is multidisciplinarily sought in recent decades. In this work, a novel megawatt-class pilot-scaled experimental investigation of Shenmu bituminous coal preheated semi-gasification combustion (PSGC), non-dimensional momentum parameters and modified binary fuels combustion organization was implemented to obtain both original ultra-low NOx emissions and high combustion efficiency. Depended on the fluidization preheated physicochemical modification for raw pulverized coal and deep reducing NOx emission methods, the modified Shenmu bituminous coal was constructed to combust with preheating ultra-low NOx methodology to obtain the deep-controlled original ultra-low NOx emission with high burnout ratio. The results showed that the thermal input was 1.64 MWth and the minimum average original NOx emission was 49.6 mg/m3 at 6%O2. Meanwhile, the combustion efficiency was 99.4% with the momentum ratio between inner and outer secondary air (MRsa) was 0.26. The upped air-to-fuel stoichiometric ratio (Φ(A/F)pa) 0.22 as fluidized preheating air ratio improved the conversion ratio (CRf) of raw fuel components and further promoted the reduction conversion ratio for both hot char-N and volatiles-N in this special phyciochemical conversing process in the fluidized preheating partial gasification combustor.